ecra chair from co to energy: carbon capture in cement...

ECRA Chair “From CO2 to Energy:

Carbon Capture in Cement Production and its Re-use”

Second Annual Report

Period: May 2014 - April 2015

Contributors to the report:

Prof. Diane Thomas, Chemical Engineering Department, UMONS

Academic coordinator of the Chair Prof. Guy De Weireld, Thermodynamics Department, UMONS Dr Lionel Dubois, Chemical Engineering Department, UMONS

Scientific coordinator of the Chair Ir Sinda Laribi, Chemical Engineering Department, UMONS Ir Nicolas Meunier, Thermodynamics Department, UMONS

Acknowledgments:

ECRA is warmly acknowledged for the financial support of the Academic ECRA

Chair at the Faculty of Engineering at UMONS (Belgium).

We would like also to acknowledge the HeidelbergCement Group for the funding of the Scientific Coordinator of the ECRA Chair.

ECRA CHAIR – First Annual Report (May 2013 – April 2014)

Table of contents

1. STATUS OF THE ECRA CHAIR ACTIVITIES .......................................................................................................... 1

1.1 FRAMEWORK OF THE ECRA CHAIR .............................................................................................................. 1

1.1.1 PHD THESES AND STUDENTS .................................................................................................................. 2

1.1.2 ASSOCIATION OF STUDENTS WORKS ..................................................................................................... 4

1.1.3 SCIENTIFIC COORDINATION OF THE CHAIR AND LINK WITH THE HEIDELBERGCEMENT-UMONS COLLABORATION ............................................................................................................................................... 5

1.2 ECRA EVENT AT UMONS .............................................................................................................................. 6

1.3 SCIENTIFIC COMMITTEE MEETINGS ECRA-UMONS ..................................................................................... 7

1.3.1 MEETING (ECRA - UMONS) AT MONS ON 26TH MAY 2014 ..................................................................... 7

1.3.2 MEETING (ECRA - UMONS) AT MONS ON 25TH NOVEMBER 2014 ......................................................... 8

1.3.3 MEETING (ECRA - UMONS) AT DUSSELDORF ON 30TH MARCH 2015 ..................................................... 9

1.4 ECRA PRIZE ................................................................................................................................................... 9

2. ADVANCES IN THE PHD THESIS OF SINDA LARIBI .......................................................................................... 11

2.1 POST COMBUSTION CO2 CAPTURE APPLIED TO FLUE GASES COMING FROM PARTIAL OXYFUEL COMBUSTION CEMENT INDUSTRIES - « HYBRID PROCESS » ............................................................................. 11

2.1.1 PRINCIPLE OF THE “HYBRID TECHNOLOGY” (PARTIAL OXYFUEL COMBUSTION OR COMBUSTION WITH ENRICHED O2) .................................................................................................................................................. 11

2.1.2 EXPERIMENTAL DEVICE AND OPERATING PARAMETERS ..................................................................... 12

2.1.3 MORE RELEVANT RESULTS ................................................................................................................... 14

2.2 SIMULATION OF A CO2 PURIFICATION UNIT APPLIED TO FLUE GASES COMING FROM OXYCOMBUSTION CEMENT INDUSTRIES .......................................................................................................................................... 18

2.2.1 SOUR COMPRESSION UNIT “SCU” (DE-SOX & DE-NOX) FLOWSHEET .................................................... 19

2.2.2 APPLICATION OF THE SCU TO FLUE GASES COMING FROM OXYCOMBUSTION POWER PLANTS AND OXYCOMBUSTION CEMENT INDUSTRIES ........................................................................................................ 20

2.2.3 PARAMETRIC STUDY FOR THE SOUR COMPRESSION UNIT .................................................................. 22

3. ADVANCES IN THE PHD THESIS OF NICOLAS MEUNIER ................................................................................. 24

3.1 DEHYDRATION UNIT .................................................................................................................................. 24

3.1.1 DESCRIPTION OF THE DEHYDRATION UNIT .......................................................................................... 24

3.1.2 SIMULATION OF THE DEHYDRATION UNIT .......................................................................................... 25

3.2 CRYOGENIC UNIT ....................................................................................................................................... 26

3.2.1 DESCRIPTION OF THE CRYOGENIC UNIT .............................................................................................. 26

3.2.2 SIMULATION OF THE CRYOGENIC UNIT ............................................................................................... 26

3.3 CO2 CONVERSION INTO METHANOL .......................................................................................................... 29

3.3.1 ADAPTATION OF THE AMERICAN PATENT ........................................................................................... 29

3.3.2 SIMULATION OF THE CO2 CONVERSION UNIT ...................................................................................... 30

3.3.3 DESIGN OF THE EXPERIMENTAL REACTOR ........................................................................................... 33

ECRA CHAIR – First Annual Report (May 2013 – April 2014)

4. POST-DOCTORAL WORKS IN THE FRAMEWORK OF THE COLLABORATION WITH HEIDELBERGCEMENT .... 35

4.1 USE OF MEMBRANES IN CEMENT INDUSTRY FOR CARBON CAPTURE INSTALLATIONS ............................ 35

4.1.1 INTRODUCTION .................................................................................................................................... 35

4.1.2 LITERATURE REVIEW ON FACILITATED TRANSPORT MEMBRANES (FTM) FOR CO2 CAPTURE ............. 35

4.1.3 TECHNOLOGICAL MONITORING ON THE POTENTIAL OF CO2 HYBRID CAPTURE SYSTEM (GAS/GAS MEMBRANES + CLASSICAL AMINE PLANT) IN THE CEMENT INDUSTRY .......................................................... 37

4.2 SIMULATION OF THE POST-COMBUSTION CO2 CAPTURE PROCESS APPLIED TO CEMENT FLUE GASES ... 40

4.2.1 INTRODUCTION .................................................................................................................................... 40

4.2.2 SIMULATION AND RESULTS .................................................................................................................. 41

4.2.3 CONCLUSION ON THE FIRST SIMULATIONS AND PERSPECTIVES ......................................................... 44

4.3 CO2 MINERALIZATION INTO OLIVINE-DERIVE COMPOUNDS ..................................................................... 45

4.3.1 INTRODUCTION ON MINERAL CARBONATION (MC) ............................................................................ 45

4.3.2 GLOBAL COMPARISON OF THE MINERAL CARBONATION OPTIONS .................................................... 47

4.3.3 CONCLUSIONS AND PERSPECTIVES FOR THE MINERAL CARBONATION .............................................. 48

5. GENERAL CONCLUSIONS AND PERSPECTIVES ................................................................................................ 51

5.1 GENERAL CONCLUSIONS ON PROGRESS OF THE ECRA CHAIR SCIENTIFIC ACTIVITIES .............................. 51

5.2 ECRA CHAIR SCIENTIFIC ACTIVITIES FOR THE NEXT YEAR .......................................................................... 51

5.3 EXTERNAL COMMUNICATION .................................................................................................................... 52

5.3.1 PUBLICATIONS ...................................................................................................................................... 52

5.3.2 FUTURE PLANNED COMMUNICATIONS ............................................................................................... 54

5.4 GLOBAL PERSPECTIVES OF THE ECRA CHAIR ............................................................................................. 55

6. REFERENCES .................................................................................................................................................... 57

7. ANNEXES ......................................................................................................................................................... 60

ECRA CHAIR – Second Annual Report (May 2014 – April 2015) 1

1. STATUS OF THE ECRA CHAIR ACTIVITIES

The main objective of the ECRA Chair at UMONS, launched in April 2013, is to create a centre of scientific expertise in the specific field of “Carbon capture in cement production and re-use” and to promote research and innovation in the topic through the achievement of different activities as listed in Figure 1.

Figure 1: “Spirit” of the ECRA Chair

Most of them have been developed as evidenced by this report.

1.1 Framework of the ECRA Chair

The different ECRA Chair activities at UMONS are supported by :

- PhD students (2 up to now): N. Meunier and S. Laribi; - a postdoctoral researcher: L. Dubois: - professors of the Faculty of Engineering of UMONS: D. Thomas, G. De Weireld and P.

Lybaert. Figure 2 presents the general framework of the ECRA Chair.


Figure 2: Framework of the ECRA Chair

1.1.1 PhD Theses and students

1°) The scientific studies were launched at the beginning of the academic year (September 2013) through two PhD theses co-funded by ECRA and UMONS (Special Fund for Research / Research Institute for Energy). We can present schematically the different parts of the research works as follows (Figure 3) and these will be more developed later in this document.

Figure 3: Research subjects considered into the ECRA Chair


- The first thesis is carried out by Nicolas Meunier (Master’s degree in Chemistry/Material Science from UMONS and TU Wien). He began on 1st September 2013.

Nicolas Meunier works on a subject entitled “CO2 capture in cement production and re-

use: optimization of the overall process”.

N. Meunier has obtained a research grant (beginning in October 2014) of 2 years renewable once by the FNRS (Belgian National Fund for Scientific Research) for carrying out his PhD thesis on the CO2 catalytic conversion into methanol. The main objectives of this research are then to perform a multi-scale characterization of the transfers of the different compounds of the catalytic reaction (i.e. CO2, hydrogen, water, and methanol) and to measure the influence of gaseous compounds (O2, SOx and NOx) on CuO/ZnO/Al2O3-type catalysts performances, stability and lifetime. To this end, laboratory and pilot scale units will be established and experiments will be performed and then modelled by homemade mathematical codes to determine the different kinetic laws and mechanisms of the reactions considered for the CO2 conversion into methanol. The influence of some promoters on performances, stability and lifetime of the CuO/ZnO/Al2O3-type catalyst used for the CO2 conversion into methanol will also be investigated. Moreover, predictive simulations (on Aspen Plus®) will also be performed in order to verify the relevance of the kinetics and mechanisms models and to set the minimal CO2 purity required for the CO2 conversion into methanol according to user-defined methanol purity. Finally, the research will propose an integrated process with optimized operating parameters and considering energetic and cost integration for the design and sizing of the installation. The subject of his thesis will address the global (capture/ purification/ conversion) process chain and the specificities of the cement industry. In his thesis N. Meunier also considers the simulation of the dehydration and cryogeny units as parts of the CO2 Purification Unit (CPU) applied to carbon dioxide coming from oxy-fuel cement plants.

- The second thesis began on 1st January 2014. Miss Sinda Laribi (Applied License in Industrial Chemistry (ESSTunis) and Master of Chemical Engineer (ENIGabes)) was recruited as a PhD student.

She works on “Purification processes applied to CO2 captured from cement industry for

conversion into methane or methanol”.

Both for post-combustion and oxy-fuel combustion CO2 capture processes, the outcoming

CO2 flux must be purified in order to be re-used, especially in the methane or methanol process.


The purpose of the PhD thesis is to review, understand and simulate (performances estimations) the different flue gas treatments needed for the post-combustion CO2 capture and for the oxy-fuel combustion capture (rich CO2 flow purification). S. Laribi focuses on two main subjects, namely the simulation of the Sour Compression Unit

(SCU) as part of the CO2 Purification Unit (CPU) applied to carbon dioxide coming from oxy-

fuel cement plants, and the experimental study of CO2 absorption process into amine-based

solvents applied to flue gases coming from O2-enriched cement plants (“hybrid CO2 capture

process”).

Regarding the first point detailed investigations and bibliographic researches are required to

implement the correct reaction mechanism in Aspen Plus software in order to obtain realistic

simulation results.

Concerning the second point, absorption tests are carried out thanks to a laboratory gas-liquid

contactor (namely a cables-bundle contactor at UMONS) to test several amine-based solvents

and other solvents such as hybrid ones (combination between an amine and another

compound such as acetal) to see if they have interesting performances at high CO2 content

(60%) into the flue gas. These are related to the possible interest for cement industry to

consider a combination of O2-enriched conditions (with or without gas recirculation) and a

post-combustion CO2 capture process.

The first CO2 capture processes investigations are made on the amine absorption-

regeneration process, a second technology (Pressure Swing Adsorption) will be also

considered in the future. .

2°) Note that from an administrative and official (UMONS) point of view, the PhD thesis academic committees (“Comités d’Accompagnement de Thèse (CAT)) with internal (UMONS) and external members: → took place on 30-10-2014 for Nicolas Meunier and on 26-01-2015 for Sinda Laribi (these

committees have to meet after roughly one year of PhD thesis, then annually up to the end of the thesis);

→ were both validated. Both reports have been sent to ECRA.

1.1.2 Association of students works

One of the objectives of ECRA Chair is also to associate student works in the scientific activities of the Chair. In this context, besides two PhD theses with large scientific content, works of undergraduate students are also achieved, related to more specific subjects as parts of the scientific topics included in the Chair: → « Modélisation et optimisation de l’absorption du CO

2 présent dans les fumées provenant

de fours de cimenterie en vue de sa réutilisation »


Nicolas DEBAISIEUX - Student Internship (funded by the Faculty of Engineering of UMONS) achieved in the Thermodynamics Department during summer 2014 → « Experimental study of CO2 absorption into amine(s) based solvents: application to cement

flue gases coming from partial-oxyfuel kilns » - Guillaume PIERROT - Master thesis achieved in the Chemical and Biochemical Engineering Department The report written in English will be available in June 2015. → « Purification des fumées riches en CO2 provenant de fours à oxycombustion – Elimination

de l’eau par adsorption » - Pol BLANCHARD & Ilyas ZARIOH - BA3 student project achieved in the Thermodynamics Department The report written in French will be available in May 2015.

1.1.3 Scientific coordination of the Chair and link with the HeidelbergCement-

UMONS collaboration

As specified in the previous report, the scientific works of the Chair are coordinated with the support of Dr Lionel Dubois, post-doctoral researcher, Engineer in Chemistry from FPMs and who carried out his PhD thesis at UMONS (presented in March 2013) on a subject related to the CO2 capture applied to cement flue gases (research project in collaboration with Holcim company). The funding of this scientific coordinator is possible thanks to the financial support (beginning on the 01-01-2014 and initially scheduled for two year) of HeidelbergCement which is also collaborating with UMONS on the subject of CO2 capture in the context of the ECRA Chair. In addition to the works linked directly to the ECRA Chair Scientific Coordination and logistic support, namely:

(1) the scientific support to the PhD theses (scientific and technical advises, meetings and discussions with PhD Students, reading and remarks on the reports, etc.);

(2) the support for reporting and publications writing; (3) the logistic organization of the Chair for event organization such as the First ECRA Chair

Scientific Event organized at UMONS on the 26-11-2014, but also for meetings planning, travel scheduling, , etc.;

(4) the support for new PhD theses establishment (subject definition) and for the recruitment procedures (job offers redaction, answers to applications, interviews arrangements with candidates, etc.);

(5) the support to any other scientific activities related to the Chair topics (co-supervision of undergraduate projects or master thesis, support for student trainee, help for the establishment of new projects relative to CO2 capture (European FEDER projects, FNRS projects, information on other projects calls, etc.);

the specific tasks carried out by the post-doctoral researcher in the framework of the HeidelbergCement collaboration were:

(1) a complementary bibliographic study on new membranes (Facilitated Transport Membranes) and technological monitoring on hybrid CO2 capture system combining membranes and amine absorption technologies;


(2) a simulation work with Aspen Hysys software on the post-combustion CO2 capture process for the application to Norcem Brevik cement plant flue gas;

(3) a preliminary bibliographic study on CO2 mineralization into olivine derived compounds.

A summary of the more relevant information in relation with these specific tasks are given in Chapter 4.

1.2 ECRA Event at UMONS

The First ECRA Chair Scientific Event has been organized at UMONS on the 26th November 2014 (see pictures of the Event on Figure 4). This can be proclaimed as a great achievement and success as 100 participants from around 20 countries were registered. This event was a great opportunity to attend very interesting presentations by industrial and academic experts, also by PhD students, on the subject of CO2 capture and reuse in the cement industry.

The program of the event and the abstracts of the communications can be found in the Annex.

Figure 4: Some pictures of the first ECRA Chair Event


Short reports (see Figure 5) about this first Scientific Event of the ECRA Chair were published in the press:

a. Cembureau article on www.cembureau.eu, section Newsroom – Eurobrief. b. Polytech News n°51, page 36. c. Athena n° 307, page 6. d. Carbon Capture Journal, janv-febr 2015, page 16. e. ECRA Newsletter, 1/2015, pages 2-3.

Figure 5: Illustration of press articles related to the First ECRA Chair Scientific Event

1.3 Scientific Committee meetings ECRA-UMONS

As stated in the convention, it is planned to hold two meetings of the scientific committee per year. This was the case during the past year. Minutes are systematically written to summarize the discussions and decisions.

1.3.1 Meeting (ECRA - UMONS) at Mons on 26th May 2014

A meeting aiming at: - discussing the scope of ECRA Chair research works (status of the ECRA PhD theses); status of

membranes study (by L. Dubois) ; - presenting the status of ECRA CCS projects (by ECRA members); - and discussing the draft of the event. took place at Mons on 26th May 2014 (Figure 6).

http://www.cembureau.eu/


,

Figure 6: Meeting ECRA - UMONS at Mons on 26th May 2014

1.3.2 Meeting (ECRA - UMONS) at Mons on 25th November 2014

This meeting was very short (one hour) as a TAB committee meeting was organized just after. A document entitled “Status and perspectives for the ECRA PhD Theses and post-doc” was sent in advance as a basis for the discussions.

Very brief information were given on the First ECRA Chair Scientific Event organized at UMONS

the day after, together with other conventional information (external communication

activities, first ECRA Award for new graduated students, works of an undergraduate student

in the framework of the ECRA Chair).

Regarding the research works, the following elements were discussed and decided : 1°) The Scientific Committee was informed that N. Meunier has obtained a research grant by

the FNRS for carrying out his PhD thesis and future works were scheduled for his PhD Thesis.

2°) This grant allows the ECRA Chair to launch a third PhD thesis in 2015.

The new PhD thesis subject must be defined by the Scientific Committee taking into account different characteristics (in accordance with ECRA interests and UMONS expertise areas, focused on simulation works and potentially with technico-economic considerations). Some topics were cited: combustion of alternative fuels and/or biomass, CO2 reuse with alternative to the methanol production, CO2 capture by bioprocesses (bacteria, microalgae) A list with more defined subjects was sent to ECRA some weeks later. 3°) The future experimental works scheduled for the PhD Thesis of S. Laribi were also presented. In parallel of her simulation works in relation with the purification processes


applied to CO2 captured from cement plants, the Scientific Committee agreed on the proposal to study the “Hybrid CO2 capture technology combining partial oxy-combustion and post-combustion for the application to cement flue gases” through simulation and experimental works, investigating the absorption/regeneration process and an adsorption technique.

1.3.3 Meeting (ECRA - UMONS) at Dusseldorf on 30th March 2015

Aiming at evaluating the progress of the different research projects of the Chair and discussing the research works, a meeting of the Scientific Committee took place at Düsseldorf, on 30th March 2015.

Beside the global status of the ECRA Academic Chair activities, the intermediate reports on

the ongoing PhD theses and post-doc, the report on ECRA’s activities (by M. Schneider and K.

Fleiger), the subject of the third PhD thesis of the ECRA Chair was more precisely defined and

confirmed as:

“Study of the potential of different CO2 conversion options for the application of Carbon

Capture and Re-use to the cement industry: simulation and technico-economic analysis”.

The purpose of this new PhD thesis will be to evaluate, in parallel of the CO2 conversion into

methanol already considered into the ECRA Chair, the potential of other options for the re-

use of CO2 captured from cement plants. This PhD thesis will include bibliographic, simulations

and optimization works (no experimental tasks). The Scientific Committee agreed with the

candidate profile for the recruitment procedure which can be initiated by UMONS as soon as

possible.

1.4 ECRA Prize

An “ECRA Prize” was created to be awarded to new graduated students for the best Master2 project/Master thesis related to the CO2 capture or reuse, or related to any improvement for the cement industry. The first ECRA Prize (Prize amount: 400 EUR) has been awarded in September 2014 at the Polytech Mons Day (Figure 7) and was split between two deserving students:

- Marvin Boulanger - “Use of membrane in cement industry for carbon capture installations” – best Master2 project 2013-2014

- Sophie Maerten – “Vapour-liquid equilibrium of 1,3-diaminopropane (DAP) solutions for the CO

2 capture by absorption-regeneration” – best master thesis (realized at NTNU

Trondheim - Norway) 2013-2014


Figure 7: ECRA award for new graduated students in September 2014


2. ADVANCES IN THE PhD THESIS OF SINDA LARIBI

As already mentioned the actual works of Sinda Laribi address the two following subjects: - solvent-based absorption/regeneration post-combustion CO2 capture process applied to flue gases coming from a partial oxycombustion process ; - simulation of the Sour Compression Unit as part of the CO2 Purification Unit (CPU) applied to carbon dioxide coming from oxy-fuel cement plants. These works are developed hereafter.

2.1 Post combustion CO2 capture applied to flue gases coming from partial oxyfuel

combustion cement industries - « Hybrid process »

2.1.1 Principle of the “Hybrid technology” (partial oxyfuel combustion or combustion

with enriched O2)

Figure 8: Partial oxyfuel combustion system Carbon Capture and Storage Technologies (CCS) applied to fossil-fuels power plants have shown some issues that have not been solved yet. On the one hand post-combustion processes treating flue gases from conventional combustion using amine-based chemical absorption is a mature and industrially developed technology which has been proved to be efficient but the solvent regeneration requires a high-intensive energy consumption. On the other hand, oxy-combustion requires a large amount of high-purity oxygen that can only be actually supplied by cryogenic units at this scale. In this case the oxygen production is its higher energy penalty. Partial oxy-combustion (Figure 8) is a hybrid technology between both technologies that proposes an optimized operation that can lead to further reductions on the overall energy consumption [Smart, 2012][ECO-SCRUB, 2013]. The minimum energy requirement (including oxygen production and CO2 capture) corresponds to an oxygen content at the inlet of the boiler intermediate between the conventional combustion (with air) using and oxy-combustion (with pure oxygen) conditions.


So this new technology means the simultaneous: - Reduction of the energy regeneration in the amine plant thanks to a more CO2-

concentrated flue gas;

- Reduction of the energy costs for the Air Separation Unit (ASU), less O2 needed in

comparison with a totally oxyfuelled system.

In this context, a master thesis is in progress relative to the absorption-regeneration

process and its aim is to: - Test the solvents capture performances for high CO2 content, namely YCO2,in between

10 and 60 % vol;

- Screen new solvents (including hybrid ones) for CO2 capture under partial oxyfuel

conditions.

A study concerning the pressure swing adsorption (PSA) is going to be developed both in simulation works and in experimental works: measurements of equilibrium isotherms and identification of efficient adsorbents will be the purpose of further works in coordination with the simulation of the PSA unit and the estimation of the energy consumption of the process under hybrid conditions.

2.1.2 Experimental device and operating parameters

The basis of this work being the choice of the solvents for the screening step, the different absorption tests were achieved with different types of solvents:

- Chemical solvents: primary alkanolamines (Monoethanolamine (MEA)), secondary

alkanolamines (Diethanolamine (DEA) and Methylmono-ethanolamine (MMEA)),

tertiary alkanolamines (N-Methyldiethanolamine (MDEA)), sterically hindered amines

(2-Amino-2-methyl-1-propanol (AMP) and 2-Amino-2-hydroxymethyl-1,3 propanediol

(AHPD)), cyclical di-amines (Piperazine (PZ)) and non-cyclical tetramines

(Triethylenetetramine (TETRA));

- A combination of a physical solvent (acetal TOU = 2,5,7,10-tetraoxaundecane) and

chemical solvents (amines such as MEA, DEA, PZ, AMP) to assure maximum absorption performances.

The CO2 absorption tests were carried out at lab scale with a cables-bundle contactor (Figure 9), the liquid flow rate being fixed at 0.185 L/min and the total gas flow rate (Gtot) at 12.9 NL/min (nominal values for this type of laboratory set-up). The advantage of the contactor is to allow to measure quite varying absorption performances (for more or less soluble and more or less reactive species) without constraint of pressure drop: this is a very efficient device for screening purposes. In these tests, the carbon dioxide (solute) is mixed with a carrier gas i.e. the nitrogen, their flow rates are controlled by the flow regulator which sends a specified gas flow rate to the humidification column (to avoid gas evaporation in the contactor). The gas enters at the bottom of the cables-bundle contactor, contacts counter-currently the solvent flowing


vertically on the cables and CO2 is absorbed. The liquid is pumped from the prepared solution and is previously pre-heated in the heat exchanger with thermostated water in order to reach a given temperature (25°C) at the inlet of the column. Analyses in the gas-liquid system are required: - The gas at the inlet and the outlet of the column is dried using a membrane system working with nitrogen as drying gas before passing into the IR analyzer which gives simultaneous values of YCO2,in and YCO2,out. - For the liquid phase, the pH via a pHmeter and the CO2 loading via the TOC analyser (with Total Carbon and Inorganic Carbon quantifications) are measured. Differences of temperatures in the liquid at the top and the bottom of the column are also controlled to observe eventual thermal effects during the absorption process. Two types of tests were carried out for this experimental laboratory device:

- Continuous tests: fresh scrubbing solutions (solutions not loaded with CO2) and gas phase

are continuously fed in the contactor, with varying CO2 contents at the inlet: yCO2, in = 10%,

20%, 30%, 40%, 50% and 60%.

- Semi-continuous tests: Recirculation of 1.3 Liter of solution fixing a CO2 inlet content of

40% in the gas phase.

Figure 9: The cables bundle contactor scheme


The absorption efficiency (A (%)) of the solvent is calculated thanks to:

A (%)= yCO2,in -

𝑋𝑜𝑢𝑡𝑋𝑖𝑛

1 − 𝑦𝐶𝑂2, 𝑖𝑛1 − 𝑦𝐶𝑂2, 𝑜𝑢𝑡 yCO2,out

yCO2,in 100

where Xin = 1 – humin, humin being calculated with the temperature of the circulating water (16,5°C) and Xout = 1 – humout, humout being calculated using the average between temperature at the top and the bottom of the contactor. Based on the absorption efficiency, the results can be explained in terms of the CO2 molar

absorption flow rate (G mol CO2,abs):

𝐺mol CO2 abs (𝑚𝑜𝑙 𝐶𝑂2ℎ⁄ ) = 𝐴 ∗ 𝑦CO2,in ∗ 𝐺in, dry

The CO2 loading (αCO2) of each solution is calculated thanks to:

𝛼𝐶𝑂2 (𝑚𝑜𝑙 𝐶𝑂2𝑚𝑜𝑙 𝑎𝑚𝑖𝑛𝑒⁄ ) =

𝐶 𝐶𝑂2

𝐶 𝑎𝑚𝑖𝑛𝑒

where CCO2 is the CO2 molar concentration into the solvent:

𝐶𝐶𝑂2(𝑚𝑜𝑙 𝐶𝑂2

𝑙⁄ ) = 𝑇𝐶 𝑙𝑜𝑎𝑑𝑒𝑑 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 − 𝑇𝐶 𝑛𝑜𝑡 𝑙𝑜𝑎𝑑𝑒𝑑 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛

1000𝑀𝑀 𝑐𝑎𝑟𝑏𝑜𝑛𝑒

with TC (Total Carbon contents) of the loaded and unloaded solutions and Camine the amine concentration of the liquid:

𝐶𝑎𝑚𝑖𝑛𝑒 (𝑚𝑜𝑙 𝑎𝑚𝑖𝑛𝑒𝑙⁄ ) =

𝑇𝐶 𝑛𝑜𝑡 𝑙𝑜𝑎𝑑𝑒𝑑 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛1000

(𝑀𝑀 𝑐𝑎𝑟𝑏𝑜𝑛𝑒) ∗(𝑛 𝑐𝑎𝑟𝑏𝑜𝑛𝑒 𝑎𝑚𝑖𝑛𝑒)

2.1.3 More relevant results

a. Continuous tests The first step of this study was to compare the solvents performances for various CO2 contents (yCO2,in) of the gas. More specifically, the purpose of the work was to measure and compare these performances at very high YCO2,in (up to 60 %vol.). The absorption results explained in terms of CO2 molar absorption flow rate (G mol CO2,abs) for different conventional solvents are given on Figure 10.


Figure 10: Comparison of different conventional solvents

Considering MEA 30% as benchmark (which is conventional for such screening works), Figure 10 shows that MMEA 30% gives better absorption performances at both low and high yCO2,in (GCO2,abs ≈ 11 mol CO2/h at yCO2,in = 60 %vol.). The absorption results measured with PZ 10% are also very important (difference with MMEA 30% only significant at yCO2,in = 50 and 60 % vol.). Figure 11 shows the absorption results obtained with activated solutions composed of these conventional solvents (AMP, DEA an MMEA 30 %) blended with 5% of an activator (namely PZ and TETRA 5%).

Figure 11: Comparison of different activated solvents (including hybrid one)

Regarding the effect of the activators on the MMEA 30% absorption performances, the comparison of Figure 10 and Figure 11 shows that the effect of the two activators is quite similar and leads to only a small increase of the performances (GCO2,abs ≈ 12 mol CO2/h at yCO2,in

= 60 %vol.), the MMEA 30% activated solutions still leading to the best absorption performances. Nevertheless, it should be noted that for AMP 30% and DEA 30% solutions, the activation effect is much more significant and is better with PZ 5% than with TETRA 5%, the


results obtained with the PZ-activated solutions leading to a GCO2, abs at yCO2,in = 60 %vol. (≥ 8 mol CO2/h) higher than the benchmark MEA 30% one (< 8 mol CO2/h). Figure 11 also illustrates the absorption results obtained with an hybrid solvent composed of a chemical part (MEA 30%) and a physical part (TOU 35%). At yCO2,in = 60 %vol., even if the absorption performances are lower than with MMEA 30% (both simple and activated solutions), the results obtained with this innovative solvent are quite similar to the one measured with activated solutions of DEA or AMP 30% with PZ 5%, which indicates a real potential to be investigated in further studies, TOU being a cheaper chemical product in comparison with some amines and especially activators such as PZ. To conclude the analysis of these results, it should be noted that for some solvents a significant increase of the liquid temperature (for example increase of 20°C with MMEA 30%) was measured between the inlet and the outlet of the gas-liquid contactor. This temperature increase is also measured in the industrial process and is linked to the exothermicity of the CO2-amine reactions (reaction heat) which is a function of the amine chemical structure, but also a function of YCO2,in, this thermal effect being more important as more CO2 is absorbed by the solution. b. Semi-continuous tests Even if the continuous tests give a first overview of the solvent performances, in the industrial CO2 capture process, the solvents are never totally regenerated and thus are still partially CO2-loaded when it enter the absorption column. For this purpose, during the semi-continuous tests, the absorption performances of the solvents were measured together with an increasing CO2-loading which was obtained thanks to the recirculation of the solution. Figure 12 shows the CO2 loading temporal evolutions during the semi-continuous tests.

Figure 12: Temporal evolution of the CO2 loading for different solvents (yCO2, in = 40%)

Figure 12 highlights that the CO2 loading of TETRA 30% increases more quickly than for other solvents and that the CO2 loading measured at the end of the test (≈ 1.1 mol CO2/mol TETRA) is clearly higher in comparison with the other solvents (< 0.8 mol CO2/mol amine). Due to this


increasing CO2 loading, the absorption performances of the solvents decrease, as illustrated on Figure 13.

Figure 13: Temporal evolution of the GCO2,abs for different solvents (yCO2, in = 40%)

It can be seen that even if MMEA 30% presented the best absorption performances at the beginning of the semi-continuous test (αCO2 ≈ 0 mol CO2/mol amine), its absorption performances decrease more quickly than with the other solvents. At the end of the test (90 min), the solvent presenting the highest GCO2, abs is not MMEA 30% but TETRA 30%. This result was linked to the absorption capacity of the solvents. Indeed, for some solvents, a sample of the solution was loaded until saturation (Table 1) in order to evaluate their absorption capacity at atmospheric pressure (yCO2=100%) and at an initial temperature of 25°C. It can be seen in Table 1 that TETRA presents a clearly higher absorption capacity in comparison with the other solvents.

Table 1: Comparison of αCO2,sat for different solvents

MEA MEA + TOU MMEA TETRA

αCO2,sat

(mol CO2/mol amine)

0.54 1.02 0.59 1.32

Finally, the GCO2,abs measured with various solvents at different experiment times are compared on Figure 14.


Figure 14: Comparison of the GCO2,abs for different solvents at different times (YCO2, in = 40%)

This graph shows that the ranking of the solvents based on their GCO2,abs is modified during the semi-continuous test due to the CO2 loading. Without analyzing all these results, Figure 14 confirms that TETRA 30% is the solvent which presents the highest GCO2,abs after 30 and 90 min. Nevertheless, such results must be considered with precaution because as the CO2 loadings of all the solvents were very significant at the end of the tests, it is more difficult to differentiate the absorption performances of each solvent (at high αCO2, GCO2,abs is varying in a smaller range from a solvent to another one). Note that some additional continuous tests were also performed with preloaded solutions (preloading of the solution with pure CO2 in a saturation cell before carrying out the continuous absorption tests). The details of these results will be presented in a forthcoming report.

2.2 Simulation of a CO2 purification unit applied to flue gases coming from

oxycombustion cement industries

Oxyfuel technology consists on realizing the combustion with pure oxygen instead of air. For this purpose the nitrogen is removed in an air separation unit (ASU, such as Cryogenic air separation, adsorption technologies, membrane systems) and the oxygen is supplied to the kiln. Consequently the concentration of carbon dioxide in flue gas is increased significantly. The gas properties are different from those in conventional kiln operation with a corresponding impact on the clinker burning process. The advantages of this include a lower flue gas volume because no nitrogen is present, and a high degree of combustion efficiency thanks to the high temperature. In addition, the CO2 generated by the oxyfuel process is relatively pure and can be more easily separated from the steam and finally sent to re-use.


A CO2 Purification Unit (CPU) deriving from the Schwarze Pump oxy-fuel power plant (Air Product’s Process) [White and al., 2013] has been simulated using Aspen Plus [Meunier and al., 2014]. This process is divided in three different steps, mainly a Sour-Compression Unit which removes SOx and NOx components, a Dehydration Unit which removes water from the purified gas and a Cryogenic Unit to remove the last impurities by condensing the CO2 to a point close to its triple point.

2.2.1 Sour Compression Unit “SCU” (De-SOx & De-NOx) flowsheet

The Sour Compression Unit (flowsheet in Figure 15) is divided in 3 levels of pressure and 2 columns. The flue gas is then compressed to 15 bar in an isentropic two-stage compressor (COMP-1 and COMP-2), and enters the first absorber tower (DESOX) of the “Sour-Compression Unit” at the bottom and flowing counter currently with aqueous solution. A splitter is used to recycle a part of the liquid flow (REC-1) to the top of the absorber and a water make-up is also provided (WATER-1). The washed gas then leaves the column at the top and is compressed to 30 bar (COMP-3) before entering the second absorber tower (DENOX) at the bottom and also flowing counter currently with aqueous solution. Another splitter is used to recycle a part of the liquid flow (REC-2) to the top of the second absorber and a water make-up (WATER-2) is also provided. This second absorber column has the same geometry (in terms of diameter, height and random packing) than the first one. The washed gas then leaves the column by the top and flows through the dehydration unit. The pressure levels together with the excess O2 content (3%) promote the oxidation of NO into NO2. The gas enters the first column with a flow rate of 120 Nm³/h (White at al., 2013) and it is absorbed into the liquid flowing with at 0.62 m³/h (ratio L/G of 0.082) which if we consider a column height of 12 m corresponds to a diameter of 0.15 m and a gas velocity of 0.12 m/s (considering 70% of flooding condition for the calculations). To promote maximum surface exchange in conditions of high pressure levels IMPT 25 random packing is used.

Figure 15: Detailed flow sheet of the Sour-Compression Unit


The thermodynamic model chosen is Elec-NRTL, as we have the formation of electrolytes during the absorptions of the gaseous components. Elec-NRTL model used in Aspen Plus provides a comprehensive electrolyte thermodynamic framework to model thermos-physical properties of all kinds of electrolyte systems.

2.2.2 Application of the SCU to flue gases coming from oxycombustion power plants

and oxycombustion cement industries

As seen in the Table 2, two cases were considered for the study of the Sour Compression Unit performances. The first one considers compositions of the flue gas of an oxyfuel power plant so inlets come from ranges taken from Air Product’s pilot test of the CO2 processing unit. The second one takes as inlet the compositions given by ECRA’s simulations for the inlet of a CO2 Processing Unit in a cement industry. In both cases pure oxygen has been used for the combustion process in the kiln, for the cement plant various cases of an oxyfuel combustion in the kiln have been simulated by ECRA trying different air intrusions in the kiln, to evaluate the combustion outcoming gases, leading to a composition presented in Table 2 which corresponds to 6 % of air intrusion in the kiln during the combustion. A first study consisted on the simulation of the oxyfuel pilot plant using the compositions concluded from Air Product’s Vattenfall Schwarze Pump pilot plant. The results showed that this purification system could be used to remove efficiently SOx (up to 100%) and NOx (up to 90-99%) from the feed CO2 stream. This leads to the next step of the work which is the comparison of performances between oxyfuel power plant and cement plant cases: For the power plant case it can be observed from Table 2 that 100% of the SOx and almost 95.2% (371 ppm down to 18 ppm) of the NOx present in the initial flue gas are removed in the first column, and the NOx concentration is further reduced in the second column (from 18 ppm to 2 ppm NOx) leading to a 99.5% global NOx removal over the sour compression unit. In fact, the first compression unit (working at 15 bar) removes all the SO2 and the bulk of NO to produce a solution of acids and ions such as HSO4

- and SO42-, the second one (at 30 bar)

removes the excess NO2 to produce a solution of HNO2/HNO3. The global abatement rate considers the NOx and SOx removal rates throughout the overall process Concerning the cement plant case, it can be observed from Table 2 that 100% of the SOx and almost 97.1% (957 ppm down to 28 ppm) of the NOx present in the initial flue gas are removed in the first column and that the NOx concentration is further reduced in the second column (from 28 ppm to 3 ppm NOx) leading to a 99.7% global NOx removal over the sour compression unit. The same conclusion can thus be drawn about the removal of the SO2 and the bulk of NO in the first absorption column, and the removal of excess NO2 in the second one.

A conclusion is that this process could be applied to cement industries with significant performances.


Table 2: Results of the application of the SCU to flue gases coming from oxycombustion

power plants and oxycombustion cement industries

Flue gas

composition (% mol)

Power plant Inlet gas*

De-SOx outlet

De-NOx outlet

Abatte-

ment rate

(%)

Cement plant

inlet gas **

De-SOx outlet

De-NOx outlet

Abatte-

ment rate (%)

CO2 72 76,05 76,07 - 83,13 83,82 83,89 - NO (ppm) 320 Trace*** Trace 100 861 Trace trace 100 NO2 (ppm) 51 18 2 96 96 28 3 97 SO2 (ppm) 700 trace trace 100 156 trace trace 100

N2 14 14,87 14,95 - 11,11 11,25 11,32 - O2 5,9 6,2 6,24 - 3,27 3,21 3,23 -

H2O 5,6 0,34 0,19 - 1 0,35 0,19 - Ar 2,39 2,54 2,56 - 1,34 1,36 1,37 -

CO (ppm) - - - - 397 trace trace -

Total gas mole flow

(mol/h)

4748 (120

Nm³/h)

4471 4444 4764 4703 2674

Notes: * [White et al., 2013] - ** ECRA simulations on oxyfuel cement kilns (Courtesy of ECRA) -

*** Trace: message given by Aspen Plus when the component concentration is extremely low

Nevertheless, according to Figure 16 the conditions of high pressure levels require an important energy demand. Thus, for the cement industry case, an optimization of the SCU is necessary considering the financial, energetical and environmental aspects through the variation of operating parameters (such as the recirculation rate and the operational pressures) and design parameters (such as the height of the columns). Moreover, the de-SOx and de-NOx performances of such a system will be studied for different NOx and SOx inlet concentrations according to the oxy-fuelled kiln emissions cases.

Figure 16: Energy requirements for the SCU


2.2.3 Parametric study for the Sour compression Unit

During the study of the pressure influence we noticed that for the De-SOx column, if we take

an operational pressure of 1 bar and also a column height of 1 m we still have 100 % of SOx

removal. To identify which reaction may have an influence in the absorption performances we

studied the chemical mechanism shown in Table 3 used up to now, knowing that our

simulations have been achieved without considering the interactions between NOx species

and SOx species.

After various intermediate simulations by varying the chemical mechanism in Aspen Plus we concluded that the reaction number 13 (oxidation of SO2 by oxygen) has an influence on the SOx abatement rate (for the first column). In fact, the SOx abatement rate decreases from 100 % to 20 % if we do not consider this equilibrium reaction. In fact, this reaction should be considered as a kinetic reaction but the lack of kinetic parameters in the literature leads us to consider it as an equilibrium reaction. We should also note that it requires temperatures well above 500°C to be significant, thus it has no influence if we are working at 30°C like in the case of the SCU. Other reactions models are under study. There are globally two teams working on Nitrogen and Sulfur absorption with water: [Ajdari and al., 2015] and [Torrente Murciano and al., 2011]. These literature sources indicate that SOx/NOx interactions influence is essential into the absorption chemical mechanism. So a chemical mechanism based on these models will be identified, studied and implemented in Aspen Plus for the more reliable modelling of the SCU. These interactions between SOx and NOx components and the complex chemistry of the liquid phase are critical for the rate of absorption of NOx and SOx from the gas to the liquid phase. Also, according to literature data, the pH level has a heavy influence on these performances. Therefore an identification of the liquid phase interactions that will be integrated

into the chemical mechanism depending on the pH of the system is in progress.


N°Re

actio

nTy

pePh

ase

ko(S

I)Ea

(kJ/

kmol

)Kc

in (2

98 K

, SI)

Units

of K

cinPa

rtial

ord

ers

A(SI

)B(

SI)

Keq(

298,

Mol

ar b

asis)

Ci b

asis

Refe

renc

e

12

NO +

O2

→2

NO2

Kine

ticGa

s1,

83E-

11-1

2281

2,59

E-09

Pa-²,

S-1

[NO]

2 [O

2]1

NANA

NApa

rtial

pre

ssur

e1

22

NO2↔

N2O4

Equi

libriu

mGa

sNA

NANA

NANA

-3,2

8E+0

16,

89E+

036,

26E-

05pa

rtial

pre

ssur

e2

3NO

+ N

O2 +

H2O

↔2H

NO2

Equi

libriu

mGa

sNA

NANA

NANA

-27,

026

4723

1,41

E-05

parti

al p

ress

ure

2, 3

4NO

2+NO

↔N2

O3Eq

uilib

rium

Gas

NANA

NANA

NA-2

8,07

647

405,

18E-

06pa

rtial

pre

ssur

e3

5N2

O3+H

2O→

2 H

NO2

Kine

ticLiq

uid

3,79

E+10

3,72

E+04

1,16

E+04

m³/

mol

.s[N

2O3]

2 [H

2O]0

NANA

NAm

olar

ity4

6N2

O4 +

H2O

→ H

NO3

+ HN

O2Ki

netic

Liqui

d2.

52E1

14,

85E+

0480

5m

³/m

ol.s

[N2O

4]2

[H2O

]0NA

NANA

mol

arity

5

72N

O2+H

2O→

HNO

3 +

HNO2

Kine

ticLiq

uid

8,10

E+09

1356

1,6

3,41

E+07

m³/

mol

.s[N

O2]2

[H2O

]0NA

NANA

mol

arity

6

8NO

+NO2

+H2O

→2H

NO2

Kine

ticLiq

uid

1,67

E+08

01,

67E+

08m

³/m

ol.s

[NO]

1 [N

O2]1

[H2O

]0NA

NANA

mol

arity

7

92H

NO2→

NO+N

O2+H

2OKi

netic

Liqui

d2,

86E+

010

2,86

E+01

m³/

mol

.s[H

NO2]

2NA

NANA

mol

arity

7

103H

NO2→

H2O+

2NO+

HNO3

Kine

ticLiq

uid

1,00

E-02

01,

00E-

02S-

1[H

NO2]

1NA

NANA

mol

arity

8

11HN

O2+H

2O↔

NO-

+ H3

O+Eq

uilib

rium

Liqui

dNA

NANA

NANA

_5,

13E+

04m

olar

ity*

12HN

O3+H

2O↔

NO3

-+ H

3O+

Equi

libriu

mLiq

uid

NANA

NANA

NA_

1,10

E+08

mol

arity

*

13SO

2 +

0,5

O2 ↔

SO3

Equi

libriu

mGa

sNA

NANA

NANA

__

mol

arity

*

14SO

2 +

2 H2

O↔ H

3O+

+ HS

O3-

Equi

libriu

mLiq

uid

NANA

NANA

NA_

0,01

3m

olar

ity*

15HS

O3- +

H2O

↔H3

O+ +

SO32

-Eq

uilib

rium

Liqui

dNA

NANA

NANA

_5,

06E-

08m

olar

ity*

16SO

3 +

2 H2

O ↔

H3O

+ +

HSO4

-Eq

uilib

rium

Liqui

dNA

NANA

NANA

__

mol

arity

*

17HS

O4- +

H2O

↔ H

3O+

+ SO

42-

Equi

libriu

mLiq

uid

NANA

NANA

NA_

1,20

E-02

mol

arity

*

18H2

SO4

+ H2

O ↔

H3O

+ +

HSO4

-Eq

uilib

rium

Liqui

dNA

NANA

NANA

_∞

mol

arity

*

19CO

2 +

2 H2

O ↔

HCO

3- +

H3O

+ Eq

uilib

rium

Liqui

dNA

NANA

NANA

_4,

37E-

07m

olar

ity*

20HC

O3- +

H2O

↔ H

3O+

+ CO

32-

Equi

libriu

mLiq

uid

NANA

NANA

NA_

_m

olar

ity*

21CO

+ 0

,5 O

2 ↔

CO2

Equi

libriu

mLiq

uid

NANA

NANA

NA_

4,64

E-11

mol

arity

*

N o x S o x C O 2

Table 3: First reaction mechanism of the SCU

Legend:

[1]: Azpitarte and al., 1971;

[2]: Holma and al., 1979;

[3]: Hoftyzer and al., 1972;

[4]: England and al., 1975;

[5]: England and al., 1974;

[6]: Cheung and al., 2000;

[7]: Park and al., 1988;

[8]: Carta and al., 1983.


3. ADVANCES IN THE PHD THESIS OF NICOLAS MEUNIER

This chapter will present three parts: - The modelling of the dehydration unit and of the cryogenic unit as complementary parts

of the Sour Compression process in the CPU;

- The comprehensive simulation of the CO2 to methanol conversion reactor, with a first

design of the experimental device.

3.1 Dehydration Unit

The dehydration unit is composed by a Temperature Swing Absorption (TSA) dual-bed and water is absorbed at high pressure (30 bar) onto a solid adsorbent which can be silica gel, activated alumina or molecular sieve alumina. Typically, regenerative desiccant dryers supply a dew point of -40°C to -70°C if required [Beery and Ladisch, 2001]. At these temperatures, the vapour pressures of ice are respectively 12.84 Pa and 0.261 Pa which leads to a very low water concentration range of 4.28 – 0.087 ppm in the gas phase. In order to simulate the dehydration step of the gas coming from the DeSOx/DeNOx unit, two different adsorbents have been considered in this study: Zeolite 13X (known to have excellent adsorption properties towards water) and Silica Gel (known to have good water adsorption uptake and lower energy demand for regeneration).However, as the dehydration of CO2 stream is uncommon in the scientific literature, the problem had to be divided in a “step by step ” way to validate as parameters as possible, especially regarding diffusive phenomena (e.g. mass transfer coefficients).

3.1.1 Description of the dehydration unit

To compare the performances of both the adsorbents, the geometry of the adsorption column was fixed and approached to a 30 cm length with an inner bed diameter of 3.3cm [Ahn and Lee, 2003]. The characteristics of the Zeolite 13X and the Silica Gel adsorbents considered are also summarized in Table 4.

Table 4: Characteristics of the adsorbents [Ahn and Lee, 2003]

Zeolite 13X Silica Gel

Bed void fraction 0.37 0.26

Bed density (kg/m³) 690 820

Mass Transfer Coefficient (MTC) (s-1) H2O 7.5x10-4 4.5x10-4

CO2 1.61x10-4 1.61x10-4(*) (*) this value is estimated Currently, the dehydration unit consists of only a single adsorption column to fully design it and evaluate/optimize its performances according to the injected feed gases. In a very close future, the Temperature Swing Adsorption (TSA) configuration (2 columns) will be investigated to quantify the thermal needs during the adsorption-regeneration cycles.


3.1.2 Simulation of the dehydration unit

Simulations of the dehydration unit were also performed on Aspen Adsorption v8.4 and the RK-ASPEN (Redlich-Kwong) thermodynamic package was selected for thermodynamic properties calculations. Thermodynamic parameters for the modelling of the adsorption isotherms of water and CO2 were obtained from the experimental isotherms [Wang and LeVan, 2009]. Furthermore, as the adsorption capacity of water and CO2 in Zeolite 13X and Silica Gel are incomparably greater than that of nitrogen and oxygen, the contribution of N2 and O2 (present in the gas exiting the sour compression unit) to the total adsorption dynamics have been neglected. The feed gas considered in these simulations has thus the following properties (Table 5):

Table 5: Properties of the feed gas entering the dehydration unit

Composition (%mol) CO2 0.9872

H2O 0.0128

Temperature (°C) 25

Pressure (bar) 1

Flow rate (NL/min) 9

Where the gas flow rate of 9 NL/min was chosen to allow the comparison between our simulated results and the experimental results obtained by Ahn and Lee [Ahn and Lee, 2003]. With these considerations, first results of simulations (Table 6) presented the differences between the Zeolite 13X and the Silica Gel in terms of breakthrough times and adsorption capacities.

Table 6: Comparison of adsorbents performances

Zeolite 13X Silica Gel

CO2 H2O CO2 H2O

Maximal adsorption capacity (mol/kg ads.)

4.591 13.417 1.031 12.33

Breakthrough Time - 7h10 - 5h30

Although these results still have to be validated by literature sources and/or experimental data, they confirm our first impression about the choice of the accurate adsorbent for this dehydration application. Indeed, Silica Gel adsorbents seem to be more adequate for this application as they adsorb less CO2 (but a similar amount of water) and require less thermal energy for their regeneration. Next steps for the simulation of the dehydration unit will include literature validation of our simulations (if possible) and the design (geometry and adsorbent) of a suitable adsorption column to treat the gas coming from the sour compression unit. Finally, dynamic and energy considerations will be then investigated through the TSA configuration.


3.2 Cryogenic Unit

The cryogenic unit is a separation step using either a distillation column or a double flash unit, to remove the residual inert gases. Pipitone et al. [Pipitone and Bolland, 2009] described this methodology for both cases and presented the differences between the use of a distillation column or a double flash unit in the last inert separation step. Posch et al. [Posch and Haider, 2012] also optimized both these configurations (distillation column versus double flash unit) and showed the impact of main design parameters on performance features such as specific power requirement, specific cooling duty, separation efficiency, and CO2 purity. In this report, a double flash unit was chosen to simulate the performances of the cryogenic unit.

3.2.1 Description of the cryogenic unit

The gas coming from the dehydration unit is cooled (COOLER-1) and flashed in a first flash (FLASH-1) at 30 bar. The vapour stream is then cooled (COOLER-2) and flashed anew in a second flash (FLASH-2) with a lowest temperature of -55°C to avoid the formation of dry ice (solid CO2) at this pressure. The vapour stream from the second flash enters then a turbine (VENT) which lowers its pressure to 1 atm and electrical energy is recovered from. Liquid streams from both flashes are finally mixed (MIX) and compressed (COMPR) to 110 bar for transport or storage. A detailed flow sheet of the unit is presented in Figure 17.

Figure 17: Detailed flow sheet of the cryogenic unit Temperatures for both flash units are operating parameters which have to be optimized regarding the CO2 molar purity required for further reuse and/or CO2 recovery of the installation.

3.2.2 Simulation of the cryogenic unit

Simulations of the cryogenic unit were also performed on Aspen Plus v8.4 and only thermodynamic equilibria are considered in this unit. The desulphurized and denitrified gas enters the cryogenic unit and has the normalized composition of the DeNOx outlet stream where water is removed after the dehydration unit.


The NO2 remaining from the sour compression unit (3 ppm) is also neglected as it will be captured during the adsorption process (dehydration unit). In the worst case, 3 ppm NO2 is far below the security limit of most CO2 conversion catalysts which are mainly based on CuO/ZnO/Al2O3 compounds [Rep et al., 2009]. The resulting inlet gas composition and flow rate which will be considered as the inlet of the cryogenic unit are presented in Table 7.

Table 7: Cryogenic inlet gas composition and flow rate

Gas composition (%mol)

CO2 N2 O2 Ar

84.05 11.34 3.24 1.37

Total Flow Rate (mol/h) 4551

Main parameters of this unit are the temperatures of both flash units. With the composition stated in Table 7, the dew point of the gas is about -18°C. As a consequence, the temperature of the first flash (T1) should be lower than -18°C to liquefy CO2 from the mixture. Moreover, the temperature of the second flash (T2) should always be higher than -55°C to avoid solid CO2 formation which can degrade the installation. Considering the temperature range of the flash units, two parametric studies were conducted to quantify the influence of these temperatures on the CO2 molar purity of the final product stream and on the CO2 recovery of the unit. The results of these parametric studies are presented in Table 8 and in Table 9.

Table 8: Parametric study: Temperatures influence on CO2 molar purity (%) of the product stream

T1 | T2 (°C) - 25 - 30 - 35 - 40 - 45 - 50 - 55

- 20 - 25 - 30 - 35 - 40 - 45 - 50

98.4

98.2 97.9

98.0 97.8 97.3

97.8 97.7 97.3 96.7

97.6 97.5 97.2 96.7 96.1

97.3 97.3 97.1 96.6 96.1 95.5

97.1 97.2 96.9 96.5 96.0 95.4 94.8

Table 9: Parametric study: Temperatures influence on the CO2 recovery of the unit

T1 | T2 (°C) - 25 - 30 - 35 - 40 - 45 - 50 - 55

- 20 - 25 - 30 - 35 - 40 - 45 - 50

78.5

84.9 85.2

89.1 89.2 89.5

91.9 92.0 92.2 92.4

94.0 94.0 94.1 94.3 94.5

95.5 95.5 95.5 95.7 95.8 96.0

96.6 96.6 96.6 96.7 96.8 97.0 97.1


These results highlighted the antagonist effects of the temperatures on the CO2 molar purity of the final product and on the global recovery: lower temperatures in the flash units cause an improvement of the recovery (up to 97.1%) but a decrease of CO2 molar purity of the final product (from 98.4% to 94.8%), where higher temperatures give a very good CO2 molar purity (up to 98.4%) of the final stream but a lower recovery (78.5%). To estimate the electrical and thermal energy requirements of the cryogenic unit, two different “operating points” were considered. In the first case (Case I), considering the CO2 molar purity of the product stream as the parameter to maximize, the temperatures of both flashes are -20°C and -25°C respectively and will lead to a 98.4% CO2 molar purity and a 78.5% CO2 recovery of the unit. In the second case (Case II), considering the CO2 recovery as the parameter to maximize, the temperatures of both flashes are -50°C and -55°C respectively and will lead to a 94.8% CO2 molar purity and a 97.1% CO2 recovery of the unit. The energy requirements of both cases were calculated and are presented in Table 10.

Table 10: Energy requirements of the cryogenic unit for Case I and II

Cas

e I

Power type Operation Power/Heat flow(kW) %

Thermal 1st cooler (-20°C) 2nd cooler (-25°C)

- 11.57 - 1.68

87 13

Electrical 110 bar pump 1 bar turbine

1.00 - 1.38

Cas

e II

Thermal 1st cooler (-50°C) 2nd cooler (-55°C)

- 19.25 - 0.18

99 1

Electrical 110 bar pump 1 bar turbine

1.16 - 0.50

It can be observed that Case II has a higher energy demand in terms of both electrical and thermal needs. This observation can be explained by the fact that, in Case II, the liquid flow rate at the outlet of the cryogenic unit is higher due to the low temperatures of the flashes leading to a major increase of the thermal energy needs of the unit (+41% in comparison to Case I), and to an increase of electrical energy requirements for pumps.

In conclusion, the temperatures of both flashes will depend on the targeted objective based on:

The required CO2 purity of the final product which depends on the following applications requirements. The range of CO2 molar purity reachable with the considered cryogenic unit is 94.8 – 98.4%. This range of purity is in agreement with CO2 purity of stream products coming from post-combustion CO2 capture which are typically ranged between 95 – 98% [Kundu et al., 2014].

The required CO2 recovery which depends on industry politics and/or country’s laws. The range of CO2 recovery of the cryogenic unit is 78.5 – 97.1% and would lead to a global CO2 recovery range of the overall process of 75.8 – 93.8%. Once again, this recovery range is in agreement with those of post-combustion CO2 capture plants which are typically between 85 – 90% [Kundu et al., 2014].

However, according to the precise objective, additional economic aspects (e.g. energy integration among the units, cooling mediums to use, etc.) will have to be considered.


3.3 CO2 conversion into methanol

In the previous ECRA CHAIR Report [ECRA CHAIR Report, 2014], a process converting CO2 into methanol was presented based on the American patent (US 5.631.302) with two catalytic reactors using a copper-containing catalyst.

3.3.1 Adaptation of the American Patent

The CO2 conversion process described in the American patent has been implemented in Aspen Plus v8.4 using the RK-ASPEN (Redlich-Kwong) package for thermodynamic properties calculations. In this process, the inlet synthesis gas is compressed (COMPR-1) and preheated (EX-1) before entering the first reactor (REA-1) at the temperature and pressure of 250°C and 80 bar respectively. The reactor is adiabatic and consists of 500 tubes of 0.264 m length and 0.03675 m diameter filled with 200 kg of a commercial copper-containing catalyst for methanol conversion. There is no recirculation in the first reactor. The outlet of the reactor is cooled to preheat the inlet synthesis gas (entrance of first reactor) in the heat exchanger (EX-1) and then fed to the second reactor (REA-2) which consists of 500 tubes of 1.075 m length and 0.03675 m diameter filled with 800 kg of the same catalyst. This second reactor is isotherm and the temperature is maintained at 260°C by circulating pressurized boiling water. The outlet of the second reactor is then cooled to preheat the inlet of the second reactor in a heat exchanger (EX-2) and further cooled (COOL-1) at the temperature of 40°C before being flashed (FLASH-1) to separate the rich-methanol mixture (PRODUCT) from other gaseous compounds which are recompressed (COMPR-2) and recirculated to the second reactor after being preheated through the heat exchanger (EX-2). It should be mentioned that the distillation step (to extract methanol from the moisture exiting the flash FLASH-1) is not implemented yet but will be considered in the future. A detailed flow sheet of the conversion process is provided in Figure 18.


Figure 18: Methanol conversion flowsheet

3.3.2 Simulation of the CO2 conversion unit

The CO2 conversion unit was simulated considering the conversion of a synthesis gas whose composition (from the American patent) is presented in Table 11 and a flow rate of 1540 Nm³/h (68.54 kmol/h). Reactors (multitubular) have volumes of respectively 0.14 m3 (200 kg catalyst) and 0.57 m3 (800 kg catalyst).

Table 11: Gaseous composition and flow rate of the inlet of the CO2 conversion unit


H2 73.9 CO2 23.9 CH4 1.2 N2 0.7 CO 0.3

Flow rate (kmol/h) 68.54

With this composition for the inlet synthesis gas (Case I), the resulting compositions, temperatures and flow rates of gases from both reactors and final mixture are presented in Table 12.


Table 12: Results from Aspen Plus simulations: Case I


Reactor 1 outlet

Reactor 2 inlet

Reactor 2 outlet

Product mixture (wt%)

H2 64.3 65.9 61.3 - CO2 18.5 5.6 3.4 2.0 CH3OH 4.1 0.2 3.3 62.9 CO 3.6 1.6 1.2

- CH4 1.3 16.6 17.6 N2 0.8 10.1 10.7 H2O 7.4 0.1 2.6 35.1

Temperature (°C) 286.3 240.0 260.0 40.0

Flow rate (kmol/h) 63.3 245.9 222.0 29.9

These results from the simulations on Aspen Plus were compared with those from the American patent summarized in Table 13.

Table 13: Results from the American patent


Reactor 1 outlet

Reactor 2 inlet

Reactor 2 outlet


H2 64.5 69.1 62.0 CO2 18.5 14.0 11.3 CH3OH 4.0 0.3 5.2 63.9 CO 3.6 3.0 2.5

CH4 1.3 8.4 9.3 N2 0.8 5.1 5.6 H2O 7.3 0.1 4.1

Temperature (°C) 286.0 240.0 260.0

It can be observed that the temperatures (Reactor 1 outlet and Reactor 2 inlet) coming from the Aspen Plus simulations are in excellent agreement with the American patent together with the purity of the final mixture which reaches 62.9 wt% methanol in the simulations and 63.9 wt% in the patent. However, there was a much higher concentrations of inert gases at the entrance of the second reactor in the simulated case in comparison to the American patent. This observation led to the insertion of a purge (SPLIT-1) added after the compressor (COMPR-2) to release excess inert gases. A sensitivity result was thus conducted to investigate the influence of the purge split ratio

(OUT

S15( see flowrate in Figure 18)) on the inert gases concentrations (CH4 and N2) at the inlet

of the second reactor. The result of this sensitivity analysis is presented in Figure 19.


Figure 19: Influence of the purge split ratio on the inert gases concentrations at the inlet of

the second reactor

It can be noticed that a split ratio of 3.7% is required to match the CH4 (NCH4) and N2 (NN2) concentrations at the inlet of the second reactor stated in the American patent. This value of purge split ratio was thus set in the Aspen Plus simulation flow sheet and new results were obtained with this change (Case II). These new results are presented in Table 14.

Table 14: Results from Aspen Plus simulations: Case II


Reactor 1 outlet

Reactor 2 inlet

Reactor 2 outlet


H2 64.3 72.5 65.1 - CO2 18.5 11.3 8.0 4.1 CH3OH 4.1 0.2 5.6 61.3 CO 3.6 2.4 1.7

- CH4 1.3 8.4 9.4 N2 0.8 5.1 5.6 H2O 7.4 0.1 4.5 34.6

Temperature (°C) 286.3 240.0 260.0 40.0

Flow rate (kmol/h) 63.3 245.9 222.0 29.9

With this change, results from the American patent (Table 13) and from the simulated process (Table 14) are in very good agreement in terms of compositions and temperature. However, it can also be noticed that the increase of the purge split ratio led to a slight decrease of the final mixture purity in methanol (WCH3OH) (from 62.9 to 61.3%). To compensate this loss and to improve the overall process, the influence of the flash (FLASH-1) temperature on the final mixture purity (WCH3OH) has been investigated and the results of this sensitivity analysis are presented in Figure 20.


Figure 20: Analysis of the influence of the FLASH-1 temperature on the final mixture purity

The results of this analysis showed that the maximal methanol purity reachable in the final mixture is 61.7 wt% for a flash temperature of 63°C but also leads to a decrease of the productivity (QCH3OH from 464.5 kg CH3OH/h to 461 kg CH3OH/h (-0.8%)). On the other hand, it can be noticed that the maximal methanol productivity (465.5 kg CH3OH/h) is reached at a flash temperature of 25°C with a slight decrease of the mixture methanol purity (61.2 wt%). In conclusion, the influence of the flash (FLASH-1) temperature on the process is quite trivial due to the additional distillation step that has to be implemented to produce a pure methanol flow from the outlet mixture of the flash whose methanol purity is about 61.5 wt%. Finally, the GHSV (Gas Hourly Space Velocity = Volumic flow rate at the inlet of the reactor in standard conditions divided by the volume of the reactor) were also calculated for both reactors (11 100 h-1 for the first reactor, and 10 100 h-1 for the second) which can be directly compared with those from the work of Fournel and Wagner [Fournel and Wagner, 2013] who presented an optimal GHSV of 10 000 h-1 for both reactors. The results from the simulated conversion unit are thus in excellent agreement with the literature.

3.3.3 Design of the experimental reactor

With these encouraging results, the design of the experimental installation has been initiated to validate these simulations with experimental data and to quantify the influence of gaseous impurities such as SOx and NOx on the catalyst performances and aging. The catalyst considered here is a commercial copper-based catalyst designed for methanol conversion. This experimental micro-pilot reactor, working under drastic conditions (80 bar and 250°C) will be sealed in an isolated oven to provide high temperatures. High pressures in the reactor will be ensured by the pressurized inlet gases (CO2, H2, SOx, and NOx) and inert gas boosters. A back pressure controller will also be set to keep the pressure constant over the experiments. Finally, several measurement devices (thermocouples, Gas Analysis Device (GC, etc.)) will be set to allow the in- and out-line characterization of samples throughout the experiments.


A schematic design of this experimental micro-pilot reactor is presented in Figure 21.

Figure 21: Schematic design of the experimental micro-pilot reactor

Regarding the design of the catalytic reactor itself, simulations and sizing are still under investigation to determine the more suitable reactor for our micro-pilot experiments. However, to a first approximation, it appears that the size of the reactor should be around 1-2 inch wide and 10-15cm length to reach a Gas Hourly Space Velocity of 10 000 h-1. Next steps for the study of the CO2 conversion into methanol will be to complete the design of the experimental micro-pilot reactor and to realize the installation in order to begin the experimental part of this topic!


4. POST-DOCTORAL WORKS IN THE FRAMEWORK OF THE COLLABORATION

WITH HEIDELBERGCEMENT

4.1 Use of membranes in cement industry for carbon capture installations

4.1.1 Introduction

The information presented in the previous annual report gave a summary of the main information related to the study of membranes processes for the CO2 capture applied to cement flues gases. The main aspects considered were: a presentation/comparison of the two CO2 capture membranes processes (gas/gas and gas/liquid technologies), an identification of the key parameters of such processes, a cost estimation of the gas/gas membrane CO2 capture technique, a calculation of intensification factors in comparison with classical amine technology, the effect of gaseous impurities (SOx, NOx, etc.) on gas/gas membranes performances and the properties and potential of hybrid capture system (gas/gas membranes + classical amine plant) for the CO2 capture in cement industry. This first study was focused on the more conventional gas permeation membranes (polymeric ones especially). Following the exchanges with HeidelbergCement, in addition to the continuation of the technological monitoring on hybrid CO2 capture systems, a bibliographic review was carried out in order to give a summary of the major aspects related to the Facilitated Transport Membranes.

4.1.2 Literature review on Facilitated Transport Membranes (FTM) for CO2 capture

As described in [IEA, 2009], the “Facilitated Transport Membranes” (FTM) are based on the formation of complexes or reversible chemical reactions of components present in a gas stream with compounds in the membrane, called carriers. These complexes or reaction products with the carriers are then transported through the membrane. The principles of FTM are illustrated on Figure 22.

Figure 22: Illustration of facilitated transport membrane principles [IEA, 2009]

As highlighted by several authors, such as for example by [Kovvali and Sirkar, 2000], one of the major advantages of FTM over conventional polymeric membranes is the higher permeabilities for reaction species such as CO2 and the resultant high selectivities towards non-reacting species such as N2. According to International Energy Agency report [IEA, 2009], on the contrary to conventional membrane technology, the use of Facilitated Transport Membranes technology is advantageous especially for the removal of CO2 from flue gases with


low concentrations in CO2, but new FTM, using specific carriers, would allow to use this technology for flue gases with higher CO2 content. Note that FTM include also “Immobilised Liquid Membranes” (ILM). In that case, the carrier is present in a solvent (usually water) and is immobilized in the pores of the membranes. The solvent is physically trapped in the membrane but not chemically bonded. The authors of IEA report [IEA, 2009] pointed out that this lack of chemical bonding limits the stability of the solvent and that could lead to solvent evaporation during the operation. Several other technologies are presented in literature, such as the “Bulk Flow Liquid Membrane” (BFLM) described in [Teramoto et al., 2003a-b]. This system is a FTM which uses a capillary membrane module with permeation of an amine carrier solution. According to [Teramoto et al., 2003a-b], with such technology, the CO2 in the feed gas can be concentrated from 5-15% to more than 98%, and the selectivity of CO2 over N2 can be in the range from 430 to 1790. This system is illustrated on Figure 23.

Figure 23: Illustration of BFLM system (from [Okabe et al., 2006])

During the tests carried out with such membranes by [Teramoto et al., 2003a-b], the stability of the membrane was highlighted as no deterioration was observed over a discontinuous testing period of one month. Note that the membrane support was polyethersulphone and amines were used as CO2 carriers. These carrier solutions were continuously supplied to the feed side (high-pressure side) of the microporous membrane where they reacted selectively with CO2. The carrier solution was then allowed to permeate to the receiving side (low-pressure side) where the CO2 is released and the liquid is returned to the feed side thanks to a pump. A more detailed literature overview on “FTM” technologies was carried out based on the studies evocated in the reports published by the International Energy Agency (IEA), and especially in [IEA, 2009]. It was shown that the literature on “Facilitated Transport Membranes” (FTM) offers a large variety of articles and studies, and on different scales (very small scale, lab scale, semi-pilot scale, etc.). One of the difficulty regarding this topic is the fact that “FTM” can be related to different systems, such as Immobilised Liquid Membranes (ILM) and Bulk Flow Liquid Membrane (BFLM) previously evocated, but also Contained Liquid Membrane permeator (CLM), Supported Liquid Membranes (SLM) and others. Therefore, it seems very difficult at this time to really evaluate the potential of such technology for the application to the cement industry. Each research teams/technology


provider/university lab highlight the advantage of their “FTM” technology and it seems that each system has some advantages and disadvantages. Considering that UMONS is not specialized in membrane technology, and even more not in FTM, giving to HeidelbergCement a precise and relevant overview on such system was difficult. For the next step of the works, in addition to the technological monitoring on hybrid process comprising a gas-gas membrane and an amine plant (see next section), no more specific researches will be carried out on FTM but UMONS will regularly check if new interesting “results” are published on this topic, especially on eventual “pilot scale results” in order to have interesting information related to the possible application to cement plant. A real “overview” of the all the FTM technologies would not be relevant at this time.

4.1.3 Technological monitoring on the potential of CO2 hybrid capture system

(gas/gas membranes + classical amine plant) in the cement industry

As presented in the previous annual report, hybrid (term used here for combined technologies) CO2 capture processes consisting of a membrane separation process combined with a conventional gas separation process (such amine plant) could offer a more cost effective solution for gas separation than using these technologies separately. Indeed, combining membranes with solvents has the potential to increase the advantages of each technology and reduce the disadvantages of each technology. Conventional membranes operate best at high partial pressures of CO2, while solvents operate best when treating low CO2 specifications. Therefore, using a hybrid system consisting of a membrane unit followed by a solvent unit seems a very interesting option to be investigated for the application of CO2 capture in the cement industry and it is necessary to carry out a regular technological monitoring on this topic. Two new relevant papers related to this hybrid technology were noticed thanks to the technological monitoring, namely: - Paper (1) of [Kundu et al., 2014] - and Paper (2) of [Esche et al., 2014]. (1) Globally the article of [Kundu et al., 2014] investigated the effectiveness of membrane processes and the feasibility of hybrid processes combining membrane permeation and conventional amine absorption processes for the post-combustion CO2 capture through simulations with Aspen Plus software. [Kundu et al., 2014] considered a cement plant composition: yCO2 = 24.1 mol.%, yN2 = 73.4 mol.% and yO2 = 2.5 mol.%. The feed stream was assumed to have been pre-treated before entering the membrane unit and free of minor components such as SOx, NOx, CO, Ar, H2O and ash. In the calculation, the gas was thus assumed to be free of water (gas composition on a dry basis). Note that as membrane replacement is a critical operating cost, pre-treatment of feed stream is necessary to extend the membrane life. The other key factors determining the cost of membranes processes are the membrane area and the power consumption for compression and/or vacuum.

The membrane considered for the calculation (specific module developed in Aspen Plus) made by [Kundu et al., 2014] is PolarisTM membrane developed by Membrane Technology and Research (MTR): permeances of 1000, 50 and 20 GPU (1 GPU = 1 Gas Permeation Unit = 3.35


10-10 mol/m² s Pa) for CO2, O2 and N2; CO2/N2 selectivity of 50; polytropic efficiency of compressors assumed to be 80% (power use in compressors and vacuum pumps considered as the primary energy required in the membrane process). These values are quite conventional for such membrane systems. The amine absorption process was modeled in Aspen Plus (targeted to capture 85% of the CO2 with a purity requirement of 98 mol.%), considering MEA and DEA as solvents.

Note that the hybrid membrane-absorption processes (Figure 24) was simulated separately and not directly combined in Aspen Plus: a first model simulates that a fraction of the CO2 is recovered from the membrane process (two-stage membrane process), and the retentate stream from the membrane unit was considered as fed to the amine process for further capture in order to achieve an overall recovery of 85%. The total energy required for the hybrid process was calculated as the sum of the power consumption in membrane unit and of the thermal energy used at the stripper reboiler of the amine unit.

Figure 24: Hybrid CO2 capture system applied to cement flue gases from [Kundu et al., 2014]

Note: as pointed out by [Kundu et al., 2014], for simplicity, the total energy use was evaluated by adding up two forms of energy (heat and power). Even if such a treatment is not uncommon when different forms of energy are used in a process, the total energy consumption should be converted into a primary energy equivalent, which will be a subject of further studies on hybrid configuration.

Table 15 gives the final comparison of the energy consumption in membrane processes, amine processes and their hybrid combinations provided in [Kundu et al., 2014] paper. It can be observed that the energy demand of the hybrid process applied to a cement plant is expected to be between the two processes components considered separately.

Table 15: Comparison of energy penalty of CO2 capture by membranes, amines and the hybrid processes from [Kundu et al., 2014]

CO2 capture technology Energy GJ/tCO2

Membrane processes, coal-fired power plant 1.49 – 2.17

Membrane processes, cement plant 1.67 – 1.71

MEA scrubbing, coal-fired power plant 3.50

MEA scrubbing, cement plant 3.55

Hybrid membrane amine processes, cement plant 1.83 – 3.70


More precisely, [Kundu et al., 2014] calculated an energy cost in the range 1.83 – 3.70 GJ/tCO2 for the hybrid process, while the membrane processes energy costs are estimated in the range 1.67 – 1.71 GJ/tCO2 and the MEA scrubbing system energy costs around the conventional value of 3.6 GJ/tCO2. It was highlighted that the total energy penalty of the hybrid process decreases as more CO2 is removed by the membranes. It is still essential to confirm the techno-economic advantage of the hybrid process for post-combustion CO2 capture applied to cement plants by carrying out more detailed economic evaluation of this process. (2) Concerning the paper of [Esche et al., 2014], it must be directly noticed that this paper is not focusing on the application of the process to cement flue gases but for the removal of CO2 from a natural gas conversion process into ethylene C2H4 (OCM = Oxidative Coupling of Methane). Indeed, CO2 is the main byproduct of the heterogeneous catalysis and an energy efficient design for its removal is essential to allow for the economic viability of the overall process concept. In a previous work, [Esche et al. 2014] investigated a simple hybrid process consisting of a PI membrane, a PEO membrane and an absorption-desorption process. This hybrid concept combined the advantage of the high CO2 selectivity of the absorption at lower pressures (< 15 bar) with the advantageous energy demand of the less selective membranes. The hybrid system shows a total energy demand of 2.64 MJ/kg CO2, with a C2H4 loss below 5%, which means a decrease of the energy demand and of the product loss of around 50%. In this context, the purpose of the new paper of [Esche et al., 2014] was to discuss the modeling and especially its assumptions made for it, and also to optimize the process. As the application considered in this article is not linked to the cement industry, giving all the details of the optimization work is not relevant. Nevertheless, some information are useful and representative of what could be an optimized configuration of such hybrid CO2 capture process. For example, [Esche et al., 2014] showed that an optimized configuration of the membrane part of the hybrid process could be a “superstructure” which comprises a maximum of six membranes and offers several options of combining the different membranes. The main structure of the hybrid system does not change with the addition of further membranes, the OCM product gas being first fed to the membrane network and the retentate outlet flow being sent to the absorption unit. The main parameters influencing the optimization of the process are: the choice of the membrane material and area, the recycle split factors, the (re)compression pressure levels, the choice of the solvent in the absorption-regeneration process, the heat duty of the solvent regeneration process and the solvent flow in the absorption process. Compared to the initial hybrid system comprising only single PI and PEO membranes and the absorption-desorption section, the optimized superstructure consisting of six PI membranes required an energy demand of roughly 2 MJ/kg CO2 at a 5% C2H4 loss, which means a reduction by 24% from the initial hybrid system. As a conclusion, it was confirmed that the hybrid CO2 capture systems have a real potential for the application to cement flue gases. More precisely, the interest of such process for the cement industry is partially linked to the flue gas composition of cement plants (CO2 content higher than in power plants flue gases. By combining the two technologies and optimizing the CO2 recovery by each process, it is possible to be more energy efficient than with each process separately. Based on these statements, even if the number of publications on this subject is very limited, it is important to continue the technological monitoring on hybrid CO2 capture technologies, especially on hybrid membrane-absorption systems even if following the publications on other hybrid systems will be also relevant.


4.2 Simulation of the post-combustion CO2 capture process applied to cement flue

gases

4.2.1 Introduction

As a reminder, the conventional post-combustion absorption-regeneration process is based on the use of two coupled columns. The first one called “absorber” creates an intimate contact between a solvent reacting with the CO2 of the gas to treat. After this step, the rich solvent is sent to a “stripper” where the temperature is increased up to the boiling point of the liquid in order to strip the CO2 out of the solvent. The lean solvent is then sent back to the absorber in order to follow the absorption-regeneration cycle. The principal challenge of this process is to reduce the operational costs, and especially the energy consumption for the solvent regeneration. In order to reduce this energy demand, new solvent technologies must be developed but another technique allowing a reduction of the operating costs is the optimization of the process linked to its configuration, such as highlighted for example in [Amrollahi et al., 2011], in [Le Moullec and Kanniche, 2011], and in [Neveux, 2013]. More precisely, [Le Moullec et al., 2013] illustrates that the process modifications can be divided into three categories: - “absorption enhancement” (promoting absorption thanks to temperature levels adjustments, not considered in the present study); - “heat integration” (promoting energy integration thanks to enhancement of the heat exchanges between the fluids, SSF configuration being simulated in this study); - and “heat pumps” (promoting heat recovery thanks to heat quality adjustments, LVC configuration being considered in the present work). [Neveux, 2013] also highlighted that as CAPEX represents only 43% of the total CO2 capture costs (48.5 €/tCO2) whose 50% is linked to the compression costs, even if alternative configurations lead to an increase of the CAPEX, the decrease of the OPEX is much more important and can allow a reduction from 8 to 13% of the total CO2 capture costs depending on the configuration considered (illustrated for SSF and LVC in [Neveux, 2013]).

The purpose of this study was therefore to simulate the CO2 capture with Aspen HysysTM software and to compare different configurations of the absorption-regeneration process in terms of energy consumption, especially the regeneration energy of the solvent. In this work, considering the benchmark monoethanolamine (MEA) 30% as solvent, we focused on three alternative configurations: the “Stripper Split Feed” (SSF), the “Lean Vapor Compressor” (LVC) and their combination.

One of the specific aspects of this work is also the fact that we considered the composition of flue gases issued from the cement industry, where the CO2 content (from 20 to 30 wt.%) is higher than the one from conventional power plants (from 5 to 15 wt.%, generally considered in other studies) and which leads to different results in terms of energy savings. Moreover, the results obtained with two packages, namely “Amine” and “Acid Gas” packages (including different: computation modes, solvent properties, thermodynamic models, etc.), were compared.


4.2.2 Simulation and results

In a first part, the results of our simulation model were validated through a comparison with the Aspen PlusTM results from [Hassan, 2005] considering the flue gas composition of the St Marys cement plant in Canada (CO2 content of 24 mol.% in the gas to treat) and the conventional configuration of the process (see the Aspen HysysTM flow sheet of the simulation base case on Figure 25 and the different model parameters in Table 16). In a second part, the results obtained with two Aspen HysysTM simulation packages were compared considering different process configurations. It must be noted that the CO2 capture efficiency of the absorption column is defined on a molar basis as the percentage of the inlet CO2 gas flow rate absorbed in this column, and that the mixer upstream of the absorption column is used to keep the MEA and water balance in the whole process.

Figure 25: Aspen HysysTM flow sheet of the conventional configuration

In order to validate our simulation model, the design and operating parameters defined by [Hassan, 2005] for Aspen PlusTM simulations (Table 16) were implemented in Aspen HysysTM v 8.0 considering the classical configuration of the process (Figure 25) and comparing the use of Amine and Acid Gas Packages.

Globally, it was shown that the regeneration energy (boiler duty) of the MEA 30% solvent calculated by our simulation model was equal to 3.7 GJ/tCO2 (with both packages) which is the same value obtained by [Hassan, 2005] on Aspen PlusTM and which is in the range of values (from 3.4 to 4 GJ/CO2) conventionally obtained for MEA 30%. Regarding the condenser cooling energy, it is quite higher using the Acid gas package (1.7 GJ/tCO2) than the Amine one (1.2 GJ/tCO2), those values being both higher than the value obtained by [Hassan, 2005] with Aspen PlusTM (1.04 GJ/tCO2) even if the order of magnitude is quite similar. The difference could probably be explained by the value of the heat of vaporization (different from a property package to another one). It could also be noticed that the differences between Aspen PlusTM and Aspen HysysTM (both package) in terms of liquid compositions (amine concentration and CO2 loading) are around 4%, which is totally acceptable.

The next step of our study was the simulation of the CO2 capture process considering different process configurations.


1°) The SSF (Stripper Split Feed) process modification belongs to the "heat integration". The aim is to reduce the exergy losses by improving heat exchanges between fluids, the exergy being defined as the useful energy which can be extracted from a heat stream or the part of the energy completely convertible into another form of energy by an ideal system. The principle of the SSF configuration (see flow sheet on Figure 26) is that a part (optimum at 30 vol.% in the present case) of the rich MEA after the absorber by-passes the internal heat exchanger in order to be directly injected at the top of the stripper.

Table 16: Design and operating parameters for the absorption-regeneration simulation in Aspen HysysTM (based on [Hassan, 2005])

Gas to treat ● Based on the composition of St Mary’s cement plant in Canada (presented in [Hassan, 2005], molar fractions): - N2: 69.71% - CO2: 23.75% - H2O: 4.16% - O2: 2.38% ● Gas flow rate: 1.713 105 m³/h

Solvent Monoethanolamine (MEA) 30 wt.%

Properties packages Amine package Acid Gas package Equilibrium modeling Rate based modeling Thermodynamic model for amine solution: Kent-Eisenberg e-NRTL

Absorber parameters ● Bubble cap tray column: - trays number: 8 - diameter: 6 m - tray space: 0.6096 m - tray volume: 17.24 m³ - weir height: 50.8 10-3 m ● Inlet liquid flow rate (lean solution): 1698 m³/h (L/G)vol. = 9.911 10-3 ● Gas and liquid inlet temperature (with the use of a cooler): 40°C ● Absorber pressure: 1.2 bar ● CO2 capture efficiency: 85%

Stripper parameters ● Bubble cap tray column: - trays number: 8 - diameter: 5.5 m, - tray space: 0.6096 m - tray volume: 14.48 m³ - weir height: 50.8 10-3 m ● Stripper pressure: 1.9 bar ● CO2 purity at the condenser outlet: 98 mol.%

Internal heat exchanger ● For the validation with Hassan 2005: rich solution preheating of 45°C ● For all the other simulations: pinch of 5°C (cold side)

Pumps ● Lean pump: from 1.9 to 2 bars ● Rich pump: from 1.2 to 2 bars For both pump: adiabatic efficiency of 75%

The principal advantages of such modification are that the “cold” MEA injected in the stripper reduces the cooling energy at the condenser (less than 1 GJ/tCO2 with both packages), and that a higher retention time in the heat exchanger (lower flow rate) leads to a higher temperature at the outlet of this exchanger and therefore to a gain in energy at the reboiler (from 4% to 7% in terms of energy savings, Figure 27).


Figure 26: Aspen HysysTM flow sheet of the Stripper Split Feed (SSF) configuration

2°) Considering the Lean Vapor Compression (LVC) configuration (see flow sheet on Figure 28), it is based on a “heat pump effect” and it couples a flash tank and a compressor after the stripper in order to re-inject in the column a hot gas flow containing water vapor (for the most part) and CO2.

Figure 27: Comparison of simulation results obtained with Amine and Acid gas packages in terms of regeneration energy savings for different process configurations

Although the compressor needs a supplementary electrical supply (pressure drop of 0.7 bar in the optimum case), the high temperature of the re-injected vapor allows a major reduction of the boiler energy consumption to 2.8 GJ/tCO2 (with the Amine package, which corresponds to 24% energy savings) and to 3.2 GJ/tCO2 (with the Acid gas package, which corresponds to 13.5% energy savings) as illustrated on Figure 27. Note that it was also highlighted that the cooling energy at the condenser is also reduced in comparison with the conventional configuration, which will lead to a reduction of the energy consumption of the cooling water pump. Moreover, it should be noted that the interest and the technical feasibility of the LVC configuration was evocated and checked in several studies (such as [Amrollahi et al., 2011] and [Fernandez et al., 2012]) and also in the European project CESAR ([van Os, 2012] and [Kvamsdal et al., 2011]) during pilot tests.

SSF


Figure 28: Aspen HysysTM flow sheet of the Lean Vapor Compression (LVC) configuration.

3°) Finally, in order to benefit from both an exergetic integration and a “heat pump effect”, it is also possible to combine the SSF and the LVC configurations previously described. As illustrated in Figure 27, the combination of these two promising configurations (SSF + LVC) leads to only a small supplementary gain in terms of energy consumption (both cooling and regeneration energies) in comparison with the LVC configuration alone. It must be noted that the parameters in relation with each configuration (cold fraction and injection stages for the SSF configuration and pressure drop for the LVC one) were previously optimized in [Gervasi et al., 2014]. Comparing the results obtained with the two packages, it was shown that the application of the “Acid Gas Package”, known to be more complete and realistic (rate based calculations) than “Amine Package” (equilibrium calculations), leads to regeneration energy savings in the range 3.5% to 15%, which is almost the half in comparison with the other package but which is more coherent with the expected gains from literature.

4.2.3 Conclusion on the first simulations and perspectives

The simulation results highlighted the energy savings (both cooling energy at the condenser and regeneration energy of the solvent) linked to alternative configurations of the absorption-regeneration process, especially in the case of CO2 capture applied to cement flue gases in comparison with power plants flue gases considered in other studies. It was also shown that the energy savings depends on the simulation packages used in Aspen HysysTM software. Among the three configurations considered, as the LVC and the combined SSF-LVC configurations lead to quite similar results (from 13.5% to 24% of regeneration energy savings, depending on the simulation package) considering the LVC configuration seems the good option to investigate for a more efficient reduction of the energy consumption by the CO2 capture process applied to cement flue gases.

As perspectives, the principle of the future simulation works will be to consider, into the Norcem Brevik Cement plant, the installation of a post-combustion CO2 capture pilot which corresponds to the one used in the European projects CASTOR and CESAR (see parameters on Figure 29).

LVC


Figure 29: Comparison between MTU and CASTOR pilots parameters

These new simulations will have several interests for ECRA and HeidelbergCement:

- all the parameters related to the Mobile Testing Unit (MTU) of Aker Clean Carbon are not

available for carrying realistic simulations;

- the CASTOR/CESAR pilot has a CO2 capture capacity 10 times higher than MTU of Aker;

- the objective is complementary to the Aker one: Aker applied a precise process

(configuration and optimized solvent) and in the present case the simulation will highlight

the interest of alternative configurations.

4.3 CO2 mineralization into olivine-derive compounds

The following bibliographic overview on CO2 mineral carbonation processes is mainly based on the excellent review work of [Sanna et al., 2014]. Some explanations were taken without any changes. Globally, the information presented were confirmed with other references.

4.3.1 Introduction on Mineral Carbonation (MC)

Mineral Carbonation (MC) is defined as the reaction of metal oxide bearing materials with CO2 to form insoluble carbonates:

Metal oxide (MO) + CO2 Metal carbonate (MCO3) + Heat

This reaction can take place either below (in situ) or above (ex situ) ground.

In-situ mineral carbonation involves the injection of CO2 into underground reservoirs to promote the reaction between CO2 and alkaline-minerals present in the geological formation to form carbonates.

Ex-situ mineral carbonation relates to above-ground processes, which requires rock mining and material comminution as MC pre-requisites. MC can take advantage of different starting


materials, which include Mg-silicate minerals and Ca or Fe rich silicates. The reactions occurring in MC processes are listed below:

Mg2SiO4 + 2 CO2 + 2 H2O 2 MgCO3 + H4SiO4 Mg3Si2O5(OH)4 + 3 CO2 + 2 H2O 3 MgCO3 + 2 H4SiO4

Fe2SiO4 + 2 CO2 + 2 H2O 2 FeCO3 + H4SiO4 CaSiO3 + CO2 + 2 H2O CaCO3 + H4SiO4

Most of the time, the metal oxide envisaged for MC are related to the generic term “olivine”. Actually different types of olivine are used such as: conventional olivine (Mg2SiO4), serpentine (Mg3Si2O5(OH)4) and Wollastonite (CaSiO3).

Mineral carbonation is a permanent and safe way for storing CO2, which does not present potential concerns over long term monitoring and liability issues, such as geological storage. Mineral resource availability, scalability, applicability to regions without geologic storage capacity, inherent stability of the reaction products and the potential revenue from MC products support the on-going development of this technology. Also, mineral carbonation can operate on flue gases directly, without CO2 pre-separation, which typically stands for 70–75% of the cost of the CCS chain. In references listed by [Sanna et al., 2014], a CO2 carbonation efficiency of ± 20% has been reported when SOx and NOx were present in the flue gas (15% CO2) using wollastonite at 40 bar and 150°C. However, very few works have been published on MC in the presence of impurities to fully assess this option.

The different Mineral Carbonation options are globally divided into three categories and in sub-categories:

- Ex-situ processes: these include both direct and indirect mineral carbonation, using gas-solid or aqueous systems, with single or multi-step(s) processes (including the addition of additives for example).

- In-situ processes: some techniques correspond to an “acceleration” of the natural carbonation process and there are also other techniques such as the “CO2 Energy Reactor” (CO2 injection under pressure for generating carbonates species).

- Other processes: such as biomineralization. Note that the potential sequestration of CO2 using environmental biotechnological processes, such as nitrification, anaerobic digestion (AD) and bio-electrochemical systems, was reviewed by several authors cited by [Sanna et al., 2014]. The global sequestration potential of biodegradable solid waste and wastewater by AD employing silicates was estimated in 0.2–0.4 wt% of the total anthropogenic CO2 emissions. Bioelectrochemical systems such as microbial fuel cells can potentially sequester more CO2 than what is produced during the organic carbon oxidation (200 wt%). However, these systems suffer from extremely low current densities and therefore further development is required. Although these bio-based processes are promising, their development is still in its infancy and is not considered by [Sanna et al. 2014] in their review.


4.3.2 Global comparison of the Mineral Carbonation options

It is generally accepted that to reduce the level of CO2 emitted in the atmosphere, a portfolio of different and complementary technologies such as renewables, change in energy uses and CCS has to be employed. Mineral carbonation has the potential to sequester billions of tonnes of CO2, but the current costs are too high for a widespread deployment of this technology. The work of Sanna et al. 2014 reviews the current state of mineral carbonation routes and the role they can play in decreasing the emissions of CO2.

In-situ MC has great potential in terms of volume of CO2 which could be permanently fixed within the hosting rocks as solid carbonates thus reducing the risk of potential seepage from the storage site. There is a large availability of minerals which can react in situ with the injected CO2, both onshore and offshore and often close to anthropogenic sources of CO2. In situ MC can also be beneficial for the worldwide development of storage projects. Abundant onshore and offshore basalts and peridotites are available for in situ low temperature mineralization. The largest layered onshore basalt formations are located in India (provinces of Deccan Traps), USA (Columbia River basalts), Russia (Siberian Traps) and UAE/Oman. In addition to political and public acceptance aspects, the current limits of in situ carbonation are due to the slow speed of the process and the need for artificial ways of enhancement of the chemical reactions which require a large amount of energy. Identifying specific sites where natural characteristics such as geothermal gradients are favorable to the carbonation process may reduce the associated costs.

Ex-situ MC presents intrinsic materials handling issues, due to the large mineral requirements and associated reaction products, which result in large process scale (larger than actual power plant materials handling). MC may be suitable to large emitters if the new plants are designed with the required infrastructures. Since for small-medium emitters, geologic sequestration may not be an economically viable option, and there are no commercialized processes that specifically address this technology gap, MC may target this market. Large ultramafic rock deposits within a 100–200 km radius of power/industrial plants emitting over 1 Mt per year CO2 are available in South Africa, China, Russia, Kazakhstan, New South Wales in Australia, USA and Europe. However, not all these resources are easily accessible.

Mg-bearing silicates such as serpentine and olivine represent the most suitable mineral resources, while other Mg-silicates and Ca-silicates are less attractive due to their low Mg content and/or low availability.

Overall, the processes that are attracting major attention and that seem to be viable at this point have in common the potential production of sellable products, the co-removal of different pollutants from the flue gas and process integration essential to lower the costs. The conceptual integration of high temperature and pressure industrial mineral carbonation facility into a developing mine site has been recently demonstrated to be feasible at an operating cost of ≈ 83 $ per tCO2.

Direct gas-solid processes, which require temperatures up to 500°C and fine grinding of minerals (5–35 µm), achieve low capture efficiency and are not viable on the industrial scale at the current scale of development. On the contrary, it is well documented in the literature that the presence of water considerably enhances the reaction rate in the carbonation process. Feedstock pre-treatment by fine grinding, thermal activation and chemicals in direct


aqueous carbonation processes shows significant improvements in CO2 capture efficiency (up to 85% with pure CO2 stream). Meanwhile, the regeneration and recyclability of additives (NaOH, NaHCO3) still need to be addressed.

The US National Energy Technology Laboratory (NETL) developed a direct carbonation process with mechanical pre-treatment, involving grinding of magnesium (or calcium) silicates at 150–200°C, 100–150 bar, where 0.64 M NaHCO3 and 1 M NaCl were added to the solutions. Activation in a planetary mill, even if effective, was found to consume too much energy for CO2 sequestration purposes. Therefore, other activation methods, such as thermal and chemical activation are preferred options to mechanical activation. NETL modified processes proposed by Brent and Shell make use of the low grade heat from power plants and from the serpentine thermal-activation to decrease the overall energy consumption. However, no public data are available to estimate the potential deployment and costs associated with these processes.

Multistep aqueous indirect processes in the presence of additives are also able to reach high carbonation efficiency using mild process conditions and short residence time as a result of faster reaction kinetics in the presence of additives. However, the energy intensive chemical regeneration step is slowing the development of this group of technologies. Also, the use of catalytic enzymes such as carbonic anhydrase (is unlikely to be effective due to their instability and very high costs.

4.3.3 Conclusions and perspectives for the Mineral Carbonation

Despite the large resources available for CO2 sequestration and the clear advantages over geological storage, the costs of both in situ and ex situ MC are currently too high for a large deployment of the technology and these technologies need more investigations to attempt to overcome the unchanged technology challenges, namely: the process energy economics, themical reaction rates and the materials handling issue (for ex-situ carbonation). The current technology research and development gaps that have to be addressed to enhance the understanding on mineral carbonation and its deployment are as follows:

scarce representative raw materials comparison; processes performance data incomplete and inaccurate; MC integration with point source not well explored; incomplete information on cost/energy balance for thermal activation; insufficient knowledge of indirect carbonation fundamentals; insufficient knowledge of carbonation fundamentals using flue gas; lack of assessed reactor technology options and cost studies. A more systematic approach

in costing the process should be addressed for comparison purpose; process scale and materials handling issue not well explored; scarce data on the environmental impact of large mining operations.

While it may not be at this time a complete solution in itself for large emitters (excluding the favorable cases where for example a large deposit of silicates is closely located to a large emitter), ex-situ mineral carbonation with inorganic wastes could be part of an integrated approach to carbon sequestration, which combines remediation of hazardous wastes such as


asbestos tailings and use of readily available fine industrial wastes such as EAFS (Electric Arc Furnace Slag) and cement-kiln dusts to meet CO2 emission goals. On the contrary, in-situ carbonation may be viable for large scale emitters if the current limitations are overcome. However, at these MC technology costs, its deployment as CCS option requires strong financial incentives.

Based on the bibliographic overview on Mineral Carbonation processes, due to the large amount of technologies available, it is necessary to precise which technology would be more deeply studied in the framework of the ECRA Chair. Focusing on ex-situ carbon mineralization technologies seems more relevant because in-situ processes have limits in common with geological storage and biomineralization processes are still too far from a large scale application (high costs, slow process kinetics, etc.). Furthermore, indirect carbon mineralization technologies seems more innovative that the direct technologies which are considered as references and typically selected to compare other technologies according to [Sanna et al., 2014]. Moreover, the direct aqueous mineral carbonation-route is not really “direct” because such technology absolutely implies the use of pre-treatments and leads to high temperature/high pressure process for reaching important conversion ratio. Among the indirect carbon mineralization technologies, the aqueous systems are options that have several advantages:

it is well proven that the presence of water promotes the CO2 mineralization; the aqueous systems can be used as “capture” step, thus it would not be necessary to

firstly capture CO2 and then using this CO2 for the mineralization step. It would be thus a combined “capture-mineralization” process;

there is still insufficient knowledge of carbonation fundamentals using flue gas, and also regarding reactor technology options and economics;

the aqueous indirect carbon mineralization processes can be tested under not too hard experimental conditions (mineralization temperature until max 100-120°C, atmospheric pressure process, etc.). Note that other steps (such as additive regeneration) are carried out at higher temperature (>300°C).

One of the CO2 mineralization process corresponding to the characteristics previously evocated is the “pH-swing CO2 mineral carbonation process” (with recyclable ammonium salts for example), illustrated on Figure 30. The proposed process consists of five steps:

1. In the first step, NH3 is used to capture CO2 from flue gas to produce NH4HCO3. 2. In the mineral dissolution step, 1.4 M NH4HSO4 is used to extract Mg from serpentine

ground to a particle size range 75–125 µm. 3. The Mg-rich solution is then neutralized by adding NH4OH, after which impurities in the

leaching solution are removed by adding NH4OH.


Figure 30: pH-swing mineral carbonation process with recyclable ammonium salts (adapted from [Sanna et al., 2014])

4. The Mg-rich solution reacts with the product from the capture step NH4HCO3 to precipitate carbonates. Since the formation and stability of hydro-carbonates is temperature dependent, MgCO3.3H2O (nesquehonite) can be converted to 4 MgCO3.Mg(OH)2.4H2O (hydromagnesite) at temperatures above 70°C. Precipitation of hydromagnesite results in a solution mainly containing (NH4)2SO4.

5. After water separation, the final step is the additive regeneration, with the decomposition of (NH4)2SO4 at ≈330°C, and producing NH3 for the capture step and NH4HSO4 for the dissolution step.

In comparison with a typical capture process where CO2 is first absorbed by chemicals (e.g. NH3) and then desorbed (to recover the sorbent) and compressed for transportation (leading to high energy consumption for stripping and compression), as carbonates are directly used in the proposed mineral carbonation, there is no need for desorption and compression of CO2. Another advantage of this pH swing process is that it is able to separate three different products: silica, magnesite and iron oxide. This process could also be integrated with the Alstom chilled ammonia CO2 capture process, which has been demonstrated to capture more than 90% of CO2. Nevertheless, the main drawback of the aqueous pH swing ammonium based process is represented by the large amount of water that needs to be separated from the salts during the regeneration step. The amount of water to be evaporated is still too high and alternative separation methods (such as mechanical ones by membranes processes or others) need to be investigated in order to make this process economically feasible.


5. GENERAL CONCLUSIONS AND PERSPECTIVES

5.1 General conclusions on progress of the ECRA Chair scientific activities

Different subjects related to CO2 capture and re-use in the cement industry are addressed in this report, as a summary of the different research activities at UMONS during this second year (April 2014 - May 2015) of the existence of the ECRA Chair. As discussed and validated by the Scientific Committee, different scientific works, namely:

- Extensive bibliographic research on various topics; - Specific technological monitoring;

- Simulation works on: o Flue gas purification for oxy-fuel processes, in particular the simulation of the

Air Products process with a sour compression step (SCU), a dehydration step and a cryogenic step in the CPU;

o Post-combustion CO2 capture, in particular the simulation of the conventional CO2 capture process into MEA, including alternative configurations;

o CO2 conversion into methanol with technology description, kinetic study for simulation implementation, allowing the design of the experimental set up;

- Experimental works namely : o First design for the experimental set up of CO2 conversion; o First CO2 capture processes investigations achieved on the amine absorption-

regeneration process, related to the possible interest for cement industry to consider a combination of O2-enriched conditions and post-combustion capture process: tests performances on several amine-based solvents and other solvents such as hybrid ones, at high CO2 content (up to 60%) into the flue gas

were carried on and are still under progress. All the planned scientific subjects were gradually, and as adequately as possible, introduced into the overall organization of the ECRA Chair.

5.2 ECRA Chair scientific activities for the next year

The following tasks are planned for the next year (period May 2015 – May 2016): Regarding the PhD Thesis of Sinda Laribi: 1/ Experimental and simulation works in relation with the post-combustion CO2 capture process by absorption-regeneration applied to cement flue gases coming from conventional and O2-enriched combustion kilns (partial oxy-fuel combustion). Regarding the comparison


with the Pressure Swing Adsorption technology (PSA), the first steps on this part will be envisaged during the next months depending on the advancements on the other topics. 2/ Continuation of the simulation works in relation with the Sour Compression Unit (SCU) process (part of the CO2 Purification Unit – CPU) for de-SOx and de-NOx. The current reaction mechanism will be adapted and implemented in Aspen Plus to take into account the SOx and NOx interactions. Concerning the PhD Thesis of Nicolas Meunier: 1/ Continuation of the simulation works in relation with the dehydration unit (part of the CPU), including (if possible) some literature validation of the simulation results and the design of a suitable column to treat the gas coming from the SCU. 2/ Continuation of the simulation works of the CO2 conversion process into methanol in order to finalize the design of the experimental micro-pilot reactor. The experimental device will be executed and the experimental works on this topic will be initialized. Finally, regarding the Post-Doc Lionel Dubois: In addition to the support works for the ECRA Chair, the specific tasks scheduled for the post-doctoral works during the next year are: 1/ Technological monitoring on hybrid membrane-amine plant CO2 capture technology. 2/ Simulation with Aspen Hysys of the post-combustion CO2 capture process applied to Norcem Brevik Cement plant flue gases. 3/ Continuation of the bibliographic/technico-economic study on CO2 mineralization process: focus on CAPEX/OPEX, comparison of technologies, complement on pH-swing process, potential of the utilization of cement wastes for the CO2 mineral carbonation, etc. The advancements on this part will depend on the eventual launching of a new PhD Thesis on this topic. 4/ Any other tasks linked to the collaboration with HeidelbergCement, for example as support to the Norcem Brevik Project.

5.3 External communication

5.3.1 Publications

Different papers were published and are planned.


Past conferences and attached publications → “CO

2 capture in cement production and re-use: first step for the optimization of the overall

process” Nicolas MEUNIER, Sinda LARIBI, Lionel DUBOIS, Diane THOMAS, Guy DE WEIRELD Energy Procedia, Vol.63 (2014), pp 6492-6503 Poster communication by L. Dubois at GHGT-12 congress (Austin, Texas, October 2014)

→ “Simulation of the post-combustion CO2 capture with Aspen HysysTM

software: study of

different configurations of an absorption-regeneration process for the application to cement flue gases” Julien Gervasi, Lionel Dubois and Diane Thomas Energy Procedia, Vol.63 (2014), pp 1018-1028 Poster communication by L. Dubois at GHGT-12 congress (Austin, Texas, October 2014)

→ “Screening tests of new hybrid solvents for the post-combustion CO2 capture process by

chemical absorption” Julien Gervasi, Lionel Dubois and Diane Thomas Energy Procedia, Vol.63 (2014), pp 1854-1862 Oral communication by L. Dubois at GHGT-12 congress (Austin, Texas, October 2014)

→ “Study of the potential of new hybrid solvents for the post-combustion CO2 capture

process” Julien Gervasi, Lionel Dubois and Diane Thomas Poster communication by D. Thomas at Distillation-Absorption 2014 (Friedrichshafen, September 2014) and publication of a paper (6 pages) in the proceedings “PhD Day GEPROC 2014” scientific event (23/10/2014, Mons, Belgium) → « Simulation d’un procédé de purification du CO

2 provenant d’unités de capture en

oxycombustion appliquée aux cimenteries » Sinda Laribi, Nicolas Meunier, Lionel Dubois, Guy De Weireld and Diane Thomas Poster presented by Sinda Laribi → « Capture du CO

2 dans l’industrie cimentière en vue de sa conversion: conversion

catalytique du CO2 en méthanol »

Nicolas Meunier, Lionel Dubois, Diane Thomas and Guy De Weireld Poster presented by Nicolas Meunier Publication of the abstracts in the proceedings See pictures taken at this event on Figure 31.


TCCS-8 – Conference on CO2 Capture,

Figure 31: The ECRA PhD students at the “PhD Day GEPROC 2014”

5.3.2 Future planned communications

1°) TCCS-8 – Conference on CO2 Capture, Transport and Storage - Trondheim, Norway –

June 2015 → “ Simulation of a CO2 purification unit applied to flue gases coming from oxy-combustion

cement industries ” Sinda Laribi, Nicolas Meunier, Lionel Dubois, Guy De Weireld and Diane Thomas → “ Solvent screening for the post-combustion CO2 capture applied to flue gases coming

from conventional and partial oxy-fuel combustion cement kilns” Guillaume Pierrot, Sinda Laribi, Lionel Dubois and Diane Thomas The two abstracts were accepted. One paper will be submitted in Energy Procedia. 2°) EMChIE 2015 - European Meeting on Chemical Industry and Environment - Tarragona, Spain - June 2015 → « Simulations with different process configurations for the CO2 capture applied to cement

flue gases » Julien Gervasi, Lionel Dubois and Diane Thomas An extended abstract was accepted and will be published in the proceedings. A poster will be presented. 3°) ICCDU 2015 - International Conference on Carbon Dioxide Utilization – Singapore - 05-09/07/2015 → “ Innovative solvents for the post-combustion CO2 capture absorption-regeneration

process applied to cement plant flue gases ” Lionel Dubois, Nicolas Meunier, Sinda Laribi, Julien Gervasi, Guy De Weireld and Diane Thomas


→ “ CO2 capture and re-use from oxyfuel cement kilns: process simulation of the CO2

purification and catalytic conversion into methanol ” Nicolas Meunier, Sinda Laribi, Lionel Dubois, Diane Thomas and Guy De Weireld Acceptance of two abstracts for posters presentations

4°) PCCC3 - 3rd

Post Combustion Capture Conference - 08-11/09/2015 – Saskatchewan, Canada → “ Post-combustion CO2 capture: optimization of the absorption-regeneration process for

the application to cement flue gases “ Guillaume Pierrot, Julien Gervasi, Sinda Laribi, Lionel Dubois and Diane Thomas Submission of two abstracts 5°) ECCE-10 – European Congress of Chemical Engineering - Nice, France – September 2015 → “ Post-combustion CO2 capture applied to cement plant flue gases: screening tests of

innovative solvents for the absorption-regeneration process “ Sinda Laribi, Lionel Dubois and Diane Thomas → “ Optimization of a sour-compression unit for CO2 purification applied to flue gases

coming from oxy-combustion cement industries ” Sinda Laribi, Nicolas Meunier, Lionel Dubois, Guy De Weireld and Diane Thomas Submission of two abstracts

5.4 Global perspectives of the ECRA Chair

In order to enable additional PhD theses to be assigned by UMONS and to keep the post-doctoral position for the Scientific Coordination of the Chair, a prolongation of the ECRA Chair is desired. The current contract implies a period of three years (from 2013 to 2016, see Phase 1 on Figure 32) and another three years period (from 2016 to 2019, see Phase 2 on Figure 32)) would be optimal to ensure a smooth continuation of the various theses and post-doc. Subject to the final approval of ECRA’s Technical Advisory Board which will be convened in May, Mr. Gauthier and Mr. Schneider underlined that another three-year period should follow after the current one which will end in spring 2016. As for the current situation, a complementary funding by HeidelbergCement should also be defined in order to ensure the different positions (PhD Theses and post-doc).


Figure 32: ECRA Academic Chair Timeline for Phase I and potential Phase II

-----------------------------------------------------------------------------------------------------------------


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Wang Y. and LeVan M. D., “Adsorption Equilibrium of Carbon Dioxide and Water Vapor on Zeolites 5A and 13X and Silica Gel: Pure Components”, J. Chem. Eng. Data, no. 54, pp. 2839-2844, 2009.

White V., Wright A., Tappe S. and Yan J., “The Air Products–Vattenfall Oxyfuel CO2 Compression and Purification Pilot Plant at Schwarze Pumpe”, Energy Procedia 37, pp. 1490 – 1499, 2013.

Internal references:

ECRA CHAIR Report – First Annual Report (May 2013 – April 2014), 2014.

Gervasi J., Dubois L., Thomas D., Simulation of the Post-combustion CO2 Capture with Aspen HysysTM Software: Study of Different Configurations of an Absorption-regeneration Process for the Application to Cement Flue Gases, Energy Procedia, 63, 1018-1028, 2014.


7. ANNEXES

- Program of the first ECRA Chair Event.

- Abstracts of the communications presented at the first ECRA Chair Event.


Program of the First ECRA Chair Scientific Event “From CO2 to energy”: CO2 capture and reuse

in the cement industry

Wednesday, 26th November 2014, 9:00 - 16:00 University of Mons - Faculty of Engineering

Boulevard Dolez, N°31 - Academic Room, 1st floor - 7000 Mons - Belgium

09:00: Welcome and registration

09:30: Introduction by Dean Pierre Dehombreux and Prof. Paul Lybaert, Faculty of Engineering – UMONS (B)

09:45: Presentation of the event and of the ECRA Chair by Prof Diane Thomas, Faculty of Engineering – UMONS (B)

10:00: EU Support to CCUS Research and Innovation by Jeroen Schuppers, European Commission – DG Research & Innovation (B)

10:20: New trends for the CO2 capture in the cement industry by Daniel Gauthier, HeidelbergCement, Technical Advisory Board ECRA (B)

10:40: ECRA’s activities and projects by Dr Martin Schneider, ECRA (D)

11:10 – 11:40: Coffee break

11:40: Oxy-fuel combustion for CO2 capture in cement plants by Giovanni Cinti, Italcementi (I)

12:00: Calcium looping for CO2 capture in cement plants by Prof. Stefano Consonni, Politecnico di Milano (I)

12:30: Post-combustion CO2 capture project at Norcem Brevik cement plant by Per Brevik, Norcem - HeidelbergCement Group (N)

13:00 – 14:15: Lunch and networking

14:15: Post-combustion CO2 capture in the cement industry: research projects at UMONS

by Dr Lionel Dubois, Faculty of Engineering – UMONS (B) 14:35: ECRA Chair projects at UMONS: CO2 capture, purification and conversion into methanol

by Sinda Laribi and Nicolas Meunier, PhD Students ECRA Chair, Faculty of Engineering – UMONS (B)

15:15: Smart CO2 Transformation (SCOT): An EU funded project aimed at Defining Europe’s Research Agenda for CO2 Utilization

by Youssef Travaly, GreenWin (B) 15:35: CO2 as building block for the chemical industry

by Dr Angelina Prokofyeva, Bayer Technology Services (D)

16:00: Closing of the day, acknowledgments and closure drink.


Abstracts of the communication presented at the First ECRA Chair Scientific Event at UMONS

EU Support to CCUS Research and Innovation by Jeroen Schuppers, European Commission – DG Research & Innovation (EU)

The re-use or utilisation of captured CO2 is gaining ground, in particular with the current

headwinds facing carbon capture and storage (CCS). Although CO2 re-use does not have

substantive global CO2 abatement potential, it can play a role in providing a moderate revenue

stream for CCS projects. Examples include the use of CO2 for enhanced oil recovery, as a

feedstock for the production of chemical and polymers, or mineralisation. In addition, the

production of synthetic natural gas (methanation) could be a promising technology for large-

scale energy storage from intermittent renewables. Horizon 2020, the EU funding programme

for research and innovation, provides support to research and innovation on the capture of CO2

from power plants or energy intensive industries such as cement production, and its subsequent

storage or re-use. In the context of energy research, the focus of CO2 re-use will be on options

that have the potential to yield a significant, net reduction of CO2 emissions in volumes

sufficient to make a meaningful contribution to our climate change objectives.

New trends for the CO2 capture in the cement industry by Daniel Gauthier, HeidelbergCement – Technical Advisory Board ECRA (B)

The application of CO2 capture at an industrial scale needs to take into account several factors

especially for allowing the process to be economically viable. In this context, the communication

will summarize important factors regarding the applicability of the CO2 capture in the cement

industry.

ECRA’s activities and projects by Dr Martin Schneider, ECRA (D)

ECRA was founded as research platform some 10 years ago and focuses on projects for the

cement industry which have a long-term and innovative character. More than 5 years ago ECRA

began its research on CCS in order to understand the technical and economic feasibility of this

technology. Today, ECRA is in the position to fully describe oxyfuel and post-combustion

technology. While oxyfuel technology is ready to be tested under industrial-scale conditions,

post-combustion is already now being tested by HeidelbergCement at its NORCEM-Brevik

plant in cooperation with different technology providers. Joining industry forces for projects

which may be too large to be undertaken by single companies alone has proved to be a very

successful concept for CCS. Other important issues such as e.g. future grinding technologies

will also be addressed soon with this research approach, which allows not only cement

producers to be involved but also relevant universities, technology providers and equipment

manufacturers.


Oxy-fuel combustion for CO2 capture in cement plants

by Giovanni Cinti, Italcementi (I)

The oxyfuel combustion technology is based on the concept of the recirculation of the process

combustion gases to the main and calciner burners, with the addition of oxygen in the amount

necessary for the fuel combustion and the recovery of a part of recirculating gases very rich in

CO2 (from combustion and from decarbonation), to be purified and sent to storage.

A few years ago ECRA has started a specific project divided in 6 stages : from the overview of

the different existing technologies up to the testing on a pilot plant of the most promising one

from the point of view in term of technical and economic feasibility. In the presentation the

different steps are described and the actual situation of the project is given.

Calcium looping for CO2 capture in cement plants by Prof. Stefano Consonni, Politecnico di Milano (I)

Calcium Looping is based on the idea of using calcium oxide as the carrier of CO2 in a circular

sequence of processes where CO2 at relatively low concentration is captured through

carbonation (CaO + CO2 CaCO3) and then released through calcination (CaCO3 CaO +

CO2) to generate a flow of nearly pure CO2. After being originally proposed as a means for

post-combustion capture, the process has been considered for integrated power/cement plants

and later for dedicated cement plant applications. This presentation gives a summary of the

activities carried out at Politecnico di Milano in collaboration with Italcementi, outlining

expected technical and economic outcomes of its large scale implementation in the cement

industry.

Post-combustion CO2 capture project at Norcem Brevik cement plant

by Per Brevik, Norcem – HeidelbergCement Group (N)

The cement industry is a major emitter of anthropogenic greenhouse gas emissions and

contributes to around 5% of the global CO2 emissions. Therefore, the cement industry needs to

be proactive in finding solutions which reduce its climate impact.

Norcem AS and its parent company HeidelbergCement Group have joint forces with the

European Cement Research Academy (ECRA) to establish a small-scale test centre for studying

and comparing various post-combustion CO2 capture technologies (namely amine scrubbing,

membrane technology, solid adsorbent technology and carbonate looping process), and

determining their suitability for implementation in modern cement kiln systems. The project

does not encompass CO2 transport and storage. The small-scale test centre has been established

at Norcem’s cement plant in Brevik (Norway). The project has received funding from Gassnova

through the CLIMIT program. It was launched in May 2013 and is scheduled to conclude in

spring 2017 (Test Step 1). The project mandate involves testing of more mature post-

combustion capture technologies initially developed for power generation applications, as well

as small scale technologies at an early stage of development.


Post-combustion CO2 capture in the cement industry: research projects at UMONS by Dr Lionel Dubois, Faculty of Engineering – UMONS (B)

The purpose of this communication is to illustrate some of the research activities carried out at

the University of Mons on the subject of post-combustion CO2 capture and especially on the

absorption-regeneration process applied to cement flue gases.

In terms of experimental works, the presentation illustrates some experimental devices developed

during a PhD thesis carried out in collaboration with Holcim, namely solvent screening apparatus

at lab scale (for separate absorption and regeneration efficiencies measurements and kinetic

parameters calculation) and also at micro-pilot scale (for combined absorption-regeneration tests

in more realistic conditions).

The different screening tests highlighted that thanks to the use of activated solutions (composed

of a sterically hindered amine and a cyclical diamine) or innovative hybrid solvents (composed

of a chemical part such as alkanolamines and a physical part such as acetal), it is possible to

significantly reduce the energy consumption for the solvent regeneration while keeping good

absorption performances.

Thanks to simulation works under Aspen HysysTM, the communication also briefly highlights

that such as for power plants, the use of alternatives configurations of the absorption-regeneration

process also allow a significant decrease of the energy consumption of the CO2 capture process

applied to cement flue gases.

The experimental and simulation works are still ongoing under the framework of the ECRA

Academic Chair and in collaboration with HeidelbergCement.

ECRA Chair projects at UMONS: CO2 capture, purification and conversion into methanol

by Sinda Laribi and Nicolas Meunier, PhD Students ECRA Chair, Fac. Engineering – UMONS (B)

Carbon Capture and Utilization (CCU) is one of the most widely studied technology to reduce

anthropogenic CO2 emissions and particularly the ones coming from power plants and cement

plants which are currently among the world’s main industrial sources of carbon dioxide. As a

result, in the framework of the ECRA Academic Chair at UMONS, this study focuses on the

optimization of an overall CCU process that should be applied to an oxyfuel cement plant, and

including the CO2 capture from flue gases and its purification in order to obtain a rich CO2 stream

that will be further converted into methanol.

To investigate the feasibility of such as process, two units (namely sour compression and

cryogenic units) have been modeled and simulated on Aspen Plus software. These simulations

were conducted considering flue gases compositions coming from both power and cement

oxyfuel plants in order to compare their respective energy demands with regard to the CO2 purity

of the end-of-pipe product and to the CO2 recovery of the overall process. It was observed that

such process applied to simulated oxyfuel cement plant flue gases has a global CO2 recovery

range of 75.8 – 93.8% and that the CO2 molar purity of the final stream is between 94.8 and

98.4%. This process appears to be completely applicable for the treatment of oxyfuel cement

plant flue gases with CO2 recovery and CO2 molar purity in agreement with requirements for the

chemical conversion of carbon. Regarding the conversion step, the future tasks will be focused

on the simulation of the catalytic conversion process (influence of operating parameters on the

conversion efficiency) and on the experimental investigation of the influence of gaseous

impurities on catalysts performances and aging.


Smart CO2 Transformation (SCOT): An EU funded project aimed at Defining Europe’s Research Agenda for CO2 Utilization

by Youssef Travaly, GreenWin (B)

"Carbon dioxide utilisation" or "CO2 recycling" are broad terms that cover a variety of

innovative industrial processes which use CO2 from point source emitters as a feedstock; and

transform it into value added products. The main products on which activity has mainly focused

so far belong to three families: low carbon building materials, synthetic fuels and chemical

building blocks.

We will present the SCOT project and the results of this first year of work focusing on the

current status of CO2 recycling in Europe and the main bottlenecks to be tackle for these

technologies/markets to develop.

CO2 as building block for the chemical industry

by Dr Angelina Prokofyeva, Bayer Technology Services (D)

The current presentation will highlight the recent achievements in the area of utilization of CO2

as C1 building block.

The synthesis of polyether-poly-carbonate polyols (CO2-PET) based on CO2 as building block

was proven to be efficient and possible on the pilot scale within the “Dream Production” project.

Production of these CO2- based polymers can be performed only in the presence of specific

catalysts which enable activation of CO2 and further, initiate the exothermic polymerization

reaction to yield CO2-PETs.

The obtained polyols are further reacted with isocyanates and processed to polyurethanes

(PUR). They are used in applications like flexible foams or lightweight materials.

In addition, the LCA analysis has proven that these new polyols show a better sustainability of

these newly developed plastics as compared to conventional ones.

ecra chair from co to energy: carbon capture in cement...

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