What is the best technology for capturing CO2?

Introducing a techno-economic screening toolPatrick Brandl1,2*, Niall Mac Dowell1,2

1Centre for Environmental Policy, Imperial College London, South Kensington Campus, London SW7 1NE, UK 2Centre for Process Systems Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK

*E-mail address: patrick.brandl16@imperial.ac.uk Tel.: +44 (0) 20 7594 7045

Affiliations

@patrick_brandl

Patrick focuses on the techno-economic assessment of climate change mitigation technologies and links molecular thermodynamics with process engineering.

1 S. Fuss et al., Betting on negative emissions, Nature Climate Change 4 (10) (2014) 850-853 doi:10.1038/2 Department of Energy and Climate Change, Energy Trends: June 2016: URN 16D/79B.3 International Energy Agency. World Energy Outlook, 2016.4 M. E. Boot-Handford et al., Carbon capture and storage update, Energy Environ. Sci.7 (1) (2014) 130-189.5 Global CCS Institute Database, available online at www.globalccsinstitute.com6 Source: Abanades et al. (2015) - Emerging CO2 capture system, Int. J. GHG Contr. 40 126-1667 J.R. Couper et al., Chemical process equipment revised selection and design, 2009 Gulf Professional Publishing.

8 Mota-Martinez MT et al., Sustainable Energy Fuels, 2017,1, 2078-2090

Process Engineer

• Wants to reduce CO2

footprint at best cost

• Heuristically selects process and solvent

Research Chemist

• Develops new CO2capture material

• Focused on specific properties instead of overall implications

Screening tool

• Bridges gap between lab and application

• Filters for best cost technologies

Technologies Readiness Levels (TRL) differ significantly6

Application

Absorption CryogenicsSolid

LoopingSolid sorbents Membranes

Physical ChemicalAir

separation

CO2 anti-

sublimationChemical Calcium Adsorption

Low T

gas/solidPolymeric Others

Post-

combustion

Pre-combustion

Oxy-combustion

Industrial

TRL 1 TRL 2 TRL 3 TRL 4 TRL 5 TRL 6 TRL 7 TRL 8 TRL 9

CO2 capture technologies are vital to meet climate targets

Most IPCC Representative Concentration Pathways (RCPs) rely on CO2 capture technologies to limit the temperature increase to sub-2°C. Those include Carbon Capture and Storage (CCS), Bioenergy with CCS (BECCS) or direct air capture. The latter two contribute to negative emissions1.

Closing the gap between lab and field in R&D pipeline CCS factsheet

• The UK has been committed to reducing the CO2 emissions by 80% from 1990 levels by 20502.

• Electricity generation from fossil fuels is one of the single biggest sources of CO2 emissions (25% of total)3.

• Capturing CO2 from the power plants’ flue gas emitted otherwise into the atmosphere can significantly reduce CO2 emissions.

• In conjunction with other technologies, CCS leads to a minimised overall cost of electricity supply in the long run4.

• In 2018, 17 CO2 capture plants are being operated worldwide. The majority captures CO2 from industrial sources (gases processing) and uses it for enhanced oil recovery (EOR)5.

Screening tool filters based on KPIs

Screening of sorbents

Other

•Bi-phasic

•Adsorbents

Ionic Liquids

(ILs)

Alkanol-amines (MEA …)

Bespoke thermodynamic unit modelling Economic evaluation

Operating Expenditure (OPEX)

• Energy requirements (MW) Electricity (MW) + Heat (MW)

• Short-Run Marginal Cost (SRMC) for the production of electricity and for the production of heat

$𝑆𝑅𝑀𝐶

MWh=$fuelMWh

𝜂plant+

$

tonCO2

∙ 𝐶𝐼MWhtonCO

2 + $O&M + $T&SCO2

Capital Expenditure (CAPEX)

Correlations based on key characteristics of each unit.7

• E.g., Heat exchangers Area, material• Annualising CAPEX using the Capital

Recovery Factor (CRF)

i = interest rate (10%)n = years (25 years)

Total Annualised Cost (TAC) Τ$ tonCO2

TAC = 𝐶𝑅𝐹 ∙ σ𝑘units𝐶𝐴𝑃𝐸𝑋𝑘 + σ𝑙𝑂𝑃𝐸𝑋𝑙 “Total cost of ownership”

𝐶𝑅𝐹 =𝑖 1 + 𝑖 𝑛

1 + 𝑖 𝑛 − 1

Using absorber height as non-monetised KPI

Screening of Ionic Liquids’ viscosity and Henry’s constant and their impact on the total costs.

*KPI = Key Performance Index

AcknowledgementsThe authors thank the UKCCSRC (Grant No. UKCCSRC-199) for funding this work. Additional funding from Canada’sOil Sands Innovation Alliance (COSIA) and the Abu Dhabi Petroleum Institute is gratefully acknowledged.

References

0 1 2 3 4 50

20

40

60

80

100

120 Viscosity

Density

Heat Capacity

Heig

ht

Ab

so

rber

(m)

Property value relative to aq. MEAbenchmark

Screening of Ionic Liquids Sensitivity study on thermo-physical properties of Alkanolamines

• Columns higher than 120m (tallest columns in world) are unfeasible

• Most Ionic Liquids require unrealistic columns

• Alkanolamines’ viscosity dominates column’s height because of impact on mass transfer8

Linking molecular structure to costs Identifying best costs solvent

Example for Ionic Liquids

Comparing different solvents in order to find process and solvent configuration at minimum cost

Next steps and outlook

• Extending the solvent study by water lean and biphasic solvents

• Introducing a graphic interface and hosting the model online

• Defining a Computer-Aided Molecular Design (CAMD) problem: Instead of screening existing molecules with their associated properties, a model utilising group contribution theories will optimise for a structure that meets ideal properties.

Summary and conclusions

A heuristic R&D approach with focus on specific properties such as e.g., CO2

solubility or associated energy penalty, misses the point of developing cost effective CO2 capture technologies.

Transport properties such as e.g., viscosity limit the feasibility of proposed CO2 capture materials such as Ionic Liquids. This proves that multi-dimensional trade-offs require a systematic evaluation.

We developed a validated tool that,

• screens thermo-physical properties

• ranks solvents according to their costs

• identifies cost saving potentials

• guides solvent development

Case-study: Focus on physical and chemical absorption

Methodology: Combining chemical process simulation with economic evaluation