Necessity analysis: Applying the method for the CPOX and Non-Catalytic reactions

Hakan S. Soyhan*, Hüseyin Karadeniz’ and Cem Sorusbay’’

* Sakarya University, Engineering Faculty, Mechanical Engineering Department, Turkey‘ BOSCH, Turkey

‘’ ITU, Turkey

Contents

1-) Motivation

2-) Catalytic Partial Oxidation Phenomenon

3-) Reaction Mechanisms

4-) Mechanism Simplification Techniques

5-) Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

6-) Results

7-) Conclusions

Increasing industrialization

Consumption of fossil fuel worldwide from 1965 to 2030

Declining natural resourcesExcessing harmful emissions

New alternatives are needed !

Syngas production (CO + H2)

1-) Motivation

(Shafiee S., Topal E., Energy Policy Volume 37, Issue 1 2009 181 – 189)

Motivation

Syngas can be used for:

• Methanol synthesis

• Fischer-Tropsch (FT) reaction

• Fuel cells (H2)

• IC engines (H2)

• Gas turbines (H2)

Motivation

How to produce syngas ? Catalytic processes

Conventional steam reforming (SR) units Drawbacks:- Energy intensive process- Long residence time- Expensive initial capital- Large scale operation- Weak heat and mass transport

Micro channel reactors with noble metal (Rh, Pt, Ru) catalysts for Advantages:- Very small dimensions- High conversion- Short contact times- Stable at extreme, cyclic conditions- Low pressure drop- Enhanced heat & mass transfer

Drawbacks:- The high cost of noble metals – optimization is needed- Coking and aging of the catalyst, coke formation

downstream the catalyst

2-) Catalytic Partial Oxidation (CPOX) Phenomenon

SR is less attractive for on-board applications: - Low start-up- Endothermic operation

General reaction equation with catalyst:

- Exothermic reaction with small amount of air- High yields of syngas

Janardhanan, V.M., Deutschmann, O., 2011. Computational Fluid Dynamics of Catalytic Reactors, Modeling and Simulation of Heterogeneous Catalytic Reactions. Wiley-VCH Verlag GmbH & Co. KGaA, pp. 251-282

Catalytic Partial Oxidation (CPOX) Phenomenon

Numerical modeling & simulation of CPOX processes:- Coupling of CFD with detailed chemistry- Example studies

CPOX of CH4

CPOX of IC8H18

Difficulties:- Coupling of chemical reactions with fluid properties- Nonlinearity- Large range of time scales of chemical reactions

3-) Reaction Mechanisms

a-) Global reactions

b-) Detailed mechanisms

• Hundreds of species

• From hundreds to thousands of reactions

• As much as fundamental information - Necessary reactions and species likely to occur- Rate parameters of elementary reactions- Thermodynamic data

c-) Skeletal mechanisms (Simplifed mechanism)- Less numbers of species- Less numbers of reactions- Similar results without loss of information

d-) Reduced mechanisms (Simplifed Mechanism)

4-) Mechanism Simplification Techniques

Mechanism simplification techniques can be classified into two main categories:

1-) Skeletal Reduction Techniques

- Sensitivity Analysis

- Reaction Flow Analysis

- Necessity Analysis

- Directed Relation Graph (DRG)

- DRGSA

2-) Lifetime Analysis

- Computational Singular Perturbation (CSP)

- Intrinsic Low Dimensional Manifolds (ILDM)

5-) Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

Flow chart of the calculation procedure of necessity analysis methodKaradeniz H., Soyhan H.S., Sorusbay C., Reduction of large kinetic mechanisms with a new approach to the necessity analysis method, Combust. Flame (2011), doi: 10.1016/j.combustflame.2011.11.011

Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

- Sensitivity analysis

- Reaction flow analysis

Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

a R Ra aN N Nj j

ij k jk ik (i,k) ( j,k) k jk ik (i,k) ( j,k)a aa 1 k 1 k 1k k

n nf r v v [S S ] r v v [S S ]

n n

a R Ra aN N Nj j

ij k jk ik (i,k) ( j,k) k jk ik (i,k) ( j,k)a aa 1 k 1 k 1k k

n nc r v v [S S ] r v v [S S ]

n n

i ij ijN max(f ,c )

- Implementing cutoff levels and obtaining skeletal mechanisms:

Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

Numerically predicted CH 4 and O 2 distribution in CPOX of methane, as a function of time, in the batch reactor: C/O = 1.0, 1005.78 K.

(Hüseyin Karadeniz , Hakan Serhad Soyhan , Cem Sorusbay, Reduction of large kinetic mechanisms with a new approach to the necessity analysis method, Combustion and Flame Volume 159, Issue 4 2012 1467 – 1480)

Remaining species numbers and reaction numbers for different skeletal mechanisms for CPOX of methane: C/O = 1.0.

Necessity Analysis with Simultaneously Combined Sensitivity and Reaction Flow Analyses

Fig. 7 Numerically predicted species distribution in CPOX of iso-octane based on the new approach and necessity analysis method, as a function of time, in the batch reactor: C/O = 1.6, 1005.78 K: (a) H2 . (b) CO2 . (c) IC 8H18 . (d)

(Hüseyin Karadeniz , Hakan Serhad Soyhan , Cem Sorusbay, Reduction of large kinetic mechanisms with a new approach to the necessity analysis method, Combustion and Flame Volume 159, Issue 4 2012 1467 – 1480)

6-) Results

Results of the DETCHEMBATCH code simulation

Initial parameters of batch simulation for C/O=0.8 Initial mole fractions for C/O=0.8

Initial parameters of batch simulation for C/O=2.0 Initial mole fractions for C/O=2.0

Results

Numerically predicted species distribution in CPOX of i-octane as a function of time in the batch reactor:

C/O=0.8, 1374.85 K: (a) IC8H18 and H2. (b) O2 and IC4H8. (c) C3H6 and H2O. (d) C2H6 and C2H4.

Results

Numerically predicted species distribution in CPOX of i-octane as a function of time in the batch reactor: C/O=2.0,

998.26 K: (a) IC8H18 and H2. (b) O2 and IC4H8. (c) C3H6 and H2O. (d) C2H6 and C2H4.

6-) Results

Results of the DETCHEMPLUG code simulation

Initial parameters of plug flow sim. for C/O=1.6 Initial mole fractions for C/O=1.6

Initial parameters of plug flow sim. for C/O=2.0 Initial mole fractions for C/O=2.0

Results

Numerically predicted species distribution as a function of axial position along the reactor: C/O=1.6, 1108 K: (a) IC8H18. (b) C2H2. (c) C2H4. (d) H2.

Results

Numerically predicted species distribution as a function of axial position along the reactor: C/O=2.0, 1112 K: (a) IC8H18. (b) C2H2. (c) C2H4. (d) H2.

Results

a b

Numerically predicted distribution of some important species as a function of gas temperature at one exact position in the

channel (20 mm) for (a) C/O=1.6 and (b) C/O=2.0

Results

Numerically predicted and experimentally measured distribution of some important species as a function of gas temperature at one exact position in the channel (20 mm): C/O=1.6

Experimental results: Kaltschmitt, T., Maier, L., Hartmann, M., Hauck, C., Deutschmann, O., Influence of gas phase reactions on catalytic reforming of isooctane.Proceedings of the Combustion Institute 2011. 33:3177-83

Conclusions

• Necessity analysis with simultaneously combined sensitivity and reaction flow analyses is successfully coupled with the DETCHEM software

•Skeletal mechanisms predict species distributions (Batch and Plug simulations)

• For a wide a range of fuel compositions (lean/rich)

• 62-63% less species, 57-59% less reactions

• Coke formation is contributed to homogeneous gas-phase reactions (fuel rich conditions)

This study was performed in correlation with;

- Sakarya University, Mechanical Engineering Department (Turkey)

- Istanbul Technical University, Mechanical Engineering Department (Turkey)

- Karlsruhe Institute of Technology, Institute for Chemical Technology and Polymer Chemistry (Germany)

Prof. Dr. Olaf DeutschmannDr. rer. nat. Steffen TischerDr. rer. nat. Lubow Maier

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