Diploma thesis presentation

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Modeling of a pilot installation for the

CO

₂

-reactive absorption with amine solvent for

power plant flue gases

Diploma thesis presentation

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Diploma thesis presentation

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Global warming context February 1993

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Diploma thesis presentation 09.11.09 3

Table of content

1. Introduction 2. Objectives 3. Modeling basis 4. Model description 5. Simulation results 6. Process improvements

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1. Introduction

• Importance of coal for electricity generation in the near-future

• Environmental concerns => Energy efficiency

=> biomass

=> Carbon Capture and Storage (CCS)

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1. Introduction

CO₂-Capture

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1. Introduction

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2. Objectives

Background: Pilot installation

• Post-combustion capture for an existing coal-fired power-plant

• 5000 Nm³ flue gas per hour / 1 ton CO₂ per hour

• Two operation trains

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2. Objectives Objectives:

• Development of a simulation model for the pilot capture installation

• Identification of clue parameters

• Optimization of the developed model • Simulation of process improvements

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3. Modeling basis

Thermodynamical equilibrium model

=> No mass transfer limitations => No reaction kinetics limitations

In the practice:

• mass transfer limitations occur

• packing efficiency can be calculated • packing efficiency reaches about 15 %

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3. Modeling basis

Reaction kinetics with MEA

• Pseudo-first order reaction with fast kinetics • Reaction only occurs in the liquid film

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4. Model description

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4. Model description

Model main characteristics • Flue gas flow: 2500 Nm³/h

• 90% CO₂-recovery rate

• captured CO₂: 566 kg/h

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5. Simulation results

Optimization of the base case

• 5.1 Lean solvent flow

• 5.2 Lean solvent concentration

• 5.3 Lean solvent inlet temperature in the absorber • 5.4 Stripper pressure

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5. Simulation results

5.1 Optimization of the lean solvent flow

3,50 3,70 3,90 4,10 4,30 4,50 10,50 11,50 12,50 13,50 14,50 15,50 Lean solvent massflow (m³/h)

T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50,00 60,00 70,00 80,00 90,00 100,00 C O 2 -R e c o v e ry ( % )

4 absorber stages 3 absorber stages CO2-Recovery

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5. Simulation results

3 contributions to the thermal energy consumption : • Solvent heating-up • Desorption enthalpy • Stripping steam Stripping Heating-up 3,50 3,70 3,90 4,10 4,30 4,50 10,50 11,50 12,50 13,50 14,50 15,50

Lean solvent massflow (m³/h)

T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 )

4 absorber stages 3 absorber stages

Stripping Heating-up

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5.2 Optimization of the lean solvent concentration

3,20 3,40 3,60 3,80 4,00 4,20 0,27 0,29 0,31 0,33 0,35 0,37 M EA-LEAN concentration (wt-%) T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100 C O 2 R e c o v e ry ( % )

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5.3 Optimization of the lean-solvent inlet temperature in the absorber 3,50 3,70 3,90 4,10 4,30 4,50 30 35 40 45 M EA-LEAN Temperature (°C) T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100 C O 2 -r e c o v e ry ( % )

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5.4 Optimization of the stripper pressure

3,50 3,70 3,90 4,10 4,30 4,50 1,2 1,4 1,6 1,8 2,0 2,2

Stripper pressure (bar)

T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100 C O 2 R e c o v e ry ( % )

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5.5 Optimization of the temperature approach at the lean-rich heat exchanger

3,50 3,70 3,90 4,10 4,30 4,50 5 6 7 8 9 10 11 12 13 LRHeatX DeltaT (°C) T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100 C O 2 -r e c o v e ry ( % )

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6. Process modifications

• 6.1 Lean vapor compression • 6.2 Absorber intercooling

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6.1 Influence of the flash pressure by the LVC

- 25 % Thermal energy consumption - 18 % Exergy consumption 2,80 3,00 3,20 3,40 3,60 3,80 1,1 1,5 1,9 2,3

Flash pressure (bara)

T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100 C O 2 R e c o v e ry ( % )

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6.2 Influence of intercooler position

- 6 % Thermal energy consumption 3,50 3,70 3,90 4,10 4,30 4,50 No inte rcoo ling 1;2 2;3 3;4 prec oolin g T h e rm a l e n e rg y c o n s u m p ti o n ( G J /t o n C O 2 ) 50 60 70 80 90 100

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7. Conclusion and perspectives

• Simulation model => coherent results in comparison with the experiments on the Castor pilot

• Reduction of the thermal energy consumption by 29% achievable (IC + LVC)

• Reduction of the process exergy consumption reaches 19,5%

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7. Perspectives: PhD Thesis

• The subject is subdivided into 2 main subjects:

1. Modeling and optimal conception of the CO₂

capture process

2. Study of the solvent degradation phenomena The final purpose is to propose optimal operating

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7. Perspectives: PhD Thesis Objectives of the Modeling:

• Optimisation of the existing process

• Proposition of new process improvements

• Test of those process improvements thanks to the simulation and selection of the best ones

• Utilization of the model in parallel with test campains on

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Objectives of the degradation study:

• Construction of a test installation for the study of solvent degradation phenomena

• Study of classical solvents

• Study of newly developed solvents and of degradation inhibitors

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7. Perspectives: PhD Thesis Degradation consequences: • Process operating cost:

- Solvent make-up

- Removal and disposal of degradation products - 4-10% of the total operating costs!

• Process performances

- Solvent loading capacity decreases - Viscosity increases

• Capital cost

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Importance of testing solvents on small scale installations before using them in larger scale pilots!

- Toxicity of the degradation products

- Viscosity, foaming, fouling,…

- Solvent make-up rate

- Removal and disposal of the degradation products - Corrosion

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38 7. Perspectives: PhD Thesis

Different reactor types

Goff G., 2005 Lepaumier H., 2008 4 x 100 ml 10 ml 500 ml Davis et al., 2005

Diploma thesis presentation 09.11.09

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Back-up slides

• Reaction kinetics is fast and neglectible in comparizon to mass transfer limitations

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Back-up slide

• Number of absorber stages / Mass transfer limitations

90,00 92,00 94,00 96,00 98,00 100,00 2 3 4 5

Number of equilibrium stages in the absorber

C O 2 -r e m o v a l (% ) N_{s, real}= H/HETP

_packing = N_{s, ideal}/N_{s, real} Castor packing:

H = 17m

HETP ~ 0,55 m

New Pilot plant packing: H = 9m

HETP ~ 0,3 m

=> N_{S, real} ~ 30

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Diploma thesis presentation 09.11.09 42 Back-up slide • Henry ‘s law: P_CO2= KH CO2/Solvent . xCO2 • Temperature dependence : CO₂ + MEA <=> CO_{2, abs.}

K’ = x_{CO2, abs.} / P_CO2 . [MEA] => K = x_CO2 / P_CO2

KH

CO2/Solvent = 1/K • Van’t Hoff:

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Back-up slide

• With -  H /R = C and H_CO2/Solvent = 1/K

• If P increases, then T also increases and KH _increases

since  H is negative (exothermic absorption)

• => The CO₂ partial pressure increases and the

regeneration is easier 1 1 ( ) ( ) exp ( ) H H ref ref k T k T C T T     _   _    

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Back-up slide

• Influence of the solvent mass flow

0,20 0,25 0,30 0,35 0,40 0,45 0,50 10,50 11,50 12,50 13,50

Lean solvent massflow (m³/h)

S o lv e n t lo a d in g (k m o l C O 2 /k m o l M E A )

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Back-up slide

• Influence of the MEA-concentration

0,20 0,25 0,30 0,35 0,40 0,45 0,50 0,55 0,27 0,29 0,31 0,33 0,35 0,37

M EA-LEAN concentration (wt-fraction)

L o a d in g (k m o l C O 2 /k m o l M E A )

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Back-up slide

• Exergy calculation

Exergy = Thermal energy * Carnot efficiency

Carnot efficiency : ₁ C H T T    Flash-pressure Thermal energy consumption Normalized Compressor duty Normalized Blower Duty Normalized Pump duty

bar GJ/ton CO2 GJ/ton CO2 GJ/ton CO2 GJ/ton CO2

2,3 1,316 - 0,057 0,006

1,90 1,225 0,025 0,057 0,006

1,50 1,118 0,056 0,057 0,006

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Diploma thesis presentation 09.11.09 47 Back-up slide Exergy consumption 1,0 1,2 1,4 1,6 1,8 2,0 1,1 1,5 1,9 2,3

Flash pressure (bara)

E x e rg y ( G J /t o n C O 2 ) Exergy consumption

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Back-up slide

• Absorber profile when Intercooling 1 2 3 4 45 50 55 60 65 70 Temperature (°C) S ta g e n u m b e r Precooling 1;2 2;3 3;4 No intercooling

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Back-up slide

Precursor model analysis

• Thermal energy consumption : 600 MWth by a flue gas

flow of 700 m³/s (500 ton CO₂h-1  0,15 ton CO₂ s-1 )

=> 0,6 MWth / 0,15 ton CO₂s-1_{=> ~ 4GJ/ton CO}

2

• Heat exchanger :

Q = 2,8 m³s-1 . _{4180 Jkg}-1_K-1 . _10°K. _{1100 kg m}-3