Heat Exchanger Design for an Oxyfuel-Process Utilizing Oxygen from

an O Transport Membranean O2-Transport MembraneVincent Verbaere,ce t e bae e,

Malte Förster, Reinhold KneerInstitute of Heat and Mass Transfer

RWTH A h U i itRWTH Aachen University

2nd International Conference on Energy Process Engineering2nd International Conference on Energy Process EngineeringEfficient Carbon Capture for Coal Power Plants

Frankfurt, June 20 – 22, 2011

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Content

■ OXYCOAL-AC

■ Process simulations■ Process simulations

■ Heat exchanger conceptp

1

OXYCOAL-AC: Introduction

Oxyfuel

2

OXYCOAL-AC: Membrane Operation Concepts

4-End Concept

3-End Concept

Transport Equation

3

OXYCOAL-AC: Introduction

?

To guarantee an effective process integration of the

Objective

To guarantee an effective process integration of themembrane module, full consideration must be given tothe design of the Feed Air Heater

4

OXYCOAL-AC: 4-End System Integration

5

OXYCOAL-AC: 3-End System Integration

6

OXYCOAL-AC: Process Constraints on the Heat Exchanger

Air Temperature 300-500°C750°C 300-500°C825°CAir Pressure 10-30 barFlue gas Temperature (Inlet) 875°C >875°CFl G P 0 85 bFlue Gas Pressure 0.85 barFlue Gas Composition CO2+H2O+O2+N2

Flue Gas Impurities SO alkaliFlue Gas Impurities - SOx, alkalisulfate/carbonate,

particles

7

Process Simulations: Targets

■ Membrane parameters

Thermodynamic Parameters

■ Heat exchanger

Design Parameters

■ Membrane parameters■ O2 separation ratio in

feed stream

■ Heat exchanger■ Heat transfer rate■ Effectiveness ε■ Heat capacity rate ratio C*

■ Pressure ratio between feed and permeate sidesfeed and permeate sides

■ Recirculation■ O2 concentration

■ Membrane■ Area■ O2 concentration

■ Heat exchanger■ Pressure drop

■ Process■ Efficiency

8

Process Simulations: Parameters

■ Air fired reference power plant North Rhine-Westphalia (process efficiency = 45.9%)■ 600 MW gross hard coal■ Steam/water cycle: 600/620°C, 285/60 bar■ 1% air ingress

Exhaust gas temperaturesaus gas e pe a u es Flue gas: 65°C (4-end), 140°C (3-end) Depleted air: 50°C Depleted air: 50 C

CO2 compression (100 bar)P it i 95 % Purity: min. 95 %

Separation ratio: min. 90%

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Process Simulations: Sensitivity Analysis – 4-End Concept

Heat Exchanger

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Process Simulations: Sensitivity Analysis – 4-End Concept

Heat Exchanger

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Process Simulations: Sensitivity Analysis – 4-End Concept

Heat ExchangerHeat Exchanger

Process Membrane

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Process Simulations: Sensitivity Analysis – 3-End Concept

Heat Exchanger

13

Process Simulations: O2 Concentration in recirculation (4-End)

Membrane parameters

Pressure ratio: 20O2 separation ratio: 0.9

Heat Exchanger Process and Membraneg

14

Process Simulations: Pressure Drop in Heat Exchanger

Pressure ratio: 20

Membrane parameters

O2 separation ratio: 0.9

Process Efficiency

15

Concept and Design

• It is acknowledged that corrosion in oxy-firing atmosphere

Materials

It is acknowledged that corrosion in oxy firing atmosphere increased when compared to air-firing

• Experience gained from advanced recuperator equipping gas turbine (N2+CO2+H2O mixture)

650°C 850°C

Stainless Steels Nickel-based alloys Ceramic

16

Concept and Design: Geometry

• 4-end: recuperator in gas turbine intermediate hx in nuclear plant

Existing Heat exchanger from other applications

4 end: recuperator in gas turbine, intermediate hx in nuclear plant• 3-end: intermediate hx in externally fired gas turbine; steam boiler

Realisation Limitation 4-End 3-End

Single unit Compactness X XSingle unit Compactness X X

Enhanced Thermal stressXsingle unit Fouling X

SizeModular unit

SizeThermal stressFouling

X

17

Concept and Design: Sizing

Boundary Conditions

Volume4-End operation

Pressure drop: 0.02 bar (x2)

Tube diameter: 40 mm

Tube spacing: 80 mm

18

Conclusion

■ Severe process constraints on membrane feed air heater: temperature, pressure differential, flue gas composition, h t t f theat transfer rate

Minimal surface area attained for: High compression ratio High O2 separation ratio in membrane 4-end: low O2 concentration in recycled flue gas Conflict with process efficiency and membrane area p y

optimums: economical optimization required Pressure drop in flue gas stream should be kept low. p g p Sizing: 1500 m³ and 30000 m² can be reached

19

Acknowledgements

This work was conducted in the framework of the project OXYCOAL-AC and was funded by:

German Federal Ministry of Economics and

Ministry for Innovation, Science, Research and Technology of the State

of North Rhine WestphaliaTechnology

of North Rhine-Westphalia

RWE Power LindeE.ON Energie

WS Wä t h ikMAN T b Hit hi P WS WärmeprozesstechnikMAN Turbo Hitachi Power Europe