oxy-fuel process for hard coal with co capture · ¨denox and fgd prior to co 2 capture ¨denox and...

2nd Workshop

International Oxy-Combustion Research Network Hilton Garden Inn Windsor, CT, USA

25th and 26th January 2007

Hosted by:

Alstom Power Inc.

PRESENTATION - 16

Oxy-Fuel Process for Hard Coal with CO2 Capture A Part of the ADECOS Project

by: Prof. Alfons Kather Technical University of Hamburg-Harburg, Germany

2nd Int'l Oxy-Combusiton Workshop Page 1

Hamburg University of Technology

Oxyfuel Process for Hard Coal with CO2 Capture

A Part of the ADECOS Project

Presented by Alfons Kather

Funded by the German Federal Ministry of Economic Affairs within the COORETEC program

Partners:Vattenfall, ALSTOM, E.ON, RWE, SIEMENS, Hitachi, TU

Dresden, TU Hamburg-Harburg

Prof A KatherC Hermsdorf

M KlostermannK Mieske

Institute of Energy Systems

Institute of Thermal and Separation Processes

Prof R EggersD Köpke

IEAGHG International Oxy-Combustion Network, 2nd Workshop26th and 27th January 2007, Windsor (CT) USA

2

98 % CO22 % N2, Ar, O2,

NOx, SO2

Oxy-Fuel Process – Simplified Process Scheme

Air

Air SeparationUnit

N2

O2

Flue Gas Recycle

H2O

89 % CO211 % Ar, N2,

O2, …

2/3

1/3

Flue GasDrying

CO2 SeparationUnit

18 %

82 %

47 % CO253 % Ar, N2,

O2, …

all percentages asmolar percentage

Coalexhaust gas

► Introduction


3

Objective

Identification of key factorsthat are decisive for the

▸ feasibility

▸ economic efficiency

particularly with regard to realistic design boundaries

IV

I

III

Current Research Projects at the TUHH

► Introduction

II

CO2

Ar,N2,O2, …

Air

exhaust gas

Air SeparationUnit

N2

O2

Coal

Flue Gas Recycle

H2O

Flue GasDrying

CO2 SeparationUnit

almost pureCO2

Ash

4

III

CO2

Ar,N2,O2, …

Air

exhaust gas

Air SeparationUnit

N2

O2

Coal

Flue Gas Recycle

H2O

Flue GasDrying

CO2 SeparationUnit

almost pureCO2

Ash

Flue Gas Recycle

► Flue Gas Recycle


5

up to 26 g dust per m³ (@STP)

Flue Gas Recycle Design Considerations

Low-dust recycle

+ using high-efficiency axial-flow fan

− temperature limited to 190 °C,270 °C with fixed blades

mill-internal coal drying (300 °C)?

today’s feed water temperature at 300 °C heat sink for cooling?

− sensitive to load fluctuations (fixed blades)

− very large dust precipitatorand long recycle ducts

High-dust recycle

− requires low-efficiency radial-flow fan

+ more robust than axial-flow fans

+ very stable with respect to load fluctuations

+ small dust precipitator andshort recycle ducts

• no increased wear of boiler expected

+ temperature up to 350 °C possiblemill-internal coal drying

max. dust load:< 0.3 g/m³ @STP


AshCoal

up to 76 g dust per m³ (@STP)

max. dust load:76 g/m³ @STP

AshCoal

6

Factors influencing the Recycle Requirement

• Condition:tadiabatic, Air = tadiabatic, O2+Recycle

• Underlying assumptions:tAir = 320 °CtO2

= 25 °CtCoal = 40 °CO2-excess: 15 %O2-purity: 98 %

tRecycle

Q&

tO2

tCoal

tadiabatic


2008

2126

°C

tad,Air

22.69

25.40

MJ/kg

NCV

21.05.001.051.008.824.4358.70

7.4013.601.580.617.253.6365.93

H2OAshNSOHC

Composition (in % by mass)


7

Oxygen Concentration in the Combustion Atmosphere

First approach: Oxygen and recycled flue gas are mixed completely prior to the combustion

The oxygen concentration

▸ rises by reducing the recycle,

▸ is always above 21 %vol(in the range of interest),

▸ is a function of both recycle rate and oxygen excess


λ = 1.15

8

Combustion

CO2

Ar,N2,O2, …

AirII

exhaust gas

Air SeparationUnit

N2

O2

Coal

Flue Gas Recycle

H2O

Flue GasDrying

CO2 SeparationUnit

almost pureCO2

Ash

► Combustion


9► Combustion

Coal: Bituminous CoalO2-purity from ASU = 99.5 %tadiabatic = 2126 °C

λ = 1.15λ = 1.10

λ = 1.20

λ = 1.15

λ = 1.10

λ = 1.20

First combustionexperiments ( )

Oxygen Concentration in the Combustion Atmosphere of the first Combustion Experiments

10

Flue Gas Treatment and CO2 Separation

► Flue Gas Treatment and CO2 Separation

I

CO2

Ar,N2,O2, …

Air

exhaust gas

Air SeparationUnit

N2

O2

Coal

Flue Gas Recycle

H2O

Flue GasDrying

CO2 SeparationUnit

almost pureCO2

Ash


11

Impurities in the Flue Gas

• O2, NOX, SO2

▸ They may influence negatively the geological storage of the injected CO2by changing transport properties or by causing geochemical reactions

The maximum permissible concentrations for these impuritiesare still to be defined

• N2, Ar▸ They are inert components which have no significant impact

underground▸ They increase auxiliary power demand during liquefaction of the CO2

(other impurities cause the same, too)

▸ Removing them during air separation (to achieve purer O2)increases the auxiliary power demand of the air separation unit

Need for optimization between air separationand CO2-liquefaction (considering also air leakage)

► Flue Gas Treatment and CO2 Separation

12

70

80

90

100

0 1 2 3 4 5 6

Air leakage as % of flue gas (wet basis)

CO

2 con

cent

ratio

n in

dry

flue

gas

(v

ol%

)

O2-purity 95.0 %mol, O2-excess 15 % O2-purity 98.0 %mol, O2-excess 15 % O2-purity 99.5 %mol, O2-excess 15 % O2-purity 99.5 %mol, O2-excess 10 %

3

Impact of Impurities on the CO2-Concentration

▸ Fuel’s nitrogen and sulfur

▸Oxygen excess3 – 3.5% / 4.5 – 5% O2-residue

▸ Air separation unit98% O2-purity: 2% Ar

95% O2-purity: 3.8% Ar + 1.2% N2

▸ Air leakageapprox. 3 % of flue gas flow fora new conventional power plantup to 10 % over the years forpower plants in use

Air leakage is a major source for impurities and needs to be reduced by appropriate design

► CO2 Separation


13

Phase Equilibrium of Argon – CO2

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

102030405060708090

100110120130140

T1 T2 T3 T4

p

molar fraction in mol/mol

► CO2 Liquefaction

14

Phase Equilibrium of SO2 – CO2

20,00

30,00

40,00

50,00

60,00

70,00

80,00

90,00

100,00

10 30 50 70 90 110 130 150

Temperature in °C

Pres

sure

in b

ar

12

3 4 5 6

87

SO2CO2


Caubet 1901


15

Phase Equilibrium of O2 – CO2

0

20

40

60

80

100

120

140

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1

molar fraction O2 in mol/mol

p in

bar


16

Multi-Component Phase Equilibrium O2 – N2 – CO2


D. Köpke, TUHH, 2006

N2 (mol/mol)

O2 (m

ol/mol)

CO2

(mol

/mol

)


17

Flue Gas Treatment for Low Purity Requirements

<1 ppm34 ppm24.62.925.247.3Stack Gas

439 ppm0.40.4450 ppm0.398.8CO2

597 ppm0.35.00.65.089.1Flue Gas, dry

NOxSO2O2ArN2CO2

1

31

2

3

2

All valuesas molar-%

• For low purity requirements of the liquefied CO2

DeNOx and FGD treat only 3 – 4 % of the total flue gas volume (referred to the total flue gas before the recycle branching)

► Flue Gas Treatment

18

Flue Gas Treatment for Higher Purity Requirements

• For higher purity requirements of the liquefied CO2

DeNOx and FGD prior to CO2 capture

DeNOx and FGD treat now 30 % of the total flue gas volume (referredto the total flue gas before the recycle branching)

<1 ppm<1 ppm24.62.825.247.3Stack Gas

43 ppm57 ppm0.4449 ppm0.399.2CO2

60 ppm47 ppm5.00.65.089.4Flue Gas, dry

NOxSO2O2ArN2CO2

1

3

2



31

2


19

Flue Gas Treatment for Highest Purity Requirements

<1 ppm<1 ppm24.72.825.247.3Stack Gas

20 ppm57 ppm0.4449 ppm0.399.2CO2

29 ppm47 ppm5.00.65.089.4Flue Gas, dry

NOxSO2O2ArN2CO2

• For highest purity requirements of the liquefied CO2

DeNOx is now needed before recycle branching

Even higher purity requirements would result in processes like adistillation plant with still higher power demands

1

3

2



3

2

1

20

Test CO2 Separation Plantat the Institute of Energy Systems

compressor

condenser

water

condenser

phase separator

water

adsorption

CO2-condenser

coolingunit

collecting vesselgas

withdrawalprobe

collecting vesselliquid

entrained flow

reactor

phase separator

► CO2 Separation

Up to now: Phase Equilibria - This test plant: Kinetic Behavior


21

Overall Process

► Overall Process

IV

CO2

Ar,N2,O2, …

Air

exhaust gas

Air SeparationUnit

N2

O2

Coal

Flue Gas Recycle

H2O

Flue GasDrying

CO2 SeparationUnit

almost pureCO2

Ash

22

• Simulation of the overall process

▸Definition of the global parameters supported by subprojects andindustry

▸Commercial software: Ebsilon®, Aspen®

▸Continuous integration of the results of the subprojects

▸Use of state of the art technology

• Objectives

▸Feasibility

▸Process optimization (overall energetic efficiency)

▸Clarification of important details (e.g. CO2 purity, part-load behavior)

▸Economic efficiency

Overall Process

► Overall Process


23

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

p-T-diagram for Single-StageCryogenic CO2 Liquefaction

► CO2 Separation

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

90%

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

90%

95%

Conditions:Air leakage: 2.0 %O2-purity: 99.5 %

Range of interest

24

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

p-T-diagram for Single-StageCryogenic CO2 Liquefaction

► CO2 Separation

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

90%

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate80%

90% CO2

Purity

95% CO2

98% CO2

90%

95%

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

Capture Rate

90%

90% CO2

Purity

95% CO2

98% CO2

-60 -50 -40 -30 -20 -10 0 100

10

20

30

40

50

60

70

80

90

100

Temperature (°C)

Pres

sure

(bar

)

90% CO2

Purity

95% CO2

98% CO2

Capture Rate

90%

Conditions:Air leakage: 2.0 %O2-purity: 99.5 %

Range of interest

133.5 kWh/tCO2↓

133.7 kWh/tCO2↓136.6 kWh/tCO2↓


25

Overall Energy Demand

Requirements: 90 % capture rate and CO2-purity > 95%

► CO2 Separation

26

Comparison of Different Processes(1% Leakage, Capture Rate 90%, Purity > 98,5%)

► Overall Process

36.6%

45.7%

38.1%36.9%

Reference Plant Simple Heat Recovery Optimised Process Optimised Processwith 3-Column-ASU

Net Efficiency

Spezifische Em Emissions in gCO2/kWhNetto

748

93 92 89


27

Thank you for your attention!

oxy-fuel process for hard coal with co capture · ¨denox and fgd prior to co 2 capture ¨denox and...

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