CO2 Quality and Other Relevant Issues

CO Quality and Other CO2 Quality and Other Relevant Issues

Oxyfuel Process(Post-Combustion Capture)(Pre-Combustion Capture)

Institute ofEnergy Systems

Introduction and Objectives of the MeetingA. Kather

Energy Systems

Hamburg University of Technology

2nd Working Group Meeting on CO2 Quality and Other Relevant Issues

7th September 2009, Cottbus

CO2 purity

Introduction• Introduction

▸What are the barriers for a successful deployment of the OxyfuelProcess?

▸Why considering the impurities?

• General Boundary Conditions of the Oxyfuel Process

▸Flue gas recycle demand; O2 excess; O2 concentration

• Impact of Impurities on the CO2 Concentration

▸Where do the impurities come from?

• R&D Project COORAL

▸Definition of required CO2 purity

• Possibilities to increase CO2 Purity

2

CO2 purity











3

What are the barriers for a successful deployment of the Oxyfuel Process?

Combustion: no problem• Combustion: no problem

▸higher oxygen content in comparison to air case

▸enhanced NOx reduction in comparison to air case▸enhanced NOx reduction in comparison to air case

• Efficiency of overall process: very important

▸The Oxyfuel Process is competing with other Capture Processes▸The Oxyfuel Process is competing with other Capture Processes

▸Oxyfuel will only succeed if its efficiency is better than Post-Combustion Capture

• CO2 Purity: very important

▸Purities between 85% and 99.9% are achievable

▸An increase in purity influences CAPEX, OPEX and capture rate and thus the economy of the process

O f l ill l d if it ll t i l th l f▸Oxyfuel will only succeed if its overall cost is lower than or equal as for the other capture technologies

4► Introduction

CO2 purity











5

Why considering the impurities?

Directive 2009/31/EC ( 23 April 2009) Article 12Directive 2009/31/EC ( 23 April 2009) Article 12

CO2 stream acceptance criteria and procedure

1. A CO2 stream shall consist overwhelmingly of carbon dioxide. To this end, no waste or other matter may be added for the purpose of disposing of that waste or other matter. However, a CO2 stream may contain incidental associated substances from the source, capture or injection process and trace substances added to assist in monitoring and verifying CO2 migration. Concentrations of all incidental and added substances shall be below levels that would:

(a) adversely affect the integrity of the storage site or the relevant transport infrastructure;transport infrastructure;

(b) pose a significant risk to the environment or human health; or

( ) b h th i t f li bl C it l i l ti(c) breach the requirements of applicable Community legislation.

6► Introduction


CO Purity: very important• CO2 Purity: very important

▸Purities between 85% and 99.9% are achievable

▸An increase in purity influences CAPEX OPEX and capture rate and▸An increase in purity influences CAPEX, OPEX and capture rate and thus the economy of the process

▸Oxyfuel will only succeed if its overall cost is lower than other capture technologies

7► Introduction


CAPEX OPEX and capture rate 15:30 17:15• CAPEX, OPEX and capture rate 15:30 – 17:15

• Requirements for the storage site 13:15 – 15:15

Geologists must define the concentration limits▸Geologists must define the concentration limits

▸Will there be different limits for different storage options?

Requirements for the transport (mainly pipeline) 11:55 12:20• Requirements for the transport (mainly pipeline) 11:55 – 12:20

▸Will there be different limits for the different transport options?

Requirements for the recycled flue gas• Requirements for the recycled flue gas

▸ Internal question of boiler design considerations, mainly related to corrosion

• Requirements for health, safety and environmental (HSE) reasons

▸Not subject of today’s discussion

8► Introduction

CO2 purity











9

Oxyfuel Process – simplified process scheme

Air SeparationUnit

N

Flue Gas Recycle

2/3Flue Gas

Air

15 % CO26 % H2O

76 % N2

66 % CO226 % H2O8 % Ar, N2,

N2

O289 % CO211 % N2, Ar,

O

1/3

Drying

23 % Ar, O2, …

, 2,O2, …

H2O

O2, …

Coalexhaust gas

18 %47 % CO253 % Ar, N2,

O2, …

exhaust gas

CO2 Separation

82 %nearly pureCO2

all percentages as

98 % CO22 % N2, Ar, O2,

NOx, SO2

10

Unitall percentages asmolar percentage

► General Boundary Conditions of the Oxyfuel Process

Factors influencing the recycle requirement (I)

Main boundary conditions for the boiler:

• Steam temperature in the boiler wall is limited to 470 °C due to material reasons

• Flue gas temperature at the exit of the combustion chamber should not exceed the temperature in the air case (slagging)

• Both conditions can approximately be fulfilled (for tRecycle < 400°C) if the condition

t = t

1250 °C1250 °C

tadiabatic, Air = tadiabatic, O2+Recycle

is used.tRecycle

tO2

tadiabatic

11

Q&tCoal

tadiabatic


Factors influencing the recycle requirement (II)

tRecycle

tO

Q&

tO2

tCoal

tadiabatic

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

man

d, , 2 y

• Underlying assumptions:tAir = 320 °C

25 °C

recy

cle

tO2= 25 °C

tCoal = 40 °CO2 excess: 15 %

12

2

O2 purity: 98 %


CO2 purity











13

Where do the impurities come from?

▸ Fuel’s nitrogen and sulfur SOx, NOx

Durch konstruktive Maßnahmen zu erzielender Falschluftanteil

► Impact of impurities on the CO2 concentration 14

)

Pollutant formation

5

6at

ion

(dry

)AirOxyfuel (treated recycle) Oxyfuel (untreated recycle) SO

3

4

conc

entr

a Oxyfuel (untreated recycle)

SONO

SO2 untreated

1

2

ndar

dize

d

Air

NOx treated

SO2 treatedNOx untreated

00 0,2 0,4 0,6 0,8 1

standardized pollutant formation rate

stan

Air

p

Effects: - smaller specific flue gas mass flow - increase of flue gas density

15

g y- increase of water content in the flue gas

► Impact of impurities on the CO2 concentration



N l ll l d NO i d d▸ Nearly all recycled NOx is reduced

▸ No sense to install DeNOx plant before the flue gas recirculation

▸Only a small part of SO2 is reduced

1616► Impact of impurities on the CO2 concentration

SO

Low temperature corrosion

SOx

• higher SOx concentration due to missing nitrogen (factor 4 - 5)

• SO3 formation promoted by higher concentrations of oxygen and water 3 p y g yg

+20....40 K higher acid dew point temperature of the flue gas

Dampfdruckkurve von Schwefelsäure

175

200

vapour pressure curve of sulphuric acid

100

125

150

erat

ur in

°C

10 ppmv

100 ppmv

Oxyfuelratu

re

25

50

75

Tem

p

pp

Air

Oxyfuel

tem

per

1717

01,0E-06 1,0E-05 1,0E-04 1,0E-03 1,0E-02Druck in bar0,001 0,01 0,1 pH2SO4

in mbar 10


Untreated recycle

to100°C feed water

preheating

FGD

76°C

350°C

76°C

H2O

CO2 capture

O

Coal

preheating

160°C

320°C55%

O214%347°C 80°C

degree of dust removal in recycle

Pprimary fanMW

Psecondary fanMW

PFGDMW

PFGD fanMW

ΣPMW

ηgross%

completely 2.0 1.8 3.5 1.5 8.8 50.2

• Elevated classifier exit temperature of 160 °C necessary (above acid dew point)

• No full load operation in air case due to SCR and FGD restrictions

18

• No full load operation in air case due to SCR and FGD restrictions


Treated recycle

350°C

320°C

feed water preheating to100°C

FGD

73°C

H2O

coal53%

350 C76°C

preheating toCO2 capture

260°C15%100°C

P P P P ΣP

O2

80°C

Pprimary fanMW

Psecondary fanMW

PFGDMW

PFGD fanMW

ΣPMW

ηgross%

1.1 0.3 3.5 5.0 9.9 49.4

• Classifier exit temperature can be maintained at 100 °C• No full load operation in air case due to SCR restrictions (not FGD)

19

No full load operation in air case due to SCR restrictions (not FGD)


Residual oxygen in flue gas

10In the Oxyfuel process the following applies for the residual oxygen in the flue gas:

10

8

vol. %(dry)

17 %18 %19 %20 %

oxygen excess for combustion

▸ The smaller the recycle rate the larger the concentration of residual oxygen

6

7

12 %13 %14 %15 %16 %17 %

resi

dual

ox

ygen

yg

▸ The concentration of residual oxygen is always significantly higher than in the 3

4

5 11 %r

≈ 4,8

air casealways significantly higher than in the air case (4.8 vs. 2.8 vol.-%, dry) 50 55 60 65 % 75

2

recycle rate

air case



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 %


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

100

ue g

as

p y ,

Durch konstruktive Maßnahmen zu erzielender

2

90

tion

in d

ry fl

uvo

l%)

Falschluftanteil

80

O2 c

once

ntra

t (v

700 1 2 3 4 5 6

CO

Air leakage as % of flue gas (wet basis)






100

ue g

as

p y ,


2

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

90

tion

in d

ry fl

uvo

l%)

Falschluftanteil95% O2-purity: 3.8% Ar + 1.2% N2

80

O2 c

once

ntra

t (v

700 1 2 3 4 5 6

CO



Energy demand for ASU and CO2 separation

Boundary conditions: capture rate = 90 %, CO2-purity > 96%, 87 % of oxygen delivered by ASU, South African hard coal, 2 % leakage air

14 %

10 %

12 %

poin

ts

CPU ASU

6,9 %

5 5 %

3,9 %

4,1 %4,1 %6 %

8 %

ncy l

oss

in %

-p

5,5 %4,4 %

2 %

4 %

effic

ien

O2 purity - ASU technology

0 %99,5%-conventional 95% - multi reboiler 95% - multi column

23

Overall net efficiency increase by decreased O2 purity by approx. 2.3 %-points






100

ue g

as

p y ,


2


90

tion

in d

ry fl

uvo

l%)

Falschluftanteil95% O2-purity: 3.8% Ar + 1.2% N2

80

O2 c

once

ntra

t (v

700 1 2 3 4 5 6

CO






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 %2


100

ue g

as

Air Leakage95% O2-purity: 3.8% Ar + 1.2% N2

▸ Air leakageapprox 3 % of flue gas flow for

90

tion

in d

ry fl

uvo

l%)

Air Leakage

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

80

O2 c

once

ntra

t (vp p

Air leakage is a major source of impurities and needs to be

d d b i t d i

700 1 2 3 4 5 6

CO

25

reduced by appropriate design Air leakage as % of flue gas (wet basis)


Impurities in the Flue Gas

• N2, Ar▸ Sources: oxygen, air ingress,…

▸ Inert components which have no significant impact underground▸ Inert components which have no significant impact underground

▸ Increase auxiliary power demand for liquefaction of the CO2(as shown above this is not very much)

▸ Removing them during air separation (to achieve purer O2)increases the auxiliary power demand of the air separation unit (as shown above this is very much)

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


Impurities in the Flue Gas

• O2, NOX, SO2 ,CO , Hg, Cl▸ May negatively influence the geological storage site by causing

geochemical reactions or the transport in pipelinesg p p p

The maximum permissible concentrations for these impuritiesare still to be defined


CO2 purity











28

Project COORAL

COORALCO2-Reinheit für Abtrennung und Lagerung

(CO2 purity for capture and storage)

• Partners:

▸ BGR, BAM, DBI, MLU, TUHH

▸ Industry: Alstom, E.ON, Vattenfall, EnBW, VNG

• Includes the whole CO chain from production to storage:• Includes the whole CO2 chain from production to storage:

Transport Injektion

I II III

Production

Storage

IV

29

Storage

► R&D project COORAL

COORAL - Objectives

• Estimation of impurities in CO2 (Post-Combustion, Oxyfuel, Pre-Combustion)

• Possibilities to influence the CO2 impurities by

▸ operation of the power plant▸ operation of the power plant

▸ CO2 separation processes (Post-Combustion, Oxyfuel, Pre-Combustion)

▸ CO2 treatment (mainly Oxyfuel)

• Examination of the effects caused by impurities on

▸ the transport chain

▸ the injection chain

▸ the geological site (geochemical reactions)

O ti i ti b t i d l t ifi d d• Optimisation between economic and plant-specific demands

Definition of the req ired CO p rit for capt re and storage

30

Definition of the required CO2 purity for capture and storage


Expected impurities in separated CO2

Component Post-Combustion Oxyfuel Pre-CombustionN2 Yes Yes YesN2 Yes Yes YesO2 Yes Yes (Yes)Ar Yes Yes YesH2O Yes Yes YesNO Y Y NNOX Yes Yes NoSOX Yes Yes NoNH3 Yes No NoHg, . . . No Yes YesgH2 No No YesH2S No No YesHCN No No YesCH No No YesCH4 No No YesCO Yes Yes YesCOS No No YesResidues from Washing Yes No Yes

31► R&D project COORAL

Scenarios of Expected Impurities - Post-Combustion

• Post I

▸ 99,93 Vol.-% CO2

• Post II

▸ 99,92 Vol.-% CO2

• Post III

▸ 99,81 Vol.-% CO2

▸ 150 ppm O2

▸ 450 ppm N2 + Ar

20 NO

▸ 150 ppm O2

▸ 450 ppm N2 + Ar

20 NO

▸ 300 ppm O2

▸ 900 ppm N2 + Ar

40 NO▸ 20 ppm NOX

▸ 10 ppm SO2

▸ 100 ppm H2O

▸ 20 ppm NOX

▸ 10 ppm SOX

▸ 100 ppm H2O

▸ 40 ppm NOX

▸ 20 ppm SOX

▸ 600 ppm H2O100 ppm H2O

▸ 10 ppm CO

100 ppm H2O

▸ 10 ppm CO

▸ 50 ppm NH3 *

600 ppm H2O

▸ 20 ppm CO

32

* approximation.


Scenarios Expected Impurities - Pre-Combustion

• Selexol

▸ 97,95 Vol.-% CO2

• Rectisol

▸ 99,7 Vol.-% CO2

▸ 1,0 Vol.-% H2

▸ 0,9 Vol.-% N2

300 A

▸ 20 ppm H2

▸ 0,21 Vol.-% N2

150 A▸ 300 ppm Ar

▸ 100 ppm H2S + COS

▸ 600 ppm H2O

▸ 150 ppm Ar

▸ 20 ppm H2S + COS

▸ 10 ppm H2Opp 2

▸ 400 ppm CO

▸ 100 ppm CH4

pp 2

▸ 400 ppm CO

▸ 100 ppm CH4

▸ 200 ppm Methanol


Scenarios of Expected Impurities - Oxyfuel

• Oxyfuel I

(Zero Emission)

85 0 V l % CO

• Oxyfuel II • Oxyfuel IV

(Distillation)

99 94 V l % CO

• Oxyfuel III

(Concentration)

98 0 % CO▸ 85,0 Vol.-% CO2

▸ 4,70 Vol.-% O2

▸ 5,80 Vol.-% N2

▸ 99,94 Vol.-% CO2

▸ 100 ppm O2

▸ 100 ppm N2

▸ 98,0 % CO2

▸ 0,67 % O2

▸ 0,71 % N2, 2

▸ 4,47 Vol.-% Ar

▸ 100 ppm NOX

pp 2

▸ 100 ppm Ar

▸ 100 ppm NOX

, 2

▸ 0,59 % Ar

▸ 100 ppm NOX

▸ 50 ppm SO2

▸ 20 ppm SO3

▸ 100 ppm H O

▸ 50 ppm SO2

▸ 20 ppm SO3

▸ 100 ppm H O

▸ 50 ppm SO2

▸ 20 ppm SO3

▸ 100 ppm H O▸ 100 ppm H2O

▸ 50 ppm CO

▸ 100 ppm H2O

▸ 50 ppm CO

▸ 100 ppm H2O

▸ 50 ppm CO


CO2 purity











35

p-T-diagram for Single-StageCryogenic CO2 Liquefaction

80

90

100

80

90

100

90% CO80

90

100

90% CO80

90

100

90% CO80

90

100

90% CO80

90

100

90% CO

Conditions:Air leakage: 2.0 %

60

70

80

ar)

60

70

80

ar)

90% CO2

95% CO260

70

80

ar)

90% CO2

95% CO260

70

80

ar)

90% CO2

95% CO260

70

80

ar)

90% CO2

95% CO260

70

80

ar)

90% CO2

95% CO2

O2-purity: 99.5 %

40

50

60

Pres

sure

(b

40

50

60

Pres

sure

(b

Purity

95% CO2

98% CO2

40

50

60

Pres

sure

(b

Purity

95% CO2

98% CO2

40

50

60

Pres

sure

(b

Purity

95% CO2

98% CO2

40

50

60

Pres

sure

(b

Purity

95% CO2

98% CO2

40

50

60

Pres

sure

(b

Purity

95% CO2

98% CO2

20

30

P

20

30

P

20

30

P

90%20

30

P

90%

95%20

30

P

90%20

30

P

90%

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

10Capture Rate80%

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

10Capture Rate80%

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

10Capture Rate80%90%

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

10Capture Rate80%90%

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

10Capture Rate

90%

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

10Capture Rate

90%Range of interest

36

Temperature (°C)

► Possibilities to increase CO2 purity

Temperature (°C)Temperature (°C)Temperature (°C)Temperature (°C)Temperature (°C)

Impact of distillation on overall power demand for CO2 capture

C id t i i i l

ure in M

W

• Consider a certain minimal temperature level (e. g. -40 °C):

▸higher flue gas pressure

or CO

2captu▸higher flue gas pressure

necessary to achieve a similar CO2 capture rate

er dem

and fo▸ increase in power demand

Overall po

we

• The additional distillation reduces the efficiency of the overall power plant process by

CO2 capture rate

Ooverall power plant process by 0.2 %-pts. for a capture rate of 90 %.

37► Possibilities to increase CO2 purity

CO2 liquefaction plantphotos


Experiments with Oxyfuel flue gas

60

7093%

95%2 phase region

• Oxyfuel Flue Gas:Combustion of hard coal in CO2

50

60 95%

96%

97%

95%

90%

80%mixture with 30 %vol O2, residual oxygen ~4 %vol

• Experiments at different

30

40

p in

bar 98%

95%

dew point curve

Experiments at different pressure and temperature conditions

C iti f d

10

20

capture ratepurity of liquid CO2

vapor

▸Composition of vapour and liquid phase

▸Experimental experience

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

T in °C

purity of liquid CO2Experiments

p p

▸Sulphur and nitrous components


CO2 purity











40Thank you for your attention!

CO Quality and Other CO2 Quality and Other Relevant Issues

Oxyfuel Process(Post-Combustion Capture)(Pre-Combustion Capture)

Institute ofEnergy Systems

Introduction and Objectives of the Meeting

Th k f A. Kather

Energy Systems

Thank you for your attention!

Hamburg University of Technology

2nd Working Group Meeting on CO2 Quality and Other Relevant Issues

7th September 2009, Cottbus

CO2 Quality and Other Relevant Issues

Documents

Transcript of CO2 Quality and Other Relevant Issues