Oxy-Pulverised Coal Combustion Technology for Power ... · • Double reboiler design 2 ... Booster...

Oxy-Pulverised Coal Combustion Technology for Power Generation with CO 2 Capture

(Fundamental Engineering Principles in Understandin g the Technology)

Stanley SantosIEA Greenhouse Gas R&D Programme

Chemical Engineering DepartmentNewcastle University

11th March 2010

Overview• Introduction – Oxyfuel Combustion• Overview to the Boiler and Burner Development

• Recycle of Flue Gas

• Overview to the Oxygen Production• 2 column design – “Oxyton Cycle”• Double reboiler design

2

• Double reboiler design

• Overview to the CO 2 Processing Unit• NOx and SOx reaction during compression• Removal of Inerts

• Concluding Remarks

3

OXY-PULVERIZED COAL COMBUSTION FOR POWER GENERATION

Introduction

IntroductionOxyfuel Combustion for Coal Fired Power Plant with CO2 Capture

4

Where Can You Extract the Recycled Flue Gas (RFG)(For some practical application using low S coal)

5

6

IMPACT OF RECYCLE FLUE GAS TO THE BOILER OPERATION

Overview to Boiler and Burner Development

Factors affecting Recycle Ratio

• Critical factors affecting the optimum amount of recycled flue gas• Burner and boiler design (heat transfer and flame

stability – oxygen distribution through burner)

7

stability – oxygen distribution through burner)• Air ingress• Purity of oxygen from the ASU• Coal type• Level of moisture content in comburent• Comburent (oxidant) temperature

7

Mass balance calculation should have a firm basis!! !

• Primary control of the boiler is in the oxygen content of the flue gas (~3.5%vd)

• Requirements of the coal mill should define the quality of the primary RFG

• Defining how the burners should operate is a

8http://www.ieagreen.org.uk

• Defining how the burners should operate is a required step… We need to establish criteria that would result to good combustion. An important element to your process control.

• Criteria for heat transfer profile should define the quality of secondary RFG• Molar ratio of the oxidant• O2 concentration in the secondary

comburent

8

Data from ANL studies (1989)

Optimum Recycle Ratio

~29%

~31%

9http://www.ieagreen.org.uk 9

~48%

32% - 36%

~48%

~31%

Impact of the moisture content of the Recycled Flue Gas

70.0

75.0

80.0

85.0

in t

he

Flu

e G

as

fro

m B

oil

er

[%v

-w

et]

10http://www.ieagreen.org.uk 10

50.0

55.0

60.0

65.0

70.0

26.5 28.0 29.5 31.0 32.5 34.0 35.5 37.0 38.5 40.0 41.5

CO

2 in

th

e F

lue

Ga

s fr

om

Bo

ile

r [%

v

O2 in the comburent [%v -dry]

Wet RFG (H2O ~ 33.4%v)

Dried RFG (H2O ~ 18.6%v)

Data from ANL studies (1987)

Flame Description – Impact of Recycle Ratio(Courtesy of IFRF)

11Figur e 3(c): O2-RFG flame with recycle ratio = 0.76 Figure 3(d): O 2-RFG flame with recycle ratio = 0.52

Figure 3(a): normal air -fired operation Figure 3(b): O 2-RFG flame with recycle ratio = 0.58

Coal Flame Photos:Air Fired vs Oxy-Fired(Courtesy of IHI)

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Air mode （（（（O2：：：：21%））））

Oxy mode（（（（O2：：：：21%）））） Oxy mode（（（（O2：：：：30%））））

Coal Flame Photos:Impact of Recycled Flue Gas(Courtesy of IFRF)

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Recycle Ratio = 0.76Recycle Ratio = 0.58(~ 0.61 include the CO 2 to transport coal)

Normalised Convective & Radiativeheat flux – Russian Coal - Dry Recycle

Dry Oxyfuel Operation Normalised to Air OperationPeak Radiation Flux, Convective heat transfer and c alculated flame temperature

Russian coal

1.2

1.4

1.6

Nor

mal

ised

Adi

abat

ic

Fla

me

Tem

pera

ture 1.2

1.4

1.6

Nor

mal

ised

Rad

iativ

e an

d C

onve

ctiv

e H

eat F

lux

Normalised Flame Temperature (calculated)

Peak Normalised Heat Flux (measured)

Normalised Convective HTC (measured)

Measured Convective Heat Transfer Coefficient indicates 74% Recycle is "Air-equivalent"

Measured Peak Radiative data indicates 74%

New Build Retrofit Avoid

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0.4

0.6

0.8

1

1.2

60% 65% 70% 75% 80%Effective Recycle Ratio

Nor

mal

ised

Adi

abat

ic

Fla

me

Tem

pera

ture

0.4

0.6

0.8

1

1.2

Nor

mal

ised

Rad

iativ

e an

d C

onve

ctiv

e H

eat F

lux

Calculated dry oxyfuel adiabatic flame temperatures are equivalent to air at 69% recycle

data indicates 74% Recycle is "Air-equivalent"

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Considerations in the Boiler Operation

O2 Purity and Air Ingress

(a.) Why not 99+% O 2 Purity(b.) Air Ingress… A Challenge for the Operator

Issue of Air Ingress (Air In-leakage)

Air Ingress in the boiler is a fact of life!!!

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fact of life!!!

1st Large Scale Demonstration of Oxy-Coal Combustion (35MWth) – What Are the Lesson Learned...

Problem with Air Ingress1st Large Scale Oxy-Coal Combustion Burner Test Experience - International Combustion Lt d.

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� 30 MWth Low NOx burner

� Because of Air Ingress the desired CO2

composition (only ~ 28% dry basis).

� Air Ingress in boilers

� approx. 3 % of flue gas flow fora new conventional power plant

� up to 10 % over the years forpower plants in use

CO2 Recovery Depends On Feed Composition

Recovery

0.4

0.6

0.8

1

18

At -55°C, 30 barFeed Composition

0

0.2

0.4

0 0.2 0.4 0.6 0.8

19

CHALLENGES TO THE DESIGN AND ENGINEERING OF THE AIR SEPARATION UNIT

Oxygen Production

Challenges to Oxygen Production• As of today, the only available technology for

oxygen production in large quantities is cryogenic air separation .

• Advances and Development in ASU could result to 25% less energy consumption.

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result to 25% less energy consumption.• These design would be based on either a

3 column design or dual reboiler design.

• Challenges are:• Cost of production of oxygen (energy

consumption)• Utilisation of nitrogen within power plant.

Air Separation PlantsSimplified Air Separation Process

Bey/L/092009/Cottbus.pptLinde AG Engineering Division 21

Air compression, -precooling and -purification

heat exchange, refrigeration,rectification and internal compression

productdistribution

Cryogenic Air Separation – Capacity Increase


1902 :5 kg/h(0,1 ton/day)

2006 :1,250 Mio kg/h(30.000 ton/day)

Air Separation Plants – Shell „Pearl“ GTL Project Qatar30.000 tons/day Oxygen


Process Description: Oxygen Supply

• Optimum oxygen purity suggested:• 95% - 97%• @ 95% O2 you will have 2% N2 and 3% Ar

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• higher purity not worthwhile due to:o Excess O2 requirement (19%)o Boiler air in leakage (1%)o ESP air in leakage (2%)

30 years of continuous Cryogenic ASU improvements

1,5

2,0

2,5

Nor

mai

lzed

Ene

rgy

Effi

cien

cy

2»/

kWh)

1998

2001 2003

1998

2001 2003

IEAGHG International Oxy-Combustion Network 05-03-2008PROPRIETARY World leader in industrial and medical gases 25

0,5

1,0

0 1 000 2 000 3 000 4 000 5 000

Normalized Productivity (« O2 »/m2)

Nor

mai

lzed

Ene

rgy

Effi

cien

cy(«

O2

1971

1976

1988

1971

1976 1971-2003� Energy efficiency : x 1,75� Productivity : x 2,8

Specific energy of separation in kWh per ton of oxygen

200

kWh/t

160

-20%� Impact on HHV

efficiency : +1 %

� Impact on COE :- 3.5%

IEAGHG International Oxy-Combustion Network 05-03-2008PROPRIETARY World leader in industrial and medical gases 26

Theoretical energy of separation (O2&N2)

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Losses 150

2007

50

110

2008

Tonnage Air Separation PlantsMega Plants for new Applications

Introduction to Different Cryogenic Air Separation Process


Air Separation Process Conventional Design (mit Einblaseturbine)

tausch

er

PG

AN

GO

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e

5.5

-6 b

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1.0

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ar


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-5.8

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� Oxygen: 95%, gaseous, at ambient pressure

Features:

� PNitrogen: up to 30% of airflow available

Air Separation Process Advanced Alternative Design (“Dual Reboiler”-Design)

me

tausche

r

GO

X

Nie

derd

ruckko

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ne

4.5

bar

1.0

5 b

ar


Wä

rm

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ine

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den

sato

r 2

Ho

ch

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nn

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UK

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Ko

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nsa

tor

1

4.3

bar


Features:

� reduced process air pressure

� reduced power consumption

Air Separation Process Advanced Alternative Design (3-column Design)

rme

tausch

er

GO

X

4.5

bar

1.0

5 b

ar

sato

r 2

ne 2


Wä

r

Booste

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Kond

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Features:

� reduced process air pressure

� reduced power consumption

Energy demand for ASU and CO2 separation

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

3,9 %

4,1 %8 %

10 %

12 %

14 %

effi

cie

ncy

loss

in %

-poi

nts

CPU ASU

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Overall net efficiency increase by decreased O 2 purity by approx. 2.3 %-points

► Impact of impurities on the CO 2 concentration

O2 purity - ASU technology

6,9 %

5,5 %

4,4 %

4,1 %

0 %

2 %

4 %

6 %

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

effi

cie

ncy

loss

in %

What are the remaining issues…• ~10,000 TPD of O 2 is required for a 500MWe

(net) oxy-coal power plant with CCS.• This means that you will need 2 single trains of 5000

TPD ASU

• Remaining Issues

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• Remaining Issues• What could be the maximum capacity of oxygen

production per train?• Operation flexibility (i.e. load following, etc…)• What will you do about the large volume of Nitrogen

produced from this ASU?

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Where are the other gaps in R&D for oxygen production?• Non-conventional oxygen production

• ITM – ions transport membrane (Air Products)• OTM – oxygen transport membrane (Praxair)• CAR – ceramics autothermal recovery (Linde /

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• CAR – ceramics autothermal recovery (Linde / BOC)

• Chemical Looping Combustion

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35

WHAT ARE THE KEY ISSUES IN DETERMINING THE DESIGN PRINCIPLES OF A CO2 PROCESSING UNIT

CO2 Processing Unit

Challenges to CO 2 Processing Unit• The CO2 processing unit could be very competitive

business (an important growth area) for industrial gas companies.

• Challenges are:• Demand of the quality requirements of the CO2 from the power plant

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• Demand of the quality requirements of the CO2 from the power plant for transport and storage. What are the Required Specification?

• Further recovery of CO2 from the vent will make oxyfuel more competitive if high recovery of CO2 is required!

• Further recovery of energy through integration with ASU or boiler would provide further energy savings.

• Need a large scale demonstration of the CO 2 processing unit using impure CO 2 as refrigerant.

Purification of Oxyfuel-Derived CO2 for Sequestration or EOR

• CO2 produced from oxyfuel requires purification• Cooling to remove water• Inert removal• Compression

• Current design has limitations

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• Current design has limitations• SOx/NOx removal• Oxygen removal• Recovery limited by phase separation

• Necessary to define CO 2 quality requirement!!!

Air Product’s “Sour Compression Process”“Sour Compression Process”

NOx SO2 Reactions in the CO2Compression System� We realised that SO 2, NOx and Hg can be removed in the CO 2

compression process, in the presence of water and o xygen.

� SO2 is converted to Sulphuric Acid, NO 2 converted to Nitric Acid:

– NO + ½ O2 = NO2 (1) Slow– 2 NO2 = N2O4 (2) Fast– 2 NO2 + H2O = HNO2 + HNO3 (3) Slow

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– 2 NO2 + H2O = HNO2 + HNO3 (3) Slow– 3 HNO2 = HNO3 + 2 NO + H2O (4) Fast– NO2 + SO2 = NO + SO3 (5) Fast– SO3 + H2O = H2SO4 (6) Fast

� Rate increases with Pressure to the 3 rd power– only feasible at elevated pressure

� No Nitric Acid is formed until all the SO 2 is converted

� Pressure, reactor design and residence times, are i mportant.

CO2 Compression and Purification System –Removal of SO2, NOx and Hg

1.02 bar 30°C67% CO28% H2O25% InertsSOx NOx

30 bar to DriersSaturated 30°C76% CO224% Inerts

� SO2 removal: 100% NOx removal: 90-99%

BFW15 bar

30 bar

Water

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NOx

Dilute H 2SO4 HNO3

Hg

BFW

Condensate

cw

30 bar

cwcw

Dilute HNO 3

Air Product’s Suggested Process Design for Suggested Process Design for Various Purity…

76%mol CO2

24% inerts (~ 5 - 6% O2)

96%mol CO2

4% inerts (~ 0.95% O2)

25%mol CO2

75% inerts (~ 15% O2)

72%mol CO2

28% inerts(~ 5 - 6% O2)

98%mol CO2

2% inerts(~ 0.6% O2)

25%mol CO2

75% inerts(~ 19% O2)

25%mol CO2

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72%mol CO2

28% inerts(~ 5 - 6% O2)

99.999%mol CO2

0.001% inerts(~ .0005% O2)

25%mol CO2

75% inerts (~ 15% O2)

72%mol CO2

28% inerts(~ 5 - 6% O2)

99.95%mol CO2

0.05% inerts(~ .01% O2)

25%mol CO2

75% inerts(~ 15% O2)

Air Product’s “Use of Membrane for further

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“Use of Membrane for further recovery of oxygen and CO2”

Use of Membrane to recover CO2 and O2 at the vent

Vent:7% CO293% inerts (~10% O2)

Product

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Product96% CO24% inerts (~0.75% O2)

Issues involving CO 2

purification process• We need to establish what is appropriate and

acceptable level of impurities in our CO 2 based on aspects of:• Health, Safety and Environment considerations

o What are the regulations to be established without disadvantaging any capture technology (What is acceptable!!!)

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technology (What is acceptable!!!)

• Quality specifications defined by transportation/delivery of CO2 to the storage sites

o Also to consider the changes to the CO2 properties by the impurities and its possible reactions

• Quality specifications defined by the storage CO2 for different storage options

• The quality of CO 2 (specific level of impurities) should be openly discussed!

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Summary and Conclusions(CO2 Processing Unit)

• Depending on the requirement of the oxygen content, processes are now available to produce CO 2 purity from 95% - 99.999%. • It should be noted that higher the purity you reduce the CO2 capture rate.• Higher purity means higher CAPEX and OPEX.

• Downstream removal of SOx and NOx depends on the

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• Downstream removal of SOx and NOx depends on the taking advantage of the “lead chamber reaction” which naturally occur during wet compression.

• Removal could be achieve by compressions and direct contact acid water wash. This should be demonstrate d in the large scale.

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SUMMARY AND CONCLUSIONS- BURNER AND BOILER DEVELOPMENT

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- BURNER AND BOILER DEVELOPMENT- OXYGEN PRODUCTION- CO2 PROCESSING UNIT

Burner & Boiler Development• Demonstration via large scale burner testing is

essential to the development of oxy-combustion.

• Key areas of R&D should focus on:• Heat transfer and flame properties

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• Heat transfer and flame properties• Coal devolatilisatoin and char combustion• Slagging, fouling deposition characteristics• Emissions (sulphur chemistry, PM and Hg + trace

metals)

• Development in CFD modelling is an essential tools to help design of future burners and boilers.

ASU & CPU

• Air Separation Unit : improvement in performance is available now

• CO2 CPU : feasibility is confirmed but design will remain conservative until pilot plants are started ; significant improvements in performance are

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achievable for cryogenic unit• Integration of ASU and CO 2 Processing Unit in the

overall oxyfuel combustion plant are key to achieve high efficiency and low capital expenditure

• Should also consider looking at novel oxygen production

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Concluding Remarks• Oxyfuel Combustion Technology is a viable option

for any coal fired power plant with CO2 Capture.• Oxyfuel Combustion Technology is an option for

new build or retrofit cases.• We need to demonstrate Oxyfuel Combustion

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• We need to demonstrate Oxyfuel Combustion Technology to build our confidence.

• Business sense, it could have a simple business model for power generation companies wherein the operation of the ASU and CO2 processing could be outsourced with a long term supply contract from the industrial gas companies.

Footprint of Capture plant – DTI Project 407

1 x ASC BT Amine Unit:- 2 x SO2 removal towers

• Oxyfuel and amine scrubbing have similar footprints

- 2 x SO2 removal towers (reduces SO2 from 10ppm at FGD outlet to 1 ppm at CO2 absorber inlet)

- 2 x Fans / Blowers- 2 x CO2 Absorber Towers

(12.5m Dia x 45m Height)- 1 x CO2 Stripper Tower (10m Dia)

1 x ASC BT Oxyfuel Unit:- 2 x ASU trains- CO2 Compression- Maximum Height – 68m

Amine Scrubbing &CO2 Compression

23,825m2

ASU &CO2 Compression

24,500m2

Acknowledgement

Gerard Beysel, LINDE EngineeringGerry Hesselman, Doosan BabcockGerry Hesselman, Doosan Babcock

Robin Iron, EOn EngineeringMinish Shah, Praxair

Jean Pierre Tranier, Air LiquideVince White, Air Products

Thank you

Email: [email protected]: http://www.ieaghg.org

Oxy-Pulverised Coal Combustion Technology for Power ... · • Double reboiler design 2 ... Booster...

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Transcript of Oxy-Pulverised Coal Combustion Technology for Power ... · • Double reboiler design 2 ... Booster...