Air Products Oxyfuel CO2 Compression and Purification Developments

Vince White1, Kevin Fogash2 and Frank Petrocelli2

1 Air Products PLC, Hersham Place, Molesey Road, Walton-on-Thames, Surrey, KT12 4RZ, UK

2 Air Products & Chemicals, Inc, 7201 Hamilton Blvd, Allentown, PA, 18195 USA

2nd Oxyfuel Combustion Conference Yeppoon, Queensland, Australia 12th-16th September 2011

Oxyfuel CO2 Purification

2

• Oxyfuel combustion of coal produces a flue gas containing:

• CO2 + H2O

• Any inerts from air in leakage or oxygen impurities

• Oxidation products and impurities from the fuel (SOx, NOx, HCl, Hg, etc.)

Steam Boiler & Turbines

Coal

MWe

Flue Gas

Recycle

Oxygen

CO2 Purification& Compression

O2 Supply CO2 Transport & Sequestration

• Purification requires:• Cooling to remove water• Compression to 30 bar: integrated SOx/NOx/Hg removal• Low Temperature Purification

• Low purity, bulk inerts removal• High purity, Oxygen removal

• Compression to pipeline pressure

Air Products Oxy-Fuel CO2 Capture and Purification –

with Air Products PRISM® Membrane

3

Raw Flue Gas

Product CO2

Offgas[To Atmosphere]

Process Condensate

Heat Recovery

SourCompression &

AP Acid Gas Column

CondensateCollection

TSA UnitMercury Removal

CO2 Compression

Auto-Refrigerated N2, Ar, O2

RemovalProcess

Boiler Steam Cycle

OptionalAPCI PRISM®

Membrane

O2 and CO2 Rich[To Boiler]

Commercial

Mature Tech, Needs Data

Needs Engineering Data

Major Utilities

Cooling WaterElectric Power

Expander

Air Products’ CO2 Purification and Compression Technology for Oxyfuel

4

Sour CompressionSOx, NOx, Hg Removal

Auto-Refrigerated Inerts Removal

Ar, N2, O2

Air Products’ PRISM® Membrane For Enhanced

CO2 + O2 Recovery

Removal minimises compression and transportation costs.

Optional O2 removal for EOR-grade CO2

CO2 capture rate of 90% with CO2

purity >95%

CO2 capture rate depends on raw

CO2 purity which depends on air ingress

Inerts vent stream is clean, at pressure and rich in CO2 (~25%) and O2

(~20%)

Polymeric membrane unit –

selective for CO2 and O2 – in vent stream will recycle CO2 and O2 rich permeate stream to the boiler.

CO2 capture rate increases to >97% and ASU size/power reduced by ~5%

Commercial

Mature Tech, Needs Data

Needs Engineering Data

SOx/NOx removed in compression system

NO is oxidised to NO2 which oxidises SO2 to SO3

The Lead Chamber Process

FGD and DeNOx systems

Optimization

Elimination

Low NOx burners are not required for oxyfuel combustion

Hg will also be removed, reacting with the nitric acid that is formed

Air Products’ CO2 Purification and Compression Technology for Oxyfuel

5

Sour CompressionSOx, NOx, Hg Removal

Auto-Refrigerated Inerts Removal

Ar, N2, O2

Air Products’ PRISM® Membrane For Enhanced

CO2 + O2 Recovery

Removal minimises compression and transportation costs.

Optional O2 removal for EOR-grade CO2

CO2 capture rate of 90% with CO2

purity >95%

CO2 capture rate depends on raw

CO2 purity which depends on air ingress

Inerts vent stream is clean, at pressure and rich in CO2 (~25%) and O2

(~20%)

Polymeric membrane unit –

selective for CO2 and O2 – in vent stream will recycle CO2 and O2 rich permeate stream to the boiler.

CO2 capture rate increases to >97% and ASU size/power reduced by ~5%

Commercial

Mature Tech, Needs Data

Needs Engineering Data

SOx/NOx removed in compression system

NO is oxidised to NO2 which oxidises SO2 to SO3

The Lead Chamber Process

FGD and DeNOx systems

Optimization

Elimination

Low NOx burners are not required for oxyfuel combustion

Hg will also be removed, reacting with the nitric acid that is formed

NOx SO2 Reactions in the CO2 Compression System –

2005 model:

6

• We realised that SO2, NOx and Hg can be removed in the CO2 compression process, in the presence of water and oxygen.

• SO2 is converted to Sulfuric Acid, NO2 converted to Nitric Acid:

– NO + ½ O2 ⇌ NO2 (1) Slow

– 2 NO2 ⇌ N2O4 (2) Fast

– 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 3rd power

– only feasible at elevated pressure

• Little Nitric Acid is formed until all the SO2 is converted

• Pressure, reactor design and residence times, are important.

Air Products’ CO2 Compression and Purification System: Removal of SO2, NOx and Hg

7

1.02 bar 30°C67% CO2

8% H2O25% InertsSOxNOx

30 bar to DriersSaturated 30°C76% CO2

24% Inerts

Dilute H2SO4

HNO3

Hg

Dilute HNO3

BFW

Condensate

cw

10- 15 bar

30 bar

Water

cwcw

30 MWth oxy-coal

pilot plant

160 kWth

oxy-coal rig

Cylinder fed

bench rig

London

Renfrew, Scotland

Schwarze Pumpe, Germany

1 MWth

slip stream

6 kWth

slip stream Batch

DOE/NETL Cooperative Agreement

Host: Alstom,Windsor, CT

0.3 MWth

slip stream

15 MWth

oxy-coal combustion unit

Ph

oto

cou

rtesy of V

atten

fallPh

oto

cou

rtesy of D

oo

san

Ba

bco

ck

Ph

oto

cou

rtesy of Im

peria

l College

Ph

oto

cou

rtesy of A

lstomP

ow

er

Path to Large-ScaleDemonstration

Large-Scale

(~300 MW)

Demo

9

AB

C

MFC

D

From NRTF

Flue Gas Cooler

Condensate

Separator

Compressor &

Receiver

Reactor

The effect of Pressure on SO2

and

NO Conversion (1 sl/min, 7 and 14 barg)

Inlet

After

Compressor &

ReceiverInlet

After

Compressor &

Receiver

(Point A) (Point C) (Point A) (Point C)

ppm SO2 900 20 98% 950 150 84%

ppm NOx 520 50 90% 390 120 68%

ConversionConversion

7 bar g14 bar g

Key Learnings from Imperial College Work

10

• NO oxidation rate confirmed to increase rapidly with increased pressure

• At low temperature (~ 30-50 °C), SO2 oxidation to SO3 / H2SO4 only occurs at an appreciable rate in presence of NO2 and a condensed phase

• Significant conversion can occur even with very small liquid phase volumes (i.e., very low L/G ratios)

– Speculation that condensation creates a fine mist with large interfacial surface area, and that reaction is occurring at the interface

– Speculation that reactions are accelerated at low pH

• Recognized need to develop internal capability to explore broader range of parameters and to increase rate of data generation

DOE/NETL Cooperative Agreement: Air Products’ Sour Compression PDU

11

Acid Reactor (C102)

Side View of PDU

• 1st campaign Jan 2010

• 2nd campaign April-May 2010

U.S. Department of Energy's National Energy Technology Laboratory under Award Number DE-NT0005309

DOE Project: Air Products’ Sour Compression PDU –Key Results

12

• For the overall process, total SO2 removal was 20-100 % (based on gas compositions).

• For the overall process, total NOx removal was 60-90 % (based on gas compositions).

• The effects of variations in the SO2/NOx feed ratio, column pressure, gas flowrate and liquid recirculation on the reactor performance were explored. Process performance was most sensitive to SO2/NOx feed ratio, over the range of parameter values investigated.

• SO2 was removed from the flue gas through both sulfite and sulfate mechanisms.

-100

0

100

200

300

400

500

600

700

20:38:24 20:52:48 21:07:12 21:21:36 21:36:00 21:50:24 22:04:48 22:19:12 22:33:36

ppm

v

Time

Oxyfuel 22 January 2010

[FLUGAS]NO.SCALED

[FLUGAS]SO2.SCALED

Condition DSOx Conversion >99%NOx conversion >90%(NOx zero +/- 20 ppmv)

Reactor Inlet Reactor Inlet Reactor Inlet Reactor Inlet

Reactor OutletReactor OutletReactor Outlet

Lab-Scale Reactor System

13

• Commissioned Sept. 2010 to further our understanding of SOx/NOx reaction chemistry during compression

• Wide range of conditions possible:

– Up to 3000 ppm SO2

– Up to 1000 ppm NOx

– Temperature range from ambient to 400 °C

– Pressure range from atmospheric to 30 atm

– 3 modes of operation:

– Dry gas

– Humidified gas

– Gas-liquid

Process Flow

CO2

O2

N2

SO2

/ N2

NO

/ N2

MFC

MFC

MFC

MFC

MFC

Gas Humidifier

Backpressure

Regulator

To Vent

To Analysis

Absorber

Column

High P

Water Pump

Recirc

Pump

Control

Valve

Water Flow

MFC

Sour Compression Modelling

14

• Concurrent with the technology demonstration projects, lab experiments and ASPEN modelling were carried out to develop a robust reaction model

• Goals of modelling:– Single reaction model to describe reactions in compression train and

in column– Use literature reactions and kinetics wherever possible– Same model can be used to describe lab data and to describe pilot

data from multiple configurations / scales (Renfrew, Windsor, Schwarze Pumpe)

• Modelling timeline:– 2005: 1st reaction model developed from literature references (no

data available at this time)– October 2009: research program with Imperial College initiated – September 2010: startup of Air Products lab reactor system– July 2011: Final version of reaction model developed from lab data

Sour Compression Model compared to experimental data

15

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0% 20% 40% 60% 80% 100%

Lab

un

it r

esu

lts

Model prediction

SO2 removal

NO conversion

N removal

N2O yield

45° line

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0% 20% 40% 60% 80% 100%

Lab

un

it r

esu

lts

Model Prediction

Compression Train Configuration

Column Configuration

Air Products Sour Compression System -Summary

16

• SOx/NOx removed in compression system

– NO is oxidised to NO2 which oxidises SO2 to SO3

– The Lead Chamber Process

• FGD and DeNOx systems

– Optimization

– Elimination

• Low NOx burners are not required for oxyfuel combustion

• Hg will also be removed, reacting with the nitric acid that is formed

Air Products’ CO2 Purification and Compression Technology for Oxyfuel

17

Sour CompressionSOx, NOx, Hg Removal

Auto-Refrigerated Inerts Removal

Ar, N2, O2

Air Products’ PRISM® Membrane For Enhanced

CO2 + O2 Recovery

Removal minimises compression and transportation costs.

Optional O2 removal for EOR-grade CO2

CO2 capture rate of 90% with CO2

purity >95%

CO2 capture rate depends on raw

CO2 purity which depends on air ingress

Inerts vent stream is clean, at pressure and rich in CO2 (~25%) and O2

(~20%)

Polymeric membrane unit –

selective for CO2 and O2 – in vent stream will recycle CO2 and O2 rich permeate stream to the boiler.

CO2 capture rate increases to >97% and ASU size/power reduced by ~5%

Commercial

Mature Tech, Needs Data

Needs Engineering Data

SOx/NOx removed in compression system

NO is oxidised to NO2 which oxidises SO2 to SO3

The Lead Chamber Process

FGD and DeNOx systems

Optimization

Elimination

Low NOx burners are not required for oxyfuel combustion

Hg will also be removed, reacting with the nitric acid that is formed

CO2 Compression and Purification System –Inerts removal and compression

18

Flue Gas Vent 1.1 bar~25% CO2

~75% inerts

Flue Gas

ExpanderAluminium plate/fin exchanger

Driers

Flue Gas

Heater

30 bar Raw CO2

Saturated 30°C75-85% CO2

CO2 product~96% CO2

~4% Inerts-60°C dp

-55°C

Auto-Refrigerated Inerts Removal

19

• Removal of impurities minimises compression and transportation costs.

• O2 can be removed for EOR-grade CO2

• CO2 capture rate of 90% with CO2 purity >95%

• CO2 capture rate depends on raw CO2 purity which depends on air ingress

– Increases from zero at 25mol% to 90% at 75mol%

– Reducing air ingress increases CO2 capture rate

Air Products’ CO2 Purification and Compression Technology for Oxyfuel

20

Sour CompressionSOx, NOx, Hg Removal

Auto-Refrigerated Inerts Removal

Ar, N2, O2

Air Products’ PRISM® Membrane For Enhanced

CO2 + O2 Recovery

Removal minimises compression and transportation costs.

Optional O2 removal for EOR-grade CO2

CO2 capture rate of 90% with CO2

purity >95%

CO2 capture rate depends on raw

CO2 purity which depends on air ingress

Inerts vent stream is clean, at pressure and rich in CO2 (~25%) and O2

(~20%)

Polymeric membrane unit –

selective for CO2 and O2 – in vent stream will recycle CO2 and O2 rich permeate stream to the boiler.

CO2 capture rate increases to >97% and ASU size/power reduced by ~5%

Commercial

Mature Tech, Needs Data

Needs Engineering Data

SOx/NOx removed in compression system

NO is oxidised to NO2 which oxidises SO2 to SO3

The Lead Chamber Process

FGD and DeNOx systems

Optimization

Elimination

Low NOx burners are not required for oxyfuel combustion

Hg will also be removed, reacting with the nitric acid that is formed

Can we improve on ~90% CO2 Capture?Vent stream is at pressure and is CO2 (and O2) rich

21

Flue Gas Vent 1.1 bar~25% CO2

~25% O2

~50% N2

Flue Gas

ExpanderAluminium plate/fin exchanger

Driers

Flue Gas

Heater

30 bar Raw CO2

Saturated 30°C75-85% CO2

CO2 product~96% CO2

~4% Inerts-60°C dp

-55°C

Air Products Oxy-Fuel CO2 Capture and Purification – with Air

Products PRISM® Membrane

22

Flue Gas Expander

Aluminium plate/fin exchanger

Driers

Flue GasHeater -55°C

Membrane

To Boiler

CO2 product~96% CO2

~4% Inerts-60°C dp30 bar Raw CO2

Saturated 30°C75-85% CO2

Advantages of Air Products’ CO2Purification Technology for Oxyfuel

23

• Inerts vent stream is clean, at pressure and rich in CO2 (~25%) and O2 (~20%)

• Polymeric membrane unit – selective for CO2 and O2 – in vent stream will recycle CO2 and O2 rich permeate stream to the boiler.

• CO2 capture rate increases to >97% and ASU size/power reduced by ~5%

Membrane skid at the Air Products – VattenfallOxyfuel Pilot Plant

The Vattenfall – Air Products Oxyfuel CPU Pilot Plant

24

Air Products’ CO2 Purification Unit (CPU) Pilot Plant at Vattenfall’s Schwarze Pumpe

25

Raw Flue Gas

CO2 ReturnedTo OxPP

Inerts Vent[To OxPP]

Process Condensate

SourCompression

CondensateCollection

TSA UnitMercury Removal

Auto-RefrigeratedInerts +O2

Removal Process

Air ProductsPRISM®

Membrane

O2 and CO2 Rich[To OxPP]

26

50/50 Flue Gas Mix From Before and After OxPP FGD

27

50/50 Flue Gas Mix From Before and After OxPP FGD

0

50

100

150

200

250

300

350

400

942 947 952 957 962 967

NO

an

d N

O2

(pp

m, D

ry)

Time (minutes)

NO

NO2

Inlet K432 Inlet Column Exit Column

NOx

Conclusions

28

• Purification of the CO2 from oxyfuel-fired coal power plants is a technology ready for commercialisation

• Several advances in CPU technology have been described which will improve the performance of the CPU and the power plant

• Air Products is developing commercial offerings for CPU plants on demonstration plants

Acknowledgment: “A portion of this material is based upon work supported by the Department of Energy's National Energy Technology Laboratory under Award Number DE-NT0005309.”

Disclaimer: “This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.”

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