The Air Products–Vattenfall Oxyfuel CO2 Compression and Purification Pilot Plant at Schwarze Pumpe

Vince White, Andrew Wright – Air Products

Stephanie Tappe, Jinying Yan – Vattenfall

3rd Oxyfuel Combustion Conference Ponferrada, Spain 9th-13th September, 2013

1

Outline • Overview of The Air Products–Vattenfall

Oxyfuel CO2 Compression and Purification Pilot Plant – The ACPP

• Issues to be Investigated by the ACPP • The Experimental Programme • Warm-End Parametric Testing • Sour Compression Reaction Modelling • Cold-End Material and Energy Balances • CO2 Phase Equilibrium Study • Mercury and Water Removal • Corrosion • Conclusions

2

Overview of The Air Products–Vattenfall Oxyfuel CO2 Compression and Purification Pilot Plant – The ACPP

• 1 MWth equivalent slipstream taken from Vattenfall’s OxPP before and/or after the flue gas desulphurisation unit

• Operated over 2 years • Designed to demonstrate three concepts that Air Products

have developed

Process Condensate

Flue Gas

CO2 (Returned to OxPP)

Inerts Vent

Cooler & Condenser

Condensate Collection

TSA & Mercury Removal

Auto-Refrigerated Inerts +O2

Removal Process

Air Products PRISM®

Membrane

O2 and CO2 Rich Stream

Process Condensate

Sour Compression

Condensate Collection

Warm End

Cold End

CO2/O2 Recovery

3

1. Flue gas cooler-condenser performance in a more acidic environment

2. Sulphur and nitrogen oxidation and acid removal

3. CO2 VLE

4. CO2 Freeze-out

5. Membrane performance

6. Dynamics of the system – start-up, shutdown, varying feed compositions

7. Mercury behaviour and distribution in the process.

8. Dehydration. Performance of TSA adsorbents

9. Potential for corrosion

4

Issues to be Investigated by the ACPP (See OCC1 Presentation, September 2009)

Cooler & Condenser

Condensate Collection

TSA & Mercury Removal

Auto-Refrigerated Inerts +O2

Removal Process

Air Products PRISM®

Membrane

Sour Compression

Condensate Collection

The Experimental Programme

• Experimental programme carried out in collaboration between Air Products and Vattenfall - Commissioning – lessons learnt and initial results - Baseline testing over the entire process – mass and heat

balance - Parametric testing on the “Warm End” – sensitivity to key

variables

• ACPP Integration with the OxPP - The ACPP could only operate when the OxPP was running and

this limited available testing time - Two different burners fitted to the OxPP and these gave

different flue gas compositions to the ACPP

• Analysis - Accurate liquid and gas phase analysis was critical - Reactions in sample lines needed to be accounted for

• CO2 VLE – separate laboratory study conducted to check accuracy

5

Warm-End Parametric Testing

6

Warm-End Parametric Testing

• 42 tests performed

• Results presented at GHGT11, November 2012

7

Parameter Units Range

Flue Gas from Upstream of OxPP FGD % 0 – 100 Flue Gas Flow Rate Nm3/h 80 – 170

15 bar Column Operating Pressure barg 10 – 13.8 30 bar Column Operating Pressure barg 25 – 29

Compressor Discharge Temperatures oC 25 – 50 Column Discharge Temperatures oC 25 – 50

15 bar Column Make-up Water Flow Rate kg/h 0 – 120 15 bar Column Recycle Water Flow Rate kg/h 0 – 900

30 bar Column Make-up Water Flow Rate kg/h 30 – 35 30 bar Column Recycle Water Flow Rate kg/h 750 – 900

Flue Gas from Downstream of FGD

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1 2 3 4 5 6 HCl 0.21 0 0 0 - - SO2 13 2 1 0 0 0 NO 238 184 87 24 11 4 NO2 20 56 110 18 17 4 N2O 0 0 0 0 0 0

FGCC 15 bar Comp.

15 bar Column

30 bar Comp.

30 bar Column

1 2 3 4 5 6

Measured Concentrations (ppm, dry)

0

10

20

30

40

50

60

70

80

90

100

4 5 6 7 8 9 10 11 12

Feed SO2/NOx Ratio with Constant 2000 ppm SO2

Burner 2(180 - 320 ppm NOx)

Burner 1(400 ppm NOx)

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9

Feed SO2/NOx Ratio with Constant 295 ppm NOx

Flue Gas from Upstream of FGD

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• The SO2 concentration of the incoming flue gas to the ACPP can be varied by taking flue gas from before the OxPP FGD, after the FGD, or a mixture of both.

• NOx to the ACPP dependent on burner operation - Typically 250 – 320 ppm for

most tests

• These results confirm the importance of NOx in the flue gas to the removal of SO2 from the flue gas

• Graph at constant NOx shows lower performance as operating conditions chosen resulted in N2O formation

SO

2 r

emov

ed f

rom

ACPP

Inle

t to

O

utlet

of

15 b

ar c

olu

mn (

%)

Sour Compression Reaction Modelling

10

Updated NOx - SOx Reaction Network

Stoichiometry Phase 2 NO + O2 → 2 NO2 V

2 NO2 ⇌ N2O4 V N2O4 + H2O → HNO3 + HNO2 L 2 HNO2 ⇌ NO + NO2 + H2O L

4 HNO2 ⇌ 2 NO + N2O4 + 2 H2O L SO2 + H2O ⇌ H2SO3 L

2 HNO2 + 2 SO2 + H2O ⇌ 2 H2SO4 + N2O L 2 HNO2 + 2 H2SO3 → 2 H2SO4 + N2O + H2O L

2 HNO2 + SO2 → H2SO4 + 2 NO L 2 HNO2 + H2SO3 → H2O + H2SO4 + 2 NO L

2 NO2 + H2O → HNO3 + HNO2 L

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NO + O2 NO2 / N2O4

+ H2O

HNO2 + HNO3

H2SO4 + N2O H2SO4 + NO

NO + NO2 / N2O4

+ SO2 / H2SO3

+ SO2 / H2SO3

Green – propagates NOx redox cycle Red – terminates NOx redox cycle

0

10

20

30

40

50

60

0 10 20 30 40 50 60

Mod

el N

O2

(ppm

)

Experiment NO2 (ppm)

0

200

400

600

800

1000

1200

1400

1600

0 200 400 600 800 1000 1200 1400 1600

Mod

el SO

2(p

pm)

Experiment SO2 (ppm)

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Mod

el N

O (p

pm)

Experiment NO (ppm)

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• Comparison of analyser and model results for the outlet of the 15 bar column

• Includes rigorous modelling of reactions in the sample lines

• No change was made in reaction rate parameters used in the model which were derived from earlier lab-scale data

15 bar Column Model and Experiment NO NO2

SO2

Cold-End Material and Energy Balances: Early Baseline Tests

13

Feed Composition Variability

14

68

70

72

74

76

78

80

82

0 24 48 72 96 120 144 168 192 216

Feed

Flue

Gas

CO

2Co

ncen

trat

ion

(%, d

ry)

Time (hours)

68

70

72

74

76

78

80

82

195 196 197 198 199 200 201 202

Feed

Flue

Gas

CO

2Co

ncen

trat

ion

(%, d

ry)

Time (hours)

0

100

200

300

400

500

600

700

800

900

1000

195 196 197 198 199 200 201 202

CO2

Prod

uct N

2an

d O

2(p

pm, d

ry)

Time (hours)

O₂N₂

Typical variation over 7 hours at “constant” conditions…

…however, CO2 product composition was relatively steady

Typical ACPP CO2 feed composition variation over 9 days: OxPP was turned down at night; air ingress to the OxPP becomes more significant at lower rates

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Feed N2-Rich Vapour CO2-Product

- Expt. Mod. Expt. Mod.

CO2 % 78.7 34.0 34.0 97.4 97.0

O2 % 6.7 20.1 20.6 1.1 1.0

N2 % 14.6 45.9 45.4 1.5 2.0

Flow % 100 29.5 29.0 70.5 71.0

-50

-40

-30

-20

-10

0

10

20

30

40

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tem

pera

ture

(°C)

Duty

Hot Stream

Cold Streams

Low Pressure CO2

Medium Pressure CO2

• 87.3% CO2 recovery, but preliminary study. Plant not optimised

• Good match of model results with product compositions and flows – validates VLE

• Need to add significant heat ingress to model in order to match experimentally measured temperatures

Low Purity CO2 Material and Heat Balance

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Feed N2-Rich Vapour CO2-Product

- Expt. Mod. Expt. Mod.

CO2 % 75.7 36.6 38.9 99.9+ 99.9+

O2 % 6.7 17.4 16.8 167 ppm 167 ppm

N2 % 17.7 46.0 44.3 207 ppm 182 ppm

Flow % 100 38.4 39.8 61.6 60.2

• 81.4% CO2 recovery, but plant not optimised

• Model set up to match O2 in CO2 product

• Learnt a great deal about controlling these processes

-60

-50

-40

-30

-20

-10

0

10

20

30

40

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Tem

pera

ture

(°C)

Duty

Hot StreamCold Streams

Low-Pressure CO2

Medium-Pressure CO2

Reboiler

High Purity CO2 Material and Heat Balance

Additional Issues Investigated

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CO2 Phase Equilibrium Study

• Acquire Experimental K-values of NO, NO2/N2O4, N2O, and SO2

• Confirm VLE from open literature for O2 and CO (considerable data exist for N2 and Ar)

• VLE measurements completed and thermo model updated O2-CO2: excellent agreement with published data; improved

accuracy using data in this work CO-CO2: good agreement with reported data at lower temperatures;

improved accuracy from this work at higher temperatures NO-CO2: No previous experimental data; VLE behavior similar to N2-

CO2 and O2-CO2

N2O-CO2: No previous experimental data; azeotrope at -50oC; CO2 relative volatility close to unity SO2-CO2: No previous experimental data; lower non-ideality than

expected NO2-CO2: No previous experimental data; lower non-ideality than

expected

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Mercury • Most of the mercury appears to removed by the

FGCC when running on flue gas upstream of the FGD (high SO2)

• Substantially all the remaining mercury then removed with the acid condensate formed at higher pressure

• However, limited mercury sampling was conducted and we did see evidence at times of at least some Hg getting to the exit of the TSA dryer (inlet of the Hg guard bed)

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• SO2 found to reduce water capacity of TSA adsorbent: blocks the openings to the microporous crystals

• SO2 is irreversibly bound to the adsorbent

• NOx doesn’t seem to have too much of an effect on the drying performance: Reversible adsorption

Water Removal

Corrosion

• Corrosion has only been a problem where it should have been expected to have been a problem (See OCC2 Presentation, September 2011)

- Important to understand where condensation occurs in the process, when SO2 and/or NOx are still present in the flue gas

- Important to check all equipment materials of construction match specifications

• Most coupons just as “shiny” as they were when they were new

• However, as expected, we have seen attack on corrosion coupons that are in the chloride containing part of the system - Which is why we have made the dirty end of the FGCC out of fibreglass

15 bar Column Sump

FGCC Sump

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• First demonstration of Sour Compression in representative equipment at the Air Products–Vattenfall Oxyfuel CO2 Compression and Purification Pilot Plant

• First demonstration of auto-refrigerated inerts removal

• Learned many lesson relevant to full scale plant design and operation

• Results allow refinement of sour compression modelling

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• In early 2013 Vattenfall and Air Products decided to conclude their joint R&D program on the ACPP

• Air Products has developed commercial offerings for CPU plants on demonstration plants based on the results and experience from the Air Products–Vattenfall Oxyfuel CO2 Compression and Purification Pilot Plant

• This marks the end of 8 years of fruitful and enjoyable collaboration

• Thanks to Vattenfall for over a decade of leadership and enthusiasm for Oxyfuel CO2 Capture

Thank you… tell me more

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