Integration Options for Post-Combustion CO2 Capture using Molten Carbonate Fuel Cells TCCS-9, Trondheim, Norway 12 – 14th June 2017 Presented by: Stuart Lodge (BP): CCP4 Capture Team

This presentation has been prepared for information purposes only. All statements

of opinion and/or belief contained in this document and all views expressed and all

projections, forecasts or statements relating to expectations regarding future events

represent the CCP’s own assessment and interpretation of information available to it

as at the date of this document.

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Contents

Section One | Molten Carbonate Fuel Cells for CO2 Capture background Section Two | Starting schemes for consideration Section Three | Key performance factors Section Four | Improved process schemes Section Five | Cost and efficiency impacts and conclusions

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Objective

The work reported in this presentation was to understand

the value of process integration that may be applied in

new-build versus retrofit applications of molten carbonate

fuel cells for high efficiency post-combustion CO2 capture.

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Background: Technology Comparison

0%

10%

20%

30%

40%

50%

60%Why study MCFC? Power plant net efficiency (LHV)

• In a previous CCP evaluation

the MCFC case is the only

capture technology which

shows an improved efficiency

compared to the base case

(NGCC + amine capture)

• This result stimulates the need

for further investigation into

application options of the

MCFC technology for high

efficiency CO2 capture

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Background: What are MCFCs?

Cathode (+)

2O2 + 4CO2 + 8e- 4CO32-

Anode (-)

CH4 + 4CO3

2- 2H2O + 5CO2 + 8e-

MCFC

Electrolyte 4CO32-

Flue Gas

(~ 4% CO2)

Gas to Stack

(low CO2)

CO2 rich gas &

exhaust syngas

Fuel feed

to MCFC

↑ Simultaneously separates CO2 and produces power @ high efficiency (~50% LHV)

↑ High operating temperature (650°C) needed to achieve conductivity of carbonate electrolyte and to provide internal natural gas reforming by an affordable catalyst

↑ Low NOX (direct destruction in MCFC) and SO2/H2S (previous capture)

Based on carbonate ions (CO32-) passing through a solid Li-K matrix electrolyte

↓ Low materials durability (corrosion) and low contaminants tolerance

↓ High CAPEX and OPEX

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Background: Using MCFC for capture Two different schemes studied

Integrated MCFC for CO2 Capture case Utilising high temperature of the gas turbine

Non-integrated MCFC for CO2 Capture case Suitable for retrofit applications

Cathode

Anode

MCFC

CO2 Separation

and Compression

HRSG Air Gas

Turbine

Natural Gas CO2 for Storage

Gas to Stack NGCC

Cathode

Anode

MCFC

CO2 Separation

and Compression

Air

Gas

Turbine

Heat

Recovery

Steam Cycle

NGCC

Natural Gas

Gas to Stack

CO2 for Storage

Preheaters

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Molten Carbonate Fuel Cell – Integrated Case In detail

Starting Design

Natural Gas

Air Gas

Turbine Cathode

Anode

MCFC

Steam Cycle

CO2 Separation

and Compression

HRSG

CO2 for Storage

Gas to Stack

Unconverted fuel / syngas

recycled to MCFC Anode

Steam for heat exchange

Steam for MCFC

Flue Gas

Preheater

to GT

Preheater

to MCFC

Key Features:

• MCFC directly downstream of the GT to use high grade heat

• Fuel for MCFC preheated by cathode exhaust directly

• Fuel cell exhausts feed the HRSG

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Molten Carbonate Fuel Cell – Non-integrated Case In detail

Key Features:

• MCFC downstream of

full Power cycle

• Heat recovery from

MCFC critical to

performance

• MCFC preheating

provided by burning fuel

Air

Gas

Turbine

Natural

Gas

Heat

Recovery

Steam Cycle

Cathode

Anode

MCFC

CO2 Separation

and Compression

NGCC

CO2 for Storage

Gas to Stack

Water

Unconverted fuel / syngas

recycled to MCFC Anode

Flue Gas

Pre-Heater

Heat

Recovery

Pre-Heater

Combustor

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Heat Integration – Key to Performance but challenges exist…

Recovery of heat from MCFC exhausts key to reaching higher

efficiency performance for both process cases

• Challenge = High operating temperature of MCFC ~ 650°C

Recuperative gas-to-gas heat exchanger design for main heat

transfer area, the MCFC pre-heater

• Challenge = Few recuperative designs at large scale

Presence of “syngas” type composition at these high temperature

presents challenges

• Challenge = “metal dusting” at the temperatures required

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Heat Integration Study

Existing industrially relevant recuperative heat

exchange designs:

• Ljungstrom type rotating wheel

• Pressed plate compact heat exchanger

Limited application at NGCC scale:

• Require significant heat exchange area

• Costs will therefore be significant

How can we optimise the necessary heat

exchange area?

Ljungstrom wheel

Pressed plate exchanger

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Non-integrated case pre-heating optimisation Recuperative heat exchange vs. burning fuel for preheat

Partial burning of Syngas identified as best balance between equipment

areas and potential cost vs. overall efficiency

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35.0%

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45.0%

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0

300000

600000

900000

Full preheat with heatexchanger

30% of syngas burntfor preheating

100% syngas topreheating

Full preheat withburning syngas &

natgas

Surf

ace a

rea –

m²

Overa

ll Effic

iency - %

LH

V

Pre-heater

exchanger area

MCFC area

Efficiency

Syngas to pre-heating combustor increases

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Heat Integration Study – Metal Dusting

What is it? a chemical damage mechanism to metal

caused by carbon ingress and over-saturation

How does it happen? High thermodynamic activity

of carbon in the gas (aC > 1), calculated from the

reaction:

CO + H2 C + H2O

High temperature syngas has high carbon activity

What are the choices? Higher chromium steels can be employed in

the heat exchanger at higher cost

Or

The heat exchange network can be re-arranged taking into

consideration CO concentrations and gas stream temperatures, in

order to avoid metal dusting conditions

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Dealing with the Challenges…

Recovery of heat from MCFC exhausts key to reaching higher

efficiency performance for both process cases

• Challenge = High operating temperature of MCFC ~ 650°C Balanced heat recovery and recycle stream combustion for preheat

Recuperative gas-to-gas heat exchanger design for main heat

transfer area, the MCFC pre-heater

• Challenge = Few recuperative designs at large scale Identified industrially relevant examples of heat exchangers

Presence of “syngas” type composition at these high temperature

presents challenges

• Challenge = “metal dusting” at the temperatures required Reconfigured process flow scheme to reduce heat exchange surface

temperatures whilst still maximising heat integration

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Molten Carbonate Fuel Cell – Integrated Case Updated process flow scheme

Starting Design

Natural Gas

Air Gas

Turbine Cathode

Anode

MCFC

Steam Cycle

CO2 Separation

and Compression

HRSG

CO2 for Storage

Gas to Stack

Unconverted fuel / syngas

recycled to MCFC Anode

Steam for heat exchange

Steam for MCFC

Flue Gas

Preheater

to GT

Preheater

to MCFC

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Molten Carbonate Fuel Cell – Integrated Case Updated process flow scheme

Natural Gas

Air Gas

Turbine Cathode

Anode

MCFC

Steam Cycle

CO2 Separation

and Compression

HRSG

Sulphur

Removal

CO2 for Storage

Gas to Stack

Unconverted fuel / syngas

recycled to MCFC Anode

Hot water for heat exchange

Steam for MCFC

Flue Gas

Preheater

to GT

Preheater

to MCFC

Key Changes:

• Sulphur removal included

• Preheating uses hot water to reduce heat exchanger surface

temperatures – limit metal dusting

• No significant change to overall efficiency (~57% LHV)

Revised Design

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Molten Carbonate Fuel Cell – Non-integrated Case Updated process flow scheme

Air

Gas

Turbine

Natural

Gas

Heat

Recovery

Steam Cycle

Cathode

Anode

MCFC

CO2 Separation

and Compression

NGCC

CO2 for Storage

Gas to Stack

Water

Unconverted fuel / syngas

recycled to MCFC Anode

Flue Gas

Pre-Heater

Heat

Recovery

Pre-Heater

Combustor

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Molten Carbonate Fuel Cell – Non-integrated Case Updated process flow scheme

Air

Gas

Turbine

Natural

Gas

Heat

Recovery

Steam Cycle

Cathode

Anode

MCFC

CO2 Separation

and Compression

NGCC

CO2 for Storage

Gas to Stack

Water Sulphur

Removal

Unconverted fuel / syngas

recycled to MCFC Anode

Flue Gas

Ljungstrom

Pre-Heater

Heat

Recovery

Key Changes:

• Pre-heater combustor

limited to 30% of

recycled syngas

• Heat recovery afforded

by a ljungstrom type heat

exchanger

Pre-Heater

Combustor

(~30% of

recycled

syngas)

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Capital cost estimates

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500

1000

1500

2000

2500

NGCC + amine MCFC Integrated MCFC Non-Integrated

Results/discussion

• Both MCFC cases have higher

overall capital costs than the base

amine case.

• The non-integrated case shows the

largest capital costs due to poorer

heat recovery resulting in larger

primary heat exchangers and

MCFC unit

• Both MCFC cases offer lower

specific capital costs due to the

additional electricity generated by

the MCFC.

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Conclusions from our evaluation

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NGCC + amine MCFC Integrated case MCFC non-integratedcase

Specific cost of CO2 avoided

$ 2

01

4 / t

CO

2 a

vo

ide

d

• The integrated MCFC is a high performing CO2 capture technology in terms of energy penalty and cost of CO2 avoided

• Utilising the high temperature heat from the gas turbine is clearly beneficial to efficiency & equipment count for the integrated case

• The non-integrated case is clearly advantaged for retrofit applications, but this comes at higher capital cost

• The higher capital cost negates the improved overall efficiency when compared to the baseline technology impacting CO2 avoided costs

• The cost of the novel MCFC equipment and their reliability continue to be a key uncertainty in the technology in both configurations

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NGCC + amine MCFC Integrated case MCFC non-integratedcase

Eff

icie

ncy -

% L

HV

Efficiency - % LHV

Further information…

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End