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Pre-Combustion Capture
Pre-combustion capture involves removal of CO2, prior to combustion, to produce hydrogen. Hydrogen combustion produces no CO2 emissions, with water vapour being the main by-product. Provided that this technology is used with carbon storage it could provide a CO2 emission free fuel for the future.
The capture process consists of three stages; firstly the hydrocarbon fuel (typically methane, or gasified coal) is converted into hydrogen and carbon monoxide (CO) to form a synthesis gas. The second step is to convert the CO into CO2 by reacting it with water and which is known as shift conversion. Finally, the CO2 is separated from the hydrogen which can then be combusted cleanly. The CO2 can then be compressed into liquid and transported to a storage site.
Pros:
- Proven industrial scale technology in oil refineries, but needs 3x scale-up for power plants.
- 90-95% of CO2 emissions can be captured.
- Applicable to natural gas, and to coal fired IGCC power plants.
- Lowest technology risk, and may become the most efficient method.
- Can produce H2 as transportable energy vector, or liquid fuels from coal - but penalties on efficiency
Cons:
- Requires a chemical plant in front of gas turbine –.
- High investment cost of dedicated new-build plant.
- High NOx emissions – will require expensive scrubbers.
- Efficiency of H2 burning turbines is lower than conventional turbines.
- May be less flexible under varying electicity generation market requirement, so base load preferred
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