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Powerfuel Power Limited is part of the Powerfuel plc Group of Companies
and is an independent power generation company formed to develop a power station adjacent to Hatfield Colliery at Stainforth
(South Yorkshire) in the United Kingdom.
THE PROJECT
Powerfuel Power Limited plans to construct the world's first large scale integrated gasification combined
cycle (IGCC), near zero emissions power station with carbon capture capability in two phases.
PHASE 1 will be the construction of an 800MW(gross) power island (CCGT) which has been
specifically designed for optimisation and performance on syngas.
PHASE 2 of the programme will be the construction and commissioning of the gasification
island allowing the power island to be converted over to a 900MW (gross) syngas mode of operation. The conversion to gasification
will require the power island to be fitted with MNQC's (Multi Nozzle Quiet Combustor) allowing fuel switching and blending
of raw gas to the turbines between syngas and natural gas.
The Government's White Paper Meeting the Energy Challenge (May 2007) stated: That over the next
two decades, the UK will need substantial investment in new electricity generation capacity to replace a number of closing
coal, oil and nuclear power stations and to meet expected increases in electricity demand. We [the government] want
to ensure we have the investment framework which encourages investment to come forward at the right time and as much as possible
in low carbon forms of generation.
The proposed 900MW Power Station has been designed, to meet the UK's need for new electricity power generation
capacity and the Government's desire for power generation from fossil fuels to become significantly cleaner and more efficient. The
proposed Power Station has been designed to facilitate a move to cleaner coal technology (SYNGAS Fuelled) power generation,
including carbon capture, based on the availability of a long-term coal feedstock from the Colliery at Hatfield.
OPERATION OF THE POWER STATION PLANT
Main Processes
The gasification process converts coal to a gaseous mixture of hydrogen and carbon monoxide by causing it
to react with oxygen at high pressure and temperature. This gas is referred to as "SYNGAS". The raw coal feedstock from the
mine is pre-processed by a milling and drying system to produce pulverised coal which facilitates the combustion process and
enables pneumatic conveying of the feed.
The Air Separation Unit (ASU) provides pure oxygen for the combustion process and pure nitrogen for purging
and inerting systems to ensure safe operation of the plant. This unit essentially compresses and cools air to high pressure
and low temperature, sufficient to liquify oxygen and nitrogen and allow separation by distillation columns.
The SYNGAS produced by the gasifier trains is saturated with steam and passes to a set of catalytic reactors
which convert the carbon monoxide to carbon dioxide and produce additional hydrogen from the steam.
The carbon dioxide and any sulphur compounds (principally hydrogen sulphide) produced in the combustion
process are then absorbed from the SYNGAS stream in the Acid Gas Removal (AGR) section. This unit brings the gas into contact
with a proprietary solvent, which absorbs the acid gas components, leaving the gas as a clean hydrogen-rich stream for use
in the gas turbines downstream. The solvent, laden with carbon dioxide and hydrogen sulphide, passes to a regeneration section,
where selective changes in temperature and pressure enable the carbon dioxide and hydrogen sulphide to be liberated as separate
streams. The regenerated solvent is then recycled to absorb more acid gas.
The carbon dioxide stream can be compressed into a pipline system for transfer to underground storage/use
offsite, while the hydrogen sulphide stream passes to a sulphur recovery unit (SRU). The latter unit converts the hydrogen
sulphide to elemental sulphur and recycles the remaining off-gas to the AGR unit. Elemental sulphur is a by-product which
is exported from the plant.
The hydrogen gas leaving the Acide Gas Removal system is diluted with nitrogen and combusted in two gas
turbines, which in turn drive two electricity generators providing power to export to the national grid. The products of combustion
are essentially steam and nitrogen which can be safely discharged to atmosphere after heat recovery.
The products of combustion leaving the gas turbines, at very high temperature but low pressure, are cooled
by a series of heat exchangers in a Heat Recovery Steam Generator (HRSG). This enables the heat recovered to generate high
pressure steam which is used to drive a steam turbine, which in turn drives another electricity generator providing power
for export to the grid. The cooled exhaust gas is finally discharged to atmosphere through the chimney stack.
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