(70) Therefore, the risk of sulphuric acid dew point attack ... - DTI Home

HRSG, the steam itself is originally raised within the gasifier). The cooled
gases are then exhausted via the stack to atmosphere.
The condensate from the low pressure LP steam turbine is passed through a
condensate preheater prior to entry to the deaerator. Here the incoming water
is heated by direct contact with steam. From the deaerator, there are three
supply lines to the HRSG, namely the HP, IP and LP lines.
The LP pump supplies feedwater directly to an LP evaporator within the
HRSG. Following evaporation, some saturated steam is extracted after the LP
evaporator and used in the dryer to remove moisture from the incoming
pulverised fuel (PF). The remaining saturated steam from the evaporator feeds
into the LP superheater. After being superheated, the LP steam is split into two
lines. One line supplies the superheated LP steam to the LP turbine another
recirculates the LP superheated steam back to the deareator.
The IP pump supplies feed water to the syngas cooler and gasifier membrane
wall where the heat from the gasification process is utilised to generate IP
steam as previously described. Some steam is also bled off and fed to the
gasifier itself as part of the gasification process. The IP steam from the gasifier
is then fed into the HRSG for superheating. Following superheating, the IP
steam is added to the exit line from the HP turbine. These lines combine and
are reheated in the HRSG before entering the IP turbine.
The HP pump supplies feedwater to the high-pressure, low-temperature
(HP/LT) economiser and then on to the HP/HT economiser. Upon leaving the
HP/HT economiser, feedwater is extracted to supply the waste heat boiler
within the gasifier (see above) as well as supplying a source of heat for the
clean fuel gas line. Saturated steam is therefore produced from both the HP
evaporator within the HRSG and the waste heat boiler within the gasifier. The
two steam lines then recombine to be superheated within the HRSG. The
superheated HP steam is then fed to the HP turbine for power generation.
The IP turbine steam supply consists of the HP turbine exit flow combined
with the HRSG IP line. The LP turbine steam supply consists of the IP turbine
exit flow combined with the HRSG LP line.
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