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The water fluid circuit includes the condenser discharge that is pumped up to
the drum through a series of pumps and feedwater heaters. The path consists of:
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Two transmission driven condensate pumps
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Condensate polisher
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Steam packing exhauster
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Five levels of low-pressure feedwater heating
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Boiler feed pump, either electric driven start-up or turbine
driven main boiler feed pump
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Three levels of high-pressure feedwater heating
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Economizer, integral to furnace, and upward to the drum
Feedwater entering the steam drum mixes with the existing saturated water and
flows down through the downcomers located outside the boiler. Water from the
downcomer is distributed to the furnace tubes via lower headers. Heat applied
by radiation and convection to the furnace tubes causes boiling of the fluid in
the tubes. Circulation will increase with heat input until the buoyancy
difference equals frictional pressure drop and other losses. The saturated
steam passes to the convection pass, enclosure wall, the primary superheater,
the platen superheater, and the secondary superheater before it goes to the
high-pressure turbine. Steam exhausted from the main turbine is reheated in the
boiler, through 3 stages of reheating and supplied to the IP and LP steam
turbines before being exhausted to the condenser.
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