Condensate Transfer Pumps. Condensate transfer pumps are used to pump
condensate from the main condensate storage/return tank to the deaerator. Two
condensate transfer pumps, each capable of handling full load operation, shall be
provided of either the horizontal split case or vertical can type. The standby
condensate transfer pump can be used for boiler fill, emergency condensate makeup to the
deaerator, and initial fill of the condenser.
Condensate Cleaning. Oil and other undesirable matter should be removed from
condensate returned from the process and fuel oil tubular heat exchangers. Oil will
cause foaming and priming in the boilers as well as scale.
Condensate containing oil should be wasted.
Filtration. Where the amount of oil-contaminated condensate is so great that
it would be uneconomical to waste it, provide cellulose, diatomite, leaf filters, or
other acceptable methods to clean the condensate.
Feedwater Heaters. Low pressure feedwater heaters are used in the condensate
system between the condensate pump discharge and boiler feed pumps, and utilize low
pressure turbine extraction or auxiliary turbine exhaust steam for heating the
condensate. High pressure feedwater heaters are used in the feedwater system between
the boiler feed pump discharge and the boiler, and utilize high pressure turbine
extraction steam for heating the feedwater. The condensate or feedwater temperature
increase for each feedwater heater will be in the range of 50 to 100 degrees F (28 to 56
degrees C) with the actual value determined by turbine manufacturer's stage location of
steam extraction nozzles. Depending on turbine size, some turbines offer alternate
number of extraction nozzles with usually a choice of using the highest pressure
extraction nozzle. The selection, in this case, of the total number of feedwater
heaters to use should be based on economic evaluation. The feedwater heater equipment
is illustrated in Figure 32.
Low Pressure Heater(s). Use one or more low pressure feedwater heaters to
raise the temperature of condensate from condensate pump discharge temperature to the
deaerator inlet temperature. The heater drains are cascaded from the higher pressure
heater to the next lower pressure heater with the lowest pressure heater draining to the
High Pressure Heater(s). Use one or more high pressure feedwater heaters to
raise the temperature of feedwater from deaerator outlet temperature to the required
boiler economizer inlet temperature. The heater drains are cascaded from heater to
heater, back to the deaerator in a fashion similar to the heater drain system for the
low pressure heaters.
Heater Drain Pumps