A hot primary air heater(HPAH)technology was introduced

which uses the heater installed on the hot primary air duct to heat condensation water

so the steam extraction amount can be reduced to increase the turbine's work ability

thus to save the energy.Moreover

the combined application of the HPAH and low pressure economizer(LPE)was studied

and the its application in a 600 MW unit was designed and calculated.The results show that

the HPAH is suitable for units with large quantity of cool air

high exhaust temperature and surplus pressure margin of primary draft fan.The energy conservation potential of the LPE is lower at low load

but the HPAH is on the contrary.The combined application of them can save net coal consumption rate by more than 3g/(kW·h)at both low and high load.