Heat Recovery Steam Generator (HRSG) consists of several components such as superheater, evaporator and economizer which each component has different functions. HRSG components can be seen as following below:
Superheater is one of HRSG components that serves to raise temperature of saturated steam to be superheated steam. Superheated steam when used to perform work by way of expansion in the turbine or steam engine will not condense, thus reducing the possibility of danger which is caused by back stroke caused by steam that condenses yet in time, so it will cause vacuum in undue area of expansion.
Evaporator is one of HRSG components which serve to convert water into saturated steam. Evaporator pipes in steam boiler are usually located on the floor (water floor) and also on the wall (water wall). In this pipes, quality of saturated steam at 0.80 to 0.98, so most are still shaped in liquid phase. Evaporator will heat water that falls from steam drum which still in liquid phase to form the saturated steam so it can be forwarded to superheater.
Figure 1: HRSG Components
Economizer is one of HRSG components that consist of water pipes that are placed on the track of flue gases after evaporator pipes. Economizer pipes are made of steel or cast iron materials that are able to withstand high heat and pressure. Economizer serves to heat feed water before it enters steam drum and evaporator. Furthermore the evaporation process can be easier by using high temperature flue gas of HRSG so increase the efficiency of HRSG because it can reduce heat loss in the Heat Recovery Steam Generator (HRSG). Water which enters evaporator is at high temperature so evaporator pipes are not easily damaged due to difference in temperature is not too high.
Preheater is one of HRSG components that serves as initial heater of water which is pumped from condenser before enter into feed water tanks. In the HRSG system, preheater serves to raise temperature before enter feed water tanks which later will be forwarded to economizer.