ESTIMATION OF CONDENSATE MASS FLOW RATE DURING PURGING TIME IN HEAT RECOVERY STEAM GENERATOR OF COMBINED CYCLE POWER PLANT

In this paper the transient modeling of heat recovery steam generator in purging time was considered. In purging time, compressed air from the gas turbine was used to purge a combustible gas from heat recovery steam generator. During this time; steam condensate was formed in the superheater stage which should be drained completely to avoid some problems such as deformation of superheaters. Because of this reason, estimation of drain formation is essential to avoid this problem. In this paper an energy model was provided and this model was solved by MATLAB software. Average model error is about 5%. Results show that, during purge time, steam temperature was decreased from 502 degrees C (superheater 2), 392 degrees C (super-heater), and 266 degrees C (Evaporators I and 2) to 130 degrees C, 130 degrees C and 220 degrees C, respectively, and also steam pressure was decreased from 52 bar to 23 bar during purge time. At end of purge time, condensate formation was about 220 (l) when inlet gas temperature was equal to 100 degrees C and purge gas mass flow rate was equal to 386.86 kg/s.