ANALYSIS OF PINCH AND APPROACH POINT OF HEAT RECOVERY STEAM GENERATOR (HRSG) OF COGENERATION PLANT

This report presents the analysis of pinch and approach point of Heat Recovery Steam Generator (HRSG) of a cogeneration plant. The analysis based on the heat recovery steam generator (HRSG) in Universiti Teknologi Petronas (UTP) Gas District Cooling (GDC) Plant. Pinch point, approach point, steam pressure and HRSG inlet gas temperature are taken as manipulative variables. Pinch point is the temperature difference between evaporator outlet gas temperature and saturation temperature while approach point is the temperature difference between saturation temperature and economizer outlet water temperature. Pinch and approach point should be taken into account in designing HRSG as both of these parameters are used to determine the heat transfer surface area of the HRSG. Designing the HRSG by using pinch and approach point can prevent the temperature cross between gas stream and water/steam stream. In single pressure stage HRSG that consists of evaporator and economizer, the selection of the steam pressure is based on the output steam temperature demand. High steam pressure will produce high steam temperature. The HRSG inlet flue gas temperature will different if different type of gas turbine is used. Different gas turbine has different exhaust gas temperature and mass flow rate of flue gas. Four analysis were performed based on these parameters to evaluate the performance of HRSG. These analysis were conducted using spreadsheet. According to the pinch point, approach point and steam pressure analysis results, decreased of these parameters value individually will increased the steam production rate and thus increased the efficiency of HRSG. For HRSG inlet gas temperature analysis, the steam production rate and efficiency were increased when this parameter value increased