Determination of optimal total area of heat recovery steam generator

Abstract

Heat recovery steam generator (HRSG) plays a critical role in recovering waste heat from exhaust gas in a combined cycle. The performance of the steam cycle in the combined cycle depends on total HRSG area. This paper presents a comprehensive study on the determination of the optimal total area of single-pressure HRSG considering various factors such as exhaust gas temperature, main steam temperature, main steam pressure, reheat steam pressure, and reheat steam temperature. The research methodology involves the development of a mathematical model of HRSG that considers the key parameters affecting the HRSG performance. It is shown that, for given exhaust gas temperature and total HRSG area, there exists the set of steam parameters that yields the maximum net power output of the steam cycle. Furthermore, the power output increases monotonically with total HRSG area. However, the power output increases at a decreasing rate as total HRSG area increases. The optimal total HRSG area is shown to depend on the unit selling price of electricity, the unit cost of heat exchanger, the capacity factor of the power plant, and the acceptable payback period for the investment in the installation cost of HRSG.