Design and Optimization of A Gas Turbine Waste Heat Recovery System

In this paper a waste heat recovery system was designed and evaluated for Olorunsogo-I Thermal Power Plant. The heat recovery steam generator (HRSG) system for eight turbine units of the plant was used to recover maximum possible waste heat from the exhaust gas and selected a suitable steam turbine according to the heat demand capacity. This generated additional power and thus converted the plant into a Combined Cycle Gas Turbine (CCGT) plant. The HRSG was modeled and optimized using the Engineering Equation Solver (ESS) software. This determined the maximum possible power output and the optimum steam pressure. Technical and practical limitation parameters - pinch point temperature, approach point temperature and sulphur dew point – in the stock were considered. The estimated maximum power output of the steam turbine is 3.827 MW. A steam turbine with a rated power output of 3.69 MW (at 12.7 bar inlet pressure) was selected as the optimum steam turbine for the desired conditions, utilizing 13284 MJ/h of recovered heat energy which is equivalent to 38.73% of total waste heat energy (34299.36 MJ/h) in the flue gas per hour. This study produced additional 29.52 MW power output to the plant per hour basis.