A waste heat recovery steam power generation system for ACE Power Embilipitiya (Pvt) Ltd, Sri Lanka

In this study, the heat recovery from exhaust gas at the ACE Power Embilipitiya (Pvt) Ltd (APE) in Sri Lanka was conceptually proposed and evaluated. APE has an installed capacity of 100 MW comprising 14 units of 7.5MW medium speed diesel engines fired with heavy fuel oil. There is only a minimum recovery of waste heat in the plant at the moment, only for fuel preheating, whereas waste heat recovery (WHR) boilers of 750kWth are equipped on eight engines. The larger portion of the waste heat is dumped into the environment without being used in any reasonable way. The objective of this work was to design a HRSG system for the remaining six engines to recover maximum possible heat from the exhaust gas and select a suitable steam turbine according to the heat demand capacity of the proposed HRSG, for generating additional power and thus converting the APE plant into a sort of a combined cycle. At the initial stage of the investigation, the amount of recoverable waste heat was estimated by evaluating the known parameters of the engines at fully loaded condition. The maximum theoretical waste heat recovery potential from the exhaust gas stream of one engine was calculated as 9807.87 MJ/h, equivalent to a heat rate of 2724.4 kW. The modelling and optimization of the proposed HRSG was done using the Engineering Equation Solver (EES) software, considering technical and practical limitations such as pinch point temperature difference, approach point temperature difference, terminal temperature difference and sulphur dew point in the stack. A commercially available steam turbine with a power output of 3.579 MW was selected as the optimum steam turbine for the desired conditions, utilising 12884.4 MJ/h of recovered waste energy amounting to 21.89% of the total available energy in the flue gas.