Abstract
This paper presents the thermodynamic analysis of a medium size dual purpose plant driven by 9.65 MW diesel engines. The water is produced by a 0.9 mgd RO plant to maintain a product ratio of 5 gallon/kWh. A scheme of two options is proposed to utilize the engine waste heat, from engine block and exhaust gases, to increase the RO production. One option is a Rankine Freon Cycle (RFC) while the other is a Brayton steam cycle (BSC). In RFC a Freon boiler (2 MPa, 75°C) generates the vapour required to drive a Freon turbine. Whereas in BSC, engine cooling water flashes to produce the steam required to drive a turbine. In either option the power generated is used to enhance the RO production.
Layout of the scheme is presented and systems are analyzed. For 15000 inhabitants community, the water produced increases by 30 percent and 37.6 percent for the RFC and BSC respectively. The engine power increases by 6.5 and 8.2 percent with RFC and BSC respectively.