Possibilities for gas turbine and waste incinerator integration

The aggressive nature of the flue gases in municipal waste incinerators does not allow the temperature of steam in the boiler to rise above 400°C. An increase in steam temperature can be achieved by external superheating in a heat recovery steam generator positioned behind a gas turbine, so that steam of a higher energy content becomes available for electricity production. The paper addresses two basic schemes. In one case, steam generated at a waste-to-energy plant is superheated in a combined-cycle plant that operates in parallel. In the other case, the exhaust from a gas turbine plant is sent through a superheater section to the waste incinerator's boiler providing preheated combustion air. Performance of these configurations together with two modified schemes was analyzed in terms of efficiency, natural gas consumption and boiler surface area. An exergy analysis of the cases was carried out. The results showed that the integrated options can effect a substantial increase in efficiency. The hot windbox configuration was found the most effective solution, offering a smaller boiler surface area along with a moderate rate of natural gas consumption.