Design and performance evaluation of a waste-to-energy plant integrated with a combined cycle

In this paper, a waste-to-energy (WTE) system integrated with a gas fuelled combined cycle is considered. The plant is designed as a possible future option for thermal utilization of urban wastes in the northern part of the Turin Province, Italy. The plant should provide electricity (about 160 MW at maximum electric load) to the grid and heat to a district heating network (about 50 MW at maximum thermal load). This kind of plants is particularly interesting because of the high net electric efficiency (about 46%) that is possible to achieve, compared with the equivalent global efficiency of the separate plants (about +7% waste utilization efficiency with respect to conventional plants), and the complex design that is required.The initial plant design is improved through a thermoeconomic procedure. The optimal plant is characterized by −0.2% unit cost of electricity and +0.6 MW electricity production with respect to the initial design.An economic analysis is also performed. Economic indicators are estimated and used to complete the comparison between the conventional and the integrated solutions under different market conditions. With respect to a stand-alone waste-to-energy plant, the integrated plant is characterized by similar pay-back period and higher net benefit cost ratio.