Thermodynamic and economic analysis of a novel design for combined waste heat recovery of biogas power generation and silicon production

A novel hybrid system based on a combination of a gas turbine cycle, a supercritical carbon dioxide cycle, and an organic Rankine cycle is devised for power generation. Based on the joint layout proposed in this study, the collaborative and efficient utilization of biogas from anaerobic digestion and flue gas from industrial silicon production can be realized. The clean biogas harvested from anaerobic digestion is exploited by a gas turbine, and the resulting hot exhaust gas is then combined with the flue gas from industrial silicon production to power the supercritical carbon dioxide cycle. Addition, the organic Rankine cycle is added as the bottom cycle in the supercritical carbon dioxide cycle to further improve the waste heat utilization efficiency. Energy, exergy, and economic analysis are performed to assess the system's performance and feasibility, the energy and exergy efficiencies are calculated as 43.61 % and 51.07 %, only 4.09 years are needed to recoup the initial investment of the design, and the net present value is as high as 136,864.14 k$.