Developing an Innovative biomass-based Power Plant for low-carbon Power production: Exergy and Exergoeconomic analyses

Abstract

In this research, a novel integration of a downdraft gasifier, an externally fired gas turbine, a molten carbonate fuel cell (MCFC), an organic Rankine cycle (ORC), and a cryogenic CO2 separation unit is developed. The exhaust air flow from the gas turbine is completely recirculated to the combustion chamber to utilize the air's high-temperature potential as the oxidizer in the syngas combustion. Produced hot gasses flow into the hot temperature heat exchanger (HTHE) to raise the compressed air temperature up to the gas turbine inlet temperature. Besides this, the MCFC unit is utilized both for producing additional power for the retrofitting CO2 separation unit. Finally, a cryogenic separation unit has been utilized for liquid CO2 production and for recovering H2 and CO from the fuel cell anode exhausts. Detailed exergy and exergoeconomic analyses have performed on the developed thermodynamic model, including a parametric analysis on critical design parameters. The overall exergy efficiency of the system results as 40.76%, the LCOE results as 77.74 USD/MWh, and specific CO2 emission results as 133.3 kgCO2/kWh. Results of the exergoeconomic analysis indicate the gasifier and the combustion chamber are identified as the components with the highest exergy destruction rates (20.18% and 15.54% with respect to the total). Exergoeconomic analysis allows to identify strategies for improving the system, focusing on the heat recovery unit (HRU) and the MCFC as the components with lowest and highest values of the exergoeconomic factor (0.47% and 96.39%), respectively due to high thermodynamic inefficiencies and high investment cost.