Thermodynamic Analysis of Biomass Gasification-Based Power Generation System Through Indirectly Heated GT and S–CO2 Cycle

Abstract

The study emphasizes on the modeling and thermodynamic performance prediction of a novel biomass gasification-based combined cycle plant. It consists of a topping indirectly heated topping gas turbine (GT) cycle and a bottoming supercritical CO2 (S–CO2) cycle for combined power generation. Sawdust is considered as the driving fuel of the plant, which is gasified in a downdraft gasifier and thus the derived producer gas is further burnt in a combustor-heat exchanger combined (CHX) unit. The CHX unit indirectly heat-up the working medium (air) of the topping GT cycle and the CHX exhaust is further utilized in the bottoming S–CO2 cycle to produce electricity in a combined manner. Simulated performance of the plant is judged over wide ranges of considered pressure ratio (rp) and the gas turbine inlet temperature (TIT). The rp value is varied between 4–16 and the TIT is varied between 900 and 1100 °C. Overall electrical efficiency of the plant is about 46% at rp = 4 and TIT = 1000 °C. At the same thermodynamic state points, calculated value of required biomass input is 0.017 kg/s and also the combined net output from the plant is about 140 kW. Overall electrical efficiency value increases with increase in rp value, for all GT TITs as well as hot end temperature difference (HETD) of the CHX unit.