Thermodynamic analysis of an MGT/solar field/gasifier plant and CFD study of combustion of high inert content syngas obtained from different biomasses

The paper deals with the numerical study of a 30 kW Micro Gas Turbine integrated with a solar field and a gasifier and fed by various biomass-derived syngases (wood waste, almond shells and rice straw), characterized by a high content of inert species. The research aims to assess the MGT response to the use of these biofuels and to estimate the development of combustion and pollutant emissions. Initially, the design and validation of the entire integrated plant are performed using a lumped parameter thermodynamic solver. After verifying the positive response of the entire plant in terms of cogeneration indices, a more detailed combustion CFD model of the single combustor is set up, including nitrogen oxide calculations. The reacting flow simulations are performed with the Ansys-Fluent® solver, introducing, for each case, the boundary conditions provided by the thermodynamic analysis. These calculations allow the combustion efficiency and pollutant emissions to be assessed, evaluating the feasibility of using alternative clean fuels with high N2 presence in the initial composition. CFD results demonstrate that the combustion process of the analyzed biofuels is not as efficient as that of natural gas, and for some critical compositions, the turbine inlet temperature target cannot be guaranteed. Indeed, the high percentage of inert compounds and the resulting lower temperatures in the combustion chamber lead to the incomplete oxidation of the synthesis gases, significant power losses up to 34%, and high levels of prompt and fuel NOx. Despite the limitations of the examined synthesis gases, these biomass-based synthesis gas fuels ensure maximum power output and sustainability in distributed power generation.