Analysis of Combustion Performance of Non-Conventional Syngas in mGT Combustor: Assessment of the Impact of the Quality of Synthesis Gas Towards Flame Stability and Emissions

The current limited availability of conventional fossil fuels, e.g., natural gas, as a result of the active demand in the industrial revival, leading to increasing prices as well as uncertainty and tension on the international market, strengthens the interest on energy source diversification to ensure sufficient sustainable resources for both heat and electricity demand. Non-conventional renewable resources like biogas, syngas, and biofuels are good candidates to achieve these energy mix goals, especially in a decentralized power production context, e.g., when used in micro Gas Turbines (mGTs) in small-scale cogeneration applications. Moreover, they also present the benefit of reducing CO2 emission and, while doing so, helping to move towards global zero emission by 2050. However, given their specific properties, i.e., a lower energy content, a lower overall conversion efficiency, different and altering composition, as well as an important steam fraction when not properly post-treated, a better characterize of these non-conventional energy sources in their combustion behavior is needed. The aim of our work is thus to identify the combustion behaviour of several characteristic syngases in a typical industrial combustor, the Turbec T100 combustion chamber, designed for operation using natural gas. The performance of the combustor has been analysed using CFD calculations, under different syngas composition with increasing remaining steam fraction, aiming to determine the maximal allowable rest steam fraction, in an attempt to limit syngas post-treatment after production towards enhanced global cycle performance. In particular, the ignition and stability of the flame has been studied under a syngas pilot flame. To study this, velocity and temperature fields are analysed, as well as the specific flue gas composition. While the simulation results using dry syngas show temperature distributions and emission prediction in line with previous observation, the steam dilution effect leads to a clear shift in both temperature and emissions. More specifically, it is found that especially NOx emissions are sensible towards changes in pilot and main flame fuel distribution alterations. These obtained results will serve as benchmark for future characterization for a specific range of diluted inlet conditions of raw syngases, as well as specific studies on the impact of pilot/main flame fuel distribution towards flame stability and emissions control, which will allow to fully exploit their potential in small-scale cogeneration application.