Numerical analysis of a microturbine combustion chamber modified for biomass derived syngas

A CFD analysis was carried out to study the performance of a modified combustion chamber of a micro gas turbine with the objective to change its fuelling from natural gas to biomass pyrolysis gas. The micro gas turbine is a component of a pilot IPRP (Integrated Regenerated Pyrolysis Plant), a distributed energy system, based on a rotary kiln reactor for the pyrolysis of biomass. This paper describes the combustion process occurring inside the combustion chamber of the micro gas turbine. In particular, a new, revised kinetic scheme was implemented in the RANS analysis to better reproduce CO oxidation and flue gases temperature, for both methane and pyrolysis gas combustion; further investigation was undertaken on NOx formation mechanisms, which are now modeled through a non-adiabatic PPDF approach, also taking into account the effects of turbulence interaction. CFD simulations for natural gas and pyrolysis gas combustion were performed for two different annular rich-quench-lean combustion chamber configurations, one with the original design for natural gas and one with a modified design optimized for syngas, in order to quantify the advantage of using a dedicated design. Furthermore, through the numerical analysis, the hot spots of the combustor have been identified and monitored the to study the possible effects of material corrosion due to high temperatures.