Design optimization of trio concept combustor geometry for low-grade biomass producer gas combustion

Abstract

Biomass as carbon-neutral fuel is a promising alternative to mitigate global warming problems. Biomass conversion into producer gas (PG) through air gasification allows the co-firing of PG burners with fossil fuel burners in boilers for large scale power generation. However, PG is highly diluted with nitrogen which reduces the heating value resulting in significantly higher PG flow, eliminating the possibility of using conventional compact gas burner designs. To burn the low-grade PG, special design for the combustor is required. Novel combustor design which combined three theories of swirl vane, cyclonic and staged combustion to facilitate PG combustion in compact geometry was elaborately investigated. Flow hydrodynamics and combustion characteristics of low-grade PG were studied using ANSYS-FLUENT simulation software. Design of Experiments (DOE) method was applied to optimize the design of the combustor geometry. The arrangement of simulations was designed based on the instruction of DOE. The optimum geometry design of combustor was 500 mm combustor length, 150 mm combustor diameter, 60° swirl vane angle and 0.4 secondary inlets position to total combustor length ratio. The combustor achieved optimum performance of 1965 K outlet temperature, 18 ppm CO emissions and 33 ppm NOx emissions at slight lean condition with equivalence ratio of 0.9.