Cylindrical particle modelling in pulverized coal and biomass co-firing process

Abstract

Numerical analysis of co-firing pulverized coal and biomass in a vertical cylindrical laboratory furnace is explored. The ratio of coal and biomass in the fuel was 80:20 by mass for all cases. The mathematical model of combustion in the furnace was established by describing physical phenomena such as turbulent flow, heat and mass transfer, devolatilization and combustion.A 3D-model of combustion in a laboratory furnace was created using the CFD software FLUENT. The shape of the biomass particles was estimated as cylindrical and was accounted for in the calculation of particle trajectories via a custom-developed model. Experimental measurements were conducted on a 20 kW laboratory furnace with controllable wall temperature. The temperature varied in the range from 1233 K to 1823 K, depending on the case. Excess air for combustion was set at 10% or 20%, depending on the case. The developed model shows better agreement with the experimental data than the existing models, which estimate particles as spheres. Analysis of the results shows that the influence of the particle size increases with the size of the particle. Also, the geometry of the cylindrical particles strongly influences the beginning and the intensity of the devolatilization process and subsequently the combustion process.