Co-Combustion of Pulverized Coal and Biomass in Fluidized Bed of Furnace

Abstract

Combustion processes of two fuels, pulverized coal and biomass, in furnaces take place at steady state. Combustion of condensed fuels involves one-way interfacial flux due to phenomena in the condensed phase (evaporation or pyrolysis) and reciprocal ones (heterogeneous combustion and gasification). Many of the species injected in the gas phase are later involved in gas phase combustion. This paper presents results of combustion process of two-phase charge contained coal and wetted biomass, where the carrier was the air with given flow rate. The furnace has three inlets with assumed inlet flow rate of coal, biomass, and air, and combustion process takes place in the furnace fluidized space. The simulation of such combustion process was carried out by numerical code of open source computational fluid dynamics (CFD) program code_saturne. For both fuels, the moist biomass with following mass contents: C = 53%, H = 5.8%, O = 37.62%, ash = 3.6, and mean diameter of molecules equal to 0.0008 m and pulverized coal with following mass contents: C = 76.65%, H = 5.16%, O = 9.9%, ash = 6.21%, and mean molecule diameter 0.000025 m were used. Devolatilization process with kinetic reactions was taken into account. Distribution of the main combustion product in furnace space is presented with disappearance of the molecules of fuels. This paper presents theoretical description of the two-phase charge, specification of the thermodynamic state of the charge in inlet boundaries and furnace space, and thermal parameters of solid fuel molecules obtained from the open source postprocessor paraview.