Advance thermal configuration using computational fluid dynamic in co-firing coal and biomass.

Abstract

In Malaysia, coal is the largest fossil fuel used to generate power electricity which is 54.05%. By burning coal, greenhouse gas (GHG) emissions will continuously increase and affect global warming. Therefore, one of the alternatives is by promoting the co-firing coal and biomass in the existing coal-fired power plant in Malaysia. The past decade has seen an increase in the use of Computational Fluid Dynamic (CFD) to analyse the thermal performance of the coal-fired power plant. A coal-fired power plant for this study is referring to a 150MW subcritical boiler with tangential burner with the design pressure and temperature are 188 bar and 540 °C. This plant burned coal from Adaro and Hatillo. CFD simulation for co-firing is using 5% of sawdust at first level burners. From this study, several CFD methods were applied including the Eulerian-Langrangian approach to solve the two-phase gas-solid equation, Reynolds Averaged Navier Stokes (RANS) equation combined with k-ɛ Model to solve the turbulence problem in the gas phase, Discrete Ordinates Method (DO) to solve the radiative transfer equation (RTE) and Weighted Sum of Gray Gases Model (WSGGM) was used to calculate the absorption coefficient of the gas mixture. Based on the contour analysis result, found out that by co-firing coal and biomass, the burnout is reduced from an average of 0.45 kg/s to 0.33 kg/s when compared to pure coal combustion. This is mainly due to high volatile matters (VM) in the biomass. The concentration per unit thermal is also reduced to 42% when co-firing with sawdust. The early devolatilization will increase the gas and local temperature at each burner zone. The CO concentration was higher at the burner zone due to devolatilization.