Development of a numerical model for co-combustion of the blended solid waste fuel in the grate boiler

Abstract

This paper presents a model developed to numerically simulate the combustion of blended solid fuel in the grate boiler. The model can efficiently reproduce the thermal conversion process through a separate definition of the participating fuel by their unique physical and chemical properties. The advantage of this consideration is its flexibility and comprehensiveness in understanding and predicting the system reaction. The model is firstly validated with lab-scale experimental results. The validation shows that after the mechanism kinetics is determined through mono-combustion, the model is able to resemble the co-combustion result through direct numerical blending. This model is then extended for application in the industrial-scale boiler to investigate the blended combustion of waste wood chips with different ash content. The mono-combustion of the fuel is verified against boiler measurements, and then the effect of blending ratio and air supply is analyzed numerically. The results show that co-combustion can enhance on-grate carbon conversion as well as overall efficiency, as the low ash fuel content increase. Moreover, increasing the primary air supply while keeping the same total air excess can also elevate the thermal efficiency effectively.