Kinetic Study of Thermal Decomposition and Co-Combustion of Straw Pellets with Coal

Abstract

The main goal of the present study is to assure a more effective use of CO2 neutral fuel (wheat straw) for cleaner energy production with reduced greenhouse carbon emissions by partially replacing a fossil fuel (crashed coal) with a renewable one. This work combines experimental study and mathematical modelling of the processes developing during the co-combustion of straw pellets and crashed coal, aimed at assessment of the influence of the elemental composition and heating values of the mixture components on the main gasification/combustion characteristics, heat output from the device and on the composition of the flue gas products. The experimental study of the development of main gasification/combustion characteristics involves a complex DTG and DTA analysis of straw pellets and crashed coal and an estimation of the main steps of their thermal decomposition, combustion of volatiles, char formation and burnout, thus providing a complex kinetic study of the mixture weight loss rates and of the formation of combustible volatiles (CO, H2) at different stages of thermal decomposition of the solid fuel mixtures. A mathematical model for the combustion of volatiles (CO, H2) downstream the combustor has been built using the MATLAB package, with an account of the CO:H2 molar ratio variations at the inlet of the combustor and the development of exothermic reactions for the H2 and CO combustion dependent on the changes in straw mass load in the mixture of solid fuels.