Thermogravimetric analysis on the co-combustion of biomass pellets with lignite and bituminous coal

This work presents comparative study on the combustion of biomass pellets (BP) with Bituminous coal (BC), and Xiao longtan lignite (XL) using thermogravimetric (TG) analysis. The results show that the combustion process of BP:BC can be divided into the release and combustion of volatile compounds, oxidation of BP char and combustion of BC char. While there are two stages for the blend of XL and BP, which are the combustion of volatile compounds and the char burning of BP and XL. With increasing BP ratio, the maximum combustion rate and combustion index increase, while the burnout temperature decreases, indicating the combustion performance of coal can be improved. In addition, interactions between BP and XL are more significant than that of BP and BC. The maximum deviations are found to be 30% BP with BC and 10% BP with XL. Reaction mechanisms are analysed using Coats–Redfern method. The first order model is found to be suitable for the first stage of biomass burn (stage 1) and coal combustion of BC:BP blends. Diffusion controlled model D3 and D4 are the most effective for the second stage of biomass burn and XL combustion, respectively. The minimum activation energies of biomass blending is obtained with a BP ratio of 30% for BC and 10% for XL.