A thermogravimetric assessment of the tri-combustion process for coal, biomass and polyethylene

Thermogravimetric analysis (TGA) was applied to evaluate the combustion behaviour of combining three feedstocks coal, biomass and polyethylene as a tri-fuel for various blend ratios. The feed materials assessed were bituminous coal (B-C), anthracite coal (A(C)), camphor wood (C-W), wheat straw (W-S) and polyethyleneterephthalate (P-ET). The kinetic parameters of the tri-fuel blends were assessed using a Coats-Redfern integral method. The kinetic analysis indicates that the tri-fuel combustion mechanisms follow the diffusion model (D1 & D4) and can be separated in to three distinct stages. TGA analysis demonstrated that an increase in the blend ratio of biomass (C-W/W-S) and plastic (P-ET) enhances the combustion properties with respect to lowering the ignition (T-i) and burnout (T-h) temperatures, along with an increase in the combustion stability indices (C-s/C-si). This enhancement of the combustion behaviour is more evident for the lower volatile anthracite coal tri-fuel blends. As the blend ratio of the anthracite coal is lowered the overall hydrocarbon-volatile content is increased as a function of increasing the biomass and plastic blend ratios. Laboratory scale analytical analysis of blending biomass, plastic with either bituminous coal or anthracite coal demonstrates a synergistic influence which is observed to benefit the overall combustion behaviour (enhanced mass loss rate and burnout). However, further investigation of tri-fuel blending streams assessing the combustion performance (T-i, T-h, C-i, C-si, E-a, flue gas emissions and ash chemistry) is required at pilot and plant scale.