Investigation of the synergistic effect and kinetic behavior of anthracite and biochar during co-combustion process in pure oxygen atmosphere

The non-isothermal thermogravimetric analysis was conducted to evaluate the combustion characteristics and kinetic behavior of Anthracite (AN), Robinia pseudoacacia char (RPC) and their blends. The physical and chemical characteristics of AN and RPC were also studied systematically to explore the contribution to fuel combustion performance. And the synergistic effects of RPC and AN were quantitatively discussed by using an interaction factor. The investigation has shown that, compared to AN, RPC has better combustion reactivity due to the lower ordering degree and the higher defecting degree and more developed porous structures. The combustion reactivity of AN can be enhanced after adding RPC, and the combustion reactivity gradually increased with increasing heating rate. The synergistic effect can be obvious observed during co-combustion process of AN and RPC. When the mass ratio of RPC at 20 similar to 80 wt % and the heating rate at less than or equal to 15 degrees C/min, interaction factors (IF) were greater than 1.15, which has a positive burning effect. The apparent activation energies and pre-exponential factors were determined by using the methods of Coats-Redfern (CR), Madhusudanan-Krishan-Ninan (MKN), Zavkovic (ZK) and Flynn-Wall-Ozawa (FWO). The accuracy of the kinetic results and calculated methods were evaluated by using kinetic compensation effect (KCE) from isoconversion and iso-heating rate methods. As a result, the applicability of the four calculation methods during co-combustion process of AN and RPC is FWO = ZK > MKN > CR. The mean of apparent activation energies of AN and RPC from FWO/ZK methods were 149.76 kJ/mol and 97.13 kJ/mol, respectively.