Experimental and numerical techniques for exploring conventional and seasonal biomass combustion optimization: insights into thermokinetics, combustion characteristics, and ash fusion analysis

Our study delves into the thermokinetics, thermal properties, and operational indices crucial for the accurate design considerations of the combustion process, offering novel insights for wheat straw (WS), hemp (H), and their optimal blend. The blends are meticulously characterized using FTIR, GCV, and CHN-S; the ash samples of pure biomasses and the best blend are analyzed using AFT and XRF to assess their behavior. The co-combustion process is executed in TGA at a non-isothermal temperature ramp of 10 °C/min, and the free radical-dependent synergistic effects are observed for WS40:H60 among the blends. Two staged thermal degradation zones of 140–380 °C and 410–510 °C with values of first-stage kinetic energy for WS100, H100, and WS40:H60 of 73–167, 34–81, and 43–102 kJ/mol, and second-stage kinetic energy of 8–309, 34–265, 12–297 kJ/mol, respectively, are observed utilizing diffusional, geometrical contraction, and reaction order models for the Coats-Redfern integral method. Primarily, ΔH^‡ and ΔG^‡ are positive, but ΔS^‡ is negative for all models in the first and second stages. The slagging and fouling behavior of WS100, H100, and the best blend of WS40:H60 ash are investigated. The SiO₂/Al₂O₃ ratio improved from 10.23 % and 11.95 % for WS100 and H100 to 9.75 %, and the flow temperature increased from 1159 to 1215 °C for the WS40:H60 blend. Adding hemp shifted the acidity index from high to medium levels on the ternary equilibrium phase diagram. Combustion parameters (ignition index, combustion index, and flammability index) concerning the propensity of biomass to ignite and burn, which are especially helpful in fire safety-related handling of these materials, provided excellent results and improved combustion performance (combustion efficiency = 96.91 %; heat release = 0.113 MJ/min). Ash fusion also supports the better suitability of the optimum blend, as identified in thermokinetic and combustion analysis, to be used as a solid fuel in direct biomass co-fired powerplants.