Influence of pretreatments on the fuel properties and pyrolytic kinetics of biomass

The hydrophilic and slagging natures of the waste biomass pose adverse effects on its storage and subsequent usage as a solid fuel in energy generation. These drawbacks demand the pretreatment of biomass to improve its quality. Therefore, in this research, two pretreatment processes, namely, demineralization and torrefaction were employed sequentially to improve the properties of raw biomass. The effectiveness of treatment was analyzed in terms of fuel properties, physicochemical aspects, and pyrolytic kinetics. The results show that acid leaching reduced the mineral content in the biomass while the torrefaction resulted in carbon enrichment. The simultaneous application of both processes improves the calorific value of the biomass by 11% and promotes the hydrophobic behavior in it. The key pyrolytic kinetic parameters, activation energy (Ea), and reaction mechanism, for the raw and modified biomass samples were determined using Coats Redfern (CR) and Criado methods. In devolatilization stages, Ea values were 165 and 196 kJ/mol for raw and demineralized biomass, respectively, and both followed a share of reaction order and diffusion-based mechanism. Ea during the carbonation stage was 94 kJ/mol, 157 kJ/mol, and 161 kJ/mole for raw, demineralized, and sequentially treated biomass, respectively. Thermodynamic analysis revealed that biomass treatment makes the material more feasible for bioenergy production. Overall, the results suggest that demineralization coupled with torrefaction can significantly improve the fuel potential of biomass as a solid fuel.