Thermal performance analysis and synergistic effect on co-pyrolysis of coal and sugarcane bagasse blends pretreated by trihexyltetradecylphosphonium chloride

This paper aims to investigate the thermochemical behavior and synergistic effects of low-rank coal, and sugarcane bagasse (SCB) blends after pretreatment by trihexyltetradecylphosphonium chloride ([P-66614] [Cl]). Three samples of coal and SCB blends, C75B25, C50B50, and C25B75, in ratios 3:1, 1:1, and 1:3 by weight, respectively, were prepared and pretreated with [P-66614] [Cl] at 150 degrees C for 3 h. Hereafter, they were subjected to thermogravimetric analysis (TGA) under an inert atmosphere at a fixed heating rate of 20 degrees C. Thermal performance and synergistic effects were evaluated and compared by reactivity, kinetic, and thermodynamic analysis. Ten different models related to four reaction mechanisms were applied to evaluate kinetic and thermodynamic parameters. During pretreatment, [P-66614] [Cl] was completely absorbed in blends and individual fuels. TGA results showed that IL treatment altered the thermal profiles of the blends at 350-500 degrees C. [P-66614] [Cl] treatment caused an increase in total weight loss of 7.15%, 2.81%, and 1.62% for C75B25, C501350, and C25B75, respectively. Peak temperatures for C75B25, C50B50, and C25B75 changed from 356, 365, and 374 degrees C to 472, 459, and 485 degrees C, respectively, after IL treatment, indicating thermal stability. The relative mean reactivity (Rm) for C75B25 increased (8.78 to 14.94%min(-1)degrees C-1), whereas for C50B50 and C25B75 (16.1 and 20.15%min(-1)degrees C-1 to 14.84 and 13.61%min(-1)degrees C-1) decreased after [P-66614] [Cl] treatment, implying synergistic effects. Among the reaction models, R-2 values in excess of 0.80 were obtained for all the samples, with activation energy of C75B25, C50B50, C25B75, C75B25 + [P-66614] [Cl], C50B50 + [P-66614] [Cl], and C25B75 [P-66614] [Cl] in the range of 12.48-51.17 kJ/mol, 12.53-46.07 kJ/mol, 10.85-45.40 kJ/mol, 8.11-35.50 kJ/mol, 6.9-33.59 kJ/mol, 6.65-41.32 kJ/mol, respectively. Entropy values suggested increased depolymerization of fuel structure due to IL treatment. Low synergy was detected in untreated as compared to IL treated blends. [P-66614] [Cl] treatment seemed to have a more significant effect on samples having higher carbon content as compared to SCB. This study could be useful in modeling and designing co-thermochemical conversion processes for coal and SCB blends after low-cost [P-66614] [Cl] pretreatment.