Pyrolysis Characteristics of Straw Fuel and Its Compound Fuel

To address the global energy crisis and valorize industrial and agricultural solid waste, a corn straw-oil sludge composite fuel (CF) with a mass ratio of 1.5:1 was prepared. Pure corn straw fuel (SF) served as the control. The pyrolysis characteristics of both pellet fuels up to 1000 °C were systematically investigated via thermogravimetric (TG) analysis at heating rates of 10, 20, and 30 °C/min. The pyrolysis characteristics were analyzed via characteristic parameters, Gaussian fitting assignments, and the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) model-free kinetic methods. Within the tested temperature range (50-1000 °C), CF exhibited higher characteristic parameters than SF, suggesting facile initiation under the conditions tested. A positive deviation between the experimental and calculated TG curves preliminarily indicated a synergistic effect during the core copyrolysis stage (170-650 °C). Gaussian fitting was tentatively assigned to four bond cleavage stages for both fuels, with the cleavage of C_al-heteroatom bonds as the dominant reaction (proportion >50%). The addition of oil sludge introduced more alkyl-substituted aromatic compounds into CF, increasing the proportion of C_ar-C_al and C_ar-heteroatom bond cleavage from 6.8% (SF) to 15.8% (CF). The average apparent activation energy of CF was higher than that of SF. Notably, CF exhibited a kinetic characteristic of low initial activation energy and high overall activation energy, which favored facile pyrolysis initiation and inhibition of side reactions.