Pyrolysis Characteristics of Straw Fuel and Its Compound Fuel

Abstract

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 Cal–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 Car–Cal and Car–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.