Co-pyrolysis of Bituminous Coal (BC) With Different Agro Residues: Kinetics and Pretreatment Effect

Abstract

On a global scale, power generation is accomplished through utilizing both fossil fuels and renewable energy sources. Fossil fuels can exhaust reserves and contribute to environmental pollution. India produces roughly 750 million tonnes of biomass yearly, mostly from agricultural leftovers, with 230 million tonnes of surplus biomass, which can be used along with coal as a secondary raw material, reducing dependency on coal. In this study, the co-pyrolysis of untreated and pretreated biomasses, Artocarpus heterophyllus (AH), Aeglemarmelos (AM), and Ocimum tenuiflorum (OT) with coal, was conducted in a semi-batch reactor at 550°C. The pretreatment of biomass using four different pretreatment methods, such as acid, alkali, DI water, and torrefaction, then co-pyrolysis with coal. The kinetic analysis was done using different isoconventional methods like: FWO (Flynn–Wall–Ozawa), KAS (Kissinger–Akahira–Sunose), and Starink models. A series of experiments was conducted to examine the effects of different biomass/coal blended ratios, specifically 75:25, 50:50, and 25:75 (weight-to-weight) between biomass and coal, resulting in increased char yields and decreased overall tar and gas production. Additionally, it was shown that adding biomass to the mixture enhances the synergistic effects on product distribution. The co-pyrolysis of coal and biomass exhibits distinct patterns of Alkali and Alkaline Earth Metals (AAEM) release, and the pretreatment effect reduces the AAEM. The results revealed that the liberation of alkali metals during the co-pyrolysis of untreated biomass with coal increases, and decreases during the co-pyrolysis of pretreated biomass with coal. This trend was observed regardless of the temperature, the ratio of biomass to coal, and the presence of biomass minerals. When comparing untreated and pretreated biomass with coal co-pyrolysis, the char obtained increases with the coal ratio, whereas the number of inorganic compounds and the AAEM value decrease to a negligible extent.