Biomass gasification to syngas of phosphogypsum as gasification agent: Thermogravimetric analysis and gasification performance

Biomass utilization in energy production is often regarded as almost carbon neutral, and biomass gasification has significant potential for obtaining products with more value and potential applications for utilizing agricultural and forestry waste. Meanwhile, Phosphogypsum (PG) is a hazardous solid waste generated as a by-product of the wet process of phosphoric acid production, resulting in significant environmental issues. Based on the above, this work proposed that solid waste be utilized effectively by producing syngas through biomass gasification using PG as a gasification agent. The thermal characteristics of biomass with PG and the distribution of gaseous products were discussed, and the effects of the ratio of PG to biomass (O/B values) and temperature were investigated. The mechanism function and activation energy (Ea) were determined by the model-free (Kissinger-Akahira-Sunose method), model-fitting (Coats and Redfern method), and Malek methods. The results indicate that the solid-phase product of the process is calcium sulfide. The experiment obtained the highest peak mass loss R p2 and comprehensive devolatilization parameter D when the O/B value of 0.5, leading to better devolatilization behavior during the devolatilization stage. The kinetics observed during the devolatilization stage show a decreased activation energy as the reaction progresses. Conversely, it gradually increases during the biochar gasification stage. The primary gaseous product emissions exhibited observable peaks in the devolatilization and biochar gasification stages. A significant amount of methane is released during the biochar gasification phase. Alkali metals and their oxides in PG are believed to serve as catalysts or facilitate the process of tar cracking during gasification.