Isoconversional kinetic analysis of the pyrolysis of Salt Lake industrial waste bischofite with isothermal reaction time predictions

Abstract

Extracting magnesium resources from Salt Lakes industrial waste bischofite by pyrolysis technology has become a feasible waste utilization method. High-temperature corrosion has become a safety issue during bischofite pyrolysis. Thus, pyrolysis behavior and kinetic analysis are essential to control pyrolysis reactions. In this study, a thermogravimetric analyzer was used to understand the pyrolysis behavior of bischofite. TG-DTG curves show that the bischofite pyrolysis includes dehydration and coexistence stages. Thermal hazards caused by corrosive gases appear in the temperature range of 174.8–202.3 °C. The kinetic parameters were calculated using three model-free methods (FWO, KAS, and FR) and a master plots method. The results show that the activation energy of the dehydration stage is smaller than the coexistence stage. The reliability of the master plots method was also investigated. The results show that the reaction models for the dehydration (II-1, II-2, and II-3) and coexistence stages (IV-3) were credible. In addition, the isothermal method was used to predict the reaction time under different temperature programs. The results show that controlling the reaction temperature at 700–800 ℃ can improve the conversion efficiency and product quality. This work provides basic data for promoting the development of bischofite pyrolysis technology.