Optimization of bischofite pyrolysis furnace system based on orthogonal experiments and exergy analysis with assessment of its green economy

Spray pyrolysis technology has the potential for valorization of industrial waste bischofite in a sustainable and environmentally friendly manner. This study utilizes Aspen Plus® to simulate and optimize the pyrolysis furnace system for bischofite. Through orthogonal experimental design, key parameters, including the air-fuel ratio, the ratios of primary and secondary air, the solids content of the bischofite precursor, and the temperature of the combustion-supporting air were determined to improve chemical recovery rate, net profit, and energy efficiency, thereby achieving sustainable and clean production. Additionally, the optimized pyrolysis process was compared with the traditional precipitation process in three dimensions: energy consumption, carbon emissions, and economic performance. The results indicate that the optimized operating conditions reduce the total exergy destruction per ton of bischofite from 2211.580 MW (127,190 kWh/t) to 1967.095 MW (113,129 kWh/t) while increasing the system exergy efficiency by 8.15 %. Specifically, the exergy destruction in the subareas of CH4 combustion, pyrolysis, and dehydration combustion is reduced by 66.01 %, 6.13 %, and 8.99 %, respectively. Compared with the current ammonia and lime precipitation methods, this optimized pyrolysis process can reduce CO2 emissions by 6.38 % and 6.28 %, respectively, while the net profit can be improved by 38.39 % and 26.54 %, respectively. The results confirm that the spray pyrolysis process has a broad application prospect in the bischofite valorization and is expected to become the preferred technical scheme in the industry.