Computational fluid dynamics modeling of rapid pyrolysis of solid waste magnesium nitrate hydrate under different injection methods

Abstract

This study developed a numerical model to efficiently treat solid waste magnesium nitrate hydrate through multi-step chemical reactions. The model simulates two-phase flow, heat, and mass transfer processes in a pyrolysis furnace to improve the decomposition rate of magnesium nitrate. The performance of multi-nozzle and single-nozzle injection methods was evaluated, and the effects of primary and secondary nozzle flow ratios, velocity ratios, and secondary nozzle inclination angles on the decomposition rate were investigated. Results indicate that multi-nozzle injection has a higher conversion efficiency and decomposition rate than single-nozzle injection, with a 10.3% higher conversion rate under the design parameters. The decomposition rate is primarily dependent on the average residence time of particles, which can be increased by decreasing flow rate and velocity ratios and increasing the inclination angle of secondary nozzles. The optimal parameters are injection flow ratio of 40%, injection velocity ratio of 0.6 and secondary nozzle inclination of 30 degrees corresponding to the maximum decomposition rate of 99.33%.