Revolutionizing the Ammonia Alkali Process for Enhanced CO₂ Conversion and Productions: Insights from Aspen Plus Modeling and Process Optimization

This study utilizes the concept of circular economy to modify the traditional ammonia alkali process and raw material source due to the low CO₂ conversion rate and environmental concerns. The entire process is modeled using Aspen Plus, incorporating the kinetics and thermodynamics of CO₂ absorption by ammonia water and the reaction mechanism of the ammonia-sodium chloride-water carbonation process. Various factors such as crystallizer temperature, brine concentration, ammonia concentration, the amounts of CO₂ flowing into the process, cold precipitation temperature, and salting out are analyzed for their effect on CO₂ absorption and the amounts of product. Results indicate that the carbonation process performs optimally at 35 °C, achieving a CO₂ conversion rate exceeding 85% and nearly 100% product purity. Furthermore, enhancing the CO₂ conversion rate is achieved by eliminating residual hydrocarbonate root ions and free ammonia through the addition of hydrochloric acid to the mother liquor post-carbonation. Notably, a sodium chloride mass fraction of 25% in salt water or an ammonia mass fraction of 30% in ammonia water results in a CO₂ conversion rate exceeding 90%. This surpasses the current ammonia alkali process, making a significant contribution to CO₂ capture and conversion in the industry.