Modeling, optimization, and system evaluation of ammonia production processes by direct chemical looping of petroleum coke/coal

Abstract

Petroleum coke, a by-product of oil refining, is characterized by high carbon content and calorific value. The combustion of petroleum coke releases substantial amounts of CO₂, posing significant environmental challenge. Chemical looping is a promising technology due to its inherent carbon capture advantage. In this study, the chemical looping ammonia processes with 85 % and 95 % of petroleum coke conversion rates are established. Additionally, a chemical looping ammonia system co-fueled by petroleum coke and coal with a 95 % conversion rate is designed. After detailed modeling and key parameters optimization for the above processes, exergy efficiency and life cycle greenhouse gas emissions are calculated to analyze their performance. The results show that the exergy efficiencies of the three chemical looping ammonia systems are 47.55 %, 53.39 %, and 51.06 %, corresponding to greenhouse gas emissions of 428, 349, and 381 kg CO₂-eq/t NH₃. Enhancing petroleum coke conversion rate and employing the co-feeding chemical looping process can significantly improve the system’s exergy efficiency and reduce greenhouse gas emissions, thus providing a promising pathway for the clean and efficient utilization of petroleum coke.