A novel ammonia production system based on Co‑gasification of coal and biomass

Coal-based ammonia synthesis is a primary method for producing synthetic ammonia. However, this route suffers from high energy consumption. The greatest source of irreversible losses in the process is coal gasification, and the process is constrained by low cold gas efficiency and the high energy demand of air separation. These factors hinder further improvements in energy efficiency. This paper proposes an ammonia production process based on a novel coal-biomass co-gasification technology which exhibits a high cold gas efficiency and uses air and water as gasifying agents to reduce air separation energy consumption. The performances of gasification are checked experimentally, and other units are modelled and simulated by Aspen plus. Thermodynamic analysis of the whole process and the influence of the gasifying agent ratio on the cold gas efficiency and overall system energy efficiency are investigated. Simulation results indicate that the new gasification method improves cold gas efficiency through biomass external combustion and recovery of syngas sensible heat, achieving a maximum of 85.81%. After optimizing the gasification agent ratio, the minimum energy consumption for ammonia synthesis is 38.04 MJ/kg, and the maximum overall system energy efficiency reaches 55.04%, which is 7.62% and 11.28% higher than the coal-water slurry gasification to ammonia and biomass gasification to ammonia reference systems. Exergy analysis indicates that the exergy efficiency of the new system is 53.15%, which is 4.78% and 12.4% higher than two reference systems. The improvement in gasification technology is the main reason for the energy efficiency enhancement of the new system. In summary, this study provides an effective system integration solution for the efficient synergistic utilization of coal and biomass and for reducing the energy consumption of the ammonia synthesis industry.