Combined nitrogen production, ammonia synthesis, and power generation for efficient hydrogen storage

Abstract

An energy-efficient combined system consisting of nitrogen separation, ammonia synthesis and power generation is proposed and evaluated in this work. The integration of combined processes is carried out using the principles of enhanced process integration (EPI) technology. EPI unites two core technologies: exergy recovery and process integration. The former circulates the energy/heat and intensifies its heat exchange in any single process. In addition, the latter facilitates heat integration and utilization among involved processes. Therefore, the exergy loss throughout the combined processes can be reduced significantly, leading to high total energy efficiency. The proposed combined-processes convert the produced hydrogen, especially from coal and other renewable energy, to ammonia. Therefore, the hydrogen can be stored and transported more efficiently and stable. Haber-Bosch process in adopted as ammonia synthesis. In addition, power generation module is also included to recover the heat produced during ammonia synthesis, as well as supply the electricity consumed for nitrogen production. From process modeling and evaluation, the proposed combined-processes show very high energy efficiency, which is about 66.92%, including NH3 conversion efficiency (66.69%) and power generation efficiency (0.23%).