Affiliation:
1. University of Connecticut, Department of Chemical & Biomolecular Engineering, Storrs, CT, USA
Abstract
Chemical looping ammonia synthesis (CLAS) is a new ammonia synthesis method capable of efficiently synthesizing ammonia at atmospheric pressure. The low-pressure operation of CLAS systems could decrease the capital and operational costs of ammonia synthesis. Despite its early developmental stage, the use of standard process engineering equipment in CLAS makes it possible to reasonably assess its economic potential. In this study, we evaluated the technoeconomic potential of CLAS systems in comparison to a Haber-Bosch (HB) synthesis process in the context of green ammonia production. CLAS is more compatible with the separate nitrogen and hydrogen feedstocks used in green ammonia production, and cost savings from CLAS could improve the economic viability of green ammonia production. Ammonia synthesis loops were modeled in Aspen Plus and the levelized cost of ammonia (LCOA) of each system was calculated. Three CLAS systems; two high temperature and one low-temperature chemical loop, were compared to a conventional HB system of equivalent size. This study found that CLAS can reduce the synthesis cost by 90% and that the low temperature CLAS as more economically viable than the high temperature CLAS. The need for an external heater in the high temperature CLAS diminished any cost savings that would have been realized due to the low-pressure operation. This work highlights the potential of CLAS to reduce ammonia synthesis costs and emphasizes the need for further development of low-temperature CLAS systems.