Advanced Design of Ammonia Production Processes from LNG: Efficient and Economical Cold Energy Utilization Methods

Abstract

Efficient green energy technologies are essential for sustainable green hydrogen applications. However, economic reasons necessitate bridging technologies between fossil fuels and green hydrogen. Natural gas, the cleanest fossil fuel, can provide non-carbon-containing energy resources, such as hydrogen and ammonia. Ammonia is suitable for economical hydrogen storage and transportation and for direct use as a fuel. In this study, efficient liquefied natural gas (LNG) cold energy utilization and recovery methods developed for producing ammonia are Design 1: energy production in an organic Rankine cycle and Design 2: energy reduction in an air separation unit (ASU). In Design 1, LNG cold energy is converted into power and supplied to the nitrogen compression stage for synthesizing ammonia. In Design 2, LNG cold energy is directly provided to the ASU to reduce the outlet temperature of nitrogen, which is sent to the compression stage, and the compression energy is consequently reduced. Through thermodynamic analysis, the process of LNG cold energy recovery is determined, and the energy consumption in each design is compared. Techno-economic analysis presents the cost reduction in the levelized cost of ammonia (LCOA). Compared with the base case, the energy consumption and LCOA in Design 2 are reduced by 11.54 and 23.02%, respectively.