Exergy and environmental footprint analysis for a green ammonia production process

Abstract

Using alternative materials in ammonia production process is of great significance in aspects of energy saving and environmental protection. To explore green and sustainable production in a practical ammonia plant, biomass is used as additives in feedstocks. Exergy efficiency and environmental footprint (GHGs footprint and water consumption footprint) are chosen as assessment indexes to evaluate the impact of different biomass contents in the whole life cycle. Main finds can be gained: 1) biomass additives show positive effects on the exergy efficiencies of shift unit and rectisol unit, with increases of 1.5% and 3.1% respectively; 2) environmental footprint concentrates on the operation stage (more than 98%), due to a large amount of feedstocks and energy consumed; 3) when the biomass content is increased to 15 wt%, about 40 kg CO2-eq/tNH3 CH4 is reduced and 0.88 m3/tNH3 water is saved in the operation stage. In conclusion, utilization of biomass additives has a promising effect on clean and sustainable production in ammonia production field. The result could be a reference for chemical factories.