Exergy analysis and purging of an ammonia storage system

Abstract

This paper proposes a method for purging a large-volume ammonia storage facility without the production of environmental contaminants. The properties of the evaporator used to gasify the nitrogen for purging the ammonia are described, and exergy analyses of the system and the chemical reaction between the ammonia and water are performed. Based on the analytical results, the optimal fin size and pipe diameter of the evaporator are determined to be 5-8 cm and 2.5-6.5 cm, respectively. The chemical exergy of the reaction between the ammonia and water is determined to be 328.7 kJ/mol. Moreover, it is determined that the exergy loss of the system is equal to the evaporator exergy loss. The exergy efficiency of the finned tube evaporator of the system is determined to be 28%. The obtained results confirm that the purging of an ammonia storage system using nitrogen gas can be efficiently accomplished using an existing finned tube evaporator.