Consequence modeling, analysis and emergency response planning for ammonia (Nh<subscript>3</subscript>) releases in urea manufacturing unit using ALOHA.

Population growth is one of the major constraints for the economic growth of India. Increase in food demand due to population growth burdens the current food supply. In order to meet the food demand and supply of an increasing population, soil productivity needs to be enhanced by employing fertilizers. Currently, these fertilizers play a vital role in the Indian agricultural sector. High nitrogen content and high solubility in water makes urea a convenient source of nitrogen. Therefore, it is widely used as a nitrogenous fertilizer. Urea is manufactured from ammonia (NH3) and carbon dioxide (CO2). The domestic production of urea in 2019-2020 was reported to be 336.97 LMT. The high demand and supply of urea requires huge quantities of ammonia for its synthesis. As ammonia has adverse effects on human health with TLV (8-hr average), TWA-STEL and IDLH values of 25 ppm, 35 ppm and 300 ppm respectively, its accidental releases can severely risk the nearby surroundings. Hence, prediction of ammonia gas dispersion in the surrounding atmosphere will aid in identification of possible affected areas with prediction of extent of consequences on human beings and environment. In the present work, open-source software, Areal Locations of Hazardous Atmospheres (ALOHA), is used for risk assessment of sudden release of stored ammonia gas in a urea manufacturing plant. ALOHA identifies toxic threat zones at particular locations depending upon the storage and meteorological conditions. Identification of affected zones as well as gas concentration at specific locations will support further emergency response planning. Identification of the most probable affected zone will help in devising a prompt warning system for affected persons to evacuate, shelter and/or lockdown. Further implementation of water scrubbers or curtains or sprayers with a quick responding communication system and medical facilities with antidotes will reduce the number of affected persons and severity of the incident. [ABSTRACT FROM AUTHOR]