Chemical Engineering Research & Design, Vol.158, 177-192, 2020
The influence of raw material availability and utility power consumption on the sustainability of the ammonia process
Trinidad and Tobago, one of the largest exporters of ammonia globally, has seen recent declines in natural gas availability making cutbacks in productivity necessary. This paper investigates, for the first time, effects of natural gas availability on environmental burden and operational profit across the ammonia process. Utilizing Aspen (R) Plus, a model ammonia plant was designed and validated against current plant operations. The results indicated that as gas charge decreases, the specific energy demand increases, due to increased steam demand for CO2 removal. The findings also showed that below a threshold of 98% gas charge, there was a direct loss in profit of US$10.3 million/year with increase in specific energy demand of up to 10%. Furthermore, a Life Cycle Assessment (LCA) indicated, through the utilization of CO2, greenhouse gas (GHG) reductions by 64.84% while fuel combustion was the main "hotspot", contributing up to 91% across all impact categories. Insights into decreasing the environmental impacts were also considered with results showing that an increase in productivity (US$79,000/year) increases environmental burden. Moreover, useful power generation provides environmental benefits by 6% across all impact categories. Thus, specific energy demand along with CO2 utilization should be carefully considered for a more sustainable ammonia process. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.