Remote, small-scale, 'greener' routes of ammonia production

The techno-economic feasibility of low-carbon based ammonia (NH3) production has been explored in this study. Black coal and a eucalyptus-based biomass, available in the vicinity of a carbon dioxide (CO2) sequestration site, have been chosen as the two carbon-based feedstocks. The scale of the production of NH3 has been chosen to match the production of a bulk industrial Ammonium Nitrate/Fuel Oil (ANFO) explosives manufacturing facility. The production of NH3 from any carbon-based feedstock implicitly involves a CO2-removal step; therefore, only CO2 pressurisation to the supercritical state is required before transporting it to the storage location. In order to gain a better understanding of the economic and environmental trade-offs, two representative flowsheets have been modelled in Aspen Plus simulation software for the two feedstocks. A Natural Gas (NG)-based NH3 process has also been modelled for comparison. Material and energy balance data from the Aspen Plus simulation has been used to predict the economics and carbon footprint of NH3 production from different feedstocks. A cradle-to-gate Life Cycle Assessment (LCA) has been performed to predict the environmental hotspots. A genetic algorithm based Multi-objective Optimisation (MOO) has generated Pareto plots that represent the minimum cost of NH3 production against different CO2 footprints. For a similar CO2 footprint, the coal-based NH3 process has been found to be more economic than the biomass-based process. However, the biomass based process has the potential to be carbon negative by capturing the biogenic CO2, which is not possible in a coal-based process. The cost of carbon capture in coal-based NH3 production has been estimated to be between 11 and 19 US $/t CO2eq, which is significantly lower than the cost of CO2 capture from coal-based power generation (usually reported to be in the range of 40-60 US $/t CO2). (C) 2018 Published by Elsevier Ltd.