Techno-economic analysis of gasification routes for ammonia production from Victorian brown coal

Abstract

The environmental, economic, and technical viability of high and low pressure gasification technologies for the production of ammonia from low rank coal was examined. Three cases were developed starting with different gasification technologies (UGI and BGL), leading to different flowsheets, mass and energy balances, and finally heat integration. Environmental and economic analyses were performed on each of the cases. Three further cases were considered for the treatment of CO2 generated in the process: direct emission, use in urea production, and carbon capture and storage.CO2 emissions for the base cases were found to be 2.36–3.15kg CO2-e/kg NH3, with a low pressure, UGI gasifier based process giving the lowest emissions. All values obtained are higher than the range of 1.25–1.80kg CO2-e/kg NH3 for natural gas based ammonia plants in Australia.In comparison with 2013 ammonia prices, the cases were found to be similarly economically unviable. At a discount rate of 15%, the break-even prices achieved are in the order of 2.5 times the current prices, at A$1500/t–A$1600/t in most cases. While no overall benefit for a particular case was clear economically or technically, the use of certain technologies gave notable results. The low-pressure UGI gasifiers, after accounting for compression costs, gave an economic benefit over the high-pressure BGL gasifiers. The liquid nitrogen wash unit, when placed before the ammonia synthesis loop, recovered methane that is suitable for power generation.