AUTHORS: Andrea Isella, Alberto Lista, Gabriele Colombo, Raffaele Ostuni, Davide Manca
ABSTRACT: Ammonia synthesis is the biggest emitter of carbon dioxide among chemical processes. Emission regulations will become even stricter over the coming decades and call for innovative sustainable pathways to meet the decarbonization targets. An answer to such a transition may be retrofitting (i.e. hybridization) the existing plants by implementing low- or zero-emission technologies. One of the most promising retrofits is introducing green hydrogen from electrolyzers into the synthesis loop. This paper compares the operational expenditures (OPEX) of a conventional gray ammonia plant and a 10%-decarbonized electrolysis-based hybrid-green ammonia plant. The OPEX terms depend primarily on natural gas costs, renewable electric energy prices, and carbon tax values. Specifically, hybrid-green ammonia proves to be competitive at current EU natural gas quotations, which have increased more than five-fold since the first semester of 2021 due to the ongoing Russia-Ukraine war.