Comparative Exergy and Economic Assessment of Fossil and Biomass-Based Routes for Ammonia Production

Due to the increasing concerns about the marked dependence on fossil resources and their intrinsic economic uncertainty, as well as motivated by more stringent environmental regulations, the pursuit of alternative energy resources for the synthetic fertilizers sector have recently gained more attention. The decarbonization of this productive sector, responsible for about 2% of the global energy consumption and an important source of CO2 emissions, might help not only improving the carbon footprint of these fundamental commodities but also reducing their dependence on the international market prices, traditionally dominated by the main natural gas producers. Accordingly, in this work, the use of biomass gasification for partially - or totally - replacing the use of non-renewable methane in ammonia production is compared with a conventional route, typically based on steam methane reforming. However, by introducing a novel approach, additional or totally different demands are created along with the need for an optimal integration of the new chemical plants to the alternative utility systems, so that the power and steam requirements remain satisfied. Therefore, a systematic methodology that allows selecting the most suitable utility systems (refrigeration, waste heat recovery and cogeneration systems) that satisfy the minimum energy requirement (MER) with the lower resources consumptions and cost is performed. On the other hand, exergy analysis is used to identify the potential improvements that may remain hidden to the energy integration analysis, especially when referring to reactive components, combined heat and power production (CHP) and avoidable exergy losses.