Analysis of H2 production processes via ammonia partial oxidation: Energy, environmental sustainability, economic aspects

Abstract

This study presents two cases of ammonia Partial Oxidation (POX) process as an alternative to the endothermic decomposition of ammonia for dihydrogen production, which requires continuous heat supply. This work evaluates each case in terms of energy, environmental, and economic aspects. Furthermore, for a quantitative analysis compared to the conventional Thermal Decomposition (TD) process, two cases for TD were presented and evaluated using the same procedure as for POX. The evaluated four cases are as follows: (Case 1) Supplying dioxygen with Oxygen to Ammonia Ratio (OAR) of 0.25, utilizing the heat which is generated by ammonia adsorbing on the catalyst or dioxygen oxidizing the catalyst, to initiate the ammonia POX. (Case 2) Supplying air with OAR of 0.13, providing an external heat source for the initiation of ammonia POX. (Case 3) Using natural gas as the fuel for the thermal decomposition reaction of ammonia. (Case 4) Using PSA off-gas as the fuel for the thermal decomposition reaction of ammonia. Compared to the TD cases, the evaluated POX cases appeared to be better options in terms of external energy consumption (Specific Energy Consumption, SEC) and Global Warming Potential (GWP), but represented a poor LCOH value. In the POX cases, Case 1 was the better option when the SEC and GWP perspectives are significant, but Case 2 was the desired option when considering the LCOH. The sensitivity analysis of technical variables showed that if the OAR and conversion rate of ammonia POX technologies were improved, the LCOH could be reduced to 6 USD/kg H2 or below, suggesting that the ammonia POX technology could also be economically viable and competitive.