How to avoid fatigue in load-flexible green ammonia plants — A scheduling and control framework

Green ammonia is emerging as a key enabler for decarbonizing fertilizer production and providing a renewable energy carrier. Its production from intermittent renewable power requires highly flexible operation of the Haber–Bosch process, which can cause rapid equipment deterioration without a suitable control strategy. This work presents an integrated framework combining plant design, rolling-horizon scheduling, and dynamic simulation of a green ammonia plant over a full year of renewables-based operation. The embedded dynamic UniSim® Design simulation provides crucial insights into the conditions in the Haber–Bosch plant, including pressure and temperature cycling. The results demonstrate that, with the developed control strategy, flexible operation of the Haber–Bosch plant down to 10 % load with load change rates of 3 % / m i n is feasible without violating fatigue limits according to ASME and EN standards. Moreover, moderate pressure reductions during part-load operation can reduce the levelized cost of ammonia by 0 . 31 % without any hardware modifications.