Simulation of an ammonia plant accident using rigorous heterogeneous models: Effect of shift converters disturbances on the methanator

Disturbance introduced into the shift converters section of the ammonia production line may lead to problems in the ammonia production line which manifest themselves in other units of the production line. A real accident that took place in an ammonia production line some years ago is simulated using rigorous models for the units of the ammonia line starting at the high temperature shift converter and ending at the exit of the methanator. Reliable mathematical models are invaluable tools for the follow-up of the sequence of events leading to an accident. The effect of various types of disturbances introduced to the shift converterʹs section are simulated. The main aim is to find out the effect of these disturbances on the methanator, which is an adiabatic fixed reactor preceding the ammonia converter and acting as a guard for the ammonia synthesis catalysts against CO and CO2 poisoning. The simulation results show, in a realistic manner, the sequences of events leading to temperature runaway in the methanator due to these disturbances in the shift converters section. The results are very valuable for understanding this complex interaction between the units and finding out the best operator response to avoid a shutdown or an accident.