A specific safety focus of a urea flowsheet is to manage the trace hydrogen (H2 ) such that an explosive composition is not created. The trace H 2 is not consumed by the urea process, which reacts ammonia (NH3 ) with carbon dioxide (CO2 ) to form urea within a synthesis loop. Therefore, hydrogen builds up and creates an operational safety challenge as oxygen (O2 ) is usually present within a urea synthesis loop to passivate the metallurgy in such a heavily corrosive environment.
The safety challenge is trace H 2 widens the flammability/explosivity risk window of ammonia gas within the process and so must be managed. For modern plant, licensors have selected catalytic H2 removal reactors to reduce the presence of H 2 in the synthesis section. Unfortunately, catalyst deactivation is a possibility and may not sufficiently be covered in the safety analysis. When deactivation is observed it requires specific attentions to keep the plant in operation.
This paper will focus on the catalytic process to react the H2 . It will also explore the deactivation challenges that can be faced when the application of the catalyst is exposed to unexpected carry-over of elements from the upstream CO 2 removal system.