At present, there are more than two hundred urea plants in China based on different raw materials such as residuum, natural gas and coal. Every urea plant has a potential risk for explosions due to the presence of hydrogen in the feed and oxygen added for passivation purposes.
Different raw materials need different H2-removal processes.
For example with residuum or coal as raw material, because different sulfides are present in the CO2 feed gas, one needs an Ambient Temperature Fine Sulfur-Removal (ATFSR) process before the dehydrogenation step.
If oil is present in the CO2 gas, an oil-removal agent is also necessary. Reciprocating compressors have the disadvantage that always some oil will enter the process stream. In case a catalyst is applied downstream these compressors oil will deactivate the catalyst causing an expensive shut down and cleaning procedure.
China with their numerous small fertilizer complexes have built up extensive experience with this kind of problem and found also effective and cost efficient solutions. This paper describes the solutions to handle dehydrogenation process even with difficult feedstock like residuum and coal and describes the solutions to solve oil fouling in gas streams caused by reciprocating compressors.