High nickel content
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Why is the nickel content in the liquid coming out of the urea synthesis tower 0.32 ppm higher, while the value for the finished product is 0.47 ppm? What about the oxygen content of 0.8%?
Several possibilities: 1. Equipment issues: such as problems with the material of the linings or trays, bolts, etc； It’s very likely. 2. Operation aspects: (1) Oxygen addition amount: Is the flow rate accurate? It cannot operate at low load for a long time, otherwise the oxygen addition amount will be only relative rather than absolute. (2) Reactor temperature: No overheating allowed.
May I ask the original poster: What process is used for your urea production? The reasons for the high nickel content vary depending on the manufacturing process. Additionally, it is recommended that the landlord first find a way to verify whether the analysis data is accurate
The most likely scenario is overheating of the low-load distillation column
The poster should also analyze the sulfur content of the CO2 entering the tower.
Reply to 3# lxq700918: We use a full-circulation aqueous solution method; the oxygenation data is accurate, and samples have been sent to other manufacturers for analysis and comparison.
It is understood that the benchmark for nickel content in urine is the mixture as a whole, rather than the urea component. If the liquid-phase nickel content in the synthesis tower is indeed 0.32 ppm, and the urea content here is just over 30%, then the nickel content in the final urea product after granulation should be around 1 ppm. Therefore, it is recommended to check the nickel content in the liquid phase of the synthesis tower. The level of 0.47 ppm in the finished product is indeed a bit high; are the system conditions normal?
Are the nickel contents still relatively high according to the analysis data from other manufacturers? If it remains high, then it indicates that the nickel content in your urea is likely indeed quite high. Has the sulfur content in CO2 been analyzed, as suggested by the expert in post 5? Also, has the urea plant received ammonia water from other plants recently? Has analysis been done on chloride ions, sulfide ions, etc., in this ammonia solution?
Reply to 8# lxq700918: We currently have two urea production systems – one uses a water solution circulation method and the other uses CO2 stripping. The efficiency of the system using water solution circulation is higher, while the CO2 used in both systems is the same.
So, has the aqueous solution circulation device received external ammonia water? Please have the original poster confirm.
Does the urea production mentioned by the poster involve deep hydrolysis? Yes, analyze the nickel content entering the system through hydrolysis.