Why is the ammonia-to-carbon ratio of the urea feed controlled at 2.89 during the initial startup?
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Why was the ammonia-to-carbon ratio controlled at 2.89 during the initial startup of the urea production process, and why was it reduced to 2.1 after production began? Was this determined through calculations? Thank you everyone for your answers
I’m not sure what urea production process the poster is referring to, but regardless of the process used for urea production, operation is generally carried out under strict control of specific parameters; in particular, it’s necessary to adjust the conditions as quickly as possible so that they fall within the specified ranges after the product is discharged. In the urea production process using carbon dioxide stripping, the ammonia-to-carbon ratio is around 2.89, and this value is used as a criterion for both startup and product discharge.
The optimal N/C ratio for the carbon dioxide stripping process is 3.0. During startup, when no material is present in the system and no ammonia is returned from the stripper, all the ammonia in the system comes from the feedstock; therefore, an N/C ratio of 3.0 is required for the feedstock. After processing, some ammonia is returned to the stripper, and this amount is roughly equal to one mole of ammonia. This ammonia enters the condenser. To maintain an N/C ratio of 3.0 in the reaction, it is necessary to keep the N/C ratio of the feedstock at 2.0. Whether during startup or normal operation, the N/C ratio of the material entering the condenser and the synthesis tower remains 3.0, while it is 2.0 for the material exiting the stripper. It can be said that one mole of ammonia is constantly circulating within the high-pressure system
The optimal N/C ratio for the carbon dioxide stripping process is 3.0. During startup, there is no material in the system, and no ammonia is returned from the stripping tower; all the ammonia in the system comes from the feed. Therefore, the required N/C ratio for the feed is 3.0–3.2. After the process starts, some ammonia is returned from the stripping tower, and this amount is roughly equal to one molecule of ammonia. This ammonia enters the condenser. In order to maintain a reaction N/C ratio of 3.0, the reaction 2NH3 + CO2 = (NH2)2CO + H2O occurs; hence, it is necessary to keep the N/C ratio of the feed at 2.05. Whether during startup or normal operation, the N/C ratio of the ammonia entering the condenser and the synthesis tower remains at 3.0, while it is 2.0 for the ammonia exiting the stripping tower. It can be said that one molecule of ammonia is constantly circulating within the high-pressure system
Reply to 3# nienidenai: Thank you very much
Keep it at 2.1 after discharging? I don’t know what technique the original poster uses? I don’t think it can be that low; otherwise the load on the cycle will be very high