I and II stage evaporation separation system
Thread Content
The first and second evaporation systems are arranged at almost the same level during design and installation; will this lead to excessive levels of biuret during production, thereby affecting product quality?
Are there U-tubes? If so, what is the design height?
No, the content of biuret is related to the residence time; it’s best for the second distillation not to exceed that of the first distillation.
No, the content of biuret is related to the residence time; it’s best for the second distillation not to exceed that of the first distillation.
Biuret is related to ammonia content, temperature, and residence time. In the evaporation stage, the ammonia content is low, resulting in a higher probability of the formation of biuret; throughout the urea production process, most of the biuret is produced in this evaporation stage. However, if the temperature and the liquid level in the secondary separator are properly controlled, it is still possible to keep the biuret content within the range of premium quality. As for the equipment layout, I think it’s fine as long as there is no air leakage between section 1 and section 2. Here, the pressure in section 2 is lower than that in section 1, but there is a U-shaped bend in between.
The analysis on the 5th floor makes sense. In actual engineering design, due to the small absolute pressure difference between the first and second evaporation stages, the outlet of the liquid outlet pipe in the second evaporation separator is located about 1 meter lower than that of the liquid outlet pipe in the first evaporation separator. This is done to ensure smooth flow of material between the two stages and to prevent the accumulation of liquid that could lead to the formation of biuret. I guess the urea system of the original poster must be similar as well; it’s just that the pressure difference is smaller, so it’s not easy to notice.
Urine from the first distillation tends to flow into the second distillation more easily; I believe this has a certain impact on the vacuum level in the second distillation stage.