Fluctuations in the first-stage evaporation of urea; the cause cannot be identified
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Our company’s urea production capacity is designed to be 800,000 tons per year. Since the plant began operating, the vacuum level in the evaporation system has often fluctuated without any apparent reason. It was found that the venting from the low-pressure system was affecting the operation of the injectors; as a result, the outlet of one of the evaporation injectors was changed from an atmospheric pressure absorption tower to the main vent line, which improved the situation to some extent. However, vacuum fluctuations still occur recently. The system load and steam pressure did not change at that time, which is quite puzzling. Have any of you encountered similar problems? Please share your experiences.
We used to do the same thing as well; the key was to control the conversion rate of high-pressure synthesis in the system, as well as the N/C and H/C ratios, as well as the high saturated steam pressure. As long as the low pressure does not exceed the limit, there will be no problems with evaporation.
If low pressure or overpressure affects the performance of the ejector, we redirect its outlet to the vent main; low pressure should not have an impact on it. But similar to issues with suction, such situations occur from time to time, which is extremely annoying.
Is the power for your injectors steam? Is it the intermittent presence of liquid in the steam that causes the problem?
I hadn’t noticed that you mentioned. I’ll check it again, thanks!
This post was last edited by WJHSWSW on 2015-7-30 00:13. Check again to see if the liquid flow at each surface cooler is normal; examine the curves to determine whether the liquid level in the ammonia tank fluctuates during evaporation, as there is a suspicion that the liquid flow at the surface coolers is not proper.