Urea evaporation system
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How do temperature and vacuum level interact during the startup of the urea evaporation system, and at what rate does the vacuum increase?
OP, what method do you use to achieve vacuum? Is it steam injection? Hydraulic jet again? In the first case, the vacuum level is controlled by regulating the steam flow rate; in the second case, it is controlled by regulating the water circulation rate.
First increase the temperature, then increase the vacuum level; when the vacuum level is first increased, the temperature will drop slightly, after which the temperature can be raised again. As long as the pressure difference isn’t too large, and care is taken to maintain a certain pressure difference between stage 1 and stage 2, keeping it above 0.03 MPa (absolute), there are generally no problems.
The evaporator used in the original poster’s facility is a traditional steam injection type (the conventional CO2 stripping process). By asking this question, the original poster hopes that you will take the time to review the operating procedures; whether they were prepared by you or downloaded from other websites, such materials provide detailed explanations of how this process is carried out.
Why must the pressure difference between stage 1 and stage 2 be maintained at above 0.03 MPa (absolute)? During the vacuum water circulation process, or after the vacuum is broken, should the pressure in stage one be maintained at 80 KPa, the pressure in stage two at 60 KPa, with a pressure difference of 20 KPa between them? Is this acceptable? Why? Thank you for the advice!
If, as you said, it is 80 kPa in the first stage and 60 KPa in the second stage, evaporation will occur until the liquid level reaches that of the first stage; in other words, the liquid level in the second stage will return to that of the first stage, rather than proceeding with granulation.