Is it necessary to keep the outlet of the pump used for cleaning and evaporating melted urine closed?
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During the shutdown cleaning for urea evaporation, the LV401 level rose slowly due to the liquid draining from the inlet drain. Could opening the outlet also be considered? In my opinion, the liquid level at the outlet, which is several dozen meters away, will be drained quickly due to the pressure difference; this way, the impeller won’t be reversed by water hammer. After the outlet is drained, opening it will also allow for faster drainage from 402-F. In this way, the condensate added at the urine inlet pump evaporates until a fluid is formed at the discharge outlet, which makes cleaning more effective. It can also prevent urine crystals from forming inside 401-C and 402-C; in my opinion, the soaking method is not as effective as fluid flushing.
Reply to 1# Blade: Evaporative cleaning is used, with water flow cleaning being more common. That is, water is added at the evaporation inlet; water flows through the entire evaporation system, and finally it is pumped to the urine tank via a melting pump. The acceptance criterion for cleaning is that the drainage from the inlet guide of the melt pump should not be slippery to the touch. It can then be discharged on-site (without affecting the environment). Check valves are generally not installed at the outlet of melt pumps, with the aim of allowing the liquid at the outlet to flow back, thereby preventing blockages in the pipelines leading to the tower. A short-term reversal of the melt pump has little impact!
If crystallization occurs inside the evaporation separator and cleaning is necessary, it is best to fill it with water and soak it, followed by rinsing. For flushing to prevent blockages during the start-up and shutdown of the evaporation process, ordinary running water is sufficient. If the melt pump reverses direction frequently, it may cause the screws at the back of the impeller to loosen and fall off.
Accidents have occurred more than once due to the reverse rotation of the melting pump, which has led to loose or fallen screws on the back of the impeller as well as damage to the impeller itself. It is essential to prevent such incidents from happening again through proper operation practices, and it is necessary to develop the habit of closing valves and shutting down the pump. As for emissions, there are valves for both import and export, allowing for separate discharge. There is excessive water inflow because the shutdown times of 401-J and 303-J were not coordinated properly. 303-J was shut down first; once it was shut down and the inlet liquid level indicator for 401-J started to drop, 401-J was immediately shut down as well, which prevents a large amount of water from accumulating. As for the crystallization issue, by the time the pump is stopped, the entire evaporation system and the granulation circulation pipelines have already been cleaned (the control room is monitoring this; otherwise they wouldn’t notify you to stop the pump), so there’s no need to worry.
Thank you to the friends upstairs. . .