Help: Use of hydrogen peroxide in the urea plant
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Experts: I would like to ask whether there are any manufacturers that add hydrogen peroxide to the system, as well as ammonia, during the period when the tower is shut down, in order to extend this shutdown time and reduce corrosion. Thank you
We have never added hydrogen peroxide to the system during shutdown periods when the tower is sealed, nor have we added ammonia to the system in order to extend the sealing time and reduce corrosion. However, it is common to add hydrogen peroxide to the system after the system is brought back online, and the results are fairly good; adding hydrogen peroxide during shutdowns does not seem to yield very good results Moreover, driving can also cause prolonged overheating of the stripper; I think adding ammonia won’t be very effective. You’ll need to flush it every two hours as well!
Adding ammonia or H2O2 isn’t very effective; ammonia is already in excess. The key is to control the pressure, time, and temperature during the sealing process. For example, it is highly inappropriate for some plants to release pressure when sealing the tower; oxygen in the gas phase and liquid phase escapes, leading to rapid corrosion.
What is the tower sealing time under your control? Also, after the dehydrogenation process, can HV202 be turned off to prevent a decrease in oxygen concentration?
The tower is normally shut down for about 12 hours. As you said, CO2 contains almost no H2; the exhaust valve of the high-pressure unit is closed at 11 MPa, and it is opened by 2–5% every 1–1.5 hours to check for any blockages.
We’ll stick to the old method; HV202 isn’t turned off, so it seems we need to make some changes.
During the tower shutdown for parking, it is rare to use ammonia or hydrogen peroxide as supplements; it is possible to increase the oxygen supply before shutting down the tower, and once the tower is shut down, as long as the system pressure and temperature are well controlled, there should be no major problems.
Before starting up after a long shutdown, we rinse the trays of the synthesis tower with hydrogen peroxide to passivate them.