What is the difference between pressure displacement and purge displacement?
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Our reactor uses two methods for purging: one involves flushing nitrogen in while simultaneously releasing nitrogen, and the other involves first raising the pressure to 2 MPa and then reducing it to 1 MPa. What are these two methods?
This is because purging and displacement result in many dead zones that cannot be effectively cleared, especially in reactors and columns with complex internals. So generally, pressure displacement is used first for the flushing process. If there are no specific requirements regarding the back pressure, it’s advisable to reduce the pressure as much as possible; for example, if you apply a pressure of 2 MPa and then release the gas to atmospheric pressure of 0.1 MPa, each such displacement can dilute the concentration of toxic gases in the reactor by a factor of 20. Usually, two or three such displacements are sufficient to meet the required conditions. If the pressure can only be reduced to 1 MPa, then around 7 or 8 displacements will be needed to achieve the desired conditions. After successful pressure displacement, purging is usually carried out for an additional period of time to ensure that the reactor is completely displaced properly. The advantage of purge replacement is that it does not require personnel to be on site continuously, allowing for prolonged replacement operations. Therefore, the two methods are used alternately to achieve the goal of successful replacement.
The second method is blast cleaning, which certainly yields better results and is used in areas where high cleanliness standards are required
In displacement, the pressure is first increased to a certain level and then reduced to a slight positive pressure; for purging, asbestos board blasting is generally used
The most thorough replacement is to evacuate and then fill with nitrogen
The main goal is to ensure that there is no air in the kettle, as air can affect the process