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Topic: How do I minimize chunks that build up on my impellers?

anonymous Last edited: 31 July 2012 At 5:32pm
In our PVC plant, the agitators in the reactor have large chunks that build up over time on the impellers. Any thought of how to minimize these chunks? They get as big as golf carts, and require some unusual de-chunking methods.

Here are some specifics: Reactor's diameter is 11'-9", with a length of 23'-6"; Impeller: speed is 56 RPM; 4 impellers; 64" diameter, TYPE A310; Motor driving Impeller: 5 Hp, 1800 RPM

Reactor mix: water, VCM, dispersants; Design parameters: Pressure-85psi, Temperature-392F
  • Avatar Dave Dickey Forum Moderator 324 Posts

    Re: How do I minimize chunks that build up on my impellers?

    Last edited: 31 July 2012 at 5:32pm
    I don't think a magic answer to your problem exists. The accumulation of PVC on reactor internals is usually a combination of problems, related less to the mixing and more to the chemistry and process operation.

    The most common problem with PVC accumulation is the result of refluxed monomer returning to the liquid surface and polymerizing on the vessel wall, baffles, or shaft and impellers. Be sure that the reactor does not operate with the liquid surface at the level of an impeller.

    The other possible solution is a slippery coating on the shaft and impellers. Many PVC reactors are glass-lined to provide a smooth and slippery surface. Realizing that is not a solution to your problem, other polymer coatings might be applied to the impeller and shaft surfaces to make adhesion of PVC less likely. Polished metal surfaces also work.

    Once polymer begins to accumulate, it seems to build continuously.

    The answers by this expert are based on the best available interpretation of the information provided. The consequences of the application of this information are the responsibility of the user. If clarification is needed, please submit a further question.
  • Avatar Filip B Community Member 2 Posts

    Re: How do I minimize chunks that build up on my impellers?

    Chunks on the impellers is severe problem not only for mixing process. When the chunk increasing it put additional weight on the shaft and it can couse vibrations and in extremly situation breaking the shaft ( due to critical speed). I have seen the Lighting A310 but I don't know what excatly construction you have, maybe this one with hexagon screws so get rid of them and use set screw. When the shape of impellers is smooth and the haven't any "suspected" objects you can change direction of rotations CW to CCW, for example: if normal operation is 56rpm CW you can try: 40rpm CCW (inverter is necessary).