Foam Suppression

[mavans]

I have a 20m3 sodium hydroxide soln recirc tank that generates foam like you wouldn't believe. We've tried knock down sprays but they just don't cut it.
Any ideas or experiences that may help us beat the foam?
I was thinking of using a venturi scrubber to draw the foam from the tank, destroy the bubbles and return the soln back to tank. I am not sure this will work; afraid it may just generate more foam.
Any comments would be graetly appreciated.

 

[butelja]

Can you add a silicone based anti-foam material? If so, Dow Corning makes a number of anti-foams that are extremely effective at only ppm levels.

 

[stevan]

Anti-foam chemicals scare us a bit. The alkalai solution is used to remove oils from metallic strip prior to continuous tin electroplating and we are afraid the anti-foam may cause some surface quality defect. I have this idea in my mind to use a venturi scrubber to draw the foam out of the tank and return the solution back. Just not sure if such a unit will work or just cause more foam?
Steve.

 

[HEC]

Before looking at Anti foam agents it is worth while checking return pipework and in particular the tank return for any leaks where air may be incorporated into the detergent. As always it is easier to prevent the problem occuring rather than trying to deal with the consequences.
Mark

 

[craigdr]

Do I understand that you are stripping oil off the strip and the mixture of NaOH and oil is returning to the tank? Can you remove the oil? absorb it?

 

[darlington]

have you ever considered fitting a mechanical device in the gas space in the vessel

A 'foam reducing pack' is sometimes fitted in a 2/3 phase primary separator for oil/gas/water services to tackle this problem. This is a vane type pack that fits in the gas space in the vessel. The general idea is that the foam is 'arrested' on the vanes.

 

[countryham]

It is always best to solve a problem such as yours mechanically rather than chemically,however there are Two (2) avenues that you may explore: (1) If you can witstand the potential fire hazzard, you can use a "knock-down spray containing a highly surface active alcohol such as isoproponal @ about 14-15 dynes/cmsq or (2) contact a supplier of "deaerators" to THE PAPER INDUSTRY where they reduce the head on paper machine water with entrained foam.