Problems with foaming in vessel

[PapaDePepe]

I just moved to a new plant and am faced with a foaming problem. We are pumping a 50% Acrylamide solution from a feed tank to holding tank. The receiving tank is filled via dip tube, but at 50% volume there is so much foam it is bubbling out of the gooseneck vent on top of vessel. The gooseneck vent is always open, allowing atmospheric conditions inside the vessel. Apparently this problem is not new. We have the same setup in other areas of the plant but don't have any issues there. Antifoaming agents are not an option. Any suggestions? I suspect there may be a leaky valve/flange somewhere in the piping allowing air into the line but any other advice would be greatly appreciated.

 

[Compositepro]

If your dip tube is "properly" designed it has a hole drilled in it near the top, inside the tank, to prevent siphoning. This is likely the source of of air in your foam. You can make this hole smaller or add some restriction at the tip of the tube to generate some back pressure but then liquid will squirt out this hole and that may also generate some foam. A vacuum breaker valve could be used in place of the hole. Or you can plug the anti-siphon hole if you can accept the possibility of siphoning under certain circumstances.

 

[StoneCold]

My thought was that you might be able to upsize the last 20ft of pipe and the dip leg to drop the velocity, but Compositepro has a good point about the antisiphon hole giving you problems..

Regards
StoneCold

 

[mfelzien]

During shutdown make sure the vessel is clean and free of sedimentation and physical obstruction. Inspect the Diptube for possible improper mixing issues (air/liquid). You may also need to look at the vessel drawing to see the design on the distributor at the end of the dip tube. The inlet flow diverter could likely be redesigned to prevent the foam. As a possible interim fix, you may want to see if there is a flow regime that would minimize the foam. But, the problem is likely mechanical or design failure.