Foaming Caustic

[PeteE]

I have recently had problems with caustic foaming in a 10% w/w caustic scrubber removing trace quantities of chlorine from air. The problem appears to be temperature related but I can not find any theory or data behind the phenomena to calculate the operating temperature that will prevent the formation of foam.
Any ideas ?
Thanks

 

[Zoobie]

I have seen the same thing in almost the same application. We found that the foaming occurred during start-up after the scrubber sump was filled with strong caustic (20% w/w). In normal operation we ran excess caustic at 20 to 40 gpl. If we filled with a dilute solution closer to the normal operating concentrations we found that the foaming did not occur. (this scrubber had dilute caustic recirculating in the bottom and fresh caustic added to trays on top)

I know that this is not a direct answer to your query but I thought you might want to consider the solution concentration in your investigation (if you haven't already).

 

[btrueblood]

Is there any chance you got some oil contamination into the caustic?

 

[PeteE]

We do have background organics in the cauastic scrubber but these were at normal levels ( ~ 10 ppm). I have heard of cases were the caustic has leached out trace contaminants from new plastic pipework but this is not the case here. Solids ( hardness salts ) have also given problems in the past but again all is normal. No oil contamination is possible.
The problem was solved by temporary raising temperature by steam addition. My question is regarding any relevant theory to predict at what temperature I may start foaming - a quick look in Perry & a search on the net has not given any useful answers.
Thanks