Curing a Foaming Problem

The simplest solution to a foaming problem is to inject a foam inhibitor. A number of practical guidelines are listed below  

A correct choice of foam inhibitor is important. This is often achieved by trial and error. Experiences were reported where injecting the wrong inhibitor aggravated a foaming problem (26, 239). Some inhibitor selection guidelines are available elsewhere (319, 339, 373). 

It is important to correctly inject the inhibitor. Injecting the inhibitor upstream of a point of high turbulence such as a pump suction or ahead of a pump letdown valve has been recommended (373). An injection point a long distance upstream of the column should be avoided whenever possible (328). It is also important to disperse the inhibitor correctly. One case has been reported (50) 

A fairly recent technique recommended by one source (328) is to inject the inhibitor into the gas as an aerosol however, little experience has been reported on the effectiveness of this technique. 

It is essential to inject the amount of inhibitor recommended by the supplier or found optimum in laboratory tests. Excessive inhibitor injection can be harmful. One experience has been reported (85) where application of three times the recommended amount of antifoam inhibited tray action, causing product purity to drop. In other circumstances, excessive inhibitor addition was reported to aggravate a foaming problem (84, 238, 239). 

---