Antifoam and Defoamer Chemistries

Various types of foams can develop in boilers—some are stable, some are very elastic, and some collapse and reappear continuously. Still other types of foam are temperature- or chemical-sensitive. 

Boiler water foaming and frothing is undesirable because it contributes to overheating, carryover, and loss of operational control. As a result, antifoam and defoamer products are commonly employed in BW treatment programs. The same active ingredients are also widely used in all types of industrial processes (industrial grades), as well as in cosmetic, food, potable water, and kosher applications (all agents typically are odorless, colorless, and tasteless). 

Sodium hydroxide, commercial solution Sodium polyacrylate (45%) 

NOTE In-use concentrations of antifoam and defoamer materials are very small, often as low as 5 to 20 ppm product, or 0.25 to 2 ppm actives . However, the persistence of the agent will vary and if not replenished will eventually fail. When antifoam is fed periodically, it usually is dosed as a stand-alone product at a higher rate, but when fed continuously, it is present at a lower concentration and forms part of a multicomponent additive. 

Foam formation in a boiler is primarily a surface active phenomena, whereby a discontinuous gaseous phase of steam, carbon dioxide, and other gas bubbles is dispersed in a continuous liquid phase of BW. Because the largest component of the foam is usually gas, the bubbles generally are separated only by a thin, liquid film composed of several layers of molecules that can slide over each other to provide considerable elasticity. Foaming occurs when these bubbles arrive at a steam-water interface at a rate faster than that at which they can collapse or decay into steam vapor. 

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