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Sample plant pictureFoaming in the column can drastically lower capacity and lead to premature flooding, liquid carry-over, and solvent losses. Foaming is a common problem with columns using high molecular weight organic solvents such as amine, glycol and potassium carbonate solutions. In such applications, presence of compounds such as liquid hydrocarbon and organic acids often promotes or induces foaming. The problem is usually aggravated by impurities, low pressure and high gas velocities. Corrosion inhibitors are often surface-active agents and generally severe foamers. Suspended solids and polymers generally tend to stabilize foams. One example is iron sulfide particles in amine solutions.

Foaming is more common in tray columns than packed column. In a moderately high foam regime, liquid will be carried up by the gas into the next tray. Alternatively, foam can carry vapour down to the tray below. In extreme cases the downcomers are filled with foam and flooding occurs, much like in a packed column.

Foam inhibitors can be added to reduce the foaming tendency. These are always insoluble materials, usually liquid, but some solids such as waxes or soaps are used.

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