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Foaming
Foaming
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.