Why is there foam in the MVR falling-film evaporator?
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The falling film evaporator contains a caprolactam aqueous solution with a mass concentration of 10–15% and an operating pressure of 2 barg; why is there a large amount of foam at the bottom of the evaporator? The foam layer is now too thick and blocks the bottom viewports. How can we reduce the foam without adding any additives or defoamers?
Material issue! It is necessary to add an antifoaming agent or reduce the evaporation intensity!
Reduce the operating pressure, control the inlet and outlet flow rates, and install a pipe demister upstream of the sight glass
Generally, the foam is caused by the properties of the material
For existing units that are already in operation and for which the use of additives for modification is not necessary, the following actions can be taken if conditions permit: 1. Reduce the evaporation pressure； 2. Increase the falling film self-circulation volume ； 3. Reduce the liquid level height at the separation end of the lower part of the falling film heating chamber.