Pulping operations multiple effect evaporator

The high purity of the caustic soda obtained by the membrane process eliminates the need for a caustic soda evaporator in cases where it is to be supplied to customers such as pulp mills which utilize a dilute caustic soda. This is in marked contrast to the diaphragm process which inevitably requires evaporation to separate sodium chloride. For the general trade, in which caustic soda at 50% concentration is required, a conventional multiple effect evaporator is generally utilized to concentrate the catholyte. Caustic soda from the membrane process contains a very slight amount of sodium chloride which does not cause corrosion of the evaporator materials or precipitation of sodium chloride, and thus allows easier and more stable evaporator operation than in the diaphragm process. 

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