Forced Circulation Crystallizer

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FORCED-CIRCULATION CRYSTALLIZER

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Most widely used crystallization method

Forced circulation is the most widely practiced method of crystallization. FC crystallizers are found in sizes ranging from 2' diameter laboratory models to over 40' diameter units for continuous processing. Per pound of product, it is ordinarily the most inexpensive type of equipment available, particularly when substantial amounts of evaporation are required.

SWENSON Forced-Circulation Crystallizers can be operated on a batch basis but their most frequent use is for continuous processing of such materials as Sodium Chloride, Sodium Sulfate, Sodium Carbonate Monohydrate, Citric Acid, Monosodium Glutamate, Urea and similar crystalline materials.

Recompression Crystallization

For applications where the solution's boiling point elevation is low, such as for Sodium Carbonate, it is possible to significantly reduce the cost of the operation by vapor recompression.

In this technique the vapor, which is removed to precipitate the crystalline product, is compressed by a positive displacement or centrifugal compressor to a pressure high enough so that it may be used as steam in the heat exchanger.

By proper heat exchange, many mechanical recompression applications can operate efficiently without any external source of heat, except for start-up purposes. For other applications, a small quantity of steam is required at the heating element to maintain the system on a continuous basis.

The drive for the compressor may be either a steam turbine or an electric motor depending on the availability and cost of power. To minimize power requirements, the heat exchanger is designed for the lowest possible Delta-T, thereby minimizing salting and scaling.

A steam booster can be used in lieu of a mechanical compressor when steam costs are relatively inexpensive compared to electrical power costs. In this case, part of the vapor is compressed by the high pressure steam in the booster and used as the first-effect heating media. Vapor not compressed goes to the second effect. The recompression crystallization technique can also be applied to the DTB or SWENSON OSLO (growth type) crystallizers.

FC Crystal 4

SWENSON Forced-Circulation Crystallizer

FC Crystal 3

Forced-Circulation thermal recompression crystallizer at FMC Corporation, Middleport, NY