In addition to having the outstanding capability to build almost any size of processing equipment anywhere in the world through its worldwide network of licensees, Swenson has an in-house staff and regionally located chemical sales engineers capable of engineering complete crystallization plants including steelwork, utilities, separation, drying and material handling equipment.

Choice of equipment

Swenson builds a wide range of general and special purpose crystallizers for the chemical process industries. For feeds where high rates of evaporation are required, where there are scaling compounds, where crystallization is achieved in inverted solubility solutions, or where the solution is of relatively high viscosity, the Forced-Circulation Crystallizer is the best choice. Its most frequent use is in the continuous processing of such materials as sodium chloride, sodium sulfate, sodium carbonate monohydrate, citric acid, monosodium glutamate, urea and other similar crystalline materials.

     Where excess nucleation makes it difficult to achieve a crystal size in the range of 10 to 30 mesh, the Draft Tube Baffle (DTB) crystallizer is preferred (U.S. Patents 3,873,275 & 3,961,904). This crystallizer, in both the adiabatic cooling and evaporative type, includes a baffle section surrounding a suspended magma of growing crystals from which a stream of mother liquor is removed containing excess fine crystals. These fines can be destroyed by adding heat (as in an evaporative crystallizer) or by adding water or unsaturated feed solution. The magma is suspended by means of a large, slow-moving propeller circulator which fluidizes the suspension and maintains relatively uniform growth zone conditions. This crystallizer design has proven very useful for producing such materials as ammonium sulfate, potassium chloride, diammonium phosphate, hypo, epsom salts, potassium sulfate, monosodium glutamate, borax, sodium carbonate decahydrate, trisodium phosphate, urea, YP soda, etc.

     For special cases requiring very low operating temperatures only achieved by extraordinarily high vacuum, the Batch Vacuum Crystallizer is still a good choice, costing less to operate than a continuous vacuum crystallizer. For operation at temperatures below which it is not economically possible to use vacuum equipment, or with solutions with very high boiling point elevations, the Surface-Cooled Crystallizer using a shell and tube exchanger is supplied. For cases at extraordinarily low temperatures where refrigerants must be used to achieve operating temperatures, a direct contact refrigeration crystallizer, wherein the refrigerant can be mixed with the slurry, would be ideal, utilizing either the Forced-Circulation or DTB principles.

     The following pages go into further depth in describing the various types of SWENSON crystallizers and briefly illustrate Swenson's design expertise in the crystallizer field, an expertise that has made Swenson the name to consider for the most carefully engineered, quality-built crystallization equipment.

Shop view of Swenson vessel in fabrication
 
 

Sample of crystals produced in a SWENSON crystallizer