Swenson Walker Crystallizer :
The Swenson-Walker Crystallizer is a cooling type, continuous, jacketed trough Crystallizer. It is an example of the scrapped surface Crystallizer and is probably the most widely used Crystallizer.
Swenson Walker Crystallizer Construction :
It consists of a long open rectangular trough with a semi-cylindrical bottom, i.e., U-shaped trough, of width 0.6 m and length 3 to 6 m. The trough is jacketed externally for circulating the coolant during operation. A spiral agitator rotating at about 7 rpm is incorporated in the trough in such a way that it is as close to the bottom of the trough as possible. The capacity of this Crystallizer can be increased by arranging a number of units in series (four troughs of 3 metre length each may be arranged). At one end of the Crystallizer, an inlet for the hot solution is provided and at the other end of the Crystallizer, an overflow gate for the crystals and mother liquor discharge is provided. The functions of the spiral agitator are : (i) to scrap the crystals from the cooling surface (i.e., to prevent accumulation of the crystals on the heat transfer surface), (ii) to lift and shower the crystals through the solution so that the crystals will be held in suspension and thereby the crystals of uniform size can be obtained (as deposition occurs mainly by build up on previously formed crystals) and (iii) to convey the crystals from one end of equipment to the other end.
The trough is formed out of metal sheets welded to an angle-iron frame at the top. A jacket is usually made of mild steel. The spiral agitator is supported at either ends outside the trough. A stuffing box assembly is attached to the cover on either ends that prevents leakage of the liquor from the opening provided for a shaft. The shaft is driven by belt, etc.
Swenson Walker Crystallizer Working :
A hot concentrated solution is fed at one end of the open trough and flows slowly towards the other end of the trough. Water is fed to the jacket in such a way that it flows in a counter current fashion with respect to the solution. The solution while flowing through the trough cools by heat transfer to water. Once the solution becomes supersaturated, crystals start forming and building. A spiral agitator keeps the crystals in suspension so that previously formed crystals grow instead of formation of new crystals and ultimately the two phase mixture of crystals and liquor leaves the Crystallizer through an overflow gate.
Advantages of this Crystallizer include : saving in floor space, in material in process and saving in labour.
This Crystallizer is suitable only when supersaturation can be achieved by cooling alone.
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FAQs :
What is Swenson Walker Crystallizer?
The Swenson-Walker Crystallizer is a cooling type, continuous, jacketed trough Crystallizer. It is an example of the scrapped surface Crystallizer and is probably the most widely used Crystallizer.
How is the Crystallizer Works ?
A hot concentrated solution is fed at one end of the open trough and flows slowly towards the other end of the trough. Water is fed to the jacket in such a way that it flows in a counter current fashion with respect to the solution. The solution while flowing through the trough cools by heat transfer to water. Once the solution becomes supersaturated, crystals start forming and building. A spiral agitator keeps the crystals in suspension so that previously formed crystals grow instead of formation of new crystals and ultimately the two phase mixture of crystals and liquor leaves the Crystallizer through an overflow gate.
What are the advantages of Crystallizer ?
Advantages of this Crystallizer include : saving in floor space, in material in process and saving in labour. This Crystallizer is suitable only when supersaturation can be achieved by cooling alone.