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The ''Swenson-Walker'' crystallizer is a model, specifically conceived by Swenson Co. around [[1920]], having a semicylindric horizontal hollow trough in which a hollow [[screw]] conveyor or some hollow discs, in which a refrigerating fluid is circulated, plunge during rotation on a longitudinal axis. The refrigerating fluid is sometimes also circulated in a jacket around the trough. Crystals precipitate on the cold surfaces on the surface of the screw/discs, from which they are removed by scrapers and settle on the bottom of the trough. The screw, if provided, pushes the slurry towards a discharge port.

A common practice is to cool the solutions by flash evaporation: Awhen a liquid at a given T₀ temperature is transferred in a chamber at a pressure P₁ such that the liquid saturation temperature T₁ at P₁ is lower than T₀, the liquid will release [[heat]] according to the temperature difference and a quantity of solvent, whose total [[latent heat]] of vaporization equals the difference in [[enthalpy]]. In simple words, I cool the liquid by evaporating a part of it.

====Evaporative crystallization====