Scraped-surface cooling

Scraped-Surface Crystallizer For relatively small-scale apph-cations a number of ciystallizer designs employing direct neat exchange between the shiny and a jacket or double wall containing a cooling medium have been developed. The heat-transfer surface is scraped or agitated in such a way that the deposits cannot build up. 

Skelland, A.H.P., Oliver, D.R. and Tooke, S. Brit. Chem. Eng. 7 (1962) 346. Heat transfer in a water-cooled scraped-surface heat exchanger. 

This type is similar in principle to the tank type, but the cooling surfaces are continually scraped or agitated to prevent the fouling by deposited crystals and to promote heat transfer. They are suitable for processing high-viscosity liquors. Scraped-surface... 

The scraped surface, or close-clearance exchanger, illustrated in Fig. 10 is required for a few very difficult situations. An example is purification by fractional crystallization, in which a refrigerant boiling in the annulus cools a solution of various substances and certain species selectively crystallize out on the surface of the inner pipe. The crystalline deposit must be continuously scraped off of the surface in order that the heat transfer rate be maintained. The crystals are eventually removed from the remaining liquid by filtration. 

N. Hall Taylor, The Operation of Scraped Surface Heat Exchangers with Very Viscous Materials during Cooling, Technology Memorandum No. 2, Crown Chemtech Ltd., Reading, United Kingdom, 1993. 

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