Scraped Surface Heat Exchangers (SSHE) are used for continuous processing, especially crystallization and the separation of organics. Continuous cooling crystallization employs a coolant that flows through an annulus to transfer heat from the inner pipe process stream. Heat transfer is most effective at the pipe wall, and as such, crystals will preferentially adhere to the wall, thereby limiting heat transfer. To maintain the heat transfer, blades scrape the crystals off the wall, which are transferred as a slurry in solution and travel downstream, and into either a filter or centrifuge where they can then be removed from the stream. The process fluid may then be recycled into a tank, holding the Mother Liquor. Also, its recycle loop continues—usually around a ten times recycle. Of course, not all processes necessitate a recycle loop, but a once through continuous crystallization would require much more surface area, and therefore more equipment and a considerably more expensive system.

Scraped Surface Heat Exchangers

SSHE are made with an outer pipe and jacket typically 6”/8”, 8”/10”, 10”/12” or 12”/14”. The most common ones found are 6”/8,” but modern designs for high volume production will be 12”/14” as this size offers the optimum heat transfer and pressure drop.  All SSHE equipment is designed to a specific process using proprietary heat transfer calculations, which are not available on commercial heat transfer programs. 

Armstrong Chemtec has supplied SSHE to many countries for many applications from:

  • Palm Oil
  • Separation of fatty acids
  • Sterane/olein separation
  • Shea bitter oil, wax
  • Lubricating oil
  • And a long list of organic chemicals with experience of over 350 mixtures.
  • More recently applications for special Chemicals relevant to the Energy Industries 

Scraped Surface Heat Exchangers

Some Inorganic chemicals may be separated, providing the solubility curve is acceptable. Flat solubility curves indicate that separation by cooling is unlikely to be successful. However, inorganic Salts such as Glauber's Salts have been successfully separated. Testing by the end-user may provide the end-user with a cooling circuit, utilities, and piping. Armstrong Chemtec will rent a Pilot Crystallizer for the customer to carry out in-house tests of crystal growth, color, and morphology, allowing the operator to determine optimum residence time and cooling MTD. All inquiries should be addressed to sales@armstrong-chemtec.com.

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