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Vacuum Dryers

Agitated Vacuum Pans
The agitated vacuum pan dryer is one of the most versatile in the Mitchell Dryers range and is widely used for the batch drying of slurries, solutions, filter cakes, damp powders and crystalline products. The dryer essentially comprises a flat bottomed, jacketed, cylindrical vessel arranged for hot water, steam, or thermal oil heating.

Dryers are available in the capacity range 75L – 2,135L incorporating optional features as noted.

Dryer feed: Wet material is fed into the dryer through a hinged, counter-balanced top cover or a hinged access manhole dependent upon dryer capacity and location. Access into the interior of the dryer for cleaning is readily available through the same top cover or manhole.

Product discharge: The discharge door is fitted in the lower side wall of the vessel and product discharge is affected by use of the agitator. Discharge time is depended upon material flow characteristics, the agitator design, and its speed or rotation.

Agitator: The rotating agitator arm sweeps all the internal heat transfer surfaces, and its gentle, effective action continually presents fresh material to the hearting surfaces and facilitates homogeneous mixing. A choice of agitator designs, which can be arranged with or without heating, is available to suit the material characteristics and process requirements.

Optional features include:

  • Vacuum or atmospheric operation
  • Agitator driver from above or below pan body
  • Fixed or variable speed agitator drive
  • Stuffing box or mechanical drive shaft seal
  • Breaker bar to increase range of application
  • Internal or external dust filters to suit process
  • Nitrogen purge facility
  • Automatic discharge
  • Counterbalanced top cover or access manhole
  • Fixed body with base lowering facility and support trolley
  • Adjustable variable speed lump breaker
  • Agitator arranged with or without heating facility
  • Cleaning in place system

Double Cone Dryers
The double cone vacuum dryer is completely jacketed, and heat transfer fluid (either hot water or oil, steam or vapour) is circulated throughout the jacket. The unique conical shape assures direct contact between the material and the heated surface so that heat is transferred rapidly by conduction.

As the dryer rotates, the rapid and through intermixing of the entire batch brings every particle in contact, time and again, with the heated surface for more rapid heat conduction. This permits high-speed drying without raising the drying temperature to the danger-point of the material being processed.

The most important effect of this thorough blending and interfolding is maintaining uniform temperature throughout the batch. This prevents recondensation because there are no cold spots, and it contributes to the speed of drying and elimination of caking.

Finally, a high vacuum is maintained to draw off the moisture under these ideal conditions of material in motion.

Easy to keep clean, the interior of the dryer consists only of the smooth side walls through which the heat is transferred to the product. The thorough mixing and blending action is obtained by the unique shape of the drying compartment. Intersections of cylinders and truncated cones are obtuse angles, so no material is trapped. There are no internal scrapers, ploughs, scoops, or vanes to trap and hold material while it cakes or prevents uniform warming and drying. The dryer may be easily cleaned for minimum process delay during change of products or of colours.

It is practical to use one dryer for many different reagent-grade chemicals of highest quality. All bearings of the dryer are external to the drying compartment and there is no possibility of contamination from the lubricant.

A breaker bar can be fitted to break down materials which are agglomerated, balled up, or fed as lumps. Drying times are reduced as the lumps are broken down and evaporation is improved. Processing is simplified with mixing, granulation, and drying being handled in one operation.

Vacuum Shelf Dryer
Mitchell Dryers’ vacuum dryers are used where materials to be dried are heat sensitive or liable to oxidation.

Solvents can readily be recovered by means of a simple condenser system and toxic materials can be processed without operator contact.

These dryers can be supplied complete with heating system, vacuum pump, solvent condenser, and service piping.

This is the simplest type of unit with the wet material carried on trays which are placed onto heating platens within the vacuum chamber. High efficiency heating platens in direct contact with the total tray surface ensure maximum heat transfer and even drying.

Circular or rectangular units can be supplied, and these are ideal for small to moderate levels of production. Sizes range from 1.25m² up to 19m² tray area.

For further information or to discuss your requirements please contact our team.