VetterTec Ring Dryers and Flash Dryers

VetterTec ring and flash dryers are used for various products, preferably when gas or oil is available and / or off heat from downstream processes should be used in the dryer. Based on the flash effect and the minimum of retention time the dryer has a minimized thermal influence on heat sensitive products.


VetterTec ring and flash dryers are co-current airstream drying systems which are ideal for drying filter cakes, fibrous materials, sludges and slurries. By its function principle these dryers have a minimum of thermal influence on heat sensitive products.

Function and Principle of Operation

VetterTec ring dryers and flash dryers are pure convection dryers and can be either designed as directly or indirectly heated dryers. The material is conveyed in a hot air stream where the wet material is in contact with the highest temperature gases which rapidly, minimum of retention time, cool as evaporation from the product occurs, product temperatures are kept to a minimum resulting in uniform product quality and minimum thermal damage.

The dryers can be configured in open circuit (once-through drying air), partially closed circuit (majority of the exhaust air is returned back to the heater as recycle) or fully closed circuit (100% of exhaust air is recycled back to the heater, usually through a direct or indirect contact condenser for removal of the evaporated water). In addition, indirectly heated partial closed circuit systems can be provided, providing the added benefit of high humidity exhaust which can be utilised very effectively in down stream process (e.g. waste heat evaporators) where a significant proportion of the latent heat can be recovered.

Flash Dryers

Flash dryers are used to produce fine granular or powdered material when short residence times are acceptable. A stream of turbulent hot air dries the product in a continuous process.

A variety of wet material feeder devices are available, optimized according to product characteristics and feed quantities. These include sling feeders (used for non-abrasive and friable materials), cold disintegrators and direct screw feeders.

The final dried material is separated from the drying air using either bag filters or cyclone technology. Two-stage collection (e.g. cyclones plus wet scrubber) is also available where required to optimise product recovery or minimise particulate emissions to atmosphere.

ring dryer

Ring Dryers

Ring dryers are flash type dryers which incorporate a centrifugal classifier to increase the product residence time selectively for the wetter and larger material. Within the classifier, the drier and finer particles are separated out from the air stream to be selectively returned back into the drier for further drying. The finer and drier material is removed from the ring dryer through the bag filter or cyclone collection system. Adjustment blades in the classifier allow the degree of separation to be set to optimize the dryer performance.

Ring dryers can be fitted with high speed hot disintegrators (fixed beater type mill), located within the hot air stream, to provide screenless grinding.

Ring dryers thus provide extended residence times, allowing many materials to be effectively dried which would not be suitable for flash drying.


VetterTec ring and flash dryers are reliably operating in the drying of:

  • bullet  Starches from Potato, Corn, Wheat, Cassava, etc.
  • bullet  Wheat and Corn Gluten
  • bullet  High protein fodder DDGS
  • bullet  Minerals
  • bullet  Cellulose
  • bullet  Pigments and dyestuffs
  • bullet  Fine chemicals
  • bullet  Zirconium Hydroxide
  • bullet  Sodium Ferro-Cyanide and Sulphate
  • bullet  Metal powders
  • bullet  Precipitated Calcium Carbonate
  • bullet  Silicate
  • bullet  Bethonite
  • bullet  Alfa Ash
  • bullet  Carbon
  • bullet  Gravy powder
  • bullet  Waste products

Your product is not on the list? Feel free to contact us: we have desired test facilities, combined with our long term experience in the drying we would be pleased to consult for the best drying solution for your product.