Ring Dryers

At 179,000ACFM volume capacity, Dedert's expertise has resulted in the world's largest partially-closed PGR Ring Dryer that is able to evaporate 34 tons of water per hour in a single unit! But what is ring drying?

Ring drying is an extension to flash drying with the addition of a manifold classifier to allow semi-dry solids to internally circulate until fully dry, which allows the ring dryer to be more energy-efficient. With its short residence time of only a few seconds, the solids are not exposed to a high-heat environment for a long duration which results in ring dried product offering the highest product quality compared to products from other drying technologies. The versatility of the ring dryer design also accommodates variations in product grades and characteristics, including changes in moisture content, evaporation rate, and product composition that could affect drying behavior. 

Learn more about ring dryers in our guide.

Ring drying is applicable to particular powders, pastes, cakes or slurries which require extended drying times over 1-pass flash drying. Example applications include:

  • Orange Peel
  • Citrus Fiber
  • Calcium Carbonate
  • Corn Gluten, Fiber, and Starch
  • Distillers Dried Grains and Solubles (DDGS)
  • High Protein DDG
  • Metal Oxide
  • Minerals
  • Starches
  • Wheat Gluten

Depending on the characteristics of the product, the ring dryer arrangement can have an important impact on the dryer performance:

Feed-Type Ring Dryer

A Feed-Type Ring Dryer is arranged so that the manifold directs the solids recycle back to the higher-temperature feed zone for maximum dryer efficiency. The manifold acts as a centrifugal classifier, selectively recycling the heavier semi-dry product through a chute to the disperser for another drying pass. This ring dryer arrangement is suitable for more resilient product types that can sustain limited exposure to high heat, such as corn fiber, corn gluten, DDGS, or minerals.

P-Type Ring Dryer

In a P-Type Ring Dryer, named after its distinguishable "P" shape, the manifold directs the solids recycle back into the lower-temperature exhaust zone for temperature-sensitive products. This arrangement offers certain harder-to-dry products the additional residence time to reach sufficient dryness without causing unwanted denaturation, such as starch gelatinization.

Full-Ring Dryer

The unique manifold design in a Full-Ring Dryer offers two functions: a) solids recycle through the hot duct to the air-swept disintegrator, and b) extended residence, if needed, within the manifold to reach sufficient dryness. Challenging drying applications needing extra milling or dynamic blending in the airstream benefit from this dryer type, such as specialty products like wood pulp or vital wheat gluten.

Energy Configurations

Each of the ring dryer types can have either Open-Circuit (OC) or Partial Gas Recycle (PGR) configuration to suit the product application or operational requirements. Under OC, ambient air is used as the 1-pass drying medium. Under PGR, additional energy efficiency is achieved by recirculating the majority of the dryer exhaust stream back to the air heater as a preheated drying medium.

With customizable designs and sizes, Dedert can support your project to meet your ring drying requirements. Contact us today to learn more!

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