Ronning’s Direct Fired Three-Stage Dryer System is the traditional configuration for our single-pass rotary dryer and is typically fired with natural gas.

In this system, the wet product or ingredient enters the Three-Stage Dryer Drum where it meets with the products of combustion and travels through three stages of flighting. The ingredients and combustion gases mix with the water vapor that evaporates from the product.

A portion of the dried product is recycled by conveyor back to the front of the dryer to be mixed with wet product to improve product flowability and to maximize the product heat transfer ratio. Finished product conveys to the Cooling & Conditioning Drum for additional evaporation, cooling to near ambient temperature and for storage if needed for a smooth flow to further processing or storage.

Direct Fired




The heat transfer capability of the Ronning Three Stage Dryer Drum provides higher capacity systems, which means lower capital cost, lower operating cost, lower maintenance cost and simplicity of system planning.

The Ronning Blending Chamber increases combustion efficiency and increases Stack Gas Recycle to maximum levels so Thermal Oxidation systems are smaller, requiring less capital and operating cost.

The Drop-out Chamber, Twin Centrifugal Separator, and Cyclone Separator provide three stages of product and air separation for maximum particulate removal.  They have pressure regain design so the external pressure drop is reduced to save the air-separation horsepower requirement.

The primary fan is a backward-curved, high-capacity, high-efficiency design which saves about 30% of the air-moving horsepower requirement over radial blade designs.

The counter-flow Cooling & Conditioning Drum finish dries and cools the product, plus it provides a surge chamber for dryer shut down.