General Information on Rotary Dryers

Rotary Dryers are flexible in processing virtually any bulk solid material, rotary dryers have made their way into an abundance of industries around the globe.

Working Principle of Rotary Dryers

When rotary Dryer is operating, it shall be in direct contact with heated gas. The dryer consists of a large rotating cylindrical tube. In order to convey the material through the underside of dryer, the dryer should be slanted slightly to ensure that the discharge end is lower than the end of material feed .

Material shall be dried to enter the dryer. When the dryer is rotating, a series of internal fins will lift the material by lining the inner wall of the dryer. When the material reaches certain height to roll the fins back, it will be fell back to the bottom of the dryer, then passing through the hot gas stream as it falls. This gas stream can either move toward the discharge end from the feed end (known as co-current flow), or toward the feed end from the discharge end (known as counter-current flow). The gas stream can be composed of a mixture of air and combustion gases from a burner, and in which case the dryer is known as a direct heated dryer. Alternatively, the gas stream may be made up of air or another (sometimes inert) gas that is preheated. When the gas stream is preheated by some means where burner combustion gases are not permitted to enter the dryer, the dryer shall be called an indirect-heated type. Indirect heated dryers are commonly used when product contamination becomes a concern.

Usage of Rotary Dryers

Highly efficient industrial drying option for bulk solids. The following is a brief overview of some of the most common industries where Rotary Dryers are being widely used:

Agriculture

Selected for their durability and high throughout, rotary dryers are used extensively in the agricultural industry, and more specifically, in the following applications:

Fertilizer and soil amendments- Rotary dryers are used to process raw feed stock and to dry final product. Materials dried include: gypsum, limestone, potash, NPK, DAP, and manure.
Animal feeds- Animal feeds are similar to fertilizer and soil amendments, in that dryers are used on both raw feed stock and the end product. Materials dried include: DDGS, DCP, MCP.
Bedding- Rotary dryers can process dairy manure digestate from anaerobic digesters, in order to produce a bedding product know as Dried Manure Solids (DMS) bedding.

Mining / Minerals and Aggregates

Due to their high capacity settings, heavy-duty make-up, and able to tolerate sometimes abrasive materials, rotary dryers are an ideal fit for the mining industry.

Additional mined materials that often employ rotary dryers include:

Bauxite
Clays
Sand
Coke

Sugar

Sugar is inclined to clump and stick together; the tumbling action, in combination with the showering action from the dryer’s internal flights, help break up any clumps, and for this reason, sugar producers have come to rely on rotary dryers as their drying equipment of choice.

Biomass

Biomass includes an assortment of organic materials such as woodchips, forest product residuals, bagasse and coconut husks.

Biomass materials can vary across types and even from within the same source of material. Therefore, rotary dryers are often selected because of their reliability in working with such a variance in feedstock.

Rotary dryers are the equipment of choice for drying biomass materials. They are cost efficient in terms of removing high volumes of water from biomass.