Droogtrommels

Droogtrommels, or drying drums, are industrial rotating cylinders designed to reduce the moisture content of bulk solids. They are used across mining, minerals processing, cement, biomass, waste treatment and chemical industries. The drum, typically made of steel, is mounted slightly inclined and rotated. Material is fed at the top end and moves gradually toward the discharge end. Internal flights or lifters lift and shower the material, promoting mixing and surface exposure.

There are two main drying modes. In direct drying, heated air or flue gas passes through the rotating drum and contacts the material directly, evaporating moisture. In indirect drying, the drum is heated from the outside (for example by steam coils), and the material is dried by heat conducted through the drum wall, reducing the risk of thermal degradation or contamination.

Key design variables include drum length and diameter, rotation speed, incline, residence time, and drying air flow. The process is often part of a broader processing line, sometimes followed by screening or classification to separate fines.

Typical applications include drying ore concentrates and minerals, coal, aggregates and sand, wood-based products such as chips and pellets, fertilizers, and sludge or separated solids in waste treatment.

Advantages of droogtrommels are their high capacity, robustness, and ability to handle large, rugged feeds. Limitations include energy intensity, potential for over-drying or dust generation, equipment wear, and relatively large footprint.

See also: rotary dryer; list of industrial dryers.