Drying, roasting or heat treatment is achieved by passing the material being processed through a rotating cylinder through which also passes a current of hot air. Lifters or flights fitted to the internal surface of the cylinder lift and cascade the material through the hot air stream. The air stream can be directed through the cylinder either in the same direction as the material (co-current) or in the opposite direction (counter-current). Co-current systems are used in most general drying applications. Counter-current systems are more efficient in terms of energy input but give rise to high product temperatures, with the associated handling problems.

Similarly, cooling may be effected by passing the material to be cooled through a rotating cylinder through which flows a current of cold air or which is externally cooled by means of a water bath or spray nozzles.

The drying air may be heated either directly by means of oil, gas or solid fuel burners or indirectly by means of suitable heat exchangers using steam or other heating media. Drying temperatures range from below 100 deg.C up to 700 deg.C.

The exhaust gas stream from any drying operation inevitably includes a significant amount of fine particles. This fine particle carryover may be collected by passing the gases through high efficiency cyclones, or bag filter or wet scrubber or a combination of any or all of these, depending upon the nature and quantity of dust involved.

The exhaust gas stream from any drying process may also contain a substantial quantity of waste heat energy. Some of this energy may be recovered by passing the exhaust gas stream, after suitable cleaning, to a heat recovery unit. Such units are designed not only to remove heat directly from the exhaust gases but may also be designed to condense out water vapour or other volatiles to recover latent heat. Clean warm air from the heat recovery unit can then be ducted to the dryer inlet air heater thus reducing the overall energy input of the drying process.

In addition to Rotary Dryers and Coolers, of both cascade and louvre type construction, R.Simon (Dryers) Ltd. design and manufacture Rotary Granulators, Coating Drums and Rotary Reactors, in a standard range of diameters from 1 Metre to 3.5 Metres and larger as required, with ancillary equipment to suit individual client's specifications.

ROTARY DRYERS - Rotary Cascade - Rotary Louvre - Rotary Steam Tube -
Construction and Operation - Machine Sizing - Materials Processed

Details of - Drum Dryers - Drum Flakers - Tubular Dryers & Coolers -
Rotary Dryers & Coolers - Calciners

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