The rotary dryers function by means of rotating drums with horizontal axle. Various types of paddles are mounted on the inside; advancing, overturning and high rendering that favour the thermal exchange between hot gases and the material to be dried.
These dryers operate in “counter flow”: the flow of hot gases is opposite to the direction of the advancing material to be dried, and in this way the output of thermal process is increased. The material enters with the hot gases on the inside of the dryer and are subject to continuous turning.
They remain inside for the necessary amount of time for the mass to be heated and for the water to be evaporated.
At the drum exit the unload head is positioned and this is where the burner is mounted and where eventually other hot gases will enter.
The dry material falls to the bottom of the collection hopper and then transported to the storage silos. The sources of heat can be multiple: Gas burners and/or combustible liquids, Burners for biomass (e.g. recovered wood) but the ideal working conditions of a rotary dryer are anyhow with the utilization of a cycle combined with energetic co-generation, so as to drastically cut down the energetic costs; for example, where there is an electricity-generating group, the gas emission (normally exit at a temperature of 450°C) can be conveyed into the mixing chamber positioned upstream of the dryer realizing in this way considerable energetic savings.
The output of the thermal exchange is directly proportional to the difference of the temperature, and subsequently the dryer is fed with gas at the maximum temperature possible compatibly with the chemical and physical characteristics of the material to be dried.
Some examples of the many types of material that can be treated are:
- Sand
- Inerts
- Calcium carbonates
- Soil & Clays
- Sludges
- Wood
- Plastic
- Etc etc
The dryers can be supplied for production rates from 10 to 60 t/h.
Production capacities out of the above mentioned range can be realized upon Customers’ request.
