This dryer operates under vacuum which lowers the boiling point of water resulting in a low temperature evaporation point. The sludge cake or food waste supplied into the dryer are dried by conduction heat from the jacket of the static drum while rotating impellers agitated the material inside the drum to improve the drying efficiency. The vacuum operation also requires less thermal energy resulting in less running costs.
- Saturated steam of higher than 120oC or hot water of higher than 85oC is used as a heat source.
- Drying at rather low temperatures eliminates the fear for fire and oxidation.
- Organic materials are difficult to decompose, which is important to sell as a fertilizer, a feed or other value-added product, or a recycled product.
- Drying under vacuum emits exhaust gases and foul smell much less than the other types of dryer.