subject: Dryer, Drying Method And Drying Paint [print this page] The mesh belt dryer of the present invention includes at least one substantially vertically orientated elongate container having an upper inlet, for receiving the charge of moisture containing particulate material, and a lower outlet for discharging the particulate material after drying. The inlet and outlet are typically open to allow for substantially continuous throughput of the particulate material.
In an alternative embodiment, the direction of air flow through the particulate charge may be reversed from one plenum zone to an adjacent plenum zone. This may be achieved by providing an air circulator in alternate plenum zones, such that air is sucked in a first direction from one plenum zone, through the charge into an opposing plenum zone, then into an adjacent plenum zone and back through the charge in a second, reverse direction, and so on. In this manner, the air flow path "zig-zags" back and forth throughout the height of the charge. The dryer may have one or more air flow paths, but preferably has only a single air flow path with a single air inlet and a single air outlet. Air exiting the dryer through the air outlet may be passed through a desiccator or refrigerator to recover moisture removed from the particulate charge. The air exiting the mesh belt dryer is preferably passed through a heat exchanger (preferably using waste heat from another industrial process) to preheat it before being recycled back to the air inlet of the dryer.
The container wall/s are preferably tapered inwardly towards the inlet and outlet. A tapered outlet assists in controlling the rate of discharge of the dried material. A tapered inlet enables the top of the bed of particulate material to form a mound. Preferably, the distance from the apex of the mound of particulate material to the uppermost gaseous openings is greater than the width of the particulate bed. Such a relationship enhances the effective ingress and egress of air through the gaseous openings rather than by leakage from the atmosphere through the open top of the mesh belt dryer. Leakage of air through the top of the particulate bed can be further reduced by biasing the pellet feed towards the air outlet side of the dryer. Preferably also particulate material being fed into the dryer does not need to drop more than about 3 metres, preferably not more than about 1 metre, to the apex of the mound of particulate material within the dryer. In this way fracturing and disintegration of the particulate material entering the dryer will be minimised.
