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 Easy Access Model • ECLN Model Description of the Centrifugal Dryer Process |
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In the early sixties, Gala launched its own centrifugal dryer for the plastics industry. Since then, over 8,000 Gala dryers have been installed worldwide. These dryers are suitable for throughputs from 2 to 70,000 kg/h. Gala currently offers two dryer series, standard "EASY ACCESS" series and the "EASY CLEAN LOW NOISE" series. How it Works The pellet-water mixture (process water) emerging from the cutting chamber of the pelletizer is guided to an agglomerate catcher installed upstream of a centrifugal dryer. The agglomerate catcher serves to protect the dryer by removing larger pellet clumps (agglomerates) that may be produced during startup before they enter the dryer's rotor area. In systems with a water throughput of less than 20 m≥/h, the entire volume of process water is separated inside the rotor section of the dryer. Larger systems are equipped with a pre-dewatering system in which, depending on the number of screening stages, up to 95 % of the process water flow is separated. In the following stage, the pellets flow with the residual process water into the rotor section of the dryer. As a result of the rotation (at speeds of up to 1,500 rpm) and the design of the lifter elements inside the rotor, the pellets are thrown against the screens and the centrifugal force moves them upward following a helical path. While the water is separated through the screens, the pellets are continuously conveyed up to the upper section of the dryer where they emerge at the pellet outlet. Depending on the polymer, the centrifugal drying process reduces the residual surface moisture to as little as 0.05 %. Final drying is achieved in the upper two thirds of the screen surface and in the pellet outlet chute of the dryer. A dry countercurrent air flow generated by an external exhaust fan removes residual surface moisture from the pellets, assisted by the actual pellet temperature. The exhaust fan also produces a slight vacuum to prevent any humid air from exiting into the production hall or condensing in downstream equipment components. The length of the water transport line has a definite influence on the residual surface moisture of the pellets. It determines the temperature of the pellets as they enter the dryer. Additional factors affecting surface moisture are: • Pellet size • Pellet shape • Surface roughness of the pellets • Hygroscopic characteristics of the product • Additional auxiliary drying and or conveying maybe required. |
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Easy Access Model • ECLN Model |
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