Hopper dryer

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One can see that the elimination of the drying operation represents a large potential energy saving. As a first step, one can use a hopper dryer so that pellets that are at the elevated drying temperature are fed to the machine. This eliminates the heat loss to the surroundings which occurs in tray dryers. Drying may be eliminated entirely in certain instances as described in two recent developments. HPM (11) has developed a vented injec-... 

Rotary dryers, batch fluid dryers, continuous or batch tray dryers, hopper dryers, multispouted bed, and vacuum tumble dryers are typical long-residence units used in polymer drying. 

Options similar to Indirect convection but hotter gases are used fluidized bed, rotary kUn, bands/bdts and open bed with specialized option hopper dryer for polymer feed to extruder. 

Open bed (direct convection) residence time minutes gas through bed 0.5 to 1 m/s. Hopper dryer for polymer feed to extruder. Hot gas < 120 °C. 

Contamination and material handling cut. There is no need to clean out larger complicated hopper dryer systems on every material or color change. The simple, lightweight, standard hopper is easier to clean. 

Less space required. The hopper dryer requires a large volume in order to get up to 5 hours of drying time. This means a heavy, large, and high hopper that may not fit into the space available. 

If stored incorrectly the material will pick up sufficient moisture to give streaks, or blisters, on the moldings. It is recommended to reduce the moisture content within the pellets to below 0.1% before use best to dry all ASA for 2 to 4 hours at 80 to 85° C (176 to 185° F) before molding. When using hopper dryers the temperature can be increased to 90° C (194° F) so as to ensure that the material is sufficiently dry prior to being molded. If a circulating air oven is used then dry for 2 hours at 80 to 85° C (176 to 185° F). 

Preheating can be done in ovens, tray dryers, and hopper dryers. Hopper dryers offer the advantages of reduced handling and less possibihty of contamination and keep the material hot in the machine hopper. The use of dehumidified air is preferable, particularly when high-humidity conditions exist. 

Dexflex, Thermoplastic olefin elastomers, Solvay Engineered Polymers Dezat, Dehumidifying hopper dryer, Nissui Corp. Di-Cup, Dicumyl peroxide, Hercules Inc. Dia-Chip, Pigments for rock imitation, Eckart America... 

SpeedBonder, Anaerobic structural adhesive, Loctite Corp., North American Group Speedryer, Thermodynamic hopper dryer, Webb... 

Hopper dryer. It is necessary to seal the top of the hopper to avoid contamination and humidity. A hot air circulation type of dryer with dehumidifier is recommended for high drying efficiency and lower running cost. 

Filtered hopper dryers generally are used except when long drying times are required. This type dryer replaces the standard machine hopper. Generally, it forces hot dehumidified air through the plastic pellets in the hopper section through a closed air circulating system. 

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