Drying drum dryer

Drum dryers are shown in Fig. 3.15c. his consists of a heated metal roll. As the roll rotates, a layer of liquid or slurry is dried. The final dry solid is scraped off the roll. The product comes ofiF in flaked form. Drum dryers are suitable for handling slurries or pastes of solids in fine suspension and are limited to low and moderate throughput. 

Cylinder Heat-Transfer Units Sometimes called can dryers or drying rolls, these devices are differentiated from drum diyers in that they are used for solids in flexible continuous-sheet form, whereas drum dryers are used for liquid or paste forms. The construction of the individual cyhnders, or drums, is similar in most respec ts to that of drum diyers. Special designs are used to obtain uniform distribution of steam within large drums when uniform heating across the drum surface is critical. 

For drying small fabrieated parts, a helieal drum dryer is often employed. This maehine eonsists of a perforated, rotating stainless steel drum eonveyor that employs a high veloeity airknife system to provide eontinuous throughput and 100 % drying of small, fabrieated parts. 

Drying the separated, sulfonated asphalt by passing it through a drum dryer... 

Drum dryers are used for liquid and dilute slurry feeds. They are an alternative choice to spray dryers when the material to be dried will form a film on a heated surface, and is not heat sensitive. 

Grains. Grains are usually prereduced powders. The quantities of sodium sulfide, hydrosulfide, and mineral salts are adjusted to give a grainy product when the paste slurry is dried on a steam-heated drum dryer. Grains offer the advantage of not being dusty. 

The standard conventional finishing process has been modified to suit the purposes for different fabrics and garments. For example, tubular knits are frequently handled using specialized equipment to control tension and to get adequate padding. Some tubular knits are subjected to wet-on-wet padding, dried and cured in large drum dryers, and steam-treated to achieve a relaxed and nondistorted knit. 

Drums for Drying. See undel Drying and Dryers (Driers)... 

Sodium and Potassium Benzoate. These salts are available in grades meeting the specifications of the National Formulary (18) and the Food Chemicals Codex (19) (Table 7). Sodium benzoate [552-52-1] is produced by the neutralization of benzoic acid with caustic soda and/or soda ash. The resulting solution is then treated to remove trace impurities as well as color bodies and then dried in steam heated double drum dryers. The product removed from the dryers is light and fluffy and in order to reduce shipping and storage space the sodium benzoate is normally compacted. It is then milled and classified into various product forms, the names of which often bear little relationship to the actual form of the product. 

The carbon black leaving the beading machine contains ca. 50 wt% water. It is dried in dryer drums, indirectly heated by burning tail gas. Dryer drums with a capacity of 2000 kg of carbon black per hour are 15-20 m long and 2-3 m in diameter. They are rotated at 5-15 rpm. Drying temperatures, generally between 150 and 250 °C, allow further modification of the carbon black properties. 

For direct drying of liquids, slurries, and pastes, drum dryers are the only competition for spray dryers, although fluidized bed dryers sometimes can be adapted to the purpose. Spray dryers are capable of large evaporation rates, 12,000-15,000 lb/hr or so, whereas a 300sqft drum dryer for instance may have a capacity of only 3000 lb/hr. The spherelike sprayed particles often are preferable to drum dryer flakes. Dust control is intrinsic to spray dryer construction but will be an extra for drum dryers. The completely enclosed operation of spray dryers also is an advantage when toxic or noxious materials are handled. 

The process of sublimation is analogous to the drying of solids so much the same kind of equipment is usable, including tray dryers (Fig. 9.6), rotary tray dryers (Fig. 9.8), drum dryers [Fig. 9.11(b)], pneumatic conveying dryers (Fig. 9.12), and fluidized beds (Fig. 9.13). The last of these requires the subliming material to be deposited on an inert carrier which is the fluidized material proper. 

Fig. I. Single-drum dryer (atmospheric). Dryers of this type may be dip or splash fed (not shown), or, as shown, equipped with applicator rolls. The latter is particularly effective for drying high-viscosity liquids or pasty materials, such as mashed potatoes, applesauce, fruit-starch mixtures, gelatin, dextrine-type adhesives, and various star dies. The applicator rolls eliminate void areas, permit drying between successive layers of fresh material and (omi me product sheet gradually. While single applications may dry to a lacy sheet or flakes, the multiple layers generally result in a product of uniform thickness and density with minimum dusting tendencies. (Bujiovak Division, BlawKnox Food Chemical Equipment. Inc)...

Fig. 2. Double-drum dryer (uttiiospheriei. Dryers of this type handle a variety of food products of widely varying densities and viscosities dilute solutions, heavy liquids, or pasty materials. A number of products can be dried successfully with this kind of configuration, inasmuch as exposure to temperature above the boiling point is restricted to just a few seconds. The movable dram permits effective control over product film thickness. Feed may be hy perforated lube mrngh. pendulum, or various special configurations. (Bufiovah Division. Blau -Knox hunt dc Chemical Equipment, Inc)...

Crumbles are formed by grinding pellets to the desired sizes. Specialty feeds such as flakes can be made by running newly manufactured pellets through a press or through use of a double drum dryer. The latter type of flakes begin as a slurry of feed ingredients and water. When the slurry is pressed between the hot rollers of the double drum dryer, wafer thin sheets of dry feed are produced that are then broken into small pieces. The different colors observed in some tropical fish foods represent a mixture of flakes, each of which contains one or more different additives that impart color. 

The strands move through large drum dryers which reduce the moisture content to about 2 or 6%, the difference being whether liquid or dry resin is to be used. Because a desired moisture level into the press is about 6—7% me, a liquid resin adds water to the system and requires a lower flake moisture than a dry resin. 

Pastes and melts are spread as a thin film on a surface where they are dried and cooled, respectively. Subsequently scraped off to yield solid product. Drum drying, flaking, melt cooling, endless belt processing, slating, pastille formation. Drum dryers, drum flakers, endless belt systems... 

A drum dryer (Fig. 6.4) consists of one or more heated metal rolls on which solutions, slurries or pastes are dried in a thin film. The thin film dries in less than one revolution of the slowly revolving rolls and is scraped off by a doctor blade to form a product in flake, chip or granular form. Drum dryers are widely used in chemical processing frequently to dry hydrates, carbonates, arsenates, acetates, phosphates, clays and food products [11]. 

FIG. 12-46 Example of the use of air impingement in drying as a secondary heat source on a double-drum dryer. [Chem. Eng., 197, (June 19,1967).]... 

At steady state, the product stream is continuously removed from the fermentor at a rate equal to feedrate. The product stream is concentrated in a desludging separator to a paste of 20 to 30% dry solids. After washing with warm water to remove adsorbed or absorbed hydrocarbons, a second desludging separator produces a cleaned paste that is ftirther dehydrated in a rotary vacuum filter. A final drying step in an atmospheric drum dryer reduces the moisture content to less than 10%, and the powdered product is packaged for the customer. 

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