Dryers, belt vacuum

Radiative Heat Transfer Heat-transfer equipment using the radiative mechanism for divided solids is constructed as a table which is stationary, as with trays, or moving, as with a belt, and/or agitated, as with a vibrated pan, to distribute and expose the burden in a plane parallel to (but not in contacl with) the plane of the radiant-heat sources. Presence of air is not necessary (see Sec. 12 for vacuum-shelf dryers and Sec. 22 for resubhmation). In fact, if air in the intervening space has a high humidity or CO9 content, it acts as an energy absorber, thereby depressing the performance. 

Coprecipitation of special cations such as antimony or cerium can improve lightfastness further [2.45]. After treatment in aqueous media, the pigments are washed on a rotary vacuum filter or a filter press until they are free of salt, and then dried using, e.g., belt, spray, or fluidized-bed dryers. 

In neither process is it commercially feasible to produce a dehydrated juice without the addition of a drying aid, although 100% orange juice has been produced with the continuous vacuum belt dehydrator (42,A3). This product is extremely hygroscopic and very temperature sensitive. As a result, the product "cakes" or hardens if exposed to moist air or to temperatures much above 24°C. The product is also subject to browning if not stored at refrigerated temperatures. Dehydrated citrus juices are produced on a vacuum belt dryer at Crystals International, Plant City, Florida, and are items of commerce. 

The vacuum pumps initially used in freeze-dryers were of the belt-drive type and, as such, extremely bulky and noisy by current standards. At present, most research-scale freeze-dryers use direct-drive pumps, which are much quieter than the previous models and also, frequently, very small. Because they are constructed from corrosion-proof materials, they are highly flexible in operation. 

Belt conveyor furnace Spray drying Fluid bed drying Rotary kiln Vacuum dryer Z-mixer... 

Spray Spray/fluid bed combination Vacuum belt dryer Pulse combustion dryers... 

Fluid/spouted beds of inert particles Spray/fluid bed combination Vacuum belt dryer Pulse combustion dryers Spouted bed of inerts Fluid bed (with solid backmixing)... 

A belt-trough dryer has been used to produce very high-quality diced potato [4,5]. Only vacuum drying or freeze-drying can produce a more porous product than products dried using a belt-trough dryer. The dryer consists of an endless, closely... 

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