Drying methods industrial dryers

Commercial dryers differ fundamentally by the methods of heat transfer employed (see classification of dryers. Fig. 12-45). These industrial-dryer operations may utilize heat transfer by convection, conduction, radiation, or a combination of these. In each case, however, heat must flow to the outer surface and then into the interior of the solid. The single exception is dielectric and microwave drying, in which high-frequency electricity generates heat internally and produces a high temperature within the material and on its surface. 

In this section, electrical drying methods are briefly discussed - examples of applications are discussed in Chapter 10. As an example, the industrial microwave dryer exhibits similar benefits to the domestic microwave oven - the energy is taken directly to the inside of the object(s) being heated, rather than having to be conducted from the surface of the particle or body. Microwave drying can be combined with conventional (hot air) drying to finish off the process, and a combination of... 

Spray drying process is one of the most common methods adopted in many industries. In this chapter, a summary is provided on the fundamentals of spray drying, the selection of spray dryers as well as usages of spray dryers in the industry. Spray dryers, both conventional and innovative, will continue to find increasing applications in various industries, but... 

Foam mat dryers can only be used to dehydrate liquid foods that are capable of forming stabilized foams. This requirement imposes a restriction on the wide applicability of the method in the food industry because only a few foods, such as whole milk, have a foam-stabilizing capability. Fruit juices have been dried successfully by adding foam stabilizers. Vegetable gum and soluble protein have successfully been used in the food industry as foam-stabilizing agents. 

Potato strips are usually dried in concurrent rotary dryers of 1-3 m diameter and 5-15 m length. The inlet and outlet air temperatures are about 500°C and 100°C, respectively. The fresh potato strips are prepared by the sheer similar to one used in the sugar industry. The potato strips are dried to a final moisture content of 12% (wb). A significant portion of the dried potato strip is utilized as livestock feed since it is the most economical method of preserving potato. The details of rotary dryer can be found in Kelly [6]. 

In this section, the more significant developments made to increase the efficiency of multicylinder dryers in recent years, and the new or novel concepts not used extensively in the papermaking industry yet, will be sununarized. Some of these methods are still at a laboratory stage but show the potential for a real breakthrough in the paper-drying technology. 

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