Drying dielectric

Dielectric drying baked goods, breakfast cereals, furniture timber blanks, veneers, plyboard, plasterboard, water-based foam plastic slabs, and some textile products... 

Freeze-thaw vacuum, inter leave-air, and solvent extraction processes offer the greatest potential in drying these types of coated- and uncoated-paper books after they have been wetted and frozen. The drained-air, vacuum-air cycle, vacuum, microwave, and dielectric drying processes work well on uncoated paper, but they fail to dry books containing this type of coated paper. Small and large units for freeze-thaw, vacuum drying have been used successfully to remove water from these frozen coated and uncoated books. 

If conduction or radiation is the predominant mode of heat transfer, the surface (and possibly the interior) moisture may literally boil regardless of the temperature or the humidity of the environment. This may be readily demonstrated by microwave drying. Thus, if control of granulation temperature is important, direct heat (convection) dryers usually offer greater control and product safety since the material s surface does not exceed the wet-bulb temperature during the steady state period. However, it will be shown later in this chapter that properly controlled dielectric drying may also be used to dry heat sensitive materials. 

Microwave or dielectric drying has been reported in the pharmaceutical literature as being comparable or superior in terms of efficiency, energy consumption, and cost... 

Scheffer TC and Morrell JJ (1998) Natural durability of wood A worldwide checklist of species. Forest Research Laboratory, Oregon State University. Research contribution 22 Schiffinann RF (1995) Microwave and dielectric drying. In Mujumdar AS (ed), Handbook of industrial drying (2nd. Edit). Marcel Dekker, New York, Vol. 1 345-72 Schneider MFl and Witt AE (2004) History of wood polymer composite commercialisation. Forest Products Journal, 54(4) 19-24... 

The extensive value of Chemical Abstracts 19 is well known. The Engineering Index 20 GONQYS the engineering field selectively, not comprehensively important engineering advances such as dielectric drying are well covered. This index, issued annually, contains major and minor subject headings, with abstracts, and extensive cross-indexing. An alphabetical list of all names mentioned in the abstracts is also included. 

Schiffmann, R.E. 1995. Microwave and dielectric drying. In Handbook of industrial drying. 2nd ed. Ed. A.S. Mujumdar, 345-372. New York Marcel Dekker. 

Criteria for Snccessfnl Microwave and Dielectric Drying Systems.299... 

FIGURE 13.4 Typical drying curves for microwave and dielectric drying systems (a) preheating with microwave or dielectrics, (b) booster drying, and (c) finish drying. 

Numerous industries use microwaves for drying, many of which are the same as those that use dielectric drying. However, there are several unique drying systems. 

There are several criteria for successful microwave and dielectric drying systems. Cost is reduced. This is often a major factor. Cost savings may be realized through energy savings, increased throughput, labor reduction, reduction in heat load in the plant, speedup of the process, operational efficiencies, and reduced maintenance costs. 

Another good summary of the economic factors to be considered in choosing a microwave or dielectric drying system is given in an early paper by Jolly [26]. Here, a detailed comparison is given for the economic considerations that enter into the choice of a new microwave system over the standard conventional procedure. 

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