Cabinet driers

Originally, predrying was conducted in ordinary cabinet driers fitted with racks. Strips or tubes intended for drying were thrown over the racks. This type of drier... 

FIg. 222. A cabinet drier for predrying powder and solvent recovery. 

Fig. 223. A cabinet drier for predrying powder 1—hole for loading, 2—hole for unloading the powder strips and tubes, 3—rails inclined towards the hole unloading, 4—air...

Solvent escapes from nitrocellulose powder at various stages of its manufacture. The largest amount volatilizes during the predrying of the freshly shaped strips or tubes in cabinet driers specially constructed for this purpose. Installations for the recovery of this solvent have therefore long been in use in factories. 

WARNING The viscosimeter must not be dried in a cabinet drier because that could lead to a permanent alteration of the capillary diameter ... 

A plant wishes to dry a certain type of fifaerboard in sheets 1.2 by 2 m by 12 mm (4 by 6 ft by in). To determine the drying characteristics, a 0,3- by 0.3-m (1- by 1-ft) sample of the board, with the edges sealed so that drying took place from the two large faces only, was suspended from a balance in a laboratoiy cabinet drier and exposed to a current of hot, dry air. The initial moisture content... 

Drying the samples in a cabinet drier, in contrast with the adsorption-contact method and that of sublimation, is probably favourable to the formation of larger aggregates from the complex salt molecules adsorbed on support surface. It is accompanied by the partial decomposition of the salt into silver oxide or even (according to X-ray data), into metallic Ag. This is indicated by electron spectra of diffused reflection of the samples dried by these methods. 

Simple vacuum driers are constructed of heated plates (on which trays containing wet material are placed) fitted in a heavily built metal cabinet with a tightly fitting door. Vacuum is applied by an external pump which often requires a condenser and sump tank to protect it. Generally, the heat transfer to the trays is poor because of uneven contact surfaces and, since under vacuum conditions most of the heat is obtained by conduction, this has a marked effect on the efficiency. 

The construction of such driers depends greatly upon the nature of the substance being dried. Tray driers, also called cabinet, compartment, or shelf driers, are used for drying solids which must be supported on trays, e.g., pasty materials such as wet filter cakes from filter presses, lumpy solids which must be spread upon trays, and similar materials. A typical device, shown schematically in Fig. 12.6, consists of a cabinet containing removable trays on which the solid to be... 

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