Drying three-stage dryer

Three-stage drying was introduced several years ago to further improve the thermal efficiency of the drying process. A typical three-stage dryer consists of the spray drying chamber as... 

Figure 10.41 shows another three-stage dryer used in the food industry [30]. In the first stage, the feed is dried to a moisture content of 10-20%, depending on... 

Figure 6-23. Drying-special three-stage assembly serving two high vacuum dryers. By permission, C. H. Wheeler Mfg. Co.

Figure 9.8. Rotary tray, through-circulation belt conveyor, and heated screw conveyor dryers, (a) Rotary tray dryer (Wyssmont Co.), (b) Action of a rotating tray and wiper assembly (Wyssmont Co.), (c) A single conveyor belt with air upflow in wet zone and downflow in dry (Proctor and Schwartz Inc.), (d) A two-stage straight-through belt conveyor dryer, (e) A three-belt conveyor dryer as the material becomes dryer, the loading becomes deeper and the belt longer (Proctor and Schwartz Inc.), (f) Screw conveyor dryer with heated hollow screw (Bepex Corp.).

Drying. The water used as solvent in the polymerization is removed from the polymerized gel by evaporation in continuous-operation, hot-air convection dryers or in contact dryers such as steam-heated drum dryers. In hot-air convection dryers, the rate of moisture removal depends on the heating gas temperature, humidity and flow rate, and the diffusion characteristics of water from the gel. Drying occurs in three general stages. For high water content in the gel, the drying rate is constant, as the rate is limited by heat transfer into the gel. At low water... 

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