Rotating drum technique

The aligned fiber mechanism behind the rotating drum technique is as follows ... 

Solution-cast film is produced on a larger scale for medical applications, battery separators, or other specialty uses with machinery of the type shown in Figure 3.2 [2], Viscous film is made by this technique. The solution is cast onto the surface of a rotating drum or a continuous polished stainless steel belt. These machines are generally enclosed to control water vapor pickup by the film as it dries and to minimize solvent vapor losses to the atmosphere. 

For mobile liquids, the use of this kind of controllable instruments is practically impossible. For these liquids, the non-controllable measurement techniques are available only and in general an apparent transient viscosity will be obtained. Nevertheless these measurements are still of great value, because in many cases they approximate industrial process conditions. Mostly used is the spinning line rheometer, where an elastic liquid is pressed through a spinneret and the liquid is pulled from the die by winding the filament around a rotating drum or by sucking the tread into a capillary tube. This is schematically shown in Fig. 15.25. A serious problem is the translation of the obtained data to the extensional viscosity. Many other non-controllable devices are discussed by,... 

FIG. 15.25 Schematic diagram of the spinning technique. The fluid leaving the nozzle is pulled downwards by a rotating drum or a sucking tube. From James and Walters (General References, 1993). Courtesy Chapmann Hall. 

The introduction of the koji process to the West is chiefly due to the work of Takamine, which started in 1891 in the USA using wheat bran to make the preparation named Taka-Koji. Takamine introduced the technique of acclimatizing the mold to various antiseptics in order to minimize growth of contaminants during the process. The process was carried out on an industrial scale in rotating drum bioreactors. Large scale trials of the use of Taka-Koji instead of malt in distilleries were carried out in the plant of Hiram Walker Sons in Ontario Canada in 1913. This was marketed as a digestive aid imder the name of Takadiastase [8]. 

In another technique, molten urea is sprayed at 148 °C onto cascading seed granules (<0.5 mm) in a rotating drum until they grow into product sized particles (2-3 mm). Heat released by the solidifying melt is removed primarily by evaporation of a fine mist of water sprayed into air that is passed through the granulation drum (Shirley, Nunelly and Cartney, 1982). 

Another technique is the development of a double-barrel dryer/mixer (see Figure 8.6). In this technique, the aggregate is dried and heated in an inner rotating drum, while mixing of the constituent materials of the asphalt (aggregates, bitumen, reclaimed asphalt, etc.) takes place in the outer shell (barrel). This provides more efficient drying and mixing at a lower... 

To circumvent the various limitations of the basic technique, several continuous zone refining methods have been developed in which feed enters at one point in the sample while the product and waste leave at other points (Figure 4). The effect of countercurrent movement of solid and liquid phases is achieved by the movement of molten zones. In addition to the horizontal continuous refiner, the zone void vertical refiner and zone transport refiner are other modifications of this class. Cross-flow zone refiners and rotating drum multistage crystallizers based on the above principle are mainly used in growing single crystals rather than in purification of materials. 

Most imiaxial measurement techniques involve extending a strand or cylindrical rod of the material and measuring the force required. To measure fluids, the fluid is extruded from a spinnerette nozzle and allowed to fall under gravity. It is then extended by being rolled up on a rotating drum (119,127,238-241). The generated force is measured by the deflection of the nozzle or tube as the latter is pulled by the filament of fluid or at the take-up roller. This method has been the basis for home-built viscometers and a commercial instrument (238,241). 

Until quite recently, bulk polymerization was not an important process for the production of poly(vinyl chloride) but the technique developed by Pechiney-St. Gobain (France) is now gaining acceptance. In this method, vinyl chloride and an initiator such as azobisisobutyronitrile or benzoyl peroxide are heated at about 60°C for approximately 12 hours in a rotating drum containing stainless steel balls. The particle size of the product may be controlled by the speed at which the drum is rotated. 

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