Material Drying

Adsorption is of technical importance in processes such as the purification of materials, drying of gases, control of factory effluents, production of high vacua, etc. Adsorption phenomena are the basis of heterogeneous catalysis and colloidal and emulsification behaviour. 

Pour the reaction mixture cautiously into 400 g. of crushed ice and acidify it in the cold by the addition of a solution prepared by adding 55 ml. of concentrated sulphuric acid to 150 ml. of water and then coohng to 0°. Separate the ether layer and extract the aqueous layer twice with 50 ml. portions of ether. Dry the combined ethereal solutions over 50 g. of anhydrous potassium carbonate and distil the filtered solution thror h a Widmer column (Figs. II, 17, 1 and II, 24, 4). Collect separately the fraction boihng up to 103°, and the dimethylethynyl carbinol at 103-107° Discard the high boiling point material. Dry the fraction of low boihng point with anhydrous potassium carbonate and redistil. The total 3 ield is 75 g. 

Fig. 8. Combustion turbines with process heat recovery (a) represents direct use of exhaust gas for process heating where industrial process includes refinery, chemicals, food processing, and ethanol production and (b) exhaust-to-water heat exchanger where industrial process includes material drying,...

Drying of the poly(vinyl alcohol) is critical to both the color and solubiHty of the final product. Excessive drying temperatures result in high product color and an increase in the crystallinity, which in turn reduces the solubiHty of the product. Drying is initially subjected to a flash regime, where the solvent not contained within the particles is flashed off. This first phase is foUowed by a period where the rate is controUed by the diffusion rate of solvent from the poly(vinyl alcohol) particles. Because the diffusion rate falls as the material dries, complete drying is not practical. The polymer is therefore generally sold at a specification of 95% soHds. 

Particle size distribution determines surface-to-mass ratios and the distance internal moisture must travel to reach the surface. Large pieces thus have higher critical moisture contents than fine particles of the same material dried under the same conditions. Pneumatic-conveyor flash dryers work because very fine particles are produced during initial dispersion and these have low critical moisture contents. 

A representative hst of materials dried in direct-heat rotaiy diyers is given in Table 12-19. 

TABLE 12-19 Representative Materials Dried in Direct-Heat Rotary Dryers ... 

Material dried Ammonium sulfate Foundry sand Metallurgical coke... 

Material dried Antioxidant Water-soluble polymer Antibiotic filter cake Petroleum coke... 

Potassium iodate [7758-05-6] M 214.0, pK 0.80 (for HIO3). Crystd twice from distilled water (3mL/g) between 100° and 0°, dried for 2h at 140° and cooled in a desiccator. Analytical reagent grade material dried in this way is suitable for use as an analytical standard. 

Before analysis the representative solid sample is usually dried at 105-110 °C, or at some higher specified temperature if necessary, to constant weight. The results of the analysis are then reported on the dry basis, viz. on a material dried at a specified temperature. The loss in weight on drying may be determined, and the results may be reported, if desired on the original moist basis these... 

Material Drying time, hours Drying temperature. ° C. Loss in weight, % HaO ... 

Ferric Picrate. [C6H2(N02)3 0]3Fe.llH20, mw 938.4, N 13.44%, yellowish-red needles. Was prepd in 1911 by Kast by treating a hot satd soln of ferric sulfate with Ba picrate (Ref 1). Hopper (Ref 2) prepd several hydrated ferric pic rates of unknown w content which expld at 295. Their impact sensitivity ranged from 6 (for material dried at 150°), to 36" (for material dried at 25°) (PicArsn app with 2kg wt)... 

A thin slab of solid material dries first by evaporation from the top surface and then by diffusion from the interior of the solid. The water movement is approximated by the diffusion equation... 

The other option available for drying involves subjecting the material to reduced pressures. By decreasing the ambient pressure, for example, by evacuation, to a level lower than the equilibrium water vapor pressure over the material, drying can be implemented. This option is particularly important when heating affects the material, in addition to drying it. 

Horizontal trough mixer, with ribbon blades, paddles or beaters Rotating element produces contra-flow movement of materials Dry and moist powders Chemicals, food, pigments, tablet granulation... 

This crude material dried over night at about 40° is practically pure and if used at once is satisfactory for the preparation of diphenylmclhum inline hydrochloride (p. 28). 

MATERIALS Dry sawdust, moth flakes (naphthalene), fuel oil (kerosene or diesel oil). 

Currently, we can produce 1.5 g of GUS protein and 0.5 g of HSA per kg of seeds. These levels correspond to 13.5kg and 4.5 kg production yields per year, respectively. Expression levels are indicated as a weight per weight of starting material (dry seeds) because the sprout fresh weight and total soluble protein content varies depending on cultivation time and conditions. 

The checkers used material dried at 70-80° for their determination of the rotation and obtained values in agreement with those reported by the submitters. 

Gunasekaran, S. 1999. Pulsed microwave-vacuum drying of food materials. Dry. Technol. 17, 395-412. 

Hydrolytic degradation of polymers is still the main reason for the occurrence of faults in processing. This form of degradation commonly causes a reduction of the IV, associated with a deterioration in the mechanical properties, particularly the tensile strength. Therefore, it is important to ensure sufficient drying of the raw materials. Drying is a crucial prerequisite of any polyester processing... 

Pan, Y.K., Zhao, L.J. and Hu, W.B., The effect of tempering-intermittent drying on quality and energy of plant materials. Drying Tech., 17 (1999a) 1795-1812. 

The results are shown in Table 1. The table shows that the greatest part of the water in the starting materials is present in the acid dianhydrides. This was verified by experimental results. That is, water content increases with time and that increase strongly depends on ambient humidity, as shown in Figure 5. Therefore, it is very important to keep the materials dry. 

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