Drying of a solid

The use of a ternary mixture in the drying of a liquid (ethyl alcohol) has been described in Section 1,5 the following is an example of its application to the drying of a solid. Laevulose (fructose) is dissolved in warm absolute ethyl alcohol, benzene is added, and the mixture is fractionated. A ternary mixture, alcohol-benzene-water, b.p. 64°, distils first, and then the binary mixture, benzene-alcohol, b.p. 68-3°. The residual, dry alcoholic solution is partially distilled and the concentrated solution is allowed to crystallise the anhydrous sugar separates. 

The study of internal moisture gradients estabhshes the particiilar mechanism which controls during the drying of a solid. The experimental determination of rehable moisture gradients is extremely difficult. 

Unsteady state diffusion processes are of considerable importance in chemical engineering problems such as the rate of drying of a solid (H14), the rate of absorption or desorption from a liquid, and the rate of diffusion into or out of a catalyst pellet. Most of these problems are attacked by means of Fick s second law [Eq. (52)] even though the latter may not be strictly applicable as mentioned previously, these problems may generally be solved simply by looking up the solution to the analogous heat-conduction problem in Carslaw and Jaeger (C2). Hence not much space is devoted to these problems here. 

Moreover, the isotherms determine the proper storage environment and the packaging conditions, especially for foods. Through the isotherms, the isosteric heat of sorption can be determined and, hence an accurate prediction can be made of the energy requirements for the drying of a solid. The utility of the isotherm is extended to the determination of the moisture sorption mechanism as well as to the degree of bound water. 

Simprosys is applied to the drying of a solid material containing ethanol. Due to the low flash (burning) point,... 

Under otherwise similar drying conditions, the drying rate depends on the surface area of the wet crystals and the air used in drying. This means that small crystals dry quickly in airflow, such as that produced by a pneumatic dryer. Instead, the drying of a solid bed of... 

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