Drying curve

FIG. 12-79 Plate dryer drying curves demonstrating impact of elevated temperature and/or operation under vacuum. (Krauss Maffei.)... 

The above drying curves have been generated via testing on a plate-diyer simulator. The test unit duphcates the physical setup of the production diyer, therefore linear scale-up from the test data can be made to the full-scale diyer. Because of the thin product layer on each plate, diying in the unit closely follows the norm diying cui ve... 

A sample ground to 40-mesh is dried in the oven for a long time (100 hours or more) at a temperature where decomposition is not too rapid at the end of this time the sample is assumed to be essentially dry. A drying curve is determined from the loss of weight at various time intervals. The sample is then permitted to absorb in a humidistat a known amount of water which can be accurately determined by weighing before and after the absorption. Drying is then repeated under conditions identical with those of the... 

A comparison of the drying curves for lyophilized and unlyophilized sweet potatoes is shown in Figure 7. It is seen that the same and constant loss of weight (8.2%) was reached with the lyophilized samples at both 60° and 70° C. No such indication is shown by the unlyophilized samples at either temperature. 

Figure 7. Drying Curves for Lyophilized and Unlyophilized Sweet Potatoes at 60° and 70° C. (27)...

Fig. 3 Drying curve plotted as drying rate versus percent water remaining.

If a material is dried by passing hot air over a surface which is initially wet, the rate of drying curve in its simplest form is represented by BCE, shown in Figure 16.3... 

Figure 16.3. The use of a rate of drying curve in estimating the time for drying...

The solvent removal can also be followed by gravimetric analysis of the weight loss. This method is used to determine the time necessary for complete solvent removal. Shown in Fig. 29 are such drying curves for 5 mm diameter cy-hndrical samples prepared with 16 wt % and 20 wt % cyclohexane. It is seen that most of the solvent is removed within the first day. However, the samples are held for an additional four days to achieve a porous structure with minimal amount of residual solvent. 

Applying this relationship to drying curves obtained at two temperatures Ti and Tj, for a given change in moisture content AX, gives... 

Features A large bulbous plant, Scilla is imported in the form of dried, curved segments of the white, bulbous root, which are tough, dirty white in colour, and approximate two inches long by a quarter-inch wide. The fracture is short, taste acrid. The powdered bulb is very hydroscopic, and should consequently be kept airtight. An Indian variety is used throughout the East, and has similar properties to the above. 

Figure 2 Drying curves for grape and apple pomace held at 105°C. The percentage moisture remaining was calculated, after withdrawals of 10-g samples from a 103-g batch and drying them at the designated intervals.

Acrylic Ester. Drying curves of poly(n-butyl methacrylate) from the three solvents are given in Figure 1 (10% RH) and Figure 2 (80% RH). 

At time intervals, air and solid moisture content was determined in order to construct the drying curves.A typical set of drying curves is presented in Figure 2. 

Corben and Newitt (C8) showed that the drying characteristics of moist porous granular material are consistent with the capillary theory of moisture movement. The difference in the form of the drying curves are primarily due to the capillary action of the pores. The rate of drying during the constant-rate period is higher for porous than nonporous materials. 

Lester and Bartlett (L2) presented a theory of drying which helps to explain the form of the drying curve but it is of little use without a great deal of experimental data. 

Figures 5-7, respectively, show the effect of humidity and slab thickness, in addition to the comparison of theoretical and experimental drying curves on the drying time. It is interesting to note that in the final stages of drying, the deviation is greater. The reason for this fact is that this stage of drying...

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