ISSN:
0001-1541
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Rate data are presented for both the constant - and the falling-rate drying of closely sized spheres of silica-alumina hydrogel. This hydrogel, which contains a fine powder, is the starting material from which petroleum cracking catalysts may be prepared. During the constant-rate period the drying rate is directly proportional to the difference between the dry- and wet-bulb temperatures of the air. In the falling-rate period the rate is proportional to the free water content, the proportionality factor being an undetermined function of the dry-bulb-wet-bulb differential.Drying severity during the falling-rate period is shown to be the major determinant of the final pellet density. At constant wet-bulb temperature, density is inversely related to the dry-bulb-wet-bulb differential. If this differential is held constant, density is directly related to the wet-bulb temperature.The variation in drying rate with position in the bed for through-circulation constant-rate drying of deep beds of particles is analyzed for the case where the direction of air flow is periodically reversed for equal time intervals. It is indicated that uniformity of drying should increase with an increase in air velocity, but decrease as bed depth is increased. At constant conditions and bed depth, large particles should dry more uniformly than small. Within normal operating ranges, air temperature and humidity should have little effect on drying uniformity.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/aic.690010310
