"The drying of clay has been studied extensively in the past by many investigators, some of whom attempted to relate this information to the structure of clay and thereby develop a more vivid picture, while others studied the mechanism of drying in its own right in order to present a useable theory that would allow improvements in the drying operation.
At present the literature is unable to present a theory of the mechanism of drying that is sufficiently general to cover the observed aspects of clay drying. Many and varied mechanisms are presented, but correlation is seldom completely evident between separate investigators.
It is without question that the drying process is divided into two portions; (l) in which the rate of water loss is a constant and (2) in which the rate of water loss is not a constant but is decreasing in magnitude.
This first drying period is designated the zone of constant rate, which appears as a straight horizontal line when the rate of water loss is plotted as the ordinate and percent water content of the sample (dry basis) as the abscissa. The second drying period or the falling rate zone is a key to the drying mechanism and is open to the most question. Norton has pictured this zone as a smooth curve slightly concave upward extending from the end of the constant rate zone to the origin. This indicates that the decrease in the rate of water loss is nearly uniform on a percent water content basis. Sherwood indicates that this falling rate zone may be separated into two parts, the first of which may or may not be a straight line while the second is slightly concave upward.
Norton also indicates that the shrinkage of the clay in drying when plotted against water content begins as soon as drying is initiated and reaches zero in the order of 20% water content. It is the purpose of this investigation to determine the nature of the falling rate zone, and the water content where shrinkage ceases in order to better define the drying mechanism for clay.
It is significant that much of the investigation into the mechanism of drying has been done on relatively small samples that may or may not characterize the drying nature of the clay itself. This study has been undertaken using samples of spherical shape whose plastic weight is in the order of 3000 grams and whose maximum wall thickness is 6 inches. It is believed that using samples of large cross section with minimum surface to volume ratio will provide more distinct definition of the particular rates at which water is lost.
Equipment has been obtained that will allow control of the wet bulb temperature, the dry bulb temperature, which in turn fixes the percent relative humidity, and the air velocity. An automatic means of recording weight loss as a function of time, and shrinkage as a time function has been built"--Introduction, pages 1-2.
Planje, Theodore J., 1919-1980
Materials Science and Engineering
M.S. in Ceramic Engineering
Missouri School of Mines and Metallurgy
vi, 42 pages
© 1954 Robert F. Grady III, All rights reserved.
Thesis - Open Access
Clay -- Drying
Clay -- Moisture
Drying -- Mathematical models
Print OCLC #
Electronic OCLC #
Link to Catalog Record
Grady, Robert F. III, "A fundamental study of clay drying using ware of large cross section" (1954). Masters Theses. 5523.