Convective drying methods

The importance of good housekeeping must be emphasized. Any accumulation of Zr dust or powder on work benches, floors or clothes of personnel must be removed promptly. The pyrophoric properties of Zr dust or powder requires the selection of either wet or dry methods of dust collection A limited amount of moisture can make Zr powder ignition sensitive, but attempts to collect the dust dry by suction or convection flow risk dust expins which are easily initiated by static discharge or spontaneous combustion. Because nitrogen will also react with Zr,... 

The evidence of a correlation between the drying induced stresses and the AE is illustrated on the cylindrical kaolin sample under convective drying. Although the AE method enables us to point out the period in which the stresses reach maximal values, we are not able yet to assess the magnitude of these stresses. 

Direct drying method involves drying or calcinations of precipitates prepared by liquid-phase method after simple washing or filtering, but without solvent-replacement and surface modification. There is direct contact between the wet solid and the convective drying medium. The following are some of the more common methods in use. 

Adhikari, B. Howes, T. Bhandari, B.R. Use of solute fixed coordinate system and method of lines for prediction of drying kinetics and surface stickiness of single droplet during convective drying. Chemical Engineering and Processing, 2007,46,405-419. 

This section examines oven-drying methods. In these methods the sample is heated under specific conditions and the weight loss is used to calculate the water content of the sample. For this determination three types of ovens can be used convection, forced draft, and vacuum. The determined water quantity is highly dependent upon the type of oven used, the conditions inside the oven, and the time and temperature of drying. 

Only recently, the possibility of using subcritical drying techniques to produce xerogels has been explored most of them will be treated in Sections 5.5.3 and 5.5.4 on vacuum and convective drying, respectively. Here, only one method close to supercritical drying as followed by Kirkbir et al (1998a, b) will be presented. Wet silica gels were first washed (e.g., with ethanol) and then heated in a pressure... 

This section summarizes research work with air drying at ambient or elevated temperature and ambient pressure. Although the temperature, moisture and velocity of the air flow are often not well defined, all these efforts will be denoted by convective drying. Such methods are cheaper and safer than all previously discussed, and they are suitable for a continuous production process. The overview first puts focus on silica gels, then on RF gels, accounting for the historical development. 

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