The investigation of internal pressure development in convective drying of shrinking and non-shrinking materials using green and fired clay as an example

Abstract

The aim of present research was to measure and analyze the dynamic changes of internal pressure in shrinking  vs.  non-shrinking materials during convective drying for the use as a possible process control method. Drying experiments were carried out on wet and fired clay at 50°C and 60°C. In addition, the shrinkage curve was investigated. Experimental measurements show the existence of 4 stages of the process. The comparison of the results for wet and fired clay shows differences in pressure trends. During drying the internal pressure changes from underpressure to overpressure at the level of 3÷5kPa, what correlates well with transition from the first to the second drying period. Keywords: ambient pressure drying; clay; shrinkage; pressure evolution