Drying Rates Under Non-isothermal Conditions

The process of drying under non-isothermal conditions has been investigated. Experiments with cement raw meal module with 10-18% moisture content were carried out in a mettler thermoanalyser at 10, 15 and 25 degrees C/min heating rates at an air flow rate of 500 ml/min. Drying rate equations were derived for nonisothermal conditions. It was observed that the drying process occurs in two stages with a transition about the boiling point of water. The activation energy for the drying rate constant for Stages I and II was about 35-55 and 90-135 kJ/mole, respectively. The activation energy values obtained for normal drying condition below boiling point of water, i.e. Stage I, were in very good agreement with the theoretical values. The rate parameters viz., activation energy and frequency factors, follow the kinetic compensation law.