Comparison of convective, vacuum, and microwave drying chlorpropamide

Drying kinetics of convective, vacuum, and microwave drying of a pharmaceutical product, chlorpropamide, has been investigated on a laboratory scale, in the temperature interval from 40 degreesC to 60 degreesC, and the range of microwave heating power from 154 W/kg(dm) to 385 W/kg(dm). The experimental data obtained were approximated with the "thin-layer" equation and a two parameter exponential model. In order to compare convective, vacuum, and microwave drying, effective diffusion coefficients and specific heat consumption were calculated for each drying method. Higher rates and shorter drying times were achieved at a higher temperature and microwave heating power. The highest drying rates and the lowest specific heat consumption were achieved with microwave drying. This leads to the conclusion that microwave heating is the most appropriate method for drying of chlorpropamide. The quality of product was not changed for all applied methods.