Experimental Study of the Drying Kinetics for Enhanced Drying

Industrial air drying often uses fossil fuels to heat ambient air for drying. In the conventional process, the exhaust air is discharged into the atmosphere and still contains usable heat that can be recovered through heat pumps. Integrating heat pumps requires re-evaluation of drying conditions due to changes in energy supply and temperature levels. It is therefore necessary to study the effects of modified drying conditions in the laboratory before applying them directly in the industrial dryer. The drying kinetics of the products in question should be determined. For simplicity, the characteristic drying curve approach is preferred over a comprehensive assessment of the drying kinetics. This approach assumes that the drying kinetics of the same material will always produce the same characteristic drying curve, regardless of the conditions, as long as they are constant. Thus, a single curve can be used to predict the drying rate for different conditions. A new prototype laboratory instrument has been developed to measure drying kinetics and evaluate the characteristic drying curve. This instrument is suitable for continuous measurement of drying of large samples by gravimetry at low temperatures. The main capability of the instrument is to provide and maintain a uniform temperature, humidity and velocity profile of the air in the drying chamber. This contribution introduces enhanced industrial drying by presenting a heat pump integration concept, and a newly developed laboratory dryer prototype with the first results.