(667g) Assessing the Effectiveness of Dry Product Recycling

Product build up on the dryer surface (i.e. rind formation) may significantly decrease the overall heat transfer and increase the drying time. In industrial practice, dry product recycling (i.e. leaving a dry product heel in the dryer at the start of the operation) is utilized in contact dryers to reduce the adhesion and build up of the wet mass on the dryer. Mixing the wet mass with the dry product decreases the overall liquid content immediately prior to the drying and increases the flowability of the wet mass. Increased flowability means better turnover of the powder bed, and better contact with the heating surface. In this study, we investigate the validity of the thermal conductivity values of particulate materials presented at the AIChE Annual meeting over the last couple of years and the extent of enhancement in the drying time with dry product recycle in a laboratory scale contact drying. The results will be presented for powders with varying physical properties such as particle size and porosity.