Performance Evaluation of an Impinging Stream Dryer for Particulate Materials

Abstract

Impinging stream dryers (ISD) belong to a unique class of dryers that has proved to be an excellent alternative to flash dryers for removing surface moisture of particulate materials due to collision of streams and particles in the dryer. However, very limited works are so far available on the fundamental study of the effects of various operating parameters on the performance of an ISD. The objective of this study was thus to investigate the effects of various operating parameters, i.e., inlet air temperature, inlet air velocity, feed rate of drying particles, and spacing between the two opposed inlets, on the overall performance of an ISD in terms of its volumetric water evaporation rates and volumetric heat transfer coefficients. In this study, it was assumed that the model material (resin) dried only in the unhindered rate period where mainly surface moisture was being removed. Resin had initial moisture content of about 81–85% (d.b.). The maximum volumetric water evaporation rate was found to be around 110 kgwater/m3h while the volumetric heat transfer coefficient was about 880 W/m3K for the average particle residence time of approximately 2 s. Empirical correlations were also developed to predict the experimental data and the maximum error of prediction was found to be about 10%.