(652f) Optimization of Classifier Height and Nozzle Angle in a Jet Mill

Our experimental study investigates the optimum height of a classifier and the optimum angle of a nozzle inside the grinding chamber for a jet mill. In these experiments, first, we prepare a mixture of different sized particles. In case 1, this mixture is prepared using two different sized particles, and in case 2 using three different sized particles. Then, the mixture is placed inside the milling chamber and air pressure is applied through the grinding nozzle. The outlet from the chamber is collected using the classifier, which is placed at the center of the milling chamber and whose height is h from the base of (inside) the chamber. Finally, output from the classifier is analyzed and its efficiency is found out for coarser particles, i.e. mass percentage of the coarse particles left inside the chamber, and for finer particles, i.e. mass percentage of finer particles in the output.

From our experiments, we found that the optimum height of a classifier (hc) and the optimum angle of a nozzle, for both the cases, as 10mm and 45°-60°, respectively. It is observed that with increasing h(<hc), the classifier efficiency increases for coarser particles and reaches its maximum (100%) at h=10mm. During this, the classifier efficiency decreases for finer particles. With Further increase in h(>hc), we do not observe any variation (increase) in the efficiency of classifier for coarser particles, but certainly decreases for the finer particles. Therefore, the optimum height of the classifier has to be 10 mm, where the efficiency for coarser particles first became 100%. It is also observed that for nozzle angles of greater or lesser than 45°, we see the decrease or increase in efficiency of the classifier for finer particles. Therefore, at the above-mentioned optimum values, the classifier produces the final product with the smaller particle sand narrow distribution, which is expected from a jet mill.