Ultrafine grinding using a fluidized bed opposed jet mill: Effects of process parameters on the size distribution of milled particles

Abstract

Ultrafine grinding is an important unit process in pharmaceutical product development. In this study, a fluidised bed opposed jet mill was used to determine the effects of three process parameters in size reduction. The size distribution of all the milled products was positively skewed and could not be fitted by the normal, log normal, Weibull and gamma functions. Thus, non-parametric statistics were applied. Variation of the rotational speed of the classifier wheel was the most efficient method for producing milled products of different sizes. A combination of a high milling pressure of 0.5 MPa and a low feed load of 250 g always resulted in the production of products with a large proportion of particles in the higher size range. A feed load of 450 g resulted in the decreased selectivity of the classifier wheel. A feed load of 350 g combined with a milling pressure of 0.5 MPa yielded a product with the smallest median particle size.