Author(s)

S. Naik and B. Chaudhuri

Abstract

Particle size reduction of dry material by milling is a key unit operation for the pharmaceutical, agricultural, food and paper industries. Knowledge of particle flow and size reduction in a hammer mill is thus critical to optimize the design and operation of such equipment. Milling experiments are performed using lactose non pareils in a laboratory scale Hammer Mill. The size and shape of the resultant progeny of particles are analyzed by sieves/light scattering and microscope/image analysis techniques respectively. Discrete Element Method (DEM) based computational methods are developed to perform a quantitative examination of granular flow, fracturing and subsequently fragmentation patterns for the same hammer mill. A parametric study was performed to understand the effect of hammer speed (rotational), feed rate, hammer-wall tolerance on size reduction process. Simulations were carried out to study the effect of mill speed on kinetic energy of particles. Keywords: discrete element method, granular flow, fragmentation, hammer mill. 1 Introduction Particle size reduction of dry granular material by mechanical means, also known as milling or communition, is undoubtedly a very important unit operation in pharmaceutical, agricultural, food, mineral and paper industries. For example, particle size reduction has a significant impact on pharmaceutical product performance and stability as it affects the solubility and bioavailability of many poorly soluble BCS Class II drugs [1]. The most commonly used mills are the rotary cutter, hammer mill, roller mill, ball mills and fluid energy mills, used in various stages of manufacturing. Size reduction is generally achieved by particle

Keywords

discrete element method, granular flow, fragmentation, hammer mill