Dem Application to Mixing and Segregation Model in Industrial Blending System
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DEM APPLICATION TO MIXING AND SEGREGATION MODEL IN INDUSTRIAL BLENDING SYSTEM
KENJI YAMANE Quality Control Department Taiho Pharmaceutical Co., Ltd. Tokusima 770-0194 Japan ABSTRACT To predict the motion of powders and grains is important in pharmaceutical industries. Many pharmaceutical engineers have studied granular flows related to powder mixing. In this study, DEM (Discrete Element Method) approach is presented as an industrial application to investigate the behavior of granular flows. The granular motion in a rotating cylinder was focused on the basic study of DEM for industrial application. Rotating cylinder is a fundamental system for commercial blenders widely used in many industrial process. In addition, segregation of particles in a rotating cylinder is very interesting phenomena. Not only industrial engineers but also physicists research this segregation mechanism. DEM simulation showed radial segregation of two different size particles in a rotating cylinder. From the viewpoint of calculated granular temperature, radial segregation system was analyzed. Particle migration in axial direction, which is the source for axial segregation, was also shown by DEM simulation. INTRODUCTION Engineers have been interested in the complicated granular flows. Mixing of granular has been studied based on flow mechanism of granular by many engineers. Because the mixing process is a important process in the industries where powders and grains are handled. Specially, on the process of powder mixing of pharmaceutical manufacturing, it is important to assure the blend uniformity of mixtures. Segregation should be avoided on blending process in order to maintain the quality of drug products. While, the phenomena of segregation has captured physicists for long time. The original study was performed by Oyama. In 1939, Oyama [1] first reported that rotating cylinders partially filled with a mixture of granular media may serve to segregate the
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individual species into bands along the rotational axis. This phenomenon is termed axial segregation. Since Oyama’s experiments, a number of studies have shown that mixtures of granular media exhibit a wide range of axial segregation (see, for example [2]-[7]). It has been found from recent studies that the reversible axial segregation of different-sized granular media in a drum mixer is related to variations of the dynamic angle of repose [8], but it is also clear that subsurface effects are critical, because axial bands that do not extend to the surface have been observed within the bulk. In order to study the dynamics beneath the surface involved in the segregation process, DEM simulation was used in the present study to demonstrate granular flow patterns within a drum mixer. Specially, On binary-disperse particles, migration to
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