Influence of the grinding method on the flow properties of barley

Abstract

Hammer mills or roller mills are used to grind grain for feed for animal husbandry. The grinding process in hammer mills is based on impact stress on the grain kernels. Roller mills, however, apply pressure and shear stress. The different working principles in hammer mills and roller mills lead to different physical properties of the ground material. The aim of the project was to quantify the physical properties of barley which was ground by a hammer mill or a roller mill. Therefore, the particle size distributions of the ground material were determined by sieving. The particle form was characterized by a form factor. Shear experiments according to Jenike were carried out to determine the flowability. The bulk density was obtained from the quotient of the filling weight and the filling volume of a test vessel. The angle of inclination was observed on bulk material, which was flowed from a hopper onto a round plate. In the result, the material from the hammer mill shows an increasing flowability with increasing particle sizes and a direct correlation between bulk density and the particle size class. The values of the angle of inclination become smaller with increasing particle size.  The material from the roller mill shows the same tendencies but to a less extent