The influence of the granulometric condition on the flow characteristics of shredded grain products in their dependence on the duration of storage

Often shredded grain is stored up to feeding as bulk material in tower silos over a longer period. Due to time-dependent consolidation the material becomes more or less incapable of flow out. In this research, the flow characteristic of pig-feed is determined in dependence on the granulometric conditions and the storage period. For the investigations three samples of mixed pig-feed were produced with a transformed median x50;3⁎ of 0.335 mm, 1.0 mm and 5.2 mm and a constant standard deviation of 0.9. The percentage of cohesive fine material with particle size x < 0.2 mm was 100%, 30% and 8.9% in order to represent the flow properties “very cohesive”, “cohesive” and “free flowing”. The material samples were pre-sheared by use of a translation-shear-device and afterwards stored for 20, 40 ore 90 h under the consolidation stress. After that followed the shearing of under reduced normal-stress. The flow function values ffc were calculated based on the measurements. Results show that the flow characteristic is mainly influenced by the fine material portion H3(0.2 mm). Extremely cohesive behavior is present at H3(0.2 mm) = 100%. At H3(0.2 mm) = 30% or 8.9%, the bulk material behaves cohesively or cohesionless. Shredded grain for animal feed should have a small standard deviation and a portion of cohesive material H3(0.2 mm) < 5%.

Three samples of pig-feed with different percentages of cohesive fine material were investigated regarding their flow characteristic by means of a Jenike shear device. Flow function values ffc were calculated according to different storage times. Results show that the flow function values are mainly influenced by the fine material portion H3(0.2 mm). This portion should be less than 5%.Figure optionsDownload as PowerPoint slideHighlights
► The consolidation of shredded grain is a main problem when emptying tower silos.
► The flow function values are reduced mainly within the first 20 h of storage.
► The flow function is influenced by the fine material portion H3(0.2 mm).
► Shredded grain for animals should have cohesive material H3(0.2 mm) less than 5%.