A study of the flow of bulk material in bins
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Authors
Reese, John Warren
Subjects
Advisors
Amrine, H.T.
Date of Issue
1954
Date
Publisher
Purdue University
Language
en_US
Abstract
The major problem in handling bulk material in bins is flow stoppage, which is the hanging-up of material within the bin. Although^ there are generalizations as to why materials cease to flow, arch, or funnel, clear expression of the problem and the factors involved is lacking. One purpose of this thesis, th3refore, is to study the background material and previous publications in an attempt to define the factors contributing to flow stoppage in a bin. In addition, an attempt will be made to isolate a particular factor to determine experimentally its contribution to flow stoppage. Flow stoppage occurs in two common configurations, arching, which is the formation of a dome or span across the bin, and ratholing, which is a void passing up through the mass much like a rathole. The formation of a void in the area directly above the discharge gate and breaking through to the surface is a special case of ratholing known as "funneling". Review of the literature resulted in a classification of the factors pertinent to flow stoppage as physical factors and design factors. The physical factors are properties of the material handled and of the confining materials. For the material handled the factors are interparticle friction, moisture content, and compaction. The friction between the wall and the material handled, for any one material, will vary with the wall material. The plane of rupture is a hybrid between the inter-particle friction and the particle-to-wall friction. It defines that plane along which material flow will commence when under confinement. The design factors are structural, consisting of the size of the discharge area, the cross-section of the bin, the nail inclination, and feeder lines. The laws of semi-fluids as formulated by Janssen and by Airy express the influence of the physical factors upon the distribution of load forces within a bin. The vertical pressure in the bottom of the bin does not increase linearly as with fluids. The pressure increase is curvilinear up to a height equivalent to two and one-half diameters beyond which the increase is negligible. The lateral pressure follows the same performance, only to a lesser magnitude. These laws do not justify the occurrence of an arch or a funnel. The theory of cohesive flow best explains the occurrence of an arch, while a modification of this concept explains funneling.
Type
Thesis
Description
URI
Series/Report No
Department
Industrial Engineering