Bin is any form of containment structure that can used to store materials. Bins are used by a many industries to store bulk solids in quantities ranging from few tonnes to thousand tonnes.
Bins are also known as bunkers and silos. (The bunkers are large size shallow bins to store grains, cement or coal and cement. In these, plane of rupture intersects the free surface of the stored grain. Usually these are rectangular or square shaped. On the other hand, silos are the deep bins and are circular in shape. In silo, the plane of rupture intersects the opposite side of the bin).
Bins can be constructed from steel or reinforced concrete and the inside material may discharge by gravity flow or mechanical discharging systems may be used. Bins may be of flat bottom type and hopper bottom type. Circular bins are more efficient structures than square or rectangular bins, as circular bins leads lower material costs.
The size of bin is determined by maximum quantity of material to be stored in it and feeding and discharge rates. For high discharge rates, deep hoppers with steep walls are required. Bins with flat bottom generally have low discharge rates and these are used when storage time is long.
A bin whose relative dimensions are such that the plane of rupture meets the grain surface before it strikes the opposite side is called ‘shallow bin’ and the bin in which plane of rupture meets the opposite side before it emerges from the grain is called ‘deep bin’.
A Squat silos are the example of shallow bin. A squat silo has a wall height to diameter ratio 0.5 or even less. A vertical silos is example of deep bin. Vertical silo often categorized in flat bottom vertical silo and hopper bottom vertical silo. Out of these, hopper bottom is more expensive and has hopper slope angles of 60° – 70° for achieving reliable mass flow.
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