Studies on the Characteristic of Stratification in a Batch Sieving Process
1973 Volume 35 Issue 2 Pages 192-199
Details
1973 Volume 35 Issue 2 Pages 192-199
The object of this study is to find out the characteristics of stratification for the undersize grain in a batch sieving process, using a ro-tap shaker.
The physical properties of grain related to stratification were the difference of size, specific gravity and characteristics of grain surface. River sand and soy bean of uniform size were used as the materials of bed.
The results were as follows:
1) The pressure applied to the bottom of soy bean bed gradually increased with the increase of the height of bed.
2) The acceleration of soy-bean in the bed was large at the under part and small at the upper part.
3) The time which the undersize grain pass through the bed increased with the increase of the grain.
When the ratio of sizes of undersize grains to those of oversize grains were nearly equal, using various sizes of undersize and oversize grains, the time to pass were approximately equal.
4) The relationship between the time to pass through the bed and the height of bed is given by the exponential function in the following.
t=aebx
Where, t: time to pass through the bed of undersize grain, x: height of bed, a, b: constant.
In the case of the same kind of undersize and oversize grain, the length of screen for the continuous screening is given by the following equation.
L=Vaex0.1934 (d/D×100)0.2831
Where, D: grain size of bed, d: undersize grain size L: length of screen, V: flowing velocity of grain.
5) The velocity to pass through the bed increased with the increase of the difference of specific gravity among grains. And it was slightly decreased with the increase of the difference of the coefficient of friction among grains.
6) The velocity of grain passing through the bed increased with the increase of the frequency.
7) In the case of separating of farm products, as for the physical property of grain to pass through the bed, it can be considered that the ratio of the size of undersize grain to that of the oversize grain is the principal facter, and the specific gravity and coefficient of friction of grain are less significant.
