Re-selection of the basic principles (1)

(I) Overview The essence of re-election is summarized as a loose-layered-separation process. A layer of loose ore (called a bed) placed in a sorting device that is loosened by fluid buoyancy, power, or other mechanical forces in order to re-elect different density (or particle size) particles. That is to achieve stratification by density. Therefore, the loose action of the fluid must obey the requirement of stratification of the particles. This is the difference between re-election and other two-phase flow engineering. The looseness of the fluid is different and the stratification results are also affected. The problem of re-election theory is simply to explore the relationship between looseness and stratification. The layered ore layers are discharged under mechanical action, that is, sorting is achieved. Therefore, looseness is a condition, stratification is the purpose, and separation is the result. The various re-selection processes described above are the means to achieve this process. Their work is governed by such basic principles:
(1) The theory of sedimentation of particles and particle groups;
(2) The theory that the particle group is layered by density;
(3) Sorting theory of particle group in slant flow.
In addition, there is sorting in the swirling flow. Although the medium moves in different ways, the basic law of action is the same except for the difference between gravity and centrifugal force.
According to the theory of density stratification, the earliest research is based on the jigging process. A lot of jigging stratification theory has been proposed, and later some special stratification in vertical flow.
The bevel flow beneficiation is the first to treat coarser ore in a thick water layer. The sorting is based on the difference in velocity of the particles along the trough. After the 1940s, the bevel flow beneficiation developed towards the film-mining process, mainly for sorting fine-grained and fine-grained grade ore. The flow state has a laminar flow and a turbulent flow. It has been consistently believed that the turbulent pulsation velocity is the basic force of the loose bed, which is difficult to explain under laminar flow conditions. The inter-layer shear repulsion mechanics proposed by RA Bagnold in 1954 complements this theoretical gap. However, as with stratification theory, it is still difficult to make reliable calculations based on existing theory.
Although re-election theory has not yet reached perfection today, like many process disciplines, it has provided basic guidance for production and can serve as the basis for mathematical statistics and similarity and simulation studies.
(II) Theory of stratification by particle size The stratification of mineral grain group by density is the core issue of re-election. Many scholars have put forward their understanding and research results, thus forming a situation with different opinions. The classification of various doctrines is not only from the two ideological systems: one is that under the action of the medium, the stratification is based on the difference in the velocity of the particles or the distance difference, which can be regarded as the kinetic system theory; It is based on the inherent imbalance of the bed as a layered basis, which can be regarded as the static system theory. Although these two kinds of doctrines have not yet been unified in mathematical relations, they can be linked together in the physical concept to obtain a coherent understanding of the hierarchical process. [next]
1. The theory of stratified dynamics system A According to the theory of differential sedimentation velocity of particles, this theory was first proposed by Lei Tingzhi. He believes that in vertical flow, the stratification of the bed is free sedimentation of light and heavy mineral particles. A speed difference occurs. Under the condition of turbulent flow, ie Newton's resistance, the sedimentation velocity of the spherical particles is.

After the relationship, and extended, the relationship between the sedimentation velocity and the particle size change when the particles of different densities settle in the same medium is plotted, as shown in Fig. 1. It can be seen from the figure that in order to achieve the stratification of the two mixed densities of different densities in the sedimentation (or relative movement with the clerk), the particle size ratio of the largest granule to the smallest granule in the granule must be smaller than the granule of the equal granule. Ratio, that is, equal ratio. This is the conclusion given by the doctrine.

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