Re-selection of the basic principles (2)

This shows that the fact that a wide level can be sorted under interference and sedimentation conditions. Although it is one step ahead of the above theory, it is still difficult to make reliable calculations because the values ​​of θ 1 and θ 2 are difficult to determine and the value of n is also a variable. However, this theory shows that as the volume concentration of the particles increases, the effect of stratification by density will improve.
The kinetic stratification theory suggests that particle size is always a limiting factor for stratification by density under conditions in which fluid dynamics are involved in looseness. This indicates that sedimentation as the main form of the sorting process, when the medium includes a layered particles relative movement, than to advance classification ungraded as well, for the metal fine particles can also be lost by the low sedimentation rate Get instructions.
However, such doctrines do not reflect the stratification causes in the absence of vertical hydrodynamic effects. Nor does it reveal the decisive role of mineral density in stratification by density and therefore cannot be considered a general principle of stratification.
2. The stratified static system theory This kind of theory no longer considers the dynamic effects of fluids, and ignores the behavior of individual particles. Instead, it considers the bed as a whole and explores the stratification from some inherent static factors. the reason.
A. According to the theory of mineral suspension density differential layer, this theory was first proposed by AA Hirst (1937) and RT Hancock. They regard the mixed bed as a local heavy mineral suspension and Composition of a local light mineral suspension. Under gravity, there is a static imbalance in the suspension, just as oil and water mix together, eventually leading to stratification by density. as shown in picture 2.

The density of local light minerals and heavy mineral suspensions are:


Lishenke used his small suspension test to think that the above relationship is correct, but the descendants have undergone a large number of tests to test, in addition to seeing the changes in the positive and negative stratification, it is found that the calculated temporary (hybrid) state rises the water flow rate. The value is always smaller than the theoretical value.
This theory is actually not verified by the suspension test. Because static fluidization conditions are destroyed as long as there is fluid power. Only when the concentration of the suspension is high and the fluid dynamics of the suspended particles are small, the static stratification conditions are approached. This doctrine has its correct composition, but it is imaginary.
B layered according to the principle of heavy medium


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