Separation principle and structural characteristics of spiral chute

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1、A brief of spiral concentrator     
Spiral concentrator is bent in a spiral groove in the process, still belong to the inclined flow processing category, but here the use of pulp in rotary motion generated in the inertial centrifugal force, LED light, heavy minerals in groove surface zonation, and continuous discharge.Centrifugal force and gravity force in the flow is of the same order of magnitude, to have the same important role separation.Since 1941, American Humphrey (Humphreys) made the first spiral.Since 60 time dressing machine, the Soviet Union made spiral chute, 70 time our country made with rotating device of rotary spiral chute, this spiral concentrator with its peculiar pulp movement form and become a system oneself.
 
2、 Spiral concentrator separation principle
     Commonly used spiral concentrator trough section shape, pitch and screw diameter is constant.The groove surface of a groove along the tangent direction of the dip angle a, known as the longitudinal angle, longitudinal the tangent of the angle equal to the pitch and the revolution of circumference ratio, i.e.:
Type: T -- R -- pitch; spiral groove face a pitch axis of rotation radius.
Visible, longitudinal dip with groove surface of a point radius decreases.In the spiral groove vertical to horizontal section at the bottom of the groove, a tangent line and the angle between the plane of the called the lateral inclination.Horizontal angle increases with radius.Longitudinal inclination and horizontal angle jointly determine the maximum angle of horizontal plane y, their relationship to.
 
 Angle R direction is toward the inner edge of the bottom groove, is the effect of particle movement in the direction of the important factors.
Spiral groove under the action of gravity force component of the pulp in the groove along the flow, at the same time by the inertial centrifugal force toward the outer edge extension.So the formation of the inner flow layer velocity is low, the outer edge of flow layer thickness, high velocity flow characteristics according to the determination, near the inner edge flow thickness of only 2 to 3 mm, a laminar flow, near the outer edge flow layer thickness of 7-16 mm, velocity of up to 1.5-2 meters / SEC, were turbulent flow, give in increased water, wet perimeter extending outwards, but on the inner flow characteristics have little effect, is shown in figure 11.7.3 with water were measured results.
   Fluid flow in addition to slot along the longitudinal flow, there exist inner edge and the outer edge of the lateral intercellular fluid fluid exchange.Called the two loop, as shown in figure 11.7.4 shown below.As a result of this circulation movement, made in the groove of the inner ring (region A) increased speed, the outer ring (region B) is falling velocity.Liquid flow vertical flow and two circulation stack result, formed of liquid flow in the tank on the surface of the spiral linear motor.The upper liquid outer lower edge trend, trend (Figure 11.7.4 below).
 
Located in the slurry of solid particles is controlled by the fluid motion characteristics of the dominant, but also by its gravity, centrifugal force and friction force of the bottom of the tank.
Ore pulp is fed to the spiral groove, in the weak turbulence flow under the action of 'loose, then according to the flow membrane separation principle of stratification.Mineral particles in the groove along the surface of rotary motion inertia centrifugal force, its size by the following equation;
 
      v1——The particles along the groove surface of rotary movement line speed,
         r——The location of the particle radius of gyration.     
 
Enter the bottom of heavy minerals in the trough bottom friction effects, motion speed is low, smaller centrifugal force, gravity force under the action of the maximum inclining trend along the groove, groove edge motion I upper light mineral particles is close to along with the pulp with movement, speed, is thrown to the outer edge of the chute.Light, heavy mineral particle trajectories as shown in diagram 11.7.5.Due to different moving directions, so in the groove surface expansion zone, heavy minerals near the inner ring, outer ring, 'light minerals are moved to the outer most pulp is suspended fine slime.This banding phenomenon in the first circle: after that show, and in the future continue to improve.Two circulation will continue along the groove bottom of mineral particles conveyed to the groove edge, and at the same time will tell the inner light mineral transfer to the outer edge, promoting belt development.To third ~ 4 circle, the movement of particles tend to balance, zoning, results as shown in figure 11.7.6.
 3、The structure of spiral chute
   Spiral chute is made of glass fiber reinforced plastic spiral blade assembly.The blade has an inner surface wear-resisting lining, polyurethane rubber or incorporation of carborundum epoxy resin coating and.Spiral groove supported on a metal frame structure, above the ore separator and the ground ore tank, lower product interception and ground ore tank, according to the different treatment needs, spiral unit can be made in different layers, which has a single head, double head, three head and four head structure.Figure 11.7.9 shows the φ 1200 four spiral chute structure.
Spiral chute and spiral concentrator distinction basically depends on.(1) spiral chute cross-section are linear or cubic parabola, (2), finishing, in tailings are in spiral groove end connected with a spiral groove, in the middle do not concentrate access device; (3) in the sorting process in general without flushing water.
The pulp in the spiral chute on the flow and separation principle and spiral concentrator is basically the same.Spiral chute is in groove surface is more smooth width, pulp is laminar flow is large, so it is suitable for treatment of fine particle grade ore.

    4、the groove structure characteristics of spiral chute

Spiral chute section curve in general by the following equation:

Take the Cartesian coordinates third quadrant as the groove in cross-section, as shown in figure 11.7.10 is the origin of coordinate O is the outer edge of the spiral chute, A points for the groove edge.OA for spiral chute of the work surface, BA and 0C as the flange groove.
Transverse plane of any point of the horizontal angle by type decision.
r——Groove face a pitch axis distance.The remaining symbols are shown in figure 11.7.10.
Cubic parabola face end OA and horizontal angle gamma is called the lower angle, its value depends on the A point coordinates:
In order to make a difference in the diameter of the spiral chute is similar to the cubic parabola section, should adopt the same lower bevel or initial angle.But different diameter spiral chute cannot select the same value, which cannot be used with a cubic parabola equation.According to the test chamber test, selecting granularity is O, 3 ~ O · 02 mm material under the angle γ, with 9 degrees of separation efficiency the best value, the approximate calculation formula for:

*This article is from the Hengchang mining machinery Company Shaking table 

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