Dashi beneficiation plant 11 production system has not been installed mechanical tapping devices, some also because often fails without tapping devices, resulting in lower grade fine screening efficiency, more serious blockage sieve, sieve products containing more - 200 mesh size, resulting in large cyclic load, low concentration on the sieve, affecting the efficiency of the second stage grinding. In order to solve the above problems, the plant installed two attached mixed soil vibrators on the two-stage two-stage fine screen machine instead of the mechanical hitting device. Entire metal sieve with a rubber metal spring support, a transistor controlled delay circuit breaker automatically opens stops the vibrator, vibration every hour, every two seconds. Practice has shown that the improved fine screening efficiency, processing capacity and other technical indicators have improved and improved. Figure 7 is a schematic view of a fine screen using a vibrator.
The two-stage fine screen machine consists of two sieve bodies welded with a length of 2,630 mm and a width of 2,900 mm. Each sieve body is equipped with a nylon fine sieve 12 with a length of 1300 mm and a width of 400 mm. Each of the six sieves is a group, divided into two groups, supported by channel steel, and each sieve is hooked with the sieve body. The vibrator is fixed in the middle part of the back of the sieve body. When the motor of the vibrator drives the two eccentric blocks to rotate at a high speed, the whole sieve body vibrates together with the 12-sieving sieve, and the sieve holes are unblocked. The elastic element is made of rubber metal spring, which is respectively installed on the upper part of the side wall of the sieve body and the lower part of the bottom plate of the sieve body, and has four support points. It is calculated that two springs are used for each support point. The spring has a large damping effect, which can reduce the impact on the bracket when the device vibrates and is easy to fix. The technical characteristics of the improved fine screen machine are: mesh size 0.2mm, screen inclination angle 55°, vibration frequency 2850 times/min, amplitude 1.5mm, vibration force 560kg, motor power 1.5Kw, vibrator weight 28kg.
After using the improved vibration device, the plant achieved the following effects:
(1) The production test of the three systems showed that the sieve screen was improved after the fine screen machine was added with the vibrator. Compared with the pre-improvement, the yield of the under-slurry product can be increased from 32.48% to 69.99%, increasing by 37.51%, and the -200 mesh fraction recovery rate is increased from 48.62% to 83.94%. , increased by 35.32%; -200 mesh size classification efficiency increased from 32.51% to 48.26%, an increase of 15.75%. The fine grade content in the sieve product decreased, and the sieve top concentration increased, which is beneficial to improve the second-stage grinding efficiency. Adding a section of mill processing capacity creates conditions.
(2) Low investment, low power consumption, increased production capacity per unit area of ​​fine screening, and reduced production costs. The total cost of the three systems is about 800 yuan, and the number of sieves used is reduced by 12, and the nylon screen can save 2640 yuan per year.
(3) The improved fine screen machine has a simple structure, small maintenance workload and easy management.
The two-stage fine-spinning tapping mechanism of Nanfen Concentrator is linked, that is, a driving mechanism is used to achieve the shock of the upper and lower fine screens. Figure 8 shows the two-stage fine screen structure of the plant. [next]
The technical characteristics of the fine screen of the factory are as follows:
Screen size (width × length) 400 × 1200mm
Screen angle 56°
Screen size 0.2mm
Separation particle size 0.1mm
Under the sieve -0.1mm content 95%
Processing capacity 6～8.5t/(h?m2)
Number of strikes 21 times / min
Motor power 2.2kW
Dimensions 4900 × 3600 × 4000mm
(length × width × height)
In order to have a comprehensive understanding of the technical performance of foreign fine screening, a list of foreign fine screening performance is listed.
B classification principle
The classification principle of the fine sieve is shown in Fig. 9. The slurry flows perpendicularly to the screen and is tangentially (parallel) to the screen surface. Due to the effect of the slurry flow velocity and the falling velocity of the slurry (mineral particles), a separate edge of each screen is produced. A mechanical "cutting" effect. The "cut", called the undersize, is not "cut", called the sieve. Secondly, the evenly fed slurry stream also has a gravity layering effect. Since both ashamed to use, be achieved by particle size-fractionated, i.e. containing the fine fraction was higher undersize amount of iron, coarse fraction containing high silica material on the sieve, serve to increase the iron ore grade effect.
Since the pulp speed, concentration (viscosity) and slurry amount vary on each of the sieve bars, it is difficult to express them in mathematical equations in practice. The following is an analysis of the motion state of the screening process. The fine screening process can be seen as being carried out in two stages. First, the fine particles in the slurry layer fall through the gaps of the large particles onto the sieve surface, and then the fine particles pass through the sieve holes to become the undersize products.
The process of dropping fine particles onto the screen surface is a random process. Therefore, its landing to a certain position on the screen surface is also a random phenomenon.
If the width of the sieve is b and the width of the sieve is a, the probability of fine particles falling on the sieve is
Because 6>>a, P 1 >>P 2 . Therefore, it can be considered that most of the particles in the undersize product are first dropped onto the sieve bar and then moved down the sieve bar to the sieve hole to be sieved. That is, the main function of the screening process is to slide through the sieve, rather than directly through the sieve. [next]
Based on the above analysis, the variable coordinate system is established as shown in Figure 10.
Origin O i through the center of gravity of spherical particles, a line parallel to the screen surface of the X i axis is perpendicular to the screen surface and the straight line passing through the lower edges see i-th screen bars illustrated as y i-axis direction.
To simplify the calculation, assume:
(1) the screen surface is straight;
(2) the ore particles are spherical particles;
(3) The fine particles in the ore slurry and the slurry layer close to the sieve surface move at the same speed.
At this time, the ore particles are only subjected to gravity, and the equation of motion is X i = υ i t + 1/2g · sina · t 2 (1) in the range of X i from 0 to (ad i /2)
y i =1/2g · cosa · t 2 (2)
Where t—the time required for the ore particles to move from the origin O i to the (x i , y i ) point.
From the equations (1), (2), the time t is obtained, and the trajectory equation of the ore particles is obtained.
Considering that the edge of the upper portion of each of the fine screens is slightly worn, it can be considered that when the ore moves to points xi, yi, that is, X i = ad i /2
y i =d i /2
And when the condition ad i /2 ≥ d i /2 is satisfied, that is, d i /2 ≤ 1, the probability that the ore having a diameter d i falls under the sieve and remains on the sieve is 1/2, so d i That is, the particle size of the mesh hole.
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