Shaking table

What are the characteristics of the shaking table?

Shaking table beneficiation is a process that uses the combined effect of mechanical shaking and water flushing to separate the ore particles by density. Shaking table is the main equipment of the gravity concentration plant, its distinctive feature is the high ratio of rich ore, it is often used to obtain the final concentrate, and at the same time can select the final tailings, can effectively deal with fine grain materials. The upper limit of particle size is 3mm, and the lower limit is 0.4mm if cassiterite and wolframite are selected, and it is mostly used to separate materials below 1 mm. The structure of the shaking table is more complex, less convenient operation, productivity is also lower, occupying a large plant area. These shortcomings are in the research and improvement.

According to the different particle sizes of the minerals sorted, it can be divided into three types, namely coarse sand shaking table, which processing minerals larger than 0.5mm, fine sand shaking table, which processing minerals between 0.5-0.07mm, and slime shaking table, which processing minerals between 0.074-0.037mm. The difference between them mainly lies in the different forms of table rifling strips.

What is the basic structure of shaking table?

Shaking table is a kind of widely used mineral processing equipment. The basic structure is divided into three main parts: table surface, head and frame. A typical shaking table structure is shown in the following Figure 1.

(1) table surface, the table surface can be made of wood, fiberglass, metal (such as aluminum, cast iron) and other materials. Its shape is commonly rectangular, trapezoidal and diamond-shaped. Along the longitudinal in the table surface nailed with many parallel strips (also known as rifling strips) or engraved with grooves, the table strip from the drive end to the opposite side of the lower, and in a diagonal line on the tip off. The table is supported by the frame or lifted by the frame. The table of the shaking table is inclined, 1.5-5 degrees in the lateral direction from the feed end to the opposite side, so that the water flow from the feed trough and rinse trough to form a thin layer of inclined water flow on the table. There is a feeding trough on the upper right side of the table, the length of which is about 1/3-1/4 of the total length of the table; there are many small holes on the side of the feeding trough to distribute the slurry evenly on the table. Connected with the feed trough is the flushing trough, which accounts for 2/3-3/4 of the total length of the table, and many small holes are also opened on the side of the feed trough, so that the flushing water can also be evenly fed along the table longitudinally. In the tank is also equipped with many flaps to adjust the distribution of water along the length of the table.

(2) table head (drive mechanism), driven by the motor, connected to the table through the tie rod, so that the table along the longitudinal direction for asymmetric reciprocating motion. When the table is moving forward, the speed from slow to fast and then quickly stop; in the backward, the speed increases rapidly from zero to maximum, after which the group slowly decreases to zero. The table surface produces longitudinal differential motion, so that the table surface ore particles can be transported in one direction. To the concentrate end of the transport forward transport, and vice versa called reverse transport.

(3) Frame or suspension mechanism, the table support mode is seated and suspended. Seated type is the table directly linked with the bracket, and the bracket is equipped with a slope adjustment device, used to adjust the transverse slope of the table. Suspension type is to use the wire rope to hang the table on a shelf, the table hanging in the air. Adjusting the slope is done by adjusting the tightness of the wire rope.

What is the sorting process and working principle of shaking table?

The rinsing water fed from the feed trough spreads over the laterally inclined table surface and forms a uniform sloping thin layer of water flow. When the material (generally the product of hydraulic classification, the concentration of 25%-30% of the slurry) is self-flowing from the feed trough to the table surface, the mineral particles are loosened and stratified by the flushing water and table vibration in the table strip grooves. The upper layer of light mineral particles are subjected to greater impulse, and most of them move downward along the table surface with lateral inclination, and are discharged as tailings. Accordingly, this side of the table is called the tailing side. The heavy mineral particles located at the bottom of the table are subject to the differential motion of the table surface along the longitudinal movement, and are discharged from the opposite side of the drive end called concentrate, and the corresponding table surface position is called concentrate end. Different densities and particle sizes of ore particles on the table are subject to different lateral and longitudinal effects, and the final direction of movement is different. Different densities and particle sizes are subjected to different lateral and longitudinal actions on the table surface, and the final direction of movement is different, while the table surface is fan-shaped, which can receive a variety of products of different quality, as shown in Figure 2.

The working principle of shaking table: shaking table sorting is achieved under the joint action of table surface and lateral water flow, table surface table bar or groove is longitudinal, and the direction of water flow is nearly perpendicular, water flowing through the groove in the lateral formation of vortex, vortex and the joint action of table shaking can make the sand layer loose and stratified by density, heavy minerals to the lower layer, light minerals to the upper layer, called this process for “Separation stratification”, the upper layer of light mineral particles by the water flow is larger impulse, while the lower layer of heavy mineral particles by a smaller impulse, so the speed of transverse movement of light mineral particles on the table is greater than the speed of transverse movement of heavy mineral particles on the table.

In the longitudinal direction, the differential motion of the table surface (at first advancing at a slow speed and gradually accelerating, then suddenly retreating when the speed reaches the maximum, gradually decreasing the speed during the retreating process, then advancing again and repeating the above process) not only promotes the loose stratification of the ore layer, but also makes the heavy ore particles move forward along the longitudinal direction at a larger speed, and makes the light ore particles move forward at a smaller speed.

The destination of the mineral grains depends on the synthetic velocity of the longitudinal and transverse velocities, as shown in Figure 3. Heavy minerals have smaller transverse velocity and larger longitudinal velocity, light minerals have larger transverse velocity and smaller longitudinal velocity, applying the parallelogram rule to synthesize the longitudinal and transverse velocities, it can be seen that the combined velocity of heavy minerals is biased toward the concentrate discharge end of the shaking table, light minerals are biased toward the tailing side of the shaking table, and medium density particles are located in the question of the two, calling this process as ” This process is called “transporting and transporting the belt”.

What are the advantages and disadvantages of shaking table beneficiation?

It is widely used in the separation of tungsten, tin, tantalum, niobium and other rare and precious metal ores, and also used in the separation of iron and manganese ores. In recent years, it has also been reported that the shaking table is used to recover iron minerals from the tailings of magnetic separation plants and to select mica and other non-metallic minerals.

The advantages of shaking table beneficiation:
①higher beneficiation ratio (the ratio of concentrate grade to original ore grade) than many other beneficiation methods, up to more than 100 times;
②one separation can get qualified concentrate and waste tailings;
③ore in the table for the fan-shaped belt, easy to observe and adjust;
④products can be separated according to the need to split the plate to pick up separately, it can get a variety of products;
⑤ no consumption of chemicals, power consumption is very little.

Disadvantages of shaking table beneficiation:
①larger area;
②larger water consumption;
③ lower processing capacity per unit area of the table.

How does the structure of the shaking table affect the separation process?

The influence of shaking table structure on its sorting process is divided as follows.
(1) The shape and size of the table surface. The geometry of the table surface is divided into rectangular, trapezoidal and rhombic, as shown in Figure 4. From the structure view, the rectangular table surface is the simplest, but the area utilization rate is low, non-mineral-flow-area is large, so the table surface is generally made into a trapezoid or rhomboid. The shaking table surface produced in China is mostly trapezoidal, with a wider feed end and a slightly narrower concentrate discharge end. (Such as the commonly used industrial shaking table size of 4500mm × 1800mm × 1500mm). rhomboid-shaped table surface not only high area utilization, and due to the extension of the sorting belt, the sorting efficiency has also improved. The disadvantage is that the configuration and operation is not convenient. This table is used more abroad. table length to width ratio has an impact on the sorting index, increase the length, extending the selection belt, can improve the grade of heavy minerals; increase the width, can make the tailings sorting opportunities more, is conducive to improving the recovery rate.

(2) Table surfacing material. The purpose of adding pavement on the table is three: to prevent leakage, improve wear resistance and ensure a certain degree of roughness (coefficient of friction). Pavement materials available thin rubber sheet, lacquer ash (raw lacquer with a certain percentage of calcined gypsum) coating, polyurethane rubber spray layer, etc..

(3) Table strip shape and configuration. The role of the table strip is to maintain a certain thickness of the mineral layer, and the layered upper layer of light minerals discharged one by one, the table strip cross-sectional shape and configuration affects the flow characteristics of the transverse water flow on the table, and therefore affects the loosening of the mineral layer and the lower limit of the recovered particle size.

There are raised table strips (wooden, bamboo, plastic or rubber strips attached to the table surface) and grooved table strips (grooves carved into the table surface). Raised table strip section shapes are rectangular, triangular, trapezoidal and serrated, etc. Several table strip section shapes are shown in Figure 5. Rectangular and trapezoidal table strips are suitable for coarse sand as shown in Fig. 5a, while serrated and triangular table strips are suitable for fine sand and mud as shown in Fig. 5b. Slotted table strips with triangular cross-sectional shape are suitable for separating mud, as shown in Figure 5c.

The height of the table strips is gradually reduced from the drive end to the concentrate discharge end, and at the end of each table strip along a 30° to 40° angle with the tailings edge line, as shown in Figure 6. And the table bar is gradually increased from the feed side to the tailing side below.

(4) Table layers. Shaking table has a single layer and multi-layer, multi-layer shaking table has large processing capacity, covers an area of small, mostly used for separation of ore mud and coal beneficiation.

What are the key points of shaking table selection, installation and operation?

The selection of shaking table should be decided according to the maximum particle size of the raw ore, processing capacity and plant area. When the feed size is larger than 0.2mm, use coarse sand shaking table; when the size is 0.2-0.074mm, use fine sand shaking table; when the size is less than 0.074mm, use slime shaking table. The finer the particle size of the material to be selected, the lower the capacity of the shaking table. For example, with cloud tin type shaking table processing tin ore, when the feed size 0.5-0.2mm coarse sand shaking table production capacity of about 0.8-1.0t / h, while the processing of 0.074-0.04mm mud shaking table production capacity of only 0.2-0.3t / h. When the plant area is small, single layer shaking table swing can not open, multi-layer shaking table can be used.

Shaking table installation requirements flat, there should be no abnormal jump during operation, the longitudinal direction is generally horizontal, but when dealing with coarse-grained raw materials, the concentrate end should be 0.5° higher to improve the selection effect; and shaking table dealing with fine mud, the concentrate end should be 0.5° lower to facilitate the forward movement of fine-grained concentrate.

The main points of shaking machine operation are as follows.
(1) The appropriate stroke of length and stroke of frequency. The appropriate value of the stroke of length and frequency is mainly related to the size of the material to be selected, followed by the shaking table load and ore density. When dealing with large particle size, thick table materials, the use of large stroke of length and small stroke of frequency; dealing with fine sand and mud is the opposite, should use a small stroke of length and large stroke of frequency. When the load on the table increases or when the selection of materials of greater density, it is appropriate to use a larger stroke of length and stroke of frequency. The appropriate value of the stroke length and stroke frequency should be carefully examined in practice to determine.

(2) Suitable transverse slope of table surface. Increasing the transverse slope, the sliding effect of the ore particles is enhanced, and the discharge speed of the tailings is increased, but the separation zone of the selection area becomes narrower. In general, when dealing with coarse-grained materials, the transverse slope should be larger; when dealing with fine-grained materials, the transverse slope should be smaller. For example, coarse sand, fine sand and slime shaking table angle adjustment range: 2.5°-4.5°, 1.5-3.5° and 1°-2 °. In addition, the transverse slope of the shaking table should also be matched with the size of the transverse water flow to reach good sorting effect.

(3) The flushing water should be appropriate. The rinse water includes two parts: feed water and wash water. The rinse water should be evenly distributed on the table and the size should be appropriate. Washing water is large concentrate grade increase, but the recovery rate is reduced. Generally, when dealing with coarse-grained materials or selection, the rinse water should be larger.
(4) The amount of ore feed is appropriate and uniform. The size of the ore feed is related to the size of the feed, the coarser the size, the larger the ore feed should be. For a specific material, the feed amount should be controlled in the table utilization rate is large, the separation zone is obvious, and the tailing grade is within the allowable range. If the feed amount is too large, the recovery rate will be significantly reduced. In addition, once the amount of feed is found, it must be maintained continuously and evenly, otherwise the separation zone will be unstable and cause fluctuations in the separation index.

(5) The quality fraction of the ore is appropriate. The general range of the mass fraction of the feed ore is between 15% and 30%, coarse-grained materials can be thinner, and fine mud should be thicker. Most of the water in the feed ore flows down the tailing belt laterally, and the fine mud is easily washed away, resulting in the loss of fine-grained metal minerals.

(6) materials in the preparation of the pre-selection. The upper limit of particle size of the shaking table is 2-3mm, and the lower limit is 0.037mm. Because the particle size has a large impact on the selection index, so the material should be graded before the selection. If the material contains a lot of micro-fine mud, not only is it difficult to recover, but also because the viscosity of the pulp increases, the heavy minerals settle slower, resulting in the loss of heavy minerals. In this case, pre-demuding should be carried out.

(7) Material in the table of the parting belt and product interception. When the operating conditions are suitable, the material in the shaking table parting belt is obvious, and the product is intercepted according to the required sorting index, which can be divided into 2 to 4 kinds of products. Medium ore is generally subject to reprocessing. When the operating conditions change, the situation will change, then the position of the pick-up must also be adjusted accordingly, in order to ensure the stability of the sorting index. Therefore, the operator of the shaking table should adhere to his post, closely monitor the situation of the separation belt, and make the necessary adjustments at any time.

What’s the appropriate feeding desity for shaking table beneficiation?

The concentration of ore feed to the shaking table beneficiation to ensure that the pulp can have sufficient mobility along the table surface and can be stratified, and the water depth can submerge the ore particles. In general, the concentration of coarse sand feed is 20% to 30%, and the concentration of fines feed is 15% to 25%.