Commonly Used Mining Thickener Types and Selection

Thickener is a continuous working thickening and clarification equipment, mainly used for the dewatering of concentrates and tailings slurry in wet beneficiation operations, and also widely used for thickening of solid-containing slurry such as coal, steel, chemicals, building materials, water sources, sewage treatment, etc.

There are currently three types of thickeners commonly used in mineral processing plants: ordinary thickeners, inclined plate thickeners and high-efficiency thickeners.

1) Ordinary Thickener

Ordinary thickeners are the most commonly used thickener in concentrators.

It can concentrate the slurry with a solid weight of 10% to 20% through gravity sedimentation into underflow slurry with a solid content of 45% to 55%. With the help of the slow-running (1/3～1/5r/min) harrow installed in the thickener, the thickened underflow slurry is discharged from the underflow port at the bottom of the thickener.

According to the rotation mode, thickener can be divided into central transmission type (small diameter) and peripheral transmission type (large diameter). According to the number of working surfaces, it can be divided into single-layer, double-layer and multi-layer thickeners.

This type of thickener is simple in structure, easy to manage, and reliable in production. However, due to the larger diameter, its area is larger and the production capacity per unit area is lower.

2) Inclined Plate Thickener

Inclined plate thickener is equipped with many inclined plates inclined to the center of the thickener on the upper part of the cylindrical pool of the ordinary thickener, these plates are along the circumference, and the angle with the horizontal is about 60°.

These plates accelerate the separation of ore particles, shorten the material settlement time, strengthen the separation and settlement process, improve the concentration efficiency, reduce the capital investment, and increase the production capacity by 3 times.

Due to its high efficiency and small settlement area, and this type of thickener is more suitable for the concentration and dehydration of fine-grained concentrates and tailings.  However, due to the complex structure, the inclined plate is easy to fall off, deform and age, and maintenance and operation are troublesome.

3) High-efficiency Thickener

The high-efficiency thickener has a special flocculant addition mechanism in addition to the inclined plates in the round pool.

In fact, it is not simple settling equipment, but a new type of dewatering equipment that combines the filtering characteristics of the mud layer.

The main feature of the high-efficiency thickener is to add a certain amount of flocculant to the slurry to be thickened, so that the ore particles in the slurry form flocs, accelerate its settling speed, and achieve the purpose of improving the efficiency of the thickener.

High-efficiency thickener’s diameter can be reduced to 1/3-1/2 of that of ordinary thickeners. It occupies only 1/9-1/4 of ordinary thickeners, while the processing capacity per unit area increases dozens of times. Therefore, it becomes more widely used recently.

Although the new high-efficiency thickener has the advantages of high processing capacity, less land occupation and low investment, it still cannot completely replace the ordinary thickener.

In the following situations, it is better to use an ordinary thickener:

• Slurry without suitable flocculant. For some ore slurry, flocculants have no obvious economic benefits or are uneconomical at all, so we should use ordinary thickener.

• Some pulps may have poor compressibility, slow thickening, and require a higher compression layer, so ordinary thickeners should be used

• The thickener which acts as a buffer and is used to store the slurry in the process should generally be an ordinary thickener

• Since the high-efficiency thickener is suitable for the treatment of medium-concentration underflow, it should not be used when the underflow concentration is too high.

• When the material viscosity is too high and the inclined plate fails to work, an ordinary thickener should be used

In addition to the above five cases, the use of high-efficiency thickeners in concentrators can obtain higher economic benefits. At present, there are also many concentrators that transform existing ordinary thickeners into high-efficiency thickeners for production. Please pay attention to the following points during the remolding：

• In order to achieve the expected flocculation effect, the slurry concentration should be adjusted, not too thick or too thin

• The drop height of the slurry from the slurry inlet pipe into the mixing drum should be small, so as to prevent the slurry from stirring up the settled mud and affecting the overflow turbidity.

• The slurry should be degassed and defoamed, and the oil and other substances that affect sedimentation should be removed. For this reason, we can add an aeration pipe or a hydrocyclone before the slurry is entered

• As the processing load is relatively large, try to consider installing devices that automatically raise the rake or adjust the speed.

Ordinary thickeners, inclined plate thickeners and high-efficiency thickeners are all commonly used thickening equipment in mineral processing plants. We should choose the really suitable type of thickener based on various considerations such as the concentration, viscosity, processing capacity, and material properties of the slurry.

We cannot directly replace ordinary thickeners with high-efficiency thickeners, otherwise it will be counterproductive. (Click to know 3 common problems and solutions of mining thickeners)

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