What Should You Know Before Choosing a Spiral Classifier?

In the beneficiation process, the classification operation often plays an extremely important role in the grinding cycle. It is necessary to fully dissociate and separate the fine-disseminated useful minerals and gangue, and grind the ore to a certain degree of fineness, but it is also essential to avoid over-grinding to prevent muddy from adversely affecting the separating process. This requires classifying equipment to separate the qualified parts of the grinding products in time to avoid unnecessary grinding, deliver the product to the sorting operation earlier and return the part with unqualified particle size to the mill for re-grinding.

It can be seen that the classification operation is of great significance to the grinding cycle in both technical and economic sense.

Generally, the classifying equipment performs the classifying operation by the force and principle such as gravity, centrifugal force, and mechanical vibration. At present, the classification equipment used in the mineral processing plant has a mechanical classifier and hydrocyclone.

The mechanical classifier also includes various types such as spiral classifier, rake classifier, and bowl classifier.

As a result, spiral classifiers and hydrocyclones have become the main choice for today's beneficiation classification operations.

Although the rapid development of hydrocyclones once caused the spiral classifier to lose its own importance, as the demand for the plant changed, it was found that the spiral classifier was indeed better than the hydrocyclone in some respects.

The high lifting height of returning sand can let the sand directly return to the feeding end of the mill and be continuous and stable.

Therefore, the spiral classifier is easy to obtain product with higher concentration, the particle size of classification product are controlled by the feeding amount and the overflow concentration and can be coarse or fine.

The operation is reliable, the cost is low, the structure is simple and the configuration operation is convenient.

So, what kinds of types are there currently in the spiral classifier market? How do we make a difference to choose the right spiral classifier?

According to the height of the weir (the position of the spiral in the sink is different from the level of the pulp surface), the spiral classifier can be divided into three types: high weir type, low weir type and submerged type.

Generally, the overflow weir of the low weir spiral classifier is often lower than the center of the bearing of overflow end, so the settling zone is too small, the overflow production capacity is too low, and the spiral agitates the slurry surface greatly. So in actual production, it is only used for rinsing sand minerals with little mud and dewatering of coarse particles, and is rarely used in grinding and classifying operations.

The overflow weir of the high weir spiral classifier is usually higher than the bearing center at the lower end of the screw shaft, lower than the upper edge of the spiral of the overflow end, so the area of the settling zone is larger than that of the low weir spiral classifier.

The height of weir can be adjusted within a certain range, which means the area of the settling zone can be slightly changed according to the classification requirements, thereby adjusting the particle size of classification.

As for the submerged spiral classifier, the overflow end generally has 4-5 turns of spiral blades, and all the spiral blades are submerged under the liquid level in the settling zone, so the area of the settling zone is large and the classification tank is deep.

According to the structure difference between the high weir type and the submerged type spiral classifier, the roles played by the two in the classifying operation are also different.

The high weir spiral classifier is more suitable for separating coarse particle larger than 0.15mm and is usually used in the first stage of grinding; and the submerged spiral classifier has even classifying level, high overflow output and fine grain size.

Therefore, it is more suitable for separating overflow products with a particle size of less than 0.15mm, and often forms a combined unit with the mill in the second stage of grinding.

According to the number of spiral axes, the spiral classifier can be divided into single spiral classifierand double spiral classifier.

The classifying performance of the two kind of spiral classifier is basically the same, but the double spiral classifier is significantly larger than the single spiral classifier in terms of sand returning capacity, overflow treatment capacity, spiral diameter, etc., and the price of the double spiral classifier is much higher than that of the single spiral classifier.

Therefore, it is more suitable to use with large and extra large-scale grinding machines.

The mineral processing experts suggest that a single spiral classifier should be used as far as possible under a certain processing capacity. According to statistics, the spiral workload of the double spiral classifier is 0.6 to 0.75 times that of the single spiral classifier, and the efficiency is relatively low.

Therefore, when selecting a spiral classifier, the appropriate spiral speed and number must be determined according to the processing capacity.

The various types of classifying equipment mentioned above all have their own functions and advantages, and have different effects on the classifying efficiency of equipment.

At present, many classifying equipment manufacturers will carry out corresponding optimization and improvement for different classifying requirements in order to obtain the classifying effect of customer satisfaction.

When selecting the spiral classifier, each mineral processing plant must clearly understand the characteristics and working principle of each type of spiral classifier and choose the best spiral classifier in combination with the needs of its own plant.