What Are the Advantages of Spiral Classifier？

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Both spiral classifier and hydrocyclone are mineral classifier. Ordinarily, the mineral classifier could be defined into four types: water-lifting hydraulic classifier, cone classifier, centrifugal classifier (hydrocyclone), mechanical classifier(rake classifier, spiral classifier, flotation tank classifier). Why we talk about spiral classifier and hydrocyclone here is that they are the main classifiers of the processing plant in our country. So here we would compare the two of them elaborately.

• 01

  Spiral classifier

• 02

  Hydrocyclone

• 03

  Advantages of hydrocyclone and spiral classifier

01

Spiral classifier

Spiral classifier is one of the mechanical classifiers. It consists with U-verse tank, spiral device, transmission device, lifting gear and supporting bearing.

Working principle of classifier 

The slurry after grinding was sent to the U-verse tank from the feeding port. Through the rotation and agitation of the spiral device, light and small granules float on the surface, and overflow from the downflow dam. Thick and heavy granules sink to the bottom, and was sent to the throat through the spiral device. And then they would go into the mill for second grinding.

Two ways to separate the spiral classifier

One is by the number of the spiral axles, which could be classified as the single spiral classifier and double spiral classifier. The other way is by the height of the dam, which could separate as high dam, low dam and submerged.

02

Hydrocyclone

Hydrocyclone is classifier equipment by centrifugal force&#;which consists with feeding pipe, cone container, cylinder shell, throat and downflow pipe.

Working principle of hydrocyclone

The slurry inpour the cylinder of the hydrocyclone through the pipe by the tangent direction with feeding pressure of 0.5 to 2.5 kg/cm^2. So that the slurry would go as rotation and create a huge centrifugal force, the granule of slurry by the centrifugal force, the thicker was thrown to the wall and sink by spiral stream expelling from the throat; the smaller float with water in the center by the up-flow spiral stream, and expel from the overflow pipe.

03

Advantages of hydrocyclone and spiral classifier

The advantage of hydrocyclone are followings: simple structure, none moving part, small area covering, big dealing capacity of the unit area, easy to operate and maintain, low cost, high rate of classifying and separation, less number and time of staying slurry and more advantages with a huge ball mill. Of course, it also has disadvantages, such as the slurry need to be conveyed by the lifting pump, a more stable working pressure, a higher standard of particle size and slurry concentration and badly born and so on.

Link to Zoneding machine

Compared with hydrocyclone, the advantages of the spiral classifier are following: reliable working condition, easy to operate, stable classifier area easy to get small overflow size, huge gradient of sink easy to company with mills for autoflow return. Besides, some mining machine manufactures have improved it, such as Yantai Xinhai have added an auto-lifting return device to the return part of spiral classifier. The disadvantages of it are: heavier, lower classifier rate, easy broken main axle but difficult to check and repair, less airtightness of the overflow bottom axle, not easy to get classified overflow fineness, especially when the required fineness is -0.074 over 90%, quite difficult to reach.

In a word, spiral classifier and hydrocyclone are both widely used in Chinese mining processing plant and each has its own advantages.

In the beneficiation process, the purpose of the classification operation is to separate the coarse and fine particles effectively, which not only avoids excessive pulverization of fine-grained minerals and reduces unnecessary energy consumption, but also enables coarse-grained minerals to be effectively pulverized again as the returning sand of grinding mill. The quality of the classification operation will directly affect the production capacity of the grinding equipment, the effect of the finished product, and the technical and economic indicators such as the concentrate grade and recovery rate in the subsequent sorting operations.

Nowadays, spiral classifier and hydrocyclone are considered to be the two mainstream classification equipment. As the first generation of classification equipment, the spiral classifier has been widely used in mineral processing plants for decades. While as the second generation classification equipment, the hydrocyclone quickly occupied a market place in the classification equipment of dressing plants with their unique advantages. Many people are puzzled that since both are mainstream classification equipment, what is the difference between them? And which type of classification equipment should I choose?

1. Material Nature of Spiral Classifier and Hydrocyclone

The common spiral classifiers include both high weir spiral classifier and submerged spiral classifier. High weir spiral classifiers are usually applied to classification of coarse-grain particles, generally with classification overflow particle size larger than 0.15mm. The submerged spiral classifier is suitable for fine particle classification, and the classificaiton overflow particle size is generally less than 0.15 mm. Compared with these two kinds of spiral classifiers, the hydrocyclone has a better classification effect when classifying finer-grained materials (the classifying size is generally 0.3-0.01 mm).

2. Floor Area of Spiral Classifier and Hydrocyclone

It is obvious that the floor area of hydrocyclone is significantly smaller than that of the spiral classifier. Usually, the hydrocyclone covers an area of only l/30 to l/50 to the spiral classifier. The equipment floor area requirement also limits the application of the spiral classifier to a certain extent.

3. Classification Efficiency of Spiral Classifier and Hydrocyclone

The spiral classifier is superior to the hydrocyclone in terms of both classification efficiency and product accuracy. A large part of the reason is that if the pressure is not up to standard, the hydrocyclone will change the position of the final material discharge. It&#;s necessary for hydrocyclones to rotate at a low speed by a spiral to agitate the slurry to suspend the fine particles, and overflow to the overflow weir. The coarse particles sink to the bottom of the tank and are transported by the screw to the discharge port for discharge. The hydrocyclone has to discharge at the side opposite the inlet, that is, once the pressure is not up to standard, the material delamination will be disordered, so that the material cannot be discharged normally from the outlet. However, this is not absolute, especially when the size of the classification is very fine (such as 0.037mm), the classification efficiency of the hydrocyclone is significantly higher than other main classification equipment.

4. Operation of Spiral Classifier and Hydrocyclone

The biggest reasons why the spiral classifier is most widely used lie in its simple structure, stable operation and easy operation. It is because of the simple operation process and stable working state that the cost for maintenance and replacement of equipment is greatly reduced and the completion time is guaranteed, making the classification operation more guaranteed. In addition, its easy-to-operate feature allow the operator to operate the hydrocyclone after a short-term training session. In other words, it has relatively low technical requirements for the operator. Relatively speaking, the operation of the hydrocyclone is more complicated, since the ore pressure, concentration and particle size will greatly affect the classification index. So there is higher requirement for the accuracy of the operation.

5. Investment Costs of Spiral Classifier and Hydrocyclone

In terms of equipment investment, the equipment price of the hydrocyclone is definitely lower than that of the spiral classifier. However, in addition to hydrocyclone itself, there still requires a series of necessary auxiliary equipment for hydrocyclone, such as dispensers, valves, pumps, etc., which increases the investment of some equipment. In terms of maintenance, the wear parts of hydrocyclones are mainly lining and overflow pipes. Of course, the frequency and extent of wear are caused by factors such as particle size, shape, and solid content. Therefore, the service life and maintenance cost can only be accurately obtained in the actual plant selection practice. The maintenance aspect of the spiral classifier is mainly to replace the spiral lining, as well as other routine maintenance. However, because the lining material of spiral classifier is relatively expensive, spiral classifier purchase and maintenance costs are high. Overall, the investment price of the spiral classifier is higher than that of the hydrocyclone.

The classifier equipment is combined with the grinding equipment in the beneficiation production line to jointly provide the ore of suitable size for the separation operation. The choice of any mineral processing equipment will not be unilaterally determined, it must be the result of comprehensive consideration. An overall consideration will not only help to improve production efficiency, but also help to obtain the best return on investment.

The above mainly compares the spiral classifier and the hydrocyclone in terms of material properties, floor space, grading efficiency, operation and investment cost, each of which has advantages and disadvantages. When selecting a classifying equipment, you can consider the characteristics of different equipment to select the one that meets the actual production.