Comparative Analysis of Spiral Classifier design and ...
Comparative Analysis of Spiral Classifier design and ...
Spiral classifier and hydrocyclone are both mineral processing classifiers. The mineral processing classifier generally include four kinds, increased flow hydrocyclone classifier, cone classifier, a centrifugal classifier( hydrocyclone ) and mechanical classifier ( rake classifier, spiral Classifier, and Floating tank classifier). Today, we will only choose Spiral classifier and hydrocyclone this two equipment to make a detailed comparison, that is because they are the most widely used classifiers in our mill plant, at present.
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Spiral Classifier is a kind of mechanical classifier, and it is composited by a u-shaped water tank, spiral device, transmission device, lifting mechanism, bearings and other parts.
The working principle of spiral classifier is: the milled pump was fed into the u-shaped slot from spiral classifier&#;s feeding mouth, after the continuous rotations and stirrings of the spiral device, the light, and fine particles were suspended in the pulp surface and flowed from the overflow weir; and the thick and heavy particles were settled to the bottom, transported by the spiral device to the port of discharge, re-entered the mill grinding.
There are generally two spiral classifier classification methods, one is in accordance with the number of the screw shaft, it can be divided into single and double spiral classifier spiral classifier; Another kind is according to the overflow weir height, it can be divided into high low weir, weir and submerged.
Hydrocyclone is a kind of using centrifugal force role grading equipment, mainly made up by the feed tube, cone, cylinder shell, sand mouth and overflow pipe, etc.
The working principle of hydrocyclone is: under the pressure of 0.5-2.5 kg / cm2 in the inlet, the pulp was feed into the cyclone cylinder along the along the tangent direction of the feed tube. A great deal of centrifugal force was produced because of the rotations of the inside part of hydrocyclone, under the action of centrifugal force, the coarser one was thrown to the wall, along with the spiral descent flow, and was discharged from the discharge mouth.
Advantages of hydrocyclone are: It is simply constructed and has no moving parts; the small size covered small footprint; it has large capacity per unit area, and it&#;s very convenient to operate and maintain, so, the cost is very low; what&#;s more, the classification efficiency and sorting accuracy are higher; and it needs lesser quantity and time for pulp to stay; the advantages are more apparent when working together with a large ball mill. Of course, the hydrocyclone has its shortcomings, such as the pulp needs the head of the pump to delivery; it needs stable working pressure when working, and it has a higher demand to the particle size and concentration of the pulp, what else is that it can be worn more serious.
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Spiral classifier has more significantly highlighting advantages compared with hydrocyclone, such as, It is reliable and easy to operate; the staging area is smooth and finer overflowed particle size can be obtained. What&#;s more, the trough slope is easier for sand returning into to the ball mill. In addition to these, some of domestic mining machine manufacturers make some improvements to a spiral classifier, for example&#;Yantai Xinhai mining machinery company has added a sand-returning automatic lifting device in the sand-returning end of the spiral classifier, in order to substitute the tablespoons head of the ball mill. That makes the ball mill run more smoothly.
Shortcomings of spiral classifier are: It&#;s relatively cumbersome and the classification efficiency is low; the spindle is frangible and the maintenance is extremely inconvenient; and it has poor overflow bearing seal at the bottom of spiral classifier; what else, a finer classification overflow fineness is difficult to get especially when the asked overflow granularity is -0.074mm and accounts more than 90%.
Overall, spiral classifier and hydrocyclone are widely applied in our country, each of them has his strong point.
Spiral Classifier
What is a spiral classifier&#;
The spiral classifier is a device that utilizes the principle of different sedimentation speeds of solid particles in a liquid based on their specific gravity for mechanical classification. It is widely used in closed-circuit processes in conjunction with ball mills to separate and classify ore sand in mining plants. It can also be applied in gravity separation plants for classifying ore sand and fine mud, as well as in metal ore dressing processes for size classification of ore pulp. Additionally, it finds application in de-sliming and dewatering operations during ore washing.
Types: There are four classifiers: high weir single spiral and double spiral, submerged single spiral and double spiral.
- High weir spiral classifier is suitable for coarse particle classification, the maximum size of overflow is generally 0.4~0.15mm;
- Submerged spiral classifier is suitable for fine particle classification, the maximum size of overflow is generally below 0.2mm.
Applications of Spiral Classifier
- Mining Plants: Used in conjunction with ball mills to form a closed-circuit for ore sand separation and classification.
- Gravity Separation: Applied for classifying ore sand and fine mud to enhance mining efficiency.
- Metal Ore Dressing: Used in the ore dressing process for size classification of ore pulp to meet subsequent process requirements.
- Ore Washing Operations: Involved in de-sliming and dewatering processes during ore cleaning.
Advantages Of Spiral Classifier
- The energy consumption of spiral classifier is 50% lower than other classification equipment, and the output is also increased by 50%.
- The water tank has a large slope, which is convenient for forming a closed-circuit ring grinding operation with the ball mill, and forms a self-flow sand return.
- Simple operating process and stable working status, greatly reducing maintenance costs.
- Its spiral structure can ensure a large enough settling area to extend the material suspension time, which is more conducive to the even distribution of materials during the classification process.
- Users can adjust the parameters of the spiral classifier according to their needs, such as spiral speed, inclination and outlet size to achieve different classification requirements.
Principle of Spiral Classifier
The working principle of the spiral classifier is based on the different sedimentation speeds of solid particles in a liquid due to their varying specific gravities. When the ore pulp enters the tank from the side feed inlet, it forms a sedimentation zone at the bottom of the tank. The slowly rotating spiral provides a certain degree of agitation to the pulp. After agitation, the light and fine particles suspend on the surface, forming an overflow that flows over the weir at the end of the water tank into the next mineral processing step. The heavy and coarse particles settle at the bottom of the tank, forming a return sand that is transported by the spiral to the discharge port for removal, thus achieving the desired classification.
Structure of Spiral Classifier
The spiral classifier mainly consists of the following components:
- Transmission Device: Includes an electric motor, reducer, cylindrical gear pair, and bevel gear, responsible for driving the rotation of the spiral.
- Spiral Body: Composed of a hollow shaft, supports, spiral blades, and lining iron, which is the main working part of the classifier.
- Tank: Holds the entire slurry and bears the weight of the machine and all its loads. Constructed by welding steel plates and various steel sections.
- Lifting Mechanism: Used to raise or lower the spiral for maintenance or to adjust the processing level within the tank.
- Lower Bearing (Bushing): Supports the spiral and bears the load during operation.
- Discharge Valve: Located at the bottom of the tank, allowing the slurry to be drained when necessary.
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