Spiral Classifier is a traditional type of classification equipment, mainly for metal mineral processing for the slurry density and particle size on the wet grade, mining operations could also be used in the flow desliming.
it is hard to get very fine product, especially for product with -200 mesh over 90%; It is not easy to automate control it, and the classification efficiency is not high; It needs a large space for installation.
In Mineral Processing, the SPIRAL Classifier on the other hand is rotated through the ore. It doesnt lift out of the slurry but is revolved through it. The direction of rotation causes the slurry to be pulled up the inclined bed of the classifier in much the same manner as the rakes do. As it is revolved in the slurry the spiral is constantly moving the coarse backwards the fine material will flow over the top and be travelling fast enough to be able to work its way downwards to escape. The Variables of these two types of classifiers are The ANGLE of the inclined bed, this is normally a fixed angle the operator will not be able to adjust it.
The SPEED of the rakes or spirals, the DENSITY of the slurry, the TONNAGE throughput and finally the SETTLING RATE of the ore itself.To be effective all of these variables must be balanced. If the incline is too steep the flow of slurry will be too fast for the rakes or spirals to separate the ore. If the angle is too flat the settling rate will be too high and the classifier will over load. The discharge rate will be lower than the feed rate, in this case. The load on the rakes will continue to build until the weight is greater than the rake or spiral mechanism is able to move. This will cause the classifier to stop and is known as being SANDED UP. If the speed of the rakes or spirals are too fast, too much will be pulled, out the top. This will increase the feed to the mill and result in an overload in either the mill or classifier as the circuit tries to process the increased CIRCULATING LOAD.
The DENSITY of the slurry is very important, too high the settling will be hampered by too many solids. Each particle will support each other preventing the heavier material from quickly reaching the bottom of the slurry. This will not allow a separation to take place quickly. The speed at which the slurry will be travelling will be slow and that will hamper effective classification. Another variable is the TONNAGE. All equipment has a limit on the throughput that anyone is able to process, classifiers are no different. This and the other factors will have to be adjusted to compensate for the last variable, the ore itself. Every ore type has a different rate of settling. To be effective each of the previous variables will have to be adjusted to conform to each ones settling characteristics.
The design of these classifiers (rake, spiral, screw) have inherent problems, First, they are very susceptible to wear, caused by the scrubbing action of the ore, that plus all of the mechanical moving parts create many worn areas to contend with. The other problem that these classifiers have is that they are easily overloaded. An overloaded classifier can quickly deteriorate into a sanded-up classifier. Once that happens the results are lost operating time, spillage and a period of poor Mineral Processing and Separation performance.
Another mechanical classifier is the spiral classifier. The spiral classifier such as the Akins classifier consists of a semi-cylindrical trough (a trough that is semicircular in cross-section) inclined to the horizontal. The trough is provided with a slow-rotating spiral conveyor and a liquid overflow at the lower end. The spiral conveyor moves the solids which settle to the bottom upward toward the top of the trough.
The slurry is fed continuously near the middle of the trough. The slurry feed rate is so adjusted that fines do not have time to settle and are carried out with the overflow .liquid. Heavy particles have time to settle, they settle to the bottom of the trough and the spiral conveyor moves the settled solids upward along the floor of the trough toward the top of the trough/the sand product discharge chute.
Spiral classifier and hydrocyclone are the main equipments for the classification operation of the concentrator. Although the rapid development of the cyclone once made the spiral classifier lose its market, but with the continuous changes in the requirements of the selection plant, it was found that the spiral classifier also has its advantages. The spiral centrifugal classifier has the advantages of strong continuous operation, large processing capacity, low energy consumption per unit output, and convenient maintenance. It can handle particles with a diameter of 1um-10mm. The horizontal spiral centrifugal classifier adopts the method of wet classification, and its processing capacity can reach 1~20 (m3 slurry) kg/h. It is widely used in minerals, metal powders, chemical raw materials, pigments, fillers, etc.
The screw classifier is based on the principle that the solid particles are different in size and specific gravity, so the settling speed in the liquid is different. Fine ore particles float in the water and overflow, and coarse ore particles sink to the bottom of the tank. Spiral classifier is widely used in beneficiation plant to match with ball mill to form a closed circuit circulation path to distribute ore sand. Filter the material powder milled in the mill, and then use the spiral piece to screw the coarse material into the ball mill inlet, and the filtered fine material is discharged from the overflow pipe. There are four classifiers: high weir single spiral and double spiral, submerged single spiral and double spiral.
The spiral classifier is widely used in the classification of the grinding circuit of the concentrator and the operations of washing, desilting and dewatering. Its main advantages are simple equipment structure, reliable work and convenient operation.
1. It is used for the separation of machine-made sandstone powder, which can control the content of machine-made sandstone powder very conveniently and meet the requirements of users.2. It is suitable for dry technology large and medium-sized sand production lines.3. The content of 0.000.75mm stone powder can be adjusted between 2%-15%.4. Stone powder quality is easy to control, fineness adjustment is convenient, flexible and reliable.5. Using frequency conversion control technology, the operation is more concise.6. It can be connected with the mill in the closed circuit of the grinding circuit. Compared with hydrocyclone, the power consumption is lower.7. The main disadvantage is that the classification efficiency is low, the equipment is bulky, and the floor space is large. Due to the limitations of equipment specifications and production capacity, it cannot generally form a closed circuit with a ball mill of 3.6m or more.
The spiral classifier is divided into two types: high weir type and submerged type. High weir classifier is suitable for coarse particle classification, the maximum size of overflow is generally 0.4~0.15mm; submerged classifier is suitable for fine particle classification, the maximum size of overflow is generally below 0.2mm.
The spiral classifier is one of the equipment in mineral beneficiation plant. The spiral classifier is a kind of equipment for mechanical classification based on the principle that the specific gravity of solid particles is different, so the speed of precipitation in the liquid is different. The coarse material is screwed into the feed port of the mill using a spiral blade, and the filtered fine material is discharged from the overflow pipe. There are four types of classifiers: high weir type single screw and double screw, submerged single screw and double screw. The classifier is mainly composed of transmission device, spiral body, trough, lifting mechanism, lower support (bearing) and discharge valve.
Spiral Classifier Advantages: 1Simple structure, easy to maintain 2Easy operation and stable performance 3Gravity connection with Ball mills; slurry pump conveying is not necessary. 4Large volume with buffering and conveying effect, better for grinding work.
Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.
DOVE Spiral Classifier, also referred to as Screw Classifier, or Spiral Mineral Separator, is highly efficient classifier designed for closed circuit wet classification and separation of the Slimes (Fines) from a sandy sized (Coarse) material. It is well suited for classification, where a two product size-split is required. Due to inherent operational qualities, DOVE Spiral Classifier is ideally suited Sizing applications, Washing Applications, and Dewatering sand or crushed material from Hydro cyclone, or lower screen residues.
DOVE Coarse and Fine Spiral Classifiers are supplied in various capacities, tub lengths, screw sizes and technical specifications. We supply total of 16 models, where 10 models are configured with single screw and 6 models with dual screw.
Spiral Screw classifier is a type of common mechanical classifier, consists primarily of an inclined tub and a transport screw for the coarse material. The fine material residue is at the lower end of the tub and the coarse material residue is at the upper end. The principle of the operation and separation of solid grains is based on the law of gravity and concept that the solid particles are different in size and specific gravity, therefore the settling speed in the water is different. Fine ore particles float in the water and overflow, and respectively coarse ore particles settles to the bottom. As a guide line, a unit with longer length classifier will dewater the same material to a higher degree, and likewise a unit with a greater diameter of screw revolving the identical speed will produce higher capacity. In the application of dewatering fine material, the screw speed is reduced to allow proper classification and dewatering.
DOVE laboratory will assay your ore samples rapidly and analyze your raw materials and recommend the most efficient processing plant according to the ore specifications, minerals composition, and ore assay results, and your project size and the geologic and topographic conditions of your mine.