fote machinery | professional mining machinery manufacturer for 40 years

fote machinery | professional mining machinery manufacturer for 40 years

Manganese ore beneficiation plant plays an important role in enriching manganese ore, and FTM has many mining equipment used for manganese ore concentration for sale.

Powder production line is made up of jaw crusher, hopper, bucket elevator, classifier, dust collector, high-pressure mill, reducer, vibrating feeder, and air-blower, etc.

The flotation separation process is an important processing technology with the widest application ranges. And it includes various machines such as jaw crusher, ball mill, classifier, and flotation machine, etc.

Henan Fote Heavy Machinery Co., Ltd. (FTM) is a large mining machinery manufacturer and exporter, located in Zhengzhou, Henan, China. Our main product categories include stone crusher machine, sand making machine, ore beneficiation plant, powder grinding machine, dryer machine, etc. We can provide not only single machine, but also complete production plant with our powerful technical support.

ball mills

ball mills

In all ore dressing and milling Operations, including flotation, cyanidation, gravity concentration, and amalgamation, the Working Principle is to crush and grind, often with rob mill & ball mills, the ore in order to liberate the minerals. In the chemical and process industries, grinding is an important step in preparing raw materials for subsequent treatment.In present day practice, ore is reduced to a size many times finer than can be obtained with crushers. Over a period of many years various fine grinding machines have been developed and used, but the ball mill has become standard due to its simplicity and low operating cost.

A ball millefficiently operated performs a wide variety of services. In small milling plants, where simplicity is most essential, it is not economical to use more than single stage crushing, because the Steel-Head Ball or Rod Mill will take up to 2 feed and grind it to the desired fineness. In larger plants where several stages of coarse and fine crushing are used, it is customary to crush from 1/2 to as fine as 8 mesh.

Many grinding circuits necessitate regrinding of concentrates or middling products to extremely fine sizes to liberate the closely associated minerals from each other. In these cases, the feed to the ball mill may be from 10 to 100 mesh or even finer.

Where the finished product does not have to be uniform, a ball mill may be operated in open circuit, but where the finished product must be uniform it is essential that the grinding mill be used in closed circuit with a screen, if a coarse product is desired, and with a classifier if a fine product is required. In most cases it is desirable to operate the grinding mill in closed circuit with a screen or classifier as higher efficiency and capacity are obtained. Often a mill using steel rods as the grinding medium is recommended, where the product must have the minimum amount of fines (rods give a more nearly uniform product).

Often a problem requires some study to determine the economic fineness to which a product can or should be ground. In this case the 911Equipment Company offers its complete testing service so that accurate grinding mill size may be determined.

Until recently many operators have believed that one particular type of grinding mill had greater efficiency and resulting capacity than some other type. However, it is now commonly agreed and accepted that the work done by any ballmill depends directly upon the power input; the maximum power input into any ball or rod mill depends upon weight of grinding charge, mill speed, and liner design.

The apparent difference in capacities between grinding mills (listed as being the same size) is due to the fact that there is no uniform method of designating the size of a mill, for example: a 5 x 5 Ball Mill has a working diameter of 5 inside the liners and has 20 per cent more capacity than all other ball mills designated as 5 x 5 where the shell is 5 inside diameter and the working diameter is only 48 with the liners in place.

Ball-Rod Mills, based on 4 liners and capacity varying as 2.6 power of mill diameter, on the 5 size give 20 per cent increased capacity; on the 4 size, 25 per cent; and on the 3 size, 28 per cent. This fact should be carefully kept in mind when determining the capacity of a Steel- Head Ball-Rod Mill, as this unit can carry a greater ball or rod charge and has potentially higher capacity in a given size when the full ball or rod charge is carried.

A mill shorter in length may be used if the grinding problem indicates a definite power input. This allows the alternative of greater capacity at a later date or a considerable saving in first cost with a shorter mill, if reserve capacity is not desired. The capacities of Ball-Rod Mills are considerably higher than many other types because the diameters are measured inside the liners.

The correct grinding mill depends so much upon the particular ore being treated and the product desired, that a mill must have maximum flexibility in length, type of grinding medium, type of discharge, and speed.With the Ball-Rod Mill it is possible to build this unit in exact accordance with your requirements, as illustrated.

To best serve your needs, the Trunnion can be furnished with small (standard), medium, or large diameter opening for each type of discharge. The sketch shows diagrammatic arrangements of the four different types of discharge for each size of trunnion opening, and peripheral discharge is described later.

Ball-Rod Mills of the grate discharge type are made by adding the improved type of grates to a standard Ball-Rod Mill. These grates are bolted to the discharge head in much the same manner as the standard headliners.

The grates are of alloy steel and are cast integral with the lifter bars which are essential to the efficient operation of this type of ball or rod mill. These lifter bars have a similar action to a pump:i. e., in lifting the product so as to discharge quickly through the mill trunnion.

These Discharge Grates also incorporate as an integral part, a liner between the lifters and steel head of the ball mill to prevent wear of the mill head. By combining these parts into a single casting, repairs and maintenance are greatly simplified. The center of the grate discharge end of this mill is open to permit adding of balls or for adding water to the mill through the discharge end.

Instead of being constructed of bars cast into a frame, Grates are cast entire and have cored holes which widen toward the outside of the mill similar to the taper in grizzly bars. The grate type discharge is illustrated.

The peripheral discharge type of Ball-Rod Mill is a modification of the grate type, and is recommended where a free gravity discharge is desired. It is particularly applicable when production of too many fine particles is detrimental and a quick pass through the mill is desired, and for dry grinding.

The drawings show the arrangement of the peripheral discharge. The discharge consists of openings in the shell into which bushings with holes of the desired size are inserted. On the outside of the mill, flanges are used to attach a stationary discharge hopper to prevent pulp splash or too much dust.

The mill may be operated either as a peripheral discharge or a combination or peripheral and trunnion discharge unit, depending on the desired operating conditions. If at any time the peripheral discharge is undesirable, plugs inserted into the bushings will convert the mill to a trunnion discharge type mill.

Unless otherwise specified, a hard iron liner is furnished. This liner is made of the best grade white iron and is most serviceable for the smaller size mills where large balls are not used. Hard iron liners have a much lower first cost.

Electric steel, although more expensive than hard iron, has advantage of minimum breakage and allows final wear to thinner section. Steel liners are recommended when the mills are for export or where the source of liner replacement is at a considerable distance.

Molychrome steel has longer wearing qualities and greater strength than hard iron. Breakage is not so apt to occur during shipment, and any size ball can be charged into a mill equipped with molychrome liners.

Manganese liners for Ball-Rod Mills are the world famous AMSCO Brand, and are the best obtainable. The first cost is the highest, but in most cases the cost per ton of ore ground is the lowest. These liners contain 12 to 14% manganese.

The feed and discharge trunnions are provided with cast iron or white iron throat liners. As these parts are not subjected to impact and must only withstand abrasion, alloys are not commonly used but can be supplied.

Gears for Ball-Rod Mills drives are furnished as standard on the discharge end of the mill where they are out of the way of the classifier return, scoop feeder, or original feed. Due to convertible type construction the mills can be furnished with gears on the feed end. Gear drives are available in two alternative combinations, which are:

All pinions are properly bored, key-seated, and pressed onto the steel countershaft, which is oversize and properly keyseated for the pinion and drive pulleys or sheaves. The countershaft operates on high grade, heavy duty, nickel babbitt bearings.

Any type of drive can be furnished for Ball-Rod Mills in accordance with your requirements. Belt drives are available with pulleys either plain or equipped with friction clutch. Various V- Rope combinations can also be supplied.

The most economical drive to use up to 50 H. P., is a high starting torque motor connected to the pinion shaft by means of a flat or V-Rope drive. For larger size motors the wound rotor (slip ring) is recommended due to its low current requirement in starting up the ball mill.

Should you be operating your own power plant or have D. C. current, please specify so that there will be no confusion as to motor characteristics. If switches are to be supplied, exact voltage to be used should be given.

Even though many ores require fine grinding for maximum recovery, most ores liberate a large percentage of the minerals during the first pass through the grinding unit. Thus, if the free minerals can be immediately removed from the ball mill classifier circuit, there is little chance for overgrinding.

This is actually what has happened wherever Mineral Jigs or Unit Flotation Cells have been installed in the ball mill classifier circuit. With the installation of one or both of these machines between the ball mill and classifier, as high as 70 per cent of the free gold and sulphide minerals can be immediately removed, thus reducing grinding costs and improving over-all recovery. The advantage of this method lies in the fact that heavy and usually valuable minerals, which otherwise would be ground finer because of their faster settling in the classifier and consequent return to the grinding mill, are removed from the circuit as soon as freed. This applies particularly to gold and lead ores.

Ball-Rod Mills have heavy rolled steel plate shells which are arc welded inside and outside to the steel heads or to rolled steel flanges, depending upon the type of mill. The double welding not only gives increased structural strength, but eliminates any possibility of leakage.

Where a single or double flanged shell is used, the faces are accurately machined and drilled to template to insure perfect fit and alignment with the holes in the head. These flanges are machined with male and female joints which take the shearing stresses off the bolts.

The Ball-Rod Mill Heads are oversize in section, heavily ribbed and are cast from electric furnace steel which has a strength of approximately four times that of cast iron. The head and trunnion bearings are designed to support a mill with length double its diameter. This extra strength, besides eliminating the possibility of head breakage or other structural failure (either while in transit or while in service), imparts to Ball-Rod Mills a flexibility heretofore lacking in grinding mills. Also, for instance, if you have a 5 x 5 mill, you can add another 5 shell length and thus get double the original capacity; or any length required up to a maximum of 12 total length.

On Type A mills the steel heads are double welded to the rolled steel shell. On type B and other flanged type mills the heads are machined with male and female joints to match the shell flanges, thus taking the shearing stresses from the heavy machine bolts which connect the shell flanges to the heads.

The manhole cover is protected from wear by heavy liners. An extended lip is provided for loosening the door with a crow-bar, and lifting handles are also provided. The manhole door is furnished with suitable gaskets to prevent leakage.

The mill trunnions are carried on heavy babbitt bearings which provide ample surface to insure low bearing pressure. If at any time the normal length is doubled to obtain increased capacity, these large trunnion bearings will easily support the additional load. Trunnion bearings are of the rigid type, as the perfect alignment of the trunnion surface on Ball-Rod Mills eliminates any need for the more expensive self-aligning type of bearing.

The cap on the upper half of the trunnion bearing is provided with a shroud which extends over the drip flange of the trunnion and effectively prevents the entrance of dirt or grit. The bearing has a large space for wool waste and lubricant and this is easily accessible through a large opening which is covered to prevent dirt from getting into the bearing.Ball and socket bearings can be furnished.

Scoop Feeders for Ball-Rod Mills are made in various radius sizes. Standard scoops are made of cast iron and for the 3 size a 13 or 19 feeder is supplied, for the 4 size a 30 or 36, for the 5 a 36 or 42, and for the 6 a 42 or 48 feeder. Welded steel scoop feeders can, however, be supplied in any radius.

The correct size of feeder depends upon the size of the classifier, and the smallest feeder should be used which will permit gravity flow for closed circuit grinding between classifier and the ball or rod mill. All feeders are built with a removable wearing lip which can be easily replaced and are designed to give minimum scoop wear.

A combination drum and scoop feeder can be supplied if necessary. This feeder is made of heavy steel plate and strongly welded. These drum-scoop feeders are available in the same sizes as the cast iron feeders but can be built in any radius. Scoop liners can be furnished.

The trunnions on Ball-Rod Mills are flanged and carefully machined so that scoops are held in place by large machine bolts and not cap screws or stud bolts. The feed trunnion flange is machined with a shoulder for insuring a proper fit for the feed scoop, and the weight of the scoop is carried on this shoulder so that all strain is removed from the bolts which hold the scoop.

High carbon steel rods are recommended, hot rolled, hot sawed or sheared, to a length of 2 less than actual length of mill taken inside the liners. The initial rod charge is generally a mixture ranging from 1.5 to 3 in diameter. During operation, rod make-up is generally the maximum size. The weights per lineal foot of rods of various diameters are approximately: 1.5 to 6 lbs.; 2-10.7 lbs.; 2.5-16.7 lbs.; and 3-24 lbs.

Forged from the best high carbon manganese steel, they are of the finest quality which can be produced and give long, satisfactory service. Data on ball charges for Ball-Rod Mills are listed in Table 5. Further information regarding grinding balls is included in Table 6.

Rod Mills has a very define and narrow discharge product size range. Feeding a Rod Mill finer rocks will greatly impact its tonnage while not significantly affect its discharge product sizes. The 3.5 diameter rod of a mill, can only grind so fine.

Crushers are well understood by most. Rod and Ball Mills not so much however as their size reduction actions are hidden in the tube (mill). As for Rod Mills, the image above best expresses what is going on inside. As rocks is feed into the mill, they are crushed (pinched) by the weight of its 3.5 x 16 rods at one end while the smaller particles migrate towards the discharge end and get slightly abraded (as in a Ball Mill) on the way there.

We haveSmall Ball Mills for sale coming in at very good prices. These ball mills are relatively small, bearing mounted on a steel frame. All ball mills are sold with motor, gears, steel liners and optional grinding media charge/load.

Ball Mills or Rod Mills in a complete range of sizes up to 10 diameter x20 long, offer features of operation and convertibility to meet your exactneeds. They may be used for pulverizing and either wet or dry grindingsystems. Mills are available in both light-duty and heavy-duty constructionto meet your specific requirements.

All Mills feature electric cast steel heads and heavy rolled steelplate shells. Self-aligning main trunnion bearings on large mills are sealedand internally flood-lubricated. Replaceable mill trunnions. Pinion shaftbearings are self-aligning, roller bearing type, enclosed in dust-tightcarrier. Adjustable, single-unit soleplate under trunnion and drive pinionsfor perfect, permanent gear alignment.

Ball Mills can be supplied with either ceramic or rubber linings for wet or dry grinding, for continuous or batch type operation, in sizes from 15 x 21 to 8 x 12. High density ceramic linings of uniform hardness male possible thinner linings and greater and more effective grinding volume. Mills are shipped with liners installed.

Complete laboratory testing service, mill and air classifier engineering and proven equipment make possible a single source for your complete dry-grinding mill installation. Units available with air swept design and centrifugal classifiers or with elevators and mechanical type air classifiers. All sizes and capacities of units. Laboratory-size air classifier also available.

A special purpose batch mill designed especially for grinding and mixing involving acids and corrosive materials. No corners mean easy cleaning and choice of rubber or ceramic linings make it corrosion resistant. Shape of mill and ball segregation gives preferential grinding action for grinding and mixing of pigments and catalysts. Made in 2, 3 and 4 diameter grinding drums.

Nowadays grinding mills are almost extensively used for comminution of materials ranging from 5 mm to 40 mm (3/161 5/8) down to varying product sizes. They have vast applications within different branches of industry such as for example the ore dressing, cement, lime, porcelain and chemical industries and can be designed for continuous as well as batch grinding.

Ball mills can be used for coarse grinding as described for the rod mill. They will, however, in that application produce more fines and tramp oversize and will in any case necessitate installation of effective classification.If finer grinding is wanted two or three stage grinding is advisable as for instant primary rod mill with 75100 mm (34) rods, secondary ball mill with 2540 mm(11) balls and possibly tertiary ball mill with 20 mm () balls or cylpebs.To obtain a close size distribution in the fine range the specific surface of the grinding media should be as high as possible. Thus as small balls as possible should be used in each stage.

The principal field of rod mill usage is the preparation of products in the 5 mm0.4 mm (4 mesh to 35 mesh) range. It may sometimes be recommended also for finer grinding. Within these limits a rod mill is usually superior to and more efficient than a ball mill. The basic principle for rod grinding is reduction by line contact between rods extending the full length of the mill, resulting in selective grinding carried out on the largest particle sizes. This results in a minimum production of extreme fines or slimes and more effective grinding work as compared with a ball mill. One stage rod mill grinding is therefore suitable for preparation of feed to gravimetric ore dressing methods, certain flotation processes with slime problems and magnetic cobbing. Rod mills are frequently used as primary mills to produce suitable feed to the second grinding stage. Rod mills have usually a length/diameter ratio of at least 1.4.

Tube mills are in principle to be considered as ball mills, the basic difference being that the length/diameter ratio is greater (35). They are commonly used for surface cleaning or scrubbing action and fine grinding in open circuit.

In some cases it is suitable to use screened fractions of the material as grinding media. Such mills are usually called pebble mills, but the working principle is the same as for ball mills. As the power input is approximately directly proportional to the volume weight of the grinding media, the power input for pebble mills is correspondingly smaller than for a ball mill.

A dry process requires usually dry grinding. If the feed is wet and sticky, it is often necessary to lower the moisture content below 1 %. Grinding in front of wet processes can be done wet or dry. In dry grinding the energy consumption is higher, but the wear of linings and charge is less than for wet grinding, especially when treating highly abrasive and corrosive material. When comparing the economy of wet and dry grinding, the different costs for the entire process must be considered.

An increase in the mill speed will give a directly proportional increase in mill power but there seems to be a square proportional increase in the wear. Rod mills generally operate within the range of 6075 % of critical speed in order to avoid excessive wear and tangled rods. Ball and pebble mills are usually operated at 7085 % of critical speed. For dry grinding the speed is usually somewhat lower.

The mill lining can be made of rubber or different types of steel (manganese or Ni-hard) with liner types according to the customers requirements. For special applications we can also supply porcelain, basalt and other linings.

The mill power is approximately directly proportional to the charge volume within the normal range. When calculating a mill 40 % charge volume is generally used. In pebble and ball mills quite often charge volumes close to 50 % are used. In a pebble mill the pebble consumption ranges from 315 % and the charge has to be controlled automatically to maintain uniform power consumption.

In all cases the net energy consumption per ton (kWh/ton) must be known either from previous experience or laboratory tests before mill size can be determined. The required mill net power P kW ( = ton/hX kWh/ton) is obtained from

Trunnions of S.G. iron or steel castings with machined flange and bearing seat incl. device for dismantling the bearings. For smaller mills the heads and trunnions are sometimes made in grey cast iron.

The mills can be used either for dry or wet, rod or ball grinding. By using a separate attachment the discharge end can be changed so that the mills can be used for peripheral instead of overflow discharge.

gold processing,extraction,smelting plant design, equipment for sale | prominer (shanghai) mining technology co.,ltd

gold processing,extraction,smelting plant design, equipment for sale | prominer (shanghai) mining technology co.,ltd

Prominer maintains a team of senior gold processing engineers with expertise and global experience. These gold professionals are specifically in gold processing through various beneficiation technologies, for gold ore of different characteristics, such as flotation, cyanide leaching, gravity separation, etc., to achieve the processing plant of optimal and cost-efficient process designs.

Based on abundant experiences on gold mining project, Prominer helps clients to get higher yield & recovery rate with lower running cost and pays more attention on environmental protection. Prominer supplies customized solution for different types of gold ore. General processing technologies for gold ore are summarized as below:

For alluvial gold, also called sand gold, gravel gold, placer gold or river gold, gravity separation is suitable. This type of gold contains mainly free gold blended with the sand. Under this circumstance, the technology is to wash away the mud and sieve out the big size stone first with the trommel screen, and then using centrifugal concentrator, shaking table as well as gold carpet to separate the free gold from the stone sands.

CIL is mainly for processing the oxide type gold ore if the recovery rate is not high or much gold is still left by using otation and/ or gravity circuits. Slurry, containing uncovered gold from primary circuits, is pumped directly to the thickener to adjust the slurry density. Then it is pumped to leaching plant and dissolved in aerated sodium cyanide solution. The solubilized gold is simultaneously adsorbed directly into coarse granules of activated carbon, and it is called Carbon-In-Leaching process (CIL).

Heap leaching is always the first choice to process low grade ore easy to leaching. Based on the leaching test, the gold ore will be crushed to the determined particle size and then sent to the dump area. If the content of clay and solid is high, to improve the leaching efficiency, the agglomeration shall be considered. By using the cement, lime and cyanide solution, the small particles would be stuck to big lumps. It makes the cyanide solution much easier penetrating and heap more stable. After sufficient leaching, the pregnant solution will be pumped to the carbon adsorption column for catching the free gold. The barren liquid will be pumped to the cyanide solution pond for recycle usage.

The loaded carbon is treated at high temperature to elute the adsorbed gold into the solution once again. The gold-rich eluate is fed into an electrowinning circuit where gold and other metals are plated onto cathodes of steel wool. The loaded steel wool is pretreated by calcination before mixing with uxes and melting. Finally, the melt is poured into a cascade of molds where gold is separated from the slag to gold bullion.

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.

home - mt baker mining and metals

home - mt baker mining and metals

In the USA, Mt. Baker Mining and Metals (MBMM) builds high quality, robust, industrial machines used across many industries. Select an industry below to learn more about how our products can help you with your projects.

We bought a turn-key ore processing system that included a hammer mill. The equipment did exactly what it was promoted to do and more. The combination of the jaw crusher with the hammer mill and shaker table did has good if not better than it was advertised by MBMM. I Read More

We have an MBMM 24 x 16 HD turnkey-scrap metal processor. We primarily process 6-8lb motor stators, smaller transformers and radiator ends to separate out the clean copper. We run this hard day after day and are very happy with how it performs and the on-going support from MBMM. This Read More

As a countertop fabricator, stone waste from the edges of the slabs is a constant headache and expense to deal with. We dispose of 5,000 lbs of cut-offs a day and the dumpster fees for disposal was getting out of hand. We purchased a crusher system from MBMM and have Read More

This customer reports they process mostlyPC boards populated with components and sell the concentrated mix of copper, base metals and precious metals to a copper refinery in Poland. Read More

The crusher (16 x 24 Jaw Crusher Module) is great! I probably have 300 hours on it and we are in the process of swapping around jaw plates. I am very impressed with your product and would have no hesitation in recommending you guys. Read More

ekcp

ekcp

EIMCO-K.C.P. Spiral Classifiers is art of separating the solid particles in a mixture of solids and liquid into fractions according to particle size or density by methods other than screening. In general, the products resulting are (1) a partially drained fraction containing the coarse material (called the underflow) and (2) a fine fraction along with the remaining portion of the liquid medium (called the overflow). The classifying operation is carried out in a pool of fluid pulp confined in a tank arranged to allow the coarse solids to settle out, whereupon they are removed by gravity, mechanical means, or induced pressure. Solids which do not settle report as overflow. EIMCO-K.C.P. Spiral Classifiers are mechanically the devices are powerfully built, and functionally they are versatile and flexible. Todays worldwide acceptance of EIMCO-K.C.P. Classifiers for washing and dewatering pulps, and in closed-circuit grinding is the result of many years of experience in solving wet classification problems. Because users needs vary so greatly, the Classifier is available in a wide range of spiral diameters and pitches, tank shapes and lengths allowing exact compliance with each users classification requirements. Spiral diameters (0.3 m to 2.25 m): Important in establishing a correct balance between overflow and raking capacity. Bears directly on accuracy of separation and control of agitation. Spiral pitches (single / double / triple): Number of ribbons is a factor in controlling degree of agitation. Each ribbon of advanced pitch gives greater raking capacity than equivalent ribbon of spiral using lesser pitch. Triple ribbon spiral highly advantageous for slow-speed operations requiring close separations and high raking capacities. Adjustable spiral speeds: Recommended speed of operation given in peripheral MPM is an individual consideration for each ore, and is governed by size, shape and gravity of particle, angle of repose of raking load and desired mesh of separation. Peripheral speeds between 6 and 60 meters per minute are available. Pool depth: Choice of pool depth is directly related to effectiveness of pool area. Series 90 units are employed for coarse separations on down to 212 micron (65 mesh); Series 125 units are employed for separations between 300 and 106 micron (48 and 150 mesh); Series 150 units are employed for separations of 150 micron (100 mesh) and finer. Lifting device: Lifting device eliminates necessity of draining tank during shutdowns. Classifier may be quickly put in operation after shutdown with tank fully sanded. Hydraulic-type standard on all units 1.2 m in diameter and larger. Fast action hand wheel-operated screw- type lift standard on 1.05 m and smaller.

The EIMCO-K.C.P. equipment product line consists of Liquid Solid Separation products for the Mining, Mineral & Metallurgical Process, Chemical Process, Food Process, Refinery, Pulp and Paper, Power Plant, FGD System, Municipal & Industrial Waste and Water Treatment and with a wide range of related services.

settling rate - an overview | sciencedirect topics

settling rate - an overview | sciencedirect topics

The spin settling rate test determines the impact of the g-forces on the separation. This test is normally conducted in a bench-top test tube spinner that can produce up to 1000 Gs. The critical time is a 90-s spin for separation. If there is good separation (and this is subjective) at 90s, then pilot testing would be recommended.

In summary, the centrifugal testing, along with pressure and vacuum testing, will narrow down the technology choices. Other process and project parameters, as previously discussed, will further dial down the process separation decision.

Although not every chemical engineering process utilizes solidliquid separation, many of them do. Examples where solidliquid separators are used consist of polymer production, waste treatment facilities, water purification, lubrication oil production, production of oil from oil sands, and removal of color bodies. While there are many different kinds of solidliquid separation equipment, a centrifuge has been used here to illustrate how Eq. (2.1) can be used in scaling up solidliquid separation equipment.

When considering this equation as it relates to a centrifuge, it should be realized that the detailed design of the centrifuge may be much more complicated than shown by this analysis. The detailed analysis can best be performed by the centrifuge supplier and his engineering staff. They will use proprietary correlations that are likely not available in the open literature. However, it will be helpful for the engineers from the Engineering and Construction and/or Operating Company to understand some of the basic concepts of centrifuge scale-up. The concept of working with the suppliers engineers is covered in Chapter7.

As indicated in the aforementioned definition of terms if physical properties are known, the settling rate in Eq. (2.32) is based on the force of gravity alone. A centrifuge operates at a high rate of rotational speed, which creates centrifugal force that serves as an additional gravitational force, thus increasing the settling rate. The enhanced gravitational constant is often referred to as a G force. The G force is calculated by dividing the centrifugal force plus the universal gravitational constant (32.2ft/s2) by the gravitational force, that is, a G force of 10 will increase the gravitational constant and the settling velocity by a factor of 10, with all else being constant. When scaling up from a bench-scale or pilot plant size centrifuge, the diameter of the centrifuge bowl is increased to provide more settling capacity. As the diameter of the centrifuge is increased, the distance that the solids must settle is also increased. The rotational speed of the centrifuge is increased to compensate for this. This can be expressed mathematically as shown in Eqs.(2.33)(2.35).

The enhanced gravitational constant (G-force) can be expressed mathematically if the rotational speed and radius of the centrifuge are known. Eq. (2.36) shows that the settling rate based on Stokes Law is proportional to r2.

While the G force should include the gravitational force, and be represented by (r*2+g), this is often simplified by leaving out the g term, because this is a very small part of the total settling force.

Stokes Law gives settling velocities accurately if the Reynolds Number is such that the settling is in laminar flow. This is likely the case with small particles and high viscosity liquids. This scenario is often the case when a centrifuge is used to obtain adequate solidliquid separation. Other correlations are required if the settling rate is such that the flow is in the intermediate or turbulent region. However, Stokes Law is generally considered valid, because the application of centrifuges is normally for small particles and/or high viscosity liquids.

The enhanced settling factor (r2) provides a simplified technique to scale-up pilot plant data to a commercial operation. However, the scale-up requires some equivalent criteria such as similar particle diameter, similar particle morphology, similar physical properties of liquid, and similar centrifuge length-to-radius ratio. In addition, the maximum rotational velocity and maximum commercial centrifuge diameter must be known. As indicated earlier, the suppliers engineering staff will be heavily involved in this scale-up.

In practice, the effective area of the bowl appears smaller than the actual bowl size. This is also true for spiral and rake classifiers. The ratio of the effective area to the actual area is known as the areal efficiency. Fitch and Roberts [3] have determined the areal efficiencies factors of different classifiers as shown in Table13.3.

The percent areal efficiency is affected by the speed of the rake. For submerged rakes, Hitzrot and Meisel [1] determined the relation between the stroke rate and areal efficiency. Their relation is reproduced in Figure13.5, where it can be seen that the areal efficiency decreases with increasing stroke rate and therefore with agitation.

For designing the pool area of a classifier, the concept of areal efficiency is necessary. Also, it is necessary to estimate the settling forces, the size of the overflow particles, the volume flow rate of the overflow or underflow stream and the settling rate of the heavier particles. The settling rate in turn depends on the shape of the particles and any disturbance in the pool. Roberts and Fitch [4] and Fitch and Roberts [3] considered these factors and stated that the product of these factors determined the settling rate. In the case of spherical particles, the settling rate is given by

To determine the pool area A, it is assumed that the settling rate was related to the volume of water passing over the weir. The quantity of overflow liquid (water) passing over the weir in unit time will be

To apply Equation (13.8) to non-spherical particles, Fitch and Roberts [3] considered S as the settling rate of spheres under ideal conditions (that is an infinite, undisturbed volume of water) and the shape factor, PS, as the deviation of the particle shape from a sphere. The values of each parameter were determined in the following manner:

For different values of reduced Reynolds number the values of the dimensionless term S/ can be determined. Such a plot is reproduced in Figure13.6 for Reynolds numbers varying between 1 and 1000. In practice, the value of ReR is estimated and the value of S/ determined from Figure13.6. Then from a known value of the value of S is determined.

For different values of Reynolds number and shape factors (see Table13.4), the function f(Re, PS) can be calculated and plotted. Such a plot is shown in Figure13.7 using data from the work of Fitch and Roberts [3]. Thus for different values of , obtained from Equation (13.12), the hindrance factor, H, can be estimated.

A slurry containing 50% solids (quartz) is to be classified at a rate of 100 t/h at a separation size of 250 m in a rake classifier. The density of the solids is 2650kg/m3 and the size analysis is given in the table below. The water recovery to the overflow is 95% at an areal efficiency of 0.5. Estimate the pool area.Particle size (m)710355180904545Cum. mass % retained1025456075100

From the data, the feed solid is 65% minus 250 m. That is, the mass fraction of solids less than the separation size is=0.65 which is also the volume fraction assuming that all solids have the same density.

From the available data,Waterinthefeed=100(100%solids)/%solids=100(10050)/50=100t/hWaterintheoverflow=1000.95=95t/h=95,000kg/h(QVL(O))=95,000/1000=95m3/h=0.0264m3/sThus,theclassifierarea,A=0.0264/0.0034=7.76m2/100t/hfeed=7.76/100=0.077m2/t/hAlso,thesolidsintheoverflow=1000.65=65t/hAndhencethe%solidsintheoverflow=65100/(65+95)=40.6%

The sedimentation of metallurgical slimes has been studied by Coe and Clevenger(2), who concluded that a concentrated suspension may settle in one of two different ways. In the first, after an initial brief acceleration period, the interface between the clear liquid and the suspension moves downwards at a constant rate and a layer of sediment builds up at the bottom of the container. When this interface approaches the layer of sediment, its rate of fall decreases until the critical settling point is reached when a direct interface is formed between the sediment and the clear liquid. Further sedimentation then results solely from a consolidation of the sediment, with liquid being forced upwards around the solids which are then forming a loose bed with the particles in contact with one another. Since the flow area is gradually being reduced, the rate progressively diminishes. In Figure 5.1a, a stage in the sedimentation process is illustrated. A is clear liquid, B is suspension of the original concentration, C is a layer through which the concentration gradually increases, and D is sediment. The sedimentation rate remains constant until the upper interface corresponds with the top of zone C and it then falls until the critical settling point is reached when both zones B and C will have disappeared. A second and rather less common mode of sedimentation as shown in Figure 5.1b, is obtained when the range of particle size is very great. The sedimentation rate progressively decreases throughout the whole operation because there is no zone of constant composition, and zone C extends from the top interface to the layer of sediment.

If the range of particle size is not more than about 6:1, a concentrated suspension settles with a sharp interface and all the particles fall at the same velocity. This is in contrast with the behaviour of a dilute suspension, for which the rates of settling of the particles can be calculated by the methods given in Chapter 3, and where the settling velocity is greater for the large particles. The two types of settling are often referred to as sludge line settling and selective settling respectively. The overall result is that in a concentrated suspension the large particles are retarded and the small ones accelerated.

Several attempts have been made to predict the apparent settling velocity of a concentrated suspension. In 1926 Robinson(3) suggested a modification of Stokes law and used the density (c) and viscosity (c) of the suspension in place of the properties of the fluid to give:

Steinour(6), who studied the sedimentation of small uniform particles, adopted a similar approach, using the viscosity of the fluid, the density of the suspension and a function of the voidage of the suspension to take account of the character of the flow spaces, and obtained the following expression for the velocity of the particle relative to the fluid up:

In each of these cases, it is correctly assumed that the upthrust acting on the particles is determined by the density of the suspension rather than that of the fluid. The use of an effective viscosity, however, is valid only for a large particle settling in a fine suspension. For the sedimentation of uniform particles the increased drag is attributable to a steepening of the velocity gradients rather than to a change in viscosity.

The rate of sedimentation of a suspension of fine particles is difficult to predict because of the large number of factors involved. Thus, for instance, the presence of an ionised solute in the liquid and the nature of the surface of the particles will affect the degree of flocculation and hence the mean size and density of the flocs. The flocculation of a suspension is usually completed quite rapidly so that it is not possible to detect an increase in the sedimentation rate in the early stages after the formation of the suspension. Most fine suspensions flocculate readily in tap water and it is generally necessary to add a deflocculating agent to maintain the particles individually dispersed. The factors involved in flocculation are discussed later in this chapter. A further factor influencing the sedimentation rate is the degree of agitation of the suspension. Gentle stirring may produce accelerated settling if the suspension behaves as a non-Newtonian fluid in which the apparent viscosity is a function of the rate of shear. The change in apparent viscosity can probably be attributed to the re-orientation of the particles. The effect of stirring is, however, most marked on the consolidation of the final sediment, in which bridge formation by the particles can be prevented by gentle stirring. During these final stages of consolidation of the sediment, liquid is being squeezed out through a bed of particles which are gradually becoming more tightly packed.

A number of empirical equations have been obtained for the rate of sedimentation of suspensions, as a result of tests carried out in vertical tubes. For a given solid and liquid, the main factors which affect the process are the height of the suspension, the diameter of the containing vessel, and the volumetric concentration. An attempt at co-ordinating the results obtained under a variety of conditions has been made by Wallis(8).

The height of suspension does not generally affect either the rate of sedimentation or the consistency of the sediment ultimately obtained. If, however, the position of the sludge line is plotted as a function of time for two different initial heights of slurry, curves of the form shown in Figure 5.2 are obtained in which the ratio OA: OA is everywhere constant. Thus, if the curve is obtained for any one initial height, the curves can be drawn for any other height.

If the ratio of the diameter of the vessel to the diameter of the particle is greater than about 100, the walls of the container appear to have no effect on the rate of sedimentation. For smaller values, the sedimentation rate may be reduced because of the retarding influence of the walls.

As already indicated, the higher the concentration, the lower is the rate of fall of the sludge line because the greater is the upward velocity of the displaced fluid and the steeper are the velocity gradients in the fluid. Typical curves for the sedimentation of a suspension of precipitated calcium carbonate in water are shown in Figure 5.3, and in Figure 5.4 the mass rate of sedimentation (kg/m2s) is plotted against the concentration. This curve has a maximum value, corresponding to a volumetric concentration of about 2 per cent. Egolf and McCabe(9), Work and Kohler(10), and others have given empirical expressions for the rate of sedimentation at the various stages, although these are generally applicable over a narrow range of conditions and involve constants which need to be determined experimentally for each suspension.

The final consolidation of the sediment is the slowest part of the process because the displaced fluid has to flow through the small spaces between the particles. As consolidation occurs, the rate falls off because the resistance to the flow of liquid progressively increases. The porosity of the sediment is smallest at the bottom because the compressive force due to the weight of particles is greatest and because the lower portion was formed at an earlier stage in the sedimentation process. The rate of sedimentation during this period is given approximately by:

Provided that the walls of the vessel are vertical and that the cross-sectional area does not vary with depth, the shape of the vessel has little effect on the sedimentation rate. However, if parts of the walls of the vessel face downwards, as in an inclined tube, or if part of the cross-section is obstructed for a portion of the height, the effect on the sedimentation process may be considerable.

Pearce(11) studied the effect of a downward-facing surface by considering an inclined tube as shown in Figure 5.5. Starting with a suspension reaching a level AA, if the sludge line falls to a new level BB, then material will tend to settle out from the whole of the shaded area. This configuration is not stable and the system tends to adjust itself so that the sludge line takes up a new level XX, the volume corresponding to the area AAXX being equal to that corresponding to the shaded area. By applying this principle, it is seen that it is possible to obtain an accelerated rate of settling in an inclined tank by inserting a series of inclined plates. The phenomenon has been studied further by several workers including Schaflinger(12).

The effect of a non-uniform cross-section was considered by Robins(13), who studied the effect of reducing the area in part of the vessel by immersing a solid body, as shown in Figure 5.6. If the cross-sectional area, sedimentation velocity, and fractional volumetric concentration are C, uc, and A below the obstruction, and C, uc, and A at the horizontal level of the obstruction, and and are the corresponding rates of deposition of solids per unit area, then:

A plot of versus C will have the same general form as Figure 5.4 and a typical curve is given in Figure 5.7. If the concentration C is appreciably greater than the value Cm at which is a maximum, C will be less than C and the system will be stable. On the other hand, if C is less than Cm, C will be greater than C and mixing will take place because of the greater density of the upper portion of the suspension. The range of values of C for which equation 5.14 is valid in practice, and for which mixing currents are absent, may be very small.

Sedimentation methods are based on the classifying of metal powders depending on the settling rate under gravity of particles situated in a fluid. This determination is based on Stokes's law of fluid dynamics by laminar current. That states that the frictional force, Fr on a spherical particle moving through a fluid at constant velocity is proportional to the product of constant velocity, the fluid velocity, v, the fluid viscosity and the radius of the sphere, r:

To ensure accurate results, convection currents must be eliminated in the suspending fluid and the relative rate of motion between the fluid and powder particles must be slow enough to guarantee laminar flow. Usually this technique is used for the subsieve size range. These methods are applicable for sedimentation in air with limitation to particles larger 5 m and, in liquids, particle sizes down to 0.1 m can be determined. As particles size decreases, this method becomes unreliable because of the Brownian motion of the particles. The upper limit is 100 m. Particles of more than 100 m cause the display of medium inertia forces, which are not taken into account by Stokes equation. The method is not suitable if particle shape strongly differs from spherical, for powders which cannot be dispersed or for agglomerated powders.

The suspension must be dilute enough to ensure independent motion to the maximum particle concentration even to 1 vol% of particles in the suspension. Compositions of dispersion liquids used for sedimentation analysis are given in Table 1.3.

Abbreviations: WD: water distillate; Cy: cyclohexanol; Cye: cyclohexanone; EA: ethyl alcohol; NS: naphtha soap; SC: sodium carbonate; Sfa: surfactant; SPP: sodium pyrophosfate (Na4P2O710H2O); SP: sodium phosphate (Na3PO4); ST: sodium tartrate

Abbreviations: WD: water distillate; Cy: cyclohexanol; Cye: cyclohexanone; EA: ethyl alcohol; NS: naphtha soap; SC: sodium carbonate; Sfa: surfactant; SPP: sodium pyrophosfate (Na4P2O710H2O); SP: sodium phosphate (Na3PO4); ST: sodium tartrate

Among the number of sedimentation methods available, only a few are usually used for metal powders. Devices based on the method of accumulation of the deposition from the suspension that were popular in former times find an application at present too. Turbidimetry methods are widely used to determine the particle size distribution of refractory metal powders, such as tungsten and molybdenum. The micromerographs find a use to determine the particle size of subsieve metal powders.

The separability of minerals by gravity separation relies on a particles settling rate in a fluid. The terminal velocity of solid spheres settling in a fluid is described by Stokes Law for fine particles (Equation (16.3)) or Newtons Law for coarse particles (Equation (16.4)). Both these equations include particle density as well as particle size.

Stokes equation is said to apply to ideal conditions where the particle is spherical and the Reynolds number is less than 1. Newtons equation applies for Reynolds numbers>1000. For particles of quartz in water, this represents an upper size limit of around 110m for Stokes Law and a lower limit of around 3.5mm for Newtons Law. Thus for particles of quartz between 110 m and 3.5mm neither equation accurately describes the settling rate of objects and this size range represents a major size range of interest in gravity separation. A number of researchers have developed empirical correlations to fill this size gap. Dietrich [3] derived a correlation from a data set of 252 values using dimensionless parameters, W* and D*, and incorporating shape and angularity factors:

Jimnez and Madsen [4] obtained values of A and B from Dietrichs data for quartz spheres from 0.06 1mm validating the equation for 0.2

Determine the settling rates for spherical particles of quartz settling in water for particles of size 38m to 16mm. The density of quartz and water are 2650 and 1000kg/m3 respectively and the viscosity of water is 0.001Pa s.

Using Equation (16.6)D*=265010009.81(0.000038)310000.0012=0.8882and from Equation (16.7), for CSF=1.0 for a sphere and P=6 for a perfect round object,R1=3.76715+1.92944(log0.8882)0.09815(log0.8882)20.00575(log0.8882)3+0.00056(log0.8882)4=3.8668R2=log111.00.85=0R3=0.651.02.83tanhlog0.88824.61+(3.562.5=1.0

By changing the particle size from 38 m to 16mm, the following table is compiled.dN (m)T Stokes (m/s)T Newton (m/s)T Dietrich (m/s)T Jimnez (m/s)Re0.0000380.0010.04320.00130.00120.050.0000500.0020.04950.00220.00210.100.0000750.0050.06070.00460.00440.330.0001060.0100.07210.00820.00830.870.0001750.0280.09260.01820.019230.000500.2250.15660.07400.0747370.000750.5060.19180.11610.1083810.00100.8990.22150.15500.13551350.00203.5970.31320.28290.21294250.004014.3880.44290.45650.313312530.006032.3730.54250.57570.387723260.008057.5520.62640.66660.449635960.010089.9250.70040.74060.503850380.0160230.2080.88590.90730.639110225

In the fine particle range (<100 m) the Stokes settling equation and Dietrich and Jimnez correlations are similar. Above 150 m the Stokes equation starts to deviate from the Dietrich and Jimnez plots. The Newton settling line is significantly different from the other plots at this size range. At the course end of the size range, as seen above, the Jimnez correlation also deviates from the Newton and Dietrich plots.

At particle sizes above about 3mm, the Newton and Dietrich plots are still close. At this point, the Reynolds number is around 1000, the region above which Newtons Law is valid. The Dietrich correlation seems to adequately describe the transition region between the Stokes and Newtonian regimes. The Jimnez correlation deviates from the Dietrich correlation above a size of around 1mm or a Reynolds number around 135.

The separation by gravity is based on the difference in settling rates or terminal velocities of particles of different density and size. However, with short distances of travel in some separation processes, particles may not have a chance to reach their terminal velocity. How long it takes particles to reach their terminal velocity and what are the displacement distances between particles when they attain their terminal velocity could be a determining factor in the concentration of particles by gravity separation.

Table16.4 summarizes the settling velocities and distances travelled for a combination of different concentration criteria and particle sizes corresponding to the size limits shown in Table16.2. The calculations indicate that the time required for a particle to reach its terminal velocity is quite short, ranging from 0.001 to 0.4s. The lighter particles reach their terminal velocity marginally ahead of the heavier particles.

For particles of 6.35mm size, the terminal velocity is reached after about 0.4s and particles of concentration criterion (CC) 2.5 are separated by several hundred millimetres and separation of particles should be easy. The separation distance between particles decreases as the concentration criterion decreases and thus separation should become more difficult with decreasing concentration criterion.

If the particles do not reach their terminal velocities then the separation distance between particles is reduced. For example, for a particle of CC=1.25, after 0.1s of settling, the settling velocities are very close and the separation distance between the particles is 3.2mm which for particles of 6.35mm diameter is insufficient to segregate into separate layers.

For 50m particles, the terminal velocity is reached after a very short time and the distance separating particles at this point is as much as 20m for particles with a concentration criterion of 2.5. For 50m particles, this is obviously insufficient for separation to occur. As settling time is increased up to 1 s, particle separation, in free settling conditions, will increase to 3.5mm for particles with a concentration criterion of 2.5. With this separation distance between heavy and light particles, segregation, and ultimately separation, may not be possible for these sized particles. Increasing the settling time further will increase the separation distance and make separation easier. However, the fact that particles of this size are not easily separated even at this value of concentration criterion indicates that other factors such as particle shape and separator characteristics come into play.

One of the complicating factors is that particles are not a single size. In any feed there is going to be a size variation, even in a closely sized sample. Consider an elutriation column with a prepared feed of 150 +125m containing a mixture of pyrite (S.G. 5.0) and arsenopyrite (S.G. 6.1). If a rising column of water is flowing at a velocity between the settling velocities of the two minerals, then the heavier mineral will be able to sink and the lighter mineral will be lifted by the water and hence a separation of the two minerals can be made. Figure16.4 shows the effect of particle size on the settling velocity and hence the water velocity required to bring about separation.

If the water velocity is above the curve, the particle will be lifted and if the water velocity is below the curve, the particle will sink. Thus, the region between the curves represents the range of possible water flows that will separate the particles. For the 150 +125m size fraction, point D, where the lower size intersects the lower particle density curve represents the water flow rate below which all particles will sink and point C, where the large size intersects the higher particle density curve represents the water flowrate above which all particles will be lifted. Flow rates between C and D will achieve a separation of some sort with some particles being lifted and some particles sinking. Point A at the intersection of the lower size and the higher density curve and point B, the intersection of the higher size and the lower density curve, will be the boundary of the region where a complete separation is possible, but only if point A lies higher than point B. In the case of Figure16.4, where the concentration criterion is 1.275, this is not the case and there will always be some contamination of the light mineral and the heavy mineral in each product. For a smaller size fraction such as 106 +90m, the window of possible separation flow rates decreases. That is, the separation would become more difficult.

For a higher concentration criterion, such as in the separation of arsenopyrite (S.G. 6.1) from gold (S.G. 18.0), Figure16.5 shows the settling curves as a function of particle size. From this plot, for the particle size fraction of 150 +125m, point A is above point B and any flow rate within this range should produce a clean separation. But how does it work in practice?

A sample of sulphide concentrate, predominantly arsenopyrite and some pyrrhotite and free gold, was sized to 150 +125m and placed in an elutriation column at a water flow rate of 9l/min. From Figure16.5, this flow rate is at the top limit of the separation zone at which all particles should have risen with the water flow. However, a very small number of particles were recovered as a sinks product. If any particles were recovered it would be expected to be predominantly the gold particles. The gold was estimated to have a density of 18,000kg/m3 as some impurities such as silver and copper occur with native gold. However, inspecting the sinks product under a microscope revealed that it contained only about 5% gold with the bulk of the product being sulphides and iron oxides. The sizes of the particles were towards the top end of the size range.

The float fraction from the elutriation column was re-tested at a water flow rate of 7l/min which should also have produced a high grade gold product. The mass recovery was also low and contained about 50% gold and 50% sulphides and iron oxides. The gold particles tended to be flatter in shape compared to the sulphides because of the malleability of the gold metal. The flatter shape of the particles would thus give the gold the appearance of similar sized particles but would actually have a lower mass than a more rounded particle of gold of the same size. Thus, the particle shape is allowing a lighter gold particle to fall into the same size fraction as a similarly weighted sulphide particle and the equally settling particles would be extremely difficult to separate by gravity.

Increasing the acceleration on the particles by using some centrifugal device will not change the ease of separation for particles with a low concentration criterion although it will improve the separation for high concentration criteria. For example, for a concentration criterion of 1.275, the difference between point A and point B in Figure16.4 is 0.2l/min for an acceleration of 1G. The minus sign indicating that point A is below point B. By increasing the acceleration to 100G the difference becomes 2.0l/min, still negative and still a poor separation. By contrast, for a concentration criterion of 3.33, an increase in acceleration from 1 to 100 G increases the difference between point A and point B in Figure16.5 from +3.6 to +84l/min indicating a broader range of separating velocities and a greater ease of separation, particularly at finer sizes.

It is well known that gravity separation efficiency decreases as the range of sizes in the feed increases [5]. This is related to the compounding effect of size and density on the weight of particles and their subsequent movement in a gravity concentrator. Thus, a gravity feed is often divided into separate size intervals for treatment on separate gravity units such as jigs or shaking tables. What should those size range limits be?

From Figure16.5, at a water velocity, B, all particles greater than 150m would sink, while all particles less than 76m, at point B, would rise. Therefore, only particles between these sizes would have any chance of separating into light and heavy fractions. The ratio of maximum to minimum particle size, the size ratio, in this case would be 150/76=1.97. This size ratio (or free settling ratio), for any given density difference between the particles, will vary with the fluid drag on the particles. For viscous resistance (Stokes Law and small particles) the size ratio will be equal to the square root of the concentration criteria. For turbulent resistance (Newtons Law and large particles), the size ratio will be equal to the concentration criterion. Thus for a CC value of 3.33, the size ratio should range from 1.82 to 3.33, depending on the type of fluid drag (particle size). From Figure16.5, the average size ratio for water velocities from 1 to 5l/min is 1.960.03.

The size ratio should vary with the density difference between the minerals to be separated, with smaller density differences requiring a closer sized feed. The size ratio for a range of concentration criteria from 1.28 to 3.94 is shown in Figure16.6. Taggart [1] found that for operating jigs, the feed size ratio was less than the free or hindered settling ratios with an average size ratio of 1.7 (range 1.22.8) from 12 plants treating minerals with concentration criteria between 2 and 4.

Splitting a wide feed size range of, say 0.50.04mm (size ratio of 12.5), into several fractions of, say 0.5+0.25, 0.25+0.14, 0.14+0.71 and 0.071+0.04mm (size ratios 1.9), an improvement in concentrate grade and recovery is frequently observed.

At fine particle sizes, separation by density difference under gravity becomes less efficient. At this size range flotation is the dominant separation process, although the application of centrifugal acceleration has extended the useful separation size by gravity processes down to 510m, provided the concentration criterion is favourable.

If we consider first only equal spherical particles, diameter d, the differential settling rate is zero and the ratio of the orthokinetic and perikinetic rate coefficients can be calculated from Eqs. (4) and (5):

For a shear rate of 10 s1 (corresponding to quite mild agitation), the collision rate coefficients are equal when the particle diameter is about 1 m. For higher shear rates and, especially, for larger particles, the orthokinetic rate becomes very much larger.

The rate coefficients for the three collision mechanisms described above are compared in Fig. 3. The rate coefficients have been calculated for collisions between a particle of diameter of 2 m and a second particle with diameter varying from 0.01 m to 30 m. The shear rate, G, is assumed to be 50 s1 and the particle density 2 g cm3. The fluid is assumed to be water at 25C. There are several important features of these results:

The perikinetic rate passes through a minimum when the particle diameters are equal. Around the minimum, the rate coefficient is approximately independent of particle size, as in Eq. (3). However, when the sizes differ significantly the rate coefficient can be greater than the constant value by an order of magnitude or more.

The differential settling rate is zero for equal particles, because they both settle at the same speed and do not collide. However, when the second particle is larger than about 2 m this mechanism becomes very important.

Of course, these conclusions would be modified if different values for the fixed particle diameter, density and shear rate were chosen. However, it can be reasonably assumed that, for particles larger than a few m in agitated suspensions, the perikinetic collision rate will be negligibly small.

Centrifugal separation can be regarded as an extension of gravity separation, as the settling rates of particles are increased under the influence of centrifugal force. It can, however, be used to separate emulsions which are normally stable in a gravity field.

Centrifugal separation can be performed either by hydrocyclones or centrifuges. The simplicity and cheapness of the hydrocyclone (Chapter 9) make it very attractive, although it suffers from restrictions with respect to the solids concentration that can be achieved and the relative proportions of overflow and underflow into which the feed may be split. Generally, the efficiency of even a small-diameter hydrocyclone falls off rapidly at very fine particle sizes and particles smaller than about 10m in diameter will invariably appear in the overflow, unless they have high density. Flocculation of such particles is limited, since the high shear forces due to the cyclonic action break up the agglomerates. The hydrocyclone is therefore inherently better suited to classification rather than thickening. Its dry counterpart, the (air) cyclone, is widely used for dust removal in a variety of industrial applications.

By comparison, centrifuges are much more costly and complex, but have a much greater clarifying power and are generally more flexible than hydrocyclones. Various types of centrifuge are used industrially (Bragg, 1983; Bershad et al., 1990; Leung, 2002), the solid bowl centrifuge (or decanter) having widest use in the minerals industry due to its versatility and ability to discharge the solids continuously.

The basic principles of a typical centrifuge are shown in Figure 15.16. It consists of a horizontal revolving shell or bowl, cylindroconical in form, inside which a screw conveyor of similar section rotates in the same direction at a slightly higher or lower speed. The feed pulp is admitted to the bowl through the center tube of the revolving-screw conveyor. On leaving the feed pipe, the slurry is immediately subjected to a high centrifugal force, causing the solids to settle on the inner surface of the bowl at a rate which depends on the rotational speed employed, this normally being between 1,600 and 8,500revmin1. The separated solids are conveyed by the scroll out of the liquid and discharged through outlets at the smaller end of the bowl. The solids are continuously dewatered by centrifugal force as they proceed from the liquid zone to the discharge. Excess entrained liquor drains away to the pond circumferentially through the particle bed. When the liquid reaches a predetermined level, it overflows through the discharge ports at the larger end of the bowl.

The actual size and geometry of these centrifuges vary according to the throughput required and the application. The length of the cylindrical section largely determines the clarifying power and is thus made a maximum where overflow clarity is of prime importance. The length of the conical section, or beach, decides the residual moisture content of the solids, so that a long shallow cone is used where maximum dryness is required.

Centrifuges are manufactured with bowl diameters ranging from 15 to 150cm, the length generally being about twice the diameter. Throughputs vary from about 0.5 to 50m3h1 of liquid and from about 0.25 to 100th1 of solids, depending on the feed concentration, which may vary widely from 0.5% to 70% solids, and on the particle size, which may range from about 12mm to as fine as 2m, or even less when flocculation is used. The application of flocculation is limited by the tendency of the scroll action to damage the flocs and thus redisperse the fine particles. The moisture content in the product varies widely, typically being in the range 520%.

Hydraulic classification of powders is based on the difference in the different size particle settling rates in a liquid medium in a gravitational field. Fig. 14.28 illustrates the relationship between the size of the spherical particles and their settling velocity. In contrast to air classification where, to prevent cohesion of particles a low concentration of particles 0.0030.3vol% in the gaseous medium is maintained, hydraulic classification can be performed under much higher solids concentrations. In fact, classification is fulfilled typically in the range 3040vol% in a wet closed circuit grinding processes. The hydraulic classification process is normally performed with a cut size in the range of 2001m.

Two principles are used: (i) separation in the flow, the direction of which coincides with that of the main active forces or oppositely directed, and (ii) separation in the flow directed angularly to them. The first principle is used by gravity classifiers, the second one by centrifugal classifiers (with separation in the field of centrifugal forces). Table 14.8 lists the major types of hydraulic classifiers that are useful for wet powder metallurgy processing.

Gravity settling reservoirs represent the simplest type of hydraulic classifier. Except for the hydroseparator, which is a modification of gravity thickeners, most gravity settling reservoirs are used for coarse size particle separation. The gravity classifier is used for separation of off-sized fractions from water-atomized powders. A classifier having a siphon unloading in comparison with a bottom outlet ensures a higher accuracy of classification (Fig. 14.29). The classifier comprises a cylindrical tank; the pulp is fed through a branch pipe and the discharge drains into a concentric overflow chute. Water is also fed from the bottom via a tube to produce a suspended layer of particles. Coarse particles reaching the lower part of the tank are removed by siphons. The suspension flow rate is adjusted by valves connected to pressure pipes. The latter are sensors of the pulp density in the medium part of the tank. At the start of the classifier work, the siphons are actuated by water supply to their lower part via pipes.

Hydrocyclones are extremely simple equipment with no moving parts except for rare modifications. The typical hydrocyclones are shown in the subsection Dehydration, in this chapter, where their use as thickeners is described. The applications of hydrocyclones for classification by size of water-atomized aluminum alloy powders are described in Chapter 16.

Hydrocyclones are manufactured in the size range 101200mm in the diameter of the cylindrical part Dc (see Fig. 14.2). Because the throughput of the hydrocyclone is reduced in proportion to the square of the unit size, very small cyclones are frequently fabricated in the form of batteries. Based on consideration of fluid mechanical efficiency, the optimum parameters of the hydrocyclones have been derived [15] as follows:

In the centrifuge, in contrast to hydrocyclones, a forced vortex prevails, which is characterized by constant angular velocity over the whole radius of the slurry pool in which centrifugal settling of particles occurs. Centrifugal classifiers are commonly classified into two types of designs: solid bowl and disc (or de Laval type). According to the design features, solid bowl centrifuges can achieve coarse to ultrafine separation while disc centrifuges are intended basically for very fine separation. The typical separation size ranges from 5 to 200m and from 0.2 to 10m, respectively.

Hydraulic classification of powders is based on the difference in the different size particle settling rates in a liquid medium in a gravitational field. Figure 11.27 illustrates the relationship between the size of the spherical particles and their settling velocity. In contrast to air classification where to prevent cohesion of particles a low concentration of particles 0.0030.3 vol% in the gaseous medium is maintained, hydraulic classification can be performed under much higher solids concentrations. In fact, classification is fulfilled typically in the range 3040 vol% in wet closed circuit grinding processes. The hydraulic classification process is normally performed with a cut size between 200 and 1 m.

Two principles are used: (i) separation in the flow, direction of which coincides with that of main active forces (or in countercurrent action), and (ii) separation in the flow directed angularly to the latter.

The first principle is used by gravity classifiers, the second one by centrifugal classifiers (with separation in the field of centrifugal forces). Table 11.8 lists major types of hydraulic classifiers that are useful for wet powder metallurgy processing.

Gravity settling reservoirs represent the simplest type of hydraulic classifier. Except for the hydro-separator, which is a modification of gravity thickeners, most gravity settling reservoirs are used for coarse size particle separation.

The gravity classifier is used for separation of off-size fractions from water-atomized powders. A classifier having a siphon unloading in comparison with bottom outlet ensures higher accuracy of classification (Figure 11.28). The classifier comprises a cylindrical tank; the pulp is fed through a branch pipe and the discharge drains into a concentric overflow chute. Water is also fed from the bottom via a tube to produce a suspended layer of particles. Coarse particles reaching the lower part of the tank are removed by siphons. The suspension flow rate is adjusted by valves connected to pressure pipes. The latter are sensors of the pulp density in the medium part of the tank. At the start of the classifier work, the siphons are actuated by water supply to their lower part via pipes.

Spiral classifiers are used for the discharge of the coarse particles in the feed pulp settled out from the pool in the reservoir, in which the spiral is partly submerged in the pool, while the fine particles overflow from the lip of the reservoir.

Hydrocyclones are extremely simple equipment with no moving parts except for rare modifications. The typical hydrocyclones are shown in the subsection Dehydration in this chapter, where their use as thickeners is described. The applications of hydrocyclones for classification by size of water-atomized aluminum alloy powders are described in Chapter 13.

Hydrocyclones are manufactured in the size range 101200 mm in the diameter of the cylindrical part Dc (see Figure 11.2). Because the throughput of the hydrocyclone is reduced in proportion to the squareof the unit size, very small cyclones are frequently fabricated in the form of batteries.

In the centrifuge, in contrast to hydrocyclones, a forced vortex prevails, which is characterized by constant angular velocity over the whole radius of the slurry pool in which centrifugal settling of particles occurs. Centrifugal classifiers are commonly classified into two types of designs: solid bowl and disc (or de Laval type). According to the design features, solid bowl centrifuges can achieve coarse to ultrafine separation, while disc centrifuges are intended basically for very fine separation. The typical separation size ranges from 5 to 200 m and from 0.2 to 10 m, respectively.

spiral classifier for mineral processing

spiral classifier for mineral processing

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.

what's the difference between sag mill and ball mill - jxsc machine

what's the difference between sag mill and ball mill - jxsc machine

A mill is a grinder used to grind and blend solid or hard materials into smaller pieces by means of shear, impact and compression methods. Grinding mill machine is an essential part of many industrial processes, there are mainly five types of mills to cover more than 90% materials size-reduction applications.

Do you the difference between the ball mill, rod mills, SAG mill, tube mill, pebble mill? In the previous article, I made a comparison of ball mill and rod mill. Today, we will learn about the difference between SAG mill vs ball mill.

AG/SAG is short for autogenous mill and semi-autogenous mill, it combines with two functions of crushing and grinding, uses the ground material itself as the grinding media, through the mutual impact and grinding action to gradually reduce the material size. SAG mill is usually used to grind large pieces into small pieces, especially for the pre-processing of grinding circuits, thus also known as primary stage grinding machine. Based on the high throughput and coarse grind, AG mills produce coarse grinds often classify mill discharge with screens and trommel. SAG mills grinding media includes some large and hard rocks, filled rate of 9% 20%. SAG mill grind ores through impact, attrition, abrasion forces. In practice, for a given ore and equal processing conditions, the AG milling has a finer grind than SAG mills.

The working principle of the self-grinding machine is basically the same as the ball mill, the biggest difference is that the sag grinding machine uses the crushed material inside the cylinder as the grinding medium, the material constantly impacts and grinding to gradually pulverize. Sometimes, in order to improve the processing capacity of the mill, a small amount of steel balls be added appropriately, usually occupying 2-3% of the volume of the mill (that is semi-autogenous grinding).

High capacity Ability to grind multiple types of ore in various circuit configurations, reduces the complexity of maintenance and coordination. Compared with the traditional tumbling mill, the autogenous mill reduces the consumption of lining plates and grinding media, thus have a lower operation cost. The self-grinding machine can grind the material to 0.074mm in one time, and its content accounts for 20% ~ 50% of the total amount of the product. Grinding ratio can reach 4000 ~ 5000, more than ten times higher than ball, rod mill.

Ball mills are fine grinders, have horizontal ball mill and vertical ball mill, their cylinders are partially filled with steel balls, manganese balls, or ceramic balls. The material is ground to the required fineness by rotating the cylinder causing friction and impact. The internal machinery of the ball mill grinds the material into powder and continues to rotate if extremely high precision and precision is required.

The ball mill can be applied in the cement production plants, mineral processing plants and where the fine grinding of raw material is required. From the volume, the ball mill divide into industrial ball mill and laboratory use the small ball mill, sample grinding test. In addition, these mills also play an important role in cold welding, alloy production, and thermal power plant power production.

The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mills crushing ratio is smaller. The feed size is usually between 20-30mm and the product size is 0-3mm.

Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear-resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small.

The feed of the ball mill contains grinding balls. In order to effectively reduce the direct impact of materials on the ball mill feed bushing and improve the service life of the ball mill feed bushing, the feeding point of the groove in the feeding part of the ball mill must be as close to the side of the mill barrel as possible. And because the ball mill feed grain size is larger, ball mill feeding groove must have a larger slope and height, so that feed smooth.

Since the power of the autogenous tumbling mill is relatively small, it is appropriate to choose dynamic and static pressure bearing. The ball bearing liner is made of lead-based bearing alloy, and the back of the bearing is formed with a waist drum to form a contact centering structure, with the advantages of flexible movement. The bearing housing is lubricated by high pressure during start-up and stop-up, and the oil film is formed by static pressure. The journal is lifted up to prevent dry friction on the sliding surface, and the starting energy moment is reduced. The bearing lining is provided with a snake-shaped cooling water pipe, which can supply cooling water when necessary to reduce the temperature of the bearing bush. The cooling water pipe is made of red copper which has certain corrosion resistance.

Ball mill power is relatively large, the appropriate choice of hydrostatic sliding bearing. The main bearing bush is lined with babbitt alloy bush, each bush has two high-pressure oil chambers, high-pressure oil has been supplied to the oil chamber before and during the operation of the mill, the high-pressure oil enters the oil chamber through the shunting motor, and the static pressure oil film is compensated automatically to ensure the same oil film thickness To provide a continuous static pressure oil film for mill operation, to ensure that the journal and the bearing Bush are completely out of contact, thus greatly reducing the mill start-up load, and can reduce the impact on the mill transmission part, but also can avoid the abrasion of the bearing Bush, the service life of the bearing Bush is prolonged. The pressure indication of the high pressure oil circuit can be used to reflect the load of the mill indirectly. When the mill stops running, the high pressure oil will float the Journal, and the Journal will stop gradually in the bush, so that the Bush will not be abraded. Each main bearing is equipped with two temperature probe, dynamic monitoring of the bearing Bush temperature, when the temperature is greater than the specified temperature value, it can automatically alarm and stop grinding. In order to compensate for the change of the mill length due to temperature, there is a gap between the hollow journal at the feeding end and the bearing Bush width, which allows the journal to move axially on the bearing Bush. The two ends of the main bearing are sealed in an annular way and filled with grease through the lubricating oil pipe to prevent the leakage of the lubricating oil and the entry of dust.

The end cover of the autogenous mill is made of steel plate and welded into one body; the structure is simple, but the rigidity and strength are low; the liner of the autogenous mill is made of high manganese steel.

The end cover and the hollow shaft can be made into an integral or split type according to the actual situation of the project. No matter the integral or split type structure, the end cover and the hollow shaft are all made of Casting After rough machining, the key parts are detected by ultrasonic, and after finishing, the surface is detected by magnetic particle. The surface of the hollow shaft journal is Polished after machining. The end cover and the cylinder body are all connected by high-strength bolts. Strict process measures to control the machining accuracy of the joint surface stop, to ensure reliable connection and the concentricity of the two end journal after final assembly. According to the actual situation of the project, the cylinder can be made as a whole or divided, with a flanged connection and stop positioning. All welds are penetration welds, and all welds are inspected by ultrasonic nondestructive testing After welding, the whole Shell is returned to the furnace for tempering stress relief treatment, and after heat treatment, the shell surface is shot-peened. The lining plate of the ball mill is usually made of alloy material.

The transmission part comprises a gear and a gear, a gear housing, a gear housing and an accessory thereof. The big gear of the transmission part of the self-grinding machine fits on the hollow shaft of the discharge material, which is smaller in size, but the seal of the gear cover is not good, and the ore slurry easily enters the hollow shaft of the discharge material, causing the hollow shaft to wear.

The big gear of the ball mill fits on the mill shell, the size is bigger, the big gear is divided into half structure, the radial and axial run-out of the big gear are controlled within the national standard, the aging treatment is up to the standard, and the stress and deformation after processing are prevented. The big gear seal adopts the radial seal and the reinforced big gear shield. It is welded and manufactured in the workshop. The geometric size is controlled, the deformation is prevented and the sealing effect is ensured. The small gear transmission device adopts the cast iron base, the bearing base and the bearing cap are processed at the same time to reduce the vibration in operation. Large and small gear lubrication: The use of spray lubrication device timing quantitative forced spray lubrication, automatic control, no manual operation. The gear cover is welded by profile steel and high-quality steel plate. In order to enhance the stiffness of the gear cover, the finite element analysis is carried out, and the supporting structure is added in the weak part according to the analysis results.

The self-mill adopts the self-return device to realize the discharge of the mill. The self-returning device is located in the revolving part of the mill, and the material forms a self-circulation in the revolving part of the mill through the self-returning device, discharging the qualified material from the mill, leading the unqualified material back into the revolving part to participate in the grinding operation.

The ball mill adopts a discharge screen similar to the ball mill, and the function of blocking the internal medium of the overflow ball mill is accomplished inside the rotary part of the ball mill. The discharge screen is only responsible for forcing out a small amount of the medium that overflows into the discharge screen through the internal welding reverse spiral, to achieve forced discharge mill.

The slow drive consists of a brake motor, a coupling, a planetary reducer and a claw-type clutch. The device is connected to a pinion shaft and is used for mill maintenance and replacement of liners. In addition, after the mill is shut down for a long time, the slow-speed transmission device before starting the main motor can eliminate the eccentric load of the steel ball, loosen the consolidation of the steel ball and materials, ensure safe start, avoid overloading of the air clutch, and play a protective role. The slow-speed transmission device can realize the point-to-point reverse in the electronic control design. When connecting the main motor drive, the claw-type Clutch automatically disengages, the maintenance personnel should pay attention to the safety.

The slow drive device of the ball mill is provided with a rack and pinion structure, and the operating handle is moved to the side away from the cylinder body The utility model not only reduces the labor intensity but also ensures the safety of the operators.

spiral classifier,screw classifier,sand classifier|spiral classifier|shicheng gaoxuan bearing bush co., ltd

spiral classifier,screw classifier,sand classifier|spiral classifier|shicheng gaoxuan bearing bush co., ltd

Spiral Classifier is widely used to control material size from Ball Mill in the beneficiation process, separate mineral sandand fine mud in the gravity concentration, and clean mud and water in washing mineral process. This machine has features of simple structure, reliable and convenient operation, etc.

1.Simple structure, stable operation, safe and reliable; 2.The main screw frame electric lifting device of the standard configuration, making the equipment operation and replacement of spare parts more easy. 3.Optimization design of the helical blade, making sure of spare parts to minimize loss.

The spiral classifier consists of cell body(Frame), speed reducer(Gear Box), motor, central shaft & Screw, spiral scatters, Weir & support parts. This machine is mainly combined with ball mill during working.

The water tank of this gold ore spiral classifier is installed obliquely. The angle of inclination is determined according to equipment configuration of equipment in the process flow. The (left, right) spirals driven by the transmission mechanism rotates in the water tank. The finely grained slurry enters the water bank from the feed inlet at one side and forms one slurry precipitation zone, whose surface area and volume depends on the value of the water tank's inclination angle and the height of overflow edge. the spirals rotating at a low speed play a certain stirring role. After the slurry is stirred, the light and fine particles float above the surface and overflow from the overflow edge. Then they flow into the next working procedure of ore dressing. The heavy and thick particles sink into the bottom of the water tank and become return sand which is transported by the spirals to the ore discharge mouth for discharge. Gold mining recovery machine,spiral classifier for mineral separation If ore grinding and classification are closed loop operation, the return sand discharged from the ore discharge mouth still goes into the mill for further grinding. The gold ore spiral classifier normally forms closed-circuit operation together with ball mill.

Spiral Classifier is widely used in mineral processing plant to match with the ball mill and form a closed-circuit circulationto process mining sand, or used in gravity mine-selection plant for classifying sand and mine mud, and grading sand according to the particle size, disliming, dewatering in the mine washing process. FG series Spiral Classifier has simple structure, reliable operation, convenient operation,etc. The spiral classifier is a kind of classifying machine that adopts the principle of settling speed difference according to different material sizes and specific gravity. fine particles floating in the water overflow out; the coarse ore grain sinks to the bottom of the chase which will be pulled to the upper by the spiral and discharging out.

spiral classifiers

spiral classifiers

The Spiral Classifier is available with spiral diameters up to 120. These classifiers are built in three models with 100%, 125% and 150% spiral submergence with straight side tanks or modified flared or full flared tanks. All sizes and models are available with single-, double- or triple-pitch spirals.

The tank is heavy plate with strong structural base. The extra heavy shaft has an improved submerged bearing. The greatest improvements, however, are found in the drive-unit which has been strengthened and improved over all other classifiers. A specially designed classifier reducer eliminates the over hang or cantilevered load normally found where the reducer shaft carries the pinion. The Classifier Reducer has an outboard bearing integral with the reducer base which provides positive alignment of the bevel gears.

The gears themselves are greatly improved as they are cast from metal patterns which have cut teeth. The accuracy of the patterns and the quality gear castings result in a cast-tooth gear of cut-tooth quality. The gears mesh smoothly, have greatly increased capacity and are noticeably more quiet than other spiral classifiers.

Spiral Classifiers are available in sizes up to 120 diameter, three tank styles, single, double and triple pitch spirals, three degrees of spiral submergence flexibility to provide a unit built for your job. Write for detailed recommendation on the correct size and type of Spiral Classifier to do your job economically and profitably.

This is the best method of determining the required pool area. However, if settling tests have not been made and it is inconvenient to make tests, the following procedure, which has been proved to be entirely satisfactory, may be used.

Example: Assume it is desired to overflow 100 tons of dry solids per 24 hours at 65 mesh in a pulp of 20 % solids. Table I shows that 6.43 tons will overflow per sq. ft. of effective pool area. Therefore, to overflow 100 tons in 24 hours, a classifier with 15.5 sq. ft. (100 divided by 6.43) effective pool area would be required.

For a 65 mesh separation it is preferable to set the classifier at 3 slope. Table II shows that at 3 slope the 30 Cross-Flow Classifier has an effective pool area from 12.9 to 16.4 sq. ft. depending on the height at which the weir is set. Therefore the 30 classifier would be the proper size for the overflow capacity desired.

Table III shows that at 65 mesh a peripheral speed of 44 ft. per min. is recommended, which on the 30 classifier corresponds to 5.6 R.P.M. At this speed the 30 classifier will convey 275 tons of solids per 24 hours, which then is ample for this job. Therefore, this size Cross-Flow Classifier will satisfy all the requirements of this problem.

But, suppose the circulating load required was 300% instead of 250% specified above. The amount of sand to be raked would be 300 tons per 24 hours. In this case it would be necessary to speed up the conveyor of the 30 classifier above the normal speed of 5.6 R.P.M. in order to handle the 300 tons of sand. In speeding up the conveyor more agitation is produced in the tank and settling is interfered with, resulting in a slightly coarser overflow. In this case it might be necessary to provide a 36 classifier.

If the classifier is to be used in open circuit it may be the shortest standard length made in that particular size. For installation in a closed grinding circuit the classifier length must be pre-determined to assure that it will close circuit with the ball mill. This is entirely a mechanical problem and the correct length is determined by making a ball mill-classifier layout to scale.

The pool area varies with the slope and since capacity at a required mesh depends on pool area, the slope cannot arbitrarily be changed to accomplish a closed circuit. With the classifier size and slope established it is necessary to make the classifier of sufficient length to close the circuit.

In general the classifier should be installed with a slope of from 3 to 4 in 1 ft. The steeper the slope the less the pool area of a given size classifier. The less the pool area the less the capacity. The maximum capacity for any mesh separation is obtained at a slope of about 3 in 1 ft. But, for very coarse separations it may be necessary to increase the slope and thus decrease the pool area so as not to cause overloading.

65 to 150 mesh3 per ft. 48 to 100 mesh3 per ft. 35 to 65 mesh..3 per ft. 28 to 48 mesh..3 per ft. 14 to 35 mesh4 per ft.

The launder from ball mill discharge to the classifier should have a slope of about 1 per ft. depending on fineness of grind and pulp density. The launder from sand discharge of the classifier to the ball mill scoop box should have a slope of from 4 to 6 per ft.

The speed of the conveyor should be just sufficient to handle the sands to be removed. The slower the speed the less the agitation in the pool and the finer the overflow. The lower the speed the longer the life of the classifier and all wearing parts.

Most efficient grinding is effected by removal of material from the ball mill as soon as it has been reduced to the required size. This eliminates over-grinding and permits utilizing all of the power applied to the ball mill in actually grinding the oversize material. This may be accomplished by using the Cross-Flow Classifier in closed circuit. The entire ball mill discharge goes to the classifier which separates the material ground to the desired size; returning the oversize material to the ball mill.

The Cross-Flow Classifier is ideal for this closed-circuit work. Its exclusive Cross-Flow principle of operation results in an extremely accurate separation. Various lengths of this classifier and variation in slope make it possible to fit the classifier to the circuit without use of expensive, troublesome equipment such as elevators, pumps, etc.

In closed grinding circuit separations are easily and efficiently made at from 20 to 100 mesh sizes. Normally, it is considered best practice to use a Hydroclassifier for separations at 100 mesh and finer. Efficiency of separation in fine mesh range requires a very large pool area. Thus, the Hydroclassifier, with its large surface area gives more efficient classification, more economically, than is possible with a spiral classifier.

Usually such separations are made on dilute pulps with a relatively small amount of slimes. Under these conditions a mechanical classifier can make efficient separations at a much finer mesh than in a closed grinding circuit where there is a higher density pulp and larger percentage of fines. The Cross-Flow Classifier will efficiently handle sand- slime separations in the range from 150 to 325 mesh, with a minimum amount of dilution water.

The Cross-Flow Classifier provides an efficient means of dewatering sands and concentrates or other granular material. A common application in this work is when the granular material is difficult to handle in a thickener. Also in many cases, where tonnage is not large, classifiers are considerably more economical than a thickener-filter installation lower in first cost lower in operating and maintenance costs require practically no attention.

A very common application of classifiers is in washing granular material to remove reagents, liquors, etc. Classifiers have the same advantage on small tonnage as in the case of dewatering lower initial and operating costs and less attention required. The particles to be washed pass successively up the inclined tanks of several classifiers, while the wash passes through the classifiers in the opposite direction. In each classifier the pulp is diluted, mixed and rabbled, the particles washed, and the liquid removed resulting in a thoroughly washed and cleaned final product.

STAND: For convenience in installing, these smaller sizes are provided with steel legs. The stand is made to give the most commonly used slope of 3 inches per foot. SHAFT: Solid, square steel. FLIGHTS: Hard, cast iron; made in short segments which fit over the square shaft. Flights may be placed on shaft so that blades form a continuous spiral, or may be staggered to obtain an interrupted spiral. DRIVE: Enclosed worm-gear speed reducer driven by motor through V-belts; cone pulleys are used to permit speed variations desirable in experimental laboratory or pilot plant work.

SHAFT: Heavy steel pipe. FLIGHTS: Hard, cast iron; made in short sections; bolted to cast iron arms which are carried on the shaft. Easily replaceable without draining tank. DRIVE: Bevel gear driven by gearmotor through sprocket and chain. Speed of drive is determined by the requirements of each installation. A variable speed drive may be furnished, at extra cost, if desired.

SHAFT: Heavy steel pipe with steel reinforcing sleeve at the lower bearing. FLIGHTS: Steel plate; bolted to cage which is carried by steel pipe shaft. Hard, cast iron wearing shoes, made in short sections, are bolted to the steel flights and are easily replaceable without draining the tank. DRIVE: Cast steel bevel gear and bevel pinion driven from a countershaft through spur gears; gearmotor and V-belts to countershaft. Speed of drive is determined by requirements of each installation. Variable speed drive may be furnished, at extra cost,if desired.

SHAFTS: Same as for corresponding sizes of simplex classifiers. FLIGHTS: Same as for corresponding sizes of simplex classifiers. DRIVE: Heavy cast steel bevel gears and bevel pinions, driven from countershaft through heavy spur gears; gearmotor and V-belt or chain drive. LIFTING DEVICE: Same as for corresponding sizes of simplex classifiers. CONVEYOR ROTATION: The two helical conveyor flights rotate in opposite directions, thus conveying the sands up the center of the tank giving free drainage back along both sides of tank.

spiral classifier-jiangxi changyi mining machinery co., ltd

spiral classifier-jiangxi changyi mining machinery co., ltd

Mineral Spiral Classifier is widely used to control material size from Ball Mill in the beneficiation process, separate mineral sand and fine mud in the gravity concentration, and clean mud and water in washing mineral process. This machine has features of simple structure, reliable and convenient operation, etc.

2.The main screw frame electric lifting device of the standard configuration, making the equipment operation and replacement of spare parts more easy. 3.Optimization design of the helical blade, making sure of spare parts to minimize loss.

The spiral classifier consists of cell body(Frame), speed reducer(Gear Box), motor, central shaft & Screw, spiral scatters, Weir & support parts. This machine is mainly combined with ball mill during working.

The water tank of this gold ore spiral classifier is installed obliquely. The angle of inclination is determined according to equipment configuration of equipment in the process flow. The (left, right) spirals driven by the transmission mechanism rotates in the water tank. The finely grained slurry enters the water bank from the feed inlet at one side and forms one slurry precipitation zone, whose surface area and volume depends on the value of the water tank's inclination angle and the height of overflow edge. The spirals rotating at a low speed play a certain stirring role. After the slurry is stirred, the light and fine particles float above the surface and overflow from the overflow edge. Then they flow into the next working procedure of ore dressing. The heavy and thick particles sink into the bottom of the water tank and become return sand which is transported by the spirals to the ore discharge mouth for discharge.

If ore grinding and classification are closed loop operation, the return sand discharged from the ore discharge mouth still goes into the mill for further grinding. The gold ore spiral classifier normally forms closed-circuit operation together with ball mill.

Spiral Classifier is widely used in mineral processing plant to match with the ball mill and form a closed-circuit circulationto process mining sand, or used in gravity mine-selection plant for classifying sand and mine mud, and grading sand according to the particle size, disliming, dewatering in the mine washing process. FG series Spiral Classifier has simple structure, reliable operation, convenient operation,etc.

Shicheng Changyi mining machine equipment manufacturing established in 1958,located in Ganjiang River source and Wuyi mountain,is a professional supplier in producing and sale kinds of bearing bushes and mining equipments

We produce high precise vibrating feederJaw crusher,Hammer crusher,Vibrating screen,spiral classifier,ball mill,belt conveyor,shaking table,centrifugal concentrator,spiral chute,jig machine,flotation cell,magnetic separator,rotary scrubber,gold trommel screen,lab mining equipment etc.

During-sale services: a. Pre-check and accept products before delivery. b. Send technicians to the jobsite for guiding the installation and adjustment. c. Training operators and finishing the check to satisfy your requiremnet.

After-sale services: a. Common problem can be solved through web in 24 hours,complex problem can be reacted immediately in 24 hours and solved as soon as possible. b. To establish long-term friendship, we will regulary contact with our customers.

spiral conveyor replacement parts - automated flexible conveyors, inc

spiral conveyor replacement parts - automated flexible conveyors, inc

AFC manufactures and stocks replacement spirals, tubes, and other parts in-house for all Spiralfeeder conveying system models, and also offers exact fit replacement parts for flexible conveyor systems from nearly all other process equipment companies. These are high quality, made in USA, parts machined and fabricated to rigorous quality standards in our New Jersey facility.

Most spiral conveyor replacement parts are shipped the same day an order is placed. For other flexible screw or spiral conveyor replacement parts that need to be produced, we can provide a quote with competitive prices within a matter of hours and quickly begin production to keep your process up and running.

spiral classifiers | screw classifiers | dove

spiral classifiers | screw classifiers | dove

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.

WE HIGHLY RECOMMEND FORWARDING SOIL SAMPLES OF YOUR MINE TO US FOR ANALYSIS, IN ORDER TO DESIGN AND RECOMMEND THE MOST EFFICIENT PROCESSING PLANT, TAILOR MAID TO YOUR MINE REQUIREMENTS, FOR HIGHEST PRODUCTION RECOVERY.

spiral classifier, dewatering screw - mt baker mining and metals

spiral classifier, dewatering screw - mt baker mining and metals

This spiral classifier/dewatering screw is a multi-purpose machine. As a classifier, it separates out the smaller waste particles from the ore processor tailings. The larger particles can then be returned to the grinding circuit for finer grinding to liberate more values.

Many locations dont have a ready source of water, so when used as a dewatering screw, the slurry particles are removed from the waste stream before the settling pond. This makes the water available for recirculating without filling the settling pond with tailings.

The size of the particles discharged to the tailings pond is controlled by two methods. First, the volume of feed water is adjusted to flush the pool at the bottom of the spiral classifier. The more water that flows in, the coarser the particles that are discharged to the tailings pond. The second adjustment is by setting the height of the water level in the classifier pool. There are three outlet ports along the side of the pool at different elevations. Choosing the upper port results in the highest water level in the pool, allowing the heavier slurry particles to settle and be augered out the top for re-grinding, and the finest particles to be discharged to the tailings pond. Choosing a lower port allows the heavier particles to flush out of the pool to the tailings pond. Tuning the flow of water and the height of the water in the classifier pool controls the size of particles discharged to the tailings pond.

We bought a turn-key ore processing system that included a hammer mill. The equipment did exactly what it was promoted to do and more. The combination of the jaw crusher with the hammer mill and shaker table did has good if not better than it was advertised by MBMM. I Read More

We have an MBMM 24 x 16 HD turnkey-scrap metal processor. We primarily process 6-8lb motor stators, smaller transformers and radiator ends to separate out the clean copper. We run this hard day after day and are very happy with how it performs and the on-going support from MBMM. This Read More

As a countertop fabricator, stone waste from the edges of the slabs is a constant headache and expense to deal with. We dispose of 5,000 lbs of cut-offs a day and the dumpster fees for disposal was getting out of hand. We purchased a crusher system from MBMM and have Read More

This customer reports they process mostlyPC boards populated with components and sell the concentrated mix of copper, base metals and precious metals to a copper refinery in Poland. Read More

The crusher (16 x 24 Jaw Crusher Module) is great! I probably have 300 hours on it and we are in the process of swapping around jaw plates. I am very impressed with your product and would have no hesitation in recommending you guys. Read More

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