molybdenum ore processing by flotation
This molybdenum flotationcircuit, based on 250-500 tons per 24 hours is designed for low-grade molybdenum ore having high-grade streaks and with pyrite-quartz gangue. It is also basically sound for many other friable sulphide ores, such as antimony, silver and even some lead ores.
The basic ideas stressed in this moly flotation flowsheet are the importance of simplicity and the quick removal of the freedmineral. Gravity flow is used as much as possible in handling the ore and pulp.
Overgrinding and colloiding the ore, which is so serious in molybdenum flotation is not only expensivebut also requires more equipment, such as larger ball mills and cleaner flotation cells and thickener.
In the crushing department, which is designed for 8-hour per day operation, a heavy duty apron feeder, with plenty of length for picking purposes, starts the ore on its way. The crusher operator with his assistant can sort out any high grade ore, waste rock and wood or tramp iron. Open circuit crushing provides simplicity, low first cost and less tendency to over-crush.
A magnetic head pulley or a stationary magnet over conveyor may be used. In remote locations it is desirable to use both in order to save secondary crusher from dangerous steel hammer heads, drill steel, etc. The suspended magnet removes tramp iron from the upper layers of the ore stream and the magnetic head pulley removes pieces close to the belt.
The Vibrating Screen removes fines ahead of the (Non-Sliming) Rod-Ball Mill. This Mill is arranged with special non-sliming features such as peripheral discharge and large diameter discharge trunnion opening (2/3 diameter of the mill). This double method of discharge prevents choking and gives additional grinding flexibility.
Rods generally produce fewer slimes but balls may be used. The large-diameter trunnion discharge aids in re-lining as well as introducing replacement rods or balls. A smaller diameter trunnion opening can be used if desired.
The peripheral rod mill discharge joins the coarse screen undersize and passes over Dillon fine screens to remove oversize before the pulp enters the four Sub-A Flotation Cells in the coarse flotation circuit.
Oversize from the fine screens goes by gravity to a small Bucket Elevator which returns it to the Peripheral Rod-Ball Mill for regrinding. A SRL Sand Pump and Spitzkasten for dewatering may possibly be used instead of the elevator.
On many molybdenum ores a high-grade concentrate can be made in this four-cell coarse flotation circuit. The Sub-A Flotation Machine is the only unit that can successfully treat such coarse feed without sanding up. Tailings from this coarse flotation circuit go to a separate regrind circuit.
This consists of a Steel Head Ball Mill in closed circuit with a Sub-A Unit Flotation Cell and Spiral Classifier. The Sub- A Unit Flotation Cell takes the ball mill spiral screen undersize, removes the freed mineral and, to the greatsatisfaction of mill men, it makes a very high grade molybdenum concentrate.
The Sub-A Unit Flotation Cell is one of the most important parts of the circuit, for it not only removes a major portion of the remaining molybdenum mineral as a high grade product, but may also be used to remove a greater tonnage of a middling product for later up-grading if the metallurgist may determine. The unit cell discharge goes by gravity to the Heavy-Duty Spiral Classifier for separation into the fine flotation feed and the coarse regrind product.
Classifier fines go to a Super Agitator and Conditioner to provide a steady flotation feed and also the necessary reagent conditioning for best flotation results. The conditioned pulp goes to Cell No. 1 of the Sub-A Rougher Flotation Machine. With the Sub-A it is often possible to remove a substantial amount of molybdenum concentrate of high enough grade to require no further cleaning. The remainder of the rougher concentrate normally requires conventional multiple cleaning. Many other ores, like antimony, silver and lead also make a high- grade product if the mineral has not been colloided in prior milling.
The flowsheet of roughing and cleaning in the six-cell Sub-A Rougher and the six-cell Sub-A Cleaner is typical of molybdenum flotation or any other mineral where recleaning steps are necessary. The recirculation is done by gravity in the Sub-A Flotation cells. With its flexibility of cell-to-cell design any change in flow can be easily made without the use of pumps.
The Standard Sub-A Rougher tailings go to the Sub-A Super Scavenger Cells. These are of the double impeller and double overflow, low pulp level type. They are used to pull out the last trace of mineral. This concentrate is sent by gravity to the cells immediately preceding.
The high grade molybdenum concentrate is sent to the heavy-duty Spiral Rake Thickener for thickening prior to filtration. The drum-type filter is placed high enough so that it can receive its feed from a Adjustable Stroke Diaphragm Pump and still be high enough so that its tank can be drained by gravity back into the thickener if necessary. The filter capacity should be sufficient so that it will handle the entire tonnage in 10 or 12 hours. It may be necessary to include a Standard Concentrate Dryer in the flowsheet before the concentrate goes to storage.
The tailings stream is cut by a Automatic Sampler with a double cutter. One cutter is for assay sample and an additional large cut is made at the same time for subsequent pilot table feed. The tailings then go to a large heavy-duty Spiral Rake Thickener for water reclamation.
Many progressive mills are using the basic principles shown in this flowsheet. Their success has been directly related to their practice of When your mineral is free, recover it as soon and as coarse as possible.
Molybdenum is found in small amounts in practically all low grade porphoritic copper ores. It is usually present as the sulphide, molybdenite, which is readily recovered in the copper flotation concentrate. Copper sulphide flotation concentrates may contain from 0.25 to 1.00% MoS2. When such ores are milled in large tonnages the amount of molybdenum present may be substantial. Practically all major copper producers now have molybdenum recovery systems.
One of the typical and quite successful treatment systems is studied. It resorts entirely to reagent control and flotation to separate the molybdenite from a copper sulphide flotation concentrate. No heat treatment, steaming or roasting steps are used. In this process sodium ferrocyanide and sodium cyanide are used as copper mineral depressants while sulphuric acid is the pH modifier.
Copper-Molybdenite FlotationThe low grade ore, after grinding in the conventional manner, is treated by bulk or selective flotation. Selective flotation is used where barren pyrite must be rejected into the mill tailings. In this case, lime is used for pH control.
The flotation steps usually consist of roughing, scavenging, cleaning and recleaning to provide a high grade copper concentrate which contains the bulk of the contained molybdenite. All of these steps may be successfully accomplished in Sub-A Flotation Machines with excellent recoveries and the resulting concentrate is a product highly desirable by the copper smelter. The free-flow type Flotation Machine is used for roughing and scavenging and the cell-to-cell type Sub-A is used for the cleaning steps. The Type M Flotation Machine may be used to advantage for the scavenging steps.
The high grade copper concentrate from the Sub-A Cleaner Flotation Cells will contain from 40% to 50% solids. At this point in the flowsheet the copper sulphides are selectively depressed and molybdenite is floated in successive steps until final high grade MoS2 concentrates are produced.
The copper concentrates at 40% to 50% solids are sent to a Super Agitator and Conditioner and during conditioning are diluted down to about 20% solids. Sulphuric acid is added to lower the alkaline pH to 7.5. Sodium ferrocyanide is added to the conditioner discharge or to the pump sump if a pump is necessary between the conditioner and the cells. This reagent depresses the copper sulphides. The conditioned sulphide pulp is then treated in a Sub-A cell-to-cell Flotation Machine for the initial molybdenum up-grading steps. These cells are usually the same size as the preceding copper cleaner cells as the entire tonnage of concentrates must be handled at this point. This flotation step produces a molybdenum rougher concentrate containing 1% to 5% MoS2. In addition to the reagents previously mentioned, sodium cyanide, fuel oil, and oronite are used. The flotation tailings from this circuit are the final copper concentrates which go to thickening and filtering as shown. The rougher molybdenum concentrates also go to a separate thickener ahead of conditioning and prior to subsequent enrichment steps by selective flotation.
The rougher molybdenum concentrate thickener underflow at 65 to 70% solids is removed by a Adjustable Stroke Diaphragm Pump discharging into a Super Agitator and Conditioner. During conditioning the pulp is diluted to about 15% solids with fresh water and sulphuric acid is added to adjust the pH to 7.5. The conditioned pulp after addition of sodium ferrocyanide goes to two banks of Flotation Cells for three stages of cleaning. Fuel oil, oronite and a frother plus additional sodium ferrocyanide are stage added as required. Exact pH control is critical and is usually done automatically. These three stages of cleaning raise the MoS2 concentrate grade to 15 to 40% and the final froth at this point will contain 30 to 50% solids. The cleaner tailing from the first cleaning step is returned to the conditioner and flotation circuit ahead of the final copper concentrate thickener or, if low in MoS2, it may be diverted direct to the final copper concentrate thickener and filter. Middlings from the second cleaner cells are returned to the rougher MoS2 concentrate thickener for retreatment, and tailings from the third cleaners are returned to the second cleaners.
The MoS2 concentrate at this point contains 15 to 40% MoS2 and goes to a regrind Ball Mill in closed circuit with a SRL Pump and Morton Duplex Cyclone classifier. Water is added as required to maintain the classifier overflow at 8 to 10% solids, while the underflow, which is returned to the regrind mill, is of a rope discharge density and contains about 70% solids.
The cyclone overflow is cleaned five successive times by flotation to bring the MoS2 up to final grade of plus 90%. Sodium cyanide, fuel oil, oronite, and a frother are stage added as required. No acid is used in this circuit since the cyanide is used to depress the chalcopyrite and pyrite. The cleaner tailing for this regrind and reflotation section is returned to the rougher molybdenum thickener for retreatment.
Sub-A cell-to-cell Machines with launders provide for multi-stage cleaning. Some molybdenum retreatment circuits may become quite complex depending upon the number of conditioning and flotation stages necessary to attain final grade with a good recovery. One operation, for example, uses over 100 cells in their MoS2 retreatment plant. These cells range in size from the 100 cubic foot No. 30 (56 x 56) machine down to the 10 cubic foot No. 12 (22 x 22) machine. In some of the small plants, the No. 8 (16 x 16) which has 3 cubic foot volume per cell has been used with good results. It is not uncommon to find as many as 24 cells in series on one floor level operating without the aid of auxiliary pumps.
In developing a retreatment method for molybdenite recovery from a specific copper ore it is best to run batch flotation tests on freshly produced copper plant concentrates. This is much more satisfactory than attempting to produce the copper concentrate in a laboratory since the amount of product available is rather limited due to the unusually high ratio of concentrations. Copper ores may also be quite erratic in molybdenite contenthence the work on a concentrate produced in a regular milling circuit will usually minimize this condition.
how antimony is processed by flotation
The problem discussed in this antimonyprocess study is limited to a concentrator capable of beneficiating 150 tons per day of antimony ore. The antimony in this study occurs as the mineral stibnite (Sb2S3) in association with small amounts of pyrite, arsenopyrite, galena and lead sulfantimonides. The gangue is composed largely of quartz but contains, in addition, a small amount of talc. The talc mineral is particularly trouble some since it tends to float with the stibnite and hence lowers the grade of the final antimony concentrate.
The crushing section with two-stage reduction is suitable for tonnages of from 100 to 300 tons of ore per 24 hours. It is designed to permit crushing sufficient ore during one 8 hour shift to operate the mill during a full 24 hours. Removing the fines with a grizzly before the jaw crusher and with a vibrating screen ahead of the secondarycrusher increases the efficiency of size reduction since thecrushers are working only on material that must be reduced. Removal of tramp iron to prevent damage to the secondary crusher is accomplished with an electromagnet and a magnetic head pulley.
The crushed ore is fed from the fine ore storage bin at a controlled rate by a Adjustable Stroke or Variable Speed Ore Feeder. Fine grinding is accomplished in a Ball Mill operating in closed circuit with a Spiral Classifier. To reduce overgrinding of the friable stibnite it is generally desirable to carry a relatively large circulating load in the ball mill-classifier circuit. If necessary sufficient lime or soda ash should be added to the ball mill feed to provide the proper pH for subsequent conditioning and flotation operations.
A head-ore sample is cut from the classifier overflow to use as the flotation circuit control and metallurgical balance. A Automatic Sampler is used. Normally the sampling interval is one cut each 15 minutes which is collected each shift as a composite sample. A Unit Flotation Cell has not been included in the ball mill-classifier circuit of this study. However, in certain instances a Unit Flotation Cell may prove particularly effective in that it is capable of recovering a significant portion of the total stibnite as a relatively high grade grannular concentrate. Thus, overall plant recovery may be increased by reducing slime losses due to overgrinding of the soft, high specific gravity stibnite.
The classifier overflow adjusted to a pH of approximately 7.5 to 7.8 is conditioned with a stibnite activator such as copper sulfate or lead acetate and a collector such as Z-11 or a liquid type Aerofloat. Depending upon the mineralogy of the ore, other auxiliary reagents may also be required to depress sulfides which tend to float with and thus lower the grade of the stibnite concentrate. For example, bleaching powder has been used effectively for the depression of arsenopyrite and cyanide for the depression of pyrite.
The conditioner overflow passes to an 8-cell Sub-A Flotation Machine, arranged to provide four rougher cells, two scavenger cells and one cell for each of two stages of cleaning. The distinctive cell-to-cell design of Sub-A Flotation Machines permits the transfer of the various pulp streams within the flotation circuit without the use of pumps. Extremely fine talcose slimes which floated with the stibnite in the rougher cells are effectively depressed in the cleaners with the aid of a small quantity of yellow dextrine.
The cleaned antimony concentrate is pumped to a Spiral Rake Thickener to remove excess water prior to filtering. A Adjustable Stroke Diaphragm Pump meters the thickened flotation concentrate to a Disc Filter.
For the efficient control of milling operations, reliable sampling is required. For this purpose Automatic Samplers are used on the heads, concentrates and tailings. A metallurgical balance is run for each shift. Sampling interval of one cut each 15 minutes has proved adequate except where quality of ore is spotty or unusual conditions are encountered.
The beneficiation of stibnite ores by flotation can frequently be a difficult problem because of the complex nature of the mineral associations often encountered. It is essential, therefore, that a comprehensive laboratory test program be carried out on a representative sample of the ore before planning a milling installation.
While antimony concentrates assaying less than 50% antimony may be salable, such low-grade concentrates require special arrangements with thesmelters. Smelter returns for antimony concentrates are based on a sliding scale which provides for 65% Sb content as the basis. Antimony payment is based on a short ton unit containing 20 lbs. antimony. A 1963 quotation for 65% antimony concentrate was $4.25 per short ton unit.
silver lead zinc ore processing method using flotation
Sulphide ore of lead and zinc containing considerable silver was submitted for testing with the purpose of determining a flowsheet for the production of separate lead and zinc concentrates for marketing at their respective smelters. It is necessary to recover as much silver as possible in the lead concentrate as a higher return for this silver is realized than for the silver in the zinc concentrate. The ore contained sphalerite, a portion of which was easily floatable but difficult to depress in the lead flotation circuit.
Also, the recovery of silver minerals occurring in a lead, zinc sulfide ore is efficiently accomplished using Flowsheet #2. The process consists of selective flotation to produce a mixed silver, lead concentrate for maximum smelter return and a separate zinc concentrate. Over-grinding of silver minerals is detrimental to efficient flotation recovery, so the Flash Flotation Unit-Cell is used in the grinding circuit to recover a large part of the silver and lead values as soon as liberated.The flowsheet is for a plant having a capacity in the range of 300 to 500-tons per day.
The crushing section of this 50-65 ton mill consists of a conventional layout of single stage crushing. The mine ore is fed from the coarse ore bin to a 9x 16 Forced Feed Jaw Crusher by means of a Apron Ore Feeder. The crushed ore is conveyed by a Belt Conveyor to the Bolted Steel Fine Ore Bin. A Adjustable Stroke Unit Flotation Cell are incorporated in the Belt Ore Feeder delivers the fine ore to the ball mill.
The Mineral Jig and the grinding circuit for immediate recovery of a substantial amount of the lead and silver at a relatively coarse grind. The 5 x 5 Steel Head Ball Mill discharges into an 8x 12 Selective Mineral Jig which in turn discharges into a small flashFlotation Cell. The tailings from the Unit Cell flow by gravity to the 30 Cross-Flow Classifier. The Mineral Jig and the flashcell treating an unclassified feed, produce high-grade concentrates of lead and silver with a minimum amount of zinc. Recovery of these important amounts of lead and silver at this point not only prevents detrimental sliming of the lead mineral and possible subsequent loss, but also increases the amount of new feed that can be fed to the ball mill. By taking advantage of recovering a clean product representing a high recovery of the lead leaves only a small amount of the lead to be recovered in the selective flotation section.
This section of the flowsheet uses two 6-cell (32 x 32) Flotation Machines. The classifier overflow is fed by gravity to the first rougher cell of the lead machine. Three rougher cells provide ample contact time for the flotation of the lead. This rougher lead flotation concentrate is then delivered by gravity to the cleaner cells. Three cleaner cells are used for triple cleaning of the lead concentrate. This triple cleaning was recommended because of the easily floatable zinc that could not be effectively depressed by conventional zinc depressant reagents. Roughing, plus triple cleaning in a 6-cell machine with no pumps or elevators is an example of flexibility a distinctive feature of Sub-A Flotation Machines.
The lead circuit tailing is then conditioned with reagents in a 6 x 6 Super-Agitator and Conditioner prior to zinc flotation. The conditioned pulp is then floated in a 6-cell No. 18 Special Sub-AFlotation Machine for the production of a cleaned zinc concentrate. This machine is arranged for four rougher cells and two cleanings of the rougher zinc concentrate.
Soda ash and zinc sulphate are fed to the ball mill by means of Cone Type Dry Reagent Feeders. Cyanide, sodium sulphite, MIBC frotherand xanthate (Z-3) are fed to the grinding circuit and lead flotation circuit using a multi-compartment Wet Reagent Feeder. Lime and copper sulphate (CuSO4) are added to the zinc conditioner and pine oil and xanthate (Z-5) are stage added to the zinc rougher circuit using Wet Reagent Feeders.
The Visual Sampler, consisting of a Suction Pressure Diaphragm Pump and a No. 13A Wilfley Concentrating Table, takes a portion of the final zinc tailing. This unit enables the operator to determine visually the results of flotation. Any necessary change of reagents is immediately indicated by observation of the concentrate streak shown on the table. Many installations of the Visual Sampler have proved this unit to be a money-saving necessity in any flotation plant.
Thickening, prior to filtration, was not recommended in this case because of the rapidity at which these concentrates filtered and the relatively small tonnage of this mill. Thickening is advisable on slower filtering ores and on larger tonnages.
The final lead-silver concentrates (including the Flash FlotationCell concentrate) are filtered on the 44-disc Filter, the filter cake discharging directly into concentrate bins. The dewatered Mineral Jig concentrate is combined with the filtered lead concentrate in the storage bin.
The above flowsheet incorporates the first rule of milling procedurerecover the mineral as soon as freedthis is accomplished by the Jig and Flash Unit Cell in the grinding circuit. Note that a high-grade lead product representing 2/3 of the total lead (very low in zinc), is recovered in the grinding circuit. This flowsheet successfully answers The Problem by recovering 84% of the total silver in the lead concentrate.
The recovery of silver minerals occurring in a lead-zinc sulfide ore is efficiently accomplished using the above flowsheet. The process consists of selective flotation to produce a mixed silver-lead concentrate for maximum smelter return and a separate zinc concentrate. Over-grinding of silver minerals is detrimental to efficient flotation recovery, so the Flash Flotation Unit-Cell is used in the grinding circuit to recover a large part of the silver and lead values as soon as liberated.The flowsheet is for a plant having a capacity in the range of 300 to 500-tons per day.
The crushing section consists of primary and secondary crushing with intermediate screening. Both crushers are located in the same building and conveniently attended by one operator. A minimum of conveying equipment is required by this arrangement. Dust collecting facilities are, likewise, limited to only one building.
The crushed ore after automatic sampling is subjected to two-stage grinding using a Rod Mill in open circuit and a Ball Mill in closed circuit with a Classifier. TheUnit Flotation Cell receives the discharge from the ball mill for recovery of a substantial amount of the granular silver minerals together with galena as soon as freed. Reagents are added to the ball mill. Tramp iron and occasional oversize gangue are removed from the circuit by the Spiral Screen attached to the ball mill and this prevents excessive wear or plugging of the unit cell. The classifier is of the latest design.
The Mineral Jig is not included in the flowsheet, but on many ores of this type it is applicable either alone or with the unit cell. The grade of jig concentrate is usually very high grade and ideal for blending with the flotation concentrate. If native silver or gold values are present, the jig is a very essential addition to the flowsheet and would be used on the rod mill discharge in this case.
The classifier overflow is treated in a conventional manner using Sub-A Flotation Machines of cell-to-cell design which enables double cleaning of the silver-lead and zinc concentrates without the need of pumps. For large tonnage operations the Sub A Free Flow Machine is optional for roughing and scavenging, but the cell to cell type is always used in the cleaner circuits where high selectivity is essential. The two flotation banks are arranged so that the banks face one another and can be conveniently controlled by one operator from a single aisle. Operation of the Conditioner can also be observed from this aisle. A Sampler is used on the zinc tailing to provide an instant means for the operator to evaluate plant results. Some plants find it beneficial to use a visual sampler on the lead tailing ahead of the zinc circuit. The Sampler is also useful for evaluating the lead or zinc concentrate.General view of the flotation section at a modern silver-lead-zincmill. The lead circuit is on the left and the zinc circuit ison the right.
The silver-lead concentrate (including the unit cell concentrate) and the zinc concentrate are separately treated through wet cyclones to remove the coarse sulfides as thick underflow products suitable for direct filtration. The cyclone overflow products are ideally suited for thickening and subsequent filtration with their respective cyclone underflows. This procedure avoids any overload of heavy sulfides in the thickeners and, therefore, simplifies the operation of the thickeners. SRL Pumps are engineered for use with wet cyclones and give trouble-free service.
In addition to the feed sample, which is cut by means of a Type C Automatic Sampler, the final silver-lead and zinc flotation concentrates are sampled using Type B cutters. The final plant tailing is also sampled in the same manner.
This flow-sheet incorporates all features of a modern day mill for optimum efficiency and general simplicity for ease of operations. Instrumentation devices can be included to facilitate automatic control of the plant circuits if desired.
Many factors affect the metallurgical results of every plant. However, in a study of this type it is interesting to note the recoveries and grades that are actually being made at successful mills. The figures of these two plants are included for their value in making economic studies of new deposits.
metso rcs flotation machines - metso outotec
Optimal mineral recovery in a flotation circuit depends on the capacity to adapt to metallurgical variability in the ore being processed. Recognizing the need for a solution that addresses these challenges, Metso has made several advances in flotation design and technology.
Combining the benefits of circular cells with the unique features of the patented DV mechanism, the RCS (Reactor Cell System) flotation technology has been developed to create ideal conditions to maximize flotation performance for all roughing, cleaning and scavenging duties. The cell can be modified to handle high density slurries.
Maximize bubble-particle contact within the mechanism and the flotation tank leads to enhanced performance. Effective air dispersion and distribution throughout the cell volume helps in smooth froth surface and removal.
Our RCS flotation machines are built with efficient air and level controls with controlled aeration rate at each cell. The pneumatically operated dart valves help in effective pulp level control followed by accurate measurement with ultrasonic level sensor and float.
Metso offers the innovative circular tank concept to minimize slurry short circuiting as well as simplifying froth handling process. The compact and modular design proves to be very beneficial for quick construction, shipment and installation. Our internal dart valves also help to minimize footprint requirements.
Metso RCS flotation machines have extended wear life due to minimized local high velocity zones inside the tank. Impellers and diffusors supplied in high abrasion-resistant elastomers, and the impeller profile is design to minimize adsorbed power.
The mechanism design produces powerful radial slurry pumping to the cell wall and gives strong return flows to the underside of the impeller to minimize sanding. Additionally, it is the only mechanism to give maximum slurry recirculation to the upper part of the impeller.
The modular dart valve design provides flexibility to capacity changes without disturbances.Full suspension of the DV mechanism from the cell superstructure leads to very simplified routine maintenance. Along with our robust design, the RCS flotation machines are built to work for you!
Metso RCS flotation machines also are found as an essential piece to a regrind circuit. Rougher cells extract majority of the valuable mineral from the fresh ore. Meanwhile, scavenger cells are going to capture the remaining valuable mineral.
Revolutionary image analysis system for live measurement of multiple froth properties such as velocity, color, bubble size distribution, texture, stability and more. Higher froth recovery with continuous monitoring and analysis of flotation cells.
flotation machine for mineral & metallurgy - jxsc machine
Application copper sulfide, gold sulfide, zinc, lead, nickel, antimony, fluorite, tungsten, and other non-ferrous metals, and also be used for coarse selection for ferrous metals and nonmetals. Type Agitating flotation machine, Self-priming, aeration flotation, flotation column. ModelXJK, SF, GF, CHF, XJC, etc. Contact us for specific & quick selection.
Flotation machine (floatation machine, planktonic concentrator) in the mineral processing plant, mainly used for separating copper, zinc, lead, nickel, gold, and other non-ferrous metal. TypeXJK series agitation impeller flotation machine (Seldom used, small capacity); SF flotation machine (Larger volume, better flotation effect); Pneumatic flotation machine (aeration and agitation, high capacity). Corollary equipmentIn front: one or two sets of mixing tank for flotation agent agitation and slurry pulp agitation. Behind: concentrate pond, thickener or filter Flotation cell According to the ore grade, mineral type and processing capacity to choose, determine the number of the flotation cells. It is recommended that carrying out the mineral flotation tests to obtain the best procedure plan, like pulp density, time, reagent selection, etc. Flotation reagentfoaming agent, collecting agent, activating agent, inhibitor, etc. BrandsWemco flotation unit, Fahrenwald Denver, Callow, BGRIMM, etc. How to select mining flotation machine1. According to the nature of the ore (washability, feed particle-size, density, grade, pulp, pH, etc.) and flotation plant scale choose the appropriate flotation machine. 2. The concentration operation is mainly to improve the ore concentrate grade. The flotation foam layer should be thin so that separates the gangue. It is not appropriate to use a flotation machine with a large aeration volume. Therefore, there are differences between the froth flotation machine of concentration, roughing and scavenging. 3. JXSC engineer team here to help do flotation mining machine selection, price inquiry, flowsheet design.
Flotation machine structureThe metallurgist flotation mainly made up of slurry tank, mixing device, aeration device, mineralized bubble discharging device and motor. Flotation machine working principleFlotation process refers to the flotation separation in mineral processing. In the flotation machine, the ore slurry treated with the added agent, by aeration and stir, some of the ore particles are selectively fixed on the air bubbles and floats to the surface of the slurry and is scraped out. The rest is retained in the pulp, thus achieve the purpose of separating different minerals. The complete froth flotation process in metallurgy consists of rougher flotation, concentrate flotation and scavenging flotation. Flotation methodFroth flotation of sulphide ores, mainly have differential flotation and bulk flotation process, improve the flotation recovery rate of fine - particle. Flotation cell manufacturerJXSC specializes in the production of a full set of mineral processing equipment, and cooperates with the Mining Research Institute to design a scientific and reliable mineral processing flowsheet, supply gold flotation, copper flotation, zinc flotation, and the like ore flotation units.
summary of fluorite ore flotation process - jxsc machine
Taking deep research on the features, extraction methods, and fluorite mining machines have a significant positive effect on running the fluorite processing plant successfully. In the following paragraphs, I have made a detailed introduction from fluorite mineral attribute to extraction methods and machines and listed 2 cases for your reference.
Fluorite (also called fluorspar) is a mineral that common in nature, consists mainly of calcium fluoride( CaF2), can be symbiotic with many other minerals. More in wiki https://baike.baidu.com/item/%E8%90%A4%E7%9F%B3/258531?fromtitle=%E8%90%A4%E7%9F%B3%E7%9F%BF&fromid=8815755&fr=aladdin
Just as is the case with almost ore processing and non-metal beneficiation, the concentrate fluorite is extracted by crushing, sieving, grinding, grading, flotation, filtration, drying, etc. How to realize the high-efficiency sorting of associated fluorite ore is a real problem in the fluorite beneficiation process. Therefore, based on the characteristics of the associated fluorite ore, summarized the beneficiation method and floating agent of the types of associated fluorite ore. We, the JXSC mining machine factory, would be delightful provide you with the flotation machines.
The separation of quartz and fluorite achieved by grinding, it is an important factor affecting the flotation of quartz-type fluorite. The ground ore of a coarse size indicates that may have many associated fluorite ore lumps, these lumps may increase the silica content, decrease the flotation effect. If the grinding particle size is too fine, although quartz and fluorite have been dissociated from the monomer, it will cause the fluorite losing easily, thus reduce the recovery rate of fluorite.
In order to dissociate the fluorite from the quartz and not to pulverize the fluorite, the stage grinding process is generally used, which can reduce the silicon content in the fluorite concentrate after flotation and increase the fluorite recovery rate.
The results show that under the same conditions of grinding fineness, the fluorite concentrate by rod mill obtains a lower Si O2 content. Compared with ball milling, the particle size of rod grinding is more uniform, rod mill control the grinding fineness better.
In order to solve the difficulties in the separation of high calcium quartz fluorite ore, researchers did a great time of experiment. Studies have shown, the fluorite beneficiation effect of 97.21% concentrate grade and 69.04% recovery rate can be obtained when the condition of -0.074 mm grain taking 83.62% percentage, flotation 6 times, the PH value of slurry is 9-10YN-12 as the capture agent, sodium silicate, tannic and the Calgon as the inhibitors. When the PH value is 6, the sodium oleate has a significant effect on the recovery of pure fluorite minerals during the flotation process. However, when the slurry contains fine-grained quartz ore, the performance of sodium oleate to capture fluorite decreases. The capture ability of the oleic acid gradually improved by adding the sodium hexametaphosphate to disperse the quartz and fluorite. In a word, fine-grained quartz type fluorite ore is better to adopt the stage grinding process method to get the best size. Besides, it is best to use Na2CO3 to adjust PH value, choose oleic acid, oxidized paraffin, sodium silicate as a combination of collector and inhibitor.
Calcite type fluorite ore mainly consists of fluorite, and calcite( more than 30%). Since both calcite and fluorite are calcium-containing minerals, they have similar surface physicochemical properties. When coexisting in solution, they are prone to the mutual transformation between minerals, making separation of the two difficult to achieve.
Fatty acid collectors can float both of calcite and fluorite, therefore, it is needed to adjust the PH value of slurry. Practice shows that the PH value has a great impact on the flotation. When the PH value in the range of 8-9.5the fatty acid collectors can display function both of the fluorite and calcite. But in the weak acidic medium, the calcite has a lower floatability. Although it is difficult to separate calcite and fluorite by flotation, we still have chance to realize it by adjusting the PH value, choosing suited inhibitor(sodium silicate, salinization sodium silicate, acidification sodium silicate, Calgon, lignin sulfonate, dextrin,tannin, etc.), and using oleic acid as the trapping agent.
The barite type fluoride ore mainly consists of barite(10%-40%) and fluoride, also associated with iron pyrite, gelenite, sphalerite, and other sulfide minerals. It is not easy to separate the barite and fluoride because of the similar floatability. In general, the flotation process of the barite type fluoride ore is divided into two steps, one is combination flotation that obtains the combination of concentrate both of barite and fluorite, another is flotation that separation the barite and the fluorite from the combination concentrate.
Flotation of the first step: Na2CO3 as the conditioner of PH value, oleic acid as the capture agent, and sodium silicate as the inhibitor. Flotation of the second step has two ways: 1 Inhibiting barite and floating fluorite: inhibitors have lignin sulfonate, sodium silicate, NAF, dextrin, aluminum salt, ferric salts; captor has oleic acid. 2 Inhibiting fluorite and floating barite: adjusting the PH value the slurry to strong alkalinity by the sodium hydrate, using the citric acid, barium chloride, ammonium salt, sodium silicate as the inhibitors, and using the oleic acid or sodium alkyl sulfate as the collector.
The mineral composition of sulfide-type fluorite is similar to that of quartz type fluorite, but the content of the metal mineral is higher than that of the quartz type, and sometimes, the content of lead and zinc can reach the industrial grade. Therefore, it is necessary to take the recovery of the other metal mineral into considered. Usually, adopt the captor for sulfide minerals to select the metal sulfide minerals preferentially, then use the captor of fatty acid to recover the fluorite from the flotation tailings. In addition, roasting, leaching, and other processes can also help to extract valuable metals and to decompose fluorite.
A great deal of research and production practice shows that flotation is a useful method for recovering fluorite ores, suit for large scale fluorite ore processing, the beneficiation method( flotation process and chemical agent) varies from the ore characteristics. if you need a fluorite ore flotation machine, pls contact us.
More ores are treated using froth flotation cells than by any other single machines or process. Non-metallics as well as metallics now being commercially recovered include gold, silver, copper, lead, zinc, iron, manganese, nickel, cobalt, molybdenum, graphite, phosphate, fluorspar, barite, feldspar and coal. Recent flotation research indicates that any two substances physically different, but associated, can be separated by flotation under proper conditions and with the correct machine and reagents. The DRflotation machine competes with Wemco and Outotec (post-outokumpu) flotation cells but are all similar is design. How do flotation cells and machinework for themineral processing industry will be better understood after you read on.
While many types of agitators and aerators will make a flotation froth and cause some separation, it is necessary to have flotation cells with the correct fundamental principles to attain high recoveries and produce a high grade concentrate. The Sub-A (Fahrenwald) Flotation Machines have continuously demonstrated their superiority through successful performance. The reliability and adaptations to all types of flotation problems account for the thousands of Sub-A Cells in plants treating many different materials in all parts of the world.
The design of Denver Sub-A flotation cells incorporates all of the basic principles and requirements of the art, in addition to those of the ideal flotation cell. Its design and construction are proved by universal acceptance and its supremacy is acknowledged by world-wide recognition and use.
1) Mixing and Aeration Zone:The pulp flows into the cell by gravity through the feed pipe, dropping directly on top of the rotating impeller below the stationary hood. As the pulp cascades over the impeller blades it is thrown outward and upward by the centrifugal force of the impeller. The space between the rotating blades of the impeller and the stationary hood permits part of the pulp to cascade over the impeller blades. This creates a positive suction through the ejector principle, drawing large and controlled quantities of air down the standpipe into the heart of the cell. This action thoroughly mixes the pulp and air, producing a live pulp thoroughly aerated with very small air bubbles. These exceedingly small, intimately diffused air bubbles support the largest number of mineral particles.
This thorough mixing of air, pulp and reagents accounts for the high metallurgical efficiency of the Sub-A (Fahrenwald) Flotation Machine, and its correct design, with precision manufacture, brings low horsepower and high capacity. Blowers are not needed, for sufficient air is introduced and controlled by the rotating impeller of the Denver Sub-A. In locating impeller below the stationary hood at the bottom of the cell, agitating and mixing is confined to this zone.
2) Separation Zone:In the central or separation zone the action is quite and cross currents are eliminated, thus preventing the dropping or knocking of the mineral load from the supporting air bubble, which is very important. In this zone, the mineral-laden air bubbles separate from the worthless gangue, and the middling product finds its way back into the agitation zone through the recirculation holes in the top of the stationary hood.
3) Concentrate Zone:In the concentrate or top zone, the material being enriched is partially separated by a baffle from the spitz or concentrate discharge side of the machine. The cell action at this point is very quiet and the mineral-laden concentrate moves forward and is quickly removed by the paddle shaft (note direct path of mineral). The final result is an unusually high grade concentrate, distinctive of the Sub-A Cell.
A flotation machine must not only float out the mineral value in a mixture of ground ore and water, but also must keep the pulp in circulation continuously from the feed end to the discharge end for the removal of the froth, and must give the maximum treatment positively to each particle.
It is an established fact that the mechanical method of circulating material is the most positive and economical, particularly where the impeller is below the pulp. A flotation machine must not only be able to circulate coarse material (encountered in every mill circuit), but also must recirculate and retreat the difficult middling products.
In the Denver Sub-A due to the distinctive gravity flow method of circulation, the rotating impeller thoroughly agitates and aerates the pulp and at the same time circulates this pulp upward in a straight line, removing the mineral froth and sending the remaining portion to the next cell in series. No short circuiting through the machine can thus occur, and this is most important, for the more treatments a particle gets, the greater the chances of its recovery. The gravity flow principle of circulation of Denver Sub-A Flotation Cell is clearly shown in the illustration below.
There are three distinctive advantages of theSub-A Fahrenwald Flotation Machines are found in no other machines. All of these advantages are needed to obtain successful flotation results, and these are:
Coarse Material Handled:Positive circulation from cell to cell is assured by the distinctive gravity flow principle of the Denver Sub-A. No short circuiting can occur. Even though the ore is ground fine to free the minerals, coarse materials occasionally gets into the circuit, and if the flotation machine does not have a positive gravity flow, choke-ups will occur.
In instances where successful metallurgy demands the handling of a dense pulp containing an unusually large amount of coarse material, a sand relief opening aids in the operation by removing from the lower part of the cell the coarser functions, directing these into the feed pipe and through the impeller of the flowing cell. The finer fraction pass over the weir overflow and thus receive a greater treatment time. In this manner short-circuiting is eliminated as the material which is bled through the sand relief opening again receives the positive action of the impeller and is subjected to the intense aeration and optimum flotation condition of each successive cell, floating out both fine and coarse mineral.
No Choke-Ups or Lost Time:A Sub-A flotation cell will not choke-up, even when material as coarse as is circulated, due to the feed and pulp always being on top of the impeller. After the shutdown it is not necessary to drain the machine. The stationary hood and the air standpipe during a shutdown protects the impeller from sanding-up and this keeps the feed and air pipes always open. Denver Sub-A flotation operators value its 24-hour per day service and its freedom from shutdowns.
This gravity flow principle of circulation has made possible the widespread phenomenal success of a flotation cell between the ball mill and classifier. The recovery of the mineral as coarse and as soon as possible in a high grade concentrate is now highly proclaimed and considered essential by all flotation operators.
Middlings Returned Without Pumps:Middling products can be returned by gravity from any cell to any other cell. This flexibility is possible without the aid of pumps or elevators. The pulp flows through a return feed pipe into any cell and falls directly on top of the impeller, assuring positive treatment and aeration of the middling product without impairing the action of the cell. The initial feed can also enter into the front or back of any cell through the return feed pipe.
Results : It is a positive fact that the application of these three exclusive Denver Sub-A advantages has increased profits from milling plants for many years by increasing recoveries, reducing reagent costs, making a higher grade concentrate, lowering tailings, increasing filter capacities, lowering moisture of filtered concentrate and giving the smelter a better product to handle.
Changes in mineralized ore bodies and in types of minerals quickly demonstrate the need of these distinctive and flexible Denver Sub-A advantages. They enable the treatment of either a fine or a coarse feed. The flowsheet can be changed so that any cell can be used as a rougher, cleaner, or recleaner cell, making a simplified flowsheet with the best extraction of mineral values.
The world-wide use of the Denver Sub-A (Fahrenwald) Flotation Machine and the constant repeat orders are the best testimonial of Denver Sub-A acceptance. There are now over 20,000 Denver Sub-A Cells in operation throughout the world.
There is no unit so rugged, nor so well built to meet the demands of the process, as the Denver Sub-A (Fahrenwald) Flotation Machine. The ruggedness of each cell is necessary to give long life and to meet the requirements of the process. Numerous competitive tests all over the world have conclusively proved the real worth of these cells to many mining operators who demand maximum result at the lower cost.
The location of the feed pipe and the stationary hood over the rotating impeller account for the simplicity of the Denver Sub-A cell construction. These parts eliminates swirling around the shaft and top of the impeller, reduce power load, and improve metallurgical results.
TheSub-A Operates in three zones: in bottom zone, impeller thoroughly mixes and aerates the pulp, the central zone separates the mineral laden particles from the worthless gangue, and in top zone the mineral laden concentrate high in grade, is quickly removed by the paddle of a Denver Sub-A Cell.
A Positive Cell Circulation is always present in theSub-A (Fahrenwald) Flotation Machine, the gravity flour method of circulating pulp is distinctive. There is no short circulating through the machine. Every Cell must give maximum treatment, as pulp falls on top of impeller and is aerated in each cell repeatedly. Note gravity flow from cell to cell.
Choke-Ups Are Eliminated in theSub-A Cell, even when material as coarse as is handled, due to the gravity flow principle of circulation. After shutdown it is not necessary to drain the machine, as the stationary hood protects impeller from sanding up. See illustration at left showing cell when shut down.
No Bowlers, noair under pressure is required as sufficient air is drawn down the standpipe. The expense and complication of blowers, air pipes and valves are thus eliminated. The standpipe is a vertical air to the heart of the Cell, the impeller. Blower air can be added if desired.
The Sub-A Flexibility allows it tobe used as a rougher, cleaner or recleaner. Rougher or middling product can be returned to the front or back of any cell by gravity without the use of pumps or elevators. Cells can be easily added when required. This flexibility is most important in operating flotation MILLS.
Pulp Level Is Controlled in each Sub-A Flotation Cell as it has an individual machine with its own pulp level control. Correct flotation requires this positive pulp level control to give best results in these Cells weir blocks are used, but handwheel controls can be furnished at a slight increase in cost. Note the weir control in each cell.
High Grade Concentrate caused by thequick removal of the mineral forth in the form of a concentrate increases the recovery. By having an adjustment paddle for each Sub-A Cell, quick removal of concentrate is assured, Note unit bearing housing for the impeller Shaft and Speed reducer drive which operates the paddle for each cell
Has Fewer Wearing Parts because Sub-A Cells are built for long, hard service, and parts subject to wear are easily replaced at low cost. Molded rubber wearing plates and impellers are light in weight give extra long life, and lower horsepower. These parts are made under exact Specifications and patented by Denver Equipment Co.
TheRugged Construction of theSub-A tank is made of heavy steel, and joints are welded both inside and out. The shaft assemblies are bolted to a heavy steel beam which is securely connected to the tank. Partition plates can be changed in the field for right or left hand machine. Right hand machine is standard.
The Minerals Separation or M.S. Sub-aeration cells, a section of which is shown in Fig. 32, consists essentially of a series of square cells with an impeller rotating on a vertical shaft in the bottom of each. In some machines the impeller is cruciform with the blades inclined at 45, the top being covered with a flat circular plate which is an integral part of the casting, but frequently an enclosed pump impeller is used with curved blades set at an angle of 45 and with a central intake on the underside ; both patterns are rotated so as to throw the pulp upwards. Two baffles are placed diagonally in each cell above the impeller to break up the swirl of the pulp and to confine the agitation to the lower zone. Sometimes the baffles are covered with a grid consisting of two or three layers each composed of narrow wood or iron strips spaced about an inch apart. The sides and bottom of the cells in the lower or agitation zone are protected from wear by liners, which are usually made of hard wood, but which can, if desired, consist of plates of cast-iron or hard rubber. The section directly under the impeller is covered with a circular cast-iron plate with a hole in the middle for the admission of pulp and air. The hole communicates with a horizontal transfer passage under the bottom liner, through which the pulp reaches the cell. Air is introduced into each cell through a pipe passing through the bottom and delivering its supply directly under the impeller. A low-pressure blower is provided with all machines except the smallest, of which the impeller speed is fast enough to draw in sufficient air by suction for normal requirements.
The pulp is fed to the first cell through a feed opening communicating with the transfer passage, along which it passes, until, at the far end, it is drawn up through the hole in the bottom liner by the suction of the impeller and is thrown outwards by its rotation into the lower zone. The square shape of the cell in conjunction with the baffles converts the swirl into a movement of intense agitation, which breaks up the air entering at the same time into a cloud of small bubbles, disseminating them through the pulp. The amount of aeration can be accurately regulated to suit the requirements of each cell by adjustment of the valve on its air pipe.
Contact between the bubbles and the mineral particles probably takes place chiefly in the lower zone. The pumping action of the impeller forces the aerated pulp continuously past the baffles into the upper and quieter part of the cell. Here the bubbles, loaded with mineral, rise more or less undisturbed, dropping out gangue particles mechanically entangled between them and catching on the way up a certain amount of mineral that has previously escaped contact. The recovery of the mineral in this way can be increased at the expense of the elimination of the gangue by increasing the amount of aeration. The froth collects at the top of the cell and is scraped by a revolving paddle over the lipat the side into the concentrate launder. The pulp, containing the gangue and any mineral particles not yet attached to bubbles, circulates to some extent through the zone of agitation, but eventually passes out through a slot situated at the back of the cell above the baffles and flows thence over the discharge weir. The height of the latter is regulated by strips of wood or iron and governs the level of the pulp in the cell. The discharge of each weir falls by gravity into the transfer passage under the next cell and is drawn up as before by the impeller. The pulp passes in this way through the whole machine until it is finally discharged as a tailing, the froth from each cell being drawn off into the appropriate concentrate launder.
No pipes are normally fitted for the transference of froth or other middling product back to the head of the machine or to any intermediate point. Should this be necessary, however, the material can be taken by gravity to the required cell through a pipe, which is bent at its lower end to pass under the bottom liner and project into the transfer passage, thus delivering its product into the stream of pulp that is being drawn up by the impeller
Particulars of the various sizes of M.S. Machines are given in Table 21. It should be noted that the size of a machine is usually defined by the diameter of its impeller ; for instance, the largest one would be described as a 24-inch machine.
The Sub-A Machine, invented by A. W. Fahrenwald and developed in many respects as an improvement in the Minerals Separation Machine, from which it differs considerably in detail, particularly in the method of aerating the pulp, although the principle of its action is essentially the same. Its construction can be seen from Figs. 33 and 34.
In common with the M.S. type of machine, it consists of a series of square cells fitted with rotating impellers. Each cell, however, is of unit construction, a complete machine being built up by mounting the required number of units on a common foundation and connecting up the pipes which transfer the pulp from one cell to the next. The cells are constructed of welded steel. The impeller, which can be rubber-lined,if required, carries six blades set upright on a circular dished disc, and is securely fixed to the lower end of the vertical driving shaft. It is covered with a stationary hood, to which are attached a stand-pipe, a feed pipe, and the middling return pipes. The underside of the hood is fitted with a renewable liner of rubber or cast-iron. The pulp, entering the first cell through the feed pipe and sometimes through the middling pipes, falls on to the impeller, the rotation of which throws it outwards into the bottom zone of agitation. The suction effect due to the rotationof the impeller draws enough air down the standpipe to supply the aeration necessary for normal operation. A portion of the pulp, cascading over the open tops of the impeller blades, entraps and breaks up the entrained air, the resulting spray-like mixture being then thrown out into the lower zone of agitation, where it is disseminated through the pulp as a cloud of fine bubbles. Should this amount of aeration be insufficient, air can be blown in under slight pressure through a hole near the top of the stand-pipe, in which case a rubber bonnet is fastenedto the lower bearing and clamped round the top of the stand-pipe so as to seal the supply from the atmosphere.
The bottom part of the cell is protected from wear by renewable cast-iron or rubber liners. Four vertical baffles, placed diagonally on the top of the hood, break up the swirl of the pulp and intensify theagitation in the lower zone. The pumping action of the impeller combined with the rising current of air bubbles carries the pulp to the quieter upper zone, where the bubbles, already coated with mineral, travel upwards, drop out many of the gangue particles which may have become entangled with them, and finally collect on the surface of the pulp as a mineralizedfroth. One side of the cell is sloped outwards so as to form, in conjunction with a vertical baffle, a spitzkasten-shaped zone of quiet settlement, where any remaining particles of gangue that have been caught and held between the bubbles are shaken out of the froth as it flows to the overflow lip at the front of the cell. The baffle prevents rising bubbles from entering the outer zone, thus enabling the gangue material released from the froth to drop down unhindered into the lower zone. A revolving paddle scrapes the froth past the overflow lip into the concentrate launder.
Should the machine be required to handle more than the normal volume of froth, it is built with a spitzkasten zone on both sides of the cell. For the flotation of ores containing very little mineral the spitzkasten is omitted so as to crowd the froth into the smallest possible space, the front of the cell being made vertical for the purpose.
Circulation of the pulp through the lower zone of agitation is maintained by means of extra holes at the base of the stand-pipe on a level with the middling return pipes. An adjustable weir provides for the discharge of the pulp to the next cell, which it enters through a feed-pipe as before. Below the weir on a level with the hood is a small sand holeand pipe through which coarse material can pass direct to the next cell without having to be forced up over the weir. The same process is repeated in each cell of the series, the froth being scraped over the lip of the machine, while the pulp passes from cell to cell until it is finally discharged as a tailing from the last one. The middling pipes make it an easy matter for froth from any section of the machine to be returned if necessary to any cell without the use of pumps.
Table 22 gives particulars of the sizes and power requirements of Denver Sub-A Machines and Table 23 is an approximate guide to their capacities under different conditions. The number of cells needed
Onemethod of driving the vertical impeller shafts of M.S. Subaeration or Denver Sub-A Machines is by quarter-twist belts from a horizontal lineshaft at the back of the machine, the lineshaft being driven in turn by a belt from a motor on the ground. This method is not very satisfactory according to modern standards, firstly, because the belts are liable to stretch and slip off, and, secondly, because adequate protection againstaccidents due to the belts breaking is difficult to provide without making the belts themselves inaccessible. A more satisfactory drive, with which most M.S. Machines are equipped, consists of a lineshaft over the top of the cells from which each impeller is driven through bevel gears. The lineshaft can be driven by a belt from a motor on the ground, by Tex- ropes from one mounted on the frame work of the machine, or by direct coupling to a slow-speed motor. This overhead gear drive needs careful adjustment and maintenance. Although it may run satisfactorily for years, trouble has been experienced at times, generally in plants where skilled mechanics have not been available. The demand for something more easily adjusted led to the development of a special form of Tex-rope drive which is shown in Fig. 35. Every impeller shaft is fitted at the top with a grooved pulley, which is driven by Tex-ropes from a vertical motor. This method is standard on Denver Sub-A Machines, and M.S. Machines are frequently equipped with it as well, but the former type are not made with the overhead gear drive except to special order.
The great advantage of mechanically agitated machines is that every cell can be regulated separately, and that reagents can be added when necessary at any one of them. Since, as a general rule, the most highly flocculated mineral will become attached to a bubble in preference to a less floatable particle, in normal operation the aeration in the first few cells of a machine should not be excessive ; theoretically there should be no more bubbles in the pulp than are needed to bring up the valuable minerals. By careful control of aeration it should be possible for the bulk of the minerals to be taken off the first few cells at the feed end of the machine in a concentrate rich enough to be easily cleaned, and sometimes of high enough grade to be sent straight to the filtering section as a finished product. The level of the pulp in these cells is usually kept comparatively low in order to provide a layer of froth deep enough to give entangled particles of gangue every chance of dropping out, but it must not be so low that the paddles are prevented from skimming off the whole of the top layer of rich mineral. Towards the end of the machine a scavenging action is necessary to make certain that the least possible amount of valuable mineral escapes in the tailing, for which purpose the gates of the discharge weirs are raised higher than at the feed end, and the amountof aeration may have to be increased. The froth from the scavenging cells is usually returned to the head of the machine, the middling pipes of the Denver Sub-A Machine being specially designed for such a purpose. The regulation of the cleaning cells is much the same as that of the first few cells of the primary or roughing machine, to the head of which the tailing from the last of the cleaning cells is usually returned.
A blower is sometimes required with the M.S. Subaeration Machine. Since each cell is fitted with an air pipe and valve, accurate regulation of aeration is a simple matter. The Denver Sub-A, Kraut, and Fagergren Machines, however, are run without blowers, enough air being drawn into the machines by suction.
In the Geco New-Cell Flotation Cellthe pneumatic principle is utilized in conjunction with an agitating device. The machine, which is illustrated in Fig. 44, consists of a trough or cell made of steel or wood, whichever is more convenient, through the bottom of which projects a series of air pipes fitted with circular mats of perforated rubber. The method of securing the mat to the air pipe can be seen from Fig. 45. Over each mat rotates a moulded rubber disc of slightlylarger diameter at a peripheral speed of 2,500 ft. per minute. It is mounted on a driving spindle as shown in Fig. 46.
Each spindle is supported and aligned by ball-bearings contained in a single dust- and dirt-proof casting, and each pair is driven from a vertical motor through Tex-ropes and grooved pulleys, a rigid steel structure supporting the whole series of spindles with their driving mechanism. The machine can be supplied, if required, however, with a quarter-twist drive from a lineshaft over flat pulleys.
The air inlet pipes are connected to a main through a valve by which the amount of air admitted to each mat can be accurately controlled. The air is supplied by a low-pressure blower working at about 2 lb. per square inch. It enters the cell through the perforations in the rubber mat and is split up into a stream of minute bubbles, which are distributed evenly throughout the pulp by the action of the revolving disc. By this means a large volume of finely-dispersed air is introduced withoutexcessive agitation. There is sufficient agitation, however, to produce a proper circulation in the cell, but not enough to cause any tendency to surge or to disturb the froth on the surface of the pulp. All swirling movement is checked by the liner-baffles with which the sides of the cell are lined ; their construction can be seen in Fig. 44. They are constructed of white cast iron and are designed to last the life of the machine, the absence of violent agitation making this possible.The pulp must be properly conditioned before entering the machine. It is admitted through a feed box at one end at a point above the first disc, and passes along the length of the cell to the discharge weir without being made to pass over intermediate weirs between the discs. The height of the weir at the discharge end thus controls the level of the pulp in the machine. The froth that forms on the surface overflows the froth lip in a continuous stream without the aid of scrapers, its depth being controlled at any point by means of adjustable lip strips combined with regulation of the air.The Geco New-Cell is made in four sizesviz., 18-, 24-, 36-, and 48-in. machines, the figure representing the length of the side of the squarecell. Particulars of the three smallest sizes are given in Table 27. Figures are not available for the largest size.
flotation cells in iron ore processing - froth flotation (sulphide & oxide) - metallurgist & mineral processing engineer
Does anybody have experience of working with WEMCO flotation cells to remove sulfur in iron ore reverse flotation circuits? Could it be a good choice for flotation of coarse and dense iron ore particles without any settlement?
I think by settlement you are referring to sanding of the flotation cell (where particles come out of suspension and settle in tank). To answer your question I think its best to consider the anatomy of forced air vs. induced air (e.g. WEMCO) flotation cells. The induced air flotation cell has the rotor position at the top of the cell as it needs to be close to the surface to pull in air; hence the majority of the mixing energy is dissipated in the top of the cell. True these cells are designed for pumping and circulating pulp throughout but as the high energy zone is generally adjacent to the rotor you would have to put in even more energy to ensure that particles entering the cell at the bottom remain suspended (especially when coarse). Conversely the forced air designs of cells have rotors at the bottom so the high energy zone of the mixing is where the particles are most likely to settle. If you think about this which arrangement is less likely to have coarse and high SG particles sanding?
In addition for a forced air cell if settling occurs you can stop the air, thus maximize the energy used for mixing/suspension, and get the material moving again (prior to turning the air back on). The mixing and air dispersion actions on an induced air cell cannot be decoupled so this is more difficult. Also it is quiet difficult for a rotor located at the top to get sanded material in the bottom of the cell moving.
There are also additional important considerations when dealing with coarse and heavy minerals; motor size and valve arrangement. Typical float cells are designed with a particle SG or around 2.8-3.0 SG if you have a majority magnetite or hematite feed then you are looking at particle SGs approaching 5.0 for the overall feed. This needs to be taken into account and an appropriate motor/mechanism selected. The valve arrangement is also important. For this type of application internal downflow dart valves are likely the best as this minimizes the chances of particles sanding within the ducting and transfer boxes. I suggest you find a manufacturer who has references in dealing with this type of material as you really cant afford to get this wrong and have the cells sanding up.
I mean sanding area. The problem during operation is that self aeration system could not suspend all particles in a cell, especially when particles are large (e.g. > 150 micron) with high specific gravity. So the materials choke in the cell and you have to stop the operation. What is the advantage of the rotor new position in WEMCO cells in comparison with others while we faced such problem in working with this cell?
In forced air cells we can control the turbulence zone by changing the air flow but in induced air cells we have to stable the froth zone manipulating the rotor speed or other mechanical parameters. Therefore, we reduce the required energy for particles suspension and sanding will emerge as a result.
May I ask what type of WEMCO cells you are referring to Tank Cells, or Trough Cells? From my experience with these cells the Tank Cells are more prone to sanding than the trough cells. As you say the high SG Iron minerals will tend to settle especially in a dilute pulp density, have you tried floating at 50-55wt% solids to see if the settling stops?
I propose to do some settling tests in laboratory with difference solid content, and then use lowest settling rate for flotation, but please note that in high concentrate pulps we will have some problems such as:
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