Acid grade fluorspar which is in great demand by the chemical and aluminum industries, must contain at least 97.5% CaF2 with not more than 1.5% SiO2 and 0.5% Fe2O3. Often the Silica is limited to 1.2% with penalties starting at 1.0% SiO2. These limitations on grade and impurities require extremely close mill control, particularly through flotation where selectivity and high recovery is essential.
Over 95% of all acid grade fluorspar is processed by flotation through Sub-A (Fluorspar Type) Flotation machines. These machines, of the cell to cell type, are designed special for fluorspar with a high degree of flexibility essential for selectivity and multiple cleaning of concentrate. Middlings and clean tailings often must be completely isolated from the separate cleaning steps and diverted to the proper part in the milling circuit for most economical and efficient retreatment.
The flowsheet illustrated above is typical for the average Sub-A Fluorspar Flotation mill treating up to 100 tons of mine run ore per 24 hour day. Actual flotation conditions and equipment requirements should always be determined by having a comprehensive test made on the ore before proceeding with any fluorspar operation. Fluorspar ores may be quite complex, particularly when associated with lead and zinc sulphides, barite, calcite, iron oxide, and siliceous impurities. For this reason, a laboratory flotation test should be the first step in establishing a flowsheet.
For the average small mill treating up to 100 tons of ore a day, primary crushing is usually adequate and very economical. Larger tonnage will require primary and secondary crushing for maximum efficiency in size reduction and subsequent ball milling.
Fluorspar ores usually require grinding to 48 or 65 mesh to liberate the calcium fluoride from the gangue impurities. Ball mill grinding with a Steel Head Ball Mill in closed circuit with classifier is the general practice. In larger plants, particularly when fine grinding is necessary, thickening of the classifier overflow is necessary to maintain proper density and feed regulation to flotation. This thickening step on fluorspar ores containing sulphides is usually between the sulphide and fluorspar flotation circuits. Reagents used for selective flotation of lead and zinc then can be rejected in the thickener overflow water.
Normally, conditioning at mill temperature willthoroughly film the fluorspar with reagent and makeit readily amenable to separation and recovery by flotation. Heating the pulp, even up to the boiling point,is often advantageous.
AnAgitator and Conditioner is ideal for fluorspar conditioning as circulation is positive and thorough reagentizing with a minimum amount of reagent is assured. Any frothing tendency is dissipated in the pulp through the stand pipe and adjustable froth collar.
Flotation of fluorspar must be extremely selective when producing acid grade concentrate. This selectivity is essential as the ratio of concentration is low, often up to 80% or more of the entire tonnage, and must be floated in the rough circuit. Cleaning by two or more stages of flotation must bring the rougher product up to acid grade and at the same time retain a high weight recovery with a minimum circulating load.
The Sub-A Flotation machine, the accepted standard in all fluorspar flotation plants, has been adapted specially for fluorspar treatment with provision for multi-stage cleaning and recirculation of middling products without the need of auxiliary pumps. Cleaner tailings may be conveniently removed at any point in the circuit. The flowsheet on the reverse side of this page shows one of the many possible cell arrangements used in treating fluorspar ore.
Thickening of fluorspar concentrates offers no special problem. Thickener capacity, however, should be adequate to handle the tonnage and have ample storage capacity during possible interruption in the filtering and drying sections. Fluorspar flotation froth has a tendency to build up on the thickener surface, but this can be taken care of by retaining rings near the overflow lip and by sprays so only clear water overflows the thickener. Thickened concentrates at 50 to 60% solids is removed by a Adjustable Stroke Diaphragm Pump, feeding by gravity to the filter.
Fluorspar is extremely rapid filtering even when ground fine, provided a non-blinding filter media is used. The rotary fluorspar type filter with stainless steel filter media, heavy duty oscillating mechanism, oversize valve and ports, and high displacement vacuum pump is standard for fluorspar flotation concentrates and will discharge a filter cake with as low as 6% moisture. In the event the filtrate is slightly turbid or contains solids, it should be diverted back to the thickener. For this reason a adjustable stroke diaphragm pump is often used in place of the conventional centrifugal filtrate pump.
Fluorspar flotation concentrates of acid grade must be dried to less than 0.5% moisture. Dust losses are kept to a minimum by providing a closed system with a cyclone to insure only vapor laden air discharging to the atmosphere. Enclosed screw conveyors, elevators and often air-born systems are used to transport the finely divided dried acid spar to the storage bins. Provisions should be made for handling efficiently the hot concentrate discharging from the dryer. The Standard Dryer is ideal for this purpose.
Fluorspar ores often contain appreciable amounts of sulphides in the form of galena, sphalerite, or both. These sulphides, when present, not only represent a valuable constituent of the ore, but also must be removed prior to fluorspar flotation to meet the market specifications for acid grade fluorspar.
If lead and zinc were present, the same flowsheet would apply to remove a bulk sulphide concentrate which could be subsequently refloated to produce the respective lead and zinc concentrates suitable for marketing.
The best approach to effectively produce separate lead and zinc concentrates should be established by test work. In some cases, selective flotation is indicated initially. This may be accomplished by removing a lead concentrate, then following this process by conditioning and flotation of the lead tailing to produce a zinc concentrate.
Conditioning of the classifier overflow is required if sulphidization is employed to effect flotation of oxidized lead. A second stage conditioning of the thickened lead tailing, after repulping with fresh water, is required for flotation of the fluorspar. Heating of the pulp at this point is often advantageous.
The lead and fluorspar are recovered by Flotation of the cell-to-cell type, permitting maximum recovery and grade of concentrate. Wide acceptance of machines is well verified when considering that over 95% of all acid grade fluorspar is processed in the Sub-A Flotation Machine. Flexibility of these machines is of prime importance where such high specifications must be met. Multiple cleaning, always necessary in acid grade fluorspar plants, can be performed without the help of pumps.
Both concentrates are thickened and filtered. The thickenedlead concentrate is filtered on the Disc Filter. Thickened fluorspar concentrate, at approximately 60% solids here, has a high filter capacity of approximately 2000 pounds per sq. ft. per 24 hours. The Fluorspar Filter with its stainless steel filter media, is especially designed for this application.
The Standard Dryer effectively dries the filtered fluorspar concentrate to less than 0.5% moisture, as required for marketing. An elevated temperature in the dryer can also be used to burn off small amounts of sulphur and lead.
A screw conveyor and bucket elevator as employed to transport the dried fluorspar to the concentrate storage bins. Bins can be conveniently discharged into rail road cars for shipment, while the filtered lead concentrate may be marketed as produced, without drying.
While many ores respond to the same general pattern of treatment, each ore is an individual problem.Such is the case of this fluorspar ore which is characterized by the presence of a portion of the fluorite inextremely close association with calcium carbonate andsilica and containing appreciable clay.
High acid grade fluorspar concentrates are difficult to obtain from this class of ores by flotation with an ordinary -65 mesh grind. The concentrates, in this study, are currently being used for production of hydrofluoric acid and synthetic cryolite. Market requirements demand that the calcium carbonate content be reduced to an absolute minimum. Moreover, the future productionnow in demand, is desirable. This study deals with a flowsheet designed to achieve high recovery of acid-grade fluorspar in an economical manner.
The typical fluorspar flotation flowsheet normally consists of stage grinding by ball mill in closed circuit with a mechanical classifier followed by conditioning of the pulp either with or without steam in the presence of reagents followed by Sub-A Flotation with three or more cleaning steps by reflotation. This particular ore does not, with the normal flowsheet, produce an acid grade concentrate of 97.5% CaF2 with less than 1.5% SiO2.
The ore being studied is crushed underground at the mine and partially beneficiated by the heavy media process. This washed ore is further crushed at the mill. Soda ash is added to the primary grinding mill which is in open circuit with a duplex Spiral Classifier. The classifier is in closed circuit with the secondary grinding mill and the classifier overflow, which is all 65 mesh, is pumped by a SRL Pump to the Conditioner where the following reagents are added:
Reagent Amount, Pounds per ton Na2Si03 (Optional) 0.2 Soda Ash 2.0 Oleic Acid up to 2.0 Quebracho 0.2
The conditions presented by this particular ore illustrate the importance of complete laboratory investigations as a great many different combinations of treatment were required to develop the final flowsheet. The deviations from the standard fluorspar flowsheet were first substantiated by locked cycle batch laboratory tests followed by a small tonnage pilot plant run to verify the laboratory results before final recommendations were made.
The rougher flotation circuit produces a final tailings while the rougher concentrate is subjected to the first cleaning stage. A 6 cell Sub A Flotation Machine, cell to cell type, is used for the rougher flotation and 6-cell Sub-A Flotation Machines are also used for the three cleaning steps.
Tailings from the first cleaners are pumped to a Morton 2-stage Cyclone for the removal of clay slimes. The ability to add clear water for washing in the classifier makes the Morton Cyclone particularly useful at this point in the flowsheet. The slimes go to final tailings and the cyclone sands, at high density, are reground in a Regrind Mill which is in closed circuit with a Hydro-Classifier. The regrind is to 325 mesh and the hydro-classifier overflow returns to the first cleaner cells for reflotation. Reagent sodium silicate is recommended to aid classification. Concentrates from the first cleaners go to the second cleaner cells where further up-grading takes place.
The middlings (tailings) from the second cleaner cells go to the hydro-classifier in the re-grind circuit. The concentrates from the second cleaners advance to the final cleaners. Tailings from the final cleaner cells are returned to the second cleaners and the final, high grade concentrates are filtered, dried and shipped to market.
The concentration of fluorspar ores for the production of acid grade concentrates is accomplished by the use of combinations of reagents such as pH regulators, depressant and fluorspar promoters. The reagents commonly used are as follows:
Factors of simplicity, initial low plant cost, together with flowsheet flexibility for maximum results on a difficult ore were basic considerations in the design of this 125-ton per day Fluorspar Flotation Mill. The design proved successful and accomplished the desired metallurgical results, with low capital expenditure and operating costs.
Following numerous laboratory tests, a flowsheet was developed that gives flexibility to handle the several types of fluorspar ores. Two stage open circuit crushing, with the average ore ground to 100 mesh,gives maximum results. Fine grained ores with some sulphides require secondary classification and a sulphide flotation stage. Due to character of most fluorspar ores heating the pulp gave improved results, and necessitated the installation of a boiler to provide hot dilution and make up flotation water for five stages of cleaning and recleaning. A Apron Feeder controls the feed from crude ore bin to jaw crusher while a wedge bar grizzly ahead of the jaw crusher removes the fines from the crusher feed. A 2x4 Dillon Screen removes the fines ahead of secondary crushing. An adjustable stroke ore feeder controls feed to the 5x8 Steel Head Ball Mill, and the spiral classifier discharge is pumped direct to flotation section or to hydroclassifier for secondary classification, depending on requirements.
The machinery was located for accessibility, ease of operation, minimum loss of floor space, resulting in reduced size of mill. The crude ore bin was constructed of natural timber on the site, on a steep slope, reducing expense of excavation and construction. An 8 clear opening rail grizzly prevented oversizegoing into bin.
The buildings for crushing section and mill are of light steel construction with corrugated sheet metal on walls and roof. The frame work and trusses lightweight for buildingsupport only and provided without insulation, because of mild climatic conditions. Account of heavy snowfalls the roof slopes are all of quarter pitch.
Launders on cleaning stages are made so that flows can be changed to regulate number of cells required, depending on the type ore being treated. Wood platforms and walkways of 2 spaced lumber are used in flotation sections, while piping between machines is carried below the floor.
All electric lighting and power wiring with ample reserve are in rigid conduit with flexible connections to motors; and motor controls are mounted on wall panels with stop and start push button stations located within sight or near each motor. Fluorescent lighting is provided over flotation section, as it gives operators better visual control of the flotation operation.The Rotary Dryer is lined with fire brick at discharge (burner) end.
With depletion of high-grade deposits, production must depend upon low-grade deposits that are highly contaminated with impurities which may be silica, calcite, barite, iron oxide, and sulphides such as pyrite, galena, and sphalerite, in close association. The flotation problem is largely one of impurity removal. The sulphide minerals are generally floatedfirst, and then the fluorite is floated from the silica, calcite, and other impurities.
Oleic acid or various mixtures of oleic and linoleic acids with soda ash and sodium silicate as silica depressant and slime controller, and quebracho to depress calcite, are the common reagents for fluorspar flotation. Sometimes pre-sulphide flotation with xanthate and a frother is necessary to remove sulphides and, often, heating the pulp to boiling temperature is advantageous in effectively depressing the silica, calcite and other associated minerals in the cleaning stages.
[/fusion_builder_column][fusion_builder_column type=1_1 background_position=left top background_color= border_size= border_color= border_style=solid spacing=yes background_image= background_repeat=no-repeat padding= margin_top=0px margin_bottom=0px class= id= animation_type= animation_speed=0.3 animation_direction=left hide_on_mobile=no center_content=no min_height=none]Geology-Where-are-Fluorspar-Deposits
This report is the fourth in a Bureau of Mines series describing the sodium fluoride-lignin sulfonate-fatty acid process of froth flotation separation of fluorspar from complex ores containing fluorspar, barite, calcite, and quartz which was developed and patented by Clemmer and Clemmons of the Bureau of Mines. At the Tucson (Ariz.) Metallurgy Research Laboratory the ores of Arizona were studied; and at the Tuscaloosa (Ala.) Metallurgy Research Center, the ores of Kentucky, Tennessee, and Illinois were studied.
The sodium fluoride-lignin sulfonate-fatty acid process is applicable to a variety of ores of different grades and mineral association for recovery of fluorspar from associated gangue materials; it has been shown to be practicable in continuous pilot plant operation as well as laboratory-scale flotation tests. This report deals with the application of the process to a complex calcareous fluorspar ore from Illinois and presents the results of laboratory batch flotation tests and continuous pilot plant flotation tests for recovery of the fluorspar in the ore.
The largest use of fluorspar is in the production of hydrofluoric acid in which no satisfactory substitute for acid-grade fluorspar is known. A prospective new outlet for hydrofluoric acid is in its addition to the oxidizer of the Atlas rocket, which will significantly increase the booster performance. The second major use of fluorspar is as a flux in the manufacture of basic open hearth and basic electric furnace steels in which no suitable materials are available to replace metallurgical-grade fluorspar, A third use of fluorspar is in the manufacture of glass and ceramic products. The specifications and prices of the various grades of fluorspar are listed in appendix A.
The complex fluorspar ore used in the investigation was from the fluorspar district near Cave-in-Rock, III. ; a 14-ton sample of ore was obtained from the Minerva Co. Crystal mine located about 5 miles west of Cave-in-Rock.
Petrographic examination showed that about 38 percent of the fluorspar reporting to the minus 48- plus 65-mesh fraction contained inclusions and that about 24 percent of the fluorspar was locked in the minus 325- plus 400-mesh fraction. However, the carbonate and quartz crystals locked in the fluorspar mineral were extremely small; in a concentrate analyzing 98.0 percent CaF2, 30 percent of the fluorspar grains were locked. The petrographic analysis revealed that no appreciable benefit to mineral liberation would be achieved by crushing finer than 65 mesh.
The primary carbonate in the ore was calcite with a considerable quantity of dolomite. The silica present was reported as quartz. Other materials consisted of 1.3 percent sphalerite and minor amounts of barite and galena. A chemical analysis of the sample is shown in table 1.
Samples of the ore were prepared for flotation by dry crushing to minus 10 mesh followed by wet stage grinding to minus 65 mesh in a laboratory pebble mill, using Tuscaloosa city tap water that had about 45 parts per million equivalent calcium carbonate total hardness. Prior to flotation, the ground ore pulp was treated, at about 40 percent solids, in a mechanically agitated flotation cell with conditioning reagents and then with a collector. A rougher fluorspar concentrate was floated off and cleaned six times.
A series of preliminary flotation tests was made of the ore to determine the quantities of sodium fluoride and calcium lignin sulfonate necessary to produce the maximum recovery and grade of fluorspar. The quantities of sodium fluoride and calcium lignin sulfonate were varied from 2.0 to 8.0 pounds per ton of ore; the quantity of oleic acid was held constant at 0.48 pound per ton of ore. The grade of fluorspar concentrate was increased with the dosages of sodium fluoride and calcium lignin sulfonate and leveled off at 5.0 pounds per ton. The summarized results of flotation tests made to determine the effect of varying the quantities of sodium fluoride and lignin sulfonate are given in table 2.
The laboratory batch flotation studies were continued to determine the optimum quantity of collector needed to obtain the maximum grade and recovery of fluorspar. The pulp was conditioned (1) with 5.0 pounds of sodium fluoride per ton of ore. to disperse the pulp and clean up the mineral faces, (2) with 5.0 pounds of calcium lignin sulfonate per ton of ore to coat the surfaces of the gangue particles and render them hydrophilic, and (3) with various quantities of sodium oleate, as a collectors to concentrate the fluorspar. In most instances an acid-grade fluorspar concentrate was obtained. The rougher concentrate contained 94.3 percent of the total fluorspar in the ore at a collector dosage of 0.30 pound per ton of ore, but the mineral particles did not adsorb enough collector to sustain their flotation during the six cleaning stages. About 0.50 pound of collector per ton of ore appeared to be the optimum dosage; the grade and recovery of fluorspar were essentially constant with larger quantities. This indicated that large quantities of sodium oleate were adsorbed by the fluorspar mineral and not by the gangue materials. The summarized results of these tests are shown in table 3.
Another series of tests was made using various quantities of oleic acid as the collector while maintaining the quantities of sodium fluoride and calcium lignin sulfonate at 5.0 pounds per ton of ore. The tests revealed that the oleic acid was as selective as the sodium oleate in producing acid-grade fluorspar concentrates ; however, the fluorspar recovery was somewhat lower with the oleic acid because it did not disperse, as well. The optimum amount of oleic acid was 0.48 pound per ton of ore. The summarized results of these tests are shown in table 4.
Additional laboratory batch flotation tests were made using the data obtained in determining the optimum quantities of reagent. The minus 65-mesh pulp was conditioned at about 40 percent solids in a mechanically agitated flotation cell for 5 minutes with 5.0 pounds each of sodium fluoride and calcium lignin sulfonate per ton of ore for dispersion of pulp and retardation of gangue minerals. Sodium oleate, 0.5 pound per ton of ore, was then added as a collector; conditioning was continued for another 5 minutes. The rougher concentrate was floated and refloated (cleaned) six times to remove gangue minerals. A concentrate analyzing 97.8 percent CaF2 and accounting for a fluorspar recovery of 84,5 percent was obtained. The results of a selected test are presented in tables 5 and 6.
Based on the results of the laboratory batch tests, a continuous pilot plant with a capacity of about 150 pounds of dry feed per hour was assembled. The process included grinding, classification, conditioning, and flotation, as shown by figure 1.
The ore was reduced by jaw and roll crushers in closed circuit to minus 3/8 inch and stored in a bin. From the bin it was transferred by a constant-weight feeder to a rod mill operated at 60 percent solids. The rod mill operated in closed circuit with a vibrating screen to grind the ore to minus 65 mesh. The screen undersize (minus 65-mesh) passed to a hydroseparator for
removal of colloidal slimes. The hydroseparator overflow represented about 1.5 percent of the weight of the ore and a loss of less than 1 percent of the total fluorspar. The hydroseparator underflow, at about 40 percent solids, passed to a conditioner where sodium fluoride and calcium lignin sulfonate were added. The discharge from the first conditioner flowed to a second conditioner where oleic acid was added as the fluorspar collector. A retention time of about 9 minutes in each conditioner gave satisfactory results. The conditioned pulp then flowed to a bank of three rougher flotation cells where a rougher concentrate was floated. The rougher tailing flowed to a single cell operating as a scavenger to recover additional fluorspar. The froth from this cell was recycled to the last rougher cell; the tails flowed to waste. The rougher concentrate was cleaned nine times, and the middlings were circulated back to the first cleaner where they were removed and thickened in a bank of three hydrocyclones (parallel). The underflow from the hydrocyclones was sent to the first conditioner, and the overflow went to waste. An emulsion-type collector (made up of 17.7 parts oleic acid 1.3 parts sodium oleate, and 361.0 parts water) was added to the second rougher cell to aid the flotation of the fluorspar.
The summarized results of a continuous flotation test are given in tables 7 and 8. The final fluorspar concentrate analyzed 96.4 percent CaF2 , a recovery of 90.0 percent of the total fluorspar in the ore. About 7 percent of the fluorspar was lost in the overflow from the cyclones.
The fluorspar concentrate was slightly below the specifications for acid-grade fluorspar; however, it meets all specifications for high-quality ceramic-grade fluorspar. It was possible to obtain an acid-grade fluorspar by introducing additional cleaners into the circuit; however, there was some sacrifice in recovery.
The laboratory batch and continuous pilot plant flotation tests demonstrated that the sodium fluoride-calcium lignin sulfonate-fatty acid method for selective flotation of fluorspar from complex calcareous fluorspar ore is an effective and practical means of producing high-grade fluorspar concentrates.
The flotation of the fluorspar in a continuous test in which the middlings were removed from the circuit, thickened, and returned for further conditioning produced a fluorspar concentrate analyzing 96.4 percent calcium fluoride, a recovery of 90.0 percent of the fluorspar in the ore. The fluorspar concentrate produced from a deposit near Cave-in Rock, III., meets all specifications for high-quality ceramic-grade fluorspar.
Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.
Dec 20, 2018 Gold flotation. The Froth Flotation Method is means separating minerals according to their different physical and chemical properties. According to classification, the flotability of gold and silver minerals is included in the first category of natural and non-ferrous heavy metal sulfides, characterized by low surface wettability and easy flotation, which can be flotation by xanthate collectors.
750tpd Lead Ore Processing Line,Lead Ore Flotation Machine Sale In India 1. Froth Flotation Introduction Ore Flotation Machine is mainly used to select non ferrous metals such as copper, zinc, lead, nickel, gold, etc., and also be used for coarse selection and selection of black metal and nonmetal. 2.
Copper Oxide Ore Froth Flotation Concentration Plant Overview Copper Ore Flotation Processing Plant is mainly composed of jaw crusher, ball mill, spiral classifier, magnetic separator, flotation machine, ore concentrator and dryer machine combining with ore feeder, bucket elevator and belt conveyor which formed a complete ore beneficiation production line.
The common gold extraction processes include gravity separation process, froth flotation process, cyanidation, etc. Froth flotation process is the most widely used in gold extraction, but for different types of gold, we can choose flotation process combined process in order to improve the return on investment.
Mineral Ore Gold Silver Copper Flotation Separator. Portable gold extraction machine SF froth flotation copper iron ore flotation. Alibaba offers 6351 silver extraction machine products. are oil pressers 11 are fruit and vegetable processing machines and 1 are mineral separator.
China Flotation Plant manufacturers - Select 2021 high quality Flotation Plant products in best price from certified Chinese Mining Equipment manufacturers, Mining Machine suppliers, wholesalers and factory on Made-in-China.com
gold recovery plant flotation separator machine. High Recovery Rate Air Inflation Copper Ore Zinc Chromite Mining Process Plant Feldspar Flotation Machine. 2500.00 Set. 1 Set . China Professional SFXKJ Mining Separator Equipment Flotation Machine. 2500.00 Set. 1 Set Min. Order High Efficient Flotation Cell For Gold Ore Extraction Equipment. 2300.
Flotation Cell Plant For Gold Processing Magnetic Separator. China Frame Construction Series Iron Ore Magnetic Separators Flotation cell for gold copper iron ore cone magnetic separator motor size wet low intensity magnetic separators he heart of the magnetic separator is the magnetic drum assembly which is composed of a stationary magnetic array mounted inside of a non magnetic drumuring ...
To participate in the 911Metallurgist Forums, be sure to JOIN & LOGIN Use Add New Topic to ask a New Question/Discussion about Flotation. OR Select a Topic that Interests you. Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent). Using Add Reply allows you to Attach Images or PDF files and provide a more complete input. Use Add Comment = to comment on someone elses ...
Based on 20 years of experience in mineral processing industry, Xinhai has been committed to the development and innovation of froth flotation process, aiming at providing professional flotation cell and comprehensive service, including from previous beneficiation test analysis, middle flotation process design and equipment selection, and later installation and debugging. Currently, Xinhai has provided the advanced professional Xinhai froth flotation process for many mineral processing projects at home and abroad.
Froth flotation process is one of the most widely mineral processing method used in the production. It uses the difference of physical and chemical properties in mineral surface, and rely on air bubbles buoyancy in the pulp to realize mineral separation process. On the basis of the flotation separation, Xinhai has developed a series of flotation reagents, which not only reduce 10% reagent consumption, but also increase 20% flotation efficiency.
Xinhai froth flotation process can be widely used in non-ferrous metal, ferrous metal and nonmetal minerals, especially used in roughing and scavenging of large and medium-sized flotation plant. It can process non-ferrous metals, such as gold, silver, copper, iron, tungsten, lead, zinc, tin, molybdenum, nickel, tantalum, niobium and manganese ore; and also process nonmetal minerals, such as fluorite, talc, etc.
Compared with common flotation reagents, Xinhai special flotation reagents not only enhances the mineral surface hydrophobicity, mineral adhesive fastness and selectivity on the bubble, but also improves more 25% mineral flotation separation speed, which plays a very important role in flotation separation efficiency and flotation index.
In May 2016, Iranian client commissioned Xinhai Mine Research Institute to conduct beneficiation test after collected 50kg samples in the site. After tested the ore properties of sample ore, Xinhai lab concluded that the ore was gold-bearing quartz vein deposit, the metal mineral were pyrite, limonite and natural gold. The ore grade is 5.61g/t.
Xinhai mineral processing plan: After finished the test in July, Xinhai Mine Research Institute carried on the preliminary exploration of its processing conditions. After compared froth flotation process with cyanide leaching process, Xinhaia Mine Research Institute found that the gold recovery rate in froth flotation process was far higher than in cyanide leaching process. Therefore, after consulting with the client, Xinhai decided to adopt two-stage closed circuit crushing, one-stage grinding and single froth flotation process to get the gold concentrate. After the grinding, then one roughing, three scavenging, three concentration, the process got 87.16% recovery rate of gold concentrate.
In August 2016, Xinhai sent professional engineers to the site to learn about the mineral resources and construction conditions. Considered its location, mineral characteristics, the project needs to solve the following problems:
1) Adopted reasonable and compact layout. Makes full use of the high difference to complete self-flow layout in the workshop design, meanwhile, makes the industrial plants as compact and warm as possible, which is easy to produce in winter.
2) Optimized froth flotation process, improved efficiency. According to ore characteristics, Xinhai timely controlled the dosage of flotation reagents, especially the dosage of xanthate, strictly controlled concentration density, and greatly improved the gold concentrate grade. At the same time, in order to complete the project construction fast and efficient, Xinhai personnel decisively abandoned home holiday arrangement, worked hard in the first line, so completed the construction of plant workshop 15 days in advance.
To help Iranian workers to operate as soon as possible, Xinhai technicians showed on-site training for plant workers, explained equipment operation notes, helped customers quickly establish own technical team, laid foundation for later stable operation.
In Iran 300 tpd gold froth flotation project, the ore grade was 5.61 g/t, gold concentrate grade was 78.85 g/t, flotation recovery rate was as high as 87.16%, the final recovery rate was up to 87.16%,the customers gave high praise for these results. From the beneficiation test, mine design, equipment manufacture, installation and debugging to the worker training and standard reached, Xinhai provided a series of froth flotation process service.
SF Flotation Plant is widely used for roughing, concentrating and counter-flotation of nonferrous metal that includes gold, copper, lead, zinc, nickel and molybdenum, ferrous metal and nonmetallic mineral.
The impeller is driven by V-belts, which can bring the centrifugal effect to form the negative pressure. On the one hand, to inhale sufficient air to mix with ore pulp; on the other hand, to stir ore pulp and mix with medication to form the mineralized froth. To adjust the height of the flashboard to control the liquid level and make the useful froth scraped by the loam board.
The flotation plant is always applied with SF series flotation machines to form a joint unit; SF flotation machine is used for inhalation slot of pulp self-absorption while the JJF series flotation machine is used for DC slot. And then, operation space is level configuration without foam pump to get high sorting indicators. JJF series and SF series also play their respective advantages. It is mainly used for copper, lead, zinc, nickel, molybdenum, gold and other non-ferrous metals, ferrous metals and non-metallic minerals roughing, selection and flotation operations.
The Flotation machine (Flotation separator) can be used for separating non-ferrous metals, ferrous metals, noble metals, non-metallic ores, and chemicals. The flotation machine can be used in roughing, scavenging, selection or reverse flotation.
The Flotation machine (Flotation separator) can be used for separating non-ferrous metals, ferrous metals, noble metals, non-metallic ores, and chemicals. The flotation machine can be used in roughing, scavenging, selection or reverse flotation. In the flotation process, after being mixed with additives, some qualified minerals float to the surface of the slurry and are scraped out while other minerals remain and are thus separated. We also provide flotation cells.
2) With three functions of air suction, slurry suction and flotation simultaneously being unique in flotation return circuit without need for any supplement and equipment, the circuit change is convenient for horizontal location.
The structure of flotation cells: this machine is mainly composed of pulp chute, mixing device, air charging system, mineralized bubble discharging device and electro motor. (1) Pulp chute: It has pulp feeding mouth and the gate device used for adjusting the liquid level and it is mainly composed of mainly composed by the chute body which is melt by the steel board and gate melt by the steel board and steel rod. (2) Mixing device: It is mainly used for mixing the pulp in order to prevent the mineral sand to deposit on the chute, and it is mainly composed by the belt wheel, impeller, vertical shaft and the impeller is made of the anti-abrasion rubber. (3) Air charging system: It is mainly composed by the inlet air pipe. When the impeller rotates, there will produce negative pressure inside the impeller chamber in order to absorb air through the hollow pump line and disperse the pulp in order to form a bubble group. This kind of pulp with large quantity of bubbles will be thrown to the stator fast by the rotary force of the impeller and further mineralize the bubbles in the pulp, and the rotary movement that is meant to eliminate the pulp flow in the flotation cell will cause large quantity of microvesicle and provide necessary condition for the flotation process. (4) Mineralized foam discharging device: This device is mainly used for scarping the foam floating on the cell and it is mainly composed by the reducer driven by the electric motor and scrapper driven by the reducer.
2) The impeller of the flotation machine begins to rotate; negative pressure is formed, which makes the air and pulp at the bottom and middle part of the tank enter the mixing zone. The pulp, air and medicament are then mixed in the mixing zone.
3) As a result of the centrifugal force, the blended pulps are led to the mineralization area. The air is in full contact with the coal particle and forms mineralized bubbles which are then equally distributed to groove wall and removed upward to the separation region. These bubbles then gather as a foam layer and are discharged by the scraping tool. Finally, clean coal foam is produced by this flotation machine.
The MAC flotation cell was developed by Kadant-Lamort Inc. It can save energy comparedto conventional flotation systems. The MAC flotation cell is mainly used in the flotation section of waste paper deinking pulping, for removal of hydrophobic impurities such as filler, ash,ink particles, etc. It can increase pulp whiteness and meet the requirements of final paper appearance quality. Table11.11 shows the features of MAC flotation cell. Kadants MAC flotation cell deinking system uses air bubbles to float ink particles to the cell surface for removal from the recycled material. The latest generation of the MAC cell deinking system incorporates a patented bubble-washing process to reduce power consumption and also fiber loss. It combines small, new, auto-clean, low-pressure injectors with a flotation cell. The function of injectors is to aerate the stock before it is pumped and sent tangentially to the top of the cell. The air bubbles collect ink particles in the cell and rise up to the top to create a thick foam mat that is evacuated because of the slight pressurization of the cell. The partially deinked stock then goes to a deaeration chamber and is pumped to the next stage. Here, the operation is exactly the same as for the first stage. This stage also has the same number of injectors and same flow (Kadant,2011). This operation is repeated up to five times for a high ink removal rate. Remixing of the air coming from downstream stages of the process helps the upstream stages and improves the overall cell efficiency. Adjustable and selective losses of fiberdepend on the application and technical requirements inks, or inks and fillers. The use of low-pressure injectors in the MAC flotation cell could save about 2530% of the energy used in conventional flotation systems (ECOTARGET,2009). The benefits of the MAC flotation cell are summarized in Table11.12.
Agitated flotation cells are widely used in the mineral processing industry for separating, recovering, and concentrating valuable particulate material from undesired gangue. Their performance is lowered, however, when part of the particulate system consists of fines, with particle diameters typically in the range from 30 to 100m. For example, it was observed difficult to float fine particles because of the reduction of middle particles (of wolframite) as carriers and the poor collision and attachment between fine particles and air bubbles; a new kinetic model was proposed .
As an alternative to agitated cells, bubble columnsused in chemical engineering practice as chemical reactorswere proposed for the treatment of fine particle systems. Flotation columns, as they came to be known, were invented back in the 1960s in Canada . The main feature that differentiates the column from the mechanical flotation cell (of Denver type) is wash water, added at the top of the froth. It was thought to be beneficial to overall column performance since it helps clean the froth from any entrained gangue, while at the same time preventing water from the pulp flowing into the concentrate. In this way, it was hoped that certain cleaning flotation stages could be gained.
Let us note that the perhaps insistence here on mineral processing is only due to the fact that most of the available literature on flotation is from this area, where the process was originated and being widely practiced. The effect of particle size on flotation recovery is significant; it was shown that there exists a certain size range in which optimum results may be obtained in mineral processing. This range varies with the mineral properties such as density, liberation, and so on, but was said to be of the order of 10100m .
Regulating the oxidation state of pyrite (FeS2) and arsenopyrite (FeAsS), by the addition of an oxidation or reduction chemical agent and due to the application of a short-chain xanthate as collector (such as potassium ethyl xanthate, KEX), was the key to selective separation of the two sulfide minerals, pyrite and arsenopyrite . Strong oxidizing agents can depress previously floated arsenopyrite. Various reagents were examined separately as modifiers and among them were sodium metabisulfite, hydrazinium sulfate, and magnesia mixture. The laboratory experiments were carried out in a modified Hallimond tube, assisted by zeta-potential measurements and, in certain cases, by contact angle measurements.
This conventional bench-scale flotation cell provides a fast, convenient, and low-cost method, based on small samples (around 2g), usually of pure minerals and also artificial mixtures, for determining the general conditions under which minerals may be rendered floatableoften in the absence of a frother (to collect the concentrate in the side tube) . This idea was later further modified in the lab replacing the diaphragm, in order to conduct dissolved air or electroflotation testssee Section 3.
Pyrite concentrates sometimes contain considerable amounts of arsenic. Since they are usually used for the production of sulfuric acid, this is undesirable from the environmental point of view. However, gold is often associated with arsenopyrite, often exhibiting a direct relationship between Au content and As grade. There is, therefore, some scope for concentrating arsenopyrite since the ore itself is otherwise of little value (see Fig.2.2). Note that previous work on pyrites usually concentrated on the problem of floating pyrite .
In the aforementioned figure (shown as example), the following conditions were applied: (1) collector [2-coco 2-methyl ammonium chloride] 42mg/L, frother (EtOH) 0.15% (v/v), superficial liquid velocity uL=1.02cm/s, superficial gas velocity uG=0.65cm/s, superficial wash water velocity uw=0.53cm/s; (2) hexadecylamine, 45mg/L; pine oil, 50mg/L; EtOH, 0.025%; uL=0.84cm/s; uG=0.72cm/s; uw=0.66cm/s; (3) Armoflot 43, 50mg/L; pine oil, 50mg/L; EtOH, 0.025%; uL=0.84cm/s; uG=0.71cm/s; uw=0.66cm/s . The pyrite (with a relatively important Au content of 21g/ton) was a xanthate-floated concentrate. The presence of xanthates, however, might cause problems in the subsequent cyanidation of pyrites when recovering their Au value, which perhaps justified the need to find alternative collectors. In general, the amines exhibited a behavior similar to that of the xanthates (O-alkyl dithiocarbonates). The benefit of the amine was in its lower consumption, as compared with the xanthate systems.
The arsenic content of the pyrite was approximately 9% (from an initial 3.5% of the mixed sulfide ore). The material was sieved and the75m fraction was used for the laboratory-scale cylindrical column experiments. The effect on metallurgical characteristics of the flotation concentrate of varying the amount of ferric sulfate added to the pulp was studied; three collectors were used and their performance was compared (in Fig.2.2). Both hexadecylamine and Armoflot 43 (manufactured by Akzo) exhibited an increased recovery but a very low enrichment, whereas 2-coco 2-methyl ammonium chloride (Arquad-2C) showed a considerable enrichment; a compromise had to be made, therefore, between a high-grade and a low recovery.
Electroflotation (electrolytic flotation) is an unconventional separation process owing its name to the bubbles generation method it uses, i.e., electrolysis of the aqueous medium. In the bottom of the microcell, the two horizontal electrodes were made from stainless steel, the upper one being perforated. The current density applied was 300 Am2. It was observed that with lime used to control pH, different behavior was observed (see Fig.2.3). Pyrite, with permanganate (a known depressant) also as modifier, remained activated from pH 5.0 to 8.0at 80% recovery, while it was depressed at the pH range from 9.0 to 12.0. A conditioning of 30min was applied in the presence of modifier alone and further 15min after the addition of xanthate. The pure mineral sample, previously hand collected, crushed, and pulverized in the laboratory, was separated by wet sieving to the45 to+25m particle size range.
Pyrite due to its very heterogeneous surface, consisting of a mosaic of anodic and cathodic areas, presents a strong electrocatalytic activity in the anodic oxidation of xanthate to dixanthogen. It is also possible that the presence of the electric field, during electroflotation, affected the reactions taking place. In order to explain this difference in flotation behavior thermodynamic calculations for the system Fe-EX-H2O have been done . It was concluded that electroflotation was capable of removing fine pyrite particles from a dilute dispersion, under controlled conditions. Nevertheless, dispersed air and electroflotation presented apparent differences for the same application.
The size of the gas bubbles produced was of the order of 50m, in diameter . Similar measurements were later carried out at Newcastle, Australia ; where it was also noted that a feature of electroflotation is the ability to create very fine bubbles, which are known to improve flotation performance of fine particles.
In fact, the two electrodes of a horizontal electrodes set, usually applied in electroflotation, could be separated by a cation exchange membrane, as only one of the produced gases is often necessary . In the lower part/separated electrode, an electrolyte was circulated to remove the created gas, and in the meantime, increase the conductivity; hence having power savings (as the electric field is built up between the electrodes through the use of the suspension conductivity). Attention should be paid in this case to anode corrosion, mainly by the chloride ion (i.e., seawater).
Microorganisms have a tremendous influence on their environment through the transfer of energy, charge, and materials across a complex biotic mineralsolution interface; the biomodification of mineral surfaces involves the complex action of microorganism on the mineral surface . Mixed cationic/anionic surfactants are also generating increasing attention as effective collectors during the flotation of valuable minerals (i.e., muscovite, feldspar, and spodumene ores); the depression mechanisms on gangue minerals, such as quartz, were focused .
Another design of a flotation cell which applies ultrasound during the flotation process has been developed by Vargas-Hernndez et al. (2002). The design consists of a Denver cell (Koh and Schwarz, 2006) equipped with ultrasonic capabilities of performing ultrasound-assisted flotation experiments. This cell is universally accepted as a standard cell for laboratory flotation experiments. In Figure 35.25, a schematic of the Denver cell equipped with two power transducers is shown operating at 20kHz. The ultrasonic transducers are in acoustic contact with the body of the flotation cell but are not immersed in the same cell. Instead, they are submerged in distilled water and in a thin membrane that separates the radiant head of the transducer from the chamber body. The floatation chamber has a capacity of 2.7l and is also equipped with conventional systems to introduce air and mechanical agitation able to maintain the suspension of metallurgical pulp. In the upper part of the cell there is an area in which the foam is recovered for analysis by a process called skimming. The block diagram of Figure 35.25 further shows that the experimental system was developed to do ultrasonic-assisted flotation experiments. The transducers operate at 20kHz and can handle power up to 400W. In the Denver cell an acoustic probe, calibrated through a nonlinear system and capable of measuring high-intensity acoustic fields, is placed (Gaete-Garretn et al., 1993, 1998). This is done in order to determine the different acoustic field intensities with a spatial scanner during the experimentation. Figure 35.26 shows the distribution of ultrasonic field intensity obtained by a spatial scanner in the central area of the flotation chamber. The Denver cell with ultrasonic capabilities, as described, is shown in Figure 35.27. The obtained results were fairly positive. For example, for fine particle recovery it worked with metallurgical pulp under 325mesh, indicating floating particles of less than 45m, and the recovery curves are almost identical to those of an appropriate size mineral for flotation. This is shown in Figure 35.28, where a comparison between typical copper recovery curves for fine and normal particles is presented. The most interesting part of the flotation curves is the increase in recovery of molybdenum with ultrasonic power, as shown in Figure 35.29. The increase in recovery of iron is not good news for copper mines because the more iron floating the lower grade of recovery. This may be because the iron becomes more hydrophobic with ultrasonic action. According to the experts, this situation could be remedied by looking for specific additives to avoid this effect. Flotation kinetics shown in Figure 35.30 with 5 and 10W of acoustic power applied also show an excellent performance. It should be noted that the acoustic powers used to vary the flotation kinetics have been quite low and could clearly be expanded.
Figure 35.28. Compared recovering percent versus applied power in an ultrasonic-assisted flotation process in a Denver cell: (a) fine and ultrafine particles recovering and (b) normal particles recovering.
These experiments confirm the potential of power ultrasound in flotation. Research on assisted flotation with power ultrasound has been also carried out by Ozkan (2002), who has conducted experiments by pretreating pulp with ultrasound during flotation. Ozkhans objective was to recover magnesite from magnesite silts with particles smaller than 38m. Their results show that under ultrasonic fields the flotation foam bubbles are smaller, improving magnesite recovery rates. When Ozkhan treated magnesite mineral with a conventional treatment the beneficial effect of ultrasound was only manifested for mineral pretreatment. The flotation performed under ultrasonic field did not show improvement. This was because power ultrasound improves the buoyancy of clay iron and this has the effect of lowering the recovery of magnesite.
Kyllnen et al. (2004) employed a cell similar to Jordan to float heavy metals from contaminated soils in a continuous process. In their experiments they obtained a high recovery of heavy metals, improving the soil treatment process. Alp et al. (2004) have employed ultrasonic waves in the flotation of tincal minerals (borax Na O710 B4 H2O), finding the same effects as described above, i.e., that power ultrasound helps in the depression of clay. However, the beneficial effect of ultrasound is weakened when working with pulps with high mineral concentration (high density), probably due to an increase in the attenuation of the ultrasonic field. Safak and Halit (2006) investigated the action mechanisms of ultrasound under different flotation conditions. A cleaning effect on the floating particles was attributed to the ultrasonic energy, making the particles more reactive to the additives put in the metallurgical pulp. Furthermore due to the fact that the solid liquid interface is weaker than the cohesive forces of the metallurgic pulp liquids, it results in a medium favorable to creation of cavitation bubbles. The unstable conditions of a cavitation environment can produce changes in the collectors and even form emulsions when entering the surfactant additives. In general, many good properties are attributed to the application of ultrasound in flotation. For example, there is a more uniform distribution of the additives (reagents) and an increase in their activity. In fact in the case of carbon flotation it has been found that the floating times are shortened by the action of ultrasound, the bubble sizes are more stable, and the consumption of the reagents is drastically lowered.
Abrego Lpez (2006) studied a water recovery process of sludge from industrial plants. For this purpose he employed a flotation cell assisted by power ultrasound. In the first stage he made a flotation to recover heavy metals in the metallurgical pulp, obtaining a high level of recovery. In the second stage he added eucalyptus wood cones to the metallurgical pulp to act as an accumulator of copper, lead, nickel, iron, and aluminum. The author patented the method, claiming that it obtained an excellent recovery of all elements needing to be extracted. zkan and Kuyumcu (2007) showed some design principles for experimental flotation cells, proposing to equip a Denver flotation cell with four power transducers. Tests performed with this equipment consisted of evaluating the possible effects that high-intensity ultrasonic fields generated in the cell may have on the flotation. The author provides three-dimensional curves of ultrasonic cavitation fields in a Denver cell filled with water at frequencies between 25 and 40kHz. A warming effect was found, as expected. However, he states that this effect does not disturb the carbon recovery processes because carbon flotation rarely exceeds 5min. They also found that the pH of tap water increases with the power and time of application of ultrasound, while the pH of the carbonwaterreagentsludge mixture decreases. The conductivity of the metallurgical pulp grows with the power and time of application of ultrasound, but this does not affect flotation. The carbon quality obtained does not fall due to the application of ultrasound and the consumption of lowered reagents. They did not find an influence from the ultrasound frequency used in the process, between 25 and 40kHz. They affirmed that ultrasound is beneficial at all stages of concentration.
Kang et al. (2009) studied the effects of preconditioning of carbon mineral pulp in nature by ultrasound with a lot of sulfur content. They found that the nascent oxygen caused by cavitation produces pyrite over oxidation, lowering its hydrophobicity, with the same effect on the change of pH induced by ultrasonic treatment. Additionally, ultrasound decreases the liquid gas interfacial tension by increasing the number of bubbles. Similar effects occur in carbon particles. The perfect flotation index increases 25% with ultrasonic treatment. Kang et al. (2008) continued their efforts to understand the mechanism that causes effects in ultrasonic flotation, analyzing the floating particles under an ultrasonic field by different techniques like X-ray diffraction, electron microscopy, and scanning electron microscopy techniques. In carbon flotation it is estimated that ultrasonic preconditioning may contribute to desulfurization and ash removal (deashing) in carbon minerals. Zhou et al. (2009) have investigated the role of cavitation bubbles created by hydrodynamic cavitation in a flotation process, finding similar results to those reported for ultrasonic cavitation flotation. Finally, Ozkan (2012) has conducted flotation experiments with the presence of hard carbon sludge cavitation (slimes), encountering many of the effects that have been reported for the case of metallurgical pulp with ultrasound pretreatment. This includes improved flotation, drastic reduction in reagent consumption, and the possible prevention of oxidation of the surface of carbon sludge. A decrease in the ash content in floating carbon was not detected. However, tailings do not seem to contain carbon particles. All these effects can be attributed to acoustic cavitation. However, according to the author, there is a need to examine the contribution of ultrasound to the probability of particlebubble collision and the likelihood of getting the bubbles to connect to the particles. The latter effects have been proposed as causes for improvements in flotation processes in many of the publications reviewed, but there is no systematic study of this aspect.
In summary, power ultrasound assistance with flotation processes shows promising results in all versions of this technique, including conditioning metallurgical pulp before floating it, assisting the continuous flotation process, and improving the yields in conventional flotation cells. The results of ultrasonic floating invariably show a better selectivity and an increase, sometimes considerable, in the recovery of fine particles. Paradoxically, in many experiments an increase has been recorded in recovering particles suitable for normal flotation. These facts show the need for further research in the flotation process in almost all cases, with the exception perhaps of carbon flotation. For this last case, in light of the existing data the research should be directed toward scale-up of the technology.
The concentrate obtained from a batch flotation cell changes in character with time as the particles floating change in size, grade and quantity. In the same way, the concentrate from the last few cells in a continuous bank is different from that removed from the earlier cells. Particles of the same mineral float at different rates due to different particle characteristics and cell conditions.
The recovery of any particular mineral rises to an asymptotic value R which is generally less than 100%. The rate of recovery at time t is given by the slope of the tangent to the curve at t, and the rate of recovery at time t1 is clearly greater than the rate at time t2. There is a direct relationship between the rate of flotation and the amount of floatable material remaining in the cell, that is:
The process is carried out in a flotation cell or tank, of which there are two basic types, mechanical and pneumatic. Within each of these categories, there are two subtypes, those that operate as a single cell, and those that are operated as a series or bank of cells. A bank of cells (Fig. 8) is preferred because this makes the overall residence times more uniform (i.e., more like plug flow), rather than the highly diverse residence times that occur in a single (perfectly mixed) tank.
FIGURE 8. Flotation section of a 80,000t/d concentrating plant, showing the arrangement of the flotation cells into banks. A small part of the grinding section can be seen through the gap in the wall. [Courtesy Joy Manufacturing Co.]
The purpose of the flotation cell is to attach hydrophobic particles to air bubbles, so that they can float to the surface, form a froth, and can be removed. To do this, a flotation machine must maintain the particles in suspension, generate and disperse air bubbles, promote bubbleparticle collision, minimize bypass and dead spaces, minimize mechanical passage of particles to the froth, and have sufficient froth depth to allow nonhydrophobic (hydrophilic) particles to return to the suspension.
Pneumatic cells have no mechanical components in the cell. Agitation is generally by the inflow of air and/or slurry, and air bubbles are usually introduced by an injector. Until comparatively recently, their use was very restricted. However, the development of column flotation has seen a resurgence of this type of cell in a wider, but still restricted, range of applications. While the total volume of cell is still of the same order as that of a conventional mechanical cell, the floor space and energy requirements are substantially reduced. But the main advantage is that the cell provides superior countercurrent flow to that obtained in a traditional circuit (see Fig. 11), and so they are now often used as cleaning units.
Mechanical cells usually consist of long troughs with a series of mechanisms. Although the design details of the mechanisms vary from manufacturer to manufacturer, all consist of an impeller that rotates within baffles. Air is drawn or pumped down a central shaft and is dispersed by the impeller. Cells also vary in profile, degree of baffling, the extent of walling between mechanisms, and the discharge of froth from the top of the cell.
Selection of equipment is based on performance (represented by grade and recovery), capacity (metric tons per hour per cubic meter); costs (including capital, power, maintenance), and subjective factors.
Among all processing industries, only in the ore and mining industries is the accent more on wear resistance than corrosion. In mining industries, the process concerns material handling more than any physical or chemical conversions that take place during the refining operations. For example, in the excavation process of iron ore, conventional conveyer systems and sophisticated fluidized systems are both used [16,17]. In all these industries, cost and safety are the governing factors. In a fluidized system, the particles are transported as slurry using screw pumps through large pipes. These pipes and connected fittings are subjected to constant wear by the slurry containing hard minerals. Sometimes, depending on the accessibility of the mineral source, elaborate piping systems will be laid. As a high-output industry any disruption in the work will result in heavy budgetary deficiency. Antiabrasive rubber linings greatly enhance the life of equipment and reduce the maintenance cost. The scope for antiabrasive rubber lining is tremendous and the demand is ever increasing in these industries.
Different rubber compounds are used in the manufacture of flotation cell rubber components for various corrosion and abrasion duty conditions. Flotation as applied to mineral processing is a process of concentration of finely divided ores in which the valuable and worthless minerals are completely separated from each other. Concentration takes place from the adhesion of some species of solids to air bubbles and wetting of the other series of solids by water. The solids adhering to air bubbles float on the surface of the pulp because of a decrease in effective density caused by such adhesion, whereas those solids that are wetted by water in the pulp remain separated in the pulp. This method is probably the more widely used separation technique in the processing of ores. It is extensively used in the copper, zinc, nickel, cobalt, and molybdenum sections of the mineral treatment industry and is used to a lesser extent in gold and iron production. The various rubber compounds used in the lining of flotation cells and in the manufacture of their components for corrosive and abrasive duties are:
Operating above the maximum capacity can cause the performance of flotation cells to be poor even when adequate slurry residence time is available (Lynch et al., 1981). For example, Fig. 11.21 shows the impact of increasing volumetric feed flow rate on cell performance (Luttrell et al., 1999). The test data obtained at 2% solids correlates well with the theoretical performance curve predicted using a mixed reactor model (Levenspiel, 1972). Under this loading, coal recovery steadily decreased as feed rate increased due to a reduction in residence time. However, as the solids content was increased to 10% solids, the recovery dropped sharply and deviated substantially from the theoretical curve due to froth overloading. This problem can be particularly severe in coal flotation due to the high concentration of fast floating solids in the flotation feed and the presence of large particles in the flotation froth. Flotation columns are particularly sensitive to froth loading due to the small specific surface area (ratio of cross-sectional area to volume) for these units.
Theoretical studies indicate that loading capacity (i.e., carrying capacity) of the froth, which is normally reported in terms of the rate of dry solids floated per unit cross-sectional area, is strongly dependent on the size of particles in the froth (Sastri, 1996). Studies and extensive test work conducted by Eriez personnel also support this finding. As seen in Fig. 11.22, a direct correlation exists between capacity and both the mean size (d50) and ultrafines content of the flotation feedstock. The true loading capacity may be estimated from laboratory and pilot-scale flotation tests by conducting experiments as a function of feed solids content (Finch and Dobby, 1990). Field surveys indicate that conventional flotation machines can be operated with loading capacities of up to 1.52.0t/h/m2 for finer (0.150mm) feeds and 56t/h/m2 or more for coarser (0.600mm) feeds. Most of the full-scale columns in the coal industry operate at froth loading capacities less than 1.5t/h/m2 for material finer than 0.150mm and as high as 3.0t/h/m2 for flotation feed having a top size of 0.300mm feeds.
Froth handling is a major problem in coal flotation. Concentrates containing large amounts of ultrafine (<0.045mm) coal generally become excessively stable, creating serious problems related to backup in launders and downstream handling. Bethell and Luttrell (2005) demonstrated that coarser deslime froths readily collapsed, but finer froths had the tendency to remain stable for an indefinite period of time. Attempts made to overcome this problem by selecting weaker frothers or reducing frother dosage have not been successful and have generally led to lower circuit recoveries. Therefore, several circuit modifications have been adopted by the coal industry to deal with the froth stability problem. For example, froth launders need to be considerably oversized with steep slopes to reduce backup. Adequate vertical head must also be provided between the launder and downstream dewatering operations. In addition, piping and chute work must be designed such that the air can escape as the froth travels from the flotation circuit to the next unit operation.
Figure 11.23 shows how small changes in piping arrangements can result in better process performance. Shown in Fig. 11.23 is a column whose performance suffered due to the inability to move the froth product from the column launder although a large discharge nozzle (11m) had been provided. In this example, the froth built up in the launder and overflowed when the operators increased air rates. To prevent this problem, the air rates were lowered, which resulted in less than optimum coal recovery. It was determined that the downstream discharge piping was air-locking and preventing the launders from properly draining. The piping was replaced with larger chute work that allowed the froth to flow freely and the air to escape. As a result, higher aeration rates were possible and recoveries were significantly improved.
Some installations have resorted to using defoaming agents or high-pressure launder sprays to deal with froth stability. However, newer column installations eliminate this problem by including large de-aeration tanks to allow time for the froth to collapse (Fig. 11.24a). Special provisions may also be required to ensure that downstream dewatering units can accept the large froth volumes. For example, standard screen-bowl centrifuges equipped with 100mm inlets may need to be retrofitted with 200mm or larger inlets to minimize flow restrictions. In addition, while the use of screen-bowl centrifuges provides low product moistures, there are typically fine coal losses, as a large portion of the float product finer than 0.045mm is lost as main effluent. This material is highly hydrophobic and will typically accumulate on top of the thickener as a very stable froth layer, which increases the probability that the process water quality will become contaminated (i.e., black water).
This phenomenon is more prevalent in by-zero circuits, especially when the screen-bowl screen effluent is recycled back through the flotation circuit, either directly or through convoluted plant circuitry. Reintroducing material that has already been floated to the flotation circuit can result in a circulating load of very fine and highly floatable material. As a result, the capacity of the flotation equipment can be significantly reduced, which results in losses of valuable coal. Most installations will combat this by ensuring that the screen-bowl screen effluent is routed directly back to the screen bowl so that it does not return to the flotation circuit. The accumulation of froth on the thickener, which tends to be especially problematic in by-zero circuitry, is also reduced by utilizing reverse-weirs and taller center wells, as this approach helps to limit the amount of froth that can enter into the process water supply. Froth that does form on top of the clarifier can be eliminated by employing a floating boom that is placed directly in the thickener (Fig. 11.24b) and used in conjunction with water sprays. The floating boom can be constructed out of inexpensive PVC piping, and is typically attached to the rotating rakes. The boom floats on the water interface and drags any froth around to the walkway that extends over the thickener, where it is eliminated by the sprays.
Column cells have been developed over the past 30 years as an alternative to mechanically agitated flotation cells. The major operating difference between column and mechanical cells is the lack of agitation in column cells that reduces energy and maintenance costs. Also, it has been reported that the cost of installing a column flotation circuit is approximately 2540% less than an equivalent mechanical flotation circuit (Murdock et al., 1991). Improved metallurgical performance of column cells in iron ore flotation is reported and attributed to froth washing, which reduces the loss of fine iron minerals entrained into the froth phase (Dobby, 2002).
The Brazilian iron ore industry has embraced the use of column flotation cells for reducing the silica content of iron concentrates. Several companies, including Samarco Minerao S.A., Companhia Vale do Rio Doce (CRVD), Companhia Siderrgica Nacional (CSN), and Mineraes Brasileiras (MBR), are using column cells at present (Peres et al., 2007). Samarco Minerao, the first Brazilian producer to use column cells, installed column cells as part of a plant expansion program in the early 1990s (Viana et al., 1991). Pilot plant tests showed that utilization of a column recleaner circuit led to a 4% increase in iron recovery in the direct reduction concentrate and an increase in primary mill capacity when compared to a conventional mechanical circuit.
There are also some negative reports of the use of column cells in the literature. According to Dobby (2002), there were several failures in the application of column cells in the iron ore industry primarily due to issues related to scale-up. At CVRD's Samitri concentrator, after three column flotation stages, namely, rougher, cleaner, and recleaner, a secondary circuit of mechanical cells was still required to produce the final concentrate.
Imhof et al. (2005) detailed the use of pneumatic flotation cells to treat a magnetic separation stream of a magnetite ore by reverse flotation to reduce the silica content of the concentrate to below 1.5%. From laboratory testing, they claimed that the pneumatic cells performed better than either conventional mechanical cells or column cells. The pneumatic cells have successfully been implemented at the Compaia Minera Huasco's iron ore pellet plant.
This chapter presents a novel approach to establish the relationship between collector properties and the flotation behavior of goal in various flotation cells. Coal flotation selectivity can be improved if collector selection is primarily based on information obtained from prior contact angle and zeta potential measurements. In a study described in the chapter, this approach was applied to develop specific collectors for particular coals. A good correlation was obtained between laboratory batches and large-scale conventional flotation cells. This is not the case when these results are correlated with pneumatic cell trial data. The study described in the chapter was aimed at identifying reasons for the noncorrelation. Two collectors having different chemical compositions were selected for this investigation. A considerable reduction in coal recovery occurred at lower rotor speeds when comparing results of oxidized and virgin coal. The degree to which a collector enhances flocculation in both medium- and low-shear applications and also the stronger bubble-coal particle adherence required for high-shear cells must, therefore, all be taken into consideration when formulating a collector for coal flotation.
I. Application, Structure and Working Principle of Mechanical Agitating Continuous Flotation Cell FX Model Mechanical Agitated Continuous Flotation Cell is applicable to separation of minerals with Flotation method in labs or pilot plant and semi industry scale. It is a unit of several combinations of several cells, varying from two to ten cells. Left or right type flotation machine can be supplied as required by customer.
Cell. It is made of welded steel plate. To adjust the level of slurry in the cell and the thickness of the scraped froth layer, use wall plates of the two cells to make intermediary cell; install slurry level regulator; and mount orifice plate onto the cover in the cell to avoid negative effects on the froth zone exerted by the chaotic motion of slurry, as well as to avoid the gangue from being taken into the concentrate by the machine.
Lining plates are installed at the cell so that the bottom of the cell will not be abraded. The lining plate can be replaced. On the outside of the cell bottom is a discharge mouth, which is used to discharge water during its cleaning.
The slurry flows through the overflow mouth of wall panel into the intermediary cell and tail cell. It flows to the lower part of the intermediary cell and the duct covered by the lower part of the cell wall and then to the next cell. In this way, it can continue to flow through all the cells of flotation machine. It flows from the feed cell and is discharged from the discharge mouth of the tail cell. The front and back of the lower part of the cell is installed feeding mouth, to make it easy to change the process flow.
Impeller system. It is a disk impeller which is installed in the center of the cell in the flotation machine and whose blades are radially arranged. It is fixed onto the lower end of the impeller shaft and revolves around the vertical shaft pipe. The upper end of the pipe lies above the pulp stone and the froth layer while its lower end is supported on the cover. When the impeller rotates, a large amount of air can be sucked along the vertical pipe. Below the cover is fixed protective disk. The gap between the safety disk and the impeller depends on the amount of sucked air. It can not be larger than 3mm at most. When the gap is too large, replace the abraded protective disc and make appropriate adjustment.
The holes in the vertical pipe are used to circulate slurry as well as mix the slurry and air. The rolling shaft installed inside the bearing shell above the impeller shaft rotates. The bearing shell is installed on the crossbeam and belt pulley is fixed on the top of the shaft which rotates through the V-belt when the motor is turned on. The tension of the V-belt is adjusted through the nuts.
Scraping device. The froth is scraped along the flotation machine through rotary scraper. The scraper is installed outside the discharge mouth of cell. At one end of the scraping shaft is installed belt pulley which rotates through the drive of worm reducer and V-belt.
The machine should be installed on the workbench. When more than four cells are under continuous use, all cell sets must be in the same horizontal plane, then the scraper shaft can be connected in the same line. Leakage from the connection joints is not allowed.
The installation site of the machine shall be accessible to 220/380V three-phase AC power. When connecting the motor terminals, pay attention to that the rotatory of the vertical shaft is counterclockwise.
During the flotation, the motor drives the main shaft and impeller through the delta belt for slurry agitation, and the scrapper motor drives the scrapper devices to rotate. The scraper directs the foam to flow out from the channel opening of the cell, and the slurry level and the height of the foam being controlled by the slurry level regulator. After the flotation, pull out the plug in the mine mouth at the bottom of the cell, and release the waste liquid within the cell.
Adjust the rotating speed of the impeller: the rotating speed of the main shaft impeller of the flotation machine has been transferred to 950 r / min before delivery. If you want to transferred it to 600 r / min or 1450 r / min, you need first to remove the protective cover, loosen the set screw on the motor seat, and adjust the delta belt to the appropriate cell position, then fasten the screws on the motor seat after tightened the belt.
ZJH mainly focus on producing and supply crushers, ore grinding equipment, mineral Beneficiation equipment, laboratory and pilot scale ore dressing equipment for Mining and Mineral Processing Industry. Our aim is to work together with Mines, Mineral Beneficiation Plantsfor helping to reduce the operating cost ,to improve the operating efficiency.
Bastnaesite, a rare-earth fluocarbonate, was separated from associated calcite and barite gangue minerals in the Mountain Pass, CA rare-earth ore beneficiation plant by froth flotation using fatty acids (tall oil) collector, lignin sulfonate depressant and soda ash modifier after high-temperature (steam) conditioning with reagents. Starting with a feed grade of 7.6% REO, concentrates having a grade of 65% REO can be produced at a recovery of around 80%. A detailed investigation consisting of Hallimond tube microflotation experiments, bench-scale tests with a laboratory Denver flotation cell, and predesigned plant campaigns was made to delineate the underlying surface chemistry involved in this separation and to develop an alternate reagent scheme to enhance the selectivity of separation for this ore. Our results clearly demonstrate the superiority of alkyl hydroxamates to the conventional fatty acid collectors that were being used in the plant. Our study also indicates the possibility of achieving the desired selectivity with alkyl hydroxamates even at room temperature, thus obviating the need for steam conditioning. A critical review of the literature on rare-earth mineral flotation suggests the possibility of designing a more selective reagent combination for the beneficiation of Mountain Pass rare-earth ore, using a methodology based on ab initio molecular modeling computations.
Bulatovic, S.M. and Salter, R.S., 1991, Flotation behavior of some oxide and rare-earth minerals during the treatment of complex oxide ores, Proceedings, XVII International Mineral Processing Congress, Dresden, September 1991, Vol. IV, pp. 3545.
Ciccu, R., Curreli, L., Ghiani, and Fuganti, A., 1993, Beneficiation of a Turkish bastnaesite ore with associated fluorspar and barite, Proceedings, XVIII International Mineral Processing Congress, Sydney, pp. 10831088.
Dekun, K., Chen, J., and Zhou, W., 1984, Application of hydroxamic acid and hydroxamic-xanthate collector system in metal ore flotation, Reagents in the Minerals Industry, M.J. Jones and R. Oblatt, eds., Inst. of Mining & Metallurgy Publication, pp. 169172.
Fuerstenau, D.W., Pradip, Khan, L.A., and Raghavan, S., 1982, An alternate reagent scheme for the flotation of Mountain Pass rare-earth ore, Proceedings, XIV International Mineral Processing Congress, Toronto, Canada, IV, pp. 6.16.12.
Fuerstenau, D.W. and Pradip, 1984, Mineral flotation with hydroxamate collectors, Reagents in the Minerals Industry, M.J. Jones and R. Oblatt, eds., Inst. of Mining & Metallurgy Publication, pp. 161168.
Harada, T., Owada, S., Takiuchi, T., and Jurita, M., 1993, A flotation study for effective separation of heavy mineral sands, Proceedings, XVIII International Mineral Processing Congress, Sydney, pp. 10171024.
Kim, J-A., Dodbiba, G., Fujita, T., and Fujii, N., 2010, Characteristics analysis of a bastnaesite rare-earth mineral for recovery of cerium, Proceedings, XXV International Mineral Processing Congress, Brisbane, Australia, pp. 29272932.
Naiphonov, T. B., Beloborodov, V. I., Zaharova, I.B., Kulakov, A.N. and Zorina, T. A., 1991, Flotation technology for beneficiation of Eudialyte rare-earth silicate ore, Proceedings, XVII International Mineral Processing Congress, Dresden, September 1991, Vol. IV, pp. 131138.
Pradip and Fuerstenau, D.W., 1983, The adsorption of hydroxamate collectors on semi-soluble minerals, Part I: Adsorption isotherms for barite, calcite and bastnaesite, Colloids and Surfaces, Vol. 8, pp. 103119.
Pradip and Fuerstenau, D.W., 1989, Alkyl hydroxamates as collectors for the flotation of bastnaesite rare-earth ores, Rare Earths - Extraction, Preparation & Application, R.G. Bautista and M.M. Wong, Eds., TMS-AIME, pp. 5570.
Pradip, Rai, B., Rao, T.K., Krishnamurthy, S., Vetrivel, R., Mielczarski, J., and Cases, J.M., 2002, Molecular modeling of interactions of alkyl hydroxamates with calcium minerals, Journal of Colloid & Interface Science, Vol. 256, No. 1, pp. 106113.
Pradip, Rai, B., Rao, T.K., Krishnamurthy, S., Vetrivel, R., Mielczarski, J., and Cases, J.M., 2002, Molecular modeling of interactions of diphosphonic acid based surfactants with calcium minerals, Langmuir, Vol. 18, pp. 932940.
Rai, B., Sathish, P., Tanwar, J., Pradip, Moon, K. S. and Fuerstenau, D.W., 2011, A molecular dynamics study of the interaction of oleate and dodecylammonium chloride surfactants with complex aluminosilicate minerals, Journal of Colloid & Interface Science, Vol. 362, pp. 510516.
Ren, J., Song, S., Lopez-Valdivieso, A., and Lu, S., 2000, Selective flotation of bastnaesite from monazite in rare-earth concentrates using potassium alum as depressant, International J Mineral Processing, Vol. 59, No. 3, pp. 237245.
Wang, C-H, Qiu, X-Y, Hu, Z., Li, H-W, Wang, T. and Zou, J-J, 2012, Study on the new beneficiation technology for rare-earth ores, Proceedings, XXVI International Mineral Processing Congress, New Delhi, India, paper no. 162, pp. 57815786.
Pradip, Fuerstenau, D.W. Design and development of novel flotation reagents for the beneficiation of Mountain Pass rare-earth ore. Mining, Metallurgy & Exploration 30, 19 (2013). https://doi.org/10.1007/BF03402335