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flotation cell blowers

flotation blowers

flotation blowers

Rotary Blower for pressure and vacuum service is universally used with gas or oil burners, furnaces forges, ovens, etc.Two inter-engaging impellers, rotating in opposite directions draw air into the pockets between the impellers and the case, and force this air into the discharge pipe. The amount of air displaced by these impellers at each revolution is definitely known, so that an R.P.M. may be selected to deliver any required amount of air. Rotary Blowers are simple in design, without valves, sliding vanes, springs, or other delicate parts to wear, break, or become noisy. All the parts are made of the best grade of material obtainable to carry the stresses placed on each particular piece. Low bearing and gear tooth loads, and small clearances between operating parts, enable these blowers to maintain their original efficiency for many years.

Supercharger Blower is an ideal unit for supplying low-pressure air to the Sub-A Flotation Machine. It is also used for supplying low-pressure air to oil and gas-fired furnaces and pneumatic conveyors, for agitation of liquids and pulps, for ventilation, or exhausting and for many applications. This unit is a centrifugal type turbo-compressor which delivers air at varying volume, with a uniform pressure, eliminating the necessity of any adjustment of the blast gate at each change of load. The Supercharger is arranged with an impelleror impellers mounted directly on the motor shaft. The impellers are fabricated from carefully selected metal, riveted or welded to strong, light-weight hubs. A special heat- treated aluminium alloy or steel of high tensile strength is used, depending upon the type and size of the machine. Each impeller is balanced several times during the process of construction, both statically and dynamically. Clearances between the moving and stationary parts are not less than 1/8inch to prevent wear and to help reduce surging at light loads, and also result in a minimum fluctuation of pressure from no load to full load. The shafts on the direct-connected machine are of ample size to support the impellers without any bearings other than those of the motor. The motor is supported by a cast bridge work mounted within the casing which evenly distributes the weight. The casing is made of heavy copper-bearing sheet steel, and the motor mounting. The casings can be built with the discharge in any of four positions. No special foundations are necessary, and the compressor can be mounted anywhere without bolting down.

The multi-stage machines are available in two types: one designed to operate at 1750 RPM and the other at 3500 RPM in more than 150 standard ratings. The low-speed units are normally furnished in pressures from 8 ounces to two pounds and in volumes up to 20,000 cu. ft. per minute. The high-speed multi-stage machines permit going to the higher pressures without the use of step-up gears or running at excessive peripheral speed, and are available in pressures from 8 ounces up to 5 pounds and in volumes up to 6000 cubic feet per minute. Blast gates can be supplied for regulating the quantity of air.

In addition to application as a supercharger this blower may also be used for supplying low-pressure air for oil and gas-fired furnaces, pneumatic conveyors, agitation of liquids and pulps, for ventilation or exhausting and many other applications.

This unit consists of a compact, very sturdily built, centrifugal type turbo-compressor which delivers air at varying volume, but with a uniform pressure. The necessity of adjustment of the blast gate at each change of load is thereby eliminated. Impeller is mounted directly on the motor shaft. Casings can be built with thedischarge in any of four positions. No special foundations are necessary, and the compressor can be mounted anywhere without bolting down. Single-stage machines are offered for installations where low first cost is desired and these units will deliver reliable air service in pressures from 4 to 16 ounces and in volumes from 110 to 2350 cubic feet per minute.

The Roots type of blower is generally used to supply the air requirements of pneumatic and air-lift flotation machines. Theconstruction of the High-Pressure High-Speed B.H.S. Type Boots Blower is shown in Fig. 47. Table 29 gives particulars of the various sizes and Table 30 the power requirements at different pressures as determined by actual tests.

The two revolving rotors run in a housing which forms the body of the machine ; they are geared together and are so shaped that they are practically touching at one point throughout the whole of every revolution, the clearance between them at that point being of the smallest possibledimensions short of actual contact. There is a similar clearance between the outer peripheral faces of the rotors and the housing. The air intake is generally situated on the underside of the machine with the discharge outlet at the top, but the blower can be run in the reverse direction if desired. An Upright type is also made with the intake at one side and the outlet at the other. Each rotor, as it revolves, entraps a certain volume of air between itself and the housing twice per revolution and delivers it to the main air-delivery pipe. The slippage of air through the clearance space between each rotor and the housing and between the rotors themselves is so small that the blower works very efficiently up to pressures of about 5 lb. per square inch. The slip varies as the square root of the discharge pressure. To keep it at a minimum the rotor facesare accurately machined, the rotor shafts are carried in roller bearings large enough to reduce wear to negligible proportions, and the gearing between the two shafts is provided with strong teeth of fine pitch in order to maintain accurately the relative positions of the rotors. The blower can be driven by belt and pulley, but it is very suitable for the more compact direct motor drive.

One advantage of this type of blower is that no lubrication is needed in the housing since there is no rubbing contact inside it. Oil can only enter from the end-plate bearings, and the leakage from this source is almost negligible, but since cases have occurred in which lubricating oil has entered a flotation machine as a fine suspension in the air supply and interfered with its operation, the blower can be supplied, if required, with independent bearings well clear of the end-plates of the housing ; there is then no possibility of the air becoming contaminated with lubricant.

productive froth flotation technology | flsmidth

productive froth flotation technology | flsmidth

There are many factors that can affect your flotation process. The two aspects that have the strongest impact on a flotation circuits efficiency and performance are metallurgical recovery and flotation cell availability. Fluctuations in feed characteristics can lead to recovery losses. The inability to handle changes in feed size and mineralogy can result in the loss of availability. At FLSmidth, we have developed solutions to these challenges and more.

Every project we take on is engineered to fit your operation, regardless of the size. Our expert solutions range from equipment only to the entire flotation island, including all auxiliary equipment (tanks, pumps, piping, blowers, etc.). Regardless of the project scope, our selection of flotation machines comes equipped with a range of drives, dart valves and automation options.

We have proven the metallurgical superiority of our flotation machines time and again in side-by-side comparative tests conducted by major mining companies. Results show that our flotation machines operate on exceptional grade recovery curves, with respect to coarse and fine particle recovery. The remarkable performance of our machines is related to flotation-favourable hydrodynamics, which produce higher active cell volumes, provide longer residence times, and complement froth removal.

The test of time has proven, as well, that competing equipment cannot match the availability of our flotation machines. The rotor-stator/disperser combinations in our redesigned forced-air (nextSTEP) and self-aspirated (WEMCO) flotation machines provide longer lifespan. In addition, using patented bypass equipment, our flotation mechanisms can be serviced or removed for maintenance without process interruption. This allows for longer production between wear parts replacement, and minimises the threat of maintenance cutting down on availability or even loss due to failure.

FLSmidth supplies two types of flotation machines: WEMCO and nextSTEP. The WEMCO machine is self-aerating, whereas the nextSTEP machine is externally aerated (forced-air). While the principles of operation for self-aerated and forced-air machines are similar in concept, the execution is different.

The main differences of execution are energy input location (via rotor placement), aeration mode and control. The WEMCO rotor is located at top of the cell, and the nextSTEP rotor is placed at the bottom of the machine. The rotor placement creates different flow patterns within the cell, which affects froth recovery. When it comes to aeration of the cells, WEMCO machines draw in and use air without the use of an external blower. They also are self-controlled, and do not require constant monitoring from an operator or moderation of air control valves. The nextSTEP requires an external blower and air flow controls to maintain proper operation.

We use a continuous process improvement program to both develop new flotation equipment and improve the performance of our existing flotation products, including validated computational fluid dynamics (CFD). CFD models help to analyse hydrodynamics inside the machine. The results help in gaining understanding of the regions of energy dissipation and quiescent zones. They also allow prediction of stress and vibration forces on impellers and stators. CFD analysis is always part of new product development in conjunction with engineering analysis, laboratory and pilot plant testing, combined with industrial application.

A flotation circuits performance is affected by both pulp and froth phase recovery. And it is inherent in mining operations that manual control by operators who look at the cell surface periodically and then take action does not really maintain stable operating conditions. Our ECS/FrothVision automation system is designed specifically to analyse froth characteristics in flotation. Comprising all necessary hardware and software to conduct froth image analysis and report information on bubble size, bubble count, froth colouranalysis, froth stability, froth texture and froth velocity, ECS/FrothVision handily assists in the process control and allows optimisation of the entire flotation circuit.

FLSmidth supplies two types of flotation machines: WEMCO and nextSTEP, the WEMCO machine is self-aerating whereas the nextSTEP machine is externally aerated. The principles of operation for self-aerated and forced-air machines are similar in concept, but the execution is different.

The main differences of execution are energy input location (via rotor placement) and aeration mode and control. The rotor of the WEMCO is at top of the cell while the nextSTEP is at the bottom of the machine. The rotor placement creates different flow patterns within the cell which affects froth recovery. When it comes to aeration of the cells, WEMCO machines draw in and use air without the use of an external blower. They are also self-controlled and do not require constant monitoring from an operator or moderation of air control valves. The nextSTEP requires an external blower and air flow controls to maintain proper operation.

FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.



Continental Industrie is supplying the mostefficiencyand secure blowers for theminingIndustry, able to work under the mostdifficult climatic conditions, such as extreme temperatures or very high altitudes. Our typical Blowers configuration aloud the easy installation and maintenance withoutnecessityof special heavy equipment.

Compared to other blowers technology, Continental Industrie Multistage Blowers deliveroil freeair without pulsation, whichguaranteea constant flow and pressure along the process. The combination betweenmechanicalrotation of the rotor and the bubbling is creating a very efficient action in catching the mineral particles to obtain the concentrate.

flotation circuit - blower sizing - froth flotation (sulphide & oxide) - metallurgist & mineral processing engineer

flotation circuit - blower sizing - froth flotation (sulphide & oxide) - metallurgist & mineral processing engineer

I am currently working on the design of a small 400 t/d gold flotation circuit that will consist of (28) DR24 equivalent 50 ft3 SubA flotation cells. (inclusive of rougher, scavenger, & cleaner circuits)

What type of blower is best for this kind of small plant and how do I go about sizing it? What is the typical discharge pressure range used in these kind of cells? Is it OK to use one large blower or is it better to have a dedicated blower for each circuit?

I'm in a similar boat as yourself in setting up a 250t/day gold float plant using DR24 Sub-A's. Even though these cells are self-aerating, i would like to add air to each cell to provide some added control. How did you add air to these cells?

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flotation machine - an overview | sciencedirect topics

flotation machine - an overview | sciencedirect topics

Industrial flotation machines can be divided into four classes: (1) mechanical, (2) pneumatic, (3) froth separation, and (4) column. The mechanical machine is clearly the most common type of flotation machine in industrial use today, followed by the rapid growth of the column machine. Mechanical machines consist of a mechanically driven impeller, which disperses air into the agitated pulp. In normal practice, this machine appears as a vessel having a number of impellers in series. Mechanical machines can have open flow of pulp between each impeller or are of cell-to-cell designs which have weirs between each impeller. The procedure by which air is introduced into a mechanical machine falls into two broad categories: self-aerating, where the machine uses the depression created by the impeller to induce air, and supercharged, where air is generated from an external blower. The incoming slurry feed to the mechanical flotation machine is introduced usually in the lower portion of the machine.Figure 7 shows a typical industrial flotation cell of each air delivery type.

The most rapidly growing class of flotation machine is the column machine, which is, as its name implies, a vessel having a large height-to-diameter ratio (from 5 to 20) in contrast to mechanical cells. The mechanism behind this machine to is provide a countercurrent flow of air bubbles and slurry with a long contact time and plenty of wash water. As might be expected, the major advantage of such a machine is the high separation grade that can be achieved, so that column cells are often used as a final concentrate cleaning step. Special care has to be exercised in the generation of fine air bubbles and controlling the feed rate to column cells.

Good mixing of pulp. To be effective, a flotation machine should maintain all particles uniformly in suspension within the pulp, including those of relatively high density and/or size. Good mixing of pulp is required for maximizing bubble-particle collision frequency.

Appropriate aeration and dispersion of fine air bubbles. An important requirement of any flotation machine is the ability to provide uniform aeration throughout as large a volume of the machine as is possible. In addition, the size distribution of the air bubbles generated by the machine is also important, but experience has shown that the proper choice of frother type and dosage generally dominates the bubble size distributions being produced.

Sufficient control of pulp agitation in the froth zone. As mentioned earlier, good mixing in the machine is important; however, equally important is that near and in the actual froth bed at the top of the machine, sufficiently smooth or quiescent pulp conditions must be maintained to ensure suspension of hydrophobed (collector coated) particles.

Efficient mass flow-mechanisms. It is also necessary in any flotation machine that appropriate provisions be made for feeding pulp into the machine and also for the efficient transport of froth concentrate and tailing slurry out of the machine.

Probably the most significant area of change in mechanical flotation machine design has been the dramatic increase in machine size. This is typified by the data ofFig. 8, which shows the increase in machine (cell) volume size that has occurred with a commonly used cell manufactured by Wemco. The idea behind this approach is that as machine size increases, both plant capital and operating costs per unit of throughput decrease.

The throughput capabilities of various cell designs will vary with flotation residence time and pulp density. The number of cells required for a given operation is determined from standard engineering mass balance calculations. In the design of a new plant, the characterization of each cell's volume and flotation efficiency is generally calculated from performing a laboratory-scale flotation on the same type of equipment on the ore in question, followed by the application of empirically derived design (scale-up) factors. Research work is currently under way to improve the understanding and performance of commercial flotation cells. Currently, flotation-cell design is primarily a proprietary function of the various cell manufacturers.

Flotation plants are built in multiple cell configurations (called banks), and the flow through various banks is adjusted in order to optimize plant recovery of the valuable as well as the valuable grade of the total recovered mass from flotation. This recovery vs grade trade-off is economically important in flotation, as increased recovery of the valuable is associated with decreased grade. For example, a 95% recovery of copper in the feed ore might give a concentrate grade of 18% Cu in the total recovered mass, while 80% Cu recovery might give a grade of 25% in the concentrate. Obviously, the higher the valuable recovery is, the higher the potential income, but if this higher recovery requires a great deal more grinding and/or expensive downstream processing (including further flotation) in order to upgrade the concentrate for metal refining such as smelting, the increase in potential recovery income may actually cause a net loss of total income. This grade-recovery optimization is generally worked out by individual flotation operators in each plant (and each mineral) and sets the operating philosophy of that plant.Figure 9 shows a typical industrial recovery vs grade trade-off curve for a copper sulfide ore containing pyrite. The higher the copper recovery is, the greater the amount of undesired pyrite contained in the concentrate.

The various banks of flotation cells in an industrial plant are given special names to denote the particular purpose of the banks. The rougher bank is the first group of cells that the pulp sees after size reduction. The goal of the roughers is to produce a concentrate with as high a recovery of valuable as possible with generally low grade of the valuable. The rejected gangue material from any bank of cells is commonly denoted as the tails or tailings. Usually, rougher tails are discarded so that valuable mineral not recovered in the rougher bank is lost. The concentrate of the rougher bank can be further concentrated, sometimes after additional grinding, in banks of cells called cleaners or recleaners. The tailings from the cleaners or recleaners can be recirculated to a bank of cells known as scavengers in order not to lose any valuable material in the upgrading process. Various banks of cells are also sometimes known by the particle size of the particular pulps being floated. Coarse particles, fine or slime particles, and middle-sized particles, denoted as middlings, can all be treated in separate banks.

As to overall capacities of flotation plants, the range is quite variable, depending on the type and value of the mineral being processed, the amount of valuable mineral in the feed ore to flotation, the degree and cost of size reduction involved, and the relative response of the valuable(s) to the flotation process. Smaller plants ranging in size from 500 to 5000 metric tons of feed per day are common, with feed materials having high amounts of valuable per ton of feed ore (>40%), such as coal, phosphate, and oxide ores. On the other hand, the sulfide minerals that are typically a small percentage of the ore (<10% and often less than 1%) require much greater capacity in order to achieve a reasonable economic return on investment. Thus, typical copper sulfide plants have capacities in the range of 20,000 to more than 60,000 metric tons of feed ore per day.

Conventional flotation machines house two functions in a single vessel: an intense mixing region where bubbleparticle collision and attachment occurs, and a quiescent region where the bubbleparticle aggregates separate from the slurry. The reactor/separator machines decouple these functions into two separate (or sometimes more) compartments. The cells are typically considered high-intensity machines due to the turbulent mixing in the reactor (see Section 12.9.5). The role of the separator is to allow sufficient time for mineralized bubbles to separate from the tailing stream which generally requires relatively short residence time (when compared to mechanical cells or columns).

Some of the earliest machine designs were of the reactor/separator-type. Figure 12.80 shows a design from a patent by Hebbard (1913). Feed slurry was mixed with entrained air in an agitation box (reactor) and flowed into the separation vessel where froth was collected as overflow. The design would be the basis for the Minerals Separation Corporation standard machine and early flotation cells used in the United States (Lynch et al., 2010).

The Davcra cell (Figure 12.81) was developed in the 1960s and is considered to be the first high-intensity machine. The cell could be thought of as a column or reactor/separator device. Air and feed slurry are contacted and injected into the tank through a cyclone-type dispersion nozzle, the energy of the jet of pulp being dissipated against a vertical baffle. Dispersion of air and collection of particles by bubbles occurs in the highly agitated region of the tank, confined by the baffle. The pulp flows over the baffle into a quiescent region designed for bubblepulp disengagement. Although not widely used, Davcra cells replaced some mechanical cleaner machines at Chambishi copper mine in Zambia, with reported lower operating costs, reduced floor area, and improved metallurgical performance.

Several attempts have been made to develop more compact column-type devices, the Jameson cell (Jameson, 1990; Kennedy, 1990; Cowburn et al., 2005) being a successful example (Figure 12.82). The Jameson cell was developed in the 1980s jointly by Mount Isa Mines Ltd and the University of Newcastle, Australia. The cell was first installed for cleaning duties in base metal operations (Clayton et al., 1991; Harbort et al., 1994), but it has also found use in coal plants and in roughing and preconcentrating duties. The original patent refers to the Jameson cell as a column method, but it can also be considered a reactor/separator machine: contact between the feed and the air stream is made using a plunging slurry jet in a vertical downcomer (the reactor), and the airslurry mixture flows downwards to discharge and disengage into a shallow pool of pulp in the bottom of a short cylindrical tank (the separator). The disengaged bubbles rise to the top of the tank to overflow into a concentrate launder, while the tails are discharged from the bottom of the vessel. Air is self-aspirated (entrained) by the action of the plunging jet. The air rate is influenced by jet velocity and slurry density and level in the separator chamber.

The Jameson cell has been widely used in the coal industry in Australia since the 1990s. Figure 12.83 shows a typical cell layout where fine coal slurry feeds a central distributor which splits the stream to the downcomers. Clean coal is seen overflowing as concentrate from the separation vessel. The major advantage of the cell in this application is the ability to produce clean concentrates in one stage of operation by reducing entrainment, especially when wash water is used. It also has a novel application in copper solvent extraction/electrowinning circuits, where it is used to recover entrained organic droplets from electrolyte (Miller and Readett, 1992).

The Contact cell (Figure 12.84) was developed in the 1990s in Canada. The feed slurry is placed in direct contact with pressurized air in an external contactor which comprises a draft tube and an orifice plate. The slurryair mixture is fed from the contactor to the column-type separation vessel, where mineralized bubbles rise to form froth. Contact cells employ froth washing similar to conventional flotation columns and Jameson cells. Contact cells have been implemented in operations in North America, Africa, and Europe.

The IMHOFLOT V-Cell (Figure 12.85(a)) was developed in the 19801990s and evolved from earlier designs developed in Germany in the 19601970s (Imhof et al., 2005; Lynch et al., 2010). Conditioned feed pulp is mixed with air in an external self-aeration unit above the flotation cell. The airslurry mixture descends a downcomer pipe and is introduced to the separation vessel via a distributor box and ring pipe with nozzles that redirect the flow upward in the cell. The separation vessel is fitted with an adjustable froth crowding cone which can be used to control mass pull. The concentrate overflows to an external froth launder, while the tailings stream exits at the base of the separation vessel. The V-Cell has been used to float sulfide and oxide ores with the largest operation being an iron ore application (Imhof et al., 2005).

The IMHOFLOT G-Cell (Figure 12.85(b)) was introduced in 2001 and employs the same external self-aerating unit as the V-Cell. The airslurry mixture which exits the aeration unit is fed to an external distributor box (located above the separation vessel) where pulp is split and fed to the separation vessel tangentially via feed pipes. The cell is unusual as an internal launder located at the center of the vessel collects froth. The centrifugal motion of the slurry enhances froth separation with residence times being ca. 30s.

The Staged Flotation Reactor (SFR) (Figure 12.86) is a recent development in the minerals industry. By sequencing the three processesparticle collection, bubble/slurry disengagement, and froth recoveryand assigning each to a purpose-built chamber, the SFR aims to optimize each of the three processes independently.

The SFR incorporates an agitator in the first (collection) chamber designed to provide high energy intensity (kWm3) and induce multiple particle passes through the high shear impeller zone, hence giving high collection efficiency. Slurry flows by gravity through the reactor stages, that is, there is no need to apply agitation to suspend solids, only for particle collection. As such, impeller speed can be adjusted online in correlation with desired recovery without sanding. The second tank is designed to deaerate the slurry (bubble disengagement) and rapidly recover froth to the launder without dropback. The froth recovery unit is tailored for use of wash water and for high solids flux. Efficient particle collection and high froth recovery translate into fewer, smaller cells, resulting in a smaller footprint and building height, with lower power consumption, and the potential for good selectivity in both roughing and cleaning applications.

Induced air flotation machines have gained a degree of popularity within certain sections of the minerals processing industry because of their ability to produce small bubbles at relatively high energy efficiency. The most common of such machines is the Jameson Cell. A downcomer protrudes out of the bubbly liquid in which is housed a plunging jet. Because this jet is at high velocity the pressure within the downcomer is low due to the Bernoulli equation, and air is induced into the downcomer creating a plume of bubbles within the liquid, which rise to form a foam. There are major problems with operating Jameson Cells because their high demand for surfactant causes downstream residual frother issues. (It is noted, as an aside, that frother strippers are being developed to remove residual frother in flotation circuits, and these are identical to foam fractionation units.) Notwithstanding that Jameson Cell technology has failed to live up to its promise, it has been successfully used as a pilot-scale foam reactor to effect the autothermal thermophilic aerobic digestion (ATAD) of high strength wastewater sludge produced at a chicken processing factory. The advantage that induced gas systems have over alternative pneumatic foam systems is their very high gasliquid surface area per unit volume of foam due to their small bubbles. This feature of the foams would also be an advantage in foam fractionation because it creates high flux of gasliquid surface. However, to the authors knowledge, no attempt has ever been made to use induced gas systems as foam fractionators.

The Denver DR flotation machine, which is an example of a typical froth flotation unit used in the mining industry, is illustrated in Figure 1.47. The pulp is introduced through a feed box and is distributed over the entire width of the first cell. Circulation of the pulp through each cell is such that, as the pulp comes into contact with the impeller, it is subjected to intense agitation and aeration. Low pressure air for this purpose is introduced down the standpipe surrounding the shaft and is thoroughly disseminated throughout the pulp in the form of minute bubbles when it leaves the impeller/diffuser zone, thus assuring maximum contact with the solids, as shown in Figure 1.47. Each unit is suspended in an essentially open trough and generates a ring doughnut circulation pattern, with the liquid being discharged radially from the impeller, through the diffuser, across the base of the tank, and then rising vertically as it returns to the eye of the impeller through the recirculation well. This design gives strong vertical flows in the base zone of the tank in order to suspend coarse solids and, by recirculation through the well, isolates the upper zone which remains relatively quiescent.

Froth baffles are placed between each unit mechanism to prevent migration of froth as the liquid flows along the tank. The liquor level is controlled at the end of each bank section by a combination of weir overflows and dart valves which can be automated. These units operate with a fully flooded impeller, and a low pressure air supply is required to deliver air into the eye of the impeller where it is mixed with the recirculating liquor at the tip of the air bell. Butterfly valves are used to adjust and control the quantity of air delivered into each unit.

Each cell is provided with an individually controlled air valve. Air pressure is between 108 and 124 kN/m2 (7 and 23 kN/m2 gauge) depending on the depth and size of the machine and the pulp density. Typical energy requirements for this machine range from 3.1 kW/m3 of cell volume for a 2.8 m3 unit to 1.2 kW/m3 for a 42 m3 unit.

In the froth flotation cell used for coal washing, illustrated in Figure 1.48, the suspension contains about 10 per cent of solids, together with the necessary reagents. The liquid flows along the cell bank and passes over a weir, and directly enters the unit via a feed pipe and feed hood. Liquor is discharged radially from the impeller, through the diffuser, and is directed along the cell base and recirculated through ports in the feed hood. The zone of maximum turbulence is confined to the base of the tank; a quiescent zone exists in the upper part of the cell. These units induce sufficient air to ensure effective flotation without the need for an external air blower.

Most of the industrial flotation machines used in the coal industry are mechanical, conventional cells. These machines consist of a series of agitated tanks (usually 48 cells) through which fine coal slurry is passed. The agitators are used to ensure that larger particles are kept in suspension and to disperse air that enters down through the rotating shaft assembly (Fig. 11.13). Air is either injected into the cell using a blower or drawn into the cell by the negative pressure created by the rotating impeller. For coal flotation, trough designs that permit open flow between cells along the bank are more common than cell-to-cell designs that are separated by individual weirs.

Some of the major manufacturers of flotation equipment include Wemco (FLSmidth), Metso, Svedala, and Outokumpu. The commercial units are very similar in basic design and function, although some slight variations exist in terms of cell geometry and impeller configuration. Machines with large specific surface areas are generally preferred for coal flotation, due to the fast flotation kinetics of coal and the large froth solids loadings. Flotation machines with individual cell volumes of up to 28m3 are commonly used due to advantages in terms of capital, operating and maintenance costs. Some manufacturers also offer tank machines, which consist of relatively short cylindrical tanks equipped with conventional impellers. The simplified structural design, which allows these machines to be much larger, can offer significant savings in terms of capital and power costs for some installations. Tank cells with volumes as large as 100m3 are already in operation at coal plants in Australia.

Unlike conventional, mechanically agitated flotation machines, which tend to use relatively shallow rectangular tanks, column cells used in the coal industry are usually tall vessels with heights typically ranging from 7 to 16m depending on the application. Unlike conventional flotation machines, columns do not use mechanical agitation and are typically characterized by an external sparging system, which injects air into the bottom of the column cell. The absence of intense agitation promotes higher degrees of selectivity and can aid in the recovery of coarse particles.

In general, feed slurry enters the column at one or more feed points located in the upper third of the column body and descends against a rising swarm of fine bubbles generated by the air sparging system (Fig. 11.14). Hydrophobic particles that collide with, and attach to, the bubbles rise to the top of the column, eventually reaching the interface between the pulp (collection zone) and the froth (cleaning zone). The location of this interface, which can be adjusted by the operator, is held constant by means of an automatic control loop that regulates a valve on the column tailings line. Varying the location of the interface will increase or decrease the height of the froth zone. The froth is transported from the froth zone into the product launder via mass action.

Methods of sparging in columns are numerous and include air lances, porous tubes, eductors, static mixers, and Cavitation-TubesTM. The air rate used in a column is selected according to the feed rate and concentrate-production requirements. This parameter typically has the largest effect on the operating point of the column with respect to the ash/yield curve. The bubbles generated by the air sparging system are sized to provide the maximum amount of bubble surface area given a constant energy input. In other words, the designs of the various sparging devices are engineered to provide the smallest size and largest number of bubbles possible.

For an equivalent volumetric capacity, the cross-sectional surface area of a column cell is much smaller than that of a conventional cell. This reduced area is beneficial for promoting froth stability and allowing deep froth beds to be formed. This is an important aspect of column flotation, as a deep froth bed facilitates froth washing for the removal of unwanted impurities from the float product. Wash water, added at the top of the column, percolates through the froth zone displacing dirty process water and non-selectively entrained particles trapped between the bubbles. In addition, froth wash water serves to stabilize and add mobility to the froth. Sufficient water must be added to ensure that all of the feed water that would otherwise normally report to the froth product is replaced with fresh or clarified water. It has been reported that less than 1% of the feed pulp and associated clays will report to the froth in a well-operated column (Luttrell et al., 1999). The ability to maintain and wash a deep froth layer is the main reason cited for the improved product grades when comparing column cells to conventional cells.

In contrast, conventional mechanical cells do not operate with deep froths. Therefore, these devices allow some portion of the ultrafine mineral slimes to be recovered with the water that reports to the froth. Consequently product quality is reduced by this non-selective hydraulic conveyance (i.e., entrainment) of gangue into the product launder. In fact, fine particles (<0.045mm) have a tendency to report to the froth concentrate in direct proportion to the amount of product water recovered. As such, the flotation operator is often forced to make the decision to either pull hard on the cells to maintain yield (e.g., wet froth), or run the cells less aggressively to maintain grade (e.g., dry froth).

The primary advantage of utilizing wash water is the ability to provide a superior product grade when compared to conventional flotation processes. This capability is illustrated by the test data summarized in Fig. 11.15, which compares column flotation technology with an existing bank of conventional cells. As shown, the separation data for the column cells utilizing wash water are far superior to those obtained from the conventional flotation bank. In fact, the data for the column cells tend to fall just below the separation curve predicted by release analysis (Dell et al., 1972). A release analysis is an indication of the ultimate flotation performance and is often regarded as wash-ability for flotation. This figure suggests that columns provide a level of performance that would be difficult to achieve even after multiple stages of cleaning by conventional machines.

There are a significant number of full-scale column installations currently in commercial service around the world. The most popular brands of columns include the CPT CoalPro (Eriez), Jameson, and Microcel columns. Although the Jameson cell does not have the traditional column geometry, it is included since it typically uses wash water to improve ash rejection. Details related to the specific design features of the various column technologies are available in the literature (McKay et al., 1988; Finch and Dobby, 1990; Yoon et al., 1992; Manlapig et al., 1993; Davis et al., 1995; Rubinstein, 1995; Wyslouzil, 1997). The primary difference between the various columns used in the coal industry is the type of air sparging system employed. These include porous bubblers, static mixers, and dynamic air injectors. Details related to the features and operation of these systems have been discussed extensively in the literature (Dobby and Finch, 1986a; Xu and Finch, 1989; Huls et al., 1991; Groppo and Parekh, 1992; Yoon et al., 1992; Finch, 1995). Ideally, the spargers should produce small, uniformly sized bubbles at a desired aeration rate. Other factors, such as equipment costs, mechanical reliability, wear resistance, and serviceability also need to be carefully considered prior to selecting an industrial sparging system.

Due to economy of scale, recent trends in the coal industry have shifted away from the installation of large numbers of smaller units toward fewer, large units with diameters up to 5m or more. Although most column installations involve the treatment of particles finer than 0.150mm, several recent column operations have been installed to treat coarser particles, such as minus 1mm feeds or deslimed 0.1500.045mm feeds. Additionally, a move to more economical cells in terms of energy efficiency has been realized as manufacturers focus on the generation of the required air bubble dispersions while using significantly less power than traditional approaches. One such device is the Eriez StackCell, which utilizes both pre-aeration methods in conjunction with traditional froth washing (Davis et al., 2011) to maximize efficiency with regard to both installation and operating cost.

The two most important requirements of laboratory flotation machines are reproducibility and performance similar to commercial operations. These two criteria are not always satisfied. The basic laboratory machines are scaled down replicas of commercial machines such as Denver, Wemco and Agitair. In the scale down, there are inevitable compromises between simplification of manufacture and attempts to simulate full scale performance. There are scaling errors, for example, in the number of impeller and stator blades and various geometric ratios. Reproducibility in semi-batch testing requires close control of impeller speed, air flow rate, pulp level and concentrate removal.

Until now, deaeration tanks always had to be placed underneath the flotation machine and also frequently in the cellar of a facility in order to ensure a sufficient height difference for the conveyance of foam. In addition, the tanks are open on top and can overflow with excess foam. That is now a thing of the past with the Deaeration Foam Pump (DFP) 4000. The new pump can be linked directly to the deinking machine and forms a clean and closed disposal system. Because it can be placed at the same level as the flotation cells, the entire flotation system saves more space than previous systems. A cellar or an additional floor height for the flotation is no longer required. The deaeration results are very impressive with the DFP 4000 from Voith Paper. The air content of the foam mass is reduced when passing through the pump from 80% to an average of 8%. Conventional deaeration systems offer approximately 12%. In addition, by using the DFP 4000, upstream foam destroyers, downstream long piping as well as pumps with high head pressures to overcome the floor height can be dispensed. With the DFP 4000, it is possible to deaerate and convey the foam, which is loaded with inks and other impurities, within a single machine. As a compact unit, it fully replaces the foam destroyer, foam tank stirring unit, and pump of previous deaeration systems. This means a clear reduction in investment costs for the tank, stirring unit, pipes, pumps, and floor space.

The DFP 4000, developed by Voith, is a compact unit that integrates several elements of the flotation deinking system. This combines the pump and deaeration machine into one unit. The deaeration foam pump replaces the foam destroyer, foam tank, stirring unit, and pump and costs less than the current suite of equipment. The DFP 4000 achieves better deaeration of the foam than conventional systems.

The DFP 4000 has two parts. In the upper part, foam is predeaerated by a mechanical foam destroyer. In the lower part, centrifugal force produced by a quick rotational movement further deaerates the foam. The resulting low-air-content suspension is brought to the required pressure so that it can be conveyed out of the machine to the next process stage. The air released during deaeration is conveyed out of the machine through a special air chamber on the side so that the airflow does not prevent the foam entering from above (Dreyer,2010).

The new pump can be linked directly to the deinking machine, forming a clean and closed disposal system. Because the deaeration pump can be placed at the same level as the flotation cells, the entire system requires less space than previous systems, so a cellar (or additional floor height) is no longer required to accommodate the system. When the foam mass passes through the DFP 4000, the foams air content is reduced from 80% to an average of 8% (Voith,2011a). Conventional deaeration systems reduce the air content to approximately 12%. The first DFP 4000 operating in a paper mill has been in service since September 2009 (Dreyer,2010). The benefits of the DFP 4000 are summarized in Table11.9 (Dreyer,2010; Voith,2011a).

Batch testing has been carried out using a specially designed 21 tumbler for mixing, and a standard Denver flotation machine for separation. A typical charge of the soil sample ranged from 200 to 600g, and the amount of coal varied depending on the contaminant concentration.

Figure 1 shows the block diagram of the 6T/day continuous unit. A slurry of contaminated soil and coal is fed at optimal solids concentration to a specially designed tumbler. In the front section of the tumbler, as a result of rotary motion, the solids are mixed and dispersed. In another section of the tumbler, layering, compaction and abrasion take place. After being discharged from the tumbler, the contents are screened into two streams. The 1mm particle size stream is directed to a high shear mixer where the oil-wetted coal particles are conditioned. The slurry is then transfered to flotation cells, where the coal microagglomerates, in the form of froth, are separated from clean soil. To facilitate dewatering and improve handleability of the combustible product, the froth can be subsequently fed into the low shear mixer for further agglomeration.

Flotation has progressed and developed over the years; recent trends to achieve better liberation by fine grinding have intensified the search for more advanced means of improving selectivity. This involves not only more selective flotation agents but also better flotation equipment. Since the froth product in conventional flotation machines contains entrained fine gangue, which is carried into the froth with feed water, the use of froth spraying was suggested in the late 1950s to eliminate this type of froth contamination. The flotation column patented in Canada in the early 1960s and marketed by the Column Flotation Company of Canada, Ltd., combines these ideas in the form of wash water supplied to the froth. The countercurrent wash water introduced at the top of a long column prevents the feed water and the slimes that it carries from entering an upper layer of the froth, thus enhancing selectivity.

The microbubble flotation column (Microcel) developed at Virginia Tech is based on the basic premise that the rate (k) at which fine particles collide with bubbles increases as the inverse cube of the bubble size (Db), i.e., k1/Db3. In the Microcel, small bubbles in the range of 100500m are generated by pumping a slurry through an in-line mixer while introducing air into the slurry at the front end of the mixer. The microbubbles generated as such are injected into the bottom of the column slightly above the section from which the slurry is with drawn for bubble generation. The microbubbles rise along the height of the column, pick up the coal particles along the way, and form a layer of froth at the top section of the column. Like most other columns, it utilizes wash water added to the froth phase to remove the entrained ash-forming minerals. Advantages of the Microcel are that the bubble generators are external to the column, allowing for easy maintenance, and that the bubble generators are nonplugging. An 8-ft diameter column uses four 4-in. in-line mixers to produce 56 tons of clean coal from a cyclone overflow containing 50% finer than 500 mesh.

Another interesting and quite different column was developed at Michigan Tech. It is referred to as a static tube flotation machine, and it incorporates a packed-bed column filled with a stack of corrugated plates. The packing elements arranged in blocks positioned at right angles to each other break bubbles into small sizes and obviate the need for a sparger. Wash water descends through the same flow passages as air (but countercurrently) and removes entrained particles from the froth product. It was shown in both the laboratory and the process demonstration unit that this device handles extremely well fine below 500-mesh material.

Another novel concept is the Air-Sparged Hydrocyclone developed at the University of Utah. In this device, the slurry fed tangentially through the cyclone header into the porous cylinder to develop a swirl flow pattern intersects with air sparged through the jacketed porous cylinder. The froth product is discharged through the overflow stream.

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.

low-pressure blowers and mining: froth flotation and tank leaching

low-pressure blowers and mining: froth flotation and tank leaching

In our last post on mining, we covered several applications that use low-pressure compressed air as a part of each process. In this post we will look at two applications froth flotation and tank leaching. We will review each application, how compressed air is used in the processes, and what type of low-pressure compression equipment might be used.

The first application covered in this post is froth flotation, which is the most widely used method for ore beneficiation. Ore beneficiation is a process in which valuable minerals are separated from worthless material, known as gangue, or other valuable minerals. This is a key process in the recovery of most of the worlds copper, lead, molybdenum, nickel, platinum group elements, silver and zinc, and in the treatment of certain gold and tin ores.

Froth flotation is a process for separating minerals from gangue by taking advantage of differences in their hydrophobicity (how much they are attracted to water) and is enhanced through the use of surfactants. Surfactants are chemicals that act as a wetting agent to attach to particles and increase their attractiveness to air bubbles. The first step in the flotation process involves crushing the ore. The powder is then mixed with water and chemicals, and the resulting pulp slurry is fed to a series of flotation cells.

Once in the flotation cell, physical separation of the desired particles will be completed based on the air bubbles ability to selectively adhere to specific mineral surfaces in the slurry. The particles attached to the air bubbles are carried to the surface and removed. Blowers provide the required air to create the small bubbles used in this process, generally at pressures less than 1 bar.

In the past, multistage blowers have been traditionally used for this process, but low-pressure screw blowers such as Atlas Copcos ZS line are becoming popular for this application. ZS screw blowers can operate at higher pressures than traditional multistage blowers, and as have the advantage of a wider turndown range. ZS screw blowers can be installed outdoors as well even with integrated VFD and controls.

Our next application is leaching through cyanidation, or the process of dissolving gold with a cyanide solution, which is the most common method used in the leaching of gold from ore material. Leaching is the process where a liquid substance extracts or dissolves minerals or other materials from a solid material. Tank leaching is carried out in multiple tanks installed in series where the gold ore is mixed with a cyanide solution, limestone and activated carbon and aerated with air bubbles.

Activated carbon is a very important component in the process of dissolved gold recovery because it adsorbs dissolved gold from gold leach pulp complex through its pores. Unfortunately, activated carbon is subject to fouling with inorganic and organic matter. Fouling means that material other than gold is absorbed onto the carbon, decreasing the efficiency to adsorb the valuable metal. It is therefore very important to supply high quality, oil-free air to the cyanidation tanks.

Atlas Copcos ZE and ZA line of low-pressure compressors provide oil free air to meet the demands of this application for pressures over 20 psi. The ZE/A line offers a heavy-duty air filter designed to provide contaminant-free air even in the harshest environment. Finally, Atlas Copco offers an industry leading 5-year warranty on the compression element to prove its unquestionable reliability.

Regardless of the application, Atlas Copco has low-pressure equipment that meets the demanding needs of the mining industry. Atlas Copcos low-pressure machines are the most efficient and most reliable options for an industry that requires just that. With a complete line of blower equipment, we can help guide the correct blower selection for the application and offer the best solution based on the customers needs.

precise air flow measurement improves flotation cell efficiency | e & mj

precise air flow measurement improves flotation cell efficiency | e & mj

A major international precious metals producer wanted to optimize froth flotation performance at one of its processing plants, where flotation cells were experiencing production efficiency issues that were resulting in lower than ideal yields at higher costs.

Froth flotation cells separate minerals from ground-ore slurries based on the difference in the hydrophobicity of the minerals and the ore waste tailings. The process separates the lighter minerals from the heavier waste tailings. Pulverized ore particles are fed downward via a pipe into a large tank where they are mixed vigorously with water, a reagent that promotes attachment of valuable minerals to air bubbles and compressed air.

Froth flotation cells rely on precision froth handling for increased recoveries in roughing, scavenging and cleaning applications. Accurate and repeatable mass air flow measurements are vital for the efficient operation of large flotation tank cells and reduced reagent costs. THE PROBLEMSThe customer performed a careful process review of its flotation cell performance and determined that the compressed air flow meters were not delivering accurate and repeatable readings. The inaccurate readings meant that sometimes not enough compressed air was being piped into the frother unit.

The existing flow meters were volumetric and not mass flow measurement meters. As the pressure and temperature of the compressed air changed, the volumetric flow meters could not adjust for the change in mass air flow. There also was not enough pipe straight run to create a repeatable flow profile, which again affected accuracy and consistency of measurement.

Measuring mass air flow (rather than volumetric flow) is critical to the efficiency and stability of the frothing process due to the large variations in ambient air temperature that occur in comparison with the smaller changes in slurry temperature. The measured air flow is closely related to the air or bubble volume within the flotation tank. Therefore, measuring mass air flow rather than volumetric air flow increases the frothing process performance efficiency.

Flotation cells are aerated with compressors or blowers and often with very little pipe straight run, which can affect the accuracy and consistency of flow meter readings. Larger processing plants also utilize modern process control systems (DCS, PLC) to optimize their operations, and the flow meters must be able to communicate with them.

In this case, the flotation cells utilized 3-, 4- and 6-in. compressed air lines (Figure 2). The customers process review had revealed that the amount of unobstructed pipe straight run was insufficient and affected the accuracy of the flow meters.

The flotation cells required an air flow rate that varied from 35 to 1,050 SCFM depending on the location and production volume, and at pressures from 4 to 7 psig [0.3 bar(g) to 0.5 bar(g)]. Typical process temperatures were 32F to 140F (0 to 60C).

Flotation cells require precise control of compressed air because the frothing process efficiency is based on the speed of the froth as it moves from the surface of the slurry to the recovery area. The speed of the froth is controlled by the air bubbles induced into the flotation cell, tank level and reagent dosages.

The accurate and repeatable measurement of the compressed air delivered to the flotation cell improves ore yields, reduces reagent cost, and provides a significant plant energy cost savings from reduced operation of the air compressors and blowers. The more efficient the frothing process, the less often the compressor runs, which reduces process energy costs. The amount of reagent consumed is also affected by the efficiency of the frothing process, which is another process cost savings related to the accuracy of the compressed air mass flow measurement. The repeatable control of the mass air flow therefore increases the frothing process efficiency.

THE SOLUTIONThe mineral producer contacted the process applications team at Fluid Components International (FCI) for advice about its compressed air measurement accuracy problem. The FCI team recommended its thermal dispersion ST100 Air/Gas Flow Meter (mass flow measurement) combined with a Vortab Insertion Panel (VIP) Flow Conditioner to eliminate the problems with the insufficient pipe straight run.

The meters mass flow sensor, with its temperature-compensated design, eliminated the accuracy problem. Its adjustable 1- to 6-in. insertion length was compatible with all the pipe sizes in use and its Profibus PA digital bus communications were compatible with the plant DCS system.

The installation of the flow conditioner at three pipe diameters upstream of the meter locations on the frother unit solved the lack of pipe straight run availability. Conditioning the flow resulted in a highly repeatable flow profile across the entire required flow measurement range, which helped solve the accuracy and repeatability issues.

The recommended mass flow meter (Figure 3) is a next-generation advanced design, offering feature-rich and function-rich electronics. This highly adaptable meter allows users to select a meter for todays measurement requirements, but have the flexibility to change in the future as process requirements or equipment changes.

The customer selected the new mass flow meter in part because of its Profibus PA digital communication capabilities. It also supports 4-20 mA analog, frequency/pulse, or other digital bus communications such as HART, Foundation Fieldbus H1 or Modbus. If a plants needs change over time, the meter adapts as necessary with a plug-in card replacement that can be changed out in the field by a plant technician.

The mass flow meters unique graphical, multivariable, backlit LCD display/readout allows plant technicians to view process information locally as necessary at the point of installation. It provides a continuous display of all process measurements and alarm status, and the ability to interrogate for service diagnostics.

This user-friendly mass flow meter stores up to five unique calibration groups to accommodate broad flow ranges, differing mixtures of the same gas and multiple gases, and obtains up to 1,000:1 turndown. Also standard is an onboard data logger with an easily accessible, removable 2-GB micro-SD memory card capable of storing data for up to 90 days.

The mass flow meter chosen for the plant can be calibrated to measure compressed air or virtually any process gas, including wet gas, mixed gases and dirty gases. The basic insertion style air/gas meter features a thermal flow sensing element that measures flow from 0.25 to 1,000 SFPS (0.07 NMPS to 305 NMPS) with an accuracy of 0.75% of reading, 0.5% of full scale.

For safety, the mass flow meter is agency approved for hazardous environments, including the entire instrument, the transmitter and the rugged, NEMA 4X/IP67 rated enclosure. Instrument approvals in addition to SIL-1 include ATEX, IECEx, FM and FMc for product reliability.

To support the plants frother cell facility layout, the insertion panel type flow conditioner (Figure 4) was installed upstream from the mass flow meters. The flow conditioner provides a low pressure-loss solution to flow profile irregularities produced by elbows, valves, blowers, compressors, and other disruptions that commonly occur in pipe and duct runs.

The flow conditioners design combines proven swirl removal technology with a unique mixing process to achieve the most thorough and efficient flow conditioning available. Tabs are located strategically within the conditioner that promote rapid mixing, creating a uniform flow profile for proper measurement by the meter.

THE OUTCOMELower compressor run-time energy expense, along with less reagent use, combined to achieve more than 7% total cost reduction, which paid for the new flow instrumentation in only one month. The installation of the rugged mass flow meter and flow conditioner solved the frother units measurement accuracy and repeatability problems and increased the units output efficiency.

The single-tap insertion style thermal mass flow meter and the insertion panel flow conditioner were compatible with the concentrators existing piping for easy installation. The flow meters Profibus PA digital communications smoothly integrated directly into the existing DCS system with reduced wiring and commissioning cost.

The thermal dispersion flow meters direct mass flow measurement and real-time temperature compensation ensured accurate measurement. There also was no need to install additional temperature or pressure sensors, which are required by some flow meter technologies. With the thermal mass flow meters no moving parts construction, there is nothing to break, clog or foul, and there is virtually no maintenance with excellent reliability, which is well suited for the harsh environment in mineral processing operations.

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operating principles - operating principles | jameson cell

operating principles - operating principles | jameson cell

The Jameson Cell consistently produces fine bubbles and intense mixing between air and slurry. This means fast, efficient flotation. While the principle of using air bubbles to recover particles is the basis of the technology, it is the way air bubbles are generated and how the bubbles and particles interact that make Jameson Cells unique.

In the Jameson Cell, particle-bubble contact takes place in the downcomer. The tank's role is froth-pulp separation and may incorporate froth washing to assist in obtaining product grade. With no agitators, blowers or compressors Jameson Cell installation is simple and operation is extremely energy efficient. As the energy for flotation is delivered by a conventional pump power consumption is significantly lower than the equivalent mechanical or column flotation cell. Optimal Jameson Cell performance is maintained by delivering a constant volumetric flowrate of pulp to each downcomer. While operating plants experience fluctuating process flows, the Jameson Cell is equipped with a tailings recycle system that automatically compensates for feed variations. In addition to maintaining consistent and optimal downcomer operation, the tailings recycle improves metallurgical performance by giving particles multiple 'passes' through the downcomer contacting zone. The Jameson Cell's ability to provide better selectivity and to control entrainment means product grade is not affected.

The Downcomer is the heart of the Jameson Cell where intense contact between air bubbles and particles occurs. Feed is pumped into the downcomer through the slurry lens orifice creating a high-pressure jet. The jet of liquid shears and entrains air from the atmosphere. Removal of air inside the downcomer creates a vacuum, causing a liquid column to be drawn up inside the downcomer. The jet plunges into the liquid column where the kinetic energy of impact breaks the air into fine bubbles which collide with the particles. The very high interfacial surface area and intense mixing results in rapid particle attachment to the air bubbles, and high cell carrying capacities.

The Tank Pulp Zone is where mineral laden bubbles disengage from the pulp. The design velocities and operating density in this zone keep particles in suspension without the need for mechanical agitation. Due to the rapid kinetics and separate contact zone in the downcomer, the tank is not sized for residence time therefore tank volumes are much smaller than equivalent mechanical or column cells. Jameson Cells are contact dependent, not residence time dependent.

In the Tank Froth Zone the grade of the concentrate is controlled by froth drainage and froth washing. Cells are designed to ensure an efficient, quiescent zone that maximises froth recovery. Froth travel distance and concentrate lip loadings are integral to the tank design.

The downcomer is where bubble-particle collision, attachment and collection occur. The different hydrodynamic regions of the downcomer are the Free Jet, Induction Trumpet, Plunging Jet, Mixing Zone and Pipe Flow Zone.

Induction Trumpet: The Free Jet impinges on the slurry in the downcomer. The impact creates a depression on the liquid surface and results in air being channelled into the area at the base of the Free Jet.

Pipe Flow Zone: Beneath the Mixing Zone, a region of uniform multiphase flow exists. The downward liquid velocity counteracts the upward flow of mineral laden air bubbles. The air bubbles and particles pack together to form a downward moving expanded bubble-particle bed. The dense mixture of bubbles and pulp discharge at the base of the downcomer and enters the tank pulp zone where the mineral laden bubbles disengage from the pulp.

used flotation cells for sale. huatao equipment & more | machinio

used flotation cells for sale. huatao equipment & more | machinio

1. Self-absorption of air. 2. Good cycling property of pulp. 3. Flotation machine's suction volume is relatively stable. 4. Medium mixing strength and good suspension of solid particles. The Mineral Flotation / f...

Paper Mill Flotation Deinking Cell for Paper Recycling Line Application&Feature: 1.Mainlyappliedtodeinkrecycledpulp,itcaneffectivelyremovetheink,lightimpuritiesandstickiesetc. 2.Highefficientflo...

Recycle paper pulping Totally Enclosed Flotation Deinking pulp Cell Application&Feature: 1.Mainlyappliedtodeinkrecycledpulp,itcaneffectivelyremovetheink,lightimpuritiesandstickiesetc. 2.Higheffic...

Biobase Lab Small Coal Mining Mineral Iron Copper Ore Denver FrothFlotationCell TankSeparator Device With Floating Catalys Product Description Introduction BK-FD12 Laboratory multiple cell floatation device is...

Flotation cell accessory packages: - new induction motors - Blowers - Sheaves - Belts - Level control systems - Spare parts D'Angelo International can outfit your new or existing flotation cells with a range of a...

- New and unused flotation cells made to order in North America - Complete with mechanism, belt guards, and motor baseplate - All necessary cell and mechanism parts coated with protective 520 natural rubber (incl...

- 32 cells available; 1 bank of 12, 2 banks of 10 - 100 cubic feet per cell - Cleaned, painted, tested - Rubber and bearings in good condition - Motors, belts, and pulleys included - - Launder boxes required - Pr...

- Arranged as: feed box - 5 cells - intermediate box - 5 cells - discharge box - Two 5-cell overflow tanks with full length launders - 10 mechanisms with existing used impellers and diffusers - Four 5 HP 575 Volt...

- Our new flotation cells are made in North America - Cells and components are interchangeable with original Denver DR flotation cells - We supply spare and wear parts packages (minimnum order applies) Rubber l...

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