rcs flotation machines brochure - metso corporation - pdf catalogs | technical documentation | brochure
The RCS flotation machine is the latest design to use the circular tank concept and combines the benefits of circular cells with the unique features of the mechanism to create the ideal conditions to maximise flotation performance for all roughing, cleaning and scavenging duties. Metso offers the full range of cell volumes required for modern ore processing plants with cell sizes from 0,8 to 200 m3. DV Flotation mechanism The patent-protected DV (Deep Vane) mechanism impeller consists of a unique arrangement of vertical vanes with shaped lower edges and air dispersion shelf. The mechanism...
RCS Flotation machine The RCS (Reactor Cell System) flotation machine has been developed to combine the benefits of the circular cell concept with the unique features of the DV mechanism to create the ideal conditions to maximize flotation performance for roughing, scavenging, and cleaning duties. Maximum flotation recovery and performance have been achieved by careful attention to tank design. A very active lower zone for good solids suspension and transport, designed to maximize and create multiple particle-bubble contacts for recovery of the full range of particle sizes present. ...
Making the big difference to our customers Everything we do is based on deep industry knowledge and expertise that makes the big difference to our customers. Decades of close customer collaboration and adapting to our customers ever changing needs have transformed us into a knowledge company. www.metso.com [email protected] Subject to alteration without prior notice
industrial plant flotation machines in banks
A centrally located paddle-wheel type impeller generates a rotating pulp vortex which extends between two stationary elements: the sand-pipe located at the top of the cell, and the draft tube located at the bottom of the cell. The hydraulic action of this rotating vortex is to develop an internal cavity vacuum while simultaneously circulating the pulp from the bottom of the cell through the. draft tube into the rotor region. The suction developed in the vortex core draws air into the central region of the rotor which is mixed with the pulp circulated from the bottom to the cell.
Mineral flotation starts with grinding of the ore, with water and reagent, down to a chosen average grain size to secure liberation of the discrete mineral particles. This step raises a difficult mineralogical question; as perfect liberation is rarely achievable without excessive over-grinding, what defines the economic compromise?
The pulp (i.e. mineral-water slurry after grinding) is commonly passed through a hydrocylone to concentrate the sands and reject the slimes (the finest size fractions, say 30um), the slimes are objectionable in several respects: they are slow to float, the consume a disproportionate share of the reagents, and they may seriously spoil the selectivity of flotation of the sands by slime-coating them. There are sound arguments, in any case, for processing coarse and fine fractions separately.
The pulp is conditioned for a few minutes with reagents designed to accentuate differences of floatability of the various mineral species. An appreciable time is required to achieve good distribution of the reagents and to allow give-and-take competition between different mineral particles.
The conditioned pulp is run into a flotation cell, which is crudely a box with a stirrer, and a means of introducing air. Typically, the cell might contain 15-30% by volume of entrained air with bubbles ranging mainly from 0.1 to 5mm in diameter; the pulp density might be 25-40% of solids having a particle size ranging from 10-100um. The flotation grains are caught by bubbles and carried to the top of the cell, forming a froth, which is automatically scraped off over the lip of the cell, where it collapses and flows away in a launder. The frothing action is quite important. A moderate depth of froth is necessary to allow some back-drainage to take place, with release of non-floated particles which have been, unavoidably, entrained to some extent between the bubbles. Here is another reason why slimes are a nuisance they remain too long in the water between the bubbles and so reduce the grade of the floated product.
The first stage of flotation of the pulp amounts to a quite short average residence time in the rougher cell before it passes out, largely depleted, from the bottom of the cell. In a conventional flotation plant no attempt is made to engineer a perfect separation in one stage. Instead, both fractions leaving the rougher are re-treated at least once in cleaner and scavenger cells, respectively. Scavenger cells, in effect, prolong the flotation time, while competition for bubble surface is reduced. The net of the recycling and re-treatraent is improvements in the separation (grade) and proportion of valuable minerals obtained (recovery). As the latter is usually a minor component of the ore, it is preferable to float it, in preference to floating the much greater proportion of gangue; but in some cases the gangue is floated (reverse flotation).
It is a characteristic feature of flotation plants that the cells are comparatively small, but rows and rows of them are run in parallel to increase through-put and in series to improve grade. If more than one mineral is to be extracted, the pulp is re-conditioned with other reagents and further stages of flotation are operated. The engineering is simple, continuous, amenable to adjustment, and needs little operator attention. The concentrates from flotation are generally filtered, washed, dried and bagged for transport as powders.
PROBLEM 2 How many No. 18 Sp. (3232) Denver Sub-A Cells are required to treat 125 tons of load-zinc ore per day, with treatment time 14 minutes for the lead, dilution 3 to 1% and with treatment time 16 minutes for the zinc dilution 3 to 1. and sp. gr. 3.4 ?
Scale-up denotes the procedures for designing larger units of equipment for which smaller units are available with known operating characteristics. Such procedures are well established for chemical engineering equipment, particularly mixers, of which flotation cells are examples, although complex ones.
The bases for extrapolating design are the principles of similitude, including both geometrical and dynamical aspects. If full geometrical similarity is maintained in an equipment family, then once a single new size aspect is selected, for example, volume or impeller diameter, then all other dimensions are automatically established through the scale factor.
The dynamic aspect refers to the fluid motions involved and for mixers and flotation cells more specifically to the impeller speeds and energy inputs. It is here that complications arise. For relatively simple mixing problems, as in conditioners, where it has been established that power intensity is a scale-up factor, it can be shown that for contant Power Number and constant power intensity the relationship
However, in a flotation cell, the presence of air and the further necessity for balancing air and pulp flows to satisfy both flotation and suspension requirements simultaneously, introduces at least one other variable: air flow Qa; and at least one other dimensionless group the Air Flow Number Qa/ND. This may also be expressed as Qa/A/ ND
A further complication is that most families of cells have grown in size without rigorous scale-up procedures, (see Harris) Wemco does appear to have scaled its impellers closely to (cell area), i.e., D/L = constant, but this is not the case for Denver or Galigher. Cell depths now increase regularly for both Denver and Wemco, but not for Galigher.
Thus, at best, no automatic procedure for scale-up appears possible. Those published by Denver and Wemco illustrate the necessary mixture of rational and experimental steps. Wemco decided upon a 28 m (1,000 cu ft) cell and apparently also upon a .76 m (30 in) impeller diameter, which continues the D/(Area) ratio of 0. 227. Extrapolation of empirical relationships among air and liquid circulations, submergences, and HP, N, and D established ranges, but actual testing with a prototype was necessary to arrive at an impeller speed and submergence combination and to establish clearances. Finally capability of the selected combination for sand suspension was established experimentally.
For its largest cell, Denver first decided to use a 56 KW (75 HP) motor, as the largest compatible with a V-belt drive; with safety factors for start-up and overload this gave a 48 KW (65 HP) design criterion. Relationships were established from measured smaller cell operating characteristics among pumping rates, power draws, depths and cell volumes. These, with HP fixed and depth selected, resulted in fixing the volume at 36 m (1275 cu ft). The effects of clearances and independent variation of air flow on power draw were tested in a prototype as were the sand suspension capabilities.
Of interest was Denvers use of averaged fluid rise velocities as design criteria for proper sand suspension. These decrease from about 4 m/min (13 ft/min) in their smaller cells to 2.8 m/min (9 ft/min) in the 36m cell. Figures are similar for the Wemco cells but increase rather than decrease. These velocities are a rough measure of the maximum particle mass which can be suspended, although suspension in the sense of uniformity is a misnomer. As both of the studies show, there is segregation of coarser sizes. Only the finer sizes move uniformly throughout the cell with water flow, while coarser sizes find more restricted flow paths in appropriately higher velocity streams in which they circulate. In the limit, if a high enough velocity region does not exist, sizes requiring such a velocity settle out.
The three principal U. S. cells have had decades of intense competition world-wide. In addition their innovations in increasing cell volumes by factors of twenty in recent years have paid dividends in much lower power intensities. If at the same time unit capacities remain reasonably close to those of smaller cells, then any new designs may have difficulties in breaking into the field. Exceptions may well be in coarse particle handling for which conventional cells definitely have limitations because of their need to be versatile over the broadest possible range, with some sacrifices necessary.
The main hope for significant improvements rests on further quantification of relationships among flow, aeration, and process kinetics as related to particle size particularly. It may be that adjustment of the cell control parameters either in separate circuits for different size ranges, or in different parts of the same circuit, with the air and impeller speed adjustments as part of the control network along with reagents, will be the trend of developments for the future.
This would follow from the decreased ratio of area to volume with increasing depth, and thereby the lowered volume flow requirements to obtain the same linear velocities for air and pulp. In the case of air, this suggests that increased depth of cell favors more efficient utilization of air because of the longer path per bubble and the greater probability thereby of maximum loading per bubble. However, for the same reason, there may be a depth limit beyond which no further increase would be obtained.
In brief outline, these include: lower investment costs, lower installation costs, lower labor costs, and lower costs for controls. If lower power intensities at constant capacity per unit volume are borne out, then power costs per tonne would also be lower. In addition the reduction in the number of units necessary and the higher capacities per unit of floor space should result in lower indirect costs for buildings. There is a probable present limit to further increases in size if only because there are no plants in sight above the 100,000 tonne/day capacity level. At this tonnage, four rows of 12 cells, or fewer rows of greater length, of the largest presently available cell sizes would be adequate.
The indicated savings in flotation equipment costs only vary for 2.8, 8.5, 14.2 and 36.1m (100, 300, 500, 1275 cu ft) cells as 1.00 /0.60 / 0.45 / 0.37 and for 1.7, 14.2 and 28.3 m (60, 500, 1000 cu ft) cells as 1.00 / 0.52 / 0.39. Even if further savings in power intensities with still larger cells do not materialize, costs per unit of capacity for equipment, installation, and building should continue to decrease, but at a lower rate with continued increases in size.
Although there has been the implication that the very large cells should be considered only for the largest plant capacities, this is not necessarily correct. Attention is being given even for smaller plants to splitting circuits between roughing and scavenging; using one or a few of the larger cells at the head of a bank, or even for the entire tonnage as roughers to take out the fastest floating 50 to 75 percent of the mineral; and the completing the scavenging with the appropriate number of smaller cells to provide the time and the appropriate conditions of aeration and agitation for the slower floating coarse, middling, or altered surface minerals. In this way controls could be centralised in roughing, particularly if the scavenger concentrate could be recycled to the rougher, and different cell conditions could be adapted to the different requirements.
Impellers are the main differences among older mechanical cells; of novel types few are entirely new; and several are revivals of concepts going back to the first decades of practice. They can be divided into the following groups: a) injection types with pressurized introduction of feed through nozzles, which simultaneously aspirate air and mix it with the feed; b) froth feed types, which add new feed into or close to the froth; and c) cells with different fluid moving mechanisms.
Three cells of this type have been in commercial development over the past two decades: (1) theHeyl and Patterson CycloCell; (2) the Deister Flotaire, originally developed by Hollingsworth for Borden Phosphate in Florida; and (3) the Davcra Cell, developed by Davis for Conzinc Rio Tinto in Australia. Although all three use nozzles for air ingestion and mixing, the CycloCell uses a pump with recycle of cell contents through the pump/nozzle; the Flotaire substitutes water-main pressure for pumping by injecting fresh water through the nozzle for air aspiration; and finally, the Davcra uses a pump/nozzle to inject feed through the side of its cell without recycle back through the pump.
The practicality of the CycloCell has been established through extensive applications to coal flotation, and it has been tested on Florida phosphate. The Davcra has been used for special applications at Palabora and Bougainville and at locations in Australia, but it is understood that its further development has been discontinued. The Flotaire Cell has only recently been taken over by Deister who are attempting to develop applications in fields other than phosphate. The injection principle appears interesting both to supply and mix air and to provide the fluid energy for particle suspension. The important question is whether external pressure supply with loss of head through external piping and a nozzle is more or less efficient than a submerged impeller whose kinetic energy is dissipated entirely within the cell and presumably for useful purposes.
Three examples of this principle are known: the Flotaire Cell, already mentioned; a cell designed in the USSR employing the principle, but calling it froth separation , and a cell designed by Paul Smith of Colorado SMR Institute All use the same arguments and general approach: a) that a major flotation problem is the recovery of the coarsest sizes; b) that much of the energy required by flotation is for suspending coarse particles; and c) that, therefore, by adding feed directly to the froth the coarse particle problem is largely eliminated.
The proponents of all three cells can show impressive results mainly with coarse phosphate feeds, although the Russian cell is apparently in operation on other applications also. But two questions must be raised. Since the principle obviously has its greatest potential for coarse feeds, how does it compare with other specialized processes such as belt flotation, spirals, and the Lang launder, all developed and in use for similar applications. A second question concerns the behavior of fines. For these sizes what is an advantage for coarse particles becomes a disadvantage: below some size limit particles will have insufficient residence time in the froth to drain out by gravity and will be carried out in the froth product. This effect could be more severe with this type of cell than with convential cells, suggesting that sized feeds may be necessary to cope with it.
Apart from the external pump, and specialized impeller designs which claim better mixing or more effective aeration, the Outokumpu Cell being an example of the latter, a novel device is the Mekhanobr Vibromachine (USSR). This utilizes a flat paddle oscillating along a vertical axis at about 600 cycles/min with a few mm amplitude; air is admitted through perforations in the paddle during the up-stroke. The effect should resemble a high-frequency jigging action which should produce a fluidized bed-type suspension, possibly with less long-range circulation of pulp than in impeller type cells. Again the principle appears interesting and possibly requires less energy for flow induction, but in the absence of comparative data, no judgments are possible.
Air flow is actually a direct consequence of liquid flow for a self-aerating cell such as the Wemco. For all other mechanical cells air and liquid flows are independently variable, air through adjustment of supply, and liquid by impeller speed variation. Table contains a number of derived properties of Denver and Wemco cells covering the full ranges of cell volumes. Although availability of such data is too recent for any firm conclusions to be drawn, there are a number of trends evident.
The important aspect of these cell characteristics is not so much the actual values cited but that they are criteria of optimum cell operation. Too often, cell aeration and impeller speed are accepted as unchangeable instead of as potential control variables capable of manipulation, and in this respect have at least equal importance to reagent control. Thus, air flow is already being used to control concentrate grade at Mt. Isa. With the trend to larger and fewer cells, and coarser grinds, it may be advisable to control impeller speeds also, particularly for very coarse feeds, and to find the balance between these two controls for each operation.
As pointed out previously, the float machines were selected as 170 cubic foot Agitair machines for circuit flexibility. In our case we might have used 300 cubic foot machines or perhaps 500 cubic foot as the trend today is to go to larger and larger units which was considered, but eliminated for the flexibility factor. If we had selected 500 cubic foot units and utilized 5 units as roughers instead of 14 and 3 units in the scavenger area instead of 8 units, the cost savings in unit cost per cubic foot would be substantial with a resultant savings in building area. Due to the costs of building concentrators in these inflationary days, the larger units must be considered. 1,000 cubic foot units are now available and will soon be in operation.
Dilution water for the flotation circuit is derived from two sources. Concentrate thickener overflow water gravitates directly to the recleaner feed sump for dilution in recleaner flotation. Process water additions are made to each of the rougher, rougher scavenger, cleaner, recleaner and cleaner scavenger concentrate launders and to the regrind cyclone feed sump.
Vertical pumps are used for froth products and horizontal pumps for tailings and cyclone feeds. All seven banks of flotation machines are fitted with bubble-tube automatic pulp level controls and are Galigher 170 machines.
routing of cleaner scavenger tail direct to final tail. routing of cleaner concentrate to final concentrate . redirection of regrind cyclone overflow from cleaner feed to recleaner feed. by-pass of the regrind cyclones and hence the regrind section. routing of rougher concentrate to recleaner feed. by-pass of concentrate thickener overflow to the regrind cyclone feed sump and tailing thickener overflow sump.
Space has been provided in the flotation section layout for a talc flotation circuit, but no detailed design has been carried out. Its implementation will be dependent on the nature of the ores to be treated and is as follows:
The process flow diagram has been developed for the flotation of these talcy ores. The process depends on the rapid flotation of talc in this rougher flotation stage followed by three stages of cleaning of the rougher talc concentrate.
The talc rougher tail and three-stage cleaner tails are all directed to the No. 1 rougher scavenger bank which in this configuration becomes No. 1 copper rougher bank. The cleaned talc concentrate is discarded to final tail.
Flotation feed passes through one stage of rougher flotation, with rougher flotation tailing passing successively through three stages of rougher scavenger flotation. The unfloated product from the third rougher scavenger section is flotation tail. Rougher concentrate is refloated successively in cleaner and recleaner stages, with the recleaner concentrate leaving the flotation circuit as final concentrate. Cleaner tailing gravitates to cleaner scavenger flotation and recleaner tailing gravitates to cleaner flotation.
metso rcs flotation machines - metso outotec
Optimal mineral recovery in a flotation circuit depends on the capacity to adapt to metallurgical variability in the ore being processed. Recognizing the need for a solution that addresses these challenges, Metso has made several advances in flotation design and technology.
Combining the benefits of circular cells with the unique features of the patented DV mechanism, the RCS (Reactor Cell System) flotation technology has been developed to create ideal conditions to maximize flotation performance for all roughing, cleaning and scavenging duties. The cell can be modified to handle high density slurries.
Maximize bubble-particle contact within the mechanism and the flotation tank leads to enhanced performance. Effective air dispersion and distribution throughout the cell volume helps in smooth froth surface and removal.
Our RCS flotation machines are built with efficient air and level controls with controlled aeration rate at each cell. The pneumatically operated dart valves help in effective pulp level control followed by accurate measurement with ultrasonic level sensor and float.
Metso offers the innovative circular tank concept to minimize slurry short circuiting as well as simplifying froth handling process. The compact and modular design proves to be very beneficial for quick construction, shipment and installation. Our internal dart valves also help to minimize footprint requirements.
Metso RCS flotation machines have extended wear life due to minimized local high velocity zones inside the tank. Impellers and diffusors supplied in high abrasion-resistant elastomers, and the impeller profile is design to minimize adsorbed power.
The mechanism design produces powerful radial slurry pumping to the cell wall and gives strong return flows to the underside of the impeller to minimize sanding. Additionally, it is the only mechanism to give maximum slurry recirculation to the upper part of the impeller.
The modular dart valve design provides flexibility to capacity changes without disturbances.Full suspension of the DV mechanism from the cell superstructure leads to very simplified routine maintenance. Along with our robust design, the RCS flotation machines are built to work for you!
Metso RCS flotation machines also are found as an essential piece to a regrind circuit. Rougher cells extract majority of the valuable mineral from the fresh ore. Meanwhile, scavenger cells are going to capture the remaining valuable mineral.
Revolutionary image analysis system for live measurement of multiple froth properties such as velocity, color, bubble size distribution, texture, stability and more. Higher froth recovery with continuous monitoring and analysis of flotation cells.
flotation machines rcs - metso automation - pdf catalogs | technical documentation | brochure
The RCS flotation machine is the latest design to use the circular tank concept and combines the benefits of circular cells with the unique features of the mechanism to create the ideal conditions to maximise flotation performance for all oughing, cleaning and r scavenging duties. Metso offers the full range of cell volumes required for modern ore processing plants with cell sizes from 0,8 to 200 m3. Enhances flotation performance: The patent-protected DV (Deep Vane) mechanism impeller consists of a unique arrangement of vertical vanes with shaped lower edges and air dispersion shelf. ...
RCS Flotation machine The RCS (Reactor Cell System) flotation machine has been developed to combine the benefits of the circular cell concept with the unique features of the DV mechanism to create the ideal conditions to maximize flotation performance for roughing, s cavenging, and cleaning duties. Maximum flotation recovery and performance have been achieved by careful attention to tank design. Modular tank design to simplify construction, shipment and site installation. A very active lower zone for good solids suspension and transport, designed to maximize and create multiple...
Metso Minerals Industries, Inc. 2715 Pleasent Valley Road, York, PA 17402, USA, Phone: +1 717 843 8671 etso Minerals (South Africa) (Pty) Ltd. M Private Bag X2006, Isando, Johannesburg,1600, South Africa, Phone: +27 11 961 4000, Fax: +27 11 397 2050 Metso Minerals (Australia) Ltd. Level 2, 1110 Hay Street, West Perth, WA 6005, Australia, Phone: +61 8 9420 5555, Fax: +61 8 9320 2500 Metso Minerals (India) Pvt Ltd 1th floor, DLF Building No. 10, Tower A, DLF Cyber City, Phase - III, Gurgaon - 122 002, India, Phone: +91 124 235 1541, Fax: +91 124 235 1601 Metso Per S.A. Calle 5 Nro....
flotation machine | henan deya machinery co., ltd
Flotation machine is for processing minerals by means of froth flotation, which is a process for separating minerals from gangue by taking advantage of differences in their hydrophobicity. Hydrophobicity differences between valuable minerals and waste gangue are increased through the use of surfactants and wetting agents. The selective separation of the minerals makes processing complex ores economically feasible. The flotation process is used for the separation of a large range of sulfides, carbonates and oxides prior to further refinement. Phosphates and coal are also upgraded by flotation technology.
Flotation is a selective process and can be used to achieve specific separations from complex ores such as lead-zinc, copper-zinc, etc. Initially developed to treat the sulphides of copper, lead, and zinc, the field of flotation has now expended to include platinum, nickel, and gold-hosting sulphides, and oxides, such as hematite and cassiterite, oxidised minerals, such as malachite and cerussite, and non-metallic ores, such as fluorite, phosphates, and fine coal.
bf series flotation machine,bf flotation machine appliciation
BF series flotation machine is the latest design to use the circular tank concept and combines the benefits of circular cells with the unique features of the mechanism to create the ideal conditions to maximise flotation performance for all roughing, cleaning and scavenging duties.
This machine has the features of the big suction capacity and low power consumption. Every slot has the triple function of suction, grout and flotation which become the complete flotation circuit without any auxiliary equipment installing the machine in a actinic line it will be easier for the flow process change, the rational slurry cycle and furthest reducing the coarse sand sinking.
When flotation machine works, slurry is inhaled from the bottom of the trough to the space between impellers. Meanwhile, the low pressure air send by fan is sent to this area through the air distributor in the hollow shaft. After sufficient mixing, the slurry is pushed out by the impeller, and then goes to the whole trough.
When the froth rises to the stable level, after the enrichment processing, froth overflows to the froth trough from the overflow weir. Another part of ore slurry flows to lower part of impeller for the remixing with air. The remained slurry flows to the next trough until it becomes residue.
an introduction to froth flotation
When I started out the information on the processing equipment was easy to come by.Over time this has changed.As a start in reversing this, I have been presenting introductions to some of the common processes and equipment used in mineral processing.Major portions of this have been excerpted from A Mining Engineers Notebook: Mineral processing (www.smartdogmining.com).
Development and use of froth flotation as a beneficiation process has been ongoing since the first part of the last century.Initial study of the flotation concept was in the late 19th century.The basic process involves the selective coating of a particle's surface to alter or enhance its surface chemical characteristics.The flotation process is widely used for treating metallic and non-metallic ores. A greater tonnage of ore is treated by flotation than by any other single process. Practically all the metallic minerals are being recovered by the flotation process and the range of nonmetallic minerals is steadily being enlarged.
Flotation, or more specifically froth flotation, is a physicochemical method of concentrating fine minerals and coal.The process involves chemical treatment of a pulp to create conditions favorable for the attachment of particles to air bubbles.Some particles are not readily wetted by water (hydrophobic), while others are readily wetted by water (hydrophilic).By the addition of chemicals these properties can be enhanced.Air bubbles are created by the rapid motion of the agitator mechanism which draws air down the hollow shaft and disperses the air into the pulp.The air bubbles carry the hydrophobic particles to the surface of the pulp and form a stabilized froth which is skimmed off while the hydrophilic particles remain submerged in the pulp.
More than any other beneficiation process, there is probably no such thing as a typical flotation circuit.Development of a flotation circuit is entirely dependent on the characteristics of the ore and what works at one operation may not work at a nearby operation.And even in one operation the requirements can and will change over time.This requires continual test work.That said there are some fairly common flotation arrangements.
One of the most common is the rougher-scavenger-cleaner arrangement; where the first couple of cells (roughers) are set to produce a high grade concentrate, which are followed by cells (scavengers) to make maximum recovery.The break between rougher and scavengers is sometimes set by concentrate grade but can vary over time.The rougher concentrate may be a final concentrate or a portion combined with the scavenger concentrate which goes to cleaner section.Often there is a regrind mill between the scavengers and the cleaners.The cleaner concentrate will often go to final concentrate while the cleaner tails and the scavenger tails are a final tail.For a complex ore, or a multi-product ore this circuitry can get to re-cleaners, secondary flotation, and even more complex circuits.All of which is beyond an introduction level article.
Most flotation cells operate in the same manner, although there are a few exceptions, but this section will deal with the general operation of the majority of cells. Later articles will deal with some of the specialized units such as column cells.
The pulp flows by gravity into each cell through the feed pipe, from which it is fed into the impeller in the mixing zone.As the pulp flows over the impeller blades it is thrown outward and upward from the impeller and diffuser by the centrifugal action of the impeller. The pulp is kept in complete circulation by the impeller action and as the flotation reaction takes place, the pulp is passed from cell to cell. Pulp flows to each succeeding cell through the tails section, which in small cells can be an overflow weir, or on larger cells be by valves controlling the outflow through the side or bottom. This gives accurate control of pulp level as the pulp passes through the machine.
It is not essential to have each individual cell with separate tails control; however, for most installations this is recommended. An alternate arrangement (for smaller rectangular type cells) is with gate control every two to four cells for pulp level control, and free pulp passage from cell to cell, by means of the ports, as well as cell to cell overflow. The arrangement is actually a "grouping" without sacrificing the positive circulation feature.
The passage of pulp through the cell and the action created in the impeller zone draws air down the standpipe (or it may be a low pressure air system). The impeller zone thoroughly mixes the air with the pulp and reagents. As this action proceeds, a thoroughly aerated live pulp is produced and furthermore, as this mixture is mixed together by the impeller action, the pulp is intimately diffused with exceedingly small air bubbles which support the largest number of mineral particles.
Aeration is accomplished by one of two methods; either natural or forced/induced aeration.Under natural aeration, the design of the impeller and diffuser natural draw air down the standpipe into the mixing zone.For some applications, this may not be sufficient or a simpler impeller design is desired, and for these a forced or induced aeration system is used, where low pressure (commonly under 10 psig (0.6 atmospheres) air is supplied to the cell.This feature is accomplished by the introduction of air from a blower or turbo-compressor through the standpipe connection into the aerating zone where it is premixed with the pulp by the impeller action. Induced air is of particular advantage for low ratio of concentration and slow-floating ores.
Throttling of air is of benefit when suppressed flotation is required. This is accomplished by cutting off or decreasing the size of air inlet on the standpipe.Suppressed flotation finds its chief use in certain nonmetallics and occasionally in cleaner or recleaner operations.
The aerated pulp, after leaving the mixing zone, passes upward by displacement to the central section of the cell. This is a quiet zone and is free from cross currents and agitation. In this zone, the mineral-laden air bubbles separate from the gangue and pass upward to the froth column without dropping their load, due to the quiescent condition. The gangue material follows the pulp flow and is rejected at the discharge weir or valve.
The mineral-laden bubbles move from the separation zone to the pulp level and are carried to the overflow by the crowding action of succeeding bubbles. To facilitate the quick removal of mineral-laden froth, some cells are equipped with froth paddles. Froth removal can be further facilitated by the use of crowding panels which create a positive movement of froth to the overflow.Cells normally have the overflow along the outside edges, while larger circular cells may have additional overflows running towards the center.These additional overflows do cause issues during agitator maintenance.
Positive circulation of all pulp fractions from cell to cell is important. Minimizing short circuiting, which can occur through the machine is important; so that every particle is subject to positive treatment. In instances where successful metallurgy demands the handling of a dense pulp containing an unusually large percentage of coarse material, the use of bottom mounted valves provides additional sand relief in the machine operation. This opening removes from the lower part of the cell the coarse fractions and passes them through the feed pipe to the impeller of each succeeding cell. The sand relief openings assure the passage of slow floating coarse mineral to each impeller and therefore it is subject to the intensive mixing, aeration and optimum flotation condition of each successive cell.The passage of the coarse fractions through each impeller minimizes short circuiting and thus, both fine and coarse mineral are subject to positive flotation.
Flotation cells are normally set up in rows or banks of equal sized cells.The size of the cells and number of cells of a flotation bank or row depends upon facts and conditions which can best be determined by test work and modified by experience. At a given/desired pulp density and reagent combination, a certain flotation contact period/residence time is required to obtain the desired recovery and grade.This contact time and pulp density determines the volume required for a given feed rate in tons per unit time.
Flotation contact time required for the ore is one of key factors in calculating capacity.If an ore is slow floating and requires twelve minute treatment time, and another ore is fast floating and requires but six minute treatment, the second ore requires only half the capacity of the first. With the residence time and knowing the pulp density and specific gravity of dry solids the cubic feet of pulp handled by the flotation machine, so are determining factors in calculating the flotation contact period.
Metallurgical results required from the flotation machine will have considerable bearing on the installed capacity. Several stages of cleaning may be required to give a high grade concentrate. Results with cells of equal volume will not necessarily be equal because they may not be equally efficient.
The volume of the flotation cell determines the time available for flotation to take place. Therefore, the capacity of any flotation machine is dependent on the volume. All flotation cells having the same volume will have approximately the same capacity, with allowance made for horsepower, the efficiency of the impeller and aeration. As the flotation contact period is very important in any flotation machine, the actual cubical content of any machine should be carefully checked as well as accurate determinations on average pulp specifications.
To determine the number of cells required, firs determine the volumetric flow (cubic feet/minute, cubic meters/minute, or similar) of pulp and multiply by the desired residence time, this gives the required flotation volume.Based on the desired operating philosophy of one, two or more rows/banks of cells divide the total volume by the number of rows/banks to get the volume per row/bank.Then divide this by the desired number of cells per row/bank.
In order to secure the maximum positive treatment of the mineral, and to produce a desired concentrate grade, it is best to have the necessary total volume divided into at least four cells and preferably five or six separate cells, so that they may be used for roughing, cleaning, or recleaning purposes.Alternatively the cleaners/recleaners can be a separate row/bank preceded by scrubbing, attrition, or modifying reagents.
Recovery in flotation is of prime importance. In studying recoveries it is essential also to investigate thoroughly the intermediate products produced. It is a simple matter to make a high recovery or a low tailing if no thought is given to the nature of the concentrate produced or circulating load.
A 'comparison of product assays does not give true and complete information with respect to the performance of a flotation machine. . Product assays for two flotation machines operating in parallel could quite conceivably be identical, yet the physical characteristics of the products recovered and discarded would be entirely dissimilar. Wide differences which would be obvious in detailed investigation might not be indicated by a cursory examination.
Higher recoveries have been possible in many instances by changes in grinding and removal of coarse primary concentrates. Recovery at a coarser grind means a decreased amount of slime mineral in the pulp. Absence of slime in concentrates is reflected in the analysis of the insoluble fraction.
flotation machine - zhongde heavy industries co.,ltd
The flotation machine is mainly used to select metal minerals such as gold, silver, copper, iron, lead, zinc, molybdenum, nickel and aluminum and can also be used for the selection of ferrous and non-metallic. Flotation is a beneficiation method that is widely used and has better effects in fine-grained materials. The flotation machine is the main ore dressing equipment in a variety of mineral flotation production lines, with high sorting precision and strong unit processing capacity. There are many structural forms of flotation machines, and mechanical agitating flotation machines are currently commonly used.
The machine is driven by the motor's V-belt drive to rotate the impeller, which generates centrifugal force to form a negative pressure. It sucks in sufficient air to mix with the slurry and the slurry is stirred into a drug mixture, and the foam is refined to make the mineral bond foam and float to the surface. The mineral slurry forms a mineralized foam. Adjust the height of the gate to control the liquid level so that the useful foam is scraped off by the scraper.
1. Long life: with the unique structural design of the flotation machine and meticulous and ingenious workmanship, the equipment quality is more durable, the failure rate is low, and the service life is greatly extended.
2. High degree of automation: the design of automatic electronic control system, the dosing device can realize unmanned quasi-metering operation, and the automatic concept of each component is integrated to achieve safe, fast and efficient production;
3. High-efficiency and high-yield: The flotation machine effectively increases the volume of flotation single tank, which makes the equipment project improve greatly, further increases the output, improves the operation efficiency, improves the flotation precision by 3-5 percentage points, and satisfies various rough selection, sweeping, and selected job mode.
4. Energy-saving and environmental protection: After continuous innovation of product technology, the flotation machine has been comprehensively reformed, so that the machine not only improves work efficiency and reduces waste of resources, but also has low energy consumption, no noise, no pollution, and better environmental protection effect.
Henan Zhongde Mining Machinery Co., Ltd is a joint-stock mining machinery manufacturing enterprise integrated with scientific research, production and marketing. With an area of 50 thousand which includes 15,000 of standard heavy duty industrial workshop, Zhongde produces and exports sandstone crushing equipment, powder grinding equipment, mineral processing equipment, dryer machine equipment, and building materials equipment, etc. We can design the machines according to your special requirements, and we provide one-stop turnkey solutions. Zhongde machines are sold directly to everyone, the details are offered, and you can click on the free online consultation at any time, and welcome to visit the factory.
please feel free to fill out the form below in detail and you can also send a message to us([email protected])
we will send you latest price within 24 hours.Besides, you can click Chat Online on the right hand side to get quotation online
machine concepts | designer & builder of innovative metal processing equipment
With Machine Concepts, you get a team of highly-skilled engineers, machinists and assembly technicians who partner with your team to design and build cutting-edge machines to operate in the most demanding manufacturing environments. We focus on the tough applications, the projects other equipment suppliers are too intimidated to take on and we do it on budget. Lets transform your challenge into opportunity.
mineral flotation - international mining
Flotation has been at the heart of the mineral processing industry for over 100 years, addressing the sulphide problem of the early 1900s, and continues to provide one of the most important tools in mineral separation today. The realisation of the effect of a minerals hydrophobicity on flotation all those years ago has allowed us to treat oxides, sulphides and carbonates, coals and industrial minerals economically, and will continue to do so in the future.
There have been a number of important changes in the industry over the years as flotation technology and equipment have advanced. Xstrata Technology considers the most noticeable has been the increase in sizes of the flotation machines, from the multiple small square cells that were initially used, to the 300 m round cells used today that are the norm in large scale plants.
Other changes have been more subtle, but equally as important. One of these has been the design of the flotation circuit to make the most of the liberation and surface chemistry effects of the minerals. In a lot of these situations it is not a matter of bigger is better, that will make the process work, but being smarter in the application of flotation technology.
Xstrata Technology is one company that believes the smarter use of flotation machines can deliver big improvements in plant performance. Through its use of the naturally aspirated Jameson Cell, Xstrata Technology has been making inroads into the processing of more complex ores. Having a small footprint, and using the high intensity mixing environment of slurry and naturally induced air in a simple downcomer, the Jameson Cell provides an ideal environment for the separation of hydrophobic particles and gangue, it says. The small footprint of the cells also makes them ideal to retrofit into a circuit especially where space is tight.
While the cell has been included in some flotation applications as the only flotation technology such as coal and SX-EW, the main applications in base metals have seen the cell operating in conjunction with conventional cells. The combination of the two technologies enables the Jameson Cell to target the quicker floating material, while the conventional cells target the slower floating material. Such a combination provides a superior overall grade recovery response for the whole circuit, than just one technology type on its own, Xstrata Technology says. Below are some of the duties for which the Jameson Cell can be used.
Jameson Cells in a scalping operation target fast floating liberated minerals, and produce a final grade concentrate from them. The wash water added to the Jameson Cell assists in obtaining the required concentrate grade due to washing out the entrained gangue. Scalping can be done at the head of the cleaner (also known as pre cleaning), or at the head of the rougher (also known as pre roughing), and minimises the downstream flotation capacity using conventional cells needed to recover the slower floating minerals.
Sometimes deleterious elements found in the orebody are naturally highly hydrophobic, and need to be removed at the start of flotation, otherwise they will report with the valuable minerals to the concentrate and effect concentrate grade. Mineral species such as talc, carbon and carbon associated minerals, such as carbonaceous pyrite, can all be difficult to depress in a flotation circuit. On the other hand, floating them off in a prefloat circuit before the rougher is an easier way to handle them. Jameson Cells acting as a prefloat cell at the head of a rougher circuit, or treating the hydrophobic gangue as a prefloat rougher cleaner, is an ideal way to produce a throw away product before flotation of the valuable minerals, minimising reagent use and circulating loads.
Jameson Cells can be used in cleaning circuits to produce consistent final grade concentrates. The ability of the cell to keep a constant pulp level, even with up stream disturbances or loss of feed, enables a constant grade to be obtained.
Xstrata Technology concludes: Importantly in a lot of these circuits, it is not the selection of one type of technology that produces therequired grade and recovery, but the selection of several technologies to get the best results. The interaction of slow floating and fast floating minerals, entrainment, hydrophobic gangue and a myriad of other variables make it rare for just one type of technology to prevail, but the combination of different flotation machines can achieve the required outcome more efficiently, as well as make the circuit robust enough to handle variations in feed quality.
The Jameson Cell has benefitted from over 20 years of continuous development. Early this year, the 300th cell was sold into Capcoals Lake Lindsay coal operation in the Bowen Basin of Australia. Around this time there were a number of coal projects taking in new Jameson Cells, including expansion projects for Wesfarmers Curragh and Gloucester Coals Stratford operations (both in Australia), Riversdales Benga project in Mozambique and Energy Resources Ukhaa Khudag coking coal project in Mongolia.
Le Huynh, Jameson Cell Manager, said the interest for coal preparation plants has remained strong, where operators needed dependable and reliable technology to treat fine coal, an important source of revenue. During 2010, the Jameson Cell business also found success in other applications, including recovering organic from a copper raffinate stream at Xstrata-Anglo Americans Collahuasi copper SX-EW plant in Chile.
Le said the consistent generation of very fine bubbles and the high intensity mixing in the Jameson Cell, was ideal for recovering very low concentrations of organic from raffinate streams, typically less than several hundred ppm. High throughput in a small footprint, simple operation and extremely low maintenance due to no moving parts in the cell are distinct advantages in this application.
The cell is designed with features specific to suit such hydrometallurgy applications including specialist materials, a flat-bottomed flotation tank with integrated pump box and tailings recycle system, and large downcomers. The Collahuasi cell was the first of its type in Chile, though there are many other large cells installed in SX-EW plants in Mexico, USA and Australia to treat both raffinate and electrolyte streams.
Dominic Fragomeni, Manager Process Mineralogy, Xstrata Process Support (XPS), notes that accurate, rapid development of a milling and flotation flowsheet for a new orebody is key to successful mine development. Time honoured conventional practice has typically favoured the extraction of a bulk sample of up to several hundred tonnes for conventional pilot plant campaigns which could operate at several hundred kilograms per hour. Where sample extraction is limited, much reliance has been placed on locked cycle tests alone to produce design basis criteria. These approaches can be lengthy, expensive, carry scale up risk, and have seen a wide range of successes and failures at commissioning and during life of a mine.
XPS has miniaturised the pilot plant process. At the same time, it has improved the representativeness of results from the pilot plant campaign by using exploration drill core to formulate the pilot plant sample. This Flotation Mini Pilot Plant (MPP) was developed in collaboration with Eriez subsidiary Canadian Processing Technologies (CPT) and operates in fully continuous mode either around the clock or can be made to demonstrate unit operations on a shift basis. The feed samples are in the range of 0.5-5 t and can consist of exploration NQ drill core which improves the sample representativeness. The MPP operates in the range of 7-20 kg/h, an order of magnitude lower in sample mass and typically at a lower cost when compared to conventional pilot plants.
XPS has developed and validated a representative sampling strategy, an appropriate quality control model for metallurgical results and has accurately demonstrated operations results using Raglan and Strathcona ores and flowsheets. These validation campaigns, in scale down mode from the full scale plants, have produced actual mill recoveries to within 0.5% at the same concentrate grade with internal material balance consistent with the
When designing a plant to recover copper, Scott Kay, Process Engineer with METS suggests (in METS Gazette, issue 32, October 2011) it would be prudent to perform some mineralogical analysis test work such as QEMSCAN (Quantitative Evaluation of Mineral by Scanning electron microscopy) to provide some knowledge on the proportion of sulphide and oxide minerals present, the grain sizes of each mineral and a suggested grind size before jumping into the bulk of the beneficiation test work.
Ideally, the characteristics of the copper bearing minerals should suggest an appropriate grinding circuit P80 of between 100 and 200 m (0.1 and 0.2 mm), which can be controlled by cyclones, or in some cases fine screens.
Flotation reagent selection is paramount and test work is necessary to ensure the optimum reagent suite is utilised. If the ore contains a low amount of iron sulphides, xanthate collectors are often suitable to float copper sulphideminerals. If native gold is present, dithiophosphates can be used which are less selective to iron sulphides. Increasing and controlling the pH within the flotation vessel to between 10 and 12 causes the process to become more selective, away from iron sulphide gangue minerals such as pyrite to produce a cleaner copper mineral concentrate. Depending on the ore mineralogy, activators and depressants may be required to achieve the optimum reagent suite.
Recovery of copper oxide minerals can be achieved with flotation by sulphidising the ore. In essence, this creates a thin layer of copper sulphide (chalcocite) on the oxide grains which can then be activated and collected in the froth. When employed, this occurs after the sulphide flotation stage, however, this is not commonly used as other beneficiation processes, such as leaching and SX-EW are often more cost effective for copper oxide minerals.
A common flotation circuit usually includes a rougher/scavenger and a cleaner stage. As most copper orebodies exhibit an in-situ grade of less than 1% Cu, the mass pull to the rougher froth is often low. This means that the throughput of the cleaner stage is significantly less than the throughput of the rougher stage which imparts a relatively low capital and operating cost to the flotation circuit.
To counteract the possible absence of a scavenger stage, a slightly higher mass pull to the rougher froth is targeted (although still low overall) to increase overall copper recovery. The rougher froth can then be reground to increase the liberation of the copper sulphides from the iron sulphides before being fed to the cleaner flotation vessels. This results in a significant upgrade in copper in the cleaner froth whilst still achieving a high copper recovery. The final flotation concentrate usually contains between 25 and 40% Cu.
Alain Kabemba, Flotation Process Specialist at Delkor notes the major trend to treating lower-grade and more finely disseminated ores and lately the re-treatment of tailings. He also points to the broad applicability of size to below 10 m.
Real systems do not fulfil ideal conditions, mainly because of feed variation or disturbances. Before considering disturbances to flotation specifically, Kabemba says it is important to emphasise the interlock between grinding and flotation, not only with respect to particle size effects, but equally to flotation feed rate variations. The grinding circuit is usually designed to produce the optimum size distribution established in testing and given in the design criteria. When the product size alters from this optimum, control requires either changing feed tonnage to the circuit or changing product volume, with either causing changes in flotation feed rates.
While grindability changes due to the variation in ore properties are disturbances to the grinding circuit, they generate feed rate changes as disturbances to the flotation circuit. The variations in ore properties which affect flotation from those assumed in the design criteria must therefore necessarily include grindability changes.
This reflects important differences in flotation machine characteristics between the two processes. Grinding circuits are built and designed with fixed total mill volumes and energy input, so the grinding intensity is not a controllable variable, instead grinding retention time is changed by variation of feed rates. In contrast, the flotation circuit is provided both with adjustable froth and pulp volume for variation of flotation intensity by aeration rate or hydrodynamic adjustment. Reagent levels and dosages provide a further means for intensity control.
One recent trend has been towards larger, metallurgical efficient and more cost effective machines. These depart from the simpler tank/mechanism combination towards design which segregates and directs flow and towards providing an external air supply for types which had been self aerating and towards the application of hydrodynamic principles to cell design, like the Delkor BQR range of flotation machines, initially the Bateman BQR Float Cells.
Bateman has steadily developed the BQR flotation cells which have been in application for the past 30 years, and with its acquisition of Delkor in 2008, decided to rebrand the equipment into the Delkor equipment range. Kabemba explains that BQR cell capacities range from 0.5 to 150 m3 currently installed, and can be used in any application as roughers, scavengers and in cleaning and re-cleaning circuits.
Provide good contact between solid particles and air bubbles
Maintain a stable froth/pulp interface
Adequately suspend the solid particles in the slurry
Provide sufficient froth removal capacity
Provide adequate retention time to allow the desired recovery of valuable constituent.
Highest possible effective volume and reduced the froth travel distance
Improved metallurgical performances in terms of grade recovery and reduced capital and operating costs based on reduced fabrication material and ease of maintenance
Kabemba says there are not many differences in terms of design between BQR Flotation cells; however, from the BQR1000 upwards, the flotation cells have internal launders to maintain the design objectives and benefits highlighted.
Operating variables, such as impeller speed, air rate, pulp and froth depths have to be adjustable over a sufficient range to provide optimum results with a given ore, grind and chemical treatment, but adjustment should not extend beyond the hydrodynamic regime in which good flotation is possible.
The largest current BQR flotation machine is shown in the table. In the near future the BQR2000 (200 m3) and BQR3000 (300 m3) will be available to the market. Kabemba also explained that circular cells reduce the amount of dead volume when compared to square cells. This enables a much higher effective pulp volume, hence increasing the effective energy input into the flotation cell. In addition tank type cells offer enhanced froth removal due to the uniform shape of the circular launders. He concluded that fully automated flotation cells are becoming more and more common with the aid of smart control and advances in software in the marketplace.
FLSmidths flotation team notes that fundamental flotation models suggest that a relationship exists between fine particle recovery and turbulent dissipation energy1. Conversely, increased turbulence in the rotorstator region is theoretically related to higher detachment rates of the coarser size range2. Conceptually, the suggested modes of recovery for the extreme size distribution regions appear to be diametrically opposed.
Industrial applications have previously confirmed that imparting greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favours an opposing approach, the FLSmidthteam believe. An improvement in the kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics.
New concept, Hybrid Energy FlotationTM (HEFTM),was recently introduced by FLSmidth. In principle it decouples regimes where fine and coarse particles are preferentially floated. HEF includes three sections:
This subject will be expanded upon at the 5th International Flotation Conference (Flotation 11) in Cape Town, South Africa. The fundamental parameters that influence fine and coarse particle recovery will be reviewed. The potential dual recovery benefit is then presented in terms of its practical implementation in a scavenging application. HEF is proposed as the preferred methodology of recovering these slow-floating size ranges; a method that opposes the traditional approach of residence time compensation.
Eriez Flotation Group introduced the StackCell flotation concept in 2009. This innovative technology recovers fine particles more efficiently than mechanical flotation cells. Weve taken the inherent advantages of mechanical flotation and adapted them to a new design that is significantly smaller and requires less energy, explained Eriez Vice President Mike Mankosa. We focused on reducing the retention time and energy consumption by implementing a completely different approach to the flotation process. This new approach provides all the performance advantages of column flotation while greatly reducing capital, installation and operation costs.
At the core of the StackCell technology is a proprietary feed aeration system that concentrates the energy used to generate bubbles and provides bubble/particle contacting in a relatively small volume. An impeller in the aeration chamber located in the centre of the cell shears the air into extremely fine bubbles in the presence of feed slurry, thereby promoting bubble/particle contact. Unlike conventional, mechanically agitated flotation cells, the energy imparted to the slurry is used solely to generate bubbles rather than to maintain particles in suspension. This leads to reduced mixing in the cell and shorter residence time requirements.
The StackCell sparging system operates with low pressure, energy efficient blowers that decrease power consumption by 50% compared to air compressors or multi-stage blowers used in other flotation devices.
The low-profile StackCell design features an adjustable water system for froth washing and also takes advantage of a cell-to-cell configuration to minimise short-circuiting and improve recovery rates. Space requirements for the StackCell design are approximately half of equivalent column circuits, with corresponding reductions in weight leading to reductions in installation costs. Units can be shipped fully assembled and lifted into place without the need for field fabrication.
This technology can provide recoveries and product qualities comparable to column flotation systems while using a low profile design. Not intended to replace the need forcolumn flotation, it does provide an alternative method to column-like performance where space and/or capital is limited. The small size and low weight of the new StackCell makes possible lower cost upgrades where a single cell or series of cells may be placed into a currently overloaded flotation circuit with minimal retrofit costs.
Steve Flatman, General Manager of Maelgwyn Mineral Services (MMS) also comments on the trend of moving towards a finer grind to improve mineral liberation. Unfortunately conventional tank flotation cells are relatively inefficient in recovering these metal fines below 30 m and very inefficient at the ultra fine grind sizes below 15 m. The incorporation of regrind mills on rougher concentrates has further exacerbated this problem. To date the conventional flotation tank cell manufacturers have attempted to counter this fall off in recovery of fine particles by inputting increasing amounts of energy (bigger agitation motors) into the system to improve bubble particle contact. Unfortunately this tends to compromise coarse particle recovery.
He says the solution is MMSs Imhoflot pneumatic flotation technology and specifically the Imhoflot G-Cell. Recent pilot plant test work at a nickel operation with a three stage Imhoflot G-Cell pilot plant enabled an additional 30% nickel to be recovered from the conventional flotation tank cell final plant tails. The recovery was predominantly associated with the minus-11 m fraction indicating that this improved recovery was not just related to additional residence time. The above results are in line with an earlier pilot plant trial using G-Cells on a zinc operation where an additional 10-20% zinc was recovered from cleaner tailings this time being associated with minus 7 m material.
It is postulated that the above improvements are related to the order of magnitude increase in terms of air rate (m/min/m pulp)for the G-Cells due to their principle of operation where forced bubble particle contact takes place in the aeration chamber rather than the cell itself with the cell merely acting as a froth separation chamber. Typically in percentage terms the G-Cell air rates are five to ten times that of conventional flotation although the overall or total air usage is approximately half.
When this additional targeted energy input is combined with the centrifugal action of the GCell and small bubbles benefits are obtained in both the flotation rate (kinetics) and overall recovery. The improved kinetics results in a much lower residence time than conventional flotation facilitating a double benefit of both reduced footprint and improved recovery.
Metso notes a main drawback of column cells being low recovery performance, typically resulting in bigger circulating loads. Its CISA sparger is derived from the patented MicrocelTM technology and enhances metallurgical performance by allowing flexibility on the graderecovery curve. Metso Cisa says the main advantages of its column technology include:
At the bottom of the column, the sparger system raises mineral recovery by increased carrying capacity due to finer bubble sizes. This maximises the bubble surface area flux which is a standard parameter in evaluating flotation device performance. It also provides maximum particle-bubble contacts within the static mixers and effective reagent activation from the mechanical operation of the pump.
It is well known that coarse particles behave poorly in a conventional flotation cell and were previously regarded as non-floatable. However, recent laboratory work demonstrates that Fluidised Bed Froth (FBF) flotation extends the upper size limit of flotation recovery by a factor of 2-3 resulting in significant concentrator performance benefits. AMIRAs P1047 project, Improved Coarse Particle Recovery by FBF Flotation, is expected to commence in 2012, and will be structured in two phases.
Early rejection of gangue with minimum mineral loss. Potential for significant increase in concentrator throughput or significant improvement in capital efficiency
Reduced energy consumption. Independent modelling predicts that if particles of 1 mm can be floated, comminution energy consumption will be lowered by at least 20%.
Better management of water requirement. FBF cells can take product straight from the milling circuit without dilution, and the feed to the FBF cell could be up to 80% w/w solids, which could lead to significant savings in process water demand.
Improve recovery of metallic and other dense minerals. In a continuous FBF Cell, dense mineral particles will tend to sink to the bottom and accumulate in the cell, thus they can be recovered in a concentrated form by emptying the cell periodically. This could be a significant benefit where the concentration of the heavy metallic material is too low to warrant a separate treatment plant to recover them.
In Australia, Northgate Minerals Stawell gold mine recently completed a project through which it aimed to increase recoveries by 3.5% by upgrading the flotation plant. This upgrade was implemented after Stawell changed its production profile to process lower grade ore at higher throughput rates.
Instead of the projected 3.5% improvement, the upgrade from Outotec Services has resulted in an increase of 4.5% since the project was completed on time and on budget last year, despite the wettest seasonal weather in recorded history. Payback was also impressive, occurring within less than four months. The projected payback was 5.5 months, so it was a pleasant surprise when it happened so soon explains Jodie Hendy, senior metallurgist at Stawell.
The project has also achieved payback in less than four months and has delivered further ongoing benefits, including easier operation and reduced maintenance costs, says Outotec Services, which worked in close partnership with Stawell Gold to ensure the site remained fully operational during the upgrade.
The mine, which has produced more than 2 Moz in its 26-year history, previously employed a flotation circuit consisting of a bank of eight mechanical trough cells in the rougher circuit, followed by two banks of 2 x OK3 Outotec cells as cleaners. The feed rate to the cells was between 90-105 t/h, at 50-55% solids. The overall flotation circuit was not performing at optimal rate due to entrainment problems in the rougher cells when feed density increased from 45% to 55% solids, typically at 105 t/h.
In anticipation of future production levels and as part of Stawells focus on operational excellence, it was decided to upgrade the flotation circuit. Following a site audit from Outotec Services, a 2 x TankCell -20 configuration equipped with larger TankCell -30 mechanisms was proposed to help optimise flotation. The larger mechanisms would allow operation at very high percent solids (50% and over).
The TankCell design also allows a much deeper froth depth and better concentrate grade through optimised launder lip length and surface area. These cells known for great performance, ease of operation and reduced power and air consumption. Outotec Services was commissioned to handle the complete turnkey solution of the new rougher circuit, including design, supply, installation and commissioning.
The schedule was demanding but achievable, in just 30 weeks. It was decided to adopt the partnering approach between Stawell and Outotec Services, because this collaborative method ensured open communication, with all parties having greater ownership of the project and its aims. This close teamwork resulted in meticulous planning and site remaining fully operational at all times. Pipework and electrical easement ducts, for example, were rerouted early in the project. Tie-in points for new cells and rerouting of pipework were also planned upfront in the project and all disruptive work was completed during shutdowns.
The project overcame a number of challenges, including an extremely limited footprint, which was adjacent to a gabion wall, close to the runof-mine pad and also close to a reagents shed, which could not be moved. Additionally, existing process requirements at Stawell required specific elevations for the new TankCells. Structural stability was the main issue when designing the tank support structure due to the height of the tanks and the limited footprint. Sufficient stiffness was required such that the operation frequencies of the TankCells would not interfere with the natural frequency of the tank support structure. Through FE modelling of the structure, section sizes and bracing orientations were optimised to produce the required stiffness.
Despite the challenges, the turnkey installation of the new rougher circuit, along with blowers for the complete flotation circuit, was completed within deadlines. Because all tie-in points had been already carefully planned upfront, commissioning was a seamless exercise.
Designed to cope with projected increases in production and considerably more operator friendly than its predecessor, the new TankCell 20 cells have quickly proved their worth at site. The air demand for the old rougher cells, for example, was estimated at over 3,000 Am3/h, whereas the estimated air demand on the Outotec TankCells is a maximum of 992 Am3/h.
The Outotec FloatForce rotor-stator mechanism, with its unique design, delivers enhanced flotation cell hydrodynamics and improved wear life and maintenance. Maintenance on the Outotec TankCells has also been minimal since the upgrade, Hendy commented. Basically we check the cells during shutdowns but there has been no maintenance required in the nine months since commissioning. The TankCells have really delivered on their reputation. Basically, they do exactly what they are supposed to do.
Turning to flotation reagents, Frank Cappuccitti, President of Flottec explains that Flottec and Cidra are working very hard jointly on developing instruments that will measure hydrodynamics in the flotation cell and circuit in a bid for better flotation control. This would be a great step forward in using a combination of reagents and sensors to optimise flotation systems. It brings together the knowledge we have developed in both how reagents effect hydrodynamics and measuring the hydrodynamics to maintain optimum conditions. He explains that back in the 1990s, when he worked at a well-known mining chemicals supplier, we spent most of our research on trying to find the best collectors. The thinking was that we could try to develop collectors with absolute specificity. In other words, we could develop a collector that would float only specific minerals and provide clients with an almost perfect flotation separation. This was our approach to flotation optimisation. Unfortunately, we discovered that there was no such thing as absolute specificity. In fact, we had trouble measuring any improvements in the circuits because they were multi-variant and highly complex. Every change made was always a trade off between grade, recovery and cost. Changing one thing in the circuit seemed to improve something but always got a negative response in some other variable. It was also very hard to measure the performance of the flotation circuit because the only real parameters you could measure on line were concentrate grades and tails of the circuits, which were always after the fact. There was little ability and understanding about what real time measurements we could take other than air rates, cell levels and flow rates. So even if we got an improvement or a response to a change, we never knew if that was a response to a change or a natural variation in the system. Every test needed long term statistical trials to get some confidence in any real change.
So, I wrote a paper in the 1990s that basically said that until we could measure the real time variables in a flotation system and learned to really understand and control the system, we were limited in our ability to work on continuous improvement in reagent optimisation. We needed new sensors that could measure the performance of the flotation circuit so we could learn to control it. Once we got this, then we could actually measure improvements and use this to develop reagents.
Fortunately, with the advent of strong computing power and software, we have moved forward tremendously in the last decade in understanding the flotation circuit. Froth cameras that tried to measure froth grade and velocity were one of the first new sensors developed to assist in optimising circuits. Through the work of universities such as McGill and organisations like JKtech, new sensors have been developed that could actually measure reliably and in real time the hydrodynamic parameters in the flotation cell. Flotation cell hydrodynamics (gas dispersion parameters) is critical to the performance of the cell. When we talk about these parameters, we are talking about measuring what is happening in a flotation cell. Flotation is really about making bubbles and using the surface area of the bubble to do the work of transporting hydrophobic minerals to the froth. In flotation cells, we add air, create bubbles of a certain size and speed that provide the surface area to do the flotation. The more bubbles and the smaller the bubble, the more surface area we have to do the work. This surface area we create is known as the surface bubble flux (Sb) and controls the kinetics of flotation. Now that we have instruments that can measure the air into a cell (known as Jg), measure the size of the bubble diameter (Db) and the gas hold up (Eg), we can figure out how the relationship between these parameters and how they affect the Sb and flotation circuit performance. We can also now do research on how reagents can be used to control these parameters as well.
Research of the last few years has shown that frothers actually play a much more important role in flotation hydrodynamics than once thought. Frothers perform two major functions. They create and maintain small bubbles in the pulp to transport the minerals and they create the froth on top of the cell to hold the minerals until they can be recovered. The froth is created because frothers allow a film of water to form on the bubbles which makes them stable enough not to break when they reach the surface of the cell. Fortunately, the water drains over a short period of time and the froth will eventually break down. Froth breakdown is essential for cleaning and transporting the concentrates. Small bubbles are essential in making flotation efficient. For the same volume of air in a cell, smaller bubbles give much higher surface area, which in turn gives much higher kinetics.
We now know that as you increase the concentration of frothers to the cell, the bubble size gets smaller, and the film of water on the bubble gets bigger. But bubble size does not keep getting smaller forever. The frother will reduce the bubble down to a certain size, which is about the same for all frothers in the same set of conditions. The concentration of frother where the bubble is at a minimum is known as the critical coalescence concentration or CCC.
Each frother has a different CCC. Each frother also has a different ability to add water to the bubble and hence provides different froth stability. This also changes with concentration. We have learned in the last few years that each frother has a hydrodynamic curve which relates the bubble size with the froth stability. Strong frothers give very high froth stability at the CCC, while weak frothers give very low stability of the froth at the CCC.
This new understanding of how frothers affect flotation cell hydrodynamics has lead to new methodologies to optimise flotation circuits. Flottec has worked on an optimisation system where a frother is added to a circuit at the CCC (which guarantees maximum kinetics or maximum Sb) and the performance is measured. Then frothers of different strength are added (always at the CCC) until the right strength for maximum performance is determined. Adding the frother at the CCC is the critical optimisation difference. By doing this you are always guaranteed to have maximum kinetics. If the frother used is too strong, the dosage will have to be cut back below the CCC or the froth will be too persistent. This lowers flotation kinetics. If the frother is too weak, too much has to be added to get the froth strength and this increases cost and likely reduces recovery. Flottec has been conducting research withMcGill University to develop the hydrodynamic curves and CCC for all families of frothers in order to implement the new methodology of frother optimisation in plants.
The next step in this research is to be able to use new sensor technology to measure and control the flotation system by controlling the hydrodynamics in the cell. With our current knowledge of how air rate, cell levels, and frother addition affect bubble size, water recovery and gas hold up, we can use these control variables to maintain the optimum hydrodynamics in the cell resulting in the optimum flotation circuit performance. Flottec is working with companies like Cidra to develop new sensors that can provide real time information on cell hydrodynamics (gas dispersion parameters) and on froth stability properties in order for us to optimise the reagents and operating strategies used in a plant. This will bring flotation performance to the next level.
Clariant Mining Solutions business is investing considerably in mining chemicals. It has opened a new laboratory at its US headquarters in Houston, Texas, dedicated to the development and optimisation of chemical solutions for North American customers. The laboratory is part of a planned multi-million dollar investment into Clariants global Mining Solutions business, which includes establishing several new Mining Solutions laboratories around the world. This network is intended to enable the business to better support customer needs and address regional challenges. Most recently, Clariant has opened new mining labs in South Africa (Johannesburg) and in China (Guangzhou). The new laboratories will complement existing facilities in Europe and Latin America.
Mining is a strategic focus area for Clariant, said Christopher Oversby, Global Head of Clariants Oil & Mining Services business unit. This investment further demonstrates Clariants ongoing commitment to providing innovative technologies and solutions for our mining customers around the world.
The Houston laboratory will process ore samples from customers in the USA and Canada. These samples were previously handled in Clariants mining laboratories located in South America and at the companys global research facility in Frankfurt, Germany. We are very excited about the new mining laboratory and the opportunity it provides us for offering our North American mineral processing customers even more localised services and attention, said Paul Gould, Global Head of Marketing and Application Development for Clariant Mining Solutions. The Houston lab will allow Clariant technicians to more efficiently develop optimised reagent solutions for our US and Canadian customers.
Additionally, Clariant is in the process of developing a new Innovation Center in Frankfurt at a cost of 50 million. Employing nearly 500 people and covering 30,000 m2, the facility will focus on customers using an integrated multidisciplinary approach to problem solving. Clariant says an open innovation approach on joint ventures with external partners will ensure the acceleration of the idea-to-market process. Mining research and development will also be part of this facility.
Axis House has been developing reagent technologies for the past 10 years, at its flotation laboratory in Cape Town, South Africa and more recently at it metallurgical labs in Sydney and Melbourne. These were acquired when Axis House bought the oxide flotation reagent technology from Ausmelt Chemicals. A practical application technology strategy was followed with Axis House providing a complimentary suite selection and optimisation service to its clients, who were then mainly interested in the Axis developed technology of combining fatty acids, hydroxamates and sulphidisation suites to effectively and economically float oxide minerals.
Early on the focus was on developing reagents to float complex ores which contained multiple minerals with varying flotation kinetics. Often the limiting factor was not only the sluggish flotation kinetics of the minerals but the process plants own equipment limitations, like flotation and conditioning times. Developing a reagent that floated a certain mineral was simply not enough. The solution was to develop suites of reagents which could function synergistically. By altering the types of collectors and the dosages, the company could optimise both the use of the processing equipment and the collecting power. It says this approach has successfully been applied to various types of base metal oxide ores.
It is now taking this innovative approach into the field of rare earth element (REE) flotation. This fits into the Axis House business plan as the chemistries are quite similar to what is in existence at Axis already. Of course some tweaks will have to be made to the reagents as well as the laboratories this process has already started, with the first batch of REE test material having arrived at Cape Town, and new reagent samples at the ready. There are a large number of REE projects coming online in the next few years. Most of these orebodies have not been previously treated at industrial level and so will face difficulties when scaling up. REO (Rare Earth Oxides) are often difficult to float and the development of multiple collector systems for these ore types would help increase the viability of these projects.
Jerry Sullivan, Global Marketing Manager-Mineral Processing, Cytec Industries Inc, discussed collectors, which contain mineralselective functional groups. They have a hydrophobic hydrocarbon tail. Changing the molecules functional group changes the preference for what mineral it will adsorb on to. Changing the length of the hydrocarbon chain changes the hydrophobicity of the molecule. This is related to the strength of the collector.
Within the collector molecule, there are donor atoms whose goal is to form bonds with acceptor atoms within the ore. Nitrogen, oxygen, and sulphur are the most important donor atoms in all reagent chemistry. Sulphur is the most important donor in sulphide collectors. Nitrogen and oxygen are additional donor atoms. Phosphorous and carbon are central atoms carrying the donors. They only have indirect participation in interactions. He noted the general characteristics of sulphide collectors to be:
Ionic collectors are stronger and less selective
Neutral, oily collectors are weaker, more selective
Higher homologues (more carbons) are stronger than lower homologues (fewer carbons)
Cytecs NCPs are very selective collectors
There is a strong case for formulated products (or blends), he continued That is because mineralogy is complex. Plant performance is also inherently variable. Mineralogy changes routinely. In addition, different minerals have different affinities for reagents. Various minerals will compete for a given reagent. Modifiers used will also influence reagent partitioning. Particle size distribution will also affect recoveries (recovery losses in coarse and fine size range). A single collector will not be sufficiently robust. Indeed, most plants use two or more collectors. The goal is to pick reagents that will get to the right minerals. Utilising a collector blend can balance cost and performance.
Cytec has multiple collectors and collector blends that are continuously being developed to tailor to the customers application. A few of the collector families that have recently been introduced to the market include the new XR Series Xanthate Replacement Collectors, developed to meet the desire to replace xanthates. This new series of collectors are cost competitive with xanthates and are strong collectors but with high selectivity. In addition, they are safer and vastly improves handling and level of toxic exposure of the personnel to product, stock safety management and simplifies plant operations.
The XD 5002 blends were developed to operate in a broad pH range 8-12 and be highly selective in Cu/Mo, Cu/Au sulphide ores, enhance Mo recovery in Cu/Mo bulk float and enhance Au recovery in Cu/Au ores. The MAXGOLDTM blends were introduced to float primary Au ores; auriferous pyrite, arsenopyrite, and tellurides and are also capable of enhancing recovery in Cu/Au ores.
It is now possible to use measurement devices based on impedance tomography to create realtime 3D images. The technology opens up entirely new possibilities in controlling flotation processes. With Flotation Watch the operator can see what takes place underneath the surface. Flotation Watch measures several parameters at the same time, on-line. The sensor can measure the stiffness of the froth, the thickness of the froth, analyse the interface area between the froth and the slurry and it can analyse the slurry too depending on the customer needs, says Jukka Hakola, Numcores Vice President of Sales and Marketing.
With Numcore measurement devices, the size and quantity of air bubbles and the solid matter content of the froth bed can be monitored by means of electric conductivity distribution. With Flotation Watch the stiffness of the flotation froth can be measured and this helps to keep the recovery in higher level. The signals for the production failures, such as hardening and collapse of the froth bed, can be seen beforehand and avoided. This way we can help to minimise the losses in the flotation process, says Hakola.
Real-time characteristics are a key in this technology; in other words, the system continuously provides the operator with factual data on what is happening in the flotation cells, for example the location of minerals and the bottom surface of the froth bed. Because it has not been possible to look inside tanks, controlling a mineral concentration process has largely been based on experience-derived knowhow. Now that operators can look inside the process, it is possible for them to maintain an optimal mix all the time, says Hakola.
Numcore has, in close co-operation with a few key customers, developed measurement technology to better serve everyday work. We have now delivered several Flotation Watch sensors to flotation cells in several markets and for different metals such as copper, zinc and gold. One of the main benefits is that contamination of the probe is taken into account in mathematical formula and the measurement probe does not need to be cleaned. Our sensor has been in a zinc rougher flotation cell for nine months and is giving accurate results to the operator. We can now offer automated control for flotation process with Flotation Watch and see that this can bring new benefits for our customers, he promises.
Numcores measurement technology is currently in test use at Inmets Pyhsalmi copper-zinc mine (IM, April 2010, pp10-18), among others. According to Seppo Lhteenmki, Processing Mill Manager, the system has provided accurate information on the condition of the froth bed, and the technology has functioned reliably. We have tested the device for a few months, and it has provided clear benefits for those operators who have received operator training for it and actively monitored the data provided by the system. The device appears to be so useful, in fact, that we are seriously considering buying it after the test period, he says.
Mettler Toledo notes that pH greatly determines the efficiency of the flotation, which minerals will float, or even if there will be any flotation at all. The critical pH value for efficient flotation depends on the mineral and the collector. Below this value the mineral will float, above it, it will not (or, in some cases, vice versa).
In a recent white paper www.mt.com/pro-phflotation, the company says in order to overcome difficulties with the hostile environment in flotation cells, sensor manufacturers are very creative in their choice of sensor design. It is possible to find pH electrodes with a ceramic, plastic, rubber or even a wood reference diaphragm. Still, their performance can be severely limited as the colloidal particles and sulphides interfere almost instantly with the reference system. The sensors maintenance requirement is therefore high, requiring very frequent cleaning and calibration, and usually sensor life is short.
Mettler Toledo has acknowledged this issue and to combat it has designed the InPro 4260i pH electrode with Xerolyt Extra solid polymer electrolyte. The InPro 4260i does not have a diaphragm and instead features an open junction, which is an opening that allows direct contact between the process medium and the electrolyte. Contrary to the miniscule capillaries of any other type of diaphragm in conventional pH electrodes, the diameter of the open junction is extremely large and much less susceptible to clogging or fouling. Another significant difference is in the choice of polymer electrolyte. Xerolyt Extra was designed specifically for service in tough environments to provide a strong and lasting barrier against sulphide poisoning.
The companys Intelligent Sensor Management (ISM) is a platform based on sensors with embedded digital technology for better pH management. The integrated system consists of a digital sensor and ISM-compatible transmitter. The key to the technology is a microprocessor which is contained within the sensor head and is powered by and read through the transmitter. Critical sensor information such as identification, calibration data, time in operation and process environment exposure are all recorded and used to continuously monitor the health of the sensor.
By constantly keeping track of process pH value, temperature and operating hours, ISM calculates when sensor calibration, cleaning or replacement will be needed. Any need for maintenance is recognised at an early stage.
In recent years, researchers at Imperial College have been focusing on measuring air recovery in industrial flotation cells and have found that a peak in metallurgical performance (improvements in both grade and recovery) corresponds well with a peak in air recovery. Major platinum and copper operations have already observed the benefits of using this methodology as developed by the researchers. JKTech is now licensed by Imperial Innovations to commercially provide this methodology and associated benefits to the global minerals industry.
The PAR technique comprises two stages evaluation and implementation. The evaluation stage involves determining the effect of the technology at a mine site, typically determining the peak air recovery for a bank (or banks) of flotation cells and evaluating the resultant metallurgical performance. The implementation stage involves setting the air rates to those that maximise the air and/or metal recovery, and support and training of site personnel including operating manuals. The implementation stage requires an end-user license to be obtained by the sites through Imperial Innovations.
GIW Industries has launched its new High Volume Froth (HVF) pump. Unlike any other pump on the market, GIW says, the HVF pump can pump froth without airlocks. It provides continuous operation without shutdown or operator intervention. The new hydraulic design actually removes air from the impeller eye while the pump is running, so you can keep your process moving and improve efficiency.
The GIW HVF can be retrofit into many existing froth applications. The pumps deaeration system includes a patent-pending vented impeller and airlock venting. This helps to eliminate sump overflow due to pump airlock; reduce downtime; and allow water use to be restricted to the bare minimum. Fewer pumps are required for less capital expense, requiring less water and power usage.
The HVF pump has been fully tested on froth and viscous liquids. The pump exceeded expectations at a large phosphate company in Finland. The companys existing pumps were not able to provide the required flow and were airlocking at only one-third of process design capacity. After installing an HVF pump, the company achieved a flow of 415 m3/h.
Traditional slurry pumps are prone to airlock when working with slurries that incorporate froth. A pump works by pulling in a liquid at a certain pressure and adding mechanical force to expel the liquid at a higher pressure. The air in the froth does not want to move to a higherpressure zone, and it is prone to build up at the lower-pressure pump entrance. The accumulation of air can eventually block the pump entrance completely, leading to airlock, which requires pump shutdown or operator intervention to avoid sump overflow.
How is GIWs HVF pump different? The main innovation is in the impeller design. Typically, air bubbles gather at the centre of the impeller as the heavier fluids are spun to the outer edges. The HVF pumps de-aeration system includes the vented impeller and airlock venting. In the HVF pump, small holes in the centre of the impeller allow air bubbles to pass through to a separate port. The port vents air up and out of the pump to normal atmospheric pressure.
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.
engineering aspects of flotation in the minerals industry: flotation machines, circuits and their simulation | springerlink
To try and cover in a single review paper all the engineering aspects of flotation in the Minerals Industry is obviously a formidable task, in front of which the present author is over awed by the breadth and scope of materials to cover, and by the existence of excellent review books or papers on the same subject. It has been felt however that a unified presentation of the state of knowledge in this field would be useful in the context of the present NATO Advanced Study Institute on the Scientific Basis of Flotation.