In small plants, it is common practice to include conditioners following the last stage of grinding. Additional conditioners are normally required between flotation operations which produce individual mineral concentrates. Each conditioner stage should consist of a minimum of two separate agitated tanks. Provision must be made to drain and clean conditioner tanks to appropriate flowsheet locations. This is particularly important in the case of conditioners which follow the grinding circuit since these tanks tend to accumulate oversize material produced during grinding circuit upsets.
Conditioners provide positions in the plant flowsheet wherein changes to the ore slurry are brought about by the addition of reagents and pH modifiers. Conditioners must always be designed to provide adequate time for chemical or physical changes induced by reagent additions to proceed to completion. Conditioners also serve a useful function in that swings in ore grade, particle size distribution, or other flotation variable tend to be partially homogenized and dampened during the conditioning unit operation. For example, in small installations it is not unusual to experience wide swings in feed grade. The conditioning unit operation provides the operator an opportunity to modify reagent additions in order to maximize recovery during periods of process instability. If possible, conditioner tanks should be arranged in tiers so that slurry overflows between sequential tanks under the influence of gravity.
The selection of flotation cell size and configuration can have a substantial influence upon installed cost and can contribute to operational efficiency. Two possible flotation configurations for a 500 metric ton per day installation are presented in Figure 5. The computational basis assumes 30 percent solids in rougher flotation, 20 percent solids in cleaner, recleaner and cleaner-scavenger flotation, a ratio of concentration in rougher flotation of 3.07 an overall ratio of concentration of 5.0, and an ore specific gravity of 2.9. This representation indicates that the flotation bay layout employing the larger flotation cells, in this case 2.83 cubic meter (100 cubic feet) machines, occupies less area and reduces installed capital cost by about 25 percent. However, there are instances when the first illustration (selection of small flotation cells) would be chosen for reasons of compactness and symmetry.
Complex multiple product flotation installations usually require a high degree of sophistication regarding operational control. Many times, in small flotation concentrators this level of sophistication is not available. If the facility is located in a remote area, experienced operational personnel may be impossible to acquire. Consequently, the flotation circuits should be as simple as possible. For an installation producing a single mineral product, the flotation scheme illustrated in Figure 6 is recommended. This system, which is compatible with configuration 2 on Figure 5, is simple to operate and eliminates the build-up of a large circulating load of scavenger concentrate. This system is also flexible in that various produced concentrates can be subjected to regrinding should changes in mineralogy or primary grind so dictate.
It must be recalled that the weight of rougher and cleaner concentrates produced from high-grade ores can be substantial. Provision to remove froth by the use of froth paddles on all flotation cells should be included in the original design. The additional capital cost required for froth paddles is a reasonable investment since these devices tend to negate errors in flotation pulp level or frother addition. The open circuit flotation system presented can be operated by individuals having minimal training. The advice of Taggart regarding the inclusion of a small pilot table as a visual sample on rougher tailings is still legitimate.
In almost all new flotation installations, the use of launders fabricated from sheet rubber is recommended. Care must be taken to insure that all launders are sloped properly. In addition, launders must be provided with appropriate sprays and sluice lines to facilitate concentrate transport. The launder water system must be carefully designed to insure functionality without excessive concentrate dilution.
In recent years it has become popular to use vertical pumps for both concentrate and tailing transport in smaller circuits. It is usually possible to employ only one, or at the most two, pump sizes for all of the required flotation pumping installations. The same size vertical pump may also be used in various locations about the plant for cleanup duty. The usage of vertical pumps reduces seal water requirements, and eliminates concrete pump bases, fabricated sumps, and the valving associated with horizontal pumps.
For the past 35 years Sub-A Flotation Machines have been serving faithfully in all parts of the world. Anniversaries of progress such as this make reminiscing very interesting and we thought you would enjoy seeing some of the Firsts in the flotation machine industry as pioneered by the Sub-A.
1928was a pioneer in the use of V-belt drives in the flotation industry. This high-head machine also had wide-spaced greaseless lower bearings. At one time this was the largest flotation machine in the world.
1930 First steel tank flotation machine. Earlier machines had wood tanks. Steel tanks met great opposition at first, later became standard. This high-head, all-steel Sub-A marked the introduction of anti-friction lower bearings.
1932 First low-head flotation machine marked a radical departure from the then accepted principle that the space between bearings must be greater than the distance beyond the lower bearing. This machine was of the cell-to-cell pulp flow design and used a quarter-turn flat belt line-shaft drive.
1933 First steel tank low-head, low-level flotation machine. It had an individual motor and a V-belt drive. This design became very popular with mill operators and thousands of cells were sold similar to those pictured above.
Laboratory Flotation Machines have made progress, too. In our early days the cast-iron tank machine with its round-belt mule drive was the latest word. Contrast it with todays modern Sub-A Laboratory Flotation Machine with its heavy glass tank and stainless steel parts.
1961 Todays demands for Sub- A Flotation Machines keep our modern factory busy. Today more Sub- A Flotation Machines are specified than all competitive makes and is the unquestioned First Choice in Flotation.
The Mega Slurry is a high-performance, low maintenance slurry pump recommended for coarse or fine particles from solids-laden waste water to aggressive slurries of an abrasive and/or corrosive nature. Capacity of pump is up to160 GPM @ 100 Ft. TDH. Impeller, chamber made from chromium wear steel alloy, to give good abrasion resistance. Hard metal Mega Slurry Pumps feature a single wall shell and a hub plate of high chrome white iron. These pumps are suitable for high discharge head, mildly corrosive slurries and a wide range of particle sizes. This chrome steel alloy offers excellent wear life along with resistance to chemical corrosion when applied in slurries with pH as low as five.
Sepor, Inc. began business in 1953 with the introduction of the Sepor Microsplitter , a Jones-type Riffle splitter, developed by geologist Oreste Ernie Alessio for his own use in the lab. Sepor grew over the next several decades to offer a complete line of mineral analysis tools, as well as pilot plant equipment for scaled operations.
Flotation utilizes the fact that the metalliferous ore particles, and the gangue minerals have different interactions with water. Fundamentally floatation relies on the fact that hydrophobic ore particles and hydrophilic gangue particles can be separated. Hydrophobic means water fearing and hydrophobic substances fundamentally repel water. Hydrophilic means water loving and layers are attracted to water. In floatation, we create bubbles as a froth that sits on the top of a suspension of crushed ore. The hydrophobic ore particles which dont want to stay in the suspension, preferentially petition to the surface of the bubbles. While the gangue minerals which are happy to stay in the suspension stay in the water below the froth and sink to the bottom. If the froth is continually replenished, then the ore particles float to the surface in the froth which can be skimmed off and the ore particles recovered. To enhance the formation of the froth we had chemicals called frothers, which are surfactants like detergents which help to create small bubbles and stable froth layer at the surface. There are our basic types of floatation cells: Mechanical; column; Jameson and reflux floatation cells. And there are many variations on these basic themes well have a look at the simplest of these the mechanical floatation cell.
Mechanical floatation cells consist of a sturdy tank air is sucked in via a simple motor shaft and the spinning in power extra break the gas into fine bubbles as well as to get the solid particle suspended. The bubbles will rise to the surface forming a froth layer, hopefully carrying the hydrophobic ore particles with them. This froth overflows and is collected as the concentrate. Water results are withdrawn from the base of the cell to remove the uncollected solids in a tailing stream. We can wash the entrain gangue mineral from the froth layer via the wash water.
Coal is somewhat naturally hydrophobic, and so it can be readily floated. However, most mineral ores are naturally hydrophilic. What makes floatation such a powerful tool for mineral processing is that we have learnt how to selectively modify the surface properly through different ore minerals to make them hydrophobic. We use various types of chemicals, remembering that we have already spoken about frothier. But theyre also collectors, activators, and depressants to control the particle surface properties.
A collector makes the surface of a particle hydrophobic. An activator makes the particle surface more responsive to the collector. A depressant makes the surface of unwanted particles less responsive to the collector, we can also add acids or bases as pH modifiers to control the responses of minerals to the collector. Flotation has the capacity to recover at different mineral species at different stages in the process. In this way we can beneficiate complex mixtures of ores, to produce a range of different mineral products. To illustrate the power of the flotation process, consider this sample of low grade copper rock. If this copper is crushed to produce a clean stream for flotation process, we end up with the powder that looks like this. After flotation, we produce a stream of tailings that looks like this and a stream of recovered ore that looks like this.
Flotation is a powerful tool to recover small amounts of valuable minerals from low grade ores. So having generated your product the next task is to get it to the customer, well take a look at how this is done in the next topic.
Aggregation or dispersion of fine hydrophilic particles affects their entrainment.Corn starch flocculated 20m fine hematite and reduced its entrainment.Corn dextrin did not flocculate fine hematite and could not lower its entrainment.Octadecylamine helped form hydrophobic flocs of 15m fine quartz.Corn starch and octadecylamine caused two stage flocculation in hematite-quartz flotation.The two stage flocculation markedly improved the separation of 20m hematite-quartz mixture.
Mechanical entrainment of 10m gangue particles affects flotation selectivity and dilutes concentrate grade in fine minerals flotation. This study investigated the effect of aggregation/dispersion behaviors of fine hydrophilic particles on their entrainment in batch flotation using quartz and hematite as model minerals. Two structurally similar polysaccharides corn starch and corn dextrin were used as polymer depressants and octadecylamine acetate (ODA) was used as a collector. Batch flotation of fine hematite-quartz mixtures indicated that lower percentages of Fe was recovered into froth using corn starch than corn dextrin; however, similar Fe recoveries in froth were obtained in coarse hematite-quartz mixtures with the two reagents. It was confirmed that the amount of Fe recovery in froth was positively correlated with the proportion of fine hematite in the feed when corn dextrin was used as a depressant. Experimental data collected from batch flotation were fitted to Warrens models, indicating that the fine hematite was primarily recovered into froth through entrainment rather than true flotation in the presence of high dosage of corn starch or corn dextrin as a depressant (>500g/t). The surface wettability of mineral particles was studied by micro-flotation and solvent extraction methods. The results showed that the surface hydrophilicity of hematite induced by corn starch or corn dextrin in the presence of ODA was in an identical range. The real-time FBRM measurements coupled with microscope imaging were carried out to monitor particle aggregation/dispersion behaviors in suspension. The results showed that corn starch can aggregate fine hematite and thus reduce their entrainment in batch flotation, while hematite remained dispersed in slurry by corn dextrin and aggravate its entrainment. In addition, a two-stage aggregation process and the formed flocs were observed in FBRM and microscope tests, which provide evidence for the feasibility of the proposed two-stage aggregation/flocculation flotation concept for fine and ultrafine mineral particles.
A novel double flotation machine allows parallel flotation tests to be run simultaneously.Hot float tests conducted in parallel circumvent the effect of pulp ageing.Selectivity curves suggest that the main effects of ageing were due to pyrrhotite.
Hot batch flotation tests are often applied to reduce risks in plant trials as they combine the benefits of matching complex plant feed stream compositions with the high precision of lab scale batch flotation testwork. One of the weaknesses of hot flotation tests is the sequential nature of the testwork, where ageing of pulp samples can influence metallurgical performance. When present this interference could at best generate inconclusive results, and at worst, inaccurate conclusions. To improve the reliability of test data, CP Kelco has developed a novel, double batch flotation machine for conducting parallel hot flotation tests on live flotation streams. Hot flotation tests with a sensitive Ni cleaner feed stream, principally containing pyrrhotite, pentlandite, magnesite and talc, were used to demonstrate the principles and potential of the device. Parallel tests with the double flotation machine were shown to afford reproducible Ni recovery-grade curves, while sequential tests conducted with a 30min ageing period showed a marked change in Ni recovery-grade curves. In this study, selectivity curves have been beneficial in identifying the sources of the changes caused by ageing, which appear to be due to an increased recovery of pyrrhotite.