The full name of the flotation is called froth flotation. It is the process of selecting minerals from the pulp by means of the buoyancy of the bubbles, depending on the difference in the surface properties of the various minerals. Where to buy flotation machines?
The specific process of flotation is to add various flotation reagents to a certain concentration of slurry, and a large number of diffuse bubbles are generated by stirring and aeration in the flotation machine. At this time, the suspended ore collides with the bubbles, and some of The floatable ore particles adhere to the bubbles, and float up to the surface of the ore to form a foam product, which is the concentrate; the non-floating mineral remains in the slurry and becomes the tailings. Thereby, achieve the purpose of mineral sorting.
Froth Flotation machine plays an indispensable role in the mineral beneficiation process, flotation is susceptible to a number of factors during the process, including grinding fineness, slurry concentration, pulp pH, pharmaceutical system, aeration and agitation, flotation time, water quality and other process factors. The factors that affect the flotation process are detailed below.
Both large ore particles (larger than 0.1mm) and small ore particles (less than 0.006mm) affect flotation efficiency and mineral recovery. In the case of flotation coarse particles, due to the heavyweight, it is not easy to suspend in the flotation machine, and the chance of collision with the bubbles is reduced. Further, after the coarse particles adhere to the air bubbles, they are easily detached from the air bubbles due to the large dropout force. Therefore, the coarse particles have a poor flotation effect under the general process conditions.
During the fine particles flotation separation process, the fine particles are small in volume and the possibility of collision with the bubbles is small. The fine grain quality is small, and when it collides with the bubble, it is difficult to overcome the resistance of the hydration layer between the ore particle and the bubble, and it is difficult to adhere to the bubble.
The content of the coarse-grained monomer must be less than the upper limit of the particle size of the mineral flotation. At present, the upper limit of flotation particle size is generally 0.25-0.3 mm for sulfide minerals; 0.5-1 mm for natural sulfur; and the upper limit of particle size for coal is 1-2 mm.3.Avoid muddy as much as possible. When the flotation particle size is less than 0.01 mm, the flotation index will decay significantly.
The most appropriate grinding fineness must be determined by testing and reference to production practice data. For some ores, the stage grinding and stage selection process are often used to avoid over-grinding of the ore, so that the dissociated ore particles are selected in time.
If the froth machine contains much ore slurry, it will bring a series of adverse effects on flotation cells mineral processing. The main influences are as follows 1 Easy to be mixed in the foam product, so that the concentrate grade is reduced. 2 Easy to cover the coarse grain surface, affecting the flotation of coarse particles. 3 Adsorption of a large number of agents, increase drug consumption. 4 The pulp is sticky and the aeration conditions are deteriorated.
The type and quantity of the agent added during the flotation process, the dosing place and the dosing method are collectively referred to as the drug system, also known as the prescription. It has a major impact on flotation indicators.
In the ore dressing, it is necessary to pass the ore selectivity test in order to determine the type and quantity of the agent, and in practice, the number, location and mode of dosing should be constantly revised and improved.
In addition to oxygen, nitrogen and inert gases, there are carbon dioxide and water vapor in the air. The gas has a selective effect on the surface of the mineral, oxygen is the most important factor affecting the surface of minerals. Oxygen is beneficial to the hydrophobicity of sulphide ores/ sulfine flotation, however, if the action time is too long, the mineral surface will return to hydrophilicity. When the gas adsorption conditions are appropriate, the mineral surface will be drained, the flotation mineral processing can be done even without a flotation agent. The Galena mine can only float up with the action of xanthate through the initial action of oxygen.
Stirring the slurry can promote the suspension of the ore particles and evenly disperse in the tank, thus promote the good dispersion of the air and make it evenly distributed in the tank, further can promote the enhanced dissolution of air in the high-pressure area of the tank, and strengthen the precipitation in the low-pressure area. Enhanced aeration and agitation are advantageous for flotation separation, but not excessively, as excessive aeration and agitation can have the following disadvantages: (1) Promoted the merger of bubbles (2) Reduced concentrate quality (3) Increased power consumption (4) Increased wear of various parts of the flotation machine (5) The volume of the slurry in the tank is reduced (this is because the volume of the tank is increased by the portion occupied by the bubble) (6) Excessive agitation may also cause the ore particles attached to the bubbles to fall off. The optimum amount of aeration and agitation in production should be determined by experimentation depending on the type and structural characteristics of the flotation machine.
Inflation and agitation are carried out simultaneous in the flotation machine. Strengthening them is beneficial to increase the flotation index, but if it is determined too much, it will cause shortcomings such as bubble merger, degraded quality, increased electric energy consumption, and mechanical wear. Therefore, aeration and agitation must be appropriate.
The slurry concentration can affect the following technical and economic indicators: (1) Recovery rate. When the slurry concentration is small, the recovery rate is low. As the concentration of the slurry increases, the recovery rate also increases, but the recovery rate exceeds the limit. The main reason is that the concentration is too high, which destroys the aeration condition of the flotation machine. (2) Quality of concentrates. The general rule is that the quality of the concentrate is higher in the flotation of the leaner slurry, and the quality of the concentrate is reduced in the flotation of the richer slurry. (3) Consumption of pharmaceuticals. When the slurry is thicker, the amount of treatment per ton of ore is less, and when the concentration of the slurry is thinner, the amount of treatment per ton of ore is increased. (4) The production capacity of the flotation equipment. As the concentration of the slurry increases, the production capacity of the froth flotation machine calculated according to the treatment amount also increases. (5) Water and electricity consumption. The thicker the pulp, the smaller the water and electricity consumption per ton of ore processed. In short, when the concentration of the slurry is thick, it is beneficial to the flotation process. However, if the slurry and bubbles do not flow freely, the aeration will deteriorate, thereby reducing the quality and recovery. In this case, the various ore sections of the flotation should determine the appropriate concentration of the slurry according to the nature of the ore and relevant technical requirements.
The most suitable ore pulp concentration during the flotation process is related to the ore property and the flotation processing conditions. The general rules as flow: (1) Pulp Density. The mineral with large flotation density uses a thicker slurry, while the mineral with a small flotation density uses a thinner slurry. Flotation of coarse-grained materials with thicker slurry, flotation of fine-grained and muddy materials with thinner ore. (2) Pulp PH Value. The pH of the pulp refers to the concentration of OH and H+ in the slurry, which is generally expressed by the PH value. Various minerals have a floating and non-floating pH when using different flotation agents for flotation, The pH of the critical pH. By controlling the critical pH, it is possible to control the effective sorting of various minerals. Therefore, controlling the pH value of the slurry is one of the important measures to control the flotation process. (3) Flotation Time. The flotation time directly affects the quality of the indicator. The time is too long, the grade of the concentrate is reduced; the time is too short and the grade of the tailings is increased. Therefore, the flotation time required for various Minerals must be determined by experimentation. (4) Water Quality. Floating water should not contain a large number of suspended particulates, nor can it contains soluble substances and various microorganisms that may interact with minerals or flotation reagents. This problem should be specially noticed when using backwater, pit water, and lake water. (5) Pulp Temperature. Flotation is generally carried out at room temperature, but sometimes it is necessary to warm the slurry in order to obtain a good sorting effect. The specific heating or not needs to be determined according to the actual situation. If it is heated, it is best to adapt to local conditions and use waste heat and exhaust gas as much as possible.
The main effects of pulp quality score on froth flotation process in metallurgy are as follows: (1) Recovery rate. Within a certain range, when the pulp mass fraction is low, the recovery rate is low; the pulp mass fraction is increased, and the recovery rate is correspondingly increased. However, the mass fraction of the slurry should not be too large. If it is too large, the flotation machine is difficult to inflate normally in the slurry, which in turn reduces the recovery rate.
(2) Concentrate grade. The general rule is that the concentrate grade is higher when ore flotation is carried out in a leaner slurry, while the concentrate grade is reduced when it is floated in a thicker slurry.
(3) The dosage of the agent. The flotation agent should maintain a certain mass fraction in the pulp to have a good flotation effect. When the pulp is thicker, the mass fraction of the medicament is correspondingly increased, that is, the required medicament mass fraction can be achieved with fewer chemicals, and the amount of medicament per tan ore is correspondingly reduced. Conversely, when the pulp is thinner, the amount of the agent increases.
Thats all 7 main variables affecting froth flotation. Contact us to know more info about industrial gold mining equipment, get free froth flotation PDF, flotation process flow chart, and related industry cases of gold froth flotation, zinc froth flotation, copper flotation, ore flotation.
Since the content of useful components in the ore that needs flotation treatment is getting lower and lower, the particle size of the impregnation is getting finer and finer, and the composition is more and more complicated and difficult to separate. Therefore, how to design an efficient mineral flotation flow is of the utmost importance.
The main ideain collecting the information youll find in the following discussion was to help you, as a flotation machine operator. Regardless of how much or how little you know about it, the ideas youll find here can help you do a better job, if you want them to.
Naturally your company is anxious to have you improve your work, because a lot depends on how well you handle those machines; but dont think that thats the only reason why you ought to do better. The big reason, for you, is that the more skillful you become, the easier it will be for you. The fellows who are always in a jam and working their heads off all shift are also the ones who dont know what its all about. The good operators see trouble coming and prepare for it and for that reason theydont often get into trouble. The jobis easier for them because they know how to do it. We want to try to make it easier for you, too.
Because we dont know how familiar you already are with the flotation process, well have to assume that you are starting about from scratch. Well the first thing you ought to learn is how the process works and what it is that you are trying to do. Well leave the chemistry of flotation out of it though, because it doesnt much matter to you why the thing works so long as it does work, and, frankly, the subject is too deep for us.
The plain facts are that in the pulp as it comes to you from the ball mill circuit is a small quantity, generally a few percent, of a mineral your company expects you to get out. To do this, you will add to the pulp one or more chemical reagents that have the property of combining with the valuable mineral in such a way that these particles of ore can no longer be wetted by water. These reagents do not combine with the waste rock particles, and therefore the latter can still be wetted. Suppose you arc working with a galena ore. After you have put in the proper reagents, if you couldtake a piece of galena out of the pulp and magnify it, you would see that water rolls off the galena as it would off a duck.
Then when the pulp goes to the flotation machines, you add another reagent that creates a froth in the pulp. That is, the reagent helps form millions of air bubbles that are circulated all through the pulp by the action of the machine. Whenever one of these bubbles hits an ore particle that is not wetted by water it sticks to that particle, and before long thereare many such mineral particles sticking to each bubble. None of thebubbles will stick to the waste material. The result is that these air bubbles collect on the surface of the pulp in the machine to form a froth, and all you have to do is see that this froth spills over the side into the proper launder. The valuable mineral is now in the launder, and the waste rock is going down the tailing flame you hope.
All you have to do is to see to it that enough of these reagents is added, but not too much, and that the machines are working properly. That doesnt sound like much of a job, but, believe us, its an art. The thing for you to do if you want to be really good at it, is to ask a lot of questions of people you can count on as knowingthe answer. Dont be afraid of asking fool questions. The mill superintendent and the metallurgist and the shift boss would a lot rather have you ask questions of them and find out how to do the job right, than to have you keep still and do the job wrong.
There are three classes of flotation reagents in general: conditioners, collectors, and frothers. Conditioners are those reagents that are added to the pulp to help the other reagents do a better job. That definition covers a multitude of sins, and we havent space to take up all of them. To list a few conditioners, there are: lime, copper sulphate, soda ash, sodium silicate. Aerosol, and several more. Each of them has a specific job, and it is up to you to learn what it is for the one you are using.
Take lime, for example, which is generally used in flotation to keep pyrite from floating and to adjust the pH of the circuit. Whats pH? Just a flashy term for a convenient way of telling how much acid or alkali there is in the flotation pulp. A pH of 7 means that the pulp is neither acid nor alkaline: above the pulp is alkaline, below 7 it is acid. Lime makes the pulp more alkaline, resulting in apHof 8, 9. 10. or so depending on how much you add. In some mills, this matter of pH is tremendously important and it will pay you big dividends in easy operation if you pay attention and keep the pH where it belongs.
Collectors are the reagents that catch hold of the mineral youre after. The xanthates. thiocarbanilide several of the Aerofloat reagents, thiophosphates, Hydroxamate; all are collectors. If you dont add enough of whichever one of these youre using, the company loses money fast, and youll have words with the shifter tomorrow when the assay sheet comes around. Of course, if you are working in a mill where the metallurgist sets the reagent feed rates, the buck is automatically passed.
Frothers are the reagents that make the bubbles that lift the mineral out of the pulp. Pine oil, fatty acid, MIBC and several other numbered reagents are the most commonly used frothers. Their action is simple. More frothcr, more bubbles. Less frother, fewer bubbles. Dont ever drop a bucketful of pine oil into the flotation machine feed box unless youre tired of working there.
Only three or four of these reagents are being used in your plant. Your job is to find out for sure exactly what each of them is for in your operation. Dont go by what somebody said he heard somebody say the fellow that grinds samples in the assay office said. Buttonhole the metallurgist, if he hasnt already told you, and make him tell you what the reagents are supposed to do. Better still, ask him to put it in writing, or you write it down as he tells you. We know from experience that some flotation operators have ideas about the reagents they are using that would give the mill superintendent the shock of his life if he knew about it. That isnt the operators fault. Nobody had ever told them the facts of life. Dont you be like that.
Now, to get right down to the actual operation, what are the elements with which you have to work? First, of course, are the reagents we mentioned before, and with regard to them we can only repeat our advice to find out as much as you can about how they work. Also, if you are permitted to adjust the reagent feeders yourself, go easy with them. Dont be rushing up every ten minutes to add more xanthate or cut down the pine oil a drop or two. By the time you have made some such small change, the pulp conditions may have changed a little, and you ll simply wear yourself out trying to catch up with conditions that stay one jump ahead of you. Dont over-control.
Aside from the reagents, you have the machine controls to work with. These arc different with different makes of machine, but, in general, they are: the tail gate at the end of each bank of cells; weirs placed in some makes between each cell; weir bars placed along the lip in each cell over which the froth flows: other types of adjustable partitions between cells: and, in some makes, a valve that controls the air admitted to each cell.
In general, you will make up your mind about how to control the machine and the reagents In the appearance of the froth coming out of the machine. We could go on here for several pages describing what a flotation froth ought to look like for all the different kinds of minerals that are now being floated, but youd be interested in only a small part of all that. Here, again, the best thing you can do is get somebody who knows to tell you when the froth in the rougher cells and the cleaner cells looks the way it ought to look. Then you take a good long look at it and try to keep it that way when youre running the machines.
There are, however, certain characteristics that apply to most flotation froths. The bubbles in the froth from a cleaner cell, or from the first couple of cells in a rougher section, should be fairly large, say an inch or so across, and they should be well loaded with mineral and should break down easily when they drop into the launder. If you look at them closely, you will see in the center of each bubble a thin spot that is almost clear, like a little window, and the surface of the bubble will have a slightly watery shine on it as though it were actually wet. These windows and this watery look are, in most cases, a good sign. They mean that the bubble is neither too tough nor too brittle, and that there is a draining action going on along the surface of the bubble that allows waste mineral, shoved up accidentally by the bubble, to drain back into the pulp, where it belongs.
The froth in the rest of the rougher cells should, in most cases, look quite different. The bubbles are smaller, more like the head on a stein of beer, and they dont carry as much mineral. Also, the froth in the roughers spills over faster; in fact, the rougher cells are spoken of as running faster. Here you dont have to worry about waste draining back into the pulp: the main idea is to get the ore mineral out fast.
Watch the froth constantly, then, and learn from it but dont stop with just watching it. You cant be sure of what that froth is carrying unless you really break it down and see. Mill- men who sweep their hands across the froth in a cell and then tell you exactly whats in it may be kidding themselves and you too. There ought to be a white-enameled vanning plaque kept down in the mill at all times, and you ought to learn to use it properly. We cant describe in words how to handle a vanning plaque, because its use requires a peculiar combination of motions that defies description, but with a little , practice and advice from someone who knows, youll get it all right. Then when you take a little froth on the vanning plaque, and break it down, and spread it out, youll see exactly what minerals are being carried by the froth, and, more important, how much of each mineral, if you do that long enough, youll be able eventually to forecast pretty accurately about what the concentrate will run when it is assayed. A vanning plaque is the best single tool you can have in the mill to helpyou decide how the machines should be operated.Another little gadget that is not so important but which is handy, nevertheless, is a froth-depth indicator.
This is simply a wood slab about a foot square and 2-in. thick, in the center of one side of which is fixed a 1 x 1 inch stick and about 18 inches long. The stick must be set perpendicularly to the slab. Set the slab in the classifier or the feed box or some place where the pulp is the same density that it is in the machine, and let it float for a moment. Then measure up from the watermark and mark the stick off in inches and halves. Then to measure the froth depth in the cell, drop the slab into the cell, let it float, and read the depth at the mark nearest the froth surface. This comes in handy because it is sometimes necessary to control the froth depth pretty closely (deeper on cleaners, thinner froth on roughers), and this indicator is the simplest way we can think of to measure froth depth accurately.
One of the best ways of keeping track of whats going on in the machine is to keep a little log of the things you observe and to note down in it the assays of the samples that were taken during that time. Did the froth look dry and tough during most of the last shift? Note it in your book, then see how the assays compare with those corresponding to other froth conditions. You can learn best by experience, and a written record of that experience is a far more reliable guide than your memory, however good your memory may be.
The thing that makes a man a really good flotation operator is his ability to see trouble coming and to avoid it. A good man watches whats going on and runs the machines instead of letting them run him. For example, by noticing little changes in the froth conditions or the pH of the pulp a man can sometimes get a warning of an approaching change in the kind of ore coming into the mill. To treat this different type of ore, he may have to use more lime or more frother or he may have to change the adjustment of the machines. Whatever he has to do, the main point is that by the time the change in ore actually arrives, he is ready for it.
A poor operator, on the other hand, usually gets caught flat-footed by such changes. He catches on only when the froth drops altogether, or begins pouring over, as the case may be, and he has to spend the next hour or so in a sweat trying to straighten things out. Then just about the time hes off rolling a cigarette and telling the shifter, Well, I got that licked, the ore changes again, the froth goes haywire, and our friend is right back in the deep hot grease. By the end of the shift, hes usually run ragged, and the tailing assay for his shift is higher than a kite. He just works too hard.
As we have already noted, the kind of froth you get and the amount of mineral it carries depend pretty much on the reagents you add. The machine controls, however, determine the rate at which the froth comes off the cells. To run a machine faster that is, to make more froth spill overyou raise the pulp level, lower the froth lips, or let in more air. To run the machines slowerthat is, to cut back on the amount of froth you simply reverse these things.
You can also speed up or slow down the amount of froth coming off by changing the amount of frother added, but remember, it is better not to. In general, you should add only just enough frother to get the sort of bubble you want. Therefore, if the machine isnt frothing to suit you, try to make it right with the machine controls first (the weir bars, the pulp level, the air controls). Only when you cant get the right conditions with the machine controls should you begin changing reagents.
One exception to this is a condition when you see quite plainly that you have altogether too much reagent. If the froth is boiling over, for example, and it has an oily look and consists of extremely tiny uniform bubbles, go look at the frother feeder. You are probably using too much. In other words dont hesitate to cut down on reagents if conditions seem to warrant it; but think twice, or three times, before you add more of anything.
There is also an order of preference, you might say, for the machine controls. In general the pulp level in a roughing machine should be carried as high as you can get it and still leave about 2 to 3 in, of froth above it. (Theres where your froth-depth indicator comes in handy.) This is done to help recover more of the mineral you want. The high pulp level holds the mineral in the machine longer, and gives the air bubbles more chances at it. The thin froth, overflowing rapidly, snaps the weakest-floating mineral over into the concentrate launder before it can drain back.
Because this high pulp level in a rougher machine is harder to regulate than the froth depth, it is better to work with the weir bars along the froth lips instead of with the tail gate, or the weirs between cells, if your machine has them. Also, if your machine has an air control (like the Agitair, the Weinig, or the Pan-American) it is better to keep the valve as wide open on the roughers as you can. This is because the more air you add, up to a certain point, the more mineral youre likely to pick up. In addition, the more air added to mechanical machines, the less power they draw and the less wear there is on the impeller. In short, dont cut the air unless you have to and then do it for as short a time as possible.
A flotation machine needs deep froth in order to allow time for unwanted mineral to drain from the froth bubbles back into the pulp. Also, a high pulp level isnt so important in a cleaner cell, because recovery isnt what youre after so much as grade of concentrate. Therefore, in a cleaner cell, a froth depth of at least 8 in. is required in most cases, and you have more leeway in adjusting the pulp level. That is why, in operating a cleaner, you can use the tail gate (or the cell weirs) more than on a rougher.
In cleaning, the rate at which the froth comes over is extremely important, and both the air control and tailing weirs should be used to get the fine adjustment that will give you the best results. Froth scraper adjustment and weir bars, it there are any, may help, but to a lesser extent. Here is where your vanning plaque comes in handy. To run a cleaner properly, you must know what is in the cleaner froth, and the only way you can really find that out is by spreading some of that froth out, not on the palm of your hand, but on a vanning plaque.
All this, remember, is a general statement applied to all operations. In your own mill there may be good reasons why you have to run the machines differently. In that case, find out what pulp level and what froth depth your metallurgist thinks are right, and then keep them that way. But the order of preference still holds, no matter what. On the roughers: weir bars first, then air, then tail gate (or cell weirs), then reagents. On the cleaners: air first, then tail gate (or cell weirs), then weir bars, then reagents. If none of these things works, see if you cant get a job down in the mine.
PNEUMATIC. Nearly everything we have said up to here applies to both air and to mechanical machines. There isnt much to add that applies only to these machines. In fact, in most cases, air machines are rather easier to control than mechanical machines, though the possible adjustment isnt so fine, for example on cleaning operations.
HOG TROUGHS. This term rather loosely describes mechanical machines built on the lines of a long trough in which the impellers are set at regular intervals. There are no pipes or weirs between cells. The type is represented by the Agitair, the Level-Type Fagergren, and the Pan-Americanmachines, the one tail gate controls the pulp level throughout each group of cells. If you want to vary the pulp level between cells somewhere up the line, the only way is to widen or narrow the opening in the partitions between impellers. There is very seldom any real need for this adjustment, and it is better not to try it.
Having the pulp level in the whole machine controllable by the one tail gate may tempt you to whirl the gate up or down every time an adjustment is indicated. Dont do it. Pick a level for the roughers that is about right (good and high, remember), and leave it there. If you have to change the gate, return to the original setting as soon as you can. You can spot this by counting the number of threads exposed above the handwheel when the gate is where you think it ought to be. This gives you the exact location of the gate and saves measuring each time.
Poke a stick into the tail box once in a while to see that it isnt sanding up. If the tail box does get partly sanded up, the pulp level will run higher than you want it and may overflow the machine. Remedy this by opening the sand bleeder gate a little, but dont open it farther than necessary. Make all the tailing come out over the tail gate if you can.
The peculiar virtue of a weir to control the pulp level in each cell is that it permits you to get an extremely nice adjustment of the rate of froth overflow down the length of the machine. One cell fast, the next slow, the next fast, and so on, if you happen to want it that way. This is an extreme example, of course, but it shows what could be done. The practical effect of this flexibility is that you can get an extremely high-grade concentrate with these cells if you handle them right.
But by the same token these individual cell weirs can get you into an awful lot of trouble you dont handle them right, Here again, we say dont over-control, and do try to anticipate trouble. If you do get caught, however, and you find the froth has dropped in all the cells, or that the machines are wildly overflowing, start with the tail-end weir, adjust it properly, and so work back up the line of cells to the head end. But take our word for it, it is better not to find the cells in that condition.
You will of course get into trouble now and again. Pipes will plug up, froth will spill out over the floor, belts will break, bearings get hot, launders leak. We just havent space to list here all the things that could happen to you and suggest remedies for them. Besides, we dont know all the things that could happen to you. The important thing, anyway, is to keep your head, figure out the cause of whatever went wrong, and then think up a way to correct it.
One jam an operator always seems to get into sooner or later, however, is this matter of oil or grease in the pulp. A case is on record where a man cleaned the black grease from under the big gear on a ball mill and tossed the goo into the flotation feed launder to get rid of it. The result was a cross between a bubble bath and the Johnstown flood. Oil and grease are frothers, too, but dont use them as such. If, somehow, oil does get into the circuit and the froth comes pouring out on the floor, all you can do is flush things out as quick as you can, tell the shift boss some miner must have dumped his oil bottle into the muck, and pray hell believe you.
The Froth Flotation Process is about taking advantage of the natural hydrophobicity of liberated (well ground) minerals/metals and making/playing on making them hydrophobic (water-repel) individually to carefully separate them from one another and the slurry they are in. For this purpose we use chemicals/reagents:
The froth flotation process was patented by E. L.Sulman, H. F. K. Pickard, and John Ballot in 1906, 19 years after the first cyanide process patents of MacArthur and the Forests. It was the result of the intelligent recognition of a remarkable phenomenon which occurred while they were experimenting with the Cattermole process. This was the beginning. When it became clear that froth flotation could save the extremely fine free mineral in the slime, with a higher recovery than even gravity concentration could make under the most favorable conditions, such as slime-free pulp, froth flotation forged ahead to revolutionize the nonferrous mining industry. The principles of froth flotation are a complex combination of the laws of surface chemistry, colloidal chemistry, crystallography, and physics, which even after 50 years are not clearly understood. Its results are obtained by specific chemical reagents and the control of chemical conditions. It not only concentrates given minerals but also separates minerals which previously were inseparable by gravity concentration.
This new process, flotation, whose basic principles were not understood in the early days, was given to metallurgists and mill men to operate. Their previous experience gave them little guidance for overcoming the serious difficulties which they encountered. Few of them knew organic chemistry. Those in charge of flotation rarely had flotation laboratories. Flotation research was done by cut and try and empirical methods. The mining industry had no well equipped research laboratories manned by scientific teams.
Froth flotation, as pointed out previously, was a part of the evolution of milling during the first quarter of the 20th centurya period during which the progress of milling was greater than in all of its previous history. It marks the passing of the stamp battery, after 400 years service to the mining industry, and the beginning of grinding with rod mills, ball mills, and tube mills without which neither the cyanide process nor the froth flotation process would have reached full realization. More than all of these, it was the time when custom and tradition were replaced by technical knowledge and technical control.
This volume, then, is dedicated to those men who, with limited means, made froth flotation what it is today. It is designed to record the impact of this great ore treatment development on the mining industry both present and future.
The single most important methodused for the recovery and upgrading ofsulfide ores, thats howG. J. Jameson described the froth flotation process in 1992. And its true: this process, used in several processing industries, is able to selectively separatehydrophobic fromhydrophilic materials,by taking advantage of the different categories of hydrophobicity that areincreased by using surfactants and wetting agents during the processalso applied to wastewater treatment or paper recycling.
The mining field wouldnt be the same without this innovation, considered one of the greatest technologies applied to the industry in the twentieth century. Its consequent development boosted the recovery of valuableminerals like copper, for instance. Our world, full of copper wires usedfor electrical conduction and electrical motors, wouldnt be the same without this innovative process.
During the froth flotation process, occurs the separation of several types ofsulfides,carbonatesandoxides,prior to further refinement.Phosphatesandcoalcan also be purified by flotation technology.
Flotation can be performed by different types of machines, in rectangular or cylindrical mechanically agitated cells or tanks, columns, aJameson Flotation Cellor deinking flotation machines. The mechanical cells are based in a large mixer and diffuser mechanism that can be found at the bottom of the mixing tank and introduces air, providing a mixing action.The flotation columnsuse airspargersto generate air at the bottom of a tall column, while introducing slurry above and generating a mixing action, as well.
Mechanical cells usually have a higher throughput rate, but end up producing lower quality material, while flotation columns work the other way around, with a lower throughput rate but higher quality material.The Jameson cell just combines the slurry with air in a downcomer: then, a high shear creates the turbulent conditions required for bubble particle contacting.
Advantages of froth flotation: first of all, almostallmineralscan be separatedbythis process. Then, the surface propertiescan be controlledandaltered by the flotationreagent. Finally, this technique is highly appropriate for the separation ofsulfideminerals.
To help towards an understanding of the reasons for the employment of specific types of reagents and of the methods of using them, an outline of the principal theoretical factors which govern their application may be of service. For a full discussion of the theory of flotation the various papers and text-books which deal with this aspect should be consulted.
The physical phenomena involved in the flotation of minerals, those, for example, of liquid and solid surface-tensions, interfacial tension, adsorption, flocculation, and deflocculation, are the manifestations or effects of the surface-energies possessed by all liquids and solids in varying degree. These, in turn, arise from the attractions which exist between the interior molecules of every substance and are responsible for their distinctive propertiesform, fluidity, cohesion, hardness, and so on. It follows, therefore, that every substance must exhibit some degree of surface-energy.
All the solids normally present in an ore i.e., metallic, non-metallic, and rock-forming mineralshave their particular contact-angle and hysteresis values and therefore tend to be wetted in varying degrees in accordance with such values. These differences, however, are not usually sufficient to allow of the effective separation of the mineral and gangue constituents from each other. It is the function of the flotation reagents employed to accentuate or magnify these differences to a degree which renders separation by flotation practicable. Some reagents (modifiers) are added with the object of decreasing the contact-angle and so increasing the degree of wetting of the unwanted particles, which are usually more prone to become wetted than the wanted minerals. Others (promoters) are added to increase the tendency toward non-wetting shown by the valuable minerals by coating them with a film of yet higher contact-angle value. Such films are said to be adsorbed in respect of the water.
In this connection reference to Fig. 28 will indicate that a reagent which decreases the surface-tension of water tends thereby to increase wetting of the solid, since, if the value of S1 and therefore of its horizontal component, is lessened, the water-edge, as at P, will tend to extend over the solid surface, making therewith a smaller contact-angle.
The reagents added to promote the separation of the wanted minerals by increasing the water/solid contact-angle consist of substances whose molecules or minute suspensions have a markedly lower attraction for water molecules than the latter exert between themselves. Finely divided oil emulsions in water, dissolved xanthates, and other promoters are typical of such reagents. Substances of such nature, when dissolved in or disseminated through water, are pre-eminently adsorbed, or thrust towards the water boundaries, where the intra-molecular attractions are less uniformly balanced. Normally, this would occur at the free or air/water surface. In a pulp, however, from which air surfaces are absent, but in which mineral particles are suspended, the same thing takes place at the water/solid boundaries, adsorption being most pronounced at those faces where the interfacial tension is greatest viz., those with the highest contact-angle value and lowest adhesion for water. The minute particles of oil or xanthate molecules are thus virtuallythrust into adherence with the more floatable solids, whose surfaces they therefore film, increasing the contact-angles to their own high values and so rendering the solid more floatable. Experimental work indicates that the film so formed is of the order of one molecule in thickness.
Adsorption can be both positive and negative. Substances whose molecules have less attraction for water than the water molecules have for each other are concentrated at the water boundaries as explained in the foregoing paragraph ; this is termed positive adsorption, but substances whose molecules have a greater attraction for water molecules than the latter have for each other will tend to be dragged away from the surface layers, at which their concentration thus becomes less than in the interior of the liquid ; this is negative adsorption. Substances that are negatively adsorbed are those which tend to form chemical compounds or definite hydrates with water, such as sulphuric acid. In froth flotation we are concerned more with positive than with negative adsorption.
In some cases a chemical reaction between the solid and the reagent occurs at the interface ; for instance, in the activation of sphalerite by copper sulphate a film of copper sulphide is deposited on the mineral following adsorption of the copper salt at its surface. In many cases there is no evidence of any chemical change, but, whether chemical action takes place or not, there is no doubt that the filming of the mineral is due primarily to the adsorption property of the liquid itself, by virtue of which the promoting reagent dissolved or suspended in it is concentrated at the interface.
The chemical action of flotation reagents has been and still is the subject of a great deal of research work, which is bringing the various theories into common agreement, but there are still too many doubtful points and unexplained phenomena to make a simple explanation possible in these pages.
The foregoing paragraphs can be summarized by stating that the reagents employed in froth flotation can be classified into three general groups, comprising frothers, promoters, and modifiers, respectively, the purposes of each class being as follows :
The operation of flotation is not always confined to the separation of the valuable constituents of an ore in a single concentrate from a gangue composed of rock-forming minerals. It often happens that two classes of floatable minerals are present, of which only one is required. The process of floating one class in preference to another is termed selective or preferential flotation , the former being perhaps the better term to use. When both classes of minerals are required in separate concentrates, the process by which first one and then the other is floated is often called differential flotation , but in modern practice the operation is described as two-stage selective flotation .
Selective flotation has, therefore, given rise to two other classes of reagents, each of which may be regarded as falling within one of the classes already mentioned. They are known as depressing and activating reagents.
The use of these reagents has been extended in recent years to three- stage selective flotation. For example, ores containing the sulphide minerals of lead, zinc, and iron, can be treated to yield three successive concentrates, wherein each class of minerals is recovered separately more or less uncontaminated by the others.
Although the flotation of the commoner ores, notably those containing copper and lead-zinc minerals, has become standardized to some extent, there is nevertheless considerable variation in the amount and nature of the reagents required for their treatment. For this reason the running costs of the flotation section of a plant are somewhat difficult to predict accurately without some test data as a basis, more especially as the cost of reagents is usually the largest item. Tables 32 and 33 can therefore only be regarded as approximations. Table 32 gives the cost of the straightforward treatment in air-lift machines of a simple ore such as one containing easily floated sulphide copper minerals, and Table 33 that of the two-stage selective flotation of a lead-zinc or similar complex ore.
From Table 32 it will be seen that the reagent charge is likely to be the largest item even in the flotation of an ore that is comparatively easy to treat, except in the case of a very small plant, when the labour charge may exceed it. At one time the power consumption in the flotation section was as expensive an item as that of the reagents, but the development of the modern types of air-lift and pneumatic machines has made great economies possible in expenditure under this heading. As a ruleCallow-Maclntosh machines require less power than those of the air-lift type to give the same results, while subaeration machines can seldom compete with either in the flotation of simple ores, although improvements in their design in recent years have resulted in considerable reductions in the power needed to drive them. It should be noted that the power costs given in the table include pumping the pulp a short distance to the flotation machines, as would be necessary in an installation built on a flat site, and the elevation of the rougher and scavenger concentrates as in circuits such as Nos. 9 and 10.
The power costs decrease with increasing tonnage because of the greater economy of larger units and the lower price of power when produced on a large scale. The cost in respect of reagents and supplies also decreases as the size of the plant increases, due to better control and organization and to lower first cost and freight rates of supplies when purchased in bulk. The great disadvantage of a small installation lies in the high labour cost. This, however, shows a rapid reduction with increase of tonnage up to 1,000 tons per day, the reason being that with modern methods a flotation section handling this tonnage requires few more operators than one designed for only 200 tons per day. For installations of greater capacity the decrease is comparatively slight, since the plant then generally consists of parallel 1,000-ton units, each one requiring the same operating force ; the reduction in the cost of labour through increase of tonnage is then due chiefly to the lower cost of supervision and better facilities for maintenance and repairs. Provided that the installation is of such a size as to assure reasonable economy of labour, research work and attention to the technical details of flotation are generally the most effective methods of reducing costs, since improved metallurgy is likely to result in a lower reagent consumption if not in decreased power requirements.
The costs given in Table 33 may be considered as applying to a plant built on a flat site for the two-stage selective flotation of a complex ore in subaeration machines with a tank for conditioning the pulp ahead of each stage and one cleaning operation for each rougher concentrate. It is evident that the reagent charge is by far the largest item of cost. This probably accounts for the more or less general use of machines of the mechanically agitated type for complex ores in spite of their higher power consumption and upkeep costs, since the high-speed conditioning action of the impellers and provision for the accurate regulation of each cell offer the possibility of keeping the reagent consumption at a minimum. As in the case of single-stage flotation, the charge for labour falls rapidly as the capacity of the plant increases to 1,000 tons per day ; beyond this point the rate of decrease of this and all other items of cost with increase of tonnage is less rapid. The remarks in the previous paragraph concerning the importance of research work and attention to technical details apply with added force, because of the possibility through improved metallurgy of reducing the much higher reagent and power costs which a complex ore of the class in question has to bear.
Customized network architecture captures the mapping relationships of training data.FlotationNet performs better than vanilla LSTM and FNN for iron prediction.The prediction accuracies for iron and silica cannot be guaranteed simultaneously.
The accurate prediction of grade/recovery is instrumental to automation control in a flotation process. It is also challenging due to the complex interactions and codependences of manipulating variables. The deep learning network FlotationNet, which was developed in this study, considers different mapping relationships between input variables and output purities by using customized architecture. To create a database for model training, 3498 raw data from a real-world froth flotation plant were collected, wrangled, and restructured. A designed loss function was embedded in FlotationNet to guarantee an accurate prediction for the main product as well as to avoid overfitting. Compared with baseline machine learning models, FlotationNet delivers the best prediction for iron but the worst prediction for silica. Finally, some advice is given to further enhance the performance of our proposed model. FlotationNet is a successful example of the advantages of customizing deep learning architecture to address real-world situations in industry.
This study develops a customized deep learning network (named FlotationNet) to predict the processed iron/silica purities in a manufacturing froth flotation plant based on industry real data. The developed network delivers better prediction accuracies than the other two baseline models.Download : Download high-res image (142KB)Download : Download full-size image
Flotation is the most widely used beneficiation method for fine materials, and almost all ores can be separated by flotation. Another important application is to reduce ash in fine coal and to remove fine pyrite from coal. The flotation machine is mechanical equipment for realizing the froth flotation process and separating target minerals from ore. At present nearly 2 billion tons of ore in the world are treated by the froth flotation process. According to rough statistics, about 90% of non-ferrous minerals are recovered by the flotation method, accounting for 50% proportion in the field of ferrous metal mineral separation.
Suitable material Sulfide minerals, oxide minerals, non-metallic minerals, silicate minerals, nonmetallic salt minerals, soluble salt minerals, rare earth minerals, etc., including gold, silver, copper, lead, zinc, galena, zinc blende, chalcopyrite, pyroxene, molybdenite, nickel pyrite, malachite, cerussite, smithsonite, hematite, cassiterite, wolframite, Ilmenite, beryl, spodumene, brimstone, graphite, diamond, quartz, mica, feldspar, fluorite, apatite, barite, and so on.
The flotation machine is composed of single or multiple flotation cells, by agitating and inflating the chemical reagent treated slurry, some mineral ore particles are adhered to the foam and float up, and then be scraped out, while the rest remains in the slurry.
Industrial flotation machines can be divided into 5 classes, mechanical agitation flotation machine, pneumatic flotation machines, flotation column, airlift flotation machine, froth separation flotation machines. At present, the mechanical flotation machine is the most commonly used in industry, followed by the column flotation which has recently set off hot spot, the pneumatic type and froth separation are not common.
Commonly used flotation models TankCell series, Wemco series, Agitair series, SuperCells, RCS(reactor cell system), Denver laboratory flotation, KYF, and XCF series flotation devices, laboratory flotation machine. Well-known flotation machine manufacturers have Outotec, Flsmidth, Metso, BGRIMM, JXSC flotation machine china; column flotation manufacturers or models have Jameson, CPT, Counter-flow inflatable flotation column.
Main parts: slurry tank, agitator device, mineralized froth discharging system, electromotor, etc. 1. Slurry tank: mainly consist of a slurry inlet, slurry tank and a gate device for controlling the slurry volume, welded with steel plate. 2. Agitator: slurry tank have a series of the mechanically driven impeller that disperses the air into the agitated pulp. 3. Mineralized forth discharging: the useful minerals are enriched in the foam, scraped out, dehydrated, and dried into concentrate products.
Whatever flotation machines design is selected, it must accomplish a series of complicated industrial requirements. 1. Good mixing function. a qualified flotation machine should mix the slurry uniformly and maintain the particles especially the target mineral particle in suspension with the pulp, maximum the froth-mineral probability. 2. Adequate ventilation and distribution of fine bubbles. Except for the flotation machine performance, the frother type and dosage also matter to the distribution of the bubbles. 3. Appropriate agitation control in the froth beds. It is should pay importance to keep froth zones smoothly, which ensures the suspension of collector coated particle.
1. The throughput capabilities of various cell designs will vary with the ore property (beneficiability, size, density, grade, pulp, PH, etc.). In the case of ore easy separated, and a small amount of air inflation required, may choose a mechanical flotation machine; if the minerals with coarse size, proper to choose the KYF, BS-F, ore CLF type; what's more, when in case of ore easy separated, fine particles, high grade, low PH, flotation column is the best, especially in the concentrating process. 2. There is a difference between the process of concentrating, rough selecting. Thin froth layer is better for separate mineral particles, thus may not choose a large air inflation flotation machine.
Mining Equipment Manufacturers, Our Main Products: Gold Trommel, Gold Wash Plant, Dense Media Separation System, CIP, CIL, Ball Mill, Trommel Scrubber, Shaker Table, Jig Concentrator, Spiral Separator, Slurry Pump, Trommel Screen.