FLOTATION APPARATUS

Abstract: The invention relates to a flotation apparatus improving the recovery of concentrate remaining with tailing. The apparatus according to the invention comprises a cell (1) for treating the ore to be beneficiated and the materials added thereto, i.e. the head material, a feed pipe (2) leading to the cell for feeding head material into the cell (1), a froth chute (3) disposed in the top portion of the cell (1) for collecting concentrate rising up in the cell, and a discharge duct (4) disposed in the lower portion of the cell for conveying the tailing out from the cell, as well as a regulating device (5) disposed in the bottom of the cell, wherethrough compressed air and water in a finely divided mixture are supplied to the cell.

Description: Flotation apparatus The invention relates to a flotation apparatus comprising a cell for treating the ore to be benefici- ated and the materials added thereto, i.e. the head material, a feed pipe leading to the cell for feeding head material into the cell, a flotation chute disposed in the top portion of the cell for collecting con¬ centrate rising up in the cell, and a discharge duct disposed in the lower portion of the cell for conveying tailing out from the cell. In the cells of the current flotation apparatus, air is introduced into the lower portion of the cell by means of an aerating apparatus. Often a special rotor or equivalent which simultaneously stirs the head material serves as the aerating apparatus. The head material is introduced into the cell from the level of the stirring apparatus. This mechanism has the purpose of making the mixture in the cell as homogeneous as possible in the suspension state. The concentrate in the head material becomes attached to the air bubbles and rises up together with the air. The concentrate is collected in a concentrate compartment provided in the top portion of the cell. The tailings descend down and are removed from the cell through a discharge duct or equivalent. When ore is beneficiated by means of such a mechanism, a relatively high amount of concentrate remains in the tailing. Furthermore, the apparatus requires a large amount of energy and is expensive in construction and operating costs. U.S. Patent No. 2 922 521 teaches an apparatus for classifying minerals and other substances by flotation, wherein the head material is pumped into the cell through a pipe in the bottom of the cell and a "mushroom-like" flow movement is thereby produced within the chamber. The air needed in the flotation is added to the head material on the suction side of the centrifugal pump. The air is mixed with the head material already prior to the entry of the mixture to be beneficiated in the flotation chamber. The stirring procedure is largely mechanical and requires a great deal of energy and wears out the mechanical construc¬ tions. It has been found in practice that if a mixture in a suspension state must be conveyed e.g. through a pipe system even for a short distance, the bubble size tends to grow and the flotation result to become substantially impaired. Maintaining the bubble size as small as possible requires an energy-consuming turbulent flow in the pipe system. U.S. Patent No. 4 639 313 describes a flotation apparatus for the beneficiation of minerals from aqueous slurries. This known apparatus includes separate, very complex apparatus for producing an advantageous air/water mixture. In maintaining an advantageous bubble size in the mixture, one arrives at the same technical problems as with the apparatus disclosed in U.S. Patent No. 2 922 521. The object of the invention is to provide a flotation apparatus wherewith a greater part of the concentrate is recovered than with the prior apparatus. A further object of the invention is to provide a flotation apparatus having a simple construction, being reliable in operation and consuming relatively little energy. The object of the invention is achieved with a flotation apparatus characterized by that which has been disclosed in the claims. In the flotation apparatus of the invention, a regulating device is disposed in the bottom of the chamber, wherethrough the supply of compressed air and water separately and finely divided to the chamber is arranged. By providing a separate compressed air and water regulating device in the bottom of the chamber, it is achieved that the compressed water and air are dispersed evenly throughout the head material without mechanical means. With the regulating device it is achieved that the water and compressed air are supplied as a very finely divided water/air mixture to the chamber, which means that the bubble size of air in the mixture is small. Thus the air bubbles effectively carry the concentrate upward. In an advantageous embodiment of the invention, the regulating device includes a compressed air duct wherein a regulating element for regulating compressed air is disposed, and a water duct for conveying water into the chamber in the immediate vicinity of the compressed air duct. By placing the compressed air duct detached from the water duct, one can regulate the amount and pressure of these mediums independently of one another. When the orifice of the water duct is in the immediate vicinity of the orifice of the com¬ pressed air duct, the compressed air and water are effectively mixed with one another. Preferably a so called throttle member is provided at the orifice of the water duct, in which case the compressed air is dis¬ charged directly after the throttle means, thereby producing an ejector phenomenon. In one embodiment of the invention, the feed pipe is placed in the vicinity of the chamber bottom. Such a solution is used when a head material having a high concentrate content is beneficiated. The water/com¬ pressed air mixture immediately acts on the head material introduced in the chamber, and the concentrates present in the head material become attached to the air bubbles and rise upward. The tailing either remains partly on the bottom of the chamber or travels down after having ascended for a short distance. The con¬ centrate rises upward and is removed from the chamber via a concentrate compartment. The tailing is removed through a discharge duct. In another embodiment of the invention, the feed pipe is disposed at a distance from the chamber bottom. Part of the concentrate in the head material becomes attached to the air bubbles immediately after the feed pipe, but part of the concentrate becomes attached only after having travelled downward for a distance. The tailings either descend directly to the bottom or travel upward entrained in the flow for a distance and then descend down. The invention will be explained more closely in the following with reference to the accompanying drawing, wherein Figure 1 shows a one-cell embodiment of a flotation apparatus according to the invention in side view. Figure 2 shows a multi-cell embodiment of the flotation apparatus according to the invention in side view, Figure 3 shows an advantageous multi-cell embodiment of the flotation apparatus of the invention in side view, Figure 4 shows the cell system of Figure 3 in top view. Figure 5 shows the cell system of Figure 3 seen from the direction N, Figure 6 shows the results of pre-flotation tests wherein the effectiveness of the pneumatic flotation apparatus of the invention was compared with the effectiveness of a convention mechanical cell, and Figure 7 shows the results of repeated flotation tests wherein the effectiveness of the pneumatic flotation apparatus of the invention was compared with the effectiveness of a conventional mechanical cell. In the embodiment of Figure 1, the flotation apparatus comprises a cell 1, a feed pipe 2 leading to the cell, a flotation chute 3 and a discharge duct 4 leading out from the cell, as well as a regulating device 5. The f ed pipe 2 is disposed at a distance from the bottom of the cell, and the ore to be benefi- ciated and the materials added thereto -- i.e. the so called head material -- are supplied through the feed pipe into the cell. The regulating device 5 provided at the bottom of the cell includes a compressed air duct 6 for the delivery of compressed air into the cell and a water duct 8 for the delivery of water into the cell. A regulating element 7 is disposed in the water duct for regulating the water flow, and correspondingly a regulating element (not shown in the figure) is disposed in the compressed air duct for regulating compressed air. In this embodiment, the water regulating element is a so called throttle member. The orifice of the water duct is in the immediate vicinity of the orifice of the compressed air duct. When the apparatus is operated, head material is fed into the cell through the feed pipe. Simultaneously, the water/air mixture is supplied from the bottom of the cell by means of the regulating device. The water and air are well intermixed, forming a finely divided, small-bubble mixture which will be effectively diffused in the cell. The concentrate particles present in the head material become attached to the air bubbles and rise upward in the cell. The froth produced is collected in the concentrate compartment 3 in the top portion of the chamber, wherefrom the concentrate is forwarded. The tailing will sink down and is discharged from the cell through a discharge duct. In the embodiment shown in Figure 2, the flota¬ tion apparatus comprises a plurality of adjacently disposed cells which form a cell system. The lower portions of the cells are connected with one another by means of openings 9. The cell system comprises a feed pipe 2 and a discharge duct 4. The feed pipe 2 is connected to the first cell and the discharge duct 4 is connected to the last cell. A regulating device 5 is disposed at the bottom of each cell for the delivery of compressed air and water into the chamber. In the top portion of each cell a froth chute 3 is disposed for collecting concentrate from the cell. When the apparatus is operated, head material is supplied via the feed pipe to the first cell. Part of the concentrate is recovered in this cell, and the remainder of the concentrate and the tailing are removed through the opening into the second cell. The operation of the cell system corresponds to that disclosed in the embodiment earlier presented. The tailing from the first cell serves as the head material for the second cell, and part of the concentrate is recovered in the second cell. The material remaining on the bottom is conveyed into the next cell etc., until the gangue material is removed from the apparatus through the discharge duct 4. In the advantageous embodiment shown in Figure 3, the flotation apparatus comprises a plurality of adjacently disposed cells which form a cell system. The apparatus comprises a feed pipe 2 wherein an aerator 10 is disposed for the removal of too large air bubbles detrimental to the flotation process from the head material, as well as a discharge duct 4. The feed pipe 2 has been connected to the first cell, and the gangue material is removed from the cell system through an effluent valve 12. A regulating device has been disposed at the bottom of each cell for conveying compressed air and water into each cell. A froth chute 3 is placed in the top portion of each cell for collecting concentrate from the cells. When the apparatus is operated, head material is supplied through the feed pipe into the first cell wherein part of the head material is flotated, and the remainder of the head material is carried over to the next cell via an ejector tube 11. The operation of the cell system corresponds to that disclosed in the embodiment according to Figure 1 above. The tailing emerging from the first cell serves as the head material for the second cell, and part of the concentrate is recovered in the second cell. The material remaining on the bottom is conveyed into the next cell etc., until the gangue material is removed from the apparatus through the discharge duct 4. The walls between the cells have orifices 14 for equalizing the pressure and level in the cell system. The bottom of the cell has been constructed to be inclined so that the tailing settled on the bottom of the cell will travel past the orifices to the opposite lower corner of the cell. The settled tailing is recycled into flotation by means of an ejector tube structure. This structure improves the yield percentage. The ejector arrangement used has been found in test runs to be very effective, mainly for the reason that thereby the tailing settled on the bottom of the cell is reintroduced into flotation with very small energy consumption (without separate sizeable and expensive pumping units ) and thereby one avoids disruptions caused by the turbulences resulting from vigorous pumping in the suspension state which is decisive for the success of the flotation. The ejector tube is disposed in that part of the cell to which the portion of head material (slurry) not rising up in the flotation travels. The ejector phenomenon is produced by supplying a small amount of water at an advantageous pressure to the tube. The ejector tube will cause the tailing to ascend and convey it as head material into the next cell. In the last cell, the gangue is discharged by means of effluent valve 12 through the discharge duct 4. Furthermore, the apparatus is furnished with a level regulator 13 governing the effluent valve 12 in the discharge duct. In a third embodiment of the invention, the flotation apparatus comprises several cell systems which have been disposed stepwise relative to one another. In a case like this, the structure of a single chamber corresponds to the structure shown in Figure 1, and in the entire apparatus the discharge duct of one cell system constitutes the feed pipe for the ad¬ jacent cell system. In the apparatus according to the invention, flotation chemicals may be added to the water supplied from the regulating device, and in that case the chemicals need not be added earlier. The following is an account of the test results obtained in the use of the novel flotation apparatus. Test flotations have been carried out with a prototype of an apparatus according to the invention for about half a year at the Siilinjarvi apatite mines of Kemira Oy. The results were compared with the mechanical flotation apparatus used in said mines, and the following was found in the comparison i - despite the small size of the apparatus, the inlet flow of the head material could be maintained on the same level as in mechanical cells, - the energy consumption is less that 10% of that of mechanical cells, - with the heads used, the yield percentages have already from the first tests been on the level of the mechanical cells, or in some grain size categories even clearly better; in the preliminary tests for- the separation of mica by the so called inversion flotation, surprisingly good results were obtained. Thus the test results obtained have resulted in the fact that Ke ira Oy has ordered for its research department a more extensive test flotation for the closer definition of the mica separating capacity, - the experience gained of the effectiveness of the apparatus and, on the other hand, of the minimal construction etc. investment costs required by the apparatus give implications of the fact that the novel type pneumatic flotation apparatus developed will in the near future have a central significance in view of the total profitability in the beneficiation of minerals. Regarding the comparative tests, particular reference is made to Figures 6 and 7 relating to the results obtained from pre-flotation and repeated flotation respectively. Curves 17 and 15 respectively have been obtained in the use of the novel pneumatic cell, and curves 16 and 14 respectively have been obtained in the use of the conventional mechanical cell. The tests were carried out by feeding simul- taneously the same head material into both cell alterna¬ tives. The measurings were carried out on samples taken simultaneously (percentages of concentrate, head material, gangue and P 2 0 5 ). The results of the pre-flotation comparative tests show that with the use of the novel pneumatic cell, an essentially better yield (about 10%) than with the use of the known mechanical cell is obtained, which in practice diminishes the amount of apatite (P 2 0 5 ) remaining in the gangue. The percentage of the concentrate obtained in the repeated flotation comparative tests with the use of the novel pneumatic cell is still very high, that is, at least on the same level as with the use of the known cell, but the yield is, on an average, more than 10% higher. The novel apparatus has been described in the foregoing mainly with reference to the beneficiation of minerals, but it is evident that the apparatus can also be used with a head material which one wishes to oxidize or whose constituent particles one wishes to classify.

Claims: C l a i m s : 1. A flotation apparatus comprising a cell (1) for treating the ore to be beneficiated and the materials added thereto, i.e. the head material, a feed pipe (2) leading to the cell for feeding head material into the cell (1), a froth chute (3) disposed in the top portion of the cell for collecting con¬ centrate, and a discharge duct (4) disposed in the lower portion for conveying the tailing out from the cell, c h a r a c t e r i z e d in that a regulating device (5) is disposed in the bottom of the cell, wherethrough compressed air and water are supplied to the cell in a finely divided mixture, the regulating device (5) including a regulatable water duct (8) wherein a regulating element (7) is disposed for regulating the flow of water, and a regulatable com¬ pressed air duct ( 6 ) for regulating air and supplying it into the cell ( 1 ) in the immediate vicinity of the water duct ( 8 ) . 2. A flotation apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the apparatus comprises a plurality of adjacently disposed cells ( 1 ) , whereby the head material is supplied through a feed pipe (2) into the first cell wherein part of the head material is flotated and the remainder of the head material is transferred to the next cell and that the final tailing is discharged from the last cell through a discharge duct (4). 3. A flotation apparatus as claimed in claim 2, c h a r a c t e r i z e d in that the apparatus comprises a plurality of adjacently disposed cells (1), an aerator (10) disposed in the feed pipe (2) for removing too large air bubbles detrimental to the flotation process, a regulating device (5) disposed in the lower portion of each cell for supplying compressed air and water simultaneously as a finely divided mixture to the apparatus, and an ejector tube (11) disposed in that part of the cell to which a portion of the head material is settled, to elevate this part of the head material and to convey it to the next cell for re- flotation. 4. A flotation apparatus as claimed in claim 2, c h a r a c t e r i z e d in that the cells are interconnected by adjustable openings (9) between the cells. 5. A flotation apparatus as claimed in any one of claims 1 to 3, c h a r a c t e r i z e d in that the feed pipe (2) is disposed in the vicinity of the bottom of the cell. 6. A flotation apparatus as claimed in any one of claims l to 3, c h a r a c t e r i z e d in that the feed pipe (2) is disposed at a distance from the bottom of the cell. 7. A flotation apparatus as claimed in claim 3, c h a r a c t e r i z e d in that the pumping capacity of the ejector tubes (11) can be regulated by regulating the amount of additional water supplied to the ejector tube. 8. A flotation apparatus as claimed in claim 2, c h a r a c t e r i z e d in that the apparatus comprises a plurality of cell systems disposed stepwise relative to one another, whereby the discharge duct of one cell system constitutes the feed pipe of the adjacent cell system. 9. A flotation apparatus as claimed in any one of claims 1 to 7, c h a r a c t e r i z e d in that a batching device is disposed in the regulating device (5) for feeding flotation chemicals into the cell together with water. 10. The use of apparatus according to any one of claims 1 to 9 for the beneficiation of minerals. 11. The use of apparatus according to any one of claims 1 to 9 for the oxidation of a head material. 12. The use of apparatus according to any one of claims 1 to 9 for the classification of the particles in a head material.

Inventors: HIRVONEN ERKKI, HIRVONEN, ERKKI
Applicants: HIRVONEN ERKKI, HIRVONEN, ERKKI
Application year: 1989
Main classification: B03D1
IPC codes: B03D1