GB1594500A - Process and device for the flotation of mineral raw materials - Google Patents

Abstract

The present invention provides a method of treating mineral raw materials by a foam flotation process wherein the raw materials are admitted into flotation cells with flotation reagents, and an intermittent pulsating supply of air is fed to said flotation cells.

Description

(54) A PROCESS AND DEVICE FOR THE FLOTATION OF MINERAL RAW MATERIALS (71) We, AKADEMIE DER WIS SENSCHAFTEN DER DDR, of 5, Rudower Shaussee, 1199 Berlin, German Democratic Republic, a Corporation organised under the laws of the German Democratic Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention is concerned with a process and device for the flotation of mineral raw materials, for example ores, coals, non-metallic minerals and other mineral raw materials.

In many mineral deposits, over the course of years, the ore content of the material obtained becomes progressively smaller. To an increasing extent, the interest in available and large deposits of poor ores become greater as the requirement for an increased production of metals increases.

Thus, there is a real need for an increased capacity of plant used for working up mineral deposits. High throughputs are also highly desirable in the case of working up materials from rich deposits.

In the case of the known flotation processes with self-aspirating air supply or independent aeration of the flotation apparatus, the amount of air fed in during the flotation process is constant (see, for example, H. Schubert, Aufbereitung fester mineralischer Rohstoffe, Vols.

1, 2 and 3; publ. VEB Deutscher Verlag fir Grundstoffindustrie, Leipzig, 23rd edition, 1967, 1974; A. Gaudin, Flotation, 2nd edition, pub. McGraw-Hill Book Company, New York, 1957; W. Giinder, Aufbereitungskunde, pub. Herman Hiihner Verlag, Goslar, 1965; S. Mitrofanov, Selektivna Flotacija, pub.

Nedra, Moscow, 1967; K. Sutherland and I.

Wark, Principles of Flotation, pub. Melbourne, 1955; Spravocnik po obogasceniju rud, Vols.

1, 2, 3 and 4, pub. Moscow, 1972; V. Klassen and Mokrousov, Uvedenie v teoriju flotacii, pub, Moscow, 1959; I. Plaksin, Glembockij and J. Klassen, Flotacija, pub. Moscow, 1971; Glembockij and V. Klassen, Flotacija, pub.

Moscow, 1973).

For carrying out a flotation, use is made of several mechanical stirrer vessels or cells connected in series, as well as of ancillary devices, such as reagent dosing devices and reaction vessels. The flotation slurry flows in the same direction through the cells and during the whole of the flotation process, is in the form of a three-phase system (solidliquid-gas). The disadvantages of these known methods of foam flotation with constant air supply are: low slurry density (only 3040% solids content); unsatisfactory flotation of coarse particles; high energy requirement per tonne of throughput; relatively high reagent requirement per tonne of throughput; large investment requirement per tonne of throughput.

It is an object of the present invention to increase the proportion of solid material in the slurry and thus to increase the throughput or to operate with the same slurry density as previously used but with a reduced speed of rotation of the stirrers used in order to reduce the energy and process costs and to improve the flotation of coarse particles.

The problem with which the present invention is concerned is to provide a process for the flotation of mineral raw materials in the course of which, in contradistinction to conventional flotation processes, continuously changing conditions are provided during flotation in the flotation device.

Thus, according to the present invention, there is provided a process for the flotation of mineral raw materials, wherein, in a flotation device comprising a series of cells or vessels, each of which is equipped with a stirrer and has an independent aeration or a self-aspirating air supply, operating is carried out with an automatically-controlled intermittent air supply in which periods of normal air supply alternate with periods in which the air supply is either completely discontinued or is reduced.

According to a preferred embodiment of the present invention, operating is carried out with a mathematical interrelationship for controlling the aeration of the slurry which includes periods of time with normal air supply and periods of time without air supply alternating during the flotation time.

According to another preferred embodiment of the present invention, operating is carried out with a second mathematical interrelationship for controlling the aeration of the slurry which includes periods of time with normal supply of air and periods of time with reduced supply of air alternating during the flotation time.

When the air supply is fed in, it is dispersed through the stirred system, a threephase mixture being formed. A supply of air is necessary for the flotation process but it disturbs the dispersion of the solid material.

Consequently, the proportion of solid material in the slurry is limited.

At the moment of the absence of the air, a two-phase system is present in which the dispersion of the solid material is markedly improved. The hydrodynamics of the process is very considerably changed and the circulation in the flotation apparatus is also ensured even in the case of doubled slurry density.

When the supply of air is renewed, a part of the material floats as a result of the contact between the solid material particles and the air bubbles. Without this pulsating air supply, in the case of a slurry density higher than usual and under normal flotation conditions, i.e.

constant but uniform air supply to the slurry, no flotation would be possible since the individual cells of the flotation battery would very quickly silt up as a result of insufficient swirling up of the solid material particles. The intermittent supply of air is preferably accomplished by incor.porating an organ into the air supply pipe, which organ interrupts or reduces the air supply and is controlled by a control device, the pulsation characteristics of which are dependent upon the raw material.

Thus, according to the present invention, there is also provided a device, wherein a flotation device comprising a series of cells or vessels, each of which is equipped with a stirrer and has an independent aeration or self-aspirating air supply, is provided with automatic control means which controls an organ in the air supply pipe for interrupting or reducing the air supply, said organ being adapted to operate according to a programme determined by the conditions of the flotation process.

The pulsating supply of air permits a successful flotation to be carried out even when the slurry density is increased to 1.5 to 2 times the normal slurry density.

The following Example is given for the purpose of illustrating the present invention, reference being made to the accompanying drawings, in which: Fig. 1 shows one type of conventional flotation apparatus with independent aera tion, modified according to the present in vention; Fig. 2 shows another type of conventional flotation apparatus without additional aera tion, also modified according to the present invention; and Fig. 3 shows a graphic representation of results obtained with and without the use of the process according to the present inven tion.

Example.

The process is carried out as follows: a slurry provided with an appropriately high proportion of solid material is fed, in the usual manner, into a flotation machine and appropriate flotation reagents added thereto.

The air for the flotation passes via a regulation valve in the form of a pulsating air current into the flotation cells. The effectiveness of the new process was confirmed experimentally with a feldspar-quartz raw material and with a tin-arsenic gravel mixed table concentrate. We have found that in the case of the same flotation time and the same success of working up, the slurry density was 1.5 to 2 times greater and, at the same time, the consumption of reagents was 1.5 times smaller, in comparison with a conventional flotation process. On the other hand, however, substantially coarser solid material particles than usual in the case of normal foam flotation pass into the concentrate. In a further development of the process, working was also carried out in such a manner that periods of time with normal air supply were alternated with a reduced supply of air.

In the following Table, there are given the experimental technological results with intermittent supply of air. Experimental results with intermittent air supply Experimental material: feldspar: 1 - 0.063 mm

offtake residue feed Slurry feldspar feldspar feldspar density content content yield content yield g/l. % wt.% % % wt.% % % 585 laboratory experiment 24.00 25.27 92.00 96.89 74.73 1.00 3.11 585 " " 30.75 29.26 93.00 88.48 70.74 5.00 11.52 617 " " 29.06 30.83 92.00 97.61 69.17 1.00 2.39 667 " " 31.05 31.09 91.00 91.12 68.91 4.00 8.88 500 semitech. experiment 29.96 28.05 91.00 94.66 71.95 2.00 5.34 100 l. cell 700 semitech. experiment 27.36 25.41 96.00 89.10 74.59 4.00 10.90 100 l. cell Experimental material: arsenopyrite-Sn-mixed table concentrate, 0.6 - 0 mm.

feed offtake residue Content Content Wt. Content Yield Wt. Content Yield As Sn % As Sn As Sn % As Sn As Sn 400 laboratory experiment 27.70 11.98 63.49 41.8 0.24 96.84 3.27 36.51 2.37 32.4 3.16 98.73 Comparative experiment with constant air feed

offtake residue feed felds par feldspar feldspar content content Yield content yield % wt. % % % wt. % % % 340 laboratory experiment 28.36 23.73 97.0 81.17 76.27 7.00 18.83 From the diagram shown in Fig. 3 of the accompanying drawings, there can be seen the experimental data of the increase in capacity in a 100 litre flotation cell. In this Fig. 3, curves 4 and 5 indicate the increase in capacity of the rotor at 6000 1.h-1 and 12,000 1.h-1, respectively, with constant supply of air and variable speed of rotation coresponding to the requirement that the solid material is still sufficiently dispersed. Curve 3 shows the capacity requirement without the supply of air in the case of constant speed of rotation but which still suffices to disperse the solid material even in the case of high slurry density.Curves 1 and 2 show the considerable reduced capacity requirement in the case of intermittent supply of air and constant speed of rotation as in the case of curve 3 during the flotation (curve 1 at 12,000 l.h-1; curve 2 at 6000 l.h-1).

The process according to the present invention has been found to be especially useful in the case of the flotation machines shown diagrammatically in Figs. 1 and 2 of the accompanying drawings.

According to Fig. 1, a flotation machine 1 is equipped with a valve 2 on a central air supply pipe, which valve 2 intermittently interrupts or reduces the air supply, and with a time switch device 4 and a compressor 5.

In the case of flotation machines with selfaspirating air supply but without additional air supply, the process can be applied in the same manner (see Fig. 2). The central pipe is sealed off and each of the aspirating pipes of the flotation cells is provided with a valve 1 which intermittently interrupts or reduces the air supply by means of a central time switch device (2).

WHAT WE CLAIM IS:1. Process for the flotation of mineral raw materials, wherein, in a flotation device comprising a series of cells or vessels, each of which is equipped with a stirrer and has an independent aeration or a self-aspirating air supply, operating is carried out with an automatically controlled intermittent air supply in which periods if normal air supply alternate with periods in which the air supply is either completely discontinued or is reduced.

2. Process according to claim 1 for the flotation of mineral raw materials, wherein operating is carried out with a mathematical interrelationship for controlling the aeration of the slurry which includes periods of time with normal air supply and periods of time without air supply alternating during the flotation time.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Comparative experiment with constant air feed

   offtake residue feed felds par feldspar feldspar content content Yield content yield % wt. % % % wt. % % % 340 laboratory experiment 28.36 23.73 97.0 81.17 76.27 7.00 18.83 From the diagram shown in Fig. 3 of the accompanying drawings, there can be seen the experimental data of the increase in capacity in a 100 litre flotation cell.In this Fig. 3, curves 4 and 5 indicate the increase in capacity of the rotor at 6000 1.h-1 and 12,000 1.h-1, respectively, with constant supply of air and variable speed of rotation coresponding to the requirement that the solid material is still sufficiently dispersed. Curve 3 shows the capacity requirement without the supply of air in the case of constant speed of rotation but which still suffices to disperse the solid material even in the case of high slurry density. Curves 1 and 2 show the considerable reduced capacity requirement in the case of intermittent supply of air and constant speed of rotation as in the case of curve 3 during the flotation (curve 1 at 12,000 l.h-1; curve 2 at 6000 l.h-1).

   The process according to the present invention has been found to be especially useful in the case of the flotation machines shown diagrammatically in Figs. 1 and 2 of the accompanying drawings.

   According to Fig. 1, a flotation machine 1 is equipped with a valve 2 on a central air supply pipe, which valve 2 intermittently interrupts or reduces the air supply, and with a time switch device 4 and a compressor 5.

   In the case of flotation machines with selfaspirating air supply but without additional air supply, the process can be applied in the same manner (see Fig. 2). The central pipe is sealed off and each of the aspirating pipes of the flotation cells is provided with a valve 1 which intermittently interrupts or reduces the air supply by means of a central time switch device (2).

   WHAT WE CLAIM IS:1. Process for the flotation of mineral raw materials, wherein, in a flotation device comprising a series of cells or vessels, each of which is equipped with a stirrer and has an independent aeration or a self-aspirating air supply, operating is carried out with an automatically controlled intermittent air supply in which periods if normal air supply alternate with periods in which the air supply is either completely discontinued or is reduced.
2. 2. Process according to claim 1 for the flotation of mineral raw materials, wherein operating is carried out with a mathematical interrelationship for controlling the aeration of the slurry which includes periods of time with normal air supply and periods of time without air supply alternating during the flotation time.
3. 3. Process according to claim 1 for the

   flotation of mineral raw materials, wherein operating is carried out with a second mathematical interrrelationship for controlling the aeration of the supply which includes periods of time with normal supply of air and periods of time with reduced supply of air alternating during the flotation time.
4. 4. Process according to claim 1 for the flotation of mineral raw materials, substantially as hereinbefore described and exemplified.
5. 5. Device for carying out the process according to any of claims 1 to 4, wherein a flotation device comprising a series of cells or vessels, each of which is equipped with a stirrer and has an independent aeration or selfaspirating air supply, is provided with automatic control means which controls an organ in the air supply pipe for interrupting or reducing the air supply, said organ being adapted to operate according to a programme determined by the conditions of the flotation process.
6. 6. Device according to claim 5, substantially as hereinbefore described and exemplified.
7. 7. Mineral concentrates, whenever obtained by the process according to any of claims 1 to 4 or with the use of the device according to claim 5 or 6.