US3909413A

US3909413A - Flotation machine

Info

Publication number: US3909413A
Application number: US499770A
Authority: US
Inventors: Tatsuya Nagahama
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 1972-02-21
Filing date: 1974-08-22
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30

Abstract

A flotation machine comprising a flotation cell, an air suction pipe to introduce air into the flotation liquid in said cell, a rotary member for stirring said flotation liquid and a diffuser, wherein the bottom plate of said flotation cell is provided with at least one suction-guide blade extending radially from a portion of the bottom plate below said rotary member toward the inner wall of said flotation cell.

Description

United States Patent Nagahama 1 1 Sept. 30, 1975 [54] FLOTATION MACHINE 2,696,913 12/1954 Anderson 209/169 2,966,266 12/1960 Coke 209 168 [751 Invent: Talsuya Nagahama Japan 3,070,229 12/1962 Benozzo 209 170 x 73 Assignee: Mitsui Mining & Smelting C0., 11, 31307-697 3/ 1967 Fahlstrom 9t 209/170 X Tokyo Japan 3,378,141 4/1968 Warman 209/170 x 3,437,203 4/1969 Nakamura 209/169 22 Filed: Aug. 22, 1974 Appl. No.: 499,770

Related U.S. Application Data Continuation of Ser. No. 333,681, Feb. 20, 1973, abandoned.

Foreign Application Priority Data Feb. 21, 1972 Japan 47-17838 U.S. Cl. 210/219; 209/169; 210/221; 261/87 Int. Cl. 801D l/14 Field of Search 209/l68l70; 210/219-221; 261/87, 93

References Cited UNITED STATES PATENTS 6/1930 Jones et al. 210/219 X Primary E.\aminer lohn Adee Assistant E.\'aminerRobert H. Spitzer Attorney, Agent, or FirmWoodhams, Blanchard and Flynn [5 7] ABSTRACT A flotation machine comprising a flotation cell, an air suction pipe to introduce air into the flotation liquid in said cell, a rotary member for stirring said flotation liquid and a diffuserQwherein the bottom plate of said flotation cell is provided with at least one suctionguide blade extending radially from a portion of the bottom plate below said rotary member toward the inner wall of said flotation cell.

6 Claims, 2 Drawing Figures US. Patent Sept. 30,1975 3,909,413

HF 1 [wife W11 FLOTATION MACHINE This is a continuation of application Ser. No. 333,681, filed Feb. 20, 1973, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flotation machine which is capable of drawing much more air than the conventional flotation machines when operated on the basis of a fixed value of power.

2. Description of the Prior Art A flotation machine is required to perform the function of generating bubbles within a flotation liquid consisting of a liquid or pulp (a mixture of solid matters and water) introduced into it and floating said bubbles while making an ingredient of the flotation liquid attach to the bubbles to thereby separate said ingredient. Therefore, there is a need for a flotation machine capable of generating a great deal of bubbles. As a matter of fact, enhancement of the flotation efficiency can be achieved in proportion to the amount of the generated bubbles to some degree.

In the prior art, adjustment of the bubbles to be generated has been achieved to some degree by the selection of the kind and amount of the floating agent. However, inasmuch as the volume or amount of bubbles to be generated generally depends on the volume of air to be introduced, such methods as increasing the introduction of air by intensifying the stirring of the flotation liquid or increasing the speed of rotation of the rotary member for stirring the flotation liquid, such as the impeller or rotor, or positively blowing a lot of air into the flotation cell have hitherto been popular. But the former method has been defective in that, when the introduction of air is increased by increasing the speed of rotation of the rotary member of the flotation machine, there is brought aboutnot only an increase in power comsumption such as electric power, but also an increase in the degree of abrasion of the rotary member as well as the part holding the support means therefor. While; the latter method of positively blowing air into the flotation cell has been defective in that the preparation and supply of pressurized air necessitates extra equipment and additional power.

BRIEF DESCRIPTION OF THE DRAWINGS In the appended drawings,

FIG. 1 is a vertical sectional view of the flotation-cell portion of a flotation machine which may be utilized in practicing one embodiment of the present invention, and

FIG. 2 is a cross-sectional view taken along the line II II in FIG. 1. In these drawings, 1 denotes the flotation cell, 2 denotes the impeller, 3 denotes the shaft, 4 denotes the stand pipe (air suction pipe), 5 denotes the fixed diffuser, 6 denotes the blades of said fixed diffuser, 7 denotes the bottom plate of the flotation cell, 8 to 8" denote respectively the suction-guide blade, and 9 denotes the froth-discharging trough.

DETAILED DESCRIPTION OF THE INVENTION The present invention is intended to provide an improved flotation machine which is capable of automatically drawing a great quantity of air therein without resorting to any special method of increasing the introduction of air such as discussed in the foregoing.

The inventorof the present invention has conducted a series of researches on how to increase the introduction of air in a flotation machine having the construction that the air suction pipe such as the stand pipe or hollow shaft is held in a position parallel to the axis of the flotation cell and the bottom portion of the flotation cell is provided with a rotary member for stirring the flotation liquid coupled with a diffuser, and as a result, he has come to the finding that, when the speed of current of the flotation liquid forced out of the center of the flotation cell toward the inner wall thereof by the rotary member is increased, the introduction of air through the air suction pipe increases, and especially when the bottom plate of the flotation cell is provided with a plate to control the direction of flow of the flotation liquid, the introduction of air increases remarkably.

The present invention is based on this finding obtained in the process of the foregoing researches.

Further particulars of the present invention will be discussed in the following by reference to the appended drawings.

Except for the provision of the suction-guide blades 8 to 8", the construction of the flotation machine shown in these drawings is almost the same as the well known conventional flotation machines.

In the drawings, when the flotation liquid is fed to the flotation cell 1 and the impeller 2 is turned by the rotation of the shaft 3 in the direction of the arrow, air is drawn in the stand pipe 4. This introduction of air is carried out by virtue of the reduced pressure inside the fixed diffuser 5 when the flotation liquid is made to flow toward the side wall of the flotation cell, passes the gaps between the plural blades 6 of said diffuser 5 and is diffused. When the suction-guide blades 8 to 8 are provided on the bottom plate of the flotation cell as shown in the drawings, there is brought about the effect that the introduction of air into the stand pipe 4 is remarkably increased. This effect is considered attributable to the fact that the volume of the flotation liquid to be drawn in at the time of rotation of the impeller 2 increases and the volume of the flotation liquid to be diffused from the diffuser 5 per unit time increases accordingly. In other words, it is considered that, as the speed of diffusion or the speed of flow of the flotation liquid to be diffused through the gaps of the blades 6 of the diffuser 5 is increased, the degree of reduction in pressure inside the diffuser 5 remarkably increases as compared with the case of dispensing with the suction-guide blades 8 to 8", and as a result, the introduction of air also increases. According to the present invention, therefore, it is possible to introduce sufficiently a great quantity of air into the flotation machine without increasing the speed of rotation of the impeller 2 while limiting to a small amount the requirement for increased power. Therefore, the volume of valuable substances to be transferred per unit time to the froth being discharged from the froth-discharging trough 9 can be increased, contributing to the rise of flotation efficiency.

Though the foregoing effect of the present invention can be obtained even when a single suction-guide blade is provided on the bottom plate of the flotation cell, the optimum number of said blades for use in the present invention is 4 or thereabouts. The shape of the suctionguide blade is desirable to be curved as indicated in the drawings, but it may be of a straight rectangular form.

As to the place of installing the suction-guide blade on the bottom plate of the flotation cell, it is desirable to fix it so that the edge of said blade is located directly below the rotary member such as impeller or rotor, but is also will sufflce to dispose said edge of blade at such a position on the bottom plate that it is spaced or less from the circumference of rotation of the rotary member. Further, the suction-guide blade can be installed in not only a round flotation cell but also flotation cells of other shapes, and in all cases, it brings about the same effect.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1 There was employed a flotation machine (a) according to the present invention having a flotation cell of the same construction as shown in the appended drawing and equipped with a motor, another flotation machine (b) according to the present invention in which the flotation machine (a) is modified by replacing the curved suction-guide blades with straight rectangular blades which are disposed crosswise relative to the bottom plate and whose edges are disposed directly below the circumference of rotation of the impeller 2 and a comparative flotation machine (c) having the same construction as shown in the appended drawing except that the suction-guide blades are omitted for the purpose of comparing efficiencies. Each flotation cell was charged with the same quantity of water and the speed of rotation of each impeller was identical. The volume of air drawn in through the stand pipe was measured respectively. The results were as shown in Table 1 below:

Table 1 Introducing quantity Flotation machine. of air (l/min./m

(flotation machine under present invention) (flotation machine under present invention) (comparative flotation machine) EXAMPLE 2 Table 2 Distribution ratio of Cu Cu concentration in tailing after flotation (ppm) Flotation machine tailing froth (a) (flotation machine Table 2-Continued Distribution ratio of Cu (7r) Cu concentration in tailing after flotation (ppm) Flotation machine tailing froth under present 0.4 L3 98.7 invention (h) (comparative 2.4 8.0 910 flotation machine) EXAMPLE 3 A zinc ore having the grade of 4.5% Zn was crushed into grains comprising 18% of grains having the grain size of 65 mesh, and then a pulp having 40% concentration of said grains was prepared. By adding copper sulfate, sodium ethyl xanthate and a frother to this pulp, flotation was effected for 10 minutes respectively by means of the same flotation machines as in Example cell having a continuous peripheral side wall and a bottom wall defining a flotation zone for containing a flotation liquid; a centrifugal pump impeller centrally located in said cell, said impeller being rotatable about a vertical axis and being disposed close to but spaced upwardly from the bottom wall of the cell, said impeller comprising a plurality of circumferentially spaced elongated impeller blades extending parallel to said bottom wall for moving the flotation liquid adjacent thereto substantially horizontally and radially outwardly toward said side wall; a stationary diffusing unit encircling said impeller and being disposed at the same vertical level in said cell as said impeller, said diffusing unit comprising an annularly arranged series of substantially uniformly circumferentially spaced-apart, outwardly extending guide vanes arranged in a circular array and located in the flow path of the liquid from the impeller for guiding and directing the flow of the liquid from the impeller outwardly from said diffusing unit toward said side wall at a vertical level located close to but spaced upwardly from said bottom wall, the inner edges of said guide vanes defining a cavity within which said impeller is disposed for rotation therein, said diffusing unit having a central opening in its bottom providing a liquid flow passage extending between said cavity and a zone located adjacent said bottom wall and disposed directly below said impeller and said diffusing unit; an air inlet pipe for introducing air into the flotation liquid being pumped by said impeller, said air inlet pipe communicating with said cavity through the upper end thereof so that air is drawn into said cavity in response to rotation of said impeller; and a plurality of circumferentially spaced-apart continuous stationary suction guide blades mounted on and projecting upwardly from said bottom wall, said suction guide blades extending inwardly from circumferentially spacedapart locations adjacent to said side wall along said bottom wall toward the center of said cell and into said zone to a position directly underneath said impeller and said central opening of said diffusing unit, said suction guide blades defining therebetwecn horizontal open flow paths for flotation liquid, said open flow paths being open along their tops and closed along their bottoms and sides, said flow paths being of progressively narrower width in a direction from said side wall toward the center of said cell for directing return flow of flotation liquid to said cavity to increase the volumetric rate of return flow of flotation liquid into said cavity in response to rotation of said impeller and thereby to increase the rate of air flow into said cavity, the upper edges of said guide blades in said zone being located directly below and closely spaced from the lower edges of said impeller and said guide vanes, so that rotation of said impeller will draw air into said cavity and will mix the air with the flotation liquid and will forward the mixture of air and flotation liquid through said diffusing unit toward said side wall, and flotation liquid will return to said impeller along said bottom wall of said cell guided by said suction guide blades for repeated flow through said diffusing unit.

2. A flotation machine according to claim 1, in which said stationary diffusing unit comprises a top plate affixed to the lower end of said air inlet pipe and said guide vanes extend vertically downwardly from said top plate around the periphery thereof and are arranged thereon in a circular array, the outer edges of said guide vanes being substantially perpendicular to said bottom wall; said suction guide blades being uniformly spaced-apart and having continuous upper edges-disposed entirely bel'ow said impeller and said diffusing unit.

3. A flotation machine according to claim 2, in which said guide vanes are forwardly curved with respect to the direction of rotation of said impeller and said suction guide blades are rearwardly curved with respect to the direction of rotation of said impeller.

4. A flotation machine according to claim 1, wherein said bottom wall is provided with four suction-guide blades.

5. A flotation machine according to claim 1, wherein said suction-guide blades are so curved as to be convex in the direction of rotation of said impeller.

6. A flotation machine according to claim 1, wherein said suction-guide blades consist of straight rectangular plates and disposed on said bottom wall in cruciform arrangement.

Claims

1. A FROTH FLOTATION MACHINE, COMPRISING: A FLOTATION CELL HAVING A CONTINUOUS PERIPHERAL SIDE WALL AND A BOTTOM WALL DEFINING A FLOTATION ZONE FOR CONTAINING A FLOTATION LIQUID, A CENTRIFUGAL PUMP IMPELLER CENTRALLY LOCATED IN SAID CELL, SAID IMPELLER BEING ROTATABLE ABOUT A VERTICAL AXIS AND BEING DISPOSED CLOSE TO BUT SPACED UPWARDLY FROM THE BOTTOM WALL OF THE CELL, SAID IMPELLER COMPRISING A PLURALITY OF CIRCUMFERENTIALLY SPACED ELONGTED IMPELLER BLADES EXTENDING PARALLEL TO SAID BOTTOM WALL FOR MOVING THE FLOTATION LIQUID ADJACENT THERETO SUBSTANTIALLY HORIZONTALLY AND RADIALLY OUTWARDLY TOWARD SAID SIDE WALL, A STATIONARY DIFFUSING UNIT ENCIRCLING SAID IMPELLER AND BEING DISPOSED AT THHE SAME VERTICAL LEVEL IN SAID CELL AS SAID IMPELLER, SAAID DIFFUSING UNIT COMPRISING AN ANNULARLY ARRANGED SERIES OF SUBSTANTIALLY UNIFORMLY CIRCUMFERENTIALLY SPACED-APART, OUTWARDLY EXTENDING GUID VANES ARRANGED IN A CIRCULAR ARRAY AND LOCATED IN THE FLOW PATH OF THE LIQUID FROM THE IMPELLER FOR GUIDING AND DIRECTING THHE FLOW OF THE LIQUID FROM THE IMPELLER OUTWARDLY FROM SAID DIFFUSING UNIT TOWARD SAID SIDE WALL AT A VERTICAL LEVEL LOCATED CLOSE TO BUT SPACED UPWARDLY FROM SAID BOTTOM WALL, THE INNER EDGES OF SAID GUIDE VANES DEFINING A CAVITY WITHIN WHICH SAID IMPELLER IS DISPOSED FOR ROTATION THEREIN, SAID DIFFUSING UNIT HAVING A CENTRAL OPENING IN ITS BOTTOM PROVIDING A LIQUID FLOW PASSAGE EXTENDING BETWEEN SAID CAVITY AND A ZONE LOCATED ADJACENT SAID BOTTOM WALL AND DISPOSED DIRECTLY BELOW SAID IMPELLER AND SAID DIFFUSING UNIT, AN AIR INLET PIPE FOR INTRODUCING AIR INTO THE FLOTATION LIQUID BEING PUMPED BY SAID IMPELLER, SAID AIR INLET PIPE COMMUNICATING WITH SAID CAVITY THHROUGHH THE UPPER END THEREOF SO THAT AIR IS DRAWN INTO SAAI CAVITY IN RESPONSE TO ROTATION OF SAID IMPELLER, AND A PLURALITY OF CIRCUMFERENTIALLY SPACED-APART CONTINUOUS STATIONARY SUCTION GUIDE BLADES MOUNTED ON AND PROJECTING UPWARDLY FROM SAID BOTTOM WALL, SAID SUCTION GUIDE BLADES EXTENDING INWARDLY FROM CIRCUMFERENTIALLY SPACE APART LOCATIONS ADJACENT TO SAID SIDE WALL ALONG SAID BOTTOM WALL TOWARD THE CENTER OF SAID CELL AND INTO SAID ZONE TO A POSITION DIRECTLY UNDERNEATHH SAAID IMPELLER AND SAID CENTRAL OPENING OF SAID DIFFUSING UNIT, SAID SUCTION GUIDE BLADES DEFINING THEREBETWEEN HORIZONTAL OPEN FLOW PATHS FOR FLOTATION LIQUID, SAID OPEN FLOW PATHS BEING OPEN ALONG THEIR TOPS AND CLOSED ALONG THEIR BOTTOMS AND SIDES, SID FLOW PATHS BEING OF PROGRESSIVELY NARROWER WIDTH IN A DIRECTION FROM SAID SIDE WALL TOWARD THE CENTER OF SAID CELL FOR DIRECTING RETURN FLOW OF FLOTATION LIQUID TO SAID CAVITY TO INCREASE THE VOLUMETRIC RATE OR RETURN FLOW OF FLOTATION LIQUID INTO SAAID CABVITY IN RESPONSE TO ROTATION OF SAAID IMPELLER AND THEREBY TO INCREASE THE RATE OF AIR FLOW INTO SAID CAVITY, THE UPPER EDGES OF SAID GUID BLADES IN SAID ZONE BEING LOCATED DIRECTLY BELOW AND CLOSELY SPACED FROM THE LOWER EDGES OF SAID IMPELLER AND SAID GUIDE VANES, SO THAT ROTATION OF SAID IMPELLER WILL DRAW AIR AINTO SAID CAVITY AN WILL MIX THE AIR WITH THE FLOTATION LIQUID AND WILL FORWARD THE MIXTURE OF AIR AND FLOTATION LIQUID THROUGH SAID DIFFUSING UNIT TOWARD SAID SIDE WALL, AND FLOTATION LIQUID WILL RETURN TO SAID IMPELLER ALONG SAID BOTTOM WALL OF SAID CELL GUIDED BY SAID SUCTION GUIDE BLADES FOR RREPEATED FLOW THROUGH SAID DIFFUSING UNIT.

2. A flotation machine according to claim 1, in which said stationary diffusing unit comprises a top plate affixed to the lower end of said air inlet pipe and said guide vanes extend vertically downwardly from said top plate around the periphery thereof and are arranged thereon in a circular array, the outer edges of said guide vanes being substantially perpendicular to said bottom wall; said suction guide blades being uniformly spaced-apart and having continuous upper edges disposed entirely below said impeller and said diffusing unit.