Title:
Aerating machine
United States Patent 2182442
Abstract:
This invention relates to an improvement in aeration machines, and more particularly to an aeration or flotation machine of the type forming the subject of my United States Patents Numbers 2,055,065 and 2,085,947, as well as of an application for United States patent, Serial No. 114,114, Henry...


Inventors:
Booth, Lionel E.
Application Number:
US17405537A
Publication Date:
12/05/1939
Filing Date:
11/11/1937
Assignee:
Booth, Lionel E.
Primary Class:
Other Classes:
209/169, 261/93
International Classes:
B03D1/16
View Patent Images:
Description:

This invention relates to an improvement in aeration machines, and more particularly to an aeration or flotation machine of the type forming the subject of my United States Patents Numbers 2,055,065 and 2,085,947, as well as of an application for United States patent, Serial No. 114,114, Henry F. Diets, applicant.

Aeration or fotation machines embodying the' inventions of the aforesaid patents and application for patent, are peculiarly efficient in producing an abundant, finely bubbled froth, which is much desired in the practice of moder flotation as applied to metallurgical and other pulps.

Patent 2,055,065 is concerned with a hollow, tight-walled mpeller, preferably conical in shape, and having a denture whose teeth or lugs are spaced circumferentially apart from one another and project from the basal rim of the cone. The impeller is disposed at the lower end of a vertical shaft and is submerged at. a low point, in a mass of' pulp. Compressed fluid, such as air, is conducted into the space enclosed by the impeller, and bubbles through the denture spaces. The initial bubbles are clipped into myriads of smaller bubbles by the teeth and are projected outwardly into and through the pulp body.

Patent 2,085,947 is concerned with peeling the bubbles emerging from the impeller, and guiding these upwardly through the pulp in an orderly 80 manner, this being accomplished by means of a plurality of blades spaced around the impeller.

Application Serial Number 114,114 is concerned with spacing the peeler blades apart from the bottom of the tank or other container constis5 tuting the cll or cells which confine the pulp, so as to provide circulation below the blades and thereby prevent the pocketing of the pulp and a consequent deposition of coarse sands on the bottom of a cell.

The present invention is concerned with.the utilization to the fullest extent, of the advantages obtainable from the combined devices of the aforesaid patents, and has for its principal objects: 4 First. To conserve the finely bubbled, mineralbearing froth in the frothing compartment or zone, and to prevent its destruction and consequent dropping of' mineral values because of coming into contact with the rotating Impeller shaft.

Second. To cause the continuous, expeditious, and careful removal of the froth from the frothing compartment or zone by means of a stationary deflector, without the use of paddles or other 5 moving elements.

Third. To provide a simple, efficient and inexpensive construction whereby the aforesaid objects are accomplished.

In the drawing, which illustrates an excellent embodiment of the invention: Fig. 1 is a plan of a flotation cell, partly in section, taken on the line 1-I in Mg. 2; Fig. 2, a vertical cross-section taken on the line 2-2 in Fig. 1; Fig. 3, a front elevation, partly in longitudinal, vertical section, and drawn to a reduced scale, of a battery of, for example, four flotation cells operatively connected one to another in series.

Referring to the drawing, the numeral 20 designates a tank or container adapted to confine a 1Z metallurgical flotation pulp in the form of a bubble column 21 having the pulp level 24.

Submerged at a low point in the bubble column is an impeller 26 which is fast on a shaft 27, this shaft being rotatably supported in a bearing stand 28. The stand in turn is supported on longitudinal beams 29, and the beams may rest on end walls 30, and partition walls 31, 31a, and t1b, forming parts of the tank structure 20. The shaft 21 may be provided with a pulley (not shown) located above the stand 28, and the pulley may be driven from any suitable source of power, such as an electric motor (not shown), all as is well known in the art.

The impeller 26 is hollow and preferably conical 20 in shape, and has a denture composed of lugs or teeth 32. The teeth are spaced apart from one another and project from the basal rim of the cone. A pipe 33," connected with any suitable source of compressed air or other fluid (not indi- '5 cated) may extend upwardly into the interior of the impeller, Spaced apart radially from the basal circum-' ference of the impeller, and spaced apart circumferentially from one another, is a plurality of peeler blades 34, 38 and 31, the.bottom edges of which are spaced apart from the bottom 28a of a cell, so as to define a circulation space 13 below the peelers. Al the peeler blades may be welded to a ring 38 so as to form a rigid, self-contained structure. The blades 38 may extend into the four corners of the cell, where they rest removably on brackets 38.

When compressed air is admitted through the pipe 33, and the impeller is simultaneously rotated at a suitable peripheral speed, for example, 1700 ft. per minute, the air tends to bubble out through the spaces between the teeth or lugs 32.

If the impeller were to stand still, the bubbles would be of comparatively large size. However, 66 because of the rotation of the impeller, its teeth clip, the bubbles into very small fragments forming tiny bubbles which emerge from the impeller, and are peeled off shortly after emergence, by * means of the peeler blades 34, 35 and 36. The peeled bubbles then are guided upwardly along the surfaces of the peeler blades as Indicated approximately by the curved broken lines in the lower part of Fig. 2. The bubbles, because of the properties of well known frothing reagents, in rising through the pulp in the bubble column 21, gather to themselves the mineral values in the pulp, and carry these values with them through and upwardly from, the pulp surface 24.

Since the mineral extraction from flotation pulp is fractional in a single cell, it is customary in practice to arrange the cells in batteries, the showing in Fig. 3 being typical. Communication through the successive cells may be effected by means of openings in the respective partitions, similar to the one indicated at 41. Pulp may be fed to a battery through a feed inlet compartment 42 at the first cell, and be discharged from a battery over a weir consisting of removable sections 43 at the last cell, the flow of pulp being retarded by a baffle 45. By means of the removable weir sections, the pulp level 24 inall the cells, may be regulated as desired.

What has been explained so far, is a brief resum6 of the disclosures in the aforesaid patents and application for patent, and does not constitute part of the present invention, excepting in combination or conjunction with what is now to be described.

The tank and its component cells, in cross-section, are preferably symmetrical on each side of the longitudinal axial plane of the impeller, and are arranged to discharge froth along the two opposing longitudinal sides of the cells. Bridging the frothing compartment of each cell longitudinally, is a trough 46 which may have the inclined sides 46a, and the horizontal bottom 46b. The trough dips into the pulp so that the bottom of the trough is below the pulp level 24. The trough divides the frothing compartment into two parts 25a and 25b, and the trough sides form deflectors, which at least partially define the frothing compartments. Since the trough sides extend upward and forward in converging relation to the wall lines 47 of the cell, each frothing compartment is given the form of an inverted wedge; the function of which will presently be explained.

Opposite each deflector 46a is a, discharge mouth 51 through which the froth leaves the cell. Each discharge mouth may contain removable weir sections 53, for the purpose of varying, as may be required, the level at which the froth overflows.

The trough may be supported by any suitable means, for example, by clip angles 49 and 50, which are fastened to the opposing cross walls of the cell.

The trough structure 46 has only one opening therein, this opening being indicated at 52 and serving to accommodate the Impeller shaft 21.

05 The opening 52 should be only large enough to provide operative clearance around the shaft.

The deflectors 46a extend above the uppermost level to which froth may rise, in order to prevent entry of froth into trough.

In operation, the abundance of fine bubbles produced by the impeller, rise through the pulp, and emerge at the pulp level in a large volume of froth which brushes against the outside surfaces of the deflectors 46a and is positively and continuously crowded or pushed through the discharge mouths. At the same time, the trough prevents any portion of the froth from entering thereinto, and therefore, from coming into contact with the rotating shaft 27.

In past practice I have found that without the g trough 46, froth piles up around the shaft 27, and coming into close contact with the moving surface of the shaft, a large part of the individual bubbles of the froth are destroyed. Such destruction of bubbles, causes mineral particles with which they were loaded, to be instantly dropped, and to be drawn down along the shaft into the lower part of the bubble column, where they must be picked up again by other bubbles. Obviously, such adverse action causes a very perceptible loss in efficiency, and cuts down the otherwise large capacity of the machine, correspondingly. The trough 46 not only prevents the objection just outlined, but at the same time, the stationary deflectors 46a, cause the froth from the frothing compartments 25a and 25b, to be automatically pushed, positively and vigorously, over the weirs 53 instead of sluggishly building up in the space occupied by the trough and only tumbling over the weirs as a last resort. It is to be noted that under even the most favorable circumstances, the bubbles are not extremely durable, so that the quicker they are gotten over the discharge weirs, the less likely is there to be an inadvertent collapse of any of the bubbles. The invention is herein particularly described in its adaptation to the flotation of metallurgical pulps, for the reason that it finds an extensive application in this art. However, it is not necessarily restricted thereto, because the bridging 3 trough with its upwardly diverging, deflecting side members, may be usefully employed in other arts where the aeration of a liquid or semi-liquid is involved in order to produce a froth which rises through the mirror surface of the liquid. So also, the term "aeration" is not restricted to ordinary air, but relates to any gaseous substance which is to be diffused through a liquid or semiliquid.

What I claim is: 1. An aerating machine, comprising means defining a bubble column, a hollow, rotatable impeller.having teeth extending outwardly from the rim thereof and being submerged at a low point in the bubble column, means for supplying compressed air to the interior of the impeller, peeler blades disposed around the impeller and spaced apart from one another and from the impeller, said peeler blades being adapted to guide upwardly, bubbles discharged by the impeller, and a trough bridging the upper part of the bubble column, the said trough including a lower portion dipping below the level surface of the pulp in the bubble column and sides inclined upwardly and outwardly from the said lower portion for the purpose of deflecting outwardly, froth rising from the bubble column.

2. A flotation machine, including in combination, a cell structure enclosing a bubble column, a hollow rotatable Impeller having teeth extend- 6 Ing from the rim thereof, the said impeller being disposed at a low point in the bubble column, means for supplying compressed air to the impeller, peeler blades disposed around the impeller and spaced apart from one another and from the impeller, the said peeler blades being disposed to guide upwardly, bubbles discharged by the impeller, means defining a discharge mouth in proximity to the top of the bubble column, and a deflector defining at least partially, an inverted 7T .,. T.F wedge-shaped frothing compartment immediately adjacent the said discharge mouth.

3. A flotation machine in accordance with claim 1, wherein a definite level surface of pulp is maintained in the bubble column and the said deflector dips below the pulp level surface.

4. A flotation machine, comprising a container having longitudinal walls and cross walls joined to the longitudinal walls and disposed to form a cell for confining a bubble column of pulp, a hollow rotatable impeller having teeth extending from the rim thereof and being submerged at a low point in the bubble column, a driving shaft extending upward from the impeller, means for supplying compressed air to the interior of the impeller, pelet blades disposed around and spaced radially apart from the impeller, the said peeler blades having their lower edges spaced apart from the bottom surface of the container and being adapted to guide upwardly, bubbles discharged by the impeller and at the same time, to permit circulation of pulp in the space between the peeler blades and the bottom of the container, a trough bridging the upper part of the bubble column from cross wall to cross wall, the said trough consisting of a lower portion closely surrounding the driving shaft and deflecting side portions extending upwardly and outwardly from said lbwer portion in order -o at least partially define a frothing compartment immediately above the pulp surface level, and means defining froth discharge openings in the said longitudinal walls, the said discharge openings being in cooperative proximity to the respective deflecting side portions of the said trough.

5. A flotation machine as recited in claim 3, in which the cell structure, the deflecting trough and the frothing compartment are each and all, symmetrical on both sides of the longitudinal axial plane of the impeller and its driving shaft.

AONEL E. BOOTH. Ai