US1579722A - ojlutxios jo souos i - Google Patents

Description

B. M. M ATEE FLOTATION 0F MINERALS Filed March 31 April 6 1926.

Patented Apr. 6, 1926.

UNITED STATES PATENT OFFICE.

BERNARD M. MCATEE, OF MIAMI, ARIZONA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

THE GENERAL ENGINEERING COMPANY. OF {SALT LAKE CITY. UTAH, A CORPORA- TION OF UTAH.

FLOTATION OF MINERALS.

Application filed March 31, 1921. Serial No. 457,306.

To 7? 10710))? it may ('(mccrw:

Be it known that I, lhnimnn M. lvlolt'rnu, a citizen of the United States, residing at ltliami, in the county of Gila, State of Arizona, have invented certain new and useful Improvements in the Flotation o't' Minerals; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to the tlota tion of ores and like metallit'erous and other substances amenable to flotation. hlore particularly, it relates to what: is known as pneumatic flotation,that is to say, the separation of the floatable constituents of an ore pulp or the like, in the presence of a flotation agent, and in a pneumatic flotation cell, wherein air is admittcd through a porous bottom or its equivalent, in such manner that, in rising through the pulp body, the air bubbles will meet the t'loat'able constituents and will carry them off in the form of a froth into an overflow launder or launders.

In pneumatic flotation apparatus of this general type, it is the common practice to arrange a series of cells or compartments in series, and to pass the ore pulp into the tirst cell or con'ipartment, and the tailings from the first cell or compartment to the second, and so on, until the tailings are finally discharged from the last cell or compartment substantially freed or stripped from contained values. In the operation of such a series of cells or compartments, accordingly, each cell or compartment supplies the feed to the next, and the tailings from the first cell or compartment undergo a series of subsequent retreatments in the .subsequent cells or compartments with gradual and progressive recovery of the values therefrom. In order to maintain the flow through such a series of cells or compartments, it is common to ar 'ange the successive cells or compartments in stepped arrangement, with each cell or compartment lower than the preceding, in order to provide a sutticient head for maintaining the necessary flow of pulp through the successive cells or compartments.

In the operation of such pneumatic flotation apparatus, the ore pulp tends to settle out on the porous bottom and to interfere with the introduction of air therethrough,

and, in order to prevent or reduce such blanketing, various expedients have been resorted to, such as the provision of inclined bottoms in the individual cells, or the provision of battles interposed along the length of the cell and whose edges are separated from the upper surface of the porous bottom for the purpose of forming scouring eddies. So also, it has been custon'iary to maintain a relatively deep body of pulp in the flotation cells or compartments, and to provide for a relatively slow velocity of the pulp through the individual cells or compartments.

The present invention is based upon the discovery that the retreatment of the tailings in a series of successive cells or compartments, with provision for maintaining ltow ot the tailings through the successive cells or COlllPtLI'tillltlltS of the series, an be eliminated, and the entire concentration operation completed upon a single body of pulp flowing with a suflicient velocity, in the form of a relatively shallow pulp body of uniform depth, through a long shallow cell or comparti'nent, so that the tailings discharged thcretrom can be permitted to go to waste without further retreatment. The present invention includes the further discovery that increased velocity of the flow ing pulp increases its transporting power to such a degree that blanketing of the porous bottom can be substantially prevented. without the aid of any auxiliary expedient such as battles, in such a horizontal pulp body of substantially uniform depth.

The transporting power of a current of water or pulp varies as the sixth power of the velocity, while the erosive power varies as the square of the velocity. The resistance to be overcome in the one case is weight, while in the other case it is cohesion. The resistance to be overcome may be due to a mixture of these two resistances, in which case the power of removing the material will vary at some rate between the square oi the velocity and the sixth power of the velocity (Prof. Leconte, Elements of Geology). It is evident, therefore, that it, for the same volume of pulp, the depth and consequent cross-section is reduced by one halt, the velocity is doubled, and the erosive power ot the resulting shallower body of pulp increased about four times while the transporting power is increased approximately sixty times.

The present invention includes both the improved method of concentration, and the improved apparatus adapted for utilization therein.

The improved apparatus of the invention comprises a long, horizontal, pneumatic cell, several times at least as long as the cell 15 wide, and with a depth which, in the preferred embodiments of the invention, is considerably less than. the cell width, said cell being provided with a. suitable pulp inlet at one end and failings outlet at the other, and with means for maintaining therein a relatively shallow body of pulp of substantially uniform depth and a froth column also of substantially uniform depth, said cell being adapted for the continuous and uninterrupted iiow therethrough of a. shallow pulp body at a suilicicnt velocity to prevent obgectionable blanketing of the porous bottom, and the cell bottom provided with a series of separate air compartments through which regulated amounts air can be supplied. Where the apparatus is used for the treatment of the crude ore, or the flotation feed from the preliminary treatment sections of mill, the cell may advantageously have a length. of, for example, 30 feet, or a length varying from 25 to l0 feet, while the cell width may not be. more than, c. g., 2 feet, and the pulp depth, e. g., 6 to 12 inches. l Vith cells of such dimensions, an unusually large tonnage can be treated, e. g, 250 tons or more a day, and the ore sutlicicntly impoverished in values in a single cell, so that the tailings therefrom can be run to waste. In a cell of these dimensions, treating about 250 tons of through 60 mesh material per day, with a ratio of water to solids of 3 to 1, the pulp velocity will be about 15 feet per minute with a pulp depth of about 12 inches, and about 7 feet per minute with a pulp depth of 6 inches. Cells of a much shorter length, and embodying certain of the novel features of the invention can, however, be. constructed and aevantageously used, for example, in the rctreatment of the froth concentrate produced by the longer cell. Shorter cells of, for example, 8 to 1'2 feet in length, and of a width and depth such as above indicated, and having a series of independent and independently regulated air compartments along the length of the cell, can thus be made and utilized with advantage for retreating the froth v concentintn. Such shorter cells, however, are to be (lifterentiated from the much longer cells in which the entire concentration operation can be completed in the first instance without retreatment of the tailings.

The improved method or process of the invention involves the treatment of the ore pulp or flotation feed in the form of a relatively shallow horizontal body of pulp of uniforn'i depth flowing at a sufficiently high velocity to prevent objectionable blanketing of the porous bottom, and with a sulliciently prolonged and extended flow, while subjected to the admission of air through the porous bottom, to remove the values therefrom in the form of a. froth concentrate, so that the resulting tailings can go to waste without further retreatment. In the carrying out of the process, the entire body of froth oonccnt ate can be collected together for retreatment, but it is advantageous, in many cases, to, collect the froth produced from difi'erent parts of the pulp body separately for further treatment.

The nature and advantages of the invention will further appear from the following more detailed description, in connection with the accompanying drawing illustrative of a preferred embodiment of the apparatus of the invention, in which the improved process of the invention can be practiced.

In the accompanying drawing, Fig. 1 represents, in vertical, longitudinal section, and with parts broken away, a. flotation cell embodying my invention;

Fig. 2 represents a plan thereof; and.

Fig. 3 a long'tudinai elevation of a somewhat modified construction.

Referring to, the drawing, the main. body portion of the cell 1 is provided with a. pulp inlet compartment 2 at one end and a regulating valve 3 at the other for the regulation of the tailing-s outflow, this regulation being el octed in the usual way by a float i which rises and lowers with the pulp level and opens or closes the valve 8 to a greater or less e .e so as to maintain a substantially uniform pulp depth in the cell. The float d is vertically adjustable and the rod carrying the valve 3 also vertically adjustable by the hand-wheel 5, so that the pulp depth can be somewhat varied, but so that this pulp depth will be i'naintained uniform with any particular adjustment.

The cell 1 is provided with a series of separate air compartments (3, separated from. each other by the transverse members 7, and each air compartment being provided with the usual porous body 8 of canvas, porous stone, or the like, customary in pneumatic flotation apparatus. llach body 8 is independent and independently rcn'iovable and replaceable. The separate air compartments 6 are separately supplied with air from the compressed air main 9 and the branch pipes 10, one for each air compartment, and the air supplied. to each compartment can be independently regulated by the individual valves ll in the branch supply pipes ll).

The froth concentrate overflows into the two side launders 12 which, in the construction illustrated in Fig. 1,. are inclined from the-ends of the cell to the middle, so that the entire froth concentrate from the cell is collected in the same launder. The flow of the concentrate in the launder can be promoted by a Water spray, and this may be of par ticular advantage in a cell of, for example, 25 to 10 feet, particularly where the cell is shallow and a single launder can have but a slight inclination it it extends throughout the length of the cell, or even from the ends of the cell to the middle.

Instead of taking otl the entire froth concentrate from the cell in a single launder, it is more advantageous, in many cases, to provide separate lauuders, each extending a portion only of the length of the cell so that, for example, the richer 't'roth com-enlrale produced near the inlet end of the cell can be taken off and recovered separatel from the leaner froth concentrate obtained trem the body of pulp during its subsequent ti eatment nearer the outlet end of the cell. A. plurality of launder-s, adapted for this pur pose, is illustrated somewhat conventionally in Fig. 3, where the cell is provided with a short launder 13 near the inlet end of the cell and a longer launder 14- for collecting the froth concentrate from the rest of the cell, the launder 14 being inclined down Wardly from its ends to the bottom o'li the cell at an intermediate point, to facilitate the flow of the truth concentrate therein.

In the usual practice, in the well-known iallow pneumatic flotation cell, having an inclined bottom, there is maintained a depth of ore pulp which, at the shallow end of the cell, is approximately (3 inches. and which 'nkogressirely increases toward the discharge end of the cell at the rate of about 33 inches to the foot, so that in a Callow cell 8 feet in length, the depth of the pulp at the discharge or tailings end is about 30 inches. In cells of the horizontal type, where batties of the kind hereinbetore referred to are employed, with resulting production of a series of successive compartments in which the pulp is successively treated, the depth of the pulpfrom end to end is approximate- 1y 30 inches. In both of these types of cell, the velocity of flow of the ore pulp is correspondingly moderate so that, in the inclined bottom cell, the inclination of the bottom is relied upon to prevent the blanketing or blinding and in the horizontal type the battles are relied upon for the same pur pose. and these battles further serve to subdivide the cell into a series of separate compartments, and the pulp into a series of successive bodies.

In the cells of the present invention, while the body of pulp is of a appreciable depth, there is nevertheless maintained a relatively shallow and uniform depth of pulp from end to end of the cell, and this body of pulp is caused to flow in the form of a continuous and uninterrupted body, and at relatively high velocity, through the cell. I have found that it is possible to maintain a depth of pulp, below the layer of froth, as low as (3 inches or even lower, and to increase it to as high as 19. inches or thereabouts, while still obtaining a sullicient pulp velocity to transport and hold in suspension the solids contained in the pulp, thereby preventing the blanlceting of the porous bottom, and, at the same time, to obtain a satistactor mineral coutentin the concentrates and a sullicient impoveri;bment of the body o i pulp so that the lailings can be disclnirgcd substantially freed trom values, and run to waste without turther retrcatmcnt. The entire com-entration operation can thus be completed upon a single body of pulp and in a single cell, as contradistinguishctl from the treatment of a series of successive bodies ol pulp in a. series ot successive cells or conniartmeuls, from one to another of which the tailings must flow and pass in succession.

Among the :ulvantages which the present invention presents may be mentiomnl the maintenance of a body of pulp oi? substantially unilorm depth throughout; the maintenance ol a tioth layer also of substantially uniform depth throughout; the innintcnance ol? a substantially uniform pulp velocity throughout the cell, without interruption or change such as results from the flow of the pulp from one cell to another or trom one compartment to another; the avoidance of the necessity for i'etreatiucnt oi the tail ings discharged from the cell after the con plction of the treatment therein; the large tonnage which can be treated in a single cell; the avoidance of obstructions or battles or connections between separate and succcs sive cells or compartments; and the avoidance of adjustments of the flow through successive cells or compartments; the possibility of independently regulating the air supply-to the air compartments so that, for example, an increased air supply can be pro vidcd near the outlet end, where a leaner "froth is produced; the possibility of separately recovering the froth from different portions of the same cell and the pulp flowing therethrough; and, generally, simplicity of construction and operation, such that a single horizontally arranged cell can be used to replace a series of separate cells or c(nnpartmcnts, such as have comnpionly heretofore been used in the art for completing the treatment of ore pulp or flotation feed before the tailings are run to waste.

In the operation of the horizontal cell of the present invention, the pulp velocity should, as above noted, he suliicicnt to maintain the solids in suspension, and preventing objectionable blanltcting oi the porous bottom. The velocity of the pulp may be, for example, 3 feet per minute, although this velocity can be Somewhat varied and materially increased, depending upon such con siderations as he size and character of the particles in suspension, etc. Inasmuch as the body of pulp of substantially uniform depth and unit'orn'i Toss-sectional area, its Velocity throughout the cell will also be substantially uniform throughout the cell, so that it can be maintained tliroughout of suliiciently increased erosive power and transporting power to maintain the pulp in suspension and. prevent objectionable blanketing of the porous bottom.

Furthermore, the moderate depth ot the pulp body maintained in the cell of the present invention permits a notable saving in the amount of air required and in the power necessary to produce the air pressure In practice, on a large scale, l have "found that, operating in accordance with the present invention, the porous bottom of the cell is kept in an open and tree condition, with a materially reduced air prc" e, and correspondingly lower power c than w h the usual inclined bottom Callow cells. be cause of the uniform pulp depth, the air pressure required by the separate compartments, is also substantially uniiei-u'i, but it may be of admntage in some cases to vary the air supplied to the diilerent compartments, for example, by increasing the air supply somewhat to the compartments near the discharge end of the cell, where a somewhat leaner froth is being produced. The provision ot a series of separate air compartments, along the length of the horizontal bottom, is therefore of advantage, even though the'cell itself horizontal, and the pulp body therein is of substantially uniform depth. The provision of a series of independent air compartments, and of porous blankets, or their equivalent, for each. compertinent, turther enables the separate air compartments to be individually renewed or repaired, and to be provided with porous material varying somewhat in character, porosity, etc, so that the operation of the cell can, to a certain extent, be regulated and controlled in this way, and the pulp body can be subjected to sou'iewhat varied treatment in successive parts oi? the cell, even though the pulp body itself is of uniform depth and uninterrupted flow throughout.

While the porous bottom of the flotation cell is shown as horizontal, and the cell can be successfully constructed and used where there is not the slightest inclination whatever, so that there will be the some lydrostatic head or depth of pulp throughoutthe length, yet some slight inclination may nevertheless be of acvantage, for example, an inclination amounting to from to of an inch per foot of length, to facilitate washing out and draining of the cell as a whole. It will beievident that such a moderate inclination does not substantially interiiere with the operation of the invention in the manner hereinbetore described.

li rom the foregoing description it will be seen that the shallow and relatively wide body oi? pulp, characteristic of the invention, preserves stratification of the pulp tlowing through the apparatus, and permits the use of such a velocity of pulp flow as is neces sary to secure satisfactory erosive and tran porting power of the pulp while subjecting it to the flotation treatment for a sui'ticient period of time to complete the recovery of the mineral.

I claim:

1. The improvement in the pneumatic flotation process tor removing substances amenable to flotation from a pulp containing the same, which comprises maintaining a prolonged unrestricted flow oi a shallow and relatively much wider body of the pulp of substantially uniform depth through a porous bottomed pneumatic flotation apparatus at a sutlicient velocity to prevent any objectionable blanlieting of the porous bottom.

The improvement in the pneumatic flotation process for removing substances amenable to flotation from a pulp containing the same, which comprises maintaining a flow of a shallow and relatively wide body oi the pulp through a porous bottomed pneumatic flotation apparatus at a suiiicient velocity to prevent any objectionable blanlieting of the porous bottom, the depth of said body of pulp not exceeding about twelve inches and being substantially uniform throughout the entire length of its flow through said apparatus.

3. The imyn'ovement in the pneumatic fio tation process for removing substances amenable to flotation t'rom a pulp containing the same, which comprises maintaining a prolonged unrestricted low of a body of the pulp of substantially uniform depth not exceeding about twelve inches and relatively much wider through a porous bottomed pneumatic flotation apparatus, the velocity oi? tlow ot the pulp through said. apparatus beingmaintained at such a rate as to retain the solids in suspension in the pulp.

i. A pneumatic flotation apparatus comprising a shallow cell having a substantially unobstructed horizontal bottom oi? much greater length than width and oi relative- 1y much g1 eater width than the depth of the cell, and means for distributing a into the cell in proximity to the bottom.

5. A pneumatic flotation apparatus comprising a shallow cell having a substantially unobstructed horizontal porous bottom of much greater length than width and of relatively much greater width than the depth of the cell.

ln testimony whereof I aiiix my signature.

BERNARD M. lilcrl'll lll.

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