US2190852A - Froth-flotation machine - Google Patents

Description

Feb. 20, 1940. s, TUCKER FRoTH-FLOTATION `MACHINE:

Filed Sept. 16. 1938 4 Sheets-Sheet 1 ATTORNEYS Feb. 20, 1940.

s. TUCKER 2,190,852

FROTH-FLOTATION MACHINE Filed Sept. 16. 1938 4 Sheets-Sheet 2 I ENT R. ad? 7224.1 BZ/ MM @J/AMY ATTORNEYS Feb. 20, 1940. s. TUCKER FROTH-FLOTATION MACHINE 4 Sheets-Sheet 5 Filed Sept. 16. 1938 INVENTOR.

MM, vfl/ ATTORNEYS S. TUCKER Feb. 20, 1940.

` FHOTH-FLOTATIONr MACHINE Filed Sept. 16. 1938 4 Sheets-Sheet 4 Patenten Feb. 2o, 1940 FROTH-FLOTATION MACHINE Stanley Tucker, London, England, assignor to Minerals Separation North American Corporation, New York, N. Y., a corporationl of Maryland Application September i6, 1938, Serial No.

1 Claim.

This invention relates to improvements in froth flotation machines.

It is an object of the invention to provide an improved form of froth notation machines 5 wherein a fine grained well aerated froth can readily be produced.I Other objects of the invention are to produce an apparatus readily capable of adjustment tov produce the best results, and in which the parts are readily accessible and not l liable to be choked by sediment should the apparatus be stopped while full of pulp containing solid matter in suspension.

According to the present invention, the froth flotation machine comprises in combination an l agitation vessel provided with a bottom inlet for introduction of pulp therein, a rotatablymounted impeller positioned in cooperative relation to said pulp inlet, a down-cast' cylinder the lower edge of which surrounds said impeller and which extends upwardly therefrom in said vessel and to which air is admitted, said down-cast cylinder having apertures for the I admission of streams of pulp to the impeller from the vessel, and bailles in the path of aerated pulp thrown outwardly by the impeller. Such apparatus embodying the present invention is specially intended for, and advantageous in, the froth flotation concentration of minerals.

Theimpeller may be of the type comprising a' and air, therefore, has access to the upper surface of the impeller blades. The position `and 40 dimensions of the down-cast cylinder are of great importance in the successful operation of the apparatus.` Conveniently the down-cast cylinder is slightly greater in diameter than the diameter of f the impeller and islocatedo-axially therewith.

If the lower end of the cylinder is located so that` l.

it is concentric with and surrounds `the upstanding blades Ajon 'the impeller, and its lcwergedge is in La horizontal` planepwhichvcuts the bladesat` an appropriate level.the power consumpticmy of the apparatus willbe at minimum forthemxicrease theaeraticngrbut will :increase thel power` consumed, whilelcw .y it bclcwvthis point will Treduce aeration. The appropriate point of ad- In Great Britain September 24,

justment ofthe cylinder is easily determined by trial.

A quiescent zone of the liquidin which froth can form could in some instances be arranged in a separate vessel, but most conveniently is 1ocated in the agitation vessel around the downcast cylinder.

In the preferred construction, the cylinder is provided with a plurality of apertures in its wall above the level of the impeller and below the 10 froth level in the surrounding agitation vessel, so that pulp may pour through the apertures into the cylinder and fall upon the impeller. These pulp circulation openings should be located at a sufficient depth below the pulp level l5 in the apparatus to insure that the jets of pulp pour into the cylinder; they should be of a sufficient area to permit adequate circulation of the pulp Without causing ilooding of the cylinder, which immediately reduces the eiciency of aera- 20 tion. i

While the invention can be employed in apparatus comprising a single agitation vessel, in practice it is frequently desirable to employ a number of vessels, and in this connection the 25 invention. contemplates apparatus as above described comprising a plurality of agitation vessels arranged side by side and each having an impeller and down-cast cylinder disposed therein, said vessels being provided with intercom- 3D munication apertures so that; pulp to be agitated can pass successively through the vessels.

In such apparatus, each'vessel may be provided with an inlet for pulp in the bottom thereof beneath the impeller, the impeller serving to 35 draw pulp into the vessel; and an outlet may be provided for pulp from the vessel, the outlet of the firstvessel ofthe group leading to the" inlet of the second, the outlet of the second' to the inlet of the third, `if ,athird vessel is pro- 40 vided, and so on throughout' as many vessels as may be provided in the. series'. Blades may be added to the underside of the impeller if desired to `assist it in drawing pulp into the vessel.

The baille in the path of` the' aerated pulp 45 maybe located in the saine `plane as the impelleri and have vertical` surfacesA disposed at an angleto the path vof pulp 2 delivered lby the impeller so thatn-the'aeratedzpulpafter iinpinging ,y upon` thetbailes'vis free: tcf rise vertically into the im mum aerating elfiic my.` Raising.thedown-casti. i cylinder abovethis point will@notmaterially..in-l

, thelimits of the blades and may even'be `greater in diameter fthangthe` ddwnscast cylinder :ifde-"n sii'ed. This may be an advantage, if additional 55 air is admitted below the impeller, as it tends to prevent such air from interfering with the flow from the down-cast cylinder into the agitation zone. However, from the point of view of accessibility of the parts, preferably the whole of the impeller is of smaller diameter than the internal diameter of the down-cast cylinder, and the cylinder is kept free of internal obstruction so that the impeller may be withdrawn upwardly for attention when desired without interference with other parts within the agitation vessel.

The following is a description by way of example of one form of apparatus embodying the invention, the apparatus being illustrated in the accompanying drawings, in which:

Figure 1 is a plan, certain parts being shown as broken away to show parts beneath them;

Figure 2 is a vertical longitudinal section upon the line 2-2 of Figure 1, looking in the direction of the arrows;

Figure 3 is a vertical cross-section upon the line 3-3 of Figure 1 looking in the direction of the arrows;

Figure 4 is a detail view of the upper side of the impeller;

Figure 5 is a similar view of the underside of the same;

Figure 6 is a detail of the upper side alternative form of impeller;

Figure '7 shows an alternative disposition of bales.

Referring to Figures 1 to 3, the apparatus comprises a plurality of agitation vessels I I, I2, I3, I4 arranged in a series side by side. It will be observed that in the drawings at the vessel I3 the apparatus is shown as broken off between chain lines and it is to be understood that any number of desired additional vessels may he interposed between the vessels I2 and I4.

The vessels are square as viewed in plan and are each provided with an impeller I5 mounted upon a vertical shaft I6 supported by bearings I1, I8 and carrying at its upper end` a driving pulley i9. An electric motor 20, mounted on a bracket 2|, is disposed between each pair of vessels II, I2 and I3, I4 and carries two pulleys 22, 23 whereby it may drive through a V belt of an the pulley I9 on the impeller shaft I6 of each of the two vessels between which it is located. This driving gear is supported upon two channel members 24, 25 which are laid with their webs horizontal and which extend along the apparatus from end to end above the agitation vessels II to I4, being supported by a suitable framing consisting of vertical members 26 and horizontals 28.

Co-axial with each of the impellers I5, there is in each of the agitation vessels a down-cast cylinder 30. The down-cast cylinder is supported at its upper end by screwed rods 3| passing through brackets 32 on the lower channel member 25 and held in adjusted position by screwthreaded hand wheels 33 above the brackets. Each of the down-cast cylinders is long enough to extend well above the liquid level in the agitation vessels II to I4. It is steadied so as to be held centrally with the impeller at its lowerI end by stays 34. Preferably the stays are adjustable for length, thereby insuring that the cylinder can be accurately set in relation to the impeller. A number of circulation apertures 35 are provided in the walls of the down-cast cylinders at a level below the pulp level in the agitation vessels. While several rows of holes have been illustrated in the drawings, it will be appreciated that a larger'or smaller number of holes will be required, depending upon the speed at which the agitators are run, the amount of solids which may be suspended in the pulp under treatment, the degree of agitation required and the like; and that in practice any holes in excess standing radial blades 31. Ihe diameter of the disc and of the outer edges of the blades thereon is slightly smaller than the internal diameter of the down-cast cylinder 30, so as to permit of the impeller being drawn upwardly without Idisturbing the cylinder 4should this be rendered necessary for purposes of examination or repair. On the underside of the disc are-two radial blades 38, as indicated in Figure 5.

As best seen in Figures 2 and 3, the lower edge of the down-cast cylinder is adjusted -so that it is at a level between the level of the upper edges of the blades 31 and the disc I5 of the agitator, the exact preferable height of this adjustment being readily determined by trial during the operation of the machine, the setting of the hand wheels 33 being adjusted for this purpose.

'I'he internal diameter of the cylinders 30 is such as to leave only a small space between the tips of the blades 31 and the inner surface near the bottom edge of the cylinder. If too large a space is left at this point, the tendency of the apparatus to flooding of the interior of the cylinder may become pronounced in the case of deep cells. In order to obviate undue wear of the bottom edge of the cylinder this may be lined with rubber or other wear-resisting material.

In the bottom of each of the agitation vessels I I to I4, there is disposed around the impeller I5 a set of baille plates. T'he baille plates are arranged in two concentric circles. The inner circle consists of a series of bale plates 40 which are vertical and are disposed at an angle to the radial position so that pulp thrown out tangentially by the impeller is flung against the faces of the baiile plates. An annular circulation space is provided between the periphery of the impeller and the inner edges of the baille plates. Outside the circle of the baille plates 40 there is a second circle of bafile plates 4I. These are similarly inclined but more numerous on account of the greater radius at which they are located. Conveniently, the baille plates consist of sheet metal, each plate having a flange formed by bending its lower edge at right angles to the plane of the plate, and the plates are secured in position by screwing them to the iioor of the agitation vessel.

In the center of the bottom of each agitation vessel there is an inlet 45 lfor pulp and this inlet, as will be seen, leads to the suction zone of the blades 38 on the underside of the impeller. An outlet46 is located in the agitation vessels II, I2 and I3 close to the side of the vessel, where it is shielded by the bailies from the direct ow of pulp from the impeller. The last agitation vessel I4 of the series is not provided with" an outlet at the position'of the outlets 46, the outlet of the pulp from that vessel being provided for by an Y beyond the vessel to the underside of a feed compartment 48 with which it is 'in communication by an I opening 49. 4The circulation casing 41 serves to convey pulp from the feed compartment 48 to the inlet 45 of the vessel II, and it is provided with a transverse partition 50 to prevent this pulp from flowing further along the circulation casing. The outlet 46 of the vessel II communicates with a second compartment of the circulation casing 41 which transfers the pulp from this outlet to the inlet 45 of the second vessel I2. Similarly the outlet 46 of the vessel I2 is connected to the next vessel I3 inthe series, and so on to the end vessel I4. The end vessel I4 has a tailings outlet 5I cut in its wall at a level well above the level of the baiiies 48, 4|;'and this outlet 5I leads over a Weir 52 to a tailings compartment 53, from whence the tailings can-flow away through an aperture 54 in the bottom of the compartment 53. The Weir 52 serves to regulate the pulp level in the apparatus.

Between the feed compartment 48 and the agitation vessel I I there is a return ow opening 55; and similar return flow openings 56, 51 and 58 are cut in the division walls between the agitation vessels II, I2, I3 and I4.

In each of ".he agitation vessels, when the apparatus is in use, the impeller I5 empties the down-cast cylinder 30 of pulp and drives air and a certain amount of pulp intothe agitation vessel against the baflies. Jets of pulp flow into each down-cast cylinder through the openings 35 and become mixed with the air which is projected into the pulp by the impeller. The amount of the pulp admitted by the openings 35 must not be sufficient to cause flooding of the downcast cylinder. The agitated pulp striking the baiiies 40, 4I, has its velocity destroyed by the impact, and air bubbles rise through the pulp from the bailies, the vertical disposition of the baiiies permitting such rise to take place freely'. Above the baiiies in the upper portion of the agitation vessel, a relatively quiescent zone of pulp is formed and the return ow openings 55, 56,

i 51, 58 are located in this quiescent zone. The suction of the impellers I5 draws in pulp through the circulation casing 41 and inlet45 into each cell. Some of this pulp is derived ultimately from the return flow openings 55-58 and some from the inlets 45 of the preceding cells. There is, therefore, a progress of the pulp from the feed box 48 through the opening 49`into the circulation casing 41, through the lower inlets 45 into the agitation vessel Il, through the outlet 46 of that agitation vessel and into another compartment of the circulation casing 41, and so on through the agitation vessels I2, I3 and I4 to the outlet 5I and into the tailings compartment 53. Simultaneously there is a return flow of pulp through the openings 58, 51, 56 and 55 in the quiescent zone of rthe apparatus. This return iiow :ls in some cases advantageous but is not an essential part ofthe invention.

s A froth forms in the agitation vessels II to I4, and if the material under treatment contains valuable ore particles and suitable reagents are added to the pulp this froth will consist of metalliferous or other values.` It will overflow the sides of the vessels over the lips 60 and 5 thence into the launders 6I which run along the sides of the apparatus;

Plugs 62 in the bottom of the circulation casing 41 afford access to the various circulation holes 49, 45 and 46, for cleaning out should the appa- 10 ratus become choked.

It will be observed that the down-cast cylinders 38 serve to screen the upper side of the impeller I from the body of the pulp in the agitation vessels, and should the apparatus for l5 any reason be stopped while loaded with pulp the solid material will settle on the bottom of the agitation vessels, but not to the same extent on the impellers or the floor of the vessels underneath the impellers. Consequently the apparatus can be started up again without draining or washing out.

Referring to Figure 6, this illustrates an alternative form of impeller in which the blades 31 on i`-ie upper side of the impeller disc are 25 curved instead of being radial as is the case of the impeller illustrated in Figure 4.

Referring to Figure 7, this shows a number of baiiies in the form of pegs 65 upstanding from the base of an agitation vessel. Such pegs can be employed in place of the baffles 40, 4I shown in the other figures of the drawings. Again, it is possible for the baiiies to be arranged as radial plates or for them to take the form of angle members arranged in concentric circles with the roots of the angles pointing towards the centre of the impeller. Again, instead of employing baiiies secured to the floor of the agitation vessel the well-known grid type of baille may be used, disposed above the level of the bottom of the down-cast tube in the space surrounding the same.

What is claimed is:

In a froth-flotation machine, an agitation vessel having a pulp inlet in the bottom thereof, a rotatably mounted impeller located above and adjacent to said inlet, said impeller comprising a disc having upstanding blades formed on its upper surface, a down-cast cylinder supported in axial alignment with said impeller and having an internal diameter somewhat greater than the maximum diameter of said impeller and terminating at its lower edge in a plane intersecting said impeller blades and extending upwardly in said vessel above the normal liquid level therein, said cylinder below said normal liquid level. being provided with apertures of suicient area to permit jets of pulp to pour into the cylinder and on to the impeller without fioodingr the inside of the cylinder, and a plurality of baiiies extending upwardly from the oor of said vessel and surrounding said impeller and in the path 'of the pulp thrown outwardly by the latter.

STANLEY TUCKER. 05

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