US2167788A - Flotation apparatus - Google Patents

Description

Aug. 1, 1939. A. J. WEINIG FLOTATION APPARATUS 2 Sheets-Sheet 1 Original Filed March l, 1935 ATTORNEY.

Allg. 1, 1939. A- 1 WElNlG 2,167,788

FLOTA'IION` APPARATUS Original Filed March l, 1935 2 Sheets-Sheet 2 INVENTOR. /J/PTHU@ d n/f/n//G Patented Aug. 1, 1939 UNITED sTATEs PATENT OFFICE FLOTATION APPARATUS orado Original application March 1, 1935, Serial No. 8,946, now Patent No. 2,143,669, dated January Divided and this application October 12, 1936, Serial No. 105,280

l Claim.

It is an object of the present invention tov control the liquid level in a froth flotation machine in order that a selective depth of froth of `uniform quality may be constantly removed from the machine.

Heretofore in the art, various types of level m regulation have been employed. An adjustable Weir is probably the most common form of level regulating device for flotation machines in commercial usage. While Weir regulation has worked very Well in practice, it has a tendency to proimote the deposit and building up of sediment, particularly when treating gritty pulps, which results in clogging the machine.

Also, Weir regulation is not responsive to minor fluctuations in the liquid level, and as a consem quence, the elevation of the froth layer with respect to the froth overflow is almost constantly changing, and froth of varying quality is discharged across the overflow.

'I'he desideratum in froth flotation operations is to maintain a froth layer of uniform depth in order that a selective thickness of froth may be removed, and by maintaining the thickness constant, a concentrate of uniform quality is obtained.

Another object of the invention is to control the tailings discharge of the machine in response to measured variations in the feed.`

Other objects reside in novel Asteps and treatments, and novel combinationsand arrangement 3;, of'parts, all of which will appear more fully in the course of the following description.

The fiotation machine and discharge control mechanism of the drawings have been described and claimed in my co-pending application, Serial 4u No. 8,946 of March 1, 1935, for Liquid level regulation apparatus and method, of which the present application is a division.

Referring to the drawings, in the several views of which like parts have been similarly desig- 45 Dated:-

Figure 1 is a front elevation, partially in section, of a multi-cell flotation machine for performing the process of the present invention;`

Figure 2- is a section taken along the line 2--2, Figure 1; and l Figure 3 is a plan view of the last cell and discharge compartment of the machineillustrated in Figure 1.

As illustrated in Figure 1, a flotation machine y comprising a tank 6, divided by partitions l, intol `connection with one of the motors.

a series of cells 8 is provided at one end with a feed compartment 9 and at its opposite end with a discharge compartment I0.

A froth overflow lip I2 extends along one side wall of the tank 6, and a launder i3 beneath the lip i2 receives the overflowing froth. The wall of the tank 6 opposite the overflow lip i2 is bent inwardly at i4 below the normal froth level and acts as a froth Crowder.` A header i5 connected with a source of compressed-air (not shown) extends along a side of the tank 6.

Each cell B is provided with an air inlet i6 beneath an impeller Il, and a flexible conduit I8 delivers air to the inlet from the header l5. If desired, regulating valves I9 may be provided for varying the' quantity of air supplied to each cell.

A baffle-element is disposed in each cell above the impeller, and a grid 2| extending across the cell above the baille-element 20 defines zones of agitation and aeration in each cell.

The partitions l have openings 22 near their lower endsproviding passages which permit the direct flow of material under treatment from cell to cell, and are particularly effective in preventing excessive accumulation of settled gangue in the respective cells.

A rotary froth skimmer or paddle 23 is mounted hear the overow lip I2 of each cell, and moves the froth toward the overflow lip.

A convenient driving assembly for the machine has been illustrated. The impellers Il are mounted for rotation on shafts 24 depending from a superstructure 25 supported above the tank 6. Pulleys 26 are mounted on the upper ends of shafts 24 and are connected by belts 21 extends beyond the tank, and a pulley 30 isI mounted on the extended end of the shaft.

The pulley 30 is driven by a motor 28, through l the intermediary of aV belt 3|, or any other suitable means, and reduction gearing contained ina housing 32 on superstructure 25 in operative Since the driving assembly is of conventional construction,

detailed description of the component parts appears unnecessary, and while the machine illustrated is a motor driven type, it will be understood that any suitable driving mechanism may vided by an orifice 33 in an end wall 34 of the tank 6 opening into the discharge compartment I0. This compartment which is open at its upper end, preferably consists of side walls 35 fitted on the end wall 34 of tank 6, a bottom 36 having an outlet 31, and an end wall 38.

In its lower portion, end wall 38 is apertured to provide a service entrance, which is normally covered by aremovable plate 39, and bolt-holes 40 are provided in its upper surface for a purpose hereinafter explained.

An elbow 4I fitted over the orifice 33 serves as an upwardly ranging conduit for tailings discharging through the orifice. A series of radial ears 42 (Figure l) extend from the upper wall of elbow 4l, andthe upper end of the conduit is smoothed to provide a valve seat 43.

A valve 44, (Figure 3) movable relative to seat 43, controls the discharge from the conduit 4I. This valve comprises a flexible diaphragm 45, held between plates 46 mounted on a rod 41. At its circumferential edge, the diaphragm 45 is clamped between a pair of rings 48, fastened on ears 42. One or more spacer rings 49 may be mounted on ears 42 to elevate the clamping rings 48 and thereby the diaphragm relative to valve seat 43, which is the tailings overflow of the machine. v

The rod 41 depends from a block 50 pivotally carried between bifurcations 5l of a lever 52. The rod 41 is threaded at 53 and adjusting nuts 54 bearing against block 50 permit adjustments of the rod relative to the block.

One end of lever 52 overhangs, the tank and a float 55 mounted on a rod 56 depending from the overhanging end of the lever 52 is disposed within the tank 6. The rod 56 is also threaded at 51, and nuts 58 bearing against lever 52, permit its lengthwise adjustment for lpredetermining the liquid level in the tank.

The lever is flexibly supported on end 4wall 38 of the discharge compartment by meansof a strip 59 of flexible material, preferably rubber, which is held between two plates 60y bolted on end wall 38. 'i

Slots 6| in plates 60 are disposed to register with bolt-holes l'60, and bolts 62 inserted through bolt-holes 4D and slots '6l serve to hold the strip against movement relative to the plates `by tightening of nuts 63.

The slots 6l permit movement of the plates 60 relative to the end wall 38, and by this means, the degree of flexibility of strips,59 may be varied, as an increase in the Idistance between the ends of 55'* plates 60 and lever 52 will increase the flexibility of strip 59, and a decrease in the distance between the plates and the lever will decrease its flexibility.

A seat 64 on rod 41 supports an upright pin 65, and provides a rest for removable weights 6'6. The discharge end of conduit 4I is at an elevation considerably lower than the normal liquid level as determined by the position of the float 55, and

as a result, the diaphragm 45 is subjected to considerable hydrostatic pressure.

The combined weight of the lever 52, rod 41 and weights 66, is directed against thediaphragm 45 `to counterbalance the hydrostatic pressure in conduit 4|, so that the volume of liquid dischargin'g'therefrom is equivalent to the volume of feed entering the tank at the inlet 9.

Once this balance has been established by placl ing the proper amount of weighton seat 64 and by minor adjustment of rod 41, the control will operate automatically thereafter. 'Ihe lever 52 is also apertured at 61 to permit suspension of an additional weight, if such an arrangement is required to facilitate balancing of the control.

Variations in feed, however slight, are communicated to the float 55, and thence to the diaphragm 45, through the lever 52, and rod 41. If more than a normal amount of feed enters the tank, float 55 rises, causing rod 41 to move diaphragm 45 farther away from the seat 43, and if the feed is sub-normal, the float descends in the tank and rod 41 moves diaphragm 45 toward or against seat 43.

While the control mechanism hereinabove described is particularly effective, it will be understood without further illustration, that other control mechanisms performing the same functions may be used in performing the 'process of the present invention.

In Figure 1, the elbow 4I has been illustrated as having a tailings discharge spout 10 in its lower portion. Whenever the coarse sands do not rise a-nd discharge freely across valve seat 43, itis advisable to maintain this spout open, to prevent an excessive accumulation of tailings at the discharge outlet.

With many pulps, however, the coarse sands will pass through the valve readily, and under such conditions the spout 10 may be plugged in any conventional manner, such as a screw cap for example, and all tailings will be discharged across valve seat 43.

It will be understood that the machine will operate substantially the same whatever arrangement is employed. When spout 10 is open, the valve 45 is not opened as wide as it would be with the spout closed, but when the initial regulation -is effected, the operation is automatic thereafter.

From the foregoing it is apparent that a normal liquid level having once been established, the control will Vary the effective size of the discharge orifice so that no more liquid can escape from the tank than is fed into the same, and when the spout 10 is closed, this condition exists even though the feed to the machine is stopped entirely.

The foregoing arrangement results in maintaining a uniform liquid level in the tank, and as a consequence, the froth layer is not subject to variations in elevation relative to the\overow lip I2.

It is possible, therefore, to retain froth in the machine at a selective depth below the top of the layer and to discharge across the overflow only concentrate of uniform quality.

Further advantage of the pulp level control is found in the control of pulp densities. In other types of flotation operations density changes will be encountered as a result of erratic froth re. moval and deposit of coarse matter in the respective cells. In the present operation, deposit of. coarse particles is eliminated by the provision of openings 22 which permit a direct ow of such material through the machine to the final tailings discharge.

Variations in feed, however slight, are immediately compensated by the control which is counter-balanced to a predetermined normal feed and hydrostatic pressure, and the discharge is immediately changed to hold the pulp level constant.

'I'he operation is entirely automatic after the initial adjustments are effected, and until a change is desired, in the depth of froth to be removed, no further adjustments are required.

The provision of a flexible mounting for the. lever 52 insures noiseless operation, as well as resistance to friction and corrosion, due to inherent qualities of the material from which the strip is made. f

ln this connection, it will be understood that the level regulation of the present invention is4 applicabe to notation machines of all types and may be used to regulate the level in one or more cells ofthe machine.

For example, in most machines the pulp is'not passed directly from cell to cell, but it is directed into a conduit or passage as it leaves a cell, by which it is directed to the impeller of the next cell in the series. Whenconstruction of this type is employed, the diaphragm Valve control may be applied to the conduit outlet from any selective cell to control the level in such cell.

lln the froth flotation operation, `it is frequently desirable to employ a number of cells as rougher ce`ls and the remaining cells of the same machine as cleaner cells. In such an operation, it is frequently preferred to have the liquid level in one series of cells at a different elevation than the level in the remaining cells of the machine.

For such requirements, one diaphragm valve may be used to control the level of the "rougher cells anda second control used for the cleaner cells. These applications of the-invention will he understood by anyone skilled in the art, and detailed description and illustration of the same appears unnecessary.

lli'or illustrative purposes, the elevation of discharge has been shown much nearer the liquid level in the tank than actually is required in practice. Preferably, the seat 43 of conduit 4| is quite close to the bottom of the tank 6, and the greater proportion of the hydrostatic pressure in the tank is directed against the diaphragm 45.

The control is counterbalanced initially against a pressure of considerable magnitude, and is rendered highly sensitive to minute feed variations thereby. This arrangement has the further advantage of improving the discharge of coarse -sands from. the machine.

'In the description and claim, the expression greater proportion of the hydrostatic pressure in the tank wherever used will mean that substantially more than one-half the volume of liquid lin the tank is above and acting upon the control.

partitions dividing the tank into a series of cells.

and a rotary impeller adjacent the bottom of each cell, there being a plurality of open passages, at different elevations in each partition providing intercommunication, between adjoining cells, the lowermost passage being at the approximate level of the impellers and passages disposed in a1inement with. the discharge outlet for the direct movement of noniioated material through the series of cells to the outlet, said outlet including a small constantly open portion and another opening provided with a valve, and means for controlling the opening of said valve in accordance with change in level of the liquid in the cells.

ARTHUR J WEINIG.

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