US2065722A - Classification of minerals - Google Patents

Description

Dec. 29, 1936.

A. C. MUNRO CLASSIFICATION OF MINERALS Filed June 15, 1954 5 Sheets-Sheet 1 INVENTOR. fileancfen CMzuwo; BY Wfi agawwa/ ATTOR YS.

Dec. 29, 1936. Q MUNRQ 2,065,722

CLASS IFICATION OF MINERALS Filed June 15, 1934 3 Sheets-Sheet 2 INVENTOR. fllexalzder'afiwzro,

A. C. MUNRO CLASSIFICATION OF MINERALS Dec. 29, 1936.

Filed June 15, 1954 3 sheets-sheet s IN VEN TOR. M m

BY CLAW/W4;

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a a M w l-JLJIP hl-LLL I-LLL .Ll-l-l-LLl-LLLL 1 7 mw Patented Dec. 29, 1936 UNITED STATES CLASSIFICATION OF MINERALS Alexander 0. Munro, Britannia Beach, British Columbia, Canada Application June 15, 1934, Serial No. 730,763

4 Claims. (Cl. 209-18) This invention relates to improvements in the concentration of ores or other minerals and the main object of the invention is to provide for effective and economical concentration by combined flotation and classifying operations.

An important object of the invention in connection with concentrating operations involving classification and grinding in closed circuit is to reduce the amount of material to be ground by suitable utilization of flotation in connection with such operations.

A further object of the invention is to provide for decreasing the dilution or increasing the thickness of the pulp in a classifying operation and particularly in a combined flotationclassifler operation. Another object of the invention is to provide for increasing the capacity of a flotation-classifier apparatus by. removal of the slimes at a suitable stage in the operation.

An important feature of the present invention in connection with a flotation classifier, is that the material to be subjected to flotation and classification is delivered first to the flotation compartment in such manner that the pulp undergoing flotation .and the settled solids are caused to move in the same direction through the flotation compartment.

The accompanying drawings illustrate embodiments of my invention and referring thereto:

.Fig. l is a longitudinal vertical section of a notation classifier provided with my improvement;

Fig. 2 is a section on line 2-2 in Fig. 1; Fig. 3 is a section on line 3-3 in Fig. 1; Fig. 4 is a section on line 4-4 in Fig. 1; Fig. 5 is a partial section on line 5-5 in Fig.

Fig. 6 is a plan view of the apparatus shown in Fig. 1, a grinding mill being shown in closed circ'uitwith the flotation classifier apparatus;

Fig. 7 is a partial longitudinal section of another form of the invention showing a modified means of supplying air to the flotation compartment;

Fig. 8 is a section on line 8-8 in Fig. "l.

The form of the invention shown in Figspl end wall 5 and is spaced from the end wall 5 and floor 4 so as to form an inlet or feed passage I between said baflle 6 and end .wall 5 and communicating with the compartment I through the passage 8 between the bottom of baflle means 6 and the floor 4. Suitable meam such as a launder as shown at I0 in Fig. 6 may be provided for supplying to the inlet passage I I the pulp or mixture of crushed or ground ore and water which is to be treated. Abaflie II is preferably provided at the other or discharge end of the tank-compartment I to permit pulp to flow from compartment I into compartment 2.

Suitable means are provided for subjecting the pulp while in tank-compartment I to a flotation operation for floating mineral concentrates therefrom and suitable means are also provided for mechanically advancing the heavier portions of pulp along the floor of compartment I and into the intake end of compartment 2. The

means for effecting flotation may be of any de- 'sired type. The form shown in the drawings comprises an air pressure line I3 connected to any suitable source of compressed air or other compressed gas and pipes I4 extending downwardly from said air pressure line or pipe to within a short distance of the bottom of compartment I. The side walls 3 of compartment l are formed with overflow lips I5, preferably beveled, over which the froth may flow into launders I6 arranged at each side of the compartment I and'leading to any suitable means for receiving the froth concentrates. Baflles I1 and Il' may be provided for suitably controlling the circulation of the pulp.

The means for mechanically advancing the heavier portions of the pulp along the floor of compartment I may comprise rakes each provided with raking blades I8 mounted on rake bars I8 which are suspended by hangers and links 2| from supporting levers 22 and 22' and are reciprocated by link connections 23 and 24 with an operating crank means 25 carried by an operating shaft 26. Said shaft is also shown as vprovided with cam means 21 operating an arm 28 on lever 22' said lever being connected by link 29 to lever 22 so that said levers operate in unlson to lift the raking means during its rearward traverse or stroke in the usual manner of raking devices of this character. Lever 22 is shown as pivotally mounted on an angle lever 30 which may be connected by link or cable 3| to a suitable windlass or other means, not shown, for adjusting the height or level of the raking means.

In connection with the flotation tank or compartment as above described, I prefer in some cases to provide means for trapping or retaining heavy concentrates or mineral values, for example, gold, as the materlal ,is raked over the bottom compartment. For this purpose a series of traps may be provided in said floor, each trap being formed as a groove or trough 32 extending transversely of or across the floor 4 and provided with walls which flare upwardly both in a direction transverse to compartment I and longitudinally thereof. Each of'said traps is preferably provided with discharge gates or valves 32 which may be operated by gravity in the usual manner so as to open automatically upon accumulation of a certain weight of material or they may be opened from time to time by hand if desired. v a

Means are also provided for removing slimes or finely dividedmtailings from the pulp, said means comprising a plurality of launders 35 which are preferably arranged in the compartment 2 adjacent the passage il' below the baffle I I, said launders being shown as extending transversely of said compartment to and through a side wall of said compartment so as to deliver the slimes to any suitable receiving means. These launders deliver the slimes separately from the concentrates delivered by the launder of the fiotation classifier, the slimes being in the nature of tailings and being generally rejected as waste. In order to provide for adjustment of the operation of these launders, each of said launders on each side thereof may be provided with an .overflow lip meansconsisting, for example, of a plurality of superimposed bars or strips 36 which are preferably beveled as. shown and are removably supported on the side of the launder in any, suitable manner. so that the overflow level at the lips of said launder may be varied according to requirements. Byproviding a plurality of such slimes overflow launders each having an overflow lip at each side thereof, the capacity of .the apparatus for drawing 01! slimes may be "multiplied to any desired extent thereby increasingrodfltoanarmflonarakemeans andsaid ing the effective capacity of the apparatus and also increasing the thickness of the-pulp carrying theslimes. In the compartment 2 is provided a discharge raking means 38 which may be similar in operation and construction tolthe discharge raking -means in compartment i, said discharge raking means comprising rake bars ll, raking blades ll mounted on said raking bars, hangers 42 connected to said rake bars and supported by links 48 from levers l4 and ll. An operating shaft 46 carries a crank 41 which is connected by connectshaft also carriesa cam ll, operating lever 45, and through link connection also operating lever 44 so as to raise the raking means in its rearward stroke. Means indicated at 52 are also preferably provided for adjusting. the level of the raking means in compartment 2. The operation oi the raking means in the respective compartments is such that each'rake is given a forward movement while in depressed position as to rake the heavier material upwardly along the floor of the compartment and then at the end of the rearward stroke is lowered to effect the raking position for the next forward stroke.

The operation .of the apparatus shown in Figs.

1 to Bis as follows:

The pulp containing suitably divided are or other mineral together with water and a flotation agent is supplied as indicated at I! to the inlet tlon compartment and flows longitudinally through said flotation compartment to the discharge passage ll' leading to the compartment 2. In passing longitudinally in the compartment l the pulp is subiected to-aflotation operation by the action of the air issuing from the pipes It,

in formation of bubbles or froth and in flotation operation all portions of the pulp are successively subjected to the operation of the flotation means so that the pulp which passes through the discharge passage Il' comprises substantially only material which is not susceptible to flotation either by reason of its surface characteristics or by reason of it being in insufllciently divided condition. The nonfioatable finely divided constituent of the pulp constituting the slimes, is removed at the overflow launders 25 which are in sufficient number and have suflicient overflow lip capacity to provide for removal of any desired proportion of the slimes from the pulp before the heavy or coarser portion of 'the pulp is drawn out of the liquid in the tank by the operation of the discharge raking means ll. In this connection it may be stated that the operation of the classifier II, theselaunders being provided in such numher that substantially the entire volume of .water supplied to the flotation compartment is removed from the classification compartment through said launders, it being understood that a small proportion of the supplied water will be contained in the froth discharged from the flotation compartment. The provision of a plurality of launders 3i provides an extended length of overflow lip so that the height of fluid pouring over thelip may be kept as short as possible. In the use of an extended overflow lip as at prwent provided by-the plurality of launders II, a relatively thick pulp may be handled as compared to the pulp concentration practicably employable in rake classiflers of the described type which are provided with the conventional side launders, and thus the handling capacity of the apparatus is materially increased. It will be a that the multiple launders 2' are actually a part of the classifier compartment 2, and are useful in connection with a classifierv operating either with or independently of a flotation compartment.

-Thereciprocating motion of the raking means It causes an appreciable movement of the liquid in the classifying compartment, but due to the opening or discharge ell, the force or surge of this liquid movement is diminishedbyvirtueofthebodyofliquidylthin the-flotation compartment. This feature prevents the customary disturbing surge adjacent the slimes overflow launders which is so characteristic of raking type classifiers due to the reflection of this surge against the endwall of the classiiiertankcorrespondingtothebsiiie H, and according to this invention a relatively quiet zone is provided adjacent the launders I so that the overflow level of the slimes may be 7 this operation resulting in agitation of thepulp preserved substantially constant, and a more 15 along the floor of said compartment and finally discharged at the upper end of said floor to any suitable receiving means, for example, to a suitable launder or other means whereby such material is conducted to the grinding mill indicated at 54, the broken lines indicating the course of material from the discharge end of compartment 2 to the grinding mill and back from the grinding mill to the inlet Ill of the compartment 1.

In the above described apparatus the suitably crushed ore coming from the mill and including the groundfeed and regroundmaterial is supplied at the end of the compartment opposite the raking-ofi or classifier compartment so that the flow of pulp proceeds. in the same direction as the motion of theheavier material under the operation of the rakes, while the removal of the slimes tailings is eifected after the pulp has passed through the flotation operation. The advantages of this method of operation are as follows:

No sulphide material is ground unnecessarily fine and the flotation capacity for a given fine material is thereby increased. In Patent No. 1,937,837 issued to me December 5, 1933, a flotation classifier apparatus is disclosed in which the flow of pulp through the flotation compartment is counter-current to the advance of the settled material under the operation of the raking means.- The provision for concurrent flow instead of the counter-current flow has certain marked advantages as above stated. A further advantage of the operation of the above-described apparatus in which the flow of pulp is concurrent (in the sense of direction) with the advance of the settled coarse material, is that it avoids the loss of fine gangue particles containing sulphide values which have neither floated nor settled by gravity to the bottom of the compartment in position to be actedupon by the raking means. It will be appreciatedthat there is considerable agitation of the pulp in the flotation compartment and such unfloatable particles as are not .sufliciently large or heavy to overcome the agitation effects will be kept in suspension in the pulp, and where such particles are carried directly to the slimes overflow launders as in the case of the showing in my U. S. Patent No. 1,937,837, they are lost with the slimes, while according to the present preferred showing such particles are carried into the classification compartment where they are in position to freely .settle toward the classifying rakes, by which they .are gently trapped'and raked toward the discharge leading to the. grinding mill.

Other important advantages of the present invention are as follows: 1

"Reduction of tonnage tobe ground, .thus-ef-, fecting as savingof grinding media consumption and power; increase-in flotation capacity which is obtained by eliminating sliming of the mineral particles such as occurs in existing classifiers wherein the pulp is ground unduly flne before being subjected to flotation. Over-sliming of the mineral which always occurs in the conventional practice not only retards flotation and thus greatly reduces the capacity of the flotation apparatus, but it increases greatly the cost of subsequent operations of recleaning, dewatering and reflltering the flotation concentrate. By means of the multiple lip overflow for the slimes, the mineral values having. already been removed in the flotation operation, a very eflicient classification is enabled in the classifler compartment 2. Moreover, as above pointed out, the use of the multiple lip overflow for the slimes tailings enables the use of a much thicker pulp in the classifying operation. As a direct consequence of such thick pulp, the use of bowl.classifiers on the withdrawn slimes may in some cases be entirely eliminated. This form of slimes overflow also enables the production of lower final 'tailings and also enables reduction of the floor space required for a given capacity.

The provision of the gold traps or heavy material traps in the bottom of the classifier compartment is of special advantage where the ore or material being treated contains gold or other heavy material which is amenable to separation by .such traps, inasmuch as it. enables separation of coarse free gold particles and their recovery by intermittent cleaning of the gold traps without disturbing the continuous operation of the flotation classifier, and furthermore it insures removal and recovery of such free gold particles before the heavy settled material is returned to the mill, thereby avoiding the loss which would result from regrinding if such free gold particles were allowed to be attritioned in the grinding mill. In this connection, the agitation or circulation due to the operation of the flotationmeans and to the operation of the raking means in the flotation compartment cooperates effectively with the gold traps in enabling settling of the heavy gold particles in such traps and the displacement of lighter gangue particles from such traps, thereby facilitating the separation and recoveryof the gold or other heavy material. The classifying compartment is without any outlet for liquid at its lower portion and the slimes overflow means 35 constitutes substantially the sole means for discharge of liquid from said compartment, the settled material being discharged from said compartment by operation.

of the mechanically operated means which moves the settled material upwardly out of the body of liquid, without removing any substantial amount of liquid.

Any suitable means may be provided for supplying air to the flotation compartment so as to efiect the flotation operation. Thus, as shown in Figs. 7 and 8, the aerating means may'comprise a pipe 66 connected to a suitable source of compressed air and extending longitudinally within the flotation compartment 61, said pipe being provided with perforations or slots 68 and with a porous or pervious fabric or other covering 69 around said pipe so that the air issuing from the pipe will be distributed into the body of the.pulp in such manner as to insure collective circulation and flotation. The construction of the flotation compartment 61 and classifying compartment 69' and the respective raking means I and 'II with their operating means maybe similar-to that above described and the heads inlet 12 and the slimes overflow 13 may be provided as shown in Fig. 7.

I claim:

1. An ore concentrating apparatus comprising: a tank including a froth flotation compartment and a classifying compartment contiguous to one end of said flotation compartment and in free communication therewith through an opening adjacent the bottom of said compartments; means for supplying dividedsolid material and liquidto the other'endof said flotation compartment; overflow means for said flotation compartment for receiving and discharging flotation concentrates therefrom; mechanically operated means at the bottom of said flotation compartment for mechanically moving settled material through said compartment toward and through said opening and into said classifying compartment; reciprocating rake means in said classifying compartment for mechanically moving settled material through said compartment and away from said opening under conditions of agitation and for discharging said settled material from said compartment; overflow means in said classifying compartment for maintaining a liquid level in both of said compartments and for removing liquid containing solids in suspension from said classifying compartment, said overflow means being disposed at the end of said classifying compartment adjacent said flotation compartment; and means for conducting away settled material discharged from said classifying compartment, wholly separate from material removed at said overflow means.

2. An ore concentrating apparatus comprising: a froth flotation compartment; means for supplying divided solid material to be treated to one end of said compartment together with liquid, said flotation compartment being provided with overflow means for receiving and discharging flotation concentrates therefrom and being further provided with an opening at the other end thereof adjacent the bottom thereof; a classifying compartment communicating at one end with said flotation compartment through said opening and provided with a bottom wall inclined upwardly away from said opening; mechanically operated means at the bottom of said flotation compartment for mechanically moving settled material therethrough in a direction away from said one end toward and into said classifying compartment through said opening; reciprocating rake means in said classifying compartment for mechanically removing settled material upwardly along said inclined bottom wall and away from said opening under conditions of agitation and for discharging said settled material from said'compartment; overflow means in said classifying compartment adjacent said one .end thereof for removing liquid containing solids in suspension from said classifying compartment and for maintaining a liquid level in both of said compartments; and means for conducting away, settled material discharged from said classifying compartment, wholly separate from material removed at said overflow means.

3. An ore concentrating apparatus comprising: a horizontally elongated tank adapted to hold a body of liquid; means defining a liquid level within said tank; baflie means intermediate the ends of said tank extending downwardly from adjacent said liquid level and having its lower end spaced from the bottom of said tank, and defining a froth flotation compartment at one side of said baflie and a classifying compartaooavaa ment at the other side of said baiile and providing a1 communicating opening therebetween, the bottom wall of said classifying compartment sloping upwardly from adjacent said opening to one end of said elongated tank; means for supplyingdivided solid material and liquid to the other end of said elongated tank at the end of said flotation compartment away from said bailie ment for mechanically removing settled material v outwardly of said classifying compartment along said upwardly sloping bottom wall and discharging said settled material from said compartment; said liquid level defining means comprising overflowmeans in said classifying compartment adjacent said baiiie means for removing liquid containing solids in suspension from said classifying compartment; and means for conducting away settled material discharged from said classifying compartment, wholly separate from material removed at said overflow means.

4. An apparatus for separating the solid constituents of an ore pulp containing water and divided solids into a flotation concentrate portion, a slimes portion, and a settled coarse portion, and for separately discharging said three portions, comprising: a horizontally extending flotation compartment; means for supplying such a pulp to one end of said flotation compartment; said flotation compartment being provided with overflow lip means for discharge of flotation concentrates and means for separately conducting away concentrates so discharged, and being also provided with an opening adjacent the bottom thereof at the end opposite said one end for outflow of the unfloatedsolid and liquid constituents of said pulp; means for aerating the pulp in said flotation compartment; mechanically operated means at the bottom of said compartment for moving'settled material from said one end toward and through said opening; a classifying compartment disposed contiguous to said opposite end of the flotation compartment and communicating therewith through said opening, so as to receive said unfloated constituents; said classifying compartment being provided with overflow means for maintaining a liquid level in both of said compartments and for discharging water containing suspended slimes, and with a means for separately conducting away water and slimes so discharged, said overflow lip means constituting substantially the sole means for outflow of water from said classifying compartment; mechanically operated means in said classifying compartment for removing settled material therefrom and discharging said settled material, substantially free from water, at a position above said liquid level; and means for conducting settled material so discharged away from said classifying compartment, wholly separate from said flotation concentrates and from water and slimes discharged at the last-named overflow lip means.

, nLEXANDER C. MUNRO.

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