US2700466A - Drum separator and method of beneficiating minerals - Google Patents

Description

Jan. 25, 1955 H. LOGUE ET ,AL

DRUM SEPARATOR AND METHOD OF BENEFICIATING MINERALS Filed May 25, 1950 ATTOR/VL'F 1 M N lH'll HHH QN m Mg, m \IMI m WM Iii m [I m N Am i l' i r" W M t v I e h\ T 8 4 m w h\ hs w w H I). u 0 6 kh m MW MM Q 1| I WW m r 1, 1 I N Jan. 25, 1955 1.. H. LOGUE ET AL 2,700,466

DRUM SEPARATOR AND METHOD OF BENEFICIATING MINERALS Filed May 25, 1950 6 Sheets-Sheet 2 INVENTORS 4544410 19. Zeal/E Poss/Pr S. BA/45w Jan. 25, 1955 H. LOGUE ETAL 2,700,456

DRUM SEPARATOR AND METHOD OF BENEFICIATING MINERALS Filed May 25, 1950 6 Sheets-Sheet 3 INVENTORS LELAA/O l-K 4061/5 /P05527- S. BAH- Y LAM,

flfI O/FA Jan. 25, 1955 L. H. LOGUE ET AL DRUM SEPARATOR AND METHOD OF BENEFICIATING MINERALS Filed May 25, 1950 6 Sheets-Sheet 6 0040s! mom was MINA/6S /6 Fe- I86 HIGH G/PA V/l' F 40W 684 V/TV FIE 1:1.

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AOEERT S. BAILEY ATTORNEY United States Patent DRUM SEPARAT OR AND METHOD OF BENE- FICIATING MINERALS J Leland H. Logue, San Francisco, Calif., and Robert S. Bailey, Tenafly, N. J., assignors to Western Machinery Corporation, San Francisco, Calif., a corporation of Utah Application May 25, 1950, Serial No. 164,158

Claims. (Cl. 209-172) This invention relates to separators for separating ores and the like to produce a clean concentrate of the mineral value or a clean waste. More particularly, it relates to drum separators for beneficiating coal, iron ore and the like, and to a method of beneficiating such materials, said separators and method employing a heavy fluid medium for effecting a simultaneous multiple gravity separation of light and heavy constituents.

Heavy medium separation is well-known in the art of separating and classifying ores, coal and the like. The medium employed is a relatively heavy fluid having a specific gravity intermediate that of the light and heavy constituents of the material treated. The medium effects a separation by floating the light constituents and sinking the heavy constituents.

Drum separators are also Well-known in the art of heavy medium separation. Such separators are generally open ended drums having inwardly projecting, radial, perforated lifters which lift the heavy or sink" material and deliver it to a trough where it is carried ofi by additional medium. Meanwhile, the light or float" material overflows an open end of the drum together with the medium. Both fractions, i. e. the sink and float fractions, are usually screened to separate medium and washed with a spray of water to eliminate adhering medium.

Cone separators are also used for the same purpose as drum separators. In these, an air lift is employed to remove the sink material.

Media employed for this purpose are artificial and generally aqueous, the selected gravity being imparted by a finely ground, dense solid such as magnetite, ferrosilicon or galena suspended in the aqueous phase. Magnetite and ferrosilicon are advantageous because their magnetic properties render them susceptible to recovery V from the aqueous phase by magnetic means.

The art of heavy medium separation has progressed to the point where separations are demanded between materials differing only a few hundredths in density. In

addition, substantially complete recovery of medium and high yields of the mineral value are also demanded.

While the art has generally fulfilled these demands, it has heretofore, in some cases, at least, succeeded only by means of plant lay outs or circuits which employ in excessive number of units and occupy a great deal of space. The expense involved makes such results possible only in very large operations and even so, the economics of the situation is not satisfactory.

It is an object of the present invention to provide improved separatory apparatus for effecting simultaneous multiple gravity separation of minerals, ores, and the like.

It is a further object of the invention to provide improved separatory apparatus of the character and for the purposes described, which is operable in the heavy medium process.

It is a further object of the invention to provide separatory apparatus operable with a heavy separation medium which elfects a two stage separation, provides a light, a heavy and a middlings product and is economical from the standpoint of space utilization and plant investrnent.

Yet another object of the invention is to provide more eflicient and/or economical methods and circuits than used heretofore to effect separations of light and heavy materials such as iron ore and low grade coal.

More particularly, it is an object of the invention to 2,700,466 Patented Jan. 25, 1955 provide circuits employing heavy medium separation which are operable to separate low grade coal, iron ore and the like into three fractions, consisting of a relatively pure, clean concentrate of the desired mineral value, a tailings product which contains relatively little of the mineral value, and a middlings product which contains a considerable proportion of mineral value and can be returned to the circuit, or othewise re-worked to recover the mineral value as a concentrate.

These and other objects of the invention, as well as those inherently possessed by the invention, will be applarent from the ensuing description and the appended c aims.

Certain forms and embodiments of the invention are exemplified in the following description and illustrated by way of example in the accompanying drawings in which:

Figure l is a view in longitudinal vertical midsection through the preferred form of drum separator of the present invention.

Figure 2 is an end elevation as seen from the right of Figure 1.

Figure 3 is a transverse section taken along the line IlI-III of Figure 1.

Figure 4 is a fragmentary view taken along the line IVI.V of Figure 1 showing the outlet or discharge end of the main feed chute or trough.

Figure 5 is a fragmentary, perspective view of one of the lifters employed in the drum separator of Figure 1.

Figure 6 is a diagrammatic flow sheet of a coal treating plant for processing low grade coal containing a high proportion of ash-producing material.

Figure 7 is a diagrammatic and pictorial flow sheet illustrating the significance of recovery of a middling product in the manner of the present invention.

Figure 8 is a diagrammatic flow sheet of a coal treating plant embodying a double or two stage drum separator of the present invention.

Figure 9 is a diagrammatic flow sheet of a plant for treating iron ore, laid out in accordance with prevailing practice.

Figure 10 is a diagrammatic flow sheet of a plant for treating iron ore, laid out in accordance with the present invention.

Fig. 11 is a diagrammatic section through a double drum separator adapted to separate the heavy fraction in the first compartrnent and to separate the light and middling fractions in the second compartment.

Referring now to the drawings, and more particularly to Figure 1, a drum separator is there illustrated, which is generally designated at 10. It comprises a cylindrical drum 11 which is mounted on a base 12 comprising a horizontal deck 13, longitudinal channels 14 and transverse channels 14a. The drum 11 is rotatably mounted on the base 12 by means of two steel tires 15 which circumscribe and are fixed to the drum at opposite ends thereof. The tires 15 ride on wheels or rollers 20 which are best shown in Figure 2. A pair of such rollers is provided at each end of the drum and they are disposed on opposite sides of the axis of the drum. Each roller 20 is provided with trunnions 21 which are journaled in bearings 22 formed in brackets 23, which are fixed to the base 12. The drum is driven by means of a sprocket 24 which circumscribes the drum and is fixed thereto by r any suitable means, such as welding, bolts, or the like. The sprocket 24 may be driven by any suitable means (not shown) and at any desired speed.

The drum 11 is divided into two compartments 26 and 27 by means of an annular divider 28. Each of the compartments 26 and 27, which will be referred to hereinafter as the first and second compartments, respectively, comprises a cylindrical body portion 29 and frusto-conical end portions 30 and 31. Each of the end portions 31 is fixed at one end to the body portion 29 of the drum of its compartment 26 or 27 and at its other end it is fixed to the annular divider 28. The first compartment 26 (as viewed in Figure 1) is formed with an inlet port 36 which is co-axial with the drum and is circumscribed by a reinforcing rim 39. Communication is provided between the compartments 26 and 27 by a transfer port 40 which is formed in the divider 28 and which is circumscribed on both sides thereof by reinforcing rims 41. The transfer port is co-axial with the drum and it will be seen that the diameter of this port is such that its lower edge 40a lies in a horizontal plane located a substantial distance above the plane of the lower edges 36a and 38a of the inlet port 36 and the outlet port 38, respectively.

Each of the compartments 26 and 27 is provided with a plurality of lifters 42. Referring more particularly to Figure 3, it will be seen that the lifters 42 are spaced uniformly about and are fixed to the inner surface of the body portion 29. Each lifter has an inwardly and radially projecting base portion 43, a body portion 44 which is angularly offset in the direction of rotation of the drum as indicated by the arrow, and an end portion 45 which is disposed at a right angle to the body portion 44. Each lifter 42 is formed with a plurality of parallel slots or louvers 46. As is best shown in Figure 5, these louvers taper toward the base portion 46 and their wide end portions 46a lie on the end portions 45 of the lifters.

The first compartment 26 is also provided with an inlet chute or trough 50 which is intended to be supplied externally of the drum 11 at 51, with solid material to be separated or classified. The trough 50 extends into the compartment 26, terminates in an end wall 52 and empties into the compartment 26 through a reversely directed I dovetail outlet 53. (See Figure 4.) The fluid level in compartment 26 is maintained at 54. As will be seen, this lies in the horizontal plane of the lower edge of a partition or weir 55 and it is below the level of the lower edge 40a of the intermediate port 46. Hence, fluid can I 56 to which it may be secured in any suitable manner.

The framework 56 comprises a pair of spaced, vertical angles 57 at each end of the drum which are reinforced by gussets 58, and spaced horizontal angles 59 which are supported by the vertical angles 57 and extend axially through the drum 11 by way of the ports 36, 38, and 40. The inlet trough 50 is also provided with a supply pipe for supplying the heavy separating medium. The supply pipe 65 communicates with the interior of the trough 50 through an opening 66, and a weir 67 and a guard plate 68 are provided adjacent the inlet.

The first compartment 26 is also provided with an outlet chute or trough 62 for separated light material, which is supported by the framework 56, and with a transfer trough or chute 69. The transfer trough 69 has a V- shaped inlet portion 70 which, as viewed in Figure 3, has a solid side wall 71 on the left and perforated side wall or screen 72 on the right. The transfer trough 69 is supported by means of brackets 73 which are fixed to the framework 56. It extends into the second compartment 27 through the transfer port 40 and terminates in a dovetail outlet 74 and an end wall 75. As will be seen from Figure 1, the lower edge of the end wall 75 lies in a horizontal plane between the plane of the lower edge 40a of port 40 and the plane of the lower edge 38a of port 38. The transfer trough 69 is provided with a supply pipe for supplying fluid separating medium thereto. The supply pipe 80 has a valve 81 for controlling the flow of medium and is connected to a supply pipe 82. The pipe 80 communicates with the interior of the transfer trough 69 through an opening 83, and a weir 84 and a guard 85 are provided adjacent this opening.

The second compartment 27, as stated hereinabove, is provided with lifters 42 similar to those in the compartment 26. It is also provided with a discharge trough or chute 69a for separated heavy material, which is supported by the framework 56 and is similar to the transfer trough 69, similar parts being similarly numbered. The trough 69a is provided with an outlet 86. It is also provided with a supply pipe 87 for supplying fluid separatmg medium, the said pipe having a control valve 88 and being connected to the supply pipe 82. The supply pipe 87 communicates with the interior of the discharge trough 69a through an opening 83, and a weir 84 and guard 85 are provided adjacent the opening 83. A trough 89 is also provided, which is supported by the framework 56 and is intended to carry off the float product.

Both compartments 26 and 27 are provided with flexible guards 92 which are mounted at 93 on brackets 94 fixed to the framework 56. The guards 92 extend below the liquid level to prevent floated light material from reaching the lifters 42 as they are rotated and becoming trapped therein, and their flexible character allows passage of large chunks of heavy sink material carried by the lifters. Similarly, the screen 72 or the outer portion thereof may be of flexible or yielding construction to allow passage of large chunks of sink material.

The separator 10 operates as follows: The drum 11 is rotated at a suitable speed and as it rotates the material to be separated or classified is supplied continuously at 51 to the inlet trough 50. A suitable fluid medium is supplied through the pipe 65 to the trough 50, and at the same time fluid medium of a different density is supplied through the pipes 80 and 87 to the transfer trough 69 and the discharge trough 69a respectively. The simultaneous delivery of the medium and material produces the best results as such feed tends to eliminate rafting and insures the immersion of all particles.

Fluid medium and the solid charge will pass down the trough 50 into the first compartment 26. The lighter material, which may be the tailings, as in the case of iron ore, or the mineral value as in the case of coal, will float to the surface of the medium and will overflow with the medium through the port 36 and the trough 62. The heavier or sink material will sink to the bottom of the com partment to be picked up by the lifters 42. The lifters will carry the sink material upwards and, once a body of such material has been lifted above the level 54, it will be free to drain through the louvers 46. The drainings will fall back into the main body of medium and the drained solid material will be dumped onto the screen 72, where further drainage occurs as it slides into the transfer trough 69. Medium introduced through the pipe 80 will flush the drained material into the second compartment 27, and will serve as the separating medium in that compartment. A middlings product will float and will overflow the bottom edge of the outlet port 38 into the middlings trough 89. The heaviest fraction will be lifted, drained and dumped into the discharge trough 69a in the manner described hereinabove with reference to the transfer trough 69. Medium introduced through the supply pipe 87 will flush the heavy fraction out through the trough 69a and its outlet 86.

As described in greater detail hereinafter with reference to the flow sheets, a lighter medium, e. g. a medium having a specific gravity of 2.9 will ordinarily be used in the first compartment 26, and a heavier, e. g. 3.2 gravity medium will be employed in the second compartment 27. ltwill be apparent that by this means a lightest fraction will be separated in the first compartment and both a heaviest fraction and a middlings fraction will be separated in the second compartment.

Certain particular process adaptations and advantages of this type of structure and this mode of operation will be described hereinafter with reference to the flow sheets. At this point, however, it may be pointed out that the apparatus of Figures 1 to 5 and the mode of operation described above, achieve a triple fractionation, produce a middlings product which may be further processed to recover values, and achieve a considerable economy in number of units, construction costs and space required for plant structure and associated apparatus.

Referring now to Figure 6, a coal treating plant is there illustrated comprising two distinct separating drums in series. This plant is intended for treating a low grade of coal containing, say, 46% ash. A feed of such material, crushed to -4 inches, 4 inch and washed to eliminate the fines, is supplied through a conduit to a drum separator 101. Fluid separating medium having a gravity of 1.50 is supplied through a conduit 162. The drum is illustrated diagrammatically and has an inlet trough 103. Float material and medium leave through a trough 104 and are screened at 105 to separate the float material from the medium. The medium, of course, is returned to the separator 101. The separated float material is carried off through a conduit 106 and it constitutes a clean coal fraction containing, in a typical case, about 7% ash and accounting for about 44% of the charge.

Sink material containing the heavy refuse is discharged through a trough 107 and is drained on a screen 108. The drained sink materialthen passes through a conduit 109 to the inlet trough 110 of a second drum separator 111. Medium having a gravity of 1.80 is supplied to the drum separator 111 through a conduit 115. Float 85 terial or middlings product is separated in the separator 111 and is discharged through a trough 116 to a screen 117 to separate the medium. The drained middlings then pass to a second, coarser screen 118, e. g., a 1 inch screen, for size separation into a 1 inch fraction and a +1 inch fraction. Sink material is removed through a trough 119 to a screen 120 for separating the medium and the drained sink material or heavy fraction is removed through a conduit or conveyor 121. This heavy fraction, in a typical case, will consist of 87% ash and will account for 47% of the charge to the plant.

The 1 inch middlings fraction is removed through a conduit 122 and will, in a typical case, contain about ash and account for 9% of the charge. This fraction may be sent to refuse, combined with the clean coal, burned in the plant boiler or subjected to further beneficiation treatment.

The +1 inch middlings fraction is removed through a conduit 123 and conveyed to a crusher 124 to crush it to 1 inch size. The crushed material is then returned through a conduit 125 to the first separator 101.

Referring now to Figure 7 of the drawings, which is a simplified, pictorial flow sheet, a high ash content coal is indicated at 130 and it comprises particles of relatively pure coal 130a, particles of refuse 13% and particles of middlings 1300. This coal is introduced into the drum separator 101 which floats a product consisting of clean coal 130a and sinks a product consisting of refuse 13011 and middlings 1300. The combined refuse and middlings, i. e., the sink product from separator 101, is transferred to the second drum separator 111 which floats a true middlings product 1300 and sinks refuse 13%. The

middlings product is then transferred to the screen 118 which separates a fine fraction, e. g., 1 inch, indicated as 131 from a coarse fraction e. g., +1 inch indicated as 132. The fine middlings 131 may go to refuse or for further processing or other utilization, and the coarse middlings 132 are sent to the crusher 124 to crush it to 1 inch particles and, as illustrated, a large proportion of the coal which had been associated with gangue material is liberated by the crushing. On return of the crushed material to the system, this liberated coal value will be separated and recovered as clean coal.

It will be understood, of course, that the pictorial representation of Figure 7 is simplified, and that the product of the crusher 124- will itself consist of relatively pure coal, relatively pure refuse and middlings. Nevertheless, the crushing step will liberate a substantial amount of coal, which can be refloated and added to the clean coal output of the plant.

Referring now to Figure 8, a high ash content coal r crushed to -4 inch, 75 inch size, is introduced into the circuit at 135 and into the inlet trough 136 of a double or two stage drum separator 137 which may be similar to that shown in Figures 1 to 5. The drum s'eparator 137 is provided with first and second compartments 138 and 139 which are supplied with fluid separating media having specific gravities of 1.5 and 1.8, respectively. The first compartment 138 separates a float product constituting clean coal containing, say, 7% ash. The float product is removed through a trough 140, medium is separated by a screen 141 and the separated, clean coal is removed at 142. The second compartment separates a sink product constituting the refuse containing, say, 87% ash. This sink product is removed through a trough 143 and is screened at 144 to recover medium, and the separated, drained refuse is removed at 145. A middlings product is floated by the second compartment 139 and is removed through a trough 146. 'It is then screened at 147 to separate and recover the fluid medium and it is then passed over a coarser screen 148 to classify the middlings into a 1 inch fraction, which is removed at 149, and a +1 inch fraction, which is conveyed through a conduit 150 into a crusher 151 which crushes the material to 1 inch and returns it to the circuit, as illustrated. The fine middlings product removed at 149, which may contain about 25 ash, may be sent to refuse, subjected to further treatment, or otherwise disposed of. It may, for example, be used as boiler fuel at the mine where the coal is being processed.

The system illustrated at Figure 8 accomplishes thesame results as that illustrated in Figure 6. It will be apparent, however, that fewer units are required, that the medium drainage screen 108 of Figure 6 is eliminated, and that a considerable saving of space is accomplished by employing a double or two-stage separator such as that shown'at 137.

Referring now to Figure 9, there is shown, diagrammatically, a plant layout or circuit such as presently used for treating iron ore. Iron ore crushed to, say, 2 inch, Az size is screened on a screen to classlfy 1t 1nto a --V2 inch, 4 inch fraction and a 2 inch, /2 inch fraction. The finer fraction is introduced into the inlet trough 161 of a drum separator 162 or other suitable separatory vessel. The drum separator 162 is supplied with a fluid separating medium having a specific gravity of 2.90. The float product is removed through a trough 163 and is treated on a screen 164 to separate and recover the fluid medium. A tailings product containing, in a typical case, about 16% iron is removed through a conduit 165. The sink product is removed from the drum separator 162 through a trough 166 and is treated on a screen 167 to separate and recover fluid medium. A concentrate containing, in a typical case, about 54% iron is removed through a conduit 168.

The coarse fraction from the screen 160 is introduced into a second drum separator 162a, which is operated in parallel to the first separator 162, and is supplied with a fluid separating medium having a specific gravity of 3.20. The float product is removed through a trough 169 and is treated on a screen 170 to separate and recover fluid medium. The separated tailings product, containing in a typical case about 28% iron, is joined with that from the screen 164 to produce a combined tailings product containing, say, 22% iron. The sink material from the drum separator 162a is removed through a trough 171 and is treated on a screen 172 to separate and recover fluid separating medium. The separated, coarse sink material is removed through a conduit 173 and is joined with the sink product or concentrate from the separator 162. In a typical case the concentrate from separator 162a will contain about 51% iron, and the combined concentrates will contain about 52% iron.

Referring now to Figure 10, a similar iron ore is supplied to the circuit there illustrated. It is introduced through the inlet trough of a double drum separator 181 having a first compartment 182 and a second compartment 183. These compartments are supplied with fluid media having specific gravities of 2.90 and 3.20, respectively. The float product from the first compartment 182 is removed through a trough 184 and is treated on a screen 185 to separate and recover fluid medium. Separated tailings product is removed through a conduit 186. This tailings product, in a typical case, will contain about 16% iron. Sink material is removed from the second compartment 183 through a trough 187 and is treated on a screen 188 to separate and recover fluid medium and produce a concentrate which is removed at 189. A middlings product is floated by the second compartment 183 and is removed through a trough 190 to a screen 191 to separate and recover fluid medium. The separated middlings product is then screened on a onehalf inch screen 192 to separate coarse middlings fraction and a fine middlings fraction. The fine middlings fraction is joined with the concentrate from the screen 188 to produce a combined concentrate, which, in a typical case, may contain about 52% iron. The coarse middlings fraction is removed at 193 and, in a typical case, it will contain about 36% iron. It may be crushed to liberate the iron value and then subjected to gravity separation.

In addition to a simplification of plant layout as compared to that of Figure 9, the circuit of Figure 10 has certain other definite advantages which indicate the advance the present invention'has produced. It will be observed that the only screening, other than the screening to recover the media, is at 192. At that point, only the middlings product is treated, and this constitutes only a fraction of the total charge. By Way of contrast, all of the charge must be screened in the circuit of Figure 9. Also, the circuit of Figure 9 produces only two products, i. e., a tailings product containing, in a typical case, about 22% iron and a concentrate. The circuit of Figure 10 produces three products, i. e., a concentrate, a tailings product and a middlings product. The latter contains, in a typical case, about 36% iron and can be re-worked to recover a substantial part of the iron value, whereas the tailings of.Figure 9 cannot be re-worked economically. The tailings of Figure 10 contain only 16% iron in a typical case. Thus, a greater recovery is effected by the circuit of Figure 10, less screening of material is required, and the plant layout is generally reduced in size and greatly simplified for operation.

By way of further explanation, the circuit of Figure 9 represents current practice and development. It employs, in fact, two parallel circuits, one for the fines and one for the coarse fraction. This has been considered necessary, because the denser, hence more viscous medium employed to sink the coarse iron particles, would be too viscous to sink the fine iron particles. Thus, it is generally considered that fine particles of hematite having a specific gravity of about 5.0, would float in a viscous medium of specific gravity 3.20. Accordingly, these fines are separated by screening, and are sunk in a lighter, less viscous medium of specific gravity 2.90.

In the present invention this limited approach to the result desired has become unimportant and unnecessary. By employing two separators in series, preferably a double drum separator, screening the middlings to separate any very fine iron particles which may have sunk in the first separator and floated in the second separator. and joining the screened fines with the coarse concentrate, such considerations of the prior practice are eliminated while at the same time producing a greater and better yield.

Thus far it has been assumed that it is desirable to effect a three-fold gravity separation of the ore by first floating the light fraction and sinking a mixture of the heavy fraction and middlings, then floating the middlings and sinking the light fraction. done; it is the preferred procedure and involves the simplest equipment. However, it is entirely feasible to sink the heavy fraction and float a mixture of the light fraction and rniddlings in the first stage, then sink the middlings and float the light fraction.

This may be done, for example, with the equipment shown in Figure 11. Referring thereto, a double drum separator 200 is there shown comprising first and second compartments 201 and 202, respectively, separated by a divider 203 having a relatively small axial opening 204. An inlet trough 205 is provided for the first compartment 201 and an outlet trough 206 is also provided which, as illustrated, discharges through an end opening 207 instead of discharging into the second compartment 202. Lifters 208 are provided which are solid and bucket-like so that they do not drain and will dump their content, including the medium, into the trough 206. Scoops 209 are provided adjacent the opening 204 which lift the float material as the drum rotates. These scoops are perforated to drain the medium from the float material, and as each scoop reaches the top of its circular travel it dumps the drained float material into a trough 215 which transfers the float material into the second compartment 202. A lower gravity medium is supplied to the second compartment to float the light fraction, which overflows an opening 216. Conventional lifters 217 lift and drain the sink material or middling product and dump it into an outlet trough 218.

In operation, a higher gravity medium (e. g., 3.20) is introduced by suitable means (not shown) into the first compartment 201 and the charge of solid material, such as iron ore, is introduced through the trough 205. In the case of iron ore, the iron concentrate is removed, together with medium, through the trough 206 and is drained to recover the medium which, of course, is recycled. The combined middling product and tailings are floated in the first compartment 201 and are transferred to the second compartment 202 by means of the scoops 209 and trough 215. This compartment is supplied with a lower gravity medium (e. g., 2.90). Separation of the middling product and tailings is elfected in the second compartment by floating the tailings and sinking the middling product.

It will thus be apparent that a novel and very successful type of separating equipment, certain novel circuits and a novel mode of operation have been provided, which represent marked improvements in the art, the advantages of which have been described hereinabove.

We claim:

1. A separating device of the character described, comprising a drum rotatable about a horizontal axis, means dividing said drum into a plurality of co-axially arranged, intercommunicating compartments, including an inlet compartment at one end and an, outlet'compartment at the other end of said drum, outlet means for said inlet Ordinarily this Will be all) compartment and outlet means for said outlet compartmentfor overflow of fluid separating medium and separated solid material floated by said medium, lifter means in each compartment for lifting sunken, heavy material, transfer means in each said compartment except said outlet compartment for receiving lifted heavy material and transfering it to the next compartment, and outlet means for receiving lifted heavy material in said outlet compartment and discharging it from said drum.

2. In a drum separator of the character described, comprising a rotatable drum having an inlet end and an outlet end, and also having an outlet for overflow of fluid separating medium and light material floated thereby, lifter means for lifting sunken heavy material to separate the same from said medium and light material, and outlet means for receiving and discharging separated. lifted heavy material, the improvement which comprises means for effecting separation of material having an intermediate density, comprising divider means dividing said drum into axially arranged compartments, and transfer means for receiving separated, sunken material in each forward compartment and transferring the same to the next compartment.

3. A separating device of the character described, comprising a drum rotatable about a horizontal axis, means dividing said drum into first and second, co-axially arranged compartments, outlet means for each compartment for overflow of fluid medium and separated solid material floated by said medium, lifter means in each compartment for lifting sunken, heavy material, transfer means for receiving lifted heavy material in said first compartment and transferring it to said second compartment, and outlet means for receiving lifted heavy material in said second compartment and discharging it from the drum.

4. A separating device of the character described comprising a drum rotatable about a horizontal axis, means dividing said drum into first and second, co-axially arranged compartments, lifter means in said first compartment for lifting a sunken heavy fraction together with fluid separating medium and dumping it into a discharge trough, a discharge trough for receiving the dumped heavy fraction and medium and discharging it from the drum, lifter and transfer means for lifting floated material in said first compartment, draining it and transferring it to said second compartment, lifter means in said second compartment for lifting a sunken intermediate fraction and dumping it into a discharge trough, a discharge trough for receiving the dumped intermediate fraction and discharging it from the drum, and overflow means for overflow of medium and a floated light fraction from said second compartment.

5 A separating device of the character described, comprising a drum rotatable about a horizontal axis, means dividing the drum into first and second, coaxially arranged compartments, outlet means for each compartment for overflow of fluid medium and separated solid material floated by said medium, perforated lifter means in each compartment for lifting sunken heavy material, trans fer means for receiving lifted heavy material in said first compartment and transferring it to said second compartment, and outlet means for receiving lifted heavy material in said second compartment and discharging it from the drum.

6. A separating device of the character described, comprising a drum open at both ends and mounted for rotation about a horizontal axis, a central transverse partition dividing said drum into first and second compartments, said partition having a central opening intercommunicating said first and second compartments, lifters in each of said compartments for lifting sunken solid material, means for supplying solid material and fluid separating medium to said first compartment, outlet means for receiving overflow of medium and a light fraction of solid material from said first compartment, a transfer trough having a receiving portion in said first compartment for receiving lifted solid material, extending through said central opening and discharging into said second compartment, a discharge trough for discharging a heavy fraction, said discharge trough having a receiving portion in said second compartment for receiving lifted solid material, and outlet means for receiving overflow of medium and an intermediate fraction.

.7. A separating. device of the character described, com- I prising a base, roller means mounted thereon, a drum carried by said roller means for rotation about a horizontal axis, said drum being open at both ends, means for rotating said drum about said axis, a transverse partition dividing said drum into first and second compartments, said partition having a central opening therein intercommunicating said compartments, radially disposed, perforated lifters in each said compartment for lifting sunken solid material, a transfer trough having a V-shaped inlet portion disposed within said first compartment for receiving solid material lifted by said lifters, said transfer trough extending through said central opening and discharging into said second compartment, a discharge trough having a V- shaped inlet portion disposed within said second compartment and projecting through the open end of said compartment for discharging a heavy fraction, a tailings outlet for receiving overflow from said first compartment of medium and a light fraction, and a middlings outlet for receiving overflow from said second compartment of medium and an intermediate fraction.

8. A separating device of the character described, comprising a drum open at both ends and mounted for rotation about a horizontal axis, a transverse partition dividing said drum into first and second compartments and having a central opening, radial, perforated lifters within each compartment for lifting sunken material from the bottom of the compartment and raising it to the upper portion thereof, a tailings outlet for said first compartment for receiving overflow of medium and a light fraction floating therein, a stationary feed trough for receiving material to be separated and medium for discharging the same into first compartment, a stationary transfer trough having an inlet portion disposed within said first compartment for receiving separated solid material from said lifters, said trough extending through said central opening and discharging into said second compartment, a stationary discharge trough having an inlet portion disposed within said second compartment for receiving a separated heavy fraction from said lifters, said trough extending through the open end of said compartment for discharging finished concentrate, means for supplying medium to said transfer trough and discharge trough, and a middlings outlet for receiving overflow of medium and a product of intermediate density floated therein.

9. A separating device of the character described, comprising a drum open at both ends and mounted for rotation about a horizontal axis, a transverse partition dividing said drum into first and second compartments and having a central opening, radial, perforated lifters within each compartment for lifting sunken material from the bottom of the compartmet and raising it to the upper portion thereof, a tailings outlet for said first compartment for receiving overflow of medium and a light fraction floating therein, a stationary feed trough for receiving material to be separated and medium and for discharging the same into said first compartment, a stationary transfer trough having an inlet portion disposed within said first compartment for receiving separated solid material from said lifters, said inlet portion having a perforated wall allowing drainage of said solid material, said trough extending through said central opening and discharging into said second compartment, a stationary discharge trough having an inlet portion disposed within said second compartment for receiving a separated heavy fraction from said lifters, said inlet portion having a perforated wall allowing drainage of said solid material, said trough extending trough the open end of said compartment for discharging finished concentrate, means for supplying medium to said transfer trough and discharge trough, and a middlings outlet for receiving overflow of medium and a product of intermediate density floated therein.

10. A separating device of the character described comprising a drum rotatable about a substantially horizontal axis; means dividing the drum into first and second, axially arranged compartments to confine a body of fluid in each compartment without interchange of fluid between the compartments; separate means for each compartment for overflow of float material therefrom; lifter means within each compartment operable, by rotation of the drum, to lift sink material therein; transfer means for transferring lifted sink material from said first compartment to said second compartment; and means for separately removing lifted sink material from said second compartment.

References Cited in the file of this patent UNITED STATES PATENTS Re. 16,674 Chance July 12, 1927 Re. 17,873 Chance Nov. 18, 1930 515,542 Webb Feb. 27, 18.94 653,340 Elmore July 10, 1900 1,887,239 Hanson Nov. 8, 1932 2,203,601 Rakowsky June 4, 1940 2,373,635 Wuensch Apr. 10, 1945 2,426,398 Lathrop Aug. 26, 1947 2,429,436 Walker Oct. 21, 1947 2,482,747 Davis Sept. 27, 1949 2,486,682 Ridley Nov. 1, 1949 2,487,845 Bird Nov. 15, 1949 2,496,703 Ekborn Feb. 7, 1950 2,516,962 Davis Aug. 1, 1950 2,521,152 Davis Sept. 5, 1950 2,563,332 Hebbard Aug. 7, 1951 FOREIGN PATENTS 33,861 Netherlands May 15, 1934 584,504 Great Britain Jan. 16, 1947 OTHER REFERENCES Quarterly of the Colorado School of Mines, vol. 43, No. 1, January 1948, page 84.

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