US3550869A - Method and apparatus for grinding and separating precious metals - Google Patents

Description

United States Patent [72] Inventor Maurice Sterling Carter P.0. Box 325, Murphys, Calif. 95247 [21] Appl. No. 739,705

I 22] Filed June 25, 1968 [45] Patented Dec. 29, 1970 [54] METHOD AND APPARATUS FOR GRINDING AND SEPARATING PRECIOUS METALS 8 Claims, 9 Drawing Figs.

[52] U.S. Cl. 241/20, 241/79.] 209/15. 209/182, 209/188 [51] Int. Cl B02c l/00, B03d H00 [50] Field of Search 209/15, 43,

Primary Examiner-Frank W. Lutter Assistant Examiner-Robert Halper Auarney--Schapp and Hatch ABSTRACT: A method and apparatus for separating precious metals by amalgamation and by selective flotation and sinking in mercury comprising a container for holding mercury and mineral bearing slurry together with means for directing the mineral bearing slurry below the mercury level in the container and agitating the mineral bearing slurry within the mercury to improve intimate contact of mercury and amalgamable material. One form of the invention calls for a partially cylindrical container having transverse paddles rotatably mounted from an axis of the cylindrical container, with the container formed to hold a mercury level therewithin and receive mineral bearing slurry at one end; the slurry being directed downwardly through the mercury by the rotating paddles, agitated therein, and moved toward exit points at the other end of the container by controlled flow where the treated slurry is withdrawn from the upper portion through a weir and where the amalgam and heavier than mercury values are withdrawn through the lower portion of the container by controlled removal therefrom. Another form of the invention comprises utilizing a potlike container having inclined bottom walls leading to a lowest point exit for removing amalgam and heavier than mercury values and an exit near the upper operating level of liquid for removing treated mineral bearing slurry, the feed for the mineral bearing slurry being effected through a vertical tubular member held for rotation and with its lower discharge end below the operating level of the mercury, a paddle carried on the lower discharge end of the tubular member and a screen held therein for effecting agitation of the mineral bearing ore within the mercury, said tubular member also being formed with a funnellike structure at the top and vanes for imparting rotary motion to the tubular member upon impingement of said vanes by the mineral bearing slurry entering at an incline. In another form, the mercury and slurry is pressurized to improve wetting and amalgamation. In its process form, one or a plurality of machines are used, and the mineral slurry is preferably preconditioned by heating and boiling in chemical water.

v PATENTEDnEc29|sm J 8550.869

SHEET 1 or 2 'INVENTOR MAURICE STERLING CAKTER BY I I ATTOEME Y5 METHOD AND APPARATUS FOR GRINDING AND SEPARATING PRECIOUS METALS BACKGROUND OF THE INVENTION The present invention relates to a METHOD AND AP- PARATUS FOR SEPARATING PRECIOUS METALS by amalgamation and/or by sinking in mercury, and more particularly to a method and apparatus which is designed to effect intimate contact between precious metals and mercury.

It is well known that gold and silverand certain other precious metals form amalgams with mercury while nonmetallic materials occurring naturally in nature do not. However, it is important to provide intimate contactwith the mercury and amalgamable material in order to neutralize the surface tensions and effect the desired amalgamation. Since the surface tension of mercury is such that contact is difficult, it is desirable to provide a method and apparatus in which the contact is improved. At the same time, it is important to provide an apparatus in which precious mercury is not lost or where losses are held to a minimum as well as to obtain efficient recovery of the precious metals from the minerals.

It is also well known that certain precious metals are heavier than mercury, and these/metals may be collected by selective flotation and sinking in mercury. For example, platinum, osmium, and iridium are heavier than mercury, and electrum is also heavier than mercury when it contains sufficient gold. However, it is important to break the surface tension between the heavier than mercury particles and the mercury in order to achieve the sinking of the heavy values. Mercury is also recovered in such processes by simply adding to the mercury present.

While certain machines have been used heretofore for carrying out the amalgamation process, these machines are capable of considerably improvement in providing the desired efficient recovery of amalgamable materials, mercury, and heavier than mercury values.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide a method and apparatus for separating precious metals by amalgamation and selective flotation in mercury in which a more intimate contact is provided'between the mercury and the mineral whereby a more efficient separation may be effected.

Another object of the present invention is to provide a method and apparatus of the character described in which a more intimate contact of mercury andmineral bearing ore is effected by mechanical means, mechanical motion due to heating, increase of pressure, and combinations thereof.

A further object of the invention is to provide an apparatus of the character described, which is relatively simple to construct and reliable in operation.

Still another object of the invention is the provision of a process providing improved contact between the amalgamable materials and mercury and a' moreeflicient recovery of same.

Further objects and advantages of the invention will be apparent as the specification progresses, and the new and useful features of the method and apparatus for separating precious metals will be fully defined in the claims attached hereto.

Briefly speaking, the apparatus for separating precious metals by amalgamation and selective flotation constructed according to the invention comprises a container for holding mercury and mineral bearing material, means for directing mineral bearing material into the container means and below the surface of mercury therein at one. location in the container, means for removing the treated mineralbearing slurry at a remote location from the entry position and from the upper portion of the container. and means'for removing the:

amalgam from the container at a position remote from the entry of mineral bearing material therefrom and at a lower portion of the container, holding means" for holding the mineral bearing material below the level of the mercury in the container, and agitating means cooperating with the holding means for agitating the mineral in the mercury to improved contact therebetween and effect efficient amalgamation of gold and other amalgamable values.

These elements may take various forms and yet achieve the desired functional operations. Thus the container means may be any general configuration capable of holding the mercury and ore slurry, while the other means providethe intimate contact therein desired. In one form, the container is an elongated cylindric section, adapted to contain a-level of mercury therein, and receive mineral bearing slurry from one end while discharging the treated mineral and slurry at the other end. The mercury may be added anywhere to the container but will also preferably be added at the intake end while the amalgam and heavier than mercury values are removed from a, lower portion of the container at the exit end.

With the container in this form, the means for directing the mineral bearing material to a level below the surface of the mercury comprises a plurality of elongated paddles adapted to rotate around the central axis of the cylinder with the ends of the paddles near the intake end adapted to carry the mineral bearing material below the level of the surface of the mercury. The paddles then operate after bringing the mineral below the surface of the mercury to cause agitation therein from the inlet end to the outlet end or throughout the length of the container. Thus in this form, the means for directing the mineral bearing slurry to a level below the surface of the mercury is integrally associated with a means for agitating the mineral in mercury to improve contact therebetween.

Contact may also be improved by utilizing ore slurry that has been preconditioned and/or by operating under pressure. Preconditioning may be achievedin any device equipped for agitation and heating. In a typical recovery process, one or more heating vessels will be provided in series followed by one or more amalgamation devices. It will be appreciated that these devices in each class may be the same or different, with the number of units and combinations desirable depending on the mineralmaterial treated.

In another form of the invention, the mineral b'earing slurry is directed below the surface of the mercury by entry through an elongated vertical tube terminating below the surface of the mercury, This tube is journaled for rotation and carries a funnellike receiving structure at the upper end thereof. It will be appreciated that the tube may be rotated by any means including a motor drive. However, for the sake of simple reliable operation this form of apparatus may be constructed with a paddle wheel effect' on the internal surface thereof whereby the slurry delivery stream impinges on vanes within a funnelshaped top and imparts rotation to the tubular member. The tubular member is formed with paddles at the slurry discharge end rotating with the tube and below the level, of mercury in the container. The holding means in this form for holding mineral bearing material below the surface takes the form of a screen located just above the paddles so as to'cooperate with the paddles in holding the mineral bearing material below the surface of the mercury while the same is being agitated.

The latter embodiment may be pressurized by enclosing the container or providing the same with a standpipe through which the tubular member extends so as to maintain the static head above the operating level for the amalgamation process.

It will be appreciated that the invention also embraces the the effluent before grinding by using a conventional amalgamation plate and trap.

of forming an aqueous slurry containing water and mineral bearing materials of say about minus 16 mesh, adding the slurry to mercury at a position below the upper level of the mercury, and agitat ing the slurry while in position below the upper levelof the mercury to neutralize the surface tensions and improve'the wetting of minerals by the mercury.

In 'a'preferred process, the slurry is preconditioned by heating in" water having its acidity adjusted and otherwise chemically treated, if desired, depending upon the particular mineral being processed. The slurry is then forced into a pool of mercury and below the upper level thereof as mentioned above in order to effect amalgamation of the minerals and float the unwanted ore to the surface of the mercury while collecting nonamalgamable but heavier than mercury precious materials below the mercury. At the same time, elemental mercury present in the slurry will add to the pool of mercury. After such treatment, the effluent slurry may be passed over an amalgam plate and trap, through a fine grinder, and back through another similar recovery process.

In a typical processing machine constructed to carry out this method, the slurry is fed below the surface of the mercury with the mercury and feed being maintained under an extra high external pressure in order to break the surface tensions and improve the amalgamation and separation by flotation. Mechanical diverter means may also be provided to assure random movements of ore particles as they pass upwardly through the mercury toward a floating position. Periodically, the amalgam and heavier than mercury values are drawn off and fresh mercury added, with the precious metals being recovered from the amalgam in the usual fashion.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred forms of the invention are illustrated in the accompanying drawings, forming a part of this description, in which:

FIG. Us a diagrammatic view illustrating a typical arrangement of a plurality of individual apparatus for separating precious metals by amalgamation and selective flotation in mercury indicating a total overall recovery operation utilizing various forms of the invention;

FIG. 2, a vertical sectional view of a portion of the apparatus shown in FIG. I substantially as seen in the plane of line 2-2 thereof;

FIG. 3, a vertical sectional view of another section of the apparatus shown in FIG. 1 taken substantially in the plane ofline 3-3 thereof; I

FIG. 4, a horizontal sectional view of the portion of the apparatus shown in FIG. I and 3 as seen substantially in the plane ofline 4-4 thereof;

FIG. 5, an enlarged front elevation of the apparatus disclosed in FIGS. 1, 3 and 4 with parts broken away to better illustrate internal parts;

FIG. 6, an enlarged front elevational view of another machine constructed according to the inventionand shown as a component of FIG. I; r

, FIG. 7, a horizontal sectional view of the apparatus shown in FIG. 6 taken substantially in the plane of line 7 7 thereof;

FIG. 8, another horizontal sectional view of the apparatus shown in FIG. 6 taken substantially in the plane of line 8-8 thereof; and

FIG. 9, an enlarged vertical sectional view of an alternate form of the invention that may be utilized in place of the apparatus shown in FIG. 6 and substituted therefor in FIG. I.

While only the preferred forms of the invention are shown and described, it should be understood that various changes or modifications may be made within the scope of the claims attached hereto without departing from the spirit of the invention.

DESCRIPTION OF THE PREFERREDEMBQDIMENTS Referring to the drawings in greater detail, there is shown in FIG. 1 a complete recovery system 11 comprising a preconditioning unit 12, and two forms of apparatus I3 and 14, each operable individually and illustrating a different embodiment of the invention, but arranged herein in tandemso that the ore processed by one machine is then-led to andproces'sed by the other machine. The preconditioning unit-.12 is designated herein as the Model B machine;thegiembodiment of the apparatus 13 is herein designated as the Model H machine;' and the embodiment of the apparatus I f is herein designated as the Model V machine. It will also be"'appreciated that an apparatus 16 is illustrated in FIG. 9 which is quite similar to the 1.

Referring more particularly to the Model-B machine or the preconditioning unit 12 illustrated in FIGS -l and 2,-- there is shown a half cylindrical container 17 formed-froma half se'ction of iron pipe or the like and equipped withend plates-=18 to complete closure of each end and provide legs such as the leg 19 for support. Between these end plates, angle irons 21 are provided to increase the support for the-container l7 and to increase the height of the vessel atthe sidesand to serve as splash plates. J ournaled through each of the end plates. .l8 is a horizontal shaft 22 carried in suitable bearings 23mg positioned in substantial axial alignement with the container 17. Fitting in telescoped relation over the-shaft 22, there is provided a hollow shaft or pipe 24, which is keyed to the shaft or otherwise secured for rotation therewith. 'A plurality of paddles 26 are attached by welding orat-he like to the pipe 24, with the paddles adapted to rotate in close clearance with the container 17. These paddles are formed of thin strips of metal with their flat faces perpendicular to the'axis of rotation. If desired, these paddles can be bent with pliers or the like into propeller shapes to increaseor'decrease' the flow of liquid from one end of the container to the other and assist in com trolling the flow.

At the outlet end of the container 17, a discharge paddle 27 is provided with the flat face of the paddle 27 being substantially coplanar with the axis of rotation of the'rotor. This paddle is somewhat wider than the paddles 24 and preferably formed to cooperate with the width of the discharge weir 28 with the flow going through the weir as indicated by arrow 29.

Suitable heating means 31 are provided for heating the lower surface of the container 17, and these heating means may take any conventional form suitable for the purpose. As here shown, two rows of gas burners 32 are provided for burning gas supplied in mixed condition'with air through fuel line 33. It will be appreciated that electric burners or oil burners could be used, if desired, but gas burners operating from bottle gas are excellent for field conditions. Since this apparatus is preferably made portable and usable in the field, the gas burners shown are preferred. T

The parts so far described in connection with FIG. 1 and 2, constitute the'basic conditioning unit, and the amalgam recovery system shown in the drawing is optional. In operation, minus 16 mesh or slurry or the like is added to the forward end of the unit as indicated by arrow 34. The material moveslongitudinally through the machine until it reaches the rear end where paddle 27 propels liquid up so that it discharges through the weir 28 as indicated by arrow 29. During the residence of the slurry within the preconditioning container, it is heated by the gas burners and conditioned in the usual fashion to render the mineral materials more easily amalgamable in the later machines.

Although only one preconditioning unit is shown in FIG. 1 of the drawing, itwill be appreciated that a plurality of such units may be provided with boiling agitation taking place in each unit or in all butthe first unit. Thus in a typical setup, three conditioning units are provided with the second unit being reversed so that its forward end received slurry from, the

discharge weir 28 of the machine shown, and then it in turn discharges into the forward end of the third machine positioned similarly to the unit 12 shown in FIG. 4. The third unit then discharges, into the apparatus 13 of FIG. 1. Accordingly, it will be appreciated that various numbers of units or various sized units may be provided, with the objective being to heat the slurry so that it discharges at a boiling temperature.

If desired, the preconditioning unit or Model B machine 12 may be utilized to effect preliminary amalgamation and separation by flotation in mercury. As here shown, the device is equipped with an outlet conduit 36 attached to a drain 37 at the lower end of the rear portion of the container 17. Conduit 36 is held by suitable holding means 38 which may provide fine adjustment of the mercury level 39 within container. From time to time, amalgam and heavier than mercury values are drawn out from conduit 36 by lowering the end thereof into a suitable collecting vessel until the desired amount of mercury, amalgam and any heavier than mercury materials present are removed. The conduit is then placed back into its holding position and fresh mercury added at the forward end of the container. Whether preliminary treatment with mercury is carried out in the Model B apparatus or not will depend upon theparticular mineral being processed and other considerations. In either event,the use of the preconditioning unit is within the ambit of the preferred form of the invention.

Referring more particularly to FIGS. 1, '3, 4 and 5 of the drawings, there is shown an apparatus-l3 or a Model H machine illustrated as the second stage of the system '11 .in FIG. 1. This apparatus 13 comprises a container 41 similarly constructed to the container 17 of the apparatus 12, and it has end plates 42 providing closures for the container and supporting legs 43, with the container being reinforced with angle irons 44. In this way, the substantially half cylindrical container is provided in horizontal orientation. I

Journaled through the end plates 42 is a horizontal shaft 46, with the shaft carrying a closed pipe section 47 secured thereto. The pipe section 47 has a plurality of paddles 48 extending longitudinally on the surface thereof and adaptedto fit closely within the annular space 49 defined between the container 41 and the pipe section 47.The apparatus l3'or Model H machine is adapted to receive feed material at one end as indicated by the arrow 29 in FlG.-l and discharge the treated feed material through a weir 51 atthe other end as indicated by arrow 50. Fresh mercury is added from the forward end and drawn out together with amalgams and any other heavy values from a lower portion of the rear end through drain 52 and plastic conduit 53. The plasticconduit 53 is held at the desired level by holding means 54, and is preferably constructed so as to show the level of mercury therein and serve as a level indicator.

It will be noted that the Model H machine is quite similar to the Model B machine except that it does not contain the heating means of the Model B machine and the rotor is constructed quite difierently. However, it will be appreciated that heating means can be added to the model l-l machine and boiling agitation also provided, if desired. As best seen in FIG. 3, the machine is adapted to be filled to the level 56 with mercury and this level will be high enough to contact the closed pipe section 47. With this construction, all of the slurry fed into the machine must be pushed through the mercury in immersed condition for a number of times as the rotor. is rotated.

will also be appreciated that the rotorwill not be moving very rapidly, and that the actual speed may be adjusted as desired according to conditions. I

Although no power source is shown-for the rotating shafts and associated rotors of the Model B and Model H machine, it will be appreciated that any conventional power source may be used. Preferably, the various rotating shafts will be geared together and driven from a single common motive source by conventional methods.

As mineral-bearing ore slurry is' .fed into the machine, treated and then ejected from the machine through weir 51, amalgamable materials will form amalgam in the mercury and heavier than mercury particles that do not amalgamate such as dirty gold" will settle. Since gold is quite a bit heavier than mercury, the gold amalgam will tend tosink toward the bottom together with any heavier than mercury materials that do not amalgamate. These materials will find their way out through the drain 52 and into the conduit 53 so that they can be removed periodically by drawing a portion of the mercury and the amalgam and heavy minerals from time to time. When this amalgam and associated materialiswithdraw, fresh mercury is added so as to maintain the level. In this way, the amalgam may be removed without interrupting the process or treating operation of the machine. v

In order to facilitate the step of drawing off the amalgam and other materiaL the machine may be tilted up to about 30 to the horizontal shaft position, first on one side and then the other. Tilting is also useful in washing the machines clean of substances after shutdown of operations. v

Referring again to the system shown in H6. 1, the effluent mineral slurry from the apparatus 13 is directed to a mercury plate 57 and trap 58 where any mercury that might be brought over the weir by entrainment or otherwisef'is caught. The mercury plate is a conventional amalgamation plate containing silver which picks up the mercury. Any small particles'not so amalgamated are caught in the trap where heavy particles tend to settle out, and complete the separation of mercury and heavy particles that may be in the'feed. The slurryis then passed into the fine grinder 59 where the material is ground so as to present fresh'surfaces for further amalgamation in the Model V apparatus 14.

Referring more particularly to F G..6, the apparatus 14 comprises a container 61, with the container having an inclined bottom wall 62 terminating in a drain 63 at the lowest portion thereof. A conduit 64 is connected to the drain and normally held with an open end above the container by'holding means 66. This conduit is preferably made of transparent plastic and adapted to be held at an adjusted level by the holdmaterials to prevent injury by the heating in thepreconditioning step.

The apparatus 14 or Model V machine also is formed with an open top at the upper portion thereof for removing treated mineral bearing slurry by overflow. If desired, a weir (not shown) may be provided so that the removal will take place in a specific position. The apparatus 14 also provides conduit Thus in operation, the preconditioned slurry enters the forward end of the machine after being conditioned in the apparatus 12. It is then pushed downwardly by paddles 48 into immersed condition in the mercury below the level 56 thereof.

As this mineral and slurry is pushed into the heavy mercury, it,

means 67 in the form of a vertical pipe and extending below the surface 68 of mercury held in container 61. The conduit means 67 is mounted for rotation and formed with a funnellike portion 69 at the upper end thereof for receiving mineral bear- 1 ing slurry. The slurry is directed againstvane 71 as indicated by arrow 72 from an inclined feed (see FIGS. l and 7) and this feed imparts rotation to the whole unit or funnel rotor through the water wheel effect. If desired, the funnellike structure can be rotated through a wheel73 powered through a belt system to any suitable power source (not shown).

At the bottom of the funn'ellike structure, a plurality of pad- 1 dles 74 are provided and these paddles have a screen 76 at the upper surface thereof. Wih this construction, mineral bearing aqueous slurry is discharged below the screen in the vicinity of the paddle and agitated outwardly through the mercury, while naled into upper bracket 78 and fitting into a dimple in the lower bracket 79 The funnel rotor is aligned with a central "rod through an inner bracket 81 and by fitting through a central opening in a rod 82 at the lower portion of the rotor. The rod 82 is weldedto the paddles 74, which in turn are fastened to the screen 76 and a ring 83 at the lower end of conduit "means 67. Just below the rod 82 is a bushing 84 which is spot welded to the shaft 77 and provides a support surface for the rod 82. In the construction shown, it will be appreciated that the entirefunnel rotor can rotate with respect to the shaft 77 and this shaft can rotate with respect to the fixed brackets. Since the friction is lowest at the contact of the shaft 77 in its lower bracket .79 (the bearing surface being lubricated by mercury), the tendency is for the shaft to rotate with the funnel rotor in total. In either event, the paddles 74 are rotated so as to direct the slurry delivered below the surface of the mercury in an outward direction to provide distribution and agitation thereof. r

In operatiomthe apparatus 14 collects amalgams and heavier than' mercury material which are recovered in the same manner as similar products from apparatus 13. The treated slurry passes out from the apparatus as indicated by arrows 86, arid since this is the last stage apparatus the slurry may be discarded. However, the slurry may be passed over anamalgamation plate to recover any entrained mercury (if desired).

r, In 9, an apparatus 16 is shown which is quite similar to the apparatus 14, but contains additional structures so as to provide amalgamation under increased pressure. As there shown, the apparatus comprises a container 61a having an inclined bottom wall 62a terminating in a drain 63a to which conduit means 64a is attached. The conduit means 64a is utilized for withdrawing amalgam and other minerals as in the embodiment of FIG. 6 serving the same function as conduit 64. The apparatus 16 also comprises a conduit means 67a extending below the surface of mercury 68a at its lower end and having a funnel rotor 75a including a funnellike structure 69a at the upper end. The funnellike structure 69a is equipped with vanes 71a for imparting rotation as in the embodiment of FIG. 6. Auxiliary drive wheel 73a is also provided if it is desired to impart rotation to the funnel rotor by external power sources. V

At the bottom of the conduit means 67a is a screen 760 and paddles 74a welded to the bottom through ring 83a and to bar or rod 820. The rod 82a rides on a bushing 840 which is welded to central shaft 770 providing for a vertical support of the funnel rotor75a. This shaft is aligned through an opening in bar 820, fits on lower bracket 79a and is held in central alignment through bracket 810.

SB far, all of these structures are equivalent to the structures shown'in FIG. 6 and operate in the same manner. However, it is noted that the container 610 has a cover 87 secured thereto through suitable fastening means with a sealing gasket 88 provided to maintain the unit against leakage. The cover 87 has a standpipe 89 so that fluid may be maintained in the space between the standpipe 89Iand the conduit means 670.

The feed slurry is withdrawn from the machine through a lateral outlet 91 which has a sloping bottom wall 92, and upwardly vertical portion or duct 93 having a pair of special baffles 94 therein. The lateral outlet terminates with an opening 96 through which tails are removed. The baffles 94 are similarly constructed and at right angles to each other along the vertical axis. Each baffle is formed in a laterally enlarged section of the vertical duct 93, which has a normally square cross section. As here shown, the duct is enlarged at each baffle by generally diamond shaped outer walls 97 and by conforming diamond shaped inner walls 98. The squares formed by inner walls 98 are open to the air, and the baffles serve to split the rising stream of slurry twice. o

It will be observed in FIG, 9 that the conduit means 67a is threaded into the funnellike constructions ,69jand that the standpipe is threaded at its upper end. 'This'allows for extensions so that a higher static head 'of 'waterirnay be used, if desired. By the same token, extensions maybeprovi'ded in the lateral outlet 91. It will also be observed that the embodiment of FIG. 6 can be converted t that of Pilot 9 by rei noval or plate 99, and addition of cover 87 and'lateral outlet 91. In reverse fashion, the embodiment of FIG. ,9 can beconverted to that ofFIG. 6. v,

In operation, the embodiment of FIG. 9 operates in the same manner as the embodiment of FIG. 6, except that external pressure is applied. This is achieved by adjusting the level of the mercury so that the level 68a will 'be depressed dow n just below the upper entry of lateral outlet 91 while lateral outlet 91 contains mercury up to a level of say 101 therein. Aqueous slurry inside the container 61a will then extend up into the standpipe 89 a-distance approximately I3.6 times the height of level 101 over level 681% so as to balance the static forces. Actually there will be an additional head in the standpipe to compensate for the water above level 101 to outlet 96 and the difference in mercury level 68a and the discharge level of mineral slurry below ring 83a; It is important to'adjust the amount of mercury in the-=container so that the mercury will go into lateral outlet 91 in this manner and support a rather high static head of water. In addition, it is important to have the mercury'level and the lateral outlet above both square baffles 94 so that an additional am algamating effect is-achieved as the mineral particles float upward in the mercury and strike each square baffle' 94. It will be observed that the lateral outlet 91 and the-baffles therein have sloping bottom walls so that any amalgam that forms in the lateral outlet will slide down the slant walls and along inclined bottom wall 62a of the container to the desired drain 63a. In this way, all of the amalgamations and heavier than mercury minerals find their way to the bottom of the container as desired. 3

' As indicated above, the J- Model is interchangeable with the V Model, with the J Model havingadditional'structure, but providing improved efficiency. The use of the J Model also facilitates control of tailings which may be advantageously passed over an amalgamation plate and trap to pick up any mercury that might otherwise be lost. o

From the foregoing description,.it is apparentthat various forms of apparatus are shown and that an'inte grated process is provided illustrating how these units may be brought together into a single recovery unit. However, it will be appreciated that various recovery units may be. provided with different combinations of apparatus, and that the preconditioning apparatusmay' be omitted in certain cases. In fact, anyone of the recovery Models H,-V and .l are satisfactory for achieving improved amalgamations and separation of heavier than mercury values when used alone. It is also seen that I have provided an'improved method and apparatus for separating precious metalsiby amalgamation and/or by theIsinking of the heavier than mercury values in mercury in which improved contact is provided between the mineral and mercury. In addition, a process is disclosedwhich provided for more complete recovery in a simple and economical portable unit. -I claim: t v v 1. An apparatus for separating preciousmetals by amalgamation and selective flotation-comprising:

an amalgamating and conditioning unit adapted to receive. mineral slurry at one end and deliver conditioned slurry which has been admixed with mercury at the other end;

an amalgam plate and trap unit positioned to receive ore slurry from the amalgamating and conditioning unit to remove mercury from the ore slurry;

a fine grinder positioned to receive ore slurry from the amalgam plate and trap unit and reduce said ore into finer particles; and r an amalgamating unit positioned to receive ore from'the fine grinder;

said amalgamating and conditioning unit comprising:

an elongated partially cylindrical container means suitable for holding mercury and formed for support with the cylindrical axis being substantially horizontal,

means for drawing mercury and amalgam and heavier than mercury materials from the bottom of the container at one end thereof;

means for directing mineral bearing slurry into the container means at the other end thereof;

a plurality of elongated paddles mounted for rotation around the axis of the cylindrical container and formed for moving in close relation to the partial cylindrical surface of the container for carrying mineral bearing slurry forcibly into and below the surface of mercury in the container and causing relative agitation as the slurry moves from the intake end toward the opposite end of the container; and means for removing the slurry from the upper portion of the container at the end opposite the means for directing mineral bearing slurry into the container where amalgam and heavier than mercury values are also removed; said containers being sufficiently elongated and the paddles formed in such a manner that each portion of the mineral bearing slurry is forced from the surface of the mercury a plurality of times as the slurry portion moves'from one end of the container to the other; and said amalgamating unit comprising:

container means for holding mercury at a controlled level and a mineral bearing slurry therein; said container being formed with aninclined bottom terminating in a restricted passage for removal of mercury amalgam and other heavy materials; means at a side of the container near the upper portion thereof for removing treated mineral bearing slurry; g conduit means extending below the surface of the mercury within said container and to a point above said container; said conduit means being mounted for rotation and adapted to carry mineral bearing slurry from an external position to a point below the mercury level in the container; paddle means associated with said tubular member and rotatable therewith for agitating mineral bearing slurry and pushing it from the central position of the container toward the peripheral portions of said container below the mercury level; and screen means located above and adjacent to the paddle means for maintaining mineral bearing materials below the surface of the mercury as it is worked from the central portion toward the periphery by the paddle means. I 2. A method of separating precious metals from mineral bearing ore comprising the following steps in the order given:

forming an aqueous slurry containing water and mineral bearing materials of say minus 16 mesh; adding the slurry to mercury held in a container at a position below the upper level thereof; heating the mercury and slurry to a temperature just below the boiling point of water; agitating the mercury and slurry and periodically allowing the slurry to float up on the mercury and bringing the slurry below the surface of the mercury a plurality of times during said agitation; removing the slurry from the container and passing it over an amalgamation plate to remove the last traces of mercury, grinding the mercury-free slurry with a fine grinder to reduce the ore size and expose fresh surfaces; adding the ground slurry to mercury in a container at a position below the upper level of the mercury; and agitating the slurry while in a position below the upper level of the mercury to improve the wetting of minerals by the mercury for more effective recovery "of said precious metals. 3. An apparatus for separating precious metals by amalgamation and selective flotation comprising:

container means for holding mercury at a controlled level and a mineral bearing slurry therein, said container being formed with an inclined bottom terminating in a restricted passage for removal of mercury amalgam and other heavy materials; means at a side of the container near the upper portion thereof for removing treated mineral bearing slurry;

conduit means extending below the surface of the mercury within said container and to a point above said container, said conduit means being mounted for rotation and adapted to carry mineral bearing slurry from an external position to a point below the mercury level in the container;

paddle means associated with said conduit means and rotatable therewith for agitating mineral bearing slurry andxpushing it from the central portion of the container toward theperipheral portions of said container below the mercury level;

screen means located above and adjacent to the paddle means for maintaining mineral bearing material below the surface of the mercury as'it is worked from the central portion toward the periphery by the paddle means; and said conduit means having a funnel-shaped configuration at the top equipped with vanes-whereby rotation of the tube may be effected by directing mineral bearing slurry against the vanes and down through the conduit means by gravity;

4. The apparatus defined in claim 3, in which said container means is equipped with a cover portion, and also has a standpipe surrounding said conduit means-whereby a static head of fluid may be maintained within the container and provide a positive pressurized contact between the mercury and mineral bearing slurry.

5. The apparatus defined in claim 4, in which a lateral outlet having an upwardly extending duct is provided and the container issealed and provided with sufficient mercury to extend above the lateral outlet whereby the static head of fluid in the standpipe is-equaled by the static head of mercury and other fluid in the upwardly extending duct.

6. The apparatus defined in claim 5, in which the lateral outlet has sloping bottom walls to allow heavier. than mercury material to drop into the container bottom and contains baffle means whereby ore moving through the upper portion of the lateral outlet and through the mercury in the upwardly exte nding duct is impeded in its flotation to increase residence time and agitation in the mercury.

7. The apparatus defined in claim 6, in which the baffle means comprises a pair of substantially square baffles each oriented with one of their diagonals substantially vertical and their planes being at substantially right angles to each other with one baffle being located above the other in the upwardly extending duct, said duct being split into two passages around each baffle whereby ore particles floating up through mercury in the duct will strike the underside of each baffle.

8. An apparatus for separating precious metals by amalgamation and selective flotation comprising:

an elongated partially cylindrical container means suitable for holding mercury and formed for support with the cylindrical axis being substantially horizontal;

means for drawing mercury and amalgam and heavier than mercury materials from the bottom of the container at one end thereof;

means for directing mineral bearing slurry into the container means at the other end thereof;

a plurality of elongated paddles mounted for rotation around the axis of the cylindrical container and formed for moving in close relation to the partial cylindrical surface of the container for carrying mineral bearing slurry forcibly into and below the surface of mercury in the container and causing relative agitation as the slurry moves from the intake end toward the opposite end of the contamer;

means for removing the slurry from the upper portion of the container at the end opposite the means for directing said plurality of elongated paddles including a plurality of rows of paddles and a plurality of paddles in each row with the paddle of each row disposed nearest said means for removing the flurry being formed substantially flat and defining a plane including said axis of the cylindrical container and the remaining paddles being formed with inclined surfaces for directing the slurry through the length of said container means.

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