US2128313A - Method and apparatus for recovering metal values - Google Patents

Description

Aug. 30, 1938. E. B. MYERS 2,128,313

METHOD AND APPARATUS FOR RECOVERING METAL VALUES Original Filed March 12, 1935 2 Sheets-Sheet 1.

Aug. 30, 1938. E. B. MYERS 2,128,313

METHOD AND APPARATUS FOR RECOVERING METAL VALUES original Filed March 12, 1955 2 sheets-sheet 22l I? /J as i .4 l v 34 1N VENTOR.

I In" Patented Aug. 3i), 1938 UNITED STATES METHOD AND APPARATUS FOR RECOVER- ING METAL VALUES Elman B. Myers, Montreal, Quebec, Canada, as-

signor to Myers Mill Corporation, Montreal, Quebec, Canada, a corporation of Quebec, Canada Application March 12, 1935, Serial No. 10,652 Renewed July 15, 1938 15. Claims.

My present invention relates generally to metallurgy, and has particular reference to a new method and apparatus for recovering gold, silver, platinum, and other metal values from ore.

The present method and apparatus is fundamentally of the amalgamation type, the metal values being recovered from the ore by causing an amalgamation thereof with mercury, and a subsequent separation of the same from the mercury.

It is a general object of my invention to provide a method and apparatus which is of greatly simplil'led character, entirely feasible and practical, and involving an unusually small expense in cost of equipment and in operating costs. For example, an apparatus constructed in accordance with my present invention can be made to operate on an entirely practical and commercial scale at a cost as low as 22o per ton of ore, and within an area of such compactness that no more than fifteen feet separate the point at which raw ore is introduced and the point at which the gold or other metal values are recovered.

My invention is characterized by a procedure which involves colloidizing the ore in a liquid dis- 25 persion medium, percolating the ore through a body of mercury, and exerting upon the tailings a maintained, high-voltage, electrolytic pressure toward the mercury. In a preferred method and apparatus, the foregoing procedural steps are coupled with a continuous subjection of the mercury to a rehabilitation which puries the mercury and separates out the metal values that are sought.

The successful accomplishment of the present objectives relies in part upon the special manner in which the ore is colloidized; the manner in which it is percolated through the mercury; the manner in which the electrolytic pressure is exerted; and, in part, upon the proper correlation of these individual procedures` For example, I

have found it to be highly important that the ore be reduced to truly colloidal form, as distinguished from the mere suspensions which are frequently loosely referred to as being colloidal. It is important that the ore be colloidized by a method and machine which involves abrasion, and which produces colloidal particles no larger than approximately one micron.

While it is possible that other methods or apparatus may be employed for thus colloidizing the ore, I have found the present desirable results to be best accomplished by the use of a colloid mill of the flexible rotor type described and claimed by me in my earlier application Serial Number 301,804, filed August 24, 1928 (presently to issue as Patent Number 1,995,549). My present invention is, however, not limited to any specific method or means for colloidization, as long as the individual particles are of a size less than one micron. It is to be understood, therefore, that the present invention is not limited to the employment of any specific type of colloid mill; but it is also to be understood that the term colloid as used herein and in the appended claims is intended to refer to an attenuation of particles to the colloidal size mentioned.

One of the features of my invention lies in causing the ore (colloidized, as hereinbefore mentioned) to percolate through a body of mercury, preferably to percolate upwardly through a coli umn of mercury. It is an important characteristic of the invention to provide a means for accomplishing the percolation in such a manner as to conduce toward amalgamation of the mercury with the colloidal particles of the metal that is sought to be recovered. Thus, it is a feature of my invention to provide a column of mercury of suflicient height to effect a material retardation upon the percolation procedure, and to impose a substantial static pressure upon the individual colloidal particles that are passing through the column.

It is a further feature to provide a special means for further retarding the percolation by means of perforated balfles or the like; and it is a further feature to provide an arrangement for guiding the percolation toward the margin of the column of mercury, thereby reducing any tendency of the mercury to flour.

A further characterizing feature of the present invention lies in the steady and maintained imposition, upon the colloidal particles in the tailings, of a high-voltage, electrolytic pressure in the direction of the mercury. This may be accomplished, for example, by connecting the high-v Voltage terminal of a suitable source of direct current to the tailings, and connecting the lowvoltage terminal of said source to the mercury column. It is important that the voltage be of the order of at least one thousand volts, and preferably substantially higher, say, for example, three thousand volts; and it is to be understood that the term high-voltage as used herein and in the appended claims is intended to refer to voltages in this category. 'Ihe effect of the electrolytic pressure is akin to the phenomena that are involved in electroplating, whereby those colloidal particles of metal which Ahave escaped amalgamation are caused to migrate rearwardly toward and into the mercury, and hence into recoverable combination With the mercury. In a sense, the electrolytic pressure constitutes a further means for retarding the percolating flow of the dispersed phase, thereby further conducing toward amalgamation.

One of the features of the invention, contributing toward the commercial feasibility of the invention, lies in the continuous procedure whereby a fixed quantity of mercury may be used and reused. The mercury is continuously Withdrawn from the column, subjected to a treatment which puries it and separates out the metal values, and returned to the column. More particularly, the mercury is subjected to a continuous distillation under vacuum.

From certain aspects, the continuous method of distilling the mercury is by itself a new and useful contribution to the art, independent of the method whereby the mercury has become amalgamated with the metal that is sought to be recovered.

The advantages and characterizing features of the present invention will be more fully appreciated after this specication has been read, and it is pertinent to point out that amalgamation processes of the ordinary type have heretofore been of almost prohibitive expense, both as to installation cost and operating cost, sometimes involving apparatus requiring an area of sixteen hundred feet or more between the introduction of ore and the actual metal recovery.

I achieve the foregoing objects, and such other objects as may hereinafter appear or be pointed out, in the manner illustratively exemplified in the accompanying drawings, wherein- Figure 1 is a diagrammatic representation, or ow sheet, of the present method and apparatus;

Figure 2 is an enlarged, longitudinal, crosssectional View through the mercury column and associated parts; and

Figure 3 is an enlarged, cross-sectional view through the retort in which the mercury is distilled.

The ore having been suitably crushed or otherwise mechanically reduced to a granular form capable of passing through a 10G-mesh screen, and having been intermixed with a liquid, preferably ordinary water, in the proportion of approximately one-thirdv solid to two-thirds liquid, it is introduced into a hopper I0 which feeds the raw suspension into an agitating tank II. A'

turbulator or agitator I2 is continuously driven by a motor I3 to prevent sedimentation. This mixture is then passed downwardly and continuously into and through a colloid mill I4, driven by a motor I 5, and preferably of the type illustrated and described in my aforementioned patent application. This mill is of a character which successfully, reliably, and continuously subjects the solid particles. to an abrasion suicient to reduce the ore to a truly colloidal state in which the particles have a size less than one micron.

The discharge from the colloid mill passes through a conduit I6 into a second agitating tank II in which an agitator I8 operates. Additional liquid may, if desired, be added at this` point, or acidulating chemicals or other aids or ingredients may be added at this point, if desired.

The colloidal solution passes thence through a pump I9, which is the instrumentality for forming a flowing stream of the ore and passing the stream upwardly through a column of mercury. More particularly, the stream is directed upwardly through the loop 2B, and thence into the bottom of a steel, cup-shaped member 2l. The latter supports the cylindrical glass tube 22 in which the column of mercury 23 is accommodated. At the top, the tube 22 carries the steel cap 24 which communicates with the rubber tubing 25. For a reason presently to be pointed out, the tubing 25 is of considerable length, and for the sake of compactness it is wound into spiral form, as shown at 26, the liquid stream ultimately emanating from the outlet 21.

That portion of the stream above the column of mercury has been referred to in the appended claims as the tailings; and it will be understood that the stream is at this stage ready to be discarded, with most of the metal values recovered. However, in the event that additional metal values or metal salts, such as tellurides or the like, are still unrecovered, it will be understood that the stream need not necessarily be discarded from the outlet 21 but may be subjected to further treatment, if desired.

In accordance with my invention, the lower portion of the member 2| (see Figure 2) carries a disc 28 composed of metal and having a multiplicity of ne, longitudinal openings therein. For the sake of explaining the general nature of the apparatus, but without intending to limit the invention to any specic dimensions, I will mention the fact that the disc 28 may, for example, be of approximately four-inch diameter, with approximately two hundred fty holes or perforations therein, each approximately one-eighth inch in diameter. With such a disc, the glass tube 22 might be, for example, approximately four and one-half feet long, and about ten inches in diameter; the distance between the disc` 28 and the mercury level 29 might be approximately thirty-two inches.

Carried by the disc 28 is the vertically extending rod 3i), and carried by the latter is the upwardly divergent, conical deflector 3|, and the substantially transverse, disc- like baiiies 32 and 33. Each of the latter baiiies is provided kwith a plurality of holes, approximately two hundred, each about one-eighth inch in diameter. Near the lower end cf the conical deflector 3l are a few openings 3d through which the mercury may be drained, when necessary.

In accordance with my invention, the deflector 3l has its peripheral edge closely adjacent to the wall of the tube 22, the clearance being preferably no greater. than about one-fourth of an inch. The peripheries of the baffles 32 and 33 are similarly arranged close to the tube 22. The result is that the flowing stream of ore is divided by the disc 28 into a multiplicity of capillary streams which enter upwardly into the mercury column and which are then deflected, as shown by the arrows of Figure 2, toward the margin of the mercury column. These fine streams` then percolate upwardly through the mercury, and while most of the percolation is directed toward the margin of the column, it is not prevented from disseminating itself, generally, throughout the mercury. The baiiies 32 and 33 have a retarding eITect upon the percolation, and they also serve to minimize turbulation of the mercury. If there is any turbulation of too great a magnitude, there is a tendency for the mercury to our.

During the upward passage of the stream through the mercury, the colloidal particles are admirably conditioned for amalgamation with the mercury, and this, in fact, takes place with remarkable reliability and to a substantial degree. At the top, the reunited stream continues its upward flow and ultimately leaves through the outlet 2l.

In accordance with my invention, the tailings are impressed with a maintained electrolytic pressure tending to cause a migration of colloidal particles downwardly toward the mercury. 'I'his is accomplished by providing any suitable source of high-voltage, direct current, designated generally by the reference numeral 35; connecting the high-voltage terminal by the lead 36 to the lsteel cap 24; and either connecting the low-voltage terminal 31 to the ground, as indicated, or establishing a direct connection with the metal member 2|, and hence with the'mercury itself. One satisfactory source of current consists, for example, -of a standard full-wave rectier and lter equipment, such as that which is used in supplying the direct current for broadcasting stations, the equipment having a capability of producing up to about thirty-ve hundred volts and supplying a current at that voltage of about two and one-half amperes.

The normal or articial acidity of the ore stream permits the circuit to be completed through the tailings back to the mercury, and, in eifect, a sort of electroplating action takes place whereby metal particles that have escaped amalgamation are thrown downwardly onto and into the mercury, there tobe given another chance at combining with the mercury. The distance between the level of the mercury 29 and the point of application of the high-voltage potential is approximately thirty-six inches, this having been found to -beabcut the right distance to maintain the impressed voltage at, say, three thousand volts. The electrical connection is facilitated by the arrangement ofa steel or metallic disc 38 in the lower portion of the cap 24, this disc having holes therein and constituting what may be termed an anode screen. The holes in the disc 38 are relatively large.

Because of the high potential that is impressed upon the stream at the screen 38, the conduit or tube 25 is rather extended in length, as hereinbefore referred to, so that a negligible and harmless voltage remains at the outlet end, the objective being obviously to cause the current to flow not toward the outlet end 2l, but through the path of lesser resistance, i. e., toward the mercury 23.

In accordance with my invention, an outlet spigot 39 connects with the member 2l at the base of the mercury column, whereby the mercury is permitted continuously to dribble into the funnel 4B, thence downwardly through the U tube 4|, and into the retort 42. Since the interior of the retort is subjected to a continuous vacuum, the U tube 4l has a length of at least thirty-two inches, so that there is always a quantity of mercury in the inlet arm of this tube.

The retort 42 may be of any suitable character and is preferably of pot-shape, as shown in Figure 3, with a removable cover 43 and a removable, cup-shaped lining 44 composed'of silica or the like. The retort is mounted in a furnace 45 heated, for example, by means of an oilburner 42, the furnace being adequate to heat the retort to approximately 500 C. 'Ihis is amply suflicient, under the continuous vacuum, to boil the mercury; and the mercury vapors leave the retort through the outlet 41 and pass downwardly through the condenser 48. The latter has the usual inlet and outlet openings 49 for cooling uid such as water. The condensed liquid mercury dribbles into the container 5l] which is direct connected, as at 5i, with any suitable vacuum pump 52, the exhaust of which is shown at 53. It is this pump which maintains the distillation at a continuous vacuum. y

Emanating from the lower end of the chamber 50 is the stand pipe 54, at least thirty-two inches long, and having its lower end immersed in a receptacle 5.5. The mercury in the tube 54 a1- ways stands at about twenty-nine and one-half inches because of the atmospheric pressure upon the-surface 56 of the mercury in the receptacle 55. An overflow outlet pipe 51 communicates with a pump 58, which in turn continuously returns thepuried mercury back into the column through the conduit 59. r

`It will thus be seen that the mercury is continuously withdrawn from the column; subjected to a rcontinuous distillation under vacuum; and returned in purified condition to the mercury column. At the same time, the metal that has been -amalgamated with the mercury is separated out in the retort 42, inasmuch as the temperatures there developed are insufficient to boil off the metal.' The result is that the mercury, constituting a xed quantity, and excepting only such small amounts as may be required'for makeup purposes, is used and reused and isv kept in a continuously pure condition, admirably suited for amalgamation with the colloidal metal particles percolating through it.

-The metal which is sought to be recovered collects in a sort of sponge-like mass at the bottom of the lining 44 in the retort 42. While the quantity will vary, depending upon the particular ore, and the size of the apparatus, mercury column, Voltage, etc., I will state merely by way of example that an apparatus ofthe approximate dimensionsherein specied has a capacity of approximately twenty-four tons of ore per day, and that as much as sixty ounces of gold have been successfully recovered, in the form of a spongy mass in the lining 44, at the expiration of a three-day operating period. This amount of recovery isa truly remarkable accomplishment when it is borne in mind that the cost of operating the present apparatus is as low as 2`2 per ton, and that a distance no greater than fifteen feet is required between the hopper l0 (at which the raw ore is deposited) and the retort 42 (in which the valuable metal is recovered).

It will be understood that the present drawings are merely illustrative. If desired, the column of Vmercury may be made longer and wider, provided that suicient strength is imparted `to thevessel which holds it. It hasbeen found satisfactory to employ a series of mercury columns in-parallel. Also, the voltages may be varied to suit requirements, and numerousrother details may be altered or modied under dif,- erent operating conditions.

In general, it will be understood that changes in the details, herein described and illustrated for the purpose vof explaining in the nature ofmy invention, may be lmade by those skilled in the art without departing from the spirit and scope of n.

the invention as expressed in the appended claims. It is, therefore, intended that these details be interpreted as illustrative, and not in a limiting sense.

Having thus described my invention, and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

l. In the herein described ore-recovery process, the steps which consist in colloidizing the ore in a liquid medium, percolating it through a body of mercury, and exerting upon the tailings a continuous, high-voltage, electrolytic pressure toward the mercury, said high voltage being in thc range between approximately 1000 and 3000 vo-ts.

2. In the herein described ore-recovery process, the steps which consist in colloidizing the ore in a liquid medium, percolating it through a body of mercury, exerting upon the tailings a continuous,

mercury, said high voltage being in the range between approximately 1000 and 3000 volts, and continuously distilling the mercury to purify it and to recover the metal amalgamated therewith.

3. In the herein described ore-recovery process, the steps which consist in colloidizing the ore in a liquid medium, percolating it through a'body of mercury, retarding the percolation to prevent louring of the mercury and to conduce toward amalgamation, and exerting upon the tailings a continuous, high-voltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts.

4. In the herein described ore-recovery process,

I the steps which consist in colloidizing the ore in a liquid medium, percolating it upwardly through a column of mercury, guiding the percolation toward the margin of the mercury columnto prevent flouring, and exerting upon the tailings a continuous, high-voltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts.

5. In the herein described ore-recovery process, the steps which consist in colloidizing the ore in a liquid medium, percolating it upwardly through a column of mercury, guiding the percolation toward the margin of the mercury column to prevent ouring, retarding the percolation to conduce toward amalgamation, and exerting upon the tailings a continuous, high-voltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts.

6. In the herein described ore-recovery process, the steps which consist in forming a owing stream composed of the ore oolloidized in a liquid medium, passing the stream upwardly through a column of mercury, and impressing upon the stream as it leaves the mercury a maintained high electric potential relative to the mercury, said high electric potential being in the range between approximately 1000 and 3000 volts.

7. In the herein described ore-recovery process, the steps which consist in forming a owing stream composed of the ore colloidized in a liquid medium, dividing the stream into a multiplicity of capillary streams and causing the latter to percolate upwardly through a column of mercury, and impressing upon the reunited stream as it leaves the mercury a maintained high electric potential relative to the mercury, said high electric potential being in the range between approximately 1000 and 3000 volts.

8. In the herein described ore-recovery process, the steps which consist in forming a flowing stream composed of the ore colloidized in a liquid medium, passing the stream upwardly through a column of mercury, impressing upon the stream as it leaves the mercury a maintainedhigh electric potential relative to the mercury, said high electric potential being in the range between approximately 1000 and 3000 volts, and continuously withdrawing the mercury from said column, subjecting it to distillation to separate it from the metal amalgamated therewith, and returning it in purified form to the column.

9. In ore-recovery apparatus of the character described, a column of mercury, means for colloidizing the ore in a liquid medium, means for percolating it through said mercury, and means for exerting upon the tailings a continuous, highvoltage, electrolytic pressure toward the mercury,

said high voltage being in the range between approximately 1000 and 3000 volts.

10. In ore-recovery apparatus of the character described, a column of mercury,v means for co1- loidizing the ore in a liquid medium, means for percolating it through said mercury, and means for exerting upon the tailings a continuous, highvoltage, electrolytic pressure toward the mercury; said last-named means comprising an insulating vessel for the mercury, a source of highvoltage, direct current, said high voltage being in` the range between approximately 1000 and 3000 volts and means for connecting the tailings and the mercury to the high and low terminals of said current source, respectively.

11. In ore-recovery apparatus of the character described, a column of mercury, means for colloidizing the ore in a liquid medium, means for percolating it through said mercury, means for exerting upon the tailings a continuous, highvoltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts and apparatus for continuously distilling the mercury to purify it and to recover the metal amalgamated therewith.

12. In ore-recovery apparatus of the character described,` a column of mercury, means for colloidizing the ore in a liquid medium, means for percolating it through said mercury, means for exerting upon the tailings a continuous, highvoltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts, and apparatus for continuously withdrawing the mercury from said column, subjecting it to distillation under vacuum, and returning it in purified condition to said column.

13. In ore-recovery apparatus of the character described, a column of mercury, means for colloidizing the ore in a liquid medium, means for percolating it through said mercury, means for exerting upon the tailings a continuous, highvoltage, electrolytic pressure towardl the mercury, said high voltage being in the range between approximately 1000 and 3000 volts, and means for retarding the percolation to prevent flouring of the mercury and to conduce toward amalgamation.

14. In ore-recovery apparatus of the character described, a column of mercury, means for colloidizing the ore in a liquid medium, means for percolating it through said mercury, means for exerting upon the tailings a continuous,.highvoltage, electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts, and means for retar-ding the percolation to prevent ouring of the mercury and to conduce towardv amalgamation; said last-named means comprising spaced, perforated bales arranged transversely across the mercury column.

15. In ore-recovery apparatus of the character described, a column of mercury, means for colloi-dizing the ore in a liquid medium, means for percolating it through said mercury, means` for exerting upon the tailings a continuous, high- Voltage electrolytic pressure toward the mercury, said high voltage being in the range between approximately 1000 and 3000 volts and deflecting means at the bottom of the mercury column for guiding the entering ore toward the margin of the column so as to prevent flouring.

ELMAN B. MYERS.

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