US2241392A - Electrical amalgamating apparatus - Google Patents

Description

May 13, 1941. H. D. BROWN ELECTRICAL AMALGAMATING APPARATUS Filed Dec. 13. 1938 2 Sheets-Sheet 1 Harry 1?. Brown.

May 13, 1941. H. D. BROWN ELECTRICAL AMALGAMATING APPARATUS 2 Shets-Sheet 2 Filed Dec. 13, 1958 [III/anion Bra wn.

Patented May 13, 1941 UNITED STATES PATENT OFFICE ELECTRICAL AMALGAMATING APPARATUS Application December 13, 1938, Serial No. 245,402

6 Claims.

This invention relates generally to electrical processes and apparatus for amalgamating metals, such as gold and silver, the general ob-.

ject of the invention being to provide an electrical process and apparatus whereby metals which are difficul-t of recovery by previously known-processes may readily be amalgamated.

The process in accordance with the present invention consists of two Stages, in the first of which the liquid is subjected to a high frequency discharge, which effectively cleans any gold which is coated or rusty and thereby prepares it for ready and efficient amalgamation, and in the second of which the pulp liquid is forced under pressure through a succession of mercury baths while being subjected to the infiuence of a direct electrical current. In a preferred and advantageous arrangement, the positive side of the source of electrical current is connected to the mercury baths, while the negative ide is connected to an electrode located in the pulp stream flowing toward the mercury bath. Under these conditions, due apparently to the positive charge on the mercury baths, the mercury is prevented from fiouring with small particles of mercury carried along by the liquid stream, such as otherwise invariably occurs to some extent. The gold and silver, or other metals, carried by the pulp stream are amalgamated in passing through the mercury pools,

and suitable traps are provided for accumulating the amalgam so produced.

With this preliminary description, the complete invention will be more fully understood by now referring to the following detailed description of a typical exemplification thereof, reference for this purpose being had to the accompanying diagrammatic drawings, in which:

Fig. 1 is a schematic view showing diagrammatically one form of apparatus in accordance with the invention;

Fig. 2 is a detail taken as indicated by line 2-2 of Fig. 1;

Fig. 3 is a section taken on line 3--3 of Fig. 2;

Fig. 4 is a detail taken on line 44 of Fig. 1;

Fig. 5 is a detail taken on line 55 of Fig. 4;

Fig. 6 is an enlarged detail taken as indicated by line 6-4 of Fi 1;

Fig. 7 is a section on line of Fig; 6; and

Fig. 8 is a section on line 8--8 of Fig. 6.

In the drawings-numeral l0 designates generally an agitation and preliminary treatment tank, which in the present instance is of insulation material, such as wood, to which the aqueous pulp liquid is introduced by a supply line H.

Any suitable means is provided for agitating the pulp liquid within tank H]; as here shown, I diagrammatically indicate for this purpose a set of paddles l2 mounted on a shaft l3 rotated through pulleys H by means of a belt |5- driven in any suitable manner. Tank I0 preferably has a conical lower portion, as indicated, and leading from its lowerend is a pipe line l6 controlled by a valve H. A pipe line I8 is used to introduce a solution of salt and water to the pulp liquid to increase its electrical conductivity.

A batch of aqueous pulp liquid, with its suspended ore and metallic particles, is delivered to agitation tank Ill, valve I! being closed. A suitable quantity of salt solution is introduced by way of line I8, and it may be stated, without intention of limiting the invention, that fifty pounds of salt (NaCl) per ton of pulp liquid has been found suitable. This salt solution has the effect of increasing the electrical conductivity of the liquid. The salt so introduced becomes dissociated, increasing the electrical conductivity of the solution, and greatly promoting cleansing of the gold or other values desired to be recovered. The presence of sodium in the pulp liquid is also beneficial in that it actsas a catalyst in the mercury amalgamation process, substantially increasing the efiiciency of recovery. While the pulp liquid and salt solution are being agitated within tank It], the mixture is subjected to a rapid succession of high frequency electrical discharges.

A typical and preferred circuit and apparatus for producing the aforementioned high frequency discharge is indicated in the drawings. A source of commercial frequency alternating current, which may, for example, be at 440 volts A. C., is indicated at 20, and connected across this source is the primary winding 20a of a high tension transformer T. The high tension secondary 2| of transformer T has output leads 22 and 23, acrosswhich is connected a condenser 24. Connected across conductors 22 and 23 are leads 25 and 26 going to terminals 21 and 28, respectively, of a rotary spark gap interrupter device generally designated at 30. This device 30, as here diagrammatically indicated, may comprise, typically, an insulation disk 3| mounted on a shaft 32 driven by a synchronous electric motor 33, disk 3| having mounted on its periphery a pair of electrically conductive spark gap elements 35, 38 (see Fig. 2). These ele-- ments 35 and 35, each of which subtends sub stantially of disk 3|, are mounted in diametric opposition on disk 3|, and spark gap tersimilar insulation disks 38 and 39, provided with peripheral conductive rings 40 and 4| (see Figs; 4 and the latter being connected to spark gap elements 35 and 36 by means of electrical conductors 42 and 43, respectively. Brushes 45 and 46 contacting said conductive rings 40 and 4| have connected thereto leads 4'5 and 48 which are connected one to paddle wheel shaft 13 and the other to electrode members 49 within tank 16. As here illustratively shown, these electrode members 49 are mounted on the sides of tank [0, and consist of bars spaced around the inside of the tank. Electrical connection between lead 41 and paddle wheel shaft [3 may be accomplished, for example, through the bearings for said shaft. The outer ends of paddles 12 are spaced from electrode bars 49 a distance proper to provide a discharge gap therebetween; in one actual case, a separation distance of approximately six inches has proved effective.

Motor 33 is a synchronous motor, and is shown as supplied with electrical current by means of ,1eads'50 and 5| connected across supply mains 20. Transformer T is typically one having a sec- ,ondary voltage of approximately 22,500 volts. In the present illustrative form of the invention,

disk 30 is driven at a number of revolutions per second equal to the frequency or cycles per second of the alternating current flowing in supply mains 20. For example, assuming 60 cycle current in mains 20, disk 30 will rotate at 3600 R. P. M. Disk 30 isso placed on motor shaft 32 that each time a discharge occurs from circuit 22, 23, elements 35 and 36 will just be coming opposite spark gap terminals 21 and 28, so

that spark discharges take place in the two gaps then formed. In particular, disk 30 is so placed on motor shaft 32 thatwhen a charge has been built up. to maximum in condenser 24 (at the peak of the half-cycle of the supply current), conductive elements 35 and 36 will then come opposite spark gap terminals 21 and 28, permitting spark discharges in the gaps between said terminals and rotating elements 35 and 36.

This discharge may take place through 90 of rotation of the disk, when elements 35 and 36 separatefrom terminals 21 and 28, allowing the charge on condenser 24 to be built up in the opposite direction during the next quarter cycle of the supply current. Conductive elements 35 and 36 then again pass under the spark gap terminals, permitting the condenser to discharge and to produce sparks in the gaps between the spark gap terminals and the rotating conductive elements, as before.

It will be evident that a rapid periodic succession of oscillatory high frequency discharges take place to conductive elements 35 and 36 on rotating disk 3|, and that there discharges will be applied, through the previously described circuiting, across rotating paddle wheel structure l2, l3, which serves as a central electrode, and

electrode elements 49. High frequency discharges occur between the paddles and electrode bars 49 as the paddles pass the latter. The pulp liquid within tank In is thus subjected to the influence of this succession of high frequency discharges while structure l2, 13 is rotated. The described treatment results in effectively cleaning any coated or rusty gold or silver, and if the material delivered from agitation tank is carefully examined, following the treatment described above, it will be found that the gold, silver or other metals present are in a highly polished condition. This is a very great advantage, since coatings such as iron oxide, which are frequently present, and which are readily removed by the present process, are quite resistant to amalgamation of the underlying metals. This cleaning action is apparently due to a differential action of the electrical current, or

electrical field established, on the gold or other values and its contaminating coating of iron oxide or other substances. That is to say, the different substances tend to be transported through the liquid with different forces, or at different speeds, which causes them to become separated. I do not limit my invention to this explanation, since it is difficult to ascertain precisely what occurs, but I believe this theory accounts for the fact, which I hadobserved in practice, that an electrical discharge through the pulp liquid removes contaminating coatings from the metallic values, and that this action is promoted and increased in the presence of a salt, such as NaCl. I further believe that the sodium and chlorine ions act both independently of and in conjunction with the electrical current or field to clean away the contaminating coatings.

The amalgamating system proper consists, in a present illustrative form, of a sinuous conduit 60 connected at one end to agitator discharge line !6, and discharging at its other end to a final collector vessel 6|.

As typically shown in the drawings, the lower end of line I6 is coupled to the upper end of the first of a series of vertical, down-flow tubes 62, which are of some suitable insulation material, such as Lucite. The lower end of each such tubes 62 is coupled to one leg of a U-shaped tube 63, preferably metallic, the other leg of which is coupled to a vertical up-flow tube 64. It is not necessary that up-fiow tubes 64 be of electrical insulation material, though it is convenient and preferable to make them of the same material as is used for down-flow tubes 62. Each up-fiow tube 64, except the last in the series,-is connected to the next down-flow tube by means of an inverted U-shaped tube 65.

The upper end of the last up-flow tube 64a is connected by line 61 to a pipe 68 extending downwardly from the lower end of conical collector vessel 6|, the lower end of vessel 6! being preferably at approximatelythe elevation of U- members 63. A Valve 69 is placed in line 61, and a gate valve 10 is placed in pipe 68 below the point of connection of line 67, as indicated.

Each of lower U-members 63 is formed on its underside with a depression or trap 12, below which is an outlet 13 controlled by a gate valve 14. Above trap 12, on the upper side of the U- tube, is an opening 75 closed by a removable plug 16.

Each upper, inverted U-tube is formed on its underside with a depression or trap 18, the lower end of which is adapted 'to discharge through gate valve"), to a tube'BO. This tube 80, which may also conveniently be formed of material such as Lucite, has at its lower end a gate valve 8|.

A quantity of mercury 85 is placed in each of U-members 63, except the last one in the series, and normally rises in each leg thereof to such an elevation as indicated by dotted lines 86. An electrode structure 8'! is disposed within each of down-flow tubes 62, and it may be stated, without intention of limiting the invention, that this electrode structure may typically be positioned approximately eight inches up from the lower end of tube 62. Electrode structure 81 as here typically and diagrammatically indicated, may comprise a plurality of carbon electrode members 88 projecting through the wall of tube 62 and into the liquid stream travelling therethrough, the outer ends of said members being electrically connected to a conductive ring 89 encircling said tube. A source of direct current 953, typically of 110 volts, is connected across electrode rings 89 and U- members 63; as here diagrammatically indicated, the negative pole of said source of direct current has branch leads 9! connected to electrode rings 89, while the positive side of said source of direct current is grounded, and each of U-members 63 is grounded, as indicated at 92. The positive pole of source 93 might, of course, simply be connected directly to members 63, instead of grounding.

It will be evident that a down-flow tube 62, a U-tube 63, an up-flow tube 64, and an inverted U-tube 65, with the appurtenances thereof, constitute a single section or unit of the system, and that any number of such sections may be employed, as required. I prefer to employ a series of approximately from three to live of such sections, followed by a final section in which the electrode structure 81 and mercury pool are omitted. Fig. 1 shows a break in the series of sec- 1 tions, and it will be understood that any required number of sections may be employed. This will depend upon the degree of final recovery aimed for, as well as upon the characteristics of the material to be treated, i. e., whether the metals of the particular ore are readily recovered, or are comparatively resistant to recovery.

Collector vessel BI is provided with a plurality of inverted conical bafiie plates 94, in the spaced, concentric arrangement indicated, these plates 94 being silver plated and coated with mercury. Preferably, the plates are formed of copper, which may readily be silver plated, and then coated with mercury. The liquid discharged upwardly into the lower end of vessel 6| flows around and through baffle plates 94, finally overflowing the upper edge of vessel 5| and being received by a launder 95.

The operation of agitator i9, and the effect on the metals within the agitator produced by the high frequency discharge, have previously been described. Agitator It] is located at a suflicient elevation above conduit to to provide a hydrostatic head suitable for the process. Without intention of limiting the invention, I may state that a dimension of 16 ft. from the upper end of tubes 62 to the top of tank It) has been found suitable when using tubes 62 of 52 in. in length.

When the pulp liquid has had suificient treatment within agitator tank I 0 to clean the metals effectively, valve 11 is opened and the liquid allowed to flow by way of line It through the system of tubes 52, 64, etc; The liquid stream passing under pressure through mercury bath 85 forces the mercury up somewhat in the outgoing leg of U-tube 63 and tube c4, as illustrated. The 7 mercury is prevented from being substantially floured and carried along with the pulp stream, however, owing to the attractive influence of the positively charged U-tube 63. The mercury being in contact with tube 63 is itself positively charged, or at a positive potential with reference to electrode elements 88, and under the conditions described, is held back against the travelling pulp stream. It is principally for this reason that the mercury pool is preferably, or in most cases, given a positive polarity, with electrodes 88 at negative polarity; however, I do not limit myself to this arrangement,'as some metals may be more readily recovered with a negative polarity at the mercury pool and positive polarity at electrodes 83, and where there is over-all advantage in use of that arrangement of polarities, notwithstanding some greater degree of fiouring and loss of the mercury, that arrangement will preferably be employed.

The pulp stream thus flows through the mercury bath, rises in tube 64, passes through inverted U-tube 65, and then descends through second down-flow tube 62 to the second mercury bath, and so on. The salt solution in the pulp liquid permits a substantial electrical current flow through the liquid passing through the lower portion of tube 62 and through U-tube 63, and the sodium present acts as a catalyst to mercury amalgamation of the carried metals.

The electrical current flow longitudinally of the liquid stream (from electrodes 88 to mercury pool results in rapid effective amalgamation of the previously cleaned or scoured metals carried by the pulp stream as they pass through the mercury bath. As a further factor, hereinabove mentioned, the presence of the sodium hastens treatment; the result noted may be due to any one or a combination of the following: cleaning of the metals, increase in electrical conductivity, and catalytic action of the sodium.

The amalgam which is produced is partly collected by trap 12, and partly carried upwardly through up-flow tube 64 by the rising pulp stream. A portion of this latter amalgam is collected by trap 18 at the bottom of inverted 'U- tube 65, while some of the amalgam passes over to descend in second down-flow tube 62. Further amalgamation occurs as the pulp liquid passes through the mercury bath in subsequent U-tubes 63, the amalgam so produced being collected by the several traps T2 and I8.

Deposition of amalgam, or concentrate, in upper traps 78 is promoted by a release or drop of pressure which occurs at these points in the sinuous conduit. The metal particles, having taken on mercury, are heavy enough to drop out of the liquid stream at these points and are thus collected. This condition (release of pressure at the upper bends of the conduit, with consequent deposition of heavy material in traps 18) occurs when the pressure in the system is suflicient toraise the mercury in the lower traps in the manner described, and a proper amount of mercury is used in the lower U-tubes. It may here be mentioned that the bulk of the material accumulated in upper traps I8 is found to consist, not of a true amalgam, but of a concentrate of mercury and metals,from which the metals are immediately released. I believe this to be explainable as follows: Some of the suspended gold, or other valuable metal, passing byele'ctrodes 88 and coming in contact with a negative charge and continuing on through a positively charged solution of mercury, picks up positively charged mercury atoms, giving it weight of sufii- .cient amount that it will sink at the first opportunity, which it doesupon passing over upper traps 18, where the concentrate is found to be deposited. f

As mentioned previously, no mercury is employed in the last trap 12 of the series. The upfiow tube 640. leading from this last trap 12 contains a series of vertically, spaced collector boxes I20, tube 64a being, in practice, broken into a number of short tube sections l2l, as indicated. Boxes. I20 are flanged, as indicated at I22, and coupling means of any suitable type, such as indicated at I23, is employed to connect the ends of tube sections I21 to these box flanges. Each box,l20 is open at one side and adapted to receive a series of parallel, sloping baflle plates I25, which are mounted on and extend horizontally from a removable gasketed closure plate I21 for the open side of the box. Bailie plates are formed of some such material as copper, and are silver plated and then coated with an amalgam of sodium and mercury. Their surfaces as thu prepared have an affinity for the metals and amalgam still carried by the liquid stream,

' which collects on said plates and may be recovered by removing them and scraping from time to time.

The liquid then passes by Way of line 61 to final collector vessel 61, through which it rises around and between conical baflle plates 94. These plates 94, which as previously explained are mercury-coated, catch and throw down a large partof any amalgam which has been carried ofi by way of discharge line 61, which material finally settles into trap 68, while the rising liquid is discharged by way of launder 95. It will of course be understood that the mercury coating on plates 94 creates an affinity for the amalgamated metal particles rising within vessel 6|, with the result that the larger proportion of such metals carried by the liquid rising within vessel 6| is caught by said baffle plate, where it clings until the accumulation is sufiicient to drop and be received by trap 68.

The amalgam accumulated within traps 12 is removed from time to time by opening gate valves '14 and allowing it to discharge at 13. The amalgam accumulated within upper traps 18 may be permitted to' drop into tubes 80 by operation of valves 19, and is discharged from tubes 80 by opening valves 8!. The amalgam accumulated on bafile plates 125 is recovered from time to time as described above.

The process as described has been successfully employed in the amalgamation of ore which has been rejected by previously known processes. The high frequency treatment employed in the first stage of the process cleans and prepares the metals for effective amalgamation; the materials thus prepared are passed, under pressure, through successive mercury baths, under the electrical current conditions described, with the result that amalgam in substantial quantities is deposited, the recovery being substantially greater than With any prior process of which I am aware.

I claim:

1. An amalgamator comprising an insulation down-flow tube, a U-tube having one leg connected to the lower end of said down-flow tube, an up-flow tube connected at its lower end to the other leg of said U-tube, a pool of mercury in said U-tube, an electrode extending inside said insulation down-flow tube, a source of direct current, and means connecting opposite poles of said source across said electrode and said mercury pool.

2. An amalgamator comprising an insulation down-flow tube, a U-tube having one leg connected to the lower end of said down-flow tube, an up-fiow tube connected at its lower end to the other end of said U-tube, a pocket formed on the underside of said U-tube, a valve-controlled discharge opening leading from said pocket, a pool of mercury in said U-tube, an electrode extending inside said insulation down-flow tube, a source of direct current, and means connecting the poles of said source across said electrode and said mercury pool.

3. An amalgamator comprising an insulation down-flow tube, a U-tube having one leg connected to the lower end of said down-flow tube, an up-fiow tube connected at its lower end to the other leg of said U-tube, an inverted U-tube having one leg connected to the upper end of said up-flow tube, a pocket formed on the underside of said U-tube, a valve-controlled discharge opening leading from said pocket, a pocket formed on the underside of said inverted U-tube, a. valve controlled discharge opening leading from said pocket, 2. pool of mercury in said U-tube, an electrode extending inside said insulation down-flow tube, a source of direct current, and means connecting the poles of said source across said electrode and said mercury pool.

4. An electrical amalgamating system embodying a sinuous conduit comprising a succession of insulation down-flow tube sections, a succession of up-flow tube sections and connections joining corresponding ends of the up-flow and down-flow tube sections to form said sinuous conduit, mercury pools in the connections between the lower ends of said tube sections, an electrode inside each of said insulation down-flow tubes, and means for maintaining a difierence of electrical potential between said electrodes and said mercury pools.

5. An amalgamator comprising a down-flow tube, a U-tube having one leg connected to the lower end of said down-flow tube, an up-fiow tube connected at its lower end to the other leg of said U-tube, a pool of mercury in said U-tube, an electrode contacting the liquid stream in the tubes at a point ahead of said mercury pool, said tubes including a section of insulation between said electrode and said mercury pool, a source of direct current, and means connecting opposite poles of said source across said electrode and said mercury pool.

6. An amalgamator comprising an insulation down-flow tube, a U-tube having one leg connected to the lower end of said down-flow tube, an insulation up-flow tube connected at its lower end to the other leg of said U-tube, an inverted U-tube having one leg connected to the upper end of said insulation up-fiow tube, a pool of mercury in said first-mentioned U-tube, an electrode extending inside said insulation down-flow tube, a source of direct current, and means connecting opposite poles of said source across said electrode and said mercury pool.

HARRY D. BROWN.

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