US1451454A - Process and apparatus for recovery of precious metals - Google Patents

Description

Apr. 10, 1923. 1,451,454

F. A. BEAUCHAMP PROCESS AND APPARATUS FOR RECOVERY OF PRECIOUS METALS Fiied Au 4, 1920.

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To allwhomitmay come m:

Be it known that l, Ennunmcn A. BEAU- cHAMr, a British subject, residing at Berkeley in the county of Alameda and State of Ca 'fornia, have invented a new and useful Improvement in Process and Apparatus for Recovery of Precious Metdls, of which the following is a specification.

. This invention.relatestor the i'gover'y of precious metalsby amalgamation witli'mw he invention includes a novel recess and mium and what is known as rusty or coated gold, all of which are not amalgamable by simple contact with a pure mercury surface.

Althou h there are on record a few instances w ere the ore has been milled in a solution of cyanide and then successfully treated by! the amalgamation process consisting of passing the pulp of ground ore and c anide solutlon over amalgamated copper plates in the usual way, yet in most instances it has been found that unless very dilute cyanide solutions'are used in the rocess the amalgam on the plates is attacke by the cyanide solution, the gold being apparently dissolved and the mercury running ofi, leaving the plates bare, and thus rendering further amalgamation impossible. Even where a satisfactory amalgamation has been recorded as having been made in this way yet the copper plates have been found to be afiacked through the coating of amalgam, necessitating their frequent renewal.

Now it is in the case of most ores a desirable procedure to mill in a cyanide solution and in the case of many ores, especially those containing coarse free gold and metallic silver, it would be beneficial to remove such coarse and freemetal by amalgamation prior to the usual methods of cyanide treatment and it is to render such a combination feasible and possible whenever 'so desired OF BERKELEY, CALIFORNIA.

were.

1920. Serial $6. $01,168.

that I have developed the machine hereinafter to be described.

my invention I produce a surface of flu1 mercury that is maintained at any angle from the horizontal that may be desired b adjusting the speed of rotation, and the pu p of ground ore and solution is kept movlng over its, surface by the hydrostatic chine ;the particles of V precious metal being heavier than the gangue are projected by the centrifugal force towards the surface of the mercury wherewith they amalgamate as soon as contact with the surface is established. A w

With particular reference to the accompanying drawing, the machine there shown is especially designed to overcome various head given to the pulp entering the maobjections in the application of the principle 7 of amalgamation by sodium amalgam in the treatment of platinum, rus gold, etc. The machine comprises a how 10 having a smooth inner surface. This bowl is carried by a vertical shaft .11 which is supported by bearings 12. The shaft and bowl are rotated by means of bevel gears 13 which are driven by a horizontal shaft 164. The bowl is formed with an inwardly projecting lip 15 at its upper end and a curved rim or hp 16 terminating above a discharge launder 17.

I A cylindrical feed spout 18 is supported on a frame 19 and extends into the bowl to a point short of the bottom thereof where it is preferably provided with a constricted neck 18". A dynamo or generator 27 is operated by the driving shaft 14. This nerator is electrically connected to the cy der 18by a connection 28 and with the bowl 958 10 by a connection'29. The cylinder 18 con-. stitntes the anode and the bowl the cathode. A mercury layer or film 20 is built up along the walls of the bowl to seal the bottom of the feed spout.

In the operation of the device, sufiicient mercury is introduced into the bowl to create a film as shown at 20 and pulp is fed into the cylinder 18. Since the cylinder extends downwardly into the film of mercury and has its exit .closed thereby, the efiect is to force the pulp through the mercury by means of hydrostatic head built up in the cylinder 18. This brings) the particles of the precious. metal into more intimate contact with the mercury than would otherwise occur. The pulp having passed over themercury surprecious metal therein, is discharged over the top of the bowl and enters the discharge launder 17 from which any particles of precious metal that may have escaped amalgamation can be recovered.

The most important result efiected by the machine above described is the provision of a fluid bed or film of mercury that is independent of the support of a plate of metal capable of being amalgamated or wetted by it, as. in the case of the ordinary amalgamated copper plate. The advantage of this is that the gold and silver amalgam formed remains fluid instead of becoming pasty or even hard as on a copper plate, and therefore the old and silver contained therein are hardly appreciably affected by the dissolving action of the cyanide solution;v neither has the mercur any supporting metal that can be attacke by the said solution. The difiiculty of applying such a principle without the use of a machine of the type specified in my invention lies in the fact that mercury in the fluid state naturally assumes the horlzontal position, and an inclined plane surface cannot be produced, and if ore pulp were passed over such a horizontal bath of fluid mercury at the proper speed for amalgamation, the coarser particles would settle thereon and silt up the surface rendering further amalgamation impossible.

It has long been known that metals such as platinum, osmiridium' and rusty gold through not amalgamable by contact with mercury alone are easily wetted and held by mercury in which metallic sodium has been dissolved, or in other words by sodium amalgam. It usually happens in such cases, however, that as soon as the sodium has been abstracted from the mercury by combination with the water in the ore-pullo, according to the reaction Na+H,O= aOH-i-H the mercury ceases to hold the particles of precious metals, which as soon as the film of mercury recedes from them are free to be carried away with the gangue by the flow of pulp. It is thus important that if the precious metal particles are to be kept wet y the mercury andthereby kept entangled by it and retained while the gangue flows away, a continual supply of metallic sodium mustbe maintained in the bath of mercury. This can best be accomplished by dissolving a sodium salt such as sodium chloride or sodium hydroxide in the water used to suspend the crushed ore, and by means of an electric current electrolyzing the sodium salt, continually depositing metallic sodium on the mercury Whlch is made the cathode 7 of the system.

The difiiculty heretofore experienced int applying this principle in practice has lain in the fact that if an inclined amalgamated copper plate be used and the. pulp allowed actress to flow over it, the thickness of the film of electrolyte is not sufficient to make it possible to have an anode in contact with theelectrolyte without its. formin an electrical contact with the cathode %in this case the amalgamated copper plate) and thereby short circuiting the current and making electrolysis impossible. There have been various schemes suggested to obviate this difiiculty. One such scheme is to have an incline plane of wood or other suitable material wherein transverse grooves or rifiies are constructed and filled with mercury; the pulp, as it passes over these rifiies is intended to be raised to such a thickness as to admit of the placing of an anode in contact with it and yet suficiently far from the mercury surface or cathode as'to allow of the electrolysis .of the electrolyte without danger of contact with the cathode and consequent short-circuiting of the current. This scheme,

however, has not proven successful in practice.

In order to obviate the above difiiculties, there has been suggested a machine consisting of a slowing revolving horizontal cylinder lined with anamalgamable metal, e. copper, at a suitable distance from whic all around the periphery, are placed horizontal bars of some conducting substance (such as iron or carbon) to act as anodes. The ground ore in a medium of solution of sodium salt is run through the cylinder, the solution being simultaneously electrolyzed by the current and sodium deposited on the amal amated copper surface, thereby causing t e particles of recious metal to adhere thereto and thus come separated from the gangue. The dificulty with this apparatus has been found to be that owin to the depth'of the bed of pulp passing t rough the machine, coupled with the agltation action produced b the revolution of the c linder, only the arger and heavier particles of precious metal can come in contact with the mercury surface and become entangled thereon, the lighter particles remaining in suspension in the electrolyte and being carried out with the tailing.

It will be seen from the foregoing that I produce an inclined surface of mercu at any angle from the horizontal that may be desired, by adjustin the speed of rotation of the machine. T e pulp in a medium of water containing a salt of sodium in solution passes between the mercury surface and the anode, during 'which period by the action of the current, sodium is deposited from the electrolyte on the mercury surface forming sodium amal am, while simultaneously the precious meta particles are, by the action of centrifugal force, carried towards the surface of the sodium amalgam where they are at once caught and held as soon as contact is established.

over the top, thus preventing The hydrostatic head under which the pulp enters the machine keeps the 'gangue particles in the pulp continually moving ing shows an apparent contact between the bottom edge of the anode and the mercury cathode but this contactis ma'd ejby an ex.-

@ tensionof non-conducting material 30 such as hard rubber or bakehte, so as to avoid electrical contact between the two electrodes.

This shape of the neck, althoughnot an es- 'sential part of the invention, has been found toenhance the effect in certain cases, since,

it thus ensures aniore intimate contact between theore particles and the sodium g m V,

I claim. and desire to secure by Letters Pat'- ent is-' 1. A machine for the recovery of precious 4 metals by amalgamation with mercury, comprising a centrifugal bowl so shaped as to confine'a layer of fluid mercury around Having thus described my ii it'figwma walls at an angle to the horizontal, a feed spout for the pulp extending downwardly into the bowl and sealed at its lower end by the mercury, the lower portion of said fegilspout being formed of insulating mate- 11 v a 2. A machine for the reccvery of precious metal by amalgamation with mercury, comprising a rotatable bowl shaped to confine a layer of fluid mercury around its walls by centrifugal action when rotating," a feed spout extending downwardly into the bowl, the lower end of said spout being formed of insulating material and adapted to'be sealed by the mercury, an electrical connection for the feed spout constituting the anode, and an electrical connection for'the bowl constituting the cathode for directing electrical current through the pulp.

my. hand in the presence of two subscribing -witnes.Ses.

' FREDERICK A. BEAUCHAMP. Witnesses:

' W. W. Emmy, M. E. Ewmc.

InTestimony whereef I havehereuntosi

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