US2154779A - Method of and means for classifying and separating suspended solids - Google Patents

Description

April ,18, 1939. SHEPHERD 2,154,779

METHOD OF AND MEANS FOR CLASSIFYING AND SEPARATING SUSPENDED SOLIDS Filed Feb. 24, 1937 2 Sheets-Sheet l mwboifm T. L. SHEPHERD April 18, 1939.

METHOD OF AND MEANS FOR GLASSIFYING AND SEPARATING SUSPENDED SOLIDS Filed Feb. 24, 1937 2 Sheets-Sheet 2 Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE METHOD OF AND MEANS FOR CLASSIFY- ING AND SOLIDS SEPARATING SUSPENDED 6 Claims.

My invention relates to improvements in method of and apparatus for classifying and separating suspended solids, and more particularly to a method and apparatus for such purpose utilizing coordinated, centrifugal forces, amalgamation and electro-chemical action.

The primary object of my invention is to provide a method of and apparatus for classifying and separating suspended solids which is of simple procedure and embodiment, which permits of continuous operation, and therein maximum recovery of classes of solids is effected.

Another object is to provide a method and apparatus, of the character described, wherein centrifugal force is employed for classification and separation, but without the use of any moving parts as customarily employed in centrifugal processes and apparatus employed for such purposes.

A further object is to provide a method and apparatus, as described, wherein the application of centrifugal force to the treated pulp is a function of pulp stream velocity, therefore providing for an extremely high capacity in terms of pulp treated per area of flow circuit.

Another object is to provide, in a method and apparatus as described, electro-chemical treatment of pulp and mercury such as to promote recovery of highly dispersed noble metals, including gold, by amalgamation, and to preclude fouling of the mercury with consequent mercury loss.

Other objects, the advantages and uses of the invention will become apparent after reading the following specification and claims, and after consideration of the drawings forming a part of the specification, wherein:

Fig. l is a vertical sectional view of an apparatus embodying features of my invention;

Fig. 2 is a top plan view of the apparatus illus-- trated in Fig. 1, parts thereof being broken away;

Fig. 3 is a flow diagram illustrating use of the apparatus of Fig. 1 in carrying out the method of my invention; and

Fig. 4 is a schematic view of a modified form 5 of the apparatus of Fig. 1.

I have selected for the purpose of this specification, an embodiment of my invention particularly suitable for the classification and separation of values from the ore pulp of precious metals, such as that containing suspended gold, platinum and silver, although it will be at once apparent that suspended solids of other character may be classified and recovered by obvious application of the procedure and apparatus herein described.

In general, my invention contemplates the feeding of a pulp stream containing the suspended solids, as from a pump A under pressure through an annular series of jets B which direct their streams tangentially outwardly into an annular pool of mercury C, thus imparting bodily whirling movement to the mercury pool and a similar whirling movement to the pulp stream. This whirling movement of the pulp stream causes each of its suspended solid components to react under centrifugal force in degrees proportional to the specific gravity of each such component. The heaviest particles, for example, gold and platinum, will assume a position at the radially outermost portion of the mercury chamber, since such metals have a greater specific gravity than mercury.

Those components of the pulp suspensions which are lower than mercury in specific gravity and which do not amalgamate with mercury will be forced upwardly with the carrier fluid of the pulp through the pool C and into an area D affording classification of the lighter particles. In its travel to the area D, for further classification, the pulp stream, which is still in whirling motion because of the jets B, is diverted radially inwardly, thus to increase its velocity. Under such increased velocity of both upward flow and rotational movement, the pulp is admitted to an annular recess E extending radially outwardly from the normal stream fiow which recess is provided with tangential outlets F through its outermost wall arranged to carry away the heavier of the suspended solids which were incapable of remaining in the pool of denser mercury.

Two or more of the recesses or chambers E may be used as requirements may dictate instead of but one, and arranged, for example, as shown in Fig. 4.

Provision is made for subjecting the pulp stream electrically to a difference in potential as between the jets B and the mercury chamber, thus to nullify the effect of the Brownian movement on colloidal suspensoids which may otherwise remain too widely disposed in the pulp fluid to admit of separation. Such electrical current Will also aid in keeping the mercury fresh and amenable to amalgamation.

With reference to Figs. 1 and 2, the apparatus illustrated therein may comprise an outer shell including a lower section 2 within which the mercury pool C is retained, and an upper section 3, within which the annular recess E is located, the upper portion 4 thereof being tapered inwardly to a central vertically aligned outlet 5. Located within the outer shell is an inner shell 6 having a substantially vertical side wall terminating at its upper end in a closed conical portion 7 of slightly greater pitch than the surrounding wall of the outer shell section 4. The inner shell is closed at its lower end by a sump 8 secured to the shell 6 by bolts 9 which pass through the section 2 but which are insulated therefrom as is the sump, by suitable insulating material II.

I prefer to construct the lower section 2 of the outer shell in two parts I 2 and I3, thus to facilitate machining, and to tie these parts together and with the upper'section 3 by tie rods [4, which may extend through suitable flanges formed on the parts l2 and I3 and section 3 respectively. In order that the lower section 2 of the outer shell may be electrically insulated I from the upper section 3, and from the inner shell,

suitable insulation material I may be interposed between the part l2 and section 3 of the outer shell and similar material [5 placed between the tie rods I l and the flanges of the shell elements 3, l2 and I3, respectively. The jets B being formed also of insulating material, in a manner hereinafter described, the section 2 is therefore electrically insulated from the inner shell 6. An inlet pipe i! may be connected directly to the sump 8 and an outlet pipe l8 to the outlet 5 of the outer shell, as shown.

With reference to Fig. 2, the jets B may be formed by cutting or otherwise providing radially directed curved grooves 2| in the opposed faces of two rings 22 of such material as hard rubber, and in placing the rings face to face between the adjacent surfaces 23 and 24 of the inner shell 6 and outer shell portion l3, as shown. The bolts 9 serve to lock the jet assembly firmly in place. For purpose of illustration, I have shown the section of the jet assembly at the right of Fig. 1 as following the curved axis of the grooves 2|.

Referring now to Fig. 1, the contour of the inner walls of the lower shell section 2 formed of the parts l2 and I3 is such that the mercury pool C retained therein may move outwardly under centrifugal force as during whirling movement under influence of the pulp streams without being displaced therefrom, and without breaking immersion of the jet rings 22 therein. Travel of the pulp after passing through the mercury pool C must be upward and radially inward by virtue of the receding walls 26 and 21 on the part l2 and shell 6, as shown, thus to increase the velocity of the whirling pulp stream as it approaches the classification zone of the apparatus. 7

In practice, I prefer to establish an electrical circuit between the incoming pulp stream from the jets B and the mercury pool 0, and for this purpose the sump 8 and outer shell section 2 may be connected to an alternating current line 28 by suitable conductors, as shown at 29 and 30. For most installations, a voltage of 110 at a frequency suitable for incandescent lighting is sufficient, although certain pulps may require higher voltages because of a deficiency of soluble salts. The current so applied, I have found, also has a desirable effect in minimizing mercury fouling, as from inorganic substances.

In operation the pulp, after proper dilution, is admitted from the pump A under pressure to the inner shell 6 by entry through the inlet pipe IT. The closed upper portion of the inner shell functions as a pressure equalizer, after the manner of an air cushion, thus to compensate for V outer shell section 2.

pump surging or change in head where hydrostatic head is used in place of the pump A.

. Such pulp, under substantially uniform pressure may pass from within the shell 6 through the jets B and directly into the mercury pool 0 which, because of the tangential feed from the jets and the pressure at which the pulp is so admitted, is caused to rotate bodily, accompanied by a whirling motion of the pulp stream. As heretofore pointed out, the effect of centrifugal force acting alike on pulp stream and mercury will be to cause the pulp suspensions, which have a specific gravity greater than mercury, to pass directly through the mercury pool C and radially outwardly to, the inner wall of the If the suspension is gold, amalgamation may'likewise take place, but in any event, such suspension will be separated from the carrier fiuid of the pulp and retained with the mercury in the section 2.

During this stage of the process, smaller particles which are capable of amalgamation, but which may otherwise be difiicult to recover, because of colloidal dispersion, will form an amalgam with the mercury, such condition being induced in part by the eifect of the difference in potential between the pulp as it leaves the jet and the mercury, provided by the electrical circuit described, and in part because of the force with which the pulp is caused to enter the body of mercury ata point beneath the surface thereof. Such latter effect I have found to be many times more effective than mere surface to surface contact as widely practiced in present day amalgamating devices, such for example, as amalgam tables, revolving amalgaming devices and the like.

It is not without reason to assume, however,

that some values of a lighter nature may successfully avoid entrapment within the lower section 2, and this may be particularly true of included values, the whole mass of which presents a specific gravity less than mercury. For the classification and separation of such values, I have provided the upper section of the apparatus with the radially extending annular recess E in the inner wall of the section 3 at a point where the velocity of the whirling pump stream 7 is increased in the manner heretofore explained. Suitable outlet pipes 32 communicating with the outermost portion of the recess E serve to conduct away the heavier suspensions of the suspended solids which have passed above the mercury chamber and in this manner further classification and separation is carried out.

The latter classification of the suspended solids, together with their separation from the pulp, may be multiplied and made effective for succeedingly lighter ends by providing additional recesses E, as indicated at E, in Fig. 4.

Having thus illustrated and described specific embodiments of my invention as applicable to the art of the recovery of noble metals from ore pulp, it will be understood that the process and apparatus of my invention may be applied with equal success to the recovery of suspended solids of other substances, and that a liquid other than mercury, but heavier than the carrier liquid of the pulp, may be used for the recovery of relatively light suspensions.

I claim:

1. In an apparatus of the character described, means providing an annular chamber located in a substantially horizontal plane, mercury in said chamber to form an annular pool free to rotate bodily about the axis of said chamber, a plurality of nozzles having their outlet orifices submerged in said mercury and positioned in such manner as to admit fiuid pulp, passing therethrough under pressure, into the mercury at the inner radial portion of the pool and spaced away from the bottom wall of said chamber and at an angle to induce bodily rotation of the pool, whereby suspensions contained in said pulp are caused to move radially outwardly through the mercury under centrifugal force in relation to the specific gravities of the suspensions and the mercury, means providing an annular classifier chamber in vertical alignment with said mercury chamber, ducts extending tangentially away from the outer region of said classifier chamber, and means for conducting the fluid pulp from said mercury chamber while still in whirling motion upwardly into said classifier chamber.

2. In an apparatus for separating metals from a fluid ore pulp by amalgamation, a chamber for confining a. pool of mercury, a nozzle projecting into said chamber and having its outlet at a point below the mercury level of said chamber, said nozzle having all of that portion thereof extending into said chamber and beneath the mercury level formed of a dielectric material, means for feeding fiuid pulp under pressure to said nozzle, said chamber providing an electrode surface of a contacting mercury contained therein, and means providing an electrode surface for contacting said pulp prior to its admittance to said nozzle.

3. In an ore separating apparatus, means forming an annular chamber having a maximum diameter in its lower region and tapering conically upwardly and inwardly to a discharge zone, an annular pool of mercury in said lower region, and means for injecting a suspension of ore pulp, of lesser average specific gravity than mercury, spirally outwardly into the inner region of said pool at points spaced radially a greater distance from the axis of said chamber than said discharge zone, whereby to cause said pulp to rotate inside said pool and thence to spiral upwardly and inwardly, and the heavier values to pass radially outwardly through said pool and be collected in said lower region of the chamber.

4. In an ore separating apparatus, means forming an annular chamber having a maximum diameter in its lower region and tapering conically upwardly and inwardly to a discharge zone, an annular pool of mercury in said lower region, and means for injecting a suspension of ore pulp, of lesser average specific gravity than mercury, spirally outwardly into the inner region of said pool at points spaced above the bottom of said pool, whereby to cause said pulp to rotate inside said pool and thence to spiral upwardly and inwardly, and the heavier values to pass radially outwardly through said pool and to be collected in said lower region of the chamber.

5. In an ore separating apparatus, a series. of nozzles directed substantially tangentially outwardly, means forming an annular chamber having a lower region into which said nozzles are arranged to discharge horizontally, and having a conical region extending upwardly and inwardly to a zone of smaller radius than that of the discharge ends of said nozzles, an annular pool of mercury in said lower region, and means for supplying to said nozzles a suspension of ore pulp having an average lesser specific gravity than mercury.

6. In an ore separating apparatus, means forming an annular chamber having a toroidal lower region and an upwardly contracting conical upper region, an annular pool of mercury in said lower region, and means for injecting into said mercury pool, at substantially the center of said toroidal region, a plurality of outwardly spiralling, substantially horizontal jets of ore pulp suspension adapted to be directed upwardly by said mercury pool.

THOMAS LAMBERT SHEPHERD.

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