CA1202285A

CA1202285A - Method and installation for concentrating heavy metals, precious metals or heavy minerals in sand or gravel

Info

Publication number: CA1202285A
Application number: CA000430754A
Authority: CA
Inventors: Gustav Schmid
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-06-18
Filing date: 1983-06-20
Publication date: 1986-03-25
Also published as: DE3222862A1; DE3222862C2

Abstract

ABSTRACT

The invention relates to a method for concentrating precious metals and heavy minerals in sand or gravel deposits and an apparatus for carrying out the method. The method comprises pre-classifying the raw material suspended as a slurry in water by means of screen means into two to six fractions. Each fraction as a slurry in water is provided with a flow velocity of about 0.25 to about 0.50 m/sec. over a length of about 3 m. The flow is retarded and stopped to provide a plurality of volumes separated from each other in the direction of flow in the lower range of the overall height of the fluidized bid. Each flowing volume is treated during the retarded flow condition in its lower range of height be means of thrust and suction shocks acting on the flowing volume from below. The apparatus of the invention provides in a raw material feed station a vibrating feeder trough which is sidewardly open at its discharge end for the conveying and disintegrating of agglomerated bulk material. The sidewalls of the trough have inwardly bent upper edges so to partially extend over the conveying bottom. Nozzles for pressurized air or water jets are provided at the lower side of the said bent upper edges. The feeder trough has associated behind it a forescreen for separating the deads and a collecting tank beneath said forescreen for collecting the produced slurry.

Description

2~-- Sch 62 ~

Method and Installation for concentrating Heavy Metais, Precious Metals or Heavy Minerals in sand or gravel This invention concerns a me-thod for concentrating of precious metals, particularly gold, heavy metals, parti-cularly copp~r, tin, plumb, or heavy minerals, particu-larly diamon~s dispersedly occuring in sandlgravel deposits, and also concerns a dressing and concentrating installation~
for carrying out this method. For recovery of small gold~
grains-from al~uvial placer occurences hitherto mainly ~
so-called sluice boxes have been used, which are operating such that grains of different specific weight are seperated from each other along a stream of water. As the grains of greater specific weight will be carried on by the stream of water more slowly *han the grains of lighter speciflc weight, they will be retarded by and will settle in front of riffles or similar transverse obstacl~s on the bottom of the sluice.

As alluvial deposits include materials of most different ~ -grain si2es, and as even by screehing homogeneous fraction of qrains cannot be a~ained economically, those sluice boxes necessarily will be fed with bulk material of qreatlv ~ j differninq grain sizes. Thiq is the ~ack_ground for opera- ~

_ / _ ~2~

Sch 62 ~ 2 ~

ting such sluice boxes with relatively hlgh flowing velocltY, high enough in order to be able to discharqe the earth roof including the greatest qxain fractions and in order to avoid obstr~ctions. However, such high flowing ~elocities will reduce the sinkinq or qravitating velocity, and for certain ranges of fine grain -sizes no gravitat1ng will occur any more under those conditions.

Experience has shown that freely occuring gold (or other heavy metals or heavy minerals) can be recovered by means of sluice boxes only in limit~ed amounts and further only to a certain minimum grain size. It would be desir~
to also recover these grains or Particles of gold, which could not~gr~sped until nowl because it is indisPensa~l for an ecomomicallY worthwhile processing of sands or qravels bearing gold and precious metals only in very small quantities, to previously enriching the contents of gold or precious meta1s. respectively.

For such enr~chment a various number of dressing ox concen-trating devices alrèady has been used, such as iigs, cone~
concentrators, HumphreY spirals, Reichert spirals, Denver spirals operating according to the principle of use of centrifugal force, shaking tables, or rocking and/or osci lating washlng troughs. It has been experienced t however, that the concentrating and classifying processes carried out under the use of the above mentioned dressing devices _ / _ ~2131Z;~

Sch 62 ~ 3 are incapable to economically enrich or concentrate the free gold occuring in relative small quantities within alluvial deposits. Especially, it has been experiencedl that any effective concentration by means o~ those Processes can oniy''be carried out when using material of substantial homogeneous grain sizes,.

For operating the before mentioned hydro-mechanical settling `
and/or classlfying methods for dressing of sands or gravels of different grain,!sizes either very high flow veloci~ies are necessary, by whlch the gravitating or depositing velocity of the solids to be concentrated will be remarkabI~
reduced, if not eleminated at all (by sluice boxes) ,-or a strong upwardly directed streaming is necessary obviating a sufficient concentration. If such upwardly directed current~
are too weak, then gravel and sand will settle together with the free solids of heavy metal or heavy mlnera~ An concentration of the specifically heavier grains is m~ssing:
the concentrating material will get lost or agglomerate such that the operability of the jiqs and other concentra ting devices is lost. The precious metal to be recovered ~
is dischargecl toqether with sand and gravel to the bulk ~, material.

It is a main ob~ect of this invention to provide a method and a device for concentrating of free gold Partlcles (and other free precious metal or heavy mineral particles~ occurinq 2~

Sch 62 _ 4 in sand or gra~el, wherein also ~hose grains, which have become lost h:Ltherto, particularY particles from the range of flnex grain sizes will be grasped, and which ln particular~are adapted for carrvinq out ~ large scale and therefore économical dressing o sands or gravel from alluvial deposits i~cludinq only relative small quantities of freely occurinq precious metals, without unusual qreater expenses and without devices and ~quipment specifically liable to wear.

The before mentioned and further objects can he achieved according to the in~ention by the following characterizing steps of the method of the kind mentioned beore:

a) Comminution of the raw material by its delivery to a prefera~l~ oscilating or shaking conveying means, b) continued decomPosing of -the raw material by .
intensive spraying water QntO the raw material and by blowinq pressurized air through the ' solid/water-mixture on its way towards a forescreen for separation of coarse bulk material, c) transferring the pre-classified raw m~erial as a suspension of water and solids into screen~
devices:~or screen classification into at least two~ preferably six fractions, d)separate subsequent treatment of the oversize fraction from each screeniny device by .

~261 2~

Sch 62 - 5 ~

adding wa~er and agitating for reestablishing a water/solid-suspension in a volumetric relation of about 1/1, .e) Seperate concentration of the solid/water-sus-pensions produced from the oversize fractions and of the undersize grain solid/water-suspen sion formed from the last screen b~ conversion :into a largely and substantially uniform flowing condition having flow velocities preferably between about 0,25 and 0r05 meter/sec. over a :Lenght generally not surmounting 3 meter, ~) :retarding and stopping the flowing ~ondition of the suspension into a plurallity of volumes separated and arranged one after each:other in flowing direction within the lower range of the overall:height of the fluidiced bed, prefarably at a height at about 1/3 to 2/3 of that overall height,~
g) ~nd treatment of the respe~tive fluidiced bed during its~retarded flow condition in its lower range of height by means of pressure and suction ~;hocks acting onto the mixture from below~and prefarably with a pulsation frequency in the range between:about t~o and three ~ertz ~cycles per :~
second).

By means of the inventional proposal it has becoma posslble the first time to handle large quantities of the material to Sch 62 - 6 -be treated as well for dressina as for concentrating ~ur~oses, which is a precondition for economy of operatlon for ~reatment of raw material having a very low peraentage of gold (heavy metals ox heav~ minerals). Already ln the stage of feeding provisions are made such that even heavllY
argillaceous bulk mat~rials will be commlnuted and the freely occuring particles of metal or heav~ minerals can be~
enucleated from the agglomerations, and further the m~jor ~art of the fed in raw material, as far as decomposable ~
will be factually decomposed into fractions of grain sizes which can be subsequently treated in a relative simPle manner.

An important feature of the inventional method is presented by the new way of concentration of the solid/water-mlxtures carefully Prepared after the screening oPeration , on pre-ferably broadly and relative slowly flowing fluidiced beds=
flowing volumes , the lower portion of which has been stopped and is exPosed to pulsations, which can be controlled accor-ding to their frequencv and amplitude in order to achieve a maximum of concentration. These pulsatlons are effective to whirl up waste particles, which possibly have already settled within the f~rst stopped volumes of the fluidiced bed and which now will be carried away bY the flowing uPper part of said fluidiced bed, while the mineral or metal to~be concentrated is enabled by its greater qravity to earlier settle, such that the concentratlon result wlll surprisingly early raise with a number of repetitions of pulsations and _/ :

8~

Sch 62 - 7 -with a number of quieted volumes one after the other in the flow direction of the fluidi~d bed already at relatively small lenghts between 1 meter to about 3 meter of the fluidi~ed bed.
.- . , It has been found to be economical, lf the solidiwater-sus-pensions produced after screen classification are treated~
when in the form o~ 10wing beds having a breadth preferabl~ ~ ;
between 1 and about 2 meter by means of pulsationa even though also greater breadth of the flowinq beds would lead to good results, while as far as the device construction is concerned, those larger embodyments would be cumbersome to handle. Further, preferably, the pulsations are introduced uniformly acting over the entire length of the flowing bed in form of a flowing flat voIume. The amplitude of the pul-sations immediately at the driven or s~mu~ated bottom of the flQwinq bed generallY amounts about 5 mm which however could be increase~ , for example for fractions of greater grain sizes! where an example of a maximum amplitude~would~
be 15 mm. At any case in practisinq of~the inve~tional method provisions ~hould be made that the pressure and suct~on strokes of the pulsation will have the effect that the grains in the quieted lower Portions (settling vessels)of the flowin~
bed are whirled up or are kept in suspension such that the~
lighter waist particles are carried away by the upper flowinq portion of the flowing bed and therefore an exchange takes place between the wanted heavier particles and the lighter Sch 62 - 8 -waist and with other words an effective concentration takes place. Dependent from the grain siæe to be treated it may become necessary to vary the length of the ~uieted Portions ,(settling vess~ s~ which are arranged one behind the other'in the flowing directi.on.

If the wanted particles of gold or heavy minerals are embedded in heavy argihaceous deposits, these argi~aceous sands and/or gravels must be exploited and dressed~too.
Until now the placer mining industry was unable to do that, because no correspondinq dressing method for qreater volumes was disponible to take into account the specific require-ments of placer mining of alluvial deposttsO As far as in the known dressing methods for small vol~es the water seperated are after depositing the waist material has been freed from mud, this has been done by using drain pools or overflow pools. Mud removal by means of drain pool necessitates a qreat ~ettling and retaining time, which is so long that neither in Alasca nor in Canada (Yukon) one single plant~is instaIled which would be able to comply with the officially issued requirements concerning the mud removal. In order to avoid polllution or clogging of the natural waters during application of the inventional method for handling large volumes, according to another feature of the invention it is proposed that the mud containing solid/water-suspension of the fine qrain waist fraction after concéntration is pumped onto the rubbel stone dump forminq the waist from coarser grain size material and effective as filter , such .

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Sch 6 2 - 9 --that the flltered water thereafter may be recixculated.
These measures make possible and effective mud removal of qreater volumes of water in an economical manner.

According to an inventional alternative emhodyment the mud contalning .solid/water-mixtu~e of the fine ~rain sized waist fraction is pumped up to a tower in order to be fed then by gravity to hydrocyclones arranged one below the other, wherein the method is repeated as long as at the outlet of the last hydrocyclone clarified water is recovered for being recycled to one of the preceding stages of the dressing and concen~rating process. Both of the before discribed mud removal processes can be carried out at rela-tively low expenses, also with respect to oPerating energy.
Further, the mud removal methods can be easily integrated into the overall process and further are efective to auto-matically fill up again the pit exploited before.

According to another aspect of the invention a dressing and concentrating inskalla~ion is provided for carrying out the above described method, wherein in a raw material feed station for conveying and comminuting especially of~
conglomerating material includes a vibratlng feed chute having side walls, the upper edges of which are provided~
with an inwardly directéd covering edqe partly covering the conveyor bottom, while below said covering edge no~zles for pressurized alr and/or water are mounted and ~ch ar~

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Sch 62 10 - .

protected from above. Said feed ehute is followed by a screen for removal of tumb material, while a collecting tank is disposed thereunder for collecting the produced solid/water-mixture.

If the alluvial deposits of sand and gravel include a greater percentage of clay such that the vibratinq feed chute cannot provide for an effective comminution under all conditions~
then according to the invention a conveyor belt wash street is arrangsd in frontof said vibrating feed chute including a plurality of relatively short conveyor belts, which are slightly upwardly inclined in feed direction and are arranged one behind the other such that the feed material will fall from step to step like on stairs f~rom the end of the upper~ :
to the beginniny of the following conveyor belt. Above ~:~
said conveyor belts comminuting means.are provided, especially in form of nozzles for pressurized air and/or water or water showers. By means of the stair-like arranyement of ~ ~ -the conveyor belts one arranged behind the other the bul~
material will tumble and roll from step to step. This ls true also for the oversized material which is d~olved, agitated and washed by means of the simultaneous use of water and the conditioning by means of pressur~zed air streams.

For making e~fective the treatmen.~ of the bulk material by means of the pressurized fluid jets the conveyor belt Sch 62 washing street expediently .is mounted in a tunnel-like housing, the bottom of which forms a conveying chute and the clrcumferential walls thereof preferably include jet nozzles , which are mounted such that they are dixected from all directions to the conveyor belts extendiny along the lonqitùdinal`centre of the tunnel. These jets will act to fl~sh or to blow away particles of finer ~rain size of the bulk material from the conveyor belt to the bottom chute. The heavier and coarse bulk material remains on the conveyor belts and further exposed to the intensive mechanical treatment by means of the stair-like steps in connection with the jet action.

In the raw material feed station the before mentioned washing street in front of the vibrating feed chute can be equipped with vibratlng conveyor channnels instead of conveyor belts, which are arranged one behind the other in a step like manner and are provided with perforated bottoms.
Preferably at least one vibrating conveyor channel in~ludes a longitudinally stepped screen deck arranged above an oscilating frame, said screen deck being arranged within the effective range of the jet nozzles mounted on the inner perifery of the tunnel-like housing. Similarly as the screen deck, the conveyor belts may be also perforated or may be carried out in form of thieves.

According to another aspect of the invention the collecting tank arranged under the coarse screen can be e~uipped with Sch 62 - 12 -agitating means or with nozzles spacidly divided about the tank walls for providing pressurized air and/or pressurized water jets for continued disso~ving and comminuting the solid portion of the mixture.

To the lower conically formed discharge exit oE each o~ said collecting tanks are connected one or a plurallty of screening machines, according to the number of the desired grain size fractions. Each screening sta~ion is connected to a distri-buting tank by means of a conveyor means, which, if necessary, may be equipped with water showers. Each distributing tank is used to simultaneously feed several or a certain number of chamber pulsators, which are all charged with the same solid/water-suspenslon. In the respective distributing tank at the latest provisions are made that the suspension to be -fed to the chamber pulsators has a relatlon of about one part solids and about two parts~water. In a preferred embody-ment the distributing tank has a the form o~ a vertically disposed cyllnder with an upper conical feed hopper and a divider cone~n the bottom and upwardly converging, while the outflow connections are arran~ed in the bottom wall between the cylinder and the circumference of the divider cone.

The so-called chamber p~sators, which-are fed with the homogenized solid/water-suspension by means of channels or pipes having flared discharge ends, according to a preferred embodirment of the invention each comprise a trough-like pulsator fràme with adjustable inclinination, with a bottom 2~i Sch 62 - 13 -in the orm of an elastic diaphragm , further comprising transversely extending and longltudinally equally spaced cross members or walls extending from thebottom up to a portion o~ the overall height of the trough, said cross walls together with the lateral walls forming a sequence of settling.chambers or settling basins, the bottom of which is activated for executing pulsation mQvements.

The diaphragm forming bottom of the trough can be sealedly clamped between an upper encircling frame an a lower pressing frame, the latter including cross members. Between those cross members and the lowe.r edges of the cross walls the diaphragm is supported and is pressed *ogether for ~ealing purposes. The diaphragm may be actuated to execute pulsation movemen~s in the area of each single settling basin by means of a respective upwardly and downwardly moved piston, and preferably a rocking frame commen to all piston is driven by a suitable oscilating drive means.

In a prefe~ed embod~ment of the settling equipment according to the invention the cross walls of the chamber pulsators consist of U or channel profiles, the open side of which.l~ .
directed downstream, while the lower leg of this proflle~.
serves as bearing.and sealing sur~ace for the diaphragm, and the upper leg of the profile covers about 1/3 of the length (in flow direction) of the respective basin, in order to avoid a too strong whirling action and an undesired scavenging of the settling basins, especially if higher and therefore :~z~

Sch 62 ~ 14 -more agyressive flow velocities are used.

The invention will be further described by way of exampleswith reference to the accompanying drawings, wherein Fig. 1 shows a more! or less schematic represen-tation of the different steps and devices used in the method according to the inven-tion, Fig. 2 a flow ~art of the inventional method similar to Fig. 1, Fig. 3 a schematic elevational view as longitudinal section of a conveyor belt washing street immedlately after the feed station of the overall dressing and concentration ~nstalla-tion, Fig. 3a - 3c schema ic perspective end views of different possible shapes of washing street tunnel or channel;

Fig. 4 another embod~ment of a washing street imme-diately follw~ng the feed station in similar representation as in Fig. 3, wherein the conveyor belts are replaced by a stepped - vibration trough, Fig. 4a a perspective partial end v~ew onto the vlbration trough of Fig. 4 also showing the perforated bottom screen of said trough, ' ,;

Fig. 4b and 4c perspective partlal end views of difEerent possible outer shapes and su~port arrangement of the tunnel including the vibration trough according to Fig. 4, Fig. 4d a schematic plan view of a vibrating or oscillating trough similar to Fig. 4 but consisting of a number of articulated sections, Fig~ 4e a schematic plan view of an alternative construction of the vibrating trough generally shown in Fig. 4, wherein the cross steps are replaced by staggered deflector means providing an extended path and time of retaining the bulk material to be treated on a relatively short length of the trough, Fig. 4f is a plan view of another vibrating trough useful in a vibrating washing street like Fig. 4, Fig. 5a and 5b a schematic perspective elevation and vertical section, respectively of a distribution;tank to be connected between a screening machine and an arrangement of chamber pulsators, Fig. 6 and 7 perspective partial views of an embodiment of a chamber pulsator comprising an upper trough-like frame having associated thereto cross walls to form settling basins, Fig. 8 another embodiment of a chamber pulsator shown by a schematic vertical longitudinal section similar to Fig. 7, ~,~

s Sch 62 - 16 ~

Fiy. 9. another perspective partial representation of the pulsating and vibrati~g frame similar to Fig. 9 and Fig. 1~ a supplemented perspective representation of the pulsator sim~lar to Fig. ~ and 10.

The bulk material to be treated is brouyht. by means of a front loader or another earth moving machine to a grizzly feeder , which in Fiy. ~ is schematically represented at the feeding station 10. In this feeding chute the bulk matexial ls shower treated at high water pressure and is agitated such that sand~
gravel is washed, argi~acous material is dissolved and an easily flowing solid/water-mixture !i5 producedi by which afterwards conglomeration is avoided. In order to support the comminution action pressurized air may be introduced by nozzles from suitable places~ The vibrating feed chute 10 indicated in Fig. ~ has side walls, the upper portions of which are inwardly directed for covsring those water and~or pressurized air nozzles. The dispersed and dissolved bulk :
material flows from the feeder chute 10 over a joining coarse screen 12 in order to discharge the coarse material either by a chute or an intermediate conveyor belt 14 to the waste conveyor beLt street 16 . Conse~uently, the coarse screen 12 removes in this method the washed tun~ material as overgrain from the further dressing and concentration process.

According to an alternative embod~ment the bulk material to be treated is fe~d to a apron feeder A (Flg. 1) having strong lateral walls similar to the lateral walls of the v~bration ~2C~2~5i Sch 62 - 17 -feeder trough, which side walls form an openlng at the dis-charge end. The upper edges of the side walls have an inwardly directed edge portion for protecting the water and/
or pressurized air nozzles for comminution of the bulk material.
As the apron féieder inc~udes transverselly extending spaces great enough, for loosing,water and solids of smaller gra'in size, a collecting tub is disposed under this apron conveyor having a forward inclination and an outlet towards,the coarse screen, wherefrom the washed tumb minerals as over size grain are discarded from,the further dressing process.

In the embod~ment shown i.n Fig. 1 , in consideration of the different heights at the pit the apron feeder A is followéd by a bucket conveyor ox elevator B for transporting the~more or less completed material suspension, which can be achieved by a non-represented treatment with water jets into a vibra-tion trough C having a coarse scre~n. The side walls of the bucket conveyor are elastic such as to get expanded and streched when the respective conveyor portion is returned at its ends.

The vibration,trough C substantially corresponds to the vibra-tion feedex trough or chute 10 in Fig. 2 with the difference that the material fed by the bucket conveyor B is already more or less treated and dissolved.-r~ ,According to a prefered emhod~-ment shown ln Fig. 3 the vi~
bration trough C in Fig. 1 or at 10 in Fig. 2 have arranged in front of them a conveyor belt washing street. It~consists _ ~ ~2¢ ;~5i of any suitable number of conveyor belts 20 in stepped relationship to each other for conveying the bulk material in flow direction. The length of the conveyor belts depends on the desired length of the washing street and the desired number of steps in the overlapping range between two belts.
This stepped arrangement has the function that the bulk material will roll and tumble from step to step as to dissolve thereby, in connection with the water and pressurized air jets the coarser grain sizes.

The vibration trough C of Fig. 1 substantiall~
corresponds to the vibrating trough of the grizzly feeder 10 in Fig. 2 with the difference, that the material brought ~long with th~-bucket--elevator s is already more or less disintegrated. As a further variant charging of material onto the apron conveyor A of Fig. 1 does not yet need to be treated by showering or water and pressurized air jets such that the material until reaching the vibrating trough C is just exposed to the disintegrating forces during the feed action of the transpor-t conveyor belts B.

2~i Sch 62 - 19 -This step-like arrangement causes the bulk material to tumble from step to step such that espe!cially the coarse fraction and aggomerations ar exposed to the treatment by the water and pressurized air jets for being washed and dis~ntegrated.

The conveyor belt washing street according to Fig. ~ is accomodated in a tunnel-like housing 22y the bottom of which forms a trough, wherein the disintegrated material falling from the conveyor belts will be further treated by tumbling flowing along downwardly. No~zles for pressuriæed water and prelssurized air are disposed around the peripherie of the tunnel-like housing at locations effective for disintegrating the bulk material. Each conveyor belt of the washing street either may be arranged in a horizontal or in a slight ascending or slight descending orientation~ Further the bottom trough 24 with its steps 26 and the driven for a vibrating movement, may be separatly or together with the entire tunnel-like housing 22. Generally, material falling down from the conveyor belt is fed by gravity to the exit of housing 22 just by the downward inclination of khe trough 24 i e. the entire housing 22.

During normal operation of the washing street according ~o Fig. ~ only the coarse bulk material remains on the conveyor belts 20 and will be discharged at the exit of the washing street. On this conveying path the bulk material will be exposed to a continuous mechanical treatment and also to the water and/or air jets acking from all sides onko the bulk _ J _ ~;2Z~

Sch 62 - 20 -material tumbling from step to step. Such a washing street allows cleaning, tumbling and washing of greater bulk material volumes i, especially the disintegration of argillaceous conglomerations until being discharged into the feeder like station'C''similar to the feeder station C in Fig. 1.

Fig. ~a, 3b and 3c just serve to illustrate that the tunnel-like housing of the washing street may have any desired cross section such as the octogonal cross section of Fig. 4a or a mere circular cros~ section of FigO 4c, while it is shown in Fig. 4b that the tunnel ~ust not be entlrely closed at its coverside but ma~ e open to form a kind of channel, which may be assembled, for example from a number of sections following each other in axial direction as shown in~FigO,4c.

Instead of the conveyor belt wa~hing street according to ~
Fig. 3 a vibration feeder trough washing street according to Fiq. 4 may be arranged in the Process forwardly from the~rlzzly feeder C in Fig. 1. As shown in Fig. 4, the step-like a~rranged~
conveyor belts are replaced by a stepped arrangement of~roughs~
30. The bottom surfaces of the feeder troughs 30 are per forated such that material of fine grain slze may pass through~
to the b'ottom of the tunnel-like housing 22. The stepped ;~
arrangement of feeder troughs 30 are mounted on an osci~àting~
frame 34. The bottom of the housing 22 may have a stepped surface 26 as shown in Fig. 3, and the perlpher ~ of the housing 22 may also be equipped with nozzles 2B for pressurized water ~ets andior air jets.

.

_ / _ .

Sch 62 - 21 -In the s~hematical ènd view of Fig. 4a the vibrating trough 30 is seen with its perforated bottom surface, the side walls of the trough and the vibrating frame 34 including longitudinal frame members to support the sides of th~ trough.

As shown in Fig. 4b one exemplary form o the housing 22~1s resiliently supported on a stationary frame in order to be vibrated by any suitable vibration drive source with vertical vibration displacement. It can further be seen from Fig. 4b that the upper slde of the housing may have a pivotally mounted cover portion. Fig. 4c serves to indicate that the cover portion of the tunnel-like housing may be separately mounted and supported from the bottom portion or channel portion of the housing 22. Preferably, the cover portion is e~uipped with the nozzles for air and water jets.

According ~o another embodiment shown in Fig~ 4d the vibratlon trough having any desired length may consist of a number of sections, one behind the other and each of them individually supported by springs or on elastic material, allowing oscila-ting movement of each section stimulated by magnetic means, for example or by unbalance or by ex~entric weight. Each section of the trough or housing o the washing street shown in Fig. 4d tapers at its exit portion, which allows osci~a-tions independent from any oscilation movement of the adjacent sections.

The schematic side view or longitudinal section of Fig. 4e serves to indicate that the vibrating trough washing street ,.,; _ / _ ~20Z%BS

Sch 62 - 22 -includes at least one upper arrangement of stepped sieve or screen sections and a lower stepped bottom below the screens.
Either the screen arrangement or the entirety of screens and bottom, i.e. the overall housing are driven for oscilating movement. Of coarse it may be possible to have mounted within the housing two or more screen decks one over the other in order to produce already at this stage of ~he dressing process a determined number of different fine grain sizes so to save special screening machines ~n the more downstream portions of the process. If several screen decks are arranged one about the other, eventually only partially overlapping in longitudinal direction the lowest screen deck above the bottom of the trough will carry and transport a medium grain size, while the finest grains will flow on the bottom of the trough.

According to the plan view of a vibrating trough of Fig. 4f to be used in a vibrating washing street like in Fig. 4 the major part of the material flow is in transverse direction by means of buffles or deflector means 40 according to the indicated direction of ~he arrows. Such arrangement may be used with advantage for installations, where the overall length of the washing street must not be too long. Again in this embodiment the flow of material takes place by action of gravity i.e. by a downwardly inclination of the trough sections having the indicated buffles. As a general remark it should be ~oted that the before discribe~washing street may also be composed of rigid trough sections alternating with oscilating trough sections or housing sections.

Sch 62 - 23 -Further in the flow chart of FigO 1, the solid/water-mixture including the undersized grain, which is separated from the deads in the forescreen t for example shown at C in Fig. 1 and 3 is collected in a collector tank D below that fore-screen. The forescreen can be used in connection with an installation~:having nozzles to direct water and pressurized air jets towards the material to be treated. The forescraen can further be embodied as a stepped arrange~ent of screens to further reduce and disintegrate the deads by the effect of tumbling from step to step.

The collecting tank D has a downwardly converging bottom, which is also inclined towards the discharge end fo~ self emptying operation~ The discharge opening of the collector tank may have a closure device which makes possible automatic opening and closing. The entire installation may be electro-nically controlled according to the interlock system such that by break-down of one step of the process all other steps beginning with the first step the functions are automatically stopped in a programmed ~e~uence.

With reference to Fig. 2, solid/water-mixture present below the forescreen 12 in the collecting~tank D is mixed and held in suspended condition by using a mechanical agitating devi~e and/or by introducing pressurized water or air jets into the mixture by vertically and horizontally directed nozzles in~the walls of the tank. This operation is also effective to addi-tionally dessolve and disintegrate the material to be treated.
The before described operations take place in a first stage ..

~. ~

Sch 62 - 24 -or station of the process and all devices belonging thereto, similar t~ all other following stages or stations may be mounted on skids or slide pats for easy transport reasons.
.
The waste material coming from the di-fferent stations of the process is conveyed to the waste conveyor belt street 16 for finally being transported to the pit, which has been excavated before. At the end of the waste conveyor belt street 16, according to Fig. 1 and 2 a slewable conveyor belt 38 may be used to discharge the waste material in form of a semi-circle about the width of the pit to be re-filled.

The second stage of the process is incorporated by an osci~ating screening machine G for seperating the different grain sizes from the solid/water~mixture as presented in the collecting tank D. This classiying operation allows to feed the settling machines or devices of third method stage with material,~wh~ch, if not already consisting of homogeneous grain sizes, at least including one fraction o grain sizes i.e. below a certain ~
mesh size, for example. In such case the different grain sizes of the classified fraction even the greater siz~d particles of sand or gravel have a~smaller settling velocity than the smallest grains (of precious metal, heavy minerals or the like~ to be concentrated.

As shown in Fig. 1 the suspension from collector tank D is fed by means of bucket conveyor E and a feed hopper F to the oscilating screening machine G. The bucket conveyor feeder may be provided as a transportable and height adjustable unit, ' Sch 62 - 25 -which can be incorporated into the second stage of process without any difflculty.

According to Fi~. 2 the bucket conveyor E can be dispensed with, if.the forescreen 12 is at a level high enough in order to provide.a~sufficient slope or inclination towards the screening machine G and in order to make possible the arrange-ment of a chute or hopper to feed the material to the upper screen deck of machine G. Under these conditions further the collecting tank D under the forescreen C would not be necessary.
The chute 40 of Fig. 3.~may be equipped with buffle plates or additionally with a vibrating drive for further disintegrate argillaceous material.

The oscilating screening machine G ~horizontal or vertical osci~ator) at least comprises two screen decks in order to produce at least three fractions of grains. The upper deck for example has a mesh opening of about 37 mm, while the lower screen deck has openings or meshes not greater than 8 mm. The oversized grain of the second screen deck then includes a :
grain fraction between 8 mm and 37 mm, while the undergrain in~ludes grains between O and 8 mm diameter. These dif~erent fractions are seprrately from each other introduced into settling:machines for concentrating the precious or heavy metal or heavy minerals included therein.

Even though the concentration technique applied in the inven-tional method provides excellent results also for bulk material with very different grain sizes, nevertheless it may be desirable .
to use more than only two fractions in connection with only two Sch 62 - 26 -screen decks. Therefore , two Ol- more screen machines may be arrange~ ne behind the other in order to provide for a greater number of grain fractions each including a smaller range of grain sizes, which will lend to better quality and greater quantities ~n the screening operation. When using two screening machines one behind the other the first one may comprise three screen decks, while the second will only have two screen decks.

The grain frations~produced in the screen machines are fed by a stationary or vibrating chute ~I (Fig. 1) to the assoc.iated settling machine. As the overgrain in the screening machines is produced substantially dewatered, these fractions, if advisable, may be transpor*ed by means of conveyor belt~:to their associated material distributers I, from which the settling machines are directly charged. The last undergrain fraction includes the essential portion of water whi.ch has been added:
during the screening:steps. This grain fraction at any case will form a solid/water-miXture having a relative high percentage of water and so may be pumped or directed to the~associated material distributer I by a chute.

The distributors I1 and I2 shown in Fig. 1 and 2 form an intermediate stage o~ the process, wherein the material to be treated is kept in suspended condition, for example by means ~
of buffle plates within the distributors, which must be passed by the mixture of solids and water. The turbulent condition of the material can be brought about by mechanical agitation or by means of hori~ontal and vertical nozzles mounted within :~2~2~

the distributor tank for generating jets of water and pressurized air. All distributor tanks I are additionally fed with water with the exception of the distributor I containing the under-grain coming from the last seperating screen of the screening machine. In cases where the material to be concentrated is transported from the screen to the distributor tank by means of a chute, then the water may be already added at this time to improve the slidability of the material.

A convenient embodiment of the material distributor I is shown in Fig. 5a and 5b including a hopper-like upper feed opening from which the material will hit on a lower cone serving an even distribution and turbulence of the suspension fed. Surrounding the base of the cone there is a number of discharge openings in the bottom plate of the distributor tank each opening being connected to an associated settling mach~ne.

In a third essential stage of the process the inventional operation of concentration is carried out in so-called chamber pulsators, each ~ulsator machine comprising any suitable number of settling basins arranged one behind the other, while the bottom of each settling basin will be pulsated, i.e. is raised and lowered in a pre-determined rhythm and frequency.
~ach settling basin of the arrangement within a pulsating machine is closed on five sides. Those pulsator machines are indicated in Fig. 1 and 2 at K, while Fig. 2 somewhat in the form of a plan view reveals that dependent from the volume of suspension to be treated for every fraction of grain sizes a smaller number of pulsator machines K arranged side by side ..~
~"

Sch 62 - 28 -are fed by the distributor tank I1, while a greater number of those pulsator machines K are fed by the distributox I2.

According to the representations of Fig. 6 - 10 each chamber pulsator 50 includes an upper pulsator frame 52 comprislng side walls 54 extending in flow direction and belong:ing to a channei or trough having a certain inclination downwardly in flow direction. The bottom of the trough is formed by a diaphragm 56, which according to Fig. 10 is laterally supported on a pressing frame 58 and is sealedly connected alonq the sides of the trough with the upper pulsa-ting frame 52~ The pressing frame 58 further supports the diaphragm by means of spaced transvers~lly extending cross~members 60.

Upwardly from those cross members there are cross balls 62 arranged between the side walls 54 dividing the trough of the pulsating machine 50 into a sequence of settling basins 64. It may be seen especially from Fig~ 8 that the bottom forming diaphragm 56 between consecutive cross members 60 is not supported and therefore may be actuated there to execute pulsat~ions of the corresponding associated settling basin 64.

The cross walls 62 accordinq to the embodiment shown in Fig. 6 and 7 consist of rectangularly bent sheets having their lower sides in sealed connection with the diaphraqm 56.
In. the embodiment shown in Fig. 9 the cross walls 62 consist of U-profile members, the open side of which is directed downstream and so partially covering the associated settling ~2~1iZ~35 Sch 62 - 29 -basin at its upper upstream end. The side walls 54 ovextop the cross walls 62, as the flowing volume (fluidiced bed) in each chamber pulsator 50 extends to a height, which is greater than the height o the calmed settling basin, this remaininq height of the flowinq volume dekending to some extent on the adjustable inclination of the pulsator trough.

As can be seen from Flg. 10, the unit foxm by the upper rame 52 , pressing frame 58 and the diaphragm 56 is supported on a machine frame and is pivotally connected thereto by h:inge means 66 such that the unit can be upwardly tilted for emptying the settling basins 64. According to Fig. 9 a pulsator piston 68 is disposed beneath each settling basin, said pistons having the form of cross members and being mounted to a common oscilatinq frame 70. This osci~ating frame 70 is supported against fallinq down to the bottom by means of butt straps 72 extending downwardly from the pressing frame 60 and by support bolts 74 secured to said straps 72, as shown in Fig. 9 The rhythmic raising and lowering of the osciDating frame 70 causes the strokes of the particular portions of the diaphragm in ea~h settling basin 64.

The mechanical drive for the pulsator movements can be effected on the osci~ating frame by means of rotatable and excentrically operating means. Further, the osci~ating frame can also be driven to execute vibrations or pulsations under the use of a polygonal disc, which is fixed on a rotating shaft. For example, the polygonal disc is in engagement with a roller mounted on the osci~ating frame such that during every revolution of a hexagonal disc the roller and the oscilating frame will _ / _ 2~5 Sch 62 - 30 -experience a number of strokes or pulsations correspondiny to the number of corners on the disc. Pulsation drives of this kind can be provided at one or at both ends of each res pective pulsator machine. Preferably the pulsator drives are infinitely variable. Another kind of driving the Pulsator machine consists in driving the osci~ating frame by means of hydraulic or pneumatic cylinders to execute oscilating move-ments.

~n important contribution to the concentrating effect of the settling machine consists in that the expandible or flexible bottom of the series of settling basins 64 arranged one behind the other is rhythmically raised and lowered, and in that as well the amplitude as the frequency of oscillations can be controlled. Further it is desirable to have the incli-nation of each single chamber pulsator adjustable.

As shown in Fig. 1 the screened fractions produced in the screening machine G are fed by a chute H1 or bucket conveyor H2 to the distributor tanks I1 and I2, respectively. The waste material produced in the chamber pulsators K may be further treated on a dewatering screen L~ The sePerated overgrain is directly discharged to the waste conveyor belt 16, while the undergrain is transported directly to ~he dump, where the watercontents are automatically filtered, or the sludge is pumped to a conveying tower 80 supporting a number of hydro-cyclons 82 one above the other. The heavily concentrated sludge from the lower discharge end of the cyclones is trans-ported to the dump, while the recovered water is recirculated into the dressing and concentrating process.

Sch 62 - 31 -Tests with prototype of the inventional chamber pulsator have been carried out with the cross walls 62 having a height of 45 mm and a width (length) of 210 mm. The oscillating frame with its upwardly protruding laterally extending pistons 68 was driven by means of hexagonal discs causing a stroke of 6 mm upwardly and downwardly.

It is the obiective oi the inventional pulsaking machine to provide a constant rhythmic thrust and suction effect and thereby a steady and smooth rollinq around of the material to be concentrated, which should be carried out completely in-dependent from the nature of the material to be treated.

Tests have shown that the inventional machine operates as well as effective in the treatment of argillaceous sand or gravels as in the treatment of material free of clay~ The continuou~
rhythmic thrust and suction movement of the pulsating machine effected by raising and lowering the diaphragm, are operable to produce a concentration of the goods to be treated and also avoid conglomeration of the material within the settling basins.~Another invenkional result is the mechanical charge of specifially lighter bodies , i.e. the discharge of sand and gravel particles , which is also enhanced by the stream of water and its flow velocity dependent from the inclination of the pulsator trough. During the tests the inventional machine has brought about concentrations in some of the settling basins, such that a concentrated gold content of more than 90 % became found.

- ~2~1Z~

Sch 62 - 32 -If for example gold bearing sands or gravels are treated duxing a certai.n period For being concentrated by the inven-tional pulsator machine, then time by time all settling basins will have been filled with gold. It is recommended the material to be treated only to feed during a certain period to the pulsating machine and to treat it therein as long as necessary to get a gold deposit in the first two thirds of all settling basins are at least partially filled with the material to be concentrated. For emptying the settlinq basins the pulsating machine and consequentlY the entire installation may be shut down.

A number of alterations and improvements may be made in the inventional process and devices without leaving the ~cope of invention~ The pulsating machine may get a locable cover~
which is possible, as no accumulations or conglomerations can take place within the settling basins.

In the tests carried out with the prototype of the inventional pulsatox machine a heavily argillaceous bulk material has been used, wherein the grain sizes differed between a minimum of about 0,01- mm until a maximum of about 7 mm, in order to test the functionality and the capacity of the settling machine under the most dificult conditions which can occur in the concentration of precious metals (particularly gold) , heavy metals and heavy minerals (especially diamonds) in sands or gravels of alluvial deposits.

The waste of these tests became afterwards treated on a shaking table and became investigated in view of eventual 2~

Sch 62 - 33 _ remaining contents of gold. As no gold could be determined any more it can be stated.that the inventional method and devices are particularly adapted for concentration of precious metal particles or heavy minerals in sands and/or gravel of alluvial deposits to an extent , which could not be achieved at all with the method and devices according to the prior art.
The capacity o~ the inventional installations may range for example between 50 m3/h up to 3000 m3/h.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method of concentrating minerals dispersed in a raw material, particularly for concentrating precious metals, heavy metals and minerals and the like, comprising the steps of:
(a) feeding a supply of mineral-containing raw material to an oscillatory conveyor means and thereby partially comminuting said supply; (b) directing jets of pressurized fluid onto said partially comminuted supply and thereby continuing disintegration of said supply; (c) removing particulates having a size exceeding a predetermined size from said supply; (d) preparing a suspension comprising the remaining supply and a fluid; (e) separating said suspension into at least two fractions, each fraction containing mineral particles in a predetermined size range; (f) adding fluid to each of said fractions and agitating said fractions for thereby providing a solid/fluid suspension; (g) flowing each of said suspensions through a separator having a plurality of chambers; (h) altering the direction of flow of said suspensions in each of said chambers and thereby substantially retarding the flow so that mineral particles settle out in each of said chambers; and (i) pulsating said chambers with alternating pressure and suction shocks so that waste particles become entrained in the flowing fluid and are therewith removed from said chambers.

2. The method as defined in Claim 1, including the steps of:
(a) providing a plurality of screen classifiers; and (b) separating said first mentioned suspension into a plurality of size fractions with said screen classifiers.

3. The method as defined in Claim 1, including the step of:
(a) pulsating said chambers from below and uniformly over the length of each of said chambers.

4. The method as defined in Claim 3, including the step of:
(a) controlling the frequency and amplitude of the pulsations in response to the flow velocity of said fluid and in response to the size of said mineral particles in said chambers.

5. The method as defined in Claim 4, including the step of:
(a) pulsating said chambers with pulses having an amplitude of from about 5 to about 6 mm.

6. The method as defined in Claim 1, including the step of:
(a) retarding said suspensions at spaced intervals of between about 60 mm to about 90 mm in the direction of flow.

7. The method as defined in Claim 1, including the step of:
(a) longitudinally and downwardly vertically moving said supply during disintegration.

8. The method as defined in Claim 7, including the steps of:
(a) removing during disintegration from said supply particles having a size less than a predetermined size; and, (b) conveying said just mentioned particles separately from the remaining supply of the raw material.

9. An installation for dressing and concentrating precious metals dispersed in an argillaceous raw material, particularly for gold, heavy metals and minerals, and diamonds, comprising:
(a) a raw material feed station; (b) a washing line for conveying and classifying the raw material comprising a plurality of successively disposed conveyors, said conveyors being disposed so that a preceding conveyor empties onto the next subsequent conveyor which has a receiving portion disposed below the emptying portion of the preceding conveyor so that the raw material topples from one conveyor onto the next and is thereby partially comminuted; and, (c) a plurality of nozzles directed at the carrying surface of said conveyors for impacting the raw material thereon with pressurized fluid and for thereby disintegrating the raw material.

10. The installation as defined in Claim 9, wherein: (a) there being a covered housing means; and, (b) each of said conveyors being disposed in said housing means.

11. The installation as defined in Claim 9, wherein: (a) said conveyors being perforated for classifying the disintegrated raw material.

12. The installation as defined in Claim 9, wherein: (a) each of said conveyors ascending in the longitudinal direction.

13. The installation as defined in Claim 10, wherein: (a) said housing including a bottom portion providing a conveying trough;
and, (b) said housing including lateral walls and said nozzles being securing to said lateral walls.

14. The installation as defined in Claim 13, wherein: (a) said housing being polygonal in cross section and having a top removably connected to said lateral walls.

15. The installation as defined in Claim 13, wherein: (a) said bottom having a wear-resistant lining.

16. An installation for dressing and concentrating precious metals dispersed in an argillaceous raw material, particularly for gold, heavy metals and minerals, and diamonds, comprising:
(a) a raw material feeder station; (b) conveying and classifying means disposed downstream of said feeder station and comprising a plurality of vibratory feeder troughs disposed one behind the other; (c) said troughs being disposed in a stepped array so that a preceding trough is disposed above the next subsequent trough; (d) each of said troughs having a perforated bottom for classifying the raw material; and, (e) a plurality of nozzles being directed at said bottoms for impacting the raw material carried thereon with high pressure fluid and for thereby disintegrating the raw material.

17. The installation as defined in Claim 16, wherein: (a) at least one of said troughs comprises a stepped screen deck;
(b) an oscillating frame being connected to said screen deck for oscillating said screen deck; and, (c) a plurality of said nozzles being directed at said screen deck.

18. An installation for dressing and concentrating precious metals dispersed in an argillaceous raw material, particularly for gold, heavy metal and minerals, and diamonds, comprising:
(a) means for providing a suspension comprising classified raw material of a predetermined size range and the suspension having a solid to fluid ratio of substantially 1:1; (b) agitation means for maintaining the suspension; (c) feed means for feeding the suspension to concentrating means; (d) said concentrating means comprising at least one trough for each of a plurality of size ranges of the raw material, said troughs having a descending bottom and longitudinally spaced cross walls extending between associated side walls for dividing said troughs into a plurality of settling basins; (e) said bottom including an elastic diaphragm means; and, (f) pulsator means being associated with said diaphragm means for applying alternating pressure and suction shocks through said diaphragm means to the material in said basins.

19. The installation as defined in Claim 18, wherein: (a) said pulsator means being disposed below and engaged with said each of said diaphragm means; and, (b) said pulsator means being disposed between consecutive cross walls.

20. The installation as defined in Claim 18, wherein: (a) said troughs each include an outer frame having side walls; (b) said cross walls being associated with trough side walls for therewith forming said settling basins; (c) a lower pressing frame being disposed below said outer frame; and, (d) said pressing frame including cross members and said diaphragm being clamped between said pressing frame and a lower edge of said cross walls for thereby sealingly clamping and supporting said diaphragm.

21. The installation as defined in Claim 20, wherein: (a) piston means being operably engaged with each of said pressing frames for pulsating said diaphragm means by raising and lowering said pressing frames.

22. The installation as defined in Claim 21, wherein: (a) an oscillating frame being operably engaged with each of said piston means for providing a common vibratory drive and for thereby causing simultaneous execution of the pulsations.

23. The installation as defined in Claim 22, wherein: (a) said cross walls including generally U-shaped channels, the open sides thereof being directed downstream; and, (b) the lower leg of said channels being sealingly engaged with said diaphragm means and the upper leg thereof covering substantially 1/3 of the width of the respective basins.

24. The installation as defined in Claim 23, wherein: (a) said basins having a width transverse to the flow direction exceeding the length.

25. The installation as defined in Claim 24, wherein: (a) said oscillatory frame being connected with one of said outer frame and said pressing frame; and, (b) said oscillatory frame being vertical movable.

26. The installation as defined in Claim 25, wherein: (a) said outer frame, said pressing frame and said diaphragm means providing an integral unit; and, (b) a base frame and said unit being pivotally mounted to said base frame to permit emptying of the contents thereof.

27. The installation as defined in Claim 26, wherein: (a) a horizontal shaft being mounted to said oscillatory frame; (b) roller means being mounted to said shaft; (c) a cam disk being mounted to said base frame and being engaged with said roller means for transmitting pulsations thereto; and, (d) means for driving said cam disk.

28. The installation as defined in Claim 20, wherein: (a) control means being associated with said pulsator means for controlling the pulsations in response to the grain size to be concentrated.