O F H EAVY M I N E RALS F RO M PU L P

Field of the Invention

This invention relates to structure of strakes for gravitational settling from pulp of such heavy minerals, in initial granulometric composition of which prevail fine-dispersed and/or lamellar particles. These strakes are meant:

Firstly, for extraction of heavy minerals from disperse enclosing strata and/or soils at mining of natural placers, tails of such natural placers, which were mined by inadequate means, crushed dumps of mining and/or metallurgical works, and ashes of thermal power-stations that use hard fuel, and,

Secondly, for exploration of natural and man-caused placers of valuable heavy minerals and estimation of their recoverable reserves.

Background Art

Strakes for gravitational settling of heavy minerals from pulp flux are well known for a long time (see, for example: LUOXHH B.H., JlonaTHH AT. «rpaBHTai4MOHHbie wieTOflbi o6orau4eHHH», -

M.: HEflPA, 1993; In English: Shokhin V.N., Lopatin A.G. «Gravitation methods of enrichment*,

Moscow: NEDRA Publishing House, 1993). They are preferable in comparison with chemical means for mining of heavy minerals, because water-based pulp, concentrates separated out from this pulp, and moist tails (i.e. mechanical mixtures of unchanged particles of enclosing strata and/or soils and rest of heavy minerals) are biologically inert. Therefore, gravitational settling is practically harmless for operating personnel and natural environment.

Unfortunately, many dredges and washing devices has been equipped until now by usual strakes of shallow filling, which have monolithic cellular carpets and hard immobile guides (see, in particular: Kapwia3 H B.H. ripoueccbi n MawHHbi ana o6oraineHMfl none3Hbix MCKonaewibix. - M: HEflPA, 1974, c. 1 15-188; in English: Karmazin V.I. Processes and machines for enrichment of minerals. - Moscow: NEDRA Publishing House, 1974, pp.115-188). These strakes are simple in design and production and easy-to-operate.

However, efficacy of gravitational settling decreases as densities of base product and enclosing strata and/or soils draws together and fraction of fine-dispersed or lamellar particles of any valuable heavy mineral increases. Moreover, use of said equipment causes sizeable losses of said particles together with tails if even above-mentioned difference of densities is significant

(for instant, in case of extraction of dispersed gold from silica sand).

In fact, the cells of said carpets can be loaded by sediment very quickly (usually for 1.5-2 hours of functioning) and tightly. Therefore, small grains and, especially, fine-dispersed and/or lamellar particles of gold skip over arisen bed and, together with pulp flux, take away into tails pile, and attainable percentage of the base product in obtained concentrate is substantially less than its eventual percentage. For example, extraction about 300 tons of gold from placers in the Amur region of Russian Federation was finished in accumulation more than 10 ⁹ m ³ tails, which - according to geologists' assessment - contain more than 600 tons of non-separated gold. In other words, the large (on reserves) and practically inaccessible (for usual extraction means) man-caused placers had appeared instead of natural placers.

Naturally, that inventors and design engineers aspire to improve strakes for gravitational settling of heavy minerals from pulp in order to increase percentage of the base product in concentrates settling in the catching carpet's cells.

For example, SU 831180 discloses a method for loosening of bed by forced oscillation of riffles of guides. However, this allows loosening only upper layer of detritus settled in the catching carpet's cells, but major portion of concentrate remains practically undisturbed.

Attempts to loosen all mass of concentrate by vibration of a strake in whole (see op cit book of Shokhin V.N. and Lopatin A.G, p.221-228) are uneconomic in terms of energy and stimulate multiple damages of the strake's basic parts. Moreover, such vibration does not provide effective loosening of concentrate settled at the bottom of the catching carpet's cells too (especially in cases if some kinds of pulp contain a black schlich, i.e. particles of natural minerals such as magnetite and ilmenite, and/or artificial minerals such as tailings of ferrous and lead shot, steel grains, dross and other heavy wastes, that settle together with gold particles).

Therefore, loosening of concentrate in order to separate any fine-dispersed and/or lamellar particles of base product from any particles of enclosing strata and/or soils (that form a base of tails of enrichment) must be more purposeful.

One strake able to such loosening is disclosed in RU 2 095 147 (see Fig.1 and its specification). This known strake comprises of:

(1 ) a flow-through gutter, at least a bottom of which is made from non-ferromagnetic material, and which, in operative position, is inclined to the horizontal line and connected by upper end to a pulp source and by lower end to a tailing pile,

(2) an elastic cellular catching carpet, which is placed on the flow-through gutter's bottom and equipped with permanent magnetic elements fixed at least under some cells,

(3) a set of kinematically linked hard guides of shallow filling, each of which - has at least two located at grade above the catching carpet rows of lengthwise undulating in plan riffles that are composed of smoothly conjoined half-sine parts, and

is connected to the drive of its reciprocal motion along the flow-through gutter's sides and said carpet,

(4) a means for excitation of vertical vibrations within the pulp flux; this means is based on a pulse alternating current generator and solenoids, windings of which are connected to the pulse generator, and upper ends of which are placed under the catching carpet's cells equipped with said permanent magnetic elements.

Optionally, the known strake can be equipped with:

(5) a set of kinematically linked hard guides of deep filling, each of which comprises of lengthwise undulating in plan riffles (these riffles are located either above the catching carpet in first strake section, or above the respective guides of shallow filling in any other strake section and connected to the proper reciprocal motion drives), and

(6) transversal riffles, which are fixed rigidly in the guide frames between the rows of said undulating riffles and between each extreme row of such riffles and respective side of the flow- through gutter, and have height that is practically equal to the height of said lengthwise undulating riffles.

The known elastic catching carpet (see Fig.2 of said RU 2095147) has:

an upper cellular layer, in which each cell is confined by a bottom and a skirting, an supporting substrate layer that, in operative position, located on the bottom of the flow- through gutter and fastened to the upper cellular layer, and

said flat permanent magnet elements, which are fixed in respect of the substrate layer and located at least under some cells of upper layer.

In this strake, the lengthwise undulating riffles and the transversal riffles of oscillated guides and the skirtings of the catching carpet's cells decelerate the pulp flux and purposefully distort the velocity field of hard particles. Thus, any 'easy particles' of enclosing strata and/or soils move off from each bulge of the lengthwise undulating riffles, which confine pulp flux in any channel, and any heavy minerals particles remain nearby of these bulges or even approach to them. Vertical vibrations of said carpet parts under action of the pulse solenoids and the permanent magnets loose concentrate settled in the carpet's cells. As a result, repeated redistribution of all hard particles in the velocity field promotes substantial enrichment of concentrate by base product.

Long exploitation of the known strake allows defining that it is effective under conditions such as substantial similarity of initial granulometric compositions of dispersed enclosing strata and/or soils and valuable heavy minerals, and stability of ratio "Hard phase/Liquid" in the pulp within preferable range from 1/10 to 1/7. In fact, excess of liquid promote entrainment of appearing bed into a tails pile and even washing-out of sediment from the carpet's cells, while excess of hard phase hampers loosening of the sediment.

However, even said favorable conditions are insufficient in order to transfer of most part of fine-dispersed and/or lamellar particles of many valuable heavy minerals into concentrate, because this undesirable transfer may be excluded only at the beginning of their sedimentation in the carpet's cells. In order to increase percentage of base product in any concentrate settling in the carpet's cells and, respectively, efficacy of extraction of valuable heavy minerals from natural and man- caused placers a more complicated strake was created (see RU 2 262 385). This strake (which is the nearest analogue of proposed further strake) comprises of:

(1 ) a flow-through gutter, at least a bottom of which is made from non-ferromagnetic material, and which, in operative position, is inclined to the horizontal line and connected by upper end to a pulp source and by lower end to a tailing pile,

(2) a preferably double-layer elastic cellular catching carpet placed, in operative position, on the flow-through gutter's bottom; this carpet has - an upper cellular layer, each cell of which is confined by a bottom and a skirting and, optionally, is equipped with a petal valve located above said bottom, and/or with filaments fastened to said bottom between the valve's petals and the skirting), and

a substrate supporting layer, which is equipped with permanent magnetic elements fixed at least under some cells of the upper cellular layer;

(3) a set of kinematically linked hard guides of shallow filling, each of which is connected to a drive of its reciprocal motion along the flow-through gutter's sides and said carpet; each said set comprises of:

(3a) located at grade above the catching carpet at least two rows of lengthwise undulating in plan riffles composed of alternated in series to bulge direction half-sine parts connected by flat insertions, height of which is practically equal to the height of said half-sine parts, and

(3b) movable plate-shaped transversal riffles that are placed in spaces between said rows of said lengthwise undulating riffles and between each extreme row of said lengthwise undulating riffles and respective side of the flow-through gutter;

(3c) axles of rotation of each row of said plate-shaped transversal riffles; these axles pierce respective said flat insertions at a level no more than the half of their height;

(4) a means for excitation of vertical vibrations within the pulp flux; this means is based on a pulse alternating current generator and solenoids, windings of which are connected to the pulse generator, and upper ends of which are placed under the catching carpet's cells equipped with said permanent magnetic elements.

In this strake each placed under respective cell of the catching carpet permanent magnetic element must be located in operative position under point of intersection of geometrical axis one of said axle and the symmetry plane one of said flat insertions.

Described above forms and arrangement of said undulating riffles and the movable plate- shaped transversal riffles, and regular placement of the permanent magnetic elements under the catching carpet's cells allow theoretically:

firstly, interrupt redistribution of 'easy particles' of enclosing strata and/or soil and heavy minerals particles in horizontal velocity field that was provided during pulp motion around each next half-sine part of lengthwise undulating riffles; this brief interruption occurs near each flat insertion placed between each pair of the half-sine parts of said undulating riffles;

secondly, shake - by vertical vibrations of sediment and pulp in a volume being found above each permanent magnetic element - practically all concentrate settling in the carpet's cells in order to suspend preferably 'easy particles' of enclosing strata and/or soils and transfer their basic part over said transversal riffles into the pulp flux and then into the tails pile.

These synchronous processes facilitate settling of valuable heavy mineral particles into concentrate. Accordingly, percentage of the base product in concentrate increases during each work cycle of the strake.

Unfortunately, said advantages were achieved as a result of substantial complication of the strake. Therefore, this strake has appeared low operate reliability.

In fact, the compound lengthwise undulating riffles having said flat insertions between said half-sine parts and the catching carpet having said permanent magnetic elements must be made and mounted very precisely in order to provide shaking of bed and sediments within the carpet's cells only in aforesaid volumes. These conditions may be kept on application of small-sized strakes during geological exploration, but are practically unrealizable during large-scale mining of placers by big strakes. Moreover, the upper cellular layer of the double-layer elastic catching carpet may drift irregularly about the lower supporting layer during each work cycle. These drifts decrease efficacy of shaking even if the known strake would use for geological exploration. And, finally, unavoidable alternating-sign deformation of the lengthwise undulating riffles causes quite often breakages of said riffles in interfaces the half-sine parts and the flat insertions of theirs.

Summary of the Invention

The invention is based on the problem - by improvement of form and arrangement of means of deceleration of a pulp flux and loosening of a sediment by vertical pushes - to create a more simple and reliable strake for catching of any fine-dispersed and/or lamellar particles of heavy minerals.

This problem, according to the invention, is solved in that a strake for gravitational settling of heavy minerals from pulp comprises of:

(1 ) a made from non-ferromagnetic material flow-through gutter, which is inclined in operative position to the horizontal line and connected by upper end to a pulp source and by lower end to a tailing pile,

(2) a cellular catching carpet placed on the flow-through gutter's bottom,

(3) a set of kinematically linked hard guides of shallow filling, which are independently connected to the drives for their reciprocal motion along the flow-through gutter's sides and said carpet; this set comprises of: (3a) a lower guide that is adjacent to the said carpet and comprises of a rigid frame and rigid preferably straight transversal riffles, and

(3b) an upper guide that is placed above the lower guide and comprises of at least two rows of lengthwise undulating in plan riffles, each of which is composed of alternated in series to bulge direction half-sine parts,

(4) an intermediate resilient support that is located under the flow-through gutter's bottom and has regular recesses, central through hole under each recess, and placed within said recesses non-ferromagnetic pushers, and

(5) a means for excitation of vertical vibrations within the pulp flux; this means is based on a pulse alternating current generator and solenoids having ferromagnetic irons, at that windings of the solenoids are connected to the pulse generator, and their irons are located under said central through holes in said resilient support and equipped additionally by lower stops.

As compared with the strake-prototype, the proposed strake is substantially simpler and trouble-free. Operational testing of the strake showed that adjustable synchronous shaking of all sediment in the said carpet's cells (by said pushers) and mechanical loosening of a bed arisen above said catching carpet (by the lower guide) are well sufficient with the view of separation of the most part of fine-dispersed and lamellar particles of heavy minerals from the pulp flux.

First additional feature consists in that said straight transversal riffles of the lower guide are practically perpendicular to the frame's sides. This provides equal conditions for loosening of the bed and transfer of 'easy particles' of detritus over said riffles.

Second additional feature consists in that each lengthwise undulating in plan riffle is composed of smoothly conjugated thin-layer circular semi-cylinders. This simplifies production of the proposed strake.

Brief Description of the Drawings

The invention will now be explained by detailed description of the improved strake with references to the accompanying drawings, in which:

Fig.1 shows the longitudinal section of the strake (without end parts);

Fig.2 shows the top view of the strake;

Fig.3 shows the cross-section of the strake;

Fig.4 shows the simplest variant of the structure of the lower guide having straight riffles, which are practically perpendicular to the sides of the guide's frame (top view);

Fig.5 shows the same as Fig.4 (longitudinal section by symmetry plane);

Fig.6 shows the more complicated structure of the lower guide having straight riffles, which are inclined to the sides of the guide's frame at an angle less than 90° (top view);

Fig.7 shows a set of examples of possible cross-section of the riffles of the lower guide;

Fig.8 shows schematic view of transfer of detritus over the riffles of the lower guide. Best Embodiments of the Invention

The proposed strake (see Fig.1) has a made from non-ferromagnetic material flow-through gutter, which comprises of sides 1 and (preferably thin-sheet) bottom 2. Said gutter is inclined in operative position to the horizontal line (usually at angle in the range from 6° to 11°) and connected by upper end to a pulp source and by lower end to a tailing pile.

A cellular (usually resilient) catching carpet 3 is placed on the flow-through gutter's bottom 2. A set of kinematically linked lower 4 and upper 5 hard guides of shallow filling are located above said carpet 3. Said guides 4 and 5 are made from non-ferromagnetic material and independently connected to the drives for their reciprocal motion along the flow-through gutter's sides 1 and said carpet 3. These drives are symbolically showed on Fig.1 by not designated especially pushers and hinges and by pairs of oppositely directed arrows.

Each lower guide 4 that is adjacent in operative position to the said carpet 3 comprises of a rigid frame 6 and rigid preferably straight transversal riffles 7 (see Figs 4 and 6). These riffles 7 are usually perpendicular to the sides of the frame 6 (see Figs 4 and 5), but may be located at other angles as it shown on Fig.6. The riffles 7 may be made as rods having different cross- section, e.g. in the form of a rectangle, a solid triangle, a solid semi-cylinder, an angle bar, a bow-shaped bar etc. (see Fig.7). In practice, the angle bar and the bow-shaped bar are preferable. It is also preferable if said straight riffles 7 are practically perpendicular to the sides of said frame 6.

Each upper guide 5 (see Fig.2) is placed in operative position above the lower guide and comprises of at least two rows of lengthwise undulating in plan riffles 8, each of which is composed of alternated in series to bulge direction half-sine parts. For the purpose of simplicity of production, these riffles 8 are usually composed of smoothly conjugated circular thin-layer circular semi-cylinders.

The strake (see Figs 1 and 3) is equipped with placed under the bottom 2 -

First, an intermediate (entire or composed of transversal strips) resilient support 9 that has not designated especially regular (preferably cylindrical) recesses, central through hole under each recess, and placed within said recesses non-ferromagnetic pushers 10 shaped usually as plain washers, and,

Second, a means for excitation of vertical vibrations within the pulp flux; this means is based on not showed especially a suitable pulse alternating current generator and solenoids 11 having ferromagnetic irons 12. In operative position, windings of the solenoids 11 are connected to the above-mentioned pulse generator, and said irons 12 are located under said central through holes in said resilient support 9 and equipped additionally by not showed especially lower stops.

The described strake can use for mining of heavy minerals and exploration placers of theirs as follows.

At first, the catching carpet 3 must be placed on the flow-through gutter's bottom 2, and said gutter must be mounted in desirable operative position. Then a personnel switch on above- mentioned drives of reciprocal motion of said guides 4 and 5, begin delivery of a pulp, and switch on solenoids 11.

Wave-like form of channels between said undulating riffles 8 and between them and the sides 1 of said flow-through gutter causes deceleration of the pulp flux and redistribution of 'easy particles' of enclosing strata and/or soils and 'heavy particles' of valuable mineral in velocity field within aforesaid channels. Reciprocal motion of said guides 5 promotes the redistribution of all said hard particles additionally.

Important features of the strake's operation are as follows (see Fig.8).

The irons 12 of the solenoids 11 actuate practically synchronous and intensity-regulated vertical impacts of plain washers-pushers 10 in the thin-sheet strake's bottom 2. These impacts shake efficiently practically all mass of concentrate settling in the cells of said carpet 3 and the bed as it forms above said carpet 3. Additional loosening of said bed provides by the transversal riffles 7 of the lower guide 4 being in the reciprocal motion.

These processes facilitate emersion of 'easy particles' of enclosing strata and/or soils and transfer of theirs over said transversal riffles 7 together with the pulp flux into the tailing pile, and falling of 'heavy (including even fine-dispersed and/or lamellar) particles' of valuable mineral along side surfaces of said riffles 7 into the cells of the catching carpet 3 and formation of concentrate.

When the cells of the catching carpet 3 would be fulfilled with concentrate of the base product, the personnel make an end of delivery of the pulp into the strake and, practically at the same time, switch off above-mentioned drives of the reciprocal motion of the guides 4 and 5 and cut off the power from the solenoids 11. Then the personnel take out the catching carpet 3 from said flow-through gutter, remove obtained concentrate from the cells of the catching carpet 3 and encase it in a not shown shielding container, which serves for storage and transportation of the concentrate to a refinery.

Further this procedure can be repeated, as described above.

It is clear for the person skilled in the art that described embodiments do not confine the scope of the invention, and that the described strake may be equipped with:

firstly, sensors suitable for measurement of current value the ratio "Hard phase/Liquid" in real pulp and other means for control of this ratio, an automatic system for control of excitation of vertical vibrations within the pulp flux, etc.,

secondly, replaceable guides 4 and 5 having different forms and dimensions of transversal

7 and undulating 8 riffles and replaceable pushers 10 having different masses, thirdly, peripherals such as any upstream catcher of ferromagnetic impurities, at least one other additional downstream strake, etc.

Industrial applicability

The strakes according to the invention can series-produce at present machine-building plants. Further they can be used preferably as output devices of dredges or other devices for industrial hydraulic mining of such both natural and man-caused placers those contain precious metals particles related to preferable shallow granulometric classes (less than 0.15 mm).

In addition, the strakes according to the invention are applicable:

For after-treatment of tails of schlich-beneficating devices and factories,

For selection of unprofitable gold and platinum admixtures to such friable build materials as sands (at the time of their hydraulic extraction),

For exploration works and researches studies of soils, residual soils, processes of supergene mineralization, and sedimentary deposits.