WO2019161515A1

WO2019161515A1 - Method for separating ore from worn steel balls or fractured steel balls that come out of a semi-autogenous grinder (sag) with the ground ore

Info

Publication number: WO2019161515A1
Application number: PCT/CL2019/050012
Authority: WO
Inventors: Gilda TITICHOCA AGUIRRE; Ricardo FERNÁNDEZ DOBERTI; Guillermo BÓRQUEZ CERPA
Original assignee: Lmagne Ingeniería Ltda.; Process Technology Spa; Comercial Engesol Ltda.
Priority date: 2018-02-21
Filing date: 2019-02-20
Publication date: 2019-08-29
Also published as: CL2018000467A1

Abstract

The present invention relates to a method for separating ore from worn steel balls or fractured steel balls that come out of a semi-autogenous grinder (SAG) with the ground ore mineral. The method also comprises the alternative of continuous recovery of near-spherical pieces of balls, which can be re-used as grinding means.

Description

PROCESS TO SEPARATE THE MINERAL FROM THE BALLS OF

SPORTS STEEL OR FRACTURED STEEL BALLS COMING OUT OF A SEMIAUTOGEN (SAG) MILL

WITH GROUND MINERAL

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process for separating the ore from spent steel balls or fractured steel balls leaving a semi-autogenous mill (SAG) together with ground ore. The process also includes the alternative of continuous recovery of ball pieces with a spherical shape that can be reused as grinding media.

BACKGROUND OF THE INVENTION

In the state of the art, in the area of mining, the separation of spent steel balls and pieces of fractured balls of the ore is done using magnets located on the conveyor belt that carries the thick fraction of the product of the semi-autogenous mill (called pebbles) and whose size is generally larger than ½ in. This operation presents problems when the metal pieces are covered by ore on the conveyor belt and / or if the magnet has failures. The problem is even more serious when the mineral contains magnetite or other mineral species with levels of magnetic susceptibility that causes them to be attracted to the magnet, so this separation process cannot be implemented. In general, in order to maximize the efficiency of In the process, the pebbles are reduced in size in crushers and subsequently returned to the semi-autogenous mill or sent to the ball mills corresponding to the next size reduction stage. The presence of metal elements does not allow the use of crushers because they are damaged causing the process to stop, so being unable to implement the process of separation prior to this requires the return of unprocessed pebbles with spent balls and pieces of fractured balls to the semi-autogenous mill, which significantly affects the efficiency of the grinding process.

The semi-autogenous grinding mills of minerals (1) are machines, which basically consist of a rotary drum with a horizontal axis, which has an inlet (6) of ore (load) to be ground at a first end and an outlet (7) of the ground ore (charge) that has reached the desired size, through a second end. Metal grinding media, generally spherical and preferably steel, corresponding to the grinding balls are also added through the inlet (6). In the case of wet milling, water is also added, in this way, the internal load of the semi-autogenous mill is composed of grinding balls, mineral and water (8) that are in permanent motion in the grinding chamber (2) while The semi-autogenous mill rotates. In Figures 1 to 3, it can be seen that the internal load (8) of the semi-autogenous mill (1) is composed of ore (10), balls (9) and water in the case of wet grinding. Both the mineral and the balls of the internal load (8) inside the grinding chamber (2) decrease in size due to the movement caused by the rotation of the semi-autogenous mill (1), where the same mineral (10) and balls (9) when falling suffer blows that cause the fracture of the mineral (10), as well as abrasion by the relative movement between the components, in addition to attrition when the ore particles (10) are subjected simultaneously to friction and compression forces by the moving load. When the mineral (10) contained in the load (8) reaches a predetermined size, it passes through the grooves (5) of a grill (4) from the grinding chamber (2) to the discharge chamber (3), and then leave the semi-autogenous mill (1) through the exit of the load (7) to the sorters or trommels classifiers (14).

One of the important elements of a semi-autogenous mineral grinding mill is the internal grill (4), which has a plurality of grooves (5) that have an opening with a predetermined size, so that the mineral (10) that has reached said size leave the semi-autogenous mill (1). The balls (9) used as milling elements in the semi-autogenous mill (1), when added to the semi-autogenous mill, are larger than the groove opening (5). As the process progresses, the balls (9) wear out by abrasion and decrease in diameter, becoming smaller balls

(1 1) that reach the slot opening size (5) and, therefore, also pass to the discharge chamber (3) and then to the exit (7), leaving the semi-autogenous mill (1) towards the classifiers (14). Also, during the grinding process, there are balls (9) that break, and thus these fractured balls (12) also reach a sufficient size to pass through the slot opening (5), as shown in the Figure 3. With the above, from the semi-autogenous mill (1) comes the ground ore (10), the spent balls (1 1) and the pieces of fractured balls (12), as well as water when it comes to wet grinding. During the operation of the semi-autogenous mill, the grill (4) can also suffer the fracture of one of its nerves, as shown in Figures 4 and 5. Thus, the exposed opening corresponds to two grooves (5) communicated generating an opening larger (13), where ore (10) and larger balls (9) can pass that should remain in the grinding chamber (2). This problem can be seen in Figure 5 of the prior art. The fracture of the grills can also occur in other areas, such as in a corner, also generating grooves with larger openings, as shown in figure 7. Like those already mentioned, there is the possibility that the fracture of the Grill happen in different ways.

According to the above, from the semi-autogenous mill, mineral and steel pieces come out, which reaches the classifiers and, both the mineral (pebbles) and balls and / or larger pieces of ball, follow the conveyor belts to the subsequent processes In general, the pebbles are reduced in size using cone crushers that are damaged if there is presence of steel elements in the feed, reaching, for example, the fracture of their components, causing their arrest for the corresponding repair. This condition forces to separate the spent balls, larger balls that have come out through a groove with a broken nerve, and fractured balls, so that said pieces of steel balls are not desired during the process. This problem is accentuated when the mineral that is part of the pebbles has contents of magnetite or other mineral species with magnetic susceptibility properties that have magnetic properties similar to steel, so it is removed from the mineral process and balls or their pieces. Therefore, it is necessary to look for technological alternatives that allow separating the mineral, for example magnetite, from spent steel balls or fractured steel balls.

Therefore, the process of the present invention, acts on the mineral and steel that leaves the mill (1), is on the surface of the harnero or classifier (14) and then passes to the conveyor belt (15), as It is shown in figure 8.

Thus, the problem to be solved in the state of the art is that mineral (pebbles) and spent balls and pieces of fractured balls are retained on the external harnero or trommel classifier (14) of the semi-autogenous mill. This mixture retained on the surface of the classifier (14), is transported on conveyor belts and on the way the metal (balls and pieces of balls) must be separated, before the ore reaches the crushers or is returned to the SAG mill without Crush. Magnetos are currently used, so that the mineral is still in the process and the metal (balls and pieces of balls) are discarded or passed to a manual separation process whose objective is the reuse of steel with a near spherical shape as a means of grinding.

In the particular case of minerals with a high content of magnetite or another mineral species with sufficiently high magnetic susceptibility, the magnets remove both the steel and the mineral, so the material that is discarded has both mineral and pieces of steel. The amount of discarded ore is important and represents a significant economic value for companies.

To recover the mineral from the mixture of the discarded product, in the mining plants, two alternatives are used: 1) Make a manual separation of what separates the magnet, which is slow and expensive; Y

2) Return the mixture (mineral plus steel) to the semi-autogenous mill, which implies reducing efficiency to the milling process, since the steel pieces do not help to grind, but they do consume energy and the mineral pieces, the pebbles, present a greater resistance to being reduced in size.

In the case of iron ores, with high magnetic susceptibility, in many parts of the world autogenous grinding, AG, is used (without metal grinding media) with higher process costs, but they avoid the problem of spent balls and pieces of fractured ball, but allows to crush the coarse fraction of the ore separated by the classifier (pebbles). When using semi-autogenous grinding, SAG, in the processing of iron ores, the mixture of spent ore and balls and fractured ball pieces must be returned, adding inefficiency to the process by maintaining a circulating load of steel that only consumes energy inside the mill .

The process of the present invention is oriented to take this mixture (pebbles and steel pieces) and separate them in line using gravitational concentration apparatus, in particular Jig, so as to:

a) effectively separate the steel to discard it as unusable material or recover those parts that can be reused as grinding media; Y

b) keep the mineral in the process and not discard it, particularly when it has magnetite contents that causes it to drag along with the steel. In the patent literature there have been only attempts to apply gravitational concentration processes to magnetite minerals. Thus, for example, RU 2307710 discloses a method of concentration of minerals, in particular magnetite minerals. The method allows to reduce the part of the ballast material (which does not require grinding and crushing). The method includes feeding the pulp-shaped material intended for magnetic separation into a humid apparatus, where using the gravitational method the pulp-shaped material is separated into two fractions: the light fraction and the heavy fraction. The heavy fraction is sent directly for crushing (joining it with the magnetic separation product), or using the magnetic field, it is divided into the non-magnetic part and the magnetic part, in which the non-magnetic part is poured into the tailings, while The magnetic part is directed to the mill or subjected to gravitational separation with the production of heavy and light products. The heavy product consisting of the particles of the useful mineral is removed avoiding a new crushing as a crude iron concentrate. The light product is sent to the rotary mill. The invention disclosed in this document allows reducing the proportion of ballast material (which does not require grinding).

RU 2246996 discloses a gravitational concentrator and deals with the field of the mining industry, mainly for the concentration of minerals for the final treatment of metal concentrates. The gravitational concentrator includes a cone-shaped chamber, a device that feeds the chamber, a container for periodic release of the batch concentrate. The camera is reversed with its apex of a cone down. The material is fed through a device in the form of a hollow shaft with a release window located inside the camera. The hollow shaft is supplied with a tearing device. The tearing device is made with a rotating capacity in the form of needles as an evolver. The chamber is provided with annular type receivers with connection tubes and control gates to ensure a uniform distribution of water in different cross sections in cone height. The surface of the cone is perforated. The concentrator contains no less than three chambers with a common drive for the simultaneous separation of fine grains from the material. The technical result is a greater efficiency of particle separation due to its density.

Document CN 2405658 discloses a trapezoidal jigger gravitational concentrator of lower movement type which refers to an improvement of the gravity selection device. The jigger gravitational concentrator has the structure of a sieve plate with a hole that is arranged in the upper part of a sieve chamber and the upper surface of the sieve plate is provided with a metal or magnetite ball of 5 to 6 Density like an artificial bed. A rubber diaphragm is arranged at the bottom of the jigger chamber. A motor and a speed reducer actuate a crank link mechanism so that the diaphragm moves up and down in an alternative way. The jigger gravitational concentrator has the advantages of simplifying the structure of the device, convenient adjustment for operating parameters, high recovery rate, energy saving, water saving, etc.

The closest document found is RU 2307710 where ore without magnetite is separated from magnetite containing material, but always in the field of mineral separation. The mineral that does not contain magnetite is removed to the tailings and the larger mineral that contains magnetite continues to the milling processes.

None of the documents of the state of the art disclose the use of a gravitational concentration separator to separate the steel (spent balls and fractured balls) from the mineral containing magnetite.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide greater understanding of the invention and constitute part of this description and further illustrate some of the preferred embodiments of this invention.

Figure 1 shows a cross-section of a semi-autogenous mineral grinding mill of the prior art, which works rotating on its axis to produce the reduction of mineral sizes.

Figure 2 shows a longitudinal section of a semi-automatic mineral grinding mill of the prior art.

Figure 3 shows the scheme of a discharge grill used inside the semi-autogenous mill of the prior art with the load inside the semi-autogenous mill passing through it.

Figure 4 shows an enlargement of a perspective view of a grill that has a fracture, causing a hole through which larger balls and ore escape and should remain in the grinding chamber. Figure 5 shows a longitudinal section of a semi-autogenous mineral grinding mill of the prior art, where the grill has suffered the fracture of one of its nerves.

Figure 6 shows a scheme of the exit of a ball of maximum size added to the mill through the hole caused by the fracture of the grill, also being able to leave pieces of ore of larger size.

Figure 7 shows an enlargement of a perspective view of a grill that has a fracture in one of its corners, causing a hole through which larger balls and ore escape and that should remain in the grinding chamber.

Figure 8 shows a schematic view of a mill, a sorter and a conveyor belt, which carries worn steel balls and pieces of steel balls together with ore.

Figure 9 shows a flow chart of the process of separating spent steel balls and pieces of steel balls from ore, in particular ore containing magnetite or other mineral species with high magnetic susceptibility, using a gravitational concentrator, where the flow of ore and balls comes directly from the SAG mill.

Figure 10 shows a flow chart of the process of separation of spent steel balls and pieces of steel balls from ore, in particular ore containing magnetite or other mineral species with high magnetic susceptibility, using a gravitational concentrator, where the flow of ore and balls comes from any part of the process, where there is some semi-autogenous grinding stage. Figure 1 1 shows a diagram of the Jig gravitational concentrator preferably used in the present invention.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for separating the mineral, in particular mineral containing magnetite or other mineral species with high magnetic susceptibility, from spent steel balls or fractured steel balls leaving a SAG mill together with ground ore. Specifically, the present invention relates to a process for separating the ore from spent steel balls or fractured pieces of steel balls using a gravitational concentration step to separate the ore and steel.

Referring to Figure 9, from the SAG mill (1) comes out mineral and worn steel balls as well as pieces of fractured steel balls. This load of ore and steel falls towards the classifier (14) where the larger ore, together with the steel, is on its surface and then falls on the conveyor belt (15), which carries the load to the mailbox (16 ) that regulates the flow of ore and steel to drive it to a conveyor belt (17). This conveyor belt can drive the material towards a sorting ram (18) whose objective is that only particles of a certain size reach up to the gravitational concentrator or Jig (23), that is, it takes out that finest fraction, for example, particles of a size smaller than 10 mm so that they do not enter the gravitational concentrator. Alternatively, it is possible for the conveyor belt (17) to direct the material directly to the gravitational concentrator or Jig (23), since with the classification that is made at the exit of the SAG mill with the classifier (14) it may be sufficient.

On the sorting hammer (18) there is a water spout (37) to form a wet mixture of mineral and steel, where the water from said spout (37) arrives through a water line (38) and this, to in turn, from a pond of water (33).

This water tank (33) receives a flow of fresh water (42), which is water that is replenished in the process and is equivalent to the amount of water lost in the steel separation circuit of the process of the present invention.

The sorting hammer (18), which is optional, separates the feed to the process into three flows, and whose objective is to control the range of sizes that will feed the gravitational concentrator. A first flow of material (24), mineral and steel, very thick for the concentrator and discarded; a second flow of material (20), mineral and steel that feeds the gravitational concentrator; and a third flow of material (19), mineral and steel, which is very fine for the gravitational concentration process and that joins the separated ore flow, and which due to its granulometric characteristic does not affect the operation of the crusher.

The first material flow (24) that contains ore and steel of thicker size established according to the slot size of the SAG mill grill being preferably greater than 65 mm, is transported through the conveyor belt (25) to the product Discard

The second material flow (20) containing mineral and steel of adequate size for the process, for example between 10 and 65 mm corresponding to the size established according to the slot size of the SAG mill grill, is conducted towards the gravitational concentrator (23), in this case Jig, to separate the material by density.

The third material flow (19) containing ore and steel of smaller size than the second material flow (20) is suitable for exiting the process through the conveyor belt (32) next to the separated ore in the gravitational concentrator, and It is able to be sent to the crushing stage.

The third material flow (19) falls into a drain screw (21) that separates the flow of ore with water (19) into a flow of water (40) and a flow of dry ore (22), which contains only moisture. This flow of dry material (22) is sent to the conveyor belt (32), which can in turn send it to the crushers since said dry material (22) has maximum sizes that do not cause damage, for example smaller to 10 mm

The water flow (40) and the second flow of mineral and steel (20) as well as an additional flow of water (39) from the pond (33), are sent to the gravitational concentrator (23), in this case Jig, which separates its content in a flow of wet mineral (27) and in a flow of steel (26).

The steel flow (26), formed by worn steel balls and / or fractured ball pieces, is sent to a ripping hammer (29) that is used to recover water from the solid material, transforming it into water flow (34) which is recovered to return it to the process through a line (36) that ends in the pond (33).

The flow of wet mineral (27) that leaves the gravitational concentrator (23) is mineral without spent steel balls and / or pieces of fractured balls, so it is sent to the drain drain (30) to separate the water (35) of the flow of dry mineral (31). The flow of dry ore (31) is sent to the conveyor belt (32), which can in turn send it to the crushers since said dry ore (31) lacks steel.

The flow of material with worn steel balls and / or pieces of fractured balls (28) that leaves the drain harness (29) is sent to a conveyor belt (41) to abandon the process by sending it to the ball rejection stock. The scrubber hammer (29) can be replaced by a double deck harnero that allows three products to be generated in three flows: a first flow with a thick product that represents balls that are still the size to be reused in ball mills or SAG mills; a second flow with an intermediate product representing the ball rejection material; and a third flow of recovered water for reuse. The discard flow (24) of the primary harnero can be joined with the thick product of this harnero, and can be considered for reuse in ball mills or SAG mills, preferably having sizes larger than 65 mm.

A similar process is shown in Figure 10 in which the mixture of ore with steel entering the mailbox (16) can come from any part of a milling process, in which steel elements are used, such as balls .

As described above, the fundamental element of the present invention is the gravitational concentrator (23), in this case Jig, whose operation is explained in Figure 1 1.

The gravitational concentrator or Jig (23) is formed by sieves, sieves or grids (43) submerged in a fluid. The fluid prints a vertical movement (44) to the mineral and steel particles (20) to be separated (by lifting and dropping them), so that due to the difference in their density, they experience differential acceleration and, therefore, the densest particles (45) are deposited at the bottom (in contact with the grid (43)), while the lighter particles (46) are deposited at the top, forming easily separable stratifications. Water pulses are regulated in strength and breadth, according to the materials and sizes to be separated, those given according to engineering specifications by a person versed in the art.

Claims

1. A process for separating the ore from spent steel balls and / or fractured steel balls leaving a SAG mill together with ground ore, which comprises the following steps:

(a) carry the load of ore and spent steel balls, as well as fractured steel balls to a mailbox (16), which regulates the flow of ore and steel to drive it towards a conveyor belt (17);

(b) separating the contents of a sorting hammer (18) into three flows: a first flow of material (24), mineral and steel that is discarded or reused as a milling medium; a second flow of material (20), mineral and steel that goes into a gravitational concentration process; and a third flow of material (19), mineral and steel with smaller particle sizes, CHARACTERIZED because it also includes the stages:

(c) eliminate the first material flow (24) with larger sizes, established according to the slot size of the SAG mill grill being preferably greater than 65 mm, to be processed by a gravitational concentrator through a conveyor belt (25 ) to abandon the process towards discards;

(d) conduct the second flow of ore and steel (20) with suitable sizes, preferably between 10 and 65 mm, the latter being defined according to the previous point, towards a gravitational concentrator (23), preferably of Jig type, to separate by density the mineral and steel;

one (e) driving the third flow of wet material (19) to a degassing screw (21) that separates the flow of wet material (19) into a water flow (40) and a flow of dry material (22);

(f) send the flow of dry material (22) to a conveyor belt (32), which in turn sends it to crushers since said dry material (22) has particle sizes that do not affect the condition of this equipment , preferably less than 10 mm;

(g) send the water flow (40) and the second flow of mineral and steel (20) as well as an additional flow of water (39) from a pond (33), to the gravitational concentrator (23) that separates its contained in a flow of wet mineral (27) and in a flow of steel (26);

(h) send the flow of steel (26) to a steam drain (29) to separate it into a flow of steel (28) and a flow of water (34);

(i) send the steel flow (28) to a conveyor belt (41) to abandon the process by sending it to the steel waste stock;

(j) send the flow of wet mineral (27) to a drain drain (30) to separate the water (35) from the flow of dry mineral (31); Y

(k) send the flow of dry ore (31) to the conveyor belt (32), which in turn sends it to crushers or to the SAG mill, where said dry ore (31) lacks steel.

2. A process according to claim 1, CHARACTERIZED in that the water tank (33) receives a flow of fresh water (42), which is water that is returned to the

two process and that is equivalent to the amount of water lost during the separation circuit of the ore from the steel.

3. A process according to claim 1 or 2, CHARACTERIZED in that the water flow (34) exiting the destemmer washer (29) and the water flow (35) exiting the desassembly harnero (30) are recovered to return them to the process by means of a line (36) that ends in the pond (33).

4. A process according to any one of claims 1 to 3, CHARACTERIZED in that in step (m) at the end of the conveyor belt (41) alternatively a deburring or similar hammer is placed to capture the balls that are still sized for recycle them to the SAG mill or ball mill, preferably having sizes larger than 65 mm.

5. A process according to claim 4, CHARACTERIZED in that the destemmer harnero (29) is a double deck harnero that generates three flows:

a first flow with the thick product representing balls that are still the size to be reused in ball mills or SAG mills, preferably sizes larger than 65 mm;

a second flow with the intermediate product representing the ball rejection material; Y

a third flow of water recovered for reuse,

3 where the discard flow (24) of the primary hanero alternatively joins with the thick product of this hanero, to be reused in ball mills or SAG mills.

6. A process according to any of the preceding claims,

CHARACTERIZED because in stage (a) where the ore load and worn steel balls are carried, as well as fractured steel balls, it previously comprises the stages of:

(a1) remove the ore load and spent steel balls, as well as fractured steel balls from the SAG mill to the classifier (14); Y

(a2) drop the ore load and worn steel balls, as well as fractured steel balls towards the conveyor belt (15).

7. A process according to any of the preceding claims, CHARACTERIZED because after stage (a) where the ore load and worn steel balls are carried, as well as fractured steel balls, optionally comprises the stage of:

(a3) send the ore load and spent steel balls, as well as fractured steel balls to a sorting horse (18).

8. A process according to claim 7, CHARACTERIZED in that it further comprises the step optionally:

4 (a4) supply water to the sorting ram (18) to form a wet mixture of mineral and steel, where the water from the dispenser (37) comes through a water line (38) and, in turn, from the water pond (33).

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