Beneficiation recovery process for dip-dyed superfine low-grade magnetite

Abstract

Raw ore is extruded and crushed through a high-pressure double-roller machine and sieved through a linear sieve, then the raw ore is fed into a coarse grain magnetic separator for ore dressing and tailing discarding, and obtained rough concentrate is subjected to ore dressing and tailing discarding through a two-stage ore grinding-magnetic separation-rotational flow classification circulation process. And the obtained second-section overflow product is subjected to dewatering screen and concentration magnetic separation to obtain concentrated iron ore concentrate pulp, the concentrated iron ore concentrate pulp is subjected to ore grinding through a moxa sand mill and then elutriation, high-grade total iron ore concentrate is obtained, elutriation overflow water returns to a linear screen to be reused, and tailings in the technological process are subjected to rotational flow classification, dewatering or concentration and filter pressing to form different tailings products. By adjusting the sequence of magnetic separation and rotational flow classification and adding the moxa sand milling procedure and the tailing treatment procedure, the method has the characteristics of simple process flow, large treatment capacity, segmented tailing discarding, low production cost, high grade of total iron ore concentrate, high comprehensive utilization rate of tailings, environmental friendliness and the like, and the utilization value of ultra-lean, fine and miscellaneous magnetite is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron ore dressing, and in particular relates to a dressing and recovery process for impregnated ultrafine low-grade magnetite. Background Art

[0002] Iron ore is an important raw material for steel smelting. Iron ore resources are abundant and varied, among which "poor, mixed, and fine" difficult-to-select ores account for a considerable proportion. As easy-to-grind and easy-to-select iron ore resources are gradually exhausted, "poor, fine, mixed" difficult-to-select ores are the main iron ores for development and utilization. Among the difficult-to-select iron ores, low-grade iron ores with ultra-fine embedded particle sizes and magnetic iron grades of only 5-15% account for a relatively high proportion. The target minerals in this type of ore are mostly distributed in the gangue minerals in the form of impregnation or fine stripes, and effective monomer dissociation can only be achieved through fine grinding. The method for processing this type of difficult-to-select magnetite in the prior art is mainly to increase the number of closed-circuit grinding stages on the basis of the beneficiation process of higher-grade magnetite to achieve the purpose of improving the magnetic iron grade. However, on the one hand, too many stages lead to an increase in equipment investment and site occupation, increase investment costs, and reduce production efficiency; on the other hand, the conventional closed-circuit grinding process is grinding-overflow classification-magnetic separation. During the classification process, the sedimentation part needs to be returned to the grinding equipment for circulation grinding. However, since the target mineral grade of the difficult-to-select magnetite is low and it is distributed in an impregnated manner, and the proportion of non-target minerals is high, overflow classification first will increase the circulation volume of the grinding process, reduce the effective dissociation degree of the target mineral, reduce the effective power of the grinding equipment, extend the beneficiation process, and increase the grinding cost, which is not conducive to energy saving and consumption reduction and the reduction of production costs, nor is it conducive to the improvement of magnetite grade and recovery rate. In addition, a large amount of tailings will be generated during the beneficiation and recovery process of this type of difficult-to-select magnetite, most of which have not been utilized or have a low degree of utilization in existing treatment methods, resulting in a large waste of resources. Summary of the invention

[0003] The purpose of the present invention is to propose a beneficiation and recovery process for impregnated ultrafine low-grade magnetite in view of the problems of high energy consumption, low beneficiation efficiency, high production cost, low recovery rate, difficulty in improving the grade of iron concentrate and low utilization rate of tailings in the existing low-grade magnetite beneficiation. By simply adjusting the existing process sequence, the grinding circulation volume can be reduced, the useful power of the grinding equipment can be improved, the dissociation degree of the target mineral can be increased, the equipment investment can be reduced, and a higher concentrate grade and recovery rate can be obtained. At the same time, the tailings can be graded and utilized to maximize the utilization of the tailings.

[0004] In order to achieve the above-mentioned purpose of the invention, the present invention proposes a mineral processing and recovery process for disseminated ultrafine low-grade magnetite, and the specific implementation steps are as follows:

[0005] S1, feed the raw ore that has been crushed to a particle size of 0-30 mm into a high-pressure double-roll mill to obtain powdered minerals with microcracks, feed the powdered minerals into a linear screen for washing and wet screening, obtain the oversize product and the undersize product, mix the oversize product with the raw ore and feed it back into the high-pressure double-roll mill for cyclic extrusion and crushing;

[0006] S2, feeding the undersize product obtained in step S1 into a coarse-grained wet magnetic separator for coarse-grained magnetic separation, obtaining a coarse concentrate from the coarse-grained magnetic separation, and discharging the coarse-grained magnetic separation tailings;

[0007] Preferably, the coarse particle wet magnetic separator in this step is a permanent magnet downstream magnetic separator, and the magnetic field strength is set to 0.28-0.30T;

[0008] S3, feeding the coarse magnetically separated coarse concentrate obtained in step S2 into a first-stage mill, feeding the first-stage grinding product into a primary magnetic separator, obtaining a primary magnetically separated coarse concentrate, discharging the primary magnetically separated tailings, feeding the primary magnetically separated coarse concentrate into a first-stage cyclone to obtain a first-stage overflow product and a first-stage underflow product, and returning the first-stage underflow product to the first-stage mill-primary magnetic separator-first-stage cyclone for a cyclic operation;

[0009] Preferably, the primary magnetic separator in this step is a wet semi-countercurrent magnetic separator, the magnetic field strength is set to 0.28T, and the overflow particle size control range of the first stage cyclone is -200 mesh, 70% to 80%;

[0010] S4, feeding the first overflow product obtained in step S3 into the second cyclone to obtain the second underflow product and the second overflow product, feeding the second overflow product into the linear dewatering screen II for impurity removal, and obtaining the second overscreen product and the second underscreen product; the second underflow product and the second overscreen product are combined and fed into the second mill, and the obtained second milling product is fed into the secondary magnetic separator to obtain the secondary magnetic separation coarse concentrate, and the secondary magnetic separation tailings are discharged; the secondary magnetic separation coarse concentrate and the first overflow product are combined and fed into the second cyclone-second mill-second magnetic separator for a cyclic operation;

[0011] Preferably, the overflow particle size control range of the second-stage cyclone in this step is -325 mesh, 65% to 75%, the mesh size of the linear dewatering screen II is set to 0.3 mm, the secondary magnetic separator is a wet semi-countercurrent magnetic separator, and the magnetic field strength is set to 0.25 T;

[0012] S5, feeding the second-stage undersize product obtained in step S4 into a concentrating magnetic separator to obtain concentrated iron ore concentrate slurry, discharging concentrated magnetic separation tailings, feeding the concentrated iron ore concentrate slurry into a three-stage mill, feeding the obtained three-stage grinding product into a tertiary magnetic separator, obtaining tertiary magnetic separation concentrate, and discharging tertiary magnetic separation tailings;

[0013] Preferably, in this step, the magnetic field strength of the concentration magnetic separator is set to 0.28T, the pulp concentration after the concentration magnetic separation is controlled in the range of 45% to 60%, the tertiary magnetic separator uses a wet semi-countercurrent magnetic separator, the magnetic field strength is set to a smaller 0.16T, the three-stage mill uses an Aisha mill, and the particle size control range of the obtained three-stage grinding product is -325 mesh, not less than 90%, so that the ultrafine iron minerals are fully dissociated;

[0014] S6, feeding the tertiary magnetic separation concentrate obtained in step S5 into a washing magnetic separator, obtaining the final total iron concentrate through the action of high-pressure water flow and composite magnetic field, and discharging the washing overflow water;

[0015] Preferably, in this step, the elutriation magnetic separator is a vertical elutriation magnetic separator, and the specific process of elutriation is as follows: after the tertiary magnetic separation concentrate is fed into the elutriation magnetic separator, high-pressure water is tangentially fed from the bottom and middle of the elutriation magnetic separator to form a spirally ascending uniform water flow in the separation area, and the gangue minerals and conjoined minerals in the tertiary magnetic separation concentrate overflow with the ascending water flow to form elutriation overflow water; the magnetic iron minerals in the monomer dissociation state descend and are discharged from the bottom under the action of the periodic composite magnetic field to form a total iron concentrate;

[0016] Furthermore, the overflow water discharged in this step is returned to step S1 as flushing water for the linear screen and recycled to save water, and the intergrown minerals overflowed with the overflow water are returned to the mineral processing process to increase the recovery rate of the iron ore.

[0017] Furthermore, in order to make full use of the tailings, the coarse-grained magnetic tailings of S2 and the primary magnetic tailings of S3 are combined and classified through a cyclone to obtain overflow tailings and sedimentation tailings. The overflow tailings, the secondary magnetic tailings of S4, the concentrated magnetic tailings and the tertiary magnetic tailings of S5 are combined and entered into a concentration tank for concentration, and then fed into a plate and frame filter press for filtration and dehydration. The dehydrated tailings are used as iron correction materials in cement plants; the sedimentation tailings are fed into a linear dewatering screen I, and the above-screen products are used as building sand, and the below-screen products are returned to the cyclone for further classification.

[0018] Beneficial Effects

[0019] One of the above technical solutions has the following advantages or beneficial effects:

[0020] 1) By adopting the process of crushing first and then high-pressure roller extrusion, and wet throwing before magnetic separation, a large number of microcracks are generated inside the ore particles before magnetic separation, part of the magnetite is dissociated in advance, and 30%-45% of the tailings are thrown away, the grade of the first-stage grinding is improved and the subsequent grinding circulation volume is reduced, the processing capacity of the mill is improved, and the grinding and beneficiation costs are reduced.

[0021] 2) By adopting the grinding-magnetic separation-cyclone classification process in the first and second mills, about 30% of the tailings in the feed of this section can be discarded in advance, achieving "early disposal if possible", reducing the circulation volume of the first and second mills, improving the useful efficiency of grinding, improving the grade of iron ore in stages, and further reducing the grinding cost.

[0022] 3) By using a combination of a dewatering screen and a secondary grinder to replace the high-frequency screen, the process bottleneck problem caused by the high-frequency screen's fine holes being easily blocked and the screen being easily damaged is effectively solved, thereby improving the overall operating rate and reducing operating costs.

[0023] 4) Utilizing the characteristics of the sand mill's "big grind big, small grind small" selective grinding and automatic internal classification of the slurry, ultra-fine particle grinding and dissociation are carried out with a higher degree of dissociation, thereby improving the recovery rate of iron ore and solving the problem of "poor and fine" ores being difficult to grind and select.

[0024] 5) By recycling all the overflow water from the washing magnetic separator back to the linear screen as flushing water, 25% of the total water consumption can be saved per hour. At the same time, some of the overflowed intergrown iron minerals re-enter the mineral processing and recovery process, further reducing metal losses and improving the recovery rate of magnetic iron.

[0025] 6) The ore dressing and recovery process of the present invention can increase the "lean, fine, and mixed" low-grade iron ore from 5% to 15% to 64% to 65% by adjusting the process sequence of magnetic separation and cyclone classification without additional equipment investment or extending the process flow, and the magnetic iron recovery rate is as high as more than 95%, and no tailings discharge is achieved. It has the characteristics of simple process flow, short ore dressing and recovery cycle, low production cost, large processing capacity, segmented tailings disposal, high total iron concentrate grade, high comprehensive utilization rate of tailings, green and environmental protection, etc., which greatly improves the utilization value of ultra-lean, fine, and mixed magnetite. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0027] Figure 1 is a process flow chart of the present invention; DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0029] The present invention provides a beneficiation and recovery process for disseminated ultrafine low-grade magnetite, and the specific implementation steps are as follows:

[0030] S1, feed the raw ore that has been crushed to a particle size of 0-30 mm into a high-pressure double-roll mill to obtain powdered minerals with microcracks, feed the powdered minerals into a linear screen for washing and wet screening, the screen hole of the linear screen is set to 3 mm, obtain the over-screen product and the under-screen product, mix the over-screen product with the raw ore and feed it back into the high-pressure double-roll mill for cyclic extrusion and crushing;

[0031] This step makes full use of the high-pressure roller mill to squeeze the raw ore. The mutual squeezing between the ores causes a large number of microcracks inside the ore particles, and some useful minerals are dissociated in advance, providing conditions for coarse-grained magnetic separation.

[0032] S2, feeding the undersize product obtained in step S1 into a coarse-grained wet permanent magnetic downstream magnetic separator for ore dressing and tailings discarding, obtaining a coarse-grained magnetic separation rough concentrate with a grade of 30-35%, and discharging 30-45% of the coarse-grained magnetic separation tailings;

[0033] S3, feeding the coarse magnetically separated coarse concentrate obtained in step S2 into a first-stage mill, feeding the first-stage milled product into a primary wet semi-countercurrent magnetic separator, performing magnetic separation at a magnetic field strength of 0.28T, obtaining a primary magnetically separated coarse concentrate with a grade of 35% to 40%, discharging 30% of the primary magnetically separated tailings, feeding the primary magnetically separated coarse concentrate into a first-stage cyclone, controlling the overflow particle size within a range of -200 mesh and 70% to 80%, obtaining a first-stage overflow product and a first-stage underflow product, and feeding the first-stage underflow product into a first-stage mill-primary magnetic separator-first-stage cyclone for a cyclic operation;

[0034] S4, feeding the first-stage overflow product obtained in step S3 into the second-stage cyclone, and controlling the overflow particle size at -325 mesh, 65% to 75%, obtaining the second-stage underflow product and the second-stage overflow product, and feeding the second-stage overflow product into the linear dewatering screen II for impurity removal, and the mesh size of the linear dewatering screen II is set to 0.3mm, and obtaining the second-stage overscreen product and the second-stage underscreen product; the second-stage underflow product and the second-stage overscreen product are combined and fed into the second-stage mill, and the obtained second-stage grinding product is fed into the secondary wet semi-countercurrent magnetic separator, and magnetic separation is performed at a magnetic field strength of 0.25T to obtain a secondary magnetic separation coarse concentrate with a grade of 45% to 50%, and discharge 30% of the feed amount of secondary magnetic separation tailings; the secondary magnetic separation coarse concentrate and the first-stage overflow product are combined and fed into the second-stage cyclone-second-stage mill-secondary magnetic separator for cyclic operation;

[0035] S5, feeding the second-stage undersize product obtained in step S4 into a concentrating magnetic separator with a magnetic field strength of 0.28T to obtain a concentrated iron ore concentrate slurry with a concentration of 45% to 60%, discharging the concentrated magnetic separation tailings, feeding the concentrated iron ore concentrate slurry into a three-stage mill, the three-stage mill uses an Aisha mill, and the obtained -325 mesh is not less than 90% of the three-stage grinding product, and feeding it into a tertiary wet semi-countercurrent magnetic separator, and magnetic separation is performed at a magnetic field strength of 0.16T to obtain a tertiary magnetic separation concentrate with a grade of more than 60%, and discharging the tertiary magnetic separation tailings;

[0036] In this step, the sand grinding belongs to the open-circuit grinding process. The principle is: under the action of high-speed rotating centrifugal force, the minerals and ceramic balls are radially distributed from the inner wall of the mill axial cylinder according to the particle size from small to large, realizing the selective grinding of "big grinding big, small grinding small"; under the action of a certain ore feeding pressure, the slurry is ground finer and finer towards the rear end, and internal classification is automatically realized, thereby achieving a grinding fineness of more than 90% of -325 mesh, and completing the dissociation of ultrafine iron minerals;

[0037] S6, after the tertiary magnetic separation concentrate obtained in step S5 is fed into the elutriation magnetic separator, high-pressure water is fed tangentially from the bottom and the middle of the elutriation magnetic separator to form a spirally ascending uniform water flow in the separation area, the gangue minerals and intergrown minerals in the tertiary magnetic separation concentrate are impacted by the ascending water flow, overflow with the ascending water flow to form elutriation overflow water for discharge, and the magnetic iron minerals in the monomer dissociation state descend under the action of the periodic composite magnetic field and are discharged from the bottom to form a total iron concentrate with a grade of more than 64%, wherein the discharged elutriation overflow water is all returned to step S1 as flushing water for the linear screen to flush the powdered material fed by the high-pressure roller mill for wet screening, and this process can greatly save water for washing ore, and can save 25% of the total water consumption per hour, and the intergrown minerals in the elutriation overflow water can be recovered by the coarse-grained magnetic separator and enter the mill, thereby reducing the loss of iron ore metals and improving the recovery rate.

[0038] Furthermore, in order to make full use of the tailings, the coarse-grained magnetic tailings of S2 and the primary magnetic tailings of S3 are combined and classified through a cyclone to obtain overflow tailings and sedimentation tailings. The overflow tailings, the secondary magnetic tailings of S4, the concentrated magnetic tailings and the tertiary magnetic tailings of S5 are combined into a concentration tank for concentration and then fed into a plate and frame filter press for filtration and dehydration. The dehydrated tailings are used as cement additives such as iron correction materials and admixtures in cement plants; the sedimentation tailings are fed into a linear dewatering screen I, and the above-screen products are used as building sand, and the under-screen products are returned to the cyclone for further classification.

[0039] For the convenience of intuitive understanding, the concentrate grade obtained in each process link in this embodiment is shown in the following table:

[0040]

[0041] As can be seen from the above table, the proportion of total iron concentrate reaching -325 mesh is 92%, the total iron grade is 64.55%, the magnetic iron grade is 63.79%, and the magnetic iron recovery rate reaches 95.8%, realizing the full recovery and utilization of the impregnated ultrafine low-grade magnetite and improving its utilization value.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the present invention.

Claims

1. A mineral processing and recovery process for disseminated ultrafine low-grade magnetite, characterized in that: The implementation steps include: S1, feed the raw ore that has been crushed to a particle size of 0-30 mm into a high-pressure double-roll mill to obtain powdered minerals with microcracks, feed the powdered minerals into a linear screen for washing and wet screening, obtain the oversize product and the undersize product, mix the oversize product with the raw ore and feed it back into the high-pressure double-roll mill for cyclic extrusion and crushing; S2, feeding the undersize product obtained in step S1 into a coarse-grained wet magnetic separator for coarse-grained magnetic separation, obtaining a coarse concentrate from the coarse-grained magnetic separation, and discharging the coarse-grained magnetic separation tailings; S3, feeding the coarse magnetically separated coarse concentrate obtained in step S2 into a first-stage mill, feeding the first-stage grinding product into a primary magnetic separator, obtaining a primary magnetically separated coarse concentrate, discharging the primary magnetically separated tailings, feeding the primary magnetically separated coarse concentrate into a first-stage cyclone to obtain a first-stage overflow product and a first-stage underflow product, and returning the first-stage underflow product to the first-stage mill-primary magnetic separator-first-stage cyclone for a cyclic operation; S4, feeding the first overflow product obtained in step S3 into the second cyclone to obtain the second cyclone underflow product and the second overflow product, feeding the second overflow product into the linear dewatering screen II for impurity removal to obtain the second screen product and the second screen product; the second underflow product and the second screen product are combined and fed into the second mill to obtain the second grinding product, which is fed into the secondary magnetic separator to obtain the secondary magnetic separation rough concentrate and discharge the secondary magnetic separation tailings; combining the secondary magnetic separation rough concentrate and the first overflow product into the second cyclone-second mill-second magnetic separator for cyclic operation; S5, feeding the second-stage undersize product obtained in step S4 into a concentrating magnetic separator to obtain concentrated iron ore concentrate slurry, discharging concentrated magnetic separation tailings, feeding the concentrated iron ore concentrate slurry into a three-stage mill, feeding the obtained three-stage grinding product into a tertiary magnetic separator, obtaining tertiary magnetic separation concentrate, and discharging tertiary magnetic separation tailings; S6, feeding the tertiary magnetic separation concentrate obtained in step S5 into a washing magnetic separator, obtaining the final total iron concentrate through the action of high-pressure water flow and composite magnetic field, and discharging the washing overflow water.

2. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: The coarse-grained magnetic tailings of S2 and the primary magnetic tailings of S3 are combined and classified through a cyclone to obtain overflow tailings and sedimentation tailings. The overflow tailings, the secondary magnetic tailings of S4, the concentrated magnetic tailings and the tertiary magnetic tailings of S5 are combined and entered into a concentration tank for concentration, and then fed into a plate and frame filter press for filtration and dehydration. The dehydrated tailings are used as iron correction materials in cement plants; the sedimentation tailings are fed into a linear dewatering screen I, and the above-screen products are used as building sand, and the under-screen products are returned to the cyclone for further classification.

3. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: In step S2, the coarse particle wet magnetic separator adopts a permanent magnet downstream magnetic separator, and the magnetic field strength is 0.28-0.30T.

4. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: In step S3, the primary magnetic separator is a wet semi-countercurrent magnetic separator, the magnetic field strength is set to 0.28T, and the overflow particle size control range of the first stage cyclone is -200 mesh, 70% to 80%.

5. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: In step S4, the overflow particle size control range of the second-stage cyclone is -325 mesh, 65% to 75%, the mesh size of the linear dewatering screen II is 0.3 mm, the secondary magnetic separator adopts a wet semi-countercurrent magnetic separator, and the magnetic field strength is set to 0.25T.

6. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: In step S5, the magnetic field strength of the concentration magnetic separator is 0.28T, the concentration of the ore pulp after the concentration magnetic separation is controlled in the range of 45% to 60%, and the tertiary magnetic separator adopts a wet semi-countercurrent magnetic separator, and the magnetic field strength is set to 0.16T.

7. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: The three-stage mill in step S5 is an Aisha mill, and the particle size of the obtained three-stage grinding product is controlled within the range of -325 mesh, not less than 90%.

8. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: The elutriation magnetic separator in step S6 is a vertical elutriation magnetic separator, and the specific process of elutriation is as follows: after the tertiary magnetic separation concentrate is fed into the elutriation magnetic separator, high-pressure water is tangentially fed from the bottom and the middle of the elutriation magnetic separator to form a spirally ascending uniform water flow in the separation area, and the gangue minerals and conjoined minerals in the tertiary magnetic separation concentrate overflow with the ascending water flow to form elutriation overflow water; the magnetic iron minerals in the monomer dissociation state descend and are discharged from the bottom under the action of the periodic composite magnetic field to form a total iron concentrate.

9. The ore dressing and recovery process of a disseminated ultrafine low-grade magnetite according to claim 1, characterized in that: The overflow water discharged from the washing in step S6 is returned to step S1 as flushing water for the linear screen and is circulated.

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