Cyclic load reducing magnetite energy-saving grinding and separation process for direct separation of discharged ore of grinding machine

Abstract

The invention discloses a circulation load reducing magnetite energy-saving grinding and separation process for direct separation of discharged ore of a mill, and belongs to the technical field of ore processing. The method comprises the following steps: mill discharged ore obtained through ore grinding operation, the mill discharged ore automatically flows into a dilution tank for dilution operation, diluted ore pulp is subjected to wet magnetic separation operation, magnetic separation concentrate automatically flows into a cyclone for grading operation, and overflow of the cyclone serves as a qualified product of the operation of the section and enters the next production process; settled sand of the cyclone automatically flows into the grinding machine to carry out closed-loop circular grinding operation. According to the method, the technical measure that magnetic separation is directly carried out through ore discharging of the mill is adopted, the traditional technological process of ore discharging of the mill, grading and grading in the ore grinding industry is broken, the phenomenon that waste is caused due to the fact that dissociated gangue enters the mill for the second time is fundamentally avoided, the amount of ore entering the mill is reduced, and therefore the cycle load of a grinding and separation system is reduced, and the energy-saving purpose is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of mineral processing, in particular to an energy-saving grinding and selection process for magnetite with reduced circulating load for direct selection of mill discharge. Background Art

[0002] In recent years, efforts to save energy and reduce carbon emissions have been continuously strengthened. As a mining enterprise in an energy-consuming industry, this requires mineral processing plants to develop more energy-saving mineral processing processes based on process characteristics and combined with modern new equipment to ensure that production indicators can meet market demand.

[0003] As one of the main sources of domestically produced iron ore, especially poor magnetite, magnetite has been mined in large quantities in recent years to supplement the resource demand for a large amount of iron ore. At present, most domestic iron ore concentrators adopt the "stage grinding, stage separation" process, that is, the "three-stage one closed-circuit crushing-high-pressure roller mill ultra-fine crushing-two-stage grinding two-stage weak magnetic separation or three-stage grinding three-stage weak magnetic separation" beneficiation process. When processing poor magnetite or ultra-poor magnetite, the third-stage separation concentrate is washed and deeply selected to improve the grade of the concentrate. Among them, the "two-stage grinding two-stage weak magnetic separation or three-stage grinding three-stage weak magnetic separation" link requires the highest energy consumption, generally reaching more than 30kW·h per ton of concentrate, and more than 50kW·h per ton of concentrate when processing poor magnetite. When processing extremely poor magnetite or iron ore with finer embedded particle size, the required energy consumption will be higher. For example, the energy consumption per ton of concentrate required for the grinding and sorting production process of Aoshan Ore Dressing Plant, Dahongshan 4 million tons Ore Dressing Plant, Heshangqiao Ore Dressing Plant, Malanzhuang Ore Dressing Plant, Baixiangshan Ore Dressing Plant, etc. is more than 51kW·h. Therefore, the core of energy saving in magnetite ore dressing plants is "grinding and sorting process optimization", and the core concept of grinding and sorting process optimization is "throw as early as possible and collect as early as possible", that is, throw out the newly dissociated gangue as much as possible at the front end of the production process, reduce the amount of ore entering the mill, and theoretically reduce the energy consumption required for grinding and sorting.

[0004] At present, the energy-saving optimization of magnetite grinding production process mostly adopts methods such as "magnetic-gravity-magnetic combined beneficiation process" and "nano-ceramic ball grinding" to reduce the energy consumption required for grinding. For example, the invention patent with patent number CN113385299B and name "A magnetic-gravity-magnetic combined beneficiation process for processing lean magnetite" discloses that the magnetite with a grade of 24% to 30% is fed through a closed-circuit grinding and a weak magnetic grinding in sequence to obtain a weak magnetic concentrate. The weak magnetic concentrate is processed in sequence through subsequent gravity-magnetic screen combination operation, secondary grinding and classification operation and three-stage magnetic separation operation to obtain the final concentrate and the final tailings. This invention simplifies the production process of lean magnetite, uses a gravity separation process to separate coarse-grained qualified concentrate in advance, reduces the over-grinding caused by the coarse-grained qualified concentrate entering the mill for the second time, and thus achieves energy saving and consumption reduction effects. However, this process is only applicable to the grinding and selection of magnetite with coarse embedded particle size. There are a large number of magnetite with fine embedded particle size in my country. Because it needs to be ground to less than 200 mesh, and some ores even need to be ground to less than 400 mesh to obtain a higher degree of dissociation, the invention process cannot obtain coarse-grained qualified concentrate in advance, so it cannot reduce the energy consumption of grinding. For example, in the invention patent with patent number CN202311740757.X and the name "A ball mill device for energy saving and consumption reduction and its application", a method is disclosed that uses light-weight and highly wear-resistant nano-ceramic balls as the main grinding medium to reduce the load of the ball mill during operation, reduce the power consumption of the ball mill, and reduce the consumption of grinding media at the same time. From the perspective of improving the grinding conditions, this invention adopts lightweight grinding media and reduces the energy consumption of the ball mill system itself, but does not optimize the grinding process and does not reduce the grinding workload. Therefore, it is necessary to study how to separate the dissociated iron ore or gangue in advance from the process flow, reduce the amount of ore entering the mill, and thus reduce the circulating load of the grinding system, so as to fundamentally reduce the energy consumption required for the magnetite grinding production process and achieve the purpose of process energy saving. Summary of the invention

[0005] The purpose of the present invention is to provide an energy-saving grinding and selection process for magnetite with reduced circulating load by directly selecting the ore discharged from the mill, adopt the technical measures of directly performing magnetic separation on the ore discharged from the mill, break the traditional process flow of "mill discharge-classification-selection" in the grinding industry, fundamentally solve the problem of waste caused by the dissociated gangue entering the mill for the second time, and at the same time reduce the circulating load of the mill to achieve the purpose of energy saving, so as to solve the shortcomings of the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A magnetite energy-saving grinding and separation process for direct separation of mill discharge with reduced circulating load comprises the following steps:

[0008] S1: feeding the produced or prepared magnetite ore into a mill for grinding, and obtaining the grinding product as mill discharge;

[0009] S2: The mill discharge flows to the dilution tank by gravity, and the circulating water of the concentrator is added for dilution to obtain diluted slurry;

[0010] S3: The diluted slurry flows by gravity to the magnetic separator for wet magnetic separation to obtain magnetic concentrate and magnetic tailings;

[0011] S4: The magnetic concentrate flows by gravity to the cyclone feed pump pool, and is transported to the cyclone group by the cyclone feed pump for classification to obtain cyclone overflow and cyclone sand settling;

[0012] S5: The overflow of the cyclone is regarded as the qualified product of this stage of operation and enters the next production process; the cyclone sediment flows by gravity into the grinding mill for closed-circuit grinding operation;

[0013] S6: When the production process is multi-stage grinding, the qualified products of one stage of grinding are used as the feed for the next stage of grinding, and the closed-loop cycle of S1 to S5 is repeated to obtain qualified concentrate products.

[0014] Furthermore, the particle size composition of the original magnetite ore in S1 is -8mm content ≥85%, iron content 15%≤TFe≤35%, and magnetic iron content 12%≤mFe≤33%.

[0015] Furthermore, the mill in S1 adopts a grate ball mill for the first-stage grinding operation, an overflow ball mill for the second-stage grinding operation, and a vertical mill for the third-stage grinding operation.

[0016] Furthermore, the grinding concentrations of the grinding operation in S1 are: first-stage grinding concentration 71%-75%, grinding time>5min; second-stage grinding concentration 68%-72%, grinding time>8min; third-stage grinding concentration 62%-65%, grinding time>8min.

[0017] Furthermore, the particle size composition of the ore discharged from the mill in S1 is as follows: the ore discharged from the first stage mill has a -8mm particle size content ≥98%, a -3mm particle size content ≥95%, a -1mm particle size content ≥85%, and a -0.074mm particle size content ≥38%; the ore discharged from the second stage mill has a -1mm particle size content ≥96%, and a -0.074mm particle size content ≥72%; the ore discharged from the third stage mill has a -0.074mm particle size content ≥92%, and a -0.043mm particle size content ≥85%.

[0018] Furthermore, the dilution tank in S2 is a square water tank with an overflow weir in the middle, which has the functions of buffering and adding water for uniform dilution; the dilution operation is that the higher concentration mill discharge flows into one side of the dilution tank by gravity, and circulating water is added at the same time for dilution. The mixed fluid after dilution overflows the overflow weir to become diluted ore slurry, completing the dilution operation.

[0019] Furthermore, the magnetic separator in S3 is: the first stage magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator with a number of magnetic poles ≥11, the magnetic field strength in the high field strength zone is 4100Gs~4600Gs, and the magnetic iron content of the tailings is mFe<0.95%; the second stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥9, the magnetic field strength in the high field strength zone is 2800Gs~3300Gs, and the magnetic iron content of the tailings is mFe<0.92%; the third stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥8, the magnetic field strength in the high field strength zone is 1600Gs~1800Gs, and the magnetic iron content of the tailings is mFe<0.85%.

[0020] Furthermore, the cyclone feed pump pool in S4 is a square frame pool with a bottom plate inclined 30° toward the pump, an overflow port 200mm deep and 1500mm wide is opened on the top, and the effective volume is 25m 3 ~30m 3 .

[0021] Furthermore, the grading operations in S4 all use a hydrocyclone group for grading, and the working parameters are: the first stage grading uses an FX660-GX cyclone, a feed pressure of 65kPa~95kPa, a feed concentration of 28±3(%), a grading particle size range of 74μm~200μm, and a grit concentration of 72±3(%); the second stage grading uses an FX350-GX cyclone, a feed pressure of 85kPa~110kPa, a feed concentration of 26±3(%), a grading particle size range of 50μm~150μm, and a grit concentration of 69±3(%); the third stage grading uses an FX250-GX cyclone, a feed pressure of 90kPa~160kPa, a feed concentration of 25±2(%), a grading particle size range of 40μm~100μm, and a grit concentration of 63±2(%).

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The energy-saving grinding process for magnetite with reduced circulating load for direct selection of mill discharge of the present invention fundamentally solves the problem of waste caused by the dissociated gangue entering the mill for the second time. The circulating load of the mill is reduced from 200% to 400% which is the conventional index in the mineral processing industry to 110% to 180%, thereby saving the energy consumption required for the operation load of the grinding system.

[0024] 2. The energy-saving grinding and selection process of magnetite with reduced circulating load by direct selection of ore from the mill of the present invention adopts the technology of direct magnetic separation of ore from the mill, and separates the gangue in the first process after the dissociation of iron ore, thereby increasing the amount of ore required to be fed into the mill, thereby improving the working efficiency of the mill and reducing the energy consumption index per ton of concentrate by more than 14 percentage points. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of the first stage grinding and selection production process of the present invention;

[0026] Figure 2 This is a two-stage grinding and selection production process flow chart of the present invention;

[0027] Figure 3 This is a three-stage grinding and selection production process flow chart of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The embodiment of the present invention provides a magnetite energy-saving grinding and separation process with reduced circulating load for direct separation of mill discharge, comprising the following steps:

[0030] S1: Feed the produced or prepared magnetite ore into the mill for grinding operation, and the product of the grinding operation is the mill discharge; wherein, the particle size composition of the magnetite ore is -8mm content ≥85%, iron content 15%≤TFe≤35%, magnetic iron content 12%≤mFe≤33%; the mill adopts a grate ball mill for the first stage grinding operation, an overflow ball mill for the second stage grinding operation, and a vertical mill for the third stage grinding operation; the grinding concentration of the grinding operation is: the first stage grinding concentration is 71%~75%, the grinding time is>5min; the second stage grinding concentration is 68 %~72%, grinding time>8min; three-stage grinding concentration is 62%~65%, grinding time>8min; the particle size composition of mill discharge is: one-stage mill discharge has -8mm particle size content ≥98%, -3mm particle size content ≥95%, -1mm particle size content ≥85%, -0.074mm particle size content ≥38%; two-stage mill discharge has -1mm particle size content ≥96%, -0.074mm particle size content ≥72%; three-stage mill discharge has -0.074mm particle size content ≥92%, -0.043mm particle size content ≥85%.

[0031] S2: The mill discharge flows by gravity into the dilution tank, and circulating water from the concentrator is added for dilution to obtain diluted slurry. The dilution tank is a square water tank with an overflow weir in the middle, which has the functions of buffering and adding water for uniform dilution. The dilution operation is that the mill discharge with higher concentration flows by gravity into one side of the dilution tank, and circulating water is added for dilution. After dilution, the mixed fluid overflows the overflow weir to become diluted slurry, completing the dilution operation.

[0032] S3: The diluted ore pulp is gravity-flowed to the magnetic separator for wet magnetic separation to obtain magnetic concentrate and magnetic tailings; wherein, the magnetic separator is: the first stage magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator with a number of magnetic poles ≥11, a magnetic field strength of 4100Gs~4600Gs in the high field strength zone, and a magnetic iron content mFe of the selected tailings <0.95%; the second stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥9, a magnetic field strength of 2800Gs~3300Gs in the high field strength zone, and a magnetic iron content mFe of the selected tailings <0.92%; the third stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥8, a magnetic field strength of 1600Gs~1800Gs in the high field strength zone, and a magnetic iron content mFe of the selected tailings <0.85%.

[0033] S4: The magnetic concentrate flows by gravity to the hydrocyclone feed pump pool, and is transported to the hydrocyclone group by the hydrocyclone feed pump for classification to obtain hydrocyclone overflow and hydrocyclone sand settling; the hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump, an overflow port 200mm deep and 1500mm wide is opened on the top, and the effective volume is 25m 3 ~30m 3 ; The grading operation adopts hydrocyclone group for grading, and the working parameters are as follows: the first stage grading adopts FX660-GX cyclone, the ore pressure is 65kPa~95kPa, the ore concentration is 28±3(%), the grading particle size range is 74μm~200μm, and the grit concentration is 72±3(%); the second stage grading adopts FX350-GX cyclone, the ore pressure is 85kPa~110kPa, the ore concentration is 26±3(%), the grading particle size range is 50μm~150μm, and the grit concentration is 69±3(%); the third stage grading adopts FX250-GX cyclone, the ore pressure is 90kPa~160kPa, the ore concentration is 25±2(%), the grading particle size range is 40μm~100μm, and the grit concentration is 63±2(%).

[0034] S5: The overflow of the cyclone is regarded as the qualified product of this stage of operation and enters the next production process; the cyclone sediment flows by gravity into the grinding mill for closed-circuit grinding operation;

[0035] S6: When the production process is multi-stage grinding, the qualified products of one stage of grinding are used as the feed for the next stage of grinding, and the closed-loop cycle of S1 to S5 is repeated to obtain qualified concentrate products.

[0036] In order to further better explain the above embodiment, the present invention also provides the following specific implementation cases:

[0037] Case 1:

[0038] The selected ore sample is a perforated core sample from a certain mining field. After crushing and screening, the particle size composition obtained is: -8mm particle size content 99.8%, -3mm particle size content 90.31%, -0.074mm particle size content 12.93%. The test results are: iron content TFe = 32.56%, magnetic iron content mFe = 29.37%, silicon content SiO2 = 20.25%, aluminum content Al2O3 = 6.59%, sulfur content S = 2.42%, and the content of other elements is not high. The ore sample is used as follows Figure 1 The process shown is processed, and the specific process technical parameters and steps are as follows:

[0039] Step 1: Feed the prepared magnetite core sample into the mill for grinding. The mill adopts a grate ball mill, model MQG2736, equipped with φ76mm forged steel balls, grinding concentration 72%, grinding time 7.50min, and the product of the grinding operation is mill discharge, and the mill discharge particle size composition is: -0.074mm particle size content 58.36%;

[0040] Step 2: Let the mill discharge flow to the dilution tank, which is a square pool with an overflow weir in the middle and a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 25±3(%), thereby obtaining a diluted slurry;

[0041] Step 3: The diluted slurry is flowed to the magnetic separator by gravity. The magnetic separator adopts a semi-countercurrent high-efficiency magnetic separator with 11 magnetic poles and a magnetic field strength of 4500Gs in the high field strength zone to perform wet magnetic separation to obtain magnetic concentrate and magnetic tailings. The magnetic concentrate TFe is 53.81%, the magnetic tailings TFe is 7.88%, and the magnetic iron content of the magnetic tailings is mFe=0.93%;

[0042] Step 4: Let the magnetic concentrate flow by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. There is an overflow port 200mm deep and 1500mm wide on the top, with an effective volume of 25m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the cyclone group, and the cyclone is classified using the FX660-GX type cyclone, with a feed pressure of 85kPa and a feed concentration of 26%, to obtain cyclone overflow and cyclone sedimentation; the cyclone overflow particle size composition is -0.074mm particle size content of 83.66%, and the sedimentation concentration is 72%;

[0043] Step 5: The cyclone overflow is regarded as the qualified product of this stage of operation and enters the next production process; the cyclone sedimentation is combined with the prepared magnetite core sample and flows into the mill by gravity for closed-loop grinding operation.

[0044] In this case, the overflow product of the cyclone was analyzed and the TFe of the product was 64.25%, which met the market index requirements and could be sold as a qualified product. Compared with the conventional grinding process in the industry, the power consumption index of the whole process of this implementation case is 17.85kW·h per ton of concentrate, which is only 71.40% of the conventional power consumption index of the same type of ore, and the energy saving effect is significant.

[0045] Implementation Case 2:

[0046] The ore samples in this case are four kinds of raw ores taken from different areas of a mining site, numbered as mining platform north, magnetite vein, mining platform west, and crushed ore production sample (sampling intercepted on the belt), respectively. They were mixed together in a ratio of 165:38:106:183 and crushed to less than -12 mm to prepare the ore samples of this embodiment. The results of chemical multi-element analysis of the ore samples are shown in Table 1.

[0047] Table 1 Results of chemical multi-element analysis of raw ore (%)

[0048] element TFe <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Na2O]]> <![CDATA[K2O]]> CaO MgO P content 21.57 33.15 11.29 3.48 1.06 5.23 2.62 0.77 element MnO <![CDATA[TiO2]]> <![CDATA[V2O5]]> CuO ZnO <![CDATA[Cr2O3]]> NiO S content 0.16 0.65 0.11 <0.01 0.01 <0.01 <0.01 0.83

[0049] The results of chemical multi-element analysis show that the content of iron element TFe in the original ore is 21.57%, the content of harmful element S is 0.83%, and the content of P is 0.77%; the contents of alkali metals Na2O and K2O are relatively high, at 3.48% and 1.06% respectively; the main components of gangue minerals are SiO2 and Al2O3, with contents of 33.15% and 11.29% respectively, which is a typical lean magnetite.

[0050] The results of the iron phase analysis of the ore sample are shown in Table 2:

[0051] Table 2 Iron phase analysis results (%)

[0052]

[0053]

[0054] The results of iron phase analysis show that the iron in the ore sample mainly exists in the form of magnetic iron, with a distribution rate of 82.80%; secondly, it exists in the form of reddish brown iron, with a distribution rate of 7.47%; the distribution rates of the remaining iron silicate, iron carbonate and iron sulfide are all less than 5%. Figure 2 The process shown is processed, and the specific process technical parameters and steps are as follows:

[0055] Step 1: Feed the prepared ore sample into a first-stage mill for a first-stage grinding operation. The first-stage mill adopts a grate ball mill, model MQG3660, equipped with φ80mm forged steel balls, a first-stage grinding concentration of 73%, a first-stage grinding time of 8.00min, and the product of the first-stage grinding operation is a first-stage mill discharge. The particle size composition of the first-stage mill discharge is: -0.074mm particle size content 43.36%;

[0056] Step 2: Let the first stage mill discharge flow to the dilution tank, which is a square pool with an overflow weir in the middle and a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 26±3(%), thereby obtaining a diluted slurry;

[0057] Step 3: The diluted slurry flows by gravity to a first-stage magnetic separator, which adopts a semi-countercurrent high-efficiency magnetic separator with 11 magnetic poles and a magnetic field strength of 4500Gs in the high field strength zone to perform a first-stage magnetic separation operation to obtain a first-stage magnetic separation concentrate and a first-stage magnetic separation tailings;

[0058] Step 4: Let the magnetic concentrate flow by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. There is an overflow port 200mm deep and 1500mm wide on the top, with an effective volume of 25m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the first stage cyclone group. The first stage classification uses FX660-GX cyclone, feed pressure 80kPa, feed concentration 25%, and performs a first stage classification operation to obtain a first stage classification overflow and a first stage classification sand settling;

[0059] Step 5: The first stage of classified sand is combined with the ore sample and flows into the first stage of the grinding mill by gravity to carry out a closed-circuit grinding operation;

[0060] Step 6: The overflow of the first stage classification is used as the qualified product of the first stage grinding operation, and is fed to the second stage concentration magnetic separation. The concentration magnetic separation adopts NCTB1240 type concentration magnetic separator with a magnetic field strength of 3000Gs to carry out the second stage concentration operation to obtain the second stage concentration magnetic separation concentrate and the second stage concentration magnetic separation tailings;

[0061] Step 7: The secondary concentrated magnetic separation concentrate is fed into the secondary mill for secondary grinding. The secondary mill adopts an overflow ball mill, model MQY3660, equipped with φ50mm hot-rolled steel balls, the secondary grinding concentration is 69%, the secondary grinding time is 9.50min, and the product of the secondary grinding operation is the secondary mill discharge. The particle size composition of the secondary mill discharge is: -0.074mm particle size content 65.36%;

[0062] Step 8: Let the secondary mill discharge to the dilution pool by gravity. The dilution pool is a square pool with an overflow weir in the middle, with a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 24±3(%), thereby obtaining a diluted slurry;

[0063] Step 9: The diluted slurry flows by gravity to the second-stage magnetic separator, which adopts a downstream high-efficiency magnetic separator with 9 magnetic poles and a magnetic field strength of 3000Gs in the highest field strength area to perform a second-stage magnetic separation operation to obtain a second-stage magnetic separation concentrate and a second-stage magnetic separation tailings;

[0064] Step 10: The secondary magnetic separation concentrate flows by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. The top has an overflow port 200mm deep and 1500mm wide, with an effective volume of 30m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the second-stage cyclone group. The second-stage classification uses FX350-GX cyclone, feed pressure 100kPa, feed concentration 24%, and performs second-stage classification operation to obtain second-stage classification overflow and second-stage classification sand settling;

[0065] Step 11: The overflow of the second stage classification is regarded as a qualified product of the operation of this embodiment and enters the next production process; the sand settling of the second stage classification and the overflow of the first stage classification are combined and flowed into the second stage concentration magnetic separator by gravity to perform a closed-circuit grinding operation;

[0066] In this case, the overflow product of the second stage classification was analyzed and the TFe of the product was 64.72%, which met the market index requirements and could be sold as a qualified product. Compared with the conventional two-stage grinding process for processing lean magnetite in the industry, the power consumption index of the whole process of this embodiment is 28.39kW·h per ton of concentrate, which is equivalent to 67.52% of the conventional power consumption index of the same type of ore, and the energy saving index is obvious.

[0067] Implementation Case 3:

[0068] A super-poor magnetite was selected, the iron grade of the ore is TFe = 17.36%, the magnetic iron grade is mFe = 12.59%, and the magnetic rate is 72.52%. The metal minerals are mainly magnetite and pyrite; the gangue minerals are mainly amphibole, plagioclase, pyroxene, chlorite, quartz and apatite. The main chemical composition analysis results of the ore samples are shown in Table 3, and the iron phase analysis results are shown in Table 4.

[0069] Table 3 Analysis of main chemical components of ore samples / %

[0070] Element Fe <![CDATA[Al2O3]]> CaO MgO <![CDATA[Na2O]]> <![CDATA[SiO2]]> S P content 17.36 9.51 13.92 9.48 1.03 55.20 0.34 1.52

[0071] Table 4 Iron phase analysis of ore samples / %

[0072] Iron phase content Distribution rate Magnetic iron 12.59 72.52 Hematite 1.68 9.68 Iron sulfide 0.72 4.15 Iron carbonate 0.85 4.90 Iron silicate 1.52 8.75 Full Iron 17.36 100.00

[0073] The ore sample was ultra-finely crushed by a high-pressure roller mill to prepare an ore sample with a particle size composition of -3 mm particle size content ≥ 85%. Figure 3 The process flow chart is used for production processing operations, and the steps are:

[0074] Step 1: Feed the prepared ore sample into a first-stage mill for a first-stage grinding operation. The first-stage mill adopts a grate ball mill, model MQG3660, equipped with φ80mm forged steel balls, a first-stage grinding concentration of 73%, a first-stage grinding time of 7.50min, and the first-stage grinding product is a first-stage mill discharge. The particle size composition of the first-stage mill discharge is: -0.074mm particle size content 36.82%;

[0075] Step 2: Let the first stage mill discharge flow to the dilution tank, which is a square pool with an overflow weir in the middle and a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 25±3(%), thereby obtaining a diluted slurry;

[0076] Step 3: The diluted slurry flows by gravity to a first-stage magnetic separator, which adopts a semi-countercurrent high-efficiency magnetic separator with 11 magnetic poles and a magnetic field strength of 4500Gs in the high field strength zone to perform a first-stage magnetic separation operation to obtain a first-stage magnetic separation concentrate and a first-stage magnetic separation tailings;

[0077] Step 4: Let the magnetic concentrate flow by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. The top has an overflow port 200mm deep and 1500mm wide, with an effective volume of 30m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the first stage cyclone group. The first stage classification uses FX660-GX cyclone, feed pressure 75kPa, feed concentration 27%, and performs a first stage classification operation to obtain a first stage classification overflow and a first stage classification sand settling;

[0078] Step 5: The first stage of classified sand is combined with the ore sample and flows into the first stage of the grinding mill by gravity to carry out a closed-circuit grinding operation;

[0079] Step 6: The overflow of the first stage classification is used as the qualified product of the first stage grinding operation, and is fed to the second stage concentration magnetic separation. The concentration magnetic separation adopts NCTB1240 type concentration magnetic separator with a magnetic field strength of 3000Gs to carry out the second stage concentration operation to obtain the second stage concentration magnetic separation concentrate and the second stage concentration magnetic separation tailings;

[0080] Step 7: The secondary concentrated magnetic separation concentrate is fed into the secondary mill for secondary grinding. The secondary mill adopts an overflow ball mill, model MQY4060, equipped with φ30mm hot-rolled steel balls and φ30mm ceramic balls, the matching ratio is 1:1, the secondary grinding concentration is 64.5%, the secondary grinding time is 10.00min, and the product of the secondary grinding operation is the secondary mill discharge. The particle size composition of the secondary mill discharge is: -0.074mm particle size content 56.29%;

[0081] Step 8: Let the secondary mill discharge to the dilution pool by gravity. The dilution pool is a square pool with an overflow weir in the middle, with a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 23±3(%), thereby obtaining a diluted slurry;

[0082] Step 9: The diluted slurry flows by gravity to the second-stage magnetic separator, which adopts a downstream high-efficiency magnetic separator with 9 magnetic poles and a magnetic field strength of 2900Gs in the highest field strength area to perform a second-stage magnetic separation operation to obtain a second-stage magnetic separation concentrate and a second-stage magnetic separation tailings;

[0083] Step 10: The secondary magnetic separation concentrate flows by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. The top has an overflow port 200mm deep and 1500mm wide, with an effective volume of 30m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the second-stage cyclone group. The second-stage classification uses FX350-GX cyclone, feed pressure 95kPa, feed concentration 23%, and performs second-stage classification operation to obtain second-stage classification overflow and second-stage classification sand settling;

[0084] Step 11: The second-stage classification sand settling merges with the first-stage classification overflow and flows into the second-stage concentration magnetic separator by gravity to perform the second-stage closed-circuit grinding operation;

[0085] Step 12: The overflow from the second stage classification is used as a qualified product of the second stage grinding operation, and is fed into the third stage concentrated magnetic separation. The concentrated magnetic separation adopts an NCTB1230 concentrated magnetic separator with a magnetic field strength of 3000Gs to perform a three-stage concentrated operation to obtain a three-stage concentrated magnetic separation concentrate and a three-stage concentrated magnetic separation tailings;

[0086] Step 13: The three-stage concentrated magnetic separation concentrate is fed into a three-stage mill for three-stage grinding. The three-stage mill adopts a vertical mill, model TGTM1000, the three-stage grinding concentration is 64%, the three-stage grinding time is 8.50min, and the product of the three-stage grinding operation is the three-stage mill discharge. The particle size composition of the three-stage mill discharge is: -0.043mm particle size content 52.71%;

[0087] Step 14: The three-stage mill discharge is gravity-fed to the dilution pool, which is a square pool with an overflow weir in the middle and a volume of 1.25m 3 , with the functions of buffering and adding water for uniform dilution, adding an appropriate amount of circulating water for dilution, and the diluted mixed fluid overflows the overflow weir to become a slurry with a concentration of 21±3(%), thereby obtaining a diluted slurry;

[0088] Step 15: The diluted slurry flows by gravity to a three-stage magnetic separator, which adopts a downstream high-efficiency magnetic separator with 9 magnetic poles and a magnetic field strength of 1800Gs in the highest field strength area, to perform a three-stage magnetic separation operation to obtain a three-stage magnetic separation concentrate and a three-stage magnetic separation tailings;

[0089] Step 16: The three-stage magnetic separation concentrate flows by gravity to the hydrocyclone feed pump pool. The hydrocyclone feed pump pool is a square-shaped pool with a bottom plate inclined 30° toward the pump. The top has an overflow port 200mm deep and 1500mm wide, with an effective volume of 30m 3 ; Then the cyclone feed pump connected to the pump pool delivers it to the three-stage cyclone group. The second-stage classification uses the FX250-GX cyclone, the feed pressure is 115kPa, and the feed concentration is 21%. The three-stage classification operation is carried out to obtain the three-stage classification overflow and the three-stage classification sand settling;

[0090] Step 17: The three-stage classification sand settling merges with the two-stage classification overflow and flows into the three-stage concentration magnetic separator by gravity to perform three-stage closed-circuit grinding operation;

[0091] Step 18: The three-stage classification overflow is regarded as a qualified product of the operation of this embodiment and enters the next production process;

[0092] By analyzing the products and process indicators obtained in this implementation case, it can be seen that the three-stage classification overflow particle size group of the product is obtained: -0.043 particle size content 88.52%, TFe = 65.51%, which meets the market indicator requirements and can be sold as a qualified product. The first stage grinding cycle load is 139%, the second stage grinding cycle load is 154%, and the third stage grinding cycle load is 176%. Compared with the grinding cycle load values ​​of metal mines in the industry, they have all been significantly reduced. Compared with the conventional three-stage grinding process of the ultra-lean magnetite concentrator, the total power consumption index of the whole process grinding of this embodiment is 43.61kW·h per ton of concentrate, which is 14.49% lower than the conventional power consumption index of the same type of ore, achieving significant energy-saving effects.

[0093] In summary, the present invention provides an energy-saving grinding process for magnetite with reduced circulating load by directly selecting the ore from the mill, which adopts the technical measure of directly performing magnetic separation on the ore from the mill, breaks the traditional process flow of "mill discharge-classification-separation" in the grinding industry, reduces the amount of ore entering the mill, thereby reducing the circulating load of the grinding system, and fundamentally solves the problem of waste caused by the dissociated gangue entering the mill for the second time, thereby achieving the purpose of energy saving.

[0094] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A magnetite energy-saving grinding process for direct separation of mill discharge with reduced circulating load, characterized in that: The following steps are involved: S1: feeding the produced or prepared magnetite ore into a mill for grinding, and obtaining the grinding product as mill discharge; S2: The mill discharge flows to the dilution tank by gravity, and the circulating water of the concentrator is added for dilution to obtain diluted slurry; S3: The diluted slurry flows by gravity to the magnetic separator for wet magnetic separation to obtain magnetic concentrate and magnetic tailings; S4: The magnetic concentrate flows by gravity to the cyclone feed pump pool, and is transported to the cyclone group by the cyclone feed pump for classification to obtain cyclone overflow and cyclone sand settling; S5: The overflow of the cyclone is regarded as the qualified product of this stage of operation and enters the next production process; the cyclone sediment flows by gravity into the grinding mill for closed-circuit grinding operation; S6: When the production process is multi-stage grinding, the qualified products of one stage of grinding are used as the feed for the next stage of grinding, and the closed-loop cycle of S1 to S5 is repeated to obtain qualified concentrate products.

2. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The particle size composition of the original magnetite ore in S1 is -8mm content ≥85%, iron content 15%≤TFe≤35%, and magnetic iron content 12%≤mFe≤33%.

3. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The mill in S1 uses a grate ball mill for the first stage of grinding, an overflow ball mill for the second stage of grinding, and a vertical mill for the third stage of grinding.

4. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The grinding concentrations of the grinding operation in S1 are: first-stage grinding concentration 71%~75%, grinding time>5min; second-stage grinding concentration 68%~72%, grinding time>8min; third-stage grinding concentration 62%~65%, grinding time>8min.

5. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The particle size composition of the discharge from the S1 medium mill is as follows: the discharge from the first stage mill has a -8mm particle size content ≥98%, -3mm particle size content ≥95%, -1mm particle size content ≥85%, and -0.074mm particle size content ≥38%; the discharge from the second stage mill has a -1mm particle size content ≥96%, and -0.074mm particle size content ≥72%; the discharge from the third stage mill has a -0.074mm particle size content ≥92%, and -0.043mm particle size content ≥85%.

6. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The dilution tank in S2 is a square pool with an overflow weir in the middle, which has the functions of buffering and adding water for uniform dilution. The dilution operation is that the higher concentration mill discharge flows into one side of the dilution tank by gravity, and circulating water is added for dilution. After dilution, the mixed fluid overflows the overflow weir to become diluted ore slurry, completing the dilution operation.

7. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The magnetic separators in S3 are as follows: the first stage magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator with a number of magnetic poles ≥11, the magnetic field strength in the high field strength zone is 4100Gs~4600Gs, and the magnetic iron content of the tailings is mFe<0.95%; the second stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥9, the magnetic field strength in the high field strength zone is 2800Gs~3300Gs, and the magnetic iron content of the tailings is mFe<0.92%; the third stage magnetic separation adopts a downstream high-efficiency magnetic separator with a number of magnetic poles ≥8, the magnetic field strength in the high field strength zone is 1600Gs~1800Gs, and the magnetic iron content of the tailings is mFe<0.85%.

8. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The cyclone feed pump pool in S4 is a square frame pool with the bottom plate inclined 30° toward the pump. The top has an overflow port 200mm deep and 1500mm wide, with an effective volume of 25m 3 ~30m 3 .

9. The energy-saving grinding and separation process for magnetite with reduced circulating load for direct separation of mill discharge according to claim 1, characterized in that: The classification operation in S4 is carried out by hydrocyclone group, and the working parameters are as follows: the first stage classification adopts FX660-GX type cyclone, the ore pressure is 65kPa~95kPa, the ore concentration is 28±3(%), the classification particle size range is 74μm~200μm, and the grit concentration is 72±3(%); the second stage classification adopts FX350-GX type cyclone, the ore pressure is 85kPa~110kPa, the ore concentration is 26±3(%), the classification particle size range is 50μm~150μm, and the grit concentration is 69±3(%); the third stage classification adopts FX250-GX type cyclone, the ore pressure is 90kPa~160kPa, the ore concentration is 25±2(%), the classification particle size range is 40μm~100μm, and the grit concentration is 63±2(%).

Images