Extremely-lean magnetite grinding slurry-making double-direct-separation low-carbon beneficiation method

Abstract

The invention discloses a double-direct-separation low-carbon beneficiation method for grinding and pulping extremely-lean magnetite, and belongs to the technical field of beneficiation. The method comprises the treatment processes of coarse crushing treatment of raw ore, primary screening, intermediate crushing, first-stage roller grinding, secondary screening, magnetic pulley waste throwing, fine ore dry separation, second-stage roller grinding, slurry making, wet screening, second-stage roller grinding, wet magnetic separation, first-stage ore grinding, dilution, first-stage magnetic separation, first-stage grading, first-stage ore grinding, concentration magnetic separation, second-stage ore grinding, second-stage magnetic separation, second-stage grading and the like. According to the invention, the traditional process of'three-section one-closed-circuit ore crushing, ultrafine crushing by a high-pressure roller mill, three-section ore grinding and three-section magnetic separation 'for treating extremely lean magnetite is optimized into the process of'two-section crushing, two-section roller milling, ball milling, vertical milling and stage magnetic separation' from the process flow; the traditional fine crushing operation is omitted, belt conveying is reduced, the amount of ore entering a mill is greatly reduced, dust generation points of a dressing plant are reduced, and the purpose of low-carbon, environment-friendly and efficient separation of extremely lean magnetite is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of mineral processing, in particular to a low-carbon mineral processing method for extremely lean magnetite ore crushing, grinding, pulping, double direct separation. Background Art

[0002] According to data, from 2014 to 2023, my country's cumulative iron ore imports exceeded 10.7 billion tons, and in 2023 alone, it reached 1.179 billion tons. It can be seen that my country's economic development has a huge demand for iron ore. The current situation of domestic high-quality iron ore scarcity is difficult to solve in a short period of time, prompting mining engineering and technical personnel to continue to conduct in-depth research on mining and selection technology to adapt to the continuous increase in the mining of lean magnetite and even ultra-lean magnetite, while improving low-grade iron ore processing technology, upgrading the beneficiation process, and improving the concentrate grade to supplement the huge market demand for iron ore resources.

[0003] At present, the mainstream beneficiation process of lean magnetite is: three-stage one closed-circuit crushing-fine crushing and dry separation-high-pressure roller mill ultra-fine crushing pre-selection and tailings discarding-stage grinding-stage weak magnetic separation-elution deep concentration, or a combination of several of these processes. They are all based on the core beneficiation theory of "more crushing and less grinding" and "early discarding when possible and early collection when possible". Tailings are discarded every time the ore is dissociated, and the production process continuously discards unnecessary gangue, while continuously improving the concentrate grade obtained in each production process, and finally reaching the concentrate index required by the market. In this process, a large amount of gangue is discarded, which greatly reduces the amount of grinding and the selection ratio, thereby achieving the purpose of energy-saving beneficiation.

[0004] The existing Chinese patent CN112170001B discloses "super-lean magnetite high-pressure roller mill-flange screen combined pretreatment system and process", including: coarse crushing equipment, pre-screening equipment, medium crushing equipment, inspection screening equipment, high-pressure roller mill, double-layer flaccid screen, magnetic pulley, dry magnetic separator, sand and gravel storage and ball mill. The process reduces the selection ratio from 17 to 6 by producing crushed stone and discarding waste before grinding. Although it greatly reduces the cost of ultra-lean magnetite grinding and magnetic separation, the production process is too lengthy, and the power consumption index of the whole process per ton of concentrate exceeds 100kW·h / t, resulting in excessive energy consumption. Another example is Chinese patent CN110064507B which discloses "a mineral processing process for recycling and reusing lean magnetite". This process improves the initial grade and concentrate grade of the ore through pre-grinding pre-selection, pre-selection concentrate treatment, pre-selection tailings classification, high-frequency stacked screening classification, and waste rock recycling, reduces the mineral processing ratio, and reduces the production cost of subsequent concentration processes. However, the high-frequency stacked screening classification efficiency it adopts is low. When processing lean magnetite with fine embedded particle size, it is impossible to obtain finer grinding indicators, resulting in unqualified fine products. Summary of the invention

[0005] The purpose of the present invention is to provide a low-carbon ore dressing method for extremely lean magnetite by crushing, grinding and slurrying, which adopts the ultra-fine crushing technology of series high-pressure roller mill, the two-stage roller mill ore discharge slurrying wet screening technology and the mill discharge direct sorting technology, cancels the traditional fine crushing operation, reduces the belt conveyor, greatly reduces the amount of ore entering the mill, and reduces the dust generation points of the ore dressing plant, so as to achieve low-carbon, environmentally friendly and efficient sorting of extremely lean magnetite, so as to solve the shortcomings of the existing technology.

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

[0007] A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping, double direct separation, comprising the following steps:

[0008] S1: coarsely crushing the mined ore with the maximum geometric size less than 1000 mm to obtain coarsely crushed ore;

[0009] S2: Screening the coarsely crushed ore to obtain an oversize ore and an undersize ore;

[0010] S3: The ore on the primary screen is subjected to secondary crushing to obtain secondary crushed ore, which is then returned to the primary screening process, forming a closed-loop cycle operation of "primary screening-secondary crushing";

[0011] S4: subjecting the primary screened ore to a first-stage roller mill process to obtain a first-stage roller mill discharge ore, and then subjecting the first-stage roller mill discharge ore to a second-stage screening process to obtain a second-stage screened ore and a second-stage screened ore;

[0012] S5: The ore on the secondary screen is subjected to magnetic pulley discarding treatment to obtain magnetic pulley concentrate and stone, and then the magnetic pulley concentrate is returned to the first-stage roller mill for treatment, forming a closed-loop cycle operation of "first-stage roller mill-secondary screening-magnetic pulley discarding";

[0013] S6: dry separation of the secondary screened ore to obtain dry separation concentrate and stone powder, and then two-stage roller milling of the dry separation concentrate to obtain two-stage roller mill discharge;

[0014] S7: subjecting the second-stage roller mill discharge to pulping to obtain second-stage roller mill pulp;

[0015] S8: wet screening the second-stage roller mill pulp to obtain wet screen ore and wet screen ore;

[0016] S9: The wet screened ore is returned to the second-stage roller mill for processing, forming a closed-loop cycle operation of "second-stage roller mill-slurry making-wet screening";

[0017] S10: subjecting the wet undersize ore to wet magnetic separation to obtain wet magnetic separation concentrate and wet magnetic separation tailings;

[0018] S11: subjecting the wet magnetic separation concentrate to a first-stage grinding process to obtain a first-stage grinding discharge;

[0019] S12: diluting the first-stage mill discharge ore to obtain the first-stage mill discharge slurry;

[0020] S13: subjecting the first-stage mill discharge slurry to a first-stage magnetic separation treatment to obtain a first-stage magnetic separation concentrate and a first-stage magnetic separation tailings;

[0021] S14: performing a stage of classification treatment on the first stage of magnetic separation concentrate to obtain a stage of classification overflow and a stage of classification sedimentation;

[0022] S15: Return the first stage of classification sand settling to the first stage of grinding treatment, forming a closed-loop cycle of "grinding-dilution-magnetic separation-classification";

[0023] S16: subjecting the overflow from the first stage of classification to concentrated magnetic separation to obtain concentrated magnetic separation concentrate and concentrated magnetic separation tailings;

[0024] S17: subjecting the concentrated magnetic separation concentrate to a second-stage grinding process to obtain a second-stage grinding discharge;

[0025] S18: diluting the second-stage mill discharge to obtain the second-stage mill discharge slurry;

[0026] S19: subjecting the slurry discharged from the second-stage grinding mill to a second-stage magnetic separation treatment to obtain a second-stage magnetic separation concentrate and a second-stage magnetic separation tailings;

[0027] S20: subjecting the second-stage magnetic separation concentrate to second-stage classification treatment to obtain concentrate and second-stage classification sand;

[0028] S21: Return the second stage sedimentation to the concentration magnetic separation process, forming a two-stage "concentration-grinding-dilution-magnetic separation-classification" closed-loop operation;

[0029] S22: The wet magnetic separation tailings, the first stage magnetic separation tailings, the concentrated magnetic separation tailings and the second stage magnetic separation tailings are combined together to obtain tailings.

[0030] Furthermore, in S1-S3, the coarse crushing treatment adopts a jaw crusher with a feed port size of >1000mm and a discharge port size of 200mm<250mm, and the coarse crushing operation obtains a coarse crushing discharge particle size composition: -200mm content >95%; the primary screening treatment adopts a heavy-duty circular vibrating screen with a sieve hole size of 30mm<45mm, and the primary screening operation obtains a primary screening ore particle size composition: -30mm content >90%; the medium crushing treatment adopts a standard cone crusher with a discharge port size of 28mm<40mm, and the medium crushing operation obtains a medium crushing discharge particle size composition: -40mm content >85%.

[0031] Furthermore, the first-stage roller mill in S4 uses a high-pressure roller mill, with 50mm<roller spacing<60mm, 1.2m / s<roller surface linear speed<1.8m / s, 4.2MPa<roller specific pressure<4.5MPa, and the first-stage roller mill operation obtains a first-stage roller mill discharge particle size composition: -8mm content>52%; the secondary screening treatment uses a relaxation screen, 8mm<sieve hole size<10mm, 16°<screen slope<30°, 10mm<amplitude<12mm, 2mm<screen movement amplitude<4mm, 500Hz<frequency<800Hz, and the secondary screening operation obtains a secondary screen under-screen particle size composition: -8mm content>85%.

[0032] Furthermore, in S5-S7, the magnetic pulley waste treatment adopts a medium-field strong magnetic pulley, 3100Gs≤surface field strength≤3200Gs, 1.6m / s<waste disposal line speed<3.0m / s, 0.8m<baffle distance<1.2m; the powder ore dry selection treatment adopts a powder ore dry separator, 420mT<magnetic induction intensity<460mT, 2.0m / s<powder ore line speed<2.8m / s; the two-stage roller mill treatment adopts a high-pressure roller mill, 30mm<roller spacing<40mm, 1.5m / s<roller surface line speed<2.0m / s, 4.5MPa<roller specific pressure<5.0MPa, the two-stage roller mill operation obtains the two-stage roller mill discharge particle size composition: -1mm content>43%; the pulping adopts the gravity pulping method of the conveyor belt head height difference drop and water curtain gullying.

[0033] Furthermore, the wet screening in S8 adopts a double-layer linear vibrating screen, with 3.0mm<upper sieve hole size<3.5mm, 0.8mm<lower sieve hole size<1.2mm, 6°<screen inclination angle<10°, 12mm<amplitude<15mm, 800Hz<frequency<950Hz, and the particle size composition of the ore under the secondary screen is obtained: -1.0mm particle size content>85%, and -0.074mm particle size content>15%.

[0034] Furthermore, in S10-S12, the wet magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator, the magnetic induction intensity in the high field strength zone is ≥450mT, the number of magnetic poles is 11, and the outer diameter of the cylinder is 1.5m; the first-stage grinding treatment adopts a grid-type ball mill, the ratio of the mill cylinder diameter to the length is 3:4, the mill is suitable for steel balls with a diameter of 76mm to 120mm, and the grinding concentration is 73% to 76%, and the first-stage grinding discharge particle size composition is obtained: -1.0mm particle size content> 96%, and -0.074mm particle size content> 28%; the dilution treatment adopts a built-in overflow weir dilution box with a volume of 2m 3 , overflow weir height 36cm, dilution frame volume 0.36m 3 .

[0035] Furthermore, in S13-S14, a first stage magnetic separation treatment adopts a semi-countercurrent high-efficiency magnetic separator, with a magnetic induction intensity of 420mT in the high field strength zone, 11 magnetic poles, and a cylinder outer diameter of 1.2m to 1.5m; a first stage classification treatment adopts an FX660-GX cyclone group, with a classification pressure of 68kPa to 96kPa, a classification concentration of 22% to 26%, and a first stage classification overflow particle size composition is obtained: -0.074mm particle size content>55%, and a first stage classification sand concentration of 71% to 75%.

[0036] Furthermore, in S16-S17, a concentrating magnetic separator is used for the concentrated magnetic separation treatment, the magnetic induction intensity of the magnetic separator drum surface is greater than 305mT, the magnetic system wrap angle is 210°~240°, and the outer diameter of the drum is 1.1m~1.5m; the second-stage grinding treatment adopts a vertical mill, the grinding media are ceramic balls and steel balls, the medium ball diameter is φ30mm, and they are assembled in a 1:1 ratio, the filling rate is 65%~72%, and the grinding concentration is 61%~66%, and the second-stage grinding discharge particle size composition is obtained: -0.074mm particle size content is greater than 45%, and -0.043mm particle size content is greater than 40%.

[0037] Furthermore, the second-stage magnetic separation treatment in S19 adopts a downstream high-efficiency magnetic separator with a magnetic induction intensity of 230mT in the high field strength area and 150mT in the unloading area. The number of magnetic poles is 9 to 11 and the outer diameter of the cylinder is 1.2m to 1.5m.

[0038] Furthermore, the second-stage classification treatment in S20 adopts FX250-GX cyclone group, with a classification pressure of 95kPa~125kPa and a classification concentration of 18%~23%, and the second-stage classification overflow particle size composition is obtained: -0.074mm particle content>88%, -0.043mm particle content>75%, and the second-stage classification sand concentration is 65%~72%.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. The low-carbon ore dressing method of extremely poor magnetite crushing, grinding and pulping double direct selection of the present invention realizes the optimization of the traditional process of processing extremely poor magnetite "three-stage one closed-circuit crushing - high-pressure roller mill ultra-fine crushing - three-stage grinding and three-stage magnetic separation" into a "two-stage crushing - two-stage roller mill - ball mill + vertical mill - stage magnetic separation" process from the process flow, shortening the process and reducing the power consumption of the whole ore dressing process by more than 12%.

[0041] 2. The low-carbon ore dressing method of extremely lean magnetite by crushing, grinding and pulping with double direct selection eliminates the fine crushing operation, reduces dust points and improves the on-site environment of ore crushing.

[0042] 3. The low-carbon ore dressing method of extremely lean magnetite crushing and slurrying double direct selection of the present invention optimizes the three-stage ball milling operation into a ball mill + vertical mill operation, reduces the noise source by more than 60%, and reduces the noise in the factory by 8Db. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] like Figure 1 As shown, the embodiment of the present invention aims at the defects or shortcomings of the existing extremely lean magnetite processing technology, and provides an extremely lean magnetite crushing and slurrying double direct separation low-carbon ore separation method, comprising the following steps:

[0046] S1: The mined ore with the maximum geometric size less than 1000mm is subjected to coarse crushing to obtain coarse crushed ore; wherein, the coarse crushing is carried out by a jaw crusher with a feed opening size of >1000mm and a discharge opening size of 200mm<250mm, and the coarse crushing operation obtains a coarse crushed ore with a particle size composition of -200mm content>95%;

[0047] S2: The coarsely crushed ore is subjected to a screening process to obtain the primary screened ore and the primary screened ore; the primary screening process uses a heavy circular vibrating screen, with a sieve hole size of 30mm < 45mm, and the particle size composition of the primary screened ore obtained by the primary screening operation is: -30mm content> 90%;

[0048] S3: The ore on the primary screen is subjected to secondary crushing to obtain secondary crushed ore, and then the secondary crushed ore is returned to the primary screening process, forming a closed-loop cycle of "primary screening-secondary crushing"; the secondary crushing process uses a standard cone crusher, 28mm<discharge port size<40mm, and the particle size composition of the secondary crushed ore obtained by the secondary crushing operation is: -40mm content>85%;

[0049] S4: subjecting the first screened ore to a roller mill process to obtain a first screened ore discharge, and then subjecting the first screened ore discharge to a secondary screening process to obtain a secondary screened ore and a secondary screened ore; wherein, the first screened ore is a high pressure roller mill, 50mm<roller spacing<60mm, 1.2m / s<roller surface linear velocity<1.8m / s, 4.2MPa<roller specific pressure<4.5MPa, and the first screened ore discharge particle size composition obtained by the first screened ore discharge is: -8mm content>52%; the secondary screening is a relaxation screen, 8mm<sieve hole size<10mm, 16°<sieve slope<30°, 10mm<amplitude<12mm, 2mm<sieve moving amplitude<4mm, 500Hz<frequency<800Hz, and the secondary screening operation obtains a secondary screened ore particle size composition: -8mm content>85%;

[0050] S5: The ore on the secondary screen is subjected to magnetic pulley discarding treatment to obtain magnetic pulley concentrate and stone, and then the magnetic pulley concentrate is returned to the first-stage roller mill for treatment, forming a closed-loop cycle operation of "first-stage roller mill-secondary screening-magnetic pulley discarding"; wherein, the magnetic pulley discarding treatment adopts a medium-field strong magnetic pulley, 3100Gs≤surface field strength≤3200Gs, 1.6m / s<discarding linear speed<3.0m / s, 0.8m<baffle distance<1.2m;

[0051] S6: dry-select the secondary screened ore to obtain dry-selected powder ore concentrate and stone powder, and then perform two-stage roller milling on the dry-selected powder ore concentrate to obtain two-stage roller mill discharge; wherein, the dry-selected powder ore adopts a dry-selected powder ore, 420mT<magnetic induction intensity<460mT, 2.0m / s<powder ore linear speed<2.8m / s; the second-stage roller mill adopts a high-pressure roller mill, 30mm<roller spacing<40mm, 1.5m / s<roller surface linear speed<2.0m / s, 4.5MPa<roller specific pressure<5.0MPa, and the particle size composition of the second-stage roller mill discharge obtained by the second-stage roller mill operation is: -1mm content>43%;

[0052] S7: The discharge from the second-stage roller mill is subjected to pulping treatment, and the pulping is carried out by gravity pulping in the form of a height difference drop at the head of a conveyor belt machine and a water curtain gully flushing method to obtain second-stage roller mill pulp;

[0053] S8: wet screening the second-stage roller mill pulp to obtain wet screen ore and wet screen ore; wherein the wet screening uses a double-layer linear vibrating screen, 3.0mm<upper screen hole size<3.5mm, 0.8mm<lower screen hole size<1.2mm, 6°<screen inclination angle<10°, 12mm<amplitude<15mm, 800Hz<frequency<950Hz, and the secondary screen ore particle size composition is: -1.0mm particle size content>85%, and -0.074mm particle size content>15%;

[0054] S9: The wet screened ore is returned to the second-stage roller mill for processing, forming a closed-loop cycle operation of "second-stage roller mill-slurry making-wet screening";

[0055] S10: The wet undersize ore is subjected to wet magnetic separation treatment, and the wet magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator, the magnetic induction intensity in the high field strength area is ≥450mT, the number of magnetic poles is 11, and the outer diameter of the cylinder is 1.5m; wet magnetic separation concentrate and wet magnetic separation tailings are obtained;

[0056] S11: subjecting the wet magnetic separation concentrate to a first-stage grinding process to obtain a first-stage grinding discharge; wherein, the first-stage grinding process uses a grate ball mill, the ratio of the mill cylinder diameter to the length is 3:4, the mill is adapted to steel balls with a diameter of 76 mm to 120 mm, the grinding concentration is 73% to 76%, and the first-stage grinding discharge particle size composition is: -1.0 mm particle size content> 96%, and -0.074 mm particle size content> 28%;

[0057] S12: dilute the first-stage mill discharge to obtain the first-stage mill discharge slurry; the dilution adopts a built-in overflow weir dilution box with a volume of 2m 3 , overflow weir height 36cm, dilution frame volume 0.36m 3 ;

[0058] S13: subjecting the first-stage grinding slurry to a first-stage magnetic separation treatment to obtain a first-stage magnetic separation concentrate and a first-stage magnetic separation tailings; wherein, the first-stage magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator, with a high-field strength zone magnetic induction intensity of 420mT, 11 magnetic poles, and a cylinder outer diameter of 1.2m to 1.5m;

[0059] S14: The first stage magnetic separation concentrate is subjected to a first stage classification treatment to obtain a first stage classification overflow and a first stage classification sedimentation; specifically, the first stage classification uses a FX660-GX type cyclone group, the classification pressure is 68kPa-96kPa, the classification concentration is 22%-26%, and the first stage classification overflow particle size composition is obtained: -0.074mm particle content> 55%, and the first stage classification sedimentation concentration is 71%-75%;

[0060] S15: Return the first stage of classification sand settling to the first stage of grinding treatment, forming a closed-loop cycle of "grinding-dilution-magnetic separation-classification";

[0061] S16: The overflow from the first stage of classification is subjected to concentrated magnetic separation treatment to obtain concentrated magnetic separation concentrate and concentrated magnetic separation tailings; wherein, the concentrated magnetic separation adopts a concentrated magnetic separator, the magnetic induction intensity of the magnetic separator drum surface is greater than 305mT, the magnetic system wrap angle is 210° to 240°, and the outer diameter of the drum is 1.1m to 1.5m;

[0062] S17: The concentrated magnetic separation concentrate is subjected to a second-stage grinding process to obtain a second-stage grinding discharge; specifically, the second-stage grinding adopts a vertical mill, the grinding media are ceramic balls and steel balls, the medium balls have a diameter of φ30mm, and are assembled in a ratio of 1:1, the filling rate is 65% to 72%, the grinding concentration is 61% to 66%, and the second-stage grinding discharge particle size composition is: -0.074mm particle size content>45%, and -0.043mm particle size content>40%;

[0063] S18: diluting the second-stage mill discharge to obtain the second-stage mill discharge slurry;

[0064] S19: subjecting the ore pulp discharged from the second-stage mill to the second-stage magnetic separation treatment to obtain the second-stage magnetic separation concentrate and the second-stage magnetic separation tailings; the second-stage magnetic separation adopts a downstream high-efficiency magnetic separator, with a magnetic induction intensity of 230mT in the high field strength area and 150mT in the unloading area, 9 to 11 magnetic poles, and an outer diameter of the cylinder of 1.2m to 1.5m;

[0065] S20: subjecting the second-stage magnetic separation concentrate to second-stage classification treatment to obtain concentrate and second-stage classification sedimentation; wherein, the second-stage classification adopts FX250-GX type cyclone group, the classification pressure is 95kPa~125kPa, the classification concentration is 18%~23%, and the second-stage classification overflow particle size composition is obtained: -0.074mm particle content>88%, -0.043mm particle content>75%, and the second-stage classification sedimentation concentration is 65%~72%;

[0066] S21: Return the second stage sedimentation to the concentration magnetic separation process, forming a two-stage "concentration-grinding-dilution-magnetic separation-classification" closed-loop operation;

[0067] S22: The wet magnetic separation tailings, the first stage magnetic separation tailings, the concentrated magnetic separation tailings and the second stage magnetic separation tailings are combined together to obtain tailings.

[0068] In order to further better explain the above embodiment, the present invention also provides the following specific implementation cases:

[0069] Step 1: Feed the extremely lean magnetite ore with an iron element TFe content of 19.21%, a magnetic iron mFe content of 14.63%, and a maximum ore size of less than 1000 mm into a C145 jaw crusher for coarse crushing to obtain a coarse crushed ore with a particle size composition of -200 mm and a content of 95%;

[0070] Step 2: Feed the coarsely crushed ore into a heavy-duty circular vibrating screen for a screening process to obtain a particle size composition: -30mm content of 92% of the first screen ore and a particle size composition of -200mm+30mm of the first screen ore;

[0071] Step 3: Feed the ore on the primary screen into the H8800 standard cone crusher for secondary crushing to obtain a secondary crushed ore with a particle size composition of -40 mm and a content of 85.5%;

[0072] Step 4: Return the medium crushed ore to the primary screening process, forming a "primary screening-medium crushing closed circuit" cycle operation; feed the primary screened ore to the 630 / 17-8A 1400PG 1E high pressure roller mill for a first-stage roller milling process to obtain a first-stage roller mill discharge ore with a particle size composition of -8mm and a content of 56%;

[0073] Step 5: Feed the discharge ore from the first roller mill into the CZS2470RD.0 type relaxation screen for secondary screening to obtain the secondary screen undersize ore with a particle size composition of -8mm and a content of 88% and the secondary screen oversize ore with a particle size composition of -30mm+8mm;

[0074] Step 6: Feed the secondary screened ore into a magnetic pulley with a surface field strength of 3200Gs for magnetic pulley discarding treatment to obtain a magnetic pulley concentrate with a TFe content of 20.35% and a stone with a TFe content of 8.72%; return the magnetic pulley concentrate to the first roller mill for treatment, forming a "first roller mill-secondary screening-magnetic pulley discarding closed-loop" cycle operation;

[0075] Step 7: Feed the secondary screened ore into a powder ore dry separator with a magnetic induction intensity of 450 mT for powder ore dry separation to obtain a magnetic pulley concentrate with a TFe content of 25.08% and a stone powder with a TFe content of 8.14%;

[0076] Step 8: Feed the powder ore dry separation concentrate into the CLM1512 high pressure roller mill for two-stage roller milling to obtain a two-stage roller mill discharge with a particle size composition of -1.0 mm content > 45%;

[0077] Step 9: The second-stage roller mill discharge is transported to the head of the belt conveyor for height difference drop and water curtain gully self-flow slurrying to obtain the second-stage roller mill slurry with a concentration of 38%;

[0078] Step 10: Feed the second-stage roller mill pulp into a double-layer linear vibrating screen for wet screening to obtain wet undersize ore with a particle size composition of -1mm content>85% and -0.074mm content>16% and wet oversize ore with a particle size composition of -8mm+1mm; return the wet oversize ore to the second-stage roller mill for processing, forming a "second-stage roller mill-pulping-wet screening closed-loop" cycle operation;

[0079] Step 11: feeding the wet undersize ore into a CTB1500X4500 high-efficiency magnetic separator with a high field strength magnetic induction intensity of 460 mT for wet magnetic separation to obtain a wet magnetic separation concentrate with a TFe content of 37.31% and a wet magnetic separation tailings with a TFe content of 7.52%;

[0080] Step 12: Feed the wet magnetic separation concentrate into a MQG3660 ball mill with a steel ball diameter of 80 mm and a grinding concentration of 75% for a first-stage grinding process to obtain a first-stage grinding discharge with a particle size composition of -0.074 mm and a content of >43%;

[0081] Step 13: feeding the first-stage mill discharge ore into a dilution box for dilution treatment to obtain a first-stage mill discharge ore slurry with a concentration of 26%;

[0082] Step 14: feeding the first-stage grinding slurry into a CTB1500X5000 high-efficiency magnetic separator with a high field strength magnetic induction intensity of 420mT for first-stage magnetic separation treatment to obtain a first-stage magnetic separation concentrate with a TFe content of 43.95% and a first-stage magnetic separation tailings with a TFe content of 7.26%;

[0083] Step 15: Feed the first-stage magnetic separation concentrate into the FX660-GX hydrocyclone group, with a classification pressure of 90 kPa and a classification concentration of 25% for first-stage classification treatment, to obtain a first-stage classification overflow with a -0.074 mm particle content of 62% and a first-stage classification sediment with a concentration of 73%; return the first-stage classification sediment to the first-stage grinding treatment, forming a "grinding-dilution-magnetic separation-classification" closed-loop cycle operation;

[0084] Step 16: feeding the first-stage classification overflow into a NCTB1240 type thickening magnetic separator with a magnetic field strength of 3000 Gs for thickening magnetic separation treatment to obtain a thickened magnetic concentrate with a concentration of 64% and a thickened magnetic tailings with a TFe content of 6.03% and an mFe content of 0.95%;

[0085] Step 17: feeding the concentrated magnetic separation concentrate into a TGTM1000 vertical mill with a filling rate of 68%, a grinding concentration of 64%, and a grinding medium of a ceramic ball and a steel ball mixed in a ratio of 1:1 for a second-stage grinding treatment to obtain a second-stage grinding discharge with a -0.074 mm particle size content of 78% and a -0.043 mm particle size content of 53%;

[0086] Step 18: feeding the secondary mill discharge ore into a dilution box for dilution treatment to obtain secondary mill discharge ore slurry with a concentration of 26%;

[0087] Step 19: Feed the secondary grinding slurry into a CTS1240 high-efficiency magnetic separator with a high field strength area magnetic induction intensity of 220mT and a discharge area magnetic induction intensity of 150mT for secondary magnetic separation to obtain a secondary magnetic separation concentrate with a TFe content of 58.83% and a secondary magnetic separation tailings with a TFe content of 6.55% and an mFe content of 0.82%;

[0088] Step 20: Feed the second-stage magnetic separation concentrate into the FX250-GX hydrocyclone group, with a classification pressure of 118 kPa and a classification concentration of 21%, and perform second-stage classification treatment to obtain a concentrate with a -0.074 mm particle content of 93% and a -0.043 mm particle content of 88%, and a second-stage classification sand settling with a concentration of 65%;

[0089] Step 21: Return the second-stage sedimentation to the concentrated magnetic separation process to form a two-stage "concentration-grinding-dilution-magnetic separation-classification" closed-loop operation; combine the wet magnetic separation tailings, the first-stage magnetic separation tailings, the concentrated magnetic separation tailings and the second-stage magnetic separation tailings to obtain tailings.

[0090] Analysis of the obtained concentrate products and the measured process indicators show that the concentrate TFe = 65.28%, the tailings TFe = 7.62% and mFe = 1.08%, reaching the industry process standards. The two-stage one closed-circuit crushing system consumes 2.13kW·h / t of electricity per ton of raw ore, the first-stage high-pressure roller mill consumes 1.37kW·h / t of electricity per ton of raw ore, and the second-stage high-pressure roller mill consumes 1.86kW·h / t of electricity per ton of raw ore. The first-stage grinding cycle load is 152%, the second-stage grinding cycle load is 186%, and the two-stage grinding system consumes 30.09kW·h / t of electricity per ton of concentrate. The total power consumption index of the whole production process is 64.97kW·h / t per ton of concentrate, which is more than 35% lower than the conventional power consumption of more than 100kW·h / t for the processing of extremely lean magnetite, achieving significant energy-saving effects and achieving the purpose of low-carbon processing of extremely lean magnetite.

[0091] In summary: the present invention provides a low-carbon ore dressing method for extremely lean magnetite by crushing, grinding and slurrying, which adopts the ultra-fine crushing technology of series high-pressure roller mill, the two-stage roller mill ore discharge slurrying wet screening technology and the mill discharge direct sorting technology, which cancels the traditional fine crushing operation, reduces the belt conveyor, greatly reduces the amount of ore entering the mill, and reduces the dust generation points in the ore dressing plant, thereby achieving the purpose of low-carbon, environmentally friendly and efficient sorting of extremely lean magnetite.

[0092] 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 low-carbon beneficiation method for extremely poor magnetite by grinding, pulping, double direct separation, characterized in that: The following steps are involved: S1: coarsely crushing the mined ore with the maximum geometric size less than 1000 mm to obtain coarsely crushed ore; S2: Screening the coarsely crushed ore to obtain an oversize ore and an undersize ore; S3: The ore on the primary screen is subjected to secondary crushing to obtain secondary crushed ore, which is then returned to the primary screening process, forming a "primary screening-secondary crushing" closed-loop cycle operation; S4: subjecting the primary screened ore to a first-stage roller mill process to obtain a first-stage roller mill discharge ore, and then subjecting the first-stage roller mill discharge ore to a second-stage screening process to obtain a second-stage screened ore and a second-stage screened ore; S5: The ore on the secondary screen is subjected to magnetic pulley discarding treatment to obtain magnetic pulley concentrate and stone, and then the magnetic pulley concentrate is returned to the first-stage roller mill for treatment, forming a "first-stage roller mill-secondary screening-magnetic pulley discarding" closed-loop cycle operation; S6: dry separation of the secondary screened ore to obtain dry separation concentrate and stone powder, and then two-stage roller milling of the dry separation concentrate to obtain two-stage roller mill discharge; S7: subjecting the second-stage roller mill discharge to pulping to obtain second-stage roller mill pulp; S8: wet screening the second-stage roller mill pulp to obtain wet screen ore and wet screen ore; S9: The wet screened ore is returned to the second-stage roller mill for processing, forming a closed-loop cycle operation of "second-stage roller mill-slurry making-wet screening"; S10: subjecting the wet undersize ore to wet magnetic separation to obtain wet magnetic separation concentrate and wet magnetic separation tailings; S11: subjecting the wet magnetic separation concentrate to a first-stage grinding process to obtain a first-stage grinding discharge; S12: diluting the first-stage mill discharge ore to obtain the first-stage mill discharge slurry; S13: subjecting the first-stage mill discharge slurry to a first-stage magnetic separation treatment to obtain a first-stage magnetic separation concentrate and a first-stage magnetic separation tailings; S14: performing a stage of classification treatment on the first stage of magnetic separation concentrate to obtain a stage of classification overflow and a stage of classification sedimentation; S15: Return the first stage of classification sand settling to the first stage of grinding treatment, forming a closed-loop cycle of "grinding-dilution-magnetic separation-classification"; S16: subjecting the first-stage classification overflow to concentrated magnetic separation treatment to obtain concentrated magnetic separation concentrate and concentrated magnetic separation tailings; S17: subjecting the concentrated magnetic separation concentrate to a second-stage grinding process to obtain a second-stage grinding discharge; S18: diluting the second-stage mill discharge to obtain the second-stage mill discharge slurry; S19: subjecting the slurry discharged from the second-stage grinding mill to a second-stage magnetic separation treatment to obtain a second-stage magnetic separation concentrate and a second-stage magnetic separation tailings; S20: subjecting the second-stage magnetic separation concentrate to second-stage classification treatment to obtain concentrate and second-stage classification sand; S21: Return the second-stage sedimentation to the concentration magnetic separation process, forming a two-stage "concentration-grinding-dilution-magnetic separation-classification" closed-loop operation; S22: The wet magnetic separation tailings, the first stage magnetic separation tailings, the concentrated magnetic separation tailings and the second stage magnetic separation tailings are combined together to obtain tailings.

2. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: In S1-S3, the coarse crushing process uses a jaw crusher with a feed port size of >1000mm and a discharge port size of 200mm<250mm. The coarse crushing operation obtains a coarse crushed discharge particle size composition of: -200mm content >95%; the primary screening process uses a heavy-duty circular vibrating screen with a sieve hole size of 30mm<45mm, and the primary screening operation obtains a first-screen undersize particle size composition of: -30mm content >90%; the medium crushing process uses a standard cone crusher with a discharge port size of 28mm<40mm, and the medium crushing operation obtains a medium crushed discharge particle size composition of: -40mm content >85%.

3. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: The first-stage roller mill in S4 uses a high-pressure roller mill, with 50mm<roller spacing<60mm, 1.2m / s<roller surface linear speed<1.8m / s, 4.2MPa<roller specific pressure<4.5MPa. The particle size composition of the first-stage roller mill discharge ore obtained by the first-stage roller mill operation is: -8mm content>52%; the secondary screening process uses a relaxation screen, 8mm<sieve hole size<10mm, 16°<screen slope<30°, 10mm<amplitude<12mm, 2mm<screen movement amplitude<4mm, 500Hz<frequency<800Hz. The secondary screening operation obtains the particle size composition of the secondary screen ore: -8mm content>85%.

4. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: In S5-S7, the magnetic pulley waste treatment adopts a medium-field strong magnetic pulley, 3100Gs≤surface field strength≤3200Gs, 1.6m / s<waste line speed<3.0m / s, 0.8m<baffle distance<1.2m; the powder ore dry selection treatment adopts a powder ore dry separator, 420mT<magnetic induction intensity<460mT, 2.0m / s<powder ore line speed<2.8m / s; the second-stage roller mill treatment adopts a high-pressure roller mill, 30mm<roller spacing<40mm, 1.5m / s<roller surface line speed<2.0m / s, 4.5MPa<roller specific pressure<5.0MPa, the second-stage roller mill operation obtains the second-stage roller mill discharge particle size composition: -1mm content>43%; the pulping adopts the gravity pulping method of the height difference drop of the conveyor belt head and the water curtain gullying.

5. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: S8 medium wet screening uses a double-layer linear vibrating screen, 3.0mm<upper sieve hole size<3.5mm, 0.8mm<lower sieve hole size<1.2mm, 6°<screen inclination angle<10°, 12mm<amplitude<15mm, 800Hz<frequency<950Hz, and obtains the particle size composition of the secondary screen ore: -1.0mm particle size content>85%, and -0.074mm particle size content>15%.

6. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: In S10-S12, the wet magnetic separation adopts a semi-countercurrent high-efficiency magnetic separator, with a high field strength zone magnetic induction intensity ≥450mT, 11 magnetic poles, and a cylinder outer diameter of 1.5m; the first-stage grinding treatment adopts a grid-type ball mill, with a ratio of mill cylinder diameter to length of 3:4, a mill-adapted steel ball diameter of 76mm to 120mm, and a grinding concentration of 73% to 76%. The particle size composition of the first-stage grinding discharge is: -1.0mm particle size content> 96%, and -0.074mm particle size content> 28%; the dilution treatment adopts a built-in overflow weir dilution box with a volume of 2m 3 , overflow weir height 36cm, dilution frame volume 0.36m 3 .

7. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: In S13-S14, the first stage magnetic separation treatment adopts a semi-countercurrent high-efficiency magnetic separator, with a magnetic induction intensity of 420mT in the high field strength zone, 11 magnetic poles, and a cylinder outer diameter of 1.2m to 1.5m; the first stage classification treatment adopts an FX660-GX cyclone group, with a classification pressure of 68kPa to 96kPa and a classification concentration of 22% to 26%, and the first stage classification overflow particle size composition is obtained: -0.074mm particle content>55%, and the first stage classification sand concentration is 71% to 75%.

8. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: In S16-S17, the concentrated magnetic separation treatment adopts a concentrated magnetic separator, the magnetic induction intensity of the magnetic separator drum surface is greater than 305mT, the magnetic system wrap angle is 210°~240°, and the outer diameter of the drum is 1.1m~1.5m; the second-stage grinding treatment adopts a vertical mill, the grinding media are ceramic balls and steel balls, the medium ball diameter is φ30mm, and they are installed in a 1:1 ratio, the filling rate is 65%~72%, and the grinding concentration is 61%~66%. The particle size composition of the second-stage grinding discharge is: -0.074mm particle size content is greater than 45%, and -0.043mm particle size content is greater than 40%.

9. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: The second-stage magnetic separation treatment in S19 adopts a downstream high-efficiency magnetic separator with a magnetic induction intensity of 230mT in the high field strength area and 150mT in the unloading area. The number of magnetic poles is 9 to 11 and the outer diameter of the cylinder is 1.2m to 1.5m.

10. A low-carbon beneficiation method for extremely lean magnetite by crushing, grinding and pulping with double direct separation as claimed in claim 1, characterized in that: The second stage classification treatment in S20 adopts FX250-GX cyclone group, with classification pressure of 95kPa~125kPa and classification concentration of 18%~23%, and the second stage classification overflow particle size composition is obtained: -0.074mm particle content>88%, -0.043mm particle content>75%, and the second stage classification sand concentration is 65%~72%.

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