Efficient short-process magnetizing roasting combined treatment method for iron ore

Abstract

The invention discloses an efficient short-process magnetizing roasting combined treatment method for iron ore, and belongs to the field of mineral processing engineering. The method comprises the following steps: crushing and screening the iron ore with the particle size of 0-300mm, and feeding into a closed-loop dry-method pulverizing system consisting of a high-pressure roller mill and a wind power concentrator to prepare ore powder with a qualified particle size; after being subjected to two-stage preheating, the mineral powder sequentially enters a roasting furnace and a reduction furnace in a suspended state to be magnetized and roasted, and high-temperature roasted sand is cooled through a waste heat boiler to recover heat; and the cooled calcine is subjected to slurry making, pre-concentration and tailing discarding, then a vertical stirring mill is adopted for wet closed-circuit ore grinding, then continuous magnetic separation and reverse flotation impurity removal are conducted, and finally high-quality iron ore concentrate is obtained. According to the method, the high-pressure roller milling dry-method powder preparation and the suspension roasting process are combined, so that the intermediate links of filtering, drying and the like in the traditional wet-type powder preparation are omitted, and the problem of high energy consumption of feeding wet ore into a furnace is solved; and meanwhile, full-process ball-free milling operation is realized by adopting a high-pressure roller mill and a vertical stirring mill, so that the crushing and grinding efficiency and the energy efficiency level are greatly improved. Compared with the prior art, the method has the remarkable advantages of being short in process, high in efficiency, energy-saving, environment-friendly and the like, and is particularly suitable for resource utilization of low-grade refractory iron ore.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology and relates to a method for efficient short-process magnetization roasting combined treatment of iron ore. Background Technology

[0002] Iron ore is the basic raw material for the steel industry, and its stable supply is of great strategic importance to national economic development. With the increasing depletion of easily beneficiated high-grade iron ore resources, the efficient development and utilization of lean, fine, and complex difficult-to-benefit iron ores (such as fine-grained hematite, limonite, siderite, and mixed iron ores containing iron carbonate), which account for the majority of China's iron ore reserves, has become a core issue that urgently needs to be addressed in the mineral processing field.

[0003] Currently, for refractory iron ores, especially weakly magnetic iron ores, magnetizing roasting-magnetic separation technology is recognized as one of the most effective processing methods. This technology converts weakly magnetic iron minerals (such as hematite and limonite) into strongly magnetic magnetite, which is then efficiently recovered using magnetic separation. Existing processes based on this technology mainly include the following technical routes: On the one hand, traditional magnetizing roasting processes mostly employ vertical furnaces or rotary kilns, which suffer from high energy consumption, low single-unit processing capacity, and significant environmental impact. To improve reaction efficiency, suspension magnetizing roasting technology has been developed in recent years. For example, Chinese patent application CN113042196A discloses a beneficiation process for hematite ore, employing a combined process of "stage grinding, coarse and fine fractionation, gravity-magnetic-flotation." Gravity separation separates the fine particles from the coarse product, allowing them to directly enter flotation to avoid over-grinding. However, this process still suffers from a relatively long flow rate, and the fine particles still require traditional wet ball milling and dewatering, resulting in high energy and water consumption.

[0004] On the other hand, to reduce energy consumption in crushing and grinding, high-pressure roller mills, as highly efficient and energy-saving pulverizing equipment, have been introduced into the iron ore beneficiation field. For example, Chinese patent application CN112588430A discloses a short-process, high-efficiency beneficiation process for carbonate-containing iron ore. This process employs two stages of continuous closed-circuit grinding, followed by fine grinding of the mixed magnetic concentrate using a stirring mill (using ceramic ball media), and then anion reverse flotation. While this process shortens the process and improves grinding efficiency, its initial grinding stage still relies on traditional ball mills and is not systematically integrated with the magnetizing roasting process. Therefore, the energy consumption problem in the roasting stage (such as wet ore entering the furnace) remains unresolved.

[0005] Furthermore, for the processing of mixed iron ore (coexisting magnetite and hematite), Chinese invention patent CN113953080B proposes a beneficiation method that preferentially extracts magnetite from the fine-grained product through weak magnetic separation, thereby reducing the feed rate and reagent consumption for subsequent reverse flotation. While this approach achieves progress in cost reduction and efficiency improvement, its core grinding operation still employs a closed-loop system of "ball mill + classifier," resulting in relatively low energy utilization efficiency. Moreover, it fails to fundamentally address the problem of high heat consumption in the suspension roasting system caused by moisture-containing ore entering the furnace.

[0006] In summary, while existing technologies have achieved some optimizations in certain stages such as crushing, grinding, and beneficiation, they generally suffer from the following technical pain points: 1) The process flow is lengthy, typically including multiple stages of crushing, wet grinding, filtration, drying, and dispersing, resulting in large equipment investment and land area requirements; 2) High energy consumption in crushing and grinding, still relying on traditional ball mills as the core grinding equipment, with energy utilization efficiency needing improvement; 3) Low energy efficiency in the roasting system, with high moisture content in the ore powder after wet grinding, leading to increased system heat consumption due to moisture evaporation absorbing a large amount of heat. Therefore, there is an urgent need in this field to develop a new high-efficiency iron ore processing technology that can organically integrate efficient dry grinding, low-energy suspension roasting, and fine grinding and beneficiation to achieve energy saving and consumption reduction throughout the entire process and simplify the process. Summary of the Invention

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the purpose of this invention is to propose a highly efficient, short-process combined magnetic roasting method for iron ore. This method systematically integrates high-pressure roller mill dry grinding, suspension magnetic roasting, and vertical stirred mill fine grinding, offering advantages such as a short process, low energy consumption, high efficiency, and strong adaptability. It is particularly suitable for the resource utilization of low-grade, difficult-to-process iron ore.

[0008] To achieve the above objectives, this invention proposes a high-efficiency, short-process combined magnetization roasting method for iron ore, comprising the following steps: Step 1: Dry milling S11. Crushing and screening: 0~300mm iron ore is crushed and screened in multiple stages to obtain 0~20mm iron ore as feed for the dry grinding system; S12. Dry grinding: The 0~20mm iron ore obtained by crushing and screening is fed into a closed-circuit dry grinding system consisting of a high-pressure roller mill and an air classifier for grinding. The coarse particles separated by the air classifier are returned to the high-pressure roller mill for re-grinding, and the qualified particles are used as feed for suspension magnetization roasting. Step 2: Suspension roasting S21. Two-stage preheating: The qualified particle size mineral powder selected in S12 is fed into a two-stage preheater for preheating. S22. Suspension roasting: The preheated mineral powder is sequentially fed into the roasting furnace and the reduction furnace in a suspended state for suspension magnetization roasting, and finally the roasted sand is obtained by gas-solid separation; S23. Heat exchange and cooling: High-temperature calcined sand enters the waste heat boiler for cooling under nitrogen protection and fluidization. Through indirect heat exchange with demineralized water in the heat exchange tube, the temperature of the calcined sand is reduced to below 250°C. At the same time, the heat is recovered to generate steam for waste heat power generation. Step 3: Grinding and Magnetic Separation S31. Stirring and pulping: The cooled calcined sand from S23 is fed into the pulping tank, mixed with water, stirred, cooled, and pulped. S32. Pre-selection tailings removal: Magnetic separation is performed on the pulp after slurry preparation to remove tailings; S33. Grinding and magnetic separation: The pre-selected concentrate obtained in S32 is subjected to wet closed-circuit grinding using a vertical stirred mill, followed by continuous magnetic separation to obtain magnetic concentrate; Step 4: Reverse flotation S41. The magnetic concentrate obtained in S33 is subjected to reverse flotation to remove impurities, and roughing, cleaning and scavenging operations are carried out in sequence to finally obtain high-quality iron concentrate.

[0009] In addition, the efficient short-process magnetization roasting combined treatment method for iron ore described above according to embodiments of the present invention may also have the following additional technical features: According to one embodiment of the present invention, the qualified particle size range of the mineral powder produced by the closed-circuit dry grinding system composed of the high-pressure roller mill and the air classifier in step S12 is: +0.5mm <2%, -74μm 40%~55%, and -18μm <30%.

[0010] According to one embodiment of the present invention, the suspension roasting furnace in step 2 is a dry feeding furnace type, and the moisture content of the qualified particle size powder produced by the dry grinding system in step S12 should be <2.5%.

[0011] According to one embodiment of the present invention, when the moisture content of the iron ore fed into the high-pressure roller mill is ≥2.5%, the air separation process in step S12 will use hot air generated by the auxiliary heating system or hot flue gas from the suspension roasting furnace as the air separation medium to simultaneously dry the ore during the dispersion and separation process.

[0012] According to one embodiment of the present invention, in order to ensure the stability of the gas pressure in the suspension roasting system and prevent gas leakage, when the dry and loose fine-grained mineral powder is fed into the suspension furnace preheating system in step S21, the inlet is sealed with a material block gas valve.

[0013] According to one embodiment of the present invention, the drying medium source of the two-stage preheater in step S21 is: the second-stage preheating uses the high-temperature flue gas of 600~650℃ discharged from the calcining furnace in step S22; the first-stage preheating uses the medium-temperature flue gas of 300~380℃ separated after the second-stage preheating.

[0014] According to one embodiment of the present invention, in step S22, the heat source of the roasting furnace is the high-temperature flue gas generated after the gas Q is fully combusted, and the roasting temperature of the mineral powder is controlled at 620~670℃; the reducing medium used in the reduction furnace is gas Q, and the reduction temperature of the mineral powder is controlled at 520~580℃.

[0015] According to one embodiment of the present invention, the gas Q is one or more mixed gases selected from metallurgical gas, water gas, natural gas, and hydrogen.

[0016] According to one embodiment of the present invention, the calcined sand after suspension magnetization roasting and cooling has weak magnetic properties, and the magnetic field strength of all magnetic separators in steps S32 and S33 is controlled to be 400~500mT.

[0017] According to one embodiment of the present invention, the present invention adopts a combination of "high pressure roller mill + vertical stirred mill" for crushing and grinding operations, that is, the iron ore raw ore is crushed by high pressure roller mill and the roasted ore is finely ground by vertical stirred mill, realizing the "ball mill-free" operation of the entire iron ore processing process.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention innovatively integrates the traditional, lengthy process of "multi-stage crushing - wet grinding - filtration - drying - dispersing - ball milling" into a shorter process of "high-pressure roller mill dry grinding - suspension roasting - vertical stirred mill fine grinding". Compared with traditional processes, it eliminates intermediate steps such as filtration, drying, and dispersing after wet grinding, significantly reducing the number of equipment, floor space, and operator requirements, and lowering infrastructure investment and operation and maintenance costs.

[0019] 2. This invention employs a combination of a high-pressure roller mill and a vertical stirred mill in the crushing and grinding stage. This fully leverages the dual advantages of the high energy utilization rate of the high-pressure roller mill's "layered crushing" and the superior grinding efficiency of the vertical stirred mill compared to traditional horizontal ball mills, achieving a completely "ball mill-free" operation and significantly reducing crushing and grinding energy consumption. Simultaneously, the suspension roasting furnace uses dry feeding, avoiding the large amount of latent heat required for moisture evaporation from wet ore entering the furnace, effectively reducing the heat consumption of the roasting system. Furthermore, the high-temperature roasted sand waste heat recovery system can generate steam for power generation, further improving the overall energy utilization level.

[0020] 3. This invention achieves fine pulverization of ore through dry grinding, which helps improve the permeability and regrindability of the ore; after the roasted ore is finely ground by a vertical stirred mill, the mineral monomers have a high degree of liberation. Combined with pre-selection tailings removal, multi-stage magnetic separation and reverse flotation to remove impurities, high-quality iron concentrate with high iron grade and low impurity content can be obtained, realizing the efficient recovery of difficult-to-process iron ore.

[0021] 4. The material preparation process of this invention adopts dry grinding, which fundamentally eliminates the large amount of industrial water required by traditional wet grinding. This has important practical significance and environmental value for resource development in water-scarce but mineral-rich areas such as western my country. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a high-efficiency, short-process magnetization roasting combined treatment process for iron ore according to the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] This invention provides an efficient, short-process magnetization roasting combined treatment process for iron ore, such as... Figure 1 As shown, it includes the following steps: Step 1: Dry milling S11. Crushing and Screening: The 0~300mm raw ore is subjected to coarse crushing, medium crushing and screening to obtain crushed products with a particle size of 0~20mm, which are used as feed for the dry grinding system.

[0025] S12. Dry Grinding: The 0~20mm crushed product is fed into a closed-loop dry grinding system consisting of a high-pressure roller mill and an air classifier. After being crushed by the high-pressure roller mill, the material is fed into the air classifier for classification. The coarse particles separated are returned to the high-pressure roller mill for regrinding, forming a closed-loop cycle. The qualified particle size mineral powder is used as feed for the suspension magnetized roasting system. When the moisture content of the feed iron ore is ≥2.5%, the air classifier uses hot air generated by the auxiliary heating system or hot flue gas from the suspension roasting furnace as the air classifier medium. During the material dispersion and classification process, the material is simultaneously dried to ensure that the final mineral powder moisture content meets the feed requirements of the roasting system. The particle size distribution of the qualified particle size mineral powder obtained in this step is controlled as follows: +0.5mm <2%, -74μm 40%~55%, -18μm <30%.

[0026] Step 2: Suspension roasting S21. Two-stage preheating: The qualified particle size mineral powder obtained in S12 is sequentially fed into a two-stage suspension preheater through a material sealing valve for preheating. The second-stage preheater uses the 600-650℃ high-temperature flue gas discharged from the roasting furnace in S22 as the drying heat source; the first-stage preheater uses the 300-380℃ medium-temperature flue gas separated from the second-stage preheater as the drying heat source. The material sealing valve effectively prevents gas leakage from the system, ensuring stable gas pressure in the suspension roasting system.

[0027] S22. Suspension Roasting: The preheated ore powder is sequentially fed into a roasting furnace and a reduction furnace in a suspended state. In the roasting furnace, the ore powder comes into contact with the high-temperature flue gas generated by the complete combustion of gas Q, and undergoes oxidative roasting at 620~670℃. Subsequently, it enters the reduction furnace, where it comes into contact with gas Q and undergoes a reduction reaction at 520~580℃, converting the weakly magnetic iron minerals in the ore into strongly magnetic magnetite. After the reaction, the material undergoes gas-solid separation to obtain high-temperature roasted sand. The gas Q is one or a mixture of any two or more of the following: metallurgical gas, water gas, natural gas, and hydrogen.

[0028] S23. Heat Exchange and Cooling: High-temperature calcined sand enters the waste heat boiler under nitrogen protection and fluidization. Through indirect heat exchange with demineralized water in the heat exchange tubes, the temperature of the calcined sand is reduced to below 250℃. The heat released during the cooling process heats the demineralized water to generate steam. The recovered steam is then sent out for waste heat power generation, achieving comprehensive energy utilization.

[0029] Step 3: Grinding and Magnetic Separation S31. Stirring and pulping: The calcined sand cooled in S23 is fed into the pulping tank, mixed with water, stirred, cooled, and pulped to obtain a mineral pulp of a certain concentration.

[0030] S32. Pre-selection and tailings removal: The pulp after slurry preparation is fed into a magnetic separator for a pre-selection and tailings removal stage to remove some of the dissociated coarse gangue minerals. The magnetic field strength is controlled at 400~500mT.

[0031] S33. Grinding and Magnetic Separation: The pre-selected concentrate obtained in S32 is subjected to wet closed-circuit grinding using a vertical stirred mill to achieve the required particle size for mineral liberation. The grinding product is then subjected to continuous magnetic separation (two or three stages), with the magnetic field strength of all magnetic separators controlled at 400~500mT to obtain magnetically separated concentrate.

[0032] Step 4: Reverse flotation S41. The magnetic concentrate obtained in S33 is subjected to reverse flotation for impurity removal, successively undergoing roughing, cleaning, and scavenging to finally obtain high-quality iron concentrate. This step adopts conventional iron ore reverse flotation reagent systems, such as using starch as an iron mineral depressant and amine cationic collectors as collectors for gangue minerals such as quartz, and is carried out under natural pH conditions or alkaline conditions (pH 8-11).

[0033] This invention uses a combination of "high-pressure roller mill + vertical stirred mill" for crushing and grinding operations, realizing "ball mill-free" operation in the entire iron ore processing process, and greatly improving crushing and grinding efficiency and energy efficiency.

[0034] Example 1 This embodiment uses Jiuquan Iron and Steel Group's Jingtieshan iron ore as raw material, with a total iron content of 32.5% and a moisture content of 2.0%.

[0035] Step 1: Dry milling S11. The 0~300mm raw ore is coarsely crushed, mediumly crushed, and screened to obtain a 0~20mm crushed product.

[0036] S12. The 0~20mm crushed product is fed into a closed-circuit dry grinding system consisting of a high-pressure roller mill and an air classifier. Since the moisture content of the raw ore is below 2.5%, there is no need to start the auxiliary heating system. The final qualified particle size distribution of the mineral powder is: +0.5mm 1.86%, -74μm 43.28%, and -18μm 23.55%, meeting the feed requirements.

[0037] Step 2: Suspension roasting S21. Qualified granulated mineral powder is fed sequentially into a two-stage preheater through a material sealing gas valve. The second-stage preheater uses 620℃ high-temperature flue gas discharged from the calcining furnace, and the first-stage preheater uses 315℃ medium-temperature flue gas separated from the second-stage preheater.

[0038] S22. The preheated ore powder is sequentially fed into a roasting furnace and a reduction furnace. The roasting furnace uses high-temperature flue gas generated from the combustion of metallurgical gas as a heat source and suspension medium, with a roasting temperature of 630℃; the reduction furnace uses metallurgical gas as a reducing medium and suspension medium, with a reduction temperature of 535℃. After the reaction is completed, calcined sand is obtained through gas-solid separation.

[0039] S23. The high-temperature calcined sand is cooled in a waste heat boiler under nitrogen protection and indirectly exchanges heat with demineralized water. The temperature of the calcined sand drops to 228°C, and the recovered heat generates steam for waste heat power generation.

[0040] Step 3: Grinding and Magnetic Separation S31. The cooled calcined sand is fed into the pulping tank, mixed with water and stirred to form a pulp with a pulp concentration of 30%.

[0041] S32. The slurry is fed into a magnetic separator for a pre-selection and tailings removal process, with a magnetic field strength of 400mT.

[0042] S33. The pre-selected concentrate was subjected to wet closed-circuit grinding using a vertical stirred mill, with a grinding fineness of -38μm content of 90.5%. The grinding product was then subjected to three stages of magnetic separation with magnetic field strengths of 450mT, 420mT, and 420mT, respectively, to obtain the magnetically separated concentrate.

[0043] Step 4: Reverse flotation S41. The magnetic concentrate is subjected to reverse flotation for impurity removal, followed by roughing, cleaning, and scavenging operations. In this embodiment, the reverse flotation uses a conventional iron ore reverse flotation reagent system, with starch as an iron mineral depressant and amine cationic collectors as quartz collectors, and is carried out under natural pH conditions (pH 8-9). The final product is a high-quality iron concentrate with a total iron content of 60.42% and a SiO2 content of 5.28%.

[0044] Example 2 This embodiment uses Jiuquan Iron and Steel Group's Jingtieshan iron ore as raw material, with a total iron content of 33.36% and a water content of 3.6%.

[0045] Step 1: Dry milling S11. The 0~300mm raw ore is coarsely crushed, mediumly crushed, and screened to obtain a 0~20mm crushed product.

[0046] S12. The 0~20mm crushed product is fed into a closed-circuit dry grinding system consisting of a high-pressure roller mill and an air classifier. Because the raw ore moisture content is higher than 2.5%, an auxiliary heating system is activated, using hot air as the air classification medium to simultaneously dry the material during the separation process. The final qualified particle size distribution of the mineral powder is: +0.5mm 1.53%, -74μm 48.32%, -18μm 26.53%, and the moisture content is reduced to 1.96%.

[0047] Step 2: Suspension roasting S21. Qualified granulated mineral powder is fed sequentially into a two-stage preheater through a material sealing gas valve. The second-stage preheater uses 650℃ high-temperature flue gas discharged from the calcining furnace, and the first-stage preheater uses 360℃ medium-temperature flue gas separated from the second-stage preheater.

[0048] S22. The preheated mineral powder is sequentially fed into a roasting furnace and a reduction furnace. The roasting furnace uses high-temperature flue gas generated by natural gas combustion as a heat source and suspension medium, with a roasting temperature of 670℃; the reduction furnace uses natural gas as a reducing medium and suspension medium, with a reduction temperature of 560℃. After the reaction is completed, calcined sand is obtained through gas-solid separation.

[0049] S23. The high-temperature calcined sand is cooled in a waste heat boiler under nitrogen protection and indirectly exchanges heat with demineralized water. The temperature of the calcined sand drops to 232°C, and the recovered heat generates steam for waste heat power generation.

[0050] Step 3: Grinding and Magnetic Separation S31. The cooled calcined sand is fed into the pulping tank, mixed with water and stirred to form a pulp with a pulp concentration of 32%.

[0051] S32. The slurry is fed into a magnetic separator for a pre-selection and tailings removal process, with a magnetic field strength of 420mT.

[0052] S33. The pre-selected concentrate was subjected to wet closed-circuit grinding using a vertical stirred mill, with a grinding fineness of -38μm content of 90.8%. The grinding product was then subjected to three stages of magnetic separation with magnetic field strengths of 450mT, 420mT, and 400mT, respectively, to obtain the magnetically separated concentrate.

[0053] Step 4: Reverse flotation S41. The magnetic concentrate is subjected to reverse flotation for impurity removal, followed by roughing, cleaning, and scavenging operations. In this embodiment, the reverse flotation uses a conventional iron ore reverse flotation reagent system, with starch as an iron mineral depressant and amine cationic collectors as quartz collectors, and is carried out under natural pH conditions (pH 8-9). The final product is a high-quality iron concentrate with a total iron content of 60.61% and a SiO2 content of 5.32%.

[0054] Example 3 This embodiment uses Jiuquan Iron and Steel Group's Jingtieshan iron ore as raw material, with a total iron content of 34.05% and a water content of 4.5%.

[0055] Step 1: Dry milling S11. The 0~300mm raw ore is coarsely crushed, mediumly crushed, and screened to obtain a 0~20mm crushed product.

[0056] S12. The 0~20mm crushed product is fed into a closed-circuit dry grinding system consisting of a high-pressure roller mill and an air classifier. Because the raw ore has a moisture content higher than 2.5%, hot flue gas from a suspension roasting furnace is used as the air classifier medium, and the material is simultaneously dried during the separation process. The final qualified particle size distribution of the mineral powder is: +0.5mm 1.23%, -74μm 53.22%, -18μm 28.26%, and the moisture content is reduced to 2.15%.

[0057] Step 2: Suspension roasting S21. Qualified particle size mineral powder is fed into a two-stage preheater sequentially through a material sealing gas valve. The second-stage preheater uses 635℃ high-temperature flue gas discharged from the calcining furnace, and the first-stage preheater uses 345℃ medium-temperature flue gas separated from the second-stage preheater.

[0058] S22. The preheated mineral powder is sequentially fed into a roasting furnace and a reduction furnace. The roasting furnace uses high-temperature flue gas generated by the combustion of hydrogen-rich gas as a heat source and suspension medium, with a roasting temperature of 650℃; the reduction furnace uses hydrogen-rich gas as a reducing medium and suspension medium, with a reduction temperature of 545℃. After the reaction is completed, calcined sand is obtained through gas-solid separation.

[0059] S23. The high-temperature roasted sand is cooled in a waste heat boiler under nitrogen protection and indirectly exchanges heat with demineralized water. The temperature of the roasted sand drops to 238°C, and the recovered heat generates steam for waste heat power generation.

[0060] Step 3: Grinding and Magnetic Separation S31. The cooled calcined sand is fed into the pulping tank, mixed with water and stirred to form a pulp with a pulp concentration of 35%.

[0061] S32. The slurry is fed into a magnetic separator for a pre-selection and tailings removal process, with a magnetic field strength of 410mT.

[0062] S33. The pre-selected concentrate was subjected to wet closed-circuit grinding using a vertical stirred mill, with a grinding fineness of -38μm content of 90.3%. The grinding product was then subjected to four stages of magnetic separation with magnetic field strengths of 470mT, 450mT, 420mT, and 400mT, respectively, to obtain the magnetically separated concentrate.

[0063] Step 4: Reverse flotation S41. The magnetic concentrate is subjected to reverse flotation for impurity removal, followed by roughing, cleaning, and scavenging operations. In this embodiment, the reverse flotation uses a conventional iron ore reverse flotation reagent system, with starch as an iron mineral depressant and amine cationic collectors as quartz collectors, and is carried out under natural pH conditions (pH 8-9). The final product is a high-quality iron concentrate with a total iron content of 60.78% and a SiO2 content of 5.12%.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for efficient, short-process combined magnetization roasting and processing of iron ore, characterized in that, Includes the following steps: Step 1: Dry milling S11: Iron ore with a diameter of 0~300mm is crushed and screened in multiple stages to obtain iron ore with a diameter of 0~20mm; S12: The obtained 0~20mm iron ore is fed into a closed-circuit dry grinding system consisting of a high-pressure roller mill and an air classifier. After being separated by the air classifier, the coarse-grained ore is returned to the high-pressure roller mill for re-grinding, and the qualified-grained ore powder is used as the feed for suspension magnetization roasting. Step 2: Suspension roasting S21: Feed qualified particle size mineral powder into two-stage preheaters for preheating; S22: The preheated mineral powder is sequentially fed into the roasting furnace and the reduction furnace in a suspended state for magnetized roasting, and then the roasted sand is obtained through gas-solid separation. S23: High-temperature calcined sand is cooled to below 250°C in a waste heat boiler under nitrogen protection to recover heat and generate steam; Step 3: Grinding and Magnetic Separation S31: The cooled calcined sand is fed into a pulping tank and mixed with water to make pulp; S32: Magnetic pre-selection and tailings removal of the pulp after slurry preparation; S33: The pre-selected concentrate is wet-circuit-milled using a vertical stirred mill, followed by continuous magnetic separation to obtain magnetic concentrate; Step 4: Reverse flotation S41: The magnetic concentrate is subjected to reverse flotation to remove impurities, and after roughing, cleaning and scavenging, iron concentrate is obtained.

2. The method according to claim 1, characterized in that, The particle size distribution of the qualified mineral powder in step S12 is as follows: +0.5mm accounts for <2%, -74μm accounts for 40%~55%, and -18μm accounts for <30%.

3. The method according to claim 1, characterized in that, The suspension roasting furnace mentioned in step 2 is a dry feeding furnace type, and the moisture content of the ore powder obtained in step S12 is <2.5%.

4. The method according to claim 1, characterized in that, When the moisture content of the iron ore fed into the high-pressure roller mill in step S12 is ≥2.5%, the air classifier uses hot air generated by the auxiliary heating system or hot flue gas from the suspension roasting furnace as the air classification medium to achieve simultaneous drying and classification.

5. The method according to claim 1, characterized in that, In step S21, when the mineral powder is fed into the preheating system, the inlet is sealed with a material block valve.

6. The method according to claim 1, characterized in that, The drying medium for the two-stage preheater in step S21 is sourced from: The second stage of preheating uses the high-temperature flue gas of 600~650℃ discharged from the roasting furnace; The first-stage preheating uses the medium-temperature flue gas of 300~380℃ separated after the second-stage preheating.

7. The method according to claim 1, characterized in that, In step S22: The heat source for the roasting furnace is the high-temperature flue gas generated by the complete combustion of gas Q, and the roasting temperature is 620~670℃. The reducing medium in the reduction furnace is gas Q, and the reduction temperature is 520~580℃.

8. The method according to claim 7, characterized in that, The gas Q is one or more of metallurgical gas, water gas, natural gas, and hydrogen.

9. The method according to claim 1, characterized in that, The magnetic field strength of the magnetic separator used in steps S32 and S33 is 400~500mT.

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