Process and system for preparing iron concentrate from high-iron red mud

Abstract

The present application belongs to the technical field of industrial waste residue and waste slurry treatment, and particularly relates to a process method and system for preparing iron concentrate from high-iron red mud. In order to improve the comprehensive utilization rate of high-iron red mud and the recovery rate of iron, the present application adjusts the slurry of the raw red mud through a red mud slurry pretreatment system, removes impurities, and then is subjected to multi-stage magnetic separation through a multi-stage magnetic separation combined process system to obtain magnetic separation iron concentrate and magnetic separation tailings. The magnetic separation iron concentrate is dried in a magnetic separation iron concentrate treatment system, and then is crushed, preheated, and magnetically reduced with a coal-based reducing agent in a coal-based magnetization roasting system to obtain roasted iron concentrate. The roasted iron concentrate is then water quenched and ball milled and weakly magnetically separated in a roasted iron concentrate treatment system to obtain iron concentrate products with an iron grade TFe of 55% to 58% and tail roasted ore. The tail roasted ore can be used as a high-activity building material, thereby realizing the reduction and effective comprehensive utilization of Guinea high-iron red mud resources, and having important economic benefits and social significance.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste residue and slurry treatment technology, specifically relating to a process and system for preparing iron concentrate from high-iron red mud. Background Technology

[0002] With the reduction in domestic bauxite reserves and the decline in grade, the quantity of imported iron-bearing trihydrate bauxite has gradually increased. It is estimated that more than half of the newly added red mud in China is high-iron red mud produced from bauxite, with the majority being Guinea high-iron red mud. Guinea high-iron red mud has a high iron mineral content (TFe can reach around 40%), and its extraction has significant economic value. However, due to the high viscosity and fine particle size of this type of red mud slurry (over 70% of particles are -0.025mm), the iron minerals it contains mainly exist in the form of hematite, goethite, and weakly magnetic iron, making the process of effectively extracting and comprehensively utilizing iron mineral resources difficult and technically demanding.

[0003] Currently, conventional beneficiation processes such as magnetic separation and gravity separation are generally used in China for processing Guinean high-speed iron ore red mud. However, while these processes yield high-grade iron concentrate, they also generate a considerable amount of refractory ore, resulting in poor economic efficiency and insignificant waste reduction. Red mud magnetization reduction roasting beneficiation technology is considered one of the effective technologies for iron extraction from red mud, especially high-speed iron ore. However, according to existing publicly available technologies and applications, both gas-based and coal-based reduction magnetization roasting have their own technical problems. The gas-based reduction magnetization roasting process is limited in its widespread application due to the need for strict control of the reducing gas usage and process parameters. The coal-based reduction magnetization roasting process often requires mixing and pressing the raw coal and red mud into balls for high-temperature magnetization roasting for several hours, hindering its application. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the current technology for iron ore beneficiation from Guinean red mud by providing a method and system for preparing iron concentrate from high-iron red mud. This invention combines a multi-stage magnetic separation process with a coal-based magnetic roasting process to produce high-grade iron concentrate while simultaneously generating highly reactive building materials as a byproduct, thus achieving full and comprehensive utilization of Guinean high-iron red mud resources and effective reduction of existing stock.

[0005] This invention discloses a method for preparing iron concentrate from high-iron red mud, comprising the following steps: Red mud ore slurry is treated by a red mud slurry pretreatment system to separate impurities, yielding a magnetic mineral slurry; the magnetic mineral slurry is then treated by a multi-stage magnetic separation combined process system to obtain magnetically separated iron concentrate and magnetically separated tailings; the magnetically separated iron concentrate is further processed by a magnetically separated iron concentrate processing system to obtain a dried magnetically separated iron concentrate filter cake; the magnetically separated iron concentrate filter cake is processed in a coal-based magnetic roasting system, and after crushing, preheating, and magnetic reduction roasting with a coal-based reducing agent, roasted iron concentrate is obtained; the roasted iron concentrate is further processed in a roasted iron concentrate processing system, and after water quenching, ball milling, and weak magnetic separation, iron concentrate products and tailings roasted ore are obtained. The iron concentrate products can be directly used as raw materials for steel production, and the tailings roasted ore is a highly active building material.

[0006] Impurities are separated in the red mud slurry pretreatment system, namely, after slurry conditioning, screening to remove particles such as sodium carbonate, and weak magnetic separation to separate non-magnetic minerals, magnetic mineral slurry is obtained; the red mud slurry contains 38% to 42% TFe, preferably 38% to 40%; mineral powder with a particle size ≤0.025mm accounts for 72%, and the slurry concentration after conditioning is 33%.

[0007] The multi-stage magnetic separation combined process system includes a first-stage high-intensity magnetic separation roughing, a second-stage high-intensity magnetic separation scavenging, cyclone separation, and thickener separation. The magnetic mineral slurry undergoes first-stage high-intensity magnetic separation roughing to obtain rough iron concentrate and iron middlings (i.e., roughing tailings). The iron middlings undergo first-stage high-intensity magnetic separation scavenging to obtain first-stage scavenged iron concentrate and first-stage scavenged tailings. The first-stage scavenged tailings undergo second-stage high-intensity magnetic separation to obtain second-stage scavenged iron concentrate and second-stage scavenged tailings. The rough iron concentrate, first-stage scavenged iron concentrate, and second-stage scavenged iron concentrate are mixed to form magnetically separated iron concentrate. The second-stage scavenged tailings are the magnetically separated tailings. After larger iron mineral particles are separated by cyclone separation, the magnetically separated tailings undergo thickener flocculation to separate the ore and slurry. The ore can be used in building materials, and the slurry is recycled in the alumina production process.

[0008] The magnetic field strength of the first-stage high-intensity magnetic separation roughing is 1.0T, the pulp concentration is 25%, and the pulp flow rate is 1.25m / s; the magnetic field strength of the first-stage high-intensity magnetic separation scavenging is 1.3T, the pulp concentration is 14.8%, and the pulp flow rate is 1.25m / s; the magnetic field strength of the second-stage high-intensity magnetic separation scavenging is 2.0T, the pulp concentration is 8%, and the pulp flow rate is 0.86m / s; the pulp flow rate of the cyclone separation is 11m / s.

[0009] The magnetically separated iron concentrate is subjected to pressure filtration and drying in the magnetically separated iron concentrate processing system to obtain a dry magnetically separated iron concentrate filter cake; the moisture content of the filter cake after pressure filtration is 22% to 24%, and the moisture content of the filter cake after drying is ≤12%.

[0010] The filter cake from the magnetically separated iron concentrate is fed into a drying and pulverizing device and pulverized into ore powder in a coal-based magnetic roasting system via a raw material feeding device. After gas-solid separation in a combined gas-solid separator, the ore powder enters a multi-stage preheater for preheating. The preheated ore powder and coal-based reducing agent are homogenized in a mixing and homogenizing device. After homogenization, the ore powder and coal-based reducing agent are fed into a magnetic reduction roasting furnace for roasting to obtain roasted iron concentrate. The hot flue gas generated by the combustion of gas in the hot blast stove first provides heat for the magnetic reduction roasting, and then together with the roasting flue gas generated by the magnetic reduction roasting, it provides heat for multi-stage preheating, drying, etc.

[0011] The temperature for magnetization and reduction roasting of magnetically separated iron concentrate with coal-based reducing agent is 600℃~800℃, and the roasting time is 20min~50min. The amount of coal-based reducing agent accounts for 5%~10% of the mass of magnetically separated iron concentrate, and the particle size of the coal-based reducing agent is 0.1mm~0.075mm. Fe2O3 is magnetized and reduced to Fe3O4, and the magnetization reduction rate is as high as 98% or more.

[0012] After processing high-iron red mud with TFe of 38% to 42% using the method of this invention, iron concentrate with an iron grade of 55% to 58% can be obtained, achieving an iron concentrate yield of 48% to 67% and an iron recovery rate of 55% to 60%; the tailings roasted ore with an iron grade of FTe < 17% can be used as high-quality building material, with a tailings roasted ore yield of 8% to 10%; and a high emission reduction rate of 60% to 65% can be achieved for red mud.

[0013] The present invention provides a process for preparing iron concentrate from high-iron red mud, comprising the following:

[0014] (1) Pump the Guinean high-speed railway red mud slurry (raw ore slurry) into the slurry mixing tank and adjust the concentration according to the process requirements;

[0015] (2) The prepared red mud slurry is fed into a cylindrical screen to remove impurities from the slurry;

[0016] (3) The impurity-removed slurry is fed into a permanent magnet separation device to remove strongly magnetic minerals from the slurry;

[0017] (4) The weakly magnetic slurry is pumped into a multi-stage magnetic separation combined process system for primary strong magnetic roughing and secondary strong magnetic scavenging. The magnetic induction intensity and magnetic separation equipment corresponding to the tertiary magnetic separation belong to the strong magnetic separation process. The magnetically separated iron concentrate is sent to its pretreatment process, while the tailings slurry is sent to a thickener for solid-liquid separation, and the separated slurry is returned to the alumina production workshop;

[0018] (5) The magnetically separated iron concentrate is filtered to remove most of the free water, resulting in a magnetically separated iron concentrate filter cake;

[0019] (6) Dry the iron concentrate filter cake and continue to remove the corresponding free water to achieve the required material moisture content for the magnetization roasting process;

[0020] (7) The dried magnetically separated iron concentrate is fed into the feed hopper of the coal-based magnetic roasting system, and then fed into the drying and pulverizing device of the system via a screw feeder. The dried powdered ore is then preheated in three stages, homogenized and mixed with the coal reducing agent, and then fed into the magnetic reduction roasting furnace for magnetic reduction process treatment, so that the magnetically separated iron concentrate is reduced to magnetic roasted iron concentrate;

[0021] (8) The roasted iron concentrate powder is sent to a water quenching tank for water quenching and cooling process to stabilize the mineral properties of the roasted iron concentrate.

[0022] (9) The cooled roasted iron concentrate is conveyed by a screw conveyor to a ball mill for weak magnetic separation to select magnetic iron concentrate (i.e., iron concentrate products with high iron grade); the tailings roasted minerals (i.e., high-activity building materials) are separated.

[0023] (10) Iron concentrate is obtained by filtering iron concentrate through a disc filter to remove excess water.

[0024] Furthermore, in process step (1), the Guinean high-speed iron red mud slurry (raw material TFe 38-42%; particle size -0.025mm accounts for 72%) is adjusted to a slurry concentration of 33% by using a slurry mixing tank.

[0025] Furthermore, in process step (2), large particles of minerals and impurities in the slurry are screened through a cylindrical screen to eliminate adverse effects on multi-stage magnetic separation.

[0026] Furthermore, in process step (3), non-magnetic substances in the ore are separated by weak magnetic separation in order to improve the magnetic material composition and separation efficiency of the slurry processed by multi-stage magnetic separation.

[0027] Furthermore, in process step (4), iron concentrate is separated by a multi-stage magnetic separation combination process. The magnetic separation combination consists of a first-stage strong magnetic roughing and a two-stage periodic strong magnetic scavenging. The first-stage roughing separates the slurry (raw material) into rough iron concentrate and iron middlings (tailings from the first roughing). The two-stage scavenging serves as the second and third stages of magnetic separation, which separates the iron middlings into scavenged iron concentrate and tailings.

[0028] Furthermore, in process step (5), the free water contained in the magnetically separated iron concentrate is filtered into a filter cake with a moisture content of 24% to 22% by plate and frame filter press;

[0029] Furthermore, in process step (6), the moisture content of the iron concentrate filter cake is reduced to ≤12% by thermal drying;

[0030] Further, in process step (7), the (magnetically separated) iron concentrate powder is magnetized and reduced to magnetic iron concentrate (magnetization reduction rate is as high as 98%) through a coal-based magnetization roasting system. The raw material feeding device of the roasting system adopts a screw feeding method; the drying and pulverizing device adopts a vortex flash airflow drying, pulverizing and grading method; the combined gas-solid separator adopts a combination of cyclone and bag separator; the multi-stage preheater adopts a three-stage cyclone phase series preheating method; the mixing and homogenizing device adopts a mechanical mixing method; the hot air furnace is a gas-fired horizontal hot air furnace; the magnetization reduction roasting furnace adopts an externally heated rotary furnace. During the magnetization reduction roasting process, the hot flue gas generated by the combustion of gas in the hot air furnace provides the heat required for the reduction reaction of the materials (magnetically separated iron concentrate, coal-based reducing agent) in the roasting furnace; together with the (hot flue gas) gas discharged from the roasting furnace, it provides heat for the three-stage preheating and drying of the materials.

[0031] Furthermore, in process step (8), water quenching cooling process is used to prevent oxidation of roasted iron concentrate and stabilize product properties;

[0032] Furthermore, in process step (9), magnetite (product) and non-magnetite (active tailings) in roasted iron concentrate are separated by ball milling and weak magnetic separation.

[0033] Furthermore, in process step (10), excess moisture in the product is removed by disc filtration to meet the product moisture content standard.

[0034] A system for preparing iron concentrate from high-iron red mud includes a red mud slurry (red mud raw ore slurry) pretreatment system, a multi-stage magnetic separation combined process system, a magnetic separation iron concentrate processing system, a coal-based magnetic roasting system, and a roasted iron concentrate processing system.

[0035] The red mud slurry pretreatment system includes a slurry mixing tank, a cylindrical screen, and a weak magnetic separation device; the multi-stage magnetic separation combined process system includes a first-stage strong magnetic separation roughing device, a two-stage strong magnetic separation scavenging device, a cyclone separator, and a thickener solid-liquid separation device; the magnetic separation iron concentrate processing system includes a filter press and a drying device; the coal-based magnetic roasting system includes a raw material feeding device, a drying and pulverizing device, a combined gas-solid separator, a multi-stage preheater, a mixing and homogenizing device, a magnetic reduction roasting furnace, and a hot blast stove; the roasted iron concentrate processing system includes a water quenching device, a ball mill, a weak magnetic separation device, and a disc filter.

[0036] The red mud slurry (red mud raw ore slurry) pretreatment system aims to first adjust the slurry concentration of the red mud slurry (raw slurry) according to the requirements of the magnetic separation process, then screen it to remove impurities, and finally use a permanent magnet separator to select strongly magnetic minerals.

[0037] The multi-stage magnetic separation combined process system aims to obtain high-grade magnetic iron concentrate with high magnetic separation efficiency through the rational optimization combination of physical multi-stage magnetic separation.

[0038] The process objective of the magnetic iron concentrate processing system is to remove most of the free water from the magnetic iron concentrate by pressure filtration and then dry it to remove the remaining water, so as to meet the minimum moisture content requirement when the magnetic iron concentrate enters the magnetizing roasting system.

[0039] The coal-based magnetized roasting system aims to reduce magnetically separated iron concentrate to roasted iron concentrate (magnetic iron concentrate) by magnetizing and roasting it with a coal-based reducing agent under indirect heat exchange. The reduction rate of the iron concentrate and the thermal efficiency of the roasting system are the main process requirements.

[0040] The roasted iron concentrate processing system aims to stabilize the physicochemical properties of roasted iron concentrate by water quenching and cooling, then to obtain high-iron grade iron concentrate products by ball milling and weak magnetic separation, and finally to remove free moisture by disc filtration to meet the product moisture requirements.

[0041] The thickener solid-liquid separation device aims to separate the iron tailings slurry (magnetic tailings) separated by a multi-stage magnetic separation combined process system into solid and liquid components, and the separated slurry can be reused in the alumina production process.

[0042] The effective advantages of the process method of this invention are as follows:

[0043] (1) This invention discloses a process for preparing iron concentrate from high-iron red mud, which is a mineral processing method that uses a combination of multi-stage magnetic separation and coal-based magnetic roasting to extract iron-containing minerals from red mud and prepare iron concentrate. This process efficiently realizes the comprehensive utilization of Guinean high-iron red mud resources, producing iron concentrate products (TFe 58%) for steel production and high-quality by-product active materials, which can be widely used in industries such as cement and construction. The iron concentrate yield can reach 75%, and the stock of Guinean high-iron red mud can be continuously reduced, with a comprehensive emission reduction rate of over 61%. At the same time, the magnetic separation tailings slurry generated after multi-stage magnetic separation in the process is recycled for alumina production, realizing the reuse of this highly alkaline slurry; the industrial exhaust gas generated by magnetic roasting is environmentally friendly, and the entire process can achieve a near-zero emission target.

[0044] (2) In the process method of the present invention, before the high-iron red mud slurry enters the multi-stage magnetic separation combined process, a cylindrical screen is added to screen large particles of sodium carbonate in the red mud; a weak magnetic separation is added to select magnetic substances in the red mud. The above process settings not only significantly increase the proportion of magnetic substances in the red mud slurry entering the multi-stage magnetic separation equipment, thereby improving the separation effect of the multi-stage magnetic separation, but also prevent large particles of sodium carbonate from damaging the magnetic separation equipment, and greatly improve the operating conditions of the multi-stage magnetic separation equipment.

[0045] (3) In the process method of this invention, the multi-stage magnetic separation combination process is a three-stage magnetic separation mineral processing process. This combination is a mineral processing magnetic separation method of one-stage roughing and two-stage scavenging: the first-stage roughing separates the red mud slurry into rough iron concentrate and iron middlings; the two-stage scavenging separates the iron middlings into scavenging iron concentrate and tailings. The three-stage magnetic separation (one-stage roughing and two-stage scavenging) are all high-gradient strong magnetic separation with different magnetic field intensities, and the two-stage scavenging is a periodic high-gradient strong magnetic separation. The three-stage magnetic separation combination increases the TFe46.42% mineral yield of red mud iron concentrate to 67.97%, which is the first of its kind in the industry. The three-stage magnetic separation combination magnetic separation process is a magnetic separation process for efficient recovery of iron minerals in red mud that has been continuously improved and optimized through production practice, and it is the first of its kind in the industry.

[0046] (4) In the process method of this invention, the magnetic separation iron concentrate (Fe2O3) is roasted and reduced to roasted iron concentrate (Fe3O4), which is a coal-based magnetized roasting process. The process method is to first dry and preheat the magnetic separation iron concentrate, mix and homogenize it with the batch coal-based reducing agent, and then send it into the magnetized reduction roasting furnace for magnetized reduction reaction, reducing the weakly magnetic iron oxide in the magnetic separation iron concentrate to magnetic iron oxide. Since the substances participating in the reaction are all fine powders with large specific surface areas, and the magnetization reaction of the materials is sufficient in the adiabatic state in the roasting furnace, the reduction rate reaches more than 98%. The roasting temperature of the material in the roasting furnace is 700℃~800℃, and the roasting time is 20min~50min. Compared with the red mud coal-based briquetting magnetized reduction roasting process, the reaction temperature and time are significantly reduced, fundamentally avoiding many technical problems such as the roasted material adhering to the equipment due to high temperature and long time; compared with the gas-based red mud magnetized reduction roasting process, this magnetized roasting process does not require gaseous reducing agent, making the system operation more reliable and stable. The high-temperature exhaust gas discharged from the roasting furnace in this roasting process system is used sequentially for the preheating and drying of materials. The system achieves full utilization of thermal energy in a stepped manner and has the advantage of high thermal efficiency.

[0047] (5) In the coal-based magnetic roasting process of the present invention, the drying and preheating process of the magnetically separated iron concentrate is a direct heat exchange method involving suspension and current carrying; the preheated magnetically separated iron concentrate and the coal reducing agent are heated by the magnetic reduction reaction in the roasting furnace through an indirect heat exchange method. After the hot blast stove generates hot flue gas to provide heat to the roasting furnace, it is used together with the roasting flue gas generated by roasting to heat the three-stage (series) preheaters and the drying and pulverizing device, thereby realizing the stepwise utilization of thermal energy. Attached Figure Description

[0048] Figure 1 This is a process flow diagram for preparing iron concentrate from high-iron red mud according to the present invention;

[0049] Figure 2 A flowchart of a multi-stage magnetic separation process;

[0050] Figure 3The flowchart shows the coal-based magnetized roasting process; where 1-raw material feeding device, 2-drying and pulverizing device, 3-combined gas-solid separator, 4-multi-stage preheater, 5-mixing and homogenizing device, 6-magnetized reduction roasting furnace, and 7-hot blast furnace. Detailed Implementation

[0051] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.

[0052] Example 1

[0053] This specific implementation method is an engineering example.

[0054] The implementation method, process flow (flow rate) is as follows: Figure 1 As shown. The process for preparing iron concentrate from high-iron red mud in this embodiment includes, in the following order: slurry (red mud slurry) pretreatment system, multi-stage magnetic separation combined process system, magnetic separation iron concentrate (pre)treatment system, coal-based magnetic roasting system, and roasted iron concentrate treatment system.

[0055] The red mud slurry pretreatment system includes a slurry mixing tank, a cylindrical screen, and a weak magnetic separation device; the multi-stage magnetic separation combined process system includes a single-stage strong magnetic roughing device, a two-stage strong magnetic scavenging device, a hydrocyclone separator, and a thickener solid-liquid separation device; the magnetic iron concentrate processing system includes a filter press and a drying device; the coal-based magnetic roasting system process flow is as follows: Figure 3 As shown, the system includes a raw material feeding device 1, a drying and pulverizing device 2, a combined gas-solid separator 3, a multi-stage preheater 4, a mixing and homogenizing device 5, a magnetic reduction roasting furnace 6, and a hot blast furnace 7 (gas-fired furnace); the roasting iron concentrate processing system includes a water quenching device, a ball milling device, a weak magnetic separation device, and a disc filter device.

[0056] The hot flue gas generated by the combustion of gas in the hot blast stove 7 provides heat for the magnetization reduction roasting. The hot flue gas first provides heat to the roasting material in the magnetization reduction roasting furnace 6 through indirect heat exchange. Then, together with the roasting flue gas generated by the magnetization reduction roasting, it preheats the material in the multi-stage preheater 4 through direct heat exchange. After the hot flue gas and roasting flue gas preheat the material and separate the gas and solid in the multi-stage preheater 4, they continue to dry the material in the drying and pulverizing device 2 through direct heat exchange. Finally, the material is discharged after gas-solid separation by the combined gas-solid separator 3.

[0057] The raw material for the production was Guinean high-iron red mud slurry produced and discharged by an alumina company in Guangxi. The iron phases contained in the red mud slurry (raw material) are shown in Table 1, and the particle size distribution and the iron grade contained in the corresponding particle size are shown in Table 2.

[0058] Table 1. Iron phases contained in red mud slurry (raw material):

[0059] Table 2. Particle size distribution of red mud slurry (raw material) and corresponding iron content of each particle size:

[0060] The red mud slurry (raw material) contains 41.16% TFe and 72% of the particles are -0.025mm.

[0061] The process for preparing iron concentrate from high-iron red mud includes the following:

[0062] (1) The Guinean high-speed railway red mud slurry (raw slurry) is sent to the red mud slurry pretreatment system and pumped to the slurry mixing tank, and the slurry concentration is adjusted to 33% according to the process requirements;

[0063] (2) Pump the prepared red mud slurry to a cylindrical screen to remove impurities, including large particles of sodium carbonate, from the slurry, so as to eliminate the adverse effects on multi-stage magnetic separation.

[0064] (3) The slurry after impurity removal is pumped to a permanent magnet weak magnetic separation device for magnetic separation to separate non-magnetic minerals in the slurry and obtain slurry containing magnetic minerals, so as to improve the magnetic material composition and separation efficiency of the slurry after multi-stage magnetic separation.

[0065] (4) The magnetic mineral slurry is pumped to a multi-stage magnetic separation combined process system for three-stage magnetic separation, including a first-stage strong magnetic roughing and a second-stage strong magnetic scavenging. The process flow is as follows: Figure 2 As shown;

[0066] The magnetic mineral slurry was fed to a primary high-intensity magnetic separator for roughing. A vertical ring high-gradient magnetic separator was used, with a magnetic field strength of 1.0T, a slurry concentration of 25%, and a slurry flow rate of 1.25 m / s. The magnetic separation results were as follows: Roughing iron concentrate TFe 49%, roughing iron concentrate yield 32.12%, iron recovery rate 38.24%; iron middlings TFe 37.45%, iron middlings yield 67.88%, iron recovery rate 61.76%.

[0067] Iron ore was fed to a primary high-intensity magnetic separation unit for primary high-intensity magnetic separation (secondary magnetic separation). A periodic high-gradient high-intensity magnetic separation was used, with a magnetic field strength of 1.3T, a slurry concentration of 14.80%, and a slurry flow rate of 1.25 m / s. Magnetic separation results: Primary iron concentrate TFe 45%, primary iron concentrate yield 25.17%, iron recovery rate 27.52%; Primary tailings TFe 33%, Primary tailings yield 42.71%, iron recovery rate 34.24%.

[0068] The tailings from the first-stage magnetic separation were sent to a second-stage high-intensity magnetic separation unit for secondary high-intensity magnetic separation (tertiary magnetic separation). A periodic high-gradient high-intensity magnetic separation was used, with a magnetic field strength of 2.0T, a magnetic slurry concentration of 8%, and a slurry flow rate of 0.86 m / s. The magnetic separation results were as follows: the second-stage iron concentrate had a TFe content of 42%, a yield of 10.68%, and an iron recovery rate of 10.89%; the second-stage tailings had a TFe content of 30%, a tailings yield of 32.03%, and these tailings are the same as the magnetic separation tailings.

[0069] The magnetic separation tailings are subjected to hydrocyclone iron collection, with a slurry flow rate of 11 m / s, to separate out the large iron ore particles.

[0070] The results were as follows: the final magnetically separated iron concentrate had a TFe content of 46.42%, a yield of 67.97%, and an iron recovery rate of 76.65%; the final magnetically separated tailings (secondary scavenging tailings) had a TFe content of 30%, a tailings yield of 32.03%, and an iron recovery rate of 23.35%.

[0071] The process method of this invention sets up a hydrocyclone in the multi-stage magnetic separation combined process to separate larger iron mineral particles in the tailings slurry after magnetic separation, so as to avoid the phenomenon of ore run-off after magnetic separation and improve the magnetic separation rate.

[0072] The magnetic separation tailings (including tailings slurry) are pumped to a thickener for flocculation, separating the ore and slurry. The separated slurry is then pumped back to alumina production for reuse.

[0073] (5) The magnetically separated iron concentrate is sent to the magnetically separated iron concentrate processing system, where most of the water is removed by a plate and frame filter press, and the iron concentrate filter cake contains 22% water.

[0074] (6) The iron concentrate filter cake is dried by a rotary dryer to further remove moisture. After drying, the filter cake has a final moisture content of 12%, which meets the material moisture requirements of the magnetization roasting process.

[0075] (7) The dried iron concentrate is conveyed to the coal-based magnetic roasting system for magnetic reduction roasting. The process is as follows:

[0076] a. The material is fed into the drying and pulverizing device (swirl flash dryer) by a raw material feeder (screw speed regulating feeder) for drying, pulverizing and classification. The drying temperature is 450℃, and the final moisture content of the dried mineral powder is <1%.

[0077] b. After drying, the mineral powder is separated by a combination of cyclone and bag gas-solid separator, and then preheated by a three-stage preheater (three-stage cyclone preheaters connected in series): the first-stage cyclone preheater has a preheating air temperature of 470℃, the second-stage cyclone preheater has a preheating air temperature of 580℃, and the third-stage cyclone preheater has a preheating air temperature of 650℃.

[0078] c. The preheated mineral powder and coal reducing agent are mechanically mixed and homogenized in a mixing and homogenizing device. The particle size of the coal reducing agent is 200 mesh, and the proportion is 8% of the mineral powder mass.

[0079] d. After homogenization of the coal-based reducing agent and ore powder, the mixture is fed into an externally heated rotary kiln (magnetic reduction roasting furnace) for magnetic reduction roasting at a temperature of 750℃ for 40 minutes. This process achieves the magnetic reduction reaction between the reducing agent and the ore powder, reducing the magnetically separated iron concentrate to magnetically roasted iron concentrate. The loss on ignition of the roasted material is 10%, and the degree of magnetic reduction is 98%.

[0080] In the magnetization reduction roasting process, the hot flue gas generated by the combustion of gas in the horizontal hot air furnace provides the heat required for the reaction, and the hot flue gas discharged from the magnetization reduction roasting furnace provides heat for the three-stage preheating and drying of the material.

[0081] (8) The roasted iron concentrate is sent to the roasted iron concentrate processing system and water quenched in the water quenching tank to prevent oxidation of the roasted iron concentrate and stabilize the mineral properties of the roasted iron concentrate.

[0082] (9) The water-quenched material is conveyed by a screw conveyor to a ball mill weak magnetic separation device to separate iron concentrate and tailings roasted ore. The weak magnetic separation field strength is 0.35T. The iron concentrate has a TFe content of 58%, an iron concentrate yield of 48.93%, and an iron recovery rate of 58.75%. The tailings roasted ore has a TFe content of 16.6%, a tailings roasted ore yield of 8.84%. The tailings roasted ore is a highly active building material and is sent to the brick production line.

[0083] (10) Remove excess water from the iron concentrate product by passing it through a disc filter. The final iron concentrate product contains 15% water and is used as a material for iron and steel smelting.

Claims

1. A process for preparing iron concentrate from high-iron red mud, characterized in that, Includes the following: The raw red mud ore slurry is processed by a red mud slurry pretreatment system to separate impurities and obtain a slurry containing magnetic minerals; The magnetic mineral slurry is processed by a multi-stage magnetic separation combined process system to obtain magnetically separated iron concentrate and magnetically separated tailings; the magnetically separated iron concentrate is processed by a magnetically separated iron concentrate processing system to obtain a dried magnetically separated iron concentrate filter cake; the magnetically separated iron concentrate filter cake is processed in a coal-based magnetic roasting system, crushed, preheated, and then magnetically reduced and roasted with a coal-based reducing agent to obtain roasted iron concentrate; The roasted iron concentrate is processed in a roasted iron concentrate processing system. After water quenching, ball milling, and weak magnetic separation, iron concentrate products and tailings roasted ore are obtained.

2. The process for preparing iron concentrate from high-iron red mud according to claim 1, characterized in that, The red mud slurry is prepared by adjusting the slurry, screening to remove sodium carbonate particles, and separating non-magnetic minerals by weak magnetic separation in the red mud slurry pretreatment system to obtain the magnetic mineral slurry; the red mud slurry contains 38% to 42% TFe, 72% mineral powder with a particle size ≤0.025mm, and the slurry concentration after adjustment is 33%.

3. The process for preparing iron concentrate from high-iron red mud according to claim 1, characterized in that, The multi-stage magnetic separation combined process system includes a first-stage high-intensity magnetic separation roughing, a two-stage high-intensity magnetic separation scavenging, cyclone separation, and thickener separation processing steps. The magnetic mineral slurry is subjected to the first-stage high-intensity magnetic separation roughing to obtain rough iron concentrate and iron middlings. The iron middlings are subjected to the first-stage high-intensity magnetic separation scavenging to obtain a first-stage scavenged iron concentrate and a first-stage scavenged tailings. The first-stage scavenged tailings are subjected to the second-stage high-intensity magnetic separation scavenging to obtain a second-stage scavenged iron concentrate and a second-stage scavenged tailings. The rough iron concentrate, the first-stage scavenged iron concentrate, and the second-stage scavenged iron concentrate are mixed to form the magnetically separated iron concentrate, and the second-stage scavenged tailings are the magnetically separated tailings.

4. The process for preparing iron concentrate from high-iron red mud according to claim 3, characterized in that, The magnetic separation tailings are then separated by cyclone separation to remove granular iron minerals, and then by thickening tank separation to obtain ore and slurry. The slurry is recycled in the alumina production process.

5. The process for preparing iron concentrate from high-iron red mud according to claim 3, characterized in that, The primary high-intensity magnetic separation roughing process has a magnetic field strength of 1.0T, a pulp concentration of 25%, and a pulp flow rate of 1.25m / s; the primary high-intensity magnetic separation scavenging process has a magnetic field strength of 1.3T, a pulp concentration of 14.8%, and a pulp flow rate of 1.25m / s; the secondary high-intensity magnetic separation scavenging process has a magnetic field strength of 2.0T, a pulp concentration of 8%, and a pulp flow rate of 0.86m / s; and the cyclone separation process has a pulp flow rate of 11m / s.

6. The process for preparing iron concentrate from high-iron red mud according to claim 1, characterized in that, The magnetically separated iron concentrate is subjected to pressure filtration and drying in the magnetically separated iron concentrate processing system to obtain the dried magnetically separated iron concentrate filter cake; the moisture content of the filter cake after pressure filtration is 22% to 24%, and the moisture content of the filter cake after drying is ≤12%.

7. The process for preparing iron concentrate from high-iron red mud according to claim 1, characterized in that, The magnetically separated iron concentrate filter cake is fed into a drying and pulverizing device and pulverized into mineral powder in the coal-based magnetized roasting system via a raw material feeding device. The mineral powder is then separated into gas and solid by a combined gas-solid separator and preheated in a multi-stage preheater. The preheated mineral powder is then homogenized with the coal-based reducing agent in a mixing and homogenizing device. After homogenization, it is sent to a magnetized reduction roasting furnace for roasting to obtain the roasted iron concentrate.

8. The process for preparing iron concentrate from high-iron red mud according to claim 1, characterized in that, The magnetic separation iron concentrate filter cake and the coal-based reducing agent are magnetized and reduced at a temperature of 600℃ to 800℃ for a time of 20 min to 50 min; the amount of coal-based reducing agent is 5% to 10% of the mass of the magnetic separation iron concentrate filter cake, and the particle size of the coal-based reducing agent is 0.1 mm to 0.075 mm. The hot flue gas generated by the combustion of gas in the hot blast furnace first provides heat for the magnetization reduction roasting, and then together with the roasting flue gas generated by the magnetization reduction roasting, it provides heat for the preheating and drying processes.

9. The system used in the process for preparing iron concentrate from high-iron red mud according to any one of claims 1 to 8, characterized in that, The process method employs a system comprising a red mud slurry pretreatment system, a multi-stage magnetic separation combined process system, a magnetic separation iron concentrate processing system, a coal-based magnetic roasting system, and a roasted iron concentrate processing system.

10. The system used in the process for preparing iron concentrate from high-iron red mud according to claim 9, characterized in that, The red mud slurry pretreatment system includes a slurry mixing tank, a cylindrical screen, and a weak magnetic separation device; the multi-stage magnetic separation combined process system includes a first-stage strong magnetic separation roughing device, a two-stage strong magnetic separation scavenging device, a cyclone separator, and a thickener separator; the magnetic separation iron concentrate processing system includes a filter press and a drying device; the coal-based magnetic roasting system includes a raw material feeding device, a drying and pulverizing device, a combined gas-solid separator, a multi-stage preheater, a mixing and homogenizing device, a magnetic reduction roasting furnace, and a hot blast stove; the roasted iron concentrate processing system includes a water quenching device, a ball mill, a weak magnetic separation device, and a disc filter.

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