Method for separating iron and aluminum by suspending and magnetizing roasting of high iron bauxite

Abstract

The present application relates to the technical field of alumina production, in particular to a method for suspending magnetization roasting and separating iron and aluminum from high-iron bauxite, which comprises the following steps: mechanically activating high-iron gibbsite-type bauxite and coal powder after crushing and grinding, suspending magnetization roasting at 500-700 DEG C for 60-300 s through multi-stage suspension preheating, using the reducing gas generated by in-situ flash gasification of the coal powder to convert weakly magnetic iron ore into strongly magnetic magnetite, cooling in an oxygen-free environment, and performing pipeline high-temperature leaching at 270-280 DEG C to drive sodium-silicon slag to be restructured into long columnar and high-crystallinity prismatic crystals, and release the encapsulated fine-grained magnetite, separating the liquid and solid after leaching, and performing magnetic separation on the iron-rich red mud to obtain high-grade iron concentrate and tailings. The present application realizes selective magnetization of iron ore, significantly improves the liberation degree of iron ore monomers by combining with the morphology reconstruction of sodium-silicon slag, and has the characteristics of high efficiency of iron and aluminum separation, significant reduction of red mud, short process and low cost.

Description

Technical Field

[0001] This invention relates to the field of alumina production technology, specifically to a method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite. Background Technology

[0002] In high-speed gibbsite bauxite, the intergrowth relationships of aluminum, iron, and silicon minerals are complex, with fine crystal grains. Furthermore, isomorphous substitution of Al³⁺ and Fe³⁺ frequently occurs within the goethite, leading to difficulties in the dissociation of individual minerals and low efficiency in separating valuable components. For this type of resource, the current alumina industry primarily employs the Bayer process, which effectively dissolves aluminum components, while valuable components such as iron accumulate in red mud, forming highly alkaline waste with high iron content. Due to the morphology of iron minerals and the complex phase composition of red mud, it is difficult to achieve stable and high-grade recovery of iron resources from red mud under low-energy consumption and short-process conditions, resulting in a dilemma of both stockpiling pressure and resource waste. Therefore, before Bayer leaching, the efficient phase reconstruction and magnetized roasting technology to directionally transform weakly magnetic iron minerals in the ore into strongly magnetic magnetite to prepare high-quality magnetized roasted ore has become an important research direction in the alumina and mineral processing fields.

[0003] Several technical approaches have been developed for the separation and phase control of iron and aluminum components in high-iron bauxite. The first type of method is direct physical beneficiation and combined beneficiation, such as the use of a fully dry grading separation process (CN122076706A), which removes iron minerals by combining air-heavy medium fluidized bed, X-ray photoelectric separation, and high-gradient magnetic separation after crushing and grading; or the use of chemical flotation, which selectively removes iron at room temperature and low reagent consumption by synthesizing a dual-active end collector containing phosphonic acid and tertiary amine groups (CN122124926A); and the use of a combined flocculation-intense magnetic separation pre-selection process (CN117696231A), which pre-groups minerals based on their magnetic differences. The non-magnetic group is flotated to obtain aluminum concentrate, while the magnetic group is mixed with reducing agents and sodium salts to form agglomerates and undergoes high-temperature directional conversion at 900–1300 °C. However, such methods are limited by the micro-particle embedding and isomorphic substitution effects, making it difficult to achieve complete single-unit dissociation of iron and aluminum in the physical sorting or pre-selection stage, and the subsequent high-temperature control process is quite complicated.

[0004] The second type of method involves wet chemical leaching and selective pretreatment processes. For example, high-iron bauxite can be directly leached with acid solutions (CN110093514A), achieving iron-aluminum separation through stepwise oxidation, reduction, and precipitation techniques. Alternatively, a mixture of oxalic acid and oxalate can be used as an iron-removing agent for atmospheric pressure wet pre-leaching (CN120311021A). The acidity and complexing properties of oxalic acid remove aluminum and iron from the aluminum-iron intercalation structure, followed by pH adjustment for co-precipitation and the use of caustic soda to remove aluminum and obtain ferric hydroxide precipitate. While these wet processes can avoid high-temperature processes, they generally face technical bottlenecks such as high consumption of strong acids or complexing reagents, complex leachate composition making purification difficult, high costs for industrial wastewater / residue treatment, and difficulty in large-scale integration with mainstream alumina production lines.

[0005] The third category of methods involves pyrometallurgical reduction and smelting processes, such as direct reduction-electric furnace smelting (CN118979147A), which separates ferrosilicon alloys from alumina through high-temperature reduction and electric arc furnace melting; or using biomass reducing agents for oxygen-free low-temperature roasting (CN119120798A), which promotes the conversion of hematite into magnetite; another example is the traditional solid-phase reduction magnetization roasting process (CN101767057A), which involves adding coke and conducting high-temperature solid-phase roasting at 900~1150 ℃ for 1.5~6 h, converting weakly magnetic iron minerals into strongly magnetic magnetite for further selection; and even using a high-temperature molten hydrogen reduction iron extraction process (CN120290872A), which involves briquetting ore powder, melting it in an electric arc furnace at 1500~1600 ℃, and introducing excess hydrogen to reduce it into molten iron, and then separating and extracting the components from the water-quenched slag. Although these pyrometallurgical and smelting processes can break the original solidified phases, they usually involve extremely high reaction temperatures, high energy consumption, and long processes. Moreover, their main goal is to obtain metallic iron, alloys, or highly vitrified byproducts, rather than the preparation of magnetized roasted ore with the premise of maintaining the efficient chemical leaching activity of aluminum minerals.

[0006] In recent years, suspension roasting technology, due to its ultra-high gas-solid heat and mass transfer rate, has been explored for the magnetization roasting process of high-iron bauxite, aiming to achieve rapid and efficient conversion of hematite and goethite into magnetite. However, existing suspension magnetization roasting technologies still have significant limitations when processing high-iron gibbsite-type bauxite to prepare high-quality magnetized roasted ore. How to achieve precise phase transformation path control within the short reaction window of the suspension roasting furnace, ensuring efficient magnetization conversion of weakly magnetic iron minerals while synergistically suppressing iron phase over-reduction, avoiding iron-aluminum spinel side reactions, and maintaining the chemical activity of the aluminum component, thereby obtaining high-quality magnetized roasted ore, is a key technological bottleneck that urgently needs to be overcome in this field. To address this, we propose a method for separating iron and aluminum through suspension magnetization roasting of high-iron bauxite. Summary of the Invention

[0007] The purpose of this invention is to provide a method for separating iron and aluminum in high-iron bauxite by suspension magnetization roasting, in order to solve the problem that the existing suspension magnetization roasting technology mentioned in the background art still has significant limitations in processing high-iron trihydrate gibbsite type bauxite to prepare high-quality magnetized roasted ore.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite, comprising the following steps:

[0009] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0010] S2: Grind the mineral powder obtained in step S1 with coal powder to make the particle size P80≤0.074 mm, and prepare a mixture;

[0011] S3: The mixture obtained in step S2 is fed into the preheating system, and multi-stage suspension preheating and partial dehydration reaction are carried out using the high-temperature flue gas discharged from the calcining furnace to obtain the preheated mixture.

[0012] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal, and the in-situ release of reducing gas transforms the weak magnetic iron minerals in the ore powder into strong magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0013] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen to obtain magnetized roasted ore.

[0014] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching. While extracting alumina, the phase transformation and crystallization path of the sodium silicate slag, a product of gangue desilication, is controlled by the high-temperature leaching hydrothermal environment, so that it is reconstructed into a long columnar, highly crystalline prismatic crystal morphology, releasing the encapsulated fine-grained magnetite.

[0015] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0016] S8: The iron-rich red mud obtained in step S7 is subjected to magnetic separation to obtain iron concentrate and magnetic separation tailings.

[0017] Preferably, in step S1, the raw material is gibbsite-type bauxite with a mass fraction of Al2O3 ≥ 40% and Fe2O3 ≥ 25%.

[0018] Preferably, in step S2, the molar ratio of fixed carbon in the pulverized coal to Fe2O3 in the raw ore is (0.5~1.2):1.

[0019] Preferably, in step S3, the multi-stage suspension preheating uses 2 to 4 stages of cyclone preheaters connected in series, and the temperature of the mineral powder after preheating is controlled at 300 to 500 ℃, and some of the free water and crystal water in the raw ore are removed during the preheating stage.

[0020] Preferably, in step S4, the magnetization calcination temperature is 500~700 ℃ and the calcination time is 60~300 s.

[0021] In step S4, the main chemical reaction occurring during the magnetization roasting process is as follows:

[0022]

[0023] Preferably, in step S5, oxygen isolation cooling is performed using a fluidized bed cooler or a cyclone cooler, and the cooling medium is an inert gas such as argon or nitrogen; the magnetized roasted ore is discharged after being cooled to below 200 ℃ to prevent secondary oxidation of the magnetite.

[0024] Preferably, in step S5, the hot air generated by heat exchange in the cooling system is introduced into the suspension magnetization roasting furnace in step S4 as secondary combustion air or material fluidization air, so as to realize the closed-loop circulation of thermal energy of the entire roasting system.

[0025] Preferably, in step S6, high-temperature leaching is used, with a leaching temperature of 270~280 ℃. The high-temperature alkaline hydrothermal environment in this temperature range drives the sodium silicate slag to transform into a long columnar, highly crystalline prismatic crystal phase.

[0026] Preferably, in step S8, the magnetic separation method is wet weak magnetic separation, the magnetic field strength is 2000~4000 Oe, and the liquid-to-solid ratio is (10~20):1.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. This invention innovatively combines high-iron bauxite ore with solid reducing agent pulverized coal through co-milling and mechanical activation pretreatment, resulting in a highly matched particle size distribution and a suspended fluidized state. This significantly increases the microscopic defects and contact area of ​​the materials. During the suspended fluidized roasting process, leveraging the extremely high gas-solid heat transfer rate within the furnace, the solid pulverized coal undergoes an in-situ flash gasification reaction within a transient timeframe of several seconds to tens of seconds, directly releasing strongly reducing gases within the micro-regions of the ore particles. This invention utilizes inexpensive solid coal to replace high-cost gaseous reducing agents, significantly reducing industrial operating costs and effectively overcoming the slow reaction caused by insufficient solid-solid contact in traditional solid-phase reduction methods. It achieves highly efficient gas-solid in-situ magnetization reduction and high-precision phase control.

[0029] 2. This invention introduces a pipeline-based high-temperature leaching reaction downstream. The high-temperature alkaline hydrothermal environment in a specific range not only maximizes the leaching rate of alumina in the roasted ore but also provides a unique effect on the directional regulation of the red mud phase morphology. Under this high-temperature hydrothermal drive, the sodium silicate slag, a byproduct of the Bayer process, changes its morphology from the amorphous colloids or disordered needle-like aggregates generated during conventional leaching, spontaneously reconstructing into long columnar, highly crystalline prismatic crystal phases. This crystal morphology transformation successfully dissociates and releases the fine-grained magnetite particles embedded and adhered within the gangue, significantly increasing the degree of individual dissociation between iron minerals and gangue components, and reducing the microviscosity of the red mud slurry. This results in a higher iron grade and higher iron recovery rate in the subsequent magnetic separation process, producing a high-quality iron concentrate.

[0030] 3. This invention employs a thermal energy reconstruction and fully isolated closed-loop cooling system throughout the entire process. By using counter-current inert gas cooling and limiting the discharge temperature, the risk of secondary rapid oxidation of fine-particle strongly magnetic magnetite upon exposure to air at high temperatures during unloading is eliminated. Simultaneously, the high-temperature hot air generated by the cooling system is directly circulated into the suspension roasting furnace, achieving closed-loop energy transfer and sensible heat recovery. The entire process is short, tightly integrated, and seamlessly compatible with mainstream alumina industrial production routes. While significantly improving aluminum extraction and iron recovery rates, it significantly reduces the total amount of red mud waste discharged and accumulated, achieving large-scale, high-value comprehensive utilization of high-iron bauxite resources and reducing red mud volume from the source. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a process flow diagram of the separation of iron and aluminum by suspension magnetization roasting of high-iron bauxite according to the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The raw material used in this embodiment of the invention is gibbsite-type bauxite with an Al2O3 mass fraction ≥40% and an Fe2O3 mass fraction ≥25%, and no requirements are made for the other components.

[0035] In this embodiment of the invention, the raw material crushing process uses a jaw crusher, and the grinding process uses a high-energy ball mill.

[0036] In this embodiment of the invention, the roasting equipment is a suspension roasting furnace.

[0037] In this embodiment of the invention, the multi-stage suspension preheating uses 2 to 4 stages of cyclone preheaters connected in series.

[0038] In this embodiment of the invention, oxygen isolation cooling is achieved using a fluidized bed cooler or a cyclone cooler.

[0039] In this embodiment of the invention, rapid solid-liquid separation is achieved using a settling tank, a filter, or a filter press.

[0040] In the embodiments of the present invention, the magnetic separation is carried out using a wet weak magnetic separator.

[0041] Example 1

[0042] In this embodiment, the raw material is gibbsite-type bauxite, and its main chemical components are:

[0043] Component weight percentage (wt. %)

[0044] Element Percentage by weight (wt.%) Al2O3 42.26% <![CDATA[Fe2O3]]> 28.44% <![CDATA[SiO2]]> 2.86% <![CDATA[TiO2]]> 2.38%

[0045] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0046] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0047] S2: Mix and grind the mineral powder obtained in step S1 with coal powder at a ratio of C:Fe2O3=0.8:1 to produce a mixture with a particle size P80≤0.074mm;

[0048] S3: The mixture obtained in step S2 is fed into the preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 400 ℃ to obtain the preheated mixture.

[0049] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 600 ℃ and a roasting time of 120 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0050] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0051] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 270 ℃. While extracting alumina, the phase transformation and crystallization path of the gangue desilication product sodium silicate slag are controlled by the high-temperature leaching hydrothermal environment, so that it is oriented to be reconstructed into a prismatic phase morphology, and the encapsulated fine-grained magnetite is released.

[0052] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0053] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 15:1, and then separated by magnetic separation under a magnetic field strength of 3000 Oe to obtain iron concentrate and magnetic separation tailings.

[0054] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1 to S8 above is 97.85%, the TFe grade of the iron concentrate obtained by magnetic separation is 65.82%, and the iron recovery rate is 85.74%.

[0055] Example 2

[0056] In this embodiment, the raw material is gibbsite-type bauxite, and its main chemical components are:

[0057] (mass percentage, wt. %) is:

[0058] Element Percentage by weight (wt.%) <![CDATA[Al2O3]]> 43.15% <![CDATA[Fe2O3]]> 29.02% <![CDATA[SiO2]]> 1.12% <![CDATA[TiO2]]> 2.45%

[0059] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0060] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0061] S2: Mix and grind the mineral powder obtained in step S1 with coal powder at a ratio of C:Fe2O3=0.5:1 to produce a mixture with a particle size P80≤0.074mm;

[0062] S3: The mixture obtained in step S2 is fed into the preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 300 ℃ to obtain the preheated mixture.

[0063] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 500 ℃ and a roasting time of 180 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0064] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0065] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 270 ℃. While extracting alumina, the phase transformation and crystallization path of the gangue desilication product sodium silicate slag are controlled by the high-temperature leaching hydrothermal environment, so that it is oriented to be reconstructed into a prismatic phase morphology, and the encapsulated fine-grained magnetite is released.

[0066] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0067] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 10:1, and then separated by magnetic separation under a magnetic field strength of 2000 Oe to obtain iron concentrate and magnetic separation tailings.

[0068] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1 to S8 above was 96.23%, the TFe grade of the iron concentrate obtained by magnetic separation was 63.14%, and the iron recovery rate was 82.36%.

[0069] Example 3

[0070] The raw materials used in this embodiment are the same as those in Example 1.

[0071] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0072] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0073] S2: The mineral powder obtained in step S1 is mixed with coal powder at a ratio of C:Fe2O3=1.2:1 and co-ground to produce a mixture with a particle size P80≤0.074mm;

[0074] S3: The mixture obtained in step S2 is fed into a preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 500 ℃ to obtain a preheated mixture.

[0075] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 700 ℃ and a roasting time of 60 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0076] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0077] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 280 ℃. While extracting alumina, the phase transformation and crystallization path of the sodium silicate slag, a product of gangue desilication, is controlled by the high-temperature leaching hydrothermal environment, so that it is reconstructed into a prismatic phase morphology and the encapsulated fine-grained magnetite is released.

[0078] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0079] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 20:1 and separated by magnetic separation under a magnetic field strength of 4000 Oe to obtain iron concentrate and magnetic separation tailings.

[0080] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1 to S8 above was 98.82%, the TFe grade of the iron concentrate obtained by magnetic separation was 67.54%, and the iron recovery rate was 89.37%.

[0081] Example 4

[0082] The raw materials used in this embodiment are the same as those in Example 2.

[0083] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0084] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0085] S2: Mix and grind the mineral powder obtained in step S1 with coal powder at a ratio of C:Fe2O3=0.9:1 to produce a mixture with a particle size P80≤0.074mm;

[0086] S3: The mixture obtained in step S2 is fed into the preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 450 ℃ to obtain the preheated mixture.

[0087] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 650 ℃ and a roasting time of 90 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0088] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0089] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 275 ℃. While extracting alumina, the phase transformation and crystallization path of the sodium silicate slag, a product of gangue desilication, is controlled by the high-temperature leaching hydrothermal environment, so that it is reconstructed into a prismatic phase morphology and the encapsulated fine-grained magnetite is released.

[0090] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0091] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 14:1 and separated by magnetic separation under a magnetic field strength of 2800 Oe to obtain iron concentrate and magnetic separation tailings.

[0092] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1 to S8 above was 97.13%, the TFe grade of the iron concentrate obtained by magnetic separation was 65.07%, and the iron recovery rate was 85.22%.

[0093] Example 5

[0094] In this embodiment, the raw material is gibbsite-type bauxite, and its main chemical composition (mass percentage, wt.%) is as follows:

[0095] Element Percentage by weight (wt.%) <![CDATA[Al2O3]]> 42.74% <![CDATA[Fe2O3]]> 27.95% <![CDATA[SiO2]]> 2.94% <![CDATA[TiO2]]> 2.31%

[0096] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0097] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0098] S2: Mix and grind the mineral powder obtained in step S1 with coal powder at a ratio of C:Fe2O3=0.7:1 to produce a mixture with a particle size P80≤0.074mm;

[0099] S3: The mixture obtained in step S2 is fed into the preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 350 ℃ to obtain the preheated mixture.

[0100] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 550 ℃ and a roasting time of 120 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0101] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0102] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 270 ℃. While extracting alumina, the phase transformation and crystallization path of the gangue desilication product sodium silicate slag are controlled by the high-temperature leaching hydrothermal environment, so that it is oriented to be reconstructed into a prismatic phase morphology, and the encapsulated fine-grained magnetite is released.

[0103] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0104] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 12:1 and separated by magnetic separation under a magnetic field strength of 2400 Oe to obtain iron concentrate and magnetic separation tailings.

[0105] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1~S2 above was 97.43%, the TFe grade of the iron concentrate obtained by magnetic separation was 64.28%, and the iron recovery rate was 84.67%.

[0106] Example 6

[0107] The raw materials used in this embodiment are the same as those in Example 5.

[0108] This invention proposes a method for separating iron and aluminum from high-iron bauxite by suspension magnetization roasting, which specifically includes the following steps:

[0109] S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm;

[0110] S2: Mix and grind the mineral powder obtained in step S1 with coal powder at a ratio of C:Fe2O3=1.0:1 to produce a mixture with a particle size P80≤0.074mm;

[0111] S3: The mixture obtained in step S2 is fed into the preheating system and subjected to multi-stage suspension preheating and partial dehydration reaction using the high-temperature flue gas discharged from the calcining furnace. The preheating temperature is 380 ℃ to obtain the preheated mixture.

[0112] S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal at a roasting temperature of 600 ℃ and a roasting time of 60 s. The in-situ release of reducing gas transforms the weakly magnetic iron minerals in the ore powder into strongly magnetic magnetite and activates the aluminum minerals to obtain roasted clinker.

[0113] S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen using a fluidized bed cooler or a cyclone cooler. After cooling to below 200 ℃, it is discharged to obtain magnetized roasted ore.

[0114] S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching at 280 ℃. While extracting alumina, the phase transformation and crystallization path of the sodium silicate slag, a product of gangue desilication, is controlled by the high-temperature leaching hydrothermal environment, so that it is reconstructed into a prismatic phase morphology and the encapsulated fine-grained magnetite is released.

[0115] S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production.

[0116] S8: The iron-rich red mud obtained in step S7 is prepared into a slurry with a liquid-to-solid ratio of 18:1 and separated by magnetic separation under a magnetic field strength of 3500 Oe to obtain iron concentrate and magnetic separation tailings.

[0117] The relative alumina dissolution rate of the magnetized roasted ore obtained in steps S1 to S8 above was 97.68%, the TFe grade of the iron concentrate obtained by magnetic separation was 65.71%, and the iron recovery rate was 86.02%.

[0118] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite, characterized in that: Includes the following steps: S1: Crush and grind the high-iron bauxite ore to make the ore particle size ≤0.5 mm; S2: Grind the mineral powder obtained in step S1 with coal powder to make the particle size P80≤0.074 mm, and prepare a mixture; S3: The mixture obtained in step S2 is fed into the preheating system, and multi-stage suspension preheating and partial dehydration reaction are carried out using the high-temperature flue gas discharged from the calcining furnace to obtain the preheated mixture. S4: The preheated mixture obtained in step S3 is fed into a suspension magnetization roasting furnace. Under the suspension fluidization state, the high temperature and high gas-solid heat transfer rate in the furnace are used to promote the in-situ flash gasification reaction of the solid reducing agent coal, and the in-situ release of reducing gas transforms the weak magnetic iron minerals in the ore powder into strong magnetic magnetite and activates the aluminum minerals to obtain roasted clinker. S5: The roasted clinker obtained in step S4 is fed into a closed-loop cooling system and subjected to multi-stage countercurrent cooling in the absence of oxygen to obtain magnetized roasted ore. S6: The magnetized roasted ore obtained in step S5 is mixed with the circulating mother liquor to prepare a slurry, which is then sent to the pipeline leaching device for leaching. While extracting alumina, the phase transformation and crystallization path of the sodium silicate slag, a product of gangue desilication, is controlled by the high-temperature leaching hydrothermal environment, so that it is reconstructed into a long columnar, highly crystalline prismatic crystal morphology, releasing the encapsulated fine-grained magnetite. S7: The slurry obtained after dissolution in step S6 is sent to a settling tank, filter or filter press for rapid liquid-solid separation to obtain leaching solution and iron-rich red mud. The leaching solution is then used in the subsequent process of Bayer process production. S8: The iron-rich red mud obtained in step S7 is subjected to magnetic separation to obtain iron concentrate and magnetic separation tailings.

2. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S1, the raw material is gibbsite-type bauxite with Al2O3 ≥ 40% and Fe2O3 ≥ 25% by mass fraction.

3. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S2, the molar ratio of fixed carbon in the pulverized coal to Fe2O3 in the raw ore is (0.5~1.2):

1.

4. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S3, the multi-stage suspension preheating uses 2 to 4 stages of cyclone preheaters connected in series. After the preheating is completed, the temperature of the mineral powder is controlled at 300 to 500 ℃, and some of the free water and crystal water in the raw ore are removed during the preheating stage.

5. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S4, the magnetization calcination temperature is 500~700 ℃, and the calcination time is 60~300 s.

6. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S5, oxygen isolation cooling is achieved using a fluidized bed cooler or a cyclone cooler, with the cooling medium being an inert gas such as argon or nitrogen; the magnetized roasted ore is discharged after being cooled to below 200 ℃ to prevent secondary oxidation of the magnetite.

7. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S5, the hot air generated by heat exchange in the cooling system is introduced into the suspension magnetization roasting furnace in step S4 as secondary combustion air or material fluidization air, so as to realize the closed-loop circulation of thermal energy of the entire roasting system.

8. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S6, high-temperature leaching is used, with a leaching temperature of 270~280 ℃. The high-temperature alkaline hydrothermal environment in this temperature range drives the sodium silicon slag to transform into a long columnar, highly crystalline prismatic crystal phase.

9. The method for separating iron and aluminum by suspension magnetization roasting of high-iron bauxite according to claim 1, characterized in that: In step S8, the magnetic separation method is wet weak magnetic separation, the magnetic field strength is 2000~4000 Oe, and the liquid-solid ratio is (10~20):1.

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