Method and device for electrophoretic separation of iron oxide from alumina raw ore pulp and underflow red mud

Abstract

According to the method for separating iron oxide particles in raw ore pulp and underflow red mud in the aluminum oxide production process through electrophoresis and the electrophoretic separation device, iron oxide moves towards a negative electrode in an electrophoresis tank and is enriched at the negative electrode to form high-iron slurry, the iron oxide is pushed downwards through a scraper blade to enter a high-iron slurry collecting tank and then is discharged for solid-liquid separation, and iron oxide solids are separated out. When the iron oxide is separated, the aluminum oxide, the calcium oxide, the titanium oxide and the like slowly move towards the negative electrode, the aluminosilicate and the aluminate carry negative charges, and the silicon oxide, the calcium aluminate, the calcium aluminosilicate and other particles move towards the positive electrode and are enriched to form low-iron slurry, a flocculating agent is added into a positive electrode area, and the low-iron slurry after the iron oxide is separated is flocculated and settled to enter a low-iron slurry collecting tank to be discharged.

Description

Technical Field

[0001] The invention relates to a method for separating iron oxide particles from raw ore pulp and red mud in the process of aluminum oxide production by electrophoresis and a device used in the method, belonging to the technical field of mineral separation. Background Art

[0002] Bauxite is associated with iron oxide minerals, which are separated from bauxite during the alumina production process and mixed with silicon oxide, calcium oxide, etc. to become waste residue (red mud) after alumina extraction. The alumina production process is to grind bauxite into slurry with sodium hydroxide solution. The alumina in the bauxite reacts with the sodium hydroxide solution to form a sodium aluminate solution, and then the sodium aluminate solution is separated from solids such as iron oxide, calcium oxide, and calcium silicate by sedimentation. The solid-liquid mixture discharged from the production process after alumina is extracted also contains iron oxide and various solid substances such as silicon oxide, calcium oxide, aluminum oxide, and calcium aluminosilicate. Because the color of iron oxide is red, it is called red mud. Iron oxide is also a mineral, which can be used as a raw material for steel smelting when separated alone.

[0003] The iron oxide in bauxite is ferrous oxide with weak magnetic properties. It is now mostly separated and recovered by magnetic separation in solid red mud after the extraction of alumina. Application No. CN201610956537 "A method for magnetic roasting and magnetic separation of red mud", Publication No. CN118127314A, Publication No. CN104818381A, Publication No. CN103290207A, U.S. Patent No. US2015203362 (A1), etc. all disclose the technology of reducing iron oxide in red mud, increasing iron magnetization and magnetic separation, which is to add carbon material to red mud for high-temperature roasting, improve the magnetic properties by carbon thermal reduction of iron oxide, and then enrich it by magnetic separation to separate iron oxide from red mud. Application No. CN202310972695 "Method for recovering fine-grained iron oxide minerals" discloses a technology of adding a magnetic adsorbent for agglomeration and then magnetic separation. The red mud containing fine-grained iron oxide minerals to be processed is mixed with iron powder and nitrite for wet grinding. A coupled redox system is constructed with iron-nitrite-iron oxide and mechanical activation is coordinated during the wet grinding process. This allows the surface of the weakly magnetic fine-grained iron oxide minerals (such as Fe2O3) in the raw material to be processed to form stable and uniform strong magnetic Fe3O4 oxides, thereby allowing the fine-grained iron oxide minerals to be relatively selectively agglomerated due to the enhanced surface magnetism, and then enriched and separated by strong magnetic separation.

[0004] There is a technology that converts iron oxide into water-soluble iron salts by subjecting red mud to an acid reaction, and then separates the iron element through precipitation, thereby achieving chemical separation and recovery of the iron element. Canada Alumina Co., Ltd. has application number CN201380010871 "Method for treating red mud", and Xi'an University of Architecture and Technology has application number CN201210164515 "Method for co-producing ultrafine ferroferric oxide and alumina from Bayer red mud", etc., which discloses the technology of soaking red mud with HCL to obtain a chloride solution containing iron ions and aluminum ions, and separating iron and aluminum by generating iron oxide and aluminum hydroxide precipitation respectively.

[0005] The existing technology for separating iron oxide from red mud uses the dried solid red mud as raw material. When red mud is discharged from the alumina production process, it is an underflow of a solid-liquid mixture. In addition to solid compounds containing particulate matter such as silicon oxide, aluminum oxide, iron oxide, calcium oxide, titanium oxide, etc., it also contains aluminates, aluminum silicates, and sodium hydroxide solutions. The aluminum silicates and aluminates in the solid-liquid mixture have gelling properties. After being dehydrated into solids, gelling bonds will occur, causing the iron oxide to wrap around other solid particles, and some will also form partially crystalline substances. Therefore, when using the dehydrated solid red mud as raw material to separate iron oxide, there are low yields, high energy consumption, and low purity. Summary of the invention

[0006] Electrophoresis separation is a method of separating charged particles by their different moving speeds in an electric field. Different substances have different moving directions and moving speeds in a certain electric field due to their different charging properties and particle sizes and shapes, so they can be separated. The direction of movement of material particles in an electric field depends on the type of charge they carry. Positively charged particles move toward the cathode of the electric field; negatively charged particles move toward the anode; particles with a net charge of zero do not move in an electric field.

[0007] The raw ore pulp after grinding bauxite with sodium hydroxide solution in the alumina production process and the bottom flow red mud discharged after refining alumina are both alkaline colloidal solid-liquid mixtures, and particles with a particle size of less than 24μm account for more than 90%. Among them, iron oxide particles carry more positive charges, while particles such as aluminum oxide, calcium oxide, and titanium oxide carry positive charges but the positive charge content is much less than that of iron oxide. In the electric field, iron oxide moves quickly to the negative electrode, while aluminum oxide, calcium oxide, titanium oxide, etc. move slowly to the negative electrode. Aluminosilicates and aluminates in the solution decompose into aluminum silicate ions, and aluminates carry negative charges. They combine with calcium aluminate and calcium aluminosilicate to form particles that move toward the positive electrode, while silicon oxide particles carry negative charges and move toward the positive electrode. The iron oxide that moves quickly to the negative electrode is separated from other particles that move slowly to the negative electrode and particles that move to the positive electrode by electrophoresis.

[0008] The present invention relates to a method for separating iron oxide particles from raw ore pulp and bottom flow red mud in the process of aluminum oxide production by electrophoresis, and a device for electrophoretically enriching and separating iron oxide used in the method.

[0009] The present invention is an electrophoresis device for separating iron oxide from raw ore pulp and red mud in the process of aluminum oxide production. The electrophoresis device body is a cylindrical or square electrophoresis tank (1). The electrophoresis tank (1) contains a positive electrode (2) and a negative electrode (3). The positive and negative electrodes are of the same height. The positive electrode (2) of the circular electrophoresis tank (1) is in the middle of the cylindrical tank body, and the negative electrode (3) is on the inner surface of the cylindrical tank. The positive electrode (2) and the negative electrode (3) of the square electrophoresis tank (1) are respectively on parallel and opposite inner surfaces. A scraper (4) is provided on the negative electrode (3). A low-iron slurry collecting tank (8) and a low-iron slurry outlet (11) are provided at the lower end of the positive electrode (2), a high-iron slurry collecting tank (9) and a high-iron slurry outlet (12) are provided at the lower end of the negative electrode (3), and an isolation edge (7) is provided between the low-iron slurry collecting tank (8) and the high-iron slurry collecting tank (9), and the isolation edge (7) is lower than the electrodes. A middle pipe (5) with an outlet at one third of the upper part of the positive electrode (2) and an upper pipe (6) with an outlet at one sixth of the upper part of the positive electrode (2) are installed near the positive electrode (2). A low-level pipe (10) is installed on the low-iron slurry collecting tank (8), and the outlet of the low-level pipe is lower than the isolation edge (7) in the tank.

[0010] The method steps for electrophoretically separating iron oxide from the raw ore slurry and bottom flow red mud in the alumina production process are as follows:

[0011] 1. Place a 10% sodium hydroxide solution into the electrophoresis tank, add iron oxide and aluminum oxide fine particle standards, energize the electrodes and adjust the power to keep the electrophoresis zone of iron oxide on the negative electrode side of the isolation edge and the electrophoresis zone of aluminum oxide on the positive electrode side of the isolation edge within the unit electrophoresis time.

[0012] 2. Add the raw ore pulp or the discharged red mud in the alumina production process into the electrophoresis tank through the upper tube, and add sodium hydroxide solution or desalted water of different concentrations into the electrophoresis tank through the middle tube to make the solid content less than 45% and the pH value greater than 11.5.

[0013] 3. After power is turned on, the iron oxide particles in the electrophoresis tank quickly move to the negative electrode and are enriched. The iron oxide particles on the negative electrode are scraped downward with a scraper and settle into the high-iron slurry collection tank. They are transported out through the high-iron slurry outlet for solid-liquid separation to separate the iron oxide solids. The separated aluminate-containing liquid enters the low-iron slurry.

[0014] 4. The solid-liquid mixture distributed on the positive electrode side of the isolation edge becomes low-iron slurry. The flocculant solution is added to the low-iron slurry collecting tank below the positive electrode through the low-level pipe, so that the particles settle into the low-iron slurry collecting tank and are transported out through the low-iron slurry outlet.

[0015] 5. During the electrophoresis process, sodium hydroxide solution of different concentrations is added into the electrophoresis tank through the center tube to adjust the solid content ratio and pH value, and keep the solid content <45% and pH value >11.5; dispersant is added into the electrophoresis tank through the center tube to accelerate the electrophoretic movement of particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attached Figure 1 flow chart

[0017] Attached Figure 2 Side view of the cylindrical electrophoresis tank

[0018] Attached Figure 3 Top view of cylindrical electrophoresis tank

[0019] Attached Figure 4 Bottom view of cylindrical electrophoresis tank

[0020] Attached Figure 5 Square electrophoresis tank side view

[0021] Attached Figure 6 Square electrophoresis tank top view

[0022] Attached Figure 7 Bottom view of square electrophoresis tank

[0023] Specific application examples

[0024] Application Example 1

[0025] 1. Separate iron oxide from the raw ore pulp in the alumina production process. Use 10% sodium hydroxide solution and iron oxide and aluminum oxide fine particle standard samples to set up the electrophoresis tank, energize the electrodes and adjust the power to keep the electrophoresis zone of iron oxide on the negative electrode side of the isolation edge and the electrophoresis zone of aluminum oxide on the positive electrode side of the isolation edge within the set electrophoresis time.

[0026] 2. Add aluminum ore and sodium hydroxide solution to the electrophoresis tank through the upper tube, mix and grind the raw ore pulp, add sodium hydroxide solution of different concentrations to the electrophoresis tank through the middle tube, and adjust the solid content in the electrophoresis tank to less than 40% and the pH value to greater than 12.6.

[0027] 3. When the electrodes are energized, the iron oxide particles quickly move to the negative electrode and are enriched. The iron oxide particles on the negative electrode are scraped downward with a scraper and settle into the high-iron slurry collection tank. They are transported out through the high-iron slurry outlet for solid-liquid separation to separate the iron oxide solids. The separated liquid enters the low-iron slurry mixture.

[0028] 4. The solid-liquid mixture distributed on the positive electrode side of the isolation edge becomes low-iron slurry. A flocculant solution is added to the low-iron slurry collecting tank through a low-level pipe to accelerate the sedimentation of the particles on the positive electrode side of the isolation edge, enter the low-iron slurry collecting tank, and are transported out through the low-iron slurry outlet.

[0029] 5. During the electrophoresis process, add sodium hydroxide solution or deionized water of different concentrations into the electrophoresis tank through the center tube to adjust the solid content and pH value in the electrophoresis tank to keep the solid content less than 40% and the pH value greater than 12.6.

[0030] Application Example 2

[0031] 1. Separate iron oxide from the bottom flow red mud discharged from alumina production. Since the bottom flow red mud contains flocculants, and the aluminum silicate after desiliconization and dissolution has a strong gelling effect, the separation process of iron oxide requires reducing the solid content and maintaining a stable pH value.

[0032] 2. Use 10% sodium hydroxide solution and iron oxide and aluminum oxide fine particles to calibrate the electrophoresis tank, energize the electrodes and adjust the power to set the electrophoresis zone of iron oxide on the negative electrode side of the isolation edge and the electrophoresis zone of aluminum oxide on the positive electrode side of the isolation edge within the set unit electrophoresis time.

[0033] 3. Add bottom flow red mud into the electrophoresis tank through the upper tube, and add sodium hydroxide solution or deionized water into the electrophoresis tank through the middle tube to keep the solid content in the electrophoresis tank less than 35% and the pH value between 11.5 and 12.6.

[0034] 4. When the electrodes are energized, the iron oxide particles quickly move to the negative electrode and are enriched. The iron oxide particles on the negative electrode are pushed downward with a scraper and settle into the high-iron slurry collecting tank. They are then transported out through the high-iron slurry outlet for solid-liquid separation to separate the iron oxide solids.

[0035] 5. The solid-liquid mixture distributed on the positive electrode side of the isolation edge becomes low-iron slurry. A flocculant solution is added to the low-iron slurry collecting tank through a low-level pipe to accelerate the sedimentation of the particles on the positive electrode side of the isolation edge, enter the low-iron slurry collecting tank, and are transported out through the low-iron slurry outlet.

[0036] 6. During the electrophoresis process, add sodium hydroxide solution or deionized water of different concentrations into the electrophoresis tank through the center tube to adjust the solid content ratio and pH value, and keep the solid content less than 35% and the pH value between 11.6 and 12.6. Add dispersant into the electrophoresis tank through the center tube to accelerate the electrophoretic movement of particles.

Claims

1. A method and device for electrophoretically separating iron oxide from alumina ore slurry and bottom red mud, characterized in that The device for separating iron oxide by electrophoresis is composed of: the main body is a cylindrical or square electrophoresis tank, there are positive and negative electrodes in the electrophoresis tank, there is a scraper on the negative electrode, there is a low-iron slurry collecting tank and a low-iron slurry outlet at the lower end of the positive electrode, there is a high-iron slurry collecting tank and a high-iron slurry outlet at the lower end of the negative electrode, there is an isolation edge between the low-iron slurry collecting tank and the high-iron slurry collecting tank, the isolation edge is lower than the electrodes, an upper tube and a middle tube are installed near the positive electrode, and a low-level tube is installed on the low-iron slurry collecting tank; the method for separating iron oxide by electrophoresis comprises the following steps: (1) Putting iron oxide and aluminum oxide powder standard samples and 10% sodium hydroxide solution into an electrophoresis tank, energizing the electrodes and adjusting the power to set the electrophoresis zone of iron oxide on the negative electrode side of the isolation edge and the electrophoresis zone of aluminum oxide on the positive electrode side of the isolation edge within a unit electrophoresis time; (2) adding the raw ore slurry or the solid-liquid mixture of the bottom red mud in the alumina production process to the electrophoresis tank through the upper tube, and adding sodium hydroxide solution or deionized water of different concentrations to the electrophoresis tank through the middle tube, so that the solid content in the electrophoresis tank is less than 45% and the pH value is greater than 11.5; (3) After power is turned on, the iron oxide particles in the electrophoresis tank quickly move to the negative electrode and are enriched. The iron oxide particles on the negative electrode are scraped downward by a scraper and enter the high-iron slurry collection tank. The particles are transported out through the high-iron slurry outlet for solid-liquid separation to separate the iron oxide solids. (4) The solid-liquid mixture distributed on the positive electrode side of the isolation edge becomes a low-iron slurry, and a flocculant solution is added to the low-iron slurry collecting tank below the positive electrode through a low-level pipe, so that the particles distributed on the positive electrode side of the isolation edge are settled into the low-iron slurry collecting tank and transported out through the low-iron slurry outlet; (5) During the electrophoresis process, sodium hydroxide solution or deionized water of different concentrations is added into the electrophoresis tank through the center tube to adjust the solid content ratio and pH value, and the solid content in the electrophoresis tank is kept at <45% and the pH value is >11.5; a dispersant is added into the electrophoresis tank through the center tube to accelerate the electrophoretic movement of the particles.

2. The method and device for electrophoretically separating iron oxide from alumina ore slurry and bottom flow red mud according to claim 1, characterized in that The positive electrode of the circular electrophoresis tank is in the middle of the cylindrical tank body, and the negative electrode is on the inner surface of the cylinder; the positive electrode and negative electrode of the square electrophoresis tank are on parallel and opposite inner surfaces.

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