Method for deironing and whitening kaolin
Through a four-step process of pulping, magnetic separation, electrolytic oxidation and reduction, the Fe²+ in kaolin is oxidized to Fe³+ and reduced to Fe²+ using an electrolytic device, solving the problem of insufficient whiteness of kaolin and improving the quality of kaolin.
Patent Information
- Application Number
- CN202510937204.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-09-16
AI Technical Summary
Existing technologies make it difficult to completely remove Fe³+ from kaolin, resulting in unsatisfactory kaolin whiteness, which affects the appearance and quality of downstream products.
The four-step process of pulping, magnetic separation, electrolytic oxidation, electrolytic reduction and dehydration is adopted. The Fe²+ is oxidized to Fe³+ and then reduced to Fe²+ through the electrolytic device, thereby separating the iron impurities in the kaolin slurry and improving the whiteness.
It significantly improves the whiteness of kaolin, solves the problem of yellowing or redness of kaolin products, and improves the quality of kaolin.
Smart Images
Figure CN120646850A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of minerals, and in particular to a method for removing iron and whitening kaolin. Background Art
[0002] Kaolin is an important non-metallic mineral widely used in industries such as ceramics, papermaking, coatings, rubber, and plastics. The whiteness and purity of kaolin directly impact its performance and market value. However, natural kaolin often contains impurities such as iron, titanium, sulfides, and organic matter, which affect the performance and appearance of downstream kaolin products. Iron is a key factor in the yellowing or reddish discoloration of kaolin. High iron content also causes porcelain made from kaolin to discolor, seriously affecting product quality.
[0003] Although traditional kaolin preparation technology can effectively remove strong magnetic iron minerals, it has a negative impact on Fe³ + The removal effect is limited, resulting in incomplete iron removal, causing the obtained kaolin to have less than ideal whiteness, affecting the appearance and quality of kaolin downstream products, which needs to be improved. Summary of the Invention
[0004] The purpose of the present invention is to provide a method for effectively removing Fe3 in kaolin in order to solve the above problems. + , thereby improving the whiteness of kaolin iron removal and whitening method.
[0005] To achieve the above object, the present invention discloses a method for removing iron and whitening kaolin, which comprises the following steps: Step 1: Slurrying: Powdered or muddy kaolin is added with water and stirred to obtain kaolin slurry, forming a uniform suspension, which is conducive to subsequent classification and magnetic separation, and facilitates the separation of impurities; Step 2: Magnetic separation: Magnetic separation is performed on the kaolin slurry to separate the ferromagnetic substances in the kaolin slurry. In this process, mechanical iron and some iron-containing minerals are removed to improve the whiteness of the kaolin; Step 3: Electrolytic oxidation, using an electrolytic device to remove the water-insoluble Fe 2+ Oxidized to Fe³ + ; Step 4: Electrolytic deferrification: use an electrolytic device to remove the water-insoluble Fe³ in the kaolin slurry. + Reduced to water-soluble Fe² + ; Step 5: Dehydration, separating the water in the kaolin slurry to obtain kaolin.
[0006] Fe 2+ It is easy to hydrolyze in water, but there will be some water-insoluble Fe in kaolin slurry. 2+Therefore, the kaolin slurry is first subjected to electrolytic oxidation to remove the water-insoluble Fe 2+ Oxidized to Fe³ + Then, the kaolin slurry is electrolytically reduced to reduce the Fe³ + Reduced to Fe² + , and then through the dehydration step to separate the water in the kaolin slurry, pure kaolin with extremely low iron content can be obtained. Through the four-step process of pulping, magnetic separation, electrolytic deironing and dehydration, the whiteness of kaolin can be effectively improved, the quality of kaolin can be improved, and at the same time, the problem of kaolin products such as yellowing or redness and low whiteness of porcelain can be solved.
[0007] In step 3, the electrolysis device includes an oxidation electrolytic cell, in which a plurality of anode plates and cathode plates are installed. The anode plates are electrically connected to the anode connecting wires, and the cathode plates are electrically connected to the cathode connecting wires. The oxidation electrolytic cell does not have an anode box and a cathode box. A small amount of electrolyte is added to the kaolin slurry, and the kaolin slurry passes between the anode and the cathode. Fe 2+ It can be oxidized to Fe³ + .
[0008] It also includes a buffer barrel, a discharge port is provided on the top of the oxidation electrolytic cell, and a feed port is provided on the bottom of the oxidation electrolytic cell. Both the discharge port and the feed port are connected to the buffer barrel through a pipeline. A circulating pump is installed on the pipeline to transport the kaolin slurry in a circular flow. The slurry circulates under the action of the circulating pump, which can prevent the kaolin slurry from settling, avoid inadequate electrolysis, and ensure the Fe² + Fully oxidized to Fe³ + , achieving efficient electrolytic oxidation reaction.
[0009] There are multiple oxidation electrolytic cells, and the input ends and output ends of the multiple oxidation electrolytic cells are connected end to end. The multiple oxidation electrolytic cells can make the kaolin slurry more fully and thoroughly oxidized, thereby improving production efficiency.
[0010] In step 4, the electrolysis apparatus includes a reduction electrolytic cell, in which a plurality of spaced-apart anode boxes and cathode boxes are installed. The anode box includes two anode box side frames, an anode plate is positioned between the two anode box side frames, and an anode box bottom frame is mounted between the lower ends of the two anode box side frames. The cathode box includes two cathode box side frames, a cathode plate is positioned between the two cathode box side frames, and a cathode box bottom frame is mounted between the lower ends of the two cathode box side frames. Two diaphragm bottom frames are mounted between the two anode box side frames, one on either side of the anode plate. A diaphragm pressure frame is mounted on the side of the diaphragm bottom frame away from the anode plate. The diaphragm is positioned between the diaphragm bottom frame and the pressure frame. The two diaphragms and the inner wall of the anode box form an anode chamber for holding anolyte. The two diaphragms are spaced apart and prevent kaolin slurry from entering the anode chamber. The anode box includes an anode plate, which is electrically connected to an anode connecting wire. The cathode box includes a cathode plate, which is electrically connected to a cathode connecting wire. The space between two adjacent anode boxes is the cathode chamber, which is arranged in the order of anode box-cathode chamber-anode box-cathode chamber...anode box. The cathode chambers are connected to each other. Kaolin slurry enters the cathode chamber through the lower feed port of the reduction electrolytic cell and flows out from the upper discharge port after the reduction reaction. The anode chamber and the cathode chamber are blocked by a diaphragm to prevent kaolin slurry from entering the anode chamber.
[0011] It also includes a buffer barrel. The reduction electrolytic cell is provided with a discharge port at the top and a feed port at the bottom. Both the discharge port and the feed port are connected to the buffer barrel via a pipeline. A circulation pump is installed on the pipeline to transport the kaolin slurry in a circular flow. During operation, the kaolin slurry to be electrolyzed is injected into the buffer barrel, and then the circulation pump is started. The kaolin slurry enters the reduction electrolytic cell from the feed port at the bottom of the reduction electrolytic cell through the pipeline. As the liquid level slowly rises, it passes through the cathode chamber and reaches the height of the discharge port. It is then discharged from the discharge port and finally flows back to the buffer barrel through the pipeline. The slurry circulates under the action of the circulation pump, which can prevent the kaolin slurry from settling, avoid inadequate electrolysis, and ensure Fe³ + Fully reduced to Fe² + , achieving efficient electrolytic reduction reaction.
[0012] The number of reduction electrolytic cells is multiple, and the input and output ends of the multiple reduction electrolytic cells are connected end to end. The advantage of multiple oxidation electrolytic cells is that the kaolin slurry can be fully oxidized in one go without the need for circulation, thereby improving production efficiency.
[0013] The pH value of the anode liquid is between 3-4. The acidic environment can enhance the reaction efficiency. The pH value between 3-4 can improve the current efficiency and reduce energy consumption.
[0014] Before entering step 1, the ore pretreatment step is carried out, specifically including: Step 0.1: Crushing: Use a jaw crusher to crush the kaolin ore into 10-20mm to obtain powdered and lumpy kaolin. Crushing the ore into uniform small pieces is convenient for subsequent grinding. The particle size range of 10-20mm balances the crushing efficiency and subsequent grinding energy consumption. Step 0.2: Grinding: Grind the powdered and lump kaolin using a Raymond mill, a ball mill, or a vertical mill. Grind the kaolin to 80-400 mesh to obtain powdered kaolin. Grind the kaolin into powder to facilitate the complete separation of impurities.
[0015] In addition, before crushing the kaolin ore, washing and screening are necessary, if necessary. The ore is rinsed with high-pressure water jets, impurities such as topsoil, gravel, and organic matter are removed using a drum washer, coarse particles are removed using a vibrating screen, and the kaolin is finely graded using a spiral classifier. Crushing and grinding can improve subsequent iron removal efficiency. Crushing to 10-20mm facilitates homogenization, while grinding to 80-400 mesh increases the specific surface area, promoting magnetic separation and electrolytic reactions.
[0016] In step 1, the mixture is mixed according to a solid content of 10-30%, and the mixed mixture is placed in a mixer for stirring to form a slurry. The solid content of 10-30% helps to balance fluidity and reaction efficiency.
[0017] Between step 1 and step 2, filtration is also included, in which the kaolin slurry is placed in a hydrocyclone or a centrifugal classifier, and large-particle impurities are separated by utilizing the difference in particle settling velocity. In this process, coarse particle impurities such as quartz and feldspar are removed, thereby improving the fineness and purity of the kaolin.
[0018] In step 2, the kaolin slurry after impurities are separated is placed in a magnetic separator for magnetic separation. The magnetic field strength is set to 0.8-1.5T, which can specifically adsorb weak magnetic impurities.
[0019] Between steps 2 and 3, a flotation step is included. Fatty acids and sodium silicate are added to the kaolin slurry after magnetic separation, and sulfides and organic matter are separated by foam flotation to increase the SiO2 / Al2O3 ratio. The fatty acids act as collectors, selectively adsorbing sulfides, while sodium silicate acts as an inhibitor, inhibiting the flotation of the kaolin. The foam produced by the flotation process adsorbs sulfides and organic matter. After the foam is screened out, both sulfides and organic matter are removed from the kaolin slurry, thereby increasing the SiO2 / Al2O3 ratio and improving the quality of the kaolin.
[0020] In step 5, the following process is specifically included: Step 5.1, using gravity to settle the solid particles and separate most of the water in the kaolin slurry to obtain kaolin mud; Step 5.2: The kaolin slurry is pumped into a plate and frame filter press through a high-pressure pump for filtration and dehydration to reduce the water content. The plate and frame filter press can reduce the water content of the slurry to 25-35%. Step 5.3: Place the filtered kaolin in a decanter centrifuge for centrifugal dehydration to further reduce the water content and obtain moist kaolin. The decanter centrifuge rotates at high speed to generate centrifugal force, separating the water from the solid particles and further reducing the water content to 15-20%. The kaolin slurry undergoes three steps of gravity sedimentation, filter press dehydration, and centrifugal dehydration to gradually reduce the moisture content of the kaolin and reduce the subsequent drying load. In addition, in order to save costs, the centrifugal dehydration step can be omitted.
[0021] The process also includes step 6: drying, wherein the wet kaolin is dried using a spray drying device with the hot air temperature set at 200-300° C. The kaolin obtained by spray drying has a uniform particle size and is suitable for high value-added products.
[0022] The process also includes step 6: drying, where the moist kaolin is dried using a flash drying device with the hot air temperature set at 200-300°C. Flash drying has low energy consumption and is suitable for processing high-humidity materials. The hot air temperature of 200-300°C prevents high temperatures from damaging the crystal structure, ensuring both production efficiency and product quality.
[0023] In summary, the beneficial effects of the present invention are: on the basis of magnetic separation, kaolin is electrolyzed by an electrolysis device to convert Fe³ + Reduced to Fe² + , Fe² + It can be dissolved in water, and then the water in the kaolin slurry can be separated to obtain pure kaolin with extremely low iron content. Through the four-step process of pulping, magnetic separation, electrolytic deironing and dehydration, the whiteness of kaolin can be significantly improved, the quality of kaolin can be improved, and at the same time, the problem of low whiteness of kaolin products such as yellowing or reddishness of porcelain can be solved. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Flow chart for iron removal and whitening of kaolin; Figure 2 This is a schematic diagram of the axial structure of the electrolysis device; Figure 3 is a schematic cross-sectional structural diagram of an electrolysis device; Figure 4 Schematic diagram of the structure of the reduction electrolytic cell; Figure 5 Schematic diagram of the structure of the oxidation electrolytic cell; Figure 6 Schematic diagram of the cross-sectional structure of the anode box Figure 7 for Figure 6Enlarged schematic diagram of part B in the middle.
[0025] In the figure: reduction electrolytic cell 1, diaphragm 2, anode chamber 3, oxidation electrolytic cell 4, anode box 5, anode plate 6, cathode box 7, cathode plate 8, buffer barrel 9, pipeline 10, circulation pump 11. DETAILED DESCRIPTION
[0026] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. Example 1,
[0027] 1. Ore pretreatment Crushing: Use jaw crusher to crush the kaolin ore to 10mm.
[0028] Grinding: Use Raymond mill to grind the crushed kaolin to 80 mesh.
[0029] The iron content of the original ore is 1.2%, and the whiteness is 73%.
[0030] 2. Pulping The ground kaolin powder was mixed with water at a solid content of 10%, and stirred in a blender at a speed of 500 r / min for 30 minutes to form a uniform kaolin slurry.
[0031] 3. Filter The kaolin slurry is pumped into a centrifugal classifier to separate out coarse particle impurities such as quartz and feldspar.
[0032] 4. Magnetic separation The kaolin slurry is introduced into an electromagnetic separator with a magnetic field strength of 0.8T to remove ferromagnetic minerals such as hematite and ilmenite. The whiteness of the slurry after magnetic separation is increased to 78%.
[0033] 5. Flotation Fatty acids and sodium silicate are added to the kaolin slurry, and a foam flotation machine is used to remove sulfides and organic matter.
[0034] 6. Electrolytic de-ferrification The kaolin slurry after flotation was precipitated and filtered, and then water was added to the 10% solid content and stirred, and then introduced into the oxidation electrolysis device and circulated for 30 minutes using a circulation pump. 2+ Oxidized to Fe 3+ ; The oxidized kaolin slurry was precipitated and filtered by filter press, and water was added to the slurry at a solid content of 10% and stirred to make slurry; the pH value was adjusted to 3.2, and the slurry was introduced into the reduction electrolysis device and circulated for 30 minutes using a circulation pump. + Reduced to Fe² + and dissolved in water.
[0035] 7. Dehydration It specifically includes the following three steps: 1) Gravity sedimentation: let the slurry stand for 2 hours and drain the supernatant; 2) Filtration: Use plate and frame filter press to dehydrate to a moisture content of 30%; 3) Centrifugal dehydration: Further dehydration to a moisture content of 15% using a horizontal screw centrifuge.
[0036] Step 9: Drying: Use a flash dryer to process the wet material, and select a hot air temperature of 200°C to obtain kaolin with a moisture content of <1%, an iron content of <0.6%, and a whiteness of ≥90%. Example 2,
[0037] 1. Ore pretreatment Crushing: Use jaw crusher to crush the kaolin ore to 20mm.
[0038] Grinding: Use a ball mill to grind the crushed kaolin to 400 mesh.
[0039] The iron content of the original ore is 1.3%, and the whiteness is 70%.
[0040] 2. Pulping The ground kaolin powder was mixed with water at a solid content of 30%, and stirred in a blender at a speed of 600 r / min for 30 minutes to form a uniform kaolin slurry.
[0041] 3. Filter The kaolin slurry is pumped into the hydrocyclone to separate out coarse particle impurities such as quartz and feldspar.
[0042] 4. Magnetic separation The kaolin slurry is introduced into a high gradient magnetic separator with a magnetic field strength of 1.3T to remove ferromagnetic minerals such as hematite and ilmenite. The whiteness of the slurry after magnetic separation is increased to 75%.
[0043] 5. Flotation Fatty acids and sodium silicate are added to the kaolin slurry, and a foam flotation machine is used to remove sulfides and organic matter.
[0044] 6. Electrolytic de-ferrification The kaolin slurry after flotation was introduced into the electrolysis device. The pH value of the cathode kaolin slurry was controlled at 4. A circulating pump was used in the electrolysis device to react for 1 hour. Fe³ + Reduced to Fe² + and dissolved in water.
[0045] 7. Dehydration It specifically includes the following three steps: 1) Gravity sedimentation: let the slurry stand for 2 hours and drain the supernatant; 2) Filtration: Use plate and frame filter press to dehydrate to a moisture content of 33%; 3) Centrifugal dehydration: Further dehydration to a moisture content of 15% using a horizontal screw centrifuge.
[0046] Step 9: Drying: Use a flash dryer to process the wet material, and select a hot air temperature of 300°C to obtain kaolin with a moisture content of <1%, an iron content of <0.7%, and a whiteness of ≥88%. Example 3,
[0047] 1. Ore pretreatment Crushing: Use jaw crusher to crush the kaolin ore to 15mm.
[0048] Grinding: Use a vertical mill to grind the crushed kaolin to 200 mesh.
[0049] The iron content of the original ore is 1.2%, and the whiteness is 75%.
[0050] 2. Pulping The ground kaolin powder was mixed with water at a solid content of 15%, and stirred in a blender at a speed of 500 r / min for 30 minutes to form a uniform kaolin slurry.
[0051] 3. Filter The kaolin slurry is pumped into the hydrocyclone to separate out coarse particle impurities such as quartz and feldspar.
[0052] 4. Magnetic separation The kaolin slurry is introduced into a high gradient magnetic separator with a magnetic field strength of 1.1T to remove ferromagnetic minerals such as hematite and ilmenite. The whiteness of the slurry after magnetic separation is increased to 79%.
[0053] 5. Electrolytic de-ferrification The kaolin slurry after flotation was introduced into the electrolysis device. The pH value of the cathode kaolin slurry was controlled at 3.5. A circulation pump was used in the electrolysis device to react for 40 minutes. + Reduced to Fe² + and dissolved in water.
[0054] 6. Dehydration It specifically includes the following three steps: 1) Gravity sedimentation: let the slurry stand for 2 hours and drain the supernatant; 2) Filtration: Use plate and frame filter press to dehydrate to a moisture content of 27%; 3) Centrifugal dehydration: Further dehydration to a moisture content of 15% using a horizontal screw centrifuge.
[0055] The kaolin with a moisture content of less than 15%, an iron content of less than 0.7% and a whiteness of ≥87% was obtained.
[0056] Conclusion: Under the premise of ensuring the whiteness of kaolin products, taking into account the energy consumption of equipment and the production cost of the electrolysis device, Implementation 1 is the most preferred embodiment of this case.
[0057] Wastewater treatment: Oxidation of Fe² in water by bubbling oxygenation + Fe³ is insoluble in water + , precipitation or flocculation, filtration and recovery of Fe2O3 in acidic wastewater. The weakly acidic water can be recycled for pulping, or it can be neutralized, purified and recycled.
[0058] Tailings utilization: Silica tailings can be used as building materials, for making bricks or cement, and reducing solid waste accumulation.
Claims
1. A method for removing iron and whitening kaolin, characterized in that: The following steps are involved: Step 1: slurry preparation, adding water to powdered or muddy kaolin and stirring to obtain kaolin slurry; Step 2: Electrolytic deferrification: use an electrolytic device to remove the water-insoluble Fe³ in the kaolin slurry. + Reduced to water-soluble Fe² + ; Step 3: Dehydration, separating the water in the kaolin slurry to obtain kaolin.
2. The kaolin deironing and whitening method according to claim 1, wherein: Between steps 1 and 2 include: Magnetic separation: Magnetic separation is performed on kaolin slurry to separate ferromagnetic substances in the kaolin slurry; Electrolytic oxidation, using electrolytic device to remove water-insoluble Fe 2+ Oxidized to Fe³ + .
3. The kaolin deironing and whitening method according to claim 2, wherein: In the electrolytic oxidation step, the electrolysis device includes an oxidation electrolytic cell (4), wherein a plurality of anode plates (6) and cathode plates (8) arranged at intervals are installed in the oxidation electrolytic cell (4), the anode plates (6) are electrically connected to the anode connecting wire, and the cathode plates (8) are electrically connected to the cathode connecting wire. The device also includes a buffer barrel (9), a discharge port is provided at the top of the oxidation electrolytic cell (4), and a feed port is provided at the bottom of the oxidation electrolytic cell (4), and both the discharge port and the feed port are connected to the buffer barrel (9) through a pipeline (10), and a circulation pump (11) for conveying kaolin slurry for circulation is installed on the pipeline (10). The number of oxidation electrolytic cells (4) is multiple, and the input ends and output ends of the multiple oxidation electrolytic cells (4) are connected end to end.
4. The kaolin deironing and whitening method according to claim 1 or 2, wherein: In step 2, the electrolysis device includes a reduction electrolytic cell (1), wherein a plurality of anode boxes (5) and cathode boxes (7) arranged at intervals are installed in the reduction electrolytic cell (1), two vertically arranged diaphragms (2) are installed in the anode box (5), and the two diaphragms (2) and the inner wall of the anode box (5) form an anode chamber (3) for containing an anode liquid, and the diaphragm (2) blocks the kaolin slurry from entering the anode chamber (3), and an anode plate (6) is installed in the anode box (5), and the anode plate (6) is electrically connected to the anode connecting wire. The cathode box ( 7) is provided with a cathode plate (8), the cathode plate (8) is electrically connected to the cathode connecting wire, and also includes a buffer barrel (9), a discharge port is provided on the top of the reduction electrolytic cell (1), a feed port is provided on the bottom of the reduction electrolytic cell (1), the discharge port and the feed port are both connected to the buffer barrel (9) through a pipeline (10), a circulation pump (11) for conveying the kaolin slurry in a circulation flow is installed on the pipeline (10), the number of the reduction electrolytic cells (1) is multiple, and the input ends and output ends of the multiple reduction electrolytic cells (1) are connected end to end.
5. The kaolin deironing and whitening method according to claim 1, wherein: Before step 1, the ore pretreatment step is carried out, specifically including: Step 0.1: Crushing: Use a crusher to crush the kaolin ore into 10-20 mm to obtain powdered and lump kaolin; Step 0.2: Grinding: Grind the powdered and lump kaolin using a Raymond mill, a ball mill, or a vertical mill to grind the kaolin to 80-400 mesh to obtain powdered kaolin.
6. The kaolin deironing and whitening method according to claim 2, wherein: In step 1, the mixture is mixed according to a solid content of 10-30%, and the mixed mixture is put into a blender and stirred to form a slurry; Before the magnetic separation step, filtration is also included, in which the kaolin slurry is placed in a hydrocyclone or centrifugal classifier to separate large-particle impurities by utilizing the difference in particle settling velocity; In the magnetic separation step, the kaolin slurry after impurities are separated is placed in a magnetic separator for magnetic separation, and the magnetic field strength is set to 0.8-1.5T.
7. The kaolin deironing and whitening method according to claim 2, wherein: Between the magnetic separation step and the electrolytic oxidation step, there is also a flotation step, in which collectors and inhibitors are added to the kaolin slurry after magnetic separation, and sulfides and organic matter are separated by foam flotation to improve the SiO2 / Al2O3 ratio.
8. The kaolin deironing and whitening method according to claim 1, wherein: In step 3, the following processes are specifically included: Step 3.1, using gravity to settle the solid particles and separate most of the water in the kaolin slurry to obtain a kaolin slurry with a high solid content; Step 3.2: Pump the kaolin slurry into a plate and frame filter press using a high-pressure pump for filtration and dehydration to reduce the water content; In step 3.3, the filtered kaolin is placed in a decanter centrifuge for centrifugal dehydration to obtain wet kaolin.
9. The kaolin deironing and whitening method according to claim 8, wherein: The method further includes step 4: drying, wherein the wet kaolin is dried by spray drying equipment, and the hot air temperature is set to 200-300°C.
10. The method for removing iron and whitening kaolin according to claim 1, wherein: The method further includes step 4: drying, wherein the wet kaolin is dried by flash drying equipment, and the hot air temperature is set to 200-300°C.