A method for preparing ultrafine kaolin by multi-force field regulation

Abstract

The present invention relates to the technical field of kaolin preparation, and discloses a method for preparing ultrafine kaolin by multi-force field regulation, comprising the following steps: adding water to kaolin ore to form kaolin slurry, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a horizontal spiral centrifuge to obtain fine-grained kaolin slurry; the fine-grained kaolin slurry is concentrated by a butterfly centrifuge, and then subjected to superconducting magnetic separation and chemical bleaching; the bleached kaolin slurry is filtered by a washing filter press; the filter cake is dispersed into 55-60% slurry by water and a dispersant, and then enters a horizontal mill for secondary grinding, and finally dehydrated and dried to obtain ultrafine kaolin. The beneficial effects of the present invention are: a multi-stage hydrocyclone is combined with a spiral centrifuge to maximize the removal of impurities such as free quartz, mica, and alunite, and fine-grained kaolin is retained and ultrafine grinding technology is used to achieve narrow particle size control of kaolin, thereby obtaining ultrafine kaolin with a finer particle size and improving the covering performance of kaolin.

Description

Technical Field

[0001] The invention relates to the technical field of kaolin preparation, and in particular to a method for preparing ultrafine kaolin by multi-force field regulation. Background Art

[0002] Ultrafine kaolin is a natural mineral material with high purity, fine particles and high specific surface area. It is widely used at home and abroad, mainly in ceramics, rubber, plastics, coatings, paints and other fields.

[0003] Domestic ultrafine kaolin processing methods mainly include wet grinding, dry grinding and chemical treatment. Wet grinding is currently a more commonly used method, which uses wet grinding machinery to grind, grade and disperse the original kaolin; dry grinding uses air flow mills and other equipment to dry process kaolin; chemical treatment methods include acid dissolution, alkali treatment, ion exchange, etc. to change the properties of kaolin.

[0004] The micron-scale ultrafine grinding process started early in foreign countries, and the technology is relatively mature and comprehensive. The domestic process technology started around the 1970s, and has made considerable progress in some technical details in recent years, but there are still defects such as excessive energy consumption and insufficient output.

[0005] The Chinese invention patent with authorization announcement number CN114247558B discloses a method for preparing kaolin with narrow particle size distribution, which adopts a combination of a vibrating screen, a horizontal centrifuge and a grinding machine, and mainly obtains narrow particle size kaolin through repeated cycle grinding and horizontal centrifuge sorting. It has high energy consumption, causes great damage to the kaolin structure, affects its dispersion performance, and limits its application in the high-end papermaking field. Summary of the invention

[0006] The purpose of the present invention is to reduce the energy consumption of kaolin production, improve the dispersibility of ultrafine kaolin, and expand the application field. In view of the above-mentioned shortcomings of the prior art, a method for preparing ultrafine kaolin by multi-force field regulation is proposed.

[0007] A method for preparing ultrafine kaolin by multi-force field regulation comprises the following steps:

[0008] S1, adding water to kaolin ore to prepare kaolin slurry, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a horizontal spiral centrifuge to obtain a fine-particle kaolin slurry;

[0009] S2, injecting the fine-particle kaolin slurry obtained in step S1 into a butterfly centrifuge for concentration, increasing the mass concentration of the slurry to 22-28%, and obtaining concentrated kaolin slurry;

[0010] S3, mixing the fine-particle kaolin slurry obtained in step S1 with the concentrated kaolin slurry obtained in S2, controlling the mass concentration of the kaolin slurry to 16-20%, and then performing superconducting magnetic separation and chemical bleaching to obtain a bleached kaolin slurry;

[0011] S4, injecting the bleached kaolin slurry obtained in step S3 into a washing filter press, filtering the bleached kaolin slurry into a filter cake with a solid content of 68±2%, and washing the filter cake in the filter press for 2000 to 3600 seconds to dilute the acid radicals and salt ions in the kaolin slurry;

[0012] S5, adding water, a dispersant and a pH adjuster into a pulping dispersion tank to disperse the filter cake obtained in step S4 into a slurry with a mass concentration of 55-60%;

[0013] S6, using a horizontal grinding machine to perform secondary grinding on the slurry dispersed in step S5 to obtain ultrafine kaolin slurry;

[0014] S7. Dehydrating and drying the ultrafine kaolin slurry with a spray dryer to obtain ultrafine kaolin.

[0015] The above technical solution is further configured as follows: hydroxyethyl urea is also added in step S5, and the added amount of hydroxyethyl urea is 1-3% of the dry ore amount of the kaolin slurry.

[0016] The above technical solution is further configured as follows: the amount of the dispersant added in step S5 is 1.5-2.5‰ of the dry ore amount of the kaolin slurry, and the dispersant is sodium polyacrylate and / or sodium hexametaphosphate.

[0017] The above technical solution is further configured as follows: the pH adjuster is liquid alkali, and the pH is adjusted to 5.5-6.5.

[0018] The above technical solution is further configured as follows: in step S7, the temperature inside the spray dryer is 350-450°C.

[0019] The above technical solution is further configured as follows: the mass concentration of the kaolin slurry in step S1 is 7.2-8.5%.

[0020] The above technical solution is further configured as follows: the multi-stage hydrocyclone includes a plurality of hydrocyclones connected in sequence, the slurry inlet pressure of the plurality of hydrocyclones is 0.15-0.4 MPa, the aperture of the sand setting spout is 2-18 mm, and the feed mass concentration is 12-16%.

[0021] The above technical solution is further configured such that the mass concentration of the slurry entering the spiral centrifuge is 10.5-12.6%, the drum speed is 2800-3100 r / min, the overflow mass concentration is 7.2-8.5%, and the overflow slurry particle size -2 μm is 86-90%.

[0022] The above technical solution is further configured as follows: the ultrafine kaolin obtained in step S4 has a particle size of -2 μm ≥ 95%, D50 ≤ 0.5 μm, and D90 ≤ 1.5 μm.

[0023] The beneficial effects of the present invention are:

[0024] 1. A multi-stage hydrocyclone combined with a spiral centrifuge is used to maximize the removal of impurities such as free quartz, mica, and alunite, retain fine-grained kaolin, and use ultrafine grinding technology to achieve narrow particle size control of kaolin. Finally, it is dehydrated and dried by a spray dryer to obtain ultrafine kaolin. Through the synergistic effect of multiple force fields, the kaolin particle size (-2μm content) is ≥95%, D50≤0.5μm, D90≤1.5μm, and kaolinite content is ≥90%, thereby enhancing fluidity and improving the dispersion performance of kaolin.

[0025] 2. Add hydroxyethyl urea to the ultrafine kaolin slurry. Under the grinding and extrusion of the horizontal mill, hydroxyethyl urea can penetrate into the interlayer of kaolin. The kaolin slurry containing hydroxyethyl urea is rapidly decomposed into gaseous products such as ammonia, methane, and ethylene under the high temperature environment in the spray dryer. Hydroxyethyl urea can instantly blast the kaolin during the decomposition process, thereby separating the kaolin layers and stripping the laminated kaolin into thinner narrow-particle kaolin. Through this setting, the kaolin can be further stripped while drying and dehydrating in the spray dryer, making full use of the energy of the spray dryer. The horizontal mill only needs to process the fine-particle kaolin slurry for a short time to obtain high-quality ultrafine kaolin.

[0026] 3. Adding dispersant to fine-grained kaolin slurry can make the kaolin slurry dispersed, which is conducive to the horizontal grinding machine to grind the kaolin. The dispersed kaolin can be fully mixed with hydroxyethyl urea, so that the hydroxyethyl urea can be evenly infiltrated into the kaolin. DETAILED DESCRIPTION

[0027] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0028] Example 1

[0029] A method for preparing ultrafine kaolin by multi-force field regulation comprises the following steps:

[0030] S1, adding water to kaolin ore to prepare kaolin slurry, the mass concentration of kaolin slurry is about 40%, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a spiral centrifuge to obtain fine-grained kaolin slurry;

[0031] The multi-stage hydrocyclone includes a group of φ150 hydrocyclones, with a grit spout aperture of 18mm, a slurry inlet pressure of 0.15~0.25Mpa, and a feed mass concentration of 16%; a group of φ75 hydrocyclones, with a grit spout aperture of 8mm, a slurry inlet pressure of 0.2~0.3Mpa, and a feed mass concentration of 15.5%; three groups of φ25 hydrocyclones, with a grit spout aperture of 2mm, a slurry inlet pressure of 0.3~0.4Mpa, and a feed mass concentration of 14%. After being treated by the multi-stage hydrocyclone, the overflow particle size of -2μm is 66.2%, and the X-ray sedimentation particle size D50 is 1.06μm.

[0032] Five horizontal spiral centrifuges are set up, with a feed concentration of 12% and a drum speed of 2900-3100 r / min. The final ultrafine kaolin slurry overflow mass concentration is 7.2%, and the overflow particle size -2μm is 86.6%.

[0033] S2, injecting the fine-particle kaolin slurry obtained in step S1 into a butterfly centrifuge for concentration, increasing the mass concentration of the slurry to 28%, and obtaining concentrated kaolin slurry;

[0034] S3, mixing the fine-particle kaolin slurry obtained in step S1 with the concentrated kaolin slurry obtained in S2, controlling the mass concentration of the kaolin slurry to 18±2%, and then performing superconducting magnetic separation and chemical bleaching to obtain a bleached kaolin slurry;

[0035] S4, injecting the bleached kaolin slurry obtained in step S3 into a washing filter press, filtering the bleached kaolin slurry into a filter cake with a solid content of 68±2%, and washing the filter cake in the filter press for 3600 seconds to dilute the acid radicals and salt ions in the kaolin slurry;

[0036] S5, adding sodium polyacrylate, liquid caustic soda, and hydroxyethyl urea to the pulping dispersion tank to make the slurry in a dispersed state, the addition amounts of sodium hexametaphosphate and hydroxyethyl urea are 2.5‰ and 1% of the dry ore mass of the fine-grained kaolin slurry, respectively, and then adding liquid caustic soda to adjust the pH to 5.5-6.5, and dispersing the filter cake obtained in step S4 into a slurry with a mass concentration of 60%;

[0037] S6, using a horizontal grinding machine to perform secondary grinding on the slurry dispersed in step S5 to obtain ultrafine kaolin slurry;

[0038] S7. Dehydrate and dry the ultrafine kaolin slurry using a spray dryer at a drying temperature of 350° C. to obtain ultrafine kaolin.

[0039] Through the above steps, the obtained ultrafine kaolin particles have a -2 μm content of 95.1%, a -1 μm content of 82.4%, an X-ray sedimentation particle size D50 of 0.34 μm, and an X-ray sedimentation particle size D90 of 1.47 μm.

[0040] Example 2

[0041] A method for preparing ultrafine kaolin by multi-force field regulation comprises the following steps:

[0042] S1, adding water to kaolin ore to prepare kaolin slurry, the mass concentration of kaolin slurry is about 40%, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a spiral centrifuge to obtain fine-grained kaolin slurry;

[0043] The multi-stage hydrocyclone includes a group of φ150 hydrocyclones, with a grit spout aperture of 18mm, a slurry inlet pressure of 0.15~0.25Mpa, and a feed mass concentration of 16%; a group of φ75 hydrocyclones, with a grit spout aperture of 8mm, a slurry inlet pressure of 0.2~0.3Mpa, and a feed mass concentration of 15.5%; three groups of φ25 hydrocyclones, with a grit spout aperture of 2mm, a slurry inlet pressure of 0.3~0.4Mpa, and a feed mass concentration of 14%. After being treated by the multi-stage hydrocyclone, the overflow particle size of -2μm is 66.2%, and the laser D50 is 1.06μm.

[0044] There are 5 horizontal spiral centrifuges with a feed concentration of 12.0% and a drum speed of 2900-3100 r / min. The final ultrafine kaolin slurry overflow mass concentration is 8.1% and the overflow particle size of -2μm is 90%.

[0045] S2, injecting the fine-particle kaolin slurry obtained in step S1 into a butterfly centrifuge for concentration, increasing the mass concentration of the slurry to 22%, and obtaining concentrated kaolin slurry;

[0046] S3, mixing the fine-particle kaolin slurry obtained in step S1 with the concentrated kaolin slurry obtained in step S2, controlling the mass concentration of the kaolin slurry to 20%, and then performing superconducting magnetic separation and chemical bleaching to obtain a bleached kaolin slurry;

[0047] S4, injecting the bleached kaolin slurry obtained in step S3 into a washing filter press, filtering the bleached kaolin slurry into a filter cake with a solid content of 68±2%, and washing the filter cake in the filter press for 2000 seconds to dilute the acid radicals and salt ions in the kaolin slurry;

[0048] S5, adding sodium polyacrylate and hydroxyethyl urea to the pulping dispersion tank to make the slurry in a dispersed state, the addition amounts of sodium polyacrylate and hydroxyethyl urea are 1.5‰ and 3% of the dry ore mass of the fine-grained kaolin slurry, respectively, and then adding liquid caustic soda to adjust the pH to 5.5-6.5, and dispersing the filter cake obtained in step S4 into a slurry with a mass concentration of 55%;

[0049] S6, using a horizontal grinding machine to perform secondary grinding on the slurry dispersed in step S5 to obtain ultrafine kaolin slurry;

[0050] S7. Dehydrate and dry the ultrafine kaolin slurry using a spray dryer at a drying temperature of 400° C. to obtain ultrafine kaolin.

[0051] Through the above steps, the obtained ultrafine kaolin particles have a -2 μm content of 95.8%, a -1 μm content of 84.5%, an X-ray sedimentation particle size D50 of 0.33 μm, and an X-ray sedimentation particle size D90 of 1.34 μm.

[0052] Example 3

[0053] A method for preparing ultrafine kaolin by multi-force field regulation comprises the following steps:

[0054] S1, adding water to kaolin ore to prepare kaolin slurry, the mass concentration of kaolin slurry is 45%, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a spiral centrifuge to obtain fine-grained kaolin slurry;

[0055] The multi-stage hydrocyclone includes a group of φ150 hydrocyclones, with a grit spout aperture of 18mm, a slurry inlet pressure of 0.15~0.25Mpa, and a feed mass concentration of 16%; a group of φ75 hydrocyclones, with a grit spout aperture of 8mm, a slurry inlet pressure of 0.2~0.3Mpa, and a feed mass concentration of 15.5%; three groups of φ25 hydrocyclones, with a grit spout aperture of 2mm, a slurry inlet pressure of 0.3~0.4Mpa, and a feed mass concentration of 14%. After being treated by the multi-stage hydrocyclone, the overflow particle size of -2μm is 66.2%, and the laser D50 is 1.06μm.

[0056] There are 10 horizontal spiral centrifuges with a feed concentration of 12% and a drum speed of 2900-3100 r / min. The final ultrafine kaolin slurry overflow mass concentration is 8.1% and the overflow particle size of -2 μm is 90%.

[0057] S2, injecting the fine-particle kaolin slurry obtained in step S1 into a butterfly centrifuge for concentration, increasing the mass concentration of the slurry to 25%, and obtaining concentrated kaolin slurry;

[0058] S3, mixing the fine-particle kaolin slurry obtained in step S1 with the concentrated kaolin slurry obtained in step S2, controlling the mass concentration of the kaolin slurry to 18%, and then performing superconducting magnetic separation and chemical bleaching to obtain a bleached kaolin slurry;

[0059] S4, injecting the bleached kaolin slurry obtained in step S3 into a washing filter press, filtering the bleached kaolin slurry into a filter cake with a solid content of 68±2%, and washing the filter cake in the filter press for 2800 seconds to dilute the acid radicals and salt ions in the kaolin slurry;

[0060] S5, adding sodium hexametaphosphate and hydroxyethyl urea to the pulping dispersion tank to make the slurry in a dispersed state, the addition amounts of sodium hexametaphosphate and hydroxyethyl urea are 2‰ and 2% of the dry ore mass of the fine-grained kaolin slurry, respectively, and then adding liquid caustic soda to adjust the pH to 5.5-6.5, and dispersing the filter cake obtained in step S4 into a slurry with a mass concentration of 58%;

[0061] S6, using a horizontal grinding machine to perform secondary grinding on the slurry dispersed in step S5 to obtain ultrafine kaolin slurry;

[0062] S7. Dehydrate and dry the ultrafine kaolin slurry using a spray dryer at a drying temperature of 375° C. to obtain ultrafine kaolin.

[0063] Through the above steps, the obtained ultrafine kaolin particles have a -2 μm content of 97.0%, a -1 μm content of 86.7%, an X-ray sedimentation particle size D50 of 0.33 μm, and an X-ray sedimentation particle size D90 of 1.20 μm.

[0064] Comparative Example 1

[0065] The difference between Comparative Example 1 and Example 3 is that: S5, sodium hexametaphosphate is added to the pulping dispersion tank to make the slurry in a dispersed state, the amount of sodium hexametaphosphate added is 2‰ of the dry mass of the fine-grained kaolin slurry, and then liquid alkali is added to adjust the pH to 5.5~6.5, and the filter cake obtained in step S4 is dispersed into a slurry with a mass concentration of 58%.

[0066] Through the above steps, the obtained ultrafine kaolin particles have a -2μm content of 92.5%, a -1μm content of 78.9%, an X-ray sedimentation particle size D50 of 0.67μm, and an X-ray sedimentation particle size D90 of 1.73μm.

[0067] It can be seen from Examples 1-3 that the kaolin particle size of -2 μm content ≥ 95%, D50 ≤ 0.5 μm, and D90 ≤ 1.5 μm can be achieved through the synergistic effect of multiple force fields; it can be seen from Example 3 and Comparative Example 1 that without adding hydroxyethyl urea, the obtained ultrafine kaolin -2 μm content, D50 and D90 are inferior to those in Example 3, especially the -1 μm content in the comparative example is greatly reduced, indicating that adding hydroxyethyl urea to the ultrafine kaolin slurry can further strip the kaolin while drying and dehydrating in the flash dryer, which can greatly increase the -1 μm content of the ultrafine kaolin particle size and reduce the X-ray sedimentation particle size D50 and D90 values.

[0068] For matters not mentioned above, the prior art applies.

[0069] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing ultrafine kaolin by multi-force field regulation, characterized in that , including the following steps: S1, adding water to kaolin ore to prepare kaolin slurry, and the kaolin slurry is sequentially classified by a multi-stage hydrocyclone and a horizontal spiral centrifuge to obtain a fine-particle kaolin slurry; S2, injecting the fine-particle kaolin slurry obtained in step S1 into a butterfly centrifuge for concentration, increasing the mass concentration of the slurry to 22-28%, and obtaining concentrated kaolin slurry; S3, mixing the fine-particle kaolin slurry obtained in step S1 with the concentrated kaolin slurry obtained in S2, controlling the mass concentration of the kaolin slurry to 16-20%, and then performing superconducting magnetic separation and chemical bleaching to obtain a bleached kaolin slurry; S4, injecting the bleached kaolin slurry obtained in step S3 into a washing filter press, filtering the bleached kaolin slurry into a filter cake with a solid content of 68±2%, and washing the filter cake in the filter press for 2000 to 3600 seconds to dilute the acid radicals and salt ions in the kaolin slurry; S5, adding water, a dispersant and a pH adjuster into a pulping dispersion tank to disperse the filter cake obtained in step S4 into a slurry with a mass concentration of 55-60%; S6, using a horizontal grinding machine to perform secondary grinding on the slurry dispersed in step S5 to obtain ultrafine kaolin slurry; S7, dehydrating and drying the ultrafine kaolin slurry using a spray dryer to obtain ultrafine kaolin; In the step S5, hydroxyethyl urea is further added, and the amount of hydroxyethyl urea added is 1-3% of the dry ore amount of the kaolin slurry.

2. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The amount of the dispersant added in step S5 is 1.5-2.5‰ of the dry ore amount of kaolin slurry, and the dispersant is sodium polyacrylate and / or sodium hexametaphosphate.

3. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The pH regulator is liquid alkali, which adjusts the pH to 5.5-6.

5.

4. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: In step S7, the temperature in the spray dryer is 350-450°C.

5. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The mass concentration of the kaolin slurry in step S1 is 7.2-8.5%.

6. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The multi-stage hydrocyclone comprises a plurality of hydrocyclones connected in sequence, the slurry inlet pressure of the plurality of hydrocyclones is 0.15-0.4 MPa, the aperture of the sand setting spout is 2-18 mm, and the feed mass concentration is 12-16%.

7. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The inlet slurry mass concentration of the spiral centrifuge is 10.5-12.6%, the drum speed is 2800-3100 r / min, the overflow mass concentration is 7.2-8.5%, and the overflow slurry particle size -2 μm is 86-90%.

8. The method for preparing ultrafine kaolin by multi-force field regulation according to claim 1, characterized in that: The ultrafine kaolin obtained in step S7 has a particle size of -2 μm ≥ 95%, an X-ray sedimentation particle size D50 ≤ 0.5 μm, and an X-ray sedimentation particle size D90 ≤ 1.5 μm.