Preparation method of superfine ultra-pure kaolin powder

Abstract

The invention discloses a preparation method of superfine ultrapure kaolin powder, which comprises the following steps: preparing a kaolin raw material into ore pulp, adding a dispersing agent, adjusting the pressure and carrying out high-pressure homogenization to obtain superfine kaolin ore pulp; the superfine kaolin ore pulp is input into an electric sedimentation device and settled in a high-voltage electric field, and after sedimentation is completed, upper-layer suspension liquid is taken and fed into a superconducting magnetic separator to be subjected to magnetic separation and purification; and carrying out filter pressing dehydration on the ore pulp subjected to magnetic separation purification, and carrying out spray drying on a filter cake obtained by filter pressing dehydration to obtain the superfine ultra-pure kaolin powder. According to the method, high-pressure homogenization, electric field sedimentation and superconducting magnetic separation are combined, trace quartz and magnetic separation impurities are deeply removed, and the ultra-pure and ultra-fine kaolin powder is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of kaolin processing, and particularly relates to a method for preparing ultrafine and ultra-pure kaolin powder. Background Art

[0002] The largest consumption field of kaolin is papermaking. With the rapid development of the papermaking industry in China, the quality and grade requirements of paper are constantly increasing. Especially for paper coating, the requirements for kaolin are relatively high. In addition to high whiteness and fine particle size, the viscosity concentration generally needs to reach more than 68%.

[0003] The viscosity concentration of kaolin is affected by indicators such as purity, structure, and particle size distribution. At present, there is less research on these indicators in domestic ore dressing and processing.

[0004] Therefore, designing a method for preparing ultrafine and ultra-pure kaolin powder, using the combination of high-pressure homogenization, electric field sedimentation, and superconducting magnetic separation to deeply remove trace quartz and magnetic separation impurities, and preparing ultra-pure and ultrafine kaolin powder has broad application prospects. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing ultrafine and ultra-pure kaolin powder.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a method for preparing ultrafine and ultra-pure kaolin powder, comprising the following steps:

[0007] (1) Prepare the kaolin raw material into pulp, add a dispersant, adjust the pressure and carry out high-pressure homogenization. Under the action of forces such as high-pressure friction, shear, and impact, strip the thick lamellae of kaolin into thin flakes to obtain ultrafine kaolin pulp;

[0008] (2) Input the ultrafine kaolin pulp obtained in step (1) into an electric sedimentation device, sediment in a high-voltage electric field. During the sedimentation process, utilize the difference in conductivity between quartz and kaolin to make the quartz particles sediment and the kaolin suspend; after the sedimentation is completed, take the upper suspension and send it into a superconducting magnetic separator for magnetic separation and purification;

[0009] (3) Press-filter and dehydrate the pulp after magnetic separation and purification in step (2), and spray-dry the filter cake obtained by press-filtering and dehydrating to obtain ultrafine and ultra-pure kaolin powder.

[0010] Preferably, in step (1), the kaolin raw material is a concentrate with a purity of 90±3%.

[0011] Preferably, the concentration of the ultrafine kaolin pulp is 15-30%.

[0012] Preferably, the dispersant is obtained by mixing sodium hexametaphosphate and sodium polyacrylate in a mass ratio of 1:1 to 2, and the dosage of the dispersant is 0.3-0.5% of the kaolin raw material.

[0013] Preferably, in step (1), the pressure used for high-pressure homogenization is 200-300 bar.

[0014] Preferably, in step (2), the voltage used in the electric sedimentation device is 30-50 kV, and the sedimentation time is 1-3 h.

[0015] Preferably, in step (2), the magnetic field intensity of the superconducting magnetic separator is 3-6 T.

[0016] The higher the purity of kaolin, the finer and more concentrated the particle size distribution, and the smaller the aspect ratio, the higher the viscosity concentration. Currently, the existing kaolin processing technology can only obtain products with a purity of 90-95% and -2μm accounting for 90%, and the viscosity concentration is generally lower than 70%. In this regard, the design principle of the present invention is as follows: The present invention further processes the purified kaolin concentrate. First, through high-pressure homogenization, under the action of forces such as high-pressure friction, shearing, and impact, the thick platelet layers of kaolin are peeled into thin flakes, and the large thin flakes are further crushed into small thin flakes. Compared with the conventional mechanical grinding method, it can effectively control the appropriate aspect ratio, the crushed particle size is finer, and the particle size distribution of kaolin is narrower; in addition, high-pressure homogenization can further dissociate trace amounts of fine quartz and micro-magnetic impurities from kaolin. Then, under the action of an electric field, using the difference in conductivity between quartz and kaolin, the quartz particles settle while the kaolin suspends, thereby removing these quartz particle impurities; finally, using the high-intensity magnetism of the superconducting magnetic separator, the micro-magnetic impurities are separated. Ultimately, the ultra-purity, ultra-fineness and improvement of the viscosity concentration of kaolin are achieved.

[0017] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0018] 1. Through the high-pressure homogenization effect of the present invention, the control of particle size, particle size distribution, and aspect ratio is effectively achieved, thereby significantly improving the particle size, viscosity concentration and other indexes of the product.

[0019] 2. By combining electric field sedimentation and superconducting magnetic separation, the present invention can deeply remove trace amounts of quartz and magnetic separation impurities, realizing the high purification of kaolin and the improvement of the viscosity concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, some of the drawings in the following description are embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a process flow diagram of ultrafine and ultra-pure kaolin processing.

[0022] Figure 2 It is a structural schematic diagram of an electric sedimentation device.

[0023] Figure 3 It is a particle size test chart of kaolin concentrate and ultrafine and ultra-pure kaolin.

[0024] Figure 4 It is a SEM photo of ultrafine and ultra-pure kaolin.

[0025] Among them, 1. quartz particle; 2. kaolin; 3. thick sheet layer; 4. thin sheet. Specific Embodiments

[0026] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] Example 1

[0028] As Figures 1-4 shown, this embodiment relates to a method for preparing ultrafine and ultra-pure kaolin powder, including the following steps:

[0029] (1) Prepare a slurry with a concentration of 20% from kaolin concentrate with a purity of 90%, add 0.3% of a dispersant, and then perform high-pressure homogenization at a pressure of 250 bar. Under the action of forces such as high-pressure friction, shear, and impact, the thick sheet layer 3 of kaolin is peeled into thin sheets 4 to obtain an ultrafine kaolin slurry;

[0030] (2) Input the ultrafine kaolin slurry obtained in step (1) into an electric sedimentation device and sediment for 2 h in a 40 kV high-voltage electric field. During the sedimentation process, due to the difference in conductivity between quartz and kaolin, the quartz particles 1 settle and the kaolin 2 remains suspended; then take the upper suspension and feed it into a superconducting magnetic separator for magnetic separation and purification under a magnetic field of 4 T;

[0031] (3) Filter press and dehydrate the ore pulp after magnetic separation. The filter cake obtained from filter press and dehydration is spray-dried to obtain ultrafine and ultra-pure kaolin.

[0032] Example 2

[0033] This example provides a method for preparing ultrafine and ultra-pure kaolin powder, including the following steps:

[0034] (1) Prepare a 15% ore pulp from kaolin concentrate with a purity of 90%, add 0.4% dispersant, and then carry out high-pressure homogenization under a pressure of 280 bar to obtain ultrafine kaolin ore pulp;

[0035] (2) Input the ultrafine kaolin ore pulp obtained in step (1) into an electric sedimentation device and sediment for 2 h in a 40 kV high-voltage electric field; then take the upper suspension and feed it into a superconducting magnetic separator for magnetic separation and purification under a 4 T magnetic field;

[0036] (3) Filter press and dehydrate the ore pulp after magnetic separation. The filter cake obtained from filter press and dehydration is spray-dried to obtain ultrafine and ultra-pure kaolin.

[0037] Example 3

[0038] This example provides a method for preparing ultrafine and ultra-pure kaolin powder, including the following steps:

[0039] (1) Prepare a 15% ore pulp from kaolin concentrate with a purity of 90%, add 0.4% dispersant, and then carry out high-pressure homogenization under a pressure of 280 bar to obtain ultrafine kaolin ore pulp;

[0040] (2) Input the ultrafine kaolin ore pulp obtained in step (1) into an electric sedimentation device and sediment for 3 h in a 45 kV high-voltage electric field; then take the upper suspension and feed it into a superconducting magnetic separator for magnetic separation and purification under a 5 T magnetic field;

[0041] (3) Filter press and dehydrate the ore pulp after magnetic separation. The filter cake obtained from filter press and dehydration is spray-dried to obtain ultrafine and ultra-pure kaolin.

[0042] Example 4

[0043] This example provides a method for preparing ultrafine and ultra-pure kaolin powder, including the following steps:

[0044] (1) Prepare a 20% ore pulp from kaolin concentrate with a purity of 88%, add 0.4% dispersant, and then carry out high-pressure homogenization under a pressure of 250 bar to obtain ultrafine kaolin ore pulp;

[0045] (2) Input the ultrafine kaolin slurry obtained in step (1) into an electric sedimentation device, and sediment it in a 40 kV high-voltage electric field for 3 h; then take the upper suspension and feed it into a superconducting magnetic separator for magnetic separation and purification under a 5 T magnetic field;

[0046] (3) Press-filter and dehydrate the slurry after magnetic separation. The filter cake obtained by press-filter dehydration is spray-dried to obtain ultrafine and ultra-pure kaolin.

[0047] Comparative Example 1

[0048] This comparative example is based on Example 1 above, and the same parts as those in Example 1 above will not be elaborated.

[0049] In this comparative example, in step (2), the ultrafine kaolin slurry obtained in step (1) is fed into a superconducting magnetic separator for magnetic separation and purification under a 4 T magnetic field.

[0050] Comparative Example 2

[0051] This comparative example is based on Example 1 above, and the same parts as those in Example 1 above will not be elaborated.

[0052] The raw materials used in this comparative example are the same as those in Example 1.

[0053] The preparation method of this comparative example is as follows: The kaolin concentrate is magnetically separated under a magnetic field intensity of 3 - 5 T, and then fed into a sand mill for grinding; then sulfuric acid is added to adjust the pH to 2 - 3, and sodium dithionite is added for reaction; finally, the slurry is press-filtered and dried to obtain a kaolin product.

[0054] Comparative Example 3

[0055] This control example is a commercially available kaolin product for papermaking in a certain city in China.

[0056] Test the high-purity quartz indexes of the above Examples 1 - 4 and Comparative Examples 1 - 3, and the test results are shown in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] It can be clearly seen from Table 1 above: As can be seen from Example 1 and Comparative Example 1, without the application of an electric field, the properties of quartz and kaolin are similar, and sedimentation separation will not occur under normal circumstances, and quartz cannot be removed to achieve the purification of kaolin;

[0061] As can be seen from Examples 1-4 and Comparative Examples 2-3, by adopting the technical solution of the present invention, the purity of kaolin can be increased to over 98%, the viscosity concentration reaches over 70%, and the particle size is finer and the distribution is narrower; all indicators are significantly better than the existing processing technology and existing products.

[0062] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing ultrafine ultrapure kaolin powder, characterized in that: The following steps are involved: (1) preparing kaolin raw materials into slurry, adding a dispersant, adjusting the pressure and performing high-pressure homogenization to obtain ultrafine kaolin slurry; (2) feeding the ultrafine kaolin slurry obtained in step (1) into an electric sedimentation device for sedimentation in a high voltage electric field; after the sedimentation is completed, taking the upper suspension and feeding it into a superconducting magnetic separator for magnetic separation and purification; (3) The slurry purified by magnetic separation in step (2) is subjected to filter pressing and dehydration, and the filter cake obtained by filter pressing and dehydration is spray-dried to obtain ultrafine ultrapure kaolin powder.

2. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: In step (1), the kaolin raw material is a concentrate with a purity of 90±3%.

3. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: The concentration of the ultrafine kaolin slurry is 15-30%.

4. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: The dispersant is prepared by mixing sodium hexametaphosphate and sodium polyacrylate in a mass ratio of 1:1-2, and the dosage of the dispersant is 0.3-0.5% of the kaolin raw material.

5. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: The pressure used in the high pressure homogenization in step (1) is 200-300 bar.

6. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: In step (2), the voltage used by the electric power settling device is 30-50 kV, and the settling time is 1-3 hours.

7. The method for preparing ultrafine ultrapure kaolin powder according to claim 1, characterized in that: In step (2), the magnetic field strength of the superconducting magnetic separator is 3-6T.

8. An ultrafine ultrapure kaolin powder, characterized in that: The ultrafine ultrapure kaolin powder is prepared by the method for preparing the ultrafine ultrapure kaolin powder according to any one of claims 1 to 7, wherein the purity of the ultrafine ultrapure kaolin powder is above 98% and the viscosity is above 70%.

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