Process for extracting high-white feldspar from lithium-containing kaolin

Abstract

This invention relates to a process for extracting high-white feldspar from lithium-containing kaolin ore, comprising: Step S1, grinding and classifying the lithium-containing kaolin ore, using a high-frequency screen for inspection and screening, merging the undersize material with the overflow from a hydrocyclone, and then feeding it into a weak magnetic separator for iron removal, while the oversize material continues to be ground in a ball mill; Step S2, subjecting the material obtained after iron removal in Step S1 to a first-stage high-gradient magnetic separation; Step S3, controlling the non-magnetic material obtained in Step S2 to enter a second-stage high-gradient magnetic separation; Step S4, subjecting the non-magnetic material obtained in Step S3 to desliming in a hydrocyclone and then entering the flotation stage; Step S5, proceeding to the roughing operation; Step S6, feeding the roughing tailings from Step S5 into the scavenging operation; Step S7, feeding the scavenging tailings from Step S6 into the scavenging operation, obtaining high-white feldspar as the scavenging tailings. This invention achieves high-white feldspar with low iron content and improves the recovery rate of lepidolite.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a process for extracting high-white feldspar from lithium-containing kaolin ore. Background Technology

[0002] Lepidolite is a widely distributed mica group mineral. Lepidolite deposits found in the Earth's crust often exist as associated minerals with other rare metals. Among them, the niobium-tantalum associated lepidolite deposit in Yichun, Jiangxi Province, China, is the largest lepidolite deposit in Asia, accounting for more than 30% of the country's lithium resources, and possesses significant strategic value. Lithium extraction from lepidolite concentrate is one of the main sources of lithium, especially with the rapid increase in the use of lithium-ion batteries in electronic devices and electric vehicles due to new energy vehicles, electronic products, and energy storage systems, leading to a gradual increase in lithium demand. Simultaneously, the output of lepidolite tailings will gradually increase. With the rapid development of lepidolite smelting for lithium carbonate, tailings products are generated during the lepidolite extraction process. Due to the rapid increase in volume, the output of tailings has increased, but the amount that the market can absorb and use has not kept pace. This is because the whiteness and iron content of common feldspar, an important raw material in the ceramics industry, affect and restrict its use and formulation.

[0003] Among feldspar products, high-white feldspar has significant advantages such as uniform particle size, high whiteness, and low iron content, giving it a greater advantage in product applications. However, high-white feldspar is often more difficult to produce and has a lower yield. To alleviate the sales problem of ordinary feldspar without affecting the production of ore dressing plants and smelters, it is necessary to extract high-white feldspar from lithium-bearing kaolin ore using new processes and methods. Summary of the Invention

[0004] In response to the problems of low high-white feldspar production efficiency in the existing technology, the applicant provides a reasonable and effective process for extracting high-white feldspar from lithium-containing kaolin ore, which achieves high-white feldspar with low iron content and improves the recovery rate of lepidolite.

[0005] The technical solution adopted in this invention is as follows: A process for extracting high-white feldspar from lithium-containing kaolin ore, comprising the following steps:

[0006] Step S1: After grinding the lithium-containing kaolin ore, it enters the spiral classifier for classification. The returned sand enters the ball mill for grinding. The overflow enters the hydrocyclone for classification. The underflow of the hydrocyclone enters the high-frequency screen for inspection and screening. The underflow material is combined with the overflow of the hydrocyclone and enters the weak magnetic separator for iron removal. The overflow material continues to enter the ball mill for grinding.

[0007] Step S2: The material obtained after iron removal by the weak magnetic separator in step S1 then enters a high gradient strong magnetic separator. The feed concentration is controlled at 25-30%, the magnetic field strength is controlled at 1.5T, and the rotating frequency is controlled at 35 Hz. After a high gradient magnetic separation, magnetic and non-magnetic materials are obtained.

[0008] Step S3: The non-magnetic material obtained in step S2 is controlled to enter the two-stage high gradient magnetic separation. The feed concentration is controlled at 25-30%, the magnetic field strength is 1.7T, and the rotating frequency is controlled at 35 Hz. After the two-stage high gradient magnetic separation, magnetic and non-magnetic materials are obtained. The obtained magnetic material is combined with the magnetic material in step S2.

[0009] In step S4, the non-magnetic material obtained in step S3 is replenished with water to maintain the slurry concentration at 20-25%. This slurry is then fed into a 250 hydrocyclone for desliming, with the pressure of the hydrocyclone controlled at 0.12 MPa. The overflow from the hydrocyclone is fed into a deep cone settling and thickening stage, while the underflow from the hydrocyclone is fed into the flotation stage.

[0010] Step S5: The underflow slurry from the hydrocyclone in step S4 is fed into the mixing tank for mixing. The slurry concentration is controlled at 38-42%. Collector and inhibitor are added, and then the slurry enters the roughing operation. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate. The lepidolite rough concentrate enters the first cleaning process, as well as the roughing tailings product.

[0011] Step S6: Feed the roughing tailings from step S5 into the scavenging operation. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. Return it to the mixing tank in step S5 for further roughing. Scavenging one yields scavenging tailings.

[0012] In step S7, the tailings from scavenging operation 1 in step S6 are fed into scavenging operation 2 to obtain frothy concentrate, which is then fed back into scavenging operation 1. The tailings from scavenging operation 2 are high white feldspar, which is dehydrated to obtain high white feldspar with a moisture content of 12%.

[0013] As a further improvement to the above technical solution:

[0014] Further steps include: Step S1 uses a 0.6×0.6mm five-layer high-frequency screen, the feed concentration is controlled within the range of 35%-40%, the vibration frequency and amplitude are controlled at 1080-1500 times / minute and 3-5mm respectively, to ensure that the content of -60 mesh under the screen is not less than 85%.

[0015] Further, the process includes: combining the magnetic material obtained in step S3 and the magnetic material obtained in step S2 and then entering them into a fine-particle flotation process; also entering the selected lepidolite obtained from the lepidolite selection process in step S5 into the fine-particle flotation process; and finally obtaining the lepidolite product through the fine-particle flotation process.

[0016] Further includes:

[0017] Step S8: The magnetic material obtained in step S3 and the magnetic material obtained in step S2 are combined and then fed into a hydrocyclone for classification. The underflow of the hydrocyclone enters a five-layer high-frequency screen for inspection and screening, and the overflow enters a deep cone for sedimentation.

[0018] In step S9, the material that is screened by the five-layer high-frequency screen in step S8 is returned to the ball mill for grinding, and the material that is screened enters the hydrocyclone. The overflow of the hydrocyclone is combined with the overflow of the hydrocyclone in step S8 and enters the deep cone. The underflow enters the flotation mixing tank.

[0019] In step S10, the collector and depressant are added to the flotation mixing tank from step S9, and then the process proceeds to roughing. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate, and the roughing tailings product is obtained. The lepidolite rough concentrate then enters the cleaning process to obtain lepidolite product, and the cleaning middlings are obtained.

[0020] Step S11: The roughing tailings from step S10 are fed into the scavenging operation. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. It is returned to the ball mill in step S1 for grinding. The scavenging tailings are obtained and returned to the roughing operation together with the middlings from step S10.

[0021] In step S12, the selected lepidolite obtained from step S5 is also introduced into the flotation stirring tank in step S10, and finally the lepidolite product is obtained through the flotation process.

[0022] Further includes:

[0023] In step S13, the scavenged tailings obtained in step S7 are distributed through a slurry distributor. One path enters the belt filter to obtain high white feldspar, and the other path is combined with the product from the overflow of the hydrocyclone in step S4 after entering the deep cone sedimentation concentration and then entering the hydrocyclone together.

[0024] In step S14, the underflow from the hydrocyclone in step S13 is fed into a belt filter to obtain ceramic feldspar, and the overflow from the hydrocyclone is fed into a deep cone settling chamber.

[0025] Further includes:

[0026] In step S15, the product after deep cone settling in step S8 is fed into a gravity separation process on a shaking table to extract tantalum minerals. After iron concentrate is extracted by two-stage flat plate magnetic separation, it is fed into the deep cone in step S14. The product is then combined with the overflow from the hydrocyclone in step S14 and settled together in the deep cone. The settled product is fed into a filter press to obtain ultrafine feldspar.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention employs a multi-stage combined screening, flotation, and magnetic separation process, representing an innovative improvement in the process flow. The use of a spiral classifier, hydrocyclone, and high-frequency screen creates favorable conditions for flotation and magnetic separation. While flotation extracts lepidolite, it also reduces the iron content of feldspar. A single stage of weak magnetic separation followed by two stages of strong magnetic separation removes mechanical and secondary iron, ultimately yielding high-quality, high-white feldspar. This innovative process route results in superior quality characteristics of the produced high-white feldspar. The final low-iron photovoltaic feldspar product of this invention contains less than 0.06% Fe2O3 and achieves a whiteness of over 70.

[0029] This invention employs a multi-stage classification, stepped magnetic separation, and separate flotation process, resulting in energy reduction, high-quality products, and high-whiteness, low-iron feldspar. Furthermore, improvements in the process, such as the transition from coarse to fine flotation concentrate and the return of fine flotation tailings for regrinding, significantly enhance the recovery rate of lepidolite, leading to more effective extraction. The invention utilizes a five-layer high-frequency screen in conjunction with a hydrocyclone and spiral classifier, providing excellent preparatory work for flotation and high-whiteness feldspar extraction. By optimizing screening parameters, the invention ensures that the -60 mesh content is not less than 85%, and the hydrocyclone improves the particle size distribution entering the magnetic separation process, thereby enhancing overall process efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the process flow of one embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the process flow for extracting ceramic feldspar and ultrafine feldspar according to the present invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0033] Reference Figure 1 As shown, this invention provides a process for extracting high-white feldspar from lithium-containing kaolin ore, the specific technical solution of which is as follows:

[0034] In step S1, the lithium-containing kaolin ore is ground and then fed into a spiral classifier for classification. The returned sand is fed into a ball mill for grinding, and the overflow is fed into a hydrocyclone for classification. The underflow from the hydrocyclone is fed into a high-frequency screen for inspection and screening. Step S1 uses a 0.6×0.6mm five-layer high-frequency screen, with the feed concentration controlled within the range of 35%-40%. The vibration frequency and amplitude are controlled at 1080-1500 times / minute and 3-5mm, respectively, to ensure that the content of -60 mesh under the screen is not less than 85%. The undersize material is combined with the overflow from the hydrocyclone and fed into a weak magnetic separator for iron removal. The oversize material continues to be fed into the ball mill for grinding.

[0035] In step S2, the material obtained after iron removal by the weak magnetic separator in step S1 then enters a high-gradient magnetic separator. The feed concentration is controlled at 25-30%, the magnetic field strength is controlled at 1.5T, and the rotating frequency is controlled at 35 Hz. After the high-gradient magnetic separator, magnetic and non-magnetic materials are obtained.

[0036] In step S3, the non-magnetic material obtained in step S2 is controlled to enter a two-stage high-gradient magnetic separation process. The feed concentration is controlled at 25-30%, the magnetic field strength is 1.7T, and the rotating frequency is controlled at 35 Hz. After the two-stage high-gradient magnetic separation, magnetic and non-magnetic materials are obtained. The resulting magnetic material is combined with the magnetic material from step S2.

[0037] In step S4, the non-magnetic material obtained in step S3 is replenished with water to maintain the slurry concentration at 20-25%. This slurry is then fed into a 250 hydrocyclone for desliming, with the pressure of the hydrocyclone controlled at 0.12 MPa. The overflow from the hydrocyclone is fed into a deep cone settling and thickening process, while the underflow from the hydrocyclone is fed into the flotation stage.

[0038] Step S5: The underflow slurry from the hydrocyclone in step S4 is fed into the mixing tank for mixing. The slurry concentration is controlled at 38-42%. Collectors and inhibitors are added, and then the process proceeds to the roughing operation. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate. The lepidolite rough concentrate enters the first cleaning process, along with the roughing tailings product.

[0039] Step S6: The roughing tailings from step S5 are fed into the scavenging process. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. It is then returned to the mixing tank in step S5 for further roughing. The scavenging process yields the scavenging tailings.

[0040] In step S7, the tailings from scavenging operation one in step S6 are fed into scavenging operation two to obtain frothy concentrate, which is then returned to scavenging operation one. The tailings from scavenging operation two are high-white feldspar, which is dehydrated to obtain high-white feldspar with a moisture content of 12%. The final low-iron feldspar product contains less than 0.06% Fe2O3 and has a whiteness of over 70.

[0041] Step S8: The magnetic material obtained in step S3 and the magnetic material obtained in step S2 are combined and then fed into a hydrocyclone for classification. The underflow of the hydrocyclone enters a five-layer high-frequency screen for inspection and screening, and the overflow enters a deep cone for sedimentation.

[0042] In step S9, the material that passes through the five-layer high-frequency screen from step S8 is returned to the ball mill for grinding in step S1. The material that passes through the screen enters the hydrocyclone. The overflow of the hydrocyclone is combined with the overflow of the hydrocyclone from step S8 and enters the deep cone. The underflow enters the flotation mixing tank.

[0043] In step S10, a collector and an inhibitor are added to the flotation mixing tank in step S9, and then the process proceeds to the roughing operation. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate, and the roughing tailings product is obtained. The lepidolite rough concentrate then enters the cleaning process to obtain lepidolite froth product, and the cleaning middlings are obtained.

[0044] In step S11, the roughing tailings from step S10 are fed into the scavenging operation. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. It is then returned to the ball mill in step S1 for grinding. The scavenging tailings are obtained and returned to the roughing operation together with the middlings from step S10.

[0045] In step S12, the selected lepidolite obtained from step S5 is also introduced into the flotation stirring tank in step S10, and finally the lepidolite product is obtained through the flotation process.

[0046] Reference Figure 2 As shown, the present invention further includes a process for extracting ceramic feldspar and ultrafine feldspar, specifically including the following steps:

[0047] In step S13, the scavenged tailings obtained in step S7 are distributed through a slurry distributor. One stream enters a belt filter to obtain high-white feldspar, while the other stream is combined with the product from the hydrocyclone overflow in step S4 after deep cone sedimentation concentration and then enters the hydrocyclone together.

[0048] In step S14, the underflow from the hydrocyclone in step S13 is fed into a belt filter to obtain ceramic feldspar, and the overflow from the hydrocyclone is fed into a deep cone settling chamber.

[0049] In step S15, the product after deep cone sedimentation in step S8 is fed into a gravity separation process on a shaking table to extract tantalum minerals. Then, iron concentrate is extracted by two-stage flat plate magnetic separation to obtain non-magnetic material. The non-magnetic material enters the deep cone in step S14 and is combined with the overflow from the hydrocyclone in step S14 to settle together in the deep cone. The settled product is fed into a filter press to obtain ultrafine feldspar.

[0050] Through the above-described process steps for extracting ceramic feldspar and ultrafine feldspar, it is possible to simultaneously produce a variety of feldspar products with different characteristics and grades, resulting in a rich variety, high production efficiency, and stronger market supply capacity.

[0051] To verify the effectiveness of the present invention, a comparative experiment with equal proportions was conducted, and the comparison groups were set up as follows:

[0052] Comparative Example 1 uses a process of grinding, classification, desliming, and flotation. The flotation tailings are then subjected to high-intensity magnetic separation to obtain feldspar and lepidolite products. Grinding is performed using a ball mill, and screening is done with a five-layer high-frequency vibrating screen (0.6×0.6mm mesh). The feed concentration is controlled within the range of 35%-40%, and the vibration frequency and amplitude are controlled at 1080-1500 times / min and 3-5mm, respectively. Desliming is performed using a hydrocyclone. Flotation employs a closed-loop process with one roughing and two scavenging stages, including the addition of collectors and depressants. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The high-intensity magnetic separation uses a magnetic field strength of 1.7T and a rotating ring frequency controlled at 35 Hz.

[0053] The feldspar products obtained from the two groups were measured and recorded. The test results of Comparative Example 1 and the embodiment of this patent are shown in Table 1 below. The lepidolite products and tailings obtained from the two groups were measured and statistically analyzed. The test results of Comparative Example 1 and the embodiment of this patent are shown in Table 2 below.

[0054]

[0055] As shown in Table 1 above, the whiteness of the high-white feldspar product obtained in this patent embodiment reaches 70, which is significantly improved compared to the whiteness of 60 in the comparative example. This achieves the product characteristics of improving whiteness and reaching a high level. The content of ferric oxide is 0.06%, which is significantly reduced compared to 0.12% in the comparative example, achieving the product characteristics of low iron content.

[0056]

[0057] As shown in Table 2 above, the recovery rate of lepidolite concentrate obtained in this patent embodiment reaches 75.58%, the lithium oxide content in the obtained lepidolite concentrate reaches 2.55%, and the content in the tailings is relatively low at 0.143%, which is a high level. Compared with the 71% recovery rate of the comparative example, it is significantly improved, and the process effect of improving the recovery rate of lepidolite is achieved. Therefore, the method of the present invention can achieve a good recovery rate of lepidolite concentrate while producing high white feldspar from lithium-containing kaolin ore, so as to efficiently recover lithium resources.

[0058] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A process for extracting high-white feldspar from lithium-containing kaolin clay, characterized in that, Includes the following steps: Step S1: After grinding the lithium-containing kaolin ore, it enters the spiral classifier for classification. The returned sand enters the ball mill for grinding. The overflow enters the hydrocyclone for classification. The underflow of the hydrocyclone enters the high-frequency screen for inspection and screening. The underflow material is combined with the overflow of the hydrocyclone and enters the weak magnetic separator for iron removal. The overflow material continues to enter the ball mill for grinding. Step S2: The material obtained after iron removal by the weak magnetic separator in step S1 then enters a high gradient strong magnetic separator. The feed concentration is controlled at 25-30%, the magnetic field strength is controlled at 1.5T, and the rotating frequency is controlled at 35 Hz. After a high gradient magnetic separation, magnetic and non-magnetic materials are obtained. Step S3: The non-magnetic material obtained in step S2 is controlled to enter the two-stage high gradient magnetic separation. The feed concentration is controlled at 25-30%, the magnetic field strength is 1.7T, and the rotating frequency is controlled at 35 Hz. After the two-stage high gradient magnetic separation, magnetic and non-magnetic materials are obtained. The obtained magnetic material is combined with the magnetic material in step S2. In step S4, the non-magnetic material obtained in step S3 is replenished with water to maintain the slurry concentration at 20-25%. This slurry is then fed into a 250 hydrocyclone for desliming, with the pressure of the hydrocyclone controlled at 0.12 MPa. The overflow from the hydrocyclone is fed into a deep cone settling and thickening stage, while the underflow from the hydrocyclone is fed into the flotation stage. Step S5: The underflow slurry from the hydrocyclone in step S4 is fed into the mixing tank for mixing. The slurry concentration is controlled at 38-42%. Collector and inhibitor are added, and then the slurry enters the roughing operation. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate. The lepidolite rough concentrate enters the first cleaning process, as well as the roughing tailings product. Step S6: Feed the roughing tailings from step S5 into the scavenging operation. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. Return it to the mixing tank in step S5 for further roughing. Scavenging one yields scavenging tailings. Step S7: The tailings from the first scavenging operation in step S6 are fed into the second scavenging operation to obtain frothy concentrate, which is then fed back into the first scavenging operation. The tailings from the second scavenging operation are high white feldspar, which is dehydrated to obtain high white feldspar with a moisture content of 12%. Further, the process includes: combining the magnetic material obtained in step S3 and the magnetic material obtained in step S2 and then entering them into a fine-particle flotation process; also entering the selected lepidolite obtained from the lepidolite selection process in step S5 into the fine-particle flotation process; and finally obtaining the lepidolite product through the fine-particle flotation process.

2. The process for extracting high-white feldspar from lithium-containing kaolin ore according to claim 1, characterized in that, Further steps include: Step S1 uses a 0.6×0.6mm five-layer high-frequency screen, the feed concentration is controlled within the range of 35%-40%, the vibration frequency and amplitude are controlled at 1080-1500 times / minute and 3-5mm respectively, to ensure that the content of -60 mesh under the screen is not less than 85%.

3. The process for extracting high-white feldspar from lithium-containing kaolin ore according to claim 1, characterized in that, Further includes: Step S8: The magnetic material obtained in step S3 and the magnetic material obtained in step S2 are combined and then fed into a hydrocyclone for classification. The underflow of the hydrocyclone enters a five-layer high-frequency screen for inspection and screening, and the overflow enters a deep cone for sedimentation. In step S9, the material that is screened by the five-layer high-frequency screen in step S8 is returned to the ball mill for grinding, and the material that is screened enters the hydrocyclone. The overflow of the hydrocyclone is combined with the overflow of the hydrocyclone in step S8 and enters the deep cone. The underflow enters the flotation mixing tank. In step S10, the collector and depressant are added to the flotation mixing tank from step S9, and then the process proceeds to roughing. The roughing time is 4-6 minutes, the flotation machine speed is 1850-1950 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃. The froth product is lepidolite rough concentrate, and the roughing tailings product is obtained. The lepidolite rough concentrate then enters the cleaning process to obtain lepidolite product, and the cleaning middlings are obtained. Step S11: The roughing tailings from step S10 are fed into the scavenging operation. The scavenging time is 4-6 minutes. The frothy product is the scavenging concentrate product. It is returned to the ball mill in step S1 for grinding. The scavenging tailings are obtained and returned to the roughing operation together with the middlings from step S10. In step S12, the selected lepidolite obtained from step S5 is also introduced into the flotation stirring tank in step S10, and finally the lepidolite product is obtained through the flotation process.

4. The process for extracting high-white feldspar from lithium-containing kaolin ore according to claim 1, characterized in that, Further includes: In step S13, the scavenged tailings obtained in step S7 are distributed through a slurry distributor. One path enters the belt filter to obtain high white feldspar, and the other path is combined with the product from the overflow of the hydrocyclone in step S4 after entering the deep cone sedimentation concentration and then entering the hydrocyclone together. In step S14, the underflow from the hydrocyclone in step S13 is fed into a belt filter to obtain ceramic feldspar, and the overflow from the hydrocyclone is fed into a deep cone settling chamber.

5. The process for extracting high-white feldspar from lithium-containing kaolin ore according to claim 4, characterized in that, Further includes: In step S15, the product after deep cone settling in step S8 is fed into a gravity separation process on a shaking table to extract tantalum minerals. After iron concentrate is extracted by two-stage flat plate magnetic separation, it is fed into the deep cone in step S14. The product is then combined with the overflow from the hydrocyclone in step S14 and settled together in the deep cone. The settled product is fed into a filter press to obtain ultrafine feldspar.

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