Process method for preparing low-iron photovoltaic feldspar from lithium mica flotation tailings

Abstract

The present application relates to a kind of lithium mica flotation tailings preparation low iron photovoltaic feldspar process method, comprising steps S1 to S10, wherein, step S1 lithium mica flotation tailings is sent into high-frequency screen and is pre-screened, step S2 the material under high-frequency screen obtained in step S1 is into 120 mesh cylinder screen and is accurately screened, the inclination and rotational speed of cylinder screen are controlled at 4 °-6 ° and 10-16 revolutions per minute respectively, and the concentration of feed is maintained in the range of 20%-25%, and the content ratio of oversize material-140 mesh is 17-25%;Step S3 controls the oversize material of cylinder screen in step S2 and is classified into hydrocyclone, and the overflow is slender feldspar product;Step S4 is classified into the underflow product of sand product in step S3, and is fed into slurry mixing barrel, so that flotation reagent and slurry are fully mixed;Step S5 is fully mixed after the slurry in step S4 is fed into roughing operation, and the foam product is lithium mica rough concentrate product.The present application realizes the accurate control of product iron content and particle size by the organic combination of multi-stage screening classification and flotation, magnetic separation.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings. Background Technology

[0002] With the rapid development of the photovoltaic industry, the quality requirements for photovoltaic glass raw materials are constantly increasing. Feldspar, as one of the important raw materials for photovoltaic glass, directly affects the light transmittance and melting quality of the glass due to its iron content and particle size distribution. Currently, the industrial requirement for feldspar used in photovoltaics is that the Fe2O3 content must be controlled below 200 ppm. At the same time, to ensure the uniformity of glass melting, there are also strict requirements on the particle size of the feldspar. In terms of feldspar raw material selection, tailings from lepidolite ore beneficiation are an ideal source of feldspar for photovoltaic applications due to their high feldspar content and good whiteness. However, the deep liberation grinding process during lepidolite beneficiation results in a fine particle size distribution of feldspar and iron minerals in the tailings, increasing the difficulty of subsequent iron removal.

[0003] In existing technologies, some beneficiation plants use a multi-stage classification-magnetic separation process to prepare photovoltaic feldspar. While this method can achieve the desired fineness, it results in the loss of a significant amount of valuable minerals. It requires complex processes such as pre-slurry preparation and desliming, and suffers from low iron removal rates, a long process flow, and high costs. Furthermore, the iron minerals in lepidolite tailings exhibit complex occurrences, including embedded iron, secondary iron, and mechanically mixed iron. Existing processes often employ only a single iron removal method, making it difficult to effectively separate iron minerals in different occurrence states. Simultaneously, the excessive grinding performed to achieve iron removal makes product fineness control difficult, failing to meet the particle size requirements for photovoltaic glass production. Therefore, developing a highly efficient beneficiation process that can simultaneously control iron content and achieve particle size standards is of great significance for improving the comprehensive utilization value of lepidolite tailings. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, such as the loss of a large amount of useful minerals, low iron removal rate, and inability to meet the requirements of raw material particle size for photovoltaic glass production, the applicant provides a reasonable and effective process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings, which is a highly efficient mineral processing technology that can achieve iron content control and particle size compliance.

[0005] The technical solution adopted in this invention is as follows:

[0006] A process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings includes the following steps: Step S1, feeding the lepidolite flotation tailings obtained in the main lepidolite beneficiation process into a high-frequency screen for pre-screening; Step S2, feeding the undersize material obtained in Step S1 into a 120-mesh cylindrical screen for precise screening, wherein the inclination angle and rotation speed of the cylindrical screen are controlled at 4°-6° and 10-16 rpm, respectively, the feed concentration is maintained within the range of 20%-25%, and the oversize material is at -140°. The content of the material is 17-25%; Step S3: Control the material oversize from the cylindrical screen in Step S2 to enter the hydrocyclone for classification, and this overflow is the feldspar product; Step S4: Feed the classified sand product from the underflow in Step S3 into the slurry mixing tank, and maintain the slurry concentration in the mixing tank to 38-40% by adding water, and add lepidolite collector to adjust the slurry so that the flotation reagents and slurry are fully mixed; Step S5: Feed the fully mixed slurry from Step S4 into the roughing operation, and the froth product... The product is lepidolite rough concentrate; in step S6, the tailings from the roughing operation in step S5 are fed into the scavenging operation for 6-8 minutes, and the froth product is the scavenging concentrate product, which is then added to the lepidolite rough concentrate product; in step S7, the material from the high-frequency screen in step S1 and all the lepidolite rough concentrate product from step S6 are fed into the grinding system of the main lepidolite beneficiation process for regrinding, with the grinding fineness controlled to be greater than 95% at -60 mesh; in step S8, the scavenging operation in step S6... The tailings are fed into the magnetic separation process to remove mechanically mixed iron and obtain weakly magnetic and non-magnetic materials; in step S9, the weakly magnetic and non-magnetic materials from step S8 are fed into high-gradient magnetic separation to remove secondary iron and obtain low-iron photovoltaic feldspar products; in step S10, the material regrinded by the grinding system in step S7 enters the flotation process of the lepidolite beneficiation main process to recover lepidolite concentrate; in step S11, the slender feldspar obtained in steps S2 and S3 is incorporated into the filtration system to obtain the final slender feldspar product.

[0007] As a further improvement to the above technical solution:

[0008] In step S1, a 0.4×0.4mm high-frequency screen is used, the feed concentration is controlled within the range of 25%-30%, the vibration frequency and amplitude are controlled at 1080-1500 times / minute and 3-5mm respectively, to ensure that the content of -70 mesh under the screen is not less than 90%.

[0009] In step S3, the hydrocyclone adopts a tangential feeding method, the feeding pressure is controlled at 0.8-0.12MPa, the feeding concentration is 15%-20%, the overflow port and underflow port diameters are 80-100mm and 40-45mm respectively, the overflow removes -200 mesh, and the yield is 5-8%.

[0010] In step S5, the roughing process takes 8-12 minutes, the flotation machine speed is 1800-1930 rpm, and the aeration rate is 0.4-0.6 m³ / min.3 / minute, with flotation temperature controlled at 18-25℃.

[0011] The flotation process in steps S5 and S6 adopts the following: flotation concentration 40%, rougher adding 400g / t of collector and 8g / t of polyacrylamide, scavenger adding 200g / t of collector; rougher adding 8 minutes of skimming and foaming, scavenger adding 6 minutes of skimming and foaming.

[0012] Step S7 further includes: Step S7-1, the material from the high-frequency screen in Step S1 and all the lepidolite rough concentrate product from Step S6 are fed into a first-stage hydrocyclone. The overflow product from the first-stage hydrocyclone is fed into a second-stage hydrocyclone. The overflow product from the second-stage hydrocyclone is feldspar product, and the underflow product is fed into Step S7-2 for processing. Step S7-2, the underflow product from the first-stage hydrocyclone in Step S7-1 passes through a first-stage rod mill and then enters a spiral classifier. The underflow return sand from the spiral classifier enters the second-stage rod mill and then enters Step S7-3. The overflow product from the spiral classifier enters the second-stage rod mill. The cyclone separator, spiral classifier, and hydrocyclone are used together for grinding and classification. In step S7-3, the underflow sediment from the spiral classifier in step S7-2 passes through the rod mill and enters the high-frequency vibrating screen. The underflow product from the high-frequency vibrating screen enters the second-stage cyclone separator, and the overflow product returns to the first-stage rod mill in step S7-2 for further processing. In step S7-4, the second-stage cyclone separator collects the overflow product from the first-stage cyclone separator in step S7-1, the overflow from the spiral classifier in step S7-2, and the underflow product from the high-frequency vibrating screen in step S7-3, and then proceeds to step S10 for further processing.

[0013] In the magnetic separation operation of step S8, weak magnetic separation is carried out by a wet permanent magnet drum magnetic separator with a magnetic field strength of 800-1500 Gauss, a feed concentration of 25%-30%, and a rotation speed of 28-32 revolutions per minute.

[0014] In step S9, the magnetic field strength of the high gradient magnetic separation is 12000-15000 Gauss, the feed concentration is 20%-25%, a mesh matrix with a gap of 2.5-3.0mm is used, and the washing water pressure is 0.2-0.25MPa.

[0015] Step S9 further includes: the magnetic separation product obtained by the high gradient magnetic separator in step S9 is fed into a magnetic hydrocyclone, and the dewatered product of the magnetic hydrocyclone is returned to step S7 and processed by the grinding system before entering the main process of lithium mica beneficiation.

[0016] Step S10 further includes: Step S10-1, the product obtained after regrinding in the grinding system in Step S10 is fed into a flotation mixing tank, flotation collector and depressant are added, and the reagents are thoroughly mixed with the slurry before entering the roughing operation. The froth product is the lepidolite roughing concentrate product, and the other part is the roughing tailings product; Step S10-2, the roughing concentrate product from Step S10-1 is fed into the cleaning operation I. The froth product is the cleaning concentrate product of Cleaning Operation I, and the other part is the middlings product of Cleaning Operation I; Step S10-3, the cleaning concentrate product from Step S10-2 is further fed into the cleaning operation II. The froth product is the lepidolite concentrate product, and the other part is the middlings product of Cleaning Operation II; Step S10-4, the middlings product of Cleaning Operation II from Step S10-3 is mixed with the middlings product from Step S10-1. The rougher and intermediate concentrate products are combined for finer separation I, forming a closed-loop operation; in step S10-5, the rougher and intermediate tailings from step S10-1 are fed back into scavenging I, resulting in frothy product as scavenging I middlings and another portion as scavenging I tailings; in step S10-6, the scavenging I concentrate obtained in step S10-5 and the finer separation I middlings obtained in step S10-2 are combined and fed back into the rougher operation, forming a large closed-loop flotation system; in step S10-7, the scavenging I tailings obtained in step S10-5 are fed back into scavenging II, resulting in frothy product as scavenging II concentrate and another portion as fine feldspar product; in step S10-8, the scavenging II concentrate obtained in step S10-7 and the rougher and intermediate tailings from step S10-1 are combined for scavenging I.

[0017] The low-iron photovoltaic feldspar product produced in step S9 contains less than 150 ppm of Fe2O3 and has a fineness of less than 20% (-140 mesh).

[0018] The beneficial effects of this invention are as follows:

[0019] (1) This invention employs a multi-stage screening process combined with flotation and magnetic separation to specifically treat iron minerals in different occurrence states. High-frequency screening, cylindrical screen and hydrocyclone classification create favorable conditions for flotation and magnetic separation. Flotation removes iron from lepidolite, and two-stage magnetic separation removes mechanical iron and secondary iron. The final product Fe2O3 content is stably controlled below 150ppm.

[0020] (2) This invention optimizes screening parameters to ensure that the -140 mesh content is controlled within 20%. The optimization of the inclination angle and rotation speed of the cylindrical screen improves the classification accuracy, and in conjunction with the de-finement effect of the hydrocyclone, it improves the particle size distribution of the magnetically selected material and ensures the stability of the final product particle size.

[0021] (3) This invention adopts a combined process of screening-flotation-magnetic separation, which reduces the number of steps and lowers production costs. The parameters of each process are optimized and well coordinated, ensuring a stable and controllable production process, simple operation, and ease of industrial production.

[0022] (4) This invention reduces mineral loss at each stage through precise classification control. The material over the high-frequency screen and the flotation foam concentrate can be recycled and reprocessed, and the material under the cylindrical screen overflowing from the hydrocyclone can be used as a fine feldspar product, thereby improving the efficiency of comprehensive resource utilization.

[0023] (5) This invention employs a combination of spiral classifiers and hydrocyclones for grinding and classification, with two sets of hydrocyclones used for particle size control. Through technological innovation in the use of spiral classifiers, hydrocyclones, and high-frequency vibrating screens, the particle size of the grinding product is guaranteed, providing favorable conditions for the subsequent flotation of lepidolite. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process flow of the present invention.

[0025] Figure 2 This is a schematic diagram of one embodiment of step S7 of the present invention. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] Reference Figure 1 As shown, Figure 1 The lepidolite beneficiation main process shown is a component of the lepidolite beneficiation technology. This lepidolite beneficiation technology obtains lepidolite flotation tailings through a flotation process. The specific technical solution of the process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings described in this invention includes the following steps:

[0028] Step S1: The lepidolite flotation tailings obtained from the main lepidolite beneficiation process are fed into a high-frequency screen for pre-screening. This step uses a 0.4×0.4mm high-frequency screen, with the feed concentration controlled within the range of 25%-30%, and the vibration frequency and amplitude controlled within 1080-1500 times / minute and 3-5mm, respectively, to ensure that the content of -70 mesh under the screen is not less than 90%.

[0029] In step S2, the material undersize from the high-frequency screen obtained in step S1 is then fed into a 120-mesh cylindrical screen for precise screening. The inclination angle and rotation speed of the cylindrical screen are controlled at 4°-6° and 10-16 rpm, respectively. The feed concentration is maintained in the range of 20%-25%. The content of the material on the screen (-140 mesh) is 17-25%, and the undersize material is a fine feldspar product.

[0030] Step S3: Control the material on the cylindrical screen in step S2 to enter the 250-type hydrocyclone for classification. The hydrocyclone adopts tangential feeding, the feeding pressure is controlled at 0.8-0.12MPa, the feeding concentration is 15%-20%, the overflow port and the underflow port diameter are 80-100mm and 40-45mm respectively, the overflow removes part of -200 mesh, the yield is 5-8%, and this overflow is fine feldspar product.

[0031] Step S4: The graded sand product from the underflow in step S3 is fed into the slurry mixing tank. Water is added to maintain the slurry concentration in the mixing tank at 38-40%. Lithium mica collector is added to adjust the slurry and ensure that the flotation reagents are fully mixed with the slurry.

[0032] Step S5: The thoroughly mixed slurry from step S4 is fed into the roughing process, where the roughing time is 8-12 minutes, the flotation machine speed is 1800-1930 rpm, and the aeration rate is 0.4-0.6 m³ / min. 3 The flotation rate is 1 / minute, the flotation temperature is controlled at 18-25℃, and the froth product is a lepidolite rough concentrate product.

[0033] Step S6: The tailings from the roughing operation in step S5 are fed into the scavenging operation for 6-12 minutes. The frothy product is the scavenging concentrate product and is added to the lepidolite rough concentrate product.

[0034] Step S7: The material from the high-frequency screen in step S1 and all the lithium mica rough concentrate products from step S6 are fed into the grinding system of the main lithium mica beneficiation process for regrinding. The grinding fineness is controlled to be greater than 95% at -60 mesh.

[0035] Optionally, refer to Figure 2 As shown, step S7 further includes:

[0036] Step S7-1: The material on the high-frequency screen in step S1 and all the lepidolite rough concentrate products in step S6 are fed into a first-stage hydrocyclone. The overflow product of the first-stage hydrocyclone is fed into a second-stage hydrocyclone. The overflow product of the second-stage hydrocyclone is feldspar product. The underflow product is fed into step S7-2 for operation.

[0037] In step S7-2, the underflow product of the first-stage hydrocyclone in step S7-1 enters the spiral classifier after passing through the first-stage rod mill. The underflow return sand of the spiral classifier enters the second-stage rod mill and then enters step S7-3. The overflow product of the spiral classifier enters the second-stage hydrocyclone. The spiral classifier and the hydrocyclone are used together for grinding and classification.

[0038] In step S7-3, the underflow sediment from the spiral classifier in step S7-2 enters the high-frequency vibrating screen after passing through the rod mill. The underflow product from the high-frequency vibrating screen enters the second-stage hydrocyclone, while the overflow product returns to the first-stage rod mill in step S7-2 for further processing.

[0039] In step S7-4, the two-stage hydrocyclone collects the overflow product from the first-stage hydrocyclone in step S7-1, the overflow from the spiral classifier in step S7-2, and the product screened by the high-frequency vibrating screen in step S7-3, and then proceeds to step S10 for further operation.

[0040] This invention employs a spiral classifier and a hydrocyclone in combination for grinding and classification. Two sets of hydrocyclones control particle size. Through technological innovation in these three devices—spiral classifier, hydrocyclone, and high-frequency vibrating screen—the particle size of the grinding product is guaranteed, providing favorable conditions for the subsequent flotation of lepidolite. By changing the combination of these three grinding and classification devices—spiral classifier, hydrocyclone, and high-frequency vibrating screen—the optimal state of the grinding system is achieved, thereby improving the grade of lepidolite concentrate and increasing production efficiency.

[0041] Step S8: The tailings from the scavenging operation in step S6 are fed into the magnetic separation operation. The tailings are subjected to weak magnetic separation by a wet permanent magnet drum magnetic separator with a magnetic field strength of 800-1500 Gauss, a feed concentration of 25%-30%, and a rotation speed of 28-32 rpm. Mechanically mixed iron is removed to obtain weakly magnetic and non-magnetic materials.

[0042] In step S9, the weakly magnetic and non-magnetic materials from step S8 are fed back into a high-gradient magnetic separator for high-gradient magnetic separation. The magnetic field strength is 12000-15000 Gauss, the feed concentration is 20%-25%, a mesh matrix with a gap of 2.5-3.0mm is used, and the washing water pressure is 0.2-0.25MPa to remove secondary iron and obtain high-quality low-iron photovoltaic feldspar products.

[0043] Optionally, step S9 further includes: the magnetically separated product obtained by the high-gradient magnetic separator in step S9 is fed into a magnetic hydrocyclone, and the dewatered product from the magnetic hydrocyclone is returned to step S7 for processing by the grinding system before entering the main process of lithium mica beneficiation.

[0044] In steps S10 and S7, the material regrinded by the grinding system enters the flotation process of the main lithium mica beneficiation process to recover lithium mica concentrate.

[0045] Optionally, step S10 further includes:

[0046] Step S10-1: The product obtained after regrinding in the grinding system in step S10 is put into the flotation mixing tank, flotation collector and depressant are added, and the reagents are thoroughly mixed with the slurry before entering the roughing operation. The froth product is the lepidolite roughing concentrate product, and the other part is the roughing tailings product.

[0047] Step S10-2: The roughing concentrate product from step S10-1 is fed into the fine cleaning I operation. The foam product is the fine cleaning I concentrate product, and the other part is the fine cleaning I middlings product.

[0048] Step S10-3: The concentrate product from step S10-2 is fed into the finer process II. The foam product is lepidolite concentrate product, and the other part is the middlings product from finer process II.

[0049] Step S10-4: Combine the mineral products from the finer II process in step S10-3 with the rougher concentrate products from step S10-1 for finer I process, forming a closed-loop operation;

[0050] Step S10-5: The roughing tailings from step S10-1 are fed into the scavenging I operation to obtain the foam product as the middlings product of scavenging I, and the other part as the tailings product of scavenging I.

[0051] Step S10-6: The scavenging concentrate product obtained in step S10-5 and the middlings product obtained in step S10-2 are combined and returned to the roughing operation to form a large closed-loop flotation system.

[0052] Step S10-7: The tailings product obtained from step S10-5 is fed to the scavenging II operation to obtain foam product as the scavenging II concentrate product, and another part as slender feldspar product.

[0053] In steps S10-8 and S10-7, the scavenging II concentrate product and the roughing tailings product from step S10-1 are combined for scavenging I operation.

[0054] Step S11: The slender stones obtained in steps S2 and S3 are incorporated into the filtration system to obtain the final slender stone product.

[0055] The present invention provides a process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings. Through the organic combination of multi-stage screening and grading with flotation and magnetic separation, precise control of the iron content and particle size of the product is achieved. The final low-iron photovoltaic feldspar product of this invention contains less than 150 ppm Fe2O3 and has a fineness of less than 20% (-140 mesh).

[0056] In step S1, high-frequency vibration effectively prevents screen clogging, improves screening efficiency, and ensures that the content of -70 mesh material under the screen is not less than 90%, while the material over the screen is returned to the lepidolite flotation process. The purpose of high-frequency screening is to remove insufficiently dissociated coarse particles, creating conditions for subsequent separation.

[0057] In step S2, by adjusting the inclination angle and rotation speed of the cylindrical screen, the rolling and sieving action of the material within the screen achieves precise material classification, controlling the -140 mesh content of the oversize material to be below 20%, while the undersize material is fed into the hydrocyclone. Appropriate feed concentration prevents screen clogging, ensures effective classification, and lays the foundation for the final product's particle size distribution.

[0058] In step S3, centrifugal force is used to separate particles, removing some of the -200 mesh material. At the same time, the subsequent flotation concentration is controlled to maintain the underflow concentration at 45%-50%. The optimization of the hydrocyclone's structural and operating parameters achieves both the removal of -200 mesh sludge and the control of the flotation concentration.

[0059] In steps S4-S6 and S7-S9, the high-concentration flotation and thorough stirring in the stirred tank ensured effective contact between the reagent and the mineral surface, and the flotation process parameters improved the separation effect of embedded iron. The two-stage magnetic separation adopted progressive magnetic field strength to specifically treat iron in different occurrence states. Reasonable feed concentration and equipment parameter optimization ensured the magnetic separation effect.

[0060] To verify the effectiveness of the present invention and to seek the optimal process conditions in the flotation process of steps S5 and S6, the process method of the present invention was subjected to the following six groups of experiments, from #1 to #6, as shown in Table 1.

[0061] Table 1

[0062]

[0063] In Group 1, the following process was used: sieving through a sieve of -45 mesh and 160 mesh, resulting in a material with a -140 mesh content of 17.75%. This material was then subjected to a roughing and scavenging flotation process with a flotation concentration of 38%. 400 g / t of collector (6-1-A) was added to the roughing process, and 200 g / t of collector was added to the scavenging process. The roughing process involved skimming bubbles for 4 minutes, and the scavenging process involved skimming bubbles for 3 minutes.

[0064] The test of Group 2 adopted the following method: sieve -45 mesh + 160 mesh, the proportion of the material with -140 mesh is 17.75%. This material is then subjected to a roughing and scavenging flotation process with a flotation concentration of 40%. 400g / t of collector (6-1-A) is added to the roughing process and 200g / t of collector is added to the scavenging process. The roughing process is skimmed for 4 minutes and the scavenging process is skimmed for 3 minutes.

[0065] The experiment of Group 3 adopted the following method: sieve -45 mesh + 160 mesh, the proportion of -140 mesh in the obtained material was 17.75%. This material was then subjected to a roughing and scavenging flotation process with a flotation concentration of 40%. 400g / t of collector (KX-236) was added to the roughing process and 200g / t of collector was added to the scavenging process. The roughing process was skimmed for 4 minutes and the scavenging process was skimmed for 3 minutes.

[0066] The test of Group 4 adopted the following method: sieve -45 mesh + 160 mesh, the resulting material with a -140 mesh ratio of 17.75% was subjected to a roughing and scavenging flotation process with a flotation concentration of 40%. The roughing process added 400g / t of collector (6-1-A) and 8g / t of polyacrylamide (PAM), and the scavenging process added 200g / t of reagent. The roughing process was followed by 4 minutes of skimming and 3 minutes of skimming and scavenging.

[0067] The experiment of Group 5 adopted the following method: sieving -45 mesh + 160 mesh, the resulting material with -140 mesh accounted for 17.75%. This material was then subjected to a roughing and scavenging flotation process with a flotation concentration of 38%. 450g / t of collector (6-1-A) was added to the roughing process, and 150g / t of collector was added to the scavenging process. The roughing process was followed by 5 minutes of skimming and 3 minutes of skimming.

[0068] The experiment of Group 6 adopted the following method: sieve -45 mesh + 160 mesh, the proportion of -140 mesh in the obtained material was 17.75%. This material was then subjected to a roughing and scavenging flotation process with a flotation concentration of 38%. The roughing was done with 450g / t of collector (6-1-A) and 8g / t of polyacrylamide (PAM), and the scavenging was done with 150g / t of reagent. The roughing was done by scraping and soaking for 5 minutes, and the scavenging was done by scraping and soaking for 3 minutes.

[0069] The test results from groups 1 to 6 show that the -140 mesh content of this invention is controlled within 20%, and the Fe2O3 content of the product is stably controlled below 150 ppm. The optimized effect is stable, and the flotation process conditions used in group 4 are the optimal group. Based on actual production conditions, the optimal flotation time for industrial production is generally adjusted to twice the flotation time in the tests. Therefore, the flotation time in the above tests is adjusted to twice the value in actual production.

[0070] This invention employs a multi-stage screening process combined with flotation and magnetic separation to specifically treat iron minerals in different occurrence states. High-frequency screening, cylindrical sieves, and hydrocyclones create favorable conditions for flotation and magnetic separation. Flotation removes iron from lepidolite, while two-stage magnetic separation removes mechanical and secondary iron. The final product's Fe2O3 content is consistently controlled below 150 ppm.

[0071] This invention optimizes screening parameters to ensure that the -140 mesh content is controlled within 20%. Optimization of the cylindrical screen's inclination angle and rotation speed improves classification accuracy, and combined with the de-finement effect of the hydrocyclone, it improves the particle size distribution of the magnetically selected material, ensuring stable particle size of the final product.

[0072] This invention employs a combined process of screening, flotation, and magnetic separation, reducing steps and lowering production costs. The optimized parameters of each process ensure smooth coordination, guaranteeing a stable and controllable production process that is easy to operate and readily suitable for industrial production.

[0073] This invention reduces mineral loss at each stage through precise classification control. Materials overlying from the high-frequency screen and flotation froth concentrate can be recycled and reprocessed, while materials underlying from the cylindrical screen overflowing from the hydrocyclone can be used as fine feldspar products, thus improving the efficiency of comprehensive resource utilization.

[0074] 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 preparing low-iron photovoltaic feldspar from lepidolite flotation tailings, characterized in that: The process includes the following steps: Step S1, feeding the lepidolite flotation tailings obtained from the main lepidolite beneficiation process into a high-frequency screen for pre-screening; Step S2, feeding the undersize material from the high-frequency screen obtained in Step S1 into a 120-mesh cylindrical screen for precise screening, with the inclination angle and rotation speed of the cylindrical screen controlled at 4°-6° and 10-16 rpm respectively, and the feed concentration maintained within the range of 20%-25%, and the oversize material having a -140 mesh content of 17-25%; Step S3, controlling the oversize material from the cylindrical screen in Step S2 to enter a hydrocyclone for classification, with the overflow being a fine feldspar product; Step S4, feeding the underflow classified sediment product from Step S3 into a slurry mixing tank, maintaining the slurry concentration in the mixing tank to 38-40% by adding water, and adding lepidolite collector to adjust the slurry, ensuring thorough mixing of the flotation reagents and the slurry; Step S5, feeding the thoroughly mixed slurry from Step S4 into the roughing stage. In the process, the foam product is the lepidolite rough concentrate product; in step S6, the tailings from the roughing operation in step S5 are fed into the scavenging operation for 6-8 minutes, and the foam product is the scavenging concentrate product, which is then added to the lepidolite rough concentrate product; in step S7, the material from the high-frequency screen in step S1 and all the lepidolite rough concentrate products from step S6 are fed into the grinding system of the main lepidolite beneficiation process for regrinding, with the grinding fineness controlled to be greater than 95% at -60 mesh; in step S8, the tailings from the scavenging operation in step S6 are fed into the magnetic separation operation to remove mechanically mixed iron, resulting in weakly magnetic and non-magnetic materials; in step S9, the weakly magnetic and non-magnetic materials from step S8 are fed into high-gradient magnetic separation to remove secondary iron, resulting in low-iron photovoltaic feldspar products; in step S10, the material regrinded by the grinding system in step S7 enters the flotation process of the main lepidolite beneficiation process to recover lepidolite concentrate. Step S11: The granulated feldspar obtained in steps S2 and S3 is incorporated into the filtration system to obtain the final granulated feldspar product. Step S7 further includes: Step S7-1: The material overpass from the high-frequency screen in step S1 and all the lepidolite rough concentrate product from step S6 are fed into a first-stage hydrocyclone. The overflow product from the first-stage hydrocyclone is fed into a second-stage hydrocyclone. The overflow product from the second-stage hydrocyclone is the granulated feldspar product, and the underflow product is fed into step S7-2. Step S7-2: The underflow product from the first-stage hydrocyclone in step S7-1 passes through a first-stage rod mill and then enters a spiral classifier. The underflow return sand from the spiral classifier enters the second-stage rod mill and then enters step S7-2. In step S7-3, the overflow product of the spiral classifier enters the second-stage hydrocyclone. The spiral classifier and the hydrocyclone are used together for grinding and classification. In step S7-3, the underflow sediment from the spiral classifier in step S7-2 passes through the rod mill and enters the high-frequency vibrating screen. The underflow product from the high-frequency vibrating screen enters the second-stage hydrocyclone, and the overflow product returns to the first-stage rod mill in step S7-2 for further processing. In step S7-4, the second-stage hydrocyclone collects the overflow product from the first-stage hydrocyclone in step S7-1, the overflow from the spiral classifier in step S7-2, and the underflow product from the high-frequency vibrating screen in step S7-3, and then proceeds to step S10 for further processing.

2. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: In step S1, a 0.4×0.4mm high-frequency screen is used, the feed concentration is controlled within the range of 25%-30%, the vibration frequency and amplitude are controlled at 1080-1500 times / minute and 3-5mm respectively, to ensure that the content of -70 mesh under the screen is not less than 90%.

3. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: In step S3, the hydrocyclone adopts a tangential feeding method, the feeding pressure is controlled at 0.8-0.12MPa, the feeding concentration is 15%-20%, the overflow port and underflow port diameters are 80-100mm and 40-45mm respectively, the overflow removes -200 mesh, and the yield is 5-8%.

4. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: In step S5, the roughing operation takes 8-12 minutes, the flotation machine speed is 1800-1930 rpm, the aeration rate is 0.4-0.6 m³ / min, and the flotation temperature is controlled at 18-25℃.

5. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: The flotation process in steps S5 and S6 adopts the following: flotation concentration 40%, rougher adding 400g / t of collector and 8g / t of polyacrylamide, scavenger adding 200g / t of collector; rougher adding 8 minutes of skimming and foaming, scavenger adding 6 minutes of skimming and foaming.

6. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: In the magnetic separation operation of step S8, weak magnetic separation is carried out by a wet permanent magnet drum magnetic separator with a magnetic field strength of 800-1500 Gauss, a feed concentration of 25%-30%, and a rotation speed of 28-32 revolutions per minute.

7. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: In step S9, the magnetic field strength of the high gradient magnetic separation is 12000-15000 Gauss, the feed concentration is 20%-25%, a mesh matrix with a gap of 2.5-3.0mm is used, and the washing water pressure is 0.2-0.25MPa.

8. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: Step S9 further includes: the magnetic separation product obtained by the high gradient magnetic separator in step S9 is fed into a magnetic hydrocyclone, and the dewatered product of the magnetic hydrocyclone is returned to step S7 and processed by the grinding system before entering the main process of lithium mica beneficiation.

9. The process for preparing low-iron photovoltaic feldspar from lepidolite flotation tailings according to claim 1, characterized in that: Step S10 further includes: Step S10-1, the product obtained after regrinding in the grinding system in Step S10 is fed into a flotation mixing tank, flotation collector and depressant are added, and the reagents are thoroughly mixed with the slurry before entering the roughing operation. The froth product is the lepidolite roughing concentrate product, and the other part is the roughing tailings product; Step S10-2, the roughing concentrate product from Step S10-1 is fed into the cleaning operation I. The froth product is the cleaning concentrate product of Cleaning Operation I, and the other part is the middlings product of Cleaning Operation I; Step S10-3, the cleaning concentrate product from Step S10-2 is further fed into the cleaning operation II. The froth product is the lepidolite concentrate product, and the other part is the middlings product of Cleaning Operation II; Step S10-4, the middlings product of Cleaning Operation II from Step S10-3 is mixed with the middlings product from Step S10-1. The rougher and intermediate concentrate products are combined for finer separation I, forming a closed-loop operation; in step S10-5, the rougher and intermediate tailings from step S10-1 are fed back into scavenging I, resulting in frothy product as scavenging I middlings and another portion as scavenging I tailings; in step S10-6, the scavenging I concentrate obtained in step S10-5 and the finer separation I middlings obtained in step S10-2 are combined and fed back into the rougher operation, forming a large closed-loop flotation system; in step S10-7, the scavenging I tailings obtained in step S10-5 are fed back into scavenging II, resulting in frothy product as scavenging II concentrate and another portion as fine feldspar product; in step S10-8, the scavenging II concentrate obtained in step S10-7 and the rougher and intermediate tailings from step S10-1 are combined for scavenging I.

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