Method for reducing calcium in metallurgical grade fluorite concentrate by strong magnetic-flotation combination

Abstract

The application discloses a method for reducing calcium in metallurgical grade fluorite concentrate by strong magnetic-flotation combination, and belongs to the technical field of mineral processing. For the metallurgical grade fluorite concentrate with CaF2 grade of 70-75% and CaCO3 content of 15-20%, the application first divides the raw material into non-magnetic products (yield of 80%±2%) and magnetic products through strong magnetic preselection, then carries out flotation calcium reduction on the non-magnetic products, and carries out regrinding and reselection on the magnetic products to recover fluorite. Through the quality separation and flow separation process of "strong magnetic preselection-non-magnetic product flotation calcium reduction-magnetic product regrinding and reselection", the technical problem of poor flotation selectivity of calcium-containing gangue and fluorite with similar properties is solved. Through pilot test verification, the fluorite concentrate with CaF2 grade of greater than or equal to 91%, CaCO3 content of less than or equal to 5.5% and comprehensive recovery rate of greater than or equal to 83% can be finally obtained, the upgrading and utilization of the metallurgical grade fluorite concentrate to the chemical grade fluorite concentrate is realized, and the added value of the fluorite resource is significantly improved.

Description

Technical Field

[0001] This invention belongs to the technical field of mineral processing, specifically relating to a method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and flotation. Background Technology

[0002] Fluorite (CaF2), a strategic mineral resource in China, is widely used in traditional fields such as metallurgy, chemicals, building materials, and optics. In recent years, it has become an indispensable source of fluorine for strategic emerging industries such as new energy and new materials. Although my country has abundant fluorite reserves, associated fluorite deposits account for more than 70% of the total reserves. After beneficiation with tungsten and other polymetallic minerals, the tailings contain large amounts of calcite, garnet, apatite, and other calcium-bearing gangue minerals with properties very similar to fluorite, making separation extremely difficult. Currently, only a few mines, such as Shizhuyuan in Hunan Province, have achieved comprehensive recovery of fluorite resources, and the concentrate products are mainly metallurgical-grade fluorite concentrate (CaF2 grade 70%~75%, CaCO3 content 15%~20%), mainly used as a flux in iron and steel smelting, with low added value.

[0003] Existing technologies have reported processes for calcium removal in fluorite beneficiation. For example, CN1285243A discloses a process for calcium removal in fluorite beneficiation, using oleic acid or its substitute as a collector for roughing and a mixture of sulfuric acid and acidic water glass as a depressant for calcium-bearing minerals. Calcium removal is achieved through a single roughing and multiple cleaning operations, yielding fluorite concentrate with lower calcium carbonate content from high-calcium fluorite ore. However, this process is designed for fluorite ore with a relatively high grade. For metallurgical-grade fluorite concentrate (CaF2 70%~75%) with a certain grade, the calcium-bearing gangue is tightly embedded with the fluorite, making efficient separation difficult using conventional flotation processes.

[0004] Another technical solution employs a combined flotation and high-intensity magnetic separation process to improve the quality of fluorite concentrate. For example, the method disclosed in CN115739403A removes some impurities through flotation and then performs high-gradient magnetic separation on the product in the flotation cell, yielding fluorite concentrate with a CaF2 grade of 98.55% and a CaCO3 content of 0.52%. However, this process involves flotation followed by magnetic separation. For metallurgical-grade concentrates with high magnetic mineral content, the loss of fluorite in the magnetic separation tailings is significant, limiting the overall recovery rate.

[0005] To address the technical challenges of improving the quality and reducing calcium content of metallurgical grade fluorite concentrate (CaF2 grade 70%~75%, CaCO3 content 15%~20%), the existing technologies have the following shortcomings: (1) Calcium-containing gangue has similar surface properties to fluorite, resulting in poor flotation selectivity and making it difficult for conventional inhibitor systems to achieve efficient removal of calcium carbonate; (2) The process combination sequence of magnetic separation and flotation is inappropriate, with flotation followed by magnetic separation leading to the inability to effectively recover fluorite from the magnetic products; (3) There is a lack of a differentiated treatment strategy for calcium-containing gangue with different embedding states in metallurgical grade concentrate, making it difficult to balance concentrate grade and recovery rate. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for reducing calcium content in metallurgical grade fluorite concentrate by strong magnetic flotation in order to solve the problems mentioned in the background art or achieve better technical effects.

[0007] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention. This invention discloses a method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and precipitation, wherein the metallurgical grade fluorite concentrate has a CaF2 grade of 70%~75% and a CaCO3 content of 15%~20%; the method includes the following steps:

[0008] S1: Metallurgical grade fluorite concentrate is subjected to high-gradient magnetic separation to obtain non-magnetic and magnetic products, with the yield of non-magnetic products controlled at 78-82%;

[0009] S2: The non-magnetic product obtained in S1 is subjected to flotation. The flotation includes 1 to 2 roughing stages and 3 to 4 cleaning stages. The roughing pH is 8.5 to 10, and the inhibitor dosage is 425 to 1100 g / t of raw ore.

[0010] S3: The magnetic product obtained in S1 is regrinded and then floated. The resulting concentrate is combined with the concentrate obtained in step S2 to form the final fluorite concentrate.

[0011] Furthermore, in S1, the magnetic field strength of the strong magnetic separation is 0.8~1.2T; the CaF2 grade of the non-magnetic product is ≥89%, and the CaCO3 content is ≤5.5%; the CaF2 grade of the magnetic product is 55%~65%.

[0012] Furthermore, in S2, the coarse pH is 9.5.

[0013] Further, in S2, the roughing conditions are: water glass dosage 200~600g / t·raw ore, soda ash dosage 500~800g / t·raw ore, inhibitor dosage 100~300g / t·raw ore, and collector dosage 200~400g / t·raw ore.

[0014] Furthermore, in S2, the selection is carried out 3 times; the inhibitor dosages are as follows: 100~200g / t·raw ore for the first time, 50~150g / t·raw ore for the second time, and 75~150g / t·raw ore for the third time.

[0015] Furthermore, in step S3, the grinding fineness of the regrinding process is -0.074 mm, accounting for 80% to 95%.

[0016] Furthermore, in S3, the flotation of the magnetic product includes one roughing process and three cleaning processes;

[0017] The roughing conditions are as follows: collector dosage 400~600g / t·raw ore, inhibitor dosage 100~300g / t·raw ore, sodium carbonate dosage 500~800g / t·raw ore, and water glass dosage 600~1000g / t·raw ore.

[0018] The inhibitor dosages for the three selection processes were as follows: 100-200 g / t of raw ore for the first time, 100-150 g / t of raw ore for the second time, and 50-150 g / t of raw ore for the third time.

[0019] Furthermore, the inhibitor is an organophosphonic acid inhibitor that selectively inhibits calcium gangue.

[0020] Furthermore, the collector is a fatty acid collector that selectively collects fluorite.

[0021] Furthermore, the final fluorite concentrate has a CaF2 grade of ≥91%, a CaCO3 content of ≤5.5%, and a CaF2 comprehensive recovery rate of ≥83%.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) This invention first divides metallurgical grade fluorite concentrate into non-magnetic products (mainly fluorite and non-magnetic calcium-containing gangue) and magnetic products (mainly magnetic calcium-containing gangue) according to magnetic differences through "strong magnetic pre-selection". This realizes the separate processing of calcium-containing gangue, solves the technical problem of mutual interference and poor selectivity of different types of calcium-containing gangue in the traditional single flotation process, and reduces the CaCO3 content of non-magnetic product flotation feed from 15%~20% to ≤5.5%, which greatly reduces the difficulty of flotation decalcification.

[0024] (2) This invention achieves effective recovery of fluorite from magnetic products by regrinding and reselecting them, overcoming the defect of severe fluorite loss in existing flotation-following magnetic separation processes. After regrinding, the fluorite is fully liberated from the magnetic gangue, and flotation can then yield fluorite concentrate with a grade of ≥87%, increasing the overall recovery rate by more than 8%.

[0025] (3) By strictly controlling key parameters such as the yield distribution of strong magnetic separation (80%±2%), flotation pH (8.5~10) and inhibitor dosage (425~1100g / t·raw ore), this invention achieves synergistic optimization of concentrate grade and recovery rate, and successfully prepares chemical grade fluorite concentrate from low value-added metallurgical grade fluorite concentrate, significantly improving the utilization value of fluorite resources.

[0026] (4) This invention has been verified by a large number of experiments. The content of magnetic calcium gangue in metallurgical grade fluorite concentrate is about 15% to 25%, and the content of non-magnetic fluorite and non-magnetic gangue is about 75% to 85%. When the yield of non-magnetic products is less than 75%, some fluorite is lost in the magnetic products due to its association with magnetic gangue, resulting in a decrease in the total recovery rate of 5% to 10%. When the yield of non-magnetic products is higher than 85%, the amount of non-magnetic calcium gangue mixed in the magnetic products increases, resulting in an increase in the CaCO3 content of the flotation feed by 1% to 2%.

[0027] (5) The present invention found through surface electrical properties measurement that when pH < 8.5, the surface potential difference between fluorite and calcium-containing gangue such as calcite is small, and the selective adsorption capacity of the collector is poor; when pH > 10, the surface of fluorite is overcharged, the adsorption amount of the collector decreases, resulting in over-floating and a decrease in recovery rate. When pH = 9.5, the surface electrical properties of fluorite and calcium-containing gangue are the greatest, and optimal selective separation can be achieved.

[0028] (6) By limiting the dosage of inhibitor to 425~1100g / t·raw ore, the calcium carbonate content in metallurgical grade fluorite concentrate is as high as 15%~20%, which is much higher than that of conventional fluorite flotation feed. A higher dosage of inhibitor is required to effectively suppress the flotation of calcium gangue.

[0029] (7) The method of the present invention has a clear process route, is easy to operate, and has strong industrial adaptability. It has wide applicability to the processing of metallurgical grade fluorite concentrate produced by the beneficiation of associated fluorite ore, and has good economic benefits and prospects for promotion and application. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation. Detailed Implementation

[0031] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0032] Unless otherwise specified, all raw materials or reagents used in the following examples are commercially available products.

[0033] This invention uses a SLon-500T vertical ring pulsating high gradient magnetic separator to perform strong magnetic separation on the processed mineral sample, with a magnetic field strength of 0.8~1.2T.

[0034] This invention, through extensive experimental research, has discovered that calcium-bearing gangue in metallurgical-grade fluorite concentrate possesses different magnetic characteristics: some calcium-bearing gangues (such as grossular and andradite) exhibit weak magnetism and can be directly separated by strong magnetic separation; others (such as calcite and apatite) are non-magnetic and require flotation separation. Based on this, this invention proposes a novel fractional separation process: "strong magnetic pre-selection - flotation of non-magnetic products to reduce calcium content - regrinding and re-selection of magnetic products." The specific technical solution is as follows:

[0035] A method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and precipitation, wherein the metallurgical grade fluorite concentrate has a CaF2 grade of 70%~75% and a CaCO3 content of 15%~20%. Figure 1 As shown, the steps are as follows:

[0036] S1: High-intensity magnetic separation impurity removal step: Metallurgical grade fluorite concentrate is subjected to high-intensity magnetic separation using a magnetic separator with a magnetic field strength of 0.8~1.2T to obtain non-magnetic and magnetic fluorite concentrates; the yield of the non-magnetic concentrate is 80%±2%, and the yield of the magnetic concentrate is 20%±2%.

[0037] The non-magnetic product has a CaF2 grade of ≥89% and a CaCO3 content of ≤5.5%; the magnetic product has a CaF2 grade of 55%~65% and mainly contains weakly magnetic calcium-bearing gangue such as grossular and andradite.

[0038] S2: Non-magnetic product flotation and calcium reduction step: The non-magnetic fluorite concentrate obtained from S1 is subjected to flotation operations, including 1-2 roughing stages and 3-4 cleaning stages:

[0039] Roughing conditions: pH 8.5~10 (preferably 9.5), roughing times 1~2 times, water glass dosage 200~600g / t·raw ore, soda ash dosage 500~800g / t·raw ore, inhibitor dosage 100~300g / t·raw ore, collector dosage 200~400g / t·raw ore;

[0040] Selection criteria: When the number of selections is 3-4, the inhibitor dosage for each selection is as follows:

[0041] First finest selection: 100~200g / t of raw ore;

[0042] Second refinement: 50~150g / t raw ore;

[0043] Third refinement: 75~150g / t raw ore;

[0044] Fourth selection: 50~150g / t raw ore.

[0045] The inhibitor is an organophosphonic acid inhibitor that selectively inhibits calcium gangue, and the collector is a fatty acid collector that selectively collects fluorite.

[0046] S3: Magnetic product regrinding and re-selection steps: The fluorite magnetic product concentrate obtained in S1 is regrinded to a fineness of -0.074mm, accounting for 80%~95%, and then flotation is carried out, including 1~2 roughing and 3~5 cleaning.

[0047] Roughing conditions: Collector dosage 400~600g / t·raw ore, depressant dosage 100~300g / t·raw ore, sodium carbonate dosage 500~800g / t·raw ore, water glass dosage 600~1000g / t·raw ore;

[0048] The number of selections is 3-5 times, and the dosage of inhibitors used in each selection is as follows:

[0049] First finest selection: 100~200g / t of raw ore;

[0050] Second refinement: 100~150g / t of raw ore;

[0051] Third-stage selection: 50~150g / t raw ore;

[0052] Fourth finest selection: 50~150g / t raw ore;

[0053] Fifth selection: 50~150g / t raw ore.

[0054] The resulting concentrate is combined with the concentrate obtained in step S2 to form the final fluorite concentrate.

[0055] This invention selects a reasonable process flow structure and a highly efficient calcium-controlling and silica-reducing agent. In the roughing calcium control experiment, the roughing agent system is optimized to achieve efficient removal of calcium carbonate in the roughing process. In the silica reduction experiment, the impurities such as silica in fluorite concentrate are reduced by magnetic separation. The recovery rate of fluorite is improved by using magnetic product regrinding and flotation, and fluorite concentrate suitable for chemical grade is obtained.

[0056] Example 1

[0057] This embodiment uses the method of the present invention to conduct flotation tests on metallurgical-grade fluorite concentrate produced by associated fluorite in Hunan. The raw ore has a CaF2 grade of 71% and a CaCO3 content of 18%, and the main gangue minerals are calcite, grossular, andradite, muscovite, etc.

[0058] (1) Strong magnetic separation steps

[0059] The SLon-500T vertical ring pulsating high gradient magnetic separator was used to perform strong magnetic separation on the treated ore sample. The magnetic field strength was 1.0T. This removed the iron-containing silicate and other gangue minerals and some intergrowths from the original low-grade fluorite concentrate, resulting in magnetic and non-magnetic products.

[0060] The sorting effect under different non-magnetic product yield conditions was investigated, as shown in Table 1 below:

[0061] Table 1. Sorting effect under different non-magnetic product yield conditions

[0062]

[0063] The results in Table 1 show that when the yield of non-magnetic products is 80%, the product quality and recovery rate reach the optimal balance.

[0064] (2) Flotation step for reducing calcium content in non-magnetic products

[0065] Non-magnetic products are subjected to flotation under the following conditions: 400 g / t of water glass for roughing, 150 g / t of collector, and 200 g / t of depressant.

[0066] The sorting effect under different pH conditions is shown in Table 2 below:

[0067] Table 2. Sorting effect under different pH conditions

[0068]

[0069] The results in Table 2 show that the optimal balance between fluorite grade and recovery rate is achieved at pH 9.5.

[0070] The sorting effects under different inhibitor dosages are shown in Table 3 below:

[0071] Table 3. Sorting effect under different inhibitor dosage conditions

[0072]

[0073] The results in Table 3 show that the inhibitor dosage of 800 g / t is the most effective.

[0074] After obtaining the rough concentrate, it undergoes three fine-tuning processes;

[0075] Fine-grained flotation conditions: 200 g / t inhibitor was added to the rough concentrate for the first fine-grained flotation (pH=9), 100 g / t inhibitor was added to the first fine concentrate for the second fine-grained flotation (pH=8), and blank flotation was performed on the third fine concentrate for the third fine-grained flotation. The fine-grained flotation yield was 70.47%, CaF2 grade was 91.89%, CaCO3 content was 4.45%, and CaF2 recovery rate was 90.72%.

[0076] (3) Re-grinding and re-selection steps for magnetic products

[0077] Fluorite was recovered from the magnetic products using a regrinding and re-selection process. The grinding fineness of the magnetic products was -0.038 mm, accounting for 85%. The flotation conditions were: collector 250 g / t, depressant 200 g / t, sodium carbonate 600 g / t, and water glass 800 g / t. After obtaining the rough and concentrate products, the rough concentrate was treated with 100 g / t hydrochloric acid and 200 g / t water glass for the first cleaning, the first concentrate was treated with 100 g / t water glass for the second cleaning, and the third concentrate was treated with 75 g / t water glass for the third cleaning. The final beneficiation results were a fluorite concentrate yield of 51.56%, a CaF2 grade of 87.47%, and a fluorite recovery rate of 76.04%.

[0078] Example 2

[0079] This embodiment was carried out on a scale-up test in the pilot continuous beneficiation workshop of Changsha Institute of Mining and Metallurgy, with a scale set at 50 kg / h and continuous operation for 72 hours.

[0080] After the ore is subjected to high-intensity magnetic separation (SLon-500 high-intensity magnetic separator, magnetic field strength 1.0T), the yield of non-magnetic products is 87.67%, the grade of CaF2 is 76.78%, and the recovery rate is 90.86%. The non-magnetic products are subjected to one roughing and three cleaning flotation (roughing pH=9.5, total depressant 800g / t, cleaning 3 times) to obtain a non-magnetic flotation concentrate with a yield of 67.17% and a grade of 91.56%.

[0081] The magnetic products, after regrinding and re-selection, were combined with the flotation concentrate. The average indicators of the 72-hour continuous stable test were: concentrate yield 67.90%, CaF2 grade 91.20%, CaCO3 content 5.44%, SiO2 content 1.68%, and CaF2 comprehensive recovery rate 83.63%.

[0082] The results of the 72-hour continuous stability test are shown in Table 4 below;

[0083] Table 4 Results of the 72-hour continuous stability test

[0084]

[0085] The experimental results in Table 4 show that the method of the present invention has a stable process and good reproducibility of indicators, and can effectively improve the quality and reduce the calcium content of metallurgical grade fluorite concentrate.

[0086] Comparative Example 1

[0087] Direct flotation without strong magnetic pre-selection

[0088] Using the same metallurgical-grade fluorite concentrate as in Example 1 (CaF2 grade 71%, CaCO3 content 18%), without strong magnetic pre-selection, the flotation process of step S2 was directly adopted for roughing and cleaning flotation.

[0089] Results: The concentrate had a CaF2 grade of 85.3%, a CaCO3 content of 8.7%, and a recovery rate of 82.1%. Due to the lack of strong magnetic pre-selection to remove the magnetic calcium-containing gangue, the magnetic gangue such as grossular and andradite in the flotation feed floated to the surface simultaneously with fluorite, making it impossible to reduce the CaCO3 content in the concentrate to below 6%, and the concentrate grade was difficult to exceed 88%.

[0090] Conclusion: Strong magnetic pre-selection is a key pre-process of the present invention, and direct flotation cannot achieve deep calcium reduction of metallurgical grade fluorite concentrate.

[0091] Comparative Example 2

[0092] Using the same raw materials and process conditions as in Example 1, only the magnetic field strength of the strong magnetic preselection was adjusted, so that the yield of non-magnetic products was 85% (exceeding the upper limit of 82% of the present invention).

[0093] Results: The non-magnetic product had a CaF2 grade of 90.2% and a CaCO3 content of 5.3%. After flotation, the final concentrate had a CaF2 grade of 89.6% and a CaCO3 content of 5.8%, with a recovery rate of 81.7%. Compared with Example 1, the grade decreased by 2.3 percentage points and the recovery rate decreased by 6.9 percentage points.

[0094] The reason is that the high yield of non-magnetic products leads to some magnetic calcium-containing gangue being mixed into the non-magnetic products, increasing the CaCO3 content in the flotation feed and increasing the decalcification burden of flotation. At the same time, some fluorite is lost in the magnetic products and cannot be recovered.

[0095] Conclusion: When the yield of strong magnetic separation deviates from the range of this invention (80%±2%), the concentrate grade and recovery rate both decrease significantly.

[0096] Comparative Example 3

[0097] Using the same raw materials and process conditions as in Example 1, the pH of the non-magnetic product flotation was adjusted to 8.0 (lower than the lower limit of 8.5 of this invention).

[0098] Results: The concentrate had a CaF2 grade of 88.7%, a CaCO3 content of 6.2%, and a recovery rate of 85.3%. Compared with Example 1, the grade decreased by 3.2 percentage points and the recovery rate decreased by 5.4 percentage points.

[0099] The reason is that at pH=8.0, the surface potential difference between fluorite and calcite is small, and the selective adsorption capacity of the collector is insufficient, resulting in a large amount of calcium-containing gangue floating up with fluorite, and the CaCO3 in the concentrate exceeding the standard.

[0100] Conclusion: When the flotation pH deviates from the range of this invention (8.5~10), the calcium reduction effect is significantly deteriorated, and it cannot meet the standard of chemical grade fluorite concentrate.

[0101] The method for reducing calcium content in metallurgical-grade fluorite concentrate using a combined strong magnetic flotation process provided by this invention can be widely applied to the deep purification of metallurgical-grade fluorite concentrate produced from associated fluorite mines. By implementing this invention, low-value-added metallurgical-grade fluorite concentrate (used as a flux in iron and steel smelting) can be upgraded to high-value-added chemical-grade fluorite concentrate (CaF2 > 90%, CaCO3 < 6%), significantly improving the utilization value of fluorite resources and the economic benefits of mining enterprises. This method plays a crucial role in promoting the upgrading of my country's comprehensive fluorite resource recycling industry.

Claims

1. A method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and precipitation, characterized in that... The metallurgical-grade fluorite concentrate has a CaF2 grade of 70%~75% and a CaCO3 content of 15%~20%. include The following steps: S1: Metallurgical grade fluorite concentrate is subjected to high-gradient magnetic separation to obtain non-magnetic and magnetic products, with the yield of non-magnetic products controlled at 78-82%; S2: The non-magnetic product obtained in S1 is subjected to flotation. The flotation includes 1 to 2 roughing stages and 3 to 4 cleaning stages. The roughing pH is 8.5 to 10, and the inhibitor dosage is 425 to 1100 g / t of raw ore. S3: The magnetic product obtained in S1 is regrinded and then floated. The resulting concentrate is combined with the concentrate obtained in step S2 to form the final fluorite concentrate.

2. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In S1, the magnetic field strength for strong magnetic separation is 0.8~1.2T; the CaF2 grade in the non-magnetic product is ≥89%, and the CaCO3 content is ≤5.5%; the CaF2 grade in the magnetic product is 55%~65%.

3. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In S2, the coarse pH is 9.

5.

4. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In S2, the roughing conditions are: water glass dosage 200~600g / t·raw ore, soda ash dosage 500~800g / t·raw ore, inhibitor dosage 100~300g / t·raw ore, and collector dosage 200~400g / t·raw ore.

5. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In S2, the refining is carried out 3 times; the inhibitor dosages are as follows: 100~200g / t·raw ore for the first time, 50~150g / t·raw ore for the second time, and 75~150g / t·raw ore for the third time.

6. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In step S3, the grinding fineness of the regrinding process is -0.074 mm, accounting for 80% to 95%.

7. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... In step S3, the flotation of magnetic products includes one roughing process and three cleaning processes. The roughing conditions are as follows: collector dosage 400~600g / t·raw ore, inhibitor dosage 100~300g / t·raw ore, sodium carbonate dosage 500~800g / t·raw ore, and water glass dosage 600~1000g / t·raw ore. The inhibitor dosages for the three selection processes were as follows: 100-200 g / t of raw ore for the first time, 100-150 g / t of raw ore for the second time, and 50-150 g / t of raw ore for the third time.

8. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... The inhibitor is an organophosphonic acid inhibitor that selectively inhibits calcium gangue.

9. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic flotation and conventional flotation, as described in claim 1, is characterized in that... The collector is a fatty acid collector that selectively collects fluorite.

10. The method for reducing calcium content in metallurgical grade fluorite concentrate using a combination of strong magnetic field and flotation according to any one of claims 1 to 9, characterized in that, The final fluorite concentrate has a CaF2 grade of ≥91%, a CaCO3 content of ≤5.5%, and a CaF2 recovery rate of ≥83%.

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