A method for preparing refined calcite powder by combining limestone ore dressing and smelting

Abstract

The present invention discloses a method for preparing refined calcite powder by combining limestone ore dressing and smelting. According to the interbedded characteristics of limestone ore, the present invention designs a process of grinding-scrubbing-magnetic separation-reverse flotation impurity removal-positive flotation selection-reduction leaching, improves the flotation reagent system, and proposes a multi-stage flotation method according to the occurrence form of impurities in the limestone ore, that is, first float the easy-to-float gangue minerals, and then suppress the difficult-to-float gangue minerals. Furthermore, for flotation concentrates with high calcium oxide content but not meeting the requirements of refined calcite powder products, a scheme of using thiourea dioxide reduction leaching is proposed, thereby meeting the requirements of refined calcite powder products. Finally, a refined calcite powder product with a CaO content of more than 54% and a Fe2O3 content of less than 0.05% is obtained. The equipment used in the present invention is conventional mineral processing equipment, the process flow is simple, and it is easy to industrialize and mass produce.

Description

Technical Field

[0001] The invention relates to the technical field of rational utilization and wet smelting of limestone ore, and in particular to a method for preparing refined calcite powder by combining limestone ore dressing and smelting. Background Art

[0002] Refined calcite powder has a wide range of applications, including in the natural rubber and synthetic rubber industries, paint and papermaking, cable, coatings, and cosmetics. Besides offering significant cost-reduction advantages, refined calcite powder can also improve the processing and mechanical properties of plastic products, enhance the gloss of coatings, paints, and paper, and provide reinforcement. It is also commonly used as an additive in coatings and paper pulp. However, in its practical applications, refined calcite powder often faces various challenges, such as high levels of impurities. The types and contents of impurities in refined calcite powder are primarily reflected in its appearance. High iron content results in a yellowish appearance, while high magnesium content results in a grayish appearance. The presence of these impurities reduces the powder's whiteness. Unrefined calcite powder often contains high levels of acid-insoluble matter, which can directly impact the processing of subsequent high-value-added products. If used as a filler in rubber, these impurities can negatively impact the properties of the resulting product. Therefore, mineral processing is essential for impurity removal and purification.

[0003] A patented process for removing impurities from calcite ore and improving its whiteness (CN116651600A) discloses a method for removing impurities and improving whiteness using photoelectric beneficiation, but this method suffers from high energy consumption and other energy loss issues. Existing methods for whitening calcite, such as the introduction of titanium dioxide or fluorescent whitening, are effective but prohibitively expensive, making them difficult to implement. Removing impurities through beneficiation to produce refined calcite powder offers lower costs, higher efficiency, and no environmental pollution, offering promising application prospects and economic benefits. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing refined calcite powder by combining limestone ore dressing and smelting. The method adopts a process of grinding-scrubbing-magnetic separation-reverse flotation impurity removal-positive flotation concentration-reduction leaching to treat the limestone ore, enrich the impurity gangue minerals into the tailings, and realize the efficient separation and enrichment of limestone ore dressing and impurity removal.

[0005] The present invention provides a method for preparing refined calcite powder by combining limestone ore dressing and smelting, comprising the following steps:

[0006] S1. Crushing and grinding the limestone ore to obtain mineral powder;

[0007] S2. The mineral powder obtained in step S1 is scrubbed to obtain a scrubbed concentrate;

[0008] S3. The scrubbed concentrate obtained in step S2 is subjected to magnetic separation to obtain a magnetic product and a non-magnetic product;

[0009] S4. The magnetic product obtained in step S3 is subjected to reverse flotation to remove impurities to obtain a coarse concentrate and black impurities;

[0010] S5. The coarse concentrate obtained in step S4 is subjected to a positive flotation roughing and five positive flotation selections to obtain a flotation concentrate and a middling;

[0011] S6. The flotation concentrate obtained in step S5 is subjected to reduction leaching to obtain a concentrate product and a leachate; the obtained concentrate product is used as the refined calcite powder.

[0012] Furthermore, in step S1, the crushing is a three-stage closed-circuit crushing, and the particle size of the product obtained by crushing is 0.5-0.8 mm.

[0013] The grinding is dry ball milling. During grinding, the volume ratio of the material to the grinding medium is 1:1. The total volume of the grinding system accounts for 2 / 3 of the ball mill solvent. The grinding time is 40 to 45 minutes. The grinding is performed until the material particle size reaches -0.074 mm, accounting for more than 98%.

[0014] According to the structural characteristics of limestone ore and the basic principles of crushing and grinding, the embedded particle size of calcite and gangue minerals is relatively fine. Only after a long period of crushing and grinding can the original ore be dissociated from the gangue minerals. This will improve the selective adsorption of subsequent flotation reagents. In addition, fully grinding the original ore is conducive to increasing the reaction sites and facilitating the efficient reduction leaching.

[0015] Furthermore, in step S2, the scrubbing process conditions are as follows: adding 200-300 g / t of oxalic acid for scrubbing, a scrubbing concentration of 25-30%, a scrubbing time of 10 min, and a scrubbing speed of 1000-1200 rpm / min.

[0016] Scrubbing exposes fresh mineral interfaces, thereby improving the interaction between subsequent flotation reagents and minerals.

[0017] Furthermore, in step S3, the process conditions of the magnetic separation are: slurry concentration of 25% to 30%, magnetic field strength of 12000 Gs to 14000 Gs, and two magnetic separations.

[0018] The raw ore contains some magnetic iron. Through the strong magnetic field and high gradient magnetic separation method, the iron impurities can be preferentially enriched. The efficiency of magnetic separation is high and the loss of raw ore is small.

[0019] Furthermore, in step S4, the reverse flotation impurity removal includes two stages of reverse flotation, namely, roughing and scavenging, wherein the reverse flotation roughing obtains rougher concentrate and rougher tailings, and the reverse flotation scavenging uses the rougher concentrate as the flotation raw material to obtain rougher concentrate and scavenging tailings; the rougher tailings and the scavenging tailings are combined to obtain black impurities;

[0020] The process conditions for reverse flotation roughing are: pulp concentration of 20% to 30%, pH value range of 8.5 to 9.5, collector of benzohydroxamic acid at a dosage of 50-75 g / t, frother of terpineol at a dosage of 50-75 g / t;

[0021] The process conditions for reverse flotation scavenging are: pulp concentration of 20% to 30%, pH value range of 8.5 to 9.5, collector of benzohydroxamic acid, collector dosage of 25-30g / t, frother of terpineol, frother dosage of 25-30g / t.

[0022] Furthermore, in step S5, the one-pass positive flotation roughing and five-pass positive flotation cleaning are specifically as follows: the pulp concentration of the positive flotation roughing and positive flotation cleaning is 25% to 30%, and the pH value range is 8.5 to 9.5; the inhibitor for the positive flotation roughing is a combination of caustic starch and water glass, wherein the amount of caustic starch is 400 to 600 g / t, the amount of water glass is 400 to 600 g / t, and the collector is sodium oleate, and the amount is 250 to 350 g / t;

[0023] The depressant for the first and second stage positive flotation separation is a combination of caustic starch and water glass, wherein the amount of caustic starch is 400-600g / t, and the amount of water glass is 400-600g / t; the collector is sodium oleate, and the amount is 100-200g / t;

[0024] The depressant in the third stage of positive flotation is a combination of caustic starch and water glass, wherein the amount of caustic starch is 400-600g / t, the amount of water glass is 400-600g / t; the collector is sodium oleate, the amount is 50-100g / t;

[0025] The depressant used in the fourth stage of positive flotation is a combination of caustic starch and water glass, wherein the amount of caustic starch is 400-600g / t, and the amount of water glass is 400-600g / t; no collector is added;

[0026] The fifth stage of positive flotation selection is blank selection.

[0027] The preparation method of the caustic starch is specifically as follows: corn starch and sodium hydroxide powder are mixed, water is added, and the mixture is heated in a water bath for a preset time to obtain the caustic starch;

[0028] The ratio of corn starch, sodium hydroxide powder and water is (1-2): (0.3-0.5): (17-18); the water bath heating temperature is 80-85° C., and the heating time is 1-1.5 hours.

[0029] The main components of the gangue minerals of limestone ore are quartz and dolomite, among which the impurity iron component mainly exists in the form of silicate, and the impurity magnesium component mainly exists in the form of dolomite. Calcite has a natural hydrophobic structure and good floatability. Quartz and silicate minerals are hydrophilic and have poor floatability. Therefore, the difference in floatability between the two can be used to effectively separate them through flotation.

[0030] Furthermore, in step S6, the reduction leaching is specifically as follows: the flotation concentrate obtained in step S5 is prepared into an 18-22% solution, a reduction leaching agent and sodium hydroxide powder are added, and heating reaction leaching is performed to obtain a reduction leaching concentrate and a leachate;

[0031] The reducing leaching agent is thiourea dioxide, and the dosage is 1% to 5% of the flotation concentrate obtained by the fifth positive flotation selection; the addition amount of sodium hydroxide powder is 0.3% to 0.5%; the heating temperature is 60 to 70°C, and the leaching time is 18 to 22 minutes; the reducing leaching agent is added to the reaction system in five times after the heating starts, and the interval time is 1 / 5 of the total leaching time.

[0032] The positive flotation concentrate produced during the positive flotation concentration process has a high calcium carbonate content, but the impurity component content is too high to reach the lower middlings of refined calcite powder. This part of the middlings has a high yield and has not yet been effectively treated. The use of reduction leaching can reduce the trivalent iron in this part, but the reduction reaction is reversible and needs to be carried out in a short time, so the reducing agent is added in stages to promote its leaching.

[0033] Principle of the present invention:

[0034] The present invention employs the synergistic use of benzohydroxamic acid and terpineol in flotation, which can separate impurity minerals introduced by crushing and grinding during actual production, such as common impurity minerals with good floatability, such as biotite. Furthermore, caustic starch is used as an inhibitor in the selection process. Anionic starch relies on electrostatic force to adsorb on the positively charged surface of hematite, or relies on hydrogen atoms on the hydroxyl groups of starch molecules to form hydrogen bonds with oxygen atoms on the surface of the iron oxide lattice, thereby producing an inhibitory effect. Starch causticized with sodium hydroxide can be hydrolyzed into starch with a smaller molecular weight, resulting in a higher selectivity. Water glass can not only be used as an inhibitor, but also as a dispersant for mineral mud. The synergistic inhibitory effect of the two inhibitors, leveraging their strengths and weaknesses, can greatly improve the selectivity of the flotation collector sodium oleate.

[0035] Beneficial effects of the present invention:

[0036] (1) The present invention utilizes the difference in mineral floatability to achieve separation of fine particles through flotation;

[0037] (2) The method of the present invention uses caustic starch and water glass to act synergistically as an inhibitor, thereby enhancing the inhibitory effect and selectivity and improving the separation between useful minerals and gangue minerals;

[0038] (3) The method of the present invention is for reduction leaching of flotation concentrate, which is time-saving and easy to operate, thereby reducing the loss of concentrate yield and ore recovery rate;

[0039] (4) The method of the present invention mixes the concentrated ore with the leached ore, thereby improving the recovery rate of the concentrate;

[0040] (5) The equipment used in the method of the present invention is conventional mineral processing equipment, the process flow is simple, and it is easy to industrialize and mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the process of Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] The present invention discloses a method for preparing refined calcite powder by combining limestone ore dressing and smelting, and the flow diagram thereof is shown as follows: Figure 1 As shown, specifically:

[0045] The limestone ore was crushed, and 200 g of the crushed limestone ore was taken, wherein the quantitative CaO content of the raw ore was 53.28%, the MgO content was 0.88%, the Fe2O3 content was 0.23%, and the SiO2 content was 1.60%. The raw ore was added into a ball mill for grinding (the ball mill was a planetary four-barrel grinding mill), and the material-ball ratio was adjusted to 1:1. The forward and reverse rotations were each for 5 minutes as one cycle, and a total of four cycles were performed. The total grinding time was 40 minutes, and the raw ore was ground to more than 98% of 200 mesh (0.074 mm) to obtain mineral powder.

[0046] The mineral powder is adjusted to a 25% concentration slurry, and slowly added to a 14000Gs high gradient magnetic separator for magnetic separation. The resulting magnetic concentrate is filtered and dried. Take 60g of magnetic concentrate for flotation (the flotation machine is a 200ml~300ml XFG hanging tank aeration flotation machine), adjust the slurry concentration to 20%, and use sodium carbonate to adjust the pH to 9 throughout the process. The reverse flotation impurity removal and roughing agent system is 50g / t of benzohydroxamic acid and 50g / t of pine oil. The reverse flotation impurity removal and scavenging agent system is 25g / t of benzohydroxamic acid and 25g / t of pine oil. The direct flotation roughing agent system is 500g / t of caustic starch, 500g / t of water glass, and 300g / t of sodium oleate. The reagent system for flotation separations 1 and 2 consisted of 500g / t caustic starch, 500g / t water glass, and 150g / t sodium oleate. The reagent system for direct flotation separation 3 consisted of 500g / t caustic starch, 500g / t water glass, and 75g / t sodium oleate. The reagent system for direct flotation separation 4 consisted of 500g / t caustic starch and 500g / t water glass. Direct flotation separation 5 was a blank flotation run. After frothing, each flotation scraping time was controlled at 3 minutes. Flotation concentrate and flotation middling were obtained, respectively. The flotation concentrate was subjected to reduction leaching. The reduction leaching conditions were a 20% slurry with 0.5% sodium hydroxide powder and 3% thiourea dioxide added, heated in a 60°C water bath, and the thiourea dioxide was added in five doses, each with a four-minute interval, for a total of 20 minutes. The reduction leaching concentrate obtained is the refined calcite powder product with a yield of 30.95%, wherein the CaO content is 54.05%, the Fe2O3 content is 0.045%, the MgO content is 0.43%, and the SiO2 content is 0.22%, which meets the requirements of the refined calcite powder product.

[0047] Example 2

[0048] The limestone ore was crushed, and 200 g of the crushed limestone ore was taken, wherein the quantitative CaO content of the raw ore was 53.28%, the MgO content was 0.88%, the Fe2O3 content was 0.23%, and the SiO2 content was 1.60%. The raw ore was added into a ball mill for grinding (the ball mill was a planetary four-barrel grinding mill), and the material-ball ratio was adjusted to 1:1. The forward and reverse rotations were each for 5 minutes as one cycle, and a total of four cycles were performed. The total grinding time was 40 minutes, and the raw ore was ground to more than 98% of 200 mesh (0.074 mm) to obtain mineral powder.

[0049] The mineral powder is adjusted to a 25% concentration slurry, and slowly added to a 14000Gs high gradient magnetic separator for magnetic separation. The resulting magnetic concentrate is filtered and dried. Take 60g of magnetic concentrate for flotation (the flotation machine is a 200ml~300ml XFG hanging tank aeration flotation machine), adjust the slurry concentration to 20%, and use sodium carbonate to adjust the pH to 9 throughout the process. The reverse flotation impurity removal and roughing agent system is 50g / t of benzohydroxamic acid and 50g / t of pine oil. The reverse flotation impurity removal and scavenging agent system is 25g / t of benzohydroxamic acid and 25g / t of pine oil. The direct flotation roughing agent system is 500g / t of caustic starch, 500g / t of water glass, and 300g / t of sodium oleate. The reagent system for flotation separations 1 and 2 consisted of 500g / t caustic starch, 500g / t water glass, and 150g / t sodium oleate. The reagent system for direct flotation separation 3 consisted of 500g / t caustic starch, 500g / t water glass, and 75g / t sodium oleate. The reagent system for direct flotation separation 4 consisted of 500g / t caustic starch and 500g / t water glass. Direct flotation separation 5 was a blank flotation run. After frothing, each flotation scraping time was controlled at 3 minutes. Flotation concentrate and flotation middling were obtained, respectively. The flotation concentrate was subjected to reduction leaching. The reduction leaching conditions were a 20% slurry with 0.5% sodium hydroxide powder and 1% thiourea dioxide added, heated in a 60°C water bath, and the thiourea dioxide was added in five doses, each with a four-minute interval, for a total of 20 minutes. The reduction leaching concentrate obtained is the refined calcite powder product with a yield of 31.46%, wherein the CaO content is 54.51%, the Fe2O3 content is 0.045%, the MgO content is 0.46%, and the SiO2 content is 0.21%, which meets the requirements of the refined calcite powder product.

[0050] Comparative Example 1

[0051] Compared with Example 1, except that the inhibitor caustic starch was replaced with corn starch, the remaining steps were exactly the same as Example 1. The yield of the obtained calcite powder product was 28.88%, and the Fe2O3 content was 0.066%, which did not meet the product technical requirements for iron content of refined calcite powder.

[0052] Comparative Example 2

[0053] Compared with Example 1, except that the reduction inhibitor thiourea dioxide was replaced with sodium hydrosulfite, a hydrosulfite, the remaining steps were identical to those of Example 1. The resulting calcite powder had a yield of 31.63% and an Fe2O3 content of 0.076%, which did not meet the product technical requirements for iron content of refined calcite powder.

[0054] Comparative Example 3

[0055] Compared with Example 1, except that the collector sodium oleate was replaced by oxidized paraffin soap, the remaining steps were identical to Example 1. The yield of the obtained calcite powder product was 12.57%, and the Fe2O3 content was 0.317%, which did not meet the product technical requirements for iron content of refined calcite powder.

[0056] Comparative Example 4

[0057] Compared with Example 1, the overall flotation process was changed to reverse flotation, which directly floats out impure gangue minerals to purify calcite. Sodium hexametaphosphate was used as a dispersant and inhibitor at a dosage of 500 g / t; benzohydroxamic acid was used as a collector at a dosage of 100 g / t; and terpineol was used as a frother at a dosage of 100 g / t. Four sweep flotations were performed. The resulting calcite powder had a yield of 77.70%, a CaO content of 53.22%, and an Fe₂O₃ content of 0.171%. The CaO content was even lower than that of the original ore. This did not meet the technical requirements for iron content for refined calcite powder.

[0058] The results of the above embodiments and comparative examples show that the present invention, based on the flotation optimization reagent system, adopts a technical solution of combined beneficiation and smelting with synergistic impurity removal, which overcomes the problems of poor recovery effect and low degree of refinement of existing limestone ore impurity removal technologies, and realizes the removal of impurities from limestone ore to efficiently prepare refined calcite powder.

Claims

1. A method for preparing refined calcite powder by combining limestone ore dressing and smelting, characterized in that: The following steps are involved: S1. Crushing and grinding the limestone ore to obtain mineral powder; S2. The mineral powder obtained in step S1 is scrubbed to obtain a scrubbed concentrate; S3 scrub the concentrate obtained in step S2 is subjected to magnetic separation to obtain a magnetic product and a non-magnetic product; S4 the non-magnetic product obtained in step S3 is subjected to reverse flotation to remove impurities to obtain a coarse concentrate and black impurities; the reverse flotation collector used for impurity removal is benzohydroxamic acid, the frother is terpineol; S5. The coarse concentrate obtained in step S4 is subjected to a positive flotation roughing and five positive flotation selections to obtain a flotation concentrate and middlings; the positive flotation roughing inhibitor is a combination of caustic starch and water glass, and the collector is sodium oleate; S6. The flotation concentrate obtained in step S5 is subjected to reduction leaching to obtain a concentrate product and a leachate; the resulting concentrate product is used as the refined calcite powder; The reduction leaching requires the addition of a reduction leaching agent and sodium hydroxide powder; the reduction leaching agent is thiourea dioxide.

2. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 1, characterized in that: In step S1, the crushing is a three-stage closed-circuit crushing, and the particle size of the crushed product is 0.5-0.8 mm; The grinding is dry ball milling, the volume ratio of the material to the grinding medium is 1:1, the total volume of the grinding system accounts for 2 / 3 of the ball mill solvent, the grinding time is 40-45 minutes, and the grinding is performed until the material particle size reaches -0.074 mm, accounting for more than 98%.

3. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 1, characterized in that: In step S2, the scrubbing process conditions are as follows: adding 200-300 g / t of oxalic acid for scrubbing, a scrubbing concentration of 25-30%, a scrubbing time of 10 min, and a scrubbing speed of 1000-1200 rpm.

4. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 1, characterized in that: In step S3, the process conditions of the magnetic separation are: slurry concentration of 25% to 30%, magnetic field strength of 12000 Gs to 14000 Gs, and two magnetic separations.

5. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 1, characterized in that: In step S4, the reverse flotation impurity removal includes two stages of reverse flotation, namely roughing and scavenging. The reverse flotation roughing obtains rougher concentrate and rougher tailings. The reverse flotation scavenging uses the rougher concentrate as the flotation raw material to obtain rougher concentrate and scavenging tailings. The rougher tailings and the scavenging tailings are combined to obtain black impurities. The process conditions for reverse flotation roughing are: pulp concentration of 20%-30%, pH value range of 8.5-9.5, collector is benzohydroxamic acid, the collector dosage is 50-75g / t, frother is terpineol, the frother dosage is 50-75g / t; The process conditions for reverse flotation scavenging are: pulp concentration of 20%~30%, pH value range of 8.5~9.5, collector is benzohydroxamic acid, the collector dosage is 25-30g / t, frother is terpineol, the frother dosage is 25-30g / t.

6. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 1, characterized in that: In step S5, the one positive flotation roughing and five positive flotation cleaning processes are specifically as follows: the pulp concentration throughout the positive flotation roughing and positive flotation cleaning is 25%-30%, and the pH value range is 8.5-9.5; the inhibitor for the positive flotation roughing is a combination of caustic starch and water glass, wherein the amount of caustic starch is 400-600 g / t, the amount of water glass is 400-600 g / t, and the collector is sodium oleate, and the amount is 250-350 g / t; The depressant for the first and second stage positive flotation separation is a combination of caustic starch and water glass, with the dosage of caustic starch being 400-600 g / t and the dosage of water glass being 400-600 g / t; the collector is sodium oleate, with the dosage being 100-200 g / t; The depressant for the third stage of positive flotation is a combination of caustic starch and water glass, with the dosage of caustic starch being 400-600 g / t and the dosage of water glass being 400-600 g / t; the collector is sodium oleate, with the dosage being 50-100 g / t; The depressant used in the fourth stage of positive flotation is a combination of caustic starch and water glass, with the dosage of caustic starch being 400-600 g / t and the dosage of water glass being 400-600 g / t; no collector is added; The fifth stage of positive flotation selection is blank selection.

7. The method for preparing refined calcite powder by limestone ore dressing and smelting according to claim 6, characterized in that: The preparation method of the caustic starch is specifically as follows: corn starch and sodium hydroxide powder are mixed, water is added, and the mixture is heated in a water bath for a preset time to obtain the caustic starch; The ratio of corn starch, sodium hydroxide powder and water is (1-2): (0.3-0.5): (17-18); the water bath heating temperature is 80-85° C., and the heating time is 1-1.5 hours.

8. The method for preparing refined calcite powder by combining limestone ore dressing and smelting according to claim 1, characterized in that: In step S6, the reduction leaching is specifically as follows: the flotation concentrate obtained in step S5 is prepared into an 18-22% solution, thiourea dioxide and sodium hydroxide powder are added, and heating reaction leaching is performed to obtain a reduction leaching concentrate and a leachate.

9. The method for preparing refined calcite powder by combining limestone ore dressing and smelting according to claim 8, characterized in that: The dosage of the thiourea dioxide is 1% to 5% of the flotation concentrate obtained by the fifth positive flotation; the addition amount of sodium hydroxide powder is 0.3% to 0.5%; the heating temperature is 60 to 70° C., and the leaching time is 18 to 22 minutes.

10. The method for preparing refined calcite powder by combining limestone ore dressing and smelting according to claim 8, characterized in that: The reducing leaching agent is added to the reaction system in five times after the start of heating, with the interval time being 1 / 5 of the total leaching time.

Images