Method for preparing high-purity calcium carbonate by step-by-step processing of calcium-containing raw ore

Abstract

This invention discloses a method for preparing high-purity calcium carbonate from calcium-containing raw ore through a tiered processing technique, belonging to the field of high-purity calcium carbonate preparation technology. This method addresses the problems of insufficient purity and low resource utilization in existing natural mineral purification techniques by employing a tiered process of "acid leaching extraction-primary carbonation" and "roasting-digestion-secondary carbonation" to achieve stepwise recovery and deep purification of calcium from calcium-containing raw ore, simultaneously producing two high-purity calcium carbonate products with different purity levels.

Description

Technical Field

[0001] This invention belongs to the technical field of high-purity calcium carbonate materials, and particularly relates to a method for preparing high-purity calcium carbonate by cascade processing of calcium-containing raw ore. Background Technology

[0002] High-purity calcium carbonate, as an important inorganic functional material, is increasingly in demand in high-end manufacturing, food and pharmaceutical, and electronic materials fields due to its excellent properties such as good chemical stability, high whiteness, and uniform particle size. Currently, the main methods for preparing high-purity calcium carbonate include chemical synthesis and natural mineral purification.

[0003] Chemical synthesis methods primarily use high-quality chemical raw materials (such as calcium chloride and sodium carbonate) and prepare the product through liquid-phase reactions. While this method can yield high-purity products, it suffers from high raw material costs, complex production processes, and environmentally unfriendly byproducts, limiting the economic viability of large-scale production. Natural mineral purification methods use calcium-containing minerals (such as limestone and calcite) as raw materials, offering advantages such as wide availability and low cost. However, natural minerals often contain impurities such as silicon, aluminum, and iron. Traditional processes often employ roasting-digestion-carbonation of the raw ore, which struggles to achieve deep removal of these impurities, resulting in product purity levels that are difficult to exceed 99%. Furthermore, the utilization rate of mineral resources is low, leading to significant waste of intermediate products and failing to meet the purity requirements of high-end calcium carbonate production.

[0004] Therefore, in view of the above problems, the present invention provides a method for preparing high-purity calcium carbonate through a stepwise processing of calcium-containing minerals. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high-purity calcium carbonate from calcium-containing raw ore through a stepwise extraction and graded purification process. This method achieves efficient recovery and deep purification of calcium elements in calcium-containing raw ore, and simultaneously prepares two high-purity calcium carbonate products with different purity levels. This improves the utilization rate of raw materials and the added value of products, and solves the problems of insufficient purity, resource waste, and high pollution risk in traditional processes.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing high-purity calcium carbonate by cascade processing of calcium-containing raw ore, comprising the following steps: Step S1: Raw material pretreatment: Wash the calcium-containing raw ore to remove impurities such as mud and dust attached to the surface, and obtain clean raw ore.

[0007] Step S2: Acid leaching reaction: Clean raw ore is added to hydrochloric acid solution for reaction. After the reaction is completed, solid-liquid separation is performed to obtain reaction liquid and solid reactants respectively.

[0008] Step S3: Primary carbonation for high-purity calcium carbonate I: The reaction solution obtained in step S2 is mixed with ammonia solution under stirring to adjust the pH to 12.5-13.5. The mixture is then stirred at room temperature for 30-60 minutes for carbonation. After carbonation, the solution is washed several times with distilled water to remove as much residual Cl as possible. - After solid-liquid separation, high-purity calcium carbonate I was obtained.

[0009] Step S4: Calcination treatment: The solid reactant obtained in step S2 is calcined to obtain the calcined product.

[0010] Step S5: Secondary digestion-carbonation to prepare high-purity calcium carbonate II: The calcined material obtained in step S4 is digested and carbonized in a continuous digestion tank to prepare high-purity calcium carbonate II.

[0011] Furthermore, in step S1 of this invention, the calcium-containing ore is selected from at least one of limestone, calcite, or marble.

[0012] Furthermore, in step S1 of this invention, the particle size of the calcium-containing ore is 1 cm to 5 cm.

[0013] In a further step of this invention, in step S2, the clean raw ore is reacted with hydrochloric acid solution at room temperature for 5 h to 12 h. After solid-liquid separation, the mixture is washed 3 to 5 times with distilled water, and the liquid and solid are collected to obtain the reaction solution and reactants.

[0014] In a further step of this invention, in step S2, the hydrochloric acid solution has a hydrochloric acid mass concentration of 3% to 8%, and a hydrochloric acid solution of 40% to 60% of the theoretical value calculated according to the reaction formula is added to ensure partial dissolution of Ca element.

[0015] Furthermore, in step S3 of this invention, the ammonia water is analytical grade ammonia water (NH3 content 25%~28%).

[0016] Furthermore, in this invention, the carbonization conditions in step S3 are as follows: carbonization temperature is 25 °C, carbon dioxide injection rate is 0.1 L / min to 0.4 L / min, stirring speed is 300 r / min to 500 r / min, and carbon dioxide gas injection is stopped when the pH value of the slurry drops below 7.5.

[0017] In a further step of this invention, in step S4, the solid reactant obtained in step S2 is placed in a vertical kiln and calcined at 850 ℃ to 1000 ℃ for 2 h to 6 h to obtain the calcined product.

[0018] Furthermore, in step S5 of this invention, the digestion-carbonization treatment includes the following steps: Step S51: Add the calcined material to an ethanol solution and digest it at 40 ℃~60 ℃ to obtain slurry one.

[0019] Step S52: Sieve the first slurry through a 200-mesh standard sieve to remove the digested residue on the sieve, and obtain the second slurry under the sieve.

[0020] Step S53: Add ethanol solution to slurry two to prepare slurry with a concentration of 5%~10%, and obtain slurry three.

[0021] Step S54: Stir and age the slurry at low speed at 25 ℃ for 12 h to 24 h, and then perform carbonization treatment to obtain carbonized slurry.

[0022] Step S55: After the carbonization process is completed, centrifuge the product, dry it at 100 ℃~120 ℃, and break it up to obtain high-purity calcium carbonate II.

[0023] In a further step of this invention, in step S51, the solid-liquid ratio of the calcined material and the ethanol solution is 1:6, and the ethanol concentration is 3%~8%.

[0024] Further, in step S54 of this invention, the carbonation process specifically involves: a carbonation temperature of 25 ℃, a carbon dioxide aeration rate of 0.1 L / min to 0.4 L / min, a stirring speed of 350 r / min to 500 r / min, and stopping the introduction of carbon dioxide gas when the pH value of the slurry drops below 7.5. The method for preparing high-purity calcium carbonate from calcium-containing raw ore through a tiered processing method of this invention preferentially extracts the easily soluble calcium components from the raw ore through acid leaching, followed by precise carbonation to obtain high-purity calcium carbonate I; then, the solid reactants remaining after acid leaching are subjected to high-temperature roasting to convert the insoluble calcium components into easily digestible calcium oxide, which is subsequently digested with ethanol-assisted digestion, graded screening, aging, and precise carbonation to obtain high-purity calcium carbonate II. The entire process effectively removes impurities such as silicon, magnesium, and iron from the raw ore through multiple purification steps, improving product purity. Compared with the prior art, this invention has the following beneficial effects: (1) High efficiency of cascade utilization: Through the cascade process of "acid leaching extraction-primary carbonization" and "roasting-digestion-secondary carbonization", the calcium element in the calcium-containing raw ore is fully recovered, the raw material utilization rate is high, and the problem of waste of intermediate products in traditional processes is avoided. (2) Stable product purity: The purity of high-purity calcium carbonate I is >99%, and the purity of high-purity calcium carbonate II is >98%, which can meet the needs of different high-end fields and the added value of the products is high.

[0025] (3) Wide adaptability of raw materials: It can process natural minerals such as limestone and calcite.

[0026] (4) Green and controllable process: Ethanol is used to assist digestion and aging, reducing the introduction of impurities. The ethanol recovery process achieves zero harmful waste discharge, which meets environmental protection requirements.

[0027] (5) Simple operation and easy to scale up: The process steps are clear, the reaction conditions are mild (mainly at room temperature, and the calcination temperature is easy to control), the equipment requirements are conventional, and it is easy to scale up industrial production. Attached Figure Description

[0028] The specific embodiments of the present invention will be further explained below with reference to the accompanying drawings.

[0029] Figure 1 This is a flowchart of the method for preparing high-purity calcium carbonate from calcium-containing raw ore through a cascade processing process according to the present invention.

[0030] Figure 2 This is a flowchart of the digestion-carbonation process in the second stage of the method for preparing high-purity calcium carbonate from calcium-containing raw ore according to the present invention. Detailed Implementation

[0031] Combination Figure 1 As shown, the method for preparing high-purity calcium carbonate from calcium ore through a cascade processing method in this embodiment specifically includes the following steps: Step S1: Raw material pretreatment: Wash the calcium-containing raw ore to remove impurities such as mud and dust attached to the surface, and obtain clean raw ore.

[0032] In this embodiment, preferably, in step S1, the calcium-containing ore is selected from at least one of limestone, calcite or marble, and the particle size of the calcium-containing ore is 1 cm to 5 cm.

[0033] Step S2: Acid leaching reaction: Clean raw ore is added to hydrochloric acid solution for reaction. After the reaction is completed, solid-liquid separation is performed to obtain reaction liquid and solid reactants respectively.

[0034] In this embodiment, preferably, in step S2, the clean raw ore and hydrochloric acid solution are reacted at room temperature for 5 h to 12 h. After the reaction, the mixture is washed with distilled water 3 to 5 times, and the liquid and solid are collected to obtain the reaction solution and reactants.

[0035] In this embodiment, preferably, in step S2, the hydrochloric acid solution has a hydrochloric acid mass concentration of 3% to 8%, and a hydrochloric acid solution with a concentration of 40% to 60% based on the theoretical value calculated according to the reaction formula is added to ensure that the Ca element is partially dissolved.

[0036] Step S3: Primary carbonation for high-purity calcium carbonate I: The reaction solution obtained in step S2 is mixed with ammonia solution under stirring to adjust the pH to 12.5-13.5. The mixture is then stirred at room temperature for 30-60 minutes for carbonation. After carbonation, the mixture is washed several times with distilled water to remove as much residual Cl as possible. - After solid-liquid separation, high-purity calcium carbonate I was obtained.

[0037] In this embodiment, preferably, the ammonia water added in step S3 is analytical grade ammonia water, wherein the NH3 content is 25%-28%.

[0038] In this embodiment, preferably, the carbonization conditions in step S3 are as follows: carbonization temperature is 25 ℃, carbon dioxide injection rate is 0.1 L / min to 0.4 L / min, stirring speed is 300 r / min to 500 r / min, and carbon dioxide gas injection is stopped when the pH value of the slurry drops below 7.5 (i.e., the pH value of the slurry does not exceed 7.5).

[0039] Step S4: Calcination treatment: The solid reactant obtained in step S2 is calcined to obtain the calcined product.

[0040] In this embodiment, preferably, in step S4, the solid reactant obtained in step S2 is placed in a vertical kiln and calcined at 850 ℃~1000 ℃ for 2 h~6 h to obtain the calcined product.

[0041] Step S5: Secondary digestion-carbonation to prepare high-purity calcium carbonate II: The calcined material obtained in step S4 is digested and carbonized in a continuous digestion tank to prepare high-purity calcium carbonate II.

[0042] In this embodiment, preferably, combined with Figure 2 As shown, in step S5, the digestion-carbonization process includes the following steps: Step S51: Add the calcined material to an ethanol solution and digest it at 40 ℃~60 ℃ to obtain slurry one.

[0043] In this embodiment, preferably, in step S51, the solid-liquid ratio of the calcined material and the ethanol solution is 1:6, and the ethanol concentration is 3%~8%.

[0044] Step S52: Sieve the first slurry through a 200-mesh standard sieve to remove the digested residue on the sieve, and obtain the second slurry under the sieve.

[0045] Step S53: Add ethanol solution to slurry two to prepare slurry with a concentration of 5%~10%, and obtain slurry three.

[0046] Step S54: Stir and age the slurry at low speed at 25 ℃ for 12 h to 24 h, and then perform carbonization treatment to obtain carbonized slurry.

[0047] In this embodiment, preferably, in step S54, the carbonization process is as follows: the carbonization temperature is 25 ℃, the carbon dioxide gas flow rate is 0.1 L / min~0.4 L / min, the stirring speed is 350 r / min~500 r / min, and the carbon dioxide gas flow is stopped when the pH value of the slurry drops below 7.5 (i.e. the pH value of the slurry does not exceed 7.5).

[0048] Step S54: After the carbonization process is completed, centrifuge the product, dry it at 100 ℃~120 ℃, and break it up to obtain high-purity calcium carbonate II.

[0049] This embodiment, based on the tiered utilization of calcium-containing raw ore and through a tiered process of "acid leaching-carbonation + roasting-ethanol digestion-carbonation", achieves the dual goals of high purity and high recovery rate. The method for preparing high-purity calcium carbonate of different purities is applicable to the efficient processing of natural calcium-containing minerals such as limestone and calcite. The resulting products can be applied in high-end fields such as plastics, rubber, coatings, food additives, and electronic ceramics. Example 1

[0050] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select limestone ore with a particle size of 1 cm to 3 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0051] Step S2: Prepare a 5% hydrochloric acid solution. Add the clean raw ore to the hydrochloric acid solution to react. Add 60% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 5 hours. After solid-liquid separation, wash with distilled water 3 times and collect the reaction liquid and solid reactants.

[0052] Step S3: Add ammonia water to the reaction solution, adjust the pH value to 13.0-13.5, stir at room temperature for 60 min, and then carbonize at 25℃, CO2 flow rate of 0.25 L / min and stirring speed of 350 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0053] Step S4: Place the reactants in a vertical kiln and calcine at 850 °C for 2 h to obtain the calcined product.

[0054] Step S5: Add the calcined material to a 5% ethanol solution at a solid-liquid ratio of 1:6 and digest at 60 °C to obtain slurry one. Remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve. Add ethanol solution to slurry two under the sieve to prepare slurry three with a concentration of 6%. Aged slurry three at 25 °C with low-speed stirring for 24 h. Then carbonize at 25 °C, CO2 flow rate of 0.2 L / min, and stirring speed of 350 r / min until the slurry pH=7.5. After centrifugation and washing several times, dry at 100 °C and break up to obtain high-purity calcium carbonate II. Example 2

[0055] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select calcite ore with a particle size of 3 cm to 5 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0056] Step S2: Prepare a 3% hydrochloric acid solution. Add the clean raw ore to the hydrochloric acid solution to react. Add 50% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 12 hours. After solid-liquid separation, wash three times with distilled water and collect the reaction liquid and solid reactants.

[0057] Step S3: Add analytical grade ammonia solution to the reaction solution, adjust the pH to 12.5, stir at room temperature for 30 min, and then carbonize at 25 ℃, CO2 flow rate of 0.1 L / min and stirring speed of 300 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0058] Step S4: Place the solid reactant obtained in step S2 into a vertical kiln and calcine it at 900 °C for 3 h to obtain the calcined product.

[0059] Step S5: Add the calcined material to a 3% ethanol solution at a solid-liquid ratio of 1:6 and digest at 50 °C to obtain slurry one. Remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve. Add ethanol solution to slurry two under the sieve to prepare 8% slurry three. Aged slurry three at 25 °C with low-speed stirring for 12 h. Then carbonize at 25 °C, CO2 flow rate of 0.3 L / min, and stirring speed of 400 r / min until the slurry pH=7.5. After centrifugation, dry and disperse at 110 °C to obtain high-purity calcium carbonate II. Example 3

[0060] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select marble ore with a particle size of 2 cm to 5 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0061] Step S2: Prepare an 8% hydrochloric acid solution. Add the clean raw ore to the hydrochloric acid solution to react. Add 40% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 7 hours. After solid-liquid separation, wash with distilled water 5 times and collect the reaction liquid and solid reactants.

[0062] Step S3: Add analytical grade ammonia solution to the reaction solution, adjust the pH to 13.5, stir at room temperature for 50 min, and then carbonize at 25 ℃, CO2 flow rate of 0.4 L / min and stirring speed of 400 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0063] Step S4: Place the solid reactant obtained in step S2 into a vertical kiln and calcine it at 950 °C for 4 h to obtain the calcined product.

[0064] Step S5: Add the calcined material to an 8% ethanol solution at a solid-liquid ratio of 1:6 and digest at 40 °C to obtain slurry one. Remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve. Add ethanol solution to slurry two under the sieve to prepare slurry three with a concentration of 10%. Aged slurry three at 25 °C with low-speed stirring for 20 h. Then carbonize at 25 °C with CO2 introduction rate of 0.1 L / min and stirring speed of 500 r / min until the slurry pH=7.5. After centrifugation, dry and disperse at 120 °C to obtain high-purity calcium carbonate II. Example 4

[0065] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select limestone ore with a particle size of 2 cm to 4 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0066] Step S2: Prepare a 6% hydrochloric acid solution. Add the clean raw ore to the hydrochloric acid solution to react. Add 50% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 9 hours. After solid-liquid separation, wash with distilled water 4 times and collect the reaction liquid and solid reactants.

[0067] Step S3: Add analytical grade ammonia solution to the reaction solution, adjust the pH to 13.0, stir at room temperature for 40 min, and then carbonize at 25 ℃, CO2 flow rate of 0.35 L / min and stirring speed of 500 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0068] Step S4: Place the solid reactant obtained in step S2 into a vertical kiln and calcine it at 1000 °C for 2 h to obtain the calcined product.

[0069] Step S5: Add the calcined material to a 5% ethanol solution at a solid-liquid ratio of 1:6 and digest at 60 °C to obtain slurry one. Remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve. Add ethanol solution to slurry two under the sieve to prepare slurry three with a concentration of 9%. Aged slurry three at 25 °C with low-speed stirring for 18 h. Then carbonize at 25 °C with CO2 introduction rate of 0.2 L / min and stirring speed of 450 r / min until the slurry pH=7.5. After centrifugation, dry and disperse at 120 °C to obtain high-purity calcium carbonate II. Example 5

[0070] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select limestone ore with a particle size of 1 cm to 3 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0071] Step S2: Prepare a 5% hydrochloric acid solution by mass. Add the clean raw ore to the hydrochloric acid solution to react. Add 50% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 5 hours. After solid-liquid separation, wash with distilled water 3 times and collect the reaction liquid and solid reactants.

[0072] Step S3: Add analytical grade ammonia solution to the reaction solution, adjust the pH to 13.0, stir at room temperature for 45 min, and then carbonize at 25 ℃, CO2 flow rate of 0.3 L / min and stirring speed of 450 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0073] Step S4: Place the solid reactant obtained in step S2 in a vertical kiln and calcine it at 850 °C for 6 h to obtain the calcined product.

[0074] Step S5: Add the calcined material to a 5% ethanol solution at a mass ratio of 1:6, digest at 55 ℃ to obtain slurry one, remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve, add ethanol solution to slurry two to prepare slurry three with a concentration of 7%, age slurry three at 25 ℃ with low-speed stirring for 14 h, and then carbonize at 25 ℃, CO2 introduction rate of 0.4 L / min, and stirring speed of 350 r / min until the slurry pH=7.5. After centrifugation, dry at 100 ℃ and break up to obtain high-purity calcium carbonate II. Example 6

[0075] The method for preparing high-purity calcium carbonate through a cascade processing of calcium ore in this embodiment includes the following steps: Step S1: Select limestone ore with a particle size of 1 cm to 3 cm (CaO content ≥ 95%), rinse the surface with clean water to remove mud and impurities, and obtain clean ore.

[0076] Step S2: Prepare a 5% hydrochloric acid solution by mass. Add the clean raw ore to the hydrochloric acid solution to react. Add 50% of the hydrochloric acid solution according to the theoretical value calculated by the reaction formula. React at room temperature for 5 hours. After solid-liquid separation, wash with distilled water 3 times and collect the reaction liquid and solid reactants.

[0077] Step S3: Add analytical grade ammonia solution to the reaction solution, adjust the pH to 13.0, stir at room temperature for 55 min, and then carbonize at 25 ℃, CO2 flow rate of 0.25 L / min and stirring speed of 350 r / min until the slurry pH=7.5, then stop the CO2 flow and wash to obtain high-purity calcium carbonate I.

[0078] Step S4: Place the solid reactant obtained in step S2 into a vertical kiln and calcine it at 900 °C for 3 h to obtain the calcined product.

[0079] Step S5: Add the calcined material to a 3% ethanol solution at a mass ratio of 1:6, digest at 45 ℃ to obtain slurry one, remove the digestion residue on the sieve through a 200-mesh standard sieve to obtain slurry two under the sieve, add ethanol solution to slurry two to prepare slurry three with a concentration of 5%, age slurry three at 25 ℃ with low-speed stirring for 24 h, and then carbonize at 25 ℃, CO2 introduction rate of 0.2 L / min, and stirring speed of 500 r / min until the slurry pH=7.5. After centrifugation, dry at 110 ℃ and break up to obtain high-purity calcium carbonate II.

[0080] Comparative Example 1

[0081] This comparative example is based on Example 1 described above, and the similarities with Example 1 will not be repeated. The difference between this comparative example and Example 1 is as follows: This comparative example did not use hydrochloric acid reaction; it was prepared directly using a calcination-digestion-carbonization process.

[0082] Comparative Example 2

[0083] This comparative example is based on Example 1 described above, and the similarities with Example 1 will not be repeated. The difference between this comparative example and Example 1 is as follows: In this comparative example, step S2 was prepared by carbonization after reaction with excess hydrochloric acid, without using the calcination-digestion-carbonization process.

[0084] Comparative Example 3

[0085] This comparative example is based on Example 1 described above, and the similarities with Example 1 will not be repeated. The difference between this comparative example and Example 1 is as follows: In this comparative example, step S3 involved the reaction with hydrochloric acid, but ammonia was not used to adjust the pH.

[0086] Comparative Example 4

[0087] This comparative example is based on Example 1 described above, and the similarities with Example 1 will not be repeated. The difference between this comparative example and Example 1 is as follows: Ethanol was not added in step S5 of this comparative example.

[0088] The CaO content of high-purity calcium carbonate I and high-purity calcium carbonate II prepared in Examples 1-6 and Comparative Examples 1-4 were tested respectively, and the Ca element recovery rate was calculated. The results are shown in the table below:

[0089] Therefore, it can be seen that the CaO content in the high-purity calcium carbonate I prepared in Examples 1-7 of this invention is greater than 99.9%, the CaO content in the high-purity calcium carbonate II is ≥98.22%, and the Ca element recovery rate is greater than 92%, which reflects the stability and reliability of the process. Compared to Comparative Example 1 (without hydrochloric acid leaching), which yielded only a single product and had a Ca element recovery rate of only 76.84%, this demonstrates that acid leaching pretreatment can efficiently extract easily soluble calcium components and improve the overall recovery rate. Comparative Example 2 (without roasting-digestion-carbonation), which used excess hydrochloric acid, achieved a Ca element recovery rate of 94.68%, but the CaO content of high-purity calcium carbonate I was only 99.22%, and the CaO content in high-purity calcium carbonate II was extremely low. This indicates that excess hydrochloric acid in the reaction introduces impurities into high-purity calcium carbonate I, reducing product purity and hindering high-value applications. Comparative Example 3 (without ammonia to adjust pH) did not yield high-purity calcium carbonate I, highlighting the crucial role of ammonia addition. Comparative Example 4, without ethanol, resulted in a CaO content in high-purity calcium carbonate II decreasing to 98.02%, demonstrating that ethanol-assisted impurity removal and optimized reaction efficiency. In summary, this invention achieves the dual goals of high purity and high recovery rate through a stepped process of "acid leaching-carbonization + roasting-ethanol digestion-carbonization", demonstrating significant technical advantages.

[0090] Many specific details have been set forth in the foregoing description to provide a thorough understanding of the present invention. However, the above description is merely a preferred embodiment of the present invention, and the present invention can be implemented in many other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed above. Furthermore, any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity calcium carbonate through a cascade processing of calcium-containing raw ore, characterized in that: Includes the following steps: Step S1: Raw material pretreatment: Wash the calcium-containing raw ore to remove impurities attached to the surface and obtain clean raw ore; Step S2: Acid leaching reaction: Clean raw ore is added to hydrochloric acid solution to react. After the reaction is completed, solid-liquid separation is performed to obtain reaction solution and solid reactants respectively. Step S3: Preparation of high-purity calcium carbonate I by primary carbonation: Add ammonia solution to the reaction solution obtained in step S2 under stirring, adjust the pH to 12.5~13.5, and then stir at room temperature for 30 min~60 min to carry out carbonation treatment. After carbonation, wash several times, and obtain high-purity calcium carbonate I after solid-liquid separation. Step S4: Calcination treatment: The solid reactant obtained in step S2 is calcined to obtain the calcined product; Step S5: Secondary digestion-carbonation to prepare high-purity calcium carbonate II: The calcined material obtained in step S4 is digested and carbonized in a continuous digestion tank to prepare high-purity calcium carbonate II.

2. The method for preparing high-purity calcium carbonate from calcium-containing raw ore through a cascade processing method according to claim 1, characterized in that: In step S1, the calcium-containing ore is selected from at least one of limestone, calcite or marble, and the particle size of the calcium-containing ore is 1 cm to 5 cm.

3. The method for preparing high-purity calcium carbonate from calcium-containing raw ore through a cascade processing method according to claim 1, characterized in that: In step S2, the clean ore reacts with hydrochloric acid solution at room temperature for 5 h to 12 h. After solid-liquid separation, the mixture is washed 3 to 5 times with distilled water, and the liquid and solid are collected to obtain the reaction solution and reactants.

4. The method for preparing high-purity calcium carbonate by graded processing of calcium-containing raw ore according to claim 1, characterized in that: In step S2, the hydrochloric acid solution has a hydrochloric acid mass concentration of 3% to 8%, and a hydrochloric acid solution with a concentration of 40% to 60% based on the theoretical value calculated according to the reaction formula is added to ensure partial dissolution of Ca element.

5. The method for preparing high-purity calcium carbonate by graded processing of calcium-containing raw ore according to claim 1, characterized in that: The ammonia solution in step S3 is analytical grade ammonia solution.

6. The method for preparing high-purity calcium carbonate from calcium-containing raw ore through a cascade processing method according to claim 1, characterized in that: The carbonization conditions in step S3 are as follows: carbonization temperature is 25 ℃, carbon dioxide injection rate is 0.1 L / min to 0.4 L / min, stirring speed is 300 r / min to 500 r / min, and carbon dioxide gas injection is stopped when the pH value of the slurry drops below 7.

5.

7. The method for preparing high-purity calcium carbonate from calcium-containing ore through a cascade processing process according to claim 1, characterized in that: In step S4, the solid reactant obtained in step S2 is placed in a vertical kiln and calcined at 850 ℃~1000 ℃ for 2 h~6 h to obtain the calcined product.

8. The method for preparing high-purity calcium carbonate by graded processing of calcium-containing raw ore according to claim 1, characterized in that: In step S5, the digestion-carbonization process includes the following steps: Step S51: Add the calcined material to an ethanol solution and digest it at 40 ℃~60 ℃ to obtain slurry one; Step S52: Sieve the first slurry to remove the digested residue on the sieve, and obtain the second slurry under the sieve; Step S53: Add ethanol solution to slurry two to prepare slurry with a concentration of 5%~10%, to obtain slurry three; Step S54: Stir and age the slurry at low speed at 25 ℃ for 12 h to 24 h, and then perform carbonization treatment to obtain carbonized slurry; Step S55: After the carbonization process is completed, centrifuge the product, dry it at 100 ℃~120 ℃, and break it up to obtain high-purity calcium carbonate II.

9. The method for preparing high-purity calcium carbonate by graded processing of calcium-containing raw ore according to claim 8, characterized in that: In step S51, the solid-liquid ratio of the calcined material and the ethanol solution is 1:6, and the ethanol concentration is 3%~8%.

10. The method for preparing high-purity calcium carbonate from calcium-containing ore through a cascade processing process according to claim 8, characterized in that: In step S54, the carbonization process is as follows: the carbonization temperature is 25 ℃, the carbon dioxide gas flow rate is 0.1 L / min~0.4 L / min, the stirring speed is 350 r / min~500 r / min, and the carbon dioxide gas flow is stopped when the pH value of the slurry drops below 7.5.

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