Preparation process of light calcium carbonate with high settling volume

Abstract

The invention relates to the technical field of preparation of light calcium carbonate, and particularly discloses a preparation process of light calcium carbonate with high settling volume. According to the preparation process of the light calcium carbonate, the calcium carbonate slurry prepared under specific process conditions is used as a seed crystal, the ammonium chloride leaching solution of the calcium-containing industrial waste residues is used as a raw material, the light calcium carbonate product with the high sedimentation volume (2.4 mL / g-6. 5mL / g) is prepared through the carbonation reaction, the process is simple, convenient and easy to implement, the cost is low, and the method is suitable for industrial production. The application field and the additional value of the light calcium carbonate product prepared by taking the calcium-containing industrial waste residue as the raw material are remarkably improved, the high-end market demand is met, and the method has relatively high popularization and application values.

Description

Technical Field

[0001] The invention relates to the technical field of light calcium carbonate preparation, and in particular to a preparation process of light calcium carbonate with high sedimentation volume. Background Art

[0002] With the rapid development of industry, the amount of calcium-containing industrial waste residues such as carbide slag, steel slag, magnesium slag, and alkali slag is increasing day by day. The annual output of these waste residues has reached tens of millions of tons or even hundreds of millions of tons, which has caused a heavy burden on the environment. Although these waste residues have potential resource value, the current comprehensive utilization rate is generally low. At present, most of these waste residues are used in low value-added fields, such as the preparation of cement, road materials, building bricks, low-end desulfurizers, etc. Although these utilization methods have alleviated the environmental pressure of waste residues to a certain extent, they have not fully utilized their higher economic value. Therefore, in order to improve the utilization rate and added value of these waste residues, it is necessary to explore more efficient and environmentally friendly utilization methods to achieve maximum resource utilization and sustainable development of the environment.

[0003] As one of the important inorganic powder materials, light calcium carbonate is widely used in industries such as plastics, papermaking, coatings, rubber, chemical building materials, daily chemicals, inks, toothpaste, adhesives, and sealing materials. The preparation of high-value-added light calcium carbonate products using the above-mentioned calcium-containing industrial waste residues as raw materials can achieve its high-value-added resource utilization, with high economic value and good environmental benefits. Therefore, the preparation of light calcium carbonate using industrial waste residues such as carbide slag as raw materials has become a hot topic of research and concern in academia and industry.

[0004] At present, the process for preparing light calcium carbonate from calcium-containing industrial waste residues is mainly to leach industrial waste residues with ammonium salts such as ammonium chloride and ammonium sulfate, or hydrochloric acid, and then use carbon dioxide, carbonates or bicarbonates to react with calcium-containing leaching solutions to generate light calcium carbonate products. Their common characteristics are that in addition to calcium ions, the reaction solution also contains a large amount of ammonium ions, chloride ions or sulfate ions. Under this environment, the products obtained all have the problem of too small sedimentation volume, and the sedimentation volume is all below 2.3mL / g. Light calcium carbonate with a high sedimentation volume means that its particles are finer and more uniform, with a larger specific surface area, and thus exhibits many excellent properties in practical applications. Therefore, the development of a preparation method that can effectively increase the sedimentation volume of light calcium carbonate, meet the high-end performance requirements of downstream industries, and take into account cost-effectiveness and achieve simple and efficient production has become a key issue that needs to be urgently addressed in the current industrial field, with extremely broad market prospects and far-reaching industry significance. Summary of the invention

[0005] In view of the problem that the existing light calcium carbonate prepared using calcium-containing industrial waste slag as raw material has a small sedimentation volume and cannot meet high-end performance requirements, the present invention provides a preparation process of light calcium carbonate with a high sedimentation volume.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] A preparation process of light calcium carbonate with high sedimentation volume comprises the following steps:

[0008] Step 1, introducing carbon dioxide gas into the lime milk to carry out carbonation reaction at 5°C to 40°C, and when the pH is 6.8 to 9.2, stopping the aeration to obtain a wet material containing calcium carbonate;

[0009] Step 2: Add Ca 2+ and NH4 + The calcium carbonate-containing wet material is added to the calcium-rich solution to obtain a suspension; wherein the concentration of CaCO3 in the suspension is not less than 0.02 mol / L;

[0010] Step 3, introducing carbon dioxide-containing gas into the suspension to carry out carbonation reaction at 5°C to 65°C. After the reaction is completed, the solid-liquid separation, washing and drying are carried out to obtain light calcium carbonate with high sedimentation volume.

[0011] If the sedimentation volume of light calcium carbonate is too low, it means that the particles are large or agglomerated, the particle size distribution is uneven, and the crystal form or morphology is poor. When used in the plastic industry, it will deteriorate the filling performance of the plastic and distribute unevenly in the plastic matrix, resulting in a decrease in the mechanical properties of the plastic products; in the papermaking industry, it will be detrimental to the optical and physical properties of the paper, reduce the opacity and whiteness of the paper, and also affect the smoothness and strength of the paper. Calcium carbonate cannot be well filled between the paper fibers, affecting the molding quality of the paper; in the coating industry, it will cause insufficient covering power of the coating, change the rheological properties of the coating, cause sedimentation and stratification, and make the difficulty and uniformity of brushing worse, thus affecting the construction performance.

[0012] Compared with the prior art, the present invention first uses lime milk as a raw material, and under specific process conditions, prepares calcium carbonate slurry through a carbonation reaction, adds the calcium carbonate slurry as a seed crystal to a calcium-rich solution, and controls the amount of the calcium carbonate slurry added, and then introduces a carbon dioxide-containing gas for a carbonation reaction, thereby preparing a light calcium carbonate product with a sedimentation volume of 2.4 mL / g to 6.5 mL / g, which meets the high-end performance requirements of downstream industries, improves the market competitiveness of the product, and has extremely broad market prospects and far-reaching industry significance.

[0013] It should be noted that in step 1 and step 2, the wet material containing calcium carbonate is a calcium carbonate-containing slurry directly obtained by stopping ventilation when the pH is 6.8-9.2, or the calcium carbonate-containing slurry is filtered to obtain a calcium carbonate-containing wet filter cake.

[0014] Furthermore, in step 1, when the pH is between 8.5 and 9.2, aeration is stopped.

[0015] Furthermore, in step 1, after adding the crystal shape control agent into the lime milk, a gas containing carbon dioxide is introduced.

[0016] Furthermore, the crystal form controlling agent is sucrose, and the added amount of the sucrose is 0% to 1.2% of the mass of Ca(OH)2 in the lime milk.

[0017] The invention uses sucrose as a crystal form control agent and controls the carbonation temperature to be 5°C-40°C, thereby obtaining a crystal seed with a cubic shape. The crystal seed can better control the particle size distribution, crystal form structure and dispersibility of a calcium carbonate product in a subsequent calcium carbonate preparation process, thereby facilitating the improvement of the sedimentation volume of the calcium carbonate product. The pH value is controlled to be 8.5-9.2 as the reaction end point, so that the calcium hydroxide in the lime milk is not completely carbonated. The calcium carbonate containing a trace amount of calcium hydroxide is used as the crystal seed, which is conducive to adjusting the pH value of the next carbonation reaction, changing the supersaturation at the initial stage of the next carbonation reaction, thereby facilitating the formation of a large number of fine crystals, reducing the product particle size, and further improving the sedimentation volume of the calcium carbonate product. The present invention uses the pre-prepared calcium carbonate slurry as a crystal seed, which can accelerate the subsequent crystallization process of calcium carbonate and reduce the induction period of crystal growth, thereby shortening the entire calcium carbonate production cycle and improving production efficiency. The prepared light calcium carbonate product has a sedimentation volume significantly higher than that of existing calcium carbonate products, has better application effects in the fields of rubber, plastics, papermaking, coatings, etc., can significantly improve the quality and performance of downstream products, and is of great significance for promoting the upgrading of related industries and meeting market demand.

[0018] It should be noted that the calcium carbonate slurry prepared by the present invention needs to be used within 14 days, preferably within 48 hours, to keep the crystal defects on the surface of the newly generated calcium carbonate crystals, these defects can be used as active sites for new crystal growth, improve the number of crystals, reduce the product particle size, and then improve the sedimentation volume. If the storage time exceeds 7 days, or the calcium carbonate slurry is dried and then powder is used as a crystal seed, or the slurry that is redispersed in water after the calcium carbonate slurry is dried is used as a crystal seed, the purpose of improving the sedimentation volume cannot be achieved, and the sedimentation volume of the calcium carbonate product prepared is all below 2mL / g.

[0019] Furthermore, in step 1, the amount of sucrose added is 0.6% to 1.2% of the mass of Ca(OH)2 in the lime milk.

[0020] The preferred amount of crystal form controller added can make the particle size distribution of calcium carbonate crystals narrower, which is conducive to obtaining calcium carbonate seeds with uniform particle size and good crystal form.

[0021] Furthermore, in step one, the crystal form controlling agent is a mixture of sucrose and soluble phosphate.

[0022] Furthermore, in step 1, the amount of sucrose added is 0.6% to 1.2% of the mass of Ca(OH)2 in the lime milk, and the amount of soluble phosphate added is 0.1% to 0.5% of the mass of Ca(OH)2 in the lime milk.

[0023] By using sucrose and soluble phosphate as a crystal form controller, the two can work together to guide and limit the growth of crystal nuclei from multiple directions and locations. On the one hand, they can adjust the formation rate of crystal nuclei and control the number of crystal nuclei; on the other hand, during the crystal growth stage, they can limit the growth rate of crystals, making the growth of crystals in all directions more uniform, thereby obtaining calcium carbonate crystals with smaller particle size and narrower particle size distribution. Using them as seed crystals can significantly increase the sedimentation volume of the subsequently prepared calcium carbonate product, and the sedimentation volume can be controlled at 3.5mL / g to 6.5mL / g.

[0024] Furthermore, in step one, the phosphate includes at least one of potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, disodium hydrogen phosphate or sodium dihydrogen phosphate.

[0025] Furthermore, in step 1, the concentration of Ca(OH)2 in the lime milk is 40g / L to 80g / L.

[0026] Furthermore, in step 1, the volume concentration of CO2 gas in the carbon dioxide-containing gas is 20% to 45%.

[0027] Furthermore, in step 2, the concentration of CaCO3 in the suspension is 0.02 mol / L to 0.1 mol / L.

[0028] Furthermore, in step 2, the calcium-rich solution is a leaching solution obtained by leaching calcium-containing industrial waste residue with ammonium chloride solution; wherein the calcium-rich solution contains Ca 2+ The concentration is 0.2mol / L~0.8mol / L, NH4 + The concentration is 1.0mol / L~2.0mol / L.

[0029] At present, the sedimentation volume of calcium carbonate products prepared by using ammonium chloride solution to soak calcium-containing industrial waste residue as raw material and introducing carbon dioxide for carbonation reaction is all below 2.3mL / g. The present invention creatively uses calcium carbonate slurry prepared under specific process conditions as a crystal seed, significantly improves the sedimentation volume of the calcium carbonate product prepared by using the above-mentioned leaching solution as raw material, realizes the resource utilization of calcium-containing industrial waste residue with high added value, and has high environmental and economic benefits.

[0030] Specifically, the calcium-containing industrial waste slag can be any one or more of carbide slag, steel slag, magnesium slag, and alkali slag.

[0031] Furthermore, in step 2, the concentration of the ammonium chloride solution is 0.3 mol / L to 0.5 mol / L, and the ammonium chloride and the Ca in the calcium-containing industrial waste slag are 2+ The molar ratio is (2.5~3.5):1.

[0032] Furthermore, in step three, the volume concentration of CO2 gas in the carbon dioxide-containing gas is 5% to 100%.

[0033] Furthermore, in step three, the pH at the end point of the carbonation reaction is 6.7 to 8.0.

[0034] The preparation process of light calcium carbonate provided by the invention uses calcium carbonate slurry prepared under specific process conditions as a crystal seed and ammonium chloride leaching solution of calcium-containing industrial waste slag as a raw material to prepare a light calcium carbonate product with a high sedimentation volume (2.4 mL / g to 6.5 mL / g) through a carbonation reaction. The process is simple and easy to operate with low cost, and the application field and added value of the light calcium carbonate product prepared with calcium-containing industrial waste slag as the raw material are significantly improved, so as to meet the needs of the high-end market and have a high value of promotion and application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] The following examples and comparative examples contain Ca 2+ and NH4 + The preparation method of the calcium-rich solution comprises the following steps:

[0037] The carbide slag is mixed with 0.3-0.5 mol / L ammonium chloride solution. The ammonium chloride reacts with the Ca in the carbide slag. 2+ The molar ratio is 3:1, soak at room temperature for 1 hour, separate the solid and liquid, and obtain the leaching solution.

[0038] The Ca content in the leaching solution was detected. 2+ The concentration is 0.2mol / L~0.8mol / L, NH4 + The concentration of Ca in the leaching solution is 1.0 mol / L to 2.0 mol / L. 2+ NH4 + The concentration is related to the calcium ion content in the carbide slag and the concentration of ammonium chloride solution.

[0039] Example 1

[0040] This embodiment provides a preparation process of light calcium carbonate:

[0041] Step 1: Control the temperature at 38°C, and introduce a mixed gas containing 45% by volume of carbon dioxide into a lime milk containing 45 g / L of calcium hydroxide. When the pH is 6.8, stop the aeration to obtain a calcium carbonate slurry;

[0042] Step 2: Add Ca 2+ 0.4mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 13 days was added to the 1.5 mol / L calcium-rich solution, and the mixture was mixed evenly to obtain a suspension, wherein the concentration of calcium carbonate in the suspension was 0.03 mol / L;

[0043] Step 3: Add a mixed gas containing 15% by volume of carbon dioxide into the above suspension, control the temperature at 22°C for carbonation reaction, stop ventilation when the pH is 7.5, filter, wash and dry to obtain a light calcium carbonate product with a purity of 98.8%.

[0044] The sedimentation volume of the light calcium carbonate product prepared in this embodiment is 2.4 mL / g.

[0045] Example 2

[0046] This embodiment provides a preparation process of light calcium carbonate:

[0047] Step 1, adding sucrose to lime milk containing 40 g / L of calcium hydroxide, the amount of sucrose added is 1.2% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 18° C., passing a mixed gas containing 30% by volume of carbon dioxide, and stopping aeration when the pH is 6.8 to obtain a calcium carbonate slurry;

[0048] Step 2: Add Ca 2+ 0.2mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 72 hours was added to the 1.0 mol / L calcium-rich solution, and mixed evenly to obtain a suspension, in which the concentration of calcium carbonate in the suspension was 0.02 mol / L;

[0049] Step 3: Add a mixed gas containing 5% carbon dioxide by volume into the above suspension, control the temperature at 22°C for carbonation reaction, stop ventilation when the pH is 7.5, filter, wash and dry to obtain a light calcium carbonate product with a purity of 98.8%.

[0050] The sedimentation volume of the light calcium carbonate product prepared in this example is 2.6 mL / g.

[0051] Example 3

[0052] This embodiment provides a preparation process of light calcium carbonate:

[0053] Step 1, adding sucrose to lime milk containing 70g / L of calcium hydroxide, the amount of sucrose added is 1.0% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 40°C, passing a mixed gas containing 33% by volume of carbon dioxide, and stopping aeration when the pH is 8.6 to obtain a calcium carbonate slurry;

[0054] Step 2: Add Ca 2+ 0.8mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 7 days was added to the 1.6 mol / L calcium-rich solution, and mixed evenly to obtain a suspension, wherein the concentration of calcium carbonate in the suspension was 0.09 mol / L;

[0055] Step 3: Add a mixed gas containing 80% carbon dioxide by volume into the above suspension, control the temperature at 5°C for carbonation reaction, stop ventilation when the pH is 7.9, filter, wash and dry to obtain a light calcium carbonate product with a purity of 99.1%.

[0056] The sedimentation volume of the light calcium carbonate product prepared in this embodiment is 2.8 mL / g.

[0057] Example 4

[0058] This embodiment provides a preparation process of light calcium carbonate:

[0059] Step 1, adding sucrose and potassium dihydrogen phosphate to lime milk containing 60g / L of calcium hydroxide, wherein the amount of sucrose added is 0.8% of the mass of calcium hydroxide in the lime milk, and the amount of potassium dihydrogen phosphate added is 0.4% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 22°C, passing a mixed gas containing 40% by volume of carbon dioxide, and stopping aeration when the pH drops to 8.8 to obtain a calcium carbonate slurry;

[0060] Step 2: Add Ca 2+ 0.8mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 12 hours was added to the 1.9 mol / L calcium-rich solution, and mixed evenly to obtain a suspension, in which the concentration of calcium carbonate in the suspension was 0.10 mol / L;

[0061] Step 3: Add a mixed gas containing 50% carbon dioxide by volume into the above suspension, control the temperature at 65°C for carbonation reaction, stop ventilation when the pH is 8.0, filter, wash and dry to obtain a light calcium carbonate product with a purity of 99.8%.

[0062] The sedimentation volume of the light calcium carbonate product prepared in this embodiment is 6.5 mL / g.

[0063] Example 5

[0064] This embodiment provides a preparation process of light calcium carbonate:

[0065] Step 1, adding sucrose and sodium dihydrogen phosphate to lime milk containing 80g / L of calcium hydroxide, wherein the amount of sucrose added is 0.6% of the mass of calcium hydroxide in the lime milk, and the amount of sodium dihydrogen phosphate added is 0.1% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 6°C, passing a mixed gas containing 45% by volume of carbon dioxide, and stopping aeration when the pH drops to 8.5 to obtain a calcium carbonate slurry;

[0066] Step 2: Add Ca 2+ 0.6mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 39 hours was added to the 1.5 mol / L calcium-rich solution, and mixed evenly to obtain a suspension, in which the concentration of calcium carbonate in the suspension was 0.05 mol / L;

[0067] Step 3: Pass pure carbon dioxide gas into the above suspension, control the temperature at 45°C for carbonation reaction, stop ventilation when the pH is 6.8, filter, wash and dry to obtain a light calcium carbonate product with a purity of 99.4%.

[0068] The sedimentation volume of the light calcium carbonate product prepared in this embodiment is 3.5 mL / g.

[0069] Example 6

[0070] This embodiment provides a preparation process of light calcium carbonate:

[0071] Step 1, adding sucrose and potassium phosphate to lime milk containing 50 g / L of calcium hydroxide, wherein the amount of sucrose added is 0.7% of the mass of calcium hydroxide in the lime milk, and the amount of potassium phosphate added is 0.3% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 10° C., introducing a mixed gas containing 20% ​​by volume of carbon dioxide, and stopping aeration when the pH drops to 9.2 to obtain a calcium carbonate slurry;

[0072] Step 2: Add Ca 2+ 0.4mol / L and NH4 + The calcium carbonate slurry prepared above and placed for 28 hours was added to the 1.0 mol / L calcium-rich solution, and mixed evenly to obtain a suspension, in which the concentration of calcium carbonate in the suspension was 0.07 mol / L;

[0073] Step 3: Add a mixed gas containing 15% carbon dioxide by volume into the above suspension, control the temperature at 15°C for carbonation reaction, stop ventilation when the pH is 6.9, filter, wash and dry to obtain a light calcium carbonate product with a purity of 99.3%.

[0074] The sedimentation volume of the light calcium carbonate product prepared in this example is 4.0 mL / g.

[0075] Example 7

[0076] This embodiment provides a preparation process of light calcium carbonate, which is different from that of embodiment 5 in that calcium carbonate wet filter cake is used in step 2. The specific steps are as follows:

[0077] Step 1, adding sucrose and potassium phosphate to lime milk containing 50 g / L of calcium hydroxide, wherein the amount of sucrose added is 0.7% of the mass of calcium hydroxide in the lime milk, and the amount of potassium phosphate added is 0.3% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 10° C., introducing a mixed gas containing 20% ​​by volume of carbon dioxide, and when the pH drops to 9.2, stopping the ventilation, filtering the slurry after the reaction, and obtaining a calcium carbonate wet cake;

[0078] Step 2: Add Ca 2+ 0.4mol / L and NH4 + The calcium carbonate wet cake prepared above was added to a 1.0 mol / L calcium-rich solution, and the mixture was mixed evenly to obtain a suspension, wherein the concentration of calcium carbonate in the suspension was 0.07 mol / L;

[0079] Step 3: Add a mixed gas containing 15% carbon dioxide by volume into the above suspension, control the temperature at 15°C for carbonation reaction, stop ventilation when the pH is 6.9, filter, wash and dry to obtain a light calcium carbonate product with a purity of 99.2%.

[0080] The sedimentation volume of the light calcium carbonate product prepared in this embodiment is 3.9 mL / g.

[0081] Comparative Example 1

[0082] This comparative example provides a method for preparing calcium carbonate. The only difference from Example 2 is that the calcium carbonate slurry prepared in step 1 of Example 2 is dried and the obtained powder is used as a seed crystal. The specific steps are as follows:

[0083] Step 1, adding sucrose to lime milk containing 40 g / L of calcium hydroxide, the amount of sucrose added being 1.2% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 18° C., passing a mixed gas containing 30% by volume of carbon dioxide, and stopping aeration when the pH is 6.8 to obtain a calcium carbonate slurry; drying the calcium carbonate slurry to obtain a calcium carbonate powder;

[0084] Step 2: Add Ca 2+ 0.2mol / L and NH4 + The calcium carbonate powder prepared above was added to the 1.0 mol / L calcium-rich solution, and the mixture was mixed evenly to obtain a suspension, wherein the concentration of calcium carbonate in the suspension was 0.02 mol / L;

[0085] Step 3: Add a mixed gas containing 5% by volume of carbon dioxide into the above suspension, control the temperature at 22°C for carbonation reaction, stop ventilation when the pH is 7.5, filter, wash and dry to obtain a light calcium carbonate product.

[0086] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.7 mL / g.

[0087] Comparative Example 2

[0088] This comparative example provides a preparation process of calcium carbonate, which is different from Example 4 only in that the calcium carbonate slurry prepared in step 1 is dried and then redispersed in water as a crystal seed. The specific steps are as follows:

[0089] Step 1, adding sucrose and potassium dihydrogen phosphate to lime milk containing 60g / L of calcium hydroxide, wherein the amount of sucrose added is 0.8% of the mass of calcium hydroxide in the lime milk, and the amount of potassium dihydrogen phosphate added is 0.4% of the mass of calcium hydroxide in the lime milk, controlling the temperature at 22°C, introducing a mixed gas containing 40% by volume of carbon dioxide, and stopping ventilation when the pH drops to 8.8 to obtain a calcium carbonate slurry; drying the calcium carbonate slurry, and dispersing it in water to obtain a calcium carbonate dispersion, wherein the concentration of the calcium carbonate dispersion is 0.81mol / L;

[0090] Step 2: Add Ca 2+ 0.8mol / L and NH4 + The calcium carbonate dispersion prepared above was added to the 1.9 mol / L calcium-rich solution, and the mixture was mixed evenly to obtain a suspension, wherein the concentration of calcium carbonate in the suspension was 0.10 mol / L;

[0091] Step 3: Add a mixed gas containing 50% by volume of carbon dioxide into the above suspension, control the temperature at 65°C for carbonation reaction, stop ventilation when the pH is 8.0, filter, wash and dry to obtain a light calcium carbonate product.

[0092] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 2.0 mL / g.

[0093] Comparative Example 3

[0094] This comparative example provides a preparation process of calcium carbonate, which is different from Example 5 only in that the concentration of calcium carbonate in the suspension in step 2 is changed to 0.01 mol / L, and the remaining steps are exactly the same as those in Example 5 and will not be repeated here.

[0095] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.9 mL / g.

[0096] Comparative Example 4

[0097] This comparative example provides a preparation process of calcium carbonate, which is different from Example 6 in that the carbonation reaction temperature in step 3 is changed to 68° C. The remaining steps are exactly the same as those in Example 6 and will not be repeated here.

[0098] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.6 mL / g.

[0099] Comparative Example 5

[0100] This comparative example provides a preparation process of calcium carbonate, which is different from Example 2 in that the carbonation reaction temperature in step 1 is changed to 45° C. The remaining steps are exactly the same as those in Example 2 and will not be repeated here.

[0101] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 2.2 mL / g.

[0102] Comparative Example 6

[0103] This comparative example provides a preparation process of calcium carbonate:

[0104] Step 1, at 20°C, mix carbide slag, ammonium chloride and water, wherein the mass ratio of water to carbide slag is 4:1, and the mass ratio of ammonium chloride to carbide slag is 1.5 times the theoretical amount, stir and react for 10 minutes, filter, and obtain a calcium-rich solution;

[0105] Step 2: prepare a citric acid solution with a mass fraction of 1% by weight by mixing citric acid and water, mix the above calcium-rich solution and the citric acid solution, the volume of the citric acid solution is 2% of the volume of the calcium-rich solution, introduce carbon dioxide gas at a flow rate of 150 mL / min, react at 20° C. for 1 h, filter, and obtain calcium carbonate and carbonated liquid;

[0106] Step 3: Dry the calcium carbonate filter cake at 300° C. for 3 hours to obtain the calcium carbonate product.

[0107] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.8 mL / g.

[0108] Comparative Example 7

[0109] This comparative example provides a preparation process of calcium carbonate:

[0110] Step 1, adding hydrochloric acid solution to carbide slag for reaction, with a molar ratio of chloride to calcium of 2.3:1, to obtain a calcium chloride solution;

[0111] Step 2: Add ammonia water to the ammonium carbonate solution to obtain a mixed solution, quickly add the calcium chloride solution obtained in the above step to the mixed solution, and carry out a mixing reaction at 20° C. for 30 minutes. The molar ratio of calcium ions, carbonate ions, and ammonia water is 1:1.2:1.2. After filtering, washing, and drying at 105° C. for 2 hours, a calcium carbonate product is obtained.

[0112] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.5 mL / g.

[0113] Comparative Example 8

[0114] This comparative example provides a preparation process of calcium carbonate:

[0115] Carbide slag is leached with ammonium chloride solution to obtain a leaching solution containing calcium chloride at a concentration of 0.45 mol / L, into which an aqueous solution with a nano-calcium carbonate concentration of 0.005 mol / L and ammonia water with a concentration of 0.3 mol / L are added, and a mixed gas with a carbon dioxide concentration of 9% is introduced for carbonation reaction. The reaction temperature is controlled at 22°C, and the reaction is stopped when the pH value drops to 7.8. The suspension after the reaction is filtered, washed, and dried to obtain a calcium carbonate product.

[0116] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 1.7 mL / g.

[0117] Comparative Example 9

[0118] This comparative example provides a preparation process of calcium carbonate:

[0119] Step 1, mixing carbide slag with 8 g / L ammonium chloride solution, leaching at 30° C. for 60 min, and filtering to obtain a leaching solution; wherein the mass ratio of carbide slag to ammonium chloride in the ammonium chloride solution is 1:2;

[0120] Step 2, adjusting the pH value of the leaching solution to 11 using 25% ammonia water, then adding ammonium bicarbonate and magnesium chloride, mixing evenly, introducing 50% by volume carbon dioxide gas at 20° C. for carbonation reaction until the pH value is equal to 7, and then terminating the carbonation reaction to obtain a reaction liquid; wherein the mass of ammonium bicarbonate is 10% of the mass of the carbide slag, and the mass of magnesium chloride is 5% of the mass of the carbide slag;

[0121] Step 3, adding sodium polyacrylate to the reaction liquid, stirring evenly to obtain a slurry; wherein the mass of the sodium polyacrylate is 1% of the mass of the carbide slag;

[0122] Step 4: Filter and dry the slurry to obtain a calcium carbonate product.

[0123] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 2.3 mL / g.

[0124] Comparative Example 10

[0125] This comparative example provides a preparation process of calcium carbonate:

[0126] Step 1: dilute the lime milk aged for 24 hours with water to obtain a slurry containing 6% calcium hydroxide;

[0127] Step 2, adding aluminum chloride with a mass percentage of 1% of calcium hydroxide as a crystal form controller to the above slurry, passing a carbon dioxide mixed gas with a concentration of 27% to carry out a first carbonation reaction, stopping aeration after pH ≤ 7.5, adding hydroxyethylidene diphosphonic acid with a mass percentage of 1% of calcium hydroxide as a crystal form controller after aging for 4 hours, and continuing to pass a carbon dioxide mixed gas with a concentration of 27% to carry out a second carbonation reaction until pH ≤ 7, and then stopping aeration to obtain a calcium carbonate suspension; the carbonation temperature is 25° C.;

[0128] Step 3: Filter and dry the suspension to obtain a calcium carbonate product.

[0129] The sedimentation volume of the calcium carbonate product prepared in this comparative example is 2.1 mL / g.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for preparing light calcium carbonate with high sedimentation volume, characterized in that: The following steps are involved: Step 1, introducing carbon dioxide gas into the lime milk to carry out carbonation reaction at 5°C to 40°C, and when the pH is 6.8 to 9.2, stopping the aeration to obtain a wet material containing calcium carbonate; Step 2: Add Ca 2+ and NH4 + The calcium carbonate-containing wet material is added to the calcium-rich solution to obtain a suspension; wherein the concentration of CaCO3 in the suspension is not less than 0.02 mol / L; Step 3, introducing carbon dioxide-containing gas into the suspension to carry out carbonation reaction at 5°C to 65°C. After the reaction is completed, the solid-liquid separation, washing and drying are carried out to obtain light calcium carbonate with high sedimentation volume.

2. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 1, characterized in that, In step 1, when the pH is between 8.5 and 9.2, stop aeration.

3. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 1, characterized in that, In step 1, after adding the crystal shape control agent into the lime milk, a gas containing carbon dioxide is introduced.

4. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 3, characterized in that, The crystal form controlling agent is sucrose, and the amount of sucrose added is 0% to 1.2% of the mass of Ca(OH)2 in the lime milk; and / or In step 1, the volume concentration of CO2 gas in the carbon dioxide-containing gas is 20% to 45%.

5. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 3, characterized in that, In step 1, the crystal form controlling agent also includes a soluble phosphate.

6. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 5, characterized in that, In step 1, the amount of soluble phosphate added is 0% to 0.5% of the mass of Ca(OH)2 in the lime milk.

7. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 1, characterized in that, In step 1, the concentration of Ca(OH)2 in the lime milk is 40 g / L to 80 g / L; and / or In step 2, the concentration of CaCO3 in the suspension is 0.02 mol / L to 0.1 mol / L.

8. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 1, characterized in that, In step 2, the calcium-rich solution is a leaching solution obtained by leaching calcium-containing industrial waste residue with ammonium chloride solution; wherein the calcium-rich solution contains Ca 2+ The concentration is 0.2mol / L~0.8mol / L, NH4 + The concentration is 1.0mol / L~2.0mol / L.

9. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 8, characterized in that, In step 2, the concentration of the ammonium chloride solution is 0.3 mol / L to 0.5 mol / L, and the ammonium chloride reacts with the Ca in the calcium-containing industrial waste residue. 2+ The molar ratio is (2.5~3.5):

1.

10. The preparation process of light calcium carbonate with high sedimentation volume as claimed in claim 1, characterized in that: In step 3, the volume concentration of CO2 gas in the carbon dioxide-containing gas is 5% to 100%; and / or In step 3, the pH at the end point of the carbonation reaction is 6.7 to 8.0.