CN112479242A - Preparation method of nano calcium carbonate with particle size less than 20nm - Google Patents
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Abstract
The invention discloses a preparation method of nano calcium carbonate with the particle size of less than 20nm, which comprises the following steps: firstly preparing calcium hydroxide coarse pulp, then sieving and aging the calcium hydroxide coarse pulp to obtain calcium hydroxide fine pulp, then carbonizing the calcium hydroxide fine pulp for multiple times, dehydrating and drying to obtain the nano calcium carbonate with the particle size of less than 20 nm. The method of the invention does not need additional equipment investment and modification, has reliable and effective scheme, small investment and high industrialization degree, can prepare the nano calcium carbonate with the grain diameter less than 20nm, and further can fully play the reinforcing role of the nano calcium carbonate.
Description
Technical Field
The invention relates to the technical field of nano calcium carbonate preparation, in particular to a preparation method of nano calcium carbonate with the particle size of less than 20 nm.
Background
The nano calcium carbonate is an important inorganic filler, is widely applied to the fields of silicone structural sealant, plastics, rubber, printing ink and the like, and can endow organic polymers with good thixotropic property and excellent mechanical property. At present, the particle size of common nano calcium carbonate products on the market is generally between 30nm and 100nm, is far inferior to fumed silica (the particle size is generally below 20 nm) in the aspect of mechanical property reinforcement, and can only be used as a semi-reinforcing filler.
CN 111606344 a discloses a method for preparing nano calcium carbonate with high specific surface area, which comprises the following steps: adding urea into the calcium hydroxide suspension, stirring and mixing, adjusting the pH to 8-9 by using ammonia water to obtain slurry A, heating the slurry A to 35-40 ℃ at a constant temperature, introducing mixed gas of carbon dioxide and nitrogen, stopping introducing the mixed gas when the pH of the slurry A is 6.5-7, continuously stirring for 1-2 hours to obtain slurry B, heating the slurry B to 80-90 ℃ at a constant temperature under the stirring condition, adding a composite modifier, keeping the temperature for 2-5 hours to obtain a nano calcium carbonate suspension, and finally filtering and freeze-drying the nano calcium carbonate suspension to obtain the nano calcium carbonate. Although the method can prepare the nano calcium carbonate with the particle size of less than 20nm, the pH of the calcium hydroxide suspension is generally more than 13, the urea is weak alkaline, and the mass fraction of the calcium hydroxide suspension must be less than 1.0% to reduce the pH of the slurry to 8-9 by adding ammonia water, so that the production efficiency is extremely low, and the calcium powder with the particle size of less than 10kg in 1 ton of slurry cannot be industrially applied at all.
CN 107986312 a discloses a preparation method of precipitated calcium carbonate with high specific surface area, which comprises the following steps: mixing quicklime obtained by calcining in a vertical kiln with slaking water in proportion, carrying out slaking reaction, removing impurities by a vibrating screen, conveying calcium hydroxide fine slurry to a stripping machine, grinding for 30-60 min, and feeding the calcium hydroxide fine slurry into a vibrating screen of 200 meshes after grindingRemoving impurities, adjusting the concentration of ground calcium hydroxide slurry to 6-10%, adjusting the temperature to 15-20 ℃, conveying the ground calcium hydroxide slurry into a carbonization kettle, immediately adding a composite crystal form control agent accounting for 0.2-0.8% of the dry weight of the precipitated calcium carbonate after the gelation process of a reaction system disappears, adding a dispersing agent accounting for 3-5% of the dry weight of the precipitated calcium carbonate when the conductivity of the reaction system is reduced to 5.0ms/cm, continuing carbonization until the reaction is finished, and finally, sequentially carrying out filter pressing, dehydration, drying, crushing and grading on the obtained calcium carbonate slurry to obtain the precipitated calcium carbonate with high specific surface area. The specific surface area of the nano calcium carbonate prepared by the method is 50m2/g～85m2The average grain diameter is more than 30nm, namely the nano calcium carbonate with the grain diameter less than 20nm can not be obtained.
Therefore, it is urgently needed to develop a method for preparing nano calcium carbonate with a particle size of less than 20nm, which is simple to operate and suitable for industrialization, and further can fully exert the reinforcing effect of the nano calcium carbonate.
Disclosure of Invention
The invention aims to provide a preparation method of nano calcium carbonate with the particle size of less than 20 nm.
The technical scheme adopted by the invention is as follows:
a preparation method of nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) calcining limestone into calcium oxide, and adding water for pulping to obtain calcium hydroxide coarse pulp;
2) sieving the calcium hydroxide coarse pulp to remove impurities, and then aging to obtain calcium hydroxide fine pulp;
3) adjusting the temperature of the calcium hydroxide fine slurry to 14-18 ℃, introducing lime kiln gas, stopping introducing the lime kiln gas until the reaction system is in a gel state, and adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas, stopping introducing lime kiln gas until the reaction system is in a gel state, and adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction to obtain a second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 1 time or more to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas until the pH of the reaction system is lower than 7.5, stopping introducing the lime kiln gas, and dehydrating and drying to obtain the nano calcium carbonate with the particle size of less than 20 nm.
Preferably, the preparation method of the nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) calcining limestone into calcium oxide, and adding water for pulping to obtain calcium hydroxide coarse pulp;
2) sieving the calcium hydroxide coarse pulp to remove impurities, and then aging to obtain calcium hydroxide fine pulp;
3) adjusting the temperature of the calcium hydroxide fine slurry to 14-18 ℃, introducing lime kiln gas, stopping introducing the lime kiln gas until the reaction system becomes a gel state, adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction, and continuously stirring for 2-3 h to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas, stopping introducing the lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction, and continuously stirring for 0.5-1 h to obtain a second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 1 time or more to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas until the pH of the reaction system is lower than 7.5, stopping introducing the lime kiln gas, and dehydrating and drying to obtain the nano calcium carbonate with the particle size of less than 20 nm.
Preferably, the content of magnesium oxide in the limestone in the step 1) is less than or equal to 0.3 percent.
Preferably, the calcination of step 1) is carried out at 950 ℃ to 1150 ℃.
Preferably, the mass ratio of the calcium oxide to the water in the step 1) is 1: 4-1: 5.
Preferably, the temperature of the water in the step 1) is 40-60 ℃.
Preferably, the sieving in the step 2) is a vibrating sieve which sequentially passes through 120 meshes, 200 meshes and 325 meshes.
Preferably, the aging time in the step 2) is 24-72 h.
Preferably, the mass fraction of the calcium hydroxide seminal plasma in the step 3) is 10-13%.
Preferably, the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt in the steps 3) and 4) is 3000g/mol to 5000 g/mol.
Preferably, the addition amount of the hydrolyzed polyacrylonitrile amine salt in the step 3) is 0.05-0.08 percent of the dry mass of calcium carbonate in slurry obtained after calcium hydroxide fine slurry is introduced into lime kiln gas.
Preferably, the lime kiln gas in the steps 3), 4) and 6) is tail gas with the carbon dioxide volume concentration of 28-33% generated by calcination in the step 1).
Preferably, the gel state in steps 3) and 4) is judged by monitoring the conductivity of the slurry in real time, and the gel state is achieved when the conductivity of the slurry drops to 0.8S/cm per minute.
Preferably, the gas flow of the lime kiln gas in the step 3) is 4000m3/h～5000m3/h。
Preferably, the gas flow of the lime kiln gas in the step 4) is 2000m3/h～4000m3/h。
Preferably, the addition amount of the hydrolyzed polyacrylonitrile amine salt in the step 4) is 0.02-0.04% of the dry mass of calcium carbonate in the slurry obtained by introducing lime kiln gas into the first-stage calcium carbonate slurry.
Preferably, the gas flow of the lime kiln gas in the step 6) is 1000m3/h～1500m3/h。
The principle of the invention is as follows: when the reaction system enters a gel state, a nucleation reaction mainly occurs, the duration of the stage is usually short, once the gelation state disappears, the reaction system immediately enters a crystal growth state, and the traditional method can not prepare the nano calcium carbonate with the particle size less than 20nm because the nucleation quantity is small and the crystal growth reaction is rapid, and the inventor of the application finds through experiments that the reaction is stopped immediately after the gelation state is stopped, the primary formation of the crystal can be prevented, and then hydrolyzed polyacrylonitrile is added, so that on one hand, the viscosity of the system is reduced, the gelation state is eliminated, the crystal nucleus coated on the surface of calcium hydroxide is dropped in the process by fully stirring, on the other hand, the hydrolyzed polyacrylonitrile amine salt can effectively inhibit the generation of the crystal, and meanwhile, the generation of the crystal nucleus can be promoted as much as possible by controlling various means such as kiln gas flow, slurry temperature and the like, and inhibiting the growth of crystals, and repeatedly inducing the generation of a large number of crystal nuclei to prepare the nano calcium carbonate with the grain diameter less than 20 nm.
The invention has the beneficial effects that: the method of the invention does not need additional equipment investment and modification, has reliable and effective scheme, small investment and high industrialization degree, can prepare the nano calcium carbonate with the grain diameter less than 20nm, and further can fully play the reinforcing role of the nano calcium carbonate.
Drawings
FIG. 1 is a transmission electron microscope image of the nano calcium carbonate prepared in example 4.
FIG. 2 is a transmission electron microscope image of the nano calcium carbonate prepared in comparative example 1.
Detailed Description
The invention will be further explained and illustrated with reference to specific examples.
The gel state in examples 1 to 4 was judged by monitoring the conductivity of the slurry in real time, and the gel state was reached when the conductivity of the slurry decreased to 0.8S/cm per minute.
Example 1:
a preparation method of nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) adding limestone with the magnesium oxide content of less than or equal to 0.2% into a vertical kiln, calcining at 1000 ℃ to obtain calcium oxide, and adding tap water at 55 ℃ according to the mass ratio of the calcium oxide to the water of 1:5 to carry out digestion reaction to obtain calcium hydroxide coarse slurry;
2) sequentially sieving the calcium hydroxide coarse pulp by using vibrating screens of 120 meshes, 200 meshes and 325 meshes, and aging for 36 hours to obtain calcium hydroxide fine pulp;
3) the quality of the calcium hydroxide fine slurryAdjusting the fraction to 13%, adjusting the temperature to 14 ℃, adding the mixture into a carbonization kettle with a cooling coil, and introducing lime kiln gas generated by the shaft kiln in the step 1), wherein the lime kiln gas is purified, the volume concentration of carbon dioxide in the lime kiln gas is 28%, and the gas flow is controlled to be 4500m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.06 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 3 hours to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 18 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, controlling the volume concentration of carbon dioxide in the lime kiln gas to be 28%, and controlling the gas flow to be 3000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.02% of dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 1h to obtain second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 1 time to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 18 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, controlling the volume concentration of carbon dioxide in the lime kiln gas to be 28 percent, and controlling the gas flow to be 1200m3And h, stopping introducing lime kiln gas until the pH value of the reaction system is lower than 7.5, and dehydrating and drying to obtain the nano calcium carbonate.
The BET specific surface area of the nano calcium carbonate is tested to be 117m2(iv)/g, average particle diameter 18 nm.
Example 2:
a preparation method of nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) adding limestone with the magnesium oxide content of less than or equal to 0.2% into a vertical kiln, calcining at 1000 ℃ to obtain calcium oxide, and adding tap water at 55 ℃ according to the mass ratio of the calcium oxide to the water of 1:5 to carry out digestion reaction to obtain calcium hydroxide coarse slurry;
2) sequentially sieving the calcium hydroxide coarse pulp by using vibrating screens of 120 meshes, 200 meshes and 325 meshes, and aging for 36 hours to obtain calcium hydroxide fine pulp;
3) adjusting the mass fraction of the calcium hydroxide fine slurry to 10%, adjusting the temperature to 16 ℃, adding the calcium hydroxide fine slurry into a carbonization kettle with a cooling coil, and introducing lime kiln gas generated by the vertical kiln in the step 1), wherein the lime kiln gas is purified, the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled to be 4200m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.06 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 3 hours to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 16 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, wherein the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled at 3000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.03 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 1h to obtain second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 2 times to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 18 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, wherein the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled to be 1000m3And h, stopping introducing lime kiln gas until the pH value of the reaction system is lower than 7.5, and dehydrating and drying to obtain the nano calcium carbonate.
The BET specific surface area of the nano calcium carbonate is 134m2(iv)/g, average particle diameter is 14 nm.
Example 3:
a preparation method of nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) adding limestone with the magnesium oxide content of less than or equal to 0.2% into a vertical kiln, calcining at 1000 ℃ to obtain calcium oxide, and adding tap water at 55 ℃ according to the mass ratio of the calcium oxide to the water of 1:5 to carry out digestion reaction to obtain calcium hydroxide coarse slurry;
2) sequentially sieving the calcium hydroxide coarse pulp by using vibrating screens of 120 meshes, 200 meshes and 325 meshes, and aging for 36 hours to obtain calcium hydroxide fine pulp;
3) adjusting the mass fraction of the calcium hydroxide fine slurry to 12%, adjusting the temperature to 18 ℃, adding the calcium hydroxide fine slurry into a carbonization kettle with a cooling coil, and introducing lime kiln gas generated by the vertical kiln in the step 1), wherein the lime kiln gas is purified, the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled at 5000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.08 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 2 hours to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 16 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, controlling the volume concentration of carbon dioxide in the lime kiln gas to be 32%, and controlling the gas flow to be 2000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.04 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 1h to obtain second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 3 times to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 16 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, wherein the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled at 1500m3And h, stopping introducing lime kiln gas until the pH value of the reaction system is lower than 7.5, and dehydrating and drying to obtain the nano calcium carbonate.
The BET ratio of the nano calcium carbonate is testedSurface area 126m2(iv)/g, average particle diameter is 16 nm.
Example 4:
a preparation method of nano calcium carbonate with the particle size of less than 20nm comprises the following steps:
1) adding limestone with the magnesium oxide content of less than or equal to 0.2% into a vertical kiln, calcining at 1000 ℃ to obtain calcium oxide, and adding tap water at 55 ℃ according to the mass ratio of the calcium oxide to the water of 1:5 to carry out digestion reaction to obtain calcium hydroxide coarse slurry;
2) sequentially sieving the calcium hydroxide coarse pulp by using vibrating screens of 120 meshes, 200 meshes and 325 meshes, and aging for 36 hours to obtain calcium hydroxide fine pulp;
3) adjusting the mass fraction of the calcium hydroxide fine slurry to 12%, adjusting the temperature to 15 ℃, adding the calcium hydroxide fine slurry into a carbonization kettle with a cooling coil, and introducing lime kiln gas generated by the vertical kiln in the step 1), wherein the lime kiln gas is purified, the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled to be 4000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.05 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 2 hours to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 20 ℃, introducing lime kiln gas generated by the shaft kiln in the step 1), purifying the lime kiln gas, wherein the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled at 4000m3Stopping introducing lime kiln gas until the reaction system is in a gel state, adding hydrolyzed polyacrylonitrile amine salt accounting for 0.03 percent of the dry mass of calcium carbonate in the reaction system for viscosity reduction, wherein the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt is 3500g/mol, and continuously stirring for 1h to obtain second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 3 times to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 18 ℃, and introducing lime kiln gas generated by the vertical kiln in the step 1), wherein the lime kiln gas is purified, and the volume concentration of carbon dioxide in the lime kiln gas is32% and the gas flow is controlled at 1200m3And/h, stopping introducing lime kiln gas until the pH of the reaction system is lower than 7.5, and dehydrating and drying to obtain the nano calcium carbonate (shown in a TEM image as figure 1).
The BET specific surface area of the nano calcium carbonate is 131m2(iv)/g, average particle diameter 15 nm.
Comparative example 1:
a preparation method of nano calcium carbonate comprises the following steps:
1) adding limestone with the magnesium oxide content of less than or equal to 0.2% into a vertical kiln, calcining at 1000 ℃ to obtain calcium oxide, and adding tap water at 55 ℃ according to the mass ratio of the calcium oxide to the water of 1:5 to carry out digestion reaction to obtain calcium hydroxide coarse slurry;
2) sequentially sieving the calcium hydroxide coarse pulp by using vibrating screens of 120 meshes, 200 meshes and 325 meshes, and aging for 36 hours to obtain calcium hydroxide fine pulp;
3) adjusting the mass fraction of the calcium hydroxide fine slurry to 12%, adjusting the temperature to 15 ℃, adding the calcium hydroxide fine slurry into a carbonization kettle with a cooling coil, and introducing lime kiln gas generated by the vertical kiln in the step 1), wherein the lime kiln gas is purified, the volume concentration of carbon dioxide in the lime kiln gas is 32%, and the gas flow is controlled to be 4000m3And/h, stopping introducing lime kiln gas until the pH of the reaction system is lower than 7.5, and dehydrating and drying to obtain the nano calcium carbonate (shown in a TEM image as figure 2).
The BET specific surface area of the nano calcium carbonate is 37m2(ii)/g, average particle diameter is 41 nm.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A preparation method of nano calcium carbonate with the particle size of less than 20nm is characterized by comprising the following steps:
1) calcining limestone into calcium oxide, and adding water for pulping to obtain calcium hydroxide coarse pulp;
2) sieving the calcium hydroxide coarse pulp to remove impurities, and then aging to obtain calcium hydroxide fine pulp;
3) adjusting the temperature of the calcium hydroxide fine slurry to 14-18 ℃, introducing lime kiln gas, stopping introducing the lime kiln gas until the reaction system is in a gel state, and adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction to obtain first-stage calcium carbonate slurry;
4) adjusting the temperature of the first-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas, stopping introducing lime kiln gas until the reaction system is in a gel state, and adding hydrolyzed polyacrylonitrile amine salt for viscosity reduction to obtain a second-stage calcium carbonate slurry;
5) repeating the operation of the step 4) for 1 time or more to obtain final-stage calcium carbonate slurry;
6) adjusting the temperature of the final-stage calcium carbonate slurry to 16-20 ℃, introducing lime kiln gas until the pH of the reaction system is lower than 7.5, stopping introducing the lime kiln gas, and dehydrating and drying to obtain the nano calcium carbonate with the particle size of less than 20 nm.
2. The method for preparing nano calcium carbonate with the particle size less than 20nm according to claim 1, which is characterized in that: the content of magnesium oxide in the limestone in the step 1) is less than or equal to 0.3 percent.
3. The process for the preparation of nano calcium carbonate with a particle size of less than 20nm according to claim 1 or 2, characterized in that: the calcination in step 1) is carried out at 950-1150 ℃.
4. The process for the preparation of nano calcium carbonate with a particle size of less than 20nm according to claim 1 or 2, characterized in that: the mass ratio of the calcium oxide to the water in the step 1) is 1: 4-1: 5.
5. The method for preparing nano calcium carbonate with the particle size less than 20nm according to claim 1, which is characterized in that: and in the step 2), the sieving is a vibrating sieve which sequentially passes through 120 meshes, 200 meshes and 325 meshes.
6. The process for the preparation of nano calcium carbonate with a particle size of less than 20nm according to any one of claims 1, 2 and 5, characterized in that: the aging time in the step 2) is 24-72 h.
7. The method for preparing nano calcium carbonate with the particle size less than 20nm according to claim 1, which is characterized in that: the mass fraction of the calcium hydroxide seminal plasma in the step 3) is 10-13%.
8. The process for the preparation of nanocalcium carbonate having a particle size of less than 20nm, according to any one of claims 1, 2, 5 and 7, characterized in that: the number average molecular weight of the hydrolyzed polyacrylonitrile amine salt in the steps 3) and 4) is 3000g/mol to 5000 g/mol.
9. The process for the preparation of nanocalcium carbonate having a particle size of less than 20nm, according to any one of claims 1, 2, 5 and 7, characterized in that: the lime kiln gas in the steps 3), 4) and 6) is tail gas with the volume concentration of 28-33% of carbon dioxide generated by calcination in the step 1).
10. The process for the preparation of nanocalcium carbonate having a particle size of less than 20nm, according to any one of claims 1, 2, 5 and 7, characterized in that: the gas flow of the lime kiln gas in the step 3) is 4000m3/h～5000m3H; the gas flow of the lime kiln gas in the step 4) is 2000m3/h～4000m3H; step 6) the gas flow of the lime kiln gas is 1000m3/h～1500m3/h。
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| CN113200559A (en) * | 2021-04-28 | 2021-08-03 | 襄阳泽东化工集团有限公司 | Method for preparing superfine calcium carbonate by using phosphogypsum and decarbonization analysis gas |
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