CN109179471B - Preparation method of light calcium carbonate with anti-sedimentation property - Google Patents
Preparation method of light calcium carbonate with anti-sedimentation property Download PDFInfo
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- CN109179471B CN109179471B CN201811139372.7A CN201811139372A CN109179471B CN 109179471 B CN109179471 B CN 109179471B CN 201811139372 A CN201811139372 A CN 201811139372A CN 109179471 B CN109179471 B CN 109179471B
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- C01F11/182—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by an additive other than CaCO3-seeds
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Abstract
The invention relates to the technical field of light calcium carbonate,in particular to a preparation method of light calcium carbonate with anti-sedimentation property. The preparation method comprises the following steps: reacting calcium oxide with water to obtain Ca (OH) 2 A slurry; ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction, adding polycarboxylate dispersant to carry out primary coating in the carbonization process, and stopping carbonization when the pH value of the reaction system is 6.5-7.5 to obtain cooked slurry; concentrating clinker slurry to Baume degree of 18-22' Be, adding polycarboxylate dispersant into the concentrated clinker slurry again, and carrying out secondary coating by adopting a turbine stirrer to obtain slurry; and dehydrating, drying, crushing and screening the materials to obtain the light calcium carbonate with sedimentation resistance. The light calcium carbonate obtained by the invention is in a spindle-shaped crystal form, the grain diameter reaches 1.4 mu m, the monodispersity reaches 56%, and the sedimentation volume ratio reaches more than 70%.
Description
Technical Field
The invention relates to the technical field of light calcium carbonate, in particular to a preparation method of light calcium carbonate with anti-sedimentation property.
Background
Light calcium carbonate is generally obtained by calcining, emulsifying and carbonating limestone. The product has the indexes of purity, density, apparent specific volume, activity, adsorptivity, refractive index, whiteness, impurity content and the like which are greatly different from those of limestone (calcium carbonate) through three phase change processes of limestone decomposition, lime emulsification and carbonation, and particularly has small apparent density, so the product is called light calcium carbonate. It is an important filler or additive in the fields of plastics, rubber, paper-making, coating, sealing material and ink, etc. its dosage is 600 ten thousand tons or more.
Most of the paint and ink contain a certain proportion of light calcium carbonate, and the light calcium carbonate can be used as white pigment filler, and can partially replace other expensive materials such as titanium pigment. Because the true specific gravity of the light calcium carbonate is about 2.70, the particles are larger, and the agglomeration phenomenon is serious, so that the sedimentation property of the light calcium carbonate is large. Although various measures are adopted in the paint formulation and production process, a plurality of problems are caused by sedimentation of the light calcium carbonate filler in the storage and use processes, the preservability of the paint is reduced, and the construction and product quality are affected. At present, dispersing agents, thickening agents, anti-sedimentation agents or thixotropic agents such as cellulose ether, fumed silica and bentonite are mostly adopted at home and abroad to reduce the sedimentation property. However, these additives are often limited by their high price, large amounts, undesirable effects or poor versatility.
Disclosure of Invention
Aiming at the problem of large sedimentation of the existing light calcium carbonate, the invention provides a preparation method of the light calcium carbonate with sedimentation resistance.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
a method for preparing light calcium carbonate with sedimentation resistance, which at least comprises the following steps:
step a, calcium oxide reacts with water to prepare Ca (OH) 2 A slurry;
step b, the Ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas for carbonization, adding polycarboxylate dispersant for primary coating in the carbonization process, and stopping carbonization when the pH value of the reaction system is 6.5-7.5 to obtain clinker slurry;
c, concentrating the clinker slurry to have the Baume degree of 18-22' Be, and adding a polycarboxylate dispersant into the concentrated clinker slurry again under the stirring condition for secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the slurry to obtain the light calcium carbonate with sedimentation resistance.
Compared with the prior art, the preparation method provided by the invention has the following advantages:
(1) The light calcium carbonate obtained by the invention is in a spindle-shaped crystal form, the grain diameter reaches 1.4 mu m, the monodispersity reaches 56%, and the sedimentation volume ratio reaches more than 70%;
(2) According to the invention, through the coating effect of the polycarboxylate dispersant, the agglomeration of fine particles is reduced to the greatest extent, and the high-dispersion activated calcium carbonate powder is obtained;
(3) The invention adopts twice coating, when the primary coating is carried out in the carbonization reaction stage, the added dispersing agent is less, the concentration in the system is lower, the dispersing agent preferentially coats particles with relatively larger particle diameters, the influence on newly generated crystal nucleus and fine particles is not great, the particles can continue to grow up, as the larger particles are coated, the new products are not easy to agglomerate with the particles, even if the agglomeration phenomenon exists, the new products are easy to depolymerize and are soft to agglomerate, the subsequent crushing process can be safely crushed, so the dispersing agent added in the carbonization stage is beneficial to preventing the earliest formed particles from excessively growing up, and the growth of the crystal nucleus of the subsequent newly formed products is not influenced, and the effect is good; after the clinker slurry is concentrated, a large amount of dispersing agent is added, and the strong stirring of a turbine stirrer is adopted, so that the phenomena of coating and preventing re-agglomeration can be effectively realized, the high dispersion performance can be kept for a long time, and the coating has obvious anti-precipitation effect after being added.
Specifically, in the step b and the step c, preferably, the total coating amount of the polycarboxylate dispersant is: 0.4-0.8% of the dry weight of calcium oxide.
Preferably, in step b, 30-35% of the total amount of polycarboxylate dispersant is added in one coating.
Preferably, in step c, 65-70% of the total amount of polycarboxylate dispersant is added during the secondary coating.
Preferably, in the step b, the polycarboxylate dispersant is prepared into a solution with the mass concentration of 10-20%, and the polycarboxylate dispersant and kiln gas enter the reaction kiln through a vent hole at the bottom of the reaction kiln at the same time.
Preferably, in the step c, the polycarboxylate dispersant is prepared into a solution with the mass concentration of 10-20%, and the polycarboxylate dispersant is introduced into the reaction kiln through the vent hole at the bottom of the reaction kiln at the same time under nitrogen.
The dispersing agent is in the form of a solution, and the polycarboxylate dispersing agent solution is introduced from the bottom by utilizing the gas flow of kiln gas or nitrogen, so that the dispersing property of the dispersing agent in the solution is better, and the carbonization reaction is more fully carried out by the kiln gas entering from the bottom.
Preferably, in step c, a turbine stirrer is used, the stirring speed is 500-800rpm, and the stirring time is 15-25min.
As the stirring time is prolonged, the average particle size of calcium carbonate is reduced and the degree of monodispersion is increased, because the intensive stirring of the turbine stirrer is a redispersion and crushing process in which agglomerated particles generated in the later stages of carbonization and during concentration can be "broken up" and the monodispersion state can be maintained in the presence of a dispersing agent, and thus the average particle size of the product is reduced and monodispersity is improved. However, when the stirring time exceeds 25min, the stirring time is too long, re-agglomeration is generated among calcium carbonate particles, the average particle size of the product is increased, the single dispersion degree is reduced instead, and the excessive stirring reduces the coating effect of the dispersing agent while crushing the particles, so that the particles which are originally coated are peeled, and the particles are seriously agglomerated.
Preferably, the carbonization reaction temperature in the step b is 25-30 ℃, and the kiln gas flow is 14-18L/h.LCa (OH) 2 An emulsion.
Preferably, CO in the kiln gas in the step b 2 The volume content is 25-31%. Preferably CO in kiln gas 2 The volume content is 29-31%.
With CO in kiln gas 2 Increased content of CaCO 3 The particle size is gradually reduced, the monodispersity is gradually increased, the particle size of the calcium carbonate can reach below 1.4 mu m or even hundreds of nanometers, and the sedimentation height of a single component of the product reaches above 70 percent. When CO 2 When the content exceeds 31%, the crystal nuclei are too much, the crystal nucleus agglomeration affects the coating effect, and the monodispersity is lowDrop, thus selecting CO 2 The volume content is 25-31%, preferably 29-31%.
Preferably, in step b, the stirring speed is 300-500rpm.
Preferably, the Ca (OH) 2 The average particle size of the slurry is 1.8-2.3 μm.
Selecting average particle diameter of 1.8-2.3 μm, ca (OH) 2 The small particle size is easy to carbonize to form more crystal nuclei and crystal grains, the crystal grains are coated by the dispersant added first to form smaller monodisperse calcium carbonate particles, meanwhile, the small-particle calcium carbonate is coated by the surfactant, the agglomeration resistance is stronger in the subsequent procedures such as continuous carbonation, concentration, filtration separation, drying, crushing and the like, and finally, the obtained calcium carbonate particles are fine. If the calcium hydroxide particles in the emulsion are relatively large, the carbonation process is relatively slow, the carbonation rate among the particles is difficult to be consistent, the sandwich-type pseudo carbonation is easy to form, the carbonation time is long, secondary agglomeration among products is caused, the particle sizes of the products are inconsistent, and coating is uneven even bare coating occurs.
Preferably, the Ca (OH) 2 The mass concentration of the slurry is 10-14%.
Preferably, in the step a, calcium oxide and water with the temperature of 55-65 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 22-26 hours at the temperature of 75-85 ℃, and Ca (OH) is obtained through a 200-300-mesh sieve 2 And (3) sizing.
During the digestion reaction, there are reactions of the following two cases: one is that calcium hydroxide is generated by hydration of the surfaces of calcium oxide particles, and is separated from the surfaces of the calcium oxide particles to be dissolved into water, when the solubility is reached or exceeded, new calcium hydroxide crystal nucleus is formed, and the crystal nucleus grows gradually to form calcium hydroxide particles; in another case, calcium hydroxide formed by hydration of the surface of calcium oxide does not separate from the surface of calcium oxide, so that the surface of calcium oxide is covered, but water molecules can pass through the product layer to enter the inside of the particles and react with calcium oxide, but the process is slower. Thus, the above reaction conditions were selected to give calcium hydroxide having an average particle diameter of 1.8 to 2.3. Mu.m.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an SEM photograph of calcium carbonate provided in test example 1 of the present invention;
FIG. 2 is an XRD photograph of calcium carbonate provided in test example 1 of the present invention;
FIG. 3 is an SEM photograph of calcium carbonate provided in test example 2 of the present invention;
FIG. 4 is an SEM photograph of calcium carbonate provided in test example 3 of the present invention;
wherein, in FIG. 1, reference numeral a-example 1, reference numeral b-example 2, reference numeral c-comparative example 1, reference numeral d-comparative example 2;
in fig. 3, reference numeral a-example 3, reference numeral b-example 4, reference numeral c-example 5, reference numeral d-example 6;
in fig. 4, reference numeral a-comparative example 7, reference numeral b-example 7, reference numeral c-example 1, and reference numeral d-example 8.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, and introducing into the kilnThe gas is carbonized at 25 ℃, the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 16.5g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas, entering the reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at the speed of 800rpm by adopting a turbine stirrer to perform secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Example 2
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 60Kg of 65 ℃ water are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 26 hours at 75 ℃, and Ca (OH) with the average grain diameter of 2.25 mu m is obtained through a 200-mesh sieve 2 Slurry, and adjusting the concentration to be 14wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 28 ℃, wherein the kiln gas flow is 18L/h, and CO in the kiln gas 2 Adding 16.5g of polycarboxylate dispersant and water to prepare a solution with the concentration of 15wt% in the carbonization process, and enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into water to prepare a solution with concentration of 20wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at the speed of 800rpm by adopting a turbine stirrer to perform secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Comparative example 1
The comparative example provides a process for the preparation of light calcium carbonate comprising the steps of:
step a, ca (OH) having an average particle diameter of 2.42 μm and a concentration of 12 wt.% 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 16.5g of polycarboxylate dispersant to prepare a solution with the concentration of 20wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into 10wt% solution and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 800rpm by a turbine stirrer to obtain slurry;
and c, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Comparative example 2
The comparative example provides a process for the preparation of light calcium carbonate comprising the steps of:
step a, ca (OH) having an average particle diameter of 2.56 μm and a concentration of 12 wt.% 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 The volume content is 28%, and 16.5g of polycarboxylate dispersant is added in the carbonization process for primary coating, and carbonization is stopped when the pH value of the reaction system is 7, so as to obtain cooked slurry;
and b, concentrating the clinker slurry to a Baume degree of 20.Be, adding 38.5g of polycarboxylate dispersant into the concentrated cooked slurry again, and stirring for 20min at 800rpm by a turbine stirrer for secondary coating to obtain slurry;
and c, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Test example 1
In order to better illustrate the characteristics of the light calcium carbonate with sedimentation resistance provided by the examples of the present invention, the following performance tests are performed on the calcium carbonate prepared in examples 1 and 2 and comparative examples 1 and 2, and the test results are shown in table 1.
Table 1 test results
As is apparent from Table 1, the calcium carbonate prepared in the examples of the present invention has a high monodispersity, a small particle diameter, a particle diameter of 1.7 μm and a sedimentation volume ratio of 70% or more.
Meanwhile, the calcium carbonate prepared in examples 1 and 2 and comparative examples 1 and 2 were subjected to scanning electron microscope analysis, and Scanning Electron Microscope (SEM) photographs are shown in fig. 1. As can be seen from fig. 1, the calcium carbonate particles of comparative example 1 and comparative example 2 are seriously agglomerated.
The calcium carbonate prepared in example 1 was also subjected to XRD analysis, and the XRD pattern is shown in fig. 2. As can be seen from figure 2, the light calcium carbonate prepared by the invention has good crystallization performance and no obvious impurity peak, and shows that the calcium carbonate product has good stability and high purity.
Example 3
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 40Kg of water at 55 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 22 hours at 85 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300 meshes of sieve 2 Slurry, and adjust the concentration to 12wt%；
Step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 15.75g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 29.25g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Example 4
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 15.75g of polycarboxylate dispersant to prepare a solution with the concentration of 20wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 29.25g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Example 5
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 15.75g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 29.25g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Example 6
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 15.75g of polycarboxylate dispersant to prepare a solution with the concentration of 15wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 29.25g of polycarboxylate dispersant into water to prepare solution with concentration of 20wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Comparative example 3
The embodiment of the invention provides a preparation method of light calcium carbonate, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 The volume content is 31.3 percent, 15.75g of polycarboxylate dispersant is added with water to prepare a solution with the concentration of 10 weight percent in the carbonization process, and the solution and kiln gas are passed through the bottom of a reaction kilnThe vent holes enter a reaction kiln for primary coating, and carbonization is stopped when the pH value of the reaction system is 7.5, so that cooked slurry is obtained;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 29.25g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Test example 2
In order to better illustrate the characteristics of the light calcium carbonate with sedimentation resistance provided in the examples of the present invention, the following performance tests are performed on the calcium carbonate prepared in examples 3 to 6 and comparative example 3, and the test results are shown in table 2.
Table 2 test results
As is apparent from Table 2, the calcium carbonate prepared in the examples of the present invention has a high monodispersity, a small particle diameter, a particle diameter of 1.6 μm and a sedimentation volume ratio of over 70%. Comparative example 3 CO in kiln gas 2 The volume content is high, the particle diameter is small, but the monodispersity is low, and the sedimentation volume ratio is low.
Meanwhile, the calcium carbonate prepared in examples 3 to 6 was subjected to scanning electron microscope analysis, and a Scanning Electron Microscope (SEM) photograph is shown in FIG. 3. As can be seen from fig. 3, the calcium carbonate prepared by the present invention is relatively uniformly dispersed and has a uniform particle size distribution.
Comparative example 4
The embodiment of the invention provides a preparation method of light calcium carbonate, which comprises the following steps:
step a, carrying out digestion reaction on 10Kg of calcium oxide and 50Kg of water at 60 ℃, sealing after the digestion reaction is finished, aging for 24 hours at 80 ℃, and sieving with a 300-mesh sieve to obtain a flat productCa (OH) having a mean particle diameter of 1.81. Mu.m 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 7.84g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 14.56g of polycarboxylate dispersant into water to prepare solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Comparative example 5
The embodiment of the invention provides a preparation method of light calcium carbonate, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 30 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 11.76g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7.5 to obtain cooked slurry;
step c, concentrating clinker slurry to have Baume degree of 22' Be, adding 21.84g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 20min at 600rpm by a turbine stirrer to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Test example 3
In order to better illustrate the characteristics of the light calcium carbonate with sedimentation resistance provided in the examples of the present invention, the calcium carbonate prepared in example 1, example 5 and comparative examples 4 to 5 were subjected to performance test, and the test results are shown in table 3.
Table 3 test results
As is apparent from Table 3, the calcium carbonate prepared in examples 1 and 5 of the present invention has a high monodispersity, a small particle diameter of 1.7 μm and a sedimentation volume ratio of 70% or more. The comparative examples 4 to 5 have a small amount of dispersant, a large calcium carbonate particle diameter, a low monodispersion ratio and a low sedimentation volume ratio.
Example 7
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 The volume content is 28 percent, and 16.5g of polycarboxylate dispersant is added with water to prepare a solution with the concentration of 10 weight percent in the carbonization process, and the solution and kiln gas are reactedThe vent hole at the bottom of the kiln enters the reaction kiln for primary coating, and carbonization is stopped when the pH value of the reaction system is 7, so that cooked slurry is obtained;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas, entering the reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 15min at the speed of 800rpm by using a turbine stirrer to perform secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Example 8
The embodiment of the invention provides a preparation method of light calcium carbonate with anti-sedimentation property, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 16.5g of polycarboxylate dispersant to prepare a solution with the concentration of 20wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into 10wt% solution and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 25min at 800rpm by a turbine stirrer for secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate with sedimentation resistance.
Comparative example 6
The embodiment of the invention provides a preparation method of light calcium carbonate, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃, wherein the kiln gas flow is 16L/h, and CO in the kiln gas 2 Adding water into 16.5g of polycarboxylate dispersant to prepare a solution with the concentration of 15wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into water to prepare a solution with concentration of 20wt% and nitrogen gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 5min at the speed of 800rpm by using a turbine stirrer to perform secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Comparative example 7
The embodiment of the invention provides a preparation method of light calcium carbonate, which comprises the following steps:
step a, 10Kg of calcium oxide and 50Kg of water at 60 ℃ are subjected to digestion reaction, sealing is carried out after the digestion reaction is finished, aging is carried out for 24 hours at 80 ℃, and Ca (OH) with the average particle size of 1.81 mu m is obtained through 300-mesh sieve 2 Slurry, and adjusting the concentration to 12wt%;
step b, ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas to carry out carbonization reaction at 25 ℃ and allowing kiln gas flowThe amount is 16L/h, and CO in kiln gas 2 Adding water into 16.5g of polycarboxylate dispersant to prepare a solution with the concentration of 10wt% in the carbonization process, enabling the solution and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln for primary coating, and stopping carbonization when the pH value of the reaction system is 7 to obtain cooked slurry;
step c, concentrating clinker slurry to 20' Be, adding 38.5g of polycarboxylate dispersant into water to prepare a solution with concentration of 15wt% and nitrogen gas, entering the reaction kiln through a vent hole at the bottom of the reaction kiln, adding the polycarboxylate dispersant into the concentrated clinker slurry again for secondary coating, and stirring for 30min at the speed of 800rpm by using a turbine stirrer to perform secondary coating to obtain slurry;
and d, dehydrating, drying, crushing and screening the material to obtain the light calcium carbonate.
Test example 4
In order to better illustrate the characteristics of the light calcium carbonate with sedimentation resistance provided in the examples of the present invention, the calcium carbonate prepared in example 1, examples 7 to 8 and comparative examples 6 to 7 were subjected to performance tests, and the test results are shown in Table 4.
Table 4 test results
As is apparent from Table 4, the calcium carbonate prepared in example 1 and examples 7 to 8 of the present invention has a high monodispersity, a small particle diameter of 1.7 μm and a sedimentation volume ratio of 70% or more. In comparative example 7, although the calcium carbonate had a small particle size, the monodispersity was low and the sedimentation volume ratio was low.
Scanning Electron Microscope (SEM) photographs of the calcium carbonate prepared in example 1, examples 7 to 8 and comparative example 6 were analyzed by Scanning Electron Microscope (SEM), as shown in fig. 4. As can be seen from FIG. 4, the calcium carbonate particles prepared in comparative example 6 are severely agglomerated.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, or alternatives falling within the spirit and principles of the invention.
Claims (7)
1. A preparation method of light calcium carbonate with sedimentation resistance is characterized in that: the preparation method at least comprises the following steps:
step a, calcium oxide is reacted with water at 55-65 ℃ to prepare Ca (OH) 2 Aging the slurry at 75-85deg.C for 22-26 hr, wherein the Ca (OH) 2 The average grain size of the slurry is 1.8-2.3 mu m;
step b, the Ca (OH) 2 Delivering the slurry into a reaction kiln, introducing kiln gas for carbonization, adding polycarboxylate dispersant for primary coating in the carbonization process, and stopping carbonization when the pH value of the reaction system is 6.5-7.5 to obtain clinker slurry;
step c, concentrating the clinker slurry to have the Baume degree of 18-22' Be, adding a polycarboxylate dispersant into the concentrated clinker slurry again under the stirring condition for secondary coating to obtain slurry, and adopting a turbine stirrer, wherein the stirring speed is 500-800rpm, and the stirring time is 15-25min;
in step b and step c, the total coating amount of the polycarboxylate dispersant is as follows: 0.4-0.8% of calcium oxide dry basis, and in the step b, 30-35% of polycarboxylate dispersant is added during primary coating; in the step c, 65-70% of the total amount of polycarboxylate dispersant is added during secondary coating;
and d, dehydrating, drying, crushing and screening the slurry to obtain the light calcium carbonate with sedimentation resistance.
2. The method for preparing the light calcium carbonate with sedimentation resistance according to claim 1, wherein the method comprises the following steps: step b, preparing a polycarboxylate dispersant into a solution with the mass concentration of 10-20%, and enabling the polycarboxylate dispersant and kiln gas to enter a reaction kiln through a vent hole at the bottom of the reaction kiln at the same time; and/or
And c, preparing a polycarboxylate dispersant into a solution with the mass concentration of 10-20%, and simultaneously introducing the polycarboxylate dispersant into the reaction kiln through a vent hole at the bottom of the reaction kiln in nitrogen.
3. The method for preparing the light calcium carbonate with sedimentation resistance according to claim 1, wherein the method comprises the following steps: in step b, the temperature in the reaction kiln is 25-30 ℃, and the kiln gas flow is 14-18L/h.LCa (OH) 2 An emulsion.
4. A process for the preparation of light calcium carbonate having resistance to sedimentation according to claim 3, characterized in that: in step b, CO in kiln gas 2 The volume content is 25-31%.
5. The method for preparing the light calcium carbonate with sedimentation resistance according to claim 1, wherein the method comprises the following steps: in step b, the stirring speed is 300-500rpm.
6. The method for preparing the light calcium carbonate with sedimentation resistance according to claim 1, wherein the method comprises the following steps: said Ca (OH) 2 The mass concentration of the slurry is 10-14%.
7. The method for preparing the light calcium carbonate with sedimentation resistance according to claim 6, wherein: in the step a, calcium oxide reacts with water at 55-65 ℃ in a mass ratio of 1:4-6, the mixture is sealed after digestion reaction is finished, aged for 22-26h at 75-85 ℃ and sieved by a 200-300 mesh sieve to obtain Ca (OH) 2 And (3) sizing.
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| CN106865589A (en) * | 2015-12-10 | 2017-06-20 | 江门市蓬江区亿艺广告设计工作室 | A kind of low oil factor activated Calcium carbonate preparation method |
| CN106928753A (en) * | 2016-11-07 | 2017-07-07 | 广西民族大学 | A kind of preparation method for PVC automobile chassis stone-impact-proof paint modified calcium carbonates |
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| CN105883882A (en) * | 2016-04-19 | 2016-08-24 | 广西大学 | Aqueous slurry of nano calcium carbonate as well as preparation method and application thereof |
| CN106928753A (en) * | 2016-11-07 | 2017-07-07 | 广西民族大学 | A kind of preparation method for PVC automobile chassis stone-impact-proof paint modified calcium carbonates |
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