CN113698793A - Method and equipment for coating nano calcium carbonate on surface of heavy calcium carbonate - Google Patents
Method and equipment for coating nano calcium carbonate on surface of heavy calcium carbonate Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/02—Compounds of alkaline earth metals or magnesium
- C09C1/021—Calcium carbonates
- C09C1/022—Treatment with inorganic compounds
- C09C1/024—Coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/1862—Stationary reactors having moving elements inside placed in series
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- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/18—Stationary reactors having moving elements inside
- B01J19/20—Stationary reactors having moving elements inside in the form of helices, e.g. screw reactors
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J4/00—Feed or outlet devices; Feed or outlet control devices
- B01J4/001—Feed or outlet devices as such, e.g. feeding tubes
- B01J4/002—Nozzle-type elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/006—Combinations of treatments provided for in groups C09C3/04 - C09C3/12
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/06—Treatment with inorganic compounds
- C09C3/063—Coating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2204/00—Aspects relating to feed or outlet devices; Regulating devices for feed or outlet devices
- B01J2204/002—Aspects relating to feed or outlet devices; Regulating devices for feed or outlet devices the feeding side being of particular interest
Abstract
The invention discloses a method and equipment for coating nano calcium carbonate on the surface of heavy calcium carbonate, which comprises the following steps: crushing natural carbonate minerals to obtain heavy calcium carbonate, mixing part of the heavy calcium carbonate with calcium hydroxide slurry with a preset mass fraction concentration, introducing a gas medium containing carbon dioxide into the mixed material to obtain mixed slurry containing nano-scale light calcium carbonate and heavy calcium carbonate, mixing the mixed slurry with a preset volume amount with the rest of the heavy calcium carbonate, introducing the gas medium containing carbon dioxide into the mixed material, further reacting to generate nano-scale calcium hydroxide, performing surface compounding on the nano-scale light calcium carbonate and the heavy calcium carbonate in the mixed slurry to form composite calcium carbonate slurry, and sequentially filtering, drying, crushing and scattering the rest of the mixed material and the composite calcium carbonate slurry to obtain the composite calcium carbonate with the nano-calcium carbonate coated surface; the heavy calcium carbonate has good surface coating effect, reliable preparation and convenient operation.
Description
Technical Field
The invention relates to the technical field of composite calcium carbonate preparation, in particular to a method and equipment for coating nano calcium carbonate on the surface of heavy calcium carbonate.
Background
Calcium carbonate is one of the most widely used inorganic fillers in polymer composites, and comprises heavy calcium carbonate and light calcium carbonate, and the light calcium carbonate and the heavy calcium carbonate have different performances, wherein the processing of the heavy calcium carbonate is mainly realized by a mechanical crushing and grinding method; the light calcium carbonate is produced by chemical reaction precipitation; from the fineness of the product, the granularity of the light calcium carbonate is much finer than that of the heavy calcium carbonate, when the light calcium carbonate is applied to the plastic material, the light calcium carbonate can be uniformly distributed, the dispersity is better than that of the heavy calcium carbonate, the color uniformity of the rubber material, the strength, toughness, fatigue resistance and other comprehensive mechanical properties of the rubber material are improved, the friction coefficient in the production and granulation process of the rubber material is small, the granulation capability of the plastic material is high, the surface of the plastic product is smooth, and the forming capability is enhanced. But due to the action of adsorption force among molecules, agglomeration easily occurs among high-fineness fillers, and the uniform distribution performance and the comprehensive mechanical energy of the fillers are reduced; therefore, if the advantages and the disadvantages of the heavy calcium carbonate and the light calcium carbonate particles can be combined, the advantages and the disadvantages are improved, the heavy calcium carbonate and the light calcium carbonate are compounded to prepare the particles, so that the heavy calcium carbonate particles have the low-cost characteristic of the heavy calcium carbonate particles, and the surfaces of the heavy calcium carbonate particles are modified by the nano light calcium carbonate to form a surface composite structure, so that the heavy calcium carbonate particles have good binding property with polymers, and the light calcium carbonate particles have wider application prospects.
Disclosure of Invention
In view of the situation of the prior art, the present invention aims to provide a method and an apparatus for coating nano calcium carbonate on the surface of heavy calcium carbonate, which have the advantages of good surface coating effect, reliable preparation and convenient operation.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
a method for coating nano calcium carbonate on the surface of heavy calcium carbonate comprises the following steps: crushing natural carbonate mineral to prepare heavy calcium carbonate, mixing part of the heavy calcium carbonate with calcium hydroxide slurry with a preset mass fraction concentration, then introducing a gas medium containing carbon dioxide into the mixed material to prepare mixed slurry containing nano-grade light calcium carbonate and heavy calcium carbonate, mixing the mixed slurry with a preset volume with the residual heavy calcium carbonate, introducing the gas medium containing carbon dioxide into the mixed material again to make the calcium hydroxide in the mixed material and the carbon dioxide in the gas medium react to generate nano-scale calcium hydroxide, the surface of the nano-grade light calcium carbonate and the heavy calcium carbonate in the mixed slurry are compounded to form composite calcium carbonate slurry, and finally the residual mixed material and the composite calcium carbonate slurry are sequentially filtered, dried, crushed and scattered to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
As a possible implementation manner, further, the scheme specifically includes the following steps:
s01, performing physical crushing on natural carbonate minerals, then performing crushing, grading and sieving on crushed products to obtain coarse heavy calcium carbonate with the granularity of less than 100 microns, then mixing the prepared coarse heavy calcium carbonate with water, adding the mixture into grinding equipment for grinding treatment, and then drying the ground products to obtain the powdery heavy calcium carbonate with the granularity of 0.1-10 microns;
s02, preparing calcium hydroxide slurry with mass fraction concentration of 19-21%, adding 100 parts of the prepared calcium hydroxide slurry into a first processing container, continuously stirring the calcium hydroxide slurry at a stirring speed of 350-550 rpm, simultaneously adding 20-30 parts of ground calcium carbonate into the calcium hydroxide slurry, stirring for 3-8 min, introducing air containing 25-40% of carbon dioxide into the lower liquid level of the mixed slurry, continuously bubbling for 30-40 min to carbonize the calcium hydroxide in the mixed slurry to generate nano-scale light calcium carbonate, mixing the nano-scale light calcium carbonate and the ground calcium carbonate to form mixed slurry, compounding part of the nano-scale light calcium carbonate on the surface of the ground calcium carbonate to form surface-coated nano calcium carbonate, wherein the stirring is kept while introducing air, stopping stirring when the bubbling treatment is finished;
s03, taking the center of the liquid level at the lower part of the mixed slurry as a material transfer point, extracting 75-85% volume of the mixed slurry, transferring the mixed slurry to a second processing container, then adding 30-50 parts of heavy calcium carbonate, continuously stirring the mixed material for 20-40 min at a stirring speed of 550-650 rpm, introducing air containing 25-40% of carbon dioxide into the liquid level of the lower layer of the mixed material when stirring for 3-5 min, bubbling the mixed material in the stirring process, and simultaneously carrying out a chemical combination reaction between calcium hydroxide in the mixed material and carbon dioxide in the air to generate nano calcium hydroxide, wherein the nano calcium carbonate and the heavy calcium carbonate are subjected to surface compounding to form the composite calcium carbonate slurry;
s04, discharging the residual mixed slurry and the composite calcium carbonate slurry prepared in the step S03, and then sequentially filtering, drying, crushing and scattering to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
As a preferred alternative, in step S01, the natural carbonate mineral is preferably a mixture of at least one of calcite, marble, and limestone.
As a preferred alternative, preferably, after the step S02 is completed, the pH of the mixed slurry is controlled to be 7.5 to 8.0; and after the step S03 is finished, controlling the pH value of the composite calcium carbonate slurry to be 7.0.
In a preferred alternative embodiment, the air containing 25 to 40% of carbon dioxide is preferably 2.5 to 3.0m in step S023Introducing the flow velocity of/h to the lower liquid level of the mixed slurry; in step S03, the air containing 25% -40% carbon dioxide is 1.5-2.0 m3And/h, introducing the flow velocity into the lower layer liquid level of the mixed material.
As a preferred alternative embodiment, in step S02, it is preferable that the nano-sized light calcium carbonate suspended in the mixed slurry at least contains nano-sized light calcium carbonate having a particle size of 40 to 600 nm; in the step S04, when the filtered material is dried, the filtered material is dried for 6-7 hours under the negative pressure at the temperature of 95-105 ℃.
As a preferred alternative embodiment, in step S03, when the ground calcium carbonate is added, a sodium polyacrylate salt is preferably added as a dispersant, wherein the addition amount of the dispersant is 0.01 to 0.03 times of the mixed slurry.
As a preferred alternative, it is preferable that the temperature of the first processing container is dynamically maintained at 30 to 50 ℃ in step S02; in step S03, the temperature of the second processing container is dynamically maintained at 20-50 ℃.
As a preferred alternative, it is preferable that the carbon dioxide-containing air is introduced into the mixed slurry or the mixed material in a stirred state at a favorable angle in steps S02 and 03.
Based on the method, the invention also provides equipment for coating the surface of the heavy calcium carbonate with the nano calcium carbonate, which applies the method; the apparatus comprises:
a first processing vessel for processing the mixed slurry;
the first stirring device is arranged on the first processing container, and the stirring end of the first stirring device penetrates into the first processing container;
the second processing container is used for processing the composite calcium carbonate slurry;
the second stirring device is arranged on the second processing container, and the stirring end of the second stirring device penetrates into the second processing container;
the material transfer device is respectively connected with the lower part in the first processing container and the second processing container and is used for conveying the material in the first processing container to the second processing container;
a gas delivery device which is connected with the first processing container and the second processing container respectively, penetrates into the lower parts of the first processing container and the second processing container, and is used for outputting air containing carbon dioxide;
the discharge auxiliary device is respectively connected with the first processing container and the second processing container and is used for collecting materials output by the first processing container and the second processing container;
the filtering device is connected with the discharging auxiliary device and is used for drying the materials collected by the discharging auxiliary device;
the drying device is connected with the filtering device and is used for drying the material obtained by filtering by the filtering device;
and the crushing and scattering device is connected with the drying device and is used for crushing and scattering the materials dried by the drying device.
By adopting the technical scheme, the invention has the beneficial effects that: the technical effect of coating the surface of the heavy calcium carbonate with the nano calcium carbonate is ingeniously realized by a two-stage synthesis method, so that the heavy calcium carbonate and the nano calcium carbonate are compounded to form a composite calcium carbonate material, wherein, the two processing containers are used for respectively processing the two-stage synthesis reaction, so that part of large-particle slurry is left in the first processing container, wherein the mixed slurry with more nano calcium carbonate with smaller particle size suspended is transferred to a second processing container to be further combined with the newly added heavy calcium carbonate, at the same time, air containing carbon dioxide is introduced for secondary reaction to generate nano-scale light calcium carbonate, so that the surface of the heavy calcium carbonate attached with the nanometer light calcium carbonate is continuously and further improved in coating rate, meanwhile, the heavy calcium surface without the attached nano-scale light calcium carbonate is coated by the nano-scale light calcium carbonate continuously generated in the mixed slurry; the scheme also changes the input angle of the air containing carbon dioxide through the structure of the gas nozzle, so that the input air can be better diffused in the mixed material in the stirring process, the efficiency and the reliability of the combination of the residual calcium hydroxide and the carbon dioxide in the mixed material are improved, and the reaction is more sufficient.
Drawings
The invention will be further elucidated with reference to the drawings and the detailed description:
FIG. 1 is a schematic flow chart of a method of the present invention;
FIG. 2 is a schematic diagram of the structure of a device according to the present invention;
FIG. 3 is one of the gas shower configurations of the apparatus of the present invention;
FIG. 4 shows a second gas shower structure of the apparatus according to the present invention.
Detailed Description
The invention relates to a method for coating nano calcium carbonate on the surface of heavy calcium carbonate, which comprises the following steps: crushing natural carbonate mineral to prepare heavy calcium carbonate, mixing part of the heavy calcium carbonate with calcium hydroxide slurry with a preset mass fraction concentration, then introducing a gas medium containing carbon dioxide into the mixed material to prepare mixed slurry containing nano-grade light calcium carbonate and heavy calcium carbonate, mixing the mixed slurry with a preset volume with the residual heavy calcium carbonate, introducing the gas medium containing carbon dioxide into the mixed material again to make the calcium hydroxide in the mixed material and the carbon dioxide in the gas medium react to generate nano-scale calcium hydroxide, the surface of the nano-grade light calcium carbonate and the heavy calcium carbonate in the mixed slurry are compounded to form composite calcium carbonate slurry, and finally the residual mixed material and the composite calcium carbonate slurry are sequentially filtered, dried, crushed and scattered to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
Specifically, with reference to fig. 1, as a possible implementation manner, the method specifically includes the following steps:
s01, performing physical crushing on natural carbonate minerals, then crushing, grading and sieving crushed products to obtain coarse heavy calcium carbonate with the granularity of less than 100 microns, then mixing the prepared coarse heavy calcium carbonate with water, adding the mixture into grinding equipment for grinding treatment, and then drying the ground products to obtain the ground calcium carbonate with the granularity of 0.1-10 microns and in a powdery form, wherein in the step, the natural carbonate minerals are formed by mixing more than one of calcite, marble and limestone;
s02, preparing calcium hydroxide slurry with mass fraction concentration of 19-21%, adding 100 parts of the prepared calcium hydroxide slurry into a first processing container, continuously stirring the calcium hydroxide slurry at a stirring speed of 350-550 rpm, simultaneously adding 20-30 parts of heavy calcium carbonate into the calcium hydroxide slurry, stirring for 3-8 min, introducing air containing 25-40% of carbon dioxide into the lower liquid level of the mixed slurry, carrying out continuous bubbling for 30-40 min, carbonizing the calcium hydroxide in the mixed slurry to generate nanoscale light calcium carbonate, mixing the nanoscale light calcium carbonate and the heavy calcium carbonate to form mixed slurry, and mixing part of the nanoscale light calcium carbonate and the heavy calcium carbonate to form the nanoscale light calcium carbonateCompounding the heavy calcium carbonate with the calcium carbonate to form surface-coated nano calcium carbonate, wherein stirring treatment is kept when air is introduced, stirring is stopped when bubbling treatment is finished, and after the treatment in the step is finished, the pH of the mixed slurry is controlled to be 7.5-8.0, wherein the air containing 25% -40% of carbon dioxide is 2.5-3.0 m3The flow velocity of the introduction is introduced into the liquid level at the lower part of the mixed slurry, and in addition, the temperature of the first processing container is dynamically kept at 30-50 ℃ in the processing process;
s03, taking the liquid level center at the lower part of the mixed slurry as a material transfer point, extracting 75-85% volume of the mixed slurry, transferring the mixed slurry into a second processing container, then adding 30-50 parts of heavy calcium carbonate, then continuously stirring the mixed materials for 20-40 min at a stirring speed of 550-650 rpm, when stirring for 3-5 min, introducing air containing 25-40% of carbon dioxide again to the lower layer liquid level of the mixed material, carrying out bubbling treatment on the mixed material in the stirring process, simultaneously, the calcium hydroxide in the mixed material and the carbon dioxide in the air are subjected to chemical combination reaction to generate nano-scale calcium hydroxide, the nanometer light calcium carbonate and heavy calcium carbonate are compounded to form composite calcium carbonate slurry, after the treatment of the step is completed, controlling the pH value of the composite calcium carbonate slurry to be 7.0, wherein the air containing 25-40% of carbon dioxide accounts for 1.5-2.0 m.3Introducing the flow velocity into the lower layer liquid level of the mixed material, and dynamically maintaining the temperature of the second processing container at 20-50 ℃;
s04, discharging the residual mixed slurry and the composite calcium carbonate slurry prepared in the step S03, and then sequentially filtering, drying, crushing and scattering to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
In the scheme, in step S02, the nano-scale light calcium carbonate suspended in the mixed slurry at least contains nano-scale light calcium carbonate with the particle size of 40-600 nanometers; in the step S04, when the filtered material is dried, the filtered material is dried for 6-7 hours under the negative pressure at the temperature of 95-105 ℃.
In this embodiment, as a preferred alternative, it is preferable that in step S03, when the ground calcium carbonate is added, a sodium polyacrylate salt is also added as a dispersant, wherein the addition amount of the dispersant is 0.01 to 0.03 times of the mixed slurry.
In this embodiment, as a preferred alternative, it is preferable that the air containing carbon dioxide is introduced into the mixed slurry or the mixed material in a stirring state at a proper angle in step S02 and step S03.
In addition, because the air containing carbon dioxide is introduced when the mixed material is in a stirring state, in the processing process, the conditions of heat release and temperature rise can occur in both reaction synthesis and stirring, the higher the temperature is, the higher the chemical combination reaction activity and the molecular activity which can be caused by the higher the temperature is, and the generated nano calcium carbonate particles can be aggregated and enlarged due to the temperature, so that the nano calcium carbonate particles can not be well coated and compounded with heavy calcium carbonate.
Referring to fig. 2, based on the above method, the present invention further provides an apparatus for coating heavy calcium carbonate with nano calcium carbonate, which uses the above method; the apparatus comprises:
a first processing vessel 1 for processing the mixed slurry;
the first stirring device 2 is arranged on the first processing container 1, and the stirring end of the first stirring device penetrates into the first processing container 1;
the second processing container 3 is used for processing the composite calcium carbonate slurry;
the second stirring device 4 is arranged on the second processing container 3, and the stirring end of the second stirring device penetrates into the second processing container 3;
the material transfer device 5 is respectively connected with the lower part in the first processing container 1 and the second processing container 3 and is used for conveying the material in the first processing container 1 into the second processing container 3, the input end of the specific material transfer device 5 is communicated with the first processing container 1 through a first material pipe 52, a first valve 51 is arranged on the first material pipe 52, and the output end of the material transfer device 5 is communicated with the upper part of the second processing container 3 through a second material pipe 53;
a gas delivery device 6 which is connected with the first processing container 1 and the second processing container 3 respectively, penetrates into the lower parts of the first processing container 1 and the second processing container 3 and is used for outputting air containing carbon dioxide, a gas nozzle 61 is arranged at the end of a pipeline connected to the first processing container 1 and the second processing container 3, a one-way valve 62 is also arranged on the pipeline connected to the gas nozzle 61 of the gas delivery device 6, and the direction of the gas flowing to the gas nozzle 61 is a passage;
the discharge auxiliary device 7 is respectively connected with the first processing container 1 and the second processing container 3 and is used for collecting materials output by the first processing container 1 and the second processing container 3;
the filtering device 8 is connected with the auxiliary discharging device 7 and is used for drying the materials collected by the auxiliary discharging device 7;
the drying device 9 is connected with the filtering device 8 and is used for drying the materials obtained by filtering of the filtering device 8;
and the crushing and scattering device 10 is connected with the drying device 9 and is used for crushing and scattering the materials dried by the drying device 9.
In the equipment, discharge valves 11 and 31 are arranged on discharge ports of a first processing container 1 and a second processing container 3
In order to better mix the introduced air with the slurry or the mixture, the gas nozzle 61 of the present embodiment has two structures, as shown in fig. 3 (configured as a gas nozzle structure 1) and fig. 4 (configured as a gas nozzle structure 2), respectively, in the structure shown in fig. 3, a plurality of gas holes 611 are formed, and the gas holes 611 penetrate through the tubular structure of the gas nozzle 61 and face the radial center of the gas nozzle 61; in the structure shown in fig. 4, a plurality of air holes 611 are provided, and the air holes 611 penetrate through the tubular structure of the gas nozzle 61 in an inclined manner, so that the output air is output in a spiral shape as a whole, and the output air can be cut into the slurry or the mixed material in a stirring state at a certain included angle.
The invention will now be further illustrated by reference to a number of examples.
Example 1
The embodiment of the invention relates to a method for coating nano calcium carbonate on the surface of heavy calcium carbonate, which specifically comprises the following steps:
s01, physically crushing calcite, crushing, grading and sieving the crushed product to obtain coarse heavy calcium carbonate with the granularity of less than 100 microns, mixing the prepared coarse heavy calcium carbonate with water, adding the mixture into grinding equipment for grinding, and drying the ground product to obtain the powdery heavy calcium carbonate with the granularity of 0.1-10 microns;
s02, preparing calcium hydroxide slurry with mass fraction concentration of 19-21%, adding 100 parts of the prepared calcium hydroxide slurry into a first processing container (the volume of the processing container is 1.5 times of the volume of the calcium hydroxide slurry), continuously stirring the calcium hydroxide slurry at a stirring speed of 400 r/min, simultaneously adding 25 parts of ground calcium carbonate into the calcium hydroxide slurry, stirring for 5min, and then adding air containing 35% of carbon dioxide at 2.5m3h, introducing the mixed slurry to the liquid level at the lower part of the mixed slurry at the introduction flow rate, carrying out continuous bubbling treatment for 35min to ensure that calcium hydroxide in the mixed slurry is carbonized to generate nano-scale light calcium carbonate, mixing the nano-scale light calcium carbonate with heavy calcium carbonate to form mixed slurry, and part of the nanometer light calcium carbonate is compounded on the surface of the heavy calcium carbonate to form surface-coated nanometer calcium carbonate, wherein, when air is introduced, the stirring treatment is kept, when the bubbling treatment is finished, the stirring is stopped, after the treatment in the step is finished, controlling the pH value of the mixed slurry to be 7.5 (when the pH value is higher than the pH value, continuously introducing carbon dioxide, and when the pH value is lower than the pH value, adding calcium hydroxide), dynamically maintaining the temperature of the first processing container at 40-45 ℃ in the processing process, in the step, the nano-scale light calcium carbonate suspended in the mixed slurry at least contains nano-scale light calcium carbonate with the grain size of 40-600 nanometers;
s03, within 5min after the step S02 is finished, taking the liquid level center at the lower part of the mixed slurry as a material moving point to extract the mixed slurry with 80% volume amount, and transferring the mixed slurryAdding into a second processing container (with volume consistent with that of the first processing container), adding 45 parts of ground calcium carbonate, stirring at 600 rpm for 30min, stirring for 4min, and stirring again at 2.0m3Introducing air containing 35% of carbon dioxide into the lower liquid level of the mixed material at the flow velocity of introduction/h, carrying out bubbling treatment on the mixed material in the stirring process, simultaneously carrying out chemical combination reaction on calcium hydroxide in the mixed material and carbon dioxide in the air to generate nano-scale calcium hydroxide, carrying out surface compounding on the nano-scale light calcium carbonate and heavy calcium carbonate to form composite calcium carbonate slurry, after the treatment of the step is finished, controlling the pH of the composite calcium carbonate slurry to be 7.0 (when the pH is higher than the pH, continuously introducing the carbon dioxide, and when the pH is lower than the pH, adding the calcium hydroxide), and dynamically maintaining the temperature of a second processing container at 30-40 ℃;
s04, discharging the residual mixed slurry and the composite calcium carbonate slurry prepared in the step S03, and sequentially filtering, drying under negative pressure at 95-105 ℃ for 6 hours, and crushing and scattering to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
In this embodiment, the gas nozzle introduced with the carbon dioxide-containing air in steps S02 and S03 has the structure shown in fig. 3, i.e., the gas nozzle structure 1.
Example 2
The present embodiment is substantially the same as embodiment 1, except that the gas nozzle for introducing the carbon dioxide-containing air in step S02 and step S03 in the present embodiment has the structure shown in fig. 4, i.e., the gas nozzle structure 2, i.e., the carbon dioxide-containing air is introduced into the mixed slurry or mixed material in a stirring state at a proper angle.
The remaining steps, parameters and operations in this embodiment are the same as those in embodiment 1, and are not described again.
Example 3
This example is substantially the same as example 2, except that in this example, in step S03, when ground calcium carbonate was added, sodium polyacrylate salt was also added as a dispersant in an amount of 0.02 times as much as the mixed slurry.
The remaining steps, parameters and operations in this embodiment are the same as those in embodiment 1, and are not described again.
Example 4
This example is substantially the same as example 2, except that in step S03, while introducing the gas containing the carbon dioxide-containing air, dry ice strips 1cm in diameter and 3cm in length were put into the second processing vessel at 2min intervals until reaching the lower liquid level of the mixed material.
Comparative example 1
This comparative example is substantially the same as example 1, except that in this comparative example, the processing was carried out in step S03 in the same vessel as in step S02, and the processing parameters were the same as those in the case of adding ground calcium carbonate twice in step S02 and step S03 of example 1, without separately removing 80% by volume of the mixed slurry and carrying out the secondary synthetic processing.
The remaining steps, parameters and operations in this embodiment are the same as those in embodiment 1, and are not described again.
Comparative example 2
This comparative example is substantially the same as example 2, except that in this comparative example, the processing was performed in the same vessel as in step S02 in step S03 without separately removing 80% by volume of the mixed slurry and performing the secondary synthesis processing.
The remaining steps, parameters and operations in this embodiment are the same as those in embodiment 2, and are not described again.
Comparative example 3
This comparative example is substantially the same as example 3, except that in this comparative example, the processing was performed in the same vessel as in step S02 in step S03 without separately removing 80% by volume of the mixed slurry and performing the secondary synthesis processing.
The remaining steps, parameters and operations in this embodiment are the same as those in embodiment 3, and are not described again.
Comparative test
And (3) performing coating rate characterization on the composite calcium carbonate products prepared in the examples 1-4 and the comparative examples 1-3, sampling 5 samples in each group of examples, and then taking the mean value of characterization results to obtain the following comparative results.
TABLE 1 comparison table of coating rate of heavy calcium carbonate
From the data in the comparison table, examples 1 to 4 based on the technical route of the present invention have excellent effect on the physical index of the nano calcium carbonate coated on the surface of the heavy calcium carbonate, while from examples 1 and comparison example 1, it is known that the improvement of the coating effect on the surface of the heavy calcium carbonate is facilitated by rapidly transferring the material in the center of the mixed slurry to another processing vessel for secondary processing, and it is mainly characterized in that when the mixed slurry is synthesized in the first processing vessel, most of the mixed slurry having large mass is separated from the stirring center due to centrifugation, and therefore, when the mixed slurry is transferred to the second processing vessel, Ph is controlled to be 7.5, and unreacted calcium hydroxide remains on the surface, and therefore, when the heavy calcium carbonate is added again and carbon dioxide is introduced, the heavy calcium carbonate transferred to the second processing vessel is followed, the nano-scale calcium carbonate attached to the heavy calcium carbonate can become a growing point of secondary synthetic calcium carbonate, so that the coating rate is improved while the volume of the heavy calcium carbonate is increased, and the newly added heavy calcium carbonate is coated and combined with the nano-scale light calcium carbonate which is generated and suspended in the mixed slurry, so that the nano-scale light calcium carbonate can be further generated and coated on the surface of the heavy calcium carbonate when air containing carbon dioxide is introduced subsequently; as can be seen from example 2, by changing the structure of the gas nozzle, the introduced air containing carbon dioxide can enter the mixed slurry at a certain angle, so that the air can be more fully contacted with the mixed slurry, because the mixed slurry is still stirred when the air is introduced, the problem of the decrease of the diffusion capability of the air containing carbon dioxide may be caused by the introduction angle of example 1; from example 3, it can be known that the addition of the dispersant can improve the dispersibility of the generated nano-grade light calcium carbonate, so that the combination effect of the nano-grade light calcium carbonate and the heavy calcium carbonate is better, and the sedimentation and agglomeration are avoided; embodiment 4 can know that adding dry ice as the carbon dioxide except air and taking place the medium on the one hand can improve the synthetic efficiency of calcium hydroxide in the thick liquids, simultaneously, dry ice still can reduce the temperature to a certain extent still, improves its consistency in short-term, makes it can combine with ground limestone better, has improved compound effect and cladding efficiency, and when dry ice sublimed, the further supplementary mixture of pneumatic can take place for a large amount of carbon dioxide bubbles that produce, improves the reaction combination of carbon dioxide and calcium hydroxide.
The foregoing is directed to embodiments of the present invention, and equivalents, modifications, substitutions and variations such as will occur to those skilled in the art, which fall within the scope and spirit of the appended claims.
Claims (10)
1. A method for coating nano calcium carbonate on the surface of heavy calcium carbonate is characterized by comprising the following steps: crushing natural carbonate mineral to prepare heavy calcium carbonate, mixing part of the heavy calcium carbonate with calcium hydroxide slurry with a preset mass fraction concentration, then introducing a gas medium containing carbon dioxide into the mixed material to prepare mixed slurry containing nano-grade light calcium carbonate and heavy calcium carbonate, mixing the mixed slurry with a preset volume with the residual heavy calcium carbonate, introducing the gas medium containing carbon dioxide into the mixed material again to make the calcium hydroxide in the mixed material and the carbon dioxide in the gas medium react to generate nano-scale calcium hydroxide, the surface of the nano-grade light calcium carbonate and the heavy calcium carbonate in the mixed slurry are compounded to form composite calcium carbonate slurry, and finally the residual mixed material and the composite calcium carbonate slurry are sequentially filtered, dried, crushed and scattered to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
2. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 1, which is characterized in that: the method specifically comprises the following steps:
s01, performing physical crushing on natural carbonate minerals, then performing crushing, grading and sieving on crushed products to obtain coarse heavy calcium carbonate with the granularity of less than 100 microns, then mixing the prepared coarse heavy calcium carbonate with water, adding the mixture into grinding equipment for grinding treatment, and then drying the ground products to obtain the powdery heavy calcium carbonate with the granularity of 0.1-10 microns;
s02, preparing calcium hydroxide slurry with mass fraction concentration of 19-21%, adding 100 parts of the prepared calcium hydroxide slurry into a first processing container, continuously stirring the calcium hydroxide slurry at a stirring speed of 350-550 rpm, simultaneously adding 20-30 parts of ground calcium carbonate into the calcium hydroxide slurry, stirring for 3-8 min, introducing air containing 25-40% of carbon dioxide into the lower liquid level of the mixed slurry, continuously bubbling for 30-40 min to carbonize the calcium hydroxide in the mixed slurry to generate nano-scale light calcium carbonate, mixing the nano-scale light calcium carbonate and the ground calcium carbonate to form mixed slurry, compounding part of the nano-scale light calcium carbonate on the surface of the ground calcium carbonate to form surface-coated nano calcium carbonate, wherein the stirring is kept while introducing air, stopping stirring when the bubbling treatment is finished;
s03, taking the center of the liquid level at the lower part of the mixed slurry as a material transfer point, extracting 75-85% volume of the mixed slurry, transferring the mixed slurry to a second processing container, then adding 30-50 parts of heavy calcium carbonate, continuously stirring the mixed material for 20-40 min at a stirring speed of 550-650 rpm, introducing air containing 25-40% of carbon dioxide into the liquid level of the lower layer of the mixed material when stirring for 3-5 min, bubbling the mixed material in the stirring process, and simultaneously carrying out a chemical combination reaction between calcium hydroxide in the mixed material and carbon dioxide in the air to generate nano calcium hydroxide, wherein the nano calcium carbonate and the heavy calcium carbonate are subjected to surface compounding to form the composite calcium carbonate slurry;
s04, discharging the residual mixed slurry and the composite calcium carbonate slurry prepared in the step S03, and then sequentially filtering, drying, crushing and scattering to prepare the composite calcium carbonate with the surface coated with the nano calcium carbonate.
3. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in step S01, the natural carbonate mineral is a mixture of at least one of calcite, marble, and limestone.
4. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: after the step S02 is finished, controlling the pH value of the mixed slurry to be 7.5-8.0; and after the step S03 is finished, controlling the pH value of the composite calcium carbonate slurry to be 7.0.
5. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in step S02, the air containing 25% -40% carbon dioxide is 2.5-3.0 m3Introducing the flow velocity of/h to the lower liquid level of the mixed slurry; in step S03, the air containing 25% -40% carbon dioxide is 1.5-2.0 m3And/h, introducing the flow velocity into the lower layer liquid level of the mixed material.
6. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in step S02, the nano-scale light calcium carbonate suspended in the mixed slurry at least contains nano-scale light calcium carbonate with the grain size of 40-600 nanometers; in the step S04, when the filtered material is dried, the filtered material is dried for 6-7 hours under the negative pressure at the temperature of 95-105 ℃.
7. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in the step S03, when the ground limestone is added, the sodium polyacrylate is also added as a dispersant, wherein the addition part of the dispersant is 0.01-0.03 times of the mixed slurry.
8. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in step S02, dynamically maintaining the temperature of the first processing container at 30-50 ℃; in step S03, the temperature of the second processing container is dynamically maintained at 20-50 ℃.
9. The method for coating the surface of the nano calcium carbonate on the heavy calcium carbonate according to claim 2, which is characterized in that: in step S02 and step S03, carbon dioxide-containing air is introduced into the mixed slurry or the mixed material in a stirred state at a proper angle.
10. An apparatus for coating nano calcium carbonate on the surface of heavy calcium carbonate, which is characterized in that the method of any one of claims 1 to 8 is applied; the apparatus comprises:
a first processing vessel for processing the mixed slurry;
the first stirring device is arranged on the first processing container, and the stirring end of the first stirring device penetrates into the first processing container;
the second processing container is used for processing the composite calcium carbonate slurry;
the second stirring device is arranged on the second processing container, and the stirring end of the second stirring device penetrates into the second processing container;
the material transfer device is respectively connected with the lower part in the first processing container and the second processing container and is used for conveying the material in the first processing container to the second processing container;
a gas delivery device which is connected with the first processing container and the second processing container respectively, penetrates into the lower parts of the first processing container and the second processing container, and is used for outputting air containing carbon dioxide;
the discharge auxiliary device is respectively connected with the first processing container and the second processing container and is used for collecting materials output by the first processing container and the second processing container;
the filtering device is connected with the discharging auxiliary device and is used for drying the materials collected by the discharging auxiliary device;
the drying device is connected with the filtering device and is used for drying the material obtained by filtering by the filtering device;
and the crushing and scattering device is connected with the drying device and is used for crushing and scattering the materials dried by the drying device.
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| CN114350180A (en) * | 2021-12-03 | 2022-04-15 | 广西大学 | Mechanical activation nano-modified heavy calcium carbonate and preparation method thereof |
| CN115140755A (en) * | 2022-07-14 | 2022-10-04 | 桂林卓瑞食品原料有限公司 | Preparation method of porous calcium carbonate |
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