CN1207209C - Eddy flow process of preparing ultramicro calcium carbonate precipitate - Google Patents
Eddy flow process of preparing ultramicro calcium carbonate precipitate Download PDFInfo
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Abstract
The present invention relates to a method for preparing superfine calcium carbonate precipitates with an eddy flow method. In the modern, a turbulence pump is used as main equipment, and the carbonation reaction is carried out in tiny gas bubbles which are produced by the high speed rotating paddles of the turbulence pump, so the grain size can be regulated within a range of 20 to 100 nm, and the timely modification of the grains can be realized on the basis of the maintenance of the original grain diameters of the grains.
Description
Technical Field
The invention relates to a method for preparing ultrafine precipitated calcium carbonate by using an eddy current method.
Technical Field
Calcium carbonate is an important inorganic chemical product, belongs to one of the most widely used inorganic fillers, and is widely applied to industries such as rubber, plastics, paint, ink and the like. The ultrafine calcium carbonate is used as a filler of rubber and plastics, and has the properties of reinforcement, tensile strength and the like besides being used as a common filler to change the processing property of products and reduce the cost. The calcium carbonate with the grain size less than 0.02 mu m has the reinforcing effect which is comparable with that of white carbon black. The use of the superfine calcium carbonate can replace or partially replace fillers such as expensive carbon black, white carbon black and the like. Calcium carbonate with a narrow particle size distribution of less than 0.08 μm is used for automotive chassis stone-impact coatings because of its good thixotropy. In recent years, with the research on various aspects of crystal form, granularity and the like of calcium carbonate and the development of surface modification technology of calcium carbonate products, the application field of calcium carbonate is increasingly expanded and deepened.
In view of the current state of the industry, calcium carbonate is an inorganic filler with low price, so that the production profit is low, and the profit is improved only by increasing the yield by adopting large-scale equipment. In addition, most of the calcium carbonate products produced at present belong tocommon precipitated calcium carbonate, the grade is low, and high-grade superfine calcium carbonate products need to be developed. The superfine calcium carbonate with the particle size of less than 2 mu m currently used in China cannot be industrially produced in a large scale, and about 95 percent of the superfine active calcium carbonate depends on import. More than ten crystal forms of calcium carbonate have been discovered, and products with different crystal forms and different particle sizes have different applications. The production method of the fine calcium carbonate mainly comprises the following steps:
a. lime milk one-step carbonization-additive method: the crystal form and the particle size of the calcium carbonate are controlled by bubbling carbon dioxide gas into the lime milk and adding a certain amount of additive to the partially carbonized lime milk during carbonization. At present, the technique commonly used at home and abroad is a bubbling precipitation method. Because the mass transfer rate of gas-solid-liquid phases in a stirring kettle or a bubble tower is slow, and the micromixing is poor, the prepared product has the following defects: uneven particle size distribution, difficult realization of continuous process, low production efficiency, high energy consumption, high cost and the like.
b. Lime milk distribution carbonization-aging method: the method divides the traditional lime milk carbonization process into three stages, namely a primary carbonization stage, an aging stage and a secondary carbonization stage, and the calcium carbonate prepared by the method has good dispersibility when being used in paint, rubber or plastics. However, the process is complicated and the energy consumption is large, so that the method is not popularized.
c. Spraying method: the method sprays calcium hydroxide suspension into a carbonization tower at a certain grain size and speed, and the calcium hydroxide suspension is in countercurrent contact with carbon dioxide to react to generate calcium carbonate. The method is not suitable for adopting high-concentration calcium hydroxide suspension, and the product is not uniform, so that the continuous production is difficult to realize.
d. The hypergravity reaction method comprises the following steps: such as the preparation method of the superfine calcium carbonate (95105343.4), the method needs to be carried out in a special reactor, has no ready standard optional equipment, needs to be specially designed by self, and has larger equipment investment. In addition, the modification of the particles needs to be separated from the original reaction system, and the generated particles are difficult to maintain the original size when the surface treatment cannot be carried out in time due to the extremely easy agglomeration of the nano particles.
US4888160 discloses a process for preparing ultrafine calcium carbonate by precipitation, the carbonization is carried out by means of a circulation line system connected to a reaction vessel, a conventional centrifugal pump is used to provide the driving force, and a carbon dioxide-containing gas is injected into a turbulent zone in the circulation line after the pump. The calcium carbonate product is obtained by controlling parameters such as pH value, reaction temperature and the like.
Disclosure of Invention
The invention aims to provide a brand new method for preparing ultrafine precipitated calcium carbonate by using a vortex method, which adopts a ready-made vortex pump as main equipment, and carries out carbonization reaction in micro bubbles divided by a blade rotated at a high speed by the vortex pump, so that the particle size is adjustable within the range of 20-1000nm, and the particles are modified in time on the basis of keeping the original particle size of the particles.
The invention content is as follows:
the invention relates to a method for preparing ultramicro precipitated calcium carbonate by an eddy current method, which adopts the precipitation reaction of conventional carbon dioxide and calcium hydroxide to prepare calcium carbonate, and the reaction equation is as follows:
the method is characterized in that: the reaction is realized by a vortex pump. The vortex pump is a commercially available alternative device commonly used for high efficiency gas dissolution.
The specific reaction steps are as follows: adding prepared calcium hydroxide suspension into a liquid storage tank, starting a vortex pump, enabling the calcium hydroxide suspension to enter the vortex pump from a liquid outlet of the liquid storage tank through a liquid inlet of the vortex pump under the action of negative pressure, and carrying out carbonization reaction with carbon dioxide or carbon dioxide-containing mixed gas sucked in from a gas inlet under negative pressure in the vortex pump, wherein the mixed gas consists of carbon dioxide and other gases which do not participate in the reaction, and reaction liquid discharged from a liquid discharge port enters the liquid storage tank from a liquid inlet of the liquid storage tank, and the liquid storage tank can be provided with stirring slurry or not. The reaction is circulated in the system. The rotating speed of the rotor of the vortex pump is controlled to be 500 plus 10000rpm in the reaction process, the vacuum degree at the air inlet of the vortex pump is 0.01-0.08MPa, the vacuum degree at the liquid inlet of the vortex pump is 0.01-0.06MPa, and the pressure at the liquid outlet of the vortex pump is 0.01-0.6 MPa. And finishing the reaction when the pH value of the reaction liquid is 7-8, and collecting the product.
In order to further reduce the particle size of the generated powder and improve the efficiency of the vortex pump, a high-shear kettle can be adopted to replace a liquid storage tank and be used as auxiliary equipment of the vortex pump, the high-shear kettle is a kettle body with a kettle body shell provided with a jacket for controlling temperature and a stirring paddle in the center of the kettle body and can be formed by refitting the liquid storage tank, an annular porous packing layer is arranged on the outer side of the stirring paddle, a liquid inlet is arranged at the upper end of the kettle body, and a liquid outlet is formed at the bottom of the kettle body. Adding a calcium hydroxide suspension into a high-shear kettle, starting the high-shear kettle and a vortex pump, stirring and shearing the calcium hydroxide suspension, then passing through an annular packing layer, enabling a liquid outlet of the high-shear kettle to enter the vortex pump through a liquid inlet of the vortex pump under the action of negative pressure, carrying out carbonization reaction on carbon dioxide or a mixed gas containing carbon dioxide sucked in the vortex pump under the negative pressure through an air inlet, returning a reaction liquid discharged from a discharge port of the vortex pump to the liquid inlet of the high-shear kettle, and controlling the rotating speed of stirring slurry of the high-shear kettle to be 10-10000rpm in the reaction process. The reaction is circularly carried out in the system, the reaction is finished when the pH value of the reaction solution is 7-8, and the product is collected.
Similar to the conventional method, the volume content of carbon dioxide in the reaction process is preferably 10-100%, the gas flow rate is 0.0001-0.01 cubic meter/min, the weight percentageconcentration of the calcium hydroxide suspension is 0.09-20%, and the carbonization reaction temperature is 0-80 ℃.
The blades of the stirring paddle in the high-shear kettle are straight, the number of the blades is 2-8, and the blades can also adopt a plurality of groups of serial connection types and are selected according to the size of the kettle. The annular filler layer can be made of metal wire mesh, rings, sheets, rods or other various porous fillers. The thickness of the annular packing layer is 0.1-0.8 times of the inner radius of the kettle, and the inner side of the annular packing layer can be provided with a flow guide baffle plate which forms an acute angle with the circumferential tangent line and has the same direction, so that the reaction liquid can smoothly enter the annular packing layer with smaller resistance.
The rotor speed of the vortex pump is preferably 2000-5000rpm, and the high shear kettle stirring slurry is 2000-5000 rpm.
In the above reaction process, a crystal form control agent can be added in a liquid storage tank or a high-shear kettle to obtain the ultrafine calcium carbonate with different crystal forms, and the crystal form control agent can be selected from those commonly used in the prior art, such as: BaCl2，ZnSO4，NH3·H2O，CaCl2，H2SO4，H3PO4EDTA and the like. The modifier can be added into a liquid storage tank or a high-shear kettle when the reaction is finished or is about to be finished, so as to modify the just-generated ultrafine calcium carbonate particles in time.
The carbonization reaction is firstly carried out in the vortex pump, the gas is sucked into the pump cavity by the tangential negative pressure through the gas inlet pipe, simultaneously the calcium hydroxide suspension entering the pumpcavity is increased in circumferential speed under the action of the turbine, the generated centrifugal force pushes the calcium hydroxide suspension to the outer edge of the rotor, the calcium hydroxide suspension meets carbon dioxide, the periphery of the impeller of the vortex pump rotor is provided with a plurality of blades which are arranged in a radial shape, and the blades generate two forces when the vortex pump rotates: friction (the force pushing the liquid in the direction of rotation) and centrifugal force (the force throwing the liquid in the cross direction). The liquid in the pump is acted by two directional forces to form vortex in the liquid passage, the pressure rises due to the action of centrifugal force continuously in the passage, high pressure is formed, and if the impedance of the outlet of the pump is increased, the pressurizing times are increased along with the increase of the impedance, the gas and the liquid are divided into bubbles with the diameter of about 10-15 mu m by the blades rotating at high speed, the contact surface of carbon dioxide and the liquid is greatly increased, the carbonization reaction speed is obviously accelerated, the generation of new crystal nuclei is facilitated, calcium carbonate crystals are crystallized on the inner wall of the bubbles and are divided into the bubbles with the diameter of about 10-15 mu m along with the bubbles, the contact surface of the carbon dioxide and the liquid is greatly increased, the carbonization reaction speed is obviously accelerated, the generation of the new crystal nuclei is facilitated, and the calcium carbonate crystals are crystallized on the inner wall of the.
Under the condition that a high-shear kettle is adopted as auxiliary equipment, reaction liquid is discharged from a discharge hole of a vortex pump and enters the high-shear kettle, and after the reaction liquid is sheared and then passes through annular packing, micro bubbles in the reaction liquid are further crushed to formmore micro bubbles with larger specific surface area.
In conclusion, the method of the invention adopts the vortex pump to greatly improve the mass transfer efficiency of the reaction, has simple and easily obtained device structure and small equipment volume, reduces the input-output ratio to the maximum extent, realizes real scale of the superfine calcium carbonate powder processing industry and greatly reduces the production cost. In addition, the method of the invention is convenient for the continuous production of synthesis and modification, and the possibility of agglomeration of the ultra-micro powder generated by precipitation reaction is reduced to the maximum extent. The high-quality calcium carbonate superfine powder with different grain diameters and different crystal forms can be conveniently prepared by controlling the reaction temperature, adding a crystal form control agent and the like.
Drawings
FIG. 1: a process flow chart for preparing superfine precipitated calcium carbonate by an eddy current method.
FIG. 2: the structure of the vortex pump is shown schematically.
FIG. 3: process flow diagram when using a high shear kettle.
FIG. 4: the high-shear kettle is a schematic structural diagram in a top view.
FIG. 5: the working principle of the vortex pump is a three-dimensional anatomical schematic diagram.
FIG. 6: schematic diagram of high-dispersion gas-liquid mixing effect of the vortex method.
FIG. 7: transmission Electron Microscope (TEM) photograph of the random calcium carbonate powder obtained in inventive example 5.
FIG. 8: a Transmission Electron Microscope (TEM)photograph of the cubic calcium carbonate powder obtained in inventive example 6.
The reference numerals on the drawings denote: 1-a vortex pump, 2-a liquid flowmeter, 3-a pressure gauge, 4-a pressure regulating valve of a vortex pump outlet, 5-a product collecting port, 6-a gate valve, 7-a liquid inlet of a liquid storage tank or a high-shear kettle, 8-a gas flowmeter, 9-an air inlet regulating valve, 10-a circulating water inlet of the high-shear kettle, 11-a vacuum indicator of the liquid inlet of the vortex pump, 12-a liquid inlet regulating valve of the vortex pump, 13-a temperature control sensor, 14-a stirring paddle of the high-shear kettle, 15-a circulating water outlet of the high-shear kettle, 16-an annular filler, 17-a liquid outlet of the liquid storage tank or the high-shear kettle, 18-an air inlet of the vortex pump, 19-a vacuum meter of the vortex pump air inlet, 20-a pH value control sensor, 21-a, 23-a liquid inlet of a vortex pump, 24-a liquid outlet of the vortex pump, 25-a blade of the vortex pump and 26-a rotor of the vortex pump.
Detailed Description
Example 1:
adding a calcium hydroxide suspension with the weight percentage concentration of 4% into a liquid storage tank 28, starting a vortex pump 1 (model: 15FPD02Z), enabling the calcium hydroxide suspension to enter the vortex pump from a liquid storage tank discharge port 17 through a vortex pump liquid inlet 23 under the action of negative pressure, sucking mixed gas of carbon dioxide and air into a pump cavity from a tangential negative pressure through a vortex pump air inlet 18, enabling the gas and the liquid to contact and generate carbonization reaction, and enabling liquid in the pump to form a vortex in a liquid passage under the action of two directional forces of friction and centrifugal force; gas-liquid quilt high speedThe rotating blade is divided into bubbles with the diameter of about 10-15 μm, and the bubbles are discharged through a liquid outlet 24 of the vortex pump and return to the liquid storage tank through a liquid inlet 7 of the liquid storage tank. And (3) introducing water with a certain temperature into the kettle jacket in the reaction process, and controlling the reaction temperature. The volume content of carbon dioxide in the mixed gas is 25%, the carbonization reaction temperature is controlled to be 15-20 ℃, the rotating speed of a rotor of the vortex pump is 10000rpm, the vacuum degree at a liquid inlet of the vortex pump is 0.025MPa, the vacuum degree at a gas inlet of the vortex pump is 0.02MPa, the pressure at a liquid outlet of the vortex pump is 0.45MPa, and the flow of the gas is 0.001m3And/min. During the reaction, H is added into a liquid storage tank2SO4The dosage of the crystal form control agent is 0.03mol/mol CaO. When the pH value of the reaction solution is 7-8, the carbonization process is finished.
The obtained product is chain spherical crystal calcium carbonate powder through TEM analysis, and the average grain diameter is 50 nm.
Example 2:
the procedure of example 1 was followed, except that the reaction was controlled to a suspension of 8% by weight calcium hydroxide. The volume content of carbon dioxide is 100%, the carbonization reaction temperature is 15-20 ℃, the rotating speed of a rotor of the vortex pump is 3000rpm, the vacuum degree at a feed inlet of the vortex pump is 0.012MPa, and the vortexThe vacuum degree at the air inlet of the flow pump is 0.015MPa, the pressure at the discharge port of the vortex pump is 0.4MPa, and the flow rate of the gas is 0.0012m3And/min. 5g of BaCl is added into a liquid storage tank in the reaction process2And (3) a crystalform control agent. When the pH value of the reaction solution is 7-8, the carbonization process is finished.
The obtained calcium carbonate is in a spherical crystal form through TEM analysis, and the average particle size is 300 nm.
Example 3:
the procedure of example 1 was followed, except that the reaction was controlled to a suspension of 8% by weight calcium hydroxide. The volume content of carbon dioxide is 50%, the carbonization reaction temperature is 15-20 ℃, the rotating speed of a rotor of the vortex pump is 5000rpm, the vacuum degree at a feed inlet of the vortex pump is 0.012MPa, the vacuum degree at an air inlet of the vortex pump is 0.015MPa, the pressure at a discharge outlet of the vortex pump is 0.4MPa, and the flow rate of gas is 0.0012m3And/min. During the reaction, H is added into a liquid storage tank2SO4The dosage of the crystal form control agent is 0.03mol/mol CaO. When the pH value of the reaction solution is 7-8, the carbonization process is finished.
The obtained calcium carbonate is in a chain spherical crystal form through TEM analysis, and the average particle size is 70 nm.
Example 4:
the procedure of example 1 was followed except that: 1500g of calcium hydroxide suspension with the mass percent of about 8 percent is adopted. Quantitative addition of NH3·H2O is used as a crystal form control agent, the volume content of carbon dioxide is 20 percent, the carbonization reaction temperature is 50 ℃, the rotating speed of a rotor of a vortex pump is 7000rpm, the vacuum degree of a liquid inlet of the vortex pump is 0.035MPa, the vacuum degree of a gas inlet of the vortex pump is 0.025MPa, the pressure of a liquid outlet of the vortex pump is 0.45MPa, the rotating speed of a high-shear blade is 5000rpm, straight 6-blade high-shear stirring with the blade width of 3cm is used, and the flow of gas is 0.009m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. The other reaction conditions were the same as in example 1, and the obtained calcium carbonate was in a spindle-shaped crystal form by TEM analysis and had an average particle diameter of 700 nm.
Example 5:
preparing calcium hydroxide suspension with the weight percentage concentration of 3%. Adding the calcium hydroxide suspension into a high-shear kettle, starting a vortex pump (model: 15FPD02Z) and high-shear blades, sucking gas into a pump cavity from a tangential negative pressure through a gas inlet pipe, increasing the circumferential speed of the calcium hydroxide suspension entering the pump cavity under the action of a turbine, and pushing the calcium hydroxide suspension to the outer edge of a rotor by the generated centrifugal force to meet and react with carbon dioxide; the liquid in the pump is acted by two directional forces of friction force and centrifugal force to form a vortex in the liquid passage; the gas-liquid is divided into bubbles with the diameter of about 10-15 mu m by a blade rotating at high speed, the bubbles are discharged through a discharge port and are further crushed by the filler in the high-shear kettle to form more tiny bubbles with large specific surface area, the precipitation reaction is carried out on the interface of the bubbles, and calcium carbonate crystals are crystallized on the inner wall of the bubbles and are precipitated along with the continuous crushing of the bubbles. And (3) introducing water with a certain temperature into the kettle jacket in the reaction process, and controlling the reaction temperature.
The length of the whole circulation line is about 1.1 m. Controlling the liquid delivery amount of a vortex pump to be 0.9t/h in the reactionprocess, adopting a mixed gas of carbon dioxide with the volume content of 20-25% of carbon dioxide and air, controlling the carbonization reaction temperature to be 16-20 ℃, the rotating speed of a rotor of the vortex pump to be 2890rpm, the vacuum degree at a feed inlet of the vortex pump to be 0.015MPa, the vacuum degree at a gas inlet of the vortex pump to be 0.01MPa, the pressure at a discharge outlet of the vortex pump to be 0.4MPa, the rotating speed of a high-shear blade to be 3000rpm, the width of the blade to be 3cm, the blade to be a straight 6-blade, the interval of 3 groups to be 1cm, and the flow control of the gas to be 0.3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished.
The obtained calcium carbonate has an average particle size of 50-60nm as shown in figure 6, when analyzed by Transmission Electron Microscopy (TEM).
Example 6:
a suspension of 3% by weight calcium hydroxide was prepared according to the procedure of example 5. 6g of EDTA (ethylene diamine tetraacetic acid) is added as a crystal form control agent within 3 minutes after the reaction starts, the volume content of carbon dioxide is 80%, the carbonization reaction temperature is 16-18 ℃, the rotating speed of a rotor of a vortex pump is 5000rpm, the vacuum degree of a liquid inlet of the vortex pump is 0.02MPa, the vacuum degree of a gas inlet of the vortex pump is 0.02MPa, the pressure of a liquid outlet of the vortex pump is 0.35MPa, the rotating speed of a high-shear blade is 2000rpm, straight 3-blade high-shear stirring with the blade width of 3cm is used, and the flow rate of gas is 6000 ml/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. The obtained calcium carbonate has an average particle size of 50nm and a cubic crystal form by TEM analysis, as shown in figure 7.
Example 7:
a suspension of 4% by weight calcium hydroxide was prepared according to the procedure of example 5. The volume content of carbon dioxide is 50%, the carbonization reaction temperature is 10-15 ℃, the rotating speed of a rotor of a vortex pump is 3000rpm, the vacuum degree of a liquid inlet of the vortex pump is 0.01MPa, the vacuum degree of a gas inlet of the vortex pump is 0.015MPa, the pressure of a liquid outlet of the vortex pump is 0.25MPa, the rotating speed of a high-shear blade is 7000rpm, straight 6-blade high-shear stirring with the blade width of 3cm is adopted, and the flow rate of gas is controlled by the high-shear stirring speed of the high-shear bladeIs 0.002m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. Quantitative addition of BaCl24.8g, the other reaction conditions were the same as in example 5, and the obtained calcium carbonate was spherical in crystal form and 100nm in average particle size by TEM analysis.
Example 8:
the procedure of example 5 was followed except that: 1500g of calcium hydroxide suspension with the mass percent of about 8 percent is adopted. Quantitative addition of H2SO43g, the volume content of carbon dioxide is 100%, the carbonization reaction temperature is 40 ℃, the rotating speed of a rotor of a vortex pump is 7000rpm, the vacuum degree at a liquid inlet of the vortex pump is 0.035MPa, the vacuum degree at a gas inlet of the vortex pump is 0.025MPa, the pressure at a liquid outlet of the vortex pump is 0.45MPa, the rotating speed of a high-shear blade is 5000rpm, straight 6-blade high-shear stirring with the blade width of 3cm is adopted, and the flow of gas is 0.009m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. The following experimental conditions were the same as in example5, and the obtained calcium carbonate was in a cubic crystal form by TEM analysis and had an average particle diameter of 30 to 40 nm.
Example 9:
a suspension of 6% by weight calcium hydroxide was prepared according to the procedure of example 5. The volume content of carbon dioxide is 60%, the carbonization reaction temperature is 40 ℃, the rotating speed of a rotor of a vortex pump is 4000rpm, the vacuum degree of an inlet of the vortex pump is 0.015MPa, the vacuum degree of an inlet of the vortex pump is 0.01MPa, the pressure of an outlet of the vortex pump is 0.25MPa, the rotating speed of a high-shear blade is 2000rpm, straight 4-blade high-shear stirring with the blade width of 3cm is adopted, and the flow of gas is0.002m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. Adding SrCl25g of calcium carbonate is used as a crystal form control agent, other experimental conditions are the same as those of example 5, and the obtained calcium carbonate is in a needle-like crystal form through TEM analysis, and the average particle size is 120 nm.
Example 10:
a7% strength by weight calcium hydroxide solution was prepared according to the procedure of example 5. The volume content of carbon dioxide is 100 percent, the carbonization reaction temperature is 30 ℃, and the rotation of a vortex pump rotorThe speed is 4000rpm, the vacuum degree at the liquid inlet of the vortex pump is 0.01MPa, the vacuum degree at the gas inlet of the vortex pump is 0.01MPa, the pressure at the liquid outlet of the vortex pump is 0.25MPa, the rotating speed of a high-shear blade is 500rpm, straight 6-blade high-shear stirring with the blade width of 3cm is used, and the flow rate of gas is 0.0012m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. Without any additives, the other reaction conditions were the same as in example 5: the obtained calcium carbonate was found to be a random crystal form by TEM analysis, and had an average particle diameter of 200 nm.
Example 11:
a suspension of 6.4% by weight calcium hydroxide was prepared according to the procedure of example 5. The volume content of carbon dioxide is 100%, the carbonization reaction temperature is 15-20 ℃, the rotating speed of a rotor of a vortex pump is 3000rpm, the vacuum degree of a liquid inlet of the vortex pump is 0.015MPa, the vacuum degree of a gas inlet of the vortex pump is 0.01MPa, the pressure of a liquid outlet of the vortex pump is 0.34MPa, the rotating speed of a high-shear blade is 7000rpm, straight 6-blade high-shear stirring with the blade width of 3cm is adopted, and the flow of gas is 0.001m3And/min. When the pH value of the reaction solution is 7-8, the carbonization process is finished. With H2SO4The amount of the additive is 0.03mol/mol CaO, other reaction conditions are the same as those of example 5, and the obtained calcium carbonate is in a chain spherical crystal form through TEM analysis, and the average grain diameter is 20-30 nm.
Claims (5)
1. A method for preparing ultramicro precipitated calcium carbonate by an eddy current method adopts the precipitation reaction of conventional carbon dioxide and calcium hydroxide to prepare the calcium carbonate, and is characterized in that: the reaction is realized by a vortex pump; adding a calcium hydroxide suspension into a liquid storage tank, starting a vortex pump, enabling the calcium hydroxide suspension to enter the vortex pump from a liquid outlet at the bottom of the liquid storage tank through a liquid inlet of the vortex pump under the action of negative pressure, and carrying out carbonization reaction on carbon dioxide or a mixed gas containing carbon dioxide sucked from an air inlet under negative pressure in the vortex pump, wherein the mixed gas consists of carbon dioxide and other gases which do not participate in the reaction, and a reaction liquid discharged from a liquid outlet of the vortex pump enters the liquid storage tank from a liquid inlet at the upper end of the liquid storage tank, and the reaction is carried out in a system in a circulating manner; in the reaction process, the rotation speed of a rotor of the vortex pump is controlled to be 500 plus 10000rpm, the vacuum degree at an air inlet of the vortex pump is 0.01-0.08MPa, the vacuum degree at an air inlet of the vortex pump is 0.01-0.06MPa, the pressure at a liquid outlet of the vortex pump is 0.01-0.6MPa, the reaction is finished when the pH value of the reaction liquid is 7-8, and a product is collected.
2. The process according to claim 1, wherein: a liquid storage tank is replaced by a high-shear kettle, the high-shear kettle is a kettle with stirring slurry in the center, a kettle body is provided with a jacket for controlling temperature, an annular porous packing layer is arranged outside the stirring slurry, a liquid inlet is arranged at the upper end of the kettle body, and a liquid outlet is arranged at the bottom of the kettle body; adding a calcium hydroxide suspension into a high-shear kettle, starting the high-shear kettle and a vortex pump, stirring and shearing the calcium hydroxide suspension, then passing through an annular packing layer, enabling a liquid outlet of the high-shear kettle to enter the vortex pump through a liquid inlet of the vortex pump under the action of negative pressure, carrying out carbonization reaction on carbon dioxide or a mixed gas containing carbon dioxide sucked in the vortex pump under the negative pressure through an air inlet, returning a reaction liquid discharged from a liquid outlet of the vortex pump to the liquid inlet of the high-shear kettle, and controlling the rotating speed of stirring slurry of the high-shear kettle to be 10-10000rpm in the reaction process.
3. The process according to claim 2, characterized in that: the blades of the stirring paddle in the high-shear kettle are straight and evenly distributed, the number of the blades is 2-8, the thickness of the annular packing layer is 0.1-0.8 times of the inner radius of the kettle, and the inner side of the annular packing layer is evenly provided with a flow guide baffle which forms an acute angle with the tangent line of the circumference and has the same direction.
4. A process according to claim 1, 2 or 3, characterized in that: the volume content of carbon dioxide is 10-100%, the flow rate of gas is 0.001-0.01 cubic meter/min, the weight percentage concentration of calcium hydroxide suspension is 0.09-20%, and the carbonization reaction temperature is 0-80 ℃.
5. The process according to claim 2 or 3, characterized in that: the rotor speed of the vortex pump is 2000 plus 5000rpm, and the stirring speed of the high-shear kettle is 2000 plus 5000 rpm.
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| CN1331742C (en) * | 2004-03-29 | 2007-08-15 | 同济大学 | Method for synthesizing ultramicro materials of spherica carbonate of alkaline earth controlled through supported liquid membrane |
| CN101362048B (en) * | 2008-09-02 | 2011-01-26 | 李发修 | Method for absorbing carbon dioxide using carbide mud residue and special carbon dioxide absorber |
| CN102744025A (en) * | 2012-07-25 | 2012-10-24 | 武汉大学 | Reaction equipment for manufacturing inorganic materials with micro-nano structure |
| CN107601541A (en) * | 2017-09-30 | 2018-01-19 | 广西华洋矿源材料有限公司 | A kind of production method of nano-calcium carbonate |
| CN108033476A (en) * | 2018-02-07 | 2018-05-15 | 东南大学 | A kind of preparation method of nano-calcium carbonate |
| CN112897561B (en) * | 2021-05-10 | 2021-07-23 | 中国科学院过程工程研究所 | System device and method for preparing calcium carbonate by using micro-nano bubbles |
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