CN113800547A - Digestion-carbonization device and calcium carbonate nano-coating process - Google Patents

Digestion-carbonization device and calcium carbonate nano-coating process Download PDF

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CN113800547A
CN113800547A CN202111172550.8A CN202111172550A CN113800547A CN 113800547 A CN113800547 A CN 113800547A CN 202111172550 A CN202111172550 A CN 202111172550A CN 113800547 A CN113800547 A CN 113800547A
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calcium carbonate
screen
reaction kettle
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digestion
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霍宁波
盖国胜
张广立
潘慧
赵美霞
王晓宁
任梦文
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Binzhou Polytechnic
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • C01F11/181—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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Abstract

The invention relates to the technical field of carbonate preparation, in particular to a digestion-carbonization device and a calcium carbonate nano-coating process. The digestion-carbonization device comprises a digestion tank and a reaction kettle which are communicated with each other, a first screen and a first stirring paddle are arranged in the digestion tank, a second screen and a second stirring paddle are arranged in the reaction kettle, and a gas channel is arranged at the bottom of the reaction kettle; the reactor also comprises a diaphragm pump, wherein a water inlet pipeline of the diaphragm pump is communicated with the reaction kettle, and a water outlet pipeline of the diaphragm pump is communicated with the digestion tank. The calcium carbonate nano-coating process comprises the steps of adding heavy calcium carbonate into a calcium hydroxide suspension, then introducing reaction gas for carbonization, and nucleating and growing the generated calcium carbonate nano-particles on the surface of the heavy calcium carbonate to obtain the heavy calcium carbonate with the nano-coated surface. The invention carries out nano coating on the surface of calcium carbonate particles, effectively utilizes the excellent characteristics of nano materials and changes the surface property of micron powder.

Description

Digestion-carbonization device and calcium carbonate nano-coating process
Technical Field
The invention relates to the technical field of carbonate preparation, in particular to a digestion-carbonization device and a calcium carbonate nano-coating process.
Background
The inorganic mineral filler is a filler commonly used in plastic and rubber products, but due to the difference in physical properties, the inorganic mineral material still has a certain degree of incompatibility with plastic, rubber and other matrixes, and the transmission of stress on the interface between the filler and the matrixes has an important influence on the performance of the composite material products. The mineral is subject to ultra-fine grinding to form a mineral particle microstructure similar to that of cullet slag, having a plurality of sharp edges and smooth surfaces, the sharp edges generally being formed by intersecting 2-3 crystal cleavage planes, and the smooth surfaces being formed by fracture of the mineral along the crystal cleavage planes. According to the related research of micro fracture mechanics, the sharp edges are often the stress concentration points in the material, and cracks are usually initiated from the sharp edges. During the extrusion process of plastics and rubber, the sharp edges can cause great abrasion to the screw of a plastic extruder, and even the microscopic edges of some siliceous mineral fillers can cause serious abrasion to the screw, so that the screw cannot be used. The smooth surface of the mineral particles makes it difficult to form an effective bond and tight entanglement with the polymeric material. The destruction of the composite material is firstly started from the weak interface, and the improvement of the bonding property between the interfaces is the key for improving the strength of the composite material. The mineral powder is directly filled, so that the shearing stress is easily generated between the interfaces, and the mechanical property of the composite material is reduced. Therefore, a surface modification treatment of the mineral particles is required.
Research shows that the surface appearance of the nano particles is atomic steps, uneven and rough in structure, atomic energy at edges and corners of the steps is high, activity is high, certain chemical action and strong physical action are easy to occur with a high molecular chain, the nano particles can be used as a filler to obtain a high-performance polymer composite material, and the method for reinforcing the polymer by adopting the nano filler is proved and gradually paid attention by industrial enterprises at present.
But the production cost of the nano powder is high and the nano powder is not easy to popularize; meanwhile, the nano powder has poor dispersibility and easy agglomeration, is difficult to uniformly disperse when being mixed with a matrix material, has poor dispersion treatment but influences the performance of the nano powder, and is difficult to exert the excellent characteristics of the nano powder. Based on this, it is necessary to provide a digestion-carbonization device and a calcium carbonate nano-coating process for polymer composite filler.
Disclosure of Invention
Aiming at the technical problems that the micron-level polymer composite material filler has poor compatibility and the nanometer-level polymer composite material filler has poor dispersibility, the invention provides a digestion-carbonization device and a calcium carbonate nanometer coating process, wherein nanometer coating is carried out on the surfaces of micron-level calcium carbonate particles, so that the excellent characteristics of a nanometer material can be effectively utilized, and the surface property of micron powder can be changed.
In a first aspect, the invention provides a digestion-carbonization device, which comprises a digestion tank and a reaction kettle which are communicated with each other, wherein a first screen and a first stirring paddle are arranged in the digestion tank, a blade of the first stirring paddle is positioned below the first screen, a second screen and a second stirring paddle are arranged in the reaction kettle, a blade of the second stirring paddle is positioned below the second screen, and a gas channel is also arranged at the bottom of the reaction kettle; the reactor is characterized by further comprising a diaphragm pump, wherein a water inlet pipeline of the diaphragm pump is communicated with the reaction kettle, and a water outlet pipeline of the diaphragm pump is communicated with the digestion tank.
Further, the digestion tank is provided with an overflow port, the overflow port is positioned above the first screen, the reaction kettle is provided with a liquid inlet, the liquid inlet is positioned above the second screen, and the overflow port is communicated with the liquid inlet pipeline.
Further, reation kettle is equipped with the circulation liquid outlet, the circulation liquid outlet is located the top of second screen cloth, the circulation liquid outlet passes through the inlet channel and the diaphragm pump intercommunication of diaphragm pump.
Further, the first screen and the second screen are both 200-mesh screens. A200-mesh screen is selected, so that larger particles can be effectively prevented from entering the material circulation between the digestion tank and the reaction kettle, and the reaction system and the material circulation system are effectively separated.
In a second aspect, the invention provides a calcium carbonate nano-coating process using the above digestion-carbonization apparatus, which comprises adding ground calcium carbonate into a calcium hydroxide suspension, obtaining a uniformly mixed suspension by mechanical force, introducing a reaction gas to carbonize calcium hydroxide, and nucleating and growing calcium carbonate nanoparticles generated by the carbonization reaction on the surface of ground calcium carbonate to obtain the ground calcium carbonate with nano-coated surface.
Furthermore, the chemical reaction of the calcium carbonate nano coating process mainly comprises six steps:
①CaO(s)+H2O(aq)＝Ca(OH)2(s)；
Figure BDA0003293864030000031
Figure BDA0003293864030000032
④CO2(aq)+OH-(aq)→HCO3 -(aq)；
⑤HCO3 -(aq)+OH-(aq)＝CO3 2-(aq)+H2O(aq)；
⑥Ca2+(aq)+CO3 2-(aq)＝CaCO3(s)。
further, the calcium carbonate nano coating process comprises the following steps:
(1) putting quicklime into a digestion tank, adding water, starting a first stirring paddle and a second stirring paddle, opening a diaphragm pump, and establishing circulation between the digestion tank and a reaction kettle, wherein the adding amount of the water meets the condition that the materials are submerged in a first screen and a second screen;
(2) adding heavy calcium carbonate into the digestion tank to circulate the materials between the digestion tank and the reaction kettle until solid and liquid are fully mixed;
(3) introducing air and carbon dioxide into the reaction kettle until the pH value of the materials in the reaction kettle reaches 7, and stopping introducing the air;
(4) and (3) carrying out solid-liquid separation on the materials in the reaction kettle, drying and crushing the solid materials to obtain the heavy calcium carbonate with the nano-coated surface.
Furthermore, the adding amount of the quicklime is 0.3 mol/L.
Further, the molar ratio of the quicklime to the ground limestone is 1: 5.
further, the stirring speed of the first stirring paddle and the second stirring paddle is 45 r/min.
Further, the flow ratio of air to carbon dioxide is 2: 1. under different flow ratios, the formation speeds of the nano coating layers are different. The flow ratio is increased, the nano coating layer formation speed is slow, but the film layer is compact; the flow ratio is reduced, the nano coating layer forming speed is high, but the film layer is sparse; when the flow ratio is 2: 1, the forming speed of the nano coating layer and the quality of the film layer can reach better levels.
The beneficial effect of the invention is that,
in a first aspect, the invention provides a digestion-carbonization device, which comprises a digestion tank and a reaction kettle, wherein material circulation of the digestion tank and the reaction kettle is realized through a diaphragm pump, so that heat generated by quicklime digestion can be dissipated, the digestion effect is improved through stirring, and the reaction time is shortened.
In a second aspect, the invention also provides a calcium carbonate nano-coating process, which is used for coating nano calcium carbonate by performing a carbonization reaction on the surface of heavy calcium carbonate, so that the inherent morphological defects of heavy calcium carbonate particles are eliminated, and particularly sharp edges and flat cleavage surfaces of the heavy calcium carbonate particles are eliminated; the process is intermittent production, and the carbon dioxide continuously reacts with calcium hydroxide in the material to produce nano calcium carbonate along with the introduction of the carbon dioxide, so that supersaturated calcium hydroxide is promoted to be continuously dissolved into a system (the reaction is
Figure BDA0003293864030000041
Figure BDA0003293864030000042
) As the nano calcium carbonate is continuously generated and coated on the surface of the heavy calcium carbonate, the Ca (OH) is realized2All the utilization of (1); heavy by the processAfter the nano calcium carbonate is coated on the surface of the calcium carbonate, the specific surface area of the material is obviously improved, the particle size is increased, and the particle size distribution is more reasonable.
Drawings
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is a schematic view showing the connection of a digestion-carbonization apparatus according to example 1.
FIG. 2 is an SEM photograph of ground calcium carbonate at a calcium hydroxide concentration of 0.2 mol/L.
FIG. 3 is an SEM photograph of ground calcium carbonate at a calcium hydroxide concentration of 0.3 mol/L.
FIG. 4 is an SEM photograph of ground calcium carbonate at a calcium hydroxide concentration of 0.4 mol/L.
Fig. 5 is an SEM photograph of the surface nano-coated heavy calcium carbonate prepared in example 4.
Fig. 6 is an SEM photograph of the surface nano-coated heavy calcium carbonate prepared in comparative example 1.
Fig. 7 is a specific surface area test curve of the surface nano-coated heavy calcium carbonate prepared in example 4.
Fig. 8 is a specific surface area test curve of the surface nano-coated heavy calcium carbonate prepared in comparative example 1.
Fig. 9 is a result of measuring the particle size distribution of the surface nano-coated heavy calcium carbonate prepared in example 4.
Fig. 10 is a result of measuring the particle size distribution of the surface-nano-coated heavy calcium carbonate prepared in comparative example 1.
In the figure, 1-a digestion tank, 2-a reaction kettle, 3-a diaphragm pump, 4-a first screen, 5-a first stirring paddle, 6-a second screen and 7-a second stirring paddle.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The diameter of the reaction kettle used in the embodiment of the invention is 0.54 meter and the height thereof is 1 meter, the diameter of the digestion tank is 0.3 meter and the height thereof is 0.8 meter, and the total volume of the reaction kettle and the digestion tank is 0.285m3(ii) a Setting the reaction time to be 4h, circulating all materials for 200 times, and designing the flow of the diaphragm pump to be more than 14.25m3/h(57m3/4h＝14.25m3/h)。
In the specific embodiment of the invention, the following raw materials are used:
calcium oxide: qingzhou Yuxin calcium industry, Inc., with a purity of 95%;
carbon dioxide: qingzhou Yuxin calcium industry, Inc., with a purity of 99.8%;
tap water: self-making;
superfine suspended calcium carbonate: hebei Huabo Fine chemical Co., Ltd., 800 mesh.
Example 1
As shown in fig. 1, a digestion-carbonization device comprises a digestion tank 1, a reaction kettle 2 and a diaphragm pump 3, wherein a first screen 4 with 200 meshes and a first stirring paddle 5 are arranged in the digestion tank 1, a blade of the first stirring paddle 5 is positioned below the first screen 4, a pH meter, a second screen 6 with 200 meshes and a second stirring paddle 7 are arranged in the reaction kettle 2, a blade of the second stirring paddle 7 is positioned below the second screen 6, and a gas channel is also arranged at the bottom of the reaction kettle 2;
digestion tank 1 is equipped with the overflow mouth, and the overflow mouth is located first screen cloth 4 top, and reation kettle 2 is equipped with the inlet, and the inlet is located second screen cloth 6 top, overflow mouth and inlet pipeline intercommunication, and reation kettle 2 is equipped with the circulation liquid outlet, and the circulation liquid outlet is located the top of second screen cloth 6, and the circulation liquid outlet passes through the inlet channel and the diaphragm pump 3 intercommunication of diaphragm pump 3, and the outlet conduit and the digestion tank 1 intercommunication of diaphragm pump 3.
Example 2
A calcium carbonate nanocoating process, implemented using the digestion-carbonization apparatus of example 1, comprising the steps of: putting a calcium hydroxide suspension into a digestion tank, wherein the calcium hydroxide suspension comprises dissolved calcium hydroxide and undissolved calcium hydroxide, the addition amount of the calcium hydroxide suspension can meet the condition that materials do not pass through a first screen and a second screen, starting a first stirring paddle and a second stirring paddle, opening a diaphragm pump, and establishing circulation between the digestion tank and a reaction kettle;
(2) adding heavy calcium carbonate into the digestion tank to circulate the materials between the digestion tank and the reaction kettle until solid and liquid are fully mixed;
(3) introducing air and carbon dioxide into the reaction kettle until the pH value of the materials in the reaction kettle reaches 7, and stopping introducing the air;
(4) and (3) carrying out solid-liquid separation on the materials in the reaction kettle, drying and crushing the solid materials to obtain the heavy calcium carbonate with the nano-coated surface.
As in example 2, in laboratory pilot-scale tests, calcium hydroxide reagent is often directly used to replace the quicklime digestion step, and calcium hydroxide suspension with corresponding concentration is directly prepared. In this case, although the calcium hydroxide solid is not completely dissolved in water due to the low solubility of calcium hydroxide, calcium hydroxide is still added to the carbonization reaction system, and the calcium hydroxide is finally completely utilized with the continuous introduction of carbon dioxide.
Example 3
A calcium carbonate nanocoating process, implemented using the digestion-carbonization apparatus of example 1, comprising the steps of:
(1) putting quicklime into a digestion tank, adding water, starting a first stirring paddle and a second stirring paddle, opening a diaphragm pump, and establishing circulation between the digestion tank and a reaction kettle, wherein the adding amount of the water meets the condition that the materials are submerged in a first screen and a second screen;
(2) adding heavy calcium carbonate into the digestion tank to circulate the materials between the digestion tank and the reaction kettle until solid and liquid are fully mixed;
(3) introducing air and carbon dioxide into the reaction kettle until the pH value of the materials in the reaction kettle reaches 7, and stopping introducing the air;
(4) and (3) carrying out solid-liquid separation on the materials in the reaction kettle, drying and crushing the solid materials to obtain the heavy calcium carbonate with the nano-coated surface.
Example 4
A calcium carbonate nanocoating process, implemented using the digestion-carbonization apparatus of example 1, comprising the steps of:
(1) calculating the input amount of quicklime according to the content of calcium hydroxide in a calcium hydroxide suspension liquid being 0.3mol/L, inputting 5.04kg (285L multiplied by 0.3mol/L multiplied by 56 g/mol/0.95) of quicklime into a digestion tank, adding 285L of water, starting a first stirring paddle and a second stirring paddle when the materials can be beyond a first screen and a second screen under the input amount, setting the stirring speed to be 45r/min, opening a diaphragm pump, and establishing circulation between the digestion tank and a reaction kettle;
(2) and circulating for 10min, adding ground calcium carbonate into the digestion tank, wherein the molar ratio of the quicklime to the ground calcium carbonate is 1: 5, circulating the materials between the digestion tank and the reaction kettle for 10min until solid and liquid are fully mixed;
(3) introducing air and carbon dioxide into the reaction kettle, and adjusting the air flow to be 4m3H, carbon dioxide flow 2m3Measuring the pH value of the materials in the reaction kettle every 10min, and stopping ventilation until the pH value of the materials in the reaction kettle reaches 7;
(4) and (3) performing filter pressing on the materials in the reaction kettle by using a plate-and-frame filter press, drying and crushing the materials by using a filter plate, and storing the dried and crushed materials to obtain the heavy calcium carbonate with the nano-coated surface.
In actual production, as in example 4, calcium hydroxide suspension obtained by slaking quicklime contains dissolved calcium hydroxide, undissolved calcium hydroxide and other large-particle impurities, and all calcium hydroxide is fed into the reaction system, and the material circulation system can keep the concentration balance of calcium hydroxide between the two reactors. With the continuous introduction of carbon dioxide in the carbonization reaction kettle and the growth of nano calcium carbonate on the surface of the coarse whiting particles, the calcium hydroxide is continuously consumed. According to the dissolution kinetics of calcium hydroxide, the calcium hydroxide in the digestion reactor is continuously dissolved in the system, so that the concentration of the calcium hydroxide in the system is always stabilized at the saturated concentration until all the calcium hydroxide is consumed, and the stable proceeding of the carbonization reaction and the nano coating behavior is ensured.
In addition, in the embodiment 4, the circulation of the digestion tank and the reaction kettle is beneficial to the dissipation of heat generated by quicklime digestion, and the digestion effect is improved by stirring. Through determination, the material is circulated for 10-20 minutes before the heavy calcium carbonate is added, and the required concentration of the calcium hydroxide suspension can be achieved.
Screening example 1
The nano coating is prepared by reacting calcium hydroxide with carbon dioxide to generate calcium carbonate, and the concentration of the calcium hydroxide in the suspension can obviously influence the surface appearance of the final nano-coated composite calcium carbonate particles. The tests were carried out at different concentrations of calcium hydroxide, respectively (the other conditions were the same as in example 4). As shown in FIG. 2, when the concentration of calcium hydroxide is 0.2mol/L, the supersaturation degree of the calcium hydroxide suspension is not enough for uniform nucleation to occur, and few coated particles are formed on the surface of heavy calcium carbonate particles, and mainly film-forming coating caused by non-uniform nucleation is formed; as shown in fig. 3, when the concentration of calcium hydroxide is 0.3mol/L, uniform nucleation may occur, and surface particle coating of heavy calcium carbonate powder particles may be formed; as shown in fig. 4, as the concentration of calcium hydroxide increases, a large number of coated particles with smaller particle size are formed, because the saturation degree of the reactant in the solution is higher when the concentration of calcium hydroxide is higher, and the reactant can be uniformly nucleated during the reaction to form a large number of calcium carbonate crystal nuclei, so that the newly generated nano calcium carbonate is coated on the crystal nuclei, and the nano calcium carbonate is not continuously coated on the surface of the heavy calcium carbonate, so that a large number of particles with smaller particle size are formed.
Comparative example 1
A calcium carbonate nano coating process comprises the following steps:
(1) slaking quicklime by using water to prepare a calcium hydroxide solution, wherein the mass ratio of the water to the quicklime is 5: 1, the digestion time is generally 4-6 hours, the total content of the calcium hydroxide lime slurry prepared after the digestion reaction is 2.22 wt%, but the calcium hydroxide belongs to a slightly soluble substance, and the solubility in water at 80 ℃ is 0.094g per 100g of water, so the actual utilization rate of the calcium hydroxide in the step is only 4.2%;
(2) in order to avoid the coarse particles in the quicklime from being mixed into the superfine ground calcium carbonate, filtering by using a 100-mesh sieve to obtain a supernatant of a calcium hydroxide solution, adding the supernatant into a reaction kettle, introducing carbon dioxide, and carrying out nucleation and growth on the surface of the superfine ground calcium carbonate, wherein the reaction time in the reaction kettle is generally more than 4 hours.
If calcium hydroxide suspension digested by quicklime is completely added into a carbonization reaction system, impurities with different particle sizes are introduced, so that the particle size distribution of the superfine and heavy calcium powder is mutated, and the service performance of the superfine and heavy calcium powder is influenced. Because the solubility of the calcium hydroxide in water is between 0.185g/100g and 0.085g/100g within the temperature range of 0-90 ℃, which is far less than the concentration of the calcium hydroxide required by the coating of the nano calcium carbonate, if a filtering mode is adopted to filter out large-particle impurities, a large amount of undissolved calcium hydroxide can be filtered out together, and the utilization rate is low. The calcium hydroxide actually added to the carbonization system is only a saturated solution thereof, and the concentration of the calcium hydroxide is not stable but continuously decreases as the reaction proceeds after the calcium hydroxide is added to the system, so that the coating effect cannot be effectively controlled.
The comparison between example 4 and comparative example 1 is shown in table 1 below and fig. 5 to 6, and it can be seen that the production route of comparative example 1 actually utilizes less calcium hydroxide, has low heavy calcium coating rate and low production efficiency; embodiment 4 is intermittent production, and with the introduction of carbon dioxide, carbon dioxide continuously reacts with calcium hydroxide to produce nano calcium carbonate and coats the surface of heavy calcium carbonate, thereby promoting the supersaturated calcium hydroxide to be continuously dissolved in the system, and finally realizing the complete utilization of calcium hydroxide.
Table 1 table comparing example 4 with comparative example 1
Figure BDA0003293864030000091
To further evaluate the surface condition of the ground calcium carbonate, the surface nano-coated ground calcium carbonate prepared in example 4 and comparative example 1 was measured for specific surface area, and the results are shown in FIGS. 7 to 8, where the specific surface area of the ground calcium carbonate prepared in example 4 was 3.19m2G, specific surface area of ground calcium carbonate prepared in comparative example 1Is 1.37m2(ii) in terms of/g. It can be seen that the surface nano-coated heavy calcium carbonate prepared in example 4 has a relatively large specific surface area, more than twice as large as that of comparative example 1. The increase of the specific surface area shows that the nano coating makes the smooth dissociation surface of the heavy calcium carbonate surface rough, and the whole sphericization degree of the particles is increased, so that the fluidity of the product is better, and the phase interface combination of the product is firmer when the product is used as a filler in the industries of plastics, rubber, papermaking and the like.
The surface nano-coated heavy calcium carbonate prepared in example 4 and comparative example 1 was subjected to particle size distribution measurement, and the measurement results are shown in tables 2 to 3 and fig. 9 to 10 below. It can be seen that the surface-nano-coated heavy calcium carbonate prepared in comparative example 1 had a majority of small particles. The specific surface area of the fine particles is larger, the particles have higher surface energy, and the particles are more favorable to become an active area of heterogeneous nucleation, and the nano coating process is mainly completed on the surface of the heavy calcium carbonate particles with smaller particle size, so that the small particles continuously grow along with the continuous carbonization reaction with stable speed in a new process, and the particle size distribution tends to be reasonable.
Table 2 particle size distribution of surface nano-coated heavy calcium carbonate prepared in example 4
Figure BDA0003293864030000101
Table 3 particle size distribution of the surface nano-coated heavy calcium carbonate prepared in comparative example
Figure BDA0003293864030000102
Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention.

Claims (10)

1. A digestion-carbonization device is characterized by comprising a digestion tank and a reaction kettle which are communicated with each other, wherein a first screen and a first stirring paddle are arranged in the digestion tank, a paddle of the first stirring paddle is positioned below the first screen, a second screen and a second stirring paddle are arranged in the reaction kettle, a paddle of the second stirring paddle is positioned below the second screen, and a gas channel is also arranged at the bottom of the reaction kettle; the reactor is characterized by further comprising a diaphragm pump, wherein a water inlet pipeline of the diaphragm pump is communicated with the reaction kettle, and a water outlet pipeline of the diaphragm pump is communicated with the digestion tank.
2. The digestion-carbonization apparatus according to claim 1, wherein the digestion tank is provided with an overflow port which is positioned above the first screen, the reaction vessel is provided with a liquid inlet which is positioned above the second screen, and the overflow port is communicated with the liquid inlet pipeline.
3. The digestion-carbonization apparatus according to claim 1, wherein the reaction vessel is provided with a circulation outlet which is located above the second screen, and the circulation outlet is communicated with the diaphragm pump through a water inlet pipe of the diaphragm pump.
4. The digestion-carbonization device according to claim 1, wherein the first screen and the second screen are each a 200-mesh screen.
5. The nano calcium carbonate coating process with the digesting and carbonizing apparatus as set forth in claim 1 includes adding heavy calcium carbonate into suspension of calcium hydroxide, mechanically acting to obtain homogeneous suspension, introducing reaction gas to carbonize calcium hydroxide, and forming and growing nano calcium carbonate particle on the surface of heavy calcium carbonate to obtain nano heavy calcium carbonate coated with nano surface.
6. The calcium carbonate nanocoating process of claim 5, comprising the steps of:
(1) putting quicklime into a digestion tank, adding water, starting a first stirring paddle and a second stirring paddle, opening a diaphragm pump, and establishing circulation between the digestion tank and a reaction kettle, wherein the adding amount of the water meets the condition that the materials are submerged in a first screen and a second screen;
(2) adding heavy calcium carbonate into the digestion tank to circulate the materials between the digestion tank and the reaction kettle until solid and liquid are fully mixed;
(3) introducing air and carbon dioxide into the reaction kettle until the pH value of the materials in the reaction kettle reaches 7, and stopping introducing the air;
(4) and (3) carrying out solid-liquid separation on the materials in the reaction kettle, drying and crushing the solid materials to obtain the heavy calcium carbonate with the nano-coated surface.
7. The calcium carbonate nanocoating process as claimed in claim 6, wherein the amount of quicklime added is 0.3 mol/L.
8. The calcium carbonate nanocoating process as claimed in claim 6, wherein the molar ratio of quicklime to ground limestone is 1: 5.
9. the calcium carbonate nanocoating process of claim 6, wherein the stirring speed of the first stirring paddle and the second stirring paddle is 45 r/min.
10. The calcium carbonate nanocoating process according to claim 6, wherein the flow ratio of air to carbon dioxide is 2: 1.
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Application publication date: 20211217