Preparation device and method of particle size controllable micron calcium carbonate

Abstract

The present application relates to the technical field of calcium carbonate preparation, and particularly relates to a preparation device and method of micron calcium carbonate with controllable particle size, which comprises a reactor body, a bottle-shaped flow guide cylinder, a gas-liquid mixer and a multi-tube bundle coil, wherein the bottle-shaped flow guide cylinder is coaxially arranged in the inside of the reactor body, the multi-tube bundle coil is arranged around the inside wall of the reactor body and is located close to the top of the bottle-shaped flow guide cylinder, the gas-liquid mixer is arranged outside the reactor body, the outlet end of the gas-liquid mixer is communicated with the inlet end of the multi-tube bundle coil, and the outlet end of the multi-tube bundle coil is located at the bottom of the bottle-shaped flow guide cylinder. The gas-liquid mixer arranged in the preparation device can improve the gas-liquid contact area, and the small tube bundles arranged in the multi-tube bundle coil can play the roles of physical dispersion and steric hindrance during the generation of calcium carbonate, so that the micron calcium carbonate with uniform particle size can be prepared by the device without adding dispersants, crystal form control agents and other additives.

Description

Technical Field

[0001] This invention relates to the field of calcium carbonate preparation technology, and in particular to an apparatus and method for preparing micron-sized calcium carbonate with controllable particle size. Background Technology

[0002] Calcium carbide slag is a solid waste generated during the production of PVC using the calcium carbide method. Its main component is calcium hydroxide, and it also contains trace amounts of organic and inorganic impurities (such as aluminum oxide, iron oxide, silicon dioxide, sulfides, etc.). It has a large output and is highly alkaline.

[0003] Using ammonium chloride as a leaching agent to leach calcium carbide slag to prepare calcium carbonate is a relatively common process. However, the article "A New Green Process for Producing Food-Grade Light Calcium Carbonate from Calcium Carbide Slag" published in Modern Chemical Industry by Yan Xin et al. indicates that the CaCl2-NH3·H2O system is not conducive to the ultrafine processing of the product, resulting in light calcium carbonate products with coarser particles and a wider particle size distribution. During the experiment, the applicant also found a similar situation, with the prepared calcium carbonate having uneven particle size and small settling volume.

[0004] To address the aforementioned issues, a common approach is to add dispersants or crystal form control agents. For example, patent CN102602973B discloses a method for synthesizing ultrafine calcium carbonate using carbide slag. This method involves adding one or more crystal form control agents, such as sulfates or citrates, during the carbonation process to prepare an ultrafine calcium carbonate slurry. The amount of crystal form control agent added is 0.1%-5% of the mass of the generated calcium carbonate. However, this method suffers from several drawbacks: the amount of crystal form control agent added is difficult to measure accurately; the system used to generate calcium carbonate needs to be stable; and the addition of crystal form control agents inevitably leads to a decrease in the purity of the product calcium carbonate, as well as the impact of the additives themselves on product performance.

[0005] Currently, most publicly disclosed patented technologies for preparing calcium carbonate from carbide slag focus on changing process conditions and adding auxiliary agents, but lack the design of related large-scale equipment, making it impossible to achieve large-scale industrial applications.

[0006] While patent CN102849771A discloses a continuous carbonation reaction apparatus and a method for preparing ultrafine calcium carbonate using it, this continuous carbonation reaction apparatus includes a carbonation reactor and a carbonation vessel mounted on a support. The carbonation reactor and the carbonation vessel are spaced apart and interconnected. During operation, the flow rate of the initial slurry entering the carbonizer and the flow rate of kiln gas entering each carbonizer are controlled. Through multiple stages of carbonation reactors, the slurry flowing out from the outlet of the last stage carbonation reactor completes the carbonation reaction, obtaining ultrafine calcium carbonate slurry, thus achieving continuous carbonation. However, this apparatus has a complex structure, and a crystal form control agent still needs to be introduced during the preparation process. Although the spiral baffles inside the apparatus play a certain role in enhancing mixing, they can also easily cause the deposition of calcium carbonate products.

[0007] Patent CN203639167U discloses a reactor for enhancing gas-liquid mixing to prepare submicron calcium carbonate. The reactor includes an outer barrel and a guide inner cylinder fitted inside the outer barrel. A calcium hydroxide slurry inlet is located on one side of the top of the outer barrel, and a calcium carbonate slurry outlet is located at the bottom of the outer barrel. A longitudinal baffle is located at the lower end of the inner wall of the outer barrel, and a spiral baffle is spirally arranged on the inner wall of the outer barrel above the longitudinal baffle. A vortex gas distributor is located between the bottom of the outer barrel and the bottom of the guide inner cylinder, with the kiln gas inlet pipe of the vortex gas distributor extending out of the outer barrel. While this device improves the gas-liquid mixing effect, this method of adding longitudinal baffles and porous spiral baffles in the interlayer between the guide cylinder and the outer barrel to accelerate gas-liquid mixing is highly susceptible to blockage and deposition of calcium carbonate and calcium hydroxide slurries, which can affect the continuous operation of the equipment. Furthermore, the specific embodiment explicitly requires the addition of sucrose as a crystal form control agent.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of this invention is to provide an apparatus and method for preparing micron-sized calcium carbonate with controllable particle size. This apparatus can prepare micron-sized calcium carbonate with uniform particle size without the need to add dispersants, crystal form control agents or other additives.

[0010] In a first aspect, the present invention provides an apparatus for preparing micron-sized calcium carbonate with controllable particle size, comprising a reactor body, a bottle-shaped guide tube, a gas-liquid mixer, and a multi-tube bundle coil.

[0011] The bottle-shaped guide tube is coaxially disposed inside the reactor body. The multi-tube bundle coil is arranged around the inner wall of the reactor body and located near the top of the bottle-shaped guide tube. The gas-liquid mixer is disposed outside the reactor body, and the outlet end of the gas-liquid mixer is connected to the inlet end of the multi-tube bundle coil. The outlet end of the multi-tube bundle coil is located at the bottom of the bottle-shaped guide tube.

[0012] As a preferred embodiment of this technical solution, the gas-liquid mixer includes a gas-liquid mixing chamber, which is provided with a mineralized liquid inlet, a flue gas inlet and a gas-liquid mixture outlet. The mineralized liquid inlet is perpendicular to the flue gas inlet, and an aeration head is provided at the end of the air inlet pipe at the flue gas inlet.

[0013] The inlet end of the multi-tube coil is connected to the outlet of the gas-liquid mixture.

[0014] As a preferred embodiment of this technical solution, the multi-tube coil has multiple small tube bundles evenly distributed inside, and the inlet end of the multi-tube coil is connected to the outlet of the gas-liquid mixture through a tube bundle distribution plug.

[0015] As a preferred embodiment of this technical solution, a gas cooling coil is further provided inside the reactor body, with one end of the gas cooling coil connected to the CO2 gas inlet and the other end connected to the flue gas inlet.

[0016] As a preferred embodiment of this technical solution, a temperature control jacket is provided around the outer side of the reactor body.

[0017] As a preferred embodiment of this technical solution, the ratio of the bottom cylinder diameter D, the middle width L, and the top cylinder diameter d of the bottle-shaped guide tube is (2-4):1:(1.5-3).

[0018] As a preferred embodiment of this technical solution, the ratio of the outer diameter φ of the multi-tube coil, the bottom cylindrical diameter D of the bottle-shaped guide tube, and the inner diameter Ω of the reactor body is 1:(6-24):(10-30).

[0019] As a preferred embodiment of this technical solution, the top and bottom of the reactor body are respectively provided with a gas outlet and a discharge port, and a clear liquid outlet is also provided on the upper side wall of the reactor body;

[0020] The reactor body is also equipped with a temperature controller, pH meter, online CO2 detector and gas flow meter.

[0021] Secondly, the present invention also discloses a method for preparing micron-sized calcium carbonate using the above-mentioned apparatus for preparing micron-sized calcium carbonate with controllable particle size, specifically including the following steps:

[0022] S1. After mixing carbide slag and ammonium chloride solution, solid-liquid separation is performed to obtain a mineralized solution of CaCl2-NH3·H2O system;

[0023] S2. After heat exchange, the CO2-containing flue gas is dispersed into fine bubbles through an aeration head and comes into cross-flow contact with the mineralized liquid in the gas-liquid mixer to obtain a gas-liquid mixture.

[0024] S3. The gas-liquid mixture enters the multi-tube coil. In the multi-tube coil, CaCl2-NH3·H2O in the mineralization solution reacts with CO2 to obtain calcium carbonate solid and ammonium chloride solution.

[0025] S4. The gas-liquid-solid three-phase mixed slurry discharged from the end outlet of the multi-tube bundle coil enters the bottle-shaped guide tube. The unreacted CO2 and its inert components in the flue gas drive the liquid to achieve circulation. The generated calcium carbonate solid settles to the bottom of the reactor body. After separation and drying, micron-sized calcium carbonate product is obtained. The unreacted CO2-containing flue gas is discharged from the reaction system after gas-liquid separation.

[0026] S5. The generated ammonium chloride solution overflows from the reactor body and is used for the leaching of carbide slag, completing the entire cycle.

[0027] As a preferred embodiment of this technical solution, in step S1, the concentration of calcium ions in the mineralization solution of the CaCl2-NH3·H2O system is controlled at 1-2 mol / L; while in step S2, the volume fraction of CO2 in the CO2-containing flue gas is 5-40%, and the temperature of the CO2-containing flue gas after heat exchange is controlled below 45℃; studies have shown that at this reactant concentration, the reaction rate can be effectively controlled, ensuring the uniformity of the particle size of the generated calcium carbonate product.

[0028] In step S4, the apparent flow velocity of the gas inside the bottom cylinder of the bottle-shaped guide tube is 0.2-0.5 cm / s. This flow velocity can maintain the stable operation of the circulation state, so that the unreacted CO2 can be further removed through the circulation process, and at the same time, the sedimentation and separation of calcium carbonate products can be achieved.

[0029] The apparatus for preparing micron-sized calcium carbonate according to the present invention has at least the following technical advantages:

[0030] 1. The apparatus for preparing micron-sized calcium carbonate with controllable particle size of the present invention includes a reactor body, a bottle-shaped guide tube, a gas-liquid mixer, and a multi-tube bundle coil. Calcium carbide slag and NH4Cl solution are mixed and separated into solid and liquid components to obtain a mineralized liquid of CaCl2-NH3·H2O system. This mineralized liquid is mixed with CO2-containing flue gas in the gas-liquid mixer and then enters a multi-tube bundle coil of a specific diameter. In the multi-tube bundle coil, the CaCl2-NH3·H2O in the mineralized liquid reacts with CO2 to generate solid calcium carbonate and regenerate ammonium chloride. The end of the multi-tube bundle coil is located at the bottle-shaped guide tube. Inside the bottom cylindrical section of the reactor, the gas-liquid-solid three-phase mixed slurry discharged from the multi-tube coil outlet can achieve slow circulation within the reactor body under the action of the bottle-shaped guide tube and the influence of unreacted CO2-containing flue gas. The generated solids rise a certain distance with the liquid and then settle to the bottom of the reactor body. After separation and drying, micron-sized calcium carbonate product can be obtained. The unreacted CO2-containing flue gas further reacts within the reactor body and then leaves the reaction system through gas-liquid separation. The newly generated ammonium chloride solution overflows from the reactor body and can be recycled for leaching of carbide slag. The gas-liquid mixer in the preparation device of this invention can increase the gas-liquid contact area. At the same time, the fine tube bundles inside the multi-tube coil can play a role in physical dispersion and steric hindrance during the calcium carbonate generation process. Therefore, micron-sized calcium carbonate with uniform particle size can be prepared by this device without the addition of dispersants, crystal form control agents, or other additives.

[0031] 2. In the preparation device of micron-sized calcium carbonate with controllable particle size of the present invention, the unreacted CO2 in the multi-tube coil can be further removed by extending the residence time through circulation, thereby maximizing the utilization of CO2. At the same time, the circulation of the bottle-shaped guide tube can realize the integrated sedimentation and separation of calcium carbonate products without mechanical stirring.

[0032] 3. The apparatus for preparing micron-sized calcium carbonate with controllable particle size of the present invention has a simple manufacturing process and can expand production by increasing the diameter of the multi-tube coil and the number of tubes, which is conducive to realizing large-scale industrial application. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the apparatus for preparing micron-sized calcium carbonate according to the present invention.

[0035] Figure 2 This is a schematic diagram of the gas-liquid mixer of the present invention;

[0036] Figure 3 This is a schematic diagram illustrating the working principle of a bottle-shaped flow guide tube.

[0037] Figure 4 The main dimensions of the bottle-shaped flow guide tube are marked;

[0038] Figure 5 This is a particle size distribution diagram for a pilot-scale production of calcium carbonate with an annual processing capacity of 1000t carbon dioxide.

[0039] Figure label:

[0040] 1: Reactor body; 2: Bottle-shaped guide tube; 3: Gas-liquid mixer; 4: Multi-tube bundle coil; 5: Gas-liquid mixing chamber; 6: Mineralized liquid inlet; 7: Flue gas inlet; 8: Aeration head; 9: Fine tube bundle; 10: Tube bundle distribution plug; 11: Gas cooling coil; 12: Temperature control jacket; 13: Gas outlet; 14: Discharge port; 15: Clear liquid outlet; 16: Gas-liquid separation zone; 17: Locking flange; 18: CO2 gas inlet; 19: Support; 20: Discharge zone. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1-4 As shown, this embodiment provides a device for preparing micron-sized calcium carbonate with controllable particle size, including a reactor body 1, a bottle-shaped guide tube 2, a gas-liquid mixer 3, and a multi-tube bundle coil 4. The bottle-shaped guide tube 2 is coaxially fixed inside the reactor body 1 by a bracket 19. The present invention does not strictly limit the specific fixing method of the bottle-shaped guide tube 2; other methods that can fix the bottle-shaped guide tube 2 without affecting the circulation effect can be used. The multi-tube bundle coil 4 is arranged around the inner wall of the reactor body 1 and is located near the top of the bottle-shaped guide tube 2. Specifically, the multi-tube bundle coil 4 has multiple small tube bundles 9 of specific diameters inside, and the material of the small tube bundles 9 is preferably seamless stainless steel. The outer diameter and wall thickness of the small tube bundles 9 can be selected according to the desired particle size of the calcium carbonate to be prepared. The gas-liquid mixer 3 is located on the outside of the reactor body 1, and the outlet end of the gas-liquid mixer 3 is connected to the inlet end of the multi-tube bundle coil 4. The outlet end of the multi-tube bundle coil 4 is located at the bottom of the bottle-shaped guide tube 2.

[0046] The following reaction occurs when carbide slag and NH4Cl solution are mixed:

[0047] Ca(OH)2+2NH4Cl=CaCl2+2NH3·H2O

[0048] After solid-liquid separation, a mineralized liquid with the main component being a CaCl2-NH3·H2O system is obtained. This mineralized liquid is pumped into a gas-liquid mixer 3. In the gas-liquid mixer 3, the mineralized liquid comes into cross-flow contact with microbubbles of CO2-containing flue gas to further increase the gas-liquid contact area and achieve maximum gas-liquid mixing. After mixing with the CO2-containing flue gas, the mineralized liquid enters a multi-tube bundle coil 4 of a specific diameter. In the multi-tube bundle coil 4, the CaCl2-NH3·H2O in the mineralized liquid reacts with CO2 to generate calcium carbonate solid and regenerate ammonium chloride.

[0049] CaCl2+2NH3·H2O+CO2+=CaCO3+2NH4Cl+H2O

[0050] At this time, since the end of the multi-tube coil 4 is located inside the bottom cylinder of the bottle-shaped guide tube 2, the gas-liquid-solid three-phase mixed slurry discharged from the outlet of the multi-tube coil 4 can achieve slow circulation in the reactor body 1 under the action of the bottle-shaped guide tube 2 and the drive of the unreacted CO2 and other inert gases. The generated solids rise with the liquid for a certain distance and then settle to the bottom of the reactor body 1. After separation and drying, micronized calcium carbonate products can be obtained. The unreacted CO2-containing flue gas further reacts in the reactor body 1 and leaves the reaction system after gas-liquid separation. The newly generated ammonium chloride solution overflows from the reactor body 1 and can be recycled for the leaching of carbide slag.

[0051] The gas-liquid mixer 3 in the preparation device of the present invention can increase the gas-liquid contact area. At the same time, the fine tube bundles 9 arranged in the multi-tube coil 4 can play a role in physical dispersion and spatial steric hindrance during the calcium carbonate generation process, ensuring the uniformity of calcium carbonate particle size. In addition, the bottle-shaped guide tube 2 allows the unreacted CO2 in the multi-tube coil 4 to be further removed by extending the residence time through circulation, thereby maximizing the utilization of CO2. At the same time, the circulation of the bottle-shaped guide tube 2 can achieve the integrated sedimentation and separation of calcium carbonate products without mechanical stirring.

[0052] Therefore, the preparation apparatus of the present invention can prepare micron-sized calcium carbonate with uniform particle size without the need to add dispersants, crystal form control agents or other auxiliary agents.

[0053] In this embodiment, the gas-liquid mixer 3 specifically includes a gas-liquid mixing chamber 5 with a length-to-diameter ratio of 4-6:1. The gas-liquid mixing chamber 5 has a mineralized liquid inlet 6, a flue gas inlet 7, and a gas-liquid mixture outlet. The mineralized liquid inlet 6 is perpendicular to the flue gas inlet 7, thereby achieving cross-flow contact between the mineralized liquid and the gas, thus improving the gas-liquid mixing effect. Furthermore, to further increase the contact area between the gas and the mineralized liquid, this embodiment has an aeration head 8 at the end of the air inlet pipe at the flue gas inlet 7. The aeration head 8 can pre-disperse the CO2-containing flue gas into fine bubbles, which further cross-flow into contact with the mineralized liquid to obtain a uniform gas-liquid mixture. The aeration head 8 is preferably a sintered metal tubular filter element with a pore size of 1-10 μm.

[0054] The inlet end of the multi-tube coil 4 is connected to the outlet of the gas-liquid mixture, so that the gas-liquid mixture can enter the multi-tube coil 4 and react in the multi-tube coil 4 to generate calcium carbonate solid and ammonium chloride.

[0055] In this embodiment, specifically, the interior of the multi-tube coil 4 is uniformly distributed with a plurality of small tube bundles 9, and the inlet end of the multi-tube coil 4 is connected to the outlet of the gas-liquid mixture through the tube bundle distribution plug 10. The outer diameter of the small tube bundle 9 is preferably any value between 0.3-3mm, and the wall thickness is preferably any value between 0.1-2mm.

[0056] Based on the above technical solution, in order to further improve the utilization rate of CO2-containing flue gas preheating, a gas cooling coil 11 is also installed inside the reactor body 1. One end of the gas cooling coil 11 is connected to the CO2 gas inlet 18, and the other end is connected to the flue gas inlet 7. After the CO2-containing flue gas exchanges heat through the gas cooling coil 11, it enters the aeration head 8 through the inlet pipe.

[0057] In addition, a temperature control jacket 12 is provided around the outside of the reactor body 1 in this embodiment to control the temperature inside the reactor body 1 and ensure the smooth progress of the reaction.

[0058] In this embodiment, the ratio of the bottom cylinder diameter D, the middle width L, and the top cylinder diameter d of the bottle-shaped guide tube 2 is (2-4):1:(1.5-3), and preferably 3:1:2. This specific size structure of the bottle-shaped guide tube 2 is a specific choice made based on ensuring the circulation and the settling effect of calcium carbonate particles.

[0059] The ratio of the outer diameter φ of the multi-tube coil 4, the bottom cylindrical diameter D of the bottle-shaped guide tube 2, and the inner diameter Ω of the reactor body 1 (specifically the inner diameter of the upper cylindrical structure) is 1:(6-24):(10-30), and preferably 1:20:26.

[0060] Studies have shown that, under the action of the multi-tube coil 4 of the above-mentioned specific size, the bottle-shaped guide tube 2 and the reactor body 1, the multi-tube coil 4 will not affect the circulation, and at the same time, under the action of the circulation, it can also prevent calcium carbonate particles from depositing on the contact surface of the multi-tube coil 4.

[0061] In addition, the reactor body 1 in this embodiment has a gas outlet 13 at the top and a discharge port 14 at the bottom. The gas outlet 13 is used to promptly discharge unreacted CO2-containing flue gas. To further avoid liquid entrainment in the discharged gas, a gas-liquid separation zone 16 can be provided above the reactor body 1 to discharge unreacted flue gas after gas-liquid separation. The present invention does not strictly limit the form of gas-liquid separation in the gas-liquid separation zone 16, and can select forms such as baffle separation, wire mesh separation, and ultrafiltration separation. The gas-liquid separation zone 16 can be fixed above the reactor body 1 by means of locking flange 17. The discharge port 14 is used to discharge the calcium carbonate product generated by the reaction. Considering the convenience of collection, the reactor body 1 can be set as a conical structure, and the bottom conical structure is collectively referred to as the discharge zone 20. In addition, a clear liquid outlet 15 is provided above the side wall of the reactor body 1 to overflow the newly generated ammonium chloride solution for leaching of carbide slag again.

[0062] Meanwhile, the reactor body 1 in this embodiment is also equipped with a temperature controller, pH meter, online CO2 detector and gas flow meter to monitor the reaction in real time.

[0063] Micronized calcium carbonate is prepared using the most preferred micronized calcium carbonate preparation device with controllable particle size, as well as calcium carbide slag raw material and flue gas after desulfurization and denitrification of thermal power plant. The specific implementation method is as follows.

[0064] Example 2

[0065] S1. After drying, the calcium carbide slag raw material is ground to 100 mesh. 5 kg of the raw material is added to 39 liters of ammonium chloride solution with a mass fraction of 14%. After stirring and reacting at room temperature for 1 hour, the mixture is filtered to obtain a mineralized solution of CaCl2-NH3·H2O system. The calcium ion concentration is measured to be 1.5 mol / L.

[0066] S2. The above-mentioned mineralized liquid is pumped into the gas-liquid mixing chamber 5 of the gas-liquid mixer 3 at a rate of 2L / min through the mineralized liquid inlet 6. The gas-liquid mixing chamber 5 is 50cm long and 10cm in diameter. The flue gas after desulfurization and denitrification of the thermal power plant (gas velocity 560L / min, inlet temperature 55℃, CO2 volume fraction 12%) is cooled to about 40℃ after heat exchange by the gas cooling coil 11. It enters the aeration head 8 (outer diameter 20mm, length 7cm, pore accuracy 1mm) through the air inlet pipe and is dispersed into fine bubbles. The bubbles come into cross-flow contact with the mineralized liquid in the gas-liquid mixing chamber 5 to obtain a gas-liquid mixture.

[0067] S3. The gas-liquid mixture enters the multi-tube coil 4 (inner diameter 1cm). 80 fine tube bundles 9 (outer diameter 1mm, wall thickness 0.1mm) are evenly distributed inside the multi-tube coil 4. In the multi-tube coil 4, CaCl2-NH3·H2O in the mineralization liquid reacts with CO2 to generate calcium carbonate solid and regenerate ammonium chloride.

[0068] The gas-liquid-solid three-phase mixed slurry discharged from the end outlet of S4 multi-tube coil 4 enters the bottom cylinder of the bottle-shaped guide tube 2 (lower cylinder diameter D = 15cm, D:L:d = 3:1:1.5). Under the action of the bottle-shaped guide tube 2 and driven by the unreacted CO2 and its inert components in the flue gas, the liquid can achieve slow circulation. The generated solid settles to the bottom of the reactor body 1 after rising a certain distance with the liquid. After separation and drying, calcium carbonate product is obtained. The unreacted CO2-containing flue gas further reacts in the reactor body 1 and then separates from the reaction system.

[0069] S5. The generated ammonium chloride solution overflows from reactor body 1 and is used for leaching of carbide slag.

[0070] The particle size distribution of the calcium carbonate product prepared in this embodiment is D10 = 0.954 μm, D50 = 2.463 μm, D90 = 5.718 μm, with a calcium carbonate content of 98.2%, whiteness of 95.4, and sedimentation volume of 2.6 mL / g. All indicators meet the industry standards for papermaking, rubber, coatings, and plastics (its basic performance is based on industry standard HG / T2226-2019 Determination of Ordinary Industrial Precipitated Calcium Carbonate).

[0071] The CO2 removal rate was calculated to be 97.5% using online CO2 detectors and gas flow meters at the inlet and outlet (1 - outlet CO2 volume fraction * outlet gas velocity / (inlet CO2 volume fraction * inlet gas velocity)).

[0072] Example 3

[0073] S1. The raw material of carbide slag is the same as in Example 2, except that a pilot-scale study of treating 1000t carbon dioxide per year was carried out by continuous operation. The raw material of carbide slag was mixed with ammonium chloride solution with a rate of 2337kg / h and a mass fraction of 14% at a rate of 243kg / h. After primary and secondary sedimentation, coarse filtration and fine filtration, a mineralized liquid of CaCl2-NH3·H2O system was obtained, and the calcium ion concentration was measured to be 1.4mol / L.

[0074] S2, the above-mentioned mineralized solution is introduced into the mineralized solution inlet 6 at a speed of 2m. 3 The gas is pumped into the gas-liquid mixing chamber 5 of the gas-liquid mixer 3 at a speed of / h. The gas-liquid mixing chamber 5 is 1m long and 20cm in diameter; the flue gas after desulfurization and denitrification in the thermal power plant (gas velocity 508m / h) 3 The gas (at an inlet temperature of 64°C and a CO2 volume fraction of 12%) is cooled by the gas cooling coil 11 and then controlled to about 40°C. It enters the aeration head 8 (outer diameter 60mm, length 17cm, pore size 3mm) through the inlet pipe and is dispersed into fine bubbles. The bubbles then come into cross-flow contact with the mineralized liquid in the gas-liquid mixing chamber 5 to obtain a gas-liquid mixture.

[0075] S3. The gas-liquid mixture enters the multi-tube coil 4 (inner diameter 10cm). 900 fine tube bundles 9 (outer diameter 3mm, wall thickness 0.1mm) are evenly distributed inside the coil. In the multi-tube coil 4, CaCl2-NH3·H2O in the mineralization liquid reacts with CO2 to generate calcium carbonate solid and regenerate ammonium chloride.

[0076] The gas-liquid-solid three-phase mixed slurry discharged from the end outlet of S4 multi-tube coil 4 enters the bottom cylinder of the bottle-shaped guide tube 2 (lower cylinder diameter D = 80cm, D:L:d = 3:1:1.5). The reactor body 1 with a conical bottom has an inner diameter of 1m and a height of 5m. Under the action of the bottle-shaped guide tube 2 and driven by the unreacted CO2 and its inert components in the flue gas, the liquid can achieve slow circulation. The generated solid settles to the bottom of the reactor body 1 after rising a certain distance with the liquid. After separation and drying, calcium carbonate product is obtained. The unreacted CO2-containing flue gas further reacts in the reactor body 1 and then separates from the reaction system.

[0077] S5. The generated ammonium chloride solution overflows from reactor body 1 and is used for leaching of carbide slag.

[0078] The particle size distribution of the calcium carbonate product prepared in this embodiment is as follows: Figure 5 As shown in the figure, the particle sizes of calcium carbonate are D10 = 1.001 μm, D50 = 4.581 μm, and D90 = 9.778 μm. Its basic performance parameters are shown in Table 1. Table 1 shows that the calcium carbonate content is 99.4%, the whiteness is 96, and the sedimentation volume is 2.7 mL / g. All indicators meet the industry standards for papermaking, rubber, coatings, and plastics.

[0079] The CO2 removal rate for a single cycle was calculated to be 98.6% using online CO2 detectors and gas flow meters at the inlet and outlet. (1 - outlet CO2 volume fraction * outlet gas velocity / (inlet CO2 volume fraction * inlet gas velocity)).

[0080] Table 1. Performance parameters of calcium carbonate obtained in Example 3

[0081]

[0082]

[0083] In summary, the preparation apparatus of the present invention, through the combined action of the gas-liquid mixer, the multi-tube coil, the reactor body, and the bottle-shaped guide tube, can prepare micron-sized calcium carbonate with uniform particle size without the addition of dispersants, crystal form control agents, or other additives.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for preparing micron-sized calcium carbonate, characterized in that, It includes the reactor body (1), the bottle-shaped guide tube (2), the gas-liquid mixer (3), and the multi-tube bundle coil (4). The bottle-shaped guide tube (2) is coaxially arranged inside the reactor body (1), the multi-tube coil (4) is arranged around the inner wall of the reactor body (1) and is located near the top of the bottle-shaped guide tube (2), the gas-liquid mixer (3) is arranged outside the reactor body (1), and the outlet end of the gas-liquid mixer (3) is connected to the inlet end of the multi-tube coil (4), and the outlet end of the multi-tube coil (4) is located at the bottom of the bottle-shaped guide tube (2); The gas-liquid mixer (3) includes a gas-liquid mixing chamber (5), which has a mineralized liquid inlet (6), a flue gas inlet (7) and a gas-liquid mixture outlet. The mineralized liquid inlet (6) is perpendicular to the flue gas inlet (7), and an aeration head (8) is provided at the end of the air inlet pipe at the flue gas inlet (7). The inlet end of the multi-tube coil (4) is connected to the outlet of the gas-liquid mixture; The multi-tube coil (4) has multiple small tube bundles (9) evenly distributed inside, and the inlet end of the multi-tube coil (4) is connected to the outlet of the gas-liquid mixture through the tube bundle distribution plug (10). The ratio of the bottom cylinder diameter D, the middle width L, and the top cylinder diameter d of the bottle-shaped guide tube (2) is (2-4):1:(1.5-3). The ratio of the outer diameter φ of the multi-tube coil (4), the bottom cylindrical diameter D of the bottle-shaped guide tube (2), and the inner diameter Ω of the reactor body (1) is 1:(6-24):(10-30).

2. The apparatus for preparing micron-sized calcium carbonate with controllable particle size according to claim 1, characterized in that, The reactor body (1) is also equipped with a gas cooling coil (11), one end of which is connected to the CO2 gas inlet (18), and the other end is connected to the flue gas inlet (7).

3. The apparatus for preparing micron-sized calcium carbonate with controllable particle size according to claim 1, characterized in that, A temperature control jacket (12) is provided around the outside of the reactor body (1).

4. The apparatus for preparing micron-sized calcium carbonate with controllable particle size according to claim 1, characterized in that, The reactor body (1) has a gas outlet (13) and a discharge port (14) at the top and bottom respectively, and a clear liquid outlet (15) is also provided above the side wall of the reactor body (1). The reactor body (1) is also equipped with a temperature controller, pH meter, online CO2 detector and gas flow meter.

5. A method for preparing micron-sized calcium carbonate using the apparatus for preparing micron-sized calcium carbonate with controllable particle size according to any one of claims 1-4, characterized in that, Includes the following steps: S1. After mixing carbide slag and ammonium chloride solution, solid-liquid separation is performed to obtain a mineralized solution of CaCl2-NH3·H2O system; S2. After heat exchange, the CO2-containing flue gas is dispersed into fine bubbles through the aeration head (8) and comes into cross-flow contact with the mineralized liquid in the gas-liquid mixer (3) to obtain a gas-liquid mixture. S3. The gas-liquid mixture enters the multi-tube coil (4). In the multi-tube coil (4), CaCl2-NH3·H2O in the mineralization liquid reacts with CO2 to obtain calcium carbonate solid and ammonium chloride solution. S4. The gas-liquid-solid three-phase mixed slurry discharged from the end outlet of the multi-tube coil (4) enters the bottle-shaped guide tube (2). The unreacted CO2 and its inert components in the flue gas drive the liquid to achieve circulation. The generated calcium carbonate solid settles to the bottom of the reactor body (1). After separation and drying, micron-sized calcium carbonate product is obtained. The unreacted CO2-containing flue gas is discharged from the reaction system after gas-liquid separation. S5. The generated ammonium chloride solution overflows from the reactor body (1) and is used for the leaching of carbide slag, completing the entire cycle.

6. The method for preparing micron-sized calcium carbonate according to claim 5, characterized in that, In step S1, the concentration of calcium ions in the mineralization solution of the CaCl2-NH3·H2O system is controlled at 1-2 mol / L; In step S2, the volume fraction of CO2 in the CO2-containing flue gas is 5-40%, and the temperature of the CO2-containing flue gas after heat exchange is controlled below 45℃. In step S4, the apparent flow velocity of the gas inside the bottom cylinder of the bottle-shaped guide tube (2) is 0.2-0.5 cm / s.

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