Preparation method of calcium carbonate whisker

Abstract

The invention discloses a preparation method of calcium carbonate whiskers, which comprises the following steps: seed crystal preparation and calcium carbonate synthesis are respectively carried out in two reaction kettles, and after calcium carbonate whisker slurry is prepared, the slurry is dehydrated, dried, crushed and packaged to obtain a calcium carbonate whisker product. The method can effectively solve the problems of harsh conditions required by whisker seed crystal synthesis and synthesis of amorphous calcium carbonate by using low-concentration tail gas, and the amorphous calcium carbonate is induced to be converted into the calcium carbonate whisker by using the whisker in the later reaction, so that the content of the calcium carbonate whisker is effectively increased.

Description

Technical Field

[0001] The invention relates to the technical field of calcium carbonate whisker production, and in particular to a method for preparing calcium carbonate whisker. Background Art

[0002] Inorganic whiskers are a new type of material with needle-like, rod-like or fibrous morphology. Due to the relatively complete structure of the whiskers, the orderly arrangement of the internal atoms and the few overall defects, the strength and modulus are close to the theoretical values ​​of complete whisker materials. In addition, inorganic whiskers have certain heat resistance and heat insulation properties, making them ideal toughening and flame retardant materials. At present, the inorganic whiskers that have been industrialized mainly include ZnO, SiC, SiN, mullite, aluminum borate, etc., but due to the high production cost, they are only used in small quantities in some fields and it is difficult to achieve large-scale application.

[0003] Calcium carbonate whiskers have the characteristics of low raw material cost, wide sources and artificial control of whisker growth, which has aroused the enthusiasm of researchers at home and abroad. According to previous studies, there are five main methods for preparing calcium carbonate whiskers: (1) double decomposition method; (2) Ca(HCO3)2 thermal decomposition method; (3) sol-gel method; (4) urea hydrolysis method; (5) carbonation method. Among these five methods, the carbonation method is the most studied and mature method. Its basic principle is to introduce carbon dioxide into the calcium hydroxide suspension and then prepare calcium carbonate whiskers through a crystal control agent. This method is consistent with the method of industrial synthesis of nano calcium carbonate. Because of its simple process operation and controllable cost, it is also the most promising method for large-scale industrial production of calcium carbonate whiskers.

[0004] Patent CN112723403A discloses a method for preparing calcium carbonate whiskers. The method uses calcium oxide as a raw material, and uses the reaction product of CO2 and potassium hydroxide and one or two of strontium chloride, sodium phosphate, and sodium citrate as whisker control agents. Lime kiln gas is introduced into the method for carbonation reaction to prepare calcium carbonate whiskers. The invention has a complex production process, uses a large amount of chemical additives, and has a low kiln gas flow rate during the reaction process, resulting in a long reaction time and high production cost, and is not suitable for industrial application.

[0005] Patent CN101570344A discloses a method for preparing aragonite calcium carbonate, which is to digest lime and water and then mature them, and then prepare rod-shaped calcium carbonate using needle-shaped magnesium hydroxide crystals as seeds. In this invention, the aging time after the digestion of lime and water is long, the flow rate of carbon dioxide in the carbonation reaction is small, the process is complicated, the production cost is high, and it is not suitable for industrial application.

[0006] Patent CN111926386A discloses a method for preparing calcium carbonate whiskers, which uses high-purity nano calcium oxide as a raw material, reacts with deionized water to prepare a slurry, then adds silk fibroin and gum arabic crystal form control agents, and performs a carbonation reaction in a supergravity carbonation reactor to prepare calcium carbonate whiskers. This method uses a supergravity reactor reaction with a high reaction temperature, and the cost is relatively high. In addition, special raw materials such as high-purity nano calcium oxide and deionized water are used. There is no clear applicable description for ordinary calcium oxide and industrial water, and the practicality of the method is relatively limited.

[0007] Patent CN111778547A discloses a method for preparing aragonite calcium carbonate whiskers. The method comprises the steps of first reacting ammonia water with calcium chloride-rich solution, then introducing CO2 into the solution, and preparing aragonite calcium carbonate whiskers by strictly controlling calcium ion concentration, reaction temperature, stirring rate and amount of ammonia water. The method has a complex synthesis process and requires an excess of ammonia water to control the calcium ion concentration in order to synthesize calcium carbonate. Furthermore, since CO2 is a weak acid and does not react directly with calcium chloride, the method is difficult to implement in industry.

[0008] In summary, magnesium ions can be used as a crystal control agent to prepare calcium carbonate whiskers when preparing calcium carbonate. In addition, the source of magnesium ions is also very wide, and the price of raw materials is relatively low. Therefore, it is an industry consensus to choose magnesium ions as a whisker control agent. However, due to process defects and the lack of corresponding industrial equipment, the industrial production of calcium carbonate whiskers is affected. Summary of the invention

[0009] The purpose of the present invention is to solve the problems existing in the prior art and to provide a method for preparing calcium carbonate whiskers.

[0010] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0011] A method for preparing calcium carbonate whiskers, using a preparation device for calcium carbonate whiskers, comprises the following steps:

[0012] Step 1: Add a crystal inhibitor and Ca(OH)2 into the side reactor, and start the emulsifying stirrer to disperse and homogenize the slurry. Then open the connecting valve between the main reactor and the side reactor, and wait for the tail gas of the mixed gas containing CO2 after the reaction in the main reactor to be introduced into the side reactor, so that the mixed gas containing CO2 reacts with Ca(OH)2 to prepare an amorphous calcium carbonate intermediate. Then, the gas pushes the slurry upward from the outside of the inner cylinder of the side reactor, and the liquid in the middle of the inner cylinder of the side reactor flows downward to form a slurry circulation flow. The prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas;

[0013] Step 2: adding tap water to the main reactor, then introducing a mixed solution of calcium chloride:magnesium chloride into the main reactor, introducing a pH regulator at the same time, turning on a spiral agitator to stir the materials, and adjusting the pH value of the solution in the main reactor, and then introducing a mixed gas containing CO2 to react; during the reaction process, the pH value remains unchanged, when the pH value is low, the flow rate of the mixed solution of calcium chloride:magnesium chloride is reduced, and the flow rate of the pH regulator is increased, when the pH value is high, the flow rate of the mixed solution of calcium chloride:magnesium chloride is increased, and the flow rate of the pH regulator is reduced, to prepare calcium carbonate whisker crystal seeds, and the tail gas after the reaction is transported to the secondary reactor through the tail gas discharge port of the main reactor;

[0014] Step 3: When the pH of the secondary reactor is reduced to a certain value, close the CO2 air inlet, spiral agitator and connecting valve of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and pH regulator to the main reactor. Then open the discharge valve II at the bottom of the secondary reactor, close the leak detection valve, mix the calcium carbonate whisker seeds in the main reactor with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor, and introduce compressed air from the tail gas port of the secondary reactor to press all the materials in the secondary reactor into the main reactor;

[0015] Step 4: After all the materials in the secondary reactor have entered the main reactor, close the discharge valve II at the bottom of the secondary reactor, open the leak detection valve, stop introducing compressed air, open the tail gas port of the secondary reactor, connect the valve and the water inlet, clean the secondary reactor, and add tap water to the secondary reactor;

[0016] Step 5: Turn on the spiral agitator of the main reactor and introduce a mixed gas containing CO2 into the material in the main reactor for reaction. When the reaction is completed, stop the reaction to prepare a calcium carbonate whisker slurry. Then, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

[0017] Preferably, the crystal inhibitor described in step 1 is a compound of one or more of tartaric acid, malic acid, and gallic acid, and the added amount is 0.1%-0.8% of the dry mass of Ca(OH)2.

[0018] Preferably, the temperature of Ca(OH)2 in step 1 is 50-70°C.

[0019] Preferably, the amount of tap water added in step 2 is 1 / 10-1 / 7 of the volume of the main reactor.

[0020] Preferably, the mass ratio of calcium chloride:magnesium chloride in step 2 is (1-5):1.

[0021] Preferably, the mass concentration of the mixed solution in step 2 is 1-10%.

[0022] Preferably, in step 2, a pH regulator is introduced, a spiral agitator is turned on to stir the material, and the pH value of the solution in the main reactor is adjusted to 10.5-11.5.

[0023] Preferably, the pH regulator is a composite solution of ammonia water and sodium hydroxide or potassium hydroxide in a ratio of 1:2-1:4.

[0024] Preferably, in step 3, when the pH of the secondary reactor drops to 9.8-10.2, the CO2 inlet, spiral agitator and connecting valve of the main reactor are closed.

[0025] Preferably, the calcium carbonate whisker preparation device comprises a main reactor and a secondary reactor, wherein the main reactor body is provided with a main reactor inner cylinder, the inner cylinder is fixed to the reactor body through a bracket, an agitator is provided in the inner cylinder, a distributor is provided at the bottom of the agitator, the distributor is placed above the porous distributor, and the porous distributor is connected to the CO2 inlet;

[0026] The upper part of the auxiliary reactor is provided with an ultrasonic level meter interface II, an auxiliary reactor air inlet, an auxiliary reactor exhaust port, a water inlet, and a Ca(OH)2 slurry inlet; the lower part of the reactor body is provided with a temperature sensor interface III, a pH sensor interface II, an auxiliary reactor discharge port, a stirring motor II and a maintenance port; the reactor is provided with an auxiliary reactor inner cylinder, which is connected to the auxiliary reactor body through an inner cylinder bracket II. After CO2 enters from the auxiliary reactor air inlet, it is connected to the bottom umbrella-shaped distributor through a pipeline, and the pipeline passes through the middle of the auxiliary reactor inner cylinder.

[0027] Technical principle of the present invention:

[0028] The principle of calcium carbonate whisker preparation technology is mainly based on the chemical reaction in the solution and the regulation of crystallization dynamics. It aims to promote the orderly arrangement and growth of calcium carbonate molecules in a specific direction by finely controlling the reaction conditions and processes, thereby generating calcium carbonate whiskers with a one-dimensional needle-like or fibrous structure. The subtlety of this preparation method lies in the synergistic effect of its multiple steps and multiple parameters. Each link is closely related and significantly affects the morphology and performance of the final product.

[0029] (I) Functions of each structure

[0030] 1. Secondary reactor: As the initial reaction site, it not only carries the reaction between calcium hydroxide and low-concentration CO2, but also promotes the circulation of slurry through a specially designed inner cylinder structure, ensuring that the reactants are fully contacted and mixed, so that the amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide. This circulation design significantly improves the reaction efficiency and uniformity, laying the foundation for the subsequent formation of whiskers.

[0031] 2. Main reactor: It is the key area for the generation of whisker seeds and the final whisker formation. By precisely controlling the amount and ratio of the calcium chloride, magnesium chloride mixed solution and pH regulator, combined with the uniform stirring of the spiral stirrer, the reaction system is ensured to be maintained within the optimal pH range, promoting the directional growth of calcium carbonate whiskers. In addition, the main reactor is also responsible for receiving the seed and raw material mixture from the secondary reactor, further promoting the continuous growth of whiskers.

[0032] (II) Necessity and importance of optimizing raw material dosage and process parameters

[0033] 1. The amount of crystal inhibitor added: Accurately controlling the amount within the range of 0.1%-0.8% of the dry mass of Ca(OH)2 is the key to preventing the formation of non-target crystal forms (such as calcite and aragonite). Too much or too little will affect the formation of amorphous calcium carbonate intermediates, and thus affect the subsequent growth quality and yield of whiskers.

[0034] 2. Reaction temperature and CO2 concentration: Maintaining the temperature at (50-70)°C and the CO2 concentration at around 30% is to provide suitable thermodynamic and kinetic conditions, promote the full reaction of CO2 and calcium hydroxide, and avoid unnecessary side reactions caused by high temperature.

[0035] 3. Fine control of pH value: During the entire reaction process, maintaining the pH value within a specific range (such as 10.5-11.5 in the main reactor) is crucial to controlling the growth rate and morphology of whiskers. The dynamic adjustment of pH value ensures the stability of the reaction system, promotes the directional growth of whiskers, and reduces the generation of impurities.

[0036] 4. The ratio of calcium chloride to magnesium chloride: By adjusting the ratio of the two (1-5):1, not only the concentration of calcium ions in the solution is affected, but also the formation and stability of whiskers are promoted by introducing the composite ion effect that may be formed by magnesium ions. The optimization of this parameter is the key to obtaining high-quality whiskers.

[0037] (II) Unexpected technical effects

[0038] 1. High purity and high yield: By carefully controlling the reaction conditions and parameters, this method can produce high-purity calcium carbonate whiskers, with the content of needle-shaped (whiskers) calcium carbonate exceeding 90%, which not only achieves a high yield but also effectively reduces production costs.

[0039] 2. Excellent dispersibility and mechanical properties: The prepared calcium carbonate whiskers have good dispersibility and reinforcement effect. Their application in composite materials such as plastics, rubber, and coatings significantly improves the mechanical properties and processing properties of the materials.

[0040] 3. Environmental protection and energy saving: The entire preparation process does not require high temperature and high pressure conditions, has low energy consumption, and the main raw materials are widely available natural resources such as limestone. The production process is green and environmentally friendly and meets the requirements of sustainable development.

[0041] In summary, the preparation method of calcium carbonate whiskers realizes the optimization of the whole process from raw materials to products through multi-step fine regulation and synergy, which not only improves product quality and production efficiency, but also brings significant economic and environmental benefits. It is an innovative technology with broad application prospects.

[0042] Compared with the prior art, the double-tower carbonation reactor design of the present invention not only represents a technological leap, but also demonstrates its incomparable advantages in multiple dimensions, profoundly affecting the future pattern of industrial production of calcium carbonate whiskers.

[0043] (1) The ingenuity of the structural design of the present invention is remarkable. The twin-tower design, as the name implies, achieves extreme simplification of the structure and convenience of installation by cleverly dividing the reaction process into two independent but closely connected stages. This design not only greatly reduces the complexity and maintenance costs of production equipment, but more importantly, it perfectly meets the needs of industrial automation control, allowing the entire production process to be carried out under highly precise and stable conditions, thereby ensuring the stability of product quality and maximization of production efficiency. This transformation is of milestone significance in promoting the transformation and upgrading of the calcium carbonate whisker production industry and achieving a win-win situation in economic and social benefits.

[0044] (2) The innovation of the present invention is to separate the two key steps of seed preparation and calcium carbonate synthesis into different reactors. This breakthrough design directly solves the problem of harsh and difficult-to-control conditions for whisker seed synthesis in traditional processes, while cleverly utilizing low-concentration tail gas resources to synthesize amorphous calcium carbonate, thereby maximizing resource utilization. More importantly, in the subsequent reaction stage, amorphous calcium carbonate is successfully converted into high-quality calcium carbonate whiskers through the induction of whiskers. This process not only significantly increases the whisker content of the product, but also greatly enhances the added value and market competitiveness of the product. This transformation from waste to high-value products is undoubtedly a significant improvement brought about by technological innovation.

[0045] (3) The present invention also exhibits excellent performance in terms of reaction efficiency and product quality. The unique design of the serrated distributor combined with the porous distributor used in the air inlet of the main reactor is like a "maze" tailored for the gas molecules, so that the introduced CO2 mixed gas can be finely dispersed into countless tiny bubbles. With the help of the spiral agitator, these tiny bubbles and the Ca(OH)2 solution achieve more sufficient and uniform contact and reaction, greatly improving the reaction efficiency. At the same time, the simple axial flow design of the agitator not only ensures the improvement of the mixing effect, but also avoids the destruction of the whisker morphology that may be caused by high-intensity shearing of the slurry, thereby ensuring that the prepared calcium carbonate whiskers have regular morphology and excellent quality.

[0046] (4) The emulsifying agitator used in the secondary reactor also played an important role. Its powerful emulsifying ability cleverly dispersed the amorphous calcium carbonate in the Ca(OH)2 solution, laying a solid foundation for the subsequent reaction process. This design not only improved the reaction efficiency, but also further ensured the uniformity and stability of the product.

[0047] (5) From the perspective of environmental protection and resource utilization, the contribution of the present invention is equally not to be ignored. Through the ingenious tail gas treatment design, the tail gas containing particulate matter produced by the main reactor is washed and purified before being discharged, which not only effectively solves the tail gas pollution problem, but also realizes the recycling and reuse of particulate matter. After these recycled particulate matter is processed by processes such as concentration and filter pressing, it can be converted into by-products with market value for sale, truly realizing the green production concept of "turning waste into treasure". This environmentally friendly and resource-saving production model has undoubtedly set a new benchmark for the sustainable development of the calcium carbonate whisker production industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural schematic diagram of a device for preparing calcium carbonate whiskers of the present invention;

[0049] Figure 2 It is the SEM picture of Example 1-5000 times;

[0050] Figure 3 It is a 5000x SEM image of Example 2;

[0051] Figure 4 It is the SEM picture of Example 3-5000 times;

[0052] Figure 5 This is a 1-5000x SEM image of the comparative example;

[0053] Figure 6 This is a 2-5000x SEM image of the comparative example;

[0054] Figure 7This is a 3-5000x SEM image of the comparative example;

[0055] Figure 1 The serial numbers and names are as follows:

[0056] 1-main reactor, 100-main reactor body, 101-stirring motor Ⅰ, 102-main reactor material inlet, 103-pH regulator and tap water inlet, 104-CO2 inlet, 105-temperature sensor interface Ⅰ, 106-temperature sensor interface Ⅱ, 107-pH sensor interface Ⅰ, 108-discharge port, 109-main reactor tail gas discharge port, 110-ultrasonic level meter interface Ⅰ, 111-stirring shaft, 112-spiral nozzle Ⅰ, 113-main reactor inner cylinder, 114-spiral agitator, 115-inner cylinder bracket Ⅰ, 116-agitator lower bearing, 117-agitator lower bearing bracket, 118-serrated distributor, 119-porous distributor, 120-discharge Material valve Ⅰ, 2-secondary reactor, 200-secondary reactor body, 201-ultrasonic level meter interface Ⅱ, 202-connecting valve, 203-secondary reactor air inlet, 204-secondary reactor exhaust port, 205-water inlet, 206-Ca(OH)2 slurry inlet, 207-temperature sensor interface Ⅲ, 208-pH sensor interface Ⅱ, 209-inspection port, 210-spiral nozzle Ⅱ, 211-secondary reactor inlet pipe, 212-secondary reactor inner cylinder, 213-inner cylinder bracket Ⅱ, 214-umbrella-shaped gas distributor, 215-emulsifying agitator, 216-stirring motor Ⅱ, 217-secondary reactor discharge port, 218-discharge valve Ⅱ, 219-leak detection port, 220-main reactor slurry inlet. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below with reference to the accompanying drawings and preferred examples:

[0058] Example 1

[0059] like Figure 1As shown, a preparation device of calcium carbonate whiskers is composed of a main reactor 1 and a sub-reactor 2; the main reactor 1 is provided with two parts, a main reactor body 100 and a main reactor inner cylinder 113, wherein the top of the main reactor body 100 is provided with a stirring motor Ⅰ101, a main reactor material inlet 102, a main reactor tail gas discharge port 109 and an ultrasonic level meter interface Ⅰ110; the outside of the main reactor body 100 is provided with a pH regulator and a tap water inlet 103, a CO2 inlet 104, a temperature sensor interface Ⅰ105, a temperature sensor interface Ⅱ106, and a pH sensor interface Ⅰ107, wherein the pH regulator and the tap water inlet 103 are directly connected to the inside of the reactor by a pipeline, and a plurality of spiral nozzles Ⅰ112 are provided for adding a pH regulator or cleaning the inside of the reactor; a discharge port 108 is provided at the bottom of the main reactor body 100, and after the reaction is completed, the discharge valve Ⅰ120 is opened to discharge the material.

[0060] The inner cylinder 113 of the main reactor is fixed to the reactor body 100 through the inner cylinder bracket Ⅰ115. A spiral stirrer 114 is arranged in the inner cylinder. The stirrer is connected to the stirring motor Ⅰ101 through the stirring shaft 111, and a serrated distributor 118 is arranged at the bottom of the stirrer. During the stirring process, the serrated distributor 118 rotates with the stirring shaft 111 to shear and break up the CO2-containing mixed gas introduced. During the stirring process, in order to avoid the shaking eccentricity of the stirring shaft 111, a stirrer lower bearing 116 is arranged at the bottom of the stirring shaft, and is connected to the main reactor body 100 through the stirrer lower bearing bracket 117; directly below the serrated distributor 118 is a porous distributor 119, which is connected to the CO2 inlet 104 through a pipeline, so that the CO2-containing mixed gas is introduced from the outside of the reactor into the bottom of the reactor for reaction.

[0061] The secondary reactor 2 comprises a secondary reactor body 200 and a secondary reactor inner tube 212. The secondary reactor body 200 is provided with an ultrasonic level gauge interface II 201, a secondary reactor air inlet 203, and a secondary reactor exhaust port 204 at the top. The mixed gas containing CO2 after the reaction in the main reactor enters the secondary reactor exhaust port 204 of the secondary reactor through the tail gas discharge port 109 of the main reactor, and then enters the secondary reactor bottom through the secondary reactor inlet pipe 211, and is dispersed by the umbrella-shaped gas distributor 214. The secondary reactor body 200 is provided with a water inlet 205, a Ca(OH)2 slurry inlet 206, a temperature sensor interface III 207, and a pH sensor interface II 208 on the outside. The water inlet 205 is directly connected to the inside of the reactor by a pipeline, and is provided with a plurality of spiral nozzles II 210 for cleaning the reactor. The secondary reactor inner cylinder 212 is arranged inside the secondary reactor body 200, connected and fixed by the inner cylinder bracket II 213, and the secondary reactor inlet pipe 211 is arranged in the middle of the inner cylinder, passing from the top to the bottom. After the CO2-containing mixed gas enters the secondary reactor, it is stirred by the secondary reactor inner cylinder 212 in an upward and downward cycle. The secondary reactor body 200 is provided with a stirring motor II 216, a secondary reactor discharge port 217, a discharge valve II 218, a leak detection port 219 and a maintenance port 209 at the bottom, wherein the emulsifying stirrer 215 connected to the stirring motor II 216 is arranged in the umbrella-shaped gas distributor 214 for emulsification and homogenization of the CO2-containing mixed body and the Ca(OH)2 slurry reaction, and the secondary reactor discharge port 217 is connected to the slurry inlet 220 of the main reactor, and the amorphous calcium carbonate prepared by the reaction is transported to the main reactor 1 through the secondary reactor discharge port 217 for the next step of reaction.

[0062] A method for preparing calcium carbonate whiskers, using the above-mentioned calcium carbonate whisker preparation device, specifically comprises the following steps:

[0063] Step 1: Add 0.8% tartaric acid crystal inhibitor and Ca(OH)2 at a temperature of 50°C added by dry basis weight of Ca(OH)2 into the secondary reactor 2 from the Ca(OH)2 slurry inlet 206, and at the same time, open the emulsifying stirrer 215 to disperse and homogenize the slurry, then open the connecting valve 202 between the main reactor 1 and the secondary reactor 2, and wait for the tail gas of the mixed gas with a CO2 concentration of about 30% after the reaction of the main reactor 1 to be introduced into the secondary reactor 2 from the tail gas discharge port 109 of the main reactor. The mixed gas with low CO2 concentration reacts with Ca(OH)2 under the action of the umbrella-shaped gas distributor 214 to prepare an amorphous calcium carbonate intermediate. Then, the gas pushes the slurry upward from the outside of the inner tube 212 of the secondary reactor, and the liquid in the middle of the inner tube 212 of the secondary reactor flows downward to form a slurry circulation flow, and the prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas.

[0064] Step 2: Add tap water to the main reactor 1 from the main reactor material inlet 102, the amount added is 1 / 10 of the volume of the main reactor 1, and then a mixed solution of calcium chloride: magnesium chloride = 5:1 with a mass concentration of 10% is introduced into the main reactor 1 from the main reactor material inlet 102, and at the same time, a composite solution pH regulator of ammonia: sodium hydroxide = 1:4 is introduced from the pH regulator and tap water inlet 103. Under the action of the spiral nozzle I 112, the composite solution is evenly distributed in the main reactor 1, the spiral agitator 114 is turned on to stir the material, and the pH value of the solution in the main reactor 1 is adjusted to 11.5, and then a mixed gas with a CO2 concentration of about 30% is introduced from the CO2 inlet 104, and reacted in the serrated distributor 118 and the porous distributor 119. During the reaction, the pH value remains unchanged. When the pH value is low, the flow rate of the calcium chloride:magnesium chloride mixed solution is reduced and the flow rate of the pH adjuster is increased. When the pH value is high, the flow rate of the calcium chloride:magnesium chloride mixed solution is increased and the flow rate of the pH adjuster is reduced to prepare calcium carbonate whisker seeds. The exhaust gas after the reaction is transported to the sub-reactor through the exhaust gas discharge port of the main reactor.

[0065] Step 3: When the pH of the secondary reactor 2 is reduced to 10.2, close the CO2 air inlet 103, the spiral agitator 114 and the connecting valve 202 of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and the pH adjuster to the main reactor 1. Then open the discharge valve II 218 at the bottom of the secondary reactor, close the leak detection valve 219, and mix the calcium carbonate whisker seeds in the main reactor 1 with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor 2. Then, introduce compressed air from the tail gas port 204 of the secondary reactor to press all the materials in the secondary reactor 2 into the main reactor 1 from the secondary reactor discharge port 217.

[0066] Step 4: After all the materials in the auxiliary reactor 2 have entered the main reactor 1, close the discharge valve II 218 at the bottom of the auxiliary reactor, open the leak detection valve 219, stop the introduction of compressed air, open the auxiliary reactor tail gas port 204, the connecting valve 202, and the water inlet 205, clean the auxiliary reactor 2, and add 1 / 2 of tap water to the auxiliary reactor 2.

[0067] Step 5: Turn on the main reactor spiral agitator 114, and introduce a mixed gas with a CO2 concentration of about 30% into the material in the main reactor 1 for reaction. When the pH of the solution reaches 7.2, stop the reaction to prepare a calcium carbonate whisker slurry. Afterwards, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

[0068] Example 2

[0069] A preparation device for calcium carbonate whiskers, same as that of Example 1.

[0070] A method for preparing calcium carbonate whiskers, using the above device, specifically comprises the following steps:

[0071] Step 1: 0.5% malic acid and Ca(OH)2 at a temperature of 60°C added with Ca(OH)2 dry basis weight are introduced into the secondary reactor 2 from the Ca(OH)2 slurry inlet 206, and at the same time, the emulsifying stirrer 215 is turned on to disperse and homogenize the slurry, and then the connecting valve 202 between the main reactor 1 and the secondary reactor 2 is opened, and the tail gas of the mixed gas with a CO2 concentration of about 30% after the reaction of the main reactor 1 is introduced into the secondary reactor 2 from the tail gas discharge port 109 of the main reactor, and the mixed gas with low CO2 concentration reacts with Ca(OH)2 under the action of the umbrella-shaped gas distributor 214 to prepare an amorphous calcium carbonate intermediate, and then the gas pushes the slurry upward from the outside of the secondary reactor inner tube 212, and the liquid in the middle of the secondary reactor inner tube 212 flows downward to form a slurry circulation flow, and the prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas.

[0072] Step 2: Add tap water to the main reactor 1 from the main reactor material inlet 102, the amount added is 1 / 8 of the volume of the main reactor 1, and then a mixed solution of calcium chloride: magnesium chloride = 3:1 with a mass concentration of 5% is introduced into the main reactor 1 from the main reactor material inlet 102, and at the same time, a composite solution pH regulator of ammonia: sodium hydroxide = 1:2 is introduced from the pH regulator and the tap water inlet 103. Under the action of the spiral nozzle I 112, the composite solution is evenly distributed in the main reactor 1, the spiral agitator 114 is turned on to stir the material, and the pH value of the solution in the main reactor 1 is adjusted to 11.0, and then a mixed gas with a CO2 concentration of about 30% is introduced from the CO2 inlet 104, and reacted in the serrated distributor 118 and the porous distributor 119. During the reaction, the pH value remains unchanged. When the pH value is low, the flow rate of the calcium chloride:magnesium chloride mixed solution is reduced and the flow rate of the pH adjuster is increased. When the pH value is high, the flow rate of the calcium chloride:magnesium chloride mixed solution is increased and the flow rate of the pH adjuster is reduced to prepare calcium carbonate whisker seeds. The exhaust gas after the reaction is transported to the sub-reactor through the exhaust gas discharge port of the main reactor.

[0073] Step 3: When the pH of the secondary reactor 2 is reduced to 10.0, close the CO2 air inlet 103, the spiral agitator 114 and the connecting valve 202 of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and the pH adjuster to the main reactor 1. Then open the discharge valve II 218 at the bottom of the secondary reactor, close the leak detection valve 219, and mix the calcium carbonate whisker seeds in the main reactor 1 with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor 2. Then, introduce compressed air from the tail gas port 204 of the secondary reactor to press all the materials in the secondary reactor 2 into the main reactor 1 from the secondary reactor discharge port 217.

[0074] Step 4: After all the materials in the auxiliary reactor 2 have entered the main reactor 1, close the discharge valve II 218 at the bottom of the auxiliary reactor, open the leak detection valve 219, stop the introduction of compressed air, open the auxiliary reactor tail gas port 204, the connecting valve 202, and the water inlet 205, clean the auxiliary reactor 2, and add 1 / 2 of tap water to the auxiliary reactor 2.

[0075] Step 5: Turn on the main reactor spiral agitator 114, and introduce a mixed gas with a CO2 concentration of about 30% into the material in the main reactor 1 for reaction. When the pH of the solution reaches 7.2, stop the reaction to prepare a calcium carbonate whisker slurry. Afterwards, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

[0076] Example 3

[0077] A preparation device for calcium carbonate whiskers, same as that of Example 1.

[0078] A method for preparing calcium carbonate whiskers, using the above device, specifically comprises the following steps:

[0079] Step 1: Ca(OH)2 with a temperature of 70°C and 0.1% gallic acid crystal inhibitor added on a dry basis weight of Ca(OH)2 is introduced into the secondary reactor 2 from the Ca(OH)2 slurry inlet 206, and at the same time, the emulsifying stirrer 215 is turned on to disperse and homogenize the slurry, and then the connecting valve 202 between the main reactor 1 and the secondary reactor 2 is opened, and the tail gas of the mixed gas with a CO2 concentration of about 30% after the reaction of the main reactor 1 is introduced into the secondary reactor 2 from the tail gas discharge port 109 of the main reactor, and the mixed gas with a low CO2 concentration reacts with Ca(OH)2 under the action of the umbrella-shaped gas distributor 214 to prepare an amorphous calcium carbonate intermediate, and then the gas pushes the slurry upward from the outside of the inner tube 212 of the secondary reactor, and the liquid in the middle of the inner tube 212 of the secondary reactor flows downward to form a slurry circulation flow, and the prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas.

[0080] Step 2: Add tap water to the main reactor 1 from the main reactor material inlet 102, the amount added is 1 / 7 of the volume of the main reactor 1, and then a mixed solution of calcium chloride: magnesium chloride = 1:1 with a mass concentration of 1% is introduced into the main reactor 1 from the main reactor material inlet 102, and at the same time, a composite solution pH regulator of ammonia: potassium hydroxide = 1:2 is introduced from the pH regulator and the tap water inlet 103. Under the action of the spiral nozzle I 112, the composite solution is evenly distributed in the main reactor 1, the spiral agitator 114 is turned on to stir the material, and the pH value of the solution in the main reactor 1 is adjusted to 10.5, and then a mixed gas with a CO2 concentration of about 30% is introduced from the CO2 inlet 104, and reacted in the serrated distributor 118 and the porous distributor 119. During the reaction, the pH value remains unchanged. When the pH value is low, the flow rate of the calcium chloride:magnesium chloride mixed solution is reduced and the flow rate of the pH adjuster is increased. When the pH value is high, the flow rate of the calcium chloride:magnesium chloride mixed solution is increased and the flow rate of the pH adjuster is reduced to prepare calcium carbonate whisker seeds. The exhaust gas after the reaction is transported to the sub-reactor through the exhaust gas discharge port of the main reactor.

[0081] Step 3: When the pH of the secondary reactor 2 is reduced to 9.8, close the CO2 air inlet 103, the spiral agitator 114 and the connecting valve 202 of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and the pH adjuster to the main reactor 1. Then open the discharge valve II 218 at the bottom of the secondary reactor, close the leak detection valve 219, and mix the calcium carbonate whisker seeds in the main reactor 1 with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor 2. Then, introduce compressed air from the tail gas port 204 of the secondary reactor to press all the materials in the secondary reactor 2 into the main reactor 1 from the secondary reactor discharge port 217.

[0082] Step 4: After all the materials in the auxiliary reactor 2 have entered the main reactor 1, close the discharge valve II 218 at the bottom of the auxiliary reactor, open the leak detection valve 219, stop the introduction of compressed air, open the auxiliary reactor tail gas port 204, the connecting valve 202, and the water inlet 205, clean the auxiliary reactor 2, and add 1 / 2 of tap water to the auxiliary reactor 2.

[0083] Step 5: Turn on the main reactor spiral agitator 114, and introduce a mixed gas with a CO2 concentration of about 30% into the material in the main reactor 1 for reaction. When the pH of the solution reaches 7.2, stop the reaction to prepare a calcium carbonate whisker slurry. Afterwards, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

[0084] Comparative Example 1

[0085] A preparation device for calcium carbonate whiskers, same as that of Example 1.

[0086] A method for preparing calcium carbonate whiskers, using the above device, specifically comprises the following steps:

[0087] Step 1: Add 0.9% tartaric acid crystal inhibitor with dry basis weight of Ca(OH)2 and Ca(OH)2 at a temperature of 75°C into the secondary reactor 2 from the Ca(OH)2 slurry inlet 206, and at the same time, open the emulsifying stirrer 215 to disperse and homogenize the slurry, then open the connecting valve 202 between the main reactor 1 and the secondary reactor 2, and wait for the tail gas of the mixed gas with a CO2 concentration of about 30% after the reaction of the main reactor 1 to be introduced into the secondary reactor 2 from the tail gas discharge port 109 of the main reactor, and the mixed gas with low CO2 concentration reacts with Ca(OH)2 under the action of the umbrella-shaped gas distributor 214 to prepare an amorphous calcium carbonate intermediate, and then the gas pushes the slurry upward from the outside of the inner tube 212 of the secondary reactor, and the liquid in the middle of the inner tube 212 of the secondary reactor flows downward to form a slurry circulation flow, and the prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas.

[0088] Step 2: Add tap water to the main reactor 1 from the main reactor material inlet 102, the amount added is 1 / 6 of the volume of the main reactor 1, and then a mixed solution of calcium chloride: magnesium chloride = 6:1 with a mass concentration of 11% is introduced into the main reactor from the main reactor material inlet 102, and at the same time, a composite solution pH regulator of ammonia: sodium hydroxide = 1:6 is introduced from the pH regulator and the tap water inlet 103. Under the action of the spiral nozzle I 112, the composite solution is evenly distributed in the main reactor 1, the spiral agitator 114 is turned on to stir the material, and the pH value of the solution in the main reactor 1 is adjusted to 10.3, and then a mixed gas with a CO2 concentration of about 30% is introduced from the CO2 inlet 104, and reacted in the serrated distributor 118 and the porous distributor 119. During the reaction, the pH value remains unchanged. When the pH value is low, the flow rate of the calcium chloride:magnesium chloride mixed solution is reduced and the flow rate of the pH adjuster is increased. When the pH value is high, the flow rate of the calcium chloride:magnesium chloride mixed solution is increased and the flow rate of the pH adjuster is reduced to prepare calcium carbonate whisker seeds. The exhaust gas after the reaction is transported to the sub-reactor through the exhaust gas discharge port of the main reactor.

[0089] Step 3: When the pH of the secondary reactor 2 drops to 10.5, close the CO2 air inlet 103, the spiral agitator 114 and the connecting valve 202 of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and the pH adjuster to the main reactor 1. Then open the discharge valve II 218 at the bottom of the secondary reactor, close the leak detection valve 219, and mix the calcium carbonate whisker seeds in the main reactor 1 with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor 2. Then, introduce compressed air from the tail gas port 204 of the secondary reactor to press all the materials in the secondary reactor 2 into the main reactor 1 from the secondary reactor discharge port 217.

[0090] Step 4: After all the materials in the auxiliary reactor 2 have entered the main reactor 1, close the discharge valve II 218 at the bottom of the auxiliary reactor, open the leak detection valve 219, stop the introduction of compressed air, open the auxiliary reactor tail gas port 204, the connecting valve 202, and the water inlet 205, clean the auxiliary reactor 2, and add 1 / 2 of tap water to the auxiliary reactor 2.

[0091] Step 5: Turn on the main reactor spiral agitator 114, and introduce a mixed gas with a CO2 concentration of about 30% into the material in the main reactor 1 for reaction. When the pH of the solution reaches 7.2, stop the reaction to prepare a calcium carbonate whisker slurry. Afterwards, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

[0092] Comparative Example 2

[0093] A preparation device for calcium carbonate whiskers, same as that of Example 1.

[0094] A method for preparing calcium carbonate whiskers is basically the same as that of Example 3, except that in step 2, the mixed solution of calcium chloride and magnesium chloride with a mass concentration of 1% (1:1) introduced into the main reactor 1 is replaced by tap water.

[0095] Comparative Example 3

[0096] A preparation device for calcium carbonate whiskers, same as that of Example 1.

[0097] A method for preparing calcium carbonate whiskers is substantially the same as that of Example 3, except that the Ca(OH)2 added with 0.1% gallic acid crystal form inhibitor on a dry basis and a temperature of 70°C in step 1 is replaced with tap water; in step 2, a spiral stirrer 114 is turned on to stir the material, and the pH value of the solution in the main reactor 1 is adjusted to 10.5, and then the same mass of Ca(OH)2 added with 0.1% gallic acid crystal form inhibitor on a dry basis and a temperature of 70°C as in step 1 is added.

[0098] The calcium carbonate prepared in Examples 1-3 of the present invention and Comparative Examples 1-3 was tested for morphology and particle size using a scanning electron microscope according to the method of GB / T19590-2023 "Nano Calcium Carbonate". The test results are as follows:

[0099]

[0100] After in-depth analysis of the detailed test data presented in the table above and Figure 2-7After observing the microstructural features revealed by the SEM (scanning electron microscope) image, we can clearly realize that the method of the present invention has made a breakthrough in the field of calcium carbonate preparation. Specifically, the calcium carbonate prepared by the unique process of the present invention has a highly consistent needle-like (whisker-like) structure in morphology. This morphology of calcium carbonate not only has extremely high application value, but also has achieved significant improvement in content, reaching an astonishing 90% or more. This achievement not only reflects the present invention's profound understanding and precise control of the growth mechanism of calcium carbonate crystals, but also marks a major leap in material synthesis technology.

[0101] Furthermore, from the perspective of size distribution, the average value of the long diameter of the calcium carbonate whiskers prepared by the present invention easily crosses the threshold of 5.5μm, which is far beyond the level that can be achieved by conventional methods, ensuring the excellent performance of the product as a reinforcing filler, adsorbent or catalyst carrier. At the same time, the average value of its short diameter is strictly controlled below 0.4μm, and the excellent characteristics of the aspect ratio exceeding 15 together constitute its advantages of high specific surface area and high aspect ratio, which are crucial to improving the overall mechanical properties, reactivity and functional properties of the material.

[0102] Looking at the experimental results of the three comparative examples, they reveal from different aspects the significant performance degradation caused by deviations from the core elements of the method of the present invention. In Comparative Example 1, since the process parameters did not fall within the optimization range of the present invention, the content of calcium carbonate whiskers dropped sharply to 40%, accompanied by the generation of a large amount of amorphous calcium carbonate, which not only reduced the purity and uniformity of the product, but also seriously affected the performance of its subsequent applications. Comparative Example 2 emphasizes the importance of the seed preparation step in the main reactor. The lack of this link directly causes the whisker content to drop to 50%, while the content of amorphous calcium carbonate increases, which once again proves the decisive role of precise control of each step in the present invention in the quality of the final product. Comparative Example 3 focuses on the value of the low-concentration carbonation process in the secondary reactor. Its absence causes the whisker content to drop sharply to 30%, and contains unfavorable forms such as cubic and spindle-shaped calcium carbonate, further highlighting the unique advantages of the present invention in promoting the efficient generation of calcium carbonate with specific morphology.

[0103] In summary, the method of the present invention not only achieves a double leap in content and morphology in the preparation of calcium carbonate whiskers, but also ensures excellent and stable product performance through strict process control and optimization. This series of significant advances not only opens up a new path for the preparation of calcium carbonate materials, but also provides strong support for technology upgrades and product innovations in related fields.

[0104] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing calcium carbonate whiskers, using a preparation device for calcium carbonate whiskers, characterized in that: The following steps are involved: Step 1: Add a crystal inhibitor and Ca(OH)2 into the side reactor, and start the emulsifying stirrer to disperse and homogenize the slurry. Then open the connecting valve between the main reactor and the side reactor, and wait for the tail gas of the mixed gas containing CO2 after the reaction in the main reactor to be introduced into the side reactor, so that the mixed gas containing CO2 reacts with Ca(OH)2 to prepare an amorphous calcium carbonate intermediate. Then, the gas pushes the slurry upward from the outside of the inner cylinder of the side reactor, and the liquid in the middle of the inner cylinder of the side reactor flows downward to form a slurry circulation flow. The prepared amorphous calcium carbonate intermediate is evenly distributed in the calcium hydroxide under the disturbance of the gas; Step 2: adding tap water to the main reactor, then introducing a mixed solution of calcium chloride:magnesium chloride into the main reactor, introducing a pH regulator at the same time, turning on a spiral agitator to stir the materials, and adjusting the pH value of the solution in the main reactor, and then introducing a mixed gas containing CO2 to react; during the reaction process, the pH value remains unchanged, when the pH value is low, the flow rate of the mixed solution of calcium chloride:magnesium chloride is reduced, and the flow rate of the pH regulator is increased, when the pH value is high, the flow rate of the mixed solution of calcium chloride:magnesium chloride is increased, and the flow rate of the pH regulator is reduced, to prepare calcium carbonate whisker crystal seeds, and the tail gas after the reaction is transported to the secondary reactor through the tail gas discharge port of the main reactor; Step 3: When the pH of the secondary reactor is reduced to a certain value, close the CO2 air inlet, spiral agitator and connecting valve of the main reactor, and stop adding the calcium chloride:magnesium chloride mixed solution and pH regulator to the main reactor. Then open the discharge valve II at the bottom of the secondary reactor, close the leak detection valve, mix the calcium carbonate whisker seeds in the main reactor with the Ca(OH)2 solution containing amorphous calcium carbonate in the secondary reactor, and introduce compressed air from the tail gas port of the secondary reactor to press all the materials in the secondary reactor into the main reactor; Step 4: After all the materials in the secondary reactor have entered the main reactor, close the discharge valve II at the bottom of the secondary reactor, open the leak detection valve, stop introducing compressed air, open the tail gas port of the secondary reactor, connect the valve and the water inlet, clean the secondary reactor, and add tap water to the secondary reactor; Step 5: Turn on the spiral agitator of the main reactor and introduce a mixed gas containing CO2 into the material in the main reactor for reaction. When the reaction is completed, stop the reaction to prepare a calcium carbonate whisker slurry. Then, send the slurry to dehydration, drying, crushing and packaging to obtain a calcium carbonate whisker product.

2. The preparation method of calcium carbonate whisker according to claim 1, wherein The crystal inhibitor described in step 1 is a compound of one or more of tartaric acid, malic acid, and gallic acid, and the added amount is 0.1%-0.8% of the dry basis mass of Ca(OH)2.

3. The preparation method of calcium carbonate whisker according to claim 1, wherein The temperature of Ca(OH)2 described in step 1 is 50-70°C.

4. The preparation method of calcium carbonate whisker according to claim 1, wherein The amount of tap water added in step 2 is 1 / 10-1 / 7 of the volume of the main reactor.

5. The preparation method of calcium carbonate whisker according to claim 1, wherein The mass ratio of calcium chloride:magnesium chloride described in step 2=(1-5):

1.

6. The preparation method of calcium carbonate whisker according to claim 1, wherein The mass concentration of the mixed solution in step 2 is 1-10%.

7. The preparation method of calcium carbonate whisker according to claim 1, wherein In step 2, a pH regulator is introduced, a spiral agitator is turned on to stir the material, and the pH value of the solution in the main reactor is adjusted to 10.5-11.

5.

8. The preparation method of calcium carbonate whisker according to claim 7, wherein The pH regulator is a composite solution of ammonia water and sodium hydroxide or potassium hydroxide in a ratio of 1:2-1:

4.

9. The preparation method of calcium carbonate whisker according to claim 1, wherein In step 3, when the pH of the secondary reactor drops to 9.8-10.2, close the CO2 inlet, spiral agitator and connecting valve of the main reactor.

10. The preparation method of calcium carbonate whisker according to claim 1, wherein The calcium carbonate whisker preparation device comprises a main reactor and a secondary reactor, wherein the main reactor body is provided with a main reactor inner cylinder, the inner cylinder is fixed on the reactor body through a bracket, an agitator is provided in the inner cylinder, a distributor is provided at the bottom of the agitator, the distributor is placed above the porous distributor, and the porous distributor is connected to the CO2 inlet; The upper part of the auxiliary reactor is provided with an ultrasonic level meter interface II, an auxiliary reactor air inlet, an auxiliary reactor exhaust port, a water inlet, and a Ca(OH)2 slurry inlet; the lower part of the reactor body is provided with a temperature sensor interface III, a pH sensor interface II, an auxiliary reactor discharge port, a stirring motor II and a maintenance port; the reactor is provided with an auxiliary reactor inner cylinder, which is connected to the auxiliary reactor body through an inner cylinder bracket II. After CO2 enters from the auxiliary reactor air inlet, it is connected to the bottom umbrella-shaped distributor through a pipeline, and the pipeline passes through the middle of the auxiliary reactor inner cylinder.

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