Highly dispersed micro-nano level spherical calcite type calcium carbonate powder and production method and system

Abstract

This invention provides a highly dispersed micro / nano-scale spherical calcite-type calcium carbonate powder and its production method and system. The system includes a storage unit, a leaching unit, a first separation unit, a mineralization unit, a second separation unit, and a post-processing unit. The leaching unit includes a leaching reaction chamber, a shaking mechanism, and a temperature adjustment mechanism. The mineralization unit includes a mineralization reaction chamber and a temperature adjustment mechanism. The first and second separation units perform solid-liquid separation. The post-processing unit performs washing and drying. The method includes reacting a calcium-based raw material with an ammonium chloride solution to undergo a leaching reaction; adding ammonia water and introducing CO2 gas to the leaching solution to induce a mineralization reaction and separate the filter cake; washing and drying to obtain the calcium carbonate powder. This invention can successfully prepare high-purity, high-whiteness spherical calcite-type calcium carbonate with high dispersibility and a micro / nano structure. The entire preparation process can use industrial solid waste as raw material, operates under low temperature and normal pressure conditions, requires no crystal form control agents, and has low economic cost.

Description

Technical Field

[0001] This invention relates to the field of calcium carbonate preparation, and more specifically, to a highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder and its production method and system. Background Technology

[0002] Calcium carbonate, due to its unique physicochemical properties, is widely used in plastics, rubber, cosmetics, papermaking, pharmaceuticals, and environmental protection, making it one of the most widely used non-metallic mineral materials. Among these, spherical calcium carbonate, compared to ordinary calcium carbonate, possesses special properties such as large surface area, good dispersibility, low density, good solubility, and excellent smoothness and flowability, which can improve the material's hiding power, whiteness, adhesion, washability, and stain resistance. Furthermore, ultrafine spherical calcium carbonate with a particle size of 1-20 μm has a reinforcing effect comparable to that of silica.

[0003] Anhydrous calcium carbonate powder exists in three crystal forms: calcite, aragonite, and aragonite. Calcite is characterized by a rhombohedral morphology, aragonite by a fibrous morphology, and aragonite by a spherical morphology. Their thermodynamic stability decreases in that order; that is, fibrous aragonite-type calcium carbonate and spherical aragonite-type calcium carbonate will eventually transform into rhombohedral calcite-type calcium carbonate. Traditionally, spherical calcium carbonate exists in the aragonite crystal form, which has poor thermodynamic stability and is detrimental to the long-term use of composite materials as a filler.

[0004] Traditional calcium carbonate production primarily uses natural mineral resources such as marble and limestone as raw materials, producing heavy calcium carbonate through crushing and ball milling; or light calcium carbonate through crushing, roasting, digestion, and carbonation. With the gradual strengthening of environmental regulations and the deepening of green mining construction, the cost of producing calcium carbonate using traditional methods that consume natural mineral resources such as marble and limestone will continue to rise, and natural mineral resources are non-renewable.

[0005] Calcium-based solid waste is a type of solid waste rich in calcium ions, including industrial by-products such as gypsum, electrolytic manganese slag, carbide slag, yellow phosphorus slag, and steel slag. Its high calcium ion content makes it suitable for calcium carbonate production. Using calcium-based solid waste as raw material to prepare spherical calcite-type calcium carbonate not only achieves high-value utilization of calcium-based solid waste but also solidifies CO2, conserving natural mineral resources such as marble and limestone.

[0006] To date, there are no reports on the preparation of high-purity, high-whiteness, and highly dispersed micro-nano-sized spherical calcite-type calcium carbonate using calcium-based solid waste as raw material and salt solution and ammonia water as additives without the need for crystal form control agents. Summary of the Invention

[0007] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art.

[0008] To achieve the above objectives, the present invention provides a production system for highly dispersed micro-nano-scale spherical calcite-type calcium carbonate.

[0009] The system may include: a storage unit, a leaching unit, a first separation unit, a mineralization unit, a second separation unit, and a post-processing unit; wherein, the storage unit includes a solid material tank, a first liquid storage tank, a second liquid storage tank, and a gas source, the solid material tank is used to store calcium-based raw materials, the first liquid storage tank is used to store ammonium chloride solution, the second liquid storage tank is used to store ammonia water, and the gas source is used to provide CO2; the leaching unit includes a leaching reaction chamber, a shaking mechanism, and a first temperature adjustment mechanism, wherein, the leaching reaction chamber is used to receive calcium-based raw materials from the solid material tank and ammonium chloride solution from the first liquid tank, the calcium-based raw materials and ammonium chloride solution can undergo a leaching reaction in the leaching reaction chamber, and the shaking mechanism can shake and rotate the leaching reaction chamber, thereby ensuring that the solid material is fully in contact with the ammonium chloride solution, and enhancing the leaching reaction. The system comprises: a first temperature adjustment mechanism capable of regulating the leaching reaction temperature; a first separation unit capable of solid-liquid separation of the products after reaction in the leaching reaction chamber to obtain leachate; a mineralization unit including a mineralization reaction chamber and a second temperature adjustment mechanism, the mineralization reaction chamber receiving the leachate separated by the first separation unit, the mineralization reaction chamber also being connected to a second storage tank and a gas source to receive ammonia and CO2, the leachate, ammonia, and CO2 undergoing a mineralization reaction in the mineralization reaction chamber; a second temperature adjustment mechanism capable of regulating the mineralization reaction temperature; a second separation unit capable of solid-liquid separation of the products after reaction in the mineralization reaction chamber to obtain a mineralized filter cake; and a post-processing unit capable of washing and drying the mineralized filter cake to obtain the highly dispersed micro-nano spherical calcite-type calcium carbonate powder.

[0010] Optionally, the system may further include a leachate buffer unit and a concentration adjustment unit connected to each other; wherein the leachate buffer unit is connected to the first separation unit and the mineralization reaction chamber respectively, and is used to store the leachate separated from the first separation unit; the concentration adjustment unit includes a calcium chloride supply mechanism and a deionized water supply mechanism, and when the calcium ion concentration in the leachate is not between 0.279 and 0.4 g / 100 mL, the calcium ion concentration of the leachate in the leachate buffer unit can be adjusted by the calcium chloride supply mechanism and / or the deionized water supply mechanism.

[0011] Optionally, the first separation unit also yields leaching residue after solid-liquid separation; the post-processing unit is also capable of cleaning and drying at least a portion of each batch of leaching residue; the system further includes a first conveying mechanism, which, when the calcium ion content in the cleaned and dried leaching residue is ≥0.5%, can convey the cleaned and dried leaching residue and / or the uncleaned and undried leaching residue to the leaching reaction chamber so that it can be used as raw material in the leaching reaction.

[0012] Optionally, the second separation unit also obtains a mineralized filtrate after solid-liquid separation; the system also includes a second transmission mechanism that can transport the mineralized filtrate to the leaching reaction chamber so that it can be used as a leaching aid in the leaching reaction.

[0013] Alternatively, the solid material tank, the first liquid storage tank, and the second liquid storage tank can all be metering tanks.

[0014] Alternatively, the system can be used to implement the method described below.

[0015] Alternatively, the raw materials of the production system and the quantitative relationships between the raw materials can be the same as those in the production method described below.

[0016] Alternatively, the process control conditions (e.g., temperature, time, etc.) involved in the production system may be the same as those in the production methods described below.

[0017] Another aspect of the present invention provides a method for producing highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder.

[0018] The method may include the following steps: mixing calcium-based raw materials with ammonium chloride solution at a solid-liquid ratio of 1:30~60 g / mL and conducting a leaching reaction, and separating the leachate after the reaction; wherein the concentration of the ammonium chloride solution is 2~5 mol / L; adding ammonia water to the leachate and introducing CO2 gas to conduct a mineralization reaction, and separating the mineralized filter cake after the reaction; wherein the volume ratio of leachate to ammonia water is 400:5~30, and the CO2 gas introduction rate is 30~300 mL / min; washing and drying the mineralized filter cake to obtain the calcite-type calcium carbonate powder.

[0019] Alternatively, the method can be implemented based on the production system described above.

[0020] Alternatively, the calcium-based raw material includes at least one of natural gypsum, natural anhydrite, and solid waste, wherein the solid waste includes at least one of industrial by-product gypsum, electrolytic manganese slag, natural gypsum tailings, natural anhydrite tailings, steel slag, carbide slag, and yellow phosphorus slag.

[0021] Optionally, when separating the leachate, a leaching residue is also obtained; the method may further include: washing and drying the leaching residue, then detecting the calcium ion content, and if the content is ≥0.5%, using the leaching residue as a raw material in the leaching reaction.

[0022] Alternatively, when separating the mineralized filter cake, a mineralized filtrate is also obtained, and the method further includes: introducing the mineralized filtrate as a leaching aid into the leaching reaction until the concentration of calcium ions in the leaching solution is lower than 0.05 g / 100 ml.

[0023] Alternatively, the leaching reaction temperature can be room temperature to 60°C, and the time can be 5 to 60 minutes, during which the leaching reaction is performed by rotating and shaking at a speed of 60 to 240 rpm; the mineralization reaction temperature is 25 to 60°C, and the time is 2 to 120 minutes.

[0024] In another aspect, the present invention provides a highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder.

[0025] The powder is prepared by the method or system described above. The morphology of the calcium carbonate powder is spheres with a diameter of 3-20 μm composed of rhombohedral particles with a size of 10-500 nm. The crystal form is calcite type, with a whiteness of ≥99.5% and a purity of ≥99.5%.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) The present invention successfully prepared high-purity, high-whiteness spherical calcite-type calcium carbonate with micro-nano structure. Compared with traditional spherical aragonite-type calcium carbonate, this powder has the most stable thermodynamic properties. It can be used as a matrix to develop other spherical calcium carbonate-based functional powders without worrying about the collapse of the spherical structure.

[0027] (2) The entire preparation process and system of the present invention can use natural mineral resources or industrial solid waste rich in calcium ions as raw materials, without the need to add crystal form control agents, and the reaction conditions are low temperature and normal pressure, and the entire preparation process has a low economic cost.

[0028] (3) The present invention can realize the recycling and recovery of additives during the production process.

[0029] (4) The calcium carbonate powder prepared by the present invention has good dispersibility and has super flowability and self-powdering ability. Attached Figure Description

[0030] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 A schematic diagram of the production system for micro / nano-scale spherical calcite-type calcium carbonate powder of the present invention is shown.

[0031] Figure 2A An XRD pattern of the calcium carbonate powder of the present invention is shown.

[0032] Figure 2B A SEM image of the calcium carbonate powder of the present invention is shown.

[0033] Figure 2C Another SEM image of the calcium carbonate powder of the present invention is shown.

[0034] Figure 2D Another SEM image of the calcium carbonate powder of the present invention is shown.

[0035] Figure 3A The XRD pattern of the calcium carbonate powder obtained in Example 1 is shown.

[0036] Figure 3B SEM images of the calcium carbonate powder obtained in Example 1 are shown.

[0037] Figure 3C SEM images of individual spherical particles of calcium carbonate powder obtained in Example 1 are shown.

[0038] Figure 3D A magnified SEM image of a single spherical particle of calcium carbonate powder obtained in Example 1 is shown.

[0039] Figure 4A The XRD pattern of the calcium carbonate powder obtained in Example 2 is shown.

[0040] Figure 4B SEM images of the calcium carbonate powder obtained in Example 2 are shown.

[0041] Figure 4C SEM images of individual spherical particles of calcium carbonate powder obtained in Example 2 are shown.

[0042] Figure 4D A magnified SEM image of a single spherical particle of calcium carbonate powder obtained in Example 2 is shown.

[0043] Figure 5A The XRD pattern of the calcium carbonate powder obtained in Example 3 is shown.

[0044] Figure 5B SEM images of the calcium carbonate powder obtained in Example 3 are shown.

[0045] Figure 5C SEM images of individual spherical particles of calcium carbonate powder obtained in Example 3 are shown.

[0046] Figure 5D A magnified SEM image of a single spherical particle of calcium carbonate powder obtained in Example 3 is shown. Detailed Implementation

[0047] In the following sections, the highly dispersed micro-nano-sized spherical calcite-type calcium carbonate powder and its production method and system of the present invention will be described in detail with reference to exemplary embodiments.

[0048] Exemplary Example 1 This exemplary embodiment provides a production system for highly dispersed micro / nano-scale spherical calcite-type calcium carbonate powder.

[0049] like Figure 1As shown, the system includes: a solid material tank, a first liquid storage tank, a second liquid storage tank, a gas source, a leaching unit, a first separation unit, a mineralization unit, a second separation unit, and a post-processing unit.

[0050] Among them, the solid tank can store calcium-based raw materials, the first liquid storage tank can be used to store ammonium chloride solution, the second liquid storage tank can be used to store ammonia water, and the gas source can be used to provide CO2 gas.

[0051] The leaching unit may include a leaching reaction chamber, a shaking mechanism, and a first temperature adjustment mechanism. The leaching reaction chamber receives calcium-based raw material from a solids tank and ammonium chloride solution from a first liquid tank. The shaking mechanism causes the leaching reaction chamber to rotate, thereby ensuring sufficient contact between the solid material and the ammonium chloride solution and enhancing the leaching reaction; the first temperature adjustment mechanism regulates the temperature of the leaching reaction.

[0052] The first separation unit can perform solid-liquid separation on the products after the reaction in the leaching reaction chamber to obtain the leachate.

[0053] The mineralization unit may include a mineralization reaction chamber and a second temperature adjustment mechanism. The mineralization reaction chamber can receive the leachate separated by the first separation unit. The mineralization reaction chamber is also connected to a second storage tank and a gas source to receive ammonia and CO2. The leachate, ammonia, and CO2 can undergo a mineralization reaction in the mineralization reaction chamber. The second temperature adjustment mechanism can regulate the temperature of the mineralization reaction.

[0054] The second separation unit can perform solid-liquid separation on the products after the reaction in the mineralization reaction chamber to obtain a mineralized filter cake.

[0055] The post-processing unit may include a cleaning mechanism and a drying mechanism, which can respectively clean and dry the mineralized filter cake to obtain micro-nano spherical calcite-type calcium carbonate powder.

[0056] In this embodiment, the solid material tank, the first liquid storage tank, and the second liquid storage tank can all be tanks with metering functions. The solid material tank is a mass metering tank, and the first and second liquid storage tanks are volume metering tanks. All three can quantitatively add materials.

[0057] In this embodiment, the solid-liquid ratio of calcium-based raw material and ammonium chloride solution in the leaching reaction chamber is 1:30~60g / mL, wherein the concentration of ammonium chloride solution is 2~5mol / L.

[0058] In this embodiment, the calcium-based raw material may include at least one of the following: industrial by-product gypsum, electrolytic manganese slag, natural gypsum, natural gypsum tailings, natural anhydrite, natural anhydrite tailings, steel slag, carbide slag, and yellow phosphorus slag.

[0059] In this embodiment, the leaching reaction temperature can be room temperature to 60°C, and the reaction time can be 5 to 60 minutes. The first temperature adjustment mechanism can adjust the temperature of the system in the leaching reaction chamber, that is, it can adjust the temperature to room temperature to 60°C, for example, 35°C, 45°C, 55°C, 59°C, etc.

[0060] The first temperature adjustment mechanism may include heating mechanisms commonly used in the art.

[0061] In this embodiment, the temperature of the mineralization reaction can be 25~60℃, and the time of the mineralization reaction can be 2~120min. The second temperature adjustment mechanism can adjust the temperature of the mineralization reaction, that is, it can adjust the temperature from room temperature to 60℃, for example, 35℃, 45℃, 53℃, 59℃, etc.

[0062] The second temperature adjustment mechanism may include heating mechanisms commonly used in the art.

[0063] In this embodiment, the mineralization reaction chamber may also be equipped with a stirring mechanism, which can stir the reaction materials at 60~240 rpm.

[0064] In this embodiment, the volume ratio of leachate to ammonia in the mineralization reaction chamber can be 400:5~30.

[0065] In this embodiment, the shaking mechanism may include a shaking table. The shaking mechanism enables the leaching reaction chamber to shake and rotate, thereby ensuring that the solid material is in full contact with the ammonium chloride solution and enhancing the leaching reaction.

[0066] In this embodiment, the height of the solid tank and the first storage tank can be higher than the height of the leaching reaction chamber to facilitate the addition of materials. Both can be equipped with control valves at their discharge ends to adjust the material addition rate and the start / stop of discharge. However, the invention is not limited to this; the height of the solid tank and the first storage tank can be equal to or lower than the leaching reaction chamber, and materials can be transported by pumps.

[0067] In this embodiment, the height of the second storage tank can be higher than the height of the mineralization reaction chamber to facilitate the addition of materials. A control valve can be installed at the discharge end to adjust the material addition rate and the start / stop of discharge. However, the invention is not limited to this; the height of the second storage tank can be equal to or lower than the height of the mineralization reaction chamber, and materials can be transported by a pump.

[0068] In this embodiment, CO2 gas can be introduced into the solution in the mineralization reaction chamber through a gas pipeline at a rate of 30-300 mL / min.

[0069] A flow control valve may be installed on the gas supply pipeline or at the outlet of the gas source to adjust the gas output rate. Alternatively, the gas source may include a gas storage tank.

[0070] In this embodiment, the system may further include a leachate buffer unit and a concentration adjustment unit connected together.

[0071] The leachate buffer unit is connected to both the first separation unit and the mineralization reaction chamber, and is used to store the leachate separated from the first separation unit.

[0072] The concentration adjustment unit includes a calcium chloride supply mechanism and a deionized water supply mechanism. When the calcium ion concentration in the leachate is not between 0.279 and 0.4 g / 100 mL, the calcium ion concentration in the leachate can be adjusted by the calcium chloride supply mechanism and / or the deionized water supply mechanism.

[0073] In this embodiment, after solid-liquid separation, the first separation unit also yields leaching residue.

[0074] The post-processing unit is also capable of cleaning and drying each batch of leaching residue.

[0075] The system also includes a first transmission mechanism, which can transport the cleaned and dried leaching residue to the leaching reaction chamber when the calcium ion content in the leaching residue after cleaning and drying is ≥0.5%, so that it can be used as raw material in the leaching reaction.

[0076] In this embodiment, the second separation unit also obtains a mineralized filtrate after solid-liquid separation.

[0077] The system may also include a second transmission mechanism, which can transport the mineralized filtrate to the leaching reaction chamber when the calcium ion concentration in the leachate is ≥0.05 g / 100 mL, so that it can be used as a leaching aid in the leaching reaction.

[0078] The system also includes an evaporation crystallization unit. When the concentration of calcium ions in the leachate is less than 0.05 g / 100 mL, the second transmission mechanism can transport the mineralized filtrate to the evaporation crystallization unit for evaporation crystallization, and recover ammonium sulfate and ammonium chloride in steps.

[0079] In this embodiment, materials can be transferred between units via conveyor belts, pumps, etc.

[0080] In this embodiment, since all reactions of the present invention are carried out at low temperature and normal pressure, each reaction device (such as the leaching reaction chamber) can be selected as an open system.

[0081] Exemplary Example 2 This exemplary embodiment provides a method for preparing highly dispersed micro / nano-scale spherical calcite-type calcium carbonate powder.

[0082] The preparation method may include the following steps: (1) Mix the calcium-based raw material with the ammonium chloride solution at a solid-liquid ratio of 1:30~60 g / mL and allow them to leach. After the reaction, separate the leachate. The concentration of the ammonium chloride solution is 2~5 mol / L.

[0083] (2) Add ammonia water to the leachate and introduce CO2 gas to cause a mineralization reaction. After the reaction, the mineralized filter cake is separated. The volume ratio of leachate to ammonia water is 400:5~30, and the CO2 gas introduction rate is 30~300 mL / min.

[0084] (3) Clean and dry the mineralized filter cake to obtain micro-nano spherical calcite-type calcium carbonate powder.

[0085] In this embodiment, the calcium-based raw material may include one or more of natural gypsum, natural anhydrite, and solid waste. The solid waste may include at least one of industrial by-product gypsum, electrolytic manganese slag, natural gypsum tailings, natural anhydrite tailings, steel slag, carbide slag, and yellow phosphorus slag.

[0086] In this embodiment, as an example, the solid-liquid ratio of the calcium-based raw material and the ammonium chloride solution can be 1:35 g / mL, 1:45 g / mL, 1:48 g / mL, 1:50 g / mL, 1:57 g / mL, 1:58 g / mL, etc.

[0087] The concentration of ammonium chloride solution can be 2.2 mol / L, 2.7 mol / L, 3.2 mol / L, 3.6 mol / L, 4 mol / L, 4.4 mol / L, 4.8 mol / L, etc.

[0088] In this embodiment, the leaching reaction temperature can be room temperature to 60°C, such as 24°C, 28°C, 35°C, 45°C, 55°C, 59°C, etc.; the reaction time can be 5 to 60 min, such as 6, 8, 18, 25, 35, 45, 55, 58 min, etc.

[0089] In this embodiment, during the leaching reaction, the reaction vessel can be stirred or rotated and shaken. The rotation speed of the rotation and shaking can be 60~240 rpm, such as 62, 80, 120, 160, 190, 210, 235 rpm, etc.

[0090] In this embodiment, the concentration of calcium ions in the leachate should be controlled within the range of 0.279~0.4 g / 100 mL, which helps to obtain a spherical calcite-type calcium carbonate matrix, for example, controlled within the range of 0.279 g / 100 mL, 0.3 g / 100 mL, 0.35 g / 100 mL, 0.39 g / 100 mL, etc.

[0091] The method may further include a step of detecting the calcium ion concentration in the leachate. If the calcium ion concentration is not within the specified range, it may be adjusted using analytical grade calcium chloride or deionized water to make the calcium ion concentration between 0.279 and 0.4 g / 100 mL.

[0092] In this embodiment, the volume ratio of leachate to ammonia is controlled at 400:5~30 because: if the amount of ammonia added is too small, it cannot provide the alkaline environment required for calcium ions to combine with CO2 gas to form thermodynamically stable crystals, thus preventing the formation of calcium carbonate powder or resulting in amorphous calcium carbonate powder; if the amount of ammonia added is too large, the concentration of ammonium ions in the system will be too high, making it easier for calcium ions to combine with carbonate ions to form thermodynamically unstable aragonite-type calcium carbonate. For example, the volume ratio of leachate to ammonia can be 400:5, 400:15, 400:22, 400:28, etc.

[0093] In this embodiment, the CO2 gas flow rate is controlled at 30~300 mL / min because: if the CO2 flow rate is too low, insufficient carbonate ions cannot be provided, thus preventing the formation of the calcium carbonate matrix; if the CO2 flow rate is too high, the resulting calcium carbonate will be rhombohedral rather than spherical. CO2 gas is continuously introduced during the mineralization reaction. For example, the CO2 flow rate can be 35, 60, 80, 130, 160, 210, 260, 295 mL / min, etc.

[0094] In this embodiment, the temperature of the mineralization reaction can be 25~60℃, such as 27, 35, 45, 55, 58℃, etc. If the reaction temperature is too low, calcium carbonate powder cannot be generated or the generated calcium carbonate will be amorphous. If the reaction temperature is too high, the resulting calcium carbonate will be rhombohedral calcite instead of spherical.

[0095] The time for the mineralization reaction can be 2 to 120 minutes, for example, 3, 10, 15, 25, 50, 80, 100, 110, 119 minutes, etc.

[0096] In this embodiment, stirring can be performed during the mineralization process, and the stirring rate can be 60~240 rpm, such as 61, 70, 120, 180, 200, 230, 238 rpm, etc.

[0097] In this embodiment, after the mineralization reaction, a mineralized filter cake is separated to obtain a mineralized filtrate. The method further includes returning the mineralized filtrate as a leaching aid to the first step of the leaching reaction until the concentration of calcium ions in the leachate is below 0.05 g / 100 mL. At this point, the leachate can be evaporated and crystallized to recover ammonium sulfate and ammonium chloride in steps.

[0098] Exemplary Example 3 This exemplary embodiment provides a highly dispersed micro / nano-scale spherical calcite-type calcium carbonate powder.

[0099] Figure 2A An XRD pattern of the calcium carbonate powder of the present invention is shown. Figure 2B , Figure 2C and Figure 2D Three SEM images of the calcium carbonate powder of the present invention are shown respectively, wherein, Figure 2B The scale bar is 20 μm. Figure 2C The scale bar is 1 μm. Figure 2D The scale bar is 400 nm.

[0100] like Figure 2A As shown, the calcium carbonate powder has a calcite crystal form. Figure 2B and 2C As shown, the calcium carbonate powder is spherical. The morphology of the calcium carbonate powder consists of spheres with a diameter of 3-20 μm composed of rhombohedral particles with a size of 10-500 nm, for example... Figure 2C and 2D The SEM image shown indicates that the calcium carbonate powder has a whiteness of over 99.5% and a purity of over 99.5%, exhibiting excellent dispersibility and flowability.

[0101] In this embodiment, the calcium carbonate powder can be prepared by the system described in Exemplary Example 1 or the method described in Exemplary Example 2.

[0102] To better understand the exemplary embodiments of the present invention described above, further explanation is provided below with reference to specific examples.

[0103] Example 1 Electrolytic manganese slag was used as raw material. The raw material was sourced from an electrolytic manganese plant in Guizhou Province. Its chemical composition included: MgO 1.97%, SiO2 32.32%, CaO 14.27%, SO3 30.77%, Fe2O3 6.32%, Al2O3 7.63%, MnO 3%, K2O 1.72%, Na2O 0.75%, and other components 1.25%.

[0104] The method for producing the highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder includes the following steps: (1) Take 20 g of electrolytic manganese slag sample and place it in a 700 mL conical flask. Add 600 mL of ammonium chloride solution with a concentration of 2 mol / L to the conical flask. Place the conical flask in a shaker at a speed of 180 r / min and react at 45 ℃ for 100 min. After filtration, the concentration of calcium ions in the filtrate (i.e., leachate) is 0.279 g / 100 mL. The filtrate is used for the preparation of calcium carbonate powder in the later stage. After washing and drying the filter cake (i.e., leachate residue), the concentration of calcium ions is measured to be 3.02%. It is then used as a raw material for CaSO4. The calcium ion content is reduced to less than 0.5% by leaching with 2H2O. The filter residue is then washed and dried at 40 °C for subsequent resource utilization.

[0105] (2) Take 400 mL of the above Ca 2+ The leachate was poured into a 500 mL beaker, and 30 mL of analytical grade ammonia was added. The beaker was placed in a water bath with a stirrer, and industrial-grade CO2 gas was introduced into the solution at a rate of 150 mL / min. After stirring at 50°C for 80 min, the mixture was filtered at a stirring speed of 120 r / min. The filter cake was washed and dried at 105 °C to obtain calcium carbonate powder. XRD and SEM tests were performed on the powder, and the results are shown below. Figure 3A and Figure 3B-3D As shown, its crystal form is obviously calcite and its morphology is spherical.

[0106] The mineralized filtrate obtained from this filtration step is recycled for use in the electrolytic manganese slag or the leaching residue of the electrolytic manganese slag containing CaSO4. After leaching with 2H2O and recycling three times, the concentration of calcium ions in the leachate was 0.01 g / 100 mL. The leachate was then evaporated and crystallized at 60 °C for 72 h to recover ammonium sulfate and ammonium chloride.

[0107] Example 2 Using phosphogypsum as raw material, which was sourced from a phosphate fertilizer plant in Deyang, Sichuan, the chemical composition of the raw material includes: 5.03% SiO2, 29.6% CaO, 39.36% SO3, 1.60% P2O5, 1.85% Al2O3, 20.74% H2O, and 1.82% other components.

[0108] The method for producing the highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder includes the following steps: (1) Take 20 g of phosphogypsum sample and place it in a 1000 mL conical flask. Add 900 mL of ammonium chloride solution with a concentration of 2.5 mol / L to the conical flask. Place the conical flask in a shaker with a shaking speed of 200 r / min. After reacting at 30 ℃ for 90 min, filter the solution. The concentration of calcium ions in the filtrate (i.e., leachate) is 0.581 g / 100 mL. Adjust the concentration of calcium ions in the leachate to 0.4 g / 100 mL with deionized water. The filtrate after adjusting the concentration is used for the subsequent preparation of calcium carbonate powder. The concentration of calcium ions in the filter cake (i.e., leachate residue) is 0.4% after washing and drying. It is used for subsequent resource utilization.

[0109] (2) Take 400 mL of the above Ca 2+ The leachate was poured into a 500 mL beaker, and 14 mL of analytical grade ammonia was added. The beaker was placed in a water bath with a stirrer, and industrial-grade CO2 gas was introduced into the solution at a rate of 200 mL / min. After stirring for 50 min at room temperature, the mixture was filtered under vacuum at a stirring speed of 150 r / min. The filter cake was washed and dried at 105 ℃ to obtain calcium carbonate powder. XRD and SEM tests were performed on the calcium carbonate, and the results are shown below. Figure 4A and Figure 4B-4D As shown, its crystal form is obviously calcite and its morphology is spherical.

[0110] In this step, the mineralized filtrate obtained by filtration is recycled for the leaching of phosphogypsum. After five cycles, the concentration of calcium ions in the leaching solution is 0.004 g / 100 mL. The leaching solution is then evaporated and crystallized at 80 °C for 72 h to recover ammonium sulfate and ammonium chloride.

[0111] Example 3 The raw material is natural gypsum, which is mined from a gypsum mine in Yanchi, Ningxia. The chemical composition of the raw material includes: 1.32% SiO2, 31.85% CaO, 44.52% SO3, 0.05% Fe2O3, 0.63% Al2O3, 20.48% H2O, and 1.15% other components.

[0112] The method for producing the highly dispersed micro-nano-scale spherical calcite-type calcium carbonate powder includes the following steps: (1) Take 10 g of natural gypsum sample and place it in a 1000 mL conical flask. Add 500 mL of ammonium chloride solution with a concentration of 4 mol / L to the conical flask. Place the conical flask in a shaker with a shaking speed of 220 r / min. After reacting at 45 ℃ for 80 min, filter the solution. The concentration of calcium ions in the filtrate (i.e., leachate) is 1.12 g / 100 mL. Adjust the concentration of calcium ions in the leachate to 0.35 g / 100 mL with deionized water. The filtrate after adjusting the concentration is used for the subsequent preparation of calcium carbonate powder. The concentration of calcium ions in the filter cake (i.e., leachate residue) is 0.32% after washing and drying. It is used for subsequent resource utilization.

[0113] (2) Take 400 mL of the above Ca 2+ The leachate was poured into a 500 mL beaker, and 22 mL of analytical grade ammonia was added. The beaker was placed in a water bath with a stirrer, and industrial-grade CO2 gas was introduced into the solution at a rate of 300 mL / min. The reaction was carried out at 45°C for 90 min with stirring, followed by filtration at a stirring speed of 180 r / min. The filter cake was washed and dried at 105 °C to obtain calcium carbonate powder. XRD and SEM tests were performed on the calcium carbonate powder, and the results are shown below. Figure 5A and Figures 5B-5D As shown, the crystal form is calcite type, and the morphology is spherical.

[0114] In this step, the mineralized filtrate obtained by filtration is recycled for the leaching of natural gypsum. After five cycles, the concentration of calcium ions in the leaching solution is 0.003 g / 100 mL. The leaching solution is then evaporated and crystallized at 65 °C for 72 h to recover ammonium sulfate and ammonium chloride.

[0115] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for producing highly dispersed micro / nano-sized spherical calcite-type calcium carbonate powder, characterized in that, The method includes the following steps: A calcium-based raw material is mixed with an ammonium chloride solution at a solid-liquid ratio of 1:30~60 g / mL and a leaching reaction is carried out. After the reaction, the leachate is separated. The concentration of the ammonium chloride solution is 2~5 mol / L. The calcium-based raw material includes at least one of natural gypsum, natural anhydrite, and solid waste, and the solid waste includes at least one of industrial by-product gypsum, natural gypsum tailings, and natural anhydrite tailings. The concentration of calcium ions in the leachate is 0.279~0.4 g / 100 mL. Ammonia water is added to the leachate and CO2 gas is introduced to induce a mineralization reaction. After the reaction, a mineralized filter cake is separated. The volume ratio of leachate to ammonia water is 400:5~30, and the CO2 gas introduction rate is 30~300 mL / min. The temperature of the mineralization reaction is 25~60℃, and the time is 2~120 min. The mineralized filter cake is washed and dried to obtain the calcite-type calcium carbonate powder.

2. The method according to claim 1, characterized in that, When the leachate is separated, a leaching residue is also obtained; the method further includes: washing and drying the leaching residue, and then detecting the calcium ion content. If the content is ≥0.5%, the leaching residue is used as a raw material in the leaching reaction. When separating the mineralized filter cake, a mineralized filtrate is also obtained. The method further includes: using the mineralized filtrate as a leaching aid in the leaching reaction until the concentration of calcium ions in the leaching solution is lower than 0.05 g / 100 ml.

3. The method according to claim 1, characterized in that, The leaching reaction is carried out at a temperature of room temperature to 60°C for a time of 5 to 60 minutes, and the mixture is rotated and shaken during the leaching reaction at a speed of 60 to 240 rpm.

4. A highly dispersed micro / nano-sized spherical calcite-type calcium carbonate powder, characterized in that, The powder is prepared by the method described in any one of claims 1 to 3. The calcium carbonate powder has the morphology of spheres with a diameter of 3 to 20 μm composed of rhombohedral particles with a size of 10 to 500 nm, the crystal form is calcite type, the whiteness is above 99.5%, and the purity is above 99.5%.

5. A production system for highly dispersed micro / nano-sized spherical calcite-type calcium carbonate powder, characterized in that, The system is used to implement the method according to any one of claims 1 to 3, and includes: a storage unit, a leaching unit, a first separation unit, a mineralization unit, a second separation unit, and a post-processing unit, wherein, The storage unit includes a solid tank, a first liquid storage tank, a second liquid storage tank, and a gas source. The solid tank is used to store calcium-based raw materials, the first liquid storage tank is used to store ammonium chloride solution, the second liquid storage tank is used to store ammonia water, and the gas source is used to provide CO2. The leaching unit includes a leaching reaction chamber, a shaking mechanism, and a first temperature adjustment mechanism. The leaching reaction chamber is used to receive calcium-based raw materials from a solid material tank and ammonium chloride solution from a first liquid tank. The calcium-based raw materials and ammonium chloride solution can undergo a leaching reaction in the leaching reaction chamber. The shaking mechanism can make the leaching reaction chamber shake and rotate. The first temperature adjustment mechanism can adjust the temperature of the leaching reaction. The first separation unit can perform solid-liquid separation on the products after the reaction in the leaching reaction chamber to obtain the leachate; The mineralization unit includes a mineralization reaction chamber and a second temperature adjustment mechanism. The mineralization reaction chamber can receive the leachate separated by the first separation unit. The mineralization reaction chamber is also connected to a second storage tank and a gas source to receive ammonia and CO2. The leachate, ammonia, and CO2 can undergo a mineralization reaction in the mineralization reaction chamber. The second temperature adjustment mechanism can regulate the temperature of the mineralization reaction. The second separation unit can perform solid-liquid separation on the products after the reaction in the mineralization reaction chamber to obtain mineralized filter cake; The post-processing unit includes the ability to wash and dry the mineralized filter cake to obtain the highly dispersed micro-nano spherical calcite-type calcium carbonate powder.

6. The production system according to claim 5, characterized in that, The system also includes a leachate buffer unit and a concentration adjustment unit connected to each other; wherein... The leachate buffer unit is connected to both the first separation unit and the mineralization reaction chamber, and is used to store the leachate separated from the first separation unit. The concentration adjustment unit includes a calcium chloride supply mechanism and a deionized water supply mechanism. When the calcium ion concentration in the leachate is not between 0.279 and 0.4 g / 100 mL, the calcium ion concentration in the leachate buffer unit can be adjusted by the calcium chloride supply mechanism and / or the deionized water supply mechanism.

7. The production system according to claim 5, characterized in that, After solid-liquid separation, the first separation unit also yielded leaching residue. The post-processing unit is also capable of cleaning and drying each batch of leaching residue. The system also includes a first transmission mechanism. When the calcium ion content in the leaching residue after cleaning and drying is ≥0.5%, the first transmission mechanism can transport the cleaned and dried leaching residue and / or the leaching residue that has not been cleaned and dried to the leaching reaction chamber so that it can be used as raw material in the leaching reaction.

8. The production system according to claim 5, characterized in that, The second separation unit also yielded a mineralized filtrate after solid-liquid separation; The system also includes a second transmission mechanism that can transport the mineralized filtrate to the leaching reaction chamber so that it can be used as a leaching aid in the leaching reaction.

9. The production system according to claim 5, characterized in that, The solid material tank, the first liquid storage tank, and the second liquid storage tank are all metering tanks.

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