An integrated system and process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas

Abstract

The present invention discloses an integrated system and process for preparing nano-scale calcium carbonate seeds by carbon capture of cement kiln flue gas, belonging to the technical field of carbon dioxide capture and utilization. The integrated system includes a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit; wherein the cement kiln flue gas carbon capture unit and the calcium ion leaching unit are connected in parallel and then connected in series with the calcium carbonate synthesis unit. The process disclosed in the present invention is an integrated system for preparing nano-scale calcium carbonate seeds by carbon capture of cement kiln flue gas as described above. The present invention captures and utilizes carbon dioxide in cement kiln flue gas, combines it with calcium in industrial solid waste and converts it into nano-calcium carbonate seeds, thereby achieving low-energy capture and efficient utilization of carbon dioxide in cement kiln flue gas, and driving deep decarbonization of the cement industry.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide capture and utilization, and in particular relates to an integrated system and process for preparing nano-scale calcium carbonate crystal seeds by capturing carbon from cement kiln flue gas. Background Art

[0002] At present, carbon emissions from China's cement industry account for about 13% of the country's total carbon emissions, and it is the main source of carbon dioxide emissions in the manufacturing industry. Facing my country's dual carbon goals, the cement industry faces the key problems of high carbon emissions and short carbon reduction cycles. Current carbon reduction technologies mainly include production energy efficiency improvement, fuel substitution, cement clinker substitution, and carbon capture, utilization and storage (CCUS). Among them, CCUS technology is considered to be the bottom-line technology for achieving the "carbon neutrality" goal of the cement industry. Among the various CCUS technologies, chemical absorption technology is widely used in the cement industry due to its simple process, high carbon dioxide absorption efficiency, and easy operation. However, chemical absorption technology faces the key problems of high energy consumption for carbon dioxide desorption and low utilization rate of captured carbon dioxide.

[0003] Therefore, studying an integrated system and process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas is of great significance for achieving deep decarbonization in the cement industry. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes an integrated system and process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An integrated system for preparing nano-scale calcium carbonate seeds by carbon capture of cement kiln flue gas, comprising a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit;

[0007] The cement kiln flue gas carbon capture unit and the calcium ion leaching unit are connected in parallel and then connected in series with the calcium carbonate synthesis unit.

[0008] Preferably, the cement kiln flue gas carbon capture unit comprises a flue gas pretreatment tower and a carbon dioxide absorption tower connected in series.

[0009] More preferably, the flue gas pretreatment tower and the carbon dioxide absorption tower are connected by a pipeline;

[0010] The carbon dioxide absorption tower includes a heat exchange device;

[0011] The top of the carbon dioxide absorption tower is provided with an outlet for discharging the flue gas after the carbon dioxide is captured;

[0012] Preferably, the calcium ion leaching unit comprises a calcium ion leaching kettle and a solid-liquid separation kettle connected in series;

[0013] More preferably, the calcium ion leaching kettle is provided with a pH detection device and a calcium ion concentration detection device;

[0014] The solid-liquid separation kettle comprises a filter screen with a mesh size of 400-800 meshes, and the bottom comprises a channel with a valve.

[0015] Preferably, the calcium carbonate synthesis unit comprises a calcium carbonate synthesis kettle, a calcium carbonate centrifugal kettle and a calcium carbonate drying kettle which are sequentially connected in series.

[0016] More preferably, the connection between the calcium carbonate centrifugal kettle and the calcium carbonate drying kettle includes a transmission device to ensure that the solid can be transferred to the calcium carbonate drying kettle;

[0017] The calcium carbonate synthesis kettle is equipped with a stirring device;

[0018] The calcium carbonate centrifugal kettle has a pipeline for discharging liquid outside the unit, and the opening and closing of the pipeline can be controlled by a valve.

[0019] Beneficial effects: The present invention is provided with a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit, so as to achieve the capture of carbon dioxide in the cement kiln flue gas, and to prepare nano-scale calcium carbonate seeds without desorption; the prepared nano-calcium carbonate seeds can be used as cement concrete admixtures. In addition, the present invention is provided with a heat exchange device in the flue gas pretreatment tower, so as to achieve the heat exchange between the flue gas and the liquid phase wetting liquid, the preparation of the absorbent and the recycling of the waste heat.

[0020] A process for preparing nano-scale calcium carbonate seeds by carbon capture from cement kiln flue gas, using the above-mentioned integrated system for preparing nano-scale calcium carbonate seeds by carbon capture from cement kiln flue gas, specifically comprises the following steps:

[0021] (1) In the cement kiln flue gas carbon capture unit, carbon dioxide in the cement kiln flue gas is captured using an organic alcohol amine solution as an absorbent to obtain a carbon dioxide absorption liquid; in the calcium ion leaching unit, calcium ions in solid waste are leached using the leaching liquid to obtain a calcium ion leaching liquid;

[0022] (2) In the calcium carbonate synthesis unit, the carbon dioxide absorption liquid and the calcium ion leaching liquid are stirred and mixed for reaction, and after the reaction is completed, centrifugal separation and drying are performed to obtain the nano-scale calcium carbonate seed crystals.

[0023] Beneficial effects: The process for preparing nano calcium carbonate seeds by capturing carbon dioxide with organic amines without desorption realizes the whole process integration from capturing carbon dioxide to converting it into products in cement production.

[0024] Preferably, the cement kiln flue gas in step (1) is cement kiln flue gas that has been treated with desulfurization, denitrification and dust removal, wherein the carbon dioxide concentration is 14.3%, the carbon monoxide concentration is 1.2%, the temperature is 107°C, and the flow rate is 45000Nm 3 / h.

[0025] Preferably, the step (1) further includes a flue gas wetting step before capturing carbon dioxide in cement kiln flue gas, specifically comprising: using a heat exchange device to heat the wetting liquid to 30-50°C using the heat of the flue gas, and reducing the flue gas temperature to 30-50°C.

[0026] The wetting fluid is water.

[0027] Beneficial effect: Wetting the flue gas before capturing carbon dioxide is beneficial to improving the capture efficiency of the absorbent for carbon dioxide in the flue gas.

[0028] Preferably, the organic alcohol amine solution in step (1) is obtained by mixing the organic alcohol amine, the alkali metal compound and the wetting liquid in a mass ratio of (5-10): (20-25): (65-75).

[0029] Preferably, the organic alcohol amine is one or any of triethanolamine, triisopropanolamine, diethanol monoisopropanolamine and monoethanol diisopropanolamine, more preferably triethanolamine;

[0030] The alkali metal compound is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, more preferably sodium hydroxide;

[0031] The wetting fluid is water.

[0032] Preferably, the calcium ion leaching in step (1) is specifically to mix the solid waste, the leachate and the dispersant and stir and leach until the calcium ion concentration in the calcium ion leachate is 0.3-6 mol / L.

[0033] More preferably, the mass ratio of the solid waste, leachate and dispersant is (27.5-52.5): (47-69.5); (0.5-3). If the calcium ion concentration in the calcium ion leachate does not reach 0.3-6 mol / L, the mass of the solid waste should be increased and the leachate concentration should be increased until the concentration reaches the above range.

[0034] Preferably, the leaching solution is one or any of ammonium chloride solution, hydrochloric acid solution, acetic acid solution and acetic acid solution, and the mass ratio of solute to solvent is (25-50): (50-75);

[0035] More preferably, the leaching liquid is ammonium chloride; when the calcium content of the solid waste is different, the leaching liquid should be increased or decreased accordingly.

[0036] Preferably, the dispersant is one of tetrachloroethylene, sodium polyacrylate, ammonium polycarbonate, and sodium polycarboxylate;

[0037] Preferably, the solid waste is carbide slag or steel slag, and the particle size should be less than 100 μm.

[0038] More preferably, the CaO content in the carbide slag is greater than 70%;

[0039] The CaO content in the steel slag is greater than 40%;

[0040] Preferably, the mass ratio of the carbon dioxide absorption liquid to the calcium ion leaching liquid added per unit time in step (2) is 1:2-5;

[0041] During the synthesis process, a stirring device is used for stirring, and the stirring rate is 500-2000 r / min.

[0042] Preferably, the centrifugal speed in step (2) is 5000-15000 r / min, and the time is 0.5-3 min.

[0043] Preferably, the drying temperature in step (2) is 60-90° C. and the drying time is 8-16 h.

[0044] A nanometer calcium carbonate is prepared by the above-mentioned process of preparing nanometer calcium carbonate crystal seeds by capturing carbon from cement kiln flue gas.

[0045] In the process of preparing calcium carbonate, the calcium ion concentration is controlled to be more than twice the carbonate concentration and triethanolamine is added to make the calcium carbonate reach the level of nano calcium carbonate.

[0046] The invention discloses an application of nano-scale calcium carbonate in cement admixture.

[0047] Preferably, the amount of the nano-scale calcium carbonate added to cement is 1-2% of the mass of cement.

[0048] Beneficial effects: The nano calcium carbonate seeds prepared by the method provided by the present invention can be added to cement as an admixture, and the admixture can improve the early mechanical properties of cement, and the 1d and 3d compressive properties are improved by 20-60%. The technical principle is mainly that after the calcium carbonate seeds are added, a nucleus effect is generated, which makes the CSH in the cement grow more uniformly and reduces the overall porosity of the cement block.

[0049] Compared with the prior art, the present invention has the following advantages and technical effects:

[0050] In view of the complex flue gas environment in a cement kiln and the synthesis conditions required for calcium carbonate seeds, the present invention sequentially arranges a cement kiln flue gas carbon capture unit and a calcium ion leaching unit in parallel, and then connects the unit in series with the calcium carbonate synthesis unit, so that the carbon dioxide in the cement flue gas completes the whole process from being absorbed to becoming a nano sodium carbonate product, and realizes the simultaneous capture of carbon dioxide in the cement kiln flue gas and the desorption-free utilization of the absorbent, and can utilize the carbon dioxide in the cement kiln flue gas as a resource, and further reacts with the solid waste leaching liquid as a raw material to prepare a calcium carbonate admixture capable of improving the mechanical properties of cement.

[0051] In the present invention, the carbon dioxide in the flue gas of the cement kiln undergoes a process of transformation from gas to solid through multiple steps such as absorption, reaction, centrifugation, and drying, thus realizing the whole process of carbon dioxide absorption, utilization, and storage. The present invention eliminates the huge consumption of the absorption liquid during desorption, and at the same time converts the carbon dioxide in the flue gas into calcium carbonate that can be used in cement, thus solving the problem of low carbon dioxide utilization in the current cement industry and contributing to the realization of "carbon peak" and "carbon neutrality". BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0053] Figure 1 This is a schematic diagram of an integrated system for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas in Example 1 of the present invention:

[0054] The reference numerals are: flue gas pretreatment tower 1; carbon dioxide absorption tower 2; calcium ion leaching kettle 3; solid-liquid separation kettle 4; calcium carbonate synthesis kettle 5; calcium carbonate centrifugal kettle 6; calcium carbonate drying kettle 7. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] The embodiment of the present invention provides an integrated system for preparing nano-scale calcium carbonate seeds by carbon capture of cement kiln flue gas, including a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit;

[0058] The cement kiln flue gas carbon capture unit and the calcium ion leaching unit are connected in parallel and then connected in series with the calcium carbonate synthesis unit.

[0059] In a preferred embodiment, the cement kiln flue gas carbon capture unit comprises a flue gas pretreatment tower and a carbon dioxide absorption tower connected in series.

[0060] In a more preferred embodiment, the flue gas pretreatment tower and the carbon dioxide absorption tower are connected by a pipeline;

[0061] The carbon dioxide absorption tower includes a heat exchange device;

[0062] The top of the carbon dioxide absorption tower is provided with an outlet for discharging the flue gas after the carbon dioxide is captured;

[0063] In a preferred embodiment, the calcium ion leaching unit comprises a calcium ion leaching kettle and a solid-liquid separation kettle connected in series;

[0064] In a more preferred embodiment, the calcium ion leaching kettle is provided with a pH detection device and a calcium ion concentration detection device;

[0065] The solid-liquid separation kettle comprises a filter screen with a mesh size of 400-800 meshes, and the bottom comprises a channel with a valve.

[0066] In a preferred embodiment, the calcium carbonate synthesis unit comprises a calcium carbonate synthesis kettle, a calcium carbonate centrifugal kettle and a calcium carbonate drying kettle which are sequentially connected in series.

[0067] In a more preferred embodiment, the connection between the calcium carbonate centrifugal kettle and the calcium carbonate drying kettle includes a transmission device to ensure that the solid can be transferred to the calcium carbonate drying kettle;

[0068] The calcium carbonate synthesis kettle is equipped with a stirring device;

[0069] The calcium carbonate centrifugal kettle has a pipeline for discharging liquid outside the unit, and the opening and closing of the pipeline can be controlled by a valve.

[0070] The embodiment of the present invention further provides a process for preparing nano-scale calcium carbonate seeds by carbon capture from cement kiln flue gas, and the integrated system for preparing nano-scale calcium carbonate seeds by carbon capture from cement kiln flue gas mentioned above specifically comprises the following steps:

[0071] (1) In the cement kiln flue gas carbon capture unit, carbon dioxide in the cement kiln flue gas is captured using an organic alcohol amine solution as an absorbent to obtain a carbon dioxide absorption liquid; in the calcium ion leaching unit, calcium ions in solid waste are leached using the leaching liquid to obtain a calcium ion leaching liquid;

[0072] (2) In the calcium carbonate synthesis unit, the carbon dioxide absorption liquid and the calcium ion leaching liquid are stirred and mixed for reaction, and after the reaction is completed, centrifugal separation and drying are performed to obtain the nano-scale calcium carbonate seed crystals.

[0073] In a preferred embodiment, the cement kiln flue gas in step (1) is cement kiln flue gas that has been treated with desulfurization, denitrification and dust removal, wherein the carbon dioxide concentration is 14.3%, the carbon monoxide concentration is 1.2%, the temperature is 107°C, and the flow rate is 45000Nm 3 / h.

[0074] In a preferred embodiment, the step (1) further includes a flue gas wetting step before capturing carbon dioxide in cement kiln flue gas, specifically comprising: using a heat exchange device to heat the wetting liquid to 30-50°C using the heat of the flue gas, and reducing the flue gas temperature to 30-50°C.

[0075] The wetting fluid is water.

[0076] In a preferred embodiment, the organic alcohol amine solution in step (1) is obtained by mixing the organic alcohol amine, the alkali metal compound and the wetting solution in a mass ratio of (5-10): (20-25): (65-75).

[0077] In a preferred embodiment, the organic alcohol amine is one or any of triethanolamine, triisopropanolamine, diethanol monoisopropanolamine and monoethanol diisopropanolamine, more preferably triethanolamine;

[0078] The alkali metal compound is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, more preferably sodium hydroxide;

[0079] The wetting fluid is water.

[0080] In a preferred embodiment, the calcium ion leaching in step (1) is specifically to mix the solid waste, the leachate and the dispersant and stir and leach until the calcium ion concentration in the calcium ion leachate is 0.3-6 mol / L.

[0081] In a more preferred embodiment, the mass ratio of the solid waste, leachate and dispersant is (27.5-52.5): (47-69.5); (0.5-3). If the calcium ion concentration in the calcium ion leachate does not reach 0.3-6 mol / L, the mass of the solid waste should be increased and the leachate concentration should be increased until the concentration reaches the above range.

[0082] In a preferred embodiment, the leaching solution is one or any of ammonium chloride solution, hydrochloric acid solution, acetic acid solution and acetic acid solution, and the mass ratio of solute to solvent is (25-50): (50-75);

[0083] In a more preferred embodiment, the leaching solution is preferably ammonium chloride; when the calcium content of the solid waste is different, the leaching solution should be increased or decreased accordingly.

[0084] In a preferred embodiment, the dispersant is one of tetrachloroethylene, sodium polyacrylate, ammonium polycarbonate, and sodium polycarboxylate;

[0085] In a preferred embodiment, the solid waste is carbide slag or steel slag, and the particle size should be less than 100 μm.

[0086] In a more preferred embodiment, the CaO content in the carbide slag is greater than 70%;

[0087] The CaO content in the steel slag is greater than 40%;

[0088] In a preferred embodiment, the mass ratio of the carbon dioxide absorption liquid to the calcium ion leaching liquid added per unit time in step (2) is 1:2-5;

[0089] During the synthesis process, a stirring device is used for stirring, and the stirring rate is 500-2000 r / min.

[0090] In a preferred embodiment, the centrifugal speed in step (2) is 5000-15000 r / min, and the time is 0.5-3 min.

[0091] In a preferred embodiment, the drying temperature in step (2) is 60-90° C. and the drying time is 8-16 hours.

[0092] The embodiment of the present invention further provides a nano-scale calcium carbonate, which is prepared by the above-mentioned process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas.

[0093] The embodiment of the present invention also provides an application of nano-scale calcium carbonate in cement admixture.

[0094] In a preferred embodiment, the amount of the nano-scale calcium carbonate added to cement is 1-2% of the mass of cement.

[0095] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources;

[0096] The flue gas in the embodiment of the present invention is the flue gas after desulfurization, denitrification and dust removal, wherein the carbon dioxide concentration is 14.3%, the carbon monoxide concentration is 1.2%, the temperature is 107°C, and the flow rate is 45000Nm 3 / h;

[0097] Steel slag: CaO content should be greater than 40%, the specific chemical composition is MgO: 3.01%, CaO: 41.7%, Al2O3: 2.8%, Fe2O: 30.4%, SiO2: 14.5%, P2O5: 1.51%, MnO: 3.32%;

[0098] Calcium carbide slag: CaO content is greater than 70%, the specific chemical composition is CaO: 90.87%, SiO2: 4.42%, Fe2O3: 6.0%, TiO2: 0.08%, K2O: 0.6%, Na2O: 0.05%, P2O5: 0.03%.

[0099] The cement used in the embodiment of the present invention is industrial cement clinker, which meets the Portland cement standard in GB 175-2007 "General Portland Cement", and its chemical composition is SiO2: 15%, Al2O3: 4.13%, Fe2O3: 4.22%, CaO: 72.68%, MgO: 0.34%, SO3: 2.69%, Na2O eq :0.145%, f-CaO:0.54%. Its mechanical properties are: 1d compressive strength is about 14.3Mpa; 3d compressive strength is about 32.8Mpa; 28d compressive strength is about 51.4Mpa.

[0100] The room temperature or normal temperature in the embodiments of the present invention refers to 25±3°C.

[0101] Example 1

[0102] An integrated system for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, such as Figure 1 As shown, it includes a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit;

[0103] Among them, the cement kiln flue gas carbon capture unit and the calcium ion leaching unit are connected in parallel and then connected in series with the calcium carbonate synthesis unit.

[0104] The cement kiln flue gas carbon capture unit comprises a flue gas pretreatment tower 1 and a carbon dioxide absorption tower 2 which are connected in series.

[0105] The flue gas pretreatment tower 1 and the carbon dioxide absorption tower 2 are connected by a pipeline;

[0106] The carbon dioxide absorption tower 2 includes a heat exchange device;

[0107] A gas outlet is provided at the top of the carbon dioxide absorption tower 2 for discharging the flue gas after the carbon dioxide is captured;

[0108] The calcium ion leaching unit comprises a calcium ion leaching kettle 3 and a solid-liquid separation kettle 4 which are sequentially connected in series;

[0109] The calcium ion leaching kettle 3 is provided with a pH detection device and a calcium ion concentration detection device;

[0110] The solid-liquid separation kettle 4 includes a filter screen with a mesh size of 400-800 meshes, and a channel at the bottom, which is provided with a valve.

[0111] The calcium carbonate synthesis unit comprises a calcium carbonate synthesis kettle 5, a calcium carbonate centrifugal kettle 6 and a calcium carbonate drying kettle 7 which are sequentially connected in series.

[0112] The connection between the calcium carbonate centrifugal kettle 6 and the calcium carbonate drying kettle 7 includes a transmission device to ensure that the solid can be transferred to the calcium carbonate drying kettle 7;

[0113] The calcium carbonate synthesis reactor 5 is equipped with a stirring device;

[0114] The calcium carbonate centrifugal kettle 6 has a pipeline for discharging liquid outside the unit, and its opening and closing can be controlled by a valve.

[0115] Example 2

[0116] A process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, using the integrated system described in Example 1, comprises the following steps:

[0117] (1) Triethanolamine, sodium hydroxide and water are mixed in a mass ratio of 10:20:70 to obtain an absorption liquid, and the absorption liquid is passed into a carbon dioxide absorption tower 2. Flue gas from a cement kiln is passed through a flue gas pretreatment tower 1 and moistened with water. After the temperature is reduced to 40°C, the flue gas is heated at 45000 Nm 3 / h is passed into the carbon dioxide absorption tower 2, and the carbon dioxide in the flue gas is captured by the absorption liquid to obtain the carbon dioxide absorption liquid.

[0118] (2) Ammonium chloride and water are mixed in a mass ratio of 30:70 to obtain an ion leachate, and the obtained ion leachate is added to the calcium ion leaching kettle 3, and then steel slag with a particle size of less than 100 μm is poured in, and tetrachloroethylene is added as a dispersant. Among them, the mass ratio of steel slag, leachate, and dispersant is 30:68:2. After stirring at a rate of 500 r / min for 20 minutes in the calcium ion leaching kettle 3, the calcium ion concentration in the solution is detected. If the calcium ion concentration does not reach 3 mol / L, 5% of the total mass of the material in the current calcium ion leaching kettle 3 is added to continue stirring and reacting until the calcium ion concentration reaches 3 mol / L and then the stirring reaction is stopped. Then sodium hydroxide is added as a pH adjuster to adjust the pH of the solution to 8, and then the solution and solid waste are passed to the solid-liquid separation kettle 4, and the solid waste is separated through the filter screen. The obtained filtrate is the calcium ion leachate.

[0119] (3) The carbon dioxide absorption liquid obtained in step (1) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 20 kg / min, and the calcium ion leaching solution obtained in step (2) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 80 kg / min, and stirred at a rate of 1000 r / min. After the introduction is completed, stirring is continued for 10 minutes. After the stirring is completed, the solution in the synthesis kettle is introduced into the calcium carbonate centrifugal kettle 6 and centrifuged at a rate of 10000 r / min for 1.5 minutes. After the centrifugation is completed, the supernatant is discharged, and the calcium carbonate precipitate is transported to the calcium carbonate drying kettle 7 and dried at 60° C. for 12 hours to obtain nano calcium carbonate seeds with a particle size of 15-90 nm.

[0120] Example 3

[0121] A process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, using the integrated system described in Example 1, comprises the following steps:

[0122] (1) Triisopropanolamine, sodium hydroxide and water are mixed in a mass ratio of 5:25:70 to obtain an absorption liquid, and the absorption liquid is passed into a carbon dioxide absorption tower 2. Flue gas from a cement kiln is passed through a flue gas pretreatment tower 1 and moistened with water. After the temperature is reduced to 30°C, the flue gas is heated at 45000 Nm 3 / h is passed into the carbon dioxide absorption tower 2, and the carbon dioxide in the flue gas is captured by the absorption liquid to obtain the carbon dioxide absorption liquid.

[0123] (2) Mix hydrochloric acid and water in a mass ratio of 40:60 to obtain an ion leachate, add it to the calcium ion leaching kettle 3, then pour in steel slag with a particle size of less than 100 μm, and add sodium polyacrylate as a dispersant. Among them, the mass ratio of steel slag, leachate, and dispersant is 40:59:1. After stirring at a rate of 800 r / min for 20 minutes in the calcium ion leaching kettle 3, the calcium ion concentration in the solution is detected. If the calcium ion concentration does not reach 0.3 mol / L, add 5% of the total mass of the material in the current calcium ion leaching kettle 3 and continue stirring the reaction until the calcium ion concentration reaches 0.3 mol / L and then stop stirring the reaction. Then add sodium hydroxide as a pH regulator to adjust the pH to 8, and then pass the solution and solid waste to the solid-liquid separation kettle 4, the solid waste is separated by a filter, and the obtained filtrate is the calcium ion leachate.

[0124] (3) The carbon dioxide absorption liquid obtained in step (1) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 20 kg / min, and the calcium ion leaching solution obtained in step (2) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 60 kg / min, and stirred at a rate of 800 r / min. After the introduction is completed, stirring is continued for 5 minutes. After the stirring is completed, the solution in the synthesis kettle is introduced into the calcium carbonate centrifugal kettle 6 and centrifuged at a rate of 8000 r / min for 1 minute. After the centrifugation is completed, the supernatant is discharged, and the calcium carbonate precipitate is transported to the calcium carbonate drying kettle 7 and dried at 80° C. for 10 hours to obtain nano calcium carbonate seeds with a particle size of 40-200 nm.

[0125] Example 4

[0126] A process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, using the integrated system described in Example 1, comprises the following steps:

[0127] (1) Diethanol monoisopropanolamine, sodium hydroxide and water are mixed in a mass ratio of 8:24:68 to obtain an absorption liquid, and the absorption liquid is passed into a carbon dioxide absorption tower 2. Flue gas from a cement kiln is passed through a flue gas pretreatment tower 1 and moistened with water. After the temperature is reduced to 30°C, the flue gas is heated at 45000 Nm 3 / h is passed into the carbon dioxide absorption tower 2, and the carbon dioxide in the flue gas is captured by the absorption liquid to obtain the carbon dioxide absorption liquid.

[0128] (2) Acetic acid and water are mixed in a mass ratio of 35:65 to obtain an ion leachate, which is added to the calcium ion leaching kettle 3, and then carbide slag with a particle size of less than 100 μm is poured in, and sodium polycarboxylate is added as a dispersant. Among them, the mass ratio of carbide slag, leachate and dispersant is 25:72.5:2.5. After stirring at a rate of 800 r / min for 20 minutes in the calcium ion leaching kettle 3, the calcium ion concentration in the solution is detected. If the calcium ion concentration does not reach 1.5 mol / L, carbide slag of 5% of the total mass of the material in the current calcium ion leaching kettle 3 is added to continue stirring and reacting until the calcium ion concentration reaches 1.5 mol / L and then the stirring reaction is stopped. Then potassium hydroxide is added as a pH regulator to adjust the pH to 8, and then the solution and solid waste are passed to the solid-liquid separation kettle 4, and the solid waste is separated through a filter screen, and the obtained filtrate is the calcium ion leachate.

[0129] (3) The carbon dioxide absorption liquid obtained in step (1) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 30 kg / min, and the calcium ion leaching solution obtained in step (2) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 90 kg / min, and stirred at a rate of 1500 r / min. After the introduction is completed, stirring is continued for 5 minutes. After the stirring is completed, the solution in the synthesis kettle is introduced into the calcium carbonate centrifugal kettle 6 and centrifuged at a rate of 12000 r / min for 1 minute. After the centrifugation is completed, the supernatant is discharged, and the calcium carbonate precipitate is transported to the calcium carbonate drying kettle 7 and dried at 75° C. for 11 hours to obtain nano calcium carbonate seeds with a particle size of 30-120 nm.

[0130] Example 5

[0131] A process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, using the integrated system described in Example 1, comprises the following steps:

[0132] (1) Triethanolamine, sodium hydroxide and water are mixed in a mass ratio of 10:25:65 to obtain an absorption liquid, and the absorption liquid is passed into a carbon dioxide absorption tower 2. Flue gas from a cement kiln is passed through a flue gas pretreatment tower 1 and moistened with water. After the temperature is reduced to 30°C, the flue gas is heated at 45000 Nm 3 / h is passed into the carbon dioxide absorption tower 2, and the carbon dioxide in the flue gas is captured by the absorption liquid to obtain the carbon dioxide absorption liquid.

[0133] (2) Acetic acid and water are mixed in a mass ratio of 35:65 to obtain an ion leachate, which is added to the calcium ion leaching kettle 3, and then carbide slag with a particle size of less than 100 μm is poured in, and sodium polycarboxylate is added as a dispersant. The mass ratio of carbide slag, leachate and dispersant is 30:67:3. After stirring at a rate of 800 r / min for 20 minutes in the calcium ion leaching kettle 3, the calcium ion concentration in the solution is detected. If the calcium ion concentration does not reach 0.9 mol / L, carbide slag of 5% of the total mass of the material in the current calcium ion leaching kettle 3 is added to continue stirring and reacting until the calcium ion concentration reaches 0.9 mol / L and then the stirring reaction is stopped. Potassium hydroxide is then added as a pH regulator to adjust the pH to 8, and then the solution and solid waste are passed to the solid-liquid separation kettle 4, and the solid waste is separated through a filter screen, and the obtained filtrate is the calcium ion leachate.

[0134] (3) The carbon dioxide absorption liquid obtained in step (1) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 30 kg / min, and the calcium ion leaching solution obtained in step (2) is introduced into the calcium carbonate synthesis kettle 5 at a rate of 70 kg / min, and stirred at a rate of 500 r / min. After the introduction is completed, stirring is continued for 5 minutes. After the stirring is completed, the solution in the synthesis kettle is introduced into the calcium carbonate centrifugal kettle 6 and centrifuged at a rate of 5000 r / min for 3 minutes. After the centrifugation is completed, the supernatant is discharged, and the calcium carbonate precipitate is transported to the calcium carbonate drying kettle 7 and dried at 90° C. for 8 hours to obtain nano calcium carbonate seeds with a particle size of 40-140 nm.

[0135] Technical effects:

[0136] Cement was used as the blank control group;

[0137] The nano-scale calcium carbonate prepared in Example 2 was added to cement in a manner of 0.5%, wherein the nano-calcium carbonate and cement clinker were mixed and stirred together with water. The obtained cement sample had a 1d compressive strength of 16.64Mpa, which was about 16% higher than that of the blank control group; a 3d compressive strength of 35.18Mpa, which was about 7% higher than that of the blank control group; and a 28d compressive strength of 52.41Mpa, which was about 2% higher than that of the blank control group.

[0138] The nano-scale calcium carbonate prepared in Example 3 was added to cement in a 2% mixing method, wherein the nano-calcium carbonate and cement clinker were mixed and stirred together with water. The obtained cement sample had a 1d compressive strength of 17.84Mpa, which was about 30% higher than that of the blank control group; a 3d compressive strength of 35.90Mpa, which was about 20% higher than that of the blank control group; and a 28d compressive strength of 52.94Mpa, which was about 3% higher than that of the blank control group.

[0139] The nano-scale calcium carbonate prepared in Example 4 was added to cement in a 5% mixing method, wherein the nano-calcium carbonate and cement clinker were mixed and stirred together with water. The obtained sample had a 1d compressive strength of 19.72Mpa, which was about 40% higher than that of the blank control group; a 3d compressive strength of 36.75Mpa, which was about 12% higher than that of the blank control group; and a 28d compressive strength of 51.55Mpa, which was similar to that of the blank control group.

[0140] The nano-scale calcium carbonate prepared in accordance with Example 5 was added to cement (instead of cement clinker) in the form of internal mixing of 2%, wherein the nano-calcium carbonate and cement clinker were mixed and stirred with water. The obtained sample had a 1d compressive strength of 15.16Mpa, which was about 6% higher than that of the blank control group, a 3d compressive strength of 33.43Mpa, which was about 2% higher than that of the blank control group, and a 28d compressive strength of 51.49Mpa, which was similar to that of the blank control group.

[0141] The average particle size of calcium carbonate, the calcium carbonate addition method, and the 1d, 3d, and 28d compressive strengths are shown in Table 1 below.

[0142] Table 1

[0143]

[0144] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An integrated process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas, characterized in that: The equipment used includes a cement kiln flue gas carbon capture unit, a calcium ion leaching unit and a calcium carbonate synthesis unit; Wherein, the cement kiln flue gas carbon capture unit and the calcium ion leaching unit are connected in parallel and then connected in series with the calcium carbonate synthesis unit; In the cement kiln flue gas carbon capture unit, carbon dioxide in the cement kiln flue gas is captured using an organic alcohol amine solution as an absorbent to obtain a carbon dioxide absorption liquid; in the calcium ion leaching unit, calcium ions in solid waste are leached using the leaching liquid to obtain a calcium ion leaching liquid; The organic alcohol amine solution is obtained by mixing the organic alcohol amine, the alkali metal compound and the wetting liquid in a mass ratio of (5-10): (20-25): (65-75); The calcium ion leaching is specifically to mix the solid waste, the leachate and the dispersant and stir and leach until the calcium ion concentration in the calcium ion leachate is 0.3-6 mol / L; In the calcium carbonate synthesis unit, the carbon dioxide absorption liquid and the calcium ion leaching liquid are stirred and mixed for reaction, and after the reaction is completed, centrifugal separation and drying are performed to obtain the nano-scale calcium carbonate seed crystals; The mass ratio of the carbon dioxide absorption liquid to the calcium ion leaching liquid added per unit time is 1:2-5.

2. The integrated process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas according to claim 1, characterized in that: The cement kiln flue gas carbon capture unit comprises a flue gas pretreatment tower and a carbon dioxide absorption tower connected in series; The calcium ion leaching unit comprises a calcium ion leaching kettle and a solid-liquid separation kettle connected in series; The calcium carbonate synthesis unit comprises a calcium carbonate synthesis kettle, a calcium carbonate centrifugal kettle and a calcium carbonate drying kettle which are sequentially connected in series.

3. The integrated process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas according to claim 1, characterized in that: The organic alcohol amine is one or any combination of triethanolamine, triisopropanolamine, diethanol monoisopropanolamine and monoethanol diisopropanolamine; The alkali metal compound is one or any combination of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; The wetting fluid is water.

4. The integrated process for preparing nano-scale calcium carbonate seeds by capturing carbon from cement kiln flue gas according to claim 3, characterized in that: The solid waste is carbide slag or steel slag, and the particle size is less than 100 μm; The leaching solution is one or any combination of ammonium chloride solution, hydrochloric acid solution and acetic acid solution, wherein the mass ratio of the solute to the solvent is (25-50): (50-75); The dispersant is sodium polyacrylate or sodium polycarboxylate.

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