Method for regulating carbonization product crystal form and improving carbonization performance of low-carbon clinker

Abstract

The application discloses a method for regulating the crystal form of carbonization products and improving the carbonization performance of low-carbon clinker, which comprises the following steps: 1) mixing low-carbon clinker, a crystal form regulating agent and water, and then performing compression molding; the crystal form regulating agent can ionize low-alkaline metal ions and sulfate ions in water; 2) drying the obtained molded sample, and then performing carbonization to obtain carbonization products. The method can change the carbonization reaction process, regulate the crystal form of CaCO3 in the carbonization products, effectively promote the formation of the aragonite crystal form, play a more effective filling and connecting role on the pores, and be beneficial to the continuous carbonization of the low-carbon clinker. Under the premise of reducing the molding amount of the low-carbon clinker, the carbonization strength and the carbon sequestration rate of the low-carbon clinker after molding and carbonization can be effectively improved, and the method is suitable for different types of low-carbon clinker.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker. Background Art

[0002] Cement manufacturing is one of the world's largest sources of CO2 emissions, primarily from the decomposition of limestone during cement production. This makes CO2 emissions a critical element of cement manufacturing that must be strictly controlled. Compared to Portland cement clinker, low-carbon cement clinker (low-calcium cement clinker) requires less limestone and is fired at a lower temperature, reducing CO2 emissions by approximately 20% during production. Furthermore, considering the CO2 absorbed by low-carbon cement clinker during subsequent carbonation (approximately 60% of theoretical carbon sequestration), total CO2 emissions can be reduced by approximately 50%. Consequently, low-carbon cement clinker has become a research hotspot in recent years.

[0003] Low-carbon clinker mainly forms strength by absorbing CO2 after molding to generate CaCO3, which fills the pores in the structure. There are three crystal forms of CaCO3 in the carbonization product, namely calcite, aragonite, and vaterite. Among them, calcite and vaterite are spherical, granular, and massive, while aragonite is needle-shaped and has a large aspect ratio. Therefore, it is believed that making the carbonization product aragonite can effectively improve the carbonization performance of low-carbon clinker. However, aragonite and vaterite are metastable and can easily be gradually converted into calcite (calcite is the most stable) under water conditions.

[0004] Existing research usually adopts chemical synthesis to prepare vaterite and aragonite. First, CaCl2 and (NH4)2CO3 are reacted under certain conditions to prepare vaterite. Then MgCl2 is added to convert vaterite into aragonite under the condition of 50-90℃. The reaction conditions need to be strictly controlled. However, low carbon clinker needs to be formed and carbonized to form strength, which is affected by the forming method, CO2 diffusion, low carbon clinker Ca 2+ Due to the influence of multiple factors such as dissolution rate, water dosage, temperature, CO2 concentration, etc., the concentration of each ion gradually changes during the carbonization process and cannot be effectively controlled; in addition, it is usually necessary to first consider the impact of carbonization conditions on the uniformity of carbonization and the final carbonization performance, and it is difficult to take into account the regulation of the crystal form of CaCO3 in the carbonization product; and the essence of the carbonization reaction of low-carbon clinker is an acid-base neutralization reaction, all of which lead to the easy formation of calcite after carbonization.

[0005] How to effectively regulate the crystal form of CaCO3 and improve the carbonization performance of low-carbon clinker under the complex carbonization conditions of low-carbon clinker has become a technical problem that needs to be solved urgently. Summary of the Invention

[0006] The purpose of the present invention is to provide a method that can regulate the crystal form of carbonization products and improve the carbonization performance of low-carbon clinker. It can change the carbonization reaction process to regulate the crystal form of CaCO3 in the carbonization product, effectively promote the formation of aragonite, play a more effective filling and connecting role on the pores, and is beneficial to the continuous carbonization of low-carbon clinker. On the premise of reducing the amount of low-carbon clinker molding, it effectively improves the carbonization strength and carbon fixation rate of low-carbon clinker molding after carbonization, and is suitable for different types of low-carbon clinker.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0009] (1) mixing low-carbon clinker, a crystal form regulator and water, and pressing to form; the crystal form regulator can ionize low-alkaline metal ions and sulfate ions in water;

[0010] (2) After the obtained molded sample is dried, it is carbonized to obtain a carbonized product.

[0011] According to the above scheme, the low-carbon clinker in step (1) is mainly composed of one or more of the common calcium silicate minerals βC2S, γC2S, C7MS4, C3S2, CS, C2AS, and C2MS2, and the mass ratio of CaO to SiO2 in the chemical composition of the low-carbon clinker is 0.8-1.9.

[0012] Preferably, the chemical components and their mass percentages in the low-carbon clinker include: CaO 42-59%, SiO2 30-47%, Al2O3 0-10%, Fe2O3 0-10%, and MgO 0-5%.

[0013] According to the above scheme, the crystal form regulator in step (1) includes at least one of MgSO4 and CuSO4, and other low-alkaline metal ions (Mg 2+ and / or Cu 2+ ) and SO4 2- of substance.

[0014] According to the above scheme, the amount of the crystal form regulator in step (1) is 0.5-5wt% of the amount of low-carbon clinker.

[0015] Preferably, in addition to the crystal form regulator, MgCl2 accounting for 0.5-5wt% of the low-carbon clinker amount can be added as a water retaining agent to improve carbonization stability.

[0016] According to the above scheme, the amount of water used in step (1) is 10-25wt% of the amount of low-carbon clinker used.

[0017] According to the above scheme, in step (2), the moisture content after drying is 4-20wt%.

[0018] Furthermore, in step (2), the sample is dried at a temperature of 20-50°C.

[0019] According to the above scheme, the carbonization conditions include: CO2 concentration of 15-100%, temperature of 20-50°C, humidity of 40-80%, and pressurization pressure of 0-0.3MPa.

[0020] According to the above scheme, the carbonization time is 6-72h.

[0021] In the carbonized product prepared according to the above scheme, the content of aragonite is greater than 6.5 wt %, and the average particle size of aragonite is greater than 24 nm.

[0022] Preferably, the aragonite content in the obtained carbonized product is greater than 15 wt%.

[0023] Furthermore, the carbonization product prepared according to the above scheme can increase the carbonization intensity by 10-30% and the carbon fixation rate by 10-60% compared with the condition without adding the crystal form modifier.

[0024] The principle of the present invention is:

[0025] The essence of the carbonization reaction of low carbon clinker is the process in which the low carbon clinker dissolves alkaline Ca(OH)2 or alkaline calcium silicate hydrate, and reacts with H2CO3 to produce CaCO3 by acid-base neutralization. This reaction is easy to occur and is an exothermic reaction. The present invention adopts a crystal form regulator suitable for the carbonization of low carbon clinker, which can be ionized into low alkaline cations (Mg 2+ or Cu 2+ etc.) and SO4 2- Taking MgSO4 as an example, the mechanism of the effect of anion on the carbonization of low-carbon clinker is the following reactions 1 to 4:

[0026] Reaction 1 is that MgSO4 promotes the conversion of Ca in low carbon clinker 2+ Dissolved as CaSO4·2H2O which is slightly soluble in water:

[0027] MgSO4+CaO·xSiO2+yH2O→Mg(OH)2·xSiO2·(y-3)H2O+CaSO4·2H2O

[0028] Reaction 2 is the dissolution of CO2 in water:

[0029] CO2+H2O→H2CO3

[0030] Reaction 3 is the carbonization of Mg(OH)2 to Mg(HCO3)2:

[0031] Mg(OH)2·xSiO2·(y-3)H2O+2H2CO3+H2O→Mg(HCO3)2+xSiO2·yH2O

[0032] Reaction 4 is the carbonization of CaSO4·2H2O by Mg(HCO3)2 to CaCO3 and the reformation of MgSO4:

[0033] Mg(HCO3)2+CaSO4·2H2O→CaCO3+CO2+3H2O+MgSO4

[0034] (1) The crystal form regulator MgSO4 can be recycled and only plays the role of a reaction aid in carbonization. It generates slightly soluble Mg(OH)2 silica gel complex and slightly soluble CaSO4·2H2O through reaction 1, which can accelerate and continuously promote the conversion of Ca in low-carbon clinker. 2+ The dissolution of Mg(HCO3)2 can be carried out through reactions 2, 3, and 4 with the help of the generated Mg(HCO3)2, effectively increasing the carbonizable amount of low-carbon clinker;

[0035] (2) The water content of low carbon clinker during carbonization is much less than that of CaCO3 synthesized by chemical synthesis, and the alkalinity of Ca(OH)2 is relatively strong, which makes the Ca in water 2+ OH - The concentration is relatively high, and the carbonization reaction of low-carbon clinker is essentially an acid-base neutralization reaction, which results in a fast rate of CaCO3 generation and a high degree of supersaturation, and calcite is easily generated after carbonization. Although the acid-base neutralization reaction has the highest priority and the fastest reaction in the double decomposition reaction, due to the low solubility and weak acidity of H2CO3, the amount of H2CO3 in water is insufficient relative to the low-carbon clinker, and it is consumed and affected by diffusion, making it impossible to completely prevent the double decomposition reaction of the crystal form regulator. Through reactions 1 to 4, the acid-base neutralization reaction is converted into a non-acid-base neutralization double decomposition reaction, generating slightly soluble CaSO4·2H2O, which reduces the alkalinity of the reaction system and further reduces the Ca in water. 2+ The concentration of Ca dissolved by the crystal form regulator 2 + It cannot be directly carbonized by H2CO3, but can only undergo carbonization through reactions 2, 3, and 4 with the help of the generated Mg(HCO3)2, which slows down the rate of CaCO3 generated by the crystal form regulator and reduces the supersaturation, thereby promoting the formation of aragonite.

[0036] (3) The addition of crystal modifier changes the carbonization reaction from acid-base neutralization reaction to non-acid-base neutralization double decomposition reaction, which not only promotes the Ca content in low-carbon clinker to increase, but also promotes the carbonization of low-carbon clinker. 2+ The dissolution of Ca 2+ The carbonization rate makes this part of Ca 2+It can be better transported with water, so that CaCO3 is generated in the pores on the surface of non-low-carbon clinker, and aragonite with a large aspect ratio is generated, which plays a more effective role in filling and connecting the pores, which is beneficial to the continuous carbonization of low-carbon clinker;

[0037] (4) For Ca itself 2+ Low carbon clinker with slow dissolution rate (low calcium-silicon ratio relative to low carbon clinker with high calcium-silicon ratio, its Ca 2+ The dissolution rate is slower, the carbonization rate is slower), the effect of the crystal form regulator is more obvious, and more aragonite can be produced;

[0038] (5) Since reaction 1 is easily generated during the pressing and molding of low-carbon clinker, CaSO4·2H2O is generated, which will reduce the molding density of the low-carbon clinker and thus reduce the water retention. Therefore, a certain amount of water-retaining agent (MgCl2) can be compounded into the crystal form regulator. However, the solubility of CaCl2 generated by reaction 1 of MgCl2 alone is high, which makes the rate of reaction 1 slower than that of MgSO4, and does not promote the formation of aragonite, and cannot achieve the effect of MgSO4.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1) The present invention uses sulfate of low alkaline metal (Mg and / or Cu) as a crystal form regulator and applies it to the carbonization process of low carbon clinker to promote the carbonization of Ca in low carbon clinker. 2+ dissolution, while reducing the alkalinity of the reaction system and reducing the dissolved Ca 2+ The carbonization rate makes this part of Ca 2+ It can be better transported with water, so that CaCO3 is generated in the pores on the surface of non-low-carbon clinker, and promotes the formation of aragonite with a large aspect ratio, which plays a more effective role in filling and connecting the pores, is conducive to the continuous carbonization of low-carbon clinker, effectively improves the carbonization strength and carbon fixation rate of low-carbon clinker after molding and carbonization, and can significantly reduce the amount of low-carbon clinker in the product, thereby reducing costs, providing a new idea for the preparation of high-performance carbonized products;

[0041] 2) The preparation method of the present invention is relatively simple, easy to operate, has wide applicability to low-carbon clinker, and is suitable for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The XRD patterns of the carbonized products obtained in Examples 1 to 5 and Comparative Example 1 are shown;

[0043] Figure 2 The XRD patterns of the carbonized products obtained in Comparative Examples 4 to 6 and 8 to 10 are shown;

[0044] Figure 3 The XRD patterns of the carbonized products obtained in Examples 6 and 7 and Comparative Examples 2, 3, and 7 are shown;

[0045] Figure 4 This is the SEM image of the carbonized product obtained in Example 1. DETAILED DESCRIPTION

[0046] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.

[0047] The following are the low-carbon clinker and chemical reagents used in the specific examples:

[0048] Different types of low-carbon clinker were obtained. The chemical composition and mineral composition of the low-carbon clinker used in the embodiment of the present invention are shown in Table 1 and Table 2, respectively, and the low-carbon clinker was ground to R45 μm ≤ 20% before use.

[0049] Table 1 Chemical composition of low carbon clinker (%)

[0050] name CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> MgO Low carbon clinker 1 56.95 32.11 3.10 1.87 3.08 Low carbon clinker 2 49.98 39.81 3.07 2.35 2.10 Low carbon clinker 3 42.33 46.86 3.27 2.58 1.73

[0051] Table 2 Mineral composition of low carbon clinker (%)

[0052] name <![CDATA[βC2S]]> <![CDATA[C7MS4]]> <![CDATA[C3S2]]> CS <![CDATA[C2AS]]> <![CDATA[C2MS2]]> <![CDATA[SiO2]]> Low carbon clinker 1 38.8 52.4 0 0 6.2 2.7 0 Low carbon clinker 2 8.0 0 56.7 15.6 4.4 13.8 1.6 Low carbon clinker 3 0 0 0 83.3 2.0 8.3 6.3

[0053] The mass ratios of CaO to SiO2 (i.e., the calcium-silicon mass ratios) in the chemical compositions of low-carbon clinkers 1, 2, and 3 are 1.77, 1.26, and 0.90, respectively.

[0054] In the following examples and comparative examples, the chemical reagents used are analytically pure MgSO4, analytically pure CuSO4·5H2O, analytically pure MgCl2·6H2O, analytically pure Na2SO4, analytically pure FeSO4, and analytically pure Mg(HCO3)2.

[0055] Example 1

[0056] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0057] 1. Ratio

[0058] Weigh 1100 parts of low carbon clinker, 2 parts of analytical grade MgSO4, and 15 parts of water;

[0059] 2. Sample preparation

[0060] First, weighed water and MgSO4 were placed in a blender and stirred until MgSO4 was completely dissolved in the water. Then, low-carbon clinker 1 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample at this time was 13.9 g. The mass of low-carbon clinker 1 contained in the sample (molding amount, the same below) can be calculated as 11.88 g according to 13.9 g * 100 g / (100 g + 15 g + 2 g).

[0061] 3. Pre-drying and carbonization

[0062] The sample was dried under natural conditions to a moisture content of 9% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of 99% carbon dioxide concentration, 30°C temperature, 60% humidity, and 0.3MPa air pressure (pressure indication 0.3MPa) to obtain a carbonized product.

[0063] Example 2

[0064] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0065] 1. Ratio

[0066] Weigh 1 100 parts of low carbon clinker, 1 part of analytical grade MgSO4, and 15 parts of water;

[0067] 2. Sample preparation

[0068] First, weighed water and MgSO4 were placed in a blender and stirred until MgSO4 was completely dissolved in the water. Then, low-carbon clinker 1 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was found to be 14.4 g. The mass of low-carbon clinker 1 contained in the sample was calculated to be 12.41 g according to 14.4 g * 100 g / (100 g + 15 g + 1 g).

[0069] 3. Pre-drying and carbonization

[0070] The sample was dried under natural conditions to a moisture content of 9% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of 99% carbon dioxide concentration, 30°C temperature, 60% humidity, and 0.3MPa air pressure (pressure indication 0.3MPa) to obtain a carbonized product.

[0071] Example 3

[0072] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0073] 1. Ratio

[0074] Weigh 1100 parts of low carbon clinker, 3 parts of analytical grade MgSO4, and 15 parts of water;

[0075] 2. Sample preparation

[0076] First, weighed water and MgSO4 were placed in a blender and stirred until MgSO4 was completely dissolved in the water. Then, low-carbon clinker 1 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was 13.7 g. The mass of low-carbon clinker 1 contained in the sample was calculated as 11.61 g according to 13.7 g * 100 g / (100 g + 15 g + 3 g).

[0077] 3. Pre-drying and carbonization

[0078] The sample was dried under natural conditions to a moisture content of 10% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication 0.3MPa) to obtain a carbonized product.

[0079] Example 4

[0080] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0081] 1. Ratio

[0082] Weigh 1100 parts of low-carbon clinker, 2 parts of analytically pure MgSO4, 2 parts of analytically pure MgCl2·6H2O, and 13.9 parts of water (15-2*108 / 203, according to the calculation, the water introduced by the analytically pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 15 parts);

[0083] 2. Sample preparation

[0084] First, weighed water, MgSO4, and MgCl2·6H2O were placed in a blender and stirred until the MgSO4 and MgCl2·6H2O were completely dissolved in the water. Then, low-carbon clinker 1 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was found to be 13.7 g. The mass of low-carbon clinker 1 contained in the sample was calculated to be 11.62 g according to 13.7 g*100 g / (100 g+13.9 g+2 g+2 g).

[0085] 3. Pre-drying and carbonization

[0086] The sample was dried under natural conditions to a moisture content of 10% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication 0.3MPa) to obtain a carbonized product.

[0087] Example 5

[0088] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0089] 1. Ratio

[0090] Weigh 1100 parts of low-carbon clinker, 4 parts of analytically pure CuSO4·5H2O, 2 parts of analytically pure MgCl2·6H2O, and 12.5 parts of water (15-4*90 / 249.5-2*108 / 203, taking into account the water introduced by the analytically pure CuSO4·5H2O and analytically pure MgCl2·6H2O according to the calculation to ensure that the total amount of water is 15 parts);

[0091] 2. Sample preparation

[0092] First, weighed water, CuSO4·5H2O, and MgCl2·6H2O were placed in a blender and stirred until the CuSO4·5H2O and MgCl2·6H2O were completely dissolved in the water. Then, low-carbon clinker 1 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was 13.6 g. The mass of the low-carbon clinker 1 contained in the sample was calculated to be 11.48 g according to 13.6 g*100 g / (100 g+12.5 g+4 g+2 g).

[0093] 3. Pre-drying and carbonization

[0094] The sample was dried under natural conditions to a moisture content of 10% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication 0.3MPa) to obtain a carbonized product.

[0095] Example 6

[0096] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0097] 1. Ratio

[0098] Weigh 2100 parts of low-carbon clinker, 2 parts of analytically pure MgSO4, 2 parts of analytically pure MgCl2·6H2O, and 18.9 parts of water (20-2*108 / 203, according to the calculation, the water introduced by the analytically pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 20 parts);

[0099] 2. Sample preparation

[0100] First, weighed water, MgSO4, and MgCl2·6H2O were placed in a blender and stirred until MgSO4 and MgCl2·6H2O were completely dissolved in the water. Then, low-carbon clinker 2 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was found to be 12.6 g. The mass of low-carbon clinker 2 contained in the sample can be calculated as 10.25 g according to 12.6 g*100 g / (100 g+18.9 g+2 g+2 g).

[0101] 3. Pre-drying and carbonization

[0102] The sample was dried under natural conditions to a moisture content of 14% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication 0.3MPa) to obtain a carbonized product.

[0103] Example 7

[0104] A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker comprises the following steps:

[0105] 1. Ratio

[0106] Weigh 3100 parts of low-carbon clinker, 2 parts of analytically pure MgSO4, 2 parts of analytically pure MgCl2·6H2O, and 18.9 parts of water (20-2*108 / 203, according to the calculation, the water introduced by the analytically pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 20 parts);

[0107] 2. Sample preparation

[0108] First, weighed water, MgSO4, and MgCl2·6H2O were placed in a blender and stirred until the MgSO4 and MgCl2·6H2O were completely dissolved in the water. Then, low-carbon clinker 3 was added and stirred for 1 minute. The mixed wet material was pressed into a cylindrical sample with a diameter of 2 cm and a height of 2 cm at a molding pressure of 10 MPa. The mass of the sample was found to be 12.6 g. The mass of low-carbon clinker 3 contained in the sample was calculated to be 10.25 g according to 12.6 g * 100 g / (100 g + 18.9 g + 2 g + 2 g).

[0109] 3. Pre-drying and carbonization

[0110] The sample was dried under natural conditions to a moisture content of 14% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication 0.3MPa) to obtain a carbonized product.

[0111] Comparative Example 1

[0112] A low-carbon clinker carbonization process, the preparation method of which is substantially the same as that of Example 1, except that no crystal form modifier is introduced, and the specific steps include the following:

[0113] Weigh 1100 parts of low-carbon clinker 1 and 15 parts of water, and press them into shape using the same method (to form a cylindrical sample of the same specifications as in Example 1). The mass of the sample at this time is 14.8 g. The mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.8g*100g / (100g+15g), which is 12.9 g (higher than the molding amount described in Example 1). The sample is then dried under natural conditions to a moisture content of 7% (the moisture content with the highest carbonization strength obtained from the carbonization test after drying to different moisture contents). Finally, it is carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3 MPa (pressure indication number 0.3 MPa) to obtain a carbonized product.

[0114] Comparative Example 2

[0115] A low-carbon clinker carbonization process, the preparation method of which is substantially the same as that of Example 6, except that no crystal form modifier is introduced, and the specific steps include the following:

[0116] Weigh 100 parts of low-carbon clinker 2 and 20 parts of water, and press into shape using the same method. The mass of the sample is 13.0 g. The mass of low-carbon clinker 2 contained in the sample can be calculated based on 13.0 g*100 g / (100 g+20 g), which is 10.8 g. The sample is then dried under natural conditions to a moisture content of 16% (the moisture content with the highest carbonization strength obtained from the carbonization test after drying to different moisture contents). Finally, it is carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3 MPa (pressure indication number 0.3 MPa) to obtain a carbonized product.

[0117] Comparative Example 3

[0118] A low-carbon clinker carbonization process, the preparation method of which is substantially the same as that of Example 7, except that no crystal form modifier is introduced, and the specific steps include the following:

[0119] Weigh 100 parts of low-carbon clinker 3 and 20 parts of water, and press into shape using the same method. The mass of the sample is 12.8 g. The mass of low-carbon clinker 3 contained in the sample can be calculated based on 12.8 g*100 g / (100 g+20 g), which is 10.7 g. The sample is then dried under natural conditions to a moisture content of 16% (the moisture content with the highest carbonization strength obtained from the carbonization test after drying to different moisture contents). Finally, it is carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3 MPa (pressure indication number 0.3 MPa) to obtain a carbonized product.

[0120] Comparative Example 4

[0121] A low carbon clinker carbonization process, the preparation method is roughly the same as that of Example 1, the components and their weight percentages are: low carbon clinker 1 100 parts, analytical pure MgCl2·6H2O 2 parts, 13.9 parts of water (15-2*108 / 203, according to the calculation, the water introduced in the analytical pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 15 parts), and the specific steps include: after pressing and molding by the same method, the mass of the sample at this time is weighed to be 14.7g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.7g*100g / (100g+13.9g+2g) to be 12.68g (higher than the molding amount described in Example 1), and then the sample is placed under natural conditions to be dried to a moisture content of 7% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20h under the conditions of carbon dioxide concentration of 99%, temperature of 30℃, humidity of 60%, and air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0122] Comparative Example 5

[0123] A low carbon clinker carbonization process, the preparation method is roughly the same as that of Example 1, the components and their weight percentages are: low carbon clinker 1 100 parts, analytical pure MgCl2·6H2O 4 parts, 12.9 parts of water (15-4*108 / 203, according to the calculation, the water introduced in the analytical pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 15 parts), and the specific steps include: after pressing and molding by the same method, the mass of the sample at this time is weighed to be 14.7g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.7g*100g / (100g+12.9g+4g) to be 12.57g (higher than the molding amount described in Example 1), and then the sample is placed under natural conditions to be dried to a moisture content of 7% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20h under the conditions of carbon dioxide concentration of 99%, temperature of 30℃, humidity of 60%, and air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0124] Comparative Example 6

[0125] A low carbon clinker carbonization process, the preparation method is roughly the same as that of Example 1, the components and their weight percentages are: low carbon clinker 1 100 parts, analytical pure MgCl2·6H2O 6 parts, 11.8 parts of water (15-6*108 / 203, according to the calculation, the water introduced in the analytical pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 15 parts), and the specific steps include: after pressing and molding by the same method, the mass of the sample at this time is weighed to be 14.7g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.7g*100g / (100g+11.8g+6g) to be 12.48g (higher than the molding amount described in Example 1), and then the sample is placed under natural conditions to be dried to a moisture content of 7% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20h under the conditions of carbon dioxide concentration of 99%, temperature of 30℃, humidity of 60%, and air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0126] Comparative Example 7

[0127] A low carbon clinker carbonization process, the preparation method is roughly the same as that of Example 6, the components and their weight percentages are: low carbon clinker 2 100 parts, analytical pure MgCl2·6H2O 4 parts, 17.9 parts of water (20-4*108 / 203, according to the calculation, the water introduced in the analytical pure MgCl2·6H2O is taken into account to ensure that the total amount of water is 20 parts), and the specific steps include: after pressing and molding by the same method, the mass of the sample at this time is weighed to be 13.1g, and the mass of the low-carbon clinker 2 contained in the sample can be calculated according to 13.1g*100g / (100g+17.9g+4g) to be 10.75g, and then the sample is placed under natural conditions to be dried to a moisture content of 11% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20h under the conditions of carbon dioxide concentration of 99%, temperature of 30℃, humidity of 60%, and air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0128] Comparative Example 8

[0129] A low-carbon clinker carbonization process, whose preparation method is roughly the same as that of Example 1, and the components and their weight proportions are: 1100 parts of low-carbon clinker 1, 2 parts of analytical pure Na2SO4, and 15 parts of water. The specific steps include: after pressing and molding using the same method, the mass of the sample at this time is weighed to be 14.8g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.8g*100g / (100g+15g+2g) to be 12.65g (higher than the molding amount described in Example 1), and then the sample is dried under natural conditions to a moisture content of 9% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0130] Comparative Example 9

[0131] A low-carbon clinker carbonization process, whose preparation method is roughly the same as that of Example 1, and the components and their weight proportions are: 1100 parts of low-carbon clinker 1, 2 parts of analytically pure FeSO4, and 15 parts of water. The specific steps include: after pressing and molding using the same method, the mass of the sample at this time is weighed to be 14.1g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.1g*100g / (100g+15g+2g) to be 12.05g (higher than the molding amount described in Example 1), and then the sample is dried under natural conditions to a moisture content of 9% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20h under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0132] Comparative Example 10

[0133] A low-carbon clinker carbonization process, whose preparation method is roughly the same as that of Example 1, and the components and their weight proportions are: 1100 parts of low-carbon clinker 1, 2 parts of analytically pure Mg(HCO3)2, and 15 parts of water. The specific steps include: after pressing and molding using the same method, the mass of the sample at this time is weighed to be 14.6g, and the mass of the low-carbon clinker 1 contained in the sample can be calculated according to 14.6g*100g / (100g+15g+2g) to be 12.48g (higher than the molding amount described in Example 1), and then the sample is dried under natural conditions to a moisture content of 7% (the moisture content with the highest carbonization strength obtained according to the carbonization test after drying to different moisture contents), and finally carbonized for 20 hours under the conditions of a carbon dioxide concentration of 99%, a temperature of 30°C, a humidity of 60%, and an air pressure of 0.3MPa (pressure indication number 0.3MPa) to obtain a carbonized product.

[0134] After carbonization, the mineral composition of each embodiment and comparative example was quantitatively analyzed by using jade on the XRD patterns and the grain size of CaCO3 was analyzed. The results are shown in Table 3 and Table 4, respectively.

[0135] Table 3 Mineral composition after carbonization (%)

[0136]

[0137]

[0138] Table 4 Average grain size of CaCO3 (nm)

[0139]

[0140]

[0141] Among them, the contents of aragonite and vaterite in some examples and comparative examples in Table 1 are relatively low, and the detection errors are relatively large, which is not conducive to the effective determination of the corresponding average grain size, and is represented by “ / ”.

[0142] The compressive strength of the sample after carbonization is the carbonization strength. The carbonization strength and carbon fixation rate of each embodiment and comparative example after carbonization are shown in Table 5.

[0143] Table 5 Carbonization intensity and carbon fixation rate

[0144] project Carbonization strength / MPa Carbon fixation rate / % Example 1 176.12 23.27 Example 2 168.77 19.96 Example 3 187.61 25.84 Example 4 183.79 26.13 Example 5 179.44 25.22 Example 6 152.57 28.89 Example 7 110.61 21.26 Comparative Example 1 151.87 17.04 Comparative Example 2 130.32 25.41 Comparative Example 3 87.42 18.65 Comparative Example 4 168.32 19.20 Comparative Example 5 167.97 18.54 Comparative Example 6 158.61 18.60 Comparative Example 7 132.32 26.09 Comparative Example 8 120.83 15.53 Comparative Example 9 138.11 20.97 Comparative Example 10 125.06 17.93

[0145] The results show that for relatively complex low-carbon clinker forming carbonization, the introduction of low-alkaline cations and SO4 2- Anionic crystal form modifiers, such as MgSO4, CuSO4, and FeSO4 used in the present invention, can help increase aragonite production. However, the order of effectiveness is MgSO4 > CuSO4 > FeSO4, from greatest to least effective. This is related to their inherent metal cation properties and the recycling efficiency of reactions 1 through 4, resulting in the poor performance of Comparative Example 9. The CaCO3 grain size obtained by XRD analysis of jade represents the average grain size. After adding the crystal form modifier, the average grain size of the resulting aragonite is already larger than that of calcite. Furthermore, aragonite is needle-rod-shaped, making its long axis significantly larger than that of calcite, effectively filling and connecting pores.

[0146] For low-carbon clinker 1 with a high calcium-silicon mass ratio: the carbonization strength and carbon fixation rate of Examples 1, 2, 3, 4, and 5 with the addition of a crystal form regulator are significantly improved compared to the comparative example 1 without the addition of a crystal form regulator; for low-carbon clinker 2 with a moderate calcium-silicon mass ratio: the carbonization strength and carbon fixation rate of Example 6 with the addition of a crystal form regulator are significantly improved compared to the comparative example 2 without the addition of a crystal form regulator; for low-carbon clinker 3 with a low calcium-silicon mass ratio: the carbonization strength and carbon fixation rate of Example 7 with the addition of a crystal form regulator are significantly improved compared to the comparative example 3 without the addition of a crystal form regulator. Among them, the lower the calcium-silicon mass ratio of low-carbon clinker, the easier it is to generate aragonite after adding the crystal form regulator, and the proportion of aragonite in the total amount of CaCO3 is higher, the grain size is large, and the low-carbon clinker with a low calcium-silicon ratio has low CO2 emissions during production, a slow carbonization rate, good adaptability to carbonization conditions (such as carbonization using a 20% CO2 concentration), a small specific gravity, and a small amount of low-carbon clinker for the same molding volume (less molding amount). The molding volume for the same amount of low-carbon clinker is larger, which is more suitable for casting molding carbonization and occasions requiring low product density. Secondly, the addition of the crystal form regulator significantly reduces the molding amount of low-carbon clinker, and the cost of the required low-carbon clinker is lower.

[0147] In Comparative Examples 4, 5, 6, and 7, only MgCl2 was added, and the acid-base neutralization reaction of carbonization could also be converted into a non-acid-base neutralization double decomposition reaction. However, the solubility of CaCl2 generated by MgCl2 through reaction 1 was high, which made the rate of reaction 1 slower than that of MgSO4, which was not conducive to the formation of aragonite (the aragonite content was reduced relative to that of Comparative Example 1 without adding a crystal form modifier). The improvement effect and potential of carbonization strength and carbon fixation rate were significantly lower than those of MgSO4 obtained in the present invention. Although only MgCl2 was added in Comparative Examples 4 and 5, compared with Comparative Example 1, the molding amount of low-carbon clinker was reduced by a small amount and the amount of calcite generated after carbonization was increased, thereby improving the carbonization performance, which was close to the performance of Example 2 added with 1% MgSO4. However, the improvement in carbonization performance was limited. After further increasing the amount of MgCl2, Comparative Example 6 caused the carbonization performance to decrease. The main reason was that increasing the amount of MgCl2 did not significantly reduce the molding amount of low-carbon clinker, did not promote the formation of aragonite, and had too strong water retention. The time required for drying to an appropriate moisture content was too long and too much reaction 1 occurred, resulting in poor moisture uniformity and volume stability of the sample before carbonization.

[0148] In Comparative Example 8, Na2SO4 is added. Since NaOH generated by Reaction 1 has high solubility and strong alkalinity, the rate of Reaction 1 is slower than that of MgSO4 (the correctness of this view can be seen from the fact that the mass of the low-carbon clinker 1 contained in the sample of Comparative Example 8 does not change compared with Comparative Example 1, and the molding density does not change). In addition, it will accelerate the dissolution of CO2 in water and form Na2CO3 and NaHCO3, increase the alkalinity of the reaction system and accelerate the rate at which CaSO4·2H2O and Ca(OH)2 are carbonized, which cannot effectively promote the formation of aragonite. 2+ It also cannot be transported well with water, which easily causes CaCO3 to form on the surface of low-carbon clinker, but reduces the carbonization intensity and carbon fixation rate.

[0149] Comparative Example 10 adds Mg(HCO3)2. Since Ca(HCO3)2 is directly generated by reaction 1, and Ca(HCO3)2 is unstable and will decompose into CaCO3 above 0°C, this is equivalent to Mg(HCO3)2 reacting with alkaline Ca(OH)2 to generate CaCO3, which will not promote the formation of aragonite and is equivalent to CaCO3 in low-carbon clinker. 2+ After dissolution, it is immediately carbonized, Ca 2+ It cannot be transported well with moisture, which easily causes CaCO3 to be generated on the surface of low-carbon clinker. Although the molding density is reduced to ensure that the carbon fixation rate is not reduced, the carbonization strength is significantly reduced.

[0150] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for regulating the crystal form of carbonized products and improving the carbonization performance of low-carbon clinker, characterized in that: The following steps are involved: (1) mixing low-carbon clinker, a crystal form regulator and water, and pressing and forming the mixture; the crystal form regulator can ionize low-alkaline metal ions and sulfate ions in water; (2) drying the obtained molded sample and then carbonizing it to obtain a carbonized product; The low alkaline metal ion is Mg 2+ 、Cu 2+ One or more of the following.

2. The method according to claim 1, characterized in that The low-carbon clinker in step (1) is mainly composed of one or more of βC2S, γC2S, C7MS4, C3S2, CS, C2AS, and C2MS2; the mass ratio of CaO to SiO2 in the chemical composition of the low-carbon clinker is 0.8-1.

9.

3. The method according to claim 1, characterized in that The amount of the crystal form regulator in step (1) is 0.5-5wt% of the amount of low carbon clinker.

4. The method according to claim 1, wherein The amount of water used in step (1) is 10-25wt% of the amount of low-carbon clinker used.

5. The method according to claim 1, wherein In step (2), the moisture content after drying is 4-20 wt%.

6. The method according to claim 1, characterized in that The carbonization conditions include: CO2 concentration of 15-100%, temperature of 20-50°C, humidity of 40-80%, and pressurization pressure of 0-0.3 MPa; and carbonization time of 6-72 hours.

7. The method according to claim 1, characterized in that The obtained carbonized product has an aragonite content of 6.5 wt % or more and an average aragonite particle size of 24 nm or more.

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