Preparation method of high-purity low-calcium calcium silicate

Abstract

The application discloses a preparation method of high-purity low-calcium calcium silicate, which comprises the following steps: uniformly mixing calcium hydroxide and silicon dioxide with water to obtain a mixture; drying the mixture, then uniformly mixing the mixture with ethanol, and then compressing and molding to form a first green body; then performing first calcination treatment on the first green body, and obtaining an intermediate product after cooling; removing the vitreous body from the intermediate product, crushing and pulverizing the intermediate product into a powder, then uniformly mixing the powder with ethanol, and then compressing and molding to form a second green body; then performing second calcination treatment on the second green body, and obtaining high-purity low-calcium calcium silicate after cooling. The application improves the existing calcium silicate firing process, is highly compatible with the existing preparation process, and has high repeatability. The low-calcium calcium silicate prepared by the application has obviously improved purity and obviously reduced interference on carbonization of the low-calcium calcium silicate in the carbonization process, and provides a basis for carbonization performance research of C3S2 and alpha-CS.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a method for preparing high-purity, low-calcium calcium silicate. Background Technology

[0002] The main sources of carbon emissions from the cement industry include fuel combustion, limestone decomposition, and electricity consumption during grinding. To reduce carbon dioxide emissions from the cement industry, carbon-fixing cementitious materials have emerged. Carbon-fixing cementitious materials refer to low-carbon cementitious materials that can spontaneously and rapidly react with CO2 gas at room temperature and pressure, bind other materials into a cohesive whole, and possess high mechanical strength. These materials mainly include clinker composed primarily of low-calcium non-hydraulic calcium silicate mineral phases such as γ-C2S, C3S2, and α-CS, and industrial solid waste rich in calcium silicate mineral phases. Among these, C3S2 and α-CS, as typical low-calcium calcium silicates, have the advantages of high carbonization reactivity and strong carbon-fixing ability, and are receiving increasing attention.

[0003] However, current research and applications of C3S2 and α-CS face several challenges. For instance, due to the similar calcium-silicon ratio and firing temperature of C3S2, α-CS, and C2S, impurities such as γ-C2S, β-C2S, and α-CS are easily generated during C3S2 preparation. Furthermore, the formation of γ-C2S and β-C2S with even higher calcium-silicon ratios also generates a certain amount of silica. The presence of these calcium silicates affects the calcium ion dissolution and carbonization process of C3S2, making it difficult to study the carbonization activity and products of C3S2. Similar problems exist in the study of the carbonization activity and carbonization products of α-CS. These issues result in a lack of clarity regarding the roles of C3S2 and α-CS in the carbonization process of solid carbon cementitious materials, a lack of theoretical guidance for adjusting the composition and properties of these materials, and a limitation on their application. Although there are existing literatures on the calcination and preparation methods of γ-C2S, γ-C2S does not have high requirements for calcination temperature and calcium-silicon ratio, and its calcination difficulty is significantly lower than that of C3S2 and α-CS. Its raw material ratio, molding method and calcination regime do not provide guidance for the calcination of high-purity C3S2 and α-CS. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method for preparing high-purity low-calcium calcium silicate, thereby solving the technical problem of the difficulty in preparing high-purity C3S2 and α-CS in the prior art.

[0005] This invention provides a method for preparing high-purity, low-calcium calcium silicate, comprising the following steps:

[0006] Calcium hydroxide and silicon dioxide are mixed with water in a certain proportion until homogeneous to obtain a mixture;

[0007] The mixture is dried, then ethanol is added and mixed evenly. It is then pressed into a first blank, and the first blank is subjected to a first calcination treatment. After cooling, an intermediate product is obtained.

[0008] After removing the vitreous phase from the intermediate product, it was crushed and ground into powder. Ethanol was then added to the powder and mixed thoroughly. The mixture was then pressed into a second preform, which was subsequently subjected to a second calcination treatment. After cooling, high-purity, low-calcium calcium silicate was obtained.

[0009] High-purity, low-calcium calcium silicate is C3S2, and the molar ratio of calcium to silicon in calcium hydroxide and silicon dioxide is (1.45–1.55):1; or,

[0010] High-purity low-calcium calcium silicate is α-CS, and the molar ratio of calcium hydroxide to silicon dioxide is (0.95~1.05):1.

[0011] Compared with the prior art, the beneficial effects of the present invention include:

[0012] This invention ensures thorough mixing of the powder by wet mixing calcium hydroxide and silicon dioxide with water; it reduces the distance between particles by pressing the powder into shape before firing, ensuring sufficient solid-phase reaction; it reduces fluctuations in the calcium-silicon ratio in certain areas of the green body by breaking and mixing the blocks after firing and then repeatedly firing; and it reduces the formation of amorphous calcium silicate by experimentally determining the optimal firing temperature and holding time. The high-purity, low-calcium calcium silicate preparation method provided by this invention improves upon existing calcium silicate firing processes, is highly compatible with existing preparation processes, and has high repeatability. The low-calcium calcium silicate prepared by this invention has significantly improved purity (over 90%), significantly reduced amorphous calcium silicate content, and significantly reduced γ-C2S and β-C2S content. This significantly reduces interference with the carbonization of low-calcium calcium silicate during carbonization, providing a foundation for the study of the carbonization performance of C3S2 and α-CS. Attached Figure Description

[0013] Figure 1 This is the XRD pattern of C3S2 prepared in Example 1 of this invention;

[0014] Figure 2 This is the XRD pattern of α-CS prepared in Example 2 of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] After repeated experiments, the applicant discovered the following problems in the existing low-calcium calcium silicate preparation process, resulting in low purity of the prepared C3S2 and α-CS. First, silica and calcium hydroxide are difficult to mix uniformly during the mixing process, leading to excessively high calcium-silicon ratios in some areas and excessively low calcium-silicon ratios in others within the green body, ultimately resulting in the formation of other types of calcium silicates. Second, C3S2 and α-CS lack a liquid phase during firing, and the relatively large spacing between silica and calcium hydroxide particles in the green body hinders sufficient contact and reaction. Furthermore, since the calcium-silicon ratios of C3S2 and α-CS are similar to those of C2S, small fluctuations in the calcium-silicon ratio in localized areas can lead to the formation of different types of calcium silicates. Finally, due to the narrow firing temperature range of α-CS and C3S2, amorphous calcium silicates are easily formed at higher temperatures. These amorphous calcium silicates, as non-reactive glassy phases, act as inert fillers, reducing the purity of calcium silicates and affecting the mechanical properties of the carbonized samples.

[0017] This invention ingeniously solves the aforementioned problems by utilizing methods such as wet mixing with water during the mixing process, pressing and shaping the green body, repeated firing, and determining the optimal firing temperature. Specifically, in the mixing stage of silica and calcium hydroxide, water is added to allow the powder to move and mix fully in the liquid, and the mixing time is extended to ensure thorough mixing of silica and calcium hydroxide, avoiding the difficulty in mixing calcium hydroxide and silica. In the green body shaping stage, pressing and shaping ensures a tighter bond between silica and calcium hydroxide, and increasing the shaping pressure further reduces the gaps between powder particles in the green body. During the firing process, the fluctuation of the calcium-silicon ratio in local areas of the green body is reduced by re-grinding, mixing, pressing and shaping, and refiring the clinker after firing; and the formation of amorphous calcium silicate during firing is reduced by determining the optimal firing temperature.

[0018] Based on this, the present invention is proposed.

[0019] This invention provides a method for preparing high-purity, low-calcium calcium silicate, comprising the following steps:

[0020] S1. Mix calcium hydroxide and silicon dioxide with water in a certain proportion until homogeneous to obtain a mixture;

[0021] S2. Dry the mixture, then add ethanol and mix evenly, then press and shape it into a first blank, then subject the first blank to a first calcination treatment, and cool it to obtain an intermediate product.

[0022] S3. After removing the vitreous body from the intermediate product, crush and grind it into powder. Then, add ethanol to the powder and mix evenly. Then, press and shape it into a second blank. Then, subject the second blank to a second calcination treatment and cool it to obtain high-purity low-calcium calcium silicate.

[0023] In some specific embodiments of the present invention, the purity of both calcium hydroxide and silicon dioxide is ≥95%.

[0024] In some specific embodiments of the present invention, the particle size of both calcium hydroxide and silicon dioxide is ≤100μm, and even more specifically ≤75μm.

[0025] In this embodiment, the high-purity low-calcium calcium silicate is C3S2, and the molar ratio of calcium hydroxide to silicon dioxide is (1.45~1.55):1, preferably 3:2.

[0026] In this embodiment, the high-purity low-calcium calcium silicate is α-CS, and the molar ratio of calcium hydroxide to silicon dioxide is (0.95~1.05):1, preferably 1:1.

[0027] In this embodiment, the amount of water added is 1 to 3 times the total mass of calcium hydroxide and silicon dioxide, and more specifically 1 to 2 times. If too little water is added, the powder will not be completely wetted, resulting in uneven mixing and ultimately a decrease in the purity of low-calcium calcium silicate. If too much water is added, the powder will settle, resulting in uneven mixing and also a decrease in the purity of low-calcium calcium silicate.

[0028] In some specific embodiments of the present invention, during the process of mixing calcium hydroxide and silicon dioxide with water in a certain proportion, the mixing time is 0.3 to 3 hours, and more specifically 0.5 to 1 hour. If the mixing time is too short, the powder will not be mixed evenly, resulting in low purity of the prepared calcium silicate; if the mixing time is too long, the powder will stick to the container wall, resulting in uneven mixing and low purity of the prepared calcium silicate.

[0029] In this embodiment, the temperature during the drying process is 100-150℃ and the humidity is ≤60%. If the humidity is too high, the water loss will be too slow, the powder will settle and become unevenly distributed, and the purity of the clinker will eventually decrease.

[0030] In this embodiment, during the process of adding ethanol after drying the mixture, the mass of ethanol is 0.1 to 0.5 times the mass of the mixture, and more specifically 0.1 to 0.3 times.

[0031] In this embodiment, during the pressing process, the peak pressure is ≥5 MPa, and the holding time is 10–60 s, more specifically 20–40 s. Too low a pressure will result in excessively large distances between powder particles, preventing sufficient reaction during calcination and leading to a decrease in the purity of low-calcium calcium silicate; too high a pressure has little impact on purity but will waste energy and prolong the preparation time. Therefore, 5–10 MPa is preferred.

[0032] In this embodiment, the thickness of both the first and second blanks does not exceed 1.2 cm; further, the thickness does not exceed 1 cm. If the blank thickness is too large, it will lead to uneven heating during the firing process, inconsistent temperatures inside and outside the blank, and ultimately reduce the purity of the calcium silicate obtained.

[0033] In this embodiment, during the grinding process, the particle size of the resulting powder is <500μm, and further <300μm. If the particle size of the material after grinding is too large, the calcium silicate in the material cannot be mixed evenly, resulting in a decrease in the purity of the calcium silicate.

[0034] In this embodiment, during the process of adding ethanol to the powder and mixing it evenly, the mass of ethanol is 0.1 to 0.5 times the mass of the powder, and more specifically 0.1 to 0.3 times.

[0035] In this embodiment, the calcination temperature is 1300-1450℃ during the first and second calcination processes.

[0036] In this embodiment, the high-purity low-calcium calcium silicate is C3S2. During the first and second calcination processes, the holding time is 1.5 to 2.5 hours, and further, 2 hours.

[0037] In this embodiment, the high-purity low-calcium calcium silicate is α-CS. During the first calcination treatment, the holding time is 0.5 to 1.5 hours, and further, 1 hour. During the second calcination treatment, the holding time is 1.5 to 2.5 hours, and further, 2 hours.

[0038] Unless otherwise specified, all raw materials required for preparation in this invention are commercially available products well known to those skilled in the art.

[0039] This invention does not impose any special restrictions on the mixing method or stirring speed. As long as the liquid can drive all the powder to move and achieve thorough mixing during the stirring process.

[0040] This invention does not impose any special limitations on drying equipment and drying time; any device well-known in the art can be selected and the process well-known can be followed.

[0041] The present invention does not impose any special restrictions on the tablet press and mold used in the compression molding process; any device well known in the art can be selected.

[0042] The present invention does not impose any special restrictions on the heating equipment used in the firing of clinker; any device well known in the art can be selected.

[0043] This invention does not impose any particular limitation on the method of removing the vitreous body; any method well-known in the art can be used. For example, since the vitreous body often adheres to the surface or edge of the molten metal and is clearly different in color from the molten metal, it can be removed by simply breaking it apart by hand.

[0044] To avoid redundancy, in the following examples and comparative examples, the calcium hydroxide and silicon dioxide used have a purity of 95% and a particle size of less than 75 μm.

[0045] Example 1

[0046] (1) Mix calcium hydroxide reagent and silicon dioxide reagent with water at a calcium-silicon ratio of 3:2. The amount of water added should be 1 times the mass of the solid. The mixing time is 1 hour.

[0047] (2) Place the uniformly mixed material into a 105℃ oven for drying, with a humidity of 50% in the oven; add ethanol to the dried powder and mix evenly, then press it into a blank. The mass of ethanol is 0.3 times that of the powder, the peak pressure is 6MPa, the holding time is 30s, and the thickness of the blank is 0.5cm; heat the blank to 1420℃ and hold it for 2h, then cool it with the furnace.

[0048] (3) After removing the glass body from the heated block, crush and grind it. The particle size after grinding is <300μm. Then, add ethanol to the powder and mix it evenly. The mass of ethanol is 0.2 times that of the powder. Then, press it to form a blank. The peak pressure is the same as that of the first pressing. The thickness of the blank is 0.5cm. Heat the blank to 1420℃ and keep it for 2h. Then cool it with the furnace to obtain high-purity C3S2.

[0049] Example 2

[0050] (1) Mix calcium hydroxide reagent and silicon dioxide reagent with water at a calcium-silicon ratio of 1:1. The amount of water added should be 1 times the mass of the solid. The mixing time is 1 hour.

[0051] (2) Place the uniformly mixed material into a 105℃ oven for drying, with a humidity of 50% in the oven; add ethanol to the dried powder and mix evenly, then press it into a blank. The mass of ethanol is 0.3 times that of the powder, the peak pressure is 6MPa, the holding time is 30s, and the thickness of the blank is 0.5cm; heat the blank to 1420℃ and hold it for 1h, then cool it with the furnace.

[0052] (3) After removing the glass body from the heated block, crush and grind it. The particle size after grinding is <300μm. Then, add ethanol to the powder and mix it evenly. The mass of ethanol is 0.2 times that of the powder. Then, press it to form a blank. The peak pressure is the same as that of the first pressing. The thickness of the blank is 0.5cm. Heat the blank to 1420℃ and keep it for 2h. Then cool it with the furnace to obtain high-purity α-CS.

[0053] Example 3

[0054] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The calcination temperature in the preparation method is 1300℃, and the rest is the same as in Example 1.

[0055] Example 4

[0056] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The calcination temperature in the preparation method is 1450℃, and the rest is the same as in Example 1.

[0057] Example 5

[0058] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The amount of water added in the preparation method is twice the mass of the solid. Other aspects are the same as in Example 1.

[0059] Example 6

[0060] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The mixing time of the powder and water in the preparation method is 0.5 h, and other aspects are the same as in Example 1.

[0061] Example 7

[0062] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. During the pressing process, the peak pressure is 5 MPa. Other aspects are the same as in Example 1.

[0063] Example 8

[0064] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. During the pressing process, the peak pressure is 10 MPa. Other aspects are the same as in Example 1.

[0065] Example 9

[0066] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. In the preparation method, the thickness of the blank is 1 cm after the first and second pressing. Other aspects are the same as in Example 1.

[0067] Comparative Example 1

[0068] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. During the drying process of the materials in the preparation method, the temperature of the drying oven is 40°C, and other aspects are the same as in Example 1.

[0069] Comparative Example 2

[0070] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The amount of water added in the preparation method is 0.5 times the mass of the solid. Other aspects are the same as in Example 1.

[0071] Comparative Example 3

[0072] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The amount of water added in the preparation method is 5 times the mass of the solid. Other aspects are the same as in Example 1.

[0073] Comparative Example 4

[0074] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The mixing time of the powder and water in the preparation method is 10 min, and other aspects are the same as in Example 1.

[0075] Comparative Example 5

[0076] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The mixing time of the powder and water in the preparation method is 5 hours, and other aspects are the same as in Example 1.

[0077] Comparative Example 6

[0078] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. In the preparation method, the mass of ethanol added before the first pressing is 0.8 times that of the powder. Other aspects are the same as in Example 1.

[0079] Comparative Example 7

[0080] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. During the pressing process, the peak pressure is 2 MPa. Other aspects are the same as in Example 1.

[0081] Comparative Example 8

[0082] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. In the preparation method, the thickness of the blank is 3 cm after the first and second pressing. Other aspects are the same as in Example 1.

[0083] Comparative Example 9

[0084] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. In the preparation method, the clinker is only fired once and the holding time is 2 hours. Other aspects are the same as in Example 1.

[0085] Comparative Example 10

[0086] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 2. In the preparation method, the clinker is only fired once and the holding time is 2 hours. Other aspects are the same as in Example 2.

[0087] Comparative Example 11

[0088] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 2. The clinker is fired 4 times in the preparation method, and the holding time is 2 hours each time. Other aspects are the same as in Example 2.

[0089] Comparative Example 12

[0090] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 1. The particle size of the powder after grinding is >1 mm in the preparation method, and other aspects are the same as in Example 1.

[0091] Comparative Example 13

[0092] The ratio of calcium hydroxide to silicon dioxide is the same as in Example 2. The glassy phase was not removed from the heated block in the preparation method. Otherwise, it is the same as in Example 2.

[0093] Comparative Example 14

[0094] Calcium carbonate reagent and silicon dioxide reagent were used as raw materials, with the same proportions and preparation methods as in Example 1.

[0095] Performance testing

[0096] (1) The low-calcium calcium silicate prepared in Examples 1 and 2 above was ground and subjected to X-ray diffraction testing. The results are as follows: Figure 1 and Figure 2 As shown;

[0097] (2) The low-calcium calcium silicate powders prepared in Examples 1-9 and Comparative Examples 1-14 were ground and mixed with 10 wt.% α-Al2O3 as an internal standard reference. X-ray diffraction tests were then performed with the following parameters: scanning angle 5-70°, step size 0.02°, and scanning rate 2° / min. The content percentage of each crystal phase was obtained by the Rietveld method. The test results are shown in Table 1.

[0098] Table 1. Phase composition of high-purity low-calcium calcium silicate prepared in Examples 1-9 and Comparative Examples 1-14

[0099]

[0100]

[0101] As can be seen from Examples 1 to 9 in Table 1, the low-calcium calcium silicate prepared by the present invention has high purity, low amorphous phase content, and low γ-C2S and β-C2S content.

[0102] A comparison of the data of the low-calcium calcium silicate prepared in Examples 1-9 and the low-calcium calcium silicate prepared in Comparative Example 1 in Table 1 shows that the temperature during the material drying process has a significant impact on the purity of the low-calcium calcium silicate. Too low a temperature will result in a longer drying time, and the precipitation of powder in the material will lead to uneven distribution of calcium hydroxide and silicon dioxide, ultimately resulting in a decrease in the purity of the low-calcium calcium silicate.

[0103] A comparison of the data from Examples 1-9 and Comparative Examples 2-5 in Table 1 shows that the amount of water added and the mixing time when mixing calcium hydroxide and silicon dioxide have a significant impact on the preparation of low-calcium calcium silicate. Too little water will result in the powder not being completely wetted, the powder not being mixed evenly, and ultimately leading to a decrease in the purity of low-calcium calcium silicate. Too much water will cause the powder to settle, the powder to be mixed unevenly, and ultimately lead to a decrease in the purity of low-calcium calcium silicate. Too short a mixing time will also result in the powder not being mixed evenly, and the prepared calcium silicate will have a low purity. Too long a mixing time will cause the powder to stick to the container wall, the mixture to be uneven, and the prepared calcium silicate will have a low purity.

[0104] A comparison of the data of low-calcium calcium silicate prepared in Examples 1-9 and the low-calcium calcium silicate prepared in Comparative Example 6 in Table 1 shows that the amount of ethanol added before pressing the green body has a significant impact on the purity of low-calcium calcium silicate. Adding too much ethanol will result in excessively large powder spacing after pressing, making it difficult to react fully during the firing process and thus reducing the purity of calcium silicate.

[0105] A comparison of the data of low-calcium calcium silicate prepared in Examples 1-9 and Comparative Examples 7-8 in Table 1 shows that the molding pressure and thickness of the green body during pressing have a significant impact on the purity of low-calcium calcium silicate. If the molding pressure is too low, the distance between the powder particles will be too large, and they will not be able to react fully during the firing process, resulting in a decrease in the purity of low-calcium calcium silicate. If the green body thickness is too large, the heating will be uneven during the firing process, and the internal and external temperatures of the green body will be inconsistent, resulting in a decrease in the purity of the final calcium silicate.

[0106] A comparison of the low-calcium calcium silicate prepared in Examples 1-9 and the low-calcium calcium silicate prepared in Comparative Examples 9-13 in Table 1 shows that the repeated firing process has a significant impact on the purity of calcium silicate. Without repeated firing, fluctuations in the calcium-silicon ratio within the green body result in lower calcium silicate purity. Excessive repeated firing increases the content of amorphous phase, leading to a decrease in calcium silicate purity. Larger particle sizes after grinding during repeated firing result in uneven mixing of calcium silicate, further reducing its purity. Failure to remove glassy material during repeated firing leads to amorphous calcium silicate being incorporated into the clinker, further decreasing the purity of the low-calcium calcium silicate.

[0107] A comparison of the data from Examples 1-9 and Comparative Example 14 in Table 1 shows that the raw materials have a significant impact on the purity of calcium silicate. If calcium carbonate is used as the calcium source, it tends to settle during the water mixing process, leading to uneven mixing and a decrease in the purity of the low-calcium calcium silicate.

[0108] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity, low-calcium calcium silicate, characterized in that, Includes the following steps: Calcium hydroxide and silicon dioxide are mixed with water in a certain proportion until homogeneous to obtain a mixture; The mixture is dried, then ethanol is added and mixed evenly, and then pressed into a first blank. The first blank is then subjected to a first calcination treatment and cooled to obtain an intermediate product. The intermediate product, after removing the vitreous phase, is crushed and ground into powder. Ethanol is then added to the powder and mixed thoroughly. The mixture is then pressed into a second preform, which is subsequently subjected to a second calcination treatment. After cooling, high-purity, low-calcium calcium silicate is obtained. In the process of mixing calcium hydroxide and silicon dioxide with water in a certain proportion, the amount of water added is 1 to 3 times the total mass of calcium hydroxide and silicon dioxide, and the mixing time is 0.3 to 3 hours. During the drying process, the temperature is 100~150℃ and the humidity is ≤60%; When adding ethanol after drying the mixture, the mass of ethanol is 0.1 to 0.5 times the mass of the mixture. When adding ethanol to the powder, the mass of ethanol is 0.1 to 0.5 times the mass of the powder. During the pressing process, the peak pressure is ≥5MPa and the holding time is 10~60s; The thickness of both the first blank and the second blank does not exceed 1.2 cm; During the grinding process, the particle size of the resulting powder is <500μm; During the first and second calcination processes, the calcination temperature is 1300~1450℃; The high-purity low-calcium calcium silicate is C3S2, and the molar ratio of calcium hydroxide to silicon dioxide is (1.45~1.55):1; the holding time is 1.5~2.5h in both the first and second calcination processes; or, the high-purity low-calcium calcium silicate is α-CS, and the molar ratio of calcium hydroxide to silicon dioxide is (0.95~1.05):1; the holding time is 0.5~1.5h in the first calcination process and 1.5~2.5h in the second calcination process.

2. The method for preparing high-purity low-calcium calcium silicate according to claim 1, characterized in that, The purity of both calcium hydroxide and silicon dioxide is ≥95%, and the particle size of both calcium hydroxide and silicon dioxide is ≤100μm.

3. The method for preparing high-purity low-calcium calcium silicate according to claim 1, characterized in that, The high-purity low-calcium calcium silicate is C3S2, and the calcium-silicon molar ratio in the calcium hydroxide and silicon dioxide is 3:2; or, the high-purity low-calcium calcium silicate is α-CS, and the calcium-silicon molar ratio in the calcium hydroxide and silicon dioxide is 1:1.

Images