Active magnesium oxide-based carbon sequestration cementing material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to an active magnesium oxide-based carbon sequestration cementing material as well as a preparation method and application thereof. The active magnesium oxide-based carbon sequestration cementing material disclosed by the invention is prepared from the following mineral components: 5wt%-22wt% of periclase, 65wt%-80wt% of calcite and 0-5wt% of lime. The active magnesium oxide-based carbon sequestration cementing material contains active magnesium oxide, is good in carbonization activity, and can be used for preparing carbonized products with relatively high strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and particularly relates to an active magnesium oxide-based carbon sequestration cementitious material and a preparation method and application thereof. BACKGROUND

[0002] As the most widely used cementitious material, the global demand for cement is growing every year. The production of cement is often accompanied by a large amount of resource consumption and carbon dioxide emissions. For every ton of clinker produced, about 1.25 tons of limestone are consumed and 0.85 tons of carbon dioxide are emitted. A large amount of resource consumption and carbon dioxide emissions hinder the rapid development of the cement industry. Therefore, reducing resource consumption and carbon dioxide emissions has become a major challenge facing the cement industry.

[0003] Recent studies have shown that silicate minerals with a low calcium-to-silicon ratio have the potential to significantly reduce carbon dioxide emissions in the cement industry. Due to the low CaO content of silicate minerals with a low calcium-to-silicon ratio, the corresponding calcination temperature and the demand for calcareous raw materials are also significantly reduced (relative to cement), thereby reducing the consumption of fossil fuels and the decomposition of carbonates (CaO is mainly derived from the decomposition of calcareous limestone) during the production process relative to the preparation of cement. In addition, silicate minerals with a low calcium-to-silicon ratio have carbonation activity and can absorb a large amount of carbon dioxide through carbonation fixation, which helps to further reduce carbon dioxide emissions. However, silicate minerals with a low calcium-to-silicon ratio are mainly prepared through solid-phase reactions between CaO and SiO2, which still requires the consumption of calcium sources and needs to be carried out at a relatively high calcination temperature (~1200℃) (which requires a large amount of energy).

[0004] Therefore, it is necessary to provide an improved technical solution to address the above-mentioned deficiencies of the prior art. SUMMARY

[0005] The present application aims to provide an active magnesium oxide-based carbon sequestration cementitious material and a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: an active magnesium oxide-based carbon sequestration cementitious material, the mineral composition of the active magnesium oxide-based carbon sequestration cementitious material comprising: 5wt%-22wt% periclase, 65wt%-80wt% calcite, and 0-5wt% lime.

[0007] The present application also provides a preparation method of an active magnesium oxide-based carbon sequestration cementitious material, which adopts the following technical solution: the preparation method of the active magnesium oxide-based carbon sequestration cementitious material as described above, comprising the following steps: (1) grinding magnesian limestone to obtain magnesian limestone powder; (2) tabletting the magnesian limestone powder to obtain magnesian limestone tablets; (3) calcining the magnesian limestone, and cooling to room temperature after calcination is completed, thereby obtaining the active magnesium oxide-based carbon sequestration material.

[0008] Preferably, the magnesium limestone has a MgO content of 5wt%-18wt%.

[0009] Preferably, in step (1), the magnesium limestone powder has a particle size of ≤75μm.

[0010] Preferably, in step (3), the calcination temperature is 400-600℃, and the calcination time is 30-90min.

[0011] Preferably, in step (3), the cooling rate is ≥500℃ / min.

[0012] The present application also provides a carbonized product, which adopts the technical scheme as follows: a carbonized product, which is prepared by carbonizing the active magnesia-based carbon fixation cementitious material.

[0013] The present application also provides a preparation method of the carbonized product as described above, which adopts the technical scheme as follows: a preparation method of the carbonized product as described above, comprising the following steps: A. uniformly mixing the active magnesia-based carbon fixation cementitious material with water to obtain a mixture; B. placing the mixture in a mold and compression molding to obtain a molded piece; C. placing the molded piece in a container and introducing a gas containing CO2 into the container for carbonization, thereby obtaining the carbonized product.

[0014] Advantages: The active magnesia-based carbon fixation cementitious material of the present application contains active magnesia, has good carbonization activity (can absorb a large amount of carbon dioxide through carbon fixation, which helps to reduce the emission of carbon dioxide), and has high strength, so it can be directly used without additional maintenance.

[0015] The present application uses magnesium limestone as a raw material to prepare an active magnesia carbon fixation cementitious material with good carbonization activity, which helps to promote the resource utilization of magnesium limestone.

[0016] The active magnesia-based carbon fixation cementitious material of the present application can be prepared at a significantly lower calcination temperature (relative to silicate minerals with a low calcium-silicon ratio), which helps to reduce energy consumption. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0018] The application will be described in detail below with reference to the embodiments. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0019] In view of the problem that the low-calcium silicate material in the prior art is mainly prepared by solid-phase reaction of CaO and SiO2, silicon source needs to be consumed, and the preparation needs to be performed at a high calcination temperature (1200 DEG C) (a large amount of energy needs to be consumed), the application provides an active magnesia-based carbon sequestration cementitious material.

[0020] The mineral composition of the active magnesia-based carbon sequestration cementitious material in the embodiments of the application includes 5 wt%-22 wt% periclase, 65 wt%-80 wt% calcite and 0-5 wt% lime. The active magnesia-based carbon sequestration cementitious material in the embodiments of the application contains active magnesia, has high carbonation activity (can absorb a large amount of carbon dioxide through carbon sequestration, and helps to reduce the emission of carbon dioxide), does not need to consume silicon source, and the active magnesia-based carbon sequestration cementitious material in the application can be prepared at a significantly lower temperature, which can significantly reduce energy consumption.

[0021] The application further provides a preparation method of the active magnesia-based carbon sequestration cementitious material. The preparation method of the active magnesia-based carbon sequestration cementitious material in the embodiments of the application includes the following steps: (1) grinding magnesian limestone to obtain magnesian limestone powder; (2) tabletting the magnesian limestone powder to obtain magnesian limestone tablets; and (3) calcining the magnesian limestone, and cooling to room temperature after the calcination is completed, to obtain the active magnesia-based carbon sequestration material.

[0022] The magnesian limestone in the prior art is usually used as concrete coarse aggregate or stone powder, and it is difficult to realize the resource utilization of the magnesian limestone. The main reason is that calcium oxide and silicon dioxide are needed for cement production; although the magnesian limestone contains calcium carbonate, due to the high calcination temperature of the cement (~1450 DEG C), the magnesia in the magnesian limestone is converted into dead-burned magnesia, the hydration activity of the dead-burned magnesia is very poor, and it usually takes one year or even a longer time to hydrate, and at the same time, the hydration of the magnesia produces significant volume expansion (~148%), which causes the concrete to crack, so the magnesium content in the clinker (≤5%) needs to be strictly controlled during the production and preparation of the cement, which also causes the magnesian limestone to be difficult to be used on a large scale. From the perspective of the smelting of metallic magnesium, although the magnesian limestone contains a small amount of dolomite, it can be used as a raw material for the smelting of metallic magnesium, but due to the low content of the dolomite, the smelting cost is significantly increased, which makes it difficult to be applied to the smelting of metallic magnesium. The application applies the magnesian limestone to the preparation of the active magnesia-based carbon sequestration cementitious material, and the prepared active magnesia-based carbon sequestration cementitious material has good carbonation activity, and can be used for the preparation of carbonated products, thereby realizing the resource utilization of the magnesian limestone.

[0023] In a preferred embodiment of the preparation method of the active magnesium oxide-based carbon sequestration cementitious material, the MgO content in the magnesian limestone is 5wt%-18wt% (for example, 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, 15wt%, 16wt% or 18wt%, etc.). If the MgO content in the magnesian limestone is too low, it cannot provide enough MgO, resulting in that the active magnesium oxide-based carbon sequestration cementitious material does not have enough cementitious property; if the MgO content in the magnesian limestone is high, the high MgO content indicates that the dolomite content in the magnesian limestone is high, which can be used as a raw material in the smelting process of metallic magnesium.

[0024] In a preferred embodiment of the preparation method of the active magnesium oxide-based carbon sequestration cementitious material, in step (1), the particle size of the magnesian limestone powder is ≤75μm. If the particle size of the magnesian limestone powder is too large, the magnesian limestone powder is difficult to completely decompose into MgO and CaCO3 in the calcination process, and still exists in the form of dolomite.

[0025] In a preferred embodiment of the preparation method of the active magnesium oxide-based carbon sequestration cementitious material, in step (3), the calcination temperature is 400-600℃ (for example, 400℃, 420℃, 450℃, 480℃, 500℃, 520℃, 540℃, 570℃ or 600℃), and the calcination time is 30-90min (for example, 30min, 40min, 50min, 60min, 70min, 80min or 90min). If the calcination temperature is too low, the dolomite in the magnesian limestone will not decompose, and it is difficult to form active magnesium oxide; if the calcination temperature is too high, the carbonation activity of the active magnesium oxide in the active magnesium oxide-based carbon sequestration cementitious material will decrease significantly. In addition, a higher calcination temperature will also cause the magnesian limestone to decompose again, forming a large amount of lime in the active magnesium oxide-based carbon sequestration cementitious material, resulting in excessive heat release during the carbonation curing process of the active magnesium oxide-based carbon sequestration cementitious material, and causing the sample to have poor stability. If the calcination time is too short, the dolomite in the magnesian limestone will not decompose completely, and it is difficult to provide enough MgO for the active magnesium oxide-based carbon sequestration cementitious material; if the calcination time is too long, the MgO formed after the decomposition of the dolomite in the magnesian limestone will merge and grow, significantly increasing the grain size of the MgO, resulting in a significant decrease in the carbonation activity of the MgO.

[0026] In a preferred embodiment of the preparation method of the active magnesium oxide-based carbon sequestration cementitious material, in step (3), the cooling speed is ≥500℃ / min. If the cooling speed is too small, it will cause the magnesium oxide to fully crystallize, and it is difficult to form crystal defects; rapid cooling helps to form crystal defects, which helps to improve the reactivity.

[0027] The application further provides a carbonized product, and the carbonized product is prepared by carbonizing the active magnesium oxide-based carbon fixation cementing material.

[0028] The application further provides a preparation method of the carbonized product, and the preparation method of the carbonized product comprises the following steps: A. uniformly mixing the active magnesium oxide-based carbon fixation cementing material with water to obtain a mixture; B. placing the mixture in a mold and performing compression molding to obtain a molded piece; and C. placing the molded piece in a container, introducing a gas containing CO2 into the container to perform carbonization, and thus obtaining the carbonized product.

[0029] The active magnesium oxide-based carbon fixation cementing material, the preparation method and the application thereof will be described in detail below through specific examples.

[0030] The sources of the main raw materials used in the following examples are as follows: the magnesian limestone is taken from Henan Qianye Material Co., Ltd., and the chemical composition of the magnesian limestone is shown in Table 1. Table 1 Chemical composition of raw materials (wt%)

[0031] Example 1 The preparation method of the active magnesium oxide-based carbon fixation cementing material of this example comprises the following steps: (1) grinding the magnesian limestone 1# according to the mass percentage to obtain magnesian limestone powder (the particle size of the magnesian limestone powder is ≤75 μm); (2) weighing a certain amount of the magnesian limestone powder and loading the magnesian limestone powder into a mold, and performing compression molding under a pressure of 6 MPa to obtain a magnesian limestone sheet with a diameter of 30 mm and a height of 10 mm.

[0032] (3) calcining the magnesian limestone sheet obtained in step (2) at 500 ℃ for 60 min; (4) after the calcination is completed, cooling to room temperature at a speed of ≥500 ℃ / min, and thus obtaining the active magnesium oxide-based carbon fixation cementing material of this example.

[0033] The carbonized product of this example is prepared by the method comprising the following steps: (1) fully mixing the active magnesium oxide-based carbon fixation cementing material powder with 10% of water (the amount of water is 10% of the mass of the active magnesium oxide-based carbon fixation cementing material powder) for 10 min; (2) then placing the mixture obtained in step (1) in a mold with a size of 20 mm×20 mm×40 mm, and performing pressure maintaining under a molding pressure of 4 MPa for 1 min to compress the mixture into a test block with a size of 20 mm×20 mm×20 mm; (3) Put the test block obtained in step (2) into a reaction kettle, exhaust the air in the reaction kettle, close the exhaust valve, and introduce CO2 (purity 99.9%) into the reaction kettle, pressurize to 0.3 MPa, and carbonize for 24 h to obtain the carbonized product of the present example.

[0034] Example 2 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Grind magnesium limestone 2# according to the mass percentage to obtain magnesium limestone powder (the particle size of the magnesium limestone powder is ≤75 μm); (2) Weigh a certain amount of magnesium limestone powder into a mold and press under a pressure of 6 MPa to obtain a magnesium limestone sheet with a diameter of 30 mm and a height of 10 mm.

[0035] (3) Calcine the magnesium limestone sheet obtained in step (2) at 500 ℃ for 60 min; (4) After the calcination is completed, cool to room temperature at a speed of ≥500 ℃ / min to obtain the active magnesium oxide-based carbon sequestration cementitious material of the present example.

[0036] The preparation method of the carbonized product of the present example is the same as that of Example 1.

[0037] Example 3 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Grind magnesium limestone 3# according to the mass percentage to obtain magnesium limestone powder (the particle size of the magnesium limestone powder is ≤75 μm); (2) Weigh a certain amount of magnesium limestone powder into a mold and press under a pressure of 6 MPa to obtain a magnesium limestone sheet with a diameter of 30 mm and a height of 10 mm.

[0038] (3) Calcine the magnesium limestone sheet obtained in step (2) at 500 ℃ for 60 min; (4) After the calcination is completed, cool to room temperature at a speed of ≥500 ℃ / min to obtain the active magnesium oxide-based carbon sequestration cementitious material of the present example.

[0039] The preparation method of the carbonized product of the present example is the same as that of Example 1.

[0040] Example 4 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Grind magnesium limestone 3# according to the mass percentage to obtain magnesium limestone powder (the particle size of the magnesium limestone powder is ≤75 μm); (2) A certain amount of magnesia limestone powder is weighed and loaded into a mold, and a magnesia limestone sheet with a diameter of 30 mm and a height of 10 mm is obtained under a pressure of 6 MPa.

[0041] (3) The magnesia limestone sheet obtained in step (2) is calcined at 400°C for 60 min; (4) After the calcination is completed, the temperature is cooled to room temperature at a rate of ≥500°C / min, and the active magnesium oxide-based carbon sequestration cementitious material of the present example is obtained.

[0042] The preparation method of the carbonized product of the present example is the same as that of example 1.

[0043] Example 5 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Magnesia limestone 3# is ground according to the mass percentage, and magnesia limestone powder (particle size of the magnesia limestone powder ≤75 μm) is obtained; (2) A certain amount of magnesia limestone powder is weighed and loaded into a mold, and a magnesia limestone sheet with a diameter of 30 mm and a height of 10 mm is obtained under a pressure of 6 MPa.

[0044] (3) The magnesia limestone sheet obtained in step (2) is calcined at 600°C for 60 min; (4) After the calcination is completed, the temperature is cooled to room temperature at a rate of ≥500°C / min, and the active magnesium oxide-based carbon sequestration cementitious material of the present example is obtained.

[0045] The preparation method of the carbonized product of the present example is the same as that of example 1.

[0046] Example 6 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Magnesia limestone 3# is ground according to the mass percentage, and magnesia limestone powder (particle size of the magnesia limestone powder ≤75 μm) is obtained; (2) A certain amount of magnesia limestone powder is weighed and loaded into a mold, and a magnesia limestone sheet with a diameter of 30 mm and a height of 10 mm is obtained under a pressure of 6 MPa.

[0047] (3) The magnesia limestone sheet obtained in step (2) is calcined at 500°C for 30 min; (4) After the calcination is completed, the temperature is cooled to room temperature at a rate of ≥500°C / min, and the active magnesium oxide-based carbon sequestration cementitious material of the present example is obtained.

[0048] The preparation method of the carbonized product of the present example is the same as that of example 1.

[0049] Example 7 The preparation method of the active magnesium oxide-based carbon sequestration cementitious material of the present example comprises the following steps: (1) Grind the magnesian limestone 3# by mass percentage to obtain magnesian limestone powder (the particle size of the magnesian limestone powder is ≤75 μm); (2) Weigh a certain amount of magnesian limestone powder and load it into a mold, and press it under a pressure of 6 MPa to obtain a magnesian limestone sheet with a diameter of 30 mm and a height of 10 mm.

[0050] (3) Calcine the magnesian limestone sheet obtained in step (2) at 500 ℃ for 90 min; (4) After the calcination is completed, cool it to room temperature at a speed of ≥500 ℃ / min to obtain the active magnesium oxide-based carbon sequestration cementitious material of the present example.

[0051] The preparation method of the carbonized product of the present example is the same as that of Example 1.

[0052] Comparative Example 1 The preparation method of the magnesium oxide-based carbon sequestration cementitious material of the present comparative example is different from that of Example 1 only in that the magnesian limestone 0# is used instead of the magnesian limestone 1#; the rest is the same as that of Example 1.

[0053] The preparation method of the carbonized product of the present comparative example is the same as that of Example 1.

[0054] Comparative Example 2 The preparation method of the magnesium oxide-based carbon sequestration cementitious material of the present comparative example is different from that of Example 3 only in that the calcination temperature is 300 ℃; the rest is the same as that of Example 3.

[0055] The preparation method of the carbonized product of the present comparative example is the same as that of Example 1.

[0056] Comparative Example 3 The preparation method of the magnesium oxide-based carbon sequestration cementitious material of the present comparative example is different from that of Example 3 only in that the calcination temperature is 700 ℃; the rest is the same as that of Example 3.

[0057] The preparation method of the carbonized product of the present comparative example is the same as that of Example 1.

[0058] Comparative Example 4 The preparation method of the magnesium oxide-based carbon sequestration cementitious material of the present comparative example is different from that of Example 6 only in that the calcination time is 10 min; the rest is the same as that of Example 6.

[0059] The preparation method of the carbonized product of the present comparative example is the same as that of Example 1.

[0060] Comparative Example 5 The preparation method of the magnesium oxide-based carbon sequestration cementing material of the present comparative example is different from that of example 6 only in that the calcination time is 120 min, and the rest is consistent with example 6.

[0061] The preparation method of the carbonized product of the present comparative example is the same as that of example 1.

[0062] Experimental example 1, The mineral composition test results are shown in Table 2 as follows: Table 2

[0063] As can be seen from Table 2, with the increase of the dolomite content in the magnesian limestone, the amount of MgO gradually increases. The calcination temperature and the calcination time also significantly affect the generation of MgO. The appropriate calcination temperature ensures the decomposition of dolomite to form MgO. However, when the calcination temperature is too high, the dolomite will further decompose to form CaO. At the same time, the calcium carbonate in the magnesian limestone will also decompose to form CaO. For the calcination time, the appropriate calcination time is also crucial, and too short calcination time cannot ensure the decomposition of dolomite.

[0064] 2, The active magnesium oxide-based carbon sequestration cementing material of the example and the comparative example is carbonized and cured, and after the carbonized product is obtained, the mechanical properties and the mineral composition thereof are analyzed by using a pressure testing machine and an X-ray diffractometer. The test results are shown in Table 3 as follows: Table 3

[0065] The results show that with the increase of the MgO content in the active magnesium oxide-based carbon sequestration cementing material, the mechanical properties of the sample show a gradually increasing trend. The lower calcination temperature makes it difficult for the active magnesium oxide-based carbon sequestration cementing material to form sufficient MgO, resulting in the decrease of the mechanical properties of the sample. When the calcination temperature is too high, the activity of MgO will decrease, which is the main reason for the decrease of the mechanical properties of the sample. Different calcination times will also significantly affect the mechanical properties and the mineral composition of the sample. Shorter calcination time leads to lower MgO content in the active magnesium oxide-based carbon sequestration cementing material, and less carbonizable substances, so the performance of the sample decreases. Longer calcination time leads to the transformation of MgO to dead-burned MgO, which significantly reduces the activity of MgO, thereby reducing the performance of the sample.

[0066] In summary: using magnesian limestone as raw material and treating the magnesian limestone according to the scheme of the present application, the active magnesium oxide-based carbon sequestration cementing material can be calcined, and the carbonized product thereof has high strength and can be directly used without additional curing.

[0067] The above merely illustrates the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An active magnesium oxide-based carbon-fixing cementitious material, characterized in that, The mineral composition of the active magnesium oxide-based carbon-fixing cementitious material includes: periclase 5wt%-22wt%, calcite 65wt%-80wt%, and lime 0-5wt%.

2. The preparation method of the active magnesium oxide-based carbon-fixing cementitious material as described in claim 1, characterized in that, Includes the following steps: (1) Magnesia limestone is ground to obtain magnesia limestone powder; (2) The magnesium limestone powder is compressed into tablets to obtain magnesium limestone tablets; (3) The magnesium limestone is calcined and cooled to room temperature after calcination to obtain the active magnesium oxide-based carbon fixation material.

3. The preparation method of the active magnesium oxide-based carbon-fixing cementitious material as described in claim 2, characterized in that, The MgO content in the magnesian limestone is 5wt%-18wt%.

4. The preparation method of the active magnesium oxide-based carbon-fixing cementitious material as described in claim 2, characterized in that, In step (1), the particle size of the magnesium limestone powder is ≤75μm.

5. The preparation method of the active magnesium oxide-based carbon-fixing cementitious material as described in claim 2, characterized in that, In step (3), the calcination temperature is 400-600℃ and the calcination time is 30-90min.

6. The method for preparing the active magnesium oxide-based carbon-fixing cementitious material as described in claim 2, characterized in that, In step (3), the cooling rate is ≥500℃ / min.

7. A carbonized product, characterized in that, The carbonized product is prepared by carbonizing the active magnesium oxide-based solid carbon cementing material as described in claim 1.

8. The method for preparing the carbonized product as described in claim 7, characterized in that, Includes the following steps: A. The active magnesium oxide-based carbon-fixing cementitious material is mixed evenly with water to obtain a mixture; B. Place the mixture in a mold and press it to form a molded part; C. Place the molded part in a container, and introduce a gas containing CO2 into the container to carbonize it, thereby obtaining the carbonized product.

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