Magnesium-fixing and carbon-reducing agent for high-magnesium cement raw material and preparation method of magnesium-fixing and carbon-reducing agent

Abstract

The invention provides a magnesium-fixing and carbon-reducing agent suitable for preparing Portland cement clinker from high-magnesium limestone and a preparation method of the magnesium-fixing and carbon-reducing agent. The magnesium fixing and carbon reducing agent comprises the following main raw materials in parts by mass: 30-50 parts of fluorine-containing sludge, 20-40 parts of manganese-rich residues, 10-30 parts of electrolytic manganese residues and 10-20 parts of aluminum ash. When the high-magnesium limestone replaces conventional limestone to prepare the cement raw material, the doping amount of the magnesium-fixing and carbon-reducing agent is 0.5-1.3%. The carbon reducing agent can effectively reduce the content of free magnesium oxide in high-magnesium limestone calcined clinker, improve the stability and strength of cement clinker and reduce carbon emission. According to the technical scheme, the safe, low-carbon and high-strength cement clinker with the high-magnesium limestone as the raw material can be prepared, large-scale application of the high-magnesium limestone in the cement industry is achieved, and an innovative low-carbon and environment-friendly technical approach is provided for cement production.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation in cement clinker production and waste resource utilization, and in particular to a magnesium-solidifying carbon-reducing agent for high-magnesium cement raw material and a preparation method thereof. Background Art

[0002] Traditional Portland cement clinker production relies primarily on limestone with a high calcium content. However, high-magnesium limestone has limited application in cement production due to its unique mineral composition (MgO content typically ranges from 5% to 20%). In recent years, with increasing attention to sustainability and resource efficiency in cement production, the efficient use of high-magnesium limestone resources to produce high-performance, low-carbon cement clinker has become a research priority in the industry.

[0003] High-magnesium limestone is relatively rarely used in Portland cement production. One major reason is that the periclase in it is difficult to fully react during calcination, typically remaining free in the cement clinker. This hydration-induced expansion of the periclase can lead to cracking in the cement paste, severely impacting the cement's stability. Therefore, optimizing the incorporation ratio of high-magnesium limestone and adjusting the cement production process to ensure that the cement meets strength and durability requirements while minimizing energy consumption and environmental impact has become a key research topic in the cement industry.

[0004] CN115724602B discloses a low-carbon multi-component cement clinker and a preparation method thereof that efficiently utilizes high-magnesium limestone. The method uses high-magnesium limestone, red mud, phosphogypsum, gold tailings, low-grade bauxite and boron mud for batching, and burns to obtain a multi-component low-carbon cement clinker. However, the components of this clinker are quite different from those of traditional silicate cement clinker, resulting in lower strength in the later stage. CN111925141B discloses a method for preparing cement clinker using high-magnesium high-alkali limestone, which uses high-magnesium high-alkali limestone, sandstone, coal gangue, iron ore waste, calcium iodide and tellurium bismuth ore for batching. However, the tellurium bismuth ore used therein is less distributed in my country, has a higher price, and is an important strategic resource, so it is difficult to achieve large-scale application in the cement industry. Summary of the Invention

[0005] The present invention addresses the technical difficulty that high-magnesium limestone is difficult to apply on a large scale in the process of preparing cement clinker, and proposes a solid magnesium carbon reducer suitable for preparing silicate cement clinker with high-magnesium limestone and a preparation method thereof. The method successfully prepares solid magnesium carbon reducer particles for cement clinker production by optimizing the material ratio and adopting extrusion granulation technology. After the solid magnesium carbon reducer is added to the raw material prepared using high-magnesium limestone as a raw material, it can effectively solidify periclase, reduce its free state during the calcination process, and prevent it from causing expansion and cracking during the cement hydration process. At the same time, the method can also effectively reduce coal consumption and carbon emissions, thereby reducing energy consumption and environmental pollution in the production process. The application of the solid magnesium carbon reducer is suitable for cement plants with limited resource conditions and no high-quality limestone resources, especially in the case of large-scale use of high-magnesium limestone raw materials, which can effectively improve the stability and sustainability of cement production.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A solid magnesium carbon reducer suitable for preparing silicate cement clinker from high-magnesium limestone, the method comprising the following steps:

[0008] (1) Batching and pre-homogenization of raw materials: weigh fluorine-containing sludge, manganese-rich slag, electrolytic manganese slag and aluminum ash, and mix the raw materials evenly in a blender;

[0009] (2) Extrusion granulation: The materials uniformly mixed in step (1) are extruded and granulated by a granulator, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0010] (3) Use of solid magnesium carbon reducer: Add solid magnesium carbon reducer to the raw material according to the amount of high magnesium limestone in the cement raw material ratio.

[0011] In the technical solution of the present invention: in step (1), the fluorine-containing sludge is a by-product of the treatment of fluorine-containing wastewater in photovoltaic enterprises; the manganese-rich slag is an intermediate by-product of the manganese ore smelting process; the electrolytic manganese slag is a by-product produced by processes such as sulfuric acid leaching and oxidation deironing in the wet smelting process of producing metallic manganese; and the aluminum ash is a by-product produced in the aluminum production process.

[0012] In the technical solution of the present invention: in step (1), the moisture content of the original fluorine-containing sludge is 20-40%, and its calcium fluoride content is 30-50%.

[0013] In the technical solution of the present invention: the weight proportions of the fluorine-containing sludge, manganese-rich slag, electrolytic manganese slag and aluminum ash in step (1) are 30-50 parts, 20-40 parts, 10-30 parts and 10-20 parts respectively;

[0014] In the technical solution of the present invention: in step (1), the manganese ratio (Mn / (Al+Fe)) in the raw material is controlled to be 0.5-1.5.

[0015] In the technical solution of the present invention: the granulator in step (2) is a double-die granulator, the granulation pressure is 6 MPa, and the scraper cutting particle size is 5 mm.

[0016] In the technical solution of the present invention: in step (3), the mass fraction content of magnesium oxide in the high-magnesium limestone is 5%-10%.

[0017] In the technical solution of the present invention: in step (3), the amount of high-magnesium limestone added to the cement raw material is 60-90 parts by mass.

[0018] In the technical solution of the present invention: in step (3), when the solid magnesium carbon reducer is used in the production of clinker in a cement kiln, the amount of the solid magnesium carbon reducer added to the raw material is 0.5-1.3 parts by mass, calculated as a percentage by mass.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The solid magnesium carbon reducer provided by the present invention effectively solves the application bottleneck of high-magnesium limestone in cement clinker production by designing the manganese ratio in the material. The control of the manganese ratio can promote the solid dissolution of MgO, generate MgO-FeO-MnO solid solution and magnesium-aluminum spinel, reduce the content of free magnesium oxide, and thus improve the mechanical properties of the clinker. In addition, the addition of fluorine-containing sludge can further promote the early appearance of the clinker liquid phase, increase the activity of the solid solution, inhibit the growth of periclase crystals, make the periclase crystals smaller and more evenly distributed, and ultimately achieve the purpose of optimizing the strength of the clinker and improving the stability of the clinker.

[0021] (2) The solid magnesium carbon reducer prepared by the present invention can reduce the coal consumption of calcining high-magnesium limestone, wherein magnesium reduces carbon emissions during cement production, and has significant energy-saving and environmental protection effects.

[0022] (3) The magnesium-rich carbon reducer used in the present invention is particularly suitable for cement plants with limited resources and no high-quality limestone. By efficiently utilizing high-magnesium limestone raw materials, the dependence on traditional high-quality limestone resources is reduced, the utilization efficiency of low-grade limestone can be improved, and the raw material diversity in cement clinker production can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a physical picture of the solid magnesium and carbon reduction agent product prepared in Example 5 of the present application;

[0024] Figure 2 X-ray diffraction analysis of the clinker fired with the solid magnesium carbon reducing agent prepared in Example 5 of the present application and the clinker fired without the solid magnesium carbon reducing agent; DETAILED DESCRIPTION

[0025] The following is a more detailed description of the specific embodiments of the present invention with reference to schematic diagrams. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are greatly simplified and not to exact scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0026] In the following examples and comparative examples of the present invention, the main constituent elements of fluorine-containing sludge, manganese-rich slag, electrolytic manganese slag and aluminum ash are as follows:

[0027] The content of F element in fluorine-containing sludge is 22.8%, Al element content is 2.8%, and Fe element content is 2.6%;

[0028] The Mn content in the manganese-rich slag is 45.2%, the Al content is 3.5%, and the Fe content is 0.9%;

[0029] The Mn content in electrolytic manganese slag is 5.8%, the Al content is 9.6%, and the Fe content is 7.3%;

[0030] The F content in the aluminum ash slag is 0.9%, the Al content is 66.3%, and the Fe content is 0.6%.

[0031] Example 1

[0032] Example 1 of the present application provides a solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, the method comprising the following steps:

[0033] (1) Weigh 40 parts by mass of fluorine-containing sludge, 20 parts by mass of manganese-rich slag, 20 parts by mass of electrolytic manganese slag, and 20 parts by mass of aluminum ash (the manganese ratio is 0.51 obtained by calculating Mn / (Al+Fe) in the raw materials), and mix the raw materials uniformly in a blender;

[0034] (2) The materials uniformly mixed in step (1) are transported to a double-die granulator via a belt, the granulation pressure is adjusted to 6 MPa, the scraper cutting particle size is 5 mm, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0035] (3) 0.5 wt.% of solid magnesium decarbonizer was added to the raw meal in which 60 wt.% of high magnesium limestone replaced the conventional limestone.

[0036] Example 2

[0037] Example 1 of the present application provides a solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, the method comprising the following steps:

[0038] (1) Weigh 50 parts by mass of fluorine-containing sludge, 20 parts by mass of manganese-rich slag, 20 parts by mass of electrolytic manganese slag, and 10 parts by mass of aluminum ash (the manganese ratio is 0.75 obtained by calculating Mn / (Al+Fe) in the raw materials), and mix the raw materials uniformly in a blender;

[0039] (2) The materials uniformly mixed in step (1) are transported to a double-die granulator via a belt, the granulation pressure is adjusted to 6 MPa, the scraper cutting particle size is 5 mm, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0040] (3) 0.7 wt.% of solid magnesium decarbonizer was added to the raw meal in which 80 wt.% of high magnesium limestone replaced the conventional limestone.

[0041] Example 3

[0042] Example 1 of the present application provides a solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, the method comprising the following steps:

[0043] (1) Weigh 40 parts by mass of fluorine-containing sludge, 30 parts by mass of manganese-rich slag, 10 parts by mass of electrolytic manganese slag, and 20 parts by mass of aluminum ash (the manganese ratio is 0.78 obtained by calculating Mn / (Al+Fe) in the raw materials), and mix the raw materials uniformly in a blender;

[0044] (2) The materials uniformly mixed in step (1) are transported to a double-die granulator via a belt, the granulation pressure is adjusted to 6 MPa, the scraper cutting particle size is 5 mm, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0045] (3) 1.0 wt.% of solid magnesium decarbonizer was added to the raw meal in which 60 wt.% of high magnesium limestone replaced the conventional limestone.

[0046] Example 4

[0047] Example 1 of the present application provides a solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, the method comprising the following steps:

[0048] (1) Weigh 30 parts by mass of fluorine-containing sludge, 30 parts by mass of manganese-rich slag, 30 parts by mass of electrolytic manganese slag, and 10 parts by mass of aluminum ash (the manganese ratio is 1.04 obtained by calculating Mn / (Al+Fe) in the raw materials), and mix the raw materials uniformly in a blender;

[0049] (2) The materials uniformly mixed in step (1) are transported to a double-die granulator via a belt, the granulation pressure is adjusted to 6 MPa, the scraper cutting particle size is 5 mm, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0050] (3) 1.0 wt.% of solid magnesium decarbonizer was added to the raw meal in which 80 wt.% of high magnesium limestone replaced the conventional limestone.

[0051] Example 5

[0052] Example 1 of the present application provides a solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, the method comprising the following steps:

[0053] (1) Weigh 30 parts by mass of fluorine-containing sludge, 40 parts by mass of manganese-rich slag, 20 parts by mass of electrolytic manganese slag, and 10 parts by mass of aluminum ash (the manganese ratio is 1.43 obtained by calculating Mn / (Al+Fe) in the raw materials), and mix the raw materials uniformly in a blender;

[0054] (2) The materials uniformly mixed in step (1) are transported to a double-die granulator via a belt, the granulation pressure is adjusted to 6 MPa, the scraper cutting particle size is 5 mm, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonizer product.

[0055] (3) 1.3 wt.% of solid magnesium decarbonizer was added to the raw meal in which 90 wt.% of high magnesium limestone replaced the conventional limestone.

[0056] The solid magnesium and carbon reducing agents obtained in Examples 1-5 were added to the raw meal in corresponding proportions, and the performance of the clinker obtained after calcination was tested.

[0057] Comparative Example 1

[0058] In this comparative example, 90 wt.% high-magnesium limestone was used to replace conventional limestone in preparing clinker.

[0059] Table 1 Chemical composition and rate values ​​of raw materials

[0060]

[0061] Table 2 Stability of cement clinker

[0062]

[0063] Table 3 Basic properties of clinker

[0064]

[0065] Table 4 5000t / d cement kiln usage status

[0066]

[0067]

[0068] The mechanical properties of the clinker were tested according to GBT17671-2021, "Test Method for Cement Mortar Strength (ISO Method)," and the clinker stability was measured according to GB / T750-1992, "Test Method for Cement Autoclave Stability." After the 5,000t / d cement rotary kiln was put into operation, the coal consumption before and after operation was calculated.

[0069] The results show that the addition of solid magnesium decarbonizer significantly improves the stability of high magnesium limestone cement clinker. In the control experiment, the clinker without solid magnesium decarbonizer showed serious stability problems. This is because the MgO in high magnesium limestone fails to interact with other minerals during the clinker firing process, resulting in a large amount of MgO existing in a free state (such as Figure 2 This caused the cement clinker to crack severely after a 6-hour autoclave test, reflecting the negative impact of free MgO on the volume stability of the clinker. After the addition of the solid magnesium decarbonizer, MgO underwent significant mineral transformation during the firing process, significantly improving the volume stability of the clinker. Specifically, the solid magnesium decarbonizer promoted the formation of solid solutions of MgO in high-magnesium limestone with other metal oxides (such as FeO, MnO) and aluminate minerals, generating stable mineral phases such as MgO-FeO-MnO solid solution, magnesium-aluminum spinel, and calcium-magnesium rhodonite, thereby effectively reducing the content of free MgO and reducing the volume expansion of the clinker. The core mechanisms of this transformation process include: on the one hand, the fluorine element in the solid magnesium decarbonizer coordinates with the metal ions in the MgO lattice, destroying the crystal structure of MgO, promoting its dissolution and reaction with other components, and reducing the free content of MgO; on the other hand, the introduction of manganese promotes the crystal growth of MgO-related minerals by controlling the liquid phase viscosity, thereby increasing the solid solubility of MgO and reducing the presence of free MgO.

[0070] The addition of solid magnesium decarburizers also significantly improves the compressive strength of cement clinker, and this effect is particularly pronounced in high-magnesium limestone raw materials. This can be attributed to the following reasons: First, solid magnesium decarburizers promote the decomposition of carbonate minerals, reduce the lattice energy of MgO, improve the burnability of the raw materials, and thus accelerate the clinker sintering reaction; second, the introduction of solid magnesium decarburizers promotes the transformation of C3S minerals in the clinker from M3 to M1, improving the hydration reaction rate of the clinker and promoting early strength gains; finally, solid magnesium decarburizers also reduce the transformation of highly reactive α-C2S to β-C2S and γ-C2S during the clinker cooling process, thereby enhancing the later strength gains. Furthermore, in its application in cement rotary kilns, the use of solid magnesium decarburizers has been found to further reduce the coal consumption required for clinker production, primarily due to the synergistic effects of F, Mn, and Mg ions.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any person skilled in the art may make various changes, modifications, substitutions and variations to these embodiments without departing from the principles and purpose of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A magnesium-containing carbon-reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, characterized in that: The method comprises the following steps: (1) Batching and pre-homogenization of raw materials: weigh fluorine-containing sludge, manganese-rich slag, electrolytic manganese slag and aluminum ash, and mix the raw materials evenly in a blender; (2) extrusion granulation: the material uniformly mixed in step (1) is extruded and granulated by a granulator, and the granules obtained by granulation are naturally stacked layer by layer to obtain a solid magnesium decarbonization agent product; (3) Use of solid magnesium carbon reducer: Add solid magnesium carbon reducer to the raw material according to the amount of high magnesium limestone in the cement raw material ratio.

2. A solid magnesium carbon reducer suitable for preparing silicate cement clinker from high magnesium limestone according to claim 1 and a preparation method thereof, characterized in that: The fluorine-containing sludge described in step (1) is a by-product of the treatment of fluorine-containing wastewater in photovoltaic enterprises; the manganese-rich slag is an intermediate by-product of the manganese ore smelting process; the electrolytic manganese slag is a by-product produced by processes such as sulfuric acid leaching and oxidation deironing during the wet smelting process of producing metallic manganese; and the aluminum ash is a by-product produced in the aluminum production process.

3. A solid magnesium-reducing carbon-reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone according to claim 2 and a preparation method thereof, characterized in that: The moisture content of the original fluoride-containing sludge is 20-40%, and its calcium fluoride content is 30-50%.

4. A solid magnesium carbon reducing agent suitable for preparing silicate cement clinker from high magnesium limestone according to claim 3 and a preparation method thereof, characterized in that: The weight proportions of the fluorine-containing sludge, manganese-rich slag, electrolytic manganese slag and aluminum ash in step (1) are 30-50 parts, 20-40 parts, 10-30 parts and 10-20 parts respectively.

5. A solid magnesium-reducing carbon-reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone according to claim 4 and a preparation method thereof, characterized in that: In step (1), the manganese ratio (Mn / (Al+Fe)) in the raw material is controlled to be 0.5-1.

5.

6. A solid magnesium carbon reducer suitable for preparing Portland cement clinker from high-magnesium limestone and a preparation method thereof according to claim 5, characterized in that: The granulator in step (2) is a double-die granulator, the granulation pressure is 6 MPa, and the scraper cutting particle size is 5 mm.

7. A solid magnesium-reducing carbon-reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone according to claim 6 and a preparation method thereof, characterized in that: The mass fraction content of magnesium oxide in the high-magnesium limestone in step (3) is 5%-10%.

8. A solid magnesium carbon reducing agent suitable for preparing Portland cement clinker from high-magnesium limestone and a preparation method thereof according to claim 7, characterized in that: In step (3), the amount of high-magnesium limestone added to the cement raw material is 60-90 parts by mass.

9. A solid magnesium carbon reducing agent suitable for preparing Portland cement clinker from high magnesium limestone according to claim 8 and a preparation method thereof, characterized in that: In step (3), when the solid magnesium carbon reducer is used in the production of clinker in a cement kiln, the amount of the solid magnesium carbon reducer added to the raw material is 0.5-1.3 parts by mass, calculated as a percentage by mass.

10. A magnesium-containing carbon-reducing agent suitable for preparing silicate cement clinker from high-magnesium limestone and a preparation method thereof, characterized in that: The composite coal-saving synergist is prepared by using the solid magnesium carbon reducing agent for preparing silicate cement clinker from high-magnesium limestone as described in any one of claims 1 to 9 and the preparation method thereof.

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