A belite cement clinker, a method for producing the same, and a belite portland cement

Abstract

The present application relates to the technical field of building materials, and particularly relates to a belite cement clinker, a preparation method thereof and a belite portland cement, the mineral composition of the belite cement clinker comprises: C3S 5%-60%, C2S 25%-80%, C3A 1%-8%, C4AF 5%-15%, C5S2Ṡ1-3%, C 10 S4ṠF21-3%, free calcium oxide is less than 1.0%, wherein, Ṡ represents sulfur trioxide. The belite cement clinker is used to prepare a cement product by adding appropriate amount of gypsum, the 3d strength of the cement product is between 13MPa and 35MPa, the 28d strength can reach 60MPa-70MPa, and the 56d strength is as high as 72MPa.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a Belite cement clinker, its preparation method, and Belite silicate cement. Background Technology

[0002] High-belite cement is cement with dicalcium silicate (C2S) as the main mineral. It has unparalleled advantages over general silicate cement, such as low firing temperature, less heat release during hydration, high later strength, and low CO2 emissions. It has been widely recognized. However, existing traditional silicate cement clinker with belite as the main mineral has very low early strength and 28-day strength, which cannot meet the requirements of modern concrete construction cycle, and its energy-saving and emission-reduction effect throughout the life cycle is also very limited. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems of the present invention, the present invention provides a Belite cement clinker, a method for preparing the same, and Belite silicate cement.

[0004] According to a first aspect of the present invention, a Belite cement clinker is provided, wherein the mineral composition of the Belite cement clinker, by weight percentage, comprises: C3S 5%~65%, C2S 20%~80%, C3A 1%~8%, C4AF 5%~15%, C5S2α 1%~3%, C 10 S4ṠF21~3%, free calcium oxide less than 1.0%, where Ṡ represents sulfur trioxide.

[0005] In the above scheme, the mineral composition of the Belite cement clinker of the present invention includes calcium sulfosilicate (C5S2Ṡ) and calcium fluorosulfosilicate (C5S2Ṡ) with a larger cell volume than dicalcium silicate. 10 S4ṠF2) minerals, these mineral components generate crystallization stress during the cooling process, and achieve multi-scale defect design goals such as point, line, surface, volume and microcracks in dicalcium silicate crystal particles, significantly improving the strength of high belite cement at all ages, greatly reducing the heat of hydration, improving durability, and enabling silicate cement with belite as the main mineral to meet the requirements of modern concrete construction cycle.

[0006] Further, by weight percentage, the mineral composition of the Belite cement clinker includes: C3S 10%~50%, C2S 25%~70%, C3A 3%~7%, C4AF 9%~13%, C5S2 1%~3%, C 10 S4ṠF21~2.5%, free calcium oxide less than or equal to 0.30%.

[0007] Furthermore, the Belite cement clinker is calcined from cement raw meal, and by weight percentage, the cement raw meal includes aluminosilicate materials, limestone, iron corrective agent, gypsum, and fluorite; wherein, the limestone contains a calcium oxide content of greater than or equal to 40% by mass; preferably, the cement raw meal includes the following components by weight percentage: aluminosilicate materials of 14%~32%, limestone of 67%~85%, iron corrective agent of 0~5.0%, gypsum (calculated as SO3) of greater than 2.0% and less than or equal to 3.5%, and fluorite (calculated as calcium fluoride) of greater than 0.38% and less than or equal to 1.53%.

[0008] In the above scheme, the cement raw materials used in Belite cement clinker include silica-alumina materials, limestone, iron corrective agents, gypsum, and fluorite. Low-grade limestone is used as the calcareous raw material, and gypsum and fluorite are used as dopants. The main component of gypsum is calcium sulfate, and the main component of fluorite is calcium fluoride. Through chemical doping technology, the direction of the electron cloud of dicalcium silicate crystals is successfully changed, which is conducive to improving the regional distribution of hydration activity. At the same time, the doping of trace elements forms calcium sulfosilicate and calcium fluorosulfosilicate minerals with relatively large cell volumes. During the cooling process, crystallization stress is generated, and the design goals of multi-scale defects such as points, lines, surfaces, volumes, and microcracks are achieved in the dicalcium silicate crystal particles. This significantly improves the strength of Belite cement at all ages, greatly reduces the heat of hydration (more than 30%), and improves durability by 15% to 200%, so that silicate cement with Belite as the main mineral meets the requirements of modern concrete construction cycle. Compared to ordinary high-belite cement clinker, the belite cement clinker of this invention exhibits significantly superior early and late strength. When applied to cement, its 3-day strength increases by more than double, its 28-day strength by more than 20 MPa, and its 56-day strength reaches a high of 93 MPa. Cement prepared using the belite cement clinker of this invention has low heat of hydration and excellent cement mortar flowability. Furthermore, comparisons using the same production line with ordinary cement clinker show that the heat consumption per ton of belite cement clinker is reduced by 5-20%. In addition, existing cement clinker preparation generally uses high-grade limestone with a calcium oxide content greater than 48% as raw material, while the preparation method of this invention only requires a calcium oxide content of 40% or greater. Reducing the amount of limestone used can reduce CO2 emissions and NOx emissions. x Emissions will be reduced by more than 50%, and the amount of ammonia used in SNCR will be reduced by more than 30%.

[0009] Furthermore, the gypsum is selected from desulfurized gypsum, phosphogypsum, fluorogypsum, or natural gypsum.

[0010] The above scheme further limits the calcium oxide content in limestone to greater than or equal to 40%, which allows for the use of lower-grade limestone, significantly improving resource utilization efficiency and reducing production costs.

[0011] Further, the silicon-aluminum material includes aluminum-based solid waste, which includes one or more of sandstone, high-silica tailings, coal-based solid waste, or red mud; and / or, the iron-based corrective material includes one or more natural materials or bulk solid waste containing iron oxide; preferably, the iron-based corrective material includes one or more of iron ore, iron tailings, steel slag, or copper slag.

[0012] In the above scheme, selecting aluminum-based solid waste, including sandstone or high-silica tailings, as raw materials can significantly improve resource utilization efficiency. The comprehensive blending ratio of high-silica tailings and siliceous aluminum solid waste (fly ash, coal gangue, red mud, etc.) can reach more than 30%, which can dispose of a large amount of industrial solid waste and save natural clay resources. At the same time, iron-based corrective materials such as iron tailings, steel slag, and red mud are used, with a blending amount of up to 15%, and the calcium oxide content of low-grade limestone with high silica and high aluminum content can be reduced to below 40%.

[0013] According to a second aspect of the present invention, the present invention also provides a method for preparing the above-mentioned Belite cement clinker, comprising the following steps: Step (1): Mix the silica-alumina material, limestone, iron corrective material, gypsum and fluorite in proportion and then grind them to form cement raw meal; Step (2): Pre-decompose the cement raw material; Step (3): Calcine the pre-decomposed material and then cool it to obtain cement clinker.

[0014] In the above scheme, the method for preparing Belite cement clinker of the present invention first mixes siliceous alumina materials, limestone, gypsum and fluorite in proportion and then grinds them to form cement raw meal. Then, the formed cement raw meal is put into a decomposition furnace for pre-decomposition. Then, the pre-decomposed material is put into a rotary kiln for calcination. After calcination, it is left to stand for a period of time and then cooled to obtain cement clinker. This realizes the large-scale industrial production of cement using a new dry process rotary kiln process system.

[0015] Furthermore, in step (1), the residue on a 0.08 mm square-hole sieve after grinding is less than 15%.

[0016] In the above scheme, limiting the particle size of the ground material is beneficial to improving the efficiency of subsequent cement raw material calcination.

[0017] Furthermore, in step (2), the outlet temperature of the pre-decomposition furnace is controlled at 855℃-875℃.

[0018] In the above scheme, limiting the outlet temperature of the decomposition furnace to a reasonable range is beneficial to maintaining the performance of the pre-decomposition products.

[0019] Furthermore, in step (3), the calcination temperature is 1300~1400℃ and the calcination time is 10min~15min.

[0020] In the above scheme, the calcination temperature during the calcination stage of the present invention is about 100°C lower than that of ordinary silicate cement clinker, thus saving heat consumption and reducing CO2 and NO. x This will reduce emissions and increase hourly output by more than 8%.

[0021] According to a third aspect of the present invention, the present invention also provides a Belite silicate cement prepared from the above-described Belite cement clinker.

[0022] Furthermore, the following method is used to prepare the belite cement clinker and gypsum: the belite cement clinker is ground with gypsum, and the particle size after grinding is such that the residue on a 0.08mm square hole sieve is less than 5% and the residue on a 0.045mm square hole sieve is greater than 5%, thus preparing the belite silicate cement.

[0023] Furthermore, Belite silicate cement has a 3-day strength of 13MPa~35MPa, a 28-day strength of 60MPa~70MPa, a 56-day strength greater than or equal to 72MPa, and a specific surface area of ​​340-360m². 2 / kg, 3-day heat of hydration ≤270J / g, 7-day heat of hydration ≤320J / g.

[0024] The technical solution provided by this invention has the following beneficial effects: The cement raw materials used in the belite cement clinker of this invention include silica-alumina materials, limestone, iron corrective agents, gypsum, and fluorite. Low-grade limestone is used as the calcareous raw material, and first gypsum and fluorite are used as dopants. The main component of gypsum is calcium sulfate, and the main component of fluorite is calcium fluoride. Through chemical doping technology, the electron cloud orientation of dicalcium silicate crystals is successfully changed, which is beneficial to improving the regional distribution of hydration activity. At the same time, the doping of trace elements forms calcium sulfosilicate and calcium fluorosulfosilicate minerals with larger cell volumes than dicalcium silicate. During the cooling process, crystallization stress is generated, and the design goals of multi-scale defects such as points, lines, surfaces, volumes, and microcracks are achieved in the dicalcium silicate crystal particles, which significantly improves the strength of high belite cement at all ages. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1This is a SEM image of the Belite cement clinker from Embodiment 4 of the present invention.

[0027] Figure 2 This is the BSE diagram of the Belite cement clinker of Embodiment 4 of the present invention.

[0028] Figure 3 O in the Belite cement clinker of Example 4 1s X-ray photoelectron spectroscopy analysis results of orbital electron chemical shift.

[0029] Figure 4 XPS-Ca in the Belite cement clinker of Example 4 2p X-ray photoelectron spectroscopy analysis results of orbital electron chemical shift. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] The beneficial effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0032] Example 1

[0033] Examples 1-5 each provide a belite cement clinker, which is produced by calcining cement raw meal. The cement raw meal includes aluminosilicate materials, limestone, iron corrective agent, gypsum, and fluorite. The aluminosilicate materials comprise 14%–32%, limestone 67%–85%, iron corrective agent 0–5.0%, gypsum (calculated as SO3) greater than 2.0% and less than or equal to 3.5%, and fluorite (calculated as calcium fluoride) greater than 0.38% and less than or equal to 1.53%. Their respective mineral compositions are shown in Table 1 below. The gypsum is selected from desulfurized gypsum, and the limestone contains 45% calcium oxide. The aluminosilicate materials include aluminum-based solid waste, which includes sandstone, high-silica tailings, coal-based solid waste, and red mud. The iron corrective agent includes iron ore, iron tailings, steel slag, and copper slag.

[0034] The preparation method of Belite cement clinker is as follows: Step (1): Mix the silicon-aluminum material, iron corrective material, limestone, gypsum and fluorite in an appropriate proportion and then grind them. After grinding, the particle size should be less than 15% on a 0.08mm square hole sieve to form cement raw meal.

[0035] Step (2): Cement raw materials enter the new dry process cement rotary kiln production process system equipped with preheating and pre-decomposition systems, and are pre-decomposed in the decomposition furnace. The outlet temperature of the decomposition furnace is controlled at 865±10℃.

[0036] Step (3): The pre-decomposed material enters a rotary kiln and is calcined at 1350±50℃. The time spent passing through the firing zone is 10min~15min, and then it is cooled to obtain Belite cement clinker. The mineral composition of the obtained Belite cement clinker is shown in Table 2 below.

[0037] Comparative Example 1

[0038] This comparative example provides a Belite cement clinker that differs from Example 1 in that it does not contain fluorite or gypsum.

[0039] Comparative Example 2

[0040] This comparative example provides a Belite cement clinker, which differs from Example 1 in that it contains gypsum but does not contain fluorite.

[0041] Comparative Example 3

[0042] This comparative example provides a Belite cement clinker, which differs from Example 1 in that it contains fluorite but does not contain gypsum.

[0043] The mineral composition of the Belite cement clinker obtained in Comparative Examples 1-3 is shown in Table 2 below.

[0044] Table 1

[0045] Table 2

[0046] The belite cement clinker from Examples 1-5 and Comparative Examples 1-3 was ground with gypsum at a weight ratio of 97.5%:2.5%. The particle size distribution after grinding was such that the residue on a 0.08mm square-hole sieve was less than 5%, and the residue on a 0.045mm square-hole sieve was greater than 5%. Belite silicate cement was thus prepared. The performance of the obtained belite silicate cement was tested according to GB / T17671-1999 standard, and the test results are shown in Table 3 below.

[0047] Table 3

[0048] As shown in Table 3, the cement prepared from the high-activity belite cement clinker of this invention has a 3-day strength between 15 and 35 MPa, a 28-day strength of 60 to 70 MPa, and a 56-day strength as high as 72 MPa. Compared with P.I42.5 silicate cement (3-day heat of hydration greater than or equal to 290 J / g, 7-day heat of hydration greater than or equal to 350 J / g), the cement prepared from the high-activity belite cement clinker of this invention has a 30-50% lower heat of hydration. At a water-cement ratio of 0.5, the cement mortar spread can reach 175 mm to 200 mm, with low heat of hydration, good stability, and excellent workability. All performance indicators of the cement fully meet or exceed the requirements of ASTM 150M and EN197-1 standards. Concrete prepared with the high-performance, high-activity belite cement of this invention exhibits a 28-day strength that is more than 10% higher than that of concrete prepared with ordinary P.I42.5 silicate cement, as well as superior durability. The chloride ion permeability coefficient and electrical flux test results are reduced by more than 50%, indicating that the high-activity belite cement clinker of this invention has the potential to replace ordinary silicate cement clinker in the large-scale production of general-purpose silicate cement.

[0049] The Belite cement clinker of Example 4 of this invention was subjected to SEM and BSE tests, and the results are as follows: Figure 1 and Figure 2 As shown, by Figure 1 and Figure 2 As can be seen, the high-activity belite cement clinker of this invention features a multi-scale crystal defect design. Its development is based on quantum mechanics, doping theory, defect design theory, high-temperature thermodynamics, and surface chemistry. By reconstructing the electron cloud distribution of belite crystals and employing a multi-scale crystal defect design method, the hydration activation points of dicalcium silicate minerals are increased, improving the grindability of the high-belite clinker and thus significantly enhancing its early and later-stage strength. The green, low-carbon silicate cement clinker, with high-activity belite as the main mineral, is produced using an existing new dry-process cement system. The cement performance meets the requirements of general silicate cement standards, achieving the goals of doubled material performance, energy saving, carbon reduction, and increased efficiency, providing strong technical support for cement enterprises to achieve green and low-carbon transformation.

[0050] like Figure 3 This shows the oxygen atom 1s (O) in the Belite cement clinker of Example 4. 1s X-ray photoelectron spectroscopy analysis results of orbital electron chemical shift. Figure 4 This shows the calcium element 2p (Ca) in the Belite cement clinker of Example 4. 2p X-ray photoelectron spectroscopy analysis results of orbital electron chemical shift were obtained through... Figure 3 and Figure 4It can be seen that the outer electrons of oxygen and calcium elements in dicalcium silicate mineral crystals have undergone significant chemical shifts, indicating that the electron cloud distribution of dicalcium silicate crystals has been reconstructed.

[0051] Industrial production trials and engineering application technology research results show that various types of cement products formulated using the belite cement clinker of this invention not only meet the requirements of current general-purpose silicate cement product standards, but also allow for the development of high-value-added, multi-functional, and multi-purpose special engineering cement products, such as high (medium) sulfate-resistant cement, marine silicate cement, nuclear power cement, dam cement, and oil well cement. High-activity belite cement can be used to formulate fiber-reinforced ultra-high performance concrete (FRUHPC) and ultra-durable concrete (UHDC) with strength grades up to 250 MPa, exhibiting significant performance, quality, cost, and environmental advantages over ordinary silicate cement, and will become a fundamental material for constructing sustainable, green, and low-carbon infrastructure.

[0052] Compared with ordinary silicate cement clinker, in addition to its excellent ultra-high cementitious properties, the belite cement clinker of this invention has typical characteristics of low energy load, low resource load, and low environmental load. After the industrialization of the research and development results, based on the annual replacement of 100 million tons of ordinary silicate cement clinker, and the heat consumption of each ton of ordinary silicate cement clinker being 110 kg of standard coal, the production of highly active belite cement clinker can save about 10% of heat consumption, equivalent to about 1.1 million tons of standard coal, saving 1.65 billion yuan in costs; CO2 emissions can be reduced by up to 5 million tons, saving about 2 billion yuan in costs; ammonia water consumption can be reduced by 150,000 tons, saving 120 million yuan in costs; 10 million tons of steel slag and 12 million tons of desulfurized gypsum can be disposed of, and 110 million tons of low-grade limestone (CaO content below 45%) can be used, reducing costs by more than 3.5 billion yuan. This not only significantly improves resource utilization efficiency but also realizes the strategic storage of high-grade original ecological natural resources. In addition, achieving green and low-carbon transformation of traditional cement enterprises based on existing production lines not only preserves the value of state-owned assets, but also stabilizes employment and maintains social stability.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A type of belite cement clinker, characterized in that, By weight percentage, the mineral composition of the Belite cement clinker includes: C3S 5%~60%, C2S 25%~80%, C3A 1%~8%, C4AF 5%~15%, C5S2α 1%~3%, C 10 S4ṠF21~3%, free calcium oxide less than 1.0%, where Ṡ represents sulfur trioxide.

2. The Belite cement clinker according to claim 1, characterized in that, By weight percentage, the mineral composition of the Belite cement clinker includes: C3S 10%~50%, C2S 25%~70%, C3A 3%~7%, C4AF 9%~13%, C5S2 1%~3%, C 10 S4ṠF21~2.5%, free calcium oxide less than or equal to 0.30%.

3. The Belite cement clinker according to claim 1, characterized in that, The Belite cement clinker is produced by calcining cement raw meal, which includes silica-alumina materials, limestone, iron corrective agents, gypsum, and fluorite; wherein the limestone contains a calcium oxide content of 40% or more by mass.

4. The Belite cement clinker according to claim 3, characterized in that, The gypsum is selected from desulfurized gypsum, phosphogypsum, fluorogypsum or natural gypsum.

5. The Belite cement clinker according to claim 3 or 4, characterized in that, The silicon-aluminate material includes aluminum-based solid waste and / or sandstone, wherein the aluminum-based solid waste includes one or more of high-silicon tailings, coal-based solid waste, or red mud. And / or, the iron-based corrective material comprises one or more natural materials or bulk solid waste containing iron oxide.

6. The Belite cement clinker according to claim 5, characterized in that, The iron-based corrective material includes one or more of iron ore, iron tailings, steel slag, or copper slag.

7. The method for preparing Belite cement clinker according to any one of claims 1-6, characterized in that, Includes the following steps: Step (1): Mix the silica-alumina material, limestone, iron corrective material, gypsum and fluorite in proportion and then grind them to form cement raw meal; Step (2): Pre-decompose the cement raw material; Step (3): Calcine the pre-decomposed material and then cool it to obtain cement clinker.

8. The method for preparing Belite cement clinker according to claim 7, characterized in that, In step (1), the particle size after grinding is required to have a sieve residue of less than 15% on a 0.08mm square hole sieve; and / or, in step (2), the outlet temperature of the pre-decomposition furnace is controlled at 855℃~875℃.

9. The method for preparing Belite cement clinker according to claim 7, characterized in that, In step (3), the calcination temperature is 1300℃~1400℃ and the time is 10min~15min.

10. A belite silicate cement, characterized in that, It is prepared from the belite cement clinker as described in any one of claims 1-6.

11. The belite silicate cement according to claim 10, characterized in that, Belite silicate cement has a 3-day strength of 13MPa~35MPa, a 28-day strength of 60MPa~70MPa, a 56-day strength of ≥72MPa, and a specific surface area of ​​340-360m². 2 / kg, 3-day heat of hydration ≤270J / g, 7-day heat of hydration ≤320J / g.

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