A dicalcium silicate-calcium fluosilicate-dodecacalcium heptaaluminate cement clinker and its preparation method

Abstract

The present invention relates to the technical field of cement clinker preparation, and specifically discloses a kind of dicalcium silicate-calcium fluoride-sulfur silicate-dicalcium heptahedralite cement clinker and preparation method thereof. In percentage by mass, the cement clinker includes the following mineral phases: dicalcium silicate 45~68%, calcium fluoride-sulfur silicate 14~26%, calcium heptahedralite 12~22%, calcium aluminum feldspar 1~5%, glass phase 2~6%, and the remainder includes unreacted raw materials and inevitable impurities. The above-mentioned clinker system of the present invention uses fluorine-containing sludge as raw material, not only realizes that fluorine-containing sludge is resource-utilized, reduces the harm of fluorine to the environment, but also converts unstable calcium sulfide silicate into stable and low-firing-temperature calcium fluoride-sulfur silicate, makes the overall firing temperature of the cement clinker system of the present invention significantly lower than traditional Portland cement, thereby effectively reducing energy consumption and reducing carbon dioxide emissions.

Description

Technical Field

[0001] The invention relates to the technical field of cement clinker preparation, and in particular to a dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker and a preparation method thereof. Background Art

[0002] In recent years, global warming has triggered a series of environmental problems, such as melting glaciers, rising sea levels, species extinction, and extreme weather. Greenhouse gas emissions are the primary cause of climate change. The global average temperature in 2019 was 0.92°C higher than the 1980-2010 average and 1.1°C higher than pre-industrial levels. Among these, carbon dioxide emissions are one of the most concerning greenhouse gases, and the relationship between carbon dioxide emissions and global warming has become a major topic of widespread attention and in-depth research worldwide. Since the production of cement clinker requires large amounts of fossil fuels, which releases large amounts of carbon dioxide and consumes a significant amount of non-renewable energy, there is an urgent need to seek technological breakthroughs to achieve carbon emission reduction targets in the building materials industry. Summary of the Invention

[0003] The present invention provides a dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker and a preparation method thereof. The overall firing temperature of the clinker system is significantly lower than that of conventional Portland cement, thereby effectively reducing energy consumption and carbon dioxide emissions. Specifically, the technical solution of the present invention is as follows.

[0004] First, the present invention discloses a dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker, which comprises the following mineral phases, calculated by mass percentage: 45-68% dicalcium silicate, 14-26% calcium fluorosulfosilicate, 12-22% dodecalcium heptaaluminate, 1-5% calcite, and 2-6% glass phase, with the remainder comprising unreacted raw materials, unavoidable impurities, and the like.

[0005] The present invention also discloses a method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecacium heptaaluminate cement clinker, comprising the steps of: uniformly mixing a calcium source, a silicon source, gypsum, an aluminum source, and fluorine-containing sludge in a suitable proportion, followed by calcining. After calcination, the calcined product is rapidly cooled and then ground to obtain the cement clinker.

[0006] Furthermore, the proportions of the raw materials are as follows: 57-85 parts by weight of calcium source, 30-48 parts by weight of silicon source, 18-35 parts by weight of gypsum, 16-27 parts by weight of aluminum source, and 14-32 parts by weight of fluorine-containing sludge. Optionally, the fineness of the components is not less than 200 mesh.

[0007] Furthermore, the calcium source includes at least one of limestone, marl, chalk, alkali slag, carbide slag, etc.

[0008] Furthermore, the silicon source includes at least one of stripping soil, silica ash, coal gangue, clay, quartz sand, diatomaceous earth, etc.

[0009] Furthermore, the gypsum includes at least one of desulfurized gypsum, phosphogypsum, fluorinated gypsum, borogypsum, and titanium gypsum.

[0010] Furthermore, the aluminum source includes at least one of bauxite, fly ash, aluminum ash, coal gangue, etc.

[0011] Furthermore, the fluorine content in the fluorine-containing sludge is not less than 15 wt.%.

[0012] Furthermore, the calcination temperature is 1100-1200° C., and the calcination time is 15-60 min.

[0013] Furthermore, the cement clinker is ground to a fineness of not less than 200 meshes.

[0014] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0015] (1) Compared with traditional silicate cement, calcium sulfosilicate has a lower formation temperature (below 1200°C). Therefore, using this mineral phase as a component of cement clinker can effectively reduce the firing temperature of cement clinker, reduce energy consumption and carbon emissions. However, the structure of calcium sulfosilicate is unstable and it is difficult to exist stably at high temperatures, resulting in a low content of this component in the prepared cement clinker. To this end, the present invention uses fluorine-containing sludge as raw material, and takes advantage of the fact that the electronegativity of the fluorine element therein is greater than that of sulfur, and the attraction of fluorine to bonding electrons is greater than that of sulfur, so that fluorine enters the crystal lattice of calcium sulfosilicate and converts it into calcium fluorosulfosilicate. This mineral phase not only has a more stable structure and can be stably retained in the cement clinker, but also maintains the characteristic of a low firing temperature. The cement clinker of the present invention has dicalcium silicate-calcium fluorosulfosilicate-dodecaluminate as the main components, and can be fired at a relatively low temperature of 1100~1200°C, effectively saving energy consumption, and also realizing the resource utilization of fluorine-containing sludge and reducing the pollution hazards of fluorine.

[0016] (2) Although the dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker of the present invention solves the problem of unstable structure of calcium sulfosilicate, which leads to a low content of this component in the prepared cement clinker, the present invention further finds that this cement clinker still has the problem of insufficient early strength. The said dodecalcium heptaaluminate overcomes the above problem well, effectively improves the early strength of the cement clinker of the present invention, and at the same time improves the setting rate, making the cement clinker system of the present invention also suitable for emergency repair projects. In addition, the hydration of the said dodecalcium heptaaluminate will generate Al(OH)4 -, which puts the pore fluid in an undersaturated state. In order to maintain the charge balance of the pore fluid, other mineral phases in the system begin to dissolve. Also, because at room temperature, the solubility product of calcium fluorosulfosilicate is greater than the solubility product of dicalcium silicate, the dissolution of calcium fluorosulfosilicate is promoted, thereby promoting the hydration process of calcium fluorosulfosilicate. At this time, the silicate ions and calcium ions in the pore fluid are in a relatively saturated state, thereby inhibiting the dissolution of dicalcium silicate. When the hydration of calcium fluorosulfosilicate is exhausted, dicalcium silicate begins to dissolve in large quantities, thereby enabling the later mechanical strength of the cement clinker of the present invention to continue to develop. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 This is a sample of dicalcium silicate-calcium fluorosulfosilicate-dodecacalcium heptaaluminate cement clinker prepared in the following Example 1. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0020] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. The reagents and raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents and raw materials used in the present invention are used in accordance with conventional methods in the art or in accordance with the product instructions.

[0021] In addition, any methods and materials similar or equivalent to those described herein can be applied to the method of the present invention. The technical solution of the present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] A method for preparing cement clinker comprises the following steps:

[0024] (1) Take the following raw materials in parts by weight: 85 parts of limestone, 42 parts of clay, 26 parts of desulfurized gypsum, 21 parts of fly ash, and 14 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0025] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0026] (3) The cake is heated to 1150°C at a heating rate of 10°C / min and calcined for 30 min. The calcined product is then rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker. Figure 1 shown.

[0027] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 67.93% dicalcium silicate, 14.12% calcium fluorosulfosilicate, 11.98% dodecahydrate heptaaluminate, 1.05% gehelite, and 4.74% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0028] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 30.45 MPa, 28d compressive strength = 48.27 MPa.

[0029] Example 2

[0030] A method for preparing cement clinker comprises the following steps:

[0031] (1) Take the following raw materials in parts by weight: 72 parts of limestone, 30 parts of clay, 18 parts of desulfurized gypsum, 27 parts of fly ash, and 29 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0032] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0033] (3) The finished cake was heated to 1150°C at a heating rate of 10°C / min and calcined for 50 min. The calcined product was then rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0034] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 44.97% dicalcium silicate, 23.51% calcium fluorosulfosilicate, 19.14% dodecaluminate heptaaluminate, 5.05% gehelite, and 4.37% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0035] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 31.51 MPa, 28d compressive strength = 50.88 MPa.

[0036] Example 3

[0037] A method for preparing cement clinker comprises the following steps:

[0038] (1) Take the following raw materials in parts by weight: 67 parts of limestone, 39 parts of diatomaceous earth, 32 parts of phosphogypsum, 18 parts of bauxite, and 28 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0039] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0040] (3) The finished cake was heated to 1125°C at a heating rate of 10°C / min and calcined for 20 minutes, and then the calcined product was rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0041] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 52.25% dicalcium silicate, 25.09% calcium fluorosulfosilicate, 14.33% dodecahydrate heptaaluminate, 3.87% gehlenite, and 1.95% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0042] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 32.04 MPa, 28d compressive strength = 52.71 MPa.

[0043] Example 4

[0044] A method for preparing cement clinker comprises the following steps:

[0045] (1) Take the following raw materials in parts by weight: 76 parts of limestone, 48 parts of silica fume, 35 parts of fluorspar, 26 parts of aluminum fume, and 32 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0046] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0047] (3) The finished cake was heated to 1100°C at a heating rate of 10°C / min and calcined for 60 min, and then the calcined product was rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0048] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 45.08% dicalcium silicate, 26.11% calcium fluorosulfosilicate, 22.06% dodecaluminate heptaaluminate, 2.33% gehlenite, and 2.37% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0049] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 34.06 MPa, 28d compressive strength = 53.47 MPa.

[0050] Example 5

[0051] A method for preparing cement clinker comprises the following steps:

[0052] (1) Take the following raw materials in parts by weight: 79 parts of calcium carbide slag, 44 parts of quartz sand, 31 parts of titanium gypsum, 22 parts of coal gangue, and 19 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0053] (2) Dry the above raw materials at 90℃ for 10 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0054] (3) The finished cake was heated to 1200°C at a heating rate of 10°C / min and calcined for 35 minutes, and then the calcined product was rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0055] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 57.46% dicalcium silicate, 14.02% calcium fluorosulfosilicate, 16.37% dodecaluminate heptaaluminate, 4.98% gehelite, and 6.08% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0056] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 29.83 MPa, 28d compressive strength = 54.95 MPa.

[0057] Example 6

[0058] A method for preparing cement clinker comprises the following steps:

[0059] (1) Take the following raw materials in parts by weight: 57 parts of limestone, 46 parts of clay, 33 parts of fluorinated gypsum, 16 parts of fly ash, and 30 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 15.1 wt.%).

[0060] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0061] (3) The finished cake was heated to 1200°C at a heating rate of 10°C / min and calcined for 15 minutes, and then the calcined product was rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0062] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 52.23% dicalcium silicate, 25.87% calcium fluorosulfosilicate, 12.08% dodecaluminate heptaaluminate, 1.41% gehlenite, and 5.84% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0063] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 30.98 MPa, 28d compressive strength = 53.09 MPa.

[0064] Example 7

[0065] A method for preparing cement clinker comprises the following steps:

[0066] (1) Take the following raw materials in parts by weight: 72 parts of limestone, 30 parts of clay, 18 parts of desulfurized gypsum, and 27 parts of fly ash.

[0067] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0068] (3) The finished cake was heated to 1150°C at a heating rate of 10°C / min and calcined for 50 min. The calcined product was then rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0069] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 69.78% dicalcium silicate, 3.46% calcium sulfosilicate, 7.59% dodecaluminate heptaaluminate, 6.21% monocalcium aluminate, 3.57% gehlenite, and 5.88% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0070] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 26.12 MPa, 28d compressive strength = 42.03 MPa.

[0071] Example 8

[0072] A method for preparing cement clinker comprises the following steps:

[0073] (1) Take the following raw materials in parts by weight: 85 parts of limestone, 42 parts of clay, 26 parts of desulfurized gypsum, and 21 parts of fly ash.

[0074] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0075] (3) The finished cake was heated to 1150°C at a heating rate of 10°C / min and calcined for 30 min. The calcined product was then rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0076] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 71.95% dicalcium silicate, 5.54% calcium sulfosilicate, 15.31% dodecaluminate heptaaluminate, 1.77% gehlenite, and 4.33% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0077] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 25.08 MPa, 28d compressive strength = 41.16 MPa.

[0078] Example 9

[0079] A method for preparing cement clinker comprises the following steps:

[0080] (1) Take the following raw materials in parts by weight: 68 parts of limestone, 32 parts of clay, 29 parts of desulfurized gypsum, 37 parts of fly ash, and 29 parts of fluorine-containing sludge (purchased from Anhui Tongxin Recycling Resources Co., Ltd., with a fluorine content of 23.7 wt.%).

[0081] (2) Dry the above raw materials at 80℃ for 12 hours, then grind them through a 200-mesh sieve. Press the obtained cement raw meal into cakes.

[0082] (3) The finished cake was heated to 1150°C at a heating rate of 10°C / min and calcined for 50 min. The calcined product was then rapidly cooled by air and then ground through a 200-mesh sieve to obtain cement clinker.

[0083] The cement clinker prepared in this example was subjected to XRD analysis and then Rietveld quantitative analysis. The results showed that the cement clinker comprised 46.45% dicalcium silicate, 22.28% calcium fluorosulfosilicate, 19.67% tricalcium aluminate, 5.95% gehlenite, and 3.88% glassy phase, with the remainder comprising unreacted raw materials and unavoidable impurities.

[0084] The 1d and 28d compressive strengths of the cement clinker prepared in this embodiment were tested in accordance with GB / T17671-2021 "Test method for strength of cement mortar (ISO method)", and the results were: 1d compressive strength = 21.87 MPa, 28d compressive strength = 45.64 MPa.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A dicalcium silicate-calcium fluorosulfur silicate-dodecalcium heptaaluminate cement clinker, characterized in that: Calculated by mass percentage, it includes the following mineral phases: 45-68% of dicalcium silicate, 14-26% of calcium fluorosulfosilicate, 12-22% of dodecaluminate heptaaluminate, 1-5% of calcite, and 2-6% of glass phase. The remainder includes unreacted raw materials and inevitable impurities.

2. The method for preparing the dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 1, characterized in that: The method comprises the following steps: using calcium source, silicon source, gypsum, aluminum source and fluorine-containing sludge as raw materials, mixing them uniformly in proportion and then calcining them; after completion, rapidly cooling the calcined product and then grinding it to obtain the cement clinker.

3. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The proportions of the components in the raw materials are: 57-85 parts by weight of calcium source, 30-48 parts by weight of silicon source, 18-35 parts by weight of gypsum, 16-27 parts by weight of aluminum source, and 14-32 parts by weight of fluorine-containing sludge.

4. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 3, characterized in that: The fineness of each component is not less than 200 meshes.

5. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The calcium source includes at least one of limestone, marl, chalk, alkali slag and carbide slag.

6. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The silicon source includes at least one of stripping soil, silica ash, coal gangue, clay, quartz sand and diatomaceous earth.

7. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The gypsum includes at least one of desulfurized gypsum, phosphogypsum, fluorinated gypsum, borogypsum, and titanium gypsum.

8. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The aluminum source includes at least one of bauxite, fly ash, aluminum ash, and coal gangue.

9. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to claim 2, characterized in that: The fluorine content in the fluorine-containing sludge is not less than 15 wt.%.

10. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to any one of claims 2 to 9, characterized in that: The calcination temperature is 1100-1200° C., and the calcination time is 15-60 minutes.

11. The method for preparing dicalcium silicate-calcium fluorosulfosilicate-dodecalcium heptaaluminate cement clinker according to any one of claims 2 to 9, characterized in that: Grind the cement clinker to a fineness of not less than 200 mesh.

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