Solid-waste-based low-calcium clinker prepared from industrial solid waste at low temperature and method

Abstract

The invention discloses a solid-waste-based low-calcium clinker prepared from industrial solid wastes at low temperature and a method, which comprises the following steps: grinding a calcium raw material, a siliceous raw material, an aluminum correction raw material, an iron correction raw material and gypsum as raw materials, and fully mixing in proportion to obtain a homogeneous mixed raw material; calcining the mixed raw material at low temperature, quickly cooling after calcining, and grinding to obtain solid waste-based low-calcium clinker; the mineral phase of the cement clinker comprises 45-50% of calcium sulphosilicate (C5S2), 25-35% of calcium sulphoaluminate (C4A3), 10-15% of an iron phase (C6AF2) and the balance of unreacted raw materials and calcium aluminate in different forms. The CaO content required by the clinker prepared by the method disclosed by the invention is 45-48% and is about 17-20% lower than the CaO content (more than 65%) in ordinary Portland cement clinker. Finally, the carbon emission generated by limestone decomposition is significantly reduced. The low-calcium cement clinker prepared by the invention has the advantages of good burnability, low firing temperature, good grindability and excellent early compressive strength.

Description

Technical Field

[0001] The invention belongs to the technical field of cementitious material preparation, and specifically relates to solid waste-based low-calcium clinker and a preparation method thereof, in particular to a solid waste-based low-calcium clinker and a method thereof prepared at low temperature using industrial solid waste. Background Art

[0002] As the world's industrialization process continues to accelerate, carbon emissions have become a critical issue that cannot be ignored. It has had a profound and extensive impact on the ecological balance of the earth and the sustainable and healthy development of human civilization. In the preparation of cement clinker, it is inevitable to involve a series of behaviors that will produce high carbon emissions, such as the large-scale consumption of natural resources, the decomposition of carbonates, and the burning of fossil fuels. For example, limestone, as one of the main raw materials for cement production, its mining will not only destroy the mountain vegetation and ecological environment, but also release a large amount of carbon dioxide during the calcination process due to the decomposition of carbonates in the limestone; at the same time, in order to provide the high temperature required for calcination, the burning of large amounts of fossil fuels such as coal will further increase carbon emissions.

[0003] In order to actively respond to low-carbon and green, the building materials industry urgently needs to seek major breakthroughs in related technologies. In this situation, the development of a cement clinker technology that can make full use of solid waste and prepare low-CaO content at low calcination temperatures is undoubtedly of great guiding significance for the healthy and sustainable development of the cement industry. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a solid waste-based low-calcium cement clinker and a preparation method thereof in view of the deficiencies in the prior art. The CaO content and calcination temperature in the chemical composition of the clinker are significantly lower than those of traditional silicate cement clinker, thereby being able to effectively reduce carbon emissions.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste, comprising: using calcium raw materials, silicon raw materials, aluminum-corrected raw materials, iron-corrected raw materials and gypsum as raw materials, grinding and fully mixing them in proportion to obtain a homogeneous mixed raw material; calcining the mixed raw material at low temperature, rapidly cooling after calcination, and grinding to obtain solid waste-based low-calcium clinker; The mixed raw material comprises, by mass percentage, 41-48 parts of calcium raw material, 2-7 parts of silicon raw material, 13-15 parts of aluminum modified raw material, 7-16 parts of iron modified raw material, and 25 parts of gypsum; The low-temperature calcination process is as follows: heating from room temperature to 850 - 950 °C at a heating rate of 10 °C / min and calcining for 30 - 60 min, and then heating to 1130 - 1150 °C and calcining for 30 - 60 min; In the obtained solid waste-based low-calcium clinker, the calcium element is calculated as CaO, and the mass content is not higher than 48%.

[0006] Specifically, the calcareous raw material is at least one of limestone, chalk, marl, and carbide slag, preferably limestone; the CaO content in the calcareous raw material is 45 - 55%.

[0007] Specifically, the siliceous raw material is at least one of sandstone, coal gangue, clay, and silica fume, preferably coal gangue; the SiO2 content in the siliceous raw material is 40 - 50%.

[0008] Specifically, the aluminous corrective raw material is at least one of bauxite, fly ash, aluminum ash, clay, and coal gangue, preferably bauxite; the Al2O3 content in the aluminous corrective raw material is 60 - 87%.

[0009] Specifically, the ferrous corrective raw material is at least one of iron powder, metal slag, steel slag, and red mud, preferably steel slag; the Fe2O3 content in the ferrous corrective raw material is 20 - 30%.

[0010] Specifically, the gypsum is at least one of natural gypsum, desulfurized gypsum, phosphogypsum, fluorogypsum, titanium gypsum, and boron gypsum, preferably desulfurized gypsum; the SO3 content in the gypsum is 30 - 40%.

[0011] Specifically, the residue on sieve of the mixed raw meal through a 74 μm aperture sieve is ≤15 wt%.

[0012] Specifically, the rapid cooling method is to rapidly cool to room temperature by air cooling; the grinding is to grind the calcined clinker to a specific surface area of 340 - 360 m 2 / kg.

[0013] Furthermore, the solid waste-based low-calcium clinker prepared by the above preparation method is also within the protection scope of the present invention.

[0014] Furthermore, in the solid waste-based low-calcium clinker prepared by the present invention, the mineral composition is by mass percentage: calcium sulfoaluminate 45 - 50%, calcium sulphoaluminate 25 - 35%, iron phase 10 - 15%, and the balance includes unreacted raw materials and different forms of calcium aluminate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) For the first time, the present invention uses steel slag, coal gangue, and desulfurized gypsum as raw materials for preparing solid waste-based low-carbon cement clinker, which contains various metal ions. During the calcination process, these ions enter the lattice of calcium sulfoaluminate, making its structure more stable and further reducing the firing temperature. To a certain extent, it promotes the coexistence of calcium silicate sulfate and calcium sulfoaluminate in the temperature range of 1100 - 1200 °C, effectively saving energy consumption. At the same time, some heavy metal ions are effectively solidified in the clinker mineral structure, greatly reducing the risk of heavy metal leaching and realizing the harmless treatment of steel slag and coal gangue.

[0016] (2) The calcium oxide content required for the calcium silicate sulfate - calcium sulfoaluminate - iron phase system cement clinker designed by the present invention is 45 - 48%, which is about 17 - 20% lower than that of ordinary Portland cement clinker. And the clinker of this system can be fired at a low temperature of 1130 °C, and the fired clinker lumps have excellent grindability.

[0017] (3) The clinker prepared by the method of the present invention has high early strength and setting rate, making the cement clinker system of the present invention suitable for emergency repair projects. In addition, Al(OH)4 generated by the hydration of calcium sulfoaluminate in the clinker - will make the pore fluid in an undersaturated state. To maintain the charge balance of the pore fluid, calcium silicate sulfate in the system accelerates dissolution. Finally, the early strength and late strength of the clinker develop in a coordinated manner, meeting the requirements of modern building materials for sustainable development and having significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The following further describes the present invention in detail in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0019] Figure 1 is the XRD pattern of the clinker obtained in each example and comparative example of the present invention.

[0020] Figure 2 is the XRD pattern and thermogravimetric curve of the hydrated paste product characterization of the clinker in Example 2. SPECIFIC EMBODIMENTS

[0021] The present invention can be better understood according to the following embodiments.

[0022] In the following examples, the chemical compositions of the raw materials used are shown in Table 1.

[0023] Table 1 Chemical composition of raw meal (wt / %)

[0024] Example 1 Preparation and testing method of solid waste-based low-calcium clinker, including the following steps: (1)Take the following raw materials in parts by weight: 16 parts of steel slag, 3 parts of coal gangue, 25 parts of desulfurized gypsum, 15 parts of bauxite, and 41 parts of limestone.

[0025] (2)Fully mix the above raw materials through a roller ball mill, and use a press to make the obtained raw meal into raw meal blocks with a size of 60mm * 60mm * 5mm.

[0026] (3)Heat the raw meal blocks at a heating rate of 10 °C / min to 900 °C and hold for 30 min, then heat at a heating rate of 10 °C / min to 1130 °C and hold for 30 min, then quickly take out and air-cool to room temperature, and then grind to a specific surface area of 340 - 360 m 2 / kg according to GB / T8074~2008.

[0027] (4)Perform XRD testing on the cement clinker prepared in this example. The XRD pattern of the product is as Figure 1 shown. Then carry out quantitative analysis based on the Rietveld method, and the quantitative results are shown in Table 3.

[0028] (5)Prepare a neat cement paste test block according to a water-cement ratio of 0.35, and then test the compressive strength of the neat cement paste test block of the cement clinker prepared in this example according to the test standard: DBJT 13-196-2021 "Design and Test Regulations for Mix Proportion of Cement Paste Materials". The test results are shown in Table 4.

[0029] Example 2

[0030] Preparation and testing method of solid waste-based low-calcium clinker, including the following steps: (1)Take the following raw materials in parts by weight: 7 parts of steel slag, 7 parts of coal gangue, 25 parts of desulfurized gypsum, 13 parts of bauxite, and 48 parts of limestone.

[0031] (2)Fully mix the above raw materials through a roller ball mill, and use a press to make the obtained raw meal into raw meal blocks with a size of 60mm * 60mm * 5mm.

[0032] (3)Heat the raw meal blocks at a heating rate of 10 °C / min to 900 °C and hold for 30 min, then heat at a heating rate of 10 °C / min to 1130 °C and hold for 30 min, then quickly take out and air-cool to room temperature, and then grind to a specific surface area of 340 - 360 m 2 / kg according to GB / T8074~2008.

[0033] (4)Perform XRD testing on the cement clinker prepared in this example. The XRD pattern of the product is as Figure 1 shown. Then carry out quantitative analysis based on the Rietveld method, and the quantitative results are shown in Table 3.

[0034] (5) Prepare the clinker neat cement specimens according to the water-cement ratio of 0.35, and then test the compressive strength of the prepared cement clinker neat cement specimens in this example according to the test standard: DBJT 13-196-2021 "Design and Test Procedures for Mix Proportions of Cement Neat Cement Materials". The test results are shown in Table 4.

[0035] Example 3

[0036] Preparation and testing method of solid waste-based low-calcium clinker, including the following steps: (1) Take the following raw materials by weight: 7 parts of steel slag, 7 parts of coal gangue, 25 parts of desulfurized gypsum, 13 parts of bauxite, and 48 parts of limestone.

[0037] (2) Thoroughly mix the above raw materials through a roller ball mill, and press the obtained raw meal into raw meal blocks of 60mm * 60mm * 5mm with a press.

[0038] (3) Heat the raw meal blocks at a heating rate of 10 °C / min to 900 °C and hold for 30 min, then heat at a heating rate of 10 °C / min to 1150 °C and hold for 30 min, then quickly take out and air-cool to room temperature, and then grind to a specific surface area of 340 - 360 m 2 / kg according to GB / T8074~2008.

[0039] (4) Conduct XRD testing on the cement clinker prepared in this example. The XRD pattern of the product is as Figure 1 shown. Then conduct quantitative analysis based on the Rietveld method, and the quantitative results are shown in Table 3.

[0040] (5) Prepare the clinker neat cement specimens according to the water-cement ratio of 0.35, and then test the compressive strength of the prepared cement clinker neat cement specimens in this example according to the test standard: DBJT 13-196-2021 "Design and Test Procedures for Mix Proportions of Cement Neat Cement Materials". The test results are shown in Table 4.

[0041] Comparative Example 1 Commercially available ordinary Portland cement clinker (Liyang Tianshan Cement Co., Ltd.).

[0042] (1) Grind to a specific surface area of 340 - 360 m² / kg according to GB / T8074~2008.

[0043] (2) Conduct XRD testing on the cement clinker in this comparative example. The XRD pattern of the product is as Figure 1 shown.

[0044] (3) The clinker paste test block was prepared according to the water-cement ratio of 0.40, and then the compressive strength of the cement clinker paste test block described in this comparative example was tested in accordance with the test standard: DBJT 13-196-2021 "Cement paste material mix design and test procedures". The test results are shown in Table 4.

[0045] (4) XRD test was performed on the commercially available ordinary Portland cement clinker in this comparative example. The product XRD pattern is shown in Figure 1 Then, a quantitative analysis based on the Rietveld method was performed, and the quantitative results are shown in Table 2.

[0046] Comparative Example 2 The preparation and testing method of solid waste-based low-calcium clinker comprises the following steps: (1) Take the following raw materials in parts by weight: 7 parts of steel slag, 7 parts of coal gangue, 25 parts of desulfurized gypsum, 13 parts of bauxite, and 48 parts of limestone.

[0047] (2) The above raw materials were fully mixed by a roller ball mill, and the obtained raw material was pressed into raw material blocks of 60 mm*60 mm*5 mm by a press.

[0048] (3) The raw material block is heated to 900°C at a heating rate of 10°C / min and kept at this temperature for 30 min, and then heated to 1250°C at a heating rate of 10°C / min and kept at this temperature for 30 min, then quickly taken out and air-cooled to room temperature, and then ground according to the national standard GB / T8074-2008 to a specific surface area of ​​340-360 m 2 / kg.

[0049] (4) The cement clinker prepared in this example was subjected to XRD test, and the product XRD pattern is shown in Figure 1 Then, a quantitative analysis based on the Rietveld method was performed, and the quantitative results are shown in Table 3.

[0050] Table 2 Mineral content of ordinary Portland cement clinker (wt / %)

[0051] Table 3 Clinker mineral content (wt / %)

[0052] Table 4 Compressive strength of clinker

[0053] Combination Figure 1And the quantitative results show that the f-CaO content in the two groups of examples calcined at 1130 °C meets the national standard (GB / T 21372-2024), and the contents of the three main mineral phases are close to the design values. The f-CaO content in Example 3 calcined at 1150 °C also meets the national standard. The early compressive strengths (1 d and 3 d) of the three groups of examples are higher than those of commercial Portland cement clinker, and the late compressive strength (28 d) of Example 2 is also similar to that of commercial Portland cement clinker. It shows excellent early compressive strength and good strength development. In addition, the early compressive strengths of Example 2 calcined at 1130 °C and Example 3 calcined at 1150 °C are similar. And Example 2 calcined at 1130 °C has better late compressive strength. In Comparative Example 2 calcined at 1250 °C, calcium sulfoaluminate decomposes in large amounts, and the contents of calcium aluminate and tricalcium aluminate increase significantly. These mineral composition contents have deviated seriously from the design values, indicating that the solid waste-based low-calcium clinker of this system cannot be fired at 1250 °C. From Figure 2 It can be seen that there is a certain amount of AH3 in the paste of Example 2 after 2 h of hydration. When hydrated for 1 d, the diffraction peak of Strätlingite can be observed in the XRD of the hydrated sample, and the hydration of calcium sulfoaluminate is accelerated.

[0054] The present invention provides an idea and method for preparing a solid waste-based low-calcium clinker using industrial solid waste at low temperature. There are many methods and ways to specifically implement this technical solution. The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste, characterized in that: The raw materials are calcium raw materials, silicon raw materials, aluminum-corrected raw materials, iron-corrected raw materials and gypsum, which are ground and fully mixed in proportion to obtain a homogeneous mixed raw material; the mixed raw material is calcined at low temperature, and after calcination, it is quickly cooled and ground to obtain a solid waste-based low-calcium clinker; The mixed raw material comprises, by mass percentage, 41-48 parts of calcium raw material, 2-7 parts of silicon raw material, 13-15 parts of aluminum modified raw material, 7-16 parts of iron modified raw material, and 25 parts of gypsum; The low-temperature calcination process is as follows: heating from room temperature to 850-950°C for 30-60 min at a heating rate of 10°C / min, and then heating to 1130-1150°C for 30-60 min; The calcium content of the obtained solid waste-based low-calcium clinker, calculated as CaO, is not higher than 48% by mass.

2. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The calcium raw material is at least one of limestone, chalk, marl and carbide slag; the CaO content in the calcium raw material is 45-55%.

3. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The siliceous raw material is at least one of sandstone, coal gangue, clay and silica fume; the SiO2 content in the siliceous raw material is 40-50%.

4. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The aluminum correction raw material is from at least one of bauxite, fly ash, aluminum ash, clay, and coal gangue; the Al2O3 content in the aluminum correction raw material is 60-87%.

5. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The iron-based amended raw material is at least one of iron powder, metal slag, steel slag and red mud; the Fe2O3 content in the iron-based amended raw material is 20-30%.

6. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The gypsum is at least one of natural gypsum, desulfurized gypsum, phosphogypsum, fluorinated gypsum, titanium gypsum and boric gypsum; the SO3 content in the gypsum is 30-40%.

7. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The residue of the mixed raw meal on a sieve with a particle size of 74 μm is ≤15 wt %.

8. The method for preparing solid waste-based low-calcium clinker at low temperature using industrial solid waste according to claim 1, characterized in that: The rapid cooling method is to rapidly cool to room temperature by air cooling; the grinding method is to grind the calcined clinker to a specific surface area of ​​340-360 m 2 / kg.

9. The solid waste-based low-calcium clinker prepared by the preparation method according to any one of claims 1 to 8.

10. The solid waste-based low-calcium clinker according to claim 9, characterized in that: Its mineral composition is calculated by mass percentage as follows: calcium sulfosilicate 45-50%, calcium sulfoaluminate 25-35%, iron phase 10-15%, and the remainder includes unreacted raw materials and different forms of calcium aluminate.

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