Carbonized activated steel slag, preparation method and application in preparation of cement clinker

Abstract

The invention discloses carbonized and activated steel slag, a preparation method and application of the carbonized and activated steel slag in preparation of cement clinker. The preparation method of the carbonized and activated steel slag comprises the following steps: activating steel slag by adopting an activating solution, adjusting the pH value to 7-8 after first stirring, and then performing second stirring, filtering, washing, drying, grinding and sieving to obtain the activated steel slag, and carbonizing the activated steel slag to obtain carbonized activated steel slag. The steel slag is subjected to chemical treatment and CO2 curing synergistic treatment, so that the existence form of CaO in the steel slag is changed into a unit from multiple elements, the existence form of CaO is optimized, the complex chemical composition of the steel slag is simplified, and the steel slag replaces limestone to serve as a raw material for calcining the cement clinker, so that the utilization rate of the limestone is reduced, and the utilization rate of the steel slag in the field of building materials is increased; the performance of the cement is also effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a carbonized activated steel slag, a preparation method and application thereof in preparing cement clinker. Background Art

[0002] As the core cementitious material in the construction industry, Portland cement is highly dependent on high-quality limestone during its production process, resulting in rapid resource consumption. Given the limited nature of limestone resources, developing alternative raw materials to achieve sustainable development is of great significance for environmental protection and resource conservation.

[0003] Steel slag is an industrial waste produced during the steelmaking process, with a large stockpile. The chemical composition of steel slag contains more CaO, Fe 2 O 3 、SiO 2 It exists, which meets the requirements for preparing cement clinker. Therefore, it is theoretically feasible to use steel slag instead of limestone to prepare cement clinker. However, CaO exists in various forms in steel slag, and the mechanism of its influence on the formation of clinker minerals is still unclear, resulting in insufficient performance of cement clinker made directly from steel slag. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, propose a carbonized activated steel slag, a preparation method and an application in the preparation of cement clinker, and solve the technical problem of insufficient performance of cement clinker directly made from steel slag in the prior art.

[0005] In a first aspect, the present invention provides a method for preparing carbonized activated steel slag, comprising the following steps: The steel slag is activated by using an activation liquid, the pH value is adjusted to 7-8 after the first stirring, and then the activated steel slag is obtained by the second stirring, filtering, washing, drying, grinding and screening. The activated steel slag is carbonized to obtain carbonized activated steel slag; wherein the activation liquid comprises: inorganic acid, complexing agent and water.

[0006] In a second aspect, the present invention provides a carbonized activated steel slag, which is obtained by the preparation method of the carbonized activated steel slag provided by the first aspect of the present invention.

[0007] In a third aspect, the present invention provides the use of the carbonized activated steel slag in the preparation of cement clinker.

[0008] In a fourth aspect, the present invention provides a cement based on carbonized activated steel slag, wherein the cement based on carbonized activated steel slag is obtained by mixing the cement clinker provided by the third aspect of the present invention and gypsum.

[0009] Compared with the prior art, the beneficial effects of the present invention include: The present invention chemically treats steel slag and CO 2 The solidification synergistic treatment changes the existence form of CaO in the steel slag from multiple to single, optimizes the existence form of CaO, simplifies the complex chemical composition of the steel slag, and uses it to replace limestone as a raw material for calcining cement clinker, which not only reduces the utilization rate of limestone and improves the utilization rate of steel slag in the field of building materials, but also effectively improves the performance of cement. The carbonized activated steel slag prepared by the present invention has good application prospects in cement clinker, and can effectively improve the reaction activity of cement clinker, thereby improving its mechanical properties. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0011] In a first aspect, the present invention provides a method for preparing carbonized activated steel slag, comprising the following steps: S1, activating the steel slag with an activation liquid, adjusting the pH to 7-8 after a first stirring, and then performing a second stirring, filtering, washing, drying, grinding, and screening to obtain activated steel slag; S2. Carbonizing the activated steel slag to obtain carbonized activated steel slag; wherein the activation solution comprises: an inorganic acid, a complexing agent and water.

[0012] In the activation solution of the present invention, the inorganic acid can react quickly with the alkaline oxide in the steel slag, thereby improving the chemical activity of the steel slag; the complexing agent can promote the dissolution of the alkaline components in the steel slag, and form a synergistic activation effect with the inorganic acid. At the same time, the steel slag itself has a certain hydration activity, and the complexing agent can form a pH buffer system, which helps to maintain the stability of the pH value during the reaction and ensure the activation reaction. The present invention uses the activation solution to activate the steel slag, which can effectively improve the carbonization activity of the steel slag on the one hand. This is because: 1. The H in the activation solution + First, it can destroy the inert mineral structure in the steel slag, such as the RO phase, thereby enhancing the activity of the steel slag; second, it can increase the specific surface area of ​​the steel slag, which can fully react during carbonization; on the other hand, the Mg-O bond can be destroyed by the activation liquid, and Mg is more likely to enter the belite mineral lattice during the subsequent calcination process, thereby improving the activity of the cement clinker based on the carbonized activated steel slag. In addition, compared with the direct use of steel slag, the existence form of Fe in the steel slag changes after being treated with the activation liquid, which can significantly reduce the Gibbs formation energy of the iron-containing intermediate phase minerals, and is conducive to the formation of intermediate phase minerals during the subsequent calcination process. In addition, adjusting the pH of the activation system to 7~8 is also conducive to the subsequent carbonization activation reaction.

[0013] In this embodiment, in step S1, the chemical composition of the steel slag includes, by weight percentage: CaO 40%-50%, SiO 2 10%-15%, Al 2 O 3 1%-4%, Fe 2 O 3 20%-30%, the balance is loss on ignition and unavoidable impurities (such as MgO, etc.).

[0014] In this embodiment, in step S1, the particle size of the steel slag is ≤75 μm.

[0015] In this embodiment, in step S1, the inorganic acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid.

[0016] In this embodiment, in step S1, the complexing agent is citric acid.

[0017] In this embodiment, in step S1, in the activation solution, the concentration of the inorganic acid is 0.009-0.09 mol / L, and the concentration of the complexing agent is 0.0009-0.012 mol / L.

[0018] In some specific embodiments of the present invention, in step S1, the activation solution is prepared by a 0.01-0.1 mol / L inorganic acid solution and a 0.01-0.1 mol / L complexing agent solution in a mass ratio of 8-10:1.

[0019] In this embodiment, in step S1, the mass ratio of the activation solution to the steel slag is (50-150):1.

[0020] In this embodiment, in step S1, the temperature of the first stirring is room temperature, and the time of the first stirring is 10 to 60 minutes.

[0021] In this embodiment, in step S1, a sodium hydroxide solution is used to adjust the pH to 7-8.

[0022] Wherein, the concentration of the sodium hydroxide solution is 0.05~0.2mol / L, further 0.1mol / L.

[0023] In this embodiment, in step S1, the temperature of the second stirring is room temperature, and the time of the second stirring is 30 to 60 minutes.

[0024] In this embodiment, in step S1, during the screening process, the mesh number of the sieve is ≥ 200 mesh, for example, it can be 200 mesh, 300 mesh, 400 mesh, 500 mesh, 1000 mesh, etc.

[0025] In this implementation, step S2 includes: The activated steel slag is dispersed in water, and then a gas containing carbon dioxide is introduced. After the reaction is completed, the slag is dried to obtain carbonized activated steel slag.

[0026] Among them, the mass ratio of water to activated steel slag is (10~40):1.

[0027] The present invention does not limit the type of carbon dioxide-containing gas, and those skilled in the art can select it according to actual conditions. 2 Carbon dioxide gas with a volume concentration of >90%, also known as CO 2 Low-concentration carbon dioxide waste gas with a volume concentration of 10~90%.

[0028] Among them, the ventilation rate of carbon dioxide-containing gas is 0.3~0.6 ml / min.

[0029] The present invention does not limit the time of the carbonization reaction, and those skilled in the art can select it according to the actual situation, and wait until the carbonization reaction is completed. The present invention can use phenolphthalein solution, pH meter, conductivity meter and other means to monitor and judge the changes in color, pH value and conductivity to determine the completion of the reaction. For example, if pH ≤ 7, the reaction is completed.

[0030] In a second aspect, the present invention provides a carbonized activated steel slag, which is obtained by the preparation method of the carbonized activated steel slag provided by the first aspect of the present invention.

[0031] In a third aspect, the present invention provides the use of the carbonized activated steel slag in the preparation of cement clinker.

[0032] Compared with CaCO in limestone, the carbonized activated steel slag of the present invention 3 It has a larger specific surface area and larger lattice defects, can effectively promote the formation of cement clinker minerals, reduce calcination temperature, increase clinker hydration activity, and improve clinker strength; at the same time, the use of the carbonized activated steel slag of the present invention to prepare cement clinker instead of limestone can also reduce the utilization rate of limestone.

[0033] In this embodiment, the mineral composition of the cement clinker includes, by weight percentage: 3 S 25~50%, C 2 S 25~50%, C 3 A 0.5~1%, C 4 AF 14~24%.

[0034] In this embodiment, the raw materials of the cement clinker include, by weight: 8-14 parts of carbonized activated steel slag, 66-73 parts of limestone, 7-15 parts of aluminum components, and 4-13 parts of silicon components.

[0035] The present invention does not limit the types of aluminum components and silicon components. Those skilled in the art can select them according to actual conditions, and any one that can provide aluminum and silicon raw materials for cement clinker for the preparation of cement clinker is sufficient. For example, the aluminum component can be slope mud, etc.; the silicon component can be high-silicon sandstone, etc.

[0036] The particle size of the raw materials of the cement clinker is ≤75 μm.

[0037] In this embodiment, the cement clinker is obtained by mixing and calcining carbonized activated steel slag, limestone, aluminum components, and silicon components, and then rapidly cooling them.

[0038] The calcination temperature is 1330-1400°C, the calcination time is 30-40 min, and the heating rate is 5-20°C / min.

[0039] The rapid cooling method is: cooling to below 100° C. within 5 minutes.

[0040] In a fourth aspect, the present invention provides a cement based on carbonized activated steel slag, wherein the cement based on carbonized activated steel slag is obtained by mixing cement clinker and gypsum.

[0041] In this embodiment, the amount of gypsum added is 3% to 5% of the cement based on carbonized activated steel slag.

[0042] In the following embodiments and comparative examples of the present invention, the main chemical components of the common steel slag, limestone, slope mud and high-silicon sandstone used are shown in Table 1 below.

[0043] Table 1

[0044] Example 1 The method for preparing carbonized activated steel slag provided in this embodiment comprises the following steps: (1) Weigh ordinary steel slag with a particle size of ≤75 μm and place it in a beaker. Add activation solution (prepared with 0.1 M dilute sulfuric acid and 0.1 M citric acid solution in a mass ratio of 8:1) and the mass ratio of activation solution to steel slag is 150:1. Stir for 10 min. (2) After stirring, add 0.1 M NaOH until the pH is 7, and then stir for 30 minutes; (3) After stirring, the slag is filtered, washed, dried, ground, and then passed through a 200-mesh sieve to obtain activated steel slag.

[0045] (4) Place the activated steel slag in a beaker, add deionized water at a water-cement ratio of 40:1, and introduce CO at a rate of 0.3 ml / min. 2(volume concentration ≥ 99%), and stop when pH = 7. The carbonized steel slag is dried to obtain carbonized activated steel slag.

[0046] The method for preparing cement clinker provided in this embodiment comprises the following steps: (a) According to the designed mineral composition of cement clinker: C 3 S 25%, C 2 S 50%, C 3 A 1%, C 4 AF 24%, accurately weigh the following raw materials in weight percentage: 14 parts of carbonized activated steel slag, 66 parts of limestone, 15 parts of slope mud, and 6 parts of high-silica sandstone.

[0047] (b) After the raw materials are evenly mixed, they are placed in a box-type high-temperature furnace, heated to 1330°C at a rate of 10°C / min, and kept at that temperature for 30 minutes. Cement clinker is obtained after rapid cooling.

[0048] The method for preparing cement based on carbonized activated steel slag provided in this embodiment comprises the following steps: The cement clinker prepared in this embodiment and gypsum are mixed and stirred evenly to obtain cement based on carbonized activated steel slag, wherein the amount of gypsum is 5% of the mass of cement.

[0049] Example 2 The method for preparing carbonized activated steel slag provided in this embodiment comprises the following steps: (1) Weigh ordinary steel slag with a particle size of ≤75 μm and place it in a beaker. Add activation solution (prepared with 0.01 M dilute sulfuric acid and 0.01 M citric acid solution in a mass ratio of 10:1) and the mass ratio of activation solution to steel slag is 50:1. Stir for 60 min. (2) After stirring, add 0.1 M NaOH to a pH of 7, and then stir for 60 min; (3) After stirring, the slag is filtered, washed, dried, ground, and then passed through a 300-mesh sieve to obtain activated steel slag.

[0050] (4) Place the activated steel slag in a beaker, add deionized water at a water-cement ratio of 10:1, and introduce CO at a rate of 0.6 ml / min. 2 (volume concentration ≥ 99%), and stop when pH = 7. The carbonized steel slag is dried to obtain carbonized activated steel slag.

[0051] The method for preparing cement clinker provided in this embodiment comprises the following steps: (a) According to the designed mineral composition of cement clinker: C 3 S 50%, C 2 S 25%, C 3 A 1%, C4 AF 24%, accurately weigh the following raw materials in weight percentage: 13 parts of carbonized activated steel slag, 68 parts of limestone, 15 parts of slope mud, and 4 parts of high-silica sandstone.

[0052] (b) After the raw materials are evenly mixed, they are placed in a box-type high-temperature furnace, heated to 1400°C at a rate of 10°C / min, and kept at that temperature for 30 minutes. Cement clinker is obtained after rapid cooling.

[0053] The method for preparing cement based on carbonized activated steel slag provided in this embodiment comprises the following steps: The cement clinker prepared in this embodiment and gypsum are mixed and stirred evenly to obtain cement based on carbonized activated steel slag, wherein the amount of gypsum is 5% of the mass of cement.

[0054] Example 3 The only difference between this embodiment and embodiment 2 is that the designed mineral composition of cement clinker in embodiment 3 is: C 3 S50%, C 2 S 35.5%, C 3 A 0.5%, C 4 AF 14%, the weight percentage of raw materials is: 8 parts of carbonized activated steel slag, 73 parts of limestone, 7 parts of slope mud, and 12 parts of high-silicon sandstone.

[0055] Example 4 The only difference between this embodiment and embodiment 1 is that the designed mineral composition of cement clinker in embodiment 4 is: C 3 S35.5%, C 2 S 50%, C 3 A 0.5%, C 4 AF 14%, the weight percentage of raw materials is: 8 parts of carbonized activated steel slag, 72 parts of limestone, 7 parts of slope mud, and 13 parts of high-silicon sandstone.

[0056] Comparative Example 1 The only difference between this comparative example and Example 1 is that in the method for preparing cement clinker, ordinary steel slag is directly used to prepare cement clinker.

[0057] The preparation method of cement is consistent with that in Example 1.

[0058] Comparative Example 2 The only difference between this comparative example and Example 1 is that in the method for preparing cement clinker, activated steel slag is directly used to prepare cement clinker.

[0059] The preparation method of cement is consistent with that in Example 1.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that in the preparation method of carbonized steel slag, the steel slag is directly carbonized without being treated with an activation liquid, as follows: Ordinary steel slag with a particle size of ≤75 μm was placed in a beaker, deionized water was added at a water-cement mass ratio of 40:1, and CO was introduced at 0.3 ml / min. 2 (volume concentration ≥ 99%), and stop when pH = 7. The carbonized steel slag is dried to obtain carbonized steel slag.

[0061] The preparation methods of cement clinker and cement are consistent with those in Example 1.

[0062] Comparative Example 4 The only difference between this comparative example and Example 1 is that, in the method for preparing carbonized activated steel slag, step (2) is not performed.

[0063] The preparation methods of cement clinker and cement are consistent with those in Example 1.

[0064] Performance Testing The cement obtained in the examples of the present invention and the comparative examples was molded into specimens according to GB / T17671 standard, and the compressive strength of the specimens at 28 days was tested. The test results are shown in Table 2.

[0065] Table 2

[0066] Please refer to Table 2. It can be seen from Table 2 that the performance of the cement prepared in Examples 1-4 is significantly better than that in Comparative Examples 1-4, and all meet the 52.5 cement standard, indicating that the carbonized activated steel slag prepared by the method of the present invention can effectively stimulate the activity of clinker minerals, and the cement clinker made using it as raw material has better compressive strength than ordinary steel slag.

[0067] It can be seen from Comparative Examples 1-4 that the performance of cement prepared in Comparative Examples 2 and 4 is even lower than that of Comparative Example 1, and the performance of cement prepared in Comparative Example 3 is equivalent to that of Comparative Example 1, indicating that only activating the steel slag will destroy the structure in the steel slag, which is not conducive to sintering; if only carbonizing the steel slag, it is equivalent to ordinary steel slag in sintering; if the pH is not adjusted after activation, it will also lead to a decrease in cement performance. It can be seen that the present invention chemically treats the steel slag (activation + alkali) and CO 2 Only by co-processing the solidification can the performance of cement be better improved.

[0068] In summary, the method of the present invention can, on the one hand, effectively solve the problem that the steel slag components are complex and directly using it as a cement raw material has an adverse effect on the cement performance; on the other hand, it improves the utilization rate of industrial waste steel slag in the building materials industry, which helps to improve the problems of large steel slag stocks and high consumption of high-quality limestone.

[0069] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing carbonized activated steel slag, characterized in that: The following steps are involved: The steel slag is activated by using an activation liquid, the pH value is adjusted to 7-8 after the first stirring, and then the activated steel slag is obtained by the second stirring, filtering, washing, drying, grinding and screening. The activated steel slag is carbonized to obtain carbonized activated steel slag; wherein, The activation solution comprises: inorganic acid, complexing agent and water.

2. The method for preparing carbonized activated steel slag according to claim 1, characterized in that: The inorganic acid is at least one of sulfuric acid, hydrochloric acid and nitric acid; and / or, The complexing agent is citric acid; and / or, In the activation solution, the concentration of the inorganic acid is 0.009-0.09 mol / L, and the concentration of the complexing agent is 0.0009-0.012 mol / L; and / or, The mass ratio of the activation solution to the steel slag is (50-150):

1.

3. The method for preparing carbonized activated steel slag according to claim 1, characterized in that: The temperature of the first stirring is room temperature, and the time of the first stirring is 10 to 60 minutes; and / or, Using sodium hydroxide solution to adjust the pH to 7-8; and / or, The temperature of the second stirring is room temperature, and the time of the second stirring is 30 to 60 minutes; and / or, During the sieving process, the mesh number of the sieve is ≥200 meshes.

4. The method for preparing carbonized activated steel slag according to claim 1, characterized in that: The process of carbonizing the activated slag comprises: The activated steel slag is dispersed in water, and then a carbon dioxide-containing gas is introduced. After the reaction is completed, the activated steel slag is dried to obtain carbonized activated steel slag; wherein, The mass ratio of the water to the activated slag is (10-40):1; and / or, The volume concentration of CO2 in the carbon dioxide-containing gas is ≥ 10%; and / or, The ventilation rate of the carbon dioxide-containing gas is 0.3-0.6 ml / min; and / or, The reaction is completed by detecting that the pH of the carbonization system is ≤7.

5. A carbonized activated steel slag, characterized in that: The carbonized activated steel slag is obtained by the preparation method of the carbonized activated steel slag according to any one of claims 1 to 4.

6. Use of the carbonized activated steel slag as claimed in claim 5 in preparing cement clinker.

7. The use of the carbonized activated steel slag in preparing cement clinker according to claim 6, characterized in that: Calculated by weight percentage, the mineral composition of the cement clinker includes: C3S 25-50%, C2S 25-50%, C3A 0.5-1%, and C4AF 14-24%.

8. The use of the carbonized activated steel slag in preparing cement clinker according to claim 6, characterized in that: The raw materials of the cement clinker include, by weight: 8-14 parts of carbonized activated steel slag, 66-73 parts of limestone, 7-15 parts of aluminum components, and 4-13 parts of silicon components; wherein, The aluminum component is slope mud; and / or, The siliceous component is high-silica sandstone; and / or, The particle size of the raw materials of the cement clinker is ≤75 μm.

9. The use of carbonized activated steel slag in preparing cement clinker according to claim 8, characterized in that: The cement clinker is obtained by mixing and calcining carbonized activated steel slag, limestone, aluminum component and silicon component, and then rapidly cooling; wherein, The calcination temperature is 1330-1400° C., the calcination time is 30-40 min, and the heating rate is 5-20° C. / min.

10. A cement based on carbonized activated steel slag, characterized in that: The cement based on carbonized activated steel slag is obtained by mixing the cement clinker according to claim 6 and gypsum.

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