A kind of high-activity large-particle calcium oxide, preparation method and application thereof

Abstract

The present invention discloses a high-activity large-particle calcium oxide, a preparation method and application thereof. Specifically, calcium carbonate mineral is used as a raw material, and a segmented step-by-step high-temperature calcination method is adopted to successfully decompose calcium carbonate into calcium oxide. This method can successfully prepare a blocky calcium oxide with high activity and large particle size. Among them, using large-particle calcium carbonate as a raw material reduces the time for crushing and has a low cost; the segmented step-by-step temperature system calcination method can reduce the calcination temperature and the insulation time, which once again reduces the cost; the obtained blocky calcium oxide with large particle size has high activity, high stability and durability, and is easy to transport and store. The present invention overcomes the problems of excessively high temperature and long insulation time of one-stage high-temperature calcination, as well as the shortcomings of chemical instability and non-durability of powdered calcium oxide. The present invention can form a target product after insulation at a lower temperature and for a shorter time, and is suitable for industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection and metallurgy, and in particular to high-activity large-particle calcium oxide, a preparation method and application thereof. Background Art

[0002] In recent years, calcium oxide has been used as an important raw material in industries such as building materials, aluminum, plastics, and environmental protection, and its demand has increased year by year. In particular, the demand for high-performance and high-quality activated calcium oxide in iron and steel metallurgical enterprises has reached new highs. At present, the production of activated calcium oxide mostly relies on the high-temperature solid-phase method. Limestone (CaCO3) decomposes into calcium oxide (CaO) and carbon dioxide (CO2) at high temperatures. This process usually requires high temperatures (about 900-1200°C) and is accompanied by high energy consumption and CO2 emissions. The high-temperature solid-phase method has a simple preparation process. It only needs to prepare the raw materials and calcine them at the appropriate particle size. The production cost is low and it can be widely used. However, due to the raw material selection and production process of calcium oxide, the current production process of activated calcium oxide generally has the following problems, such as high decomposition temperature, high energy consumption, high energy consumption and high CO2 emissions, and uncontrolled pulverization rate of calcium oxide products.

[0003] In order to increase the effective calcium oxide content and activity of active calcium oxide, and at the same time improve calcination efficiency and reduce energy consumption, some companies precisely control the particle size of the raw limestone to ensure that it is crushed to a particle size of less than 1mm, so as to complete the calcination at a lower calcination temperature (950-1100℃), which not only improves the calcination efficiency, but also saves energy consumption, achieving the effect of energy conservation and emission reduction. However, this method also brings about the problem of high pulverization rate, because small-particle limestone is easy to generate smaller calcium oxide particles during the calcination process, resulting in the instability of active calcium oxide. Relatively speaking, the use of large-particle (5-40mm) limestone in the kiln for calcination can reduce the pulverization rate and avoid particle crushing, but due to the slow heat transfer rate, a higher calcination temperature (1100-1200℃) is required, resulting in higher energy consumption and CO2 emissions. Existing technologies face the challenge of how to effectively control the pulverization rate, reduce the calcination temperature, improve the calcination efficiency, and reduce high energy consumption and high carbon emissions while increasing the active calcium oxide. Therefore, it is necessary to develop a new preparation process to solve the shortcomings of the above preparation method, such as high calcination temperature and high calcium oxide pulverization rate, and to further improve the activity of calcium oxide. Summary of the invention

[0004] In order to solve the shortcomings of the prior art, the present invention provides a high-activity large-particle calcium oxide, a preparation method and application thereof, and adopts a staged step-by-stage high-temperature calcination method to prepare the active calcium oxide. This method can successfully prepare high-activity and large-particle block calcium oxide.

[0005] The present invention provides the following technical solution: a method for preparing high-activity large-particle calcium oxide, comprising the following steps: 1) Preliminary crushing of limestone minerals to obtain large-sized bulk limestone as a reaction raw material; 2) weighing deionized water and sodium hydroxide according to a stoichiometric ratio to prepare a sodium hydroxide alkaline solution; 3) placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and allowing the solution to stand to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high-temperature furnace and calcined at high temperature in a stepwise manner to obtain block active calcium oxide.

[0006] Preferably, in step 1), the limestone mineral is crushed into large-sized block limestone, and its particle size range is: 20-60mm.

[0007] As a preferred embodiment, the limestone mineral is crushed into large-size block limestone, and its particle size range is: 50-60mm.

[0008] As the most preferred embodiment, the limestone mineral is crushed into large-size block limestone, and its particle size is 50 mm.

[0009] The invention uses calcium carbonate with large particle size as raw material, which reduces the time of crushing and has low cost.

[0010] Preferably, in step 2), the concentration of sodium hydroxide is 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L.

[0011] As a preferred embodiment, the sodium hydroxide concentration is: 1 mol / L, 2 mol / L or 3 mol / L.

[0012] In step 3), the reaction raw materials are immersed in the sodium hydroxide solution for 8 hours, 16 hours, 24 hours, 32 hours, 40 hours, 48 ​​hours or 56 hours. The preferred time is 24 hours, 32 hours or 40 hours.

[0013] In step 4), the temperature range of the oven is 60-100°C, and the drying time range is 12-24h. The preferred temperature is 80°C and the time is 16 hours.

[0014] In step 5), the temperature of the staged high-temperature calcination is to keep it at 800°C for 1h, 2h or 3h, preferably keep it at 800°C for 1-2h, then raise the temperature to 1000°C and keep it for 2-3h, then take it out and cool it rapidly in the air to obtain block-shaped active calcium oxide.

[0015] The block active calcium oxide has a content of 90-99%, a relatively large particle size of 20-60 mm, and a relatively high activity of 380-440 mL.

[0016] The second object of the present invention is to provide a high-activity large-particle calcium oxide prepared by the above method, wherein the high-activity large-particle calcium oxide has the following molecular formula: CaO-xNaO. The x value is defined as follows: x≤5mol%, and x represents the mol amount of NaO doped in the target product calcium oxide.

[0017] Another object of the present invention is to provide an application of high-activity large-particle calcium oxide in high-activity metallurgical lime.

[0018] In the work, the present invention prepares high-activity large-particle calcium oxide by a step-by-step high-temperature calcination method. The preparation process is simple, the cost is reduced, and it has more industrial production value than the traditional single-temperature high-temperature solid-phase method, and overcomes the shortcomings of the high-temperature solid-phase method of too high calcination temperature and too much insulation time. The preparation method of the present invention can form the target product after insulation at a lower temperature (for example: 800°C + 1000°C), which is suitable for industrial application. The calcium oxide prepared according to the method of the present invention can also obtain high-activity metallurgical lime with higher activity and more active calcium oxide content by adjusting the concentration of sodium hydroxide and the soaking time. Among them, during the application process, the block active calcium oxide is basically not pulverized, has a very low pulverization rate and high stability and durability, and is more conducive to long-distance transportation and long-term storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the temperature system of the step-by-step high-temperature calcination in Example 1 of the present invention, Figure 2 is the XRD diagram of the sample obtained by stepwise high-temperature calcination in Example 1 of the present invention, Figure 3 This is the XRD diagram of the active calcium oxide produced by the method of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific embodiments and drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0021] Example 1 A method for preparing highly active large-particle calcium oxide comprises the following steps: 1) The limestone mineral is initially crushed to obtain large-sized block limestone with a particle size range of 50-60 mm as the reaction raw material; 2) Deionized water and sodium hydroxide are taken in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution with a concentration of 1 mol / L; 3) slowly placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and soaking for 24 hours to corrode the reaction raw material to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven at 80° C. for 16 h to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high temperature calcination, first heated to 800°C and kept for 1 hour, then heated to 1000°C and kept for 2 hours, and rapidly cooled in air to obtain block active calcium oxide; the temperature in Example 1 is as follows Figure 1 shown.

[0022] Example 2 A method for preparing highly active large-particle calcium oxide comprises the following steps: 1) The limestone mineral is initially crushed to obtain large-sized block limestone with a particle size of 50 mm as the reaction raw material; 2) Deionized water and sodium hydroxide are taken in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution with a concentration of 1 mol / L; 3) slowly placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and soaking for 24 hours to corrode the reaction raw material to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven at 80° C. for 16 h to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high temperature furnace for calcination, first heated to 800°C and kept for 1 hour, then heated to 1000°C and kept for 2 hours, and rapidly cooled in air to obtain block active calcium oxide.

[0023] Example 3 A method for preparing highly active large-particle calcium oxide comprises the following steps: 1) The limestone mineral is initially crushed to obtain large-sized block limestone with a particle size range of 20-40 mm as the reaction raw material; 2) Deionized water and sodium hydroxide are taken in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution with a concentration of 1 mol / L; 3) slowly placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and soaking for 24 hours to corrode the reaction raw material to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven at 80° C. for 16 h to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high temperature furnace for calcination, first heated to 800°C and kept for 1 hour, then heated to 1000°C and kept for 2 hours, and rapidly cooled in air to obtain block active calcium oxide.

[0024] Example 4 A method for preparing highly active large-particle calcium oxide comprises the following steps: 1) The limestone mineral is initially crushed to obtain large-sized block limestone with a particle size range of 50-60 mm as the reaction raw material; 2) Deionized water and sodium hydroxide are taken in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution with a concentration of 2 mol / L; 3) slowly placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and soaking for 24 hours to corrode the reaction raw material to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven at 80° C. for 16 h to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high temperature furnace for calcination, first heated to 800°C and kept at this temperature for 2 hours, then heated to 1000°C and kept at this temperature for 2 hours, and then rapidly cooled in air to obtain block active calcium oxide.

[0025] Example 5 A method for preparing highly active large-particle calcium oxide comprises the following steps: 1) The limestone mineral is initially crushed to obtain large-sized block limestone with a particle size range of 50-60 mm as the reaction raw material; 2) Deionized water and sodium hydroxide are taken in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution with a concentration of 1 mol / L; 3) slowly placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and soaking for 32 hours to corrode the reaction raw material to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven at 80° C. for 16 h to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high temperature furnace for calcination, first heated to 800°C and kept at this temperature for 2 hours, then heated to 1000°C and kept at this temperature for 2 hours, and then rapidly cooled in air to obtain block active calcium oxide.

[0026] The specific performance and tests are as follows: Taking Example 1 as an example, the large-particle-size block-shaped active calcium oxide prepared by the step-by-step high-temperature calcination method in Example 1 is not broken and is not easy to pulverize. Its structural formula is CaO-xNaO. The above active calcium oxide is subjected to X-ray diffraction analysis, and the obtained XRD results are as follows: Figure 2 As shown. The sample in the figure is prepared in Example 1, and the standard product is the CaO standard spectrum. By comparing with the standard spectrum card PDF48-1467, it can be found that the peak shape of the sample is completely consistent with the standard spectrum, and there is no impurity peak, indicating that the step-by-step high-temperature calcination method successfully prepared a calcium oxide sample with a high degree of crystallinity. In addition, it can be found from the figure that the peak position of the sample is slightly shifted to the right, which shows that the influence of Na ions causes lattice distortion and the lattice becomes smaller. This is because the sodium ions Na + The ionic radius (0.098nm) is smaller than that of calcium ion Ca 2+ The ionic radius (0.106 nm) of MgO is small. Table 1 below shows the parameter values ​​of the unit cell parameters and the unit cell volume.

[0027] Table 1: It can be seen from Table 1 that the unit cell parameters and the decrease in unit cell volume are consistent. The above conclusions show that Na ions successfully enter the lattice of calcium oxide, causing lattice distortion, which will affect its lattice energy.

[0028] The chemical titration method with sucrose was used to test the active calcium oxide content and the activity of samples 1 to 5 corresponding to Examples 1 to 5, respectively. In order to test the durability of the sample performance, the performance of the samples after being placed for a certain period of time was also tested. The specific parameter values ​​are shown in Table 2.

[0029] Table 2: As shown in Table 2, the active calcium oxide content of the samples shown in the embodiment is relatively high (greater than 92%), and the activity determined by the hydrochloric acid titration is also greater than 400 mL when using hydrochloric acid titration; and after being placed for 15 days, the active calcium oxide content and activity are basically unchanged, indicating that the method of the present invention can obtain high-quality active calcium oxide. In summary, using limestone as raw material, soaking in sodium hydroxide, and then preparing large-particle active calcium oxide by step-by-step high-temperature calcination method can be used as a high-activity metallurgical lime for construction, metallurgy, environmental protection and other industries.

[0030] The blocky active calcium oxide is obtained by calcining the large-sized limestone using a step-by-step temperature increase system. The reaction equation is: The invention obtains active calcium oxide with large particle size, low pulverization rate and high activity at a relatively low temperature. Compared with the previous production experience, the limestone raw material with large particle size can be initially crushed to obtain the active calcium oxide, which is easy to obtain and easy to transport over long distances. The limestone raw material with large particle size is soaked in a sodium hydroxide solution, and the corrosive effect of sodium hydroxide can be utilized to corrode the limestone, so that a porous limestone structure is formed at a microscopic level, and a channel is provided for the overflow of CO2 when the limestone is decomposed, thereby avoiding the crushing of the limestone. The sodium hydroxide soaking makes the limestone uniformly dissolved with sodium ions, which can be used as a co-solvent to reduce the decomposition temperature of the limestone. At the same time, the sodium ions, as doping elements, can change the crystal structure of the calcium oxide, reduce its lattice energy, and thus improve its activity.

[0031] Comparative Example 1 A method for preparing active calcium oxide by high temperature calcination comprises the following steps: 1) Preliminary crushing of limestone minerals to obtain large-sized block limestone with a particle size range of 50-60 mm as the reaction raw material; 2) Put the lump limestone raw material obtained in step 1) into a high-temperature furnace, calcine it at high temperature to 1000° C. and keep it at that temperature for 4 hours, and rapidly cool it in the air to obtain lump active calcium oxide.

[0032] The specific performance and tests are as follows: In Comparative Example 1, steps 2-4 in Example 1 are missing. The block limestone raw material is not immersed in a sodium hydroxide solution of a certain concentration (1 mol / L, 2 mol / L), no corrosion occurs, and there is no drying process. The high-temperature calcination process in step 2) is not step-by-step, but directly heated to 1000°C and kept warm for 4 hours, which is different from Example 1. When the sample was taken out of the high-temperature furnace, it was found that there were a lot of fine powders in it, indicating that the sample was pulverized; the middle sample was in blocks without discoloration, and there was a raw burning situation. The performance of the comparative sample was measured by chemical titration. The active calcium content was 89.1% in 1 day and 80.4% in 15 days, indicating that after being placed for a period of time, the performance of the sample was unstable and the durability was low. Figure 3This is the XRD pattern of the active calcium oxide prepared by the method of comparative example 1 of the present invention after being placed for 15 days. In the figure, the reference substance is the powder obtained after calcination in comparative example 1, and the standard substance is the standard spectrum of calcium oxide. By comparing with the standard spectrum card PDF 48-1467, it can be found that the peak shape of the reference substance has many more peaks than the standard spectrum. After analysis, it can be known that in addition to calcium oxide, another substance formed in comparative example 1 is calcium hydroxide (Ca(OH)2), which means that the sample undergoes hydration reaction after being placed for a period of time, which is not conducive to long-distance transportation and long-term storage.

[0033] The active calcium oxide with large particle size is prepared by the step-by-step high-temperature calcination method of the present invention, and the method can successfully prepare high-quality active calcium oxide without impurities. The preparation method of the present invention overcomes the disadvantages of the high-temperature solid phase method that the decomposition temperature is too high and the time is too long. The preparation method of the present invention can form the target product at a lower temperature (for example: 800°C + 1000°C) and a shorter insulation time (for example: 1h + 2h or 2h + 2h), and the product has high durability and is suitable for industrial application.

[0034] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing highly active large-particle calcium oxide, characterized in that: The following steps are involved: 1) Preliminary crushing of limestone minerals to obtain large-sized block limestone as reaction raw materials; 2) taking deionized water and sodium hydroxide in a stoichiometric ratio to obtain a sodium hydroxide alkaline solution; 3) placing the reaction raw material obtained in step 1) into the sodium hydroxide alkaline solution obtained in step 2) and allowing the solution to stand to obtain corroded porous block limestone; 4) drying the porous block limestone obtained in step 3) in an oven to obtain dry block limestone; 5) The dried limestone block obtained in step 4) is placed in a high-temperature furnace and calcined at high temperature in a stepwise manner to obtain block active calcium oxide.

2. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: In step 1), the limestone mineral is crushed into large-size block limestone, and its particle size range is: 20-60mm.

3. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: In step 2), the concentration of sodium hydroxide is 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L or 4 mol / L.

4. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: In step 3), the reaction raw materials are immersed in the sodium hydroxide solution for 8 h, 16 h, 24 h, 32 h, 40 h, 48 h or 56 h.

5. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: In step 4), the temperature range of the oven is 60-100°C, and the drying time range is 12-24h.

6. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: In step 5), the high-temperature calcination is carried out in stages. After being kept at 800°C for 1h, 2h or 3h, the temperature is raised to 900-1000°C and kept for 1-5h. The mixture is then taken out and rapidly cooled in air to obtain block-shaped active calcium oxide.

7. The method for preparing high-activity large-particle calcium oxide according to claim 1, characterized in that: The content of the block active calcium oxide: 90-99%; Particle size: 20-60mm; activity: 380-440mL.

8. A highly active large-particle calcium oxide, characterized in that: The calcium oxide is prepared by the method for preparing high-activity large-particle calcium oxide according to any one of claims 1 to 7.

9. Use of the high-activity large-particle calcium oxide according to claim 8 in high-activity metallurgical lime.

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