Method for producing calcium aluminate

Abstract

To provide a manufacturing method capable of easily producing calcium aluminate that contains specific amounts of CaO_2Al2O3 and Fe2O3, even at low temperatures.SOLUTION: The present invention relates to a method for producing calcium aluminate that contains 70 mass% or more of CaO_2Al2O3 and 0.5 to 15 mass% of Fe2O3. A CaO-Al2O3-based clinker having a molar ratio of CaO / Al2O3 of 0.5 to 1.8 and a content of SiO2 of 0.5 to 10 mass%, a material that contains alumina, and a material that contains iron are used as raw materials, the raw materials are granulated with water, and then calcined at 1350 to 1600°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing calcium aluminate used as an admixture for concrete.

Background Art

[0002] In the field of cement and concrete, a method (Patent Document 1) has been proposed to improve the chloride ion penetration resistance by using a cement admixture containing calcium aluminate with a CaO / Al2O3 molar ratio of 0.3 to 0.7 for the purpose of preventing the corrosion of reinforcing bars. In addition, a technique has been proposed to produce alumina cement and the like by adding a CaO raw material or an Al2O3 raw material to slag containing calcium aluminate and adjusting the components (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, in the field of cement and concrete as well, there has been a movement to build a resource recycling-based society by reducing the energy consumption per unit for CO2 emission reduction and by using waste and by-products discharged from industries.

[0005] However, since calcium aluminate has a high melting point, firing at a high temperature is required. When the firing temperature is low, unreacted substances remain, which affects the hydration activity of calcium aluminate, and a predetermined chloride ion penetration resistance may not be sufficiently obtained.

[0006] As described above, an object of the present invention is to provide a production method capable of easily producing calcium aluminate containing specific amounts of CaO·2Al2O3 and Fe2O3 even at low temperatures.

Means for Solving the Problems

[0007] As a result of various studies on the above problems, the present invention has found that calcium aluminate having a target composition can be easily synthesized even at low temperatures by using a CaO-Al2O3-based clinker containing CaO and Al2O3, a substance containing alumina, and a substance containing iron as raw materials, and has thus completed the present invention. That is, the present invention is as follows.

[0008] [1] A method for producing calcium aluminate containing 70% by mass or more of CaO·2Al2O3 and 0.5 to 15% by mass of Fe2O3 as a chemical component, using a CaO-Al2O3-based clinker having a CaO / Al2O3 molar ratio of 0.5 to 1.8 and an SiO2 content of 0.5 to 10% by mass, a substance containing alumina, and a substance containing iron as raw materials, granulating the raw materials with water, and firing at 1350 to 1600°C, characterized in that it is a method for producing calcium aluminate. [2] The method for producing calcium aluminate according to [1] above, characterized in that the CaO-Al2O3-based clinker, the substance containing alumina, and the substance containing iron are mixed and pulverized.

Effects of the Invention

[0009] According to the present invention, it becomes possible to easily produce calcium aluminate containing specific amounts of CaO·2Al2O3 and Fe2O3 even at low temperatures.

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments (the present embodiment) of the present invention will be described in detail, but the present invention is not limited to the present embodiment. In addition, "%" in this specification is based on mass unless otherwise specified.

[0011] The method for producing calcium aluminate according to this embodiment is a method for producing calcium aluminate containing 70% by mass or more of CaO·2Al2O3 and 0.5 to 15% by mass of Fe2O3 as a chemical component, wherein the CaO / Al2O3 molar ratio is 0.5 to 1.8 and the SiO2 content is 0.5 to 10% by mass. A CaO-Al2O3 based clinker, a substance containing alumina, and a substance containing iron are used as raw materials, and the raw materials are granulated with water and fired at 1350 to 1600 °C.

[0012] The CaO-Al2O3 based clinker used as a raw material in the present invention contains CaO and Al2O3, the CaO / Al2O3 molar ratio is in the range of 0.5 to 1.8, and the SiO2 content is 0.5 to 10% by mass. If the CaO / Al2O3 molar ratio of the CaO-Al2O3 based clinker is outside the range of 0.5 to 1.8, or if the SiO2 content is outside the range of 0.5 to 10% by mass, there is a possibility that calcium aluminate having the target composition cannot be easily produced at a low temperature. Examples of the main compounds constituting the CaO-Al2O3 based clinker include 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3, CaO·2Al2O3, CaO·6Al2O3, etc. In the present invention, among the above compounds, it is preferable to contain 12CaO·7Al2O3, CaO·Al2O3, and CaO·2Al2O3, and it is more preferable to contain CaO·Al2O3.

[0013] The CaO / Al2O3 molar ratio of the CaO-Al2O3 based clinker is 0.5 to 1.8. Further, it is preferably 0.5 to 1.7, and more preferably 0.7 to 1.5. When the CaO / Al2O3 molar ratio is within the above range, it is easy to produce calcium aluminate having the target composition with high purity even at a low temperature in a short time.

[0014] The SiO₂ content in the CaO-Al₂O₃ system clinker is 0.5 to 10% by mass. Further, it is preferably 1 to 8% by mass, more preferably 1.5 to 7% by mass, and even more preferably 2 to 7% by mass. When the SiO₂ content is within the above range, it is easy to produce calcium aluminate of the target composition with high purity even at low temperature in a short time.

[0015] General industrial raw materials used as the CaO-Al₂O₃ system clinker may contain impurities such as MgO, Fe₂O₃, TiO₂, K₂O, Na₂O, and V. However, if these impurities are within the range of 10% or less, the blending ratios of the CaO raw material and the Al₂O₃ raw material required for component adjustment can be reduced, and it becomes easier to sinter the calcium aluminate of the target composition at low temperature. Also, within the above range, these impurities may be added for the purpose of lowering the melting point.

[0016] In addition, as the CaO-Al₂O₃ system clinker used in the present invention, by-products generated in the metal refining process can be used. For example, metallic vanadium is produced by roasting spent desulfurization catalysts and combustion ash of heavy oil boilers to produce high-purity V₂O₅ and then reducing V₂O₅. As substances for reducing V₂O₅, metallic calcium, metallic aluminum, metallic magnesium, etc. are used, and metallic vanadium is taken out. The CaO-Al₂O₃ system clinker generated as the residue can be used.

[0017] The substance containing alumina may be any substance containing Al₂O₃. For example, bauxite, aluminum oxide powder, aluminum hydroxide powder, dust collected from sintered alumina, etc. can be used. The Al₂O₃ content in the substance containing alumina is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. When the Al₂O₃ content is within the above range, it is easy to produce calcium aluminate of the target composition with high purity even at low temperature. The upper limit is not particularly limited, and it may be 100% by mass.

[0018] The substance containing iron is not particularly limited, and Fe2O3 obtained by pulverizing, processing, and purifying iron ore commercially available as an industrial raw material, Fe2O3 obtained by recovering and purifying from pickling waste hydrochloric acid of steel materials, etc. can be used. Further, FeO, Fe3O4, or even pure iron can be used after heat treatment in an oxidizing atmosphere.

[0019] The iron content in the substance containing iron is preferably 90% by mass or more, more preferably 95% by mass or more in terms of Fe2O3 conversion. When the iron content is within the above range, calcium aluminate of the target composition can be easily produced even at a low temperature. The upper limit is not particularly limited, but it may be 100% by mass.

[0020] In the present invention, it is preferable to mix and pulverize a CaO - Al2O3 - based clinker, a substance containing alumina, and a substance containing iron from the viewpoint of workability and because the yield of calcium aluminate of the target composition is increased. For the mixing and pulverization, general pulverization equipment such as a vibration mill or a ball mill can be used.

[0021] The powder fineness of the CaO - Al2O3 - based clinker, the substance containing alumina, and the substance containing iron is preferably 2000 - 8000 cm 2 / g in terms of the Blaine specific surface area, and more preferably 2500 - 6000 cm 2 / g. When the Blaine specific surface area is within the above range, the firing temperature can be made lower, and since there is no need to pulverize more than necessary, calcium aluminate of the target composition can be easily produced.

[0022] In the present invention, the raw materials are granulated with water. If granulation is not carried out, the reactivity deteriorates, and there is a risk that calcium aluminate with the target composition cannot be produced at low temperatures. It is preferable to use a granulator for granulation. There are granulation methods such as the briquetting method and the method using a pan-type granulator. In the present invention, it is preferable to use a pan-type granulator and granulate with water as a binder. The amount of water is preferably 5 to 30 parts by mass, more preferably 10 to 25 parts by mass, per 100 parts by mass of the raw materials. When within the above range, granulation is easy, and firing is easy at low temperatures.

[0023] In the present invention, the raw materials are granulated and fired at 1350 to 1600°C. Firing is usually carried out by heat treatment such as firing in a kiln or melting in an electric furnace. If the firing temperature is less than 1350°C, the reaction does not proceed efficiently and unreacted Al2O3 remains, and calcium aluminate may not be obtained. If it exceeds 1600°C, coating is likely to adhere to the inner surface of the rotary kiln during firing, which not only makes operation difficult but also may reduce energy efficiency. The firing temperature is preferably 1400 to 1550°C, more preferably 1450 to 1500°C.

[0024] The calcium aluminate produced by the production method of the present invention contains 70% by mass or more of CaO·2Al2O3. Calcium aluminate with a CaO·2Al2O3 content of less than 70% by mass may have insufficient chloride ion penetration resistance. Also, the CaO·2Al2O3 content in calcium aluminate is preferably 80% by mass or more, more preferably 90% by mass or more. It may also be 100% by mass. When the CaO·2Al2O3 content in the produced calcium aluminate is within the above range, the chloride ion penetration resistance becomes better. The CaO·2Al2O3 content in calcium aluminate can be measured and quantified, for example, by powder X-ray diffraction (XRD) / Rietveld method using SmartLab manufactured by Rigaku Corporation.

[0025] The calcium aluminate produced by the production method of the present invention contains 0.5 to 15% by mass of Fe2O3 as a chemical component. Calcium aluminate with an Fe2O3 content of less than 0.5% by mass cannot produce calcium aluminate with the target composition at low temperatures, resulting in the formation of calcium aluminate different from the target composition or the remaining unreacted raw materials, which may cause rapid hardening in a high-temperature environment, impair workability, or deteriorate the chloride ion penetration resistance. Calcium aluminate with a content exceeding 15% by mass may have insufficient chloride ion penetration resistance. In addition, the Fe2O3 content in calcium aluminate is preferably 1 to 12% by mass, more preferably 3 to 10% by mass. In the present invention, "as a chemical component" refers to the state of being dissolved in the crystal and can be confirmed by using fluorescent X-ray analysis (XRF) and X-ray diffraction method (XRD). When no peak corresponding to Fe2O3 is confirmed by XRD and a peak corresponding to Fe2O3 is confirmed by XRF, it can be determined that Fe2O3 is in a state of being dissolved in the crystal, and the content can be further measured. The Fe2O3 content in calcium aluminate can be measured, for example, by the fluorescent X-ray analysis method using ZSX Primus IV manufactured by Rigaku Corporation.

Example

[0026] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples as long as the gist thereof is not deviated.

[0027] [Experimental Example 1] Using the following raw materials in the mixing ratios shown in Table 1, the specific surface area of the raw materials was 4000 cm 2Prepared in / g, formulated so that CaO / Al2O3 = 0.5, which is the composition of the target calcium aluminate, and mixed and ground with a pot mill. 20 parts by mass of water was added to 100 parts by mass of the mixture, granulated to a diameter of 20 mm, and fired in an electric furnace at 1450 °C for 30 minutes to produce calcium aluminate. The produced calcium aluminate was ground with a disk mill, and the content of CaO·2Al2O3 was quantified by the XRD / Rietveld method, and the content of Fe2O3 was quantified by XRF. The results are shown in Table 1.

[0028] <Materials Used> CaO-Al2O3 system clinker A: CA by-product from V refining, CaO / Al2O3 molar ratio 1.0, SiO2 content 3.0 mass%, V content 0.5 mass%, particle size below 25 mm. Substance containing iron: Iron oxide, Fe2O3 content 99.1 mass%. Substance containing alumina: Bauxite, CaO content 1.7 mass%, Al2O3 content 71.5 mass%, SiO2 content 11.8 mass%, Blaine specific surface area 2000 cm 2 / g. Water: Tap water.

[0029] <Test Method> Powder X-ray diffraction method (XRD) / Rietveld method: Measurements were carried out using a SmartLab manufactured by Rigaku. Target CuKα, tube voltage 40 kV, tube current 40 mA, scanning range 5 - 65 deg. 2θ, step width 0.02, semiconductor high-speed detector, SIROQUANT Ver3.0. X-ray fluorescence analysis method (XRF): Measurements were carried out using a ZSX Primus IV manufactured by Rigaku. Powder briquette sample, fundamental parameter method.

[0030]

Table 1

[0031] [Experimental Example 2] The CaO-Al2O3 system clinker was changed to the following, and calcium aluminate was produced in the same manner as No. 1-1 of Experimental Example 1, except that firing (30 minutes, 1450 °C) was repeated until the CaO·2Al2O3 content in calcium aluminate reached 100%. The number of firing times and the measurement results are shown in Table 2. In addition, Experimental Example No. 2-9 using calcium carbonate J shown below instead of the CaO-Al2O3 system clinker is also shown in Table 2.

[0032] <Materials Used> CaO-Al2O3 system clinker B: CaO / Al2O3 molar ratio 1.0, SiO2 content 0.1 mass%, particle size below 25 mm. CaO-Al2O3 system clinker C: CaO / Al2O3 molar ratio 1.0, SiO2 content 0.5 mass%, V content 0.1 mass%, particle size below 25 mm. CaO-Al2O3 system clinker D: CaO / Al2O3 molar ratio 1.0, SiO2 content 1.0 mass%, V content 0.1 mass%, particle size below 25 mm. CaO-Al2O3 system clinker E: V-refining by-product CA, CaO / Al2O3 molar ratio 1.0, SiO2 content 7.0 mass%, V content 1.3 mass%, particle size below 25 mm. CaO-Al2O3 system clinker F: V-refining by-product CA, CaO / Al2O3 molar ratio 1.0, SiO2 content 10.0 mass%, V content 1.5 mass%, particle size below 25 mm. CaO-Al2O3 system clinker G: CaO / Al2O3 molar ratio 2.0, SiO2 content 3.0 mass%, V content 0.1 mass%, particle size below 25 mm. CaO-Al2O3 system clinker H: CaO / Al2O3 molar ratio 1.5, SiO2 content 3.0 mass%, V content 0.1 mass%, particle size below 25 mm. CaO-Al2O3 system clinker I: CaO / Al2O3 molar ratio 0.7, SiO2 content 3.0 mass%, V content 0.1 mass%, particle size below 25 mm. Calcium carbonate J: CaO content 96 mass%, pulverized limestone product.

[0033]

Table 2

[0034] [Experimental Example 3] Calcium aluminate was produced in the same manner as No. 1-1 of Experimental Example 1, except that the firing temperature was changed to the values shown in Table 3 below. The results are shown in Table 3.

[0035]

Table 3

[0036] [Experimental Example 4] Calcium aluminate was produced in the same manner as No. 1-1 of Experimental Example 1, except that the amount of water for granulation with respect to 100 parts by mass of the raw material mixture was changed to the values shown in Table 4 below. The results are shown in Table 4.

[0037]

Table 4

[0038] [Experimental Example 5] The test was conducted in the same manner as Experimental Example No. 1-1, except that the raw materials were mixed and pulverized with a pot mill and the Blaine specific surface area was adjusted to the values described in Table 5 below. The results are shown in Table 5.

[0039]

Table 5

Industrial Applicability

[0040] The present invention enables the production of calcium aluminate containing CaO·2Al2O3 and Fe2O3 at a lower temperature compared to the prior art, and is thus suitable for the civil engineering and construction fields.

Claims

1. CaO·2Al ２ O ３ is 70% by mass or more, and Fe ２ O ３ is included as a chemical component in an amount of 0.5 to 15% by mass. A method for producing calcium aluminate CaO / Al ２ O ３ The molar ratio is 0.5 to 1.8, and the SiO ２ content is 0.5 to 10% by mass. A CaO—Al ２ O ３ system clinker, a substance containing alumina, and a substance containing iron are used as raw materials, and the raw materials are granulated with water and fired at 1350 to 1600°C. A method for producing calcium aluminate, characterized by this.

2. The above CaO—Al ２ O ３ The method for producing calcium aluminate according to claim 1, characterized in that the CaO—Al system clinker, the substance containing alumina, and the substance containing iron are mixed and pulverized.

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