JP4920321B2 - Method for producing calcium aluminate - Google Patents

Description

The present invention relates to a spheroidized calcium aluminate mainly composed of CaO and Al ₂ O ₃ as chemical components and a method for producing the same. Specifically, a CaO raw material and an Al ₂ O ₃ raw material are charged into a melting apparatus, heated and melted, and then spherical calcium aluminate obtained by spraying high-pressure water on the melt, alumina containing the calcium aluminate The present invention relates to producing a spheroidized calcium aluminate by heating and melting a cement composition, a CaO raw material and an Al ₂ O ₃ raw material, and then spraying high-pressure water on the melt.

Alumina cement powders are used in various applications, but some of them are preferably spherical. For example, when spherical hydraulic powder is used, the fluidity of paste, mortar, castable or concrete can be improved, and the strength can be improved.

Alumina cement generally uses calcium aluminate produced by a firing method or a melting method using limestone or quicklime as a CaO raw material and alumina, aluminum hydroxide, bauxite, aluminum residual ash, etc. as an Al ₂ O ₃ raw material. Manufactured by pulverizing the clinker as a component alone or by adding alumina and various additives to the clinker and mixing and pulverizing them. A general method for producing alumina cement and its characteristics are widely known (Non-Patent Document 1).
Yasuo Yukihira, Masataka Sato, "About the Properties of Alumina Cement", Refractory, Refractory Technology Association, 1977, Vol. 29, No. 7, p.368

As a method for producing a spheroidized alumina cement, there are patents as shown below. For example, Patent Document 2 discloses a spheroidized calcium aluminate powder obtained by heating and melting and then blowing off the melt. It is disclosed.
JP 5-229857 A JP2002-187749 JP2002-68769

  It has been reported that paste, mortar, castable or concrete can be fluidized and strengthened by spheroidizing cement. However, there is a problem that an inexpensive cement cannot be obtained due to poor productivity and a small generation ratio of the spheroidized powder.

In view of the above situation, an object of the present invention is to provide a spheroidized calcium aluminate that has high productivity and can obtain good fluidity and strength when used as a hydraulic material, and an alumina cement composition including the same. Is to provide.

That is, the present invention is a calcium aluminate mainly composed of CaO and Al ₂ O ₃ as chemical components. After heating and melting the CaO raw material and the Al ₂ O ₃ raw material, high pressure water is sprayed on the melt. A spheroidized calcium aluminate having an average sphericity of 0.7 to 1.0, and an alumina cement composition containing a spheroidized calcium aluminate. Further, the calcium aluminate production method is characterized in that a CaO raw material and an Al ₂ O ₃ raw material are put into a melting apparatus, heated and melted, and then spheroidized by spraying high pressure water on the melt.

The spheroidized calcium aluminate of the present invention and the alumina cement composition containing the same can obtain a high fluidity that is unprecedented due to the ball bearing effect due to the spheroidization of calcium aluminate. And when obtaining workability | operativity equivalent to the conventional alumina cement composition, it is possible to reduce the amount of water, As a result, high intensity | strength is attained. Furthermore, according to the present invention, a production method that is easy to spheroidize and has high productivity is provided.

The present invention will be described in detail below. Calcium aluminate powder according to the present invention is a high-purity alumina obtained by refining natural raw materials such as red bauxite by a purification method such as the buyer process, Al ₂ O ₃ sources such as bauxite, limestone, quick lime, etc. The CaO source was blended so as to have a predetermined component ratio, and obtained by spraying high-pressure water on the melt after melting in facilities such as an electric furnace, a reflection furnace, a vertical furnace, and a flat furnace. Yes, it has hydraulic properties.

The above-mentioned calcium aluminate raw material powder is melted at a high temperature, and the melt is poured off. When water is sprayed from the nozzle at high pressure onto the flowing melt, it is cooled to become a fine calcium aluminate powder. The obtained calcium aluminate powder has a high average sphericity of 0.7 to 1.0. Furthermore, compared with the conventional spheroidized calcium aluminate powder obtained by blowing off the melt, the production rate of the spheroidized powder is large and the productivity is high.

The pressure for spraying water from the nozzle to the molten calcium aluminate is preferably 0.1 MPa or more. If the pressure is less than 0.1 MPa, the sphericity may decrease. What is necessary is just to spheroidize a molten material, and the number of nozzles, a shape, etc. are not specifically limited. In order to increase productivity, it is preferable to use a plurality of nozzles.

  The average sphericity is obtained by taking a particle image taken with a stereomicroscope (for example, model “SMZ-10” manufactured by Nikon Corporation), a scanning electron microscope, etc. into an image analyzer (for example, manufactured by Nippon Avionics Co., Ltd.). To measure.

The projected area (A) and perimeter (PM) of the particle are measured from the particle image. If the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle can be displayed as A / B. Assuming a true circle having a peripheral length of the same and the peripheral length (PM) of the sample particles, PM = 2.pi.r, because it is ^{B = πr 2, B = π} × (PM / 2π) 2 , and the spherical individual particles The degree can be calculated as sphericity = A / B = A × 4π / (PM) ² . The sphericity of 200 arbitrary particles thus obtained is obtained, and the average value is defined as the average sphericity. The average sphericity is preferably 0.7 to 1.0 in terms of average sphericity in order to obtain a good ball bearing effect. If the average sphericity is less than 0.7, the strength may decrease.

In addition to this method, it can also be determined from the sphericity of individual particles quantitatively and automatically measured by a particle image analyzer (for example, “FPIA-1000” manufactured by Sysmex Corporation). The spheroidized calcium aluminate powder can be adjusted to an arbitrary average particle size by performing classification operation, grinding to such an extent that the particle shape is not destroyed, and the like.

The average particle diameter according to the present invention is a median diameter, and can be measured by a particle size distribution measuring device such as a laser diffraction method or a laser scattering method (for example, “Microtrack particle size distribution measuring device” manufactured by Nikkiso Co., Ltd.). The average particle diameter is preferably 1 to 100 μm, more preferably 1 to 40 μm.

Alumina can be added to the spheroidized calcium aluminate according to the present invention for the purpose of improving fire resistance and corrosion resistance. This alumina is made by sintering or melting an Al ₂ O ₃ source such as aluminum hydroxide or calcined alumina by a firing device such as a rotary kiln or a melting device such as a gasification melting furnace into a predetermined size. And sieved (hereinafter referred to as additive alumina). The mineral composition is aluminum oxide indicated as α-Al ₂ O ₃ , β-Al ₂ O ₃ or the like, which is called sintered alumina, calcined alumina, easily sintered alumina, or the like. Usually, α-Al ₂ O ₃ having the characteristics of being chemically stable, having a high melting point, a high mechanical strength, and a high hardness is most preferred as the alumina for addition.

Furthermore, in the present invention, for the purpose of improving fluidity, it is possible to use additives such as a curing retarder, a curing accelerator, a fluidizing agent, etc., which are usually blended in an amorphous refractory.

Examples of the curing accelerator include lithium salts and hydroxides such as Li ₂ CO ₃ , Ca (OH) ₂ , NaOH, and KOH. Among these, lithium salts are preferable because they have a strong curing promoting action. Examples of the curing retarder include carboxylic acids, boric acids, polyacrylic acids, polymethacrylic acids, and alkali salts such as hexametaphosphoric acid, tripolyphosphoric acid, and pyrophosphoric acid.

The method of blending the additive is not particularly limited, and each additive is blended in a predetermined ratio, and mixing such as V-type blender, corn blender, nauter mixer, pan-type mixer, and omni mixer is performed. Mix evenly using a machine.

As the refractory aggregate according to the present invention, a refractory aggregate usually used for an amorphous refractory can be used, and specifically, fused magnesia, sintered magnesia, natural magnesia, light-burned magnesia, and the like. Magnesia, fused magnesia spinel and magnesia spinel such as sintered magnesia spinel, fused alumina, sintered alumina, light calcined alumina, alumina such as easily sintered alumina, silica fume, colloidal silica, light calcined alumina, and easily sintered Ultrafine powders such as alumina, others, fused silica, calcined mullite, chromium oxide, bauxite, andalusite, sillimanite, chamotte, quartzite, rholite, clay, zircon, zirconia, dolomite, perlite, vermiculite, brick waste, ceramic waste, Silicon nitride, boron nitride, silicon carbide, silicon iron iron, etc. can be used That.

Among these, from the viewpoint of corrosion resistance, durability, and fire resistance, it is selected from magnesia, magnesia spinel, chamotte, alumina, silicon carbide, and ultrafine powder, and carbonaceous aggregates such as oil pitch, tar, and scale graphite. It is preferable to use one or two or more kinds of refractory aggregates for low cement castables having 99 to 92 parts by mass of refractory aggregate and 1 to 8 parts by mass of the alumina cement composition.

Furthermore, the amorphous refractory of the present invention is made of metal powder such as metal aluminum or silicon alloy, organic fiber such as vinyl fiber or polypropylene, nitrogen-containing gas, etc. for the purpose of preventing explosion that tends to occur when the cured product is dried. The product and an anti-explosion agent such as dextrin can be blended as necessary. The amount of the explosion-preventing agent to be used should be determined as appropriate according to the intended explosion resistance and cannot be uniquely determined. Generally, it is 0.05 to 100 parts by mass with respect to 100 parts by mass of the amorphous refractory. It is preferable to mix about 5 parts by mass, and more preferably 1 to 4 parts by mass. If the amount is less than 0.05 parts by mass, the explosion preventing effect may not be obtained. If the amount exceeds 5 parts by mass, the fluidity may decrease.

The method for producing the amorphous refractory according to the present invention is not particularly limited, and in accordance with the usual method for producing an irregular refractory, each constituent raw material is blended to a predetermined ratio, and a V-type blender It is possible to mix evenly using a mixer such as a cone blender, a nauter mixer, a bread mixer, and an omni mixer, or to directly weigh into a kneader when performing kneading at a predetermined ratio. is there.

Using high alumina alumina as the Al ₂ O ₃ source and calcium oxide as the CaO source, blending the raw materials so that the CaO / Al ₂ O ₃ mol ratio is a predetermined ratio, melting at 1650 ° C. in an electric furnace, Spherical calcium aluminate clinker was prepared by spraying water from the nozzle at a pressure of 0.2 MPa to the melt. Next, the obtained clinker was classified with a cyclone to obtain a spheroidized calcium aluminate powder. The results are shown in Table 1. As a comparative example, spheroidized calcium aluminate clinker was produced by blowing air from a nozzle to 1-4 at a pressure of 0.2 MPa. The obtained clinker was similarly classified with a cyclone to obtain a spheroidized calcium aluminate powder.

<Materials used>
(1) Al ₂ O ₃ source: Commercial product (Al ₂ O ₃ purity = 99.0%, Na ₂ O = 0.3%)
(2) CaO source: Commercial product (CaO purity = 98.0%, Igloss = 1.0%)
(3) Sintered alumina: commercial product (Al ₂ O ₃ purity = 99.0%, Na ₂ O = 0.2%, particle size; 3-1 mm: 28%, 1-0.5 mm: 17%, 0.6-0.2 mm: 15% (0-0.3mm: 14%, 0-0.045mm: 6%)
(4) Fine alumina: Commercial product (Al ₂ O ₃ purity = 99.7%, Na ₂ O = 0.3%)

<Evaluation method>
(1) Average particle size: The sample was dispersed in an ethanol solvent by ultrasonic waves, and then measured with a “Microtrac particle size distribution analyzer” manufactured by Nikkiso Co., Ltd.
(2) Chemical composition: Measured by a calibration curve method using a fluorescent X-ray apparatus “RIX-3000” manufactured by Rigaku Corporation.
(3) Average sphericity: The average sphericity of the produced calcium aluminate powder was measured using a flow type particle image analyzer (trade name “FPIA-1000”) manufactured by Sysmex Corporation.
(4) Yield (%): Percentage of the sphere Katachido 0.7 or higher

Spherical calcium aluminate A 7.5 parts by mass produced in Experiment No. 1-1 of Example 1, 80 parts by mass of sintered alumina and 12.5 parts by mass of alumina (fine powder alumina) with an average particle size of 4 μm as aggregates Blended to produce an amorphous refractory. For comparison, a calcium aluminate clinker having the same component as the spheroidized calcium aluminate A produced in Experiment No. 1-1 was ground by a ball mill, and calcium aluminate (calcium aluminum aluminate having an average sphericity of 0.60 and an average particle size of 10.3 μm was used. Nate E ) was prepared.
Next, water was added at a predetermined ratio, and after kneading for 3 minutes with a mortar mixer, the characteristics at 20 ° C. were evaluated. The results are shown in Table 2.

<Evaluation method>
(1) Fluidity: The kneaded material was allowed to stand in a constant temperature room at 20 ° C. for a predetermined time, and then subjected to 15 falling motions in accordance with the JIS R2521 flow test, and the flow value was measured.
(2) Curing time: When the kneaded material was allowed to stand in a constant temperature room at 20 ° C., the time from the injection of water until the exothermic temperature reached the maximum was measured using a temperature recorder to obtain the curing time.
(3) Curing strength: The kneaded product was put in a 4 × 4 × 16 cm mold and cured in a constant temperature room at 20 ° C. for 24 hours, and then the compressive strength was measured.
(4) Drying strength: The kneaded product was put into a 4 × 4 × 16 cm mold, cured in a constant temperature room at 20 ° C. for 24 hours, then dried at 110 ° C. for 24 hours, and the compressive strength was measured.

Schematic which shows an example of the manufacturing apparatus of the spheroidized calcium aluminate of this invention.

Claims (1)

A method for producing calcium aluminate, characterized in that a CaO raw material and an Al ₂ O ₃ raw material are charged into a melting apparatus, heated and melted, and then spheroidized by spraying high-pressure water on the melt.