JP2006051731A - Solidified body obtained by using inorganic powder, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for manufacturing a solidified body superior in physical property by using inorganic powder. <P>SOLUTION: The method of manufacturing the solidified body by using the inorganic powder is characterised by containing a step for obtaining a mixture by mixing the inorganic powder composed of a crushed matter of fly ash or a refractory and 35-100 mass% of an alkali hydroxide water solution of a concentration of 0.6-3.5 mol/liter to the mass of the inorganic powder; a step for casting the mixture into a formwork; and a step for irradiating the mixture cast into the formwork with a microwave to dry it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for producing a high-strength solidified body from an inorganic powder such as a powder obtained by pulverizing fly ash or refractory. The solidified body manufactured from the inorganic powder is used as a heat insulating material, for example.

  A large amount of waste is generated from various industrial facilities, but in recent years, recycling of waste is strongly demanded from the viewpoint of protecting the global environment and effectively using resources. As waste, various compounds such as organic compounds, inorganic compounds, polymers, and metals are generated.

  One example of the inorganic compound is inorganic powder. As inorganic powders, fly ash generated at thermal power plants scattered in various places; alumina-silicon carbide-carbon refractories (ASC) for chaotic vehicles, refractories for lances (M lance), refractories for tundish Examples thereof include powder obtained by pulverization of a refractory such as (TD) (hereinafter also referred to as “refractory powder”). Since the amount of fly ash and refractory powder produced is large, if they can be recycled, this will greatly contribute to global environmental protection and effective use of resources.

As a method of recycling inorganic powder, a method of solidifying fly ash and reusing the formed solidified body as a heat insulating material or a building material has been proposed. For example, Patent Document 1 discloses a method in which a specific amount of Portland cement, steel slag, or fluidized bed ash is added to a mixture of fly ash and desulfurized sludge to form and harden. Patent Document 2 discloses a method of blending an organic binder and a granular fly ash sintered body with fly ash, adding water and kneading, and then pressure-molding and firing the kneaded product. In Patent Document 3, cement and water are added to fly ash and mixed. Further, an anti-settling agent, a thickener, a surfactant, a foaming agent, water and the like are added to prepare a slurry. A method of manufacturing a heat insulating material by casting in a mold and molding is disclosed.
JP-A-5-301749 JP-A-5-330898 JP 2001-270760 A

  As a method for recycling inorganic powders, solidified bodies obtained by solidifying inorganic powders have been proposed. In order to promote recycling of inorganic powders and contribute to global environmental protection and effective use of resources, solidified bodies have been proposed. It is preferable to further improve the physical properties. For example, if the strength and heat insulating property of the solidified body can be increased, it is considered that the motivation for recycling inorganic powder can be increased by expanding the use of the solidified body and improving convenience.

  Accordingly, an object of the present invention is to provide means for producing a solidified body having excellent physical properties using inorganic powder. Moreover, the objective of this invention is providing the solidified body excellent in the physical property manufactured using the inorganic powder.

The present invention
(1) Mixing inorganic powder made of pulverized product of fly ash or refractory with an aqueous alkali hydroxide solution having a concentration of 0.6 to 3.5 mol / liter of 35 to 100% by mass relative to the mass of the inorganic powder. And a step of pouring the mixture into a mold, and a step of irradiating the mixture poured into the mold with microwaves and drying the mixture. A method for producing a solidified body using powder,
(2) The production method according to (1), wherein the alkali hydroxide is sodium hydroxide or potassium hydroxide,
(3) The mixture is irradiated with 4 to 40 kW of microwaves per ton of the mixture, (1) or (2),
(4) Any one of (1) to (3), further comprising a step of boiling the solidified body obtained by drying the mixture in water and a step of drying the boiled solidified body. Production method according to
(5) Mixing inorganic powder composed of pulverized product of fly ash or refractory and alkali hydroxide aqueous solution having a concentration of 0.6 to 3.5 mol / liter of 35 to 100% by mass with respect to the mass of the inorganic powder. Then, obtaining a mixture, pouring the mixture into a mold, irradiating the mixture poured into the mold with microwaves, and drying the mixture,
It is.

  The solidified body produced by the present invention is excellent in physical properties such as strength and heat insulation performance, and is useful for various applications. Further, the production method of the present invention is relatively simple, and a solidified body having excellent physical properties can be obtained relatively easily.

The first of the present invention relates to a method for producing a solidified body using inorganic powder. The present inventors have examined recycling of inorganic powder, mixed inorganic powder and alkali hydroxide, irradiated the microwave to the mixture and dried, resulting in high strength, high porosity and excellent heat insulation. It has been found that a solidified body can be produced in a short time. The mechanism by which the physical properties of the solidified body are improved by mixing inorganic powder and alkali hydroxide and irradiating with microwaves is not clear so far. As the mechanism, the following mechanism is presumed, but these are merely presumptions, and the technical scope of the present invention is not limited to the following mechanism. (1) A mechanism in which the strength of a solidified body is improved by a water glass bond formed by reacting SiO ₂ and alkali hydroxide contained in an inorganic powder in a microwave heating field. For example, when NaOH is used as the alkali hydroxide, Na ₂ O · SiO ₂ is formed. (2) When SiO ₂ , Al ₂ O ₃ or CaO contained in the inorganic powder and NaOH undergo a pozzolanic reaction, a stronger bond is formed between the inorganic powders by the action of microwaves, and the solidified body Mechanism to improve the strength of the.

  Hereinafter, the production method of the present invention will be described in detail in the order of steps.

  First, an inorganic powder is prepared. The inorganic powder is made of fly ash or pulverized refractory. Both fly ash and ground refractory may be included. The average particle size of the inorganic powder is usually 75 μm or less, but is not particularly limited. In some cases, materials other than fly ash and pulverized refractory may be included.

  Fly ash is generated in large quantities in a thermal power plant, but is not particularly limited to thermal power plants, and fly ash generated in other facilities may be used. Examples of the refractory pulverized material include powders obtained by pulverizing various refractory materials such as ASC, M lance, and TD. By reusing fly ash and refractories after use, resources are effectively used.

  The inorganic powder and an aqueous alkali hydroxide solution having a concentration of 0.6 to 3.5 mol / liter are mixed. The amount of the alkali hydroxide aqueous solution to be mixed is 35 to 100% by mass with respect to the mass of the inorganic powder. Examples of the alkali hydroxide aqueous solution include an aqueous solution obtained by dissolving an alkali compound such as a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution in water. Considering material costs, the aqueous alkali hydroxide solution is preferably an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution. In some cases, two or more alkali hydroxides may be used in combination.

  The concentration of the aqueous alkali hydroxide solution mixed with the inorganic powder is 0.6 to 3.5 mol / liter, preferably 1 to 3 mol / liter. If the alkali hydroxide concentration is too low, the strength of the dried solidified product may not be obtained. Moreover, when the formed solidified body is immersed in water, the particles forming the solidified body may fall off and become a slurry. On the other hand, if the concentration of the alkali hydroxide is too high, white precipitates presumed to be NaOH are deposited on the solidified surface at the end of drying and solidification, which may cause a problem in handling the solidified product. Moreover, when the solidified body is immersed in water, the particles forming the solidified body may fall off and the solidified body may become brittle. In addition, when 2 or more types of alkali hydroxides are used together, it is controlled so that the total concentration of alkali hydroxides in the alkali hydroxide aqueous solution is 0.6 to 3.5 mol / liter.

  The concentration of the alkali hydroxide is calculated on the basis of the total aqueous alkali hydroxide solution mixed with the inorganic powder and the total water content. When the alkali hydroxide aqueous solution mixed with the inorganic powder is one type, the concentration of the alkali hydroxide aqueous solution corresponds to the concentration of the alkali hydroxide aqueous solution mixed with the inorganic powder. When two or more kinds of alkali hydroxide aqueous solutions are used in combination or when water is added to the inorganic powder by another route, the concentration of alkali hydroxide is calculated from the amount of alkali hydroxide and the total volume of water. However, in a mode in which a high-concentration alkali hydroxide aqueous solution and inorganic powder are mixed and then water is added to the mixture, there is a possibility that local adverse effects may occur around the high-concentration alkali hydroxide aqueous solution. It is preferable to use an alkali hydroxide aqueous solution prepared in advance to the above concentration.

  The amount of the aqueous alkali hydroxide solution mixed with the inorganic powder is 35 to 100% by mass, preferably 40 to 80% by mass, based on the mass of the inorganic powder. If the amount of the aqueous alkali hydroxide solution is too small, the powder cannot be sufficiently wetted, and there is a possibility that it becomes a dumpling and a solidified product cannot be obtained. If the amount of the aqueous alkali hydroxide solution is too large, the aqueous solution may float on the surface of the mixture at the stage of forming the mixture, which may increase the time required for drying.

  When a mixture of inorganic powder and aqueous alkali hydroxide is obtained, the mixture is poured into a mold. The shape of the mold may be determined according to the use of the solidified body. For example, when it is desired to produce a cylindrical solid body, a cylindrical formwork may be used. When the solidified body is processed into a desired shape by cutting or cutting after manufacturing, the solidified body may be temporarily processed into a shape such as a rectangular parallelepiped.

  The formwork supplied with the mixture is irradiated with microwaves, and the mixture is dried. The amount of microwave irradiation is not particularly limited, but from the viewpoint of suppressing an increase in equipment costs associated with an increase in the size of microwave equipment, it is preferably 4 to 40 kW, more preferably 6 to 20 kW per ton of mass of the mixture. Of microwaves.

  Although the drying temperature at the time of drying the mixture by microwave irradiation is not specifically limited, Preferably the temperature of a mixture is heated up to 150 degreeC or more. By raising the temperature of the mixture to such a temperature, a solidified body having excellent physical properties such as strength and heat insulating properties can be obtained. The upper limit of the drying temperature is not particularly limited. However, if the temperature is raised excessively, the thermal efficiency may be lowered, so that it is actually preferable to set the drying temperature to 250 ° C. or lower.

  The heating time of the mixture is not particularly limited as long as the solidified body is produced by microwave irradiation. Usually, a solidified body is obtained by microwave irradiation for about 12 to 48 hours.

  The temperature rise rate of the mixture by microwave irradiation is also affected by the type of inorganic powder to be heated. For example, when fly ash is used as the inorganic powder, the higher the total carbon (total-C) contained in the fly ash, the higher the temperature rise by the microwave.

  Microwave irradiation can be performed using a known microwave irradiation apparatus, or newly developed microwave irradiation may be used. As the microwave, for example, a microwave having a frequency of 0.915 GHz using a magnetron as an oscillation tube, a microwave having a frequency of 2.45 GHz employed in a microwave oven, or a microwave of 28 GHz using a gyratorron as an oscillation tube For example, microwaves having various frequencies can be used. A microwave optical waveguide that guides the microwave to a desired site may be used.

  The microwave irradiation apparatus may include a heating unit that assists heating by microwave irradiation. For example, hot air may be supplied together with microwave irradiation.

  By heating using microwaves, a solidified body having excellent physical properties can be obtained. If this invention is used, it is possible to obtain the solidified body which is excellent in intensity | strength and excellent in heat insulation. The production method of the present invention requires a facility for irradiating microwaves, but is a solidified product having excellent physical properties by a relatively simple operation of mixing an inorganic powder and an aqueous alkali hydroxide solution and irradiating microwaves. Can be manufactured.

  After drying a mixture of inorganic powder and alkali hydroxide to obtain a solidified body, the solidified body may be boiled in water. In the production method of the present invention, since alkali hydroxide is used, the physical properties of the solidified body may be reduced by the alkali hydroxide contained in the solidified body. In particular, when the solidified body is used in a high temperature environment such as 600 ° C. or higher, it is preferable to remove the alkali hydroxide. In some applications, it may be preferable to avoid elution from the alkali hydroxide solidified product. By boiling the solidified body in water and removing the alkali hydroxide from the solidified body, it is possible to prevent problems caused by the alkali hydroxide in the solidified body. After boiling the solidified body, the solidified body is dried again. For drying, forcible drying means such as a hot air supply device or a vacuum vessel may be used, and natural drying may be employed if there is no particular problem.

  The boiling conditions are not particularly limited, but the boiling is preferably performed in a state where the solidified body is sufficiently submerged. The boiling time is not particularly limited, but usually the solidified body is boiled for about 2 to 20 minutes.

  The boiling of the solidified body in water is preferably performed twice or more. FIG. 1 is a graph showing the relationship between the number of boiling treatments and the pH transition of the boiling treatment liquid when the solidified body is boiled in water. As shown in FIG. 1, when the boiling process is performed twice, the pH is greatly reduced as compared to the time of one boiling. In addition, when the mass change of the sample was measured before and after the boiling treatment, no significant mass decrease was confirmed, and it was confirmed that a solidified body was formed.

  2nd of this invention is related with the solidified body manufactured by using inorganic powder as a raw material. Specifically, the second of the present invention is an inorganic powder composed of fly ash or refractory pulverized material, and 0.6 to 3.5 mol / liter of 35 to 100% by mass with respect to the mass of the inorganic powder. Solidified solution obtained by mixing with an aqueous alkali hydroxide solution of a concentration to obtain a mixture, pouring the mixture into a mold, irradiating the mixture poured into the mold with microwaves, and drying the mixture Is the body.

  2nd of this invention is related with the solidified body obtained by 1st of this invention. Since the details of the manufacturing method have been described in the first aspect of the present invention, the description thereof is omitted here.

  The solidified body of the present invention has a high porosity and excellent heat resistance. The porosity of the solidified body of the present invention can be evaluated as an apparent porosity. The apparent porosity of the solidified body of the present invention is preferably 35% or more, more preferably 40% or more. Apparent porosity can be measured by the method described in JIS R2205 based on the Archimedes method.

  The solidified body of the present invention has excellent strength. The compression strength of the solidified body of the present invention is preferably 16 MPa or more, more preferably 18 MPa or more, and further preferably 20 MPa or more. The compressive strength can be measured according to JIS R2206.

<Example 1>
Fly ash (19 kg), which is an inorganic powder, and a sodium hydroxide aqueous solution (9.5 kg) having a concentration of 3.5 mol / liter were mixed. The composition of the fly ash, total-Fe (2.46 wt%), CaO (0.43 _wt%), SiO 2 (58.85 _{wt%), Al 2 O 3 (} 26.53 wt%), total- C (3.69 _wt%), Na 2 O (0.32 _wt%), K 2 O (1.29 wt%), and was _TiO 2 (1.33 wt%). The fly ash had a 50% diameter of 12.765 μm and a specific surface area of 8.32 m ² / g. Mixing was performed for 3 minutes using a cake mixer.

  After mixing, a mixture consisting of fly ash and an aqueous sodium hydroxide solution was poured into a SUS mold without vibration. The size of the mold was 200 × 200 × 200 mm. Three thermocouples were installed at the bottom of the mold for the purpose of observing temperature changes. The container was placed in an applicator capable of microwave irradiation and irradiated with microwaves. The microwave output was set to 8 kW per ton of the slurry-like mixture (actual output 0.3 kW, reflection 0.1 kW). The mixture was supplied with hot air at 150 ° C. together with microwave irradiation. The microwave irradiation time was 40 hours.

  A sample was randomly cut out from the solidified product obtained by drying the mixture, and the compression strength was measured. When compressive strength was measured about five samples, it had high compressive strengths, such as 24MPa, 17MPa, 20MPa, 24MPa, and 18MPa (average 21MPa). When the apparent porosity of the solidified body was evaluated, it was 50.8%.

<Example 2>
A solidified body was produced in the same manner as in Example 1 except that as the inorganic powder, a powder obtained by pulverizing ASC after use was used instead of fly ash. The compressive strength of the solidified body was 22 MPa. When the apparent porosity of the solidified body was evaluated, it was 59.3%.

<Example 3>
A solidified body was produced in the same manner as in Example 1, except that the powder obtained by pulverizing the M lance after use was used as the inorganic powder instead of fly ash. The compressive strength of the solidified body was 26 MPa. When the apparent porosity of the solidified body was evaluated, it was 60.3%.

<Example 4>
A solidified body was produced in the same manner as in Example 1 except that as the inorganic powder, a powder obtained by pulverizing TD after use was used instead of fly ash. The compressive strength of the solidified body was 31 MPa. When the apparent porosity of the solidified body was evaluated, it was 54.7%.

<Comparative Example 1>
The fly ash (19 kg) used in Example 1 was mixed with a sodium hydroxide aqueous solution (9.5 kg) having a concentration of 0.5 mol / liter. Mixing was performed for 3 minutes using a cake mixer.

  After mixing, a mixture consisting of fly ash and an aqueous sodium hydroxide solution was poured into a SUS mold without vibration. The size of the mold was 200 × 200 × 200 mm. The container was placed in an applicator capable of microwave irradiation and irradiated with microwaves. The output of the microwave was set to 16 kW per ton of mass of the slurry mixture (actual output 0.6 kW, reflection 0.1 kW). The mixture was also supplied with hot air at 150 ° C. along with microwave irradiation. The microwave irradiation time was 30 hours.

  When a sample was cut out from the solidified body obtained by drying the mixture and the compression strength was measured, the compression strength of the solidified body was as low as 2 MPa. In order to measure the porosity, boiling in water was performed. As a result, the powder was dissolved from the solidified body in water, and again became a mixed slurry state.

<Comparative example 2>
The fly ash (19 kg) used in Example 1 was mixed with a sodium hydroxide aqueous solution (9.5 kg) having a concentration of 5.0 mol / liter. Mixing was performed for 3 minutes using a cake mixer.

  After mixing, a mixture consisting of fly ash and an aqueous sodium hydroxide solution was poured into a SUS mold without vibration. The size of the mold was 200 × 200 × 200 mm. The container was placed in an applicator capable of microwave irradiation and irradiated with microwaves. The output of the microwave was set to 16 kW per ton of mass of the slurry mixture (actual output 0.6 kW, reflection 0.1 kW). The mixture was also supplied with hot air at 150 ° C. along with microwave irradiation. The microwave irradiation time was 30 hours.

  White precipitates adhered to the surface of the solidified body obtained by drying the mixture. When the compressive strength of the solidified body was measured, the compressive strength of the solidified body showed a large value of 24 MPa. When boiling in water to measure the porosity, powder particles spilled from the solidified body, and the porosity could not be measured.

  As shown in Table 1, the solidified body of the present invention has a high compressive strength. Moreover, since the porosity is high, it is estimated that it is excellent also in heat insulation performance.

  According to the present invention, the inorganic powder can be effectively used. The solidified body manufactured from the inorganic powder is used for, for example, a heat insulating material, a sound insulating material, a tile, an exterior material, and an interior material.

It is a graph which shows the relationship between the frequency | count of a boiling process at the time of boiling a solidified body in water, and pH transition of a boiling process liquid.

Claims (5)

Mixing inorganic powder consisting of fly ash or pulverized refractory with an alkali hydroxide aqueous solution having a concentration of 0.6 to 3.5 mol / liter of 35 to 100% by mass with respect to the mass of the inorganic powder, Obtaining a mixture;
Pouring the mixture into a mold;
Irradiating the mixture poured into the mold with microwaves and drying the mixture;
The manufacturing method of the solidified body using inorganic powder characterized by including these.   The method according to claim 1, wherein the alkali hydroxide is sodium hydroxide or potassium hydroxide.   The manufacturing method according to claim 1, wherein the mixture is irradiated with 4 to 40 kW of microwave per ton of mass of the mixture. Boiling the solidified product obtained by drying the mixture in water;
Drying the boiled solidified body,
The manufacturing method according to claim 1, further comprising:   Mixing inorganic powder consisting of fly ash or pulverized refractory with an alkali hydroxide aqueous solution having a concentration of 0.6 to 3.5 mol / liter of 35 to 100% by mass with respect to the mass of the inorganic powder, A solidified body obtained by obtaining a mixture, pouring the mixture into a mold, irradiating the mixture poured into the mold with microwaves, and drying the mixture.

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