JP2023130121A - Production method of calcined product containing wollastonite and use of calcined product containing wollastonite - Google Patents

Abstract

To provide a wollastonite-containing material useful as a material to be blended into cement or the like by using biomass ash.SOLUTION: A method for producing a wollastonite-containing calcined product comprises preparing a raw material composition for calcination containing 30 mass% or more of biomass ash and calcining the raw material composition for calcination to form wollastonite (CaSiO3). The method for producing a cured body using the wollastonite-containing calcined product comprises preparing a hydraulic composition using the wollastonite-containing calcined product obtained by the producing method as a material, kneading the hydraulic composition by adding water to obtain a kneaded product, and curing the kneaded product. When the kneaded material is cured, carbonation is preferably performed.SELECTED DRAWING: None

Description

The present invention relates to a wollastonite-containing material useful as a material to be mixed into cement and the like.

Wollastonite (CaSiO ₃ ), known as a silicate mineral, is used in many fields such as resins, paints, building materials, rubber, and ceramics. Among these, cement-based building materials and carbonated curing concrete are useful as hardening materials because they develop strength by reacting with carbon dioxide, and because carbon dioxide is absorbed and fixed at that time, _CO2 reduction is achieved. It is also attracting attention from the viewpoint of (see Non-Patent Document 1).

On the other hand, in recent years, there has been a rush to construct and operate biomass power generation facilities due to various efforts by various business entities to popularize renewable energy. Along with this, the amount of combustion ash (biomass ash) generated in biomass power generation is also increasing, and it is hoped that it will be recycled as a raw material for cement, similar to the incineration ash generated from municipal garbage.

Hyodo et al. “CO2 absorption and fixation in cementitious materials through carbonation” Taiheiyo Cement Research Report No. 179 (2020) pp. 15-30

Until now, there was little knowledge about the technology for artificially producing wollastonite using biomass ash.

An object of the present invention is to provide a wollastonite-containing material that is useful as a material to be mixed into cement, etc., using biomass ash.

In view of the above issues, the inventors of the present invention conducted extensive studies and found that wollastonite (CaSiO ₃ ), known as a silicate mineral, is formed by using biomass ash as a raw material and subjecting it to a firing process. This discovery led to the completion of the present invention.

That is, the present invention is configured as follows.
[1] Production of a wollastonite-containing fired product by preparing a firing raw material composition containing 30% by mass or more of biomass ash, and firing the firing raw material composition to form wollastonite (CaSiO ₃ ). Method.
[2] The method for producing a wollastonite-containing fired product according to [1] above, wherein fine powder obtained by classifying raw material biomass ash is used as the biomass ash.
[3] The wollastonite-containing fired product according to [1] above, wherein the biomass ash is used by washing the raw material biomass ash with water, or by washing the fine powder obtained by classifying the raw material biomass ash with water. manufacturing method.
[4] The wollastonite-containing fired product according to any one of [1] to [3] above, wherein the CaO/SiO ₂ mass ratio of the raw material composition for firing is 0.5 to 1.2. Production method.
[5] The method for producing a wollastonite-containing fired product according to any one of [1] to [4] above, wherein the raw material composition for firing is fired at a temperature of 900°C to 1,300°C.
[6] The method for producing a wollastonite-containing fired product according to any one of [1] to [5] above, in which the biomass ash has an amorphous content of 30% by mass or more.
[7] The method for producing a wollastonite-containing fired product according to any one of [1] to [6] above, wherein the biomass ash has a silicic acid ratio of 3.0 to 20.0. .
[8] Obtain a wollastonite-containing fired product by the production method according to any one of [1] to [7] above, prepare a hydraulic composition using the wollastonite-containing fired product as a material, A method for producing a cured body using a wollastonite-containing fired product, which comprises adding water to the hydraulic composition, kneading it to obtain a kneaded product, and curing the kneaded product.
[9] Obtain a wollastonite-containing fired product by the production method according to any one of [1] to [7] above, prepare a hydraulic composition using the wollastonite-containing fired product as a material, and preparing an aggregate to be combined with a hydraulic composition made of the wollastonite-containing fired product, adding water to the aggregate and the hydraulic composition and kneading to obtain a kneaded product, A method for producing a cured product using a wollastonite-containing fired product, which comprises curing the kneaded product.
[10] The method for producing a cured product according to [8] or [9] above, wherein the kneaded product is subjected to a carbonation treatment when being cured.
[11] The biomass ash is classified, and the fine powder obtained by the classification is fired to obtain a wollastonite-containing fired product, and the coarse powder obtained by the classification is used as a material for a hardened body of a hydraulic composition. A method for recycling biomass ash.
[12] The method for recycling biomass ash as described in [11] above, wherein the wollastonite-containing fired product is used as a material for a cured product of a hydraulic composition.
[13] The biomass ash resource described in [11] or [12] above, wherein the coarse powder obtained by classifying the biomass ash is used as aggregate for concrete, concrete admixture, cement mixture, or cement clinker raw material. method.
[14] The method for recycling biomass ash according to any one of [11] to [13] above, wherein the fired material containing wollastonite is used as an aggregate for concrete, a concrete admixture, or a cement admixture. .
[15] Obtaining the cured body by using the wollastonite-containing fired product and the coarse powder obtained by classifying the biomass ash as common materials for the cured body, [11] to [14] above. The method for recycling biomass ash according to any one of the above.

According to the present invention, a wollastonite-containing material useful as a material to be mixed into cement or the like can be easily obtained through a process using biomass ash. Moreover, this allows biomass ash to be effectively recycled.

FIG. 2 is a flow diagram illustrating one embodiment of the present invention. It is a flow diagram explaining other embodiments of the present invention. Results of comparing the amount of wollastonite produced by different raw materials (Level 4, Level 11, Level 13, Level 15: heating temperature 1,100 ° C. CaO / SiO ₂ mass ratio 0.7, and Level 8, Level 12, Level 14, Level 16: A chart showing heating temperature 1,100° C. and CaO/SiO ₂ mass ratio 1). 2 is a chart showing the results of comparing the amount of wollastonite produced at different heating temperatures (levels 1 to 7: CaO/SiO ₂ mass ratio 0.7). It is a chart showing the results of comparing the wollastonite production amount depending on the difference in CaO/SiO ₂ mass ratio (Level 4, Level 8, Level 9: heating temperature 1,100° C.).

As shown in Figure 1, the present invention uses biomass ash as a raw material and processes it to form wollastonite (CaSiO ₃ ), which is known as a silicate mineral. A fired product containing wollastonite is obtained. As described later, the raw material biomass ash may be used after being washed with water.

Further, as shown in FIG. 2, in the present invention, the biomass ash used as the raw material for firing may be used after the raw material biomass ash is subjected to a classification process to adjust its particle size.

The present invention will be explained in more detail below. In addition, in this specification, the description of "%" shall be an inner division percentage in terms of mass present in the total mass, unless otherwise specified.

[1. Raw materials for firing]
<Biomass ash>
As used herein, "biomass ash" has the same meaning as generally understood by those skilled in the art. In other words, it is the ash that remains after incinerating or burning biomass, which is made up of organic resources derived from animals and plants (excluding fossil resources). Typically, examples include incineration ash of plants, trees, bamboo, and incineration ash of food residue. Alternatively, it may be combustion ash obtained by mixing biomass with coal and burning it. From the perspective of promoting effective utilization of biomass, the proportion of ash derived from biomass contained in biomass ash is preferably 50% by mass to 100% by mass, more preferably 60% by mass to 95% by mass. , particularly preferably from 70% by weight to 90% by weight.

As the biomass ash used in the present invention, palm shell ash (PKS ash) obtained by using palm shells as fuel is preferably exemplified among combustion ash of plants, trees, and bamboo. Palm shells are a by-product of palm oil production and are primarily used in the natural biomass and energy industry. Palm shell is a yellow-brown fibrous substance with a low ash content, and its particle size is approximately 5 mm to 40 mm, and its calorific value is approximately 4000 Kcal/kg. , its use as a fuel for biomass power generation is increasing.

The mode of incinerating or burning biomass is not particularly limited, and may be, for example, a method using a stoker type combustion furnace, a method using a fluidized bed type combustion furnace, etc. In particular, in fluidized bed combustion furnaces, limestone is added for the purpose of desulfurization in the combustion furnace, so it contains calcium and sulfur, and biomass ash mainly contains gypsum ( _CaSO4.2H ). ₂ O). When wollastonite (CaSiO ₃ ) is formed by firing, it also acts as a CaO source. In addition, fly ash from a fluidized bed type combustion furnace has fine particles and is easy to crush and mix, making it highly easy to burn. Therefore, it is preferable to use fly ash from a fluidized bed combustion furnace as the biomass ash. Examples of fluidized bed combustion furnaces include circulating fluidized bed combustion furnaces, pressurized fluidized bed combustion furnaces, and the like.

<Pretreatment of biomass ash>
The biomass ash used in the present invention may be obtained from a biomass power generation facility equipped with equipment such as a fluidized bed combustion furnace and used as is, or may be subjected to pretreatment such as classification and water washing as necessary. It may be used after that.

- Classification In the present invention, it is preferable to classify the raw material biomass ash and use its fine powder for the following reasons.

In fluidized bed combustion furnace equipment, sand containing quartz as a main component is introduced as a fluidized medium. For this reason, biomass ash includes glass that has been fused or solidified, particles derived from sand (relatively coarse particles), and particles derived from the aforementioned limestone or biomass that contain alkali metals and chlorine (relatively fine particles). particles) are included. Therefore, in the particle size distribution of biomass ash obtained from biomass power generation facilities equipped with equipment such as fluidized bed combustion furnaces, there is a peak on the small particle size side and a peak on the large particle size side. By using a particle size arbitrarily selected between them as a classification point, biomass ash can be separated into coarse particles and fine particles and collected.

In general, the Blaine specific surface area of biomass ash recovered from equipment such as fluidized bed combustion furnaces is typically, for example, 1,000 cm ² /g to 4,000 m ² /g, more typically 1 , 500 cm ² /g to 3,500 cm ² /g, even more typically 2,000 to 3,000 cm ² /g. When this raw material biomass ash is classified to collect fine powder, its Blaine specific surface area is typically, for example, 2,500 cm ² /g to 7,000 cm ² /g, more typically 3, 000 cm ² /g to 6,000 cm ² /g, even more typically from 4,000 cm ² /g to 5,000 cm ² /g. On the other hand, the Blaine specific surface area of the coarse powder remaining after collecting the fine powder is typically, for example, from 250 cm ² /g to 2,000 cm ² /g, more typically from 500 cm ² /g. 1,500 cm ² /g, even more typically between 750 cm ² /g and 1,250 cm ² /g.

The fine powder obtained by classifying the raw material biomass ash contains a relatively large amount of CaO, and has a good balance between the CaO source and the SiO ₂ source necessary for forming wollastonite (CaSiO ₃ ). In addition, since it has a high powder degree and is easily fired even without pulverization, wollastonite can be produced at a relatively low firing temperature or a short firing time. On the other hand, although it contains relatively large amounts of chlorine and sulfur, they may be removed by washing with water, which will be described later, if necessary, or they may be removed by volatilization during firing, depending on the content.

On the other hand, the coarse powder obtained by classifying raw material biomass ash has a high silicon content and low chlorine and sulfur content, so it is suitable for use as a general cement clinker raw material, especially as an alternative raw material for clay and coal ash. . In addition, when using it as a cement mixture, a concrete mixture, or a silicic acid material for ALC/calcium silicate plates, it is preferable to crush it to increase the reactivity. The coarse powder can also be used as fine aggregate (sand) for concrete, mortar, and carbonated hardened products without being crushed.

As described above, biomass ash can be recycled more rationally by taking advantage of the characteristics of the components separated by classification. In other words, the fine powder obtained by classifying raw material biomass ash can be used as a raw material for forming wollastonite by firing, and the coarse powder obtained by classification can be used as aggregate for concrete, concrete It may be used as a material for hardened products of hydraulic compositions, such as admixtures, cement mixtures, cement clinker raw materials, etc. In addition, for the fired product obtained by forming wollastonite from fine powder by firing, the particle size is adjusted as necessary, and the chlorine and sulfur content is removed, and this is also used as aggregate for concrete. It can be used as a material for hardened products of hydraulic compositions, such as concrete admixtures, cement admixtures, etc. In this case, if materials from fine powder and materials from coarse powder are used as common materials for the hardened material, the resource recovery rate from the raw material biomass ash per hardened material produced will be increased, making it more efficient. It is. For example, a fired product obtained using fine powder as a raw material is used as a material for a hydraulic composition, and this is used to obtain a hardened product, while coarse powder is used as the aggregate of the hardened product or crushed to form a mixed material (admixture). For example, it can be used as a material.

When classifying raw material biomass ash into fine powder and coarse powder, the classification point is preferably 10 μm to 100 μm, more preferably 30 μm to 90 μm, particularly preferably from the viewpoint of separation of components as described above. It can be arbitrarily selected within the range of 38 μm to 75 μm.

The classification means may be any means that can classify biomass ash at the classification point on the μm order as described above, and is not particularly limited, but examples include a sieve, gravity sedimentation, inertial classifier, centrifugal classifier, and gravity classifier. Examples include. Among these, from the viewpoint of classification accuracy, cyclone type air separators, vortex type centrifugal classifiers, sieving devices, etc. are preferred.

Note that when classification is performed wet, chlorine is dissolved in water, so even fine particles with a relatively high chlorine content have almost all of the chlorine removed.

In addition, fluidized bed incinerators include equipment for recovering incinerated ash that has settled in the boiler, air preheater, high-temperature gas flow path, etc., incinerated ash recovery equipment using cyclones, and incinerated ash recovery equipment using bag filters. may be provided. The particle size of the incinerated ash recovered by these recovery facilities differs depending on the recovery facility, and biomass ash of a specific particle size can be recovered from a specific recovery facility. Therefore, instead of classifying the raw material biomass ash, biomass ash having a desired particle size may be prepared by appropriately selecting the above-mentioned equipment and recovering the biomass ash.

-Water washing In any non-limiting embodiment of the present invention, the biomass ash serving as a raw material may be used after being subjected to a water washing process. The water washing process can remove components such as chlorine, sulfur, and potassium that are avoided as materials to be mixed into hydraulic compositions such as cement and concrete.

The method of washing with water is not particularly limited, and any conventional method may be used. For example, the biomass ash processing method described in International Publication No. 2021/193668 may be appropriately referred to as described below. However, it goes without saying that the method of washing with water is not limited to the specific example described below.

The treatment method includes, for example, a slurrying step in which water is added to biomass ash to form a slurry, a washing step in which the slurry is washed with water, and a dehydration step in which the slurry after washing is dehydrated. Slurrying may be performed using a powder dissolution tank that includes at least a container for containing biomass ash and water and a stirring means for mixing them into a slurry. Washing with water is performed by allowing the slurry to stand still or stirring for a predetermined period of time. This results in a slurry in which the soluble components of the biomass ash are eluted into the liquid phase of the slurry. The slurry in this state is discharged from the powder dissolving tank and dehydrated using a solid-liquid separator such as a filter press.

The mass ratio (W1/M1) of biomass ash (referred to as M1) and water (referred to as W1) in the slurry forming step is preferably 4 to 10, more preferably 4 to 7, and particularly preferably 4 to 5. If the mass ratio (W1/M1) is smaller than 4, the reforming effect may become insufficient, such as insufficient elution of cement repellent components such as chlorine from the biomass ash. Moreover, if the mass ratio (W1/M1) is larger than 10, the amount of waste water will increase.

The time required for the water washing step is preferably 30 minutes or more, more preferably 45 minutes or more, in order to sufficiently treat the biomass ash with water. In addition, the higher the temperature condition, the better the elution efficiency of repellent components such as chlorine from biomass ash, but from the viewpoint of processing costs, it is preferably 5°C to 50°C, and 25°C to 50°C. is more preferable.

In the dehydration step, in order to prevent repellent components such as chlorine contained in the slurry from remaining together with the liquid phase, the moisture content of the dehydrated product is preferably 20% by mass to 90% by mass, and 30% by mass to 70% by mass. % is more preferable. Moreover, if necessary, fresh water is added to the dehydrated product and dehydration is performed again. According to this, most of the liquid phase of the slurry is replaced with water, which is more preferable.

In the above treatment method, preferably, the pH during washing with water is adjusted to the acidic side. That is, by reducing the pH, chlorine can be removed more efficiently than when the pH is not adjusted. There are no particular limitations on the pH adjuster as long as it can reduce the pH of the slurry. Examples include acid solutions, _CO2- containing gases, and the like. That is, for example, since combustion exhaust gas from rotary kilns in cement manufacturing equipment, combustion exhaust gas from biomass incineration equipment, and biomass power plants contains carbon dioxide (CO ₂ ), by blowing the combustion exhaust gas into the slurry, The pH can be reduced to slightly alkaline. The CO2 _- containing gas only needs to contain carbon dioxide, but in order to promote efficient carbonation, the carbon dioxide concentration is preferably 10% by volume or more, more preferably 20% by volume. In addition, among the combustion exhaust gases, the gas after collecting chlorine bypass dust from cement manufacturing equipment contains harmful gases such as sulfur oxides (SOx), so the effect of fixing these gases can be expected.

The pH conditions for washing the slurry with water are preferably pH 4 to 12.5, more preferably pH 5 to 12.

- Dry ash In any non-limiting embodiment of the present invention, dry ash may be used as the raw material biomass ash. Dry ash is ash that has never been sprayed with water, is not granulated, and does not form hydrates. On the other hand, once water is sprayed and becomes granular or chlorine is incorporated into the generated hydrate, it is not possible to separate the characteristic components by classification or water washing as described above. It can be difficult. Therefore, when dry ash is used as the raw material biomass ash and water washing is performed in addition to the classification process described above, the classification process is performed before the water washing process, for example, to remove the fine powder. It is preferable to wash this with water.

It is preferable that Friedel's salt or ettringite, which is a hydrate, is not detected in the dry ash by, for example, powder X-ray diffraction. Further, the water content is preferably 10% or less, more preferably 5% or less. Further, it is preferable that the loss on ignition is 10% or less. Here, the moisture content can be determined as the mass reduction rate when dried at 105°C. Further, the ignition loss can be determined as the mass reduction rate when an object dried at 105°C is heated at 975°C.

<Compositional characteristics of biomass ash>
Hereinafter, typical compositional characteristics of biomass ash, which is used as a raw material for firing, will be explained, although not limited thereto.

The proportion of CaO in the biomass ash used as the raw material for firing (based on the ignited raw material) is preferably 10% by mass to 40% by mass, more preferably 15% by mass to 35% by mass. If the proportion of CaO is within the above range, the amount of added CaO source required to form wollastonite (CaSiO ₃ ) will be small, or it will not be necessary when classification is performed, so it may be necessary to add additional equipment or The cost of adding drugs can be kept low.

The silicic acid ratio (S.M.) of the biomass ash used as a raw material for firing is preferably 3.0 to 20.0, more preferably 4.0 to 18.0, and even more preferably 5.0 to 16.0. 0, particularly preferably 8.0 to 13.0. If the silicic acid ratio is within the above range, the total amount of Al ₂ O ₃ and Fe ₂ O ₃ relative to SiO ₂ can be kept small, so the amount of wollastonite produced can be increased. Therefore, when the fired product is used as a material for a hydraulic composition, its strength development properties can be further improved. On the other hand, when the silicic acid ratio exceeds the above range, it may become difficult to secure the amount of ash derived from biomass.

The proportion of Al ₂ O ₃ in the biomass ash used as the raw material for calcination (based on the ignited raw material) is preferably 10% by mass or less, more preferably 5% by mass or less, particularly preferably 3% by mass or less. If the proportion of Al ₂ O ₃ exceeds the above range, a large amount of non-reactive melilite may be produced during firing. Note that biomass ash has a lower proportion of Al ₂ O ₃ than general coal ash and is therefore suitable.

From the viewpoint of the production rate of wollastonite, the amorphous mass (amorphous amount) in the biomass ash used as a raw material for firing is preferably 30% by mass or more, more preferably 35% by mass or more, and particularly preferably 40% by mass. That's all.

The proportion of alkali metal in the biomass ash used as the raw material for firing (based on the ignited raw material) is preferably 1.0% by mass to 5.0% by mass, more preferably 1% by mass in terms of oxide (R ₂ O). .5% by mass to 4.0% by mass. If the proportion of the alkali metal is less than the above range, the rate of wollastonite production may become slow. On the other hand, if the proportion of alkali metal exceeds the above range, a large amount of non-reactive feldspar will be generated during the firing process, melting during firing, or large lumps will easily occur, making it difficult to fire in a kiln. It may become difficult. Furthermore, when the fired product is used as a cement mixture, concrete admixture, or concrete aggregate, there is a risk that an alkaline aggregate reaction may occur.

Note that the ratio of alkali metal (R) in terms of oxide (R ₂ O) should be calculated from the respective ratios (mass%) of Na ₂ O and K ₂ O in the sample using the following formula (1). I can do it.
_R2O = _Na2O + _0.658K2O ...(1)

<Raw material composition for firing>
Biomass ash provides both CaO and SiO ₂ sources necessary for wollastonite formation. Therefore, the obtained biomass ash or pretreated biomass ash may be used for firing as is. That is, for example, the raw material composition for firing may contain 100% by mass of biomass ash.

On the other hand, other raw materials may be appropriately added to the biomass ash to form a raw material composition for firing. However, from the viewpoint of efficiently producing wollastonite, the content of biomass ash in the raw material composition for firing shall be at least 30% by mass or more. The content of biomass ash in the raw material composition for firing is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 75% by mass or more, and particularly preferably 90% by mass or more. % by mass or more.

・Other raw materials Other raw materials that can be used as the SiO ₂ source include, for example, construction generated soil (soil incidentally generated at construction sites, construction sites, etc., earth and sand, residual soil, waste soil, construction sludge), Examples include volcanic materials such as volcanic ash, silica, and clay. These may be used alone or in combination of two or more.

Other raw materials that can be used as a CaO source include, for example, limestone, quicklime, slaked lime, shells, and industrial or general waste containing calcium. Industrial waste containing calcium includes, for example, ready-mixed concrete sludge, various sludges (e.g., sewage sludge, purified water sludge, steelmaking sludge, etc.), construction waste, concrete waste, and various incineration ash (e.g., biomass ash, coal ash, chicken manure, etc.) Examples include ash, livestock manure ash, sludge incineration ash), foundry sand, rock wool, waste glass, secondary blast furnace ash, various by-products, and unused resources (materials that remain unused, etc.). Examples of general waste containing calcium include dried sewage sludge powder and municipal waste incineration ash. These may be used alone or in combination of two or more.

The raw material composition for firing may appropriately contain general raw materials used for manufacturing cement clinker within a range that does not impede the effects of the present invention. Examples include aluminum-containing raw materials (Al ₂ O ₃ source) such as clay, iron-containing raw materials (Fe ₂ O ₃ source) such as iron slag and iron cake, and the like.

The raw material composition for firing can be prepared by suitably mixing predetermined amounts of the above-mentioned biomass ash and other raw materials such as a CaO source and a SiO ₂ source. Moreover, at that time, the raw material may be pulverized if necessary. The means for preparing the raw materials is not particularly limited, and for example, a conventional device such as a mixer may be used. Further, as the crushing means, for example, a conventional device such as a ball mill can be used.

<Compositional characteristics of raw material composition for firing>
Hereinafter, typical compositional characteristics of the raw material composition for firing will be explained, although they are not limited to these.

The mass ratio of CaO to SiO ₂ (CaO/SiO ₂ ) in the raw material composition for firing is preferably 0.5 to 1.2, more preferably 0.5 to 1, from the viewpoint of the amount of wollastonite produced. .1, more preferably 0.6 to 1.0, particularly preferably 0.7 to 0.9.

The silicic acid ratio (S.M.) of the raw material composition for firing is preferably 3.0 to 20.0, more preferably 4.0 to 19.0, even more preferably 5.0 to 18.0, and even more preferably 5.0 to 18.0. More preferably 8.0 to 17.0, particularly preferably 10.0 to 17.0, most preferably 12.0 to 17.0. If the silicic acid ratio is within the above range, the total amount of Al ₂ O ₃ and Fe ₂ O ₃ relative to SiO ₂ can be kept small, so the amount of wollastonite produced can be increased. Therefore, when the fired product is used as a material for a hydraulic composition, its strength development properties can be further improved. On the other hand, when the silicic acid ratio exceeds the above range, it may become difficult to secure the amount of ash derived from biomass.

The proportion of Al ₂ O ₃ in the raw material composition for firing (based on the ignited raw material) is preferably 1.0% by mass to 7.0% by mass, more preferably 1.5% by mass to 5.0% by mass, Particularly preferred is 2.0% by mass to 3.0% by mass. If the proportion of Al ₂ O ₃ is within the above range, the amount of wollastonite produced can be increased. However, if the proportion of Al ₂ O ₃ exceeds the above range, a large amount of non-reactive melilites may be produced during firing.

The proportion of alkali metal in the raw material composition for firing (based on ignited raw materials) is preferably 0.3% by mass to 4.0% by mass, more preferably 1.1% by mass in terms of oxide (R ₂ O). % to 3.0% by weight, particularly preferably 1.2% to 2.5% by weight. If the proportion of the alkali metal is less than the above range, the rate of wollastonite production may become slow. On the other hand, if the proportion of alkali metal exceeds the above range, a large amount of non-reactive feldspar will be generated during the firing process, melting during firing, or large lumps will easily occur, making it difficult to fire in a kiln. It may become difficult. Furthermore, when the fired product is used as a cement mixture, concrete admixture, or concrete aggregate, there is a risk that an alkaline aggregate reaction may occur.

Note that the ratio of alkali metal (R) in terms of oxide (R ₂ O) can be calculated using the above-mentioned formula (1). In addition, when the proportion of alkali metal (R ₂ O) in the raw material composition for firing is high or when it is desired to reduce the alkali metal content in the fired product, the alkali metal can be added by adding chlorine and performing the firing described below. may be removed by chlorination and volatilization or by washing the product with water.

[2. Firing]
In the present invention, a fired product containing wollastonite (CaSiO ₃ ), which is known as a silicate mineral, is obtained by subjecting the above-described raw material composition for firing to a firing process.

<Baking treatment>
The firing conditions are not particularly limited as long as they can form wollastonite using biomass ash as a raw material, but the above-mentioned raw material composition for firing is preferably heated at 900°C to 1300°C, more preferably at 1. ,000°C to 1,250°C, more preferably 1,100°C to 1,200°C.

The firing means is not particularly limited, and for example, a conventional device such as a rotary kiln can be used. When performing firing using a rotary kiln, waste oil, waste tires, waste plastics, etc., may be used as fuel alternative waste.

<Wollastonite-containing fired product>
The fired product obtained by the above-described firing process contains wollastonite (CaSiO ₃ ), which is known as a silicate mineral. It is known that wollastonite exists in the form of wollastonite (α type, low temperature type) and pseudowollastonite (β type, high temperature type). The wollastonite-containing fired product provided by the present invention may contain one of these forms singly, or may contain a plurality of forms in combination. The content of wollastonite (if it contains multiple forms in a composite manner, the total) is preferably 10% by mass or more, more preferably 20% by mass or more, particularly preferably 30% by mass or more. be. Note that pseudowollastonite has higher carbon dioxide absorption activity. Therefore, when using the wollastonite-containing fired product provided by the present invention for the purpose of absorbing carbon dioxide, it is preferable that the wollastonite is mostly in the form of pseudowollastonite. It is more preferable that it occupies half or more of the form.

The fired product obtained by the above-described firing process may contain other mineral components in addition to wollastonite. For example, rankinite (3CaO.2SiO ₂ ) can be mentioned. Rankinite has reactivity with carbon dioxide and also develops strength due to this reaction. However, from the viewpoint of ensuring the wollastonite content, in the wollastonite-containing fired product provided by the present invention, the rankinite content is preferably 20% by mass or less, and preferably 10% by mass or less. It is more preferable. Other examples include melilites. That is, the okermanite component (Ca ₂ MgSi ₂ O ₇ ), the ferrookermanite component (Ca ₂ FeSi ₂ O ₇ ), the gehlenite component (Ca ₂ Al ₂ SiO ₇ ), and the sodamerite component (CaNaAlSi ₂ O ₇ ). , hardystone component (Ca ₂ ZnSi ₂ O ₇ ), gougiaite component (Ca ₂ BeSi ₂ O ₇ ), Okayama stone component (Ca ₂ B ₂ SiO ₇ ), ferligerenite component (Ca ₂ Fe ₃ +2SiO ₇ ) , and ferrialuminium gehlenite components (Ca ₂ Fe ₃ +AlSiO ₇ ). Here, melilites have poor reactivity with carbon dioxide and poor strength development due to the reaction. Therefore, in the wollastonite-containing fired product provided by the present invention, the content of melilites is preferably 20% by mass or less, more preferably 10% by mass or less.

The fired product obtained by the above-described firing process may contain belite (2CaO.SiO ₂ ) as an intermediate reaction mineral component. Alternatively, unreacted mineral components may include quicklime, quartz, feldspars, amorphous phases, and the like. Here, from the viewpoint of ensuring the wollastonite content, in the wollastonite-containing fired product provided by the present invention, the quicklime content is preferably 2% by mass or less, and the quartz content is 8% by mass or less. The content of feldspars is preferably at most 8% by mass. Further, the amorphous mass is preferably 45% by mass or less, more preferably 35% by mass or less, and most preferably 25% by mass or less. Further, the total amount of the above-mentioned intermediate reaction mineral component and unreacted mineral component is preferably 50% by mass or less, more preferably 40% by mass or less, and most preferably 30% by mass or less.

In this specification, "mineral" refers to minerals that are geologically formed as natural products, as well as minerals that are formed by the above-mentioned firing process and have a similar composition and crystal structure to natural minerals. This term also includes artificial minerals. The morphology of mineral components can be measured using powder X-ray diffraction, microscopic observation, electron backscatter diffraction (EBSD), etc. according to conventional methods. Further, the content of mineral components can be measured by the Rietveld method in the case of powder X-ray diffraction, or by point counting in the case of microscopic observation or electron beam backscatter diffraction.

[3. Uses of fired products]
The wollastonite-containing fired product provided by the present invention can be used as it is, or after particle size adjustment such as coarse crushing, for civil engineering materials such as roadbed materials and backfilling materials. . Alternatively, it can also be used as aggregate for mortar and concrete. That is, although sand or the like is normally used as the fine aggregate and gravel or the like as the coarse aggregate, they can be used instead.

The wollastonite-containing fired product provided by the present invention can also be used as a filler for resin reinforcement, a cement mixture, a concrete admixture, and a silicic acid material for ALC/calcium silicate plates. It is. In this case, it is preferable to perform pulverization or classification as necessary to adjust the particle size as appropriate. For example, the Blaine specific surface area is preferably 2,500 to 10,000 cm ² /g, more preferably 3,000 to 9,000 cm ² /g. During the grinding, conventional gypsum and grinding aids may be added. The crushing means is not particularly limited, and a conventional device such as a ball mill can be used. The classification means is not particularly limited, and a conventional device such as a centrifugal air classifier with rotating blades can be used.

When the wollastonite-containing fired product provided by the present invention is used as a cement mixture, concrete admixture, etc. after adjusting the particle size appropriately as described above, bleeding can be reduced when kneaded with water and hardened. It can be expected to have effects such as improving fluidity and reducing heat of hydration.

In addition, the wollastonite-containing fired product provided by the present invention may be prepared by adjusting the particle size appropriately as described above, and then using the powdered product as an early-strength Portland cement, an early-strength Portland cement clinker, or a high-C3A content cement (for example, a C3A content of 10% by mass or more). 15 mass%) or C3A high content cement clinker (for example, C3A content 10 mass% to 15 mass%), etc., in an amount that is 5 parts by mass to 25 parts by mass, based on 100 parts by mass of existing cement. When used in combination, it is possible to obtain cement of the same quality as ordinary Portland cement.

The wollastonite-containing fired product provided by the present invention can be produced using a smaller amount of limestone as a raw material and at a lower firing temperature when compared to existing cements such as Portland cement. Therefore, by using it as a material for a hydraulic composition instead of cement as described below, the overall amount of carbon dioxide emissions related to cement production can be further reduced.

<Hydrocurable composition>
As described above, the wollastonite-containing fired product provided by the present invention can be used as a material for hydraulic compositions such as cement, mortar, and concrete. Here, in this specification, the term "hydraulic composition" has the same meaning as generally understood by those skilled in the art. That is, it is a composition that hardens by kneading it with water. Typically, such compositions are prepared in powder form before being combined with water.

When using the wollastonite-containing fired product provided by the present invention as a material for a hydraulic composition, it may be used after being subjected to pulverization or classification as necessary to adjust the particle size as appropriate. For example, the Blaine specific surface area is preferably 2,500 cm ² /g to 10,000 cm ² /g, more preferably 3,000 cm ² /g to 9,000 cm ² /g. If the Blaine specific surface area is 2,500 cm ² /g or more, the strength of the resulting cured product will be greater. On the other hand, if the Blaine specific surface area is 10,000 cm ² /g or less, the energy required for pulverization can be kept lower from the viewpoint of manufacturing cost.

The crushing means is not particularly limited, and a conventional device such as a ball mill can be used. The classification means is not particularly limited, and a conventional device such as a centrifugal air classifier with rotating blades can be used.

・Cement When using the wollastonite-containing fired product provided by the present invention as a material for a hydraulic composition, the hydraulic composition may contain conventional materials from the viewpoint of increasing the strength of the resulting cured product. Preferably, the cement includes: Such cements are not particularly limited, and include, for example, various Portland cements such as ordinary Portland cement, early-strength Portland cement, medium-heat Portland cement, and low-heat Portland cement, ecocement, quick-hardening cement, and super-fast-hardening cement. Examples include cement. These may be used alone or in combination of two or more. Among these, from the viewpoint of strength development and cost, at least one of ordinary Portland cement and early strength Portland cement is preferred. When using the wollastonite-containing fired material as a material for a hydraulic composition, for example, it may be 5 parts by mass to 50 parts by mass, and 10 parts by mass to 35 parts by mass in 100 parts by mass of the cement composition. 15 parts to 25 parts by weight. In addition, when producing a carbonated cured body from a hydraulic composition, the proportion of the above-mentioned baked product contained in the hydraulic composition is such that the amount of carbon dioxide absorbed is increased and the resulting cured body is From the viewpoint of increasing the strength, the lower limit of the proportion may be, for example, 20 parts by mass or more, 30 parts by mass or more, 50 parts by mass in 100 parts by mass of the cement composition. The amount may be 75 parts by mass or more. On the other hand, from the viewpoint of increasing the strength of the cured product during demolding or making the demolding process earlier, it is necessary to increase the above ratio. The upper limit may be, for example, 95 parts by mass or less, 90 parts by mass or less, more preferably 75 parts by mass or less, and 60 parts by mass in 100 parts by mass of the cement composition. % or less, and may be 50 parts by mass or less.

Note that the above-mentioned hydraulic composition may be in a conventional cement-free form, and for example, the wollastonite-containing fired product provided by the present invention may be used as it is. That is, for example, the hydraulic composition may contain 100% by mass of the wollastonite-containing fired product provided by the present invention. However, when used in a manner that does not contain existing cement or contains only a small amount of cement, the Blaine specific surface area should be increased from the viewpoint of strength development, for example, from 8,000 cm ² /g to 12 It is preferable to carry out at least one of these methods, such as pulverizing the powder to a particle size of 1,000 cm ² /g, or curing with heat when kneading it with water and curing it.

- Gypsum The above-mentioned hydraulic composition may contain gypsum as a material from the viewpoint of fluidity and workability of the kneaded product before hardening. The gypsum is not particularly limited, and examples thereof include natural dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, and the like. Furthermore, examples of forms of gypsum include dihydrate gypsum, hemihydrate gypsum, and anhydrite gypsum. These may be used alone or in combination of two or more.

The amount of gypsum to be blended is preferably 1 part by mass to 6 parts by mass, based on 100 parts by mass of the hydraulic composition (powder), from the viewpoint of fluidity and workability of the kneaded product before hardening. , more preferably 3 parts by mass to 5 parts by mass.

Note that as the gypsum to be blended as a material in the above-mentioned hydraulic composition, gypsum powder that has been ground in advance may be used, but the wollastonite-containing fired product provided by the present invention may be ground to form an appropriate gypsum powder. When adjusting the particle size, gypsum may also be pulverized so that the gypsum is included in the hydraulic composition.

-Amines The above-mentioned hydraulic composition may contain amines as its material. It is known that amines have the effect of promoting the production of carbonate ions by reacting with carbon dioxide, and when a hydraulic composition contains amines, the carbonate of the calcium component contained in the hydraulic composition is The carbonation proceeds more efficiently, and the strength of the carbonated cured product described below can be increased.

The amines are not particularly limited as long as they have an amino group and a hydroxyl group in the molecule, but examples include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), and diglycolamine. (DGA), diisopropanolamine (DIPA), methyldiethanolamine (MDEA), triisopropanolamine (TIPA), and the like. Note that these amines are generally known as grinding aids. Further, as the amines, a waste liquid containing used amines recovered from an amine-based carbon dioxide recovery device for recovering carbon dioxide from exhaust gas of a factory or the like may be used. That is, although such used amines are normally disposed of as waste liquid, they can be effectively reused by using them as the above-mentioned amines.

The amount of amines to be added is determined based on 100 parts by mass of the hydraulic composition (powder) from the viewpoint of accelerating carbonation of the cured product or, for example, from the viewpoint of increasing its strength development when performing carbonation curing. , preferably from 0.002 parts by mass to 1 part by mass, more preferably from 0.01 parts by mass to 0.1 parts by mass.

The amines are used as grinding aids when grinding the wollastonite-containing fired product provided by the present invention to obtain an appropriate particle size, and the amines are contained in the hydraulic composition. You may also do so.

-Other materials The above-mentioned hydraulic composition may contain other materials as necessary within a range that does not impede the object of the present invention. Examples of other materials include various additives such as water reducing agents, antifoaming agents, and shrinkage reducing agents, and various admixtures such as fly ash, silica fume, pulverized blast furnace slag, and pulverized limestone. Further, in order to increase the initial strength and improve handling, a rapid hardening agent, a hardening accelerator, etc. may be added. The proportion of other materials in the hydraulic composition varies depending on the type of material, but is typically, for example, 20% by mass or less, preferably 10% by mass or less.

- Content of gypsum and free lime The content of gypsum in the above hydraulic composition is preferably 5.0% by mass or less, more preferably 1.0% to 4.0% by mass in terms of _SO3 . be. If the content of gypsum is within the above range, the fluidity of the kneaded product before hardening will be further improved.

The proportion of free lime in the hydraulic composition is preferably 2.0% by mass or less, more preferably 0.2 to 1% by mass, from the viewpoint of strength development in the carbonation curing process described below. .5% by mass.

In addition, when the above-mentioned hydraulic composition is formed by blending materials other than the wollastonite-containing fired product provided by the present invention, the above-mentioned gypsum and free lime contents include those derived from the materials. It shall contain gypsum and free lime.

<Cured body>
By kneading the above-mentioned hydraulic composition with water and curing it, a cured body using a wollastonite-containing fired product can be obtained.

- Water The water for obtaining the above-mentioned cured product is not particularly limited, and examples include tap water, sludge water, and the like. The mass ratio of water to the hydraulic composition (powder) (water/powder hydraulic material) is preferably 0.3 to 1.0, more preferably 0.4 to 0.7. When the ratio is 0.3 or more, air permeability is ensured and the carbon dioxide absorption effect becomes greater. Moreover, the workability of the kneaded product of the hydraulic composition is improved. If the ratio is 1.0 or less, the strength of the cured product can be ensured.

- Aggregate When curing the hydraulic composition, an aggregate may be used to form the body of the resulting cured product. Examples of fine aggregates include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag, lightweight fine aggregate, recycled aggregate, artificially fired aggregate, or mixtures thereof. can be mentioned. Further, examples of the coarse aggregate include river gravel, mountain gravel, land gravel, crushed stone, slag, lightweight coarse aggregate, recycled aggregate, artificially fired aggregate, or a mixture thereof.

As the aggregate used when curing the hydraulic composition, the wollastonite-containing fired product provided by the present invention may be used (hereinafter, the wollastonite-containing fired product provided by the present invention). When used as aggregate, it is sometimes referred to as ``fired aggregate.'') According to this, wollastonite is present on most of the surface of the fired aggregate, and by carbonation of the wollastonite, the total amount of carbon dioxide absorbed by the hardened material can be increased, and By making the interface between the cement paste and the aggregate denser due to the carbonation reaction, the strength of the hardened product can be increased.

When the fired aggregate is used in the hydraulic composition, it can be used as at least one of fine aggregate and coarse aggregate. In this case, the wollastonite-containing fired product provided by the present invention may be crushed or crushed to a particle size suitable for use as a desired aggregate (fine aggregate, coarse aggregate, etc.). It is preferable to make adjustments and use the fired aggregate prepared in this way.

When the above-mentioned fired aggregate is used in the above-mentioned hydraulic composition, for example, when the cured product of the hydraulic composition resembles a conventional mortar, it can be used as a substitute for the fine aggregate normally used in such mortar. Alternatively, if the cured product of the hydraulic composition is similar to existing concrete, it may be included as a substitute for at least one of the fine aggregate and coarse aggregate normally used in such concrete. However, from the viewpoint of increasing the total amount of carbon dioxide absorbed by the hardened material, it is preferable that it be included as a substitute for the normally used fine aggregate.

When using the above-mentioned fired product aggregate in the above-mentioned hydraulic composition, in addition to the above-mentioned fired product aggregate, other aggregates may be used. Examples of aggregates include, as described above, examples of fine aggregates include river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag, lightweight fine aggregate, recycled aggregate, and artificially fired aggregate. , or a mixture thereof. Further, examples of the coarse aggregate include river gravel, mountain gravel, land gravel, crushed stone, slag, lightweight coarse aggregate, recycled aggregate, artificially fired aggregate, or a mixture thereof.

When using the above-mentioned fired product aggregate in the above-mentioned hydraulic composition, the proportion of the above-mentioned fired product aggregate in the total amount of aggregate used may preferably be 20% by mass or more, and 25% by mass as the lower limit. It may be 30% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass. If the proportion of the above-mentioned fired aggregate in the total amount of aggregate used is above the above range, the total amount of carbon dioxide that can be absorbed by the resulting hardened material will be higher than when using general aggregate. can be further increased, and the strength of the obtained cured product can be further increased.

Further, when the above-mentioned fired product aggregate is a fine aggregate, the proportion of the above-mentioned fired product aggregate in the total amount of fine aggregate may preferably be 20% by mass or more, and 25% by mass or more as the lower limit. It may be 30% by mass or more, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass. If the proportion of the above-mentioned fired aggregate in the total amount of fine aggregate used is above the above range, the resulting hardened material will be able to absorb more carbon dioxide than when ordinary aggregates are used. The total amount can be further increased, and the strength of the obtained cured product can be further increased.

When aggregate is used in the above-mentioned hydraulic composition, the amount of aggregate (total amount if fine aggregate and coarse aggregate are used together) is per 100 parts by mass of the hydraulic composition (powder). The amount is preferably 200 parts by mass to 700 parts by mass, more preferably 200 parts by mass to 600 parts by mass. If the blending amount of the aggregate is within the above range, the strength of the resulting cured product will be good, while the shrinkage rate will be suppressed to a low level.

When a combination of fine aggregate and coarse aggregate is used in the above-mentioned hydraulic composition, the fine aggregate ratio (the percentage of the mass of fine aggregate to the total mass of aggregate) is preferably 5% to 60%. If the fine aggregate ratio is within the above range, the workability and ease of molding of the kneaded product will improve. Further, the coarse particle ratio is preferably 1.0 to 7.0, more preferably 1.5 to 6.5.

<Carbonated hardened body>
By kneading the above-mentioned hydraulic composition with water and curing it, a cured body using a wollastonite-containing fired product can be obtained. Furthermore, by performing carbonation treatment during curing, a carbonated cured product that absorbs carbon dioxide can be obtained. Here, in this specification, "carbonation" refers to an alkaline component in the cured product of the hydraulic composition reacting with carbon dioxide to lower the pH of the alkaline component.

Hereinafter, as an example, (A) a hydraulic composition (powder), (B) water, and (C) aggregate are kneaded to obtain a kneaded product of the hydraulic composition, and A method for obtaining a carbonated hardened body by pouring it into a mold and curing it will be explained.

[Kneaded product preparation process]
This step is a step of preparing a kneaded product by kneading the above-mentioned (A) hydraulic composition (powder), (B) water, and (C) aggregate.

The method of kneading each material is not particularly limited. Further, the device used for kneading is not particularly limited, and for example, conventional mixers such as an omni mixer, a pan-type mixer, a biaxial kneading mixer, and a tilting mixer can be used.

[Pouring process]
This step is a step of pouring the kneaded material obtained in the above step into a mold.

The casting method is not particularly limited, and conventional methods such as casting can be used.

The curing method after pouring the kneaded material into the mold until it is removed from the mold is not particularly limited, and common methods such as air curing, humid air curing, underwater curing, and steam curing may be used. A curing method can be adopted.

[Demolding process]
This step is a step of removing the cured product of the hydraulic composition obtained by hardening the kneaded material from the mold after the kneaded material in the mold is cured.

[High strength curing process]
This step is a step optionally provided between the demolding step and the carbonation curing step, and is a step for increasing the strength of the cured product of the hydraulic composition.

In this step, the compressive strength of the cured product of the hydraulic composition removed from the mold is preferably 3 N/mm ² or more, more preferably 5 N/mm ² or more, particularly preferably 10 N/mm ² or more. By curing until , the strength of the carbonated hardened body after carbonation curing (for example, compressive strength of mortar, compressive strength of concrete) can be increased.

The curing method is not particularly limited, and for example, general curing methods such as air curing, humid air curing, underwater curing, and steam curing can be used. Note that "curing" in the high-strength curing process does not include carbonation curing.

[Carbonation curing process]
This step is a step in which the cured product of the hydraulic composition removed from the mold is carbonated and cured to obtain a carbonated cured product obtained by carbonating the cured product of the hydraulic composition.

The concentration of carbon dioxide gas used for carbonation curing in this step is preferably 1% by volume or more, more preferably 3% by volume or more, still more preferably 10% by volume or more, even more preferably 50% by volume or more, particularly preferably is 60% by volume or more. If the above concentration is 1% by volume or more, the amount of carbon dioxide absorbed in the carbonation curing process can be increased.

The upper limit of the concentration of carbon dioxide gas is not particularly limited, and the higher the concentration of carbon dioxide gas, the more the amount of carbon dioxide absorbed can be increased, but on the other hand, from the perspective of lowering the cost of curing equipment, etc. The content is preferably 90% by volume or less, more preferably 70% by volume or less, particularly preferably 50% by volume or less.

Further, the temperature in the carbonation curing step is not particularly limited, but is preferably 5°C to 100°C, more preferably 10°C to 50°C, particularly preferably 15°C to 35°C. If the temperature during carbonation curing is within the above range, the strength of the carbonated hardened product can be increased. Furthermore, the productivity of products made of carbonated hardened products is improved.

Further, the carbonated cured product of the present invention has a large effect of reducing carbon dioxide emissions even when carbonated and cured at a relatively low temperature (eg, 5° C. to 30° C.).

The relative humidity in this step is not particularly limited, but is preferably 20% to 90%, more preferably 30% to 80%, particularly preferably 40% to 70%. If the above-mentioned relative humidity is 20% or more, the productivity of the carbonated cured product will be further improved, and the strength of the carbonated cured product will be further increased. It is difficult to make the relative humidity above 90%, and the cost for equipment etc. becomes excessive.

In the carbonation curing step, carbonation curing is carried out so that the carbonation depth from the surface of the carbonated hardened body is preferably 2 mm or more, more preferably 5 mm or more, even more preferably 8 mm or more, particularly preferably 10 mm or more. It is preferable to do this. By performing carbonation curing so that the carbonation depth is 2 mm or more, more carbon dioxide can be absorbed by the carbonated hardened product. Specifically, the carbonation depth can be made 2 mm or more by appropriately adjusting the values of the concentration, temperature, and relative humidity of carbon dioxide gas and the curing time in the carbonation curing process described above. .

In addition, from the viewpoint of absorbing carbon dioxide in a short time, preferably the carbonation depth is set to 2 mm or more at the age of the material (after demolding) for 1 day, more preferably for the age of the material (after demolding) for 3 days. It is preferable to carry out carbonation curing.

Note that the "carbonation depth from the surface of the carbonated hardened body" can be measured in accordance with "JIS A 1152:2018 (method for measuring carbonation depth of concrete)".

The obtained carbonated hardened product can be used as a roadbed material, interlocking block, etc. Furthermore, even after being installed as a roadbed material, etc., carbon dioxide can be continuously absorbed and fixed.

In addition, when the hydraulic composition contains fired aggregate (aggregate made of the above-mentioned fired product), from the viewpoint of densification and increasing the strength of the aggregate, the fired aggregate should be added before the kneaded material preparation process. Then, carbonation treatment may be performed. The carbonation treatment may be performed, for example, by keeping the material in a wet state and leaving it in the presence of carbon dioxide gas. At this time, if the fired aggregate is carbonated excessively, the carbonation reaction will not occur during carbonation curing, so the strength of the carbonated hardened material may not improve after carbonation curing. be.

The carbonated hardened body obtained by the above production method can be obtained by using ordinary Portland cement instead of the pulverized sintered product (the pulverized sintered product described above), or when using the sintered aggregate instead of The amount of carbon dioxide emitted during the production of the carbonated hardened body is preferably 15% or more, more preferably 20% or more, even more preferably 30% or more, compared to the case of using general aggregate, Particularly preferably, it is reduced by 40% or more. Further, the rate of decrease in strength (for example, compressive strength) of the carbonated cured product is preferably 50% or less, more preferably 40% or less.

Hereinafter, the present invention will be explained in more detail with reference to test examples. However, the scope of the present invention is not limited by these test examples.

[1. Test sample]
・Biomass ash powder: fly ash generated from a biomass power plant (furnace type: circulating fluidized bed boiler (CFB), fuel: 100% coconut shell (PKS)) (hereinafter referred to as "raw powder")
・Coarse powder of biomass ash*: 53 μm sieved material of raw powder (hereinafter referred to as "coarse powder")
・Biomass fine ash powder *: Raw powder that passes through a 53μm sieve (hereinafter referred to as "fine powder")
・Silica sand: Kashima No. 6 silica sand (hereinafter referred to as "silica sand")
・Calcium carbonate: Special grade (95.5% or more) CaCO ₃ powder, used as a CaO concentration regulator *Classifier: Spin air sieve (SAR-75) (manufactured by Seishin Enterprises)

[2. Analysis method]
・Chemical composition of biomass ash (before washing): using a fluorescent X-ray device (manufactured by Rigaku Co., Ltd., "ZSX Primus II") (calibration curve (clay) method)
・Chemical composition of biomass ash (after washing with water) and chemical composition of fired product: using a fluorescent X-ray device (manufactured by Rigaku Co., Ltd., "ZSX Primus II") (FP method: fundamental parameter method)
・Mineral content: Using a sample to which 10% corundum (Al ₂ O ₃ ) was added as an internal standard substance, X-ray analysis was performed using an X-ray diffractometer (D8 ADVANCE A-25 manufactured by Bruker AXS). The diffraction pattern was measured.

The measurement conditions for X-ray diffraction were CuKα rays, tube voltage of 50 kV, tube current of 40 mA, scanning range of 10° to 65° (2θ), step width of 0.0234, and scanning speed of 0.13 sec/step. Next, Rietveld analysis was performed using software (TOPAS Ver. 6.0 manufactured by Bruker AX) using the obtained diffraction pattern to obtain quantitative results of mineral composition. Among the obtained results, the amorphous mass was calculated from the corundum quantitative value using the following formula (2).

G=100・(AR)/{A・(100−R)/100}…(2)
In addition, in formula (2), G is the amorphous mass (%), R is the mixing ratio of Al ₂ O ₃ (%), and A is the quantitative value of Al ₂ O ₃ (%).

In addition, the quantitative results obtained from the Rietveld analysis were standardized so that the total amount of the composition excluding the quantitative value of corundum was 100%, and then further standardized by the ratio of this value excluding the amorphous mass. The value was used as the mineral composition of each biomass ash.

[3. Characteristics of test sample]
Table 1 shows the chemical composition of the test samples.

Table 2 shows the XRD qualitative analysis results of the test samples.

Table 3 shows the XRD/Rietveld analysis results of the test samples.

Table 4 shows the Blaine specific surface area and CaO/SiO ₂ mass ratio of the test samples.

[3. Characteristics of test sample]
(Water washing process)
Chlorine contained in raw powder, coarse powder, and fine powder was removed by washing with water in advance.
・Washing water ratio: 1:4 (100g of biomass ash to 400g of water)
- Stirring conditions: rotation speed 400 rpm, time 30 minutes, water temperature at room temperature - Cake washing water ratio: 1:4 (400 g water to 100 g biomass ash)

(powderness adjustment)
In order to eliminate the influence of fineness during firing, the Blaine values of the raw powder/washed product, coarse powder/washed product, and silica sand are pulverized using a pulverizer (disc mill) so that the Blaine value of the fine powder/washed product is equal to the Blaine value of the fine powder/washed product. It was adjusted.

Table 5 shows the chemical composition of the sample after pretreatment.

Table 6 shows the XRD qualitative analysis results of the sample after pretreatment.

Table 7 shows the results of the XRD Rietveld analysis of the sample after pretreatment.

Table 8 shows the Blaine specific surface area and CaO/SiO ₂ of the sample after pretreatment.

[4. Test conditions/levels]
In order to investigate the conditions for wollastonite formation, various levels were set for firing temperature and CaO/SiO ₂ mass ratio.

Table 9 shows the test levels.

Table 10 shows the formulations for the test levels.

Table 11 shows the chemical composition of the samples after adjusting the formulation for the test level.

[5. Heat treatment and results]
(Heating conditions)
・Furnace used during heating: Box-type electric furnace (S7-2035D-OP manufactured by Motoyama)
・Heating temperature: As per test standard ・Heating time: 60 minutes

Table 12 shows the results of the XRD Rietveld analysis of the heat-treated products.

Table 13 shows the chemical composition of the heat-treated products.

Furthermore, Fig. 3 shows the results of comparing the amount of wollastonite produced by different raw materials (Level 4, Level 11, Level 13, Level 15: heating temperature 1,100°C, CaO/SiO ₂ mass ratio 0.7, and level 8, level 12, level 14, level 16: heating temperature 1,100° C. CaO/SiO ₂ mass ratio 1).

As a result, as shown in Table 12, Table 13, and Figure 3, when raw biomass ash powder, fine powder or coarse powder obtained by classification is heat-treated, wollastonite (CaSiO ₃ ) amount increased. Therefore, it can be seen that by using biomass ash as a raw material, the wollastonite production reaction is accelerated and a wollastonite-containing fired product can be easily obtained. In particular, those made from fine powder have a high amount of wollastonite (CaSiO ₃ ), a low amount of intermediate reaction mineral components and unreacted mineral components, and the sintering reaction progresses quickly. Note that those made from coarse powder have a low amount of wollastonite (CaSiO ₃ ) and a slow rate of wollastonite formation, but CaO and SiO ₂ after heating are higher than those made from raw ash or fine powder. Since the wollastonite content is also high (low SM, low R ₂ O, low MgO, low SO ₃ ), it is thought that the wollastonite content can be further increased by firing at a higher temperature or for a longer time. .

FIG. 4 shows the results for Levels 1 to 7, comparing the wollastonite content in the heated product depending on the difference in heating temperature.

As shown in FIG. 4, in order to form wollastonite using biomass ash as a raw material, it was considered that a temperature condition of over 1,000° C. was preferable. In particular, it can be seen that at temperatures above 1,200°C, pseudowollastonite increases, and intermediate reactive mineral components and unreacted mineral components decrease.

FIG. 5 shows the results of Level 4, Level 8, and Level 9, and the wollastonite content in the heated product was compared based on the difference in the CaO/SiO ₂ mass ratio in the firing raw material composition.

As shown in FIG. 5, when forming wollastonite using biomass ash as a raw material, the CaO/SiO ₂ mass ratio in the raw material composition for firing may be in the range of approximately 0.5 to 1.2. It was thought that good results could be obtained if Note that the higher the CaO/ _SiO2 mass ratio, the lower the wollastonite content, and the slower the wollastonite production rate, but the wollastonite content can be further increased by firing at a higher temperature or for a longer time. considered to be a thing.

Table 14 shows the results of comparing the produced minerals with respect to whether or not the fine powder was washed with water (level 4 and level 10) (heating temperature 1,100° C.).

Furthermore, Table 15 shows the results of comparing the chemical compositions of fine powders with and without water washing (level 4 and level 10) (heating temperature 1,100° C.).

As shown in Tables 14 and 15, the heat-treated product obtained by washing fine powder of biomass ash with water and heat treatment produces the same amount of wollastonite and has a lower chlorine content than the case without washing with water. has become lower.

Claims (15)

A method for producing a wollastonite-containing fired product, comprising preparing a firing raw material composition containing 30% by mass or more of biomass ash, and firing the firing raw material composition to form wollastonite (CaSiO ₃ ). The method for producing a wollastonite-containing fired product according to claim 1, wherein fine powder obtained by classifying raw material biomass ash is used as the biomass ash. 2. The method for producing a wollastonite-containing fired product according to claim 1, wherein raw material biomass ash is used after being washed with water, or fine powder obtained by classifying raw material biomass ash is used as the biomass ash. The method for producing a wollastonite-containing fired product according to any one of claims 1 to 3, wherein the CaO/SiO ₂ mass ratio of the raw material composition for firing is 0.5 to 1.2. The method for producing a wollastonite-containing fired product according to any one of claims 1 to 4, wherein the raw material composition for firing is fired at a temperature of 900°C to 1,300°C. The method for producing a wollastonite-containing fired product according to any one of claims 1 to 5, wherein the biomass ash has an amorphous content of 30% by mass or more. The method for producing a wollastonite-containing fired product according to any one of claims 1 to 6, wherein the biomass ash has a silicic acid ratio of 3.0 to 20.0. A wollastonite-containing fired product is obtained by the production method according to any one of claims 1 to 7, a hydraulic composition is prepared using the wollastonite-containing fired product as a material, and the hydraulic composition is A method for producing a cured product using a wollastonite-containing fired product, which comprises adding water and kneading to obtain a kneaded product, and curing the kneaded product. A wollastonite-containing fired product is obtained by the manufacturing method according to any one of claims 1 to 7, a hydraulic composition is prepared using the wollastonite-containing fired product as a material, and the wollastonite-containing fired product is prepared as a material. Prepare aggregate to be combined with the hydraulic composition, which is made from the containing fired product, add water to the aggregate and the hydraulic composition, knead to obtain a kneaded product, and harden the kneaded product. , a method for producing a cured product using a fired product containing wollastonite. The method for producing a cured product according to claim 8 or 9, wherein carbonation treatment is performed when the kneaded product is cured. The biomass ash is classified, the fine powder obtained by the classification is fired to obtain a wollastonite-containing fired product, and the coarse powder obtained by the classification is used as a material for a hardened body of a hydraulic composition. How to recycle biomass ash as a resource. The method for recycling biomass ash according to claim 11, wherein the fired product containing wollastonite is used as a material for a cured product formed by a hydraulic composition. The biomass ash resource recycling method according to claim 11 or 12, wherein the coarse powder obtained by classifying the biomass ash is used as concrete aggregate, concrete admixture, cement mixture, or cement clinker raw material. The method for recycling biomass ash according to any one of claims 11 to 13, wherein the fired material containing wollastonite is used as an aggregate for concrete, a concrete admixture, or a cement admixture. According to any one of claims 11 to 14, wherein the calcined product containing wollastonite and the coarse powder obtained by classifying the biomass ash are used as common materials for a cured body to obtain the cured body. The described method for recycling biomass ash.