JP7708618B2 - CEMENT PRODUCTION METHOD, CEMENT PRODUCTION SYSTEM, AND PRODUCTION METHOD FOR HARDENED CEMENT PRODUCT - Google Patents

Description

The present invention relates to a cement production method and a cement production system, and in particular to a cement production method and a cement production system that utilizes biomass ash as a cement raw material. The present invention also relates to a method for producing hardened cement using biomass ash.

In recent years, with disposal sites becoming increasingly scarce, it is hoped that the incineration ash generated by the incineration of municipal waste will be recycled as a raw material for cement, etc. In addition, due to various initiatives by various business entities to promote the spread of renewable energy, the construction and operation of biomass power generation facilities is progressing, and the amount of incineration ash (biomass ash) generated from biomass power generation is also increasing. For this reason, it is hoped that biomass ash will also be recycled as a raw material for cement, etc., in the same way as incineration ash from municipal waste, etc.

In relation to these issues, for example, the following non-patent document 1 considers the use of biomass ash as a cement admixture.

Takahiro Sagawa et al., "Application of wood biomass incineration ash to cement admixtures", Abstracts of the 70th Cement Technology Conference, 2016 [1307]

In the above-mentioned Non-Patent Document 1, biomass ash is used as it is as a cement admixture. However, this method has the problem that the strength of the hardened cement products such as concrete and mortar using the obtained cement is significantly reduced.

The present invention aims to provide a cement production method and cement production system that can effectively utilize biomass ash while suppressing a decrease in the strength of the resulting hardened cement.

The method for producing cement according to the present invention comprises the steps of:
A step (a) of classifying biomass ash into coarse powder and fine powder;
and a step (b) of feeding the fine powder obtained in the step (a) to at least one of a cement clinker raw material to be fed into a cement kiln, cement clinker obtained from the cement kiln, or cement after a crushing treatment of the cement clinker.

Biomass ash has low activity, but the finer the particle size, the more active it is and the higher the alkali metal content. For this reason, as in the above method, the fine powder obtained after classifying biomass ash is mixed with cement clinker raw materials, cement clinker (hereinafter, both may be collectively referred to as "cement raw materials"), or cement, activating the pozzolanic reaction. As a result, the strength of the hardened cement is increased compared to when unclassified biomass ash (hereinafter, referred to as "raw ash") is added to cement raw materials or cement.

Specific methods for the above step (b) include feeding into raw material mixing equipment such as mixers and grinders for mixing the raw materials for cement clinker, feeding into the preheater top or calciner in front of a cement kiln (rotary kiln), feeding into the bottom of a cement kiln, feeding into the front of a cement kiln, feeding into a clinker cooler for cooling the cement clinker obtained by burning, feeding into a grinding device (mill) for grinding cement clinker, feeding into a mixer for producing mixed cement, feeding into a concrete mixer, etc. In other words, the fine powder of biomass ash obtained in step (a) can be fed into various stages during cement production and can be suitably used as a cement clinker raw material, a cement mixture, or a cement admixture.

In the following, in order to avoid redundancy by using the term "mixture or admixture," when the term "mixture" is used, it refers to a material that is added to cement clinker or cement, regardless of the cement production stage.

This step (a) is preferably performed on biomass ash (preferably dry ash) to which water has not been added and to which the hydrate formation reaction has not progressed. For example, if the biomass ash is wet ash and has aggregated or formed hydrates, there is a possibility that the coarse powder will contain a large amount of chlorine even after classification.

In this specification, "dry ash" refers to biomass ash that is collected in a dry state, to which no water has been added before classification, and to which no aggregation or hydrates have been formed. The above-mentioned dry ash also includes cases in which water has been added before classification, but in which a large amount of water has been added and the ash is dispersed, and no hydrates have been formed due to long-term storage. In this specification, "wet ash" refers to, for example, bottom ash, which is the incineration residue discharged from the bottom of an incinerator, or fly ash collected by a dust collector, which has been collected in a state containing moisture due to being cooled with water or sprayed with water, or which has been dried. Generally, wet ash has a moisture content of 15% by mass or more.

The method for producing cement includes a step (c) of washing the biomass ash with water,
The step (b) may be a step of adding the fine powder after it has been washed with water in the step (c).

According to the study by the inventors, biomass ash contains harmful components in cement and concrete, and has poor quality stability due to the presence of easily reactive calcium components, which has led to concerns about restrictions on its use as a resource for cement raw materials, etc. In contrast, according to the above method, biomass ash that has undergone the water washing process (c) is added to cement raw materials (cement clinker raw materials, cement clinker) or cement, so that the added biomass ash has efficiently removed chlorine, which is a cement-repellent component, and can suppress corrosion of reinforcing bars in concrete as a hardened cement product. In addition, heavy metals such as selenium and chromium that may pollute the environment, and easily reactive calcium oxide and calcium hydroxide are removed, making it possible to homogenize the quality of the cement. When biomass ash that has undergone the water washing process (c) is used as a clinker raw material, clogging due to adhesion of low-melting point substances to the preheater, kiln bottom, and kiln is suppressed.

This washing step (c) preferably includes a step (c1) of adding water to the biomass ash to form a slurry, a step (c2) of supplying washing water to the slurry to wash it, and a step (c3) of dewatering the slurry after washing. The slurry is washed with water after it is made, and then dewatered to obtain a dehydrated product, which allows the removal of chlorine and heavy metals.

Step (c) may involve washing only the fine powder obtained in step (a).

According to the inventors' research, when comparing the coarse powder and fine powder obtained after classifying biomass ash, it was confirmed that most of the chlorine contained in the biomass ash is contained in the fine powder. Therefore, according to the above method, it is possible to efficiently remove the chlorine contained in the biomass ash while suppressing the amount of water used for washing.

The cement production method may include a step (d) of oxidizing the biomass ash during or after the step (c).

According to the above method, the pH during washing is adjusted to the acidic side, so chlorine can be removed more efficiently. In addition, even if the biomass ash contains a large amount of easily reactive calcium oxide or calcium hydroxide, it can be completely replaced with calcium carbonate or calcium sulfate, so the quality of the cement, such as its fluidity, can be homogenized.

In step (d), an acid solution may be added during the washing of the biomass ash, or a gas containing carbon dioxide (CO _{2 )} may be blown into the biomass ash after the washing process. In particular, by using combustion exhaust gas from a cement kiln, chlorine bypass extraction gas, or combustion exhaust gas from a biomass incineration facility or a biomass power plant as the CO ₂ -containing gas, the CO ₂ contained in these gases can be converted to calcium carbonate and fixed in the biomass ash, so that a reduction in CO ₂ emissions can be expected. In addition, harmful gases such as sulfur acids (SO _x ) contained in the exhaust gas can be converted to calcium sulfate and fixed in the biomass ash.

In addition, particularly in step (d), by subjecting the biomass ash to a carbonation treatment during the water washing in step (c), the calcium content contained in the wastewater after water washing can be precipitated as calcium carbonate, thereby suppressing the generation of scale. This makes it possible to suppress blockage of pipes for wastewater treatment, etc.

The cement production method may also include a step (e) of removing unburned carbon contained in the biomass ash during the execution of the step (c).

Biomass ash can contain a large amount of unburned carbon. For this reason, when biomass ash that contains a lot of carbon is used as a cement clinker raw material, it may cause the preheater to become too hot, and when used as an admixture, it may cause the concrete to darken or the water-reducing agent to adsorb to the carbon, resulting in a decrease in fluidity.

In contrast, the above method can remove unburned carbon during washing, preventing the problems mentioned above. Specifically, the amount of unburned carbon contained can be reduced by mixing a carbon removal agent such as oil or a surfactant and performing flotation.

The step (b) may be a step of adding the cement to at least either the cement clinker obtained from the cement kiln or the cement obtained after the cement clinker has been crushed.

According to this method, the fine powder obtained after classifying the biomass ash is used as an admixture, so the strength of the hardened cement product is higher than when unclassified biomass ash is used as an admixture.

Step (b) may also be a step of mixing at least one of a latent hydraulic substance and a pozzolan in addition to the fine powder.

When fine powder from classified biomass ash is added during cement production, cement with a high alkali metal content can be produced. When this cement is mixed with aggregate to produce concrete, alkali-reactive minerals (such as amorphous silica) in the aggregate react with the alkali metals to produce water-absorbent alkali silica gel, which can cause cracks in the concrete (alkali aggregate reaction).

In contrast, the above method uses latent hydraulic substances such as blast furnace slag and pozzolans (including natural pozzolans such as silica powder and stone powder, and artificial pozzolans such as fly ash and calcined clay) added together with fine powder, which can suppress the alkali-aggregate reaction.

However, by using aggregate that is less likely to cause alkali-aggregate reaction as the aggregate mixed in the concrete production process, it is possible to suppress the alkali-aggregate reaction without mixing in latent hydraulic substances or pozzolans.

The step (a) is preferably a step of classifying the powder with a classification point of 20 μm or more and 100 μm or less. This is efficient because chlorine and sulfur in particular are distributed predominantly to the fine powder side.

The cement manufacturing system according to the present invention comprises:
A classification facility that separates biomass ash into coarse and fine powders;
a cement kiln for burning cement clinker raw materials to produce cement clinker;
and a grinding facility for grinding the cement clinker obtained from the cement kiln to produce cement,
The fine powder obtained by the classification device is added to at least one of the cement clinker raw material, the cement clinker obtained from the cement kiln, or the cement obtained from the grinding facility.

According to the above system, the fine powder obtained after classifying the biomass ash is added to the cement raw materials or cement, which increases the strength of the hardened cement compared to when raw ash is mixed with the cement raw materials or cement.

The method for producing a hardened cement product according to the present invention further comprises the steps of:
A step (a) of classifying biomass ash into coarse powder and fine powder;
The method is characterized by comprising a step (b) of adding the fine powder obtained in the step (a), the cement after the pulverization treatment, and water.

For the same reasons as described above, this method also makes it possible to obtain a hardened cement product with higher strength than when raw ash before classification is added. Examples of hardened cement products include concrete and mortar. In either case, appropriate aggregate may be added in addition to the fine powder, cement, and water. After these are added, they may be mixed in a concrete mixer, for example.

The present invention makes it possible to effectively utilize biomass ash in cement production while suppressing the decrease in strength of the resulting hardened cement product.

1 is a diagram illustrating a process flow of a cement production method according to a first embodiment. FIG. 1 is a block diagram illustrating a structure of a cement production system according to a first embodiment. 1 is a graph showing the particle size distribution of incineration fly ash from the biomass power generation facility P1 of Example 1. 1 is a diagram illustrating a process flow of a cement production method according to a second embodiment. 1 is a diagram illustrating an example of a detailed processing flow of a water washing step. FIG. 11 is a block diagram illustrating a structure of a cement production system according to a second embodiment. FIG. 7 is a block diagram showing an example of the structure of a water washing facility provided in the cement production system of FIG. 6. 10 is a diagram illustrating a schematic diagram of another example of a process flow of the cement production method according to the second embodiment. FIG. 1 is a block diagram showing a schematic example of a structure of a water washing facility. 13 is a diagram illustrating a process flow of a cement production method according to a third embodiment. FIG. 11 is a block diagram illustrating a structure of a cement production system according to a third embodiment. FIG. 11 is a block diagram illustrating a structure of a cement production system according to another embodiment. FIG. 11 is a block diagram illustrating a structure of a cement production system according to another embodiment. FIG. 11 is a block diagram illustrating a structure of a cement production system according to another embodiment.

[Biomass ash]
The present invention relates to a technique for using biomass ash in cement production. First, the biomass ash to which the present invention is applied will be described.

Biomass ash to which the present invention is applicable broadly and generally includes biomass incineration ash, such as ash from plants and bamboo, and ash from food waste. Biomass ash contains water-soluble alkali metal chlorides, alkali metal sulfates, and alkali metal carbonates. Compared to municipal waste incineration ash and chlorine bypass dust, biomass ash has the advantage of having a higher proportion of alkali metal sulfates and alkali metal carbonates, and a lower concentration of alkali chlorides.

Biomass ash is incineration ash, so it contains glass components with pozzolanic activity like coal ash. Among biomass ash, the incineration ash of grass and bamboo has a relatively high content of _K2O , with more than half of the potassium ( _K2O ) embedded in the glass phase. Therefore, biomass ash has high activity when used as an admixture, so it is preferable to use it in cement production.

The K ₂ O content of the biomass ash is preferably 2% by mass to 10% by mass, more preferably 3% by mass to 8% by mass, and even more preferably 3% by mass to 5% by mass. If the K ₂ O content of the biomass ash is less than 2% by mass, the strength of the cement may be reduced when used as an admixture, and there is a risk that the necessary amount of the material to be added to the cement may not be secured in the first place. On the other hand, if the K ₂ O content of the biomass ash exceeds 10% by mass, the amount of use when used as a raw material for cement clinker may be limited, or the occurrence of alkali aggregate reaction may increase when used as an admixture.

The total alkali concentration in the biomass ash is preferably 2% by mass to 11% by mass, and more preferably 3% by mass to 6% by mass, calculated as _R2O ( _R2O = _Na2O + 0.658 x _K2O ). The sulfur oxide ( _SO3 ) concentration in the biomass ash is preferably 0.5% by mass to 6% by mass, and more preferably 1% by mass to 5% by mass.

In biomass power plants, biomass and coal may be mixed and burned, and the biomass ash to which the present invention is applied includes ash generated when such mixed combustion is performed. However, since coal ash obtained by burning coal generally has a low _K2O content, the activity of the biomass ash varies depending on the amount of coal used during mixed combustion. Therefore, from the viewpoint of recycling as a mixture for cement production, when mixed with coal, it is preferable that the ash is obtained from a fuel with a biomass ratio of 50 mass% or more.

As biomass ash to which the present invention can be applied, palm kernel shell ash (PKS ash) obtained by using palm kernel shells as fuel, among the incineration ash of plants and bamboo, is a suitable example. Palm kernel shells are a by-product of palm oil production and are mainly used in the natural biomass energy industry. Palm kernel shells are a yellowish-brown fibrous material with low ash content, with particle sizes of about 5 mm to 40 mm and a calorific value of about 4000 Kcal/kg. Therefore, in energy production using renewable resources, palm kernel shells have been increasingly used as fuel for biomass power generation in recent years.

Generally, combustion furnaces for biomass power generation are of the stoker type and the fluidized bed type, but in the case of the circulating fluidized bed type and the pressurized fluidized bed type, which are fluidized bed types, limestone is added to perform desulfurization in the furnace. Therefore, the biomass ash from such combustion furnaces contains a large amount of calcium and sulfur components, and for example, the CaO content is generally 5% to 45% by mass. In addition, the form of Ca compounds derived from the added limestone includes CaO (quicklime), Ca(OH) ₂ (slaked lime), CaCO ₃ (limestone), CaSO ₄ (gypsum), etc.

The CaO content of the biomass ash to which the present invention is applied is preferably 10% by mass to 40% by mass, and more preferably 15% by mass to 30% by mass, from the viewpoint of the strength of the cement when it is recycled as a mixed material.

The type of biomass ash to which the present invention is applicable may be bottom ash remaining at the bottom of a combustion furnace for biomass power generation, or fly ash obtained by collecting soot dust suspended as a gas contained in combustion exhaust gas using a dust collector. Of these, fly ash is preferred because it has higher concentrations of alkali metals and chlorine, and chlorine can be easily separated by washing with water, making it more efficient.

Also, the biomass ash is preferably dry ash. Once water has been sprayed on the biomass ash, it may become granular, or chlorine may be incorporated into the hydrates that are produced, making it difficult to separate the chlorine by classification or washing with water. For example, it is preferable that the dry ash does not contain Friedel's salt or ettringite, which are hydrates, detected by powder X-ray diffraction. Alternatively, the moisture content is preferably 10% by mass or less, and more preferably 5% by mass or less. Alternatively, the loss on ignition is preferably 10% or less. The moisture content can be determined as the mass loss rate when dried at 105°C. Also, the loss on ignition can be determined as the mass loss rate when an object dried at 105°C is heated at 975°C.

The amount of structural water in the hydrates in the biomass ash may also be calculated as the amount of hydrates produced by subtracting the amount of decarbonation by calcium carbonate from the loss on ignition. The amount of hydrates produced is preferably 5% or less, and more preferably 3% or less.

The particle size of the biomass ash is preferably 200 μm or less in median diameter (D ₅₀ ), more preferably 150 μm or less, and even more preferably 90 μm or less, which increases the strength of the cement. The particle size can be measured using a laser diffraction/scattering particle size distribution measuring device, for example, a MW3300EXII manufactured by Microtrac-Bell, using ethanol as a dispersion medium, and measuring after ultrasonic dispersion for 1 minute. The D ₅₀ value means the particle size at 50% cumulative in the volume-based particle size distribution.

[First embodiment]
A first embodiment of a cement production method and a cement production system will be described. Fig. 1 is a diagram showing a process flow of the cement production method in this embodiment. Fig. 2 is a block diagram showing a structure of the cement production system in this embodiment.

The cement production system 1 shown in FIG. 2 includes a raw material tank 3 in which cement clinker raw material Y1 is stored, a powder storage tank 5 in which biomass ash B1 is stored, a clinker production facility 10, a classification facility 20, and a crushing facility 30. The clinker production facility 10 is a facility that burns the cement clinker raw material Y1 to produce cement clinker Cn1, and includes a cement kiln 12 for burning, a preheater 11 that heats the cement clinker raw material Y1 in advance before it is charged into the cement kiln 12, and a clinker cooler 13 that cools the burned cement clinker Cn1.

As shown in FIG. 1, the cement production method of this embodiment includes a step S10 of classifying biomass ash B1, and a step S20 of feeding or adding the classified biomass ash B1 to a cement raw material or the like. In the following, the feeding or adding steps are collectively referred to as the "feeding" step.

(Classification step S10)
The biomass ash B1 stored in the powder storage tank 5 is classified into a coarse powder B1C having a coarse particle size and a fine powder B1F having a fine particle size based on a predetermined classification point by the classification equipment 20. The classification point determined in the classification step S10 is preferably 20 μm or more and 100 μm or less, more preferably 30 μm or more and 90 μm or less, and particularly preferably 38 μm or more and 75 μm or less.

The classification equipment 20 is not particularly limited as long as it is a device that can classify the biomass ash B1 at the classification points on the order of μm as described above. For example, a sieve, an inertial classifier, a centrifugal classifier, a gravity classifier, etc. can be suitably used, and from the viewpoint of classification accuracy, it is particularly preferable to use a cyclone-type air separator or a sieving device. If washing with water is performed, it is more efficient to do it in a wet manner.

Fluidized bed incinerators are fed with sand, mainly composed of quartz, as a fluidizing medium, and limestone for desulfurization. The biomass ash fly ash from such incinerators contains relatively coarse molten solidified or agglomerated glass and sand-derived materials, as well as relatively fine volatilized alkali metal salts and the aforementioned limestone-derived materials. If the particle size distribution of biomass ash is expressed as a frequency, and the classification point is set between the peaks on the fine and coarse sides, the chlorine, sulfur, and calcium components can be efficiently separated.

Figure 3 is a graph showing the particle size distribution of incineration fly ash from biomass power generation facility P1 in Example 1 described below. The graph in Figure 3 confirms that peaks appear on both the fine and coarse particle sides. The fine particle side is thought to be derived from limestone and alkali metal salts, while the coarse particle side is thought to be derived from quartz and glass. Therefore, it can be seen that chlorine, sulfur, and calcium can be efficiently separated by classifying the particle size of the area between these peaks (valley area) as the classification point.

The classification equipment 20 may be provided with a storage tank for the biomass ash B1. In addition, a supply device may be provided for supplying a quantitative amount of the biomass ash B1 from the storage tank to the classification equipment 20. These storage tanks and supply devices may be used appropriately depending on the condition of the received biomass ash B1.

Indicators for classification in the classification step S10 include the activity index of the fine powder B1F, the yield of the fine powder B1F, the chlorine concentration, sulfur oxide concentration, and calcium oxide concentration of the fine powder B1F and coarse powder B1C, etc.

The activity index of the fine powder B1F obtained in the classification step S10 is higher than that of the biomass ash (raw ash) B1, typically 70% or more in 7 days and 65% or more in 28 days, and more typically 75% or more in 7 days and 70% or more in 28 days.

The activity index contained in biomass ash B1 (B1C, B1F, etc.) can be measured by a known method, and a preferred example is a method that complies with JIS A 6201:2015 "Fly ash for concrete."

The yield of fine powder B1F is preferably 10% to 80%, more preferably 20% to 70%, and even more preferably 30% to 60%. The yield of fine powder B1F may be the ratio of the total mass of the obtained fine powder B1F to the total mass of the biomass ash B1 before the classification process S10 is performed.

The chlorine concentration ratio of the fine powder B1F to the coarse powder B1C is preferably 4 or more, more preferably 8 or more, and even more preferably 12 or more. The chlorine concentration of the fine powder B1F is, for example, typically 0.2% by mass to 2% by mass, and more typically 0.3% by mass to 1.5% by mass. On the other hand, the chlorine concentration of the coarse powder B1C is typically reduced to 0.01% by mass to 0.2% by mass, and more typically 0.02% by mass to 0.1% by mass.

The chlorine concentration in biomass ash B1 (B1C, B1F, etc.) can be measured by known methods, such as a method in which the chlorine concentration is measured by potentiometric titration after acid decomposition treatment.

The ratio of the total alkali concentration of the fine powder B1F to that of the coarse powder B1C is preferably 1.05 or more, more preferably 1.1 or more, and even more preferably 1.2 or more, calculated as R ₂ O (R _{2 O} = Na 2 O + 0.658 x K ₂ O). The total alkali concentration of the fine powder B1F is typically 2% by mass to 10% by mass, and more typically 3% by mass to 8% by mass. On the other hand, the total alkali concentration of the coarse powder B1C is typically reduced to 0.5% by mass to 6% by mass, and more typically reduced to 2% by mass to 5% by mass.

The total alkali concentration contained in biomass ash B1 (B1C, B1F, etc.) can be measured by known methods, such as a method conforming to JIS R 5204 "Method for X-ray fluorescence analysis of cement."

The sulfur oxide concentration ratio of the fine powder B1F to the coarse powder B1C is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. The sulfur oxide concentration of the fine powder B1F is, for example, typically 1% to 6% by mass, and more typically 2% to 5% by mass. On the other hand, the sulfur oxide concentration of the coarse powder B1C is typically reduced to 0.01% to 2% by mass, and more typically 0.05% to 1% by mass.

The concentration of sulfur oxides contained in biomass ash B1 (B1C, B1F, etc.) can be measured by known methods, such as a calibration curve method using an X-ray fluorescence device.

The calcium oxide concentration ratio of the fine powder B1F to the coarse powder B1C is preferably 1.5 or more, more preferably 2 or more, and even more preferably 3 or more. The calcium oxide concentration of the fine powder B1F is, for example, typically 8% by mass to 40% by mass, and more typically 15% by mass to 35% by mass. On the other hand, the calcium oxide concentration of the coarse powder B1C is typically reduced to 3% by mass to 15% by mass, and more typically reduced to 5% by mass to 10% by mass.

The calcium oxide concentration contained in biomass ash B1 (B1C, B1F, etc.) can be measured by known methods, such as the calibration curve method using an X-ray fluorescence device.

This classification process S10 corresponds to process (a).

(Feeding process S20)
The fine powder B1F obtained in the classification step S10 is input (added) as a raw material for cement clinker or as an admixture to cement clinker or cement. In the example of Fig. 2, the fine powder B1F is mixed with the cement clinker Cn1 obtained from the clinker production facility 10 and, if necessary, gypsum in the grinding facility 30, and is subjected to a grinding process to produce a mixed cement. At that time, water is sprayed or a grinding aid is added as necessary.

The fine powder B1F has a finer particle size than the coarse powder B1C and therefore exhibits high reactivity. For this reason, it is preferable to recover the fine powder B1F obtained after the classification step S10 and use it in a cement mixture. This activates the pozzolanic reaction and increases the strength of the hardened cement.

As the pulverizing equipment 30, a general mill used in the finishing process such as a tube mill can be used. The mill is also called a finishing pulverizer, and in a cylindrical drum, steel balls, cement clinker Cn1, and gypsum, which is added as necessary, are pulverized while colliding with each other as the drum rotates. When gypsum is used, the gypsum is not particularly limited, and examples include natural gypsum dihydrate, flue gas desulfurization gypsum, phosphate gypsum, titanic gypsum, and hydrofluoric gypsum. These may be used alone or in combination of two or more types.

The fine powder B1F is used to replace a part of the cement raw material, and is preferably added in an amount of 0.5% to 30% by mass relative to the mass of the cement raw material. In addition, it is preferable to add gypsum in an amount of 1.5% to 5.0% by mass, calculated as _SO3 , in order to improve the strength development and fluidity of the cement.

As an alternative method, the fine powder B1F obtained in the classification step S10 may be directly fed into the clinker cooler 13. One method of feeding is to drop it from the top of the clinker cooler 13 at a position within the clinker cooler 13 at the desired temperature. The amount fed is preferably set to about 0.5% to 20% by mass relative to the mass of cement. Note that it is preferable to use an air quenching cooler as the clinker cooler 13, since this allows the fine powder B1F to be fed into a predetermined position within the clinker cooler 13.

When the fine powder B1F is fed into the clinker cooler 13, it is convenient to evaporate and remove the moisture using thermal energy that is not directly related to the production of cement clinker Cn1. Also, in order to prevent a large amount of dust from being generated inside the clinker cooler 13, it is preferable that the fine powder B1F has a moisture content of 50% by mass or less and is fed in the form of lumps or granules.

Although not shown in FIG. 2, the recovered fine powder B1F may be mixed with the cement obtained after the cement clinker Cn1 is crushed in the crushing equipment 30. The timing of this mixing may be on the route to the cement silo in which the cement is stored downstream of the crushing equipment 30, or may be in the cement silo, or may even be during the concrete mixing process when the cement is used. Since the fine powder B1F exhibits high reactivity, the effect of increasing the strength of the hardened cement product can be obtained regardless of the timing of mixing the fine powder B1F. However, more strictly speaking, it is preferable that the fine powder B1F is added to the cement clinker Cn1 or the crushing equipment 30, since the fine powder B1F has a finer particle size and is more reactive than when it is mixed with the cement obtained after the cement clinker Cn1 is crushed in the crushing equipment 30.

On the other hand, the coarse powder B1C obtained after the classification step S10 has a lower reactivity than the fine powder B1F, and has a lower alkali metal concentration, calcium concentration, chlorine concentration, and sulfur concentration than the fine powder B1F. For this reason, as shown in FIG. 2, it can be used in the clinker production facility 10 together with the cement clinker raw material Y1. For example, it can be fed into a mixer for mixing the cement clinker raw material Y1 in the clinker production facility 10, fed into a preheater 11 or a calciner, fed into the kiln end or kiln front of the cement kiln 12, and can be suitably used as a raw material for cement clinker Cn1 that can be fed into various stages of cement production.

As mentioned above, the chlorine concentration of the coarse powder B1C is greatly reduced by the classification process S10. Furthermore, the sulfur content is greatly reduced, which suppresses blockages caused by adhesion of low-melting-point substances to the preheater, kiln bottom, and kiln. After separately crushing to increase reactivity, it can be used as a cement admixture in the same way as the fine powder B1F.

This input step S20 corresponds to step (b).

[Second embodiment]
A second embodiment of a cement production method and a cement production system will be described, focusing on differences from the first embodiment. Fig. 4 is a diagram showing a process flow of the cement production method in this embodiment. Fig. 5 is a diagram showing an example of a detailed process flow of a water washing step S30 described later. Fig. 6 is a block diagram showing a structure of a cement production system in this embodiment.

The cement production system 1 of this embodiment shown in FIG. 6 differs from the first embodiment in that it includes a water washing facility 40. The water washing facility 40 is a facility for washing the biomass ash B1 with water, and is provided for the purpose of reducing the concentration of cement-repellent components, such as chlorine, contained in the biomass ash B1. An example of the detailed structure of the water washing facility 40 will be described later with reference to FIG. 7.

(Water washing step S30)
The biomass ash B1 is subjected to a water washing process by the water washing equipment 40. More specifically, as shown in Fig. 5, a step S31 of forming a slurry from the biomass ash B1, a step S32 of washing the slurry with water, and a step S33 of dehydrating the slurry are performed.

As an example, the water washing equipment 40 shown in FIG. 7 includes a powder dissolution tank 43 for adding water W1 to the stored biomass ash B1 to form slurry Lr1 for water washing, a solid-liquid separation device 46 for dewatering the slurry Lr2 discharged from the powder dissolution tank 43 after water washing, and a transport device 47 for transporting the dehydrated material Ck1 separated by the solid-liquid separation device 46.

In the example of the water washing equipment 40 shown in FIG. 7, the powder dissolution tank 43 is provided with a powder supplying device 41 for supplying biomass ash B1 and a liquid supplying device 42 for supplying water W1. In addition, a slurry mixing device 44 equipped with a mixing blade is provided for mixing the biomass ash B1 and the water W1 and for mixing the slurry Lr1 produced by the mixing.

In the powder dissolution tank 43, a slurrying process S31 is carried out in which the biomass ash B1 and water W1 are mixed and stirred to produce a slurry Lr1, and a water washing process S32 is carried out in which cement-repellent components such as chlorine are dissolved in the slurry Lr1 into the liquid phase. As the slurry stirring device 44 used for this purpose, for example, a general stirring device such as a paddle type or a screw type can be used.

In the slurrying step S31, the mass ratio (W1/B1) of biomass ash B1 to water W1 is preferably 2 to 10, more preferably 3 to 7, and particularly preferably 4 to 5. If the mass ratio (W1/B1) is less than 2, the modification effect may be insufficient, such as insufficient elution of water-soluble components such as chlorine from the biomass ash B1. Furthermore, if the mass ratio (W1/B1) is greater than 10, the amount of wastewater W3 will be large.

The water washing step S32 is performed by leaving the slurry Lr1 to stand or stirring it for a predetermined period of time. This results in a slurry Lr2 in which the soluble components of the biomass ash B1 have dissolved into the liquid phase of the slurry.

The time required for the water washing step S32 is preferably 30 minutes or more, more preferably 45 minutes or more, in order to sufficiently modify the biomass ash B1 with the water W1. In addition, the higher the temperature condition, the more efficient the elution of water-soluble components such as chlorine from the biomass ash B1 becomes, but from the viewpoint of the cost of treatment, a temperature of 5°C to 50°C is preferable, more preferably 25°C to 50°C.

After the water washing step S32, the slurry Lr2 in which the cement-repellent components such as chlorine have been dissolved into the liquid phase in the slurry is discharged from the powder dissolution tank 43 and transferred to the solid-liquid separation device 46. A normal slurry liquid transport device (not shown), such as a slurry centrifugal pump, piston pump, or mono pump, may be used to transport the slurry Lr2.

In the solid-liquid separation device 46, the slurry Lr2 is separated into solid and liquid to obtain the dehydrated product Ck1 (dehydration process S33). As the solid-liquid separation device 46, a typical filtration device such as a filter press, a pressurized leaf filter, a screw press, a belt press, a belt filter, or a sedimentation separator can be used.

In the dehydration step S33, in order to prevent water-soluble components such as chlorine contained in the slurry Lr2 from remaining in the liquid phase, the moisture content of the dehydrated product is preferably 20% to 90% by mass, and more preferably 30% to 70% by mass.

The components dissolved in the liquid phase of the slurry Lr2 are removed into the wastewater W3, so the resulting dehydrated product Ck1 has a reduced amount of cement-repellent components such as chlorine compared to the raw ash. On the other hand, the heavy metals and other substances contained in the raw ash have also been dissolved into the wastewater W3, so it may be discharged into the environment after undergoing appropriate water purification treatment.

As shown in FIG. 7, a water washing device 49 may be attached to the solid-liquid separator 46, and water W2 may be added to the dehydrated material Ck1 before it is dehydrated again. In this way, most of the liquid phase of the slurry Lr2 is replaced with water, so that the eluted components can be removed more reliably.

This water washing step S30 corresponds to step (c).

The dehydrated material Ck1 obtained through the water washing process S30 is in a modified state of biomass ash B1 (modified biomass ash B2), and the content of cement-repellent components such as chlorine has been reduced, and the content of easily reactive calcium oxide and calcium hydroxide that affect the strength expression and fluidity of cement has been sufficiently reduced. Therefore, by using this modified biomass ash B2 and carrying out the classification and mixing processes as in the first embodiment, it is easy to maintain a uniform quality as a cement mixture. In particular, by using biomass ash B1 discharged from a fluidized bed combustion furnace into which limestone containing calcium components has been added, the above effect can be significantly achieved.

The wastewater W3 obtained in the dehydration process S33 may be mixed with the cement clinker Cn1 after the chloride ion content has been reduced by known methods such as ion exchange resins, membrane separation, and precipitation with silver or lead ions. This makes it possible to effectively utilize the alkali metals contained in the wastewater W3, which have a strength-enhancing effect, while removing the chloride that causes rebar corrosion. As in this embodiment, the activity of the modified biomass ash B2 obtained by performing the water washing process S30 is reduced by water washing, so the weak point of the reduced activity of the modified biomass ash B2 can be compensated for by adding the washed wastewater W3 as a cement additive.

In particular, since biomass ash B1 has a lower chlorine concentration than municipal waste incineration ash, it is easy to separate the chlorine contained in wastewater W3, and a large amount of alkali metal sulfates and carbonates can be obtained from wastewater W3. Therefore, by introducing wastewater W3 on the route from the clinker cooler 13 to the crushing equipment 30, more alkali metals can be used as cement additives.

By feeding wastewater W3 between the clinker cooler 13 and the grinding equipment 30, it can be used as a cement additive while also serving as water for cooling the cement clinker Cn1 and for adjusting the temperature inside the grinding equipment 30, without drying or solidifying. More specific feeding points include the clinker cooler 13 at 400°C or less in the cement manufacturing facility, and the subsequent transport equipment and grinding equipment 30. If it exceeds 400°C, it will evaporate instantly and will not be easily incorporated into the cement, and if it is fed after the grinding equipment 30, moisture will remain in the cement and there is a risk of the quality deteriorating due to the effects of weathering and hydration.

It is also possible to feed the wastewater W3 between the clinker cooler 13 and the crushing equipment 30 after reducing the moisture content by drying or other methods. This allows more alkali metals to be used as cement additives without causing the cement to weather. In particular, if the wastewater W3 is dried and solidified, it can be fed into crushed cement or during concrete mixing, and any amount can be easily added.

The most preferred means for reducing the amount of chloride ions is the use of amphoteric ion exchange resins or nanofiltration membranes. This allows selective separation of sulfate ions, carbonate ions, and chloride ions, resulting in water with high sulfate ion and carbonate ion concentrations and low chloride ion concentrations, and water with low sulfate ion and carbonate ion concentrations and high chloride ion concentrations.

Wastewater W3 obtained after washing biomass ash B1 often contains selenium and hexavalent chromium. By using the above-mentioned amphoteric ion exchange resin or nanofiltration membrane, selenium and hexavalent chromium, which have the same form as sulfate ions, are separated into water with a low chlorine concentration. Water with a high chlorine concentration is disposed of, but this water also has low concentrations of selenium and hexavalent chromium, making wastewater treatment easier. In addition, the amount of water can be reduced (the alkali metal concentration can be increased) without drying, and when it is introduced between the clinker cooler 13 and the crushing equipment 30, more alkali metals can be used as cement additives with the same amount of water sprayed.

As described above, the wastewater W3 (cement additive) obtained from the washing water and the washed modified biomass ash B2 can be used simultaneously as a cement mixture, so the biomass ash B1 can be used without waste. This is expected to have the effect of reducing the amount of wastewater to be disposed of and the wastewater treatment load.

In this embodiment, it is also possible to execute the oxidation process S41 and the unburned carbon removal process S42 together with the water washing process S30 (see Figures 8A and 8B). These processes may be executed in parallel with the execution of the water washing process S30, or may be executed after the execution of the water washing process S30. It is also possible to execute only one of the oxidation process S41 and the unburned carbon removal process S42.

Figure 8A is a diagram showing a schematic process flow in the present embodiment in which both the oxidation process S41 and the unburned carbon removal process S42 are performed, and Figure 8B is a diagram showing a schematic structure of the water washing equipment 40 in this case, following Figure 7. Note that Figure 8B also shows the gas supply device 51 and the flotation device 53, along with the water washing equipment 40.

(Oxidation step S41)
The oxidation step S41 is a step of oxidizing the biomass ash B1. As an example, the oxidation step S41 can be performed by adding a pH adjuster to the powder dissolution tank 43 in the water washing step S30 and washing with water. In this way, the water washing step S30 and the oxidation step S41 are performed in parallel.

By adjusting the pH during water washing to the acidic side, the chlorine contained in the biomass ash B1 can be dissolved in water more efficiently than when the pH is not adjusted. In addition, the calcium components contained in the biomass ash B1 can be more easily stabilized into the form of slow-reacting calcium carbonate or calcium sulfate that is added to cement clinker Cn1 during cement production, making the modified biomass ash B2 obtained after the water washing process S30 suitable as a cement admixture with little quality variation.

The pH condition of the slurry Lr1 in the oxidation step S41 is preferably pH 4 to 13, and more preferably pH 5 to 12.

There are no particular limitations on the pH adjuster as long as it can adjust the pH of the slurry Lr1 to the acidic side, and examples include an acid solution such as sulfuric acid and a CO2 _- containing gas. As the _CO2- containing gas, the combustion exhaust gas from the cement kiln 12, or the combustion exhaust gas from a biomass incineration facility or a biomass power plant can be used. Since these exhaust gases contain carbon dioxide ( _CO2 ), the pH can be adjusted to the acidic side by injecting the combustion exhaust gas into the slurry Lr1. This makes it easier to carbonate the calcium component contained in the biomass ash B1 and stabilize it in the form of calcium carbonate.

8B shows, as an example, a case where a CO2 _- containing gas G1 is supplied from a gas supply device 51 to a slurry Lr1 in a powder dissolution tank 43. In this case, the gas supply device 51 corresponds to the device for supplying the combustion exhaust gas from the cement kiln 12, the combustion exhaust gas from a biomass incineration facility, a biomass power plant, or the like to the powder dissolution tank 43.

The _CO2- containing gas G1 may contain carbon dioxide, but in order to promote efficient carbonation, the carbon dioxide concentration is preferably 10% or more, and more preferably 20% or more. In addition, since the combustion exhaust gas, particularly the gas after collecting the chlorine bypass dust from the clinker manufacturing facility 10, contains harmful gases such as sulfur oxides ( _SOx ), blowing this gas into the slurry Lr1 can be expected to have the effect of fixing the sulfur oxides.

In this way, by using the combustion exhaust gas from the clinker production facility 10, it is possible to obtain combustion exhaust gas containing carbon dioxide on-site and use it to reform the biomass ash B1, and the reformed biomass ash B2 can be used as a cement admixture. Also, by using the combustion exhaust gas from a biomass incineration facility or a biomass power plant, it is possible to reform the biomass ash B1 using the combustion exhaust gas containing carbon dioxide obtained on-site, and if this is transported to a cement production facility such as the clinker production facility 10 or the crushing facility 30, it can be immediately used as a cement admixture.

Furthermore, in the water washing step S30, the waste liquid obtained from the amine-based carbon dioxide recovery device may be added to the powder dissolution tank 43 to perform water washing. In an amine carbon dioxide recovery device for recovering carbon dioxide from exhaust gases from factories, etc., the liquid containing degraded amines is usually discarded, but this method allows the waste liquid to be effectively utilized.

Amines are known to react with carbon dioxide to promote the production of carbonate ions, and can efficiently promote the carbonation of calcium components. Amines are also known to function as grinding aids when grinding cement clinker Cn1 in the grinding equipment 30. Amines have an amino group and a hydroxyl group in the molecule, and examples of amines used as grinding aids in particular include monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diglycolamine (DGA), diisopropanolamine (DIPA), and methyldiethanolamine (MDEA). Therefore, the modified biomass ash B2 that incorporates amines brought in from the added waste liquid is expected to be functional as a grinding aid in the subsequent process, making it suitable as a cement admixture.

In addition, _CO2- containing gas G1 may be blown into the dehydrated material Ck1 obtained through the dehydration step S33. This allows the easily reactive calcium components remaining in the dehydrated material Ck1 to be carbonated, and the quality of the resulting modified biomass ash B2 can be further homogenized, making it suitable as a cement admixture. It is also useful for drying the moisture contained in the dehydrated material Ck1.

The gas injection means (gas supply device 51) may be any method that can bring the dehydrated material Ck1 into contact with the _CO2- containing gas. For example, a _CO2- containing gas may be passed through a container filled with the dehydrated material Ck1, or the dehydrated material Ck1 may be passed through an exhaust gas duct. In addition, as in the above-mentioned injection into the slurry Lr1, the combustion exhaust gas from the cement kiln 12 or the combustion exhaust gas from a biomass incineration facility or a biomass power plant may be injected into the dehydrated material Ck1.

This oxidation step S41 corresponds to step (d).

(Unburned carbon removal step S42)
The unburned carbon removal step S42 is a step of removing unburned carbon contained in the biomass ash B1. Since the biomass ash B1 contains a large amount of unburned carbon, when the biomass ash B1 is used as a raw material for the cement clinker Cn1, it may cause the preheater 11 to become too hot, and when the biomass ash B1 is used as an admixture, it may cause the concrete to become dark and the fluidity to decrease.

Specifically, when the water washing step S30 is performed, a method can be adopted in which an unburned carbon removal agent D1 such as oil or a surfactant is added from the unburned carbon removal agent supply device 52 to the powder dissolution tank 43, and processing such as stirring is then performed. The obtained slurry Lr2a is subjected to a flotation process in the flotation device 53, for example by adding a specified foaming agent, and is separated into a froth containing unburned carbon and a tail in which unburned carbon has been removed or reduced. The tail slurry Lr2b is then sent to the solid-liquid separation device 46 and separated into solid and liquid.

This allows the water washing process S30 and the unburned carbon removal process S42 to be carried out in parallel and continuously.

This unburned carbon removal process S42 corresponds to process (e).

(Classification step S10)
By employing a method similar to that described above in the first embodiment, the modified biomass ash B2 is classified into coarse powder B2C and fine powder B2F.

The water washing step S30 and the classification step S10 may be performed simultaneously. Specific examples include water sieving, liquid cyclone, and centrifugal separation.

The activity index of the fine powder B2F obtained through the water washing step S30 and the classification step S10 is higher than that of the biomass ash (raw ash) B1, typically 70% or more in 7 days and 65% or more in 28 days, and more typically 73% or more in 7 days and 68% or more in 28 days.

The chlorine concentration of this fine powder B2F is typically reduced to, for example, 0.01% to 0.2% by mass, and more typically reduced to 0.02% to 0.1% by mass.

The total alkali metal concentration of this fine powder B2F is typically reduced to, for example, 1% to 8% by mass, and more typically reduced to 3% to 6% by mass.

The sulfur oxide concentration of this fine powder B2F is typically reduced to, for example, 0.5% to 4% by mass, and more typically reduced to 1% to 3% by mass.

The amount of selenium leaching from this fine powder B2F is typically reduced to 0.002 mg/L to 0.02 mg/L, more typically 0.005 mg/L to 0.01 mg/L, for example.

The amount of hexavalent chromium leaching from this fine powder B2F is typically reduced to 0.01 mg/L to 0.1 mg/L, more typically 0.02 mg/L to 0.05 mg/L, for example.

The amounts of eluted selenium (Se) and hexavalent chromium (Cr ⁶⁺ ) can be measured by known methods. A suitable example of the measurement method is to prepare a test solution in accordance with JIS K 0058-1 "Testing methods for chemical substances in slags - Part 1: Leaching test method 5. Testing as used", and then measure selenium (Se) by ICP mass spectrometry and hexavalent chromium (Cr ⁶⁺ ) by diphenylcarbazide absorptiometry.

In addition, as shown in the examples described below, the water washing step S30 sufficiently reduces the content of easily reactive calcium oxide and calcium hydroxide, which affect the strength development and fluidity of the cement, and stabilizes the calcium component in the form of calcium carbonate, thereby suppressing quality fluctuations.

For example, the calcium hydroxide content of the modified biomass ash B2 after the water washing step S30 is typically 0.5% by mass or less, more typically 0.1% by mass or less.

Also, for example, the calcium sulfate (gypsum) content of the modified biomass ash B2 is typically 0.5 mass% or more, and more typically 3 mass% or more, calculated as _SO3 .

The chlorine concentration can be measured by known methods, such as a method of measuring the chlorine concentration by potentiometric titration after acid decomposition.

The calcium hydroxide content can be measured by known methods, such as a method of determining the amount of heat required for dehydration at around 400°C using a DSC (differential scanning calorimeter).

The content of calcium sulfate (gypsum) can be measured by known methods, such as a method of quantitatively determining the amount of calcium sulfate by the Rietveld method based on the X-ray powder diffraction pattern.

(Feeding process S20)
The same method as described above in the first embodiment can be adopted. That is, the procedure of feeding may be such that the fine powder B1F in the first embodiment is replaced with the fine powder B2F obtained through the water washing step S30, and the coarse powder B1C is replaced with the coarse powder B2C obtained through the water washing step S30.

In particular, in this embodiment, since the water washing step S30 is performed before the feeding step S20, the fine powder B2F obtained after classification may contain more moisture than the fine powder B1F obtained in the first embodiment. Therefore, the moisture contained in the fine powder B2F can be used to control the temperature in the grinding equipment 30 to prevent deterioration of the gypsum. If the fine powder B2F contains too much moisture, it can be easily dehydrated by settling separation, etc., and conversely, if there is a shortage of moisture, an appropriate amount of water can be sprayed on the grinding equipment 30.

As described above in the first embodiment, the fine powder B2F obtained after classification can also be directly charged into the clinker cooler 13. The temperature in the clinker cooler 13 is usually 200 to 1200°C, and the heating temperature can be selected according to the charging position. However, when the above-mentioned oxidation step S41 is performed, the modified biomass ash B2 contains a large amount of _CaCO3 obtained by fixing _CO2 . In this case, it is preferable to charge the modified biomass ash B2 into a low-temperature part of the clinker cooler 13 at 200°C to 800°C so that the _CaCO3 contained in the modified biomass ash B2 does not decompose to generate quicklime (CaO) or release carbon dioxide.

Although the alkali metal content of the modified biomass ash B2 obtained by the method of this embodiment is reduced by performing the water washing process S30, it is still expected to have a higher alkali metal content than coal ash. For this reason, if this modified biomass ash B2 is used as a raw material for cement clinker Cn1, cement with a high alkali metal content may be produced. In addition, the main component of the cement additive obtained from the wastewater W3 is alkali metal salt. Therefore, if these are contained in large amounts in concrete, there is a possibility that an alkali-aggregate reaction will occur depending on the aggregate.

Therefore, in order to reduce the possibility of alkali-aggregate reaction, latent hydraulic substances such as blast furnace slag, and pozzolanic substances such as fly ash, volcanic ash, volcanic rock, and burnt clay may be introduced (added) together with the modified biomass ash B2. Note that the introduction (addition) of such latent hydraulic substances and pozzolanic substances is also applicable when using fine powder B1F without performing the water washing process S30 as in the first embodiment.

[Third embodiment]
A third embodiment of the cement production method and the cement production system will be described, focusing on differences from the first and second embodiments. Fig. 9 is a diagram showing a process flow of the cement production method in this embodiment. Fig. 10 is a block diagram showing a structure of the cement production system in this embodiment.

This embodiment is different from the second embodiment only in that the water washing step S30 is performed after the classification step S10, and is otherwise the same as the second embodiment. In this embodiment, the water washing step S30 is performed only on the fine powder B1F classified by the classification step S10.

Comparing the coarse powder B1C and fine powder B1F obtained by classifying biomass ash B1 in the classification process S10, more chlorine is contained in the fine powder B1F than in the coarse powder B1C. Therefore, according to this embodiment, the cement-repellent components such as chlorine contained in biomass ash B1 can be efficiently reduced while reducing the amount of water required to perform the water washing process S30.

In this embodiment, as in the second embodiment, the oxidation step S41 and the unburned carbon removal step S42 may be performed. The rest is the same as in the above embodiments, so the explanation is omitted.

[Another embodiment]
Another embodiment will be described below.

<1> As shown in FIG. 11, of the coarse powder B1C and fine powder B1F obtained by classifying biomass ash B1 in classification equipment 20, the coarse powder B1C may be washed with water in water washing equipment 40. The chlorine and sulfur content of the coarse powder B1C is reduced by the classification process S10, and these concentrations are further reduced by the water washing process S30. Therefore, it can be used as a raw material for cement clinker Cn1.

In this case, the wastewater W3 obtained in the water washing step S30 has a low chlorine concentration because it is obtained after washing the coarse powder B1C, which originally contains little chlorine. Therefore, the wastewater W3 may be mixed with the cement clinker Cn1 without taking measures to reduce the chlorine ion content, as described above in the second embodiment.

On the other hand, the fine powder B1F may be subjected to a separate water washing process if necessary, and then mixed with the cement clinker Cn1 or cement.

As shown in FIG. 12, the fine powder B1F obtained by classifying the biomass ash B1 in the classification equipment 20 may be washed with water in the water washing equipment 40, and the resulting modified biomass ash B2F may be used as a raw material for cement clinker Cn1. Specifically, the fine powder B1F may be fed into raw material mixing equipment such as a mixer or pulverizer for mixing the raw materials for cement clinker, fed into the preheater top or calciner before the cement kiln, fed into the bottom of the cement kiln, or fed into the high temperature part before the cement kiln (rotary kiln). Although the fine powder B1F contains higher concentrations of chlorine and sulfur than the coarse powder B1C, the concentration of chlorine and sulfur contained in the biomass ash B1 is reduced by washing with water, so it can be used as a raw material for cement clinker Cn1.

This prevents clogging of the preheater, kiln bottom, and kiln caused by low-melting-point substances adhering to them, and also reduces the chlorine content of the cement clinker Cn1, compared to when water washing is not performed. It also increases the alkali metal content of the cement clinker Cn1, making it possible to obtain a stronger cement. In particular, when coarse powder B1C is added as a cement admixture, or when latent hydraulic substances such as blast furnace slag, or pozzolanic substances such as fly ash, volcanic ash, volcanic rock, and burnt clay are added, the alkali metals supplied from the cement clinker activate the reaction of these admixtures.

On the other hand, the coarse powder B1C obtained in the classification process S10 has a lower chlorine content than the biomass ash B1, and can therefore be used as an admixture for cement clinker Cn1 or cement. Figure 12 illustrates an example in which the coarse powder B1C is mixed after being crushed in the crushing equipment 30.

〈3〉 In the third embodiment (see Figures 9 and 10), the fine powder (modified biomass) B2F obtained after the classification process S10 and the water washing process S30 may also be used in the clinker production facility 10 as a raw material for cement clinker Cn1, similar to the coarse powder B1C (see Figure 13).

〈4〉 In each of the above embodiments, the process of producing cement by crushing the cement clinker Cn1 in the crushing equipment 30 has been described. However, in the input step S20, the fine powder of biomass ash (B1F, B2F) obtained in each embodiment may be input to cement and water and kneaded to produce a hardened cement product such as concrete or mortar.

[Example 1]
Incineration fly ash BA-1 (particle size _D50 (frequency) 47.2 μm, ignition loss at 975°C (ig.loss) 4.17%) was obtained from biomass power generation facility P1, which uses palm kernel shells as fuel to generate electricity in a circulating fluidized bed furnace, and the effect of classifying this on the component composition of the biomass ash was examined. The coal content of the palm kernel shell and coal mixed fuel was 10 mass%. The particle size distribution of this incineration fly ash (laser diffraction particle size distribution measuring device: Microtrac Bell MT3300EX II was used) is shown in Figure 3.

Test Method
The test method is described below.

<1. Classification>
The biomass ash B1 was sieved using a sieve (Spin Air Sieve: SAR-75/200 manufactured by Seishin Enterprises) with openings set to obtain the classification points shown in Table 1, and fine powder B1F was obtained as the sieve-passing portion, and coarse powder B1C was obtained as the sieve residue. This process corresponds to the classification step S10. The classification points were set based on the particle size distribution shown in FIG. 3. In the test, biomass ash B1 was classified at three classification points of 32 μm, 45 μm, and 90 μm. In the following, biomass ash B1 may be referred to as "raw ash B1" in order to clarify that it is before classification.

The particle size distribution of the biomass ash after classification is shown in Table 1. Table 1 also shows the coarse powder B1C obtained after classifying incineration fly ash BA-2 obtained from biomass power generation facility P2, which is separate from biomass power generation facility P1, with a classification point of 45 μm. The particle size distribution was measured using a laser diffraction particle size distribution measuring device (Microtrac Bell MT3300EX II).

<2. Chemical composition analysis>
The chemical components of raw ash B1 (#1), each coarse powder B1C (#2, #4), and each fine powder B1F (#3, #5) derived from incineration fly ash BA-1, the raw ash B1 was wet-ashed by the following method (#1W), and the wet-ashed raw ash B1 (#1W) was classified at 45 μm to obtain coarse powder B1C (#2W). The raw ash B1 was also classified at a classification point of 20 μm to obtain coarse powder B1C (#9) and fine powder B1F (#10), and the chemical components of these were also measured. Furthermore, the raw ash B1 (#1) and the fine powder B1F (#3) classified at 45 μm were prepared by washing with water by the following method (#1Wp, #3Wp), and the chemical components were measured in the same manner.

The wet ashing method is as follows. 20% by mass of water (moisture content 16.7% by mass) was added to raw ash B1 (code #1), which was then stored at 20°C for three days and dried at 105°C to produce wet ash. Raw ash B1 wet ashed in this manner corresponds to "code #1W", and the coarse powder B1C obtained by classifying this wet ashed raw ash #1W corresponds to "code #2W". An air jet sieve (e200LS, manufactured by Hosokawa Micron Corporation) was used to classify the wet ashed raw ash B1 (#1W).

The water washing treatment is carried out as follows. This treatment corresponds to the water washing step S30.
(Step 1) 100 g of biomass ash (B1, B1F) and 400 g of tap water were put into a beaker, made into a slurry, and stirred with a stirrer at 400 rpm for 30 minutes. At this time, when pH adjustment was performed by introducing _CO2 gas during water washing, the flow rate was adjusted while monitoring the pH in the liquid with a pH meter.
(Step 2) After stopping the stirring, the mixture was filtered using a Buchner funnel, and 400 g of tap water was added to the resulting cake on the filter paper to wash the slurry, which was then recovered.
(Step 3) The collected cake was naturally dried, and then its mass was measured and various analyses were carried out.

The resulting coarse powder was then pulverized using a ball mill.

"analysis"
The chemical components were measured by the following methods.
The chemical components of each of the prepared samples (#1-#5, #9-#10, #1W, #2W, #1Wp, #3Wp) were measured by the calibration curve (coal ash) method using an X-ray fluorescence analyzer (Rigaku Corporation, ZSX Primus II). The results are shown in Table 2. The ignition loss of each sample was measured according to JIS R 5202 "Methods for chemical analysis of cement."

The amount of calcium carbonate in the incineration fly ash and the obtained samples was calculated by measuring the mass loss at around 600°C to 700°C when about 50 mg of the sample was heated to 1000°C at a heating rate of 20°C/min in a nitrogen atmosphere, and calculating the ratio of the mass loss to the weight loss of the reagent (using TG-DTA 2000SR manufactured by NETZSCH). As a result, the calcium carbonate amount of the raw ash B1 was 5.5%, and that of the wet ashed sample (#1W) was 5.6%.
The amount of hydrates formed was calculated by subtracting the amount of decarbonated calcium carbonate volatilized from the amount of calcium carbonate from the ignition loss. As a result, the amount of hydrates formed in raw ash B1 was 1.8%, and in the case of the wet ashed material (#1W), it was 6.0%.

According to Table 2, when raw ash B1, which is dry ash, is classified using the point between the peaks on the fine side and the peaks on the coarse side when the particle size distribution is expressed as frequency, most of the chlorine and sulfur components ( _SO3 ) are contained in the fine powder (B1F). It was also confirmed that the chlorine components can be efficiently removed by washing this with water (B2F). For this reason, it can be seen that the fine powder after washing in particular is suitable as a cement admixture.

On the other hand, the reduction in alkali metals in the coarse powder (B1C) obtained by classifying raw ash is small, but it contains almost no chlorine or sulfur components, and has a reduced amount of CaO and an increased amount of _SiO2 compared to raw ash. Therefore, the coarse powder has a chemical composition close to that of coal ash, and is suitable as a raw material for cement clinker.

In addition, when comparing the wet ashing of raw ash B1 (#1W) with the coarse powder B1C (#2W) that was classified at 45 μm, it was confirmed that the degree of reduction in chlorine concentration due to classification was low. This is presumably because coagulation and hydration reactions occurred when raw ash B1 was wet ashed, and chlorine (Cl) was absorbed into the hydrates that were produced, resulting in a reduction in the removal rate due to classification. Hydration reactions occurred in the wet ashing of raw ash B1 (#1W), and the loss on ignition was greater than that of raw ash B1, which is dry ash.

3. Physical Testing
The Blaine specific surface area, flow value ratio, and activity index of the raw ash B1 (#1) derived from the incineration fly ash BA-1, the coarse powder B1C (#2) obtained with a classification point of 45 μm, and the fine powder B1F (#3) were measured by a method conforming to Appendix C of JIS A 6201 "Fly ash for concrete". Furthermore, the coarse powder B1C (#2) was pulverized in a mill to have a particle size equivalent to that of the fine powder B1F, and the Blaine specific surface area, flow value ratio, and activity index were measured in the same manner. The pulverized material (#2C) obtained by pulverizing the coarse powder B1C is, for example, a simulation of the coarse powder B1C after classification pulverized in the pulverizing equipment 30 in FIG. 12 (for convenience, referred to as "B1Cp"). The measurement results are shown in Table 3.

According to Table 3, it was confirmed that when fine powder B1F, which is obtained by classifying raw ash B1, is used as an admixture, it has a higher activity index than raw ash B1. It was also revealed that coarse powder B1C does not contain chlorine, and if it is pulverized until the Blaine specific surface area reaches 4000 ^cm2 /g or more (B1Cp), it can be used as a pozzolanic admixture with a higher reactivity than raw ash.

[Example 2]
Fly ash (particle size _D50 (frequency) 45.3 μm, ignition loss at 750°C (ig.loss) 2.3%) was obtained from biomass power generation facility P2, which uses woody biomass (thinned wood) as fuel to generate electricity in a circulating fluidized bed furnace. The effects of washing this with water and the presence or absence of an oxidation process (particularly a carbonation process) during the washing process on its component composition were examined.

Test Method
The test was carried out in the following procedure.
(Step 1) 100 g of biomass ash and 400 g of tap water were put into a beaker, made into a slurry, and stirred with a stirrer at 400 rpm for 30 minutes. At this time, when pH adjustment was performed by introducing _CO2 gas during water washing, the flow rate was adjusted while monitoring the pH in the liquid with a pH meter.
(Step 2) After stopping the stirring, the mixture was filtered using a Buchner funnel, and 400 g of tap water was added to the resulting cake on the filter paper to wash the slurry, which was then recovered.
(Step 3) The collected cake was naturally dried, and then its mass was measured and various analyses were carried out.

Table 4 below shows the levels for each water washing condition.

"analysis"
The obtained samples were analyzed by the following methods.
Quantitative determination of Cl: After a sample was decomposed with nitric acid, the content was measured by potentiometric titration.
Quantitative determination of K and Na: After subjecting a sample to acid decomposition treatment, the contents were measured by ICP emission spectrometry.
Leaching test for Se and Cr6 ⁺ : Test solutions were prepared in accordance with JIS K 0058-1 "Testing methods for chemical substances of slags - Part 1: Leaching test method 5. Testing as used", and then Se was measured by ICP mass spectrometry and Cr6 ⁺ was measured by diphenylcarbazide absorptiometry.
Quantitative determination of C, Mg, Al, Si, P, S, Ca, and Fe: Samples dried at 40° C. were measured using a fluorescent X-ray analyzer (FP method: fundamental parameter method). The measurement results are shown in Tables 5 and 6.

According to Table 5, most of the chlorine is effectively removed by washing the raw ash with water, and it has been confirmed that when used as an admixture, after the cement hardens with water, the content meets the allowable standard of 0.035% by mass or less, which is evaluated as having no risk of corroding reinforcing bars, etc. In other words, when the biomass ash after washing is classified, it is found that there is almost no chlorine in either the fine or coarse powder side.

In addition, according to Table 5, the water-soluble selenium and hexavalent chromium contained in the raw ash were effectively removed by washing with water, and it was revealed that the risk of leaching of heavy metals is reduced when the raw ash is used as an admixture.

As shown in Table 6, this biomass ash is composed mainly of _SiO2 and CaO, and it has become clear that it is useful as a highly reactive pozzolanic admixture.

According to the results of Level 2-2, it was revealed that washing with water while blowing in _CO2 gas increased the _CO2 content of the biomass ash after washing. Therefore, it is considered that at least a part of the components for adjusting the pH was fixed in the ash after the washing operation, and calcium carbonate was generated. In addition, calcium hydroxide disappeared by washing with water while blowing in _CO2 gas. In Table 6, a calcium hydroxide content of less than 0.01% means that it is below the detection limit.

Table 7 below shows the results of investigating the form of calcium in the ash using the XRD method (X-ray diffraction method).

According to Tables 6 and 7, the presence of each Ca compound, CaO (quicklime), Ca(OH) ₂ (slaked lime), _CaCO3 (limestone), and _CaSO4 (gypsum), was confirmed as the form of calcium component in the raw ash. In contrast, in level 2-1, where washing was performed without pH adjustment, the presence of CaO (quicklime) disappeared, and the presence of Ca(OH) ₂ (slaked lime) was reduced. In level 2-2, where washing was performed under a pH 9 condition while injecting _CO2 gas, the presence of CaO (quicklime) and Ca(OH) ₂ (slaked lime) disappeared.

[Example 3]
Fly ash (particle size _D50 (frequency) 20.0 μm, ignition loss at 750° C. (ig. loss) 6.1%) was obtained from biomass power generation facility P3, which uses wood pellets and palm kernel shells as fuel to generate electricity in a stoker furnace, and the same test as in Example 2 was conducted. The results are shown in Tables 8 and 9. In level 3-2, sulfuric acid was added during water washing to adjust the pH.

According to Table 8, it was confirmed that most of the chlorine is effectively removed by washing the raw ash with water, and when used as an admixture, after the cement hardens with water, it meets the allowable standard of 0.035% by mass or less, which is evaluated as having no risk of corroding reinforcing bars, etc. In other words, when the biomass ash after washing is classified, it is found that there is almost no chlorine in either the fine or coarse powder side.

In addition, according to Table 8, the water-soluble selenium and hexavalent chromium contained in the raw ash were effectively removed by washing with water, and it was revealed that the risk of leaching of heavy metals is reduced when the raw ash is used as an admixture.

As shown in Table 9, this biomass ash is mainly composed of _SiO2 and CaO, and it is clear that it is useful as a highly reactive pozzolanic admixture. Furthermore, it was clear that the _SO3 content increases by adding sulfuric acid and washing with water. Therefore, it is considered that at least a part of the sulfuric acid component for adjusting the pH is fixed in the ash after the water washing operation.

1: Cement manufacturing system 3: Raw material tank 5: Powder storage tank 10: Clinker manufacturing equipment 11: Preheater 12: Cement kiln 13: Clinker cooler 20: Classification equipment 30: Crushing equipment 40: Water washing equipment 41: Powder supply device 42: Liquid supply device 43: Powder dissolving tank 44: Slurry agitator 46: Solid-liquid separator 47: Conveyor device 49: Water washing device 51: Gas supply device 52: Unburned carbon removal agent supply device 53: Flotation device B1: Biomass ash B1C: Coarse powder B1F: Fine powder B2: (Modified) biomass ash B2C: (Modified) Coarse powder B2F: (Modified) Fine powder Ck1: Dehydrated material Cn1: Cement clinker D1: Unburned carbon removal agent G1: _CO2- containing gas Lr1 : Slurry Lr2 (Lr2a, Lr2b) : Slurry W1, W2 : Water W3 : Drainage Y1 : Cement clinker raw material

Claims (9)

A step (a) of classifying the biomass ash into coarse powder and fine powder with a classification point of 20 μm or more and 100 μm or less ;
(b) adding the fine powder obtained in the step (a) to at least one of a cement clinker raw material to be added to a cement kiln, a cement clinker obtained from the cement kiln, or a cement obtained after a grinding treatment of the cement clinker ;
and (c) washing the biomass ash with water;
A method for producing cement, wherein the step (b) is a step of adding the fine powder after being washed with water in the step (c) . 2. The method for producing cement according to claim 1 , wherein the step (c) is a step of washing only the fine powder obtained in the step (a) with water. 3. The method for producing cement according to claim 1 or 2 , further comprising a step (d) of oxidizing the biomass ash during or after the step (c). The method for producing cement according to any one of claims 1 to 3 , further comprising a step (e) of removing unburned carbon contained in the biomass ash during the execution of the step (c). The method for producing cement according to any one of claims 1 to 4, wherein the step (b) is a step of adding the fine powder to at least one of the cement clinker obtained from the cement kiln and the cement obtained after the cement clinker has been subjected to a crushing treatment. The method for producing cement according to any one of claims 1 to 4 , wherein the step (b) is a step of adding the fine powder to the cement clinker raw material to be added to the cement kiln. The method for producing cement according to any one of claims 1 to 6 , wherein the step (b) is a step of adding at least one of a latent hydraulic material and a pozzolan in addition to the fine powder. The method for producing cement according to any one of claims 1 to 7 , wherein the biomass ash is fly ash generated from a fluidized bed combustion furnace and is dry ash. A classification device that classifies the biomass ash into coarse powder and fine powder with a classification point of 20 μm or more and 100 μm or less ;
a cement kiln for burning cement clinker raw materials to produce cement clinker;
a grinding facility for grinding the cement clinker obtained from the cement kiln to produce cement ;
and a water washing facility for washing the biomass ash with water .
A cement production system, characterized in that the fine powder after being washed by the water washing equipment is added to at least one of the cement clinker raw material, the cement clinker obtained from the cement kiln, or the cement obtained from the grinding equipment.