JP2021146236A - Alkali metal removal method and alkali metal removal device - Google Patents

Abstract

To provide an alkali metal removal method for effectively removing alkali metals from flying ashes of woody biomass ashes to effectively utilize the alkali metals as a cement raw material.SOLUTION: A method for removing alkali metals from flying ashes of woody biomass combustion ashes includes: a step (a) of classifying flying ashes into fine powder and coarse powder; a step (b) of acquiring a pulverized object by pulverizing a surface part of the coarse powder that is acquired from the step (a); a step (c) of classifying the pulverized object that is acquired from the step (b) into pulverized fine powder and pulverized coarse powder; a step (d) of acquiring a heat treatment object by heating the pulverized fine powder that is acquired from the step (c) together with a chlorine source; and a step (e) of washing with water the fine powder that is acquired from the step (a) and the heat treatment object that is acquired from the step (d).SELECTED DRAWING: Figure 1

Description

The present invention relates to an alkali metal removing method and an alkali metal removing device. In particular, the present invention relates to an alkali metal removing method and an alkali metal removing device for effectively using the combustion ash of woody biomass as a raw material for cement and the like.

For woody biomass such as tree trunks and branches, cutting chips, ash powder, bark, wood pellets, PKS (palm kernel shell), and construction waste, in parallel with technological development using fuel for power generation boilers, wood quality Development of an effective utilization technology for combustion ash (hereinafter sometimes referred to as "woody biomass ash") generated by combustion of biomass is also underway.

Woody biomass ash is characterized by having a high content of alkali metals, particularly potassium, as compared with, for example, coal ash and waste incineration ash. Therefore, for example, when applying the cement raw material technology that enables effective utilization of a large amount of coal ash and waste incineration ash to woody biomass ash, woody biomass ash because the cement uses an alkali metal component as a repellent component. It is necessary to remove the alkali metal from. Furthermore, if alkali metals can be removed from the flying ash of woody biomass ash, it will be possible to develop applications for using flying ash of woody biomass ash as a concrete admixture or cement mixture, as is the case with coal ash (fly ash). Become.

As a technique for removing an alkali metal component from woody biomass ash, for example, in Patent Document 1 below, woody biomass ash (fly ash) collected by a bag filter is classified at a predetermined classification point to have a high potassium concentration. A combustion apparatus and a combustion ash treatment method for separating and recovering fine powder combustion ash are disclosed.

Japanese Unexamined Patent Publication No. 2017-122550

However, since the flying ash of woody biomass ash contains alkali metals in ash of all particle sizes, it is not enough to use it as a raw material for cement or the like simply by removing the alkali metals present in the fine powder.

In view of the above problems, the present invention efficiently removes alkali metals from fly ash of woody biomass ash (hereinafter, may be referred to as "biomass ash") and effectively uses it as a raw material for cement or the like. It is an object of the present invention to provide an alkali metal removing method and an alkali metal removing device used for carrying out the method.

As a result of diligent research, the present inventors have found that there are two types of alkali metals contained in biomass ash: those that are water-soluble and those that are sparingly soluble in water (hereinafter, simply referred to as "poorly soluble"). It was also found that a large amount of water-soluble alkali metal was present on the fine powder side of the biomass ash, while a large amount of sparingly soluble alkali metal was present on the coarse powder side of the large particle size.

Furthermore, the present inventors have found that the poorly soluble alkali metal that is abundantly present in the coarse powder of biomass ash is ubiquitous in the peripheral portion of the crude powder, and that the poorly soluble alkali metal is ubiquitous in the peripheral portion of the coarse powder. It has been found that the alkali metal can be separated from the coarse powder particles by colliding the coarse powders with each other at high speed.

Furthermore, we have found that the sparingly soluble alkali metal separated and recovered from the periphery of the crude powder is a water-soluble salt (alkali metal chloride) by a treatment (so-called "chloride roasting") in which it is heated together with a chlorine source. ) Was found to be changed.

Furthermore, the present inventors perform a special pretreatment because the alkali metal content of the crude powder residue after the sparingly soluble alkali metal is separated and recovered is as low as about 1.0% by mass. It was found that it can be used as a raw material for cement without any trouble.

That is, it is effective to separate and recover the sparingly soluble alkali metal existing in the periphery of the coarse powder of biomass ash, roast it with chloride to make it a water-soluble salt, and then wash it with water together with the fine powder of biomass ash. Moreover, the alkali metal contained in the biomass ash can be efficiently removed. Therefore, according to this method, biomass ash can be effectively used as a raw material for cement or the like.

That is, the present invention is a method for removing an alkali metal from fly ash of combustion ash of woody biomass.
The step (a) of classifying the fly ash into fine powder and coarse powder, and
The step (b) of crushing the surface portion of the coarse powder obtained in the step (a) to obtain a pulverized product,
The step (c) of classifying the pulverized product obtained in the step (b) into pulverized fine powder and pulverized coarse powder, and
The step (d) of heating the crushed fine powder obtained in the step (c) together with a chlorine source to obtain a heat-treated product,
It is characterized by including a step (e) of washing the fine powder obtained in the step (a) with water and the heat-treated product obtained in the step (d).

According to the above method, the biomass ash (fly ash) is previously classified into fine powder and coarse powder by the step (a). As described above, since the fine powder of biomass ash contains a large amount of water-soluble alkali metal, the alkali metal can be removed by washing with water as it is. In addition, the coarse powder of biomass ash contains a large amount of alkali metal showing poor solubility, but the surface portion thereof is crushed in the step (b), so that the coarse powder of biomass ash is ubiquitous in the peripheral portion of the coarse powder. Alkali metal is fragmented.

Next, by classifying the pulverized material in the step (c), the above-mentioned small pieces, that is, the sparingly soluble alkali metal-derived fine powder (crushed fine powder) and the alkali metal unevenly distributed in the peripheral portion are removed. It is divided into the rest of the coarse powder of biomass ash (crushed coarse powder). Of these, the pulverized fine powder containing a sparingly soluble alkali metal is heated together with a chlorine source in step (d) and roasted by chloride, so that the alkali metal changes to a water-soluble salt. As a result, both the alkali metal contained in the fine powder side of the biomass ash and the alkali metal contained in the coarse powder side of the biomass ash and recovered as crushed fine powder are dissolved in water by the washing treatment according to the step (e). Can be removed.

The step (a) may be a step of classifying with a classification point of 5 μm or more and 30 μm or less.

According to the above method, even if the biomass ash has different discharge sources, it is possible to secure fine powder corresponding to 20% by mass or more and 50% by mass or less of the total amount of most of the biomass ash.

The step (c) may be a step of classifying with a classification point of 5 μm or more and 30 μm or less.

According to the above method, the surface portion (crushed fine powder) of the crude powder containing a large amount of sparingly soluble alkali metal, which was separated by breaking the coarse powder of biomass ash in the pulverization step (b), is removed. It can be separated from the remaining coarse powder (crushed coarse powder). By the pulverization step (b), it is possible to secure pulverized fine powder corresponding to 20% by mass to 45% by mass of the total amount of most of the biomass ash even if the biomass ash has different discharge sources. This crushed fine powder contains most of the poorly soluble alkali metal contained in the coarse powder of biomass ash.

The step (d) may be a step of heating at a temperature of 650 ° C. or higher and 1000 ° C. or lower.

According to the above method, the sparingly soluble alkali metal contained in the coarse powder of biomass ash (more specifically, crushed fine powder) can be converted into a water-soluble salt at a high ratio. When the heating temperature is less than 650 ° C., chloride roasting may be difficult to occur because the temperature is low. If the heating temperature exceeds 1000 ° C., the biomass ash may be partially melted or the diameter may be increased, and the reaction rate of chloride roasting may be slowed down.

The chlorine source used in the step (d) may include flammable waste mixed with waste plastic and inorganic compound chlorine.

According to the above method, wastes and the like, which have a high chlorine content and are poorly used for recycling, can be effectively used for removing alkali metals contained in biomass ash.

The chlorine source used in the step (d) may have a size of 80 mm or less.

By using a chlorine source of the above size in the heat treatment according to step (d), a high proportion of the sparingly soluble alkali metal contained in the coarse powder of biomass ash (more specifically, crushed fine powder) becomes a water-soluble salt. Can change. When the size of the chlorine source is larger than 80 mm, the chlorine from the chlorine source may not be sufficiently volatilized during the heat treatment according to the step (d), and the chlorination roasting of the biomass ash may be difficult to occur. The size of the chlorine source is the size of the opening of the sieve, and the size of 80 mm or less means that the chlorine source passes through the sieve having an opening of 80 mm.

In the step (d), the ratio (B / A) of the molar amount (B / A) of the total chlorine of the chlorine source to the molar amount (A) of the total alkali metal component of the crushed fine powder is 1.5 or more and 5 or less. It may be a step of heating the mixture of the pulverized fine powder and the chlorine source mixed within the above range.

According to the above method, most of the sparingly soluble alkali metals contained in the pulverized fine powder can be efficiently converted into water-soluble salts. If the B / A value exceeds 5, chlorine that does not contribute to chlorination roasting remains, and there is a risk that some chlorine sources will be wasted. Further, when the B / A value is less than 1.5, the heat-treated product obtained after the completion of the step (d) may still contain a certain amount of sparingly soluble alkali metal.

The crushed coarse powder obtained in the step (c) is the coarse powder of the biomass ash classified in the step (a) after the sparingly soluble alkali metal, which was unevenly distributed in the peripheral portion, was separated and recovered. It is powder. Therefore, the alkali metal content is extremely low. Further, the water-washed product obtained in the step (e) is washed with water against fine powder of biomass ash containing an alkali metal showing water solubility and crushed fine powder in which the alkali metal is changed to a water-soluble salt by chlorination roasting. It has been treated and the alkali metal component has been dissolved and removed. That is, the content of the alkali metal in both the crushed coarse powder obtained in the step (c) and the washed product obtained in the step (e) is significantly lower than that of the initial biomass ash. .. Therefore, these crushed coarse powder and the washed product can be used as a raw material for cement and the like.

Further, the alkali metal removing device according to the present invention is a device for removing alkali metals from flying ash of combustion ash of woody biomass.
The first classification device that classifies the fly ash into fine powder and coarse powder,
A pulverizer for obtaining a pulverized product by pulverizing the surface portion of the coarse powder obtained by the first classifier.
A second classifying device for classifying the crushed product obtained by the crushing device into crushed fine powder and crushed coarse powder, and a second classifying device.
A heating device for obtaining a heat-treated product by heating the pulverized fine powder obtained by the second classifying device together with a chlorine source.
It is characterized by including a water washing device for washing the fine powder obtained by the first classifying device and the heat-treated product obtained by the heating device with water.

According to the above apparatus, it is possible to selectively perform chloride roasting on the peripheral portion of the coarse powder of biomass ash containing a large amount of sparingly soluble alkali metal, and efficiently remove the alkali metal from the biomass ash. be able to.

The first classifier and the second classifier may be composed of a centrifugal air classifier having rotating blades such as a cyclone type air separator.

According to such a configuration, the classification points of the biomass ash and the pulverized product can be easily adjusted, and the classification treatment can be continuously performed.

When the crushing device is equipped with a classification function, the second classifying device is not always necessary. That is, the alkali metal removing device according to the present invention is a device for removing alkali metals from the flying ash of combustion ash of woody biomass.
The first classification device that classifies the fly ash into fine powder and coarse powder,
A crushing device that crushes the surface portion of the coarse powder obtained by the first classifying device to obtain a pulverized product, and then classifies the pulverized product into crushed fine powder and crushed coarse powder.
A heating device that heats the crushed fine powder obtained by the crushing device together with a chlorine source to obtain a heat-treated product, and a heating device.
Another feature is to include a water washing device for washing the fine powder obtained by the first classifying device and the heat-treated product obtained by the heating device with water.

The crushing device may be composed of a jet mill.

According to such a configuration, it is possible to collide the coarse powders of biomass ash with each other to destroy and separate the surface portion of the coarse powder without using a crushing medium, and the obtained crushed product is other than the biomass ash. No contamination by contaminants. Further, since the classification function is installed, a separate second classification device is not required.

The heating device may be composed of a rotary kiln.

According to such a configuration, since the pulverized fine powder and the chlorine source are well mixed and uniformly heated in the heating device, it is possible to efficiently generate chloride roasting of the alkali metal. Such heat treatment can be carried out continuously. The combustion method of the rotary kiln is not particularly limited, and may be an internal combustion type or an external heat type.

According to the present invention, alkali metals can be efficiently removed from biomass ash. As a result, biomass ash can be used as a raw material for cement and the like.

It is a flowchart which shows typically the procedure of the alkali metal removal method which concerns on this invention. It is a block diagram which shows typically one structural example of the alkali metal removing apparatus which concerns on this invention. It is a block diagram which shows typically another structural example of the alkali metal removing apparatus which concerns on this invention. It is a scanning electron microscope (SEM) photograph of the cross section of the coarse powder particles of biomass ash.

The biomass ash to which the present invention is applied contains alkali metal (Na, K) as chloride, carbonate, sulfate, or silicate glass, and is _{converted to R 2} O (R ₂ O = Na ₂ O + 0.658). × K ₂ O) contains about 3% by mass or more and 50% by mass or less. Among the aspects of this alkali metal, chlorides, carbonates and sulfates are water-soluble, and silicate glass is sparingly soluble.

Chloride, carbonate, and sulfate, which are water-soluble salts of alkali metals, are abundantly present on the fine powder side of biomass ash, and poorly soluble silicate glass is abundantly present on the coarse powder side of biomass ash. ..

Furthermore, since the distribution of alkali metals in the coarse powder of biomass ash is ubiquitous in the periphery of the particles and the concentration of alkali metals in the center of the particles is around 1.0% by mass, the inside of the coarse powder of biomass ash is inside the particles. Can be used as it is as a raw material for cement and the like.

According to the alkali metal removal process of the present invention, the concentration of the alkali metal contained in the biomass ash, the R ₂ O converted at 2.0 wt% or less, more typically reduced to below 1.5 wt% Therefore, the biomass ash can be effectively used as a raw material for cement and the like. The concentration of the alkali metal in the biomass ash can be measured by a well-known method, and for example, a method based on JIS R 5204 "Fluorescent X-ray analysis method of cement" is preferably exemplified.

Hereinafter, the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the aspects described with these drawings.

FIG. 1 is a flowchart schematically showing a procedure of an alkali metal removing method according to the present invention. Further, FIG. 2 is a block diagram schematically showing an example of an apparatus (hereinafter, referred to as “alkali metal removing apparatus”) that implements the alkali metal removing method shown in FIG. In FIG. 2, the flow of solids such as biomass ash is indicated by a solid line with an arrow, and the flow of air or exhaust gas is indicated by a broken line with an arrow.

FIG. 3 is a block diagram schematically showing a configuration example of an alkali metal removing device different from that of FIG. 2. In the following, the alkali metal removing method according to the present invention will be described mainly with reference to FIGS. 1 and 2, and FIG. 3 will also be referred to as necessary.

As shown in FIG. 1, the alkali metal removing method according to the present invention includes a first classification treatment step S1, a crushing treatment step S2, a second classification treatment step S3, a heat treatment step S4, and a water washing treatment step S5.

Further, as shown in FIG. 2, the alkali metal removing device 1 according to the present invention includes a first classification device 3, a crushing device 4, a heating device 7, and a water washing device 9.

Hereinafter, the processing contents in each step shown in FIG. 1 will be described in detail with reference to FIG. 2 as appropriate.

(First classification processing step S1)
In the first classification treatment step S1, the supplied biomass ash BA1 is separated into fine powder BA2 containing a large amount of water-soluble alkali metal salt and coarse powder BA3 containing a large amount of sparingly soluble alkali metal salt, and each is recovered separately. It is a process. In the alkali metal removing device 1 shown in FIG. 2, the first classifying process step S1 is executed by the first classifying device 3. The fine powder BA2 is sent from the discharge port 3a of the first classification device 3 to the water washing device 9 side described later, and the coarse powder BA3 is sent to the crushing device 4 side described later from the discharge port 3b of the first classification device 3. NS.

Here, the biomass ash fine powder BA2 (hereinafter, simply abbreviated as "fine powder BA2") refers to biomass ash having a particle size finer than a predetermined classification point, and is a biomass ash coarse powder BA3 (hereinafter, simply abbreviated as "fine powder BA2"). "Coarse powder BA3") refers to biomass ash having a particle size coarser than the classification point. The classification point defined in the first classification treatment step S1 is preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less, and particularly preferably 5 μm or more and 10 μm or less.

In the present specification, the particle size of biomass ash refers to a value measured by a laser diffraction particle size distribution measurement method using ethyl alcohol as a solvent, unless otherwise specified. The particle size of general biomass ash that can be obtained varies depending on the type of biomass that is the fuel, the type of boiler that burns the biomass, and the operating method, but the D ₅₀ value by the laser diffraction particle size distribution measurement method is 15 μm or more and 35 μm or less. The maximum value of the particle size (D ₁₀₀ ) is 150 μm or more and 1000 μm or less. The D ₅₀ value means a cumulative 50% particle size in a volume-based particle size distribution.

The first classification device 3 is not particularly limited as long as it is a dry type device that can classify the biomass ash BA1 at the classification points on the order of μm as described above. Is preferable, and a centrifugal air classifier with a rotating blade such as a cyclone type air separator or a turbo classifier is preferably used because it is particularly good at classifying with a particle size of 1 μm or more and 20 μm or less. In the embodiment shown in FIG. 2, the case where the first classification device 3 is composed of a cyclone type air separator is shown.

The first classifier 3 may be provided with a storage tank for biomass ash BA1. Further, a supply device for quantitatively supplying the biomass ash BA1 from the storage tank to the first classification device 3 may be provided. These storage tanks and supply devices may be appropriately used depending on the state of the received biomass ash BA1.

The first classification processing step S1 corresponds to the step (a).

(Crushing process S2, second classification process S3)
The pulverization treatment step S2 is a step of separating small pieces having a high alkali metal salt content from the crude powder BA3 by pulverizing the surface portion of the crude powder BA3 in which the sparingly soluble alkali metal salt is unevenly distributed. Further, in the second classification treatment step S3, small pieces having a high alkali metal salt content (crushed fine powder BA4) and residual coarse powder (remaining coarse powder) from which the alkali metal salt is separated from the crushed product BA3a produced by the crushing treatment step S2 (crushed fine powder BA4). This is a step of separating into crushed coarse powder BA5) and collecting each separately.

In the alkali metal removing device 1 shown in FIG. 2, the crushing process S2 and the second classification process S3 are executed by the crushing device 4.

The crushing device 4 crushes the surface portion by colliding the coarse powders BA3 with each other at high speed. The poorly soluble alkali metal salt present on the surface of BA3 of the crude powder is an embodiment of silicate glass, and this silicate glass is characterized in that it is fragile to impact due to its high hardness. Therefore, by colliding the crude powders BA3 with each other at high speed, the silicate glasses or the internal constituent phases of the silicate glass and the crude powder of the biomass ash, and further, the silicate glass and the pulverizer When a collision with the wall surface of the sample chamber occurs, the silicate glass is broken into small pieces and separated from the coarse powder BA3.

The crushing device 4 is not particularly limited as long as it is a device capable of separating and recovering fine powder while colliding the coarse powder BA3 with each other at high speed to the extent that the surface portion of the coarse powder BA3 is destroyed and separated. Etc. are preferred.

The crushed product BA3a obtained in the crushing treatment step S2 includes a silicate glass broken into small pieces (crushed fine powder BA4) and a crushed fine powder BA4 separated from the surface portion of the coarse powder BA3 (crushed fine powder BA4). Coarse powder BA5) is mixed. In the second classification treatment step S3, these crushed fine powder BA4 and crushed coarse powder BA5 are separately recovered.

When a jet mill is used as the crushing device 4, and the jet mill also has a classification mechanism, the crushing device 4 executes the second classification processing step S3 together with the crushing processing step S2. That is, the crushing apparatus 4 crushes the coarse powder BA3 and then separates and collects the crushed fine powder BA4 and the crushed coarse powder BA5.

On the other hand, when the crushing device 4 is not equipped with a classification mechanism, the alkali metal removing device 1 may be provided with a separate second classifying device 6, as shown in FIG. In this case, the second classifying device 6 can adopt the same structure as the first classifying device 3 described above.

The classification point in the second classification treatment step S3 is preferably 5 μm or more and 30 μm or less. By setting the classification point in the second classification treatment step S3 within this range, 50 area% to 100 area% of the poorly soluble alkali metals contained in the crude powder BA3 are separated from the coarse powder BA3 particles. It can be collected as debris (crushed fine powder BA4). Here, the area% regarding the recovery rate of the sparingly soluble alkali metal indicates a value based on the area of the glass phase on the particle surface in the scanning electron microscope (SEM) image of the cross section of the coarse powder BA3 particles before and after the pulverization treatment step S2. ..

In the pulverization treatment in the pulverization treatment step S2, in order not to excessively pulverize the coarse powder BA3, and the small pieces of silicate glass (crushed fine powder BA4) separated by pulverization are the particle internal constituent phases of the crude powder BA3 (crushed crude powder BA5). ), And the crushing time must be short while ensuring the appropriate crushing strength. Specifically, immediately after the execution of the pulverization treatment step S2, the second classification treatment step S3 may be executed to collect the separated small pieces of silicate glass (crushed fine powder BA4).

The crushing device 4 may be provided with a storage tank for coarse powder BA3. Further, a supply device for quantitatively supplying the coarse powder BA3 from the storage tank to the crushing device 4 may be provided. These storage tanks and supply devices may be appropriately used depending on the state of the supplied crude powder BA3.

The crushing treatment step S2 corresponds to the step (b), and the second classification treatment step S3 corresponds to the step (c).

(Heat treatment step S4)
The heat treatment step S4 is a step of heating the crushed fine powder BA4 obtained by classification in the second classification treatment step S3 together with the chlorine source CL. By this heat treatment step S4, the poorly soluble alkali metal salt contained in the pulverized fine powder BA4 is changed to a water-soluble alkali metal salt (alkali metal chloride). In the alkali metal removing device 1 shown in FIG. 2, the heat treatment step S4 is executed by the heating device 7.

The alkali metal removing device 1 shown in FIG. 2 includes a chlorine source supply device 5 for supplying the received chlorine source CL to the heating device 7. The chlorine source CL is not particularly limited as long as it contains chlorine, but is flammable in which waste plastic containing at least one organic chlorine in a monomer such as waste polyvinyl chloride or inorganic compound chlorine such as calcium chloride is mixed. Sexual waste can be preferably used. The chlorine source supply device 5 may be provided with a storage tank for the received chlorine source CL.

The chlorine source CL preferably contains 0.8% by mass or more, more preferably 1.2% by mass or more, and particularly preferably 2% by mass or more. The concentration of chlorine in the chlorine source CL referred to here can be measured by a well-known method, and for example, a method based on JIS R 5204 "Fluorescence X-ray analysis method of cement" can be used.

From the viewpoint that the chlorine source CL sufficiently causes chlorine volatilization from the chlorine source CL while forming a good mixed state with the pulverized fine powder BA4 in the heating device 7, chloride volatilization of the alkali metal is efficiently generated. The size is preferably 80 mm or less, more preferably 40 mm or less, and particularly preferably 10 mm or less. The size of the chlorine source CL refers to the minimum opening of the sieve through which the chlorine source CL passes.

From the above viewpoint, on the upstream side of the storage tank attached to the chlorine source supply device 5, a classifying device for removing coarse substances from the received chlorine source CL and a crushing classifying device for making the coarse substances into a predetermined particle size are provided. It may be attached. These classifying devices and crushing classifying devices may be appropriately used depending on the state of the received chlorine source CL.

The chlorine source supply device 5 is provided with an emission amount adjusting device such as an emission amount adjusting valve, and has a configuration capable of adjusting the supply amount of the chlorine source CL to the heating device 7. Therefore, by appropriately controlling the discharge amount adjusting device, it is possible to appropriately control the amount of chlorine supplied to the heating device 7.

More specifically, the ratio of the crushed fine powder BA4 treated in the heat treatment step S4 to the chlorine source CL is the molar amount of all alkali metal components in the crushed fine powder BA4 subjected to the heat treatment step during a unit time (A). ), The value of the ratio (B / A) of the molar amount (B) of total chlorine in the chlorine source CL to be subjected to the heat treatment step during the unit time is set to be 1.5 or more and 5 or less. Is preferable. The value of the ratio (B / A) is more preferably 2 or more and 5 or less. When the value of the ratio (B / A) is less than 1.5, a large amount of alkali metal components that cannot react with chlorine may remain among the alkali metal components in the pulverized fine powder BA4 due to the small amount of chlorine. On the contrary, if the ratio (B / A) value exceeds 5, the amount of chlorine volatilized and dissipated increases, which may accelerate the progress of corrosion of the equipment.

As described above, the heating device 7 heats the pulverized fine powder BA4 and the chlorine source CL together. Specifically, the chlorine source CL is supplied from the chlorine source supply device 5 and the crushed fine powder BA4 is supplied from the crushing device 4 (or the second classification device 6) to the heating device 7, and the chlorine source CL is supplied in the heating device 7. And the crushed fine powder BA4 are heated together. As a result, the alkali metal in the pulverized fine powder BA4 reacts with chlorine volatilized from the chlorine source CL to produce a water-soluble alkali metal salt.

The heating temperature in the heat treatment step S4 is 650 ° C. or higher and 1000 ° C. or lower from the viewpoint of not melting the crushed fine powder BA4 while efficiently producing chloride roasting by the alkali metal in the crushed fine powder BA4 and chlorine in the chlorine source CL. Is preferable, 700 ° C. or higher and 950 ° C. or lower is more preferable, and 750 ° C. or higher and 950 ° C. or lower is particularly preferable. If the heating temperature is less than 650 ° C., the reaction of chlorination roasting becomes insufficient, and in some cases, water-soluble alkali metal salts may not be produced or the production efficiency may be low. On the other hand, if the heating temperature exceeds 1000 ° C., the crushed fine powder BA4 may be partially melted or the diameter may be increased, resulting in a decrease in the production efficiency of the water-soluble alkali metal salt.

The heating time in the heat treatment step S4 may be appropriately set within a range of 10 minutes or more and 2 hours or less depending on the heating temperature. From the viewpoint of sufficiently reacting the alkali metal in the pulverized fine powder BA4 with the chlorine in the chlorine source CL, this heating time needs to be short when the heating temperature is high and long when the heating temperature is low. Specifically, when the heating temperature is 650 ° C., it is preferably 30 minutes or more and 2 hours or less, and when the heating temperature is 1000 ° C., it is preferably 10 minutes or more and 30 minutes or less.

The atmosphere in the heating device 7 is not particularly limited and may be an oxidizing atmosphere or a reducing atmosphere, but the atmosphere is preferable from the viewpoint of convenience. In the example shown in FIG. 2, the atmosphere G1 for combustion is sent into the heating device 7 from the intake fan 33.

In order to efficiently cause the formation reaction of the water-soluble alkali metal salt in the heating device 7, it is desirable that the pulverized fine powder BA4 and the chlorine source CL are heated in a sufficiently mixed state. From this point of view, the heating device 7 can be configured by an internal combustion type rotary kiln. If the firing furnace is a rotary kiln that rotates, the heat treatment can be performed while physically and continuously mixing and stirring the pulverized fine powder BA4, which is the object to be heated, and the chlorine source CL.

In the rotary kiln, the atmosphere G1 used as the combustion air of the internal combustion burner 31 by the intake fan 33 flows inside the kiln in a direction facing the flow of the crushed fine powder BA4 and the chlorine source CL, and then becomes the combustion exhaust gas G2. Exhausted outside the kiln.

The heating device 7 is not particularly limited as long as it can heat a mixture of crushed fine powder BA4 and chlorine source CL in a temperature range of 650 ° C. or higher and 1000 ° C. or lower, and is a fixed furnace, a stoker furnace, a rotary kiln, or a fluidized bed furnace. , Vertical furnaces, multi-stage furnaces and other heating furnaces can be used. Of these, the rotary kiln described above is preferable from the viewpoint of being able to physically stir.

Further, the heating device 7 may be provided with a storage tank for the supplied crushed fine powder BA4. Further, a supply device for quantitatively supplying the pulverized fine powder BA4 from the storage tank to the heating device 7 may be provided. These storage tanks and supply devices may be appropriately used depending on the state of the supplied pulverized fine powder BA4.

From the heating device 7, the heat-treated product P1 which is a mixture of the pulverized fine powder BA4 in which the sparingly soluble alkali metal is changed to a water-soluble salt and the incineration residue of the chlorine source CL is discharged. The discharged heat-treated product P1 is sent to the water washing device 9.

This heat treatment step S4 corresponds to the step (d).

(Water washing process S5)
The water washing treatment step S5 is a step of washing the fine powder BA2 separated and recovered in the first classification treatment step S1 and the heat-treated product P1 obtained in the heat treatment step S4 with water. By this water washing treatment step S5, the water-soluble alkali metal salt contained in the fine powder BA2 and the heat-treated product P1 is dissolved and removed. In the alkali metal removing device 1 shown in FIG. 2, the water washing treatment step S5 is executed by the water washing device 9.

Water is preferable as the solvent used in the water washing treatment step S5.

In the water washing device 9, the fine powder BA2 separated and recovered by the first classifying device 3 and supplied from the discharge port 3a and / or the heat-treated product P1 supplied from the heating device 7 and water W1 are mixed and the slurry Lr1 After the above, the stirring of the slurry Lr1 is continued to dissolve the water-soluble alkali metal salt in the fine powder BA2 and / or the heat-treated product P1 in water.

As an example, the water washing device 9 shown in FIG. 2 is provided with a supply hopper 11 for the fine powder BA2 and the heat-treated product P1 and a water W1 supply device 13. Further, the water washing device 9 is provided with a slurry stirring device 35 for mixing the fine powder BA2 and / or the heat-treated product P1 and water W1 and stirring the slurry Lr1 produced by the mixing. As the slurry stirring device 35, for example, a general paddle type or screw type may be used, and in the embodiment shown in FIG. 2, a stirring blade is provided.

A crushing device for crushing the large-diameter material in the received heat-treated product P1 to an appropriate size may be attached to the upstream side of the supply hopper 11. This crushing device may be appropriately used depending on the state of the heat-treated product P1 supplied from the heat treatment step S4.

The solubility of water-soluble alkali metal salts in water is very high, and the solubility does not change significantly even if the water temperature is changed. Therefore, as the solvent used in the washing treatment step S5, water at room temperature is the total amount (mass) of a mixture of the fine powder BA2 and the heat-treated product P1 (hereinafter, may be referred to as “water-washed product”). It is sufficient to use only an amount of 3 times or more, preferably 4 times or more, more preferably 5 times or more of the amount.

The stirring time of the slurry Lr1 composed of the washed product and water in the water washing treatment step S5 is preferably 10 minutes or more, more preferably 15 minutes or more, and particularly preferably 20 minutes or more. Generally, the water-soluble alkali metal salt is very soluble in water, so no special conditions are required for stirring the slurry Lr1.

In the water washing treatment step S5, the alkali metals contained in both the fine powder BA2 and the coarse powder BA3, in which the biomass ash BA1 is classified, are both dissolved in water. The slurry Lr1 in which the alkali metal is dissolved in water has a solid substance (cake C1) and wastewater W3 whose water content is effectively reduced by the solid-liquid separation device 17 installed in the subsequent stage and can be used as a cement raw material or the like. Is separated into.

When transporting the slurry Lr1 to the solid-liquid separation device 17, a general-purpose slurry liquid transport device (not shown) such as a slurry centrifugal pump, a piston pump, and a mono pump or a hose pump may be used.

As the solid-liquid separation device 17, a general-purpose filtration device such as a filter press, a pressurized leaf filter, a screw press, a belt press, or a belt filter may be used. In the embodiment shown in FIG. 2, the case where the solid-liquid separation device 17 is configured by a filter press is shown.

The solid-liquid separation device 17 is provided with a washing water W2 supply device 15, and the transported slurry Lr1 is mixed with the cake C1 (solid phase) of the washed product and the drainage W3 (liquid phase) containing an alkali metal. Separate into and. At this time, the cake C1 is separated while being washed with the washing water W2. As the washing water W2, water at room temperature may be used in an amount of 3 times or more, preferably 4 times or more, more preferably 5 times or more the mass of the washed product.

The cake C1 separated by the solid-liquid separator 17 has an alkali metal component concentration of 2.0% by mass or less, more typically 1.5% by mass or less, and is therefore effective as a cement raw material or the like. Can be used for. The alkali metal concentration referred to here is an analysis value by a well-known method, for example, an analysis value by a method based on JIS R 5204 "X-ray fluorescence analysis method of cement", or ICP emission spectroscopic analysis of an acid decomposition sample. Refers to the analysis value by the method.

This water washing treatment step S5 corresponds to the step (c).

Usually, among all the alkali metal components contained in biomass ash BA1, the alkali metal component in the form of a water-soluble salt is 25% or more and 45% or less of 100% of the total in terms of molars, and is a poorly soluble salt. The alkali metal component in the form is 55% or more and 75% or less in 100% of the whole.

Further, among the total alkali metal components contained in the biomass ash BA1, the biomass ash having a particle size of 30 μm or less, that is, the total alkali metal components contained in the fine powder BA2 is 40% or more of the total 100% in terms of molars. It is 60% or less, of which 70% or more and 90% or less is a water-soluble alkali metal component.

Therefore, after the biomass ash BA1 is classified into the fine powder BA2 and the coarse powder BA3 in the first classification treatment step S1, the fine powder BA2 is washed with water in the water washing treatment step S5, whereby all the alkali metal components contained in the biomass ash BA1 are mixed. Of these, 30% or more and 50% or less can be removed.

When the classification point of the biomass ash BA1 in the first classification treatment step S1 is 10 μm, the fine powder BA2 having a particle size of 10 μm or less classified in the first classification treatment step S1 is washed with water in the water washing treatment step S5. As a result, 20% or more and 35% or less of the total alkali metal components contained in the biomass ash BA1 can be removed.

Further, with respect to the crude powder BA3 containing a large amount of alkali metal components in the form of a sparingly soluble salt, the alkali metal unevenly distributed on the surface portion is separated as pulverized fine powder BA4 through the pulverization treatment step S2 and the second classification treatment step S3. Then, the alkali metal component in the form of a sparingly soluble salt, which is abundantly contained in the crushed fine powder BA4, is chlorinated and roasted by being heated together with the chlorine source CL, and is changed to a water-soluble salt. As a result, most of them are removed by washing with water in the water washing treatment step S5.

Of the crude powder BA3, the remainder (crushed crude powder BA5) in which the alkali metal unevenly distributed on the surface is separated has an extremely low alkali metal content (around 1.0% by mass), so the cement is used as it is. It can be used as a raw material.

Hereinafter, specific test examples will be shown in order to explain the present invention in more detail, but the present invention is not limited to the aspects of these test examples.

As the biomass ash BA1, fly ash collected by an exhaust gas dust collector (bug filter) of a biomass power plant (circulating fluidized bed boiler) using PKS as a main fuel was used. Table 1 below shows the chemical composition of biomass ash BA1 obtained by ICP emission spectroscopy analysis of acid-decomposed samples for alkali metals and fluorescent X-ray analysis of pellet samples for other chemical components. Is shown. As described above, “R ₂ O” in Table 1 is a value calculated _{as “R 2} O = Na ₂ O + 0.658 × K ₂ O” as the total amount of alkali metal components in the composition. Is shown.

Moreover, when the particle size distribution of the biomass ash BA1 shown in Table 1 was measured based on the laser diffraction / scattering method, the D ₁₀ value was 4.4 _{μm, the D 50} value was 19.5 μm, and the D ₉₀ value was 63.5 μm. ..

A scanning electron microscope (SEM) image of the cross section of the coarse powder BA3 of biomass ash is shown in FIG. As can be seen in FIG. 4, the coarse powder BA3 has different textures at the periphery and inside the particles. From detailed analysis such as electron diffraction, it was found that the peripheral portion is a glass phase and the inside of the particles is a crystal phase.

Furthermore, when the potassium concentration of the peripheral portion and the inside of the particle was measured using energy dispersive X-ray spectroscopy (SEM-EDX), the potassium concentration inside the particle was 0.8% by mass, whereas the potassium in the peripheral portion was measured. The concentration was 6.1% by mass.

The chlorine source CL is the ratio of the chlorine content B (mol) in the chlorine source CL to the content A (mol) of _{the alkali metal component R 2} O in the pulverized fine powder BA4, and the amount such that B / A = 2. A crushed product of waste polyvinyl chloride that had been passed through a sieve having a mesh size of 1 mm was used.

The main operating factors of the first classification treatment step S1, the second classification treatment step S3, the heat treatment step S4, and the water washing treatment step S5 in the examples were set as follows. In the crushing treatment S2, a single track jet mill (manufactured by Seishin Enterprise Co., Ltd.) was used.

(First classification processing step S1)
Biomass ash BA1 classification point: 10 μm

(Second classification processing step S3)
Classification point of crushed product BA3a of coarse powder BA3: 20 μm

(Heat treatment step S4)
Heating temperature and heating time for a mixture of crushed fine powder BA4 and chlorine source CL: 950 ° C ± 25 ° C x 15 minutes

(Water washing process S5)
Amount of water W1 used: 4 times the mass of the mixture of fine powder BA2 and heat-treated product P1 Stirring time: 10 minutes Washing water W2 used in the solid-liquid separator 17: 4 times the mass of cake C1

Total alkali metal component weight biomass ashes after undergoing each step containing (R ₂ O), was confirmed by ICP emission spectrometry acidolysis sample. The analysis results are shown in Table 2. The mass ratio in Table 2 is a value indicating the ratio (mass%) of the biomass ash in each step to 100% by mass of the biomass ash BA1.

As can be seen from Table 2, according to the alkali metal removing method of the present invention, 35% by mass of the whole is heat-treated and 65% by mass of the whole is washed with water, so that the crushed coarse powder BA5 and cake C1 are contained. The proportion of alkali metals produced can be reduced to 0.9% by mass. Considering that the proportion of the alkali metal contained in the biomass ash BA1 before the treatment was 4.3% by mass, the alkali metal in the biomass ash BA1 could be reduced by 70% or more by the method of the present invention. This makes it possible to use the combustion ash of woody biomass as a raw material for cement.

1: Alkali metal removing device 3: First classification device 3a: Discharge port 3b: Discharge port 4: Crushing device 5: Chlorine source supply device 6: Second classification device 7: Heating device 9: Water washing device 11: Supply hopper 13: Water supply device 15: Washing water supply device 17: Solid-liquid separation device 31: Internal combustion burner 33: Intake fan 35: Slurry stirrer BA1: Biomass ash BA2: Fine powder BA3: Coarse powder BA3a: Crushed product BA4: Crushed fine powder BA5: Crushed Coarse powder C1: Cake CL: Chlorine source G1: Atmosphere G2: Combustion exhaust gas Lr1: Slurry P1: Heat-treated product W1: Water W2: Washing water W3: Drainage

Claims (12)

A method of removing alkali metals from the fly ash of the combustion ash of woody biomass.
The step (a) of classifying the fly ash into fine powder and coarse powder, and
The step (b) of crushing the surface portion of the coarse powder obtained in the step (a) to obtain a pulverized product,
The step (c) of classifying the pulverized product obtained in the step (b) into pulverized fine powder and pulverized coarse powder, and
The step (d) of heating the crushed fine powder obtained in the step (c) together with a chlorine source to obtain a heat-treated product,
A method for removing an alkali metal, which comprises a step (e) of washing the fine powder obtained in the step (a) with water and the heat-treated product obtained in the step (d). The alkali metal removing method according to claim 1, wherein the step (a) is a step of classifying with 5 μm or more and 30 μm or less as a classification point. The alkali metal removing method according to claim 2, wherein the step (c) is a step of classifying with 5 μm or more and 30 μm or less as a classification point. The alkali metal removing method according to any one of claims 1 to 3, wherein the step (d) is a step of heating at a temperature of 650 ° C. or higher and 1000 ° C. or lower. The alkali metal according to any one of claims 1 to 4, wherein the chlorine source used in the step (d) contains flammable waste mixed with waste plastic and inorganic compound chlorine. Removal method. The alkali metal removing method according to any one of claims 1 to 5, wherein the chlorine source used in the step (d) has a size of 80 mm or less. In the step (d), the ratio (B / A) of the molar amount (B / A) of the total chlorine of the chlorine source to the molar amount (A) of the total alkali metal component of the crushed fine powder is 1.5 or more and 5 or less. The method for removing an alkali metal according to any one of claims 1 to 6, wherein the step is to heat a mixture of the pulverized fine powder and the chlorine source, which is mixed within the above range. A device for removing alkali metals from the fly ash of the combustion ash of woody biomass.
The first classification device that classifies the fly ash into fine powder and coarse powder,
A pulverizer for obtaining a pulverized product by pulverizing the surface portion of the coarse powder obtained by the first classifier.
A second classifying device for classifying the crushed product obtained by the crushing device into crushed fine powder and crushed coarse powder, and a second classifying device.
A heating device for obtaining a heat-treated product by heating the pulverized fine powder obtained by the second classifying device together with a chlorine source.
An alkali metal removing device comprising a water washing device for washing the fine powder obtained by the first classifying device and the heat-treated product obtained by the heating device with water. A device for removing alkali metals from the fly ash of the combustion ash of woody biomass.
The first classification device that classifies the fly ash into fine powder and coarse powder,
A crushing device that crushes the surface portion of the coarse powder obtained by the first classifying device to obtain a pulverized product, and then classifies the pulverized product into crushed fine powder and crushed coarse powder.
A heating device that heats the crushed fine powder obtained by the crushing device together with a chlorine source to obtain a heat-treated product, and a heating device.
An alkali metal removing device comprising a water washing device for washing the fine powder obtained by the first classifying device and the heat-treated product obtained by the heating device with water. The alkali metal removing device according to claim 8, wherein the first classifying device and the second classifying device are composed of a centrifugal air classifier having rotary blades. The alkali metal removing device according to claim 9, wherein the crushing device is composed of a jet mill. The alkali metal removing device according to any one of claims 8 to 11, wherein the heating device is composed of a rotary kiln.

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