JP7503010B2 - Method and apparatus for removing alkali metals - Google Patents

Description

The present invention relates to an alkali metal removal method and an alkali metal removal device. In particular, the present invention relates to an alkali metal removal method and an alkali metal removal device for effectively utilizing combustion ash of wood biomass as a cement raw material, etc.

As for wood biomass, such as tree trunks and branches, cutting chips, sawdust, bark, wood pellets, PKS (palm kernel shells), and construction waste, in parallel with the development of technology to use it as fuel for power generation boilers, etc., development is also underway for the effective use of combustion ash (hereinafter sometimes referred to as "wood biomass ash") generated by the combustion of wood biomass.

Compared to coal ash and waste incineration ash, for example, wood biomass ash is characterized by its high content of alkali metals, especially potassium. For this reason, for example, when applying cement raw material technology that enables the effective use of large amounts of coal ash and waste incineration ash to wood biomass ash, it is necessary to remove the alkali metals from the wood biomass ash so that cement will avoid the alkali metal components. Furthermore, if the alkali metals can be removed from wood biomass ash fly ash, it will be possible to develop applications for wood biomass ash fly ash as a concrete admixture or cement mixture, just like coal ash (fly ash).

As a technique for removing alkali metal components from woody biomass ash, for example, Patent Document 1 below discloses a combustion device and a combustion ash processing method in which woody biomass ash (fly ash) collected by a bag filter is classified at a predetermined classification point to separate and recover fine combustion ash with a high potassium concentration.

JP 2017-122550 A

However, since alkali metals are present in all particle sizes of wood biomass fly ash, simply removing the alkali metals present in the fine powder is insufficient for use as a cement raw material, etc.

In view of the above problems, the present invention aims to provide an alkali metal removal method and an alkali metal removal device for use in carrying out the method, for efficiently removing alkali metals from fly ash of wood biomass ash (hereinafter sometimes referred to as "biomass ash") and effectively utilizing the alkali metals as a cement raw material, etc.

As a result of extensive research, the inventors have discovered that there are two types of alkali metals contained in biomass ash: water-soluble and poorly soluble in water (hereinafter simply referred to as "poorly soluble"). They have also discovered that water-soluble alkali metals are abundant in the fine powder side of biomass ash, which has a small particle size, while poorly soluble alkali metals are abundant in the coarse powder side, which has a large particle size.

Furthermore, the inventors have found that poorly soluble alkali metals can be converted into water-soluble salts (alkali metal chlorides) by heating them together with a chlorine source (so-called "chlorination roasting").

Based on the above new findings, the inventors have discovered that the alkali metals contained in the biomass ash can be effectively and efficiently removed by converting the poorly soluble alkali metals contained in the coarse powder of the biomass ash into water-soluble salts using chlorination roasting, and then washing the salts together with the fine powder of the biomass ash with water.

That is, the present invention is a method for removing alkali metals from fly ash of combustion ash of woody biomass, comprising the steps of:
(a) classifying the fly ash into fine powder and coarse powder;
A step (b) of heating the coarse powder obtained in the step (a) together with a chlorine source to obtain a heat-treated product;
The method is characterized by including a step (c) of washing the fine powder obtained in the step (a) and the heat-treated product obtained in the step (b) with water.

According to the above method, biomass ash (fly ash) is previously classified into fine powder and coarse powder in step (a). As described above, the fine powder of biomass ash contains a large amount of water-soluble alkali metals, so the alkali metals can be removed by simply washing with water. The coarse powder of biomass ash also contains a large amount of poorly soluble alkali metals, but in step (b), this coarse powder is heated together with a chlorine source to carry out chlorination roasting, and the alkali metals are converted into water-soluble salts. As a result, both the alkali metals contained in the fine powder side of the biomass ash and the alkali metals contained in the coarse powder side of the biomass ash can be dissolved in water and removed by the water washing treatment in step (c).

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

According to the above method, even if the biomass ash comes from different sources, fine powder equivalent to 20% by mass or more and 50% by mass or less of the total amount of biomass ash can be obtained for most biomass ash. In other words, the coarse powder to be subjected to the heat treatment in step (b) corresponds to 50% by mass or more and 80% by mass or less of the total amount of biomass ash. In other words, since there is no need to heat the entire biomass ash, alkali metals can be removed with high heating efficiency.

Step (b) may be a heating step at a temperature of 650°C or more and 1200°C or less.

The above method can convert a high percentage of sparingly soluble alkali metals contained in the coarse powder of biomass ash into water-soluble salts. If the heating temperature is less than 650°C, chlorination roasting may not occur easily due to the low temperature. If the heating temperature exceeds 1200°C, partial melting and enlargement of the biomass ash may occur, slowing down the reaction rate of chlorination roasting.

As a result of intensive research by the present inventors, it was found that the coarse powder of biomass ash may contain potassium in the form of potassium feldspar (KAlSi ₃ O ₈ ). In particular, when the powder contains a large amount of potassium feldspar, it is easily converted into an alkali metal salt by heating at a temperature of 1000°C to 1200°C.

Step (b) may be a step of heating in an atmosphere with an oxygen concentration of 10% or less.

As a result of intensive research by the inventors, it was newly discovered that alkali metals can be removed more efficiently by performing chlorination roasting in an atmosphere with a low oxygen concentration. The reason for this is believed to be that performing chlorination roasting in an atmosphere with a low oxygen concentration suppresses the volatilization of chlorine, making it easier to convert alkali metals into alkali metal chlorides. Details will be described later in the section "Mode for carrying out the invention" with reference to the examples.

The oxygen concentration in the atmosphere during chlorination roasting is preferably 10% or less, and more preferably 5% or less. The gas other than oxygen contained in the atmosphere is typically nitrogen, but other gases such as carbon dioxide may also be contained.

The chlorine source used in step (b) may include waste plastics and combustible waste mixed with inorganic chlorine.

The above method makes it possible to effectively utilize waste materials that have a high chlorine content and therefore are poorly suited for recycling, in order to remove alkali metals contained in biomass ash.

The chlorine source used in step (b) may be 80 mm or less in size.

By using a chlorine source of the above size in the heat treatment in step (b), a high percentage of the poorly soluble alkali metals contained in the coarse powder can be converted into water-soluble salts. If the size of the chlorine source is larger than 80 mm, chlorine may not be sufficiently volatilized from the chlorine source during the heat treatment in step (b), making it difficult to chlorinate the biomass ash. The size of the chlorine source refers to the size of the sieve openings, and a size of 80 mm or less refers to one that passes through a sieve with an opening of 80 mm.

The step (b) may be a step of heating a mixture of the coarse powder and the chlorine source in which the ratio (B/A) of the molar amount (B) of the total chlorine in the chlorine source to the molar amount (A) of the total alkali metal components in the coarse powder is in the range of 1 to 5.

According to the above method, most of the sparingly soluble alkali metals contained in the coarse powder can be efficiently converted into water-soluble salts. If the value of B/A exceeds 5, chlorine that does not contribute to chlorination roasting remains, and some of the chlorine source may be wasted. Also, if the value of B/A is below 1, the heat-treated product obtained after completion of step (b) may still contain a certain amount of sparingly soluble alkali metals.

The alkali metal removal method includes a step (d) of pulverizing the coarse powder obtained in the step (a) to obtain a pulverized coarse powder,
The step (b) may be a step of heating the coarsely pulverized product obtained in the step (d) together with the chlorine source.

It is assumed that the coarse powder contains poorly soluble alkali metals evenly throughout. As in the above method, by performing the grinding process (d) before the heating step (b), the exposed area of the alkali metal increases, improving its reactivity with the chlorine contained in the chlorine-containing material in the heating step (b), and enabling it to be converted to alkali metal chloride more efficiently.

The alkali metal removal apparatus according to the present invention is an apparatus for removing alkali metals from fly ash generated by combustion of woody biomass, comprising:
A classifier for classifying the fly ash into fine powder and coarse powder;
a heating device for heating the coarse powder obtained by the classifier together with a chlorine source to obtain a heat-treated product;
The present invention is characterized by including a water washing device for washing the fine powder obtained by the classifying device and the heat-treated product obtained by the heating device with water.

The above-mentioned device makes it possible to selectively apply chlorination roasting to coarse biomass ash powder that contains a large amount of sparingly soluble alkali metals, allowing efficient removal of alkali metals from biomass ash.

The classification device may be a centrifugal air classifier with rotating blades, such as a cyclone-type air separator.

This configuration makes it easier to adjust the classification point of the biomass ash and allows the classification process to be carried out continuously.

The heating device may be a rotary kiln.

With this configuration, the coarse biomass ash powder and the chlorine source are mixed well and heated homogeneously in the heating device, making it possible to efficiently produce chlorinated roasting of alkali metals and to carry out such heating treatment continuously. The combustion method of the rotary kiln is not particularly limited, and may be either an internal combustion type or an external heat type.

The alkali metal removal device may be equipped with a gas source that introduces combustion gas having an oxygen concentration of 10% or less to the heating device.

With this configuration, the atmosphere in which the coarse powder and chlorides are heated in the heating device can be made to have a low oxygen concentration, so the alkali metals contained in the coarse powder can be converted to alkali metal chlorides with high efficiency.

the alkali metal removal device includes a pulverizer that pulverizes the coarse powder obtained by the classification device,
The heating device may be one that heats the coarse powder pulverized by the pulverizer together with the chlorine source.

According to the present invention, alkali metals can be efficiently removed from biomass ash. This allows the biomass ash to be used as a raw material for cement, for example.

1 is a flow chart showing a schematic procedure of an alkali metal removal method according to the present invention. 1 is a block diagram showing a schematic configuration example of an alkali metal removal device according to the present invention. FIG. 4 is a block diagram showing a schematic configuration example of an alkali metal removal device according to the present invention. 4 is a flow chart showing another example of the procedure of the alkali metal removal method according to the present invention. 1 is a graph showing the results of potassium removal rate when granite soil is heated in different heating atmospheres and at different heating temperatures, and corresponds to the results in Table 8 described below. TG curves obtained when calcium chloride was heated in different heating atmospheres. 1 is a graph showing the relationship between the potassium removal rate and the oxygen concentration when biomass ash coarse powder is heated with different oxygen concentrations in the heating atmosphere, and corresponds to the results in Table 9 described below.

Biomass ash to which the present invention is applicable contains alkali metals (Na, K) as chlorides, carbonates, sulfates, or silicate glass, and contains about 3% by mass to 50% by mass calculated as _R2O ( _R2O = _Na2O + 0.658 x _K2O ). Of these alkali metal forms, chlorides, carbonates, and sulfates are water-soluble, while silicate glass is sparingly soluble.

The water-soluble salts of alkali metals, such as chlorides, carbonates, and sulfates, are found in large amounts in the fine powder portion of biomass ash, while sparingly soluble silicate glass is found in large amounts in the coarse powder portion of biomass ash.

According to the method for removing alkali metals of the present invention, the concentration of alkali metals contained in biomass ash can be reduced to 2.0 mass% or less, more typically 1.5 mass% or less, calculated as _R2O , making it possible to effectively utilize the biomass ash as a cement raw material, etc. The concentration of alkali metals in biomass ash can be measured by a well-known method, and a preferred example of such a method is one that complies with JIS R 5204 "Method for fluorescent X-ray analysis of cement."

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

Figure 1 is a flow chart showing the steps of the alkali metal removal method according to the present invention. Figure 2 is a block diagram showing an example of an apparatus (hereinafter referred to as "alkali metal removal apparatus") for carrying out the alkali metal removal method shown in Figure 1. In Figure 2, the flows of solids such as biomass ash and liquids such as water are shown by solid lines with arrows, and the flows of gas are shown by dashed lines with arrows. The same applies to Figure 3 described below.

As shown in FIG. 1, the alkali metal removal method according to the present invention includes a classification process S1, a heat treatment process S2, and a water washing process S3.

As shown in FIG. 2, the alkali metal removal device 1 according to the present invention is configured with a classification device 3, a heating device 7, and a water washing device 9.

The processing steps in each step shown in Figure 1 will be described in detail below, with reference to Figure 2 as appropriate.

(Classification process S1)
In the classification process S1, the supplied biomass ash BA1 is separated into a fine powder BA2 containing a large amount of water-soluble alkali metal salts and a coarse powder BA3 containing a large amount of sparingly soluble alkali metal salts, and each is separately recovered. In the alkali metal removal device 1 shown in FIG. 2, the classification process S1 is performed by a classifier 3.

Here, biomass ash fine powder BA2 (hereinafter simply abbreviated as "fine powder BA2") refers to biomass ash with a finer particle size than the determined classification point, and biomass ash coarse powder BA3 (hereinafter simply abbreviated as "coarse powder BA3") refers to biomass ash with a coarser particle size than the classification point. The classification point determined in the classification process 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 this specification, unless otherwise specified, the particle size of biomass ash refers to a measurement value obtained by a laser diffraction particle size distribution measurement method using ethyl alcohol as a solvent. The particle size of commonly available biomass ash varies depending on the type of biomass fuel and the type and operation method of the boiler that burns the biomass, but the _D50 value obtained by the laser diffraction particle size distribution measurement method is 15 μm to 35 μm, and the maximum particle size ( _D100 ) is 150 μm to 1000 μm. The _D50 value means the particle size at 50% cumulative in the volume-based particle size distribution.

The classifier 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. For example, an inertial classifier, a centrifugal classifier, a gravity classifier, etc. can be suitably used. In particular, it is preferable to use a centrifugal air classifier with rotating blades, such as a cyclone air separator or a turbo classifier, because they are good at classifying particles with a particle size of 1 μm or more and 20 μm or less. In the embodiment shown in Figure 2, the classifier 3 is illustrated as being composed of a cyclone air separator.

The classification device 3 may be provided with a storage tank for the biomass ash BA1. In addition, a supply device may be provided for supplying a quantitative amount of the biomass ash BA1 from the storage tank to the classification device 3. These storage tanks and supply devices may be used appropriately depending on the condition of the received biomass ash BA1.

This classification process step S1 corresponds to step (a).

(Heat treatment step S2)
The heat treatment step S2 is a step of heating the coarse powder BA3 obtained by classification in the classification step S1 together with a chlorine source CL. The heat treatment step S2 converts poorly soluble alkali metal salts contained in the coarse powder BA3 into water-soluble alkali metal salts (alkali metal chlorides). In the alkali metal removal device 1 shown in FIG. 2, the heat treatment step S2 is performed by a heating device 7.

The alkali metal removal device 1 shown in FIG. 2 is equipped with 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 suitable materials include waste plastics such as waste polyvinyl chloride that contain at least one organic chlorine in the monomer, and combustible waste that contains inorganic chlorine compounds such as calcium chloride. 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 of chlorine, 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 can be measured by a known method, for example, a method conforming to JIS R 5204 "Method for X-ray fluorescence analysis of cement".

The chlorine source CL is preferably 80 mm or less in size, more preferably 40 mm or less in size, and particularly preferably 10 mm or less in size, from the viewpoint of efficiently volatilizing the alkali metal chloride from the chlorine source CL by forming a good mixed state with the coarse powder BA3 in the heating device 7 and sufficiently volatilizing the chlorine from the chlorine source CL. Note that the size of the chlorine source CL refers to the smallest sieve opening through which the chlorine source CL passes.

From the above viewpoint, a classification device for removing coarse objects from the received chlorine source CL and a crushing and classification device for reducing the coarse objects to a predetermined particle size may be attached upstream of the storage tank attached to the chlorine source supply device 5. These classification devices and crushing and classification devices may be used appropriately depending on the condition of the received chlorine source CL.

The chlorine source supply device 5 is provided with an emission control device such as an emission control valve, making it possible to adjust the amount of chlorine source CL supplied to the heating device 7. Therefore, by appropriately controlling this emission control device, it is possible to appropriately manage the amount of chlorine supplied to the heating device 7.

More specifically, the ratio of the coarse powder BA3 and the chlorine source CL treated in the heat treatment step S2 is preferably set so that the ratio (B/A) of the molar amount (A) of the total alkali metal components in the coarse powder BA3 subjected to the heat treatment step during a unit time to the molar amount (B) of the total chlorine in the chlorine source CL subjected to the heat treatment step during a unit time is 1 or more and 5 or less. The value of the ratio (B/A) is more preferably 2 or more and 5 or less. If the value of the ratio (B/A) is less than 1.5, the amount of chlorine is small, so that a large amount of alkali metal components that cannot react with chlorine may remain among the alkali metal components in the coarse powder BA3. On the other hand, if the value of the ratio (B/A) exceeds 5, the amount of chlorine that volatilizes and dissipates increases, which may accelerate the progression of corrosion of the equipment.

As described above, the heating device 7 heats the coarse powder BA3 and the chlorine source CL together. Specifically, the chlorine source CL is supplied from the chlorine source supply device 5, and the coarse powder BA3 is supplied from the outlet 3b of the classifier 3 to the heating device 7, and the chlorine source CL and the coarse powder BA3 are heated together in the heating device 7. As a result, the alkali metal in the coarse powder BA3 reacts with the chlorine volatilized from the chlorine source CL to produce a water-soluble alkali metal salt.

The heating temperature in the heat treatment step S2 is preferably 650°C to 1200°C, more preferably 800°C to 1200°C, from the viewpoint of efficiently causing chlorination roasting by the alkali metal in the coarse powder BA3 and the chlorine in the chlorine source CL while not melting the coarse powder BA3. If the heating temperature is less than 650°C, the chlorination roasting reaction will be 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 1200°C, partial melting or enlargement of the coarse powder BA3 may occur, reducing the efficiency of production of water-soluble alkali metal salts.

As described below, the more preferable temperature conditions vary depending on the form of the alkali metal contained in the coarse powder BA3. Coarse powder BA3 may contain alkali metals in the form of feldspar, and if the amount of alkali metal present in this form is large, the effect of chlorination roasting may not be sufficient at temperatures of around 800°C, so a temperature of 1000°C to 1200°C is more preferable. However, depending on the amount of potassium feldspar contained in coarse powder BA3, the alkali metal contained in coarse powder BA3 can be efficiently converted to an alkali metal salt even at around 800°C, so the heating temperature may be adjusted appropriately within the range of 800°C to 1200°C.

The heating time in the heat treatment step S2 may be set appropriately within a range of 10 minutes to 2 hours depending on the heating temperature. From the viewpoint of sufficiently reacting the alkali metal in the coarse powder BA3 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 preferable to set the heating time to 30 minutes to 2 hours, and when the heating temperature is 1000°C, it is preferable to set the heating time to 10 minutes to 30 minutes.

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

However, as a result of intensive research by the present inventors, it has been newly discovered that when this heat treatment step S2 is carried out at a high temperature, particularly at 800°C or higher, the alkali metal can be converted to an alkali metal chloride with higher efficiency by setting the atmosphere during heating to a low oxygen concentration. Specifically, the oxygen concentration in the atmosphere is preferably 10% or less, and more preferably 5% or less. The lower limit of the oxygen concentration in the atmosphere is 0%, and is typically a nitrogen atmosphere.

The inventors believe that the reason for this is that when the atmosphere contains a lot of oxygen (e.g., air atmosphere), the reaction of the following formula (1) becomes dominant, and when the atmosphere contains little oxygen (e.g., nitrogen atmosphere), the reaction of the following formula (2) becomes dominant. Note that in the following formulas (1) and (2), _CaCl2 (calcium chloride) is given as an example of the chlorine source CL. As will be described later with reference to the examples, it has been confirmed that the volatilization rate of _CaCl2 is slower than that of _Cl2 (chlorine).
_CaCl2 (s) + 1/ _2O2 (g) → CaO(s) + _Cl2 (g) ... (1)
_CaCl2 (s) → _CaCl2 (g) … (2)

Here, the volatilization of chlorine by the reaction of formula (1) becomes significant when the heating temperature is particularly high, exceeding 850°C, and becomes even more significant when the heating temperature exceeds 1000°C. In other words, when the heat treatment step S2 is performed at a high temperature of 800°C or higher, more typically 1000°C or higher, it is preferable to have an atmosphere with a low oxygen concentration.

In order to efficiently generate the reaction that produces the water-soluble alkali metal salt in the heating device 7, it is desirable to heat the coarse powder BA3 and the chlorine source CL in a state of being thoroughly mixed. From this perspective, the heating device 7 can be configured as an internal combustion rotary kiln. If the firing furnace is a rotary kiln that rotates, it is possible to perform the heat treatment while physically and continuously mixing and stirring the coarse powder BA3 and the chlorine source CL, which are the objects to be heated.

When the heating atmosphere in the heating device 7 (typically a rotary kiln) is the atmosphere G1, the atmosphere G1 is supplied to the heating device 7 as combustion air from the intake fan 33. In the rotary kiln, the atmosphere G1 used as the combustion air for the internal combustion burner 31 by the intake fan 33 flows inside the kiln in a countercurrent direction to the flow of the coarse powder BA3 and the chlorine source CL, and is then discharged outside the kiln as combustion exhaust gas G2.

When the heating atmosphere is a gas with a low oxygen concentration (e.g., nitrogen), as shown in FIG. 3, a gas G1a with a low oxygen concentration is sent from a gas source 34 through an intake fan 33 into the heating device 7. The gas source 34 may be an air separation device that separates oxygen from air, or a gas exhaust path through which exhaust gas from another combustion furnace is discharged. Furthermore, as shown in FIG. 2, the oxygen concentration of the atmosphere in the heating device 7 may be reduced by adjusting the amount of intake air and the amount of fuel burned while air is introduced into the heating device 7 through the intake fan 33.

The heating device 7 is not particularly limited as long as it can heat the mixture of the coarse powder BA3 and the chlorine source CL in the temperature range of 650°C to 1200°C, and a heating furnace such as a fixed furnace, a stoker furnace, a rotary kiln, a fluidized bed furnace, a vertical furnace, or a multi-tier furnace can be used. Among these, the above-mentioned rotary kiln is preferable from the viewpoint of physical stirring.

In addition, since alkali metals and chlorine are both components that tend to volatilize during heat treatment, the combustion exhaust gas G2 may contain alkali metals and chlorine. Therefore, for example, in the flue of the exhaust system of the heating device 7, at locations where the temperature is below the freezing point of the chloride of the alkali metal, precipitation of the chloride may occur. Such chlorides can be recovered and used as fertilizer, etc.

The heating device 7 may also be provided with a storage tank for the supplied coarse powder BA3. Furthermore, a supply device may be provided for supplying a quantitative amount of the coarse powder BA3 from the storage tank to the heating device 7. These storage tanks and supply devices may be used appropriately depending on the state of the supplied coarse powder BA3.

The heating device 7 discharges the heat-treated material P1, which is a mixture of coarse powder BA3 in which sparingly soluble alkali metals have been converted into water-soluble salts, and the incineration residue of the chlorine source CL. The discharged heat-treated material P1 is sent to the water washing device 9.

This heat treatment step S2 corresponds to step (b).

(Crushing process S1a)
As shown in Fig. 4, the coarse powder BA3 classified by the classification process S1 may be subjected to a pulverization process S1a for reducing the particle size, and then sent to a heat treatment process S2. The alkali metal removal device 1 shown in Fig. 3 is a schematic example in which the pulverization process S1a is scheduled to be performed, and the pulverization process S1a is performed by a pulverizer 4.

It is assumed that the coarse powder BA3 contains poorly soluble alkali metal salts evenly throughout. By carrying out this pulverization process S1a before the heat treatment process S2, the exposed area of the alkali metal increases, improving its reactivity with the chlorine contained in the chlorine source CL in the heat treatment process S2, and enabling it to be converted to alkali metal chloride more efficiently. The pulverized coarse powder BA3a obtained by pulverizing the coarse powder BA3 in the pulverization process S1a is subjected to the heat treatment process S2. However, it is optional whether or not this pulverization process S1a is carried out before the heat treatment process S2.

The particle size of the coarsely ground product BA3a after being ground in the grinding process S1a is preferably 5 mm or less, more preferably 4 mm or less, and particularly preferably 3 mm or less. There is no particular lower limit to the particle size of the coarsely ground product BA3a, but it is 1 μm or more from the viewpoint of preventing the coarsely ground product BA3a from being discharged outside the heating furnace of the heating device 7 by the combustion exhaust gas in the above-mentioned heating process S2 executed in the latter stage.

The crushing device 4 desirably crushes the lump-shaped coarse powder BA3 to a particle size of 5 mm or less, and the equipment specifications may be set appropriately according to the properties of the lump-shaped coarse powder BA3. The crushing device 4 may be a combination of multiple devices.

Specifically, the crushing device 4 can be suitably used with a tube mill, a vertical roller mill, a jaw crusher, a gyratory crusher, a cone crusher, an impact crusher, a roll crusher, an aerofoil mill, or the like. When a plurality of these devices are combined to form the crushing device 4, a classifier is provided between each crusher to construct a closed circuit crushing system, thereby efficiently obtaining a coarsely crushed product BA3a with a uniform particle size. In this case, the classifier is not particularly limited as long as it can classify the coarsely crushed product BA3a at a predetermined classification point, and a sieve (in-plane motion sieve, vibrating sieve), a gravity classifier, an inertia force classifier, a centrifugal classifier such as a cyclone, a centrifugal classifier with a rotating blade such as a cyclone air separator, or the like can be suitably used. Among them, a centrifugal classifier with a rotating blade such as a cyclone air separator is preferred because of the simplicity of the equipment and the ease of operation and adjustment. A grinding machine with a built-in classifier or sieve can also be used as the grinding device 4.

This grinding process step S1a corresponds to step (d).

(Water washing process S3)
The water washing process S3 is a process for washing the fine powder BA2 separated and recovered in the classification process S1 and the heat-treated product P1 obtained in the heat treatment process S2 with water. This water washing process S3 dissolves and removes water-soluble alkali metal salts contained in the fine powder BA2 and the heat-treated product P1. In the alkali metal removal device 1 shown in FIG. 2, this water washing process S3 is performed by a water washing device 9.

Water is the preferred solvent used in this water washing process S3.

In the water washing device 9, the fine powder BA2 separated and recovered by the classification device 3 and supplied from the discharge port 3a, and/or the heat-treated material P1 supplied from the heating device 7, are mixed with water W1 to generate slurry Lr1, and the slurry Lr1 is then continuously stirred to dissolve the water-soluble alkali metal salts in the fine powder BA2 and/or the heat-treated material P1 in the 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 material P1, and a supply device 13 for water W1. The water washing device 9 is also provided with a slurry agitator 35 for mixing the fine powder BA2 and/or the heat-treated material P1 with the water W1, and for agitating the slurry Lr1 produced by the mixing. As the slurry agitator 35, for example, a general paddle type or screw type may be used, and in the embodiment shown in FIG. 2, it is provided with an agitator blade.

A crushing device may be provided upstream of the supply hopper 11 to crush large-diameter objects in the received heat-treated object P1 to an appropriate size. This crushing device may be used appropriately depending on the condition of the heat-treated object P1 supplied from the heat treatment process S2.

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. For this reason, room temperature water is used as the solvent in the water washing process S3 in an amount of at least three times, preferably at least four times, and more preferably at least five times the total amount (mass) of the mixture of fine powder BA2 and heat-treated product P1 (hereinafter sometimes referred to as the "water-washed product").

In the water washing process S3, the stirring time of the slurry Lr1 consisting of the washed material and water is preferably 10 minutes or more, more preferably 15 minutes or more, and particularly preferably 20 minutes or more. Usually, water-soluble alkali metal salts are highly soluble in water, so no special conditions are required for stirring the slurry Lr1.

By this water washing process S3, the alkali metals contained in both the fine powder BA2 and the coarse powder BA3, which are obtained by classifying the biomass ash BA1, are dissolved in water. The slurry Lr1 in which the alkali metals are dissolved in water is separated by the solid-liquid separator 17 installed downstream into a solid material (cake C1) that has a reduced moisture content and can be used as a cement raw material, etc., and wastewater W3.

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, piston pump, mono pump, or hose pump may be used.

As the solid-liquid separator 17, a general-purpose filter 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 solid-liquid separator 17 is illustrated as being composed of a filter press.

The solid-liquid separator 17 is equipped with a supply device 15 for washing water W2, which separates the transported slurry Lr1 into a cake C1 (solid phase) of the washed product and wastewater W3 (liquid phase) containing alkali metals. At this time, the cake C1 is separated while being washed with the washing water W2. As the washing water W2, room temperature water may be used in an amount of at least three times, preferably at least four times, and more preferably at least five times the mass of the washed product.

The cake C1 separated by the solid-liquid separator 17 has an alkali metal component concentration reduced to 2.0% by mass or less, more typically 1.5% by mass or less, and can be effectively used as a cement raw material, etc. The alkali metal concentration here refers to an analytical value obtained by a known method, for example, an analytical value obtained by a method conforming to JIS R 5204 "Method of X-ray fluorescence analysis of cement," or an analytical value obtained by ICP atomic emission spectrometry on an acid-digested sample.

This water washing process step S3 corresponds to step (c).

Of the total alkali metal components contained in biomass ash BA1, alkali metal components in the form of water-soluble salts typically account for 25% to 45% of the total, in molar terms, and alkali metal components in the form of sparingly soluble salts typically account for 55% to 75% of the total, in molar terms.

Of the total alkali metal components contained in biomass ash BA1, the total alkali metal components contained in biomass ash with a particle size of 30 μm or less, i.e., fine powder BA2, is 40% to 60% of the total 100% in molar terms, and of that, 70% to 90% are water-soluble alkali metal components.

Therefore, after classifying the biomass ash BA1 into fine powder BA2 and coarse powder BA3 in the classification process S1, the fine powder BA2 is washed with water in the water washing process S3, thereby removing 30% to 50% of the total alkali metal components contained in the biomass ash BA1.

When the classification point of biomass ash BA1 in classification process S1 is set to 10 μm, fine powder BA2 with a particle size of 10 μm or less classified in classification process S1 is washed with water in water washing process S3, thereby removing 20% to 35% of the total alkali metal components contained in biomass ash BA1.

Furthermore, the alkali metal components contained in the coarse powder BA3 in the form of sparingly soluble salts are chlorinated and roasted by heating together with the chlorine source CL, and are converted into water-soluble salts. As a result, most of them are removed by washing with water in the water washing process S3.

Specific test examples are presented below to explain the present invention in more detail, but the present invention is not limited to the aspects of these test examples.

(Verification 1)
Biomass ash BA1 was collected by a dust collector (bag filter) from a biomass power plant (circulating fluidized bed boiler) that uses PKS as the main fuel. Table 1 below shows the chemical composition of biomass ash BA1, with alkali metals obtained by analyzing an acid-decomposed sample by ICP emission spectrometry, and other chemical components obtained by analyzing a pellet sample by X-ray fluorescence spectrometry. Note that " _R2O " in Table 1 indicates the value calculated as the total amount of alkali metal components in this composition by " _R2O = _Na2O + 0.658 x _K2O ", as described above.

Furthermore, when the particle size distribution of the biomass ash BA1 shown in Table 1 was measured based on a laser diffraction/scattering method, the _D10 value was 4.4 μm, the _D50 value was 19.5 μm, and the _D90 value was 63.5 μm.

As the chlorine source CL, crushed waste _polyvinyl chloride that had been completely passed through a sieve with 1 mm mesh was used in an amount such that the ratio of the chlorine content B (mol) in the chlorine source CL to the content A (mol) of the alkali metal component R2O in the biomass ash coarse powder BA3 was B/A = 2.

In the examples, the main operating parameters for the classification process S1, the heat treatment process S2, and the water washing process S3 were set as follows:

(Classification process S1)
Biomass ash BA1 classification point: 10 μm

(Heat treatment step S2)
Heating temperature and heating time for the mixture of coarse powder BA3 and chlorine source CL: 950°C ± 25°C x 15 minutes

(Water washing process S3)
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 Amount of washing water W2 used in solid-liquid separator 17: 4 times the mass of cake C1

As a comparative example, only the water washing treatment step S3 was carried out on biomass ash BA1 of all particle sizes. The operating parameters at this time were set as follows:
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 Amount of washing water W2 used in solid-liquid separator 17: 4 times the mass of cake C1

The total amount of alkali metal components ( _R2O ) contained in the biomass ash after each process was confirmed by ICP atomic emission spectroscopy of the acid decomposition sample. The analysis results are shown in Table 2. The mass ratio in Table 2 indicates the classification ratio (mass %) of fine powder BA2 and coarse powder BA3 relative to 100 mass % of biomass ash BA1.

As can be seen from Table 2, when the water washing treatment process (S3) was simply performed on the whole-grain biomass ash BA1, the proportion of alkali metals contained in the biomass ash BA1 before treatment was 4.3% by mass, whereas the proportion of alkali metals contained in the cake C1 after treatment was 2.8% by mass, a decrease of approximately 35% by mass.

In contrast, according to the alkali metal removal method of the present invention, the proportion of alkali metals contained in the cake C1 after treatment can be reduced to 1.4% by mass simply by heating 70% of the total before washing the entire amount with water, and the proportion of contained alkali metals can be reduced by about 70% by mass compared to the biomass ash BA1 before treatment. This shows that the proportion of alkali metals contained in cake C1 can be significantly reduced compared to the comparative example. In other words, according to the alkali metal removal method of the present invention, it is believed that the poorly soluble alkali metals contained in large amounts in coarse powder BA3 are converted into water-soluble alkali metal salts by chlorination roasting before the water washing process is performed, which allows more alkali metals to be removed than in the comparative example.

In Table 2, the proportion of alkali metal components contained in the fine powder BA2 obtained after the classification process S1 is higher than the proportion of alkali metal components contained in the biomass ash BA1 because the fine powder BA2 contains more alkali metal components than the coarse powder BA3. However, as mentioned above, the alkali metals contained in the fine powder BA2 contain a large amount of water-soluble alkali metal salts, and most of these are removed by the water washing process S3 carried out later.

(Verification 2)
The biomass ash BA1 was subjected to a classification process S1 with a classification point of 10 μm, and the resulting coarse powder BA3 was subjected to a heat treatment process S2 under two different heating conditions, and then a water washing process S3 was carried out.

The type and amount of chlorine source CL added in the heating process S2 was the same as in Verification 1. The conditions for the water washing process S3 were the same as in Verification 1, except that the stirring time was 30 minutes.

Table 3 shows the chemical composition of the biomass ash BA1 as raw powder, the fine powder BA2 obtained in the classification process S1, and the coarse powder BA3. The alkali metals were determined by analysis of the acid-digested samples using ICP atomic emission spectrometry, and the other chemical components were determined by analysis of the pellet samples using X-ray fluorescence spectrometry.

Table 4 also shows the results of XRD analysis for the biomass ash BA1 as the raw powder, the fine powder BA2 obtained in the classification process S1, and the coarse powder BA3. In Table 4, the results of the XRD analysis indicate that the substance was present, "○", that a trace amount of the substance was present, "△", and that no substance was present at all, "×".

Table 5 shows the results obtained in this verification experiment.

In Table 5, the K removal rate was calculated using the following formula (3). The calculation method is the same for other verifications described later.
K removal rate = [d1 - {(1 - d2) - d3} x d4] / d1 ... (3)
Here, the symbols in the formula (3) have the following values.
d1: Content (concentration) of K (potassium) contained in the alkali metal-containing material (coarse biomass ash powder BA3; in Verification 4 described below, granite soil) before heat treatment
d2: Weight reduction rate of the alkali metal-containing material due to the heat treatment step S2; d3: Weight reduction rate of the alkali metal-containing material due to the water washing treatment step S3; d4: Content (concentration) of K contained in the cake C1 obtained after solid-liquid separation.

The K content d1 of the coarse biomass ash powder BA3 used in the experiment before treatment was 3.4%.

The results in Table 5 suggest that by using a nitrogen atmosphere and increasing the heating temperature in the heat treatment step S2, K (potassium) as an alkali metal can be efficiently removed.

One of the reasons for this is thought to be that coarse powder BA3 contains more K (potassium) in the form of feldspar (potassium feldspar) than fine powder BA2, as shown in Table 4. Other than biomass ash, there is also granite soil which contains a lot of potassium feldspar. As shown in the results of verification 4 described below, it is also found that the K removal rate can be increased for granite soil by increasing the heating temperature to 1000°C or higher.

Biomass ash BA1 is generally obtained by incinerating biomass in a fluidized bed furnace. Since the fluidized sand used in this fluidized bed is contained in the biomass ash BA1, it is presumed that potassium feldspar derived from the fluidized sand is mixed into the biomass ash BA1. Since the particle size of the fluidized sand is relatively large, it is easily distributed to the coarse powder BA3 side after the classification process S1 (see Table 4).

(Verification 3)
The effect of temperature when alkali metal-containing material including potassium feldspar is heated with a chlorine source CL was examined using decomposed granite soil. Table 6 shows the chemical composition of the decomposed granite soil used in the examination, obtained by analyzing the alkali metals by ICP atomic emission spectrometry of an acid digested sample, and by analyzing the pellet sample by X-ray fluorescence spectrometry for other chemical components.

Table 7 shows the results of the XRD analysis of this sand. Table 7 confirms that the sand also contains potassium in the form of feldspar (potassium feldspar), just like the biomass ash coarse powder BA3. In Table 7, the results of the XRD analysis indicate that potassium was present in large quantities with a "◎", that it was present with a "○", and that it was present in trace amounts with a "△".

The above-mentioned masami soil as an alkali metal-containing material was mixed with a chlorine-containing material ( _CaCl2 reagent powder) having twice the molar amount of potassium contained (mol) as an alkali metal component in the masami soil, and then the mixture was left to stand in a thermostatic electric furnace for 60 minutes with the temperature and atmosphere set to the conditions shown in Table 7 to obtain a heat-treated product P1. Thereafter, water washing and solid-liquid separation were performed under the same conditions as in Verification 1 to obtain a cake C1.

The content of alkali metal components in the resulting cake C1 was determined by analyzing the acid-digested sample using ICP atomic emission spectrometry. The results are shown in Table 8 and Figure 5. The K content d1 of the granite before treatment was 3.6%.

In Table 8, level codes such as #B11 and #B21 are used to identify the test conditions, and the alphabet following the # in the code indicates the type of sample used as the alkali metal-containing material, with "B" corresponding to granite. In Table 9 described below, level codes such as #A11 and #A21 are used, and the alphabet "A" following the # in the code indicates that the sample used as the alkali metal-containing material is biomass ash (coarse powder BA3).

The numbers (1, 2) displayed after the alphabet indicate the atmosphere during heating, with "1" corresponding to an oxygen concentration of 15% or more, including air, and "2" corresponding to an oxygen concentration of 10% or less, including nitrogen. The last number corresponds to an identifier for distinguishing between them. The same applies to Table 9 below.

Table 8 shows the comparative results of the amount of potassium removed when the heating temperature was changed from 800°C to 1200°C for the cases where the amount of chlorine source CL mixed was the same when using decomposed granite soil as the alkali metal-containing material, and the heating atmosphere was air (levels #B11 to #B14) and nitrogen (levels #B21 to #B24). Figure 5 is a graph of the results of Table 8.

Comparing level #B12 with level #B22, level #B13 with level #B23, and level #B14 with level #B24, it can be seen that when the heating temperature is 1000°C or higher, the potassium removal rate is higher in a nitrogen atmosphere than in an air atmosphere, even if the heating temperature and the mixed amount of chlorine source CL are the same.

In contrast, when the heating temperature is 800°C, comparing level #B11 and level #B21, no substantial difference in the potassium removal rate is observed between air and nitrogen atmospheres. This result is presumably due to the fact that in the case of granite, potassium is present in large amounts in the form of potassium feldspar, and so the reaction rate with chlorine is slow at 800°C, resulting in no difference in the amount of reaction due to the atmosphere.

In other words, from the results of Table 8 and Figure 5, when using granite as the material from which alkali metals are to be removed (alkali metal-containing material), in other words when using a material that contains a lot of potassium in the form of potassium feldspar, it is preferable to set the heating temperature to 1000°C or higher and to set the heating atmosphere to a low oxygen concentration.

The results of this verification 3 are consistent with the results of verification 2. That is, in verification 2, when the nitrogen atmosphere was used and the heating temperature was set to 1000°C (level #2), the potassium removal rate was improved compared to when the air atmosphere was used and the heating temperature was set to 950°C (level #1). The reason for this is thought to be that, as shown in Table 4, coarse powder BA3 contains a certain amount of potassium in the form of potassium feldspar.

(Verification 4)
From the results of verification 3, the reason why the removal rate of alkali metals (particularly potassium) was improved by setting the heating temperature to a high temperature and creating an atmosphere with a low oxygen concentration was verified.

Calcium chloride, an example of a chlorine source CL, was placed in a thermogravimetric differential thermal analyzer (TG-DTA) and the change in weight was measured while changing the temperature in two patterns, air and nitrogen atmosphere. The results are shown as a TG curve in Figure 6. In Figure 6, the horizontal axis indicates temperature [°C] and the vertical axis indicates the ratio of the weight loss (weight after treatment - weight before treatment) to the weight of the sample before treatment.

According to Figure 6, when heated to around 800°C, there is almost no weight loss due to temperature increase. However, when the temperature exceeds 850°C, the rate of weight loss due to temperature increase is higher in an air atmosphere than in a nitrogen atmosphere. In particular, when calcium chloride is heated in a nitrogen atmosphere within the range of 800°C to 1300°C, the amount of weight loss is less than in an air atmosphere. It has been confirmed that even in the case of a nitrogen atmosphere, the rate of weight loss increases as the temperature increases under temperature conditions exceeding 1200°C.

When calcium chloride is heated in an atmosphere containing a lot of oxygen, such as air, the reaction of formula (1) above becomes dominant, and it is believed that the weight is reduced by the evaporation of chlorine.
_CaCl2 (s) + 1/ _2O2 (g) → CaO(s) + _Cl2 (g) ... (1)

On the other hand, when calcium chloride is heated in an atmosphere with a low oxygen concentration or without oxygen (here, a nitrogen atmosphere), the reaction of the above formula (2) becomes dominant, and it is considered that the calcium chloride itself, which is the object to be heated, volatilizes, resulting in a weight loss.
_CaCl2 (s) → _CaCl2 (g) … (2)

The results of FIG. 6 suggest that the volatilization rate of chlorine is faster than that of calcium chloride. In other words, assuming that the mixture of the chlorine source CL and the coarse powder BA3 (or its pulverized product BA3a) is heated at about 1000° C. in the heat treatment step S2, when the heating furnace of the heating device 7 is in an air atmosphere, chlorine is easily volatilized from the chlorine source CL, and the reaction efficiency with the alkali metal contained in the coarse powder BA3 is reduced. On the other hand, when the heating furnace of the heating device 7 is in a nitrogen atmosphere, the volatilization of chlorine is suppressed, and the contact probability between the chlorine contained in the chlorine source CL and the alkali metal contained in the coarse powder BA3 can be maintained high, and it can be seen that the alkali metal chloride can be generated with high efficiency. In this verification, the case where CaCl ₂ (calcium chloride) is used as the chlorine source CL is taken up, but the same results can be obtained even when MgCl ₂ (magnesium chloride) or BaCl ₂ (barium chloride) is used.

(Verification 5)
The effect of the oxygen concentration in the heating atmosphere was examined. Specifically, for the same coarse powder BA3 as in Examination 2, the heating temperature and the mixed amount of the chlorine source CL were kept the same (heating temperature 800°C, Cl/K=1), and the amount of potassium removed was compared when the oxygen concentration in the heating atmosphere was changed within the range of 0% to 21%. The results are shown in Table 9 and FIG. 7. FIG. 7 is a graph of the results in Table 9.

In Table 9, an oxygen concentration of 0% in the atmosphere corresponds to a nitrogen atmosphere, and an oxygen concentration of 21% in the atmosphere corresponds to an air atmosphere.

Figure 7 shows that when the oxygen concentration in the atmosphere is changed within the range of 0% to 10%, the K removal rate decreases almost linearly as the oxygen concentration increases. In contrast, when the oxygen concentration exceeds 10%, the degree of decrease in the K removal rate is mitigated. In particular, when the oxygen concentration is 15% or higher, there is no significant difference in the K removal rate value compared to the air atmosphere.

In other words, the results of Table 9 and Figure 7 show that by performing heat treatment with an oxygen concentration of 10% or less, the potassium removal rate can be increased even if the amount of chlorine source CL used in the heat treatment step S2 is the same. This result suggests that by lowering the oxygen concentration in the atmosphere, the reaction of formula (2) becomes more dominant than the reaction of formula (1) above, and as a result, the progress of chlorine volatilization is suppressed, the probability of contact between chlorine and the alkali metal contained in the coarse powder BA3 is maintained at a high level, and alkali metal chlorides can be produced with high efficiency.

In this verification 5, the heating temperature was 800°C. However, in consideration of the results of verification 2 (see Table 5) and verification 3 (see Table 8 and Figure 5), it is suggested that when the coarse powder BA3 is heated together with the chlorine source CL in the heat treatment step S2, the potassium removal rate can be further increased by setting the heating temperature to 1000°C or higher and the oxygen concentration of the atmosphere to 10% or less.

1: Alkali metal removal device 3: Classification device 3a: Discharge outlet 3b: Discharge outlet 4: Crushing device 5: Chlorine source supply 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 stirring device BA1: Biomass ash BA2: Fine powder BA3: Coarse powder BA3a: Coarse powder crushed material C1: Cake CL: Chlorine source G1: Air G1a: Gas G2: Combustion exhaust gas Lr1: Slurry P1: Heat treatment material W1: Water W2: Washing water W3: Wastewater

Claims (13)

A method for removing alkali metals from fly ash of woody biomass combustion ash, comprising the steps of:
(a) classifying the fly ash into fine powder and coarse powder;
A step (b) of heating the coarse powder obtained in the step (a) together with a chlorine source to obtain a heat-treated product;
A method for removing an alkali metal, comprising: a step (c) of washing with water the fine powder obtained in the step (a) and the heat-treated product obtained in the step (b). The method for removing alkali metals according to claim 1, characterized in that step (a) is a step of classifying the particles with a classification point of 5 μm or more and 30 μm or less. The method for removing alkali metals according to claim 1 or 2, characterized in that step (b) is a step of heating at a temperature of 650°C or more and 1200°C or less. The method for removing alkali metals according to any one of claims 1 to 3, characterized in that step (b) is a step of heating in an atmosphere with an oxygen concentration of 10% or less. The method for removing alkali metals according to any one of claims 1 to 4, characterized in that the chlorine source used in step (b) includes waste plastics and combustible waste mixed with inorganic chlorine. The method for removing alkali metals according to any one of claims 1 to 5, characterized in that the chlorine source used in step (b) has a size of 80 mm or less. The method for removing alkali metals according to any one of claims 1 to 6, characterized in that step (b) is a step of heating a mixture of the coarse powder and the chlorine source in which the ratio (B/A) of the molar amount (B) of the total chlorine in the chlorine source to the molar amount (A) of the total alkali metal components in the coarse powder is in the range of 1 to 5. The step (d) includes pulverizing the coarse powder obtained in the step (a) to obtain a pulverized coarse powder,
The method for removing an alkali metal according to any one of claims 1 to 7, wherein the step (b) is a step of heating the coarsely pulverized product obtained in the step (d) together with the chlorine source. An apparatus for removing alkali metals from fly ash of woody biomass combustion ash, comprising:
A classifier for classifying the fly ash into fine powder and coarse powder;
a heating device for heating the coarse powder obtained by the classifier together with a chlorine source to obtain a heat-treated product;
An alkali metal removal apparatus comprising a water washing device for washing with water the fine powder obtained by the classifying device and the heat-treated product obtained by the heating device. The alkali metal removal device according to claim 9, characterized in that the classification device is composed of a centrifugal air classifier with rotating blades. The alkali metal removal device according to claim 9 or 10, characterized in that the heating device is composed of a rotary kiln. The alkali metal removal device according to any one of claims 9 to 11, characterized in that it is provided with a gas source for introducing combustion gas having an oxygen concentration of 10% or less into the heating device. A crushing device is provided for crushing the coarse powder obtained by the classifying device,
13. The alkali metal removal apparatus according to claim 9, wherein the heating device heats the coarse powder pulverized by the pulverizer together with the chlorine source.

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