JP2022135387A - Alkali metal-containing matter treatment method, and alkali metal-containing matter treatment system - Google Patents

Abstract

To provide an alkali metal-containing matter treatment method which can efficiently remove alkali metal from an alkali-metal containing matter by a method different from chlorination roasting.SOLUTION: An alkali metal-containing matter treatment method includes a step (a) of adding water to an alkali metal-containing matter and obtaining a slurry, a step (b) of adjusting a relation between a pH and an oxidation reduction potential (ORP) of the slurry so as to satisfy the following expression (1), a step (c) of eluting alkali metal contained in the alkali metal-containing matter in the slurry during or after execution of the step (b) into a liquid phase in the slurry, and a step (d) of solid-liquid separating the slurry after execution of the step (b) and the step (c), and obtaining a cake whose percentage content of the alkali metal is reduced compared to the alkali metal-containing matter. Expression (1): (ORP(mV))≤28×(pH)-575. In the expression (1), a range of the pH is 10≤pH≤14.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for treating alkali metal inclusions, and more particularly to a method for removing alkali metals from clay substitutes for coal ash. The invention also relates to a treatment system for alkali metal inclusions suitable for carrying out this method.

In recent years, in view of the impact on global warming, there is a trend to reduce the utilization rate of coal-fired power plants, and a decrease in the amount of coal ash generated is expected. For this reason, it is expected that there will be a shortage of coal ash for use as a raw material for cement, and there is a need to secure substitutes for clay to replace coal ash.

However, many clay substitutes other than coal ash contain high concentrations of alkali metals. When a large amount of alkali metal is contained in cement, alkali-aggregate reaction or the like occurs, so alkali metal is generally regarded as a repellent component for cement. Therefore, in order to use a clay substitute other than coal ash as a cement raw material to replace coal ash, it is necessary to remove alkali metals, and the development of removal technology is underway (for example, patent documents 1, see Patent Document 2).

JP-A-2003-39038 JP-A-2004-59754

Examples of clay substitutes other than coal ash include combustion ash generated by combustion of woody biomass (hereinafter sometimes referred to as "woody biomass ash"), construction soil, recycled fine powder of waste concrete, and the like. These clay substitutes have a high content of alkali metals, especially potassium, compared to coal ash, refuse incineration ash, and the like. Therefore, in order to utilize these clay substitutes as raw materials for cement, it is necessary to remove alkali metals efficiently.

By the way, as described in Patent Document 1 and Patent Document 2, conventionally, as a method for removing alkali metals from an alkali metal-containing material, the alkali metal-containing material is heated together with the chlorine-containing material to remove the alkali metal-containing material from the alkali metal-containing material. There is known a method (so-called "chlorination roasting") of changing the alkali metal contained in to a water-soluble salt (alkali metal chloride). However, according to this method, since heat treatment at high temperature is required, the treatment for removing the alkali metal is very costly. In addition, since CO ₂ is emitted with heating, it is preferable to establish a method for removing alkali metals by a method different from chlorination roasting from the viewpoint of global warming prevention.

In view of the above problems, the present invention provides a method and treatment for an alkali metal-containing material that makes it possible to efficiently remove the alkali metal from the alkali metal-containing material while using a method different from chlorination roasting. The purpose is to provide a system.

The method for treating an alkali metal-containing material according to the present invention comprises:
a step (a) of adding water to the alkali metal-containing material to obtain a slurry;
a step (b) of adjusting the relationship between the pH of the slurry and the ORP so that the relationship between the pH of the slurry and the oxidation-reduction potential (ORP) satisfies the following formula (1);
a step (c) of eluting the alkali metal contained in the alkali metal-containing substance in the slurry into a liquid phase in the slurry during or after the step (b);
a step (d) of solid-liquid separating the slurry after the step (b) and the step (c) are performed to obtain a cake having an alkali metal content lower than that of the alkali metal-containing material. It is characterized by
(ORP (mV)) ≤ 28 x (pH) - 575 (1)
However, in the formula (1), the range of pH is 10≤pH≤14.

As a result of extensive research by the present inventors, a slurry obtained by adding water to an alkali metal-containing material has a pH range of 10 ≤ pH ≤ 14, and the relationship between pH and ORP is expressed by the above formula (1). It was newly discovered that the alkali metal contained in the alkali metal-containing substances in the slurry can be efficiently eluted by placing the slurry in an environment that satisfies the conditions. In other words, according to the above method, there is no need to heat at a high temperature of 500 ° C to 1000 ° C like conventional chlorinated roasting, so the running cost can be reduced and it can contribute to the suppression of global warming. .

Since the cake obtained by the above method has a significantly lower alkali metal content than the alkali metal-containing material before treatment, it can be effectively used as a raw material for cement in place of coal ash.

The step (b) may be a step of adjusting the pH and ORP of the slurry so that the relationship between the pH and ORP of the slurry satisfies the following formula (2).
(ORP (mV)) ≤ -55 x (pH) + 340 (2)
However, in the formula (2), the range of pH is 11≤pH≤14.

By placing the slurry in an environment that satisfies the condition of the formula (2), it becomes possible to elute a larger amount of the alkali metal into the liquid phase in the step (c). Details are described below with reference to examples in the Detailed Description section.

The step (b) may include adding at least one of a pH adjuster and an ORP adjuster to the slurry.

Further, the step (b) is
A step (b1) of measuring the pH and ORP of the slurry;
When the relationship between the slurry pH and ORP measured in the step (b1) does not satisfy the formula (1), the above A step (b2) of adding at least one of a pH adjuster and an ORP adjuster to the slurry may be included.

In the above, the pH adjuster may contain one or more selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, citric acid, sodium hydroxide, potassium hydroxide, and calcium hydroxide. Also, the ORP regulator may contain one or more selected from the group consisting of sodium hydrogen sulfide and sodium sulfide.

In the method for treating an alkali metal-containing material, the wastewater obtained by solid-liquid separation of the slurry in the step (d) is treated in the step (a), the step (b), and the step (c). It may be reused when executing at least one of the steps.

The waste water collected through step (d) contains alkali metal components eluted from the alkali metal-containing substances, but can be reused because it has a suitable oxidation-reduction potential (ORP).

The step (c) may include a step of stirring the slurry while maintaining the temperature of the slurry at 5°C to 60°C.

By stirring under this temperature condition, the alkali metal contained in the alkali metal-containing material can be efficiently eluted into the liquid phase.

The alkali metal-containing material may contain at least one selected from the group consisting of fly ash of woody biomass combustion ash, bottom ash of woody biomass combustion ash, construction soil, and recycled fine powder of waste concrete. .

Since these alkali metal-containing substances contain water-insoluble alkali metals, the alkali metals cannot be sufficiently removed by simply washing with water. However, by treating with the above method, even water-insoluble alkali metals can be efficiently eluted into the liquid phase of the slurry, so that the subsequent solid-liquid separation process reduces the content of alkali metals. You can get a cake made with

The method for treating the alkali metal-containing material may include a step (e) of pulverizing the alkali metal-containing material before performing the step (a). Through this step (e), the powder is pulverized to a particle size of, for example, 5 mm or less.

It is assumed that the alkali metal-containing material contains the alkali metal evenly throughout. As in the above method, by performing the pulverization step (e) before the step (a) of adding water, the exposed area of the alkali metal increases, so in the elution step (c), the alkali metal-containing material in the slurry Alkali metal contained can be eluted with high efficiency. In this specification, the term "particle size" refers to the minimum opening of a sieve through which an object passes.

The method for treating the alkali metal-containing material may have a step (f) of preliminarily washing the alkali metal-containing material with water before performing the step (a).

According to this method, when a soluble alkali metal is contained in the alkali metal-containing material, the soluble alkali metal can be removed in the preceding stage of slurrying, so that the removal rate of the alkali metal can be further increased.

In addition, the system for treating alkali metal-containing substances according to the present invention includes:
a reactor for slurrying the contained alkali metal inclusions;
an adjusting device for adjusting the relationship between the pH and the ORP of the slurry contained in the reaction tank so that the relationship between the pH and the oxidation-reduction potential (ORP) of the slurry satisfies the following (1);
and a solid-liquid separator for solid-liquid separation of the slurry discharged from the reaction tank.
(ORP (mV)) ≤ 28 x (pH) - 575 (1)
However, in the formula (1), the range of pH is 10≤pH≤14.

According to the above-described treatment system, alkali metals can be efficiently removed from alkali metal-containing substances, particularly those containing water-insoluble alkali metals, without heat treatment at high temperatures.

The adjusting device is configured to be able to introduce at least one of a pH adjusting agent and an ORP adjusting agent into the slurry contained in the reaction tank,
a measuring device for measuring the pH and ORP of the slurry contained in the reaction tank;
The pH adjuster added to the slurry so that the relationship between the pH and ORP of the slurry satisfies the above (1) by controlling the adjustment device based on the measurement result of the measurement device. and a control device that changes the amount of at least one of the ORP regulators.

According to the above configuration, the amount of at least one of the pH adjuster and the ORP adjuster is automatically adjusted according to the pH and ORP values of the slurry. As a result, it is possible to prevent excessive cost from using chemicals for pH adjustment or ORP adjustment.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to perform the process which reduces the content rate of an alkali metal with respect to an alkali metal containing material, without heat-processing at high temperature of several hundred degrees C or more.

BRIEF DESCRIPTION OF THE DRAWINGS It is a flowchart which shows typically the procedure of the processing method of the alkali-metal containing material which concerns on this invention. 2 is a block diagram schematically showing an example of a processing system that implements the method shown in FIG. 1; FIG. 1. It is a flowchart which shows typically an example of the detailed processing procedure of water washing processing process S2 in FIG. 4 is another flow chart schematically showing the procedure of the method for treating an alkali metal-containing material according to the present invention. FIG. 2 is a diagram showing the relationship between pH and oxidation-reduction potential (ORP) showing the applicable range of the present invention.

The alkali metal-containing material to be treated to which the present invention is applied is not particularly limited as long as it contains an alkali metal component at a high concentration. Examples include fly ash of woody biomass ash and Examples include bottom ash, construction soil, and recycled fine powder of waste concrete.

For example, woody biomass ash contains alkali metals (Na, K) as chlorides, carbonates, sulfates, silicate glasses, and is converted to R ₂ O (R ₂ O = Na ₂ O + 0.658 × K ₂ O ), the fly ash of woody biomass ash contains about 3% to 50% by weight, and the bottom ash of woody biomass ash contains about 3% to 20% by weight.

In addition, the recycled fine powder of construction soil and waste concrete contains about 2% to 8% by mass of alkali metals (Na, K) in terms of R ₂ O.

According to the present invention, the concentration of the alkali metal component contained in the alkali metal-containing material as described above is reduced to 2.5% by mass or less, more typically 2.0% by mass or less in terms of R ₂ O. can be reduced to And this can be effectively utilized, for example, as a raw material for cement. The alkali metal concentration in the alkali metal-containing material can be measured by a well-known method, and a preferred example thereof is a method based on JIS R 5204 "Method for fluorescent X-ray analysis of cement".

Hereinafter, the present invention will be described more specifically with reference to the drawings. However, the present invention is not limited to the embodiments described with these drawings.

FIG. 1 is a flow chart schematically showing the procedure of the method for treating an alkali metal-containing material according to the present invention. FIG. 2 is a block diagram schematically showing an example of a system (hereinafter referred to as "processing system 1") that implements the method shown in FIG.

The method shown in FIG. 1 includes a pulverization treatment step S1, a water washing treatment step S2 and a solid-liquid separation treatment step S3. Further, as shown in FIG. 2, the processing system 1 for carrying out the method shown in FIG. be done. As will be described later, the pulverizing step S1 can be omitted as appropriate, and in this case, the processing system 1 does not have to include the pulverizing device 6.

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

(Pulverization treatment step S1)
The pulverization treatment step S1 is a step of pulverizing the supplied solid alkali metal-containing material A1 into a size that can be processed more efficiently in the subsequent steps S2 and S3. In the processing system 1 shown in FIG. 2, the pulverization processing step S1 is performed by the pulverizer 6. As shown in FIG.

Specifically, the particle size of the ground material containing alkali metal A2 obtained through the grinding treatment step S1 is preferably 5 mm or less, more preferably 4 mm or less, and particularly preferably 3 mm or less. Although the lower limit of the particle size of the pulverized material containing alkali metal A2 is not particularly limited, it is 5 μm or more from the viewpoint of the energy and cost required for pulverization. As described above, the "particle diameter" in this specification refers to the minimum opening of the sieve through which the target material (here, the pulverized material containing alkali metal A2) passes.

The pulverizer 6 preferably pulverizes the lump-like alkali metal-containing material A1 so that the particle size becomes 5 mm or less, and the equipment specifications may be appropriately set according to the properties of the lump-like alkali metal-containing material A1. . The crushing device 6 may be a combination of multiple devices.

Specifically, as the crushing device 6, a tube mill, a vertical roller mill, a jaw crusher, a gyratory crusher, a cone crusher, an impact crusher, a roll crusher, an aerofol mill, or the like can be suitably used. When a plurality of these devices are combined to form the pulverizer 6, a classifier is installed between each pulverizer to construct a closed-circuit pulverization system, whereby pulverized alkali metal-containing material A2 having a uniform particle size is produced. can be obtained efficiently. The classifier in this case is not particularly limited as long as it can classify the pulverized material containing alkali metal A2 at a predetermined classification point. A classifier, a centrifugal classifier such as a cyclone, and a centrifugal classifier with rotating blades such as a cyclone air separator can be preferably used. Among them, a centrifugal classifier with rotating blades such as a cyclone air separator is preferable because of the simplicity of equipment and ease of operation and adjustment. As the pulverizer 6, a pulverizer with a built-in classifier or sieve mesh can also be used.

In addition, when the supplied solid alkali metal-containing material A1 satisfies the above preferable particle size in the physical state, the pulverization treatment step S1 can be omitted. In FIG. 1, both the case where the alkali metal-containing material A1 is sent to the washing treatment step S2 after the crushing treatment step S1 and the case where it is sent directly to the washing treatment step S2 without going through the crushing treatment step S1 are schematically shown. Illustrated. In FIG. 2, the supplied alkali metal-containing material A1 is pulverized in the pulverizer 6 and the pulverized alkali metal-containing material A2 obtained is sent to the reaction tank 2, and the case where the supplied alkali metal-containing material A1 is sent directly to the reaction tank 2, both of which are shown schematically.

This crushing treatment step S1 corresponds to step (e).

(Water washing process S2)
The water washing step S2 is a step of slurrying the alkali metal-containing material A1 or the ground alkali metal-containing material A2 under predetermined pH/oxidation-reduction potential (ORP) conditions. In the treatment system 1 shown in FIG. 2 , the water washing treatment step S2 is performed in the reaction tank 2 . To avoid complication, the alkali metal-containing material A1 and the pulverized alkali metal-containing material A2 introduced into the reaction vessel 2 are hereinafter representatively referred to as "alkali metal-containing material A1".

FIG. 3 is a flow chart schematically showing an example of a detailed processing procedure of this water washing processing step S2. Hereinafter, the contents of the water washing treatment step S2 will be described in detail while also referring to the flowchart of FIG.

(Step S21)
Alkali metal-containing material A1 and water W1 are introduced into reaction vessel 2 and stirred to form slurry Lr1. As shown in FIG. 2, the reaction tank 2 is preferably provided with a stirring blade 21, and the stirring blade 21 may be used for stirring. As the stirring blade 21, for example, a general screw type one can be used.

Industrial water (fresh water) is preferable as the water W1. The amount of water W1 to be introduced is at least 3 times the mass of the alkali metal-containing material A1, preferably at least 4 times, more preferably at least 5 times.

This step S21 corresponds to step (a). Note that the stirring process may be continuously performed during steps S22 to S25, which will be described later.

(Step S22)
The pH and ORP of the slurry Lr1 in the reaction tank 2 are measured. This measurement result is transmitted to the control device 5 .

In the example shown in FIG. 2, the reaction tank 2 is equipped with a pH measuring device 22 and an ORP measuring device 23, and these measuring devices are configured to continuously measure the pH and ORP of the slurry Lr1. there is As the ORP measuring device 23, a known measuring device may be used, and it is particularly preferable to use a measuring device for high-concentration suspension. Incidentally, the pH measuring device 22 and the ORP measuring device 23 may be integrated.

However, since the pH of the slurry Lr1 usually does not change greatly, it does not have to be measured continuously like the ORP. For example, the pH measuring device 22 may measure the pH at a predetermined timing (for example, immediately after the slurry Lr1 is homogenized) and transmit the result to the control device 5.

This step S22 corresponds to step (b1).

(Step S23)
In the controller 5, it is confirmed whether the relationship between the pH of the slurry Lr1 and the ORP satisfies the above formula (1). Formula (1) is shown again below.
(ORP (mV)) ≤ 28 x (pH) - 575 (1)
However, in the formula (1), the range of pH is 10≤pH≤14.

(Step S24)
When the controller 5 confirms that the relationship between the pH of the slurry Lr1 and the ORP does not satisfy the above formula (1) (No in step S23), the pH or ORP in the slurry Lr1 is adjusted. Specifically, at least one of the ORP adjuster α1 and the pH adjuster α2 is added to the slurry Lr1 from the adjustment device 3 under control based on a signal from the control device 5 .

In the example of FIG. 2, the adjusting device 3 includes an ORP adjusting agent adding device 3a and a pH adjusting agent adding device 3b. Based on the signal from the control device 5, the adjustment device 3 supplies a predetermined amount of the ORP adjuster α1 from the ORP adjuster addition device 3a into the reaction tank 2 and/or supplies the reaction tank from the pH adjuster addition device 3b. 2 with the required amount of pH adjuster α2.

Sodium hydrogen sulfide, sodium sulfide, or the like can be used as the ORP adjuster α1. Hydrochloric acid, nitric acid, sulfuric acid, citric acid, sodium hydroxide, potassium hydroxide, calcium hydroxide, or the like can be used as the pH adjuster α2. Two or more kinds of materials may be used for each of the ORP adjuster α1 and the pH adjuster α2.

By introducing the ORP adjuster α1 and/or the pH adjuster α2 into the slurry Lr1, the ORP and/or pH of the slurry Lr1 fluctuate. As a result, the relationship between the pH of the slurry Lr1 and the ORP is adjusted.

This step S24 corresponds to the step (b), more specifically to the step (b2).

After the ORP adjuster α1 and/or the pH adjuster α2 have been introduced into the slurry Lr1 in step S24, the process returns to step S22 to measure the pH and ORP of the slurry Lr1 in the reaction tank 2. S23 verifies whether or not the relationship between the pH of the slurry Lr1 and the ORP satisfies the formula (1).

When the slurry Lr1 is produced using general biomass ash as the alkali metal-containing material A1, its oxidation-reduction potential (ORP) is about -50 mV and its pH is about 10. Therefore, it is usually necessary to add at least ORP adjuster α1.

(Step S25)
When the controller 5 confirms that the relationship between the pH of the slurry Lr1 and the ORP satisfies the above formula (1) (Yes in step S23), the slurry Lr1 is stirred until a predetermined stirring time is reached while maintaining this relationship. is stirred.

The ORP of the slurry Lr1 is more variable than the pH, and there is a possibility that the ORP will fluctuate during stirring and will not satisfy the above formula (1). Therefore, steps S22 to S24 may be repeated until the stirring time elapses so that the relationship between pH and ORP satisfies the formula (1).

However, as long as the relationship between pH and ORP satisfies the formula (1), it is preferable not to excessively decrease ORP due to the cost of using the ORP adjuster α1. As an example, the lower limit of ORP is preferably about -700 mV, more preferably about -600 mV, and particularly preferably about -500 mV.

While maintaining the relationship between the pH of the slurry Lr1 and the ORP in the range that satisfies the formula (1), the stirring of the slurry Lr1 is continued until the predetermined stirring time is reached, so that the alkali metal-containing material A1 in the slurry is The contained alkali metal is efficiently eluted into the liquid phase in the slurry. That is, this step S25 corresponds to step (c). The fact that the alkali metal can be efficiently eluted by maintaining the relationship between the pH of the slurry Lr1 and the ORP in the range that satisfies the formula (1) will be described later with reference to Examples.

Here, the stirring time required for the elution of the alkali metal is preferably 30 minutes or more, particularly preferably 45 minutes or more, in order to promote the elution of the alkali metal.

The slurry Lr1 is preferably maintained at a predetermined temperature during the stirring step of the slurry Lr1. For example, as shown in FIG. 2, the reaction tank 2 is provided with a thermometer 24 and a heating facility 25, and the temperature of the slurry Lr1 measured by the thermometer 24 is controlled by the heating facility 25. As the heating equipment 25, for example, equipment that uses an air diffuser to supply the high-temperature gas G1 such as the exhaust gas into the slurry Lr1, general low-frequency induction heating equipment, or the like can be used. In the former case, high-temperature exhaust gas from the cement manufacturing facility 11 can be suitably used as the high-temperature gas G1.

More specifically, as shown in FIG. 2, the controller 5 controls the heating equipment 25 based on the signal from the thermometer 24 to maintain the temperature of the slurry Lr1 at a predetermined temperature. This is for further promoting the elution of alkali metals. The temperature is preferably 5°C to 60°C, particularly preferably 25°C to 60°C.

(Solid-liquid separation treatment step S3)
Slurry Lr1 in which the alkali metal is dissolved in water in the water washing step S2 is effectively reduced in water content by the solid-liquid separator 4 installed in the subsequent stage, and solid matter ( It is separated into cake C1) and waste water W2. The moisture content of the cake C1 separated in this solid-liquid separation treatment step S3 is 30% by mass to 70% by mass in order to prevent the alkali metal eluted into the liquid phase of the cake C1 from remaining together with the liquid phase. preferably.

When the slurry Lr1 is transported to the solid-liquid separation device 4, a general-purpose slurry transport device (not shown) such as a centrifugal pump for slurry, a piston pump, a mono pump, and a hose pump may be used.

As the solid-liquid separation device 4, general-purpose filtering devices such as a filter press, a pressurized leaf-shaped filtering device, a screw press, a belt press, and a belt filter may be used.

The solid-liquid separation device 4 shown in FIG. 2 is provided with a water washing device 4a for the cake C1 in order to reliably recover the eluted components. As the washing water used in the water washing device 4a, normal temperature water 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 cake C1. However, this water cleaning device 4a can be omitted.

This solid-liquid separation treatment step S3 corresponds to the step (d).

As a preferred embodiment, the waste water W2 separated by the solid-liquid separator 4 may be recovered. The recovered waste water W2 contains the alkali metal eluted from the alkali metal-containing material A1, but since the ORP is in a suitable state, it can be supplied to the reaction tank 2 and reused when the slurry Lr1 is generated. be. In the treatment system 1 shown in FIG. 2, a configuration is adopted in which waste water W2 collected as a liquid phase after the solid-liquid separation through the solid-liquid separator 4 is sent to the reaction tank 2 by a liquid sending device (not shown). ing. As the liquid-sending device, a general liquid-sending pump such as a centrifugal pump, a propeller pump, or a rotary pump may be used.

(Post-process)
The cake C1 separated by the solid-liquid separator 4 has an alkali metal component concentration of 2.5% by mass or less, more typically 2.0% by mass or less, so it is effective as a cement raw material. can be used for The alkali metal concentration referred to here is an analytical value obtained by a well-known method, for example, an analytical value obtained by a method conforming to JIS R 5204 “Method for Fluorescent X-ray Analysis of Cement”, or an ICP emission spectroscopic analysis of an acid-decomposed sample. It refers to the analysis value by the law.

In the example of the processing system 1 shown in FIG. 2, the cake C1 separated by the solid-liquid separator 4 is conveyed to the cement manufacturing facility 11 by the cake conveying device 12 . As the cake conveying device 12, for example, a general cake conveying device such as a belt conveyor, a screw conveyor, a pipe conveyor is used.

[Another configuration example]
Another configuration example will be described below.

<1> In step S23, it may be confirmed whether or not the relationship between the pH of the slurry Lr1 and the ORP satisfies the formula (2) in addition to the formula (1). Equation (2) is shown again below.
(ORP (mV)) ≤ -55 x (pH) + 340 (2)
However, in the formula (2), the range of pH is 11≤pH≤14.

By stirring the slurry Lr1 for a predetermined time in a state where the relationship between the pH and the ORP of the slurry Lr1 is adjusted to satisfy the formulas (1) and (2), the alkali metal contained in the slurry is further efficiently removed. can be eluted into the liquid phase. This point will be described later with reference to examples.

<2> In the above embodiment, the adjusting device 3 is provided with the ORP adjusting agent adding device 3a and the pH adjusting agent adding device 3b. However, as described above, the pH of slurry Lr1 does not fluctuate greatly unlike ORP. Further, when biomass ash is used as the alkali metal-containing material A1, the resulting slurry Lr1 may have a pH of 10-13. In this case, the formula (1) can be satisfied by adjusting the ORP without adjusting the pH of the slurry Lr1 in step S24.

That is, in the water washing step S2 shown in FIG. 1, only the ORP adjuster α1 may be added without adding the pH adjuster α2. In this case, the adjustment device 3 may include only the ORP adjuster addition device 3a without the pH adjuster addition device 3b.

<3> As shown in FIG. 4, a preliminary water washing process S4 may be performed before the water washing process S2. As a result, if the alkali metal-containing material A1 contains a soluble alkali metal, it can be removed by washing with water in advance, so the alkali metal content of the cake C1 obtained through the subsequent water washing treatment step S2 and solid-liquid separation treatment step S3 can be further reduced.

<4> In the above embodiment, the amount of the ORP adjuster α1 or the pH adjuster α2 introduced from the adjusting device 3 into the reaction vessel 2 is automatically controlled based on the signal from the control device 5. did. However, it is also within the scope of the present invention that the amount of ORP adjuster α1 or pH adjuster α2 introduced is manually adjusted.

<5> The processing system 1 shown in FIG. 2 includes the heating device 25 for heating the inside of the reaction vessel 2, but the heating device 25 is not essential. For example, the slurry Lr1 may be stirred at room temperature. However, if the temperature is increased by about 10° C. to 30° C. higher than the room temperature using the heating device 25, the effect of eluting the alkali metal more efficiently may be obtained.

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

Fly ash of woody biomass ash collected by an exhaust gas dust collector (bag filter) of a biomass power plant (circulating fluidized bed boiler) was used as the alkali metal-containing material A1. Table 1 shows the results obtained by analyzing acid-decomposed samples by ICP emission spectroscopy for alkali metals, and by analyzing pellet samples by fluorescent X-ray analysis for other chemical components. indicate. As described above, R ₂ O in Table 1 indicates a value calculated by "R ₂ O=Na ₂ O+0.658×K ₂ O" as the amount of total alkali metal components in the present composition.

Moreover, Table 2 shows the XRD analysis results of the woody biomass ash as the material of the alkali metal-containing material A1.

The alkali metal-containing material A1 of the above material was mixed with tap water as water W1 in an amount four times the mass of the alkali metal-containing material A1 to generate slurry Lr1. This slurry Lr1 had a pH of 10 and an oxidation-reduction potential (ORP) of -52 mV (corresponding to level #1 in Table 3, which will be described later).

After that, by varying the amount of ORP adjuster α1 and pH adjuster α2 added to the slurry Lr1 produced, multiple types of samples with different ORP and pH were prepared, and each was stirred at 20 to 25° C. for 60 minutes. did. A 25% by mass aqueous solution of sodium hydrogen sulfide was used as the ORP adjuster α1. A 50% by mass aqueous solution of sodium hydroxide was used as the pH adjuster α2.

The temperature, pH and ORP data of the slurry Lr1 were measured by a portable pH/ORP/electrical conductivity meter (model number D-74) manufactured by Horiba, Ltd.

After that, the slurry Lr1 after stirring is solid-liquid separated by a filter press, and washed and filtered with the same amount of water (4 times the amount of the alkali metal-containing material A1 in terms of mass) as when preparing the slurry Lr1, to prepare a cake C1. did. Then, the content of alkali metal components in the resulting cake C1 was determined by analyzing an acid-decomposed sample by ICP emission spectrometry. The results are shown in Table 3 and FIG. FIG. 5 is a diagram showing the relationship between pH and ORP, based on Table 3, showing the applicable range of the present invention.

As the K removal rate in Table 3, the value calculated by the following formula (3) was adopted.
K removal rate={d1-(1-d2)×d3}/d1 (3)
However, each symbol in the formula (3) is the following value.
d1: Content rate (concentration) of K (potassium) contained in the alkali metal-containing material A1 before the water washing step S2
d2: Weight reduction rate of alkali metal-containing material A1 by water washing treatment step S2 and solid-liquid separation treatment step S3 d3: K content (concentration) contained in cake C1 obtained after solid-liquid separation treatment step S3

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

In Table 3, levels #1 to #4 correspond to samples obtained by adding different amounts of ORP adjuster α1 to slurry Lr1 without adding pH adjuster α2.
Levels #5 to #8 correspond to samples obtained by fixing the amount of pH adjuster α2 added to slurry Lr1 (addition amount x1) and varying the amount of ORP adjuster α1 added.
Levels #9 to #12 are obtained by fixing the addition amount of pH adjuster α2 to slurry Lr1 at an amount larger than addition amount x1 (addition amount x2) and varying the addition amount of ORP adjuster α1. corresponds to the sample obtained.
Levels #13 to #16 were obtained by fixing the addition amount of pH adjuster α2 to slurry Lr1 at an amount larger than addition amount x2 (addition amount x3) and varying the addition amount of ORP adjuster α1. corresponds to the sample obtained.
Levels #17 to #20 were obtained by fixing the addition amount of pH adjuster α2 to slurry Lr1 at an amount larger than addition amount x3 (addition amount x4) and varying the addition amount of ORP adjuster α1. corresponds to the sample obtained.

In Table 3, levels #1, #5, #9, #13, and #17 have the same amount of ORP adjuster α1 added (addition amount y1). In addition, since the amount of the pH adjuster α2 added to the slurry Lr1 is different for each, the ORP values are different from each other due to the difference in the pH value.
Levels #2, #6, #10, #14, and #18 are common to each other in y2, where the added amount of ORP adjuster α1 is greater than y1.
Levels #3, #7, #11, #15, and #19 are common to each other in y3, where the added amount of ORP adjuster α1 is greater than y2.
Levels #4, #8, #12, #16, and #20 are common in y4, where the amount of ORP adjuster α1 added is greater than y3.

In FIG. 5, line L1 corresponds to the function of ORP=28×(pH)−575 and line L2 corresponds to the function of ORP=−55×(pH)+340. According to FIG. 5, at 10 ≤ pH ≤ 14, the K removal rate is 17% or more within the range of ORP ≤ 28 × (pH) - 575, that is, within the hatched area in Fig. 5 . , and it can be seen that K (potassium) can be efficiently removed by stirring the slurry Lr1 in a state where the relationship between the pH and the ORP is within this range.

Furthermore, according to FIG. 5, at 11≦pH≦14, ORP≦28×(pH)−575 and ORP≦−55×(pH)+340, that is, within the cross-hatched area in FIG. , the K removal rate is 23% or more, and it can be seen that K (potassium) can be removed more efficiently by stirring in a state where the relationship between the pH and ORP of the slurry Lr1 is within this range.

Although the reason for this is not clear, since the biomass ash as the alkali metal-containing material A1 contains potassium in the form of glass, washing the slurry Lr1 with water in an alkaline atmosphere dissolved the glass and corroded the potassium. It is speculated that the reason for this is that the solubility of the glass is further improved by lowering the ORP of the slurry Lr1 and washing with water in a reducing atmosphere. In other words, it can be seen that the alkali metal can be efficiently removed from the alkali metal-containing material such as biomass ash by performing the water washing step S2 in an environment in which both the alkalinity and the reducing property are increased. Moreover, according to the above method, a heat treatment at a high temperature is unnecessary when removing the alkali metal.

1: Treatment system 2: Reaction tank 3: Adjusting device 3a: ORP adjusting agent adding device 3b: pH adjusting agent adding device 4: Solid-liquid separating device 4a: Water cleaning device 5: Control device 6: Grinding device 11: Cement manufacturing facility 12: Cake conveying device 21: Stirring blade 22: pH measuring device 23: ORP measuring device 24: Thermometer 25: Heating equipment A1: Alkali metal-containing material A2: Alkali metal-containing material pulverized material C1: Cake G1: Hot gas Lr1: Slurry W1: Water W2: Drainage α1: ORP adjuster α2: pH adjuster

Claims (10)

a step (a) of adding water to the alkali metal-containing material to obtain a slurry;
a step (b) of adjusting the relationship between the pH of the slurry and the ORP so that the relationship between the pH of the slurry and the oxidation-reduction potential (ORP) satisfies the following formula (1);
a step (c) of eluting the alkali metal contained in the alkali metal-containing material in the slurry into the liquid phase of the slurry during or after the step (b);
a step (d) of solid-liquid separating the slurry after the step (b) and the step (c) are performed to obtain a cake having an alkali metal content lower than that of the alkali metal-containing material. A method for treating an alkali metal-containing material, characterized by:
(ORP (mV)) ≤ 28 x (pH) - 575 (1)
(However, in the formula (1), the range of pH is 10≤pH≤14.) 2. The method according to claim 1, wherein the step (b) is a step of adjusting the pH and ORP of the slurry so that the relationship between the pH and ORP of the slurry satisfies the following formula (2). A method for treating an alkali metal-containing material.
(ORP (mV)) ≤ -55 x (pH) + 340 (2)
(However, in the formula (2), the pH range is 11 ≤ pH ≤ 14.) 3. The method for treating an alkali metal-containing material according to claim 1, wherein said step (b) includes adding at least one of a pH adjuster and an ORP adjuster to said slurry. The step (b) is
A step (b1) of measuring the pH and ORP of the slurry;
When the relationship between the slurry pH and ORP measured in the step (b1) does not satisfy the formula (1), the above 3. The method for treating an alkali metal-containing material according to claim 1, comprising a step (b2) of adding at least one of a pH adjuster and an ORP adjuster to the slurry. The pH adjuster contains one or more selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, citric acid, sodium hydroxide, potassium hydroxide, and calcium hydroxide,
5. The method for treating an alkali metal-containing material according to claim 3, wherein said ORP adjuster contains one or more selected from the group consisting of sodium hydrogen sulfide and sodium sulfide. Wastewater obtained by solid-liquid separation of the slurry in the step (d) is discharged during the execution of at least one of the steps (a), (b), and (c). The method for treating an alkali metal-containing material according to any one of claims 1 to 5, characterized in that the material is recycled. The alkali according to any one of claims 1 to 6, wherein the step (c) includes a step of stirring the slurry while maintaining the temperature of the slurry at 5 ° C. to 60 ° C. A method for treating metal inclusions. The alkali metal-containing material contains at least one selected from the group consisting of fly ash of woody biomass combustion ash, bottom ash of woody biomass combustion ash, soil generated from construction, and recycled fine powder of waste concrete. The method for treating an alkali metal-containing material according to claims 1 to 7. a reactor for slurrying the contained alkali metal inclusions;
an adjusting device for adjusting the relationship between the pH and the ORP of the slurry contained in the reaction tank so that the relationship between the pH and the oxidation-reduction potential (ORP) of the slurry satisfies the following (1);
and a solid-liquid separation device for solid-liquid separation of the slurry discharged from the reaction tank.
(ORP (mV)) ≤ 28 x (pH) - 575 (1)
(However, in the formula (1), the range of pH is 10≤pH≤14.) The adjusting device is configured to be able to introduce at least one of a pH adjusting agent and an ORP adjusting agent into the slurry contained in the reaction tank,
a measuring device for measuring the pH and ORP of the slurry contained in the reaction tank;
The pH adjuster added to the slurry so that the relationship between the pH and ORP of the slurry satisfies the above (1) by controlling the adjustment device based on the measurement result of the measurement device. and a controller for changing the amount of at least one of said ORP regulator.

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