JP2023013998A - Method for washing refuse incineration ash with water - Google Patents

Abstract

To provide a method for washing refuse incineration ash with water, in which refuse incineration ash to be converted to cement raw fuel is mixed with water to prepare slurry, the slurry is subjected to pressure filtration of a penetration washing system, and in addition, a filtration residue is washed with water, so as to obtain washed ash (a dewatered cake) with reduced amounts of chlorine and the like that cause damage when the refuse incineration ash is used as cement raw fuel, and in which the obtained dewatered cakes have high uniformity enabling easy handling, while a use amount of water is reduced as much as possible.SOLUTION: A use amount of water in preparing refuse incineration ash slurry is 3.5-8.5 times by mass relative to refuse incineration ash, and preferably 5.0 times by mass or less, and a use amount of washing water in washing a pressure-filtrated and dewatered filtration residue, with water, is 1.5-5 times by mass relative to the refuse incineration ash, and preferably more than 1.5 to 3 times by mass.SELECTED DRAWING: None

Description

The present invention relates to a method for treating refuse incineration ash. More specifically, the present invention relates to a method for treating waste incineration ash that can reduce the amount of chlorine, which is a problem when used as a raw material and fuel for cement production.

Incineration fly ash from municipal waste, etc. is characterized by its large amount, high chlorine content, heavy metal content, dioxin content, and composition that varies greatly depending on the location of generation, and its usage is limited. there is

One of the utilization methods is to use it as raw material and fuel for cement. However, it cannot be used unlimitedly even if it is used as a raw material or fuel for cement. In particular, in order to keep the chlorine content in the final cement product within the JIS standard, it is necessary to wash the incinerated ash and reduce the chlorine content. (Patent Documents 1 to 4, Non-Patent Document 1, etc.).

In addition, since chlorine can cause process troubles in the cement production process, it is necessary to reduce the chlorine content of waste incineration ash when bringing it into the production system as a raw material and fuel from the viewpoint of stable production. There is

However, there is a problem that the amount of chlorine in the obtained washed ash may not be sufficiently reduced even if the filtration residue is washed with a large amount of water after filtering the incinerated ash slurry. The present inventors have found that even if the amount of washing water for the filtration residue is increased, the effect of reducing the amount of chlorine reaches a ceiling to some extent, and the effect of the amount of water during preparation of the slurry on reducing the amount of chlorine is generally proportional. We have found out the above-mentioned problems, and have already proposed a method for improving the above problem (Patent Document 4).

JP-A-11-351546 JP 2010-132463 A Japanese Patent Application Laid-Open No. 2003-103231 JP 2013-95605 A

Joan Hajime, "Perfect Recycling of Waste Incineration Ash Using Cement Kiln - Use of Waste Incineration Ash as Raw Material for Cement", High Tech Information, Chugoku Technology Promotion Center, February 28, 2001, Vol. 128, pp. 14-19

However, even the method described in Patent Document 4 still has some points to be improved. That is, in the technique proposed in the document, as much of the usable water as possible is used for adjusting the slurry, but there is a problem that the obtained filtration residue is uneven when filtering the slurry.

In view of the above problems, the inventors of the present invention conducted intensive studies. As a result, in the filtration and cleaning of the incinerated ash slurry by the filter press of the penetrating cleaning method, depending on the slurry concentration (the ratio of incinerated ash in the slurry) at the time of slurry preparation, it is easy to control the injection and the unevenness of the filtration residue. is determined. In addition, if the soluble components of the target incinerated ash are different and fluctuate, the slurry solid content concentration (the ratio of insoluble components in the slurry) determines the ease of injection control and the ease of occurrence of unevenness in the filtration residue. I found out. Furthermore, based on these findings, when filtering the slurry adjusted to the concentration that makes it difficult for unevenness to occur in the filtration residue or the slurry solid content concentration, the range of water amount that is excellent in the chlorine concentration reduction effect was examined. As a result, the total amount of water used ( The total amount of slurry water used when adjusting the slurry and the washing water used when washing the filtration residue) is small, the chlorine concentration is reduced, and the filtration residue (washing ash) in a stable shape can be obtained. I have perfected my invention.

That is, the first aspect of the present invention includes a step of mixing incinerated ash with water to prepare a slurry, applying the slurry to a through-cleaning filter press to separate the washed ash and washing water, and then filtering residue. In a water washing method for using waste incineration ash as raw material and fuel for cement,
The amount of water used is 3.5 to 8.5 times the weight of the incinerated ash when preparing the slurry, and the amount of washing water used in washing the filtered residue is 1.5 to 5.0 times that of the incinerated ash. A method for washing waste incineration ash with water, characterized by doubling the mass.

That is, the second aspect of the present invention includes a step of mixing incinerated ash with water to prepare a slurry, applying the slurry to a through-cleaning filter press to separate the cleaning ash and cleaning water, and then filtering residue. In a water washing method for using waste incineration ash as raw material and fuel for cement,
The amount of water used for the incinerated ash during slurry preparation is adjusted so that the slurry solid content concentration is 6.0 to 16.0%, and the amount of washing water used when washing the filtration residue is adjusted to the filter press. A method for washing incinerated ash with water, characterized in that the volume of the filter chamber is at least two times as large as the volume of the filter chamber.

According to the present invention, it is easy to control the injection during filtration and washing, and with a relatively small amount of water, a stably treated waste incineration ash (washed ash) that has a low chlorine content and has uniform properties. can be obtained. As a result, even if the incinerated ash is used as a raw material and fuel for cement, it is easy to handle and the amount of chlorine in the manufactured cement can be suppressed. becomes easier.

The figure which shows the amount of washing water of the filtration residue of the refuse incineration ash slurry from which the amount of water used with respect to refuse incineration ash differs, and chlorine content. The figure which shows the amount of washing water of the filtration residue of the refuse incineration ash slurry with different slurry solid content concentration, and chlorine content.

(garbage incineration ash)
The waste incineration ash to be treated in the present invention is not particularly limited, but it is produced in a large amount, has virtually no useful uses other than as a raw material for cement, and has a relatively high chlorine content. It is preferable to target municipal waste incineration ash.

Of the incineration ash discharged from municipal waste incinerators, the bottom ash is the waste incineration ash that is mainly discharged as cinders from the lower part of the stoker furnace. % (mass) is obtained as a mass. Also, its chlorine content ranges from 0.5 to 5.0% (by mass). On the other hand, fly ash is a fine powder obtained from exhaust gas from a stoker furnace or from a fluidized bed furnace, and generally contains chlorine at a rate of about 5 to 30% (mass).

The bottom ash may contain a large amount of foreign matter such as empty cans and wires, and it is preferable to remove these in advance. Further, since bottom ash is a lump, it is necessary to adjust the average particle size to 500 μm or less, preferably 200 μm or less, more preferably 50 to 150 μm. Furthermore, even after crushing main ash, it is preferable to remove uncrushed matter and foreign substances that have not been removed before crushing.

On the other hand, since fly ash contains a large amount of dioxins compared to bottom ash, it is preferable that dioxins have been removed in advance.

The method for removing dioxins is not particularly limited and may be carried out under known conditions. For example, fly ash may be treated at a temperature of 300 to 600°C, preferably 350 to 500°C, in an oxygen-free atmosphere. The oxygen-free atmosphere includes not only the case where oxygen is completely absent, but also a mode in which oxygen that inevitably enters due to the structure of the apparatus or the like, oxygen that accompanies the object to be processed, etc. is contained. In removing dioxins, it is preferable to form an oxygen-free atmosphere with nitrogen gas and perform heating with a heater. Mercury can also be volatilized and removed by heating in dioxin removal treatment, and it is effective as a pretreatment of municipal waste incineration ash containing relatively high concentrations of mercury.

Here, the method for washing incinerated ash with water according to the first aspect of the present invention includes a step of mixing incinerated ash with water to prepare a slurry, and subjecting the slurry to a through-cleaning filter press to obtain washed ash and washing water. In a water-washing method for using incinerated waste ash as a raw material or fuel for cement, the water-washing method for using the incinerated waste ash as a raw material or fuel for cement, which comprises a step of washing the filtration residue after separating it into 3 parts of the incinerated waste ash. .5 to 8.5 times by mass, and the amount of washing water used in washing the filtered residue is 1.5 to 5 times by mass that of the incinerated ash.
In addition, the method for washing incinerated ash with water according to the second aspect of the present invention comprises a step of mixing incinerated ash with water to prepare a slurry, and subjecting the slurry to a through-cleaning filter press to separate the washed ash and washing water. In a water washing treatment method for using waste incineration ash as a raw material and fuel for cement, which comprises a step of washing the filtration residue after separating into
The amount of water used during preparation of the slurry is adjusted so that the slurry solid content concentration is 6.0% to 16.0%, and the amount of washing water used when washing the filtration residue is the filter chamber volume of the filter press. It is characterized by being at least twice the capacity of .
A detailed description will be given below.

<First Invention>
(1) Step of preparing slurry In the present invention, the incinerated refuse ash such as bottom ash and fly ash pretreated as described above is individually or simultaneously mixed with water to form a slurry. The slurrying method is not particularly limited, and a known method may be selected as appropriate. For example, there is a method of putting incinerated ash and water into a slurry storage tank and stirring them.

Here, if the slurry concentration of the incinerated ash slurry becomes too high, the fluidity becomes low and it becomes difficult to handle, and it becomes difficult to control when the slurry is introduced into the filter press device. Furthermore, when the concentration is high, it is difficult to make the entire slurry uniform. Therefore, in such a slurry, even in the same filter chamber, there are likely to be parts with a large amount of eluted components and parts with a small amount of eluted components. The thickness of the (dehydrated cake) becomes uneven and, in extreme cases, holes are formed. Furthermore, such a portion often collapses.

On the other hand, if the slurry concentration is low, the above problems are less likely to occur. However, if the slurry concentration is too thin, the solid content tends to settle in the filter chamber before the completion of pressing (dehydration), and the thickness of the residue is thin at the top and thick at the bottom, and coarse particles accumulate at the bottom. It is easy to become uneven as if

Such a residue with low uniformity (many unevenness) is difficult to handle when used as a raw material or fuel for cement. More specifically, residues with large unevenness (hereinafter also referred to as "dehydrated cake") are said to be unable to maintain their shape when used as cement raw materials, and some adhere to the walls of the process. This may cause problems. Therefore, in the present invention, in order to obtain a uniform slurry that is easy to handle and to obtain a filtration residue with a stable shape by processing it, the amount of water used relative to the incinerated ash during preparation of the slurry is 3.5 times the amount of the incinerated ash. 8.5 times the mass. From the viewpoint of reducing the amount of water used, it is more preferably 5.0 times or less by mass.

The temperature of the water when preparing the slurry is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher, and most preferably 20°C or higher. As the water used at this time, general industrial water, ground water, tap water, or the like can be used.

The stirring time may be such that the slurry becomes homogeneous as a whole, and depending on the stirrer, generally about 5 to 60 minutes is sufficient.

(2) Step of Separating into Washed Ash and Washed Water by Filter Press Next, the slurry prepared as described above is subjected to solid-liquid separation. In the present invention, a filter press is used for the separation in terms of separation efficiency, dehydration rate, and easy washing of solids after separation. Furthermore, in the present invention, by adopting a through-cleaning system for the filter press, the amount of water used can be relatively reduced compared to the normal cleaning system.

(3) Process of washing the filtration residue with water After separation into water and solid content (filtration residue) by a filter press, the chlorine contained in the filtration residue that could not be separated (mostly contained in the washing water that could not be filtered ), the solid content is further washed with water, and in the present invention, the total amount of water used can be reduced by setting the amount of water at this time within the specific range described later. The water temperature in this washing step is not particularly limited, but is preferably 10° C. or higher, more preferably 15° C. or higher, and most preferably 20° C. or higher.

A further feature of the present invention is that the amount of washing water after filtration is 1.5 to 5.0 times the mass of incinerated ash. This is because when a through-cleaning filter press is used, the chlorine concentration in the filtered residue after cleaning will hardly change if the amount of cleaning water after filtering is 1.5 times the mass of the incinerated ash or more. It is derived from the knowledge of More specifically, at 1.5 times by mass or more, there is almost no change, and at 5 times by mass or more, it stabilizes. Since the inflection point is obtained between 1.5 and 5 mass times, the use of 1.5 to 5 mass times water is important. Therefore, in the present invention, the lower limit is set to 1.5 times by mass from the viewpoint of further reducing the amount of water used, and the upper limit is set to be 5 times by mass because the use of more water is substantially wasteful. Of course, if water can be used unlimitedly, a large amount of washing water can be used, but from the viewpoint of reducing the chlorine concentration, it is more wasteful. The content is preferably 3 parts by mass or less. On the other hand, it is preferable to use slightly more than 1.5 times the weight, as just 1.5 times the weight may result in batch-to-batch instability.

As described above, in the present invention, the slurry preparation water is 3.5 times or more and 8.5 times or less by weight, preferably 3.5 times or more and 5.0 times or less by weight, the incinerated ash. . Therefore, in the present invention, the amount of water used for refuse incineration ash during slurry preparation for obtaining a stable slurry and a stable filtration residue, and the total amount of washing water used when washing the filtration residue is 5.0 to 5.0. 13.5 times the mass. It is preferably 5.0 to 12.0 times by mass, more preferably 5.0 to 10.0 times by mass, particularly preferably 8.0 times by mass or less.

In the present invention, it is possible to obtain a stable residue (washed ash) with a significantly reduced amount of chlorine, which is easy to handle, and with a relatively small amount of total water consumption.

The present invention as described above is particularly effective in obtaining a water-washed residue with stable properties because the amount of water that can be used is limited. The effectiveness is high when the mass is less than or equal to 8.0 times by mass.

In the present invention, the residue (washed ash: dehydrated cake) obtained in the above washing process is mainly composed of calcium compounds and silica, has a significantly reduced chlorine content, and has stable properties. It is used as a raw material for cement in In this case, since the solid content contains moisture, it is preferable to supply the solid content to the suspension preheater through a dryer together with the cement raw material in the raw material preparation process. Moreover, the wastewater obtained in the present invention may be discharged as treated wastewater after a known wastewater treatment.

<Second invention>
(1) Step of preparing slurry In the present invention, the incinerated refuse ash such as bottom ash and fly ash pretreated as described above is individually or simultaneously mixed with water to form a slurry. The slurrying method is not particularly limited, and a known method may be selected as appropriate. For example, there is a method of putting incinerated ash and water into a slurry storage tank and stirring them.

Here, if the slurry concentration or slurry solid content concentration of the incinerated ash slurry becomes too high, the fluidity becomes low and it becomes difficult to handle, and it becomes difficult to control when the slurry is introduced into the filter press device. Furthermore, when the concentration is high, it is difficult to make the entire slurry uniform. Therefore, in such a slurry, even in the same filter chamber, there are likely to be parts with a large amount of eluted components and parts with a small amount of eluted components. The thickness of the (dehydrated cake) becomes uneven and, in extreme cases, holes are formed. Furthermore, such a portion often collapses.

On the other hand, if the slurry concentration is low, the above problems are less likely to occur. However, if the slurry concentration is too thin, the solid content tends to settle in the filter chamber before the completion of pressing (dehydration), and the thickness of the residue is thin at the top and thick at the bottom, and coarse particles accumulate at the bottom. It is easy to become uneven as if

Such a residue with low uniformity (many unevenness) is difficult to handle when used as a raw material or fuel for cement. More specifically, residues with large unevenness (hereinafter also referred to as "dehydrated cake") are said to be unable to maintain their shape when used as cement raw materials, and some adhere to the walls of the process. This may cause problems. Therefore, in the present invention, in order to obtain a uniform slurry that is easy to handle and to obtain a filtration residue with a stable shape by processing it, the amount of water used relative to the incinerated ash during preparation of the slurry is adjusted so that the solid content concentration of the slurry is 6.5. Adjust to be 0 to 16.0%. By adjusting the slurry by adjusting the slurry solid content concentration, it becomes easier to obtain a relatively stable dewatered cake even if the amount of soluble components in the target incinerated ash fluctuates. From the viewpoint of reducing the amount of water used, it is more preferably 10% or more.

The temperature of the water when preparing the slurry is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher, and most preferably 20°C or higher. As the water used at this time, general industrial water, ground water, tap water, or the like can be used.

The stirring time may be such that the slurry becomes homogeneous as a whole, and depending on the stirrer, generally about 5 to 60 minutes is sufficient.

(2) Step of Separating into Washed Ash and Washed Water by Filter Press Next, the slurry prepared as described above is subjected to solid-liquid separation. In the present invention, a filter press is used for the separation in terms of separation efficiency, dehydration rate, and easy washing of solids after separation. Furthermore, in the present invention, by adopting a through-cleaning system for the filter press, the amount of water used can be relatively reduced compared to the normal cleaning system.

(3) Process of washing the filtration residue with water After separation into water and solid content (filtration residue) by a filter press, the chlorine contained in the filtration residue that could not be separated (mostly contained in the washing water that could not be filtered ), the solid content is further washed with water, and in the present invention, the total amount of water used can be reduced by setting the amount of water at this time within the specific range described later. The water temperature in this washing step is not particularly limited, but is preferably 10° C. or higher, more preferably 15° C. or higher, and most preferably 20° C. or higher.

A further feature of the present invention is that the volume of washing water after filtration is 2 to 5 times the volume of the filter chamber of the filter press. This is because when a through-cleaning filter press is used, the chlorine concentration in the filtered residue after cleaning is almost It is derived from the knowledge that it does not change. More specifically, when the capacity is doubled or more, there is almost no change, and when the capacity is doubled or more, the capacity is stabilized. Therefore, in the present invention, the lower limit is set to 2 times the volume from the viewpoint of further reducing the amount of water used, and the upper limit is set to 5 times the volume from the viewpoint that the use of more water is substantially wasteful. Of course, if water can be used unlimitedly, a large amount of washing water can be used, but from the viewpoint of reducing the chlorine concentration, it is more wasteful. Preferably, the volume is 4 times or less. On the other hand, it is preferable to use slightly more than 2 times the volume, as using just 2 times the volume may lead to batch-to-batch erratic results.

As described above, in the present invention, the slurry preparation water has a slurry solid content concentration of 6.0 to 16.0%, preferably 7.0% or more and 15.0% or less. Therefore, in the present invention, the amount of water used for refuse incineration ash during slurry preparation to obtain a stable slurry and a stable filtration residue, and the total amount of washing water used when washing the filtration residue are subject to Although it varies depending on the amount of soluble components in the refuse incineration ash, it is approximately 5.0 to 10.0 times the mass. It is preferably 5.0 to 9.0 times by mass, more preferably 5.0 to 8.0 times by mass or less, and particularly preferably 7.0 times by mass or less.

In the present invention, it is possible to obtain a stable residue (washed ash) with a significantly reduced amount of chlorine, which is easy to handle, and with a relatively small amount of total water consumption.

The present invention as described above is particularly effective in obtaining a water-washed residue with stable properties because the amount of water that can be used is limited. The effectiveness is high when the mass is less than or equal to 8.0 times by mass.

In the present invention, the residue (washed ash: dehydrated cake) obtained in the above washing process is mainly composed of calcium compounds and silica, has a significantly reduced chlorine content, and has stable properties. It is used as a raw material for cement in In this case, since the solid content contains moisture, it is preferable to supply the solid content to the suspension preheater through a dryer together with the cement raw material in the raw material preparation process. Moreover, the wastewater obtained in the present invention may be discharged as treated wastewater after a known wastewater treatment.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

The chlorine concentration in the incinerated ash in each experimental example was measured by fluorescent X-ray analysis after drying the sample incinerated ash at 100°C.

Examples 1-4 and Comparative Examples 1-11
An incinerated ash slurry was obtained by adding 2 to 10 times the mass of water (water temperature 15° C.) to the incinerated ash obtained from a municipal waste incinerator. This slurry was introduced into a filter press for solid-liquid separation. Furthermore, the filtration residue (solid content) was penetrated and washed with water equivalent to 0 to 4.2 times the mass of the incinerated ash. Table 1 shows the results of measuring the amount of chlorine in the cleaning residue after cleaning together with the amount of water used for cleaning.

Regardless of the examples and comparative examples, the amount of chlorine in the washing residue decreases until the amount of washing water is 1.5 times the amount of incinerated ash, but even if the amount of washing water is increased further, the amount of chlorine decreases significantly. no.

Regarding the amount of water used during slurry preparation, if the amount is less than 3.5 times by mass, the concentration of solids is high and difficult to handle. It was observed that the residue collapsed, presumably due to the elution of undissolved matter from the substance. This was more remarkable in Comparative Examples 1 to 3, in which the amount of water used for slurry preparation was small.

On the other hand, in the slurry prepared by adding more than 8.5 times the mass of water to the incinerated ash, the concentration of the slurry is uneven during filtration, and the thickness of the washing residue is thin at the top of the filter chamber and thick at the bottom. The state was observed, and further, unevenness was observed such that coarse particles were deposited at the bottom.

On the other hand, in the examples in which the amount of water used during slurry preparation was 3.5 to 8.5 times the mass of the incinerated ash, and the amount used during water washing was 1.5 times or more by mass, in either case Also, the chlorine concentration was sufficiently reduced, and the thickness of the washing residue obtained was uniform and easy to handle.

Examples 5-8 and Comparative Examples 12-22
Slurry water was added to refuse incineration ash obtained from a municipal refuse incinerator so that the slurry solid content concentration was 5.5% to 23.5% (water temperature: 15°C) to obtain a slurry. This slurry was introduced into a filter press for solid-liquid separation. Further, the filtration residue (solid content) was penetrated and washed with water equivalent to 0 to 5 times the volume of the filter chamber volume of the filter press with respect to the incinerated ash. Table 1 shows the results of measuring the amount of chlorine in the cleaning residue after cleaning together with the amount of water used for cleaning.

Regardless of the examples and comparative examples, the amount of chlorine in the washing residue decreases when the washing water is up to 2 times the volume of the filter chamber volume of the filter press against the incinerated ash, but even if the washing water amount is increased more than that. There is no significant decrease in chlorine content.

Regarding the amount of water used during slurry preparation, if the slurry solids concentration exceeds 16%, the solids concentration is high and difficult to handle. It was observed that the residue collapsed, probably due to the elution of the undissolved portion of This was more remarkable in Comparative Examples 12 to 14, in which the amount of water for slurry preparation was small.

On the other hand, with the slurry adjusted so that the solid content concentration of the slurry is less than 6% with respect to the incinerated ash, the slurry concentration is uneven during filtration, and the thickness of the washing residue is thin at the top of the filter chamber and thick at the bottom. In addition, unevenness such as deposition of coarse particles was observed at the bottom.

On the other hand, the amount of water used during slurry preparation is adjusted so that the slurry solid content concentration is 6.0% to 16.0%, and the amount used during water washing is twice the volume of the filter chamber volume of the filter press. In all of the examples described above, the chlorine concentration was sufficiently low, and the thickness of the washing residue obtained was uniform and easy to handle.

Claims (2)

Garbage comprising a step of mixing incinerated garbage ash with water to prepare a slurry, applying the slurry to a through-cleaning filter press to separate washing ash and washing water, and then washing the filtered residue with water. In a water washing method for using incinerated ash as raw material and fuel for cement,
The amount of water used when preparing the slurry is 3.5 to 8.5 times the mass of the incinerated ash, and the amount of washing water used when washing the filtered residue is 1.5 to 5 mass of the incinerated ash. A method for washing waste incineration ash with water, characterized by doubling. Garbage comprising a step of mixing incinerated garbage ash with water to prepare a slurry, applying the slurry to a through-cleaning filter press to separate washing ash and washing water, and then washing the filtered residue with water. In a water washing method for using incinerated ash as raw material and fuel for cement,
The amount of water used during preparation of the slurry is adjusted so that the slurry solid content concentration is 6.0% to 16.0%, and the amount of washing water used when washing the filtration residue is the filter chamber volume of the filter press. A method for washing incinerated ash with water, characterized in that the volume of the waste incineration ash is 2 times or more.

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