JP2012183503A - Pretreatment method of incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pretreatment method of incineration ash advantageous in reforming incineration ash for a safe state by effectively keeping temperature conditions of the incineration ash during pretreatment so that a substance at an eluting state into water from among substances such as salts, heavy metals and organic substances contained in the incineration ash is promoted for elusion, while a substance at a hardly eluting state is made hardly soluble.SOLUTION: In the pretreatment method of incineration ash, the incineration ash is held in a pretreatment tank 12 and subjected to pretreatment of watering and ventilation, before reclamation or before reuse as an aggregate, a filling material, a backfilling material or the like. The incineration ash is kept at a temperature of 20°C or higher and 60°C or lower for at least 10 days since the beginning of the pretreatment.

Description

  The present invention is performed before incineration ash (bottom ash: main ash, hereinafter referred to as incineration ash) is disposed of in a final disposal site, or before being reused as aggregate, embankment material, backfill material, etc. In particular, the present invention relates to a technique that is effective when applied to washing out organic substances, heavy metals, salts, etc., or suppressing elution.

  The waste disposal site has a strong image as a nuisance facility for local residents. There is a strong sense of anxiety about the impact on the surrounding environment, and it is difficult to obtain public consent for the construction of a disposal site. As a result, new construction has become difficult throughout Japan.

  Under such circumstances, various treatments (pretreatment) have been proposed in which waste is changed (stabilized) in advance to a state with little influence on the surrounding environment before the waste is landfilled in the final disposal site. That is, this pretreatment method is a technique for artificially stabilizing organic substances, salts, heavy metals, and the like contained in the landfill waste in a highly safe state that is difficult to elute before landfill.

  As such a technique, for example, as described in Patent Document 1, there is a method of cleaning waste before landfill. By mechanically washing the waste, organic matter and salts contained in the waste are washed out to stabilize the waste. Further, as described in Patent Document 2, there is a method of promoting stabilization by sprinkling and ventilating waste before landfill. It is a method of washing out or insolubilizing organic substances, salts, heavy metals, etc. in wastes by watering and aeration. This technique promotes the stabilization of waste.

Patent Document 3 describes a technology relating to a system that removes harmful substances such as heavy metals and dioxins from incinerated ash (bottom ash, or bottom ash and fly ash) and uses them as valuable resources.
However, as described in Patent Documents 1 and 2, the pretreatment method is divided into a case where the waste is mechanically washed and a method where the waste is sprinkled and ventilated. The mechanical cleaning method requires equipment and power for cleaning and treatment of a relatively large amount of cleaning water. On the other hand, in the method using watering / venting, the processing load of mechanical equipment and cleaning water is less than that of mechanical cleaning. However, on the other hand, the pretreatment period for stabilization becomes longer. Therefore, in such a method, an increase in site area for pretreatment occurs incidentally.
Therefore, the present applicant has applied for a waste disposal method for solving these problems (Patent Documents 4, 5, and 6).

JP 2002-59106 A JP 2006-281006 A JP 2003-53298 A JP 2008-246367 A JP 2009-131757 A JP 2009-241053 A

The present invention relates to an improvement over earlier applications.
The inventors continue to intensively study the pretreatment of incineration ash, which is a waste, and pay attention to the fact that the pretreatment effect and pretreatment period of the incineration ash are affected by the temperature of the incineration ash during the pretreatment period. It came to.
That is, the test results of examining the influence of the difference in temperature and atmosphere temperature between seasons on the incineration ash temperature, pretreatment effect and pretreatment period are shown below.
Test method:
In the test, incineration ash is carried in and placed in a test tank of width: 4 m x depth: 4 m x depth: 0.4 m so that the depth of incineration ash is 0.3 m and the density is 1.3 g / cm ^3. Water was sprayed from the upper surface (1.3 mm / time × 3 times / day = 4 mm / day), and ventilation (linear velocity: 2 mm / second) was performed from the lower surface. As shown in Table 1, the ambient temperature is expected to be summer (period average temperature: 29.6 ° C), autumn (period average temperature: 10.2 ° C), and winter (period average temperature: 7.3 ° C). It was.

Test results:
FIG. 1 shows temporal changes in ambient temperature (air temperature) and incinerated ash temperature during the pretreatment test period in summer, autumn and winter.
As an index of the pretreatment effect, FIG. 2 shows the EC (electric conductivity) value of the leachate, and FIG. 3 shows the concentration of TOC (total organic carbon) contained in the leachate.
As shown in FIG. 1, the temperature of the incineration ash changes so as to substantially follow the change in the atmospheric temperature, except for a period in which the atmospheric temperature shows a sudden change. In winter and autumn, the incinerated ash temperature immediately after the start of the test tended to be higher than the ambient temperature, but after about 10 days after the start of the test, the incinerated ash temperature changed at almost the same temperature as the ambient temperature.
In addition, as shown in FIGS. 2 and 3, leachate during the period when the average temperature is high (summer: 29.6 ° C.) and low (winter: 7.3 ° C., autumn: 10.2 ° C.) Differences were observed in the EC value and TOC concentration over time. The period until the EC value of leachate showed 1.2 S / m or less was around 30 days in the summer, but more than 60 days in the winter. A similar tendency was shown in the TOC concentration.

From these results, it is suggested that the incineration ash temperature during the pretreatment period affects the pretreatment effect and the pretreatment period, and the present inventors are influenced by the temperature of the incineration ash during the pretreatment period. I came to pay attention.
The present invention has been devised in view of the above circumstances.
When the atmospheric temperature during the pretreatment period affects the temperature of the incineration ash in an area where there is a temperature difference depending on the season, the pretreatment period and the effect of the incineration ash vary from season to season.
The object of the present invention is to effectively maintain the temperature conditions of the incineration ash during the pretreatment period, so that it can be easily eluted in water among substances such as salts, heavy metals and organic substances contained in the incineration ash. Providing a pretreatment method for incineration ash that is advantageous in reforming incineration ash to a highly safe state by promoting the elution of substances and making it difficult to dissolve substances that are difficult to elute in water It is in.

  That is, the present invention is to store the incinerated ash in a pretreatment tank before reclaiming the incinerated ash or to reuse it as an aggregate, embankment material, backfilling material, etc. A pretreatment method for incineration ash that performs pretreatment with aeration, wherein the temperature of the incineration ash is maintained at 20 ° C. or more and 60 ° C. or less for at least 10 days from the start of pretreatment.

In addition, the present invention is configured such that the heat generated from the incinerated ash at the initial stage of stacking is maintained in the pretreatment tank by setting the stacked height of the incinerated ash from the bottom surface of the pretreatment tank to 0.8 m or more. Features.
Further, the present invention is characterized in that an upper surface of the stacked incineration ash is covered with a mat having heat insulating properties and water permeability so as to suppress a temperature drop of the incinerated ash.
Further, according to the present invention, the pretreatment tank has a bottom wall and a side wall standing from the periphery of the bottom wall, and the bottom wall and the side wall are provided with heat insulation to suppress a temperature drop of the incinerated ash. It was made to do.
Further, in the present invention, the pretreatment tank has a bottom wall and a side wall standing from the periphery of the bottom wall, the incineration ash is heated from the bottom wall or the side wall, and the temperature of the incineration ash is reduced. It is characterized by being suppressed.
Further, the present invention is characterized in that the watering treatment is performed by sprinkling water from above the pretreatment tank, and the aeration treatment is performed by flowing air upward from the bottom of the pretreatment tank. To do.
Further, the present invention is characterized in that the temperature of the incinerated ash is maintained at 20 ° C. or higher and 60 ° C. or lower for at least 40 days from the start of pretreatment.

According to the present invention, by effectively maintaining the temperature condition of the incinerated ash during the pretreatment period, the elution of a substance that is easily eluted in water is promoted, and the substance that is difficult to be eluted in water. Can be made slightly soluble, and the EC value and TOC concentration of incinerated ash can be reduced in a short period of time.
When maintaining the temperature conditions of the incineration ash during the pretreatment period, the heat generated from the incineration ash is kept in the pretreatment tank at the initial stage of stacking. This is advantageous in reducing the energy consumed by the heater for maintenance.

It is a figure which shows the time-dependent change of the atmospheric temperature (air temperature) and the temperature of incineration ash during a pre-processing test period, (A), (B), (C) has shown the case of summer, autumn, and winter, respectively. It is a figure which shows EC value (electrical conductivity) of leachate. It is a figure which shows the density | concentration of TOC (total organic carbon) contained in leachate. It is a figure which shows the result of the concentration analysis of EC value and TOC, Ca, and Na. It is a front view of the pre-processing apparatus of an Example. It is a top view of the pre-processing apparatus of an Example. It is explanatory drawing of the water collection tank used in the Example. It is a figure which shows the time-dependent change of the incineration ash temperature and external temperature during a pre-processing period. It is a figure which shows the time-dependent change of EC value of the leachate during a pre-processing period. It is a figure which shows a time-dependent change of the TOC density | concentration of the leaching water during a pre-processing period.

In the present invention, for example, the pretreatment device is provided in a part of the final disposal site where the incineration ash is landfilled or in a part of the place where the incineration ash is reused as an aggregate, embankment material, backfilling material, etc. Provide. The pretreatment device is not limited to a fixed type, and various conventionally known configurations such as a movable container method can be adopted.
The incinerated ash is put into a pretreatment tank, and after charging, it is squeezed out with a predetermined density and a predetermined layer thickness using a backhoe or the like.
And when performing pre-processing of sprinkling process and aeration process to incineration ash, the temperature of incineration ash is maintained at 20 degreeC or more and 60 degrees C or less for at least 10 days from the start of pretreatment.

In the pretreatment, elution is promoted and poorly soluble at the same time.In order to stabilize the quality of the leachate at an early stage, it is necessary to set a temperature that promotes poor solubility while promoting elution without increasing the leachate concentration. Although it is necessary and the temperature setting is difficult, the set temperature range of the pretreatment temperature was set by the following procedure.
(1) Setting of lower limit In the test results (FIGS. 2 and 3) of the conventional method (when the pretreatment temperature is affected by the ambient temperature), both the EC value and the TOC concentration are between 7 ° C. and 29 ° C. Decrease in EC value and TOC concentration of leachate was promoted when pretreatment temperature was high, so elution was difficult and difficult in the range between 7 ° C and 29 ° C that did not affect leachate concentration. Considering that the temperature at which the solubilization effect changes can be set, the effect of temperature on the concentration of leachate and the effect of temperature on elution of incinerated ash were evaluated, and the lower limit of pretreatment temperature was examined.

Method:
50 g (wet weight) of incinerated ash was sealed and stored in a 1000 ml polyethylene container, and left in a thermostat holding temperatures of 5 ° C., 20 ° C., 40 ° C. and 80 ° C. After standing for 40 days, 500 ml of distilled water was added and shaken for 6 hours, and the supernatant (eluate) was subjected to EC, TOC, Ca and Na concentration analysis. The analysis results are shown in FIGS.
Results analysis:
Temperature range to suppress elution:
In the range of 5 ° C. to 40 ° C., it was confirmed that the EC value and Ca concentration decreased as the pretreatment temperature increased. Further, in the range of 7 ° C. to 29 ° C. shown in the conventional method, the rate of decrease in the EC value of leachate increases as the pretreatment temperature increases, so that salts such as Ca that affect the EC value are difficult. It was thought that it was melted. From these facts, in the range of 5 ° C. to 40 ° C., the effect of suppressing elution from the incinerated ash can be expected by keeping the pretreatment temperature high.

It was confirmed that in the range of 5 ° C. to 40 ° C., the TOC concentration and Na concentration increased as the pretreatment temperature increased in the temperature range in which elution was promoted within a range not affecting the leachate concentration. Na is a salt that affects the EC value, but in the range of 7 ° C. to 29 ° C. shown in the conventional method, the rate of decrease in the EC value of leachate increases as the pretreatment temperature increases. In this case, the promotion of Na elution was considered to be an elution promotion within a range that does not affect the concentration of leachate.
As for TOC, elution at 20 ° C. to 40 ° C. is promoted compared to 5 ° C., but in the range of 7 ° C. to 29 ° C. shown in the conventional method, leachate is increased as the pretreatment temperature becomes higher. Since the rate of decrease in the TOC concentration is increasing, the promotion of TOC elution in this case is considered to be the elution promotion within the range that does not affect the TOC concentration of the leachate, and the leaching water at 20 ° C. in the TOC. The lower limit temperature was considered to promote elution within a range that does not affect the TOC concentration.

  From the above results, the lower limit of the temperature that promotes poor solubilization was set to 20 ° C. while promoting elution within a range where the concentration of leachate was not increased.

(2) Setting the upper limit From the dissolution test results shown in FIG. 4, it is possible to suppress the elution of some salts and promote the elution of TOC as the temperature increases. The upper limit is 60 ° C., but the self-heating phenomenon of incinerated ash during the pretreatment period is considered to be an actual setting considering the input energy for setting and the like. It was considered appropriate to set the pretreatment temperature in the range (including the case with heat insulation measures). In that case, the incineration ash does not refuse to reach a temperature exceeding 60 ° C.

Temperature that requires heating or heat insulation during pretreatment:
From the result of (1) above, in order to maintain the pretreatment effect, when the incineration ash temperature during the pretreatment period is lower than 20 ° C, it is maintained at 20 ° C or more by heat insulation or heating of the pretreatment tank. I thought it was necessary.

Further, if the above temperature management is at least 40 days from the start of the pretreatment, as shown in FIGS. 9 and 10, the TOC concentration and the EC value become extremely low after 40 days. This is advantageous in stabilizing to a low value.
However, when heating is necessary, it is not refused that the heating period is less than 40 days from the viewpoint of efficient energy use. For example, the heating period can be set to 10 days from the start. In other words, the temperature management can be set to at least 10 days from the start of the pretreatment. As a basis for the effect, it can be seen from FIGS. 2 and 3 that the EC value and the TOC concentration value are greatly decreased in the initial 10 days in the summer when the temperature is high. Because it was not obtained). On the other hand, the reduction range of the EC value and the TOC concentration is not significantly changed after 10 days compared to the case where the temperature is low. From these facts, it is shown that the initial temperature management, that is, the temperature management for at least 10 days from the start of the pretreatment is important, and it can be said that the effect of heating can be further obtained in the initial stage.

On the other hand, heat is generated from the incinerated ash at the initial stage of landfill. Therefore, if the heat generated from the incineration ash is kept in the pretreatment tank at the initial stage of stacking and this heat is used, the energy consumed by the heater and the like for maintenance of temperature conditions can be reduced by the ambient temperature. It is advantageous in planning.
As one aspect of maintaining heat generated from the incineration ash in the pretreatment tank in the initial stage of stacking, the height of the incineration ash from the bottom of the pretreatment tank is set to 0.8 m or more. The reason why the height of the incinerated ash is 0.8 m or more is that it is advantageous for suppressing the cooling from the upper surface and maintaining the temperature of the incinerated ash. It is the thickness of the incinerated ash layer required to hold in the treatment tank.
However, as shown in FIG. 8, since the temperature rise is recognized even at 0.4 m from the upper layer, it is possible to maintain the temperature even at 0.4 m or more by taking heat insulation measures such as covering the upper surface with a mat. it is conceivable that. However, from the viewpoint of performing efficient pretreatment of incinerated ash, the stacking height was set to 0.8 m or more here.

In order to maintain the temperature of the incineration ash at 20 ° C. or more and 60 ° C. or less, the top surface of the incinerated ash has heat insulation and water permeability depending on the ambient temperature in addition to the height of the incineration ash that is 0.8 m or more. Cover with mat to suppress the temperature drop of incinerated ash. Or heat insulation is given to the bottom wall and side wall of a pretreatment tank, and the temperature fall of incineration ash is suppressed.
This is even more advantageous in reducing the energy consumed by the heater or the like for maintaining the temperature conditions.
Various conventionally known materials can be used as the heat insulating material used when the bottom wall or the side wall is provided with heat insulating properties. If the self-heating of the incinerated ash can be maintained sufficiently, the material of the heat insulating material and the method of installing the heat insulating material are not particular.
Depending on the atmospheric temperature, the temperature of the incineration ash is further maintained at 20 ° C. or more and 60 ° C. or less, so that the incineration ash is heated from the bottom wall or the side wall of the pretreatment tank to suppress the temperature drop of the incineration ash.
By maintaining the self-heating of the incinerated ash in the incinerated ash layer in this way, the incinerated ash temperature during the pretreatment period is maintained within a desired temperature range above the ambient temperature, that is, 20 ° C. or higher and 60 ° C. or lower. It becomes possible, and it becomes possible to advance pretreatment of incineration ash effectively.

The incinerated ash stacked in a predetermined layer thickness is intermittently sprinkled at a predetermined interval, and when intermittently sprinkled, ventilation is also given to the incinerated ash. That is, a predetermined amount of artificial watering and an aeration process at a predetermined flow rate are performed on the incinerated ash sprinkled to a predetermined density and a predetermined layer thickness.
In this case, if ventilation is performed against the water permeation direction passing through the incinerated ash layer, the change over time of the water permeation speed through the incinerated ash layer after the start of watering is reduced, and There is little change over time in the elution amount of the eluate, which is advantageous for ensuring a stable elution state and ensuring reliable pretreatment quality.

Examples of this method are shown in FIGS.
The pretreatment facility 10 includes a pretreatment tank 12, a sprinkler 14, a venting device 16, a leachate collecting device 18, and a control device 20.
(Pretreatment tank 12)
The pretreatment tank 12 was a steel plate storage tank.
The steel plate storage tank includes a bottom wall and a casing in which the side walls rising from the periphery of the bottom wall are all made of a steel plate, and the inside of the steel plate storage tank has a width of 4.7 m, a depth of 7.0 m, and a depth of 4.0 m. A storage space of a size is formed.
On the bottom wall of the pretreatment tank 12, a urethane foam heat insulating material having a width of 80 cm and a thickness of 15 cm was laid with a space of 10 cm, and a water collection / ventilation groove having a width of 10 cm was arranged at intervals of 90 cm. A perforated tube having a nominal diameter of 50A was used for the water collecting / venting groove constituting both the venting device 16 and the leachate collecting device 18. Gravel was added to the upper end of the water collecting / venting groove to protect the perforated pipe, and a water / venting layer comprising gravel and a water collecting / venting groove was provided on the bottom wall.

(Incineration of ash into pretreatment tank 12)
The incinerated ash is carried by the backhoe into the pretreatment tank 12 and spread.
The incineration ash was carried in while installing a temperature sensor (thermocouple) at a depth of 0.4 m, 0.8 m, and 1.4 m from the surface of the incineration ash, and it was completed when 81 t was carried in. At this time, the depth of the incinerated ash from the upper surface of the water / air-permeable layer was 1.8 m, and the packing density was 1.37 g / cm ³ .

(Sprinkler 14 and leachate collector 18)
Watering was branched from the tap and supplied. Sprinkling is set up in the central part of the pretreatment tank 12 with a sprinkler area of 4.7 m × 4.7 m, and four sprinklers with a sprinkler radius of about 5 m and a sprinkler range (angle) of 90 degrees are installed at the four corners of the sprinkler area. .
The amount of watering was determined by setting the number of watering per day (watering interval) and the amount of watering per time. The sprinkling interval is controlled by a timer, and the solenoid valve is opened at the set time to start watering.After the watering starts, when the watering amount reaches the set watering amount based on the flow rate integrated value of the flowmeter, Closed water and finished watering.
The leachate was collected in the water collecting basin via the water collecting / venting groove at the bottom of the pretreatment tank 12. In order to maintain ventilation from the bottom of the incinerated ash, the water collecting basin has a water-sealed structure as shown in FIG.

(Ventilation device 16)
Outside air was supplied from the blower (air supply fan) installed outside the pretreatment tank 12 to the perforated pipe constituting the water collecting / venting groove installed at the bottom of the pretreatment tank 12 to ventilate the incineration ash layer. .
Various operations of the water sprinkler 14, the leachate collector 18 and the aeration device 16 are controlled by the controller 20.
In the examples, aeration was performed against the water permeation direction of water spray passing downward through the incinerated ash layer. In the watering process, by performing such aeration process, the change with time of the water permeation speed passing through the incinerated ash layer of the sprinkled water after the start of watering is smaller than in the case where such aeration process is not performed.
That is, the amount of elution of heavy metals, organic substances, etc. in the incinerated ash layer into the permeated water is greatly affected by the water permeation rate, but the pretreatment by watering reduces the change in water permeation rate over time as described above. In addition, the elution amount of the eluate in the leachate is little changed with time, and a stable elution state is ensured. As a result, a slow change due to the passage of time of the water permeation rate is suppressed, and the variation with time of the elution amount is stabilized. As a result, it is possible to ensure a highly reliable pretreatment quality.
In addition, if water is sprayed without using aeration treatment, a water-permeable road is inevitably formed in the incinerated ash layer, and water tends to flow along the road. However, when aeration treatment is performed from below against the water permeation direction, water infiltrates through the incinerated ash layer on average, and unevenness of the water permeation location is suppressed.
Such aeration treatment may be performed in parallel with watering. Alternatively, the watering process and the aeration process may be performed in succession. In such a case, the sprinkling process may be performed first or the aeration process may be performed first, but it is necessary not to perform both processes with an excessive time interval. Preferably, the subsequent processing may be continued after the end of the previous processing.

(Operating conditions of pretreatment facility)
(Watering conditions)
Sprinkling amount 1.2m ³ / day Leaching water amount 0.96m ³ / day Leaching water amount / watering amount 80%
Liquid-solid ratio at the time of 50 days elapsed 0.6
(Ventilation conditions)
Almost constant at a line velocity of 1.8 mm / sec

(effect)
(1) Maintenance of incineration ash temperature FIG. 8 shows changes over time in the incineration ash temperature and the outside air temperature during the pretreatment period.
(Maintain incineration ash temperature by self-heating phenomenon)
A state higher than the outside air temperature has been maintained since the start of the pretreatment, and an increase in the incineration ash temperature is observed due to the self-heating phenomenon of the incineration ash. This state decreased after peaking around 10 days after the start of pretreatment, and was maintained higher than the outside air temperature until the end of pretreatment. The change over time of the incinerated ash temperature at a depth of 0.3 m shown in the conventional method showed the same tendency as the outside air temperature in the early period after the start of the pretreatment even in the summer, so the landfill depth of the incinerated ash was increased. By taking it, it is clear that the temperature of the incinerated ash is effective.

(Incineration ash temperature change in upper layer)
Looking at the changes over time of the incineration ash temperatures of the upper layer (depth 0.4 m) and the middle layer (depth 0.8 m), the upper layer is not as low as the temperature drop at the landfill depth 0.3 m shown in the conventional method. There is a tendency that the temperature drop of the upper layer is quicker than that of the middle layer. This is because, by increasing the landfill depth, the temperature drop of the upper layer can be suppressed by the movement of heat from the middle layer, but the depth of about 0.4 m is considered to be affected by the outside air. Therefore, it is considered that a landfill depth of 0.8 m or more is desirable in order to maintain the incineration ash temperature using at least the self-heating phenomenon of the incineration ash.

(Lower incineration ash temperature change)
Looking at the changes over time in the incineration ash temperatures of the lower layer (depth 1.4m) and the upper layer (depth 0.4m), the bottom surface was insulated with urethane foam (thickness 15cm) until about 10 days after the start of pretreatment. Despite this, there was a period when the temperature was lower than the upper layer. This was thought to be due to the cooling effect due to the supply air from the bottom, but showed an upward trend until about 10 days after the start of pretreatment, and the amount of heat generated by the self-heating phenomenon of the incineration ash reduced the cooling due to the supply air. It was thought that it was higher. Further, the temperature of the upper layer was reversed about 15 days after the start of the pretreatment, and after about 30 days, it was reversed with the incineration ash temperature of the middle layer (depth 0.8 m). It is clear that it is effective for maintenance and management.

(Pretreatment effect)
(Effect on leachate EC value)
FIG. 9 shows the change over time in the EC value of leachate during the pretreatment period. The EC value was 1.2 S / m around 30 days after the start of pretreatment, and the EC value was below 1.0 S / m after 40 days. The pretreatment conditions shown in the conventional method are the landfill depth (conventional method: depth 0.3 m, example: depth 1.8 m), initial peak EC value (conventional method: about 3 S / m, example: about 4S / m), but the time-dependent change in the EC value with time of the leachate shown in the summer of the conventional method is almost the same as that of the leachate, and the landfill depth in the landfill and pretreatment conditions shown in the examples. It is clear that an effect equivalent to 0.3 m can be obtained.

(Effect on TOC concentration of leachate)
FIG. 10 shows changes with time in the TOC concentration of leachate during the pretreatment period. The TOC concentration was about 500 mg / l around 30 days after the start of pretreatment, and the TOC concentration was less than about 250 mg / l after 40 days. As mentioned in the time-dependent change of the EC value, the pretreatment conditions shown in the conventional method are the landfill depth (conventional method: depth 0.3 m, example: depth 1.8 m), initial peak TOC concentration (conventional Method: about 800 mg / l, Example: about 2000 mg / l), but the TOC concentration change over time is almost the same as the change in TOC concentration of leachate shown in the summer in the conventional method. After 50 days, it was confirmed that the concentration dropped to about 1/10 of the initial peak TOC concentration.

  Judgment of completion of pre-treatment should be based on the acceptance criteria of the recipients such as final disposal sites, taking into account the environmental impact of leachate, and adopting a judgment indicator. For example, when the acceptance standard is the elution value of incineration ash, an index indicating the concentration of organic matter or salt in the leachate when the incineration ash satisfies the elution value of the acceptance standard may be adopted as an index for determination. However, even if the incineration ash meets the acceptance criteria, or the acceptance criteria of the recipient are not determined, consider the environmental impact of the leachate at the recipient, and add organic matter in the leachate as an additional criterion. And an index representing the salt concentration may be adopted as a judgment index. For example, the TOC concentration or the like may be determined as an index that represents the organic substance concentration in the leachate. For example, it may be determined that the pretreatment is completed when the TOC concentration of the leachate reaches 100 mg / l. In order to reach such a criterion, it was confirmed by experiments that pretreatment was completed in about 40 to 50 days, although there were some differences due to the effects of the properties of incinerated ash. Of course, an EC value or the like may be used as an index for determination as an index indicating other salt concentrations. The advantage of using the TOC concentration as a determination index is that it is a numerical value that directly indicates the index substance as compared with the case where the TOC concentration is not used as an index. Incidentally, when other EC values or the like are used as an index for determination, for example, a numerical value of 1.0 S / m may be adopted as a reference.

According to the pretreatment described above, it is possible to reduce the TOC concentration and EC value of incinerated ash in a shorter period of time, and it is advantageous in reducing the amount of water used for the watering treatment.
In particular, as shown in FIG. 8, in regions and seasons where the temperature of the outside air changes between 18 ° C. and 28 ° C., the heat generated from the incineration ash at the initial stage of stacking without heating the incineration ash from the side or bottom surface. Since it can be held in the pretreatment tank, the temperature of the incineration ash can be maintained within a desired temperature range higher than the outside air temperature without using a heater, etc., and also in order to reduce the energy consumed for the pretreatment of the incineration ash. It will be advantageous.
The pretreated incineration ash that has been pretreated in this way is landed in a prescribed manner by dropping it into the storage structure of the final disposal site, or aggregate, embankment material, backfill material, etc. As reused.

  DESCRIPTION OF SYMBOLS 10 ... Pretreatment facility, 12 ... Pretreatment tank, 14 ... Sprinkling device, 16 ... Aeration device, 18 ... Leachate water collecting device, 20 ... Control device.

Claims (7)

Before incineration ash is reclaimed or reused as aggregate, embankment material, backfill material, etc., the incineration ash is accommodated in a pretreatment tank, and pretreatment of the incineration ash with sprinkling treatment and aeration treatment A pretreatment method for incinerated ash,
The temperature of the incinerated ash was maintained at 20 ° C. or higher and 60 ° C. or lower for at least 10 days from the start of pretreatment.
A pretreatment method for incinerated ash characterized by the above. The stacking height of the incineration ash from the bottom of the pretreatment tank was set to 0.8 m or more, and heat generated from the incineration ash at the initial stage of stacking was held in the pretreatment tank.
The pretreatment method for incinerated ash according to claim 1. The upper surface of the incinerated ash was covered with a mat having heat insulating properties and water permeability so as to suppress the temperature drop of the incinerated ash.
The pretreatment method for incinerated ash according to claim 2. The pretreatment tank has a bottom wall and a side wall rising from the periphery of the bottom wall,
The bottom wall and the side wall were given heat insulation properties so as to suppress the temperature drop of the incinerated ash,
The pretreatment method for incinerated ash according to claim 2 or 3. The pretreatment tank has a bottom wall and a side wall rising from the periphery of the bottom wall,
The incineration ash is heated from the bottom wall or the side wall, and the temperature drop of the incineration ash is suppressed.
The pretreatment method for incinerated ash according to any one of claims 2 to 4, wherein: The watering treatment is performed by watering from above the pretreatment tank,
The aeration treatment is performed by flowing air upward from the bottom of the pretreatment tank.
The pretreatment method for incinerated ash according to any one of claims 1 to 5. The temperature of the incinerated ash was maintained at 20 ° C. or higher and 60 ° C. or lower for at least 40 days from the start of pretreatment.
The pretreatment method for incinerated ash according to any one of claims 1 to 6.

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