JP2000070902A - Determining method of necessary addition amount of chelate heavy portal fixing agent, judging method of fixing effect of heavy metal in treated ash and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately determine the proper addition amt. of a chelating agent to ash containing heavy metals to prevent elusion of heavy metals, and to easily and accurately judge the effect to fix heavy metals in the ash which is treated to prevent elusion of heavy metals by adding a chelating agent to the ash containing heavy metals. SOLUTION: A chelating agent is added to a water slurry of ash containing heavy metals to measure the ORP. The amt. of the chelating agent added till decrease in the ORP is terminated is obtd., and the proper addition amt. of the chelating agent is determined from the measured amt. The effect to fix heavy metals in the treated ash is judged from the results of measuring the changes in the ORP when the chelating agent is added to the water slurry of the treated ash and by comparing the measured changes to the predetermined values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a required amount of a chelating heavy metal fixing agent for adding a chelating heavy metal fixing agent to a heavy metal-containing ash to prevent elution of heavy metals from the heavy metal-containing ash. The present invention relates to a method for easily and accurately determining the value and a device therefor. The present invention also provides a simple and accurate method for immobilizing heavy metals on treated ash which has been subjected to a treatment for preventing the elution of heavy metals from the heavy metal-containing ash by adding a chelating heavy metal fixing agent to the heavy metal-containing ash. The present invention relates to a determination method and an apparatus therefor.

[0002]

2. Description of the Related Art Ashes discharged from municipal waste incineration plants and the like include fly ash collected by a dust collector in a flue and incineration ash that is incinerated in an incinerator. Of these, fly ash with a high heavy metal content is required to be appropriately treated by the method specified by the Ministry of Health and Welfare.

[0003] One of the treatment methods specified by the Ministry of Health and Welfare is a chemical treatment method. As treatment chemicals, chelating agents and inorganic agents are generally used.

[0004] In such a chemical treatment, it is important to add the chemicals in an appropriate amount without excess or deficiency in order to prevent the elution of heavy metals while suppressing the chemical cost. .

[0005] Further, if the effect of preventing heavy metal elution of the treated ash is not sufficient, it is necessary to immediately reprocess the ash. Therefore, it is determined whether the treated ash has a sufficient effect of immobilizing heavy metal. It is important to do this quickly on site.

However, since the properties of incinerated fly ash vary greatly depending on the refuse and raw materials burned in the incinerator, it is very difficult to determine an appropriate chemical addition rate. Also,
At present, no method has been proposed for quickly and simply performing the effect of fixing the heavy metal of the treated ash on site.

Heretofore, some inorganic drugs have a method for determining the optimum addition rate, but there are no methods for determining the optimum addition rate for liquid chelating drugs. For this reason, in general, the addition rate is set to an excessive degree with respect to the properties of fly ash, or after the addition and kneading of the chemical, the dissolution test method specified by the Environment Agency (Test Method No. 13 by the Environment Agency) is used. In addition, a technique of measuring the elution concentration of heavy metals (particularly, lead and cadmium) and determining the optimum amount to be added has been adopted.

[0008] Further, after the fly ash is added with a chelating agent and kneaded, the mixture is treated under the same conditions as those of the Environment Agency Notification No. 13 test.
That is, a heavy metal is eluted into water over a long period of 6 hours, and the redox potential (ORP) of the eluate is measured to determine the amount of drug added (Japanese Patent Laid-Open No. 8-30931).
No. 2) has been proposed, but it is difficult to stably perform the processing because it is not possible to determine a processing specification that immediately responds to a change in the properties of fly ash.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems by adding a chelating heavy metal fixing agent to heavy metal-containing ash to prevent elution of heavy metal from the heavy metal-containing ash. An object of the present invention is to provide a method for determining a required amount of a chelating heavy metal fixing agent that can easily and accurately determine a required amount of a chelating heavy metal fixing agent, and an apparatus therefor.

[0010] The present invention also provides a simplified treatment of a heavy metal-containing ash by adding a chelating heavy metal fixing agent to the ash to prevent the elution of the heavy metal from the heavy metal-containing ash. It is an object of the present invention to provide a method for determining the effect of immobilizing heavy metals on treated ash, which can be accurately and accurately determined, and an apparatus therefor.

[0011]

According to a first aspect of the present invention, there is provided a method for determining a required amount of a chelating heavy metal fixing agent, the method comprising adding a chelating heavy metal fixing agent to a heavy metal-containing ash and eluting the heavy metal from the heavy metal-containing ash. The method for determining the required amount of the chelating heavy metal fixing agent to prevent the addition of the chelating heavy metal fixing agent to a slurry of the heavy metal-containing ash and water to reduce the oxidation-reduction potential of the slurry. The amount of the chelating heavy metal immobilizing agent added until the change in the oxidation-reduction potential per the amount of the chelating heavy metal immobilizing agent reaches a predetermined value is determined. And determining the required addition amount.

According to a second aspect of the present invention, there is provided a method for determining a heavy metal-immobilizing effect of a treated ash, in which a chelate-based heavy metal-immobilizing agent is added to the heavy metal-containing ash to perform a treatment for preventing elution of the heavy metal from the heavy metal-containing ash. In the method for judging the effect of immobilizing heavy metals on treated ash, the method comprises adding the chelating heavy metal fixing agent to a slurry of the treated ash and water, and oxidizing and reducing the slurry before and after the addition of the chelating heavy metal fixing agent. The amount of change in the potential is measured, and the amount of change is compared with a preset value to determine the effect of the treated ash on immobilizing heavy metals based on the result.

According to a third aspect of the present invention, there is provided an apparatus for determining the required amount of a chelate-based heavy metal-immobilizing agent for adding a chelate-based heavy metal-immobilizing agent to a heavy metal-containing ash to prevent elution of the heavy metal from the heavy metal-containing ash. A device for determining the required addition amount of the chelating heavy metal fixing agent, a means for adding the chelating heavy metal fixing agent to a slurry of the heavy metal-containing ash and water and measuring an oxidation-reduction potential of the slurry; Means for calculating the change in the oxidation-reduction potential per the amount of the chelate-based heavy metal fixing agent, and the chelating-based heavy metal fixing agent required until the calculated change in the oxidation-reduction potential reaches a preset value And a means for calculating the required addition amount based on the calculated addition amount.

According to a fourth aspect of the present invention, the apparatus for determining the effect of immobilizing heavy metals on treated ash includes a treatment for preventing the elution of heavy metals from the heavy metal-containing ash by adding a chelating heavy metal fixing agent to the heavy metal-containing ash. In a device for determining the effect of immobilizing heavy metals on the treated ash, the chelating heavy metal fixing agent is added to the slurry of the treated ash and water, and the oxidation reduction of the slurry before and after the addition of the chelating heavy metal fixing agent is performed. It is characterized by comprising means for measuring the amount of change in potential, and means for comparing the amount of change with a preset value and determining the effect of the treated ash on immobilizing heavy metals based on the result.

That is, the present inventors added a chelating heavy metal fixing agent (hereinafter simply referred to as "chelating agent") to heavy metal-containing ash to prevent heavy metal from eluting. Minimum amount of chelating agent that can be prevented (hereinafter referred to as “appropriate amount”
Called. After various investigations on the method for determining
As the chelating agent is added to the water slurry of the heavy metal-containing ash, the oxidation-reduction potential (ORP) decreases, and this OR
The amount of the chelating agent added up to the point at which P stops decreasing (hereinafter, referred to as “end ORP”) (hereinafter, this amount is referred to as “titration”) is correlated with the appropriate addition amount. I found to do.

The inventions of claims 1 and 3 are based on such knowledge, and the titration and the proper addition amount of several kinds of heavy metal-containing ash are checked in advance, and the proper quantification and the proper addition amount are determined. Calibration curve showing the correlation of is prepared in advance, and titration is determined for heavy metal-containing ash to determine the appropriate addition amount,
The appropriate addition amount corresponding to the titer is determined from the calibration curve.

The present inventors have also conducted various studies on a method for accurately determining the effect of immobilizing heavy metals on treated ash obtained by adding a chelating agent to heavy metal-containing ash and performing a treatment to prevent elution of heavy metals. The amount of change in ORP when the chelating agent is added to the water slurry is correlated with the heavy metal fixing effect of the treated ash. If this change is equal to or less than a predetermined value, the heavy metal fixing effect is sufficient. When it exceeds, it was found that the effect of immobilizing heavy metals was insufficient.

The invention according to claims 2 and 4 is based on such knowledge, and measures a change amount of ORP of the treated ash and water when a chelating agent is added to the slurry, The change amount is compared with a preset value, and the heavy metal fixing effect of the treated ash is determined based on the result.

In determining the effect of immobilizing heavy metals, a chelating agent is added to the water slurry of the treated ash to increase the ORP.
Is determined, the point at which the ORP stops decreasing, that is, the amount of the chelating agent added until the “end ORP” is reached, that is, the “titration amount” is determined. From this, it is also possible to determine the necessary additional amount for reprocessing the treated ash.

It should be noted that the calibration curve for obtaining the required addition amount is not a general calibration curve obtained from ORP titration of various heavy metal-containing ash having different collection sites and collection dates and times.
It is desirable to create a calibration curve limited to heavy metal-containing ash that differs only in the collection date and time at the same collection site, and use this to determine the required additional amount of heavy metal-containing ash at that site.

In particular, when the treatment effect on the treated ash after the treatment with the chelating agent is judged and the chelating agent is additionally added to the treated ash judged to be insufficient in effect, the additional amount is extremely small. Therefore, it is necessary to more accurately determine the required additional amount. For this purpose, it is preferable to use a calibration curve prepared using a heavy metal-containing ash at the same sampling site as a sample.

[0022]

Embodiments of the present invention will be described below in detail.

First, the method and apparatus for determining the required amount of the chelating agent of the present invention will be described.

In order to determine the appropriate amount of the chelating agent according to the method for determining the required amount of the chelating agent of the present invention,
First, using several types of heavy metal-containing ash as samples, a calibration curve showing the relationship between the titration amount and the appropriate addition amount is prepared. The titer for preparing this calibration curve can be determined according to a method for measuring the end ORP and the titer described later. In addition, the appropriate addition amount may be determined by conducting a test of the Environment Agency Notification No. 13, and determining the minimum addition amount of the chelating agent which can surely prevent the elution of heavy metals, that is, satisfy the reference value.

It is preferable to use as many heavy metal-containing ash as a sample for preparing the calibration curve from the viewpoint of accuracy. Generally, it is sufficient to prepare about 5 to 20 types of heavy metal-containing ash from the relationship between the accuracy of the calibration curve and the number of operations. Further, as described above, in order to determine the amount of addition more accurately, it is desirable to use heavy metal-containing ash collected from the same site on different collection dates.

Next, a method for measuring the end ORP and the titer in the method for determining the required amount of the chelating agent of the present invention will be described.

First, a heavy metal-containing ash is added to water to make it 1-1.
Stir and mix for about 0 minutes to prepare a slurry. In preparing this slurry, the mixing ratio of heavy metal-containing ash and water was
The solid-liquid ratio (L (mL) / s (g)) is preferably about 10 to 1,000, particularly about 800 to 1,000.

Next, a chelating agent is dropped into the slurry little by little, and the ORP is measured for each drop.

As described above, when the chelating agent is dropped little by little, the ORP decreases while the total amount of the chelating agent is small, but eventually the ORP changes only slightly (stops decreasing) even when the chelating agent is further dropped. The dropping amount of the chelating agent required so far (the amount of the chelating agent added until reaching the end ORP) is determined as a titration amount.

When the dropping stops, the inclination of the titration curve in the graph of the titration curve in which the abscissa indicates the amount of the chelating agent dropped (weight% vs. ash containing heavy metal) and the ordinate indicates the measured value of ORP (mV). It can be obtained as a point in time at which a preset value is reached, and the set value is preferably -10 to 0, and particularly preferably -7 to -2.

Further, such a titration operation is performed plural times,
The average value of the titration amounts may be used for calculating the appropriate addition amount.

After the titer is determined in this way, an appropriate addition amount corresponding to the titer is determined from a calibration curve prepared in advance, and a necessary addition amount of the chelating agent is determined.

The method for determining the required amount of the chelating agent according to the present invention comprises a means for measuring the ORP by adding the chelating agent to the water slurry of the heavy metal-containing ash, and a method for measuring the change in the ORP per the amount of the chelating agent added. Means for calculating the amount, means for calculating the addition amount of the chelating agent required until the calculated change amount of ORP reaches a preset value, and calculating an appropriate addition amount based on the calculated addition amount It can be easily implemented using the apparatus of the present invention comprising

Next, a method and an apparatus for determining the effect of immobilizing heavy metals on treated ash according to the present invention will be described.

In order to determine the heavy metal fixing effect of the treated ash according to the method for determining the heavy metal fixing effect of the treated ash according to the present invention, the amount of ORP change per chelating agent added amount when the chelating agent is added to the treated ash And comparing this change amount with a preset value, if it is larger than this set value, it is determined that the heavy metal fixing effect is insufficient, and if it is less than this set value, it is determined that the heavy metal fixing effect is sufficient. I do.

In carrying out the method of the present invention for determining the effect of immobilizing heavy metals on treated ash, more specifically, the effect of immobilizing heavy metals is determined as follows, and the above-described chelating agent of the present invention is used. It is preferable to use the calibration curve in the description of the method for determining the required addition amount to determine the required additional addition amount of the chelating agent when the treated ash determined to be processing failure is reprocessed.

First, the treated ash is added to water and stirred and mixed for about 1 to 10 minutes to prepare a slurry. In preparing this slurry, the mixing ratio of the treated ash and water is determined by the solid-liquid ratio (L
(ML) / s (g)) from 10 to 1000, especially from 800 to
It is preferred to be about 1000.

Next, a chelating agent is dropped into the slurry little by little, and the ORP is measured for each drop.

As described above, when the chelating agent is dropped little by little, the ORP hardly changes and stops decreasing when the heavy metal fixing effect is sufficient.
Such treated ash can be determined to have a sufficient heavy metal fixing effect.

If the treated ash has an insufficient effect of immobilizing heavy metals, if the chelating agent is added dropwise little by little,
The ORP decreases while the total amount of the drops is small, but eventually the ORP changes only slightly even when the amount is further dropped, and stops decreasing. Chelating agent dripping amount required so far,
That is, the amount of the chelating agent added up to the end of the ORP is determined as a titer.

At the time when the dropping stops, the drop amount of the chelating agent (weight% vs. ash containing heavy metal) is plotted on the horizontal axis, and the measured ORP value (mV) is plotted on the vertical axis.
It can be obtained as a point in time at which the inclination of the titration curve becomes a preset value, and the set value is preferably -10 to 0, and particularly preferably -7 to -2.

After obtaining the titer in this manner, an appropriate addition amount corresponding to the titer is obtained from a calibration curve prepared in advance, and this is determined by the necessity of a chelating agent for reprocessing the treated ash. Add the amount to be added.

According to the method for determining the effect of immobilizing heavy metals on treated ash of the present invention, a chelating agent is added to a slurry of treated ash and water, and the OR of the slurry before and after the addition of the chelating agent is determined.
Using the apparatus of the present invention comprising means for measuring the amount of change in P and means for comparing the amount of change with a preset value and determining the effect of fixing the heavy metal of the treated ash based on the result. , Can be easily implemented.

[0044]

The present invention will be described more specifically with reference to the following examples.

In the following examples, as a chelating agent, "Ashnite S-80" manufactured by Kurita Kogyo KK
A 100-fold dilution of "1" was used.

Example 1 (I) Preparation of Calibration Curve (I) -1 Properties of Test Fly Ash Table 1 shows the results of component analysis of some of the fly ash used in preparing the calibration curve.

[0047]

[Table 1]

Table 2 shows the results of the harmful heavy metals elution test performed on the fly ashes A to C by the test method of Notification No. 13 of the Environment Agency.

[0049]

[Table 2]

(I) -2 Measurement of ORP and Titration The blank ORP, the end ORP, and the titration were determined by the following procedures for a total of nine test fly ashes including the above fly ashes A to C.

In a 500 mL beaker, 30 g of fly ash and 300 mL of pure water are added (solid-liquid ratio = 10), and the mixture is gently stirred with a stirrer. 3 mL (0.3 g-fly ash) of the fly ash slurry having the solid-liquid ratio = 10 was collected with a microsyringe, and another 500 mL
Add 300 mL of pure water to a beaker (solid-liquid ratio = 100
0) Stir with a stirrer for 5 minutes. After stirring for 5 minutes, turn on the ORP meter. When the ORP is stabilized, read the value and measure the blank ORP. Next, the chelating agent is added dropwise in small amounts (0.2% by weight based on fly ash), and the mixture is stirred for 5 minutes each time the ORP is stabilized. The dropping amount (titration) of the chelating agent when the ORP stops decreasing (when the ORP reaches the end). Here, when the ORP change rate is about 2 mV / the amount of the chelating agent dropped (weight% vs. fly ash), that is, the measured ORP value (m
V) is the vertical axis, and the drop amount of the chelating agent (weight% vs. fly ash) is a horizontal axis, and the drop amount of the chelating agent until the slope becomes -2 (mV / weight% vs. fly ash) is plotted. Was determined as the titer.

FIG. 1 shows the relationship between the dropping amount of the chelating agent for fly ashes A to C and the change in ORP among the test fly ash. Also,
Table 3 shows the blank ORP, end ORP, and titer of these fly ashes A to C.

[0053]

[Table 3]

(I) -3 Measurement of Proper Addition Amount of Chelating Agent In order to make the elution amount of lead and cadmium 0.05 mg / L or less for a total of nine test fly ashes including the fly ashes A to C described above. The required amount of chelating agent added was determined.

The test was conducted according to the method of the Environment Agency Notification No. 13 test.

Fly ash 50 in a 500 mL poly beaker
g and 10 mL (20%) of water are added, a predetermined amount of a chelating agent is added, and the mixture is thoroughly kneaded with a spatula to prepare a test sample. 50 g of this test sample and 500 mL of water are placed in a 1-L polyvin and shaken for 6 hours. Thereafter, the mixture is filtered through a 1 μm glass fiber filter paper, and the filtrate is analyzed. The above procedure is repeated, and the minimum amount of the chelating agent added at which the elution amount of lead and cadmium becomes 0.05 mg / L or less is determined.

Table 4 shows the appropriate amounts of the chelating agents for fly ashes A to C among the test fly ash.

[0058]

[Table 4]

(I) -4 Preparation of Calibration Curve For the 11 kinds of test fly ash, the calibration curve was obtained from the appropriate addition amount of the chelating agent determined in (I) -3 and the titration determined in (I) -2. Create

The calibration curve created here was as shown in FIG.

(II) Determination and Confirmation of Appropriate Addition (II) -1 Determination of Appropriate Addition For fly ash D, an appropriate addition of a chelating agent was determined in accordance with the present invention.

Tables 5 and 6 show the results of the component analysis of the fly ash D and the results of the harmful heavy metals elution test by the Environment Agency Notification No. 13 test method, respectively.

[0063]

[Table 5]

[0064]

[Table 6]

When the fly ash D was titrated in the same procedure as in the above (I) -2, a titration curve shown in FIG. 3 was obtained, and the titer was 2% by weight to fly ash.

When an appropriate amount of the chelating agent was determined from the appropriate amount based on the calibration curve of FIG. 2, the appropriate amount was estimated to be 3% by weight.

(II) -2 Confirmation of proper addition amount For fly ash D, in the same manner as in (I) -3, changing the addition amount of the chelating agent, the leaching test of harmful heavy metals by the Environmental Agency Notification No. 13 test method was carried out. Table 7 shows the results.

[0068]

[Table 7]

As is evident from Table 7, when the amount of the chelating agent added is 3% by weight or more, the elution amount of lead and cadmium is 0.05 mg / L or less, and the appropriate addition amount "3" % By weight "was actually confirmed to be effective in preventing elution of heavy metals.

Example 2 (I) Preparation of Calibration Curve In the same manner as (I) of Example 1, calibration curves were prepared for five types of fly ash collected from site H at different collection dates.

The ORP is performed in the same manner as in (I) -2 of the first embodiment.
FIG. 4 shows a chelate titration curve obtained by titration. However, when the ORP stopped decreasing (when the ORP ended), the dropping amount (titration) of the chelating agent was about 6 mV / change rate of the ORP / dropping amount of the chelating agent (weight% vs. fly ash). In other words, in a graph in which the measured value of ORP (mV) is the vertical axis and the amount of the chelating agent dropped (weight% vs. fly ash) is the horizontal axis, the slope is -6 (mV / weight% vs. fly ash). The amount of the chelating agent dropped until the time was reached.

The amount of the chelating agent added when the appropriate amount of the chelating agent was determined in the same manner as in (I) -3 of Example 1 and the amount of lead eluting in the eluate according to the Environment Agency Notification No. 13 test, The proper addition amount (minimum amount of the chelating agent added necessary to reduce the amount of lead eluted to 0.05 mg / L or less) is as shown in Table 8.

[0073]

[Table 8]

The calibration curves prepared from FIG. 4 and Table 8 are as shown in FIG.

(II) Judgment of treatment effect and determination and confirmation of necessary additional amount One of the five types of fly ash at Site H (2/16
(Fly ash) For each of the treated ash (1) to (4) treated by adding a chelating agent at 0% by weight, 1% by weight, 2% by weight, 3% by weight, and 4% by weight, judgment of the processing effect and necessity In order to determine the additional amount, the titration curve and the titration amount of the amount of chelating agent-ORP were determined for each treated ash by the following procedure.

30 g of treated ash in a 500 mL beaker
And 300 mL of pure water (solid-liquid ratio = 10) and lightly stirred with a stirrer. 3 mL (0.3 g-fly ash) of the treated ash slurry having a solid-liquid ratio of 10 was collected with a microsyringe, and another 500 m
Add 300 mL of pure water to L beaker (solid-liquid ratio = 10
00) Stir with a stirrer for 5 minutes. After stirring for 5 minutes, turn on the ORP meter. When the ORP is stabilized, read the value and measure the blank ORP. Next, the chelating agent is added dropwise in small amounts (0.4% by weight with respect to the treated ash), and the mixture is stirred for 5 minutes each time the ORP is stabilized. The dropping amount (titration) of the chelating agent when the ORP stops decreasing (when the ORP reaches the end). Here, when the rate of change of the ORP is about 6 mV / the amount of the chelating agent dropped (weight% vs. fly ash), that is, the measured value of the ORP (m
V) is the vertical axis, and the drop amount of the chelating agent (weight% vs. fly ash) is a horizontal axis, and the drop amount of the chelating agent until the slope becomes -6 (mV / weight% vs. fly ash) is plotted. Was determined as the titer.

FIG. 6 shows the obtained titration curve. In addition,
FIG. 6 also shows the result of untreated 2/16 fly ash for comparison.

The following is clear from FIG.

The treated ash (4), in which the added amount of the chelating agent was 4% by weight to the fly ash, was 0% even when titrated with the chelating agent.
RP has already stopped decreasing, and it can be determined that the effect of immobilizing heavy metals is sufficient.

Further, in the case of treated ash (1) in which the chelating agent was added by 1% by weight with respect to fly ash, the titer was 2.4% by weight with respect to fly ash, which was necessary compared to the calibration curve of FIG. The added amount is 3% by weight to fly ash. That is, the total amount of the chelating agent added is 4 (= 1 + 3)% by weight to fly ash. Similarly,
In the treated ash (2) in which the chelating agent was added at 2% by weight to fly ash, the required additional amount was 2% by weight to fly ash, and the total amount of the chelating agent added was 4% by weight to fly ash.

From these results, it can be understood that the effect of immobilizing heavy metals can be determined from the amount of change in ORP, and that the required additional amount can be determined from the titration amount and a previously prepared calibration curve.

[0082]

As described in detail above, according to the method and apparatus for determining the required amount of the chelating heavy metal fixing agent of the present invention, it is possible to easily and appropriately control the amount of the chelating agent added prior to the treatment of the heavy metal-containing ash. Since it can be accurately determined and measurement at the site is easy, immediate and fine chemical injection control can be performed in response to fluctuations in the properties of the heavy metal-containing ash to be processed, thereby ensuring stable and reliable Processing can be performed. The excessive addition of the chelating agent becomes unnecessary, and the cost of the drug can be reduced. Such an effect is produced.

Further, according to the method and apparatus for judging the effect of immobilizing heavy metals on treated ash of the present invention, the effect of immobilizing heavy metals on the treated ash after adding a chelating agent to the ash containing heavy metal can be easily and easily obtained. It can be obtained accurately, the judgment on site is easy, and the required additional amount can be easily obtained. More reliable processing can be performed.

[Brief description of the drawings]

FIG. 1 is a graph showing titration curves of fly ashes A to C obtained in Example 1.

FIG. 2 is a graph showing a calibration curve obtained in Example 1.

FIG. 3 is a graph showing a titration curve of fly ash D obtained in Example 1.

FIG. 4 is a graph showing titration curves of five types of fly ash at site H obtained in Example 2.

FIG. 5 is a graph showing a calibration curve obtained in Example 2.

FIG. 6 is a graph showing titration curves of treated ash and 2/16 fly ash obtained in Example 2.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichiro Ito 3-4-7 Nishi-Shinjuku, Shinjuku-ku, Tokyo Kurita Kogyo Co., Ltd. (72) Keiichi Mizuguchi 3-4-2, Nishishinjuku, Shinjuku-ku, Tokyo Kurita Industry Co., Ltd.

Claims (4)

[Claims] 1. A method for determining a required amount of a chelating heavy metal fixing agent for adding a chelating heavy metal fixing agent to a heavy metal-containing ash to prevent elution of heavy metals from the heavy metal-containing ash, The chelate-based heavy metal fixing agent is added to the heavy metal-containing ash and water slurry, and the oxidation-reduction potential of the slurry is measured. The change in the oxidation-reduction potential per the added amount of the chelate-based heavy metal fixing agent is determined. The required addition amount of the chelate-based heavy metal fixing agent is obtained by determining the added amount of the chelating-based heavy metal fixing agent added until the value reaches a preset value, and determining the required addition amount based on the added amount. How to determine. 2. A method for judging a heavy metal-immobilizing effect of a treated ash which has been treated by adding a chelating heavy metal fixing agent to a heavy metal-containing ash to prevent elution of heavy metals from the heavy metal-containing ash. Adding the chelating heavy metal fixing agent to the slurry of the treated ash and water, measuring the amount of change in the oxidation-reduction potential of the slurry before and after adding the chelating heavy metal fixing agent, and presetting the amount of change A method for determining the heavy metal fixing effect of the treated ash on the basis of this result in comparison with the determined value. 3. An apparatus for determining a required amount of a chelating heavy metal fixing agent for adding a chelating heavy metal fixing agent to a heavy metal-containing ash to prevent elution of heavy metals from the heavy metal-containing ash, Means for adding the chelating heavy metal fixing agent to the slurry containing the heavy metal-containing ash and water to measure the oxidation-reduction potential of the slurry; and a change in the oxidation-reduction potential per amount of the chelating heavy metal fixing agent added. Means for calculating the amount of the chelating heavy metal fixing agent required until the calculated amount of change in the oxidation-reduction potential reaches a preset value, and based on the calculated amount of addition. Means for calculating the required addition amount. An apparatus for determining the required addition amount of a chelate-based heavy metal fixing agent, comprising: means for calculating the required addition amount. 4. An apparatus for judging the effect of immobilizing heavy metals on treated ash which has been subjected to a treatment for adding a chelating heavy metal fixing agent to heavy metal-containing ash to prevent elution of heavy metals from said heavy metal-containing ash. Means for adding the chelating heavy metal fixing agent to the slurry of the treated ash and water, and measuring the change in the oxidation-reduction potential of the slurry before and after the addition of the chelating heavy metal fixing agent; Means for determining the effect of fixing the heavy metal of the treated ash based on the result of comparison with a preset value, and determining the effect of fixing the heavy metal of the treated ash.