JP2003290736A - Method of treating fly ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating fly ash by which an increase in running cost of water to be used for the washing of the fly ash or of a neutralizer to be used for neutralizing washing water obtained after the washing of the fly ash are prevented and the residue obtained after the washing of the fly ash is effectively used. <P>SOLUTION: The method of treating the fly ash is composed of a 1st process for washing the fly ash containing chlorine, calcium and heavy metals and separating the washed fly ash into a residue and a liquid, a 2nd process for washing the residue and separating the washed residue into a residue and a liquid and a 3rd process for neutralizing the liquid obtained in the 1st process with the neutralizer and separating the neutralized liquid into a residue and a liquid, and the liquid obtained in the 2nd process is used for the washing in the 1st process, a refinery waste water is used for the washing in the 2nd process and a liquid in the refinery process is used as the neutralizer in the 3rd process. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating fly ash, and particularly to a fly ash generated from an incinerator or a melting furnace in a municipal waste incinerator or an industrial waste incinerator, or a cement kiln for treating sludge. It relates to a method of treating ash.

[0002]

2. Description of the Related Art Garbage (referred to as "urban waste" or "general waste") and shredder dust (abandoned home appliances, abandoned automobiles, etc.) emitted from general offices and homes
Are collected and incinerated in municipal waste incineration facilities or industrial waste incinerators. At that time, incineration ash and fly ash generated from the incinerator are deposited at the final disposal site after intermediate treatment.

In the intermediate treatment of fly ash, slaked lime is blown into fly ash in order to neutralize hydrogen chloride gas generated by incineration of waste. The amount of slaked lime used is 3 to 5 which is a theoretical amount. It is said that double is needed.

Further, as a general treatment method of fly ash, a method of landfilling fly ash after preventing elution of heavy metals by neutralization with an acid, or a method of washing fly ash with water and returning it to a melting furnace or a cement kiln (melting) Treatment, cement kiln treatment).

[0005]

However, in the method of landfilling fly ash after preventing elution of heavy metals by neutralization with acid, elution of salts and heavy metals in the ash after landfill is a problem, and final disposal The place is tight. Also,
The melting process can reduce the volume of fly ash, but there is a problem that fly ash is generated again due to melting. Further, in the cement kiln treatment, landfill disposal is not performed, but unreacted slaked lime and heavy metals in fly ash cannot be reused and recycled, and fly ash is also generated.

In the fly ash washing method, the water used for washing the fly ash and the neutralizing agent used for neutralizing the wash water containing a trace amount of heavy metals generated during the washing. There is a problem with the increase in running cost and the method of utilizing the residue obtained after washing the fly ash with water.

Therefore, in view of such conventional problems, it is an object of the present invention to provide a method for treating fly ash which can prevent an increase in running cost of water used for washing fly ash. And

Further, the present invention provides a method for treating fly ash, which can prevent an increase in running cost of a neutralizing agent used for neutralizing washing water obtained after washing fly ash with water. With the goal.

A further object of the present invention is to provide a method for treating fly ash, which can utilize the residue obtained after washing the fly ash with water.

[0010]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the inventors of the present invention washed the fly ash containing chlorine, calcium and heavy metals with water to form a first residue and a first liquid. The first step of separating and the second residue after washing the first residue with water
Residue and a second step of separating into a second liquid, wherein the second liquid obtained in the second step is used for the water washing in the first step, and the smelter is used for the water washing in the second step. The inventors have found that a method of treating fly ash using waste water can prevent an increase in running cost of water used for washing fly ash, and have completed the present invention.

That is, the method of treating fly ash according to the present invention comprises a first step of washing fly ash containing chlorine, calcium and heavy metals with water to separate it into a first residue and a first liquid, and the first step.
The second residue is washed with water to separate it into a second residue and a second liquid.
The second liquid obtained in the second step is used for the water washing in the first step, and the smelter drainage is used for the water washing in the second step.

This method for treating fly ash includes a third step of neutralizing the first liquid obtained in the first step with a neutralizing agent to separate it into a third residue and a third liquid. Is preferred.

The method for treating fly ash according to the present invention comprises a first step of washing fly ash containing chlorine, calcium and heavy metals with water to separate it into a first residue and a first liquid, and the first step. It is characterized by comprising a third step of neutralizing the first liquid obtained in the step with a neutralizing agent to separate it into a third residue and a third liquid.

In the above method for treating fly ash, it is preferable to use the liquid in the smelter process as the neutralizing agent in the third process. Further, it is preferable to use the third residue obtained in the third step in the smelting step. Furthermore, it is preferable to treat the third liquid obtained in the third step with activated carbon for wastewater treatment.

Further, the method of treating fly ash according to the present invention is
The first step of washing fly ash containing chlorine, calcium and heavy metals with water to separate it into a first residue and a first liquid, and washing the first residue with water to form a second residue and a second liquid. A second step of separating, and a third step of neutralizing the liquid obtained in the first step with a neutralizing agent to separate into a third residue and a third liquid, the first step The second obtained in the second step for washing with water in
Is used, the smelter wastewater is used for washing in the second step, and the smelter in-process solution is used as the neutralizing agent in the third step.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for treating fly ash according to the present invention will be described in detail below with reference to the treatment process chart of FIG.

First, as shown in FIG. 1, the fly ash is washed with primary water, and then solid-liquid separated into a primary wash residue and primary wash water.

Next, the smelter wastewater is used to wash the primary washing residue with secondary water, and then the secondary washing residue (recovered slaked lime).
And solid-liquid separation into secondary washing water.

The secondary washing water obtained by this solid-liquid separation is used for the primary washing of fly ash. In addition, the secondary washing residue is used as a neutralizing agent in a smelter or a waste treatment plant. That is, as shown in FIG. 2, when the acidic smelter process liquid (the undiluted liquid of the wastewater before neutralization) is neutralized with slaked lime and the neutralization residue is used in the smelting process, Use the secondary washing residue for neutralization in the smelter.

On the other hand, after the primary washing water obtained by solid-liquid separation after the primary washing is neutralized with the liquid (acidic liquid) in the process of the smelter, it is solid-liquid into the neutralization residue and the neutralized liquid. To separate. The neutralization residue thus obtained is used in the smelting process. In addition, after the pH of the solution after neutralization is adjusted, it is treated with activated carbon if necessary, and then treated with waste water.

In the embodiment of the method for treating fly ash according to the present invention, when the fly ash is treated in the smelter, the fly ash is washed with water or neutralized with wash water by using the smelter process liquid or waste water. By reducing the running cost by carrying out, and by using the washing residue obtained by washing the fly ash as a neutralizing agent in the smelting process, the unreacted slaked lime in the fly ash is reused, and the washing residue and washing water are reused. Heavy metals are recycled by using the neutralization residue as a neutralizing agent in the smelting process and returning it to the furnace of the smelter. In addition, by using all wastewater other than salt-dissolved wastewater as raw materials in a smelter or a waste treatment plant, new waste other than wastewater is not generated and the amount of fly ash landfill is reduced. , Reuse, Rec
ycle) to build.

In the embodiment of the method for treating fly ash according to the present invention, the fly ash is washed with water to recover the unreacted slaked lime in the fly ash and use it as a neutralizing agent in a smelter or a waste treatment plant. This is a process that does not generate new waste other than wastewater. In this treatment method, the wastewater generated in the smelting process is used for washing fly ash to reduce the water cost. Further, the chemical process cost is reduced by using the acidic in-process liquid generated in the smelting process as a neutralizing agent for the wash water containing a trace amount of heavy metals generated when the fly ash is washed with water.

In the embodiment of the method for treating fly ash according to the present invention, the fly ash is general waste, industrial waste,
Includes hydrochloric acid gas generated when incinerating shredder dust, etc., with slaked lime, and hydrochloric acid gas generated from a melting furnace or cement kiln, etc., with slaked lime. Includes all the fly ash generated by neutralizing the hydrochloric acid gas generated in 1. with slaked lime. Fly ash contains, in addition to calcium and chlorine, heavy metals such as lead, zinc, copper and cadmium, and calcium may be calcium chloride or slaked lime.
Further, by washing the fly ash with water, the quality of Cl in the recovered slaked lime that can be used in smelting becomes 1% or less.

In the embodiment of the method for treating fly ash according to the present invention, by using the smelter wastewater as the water used for washing fly ash, the total wastewater discharged from the smelter is not increased and the water cost is reduced. Reduce. The pulp concentration and the number of washing stages for washing fly ash with water are determined in consideration of the amount of water that can be used for washing and the equipment cost. When washing with water in multiple stages, the total amount of water used is reduced by using the washing water generated after washing in the subsequent process in the previous stage.

Here, the smelter effluent is a liquid obtained by subjecting the process effluent discharged from the wet treatment process of the smelter to a detoxification treatment such as neutralization and filtration, and containing almost no heavy metals,
It is a liquid containing a small amount of calcium, chlorine, lead, zinc, etc. On the other hand, since fly ash also contains chlorine, lead and zinc, mixing fly ash with smelter effluent does not cause any special chemical reaction and causes no problem. Furthermore, if solid-liquid separation is performed after this mixing,
In addition to having the effect of dechlorinating fly ash, metals from smelter effluent can also be added to the residue and contribute to the recovery of metals in smelter effluent.

Since the fly ash wash water has a high alkali pH of about 11 and a Cl concentration of about 15 to 20 g / L, the fly ash wash water contains several to several tens mg / L of Pb and Zn. It dissolves to some extent. Neutralization with an acid such as hydrochloric acid or sulfuric acid to remove these Pb and Zn makes it difficult to agglomerate / separate because of the small amount of residue generated. Therefore, by neutralizing the wash water of fly ash using the liquid in the smelter process, the amount of residue generated is increased, aggregation and sedimentation are improved, and the cost of the neutralizing agent is reduced. . This neutralization is p
H8.5 to 10.5, preferably pH 9.5 to 10.5. This is because this range is suitable for recovering the lead and the like eluted from the fly ash by sedimentation (residue).

Here, the smelting process liquid is a liquid after leaching the ore with an acid, a liquid used for electrolytic smelting or the like, and a waste acid liquid generated in the smelter, which is mainly acidic. And
It contains sulfuric acid and has a pH of 2 or less. The smelter process liquid contains heavy metals such as zinc, aluminum, iron, and cadmium, and contains 5 to 60 g / L of zinc, 0 to 15 g / L of aluminum, and 5 mg / L to 10 g / L of iron. In addition, the total of zinc, aluminum and iron is preferably 0.4 g / L or more. This is because if the amount is 0.4 g / L or less, the amount of the in-process liquid used in the method for treating fly ash according to the present invention is large and the cost may increase.

COD in the wash water is also obtained by washing the fly ash with water.
If it is expected that the water will exceed the drainage standard,
It is desirable to use activated carbon in combination.

The washing residue can be used as a neutralizing agent in a smelting plant or a wastewater treatment plant, but it is preferable to use it in the smelting plant because heavy metals in the washing residue are also recycled in the smelting process. .

The neutralization residue is Z derived from the liquid in the smelter process.
Since a large amount of n, Fe and the like is contained, these valuable heavy metals can be recycled by removing the attached salts by washing with water and then returning to the smelter process.

[0031]

EXAMPLES Examples of the method for treating fly ash according to the present invention will be described in detail below.

[Example 1] First, fly ash (Ca31.3%, Cl10.9%, Pb1,197m) from general waste.
g / kg, Zn4,433mg / kg, Cu535mg
/ Kg, Cd 66mg / kg) and smelter wastewater (Ca
0.47 g / L, Cl 0.44 g / L, Pb <0.05
mg / L, Zn 1.16 mg / L, Cu <0.01 mg
/ L, Cd <0.01 mg / L) were prepared.

Next, 1 kg of the fly ash was placed in a 20 L bucket, and the smelter drainage was added to make it 10 L. After stirring with a stirrer for 30 minutes to carry out primary washing, Using a pressure filter, solid-liquid separation was performed into a primary washing residue and primary washing water. The primary washing water obtained by this solid-liquid separation is
Ca 4.99 g / L, Cl 12.84 g / L, Pb2
7.8 mg / L, Zn 4.49 mg / L, Cu 0.19
Water containing mg / L, Cd <0.01 mg / L.

Next, the smelter wastewater is added to the primary water-washing residue obtained by the above solid-liquid separation, and the mixture is stirred for 30 minutes with a stirrer to carry out a secondary water wash, and then with a pressure filter. Solid-liquid separation was performed into a secondary washing residue (recovered slaked lime) and secondary washing water.
The secondary washing residue obtained by this solid-liquid separation is Ca3
2.2%, Cl 0.30%, Pb998mg / kg, Z
n5,700mg / kg, Cu668mg / kg, Cd
The recovered slaked lime contained 82 mg / kg and had a Cl grade of 1% or less. In addition, the secondary washing water is Ca1.21g / L,
Cl1.58 g / L, Pb14.6 mg / L, Cu1.
The washing water contained 0 mg / L and Cd 0.13 mg / L and was usable for the primary washing.

Further, liquid in the smelter process (Ca 0.70 g /
L, Cl 0.66 g / L, Pb <0.05 mg / L, Z
n 19.12 g / L, Cu 0.05 mg / L, Cd0.
01 mg / L, Fe 6.8 g / L, Al 10.2 g /
L) was prepared, and the solution in the smelter process was added to the above-mentioned primary washing water (pH = 12.3) with stirring and adjusted to maintain pH = 10.0 for 30 minutes. The mixture was solid-liquid separated into a neutralization residue and a liquid after neutralization with a pressure filter. The neutralization residue obtained by this solid-liquid separation is Ca 20.6%, Cl
1.0%, Pb 3,726 mg / kg, Zn 4.90
%, Cu 60 mg / kg, Cd 1.1 mg / kg. After neutralization, the solution is Ca 3.39 g / L, Cl
12.1g / L, Pb0.06mg / L, Zn0.57
mg / L, Cu 0.01 mg / L, Cd <0.01 mg
It was a liquid containing / L and COD 8.7 mg / L.

Next, the neutralized liquid obtained by the above solid-liquid separation was adjusted to pH = 7 with 3.5% hydrochloric acid, and then passed through activated carbon at SV = 2.5 for treatment with activated carbon. It was The liquid after this activated carbon treatment is Ca 3.39 g / L, Cl 12.1 g
/ L, Pb <0.05 mg / L, Zn 0.49 mg /
L, Cu 0.01 mg / L, Cd <0.01 mg / L,
It was a liquid containing 3.3 mg / L of COD.

On the other hand, the neutralization residue obtained by the above solid-liquid separation was washed with 10 times the amount of water and subjected to solid-liquid separation.
It became 0.5%, and Cl <1% which can be supplied to the smelting process.

Example 2 First, fly ash (23.4% Ca, 16.5% Cl, Pb 1,5867 from industrial waste).
mg / kg, Zn3,500mg / kg, Cu784m
g / kg, Cd 17 mg / kg) and smelter wastewater (C
a 0.48 g / L, Cl 0.51 g / L, Pb <0.0
5mg / L, Zn1.1mg / L, Cu <0.01mg
/ L, Cd <0.01 mg / L) were prepared.

Next, 1 kg of the fly ash was placed in a 20 L bucket, and the smelter wastewater was added to make it 10 L. After stirring with a stirrer for 30 minutes to perform primary water washing, Using a pressure filter, solid-liquid separation was performed into a primary washing residue and primary washing water. The primary washing water obtained by this solid-liquid separation is
Ca 1.83 g / L, Cl 16.2 g / L, Pb 37.
9 mg / L, Zn 0.39 mg / L, Cu 0.63 mg
/ L, water containing Cd <0.01 mg / L.

Next, the smelter wastewater is added to the primary water-washing residue obtained by the above solid-liquid separation, and the mixture is stirred for 30 minutes with a stirrer to carry out secondary water washing, and then with a pressure filter. Solid-liquid separation was performed into a secondary washing residue (recovered slaked lime) and secondary washing water.
The secondary washing residue obtained by this solid-liquid separation is Ca3
2.5%, Cl 0.10%, Pb 1,577 mg / k
g, Zn 5,220 mg / kg, Cu 1,108 mg /
It was recovered slaked lime containing Cl and 19 mg / kg of Cd and having a Cl grade of 1% or less. The secondary washing water is Ca1.0
6 g / L, Cl 1.62 g / L, Pb 34.9 mg /
L, Zn 1.90 mg / L, Cu 0.45 mg / L, C
The washing water contained d <0.01 mg / L and was usable for the primary washing.

Further, the liquid in the smelter process (Ca 0.68 g /
L, Cl 0.45 g / L, Pb <0.05 mg / L, Z
n20.5g / L, Cu0.01mg / L, Cd0.0
1 mg / L, Fe 6.8 g / L, Al 10.2 g / L)
And prepare the above-mentioned primary washing water (p
H = 12.3) with stirring and pH for 30 minutes
After adjusting so as to hold = 10.0, the mixture was subjected to solid-liquid separation into a neutralization residue and a liquid after neutralization with a pressure filter. The neutralization residue obtained by this solid-liquid separation was Ca 12.7%, Cl 3.
06%, Pb7,306mg / kg, Zn106,62
0%, Cu174mg / kg, Cd1.91mg / kg
Was included. The solution after neutralization is Ca 1.11 g /
L, Cl 5.6 g / L, Pb <0.05 mg / L, Zn
0.86 mg / L, Cu 0.01 mg / L, Cd <0.
It was a liquid containing 01 mg / L and COD 5 mg / L.

Next, the neutralized liquid obtained by the above solid-liquid separation was adjusted to pH = 7 with 3.5% hydrochloric acid, and then passed through activated carbon at SV = 2.5 for treatment with activated carbon. It was The liquid after this activated carbon treatment was Ca 1.22 g / L, Cl 12.45
g / L, Pb <0.05 mg / L, Zn 0.27 mg /
L, Cu <0.01 mg / L, Cd <0.01 mg /
It was a liquid containing L and COD 2 mg / L.

On the other hand, when the neutralization residue obtained by the above solid-liquid separation was washed with 30 times the amount of water and solid-liquid separated, Cl <1% which could be supplied to the smelting process was obtained.

Example 3 First, 700 g of fly ash obtained from general waste was placed in a 10 L beaker, 7 L of smelter wastewater was added, and the mixture was stirred with a stirrer to perform primary washing, and then added. A pressure filter was used to perform solid-liquid separation into a primary washing residue and primary washing water. Next, the primary water washing residue obtained by this solid-liquid separation is placed again in a 10 L beaker, and 7 L of smelter wastewater is added,
After stirring with a stirrer to carry out secondary washing, solid-liquid separation was carried out with a pressure filter to obtain a secondary washing residue and secondary washing water. Table 1 shows the analytical values of the filtrate (secondary washing water) obtained by this solid-liquid separation.
The number of repetitions of is shown as the first time.

Further, the above secondary washing water is mixed with 1 of the above fly ash.
After being used for the subsequent water washing, the same secondary water washing as described above was performed, and solid-liquid separation was performed by a pressure filter into a secondary water washing residue and secondary water washing water. The analytical values of the filtrate (secondary washing water) obtained by this solid-liquid separation are shown in Table 1 for the second repetition.

As shown in Table 1, no significant difference was observed in the concentration of each element between the first and second times, and it was found that the secondary washing water can be repeatedly used.

Further, when fly ash obtained from industrial waste was subjected to the same operation, as shown in Table 1, it was found that secondary washing water can be repeatedly used in the same manner.

[0048]

[Table 1]

[0049]

As described above, according to the present invention, during the treatment of fly ash, the water used for washing fly ash and the wash water obtained after washing fly ash are used for neutralization. It is possible to prevent an increase in the running cost of the disinfectant, and it is possible to utilize the residue obtained after washing the fly ash with water.

[Brief description of drawings]

FIG. 1 is a processing step diagram showing an embodiment of a method for processing fly ash according to the present invention.

2 is obtained by the method for treating fly ash according to the present invention.
FIG. 6 is a process step diagram showing a step of using the next washing residue as a neutralizing agent in a smelter.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keishi Takemasa             1-8-2 Marunouchi, Chiyoda-ku, Tokyo             Within Wa Mining Co., Ltd. F-term (reference) 4D004 AA37 AC05 CA13 CA15 CA40                       CC20                 4D024 AA04 AB02 AB16 BA02 DB03                       DB20 DB21

Claims (7)

[Claims] 1. A first step of washing fly ash containing chlorine, calcium and heavy metal with water to separate into a first residue and a first liquid, and a first step of washing the first residue with water to form a second residue. A second step of separating into a second liquid, wherein the second liquid obtained in the second step is used for the water washing in the first step, and the smelter wastewater is used for the water washing in the second step. A method for treating fly ash, which is characterized by being used. 2. The method further comprises a third step of neutralizing the first liquid obtained in the first step with a neutralizing agent to separate a third residue and a third liquid. The method for treating fly ash according to claim 1. 3. A first step of washing fly ash containing chlorine, calcium and heavy metal with water to separate it into a first residue and a first solution, and a first solution obtained in this first step. A method for treating fly ash, comprising a third step of neutralizing with a neutralizing agent to separate into a third residue and a third liquid. 4. The method for treating fly ash according to claim 2, wherein a smelter process liquid is used as the neutralizing agent in the third process. 5. The third residue obtained in the third step is used in a smelting step, wherein the third residue is used.
The method for treating fly ash according to any one of 1. 6. The method for treating fly ash according to claim 2, wherein the third liquid obtained in the third step is treated with activated carbon for wastewater treatment. 7. A first step of washing fly ash containing chlorine, calcium and heavy metal with water to separate into a first residue and a first liquid, and a first step of washing the first residue with water to form a second residue. A second step of separating into a second liquid and a first step obtained in the first step.
The third step of neutralizing the solution of No. 3 with a neutralizing agent to separate it into a third residue and a third solution, and the second step obtained in the second step in the washing with water in the first step. A smelter wastewater is used for washing in the second step, and a smelter process liquid is used as the neutralizing agent in the third step. Processing method.