JP2003181413A - Treatment method of fly ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method of fly ash which separates a useful heavy metal in fly ash from salts of chlorine and calcium, etc., and enables separation recovery in a reusable form in a refining process. <P>SOLUTION: This treatment method of fly ash comprises a heavy metal elution process in which preferably a solution of sodium hydroxide as an alkali agent is added to the fly ash and, thereby, the fly ash is slurrified, a calcium separating process in which the slurry is diluted and is fractionated into a calcium-containing deposit and a heavy metal-containing filtrate, a heavy metal separating process in which a mineral acid is added to the heavy metal- containing filtrate, thereby, the filtrate is adjusted to pH 7-10 and, thereafter, the heavy metal is fractionated to hydroxides or sulfates or a lead separating process in which sulfuric acid as the mineral acid is added to the heavy metal- containing filtrate and the filtrate is adjusted to ≤pH 5, preferably ≤pH 4 and, thereafter, is fractionated to a lead-containing deposit and a zinc-containing filtrate and a zinc separating process in which the alkali agent is added to the zinc-containing filtrate, the zinc-containing filtrate is adjusted to pH 7-10, preferably, to pH 8-9 and, thereafter, is fractionated to a zinc-containing deposit and a salt-containing filtrate. <P>COPYRIGHT: (C)2003,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 in particular, copper generated from incinerators and melting furnaces in municipal waste incinerators and industrial waste incinerators, or cement kilns for treating sludge. The present invention relates to a method for treating fly ash containing chlorine and calcium in addition to heavy metals such as lead, lead and zinc.

[0002]

2. Description of the Related Art Garbage discharged from general offices and households (referred to as "urban waste" or "general waste") is collected in municipal waste incinerators or industrial waste incinerators. It is incinerated. At that time, incineration ash and fly ash generated from the incinerator are subjected to intermediate treatment such as chemical treatment, melting treatment, and cement kiln treatment, and are deposited at the final disposal site.

However, in the intermediate treatment such as the melting treatment and the cement kiln treatment, heavy metals such as lead, zinc and cadmium having a high vapor pressure are volatilized into the exhaust gas in the furnace, and the heavy metal contained in the exhaust gas is exhausted. There was a problem that it was pseudo-compressed in the processing equipment and turned into fly ash again.

The fly ash again contains a large amount of heavy metals such as lead, copper, zinc and cadmium in addition to chlorine, sodium and calcium, and a stable treatment method including recovery of these is required. It was

Regarding such fly ash, JP-A-7-10
In Japanese Patent No. 9533, fly ash is suspended in water in a tank, and the pH of the suspension is adjusted to an appropriate value in an alkaline range by adding an acid or an alkali to remove heavy metals in the fly ash from hydroxide. Is disclosed, and a method of recovering the precipitate is disclosed. The present applicant has also disclosed a method of coping with the wet processing method (Japanese Patent Laid-Open No. 8-117).
724, JP-A-8-141539).

In Japanese Patent Laid-Open No. 8-117724, a first step in which fly ash is slurried with water, pH is adjusted and solid-liquid separation is carried out, and the starch from this first step is repulped with an acid solution, p
After adjusting to H3 or less, solid-liquid separation to obtain lead residue
Step, and a third step in which a neutralizing agent is added to the acidic filtrate from the first step and the second step and sodium hydrosulfide is added to filter out a precipitate containing zinc and copper, and the filtered water is used as a drainage liquid. A method consisting of is disclosed. In addition, JP-A-8-14153
No. 9 discloses a first step of neutralizing fly ash with water and a neutralizing agent for solid-liquid separation, and repulping the starch from the first step,
After adjusting the pH to around 3 with sulfuric acid, solid-liquid separation is performed to obtain a lead residue, and an alkaline neutralizing agent is added to the filtrate from this second step to filter out the precipitate containing zinc and copper. There is disclosed a method comprising three steps, wherein the filtered water of the third step is repeatedly used as a neutralizing solution of the first step, and a sulphating agent is added to the filtrate from the first step to perform drainage treatment.

[0007] By such a wet treatment method, heavy metals contained in fly ash are separated in a stable form and are effectively recovered as heavy metal resources, and the wastewater after wet treatment of fly ash is the national wastewater standard. It became possible to render it harmless in accordance with (Regulations of Article 3, Paragraph 1 of the Water Pollution Control Law).

[0008]

However, in the method disclosed in JP-A-7-109533, lead, copper, and chlorine as an oxychloride which is a sparingly soluble compound enter into the recovered heavy metal precipitate. In some cases, bringing in chlorine is disliked in the smelting process, so there is still a problem in terms of recycling heavy metals. Further, in heavy metal starch recovered from fly ash containing calcium, most of calcium is in the form of dihydrate gypsum from several% to several 1
Since 0% is contained, and this calcium is an unnecessary element in the smelting process, the treatment cost in the smelting process becomes high, and it is difficult to progress the heavy metal recycling from fly ash.

In order to recover heavy metals such as lead and zinc from fly ash, there are methods for eluting these heavy metals from fly ash, such as elution with a mineral acid or an alkaline agent. In many cases, the heavy metal is used for elution, and then an alkaline agent is added to the eluate to neutralize the heavy metal to recover the heavy metal as a neutralized precipitate. Sulfuric acid is often used as a mineral acid. When sulfuric acid is used, in fly ash containing calcium, most of lead in fly ash is precipitated as lead sulfate, and calcium is precipitated as gypsum dihydrate. Therefore, lead cannot be directly separated and recovered, and in order to separate lead sulfate as gypsum dihydrate, it is conceivable to use a separation method utilizing a difference in specific gravity (eg, cyclone) from the precipitate. However, this method has a problem that it is not suitable for use as a raw material for smelting because the separation efficiency of lead sulfate and gypsum dihydrate is poor and the lead quality in the recovered sediment is low. Further, since the dioxin in the fly ash is concentrated in this starch, it is necessary to decompose the dioxin in this starch in order to use it as a smelting raw material. However, it is difficult to recover lead from fly ash at low cost. When hydrochloric acid is used as the mineral acid, calcium in the fly ash elutes as calcium chloride, but lead and zinc elute at the same time, so this filtrate is neutralized after solid-liquid separation. Even if heavy metals are precipitated as hydroxides, calcium and lead cannot be separated and removed. In addition, since the chlorine concentration in the liquid increases due to the use of hydrochloric acid, the generation of oxychloride in the heavy metal starch increases, and the chlorine concentration in the starch increases, so that a satisfactory smelting raw material can be obtained. There is a problem that you can not.

As a method for eluting heavy metals using an alkaline agent, for example, JP-A-2001-149884 is used.
There is a method disclosed in. However, in this method, the amount of heavy metals eluted is small, and the heavy metals have not yet been recovered from the obtained eluate.

Therefore, in view of such conventional problems, the present invention separates useful heavy metals in fly ash from salts such as chlorine and calcium, and separates and recovers them in a reusable form in the smelting process. It is an object of the present invention to provide a method of treating fly ash that can be used.

[0012]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have added an alkaline agent to a fly ash containing at least one of zinc and lead, and chlorine and calcium to form a slurry. Of the heavy metal obtained in this second step, and the second step of adding water to the slurry of this first step to solid-liquid separate the calcium-containing starch and the heavy metal-containing filtrate A fly ash treatment method comprising a third step of adding a mineral acid to the contained filtrate to adjust the pH to 7 to 10 and performing solid-liquid separation into a heavy metal-containing starch and a chlorine-containing filtrate, or zinc and lead. Of the fly ash containing at least one of the above and chlorine and calcium to form a slurry by adding an alkali agent to elute the heavy metal, and water is added to the slurry of the first step to add calcium-containing starch and heavy metal. A second step of solid-liquid separation into a filtrate, and a mineral acid is added to the heavy metal-containing filtrate obtained in the second step to adjust the pH to 5 or less, so that the lead-containing starch and the zinc-containing filtrate are solid-liquid separated. The third step of separating and adding an alkaline agent to the zinc-containing filtrate obtained in the third step to adjust the pH to 7 to 1
The useful heavy metal in the fly ash is separated from salts such as chlorine and calcium by a method of treating fly ash, which is adjusted to 0 and includes a fourth step of solid-liquid separation into a zinc-containing starch and a chlorine-containing solution. ,
The inventors have found that they can be separated and recovered in a reusable form in the smelting process, and have completed the present invention.

That is, the method of treating fly ash according to the present invention comprises adding an alkaline agent to fly ash containing at least one of zinc and lead, chlorine and calcium to form a slurry,
A first step of eluting heavy metals, a second step of adding water to the slurry of the first step to perform solid-liquid separation into a calcium-containing starch and a heavy metal-containing filtrate, and a heavy metal-containing filtrate obtained in this second step And a pH of 7 to 10 by adding a mineral acid to the mixture, and a third step of performing solid-liquid separation into a heavy metal-containing starch and a chlorine-containing filtrate. In this fly ash processing method, the calcium concentration of the heavy metal-containing starch is 2 wt%
The following is preferable.

Further, the method for treating fly ash according to the present invention comprises a first step in which a fly ash containing at least one of zinc and lead, chlorine and calcium is added with an alkali agent to form a slurry, and heavy metals are eluted, The second step of adding water to the slurry of the first step to perform solid-liquid separation into a calcium-containing starch and a heavy metal-containing filtrate, and a mineral acid to the heavy metal-containing filtrate obtained in the second step to adjust the pH. A third step of adjusting the pH to 5 or less and performing solid-liquid separation into a lead-containing starch and a zinc-containing filtrate, and adding an alkaline agent to the zinc-containing filtrate obtained in this third step to adjust the pH to 7 to 10. However, a fourth step of solid-liquid separation into a zinc-containing starch and a chlorine-containing solution is included. In this fly ash treatment method, the calcium concentration of the lead-containing starch and the zinc-containing starch is preferably 2 wt% or less.

Further, in the above method for treating fly ash, the alkaline agent used in the first step is at least one oxide or hydroxide selected from Na and K in a concentration of 10 to 50 wt% in water. It is preferable that the alkaline agent is dissolved in. The amount of the alkaline agent added is preferably 50 to 3000 parts by weight with respect to 100 parts by weight of fly ash.
The amount of water added in the second step is preferably 1 to 20 times the weight of the slurry. The mineral acid used in the third step is preferably 4-98 wt% sulfuric acid. The alkaline agent used in the fourth step is
It is preferable to use an alkaline agent in which at least one oxide or hydroxide selected from Na and K is dissolved in water at a concentration of 10 to 50 wt%. At least one of heavy metal-containing starch or lead-containing starch and zinc-containing starch is preferably used as a smelting raw material.

Further, the smelting raw material according to the present invention is characterized in that it contains at least one of zinc and lead and contains 2 wt% or less of chlorine and 0.1 to 2 wt% of calcium.

The smelting raw material according to the present invention is a smelting raw material obtained by treating fly ash containing at least one of zinc and lead, chlorine and calcium, and contains 2 wt% or less of chlorine. It is characterized by containing 0.1 to 2 wt% of calcium.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described with reference to the process flow charts of FIGS. 1 to 4 by way of example of a method of treating secondary fly ash generated in the incineration ash treatment of municipal waste incineration facilities. An embodiment of a method for treating fly ash according to the above will be described.

First, as shown in FIG. 1, fly ash is separated into a heavy metal-containing filtrate and a calcium-containing precipitate through a heavy metal elution step. That is, as shown in FIG. 2, fly ash is mixed with an alkaline agent to form a slurry, and the elution reaction is allowed to proceed while stirring the slurry, and heavy metals such as lead and zinc and salts such as chlorine and sodium are liquefied. To the side (heavy metal elution step). As the alkaline agent used in this case, at least one hydroxide selected from Na and K dissolved in water at a concentration of 10 to 50 wt% can be used. Those dissolved in water at a concentration of 50 wt% are preferred. This is because the cost of K is high, and the higher the concentration, the higher the leaching efficiency of heavy metals, and the lower the concentration, the larger the amount of the alkaline agent used. The amount of the alkaline agent added is 50 to 3000 parts by weight with respect to 100 parts by weight of fly ash. In addition, here 50-30
The reason why the amount is set to 00 parts by weight is that if the amount is less than 50 parts by weight, the viscosity of the slurry becomes high, and expensive equipment is required, resulting in an increase in equipment cost. is there. This addition amount is determined by the heavy metal content in the fly ash, the higher the heavy metal content,
It is necessary to increase the amount of alkaline agent used. Therefore, it is desirable to determine the addition amount in consideration of the heavy metal content rate and the heavy metal extraction rate in the fly ash.

Fly ash contains many kinds of heavy metals,
The types and amounts of the ingredients vary. In particular, when heavy metals in fly ash combine with chlorine, fly ash becomes difficult to dissolve in an alkaline agent. The method of treating fly ash according to the present invention does not limit the components of fly ash, but in particular, chlorine in fly ash is 10 w.
It can be applied to difficult-to-treat fly ash containing t% or more or calcium of 2 wt% or more.

Next, if necessary, water is added to the slurry to dilute it and then solid-liquid separation is carried out, whereby a calcium-containing starch having a low content of heavy metals, heavy metals such as lead and zinc, and salts such as chlorine and sodium. Solid-liquid separation is carried out into a heavy metal-containing filtrate containing water (calcium separation step). The reason for diluting with water here is that solid-liquid separation is not possible when the slurry concentration is high, and the temperature rise due to the heat of neutralization during the neutralization treatment and recovery of heavy metals in a later step. This may occur because there is no need to provide special protection to equipment for preventing this, and equipment costs are reduced. The amount of water added is 1 to 20 times, preferably about 10 times. The amount of water added is preferably an amount added according to the properties of fly ash, since the amount of alkali agent added is determined by the properties of fly ash, particularly the content of heavy metals.

As described above, it becomes possible to separate heavy metals such as lead and zinc from calcium. The calcium-containing starch is mainly slaked lime, and can be returned to a melting furnace or the like to be melted and solidified, recycled to a roadbed material, or used as an exhaust gas treating agent for an incinerator.

Next, as shown in FIG. 3, the heavy metal-containing filtrate is adjusted to pH 7 to 10, preferably pH 8 to 9 by adding a mineral acid such as sulfuric acid, to thereby obtain lead and zinc in the filtrate. Is precipitated as hydroxide and solid-liquid separated into a heavy metal-containing precipitate and a salt solution containing chlorine and sodium (heavy metal separation step). The obtained heavy metal-containing starch is washed with water as required to be a smelting raw material. The chlorine content of the smelting raw material is preferably as small as possible, and particularly preferably 2 wt% or less.

As the hydroxide of the heavy metal recovered at this time, one having a very low chlorine content can be obtained. This is currently not clear,
It is estimated as follows. When the heavy metal is eluted on the acidic side, the metal is present in the liquid as an ion such as M ^{n +} . When this metal ion is neutralized in a liquid having a high chlorine concentration, a sparingly soluble oxychloride such as M (ClO) _x .yH ₂ O is produced and precipitated. However, when heavy metals are eluted in a high-concentration alkali as in the present invention, MO _x
It exists in the liquid in the form of ions such as ^n- . When this is neutralized, the oxychloride is not synthesized but precipitates as a hydroxide, and it is presumed that a precipitate having an extremely low chlorine content can be obtained.

When it is necessary to separate and collect lead and zinc depending on the collection destination of the target fly ash or heavy metal, they are separated and collected by the method shown in FIG. That is, sulfuric acid is added to the filtrate containing heavy metals to adjust the pH to 5 or less, preferably 4 or less. As a result, the lead in the filtrate is precipitated as lead sulfate, and by solid-liquid separation,
Separate into lead sulfate and zinc-containing filtrate (lead separation step). The obtained lead sulfate is washed with water as required to be a smelting raw material.
Next, caustic soda as an alkaline agent is added to the zinc-containing filtrate to adjust the pH to 7 to 10, preferably pH 8 to 9, to precipitate zinc in the filtrate as hydroxide, and to perform solid-liquid separation. Separation into zinc hydroxide and chlorine- and sodium-containing filtrate (zinc separation step). Zinc hydroxide is washed with water as needed to be a smelting raw material. The lead sulfate and zinc hydroxide obtained here have extremely low chlorine contents. This is because lead sulfate does not form oxychloride as described above, and zinc hydroxide precipitates as oxychloride because the solubility of oxychloride is higher than that of lead. It is considered to be difficult.

The chlorine- and sodium-containing filtrate can be rendered harmless by subjecting it to wastewater treatment by the iron pillow method which is widely used industrially or by passing it through a chelating agent.

As described above, in the embodiment of the method for treating fly ash according to the present invention, fly ash from a refuse incineration facility or the like is treated and heavy metals such as copper, zinc and lead contained in the fly ash are treated. Can be recovered in a state where it can be used as a smelting raw material after being separated from salts.

In the present specification, the numerical values of wt% of the components of starch and fly ash are based on the dry weight excluding water.

[0029]

EXAMPLES Hereinafter, a method for treating fly ash according to the present invention will be described in detail based on examples.

[Example 1] In a 1-liter beaker, 17
% NaOH solution 600 g (N for 100 parts by weight of fly ash)
a ash (content in ash: Pb 5.0 wt%, Zn 18.2)
wt%, Ca 4.1 wt%, Cl 15.3 wt%) 50
After adding g to form a slurry and stirring for 10 minutes (heavy metal elution step), solid-liquid separation was performed into a calcium-containing starch and a heavy metal-containing filtrate (calcium separation step). Next, 98% sulfuric acid was added as a neutralizing agent to the obtained filtrate containing heavy metals to adjust the pH to 9, and the mixture was maintained for 30 minutes, and then filtered by a heavy metal-containing precipitate containing mainly heavy metals, It was separated into a salt-containing filtrate containing mainly salts (heavy metal separation step). At that time, 1 L of water was used as the cake washing water.

In the heavy metal-containing precipitate recovered by the treatment of this example, the grades of Pb, Zn, Ca and Cl were 15.1 wt%, 40 wt% and 0.1 wt%, respectively.
It is 0.2 wt%, the grade of lead and zinc is high, the grade of unnecessary calcium in the smelting process is extremely low at 0.1 wt%, and the grade of chlorine that is disliked to be brought into the smelting process is 0.
It was 3 wt% or less, and it was found that the treatment was performed so that it could be sufficiently used as a smelting raw material. Further, the recoveries of Pb and Zn were 30% and 22%, respectively, and the recoverability was also good, indicating that the treatment of Example 1 was totally good.

[Embodiment 2] A 1-liter beaker was charged with 48
% NaOH solution 100 g (N for 100 parts by weight of fly ash)
a ash (content in ash: Pb 5.0 wt%, Zn 18.2 w)
t%, Ca 4.1 wt%, Cl 15.3 wt%) 150
After adding g to form a slurry and stirring for 10 minutes (heavy metal elution step), solid-liquid separation was performed into a calcium-containing starch and a heavy metal-containing filtrate (calcium separation step). Next, 98% sulfuric acid was added as a neutralizing agent to the obtained filtrate containing heavy metals to adjust the pH to 9, and the mixture was maintained for 30 minutes, and then filtered by a heavy metal-containing precipitate containing mainly heavy metals, It was separated into a salt-containing filtrate containing mainly salts (heavy metal separation step). At that time, 2 L of water was used as the cake washing water.

In the heavy metal-containing precipitate recovered by the treatment of this example, the grades of Pb, Zn, Ca and Cl were 17.2 wt%, 38.8 wt% and 0.1 wt%, respectively.
Below is 0.3wt%, the grade of lead and zinc is high, the grade of unnecessary calcium in the smelting process is extremely low at 0.1wt% or less, and the grade of chlorine that is unfavorable to bring into the smelting process is 0. It was found to be 0.3 wt% or less, and it was found that it was treated so that it could be sufficiently used as a smelting raw material. The recovery rates of Pb and Zn are 24% and 15%, respectively.
%, The recoverability was somewhat good, and the treatment of Example 2 was found to be slightly good overall.

[Embodiment 3] A 1-liter beaker was charged with 48
% NaOH solution 600 g (N for 100 parts by weight of fly ash)
a 960 parts by weight) and fly ash of the B treatment plant (content in ash: Pb 9.7 wt%, Zn 33.5 wt%, Ca 2.
5wt%, Cl16.6wt%) 30g, and put 10
After stirring for a minute (heavy metal elution step), solid-liquid separation was carried out into a calcium-containing starch and a heavy metal-containing filtrate (calcium separation step). Next, 98% sulfuric acid was added as a neutralizing agent to the heavy metal-containing filtrate to adjust the pH to 1, and after maintaining for 30 minutes, a lead-containing starch mainly containing lead sulfate and salts were filtered out. It was separated into a main zinc-containing filtrate (lead separation step). Then, 20% Na was added to the obtained zinc-containing filtrate.
The pH was adjusted to 9 by adding an OH liquid and maintained for 30 minutes, and then solid-liquid separation was performed into a zinc-containing starch and a chlorine-containing filtrate by a filtration operation (zinc separation step). At that time, 3 L of water was used as the cake washing water.

In the lead-containing starch recovered by the treatment of this example, the grades of Pb, Zn, Ca and Cl were 56.4 wt%, 0.2 wt%, 0.1 wt% and 0.1%, respectively.
It is 1 wt%, the grade of lead is high, the grade of unnecessary calcium in the smelting process is extremely low at 0.1 wt%, and the grade of chlorine, which is disliked to be brought into the smelting process, is 0.3 wt% or less. It was found that it was treated so that it could be sufficiently used as a smelting raw material.

Further, in the zinc-containing starch recovered by the treatment of this example, the grades of Pb, Zn, Ca and Cl are 0.4 wt%, 57.4 wt% and 0.1 w, respectively.
t% or less, 0.1 wt% or less, high grade of zinc, unnecessary grade of calcium in smelting process is 0.1 wt%
It was found that the content of chlorine, which is extremely small as shown below, and which is unacceptable to bring into the smelting process, was 0.3 wt% or less, and was treated so that it could be sufficiently used as a smelting raw material.

Further, it was found that the recoveries of Pb and Zn were 100% and 98%, respectively, and the recoverability was also very good, and the treatment of Example 3 was totally good.

[Comparative Example 1] In a 10-liter beaker, 5 liters of water and fly ash of a C treatment factory (content in ash: Pb1.
6 wt%, Zn 8.7 wt%, Ca 9.0 wt%, Cl
13.9wt%) 500g to make a slurry, 30
After stirring for 1 minute, solid-liquid separation was carried out into a salt-removed washed precipitate and a salt-containing filtrate. Then, 6% is added to the washed starch obtained.
900g of NaOH solution (Na to 100 parts by weight of fly ash)
OH (11 parts by weight) to adjust the pH to 14 or more, and 3
After stirring for 0 minutes (heavy metal elution step), solid-liquid separation was performed into a calcium-containing starch and a heavy metal-containing filtrate (calcium separation step). Then, 98% sulfuric acid was added to the heavy metal-containing filtrate as a neutralizing agent to adjust the pH to 9, and the pH was maintained for 30 minutes, followed by solid-liquid separation into a heavy metal-containing starch and a chlorine-containing filtrate by a filtration operation. (Heavy metal separation step).

In the heavy metal-containing precipitate recovered by the treatment of this comparative example, the grades of Pb, Zn, Ca and Cl were 0.1 wt%, 12.8 wt% and 0.1 wt%, respectively.
0.4wt%, zinc quality is slightly high, lead quality is low, and unnecessary calcium quality is 0.1w in the smelting process.
Although it was extremely small at t%, the recoveries of Pb and Zn were 0% and 4%, respectively, and the recoverability was poor, indicating that the treatment of Comparative Example 1 was not good overall.

[Comparative Example 2] 5 liters of water and fly ash (content in ash: Pb1.
6 wt%, Zn 8.7 wt%, Ca 9.0 wt%, Cl
13.9wt%) 500g to make a slurry, 30
After stirring for 1 minute, solid-liquid separation was carried out into a salt-removed washed precipitate and a salt-containing filtrate. Then, 6% is added to the washed starch obtained.
Sulfuric acid of 3950 g (H ₂ SO for 100 parts by weight of fly ash)
₄ 747 parts by weight) to adjust the pH to 1 or less, and
After stirring for a minute (heavy metal elution step), solid-liquid separation was performed into a lead-containing starch and a heavy metal-containing filtrate (lead separation step). Then
After adding a 20% NaOH solution as a neutralizing agent to the heavy metal-containing filtrate to adjust the pH to 10 and maintaining it for 30 minutes, a zinc-containing starch and a chlorine-containing filtrate were subjected to solid-liquid separation by filtration. Separation step).

In the lead-containing starch recovered by the treatment of this comparative example, the grades of Pb, Zn, Ca and Cl were 3.3 wt%, 1.6 wt%, 17.0 wt% and 0.
It is 1 wt%, the grade of lead is low, and the grade of chlorine, which is disliked to be brought into the smelting process, is 0.3 wt% or less,
It was found that unnecessary calcium was insufficiently separated in the smelting process, and the calcium content was 10 wt% or more, which was not suitable for use as a smelting raw material.

Further, in the zinc-containing starch recovered by the treatment of this comparative example, the grades of Pb, Zn, Ca and Cl were 0.0 wt%, 19.0 wt% and 0.9 w, respectively.
It was t% and 0.4 wt%.

Further, the recoveries of Pb and Zn were 100% and 88%, respectively, indicating that the recoverability was quite good, but the treatment of Comparative Example 2 was not overall good.

[Comparative Example 3] In a 10-liter beaker, 5 liters of water and fly ash of a C treatment factory (content in ash: Pb1.
6 wt%, Zn 8.7 wt%, Ca 9.0 wt%, Cl
13.9wt%) 500g to make a slurry, 30
After stirring for 1 minute, solid-liquid separation was carried out into a salt-removed washed precipitate and a salt-containing filtrate. Next, 4% is added to the resulting washed starch.
4200g of hydrochloric acid (HCl3 to 100 parts by weight of fly ash)
(4 parts by weight) was added, the pH was adjusted to 1 or less, and the mixture was stirred for 30 minutes (heavy metal elution step), and then solid-liquid separated into an elution residue and a heavy metal-containing filtrate. Then, a 20% NaOH solution as a neutralizing agent was added to the heavy metal-containing filtrate to adjust the pH to 10, and the pH was maintained for 30 minutes, followed by solid-liquid separation into a zinc-containing starch and a chlorine-containing filtrate by a filtration operation. (Heavy metal separation step).

In the elution residue recovered by the treatment of this comparative example, the grades of Pb, Zn, Ca and Cl are 3.5 wt%, 2.1 wt%, 2.5 wt% and 3.6 w, respectively.
t%, the grade of lead and zinc is low, the grade of unnecessary calcium in the smelting process is high at 2.5 wt%, and the grade of chlorine that is unfavorable to bring into the smelting process is 2 wt% or more,
It was found to be unsuitable for use as a smelting raw material.

In the zinc-containing starch recovered by the treatment of this comparative example, the grades of Pb, Zn, Ca and Cl were 2.1 wt%, 17.8 wt% and 7.6 w, respectively.
t%, 20.0 wt%, the grade of zinc is slightly high, but the grade of unnecessary calcium in the smelting process is 7.6 wt%
The quality of chlorine, which is unacceptable to bring into the smelting process, is 2 wt% or more, which is not suitable for use as a smelting raw material.

Further, the recoveries of Pb and Zn were 93% and 91%, respectively, indicating that the recoverability was fairly good, but the treatment of Comparative Example 3 was not overall good.

The results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Tables 1 and 2.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described above, according to the present invention, heavy metals in fly ash are eluted by using an alkaline agent, and the heavy metal-containing filtrate is neutralized with a mineral acid to recover heavy metals. A smelting raw material that has a high rate, has extremely low amounts of unnecessary calcium in the smelting process and chlorine that is disliked to be brought into the smelting process, and has a low equipment cost. Further, this makes it possible to separate and collect heavy metals, and reduce the burden of heavy metal recovery processing work in the smelting process.

[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.

FIG. 2 is a processing step diagram showing heavy metal elution and calcium separation steps in the embodiment of the method for processing fly ash according to the present invention.

FIG. 3 is a processing step diagram showing a heavy metal separation step in the embodiment of the method for processing fly ash according to the present invention.

FIG. 4 is a processing step diagram showing another heavy metal separation step in the embodiment of the method for processing fly ash according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22B 19/00 C22B 19/22 (72) Inventor Kenji Ichigo 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. F-term (reference) 4D004 AA37 AB03 AB06 BA05 CA13 CA15 CA34 CA35 CA41 CB05 CC03 CC12 DA03 DA10 4K001 AA20 AA30 BA14 CA08 DB05 DB23

Claims (5)

[Claims] 1. A first step in which a fly ash containing at least one of zinc and lead and chlorine and calcium is added with an alkali agent to form a slurry, and a heavy metal is eluted, and water is added to the slurry in the first step. A second step of solid-liquid separation into a calcium-containing starch and a heavy metal-containing filtrate, and a mineral acid is added to the heavy metal-containing filtrate obtained in the second step to adjust the pH to 7 to 10, And a third step of performing solid-liquid separation into a chlorine-containing filtrate and a method for treating fly ash. 2. The method for treating fly ash according to claim 1, wherein the heavy metal-containing starch has a calcium concentration of 2 wt% or less. 3. A first step in which an alkali agent is added to fly ash containing at least one of zinc and lead, chlorine and calcium to make a slurry, and heavy metals are eluted, and water is added to the slurry in the first step. , A second step of solid-liquid separation into a calcium-containing starch and a heavy metal-containing filtrate, and a mineral acid is added to the heavy metal-containing filtrate obtained in this second step to adjust the pH to 5 or less, and the lead-containing starch And a zinc-containing filtrate are subjected to solid-liquid separation, and an alkali agent is added to the zinc-containing filtrate obtained in the third step to adjust the pH to 7 to 10. And a fourth step of solid-liquid separation into a liquid and a method for treating fly ash. 4. The method for treating fly ash according to claim 3, wherein the lead-containing starch and the zinc-containing starch have a calcium concentration of 2 wt% or less. 5. Containing at least one of zinc and lead,
A smelting raw material characterized by containing 2 wt% or less of chlorine and 0.1 to 2 wt% of calcium.