JPH0841555A - Fractional recovery of lead and zinc from incinerated ash - Google Patents

Abstract

PURPOSE:To successively precipitate the lead and zinc in an incinerated ash as the sulfides and to fractionally recover the lead and zinc efficiently by supplying sodium sulfide to a soln. containing eluted heavy metals from the ash and regulating the pH of the soln. CONSTITUTION:The incinerated ash of refuse, etc., is mixed with hydrochloric acid to elute the heavy metals from the ash, and solid is separated from liq. to prepare the soln. of the heavy metals. Sodium sulfide or gaseous hydrogen sulfide is supplied while agitating the soln., and the pH is regulated to 0.4-1.2 to precipitate lead as the sulfide, which is separated and recovered. Sodium sulfide or gaseous hydrogen sulfide is then supplied to the soln. separated from the precipitate, and the pH is regulated to >=2 to precipitate the zinc as the sulfide, which is separated and recovered. Consequently, lead and zinc are fractionally separated from the incinerated ash efficiently, and the waste water generated in the recovery is made harmless.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating and recovering lead and zinc from incinerated ash, and more specifically, a method for separately recovering lead and zinc from incinerated ash of municipal waste and / or incinerated ash of industrial waste. In particular, it relates to a method for separately collecting lead and zinc from incinerated ash as a lead-containing compound (sulfide) and a zinc-containing compound (sulfide) having a purity that can be used as a non-ferrous refining raw material.

[0002]

[Prior Art] When incinerating municipal waste or industrial waste,
Bottom ash (residue) containing harmful heavy metals such as lead, zinc, cadmium and copper, and fly ash (fly ash) are generated. The former bottom ash is landfilled as it is or after solidification of cement or the like. The latter fly ash is designated as specially controlled general waste due to its high content of harmful heavy metals, etc., and it is obliged to treat it as pollution-free by the waste cleaning method.Therefore, cement solidification, chelate solidification, melt solidification, etc. Although some have been effectively used after the above treatment, most of them have not yet become sufficiently satisfactory treatment techniques.

With regard to such treatment technology, in particular, since it has recently become difficult to secure landfill sites, further improvement of technology for melting bottom ash and fly ash to form slag in order to reduce the amount of incinerated ash. Is desired.
In this technology, heavy metals are fixed in the slag-formed solid, but fly ash called volatilized ash is generated when the incinerated ash is melted into slag, and heavy metal with a low boiling point (lead, zinc , Cadmium, copper, etc.) are concentrated and contained in a large amount, and therefore, problems still remain.

On the other hand, as a method of treating fly ash (fly ash), a method has been developed in which after fly ash is pelletized into pellets, the fly ash is baked at a high temperature to fix heavy metals and used as aggregates and the like. There is. However, also in this case, volatilized ash is generated at the time of firing, and since the volatilized ash contains concentrated heavy metals, the problem still remains.

As described above, in the conventional ash treatment technology, a method for surely recovering heavy metals from all incinerated ash including volatilized ash generated during high temperature treatment such as melting and firing of ash has not been established.

By the way, various proposals have been made as a method for recovering or treating heavy metals from incinerated ash of municipal waste and industrial waste (for example, Japanese Patent Laid-Open No. 49-113703).
JP-A-53-25081, JP-A-58-46353, JP-B
58-53594, JP-B-60-7948, JP-A 4-2651
89 publication). It is shown in these documents that a heavy metal sulfide or hydroxide can be obtained by adding an alkali source such as sodium sulfide or sodium hydroxide to a heavy metal-dissolved aqueous solution containing heavy metals in incinerated ash. However, these methods are still insufficient as a technique for detoxifying harmful heavy metals in incinerated ash and recovering valuable heavy metals for effective use. Because, in these methods, the sulfides or hydroxides of the heavy metals are collectively precipitated and separated from the aqueous solution containing the heavy metals and separated, so that the content of valuable heavy metals in the obtained sulfides or hydroxides is increased. Has a low purity and is required as a non-ferrous refining raw material (for example, lead content:
This is because the quality of 40 wt% or more and zinc content: 50 wt% or more) is not satisfied, so heavy metals are not recycled, and eventually they have to be disposed of after being treated by some method.

[0007]

As described above, there are problems to be solved in the above conventional incineration ash treatment technology, particularly in the method for recovering heavy metals from incineration ash. That is, when practically recovering heavy metals from the incineration ash of municipal waste or industrial waste, the wastewater generated during the recovery of heavy metals should be made harmless, and the quality (purity) of the heavy metals obtained should be high and non-ferrous. It is necessary to make it a level that can be recycled as a refining raw material, and it is necessary to meet such requirements, but in the conventional method of recovering heavy metals from incinerated ash, there is a problem that such requirements cannot be met. is there.

More specifically, in the conventional method, little consideration has been given to a fractional recovery method for improving the recovery rate and quality of heavy metals, and there is no indication of an appropriate pH range for the fractional precipitation. However, chlorine content from the viewpoint of properties of non-ferrous refining raw materials has not been taken into consideration. Therefore, it has not been possible to establish a technology for recovering heavy metals of high grade that can be used as non-ferrous refining raw materials, and the incineration of municipal waste and industrial waste has not been established. There is a problem that valuable heavy metals such as lead and zinc cannot be practically recovered from ash.

The present invention has been made in view of such circumstances, and its purpose is to incinerate ash of municipal waste and industrial waste (volatilized ash generated during high temperature treatment such as melting and burning of ash). From the incineration ash, it is possible to efficiently separate and recover lead and zinc from the incineration ash as a lead-containing substance and a zinc-containing substance having a purity that can be used as a non-ferrous refining raw material, An object of the present invention is to provide a method for separately collecting lead and zinc from incinerated ash that can render wastewater generated during this recovery harmless. Here, the target value of the grade (purity) of the separated and recovered substance was set to a value of 40 wt% or more for the lead-containing substance and a zinc content of 50 wt% or more for the zinc-containing substance. In addition, the amount of chlorine in these separately collected substances is 1 from the viewpoint of maintenance of non-ferrous refining equipment.
It is desirable to set it to wt% or less.

[0010]

In order to achieve the above object, the method for separately collecting lead and zinc from incinerated ash according to the present invention has the following constitution. That is, the method for separately collecting lead and zinc from incinerated ash according to claim 1 supplies sodium sulfide or hydrogen sulfide gas to a heavy metal-dissolved solution containing the heavy metal in the incinerated ash that is dissolved and contained, and the pH of the solution. To
By setting 0.4 to 1.2, lead is precipitated and separated as sulfide, and then sodium sulfide or hydrogen sulfide gas is supplied to the solution after separation of the precipitate, and the pH of this solution is
Is set to 2 or more, zinc is precipitated and separated as a sulfide, and the lead and zinc are separated and recovered from the incineration ash.

According to a second aspect of the present invention, there is provided a method for separately collecting lead and zinc from incinerated ash, wherein the lead content in the sulfide in the precipitate obtained by precipitating and separating lead as sulfide is 40 wt% or more. The method for fractionating and recovering lead and zinc from incinerated ash according to claim 1, wherein the zinc content in the sulfide in the precipitate obtained by precipitating and separating zinc as sulfide is 50 wt% or more. .

According to a third aspect of the method for separately collecting lead and zinc from incinerated ash, after the lead is precipitated as a sulfide and separated, the precipitate is dried to obtain a lead-containing compound for a non-ferrous refining raw material, After precipitating and separating the zinc as sulfide,
The method for fractionating and recovering lead and zinc from incinerated ash according to claim 1 or 2, wherein the precipitate is dried to obtain a zinc-containing compound for a non-ferrous refining raw material.

According to the method for separately collecting lead and zinc from incinerated ash according to claim 4, after the lead is precipitated as a sulfide and separated, the precipitate is washed with water to remove chlorine in the precipitate by 1%.
After the content of the zinc is less than wt%, the zinc is precipitated as a sulfide and separated, and then this precipitate is washed with water to remove chlorine in the precipitate to 1%.
The method for separating and recovering lead and zinc from incinerated ash according to claim 1, 2 or 3, wherein the content is less than wt%.

According to the method for separately collecting lead and zinc from incinerated ash according to claim 5, the pH of the solution for precipitating lead as a sulfide is set to 0.9 to 1.2, and the pH for precipitating zinc as a sulfide is set. The pH of the solution is set to 2 to 3, 4.
Alternatively, it is a method for separately collecting lead and zinc from the incinerated ash described in 4.

[0015]

In order to achieve the above object, the present invention conducts a precipitation and separation test of heavy metals under various conditions on a heavy metal solution containing elution of heavy metals in incinerated ash. It was completed on the basis of the knowledge obtained as a result of the component analysis of the generated wastewater.

That is, sodium sulfide or hydrogen sulfide gas is supplied as a precipitating agent to a solution (heavy metal dissolving solution) in which the heavy metal in the incinerated ash is dissolved and the heavy metal is dissolved, and the pH of this solution is adjusted. When it is 0.4 to 1.2, lead and copper in the solution are preferentially precipitated as sulfides with a recovery rate of 90% or more, and the lead content in the precipitate is equal to the total sulfides in the precipitate. On the other hand, when the content of the solution is 40 wt% or more, and the solution after separating the precipitate is supplied with sodium sulfide or hydrogen sulfide gas as a precipitant and the pH of the solution is set to 2 or more, the solution is mainly in the solution. Each of zinc and cadmium
It was found that the sulfide was precipitated at a recovery rate of 99% or more, and the zinc content in this precipitate was 50% by weight or more based on the total sulfide in the precipitate. In addition, it was found that the concentration of harmful substances in the wastewater generated in this precipitation separation process was less than the standard concentration of regulated wastewater (nationwide uniform standard value for public water bodies shown in Table 3), and was rendered harmless.

Therefore, in the method for separately collecting lead and zinc from incinerated ash according to the present invention, sodium sulfide or hydrogen sulfide gas is supplied to a heavy metal-dissolved solution containing the heavy metal in the incinerated ash dissolved therein, and this solution is also supplied. By precipitating lead as a sulfide and separating it by adjusting the pH of the solution to 0.4 to 1.2, sodium sulfide or hydrogen sulfide gas is supplied to the solution after separating the precipitate, and the pH of this solution is 2 or more. By this, zinc was precipitated as sulfide and separated. Therefore, it is possible to efficiently separate and recover lead and zinc from incinerated ash as a lead-containing substance (lead content: 40 wt% or more) and a zinc-containing substance (zinc content: 50 wt% or more) with a purity that can be used as a non-ferrous refining raw material. At the same time, the waste water generated during this recovery can be rendered harmless, and therefore lead and zinc can be practically recovered from the incinerated ash.

Here, the pH of the solution when precipitating lead as a sulfide is 0.4 to 1.2. When the pH is less than 0.4, the amount of lead precipitated is reduced and the lead recovery rate is reduced (90%). Less than), and as the purity of the lead-containing compound decreases,
When the zinc-containing compound was recovered at pH 2 or higher, the lead that remained in the solution was precipitated and mixed as an impurity, and the purity of the zinc-containing compound also decreased. If it exceeds 1.2, the amount of zinc sulfide precipitates will increase and lead-containing As the purity of the compound decreases, the pH
This is because the zinc yield becomes poor when the zinc-containing compound is recovered when the amount is 2 or more.

Of the solution in which zinc is precipitated as sulphide
The pH is set to 2 or more. When the pH is set to be less than 2, the precipitation recovery rate of zinc is reduced, the purity of the zinc-containing compound is lowered, and the zinc concentration and cadmium concentration in the wastewater exceed the wastewater standard value. Because.

After the lead is precipitated as a sulfide and separated, the precipitate is dried to obtain a lead-containing compound for a non-ferrous refining raw material. After the zinc is precipitated as a sulfide and separated, the precipitate is dried to obtain a zinc-containing compound for a non-ferrous refining raw material (claim 3).

After the lead is precipitated as a sulfide and separated, the precipitate is washed with water to obtain 1 wt% of chlorine in the precipitate.
% Or less, and after the zinc is precipitated as a sulfide and separated, the precipitate is washed with water so that chlorine in the precipitate is less than 1 wt% (method according to claim 4). . This is because, when these are used as non-ferrous refining raw materials, it is desired to be 1 wt% or less from the viewpoint of maintenance of non-ferrous refining-related equipment.

The pH of the solution when precipitating lead as sulfide is 0.9 to 1.2, and the pH of the solution when precipitating zinc as sulfide is 2-3. Method described). More surely, the precipitation amount of lead is increased to improve the recovery rate of lead, and the precipitation amount of zinc is increased to improve the recovery rate of zinc. This is because it is possible to avoid that the purity starts to fall and the purity decreases.

In order to obtain a heavy metal-dissolved solution containing the heavy metal in the incineration ash by elution, the incineration ash and the solution may be mixed to dissolve the incineration ash to elute the heavy metal. At this time, as a solution for elution of heavy metals, water or acid can be used, but an increase in the elution amount of heavy metals and a post-process
It is desirable to use an acid from the viewpoint of simplifying pH adjustment.

When sodium sulfide or hydrogen sulfide gas is supplied to the heavy metal-dissolved solution, and further when the pH of the solution is adjusted,
When the solution is stirred, the solution pH is easily made uniform and a precipitate is easily formed. When supplying sodium sulfide or hydrogen sulfide gas to the solution after separating the precipitate, and further when adjusting the pH of the solution, the solution may be stirred in the same meaning as above.

When sodium sulfide is supplied to the solution for dissolving heavy metals, the pH of the solution increases. Therefore, if the pH of the heavy metal solution (solution before supplying the precipitant) is high, the pH of the solution after supplying the precipitant becomes even higher, sometimes exceeding 1.2. The pH needs to be adjusted to 0.4-1.2. Alternatively, it is necessary to add an acid to the solution before supplying the precipitant to reduce the pH in advance. On the other hand, when the pH of the solution before supplying the precipitant is low, the acid addition is not necessary, and thus the number of steps can be reduced accordingly. From this point of view, it is desirable to use an acid as the solution for eluting heavy metals.

The pH of the solution after precipitation and separation of the precipitate by supplying the above precipitant and adjusting the pH of the solution is 0.4 to 1.2. In order to supply a precipitant to the solution and adjust the pH of the solution to 2 or more, when sodium sulfide is supplied as the precipitant, the pH can be adjusted to 2 or more depending on the supply amount of this sodium sulfide, but the supply amount is small and that much. Then, if the pH cannot be adjusted to 2 or more, alkali may be added, and if hydrogen sulfide gas is supplied as a precipitant, alkali may be added.

[0027]

【Example】

(Example 1) Municipal refuse incineration fly ash and 3N hydrochloric acid were mixed at the ash concentration of 20 wt / vol%, and the heavy metals in the ash were dissolved at a dissolution time of 60 min at a dissolution temperature of room temperature, This is solid-liquid separated to dissolve heavy metal solution (lead: 1472 mg / l, zinc: 1644 mg
/ l, cadmium: 81.9 mg / l, copper: 344.2 mg / l) were obtained.

The above-mentioned heavy metal dissolved solution: 100 ml of sodium sulfide was added to the solution while stirring, the pH of the solution was adjusted to a predetermined value, and the heavy metal was precipitated and separated and collected as a sulfide to determine the recovery rate of each heavy metal. The relationship with pH was investigated. Here, the pH of the solution was changed as a parameter. The recovery rate of each heavy metal was determined from the difference between the content of each heavy metal in the solution after precipitation and before separation, and the content of each heavy metal in the solution (filtrate) after separation by precipitation.

Table 1 shows the recovery rate of each heavy metal obtained at each solution pH. Solution pH: When the pH is 0.4 or more, the lead recovery rate is 90% or more. The solution pH for obtaining a recovery rate of 99.9% or higher is 0.9 or higher for lead, 2 or higher for zinc and cadmium, and 2 for copper.
It is 0.1 or more. In addition, lead recovery rate: 99.9% or more is obtained. PH range: 0.9-1.2 zinc recovery rate is 7-
Since it is 15% and zinc hardly precipitates, when the pH of the solution is set to 0.9 to 1.2, sulfides containing a large amount of lead and a small amount of zinc (sulfides containing lead as a main component) are separated. It turns out that it can be recovered. Further, it is suggested that the pH of the solution at that time should be 2 or more in order to precipitate the sulfide containing zinc as a main component from the solution after the fractional recovery of the sulfide (after the precipitation separation).

(Example 2) Sodium sulfide was added to 3.0 liters (l) of the same heavy metal solution as in Example 1 by the same method, and the pH of the solution was adjusted to 1.0 to contain lead as a main component. Sulfide is precipitated and separated, and thereafter, sodium sulfide is added to the solution after separation of the precipitate and stirred, and
The pH of this solution was adjusted to 2 or 3 and the sulfide containing zinc as the main component was precipitated. This was filtered and solid-liquid separated, and then the concentration of harmful substances in the obtained filtrate was analyzed to obtain the standard concentration of wastewater. We compared and examined. The results are shown in Table 2. As can be seen from Table 2, the filtrate is below the national uniform drainage standard for public water bodies for all harmful substances, and is harmless as drainage. In addition, zinc and copper in the filtrate are 0.1-0.8 mg / l,
It was 0.05 to 1 mg / l, and it was confirmed that the drainage standards for substances other than other harmful substances also met the regulation values.

Example 3 Sodium sulfide was added to 3.0 liters of the same heavy metal solution as in Example 1 by the same method, and the pH of the solution was adjusted to 0.9 to obtain a sulfide containing lead as a main component. Precipitated and separated, and thereafter, sodium sulfide was added to the solution after the precipitation was separated and stirred, and the pH of this solution was adjusted to 3 to precipitate and separate the sulfide containing zinc as a main component. X-ray diffraction and heavy metal content analysis were performed on the sulfides. On the other hand, for comparison, sodium sulfide was added to 3.0 liters of the same heavy metal solution as in Example 1, the pH of the solution was adjusted to 3 and the heavy metals were collectively precipitated as sulfides and separated. Line diffraction and heavy metal content analysis were performed.

As a result, the heavy metal content in the obtained sulfide is shown in Table 3, and the X-ray diffraction result of the sulfide is shown in FIG.
As is clear from these results, the lead-containing sulfide obtained by precipitation separation at the above pH of 0.9 had a lead content of 5%.
The sulfide containing 4.7% of zinc and the zinc-based sulfide obtained by precipitation separation at pH 3 had a zinc content of 53.2%. The chlorine content in these sulfides was about 8%. On the other hand, the sulfide obtained by precipitating and separating by the batch precipitation method according to the comparative example was a sulfide having a lead content of 25.7% and a zinc content of 30.2%, and was inferior in quality. (Example 4)

For the lead-containing sulfide (precipitate) and the zinc-containing sulfide (precipitate) obtained in Example 3, each precipitate was used to reduce the chlorine content. To the product, 5.0 liters of tap water was added and stirred for 10 minutes to wash each precipitate. As a result, the chlorine content is about 8%
Reduced to the level of 0.6-0.7%. Further, it was confirmed that the washing effect was slightly improved when alkaline water having a pH of 8 or hot water having a temperature of 80 ° C. was used instead of the tap water.

The method for separately collecting lead and zinc from incinerated ash according to the present invention is carried out, for example, by the apparatus and process flow shown in FIG. In FIG. 1, 1 is a hydrochloric acid tank, 2 is a sodium sulfide tank, 3 is a volatilized ash hopper, 4 is a dissolution tank (heavy metal elution tank from ash), 5 is a dissolution residue filter, 6 is a compressor, and 7 is a dissolution liquid. Tank, 8
Is a Pb precipitation tank, 9 is a filtrate tank after Pb precipitation, 10 is a Zn precipitation tank,
Reference numeral 11 is a sulfide filter, 12 is a filtrate tank after Zn precipitation, 13 is a hydrogen sulfide gas removal tower, 14 is a slaked lime hopper, and 15 is a neutralization tank.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

EFFECT OF THE INVENTION According to the method for separately collecting lead and zinc from incinerated ash according to the present invention, a lead-containing substance (lead content:
(40 wt% or more) and zinc-containing substances (zinc content: 50 wt% or more) can be efficiently separated and collected, and wastewater generated during this collection can be rendered harmless, so that lead and zinc can be practically used from incineration ash. It can be collected and used effectively.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a process flow of a method for separately collecting lead and zinc from incinerated ash according to the present invention.

FIG. 2 is a diagram showing an X-ray diffraction result of a sulfide obtained by the precipitation method according to Example 3, where (A) of FIG. 2 is a sulfur-containing sulfide containing lead as a main component obtained by the two-step precipitation method. X-ray diffraction results of the sulfide obtained by the two-step precipitation method, (B) X-ray diffraction results of the sulfide containing zinc as the main component, and (C) of the sulfide obtained by the batch precipitation method. It is an X-ray diffraction result.

[Explanation of symbols]

1--hydrochloric acid tank, 2--sodium sulfide tank, 3--ash hopper, 4--dissolution tank, 5--dissolution residue filter, 6--compressor, 7--dissolution tank, 8--Pb precipitation Tank, filtrate tank after 9--Pb precipitation, 10--Zn precipitation tank, 11--sulfide filter, 12--Zn
After precipitation, filtrate tank, 13--hydrogen sulfide gas removal tower, 14--slaked lime hopper, 15--neutralization tank.

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[Procedure amendment]

[Submission date] November 4, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

[0036]

[Table 2]

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication C22B 19/30 B09B 3/00 304 G (72) Inventor Tadashi Ito 1-3 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo No. 18 Kobe Steel Co., Ltd. Kobe Head Office (72) Inventor Hiroaki Kawabata 1-3-18 Wakihamacho, Chuo-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd. Kobe Head Office

Claims (5)

[Claims] 1. Precipitating lead as a sulfide by supplying sodium sulfide or hydrogen sulfide gas to a heavy metal-dissolving solution containing eluted heavy metals in incinerated ash and adjusting the pH of the solution to 0.4 to 1.2. After that, sodium sulfide or hydrogen sulfide gas is supplied to the solution after the separation of the precipitate, and the pH of the solution is set to 2 or more to precipitate and separate zinc as a sulfide. A method for separately collecting lead and zinc from incinerated ash. 2. A precipitate obtained by precipitating and separating lead as sulfide, wherein the content of lead in the sulfide is 40 wt% or more, and the precipitate obtained by precipitating and separating zinc as sulfide. The method for fractionating and recovering lead and zinc from incinerated ash according to claim 1, wherein the zinc content of sulfide in the product is 50 wt% or more. 3. After precipitating and separating lead as a sulfide, this precipitate is dried to obtain a lead-containing compound for a non-ferrous refining raw material, and after precipitating and separating zinc as a sulfide, separating the precipitate. The method for fractionating and recovering lead and zinc from incinerated ash according to claim 1 or 2, wherein the zinc-containing compound for a non-ferrous refining raw material is obtained by drying. 4. The lead is precipitated and separated as a sulfide, and the precipitate is washed with water to obtain 1 wt% of chlorine in the precipitate.
% Or less, and the zinc is precipitated as a sulfide and separated, and then this precipitate is washed with water to obtain 1 wt% of chlorine in the precipitate.
% Or less, the method for separately collecting lead and zinc from incinerated ash according to claim 1, 2 or 3. 5. The pH of the solution when the lead is precipitated as a sulfide is 0.9 to 1.2, and the pH of the solution when the zinc is precipitated as a sulfide is 2 to 3. Alternatively, the method for separately collecting lead and zinc from the incinerated ash as described in 4 above.