JP2003138321A - Method for recovering valuable material from fused fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering valuable material from fused fly ash, by which lead and zinc contained in the fused fly ash can simply be recovered in few number of treating processes. SOLUTION: In the case of recovering the valuable material from the fused fly ash containing heavy metals of lead and zinc, etc., water-soluble salts discharged from a waste fusing facility, (a) a process, in which water is added to the fused fly ash and the water-soluble salts are eluted in the water and successively, pH is adjusted to 9-12 by adding alkaline agent or acidic agent into this solution and the water-soluble heavy metals incorporated in the heavy metals are made to be insoluble and successively, the heavy metals are coagulated and thereafter, the coagulated heavy metals are separated from the solution and the heavy metals are recovered as the insoluble residue containing lead and zinc, and (b) a process, in which the treated water is recovered by removing impurities contained in the separated solution separated with the heavy metals in the (a) process, are included.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for recovering valuable materials from molten fly ash obtained by melting waste such as municipal waste.

[0002]

2. Description of the Related Art Conventionally, as a method for recovering heavy metals from molten fly ash, for example, in JP-A-6-170354, a mineral acid is added to molten fly ash to elute heavy metals other than lead into the mineral acid. Then, solid-liquid separation is performed to recover lead as a lead residue, and an alkaline agent is added to the filtrate from which lead has been separated to recover zinc as a hydroxide mainly containing zinc.

Further, in JP-A-10-204552, an acid is added to molten fly ash to extract heavy metals other than lead,
Lead is extracted by adding a solubilizing agent to the lead-containing residue obtained by solid-liquid separation of this, and further insolubilizing agent is added to the filtrate obtained by solid-liquid separation to insolubilize lead and recover it. How to do is described. When recovering heavy metals other than lead, such as zinc, in this method, zinc is further insolubilized and recovered.

Further, in Japanese Patent Laid-Open No. 11-61286, an acid chemical is added to molten fly ash to extract zinc, and an insolubilizing agent is added to a zinc-containing filtrate obtained by solid-liquid separation. Zinc is recovered as an insoluble matter, and then a solubilizing agent is added to the lead-containing residue obtained by the above solid-liquid separation to extract lead, and this is further solid-liquid separated into a lead-containing filtrate obtained. A method for recovering lead as an insolubilized product by adding an insolubilizing agent is described.

Furthermore, Japanese Patent Laid-Open No. 2000-119761.
In the publication, a zinc solubilizing agent is added to molten fly ash to extract zinc, and the filtrate containing the zinc obtained by solid-liquid separation is added with an insolubilizing agent to insolubilize the zinc. Liquid is separated to recover zinc as a zinc insolubilization residue, and then impurities in the filtrate from which zinc is separated are removed, and then evaporated and concentrated to collect salts as a solid salt, and evaporated water is coagulated to collect water. Then, a lead solubilizing agent is added to the zinc extraction residue to extract lead, and the insoluble agent is added to the filtrate containing lead obtained by solid-liquid separation to insolubilize the lead. Lead is recovered as a lead insoluble matter by liquid separation, then impurities in the filtrate from which lead has been removed are removed to recover a lead solubilizing agent liquid, and impurities removed from the filtrate from which zinc has been separated, The lead extraction residue separated from the above-mentioned lead-extracted liquid and the above-mentioned lead were removed from the separated filtrate. How to recover are described respectively as molten slag impurities of sludge that is.

[0006]

However, in any of these methods, lead and zinc are separately recovered, and the lead or zinc to be recovered is once extracted and recovered in a solubilizing agent or the like, so that the treatment There is a problem that the number of steps is large and the processing is complicated.

[0007] Therefore, it is an object of the present invention to provide a method for recovering valuables from molten fly ash which can easily recover lead and zinc contained in the molten fly ash with a small number of treatment steps. is there.

[0008]

In order to solve the above-mentioned problems, the method for recovering valuable substances from the molten fly ash of the present invention is a heavy metal such as lead and zinc discharged from a waste melting facility and water-soluble salts. When the heavy metals are recovered from the molten fly ash containing and recycled, the following two steps are included.

(A) Water is added to the above-mentioned molten fly ash to elute water-soluble salts into water, and then an alkaline chemical agent or an acidic chemical agent is added to this solution to adjust the pH to 9 to 12 so that it is contained in heavy metals. A step of insolubilizing water-soluble heavy metals, then adding a polymer flocculant to agglomerate heavy metals, and then separating the agglomerated heavy metals from the liquid to recover the heavy metals as an insolubilized residue containing lead and zinc. .

(B) A step of removing the impurities contained in the separated liquid separated from the heavy metals in the step (a) to recover the treated water. The invention according to claim 2 is characterized in that, in the above invention, impurities are insolubilized by adding a heavy metal fixing agent to the separated liquid.

Further, in the invention described in claim 3, in the above invention, a step of evaporating and concentrating the treated water to recover water-soluble salts as a solid salt and condensing the evaporative water to recover water is added. It is characterized by having done.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the present invention, first, water is added to the molten fly ash to dissolve water-soluble salts such as potassium chloride, sodium chloride, and calcium chloride contained in the molten fly ash into water, and then the liquid is added depending on its pH. The pH is adjusted to 9 to 12 by adding an alkaline agent or an acidic agent to insolubilize the water-soluble heavy metals contained in the heavy metals.

Here, the alkaline chemicals or acidic chemicals act as pH adjusters, and also have the effect of reacting these chemicals with water-soluble heavy metals to produce insoluble heavy metal compounds.

Then, a polymer coagulant is added to the above liquid to coagulate the insolubilized heavy metals and the originally insoluble heavy metals contained in the molten fly ash. Then, when this liquid is subjected to solid-liquid separation, an insolubilized residue containing lead and zinc and a separated liquid containing water-soluble salts are obtained, and lead and zinc contained in the molten fly ash are recovered as an insolubilized residue. On the other hand, impurities contained in the separated liquid are removed by coagulation-sedimentation treatment, filtration treatment, etc., and treated water containing no impurities is obtained.

Further, if necessary, the treated water is evaporated and concentrated to recover water-soluble salts as solid salts, and the evaporated water is condensed to recover water containing no salts. For example, when the concentration of the salt in the treated water exceeds the regulated value and the treated water cannot be discharged to a river or the like, the water-soluble salt is recovered from the treated water.

In the present invention, the amount of water added to the molten fly ash is preferably 2 to 20 parts by mass with respect to 100 parts by mass of the molten fly ash. When the amount of water is less than 2 parts by mass, the fluidity of a molten fly ash liquid obtained by adding water, such as a slurry, becomes poor, and the elution rate of water-soluble salts into water is likely to decrease. On the other hand, if the amount exceeds 20 parts by mass, the liquid amount becomes large, and the equipment capacity for treating the liquid may have to be increased.

Further, as an alkaline chemical used for adjusting the pH of a liquid obtained by adding water to molten fly ash, sodium hydroxide,
Examples thereof include potassium hydroxide and slaked lime, and examples of the acidic agent include hydrochloric acid and sulfuric acid. Also, the pH of the above liquid
Is preferably in the range of 9 to 12, and when the pH is less than 9 or exceeds 12, the insolubilization rate of insoluble heavy metals tends to decrease.

If necessary, a heavy metal fixing agent such as a dithiocarbamic acid compound or sodium hydrosulfide may be added to the above liquid in order to ensure the insolubilization of the heavy metals.
Further, examples of the polymer coagulant added to the pH-adjusted liquid include an anionic polymer coagulant such as polyacrylamide. The amount of addition is preferably 0.2 to 2 kg per ton of molten fly ash. If the addition amount is less than 0.2 kg, the aggregation effect of heavy metals may be insufficient and it may be difficult to separate the heavy metals from the liquid. On the other hand, even if it exceeds 2 kg, the aggregation effect corresponding to it may not be improved. Not recognized,
Rather, the cost of the drug is high.

In the present invention, in order to separate the agglomerated heavy metals from the liquid, dehydration treatment, precipitation treatment or the like is used together, whereby the heavy metals are recovered as an insolubilized residue containing lead and zinc. It

Further, impurities such as heavy metals remaining in the separated liquid separated from the insolubilized residue containing the lead and zinc are, for example, dithiocarbamic acid compound,
A heavy metal fixing agent such as sodium hydrosulfide is added to insolubilize residual heavy metals and other impurities, and then an inorganic coagulant such as ferric chloride is added and an alkaline agent is added to adjust the pH to 9 to 12, and An anionic polymer flocculant such as polyacrylamide is added to perform flocculation and sedimentation treatment, and then the supernatant water is removed by sand filtration, filtration treatment with a fiber cartridge filter, or the like.
If necessary, impurities remaining in the filtrate are removed by adsorption treatment with a chelate resin or activated carbon, ultrafiltration with an ultrafiltration membrane, reverse osmosis treatment with a reverse osmosis membrane, and the like.

The amount of each of the above-mentioned chemicals added to the above-mentioned separated liquid is 50 to 200 heavy metal fixing agents per 1 liter of the separated liquid.
0 mg (undiluted solution), inorganic coagulant 300-3000 mg
(Purified), Anionic polymer flocculant 3-30mg
(Pure content conversion) is preferable.

When the treated water cannot be discharged into a river or the like because the concentration of the water-soluble salt contained in the treated water exceeds the regulated value, the treated water is evaporated and concentrated to convert the water-soluble salt into a solid salt. And collect the water by condensing the evaporated water.

In order to evaporate the treated water, a heat evaporation treatment is usually carried out, but it is preferable to heat evaporate under reduced pressure rather than under normal pressure because the treatment time can be shortened. Further, the concentration treatment is preferably performed by crystallization and then centrifugal separation, rather than simple evaporation to dryness, since the water-soluble salt can be recovered as a high-purity solid salt and the solid salt can be recovered as a crystalline salt.

The present invention will be described in more detail below with reference to the drawings. FIG. 1 is a schematic flow chart showing an example of the method of the present invention. In FIG. 1, the equipment for treating the molten fly ash comprises a heavy metal recovery equipment 1, an impurity removal equipment 6 and a salt recovery equipment 13. The heavy metal recovery equipment 1 is composed of a diluting tank 2, a pH adjusting tank 3, an aggregating tank 4 and a dehydrator 5, and an impurity removing equipment 6 is a first aggregating reaction tank 7, a second aggregating reaction tank 8 and a third aggregating reaction. Tank 9, settling tank 1
0, the neutralization tank 11 and the filter 12, and the salt recovery facility 13 is composed of a crystallization can 14 and a salt separator 15.

In the equipment of the above construction, the molten fly ash A containing heavy metals such as lead and zinc and water-soluble salts is diluted in the tank 2.
Then, water B is added thereto to dissolve the water-soluble salts contained in the molten fly ash A into water, and the molten fly ash A is made into a slurry liquid. Then, an alkaline chemical agent or an acidic chemical agent C is added to the slurry-like liquid in the pH adjusting tank 3 in accordance with the pH, and the pH of the liquid is adjusted to a predetermined pH to melt the fly ash A.
The water-soluble heavy metals contained in are insolubilized. After insolubilizing the water-soluble heavy metals, the polymer coagulant D is added in the coagulation tank 4 to coagulate the heavy metals. Thereafter, the slurry-like liquid containing the aggregated heavy metals is dehydrated by the dehydrator 5 and separated into the insolubilized residue E containing lead and zinc and the dehydrated filtrate F, and the insolubilized residue E is recovered.

On the other hand, the dehydrated filtrate F separated from the insolubilized residue E is sent to the first flocculation reaction tank 7 of the impurity removing equipment 6. Here, the heavy metal fixing agent G is added to insolubilize the impurities contained in the dehydrated filtrate F. Further, in the second aggregating reaction tank 8, the inorganic aggregating agent H and the alkaline agent I are added, and further in the third aggregating reaction tank 9, the polymer aggregating agent D is added to aggregate the impurities. Next, the aggregated impurities are sent to the settling tank 10, where the impurities are settled, and the sludge J generated thereby is returned to the dilution tank 2.

On the other hand, the supernatant liquid from which impurities have been removed is sent to the neutralization tank 10, where hydrochloric acid is added as a neutralizing agent K,
The supernatant is neutralized. The neutralized supernatant is separated from the solid content remaining in the supernatant by the filter 12 to obtain treated water L.

The treated water L is sent to the crystallization can 14 of the salt recovery facility 13 as needed. Here, the treated water L is heated by the steam M, and the water-soluble salts contained in the treated water L are crystallized. Next, the crystallized water-soluble salt is separated from the residual liquid by a salt separator 15 such as a centrifuge, and is recovered as a crystalline salt P. Then, the salt separation liquid Q separated from the crystal salt P is returned to the crystallization can 14. On the other hand, the evaporated water N generated during crystallization is cooled by the condenser 16 and collected as condensed water R. (Examples) Next, the present invention will be described more specifically by way of examples.

In the following Examples, "%" means "% by mass" except "%" which shows recovery rate and purity (content rate). Example 1 1.44% of Pb, Zn6., Discharged from the waste melting facility.
81%, Cd 0.0065% and other heavy metals and KC
1, 10.0 kg of molten fly ash A containing 80.1% of water-soluble salts such as NaCl and CaCl _{2 is} charged into the diluting tank 2 of the above heavy metal recovery equipment 1, and 40 liters of water B is added thereto to form a slurry liquid. Then, the water-soluble salts contained in the molten fly ash A were eluted in water. Then, a solution of a dithiocarbamic acid compound having a concentration of 10% as a heavy metal fixing agent G was added in a pH adjusting tank 3 at a concentration of 300 mg per 1 liter of the liquid (converted to the undiluted solution), and the concentration of the alkaline drug C was adjusted to 24 at a pH of 11.0. 5% aqueous sodium hydroxide solution
The heavy metals were insolubilized by adding 00 ml. Thereafter, 7 liters of a 0.1% polyacrylamide solution was added as the polymer flocculant D in the flocculation tank 4 to flocculate the suspension, and then the flocculated suspension was washed with water using a dehydrator 5. While solid-liquid separation, insolubilized residue E containing lead and zinc
Was recovered.

On the other hand, the dehydrated filtrate F separated from the insolubilized residue E is sent to the first flocculation reaction tank 7 of the impurity removal facility 6, where a solution of a dithiocarbamic acid compound having a concentration of 10% is used as a heavy metal fixing agent G. 200 mg per 1 liter of dehydrated filtrate F (as a stock solution) was added to insolubilize residual impurities such as heavy metals. Next, in the second flocculation reaction tank 8, an aqueous ferric chloride solution having a concentration of 10% was added as an inorganic flocculant H in an amount of 700 mg per 1 liter of the dehydrated filtrate F (in terms of pure content), and an alkaline chemical I had a concentration of 24% sodium hydroxide. Add 270 ml of aqueous solution to adjust pH to 1
The concentration was adjusted to 1.0, and a polyacrylamide solution having a concentration of 0.1% was added as a polymer flocculant D in the third flocculation reaction tank 9 by adding 15 mg (in terms of pure content) per liter of the dehydrated filtrate F to cause flocculation. . Thereafter, the flocculation flocs such as suspensions are settled in the settling tank 10, and the sludge J thus settled is settling tank 1
It was pulled out from the lower part of 0 and returned to the diluting tank 2.

On the other hand, 580 ml of 10% hydrochloric acid as a neutralizing agent K was added to the supernatant water obtained in the settling tank 10 to adjust the pH to 7.0, and then sand and anthracite ( Treated water L was obtained by removing the remaining suspension with a filter 12 filled with crushed coal.

Table 1 shows the results of the composition analysis of the insolubilized residue E containing lead and zinc thus recovered and the treated water L, the recovery rate and the results of the elution test. As is clear from Table 1, 2.62 kg of the insolubilized residue E was recovered as a dry amount, and the recovery rates of Pb and Zn were 97.9% and 98.%, respectively.
The purity of Pb and Zn in the recovered insolubilized residue E was 5.38% and 25.6%, respectively.
Further, the treated water had a clear water quality containing almost no harmful substances such as lead. Further, the obtained insolubilized residue E had low dissolution test values by Pb 0.18 mg / L and Cd 0.11 mg / L according to the Environmental Agency Notification No. 13 method, respectively.

Therefore, according to the present invention, as compared with the conventional method, it is possible to recover lead and zinc in the molten fly ash with a high yield and a high purity by a simple method, and a good water quality is treated. It turns out that water can be recovered. Example 2 Molten fly ash A similar to that in Example 1 was treated in the same manner as in Example 1 to obtain treated water L.

Further, the treated water L was filled in a cylindrical cartridge filter (three fiber cloths having a pore size of about 1 μm were laminated to form a cylindrical shape) in a precision filter to have a linear velocity LV = 2 (m ³ / m ³ / m ² · h) to remove a small amount of suspended solids, and then to pass through an adsorption tower filled with a chelating resin for adsorbing heavy metals at a space velocity SV = 2 (L / L · h) Then, the trace amount of heavy metals remained was removed. Then, water was passed through an adsorption tower filled with activated carbon (particle size: about 0.4 to 0.5 mm) at a space velocity of 2 (L / L · h) to obtain highly decolorized treated water.

This highly treated water is sent to the crystallization can 14 of the salt recovery facility 13, and the pressure in the crystallization can 14 is set to about 48 kPa.
The pressure was reduced to 1, and the water-soluble salts contained in the highly treated water were crystallized by heating with steam M to about 76 ° C. to obtain a salt slurry. The evaporated water N evaporated by heating was cooled by the condenser 16 and collected as condensed water R.

The crystallized salt slurry was subjected to solid-liquid separation by a centrifugal salt separator 15 to recover water-soluble salts as crystalline salt P. On the other hand, the salt separation liquid Q separated from the water-soluble salts was returned to the crystallization can 14.

Table 1 shows the results of composition analysis, recovery rate and elution test of the insolubilized residue E containing lead and zinc thus recovered, the treated water L, the crystalline salt P and the condensed water R.

[0038]

[Table 1] As is clear from Table 1, the insolubilized residue E was recovered in a dry amount of 2.24 kg, and the recovery rates of Pb and Zn were 98.8% and 99.7%, respectively. The purity of Pb and Zn of each is 6.34
% And 30.3%. In addition, crystalline salt P of water-soluble salt
7.36 kg was recovered, and the value obtained by subtracting the amount of water-soluble salts in the insolubilized residue from the amount of water-soluble salts in the molten fly ash (1
0.0 x 0.81 kg-2.24 x 0.353 kg = 7.2
2kg), its recovery was 102.0% and its purity was 98.3%. Crystal salt P has the above value of 7.22
The fact that 7.36 kg was recovered in excess of kg is probably due to the influence of sodium hydroxide and hydrochloric acid used for pH adjustment in the impurity removal facility 6, but from the concentration of water-soluble salts in the condensed water R If so, it is considered that the water-soluble salts in the dehydrated filtrate F were recovered as crystalline salts in high yield and high purity. Furthermore, 36.8 kg of condensed water R was recovered, the recovery rate was 92.1%, and the content of water-soluble salts in condensed water R was 0.52 mg / L, which was an extremely low clear water quality. there were. Furthermore, the obtained insolubilized residue E has a dissolution test value of Pb according to the Environmental Agency Notification No. 13 method.
The low values were 0.02 mg / L and Cd 0.01 mg / L, respectively.

Therefore, according to the present invention, the lead and zinc in the molten fly ash can be recovered in high yield and high purity by a simple method, and the treated water of good water quality can be recovered. Moreover, it can be seen that the water-soluble salts and condensed water can be recovered in high yield and high purity.

[0040]

As described above, according to the present invention, the heavy metals contained in the molten fly ash are insolubilized and are collectively recovered as an insolubilized residue containing lead and zinc. The lead and zinc contained in the molten fly ash can be easily recovered with few treatment steps, and the water used for recovering lead and zinc can be recovered as treated water with few impurities. Therefore, there is no risk of polluting the environment. The insolubilized residue thus recovered is reused as a non-ferrous smelting raw material and the treated water is reused as industrial water.

According to the second aspect of the invention, since the heavy metal fixing agent is added to the separated liquid separated from the heavy metals to insolubilize the impurities, the treated water containing less impurities can be recovered.

Further, according to the invention described in claim 3,
The water-soluble salts contained in the molten fly ash can be recovered as a solid salt with a high recovery rate, and the water can be recovered as condensed water of high purity. The solid salt thus recovered is reused as a raw material for chemical industry, etc., and the recovered water is reused as cooling water or the like in the treatment process of molten fly ash.

[Brief description of drawings]

FIG. 1 is a schematic flow chart showing an example of the method of the present invention.

[Explanation of symbols]

1 Heavy metal recovery equipment 2 dilution tank 3 pH adjustment tank 4 coagulation tank 5 dehydrator 6 Impurity removal equipment 7 First aggregation reaction tank 8 Second agglutination reaction tank 9 Third agglutination reaction tank 10 settling tank 11 Neutralization tank 12 Filter 13 Salt recovery equipment 14 Crystallizer 15 salt separator 16 condenser A molten fly ash B water C Alkaline drug or acidic drug D Polymer flocculant E Insolubilization residue F dehydrated filtrate G Heavy metal fixative H inorganic coagulant I Alkaline drugs J sludge K neutralizer L treated water M water vapor N evaporated water P crystalline salt Q salt separation liquid R condensed water

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 1/56 C22B 19/30 4K001 1/62 B09B 3/00 304G C22B 3/44 ZAB 13/00 C22B 3 / 00 Q 19/30 13/04 (72) Inventor Yutaka Sakawa, 1-2-47 Shikitsu East, Naniwa-ku, Osaka City, Osaka Prefecture Kubota F-Term Co., Ltd. (reference) 4D004 AA37 AB03 AC05 BA05 CA13 4D015 BA19 BB09 BB12 CA17 DA16 DC02 EA32 EA39 FA01 FA11 FA30 4D034 AA27 BA01 BA03 CA12 4D037 AB08 BA14 CA02 CA08 CA14 4D038 AA10 AB69 AB71 AB74 BA04 BB13 BB17 BB18 4K001 AA20 AA30 BA14 CA05 DB23 DB35 DB36 EA06

Claims (3)

[Claims] 1. A method of recovering valuable materials from molten fly ash containing heavy metals such as lead and zinc and water-soluble salts discharged from a waste melting facility, and includes the following two steps. A method of recovering valuable materials from molten fly ash. (A) Water is added to the molten fly ash to dissolve water-soluble salts in water, and then an alkaline agent or an acidic agent is added to the solution to adjust the pH to 9 to 12 so that water-soluble salts contained in heavy metals are contained. A step of insolubilizing the heavy metals, then adding a polymer flocculant to agglomerate the heavy metals, separating the agglomerated heavy metals from the liquid, and collecting the heavy metals as an insolubilized residue containing lead and zinc. (B) A step of collecting the treated water by removing impurities contained in the separated liquid separated from the heavy metals in the step (a). 2. The method for recovering valuable substances from molten fly ash according to claim 1, wherein a heavy metal fixing agent is added to the separated liquid to insolubilize impurities. 3. The method according to claim 1, further comprising the step of collecting the water-soluble salt as a solid salt by evaporating and concentrating the treated water, and collecting the water by condensing the evaporated water. A method for recovering valuable materials from the described molten fly ash.