JP2005068535A - Method of treating gas or flying ash containing lead and zinc - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of recovering lead and/or zinc from lead and/or zinc-containing gas or flying ash without generating waste water. <P>SOLUTION: A suspension containing an insoluble lead and/or zinc compound is obtained from a lead and/or zinc-containing treatment liquid obtained by subjecting lead and/or zinc-containing gas or flying ash to washing treatment. The suspension is subjected to solid-liquid separation. The obtained solid component is next subjected to a stage so as to be washed with water and thereafter to be subjected to solid-liquid separation for at least one time. The obtained solid component in which the concentration of chlorine is reduced is discharged as the raw material for mine return for recovering lead and/or zinc. Further, the separation liquid obtained by the solid-liquid separation is subjected to calcium removal treatment and chlorine removal treatment. The obtained water is circularly used as washing water for the solid component in the above stage where the solid component is washed with water, and is subjected to solid-liquid separation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recovering heavy metals from a cleaning liquid containing heavy metals obtained by cleaning gas or fly ash generated when heat treating municipal waste or industrial waste.

  Municipal waste, industrial waste, and the like are reduced in volume by incineration or melting at a waste disposal site, and solids such as incineration residues that are finally discharged are landfilled at a landfill site. Among these solids, fly ash generated when incinerated or melted contains heavy metals such as zinc and lead, so fly ash is stabilized by cement solidification, chemical treatment, etc. Landfilled after being processed.

  However, such a disposal method requires a landfill disposal site, and in recent years it has become very difficult to secure such a disposal site. In addition, even in the case of stabilization treatment, there is a risk that heavy metals eluted from landfilled fly ash will cause environmental pollution in the ultra-long term. There is also a problem that even if resources are included, these useful resources are not used.

Therefore, various methods for removing and recovering heavy metals from fly ash have been proposed.
Patent Document 1 discloses a method for treating fly ash containing salts mainly containing chlorine and sodium generated from incinerators and melting furnaces, and heavy metals mainly containing zinc, copper, and lead. First step of solid-liquid separation after adjusting the pH of the liquid to 8.0 to 11.0 by adding water and a neutralizing agent; adding the water to the obtained residue and repulping the pH to 3 or less The second step of adjusting and eluting the heavy metal component mainly composed of zinc and copper, and then filtering out the residue containing the heavy metal mainly composed of lead; and obtained in the first step and the second step. A neutralizing agent is added to the filtrate to neutralize it to pH 7 or higher to produce a heavy metal hydroxide mainly composed of zinc, and if necessary, a sulfiding agent is added to the filtrate to sulfidize the remaining heavy metals. By subjecting to a third step of precipitating as a product and filtering off these precipitates. Separate and separate heavy metals contained in fly ash as residue (mainly containing lead), hydroxide starch (mainly containing zinc), and sulfide starch (mainly lead and zinc sulfide) , Methods are described that can be used as non-ferrous smelting raw materials.
However, depending on this method, the heavy metal-containing residue contains a large amount of chlorine, and when this is used as a raw material for non-ferrous smelting, the chlorine or chlorine compound causes various problems. There is.

  In order to solve the above problem, in Patent Document 2, water is added to fly ash collected when the waste incineration residue is melt-treated, and an alkali is further added as necessary to form a slurry. Separating the solution from which soluble salts are eluted by solid-liquid separation into a residue containing heavy metal, and then subjecting the separated residue to high-temperature heat treatment to remove chlorine and dioxins in the residue, A method of recovering as a raw material for smelting has been proposed. However, this method requires a separate high-temperature heat treatment step.

  In Patent Document 3, the fly ash containing heavy metals such as lead discharged from an incinerator or melting furnace is added with acid to extract heavy metals other than lead, followed by solid-liquid separation, and then solid-liquid Extract the lead by adding a solubilizing agent to the lead-containing residue obtained by separation, then solid-liquid separate it, and further insolubilize the lead by adding an insolubilizing agent to the filtrate obtained by solid-liquid separation A method for recovering lead in fly ash consisting of solid-liquid separation after making a product is described.

  In Patent Document 4, water is added to fly ash, and an alkali is added as necessary to prepare a slurry having a pH of 7 to 11, and the slurry is solid-liquid separated to concentrate the solution from which soluble salts are eluted and heavy metals. Water is added to the residue enriched with heavy metals, and sulfuric acid is further added to prepare a slurry having a pH of 4 to 6, and the slurry is solid-liquid separated to obtain a solution containing heavy metals mainly composed of zinc; It is described that it is divided into residues containing heavy metals mainly composed of lead.

All of the above methods target fly ash generated by waste treatment.
On the other hand, in recent years, waste is heat-treated in a reducing heat treatment furnace as a waste treatment method that replaces the incineration and melting treatments described above. As an example of such a processing method, a gasification melting process by a gasification reforming method (thermoselect method) has been attracting attention. This method includes a step of washing the gas discharged from the high-temperature reactor with an acidic aqueous solution, so fly ash is not generated, but heavy metals such as zinc and lead are contained in the gas discharged from the high-temperature reactor. Since it is contained and dissolves in the washing water in the acid washing step, it is necessary to remove the heavy metals from the washing water for effective use.

And patent document 5 has proposed the method of collect | recovering heavy metals from wash water in the waste processing by a gasification reforming system.
In this method, a gas generated by gasification of waste is cooled and washed with an acidic aqueous solution adjusted to 2 ≦ pH ≦ 3, and then washed with a washing liquid, and the acidic aqueous solution used for the cooling and washing or further the washing An alkali is added to a part of the cleaning liquid used in the above, and the obtained treatment liquid is separated into a solid and a liquid using a solid-liquid separation apparatus such as a membrane separation apparatus.

  This method is intended to recover valuable substances such as Zn and Pb in gas generated by gasification of waste, but has a problem that a large amount of waste water is generated by solid-liquid separation. Further, in order to use a residue containing a valuable substance as a raw material for Yamamoto reduction, it is necessary to reduce the chlorine content in the residue, but Patent Document 5 does not describe means for reducing the chlorine content.

Therefore, in order to reduce the chlorine content from this residue, it is considered necessary to perform a treatment such as washing the residue with water, but this will generate a larger amount of wastewater, increasing the environmental burden. There was a problem to do. In addition, it is not a good idea to carry out such a process that generates a large amount of wastewater at a waste disposal plant in an urban area because it requires additional water treatment facilities.
For this reason, development of the heavy metal recovery process which can obtain the residue containing the valuable substance which can become the raw material of Yamamoto reduction in a waste disposal site as it is without generating waste water is desired.

JP-A-8-141539 Japanese Patent Laid-Open No. 10-204548 JP-A-10-204552 Japanese Patent Laid-Open No. 10-109077 JP 2003-1041 A

  The present invention generates waste water from gas or fly ash (including molten fly ash) containing lead or zinc generated in a process of heat treating municipal waste or industrial waste (hereinafter also referred to as “waste”). It is an object to provide a method for recovering lead and / or zinc.

  As a result of intensive studies on the method for achieving the above-mentioned object, the present inventors have washed or eluted the gas or fly ash containing lead and / or zinc generated in the step of heat treating the waste (hereinafter referred to as the following). After the washing treatment and the elution treatment are referred to as washing treatment), a suspension containing an insoluble lead and / or zinc compound is obtained, then this is subjected to solid-liquid separation, and the obtained solid residue is washed with water. After performing the solid-liquid separation step at least once, the solid residue obtained by solid-liquid separation is used as a raw material for Yamamoto reduction, while the separation liquid obtained by solid-liquid separation is washing water for washing the solid residue. As a result, a part of the separated liquid is returned to the washing water for washing the solid residue through the decalcification process and the dechlorination process, thereby efficiently recovering lead and zinc without generating waste water. To obtain a knowledge that bets can be one in which the present invention has been completed.

That is, the present invention is as described below.
(1) In a method for treating a gas cleaning liquid containing lead and zinc obtained by cleaning a gas containing lead and / or zinc, an alkali is added to the cleaning liquid to form an insoluble lead and / or zinc compound. It is obtained by the final solid-liquid separation after subjecting it to a solid-liquid separation, and then subjecting the obtained solid content to at least one solid-liquid separation after washing with water. The solid content with reduced chlorine concentration was taken out as a raw material for Yamamoto reduction for lead and / or zinc recovery, and the separation liquid obtained by solid-liquid separation was subjected to decalcification treatment and dechlorination treatment. A method for treating a gas cleaning liquid containing lead and / or zinc, wherein the desalted water is recycled as the solid cleaning water in the step of solid-liquid separation after washing the solid with water.
(2) The method for treating a gas cleaning liquid containing lead and / or zinc as described in (1) above, wherein the gas is a gas generated by gasification reforming treatment of waste.
(3) The lead and / or zinc described in (1) above, wherein the gas is a gas generated when fly ash generated by incineration of waste is melted in an oxidizing atmosphere. A method for treating the contained gas cleaning liquid.
(4) The above-mentioned (1), wherein the cleaning liquid containing lead and / or zinc is obtained by cooling and cleaning using an acidic aqueous solution whose gas is adjusted to 2 ≦ pH ≦ 5. )-(3) The processing method of the gas cleaning liquid containing lead and / or zinc in any one of.

(5) In a method for treating a cleaning liquid containing insoluble lead and / or zinc compounds obtained by washing a gas generated in an environment that becomes an oxidizing atmosphere after melting fly ash in a reducing atmosphere, The washing liquid is subjected to solid-liquid separation, and then the solid content obtained is washed with water and then subjected to solid-liquid separation at least once, and then the solid content with reduced chlorine concentration obtained by the last solid-liquid separation is obtained. Is taken out as a raw material for Yamamoto reduction for lead and / or zinc recovery, and the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment. A method for treating a gas cleaning liquid containing lead and / or zinc, wherein the cleaning liquid is used as a cleaning water for solid content in a step of solid-liquid separation after washing with water.
(6) The lead and / or zinc according to any one of (1) to (5) above, wherein the chlorine concentration of the suspension before the last solid-liquid separation is 2% by mass or less Gas cleaning solution treatment method.
(7) The above (1) to (1), wherein the dechlorination step is performed by any one method selected from a reverse osmosis method, an electroosmosis method and an evaporation to dryness method or a combination of two or more methods. 6) A method for treating a gas cleaning liquid containing lead and / or zinc according to any one of the above.
(8) The lead according to any one of (1) to (6), wherein the dechlorination step is a step of concentrating and crystallizing salt-containing water to separate into demineralized water and precipitated salt. And / or a method for treating a gas cleaning liquid containing zinc.
(9) In a treatment method for a treatment liquid containing lead and / or zinc obtained by treating fly ash collected from a gas generated when fly ash is melt-treated in an oxidizing atmosphere with an acidic aqueous solution, the treatment The liquid is subjected to solid-liquid separation, and then an alkali is added to the obtained separation liquid to obtain a suspension containing an insoluble lead and / or zinc compound, which is subjected to solid-liquid separation, and the obtained solid content After the solid-liquid separation process is performed at least once after washing with water, the solid content with reduced chlorine concentration obtained by the last solid-liquid separation is used as a raw material for reducing Yamamoto to recover lead and / or zinc. In addition, the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment, and the obtained demineralized water is washed with water and then solid-liquid separated in the step of solid-liquid separation. Recycle as cleaning water Processing method of the processing liquid containing the lead and / or zinc, characterized in.
(10) A treatment liquid containing lead and / or zinc obtained by treating fly ash recovered from a gas generated in an environment that becomes an oxidizing atmosphere after melting the fly ash in a reducing atmosphere. In the treatment method, the treatment liquid is subjected to solid-liquid separation, and the solid content obtained is washed with water and then subjected to solid-liquid separation at least once, and then the chlorine concentration obtained by the last solid-liquid separation is obtained. The reduced solid content is taken out as a raw material for Yamamoto reduction for lead and / or zinc recovery, and the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment, and the obtained demineralized water is used as the above-mentioned demineralized water. A method for treating a treatment liquid containing lead and / or zinc, wherein the solid content is washed with water and then recycled as solid content washing water in a step of solid-liquid separation.

  Since the method of the present invention does not discharge wastewater, it has an effect that a raw material for reducing Yamamoto containing lead and zinc at a high concentration and having a low chlorine concentration can be obtained at a waste treatment plant.

The method of the present invention will be described with reference to the drawings by taking the gasification reforming system described above as an example.
First, one example of the gasification reforming system will be described with reference to FIG.
The gasification reforming method shown in FIG. 1 includes the following processes.

1. Press / degas channel
(1) Garbage compression, (2) Drying and pyrolysis High-temperature reactor / homogenization furnace
(3) Gasification melting, (4) Slag homogenization, (5) Gas reforming. Gas purification
(6) Rapid cooling (rapid cooling / acid cleaning, acid cleaning), (7) Gas purification (alkali cleaning, desulfurization, dehumidification)
4). Water treatment
(8) Water treatment (precipitation, desalination, etc.)

This method will be described along the flow as follows.
Wastes such as municipal waste accumulated in the pits are compressed by a press and then heated and dry-distilled by indirect heating in a dry pyrolysis process and sent into a high-temperature reactor. A burner is disposed at the lower part of the high-temperature reactor, and fuel gas and oxygen are introduced into the furnace by the burner, and the oxygen gas gasifies carbon in the dry distillate to produce carbon monoxide and carbon dioxide. In addition, when high-temperature steam is present, a water gasification reaction occurs between carbon and steam to generate carbon monoxide and hydrogen. Further, the organic compound is thermally decomposed to generate carbon monoxide and hydrogen.
As a result of the above reaction, the crude synthesis gas is discharged from the top of the high temperature reactor.

  On the other hand, the melt produced in the lower part of the high temperature reactor flows out from the high temperature reactor to the homogenization furnace. This melt contains carbon, trace amounts of heavy metals, and the like, and carbon is gasified with sufficient oxygen and water vapor in a homogenization furnace to generate carbon dioxide, carbon monoxide, and hydrogen. In the homogenization furnace, the metal melt has a large specific gravity and therefore accumulates in the lower part of the slag. The melt flows down to the granulation system and is cooled and solidified, and the metal-slag mixture is separated into metal and slag by magnetic separation.

  The crude synthesis gas discharged from the high temperature reactor is rapidly cooled from about 1200 ° C. to about 70 ° C. by injecting acidic water with a quenching device to prevent the formation of dioxins. At this time, the gas is washed with acidic water, and heavy metal components such as Zn and Pb and chlorine contained in the crude synthesis gas are dissolved in the washing liquid.

The acid-cleaned synthesis gas is further acid-washed if necessary, and then alkali-washed, and the remaining acidic gas such as hydrogen chloride gas is neutralized and removed. Next, hydrogen sulfide in the gas is converted into sulfur by a desulfurization washing apparatus and discharged as a sulfur cake. Next, the synthesis gas is used as a refined fuel gas after moisture is removed in a low temperature dehumidification process.
On the other hand, metal components such as iron and zinc are removed from the cleaning liquid in the water treatment apparatus.

The present invention is characterized by the configuration for recovering zinc and lead from the washing water containing zinc and lead as described above. Hereinafter, the gas cleaning method and the cleaning water treatment method will be described in more detail.
First, a gas cleaning method will be described.

  In FIG. 1, the gas generated by gasification of the waste discharged from the top of the high temperature reactor is rapidly cooled by being injected with an acidic aqueous solution having a pH of 2 to 5 in the course of being supplied to the gas purification facility.・ Acid cleaning treatment. Chlorine contained in the waste is mainly present in the synthesis gas as hydrogen chloride, and this hydrogen chloride dissolves in the cooling / cleaning liquid. The crude synthesis gas is washed with the acidic aqueous solution containing hydrogen chloride, and heavy metal components such as zinc and lead are removed. The cleaning liquid is sent to a precipitation tank to remove carbon fine particles, indirectly cooled by a heat exchanger, and then recirculated for gas quenching. The reason why the acidic aqueous solution is adjusted to pH 2 to 5 is to effectively dissolve and absorb heavy metals in the cooling / acid-washed water, and if the pH is out of this range, effective dissolution / absorption is not performed.

  During this quenching and acid cleaning process, the high-temperature product gas is quenched, preventing the synthesis of dioxins, and ammonia, iron chloride, evaporated zinc, evaporated lead and fine carbon particles in the generated gas are dissolved in the acidic aqueous solution. Or captured.

  The rapidly cooled and acid-washed product gas is further washed as necessary, and absorbed and removed by HCl that could not be absorbed or captured by the acidic aqueous solution, and then subjected to treatment such as desulfurization in the gas purifier. The purified gas is effectively used as a fuel gas.

Next, a method for treating cleaning water obtained by gas cleaning will be described with reference to FIG.
Washing water generated in the rapid cooling / acid washing step is fed to the first neutralization layer, and an alkali agent such as NaOH is added to adjust to pH 4-7. As a result, iron ions and aluminum ions are selectively precipitated as hydroxides. The obtained precipitate is subjected to solid-liquid separation with a first solid-liquid separator, and iron hydroxide and aluminum hydroxide are separated and recovered as solids. This iron hydroxide, aluminum hydroxide, etc. can be recycled to the high temperature reaction tower and recovered and reused as metal and slag.
The step of separating iron hydroxide and aluminum hydroxide is performed to improve the purity of zinc and lead. However, for the reduction of Yamamoto containing zinc and lead in a form containing iron and aluminum. In the case of obtaining a refining raw material, this step can be omitted.

  Next, the separated water from which iron hydroxide and aluminum hydroxide have been separated by solid-liquid separation is fed to the second neutralization tank, and an alkali agent such as NaOH is added, so that the water to be treated becomes about 7 to 11 Increase. Thereby, zinc ions and lead ions in the water to be treated are selectively deposited as zinc hydroxide and lead hydroxide, respectively. The obtained suspension is fed to a second solid-liquid separation device for solid-liquid separation, and separated into solid content containing valuable substances such as zinc hydroxide and lead hydroxide, and separated water.

  The obtained solid content is sent to a re-dispersion tank, where the solid content is re-dispersed and washed with demineralized water fed from the desalting step, followed by solid-liquid separation. The step of re-dispersing, washing and solid-liquid separation is performed at least once. Since the chlorine content in the solid content is reduced by this step, the chlorine concentration in the solid content can be further reduced by repeating this step. Usually, it is desirable that the chlorine concentration on the liquid side before the final solid-liquid separation step is 2% by mass or less. If the chlorine concentration exceeds 2% by mass, a relatively low boiling point compound is formed in the smelting furnace during the Yamamoto reduction, and this is not preferable.

On the other hand, the separated water from which the solid content has been removed in the solid-liquid separation step is removed in the form of calcium carbonate or the like by adding a chemical such as Na ₂ CO ₃ in the next decalcification step. The separated water after decalcification is sent to the next desalting step, where the salt content is removed by methods such as evaporation, reverse osmosis, and electrodialysis, and then circulated to the redispersion tank and reused as washing water. The salt content concentrated in the desalting step is further concentrated by a method such as crystallization, then separated into solid and liquid and discharged as a mixed salt.

  As described above, according to the present invention, the environmental pollutants in the wash water are not discharged as waste water by making the wash water of the solid content into a closed loop. The decalcification process and the dechlorination process are necessary steps for stably operating the apparatus by making the wash water into a closed loop. That is, the decalcification treatment is necessary for preventing scaling when the reclaimed water is obtained by the concentration operation, and the dechlorination treatment is necessary for reducing solid chlorine containing the heavy metal oxide to be recovered. And by said operation, solid content with which lead and zinc as a raw material for Yamamoto reduction were concentrated can be obtained, without generating waste_water | drain.

  In the present invention, as a solid-liquid separation method, a specific gravity sedimentation separation method, a centrifugal separation method, a filtration method using a filter medium such as a filter press, or the like can be suitably used.

Next, the case where the method of the present invention is applied to the gas generated when the fly ash obtained when the waste is incinerated is melted will be described.
The fly ash may be further melted to further reduce the volume and make the heavy metal stable and detoxified. And since this fly ash contains salts such as sodium chloride and sodium chloride, and heavy metals such as zinc and lead, when it is melted at a high temperature, most of the heavy metals having a low boiling point are volatilized as gas. Discharged.

  When fly ash is melted in an oxidizing atmosphere, heavy metals are contained in the gas in the form of chlorides, so this gas is applied to the gas discharged from the high-temperature reactor of the gasification reforming method described above. Heavy metal can be recovered by performing the same process as described above.

  In addition, when the fly ash is melted in a reducing atmosphere and the gas generated at this time is processed in an oxidizing atmosphere, the volatilized heavy metal is in the form of an oxide. Gas containing substances can be reduced in chloride by washing with water. Then, the treated water obtained by this water washing is subjected to solid-liquid separation, the obtained solid content is subjected to redispersion treatment with demineralized water, and then dehydrated with a filter press, so that the obtained solid content is reduced to Yamamoto. The chlorine content is reduced to a suitable concentration for use.

Next, the case where the method of this invention is applied to fly ash is demonstrated based on FIG.
When waste or fly ash containing chlorine is heat-treated in an oxidizing atmosphere, heavy metals such as zinc and lead are volatilized mainly as chlorides of heavy metals and are contained in the exhaust gas. When the exhaust gas is collected with a bag filter or the like, the heavy metal chloride is contained in the collected fly ash or molten fly ash (hereinafter, fly ash and molten fly ash together). The fly ash is washed (eluted) with hydrochloric acid (or hydrochloric acid recovered from waste) at pH 2 to 5 to remove acid-insoluble matter such as silicon.

  By adding sodium hydroxide to the obtained separated liquid, the pH is adjusted to 7 to 11 (preferably pH 8.5 to 10), and zinc and lead are precipitated as zinc hydroxide and lead hydroxide. After separating this by coagulation precipitation, it is dehydrated with a filter press or the like to remove salts such as sodium chloride adhering to the particles. Preferably, the salt water is further removed by flowing air or the like. Next, the obtained metal hydroxide is redispersed in demineralized water at a solid-liquid ratio of 1/1 to 1/10. In this case, the solid-liquid ratio is preferably about 1/5. This dispersion is dehydrated through a filter press to further remove salts such as sodium chloride attached to the particles. Further, preferably, salt water is further removed by flowing air or the like. Since the obtained dechlorinated metal hydroxide has a chlorine content reduced to 2% by mass or less, it can be used as a raw material for Yamamoto reduction.

  Further, since the liquid recovered by the filter press contains calcium, decalcification treatment and desalination treatment are performed, and the obtained desalted water is a solvent for redispersion of the metal hydroxide described above. Use as a circulation. Further, the salt water concentrated in the desalination facility is treated with a salt production device such as a crystallizer to recover the mixed salt.

Next, the case where the molten fly ash obtained by fusing the fly ash in a melting furnace in a reducing atmosphere and then collecting the gas generated when the oxidizing atmosphere is collected with a bag filter will be described.
When fly ash is melted in a reducing atmosphere in a melting furnace, heavy metals volatilize. When this is placed in an oxidizing atmosphere, the heavy metal is in the form of an oxide, and when this is collected by a bag filter, the heavy metal oxide is contained in the resulting molten fly ash.

This molten fly ash is treated with water to reduce the contained chlorine. The treated water obtained is solid-liquid separated with a filter press or the like. The solid content is redispersed with demineralized water, and then this is treated with a solid-liquid separation means such as a filter press to obtain a solid content. Since the solid zinc concentrate in this solid content has a chlorine content reduced to 2% by mass or less, it is used as a Yamamoto reduction material.
Further, the aqueous solution containing the separated salt is subjected to decalcification treatment and desalting treatment, and the reused water obtained is reused as a solvent for dispersion in the redispersion tank.

[Comparative Example 1]
The heavy metals such as zinc and lead generated when the waste is treated in the gasification reforming furnace shown in FIG. 1 are rapidly cooled and acid washed with an acidic cleaning solution having a pH of 2 to 3, so that the heavy metals are dissolved in the cleaning solution. Next, sodium hydroxide is added to adjust pH to remove iron and aluminum, and then alkalinity is adjusted to pH 8 to 9.5 to precipitate metal hydroxide, which is separated into solid and liquid by a filter press to form zinc. And the metal hydroxide containing lead was obtained. The water content of the obtained metal hydroxide was about 80% by mass, zinc was 45% by mass on a dry basis, lead was 5% by mass, and the chlorine content was 5% by mass on a dry basis.

  The metal hydroxide having a chlorine content of 5% by mass obtained in Comparative Example 1 was further dispersed in 5 times the amount of demineralized water on a wet basis, and then solid-liquid separated with a filter press. The water content of the solid was about 80% by mass, and the chlorine content was 0.5% by mass on a dry basis. Moreover, the separated water after washing was subjected to a reverse osmosis apparatus to separate into desalted water and concentrated salt water. The demineralized water was returned to the redispersion tank and used as washing water for the solid content. The concentrated salt water was returned to the plant water treatment line and finally recovered as a mixed salt.

  Waste containing chlorine was heat-treated in an oxidizing atmosphere, and exhaust gas was collected by a bag filter. The fly ash obtained by dust collection was washed with a hydrochloric acid aqueous solution having a pH of 2 to 5 to remove acid-insoluble components such as silicon. By adding sodium hydroxide to the obtained separated liquid, the pH was adjusted to 8.5 to 10 to deposit a metal hydroxide precipitate containing zinc hydroxide and lead hydroxide. This was dehydrated through a filter press. The liquid collected by the filter press was returned to the preceding settling tank. The separated metal hydroxide was dried and the proportion of chlorine was measured to be 2% by mass. This metal hydroxide was redispersed in demineralized water at a solid-liquid ratio of 1/5 to elute the chlorine content, and then the metal hydroxide was recovered with a filter press. The obtained dechlorinated metal hydroxide had a chlorine content (eg, Cl: 0.5%) and could be reduced by Yamamoto.

  In addition, sodium carbonate was added to the liquid collected by the filter press to remove calcium contained in the liquid as calcium carbonate so as not to adversely affect the subsequent desalting apparatus. Next, the liquid from which the calcium content has been removed is desalted with an evaporative recovery device to obtain desalted water, and the salt water concentrated with the desalting equipment is treated with a crystallizer to form a mixed salt mainly composed of sodium chloride. It was collected. Since hydrochloric acid was used as the mineral acid in the washing step, a mixed salt having a relatively high sodium chloride concentration could be obtained.

After incinerating the waste, the exhaust gas was treated with a two-stage bag filter. The first stage bag filter collected only fly ash without adding desalting agent. In the second stage bag filter, slaked lime was blown to remove hydrogen chloride in the exhaust gas.
The obtained main ash and fly ash were melted in a reducing atmosphere in a plasma melting furnace. Coke was added to create a reducing atmosphere. The obtained gas is a fuel gas and contains a volatile heavy metal such as zinc. The heavy metal volatilized by burning this fuel gas was made into an oxide form, and dust was collected by a bag filter to collect the molten fly ash containing the heavy metal oxide.

  The obtained molten fly ash was washed with reused water obtained by the desalting treatment, and this washing liquid was then solid-liquid separated with a filter press. Next, after the solid content was redispersed with demineralized water in a redispersion tank, the solid content was separated with a filter press. The solid zinc concentrate obtained by solid-liquid separation had a dry base zinc concentration of 50% and a chlorine concentration of 0.5%. By blowing an exhaust gas containing carbon dioxide into the separated liquid containing salt, the calcium content was removed as calcium carbonate, and further evaporated and condensed to obtain recycled water substantially free of salt.

  Since the present invention can recover valuable materials such as zinc and lead from municipal waste and industrial waste without discharging waste water, its utility is reduced from the viewpoint of reduction of waste discharge and resource recycling. high.

It is the figure which showed the outline | summary of the waste processing by a gasification reforming system. It is the figure which showed the process process of the processing method of the gas cleaning liquid of this invention. It is the figure which showed an example of the process of collect | recovering heavy metals from fly ash. It is the figure which showed the other example of the process of collect | recovering heavy metals from fly ash.

Claims (10)

  In a method for treating a gas cleaning solution containing lead and / or zinc obtained by cleaning a gas containing lead and / or zinc, an alkali is added to the cleaning solution to contain an insoluble lead and / or zinc compound. A suspension was obtained, and this was subjected to solid-liquid separation. Then, the obtained solid was washed with water and then subjected to solid-liquid separation at least once, and then obtained by the final solid-liquid separation. The solid content having a reduced chlorine concentration is taken out as a raw material for Yamamoto reduction for lead and / or zinc recovery, and the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment, and the obtained dehydration treatment. A method for treating a gas cleaning liquid containing lead and / or zinc, wherein salt water is circulated and used as a solid cleaning water in the step of solid-liquid separation after washing the solid with water.   2. The method for treating a gas cleaning liquid containing lead and / or zinc according to claim 1, wherein the gas is a gas generated by gasification reforming treatment of waste.   The gas cleaning liquid containing lead and / or zinc according to claim 1, wherein the gas is a gas generated when the fly ash generated by incineration of waste is melted in an oxidizing atmosphere. Processing method.   The cleaning liquid containing lead and / or zinc is obtained by cooling and cleaning using an acidic aqueous solution whose gas is adjusted to 2 ≦ pH ≦ 5. The processing method of the gas cleaning liquid containing the lead and / or zinc in any one.   After the fly ash is melt-treated in a reducing atmosphere, the gas generated in an oxidizing atmosphere is washed to obtain a suspension containing an insoluble lead and / or zinc compound. The solid content obtained is separated and then subjected to a solid-liquid separation step after washing with water and then subjected to solid-liquid separation, and the solid content having a reduced chlorine concentration obtained by the last solid-liquid separation is converted to lead and / or Alternatively, it is taken out as a raw material for Yamamoto reduction for zinc recovery, and the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment, and the obtained desalted water is washed with water. A method for treating a gas cleaning liquid containing lead and / or zinc, characterized in that it is circulated and used as cleaning water for solid content in the solid-liquid separation step.   6. The method for treating a gas cleaning liquid containing lead and / or zinc according to claim 1, wherein the chlorine concentration of the suspension before the last solid-liquid separation is 2% by mass or less. .   The dechlorination step is performed by any one method selected from a reverse osmosis method, an electroosmosis method, and an evaporation to dryness method, or a combination of two or more methods. The processing method of the gas cleaning liquid containing lead and / or zinc as described.   The lead and / or zinc according to any one of claims 1 to 6, wherein the dechlorination step is a step of concentrating and crystallizing salt-containing water to separate it into demineralized water and precipitated salt. Gas cleaning solution treatment method.   In a treatment method for a treatment liquid containing lead and / or zinc obtained by treating fly ash recovered from a gas generated when a fly ash is melted in an oxidizing atmosphere with an acidic aqueous solution, the treatment liquid is solidified. Liquid separation is carried out, and then an alkali is added to the obtained separation liquid to obtain a suspension containing an insoluble lead and / or zinc compound, which is subjected to solid-liquid separation. The solid content with reduced chlorine concentration obtained by the last solid-liquid separation is taken out as a raw material for Yamamoto reduction for recovery of lead and / or zinc. As a washing water for solids in the step of subjecting the separated liquid obtained by solid-liquid separation to decalcification treatment and dechlorination treatment, and washing the obtained solids with water, followed by solid-liquid separation. Specially used for circulation Processing method of the processing liquid containing the lead and / or zinc to.   In a treatment method for a treatment liquid containing lead and / or zinc obtained by treating fly ash recovered from a gas generated in an environment that becomes an oxidizing atmosphere after melting the fly ash in a reducing atmosphere The solid obtained by solid-liquid separation of the treatment liquid, and the solid content thus obtained is washed with water and then subjected to solid-liquid separation at least once. Is taken out as a raw material for Yamamoto reduction for lead and / or zinc recovery, and the separation liquid obtained by solid-liquid separation is subjected to decalcification treatment and dechlorination treatment, and the obtained demineralized water is used as the solid content. A method for treating a treatment liquid containing lead and / or zinc, wherein the treatment liquid is used as a washing water for solid content in a step of solid-liquid separation after washing with water.

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