JP2003211127A - Treatment of chloride-containing dust - Google Patents

Abstract

(57) [Abstract] [Problem] Lead and zinc contained in chloride-containing dust,
Provided is a method for treating chloride-containing dust that can separate chlorine and recover the chlorine at a high recovery rate. SOLUTION: The method for treating chloride-containing dust includes a step (A) of mixing chloride-containing dust and hydrochloric acid, and then performing solid-liquid separation to obtain a liquid component containing lead and the like. A step (B) of bringing a liquid component containing a zinc extractant into contact with an organic solvent containing a zinc extractant to obtain a liquid component containing a lead component and the like and an organic solvent containing a zinc component.
And contacting an organic solvent containing a zinc component with a back-extraction solvent to obtain a back-extraction solvent containing a zinc component, and a liquid component containing a lead component and the like obtained in the step (B). Adding a sulfurizing agent to obtain a liquid component containing lead sulfide and chlorine (D);
(E) obtaining a zinc sulfide by adding a sulfide agent to the zinc-containing back-extraction solvent obtained in the step (C), and (D)
Heating and evaporating the liquid component containing the chlorine component obtained in the above, and recovering the chlorine component in the liquid component as chloride (F).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chloride for separating lead content, zinc content, and chlorine content from chloride-containing dust (particularly, soot dust containing a large amount of lead content, zinc content, chlorine content, etc.). The present invention relates to a method for treating substance-containing dust.

[0002]

2. Description of the Related Art In recent years, a technique has been developed for recycling wastes such as soot and dust discharged from garbage incineration facilities and the like. For example, the lead content and zinc content contained in soot dust can be used as a refining raw material if they are separated and collected as a lead compound and a zinc compound, respectively. Further, the chlorine content contained in the soot dust can be used as an industrial raw material if it is recovered as a chloride such as sodium chloride. Furthermore, since the solid content after removing heavy metals such as lead content and chlorine content from soot dust generally contains a large amount of calcium content, it can be used as a cement raw material or the like. Under such circumstances, various methods have been proposed for collecting and removing heavy metals such as lead and chlorine from the chloride-containing dust by separating them.

[0003] For example, in Japanese Unexamined Patent Publication No. 2001-58170, when waste (eg, molten slag fly ash) is treated with sulfuric acid and solid-liquid separated, solid components containing lead and the like and zinc and the like are separated. Obtaining a liquid content containing, and, for solid content, lead sulfide can be obtained by performing treatment such as alkali leaching, and for liquid content, zinc sulfide etc. can be obtained by performing treatment such as substitution precipitation. Is obtained. Further, in the publication, before treating the waste with sulfuric acid,
It is described that when water is added so as to obtain an appropriate solid-liquid ratio and solid-liquid separation is performed, a water-soluble chlorine compound (chlorine content) contained in waste is eluted in water.

[0004]

As described in the above publication, in order to separate lead and zinc from waste (for example, molten slag fly ash) and recover the waste, the waste is generally treated with sulfuric acid. A method is adopted in which the lead content remains in the solid content and the zinc content is eluted in sulfuric acid by treatment. However, when a waste material (for example, molten slag fly ash) is treated with sulfuric acid, a liquid containing a large amount of sulfate ions or a sulfate salt is generated. For example, when recycling waste containing a large amount of calcium as a raw material for cement, treating the waste with sulfuric acid produces gypsum (calcium sulfate). If this is used as a raw material for cement, the melting point of the raw material will decrease. It is not preferable because it easily adheres and causes a trouble in the manufacturing process such as clogging of the cyclone. Therefore, it is necessary to add an alkaline solution such as a sodium hydroxide solution to gypsum to generate calcium hydroxide and use it as a cement raw material. At that time, a liquid containing a large amount of sulfate ions is produced together with calcium hydroxide which is a solid content. In order to process this liquid, it is necessary to provide additional steps, which complicates the processing steps.

On the other hand, in the treatment method described in the above publication, waste (eg, molten slag fly ash) is treated before the sulfuric acid treatment.
If the chlorine content is washed out with water after washing with water, some heavy metals such as lead will also be eluted into the water. In this respect, if it is possible to treat the same heavy metal (eg lead) contained in the waste so as not to separate it into solid and liquid components, the recovery process of this heavy metal (eg lead) can be simplified. Can be converted. Also, chlorine can be used as a high-quality industrial raw material if it can be separated and collected as various chlorides (for example, potassium chloride) without mixing heavy metals such as lead. Therefore,
The present invention, without using sulfuric acid, by a simple method, lead, zinc, chlorine contained in the chloride-containing dust, a method for treating chloride-containing dust that can be separated and collected at a high recovery rate chlorine. The purpose is to provide.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventor has found that the lead and zinc components can be removed by using an acid capable of eluting both lead and zinc components. After elution into the liquid, target this liquid,
If only the zinc content is extracted and back-extracted, the lead content and the zinc content can be easily separated, and
It is possible to easily recover the separated lead and zinc as sulfides, etc., and further to separate chlorides such as sodium chloride from the liquid (filtrate) after the recovery of lead by the crystallization method. The present invention has been completed based on the idea that they can be obtained.

That is, the invention described in claim 1 of the present application is
(A) Chloride-containing dust containing lead, zinc, and chlorine components (for example, soot dust such as molten fly ash and chlorine bypass dust), and an acid capable of eluting lead and zinc (for example, , Hydrochloric acid) to obtain a slurry, and then solid-liquid separation of the slurry to obtain a solid content and a heavy metal elution step for obtaining a liquid content containing each of a lead content, a zinc content, and a chlorine content component,
(B) Contacting a liquid component containing each of the lead, zinc, and chlorine components with an organic solvent (eg, kerosene) containing a zinc extractant (eg, di (2-ethylhexyl) phosphoric acid) A zinc extraction step of obtaining an organic solvent containing a zinc content and a zinc extractant, a liquid content containing a lead content and a chlorine content, (C) an organic solvent containing the zinc content and the zinc extractant, and a back extraction solvent (for example, , Dilute sulfuric acid) to obtain a zinc-containing back-extraction solvent, and (D) the zinc-extracting step (B), in which the lead-containing and chlorine-containing liquid is obtained. ,
Sulfiding agents (eg sodium hydrosulfide) and / or alkaline agents (eg sodium hydroxide) are added to lead sulfide and / or
Alternatively, a lead recovery step of obtaining a liquid content containing a solid content of lead hydroxide and a chlorine content, and (E) a zinc back-extraction solvent obtained in the above-mentioned zinc back-extraction step (C), a sulfurizing agent (For example, sodium hydrosulfide) and / or an alkali agent (for example, sodium hydroxide) are added to obtain a solid content of zinc sulfide and / or zinc hydroxide and a zinc-removed back extraction solvent. And a process. According to the method for treating chloride-containing dust of the present invention, the lead content, zinc content, and chlorine content contained in chloride-containing dust can be separated by a simple method and can be recovered at a high recovery rate.

In the method of treating chloride-containing dust, the chlorine-containing liquid obtained in the lead recovery step (D) is heated and evaporated, and the chlorine contained in the liquid is recovered as chloride. A chlorine recovery step (F) may be included (Claim 2).
According to the method of heating and evaporating the liquid component as described above, various chlorides can be separated and deposited by changing the temperature of the liquid component. In the method for treating chloride-containing dust, a preferred example of the acid used in the heavy metal elution step (A) is hydrochloric acid (claim 3). By using hydrochloric acid as an acid for eluting lead and zinc in this way, sulfate ions and the like are not present in the liquid or solid after the treatment, and the post-process can be simplified. it can. Examples of the chloride-containing dust include soot dust (specifically, molten fly ash, chlorine bypass dust, etc.) (claim 4).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The chloride-containing dust treated in the present invention contains lead, zinc and chlorine. Here, the terms "lead content" and "zinc content" are used to broadly include salts, complexes, ions, etc., as well as metals consisting of simple elements. Further, the term “chlorine content” is used to mean a water-soluble chlorine component, specifically, a chloride ion when eluted in water, and a chloride ion. Specific examples of the chloride-containing dust include soot dust, incineration ash discharged from the furnace bottom of an incinerator, and the like. In particular, soot dust is suitable as the object to be treated in the present invention because it has a higher content of lead and zinc than incineration ash and the like. Specific examples of soot dust include soot dust (melt fly ash) discharged from a facility for melting dust and incineration ash, soot dust (incinerator fly ash) emitted from a facility for incinerating dust and sewage sludge, cement kiln and industrial waste. Examples include soot dust (including chlorine bypass dust) emitted from the high temperature treatment process of the treatment facility.

Chlorine bypass dust is a chlorine bypass technology for extracting a high concentration of chlorine contained in combustion gas in a cement burning process, and is a crude exhaust gas from a high temperature exhaust gas extracted from a kiln and sent to a cyclone. It refers to fine dust that precipitates by cooling the gas content after removing the dust. According to this chlorine bypass technology, about 2% of the exhaust gas from the kiln can be extracted to remove about 80% of the chlorine content from the combustion system. The main components of chlorine bypass dust are 23 wt% calcium, 30 wt% potassium, 10 wt% sulfur, 22 wt% chlorine, 3.4 wt% lead, and 0.1 wt% zinc (however, chlorine, lead,
Excluding zinc, it is a value converted to oxide. ). The content of chlorine in chlorine bypass dust is higher than that of general municipal waste incineration ash.

The method for treating chloride-containing dust of the present invention is
It includes the following steps (A) to (F). (A) A chloride-containing dust containing lead, zinc, and chlorine components and an acid capable of eluting lead and zinc are mixed to obtain a slurry, and then the slurry is solidified. A heavy metal elution step of liquid separation to obtain a solid content and a liquid content containing lead, zinc, and chlorine components. (B) Lead content, zinc content obtained in the heavy metal elution step (A),
A zinc extraction step of obtaining a liquid component containing a lead component and a chlorine component and an organic solvent containing a zinc component and a zinc extractant by contacting a liquid component containing each component of a chlorine component with an organic solvent containing a zinc extractant . (C) Zinc extraction step The zinc back extraction step of contacting the organic solvent containing the zinc component and the zinc extractant obtained in (B) with the back extraction solvent to obtain the back extraction solvent containing the zinc content. (D) A solid component consisting of lead sulfide and / or lead hydroxide, and chlorine, by adding a sulfidizing agent and / or an alkaline agent to the liquid component containing lead and chlorine obtained in the zinc extraction step (B). Lead recovery process to obtain liquid containing water. (E) Zinc back-extraction step (C) The zinc-containing back extraction solvent is added with a sulfidizing agent and / or an alkaline agent to form a solid content of zinc sulfide and / or zinc hydroxide and a zinc content. A zinc recovery step of obtaining a back extraction solvent from which is removed. (F) A chlorine recovery step of heating and evaporating the liquid content containing chlorine obtained in the lead recovery step (D), and recovering the chlorine content in the liquid content as a chloride.

The method of treating chloride-containing dust according to the present invention will be described step by step with reference to the drawings. FIG. 1 is a flow chart showing an example of a method for treating chloride-containing dust of the present invention. [(A) Heavy Metal Leaching Step] Chloride-containing dust (for example, chlorine bypass dust) which is the object to be treated by the method of the present invention.
And an acid capable of eluting lead and zinc components are mixed in a mixing tank to form a slurry, and the lead and zinc components contained in the chloride-containing dust are eluted into the liquid. Here, examples of the acid capable of eluting the lead content and the zinc content include hydrochloric acid, nitric acid and the like. Among them, hydrochloric acid is preferably used because its chloride ion can be recovered in the subsequent chlorine recovery step (F) together with the chlorine component (chloride ion) eluted from the chloride-containing dust.

The liquid amount of the acid is preferably 300 parts by weight or more per 100 parts by weight of the chloride-containing dust. If the liquid amount is less than 300 parts by weight, the amount of chlorine content attached to the solid content after the solid-liquid separation of the slurry containing chloride-containing dust and the acid will increase, and in the chlorine recovery step (F) in the subsequent step. The recovery rate (dechlorination rate) of the recovered chlorine component decreases. The concentration of the acid is preferably adjusted so that the pH of the slurry containing the acid and the chloride-containing dust is 4 or less. p
When H is 4 or less (particularly preferably 0.5 to 2), most of the lead content and zinc content contained in the chloride-containing dust can be eluted in the liquid, and the lead content and zinc content can be recovered. The rate can be increased. When the object to be treated is soot dust such as chlorine bypass dust or molten fly ash, the acid concentration is, for example,
It is 0.5 to 3N.

The slurry consisting of chloride-containing dust and acid is subjected to solid-liquid separation by filtration using a belt filter or a filter press. Solid-liquid separation gives solids containing calcium (calcium compounds that do not elute in the liquid) and liquids containing lead, zinc, chlorine (chloride ions), calcium (calcium ions), etc. . A solid content containing calcium hydroxide is obtained by mixing a solid content containing calcium and an alkaline solution such as a sodium hydroxide solution and then performing solid-liquid separation by filtration or the like. Since this solid content (calcium hydroxide) does not contain heavy metals such as lead or chlorine, it can be suitably used as a cement raw material. The liquid component containing lead and the like is processed by the steps described below.

[(B) Zinc Extraction Step] When a liquid content containing lead, zinc, etc. obtained by solid-liquid separation in the heavy metal elution step (A) is mixed with an organic solvent containing a zinc extractant, A liquid content (aqueous phase) containing lead and the like and an organic solvent (organic phase) containing zinc content and a zinc extractant are obtained. At the time of mixing, in order to efficiently extract the zinc content, an acid (for example, hydrochloric acid or the like) or an alkaline agent (for example, sodium hydroxide solution or the like) is added to adjust the pH within the range of 3.5 to 4.5. adjust. As the zinc extractant, for example, di (2-ethylhexyl) phosphoric acid, 2-ethylhexylphosphoric acid / mono-2-ethylhexyl ester, etc. are used. The zinc extractant is a chelating agent that moves freely in an organic solvent (organic phase), and supports zinc content at the interface with an aqueous liquid content (aqueous phase) containing lead, zinc, etc. , Zinc can be transferred from the aqueous phase to the organic phase. A nonpolar solvent such as kerosene is used as the organic solvent. The mixing ratio of the organic solvent and the zinc extractant is not particularly limited, but is, for example, 9 by volume.
It is 0:10 to 60:40. The mixing ratio of the liquid component (aqueous phase) containing the lead component, zinc component, etc. and the organic solvent containing the zinc extractant (organic phase) is not particularly limited, but is, for example, 1: 3 to 1: 1 by volume. is there.

[(C) Zinc Back Extraction Step] By mixing the organic solvent containing the zinc component and the like obtained in the zinc extraction step (B) with the back extraction solvent, a back extraction solvent containing the zinc component is obtained. As the back extraction solvent, for example, dilute sulfuric acid is used. The pH of the dilute sulfuric acid is preferably 0.3 to 1, particularly preferably 0.4 to 0.6. The back extraction solvent can be used repeatedly. The mixing ratio of the organic solvent (organic phase) containing a zinc component and the back extraction solvent (aqueous phase) is not particularly limited, but is, for example, 2: 1 to 8: 1 by volume ratio. The concentration of the zinc component in the back extraction solvent can be increased by repeating the back extraction operation of mixing the organic solvent containing the zinc component and the back extraction solvent (dilute sulfuric acid).

[(D) Lead recovery step] Zinc extraction step (B)
An alkaline agent such as sodium hydroxide is added to the liquid component containing the lead and chlorine components obtained in step 1 to adjust the pH to near neutral (usually about 7 to 8). Next, a sulfidizing agent (eg, sodium hydrosulfide (NaHS), sodium sulfide (Na ₂ S), etc.) is added to the liquid after pH adjustment to precipitate lead sulfide, and then solid-liquid separation is performed by filtration or the like. By doing so, a solid component made of lead sulfide (PbS) and a liquid component containing chlorine can be obtained. The obtained lead sulfide can be used as a refining raw material or the like. In addition, the pH is adjusted to 8 or more by adding an alkaline agent such as sodium hydroxide to the liquid component containing lead and chlorine components obtained in the zinc extraction step (B), and the lead component in the liquid component is adjusted. Can also be precipitated as lead hydroxide. In this case, it is also possible to collect the lead component as a mixture of lead sulfide and lead hydroxide by using a sulfurizing agent together. Lead hydroxide can be recovered as a solid content by solid-liquid separation by filtration or the like. However, lead hydroxide has poorer filterability than lead sulfide and has a high water content of the solid content after solid-liquid separation. Therefore, in the present invention, the lead content is preferably recovered as lead sulfide.

[(E) Zinc recovery step] To the zinc back-extraction solvent obtained in the zinc back-extraction step (C), an alkaline agent such as sodium hydroxide is added to adjust the pH to near neutral (usually). , About 7 to 8). Then, to the back extraction solvent after pH adjustment, a sulfidizing agent (for example, sodium hydrosulfide, sodium sulfide, etc.) is added to precipitate zinc sulfide, and then solid-liquid separation is performed by filtration or the like to obtain zinc sulfide (ZnS And a solid content consisting of (4) and a zinc content-removed back extraction solvent are obtained. The obtained zinc sulfide can be used as a refining raw material or the like.
The pH is adjusted to 8 or more by adding an alkaline agent such as sodium hydroxide to the zinc-containing back extraction solvent obtained in the zinc back extraction step (C) to remove the zinc content in the liquid content. It can also be deposited as zinc hydroxide. In this case, the zinc component can also be recovered as a mixture of zinc sulfide and zinc hydroxide by using a sulfurizing agent together. Zinc hydroxide is
By performing solid-liquid separation by filtration or the like, it can be collected as a solid content. However, zinc hydroxide has poorer filterability than zinc sulfide and has a high water content of the solid content after solid-liquid separation. Therefore, in the present invention, the zinc content is preferably recovered as zinc sulfide.

[(F) Chlorine recovery step] Lead recovery step (D)
Since the liquid component containing chlorine obtained in step 1 usually contains calcium ions eluted from chloride-containing dust, it is composed of calcium carbonate by adding a carbonic acid source (for example, carbon dioxide or carbonate such as sodium carbonate). Generate solids. The solid content is filtered by solid-liquid separation such as filtration. The filtered solid content (calcium carbonate) does not contain lead or zinc, and can be used as a cement raw material or the like by washing with water to remove chlorine.

Then, the filtrate containing chlorine after filtering out calcium carbonate is heated under reduced pressure to evaporate the liquid to concentrate it, and then the liquid temperature of the filtrate is changed to precipitate crystals. Based on the difference in temperature, various chlorides can be fractionated and deposited. For example, in order to separate and collect sodium chloride and potassium chloride, first, the temperature of the filtrate should be 50
After the temperature is raised to 30 ° C or higher, sodium chloride is precipitated, and this is separated by filtration and collected, and then the temperature of the filtrate is cooled to 30 ° C or lower,
Potassium chloride may be deposited, and this may be collected by filtration. That is, a procedure of recovering sodium chloride in the high temperature crystallization step and then recovering potassium chloride in the low temperature crystallization step may be performed. Among the collected chlorides, sodium chloride can be used as a soda raw material and the like, and potassium chloride can be used as a fertilizer and the like.

[0021]

EXAMPLES Examples of the present invention will be described below. In addition, "%" in the examples is a numerical value based on weight unless otherwise specified. [Example 1] Chlorine bypass dust (CaO: 23%, SO ₃ : 10%,
Na ₂ O: 2.0%, K ₂ O: 25%, Cl: 20%, Pb: 3.3%, Zn: 0.1%) 1k
To g, add 4 kg of a 1 mol / liter hydrochloric acid aqueous solution, and p
After obtaining the H1 slurry, the mixture was stirred for 0.5 hours. Then, the slurry was filtered to collect the filtrate. An organic solvent 30 prepared by diluting 100 ml of this filtrate with di (2-ethylhexyl) phosphoric acid to 20% by volume with kerosene.
0 ml was added and mixed for 20 minutes while adjusting the pH to 4 with sodium hydroxide. Then, the mixture was allowed to stand for 1 minute, and an organic phase (extracted zinc-containing organic solvent) and a lead-containing aqueous phase were recovered. Further, 75 ml of dilute sulfuric acid having a pH of 0.5 was added to this organic phase, mixed for 5 minutes, and allowed to stand for 1 minute to recover an organic phase and an aqueous phase containing a back-extracted zinc content. While adjusting the pH to 7 by adding sodium hydroxide to the aqueous phase containing zinc, sodium hydrosulfide is added,
Zinc sulfide was deposited. Zinc sulfide was collected by filtration as a solid content. The weight of zinc sulfide recovered is 1.3 g.
Met.

On the other hand, after adjusting the pH to 8 by adding sodium hydroxide to the aqueous phase containing lead, sodium hydrosulfide was added to precipitate lead sulfide. Lead sulfide was collected by filtration as a solid content. The weight of the recovered lead sulfide was 34 g. Carbon dioxide was added as a carbonic acid source to the filtrate after filtering off lead sulfide to generate calcium carbonate, and then calcium carbonate was filtered off. After the calcium carbonate was filtered off, the filtrate was heated to 70 ° C. under reduced pressure to evaporate the liquid content to precipitate sodium chloride and then filtered to recover 35 g of sodium chloride. Further, this filtrate was cooled to 25 ° C. to precipitate potassium chloride and then filtered to recover 350 g of potassium chloride.

[0023]

The method for treating chloride-containing dust of the present invention comprises a step of eluting lead and the like in chloride-containing dust with hydrochloric acid and a step of recovering the eluted zinc by extraction and back extraction. And a lead content and a zinc content contained in the chloride-containing dust can be easily separated and recovered. Further, the chlorine content contained in the chloride-containing dust can also be collected separately from the lead content and the zinc content.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a method for treating chloride-containing dust according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22B 7/02 C22B 13/04 13/00 3/00 H 19/30 QRF term (reference) 4D004 AA36 AA37 AB03 AB06 BA02 BA05 BA06 CA13 CA15 CA34 CA40 CA50 CB26 CC04 CC06 CC12 4D056 AB03 AB08 AC02 AC22 BA04 CA01 CA14 CA15 CA17 CA27 CA39 4K001 AA20 AA30 BA14 DB02 DB26 DB34

Claims (4)

[Claims] 1. A slurry is obtained by mixing (A) a chloride-containing dust containing lead, zinc and chlorine components and an acid capable of eluting lead and zinc. A heavy metal elution step of solid-liquid separating the slurry to obtain a solid content and a liquid content containing lead, zinc, and chlorine components; and (B) each of the lead, zinc, and chlorine components. A zinc extraction step of bringing a liquid component containing a component into contact with an organic solvent containing a zinc extractant to obtain a liquid component containing lead and chlorine, and an organic solvent containing a zinc component and a zinc extractant; ) A zinc back-extracting step of contacting an organic solvent containing the zinc content and the zinc extractant with a back-extracting solvent to obtain a back-extracting solvent containing a zinc content; and (D) Obtained in the zinc extraction step (B) A sulfurating agent and / or an alkaline agent is added to the liquid content containing the above-mentioned lead content and chlorine content, and lead sulfide and / or hydroxide is added. And a lead recovery step for obtaining a liquid content containing a chlorine content, and (E) a zinc back-extraction solvent obtained in the above-mentioned zinc back-extraction step (C), a sulfurizing agent and / or an alkali. A method for treating chloride-containing dust, comprising a solid content consisting of zinc sulfide and / or zinc hydroxide by adding an agent, and a zinc recovery step of obtaining a back extraction solvent from which the zinc content has been removed. 2. A chlorine recovery step of (F) heating and evaporating the liquid content containing chlorine obtained in the lead recovery step (D), and recovering the chlorine content in the liquid content as a chloride. Claim 1
The method for treating chloride-containing dust according to 1. 3. The method for treating chloride-containing dust according to claim 1, wherein the acid used in the heavy metal elution step (A) is hydrochloric acid. 4. The method for treating chloride-containing dust according to claim 1, wherein the chloride-containing dust is soot dust.