JP7299380B2 - How to treat collected dust - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for treating collected dust, and more particularly to a method for treating collected dust containing suspended solids and pentacyanocarbonyl iron complex obtained by subjecting exhaust gas to wet dust collection.

For example, gas generated from a blast furnace, a converter, or the like in a steel plant contains dust. Therefore, as shown in FIG. It is By this wet dust collection treatment, dust collection water containing dust as suspended matter is obtained. Regarding the collected dust water, in the collected dust water treatment system 1, the collected dust water is sent from the wet dust collector 2 to the first sedimentation tank (thickener) 4, and suspended in the collected dust water in the first sedimentation tank 4. A process is carried out to separate and remove the material.

Fine suspended matter and salts derived from the dust contained in the gas are often suspended or dissolved in collected dust water, so the dust (suspended matter) contained in the gas is It is difficult to purify collected dust water only by solid-liquid separation treatment for removal. Therefore, the liquid component (separated liquid) separated from the dust by the solid-liquid separation process is used in a method of being circulated to the wet dust collector 2 in the circulation equipment 5 as shown in FIG. Additional treatments are sometimes used to remove matter and soluble materials.

For example, when the separated liquid (collected water) contains cyan components such as cyanide ions and cyano complexes, the cyan components are removed from the separated liquid to obtain treated water from which the cyan components have been removed. Is required. Known techniques for removing cyanide components in water include the alkaline chlorine method using sodium hypochlorite, the Prussian blue method using iron salt, and the reduced copper salt method using copper salt and a reducing agent (see FIG. 6). ing. As a reduced copper salt method, for example, Patent Document 1 discloses a method for treating cyanide-containing wastewater in which a copper salt and a reducing agent are present in wastewater containing free cyanide and a cyanide complex salt to generate and separate a sparingly soluble precipitate. It is

JP-A-63-39693

The above-described alkali chlorine method can remove alkali metal salts such as sodium cyanide and easily decomposable cyano complexes such as zinc cyano complexes and copper cyano complexes, but cannot remove iron cyano complexes.

In the Prussian blue method and the reduced copper salt method, ferrocyanide ions and iron cyano complexes such as ferricyanide ions in wastewater are also said to be able to be removed from wastewater by generating sparingly soluble salts. . However, as a result of studies by the present inventors, it has been found that some cyano complexes are difficult to remove from wastewater by the Prussian blue method or the reduced cuprate method. For example, the Prussian blue method can effectively remove pentacyanocarbonyl iron complexes ([Fe ^II (CN) ₅ (CO)] ³⁻ , [Fe ^III (CN) ₅ (CO)] ²⁻ etc.) from wastewater. I know you can't.

Furthermore, the reduced copper salt method requires a two-step process of adding a copper salt and a reducing agent to the waste water and allowing them to react, followed by solid-liquid separation treatment. Therefore, generally, as shown in FIG. 6, a reaction tank 6 for adding and reacting a copper salt and a reducing agent, followed by a second sedimentation tank for removing sparingly soluble salts produced by the reaction. 7 is required, and the installation cost of the equipment required to obtain treated water is high.

In view of the above prior art, the present invention provides a solid-liquid separation treatment of the suspended matter without requiring an additional sedimentation tank after solid-liquid separation of the suspended matter in the collected water by solid-liquid separation equipment. To provide a method for treating dust-collected water capable of removing even the cyanide component in the dust-collected water.

According to the present invention, solid-liquid separation equipment for solid-liquid separation of suspended matter in dust collection water obtained by wet dust collection treatment of exhaust gas; and a circulation facility for the wet dust collection treatment as a method for treating the collected dust water, wherein the collected dust water further contains a pentacyanocarbonyl iron complex, and the suspension in the collected dust water The dust-collected water satisfies at least one of Condition 1 in which turbidity substances contain one or both of zinc and copper, and Condition 2 in which one or both of zinc salts and copper salts are further added to the dust-collected water. and adding a cationic compound having an amine structure to solid-liquid separation treatment in the solid-liquid separation equipment.

According to the present invention, even if an additional sedimentation tank is not required after the solid-liquid separation of the suspended solids in the collected dust water by the solid-liquid separation equipment, the cyanide in the collected dust water is removed during solid-liquid separation of the suspended solids. It is possible to provide a method for treating collected dust that can also remove components.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing a first example of a collected water treatment system that can be used in a collected water treatment method according to an embodiment of the present invention; FIG. 2 is a schematic configuration diagram showing a second example of a collected water treatment system that can be used in the collected water treatment method of one embodiment of the present invention. FIG. 3 is a schematic configuration diagram showing a third example of a collected water treatment system that can be used in the method for processing collected water according to one embodiment of the present invention. FIG. 4 is a schematic configuration diagram showing a fourth example of a collected water treatment system that can be used in the collected water treatment method of one embodiment of the present invention. FIG. 10 is a schematic configuration diagram showing a fifth example of a collected water treatment system that can be used in the method for processing collected water according to one embodiment of the present invention. 1 is a schematic configuration diagram showing an example of a conventional treatment system that can be used in a method for treating collected dust containing a cyan component. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In addition, the same code|symbol is attached|subjected about the part which is common in each figure in drawing, and the description may be abbreviate|omitted. Also, the arrows in the drawing represent the flow of substances, and the lines of the arrows are sometimes shown as the flow paths of the substances.

1 to 5 show dust-collected water treatment systems 11 and 12 of first to fifth examples, respectively, as examples of dust-collected water treatment systems that can be used in the dust-collected water treatment method of one embodiment of the present invention. , 13, 14, and 15. FIG. The method for treating dust-collected water according to the present embodiment includes solid-liquid separation equipment 40 for solid-liquid separation of suspended substances in dust-collected water obtained by wet dust collection treatment of exhaust gas, and separation obtained by the solid-liquid separation equipment 40. A circulating facility 50 is used in which part of the liquid is used as washing water for wet dust collection. Hereinafter, the method for treating collected water in the collected water treatment system 11 to 15 including the solid-liquid separation equipment 40 and the circulation equipment 50 will be described as an example of the method for treating collected dust water according to the present embodiment. Since the dust collection water treatment systems 11 to 15 are systems for processing dust water obtained by wet dust collection treatment of exhaust gas, the gas and the wet dust collector 2 are indicated by dashed lines ( long dashed line). The dust collection water treatment systems 11 to 15 may be configured as part of an exhaust gas treatment system including the wet dust collector 2 .

In the method for treating dust-collected water of the present embodiment, the object of treatment is dust-collected water obtained by wet-type dust-collecting treatment of exhaust gas and containing suspended solids and pentacyanocarbonyl iron complex. Collected water is obtained by subjecting the exhaust gas to wet dust collection by the wet dust collector 2 . In addition, in order to remove suspended matter in the dust collection water by solid-liquid separation treatment, the dust collection water is supplied from the wet dust collector 2 through the flow path (first flow path) 31 to the solid-liquid separation equipment 40. can be done.

Exhaust gas contains, for example, dust containing iron, cyan components such as hydrogen cyanide, and carbon monoxide, since contact with the washing water in the wet dust collector 2 may produce a pentacyanocarbonyl iron complex. exhaust gas is preferred. Such exhaust gas includes, for example, exhaust gas generated from ironworks, exhaust gas generated from metal refining equipment such as melting furnaces (refining furnaces), exhaust gas generated from cement manufacturing equipment, and waste incineration for incinerating waste such as various garbage. Exhaust gas etc. which arise from a facility can be mentioned.

Examples of gas components in the exhaust gas include, but are not limited to, carbon monoxide (CO), cyanide components, carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and the like. Solid components contained in the dust in the exhaust gas include, but are not limited to, iron (such as iron, iron oxide, and iron hydroxide), zinc, and copper. Among these, when the suspended matter in the dust collection water contains one or both of zinc and copper, a cationic compound having an amine structure (hereinafter simply referred to as a "cationic compound") is added to the dust collection water as described later. The dust and suspended solids preferably contain one or both of zinc and copper, because the collected water can be treated effectively simply by adding .

When the suspended solids contain one or both of zinc and copper, the total content of zinc and copper in the collected water is preferably 1 to 1000 mg (Zn+Cu)/L, and 2 to 200 mg (Zn+Cu)/L. and more preferably 10 to 100 mg (Zn+Cu)/L.

The dust collection water to be treated in this method contains suspended solids (SS) as dust contained in the exhaust gas. The suspended solids (SS) concentration in the collected water is preferably 100 to 10000 mg/L, more preferably 200 to 5000 mg/L, even more preferably 500 to 3000 mg/L.

In addition, the collected dust water contains a pentacyanocarbonyl iron complex in addition to suspended solids. As used herein, pentacyanocarbonyl iron complexes include [Fe ^II (CN) ₅ (CO)] ³⁻ and [Fe ^III (CN) ₅ (CO)] ²⁻ , and salts of their complex ions (complex salts). and its hydrates. The collected water may contain a cyan component other than the pentacyanocarbonyl iron complex. Other cyanide components include, for example, cyanide ion (CN ⁻ ; also called free cyanide or free cyanide), ferrocyanide ion ([Fe(CN) ₆ ] ⁴⁻ ; hexacyanoferrate(II) ion ), ferricyanide ion ([Fe(CN) ₆ ] ^3- ; also called hexacyanoferrate(III) ion), and [Fe(CN) ₄ (CO) ₂ ] ^2- etc. can be mentioned.

The pH of the dust collection water is not particularly limited, but is preferably 5.0 to 10.0, more preferably 5.5 to 9.5, when adding the cationic compound described later to the dust collection water. 5 to 9.0 is more preferred. A pH adjuster may be added to the dust collection water to adjust the pH of the dust collection water within the above range. The pH adjuster is not particularly limited, and known pH adjusters such as acids such as hydrochloric acid and sulfuric acid and bases such as sodium hydroxide, calcium hydroxide and sodium carbonate can be used as appropriate.

The temperature of the dust collection water is also not particularly limited. The above-mentioned suitable exhaust gas is often in a relatively high temperature state, and from the viewpoint that the dust-collected water obtained by wet dust collection treatment of such exhaust gas is preferable, the temperature of the dust-collected water is The temperature is preferably 20 to 80°C, more preferably 35 to 80°C, when the cationic compound described later is added. By keeping the temperature of the dust collection water within the above range, it is possible to sufficiently react the cationic compound described later and the optionally used zinc salt and/or copper salt with the dust collection water.

In this method, at least one of Condition 1 in which suspended solids in the dust collection water contain zinc and/or copper, and Condition 2 in which zinc salts and copper salts are added to the dust collection water is collected. A cationic compound having an amine structure is added to the dust. That is, when the suspended solids in the dust collection water contain one or both of zinc and copper, at least Condition 1 above is satisfied, so a cationic compound may be added to the dust collection water. If the suspended matter in the dust collection water contains neither zinc nor copper, a cationic compound and one or both of a zinc salt and a copper salt may be added to the dust collection water so as to satisfy the condition 2 above. good. Under the above conditions, by adding a cationic compound having an amine structure to the dust collection water, the pentacyanocarbonyl iron complex in the dust collection water is rendered insoluble and/or insoluble. Poorly soluble substances and/or insoluble substances (hereinafter, including poorly soluble substances may be simply referred to as “insolubilized substances”) can be produced.

As described above, a cationic compound and, if necessary, a zinc salt and/or a copper salt are added to the dust collection water, and the dust collection water to which they are added is collected by the solid-liquid separation equipment 40. Solid-liquid separation processing of suspended matter in dust water is performed. As a result, the insolubilized matter generated in the dust collection water can be solid-liquid separated together with the suspended matter as a solid component and removed. Thus, it is possible to separate and remove the pentacyanocarbonyl iron complex in the dust collection water as an insolubilized substance by the solid-liquid separation treatment simultaneously with the solid-liquid separation treatment for removing the suspended matter in the dust collection water. Since the dust collection water can fluctuate from moment to moment, it is possible that the suspended solids may change whether or not they contain zinc and/or copper, and their concentrations may also change. is likely to increase, it is preferable to satisfy both conditions 1 and 2 above. That is, it is preferable that the suspended matter in the dust collection water contains one or both of zinc and copper, and the cationic compound and one or both of the zinc salt and the copper salt are added to the dust collection water.

The solid-liquid separation equipment 40 used for solid-liquid separation of suspended solids and the like includes, for example, a sedimentation device such as a thickener capable of performing a sedimentation treatment, a membrane separation device capable of performing a membrane separation treatment, a filtration device capable of performing a filtration treatment, and the like. can be mentioned. Among these, precipitation treatment using a precipitation apparatus is preferred. The solid-liquid separation equipment 40 may be provided with a stirring mechanism 48 (see FIGS. 2 to 5).

The place where the cationic compound and optionally used zinc salt and/or copper salt are added to the dust collection water is the cationic compound, zinc salt and/or copper salt in the dust collection water to be subjected to solid-liquid separation treatment. Since it is sufficient that the salt is added, it may be added before the solid-liquid separation equipment 40 and/or the solid-liquid separation equipment 40 . Before the solid-liquid separation equipment 40, it may be between the wet dust collector 2 and the solid-liquid separation equipment 40, for example, a cationic compound, a zinc salt and / or a copper salt in the middle of the first flow path 31 may be provided.

Although not shown, a receiving tank for receiving the collected dust flowing through the first flow path 31 from the wet dust collector 2 and solidifying the collected dust from the receiving tank are provided between the wet dust collector 2 and the solid-liquid separation equipment 40. A channel or the like for sending to the liquid separation equipment 40 may be provided. The receiving tank, the flow path from the receiving tank to the solid-liquid separation equipment 40, or the like may be used as the addition position of the cationic compound or the like.

Furthermore, as shown in FIGS. 2 to 5, the solid-liquid separation equipment 40 includes a channel (second channel ) 32 is preferably laid. The second flow path 32 is used as the addition position of the cationic compound, zinc salt and / or copper salt, and in the second flow path 32, the cationic compound and, if necessary, the dust collection water Preferably, the zinc and/or copper salts are brought into contact with each other and flowed through the second flow path 32 to the solid-liquid separation facility 40 . The second flow path 32 may be configured as the same flow path as the first flow path 31 or may be connected to the first flow path 31 .

As shown in FIGS. 1 to 5, a device (cationic compound addition device) 42 for adding a cationic compound to the collected water is provided in the solid-liquid separation equipment 40, the second flow path 32, and the like. can be done. The cationic compound addition device 42 can include, for example, a tank for storing the cationic polymer, a pump and a supply pipe for supplying the cationic compound, and the like.

When the suspended matter in the dust collection water does not contain zinc and copper, a device for adding zinc salt to the dust collection water (zinc salt addition device) 44 and a device for adding copper salt (copper salt addition device) ) 46 is preferably provided in the solid-liquid separation equipment 40, the second channel 32, or the like. As shown in FIG. 3, it is more preferable to provide at least one of the zinc salt addition device 44 and the copper salt addition device 46 so that the second flow path 32 becomes the addition position of the zinc salt and the copper salt. The zinc salt addition device 44 and the copper salt addition device 46 can include, for example, a tank for storing each material (zinc salt or copper salt), and a pump and supply pipe for supplying each material.

If the suspended matter in the dust collection water contains one or both of zinc and copper, the zinc salt addition device 44 and the copper salt addition device 46 may not be provided (see FIGS. 1 and 2), but the above-described As described above, since it is preferable to satisfy both the above conditions 1 and 2, it is preferable to provide the zinc salt addition device 44 and/or the copper salt addition device 46 (see FIGS. 3 to 5). Although both the zinc salt addition device 44 and the copper salt addition device 46 are shown in FIG. 3, either one may be used. 4 and 5 to show that the zinc salt addition device 44 and the copper salt addition device 46 may not be provided when the suspended solids in the dust collection water contain one or both of zinc and copper. , the zinc salt addition device 44 and the copper salt addition device 46 are indicated by dashed lines.

The amine structure in the cationic compound may be at least one structure selected from the group consisting of primary amines, secondary amines, tertiary amines, and quaternary ammoniums. A cationic compound having an amine structure is utilized as a water-soluble cation in water. As used herein, an amine structure refers to a structure in which hydrogen atoms in the structure of ammonia (NH ₃ ) are substituted with atomic groups (hydrocarbon groups that may contain heteroatoms). Then, when the number of substitutions is one, the structure of the primary amine, when two, the structure of the secondary amine, when three, the structure of the tertiary amine, the nitrogen atom in the structure of the tertiary amine A structure in which a hydrocarbon group is further bonded is called a quaternary ammonium structure.

A cationic compound having an amine structure may be a monomer, an oligomer, or a polymer. Among these, at least one selected from the group consisting of primary, secondary, and tertiary amine structures from the viewpoint of easily suppressing foaming when a cationic compound is added to the collected water and mixed. A cationic monomer having one structure and a cationic polymer having an amine structure are preferred, and a cationic monomer having a primary amine structure and a cationic polymer having an amine structure are more preferred. Oligomers are also included in the following cationic polymers having an amine structure.

Cationic monomers having primary to tertiary amine structures include, for example, n-octylamine, 2-ethylhexylamine, 3-(2-ethylhexyloxy)propylamine, dodecylamine, oleylamine, palm alkylamine. , beef tallow alkylamines, and soybean alkylamines having a hydrocarbon group of 7 or more carbon atoms, and fatty acid amidoamines having a hydrocarbon group of 7 or more carbon atoms such as N-oleoylethylenediamine. Primary amine compounds having a hydrocarbon group of 7 or more atoms; di(2-ethylhexyl)amine, di(n-octyl)amine, didecylamine, N-(2-hydroxyethyl)dodecylamine, and N-(2- Secondary amine compounds having a hydrocarbon group of 7 or more carbon atoms such as hydroxyethyl)oleylamine; dimethyloctylamine, dimethyldecylamine, dimethyldodecylamine, tri-n-octylamine, N,N-bis(2-hydroxy tertiary amine compounds having a hydrocarbon group of 7 or more carbon atoms such as ethyl)dodecylamine and N,N-bis(2-hydroxyethyl)oleylamine; Further, the cationic monomer having a primary to tertiary amine structure includes two or more structures selected from a primary amine structure, a secondary amine structure, and a tertiary amine structure, and a structure having 7 carbon atoms. Compounds having the above hydrocarbon groups in one molecule can also be used. Examples of such cationic monomers include N,N-bis(aminopropyl)dodecylamine, N-oleylpropylenediamine, N-oleylethylenediamine, and the like. Further, specific examples of the cationic monomers listed above may be salts (eg, hydrochlorides, sulfates, acetates, sulfamates, carbonates, citrates, etc.). Of these salts, hydrochlorides and sulfates are more preferred. Examples of cationic monomers having a quaternary ammonium structure (quaternary ammonium cation) include didecyldimethylammonium salt, hexadecyltrimethylammonium salt, dioctyldimethylammonium salt, didodecyldimethylammonium salt, trioctyl Methylammonium salt, benzyldodecyldimethylammonium salt and the like can be mentioned. The anion paired with the quaternary ammonium cation in these is preferably a halide ion, more preferably a chloride ion and a bromide ion.

When a polymer (cationic polymer) is used as the cationic compound, the weight average molecular weight (Mw) of the cationic polymer is preferably 1,000 to 1,000,000, and is 5,000 to 800,000. is more preferable, and 10,000 to 500,000 is even more preferable. Mw of the cationic polymer is determined by size exclusion chromatography (SEC) (gel permeation chromatography (GPC) or gel filtration chromatography (GFC)), or by analogy from viscosity measurements, polyethylene glycol as a standard It can take conversion values.

Cationic polymers having an amine structure include, for example, allylamine polymers such as allylamine polymers, allylamine hydrochloride polymers, and allylamineamide sulfate polymers; diallylamine polymers, diallylamine hydrochloride polymers, and methyldiallylamine hydrochloride. Polymer, methyldiallylamine acetate polymer, methyldiallylamine amide sulfate polymer, diallylamine hydrochloride/sulfur dioxide copolymer, diallylamine acetate/sulfur dioxide copolymer, diallylamine/acrylamide copolymer, diallylamine hydrochloride/acrylamide Copolymer, methyldiallylamine hydrochloride/sulfur dioxide copolymer, diallyldimethylammonium chloride polymer, diallylmethylethylammonium ethylsulfate polymer, diallylmethylethylammonium ethylsulfate/sulfur dioxide copolymer, diallyldimethylammonium chloride・Sulfur dioxide copolymer, diallyldimethylammonium chloride/acrylamide copolymer, methyldiallylamine/diallyldimethylammonium chloride copolymer, diallyldimethylammonium chloride-diallylamine hydrochloride derivative copolymer, and other diallylamine polymers; allylamine/diallylamine Allylamine/diallylamine copolymers such as polymers, allylamine hydrochloride/diallylamine hydrochloride copolymers, allylamine acetate/diallylamine acetate copolymers, and allylamine/diallyldimethylammonium chloride copolymers; Modified allylamine polymers such as coalescence, partially methylcarbonylated allylamine acetate polymer, partially ureaized allylamine polymer, and partially carboxylmethylated polyallylamine polymer;

Examples of the cationic polymer having an amine structure include dicyandiamide/diethylenetriamine polycondensate; dicyandiamide/formaldehyde polycondensate; dimethylamine/epichlorohydrin polycondensate; dimethylamine/ammonia/epichlorohydrin polycondensate. dimethylamine/ethylenediamine/epichlorohydrin polycondensate; dimethylamine/epichlorohydrin/polyethylenepolyamine polycondensate; polyamidepolyamine-epichlorohydrin polycondensate; polyethyleneimine;

One or more of the cationic compounds listed above can be used. Among them, the cationic compound is a cationic polymer having an amine structure from the viewpoint of easily insolubilizing the pentacyanocarbonyl iron complex in the dust collection water and easily suppressing foaming when mixed with the dust collection water. preferably included. Among them, cationic compounds include dimethylamine/epichlorohydrin polycondensate, dicyandiamide/formaldehyde polycondensate, diallyldimethylammonium chloride polymer, dimethylamine/epichlorohydrin/polyethylene polyamine polycondensate, and allylamine hydrochloride. More preferably, it contains at least one selected from the group consisting of polymers and allylamine hydrochloride/diallylamine hydrochloride copolymers.

Among the above cationic polymers, the cationic compound more preferably contains a diallyldimethylammonium chloride polymer from the viewpoint of making the pentacyanocarbonyl iron complex in the collected water easier to insolubilize. In addition, among the cationic polymers described above, the cationic compounds are dimethylamine/epichlorohydrin polycondensates, dicyandiamide, and It is more preferable to contain at least one selected from the group consisting of formaldehyde polycondensates and allylamine hydrochloride/diallylamine hydrochloride copolymers.

In addition, as a cationic compound, it is easy to insolubilize the pentacyanocarbonyl iron complex in the dust collection water, it is easy to suppress foaming when mixed with the dust collection water, and it has a relatively low viscosity and can be sent by a pump or the like. Oleylamine is also more preferable because addition and the like are easy to perform. Furthermore, the mixture of oleylamine and didecyldimethylammonium chloride is used because it is easier to insolubilize the pentacyanocarbonyl iron complex in the dust collection water, and because it has a relatively low viscosity and can be easily fed and added by a pump or the like. It is also more preferable to use As for the mixing ratio of oleylamine and didecyldimethylammonium chloride, the ratio of the mass of didecyldimethylammonium chloride to the mass of oleylamine is 0.5 to 2 from the viewpoint of further enhancing the insolubilizing ability while maintaining the above effects of oleylamine. is preferred, and a range of 1 to 2 is more preferred.

Examples of the form of the cationic compound when adding the cationic compound to the collected water include a powder form and a solution (aqueous solution, etc.) form in which the compound is dissolved in water or the like, and it is preferably used in the form of an aqueous solution. .

A compound capable of generating zinc ions (Zn ²⁺ ) in water can be suitably used as the zinc salt that is optionally added to the dust collection water together with the cationic compound. Suitable zinc salts include, for example, zinc sulfate, zinc acetate, zinc nitrate, zinc chloride, zinc carbonate, zinc sulfite, and the like. These 1 type(s) or 2 or more types can be used. Among these, zinc sulfate is preferred. The form of the zinc salt when it is added to the collected water may be powder, or a solution (aqueous solution, etc.) dissolved in water or the like, and it is preferably used in the form of an aqueous solution.

Both copper (I) salts and copper (II) salts can be used as the copper salt that is optionally added to the dust collection water together with the cationic compound ^. Alternatively, a compound capable of generating copper (II) ions (Cu ²⁺ ) can be preferably used. Suitable copper(I) salts include, for example, copper(I) chloride, copper(I) oxide (cuprous oxide), copper(I) bromide, copper(I) acetate, and copper(I) sulfide. can be mentioned. Suitable copper(II) salts include, for example, copper(II) chloride, copper(II) sulfate, copper(II) acetate, copper(II) oxide, and copper(II) nitrate. One or more of copper(I) salts and copper(II) salts can be used, with copper(I) oxide and copper(II) sulfate being preferred. The form of the copper salt to be added to the dust collection water may be a powder form, a solution form, or the like, and it is preferably used in the form of a solution form. Examples of the solvent when used in the form of a solution include water; acids such as dilute hydrochloric acid and dilute sulfuric acid; bases such as aqueous ammonia;

The amount of the cationic compound added to the dust collection water (concentration of the cationic compound in the dust collection water) is preferably 1 to 500 mg/L, more preferably 2 to 100 mg/L, as the cationic compound (active ingredient amount). more preferably 3 to 25 mg/L. In addition, when zinc salt is added to dust-collected water, the amount of zinc salt added to dust-collected water (concentration of zinc salt in dust-collected water) is preferably 0.1 to 100 mg/L as zinc salt. , more preferably 0.5 to 40 mg/L, more preferably 1 to 20 mg/L. Furthermore, when a copper salt is added to the dust-collected water, the amount of the copper salt added to the dust-collected water (the concentration of the copper salt in the dust-collected water) is preferably 0.1 to 100 mg/L as the copper salt. , more preferably 0.5 to 40 mg/L, more preferably 1 to 15 mg/L. When two or more of the above cationic compound, zinc salt, and copper salt are used, the total amount of the two or more added is indicated.

In the solid-liquid separation treatment, a flocculating agent may be used in addition to the above-described cationic compound, zinc salt, and copper salt. The type of flocculant is not particularly limited, and examples include inorganic flocculants such as polyaluminum chloride, aluminum sulfate, polyferric sulfate, and ferric chloride, and polymer flocculants such as anionic polymer flocculants. 1 type or 2 types or more can be used.

In solid-liquid separation treatment of collected dust water to which a cationic compound having an amine structure and optionally zinc salt and/or copper salt have been added, the collected dust water, the cationic compound, and necessary The zinc salt and/or copper salt added according to is preferably mixed for a predetermined time. The mixing time is, for example, preferably 2 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, even more preferably 10 seconds to 5 minutes. Even in such a short time, the effect of adding the cationic compound and zinc salt and/or copper salt to the collected water can be obtained. If the solid-liquid separation equipment (more preferably, the precipitation device) 40 in which the second flow path 32 described above is laid is used, in the second flow path 32, the collected water, the cationic compound, and, if necessary, The zinc and/or copper salts used can be mixed (see Figures 2-5).

In the solid-liquid separation equipment 40, part of the liquid (separated liquid) separated from the solid content (suspended solids, insoluble matter, etc.) is subjected to a wet dust collection process ( It is supplied to the wet dust collector 2). As a result, even when a cyan component such as a pentacyanocarbonyl iron complex remains slightly in the separated liquid, the concentration of cyanide in water can be further reduced by circulating and repeating the treatment.

Part of the separated liquid separated from the solid content in the solid-liquid separation equipment 40 can be supplied to the circulation equipment 50 through a channel (third channel) 33 such as a pipe. The circulation equipment 50 includes a storage tank 52 for storing the separated liquid obtained in the solid-liquid separation equipment 40, and a flow path (fourth It is preferably configured with a flow path 54 and a circulation pump 56 .

In addition, in the method for treating collected dust water of the present embodiment, part of the separated liquid obtained by the solid-liquid separation process (the solid-liquid separation equipment 40) is blown separately from the washing water used for the wet dust collection process. It can be discharged outside the circulation facility as water. For example, the separated liquid obtained by the solid-liquid separation process is sent to the storage tank 52 of the circulation facility 50 through the third flow path 33, and part of the separated liquid in the storage tank 52 is used as blow water, and a flow path such as piping ( 5th channel) 35 can be discharged. In addition, although not shown, the solid-liquid separation equipment 40 and the fifth flow path (35) are connected, and apart from the separated liquid sent to the circulation equipment 50, the solid-liquid separation equipment 40 to the fifth flow path (35) Blow water may be discharged through

In this method, it is possible to separate and remove suspended solids in the dust collection water as well as pentacyanocarbonyl iron as insolubilized substances by solid-liquid separation treatment. It is possible to obtain treated water with a concentration of 1 mg(CN)/L or less (see FIGS. 1 to 3). Moreover, after the storage tank 52 of the circulation equipment 50, a further sedimentation tank 7 (see FIG. 6) that is required in the above-described reduction copper salt method is unnecessary, so the installation cost of the equipment is reduced to can be kept lower than

On the other hand, when the dust collection water contains cyanide ions as well as pentacyanocarbonyl iron as a cyan component, the separated liquid obtained by the solid-liquid separation treatment may contain cyanide ions. Therefore, when the dust-collected water further contains cyanide ions, the method for treating the dust-collected water of the present embodiment is to use the dust-collected water and the separated liquid obtained in the solid-liquid separation equipment 40, and the circulation equipment 50 and/or the separated liquid supplied to the circulation facility 50 (more preferably the separated liquid in the storage tank 52). As a result, when cyanide ions remain in the dust collection water or separated liquid, the cyanide ions can be oxidatively decomposed. In addition, by circulating a part of the separated liquid thus treated in a circulation facility, even if the collected water contains cyanide ions, the treated water in which the cyanide components are effectively reduced, such as Treated water having a total cyanide concentration of 1 mg(CN)/L or less of the wastewater standard can be obtained. Moreover, in this case also, after the storage tank 52 of the circulation equipment 50, a further sedimentation tank 7 (see FIG. 6) that is required in the above-described reduced copper salt method is unnecessary, so the installation cost of the equipment can be reduced. It can be kept lower than in the case of the salt method.

When an oxidizing agent is added to at least one of the collected water, the separated liquid before being supplied to the circulation system 50, and the separated liquid supplied to the circulation system 50, as shown in FIGS. , a device for adding an oxidant (oxidant addition device) 62 can be used. In order to add an oxidizing agent to the dust collection water, the separated liquid before being supplied to the circulation facility 50, and the separated liquid supplied to the circulation facility 50 (preferably the separated liquid in the storage tank 52), for example, It is preferable to provide the oxidant addition device 62 so that at least one of the second flow path 32, the solid-liquid separation equipment 40, the third flow path 33, and the storage tank 52 serves as the oxidant addition position. The oxidant addition device 62 can include, for example, a tank for storing the oxidant, a pump and a supply pipe for supplying the oxidant, and the like. A plurality of oxidant addition devices 62 may be provided according to the type of oxidant to be used. In FIG. 5, the oxidant addition device 62 is indicated by a dashed line so as to indicate that the oxidant addition device 62 may not be provided when the dust collection water does not contain cyanide ions (see FIGS. 1 to 3). is shown.

The oxidizing agent includes hydrogen peroxide, oxygen, ozone, hypochlorous acid or its salts, chlorous acid or its salts, chloric acid or its salts, hypobromous acid or its salts, bromous acid or its salts, and An iodine compound etc. can be mentioned. These 1 type(s) or 2 or more types can be used. Among these, the oxidizing agent to be used preferably contains at least hydrogen peroxide from the viewpoints of oxidative decomposition of cyanide ions and less corrosion of equipment. A reaction aid for the oxidant may also be used together with the oxidant. As the reaction aid, for example, a copper salt as a catalytic amount, a reducing sulfur compound, and the like can be mentioned, and one or more of them can be used.

In addition, from the viewpoint of oxidizing and decomposing cyanide ions in the dust collection water and the separated liquid more easily, the oxidizing agent is a combination of hydrogen peroxide and hypochlorous acid or a salt thereof; A combination with a copper salt as; a combination of hydrogen peroxide and a reducing sulfur compound; a combination of hypochlorous acid or a salt thereof and a reducing sulfur compound; at least one combination selected from the group consisting of It is preferable to use Among these, the oxidizing agent is a combination of hydrogen peroxide and hypochlorous acid or a salt thereof; and a combination of hydrogen peroxide and a copper salt as a catalytic amount. More preferably, it contains It is more preferable to use the oxidizing agents in each combination described above in the form of a solution (aqueous solution, etc.) dissolved in water or the like.

Examples of hypochlorite include sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and magnesium hypochlorite. A catalytic amount of copper salt refers to an amount of copper to cyanide ion and/or cyano complex in a molar ratio of less than 1:1. Copper salts include, for example, copper (I) salts such as copper (I) chloride, copper (I) oxide (cuprous oxide), copper (I) bromide, copper (I) acetate, and copper (I) sulfide. , and copper(II) salts such as copper(II) sulfate, copper(II) chloride, copper(II) oxide, copper(II) acetate, and copper(II) nitrate. Examples of reducing sulfur compounds include thiosulfate, sulfide salt, polysulfide salt, thiocyanate, mercaptoacetic acid, mercaptoethanol, cysteine, cysteine hydrochloride, thioglycolic acid, thiodiglycol, thioethanol, and thiolingo. Acids, thiomalates, and mercaptobenzimidazoles can be mentioned. Examples of thiosulfates include sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, calcium thiosulfate, and magnesium thiosulfate. Examples of sulfide salts include sodium hydrogen sulfide, potassium hydrogen sulfide, sodium sulfide, potassium sulfide, ammonium sulfide, and iron (II) sulfide. Examples of polysulfide salts include sodium polysulfide, calcium polysulfide, potassium polysulfide, and magnesium polysulfide. Thiocyanates include, for example, potassium thiocyanate, sodium thiocyanate, ammonium thiocyanate, and calcium thiocyanate.

The amount of the oxidizing agent added to the dust collection water or the separated liquid (concentration of the oxidizing agent in the dust collection water or the separated liquid) is preferably 1 to 1000 mg/L as the oxidizing agent (active ingredient amount), and is preferably 2 to 1000 mg/L. More preferably 500 mg/L, even more preferably 5 to 160 mg/L. When two or more oxidizing agents are used, the amount of the oxidizing agent added indicates the total amount of the two or more oxidizing agents added.

The pH of the dust collection water or the separated liquid when adding the oxidizing agent is not particularly limited, but is preferably 5.0 to 10.0, more preferably 5.5 to 9.5. .0 to 9.0 is more preferable. A pH adjuster may be added to the dust collection water or the separated liquid before adding the oxidizing agent to adjust the pH of the dust collection water or the separated liquid within the above range. For pH adjustment, as described above, a known pH adjuster can be used as appropriate.

After adding an oxidizing agent to the dust collection water or separation liquid, the dust collection water or separation liquid is added with an oxidizing agent so that the cyanide ions in the dust collection water or separation liquid can sufficiently react with the oxidizing agent. is preferably stirred for a predetermined period of time. The stirring time is, for example, preferably 1 to 60 minutes, more preferably 2 to 45 minutes, even more preferably 5 to 30 minutes. When the oxidizing agent is added to the collected water, it is preferable to stir in the solid-liquid separation equipment 40, and when adding the oxidizing agent to the separated liquid, it is stirred in the storage tank 52 of the circulation equipment 50. is preferred. For example, stirring can be performed in a solid-liquid separation facility 40 equipped with a stirring mechanism 48 or in a storage tank 52 equipped with a stirring mechanism (not shown).

Either one or both of concentration treatment and dehydration treatment are performed on the slurry containing the solid content (suspended matter, insolubilized matter, etc.) separated from the liquid content in the solid-liquid separation equipment 40, and the dehydrated cake and the separated water are separated. It is preferable to obtain Moreover, it is preferable to send the obtained separated water to the above-mentioned solid-liquid separation treatment (solid-liquid separation equipment 40). This makes it possible to more stably remove the cyan component in the dust collection water.

For example, as shown in FIG. 5, the slurry containing the solid content separated from the liquid content in the solid-liquid separation equipment 40 is sent to the dehydrator 80 through a channel (sixth channel) 36 such as a pipe, A dehydrated cake and separated water can be obtained by the dehydration treatment. Concentration processing by a concentration tank (not shown) may be used instead of the dehydration processing by the dehydrator 80, and the concentration processing by the concentration tank and the dehydration processing by the dehydrator 80 may be used together. The separated water (dehydrated filtrate) obtained by the dehydrator 80 passes through a flow path (seventh flow path) 37 such as piping, and more preferably further through the second flow path 32, to the solid-liquid separation equipment. 40 preferably. In this case, it is preferable that the seventh channel 37 and the second channel 32 are connected. The separated water (dehydrated filtrate) obtained by the dehydrator 80 may be sent to the solid-liquid separation equipment 40, as well as the separated water obtained by the concentration tank, or surplus slurry may be sent.

The method for treating dust-collected water according to the present embodiment may include measuring the total cyanide concentration in the dust-collected water or the separated liquid and the cyanide ion concentration in the dust-collected water, the separated liquid, or the treated water. . Cationic compounds, zinc salts, copper salts, and oxidation The amount of each agent added can also be adjusted.

As described in detail above, according to the method for treating dust-collected water of the present embodiment, by adding a cationic compound having an amine structure to dust-collected water under specific conditions, iron pentacyanocarbonyl is added to dust-collected water. An insolubilized product of the complex can be produced. Then, the insolubilized pentacyanocarbonyl iron complex and the suspended matter generated in the collected water can be separated and removed together by solid-liquid separation treatment. Therefore, according to the present method, the suspended solids in the dust-collected water are separated and removed at the same time without requiring an additional sedimentation tank after the solid-liquid separation of the suspended solids in the dust-collected water. A cyan component (pentacyanocarbonyl iron complex) can also be effectively removed. Therefore, it is possible to obtain treated water in which the concentration of cyanide is effectively reduced while keeping the installation cost of equipment low as compared with the conventional technology.

In addition, as one aspect of the method for treating dust-collected water of the present embodiment, an oxidizing agent can be added to at least one of the dust-collected water and the separated liquid obtained by the solid-liquid separation treatment. Therefore, when cyanide ions remain in the dust collection water or the separated liquid, a separated liquid can be obtained by removing the cyanide ions by oxidative decomposition, and a part of the separated liquid can be recycled in the circulation equipment. By doing so, it is possible to obtain treated water in which cyanide ions are also more effectively reduced.

It should be noted that the method for treating collected dust according to one embodiment of the present invention can have the following configuration.
[1] solid-liquid separation equipment for solid-liquid separation of suspended solids in dust collection water obtained by wet dust collection treatment of exhaust gas; A method for treating the collected dust using a circulation facility for dust collection,
The dust collection water further contains a pentacyanocarbonyl iron complex,
Satisfies at least one of condition 1 that the suspended matter in the dust-collected water contains one or both of zinc and copper, and condition 2 that one or both of zinc salt and copper salt is further added to the dust-collected water. A method for treating collected dust, comprising adding a cationic compound having an amine structure to the collected dust under conditions and subjecting the collected water to solid-liquid separation treatment in the solid-liquid separation equipment.
[2] the suspended matter in the dust collection water contains one or both of zinc and copper;
The method for treating dust-collected water according to the above [1], comprising adding the cationic compound to the dust-collected water under conditions satisfying at least condition 1 above.
[3] The method for treating dust-collected water according to the above [1] or [2], wherein as the condition 2, one or both of the zinc salt and the copper salt are added to the dust-collected water.
[4] The cationic compound includes dimethylamine/epichlorohydrin polycondensate, dicyandiamide/formaldehyde polycondensate, diallyldimethylammonium chloride polymer, dimethylamine/epichlorohydrin/polyethylene polyamine polycondensate, and allylamine hydrochloride. The method for treating collected dust according to any one of [1] to [3] above, which contains at least one selected from the group consisting of a salt polymer and an allylamine hydrochloride/diallylamine hydrochloride copolymer.
[5] The method for treating collected dust according to any one of [1] to [4] above, wherein the cationic compound contains a diallyldimethylammonium chloride polymer.
[6] The method for treating collected dust water according to any one of [1] to [3] above, wherein the cationic compound contains oleylamine.
[7] The method for treating collected dust according to any one of [1] to [3] above, wherein the cationic compound contains a mixture of oleylamine and didecyldimethylammonium chloride.
[8] The dust collection water further contains cyanide ions,
The above [1] comprising adding an oxidizing agent to at least one of the dust collection water; the separated liquid before being supplied to the circulation facility; and the separated liquid supplied to the circulation facility. The method for treating collected dust according to any one of to [7].
[9] The method for treating dust collection water according to the above [8], wherein the oxidizing agent contains at least hydrogen peroxide.
[10] The oxidizing agent is a combination of hydrogen peroxide and hypochlorous acid or a salt thereof; a combination of hydrogen peroxide and a copper salt as a catalytic amount; a combination of hydrogen peroxide and a reducing sulfur compound combination; combination of hypochlorous acid or a salt thereof and a reducing sulfur compound; The method for treating dust collection water according to the above [8], comprising at least one combination selected from the group consisting of.

Hereinafter, the effects of the method for treating collected dust according to one embodiment of the present invention will be described in more detail with reference to test examples, but the present invention is not limited to the following test examples.

<Simulated dust collection water>
In this test example, simulated dust water prepared by mixing raw water containing a cyanide component and suspended solids described below was used as the dust water to be treated.

(Raw water)
Supernatant water was prepared by sedimentation separation of wastewater containing suspended solids such as unburned carbon, iron and zinc discharged from an exhaust gas treatment apparatus for cleaning exhaust gas in a predetermined factory. Using this supernatant water as raw water, three types of raw water No. 1 to 3 were prepared. For these raw waters, the total cyanide (T-CN) concentration was measured by the total cyanide measurement method in JIS K0102: 2013, and the free cyanide (F -CN) concentrations were measured. Further, a value obtained by subtracting the measured value of the F-CN concentration from the measured value of the T-CN concentration was calculated as the cyano complex concentration. Table 1 shows the results.

In addition, raw water No. The filtrate obtained by filtering each raw water of 1 to 3 with 5 type C filter paper was subjected to liquid chromatography (LC; trade name "Alliance 2695", manufactured by Nippon Waters Co., Ltd.), and an inductively coupled plasma mass spectrometer (ICP- MS; product name "ICP-MS7500", manufactured by Agilent Technologies) as a detector (LC-ICP-MS), under the following measurement conditions, the soluble cyano complex in the raw water Concentration was analyzed.
(Measurement condition)
Column: ODS column (trade name “L-Column2”; particle size 5 μm, inner diameter 4.6 mm, column length 150 mm, 2 columns; manufactured by Chemicals Evaluation and Research Institute)
Mobile phase: A mixture of acetonitrile and 25 mM phosphate buffer (pH 7.0, containing 15 mM tetrabutylammonium dihydrogen phosphate as an ion pair reagent) at a volume ratio of 40:60 Flow rate: 0.8 mL/min Column temperature: 40°C
Detector; ICP-MS and photodiode array (PDA) (detection wavelength: 210-400 nm)
Elements to be detected in ICP-MS: Fe (atomic weight 56), Cu (atomic weight 63), Ni (atomic weight 60), Co (atomic weight 59), Zn (atomic weight 66)
Injection volume: 50 to 100 μL

As a result of the above analysis, raw water No. 1 to 3 are all [Fe(CN) ₅ (CO)] ³⁻ , [Fe(CN) ₄ (CO) ₂ ] ²⁻ , [Fe(CN) ₆ ] ⁴⁻ , and [Fe(CN) ₆ ] It was confirmed to contain ^3- . The total concentration of these cyano complexes is the raw water No. 1 is 3.0 mg-CN/L, raw water No. 2, 2.8 mg-CN/L, raw water No. 3 was 1.2 mg-CN/L. The concentration of the pentacyanocarbonyl iron complex in these raw waters was compared with the cyano complex concentration obtained by subtracting the F-CN concentration from the T-CN concentration shown in Table 1, and the majority of the cyano complex in the raw water (50% by mass super) was found to be a pentacyanocarbonyl iron complex. As a result of the above analysis, raw water No. The breakdown of the cyano complex concentration of No. 1 is as follows: [Fe(CN) ₅ (CO)] ³⁻ : 1.8 mg/L, [Fe(CN) ₄ (CO) ₂ ] ²⁻ : 0.3 mg/L, [Fe (CN) ₆ ] ⁴⁻ : 0.6 mg/L and [Fe(CN) ₆ ] ³⁻ : 0.3 mg/L. In addition, raw water No. The breakdown of the cyano complex concentration of 2 is as follows: [Fe(CN) ₅ (CO)] ³⁻ : 1.7 mg/L, [Fe(CN) ₄ (CO) ₂ ] ²⁻ : 0.3 mg/L, [Fe (CN) ₆ ] ⁴⁻ : 0.5 mg/L and [Fe(CN) ₆ ] ³⁻ : 0.3 mg/L. Furthermore, raw water No. The breakdown of the cyano complex concentration of 3 is as follows: [Fe(CN) ₅ (CO)] ³⁻ : 0.7 mg/L, [Fe(CN) ₄ (CO) ₂ ] ²⁻ : 0.1 mg/L, [Fe (CN) ₆ ] ⁴⁻ : 0.3 mg/L and [Fe(CN) ₆ ] ³⁻ : 0.1 mg/L.

(suspended solids)
Suspended solids containing unburned carbon, iron, zinc, etc. (SSNo. 1) and suspended solids free of zinc and copper (SSNo. 2) was prepared. The elemental compositions of these suspended solids (SS) were determined by fluorescent X-ray analysis and are shown in Table 2. As will be described later, these suspended solids (SS No. 1 or SS No. 2) were mixed with the above raw water (any of raw water Nos. 1 to 3) to prepare simulated dust collection water.

In addition, as will be described later, in order to prepare SS with a different composition, raw water, SS No. 2 and a predetermined amount of a metal hydroxide suspension prepared by mixing sodium hydroxide with a metal salt solution described below. Simulated dust collection water modified as shown in 3-13 was also prepared. As a solution of the above metal salt, SSNo. 3 to 6, an aqueous solution of zinc sulfate heptahydrate, which is a Zn ²⁺ source; 7 to 10, a solution of cuprous oxide, a Cu ⁺ source, dissolved in hydrochloric acid; In SS No. 11, an aqueous solution of ferrous chloride, which is a Fe ²⁺ source, was used. In SS No. 12, an aqueous solution of nickel sulfate hexahydrate, which is a Ni ²⁺ source, was used. 13 used an aqueous solution of manganese sulfate pentahydrate, which is a source of Mn ²⁺ .

In Table 2, SSNo. is shown as an overview of each suspended substance (SSNo. 1 is "Zn-containing SS", SSNo. 2 was described as "Zn and Cu-free SS". Also, SSNo. 3 is SS No. By adding zinc sulfate to 2, the Zn content (% by mass) in SS was adjusted to 0.1% by mass, so it was described as "Zn and Cu-free SS + Zn 0.1%". SS No. 4 to 13 also have SSNo. The outline is described in the same manner as in 3.

(Preparation of simulated dust collection water)
Raw water (any of raw water Nos. 1 to 3) was placed in a 100 mL beaker, heated to 50° C. with stirring, and adjusted to pH 7.5 with hydrochloric acid. Suspended solids (SSNo.1 or SSNo.2) or SSNo. 2 and the above metal hydroxide suspension were added so that the total SS concentration was as shown in the test examples described later. In this manner, simulated dust collection water containing cyan components and suspended solids (any of SS Nos. 1 to 13) was prepared. The type (No.) of the raw water and suspended solids (SS) used in the simulated dust-collected water treated in each test example, the SS concentration in the dust-collected water, zinc (Zn), copper (Cu), The concentration of nickel (Ni) or manganese (Mn) is shown in the columns of simulated dust collection water in Tables 5 to 10 below.

<Preliminary test>
Raw water no. 1 was placed in a 100 mL beaker, heated to 50° C. with stirring, and adjusted to pH 7.5 with hydrochloric acid. SSNo. 2 was added at 2000 mg/L to prepare simulated dust-collected water, and 10% by mass aqueous solution of zinc sulfate heptahydrate was added to the simulated dust-collected water at 10 mg/L as zinc sulfate (ZnSO ₄ ), Table 4 below. 10 mg/L of the cationic compound A shown in was added. After these additions, the mixture was stirred for 20 seconds (preliminary test 1) and 300 seconds (5 minutes) for preliminary test 2, and reacted to obtain a reaction solution. The resulting reaction solution was filtered through filter paper (5 type C) to obtain a filtrate. The total cyanide (T--CN) concentration in this filtrate was measured in the same manner as in "Measurement of T--CN concentration in treated water" below. The results of preliminary tests 1 and 2 were compared with raw water no. Table 3 along with the T-CN concentration values of 1.

From the results of preliminary tests 1 and 2, after adding zinc salt and cationic compound to simulated dust collection water, treated water with sufficiently reduced T-CN concentration was obtained even if the mixing time was 20 seconds or 5 minutes. confirmed to be obtained. Therefore, by mixing the dust collection water, the cationic compound, and the zinc salt in the second flow path 32 (see FIGS. 2 to 5) in the dust collection water treatment systems 12 to 15 described above, sufficient treatment can be achieved. It is recognized that it can be done. Based on the results of Preliminary Tests 1 and 2, in the following test examples, the conditions for the mixing time of the simulated dust collection water and the cationic compound and the like were set to 5 minutes.

<Cationic compound>
In the test examples described below, compounds A to L shown in Table 4 below were used as cationic compounds, and an acrylamide/sodium acrylate copolymer was used as compound M for comparison. Compounds AH are cationic polymers having an amine structure. Compound I is a cationic monomer having a quaternary ammonium structure, and Compound J is a cationic monomer having a primary amine structure. Compounds K and L are mixtures of two cationic compounds (oleylamine and didecyldimethylammonium chloride), but are referred to as compounds for convenience.

<Test example 1 series>
(Test method)
As described in the above "preparation of simulated dust collection water", raw water No. 1 to SSNo. 2 was added so that the SS concentration was 2000 mg/L, and the simulated dust collection water prepared was treated. To this simulated dust collection water at 50°C and pH 7.5, 10 mg/L of the cationic compound A shown in Table 4 and a metal salt solution were added at concentrations of metals shown in the treatment conditions column of Table 5 below (in metal salt (addition concentration in terms of metal element) and stirred for 5 minutes, and then the liquid containing the simulated dust collection water (hereinafter referred to as the reaction liquid) was filtered with filter paper (Type 5 C). The obtained filtrate was used as treated water. However, in Test Example 1-1, as a blank test, the test was performed without adding either the cationic compound A or the metal salt solution to the simulated dust collection water, and in Test Example 1-2, no metal salt was added. was tested on. The above metal salt solutions include an aqueous solution of zinc sulfate heptahydrate as a Zn2 ⁺ source, a hydrochloric acid solution of cuprous oxide as a Cu ⁺ source, an aqueous solution of copper sulfate pentahydrate as a Cu2 ⁺ source, and sulfuric acid as a Ni2 ⁺ source. An aqueous solution of nickel hexahydrate, an aqueous solution of manganese sulfate pentahydrate as Mn ²⁺ source, and an aqueous solution of ferrous chloride as Fe ²⁺ source were used (Zn ²⁺ , Cu ⁺ , Cu ²⁺ , referred to as Ni ²⁺ , Mn ²⁺ and Fe ²⁺ ).

(Measurement of T-CN concentration in treated water)
The resulting treated water is pretreated with "hydrogen cyanide generated at pH 2 or less" defined in 38.1.2 of JIS K0102, and "4-pyridinecarboxylic acid-pyrazolone" defined in 38.3 of JIS K0102. The total cyan (T-CN) concentration was measured by using a method according to "Absorptiometry". The results are shown in the column of treated water in Table 5.

<Test example 2 series>
As described in the above "preparation of simulated dust collection water", raw water No. In 1, simulated dust water prepared to contain 2000 mg/L of suspended solids (any of SS No. 2 to 13) shown in the simulated dust water column of Table 6 below was treated. To this 50° C., pH 7.5 simulated dust collection water, the cationic compound A shown in Table 4 was added at the addition concentration shown in the treatment conditions column of Table 6 below, stirred for 5 minutes, and then the reaction solution was filtered with filter paper ( Filtration was carried out with 5 type C). The obtained filtrate was used as treated water. However, in Test Examples 2-1 to 2-8, tests were conducted without adding the cationic compound A to the simulated dust collection water. The total cyanide (T-CN) concentration in the resulting treated water was measured in the same manner as in "Measurement of T-CN concentration in treated water" above. The results are shown in the column of treated water in Table 6.

<Test example 3 series>
As described in the above "preparation of simulated dust collection water", raw water No. In 1, simulated dust water prepared to contain suspended solids (SS No. 1 or SS No. 6) shown in the simulated dust water column of Table 7 below at the SS concentration shown in the relevant column was treated. 10 mg/L of the cationic compound A shown in Table 4 was added to the simulated dust collection water at 50° C. and pH 7.5, and after stirring for 5 minutes, the reaction solution was filtered through filter paper (Type 5 C). The obtained filtrate was used as treated water. However, in Test Examples 3-1 to 3-6, tests were conducted without adding the cationic compound A to the simulated dust collection water. The total cyanide (T-CN) concentration in the resulting treated water was measured in the same manner as in "Measurement of T-CN concentration in treated water" above. The results are shown in the column of treated water in Table 7.

<Test example 4 series>
As described in the above "preparation of simulated dust collection water", raw water No. 1 to SSNo. A simulated dust collection water prepared by adding 2500 mg/L of 1 was treated. 15 mg/L of one of the compounds A to M (see Table 4) shown in the treatment conditions column of Table 8 below was added to the simulated dust collection water at 50°C and pH 7.5, and Test Examples 4-3 and 4- 15 to 4-29, the metal salt solution of the “Zn ²⁺ source” or “Cu ⁺ source” described in the Test Example 1 series was added at the concentration of the metal shown in the treatment conditions column of Table 8 below (the concentration in the metal salt added concentration in terms of metal element), stirred for 5 minutes, and then filtered through filter paper (Type 5 C). The obtained filtrate was used as treated water. However, in Test Example 4-1, the test was conducted without adding any of the compounds A to M to the simulated dust collection water. The total cyanide (T-CN) concentration in the resulting treated water was measured in the same manner as in "Measurement of T-CN concentration in treated water" above. The results are shown in the column of treated water in Table 8.

<Test Example 5 series>
As described in the above "preparation of simulated dust collection water", raw water No. 2 to SS No. The simulated dust collection water prepared by adding 1 so that the SS concentration was 2000 mg/L was treated. To this 50° C., pH 7.5 simulated dust collection water, 20 mg/L of any of compounds A to M (see Table 4) shown in the treatment conditions column of Table 9 below was added, and the agent shown in the same column was added. was added according to the conditions of each test example and stirred for 5 minutes. However, Test Examples 5-1 to 5-3 were tested without adding any of the compounds A to M to the simulated dust collection water. As the above chemicals, 35% by mass hydrogen peroxide solution, 12% by mass hypochlorous acid aqueous solution, and 1% by mass aqueous copper (II) sulfate pentahydrate solution were used. Addition concentration of hydrogen peroxide water as H ₂ O ₂ in each test example (mg (H ₂ O ₂ ) / L), addition concentration of hypochlorous acid aqueous solution as NaClO (mg (NaClO) / L), sulfuric acid Addition concentration (mg(Cu)/L) of copper (II) aqueous solution as Cu is shown in Table 9 in the chemical column.
After stirring for 5 minutes, the remaining hydrogen peroxide and hypochlorous acid are removed by adding sodium bisulfite, and the reaction solution is filtered through filter paper (5 type C). The obtained filtrate is treated water. bottom. The total cyanide (T-CN) concentration in the resulting treated water was measured in the same manner as in "Measurement of T-CN concentration in treated water" above. The results are shown in the column of treated water in Table 9.

<Test example 6 series>
As described in the above "preparation of simulated dust collection water", raw water No. 3 to SS No. The simulated dust collection water prepared by adding 1 so that the SS concentration was 2000 mg/L was treated. To this 50° C., pH 7.5 simulated dust collection water, 20 mg/L of one of the compounds A to M (see Table 4) shown in the treatment conditions column of Table 10 below was added, and the agent shown in the same column was added. was added according to the conditions of each test example and stirred for 5 minutes. However, Test Examples 6-1 to 6-3 were tested without adding any of the compounds A to M to the simulated dust collection water. As the above chemicals, 35% by mass hydrogen peroxide solution, 12% by mass hypochlorous acid aqueous solution, and 1% by mass aqueous copper (II) sulfate pentahydrate solution were used. Addition concentration of hydrogen peroxide water as H ₂ O ₂ in each test example (mg (H ₂ O ₂ ) / L), addition concentration of hypochlorous acid aqueous solution as NaClO (mg (NaClO) / L), sulfuric acid Addition concentration (mg(Cu)/L) of copper (II) aqueous solution as Cu is shown in Table 10, chemical agent column.
After stirring for 5 minutes, the remaining hydrogen peroxide and hypochlorous acid are removed by adding sodium bisulfite, and the reaction solution is filtered through filter paper (5 type C). The obtained filtrate is treated water. bottom. The total cyanide (T-CN) concentration in the resulting treated water was measured in the same manner as in "Measurement of T-CN concentration in treated water" above. The results are shown in the column of treated water in Table 10.

As a result of each test example in the above test examples 1 to 6 series, the simulated dust collection water containing suspended solids and pentacyanocarbonyl iron complex was treated under various conditions, and total cyanide (T-CN) Treated water with a concentration of 1 mg (CN) / L or less of the wastewater standard was obtained (Test Examples 1-3 to 12, Test Examples 2-13 to 24, Test Examples 3-7 to 12, Test Example 4-4 ~29, Test Examples 5-5 to 15, and Test Examples 6-5 to 17).

Specifically, for collected dust containing a cyano complex such as pentacyanocarbonyl iron and suspended solids, when the suspended solids in the collected dust do not contain zinc and copper, a cationic compound having an amine structure It was confirmed that by adding a compound and a zinc salt or a copper salt and performing solid-liquid separation treatment, treated water in which the T-CN concentration was effectively reduced was obtained (Test Examples 1-3 to 1-12). .

Further, when the suspended matter in the dust-collected water contains zinc or copper, a cationic compound having an amine structure is added to the dust-collected water containing a cyano complex such as pentacyanocarbonyl iron and suspended matter. It was confirmed that treated water with effectively reduced T-CN concentration can be obtained by solid-liquid separation treatment (Test Examples 2-13 to 2-24). The effect in this case was observed even when the SS concentration in the dust collection water changed (Test Examples 3-7 to 12 and Test Examples 4-4 to 29), and furthermore zinc salt or copper salt was added to the dust collection water. , it was found that treated water with a lower T-CN concentration can be easily obtained (Test Examples 4-15 to 4-29).

Furthermore, for collected water containing cyano complexes such as pentacyanocarbonyl iron, cyanide ions, and suspended solids, under the condition that the suspended solids in the collected water contain zinc, a cationic compound having an amine structure is used. It was confirmed that solid-liquid separation treatment by adding a compound and an oxidizing agent yields treated water in which the T-CN concentration is effectively reduced (Test Examples 5-5 to 15 and Test Example 6- 5-17).

From the above results, it can be concluded that under conditions where suspended solids in the collected water contain zinc and/or copper, or under conditions where zinc salts and/or copper salts are further added to the collected water, of the pentacyanocarbonyl iron complex, which can be separated and removed together with suspended solids by solid-liquid separation treatment. In addition, when the dust collection water further contains cyanide ions, it was found that the cyanide ions in the dust collection water can be oxidatively decomposed by adding an oxidizing agent to the dust collection water or the separated liquid obtained after the solid-liquid separation treatment. be done.

Furthermore, test examples using compounds A to H and J (No. 1-3 to 12; 2-13 to 24; 3-7 to 12; 4-4 to 10, 12, 15 to 21, 23 and 25-27; 5-5-12 and 14; 6-5-14 and 16), compared to test examples using compound I (No. 4-11, 22 and 28; 5-13; 6-15) Therefore, foaming was suppressed when the compound was added to the simulated dust collection water. Also, test examples using compounds C, E, H, J, K and L (No. 4-5, 7, 10, 12-14, 16, 18, 21, 23, 24, 26 and 29; 5- 12, 14 and 15; 6-14, 16 and 17) were less viscous and easier to pump than the other compounds.

From the results of the above test examples, it was found that the method for treating dust water according to the embodiment using the above-described solid-liquid separation equipment and circulation equipment was actually applied to dust water obtained by wet dust collection treatment of exhaust gas. was found to be very useful. This is because the solid-liquid separation equipment can separate and remove the pentacyanocarbonyl iron complex together with the suspended matter in the collected water. Further, as a result, the pentacyanocarbonyl iron complex in the dust-collected water can be effectively removed without requiring an additional sedimentation tank after the solid-liquid separation of the suspended matter in the dust-collected water. This is because it is possible to obtain treated water in which the concentration of cyanide is effectively reduced while keeping installation costs of the equipment low.

11, 12, 13, 14, 15: Dust collection water treatment system 2: Wet dust collector 31, 32, 33, 35, 36, 37: Flow path 40: Solid-liquid separation equipment 42: Cationic compound addition device 44: Zinc salt Addition device 46: Copper salt addition device 50: Circulation equipment 52: Storage tank 54: Flow path 56: Circulation pump 62: Oxidant addition device

Claims (9)

Solid-liquid separation equipment for solid-liquid separation of suspended matter in dust collection water obtained by wet dust collection treatment of exhaust gas, and said wet dust collection treatment using a part of the separated liquid obtained by said solid-liquid separation equipment as washing water. A method of treating the collected dust water using a circulation facility provided for
The dust collection water contains the suspended solids and a pentacyanocarbonyl iron complex, and the concentration of the suspended solids in the dust collection water is 500 to 10000 mg/L,
Satisfies at least one of condition 1 that the suspended matter in the dust-collected water contains one or both of zinc and copper, and condition 2 that one or both of zinc salt and copper salt is further added to the dust-collected water. Under the condition, the dust-collected water before solid-liquid separation treatment in the solid-liquid separation equipment, wherein the dust-collected water in a flow path for supplying the dust-collected water to the solid-liquid separation equipment has an amine structure by adding a cationic compound having and solid-liquid separation treatment in the solid-liquid separation equipment to remove the poorly soluble matter and / or insoluble matter together with the suspended matter as a solid component,
The cationic compound includes a dimethylamine/epichlorohydrin polycondensate, a dicyandiamide/formaldehyde polycondensate, a diallyldimethylammonium chloride polymer, a dimethylamine/epichlorohydrin/polyethylene polyamine polycondensate, and an allylamine hydrochloride polymer. and at least one selected from the group consisting of allylamine hydrochloride/diallylamine hydrochloride copolymer . Solid-liquid separation equipment for solid-liquid separation of suspended matter in dust collection water obtained by wet dust collection treatment of exhaust gas, and said wet dust collection treatment using a part of the separated liquid obtained by said solid-liquid separation equipment as washing water. A method of treating the collected dust water using a circulation facility provided for
The dust collection water contains the suspended solids and a pentacyanocarbonyl iron complex, and the concentration of the suspended solids in the dust collection water is 500 to 10000 mg/L,
Satisfies at least one of condition 1 that the suspended matter in the dust-collected water contains one or both of zinc and copper, and condition 2 that one or both of zinc salt and copper salt is further added to the dust-collected water. Under the condition, the dust-collected water before solid-liquid separation treatment in the solid-liquid separation equipment, wherein the dust-collected water in a flow path for supplying the dust-collected water to the solid-liquid separation equipment has an amine structure by adding a cationic compound having and solid-liquid separation treatment in the solid-liquid separation equipment to remove the poorly soluble matter and / or insoluble matter together with the suspended matter as a solid component,
A method for treating collected dust , wherein the cationic compound contains a diallyldimethylammonium chloride polymer . Solid-liquid separation equipment for solid-liquid separation of suspended matter in dust collection water obtained by wet dust collection treatment of exhaust gas, and said wet dust collection treatment using a part of the separated liquid obtained by said solid-liquid separation equipment as washing water. A method of treating the collected dust water using a circulation facility provided for
The dust collection water contains the suspended solids and a pentacyanocarbonyl iron complex, and the concentration of the suspended solids in the dust collection water is 500 to 10000 mg/L,
Satisfies at least one of condition 1 that the suspended matter in the dust-collected water contains one or both of zinc and copper, and condition 2 that one or both of zinc salt and copper salt is further added to the dust-collected water. Under the condition, the dust-collected water before solid-liquid separation treatment in the solid-liquid separation equipment, wherein the dust-collected water in a flow path for supplying the dust-collected water to the solid-liquid separation equipment has an amine structure by adding a cationic compound having and solid-liquid separation treatment in the solid-liquid separation equipment to remove the poorly soluble matter and / or insoluble matter together with the suspended matter as a solid component,
A method for treating collected dust , wherein the cationic compound contains oleylamine . Solid-liquid separation equipment for solid-liquid separation of suspended matter in dust collection water obtained by wet dust collection treatment of exhaust gas, and said wet dust collection treatment using a part of the separated liquid obtained by said solid-liquid separation equipment as washing water. A method of treating the collected dust water using a circulation facility provided for
The dust collection water contains the suspended solids and a pentacyanocarbonyl iron complex, and the concentration of the suspended solids in the dust collection water is 500 to 10000 mg/L,
Satisfies at least one of condition 1 that the suspended matter in the dust-collected water contains one or both of zinc and copper, and condition 2 that one or both of zinc salt and copper salt is further added to the dust-collected water. Under the condition, the dust-collected water before solid-liquid separation treatment in the solid-liquid separation equipment, wherein the dust-collected water in a flow path for supplying the dust-collected water to the solid-liquid separation equipment has an amine structure by adding a cationic compound having and solid-liquid separation treatment in the solid-liquid separation equipment to remove the poorly soluble matter and / or insoluble matter together with the suspended matter as a solid component,
A method for treating collected dust , wherein the cationic compound contains a mixture of oleylamine and didecyldimethylammonium chloride . the suspended matter in the dust collection water contains one or both of zinc and copper;
The method for treating dust-collected water according to any one of claims 1 to 4 , comprising adding the cationic compound to the dust-collected water under the condition that at least condition 1 is satisfied. The method for treating dust-collected water according to any one of claims 1 to 4, wherein the condition 2 includes adding one or both of the zinc salt and the copper salt to the dust-collected water. The dust collection water further contains cyanide ions,
1-, comprising adding an oxidizing agent to at least one of the collected dust water; the separated liquid before being supplied to the circulation facility; and the separated liquid supplied to the circulation facility. 5. The method for treating collected dust water according to any one of 4 . The method for treating collected dust according to claim 7 , wherein the oxidizing agent contains at least hydrogen peroxide. The oxidizing agent is a combination of hydrogen peroxide and hypochlorous acid or a salt thereof; a combination of hydrogen peroxide and a copper salt as a catalytic amount; a combination of hydrogen peroxide and a reducing sulfur compound; The method for treating collected dust according to claim 7 , comprising at least one combination selected from the group consisting of a combination of chlorous acid or a salt thereof and a reducing sulfur compound.

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