JP2010248573A - Method and apparatus for treating metal residue - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for treating metal residue by which hexavalent chrome in the metal residue can be suitably removed and thereby treatment cost is suppressed and value of treated metal is raised. <P>SOLUTION: A reaction tank 1 is provided with a first charging line 2 for charging the metal residue containing hexavalent chrome, a second charging line 3 for charging water, an organic substance and an acid and further is provided with a stirring means 4 for stirring the metal residue, water, the organic substance and the acid in the reaction tank. Hexavalent chrome is reduced to trivalent chrome by reaction: Cr<SB>2</SB>O<SB>7</SB><SP>2-</SP>+14H<SP>+</SP>+6e<SP>-</SP>→ 2Cr<SP>3+</SP>+7H<SB>2</SB>O. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a metal residue treatment method and a treatment apparatus for treating a metal residue containing hexavalent chromium.

  Usually, when a metal alloy containing chromium is subjected to electrolytic processing, a metal residue such as processed sludge is generated, and the metal residue contains hexavalent chromium due to a high potential of electrolytic processing.

  For this reason, when a metal residue generated by electrolytic processing is collected by a waste disposal contractor, the waste disposal contractor is paid for it due to the presence of harmful hexavalent chromium and is collected for a fee.

  On the other hand, if harmful hexavalent chromium in the metal residue can be removed, it is possible to have the treated metal residue collected at a waste disposal contractor free of charge or reversely charged. Various methods of reducing to trivalent chromium have been studied.

  As a first example, there is a method of reducing hexavalent chromium by adding heated hydrofluoric acid to a solution containing hexavalent chromium (see, for example, Patent Document 1), and as a second example, hexavalent chromium. There is a method in which carbonaceous raw materials such as carbon powder are added to reducing waste containing carbon and heated at 1700 to 2200 ° C. to reduce hexavalent chromium (for example, see Patent Document 2). As a third example, iron powder There is a method of reducing hexavalent chromium by passing water containing hexavalent chromium through a layer in which sand and sand are mixed (see, for example, Patent Document 3), and a fourth example is a waste material containing hexavalent chromium. There is a method of reducing the hexavalent chromium by mixing an anaerobic fermentation by mixing wheat bran, rice bran, etc. (see, for example, Patent Document 4). A method of reducing hexavalent chromium by mixing sulfuric acid with a reducing agent such as sulfite It is (e.g., see Non-Patent Document 1).

Japanese Patent Laid-Open No. 3-8491 JP-A-11-169814 JP 2004-223472 A JP 2005-177740 A

Pollution Prevention Technology and Regulations Editorial Committee “Pollution Prevention Technology and Regulations Water Quality (5th edition)” Maruzen Publishing, p248-253

  However, in the treatment method of the first example, since heated hydrofluoric acid is used, there is a problem that treatment cannot be easily performed and there is a danger. Moreover, since it is necessary to heat at 1700-2200 degreeC in the processing method of a 2nd example, there exists a problem that very enormous energy is required and processing cost starts. Furthermore, in the third example of the processing method, there is a problem that the quality and value of the processed residue are lowered because foreign matters such as sand remain after the reduction. Furthermore, the treatment method of the fourth example has a problem that it takes a long time to reduce hexavalent chromium because it is treated by anaerobic fermentation. In addition, in the treatment method of the fifth example, since sulfuric acid is mixed with the treated material, the sulfur content remains in the treated residue and the quality is lowered, and the treated residue is collected for a fee to the waste disposal contractor. There was a problem that the value of the residue was lowered when it was made.

  In view of such circumstances, the present invention intends to provide a method and apparatus for treating a metal residue that appropriately removes hexavalent chromium from the metal residue, suppresses the treatment cost, and increases the value of the treated metal residue. It is what.

In the method for treating a metal residue of the present invention, a metal residue containing hexavalent chromium is mixed with an organic substance and an acid,
_{^{Cr 2 O 7 2- + 14H +}} + 6e - → 2Cr 3+ + 7H 2 O
By this reaction, hexavalent chromium in the metal residue is reduced to trivalent chromium, and the hexavalent chromium is removed from the metal residue.

  In the method for treating a metal residue according to the present invention, the organic substance is preferably a volatile organic substance.

  Furthermore, in the method for treating a metal residue according to the present invention, the acid is preferably composed of an acid other than sulfuric acid.

  Furthermore, in the method for treating a metal residue of the present invention, the metal residue is preferably a metal residue generated from electrolytic processing of a chromium-containing alloy.

Processor of metal residues present invention, a metal residue containing hexavalent chromium, a mixture of organic matter and acid _{^{Cr 2 O 7 2- + 14H +}} + 6e - → 2Cr 3+ + 7H 2 O
The reaction process part which performs reaction of this is provided.

  In the metal residue treatment apparatus of the present invention, the reaction treatment section is preferably a reaction vessel that performs a reaction treatment by mixing a metal residue with an organic substance, an acid, and water.

  Furthermore, in the metal residue processing apparatus of the present invention, it is provided with an extraction line for extracting the metal residue from which hexavalent chromium has been removed from the reaction tank, and a return line for returning the organic matter and acid extracted from the reaction tank to the reaction tank. Is preferred.

  Furthermore, in the metal residue processing apparatus of the present invention, the reaction processing unit preferably includes a transport unit that transports the mixture by mixing the metal residue, the organic substance, and the acid, and a heating unit that heats the mixture. .

  According to the method and apparatus for treating a metal residue of the present invention, the hexavalent chromium in the metal residue is reduced to trivalent chromium by organic matter and acid to remove harmful hexavalent chromium from the metal residue. When the metal residue is collected by a waste disposal contractor, it can be collected free of charge or reversely charged. Moreover, since organic substance and acid are used without using heated hydrofluoric acid, hexavalent chromium can be safely reduced and appropriately treated. Furthermore, since the process which heats at 1700-2200 degreeC is unnecessary, a huge energy is unnecessary and it can process at low cost. Furthermore, since an organic substance and an acid are used, it can suppress that foreign materials, such as sand, remain after reduction | restoration, and can prevent that the quality and value of a processed metal residue fall. In addition, since hexavalent chromium in the metal residue is treated with an organic substance and an acid, compared to anaerobic fermentation, the hexavalent chromium can be reduced in a short time and can be appropriately treated. Can play.

It is a whole conceptual diagram which shows the 1st example of the processing method and processing apparatus of the metal residue of this invention. It is a whole conceptual diagram which shows the 2nd example of the processing method and processing apparatus of the metal residue of this invention.

  Hereinafter, a first example of an embodiment of the present invention will be described with reference to FIG.

  The first example of the metal residue processing method and the processing apparatus according to the embodiment includes a reaction tank 1 of a reaction processing section that can be charged with a metal residue containing hexavalent chromium.

  The reaction tank 1 includes a first charging line 2 that can be charged with a metal residue containing hexavalent chromium, and a second charging line 3 that can be charged with water, organic matter, and acid. And a stirring means 4 such as a stirring blade for stirring the metal residue, water, organic matter and acid. Here, the reaction tank 1 is preferably provided with heating means (not shown) such as a heater for heating the inside in order to accelerate the reaction.

  Further, the reaction tank 1 is provided with a take-out line 5 for taking out the treated metal residue after the reaction treatment, and the take-out line 5 includes a separating means such as a filter press for separating the treated metal residue, organic matter and acid. 6 is arranged. Here, the separation means 6 is not limited to the filter press as long as it can separate the processed metal residue, organic matter, and acid, and other methods and configurations may be used.

  Further, the separation means 6 is connected with a conveyance line 7 for conveying the treated metal residue and a return line 8 for returning the separated organic matter, acid and the like to the reaction tank 1.

  Here, the metal residue is not particularly limited as long as it contains hexavalent chromium, but is preferably a metal residue generated from electrolytic processing of a chromium-containing alloy. Further, the chromium-containing metal is not particularly limited as long as it contains chromium, but to give an example, it is Inconel 718 (registered trademark) used for parts of a jet engine, and Inconel 718 (registered). (Trademark) has a composition of nickel 54%, chromium 18%, iron 18.5%, and the like.

  The organic substance is an organic compound that does not correspond to an inorganic compound, and is a chain compound or a cyclic compound. Here, the organic substance may have any functional group such as an alcohol group, a carboxyl group, a formyl group, and a carbonyl group, but preferably does not contain sulfur like thiol or sulfonic acid. The organic substance is preferably a volatile organic substance such as methanol, ethanol, acetone, toluene, benzene, or dichloromethane.

  The acid is a strong acid that is almost completely dissociated in an aqueous solution, and is nitric acid and hydrochloric acid excluding sulfuric acid. Here, when the acid is a weak acid, the proton concentration in the liquid is thin, so that the reaction takes a long time and cannot be used appropriately.

  The operation of the first embodiment of the present invention will be described below.

  When the metal residue containing hexavalent chromium is treated, the metal residue containing hexavalent chromium is charged into the reaction tank 1 from the first charging line 2. Here, the metal residue containing hexavalent chromium generates hexavalent chromium by electrolytic processing of the chromium-containing alloy, while the metal component is contained in a high concentration.

  Next, methanol or / and ethanol is selected as the organic substance, nitric acid is selected as the acid, and methanol or / and ethanol and nitric acid are charged into the reaction tank 1 from the second charging line 3 together with water. At this time, the order of adding water, methanol and nitric acid is not particularly limited before and after the metal residue is charged.

In the reaction tank 1, the stirring unit 4 stirs the metal residue containing hexavalent chromium, water, methanol or / and ethanol, nitric acid,
^{_{Cr 2 O 7 2- + CH 3}} OH + 8HNO 3 → 2Cr 3+ + 6H 2 O + CO 2 + 8NO 3 -
Or / and Cr ₂ O ₇ ²⁻ + 0.5C ₂ H ₅ OH + 8HNO ₃ → 2Cr ³⁺ + 5.5H ₂ O + CO ₂ + 8NO ₃ ⁻
Through the reaction, hexavalent chromium is changed to trivalent chromium.

  Subsequently, after the reaction is completed, water, methanol, and nitric acid are taken out from the reaction tank 1 through the extraction line 5 together with the treated metal residue, and are sent to the separation means 6 such as a filter press and processed by the separation means 6. The metal residue is separated into water, methanol, and nitric acid.

  The treated metal residue separated by the separating means 6 is transported to a predetermined location by the transport line 7 and becomes a treated metal residue after washing. On the other hand, the water, methanol, and nitric acid separated by the separation means 6 are returned to the reaction tank 1 by the return line 8. Here, in the return line 8 or the reaction tank 1, pH and hexavalent chromium may be appropriately measured, and the amount of nitric acid and the like may be adjusted and charged in the next treatment.

  Hereinafter, a test is performed by mixing a metal residue containing hexavalent chromium, an organic substance, and an acid, and shows the results.

[Test 1]
The object to be treated (metal residue) was Cr (VI) 21000 mg / kg-dry in the object to be treated (metal residue), 200 g / L of methanol was used as the organic substance, and 10 M nitric acid was used as the acid. Then, methanol + nitric acid was added to the treatment object at a treatment object / (methanol + nitric acid) = 0.3 and mixed.
[Result 1]
Hexavalent chromium concentration
175mg / kg-dry after heating at 20 ℃ for 2hrs
0.2mg / kg-dry after heating at 80 ℃ for 2 hours
It became. As a result, it is clear that hexavalent chromium has been removed from the object to be treated.

[Test 2]
The object to be treated (metal residue) was Cr (VI) 21000 mg / kg-dry in the object to be treated (metal residue), 200 g / L of methanol was used as the organic substance, and 10 M nitric acid was used as the acid. Then, methanol + nitric acid was added to the treatment object at a treatment object / (methanol + nitric acid) = 0.3, mixed, and allowed to stand at room temperature.
[Result 2]
Hexavalent chromium concentration
2hr storage 16mg / kg-dry
6hr left 0.2mg / kg-dry
15mg left 0.2mg / kg-dry
It became. As a result, it is clear that hexavalent chromium has been removed from the object to be treated.

  Thus, according to the first example of the embodiment as described above, since hexavalent chromium in the metal residue is reduced to trivalent chromium by organic matter and acid, harmful hexavalent chromium is removed from the metal residue. When the treated metal residue is collected by a waste disposal contractor, it can be collected free of charge or reversely. Here, when nickel is included in the metal residue, it can be picked up with a reverse charge, and when the metal residue contains a rare metal such as indium or a noble metal such as gold, it is reverse charged and at a high price. Can be taken over.

  Compared with the conventional example, since organic matter and acid are used without using heated hydrofluoric acid, hexavalent chromium can be safely reduced and appropriately treated. Furthermore, since the process which heats at 1700-2200 degreeC is unnecessary, a huge energy is unnecessary and it can process at low cost. Furthermore, since an organic substance and an acid are used, it can suppress that foreign materials, such as sand, remain after reduction | restoration, and can prevent that the quality and value of a processed metal residue fall. Moreover, since hexavalent chromium in a metal residue is processed with an organic substance and an acid, compared with the case of anaerobic fermentation, a reduction | restoration of hexavalent chromium can be performed in a short time and it can process appropriately.

  In the first example of the embodiment, when the organic substance is a volatile organic substance, the reaction between the metal residue containing hexavalent chromium, the organic substance, and the acid can be suitably performed. Therefore, the reduction of the hexavalent chromium can be easily performed. In addition, it can be performed at low cost, and when the treated metal residue is collected by a waste disposal contractor, it can be collected free of charge or reversely charged.

  In the first example of the embodiment, when the acid is composed of other acids excluding sulfuric acid, the sulfur content in the treated metal residue is suppressed, and the quality and value of the treated metal residue are reduced. It is possible to prevent and collect the treated metal residue to a waste disposal contractor for a reverse charge.

  In the first example of the embodiment, if the metal residue is a residue resulting from electrolytic processing of a chromium-containing alloy, even if it is a metal residue containing hexavalent chromium, other metals may contain useful metals. Therefore, when the treated metal residue is collected by a waste disposal contractor, it can be easily collected free of charge or reversely charged.

  In the first example of the embodiment, the reaction processing unit is a reaction tank 1 in which a metal residue and an organic substance, an acid, and water are mixed and subjected to a reaction treatment. The hexavalent chromium can be reduced easily and at a low cost, and when the treated metal residue is collected by a waste disposal contractor, it can be suitably collected free of charge or reversely charged. be able to.

  In the first example of the embodiment, it is provided with an extraction line 5 for extracting the metal residue from which hexavalent chromium has been removed from the reaction tank 1 and a return line 8 for returning the organic matter and acid extracted from the reaction tank 1 to the reaction tank 1. After the metal residue is subjected to the reaction treatment, the treated metal residue is easily taken out from the reaction vessel 1 by the take-out line 5 and the organic substance and the acid are returned to the reaction vessel 1 by the return line 8 for treatment. Chromium can be reduced easily and at low cost, and when the treated metal residue is collected by a waste disposal contractor, it can be suitably collected free of charge or reversely charged.

  Hereinafter, a second example of the embodiment of the present invention will be described with reference to FIG.

  The second example of the metal residue processing method and processing apparatus according to the embodiment is obtained by changing the reaction processing unit into which the metal residue containing hexavalent chromium can be introduced into another structure.

  The reaction processing section includes a screw feeder conveying means 11 for kneading and conveying a metal residue containing hexavalent chromium, and a heating means 12 such as a heater installed on the outer periphery of the conveying path of the conveying means 11.

  The conveying means 11 of the screw feeder is provided with an inlet 13 into which a metal residue containing hexavalent chromium can be introduced. Inside the conveying means 11, the metal residue is kneaded (stirred) directly below the inlet 13. A kneading screw 14 is provided, and a conveying screw 15 is provided on the downstream side of the kneading screw 14 and conveys the metal residue to the outlet side while further kneading. Further, an intermediate position input line 16 for supplying an organic substance and an acid is connected between the kneading screw 14 and the conveying screw 15 at the intermediate position of the conveying means 11.

  The heating means 12 such as a heater is installed so as to be located around the downstream side of the transport screw 15 of the transport means 11, and heats the downstream side of the transport screw 15 to about 100 ° C. or less.

  Here, as in the first example, the metal residue is not particularly limited as long as it contains hexavalent chromium, but is preferably a metal residue generated from electrolytic processing of a chromium-containing alloy. Further, the chromium-containing metal is not particularly limited as long as it contains chromium, but to give an example, it is Inconel 718 (registered trademark) used for parts of a jet engine, and Inconel 718 (registered). (Trademark) has a composition of nickel 54%, chromium 18%, iron 18.5%, and the like.

  The organic substance is an organic compound that does not correspond to an inorganic compound, and is a chain compound or a cyclic compound. Here, the organic substance may have any functional group such as an alcohol group, a carboxyl group, a formyl group, and a carbonyl group, but preferably does not contain sulfur like thiol or sulfonic acid. The organic substance is preferably a volatile organic substance such as methanol, ethanol, acetone, toluene, benzene, or dichloromethane.

  The acid is a strong acid that is almost completely dissociated in an aqueous solution, and is nitric acid and hydrochloric acid excluding sulfuric acid. Here, when the acid is a weak acid, the proton concentration in the liquid is thin, so that the reaction takes a long time and cannot be used appropriately.

  The operation of the second embodiment of the present invention will be described below.

  When processing the metal residue containing hexavalent chromium, the metal residue containing hexavalent chromium is put into the conveying means 11 of the screw feeder. Here, the metal residue containing hexavalent chromium generates hexavalent chromium by electrolytic processing of the chromium-containing alloy, while the metal component is contained in a high concentration.

  Next, methanol or / and ethanol is selected as the organic substance, nitric acid is selected as the acid, and methanol or / and ethanol and nitric acid are introduced into the conveying means 11 of the screw feeder from the midway position introduction line 16.

In the conveying means 11 of the screw feeder, the metal residue is cut and kneaded by the kneading screw 14, and then the metal residue containing hexavalent chromium, methanol or / and ethanol, nitric acid is kneaded from the conveying screw 15 as a mixture,
Cr ₂ O ₇ ²⁻ + CH ₃ OH + 8HNO ₃ → 2Cr ³⁺ + 6H ₂ O + CO ₂ + 8NO ₃ ⁻
Or / and Cr ₂ O ₇ ²⁻ + 0.5C ₂ H ₅ OH + 8HNO ₃ → 2Cr ³⁺ + 5.5H ₂ O + CO ₂ + 8NO ₃ ⁻
Through the reaction, hexavalent chromium is changed to trivalent chromium.

  Subsequently, after the reaction is completed, the treated metal residue is taken out. Here, in the second example, it is necessary to further separate methanol or / and ethanol and nitric acid from the mixture by kneading under the condition that methanol or / and ethanol and nitric acid are added in the minimum amount without adding water. There is no.

  Thus, according to the second example of the embodiment as described above, it is possible to obtain the same effect as the first example.

  In the second example of the embodiment, when the reaction processing unit includes a transport unit 11 that transports the mixture by mixing a metal residue, an organic substance, and an acid, and a heating unit 12 that heats the mixture, hexavalent chromium. As a result, it is possible to favorably reduce the hexavalent chromium at a low cost and take the treated metal residue to a waste disposal contractor. It is possible to make a good pick-up with no charge or reverse charge. Further, since the conveying means 11 of the screw feeder is used to reduce the methanol or / and ethanol and nitric acid to the minimum necessary amounts for reaction, hexavalent chromium can be reduced at a very low cost.

  In addition, the processing method and processing apparatus of the metal residue of this invention are not limited only to the above-mentioned illustration example, Of course, various changes can be added within the range which does not deviate from the summary of this invention.

DESCRIPTION OF SYMBOLS 1 Reaction tank 5 Extraction line 7 Conveyance line 8 Return line 11 Conveyance means 12 Heating means

Claims (8)

Mixing a metal residue containing hexavalent chromium with an organic substance and an acid,
Cr ₂ O ₇ ²⁻ + 14H ⁺ + 6e ⁻ → 2Cr ³⁺ + 7H ₂ O
A method for treating a metal residue, comprising: reducing hexavalent chromium in the metal residue to trivalent chromium by the reaction, and removing the hexavalent chromium from the metal residue.   The method for treating a metal residue according to claim 1, wherein the organic substance is a volatile organic substance.   The method for treating a metal residue according to claim 1, wherein the acid comprises an acid other than sulfuric acid.   The method for treating a metal residue according to claim 1, wherein the metal residue is a metal residue generated from electrolytic processing of a chromium-containing alloy. Cr ₂ O ₇ ²⁻ + 14H ⁺ + 6e ⁻ → 2Cr ³⁺ + 7H ₂ O by mixing a metal residue containing hexavalent chromium with an organic substance and an acid
An apparatus for treating a metal residue, comprising: a reaction processing unit that performs the above reaction.   6. The apparatus for treating a metal residue according to claim 5, wherein the reaction processing unit is a reaction vessel that performs a reaction process by mixing the metal residue with an organic substance, an acid, and water.   The apparatus according to claim 6, further comprising: a take-out line for taking out the metal residue from which hexavalent chromium has been removed from the reaction tank; and a return line for returning the organic matter and acid taken out from the reaction tank to the reaction tank. Metal residue processing equipment.   6. The processing of a metal residue according to claim 5, wherein the reaction processing unit includes a transport unit that transports the mixture by mixing the metal residue, the organic substance, and the acid, and a heating unit that heats the mixture. apparatus.

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