JP5415013B2 - Method for recovering metals from processed materials - Google Patents

Description

  The present invention relates to a method for recovering a metal from a processed material in order to recover the metal by melting the processed material using a reduction melting furnace.

  In recent years, the need to construct a resource recycling system has increased from the aspect of resource security, and recovery of metals from processed products containing metals such as waste incineration ash, waste of electronic devices such as mobile phones, and waste of dental crown materials Has become a keen eye.

  2. Description of the Related Art Conventionally, as a method of recovering a metal from a processed product containing metal, a method of melting the processed product containing metal in a reduction melting furnace and recovering the metal as molten metal or molten fly ash is known. Since the inside of the reducing and melting furnace is at a high temperature and in a reducing atmosphere, the metal component is reduced and recovered as a simple substance in the molten metal or molten fly ash.

  For example, as a technique for extracting metal from incineration ash, there is a melting process of refuse incineration ash using a submerged arc furnace (for example, Patent Document 1). The submerged arc furnace is a furnace in which the processed material itself is energized through a carbon electrode inserted into the furnace and heated by Joule heat, and can be melted in a strong reducing atmosphere with little oxygen. . For this reason, metal components such as Fe, Pb, Cr, Cd, Zn, Cu, Au, and Ag in the waste incineration ash are reduced to simple metals, and Zn, Pb, Cd, etc., which are low-boiling components, are used as molten fly ash. Fe, Au, Ag, Cu, and the like, which are collected by a dust collector and are high-boiling components, gather under the molten slag and can be collected as valuable materials. Also, the molten slag has extremely less elution of heavy metals than the waste incineration ash before melting, and the safety is high even if landfill disposal is performed as it is. Moreover, since the volume reduction effect is great, the life of the landfill site can be extended.

JP-A-9-196573

  However, in the metal recovery method from the processed material using the conventional reduction melting furnace, what proportion of various metals contained in the processed material is distributed to molten slag, molten metal, and molten fly ash. As for Pb, Zn, Cu, Au, Pd, Pt and Ag, it was known to some extent, but other rare metals and other metals were not studied in detail. For this reason, it has been difficult to efficiently recover metals such as molten slag, molten metal, and rare metals contained in molten fly ash obtained using a reducing melting furnace.

  The present invention has been made in view of the above-described conventional situation, and in a method for recovering metal from a processed material using a reduction melting furnace, various kinds of metals such as molten slag, molten metal, and rare metal contained in molten fly ash are provided. It is an issue to be solved to provide a method for efficiently recovering and using these metals.

  The inventors have made a detailed examination on the relationship between the melting conditions and the distribution ratios of various metals contained in molten slag, molten metal, and molten fly ash in a method for recovering metal from a processed product using a reducing melting furnace. . As a result, by controlling the chlorine content concentration in the processed material containing the metal as a raw material, the temperature of the molten material when the processed material is melted, and the time interval at which the molten material is taken out, molten slag, molten metal, It has been found that the distribution ratio of various metals such as rare metals contained in the molten fly ash can be controlled, and the present invention has been completed.

That is, the method for recovering a metal from the processed product of the present invention includes a charging step of charging a processed product containing metal into a reduction melting furnace, a melting step of melting the processed product to form a molten product, In a method for recovering metal from a processed product including a metal comprising a recovery step of recovering molten fly ash discharged from the reduction melting furnace while recovering molten slag and molten metal by taking out and cooling outside the furnace,
Included in molten slag, molten metal and molten fly ash by controlling the chlorine content concentration in the treated product in the charging step, the temperature of the molten material in the melting step, and the time interval for taking out the molten material in the recovery step The distribution ratio of various metals is controlled.

  In the method for recovering metal from the processed product of the present invention, a reduction melting furnace is used for melting the processed product containing metal. Here, the reductive melting furnace refers to a furnace that melts in a reducing atmosphere. As such a furnace, for example, an electric melting furnace (AC arc melting furnace, AC electric resistance melting furnace, DC electric resistance melting furnace, plasma melting furnace, induction melting furnace, etc.) that melts by electric energy, Fuel combustion type melting furnace that burns and melts fuel such as heavy oil and gas (rotary surface melting furnace, reflection type surface melting furnace, radiation type surface melting furnace, swirl flow type melting furnace, rotary kiln type melting furnace, coke bed type Ash melting furnace), direct melting furnace (coke bed melting furnace, pyrolysis / swirl flow melting furnace, internal melting furnace, etc.). However, in order to perform the melting step in a reducing atmosphere, it is necessary to add a carbonaceous material together and create a reducing atmosphere by the reducing action of the carbonaceous material. The carbonaceous substance is a substance mainly composed of carbon, and usually coke is used, but a carbonaceous substance such as garbage carbide powder obtained from combustible garbage may be mixed. Moreover, you may throw in the carbide | carbonized_material interior pellet which mixed refuse carbide | carbonized_material, fly ash, and incineration ash. Since the inside of the reductive melting furnace is substantially cut off from the outside, a reducing atmosphere is created, the metal content in the treated product is reduced, and a part of the metal sinks to the bottom of the melt as molten metal.

  The processed product containing the metal charged into the reduction melting furnace is melted in the melting step to become a melt. Then, the melt is taken out from the furnace bottom every predetermined time, placed in a container and cooled. At this time, the molten metal precipitates in the lower layer of the melt, and is cooled and solidified with the molten slag floating thereon. The molten fly ash discharged together with the exhaust gas from the reduction melting furnace is collected by a bag filter or the like.

  In the metal recovery method from the processed product of the present invention, the chlorine concentration in the processed product in the charging step, the temperature of the melt in the melting step, and the time interval for taking out the melt in the recovery step are controlled. According to the test results of the inventors, the distribution ratio of various metals contained in molten slag, molten metal, and molten fly ash is the concentration of chlorine in these processed products, the temperature of the melt, and the time for taking out the melt. Therefore, by controlling these factors, it can be selectively collected in molten metal or molten fly ash. If the metal selectively collected in the molten metal or the molten fly ash is recovered in this way, an efficient metal recovery method is obtained.

  For example, the melting temperature of the melt in the melting process is set to 1300 ° C or more and less than 1500 ° C, the time interval for taking out the melt in the recovery process is set to 1 hour or more and less than 5 hours, and the chlorine concentration in the processed product in the charging process is less than 2% If so, most of Bi, Ga, Ge, Sb and Te gather in the molten fly ash. For this reason, in order to recover these metals from the molten fly ash, the reduction melting furnace may be operated under these conditions.

Further, the melting temperature of the melt in the melting step is set to 1300 ° C. or more and less than 1500 ° C., the time interval for taking out the melt in the recovery step is set to 5 hours or more and less than 10 hours, and the chlorine concentration in the treated product in the charging step is set to If it is less than 2%, a large amount of Zn and Pb collects in the molten fly ash (that is, both the concentration and the total amount of Zn and Pb in the molten fly ash increase). For this reason, in order to recover these metals from the molten fly ash, the reduction melting furnace may be operated under these conditions.
Also, under this condition, the concentration and total amount of tungsten in the molten metal are significantly increased. For this reason, in order to collect | recover tungsten from a molten metal, what is necessary is just to operate a reduction | restoration melting furnace on these conditions.

  Furthermore, the melting temperature of the melt in the melting step is set to 1500 ° C. or more and less than 1600 ° C., the time interval for taking out the melt in the recovery step is set to 1 hour or more and less than 5 hours, and the chlorine content concentration in the processed product in the charging step is set to If the content is less than 2%, Cu, Ag, Au, Ge and V in the molten metal are both high in concentration and total amount. For this reason, in order to recover these metals from the molten metal, the reduction melting furnace may be operated under these conditions.

  In addition, the melting temperature of the melt in the melting step is set to 1300 ° C. or more and less than 1500 ° C., the time interval for taking out the melt in the recovery step is set to 1 hour or more and less than 5 hours, and the chlorine concentration in the processed product in the charging step is set to If it is 2% or more and less than 30%, both the concentration and the total amount of Ag in the molten metal are increased. For this reason, in order to collect Ag from the molten metal, the reducing melting furnace may be operated under these conditions.

(Embodiment)
As an embodiment of the present invention, a metal recovery method from waste incineration ash using a submerged arc furnace will be described below. However, it is needless to say that the metal recovery method from the processed product of the present invention can be applied to all the above-described reduction melting furnaces other than the submerged arc furnace.

  In the submerged arc furnace used in the embodiment, a carbon electrode is installed in the furnace. As the power source, a single-phase or three-phase AC power source or DC power source is used, and is energized through a carbon electrode in the furnace. In the submerged arc furnace, the molten slag in the furnace is covered with the incinerated ash that has not yet melted, so that the slag can be melted by the electric arc and the electric resistance Joule heat. Since the molten incineration ash has electrical conductivity, it forms an electric circuit and generates Joule heat when energized. In addition, when coke is added together with incinerated ash, Joule heat is also generated due to the electrical conductivity of the coke. For this reason, if the input amount of coke is increased, the temperature in the furnace rises and the temperature of the molten slag and molten metal also increases. In addition, a furnace lid is necessary to block harmful gas generated from the charged raw material during operation from the outside air. In order to realize the submerged arc electric melting method by sequentially charging raw materials such as incinerated ash during operation, a charging hole is provided in the furnace lid to allow charging of airtight granular raw materials. At the same time, it is preferable to achieve uniform dispersion of the charged granular material. Incinerated ash melts in the furnace, a molten slag layer is formed in the upper layer, and a molten metal layer is formed in the lower layer. And the incinerated ash and coke which have not yet melt | dissolved floated on the molten slag layer. In addition, a tapping outlet is provided at the bottom of the furnace, and molten slag and molten metal are taken out every predetermined time, once transferred to an iron ladle, and the molten slag and molten metal are separated separately from the ladle. Separated into other containers. Further, the exhaust gas generated from the furnace is discharged together with the molten fly ash, and is captured and collected by an electric dust collector or a bag filter.

  In the metal recovery method from the processed product of the present invention, the molten slag is controlled by controlling the chlorine content concentration in the processed product, the temperature of the melt in the melting step, and the time interval for taking out the melt in the recovery step. Controls the distribution ratio of various metals contained in molten metal and molten fly ash. The treated product contains a large amount of sodium chloride, and in order to adjust the salt concentration, the treated product is poured into water to remove the salt, and the treated product from which the salt content has been removed is appropriately used. By mixing, the chlorine concentration can be adjusted. Further, the temperature of the molten slag and the molten metal can be controlled by the amount of coke supplied to the incinerated ash as described above.

(Example)
Hereinafter, an embodiment in which a method for recovering a metal from a treated product of the present invention is further embodied will be described with reference to the drawings.
In the examples, an AC submerged electric furnace having a diameter of 3.3 m, a depth of 1.8 m, and a volume of 15.4 m ³ was used. In this AC submerged electric furnace, as shown in FIG. 1, a cylindrical container-shaped electric furnace main body 1 is covered with a furnace lid 2, and three carbon electrodes 3 a, 3 b, 3 c are positively connected to the furnace lid 2. It is erected so that the height can be adjusted at the position of the apex of the triangle. The carbon electrodes 3a, 3b, 3c are connected to a three-phase AC power source 4. Further, the furnace lid 2 is provided with a raw material charging port 5, so that incineration ash and coke A carried by the screw feeder 6 can be charged into the electric furnace main body 1 from the raw material charging port 5.
An exhaust gas pipe 7 is attached to the furnace lid 2, and the exhaust gas pipe 7 is connected to a bag filter (not shown).
Furthermore, a hot water outlet 8 is connected to the bottom of the electric furnace body 1 so as to be openable and closable, and the molten slag S and the molten metal M of the electric furnace body 1 can be taken out into the iron pan 9.

  The incineration ash was melted by the AC submerged arc furnace configured as described above under the four conditions shown in Table 1 (basic conditions, conditions 1, conditions 2 and 3). The residence time in the table refers to a time interval at which molten slag and molten metal are periodically taken out from the tap 8. In addition, the chlorine content is adjusted by adding desalted incineration ash obtained from a waste incineration facility to the water, extracting the salt to remove the desalted incineration ash, and using the waste incineration ash without any treatment. It adjusted with the mixing ratio with the treatment waste incineration ash. The current was 13,000 A and the voltage was 150V.

  Table 2 shows the temperature of the slag discharged from the hot water outlet 8 under four conditions (basic conditions, condition 1, condition 2 and condition 3) and the calculated ratios of the recovered molten fly ash, molten slag and molten metal.

  After pulverizing the molten fly ash, molten slag and molten metal obtained under the four conditions (basic conditions, condition 1, condition 2 and condition 3) in this way, after pre-treatment (solution) by the method shown in Table 3 The elements contained in the solution were measured by ICP-AES, ICP-MS, atomic absorption, and ion chromatography. The analyzed elements are as shown in Table 4, and the details of the analysis method are as shown in Table 5.

<Analysis results>
FIG. 2 shows the concentration of the metal contained in the molten fly ash, FIG. 3 shows the concentration of the metal in the molten metal, and FIG. 4 shows the concentration of the metal in the molten slag.
Figure 2 shows that Zn, which is abundantly contained in molten fly ash, is condition 1 (increase the amount of coke added to increase the melting temperature), condition 2 (add untreated waste incineration ash and add chlorine to the basic condition) ), And the content under condition 3 (increase the residence time) is high. Among them, the content was the highest under the condition 3 where the residence time was increased to 6 hours. In the case of lead, it was found from the analysis data described later that the contents in the molten fly ash were slightly higher in the conditions 1, 2 and 3 than in the basic conditions.

  Further, as shown in FIG. 3, the content of Cu contained in a large amount in the molten metal was high under the condition 1 (the melting temperature and the reduction degree were increased by increasing the amount of coke added). Further, Au, Ag, and Pb are also in the condition 1, and the content in the molten metal is high. Sb is high in conditions 1 and 2. The contents of Pb and Zn in the slag were higher under the basic conditions than under the conditions 1, 2 and 3. This is presumed to be due to the fact that many Pb and Zn migrated to molten fly ash or molten metal under conditions 1, 2, and 3.

  The optimum conditions for metal recovery are those evaluated only from the viewpoint of the concentration of molten metal and the metal contained in molten fly ash. Whether or not is related to the amount in addition to the concentration. That is, if a valuable metal is contained in a high concentration and is produced in a large amount, it has a resource value (that is, region B in FIG. 5). Therefore, calculate the total amount of metal contained in the molten fly ash or molten metal generated when melting 1 kg of the processed material, and plot it together with the concentration of the metal in the molten fly ash or molten metal. Evaluation of melting conditions was performed.

(Molten fly ash)
The results for the molten fly ash are shown in FIG. Condition 3 is optimal for Zn and Pb in the metal elements distributed to the molten fly ash. Basic conditions are optimal for Bi, Ga, Ge, Sb, and Te. Although the absolute amount of Ag is small, the content is high under conditions 1 and 2.

(Molten metal)
As for the molten metal, as shown in FIG. 7, Cu, Ag, Au, Ge, and V are both high in content and absolute amount under condition 1. W is significantly higher in content and absolute amount in Condition 3 than in other conditions. The content and absolute amount of Sb increase by changing from basic conditions to conditions 1, 2, and 3.

  As described above, in the metal recovery method from the processed product of the present invention, in the metal recovery method from the processed product using the reduction melting furnace, by controlling the melting conditions, the molten slag, the molten metal, or the molten fly ash Various metals such as rare metals contained in can be efficiently recovered and used.

  The present invention is not limited to the description of the embodiments of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

It is a schematic diagram of the submerged arc furnace used in the Example. It is a graph which shows the analysis result of molten fly ash. It is a graph which shows the analysis result of a molten metal. It is a graph which shows the analysis result of molten slag. It is a conceptual diagram which shows optimal melting conditions. It is the graph which plotted the quantity of the metal which generate | occur | produces when melt-treating 1kg of processed materials about molten fly ash, and the density | concentration of the metal of molten fly ash. It is the graph which plotted the quantity of the metal which generate | occur | produces when melt-treating 1kg of processed materials about a molten metal, and the density | concentration of the metal of molten fly ash.

Explanation of symbols

A ... Waste incineration ash C ... Coke (carbonaceous material)
S ... Molten slag M ... Molten metal

Claims (6)

A charging process in which a processed material containing metal is charged into a reduction melting furnace, a melting process in which the processed material is melted to form a molten material, and the molten material is taken out of the furnace and cooled to recover molten slag and molten metal. In the method for recovering metal from the processed material including the metal, comprising a recovery step of recovering the molten fly ash discharged from the reduction melting furnace,
The chlorine concentration in the treated product in the charging step is less than 2% , the temperature of the melt in the melting step is 1300 ° C. or more and less than 1500 ° C., and the time interval for taking out the melt in the recovery step is 1 hour or more and 5 hours A method for recovering a metal from a treated product, characterized by comprising less than A charging process in which a processed material containing metal is charged into a reduction melting furnace, a melting process in which the processed material is melted to form a molten material, and the molten material is taken out of the furnace and cooled to recover molten slag and molten metal. In the method for recovering metal from the processed material including the metal, comprising a recovery step of recovering the molten fly ash discharged from the reduction melting furnace,
The chlorine concentration in the treated product in the charging step is less than 2% , the temperature of the melt in the melting step is 1300 ° C. or more and less than 1500 ° C., and the time interval for taking out the melt in the recovery step is 5 hours or more and 10 hours. A method for recovering a metal from a treated product, characterized by comprising less than A charging process in which a processed material containing metal is charged into a reduction melting furnace, a melting process in which the processed material is melted to form a molten material, and the molten material is taken out of the furnace and cooled to recover molten slag and molten metal. In the method for recovering metal from the processed material including the metal, comprising a recovery step of recovering the molten fly ash discharged from the reduction melting furnace,
The chlorine content concentration in the treated product in the charging step is less than 2% , the temperature of the melt in the melting step is 1500 ° C. or more and less than 1600 ° C., and the time interval for taking out the melt in the recovery step is 1 hour or more and 5 hours A method for recovering a metal from a treated product, characterized by comprising less than A charging process in which a processed material containing metal is charged into a reduction melting furnace, a melting process in which the processed material is melted to form a molten material, and the molten material is taken out of the furnace and cooled to recover molten slag and molten metal. In the method for recovering metal from the processed material including the metal, comprising a recovery step of recovering the molten fly ash discharged from the reduction melting furnace,
The chlorine content concentration in the treated product in the charging step is 2% or more and less than 30% , the temperature of the melt in the melting step is 1300 ° C. or more and less than 1500 ° C., and the time interval for taking out the melt in the recovery step is 1 hour A method for recovering a metal from a treated product, characterized in that it is less than 5 hours . The method for recovering metal from a treated product according to any one of claims 1 to 4 , wherein the reduction melting furnace is a submerged arc furnace. 6. The method for recovering metal from a treated product according to claim 5, wherein the melting temperature of the melt in the melting step is controlled by the amount of carbonaceous material introduced.

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