Method for producing gold-containing material

Abstract

To provide a technique capable of increasing the concentration of gold in reduction melting of incineration ash.SOLUTION: The method for producing a gold-containing material includes reducing and melting incineration ash containing gold by using a reduction-melting furnace including a bottomed cylindrical melting furnace main body, an electrode provided inside the main body so as to be capable of ascending and descending, and an electrode ascending and descending device, the melting furnace main body having a first molten metal layer in which a gold-containing amount is equal to or more than 520 ppm, a discharge port provided vertically above the recessed portion in a side surface portion, and separating the first molten metal layer, a second molten metal layer generated above the first molten metal layer and having a gold-containing amount of less than 5,200 ppm, and a slag layer generated above the second molten metal layer into the first molten metal layer, the second molten metal layer, and the slag layer by descending the electrode at a speed of 15 mm / sec to 45 mm / sec and pushing the electrode into the first molten metal layer; And a third step of taking out the first molten metal layer by allowing the first molten metal layer to overflow from the tapping hole.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing a gold-containing material. [Background technology]

[0002] Conventionally, methods have been proposed for recovering valuable metals from incineration ash containing metals using a reducing melting furnace (for example, Patent Document 1). Metal components reduced in the reducing melting furnace are recovered as molten metal or molten fly ash. Patent Document 1 discloses that the molten metal located below the molten slag contains high-boiling point components such as iron and copper. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-249711 Summary of the Invention [Problem to be solved by the invention]

[0004] While the technology of Patent Document 1 is an excellent technology as a metal recovery method in the reduction melting of incineration ash, there is room for improvement in terms of increasing the gold concentration. Therefore, there is a demand for a manufacturing technology that increases the gold concentration in the reduction melting of incineration ash. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided a method for producing a gold-bearing material, which uses a reducing melting furnace including a cylindrical melting furnace body with a bottom, an electrode provided in the melting furnace body so as to be able to rise and fall, and an electrode lifting device capable of adjusting the lifting speed of the electrode, wherein the melting furnace body has a recess formed in the furnace bottom, in which a first molten metal layer having a gold content of 520 ppm or more is accumulated, and a tapping port provided in a side portion vertically above the recess, and by reducing and melting incineration ash containing gold, the first molten metal layer and the The method includes a first step of separating a first molten metal layer into a second molten metal layer having a gold content of less than 520 ppm and a slag layer formed above the second molten metal layer, a second step of removing the slag layer and the second molten metal layer through the tapping hole, and a third step of lowering the electrode at a speed of 15 mm / sec to 45 mm / sec to force the first molten metal layer into the first molten metal layer, thereby overflowing and removing the first molten metal layer through the tapping hole. This method of producing a gold-containing material involves collecting the first molten metal layer in a recess formed in the bottom of the furnace, and then lowering the electrode at a speed of 15 mm / sec to 45 mm / sec to force the electrode into the first molten metal layer, thereby overflowing and removing the first molten metal layer from a tapping hole located vertically above the recess, thereby achieving a high gold concentration.

[0007] (2) In the method for producing a gold-bearing material described in (1) above, the silver content in the first molten metal layer may be 0.65 mass % or more. This method for producing a gold-bearing material with a high silver concentration can be used.

[0008] (3) In the method for producing a gold-containing material according to (1) or (2), the electrode may be lowered at a speed of 30 mm / sec or more and 45 mm / sec or less in the third step. This method for producing a gold-containing material can achieve a higher gold concentration.

[0009] The present disclosure can be realized in various forms, for example, an apparatus for manufacturing a gold-containing material, a method for controlling an apparatus for manufacturing a gold-containing material, a method for manufacturing a gold-silver-containing material, an apparatus for manufacturing a gold-silver-containing material, a method for controlling an apparatus for manufacturing a gold-silver-containing material, a method for recovering a gold-containing material from incineration ash, a method for recovering a gold-silver-containing material from incineration ash, etc. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram showing the general configuration of an apparatus used in the method for producing a gold-containing material. [Figure 2] FIG. 1 is a process diagram showing a method for producing a gold-containing material. DETAILED DESCRIPTION OF THE INVENTION

[0011] A. Equipment configuration Figure 1 is a schematic diagram showing the general configuration of a reducing melting furnace 10 used in a method for producing a gold-bearing material according to one embodiment of the present disclosure. The reducing melting furnace 10 melts incineration ash containing metals such as iron, copper, gold, and silver under a reducing atmosphere. The incineration ash is obtained, for example, by incinerating general garbage or industrial waste at an incineration facility.

[0012] The furnace for reducing melting 10 comprises a melting furnace body 20, a furnace cover 30, electrodes 40, and an electrode lifting device 45. The furnace for reducing melting 10 of this embodiment is a submerged arc furnace. Note that Fig. 1 shows an example of the configuration of the furnace for reducing melting 10. Also, Fig. 1 is merely a schematic diagram, and the dimensional relationship of the device and the like differ from the actual one.

[0013] The melting furnace body 20 has a cylindrical external shape with a bottom, and includes a furnace bottom 22 and a side portion 24. In this embodiment, the side portion 24 is formed in a cylindrical shape. The inner diameter of the melting furnace body 20 is not particularly limited, but is preferably 2.0 m or more and 5.0 m or less, and more preferably 3.0 m or more and 4.0 m or less. The depth of the melting furnace body 20 is not particularly limited, but is preferably 1.0 m or more and 4.0 m or less, and more preferably 1.5 m or more and 2.5 m or less. The volume of the melting furnace body 20 is not particularly limited, but is preferably 5 m or more.3 More than 30m 3 Preferably less than 10m 3 More than 20m 3 It is more preferable that the following conditions are met: The configuration of the melting furnace body 20 will be described in detail later.

[0014] The furnace lid 30 covers the top of the melting furnace body 20. The furnace lid 30 is provided with a raw material inlet 32 ​​and an exhaust gas pipe 34. The raw material inlet 32 ​​receives the combustion ash 72 transported by the screw feeder 180 into the melting furnace body 20. The combustion ash 72 may be supplied by a belt conveyor or the like, instead of the screw feeder 180. The exhaust gas pipe 34 discharges the exhaust gas and molten fly ash generated by the reducing melting inside the melting furnace body 20. The discharged molten fly ash is captured and collected in a bag filter or electrostatic precipitator (not shown) connected to the exhaust gas pipe 34.

[0015] The electrodes 40 are provided inside the melting furnace body 20 and are capable of being raised and lowered. The electrodes 40 are raised and lowered by an electrode lifting device 45. The electrodes 40 are raised and lowered to adjust the melting power and current. In this embodiment, the electrodes 40 are lowered when the first molten metal layer 91 (described later) is tapped. The electrodes 40 in this embodiment are formed of carbon electrodes and are provided so as to hang down through the furnace lid 30. The furnace 10 for reducing melting in this embodiment is equipped with three electrodes 40. The three electrodes 40 are arranged so as to be positioned at the vertices of an equilateral triangle when viewed from above. In this embodiment, the electrodes 40 are connected to a three-phase AC power supply 190, but may be connected to any power source, such as a single-phase AC power supply or a DC power supply. The number of electrodes 40 is not particularly limited, but in a configuration where the electrodes are connected to the three-phase AC power supply 190, a multiple of three, such as three or six, is preferred. The thickness (diameter) of electrode 40 is not particularly limited, but is preferably 10 inches or more, more preferably 20 inches or more, from the viewpoint of ensuring the volume of electrode 40 to be pushed into first molten metal layer 91. From the same viewpoint, it is preferably 1 / 10 or more, more preferably 1 / 8 or more, and even more preferably 1 / 7 or more of the inner diameter of melting furnace body 20. From the viewpoint of design constraints in reducing melting furnace 10, the thickness of electrode 40 is preferably 40 inches or less, more preferably 30 inches or less, and from the same viewpoint, it is preferably 1 / 3.5 or less, more preferably 1 / 4 or less, and even more preferably 1 / 4.5 or less of the inner diameter of melting furnace body 20.

[0016] The electrode lifting device 45 lifts and lowers the electrode 40. The electrode lifting device 45 is configured to be able to adjust the lifting speed of the electrode 40. The lifting speed of the electrode 40 will be described in detail later.

[0017] In the reducing melting furnace 10, the incineration ash 72 is reduced and melted by energizing the electrodes 40. To melt the incineration ash 72 in a reducing atmosphere, a reducing agent 74 is preferably introduced into the melting furnace body 20 along with the incineration ash 72. The reducing agent 74 is not particularly limited, but is preferably a substance containing carbon as a main component, such as coke. The reducing agent 74 is not limited to coke; it may be a mixture of, for example, carbide powder obtained from combustible waste, or carbide-containing pellets containing carbide and fly ash. When the incineration ash 72 is reduced and melted, a slag layer 80 is formed on top, and a molten metal layer 90 is formed below. The unmelted incineration ash 72 and the reducing agent 74 float on top of the slag layer 80.

[0018] In the method for producing a gold-containing material according to the present disclosure, as described below, a first molten metal layer 91 having a high gold content and a second molten metal layer 92 having a low gold content are separated and recovered from a molten metal layer 90 produced by reduction melting. In the present disclosure, the term "first molten metal layer 91" refers to a molten metal layer 90 having a gold content of 520 ppm or more. The first molten metal layer 91 corresponds to the "gold-containing material" in the present disclosure. The gold content of the first molten metal layer 91 is preferably 550 ppm or more, more preferably 580 ppm or more, even more preferably 600 ppm or more, and even more preferably 650 ppm or more. The main component of the first molten metal layer 91 is preferably copper. The copper content of the first molten metal layer 91 is preferably 65 mass% or more, more preferably 66 mass% or more, even more preferably 68 mass% or more, even more preferably 70 mass% or more, and even more preferably 72 mass% or more. In this disclosure, "ppm" means mass fraction and is synonymous with "g / t." The gold content can be measured by the method described in JIS M8111 (1998). The copper content can be analyzed using an energy dispersive X-ray fluorescence analyzer (EDX).

[0019] First molten metal layer 91 may contain silver. The silver content in first molten metal layer 91 is preferably 0.65 mass% or more, more preferably 0.66 mass% or more, even more preferably 0.68 mass% or more, still more preferably 0.70 mass% or more, and even more preferably 0.72 mass% or more. The silver content can be measured by the method specified in JIS M8111 (1998).

[0020] When the copper concentration (%) is x and the gold concentration (g / t) is y1, first molten metal layer 91 preferably satisfies "y1≧12x-260". When the copper concentration (%) is x and the silver concentration (g / t) is y2, first molten metal layer 91 preferably satisfies "y2≧100x". In either inequality, the value of x is preferably 65 or greater.

[0021] In this disclosure, "second molten metal layer 92" refers to a molten metal layer 90 having a gold content of less than 520 ppm and a specific gravity lower than that of first molten metal layer 91. The copper content of second molten metal layer 92 is preferably less than 65 mass%, more preferably less than 60 mass%, even more preferably less than 55 mass%, and even more preferably less than 55 mass%. Second molten metal layer 92 is preferably composed primarily of iron. Because second molten metal layer 92 has a specific gravity lower than that of first molten metal layer 91, it is formed above first molten metal layer 91.

[0022] The melting furnace body 20 has a recess 26 and a tap hole 28. The recess 26 is formed in the furnace bottom 22. The first molten metal layer 91 accumulates in the recess 26. The depth of the recess 26 is not particularly limited, but from the viewpoint of ensuring a settling distance and improving the separation efficiency between the first molten metal layer 91 and the second molten metal layer 92, it is preferably 200 mm or more, more preferably 250 mm or more, and even more preferably 300 mm or more. Furthermore, from the viewpoint of preventing the load of the reducing melting furnace 10 from becoming excessively large, the depth of the recess 26 is preferably 500 mm or less, more preferably 450 mm or less, and even more preferably 400 mm or less. The depth of the recess 26 may be, for example, 250 mm or more and 400 mm or less. The volume of recess 26 is not particularly limited, but is preferably 5% to 25% and more preferably 10% to 20% of the volume of melting furnace body 20, from the viewpoint of suppressing a decrease in the recovery efficiency of first molten metal layer 91. The size (cross-sectional area and inner diameter) of recess 26 in a direction perpendicular to the depth direction may be the same as or smaller than that of melting furnace body 20.

[0023] The tapping port 28 is provided on the side of the side portion 24 near the hearth 22. The tapping port 28 is provided vertically above the recess 26. The tapping port 28 is configured to be openable and closable, and is normally closed. By opening the tapping port 28 at predetermined intervals, the slag layer 80, first molten metal layer 91, and second molten metal layer 92 produced by reduction melting are discharged to the outside of the melting furnace body 20.

[0024] In this embodiment, a tiltable ladle 50 is installed at the outlet of the tap hole 28. The ladle 50 is, for example, an iron ladle, and has a spout 52 formed at the top. The slag layer 80, first molten metal layer 91, and second molten metal layer 92 discharged from the tap hole 28 are gravity-separated in the ladle 50. By gravity separation, the molten metal is separated into the first molten metal layer 91, the second molten metal layer 92, and the slag layer 80, in that order from the bottom. The slag layer 80 floats in a liquid state on the second molten metal layer 92, making it easy to recover. When the ladle 50 is tilted, the second molten metal layer 92 and the first molten metal layer 91 are separated and recovered into separate iron ladles 60 or the like through the spout 52.

[0025] B. Method for producing gold-containing materials FIG. 2 is a process diagram showing a method for producing a gold-containing material. Prior to producing the gold-containing material, incineration ash 72 containing gold is prepared. The incineration ash 72 used as a raw material may have its basicity, chlorine content, etc. adjusted as necessary. The incineration ash 72 is introduced into the melting furnace body 20 (step P100). In step P100, a reducing agent 74 is introduced into the melting furnace body 20 together with the incineration ash 72. The ratio of the amount of reducing agent 74 to the amount of incineration ash 72 introduced may be adjusted as appropriate.

[0026] The gold-containing combustion ash 72 is subjected to reduction melting to separate it into a first molten metal layer 91, a second molten metal layer 92 formed above the first molten metal layer, and a slag layer 80 formed above the second molten metal layer 92 (step P110). For convenience, step P110 is also referred to as the "first step." In the first step, an electric arc and Joule heat are generated by applying current to the electrode 40. As the reduction melting progresses, the liquid levels of the layers 80, 91, and 92 rise. In the first step, the tap hole 28 is closed. The first step continues for a predetermined time. This time may be set depending on the volume of the melting furnace body 20, the melting temperature, and the like. The time is not particularly limited, but is preferably between 4.5 and 10 hours, and more preferably between 5 and 6 hours, from the perspective of reducing heavy metals and rendering the slag harmless, and from the perspective of economy.

[0027] The slag layer 80 and the second molten metal layer 92 are removed from the tap outlet 28 (step P120). For convenience, step P120 is also referred to as the "second step." In the second step, the tap outlet 28 is opened, and the second molten metal layer 92 and the slag layer 80, which are located vertically at the same level as or above the tap outlet 28, are discharged from the melting furnace body 20 to the outside. Note that, because the tap outlet 28 is located vertically above the recess 26 in which the first molten metal layer 91 accumulates, the first molten metal layer 91 is prevented from flowing out of the tap outlet 28 in the second step.

[0028] In this embodiment, after the second step, the second molten metal layer 92 removed in the second step is weighed (step P122). Then, it is confirmed whether the cumulative discharge amount of the removed second molten metal layer 92 exceeds a preset amount (step P124). If the cumulative discharge amount of the second molten metal layer 92 is less than the preset amount (step P124: NO), the process returns to step P100. On the other hand, if the cumulative discharge amount of the second molten metal layer 92 exceeds the preset amount (step P124: YES), the process proceeds to step P130. Note that the "cumulative discharge amount" refers to the total amount of the second molten metal layer 92 removed during the multiple repetitions of steps P100 to P120. The set amount is not particularly limited, but from the viewpoint of increasing the efficiency of separation between first molten metal layer 91 and second molten metal layer 92, it is preferably at least 0.8 times, more preferably at least 1.0 times, and even more preferably at least 1.2 times the mass of second molten metal layer 92 corresponding to the volume of recess 26. Furthermore, from the viewpoint of suppressing a decrease in the recovery efficiency of first molten metal layer 91, the set amount is preferably at most 2.5 times, more preferably at most 2.0 times, and even more preferably at most 1.7 times the mass of second molten metal layer 92 corresponding to the volume of recess 26.

[0029] The electrode 40 is lowered at a speed of 15 mm / s to 45 mm / s, forcing it into the first molten metal layer 91, causing the first molten metal layer 91 to overflow and be removed from the tap hole 28 (step P130). For convenience, step P130 is also referred to as the "third step." As described above, the electrode 40 is configured to be movable up and down. In the first and second steps, the tip of the electrode 40 does not reach the first molten metal layer 91. In the third step, the electrode 40 is lowered and the tip of the electrode 40 is forced into the first molten metal layer 91, thereby raising the liquid level of the first molten metal layer 91 and causing the first molten metal layer 91 to overflow from the tap hole 28. The molten metal layer 91 removed from the tap hole 28 has a gold content of 520 ppm or more and is a high-grade gold-containing material. The third step may be performed continuously from the second step in which the tapping port 28 is open. The third step is also performed in a state in which the supply of current to the electrode 40 is stopped. Therefore, in the third step, the fluidity of the first molten metal layer 91 decreases.

[0030] The descent speed of the electrode 40 in the third step is set to 15 mm / sec or more to increase the gold concentration in the gold-containing material. A descent speed of 15 mm / sec or more prevents the time required for the third step from becoming excessively long, allowing the first molten metal layer 91 to be recovered before its fluidity decreases excessively. This prevents a decrease in the recovery rate of the first molten metal layer 91. Furthermore, it prevents copper contained in the first molten metal layer 91 that has not been fully recovered from becoming copper sulfide in a low-temperature atmosphere. The descent speed of the electrode 40 in the third step is set to 45 mm / sec or less to prevent the electrode 40 from contacting the hearth bottom 22. The descent speed of the electrode in the third step is preferably 20 mm / sec or more and 45 mm / sec or less, more preferably 25 mm / sec or more and 45 mm / sec or less, and even more preferably 30 mm / sec or more and 45 mm / sec or less. The electrode lowering speed in the third step is preferably faster than the electrode lowering speed executed during reduction melting.

[0031] In this embodiment, the slag layer 80 and second molten metal layer 92 removed in the second step and the first molten metal layer 91 removed in the third step are gravity-separated in the ladle 50. Gravity-separating in the ladle 50 prevents a decrease in recovery efficiency when the layers 80, 91, and 92 are separated and recovered. Completion of the third step (step P130) completes the production of the gold-bearing material. After completion of step P130, the process may return to step P100 to continuously produce the gold-bearing material.

[0032] According to the method for producing a gold-bearing material of this embodiment described above, a first molten metal layer 91 with a high gold content is formed in the recess 26 formed in the hearth 22, and then the electrode 40 is lowered at a speed of 15 mm / sec to 45 mm / sec to push the electrode 40 into the first molten metal layer 91, causing the first molten metal layer 91 to overflow and be removed from the tap hole 28. This makes it possible to prevent the separated first molten metal layer 91 and second molten metal layer 92 from mixing, and as a result, a high-quality gold-bearing material can be recovered.

[0033] In the manufacturing method of this embodiment, the first molten metal layer 91 is discharged from the tapping port 28 that discharges the slag layer 80 and the second molten metal layer 92. This allows the tapping port 28 to be used for both purposes, eliminating the need to provide a separate recovery port for recovering the first molten metal layer 91 near the hearth 22, for example. If a separate recovery port for recovering the first molten metal layer 91 were provided, the recovery port could become clogged and prevent the molten metal from being tapped if the first molten metal layer 91 is tapped infrequently. However, in the manufacturing method of this embodiment, the first molten metal layer 91 is tapped using the tapping port 28, which is opened and closed each time the slag layer 80 and the second molten metal layer 92 are discharged. This prevents the tapping port 28 from becoming clogged even if the first molten metal layer 91 is tapped infrequently.

[0034] Furthermore, in the manufacturing method of this embodiment, the liquid level of first molten metal layer 91 is raised using electrode 40, which is configured to be able to rise and fall in order to adjust the melting power and current. Therefore, electrode 40 can also serve as the structure for raising the liquid level of first molten metal layer 91 and causing it to overflow from outlet 28, eliminating the need for a separate structure for raising the liquid level of first molten metal layer 91. As a result, the structure of the device can be prevented from becoming complicated, and therefore the manufacturing costs of the device and the number of steps required for maintenance can be prevented from increasing.

[0035] Furthermore, in the method for producing a gold-containing material of this embodiment, electrode 40 is lowered to cause first molten metal layer 91 to overflow from tapping port 28 only when the cumulative discharge amount of second molten metal layer 92 exceeds a preset amount. In this manner, first molten metal layer 91 can be tapped after first molten metal layer 91 and second molten metal layer 92 are separated and a predetermined amount of first molten metal layer 91 has accumulated in recess 26, thereby preventing a decrease in the recovery efficiency of first molten metal layer 91.

[0036] C. Variations: The configuration of the apparatus used in the method for producing a gold-containing material according to the above embodiment is merely an example and can be modified in various ways. For example, the reducing melting furnace 10 is not limited to a submerged arc furnace, but may be an electric melting furnace (such as an AC arc melting furnace, an AC electric resistance melting furnace, or a DC electric resistance melting furnace) that melts using electrical energy. Furthermore, for example, the ladle 50 may be omitted.

[0037] Furthermore, the steps in the method for producing a gold-containing material according to the above embodiment are merely examples and can be modified in various ways. For example, steps P122 and P124 may be omitted. Alternatively, instead of steps P122 and P124, the process may proceed to step P130 if a predetermined condition is met, such as whether a predetermined period of time has elapsed, and if not, return to step P100. [Example]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "high-grade metal" refers to a gold content of 520 ppm or more and corresponds to first molten metal layer 91 in the above embodiment, and "molten metal" refers to second molten metal layer 92 in the above embodiment. In the following description, "%" means mass %.

[0039] The reduction melting furnace has a diameter of 3.3m, a depth of 1.8m, and a volume of 15.4m 3 Experiments were conducted using an AC submerged electric furnace. The reducing melting furnace was equipped with three carbon electrodes that could be raised and lowered, arranged at the vertices of an equilateral triangle when viewed from above. The three electrodes were connected to a three-phase AC power supply. The electrodes were connected to an electrode lifting device, and the lifting speed was adjusted. The reducing melting furnace used in Examples 1 and 2 had a recess with a depth of 300 mm formed in the bottom of the furnace and a tapping port provided vertically above the recess. The reducing melting furnace used in the comparative example was a reducing melting furnace in which the recess in the bottom of the furnace was omitted and a tapping port was provided near the bottom of the furnace.

[0040] The raw material incineration ash was waste incineration ash, adjusted so that the slag basicity was 0.7-1.0. The ratio of coke to incineration ash was controlled to 1-4%. The chlorine content was controlled to 2-30%. The melting temperature was 1300-1500°C. The refining time (melting time) from the tapping of molten metal to the next tapping of molten metal was 4.5 hours or more, and new raw materials were added each time molten metal was tapped. The maximum voltage was 275V, and the current was 10,000A.

[0041] Refining operations (melting treatment) were carried out continuously for one month. Each time the molten metal was tapped, the molten metal was weighed and its composition was analyzed. This determined the copper content of the molten metal for each tap. An EDX7000 X-ray fluorescence analyzer (manufactured by Shimadzu Corporation) was used for the composition analysis. In Examples 1 to 3, the electrode was lowered every time the cumulative discharge amount of molten metal reached approximately 30 tons, forcing the high-quality metal accumulated in the recessed portion of the furnace bottom to be tapped. In Examples 1 to 3, the number of times high-quality metal was tapped by electrode lowering was two times in each month of refining operations. The electrode lowering speed in Examples 1 and 2 was 30 mm / sec. The electrode lowering speed in Example 3 was 15 mm / sec. In Comparative Example 1, the electrode lowering to tap the high-quality metal was not carried out. In Comparative Examples 2 to 4, a plasma furnace was used instead of a reducing melting furnace to melt the combustion ash.

[0042] The percentage of high-grade metal obtained in Examples 1 to 3 and Comparative Example 1 was determined. The percentage of high-grade metal (%) was calculated by dividing the total mass of high-grade metal discharged during one month of refining operation by the total mass of incineration ash input during one month of refining operation (the amount of incineration ash processed), and multiplying the result by 100. For convenience, in Comparative Example 1, the molten metal tapped and having a copper content of 65 mass% or more was defined as "high-grade metal." The gold, silver, and copper contents of the high-grade metal were determined for Examples 1 to 3 and Comparative Example 1. The gold, silver, and copper contents of the molten alloy obtained by melting the incineration ash were determined for Comparative Examples 2 to 4. The gold and silver contents were determined using the method specified in JIS M8111 (1998), and the copper content was determined using an EDX7000 X-ray fluorescence analyzer (Shimadzu Corporation). The results are shown in Table 1. In Table 1, "molten metal discharge interval (t)" means the cumulative amount of molten metal discharged between electrode drops, "maximum Cu content (%)" means the copper content of the molten metal with the highest copper content (maximum copper content in the molten metal) among multiple taps of molten metal, and "average Cu content (%)" means the average copper content contained in the molten metal among multiple taps of molten metal.

[0043] [Table 1]

[0044] The results shown in Table 1 reveal the following. In Comparative Example 1, in which the recess was omitted and the electrode was not lowered, the ratio of high-quality metal discharged to the amount of incineration ash processed was extremely low, at 0.07%. Furthermore, in Comparative Example 1, the average Cu content (%) in the molten metal tended to be higher than in Examples 1 to 3, and the maximum Cu content (%) was very high, at 22.6%. These findings suggest that in Comparative Example 1, copper did not concentrate and copper flowed out into the molten metal. It is believed that gold and silver also flowed out into the molten metal in Comparative Example 1.

[0045] In contrast, in Examples 1 to 3, the ratio of high-grade metal discharged to the amount of incineration ash processed was high, ranging from 0.15% to 0.35%. In Examples 1 to 3, the high-grade metal and molten metal were separated, and the high-grade metal was accumulated in a recess in the reducing melting furnace. The electrode was then lowered, causing the high-grade metal to overflow and be tapped from the tap hole. This arrangement prevented the high-grade metal and molten metal from mixing, which is believed to have resulted in a large amount of high-grade metal being recovered. Furthermore, in Examples 1 and 2, the ratio of high-grade metal discharged to the amount of incineration ash processed was particularly high, ranging from 0.28% to 0.35%. This demonstrates that the recovery rate of high-grade metal can be further increased by increasing the electrode descent speed. Furthermore, the high-grade metals of Examples 1 and 2 had higher gold and silver contents than those of Example 3. Therefore, it was shown that by increasing the electrode descent speed, the gold concentration in the high-grade metal can be increased, and the silver concentration can also be increased. Furthermore, in Comparative Examples 2 to 4, in which melting was performed using a plasma furnace, the gold and silver contents in the molten alloy were extremely low compared to the high-grade metals in Examples 1 to 3. Furthermore, the copper content in the molten alloy was also low compared to the high-grade metals in Examples 1 to 3.

[0046] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in each embodiment corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0047] 10... reduction melting furnace, 20... melting furnace body, 22... furnace bottom, 24... side portion, 26... recess, 28... tapping hole, 30... furnace cover, 32... raw material inlet, 34... exhaust gas pipe, 40... electrode, 50... ladle, 52... spout, 60... iron pot, 72... incineration ash, 74... reducing agent, 80... slag layer, 90... molten metal layer, 91... first molten metal layer, 92... second molten metal layer, 180... screw feeder, 190... three-phase AC power supply

Claims

1. A method for producing a gold-containing material, comprising: A reducing melting furnace is used, which includes a bottomed cylindrical melting furnace body, an electrode that is provided in the melting furnace body so as to be able to rise and fall, and an electrode lifting device that can adjust the lifting speed of the electrode. The melting furnace body is a recess formed in the bottom of the furnace, in which a first molten metal layer having a gold content of 520 ppm or more is accumulated; a tapping port provided vertically above the recessed portion in the side portion; and a first step of separating incineration ash containing gold into the first molten metal layer, a second molten metal layer having a gold content of less than 520 ppm and formed above the first molten metal layer, and a slag layer formed above the second molten metal layer by reducing and melting the incineration ash containing gold; a second step of removing the slag layer and the second molten metal layer from the tap hole; a third step of lowering the electrode at a speed of 15 mm / sec or more and 45 mm / sec or less into the first molten metal layer, thereby causing the first molten metal layer to overflow and be removed from the tapping hole; A method for producing a gold-containing material, comprising:

2. 2. The method for producing a gold-containing material according to claim 1, The silver content in the first molten metal layer is 0.65 mass% or more. Methods for producing gold-bearing materials.

3. 3. The method for producing a gold-containing material according to claim 1 or 2, In the third step, the electrode is lowered at a speed of 30 mm / sec or more and 45 mm / sec or less. Methods for producing gold-bearing materials.

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