Melting furnace

Abstract

To provide a fusion furnace capable of efficiently recovering a useful metal capable of being recycled from an objected to be treated containing metal.SOLUTION: A fusion furnace comprises a furnace chamber that fuses an object to be treated containing useful metal, a slag hole that discharges fused slag generated in the fusion treatment, and a hearth that guides the fused slag to the slag hole. The hearth is provided with a retention mechanism that retains the fused metal contained in the fused slag. The retention mechanism is composed of a concave part formed in front of the slag hole in the flat hearth, and is configured to cause the fused metal to settle in the concave part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a melting furnace capable of efficiently recovering valuable metals contained in an object to be processed.

Background Art

[0002] Miscellaneous wastes such as organic sludge such as sewage sludge, livestock manure, and methane fermentation residues of food waste, combustibles such as plastics, paper, RPF, and recycling residues containing plastics and metals, and incombustibles such as incineration ash, contaminated soil, waste glass, waste pottery, and asbestos are melted and processed in a melting furnace as objects to be processed.

[0003] For example, a surface melting furnace is configured to include a furnace chamber in which a slag discharge port is formed and an object to be processed supply mechanism that supplies an object to be processed toward the furnace chamber, and the object to be processed supplied to the furnace chamber by the object to be processed supply mechanism melts from the surface and flows down to the slag discharge port, and miscellaneous wastes are melted and processed.

[0004] In such a melting furnace, in order to volatilize heavy metals contained in the object to be processed and remove them from the slag, the inside of the furnace is adjusted to a reducing atmosphere.

[0005] Further, Patent Document 1 proposes a surface melting furnace that suppresses the volatilization of phosphorus contained in an object to be processed during melting treatment. The surface melting furnace includes a furnace chamber in which a burner and an air supply mechanism are installed and a slag discharge port is formed, and an object to be processed supply mechanism that supplies an object to be processed from an object to be processed storage unit provided in communication with the furnace chamber to the furnace chamber. The object to be processed contains phosphorus and combustibles, and an edge air supply mechanism that supplies air toward the surface of the object to be processed in the furnace chamber in the vicinity where the furnace chamber and the object to be processed storage unit communicate is provided.

[0006] According to the surface melting furnace, the fixed carbon content remaining near the surface of the object to be processed due to thermal decomposition of the combustible is burned by the air supplied from the edge air supply mechanism toward the surface of the object to be processed, and further, the reduction reaction of phosphorus compounds and phosphoxides is suppressed by the remaining oxygen, thereby suppressing the volatilization of phosphorus.

[0007] In Patent Document 2, when melting a phosphorus-containing substance such as sewage sludge, a melting method of a phosphorus-containing substance is proposed in which the phosphorus component contained in the phosphorus-containing substance is suppressed from volatilizing into the exhaust gas and the phosphorus component is captured in the slag. The melting method includes a pretreatment step of adjusting the water content with respect to a phosphorus-containing substance containing phosphorus in an amount of 0.04 wt% or more in terms of dry matter, a melting step of charging the phosphorus-containing substance whose moisture has been adjusted in the pretreatment step into a melting furnace and melting it, and a cooling step of cooling and solidifying the slag melted in the melting step.

[0008] Then, the melting method executes an iron compound addition step of adding a divalent or trivalent iron compound to the phosphorus-containing substance before, during, or after the pretreatment step, thereby preventing the volatilization of the phosphorus component contained in the phosphorus-containing substance in the melting step, and capturing it in the slag while suppressing the transfer of the phosphorus component to a metal phosphorus compound containing iron phosphide.

[0009] When such a mixture of a divalent or trivalent iron compound and a phosphorus-containing substance is charged into a melting furnace, a melting point lowering action is exhibited by the charged ferrous oxide (FeO) or ferrous oxide (FeO) generated from the divalent or trivalent iron compound during the melting process. For example, at a melting temperature of about 1300 °C, a fluidity of 60% or more can be ensured in a range wider than the preferable basicity of 0.4 to 0.8 of the phosphorus-containing substance with respect to iron, and moreover, the volatilization of the phosphorus component in the material to be melted is suppressed and phosphorus is captured in the slag in a form other than a metal phosphorus compound.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0011] As described above, in order to suppress the volatilization of useful metals contained in the object to be processed, the furnace atmosphere is adjusted to an oxidizing atmosphere, or in order to suppress the alloying of useful metals contained in the object to be processed and confine them in the slag, a method of operating a melting furnace in which a melting aid is added is known. In this specification, a single metal or alloy that can be recovered from the slag and reused among the metals contained in the object to be processed is referred to as a useful metal. Useful metals include, in addition to iron, nickel, copper, etc., precious metals such as silver, gold, platinum, and their alloys.

[0012] In order to recover the useful metals contained in the object to be processed, the slag obtained by melting treatment is pulverized and subjected to separation treatment such as specific gravity separation or magnetic separation, whereby the useful metals can be recovered from the slag.

[0013] However, the particle size of the metals contained in the slag is very small, and the recovery ratio of the metals by specific gravity separation or magnetic separation is low. Further improvement has been desired from the viewpoint of improving the metal recovery rate.

[0014] An object of the present invention is to provide a melting furnace capable of efficiently recovering reusable useful metals from an object to be processed containing metals.

Means for Solving the Problems

[0015] To achieve the above object, a first characteristic configuration of the melting furnace according to the present invention is a melting furnace including a furnace chamber for melting an object to be processed containing useful metals, a slag discharge port for discharging the molten slag generated by the melting treatment, and a furnace bottom for guiding the molten slag to the slag discharge port, The melting furnace is composed of an inner cylinder that divides the furnace chamber, an outer cylinder that is arranged on the outer periphery of the inner cylinder, a storage section for the object to be treated that is formed between the inner cylinder and the outer cylinder, and a rotary surface melting furnace in which the object to be treated that is fed from the storage section to the furnace chamber is melted from the surface by the relative rotation of the inner cylinder and the outer cylinder, and the molten slag flows down and is discharged from the slag discharge port that is formed in the center of the hearth, on the furnace bottom, The recess formed in front of the slag outlet a retention mechanism for retaining the molten slag and causing the molten metal contained in the molten slag to settle and a second dam on the outer periphery of the recess for preventing the inflow of the unmelted processing object into the recess; is provided.

[0016] The objects to be treated that are cut out from the storage section into the furnace chamber are piled up in a mortar shape, and the molten slag that is produced by melting and processing the objects on the surface flows down toward the slag outlet formed in the center of the hearth. When the molten slag flows into a recess formed in the hearth just before the slag outlet, the recess acts as a basin of hot water, thickening the molten layer of the molten slag and slowing down the flow rate of the molten material. Therefore, in the recess, a small amount of molten metal suspended in the molten slag and having a higher specific gravity than the molten slag sinks, while the molten slag with a lower specific gravity flows down toward the slag outlet. If such a state continues, the molten metal that has settled in the recess and become concentrated will accumulate in the form of a lump. At this time, if the unmelted objects to be treated that have accumulated in a mortar shape inside the furnace chamber flow into the recess, it becomes difficult to properly accumulate the molten metal in the recess. Even in such a case, by providing a second dam around the outer periphery of the recess, the molten material that has overflowed the second dam can flow into the recess while blocking the unmelted objects to be treated.

[0017] The second characteristic configuration is a melting furnace comprising a furnace chamber for melting a processing object containing useful metals, a slag outlet for discharging molten slag generated by the melting process, and a hearth for guiding the molten slag to the slag outlet, the melting furnace being composed of an inner cylinder that divides the furnace chamber, an outer cylinder arranged on the outer periphery of the inner cylinder, a storage section for the processing object formed between the inner cylinder and the outer cylinder, and a rotary surface melting furnace in which the processing object cut from the storage section to the furnace chamber is melted from the surface by the relative rotation of the inner cylinder and the outer cylinder, and the molten slag flows down and is discharged from the slag outlet formed in the center of the hearth, Among the hearths formed on the plane, at the Around it in an arc shape in plan view formed , are distributed concentrically first weir and a second weir body for preventing the inflow of unmelted material to be treated on the outer periphery of the first weir body. by , retaining the molten slag to precipitate the molten metal contained in the molten slag a retention mechanism is configured to precipitate molten metal on the upstream side of the first weir By arranging the first weir bodies concentrically around the tapping port, the residence time in the furnace chamber can be increased for the slag melted from the surface of the object to be processed, and the accumulation opportunity due to sedimentation can be efficiently ensured for the molten metal suspended in the molten slag during retention. The molten slag blocked by the first weir body flows along the first weir body formed in an arc shape in plan view and flows out from the edge of the first weir body to the tapping port. At this time, when the unmelted object to be processed deposited in a mortar shape inside the furnace chamber flows into the first weir body, it becomes difficult to ensure the accumulation opportunity due to sedimentation for the molten metal. Even in such a case, by providing a second weir body on the outer periphery of the first weir body, while blocking the unmelted object to be processed with the second weir body, the molten slag that overflows the second weir body or flows down from the edge of the second weir body can be guided to the first weir body point.

[0018] Three .

[0019] Same as the One characteristic configuration is, in addition to the characteristic configuration of the above-mentioned Four , that it is provided with a take-out mechanism for taking out the molten metal sedimented in the recess.

[0020] Since a cooling mechanism is provided on the hearth near the slag discharge port to avoid damage to the refractory due to high temperature, if the molten metal sedimented and accumulated in the recess solidifies due to cooling, the function of the recess to precipitate and accumulate molten metal will be impaired thereafter. Even in such a case, by providing a take-out mechanism, the molten metal sedimented in the recess can be taken out, and the intended function of the recess is maintained.

[0021] Same as the Three characteristic configuration is, in addition to the characteristic configuration of the above-mentioned Five , that the take-out mechanism is composed of a guide flow path that communicates with the bottom of the recess and allows molten metal to flow out.

[0022] By communicating the guide flow path with the bottom of the recess, the metal sedimented and accumulated in the recess can be made to flow out in a molten state.

[0023] Same as the Three characteristic configuration is, in addition to the characteristic configuration of the above-mentioned Six , that the take-out mechanism is composed of a gas nozzle that communicates with the bottom of the recess and overflows molten metal from the recess.

[0024] A gas nozzle is communicated with the bottom of the recess, and by injecting gas, the molten metal that has settled and accumulated in the recess overflows from the recess and is guided to the slag outlet. Note that an inert gas such as nitrogen is preferably used as the gas.

[0025] Same as the One characteristic configuration is that, in addition to any of the characteristic configurations of the above-described Three , Five to Seven , a heating mechanism for remelting the metal that has settled and solidified in the recess is provided.

[0026] Even if the molten metal that has settled and accumulated in the recess solidifies, by remelting it again by the heating mechanism, the viscosity of the molten metal is reduced, and it can be flushed toward the slag outlet by the flow of the molten slag flowing into the recess from the upstream side. Note that as the heating mechanism, for example, a combustion burner that heats from the space immediately above the recess, a heater arranged near the bottom of the recess, etc. can be appropriately configured.

[0027] Same as the Three characteristic configuration is that, in addition to the characteristic configuration of the above-described Eight , a take-out mechanism for taking out the molten metal that has settled near the upstream side of the first weir body is provided.

[0028] A cooling mechanism is provided on the furnace bottom near the slag outlet to avoid damage to the refractory due to high temperature. Therefore, when the molten metal that has settled and accumulated on the upstream side of the first weir body solidifies due to cooling, the function of the first weir body, which is the accumulation of the molten metal due to sedimentation, is impaired with respect to the molten slag that has flowed down thereafter. Even in such a case, by providing a take-out mechanism, the molten metal that has settled on the upstream side of the first weir body can be taken out, and the intended function of the first weir body is maintained.

[0029] Same as the Seven characteristic configuration is that, in addition to the characteristic configuration of the above-described Nine , the take-out mechanism is composed of a guide flow path that communicates with the bottom near the upstream side of the first weir body and allows the molten metal to flow out.

[0030] By connecting the guide channel to the bottom of the concave portion, the metal that has settled and accumulated on the upstream side of the first weir can be caused to flow out in a molten state.

[0031] Same as the Seven The characteristic configuration is, in addition to the characteristic configuration of the above-described Ten that the take-out mechanism is configured by a gas nozzle that communicates with the bottom near the upstream side of the first weir and overflows molten metal from the first weir.

[0032] By connecting a gas nozzle to the bottom near the upstream side of the first weir and injecting gas, the molten metal that has settled and accumulated near the upstream side of the first weir flows along the first weir and is guided to the slag outlet. Note that an inert gas such as nitrogen is preferably used as the gas.

[0033] Same as the Seven The characteristic configuration is, in addition to any of the characteristic configurations of the above-described third, Nine from the

Figure 1

[0034] Even if the molten metal that has settled and accumulated on the upstream side of the first weir solidifies, by remelting it again by the heating mechanism, the viscosity of the molten metal is lowered, and it can be pushed toward the slag outlet by the flow of the molten slag flowing from the upstream side toward the first weir. Note that as the heating mechanism, for example, a combustion burner that heats from the upper space above the upstream side of the first weir, a heater disposed near the bottom of the upstream side of the first weir, etc. can be appropriately configured.

Advantages of the Invention

[0035] As described above, according to the present invention, it has become possible to provide a melting furnace capable of efficiently recovering reusable useful metals from a processing object containing metal.

Brief Description of the Drawings

[0036]

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0037] Hereinafter, embodiments of the melting furnace according to the present invention will be described

[0038] [Configuration of Surface Melting Furnace] FIG. 1 shows a rotary surface melting furnace 1 which is an example of a surface melting furnace. The surface melting furnace 1 is a furnace for melting various wastes, and the treatment objects include organic sludges such as sewage sludge, livestock manure, and methane fermentation residues of food waste, combustibles such as plastics, paper, RPF, and recycling residues containing plastics and metals, incombustibles such as incineration ash, contaminated soil, waste glass, waste pottery, and asbestos. The metals include useful metals such as iron, nickel, copper, silver, and gold, as well as heavy metals. Hereinafter, the case where a mixture of a recycling residue containing plastics and metals and incineration ash is the treatment object will be described, but other wastes may be included.

[0039] The rotary surface melting furnace 1 includes an inner cylinder 2 and an outer cylinder 3 arranged concentrically, and a storage part 15 for the treatment object is formed between the inner cylinder 2 and the outer cylinder 3. A furnace ceiling 5 is provided inside the inner cylinder 2, and a furnace bottom 6 extending from the lower part of the outer cylinder 3 toward the center is formed. A slag discharge port 7 is formed at the central part of the furnace bottom 6, and a water-cooled cooling mechanism 14 is arranged around the slag discharge port 7. A furnace chamber 4 is formed in the space surrounded by the inner cylinder 2, the furnace ceiling 5, and the furnace bottom 6, and the inner walls thereof are covered with refractories. The inner cylinder 2 and the outer cylinder 3 are hermetically configured by a water seal mechanism 13.

[0040] It is provided with a screw conveyor mechanism 11 for conveying the treatment object to the storage part 15, and the treatment object is dropped and supplied to the storage part 15 through a double damper mechanism 12 so that outside air does not flow into the furnace chamber 4.

[0041] When the outer cylinder 3 rotates relative to the inner cylinder 2, the treatment object stored in the storage part 15 is put into the furnace chamber 4 by the cutting blades 9 provided at the lower part of the inner cylinder 2, and the treatment object is distributed in a mortar shape toward the slag discharge port 7. The inside of the furnace is heated to a high temperature of about 1300 °C by two combustion burners 8 provided on the central side of the furnace ceiling 5, and the treatment object melts from the surface and flows down toward the slag discharge port 7 on the downstream side from the upstream side. In addition, a plurality of nozzles 10 for supplying combustion air are provided on the outer side in the radial direction of the furnace ceiling 5.

[0042] The object to be processed fed into the furnace chamber 4 first has its combustible components such as waste plastics vaporized on the upstream side and then undergoes gas combustion by the combustion air or oxygen gas supplied from the nozzle 10. At this time, the upstream side becomes a weakly reducing atmosphere, and the heavy metals contained in the object to be processed are reduced and volatilized, flowing down to the secondary combustion chamber together with the exhaust gas. The object to be processed heated by the radiant heat from the combustion burner 8 and the furnace ceiling 5 melts from the surface and flows down toward the slag discharge port 7. At this time, the thickness of the molten layer is several tens of millimeters. The reference symbol A in FIG. 1 indicates the unmolten object to be processed, the reference symbol B indicates the molten layer, and the reference symbol C indicates the gasification combustion part.

[0043] FIG. 1 exemplifies the figures showing waste plastics, incineration ash, metal, molten slag, and molten metal contained in the object to be processed. Under the weakly reducing atmosphere, the useful metals contained in the object to be processed melted in the furnace chamber 4 flow down toward the slag discharge port 7 in a state of being suspended as molten metal of an alloy in the molten slag without being oxidized.

[0044] Below the slag discharge port 7, a conveying mechanism equipped with a water tank for cooling the molten slag is arranged and discharged outside the furnace as granulated slag. Further, the combustion gas generated in the furnace chamber 4 is burned in the secondary combustion chamber provided on the downstream side of the slag discharge port 7, purified by the exhaust gas treatment facility, and then exhausted to the atmosphere from the chimney. The furnace chamber 4 is maintained at a negative pressure by the induced draft fan arranged on the upstream side of the chimney.

[0045] [Configuration of the retention mechanism] FIG. 2(a) shows the cross-sectional view of the main part of the surface melting furnace 1. The object to be processed A cut out from the storage part 15 formed between the outer cylinder 3 and the inner cylinder 2 accumulates in a mortar shape in the furnace chamber 4. A molten layer B is formed on its surface, and the molten slag flows down toward the slag discharge port 7. In the molten slag, a small amount of molten metal M in which the useful metals contained in the object to be processed A are melted is dispersed in a suspended state.

[0046] As shown in FIG. 2(b), if the entire hearth 6 is formed as a flat surface, a small amount of molten metal M will drip from the slag discharge port 7 together with the suspended molten slag. This means that the slag solidified as granulated slag will contain small particles of molten metal M dispersed therein. Even if the slag is crushed and separated by gravity, it will be very difficult to efficiently recover the useful metals.

[0047] Therefore, a retention mechanism for retaining the molten slag is formed in the hearth 6. When the molten slag generated in the melting process flows down toward the slag discharge port 7, the retention mechanism in the hearth 6 retains the molten slag. In the retention area, a small amount of molten metal with a higher specific gravity than the molten slag settles, and gradually a part with a high metal concentration is formed in the slag. Then, the molten slag with a low specific gravity eventually flows down toward the slag discharge port 7. When a part with a high metal concentration is formed in the slag in this way, for example, it can be easily separated by specific gravity or magnetic force from the slag that is later cooled and solidified and crushed, and the recovery efficiency of useful metals is increased.

[0048] 2(c) and 3(a) show an example in which a retention mechanism is formed by a recess 6A formed in front of the slag discharge port 7 of the hearth 6 formed on a flat surface. When the molten slag generated by the melting process flows into the recess 6A, the recess 6A acts as a basin, the molten layer of the molten slag becomes thicker, and the flow rate of the molten material decreases. Therefore, a small amount of molten metal suspended in the molten slag and having a higher specific gravity than the molten slag sinks in the recess, while the molten slag with a lower specific gravity flows down toward the slag discharge port 7. If such a state continues, the concentration of the molten metal that has settled in the recess 6A increases and accumulates in a lump. If a large coagulation force acts, it may coagulate into a lump of metal with a large particle size.

[0049] As shown in Fig. 3(a), since the recess 6A is formed in an annular shape in plan view around the slag outlet 7, the molten slag passes through the recess 6A before reaching the slag outlet 7, and the molten metal accumulates. Note that the recess 6A does not necessarily need to be formed continuously in an annular shape around the slag outlet 7. As shown in Fig. 3(b), a plurality of recesses 6A may be arranged in an annular shape in plan view around the slag outlet 7. Fig. 3(b) shows an example composed of two, but it may be three or more.

[0050] As shown in Fig. 2(d), it is preferable to provide a weir 62 on the outer periphery of the recess 6A to prevent the unmolten object to be treated A from flowing into the recess 6A. When the unmolten object to be treated A deposited in a mortar shape inside the furnace chamber 4 flows into the recess 6A, it becomes difficult to accumulate molten metal in the recess 6A. By providing the weir 62 on the outer periphery of the recess 6A, while blocking the unmolten object to be treated A, the melt overflowing the weir 62 can be made to flow into the recess 6A. The weir 62 serves as the second weir of the present invention.

[0051] As shown in Fig. 4(a), a cooling mechanism 14 is provided on the furnace floor near the slag outlet 7 to avoid damage to the refractory due to high temperature. Therefore, when the molten metal sedimented in the recess 6A solidifies by cooling, there is a risk that the functions of the recess 6A, such as the increase in concentration and accumulation due to the sedimentation of the molten metal, will be impaired. Therefore, it is preferable to provide a take-out mechanism for taking out the molten metal sedimented in the recess 6A.

[0052] Fig. 4(b) shows a guide channel 70 as an example of the take-out mechanism. The guide channel 70 communicates with the bottom of the recess 6A and is configured to allow the molten metal to flow out of the recess 6A. A valve 71 is provided in the guide channel 70 and is adjusted to open the valve 71 to take out the molten metal when a predetermined amount of molten metal accumulates in the recess 6A, and then close the valve 71.

[0053] FIG. 4(c) shows a gas nozzle 72 as an example of the discharging mechanism. The gas nozzle 72 communicates with the bottom of the recess 6A and is configured to inject gas into the recess 6A before the settled metal solidifies. By injecting gas, the molten metal that stays, settles, and accumulates in the recess 6A overflows from the recess 6A and is guided to the tapping spout 7. Inert gases such as nitrogen gas and argon gas are preferably used as the gas. Note that it is preferable to provide a shutter mechanism that opens the nozzle 72 when injecting gas and closes the nozzle when stopping the gas injection.

[0054] FIG. 4(d) shows a heating mechanism 74 as an example of the discharging mechanism. As the heating mechanism 74, a combustion burner that heats the metal M that has settled and solidified in the recess 6A from the space immediately above the recess 6A can be used. The heating burner can be attached to the furnace ceiling 5 so as to be movable up and down, and periodically descends directly above the recess 6A to remelt the metal M solidified in the recess 6A, thereby reducing the viscosity of the molten metal and allowing it to be washed away toward the tapping spout 7 by the flow of molten slag flowing into the recess 6A from the upstream side.

[0055] As the heating mechanism, it is also possible to arrange a heater near the bottom of the recess 6A in addition to the combustion burner.

[0056] The recess 6A preferably has an arcuate cross-section, and the depth is preferably in the range of 100 to 200 mm. Also, the width of the recess 6A is preferably in the range of 10% to 20% of the radius of the furnace bottom 6 and in the range of 200 to 500 mm.

[0057] As described above, a plurality of examples of the discharging mechanism have been described, but it is also possible to employ a plurality of each discharging mechanism. For example, when the metal settled in the recess 6A solidifies, after remelting the metal by the heating mechanism 74, gas may be injected from the gas nozzle 72 by combining the heating mechanism 74 and the gas nozzle 72. Also, when the metal settled in the recess 6A solidifies, after remelting the metal by the heating mechanism 74, the molten metal may be taken out from the guide channel 70 by combining the heating mechanism 74 and the guide channel 70.

[0058] By operating any of the above-described take-out mechanisms at an appropriate time during furnace operation or just before the furnace stops, the metal M that has settled in the recess 6A can be appropriately taken out. Further, after the furnace stops, the operator may be configured to perform an operation of scraping off the metal that has settled in the recess 6A.

[0059] [Other configurations of the retention mechanism] FIGS. 5(a) and 5(b) show other embodiments of the retention mechanism.

[0060] A pair of first weirs 61 formed in an arc shape in plan view are dispersedly arranged on concentric circles so as to surround the tapping hole 7 on the front side of the tapping hole 7 in the hearth 6 formed in a plane.

[0061] When the object to be processed cut out from the storage section accumulates in a mortar shape in the furnace chamber 4 and the molten slag generated by melting treatment on its surface flows downward toward the tapping hole 7 formed in the central portion of the hearth 6, it is blocked by the first weir 61 arranged around the tapping hole 7 and stays, and then bypasses the first weir 61 and flows down to the tapping hole 7. In the retention area, a small amount of molten metal suspended in the molten slag and having a specific gravity greater than that of the molten slag settles, and gradually a portion with a high metal concentration is formed in the slag. Then, the portion with a high metal concentration is discharged from the tapping hole 7 together with the molten slag.

[0062] Since the first weirs 61 are dispersedly arranged on concentric circles around the tapping hole 7, it is possible to gain a residence time in the furnace chamber 4 for the slag melted from the surface of the object to be processed, and by settling the molten metal suspended in the molten slag during residence, it is possible to efficiently increase the concentration of the metal component and ensure an opportunity for accumulation. The molten slag blocked by the first weir 61 flows in the circumferential direction along the arc-shaped surface of the first weir 61 and flows out from the edge of the first weir 61 to the tapping hole 7. The dashed-dotted line shown in FIG. 5(a) indicates the flow of the molten slag.

[0063] In this example, a pair of arc-shaped weirs 61 are arranged on a concentric circle with the center of the slag outlet 7 in plan view. However, the number of the arc-shaped weirs 61 may be three or more. Also, a plurality of arc-shaped weirs 61 may be installed in multiple stages in the radial direction on a concentric circle with the center of the slag outlet 7 in plan view. In that case, by arranging the gaps between the weirs 61 arranged on the inner side in the radial direction to be covered by the weirs 61 arranged on the outer side in the radial direction, it is possible to avoid the molten slag flowing down toward the slag outlet 7 in a straight path. Further, the arc shape is not limited to a circular arc, and includes, for example, a shape like the letter "C" of the alphabet, and further includes a concept such as a shape in which a plurality of rectangular weirs in plan view are connected on a concentric circle and become substantially arc-shaped as a whole.

[0064] As shown in FIGS. 6(a) and 6(b), it is preferable to provide a second weir 62 that blocks the inflow of the unmelted object to be processed into the retention mechanism (the first weir 61) on the outer periphery of the first weir 61.

[0065] When the unmelted object to be processed A deposited in a mortar shape inside the furnace chamber 4 flows into the first weir 61, it becomes difficult to ensure a good retention opportunity for the molten metal M. By providing the second weir 62 on the outer periphery of the first weir 61, while blocking the unmelted object to be processed A with the second weir 62, only the molten slag that overflows the second weir 62 or flows down from the edge of the second weir 62 can be retained by the first weir 61.

[0066] Note that the first weir 61 may be composed of a single annular weir 61 that surrounds the slag outlet 7, and the molten metal may be settled and accumulated upstream of the weir 61, and the molten slag may be configured to overflow the weir 61 and flow down to the slag outlet 7. In this case, the height of the annular weir 61 may be formed to be constant in the circumferential direction or may be made partially different. The molten slag can overflow from a portion where the height is partially low. Note that such an aspect regarding the height of the weir 61 is also applicable to the arc-shaped weir 61 described above.

[0067] In any aspect, it is preferable to be provided with a take-out mechanism for taking out the molten metal that has settled near the upstream side of the first dam body 61, in the same manner as described with reference to FIGS. 4(a) to 4(d). When a plurality of dam bodies 61 are dispersedly arranged concentrically with the tapping port 7, although the molten metal flows out to the tapping port 7 together with the molten slag from the edge of each dam body 61, it is because the molten metal that settles on the hearth 6 side may solidify due to the influence of the cooling mechanism 14.

[0068] As shown in FIG. 7(a), as the take-out mechanism, it can be configured by a guide flow path 70 that communicates with the bottom near the upstream side of the first dam body 61 and allows the molten metal to flow out.

[0069] As shown in FIG. 7(b), as the take-out mechanism, it can be configured by a gas nozzle 72 that communicates with the bottom near the upstream side of the first dam body 61 and allows the molten metal to flow out from the upper reaches of the first dam body 61 toward the tapping port 7. By communicating the gas nozzle 72 with the bottom near the upstream side of the first dam body 61 and injecting gas, the molten metal that has settled and accumulated near the upstream side of the first dam body flows along the first dam body and is guided to the tapping port. Note that an inert gas such as nitrogen is preferably used as the gas.

[0070] As shown in FIG. 7(c), it is preferable to provide a heating mechanism for remelting the metal that has settled and solidified near the upstream side of the first dam body 61.

[0071] Even if the molten metal that has settled and accumulated on the upstream side of the first dam body solidifies, by remelting it again by the heating mechanism, the viscosity of the molten metal is reduced, and it can be pushed toward the tapping port by the flow of the molten slag flowing from the upstream side toward the first dam body. As the heating mechanism 74, for example, it can be appropriately configured such as a combustion burner that heats from the upper space above the upstream side of the first dam body 61, or a heater arranged near the bottom of the upstream side of the first dam body 61.

[0072] In the above description, an example in which a rotary surface melting furnace is provided with a retention mechanism for retaining molten metal suspended in molten slag has been described. However, the melting furnace to which the present invention is applied may be other than a rotary surface melting furnace.

[0073] For example, as shown in Fig. 8(a), a slag discharge port 7 is formed at the center of the furnace bottom 6, and it is also possible to provide a retention mechanism (recess 6a or weir) on the furnace bottom 6 of the surface melting furnace 1 in which a plurality of pushing-in charging mechanisms 30 for charging the object to be treated are arranged around the furnace bottom 6. The surface melting furnace 1 is of a type in which both the outer cylinder 3 integrally formed with the furnace bottom 6 and the inner cylinder 2 integrally formed with the furnace ceiling 5 are fixed, and the object to be treated is supplied into the furnace chamber by the pushing-in charging mechanism 30.

[0074] Also, as shown in Fig. 8(b), a slag discharge port 7 is formed at the end of the furnace bottom 6, and it is also possible to provide a retention mechanism (recess 6a or weir) on the furnace bottom 6 of the surface melting furnace 1 in which a plurality of pushing-in charging mechanisms 30 for charging the object to be treated are arranged on the opposite side. In each of the surface melting furnaces 1, the tips of a plurality of stages of nozzles are arranged so as to be located near the melting surface from the upstream side to the downstream side of the object to be treated pushed into the furnace chamber 4. In either case, the shape of the retention mechanism (recess 6a or weir) may be appropriately set based on the shape of the furnace bottom 6 and the flow direction of the molten slag.

[0075] The metal-containing slag obtained by dripping from the slag discharge port 7 is pulverized into fine particles by a pulverizer and then separated into metal and slag by a specific gravity separator.

[0076] The above-described embodiments are merely examples of the present invention, and the specific configurations of each part can be appropriately changed and designed within the range in which the functions and effects of the present invention are achieved.

Explanation of Reference Numerals

[0077] 1: Surface melting furnace 2: Inner cylinder 3: Outer cylinder 4: Furnace chamber 5: Furnace ceiling 6: Furnace bottom 6A: Recess (retention mechanism) 7: Slag discharge port 8: Combustion burner 9: Cut-out blade 15: Storage section 61: First weir body (retention mechanism) 62: Second weir body 70: Guide flow path 71: Valve 72: Gas nozzle 74: Heating mechanism A: Unmelted object to be processed B: Molten layer on the surface of the object to be processed C: Gasification combustion section M: Molten metal

Claims

1. A melting furnace comprising a furnace chamber for melting a workpiece containing a useful metal, a slag discharge port for discharging molten slag generated by the melting process, and a furnace bottom for guiding the molten slag to the slag discharge port, wherein the melting furnace is a rotary surface melting furnace configured by an inner cylinder partitioning the furnace chamber, an outer cylinder disposed on the outer periphery of the inner cylinder, a storage portion for the workpiece formed between the inner cylinder and the outer cylinder, and the workpiece cut out from the storage portion to the furnace chamber by relative rotation of the inner cylinder and the outer cylinder is melted from the surface, and the molten slag flows down and is discharged from the slag discharge port formed at the central portion of the furnace bottom, the furnace bottom is provided with a retention mechanism for retaining the molten slag by a recess formed on the front side of the slag discharge port to precipitate the molten metal contained in the molten slag, and a second weir for preventing the inflow of the unmelted workpiece to the recess on the outer periphery of the recess.

2. A melting furnace comprising a furnace chamber for melting a workpiece containing a useful metal, a slag discharge port for discharging molten slag generated by the melting process, and a furnace bottom for guiding the molten slag to the slag discharge port, wherein the melting furnace is a rotary surface melting furnace configured by an inner cylinder partitioning the furnace chamber, an outer cylinder disposed on the outer periphery of the inner cylinder, a storage portion for the workpiece formed between the inner cylinder and the outer cylinder, and the workpiece cut out from the storage portion to the furnace chamber by relative rotation of the inner cylinder and the outer cylinder is melted from the surface, and the molten slag flows down and is discharged from the slag discharge port formed at the central portion of the furnace bottom, a retention mechanism for retaining the molten slag to precipitate the molten metal contained in the molten slag is configured by a first weir formed in an arc shape in a plan view around the slag discharge port and concentrically and dispersedly arranged among the furnace bottom formed in a plane, and a second weir for preventing the inflow of the unmelted workpiece to the outer periphery of the first weir, and the melting furnace for precipitating the molten metal on the upstream side of the first weir.

3. The melting furnace according to claim 1, further comprising a taking-out mechanism for taking out the molten metal precipitated in the recess.

4. The melting furnace according to claim 3, wherein the taking-out mechanism is a guiding flow path communicating with the bottom of the recess and allowing the molten metal to flow out.

5. The melting furnace according to claim 3, wherein the taking-out mechanism is a gas nozzle communicating with the bottom of the recess and overflowing the molten metal from the recess.

6. The melting furnace according to any one of claims 1, 3 to 5, which is provided with a heating mechanism for remelting the metal that has settled and solidified in the concave portion.

7. The melting furnace according to claim 2, which is provided with a take-out mechanism for taking out the molten metal that has settled in the vicinity of the upstream side of the first weir body.

8. The melting furnace according to claim 7, wherein the take-out mechanism is composed of a guide flow path that communicates with the bottom of the vicinity of the upstream side of the first weir body and allows the molten metal to flow out.

9. The melting furnace according to claim 7, wherein the take-out mechanism is composed of a gas nozzle that communicates with the bottom of the vicinity of the upstream side of the first weir body and allows the molten metal to overflow from the first weir body.

10. The melting furnace according to any one of claims 2, 7 to 9, which is provided with a heating mechanism for remelting the metal that has settled and solidified in the vicinity of the upstream side of the first weir body.

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