Melting furnace and method of operating the same

Abstract

To provide a fusion furnace that appropriately performing treatment such as volatilization, slagging or metalization according to the type of metal, when fusing an object to be treated containing plural types of metal.SOLUTION: A fusion furnace comprises: a furnace chamber in which an object to be treated containing plural types of metal is put from an upstream side, and fused slag generated by fusing the object to be treated from a surface by a heating mechanism provided on a furnace ceiling flows down toward a downstream side; and a slag hole that discharges the fused slag having flowed down. The fusion furnace comprises: a plurality of stages of nozzles arranged from the upstream side to the downstream side of the furnace chamber; and an atmosphere adjustment mechanism that adjusts the atmosphere in the vicinity of a fused surface to either an oxidizing atmosphere or a reducing atmosphere for each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, and therefore adjusts target metal among plural types of metal so that the target metal is fused as separable fused metal from the fused slag or confined in the fused slag as a metal compound.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a melting furnace and a method for operating a melting furnace. [Background technology]

[0002] A variety of waste materials are melted in the melting furnace, including organic sludge such as sewage sludge, livestock manure, and methane fermentation residues of food waste; combustible materials such as plastics, paper, RPF, and recycling residues containing plastics and metals; and non-combustible materials such as incineration ash, contaminated soil, waste glass, waste ceramics, and asbestos.

[0003] For example, miscellaneous waste is melted and treated in a surface melting furnace that is equipped with a furnace chamber with a slag discharge port and a treatment object supply mechanism for supplying the treatment object toward the furnace chamber, and is configured so that the treatment object supplied to the furnace chamber by the treatment object supply mechanism melts from the surface and flows down to the slag discharge port.

[0004] In such melting furnaces, the interior of the furnace is adjusted to a reducing atmosphere in order to volatilize and remove heavy metals contained in the material to be treated from the slag.

[0005] Patent Document 1 also proposes a surface melting furnace that suppresses the volatilization of phosphorus contained in the material to be treated during melting. The surface melting furnace is configured with a furnace chamber in which a burner and an air supply mechanism are installed and in which a slag outlet is formed, and a material supply mechanism that supplies the material to be treated from a material storage unit that is provided in communication with the furnace chamber to the furnace chamber, the material to be treated containing phosphorus and combustibles, and an edge air supply mechanism that supplies air toward the surface of the material to be treated in the furnace chamber near where the furnace chamber and the material storage unit communicate with each other.

[0006] In this surface melting furnace, fixed carbon remaining near the surface of the workpiece due to the thermal decomposition of combustible materials is burned by air supplied toward the surface of the workpiece from the edge air supply mechanism, and the surplus oxygen suppresses the reduction reaction of phosphorus compounds and phosphorus oxides, thereby suppressing the volatilization of phosphorus.

[0007] Patent Document 2 proposes a melting treatment method for phosphorus-containing substances such as sewage sludge, which suppresses the volatilization of phosphorus components contained in the phosphorus-containing substances into exhaust gas and captures the phosphorus components in slag when melting the phosphorus-containing substances. The melting treatment method includes a pretreatment step of adjusting the moisture content of the phosphorus-containing substances containing 0.04 wt% or more of phosphorus in terms of dry substance, a melting step of feeding the phosphorus-containing substances whose moisture content has been adjusted in the pretreatment step into a melting furnace and melting the phosphorus-containing substances, and a cooling step of cooling and solidifying the slag produced by the melting step.

[0008] In addition, in this melting treatment method, an iron compound addition step of adding a divalent or trivalent iron compound to the phosphorus-containing substance is carried out either before or after the pretreatment step, thereby preventing the phosphorus components contained in the phosphorus-containing substance from volatilizing in the melting step and capturing the phosphorus components in the slag while suppressing their migration to metallic phosphorus compounds including 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, the ferrous oxide (FeO) charged or the ferrous oxide (FeO) generated from the divalent or trivalent iron compound during the melting process exerts a melting point lowering effect, and for example, at a melting temperature of approximately 1300°C, a solubility of 60% or more can be ensured in a wider range than the preferred basicity of the phosphorus-containing substance relative to iron, which is 0.4 to 0.0, and further, the volatilization of the phosphorus component in the melted material is suppressed, so that phosphorus is captured in the slag in a form other than a metallic phosphorus compound. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2015-190701 A [Patent Document 2] JP 2015-033691 A Summary of the Invention [Problem to be solved by the invention]

[0011] As described above, known methods of operating a melting furnace include adjusting the atmosphere inside the furnace to an oxidizing atmosphere in order to suppress the volatilization of metals and other substances contained in the material to be treated, and introducing melting aids to suppress metal alloying of the metals and other substances contained in the material to be treated and confine them in slag.

[0012] When melting an object to be treated, it is desirable to separate and recover certain metals contained in the object from the slag and use them as recycled resources, but there are also cases where it is desirable to confine certain metals contained in the object to be treated in the slag.

[0013] For example, there are cases where it is desired to recover iron or nickel contained in the material to be treated as metals, and there are also cases where it is desired to trap the iron or nickel in the form of a compound in slag.

[0014] However, since the material to be treated contains multiple metals, there is a problem that the intended purpose cannot be achieved if the inside of the furnace is uniformly adjusted to a constant oxidizing or reducing atmosphere. For example, in order to volatilize the heavy metals contained in the material to be treated, it is necessary to adjust the atmosphere to a weak reducing atmosphere, but in order to recover nickel as molten metal in a state that can be separated from the molten slag, it is necessary to adjust the atmosphere to a strong reducing atmosphere. Conventional melting furnaces could not handle cases where the material to be treated contains not only heavy metals but also nickel.

[0015] An object of the present invention is to provide a melting furnace and an operating method of a melting furnace which can appropriately perform each of the processes of volatilization, slagging, and metallization according to the type of metal when melting a processing object containing multiple types of metals. [Means for solving the problem]

[0016] In order to achieve the above-mentioned object, the first characteristic configuration of the surface melting furnace according to the present invention is a melting furnace having a furnace chamber into which a workpiece containing a plurality of types of metals is introduced from the upstream side, and in which the workpiece is melted from the surface by a heating mechanism provided on the furnace ceiling, and the molten slag generated by the melting process flows downstream, and a slag outlet for discharging the molten slag that flows down, and a plurality of nozzles are provided along the upstream side to the downstream side of the furnace chamber, and the type and / or composition of the gas supplied from each nozzle is made different, so that the atmosphere near the melting surface is controlled in each of a plurality of regions from the upstream side to the downstream side. Adjust Atmosphere control mechanism and the atmosphere adjusting mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, and adjusts the atmosphere near the melting surface on the downstream side to a strong reducing atmosphere to melt the target metal among the multiple types of metals as molten metal that can be separated from the molten slag. It's at the point.

[0017] The type and / or composition of gas supplied from each of the multiple nozzles arranged along the upstream side to the downstream side of the furnace chamber is adjusted by an atmosphere adjustment mechanism, so that the atmosphere near the melting surface in each of the multiple regions from the upstream side to the downstream side is adjusted to either an oxidizing atmosphere or a reducing atmosphere. When the atmosphere near the melting surface on the upstream side of the object to be treated that has been put into the furnace chamber is adjusted to a weakly reducing atmosphere, the heavy metals contained in the object to be treated are reduced and then volatilized. When the atmosphere near the melting surface on the downstream side is adjusted to a strongly reducing atmosphere, the target metals are melted as molten metals that can be separated from the molten slag. Therefore, the heavy metals contained in the object to be treated are not mixed into the slag, and the target metals are separated from the slag and recovered after the melting process.

[0018] Same number two Features and configuration is a melting furnace having a furnace chamber into which a workpiece containing a plurality of types of metals is introduced from the upstream side, and in which the workpiece is melted from the surface by a heating mechanism provided on the furnace ceiling, and the molten slag generated by the melting process flows downstream, and a slag outlet for discharging the molten slag that flows down, the furnace having a plurality of nozzles arranged along the furnace chamber from the upstream side to the downstream side, and an atmosphere adjustment mechanism that adjusts the atmosphere near the melting surface for each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, The atmosphere adjusting mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, and adjusts the atmosphere near the melting surface on the downstream side to an oxidizing atmosphere or a weak reducing atmosphere to confine target metals among the multiple types of metals in the molten slag as metal compounds. R It's at the point.

[0019] When the atmosphere near the melting surface on the upstream side of the object to be treated that has been put into the furnace chamber is adjusted to a weakly reducing atmosphere, the heavy metals contained in the object to be treated are reduced and then volatilized. When the atmosphere near the melting surface on the downstream side is adjusted to an oxidizing or weakly reducing atmosphere, the target metals are trapped in the molten slag as metal compounds. Therefore, the heavy metals contained in the object to be treated are not mixed into the slag, and the target metals are recovered after the melting process in a state where they are trapped in the slag as metal compounds.

[0020] Same number threeThe characteristic configuration of A melting furnace having a furnace chamber into which a workpiece containing a plurality of types of metals is introduced from the upstream side, and in which the workpiece is melted from the surface by a heating mechanism provided on the furnace ceiling, causing the molten slag generated to flow downstream, and a slag outlet for discharging the molten slag that has flowed down, the furnace chamber having a plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber, and an atmosphere adjustment mechanism for adjusting the atmosphere near the melting surface in each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, The atmosphere adjusting mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, adjusts the atmosphere near the melting surface on the downstream side to a weak reducing atmosphere, and adjusts the temperature of the melting surface to 1400 to 1600 ° C. to melt the target metal among the multiple types of metals as molten metal that can be separated from the molten slag. R It is at the point.

[0021] When the atmosphere near the melting surface on the upstream side of the object to be treated that has been put into the furnace chamber is adjusted to a weakly reducing atmosphere, the heavy metals contained in the object to be treated are reduced and then volatilized. When the atmosphere near the melting surface on the downstream side is adjusted to a weakly reducing atmosphere and the temperature of the melting surface is adjusted to 1400-1600°C, the reduction of iron and nickel is suppressed, and for example, gold, silver, copper, etc. are recovered as molten metals that can be separated from the molten slag.

[0022] Same number four The characteristic configuration of the above is the first to second three In addition to any one of the above characteristic configurations, the melting furnace includes an inner cylinder that defines the furnace chamber, an outer cylinder that is disposed on the outer periphery of the inner cylinder, a storage section for objects to be treated that is formed between the inner cylinder and the outer cylinder, and a melting process is performed on the surface of the object to be treated that is fed from the storage section to the furnace chamber by the relative rotation of the inner cylinder and the outer cylinder, and the molten slag flows down. Furnace The furnace is a rotary surface melting furnace in which the slag is discharged from the slag discharge port formed in the center of the floor, and multiple stages of nozzles are arranged along the upstream side to the downstream side of the furnace chamber on the furnace ceiling, or The above The difference is that it is placed on the hearth.

[0023] By arranging multiple stages of nozzles on the furnace ceiling or hearth of a rotary surface melting furnace along the upstream side to the downstream side of the furnace chamber, gas for adjusting the atmosphere can be supplied to the melting surface of the object to be treated.

[0024] A first characteristic configuration of the method for operating a melting furnace according to the present invention is a method for operating a melting furnace having a furnace chamber into which a workpiece containing a plurality of types of metals is introduced from the upstream side, and in which the workpiece is melted from the surface by a heating mechanism provided on the furnace ceiling, and the molten slag generated by the melting process flows downstream, a slag outlet for discharging the molten slag that has flowed down, and a plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber, wherein the type and / or composition of gas supplied from each nozzle is made different, The atmosphere near the melting surface on the upstream side is adjusted to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, and the atmosphere near the melting surface on the downstream side is adjusted to a strong reducing atmosphere to melt the target metal among the multiple types of metals as molten metal that can be separated from the molten slag. It's at the point.

[0025] The second characteristic configuration is a method for operating a melting furnace having a furnace chamber in which a material to be treated containing multiple types of metals is introduced from the upstream side, and the material to be treated is melted from its surface using a heating mechanism provided on the furnace ceiling, resulting in the molten slag flowing downstream, a slag outlet for discharging the molten slag that has flowed down, and multiple stages of nozzles arranged along the upstream side to the downstream side of the furnace chamber, in which the type and / or composition of gas supplied from each nozzle is made different to adjust the atmosphere near the melting surface on the upstream side to a weakly reducing atmosphere, thereby volatilizing heavy metals among the multiple types of metals, and the atmosphere near the melting surface on the downstream side to an oxidizing atmosphere or a weakly reducing atmosphere, thereby adjusting the target metal among the multiple types of metals to be trapped in the molten slag as a metal compound.

[0026] The third characteristic configuration is a method for operating a melting furnace having a furnace chamber in which a material containing multiple types of metals is fed from the upstream side, and the material is melted from the surface by a heating mechanism provided on the furnace ceiling, resulting in molten slag that flows downstream, a slag outlet for discharging the molten slag that flows down, and multiple stages of nozzles arranged along the upstream side to the downstream side of the furnace chamber, in which the type and / or composition of gas supplied from each nozzle is made different to adjust the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere, thereby volatilizing heavy metals among the multiple types of metals, and adjusting the atmosphere near the melting surface on the downstream side to a weak reducing atmosphere, and adjusting the temperature of the melting surface to 1400 to 1600 ° C., thereby adjusting the target metal among the multiple types of metals to melt as molten metal that can be separated from the molten slag. Effect of the Invention

[0027] As described above, according to the present invention, it is possible to provide a melting furnace and an operating method of a melting furnace that can appropriately perform each of the processes of volatilization, slagging, and metallization depending on the type of metal when melting a treatment object containing multiple types of metals. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is an explanatory diagram of a rotary surface melting furnace, which is an example of a melting furnace to which the present invention can be applied. [Diagram 2] FIG. 1(a) is an explanatory diagram of the main part of a melting furnace in which a nozzle for adjusting the combustion atmosphere near the melting surface is arranged on the furnace ceiling; FIG. 1(b) is an explanatory diagram of the main part showing another embodiment in which a part of the nozzle in FIG. 1(a) has a different shape; and FIG. 1(c) is an explanatory diagram showing the shape of the nozzle as viewed in the direction of the arrow A in FIG. [Diagram 3] FIG. 1( a ) is an explanatory diagram of the main part of a melting furnace in which a nozzle for adjusting the combustion atmosphere near the melting surface is arranged on the hearth, and FIG. 1( b ) is an explanatory diagram of the main part of another embodiment of a melting furnace in which a nozzle for adjusting the combustion atmosphere near the melting surface is arranged on the furnace ceiling. [Figure 4] An illustration of the redox characteristics of metals contained in the material to be treated based on oxygen partial pressure and CO2 / CO ratio. [Diagram 5] 1A and 1B are explanatory diagrams of a surface melting furnace showing another embodiment of the melting furnace to which the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, embodiments of the melting furnace and the method of operating the melting furnace according to the present invention will be described.

[0030] 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 and treating miscellaneous waste, and the materials to be treated include organic sludge such as sewage sludge, livestock manure, and methane fermentation residue of food waste, combustible materials such as plastic, paper, RPF, and recycling residue containing plastic and metal, and incombustible materials such as incineration ash, contaminated soil, waste glass, waste ceramics, and asbestos. Metals include useful metals such as iron, nickel, copper, silver, and gold, as well as heavy metals. In the following, a case will be described in which the material to be treated is a mixture of recycling residue containing plastic and metal and incineration ash, but other waste materials may also be included.

[0031] The rotary surface melting furnace 1 comprises an inner cylinder 2 and an outer cylinder 3 arranged concentrically, and a storage section 15 for materials to be treated 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 hearth 6 is formed extending from the lower part of the outer cylinder 3 toward the center. A slag outlet 7 is formed in the center of the hearth 6. The space surrounded by the inner cylinder 2, furnace ceiling 5, and hearth 6 forms the furnace chamber 4, and the inner walls of each are covered with refractory material. The inner cylinder 2 and the outer cylinder 3 are configured to be airtight by a water sealing mechanism 13.

[0032] A screw-type conveyor mechanism 11 is provided to transport the material to be treated to the storage section 15, and the material to be treated is dropped into the storage section 15 via a double damper mechanism 12 to prevent outside air from entering the furnace chamber 4.

[0033] As the outer cylinder 3 rotates relative to the inner cylinder 2, the materials to be treated stored in the storage section 15 are fed into the furnace chamber 4 by the cutting blades 9 provided at the bottom of the inner cylinder 2, and the materials to be treated are distributed in a cone shape toward the slag discharge port 7. The inside of the furnace is heated to a high temperature of approximately 1300°C by two combustion burners 8 provided at the center of the furnace ceiling 5, and the materials to be treated melt from the surface and flow down from the upstream side toward the slag discharge port 7 on the downstream side.

[0034] When the material is put into the furnace chamber 4, combustible components such as waste plastics are first vaporized upstream and combusted into gas. At this time, the upstream side is a weakly reducing atmosphere, and heavy metals contained in the material are reduced and volatilized, and flow down together with exhaust gas into the secondary combustion chamber. The material is heated by radiant heat from the combustion burner 8 and furnace ceiling 5, melting from the surface and flowing down toward the slag outlet 7. At this time, the molten layer is several tens of mm thick. In Figure 1, symbol A indicates the unmelted material, symbol B indicates the molten layer, and symbol C indicates the gasification combustion section.

[0035] In Fig. 1, diagrams showing waste plastics, incineration ash, metal, molten slag, and molten metal contained in the material to be treated are illustrated. The material to be treated is melted in the furnace chamber 4, and becomes molten slag and molten metal, which drip downward from the slag outlet 7.

[0036] A transport mechanism equipped with a water tank for cooling the molten slag is installed below the slag discharge port 7, and the molten slag is discharged outside the furnace as granulated slag. The combustion gas generated in the furnace chamber 4 is burned in a secondary combustion chamber installed downstream of the slag discharge port 7, and after being purified in an exhaust gas treatment facility, is exhausted to the atmosphere through a chimney. A negative pressure is maintained in the furnace chamber 4 by an induced draft fan installed upstream of the chimney.

[0037] As shown in Fig. 2(a), the furnace ceiling 5 is provided with multiple stages of nozzles N1, N2, and N3 arranged at different distances along the radial direction of a circle centered on the slag outlet 7 from the upstream side of the furnace chamber 4, i.e., the storage section 15 side, to the downstream side, i.e., the slag outlet 7 side. The nozzles N1, N2, and N3 are attached at a predetermined interval so that they are arranged on concentric circles in a plan view.

[0038] Each nozzle N1, N2, N3 is positioned so that its tip is located near the melt surface, and is configured so that the atmosphere near the melt surface can be adjusted to either an oxidizing atmosphere or a reducing atmosphere for each of multiple regions extending from the upstream side to the downstream side.

[0039] For this purpose, an atmosphere adjustment mechanism 16 is provided for adjusting the type and / or composition of gas supplied from each of the nozzles N1, N2, and N3. The atmosphere adjustment mechanism 16 is composed of a control mechanism for adjusting the type and / or composition of gas supplied from each of the nozzles N1, N2, and N3 from among air, oxygen, and combustible gases.

[0040] For example, an oxidizing atmosphere is formed near the molten surface at the tip of the nozzle when oxygen is supplied, and a reducing atmosphere is formed near the molten surface at the tip of the nozzle when a combustible gas is supplied. By varying the type and / or composition of the gas, the atmosphere near the molten surface at the tip of the nozzle can be adjusted to a weakly reducing atmosphere, a strong reducing atmosphere, a weakly oxidizing atmosphere, a strong oxidizing atmosphere, or the like.

[0041] The gas supplied from each of the nozzles N1, N2, N3 is supplied concentrically to the melt surface as the outer cylinder 3 rotates, so that it is possible to adjust the atmosphere in the vicinity of the melt surface from the upstream side to the downstream side to be different.

[0042] Although the number of nozzles N1, N2, and N3 is not particularly limited, the number of nozzles N1 on the most upstream side is increased compared to the number of nozzles N2 and N3 on the inner side. Therefore, as shown in Figures 2(b) and (c), if the nozzles N1 are arranged so that their blowing ports are aligned in the rotation direction of the outer cylinder 3, in other words, in the circumferential direction of a circle centered on the slag outlet 7, the number of nozzles to be installed can be reduced.

[0043] As described above, each nozzle N1, N2, N3 is attached to the furnace ceiling 5 so that it is arranged on a concentric circle at a predetermined interval when viewed in a plane, and is equipped with an atmosphere adjustment mechanism that adjusts the atmosphere near the melting surface in each of multiple regions from the upstream side to the downstream side to either an oxidizing atmosphere or a reducing atmosphere so that the target metal among multiple types of metals is melted as molten metal that can be separated from the molten slag, or is trapped in the molten slag as a metal compound.

[0044] As shown in Fig. 3(a), each of the nozzles N1, N2, and N3 may be installed on the hearth 6 and positioned so that its tip is located near the molten layer B of the material to be treated. In this embodiment, it is necessary to cover each of the nozzles N1, N2, and N3 with a refractory material. If the hearth 6 rotates integrally with the outer cylinder 3, the configuration of the piping for supplying gas to each of the nozzles N1, N2, and N3 becomes complicated, so the hearth 6 may be fixed.

[0045] As shown in FIG. 3(b), the nozzle N2 in the middle stage among the three stages of nozzles N1, N2, and N3 arranged in order from the upstream side to the downstream side of the furnace chamber 4 may be arranged so that the tip of the nozzle N2 is located at a position spaced above the melting surface. Also, the nozzles N1, N2, and N3 arranged in the circumferential direction of the furnace ceiling 5 may be arranged so that the tip positions of the nozzles N1, N2, and N3 are different between a position spaced above the melting surface and a position near the melting surface. For example, the tip positions of the nozzles N1, N2, and N3 may be arranged so that they alternate between a position spaced above the melting surface and a position near the melting surface. By adopting such a configuration, it is possible to simultaneously adjust the atmosphere in the entire internal space of the furnace chamber 4 and the atmosphere near the melting surface.

[0046] In the area adjusted to a reducing atmosphere by the atmosphere adjustment mechanism 16, the metal to be treated (hereinafter simply referred to as the "target metal") becomes a molten metal that can be separated from the molten slag, while in the area adjusted to an oxidizing atmosphere, the target metal is trapped in the molten slag as a metal compound.

[0047] Figure 4 shows a table of the redox characteristics of several target metals. Aluminum, titanium, and chromium belong to the group that are easily oxidized, while iron, cobalt, nickel, and copper belong to the group that are difficult to oxidize, and silver and gold belong to the group that are not oxidized. The table shows a list of oxygen partial pressure, CO2 / CO ratio, and the oxidizability of various metals (theoretical values), and it can be understood that the atmosphere can be adjusted by measuring the oxygen partial pressure and CO2 / CO ratio in the furnace chamber.

[0048] From this table, it can be seen that when the furnace temperature is 1300℃ and the CO2 / CO ratio is 100, copper is not oxidized and is included in the metal, while nickel is oxidized and fixed to the slag side. In the following, an atmosphere where nickel is reduced and melted into a molten metal is referred to as "strong reduction," and an atmosphere where only copper is reduced is referred to as "weak reduction to oxidation."

[0049] When the target metal is iron, nickel, cobalt, or the like, the atmosphere adjustment mechanism 16 adjusts the atmosphere near the molten surface on the upstream side from a weakly reducing atmosphere to an oxidizing atmosphere, preferably a weakly reducing atmosphere, thereby volatilizing heavy metals among the multiple types of metals contained in the treatment target, while maintaining the other metals in their metallic state, and maintaining the oxides of the metals in their oxidized state.

[0050] When it is necessary to recover metals such as iron, nickel, and cobalt, the atmosphere adjustment mechanism 16 adjusts the atmosphere downstream near the melting surface to a strongly reducing atmosphere so that the target metals are melted into molten metals that can be separated from the molten slag.

[0051] When it is not necessary to recover metals such as iron, nickel, and cobalt, the atmosphere adjustment mechanism 16 adjusts the atmosphere downstream near the molten surface from a weakly reducing atmosphere to an oxidizing atmosphere, preferably a weakly reducing atmosphere, so as to confine the target metals in the molten slag as metal compounds (metal oxides).

[0052] When the target metal is aluminum, chromium, or the like, the atmosphere adjustment mechanism 16 adjusts the atmosphere near the molten surface on the upstream side from a weakly reducing atmosphere to an oxidizing atmosphere, preferably a weakly reducing atmosphere, thereby volatilizing heavy metals among the multiple types of metals contained in the treatment target, while maintaining the other metals in their metallic state, and maintaining the oxides of the metals in their oxidized state.

[0053] When it is necessary to recover aluminum, chromium, or other metals, the atmosphere adjustment mechanism 16 adjusts the atmosphere downstream near the melting surface to a strong reducing atmosphere, and adjusts the atmosphere so that the target metals are melted into molten metals that can be separated from the molten slag by increasing the degree of reduction by burning the combustion burner at a low air ratio or by blowing in a combustible gas to perform reducing combustion. At this time, it is preferable to adjust the temperature inside the furnace to 1300°C and the CO2 / CO ratio to ≦0.0007.

[0054] When it is not necessary to recover aluminum, chromium, etc. as metals, the atmosphere adjusting mechanism 16 adjusts the atmosphere downstream near the melting surface from a weakly reducing atmosphere to an oxidizing atmosphere, preferably a weakly reducing atmosphere, so that the target metals are trapped in the molten slag as metal compounds (metal oxides). At this time, it is preferable to supply unburned gas and oxygen for combustion from a nozzle to maintain the temperature inside the furnace at 1300°C.

[0055] When the target metal is gold, silver, copper, or the like, the atmosphere adjustment mechanism 16 adjusts the atmosphere near the molten surface on the upstream side from a weakly reducing atmosphere to an oxidizing atmosphere, preferably a weakly reducing atmosphere, thereby volatilizing heavy metals among the multiple types of metals contained in the treatment target, while maintaining the other metals in their metallic state, and maintaining the oxides of the metals in their oxidized state.

[0056] When gold, silver, copper, etc. are to be recovered as metals, the atmosphere adjustment mechanism 16 maintains the atmosphere near the melting surface on the downstream side as a weakly reducing atmosphere and raises the temperature inside the furnace to 1400-1600°C. The combustion burner is operated at an appropriate air ratio, and combustible gas and oxygen gas are blown in from the nozzle. This makes it possible to suppress the reduction of iron, etc., while lowering the viscosity of the slag at high temperatures and improving the metal recovery rate.

[0057] The molten metal drips from the slag discharge port 7 together with the molten slag and is cooled in a water tank. The granulated slag that is discharged outside the furnace is crushed and then gravity-separated to separate the slag and metal.

[0058] In the above explanation, the present invention has been described with reference to a rotary surface melting furnace, but the present invention can also be applied to melting furnaces other than rotary surface melting furnaces.

[0059] For example, as shown in Fig. 5(a), it is also possible to apply a surface melting furnace 1 in which a slag outlet 7 is formed in the center of the hearth 6, and multiple push-in feeding mechanisms 30 for feeding the workpiece are arranged around the hearth 6. The surface melting furnace 1 is of a type in which both the outer cylinder 3 formed integrally with the hearth 6 and the inner cylinder 2 formed integrally with the furnace ceiling 5 are fixed, and the workpiece is fed into the furnace chamber by the push-in feeding mechanism 30.

[0060] 5(b), it is also possible to apply the present invention to a surface melting furnace 1 in which a slag outlet 7 is formed at the end of the hearth 6 and multiple push-in mechanisms 30 for feeding the workpiece are arranged on the opposite side. In either surface melting furnace 1, multiple stages of nozzles are arranged so that the tips of the nozzles are located near the melting surface of the workpiece pushed into the furnace chamber 4 from the upstream side to the downstream side.

[0061] As described above, the method of operating a melting furnace according to the present invention is a method of operating a melting furnace having a furnace chamber in which a material to be treated containing multiple types of metals is introduced from the upstream side and the material to be treated is melted from its surface by a heating mechanism provided on the furnace ceiling, resulting in the molten slag flowing downstream, a slag outlet for discharging the molten slag that has flowed down, and multiple stages of nozzles arranged along the upstream side to the downstream side of the furnace chamber, and the type and / or composition of the gas supplied from each nozzle is varied to adjust the atmosphere near the melting surface in each of multiple regions from the upstream side to the downstream side to either an oxidizing atmosphere or a reducing atmosphere, thereby adjusting the target metal among the multiple types of metals to be melted as a molten metal that can be separated from the molten slag, or to be trapped in the molten slag as a metal compound.

[0062] In the above embodiment, the case where the object to be treated contains natural components such as waste plastics has been described. If the amount of air supplied from the nozzle N1 is reduced when the natural components contained in the object to be treated are gasified and burned, the atmosphere can be suitably adjusted to a reducing atmosphere. If the object to be treated does not contain natural components, the atmosphere can be adjusted to a reducing atmosphere by supplying a combustible gas from the nozzle N1.

[0063] The above-described embodiments are merely examples of the present invention, and the specific configuration of each part can be appropriately modified and designed within the scope in which the effects of the present invention are achieved. [Explanation of symbols]

[0064] 1: Surface melting furnace 2: Middle tube 3: Outer cylinder 4: Furnace room 5: Furnace roof 6: Hearth 7: Slag mouth 8: Combustion burner 9: Cut-out feathers 15: Storage section A: Unmelted material to be processed B: Molten layer on the surface of the object to be treated C: Gasification and combustion section

Claims

1. A melting furnace having a furnace chamber in which a material to be treated containing a plurality of types of metals is introduced from the upstream side, and the material to be treated is melted from the surface by a heating mechanism provided on the furnace ceiling, and the molten slag generated flows downstream, and a slag outlet for discharging the molten slag that flows downstream, A plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber; an atmosphere adjusting mechanism for adjusting the atmosphere near the melt surface for each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, The atmosphere adjustment mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, and adjusts the atmosphere near the melting surface on the downstream side to a strong reducing atmosphere to melt the target metal among the multiple types of metals as molten metal that can be separated from the molten slag.

2. A melting furnace comprising: a furnace chamber into which a workpiece containing multiple types of metals is fed from the upstream side; a heating mechanism provided on the furnace roof melts the workpiece from its surface, causing the molten slag to flow downstream; and a slag outlet for discharging the molten slag, A plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber; an atmosphere adjusting mechanism for adjusting the atmosphere near the melt surface for each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, The atmosphere adjustment mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, and adjusts the atmosphere near the melting surface on the downstream side to an oxidizing atmosphere or a weak reducing atmosphere to confine the target metal among the multiple types of metals in the molten slag as a metal compound.

3. A melting furnace comprising: a furnace chamber into which a workpiece containing a plurality of types of metals is fed from the upstream side; a heating mechanism provided on the furnace roof melts the workpiece from its surface, producing molten slag that flows downstream; and a slag outlet for discharging the molten slag that has flowed downstream; A plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber; an atmosphere adjusting mechanism for adjusting the atmosphere near the melt surface for each of a plurality of regions from the upstream side to the downstream side by varying the type and / or composition of gas supplied from each nozzle, The atmosphere adjustment mechanism adjusts the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among the multiple types of metals, adjusts the atmosphere near the melting surface on the downstream side to a weak reducing atmosphere, and adjusts the temperature of the melting surface to 1,400 to 1,600°C to melt the target metal among the multiple types of metals as molten metal that can be separated from the molten slag.

4. The melting furnace is a rotary surface melting furnace, which is composed of an inner tube that divides the furnace chamber, an outer tube that is arranged on the outer periphery of the inner tube, a storage section for the object to be treated that is formed between the inner tube and the outer tube, and a surface of the object to be treated that is fed from the storage section to the furnace chamber by the relative rotation of the inner tube and the outer tube, and the molten slag flows down and is discharged from the slag discharge port that is formed in the center of the hearth, 4. The melting furnace according to claim 1, wherein a plurality of stages of nozzles are arranged along the upstream side to the downstream side of the furnace chamber, and are arranged on the furnace ceiling or on the hearth.

5. A method for operating a melting furnace comprising: a furnace chamber into which a workpiece containing a plurality of types of metals is introduced from the upstream side, and in which the workpiece is melted from the surface by a heating mechanism provided on the furnace ceiling, and the molten slag generated flows downstream; a slag outlet for discharging the molten slag that flows downstream; and a plurality of nozzles arranged along the upstream side to the downstream side of the furnace chamber, A method for operating a melting furnace in which the type and / or composition of gas supplied from each nozzle is varied to adjust the atmosphere near the melting surface on the upstream side to a weak reducing atmosphere to volatilize heavy metals among a plurality of types of metals, and the atmosphere near the melting surface on the downstream side to a strong reducing atmosphere to melt the target metal among a plurality of types of metals as molten metal that can be separated from the molten slag.

6. A method for operating a melting furnace comprising: a furnace chamber into which a workpiece containing multiple types of metals is fed from the upstream side, the workpiece is melted from the surface by a heating mechanism provided on the furnace roof, and the molten slag produced flows downstream; a slag outlet for discharging the molten slag that has flowed downstream; and a multiple-stage nozzle disposed along the upstream side to the downstream side of the furnace chamber, A method for operating a melting furnace in which the type and / or composition of gas supplied from each nozzle is varied to adjust the atmosphere near the melting surface on the upstream side to a weakly reducing atmosphere to volatilize heavy metals among a plurality of types of metals, and the atmosphere near the melting surface on the downstream side to an oxidizing atmosphere or a weakly reducing atmosphere to confine target metals among a plurality of types of metals in the molten slag as metal compounds.

7. A method for operating a melting furnace comprising: a furnace chamber into which a workpiece containing multiple types of metals is fed from the upstream side, the workpiece is melted from the surface by a heating mechanism provided on the furnace roof, and the molten slag produced flows downstream; a slag outlet for discharging the molten slag that has flowed downstream; and a plurality of nozzle stages arranged along the furnace chamber from the upstream side to the downstream side, A method for operating a melting furnace, comprising adjusting the type and / or composition of gas supplied from each nozzle to a weakly reducing atmosphere near the melting surface on the upstream side to volatilize heavy metals among a plurality of types of metals, adjusting the atmosphere near the melting surface on the downstream side to a weakly reducing atmosphere, and adjusting the temperature of the melting surface to 1400-1600°C to melt the target metal among a plurality of types of metals as molten metal that can be separated from the molten slag.

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