Drying method for sulfide concentrate and melting and refining equipment using the same

Abstract

To provide a method capable of dehydrating a raw material such a copper concentrate, without being specifically restricted by a hot blast stove that supplies hot blast to a drying furnace.SOLUTION: The sulfide concentrate that has been dried with hot air in a drying furnace 2 is blown into a self-fluxing furnace 4 together with air or oxygen-enriched air to oxidize and burn it to generate a matte layer and a slag layer in molten states, and after that, the slag layer is extracted and electrically heated in a slag cleaning furnace 5 for separation into the matte layer and the slag layer. In such a melting and smelting process, an exhaust gas discharged from the upper space in the slag cleaning furnace 5 is used as hot air in the drying furnace 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for drying sulfide concentrate used as a raw material for dry non-ferrous metal smelting and a melt smelting facility using the same, and more particularly to a method for charging sulfide concentrate into a drying furnace and drying it with hot air before melt smelting in a flash furnace, and a melt smelting facility using the same. [Background technology]

[0002] In dry nonferrous metal smelting, smelting is performed to recover high-grade nonferrous metals by heating raw ore and removing impurities in a molten state. For example, in dry copper smelting, copper concentrate (sulfide concentrate) consisting mainly of chalcopyrite with a copper content of about 30% obtained by pretreatment such as flotation is sequentially heated in a flash furnace and a smelting pot, as shown in Patent Document 1, to separate and remove the iron and silica contained in the copper concentrate as slag. The matte thus produced, with a copper content of about 60-65%, is further processed in a converter and a refining furnace to produce blister copper with a copper content of about 99%. The blister copper thus produced is cast into an anode and electrolytically refined for shipping as electrolytic copper with a copper content of 99.99%.

[0003] In the flash smelting furnace, raw copper concentrate is blown into the concentrate burner at the top of the reaction tower through gas-solid contact with air or oxygen-enriched air, causing a combustion reaction. The resulting heat from the oxidation reaction of the copper concentrate is used to produce molten matte and slag. To improve combustion efficiency in the concentrate burner, the copper concentrate is preferably ignited immediately after being ejected from the concentrate burner and maintained at a high temperature. However, if the copper concentrate is wet, the gas-solid contact is hindered, or the temperature of the copper concentrate decreases due to the latent heat of evaporation of water, resulting in a decrease in the combustion reaction rate. Therefore, prior to smelting in the flash smelting furnace, the wet copper concentrate is loaded into a drying furnace, typically a rotary kiln, and dried by blowing combustion gas generated in a hot blast stove into the drying furnace.

[0004] Because the drying process described above consumes a large amount of thermal energy, various technologies have been proposed to improve efficiency. For example, Patent Document 2 discloses a technology in which high-temperature gas discharged from a flash smelting furnace is introduced into a waste heat boiler to generate steam, and nitrogen heated by heat exchange with the steam is introduced into a drying furnace, thereby drying wet sulfide concentrate charged as a raw material into the flash smelting furnace. This reduces the amount of combustion gas that serves as a heat source for the drying furnace, thereby reducing the amount of heavy oil fuel consumed in the hot stove that generates the combustion gas and making it possible to mitigate the problem of environmental pollution caused by sulfur dioxide generated by the combustion of the sulfur content in the heavy oil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-241423 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-119525 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, when the combustion gas generated in the hot stove is blown into a drying furnace as hot air to dry a wet raw material such as copper concentrate, the temperature of the hot air and the amount of hot air generated suitable for the drying process can be determined from processing conditions such as the amount of wet raw material charged into the drying furnace per unit time and its moisture content. However, in general, hot stoves are sometimes unable to sufficiently increase the temperature of the combustion gas and the amount of the combustion gas generated due to restrictions such as the heat resistance temperature of refractories near their fuel burners, and this can become a bottleneck, restricting the amount of raw material such as copper concentrate that can be charged into the drying furnace.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a method that allows for drying raw materials such as copper concentrate in a drying furnace without being particularly restricted by the specifications of the hot air stove that generates the hot air to be introduced into the drying furnace. [Means for solving the problem]

[0008] As a result of intensive research into achieving the above object, the inventors have noticed that in dry copper smelting, in which wet copper concentrate is dried in a drying furnace and then melted and smelted in a flash furnace and a smelting furnace, thermal energy is supplied to the smelting furnace to maintain the temperature, and this thermal energy can serve as a high-temperature heat source for drying the copper concentrate in the drying furnace.Further research has led to the discovery that the smelting furnace exhaust gas, which is discharged in large quantities from the smelting furnace, can be used as hot air to be blown into the drying furnace, thereby completing the present invention.

[0009] That is, the method for drying sulfide concentrate according to the present invention is characterized in that, in the melt smelting process, sulfide concentrate that has been dried with hot air in a drying furnace is blown into a flash smelting furnace together with air or oxygen-enriched air and subjected to oxidative combustion to produce a molten matte layer and a slag layer, and the slag layer is then extracted and electrically heated in a smelting furnace to separate the matte layer and the slag layer, using exhaust gas discharged from the upper space in the smelting furnace as the hot air.

[0010] The sulfide concentrate melting and smelting equipment according to the present invention is a sulfide concentrate melting and smelting equipment comprising a drying furnace that dries the sulfide concentrate with hot air, a flash smelting furnace that oxidizes and burns the dried sulfide concentrate to produce a molten matte layer and a slag layer, and a smelting furnace that electrically heats the slag layer extracted from the flash smelting furnace to separate the slag layer into the matte layer and the slag layer, and is characterized in that exhaust gas discharged from an upper space in the smelting furnace is used as the hot air. [Effects of the Invention]

[0011] According to the present invention, wet raw materials such as copper concentrate can be dried without being particularly restricted by the type of hot air stove that supplies hot air to the drying furnace. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a process flow diagram of a smelting facility including a hot stove, a drying furnace, a flash furnace, and a smelting pot furnace to which a method for drying sulfide concentrate according to an embodiment of the present invention is applied. FIG. [Figure 2] FIG. 1 is a schematic flow diagram showing a specific example of a piping system for sending exhaust gas discharged from a smelting furnace to a hot stove, the piping system being provided for carrying out a method for drying sulfide concentrate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] A method for drying sulfide concentrate according to an embodiment of the present invention will be described below with reference to Figure 1, taking the case where the sulfide concentrate is copper concentrate as an example. Generally, wet copper concentrate with a moisture content (also called moisture content) of about 7 to 10% that has been pretreated at the mining site is transported by dedicated ship, then unloaded and temporarily stored in ore storage shed 1. The copper concentrate in this ore storage shed 1 is blended with copper concentrate from other lots as needed, and then charged into a rotary kiln-type drying furnace 2 (also called a flash dryer).

[0014] A rotary kiln is a rotary drying device with a cylindrical body that is rotatably mounted with its central axis slightly tilted from horizontal. Copper concentrate is loaded into the body from its upper end using a constant volume feeder such as a screw feeder. As the body rotates, the copper concentrate is stirred by a blade-like lifter installed inside and gradually moves toward the lower end. During this stirring and movement, the copper concentrate is efficiently dried by hot air introduced from the upper end of the body. Rotary drying devices that use steam as a heat source for drying are sometimes called rotary steam dryers to distinguish them from the rotary kilns described above.

[0015] The hot air introduced into the drying oven 2 is generated in a hot air stove 3 located adjacent to the drying oven 2. The hot air stove 3 is composed of a combustion chamber equipped with a fuel burner and a mixing chamber adjacent to the combustion chamber. In the combustion chamber, the fuel burner burns fossil fuel such as heavy oil to generate high-temperature combustion gas, which is then mixed in the mixing chamber with outside air taken in from outside the system and the smelting furnace exhaust gas discharged from the smelting furnace (described later). This generates hot air with a temperature of approximately 400 to 600°C.

[0016] The copper concentrate that has been dried to a moisture content of about 0.2 to 0.4% in the drying furnace 2 as described above is then charged into the flash smelting furnace 4. The flash smelting furnace 4 is a device that uses the heat from the oxidation reaction of the copper concentrate itself to perform smelting, making it possible to reduce fuel consumption compared to reverberatory furnaces and electric furnaces. Furthermore, as mentioned above, the amount of heat required to evaporate the moisture from the copper concentrate is reduced by the drying process in the preceding drying furnace 2, making it possible to further reduce fuel consumption in the flash smelting furnace 4.

[0017] The flash smelting furnace 4 is mainly composed of a cylindrical reaction tower (reaction shaft) equipped at its top with a concentrate burner for burning the copper concentrate, a settler that acts as a storage section for separating the matte and slag produced by the combustion of the copper concentrate into layers, and an uptake that acts as a flue gas passage connected to one end of the settler opposite to the end connected to the lower end of the reaction tower. The copper concentrate dried in the drying furnace 2 is blown into the flash smelting furnace 4 via the concentrate burner, along with air or oxygen-enriched air, and, if necessary, auxiliary fuel and silicic acid called flux. This causes the copper concentrate to instantly oxidize and burn, resulting in smelting and refining, producing matte (matte) composed of sulfides with a copper content of approximately 60 to 65%, and slag (calami) composed of iron oxide, silicic acid, and the like.

[0018] The matte and slag produced as described above are separated into a lower matte layer and an upper slag layer in the settler. The matte layer is extracted from the flash smelting furnace 4 and charged into a converter 6, where it is oxidized by blowing oxygen-enriched air into it, and iron and sulfur are removed to produce blister copper with a copper content of approximately 98-99%. However, there is a limit to how much the copper content of the slag layer can be reduced in the flash smelting furnace 4 due to the chemical dissolution of copper and the suspension (floating) of particulate matte. Therefore, using the slag layer extracted from the flash smelting furnace 4 as aggregate for concrete, etc., would result in a significant economic loss.

[0019] The slag layer from the flash smelting furnace 4 is then transferred to a slag furnace 5, where the copper contained in the slag layer is recovered. The slag furnace 5 generally has a structure in which multiple graphite rod-shaped electrodes are inserted into a furnace lined with heat-resistant bricks. When electricity is passed through these electrodes, the slag layer transferred from the flash smelting furnace 4 is heated by Joule heat, and the matte contained in the slag layer separates, forming a new matte layer below the slag layer. This lower matte layer is then extracted from the slag furnace 5 and treated in a converter 6, similar to the matte extracted from the flash smelting furnace 4. Meanwhile, the upper slag layer, which is in a molten state (or semi-fluid state) at approximately 1200 to 1300°C, is extracted from the slag furnace 5 and subjected to water granulation using a water granulator or similar device.

[0020] An upper space is formed inside the kiln 5, and the gas in this upper space is heated to approximately 500°C because it is in contact with the molten, high-temperature slag layer. However, since the gas in the upper space of the kiln 5 contains traces of sulfur components released from the slag and matte layers, conventionally, the gas in the upper space of the kiln was discharged as kiln exhaust gas and sent to an environmental smoke collection system (also called an environmental collection system). For example, in the packed tower of the environmental collection system, the sulfur components were absorbed with an alkali such as an aqueous solution of caustic soda to render the gas harmless, and then the gas was released into the atmosphere through a chimney.

[0021] In a method for drying sulfide concentrate according to an embodiment of the present invention, a high-temperature slag layer stably stored in a molten state in the slag furnace 5 is used as a heat source for drying the copper concentrate, and the gas in the upper space of the slag furnace 5 is used as a heat medium. Specifically, as shown by the dotted line in Figure 1, a branch pipe 9 is provided branching off from a flue 8 for transporting the slag furnace exhaust gas discharged from the upper space of the slag furnace 5 to a collection facility, and the tip of this branch pipe 9 is connected to the hot stove 3. This allows a portion of the slag furnace exhaust gas discharged from the upper space of the slag furnace 5 to be extracted through this branch pipe 9 and sent to the hot stove 3 as a heat transfer gas, making it possible to replace at least a portion of the air used as the heated gas in the hot stove 3 with the slag furnace exhaust gas discharged from the slag furnace 5. As shown by the dashed line in Figure 1, the branch pipe 9 branching off from the flue 8 may be connected not to the hot air stove 3 but to a supply pipe that sends the hot air generated in the hot air stove 3 to the drying oven 2.

[0022] The smelting furnace exhaust gas discharged from the upper space of the smelting furnace 5 is pressurized by the suction fan 7 for the circulating system installed in the flue 8 before being sent to the circulating system. Therefore, the operating pressure of the hot stove 3 and the drying furnace 2, which are generally operated at negative pressure, may be lower than the pressure at the branch point of the branch pipe 9 located on the discharge side of the circulating system suction fan 7 in the flue 8. In this case, as shown in Figure 2, by installing a branch-side damper 10 in the branch pipe 9 and adjusting its opening, it is possible to adjust the amount of exhaust gas discharged from the smelting furnace 5 that is supplied to the hot stove 3. Alternatively, depending on the equipment configuration, the operating pressure of the circulating system may be lower than the operating pressure of the hot stove 3 or the drying furnace 2. In this case, instead of the branch-side damper 10, a flue-side damper 11 may be installed in the flue 8 downstream of the branch point of the branch pipe 9.

[0023] Alternatively, both a branch-side damper 10 and a flue-side damper 11 may be provided, and the amount of gas supplied to the hot stove 3 may be adjusted by adjusting the apertures of these dampers 10, 11. In this case, to increase the amount of gas supplied to the hot stove 3, the aperture of the branch-side damper 10 is adjusted in the open direction and the aperture of the flue-side damper 11 is adjusted in the closed direction, and to decrease the amount of gas supplied to the hot stove 3, these dampers 10, 11 are adjusted in the opposite direction. Note that a manual valve 12 is preferably provided on the primary side (upstream side) of the branch-side damper 10 in the branch pipe 9. A thermometer 13 and a flow meter 14 are also preferably provided in the branch pipe 9.

[0024] Typically, only the upper slag layer, which contains almost no volatile components and has separated in the flash smelting furnace 4, is charged into the slag furnace 5. Therefore, the slag exhaust gas discharged from the upper space of the slag furnace 5 is a mixture of the gas originally present in the upper space of the slag furnace 5 and the outside air drawn in from outside the slag furnace 5 by the suction fan 7 for the collection system. Therefore, as mentioned above, even if the slag contains only a small amount of sulfur, it can be handled together with the sulfur contained in heavy oil and copper concentrate, so there is no particular problem with introducing it directly into the drying furnace 2 as hot air. However, if it is desired to prevent oxygen from being introduced into the drying furnace 2, an inert gas such as nitrogen can be introduced into the upper space of the slag furnace 5 in advance as a heat transfer gas.

[0025] Although the hot air used for the drying process in the drying oven 2 contains almost no sulfur components as described above, it also contains fine particles that cannot be completely removed by the cyclone. Therefore, it is sucked in by the drying oven exhaust gas suction fan 21 and discharged from the drying oven 2 as drying oven exhaust gas, and then treated in a drying oven exhaust gas treatment facility 22, preferably a bag filter or an electrostatic precipitator, before being released into the atmosphere via a chimney 23. Note that there is a SO 4 filter at the outlet of the exhaust gas treatment facility. X A concentration meter 24 is installed to measure the SO in the exhaust gas released into the atmosphere. X It is preferable to constantly check that the concentration meets the specified value. Also, it is preferable to provide a drying oven exhaust gas damper 25 on the suction side of the drying oven exhaust gas suction fan 21.

[0026] As described above, the method for drying sulfide concentrate according to the embodiment of the present invention can supply a large amount of heat to the drying furnace 2 without making costly capital investments such as adding fuel burners to the hot stove 3 or increasing the consumption of heavy oil, which is the raw material for generating hot air. Therefore, SO 2 derived from heavy oil can be reduced. X This makes it possible to dry larger amounts of copper concentrate at low cost without increasing the cost of treating exhaust gas containing copper. [Example]

[0027] (Example) In a smelting facility for producing blister copper from copper concentrate as shown in Figure 1, part of the exhaust gas from the smelting furnace 5 was mixed with hot air generated by burning heavy oil in the hot stove 3, and the resulting mixed gas was used as the hot air introduced into the drying furnace 2. When the amount of copper concentrate charged into the drying furnace 2 was varied and the outlet temperature of the drying furnace 2 was investigated, it was found that the copper concentrate could be dried to the specified moisture content without any problems even when the charge amount was increased to 81.7 wt / h.

[0028] (Comparative Example) The operation was carried out in the same manner as in the above example, except that the exhaust gas from the smelting furnace 5 was not used as the hot air introduced into the drying furnace 2. The amount of copper concentrate charged to be dried in the drying furnace 2 was varied and the outlet temperature of the drying furnace 2 was investigated. It was found that the process was successful at 75 wt / h or less, but at 81.7 wt / h the outlet temperature of the drying furnace 2 fell below the set temperature, and the drying process was insufficient. [Explanation of symbols]

[0029] 1. Ore storage building 2 Drying oven 3 hot stove 4 Flash-melting furnace 5. Smelting furnace 6. Converter 7. Suction fans for environmental collection equipment 8 flue 9 Branch Pipe 10 Branch side damper 11 Flue-side damper 12 Manual valve 13 Thermometer 14 Flow meter 21 Drying furnace exhaust gas suction fan 22 Drying furnace exhaust gas treatment equipment 23 Chimney 24 SO X concentration meter 25 Drying furnace exhaust gas damper

Claims

1. A method for drying sulfide concentrate in a melting smelting facility in which sulfide concentrate that has been dried with hot air in a drying furnace is blown into a flash smelting furnace together with air or oxygen-enriched air to cause oxidative combustion to produce a molten matte layer and a slag layer, and the slag layer is then extracted and electrically heated in a smelting furnace to separate the matte layer and the slag layer, characterized in that exhaust gas discharged from an upper space in the smelting furnace is used as the hot air.

2. 1. A sulfide concentrate melting and smelting facility comprising a drying furnace for drying sulfide concentrate with hot air, a flash smelting furnace for oxidatively burning the dried sulfide concentrate to produce a molten matte layer and a slag layer, and a smelting furnace for electrically heating the slag layer extracted from the flash smelting furnace to separate the matte layer and the slag layer, characterized in that the facility also comprises means for supplying exhaust gas discharged from an upper space within the smelting furnace to the drying furnace.

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