Foreign matter separation device

Abstract

To provide a foreign matter separator and a foreign matter separation method that allow separation of metal wires being foreign matters contained in dust collected by a dust collector.SOLUTION: Dust collected by a dust collector 1 is mechanically sieved with a sieve 5, and the sieved dust is guided to a vertical pipe 7. Then, a gaseous matter is flown in from a lower part of the vertical pipe 7 to generate upward current inside the vertical pipe 7. Further, dust which has been separated according to flotation caused by the upward current is guided to a dust storage tank 8, and metal wires in the sieved dust are sedimented to be separated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foreign matter separating device and a foreign matter separating method for separating metal wires from dust that is collected by a dust collector and contains metal wires in addition to lumps of foreign matter. [Background technology]

[0002] In addition to clumps, foreign matter including metal wires may be present in the dust collected by the dust collector. Below, we will explain the combustible dust that accompanies the pyrolysis gas from a waste melting furnace as an example. Patent Document 1 discloses a technique for collecting combustible dust accompanying pyrolysis gas from a waste melting furnace using a dust collector such as a cyclone and then blowing the collected combustible dust through the tuyeres of the waste melting furnace. Patent Document 2 also discloses a dust treatment technique for blowing the combustible dust collected by the dust collector into the tuyeres of the waste melting furnace. Specifically, Patent Document 2 discloses a combustible dust hopper and a dust blowing device along a transport path for the combustible dust from the combustible dust hopper to the blowing device, which includes a screw conveyor for cutting out the combustible dust, a cylindrical rotating drum cooling device for cooling the combustible dust that is connected coaxially with the screw conveyor, and a cylindrical rotating sieve that is connected coaxially with the rotating drum cooling device. A combustible dust outlet is provided below the rotating sieve, and a discharge outlet for agglomerates (large lumps) that are foreign matter in the combustible dust is provided below the outlet of the rotating sieve. This technology is characterized by the use of a rotating drum type cooling device that combines the cooling and screening of combustible dust into one device. It is also stated that cooling water is supplied to this rotating drum type cooling device via the screw shaft of the screw conveyor.

[0003] In Patent Document 2, high-temperature combustible dust collected by a dust collector is cooled in a cylindrical rotating drum cooling device, and then a cylindrical rotary sieve is connected to separate foreign matter, such as clumps, that may interfere with air transport to or blowing into the tuyere. This cylindrical rotary sieve is a mechanical sieve with punched or slit openings of approximately 7 mm, and is capable of separating large clumps larger than approximately 7 mm. However, the combustible dust collected by the dust collector contains metal wires as foreign matter in addition to the clumps. Even if the metal wires are longer than approximately 7 mm, they easily pass through the approximately 7 mm punched or slit openings in the cylindrical rotary sieve and cannot be separated by the cylindrical rotary sieve. Therefore, the undersize portion of the cylindrical rotary sieve contains metal wires as foreign matter in addition to combustible dust. These metal wires may cause blockages in the air transport pipe (nominal diameter: approximately 32A) to the tuyere or the tuyere itself. In this case, it becomes impossible to blow combustible dust through the tuyere, and as a result, the dust collector stops functioning, causing a large amount of combustible dust to flow into the combustion chamber at the subsequent stage. This causes the combustion chamber to become hot due to the combustion of a large amount of combustible dust, and the burned combustible dust adheres to the inner wall of the combustion chamber as molten clinker and grows, causing a major disruption to the operation of the waste melting furnace.

[0004] The combustible dust accompanying the pyrolysis gas from the waste melting furnace is very fine, with an average particle size of approximately 30 μm, and contains approximately 40% unburned carbon by mass, making it highly combustible. Furthermore, the amount of combustible dust generated varies greatly depending on the furnace conditions, making it virtually impossible to control. Therefore, if a large amount of combustible dust is not captured by a dust collector and flows into the downstream combustion chamber, the combustion chamber heats up in a short time, making temperature control difficult. This leads to the growth of clinker, as described above, and creates a major obstacle to the operation of the waste melting furnace.

[0005] Therefore, it is necessary to reliably capture the combustible dust accompanying the pyrolysis gas from the waste melting furnace with a dust collector and return it to the waste melting furnace through the tuyere, and for this purpose, it is necessary to separate the metal wires contained in the combustible dust captured by the dust collector. Furthermore, the need to separate the metal wires contained in the dust captured by the dust collector is not limited to combustible dust accompanying the pyrolysis gas from the waste melting furnace, but there is also a wide range of needs in other fields for technology to sieve dust containing metal wires that cannot be separated by mechanical sieves alone, making this technology highly applicable. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-285250 [Patent Document 2] JP 2004-85174 A (Patent No. 4129191 A) Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a foreign matter separating device and method capable of separating metal wires as foreign matter contained in dust collected by a dust collector. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided the following foreign matter separation device. A foreign matter separation device that separates lumps and metal wires from dust that is collected by a dust collector and contains the lumps and metal wires as foreign matter, The dust collector is provided with a sieve for mechanically separating lumps in the dust, and a guide chute for guiding the dust below the sieve, which contains metal wires, into a vertical pipe; A foreign matter separation device in which gas flows in from the bottom of the vertical pipe to generate an ascending air current within the vertical pipe, and the dust that rises and is separated by the ascending air current is guided to a dust storage tank, where metal wires in the dust that falls below the sieve are separated by settling them.

[0009] According to another aspect of the present invention, there is provided the following foreign matter separation method. A method for separating lumps and metal wires from dust collected by a dust collector and containing the lumps and metal wires as foreign matter, comprising the steps of: A method for separating foreign matter by mechanically sieving clumps in dust collected by a dust collector, guiding the under-sieve dust containing metal wires into a vertical pipe, causing gas to flow in from the bottom of the vertical pipe to generate an ascending air current within the pipe, and guiding the dust separated by the ascending air current to a dust storage tank, where the metal wires in the under-sieve dust are separated by settling them. [Effects of the Invention]

[0010] According to the present invention, metal wires as foreign matter contained in dust collected by a dust collector can be separated. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a vertical cross-sectional view conceptually showing the overall configuration of a foreign matter separation device according to an embodiment of the present invention; [Figure 2] 2 is an enlarged longitudinal cross-sectional view conceptually showing a double-plate structure portion of the foreign matter separation device of FIG. 1. FIG. [Figure 3] FIG. 2 is a perspective view conceptually showing an example of the configuration of the under-screen portion of the foreign matter separation device of FIG. 1. [Figure 4] FIG. 10 is a vertical cross-sectional view conceptually showing the overall configuration of a foreign matter separation device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Fig. 1 conceptually shows in longitudinal section the overall configuration of a foreign matter separation device according to one embodiment of the present invention. Fig. 2 conceptually shows in longitudinal section an enlarged view of the double plate structure portion of the foreign matter separation device of Fig. 1, and Fig. 3 conceptually shows in perspective a configuration example of the under-screen portion of the foreign matter separation device of Fig. 1. In Figure 1, cyclone 1 is an example of a dust collector that collects combustible dust accompanying pyrolysis gas from a waste melting furnace (not shown), and the combustible dust collected by cyclone 1 contains metal wires as foreign matter in addition to clumps of material. This combustible dust is introduced into screw conveyor 3 through combustible dust inlet 2, and is then introduced by screw conveyor 3 into rotary sieve 5 inside casing 4. Rotary sieve 5 is a cylindrical punched metal with punched holes of approximately 7 mm in diameter.

[0013] Combustible dust A that falls below the sieve size after being sieved by the rotary sieve 5 is collected and guided by a guide chute 6 into the middle of the vertical pipe 7, and is ultimately guided to a dust storage tank 8, as will be described in detail below. In this embodiment, the dust storage tank 8 is located directly below the rotary sieve 5 and is connected to the rotary sieve 5 via a dust chute 9. The vertical pipe 7 is provided outside the dust chute 9. The guide chute 6 is partitioned so as not to directly communicate with the dust chute 9 inside the dust chute 9, but passes through the dust chute 9 to communicate with the vertical pipe 7. The upper part of the vertical pipe 7 is connected to the dust chute 9, and the gas inside the dust chute 9 is sent to the lower part of the vertical pipe 7 by a circulation fan 10. Specifically, a circulation fan 10 is provided in a pipe 11 connecting the dust chute 9 and the lower part of the vertical pipe 7, and operation of the circulation fan 10 sends the gas in the dust chute 9 through the pipe 11 to the lower part of the vertical pipe 7. A heat exchanger 12 that cools the gas in the pipe 11 is provided on the discharge side of the circulation fan 10 in the pipe 11. The heat exchanger 12 may be, for example, a water-cooled shell-and-tube type.

[0014] Lumps (foreign matter) B on the sieve of the rotary sieve 5 are discharged through a substantially vertical foreign matter chute 13. The foreign matter chute 13 and the lower part of the vertical pipe 7 are connected by a connecting pipe 14. This connecting pipe 14 is horizontal or inclined downward toward the foreign matter chute 13. A sloped plate 15a is installed at the lower part of the vertical pipe 7, facing the connecting pipe 14. A eaves plate 15b is installed above the sloped plate 15a with a gap G1 (see FIG. 2) to form a double-plate structure 15. A gap G2 (see FIG. 2) is provided between the double-plate structure 15 (the tip of the sloped plate 15a) and the bottom surface of the connecting pipe 14. The inclination angle of the lower sloped plate 15a in the double-plate structure 15 is variable by rotating the sloped plate 15a around a rotation axis 15c. Changing the inclination angle of the sloped plate 15a mainly changes the size of the gap G2. For example, the size of the gap G1 is set to about 10 mm, and the size of the gap G2 is changed within the range of 10 to 20 mm.

[0015] The air supply position of the circulation fan 10 is below the double-plate structure 15, and the airflow is blown out from the gap G1 in the double-plate structure 15 and the gap G2 between the double-plate structure 15 and the bottom surface of the connecting pipe 14. That is, the airflow blown out from the gap G1 transports foreign matter, including the metal wire C, on the inclined plate 15a to the bottom side of the connecting pipe 14, and the airflow blown out from the gap G2 transports the foreign matter moved to the bottom side to the foreign matter chute 13. A damper 16 is provided at the outlet of the connecting pipe 14 to limit the amount of gas flowing into the foreign matter chute 13. That is, by adjusting the opening degree of the damper 16, the volume ratio of the airflow blown out from the gap G1 and the gap G2 to the volume of gas flowing into the foreign matter chute 13 and the volume of gas that reverses direction within the connecting pipe 14 and becomes an updraft that rises up through the vertical pipe 7 from the bottom of the vertical pipe 7 is adjusted. For example, the amount of gas flowing into the foreign object chute 13 side is set to about 10% by volume, and the amount of gas that becomes an ascending air current is set to about 90% by volume.

[0016] In the above configuration, combustible dust A that falls below the sieve size after being sieved by the rotary sieve 5 falls into the guide chute 6, where it is collected and flows into the vertical pipe 7 from the middle of the pipe. As described above, gas in the dust chute 9, which is connected to the dust storage tank 8, is sent to the lower part of the vertical pipe 7 by the circulation fan 10. Specifically, the gas in the dust chute 9 is blown into the lower part of the vertical pipe 7 by the circulation fan 10 via a heat exchanger 12. Here, the gas in the dust chute 9 that is sucked in by the circulation fan 10 is nitrogen gas that fills the entire casing 4, and its temperature at the time of suction is about 150°C. However, in the pipe 11 outside the casing 4, the gas is cooled to about 50°C by the heat exchanger 12 provided on the discharge side of the circulation fan 10, and is sent to the lower part of the vertical pipe 7.

[0017] The gas blown into the lower part of the vertical pipe 7 enters directly below the double-plate structure 15 and then ejects from the gap G1 in the double-plate structure 15 and the gap G2 between the double-plate structure 15 and the bottom of the connecting pipe 14. Approximately 90% by volume of the ejected airflow reverses inside the connecting pipe 14, enters the lower part of the vertical pipe 7, and forms an ascending airflow in the vertical pipe 7. Due to this ascending airflow, the combustible dust A that has flowed into the lower part of the vertical pipe 7 from the guide chute 6 rises along with the ascending airflow within the vertical pipe 7, and only the powder that is floated and separated by this ascending airflow flows from the upper part of the vertical pipe 7 into the dust chute 9 and passes through the dust chute 9 into the dust storage tank 8. Here, as shown in Figures 1 and 3, a baffle plate 17 is installed vertically within the dust chute 9 to prevent the circulation fan 10 from directly sucking in the combustible dust within the dust chute 9. In Fig. 1, the circulating flow including the ascending air current in the vertical pipe 7 is indicated by the black arrows. This also applies to Fig. 4 described later.

[0018] Meanwhile, metal wires C as foreign matter contained in the combustible dust that has flowed into the vertical pipe 7 via the guide chute 6 settle in the vertical pipe 7 due to the so-called air flow classification effect, and fall onto the double-plate structure 15 at the bottom of the vertical pipe 7. Then, the metal wires C that have fallen onto the double-plate structure 15 are moved toward the foreign matter chute 13 by the airflow blowing out from the gaps G1 and G2, and finally flow into the foreign matter chute 13 and are discharged by the foreign matter discharge damper 13a.

[0019] As a condition for air classification of metal wires in the vertical pipe 7, the ascending air velocity just before connecting with the guide chute 6 at the bottom of the vertical pipe 7 is preferably about 5 to 7 m / s. Furthermore, because air classification mainly takes place at the connecting part with the guide chute 6, it is preferable to stabilize the gas flow just before this connecting part. Therefore, it is preferable to ensure a straight pipe length h (see FIG. 1) of the vertical pipe 7, which is the inlet length of the ascending air current leading to this connecting part. Specifically, the straight pipe length h of the vertical pipe 7, which is the inlet length of the ascending air current, is preferably 1.5D to 3D, where D is the diameter of the vertical pipe 7.

[0020] A portion of the airflow ejected from gaps G1 and G2 also flows into the foreign object chute 13. The volumetric ratio of this flow can be adjusted by adjusting the opening of the damper 16 at the outlet of the connecting pipe 14, as described above. The gas flowing into the foreign object chute 13 from the outlet of the connecting pipe 14 along with the settled metal wires flows through the foreign object chute 13 and the rotary sieve 5 into the guide chute 6. The gas then flows into the vertical pipe 7 together with the undersized combustible dust A, forming a circulating flow that merges with the gas flowing in from the bottom of the vertical pipe 7. This circulating flow promotes the flow of very fine and light combustible dust (average particle size approximately 30 μm and bulk density approximately 0.3) out of the guide chute 6, preventing the combustible dust from accumulating or clogging the guide chute 6. This circulating flow is indicated by the open arrows in Figure 1. This is also true in Figure 4, which will be described later.

[0021] Here, the combustible dust guided into the vertical pipe 7 by the guide chute 6 is at a high temperature of approximately 500°C. However, since the temperature of the gas blown into the lower part of the vertical pipe 7 is approximately 50°C as mentioned above, the dust is efficiently cooled in a short time by this ascending air current at approximately 50°C. Note that in the rotating drum dust cooler disclosed in the aforementioned Patent Document 2, only the dust in contact with the drum surface is cooled. To cool the entire dust, a large heat transfer surface is required, even considering the agitation effect of the drum rotation, resulting in a large size. In contrast, dust classified by the air current in this embodiment is cooled very effectively because individual dust particles come into contact with the cooling gas. As a result, the temperature of both the combustible dust and the gas when they enter the dust storage tank 8 is approximately 150°C.

[0022] As a result of the above-mentioned actions, the combustible dust A stored in the dust storage tank 8 becomes a low-temperature powder or granular material that does not contain foreign matter such as metal wires and is suitable for injection through the tuyere, and can be quantitatively cut out by the dust cutting device 18 and stably transported and injected into the tuyere by the blower 19. Furthermore, in this embodiment, a heat exchanger 12 is provided midway along the pipe 10 that runs from the discharge side of the circulation fan 10 to the bottom of the vertical pipe 7, so that there is no need for a rotary drum-type cooling device as in Patent Document 2, and the combustible dust is sent directly from the combustible dust inlet 2 to the rotary sieve 5, making the device configuration very compact.

[0023] FIG. 4 conceptually shows, in a longitudinal cross-sectional view, the overall configuration of a foreign matter separation device according to another embodiment of the present invention. In the previous embodiment, the dust storage tank 8 was located directly below the rotary sieve 5 and connected to the rotary sieve 5 via a dust chute 9. However, in this embodiment, the dust storage tank 8 is not connected to the rotary sieve 5 via the dust chute 9, but is instead located at a location other than directly below the rotary sieve 5. The upper portion of the vertical pipe 7 is connected to the upper portion 8a of the dust storage tank 8 via a dust transfer pipe 20. The gas in the upper portion 8a of the dust storage tank 8 is delivered to the lower portion of the vertical pipe 7 by a circulation fan 10. Other configurations are essentially the same as those of the previous embodiment. Therefore, in FIG. 3, components that are essentially the same as those of the previous embodiment are designated by the same reference numerals, and their description will be omitted.

[0024] According to this embodiment, the dust storage tank 8 can be placed separately at any position other than directly below the rotary sieve 5, which reduces the overall height of the foreign matter separation apparatus and increases the degree of freedom in layout. On the other hand, in the previous embodiment, although the overall height of the foreign matter separation apparatus is increased, the dust storage tank 8 is located directly below the rotary sieve 5, so the entire foreign matter separation apparatus can be made into a single unit.

[0025] In the above embodiment, the rotary sieve 5 is used as a sieve for mechanically sieving the dust, but this is not limiting and, for example, a vibrating sieve can also be used. In short, any sieve can be used as long as it can mechanically sieve out lumps of a target particle size or larger. In the above embodiment, a heat exchanger 12 is provided in the pipeline 10 extending from the discharge side of the circulation fan 10 to the lower part of the vertical pipe 7. However, in cases where a rotating drum type cooling device is provided as in the above-mentioned Patent Document 2, it is not necessary to provide a heat exchanger 12. Furthermore, in the above embodiment, the target of treatment was combustible dust collected by cyclone 1 and accompanying pyrolysis gas from a waste melting furnace, but this is not limited to this. In other words, the present invention can be applied to any dust collected by a dust collector that contains metal wires as foreign matter. [Explanation of symbols]

[0026] 1 Cyclone (dust collector) 2 Combustible dust inlet 3. Screw conveyor 4 Casing 5 Rotating sieve 6 Guide Chute 7 Vertical Pipe 8 Dust storage tank 8a Top of dust storage tank 9 Dust Chute 10 Circulation Fan 11 Conduit 12 Heat exchanger 13 Foreign Object Shot 13a Foreign object discharge damper 14 Connecting pipe 15 Double plate structure 15a slope plate 15b Eave board 15c Rotation axis 16 Damper 17 Baffle plate 18 Dust extraction device 19 Blois 20 Dust transfer pipe A Combustible dust under the sieve B Lump (foreign object) C Metal wire (foreign object)

Claims

1. A foreign matter separation device that separates lumps and metal wires from dust that is collected by a dust collector and contains the lumps and metal wires as foreign matter, The dust collector is provided with a sieve for mechanically separating lumps in the dust, and a guide chute for guiding the dust below the sieve, which contains metal wires, into a vertical pipe; Gas is introduced into the lower part of the vertical pipe to generate an ascending air current within the vertical pipe, and the dust separated by the ascending air current is guided to a dust storage tank, where metal wires in the dust below the sieve are separated by settling them down; The dust storage tank is located directly below the sieve and is connected to the sieve via a dust chute; the vertical pipe is provided outside the dust chute, the guide chute is separated from the dust chute inside the dust chute and passes through the dust chute to communicate with the vertical pipe; The upper part of the vertical pipe is in communication with the dust chute, and the gas inside the dust chute is sent to the lower part of the vertical pipe.

2. A foreign matter separation device that separates lumps and metal wires from dust that is collected by a dust collector and contains the lumps and metal wires as foreign matter, The dust collector is provided with a sieve for mechanically separating lumps in the dust, and a guide chute for guiding the dust below the sieve, which contains metal wires, into a vertical pipe; Gas is introduced into the lower part of the vertical pipe to generate an ascending air current within the vertical pipe, and the dust separated by the ascending air current is guided to a dust storage tank, where metal wires in the dust below the sieve are separated by settling them down; an upper portion of the vertical pipe is connected to an upper portion of the dust storage tank via a dust transfer pipe; A foreign matter separation device in which gas from the upper part of the dust storage tank is sent to the lower part of the vertical pipe.

3. A foreign matter chute is provided to discharge foreign matter on the sieve. The lower part of the vertical pipe and the foreign object chute are connected by a connecting pipe that is horizontal or inclined downward toward the foreign object chute, A sloped plate facing the connecting pipe is installed at the bottom of the vertical pipe, and a eaves plate is installed above the sloped plate with a gap to form a double plate structure. The position of the gas supply in the dust chute or in the upper part of the dust storage tank is below the double-plate structure, and the gas supply airflow is jetted out from the gap in the double-plate structure and the gap between the double-plate structure and the bottom surface of the connecting pipe, 3. The foreign matter separating apparatus according to claim 1, further comprising a damper provided at an outlet of said connecting pipe for limiting the amount of gas flowing into said foreign matter chute.

4. 4. The foreign matter separation device according to claim 3, wherein the gas flowing into the foreign matter chute from the outlet of the connecting pipe together with the settled metal wire flows into the guide chute via the foreign matter chute and the sieve, and further flows into the vertical pipe together with dust to form a circulating flow that merges with the gas flowing in from the lower part of the vertical pipe.

5. A foreign matter separation device as described in any one of claims 1 to 4, wherein a heat exchanger for cooling gas in the pipeline is provided midway along the pipeline extending from the upper part of the dust chute or the dust storage tank to the lower part of the vertical pipe.

6. 6. The foreign matter separating device according to claim 1, wherein the dust remover collects combustible dust accompanying pyrolysis gas from a waste melting furnace.

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