Dust collection system

Abstract

To provide a dust collection system that can suppress a risk of generating such as a fire or explosion caused by merging an exhaust gas having high-CO concentration with atmospheric air.SOLUTION: A dust collection system includes a merging part 4 for causing atmospheric air to merge with an exhaust gas in the middle of piping 3 that forms a gas flow passage connecting an electric furnace 1 to a dust collector 2; and a fire extinguisher introduction part 10 installed upstream of the merging part 4 of the gas flow passage to introduce a fire extinguisher for suppressing burning or explosion of the exhaust gas into the gas flow passage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a dust collection system that filters exhaust gas discharged from a furnace with a dust collector.

Background Art

[0002] A dust collection system that introduces exhaust gas discharged from an electric furnace into a dust collector, filters the exhaust gas with the dust collector, and sends it into the atmosphere is in practical use. Regarding such a dust collection system, various inventions have been proposed so far.

[0003] For example, Patent Document 1 discloses a technique in which dust discharged from a dust collector by filtering exhaust gas is formed into dust pellets by a granulator, and the dust pellets are returned to an electric furnace facility by pneumatic transportation and processed in the electric furnace.

[0004] When charging iron scrap as a recycled raw material into an electric furnace for processing, if impurities such as vinyl chloride are mixed in addition to the iron scrap, incomplete combustion may occur. Incomplete combustion increases the concentration of CO (carbon monoxide) contained in the exhaust gas generated in the electric furnace. The exhaust gas generated in the electric furnace is merged with the atmosphere before being introduced into the dust collector for the purpose of suppressing the generation of dioxins and reducing the gas temperature.

[0005] Depending on the CO concentration of the exhaust gas, there is a possibility of becoming an explosive state by merging with the atmosphere sufficiently containing O2 (oxygen). Also, even if an explosion does not occur, there is a concern that a flame may occur and the filter cloth inside the dust collector may burn. Thus, when the CO concentration increases in the gas flow path from the electric furnace to the dust collector or inside the dust collector, the risk of fire and explosion increases.

[0006] The current measure involves temporarily shutting down the electric furnace when the CO concentration exceeds a certain level, releasing the CO through a dust collector, and then restarting the furnace. In other words, operational measures are being taken to prevent fires and explosions. However, shutting down the electric furnace reduces yield. Furthermore, the furnace temperature drops when the furnace is shut down, requiring reheating, which significantly reduces efficiency. For this reason, temporarily shutting down the electric furnace is generally undesirable. In recent years, the amount of impurities has been increasing, so new countermeasures are expected. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-86845 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of the above-mentioned conventional problems, and aims to provide a dust collection system that can reduce the risk of fire and explosion caused by mixing exhaust gas with high CO concentration with the atmosphere. [Means for solving the problem]

[0009] To achieve the above objective, a dust collection system according to one aspect of the present invention is configured as follows: In a dust collection system that filters exhaust gas discharged from a furnace with a dust collector, the gas flow path connecting the furnace and the dust collector has a confluence section in the middle where atmospheric air is added to the exhaust gas, and an introduction section is provided for introducing combustion suppression means into the gas flow path to suppress combustion and explosion of the exhaust gas.

[0010] Herein, the dust collection system according to the present invention may include a sensor for measuring the CO concentration of exhaust gas discharged from a furnace, and if the CO concentration measured by the sensor exceeds or is likely to exceed a predetermined threshold, a combustion suppression means may be introduced into the gas flow path.

[0011] Furthermore, a fire extinguishing agent can be used as a means of suppressing combustion. Alternatively, an inert gas can also be used as a means of suppressing combustion. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a dust collection system that can reduce the risk of fire and explosion caused by mixing exhaust gas with high CO concentration with the atmosphere. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example configuration of a dust collection system according to the first embodiment of the present invention. [Figure 2] This figure shows an example configuration of a dust collection system according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0014] A dust collection system according to one aspect of the present invention will be described with reference to the drawings. In the following description, a dust collection system for processing exhaust gas discharged from an electric furnace will be used as an example, but the present invention can also be applied to dust collection systems for processing exhaust gas discharged from furnaces other than electric furnaces, such as high-frequency heating circuits and low-frequency heating circuits.

[0015] [First Embodiment] Figure 1 shows an example of the configuration of a dust collection system according to the first embodiment. The dust collection system is basically configured to filter the exhaust gas discharged from the electric furnace 1 with a dust collector 2. The electric furnace 1 and the dust collector 2 are connected by piping 3 that forms a gas flow path for the exhaust gas. If there are multiple electric furnaces 1, the exhaust gas discharged from each electric furnace 1 is introduced into the dust collector 2 through a common or individual gas flow path. A confluence section 4 is provided in the middle of the piping 3 to combine the exhaust gas in the piping 3 with the atmosphere. Therefore, the exhaust gas discharged from the electric furnace 1 is combined with the atmosphere at the confluence section 4 before being introduced into the dust collector 2. As mentioned above, the confluence section 4 is provided to combine the exhaust gas with the atmosphere in order to suppress the generation of dioxins and the gas temperature generated from the furnace.

[0016] Depending on the CO concentration of the exhaust gas emitted from electric furnace 1, the mixture with the atmosphere can create conditions that make it prone to fire or explosion. A CO concentration of 8-11% makes it easy to ignite, while a concentration exceeding 20% ​​makes it less likely to explode.

[0017] As a countermeasure, the dust collection system according to the first embodiment is provided with a fire extinguishing agent introduction section 10 upstream of the confluence section 4 of the gas flow path (piping 3) for introducing the fire extinguishing agent into the gas flow path. The fire extinguishing agent is an example of a combustion suppressant used to suppress the combustion and explosion of exhaust gas, and for example, a powdered fire extinguishing agent mainly composed of ammonium phosphate is used. Liquid or foamy fire extinguishing agents such as potassium carbonate aqueous solution may also be used, but those with high volatility are preferable to facilitate subsequent maintenance.

[0018] The configuration of the dust collection system according to the first embodiment will now be described in more detail. The dust collection system according to this embodiment includes a sensor 5 for measuring the CO concentration of exhaust gas discharged from the electric furnace 1, a tank 11 for storing fire extinguishing agent, a rotary valve 12 for introducing the fire extinguishing agent in the tank 11 into the piping 3, and a controller 6 for controlling the rotary valve 12 according to the CO concentration measured by the sensor 5. The tank 11 and the rotary valve 12 constitute the fire extinguishing agent introduction section 10. In Figure 1, the fire extinguishing agent introduction section 10 is located in one place, but the fire extinguishing agent introduction sections 10 may be located at multiple locations along the gas flow path.

[0019] Sensor 5 is positioned upstream of the gas flow path confluence 4, in a location where it can measure the CO concentration of the exhaust gas moving through the gas flow path without any problems. Rotary valve 12 is positioned upstream of the gas flow path confluence 4, in a location where the CO concentration of the exhaust gas can be sufficiently reduced by the combustion inhibitor before it reaches the confluence 4. For example, if the length of piping 3 is 100m and the confluence 4 is located about 15m from the dust collector side, then sensor 5 is positioned about 40m from the electric furnace side, and rotary valve 12 is positioned about 10m downstream from it. Note that it is not necessarily required to arrange sensor 5 and rotary valve 12 in that order; they may be arranged in the reverse order.

[0020] Sensor 5 transmits a sensor signal containing the measurement result of the CO concentration of the exhaust gas to controller 6. Based on the sensor signal received from sensor 5, controller 6 determines whether the CO concentration of the exhaust gas exceeds a predetermined threshold. The threshold is set to 5%, for example, with safety in mind. If the CO concentration of the exhaust gas exceeds the threshold, controller 6 transmits a control signal to rotary valve 12 to instruct it to open the valve; otherwise, it transmits a control signal to rotary valve 12 to instruct it to close the valve. Rotary valve 12 opens and closes the valve according to the control signal received from controller, switching between introducing or stopping the fire extinguishing agent into the gas flow path. Controller 6 may also control the amount of fire extinguishing agent introduced to increase as the CO concentration of the exhaust gas increases.

[0021] As described above, in the dust collection system according to the first embodiment, a confluence section 4 for merging air into the exhaust gas is provided in the middle of the pipe 3 forming the gas flow path connecting the electric furnace 1 and the dust collector 2, and an extinguishing agent introduction section 10 for introducing an extinguishing agent for suppressing combustion and explosion of the exhaust gas into the gas flow path is provided upstream of the confluence section 4 of the gas flow path. With such a configuration, when the CO concentration of the exhaust gas exceeds the threshold value, the extinguishing agent in the tank 11 is introduced into the pipe 3 upstream of the confluence section 4, so that the risk of fire and explosion due to merging high-CO-concentration exhaust gas with air can be suppressed.

[0022] In the first embodiment, an explanation has been given of arranging the combustion inhibitor upstream of the confluence section. However, depending on the layout of the furnace and the dust collector, the combustion inhibitor may be arranged downstream of the confluence section. In this case, it is necessary to supply the combustion inhibitor in the direction opposite to the flow direction of the exhaust gas. Depending on the layout of the furnace, the dust collector, and various devices, by supplying the combustion inhibitor from the downstream side of the confluence section, it is possible to suppress CO explosion while maintaining the layout of the devices.

[0023] In addition, although the combustion inhibitor is supplied when the CO concentration of the exhaust gas exceeds a predetermined threshold value, the combustion inhibitor may be supplied even if the CO concentration does not exceed the threshold value. For example, the sensor 5 measures the concentration change of the CO concentration to such an extent that there is a possibility of reaching the CO concentration at which there is a risk of explosion, and when the concentration change may reach the CO explosion concentration, the combustion inhibitor may be supplied. In this case, a further suppression of CO explosion can be achieved.

[0024] [Second Embodiment] Figure 2 shows an example of the configuration of a dust collection system according to the second embodiment. The dust collection system according to the second embodiment is provided with an inert gas introduction section 20 instead of a fire extinguishing agent introduction section 10, and the other configurations are basically the same as those of the first embodiment. That is, in the dust collection system according to the second embodiment, an inert gas introduction section 20 is provided upstream of the confluence section 4 of the gas flow path to introduce an inert gas into the gas flow path. An inert gas is an example of a combustion suppressant used to suppress the combustion and explosion of exhaust gas, and gases such as N2 (nitrogen) and CO2 (carbon dioxide) are used to lower the O2 concentration.

[0025] The configuration of the dust collection system according to the second embodiment will be described in more detail. The dust collection system according to this embodiment includes a sensor 5 for measuring the CO concentration of exhaust gas discharged from the electric furnace 1, a tank 21 for storing inert gas, a nozzle 22 for introducing the inert gas in the tank 21 into the piping 3, and a controller 6 for controlling the nozzle 22 according to the CO concentration measured by the sensor 5. The tank 21 and the nozzle 22 constitute the inert gas introduction section 20. In Figure 2, the inert gas introduction section 20 is located in one place, but the inert gas introduction sections 20 may be arranged at multiple locations along the gas flow path.

[0026] The controller 6 sends a control signal to the nozzle 22 to instruct it to open the nozzle if the CO concentration in the exhaust gas exceeds a threshold (for example, 5%), and to instruct it to close the nozzle otherwise. The nozzle 22 opens and closes the nozzle according to the control signal received from the controller, switching between introducing or stopping the inert gas into the gas flow path. The controller 6 may also control the amount of inert gas introduced to increase as the CO concentration in the exhaust gas increases.

[0027] As described above, in the dust collection system according to the second embodiment, a confluence section 4 is provided in the middle of the piping 3 that forms a gas flow path connecting the electric furnace 1 and the dust collector 2, where the exhaust gas is combined with the atmosphere. Upstream of the confluence section 4 in the gas flow path, an inert gas introduction section 20 is provided to introduce an inert gas into the gas flow path to suppress combustion and explosion of the exhaust gas. With this configuration, when the CO concentration of the exhaust gas exceeds a threshold, the inert gas in the tank 21 is introduced into the piping 3 upstream of the confluence section 4, thereby reducing the risk of fire and explosion caused by combining exhaust gas with a high CO concentration with the atmosphere.

[0028] In the dust collection system according to the first embodiment, a fire extinguishing agent introduction unit 10 is provided, and in the dust collection system according to the second embodiment, an inert gas introduction unit 20 is provided. However, a combination of these configurations is also possible. That is, a dust collection system equipped with both a fire extinguishing agent introduction unit 10 and an inert gas introduction unit 20 is also possible. This makes it possible to further enhance the effect of suppressing the risk of fire and explosion caused by mixing exhaust gas with high CO concentration with the atmosphere.

[0029] Furthermore, in the first and second embodiments, the introduction of combustion inhibitors (fire extinguishing agents and inert gases) is controlled based on the CO concentration of the exhaust gas measured by the sensor 5, but the introduction of combustion inhibitors may also be controlled according to other conditions. For example, combustion inhibitors may be introduced continuously after a certain period of time has elapsed since the electric furnace 1 began operation. As another example, a means for determining the type of raw material to be fed into the electric furnace 1 may be provided, and if a specific type of raw material that is prone to incomplete combustion is fed in, combustion inhibitors may be introduced for a certain period of time thereafter.

[0030] Furthermore, measures other than the fire extinguishing agent introduction section 10 and the inert gas introduction section 20 may be added to prevent fires and explosions caused by the merging of exhaust gas with a high CO concentration with the atmosphere. For example, measures can be taken against ignition sources that cause fires and explosions, such as static electricity, combustion residue from the furnace, and scattering of molten iron. As an example, an electrostatic discharge section that uses ions to discharge static electricity may be provided upstream of the merging section 4. As another example, an ignition source collection section (e.g., preduster, cyclone, impact type louver, filter) that collects combustion residue from the furnace and molten iron may be provided upstream of the merging section 4.

[0031] Although the dust collection system according to the present invention has been described above based on several embodiments, the present invention is not limited to the configuration described in the above embodiments, and its configuration can be modified as appropriate without departing from the spirit of the invention. [Industrial applicability]

[0032] This invention can be used in a dust collection system that filters exhaust gas discharged from a furnace using a dust collector. [Explanation of Symbols]

[0033] 1 Electric furnace 2. Piping (gas flow path) 3. Dust collector 4. Confluence 5 sensors 6 Controllers 10. Fire extinguishing agent introduction section 11 tanks 12 Rotary Valves 20 Inert gas introduction section 21 tanks 22 nozzles

Claims

1. A dust collection system for filtering exhaust gas discharged from an electric furnace with a dust collector, In the gas flow path connecting the electric furnace and the dust collector, there is a confluence section that combines the exhaust gas with the atmosphere in order to suppress the generation of dioxins and lower the gas temperature. A dust collection system characterized by having an introduction section for introducing combustion suppression means into the gas flow path to suppress the combustion and explosion of CO in the exhaust gas generated by the reaction with the combined atmosphere.

2. In the dust collection system according to claim 1, The system includes a sensor for measuring the CO concentration of exhaust gas discharged from the electric furnace, A dust collection system characterized in that, when the CO concentration measured by the sensor exceeds a predetermined threshold or is likely to exceed a predetermined threshold, the combustion suppression means is introduced into the gas flow path.

3. In the dust collection system according to claim 1 or claim 2, The dust collection system is characterized in that the combustion suppression means is a fire extinguishing agent.

4. In the dust collection system according to claim 1 or claim 2, The dust collection system is characterized in that the combustion suppression means is an inert gas.

Images