Gas detection device

Abstract

To provide a gas detector capable of keeping the inside of a heating furnace in a high temperature state while suppressing unexpected combustion or explosion.SOLUTION: The gas detector 6 includes a gas concentration detector 14 for detecting the concentration of the fuel gas in the heating furnace 4, a temperature sensor 10 for detecting the temperature in the heating furnace 4, and a controller 24 for determining whether the temperature is lower than the self-combustion temperature of the fuel gas and causing the gas concentration detector 14 to detect the concentration of the fuel gas until the temperature reaches the self-combustion temperature of the fuel gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a gas detection device. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2007-315085 discloses a gas furnace, which is an example of a heating furnace for heat treating steel. This gas furnace is equipped with two or more radiant tubes each with a built-in burner. In this gas furnace ignition control method, the CO concentration of the exhaust gas from the two or more radiant tubes is detected in sequence at a fixed interval, and misfire of each burner is determined. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-315085 Summary of the Invention [Problem to be solved by the invention]

[0004] Such heating furnaces burn fuel gas inside the furnace to heat treat steel. These heating furnaces are inspected and maintained on a regular or irregular basis. When inspected and maintained, fuel gas is introduced into the furnace, and the fuel gas is burned to heat the furnace interior to a high temperature. In this process of burning the fuel gas to heat the interior to a high temperature, there is a risk of unexpected combustion or explosion.

[0005] The applicant's intention is to provide a gas detection device that can maintain a high temperature inside a heating furnace while suppressing unexpected combustion or explosion. [Means for solving the problem]

[0006] The gas detection device disclosed in the present specification is a gas concentration detector for detecting the concentration of fuel gas in the heating furnace; a temperature sensor for detecting the temperature inside the heating furnace; and, a controller that determines whether the temperature is lower than the self-combustion temperature of the fuel gas, and causes the gas concentration detector to detect the concentration of the fuel gas until the temperature reaches the self-combustion temperature of the fuel gas; Equipped with.

[0007] Preferably, the furnace has multiple zones, The gas detection device includes a sampling tube for extracting gas from each of the plurality of zones; an introduction pipe for introducing the gas from the sampling pipe to the gas concentration detector; and an on-off valve for opening and closing the flow path of the sampling pipe; The controller: The on-off valve is opened and closed, and the gas concentration detector is caused to detect the concentration of the fuel gas for each zone.

[0008] Preferably, the controller causes the gas concentration detector to detect the concentration of the fuel gas for each zone at predetermined time intervals.

[0009] Preferably, the controller determines whether the temperature of the zone is below the self-ignition temperature of the fuel gas, and causes the gas concentration detector to detect the concentration of the fuel gas in the zone until the temperature reaches the self-ignition temperature of the fuel gas.

[0010] The gas concentration detection method disclosed in the present specification includes: Fuel gas is burned in the heating furnace, Detecting the temperature inside the heating furnace; determining whether the temperature is less than the self-combustion temperature of the fuel gas; The concentration of the fuel gas in the heating furnace is detected until the temperature reaches the self-ignition temperature of the fuel gas.

[0011] Preferably, the gas concentration detection method includes: a pre-purging step for removing the fuel gas from the heating furnace prior to the combustion of the fuel gas in the heating furnace; determining whether the concentration of the fuel gas in the heating furnace is less than a set concentration; After determining that the concentration of the fuel gas is less than a set concentration, introducing the fuel gas into the heating furnace; The fuel gas is combusted in the heating furnace.

[0012] Preferably, the gas concentration detection method includes: In the heating furnace having a plurality of zones, a temperature is detected for each of the zones; determining whether the temperature is less than the self-combustion temperature of the fuel gas for each of the zones; For each of the zones, the concentration of the fuel gas in the zone is detected until the temperature reaches the self-ignition temperature of the fuel gas.

[0013] Preferably, in this gas concentration detection method, the concentration of the fuel gas is detected for each zone at predetermined time intervals. [Effects of the Invention]

[0014] This gas detection device and gas concentration detection method can maintain a high temperature inside the heating furnace while suppressing unexpected combustion or explosion. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of a heat treatment facility including a gas detection device according to one embodiment. [Figure 2] FIG. 2 is a flowchart of the heating process of the heating furnace of the heat treatment facility of FIG. [Figure 3] FIG. 3 is a flowchart of a gas concentration detection method for the gas detection device of the heat treatment facility of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, preferred embodiments will be described in detail with reference to the drawings as appropriate.

[0017] FIG. 1 shows a metal heat treatment facility 2. This heat treatment facility 2 is used, for example, to heat treat blooms obtained by casting molten steel. This heat treatment facility 2 heats the blooms to a high temperature. The blooms heated to a high temperature are then bloomed and processed into billets of a predetermined shape. This heat treatment facility 2 includes a heating furnace 4 and a gas detection device 6.

[0018] In the heating furnace 4, the bloom is heated while being transported from an entrance 4A to an exit 4B. An arrow F1 in Fig. 1 indicates the direction in which the bloom is transported. The heating furnace 4 is a so-called continuous furnace.

[0019] The heating furnace 4 has multiple zones 8 with different setting conditions such as ignition timing and set temperature. This heating furnace 4 has a first zone 8A, a second zone 8B, a third zone 8C, and a fourth zone 8D. For example, when the heating furnace 4 starts up, the burner ignition timing differs between the first zone 8A and the second zone 8B. Furthermore, the number of burners that are ignited and the set temperature differ between the first zone 8A and the second zone 8B. The number of zones 8 that the heating furnace 4 has is not particularly limited and may be one or a multiple number other than four.

[0020] Arrow F2 in FIG. 1 indicates the direction of gas flow within the heating furnace 4. Within the heating furnace 4, the gas flow direction F2 is opposite to the plume transport direction F1. The gas within the heating furnace 4 flows sequentially from the fourth zone 8D to the third zone 8C, from the third zone 8C to the second zone 8B, and from the second zone 8B to the first zone 8A. The gas that reaches the first zone 8A is discharged from the flue 4C. Note that this gas flow direction F2 is merely an example and is not limited to the direction shown in FIG. 1. For example, the gas flow direction F2 may be from the first zone 8A to the fourth zone 8D.

[0021] The gas detection device 6 includes a plurality of temperature sensors 10. The gas detection device 6 includes a first temperature sensor 10A that detects the temperature of the first zone 8A, a second temperature sensor 10B that detects the temperature of the second zone 8B, a third temperature sensor 10C that detects the temperature of the third zone 8C, and a fourth temperature sensor 10D that detects the temperature of the fourth zone 8D.

[0022] The gas detection device 6 includes a plurality of sampling pipes 12. The gas detection device 6 includes a first sampling pipe 12A that extracts gas from the first zone 8A. The first sampling pipe 12A opens into the ceiling of the heating furnace 4 in the first zone 8A. The position of the opening of the first sampling pipe 12A is not particularly limited as long as it is possible to extract gas from the first zone 8A. Similarly, the gas detection device 6 includes a second sampling pipe 12B that extracts gas from the second zone 8B, a third sampling pipe 12C that extracts gas from the third zone 8C, and a fourth sampling pipe 12D that extracts gas from the fourth zone 8D.

[0023] The gas detection device 6 includes a gas concentration detector 14 that detects the concentration of fuel gas, and an inlet pipe 16 that introduces gas to the gas concentration detector 14. The inlet pipe 16 is connected to each of the first sampling pipe 12A, the second sampling pipe 12B, the third sampling pipe 12C, and the fourth sampling pipe 12D.

[0024] Gas detection device 6 includes a plurality of on-off valves 18. Gas detection device 6 includes first on-off valve 18A that opens and closes the flow path of first sampling pipe 12A, second on-off valve 18B that opens and closes the flow path of second sampling pipe 12B, third on-off valve 18C that opens and closes the flow path of third sampling pipe 12C, and fourth on-off valve 18D that opens and closes the flow path of fourth sampling pipe 12D.

[0025] Gas detection device 6 includes gas concentration detector 14, exhaust fan 20 that exhausts gas from inlet pipe 16, and exhaust pipe 22 through which gas is exhausted by exhaust fan 20.

[0026] The gas detection device 6 includes a plurality of temperature sensors 10 , a gas concentration detector 14 , a plurality of on-off valves 18 , and a controller 24 that controls an exhaust fan 20 .

[0027] For example, the controller 24 controls the first on-off valve 18A to open the flow path of the first sampling pipe 12A. The controller 24 controls the second on-off valve 18B to the fourth on-off valve 18D to close the flow paths from the second sampling pipe 12B to the fourth sampling pipe 12D. The controller 24 controls the exhaust fan 20 to draw gas from the first zone 8A into the inlet pipe 16. The controller 24 controls the gas concentration detector 14 to detect the fuel gas concentration of the gas in the inlet pipe 16. Next, the controller 24 controls the first on-off valve 18A to close the flow path of the first sampling pipe 12A and the second on-off valve 18B to open the flow path of the second sampling pipe 12B. The controller 24 controls the exhaust fan 20 to exhaust gas from the first zone 8A from the inlet pipe 16 to the exhaust pipe 22 and draw gas from the second zone 8B into the inlet pipe 16. The controller 24 causes the gas concentration detector 14 to detect the fuel gas concentration of the gas in the inlet pipe 16. In this way, in the gas detection device 6, the controller 24 controls the gas concentration detector 14, the multiple on-off valves 18, and the exhaust fan 20 to detect the fuel gas concentration in each of the first zone 8A to fourth zone 8D.

[0028] 2 shows a flowchart of a method for starting up the heat treatment equipment 2 after the operation has been stopped and maintenance and inspection has been completed. The method for starting up the heat treatment equipment 2 will be described below.

[0029] In the heat treatment equipment 2, the heating furnace 4 is pre-purged (STEP 1A). The gas inside the heating furnace 4 is sucked out, and outside air is drawn into the heating furnace 4. As a result, the gas inside the furnace is replaced with outside air.

[0030] The controller 24 detects the fuel gas concentrations in the first zone 8A to the fourth zone 8D (STEP 2A). The controller 24 detects the fuel gas concentration in the first zone 8A, the fuel gas concentration in the second zone 8B, the fuel gas concentration in the third zone 8C, and the fuel gas concentration in the fourth zone 8D, in that order.

[0031] The controller 24 determines whether the fuel gas concentrations in all the zones 8 are lower than the set concentration (STEP 3A). If the fuel gas concentrations in all the zones 8 are lower than the set concentration, the controller 24 supplies fuel gas to the heating furnace 4 (STEP 4A). In the first zone 8A, the second zone 8B, the third zone 8C, and the fourth zone 8D, the burners are ignited at predetermined ignition timings (STEP 5A). Each of the first zone 8A, the second zone 8B, the third zone 8C, and the fourth zone 8D is set to a predetermined temperature state.

[0032] The controller 24 determines whether the fuel gas concentrations in all the zones 8 are lower than the set concentration (STEP 3A), and issues an alarm if the fuel gas concentration in any of the zones 8 is equal to or higher than the set concentration (STEP 6A). The alarm is not particularly limited, but examples include the illumination of an alarm light, an alarm sound, etc. This alarm prompts the heat treatment equipment 2 to check for any abnormalities and take any necessary measures.

[0033] Fig. 3 shows a flowchart of a gas concentration detection method in the process of fuel gas supply (STEP 4A) and ignition (STEP 5A) in Fig. 2. This gas concentration detection method will be described below.

[0034] When the fuel gas supply (STEP 4A) shown in FIG. 2 is performed, the controller 24 detects the fuel gas concentration in the first zone 8A (STEP 1B), as shown in FIG. 3. The controller 24 determines whether the fuel gas concentration in the first zone 8A is less than a first set concentration (STEP 2B). This first set concentration is a preset concentration. The unit of concentration here is not particularly limited, but may be, for example, volume percent. If the fuel gas concentration is less than the first set concentration, the controller 24 determines whether the temperature in the first zone 8A is less than the self-ignition temperature of the fuel gas (STEP 3B). This self-ignition temperature refers to the temperature at which the fuel gas ignites even in the absence of a fire source in the furnace. If the temperature in the first zone 8A is less than the self-ignition temperature, the controller 24 waits a predetermined time and then again executes the steps of detecting the fuel gas concentration (STEP 1B), determining whether the concentration is less than the first set concentration (STEP 2B), and determining whether the concentration is less than the self-ignition temperature (STEP 3B). When the temperature of the first zone 8A reaches the self-ignition temperature of the fuel gas, the controller 24 ends detection of the fuel gas concentration in the first zone 8A (STEP 4B). In this way, until the temperature of the first zone 8A reaches the self-ignition temperature, the controller 24 repeatedly executes detection of the fuel gas concentration (STEP 1B), determination that the concentration is below the first set concentration (STEP 2B), and determination that the concentration is below the self-ignition temperature (STEP 3B) at predetermined intervals.

[0035] On the other hand, if the fuel gas concentration is equal to or greater than the first set concentration in the determination of whether the concentration is less than the first set concentration (STEP 2B), the controller 24 issues an alarm (STEP 5B). Examples of the alarm include, but are not limited to, lighting an alarm light, sounding an alarm, etc. The controller 24 issues the alarm and stops the supply of fuel gas to the first zone 8A (STEP 6B). Furthermore, the controller 24 determines whether the fuel gas concentration in the first zone 8A is less than a second set concentration (STEP 7B). This second set concentration is a concentration that is even higher than the first set concentration and is a preset concentration. If the fuel gas concentration is equal to or greater than the second set concentration, the controller 24 issues an alarm (STEP 8B). The controller 24 issues the alarm and closes the on-off valve of the main pipe that supplies fuel gas to the heat treatment equipment 2, shutting off the main pipe (STEP 9B).

[0036] Similar to the first zone 8A, the controller 24 detects the fuel gas concentration (STEP 1B), determines whether the concentration is less than the first set concentration (STEP 2B), determines whether the concentration is less than the self-combustion temperature (STEP 3B), and ends detection of the fuel gas concentration (STEP 4B) in each of the second zone 8B, third zone 8C, and fourth zone 8D. Furthermore, if the conditions are satisfied, the controller 24 issues an alarm (STEP 5B), stops the fuel gas supply (STEP 6B), determines whether the concentration is less than the second set concentration (STEP 7B), issues an alarm (STEP 8B), and shuts off the fuel gas main pipe (STEP 9B) in each of the second zone 8B, third zone 8C, and fourth zone 8D.

[0037] Specifically, for example, the controller 24 detects the fuel gas concentration in the first zone 8A (STEP 1B), determines whether the concentration is less than the first set concentration (STEP 2B), and determines whether the concentration is less than the spontaneous combustion temperature (STEP 3B). As described above, if the temperature of the first zone 8A is less than the spontaneous combustion temperature, the controller 24 waits a predetermined time and then detects the fuel gas concentration in the first zone 8A again (STEP 1B).

[0038] During a predetermined time period after determining that the temperature in the first zone 8A is below the spontaneous combustion temperature (STEP 3B), the controller 24 detects the fuel gas concentration in the second zone 8B (STEP 1B), determines that the concentration is below the first set concentration (STEP 2B), and determines that the concentration is below the spontaneous combustion temperature (STEP 3B). If the temperature in the second zone 8B is below the spontaneous combustion temperature, the controller 24 waits a predetermined time period and then again detects the fuel gas concentration in the second zone 8B (STEP 1B).

[0039] During a predetermined time period after determining that the temperature in the second zone 8B is below the spontaneous combustion temperature (STEP 3B), the controller 24 detects the fuel gas concentration in the third zone 8C (STEP 1B), determines that the concentration is below the first set concentration (STEP 2B), and determines that the concentration is below the spontaneous combustion temperature (STEP 3B). If the temperature in the third zone 8C is below the spontaneous combustion temperature, the controller 24 waits a predetermined time period and then again detects the fuel gas concentration in the third zone 8C (STEP 1B).

[0040] During a predetermined time period after determining that the temperature in the third zone 8C is below the spontaneous combustion temperature (STEP 3B), the controller 24 detects the fuel gas concentration in the fourth zone 8D (STEP 1B), determines that the concentration is below the first set concentration (STEP 2B), and determines that the concentration is below the spontaneous combustion temperature (STEP 3B). If the temperature in the fourth zone 8D is below the spontaneous combustion temperature, the controller 24 waits a predetermined time period and then again detects the fuel gas concentration in the fourth zone 8D (STEP 1B).

[0041] During a predetermined time after determining that the temperature is below the spontaneous combustion temperature in the fourth zone 8D (STEP 3B), the controller 24 returns to the first zone 8A and performs detection of the fuel gas concentration (STEP 1B), determination that the concentration is below the first set concentration (STEP 2B), and determination that the concentration is below the spontaneous combustion temperature (STEP 3B).

[0042] The controller 24 repeatedly detects the fuel gas concentration in each of the first zone 8A, the second zone 8B, the third zone 8C, and the fourth zone 8D until the spontaneous combustion temperature is reached. The controller 24 ends detection of the fuel gas concentration in the zone 8 among the first zone 8A, the second zone 8B, the third zone 8C, and the fourth zone 8D that has reached the spontaneous combustion temperature, and repeatedly detects the fuel gas concentration in the other zones 8 except for the zone 8 that has reached the spontaneous combustion temperature until the spontaneous combustion temperature is reached. The controller 24 ends detection of the fuel gas concentration when all of the zones 8 have reached the spontaneous combustion temperature.

[0043] In this gas detection device 6, controller 24 determines whether the temperature of first zone 8A is below the self-combustion temperature of the fuel gas. Controller 24 causes gas concentration detector 14 to detect the concentration of the fuel gas until the temperature of first zone 8A reaches the self-combustion temperature of the fuel gas. This gas detection device 6 can prevent unexpected combustion or explosion caused by fuel gas remaining in first zone 8A.

[0044] In this heat treatment equipment 2, the heating furnace 4 has first zone 8A to fourth zone 8D. The gas detection device 6 is equipped with a sampling pipe 12 that extracts gas for each zone 8, and an on-off valve 18 that opens and closes the flow path of the sampling pipe 12. The gas detection device 6 is equipped with an introduction pipe 16 that leads gas from each sampling pipe 12 to a gas concentration detector 14. A controller 24 opens and closes the on-off valve 18, causing the gas concentration detector 14 to detect the concentration of fuel gas for each zone 8. This gas detection device 6 can suppress unexpected combustion or explosion in multiple zones 8 that have different setting conditions such as set temperature and ignition timing.

[0045] Controller 24 causes gas concentration detector 14 to detect the concentration of fuel gas for each zone 8, from first zone 8A to fourth zone 8D, at predetermined time intervals. Gas detection device 6 can detect the concentration of fuel gas in multiple zones 8 with one gas concentration detector 14. Gas detection device 6 can reduce equipment costs and installation space.

[0046] In this gas concentration detection method, prior to combustion of the fuel gas, a pre-purge is performed to remove the fuel gas from inside the heating furnace 4. This gas concentration detection method determines whether the concentration of the fuel gas inside the heating furnace 4 is below a set concentration, and after determining that the concentration of the fuel gas is below the set concentration, the fuel gas is introduced into the heating furnace 4 and burned inside the heating furnace 4. This gas concentration detection method can safely prevent unexpected combustion or explosion from occurring.

[0047] In this gas concentration detection method, the controller 24 determines the concentration of fuel gas at a plurality of set concentrations, including a first set concentration and a second set concentration higher than the first set concentration. When the controller 24 detects a concentration equal to or higher than the first set concentration, it stops the supply of fuel gas to the detected zone 8. When the controller 24 detects a concentration equal to or higher than the second set concentration, it shuts off the main pipe through which the fuel gas is supplied. This gas concentration detection method determines the fuel gas concentration at a plurality of set concentrations in a stepwise manner, thereby minimizing the range of corresponding treatments while ensuring safety. This gas concentration detection method can suppress a decrease in productivity while ensuring safety. It is preferable that the gas concentration detection method determine the fuel gas concentration at a plurality of set concentrations in a stepwise manner.

[0048] 1, gas in the heating furnace 4 flows from the fourth zone 8D toward the first zone 8A. When the fuel gas concentration in the first zone 8A, which is located downstream in the gas flow, is equal to or greater than a first set concentration, the cause may be one of the upstream zones 8B through 8D. Therefore, from a safety standpoint, the supply of fuel gas to the zone 8 where the fuel gas concentration is detected to be equal to or greater than the first set concentration and to the zones 8 upstream of this zone 8 may be stopped. [Explanation of symbols]

[0049] 4...Heating furnace 6. Gas detection equipment 8 Zone 10. Temperature sensor 12. Sampling tube 14 Gas concentration detector 16...Introduction tube 18. On-off valve 24 Controller

Claims

1. a gas concentration detector for detecting the concentration of fuel gas in the heating furnace; a temperature sensor for detecting the temperature inside the heating furnace; and, a controller that determines whether the temperature is lower than the self-combustion temperature of the fuel gas, and causes the gas concentration detector to detect the concentration of the fuel gas until the temperature reaches the self-combustion temperature of the fuel gas; A gas detection device comprising:

2. the furnace has multiple zones; a sampling tube for extracting gas from each of the plurality of zones; an introduction pipe for introducing the gas from the sampling pipe to the gas concentration detector; and an on-off valve for opening and closing the flow path of the sampling pipe; The controller:

2. The gas detection device according to claim 1, wherein the on-off valve is opened and closed to cause the gas concentration detector to detect the concentration of the fuel gas for each of the zones.

3. 3. The gas detection device according to claim 2, wherein the controller causes the gas concentration detector to detect the concentration of the fuel gas for each of the zones at each predetermined time interval.

4. 4. The gas detection device according to claim 2, wherein the controller determines whether the temperature of the zone is less than the self-combustion temperature of the fuel gas, and causes the gas concentration detector to detect the concentration of the fuel gas in the zone until the temperature reaches the self-combustion temperature of the fuel gas.

5. Fuel gas is burned in the heating furnace, Detecting the temperature inside the heating furnace; determining whether the temperature is less than the self-combustion temperature of the fuel gas; a gas concentration detection method for detecting a concentration of the fuel gas in the heating furnace until the temperature reaches a self-combustion temperature of the fuel gas.

6. a pre-purging step for removing the fuel gas from the heating furnace prior to the combustion of the fuel gas in the heating furnace; determining whether the concentration of the fuel gas in the heating furnace is less than a set concentration; After determining that the concentration of the fuel gas is less than a set concentration, introducing the fuel gas into the heating furnace; The gas concentration detection method according to claim 5 , wherein the fuel gas is combusted in the heating furnace.

7. In the heating furnace having a plurality of zones, a temperature is detected for each of the zones; determining whether the temperature is less than the self-combustion temperature of the fuel gas for each of the zones; 7. The gas concentration detection method according to claim 5, wherein the concentration of the fuel gas in each of the zones is detected until the temperature reaches a self-combustion temperature of the fuel gas.

8. 8. The gas concentration detection method according to claim 7, wherein the concentration of the fuel gas is detected for each zone at predetermined time intervals.

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