Non-oxidation heat treatment furnace radiant tube burn-through detection method

Abstract

The invention belongs to the technical field of radiant tube on-line leakage detection, and particularly relates to a non-oxidation heat treatment furnace radiant tube burn-through detection method which can detect whether a radiant tube is burnt through or not under the condition of continuous production and check out specific burn-through reasons, the accuracy rate is 90% or above, and the detection efficiency is high. Therefore, the corresponding burner can be closed in time or the problem that the gas pipeline valve is not closed tightly is effectively solved, the safety problem caused by CO overflow is avoided, the normal burner can be prevented from being shut down by mistake, and the heating quality and the heating efficiency of a steel plate are improved.

Description

Technical Field

[0001] The invention relates to the technical field of online leakage detection of radiation tubes, in particular to a method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace. Background Art

[0002] In Laigang's wide and thick plate heat treatment production line, the shell of the heat treatment furnace is completely sealed and welded, and the pipes connected to the furnace shell are all sealed and welded to ensure its integrity and sealing. The furnace is filled with nitrogen, and the steel plate is heated under a protective atmosphere to avoid oxidation and decarburization. Advanced straight radiant tubes are used for indirect heating, and SiC flame inner tubes with high thermal conductivity are installed inside to reduce the load on the metal radiant tubes, and ensure the temperature uniformity along the length of the radiant tubes, thereby ensuring the service life of the radiant tubes.

[0003] The service life of the existing heat treatment line equipment of Laigang has reached about 15 years. As the service life of the heat treatment line equipment increases, the equipment failures increase year by year. After the radiation tube is burned through, the oxidizing gas enters the furnace from the burn-through point of the radiation tube, causing defects such as oxidation and decarburization of the steel plate. Due to continuous production, it is impossible to visually check the condition of the radiation tube in the furnace, and it can only be judged by experience, and it is impossible to close the burner of the radiation tube burn-through in time and accurately. It can only be replaced after entering the furnace for inspection when the furnace is shut down for overhaul every year.

[0004] Chinese patent document CN110926713A (201911194195.7) A detection method for checking the leakage of the radiation tube of a non-oxidizing heat treatment furnace, the steps are: the heat treatment furnace is in the furnace ignition state, the burners in each zone of the heat treatment furnace are closed; the residual oxygen content in the heat treatment furnace is reduced to a specified value, and each burner is ignited zone by zone; the residual oxygen content in the heat treatment furnace is detected after the single zone burner is ignited, and it is determined whether the residual oxygen content is higher than the specified value of the residual oxygen content; the burner air inlet pipeline of the heat treatment furnace that is higher than the specified value of the residual oxygen content is closed, and the detection is completed and repaired. The above detection method only infers whether there is a leakage problem through the residual oxygen content, but there are many reasons for the residual oxygen content to be higher than the specified value. The above method cannot clearly determine whether the radiation tube has a burn-through problem and the cause of the burn-through, which is easy to cause the burner to be closed by mistake. Since the furnace can only be shut down for maintenance at the end of the year, it is judged that the burner is closed by mistake. In order to ensure the heat treatment quality of steel, the radiation tubes are arranged at even intervals along the length of the heat treatment furnace. Closing the burner will affect the uniformity of the temperature of the steel in the heat treatment furnace, thereby affecting the heat treatment quality of the steel and easily causing a reduction in the subsequent heating efficiency. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for detecting burn-through of a radiant tube in a non-oxidation heat treatment furnace. By detecting the exhaust components of the radiant tube and measuring the oxygen content and CO content, it is possible to effectively detect whether the radiant tube is burned through and whether there is a problem of a gas pipeline valve not being tightly closed, and then the burner can be closed in time or the gas pipeline valve can be repaired or replaced, thereby effectively ensuring the quality and efficiency of steel heat treatment and effectively avoiding safety accidents.

[0006] The technical problem to be solved by the present invention is achieved by adopting the following technical solution: a method for detecting burn-through of a radiation tube in a non-oxidation heat treatment furnace, wherein the outer side of the radiation tube is protected by nitrogen, comprising the following steps:

[0007] Close the burner, gas pipeline valve and air pipeline valve corresponding to the radiation tube to be tested, and wait for 1-2 minutes;

[0008] The gas in the radiation tube is extracted through the burner exhaust port for component detection, oxygen content and CO content;

[0009] The following judgments are made based on the detection situation:

[0010] The first case: when the oxygen content is ≥M%, the radiation tube is normal;

[0011] The second situation: when the oxygen content is less than M%, and the CO content is less than or equal to Nppm, there is a problem of the radiation tube burning through, and the corresponding burner is closed. When repairing later, a new radiation tube is replaced;

[0012] The third situation: when the oxygen content is less than M%, and the CO content is greater than Nppm, there is a problem of the radiation tube burning through and / or the gas pipeline valve not being closed tightly;

[0013] For the third case, replace the gas pipeline valve with a new one and retest. When the oxygen content is ≥M%, it means that the gas pipeline valve is not tightly closed and the radiation tube is normal. When the oxygen content is <M% and the CO content is ≤Nppm, it means that the radiation tube is burned through. Close the corresponding burner and replace the radiation tube with a new one during later maintenance.

[0014] The above-mentioned M and N are preset values ​​and can be set according to the accuracy, performance and monitoring analysis of the gas detection equipment.

[0015] Preferably, for the second case, during maintenance, the heat exchanger of the burner is checked to determine whether there is a fault. If there is a fault, a new burner is replaced to avoid replacing only the radiation tube, which may cause the radiation tube to be burned through again in a short time.

[0016] Preferably, the specific method of extracting the gas in the radiation tube through the burner exhaust port to detect the components is: inserting a plug connector matching the burner exhaust port into the burner exhaust port, and connecting the plug connector to a portable vacuum pump through a conduit;

[0017] Start the portable vacuum pump, align the air outlet of the portable vacuum pump with the detection port of the portable oxygen content detector, wait for more than 10 seconds, and observe the value of the portable oxygen content detector;

[0018] Then, align the portable vacuum pump outlet with the portable CO alarm detection port, wait for more than 10 seconds, and observe the value of the portable CO alarm. Use the portable oxygen content detector and portable CO alarm to detect the oxygen content and CO content of the gas in the radiation tube respectively. Since only one gas is detected at a time, the detection efficiency is faster.

[0019] Preferably, in the present invention, when a portable oxygen content detector or a portable CO alarm is used for detection, the waste gas discharged from the radiation tube is introduced into the respective detection ports for 11-15 seconds.

[0020] Preferably, the specific method of extracting the gas in the radiation tube through the burner exhaust port to detect the components is: inserting a plug connector matching the burner exhaust port into the burner exhaust port, and connecting the plug connector to a portable gas analyzer with a pumping function through a conduit;

[0021] Start the portable gas analyzer to extract the gas in the radiation tube and detect the oxygen content and CO content in the gas at the same time. Directly using a portable gas analyzer with a pumping function to extract the gas in the radiation tube for detection has higher detection accuracy.

[0022] Preferably, the plug connector is detachably arranged at the end of the conduit, so that different plug connectors can be easily replaced according to different exhaust ports of the burner, thereby achieving the purpose of online rapid detection.

[0023] Working principle of the present invention: The technicians of the present invention found that the damage of the radiation tube is mainly caused by the following reasons: the burner heat exchanger is damaged and not replaced in time, and the local high temperature causes the radiation tube to burn through; the gas valve is not closed tightly, the detection component fails, causing the burner to burn all the time, and the long-term high temperature causes the radiation tube to burn through. Among them, the failure of the detection component is to set two temperature measuring thermocouples in each combustion area. If the deviation of the two measured values ​​is large, it means that there is a situation of inaccurate measurement failure. The corresponding problem can be found and eliminated through manual regular inspection and verification. In actual application, it is difficult for technicians to determine whether the radiation tube is burned through due to damage to the burner heat exchanger or lax closure of the gas valve. Usually, after the radiation tube is damaged, only the corresponding burner is closed, and the radiation tube is replaced during the annual overhaul. However, if the radiation tube is burned through due to lax closure of the gas valve, even if the burner is closed, although the quality of steel heat treatment can be guaranteed, it will still cause the gas to be discharged through the exhaust port of the burner, causing a safety accident. In addition, due to the limited number of radiation tubes in the heat treatment furnace, there is a possibility that the radiation tubes are not burned through, but the gas valve is not closed tightly, resulting in the oxygen content being lower than the alarm value, which leads to the misjudgment that the radiation tubes are burned through and the incorrect closure of the normal burners, which in turn causes uneven temperature in the heat treatment furnace, affecting the heat treatment quality of the steel and reducing the heat treatment efficiency.

[0024] The working principle of the radiant tube is to pass gas, which is mainly CO, into the burner through the gas channel, and pass air into the radiant tube through the air channel. After the burner is turned on, CO and oxygen in the air burn in the radiant tube to heat the radiant tube, and the exhaust gas generated by the combustion is discharged from the radiant tube through the exhaust port of the burner. Under normal circumstances, after closing all valves of the burner, the gas in the burner is mainly air and a small amount of exhaust gas generated by combustion and a very small amount of CO. Using existing gas detection devices, it is found that the oxygen content in the mixed gas is generally ≥19.5%, and the CO content is ≤50ppm. When the radiation tube has a burn-through failure, the nitrogen gas on the outside that plays a protective role enters the radiation tube and dilutes the oxygen content, resulting in an oxygen content of less than 19.5%; when the gas pipeline valve is not closed tightly, the gas enters the radiation tube through the pipeline, the CO content will increase, and the corresponding oxygen content will decrease, resulting in a CO content of more than 50ppm and an oxygen content of less than 19.5%. At this time, it can be inferred that the gas pipeline valve is not closed tightly or the radiation tube has burned through. By replacing a new gas pipeline valve, it is possible to further check whether the radiation tube really has a burn-through problem.

[0025] Compared with the prior art, the invention has the following beneficial effects: the method is simple and the tools are simple to use. The method can relatively accurately judge whether the radiant tube has a burn-through problem and check whether the gas pipeline valve is not tightly closed without stopping the furnace and without personnel entering the furnace, so as to close the corresponding burner in time and replace the gas pipeline valve, and avoid erroneous shutdown of normal burners, thereby improving the heating quality and heating efficiency of the steel plate.

[0026] After adopting this method, the quality of steel plates produced by Laigang's heat treatment furnace has been greatly improved, the downtime caused by treatment quality problems has been reduced, and production efficiency has been improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to Example 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the equipment used in the method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to Example 1 of the present invention;

[0029] Figure 3 It is a schematic structural diagram of the equipment used in the method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to Example 2 of the present invention;

[0030] In the figure, 1 is a radiation tube, 2 is a gas channel, 3 is an air channel, 4 is a plug connector, 5 is a conduit, 6 is a portable vacuum pump, 7 is a portable oxygen content detector, 8 is a portable CO alarm, and 9 is a portable gas analyzer;

[0031] 100 burner exhaust port. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0033] Example 1

[0034] like Figure 1 and Figure 2 As shown, a method for detecting burn-through of a radiation tube in a non-oxidation heat treatment furnace is provided, wherein the outer side of the radiation tube 1 is protected by nitrogen, and the method comprises the following steps:

[0035] Close the burner, gas pipeline valve and air pipeline valve corresponding to the radiation tube 1 to be tested, and wait for 1-2 minutes; the gas pipeline valve and air pipeline valve are respectively set at the inlet of the gas channel 2 and the air channel 3 (not shown in the figure).

[0036] The gas in the radiation tube is extracted through the burner exhaust port for component detection, oxygen content and CO content;

[0037] The first case: when the oxygen content is ≥19.5%, the radiation tube is normal.

[0038] The second case: when the oxygen content is less than 19.5% and the CO content is less than or equal to 50ppm, there is a problem of the radiation tube burning through, and the corresponding burner is closed. When it is repaired later, a new radiation tube is replaced. For the second case, during maintenance, the heat exchanger of the burner is checked to determine whether there is a fault. If there is a fault, a new burner is replaced. Since the burner has been removed, technicians in this field can use existing technology to check, and the specific troubleshooting method is not repeated here.

[0039] The third situation: when the oxygen content is less than 19.5% and the CO content is greater than 50 ppm, there is a problem of the radiation tube burning through and / or the gas pipeline valve not being closed tightly.

[0040] For the third case, replace the gas pipeline valve with a new one and retest. When the oxygen content is ≥19.5%, it means that the gas pipeline valve is not closed tightly and the radiation tube is normal. When the oxygen content is <19.5% and the CO content is ≤50ppm, it means that the radiation tube is burned through. Close the corresponding burner and replace it with a new one during later maintenance.

[0041] In this embodiment, M is 19.5 and N is 50, which are the alarm values ​​set for the portable oxygen content detector 7 and the CO alarm 8 respectively.

[0042] The specific method of extracting the gas in the radiation tube 1 through the burner exhaust port 100 to detect the components is as follows: insert the plug connector 4 matching the burner exhaust port 100 into the burner exhaust port 100 to achieve a quick connection, and connect the plug connector 4 to the portable air pump 6 through the conduit 5. The plug connector 4 is detachably arranged at the end of the conduit 5. The plug connector 4 and the burner exhaust port 100 can be sealed or not sealed. It is sufficient to insert the plug connector 4 into the burner exhaust port 100. Since the air pressure in the radiation tube is greater than the external atmospheric pressure, it does not cause external air to enter the radiation tube from the burner exhaust port 100 to affect the detection results.

[0043] Start the portable vacuum pump 6, align the air outlet of the portable vacuum pump 6 close to the detection port of the portable oxygen content detector 7, wait for more than 10 seconds (preferably 11-15 seconds), and observe the value of the portable oxygen content detector 7.

[0044] Then, align the air outlet of the portable vacuum pump 6 with the detection port of the portable CO alarm 8, wait for more than 10 seconds (preferably 11-15 seconds), and observe the value of the portable CO alarm. The lower the oxygen content, the greater the probability of the radiation tube burning through.

[0045] The method of the invention is applicable to a nitrogen-protected atmosphere radiation tube heat treatment furnace. The method of the invention can detect whether the radiation tube is burned through and find out the specific cause of the burn-through under continuous production conditions, with an accuracy rate of more than 90%. The problem of reduced heat treatment quality and reduced heat treatment efficiency caused by incorrect closing of the burner is avoided, the heating quality of the steel plate is effectively guaranteed, and the corresponding burner can be closed in time or the problem of lax closing of the gas pipeline valve can be effectively eliminated, thereby avoiding safety problems caused by CO overflow.

[0046] Example 2

[0047] like Figure 3 As shown, the difference from Example 1 is that the specific method of extracting the gas in the radiation tube 1 through the burner exhaust port 100 to detect the components is: inserting the plug connector 4 matching the burner exhaust port 100 into the burner exhaust port 100 to achieve a quick sealing connection, and connecting the plug connector 4 to a portable gas analyzer 9 with a pumping function through a conduit 5;

[0048] The portable gas analyzer 9 is started to extract the gas in the radiation tube 1 and detect the oxygen content and CO content in the gas at the same time.

Claims

1. A method for detecting burn-through of a radiation tube in a non-oxidation heat treatment furnace, wherein the outer side of the radiation tube is protected by nitrogen, and wherein: The following steps are involved: Close the burner, gas pipeline valve and air pipeline valve corresponding to the radiation tube to be tested, and wait for 1-2 minutes; The gas in the radiation tube is extracted through the burner exhaust port for component detection, oxygen content and CO content; The first case: when the oxygen content is ≥M%, the radiation tube is normal; The second situation: when the oxygen content is less than M%, and the CO content is less than or equal to Nppm, there is a problem of the radiation tube burning through, and the corresponding burner is closed. When repairing later, a new radiation tube is replaced; The third situation: when the oxygen content is less than M%, and the CO content is greater than Nppm, there is a problem of the radiation tube burning through and / or the gas pipeline valve not being closed tightly; For the third case, replace the gas pipeline valve with a new one and retest. When the oxygen content is ≥M%, it means that the gas pipeline valve is not tightly closed and the radiation tube is normal. When the oxygen content is <M% and the CO content is ≤Nppm, it means that the radiation tube is burned through. Close the corresponding burner and replace the radiation tube with a new one during later maintenance. The above M and N are preset values.

2. The method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to claim 1, characterized in that: For the second case, during maintenance, the heat exchanger of the burner is checked to determine whether there is a fault. If there is a fault, replace the burner with a new one.

3. The method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to claim 1, characterized in that: The specific method of extracting the gas in the radiation tube through the burner exhaust port to detect the composition is as follows: inserting a plug connector matching the burner exhaust port into the burner exhaust port, and connecting the plug connector to a portable exhaust pump through a conduit; Start the portable vacuum pump, align the air outlet of the portable vacuum pump with the detection port of the portable oxygen content detector, wait for more than 10 seconds, and observe the value of the portable oxygen content detector; Then, align the air outlet of the portable vacuum pump close to the detection port of the portable CO alarm, wait for more than 10 seconds, and observe the value of the portable CO alarm.

4. The method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to claim 3, characterized in that: When using a portable oxygen content detector or a portable CO alarm for testing, the exhaust gas discharged from the radiation tube is introduced into the respective detection ports for 11-15 seconds.

5. The method for detecting burn-through of radiation tubes in a non-oxidation heat treatment furnace according to claim 1, characterized in that: The specific method of extracting the gas in the radiation tube through the burner exhaust port to detect the composition is as follows: inserting a plug connector matching the burner exhaust port into the burner exhaust port, and connecting the plug connector to a portable gas analyzer with a pump suction function through a conduit; Start the portable gas analyzer to extract the gas in the radiation tube and detect the oxygen and CO contents in the gas at the same time.

6. The method for detecting burn-through of a radiation tube in a non-oxidation heat treatment furnace according to any one of claims 3 to 5, characterized in that: The plug connector is detachably arranged at the end of the catheter.

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