A method for on-line troubleshooting of a cold rolling annealing furnace radiation tube

Abstract

This invention discloses an online troubleshooting method for radiant tubes in a cold rolling annealing furnace. It involves collecting and establishing a baseline dataset of CO, CO2, and O2 concentrations in each layer of flue gas branch pipes under normal production conditions. During normal furnace operation, the CO concentration ai1 in each layer of flue gas branch pipes is monitored in real time. When the CO concentration ai1 in the i-th layer of flue gas branch pipe exceeds the baseline range, a troubleshooting mechanism is triggered. The operating status of each radiant tube in the i-th layer is retrieved and monitored, and the dynamic response of the CO concentration in that layer of flue gas branch pipe is monitored simultaneously. Step S4: Multiple rounds of iterative troubleshooting are repeated to confirm all faulty radiant tubes and shut them down. Subsequently, it is verified whether the flue gas composition has returned to the baseline range. This method solves the technical problems of existing technologies, such as the need for machine shutdown for radiant tube leak detection, high reliance on manual labor, and high misjudgment rate.

Description

Technical Field

[0001] This invention relates to the field of fault detection technology for radiant tubes in cold rolling annealing furnaces, and specifically to an online troubleshooting method for radiant tubes in cold rolling annealing furnaces. Background Technology

[0002] The cold rolling annealing furnace is a key piece of equipment on the cold rolling production line, used for recrystallization annealing of cold-rolled strip steel. Under the combined effects of high temperature, mechanical impact, and alternating hot and cold temperatures, the radiant tubes inside the annealing furnace are prone to problems such as tube wall cracking or heat exchanger leakage after long-term operation. These failures not only significantly reduce the heating efficiency of the annealing furnace, leading to increased fuel consumption, but also affect the stability of the furnace atmosphere due to the infiltration of the protective atmosphere or external air, ultimately causing stains on the strip steel surface and severely impacting product quality.

[0003] Currently, leak detection for radiant tubes is mainly divided into two categories: shutdown leak detection and online leak detection. Traditional shutdown leak detection requires sealing the radiant tube ports to create a closed space after the annealing furnace has been shut down and cooled, then introducing tracer gas or protective gas for detection. While this method is intuitive, the preparation is cumbersome, the detection cycle is long, and frequent furnace shutdowns and restarts negatively impact production rhythm and equipment lifespan. Existing online leak detection technologies largely rely on manual observation of the location of stains on the strip surface or simply on detecting the overall trend of changes in components such as O2 and CO in the flue gas. However, because the furnace conditions themselves fluctuate during normal operation, relying solely on component threshold alarms is prone to misjudgment. Furthermore, traditional online inspections often require manual testing of each tube individually, which is labor-intensive, slow, and difficult to meet the efficient operation and maintenance requirements of modern continuous production. Summary of the Invention

[0004] The purpose of this invention is to provide an online troubleshooting method for radiant tubes in cold rolling annealing furnaces, so as to solve the technical problems of existing technologies, such as the need to shut down the machine for radiant tube leak detection, high dependence on manual labor, and high misjudgment rate.

[0005] To achieve the above technical objectives, this invention provides an online troubleshooting method for radiant tubes in cold-rolled annealing furnaces, comprising the following steps: Step S1: Deploy an online flue gas monitoring system on each layer of flue gas branch pipes of the annealing furnace, collect and establish a benchmark dataset of CO, CO2, and O2 concentrations in each layer of flue gas branch pipes under normal production conditions; the benchmark dataset includes the average CO concentration ai0, the average CO2 concentration bi0, and the average O2 concentration ci0 in each layer of flue gas branch pipes, where i is the layer number of the radiant tube, i∈[1,n], and n is the total number of radiant tube layers; Furthermore, by analyzing that the sum of CO and CO2 concentrations in each radiant tube branch remains consistent, i.e. C is conserved and O2 concentration is relatively stable, it is further confirmed that this is the normal operating state of the radiant tube (the radiant tube is fault-free).

[0006] Step S2: During the normal operation of the annealing furnace, monitor the CO concentration ai1 in each layer of flue gas branch pipe in real time; when the CO concentration ai1 in the i-th layer of flue gas branch pipe exceeds the reference range, i.e. ai1-ai0≥30ppm, trigger the fault troubleshooting mechanism. Step S3: Retrieve and monitor the operating status of each radiant tube in the i-th layer, and simultaneously monitor the dynamic response of CO concentration in the flue gas branch pipe of that layer; if the CO concentration in that layer drops back to the reference range when a radiant tube is in the closed state, but the CO concentration exceeds the reference range when the radiant tube is in the open state, then the radiant tube is determined to be a faulty radiant tube (that is, if the CO exceeds the standard when a radiant tube is open and drops back when it is closed, the radiant tube is determined to be faulty). Step S4: Repeat step S3 for multiple rounds of iterative troubleshooting to confirm all faulty radiant tubes and shut them off. Then verify whether the flue gas composition has returned to the baseline range.

[0007] Furthermore, the dynamic response of the CO concentration in the flue gas branch pipe of this layer in step S3 specifically includes: A mapping relationship between radiator status and flue gas composition is established. When the radiator is in the open state and the flue gas CO concentration remains within the reference range, the radiator is considered normal. Combining multi-cycle data, when the radiator is in the closed state, the flue gas CO concentration drops back to the reference range. When the radiator is in the open state, the flue gas CO concentration exceeds the reference range, and the radiator is considered faulty.

[0008] Furthermore, the fault diagnosis mechanism adopts a multi-round iterative diagnosis strategy, which can locate the faulty radiator in the fastest one round (that is, if the CO concentration drops back to the baseline range after the first shutdown of a radiator, the faulty radiator can be located in the first round of switching), and the slowest number of diagnosis times is equal to the total number of radiators n in that layer; in each round of diagnosis, the start-stop state sequence of the radiator and the corresponding CO concentration time sequence are recorded, and false data are eliminated by cross-comparison.

[0009] Furthermore, the flue gas online detection system is communicatively connected to the annealing furnace production control system to achieve two-way data interaction and linkage control; wherein, the flue gas online detection system is responsible for collecting physical signals of flue gas composition and converting them into digital signals, and the production control system receives the digital signals and executes the start and stop control commands of the radiant tubes.

[0010] Furthermore, the criteria for determining the faulty radiant tube also include auxiliary verification of CO2 and O2 concentrations; when there is a leak in the radiant tube body, H2 in the protective gas seeps in, causing a decrease in combustion efficiency, which is manifested as an increase in CO concentration and a decrease in O2 concentration in the flue gas inside the radiant tube; when there is a leak in the radiant tube heat exchanger, external air seeps in and interferes with combustion, which is manifested as an increase in O2 concentration in the flue gas.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention makes full use of existing flue gas online monitoring systems and production control systems, enabling fault location without shutdown, thus reducing the impact on normal production.

[0012] 2. This invention improves the accuracy of troubleshooting by dynamically analyzing the changes in the physical state (on / off) and the chemical composition (CO concentration) of the flue gas during the operation of the radiant tube, and avoids false alarms caused by a single threshold judgment.

[0013] 3. The method of the present invention uses an iterative troubleshooting algorithm to locate faults in as little as one switchover and only requires traversing all radiant tubes in the same layer at the slowest time. No manual intervention is required throughout the process, which improves the efficiency of radiant tube leak detection and reduces labor intensity and leak detection time. Detailed Implementation

[0014] The present invention provides an online troubleshooting method for radiant tubes in cold-rolled annealing furnaces, comprising the following steps: Step S1: Deploy an online flue gas monitoring system on each layer of flue gas branch pipes of the annealing furnace, collect and establish a benchmark dataset of CO, CO2, and O2 concentrations in each layer of flue gas branch pipes under normal production conditions; the benchmark dataset includes the average CO concentration ai0, the average CO2 concentration bi0, and the average O2 concentration ci0 in each layer of flue gas branch pipes, where i is the layer number of the radiant tube, i∈[1,n], and n is the total number of radiant tube layers; Step S2: During the normal operation of the annealing furnace, monitor the CO concentration ai1 in each layer of flue gas branch pipe in real time; when the CO concentration ai1 in the i-th layer of flue gas branch pipe exceeds the reference range, i.e. ai1-ai0≥30ppm, trigger the fault troubleshooting mechanism. Step S3: Retrieve and monitor the operating status of each radiator in the i-th layer, and simultaneously monitor the dynamic response of CO concentration in the flue gas branch pipe of that layer; if the CO concentration in that layer drops back to the reference range when a radiator is in the closed state, but the CO concentration exceeds the reference range when the radiator is in the open state, then the radiator is determined to be a faulty radiator. The dynamic response specifically includes: establishing a mapping relationship between the radiator status and flue gas composition; when the radiator is in the open state and the flue gas CO concentration remains within the benchmark range, the radiator is determined to be normal; combining multi-cycle data, when the radiator is in the closed state, the flue gas CO concentration falls back to the benchmark range; when the radiator is in the open state, the flue gas CO concentration exceeds the benchmark range, and the radiator is determined to be a faulty radiator.

[0015] Step S4: Repeat step S3 for multiple rounds of iterative troubleshooting to confirm all faulty radiant tubes and shut them off. Then verify whether the flue gas composition has returned to the baseline range.

[0016] The above-mentioned fault diagnosis mechanism adopts a multi-round iterative diagnosis strategy, which can locate the faulty radiation tube in one round at the fastest, and the slowest number of diagnosis times is equal to the total number of radiation tubes in that layer, n. In each round of diagnosis, the start-stop state sequence of the radiation tube and the corresponding CO concentration time series are recorded, and false data are eliminated by cross-comparison.

[0017] The flue gas online monitoring system is communicatively connected to the annealing furnace production control system to achieve two-way data interaction and linkage control. The flue gas online monitoring system is responsible for collecting physical signals of flue gas composition and converting them into digital signals. The production control system receives the digital signals and executes the start and stop control commands of the radiant tubes.

[0018] The criteria for determining the faulty radiant tube also include auxiliary verification of CO2 and O2 concentrations; when there is a leak in the radiant tube body, H2 in the protective gas seeps in, causing a decrease in combustion efficiency, which is manifested as an increase in CO concentration and a decrease in O2 concentration in the flue gas inside the radiant tube; when there is a leak in the radiant tube heat exchanger, external air seeps in and interferes with combustion, which is manifested as an increase in O2 concentration.

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] This embodiment takes a cold rolling annealing furnace with six layers of radiant tubes from top to bottom as an example (from bottom to top, they are the first layer, the second layer, the third layer, the fourth layer, the fifth layer, and the sixth layer) to illustrate the specific implementation process of the present invention.

[0021] Step 1: Under normal operating conditions of the annealing furnace, continuously collect CO, CO2, and O2 concentration data using online flue gas analyzers installed on each layer of flue gas branch pipes (including the drive side and the operating side). Calculate and record the average values ​​for each layer to establish a benchmark database (as shown in Table 1). The benchmark dataset includes the average CO concentration ai0, the average CO2 concentration bi0, and the average O2 concentration ci0 in each layer of flue gas branch pipes, where i is the layer number of the radiant tube, i∈[1,n], and n is the total number of radiant tube layers.

[0022] Table 1. Average concentrations of CO, CO2, and O2 in the flue gas branches of each layer of the annealing furnace. Step 2: During normal production, if the CO concentration in the flue gas of the fourth-layer drive-side branch pipe instantly jumps to 1634 ppm, far exceeding its benchmark value of 4.92 ppm (difference greater than 30 ppm), an anomaly is determined in that layer. The fourth layer is immediately identified as the target for investigation, and the operating status (on or off) of each radiator in that layer is recorded. The changes in CO concentration in the flue gas branch pipe of that layer are monitored under different states of each radiator.

[0023] If a radiant tube is in the open state and the CO concentration in the branch flue gas remains at a normal level (ai0), then the radiant tube is ruled out as faulty. If a radiant tube is in the closed state and the CO concentration in the branch flue gas returns to a normal level (ai0), and when the radiant tube is in the open state and the CO concentration in the flue gas ai1-ai0 ≥ 30ppm, then the radiant tube is determined to be faulty.

[0024] Step 3: During the normal production process of the annealing furnace, conduct multiple rounds of inspections and verifications to complete the inspection of faulty radiant tubes and shut down the faulty radiant tubes, as shown in Table 2.

[0025] (1) After the third inspection, the CO in the branch flue gas of radiant tubes 1, 5, 6, 7, 9, 11 and 12 did not exceed the standard when they were in the open state, and they were judged to be normal radiant tubes.

[0026] (2) Based on the first, second and third investigations, it is determined that radiation tube 3, radiation tube 4, radiation tube 8 and radiation tube 10 may be faulty.

[0027] (3) Through the fifth inspection, radiation tube 2, radiation tube 3 and radiation tube 10 were confirmed to be normal radiation tubes. Based on the fourth, fifth, sixth and seventh inspections, the faulty radiation tubes were determined to be radiation tube 4 and radiation tube 8.

[0028] (4) After shutting down radiation tubes 4 and 8, the monitoring data a41=10ppm appeared on the fourth layer transmission side branch pipe, which is within the normal range. It was confirmed that the faulty radiation tubes were radiation tubes 4 and 8.

[0029] (5) Upon on-site inspection, it was found that both the fourth-layer radiant tube 4 and radiant tube 8 were faulty, which was consistent with the investigation results.

[0030] Table 2. CO exceedance status of flue gas in the fourth-layer transmission side branch pipe and the status of each radiant pipe. .

Claims

1. A method for online troubleshooting of radiant tube faults in a cold-rolled annealing furnace, characterized in that, Includes the following steps: Step S1: Deploy an online flue gas monitoring system on each layer of flue gas branch pipes of the annealing furnace, collect and establish a benchmark dataset of CO, CO2, and O2 concentrations in each layer of flue gas branch pipes under normal production conditions; the benchmark dataset includes the average CO concentration ai0, the average CO2 concentration bi0, and the average O2 concentration ci0 in each layer of flue gas branch pipes, where i is the layer number of the radiant tube, i∈[1,n], and n is the total number of radiant tube layers; Step S2: During the normal operation of the annealing furnace, monitor the CO concentration ai1 in each layer of flue gas branch pipe in real time; when the CO concentration ai1 in the i-th layer of flue gas branch pipe exceeds the reference range, i.e. ai1-ai0≥30ppm, trigger the fault troubleshooting mechanism. Step S3: Retrieve and monitor the operating status of each radiant tube in the i-th layer, and simultaneously monitor the dynamic response of CO concentration in the flue gas branch pipe of that layer; If the CO concentration in a layer drops back to the reference range when a radiation tube is in the off state, but the CO concentration exceeds the reference range when the radiation tube is in the on state, then the radiation tube is determined to be a faulty radiation tube. Step S4: Repeat step S3 for multiple rounds of iterative troubleshooting to confirm all faulty radiant tubes and shut them off. Then verify whether the flue gas composition has returned to the baseline range.

2. The method for online troubleshooting of radiant tube faults in a cold-rolled annealing furnace according to claim 1, characterized in that, The specific steps in step S3, including synchronously monitoring the dynamic response of CO concentration in the flue gas branch pipe of that layer, include: A mapping relationship between radiator status and flue gas composition is established. When the radiator is in the open state and the flue gas CO concentration remains within the reference range, the radiator is considered normal. Combining multi-cycle data, when the radiator is in the closed state, the flue gas CO concentration drops back to the reference range. When the radiator is in the open state, the flue gas CO concentration exceeds the reference range, and the radiator is considered faulty.

3. The method for online troubleshooting of radiant tube faults in a cold-rolled annealing furnace according to claim 1, characterized in that, The fault diagnosis mechanism adopts a multi-round iterative diagnosis strategy, which can locate the faulty radiator in one round at the fastest, and the slowest number of diagnosis times is equal to the total number of radiators n in that layer. In each round of diagnosis, the start-stop state sequence of the radiator and the corresponding CO concentration time sequence are recorded, and false data are eliminated by cross-comparison.

4. The method for online troubleshooting of radiant tube faults in a cold-rolled annealing furnace according to claim 1, characterized in that, The flue gas online detection system is communicatively connected to the annealing furnace production control system to achieve two-way data interaction and linkage control. The flue gas online detection system is responsible for collecting physical signals of flue gas composition and converting them into digital signals. The production control system receives the digital signals and executes the start and stop control commands of the radiant tubes.

5. The method for online troubleshooting of radiant tube faults in a cold-rolled annealing furnace according to claim 1, characterized in that, The criteria for determining the faulty radiant tube also include auxiliary verification of CO2 and O2 concentrations; when there is a leak in the radiant tube body, H2 in the protective gas seeps in, causing a decrease in combustion efficiency, which is manifested as an increase in CO concentration and a decrease in O2 concentration in the flue gas inside the radiant tube; when there is a leak in the radiant tube heat exchanger, external air seeps in and interferes with combustion, which is manifested as an increase in O2 concentration.

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