Leakage checking and leaking stoppage method for water-cooling flue
By detecting the difference in flue gas water content, the problem of poor accuracy in the prior art is solved, efficient leakage point positioning and repairing is achieved, and production furnace shutdown time is reduced.
Patent Information
- Application Number
- CN202510555784.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-08-01
AI Technical Summary
In the prior art, the accuracy of the judgment of water-cooled flue leakage is poor, there are many influencing factors and cannot be continuously monitored, resulting in misjudgment and long production shutdown time.
By detecting the water content in the flue gas for a predetermined time interval, the difference between the detection value and the theoretical value is calculated. If the difference is greater than 0.5%, the water-cooled flue leakage will be judged, and the air is rest, cooling, positioning the leakage point and repairing will be carried out.
It improves the accuracy of water-cooled flue leakage judgment, shortens the leakage point positioning time, reduces the impact of production furnace shutdown, reduces detection errors, and achieves uninterrupted leakage monitoring.
Smart Images
Figure CN120402718A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of leak detection and repair of water-cooled flue ducts, and particularly to a method for detecting and plugging leaks in a water-cooled flue duct. Background Art
[0002] The water-cooled flue duct of a smelting reduction furnace is a key component used in the metallurgical industry to handle high-temperature flue gas (1600 °C), and mainly undertakes functions such as flue gas cooling, equipment protection, and waste heat recovery. The water-cooled flue duct is a flue duct structure formed by enclosing multiple water-cooled pipes. The flue gas generated during the smelting process of the smelting reduction furnace is transported through the flue duct, and a cooling medium circulates inside the water-cooled pipes to cool the flue gas inside the flue duct and reduce the flue gas temperature.
[0003] Since the flue gas contains solid impurity particles such as semi-coke particles, when the impurity particles continuously erode the inner wall of the water-cooled flue duct for a long time, and combined with reasons such as flue gas corrosion, leak points will be generated in the water-cooled flue duct. After the leak points are generated, cracks will be generated in the surrounding pipe walls due to thermal stress, increasing the leakage. In addition, after the leaked cooling medium comes into contact with the high-temperature flue gas, it will instantly vaporize, resulting in an increase in the internal pressure of the flue duct and posing an explosion risk. Therefore, it is necessary to timely detect and repair the leak points during operation.
[0004] The steam drum is connected to the water-cooled pipes to supply the cooling medium to the water-cooled pipes and receive the return water of the water-cooled pipes. Therefore, in the prior art, a method for detecting the level of the steam drum to determine whether the water-cooled flue duct leaks is proposed. When there is a liquid level difference in the steam drum, that is, a difference between the water supply volume and the return water volume, it is inferred that part of the cooling medium leaks and leak points appear in the water-cooled flue duct. However, there are too many factors affecting the liquid level of the steam drum, such as the steam drum drainage and steam drum water replenishment processes. In addition, factors such as the internal pressure, temperature, and steam ratio of the steam drum will also affect the liquid level. Therefore, the method for judging whether there is a leak inside the water-cooled flue duct according to the liquid level difference of the steam drum has poor accuracy. For this reason, a method for detecting and plugging leaks in a water-cooled flue duct is proposed to improve the accuracy of leak judgment in the water-cooled flue duct. Summary of the Invention
[0005] The main purpose of the present invention is to provide a method for detecting and plugging leaks in a water-cooled flue duct, aiming to improve the accuracy of leak judgment in the water-cooled flue duct.
[0006] To achieve the above object, the method for detecting and plugging leaks in a water-cooled flue duct proposed by the present invention is applied to a smelting reduction furnace, which includes a water-cooled flue duct formed by enclosing water-cooled pipes and a steam drum, and the steam drum is connected to the water-cooled pipes. The method includes: S1. Detect the water content in the flue gas at predetermined time intervals, denoted as detection values A1, A2... An respectively. Calculate the theoretical values of the water content in the flue gas, denoted as theoretical values B1, B2... Bn respectively, based on the furnace conditions at the time of obtaining the detection values. Calculate the differences between the detection values and the theoretical values, denoted as Δ1, Δ2... Δn respectively, and calculate Δn - Δ n-1 , if Δn - Δ n-1 ≥0.5%, it is determined that the water-cooled flue duct has a leak; S2. After determining the occurrence of the leak, shut down the melting reduction furnace, discharge the residual flue gas in the water-cooled flue duct, and replace the water in the steam drum to reduce the temperature and pressure; S3. After the temperature and pressure reduction of the steam drum are completed, close all the drain valves of the steam drum and the water-cooled pipes, replenish water to the steam drum to build pressure. As the pressure increases, the leakage phenomenon at the leak point becomes more obvious. At this time, search for and locate the leak point in the water-cooled flue duct; S4. After locating the leak point, stop replenishing water to build pressure, open the drain valves of the steam drum and the water-cooled flue duct, drain the cooling medium in the water-cooled pipe to below the leak point, and connect the water-cooled flue duct near the furnace mouth section of the melting reduction furnace to the temporary cooling circulating water; S5. Repair the leak point.
[0007] Optionally, in an embodiment of the present invention, in step S1, the mass fractions of , CO, in the flue gas are detected in real time, and the standard value is calculated according to the following formula:
[0008] Where: Q is the standard value of the water content in the flue gas; R is the conversion coefficient of water in the water-gas reverse reaction involved in the melting reduction process, and its value range is 1.0 - 1.8; is the mass fraction of hydrogen in the flue gas, in %; CO is the mass fraction of carbon monoxide in the flue gas, in %; is the mass fraction of carbon dioxide in the flue gas, in %.
[0009] Optionally, in an embodiment of the present invention, when the molten bath temperature of the melting reduction furnace is 1400°C - 1420°C, the furnace pressure is 70 kPa - 80 kPa, and the secondary combustion rate is 55% - 60%, the value of R is 1.00 - 1.30; When the molten bath temperature is 1420°C - 1440°C, the furnace pressure is 65 kPa - 75 kPa, and the secondary combustion rate is 50% - 55%, the value of R is 1.3 - 1.5; When the molten pool temperature is 1380°C - 1400°C, the furnace pressure is 55 kPa - 65 kPa, and the secondary combustion rate is 45% - 50%, the value of R ranges from 1.5 to 1.80.
[0010] Optionally, in an embodiment of the present invention, in step S2, when cooling down with replacement water, the makeup water volume of the steam drum is adjusted to 20 - 80 t / h, the steam drum liquid level is gradually filled to 80% - 95% of the full liquid level, and then all the drain valves of the steam drum and the water-cooled flue are opened. By controlling the opening degree of the drain valves, ensure that the steam drum liquid level is maintained at 80% - 95% of the full liquid level during the draining process, and control the cooling rate of the steam drum at 0.3 - 0.5 °C / min.
[0011] Optionally, in an embodiment of the present invention, the inside of the smelting reduction furnace has a water-cooled wall cooling system. The water-cooled wall cooling system includes a water inlet pipeline and a water return pipeline. In step S4, the water-cooled flue at the furnace mouth section is connected to the water return pipeline, and the return water in the water-cooled wall cooling system is used to temporarily cool the water-cooled flue at the furnace mouth section.
[0012] Optionally, in an embodiment of the present invention, step S5 includes: S51. On the pipe wall of the water-cooled pipe, with the leak point as the center, cut a square area with a length of 0.5 m - 2 m and a width of 0.2 m - 1 m to form a repair hole; S52. Cut a repair plate on the prepared pipe plate with the same size as the repair hole, and open an operation hole on the repair plate; S53. Weld positioning parts at the corresponding positions of the repair plate and the water-cooled pipe, and position the repair plate at the repair hole through the positioning parts; S54. Weld the repair plate to the water-cooled pipe inside the water-cooled pipe through the operation hole. After the repair plate welding is completed, repair the operation hole to complete the leak point repair.
[0013] Optionally, in an embodiment of the present invention, in step S3, when making up water and maintaining pressure, add a fluorescent reagent to the cooling medium, and use a fluorescent lamp to locate the leak point.
[0014] Optionally, in an embodiment of the present invention, the method further includes: S6. Close all the valves of the steam drum and the water-cooled pipe, pressurize the steam drum, and measure whether the pressure drop in the water-cooled pipe and the steam drum exceeds a predetermined range. If the pressure drop exceeds the predetermined range and there is no welding problem with the repair plate, repeat steps S3 - S6 until the pressure drop is within the predetermined range; S7. After the pressure drop is within the predetermined range, inject a cooling medium into the steam drum and the water-cooled pipe for a trial circulation. If there is a problem with the trial circulation and there is no welding problem with the repair plate, repeat steps S3 - S7 until the trial circulation has no problem, then make up water to the steam drum and restart the blast in the smelting reduction furnace.
[0015] Optionally, in an embodiment of the present invention, the water-cooled flue duct includes a furnace inlet section, a rising section, a turning section, and a descending section. Drain valves are respectively provided for each section of the water-cooled flue duct. When the drain valves of the water-cooled flue duct are opened, the drain valves are successively opened in the order of increasing temperature of the pipe sections.
[0016] Optionally, in an embodiment of the present invention, in step S2, after the steam flow rate in the steam drum drops to 0 t / h, the steam pipeline valve of the steam drum is closed, and the steam drum is cooled by replacing the water. The steam drum is cooled by replacing the water until the temperature of the steam drum does not exceed 110 °C, and the pressure of the steam drum is controlled to drop at a rate of 7 - 15 kPa / min until the pressure of the steam drum does not exceed 0.15 MPa.
[0017] One of the methods for judging whether the water-cooled flue duct leaks in the prior art is to detect whether there is a liquid level difference in the steam drum. However, after the cooling medium in the steam drum circulates for a period of time, its purity will decrease, resulting in a decrease in the cooling effect. Therefore, the steam drum needs to drain water regularly and replace the cooling medium to ensure the purity of the cooling medium. The process of draining water and replenishing water usually lasts for 4 - 5 hours, during which leakage monitoring cannot be carried out. In addition, in addition to leakage, the cooling medium will be lost due to other factors. If the amount of the cooling medium in the entire system is too low, the automatic water replenishment function of the steam drum will be triggered. Both the process of draining, replacing, and replenishing water will cause the liquid level difference judgment method to be inapplicable.
[0018] In addition, when leakage occurs, the pressure, temperature, etc. in the steam drum will also be affected, which may cause the gaseous cooling medium in the steam drum to be converted into a liquid cooling medium, misleading the liquid level difference and affecting the accuracy of the judgment result.
[0019] Different from the prior art, during the process of detecting the water content, the water content in the flue gas is detected at intervals of a predetermined time, recorded as the detection value, and the obtained detection values are respectively recorded as A1, A2... An for distinction. At the same time as obtaining the detection values, the theoretical values of the water content in the flue gas under this furnace condition are calculated, respectively recorded as B1, B2... Bn for distinction. The differences between multiple groups of corresponding detection values and theoretical values are respectively calculated, recorded as Δ1, Δ2... Δn, and Δn - Δ is monitored in real time. n-1 between the differences, if Δn - Δ n-1 ≥ 0.5%, it is determined that the water-cooled flue duct has leaked; It can be understood that the factors affecting the fluctuation of the water content in the flue gas are not only leakage, but also detection errors and other factors. When the value of the difference Δn gradually increases, it means that the water content in the flue gas is gradually increasing. When there is a leak point on the inner wall of the water-cooled flue duct, the cooling medium will directly spray onto the inner wall of the water-cooled flue duct, contact with the high-temperature flue gas and vaporize, resulting in an increase in the water content in the flue gas. To weaken the influence of detection errors, it is set that when n - Δ n-1When it is ≥0.5%, it is determined that the increase in the water content in the flue gas is due to leakage. If n - Δ n-1 <0.5%, it is determined that the increase in the water content in the flue gas is caused by measurement error or other factors other than leakage.
[0020] Compared with the prior art, the present solution is not affected by processes such as drum water replenishment and drainage, can continuously measure the water content in the flue gas, and the leak detection time can cover the operation time of the smelting reduction furnace. In addition, when judging the occurrence of leakage, various factors such as errors are considered and excluded from affecting the water content, and the judgment is more accurate, solving the technical problem of poor accuracy in judging the leakage of the water-cooled flue in the current situation. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.
[0022] Figure 1 It is a flowchart of a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 2 It is a schematic connection structure diagram of a smelting reduction furnace and a water-cooled flue in a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 3 It is a top view of a water-cooled flue in a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 4 It is a schematic structure diagram of a repair hole during leak point repair in a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 5 It is a schematic structure diagram of a repair plate during leak point repair in a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 6 It is a side view of the water-cooled pipe of the repair plate after opening an operation hole in a method for detecting and plugging leaks in a water-cooled flue according to the present invention; Figure 7 It is an analysis line graph in a method for detecting and plugging leaks in a water-cooled flue according to the present invention.
[0023] Explanation of the reference numerals in the drawings: 100, water-cooled flue; 110, furnace mouth section; 120, rising section; 130, turning section; 140, descending section; 150, water-cooled pipe; 200, steam drum; 310, repair hole; 320, repair plate; 330, operation hole; 400, positioning member; 410, first positioning block; 420, second positioning block; The implementation, functional features, and advantages of the present invention will be further described in conjunction with embodiments with reference to the accompanying drawings. Detailed implementation manners
[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0025] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.
[0026] In the present invention, unless otherwise clearly defined and limited, terms such as "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.
[0027] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions conflicts with each other or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.
[0028] A water-cooled flue 100 and a steam drum 200 are connected through a pipeline to realize the flow of a liquid cooling medium and a gaseous cooling medium.
[0029] Referring to Figures 1 to 7 , the present invention provides a method for detecting and plugging leaks in a water-cooled flue, which is applied to a smelting reduction furnace.
[0030] Specifically, the method includes: S1. Detect the water content in the flue gas at a predetermined time interval, denoted as detection values A1, A2... An respectively. Calculate the theoretical values of the water content in the flue gas, denoted as theoretical values B1, B2... Bn respectively, according to the furnace conditions at the time of obtaining the detection values. Calculate the differences between the detection values and the theoretical values, denoted as Δ1, Δ2... Δn respectively, and calculate Δn - Δ in real time n-1 , if Δn - Δ n-1 ≥0.5%, it is determined that the water-cooled flue duct has a leak; S2. After determining the occurrence of the leak, shut down the melting reduction furnace, discharge the residual flue gas in the water-cooled flue duct, and replace the water in the steam drum to reduce the temperature and pressure; S3. After the temperature and pressure reduction of the steam drum are completed, close all the drain valves of the steam drum and the water-cooled pipes, replenish water to the steam drum to build pressure. As the pressure increases, the leakage phenomenon at the leak point becomes more obvious. At this time, search for and locate the leak point in the water-cooled flue duct; S4. After locating the leak point, stop replenishing water to build pressure, open the drain valves of the steam drum and the water-cooled flue duct, drain the cooling medium in the water-cooled pipes below the leak point, and connect the water-cooled flue duct near the furnace mouth section of the melting reduction furnace to the temporary cooling circulating water; S5. Repair the leak point.
[0031] Detect the water content in the flue gas at a predetermined time interval, denoted as the detection value, and denote the obtained detection values as A1, A2... An respectively for distinction. At the same time as obtaining the detection values, calculate the theoretical values of the water content in the flue gas under this furnace condition, denoted as B1, B2... Bn respectively for distinction. Calculate the differences between the corresponding multiple groups of detection values and theoretical values, denoted as Δ1, Δ2... Δn respectively, and monitor Δn - Δ in real time n-1 the difference between them. If Δn - Δ n-1 ≥0.5%, it is determined that the water-cooled flue duct has a leak; When obtaining the detection values, theoretical values and differences, record the relevant data to form an analysis line graph. In addition to the aforementioned judgment method, according to the trend of the analysis line graph, add another judgment method.
[0032] ① Observe the change trend of Δn in the analysis line graph. If Δn shows a significant increase compared to Δ n-1 , that is, the situation where Δn - Δ n-1 ≥0.5%, it is determined that there is a leak point in the water-cooled flue duct; ② Observe the change trend of Δn in the analysis line graph. If the analysis line shows an increase and maintains the increased value, it is also determined that there is a leak point in the water-cooled flue duct.
[0033] Among them, Method ① completes the leakage judgment during the initial stage of the leakage point appearance and the process of the leakage point expansion, and can give an alarm when the leakage point first appears to avoid the subsequent impact of the leakage; Method ② is a new judgment method added according to the analysis line graph. It completes the leakage judgment when the leakage point is stable after the leakage point appears for a period of time. The period of time here refers to compared with Method ①, not after a long time.
[0034] It can be understood that Method ② can be used as a fallback judgment for Method ① to improve the stability of this solution.
[0035] Refer to Figure 7 , this figure is an example diagram of the analysis line, and the detection interval is set to one second in this figure. Before the 8th second, the Δn analysis line is in a relatively stable state; in the stage from 8s to 10s, the Δn analysis line rises rapidly. Among them, Δ9 - Δ8 ≥ 0.5%, it is determined that there is a leakage point in the water-cooled flue, and the melting reduction furnace needs to be shut down for maintenance and subsequent operations.
[0036] Taking this figure as an example, Method ② is also described. Among them, 8 - 10s is the rising stage. If in a relatively extreme case, both Δ9 - Δ8 and the difference of Δ9 - Δ8 are less than 0.5%, such as 0.45% and 0.48% respectively, at this time there has already been a leakage point, but Method ① fails to judge it. However, the trend of the analysis line from 8s to 13s conforms to the judgment of Method ②, and at this time, the leakage can be judged through Method ②.
[0037] Specifically, the device for measuring the detection value can select flue gas humidity instruments such as capacitive flue gas humidity meters, ceramic humidity sensors, laser flue gas humidity analyzers, etc. Preferably, it is a laser flue gas humidity analyzer, which is not limited here.
[0038] Optionally, the detection interval of the detection value can be selected as 1s, 2s... In the initial stage of the water-cooled flue 100 being put into use or after major repairs, at this time, the inner wall of the water-cooled flue 100 is relatively stable and it is not easy to have leakage points, so a longer time interval can be selected; when the water-cooled flue 100 has been in use for a long time, the possibility of leakage points appears, and the detection interval can be shortened to improve the sensitivity of detection. In other words, the selection of the detection interval is negatively correlated with the operation time of the water-cooled flue.
[0039] In the existing method of judging whether the water-cooled pipe 150 leaks by measuring the liquid level difference in the steam drum 200, it is greatly affected by other processes of the steam drum, resulting in the monitoring time of this method being unable to fully cover the operation time of the melting reduction furnace. In addition, whether there is a leakage point on the inner wall or the outer wall of the water-cooled flue 100, the steam drum will generate a liquid level difference. Therefore, this method cannot judge whether it is the inner wall or the outer wall of the water-cooled flue 100 that has leaked.
[0040] In this solution, since the directly measured water content is the water content in the flue gas, when the leakage is judged by using this method, the leakage location can be determined as the inner wall of the water-cooled flue 100. After the blast is stopped, the leakage point can be directly found on the inner wall of the water-cooled flue 100, which can improve the efficiency of leakage point positioning. It should be noted that although this method cannot detect the leakage of the outer wall of the water-cooled flue, the leakage of the outer wall of the water-cooled flue can be detected by manual inspection. In addition, the risk brought by the leakage of the inner wall of the water-cooled flue is much greater than that of the outer wall of the water-cooled flue. Therefore, the inner wall of the water-cooled flue is the part that needs to be focused on.
[0041] Furthermore, after the smelting reduction furnace operates for a period of time, its furnace condition will remain in a relatively stable state. However, when factors such as raw materials change or at the initial stage of the start-up of the smelting reduction furnace, its furnace condition will change, and the change of the furnace condition will affect the standard value.
[0042] In addition, although the method proposed in this solution does not require the furnace to be stopped, the blast stoppage will also suspend production and affect the output. Therefore, the accuracy of the judgment of whether leakage occurs will affect the production efficiency. If the blast is stopped and the leakage point is located due to a false alarm, and it is confirmed as a false alarm and the blast is resumed again, the production suspension time will be as long as several hours or even more than ten hours. Therefore, the accuracy of the leakage judgment will affect the output of the smelting reduction furnace.
[0043] In this method, the core parameter for improving the accuracy of leakage judgment is the accuracy of calculating the standard value of the water content in the flue gas. The furnace condition and the degree of reaction progress will both affect the standard value of the water content. For this reason, a calculation method for the standard value of the water content is proposed to improve the accuracy of judgment.
[0044] Specifically, first measure the concentration in the flue gas, and calculate the standard value Q of the water content through the concentration.
[0045]
[0046] Among them: Q is the standard value of the water content in the flue gas; R is the conversion coefficient of water in the water-gas reverse reaction involved in the smelting reduction process, and its value range is 1.0 - 1.8; The remaining parameters are respectively the mass fractions of CO, in the flue gas.
[0047] It should be noted that represents the progress of the water-gas reverse reaction in the furnace in the formula.
[0048] Furthermore, the value of the conversion coefficient R is related to the furnace condition, and the optimal value range of R is proposed here according to different furnace conditions.
[0049] When the molten bath temperature of the smelting reduction furnace is 1400°C - 1420°C, the furnace pressure is 70 kPa - 80 kPa, and the secondary combustion rate is 55% - 60%, the value of R is 1.00 - 1.30; When the molten bath temperature is 1420°C - 1440°C, the furnace pressure is 65 kPa - 75 kPa, and the secondary combustion rate is 50% - 55%, the value of R is 1.3 - 1.5; When the molten bath temperature is 1380°C - 1400°C, the furnace pressure is 55 kPa - 65 kPa, and the secondary combustion rate is 45% - 50%, the value of R is 1.5 - 1.80.
[0050] The above three furnace conditions are all the furnace conditions when the smelting reduction furnace is in the normal production stage. According to different production products and different product composition indexes, the furnace conditions will be adjusted. When the furnace conditions of the smelting reduction furnace are different, the degree of the reverse water-gas reaction in the furnace is also different. Therefore, it is necessary to calculate the water content according to the degree of this reverse reaction.
[0051] In the calculation process of the standard value of the flue gas water content, detecting the concentrations of hydrogen, carbon monoxide and carbon dioxide in the flue gas, determining the value of R according to the furnace condition, and substituting it into the formula for calculation can accurately calculate the standard value of the water content in the flue gas, thereby improving the accuracy of leakage judgment and avoiding unnecessary furnace shutdown.
[0052] It can be understood that the above-mentioned parameters such as the molten bath temperature, furnace pressure, and secondary combustion rate can all be obtained through corresponding detection devices, calculation formulas, etc., and the acquisition methods of these parameters are well-known to those skilled in the art and will not be elaborated here.
[0053] When searching for the leakage point, the temperature inside the water-cooled flue 100 is relatively high. After the cooling medium leaks, it will instantly vaporize, plus the flue gas inside the water-cooled flue 100, resulting in extremely poor visibility inside the water-cooled flue 100. Therefore, it is necessary to adjust the inside of the water-cooled flue 100 to improve the visibility for leakage point search and positioning.
[0054] First, adjust the furnace condition of the smelting reduction furnace to meet the conditions for furnace shutdown, and then carry out furnace shutdown. After furnace shutdown, open the smoke exhaust valve of the water-cooled flue 100 to quickly discharge the flue gas in the water-cooled pipeline 150. After furnace shutdown, the temperature of the water-cooled flue 100 will gradually decrease, but the natural cooling process is relatively long. Limited by the total furnace shutdown duration and production considerations, it is necessary to accelerate the cooling. For this reason, replace the cooling medium in the steam drum 200. Before replacing the cooling medium, it is necessary to wait until no more steam enters the steam drum 200. If the cooling medium is replaced and the temperature is reduced when steam still enters the steam drum 200, the steam drum 200 will be deformed or have other adverse effects due to too rapid temperature change (the entering steam will increase the temperature of the steam drum, and the temperature difference between the steam and the newly entered cooling medium is too large).
[0055] It can be understood that by replacing the cooling medium, the temperature of the water-cooled flue 100 will also decrease, creating conditions for subsequent leak point repair. Before replacing the water to reduce the temperature, after furnace shutdown, it is necessary to wait until no steam enters the steam drum, and close the steam pipeline valve of the steam drum before replacing the water to reduce the temperature. When the temperature in the steam drum 200 drops below 110 °C and the pressure in the steam drum 200 is below 0.15 MPa during the replacement water cooling process, the replacement cooling is completed, and the replacement of the cooling medium is stopped.
[0056] In a preferred embodiment, when replacing the cooling medium and reducing the temperature of the steam drum 200, make up water at a water supply rate of 20 - 80 t / h, gradually fill the liquid level of the steam drum 200 to 80% - 95% of the full liquid level. Thereafter, open all the drain valves of the steam drum 200 and the water-cooled flue 100, and carry out water supply and drainage simultaneously. By adjusting the opening degree of the drain valve, control the drainage rate so that the liquid level of the steam drum 200 is maintained at 80% - 95% of the full liquid level during the drainage process, and control the temperature reduction rate of the steam drum 200 at 0.3 - 0.5 °C / min and the pressure drop rate at 7 - 15 kPa / min by regulating the drainage rate or the water supply rate.
[0057] Refer to Figure 2 As shown, starting from the smelting reduction furnace, the water-cooled flue 100 successively includes a furnace mouth section 110, a rising section 120, a turning section 130, and a descending section 140. During the drainage in the process of replacing the water and reducing the temperature, when opening the drain valves of the steam drum 200 and the water-cooled flue 100, first open the drain valve of the steam drum 200, and the water-cooled flue 100 is opened successively according to the furnace section temperature at the drain valve from low to high. Specifically, open the descending section 140, the turning section 130, the rising section 120, and the furnace mouth section 110 in sequence. This sequence can avoid adverse effects caused by too large temperature difference between the water-cooled flue 100 or the steam drum 200 after the drain valve is opened.
[0058] In this preferred embodiment, control the relevant parameters during the replacement and temperature reduction of the steam drum 200 to accelerate the temperature reduction speed on the premise of ensuring that the steam drum 200 will not be affected.
[0059] The cooling medium in the steam drum 200 exists in two states: gaseous and liquid. For the convenience of description, the part where the gaseous cooling medium exists is called the upper part of the steam drum 200, and the part where the liquid cooling medium exists is called the lower part of the steam drum 200.
[0060] Since the temperature of the gaseous cooling medium is higher than that of the liquid cooling medium, there is a temperature difference between the upper and lower parts of the steam drum 200. In order to reduce the amount of steam in the steam drum 200, the liquid level of the steam drum 200 is increased by adding water. Since the newly added cooling medium has not undergone a cooling cycle, its temperature is lower than that of the cooling medium in the steam drum 200. Adding the cooling medium can reduce the proportion of the gaseous cooling medium in the steam drum 200 and cause a part of the gaseous cooling medium to be converted into a liquid cooling medium through temperature reduction. When replacing the cooling medium, the liquid cooling medium with a lower temperature enters the steam drum 200. The lower part of the steam drum 200 is in direct contact with the supplemented cooling medium, and the temperature reduction speed is relatively fast, which will further increase the temperature difference between the upper and lower parts of the steam drum 200.
[0061] The following explains the parameter selection for the relevant replacement water temperature reduction: When the temperature reduction speed of the steam drum is 0.3 °C / min, the temperature difference change of the steam drum is small but the temperature reduction time is long; when the temperature reduction speed of the steam drum is 0.5 °C / min, the temperature reduction time of the steam drum is short but the temperature difference change of the steam drum is large.
[0062] When the pressure reduction of the steam drum is less than 7 kPa / min, the safety is high, but the pressure drop speed is slow, the adjustment time of the steam drum is long, and the repair time is less. The pressure drop speed of the steam drum cannot be increased blindly. Rapid pressure reduction will disrupt the circulation of the cooling medium. When the pressure reduction rate exceeds 15 kPa / min, the steam in the water-cooled pipe 150 will condense to form a local vacuum, resulting in a water hammer effect and generating a large instantaneous pressure, leading to problems such as leakage or deformation of the water-cooled pipe.
[0063] During the replacement water temperature reduction process, the liquid level of the steam drum 200 is maintained at 80%-95% of the full liquid level. When the liquid level of the steam drum is maintained at 80%, the temperature reduction speed is low, but a large space is reserved for the steam in the steam drum to avoid excessive pressure in the steam drum; when the liquid level of the steam drum is maintained at 95%, the temperature reduction speed of the replacement water in the steam drum is fast at this time, but the space for steam is small and the pressure in the steam drum is large.
[0064] Controlling the make-up water volume within 20 - 80 t / h can avoid damage to the steam drum 200 caused by excessive temperature difference between the upper and lower parts during the make-up water process. When the make-up water volume is 20 t / h, the cooling rate of the replacement water is slow, and the temperature difference inside the steam drum during the replacement water process is also small; when the make-up water volume is 50 t / h, the cooling rate of the replacement water is moderate, and the temperature difference inside the steam drum is also within the tolerance range of the steam drum, which will not cause the steam drum to deform due to excessive temperature difference; however, when the make-up water volume is 80 t / h, the cooling rate is the fastest at this time, but the temperature difference inside the steam drum is also large. Therefore, when selecting the make-up water volume at the maximum rate, it is necessary to closely monitor the water inflow to avoid the steam drum deforming due to excessive temperature difference caused by an increase in the water inflow volume.
[0065] The specific selection of the above parameters can be determined according to the actual situation.
[0066] In addition, during the replacement cooling process, the water inflow and drainage volume of the entire water-cooling system (steam drum 200 and water-cooled flue 100) are extremely large, up to hundreds of tons. In the actual production process, demineralized water is used as the cooling medium, and the unit price of demineralized water per ton is relatively high (about a thousand yuan per ton). Therefore, the cost during the replacement cooling process is extremely high.
[0067] The parameters proposed in this preferred embodiment are put forward by comprehensively considering the replacement cost, the temperature drop rate, and the temperature difference tolerance of the steam drum 200 and the water-cooled flue 100. In addition, under the above parameters, the temperature drop rate of the steam drum 200 matches the pressure drop rate, and it will not cause damage to the forced circulation pump in the water-cooled flue 100.
[0068] After completing the replacement and cooling, close the drain valves of the steam drum 200 and the water-cooled pipe 150, and only make up water into the steam drum 200 to increase the internal pressure of the steam drum 200. As the pressure of the steam drum 200 gradually increases, the leakage and gushing phenomenon at the leakage point will gradually become obvious. When making up water and maintaining pressure, insert a visual device such as an industrial endoscope into the water-cooled flue 100 to search for and locate the leakage point.
[0069] Preferably, during the process of making up water and maintaining pressure, a fluorescent reagent can be added to the supplementary cooling medium during water make-up. When there is a leakage, the fluorescent reagent will gather near the leakage point, and a corresponding fluorescent lamp can be used to search for the distribution points of the fluorescent reagent inside the water-cooled flue 100, thereby quickly locating the leakage point.
[0070] It should be noted that after the leakage point is repaired, the cooling medium inside the steam drum 200 and the water-cooled pipe 150 will be replaced before the blast is resumed. Therefore, the residual fluorescent reagent will be discharged from the steam drum and the water-cooled pipe, and the fluorescent reagent will not affect the subsequent cooling cycle. The amount of fluorescent reagent remaining on the inner wall of the water-cooled flue 100 is small and will not affect the flue gas cooling.
[0071] After locating the leakage point, stop the water replenishment and the circulation of the cooling medium, open the drain valves of the steam drum 200 and the water-cooled pipeline 150, and gradually drain the cooling medium in the water-cooled pipeline 150 until the liquid level in the water-cooled pipeline 150 is lower than the leakage point to facilitate subsequent repair operations. During the process of replacing water and reducing the temperature in step S2, the cooling medium has been reduced to below 110°C, and the pressure of the steam drum has been reduced to below 0.15 MPa, avoiding potential safety hazards caused by splashing when draining the high-temperature cooling medium with a relatively high temperature and large pressure at this time. When reducing the pressure of the steam drum to below 0.15 MPa, the increase range of the steam drum pressure during subsequent water replenishment and pressure buildup has been considered, so that even after water replenishment and pressure buildup, there will be no significant splashing during drainage.
[0072] The visual device can be used to judge whether the liquid level in the water-cooled pipeline 150 is lower than the leakage point. After the liquid level in the water-cooled pipeline 150 is lower than the leakage point, no cooling medium will flow out from the leakage point.
[0073] At this point, the circulation of the cooling medium in the water-cooled pipeline 150 stops. Since the smelting reduction furnace is in a state of blast outage rather than furnace shutdown, although the temperature in the smelting reduction furnace decreases at this time, it still remains around 1400°C. The molten pool continuously transfers high temperature to the water-cooled flue 100, especially the temperature of the furnace mouth section 110 is extremely high. Therefore, it is necessary to separately connect the water-cooled flue 100 of the furnace mouth section 110 to the temporary cooling circulating water to prevent deformation of this section of the water-cooled flue 100 due to high temperature.
[0074] Generally, a water-cooled wall cooling system is installed inside the smelting reduction furnace to cool and reduce the temperature inside the smelting reduction furnace. Preferably, when connecting the temporary cooling circulating water to the flue of the furnace mouth section 110, it is preferred to connect the return water pipeline in the water-cooled wall cooling system to the flue of the furnace mouth section 110.
[0075] Using the return water of the water-cooled wall cooling system for temporary cooling circulation of the flue of the furnace mouth section 110 has the advantages that the structure is relatively simple. The cooling circulation can be directly completed by using the circulating pump in the water-cooled wall cooling system without the need to separately lay temporary pipelines and circulating pumps. In addition, in the blast outage state, it is necessary to ensure that the temperature inside the furnace is not lower than the solidification temperature of the molten iron. If the molten iron solidifies, it will block the molten iron discharge channel of the pre-furnace and a furnace shutdown for iron discharge is required. Since the temperature of the furnace mouth section 110 is relatively high, this temperature will increase the return water temperature of the water-cooled wall cooling system. After the return water is heated, it circulates in the water-cooled wall system, and the high-temperature circulating water can slow down the temperature drop rate inside the furnace and extend the blast outage time. In the blast outage state, due to the decrease in the temperature inside the furnace, the temperature of the cooling medium in the water-cooled wall cooling system can be moderately increased without adverse effects.
[0076] It should be noted that in the actual production process, there are generally no leakage points in the flue of the furnace mouth section 110. Since the flue of the furnace mouth section 110 is directly connected to the inside of the smelting reduction furnace, a relatively thick solidified slag covers the inner wall of the flue of the furnace mouth section 110. The slag wraps the inner wall of the furnace mouth section 110, and it is not easy to have leakage points.
[0077] Finally, repair the leakage point. After the repair is completed, adjust each parameter, and the smelting reduction furnace resumes blowing and re-enters production.
[0078] Specifically, referring to Figures 3 to 6 , in this solution, the water-cooled flue 100 is formed by enclosing multiple water-cooled pipes 150. The multiple water-cooled pipes 150 are connected by a plate-shaped structure, that is, a membrane wall water-cooled flue.
[0079] Referring to Figure 4 , when repairing the leakage point, first draw a square area with a length of 0.5 m to 2 m and a width of 0.2 m to 1 m centered on the leakage point, and cut and remove this square area as a whole to form a repair hole 310. After that, cut a repair plate 320 of the same size as the repair hole 310 on the spare pipe material.
[0080] Before welding the repair plate 320, cut and open an operation hole 330 on the water-cooled pipe 150 of the repair plate 320, and the operation hole 330 is opened towards the operator. After the operation hole 330 is opened, place the repair plate 320 at the repair hole 310, align the water-cooled pipes 150 in the repair plate 320 with the water-cooled pipes 150 above and below it, and insert a welding tool through the operation hole 330 to complete the welding connection of the inner wall of the pipe. After that, complete the welding repair of the operation hole 330 and weld the periphery of the repair plate 320 to the water-cooled flue 100. Thus, the repair of the leakage point is completed.
[0081] Due to the existence of the plate-shaped structure, welding cannot be carried out externally, and the size of the water-cooled pipe 150 is small. Therefore, the method of opening the operation hole 330 is selected to increase the operation space and carry out internal welding to ensure that the repair plate 320 is completely connected to the water-cooled flue 100.
[0082] Specifically, the size, quantity and position of the operation hole 330 can be determined according to the axial length of the repair plate 320. In addition, when opening the operation hole 330, it is necessary to consider whether the subsequent welding is convenient. Preferably, the central angle of the operation hole 330 is between 150° and 180°.
[0083] Further, in an embodiment, the positioning member 400 includes a first positioning block 410 and a second positioning block 420. After the cutting of the repair plate 320 is completed, the first positioning blocks 410 are welded to both sides of the repair plate 320, and the second positioning blocks 420 are welded to both sides of the repair hole 310 of the water-cooled flue 100. The first positioning block 410 is placed on the second positioning block 420, so that the repair plate 320 can be temporarily placed at the position of the repair hole 310, facilitating the welding and fixing of the repair plate 320. In addition, the setting of the positioning member 400 can prevent the repair plate 320 from passing through the repair hole 310 and falling into the interior of the water-cooled flue.
[0084] Specifically, two first positioning blocks 410 can be provided. The two first positioning blocks 410 are respectively located at the two ends of the diagonal of the repair plate 320. Four first positioning blocks 410 can also be provided, and the four first positioning blocks 410 are respectively located at the four corners of the repair plate 320. It can be understood that the number of the second positioning blocks 420 is the same as that of the first positioning blocks 410.
[0085] When a leakage point appears, it indicates that the leakage point area is the area where particles wash heavily, and the pipe wall around the leakage point has also been worn to a certain extent. At this time, leakage points are also likely to occur in its surrounding area during subsequent use. Synchronously cutting the surrounding area of the leakage point and performing a planar replacement repair on the water-cooled flue 100 instead of repairing a single leakage point can avoid the recurrence of leakage points in the surrounding area in a short time after repairing a single leakage point, resulting in the high-frequency blast furnace shutdown affecting production in a short time. Further, when repairing the leakage point, a wear-resistant and anti-corrosion coating can be sprayed on the inner wall of the repair plate 320 and the inner wall of the surrounding water-cooled flue 100 to extend the service life. Optionally, the coating is a metal oxide ceramic coating.
[0086] After the leakage point repair is completed, pressure testing and water testing are required to check the repair effect. First, close the valves of the steam drum 200 and the water-cooled pipe 150 to make it a closed environment. Pressurize the steam drum 200 and detect whether the pressure drop value of the steam drum 200 within a predetermined time is within a predetermined range. If the pressure drop exceeds the predetermined range, it indicates that there are still undetected leakage points in the water-cooled flue 100 or there are welding problems with the repair plate 320. First, check the welding quality of the repair plate 320. If there is no problem with the welding, repeat steps S3 - S6 to find other leakage points and repair them until the pressure drop is within the predetermined range.
[0087] After the pressure test is problem-free, inject a cooling medium into the steam drum 200 and the water-cooled pipeline 150 for a trial circulation. During the trial circulation, to control costs, the total amount of the cooling medium can be 30% - 70% of that during normal circulation. If there are problems during the trial circulation, first check whether there are welding problems with the repair plate 320. If the welding is problem-free, repeat steps S3 - S7 to find other leakage points. After the trial circulation is problem-free, replenish water to the steam drum 200, resume the blast in the smelting reduction furnace, and re-enter the normal production state.
[0088] It should be noted that the "drainage" mentioned in this solution does not solely refer to discharging the single medium of "water", but rather refers to "discharging liquid".
[0089] The leak detection and plugging method proposed by the present invention can at least produce the following beneficial effects: Ⅰ. It can achieve continuous detection without detection intervals, and the detection time covers the operation time of the smelting reduction furnace. Ⅱ. During the judgment process, other factors that cause an increase in the water content in the flue gas except for leakage are excluded, and the accuracy of leakage judgment is higher. Ⅲ. Independently detect the internal leakage points of the water-cooled flue, shortening the leakage point positioning time. Ⅳ. There is no need to stop the furnace, and the leakage point can be repaired after the blast is stopped, reducing the impact on production. Ⅴ. By adjusting the furnace condition and feeding back the temperature in the furnace through the temperature of the flue at the furnace mouth section, the blast stop time is extended, and there is sufficient time to complete the repair of the leakage point. Ⅵ. Synchronously repair the weak areas around the leakage point, reducing the repair frequency.
[0090] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.
Claims
1. A method for detecting and plugging leaks in a water-cooled flue, which is applied to a smelting reduction furnace. The smelting reduction furnace includes a water-cooled flue formed by enclosing water-cooled pipes and a steam drum. The steam drum is connected to the water-cooled pipes. It is characterized in that, The method includes: S1. Detect the water content in the flue gas at predetermined time intervals, denoted as detection values A1, A2... An respectively. Calculate the theoretical values of the water content in the flue gas, denoted as theoretical values B1, B2... Bn respectively, according to the furnace conditions at the time of obtaining the detection values. Calculate the differences between the detection values and the theoretical values, denoted as Δ1, Δ2... Δn respectively. Calculate Δn - Δ n-1 , if Δn - Δ n-1 ≥ 0.5%, it is determined that the water-cooled flue duct has a leak; After it is determined that a leakage has occurred in S2, the smelting reduction furnace is shut down, the residual flue gas in the water-cooled flue is discharged, and the water in the steam drum is replaced to reduce the temperature and pressure. After the temperature and pressure reduction of the steam drum are completed in S3, all drain valves of the steam drum and the water-cooled pipeline are closed, the steam drum is filled with water to build pressure. As the pressure increases, the leakage phenomenon at the leakage point becomes more obvious. At this time, the leakage point is searched and located in the water-cooled flue. After the leakage point is located in S4, the water filling and pressure building are stopped, the drain valves of the steam drum and the water-cooled flue are opened, the cooling medium in the water-cooled pipeline is drained below the leakage point, and the water-cooled flue near the furnace mouth section of the smelting reduction furnace is connected to the temporary cooling circulating water. In S5, the leakage point is repaired.
2. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that, In step S1, the mass fractions of , CO, in the flue gas are detected in real time, and the standard value is calculated according to the following formula: Wherein: Q is the standard value of the water content in the flue gas; R is the conversion coefficient of water in the reverse water-gas reaction involved in the smelting reduction process, and its value range is 1.0 to 1.8; is the mass fraction of hydrogen in the flue gas, with the unit of %; CO is the mass fraction of carbon monoxide in the flue gas, and the unit is %; is the mass fraction of carbon dioxide in the flue gas, with the unit of %.
3. The method for detecting and plugging leaks in the water-cooled flue according to claim 2, characterized in that When the molten pool temperature of the smelting reduction furnace is 1400°C to 1420°C, the furnace pressure is 70 kPa to 80 kPa, and the secondary combustion rate is 55% to 60%, the value of R is 1.00 to 1.30; When the molten pool temperature is 1420°C to 1440°C, the furnace pressure is 65 kPa to 75 kPa, and the secondary combustion rate is 50% to 55%, the value of R is 1.3 to 1.5; When the molten pool temperature is 1380°C to 1400°C, the furnace pressure is 55 kPa to 65 kPa, and the secondary combustion rate is 45% to 50%, the value of R is 1.5 to 1.
80.
4. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that In step S2, when replacing water to reduce the temperature, the water make-up amount of the steam drum is adjusted to 20 to 80 t / h, the liquid level of the steam drum is gradually filled with water to 80% to 95% of the full liquid level, and then all drain valves of the steam drum and the water-cooled flue are opened. By controlling the opening degree of the drain valve, ensure that the liquid level of the steam drum is maintained at 80% to 95% of the full liquid level during the drainage process, and control the temperature reduction rate of the steam drum at 0.3 to 0.5°C / min.
5. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that, The inside of the smelting reduction furnace is equipped with a water-cooled wall cooling system. The water-cooled wall cooling system includes an inlet pipeline and a return pipeline. In step S4, the water-cooled flue at the furnace mouth section is connected to the return pipeline, and the return water in the water-cooled wall cooling system is used to temporarily cool the water-cooled flue at the furnace mouth section.
6. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that Step S5 includes: S51. On the pipe wall of the water-cooled pipeline, with the leakage point as the center, cut a square area with a length of 0.5 m to 2 m and a width of 0.2 m to 1 m to form a repair hole; S52. Cut a repair plate with the same size as the repair hole on the prepared pipe plate, and open an operation hole on the repair plate; S53. Weld positioning parts at the corresponding positions of the repair plate and the water-cooled pipeline, and position the repair plate at the repair hole through the positioning parts; S54. Weld the repair plate to the water-cooled pipeline inside the water-cooled pipeline through the operation hole. After the repair plate is welded, repair the operation hole to complete the repair of the leakage point.
7. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that, In step S3, a fluorescent reagent is added to the cooling medium during water filling and pressure building, and a fluorescent lamp is used to locate the leakage point.
8. The method for detecting and plugging leaks of the water-cooled flue according to claim 1, characterized in that, The method also includes: S6. Close all the valves of the steam drum and the water-cooled pipes, pressurize the steam drum, and measure whether the pressure drop in the water-cooled pipes and the steam drum exceeds the predetermined range. If the pressure drop exceeds the predetermined range and there is no welding problem with the repair plate, repeat steps S3 - S6 until the pressure drop is within the predetermined range; S7. After the pressure drop is within the predetermined range, inject a cooling medium into the steam drum and the water-cooled pipes for a trial circulation. If there is a problem with the trial circulation and there is no welding problem with the repair plate, repeat steps S3 - S7 until there is no problem with the trial circulation, replenish water to the steam drum, and resume blowing-in of the smelting reduction furnace.
9. The method for detecting and plugging leaks in the water-cooled flue according to claim 4, wherein The water-cooled flue includes a furnace mouth section, a rising section, a turning section, and a descending section. Drain valves are respectively provided for each section of the water-cooled flue. When the drain valves of the water-cooled flue are opened, the drain valves are opened successively in the order of increasing pipe section temperature.
10. The leak detection and plugging method of the water-cooled flue according to claim 4, characterized in that, In step S2, after the steam flow rate in the steam drum drops to 0 t / h, close the steam pipe valve of the steam drum, replace the water in the steam drum to cool it down, and replace the water in the steam drum to cool it down until the temperature of the steam drum does not exceed 110 °C. Control the pressure of the steam drum to drop at a rate of 7 - 15 kPa / min until the pressure of the steam drum does not exceed 0.15 MPa.