A high-pull supplementary blowing anti-explosion method for smelting high-carbon steel by dry dust removal converter

Abstract

The application provides a high-pull compensation blowing anti-explosion method for smelting high-carbon steel by a dry dedusting converter, and belongs to the technical field of iron and steel metallurgy. The process comprises high-pull carbon and pre-control treatment, sampling and detecting carbon content of molten steel, grading compensation blowing oxygen supply control and end point confirmation; in the high-pull carbon stage, the oxygen flow is reduced before the lance is lifted, and nitrogen is supplemented into the flue at the outlet of the evaporative cooler to dilute the flue gas; after sampling and detection, the compensation blowing oxygen supply is controlled according to the high and low of the carbon content of the molten steel, different carbon content intervals correspond to different oxygen supply modes and oxygen supply intensities, nitrogen is supplemented and low oxygen constant flow compensation blowing is adopted when the carbon content is high, the oxygen supply flow is gradually increased by adopting the climbing blowing oxygen mode when the carbon content is in the medium-high interval, and direct compensation blowing is adopted when the carbon content is low. The application can effectively avoid the explosion risk of the electrostatic precipitator in the compensation blowing process, improve the end point carbon qualification rate and increase the ton steel coal gas recovery amount, and is suitable for smelting high-carbon steel by a converter equipped with a dry dedusting system.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and relates to a high-tension blowing method for preventing explosions in dry dust removal converters for smelting high-carbon steel. Background Technology

[0002] High-pressure blowing is the mainstream endpoint control method for high-carbon steel smelting in oxygen top-blown converters. The key points of its operation are: when the carbon content is slightly higher than the steel grade specification at the endpoint, the carbon content is removed in advance, and after sampling and testing, the blowing is adjusted according to the actual carbon content. Compared with the carbon increase method, this method has advantages such as less iron loss, lower oxygen content in molten steel, higher alloy yield, and fewer inclusions. Therefore, it has been widely used in high-carbon steel production.

[0003] With increasingly stringent environmental protection requirements, dry dust removal technology has become the mainstream process for purifying converter steelmaking flue gas. Dry dust removal uses electrostatic precipitators to perform fine dust removal on converter flue gas, and the emission concentration can be stably kept below 10mg / m³. It has outstanding advantages such as high dust removal efficiency, low energy consumption, and small footprint, and has become the preferred dust removal process for new and upgraded converters. However, when implementing high-pressure supplementary blowing on dry dust removal converters, the following technical contradictions exist: After the second lance is applied during the supplementary blowing stage, the carbon-oxygen reaction in the converter intensifies again, and the CO content in the furnace gas rises sharply. At the same time, due to sampling and furnace turning operations before supplementary blowing, a large amount of air is mixed into the flue gas system, and the O2 content in the flue gas is also at a high level. When high concentrations of CO and O2 mix in the electrostatic precipitator, they can easily reach the explosion limit of CO. Under the action of the high-voltage electric field of the electrostatic precipitator, a discharge explosion accident is triggered. The explosion not only causes production interruption, but may also directly damage the electrode system and insulators of the electrostatic precipitator, leading to long-term equipment downtime and causing significant economic losses.

[0004] While there are reports on preventing explosions in existing dry dust removal systems, most of them focus on the overall control of conventional blowing processes. There are no systematic control methods that combine pre-oxygen reduction, nitrogen dilution, and staged oxygen supply to address the sudden increase in carbon-oxygen reaction caused by secondary lance insertion during high-pressure blowing operations. Explosions severely restrict the production stability and operational safety of high-carbon steel. Each explosion is accompanied by equipment failures such as short circuits in the electrostatic precipitator field and insulator damage. The direct equipment maintenance costs and production losses caused by a single accident are significant.

[0005] Therefore, developing a high-pulling and supplemental blowing oxygen control explosion-proof process suitable for high-carbon steel smelting in dry dust removal converters is of great significance for engineering applications and safe production. This process involves reducing oxygen levels in advance during the high-pulling stage to slow down the carbon-oxygen reaction rate, introducing nitrogen to dilute the concentration of combustible gases in the flue, and controlling the oxygen supply intensity and mode in stages according to the actual carbon content in the furnace during the supplemental blowing stage. This reduces the mixed concentration of CO and O2 at the inlet of the electrostatic precipitator from the source, keeping it away from the explosion limit. Summary of the Invention

[0006] This invention aims to provide a high-pulling and supplemental blowing oxygen control explosion-proof process for high-carbon steel smelting in dry dust removal converters. By reducing oxygen and supplementing nitrogen dilution in advance during the high-pulling carbon stage, and controlling the oxygen supply intensity and mode according to the carbon content in the furnace during the supplemental blowing stage, the mixed concentration of CO and O2 at the inlet of the electrostatic precipitator is effectively reduced, avoiding reaching the explosion limit, thereby minimizing the risk of explosion leakage, while ensuring a high hit rate of carbon and temperature at the end point.

[0007] To achieve the above objectives, the present invention provides a high-tension blowing method for preventing and venting explosions in a dry dust removal converter for smelting high-carbon steel, comprising the following steps: Step 1, High-Temperature Carbon Drawing and Pre-Control Treatment: When the main blowing stage of the converter reaches the point where the carbon content shown by the TSC test is 0.10~0.20% higher than the upper limit of the target steel grade specification, prepare to lift the lance and stop the main blowing. 20~30 seconds before lifting the lance, perform the following pre-control operations: The oxygen flow rate is gradually reduced from the rated value to 45-55% of the rated flow rate to slow down the carbon-oxygen reaction rate and reduce the CO generation rate. At the same time, nitrogen is introduced into the flue gas outlet of the evaporator cooler, with the nitrogen flow rate controlled at 6000-9000 Nm³ / h for 20-40 seconds. The inert dilution effect of nitrogen is used to reduce the concentration of CO and O2 in the flue gas. After the pre-control operation is completed, the lance is lifted and the blowing is stopped.

[0008] In the aforementioned pre-control treatment steps, the technical purpose of reducing oxygen in advance is to proactively reduce the oxygen supply intensity shortly before lifting the lance, thereby reducing the intensity of the carbon-oxygen reaction in the furnace and thus reducing the instantaneous generation of CO. The technical purpose of nitrogen replenishment is to utilize the inert gas properties of nitrogen to dilute the flue gas in the flue between the outlet of the evaporator cooler and the inlet of the electrostatic precipitator, reducing the volume concentration of CO and O2 and keeping them away from the explosion limit range. The two measures work together to create safe flue gas conditions for the subsequent lance lifting operation.

[0009] Step 2, Sampling and Testing: Molten steel in the furnace is obtained by sampling with a secondary lance or manually to determine carbon content and temperature. Sampling is carried out after the blowing is stopped by lifting the lance to ensure sampling safety. The carbon content obtained is used as the basis for determining the subsequent staged blowing and oxygen supply control.

[0010] Step 3, Staged supplemental oxygen supply control: Based on the detected carbon content, the following graded oxygen supply strategy will be implemented: When the carbon content is below 0.15%, the carbon-oxygen reaction is relatively mild. You can directly start the oxygen blowing process with the rated oxygen flow rate and control the supplementary blowing time to 0.5~1.0 minutes without additional nitrogen. The purpose of this range is that the carbon content is already low, so even if all oxygen is supplied, the carbon-oxygen reaction will not be too violent. Therefore, it is safe to supplement the blowing process without taking any additional dilution measures.

[0011] When the carbon content is 0.15~0.20%, nitrogen is injected into the flue gas simultaneously with the bottom of the nozzle, with a nitrogen flow rate of 6000~9000 Nm³ / h. Then, supplementary blowing is carried out at the rated oxygen flow rate for 0.5~1.0 minutes. The technical purpose of this range is that the carbon content is at a low to medium level, but there is still a risk of accelerated carbon-oxygen reaction in the early stage of supplementary blowing. Therefore, nitrogen is injected at the same time as the bottom of the nozzle to use the dilution effect of nitrogen to suppress the instantaneous increase of CO and O2 concentration in the flue gas. After the reaction tends to stabilize, supplementary blowing is completed with full oxygen supply.

[0012] When the carbon content is 0.20~0.40%, the climbing oxygen blowing mode is executed; after the nozzle is lowered, the oxygen flow rate starts from 30% of the rated flow rate and is increased to 100% of the rated flow rate within 30~60 seconds to avoid the sudden large amount of oxygen entering the gas, which would cause the carbon-oxygen reaction to accelerate rapidly. The total duration of supplemental blowing is controlled within 1.0~1.5 minutes. The technical purpose of the climbing oxygen blowing mode is that when the carbon content is at a medium level, if the full oxygen flow rate is supplied directly, the carbon-oxygen reaction will be instantly intensified, leading to a sharp increase in CO concentration. Therefore, the oxygen flow rate is gradually increased to make the carbon-oxygen reaction accelerate slowly, giving the flue gas system sufficient dilution and buffer time, thereby preventing the CO concentration from reaching the explosion limit.

[0013] When the carbon content is higher than 0.40%, nitrogen is simultaneously injected into the flue gas at the bottom of the nozzle, with a nitrogen flow rate of 6000~9000 Nm³ / h. The oxygen flow rate is set to 60~70% of the rated flow rate, and the injection is carried out at a constant low oxygen intensity for 1.0~1.5 minutes. If the flame is bright and the CO concentration in the flue gas rises rapidly during the injection process, the oxygen supply intensity can be further reduced to 50% of the rated flow rate. The technical purpose of this range is that the carbon content is high and has a large reaction potential. If full oxygen supply is used, it will trigger a violent carbon-oxygen reaction. Therefore, low oxygen intensity oxygen supply must be used and nitrogen dilution must be used throughout the process to strictly control the CO generation rate and the gas concentration in the flue gas.

[0014] Step 4: Destination Confirmation: After the supplementary blowing is completed, the lance is lifted, and the carbon content and temperature of the molten steel are sampled again. If the steel grade requirements are met, the steel is tapped. If not, the graded supplementary blowing operation in step three can be repeated, but the total number of supplementary blowing operations shall not exceed 3 times, and the duration of each supplementary blowing operation shall not exceed 1.5 minutes. The technical purpose of the above restrictions is that multiple supplementary blowing operations will increase the cumulative risk of explosion leakage. Therefore, by limiting the total number of supplementary blowing operations, the operator is forced to improve the accuracy of each supplementary blowing operation, while avoiding frequent fluctuations in the flue gas system caused by repeated lance operation.

[0015] As a preferred technical solution, it also includes slag formation optimization control: The amount of slag left should be controlled between 1.5 and 2.5 tons to avoid over-oxidation of the slag; The low-high-low lance position control is adopted: the lance position is 1.3~1.5 meters in the early stage of blowing to facilitate slag dephosphorization, 1.6~2.0 meters in the middle stage to stabilize decarburization, and reduced to 1.1~1.3 meters when pulling carbon. The first batch of slag is added after iron mixing and before the lance is lowered to avoid delaying ignition.

[0016] The technical objective of the above-mentioned slag control scheme is to maintain a stable carbon-oxygen reaction throughout the entire blowing process by optimizing the slag system and lance position control, avoiding sudden changes in the carbon-oxygen reaction caused by slag re-drying or splashing, and reducing the instantaneous peak value of CO concentration from the source.

[0017] As a further preferred technical solution, online monitoring and linkage control are also included: An online CO and O2 analyzer is installed in the flue gas outlet of the evaporative cooler to monitor the composition of the flue gas in real time. When the CO volume concentration is ≥12% and the O2 volume concentration is ≥6%, the control system will automatically issue an early warning and perform one or a combination of the following linkage operations: reduce the oxygen supply flow rate to less than 50% of the rated value, stop the oxygen supply and lift the lance, and increase the nitrogen replenishment to more than 10,000 Nm³ / h.

[0018] The technical purpose of the above-mentioned online monitoring and linkage control scheme is to automatically trigger the safety interlock when the flue gas composition approaches the explosion limit, so as to perform emergency operations without manual judgment and maximize the safety of equipment and personnel.

[0019] The beneficial effects of this invention are as follows: 1. This invention reduces the intensity of carbon-oxygen reaction in the furnace by taking synergistic pre-control measures of reducing oxygen and supplementing nitrogen for dilution in advance during the high carbon extraction stage. At the same time, it uses the inert properties of nitrogen to dilute the flue gas in the flue, reducing the volume concentration of CO and O2, thereby avoiding the explosion accident of the electrostatic precipitator during the supplementary blowing process.

[0020] 2. This invention uses a graded supplementary oxygen supply control strategy to precisely match the oxygen supply intensity and mode according to the actual level of carbon content in molten steel, thereby significantly improving the final carbon qualification rate and the final temperature qualification rate.

[0021] 3. By reducing the number of ineffective replenishment blows and shortening the duration of each replenishment blow, this invention enables the converter gas recovery window to be fully and effectively utilized, thereby significantly increasing the amount of gas recovered per ton of steel.

[0022] In summary, this invention can effectively reduce the final oxygen content of molten steel, improve the cleanliness of molten steel, and reduce the consumption of deoxidizers and alloys, thereby reducing raw material costs. In addition, this invention does not require large-scale modification of existing equipment, has low implementation costs, and is applicable to the production of high-carbon steel in converters equipped with dry dust removal systems. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below, based on the actual production data of two 100t converters involved in the steelmaking project of a certain enterprise.

[0024] The converter has a nominal capacity of 100t and a maximum steel output of 110t. It is equipped with an LT dry dust removal system. The inlet flue gas temperature of the electrostatic precipitator is controlled at 150~200℃, the rated oxygen flow rate is 5500Nm³ / h, and the rated nitrogen flow rate is 8000Nm³ / h.

[0025] The steel grades smelted are high-carbon steel, including J82B, 87B-2, 65# and 70# steel grades, with a final carbon content target range of 0.25~0.80%.

[0026] Before adopting the process of this invention, when these two converters were smelting the above-mentioned high-carbon steel grades, the high-pulling and supplementary blowing operation did not carry out advance oxygen reduction and graded oxygen supply control. The operators only judged the timing of supplementary blowing and the intensity of oxygen supply based on experience, and lacked a systematic graded control strategy.

[0027] After adopting the process of this invention, operators strictly followed the four steps of high carbon extraction and pre-control treatment, sampling and testing, staged oxygen supply control, and endpoint confirmation, achieving significant technical results. The process of this invention is described in detail below through several specific embodiments.

[0028] Example 1 Furnace number 26203776, steel grade J82B, target carbon content 0.60~0.70%.

[0029] During the main blowing stage, an oxygen flow rate of 5500 Nm³ / h was used, the lance position was 1.4 meters, and the blowing time was 11.7 minutes. TSC testing showed a temperature of 1511℃ and a carbon content of 0.5332%. The results indicated that the carbon content exceeded the upper limit of the target steel grade, necessitating a high-carbon drawing operation. Twenty-five seconds before lifting the lance, a pre-control operation was performed: the oxygen flow rate was gradually reduced from 5500 Nm³ / h to 2500 Nm³ / h (45% of the rated flow rate) to slow the carbon-oxygen reaction rate. Simultaneously, nitrogen was introduced into the evaporative cooler outlet flue at a flow rate of 8000 Nm³ / h for 30 seconds, utilizing the inert dilution effect of nitrogen to reduce the concentration of CO and O₂ in the flue. After the pre-control operation, the lance was lifted, and blowing was stopped.

[0030] After the lance was lifted, a sample was taken and tested using the secondary lance. The carbon content of the furnace was 0.564%, which meets the target carbon content requirement of J82B steel. No additional blowing is required. There was no explosion leakage throughout the process. The electrostatic precipitator operated smoothly, and the gas recovery time reached 6.0 minutes, with a gas recovery volume of 16018 Nm³.

[0031] This embodiment fully demonstrates the effectiveness of the pre-control measures in the high carbon extraction stage. Even without supplemental blowing, the synergistic effect of pre-oxygen reduction and nitrogen dilution in the pre-control operation ensures a smooth transition of flue gas composition before and after lifting the lance, avoiding drastic fluctuations in flue gas composition caused by oxygen supply interruption at the moment of lifting the lance, and providing a safety guarantee for the entire smelting process.

[0032] Example 2 Furnace number 26203774, steel grade J82B, target carbon content 0.60~0.70%.

[0033] During the main blowing stage, an oxygen flow rate of 5500 Nm³ / h was used, with a blowing time of 11.3 minutes. TSC monitoring showed a temperature of 1545℃ and a carbon content of 0.6158%. Before lifting the lance, a pre-control operation was performed: oxygen was reduced to 2500 Nm³ / h, and nitrogen was added at 8000 Nm³ / h for 30 seconds. After the pre-control operation, the lance was lifted, and blowing was stopped. Sampling and testing revealed the following composition: carbon 0.695%, silicon 0.002%, manganese 0.308%, phosphorus 0.0113%, and sulfur 0.0221%. Since the carbon content of 0.695% was slightly higher than the target upper limit of 0.70%, a supplementary blowing operation was required.

[0034] Based on the detected carbon content of 0.695%, which is higher than 0.40%, a high-carbon range graded supplementary blowing mode was implemented. The specific operation was as follows: nitrogen was simultaneously injected into the flue gas at the lowering of the lance, with a nitrogen flow rate of 8000 Nm³ / h and an oxygen flow rate set to 65% of the rated flow rate, i.e., 3575 Nm³ / h. Supplementary blowing was carried out at a constant low oxygen intensity for 0.7 minutes. During the supplementary blowing process, the operator closely observed the furnace flame. The flame brightness was normal, and the CO concentration in the flue gas rose steadily. After the supplementary blowing was completed, the lance was lifted, and a sample was taken again for testing. The carbon content dropped to 0.672%, which met the target carbon content requirement for J82B steel.

[0035] There was no explosion leakage throughout the entire process. The electrostatic precipitator operated at a stable current, and the gas recovery time was 5.2 minutes with a recovery volume of 14190 Nm³.

[0036] This embodiment demonstrates that for furnaces with a carbon content higher than 0.40%, the high-carbon make-up blowing mode, which uses low-oxygen constant flow oxygen supply and nitrogen dilution throughout the process, can effectively control the rate of carbon-oxygen reaction and CO generation rate while ensuring make-up blowing efficiency, thus completing the make-up blowing operation safely and efficiently.

[0037] Example 3 Furnace number 26203762, steel grade J82B, target carbon content 0.60~0.70%.

[0038] During the main blowing stage, an oxygen flow rate of 5500 Nm³ / h was used, with a blowing time of 9.2 minutes. TSC testing showed a temperature of 1525℃ and a carbon content of 0.5437%. Before lifting the lance, a pre-control operation was performed, reducing the oxygen flow rate to 2500 Nm³ / h and supplementing with nitrogen at 8000 Nm³ / h for 30 seconds. Sampling and testing after lifting the lance revealed the following composition: carbon 0.552%, silicon 0.001%, manganese 0.277%, phosphorus 0.0113%, and sulfur 0.0366%. The carbon content of 0.552% was below the target lower limit of 0.60%, necessitating a supplementary blowing operation.

[0039] During the first replenishment blowing, the carbon content was measured at 0.552%, which is higher than 0.40%, so a high-carbon replenishment blowing mode was executed. Nitrogen was added at the same time as the nozzle was lowered, with a nitrogen flow rate of 8000 Nm³ / h and an oxygen supply flow rate set at 3575 Nm³ / h, which is 65% of the rated flow rate. The blowing was kept constant for 1.2 minutes. After the replenishment blowing was completed, a sample was taken for testing, and the carbon content was 0.53%, which is still too low.

[0040] At this point, the carbon content had dropped to the range of 0.20-0.40%. The second supplementary blowing was carried out in the climbing oxygen blowing mode. Nitrogen was added at the bottom of the nozzle with a nitrogen flow rate of 8000 Nm³ / h. The oxygen flow rate was linearly increased from 30% of the rated flow rate, i.e., 1650 Nm³ / h, to 100% of the rated flow rate, i.e., 5500 Nm³ / h, within 40 seconds. The total supplementary blowing time was 0.2 minutes. After the supplementary blowing was completed, a sample was taken for testing, and the carbon content continued to decrease.

[0041] During the third supplementary blowing, the carbon content was already below 0.15%, and the low-carbon supplementary blowing mode was implemented. The process involved direct oxygen blowing at the rated flow rate of 5500 Nm³ / h for 0.6 minutes with minor adjustments, resulting in a total of 3 supplementary blowing cycles, which did not exceed the process limit of 3 cycles. Because each stage of supplementary blowing strictly followed the graded oxygen supply strategy, and necessary nitrogen dilution measures were used throughout the process, no explosions occurred. The gas recovery time was 4.0 minutes, and the recovery volume was 10710 Nm³.

[0042] This embodiment demonstrates the flexible application of graded oxygen supply control during multiple replenishment purgings. Although there are many replenishment purgings, the oxygen supply mode is dynamically adjusted according to the gradual decrease in carbon content. The process transitions from constant replenishment purging with high carbon and low oxygen to replenishment purging with medium carbon and then to fine-tuning with low carbon and full oxygen, always keeping the carbon-oxygen reaction intensity within a safe range and effectively suppressing the risk of explosion leakage.

[0043] Example 4 Furnace number 26203487, steel grade 65#, target carbon content 0.62~0.70%.

[0044] During the main blowing stage, the TSC detection showed a carbon content of 0.4191%. Before lifting the lance, a pre-control operation was performed to reduce the oxygen content to 2500 Nm³ / h and replenish the nitrogen content to 8000 Nm³ / h for 30 seconds. After lifting the lance and taking samples, the composition of the furnace was found to be 0.503% carbon, 0.001% silicon, 0.202% manganese, 0.006% phosphorus, and 0.0207% sulfur. The carbon content of 0.503% was lower than the target lower limit, so additional blowing was required.

[0045] During the first supplementary blowing, the carbon content was 0.503%, which was higher than 0.40%. The high-carbon mode was implemented, with a constant oxygen supply of 3575 Nm³ / h for 1.0 minute of supplementary blowing. After the supplementary blowing, the carbon content rose to 0.55%, but it was still lower than the target lower limit.

[0046] During the second supplementary blowing, the carbon content was 0.55%, which is now in the 0.20~0.40% range. The climbing oxygen blowing mode was then implemented, and the oxygen flow rate increased from 1650 Nm³ / h to 5500 Nm³ / h within 45 seconds. The supplementary blowing lasted for 0.8 minutes, and the carbon content was adjusted again after the supplementary blowing.

[0047] During the third supplementary blowing, the carbon content was already below 0.15%, and a fine-tuning of all oxygen was performed for 0.2 minutes.

[0048] There was no explosion leakage throughout the process, the gas recovery time was 4.6 minutes, and the recovery volume was 11949 Nm³.

[0049] Example 5 Furnace number 26204512, steel grade 87B-2, target carbon content 0.55~0.65%.

[0050] During the main blowing stage, the oxygen flow rate was 5500 Nm³ / h, the blowing time was 10.8 minutes, and the TSC test showed a carbon content of 0.5012%. 28 seconds before lifting the lance, a pre-control operation was performed: the oxygen flow rate was reduced to 2750 Nm³ / h, which is 50% of the rated flow rate, and nitrogen was added at 9000 Nm³ / h for 35 seconds. When the lance was lifted and a sample was taken for testing, the carbon content was 0.512%, which was lower than the target lower limit, and additional blowing was required.

[0051] Based on the carbon content of 0.512% being higher than 0.40%, the high-carbon supplementary blowing mode is executed; nitrogen is supplemented at the bottom of the nozzle with a nitrogen flow rate of 9000 Nm³ / h, and the oxygen supply flow rate is set to 70% of the rated flow rate, i.e., 3850 Nm³ / h, with constant supplementary blowing for 1.3 minutes.

[0052] After supplementary blowing, the carbon content was measured at 0.561%, meeting the requirements for 87B-2 steel grade. There was no explosion leakage throughout the process. The gas recovery time was 5.5 minutes, with a recovery volume of 15230 Nm³. The final oxygen content was 45 ppm, indicating good steel quality.

[0053] Example 6 Furnace number 26205123, steel grade 70#, target carbon content 0.65~0.75%.

[0054] During the main blowing stage, the oxygen flow rate was 5500 Nm³ / h, the blowing time was 12.1 minutes, and the TSC test showed a carbon content of 0.5890%. 22 seconds before lifting the lance, a pre-control operation was performed: the oxygen flow rate was reduced to 2475 Nm³ / h, which is 45% of the rated flow rate, and nitrogen was added at 6500 Nm³ / h for 25 seconds. When the lance was lifted and a sample was taken for testing, the carbon content was 0.601%, which was lower than the target lower limit, and additional blowing was required.

[0055] During the first supplemental blowing, the carbon content was 0.601%, higher than 0.40%, so a high-carbon mode was implemented with an oxygen supply flow rate of 3575 Nm³ / h for 1.0 minute of supplemental blowing. After the supplemental blowing, the carbon content dropped to about 0.58%, which was still low. During the second supplemental blowing, the carbon content entered the range of 0.20-0.40%, so an uphill oxygen blowing mode was implemented, with the oxygen flow rate increasing from 1650 Nm³ / h to 5500 Nm³ / h within 50 seconds for 1.0 minute of supplemental blowing.

[0056] After supplemental blowing, the carbon content rose to 0.632%, meeting the requirements for 70# steel. There was no explosion leakage throughout the process. The gas recovery time was 5.0 minutes, the recovery amount was 13870 Nm³, the final oxygen content was 42 ppm, and the final temperature was 1560℃, all of which met the process requirements.

[0057] The above embodiments fully verify that the process of the present invention has applicability and stability under different steel grades, different carbon content ranges, and different number of blow cycles.

[0058] The technical effects of each embodiment and application data are summarized and analyzed below.

[0059] Table 1 summarizes the changes in various key indicators before and after adopting the process of the present invention.

[0060] Table 1 Summary of Industrial Application Effects Regarding the average number of explosion venting incidents per month, the number was 3-5 before adopting the process of this invention, and dropped to 0 after adopting the process of this invention. The complete elimination of explosion venting incidents fundamentally ensures the safety of electrostatic precipitators, avoids electric field short circuits and insulator damage caused by explosion venting, and significantly reduces equipment maintenance costs and unplanned downtime.

[0061] Regarding the final carbon qualification rate, it was about 70% before adopting the process of this invention, and increased to over 85% after adopting the process of this invention. The graded supplementary blowing strategy makes the supplementary blowing operation more precise. Operators execute the corresponding oxygen supply mode according to the carbon content detection results, avoiding blind supplementary blowing and excessive supplementary blowing. The accuracy of final control is significantly improved, and the final temperature qualification rate is simultaneously increased to over 85%, providing excellent steel temperature conditions for subsequent continuous casting processes.

[0062] Regarding the average number of supplementary blowing operations, the number was 2-3 before adopting the process of this invention, and it was reduced to 1-2 after adopting the process of this invention. The graded oxygen supply control strategy improved the hit rate of a single supplementary blowing operation, reduced ineffective supplementary blowing and repeated supplementary blowing, reduced the impact of supplementary blowing operations on the production rhythm, and reduced the cumulative risk of flue gas system fluctuations during the supplementary blowing process.

[0063] Regarding the duration of a single supplementary blowing cycle, it was 1.5 to 2.5 minutes before adopting the process of this invention, and shortened to 0.5 to 1.5 minutes after adopting the process of this invention; the graded oxygen supply control significantly improves the supplementary blowing efficiency, and the supplementary blowing task can be completed in a shorter time, reducing the energy consumption and flue gas treatment load during the supplementary blowing stage.

[0064] In terms of the amount of gas recovered per ton of steel, the process of this invention increases by about 20% compared with the process before this invention, and the gas recovery time is extended from 3-4 minutes to 5-6 minutes. The reduction in the number of supplementary blowing and the duration of supplementary blowing allows the converter gas recovery window to be fully and effectively utilized, and the total amount and quality of recovered gas are significantly improved.

[0065] Regarding the final oxygen content, it was 80~120ppm before adopting the process of this invention, and decreased to 41~48ppm after adopting the process of this invention. The reduction in the final oxygen content means the improvement of the oxidizability of the molten steel, which is conducive to reducing the content of inclusions in the steel, improving the cleanliness of the molten steel, and reducing the consumption of deoxidizer and alloy. The carbon content is stably controlled above 0.25%, and the amount of carbon raiser is reduced.

[0066] The above embodiments are merely preferred embodiments of the present invention and do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preventing explosions by high-tension blowing and replenishing air in a dry dust removal converter for smelting high-carbon steel, characterized in that, Includes the following steps: Step 1, High Carbon Content and Pre-control Treatment: When the carbon content of the molten steel is detected to be higher than the upper limit of the target steel grade, before lifting the lance to stop blowing, reduce the oxygen flow rate to 45-55% of the rated flow rate and continue for 20-30 seconds. At the same time, from the start of oxygen reduction, nitrogen is added to the outlet flue of the evaporator cooler and continued for 20-40 seconds. Then lift the lance to stop blowing. Step 2: Take samples to test the carbon content of the molten steel; Step 3, Staged Oxygen Supply Control: Based on the detected carbon content of the molten steel, implement the following staged oxygen supply strategy: When the carbon content of the molten steel is below 0.15%, supplement the blowing with the rated oxygen flow rate for 0.5 to 1.0 minutes; When the carbon content of the molten steel is 0.15~0.20%, nitrogen is introduced at the same time as the lance is lowered, and then oxygen is added at the rated flow rate for 0.5~1.0 minutes. When the carbon content of the molten steel is 0.20~0.40%, the climbing oxygen blowing mode is implemented, and the oxygen flow rate is increased from 30% of the rated flow rate to 100% of the rated flow rate within 30~60 seconds, with a total supplementary blowing time of 1.0~1.5 minutes; When the carbon content of the molten steel is higher than 0.40%, nitrogen is introduced at the same time as the lance is lowered, and oxygen is supplied at a constant rate of 60-70% of the rated flow rate for 1.0-1.5 minutes. Step 4: After the supplementary blowing is completed, take another sample to test the carbon content of the molten steel. If it meets the requirements of the steel grade, the steel is tapped. If it does not meet the requirements, repeat step 3. The total number of supplementary blowing times shall not exceed three.

2. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, The converter is a top-and-bottom combined blowing converter, equipped with an LT dry dust removal system, with a rated oxygen flow rate of 5000~5600 Nm³ / h.

3. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, The high-carbon steel shall include at least J82B, 87B-2, 65# and / or 70# steel grades, and the final carbon content shall be required to be 0.25~0.80%.

4. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, The flow rate of nitrogen added in step 1 is 6000~9000 Nm³ / h.

5. The high-tension, replenishing-blowing, explosion-proof process for smelting high-carbon steel in a dry dust-removing converter according to claim 1, characterized in that, It also includes slag control: The amount of slag left is 1.5~2.5 tons, and the gun position is controlled at 1.3~1.5 meters in the early stage, 1.6~2.0 meters in the middle stage, and 1.1~1.3 meters when pulling carbon.

6. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, It also includes online monitoring and linkage control: An online CO and O2 analyzer is installed at the outlet of the evaporator cooler. When the CO volume concentration is ≥12% and the O2 volume concentration is ≥6%, at least one of the following operations is automatically executed: reducing the oxygen supply flow rate, lifting the lance to stop the blowing process, or increasing the nitrogen supply.

7. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, In the aforementioned uphill oxygen blowing mode, the oxygen flow rate is increased either linearly or in a stepwise manner.

8. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, In step 3, when the carbon content of the molten steel is higher than 0.40% and the rate of increase of CO concentration in the flue gas exceeds a preset value during the supplementary blowing process, the oxygen flow rate is reduced to 50% of the rated flow rate.

9. The high-tension, replenishing-blowing, explosion-proof process for dry dust removal converter smelting of high-carbon steel according to claim 1, characterized in that, In step 3, the flow rate of nitrogen added is 6000~9000 Nm³ / h.

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