KR molten iron desulfurization whole process automatic control method

Abstract

The present application belongs to the technical field of steel metallurgy, and specifically discloses a KR molten iron desulfurization full-process automatic control method, which comprises the following steps: S1: obtaining the initial sulfur content, target sulfur content and current molten iron tonnage of the molten iron before pretreatment, and presetting a medium desulfurization process model to automatically output a full set of process control parameters; S2: according to the process control parameters output by the medium desulfurization process model, the stirring paddle speed is raised in stages and the immersion depth is deepened synchronously, and mixed desulfurization powder is added in time; S3: when desulfurization is carried out to a preset time node, the stirring paddle speed is raised to a high speed gear and the immersion depth is continuously deepened, after entering the final stage of desulfurization, the stirring paddle speed is gradually reduced and the paddle position is synchronously raised; S4: after reaching a preset total desulfurization time, the stirring paddle is gradually raised, the stirring speed is synchronously reduced with the decrease of the immersion depth, after the stirring paddle leaves the molten iron liquid surface, slag throwing and paddle cleaning operation is performed, and full-process desulfurization is completed.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to an automatic control method for the entire desulfurization process in KR molten iron. Background Technology

[0002] With the continuous upgrading of products and the increasing demands for quality control in the steel industry, the requirements for controlling the sulfur content of molten iron in converter steelmaking are becoming increasingly stringent. The KR mechanical stirring desulfurization method, with its advantages of high desulfurization efficiency, small temperature drop in molten iron, and no need for an additional heat source, has become the mainstream process for molten iron pretreatment desulfurization.

[0003] Currently, the core parameters of the KR desulfurization process generally rely on the manual experience of operators. Based on the approximate range of initial sulfur content in molten iron, parameters such as stirring paddle speed, immersion depth, amount of desulfurization powder added, and stirring time are selected based on experience, lacking quantitative control basis and unified standards.

[0004] This manual control mode has several technical defects: First, the desulfurization effect is not stable enough. The parameter setting is significantly affected by the operator's skill level and the differences between work groups. The final sulfur content of molten iron with a similar initial sulfur content fluctuates greatly after pretreatment, making it difficult to consistently meet the requirements of converter smelting for the stability of molten iron composition. Second, the consumption of desulfurization powder is too high. In order to ensure that desulfurization meets the standards, a conservative strategy of excessive addition is generally adopted, resulting in powder waste and increased smelting costs. Third, standardized operations are difficult to implement. Especially for medium-duty desulfurization, there has been a long-term lack of quantitative control specifications. There are obvious differences in process execution between different work groups and equipment, and the level of intelligentization and standardization of the process is insufficient.

[0005] Therefore, there is an urgent need for an automatic control method for KR desulfurization that can automatically match the optimal process parameters based on the initial sulfur content of molten iron. Summary of the Invention

[0006] The purpose of this invention is to provide an automated control method for the entire desulfurization process in KR hot metal, in order to solve the problems of existing KR hot metal desulfurization processes relying on manual experience to set parameters, resulting in large fluctuations in desulfurization effect and high powder consumption.

[0007] To achieve the above objectives, the basic solution provided by this invention is: an automatic control method for the entire desulfurization process in KR molten iron, comprising the following steps: S1: Before molten iron pretreatment, obtain the initial sulfur content, target sulfur content and current molten iron tonnage, preset the intermediate desulfurization process model, and automatically output the complete set of process control parameters such as stirring paddle speed, immersion depth, stirring time and desulfurization powder addition amount from the intermediate desulfurization process model. S2: Based on the process control parameters output by the medium desulfurization process model, control the agitator to start descending and immersing in the molten iron at a low speed, gradually increase the agitator speed and simultaneously deepen the immersion depth. When the agitator reaches the medium speed rated speed and the corresponding immersion depth, add all the mixed desulfurization powder, continue to stir at medium speed until the powder is fully melted, and further deepen the agitator immersion depth. S3: When the desulfurization process reaches the preset time node, increase the speed of the agitator to the high speed and continue to deepen the immersion depth to enhance the desulfurization reaction in the middle and late stages. After entering the final stage of desulfurization, gradually reduce the speed of the agitator and simultaneously increase the agitator position. S4: After reaching the preset total desulfurization time, gradually raise the stirring paddle and reduce the stirring speed synchronously as the immersion depth decreases. After the stirring paddle leaves the molten iron surface, perform slag removal and paddle cleaning operations to complete the entire desulfurization process.

[0008] The working principle of this invention is as follows: This method takes the medium-sulfurization process model as the core, and automatically outputs a complete set of process parameters based on the initial sulfur content, target sulfur content and tonnage of the molten iron, replacing manual experience judgment; the desulfurization process is matched and controlled in stages. In the early stage, the paddle is lowered at a low speed and gradually increased. When the medium-speed condition is reached, all the desulfurization powder is added and melting is promoted. In the middle and late stages, the rotation speed is increased and the immersion depth is deepened to enhance mass transfer desulfurization. In the final stage, the speed is gradually reduced and the paddle is raised to complete the paddle cleaning. The whole process is automatically executed according to the preset time sequence, realizing precise and controllable desulfurization of medium-sulfur molten iron.

[0009] The beneficial effects of this invention are as follows: This method solidifies the optimal parameters through a model, eliminates reliance on manual experience, removes operational differences, fills the gap in standardized desulfurization operations, and ensures that the sulfur content at the desulfurization endpoint is stably up to standard; at the same time, it accurately matches the amount of powder used, avoids excessive addition, and reduces the consumption of desulfurization powder; the fully automatic control of the entire process has a fast response and a stable desulfurization cycle, which can be efficiently matched with the converter smelting cycle, thereby improving the overall operating efficiency and economic benefits of steelmaking.

[0010] Option 2, which is the preferred option of the basic option, is based on the rule of adjusting the height of the molten iron in step S1: with 110t of molten iron corresponding to a liquid level height of 4500mm as the benchmark, the liquid level height increases or decreases by 200mm for every 10t increase or decrease in the tonnage of molten iron.

[0011] Option 3, which is a preferred option of Option 2, includes the following specific methods in step S2 for gradually increasing the stirring impeller speed and simultaneously deepening the immersion depth: (1) Control the stirring paddle to start descending at an initial speed of 30 rpm, immerse it in the molten iron to a depth of 300 mm and hold it for 30 seconds, then gradually increase the speed to 40 rpm; (2) Increase the speed of the agitator to medium speed of 70 rpm within 1 minute, and at the same time increase the immersion depth to 800 mm. At this time, add all the mixed desulfurization powder at once. (3) After stirring at a medium speed of 70 rpm for 5 minutes, continue to deepen the immersion depth of the stirring paddle to 1200 mm.

[0012] Option 4, which is the preferred option of Option 3, is a mixed desulfurization powder composed of 92% lime powder and 8% fluorite powder by mass. The activity of the lime powder is not less than 320 and the effective calcium oxide content is not less than 88%.

[0013] Option 5, which is the preferred option of Option 4, includes the following specific steps in step S3: When the desulfurization pretreatment time reaches 6 minutes, maintain the immersion depth of the agitator at 1200 mm, increase the agitator speed from 70 rpm to 120 rpm, and complete the speed-up process within 1 minute. When the desulfurization time reaches 8 minutes, the immersion depth of the agitator is further increased to 1300 mm. When the desulfurization time reaches 9 minutes, the desulfurization process enters its final stage, and the speed of the agitator is gradually reduced while the agitator position is simultaneously raised.

[0014] Option 6, which is the preferred option of Option 5, involves the following steps in step S4: When the desulfurization time reaches 10 minutes, the stirring paddle is automatically raised. The stirring paddle is gradually raised from a depth of 1200 mm. When the immersion depth is detected to be less than 1000 mm, the stirring paddle speed is automatically reduced to 70 rpm. When the immersion depth is detected to be less than 500 mm, the stirring paddle speed is automatically reduced to 30 rpm. When the stirring paddle is raised to a position 100 mm above the molten iron surface, the stirring paddle speed is automatically adjusted to 70 rpm. The slag removal and stirring paddle cleaning operation is performed for 15 seconds to remove the slag adhering to the surface of the stirring paddle.

[0015] Option 7, which is the preferred option of Option 6, controls the initial temperature of molten iron at 1250℃~1400℃, the target sulfur content at the end of the desulfurization process is S≤0.020%, and the maximum allowable immersion depth of the agitator is 1500mm. Detailed Implementation

[0016] The present invention will be further described in detail below through specific embodiments: Example An automated control method for the entire desulfurization process in KR molten iron includes the following steps: S1: Before molten iron pretreatment, obtain the initial sulfur content, target sulfur content, and current molten iron tonnage. The initial temperature of the molten iron is controlled at 1250℃~1400℃. A pre-set desulfurization process model is used, which automatically outputs a complete set of process control parameters, including stirring paddle speed, immersion depth, stirring time, and desulfurization powder addition. The target sulfur content at the end of the desulfurization process is S≤0.020%. The corresponding rule for adjusting the molten iron level is: based on a molten iron tonnage of 110t corresponding to a molten iron level of 4500mm, for every 10t increase or decrease in molten iron tonnage, the corresponding molten iron level increases or decreases by 200mm. The maximum allowable immersion depth of the stirring paddle is 1500mm. S2: Based on the process control parameters output by the medium-speed desulfurization process model, the stirring paddle is controlled to initially descend and immerse in the molten iron at a low speed. The stirring paddle speed is gradually increased while simultaneously deepening the immersion depth. When the stirring paddle reaches the medium-speed rated speed and the corresponding immersion depth, all the mixed desulfurization powder is added. Medium-speed stirring is continued until the powder is fully melted, and the immersion depth of the stirring paddle is further increased. The specific method includes: (1) Control the stirring paddle to start descending at an initial speed of 30 rpm, immerse it in the molten iron to a depth of 300 mm and hold it for 30 seconds, then gradually increase the speed to 40 rpm; (2) Within 1 minute, increase the stirring speed to medium speed of 70 rpm and at the same time increase the immersion depth to 800 mm. At this time, add all the mixed desulfurization powder at once. The mixed desulfurization powder is composed of lime powder with a mass ratio of 92% and fluorite powder with a mass ratio of 8%. The activity of lime powder is not less than 320 and the effective calcium oxide content is not less than 88%. (3) After stirring at a medium speed of 70 rpm for 5 minutes, continue to deepen the immersion depth of the stirring paddle to 1200 mm; S3: When desulfurization reaches the preset time point, increase the agitator speed to high speed and continue to deepen the immersion depth to enhance the desulfurization reaction in the middle and late stages. After entering the final stage of desulfurization, gradually reduce the agitator speed and simultaneously raise the agitator position. Specific details include: When the desulfurization pretreatment time reaches 6 minutes, maintain the immersion depth of the agitator at 1200 mm, increase the agitator speed from 70 rpm to 120 rpm, and complete the speed-up process within 1 minute. When the desulfurization time reaches 8 minutes, the immersion depth of the agitator is further increased to 1300 mm. When the desulfurization time reaches 9 minutes, the desulfurization period begins, and the speed of the agitator is gradually reduced while the agitator position is raised simultaneously. S4: After reaching the preset total desulfurization time, gradually raise the stirring paddle and reduce the stirring speed synchronously as the immersion depth decreases. After the stirring paddle leaves the molten iron surface, perform slag removal and paddle cleaning operations to complete the entire desulfurization process. When the desulfurization time reaches 10 minutes, the paddle lifting operation is automatically started. The stirring paddle is gradually raised from a depth of 1200 mm. When the immersion depth is detected to be <1000 mm, the stirring paddle speed is automatically reduced to 70 rpm. When the immersion depth is detected to be <500 mm, the stirring paddle speed is automatically reduced to 30 rpm. When the stirring paddle is raised to a position 100 mm above the molten iron surface, the stirring paddle speed is automatically adjusted to 70 rpm, and the slag removal operation is continuously performed for 15 seconds to remove the slag adhering to the surface of the stirring paddle.

[0017] The implementation method of this embodiment is as follows: Before the molten iron is pretreated, the basic parameters of the molten iron to be treated are obtained through an automatic detection system: the current temperature of the molten iron is 1320℃, which is within the allowable range of 1250℃~1400℃; the initial sulfur content is 0.045%; the target sulfur content of the molten iron entering the converter as required by the smelting plan is 0.018%, which meets the applicable conditions for the medium desulfurization mode; the metering system shows that the actual tonnage of the current molten iron is 110t.

[0018] The intermediate desulfurization process model is pre-installed in the control system. After acquiring the above parameters, the model uses the molten iron level height of 4500mm corresponding to a standard tonnage of 110t as a benchmark to check the control zero point of the stirring paddle immersion depth. In this embodiment, the molten iron tonnage is exactly the standard value of 110t, the molten iron level benchmark remains unchanged at 4500mm, and the maximum allowable immersion depth of the stirring paddle is set to 1500mm. Based on the difference between the target sulfur content of 0.018% and the initial sulfur content of 0.045%, combined with the molten iron temperature of 1320℃, the intermediate desulfurization process model automatically calculates and outputs a complete set of process control parameters, mainly including: the stirring paddle's full-process rotation speed-time curve, the immersion depth-time curve, the total amount of desulfurization powder added, the duration of each stage, and the slag removal operation parameters. The calculated amount of desulfurization powder added is 530kg.

[0019] The mixed desulfurization powder was pre-prepared, consisting of 92% lime powder and 8% fluorite powder by mass. The lime powder had an activity of 340 and an effective calcium oxide content of 90.2%, both meeting the quality requirements of lime activity not less than 320 and effective calcium oxide content not less than 88%.

[0020] The following details the implementation process of the full-process automatic control for this desulfurization operation, using the time axis parameter table.

[0021] Table 1 Time Axis Parameters

[0022] 1. Preparation and Launch Phase During preparation, the agitator is in standby position, immersed to a depth of 0 mm, and rotates at 0 rpm. After the desulfurization process model completes parameter calculations and confirms that the molten iron conditions are qualified, it sends a start command to the KR desulfurization control system, and agitation begins.

[0023] 2. Initial propeller lowering and low-speed immersion stage After stirring begins, the control system, based on the parameters output by the model, controls the stirring paddle to rotate at a low speed of 30 rpm and begin to descend, allowing the stirring paddle to be smoothly immersed below the surface of the molten iron. When the stirring paddle reaches an immersion depth of 300 mm, the cumulative time is 30 seconds, during which time the stirring paddle speed is maintained at 30 rpm.

[0024] This stage, with its combination of a low rotation speed of 30 rpm and a shallow immersion depth, effectively reduces the load impact at the moment of stirring start-up, ensuring that the rated operating current of the stirring paddle is well below the safety threshold of 300A. An immersion depth of 300 mm in molten iron is defined as the initial immersion point.

[0025] 3. Accelerated feeding and medium-speed mixing stage Between 30 seconds and 1 minute, the control system gradually increases the speed of the agitator from 30 rpm to 40 rpm and then to the medium-speed rated speed of 70 rpm within 1 minute; at the same time, the agitator continues to descend from a depth of 300 mm, simultaneously increasing the immersion depth to 800 mm.

[0026] When the time axis reaches 1 minute and the immersion depth reaches 800 mm, the control system triggers the feeding command, adding all 530 kg of pre-calculated mixed desulfurization powder to the molten iron at once, with an input quantity of 100%. At this time, the stirring paddle speed is 70 rpm to ensure that the desulfurization powder is quickly drawn into and dispersed on the surface of the molten iron, avoiding powder accumulation and crusting.

[0027] Between 1 and 1.5 minutes, continue to increase the immersion depth of the agitator from 800 mm to 1200 mm, while maintaining a constant speed of 70 rpm. After reaching a depth of 1200 mm at 1.5 minutes, maintain this depth and speed of 70 rpm for medium-speed mixing until 6 minutes.

[0028] The medium-speed stirring stage lasted for 5 minutes. This served two purposes: first, it ensured the mixed desulfurization powder was fully melted, dispersed, and evenly distributed in the molten iron under medium-speed stirring at 70 rpm, establishing favorable desulfurization reaction kinetics; second, the 1200 mm immersion depth ensured the stirring vortex covered sufficient depth of the molten iron, improving the effective utilization rate of the desulfurizing agent. Throughout the feeding and medium-speed stirring stages, the control system monitored the stirring paddle's operating current in real time. In this embodiment, the actual current fluctuation range was between 185A and 220A, far below the rated value of 300A, ensuring reliable equipment safety.

[0029] 4. Strengthen desulfurization and accelerate the final stage As the desulfurization reaction enters its middle and late stages, the control system implements a coordinated adjustment strategy for rotation speed and depth according to preset time nodes.

[0030] When the total desulfurization time reached 6 minutes, the immersion depth of the agitator remained constant at 1200 mm. The control system issued an acceleration command, and the agitator speed began to increase from 70 rpm. To ensure a smooth transition, the speed was first increased to 90 rpm at the 6-minute mark, and then continued to increase, completing the acceleration before the 7-minute mark, stabilizing the speed at the high-speed rated value of 120 rpm. This acceleration process was completed within 1 minute to avoid power grid impact and equipment mechanical vibration caused by sudden speed changes.

[0031] During the 7-8 minute period, the agitator maintains an immersion depth of 1200 mm and a high speed of 120 rpm. High-speed agitation enhances the internal circulation of the molten iron and accelerates the reaction between the remaining desulfurizing agent and residual sulfur, which is a key control measure to ensure that the final sulfur content meets the standard.

[0032] When the total desulfurization time reaches 8 minutes, the control system continues to increase the immersion depth of the agitator from 1200 mm to 1300 mm, while maintaining the rotation speed at 120 rpm. 1300 mm is the maximum immersion depth in this desulfurization operation, allowing the high-speed agitation vortex to extend further into the deep layers of the molten iron, fully treating the molten iron in the bottom area of ​​the ladle, eliminating desulfurization dead zones, and improving the overall desulfurization rate.

[0033] During the period from 8 to 9 minutes, maintain a depth of 1300 mm and a speed of 120 rpm for 1 minute.

[0034] When the total desulfurization time reaches 9 minutes, the desulfurization process enters its final stage. After sufficient reaction in the early stage, the sulfur content of the molten iron has dropped to near the target level. The control system determines that the high-intensity enhanced desulfurization stage can be ended, preparing for the subsequent desulfurization process to end with the paddle lifting.

[0035] 5. Gradually raising the paddle to reduce speed and leaving the liquid surface The total desulfurization time reached 10 minutes, the current immersion depth of the agitator was 1200 mm, and the rotation speed was 120 rpm. The control system automatically started the agitator lifting and deceleration linkage program, and began to gradually lift the agitator.

[0036] Between 10 and 11 minutes, the immersion depth of the agitator was increased uniformly from 1200 mm to 1100 mm, while the rotation speed was maintained at 120 rpm.

[0037] Between 11 and 12 minutes, the immersion depth continued to increase from 1100 mm to 1000 mm, while the rotation speed remained at 120 rpm. At this time, the control system monitored the propeller position in real time and detected that the immersion depth was about to fall below 1000 mm, thus setting a trigger signal for the next stage of speed reduction.

[0038] Between 12 and 13 minutes, when the immersion depth further decreases to less than 1000 mm, the control system automatically adjusts the agitator speed from 120 rpm to a medium speed of 70 rpm. The purpose of reducing the speed is that as the agitator gradually withdraws from the molten iron surface, the damping torque of the molten iron on the agitator blades decreases significantly. Reducing the speed can effectively prevent the agitator from violently thrashing or causing equipment instability under conditions of high speed at shallow liquid levels.

[0039] Between 13 and 14 minutes, the immersion depth was increased from 800 mm to 500 mm while the rotation speed remained at 70 rpm. When the immersion depth was detected to be ≤500 mm, the control system triggered a speed reduction command again, further reducing the rotation speed from 70 rpm to 30 rpm to ensure that the agitator smoothly left the liquid surface at an extremely low speed.

[0040] At 14 minutes, the agitator was raised to a depth of 500 mm. Between 14 and 15 minutes, the agitator was slowly raised completely from the surface of the molten iron at a speed of 30 rpm. At 15 minutes, the agitator level gauge showed an immersion depth of 0 mm.

[0041] 6. Slag removal, cleaning, and final stage After the agitator completely leaves the molten iron surface, the control system continues to lift the agitator upwards. When the bottom of the agitator is 100mm above the molten iron surface, it stops and automatically adjusts the agitator speed to 70rpm to perform slag removal. Slag removal lasts for 15 seconds, using centrifugal force to throw the liquid iron slag adhering to the agitator surface back into the ladle, completing the agitator's self-cleaning process.

[0042] After the slag removal operation was completed, the stirring paddle speed was reduced to 0 rpm and raised to a safe standby position. The control system recorded all process data of this desulfurization operation and generated a production report. On-site sampling analysis showed that the final sulfur content of the molten iron was 0.015%, meeting the desulfurization target of S≤0.020%.

[0043] This embodiment fully reproduces the automatic control process of the entire KR hot metal desulfurization process using the intermediate desulfurization process model. From the precise determination of the charging timing to the coordinated operation of the rotation speed and depth at each stage, the output and execution of all process parameters are automatically completed by the model, eliminating the need for manual parameter adjustments by operators. Compared with manual experience-based control, this method eliminates parameter setting differences between different operators and shifts, solidifying the optimal process path. Actual operation data shows that statistical results from 100 consecutive heats indicate that the compliance rate of sulfur content ≤0.020% at the intermediate desulfurization endpoint reached 93%, desulfurization powder consumption was reduced by approximately 8.5% compared to the traditional operation mode, and the single-heater desulfurization cycle was stably controlled within 15 minutes, which matches the converter smelting cycle well, significantly improving the overall steelmaking production efficiency and economic benefits.

[0044] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A fully automated control method for the desulfurization process in KR molten iron, characterized in that, Includes the following steps: S1: Before molten iron pretreatment, obtain the initial sulfur content, target sulfur content and current molten iron tonnage, preset the intermediate desulfurization process model, and automatically output the complete set of process control parameters such as stirring paddle speed, immersion depth, stirring time and desulfurization powder addition amount from the intermediate desulfurization process model. S2: Based on the process control parameters output by the medium desulfurization process model, control the agitator to start descending and immersing in the molten iron at a low speed, gradually increase the agitator speed and simultaneously deepen the immersion depth. When the agitator reaches the medium speed rated speed and the corresponding immersion depth, add all the mixed desulfurization powder, continue to stir at medium speed until the powder is fully melted, and further deepen the agitator immersion depth. S3: When the desulfurization process reaches the preset time node, increase the speed of the agitator to the high speed and continue to deepen the immersion depth to enhance the desulfurization reaction in the middle and late stages. After entering the final stage of desulfurization, gradually reduce the speed of the agitator and simultaneously increase the agitator position. S4: After reaching the preset total desulfurization time, gradually raise the stirring paddle and reduce the stirring speed synchronously as the immersion depth decreases. After the stirring paddle leaves the molten iron surface, perform slag removal and paddle cleaning operations to complete the entire desulfurization process.

2. The fully automated control method for desulfurization of KR molten iron according to claim 1, characterized in that, In step S1, the rule for adjusting the molten iron level is as follows: with 110t of molten iron corresponding to a molten iron level of 4500mm as the benchmark, for every 10t increase or decrease in the molten iron tonnage, the corresponding molten iron level increases or decreases by 200mm.

3. The fully automated control method for desulfurization of KR molten iron according to claim 2, characterized in that, The specific method for step S2, which involves gradually increasing the impeller speed and simultaneously deepening the immersion depth, includes: (1) Control the stirring paddle to start descending at an initial speed of 30 rpm, immerse it in the molten iron to a depth of 300 mm and hold it for 30 seconds, then gradually increase the speed to 40 rpm; (2) Increase the speed of the agitator to medium speed of 70 rpm within 1 minute, and at the same time increase the immersion depth to 800 mm. At this time, add all the mixed desulfurization powder at once. (3) After stirring at a medium speed of 70 rpm for 5 minutes, continue to deepen the immersion depth of the stirring paddle to 1200 mm.

4. The fully automated control method for desulfurization of KR molten iron according to claim 3, characterized in that, The mixed desulfurization powder is composed of 92% lime powder and 8% fluorite powder by mass. The activity of the lime powder is not less than 320 and the effective calcium oxide content is not less than 88%.

5. The fully automated control method for desulfurization of KR molten iron according to claim 4, characterized in that, The specific content of step S3 includes: When the desulfurization pretreatment time reaches 6 minutes, maintain the immersion depth of the agitator at 1200 mm, increase the agitator speed from 70 rpm to 120 rpm, and complete the speed-up process within 1 minute. When the desulfurization time reaches 8 minutes, the immersion depth of the agitator is further increased to 1300 mm. When the desulfurization time reaches 9 minutes, the desulfurization process enters its final stage, and the speed of the agitator is gradually reduced while the agitator position is simultaneously raised.

6. The fully automated control method for desulfurization of KR molten iron according to claim 5, characterized in that, In step S4, the specific process of gradually raising the agitator is as follows: when the desulfurization time reaches 10 minutes, the agitator raising operation is automatically started. The agitator is gradually raised from a depth of 1200 mm. When the immersion depth is detected to be <1000 mm, the agitator speed is automatically reduced to 70 rpm. When the immersion depth is detected to be <500 mm, the agitator speed is automatically reduced to 30 rpm. When the agitator is raised to a position 100 mm above the molten iron surface, the agitator speed is automatically adjusted to 70 rpm, and the slag removal and agitator cleaning operation is continuously performed for 15 seconds to remove the slag adhering to the surface of the agitator.

7. The fully automated control method for desulfurization of KR molten iron according to claim 6, characterized in that, The initial temperature of the molten iron is controlled at 1250℃~1400℃, the target sulfur content at the end of the desulfurization process is S≤0.020%, and the maximum allowable immersion depth of the agitator is 1500mm.

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