A high-efficiency KR desulfurization method

Abstract

The present invention belongs to the technical field of converter steelmaking, and specifically relates to a method for efficient KR desulfurization. The method comprises the following steps: (1) before desulfurization, slag is first removed from the molten iron, and then the temperature of the molten iron is measured and the sulfur content in the molten iron components is sampled and tested; then the amount of desulfurizer to be added is determined; (2) a stirring paddle is inserted into the molten iron to start stirring; after stirring, the desulfurizer is blown into the molten iron tank through low-pressure nitrogen spraying; (3) after the desulfurizer is added, the speed of the stirring paddle is increased to the working speed; and the insertion depth of the stirring paddle is lowered in time periods; (4) after stirring, slag removal or slag scooping operation is performed; (5) after slag removal or slag scooping is completed, the temperature of the molten iron is measured and sampled, and a heat preservation agent is added to keep the temperature. This KR desulfurization method improves the desulfurization efficiency, forms a desulfurization slag with good fluidity, achieves the purpose of rapid slag removal, uses a relatively low-cost desulfurizer to achieve a better desulfurization effect, and further reduces the desulfurization cost.

Description

Technical Field

[0001] The invention belongs to the technical field of converter steelmaking, and specifically relates to a high-efficiency KR desulfurization method. Background Art

[0002] Sulfur is a harmful element for most steel grades, making desulfurization a fundamental task in steelmaking. The thermodynamic requirements for desulfurization are high temperature, high alkalinity, and low FeO. However, the converter smelting process cannot simultaneously meet these requirements, resulting in a desulfurization rate of less than 40%. Desulfurization is relatively easy to perform during hot metal pretreatment and refining, with desulfurization efficiencies exceeding 90%. Because the refining process requires complex operations such as adjusting the composition, raising the temperature, and calcifying the molten steel, desulfurization is currently primarily accomplished during hot metal pretreatment. Using hot metal pre-desulfurization technology not only reduces the operating pressure of low-sulfur steel produced in converters, but also offers lower costs and greater ease of operation than LF furnace desulfurization, and is essential for producing finished low-sulfur steel with a [S] ≤ 0.005wt%.

[0003] KR desulfurization is a common desulfurization method. It typically uses a "cross-shaped" or "three-leaf" agitator to rotate and stir the molten iron in the ladle. This external force creates a vortex in the molten iron, which is then fed into the vortex via a telescopic chute. The desulfurizer mixes with the molten iron and initiates a desulfurization reaction. After the KR agitation is complete, the agitator is lifted and slag is skimmed or removed to prevent resulfurization.

[0004] Cross-shaped or trilobed agitators have their paddles parallel to the drive shaft, driving the molten iron in horizontal motion during stirring. Due to their insertion position, these agitators have a weak stirring effect in some areas of the ladle, creating dead zones. Existing trilobed agitators have a desulfurization rate of approximately 85%, and due to uneven mixing, the composition varies significantly across different areas, resulting in a high level of resulfurization.

[0005] Currently, desulfurizers typically consist of 90wt% lime and 10wt% fluorite. The ratio of lime and fluorite particles with a particle size between 0.5 and 1.0mm should be greater than 80%, and the ratio of particles smaller than 0.3mm and larger than 1.2mm should be less than 10%. However, the addition of fluorite (also known as fluorspar, CaF2) to the desulfurizer releases a large amount of fluoride during use, making the KR process hot metal pretreatment a source of fluoride pollution, causing environmental contamination.

[0006] In order to eliminate fluorine pollution and achieve "green" KR desulfurization, some existing technologies use fluorine-free desulfurizers with lime and aluminum powder. However, the price of aluminum powder is 20-25 times that of lime. The fluorine-free desulfurizer with lime and aluminum powder will cause a substantial increase in desulfurization costs.

[0007] Currently, KR desulfurization cycles are long, typically 50 minutes, and efficiency remains low. Key constraints to KR desulfurization efficiency include: first, the agitation efficiency of the impeller; second, the desulfurizer currently used in KR desulfurization primarily utilizes inexpensive lime mixed with a certain amount of fluorite, resulting in a relatively low desulfurization capacity; and third, the fluidity of the desulfurized product needs to be improved. Therefore, a KR desulfurization method is urgently needed that can both improve desulfurization efficiency and minimize costs. Summary of the Invention

[0008] The present invention provides a highly efficient KR desulfurization method that improves desulfurization efficiency, forms desulfurization slag with good fluidity, achieves the purpose of rapid slagging, utilizes a relatively low-cost desulfurizer to achieve a good desulfurization effect, and further reduces desulfurization costs.

[0009] The specific technical solutions are as follows:

[0010] A method for efficient KR desulfurization comprises the following steps:

[0011] (1) Before desulfurization, the molten iron is first slag-scraped to facilitate subsequent molten iron temperature measurement and sampling; then the molten iron temperature is measured and the sulfur content in the molten iron is sampled and tested; then the amount of desulfurizer to be added is determined based on the molten iron temperature and sulfur content; the details are as follows:

[0012] ① Determine the planned desulfurization amount, which is calculated as follows: planned desulfurization amount = sulfur content before desulfurization - target sulfur content. Based on the planned desulfurization amount, use a desulfurizer ratio of 0.10-0.20 kg / t for every 0.001% desulfurization. (0.10-0.20 kg / t means 0.10-0.20 kg of desulfurizer is used per ton of molten iron.)

[0013] ②Determine the amount of desulfurizer added based on the molten iron temperature:

[0014] When the molten iron temperature is between 1280-1400℃, the addition amount is determined according to the formula 0.20kg / t-(molten iron temperature-1280℃) / 120℃×0.10kg / t;

[0015] When the molten iron temperature is higher than 1400℃, add according to the lower limit of the proportion standard in ①;

[0016] When the molten iron temperature is lower than 1280℃, add according to the upper limit of the proportion standard in ①.

[0017] (2) Insert the stirring paddle into the molten iron, wherein the lower end of the stirring paddle is inserted into the molten iron tank at a depth of 1 / 3 of the depth of the molten iron; start stirring, and maintain the rotation speed of the stirring paddle at 20 to 60 rpm; after stirring for 1 to 3 minutes, blow the desulfurizer into the molten iron tank through low-pressure nitrogen of 0.04 to 0.08 MPa.

[0018] The above insertion depth ensures that the stirring paddle is always below the liquid surface after the vortex is formed during the stirring process. If the insertion is too shallow, the stirring paddle wings will easily be exposed to the molten iron after stirring begins, affecting the stirring effect.

[0019] The speed of the stirring paddle is controlled at 20 to 60 rpm. If the speed is higher than 60 r / min, the splashing of the molten iron will increase during stirring, affecting the feeding of the desulfurizer. If the speed is less than 20 r / min, the eddy current formed in the molten iron is small, the "entrainment" effect on the desulfurizer is weak, and the desulfurizer is not easy to enter the molten iron.

[0020] The stirring time is controlled within 1-3 minutes, which is conducive to the formation of a vortex in the molten iron tank, and the molten iron slag gathers on the tank wall, increasing the contact area between the desulfurizer and the molten iron. Low-pressure nitrogen injection of the desulfurizer facilitates the discharge of the desulfurizer.

[0021] (3) After the desulfurizer is added, increase the speed of the stirring blade to 90-130 rpm; and lower the insertion depth of the stirring blade in different time periods:

[0022] Maintain the insertion depth of the lower end of the stirring paddle at 1 / 3 of the depth of the molten iron in the molten iron tank; at this time, the stirring paddle stirs the upper layer, which can promote the full mixing of the upper desulfurizer and the molten iron;

[0023] Maintain the speed at 90-100 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 1 / 2 of the depth of the molten iron in the molten iron tank;

[0024] Keep the speed at 100-110 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 2 / 3 of the depth of the molten iron in the molten iron tank;

[0025] Maintain the speed at 110-120 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 3 / 4 of the depth of the molten iron in the molten iron tank, maintain the speed at 120-130 rpm, and finally stir for 1-2 minutes.

[0026] The operating speed is determined by the erosion of the stirring paddle refractory material and the current intensity fed back during the stirring process.

[0027] The paddles gradually increase the stirring depth in different time periods, enhancing the stirring of different layers of molten iron and promoting the full reaction between the desulfurizer and the molten iron. As the insertion depth increases, the speed increases to ensure a continuous stirring effect.

[0028] The current conventional stirring operation is to insert the stirring paddle as deep as possible into the center of the molten iron ladle, and enhance the desulfurization effect by increasing the amount of desulfurizer added and increasing the stirring time. This method not only wastes costs and increases the amount of desulfurization slag, but also prolongs the desulfurization cycle.

[0029] (4) After the stirring is completed, the slag is scraped or removed; the entire stirring time is determined according to the amount of desulfurizer added and the target sulfur, and is generally controlled at 6 to 8 minutes. Steelmaking desulfurization slag refers to the waste slag produced during the pre-desulfurization treatment of molten iron before entering the converter. After the pre-desulfurization treatment reaction is completed, the dry and thick slag generated floats to the surface of the molten iron and mixes with the small amount of blast furnace slag in the ladle. The purpose of desulfurization is achieved by scraping off these slags. The scraped desulfurization slag enters the slag pot and becomes the main part of the desulfurization slag. In addition, during the slag scraping process, more or less molten iron or iron beads will fall into the slag pot along with the slag scraping process and settle at the bottom of the pot, becoming another component of the desulfurization slag.

[0030] (5) After slag removal or slag scooping is completed, the molten iron temperature is measured and sampled, and insulation is added to keep it warm.

[0031] In the present invention, the stirring blade in step (2) of the high-efficiency KR desulfurization method is a three-leaf spiral. Since the shape of the molten iron tank is an open shape with a large top and a small bottom, the traditional three-leaf stirring blade structure is as follows Figure 1 As shown, this structure can only form horizontal movement of molten iron, and has a weak stirring effect on the molten iron at the bottom of the tank. The positive three-leaf spiral stirring impeller of the present invention has a structure as shown in FIG. Figure 2 As shown in the figure, the spiral structure not only provides horizontal stirring for the molten iron, but also forms a vertical stirring effect from top to bottom, so that the molten iron at the bottom of the tank can also be effectively stirred, thereby enhancing the stirring effect of the entire tank of molten iron, reducing the dead angle of stirring, and the desulfurization rate can be increased to more than 90%, and effectively suppressing the backsulfurization.

[0032] The molten iron moves vertically during stirring, which increases the stirring effect.

[0033] Furthermore, the helical angle of the three-blade spiral stirring impeller is 10 to 30 degrees.

[0034] Furthermore, the helical angle of the three-blade spiral stirring impeller is 15°. Water model experiments show that when the helical angle is 15°, the molten iron in the tank is best mixed.

[0035] In the present invention, the rotational speed of the stirring paddle in step (2) and step (3) of the high-efficiency KR desulfurization method is controlled by a current of 200A or 300A. The rotational speed is adjusted according to the erosion of the stirring paddle, and the rotational speed of the stirring paddle is increased when the erosion is severe. When the stirring paddle is severely eroded, the stirring resistance is small, and the feedback current of the stirring paddle motor is reduced. According to the feedback current of the stirring paddle motor, when the stirring paddle erosion is small, the rotational speed is controlled by a current of 300A; when the stirring paddle erosion is severe, the rotational speed is controlled by a current of 200A.

[0036] In the present invention, the pressure of the low-pressure nitrogen in step (2) of the high-efficiency KR desulfurization method is 0.06 MPa.

[0037] In the present invention, the desulfurizer used in the highly efficient KR desulfurization method is a mixture of lime and aluminum slag particles. Aluminum slag is an industrial solid waste that contains approximately 60% Al2O3 and 15% elemental aluminum. The aluminum-containing substances in the slag can reduce the oxygen potential of molten iron. The formation of Al2O3 promotes the formation of low-melting-point desulfurization products, prevents desulfurization slag from agglomerating, and improves the fluidity of the resulting desulfurization slag. Furthermore, the price of aluminum slag is similar to that of lime. Using this desulfurizer can significantly reduce the cost of aluminum-containing desulfurizers while maintaining desulfurization performance, achieving low-cost, high-efficiency desulfurization.

[0038] Furthermore, the mass ratio of lime to aluminum slag particles in the desulfurizer is 9:1.

[0039] Furthermore, the particle size of the lime and aluminum slag particles in the desulfurizer is 1 mm to 3 mm.

[0040] In the present invention, the heat preservation agent in step (5) of the high-efficiency KR desulfurization method is carbonized rice husk. The heat preservation agent can be a conventional high-carbon or low-carbon heat preservation agent.

[0041] The beneficial effects of the present invention are as follows: the high-efficiency KR desulfurization method of the present invention comprehensively considers multiple angles from the perspectives of the design of the stirring paddle structure, the time-varying insertion depth of the stirring paddle, and the desulfurization effect and cost of the desulfurizer.

[0042] (1) The three-blade spiral stirring paddle is used, and the insertion depth of the stirring paddle is adjusted in different time periods. The stirring speed is adjusted accordingly according to the insertion depth, thereby increasing the stirring at various positions in the tank, enhancing the stirring effect of the entire tank of molten iron, and improving the desulfurization efficiency.

[0043] (2) The use of the desulfurizer can quickly form a low-melting-point desulfurization product, preventing the desulfurization slag from agglomerating and forming a desulfurization slag with good fluidity. The slag removal plate is welded with ordinary low-carbon steel plates. The molten iron ladle is appropriately tilted during slag removal, and the good fluidity of the desulfurization slag allows for rapid slag removal. Using a lower-cost desulfurizer to achieve better desulfurization results further reduces desulfurization costs by 10%-15% compared to existing KR desulfurization.

[0044] The KR desulfurization method of the present invention enhances the desulfurization effect, increasing desulfurization efficiency by 5%-15% compared to existing KR desulfurization methods. Desulfurization stirring time is shortened by 15%-20% compared to existing technologies, and slag removal time is shortened by 10%-20%. The improved fluidity of the desulfurized product prevents agglomeration and caking of the upper slag, effectively reducing the amount of iron in the slag removal process and reducing the iron content of the desulfurized slag by 2%. This significantly improves the efficiency and economic indicators of the desulfurization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1This is a top view of a traditional three-blade impeller structure.

[0046] Figure 2 This is a top view of the three-blade spiral stirring impeller structure described in the present invention.

[0047] Figure 3 This is a diagram showing the relationship between the stirring blade spiral angle and the molten iron mixing time in Experimental Example 3 of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0049] Example 1

[0050] The method for efficient KR desulfurization comprises the following steps:

[0051] (1) After slagging, the molten iron temperature was measured to be 1385°C. The sulfur content of the molten iron sampled and tested was 0.055wt%. The target sulfur content was 0.005wt%, so the planned desulfurization amount = 0.055% - 0.005% = 0.050%. Combined with the molten iron temperature of 1385°C, the desulfurization agent addition amount was determined to be 5.6kg / t according to the calculation formula of 0.20kg / t - (1385-1280°C) / 120°C × 0.10kg / t per 0.001% desulfurization.

[0052] (2) inserting a three-blade spiral stirring paddle with a spiral angle of 15° into the molten iron, wherein the lower end of the stirring paddle is inserted into the depth of 1 / 3 of the depth of the molten iron in the molten iron tank; starting stirring, the rotation speed of the stirring paddle is maintained at 30 rpm; after stirring for 1 minute, a desulfurizer is blown into the molten iron tank through a low-pressure nitrogen gas of 0.06 MPa; the desulfurizer is formed by mixing lime and aluminum slag particles in a mass ratio of 9:1; wherein the particle size of the lime and aluminum slag particles is 2 mm.

[0053] (3) After the desulfurizer is added, increase the speed of the stirring blade to 90 rpm; and lower the insertion depth of the stirring blade in different time periods:

[0054] Maintain the insertion depth of the lower end of the stirring paddle at 1 / 3 of the depth of the molten iron in the molten iron tank;

[0055] Maintain the speed at 90 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle to 1 / 2 the depth of the molten iron in the molten iron tank;

[0056] Maintain the speed at 100 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle to 2 / 3 of the depth of the molten iron in the molten iron tank;

[0057] Maintain the speed at 110 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle to 3 / 4 of the depth of the molten iron in the molten iron tank, maintain the speed at 120 rpm, and stir for a final 2 minutes;

[0058] (4) After stirring is completed, the stirring paddle is lifted out of the molten iron ladle and the slag removal operation is carried out. The slag removal time is 13.2 minutes.

[0059] (5) After slag removal or slag scooping is completed, the molten iron temperature is measured and sampled, and insulation is added to keep it warm.

[0060] The obtained desulfurization slag was tested by a slag sample detection spectrometer, and the iron content in the desulfurization slag was measured to be 7.55%.

[0061] Example 2

[0062] The method for efficient KR desulfurization comprises the following steps:

[0063] (1) After slagging, the molten iron temperature is measured to be 1425°C. The sulfur content of the molten iron sampled and tested is 0.042wt%. The target sulfur content is 0.003wt%. The planned desulfurization amount = 0.042% - 0.003% = 0.039%. Considering that the molten iron temperature is 1425°C and the temperature exceeds 1400°C, the consumption for each 0.001% desulfurization is 0.10kg / t according to the lower limit calculation, and the desulfurizer addition amount is determined to be 3.9kg / t.

[0064] (2) inserting a three-blade spiral stirring paddle with a spiral angle of 15° into the molten iron, wherein the lower end of the stirring paddle is inserted into the depth of 1 / 3 of the depth of the molten iron in the molten iron tank; starting stirring, the rotation speed of the stirring paddle is maintained at 45 rpm; after stirring for 1 minute, a desulfurizer is blown into the molten iron tank through a low-pressure nitrogen gas of 0.06 MPa; the desulfurizer is formed by mixing lime and aluminum slag particles in a mass ratio of 9:1; wherein the particle size of the lime and aluminum slag particles is 2 mm.

[0065] (3) After the desulfurizer is added, increase the speed of the stirring blade to the working speed of 100 rpm; and lower the insertion depth of the stirring blade in different time periods:

[0066] Maintain the insertion depth of the lower end of the stirring paddle at 1 / 3 of the depth of the molten iron in the molten iron tank;

[0067] Maintain the speed at 100 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle to 1 / 2 the depth of the molten iron in the molten iron tank;

[0068] Maintain the speed at 110 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle to 2 / 3 of the depth of the molten iron in the ladle;

[0069] Maintain the speed at 120 rpm, stir for 2 minutes, then insert the lower end of the stirring paddle into the molten iron tank to 3 / 4 of the depth, maintain the speed at 130 rpm, and stir for a final 2 minutes.

[0070] (4) After stirring is completed, lift the stirring paddle out of the molten iron ladle and perform the slag removal operation. The slag removal time is 12.5 minutes.

[0071] (5) After slag removal or slag scooping is completed, the molten iron temperature is measured and sampled, and insulation is added to keep it warm.

[0072] The obtained desulfurization slag was tested by a slag sample detection spectrometer, and the iron content in the desulfurization slag was measured to be 7.20%.

[0073] Comparative Example 1

[0074] The KR desulfurization method described in this comparative example comprises the following steps:

[0075] (1) Before desulfurization, the molten iron is slag-scraped and the molten iron temperature is measured at 1412°C. The sulfur content of the molten iron is 0.052 wt% when sampled and tested. The target sulfur content is 0.003 wt%, so the planned desulfurization amount = 0.052% - 0.003% = 0.049%; considering that the molten iron temperature is 1412°C and the temperature exceeds 1400°C, the consumption of 0.10 kg / t for every 0.001% desulfurization is determined according to the lower limit, and the amount of desulfurizer added is determined to be 4.9 kg / t; based on the weight of the molten iron of 149 t, the amount of desulfurizer added is determined to be 730 kg;

[0076] (2) Insert the lower end of the stirring paddle to a depth of 2 / 3 of the depth of the molten iron in the molten iron tank, start stirring, maintain the speed at 40 rpm, and after 2 minutes of stirring, use low-pressure nitrogen to spray a common desulfurizer into the molten iron tank at a nitrogen pressure of 0.06 MPa;

[0077] (3) After the material is unloaded, increase the stirring speed to 110 rpm and stir for 9 minutes;

[0078] (4) After stirring is completed, the stirring paddle is lifted out of the molten iron ladle and the slag removal operation is carried out. The slag removal time is 15.8 minutes.

[0079] (5) After slag removal, take temperature samples of the molten iron and add heat preservation agent to keep it warm.

[0080] The iron content of the desulfurization slag was detected to be 9.55%.

[0081] Experimental Example 1

[0082] 1. Experimental purpose: To further investigate the KR desulfurization method of the present invention and the KR desulfurization method of Comparative Example 1.

[0083] 2. Experimental method: 20 cans of molten iron with a continuous treatment temperature of 1260-1450°C and a sulfur content of 0.035-0.055wt% in a 150t molten iron tank of a domestic steel plant were used. According to the calculation formula for the amount of desulfurizer added, 10 cans of molten iron were treated with the KR desulfurization method described in the present invention, marked as A1-A10; the other 10 cans of molten iron were treated with the KR desulfurization method with a fixed depth, fixed speed and fixed stirring time described in Comparative Example 1, marked as B1-B10.

[0084] 3. The corresponding desulfurization data of the above 20 tanks of molten iron are summarized in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] As can be seen from Table 1, the average sulfur consumption of the desulfurizer using the KR desulfurization method of the present invention (0.001% sulfur) is 0.124 kg / t; the average sulfur consumption of the desulfurizer using the KR desulfurization method described in Comparative Example 1 is 0.133 kg / t, which is similar to the consumption of the comparative example.

[0089] Compared with the comparative example, the method of the present invention reduces the stirring time by an average of 18%, reduces the slagging time by an average of 14.6%, increases the desulfurization rate by an average of 5.5%, and reduces the iron content of the desulfurization slag by an average of 2.03%, thereby achieving efficient desulfurization and reducing desulfurization costs.

[0090] Experimental Example 2

[0091] 1. Experimental purpose: To investigate the desulfurization effect of different desulfurizers.

[0092] 2. Experimental method: The KR desulfurization method described in Example 1 was used, except that different desulfurization agents shown in Table 2 were used. Other procedures were the same as in Example 1.

[0093] 3. The experimental results are shown in Table 2.

[0094] Table 2

[0095]

[0096] As can be seen from Table 1, the desulfurization agent consumption of 90% lime + 10% aluminum slag is the lowest and the desulfurization rate is the highest.

[0097] Experimental Example 3

[0098] 1. Experimental purpose: To investigate the effect of different spiral angles of a three-blade spiral agitator on the stirring and mixing effect of desulfurizer and molten iron.

[0099] 2. Experimental method: Water model experiment is used, and the specific operation is as follows:

[0100] 1. Make a container in the same proportion as the shape of the molten iron ladle, and inject distilled water according to the actual filling ratio of the molten iron ladle;

[0101] 2. Make a stirring paddle model with different spiral angles of a three-blade spiral stirring paddle. The stirring paddle model is vertically inserted into the water surface at a depth of 2 / 3 and can rotate according to the stirring paddle speed.

[0102] 3. Specific reagent detection instruments are installed on the bottom and side walls of the container, and feedback signals are generated when the detection instruments detect the reagents at the same time.

[0103] 4. Add the detection reagent and start the stirring paddle at the same time to detect the signal feedback time.

[0104] 3. Experimental results Figure 3 shown.

[0105] Depend on Figure 3 It can be seen from the water model experiment that when the spiral angle is 15°, the time used for the molten iron signal feedback in the tank is the shortest and the mixing effect of the molten iron in the tank is the best.

[0106] The process parameters (such as molten iron temperature, sulfur, etc.) of the present invention can realize the method by taking upper and lower limits and interval values, and the embodiments are not listed here one by one.

[0107] Any content not described in detail in the present invention can be based on conventional technical knowledge in the art.

Claims

1. A method for efficient KR desulfurization, characterized in that: The following steps are involved: (1) Before desulfurization, the molten iron is first slag-removed, and then the molten iron temperature is measured and the sulfur content in the molten iron is sampled and tested; then the amount of desulfurizer to be added is determined based on the molten iron temperature and sulfur content; the details are as follows: ① Determine the planned desulfurization amount, which is calculated as follows: planned desulfurization amount = sulfur content before desulfurization - target sulfur content; based on the obtained planned desulfurization amount, use a desulfurizer ratio of 0.10-0.20 kg / t for every 0.001% desulfurization; ②Determine the amount of desulfurizer added based on the molten iron temperature: When the molten iron temperature is between 1280-1400℃, the addition amount is determined according to the formula 0.20kg / t-(molten iron temperature-1280℃) / 120℃×0.10kg / t; When the molten iron temperature is higher than 1400℃, add according to the lower limit of the proportion standard in ①; When the molten iron temperature is lower than 1280℃, add according to the upper limit of the proportion standard in ①; (2) Insert the stirring paddle into the molten iron, wherein the lower end of the stirring paddle is inserted into the depth of 1 / 3 of the depth of the molten iron in the molten iron tank; start stirring, and keep the speed of the stirring paddle at 20~60 rpm; after stirring for 1-3 minutes, blow the desulfurizer into the molten iron tank through low-pressure nitrogen gas of 0.04~0.08MPa; The stirring paddle in step (2) is in the shape of a three-leaf spiral; the spiral angle of the three-leaf spiral stirring paddle is 15°; (3) After the desulfurizer is added, increase the speed of the stirring blade to the working speed of 90~130 rpm; and lower the insertion depth of the stirring blade in different time periods: Maintain the insertion depth of the lower end of the stirring paddle at 1 / 3 of the depth of the molten iron in the molten iron tank; Maintain the speed at 90-100 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 1 / 2 of the depth of the molten iron in the ladle; Keep the speed at 100-110 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 2 / 3 of the depth of the molten iron in the molten iron tank; Maintain the speed at 110-120 rpm, stir for 1-2 minutes, then insert the lower end of the stirring paddle to 3 / 4 of the depth of the molten iron in the molten iron tank, maintain the speed at 120-130 rpm, and stir for a final 1-2 minutes; (4) After the mixing is completed, the slag is removed or scraped; (5) After slag removal or slag removal, the molten iron is temperature-measured and sampled, and a heat preservation agent is added to keep it warm; The desulfurizer is formed by mixing lime and aluminum slag particles; the mass ratio of lime to aluminum slag particles in the desulfurizer is 9:

1.

2. The method for efficient KR desulfurization according to claim 1, characterized in that: The rotation speed of the stirring blade in step (2) and step (3) is controlled by a current of 200A or 300A.

3. The method for efficient KR desulfurization according to claim 1, characterized in that: The pressure of the low-pressure nitrogen in step (2) is 0.06 MPa.

4. The method for efficient KR desulfurization according to claim 1, characterized in that: The particle size of the lime and aluminum slag particles in the desulfurizer is 1 mm to 3 mm.

5. The method for efficient KR desulfurization according to claim 1, characterized in that: The heat preservation agent in step (5) is carbonized rice husk.

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