A method for semi-steel desulphurization

Abstract

The present application relates to a kind of semi-steel desulphurization method, the method includes the following steps: desulfurizer is injected into molten iron and carries out first mechanical mixing, after injection, second mechanical mixing is carried out, and semi-steel after desulphurization is obtained by slagging;The rotating speed of the first mechanical mixing is 20-30r / min;The rotating speed of the second mechanical mixing is 80-100r / min.The semi-steel desulphurization method provided by the present application, by combining KR desulphurization method and injection desulphurization method, reasonable mechanical mixing and injection process parameters are matched, while the relative position relationship of injection device and stirrer is strictly controlled, can shorten desulphurization processing time, reduce molten iron temperature drop, while the target desulphurization rate of semi-steel can be met.

Description

Technical Field

[0001] This invention relates to the field of steelmaking technology, and specifically to a method for desulfurizing semi-steel. Background Technology

[0002] In the steel smelting process, sulfur, as a harmful element, degrades the quality of steel, easily causes low-temperature brittleness, reduces the hot plasticity of steel, and leads to surface cracking of the billet, thereby reducing the corrosion resistance of steel. Therefore, it is necessary to strictly control the sulfur content in steel and improve the cleanliness of steel. Semi-steel desulfurization has become a key process for reducing the sulfur content in steel.

[0003] CN 112593048A discloses a method for desulfurizing semi-steel. This invention adds a desulfurizing agent during the tapping process, utilizing the impact kinetic energy of the steel flow to agitate the agent, causing it to react with the sulfur in the semi-steel and remove it. This reduces the desulfurization burden on the original desulfurization station, distributing some of the desulfurization task to the vanadium-extraction converter tapping process. However, this semi-steel desulfurization method involves pre-desulfurization and desulfurization treatment, making the process relatively complex and the desulfurization time still relatively long, resulting in a high temperature drop in the molten iron.

[0004] CN 107893148A discloses a method for pre-desulfurization of semi-steel. This invention reduces production costs and the sulfur content of the semi-steel entering the furnace by replacing the original magnesium granules with aluminum-containing refining slag. During the injection process, fluorite powder lowers the melting point of the refining slag, causing the CaO in the refining slag to react with the sulfur in the semi-steel, generating sulfides that enter the slag. These sulfides are then removed after slag removal, reducing the sulfur content of the semi-steel entering the furnace. However, the desulfurization rate of the semi-steel treated by this method still needs further improvement.

[0005] CN 103103312A discloses a semi-steel desulfurizing agent and a desulfurization method using the same agent. The semi-steel desulfurizing agent comprises the following components by mass percentage: CaF2 7-15%, Mg 1%-8%, with the remainder being CaO and unavoidable impurities. The desulfurization method employs the KR process, and the aforementioned semi-steel desulfurizing agent is used. While the desulfurizing agent provided by this invention achieves a high desulfurization rate, the desulfurization process still requires a relatively long time, resulting in high operating costs.

[0006] In view of the shortcomings of existing technologies, there is an urgent need to provide a semi-steel desulfurization method that is short in desulfurization time, highly efficient and low in cost. Summary of the Invention

[0007] The purpose of this invention is to provide a method for desulfurizing semi-steel, which introduces a jetting process on the basis of KR desulfurization. By combining the kinetic parameters of KR desulfurization with the reasonable process parameters of jetting desulfurization, the temperature drop during desulfurization can be significantly reduced, the desulfurization time can be shortened, and a high desulfurization rate can be guaranteed at the same time.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for desulfurizing semi-steel, the method comprising the following steps:

[0010] The desulfurizing agent is injected into the molten iron and subjected to the first mechanical mixing. After the injection is completed, the second mechanical mixing is carried out. After slag removal, the desulfurized semi-steel is obtained.

[0011] The rotational speed of the first mechanical mixing is 20-30 r / min;

[0012] The rotational speed of the second mechanical mixing is 80-100 r / min.

[0013] The semi-steel desulfurization method provided by this invention combines the KR mechanical stirring desulfurization method with the injection desulfurization method. The KR desulfurization method has good kinetic conditions, which can fully mix the desulfurizing agent with the molten iron; while the injection desulfurization method can increase the contact area between the desulfurizing agent and the molten iron, shorten the desulfurization treatment time, thereby reducing the temperature drop of the molten iron during the desulfurization process and increasing the physical heat of the molten iron, which provides favorable conditions for increasing the scrap steel ratio in the steelmaking process. This invention, by combining reasonable mechanical mixing process parameters and injection process parameters, and strictly controlling the relative positional relationship between the injection device and the stirrer, can achieve a high desulfurization rate and meet the target desulfurization value of the semi-steel.

[0014] The rotational speed of the first mechanical mixing is 20-30 r / min, for example, it can be 20 r / min, 22 r / min, 25 r / min, 28 r / min or 30 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] The rotational speed of the second mechanical mixing is 80-100 r / min, for example, it can be 80 r / min, 85 r / min, 90 r / min, 95 r / min or 100 r / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] The purpose of the first and second mechanical mixing settings in this invention is to use a lower rotation speed when injecting the desulfurizing agent, so that the desulfurizing agent is initially mixed with the molten iron, and to avoid excessively high rotation speed causing the desulfurizing agent to agglomerate; after the injection is completed, the rotation speed can be increased to further and fully mix the molten iron and the desulfurizing agent.

[0017] Preferably, the first mechanical mixing time is 1-1.5 min, for example, it can be 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min or 1.5 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the second mechanical mixing time is 2-5 minutes, for example, it can be 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes or 5 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the blowing time is 1-1.5 min, for example, it can be 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min or 1.5 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the blowing pressure is 0.7-1.2 MPa, for example, it can be 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa or 1.2 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] The injection pressure needs to be controlled within a reasonable range. If the injection pressure is too high, the molten iron surface will churn excessively, resulting in an excessive temperature drop. If the injection pressure is too low, the desulfurizing agent cannot be successfully injected into the molten iron, and the desulfurizing agent cannot be completely mixed with the molten iron.

[0022] Preferably, the desulfurizing agent includes any one or a combination of at least two of passivated magnesium, lime, or fluorite powder. Typical but non-limiting combinations include a combination of passivated magnesium and lime, a combination of lime and fluorite powder, or a combination of passivated magnesium, lime, and fluorite powder.

[0023] Preferably, the molten iron is placed in a ladle, the outer diameter of which is 3110-3130 mm and the inner diameter is 2820-2840 mm.

[0024] The molten iron ladle described in this invention is based on an 80-ton ladle, and the capacity can be adjusted accordingly for different molten iron ladles.

[0025] The outer diameter of the molten iron ladle is 3110-3130mm, for example, it can be 3110mm, 3115mm, 3120mm, 3125mm or 3130mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] The inner diameter of the molten iron ladle is 2820-2840mm, for example, it can be 2820mm, 2825mm, 2830mm, 2835mm or 2840mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, the stirrer including a cross-shaped stirring head.

[0028] Preferably, the length of the protrusion of the cross-shaped stirring head is 360-400mm, the width is 360-400mm, and the side height is 800-1000mm.

[0029] The "length" of the protrusion of the cross-shaped stirring head refers to the distance the protrusion extends along the direction of the cross axis.

[0030] The “width” of the protrusion of the cross-shaped stirring head refers to the distance the protrusion extends in a direction perpendicular to its length and on the same plane.

[0031] The "side height" of the protrusion of the cross-shaped stirring head refers to the thickness of the protrusion in the direction perpendicular to the plane containing the cross axis.

[0032] The length of the protrusion of the cross-shaped stirring head is 360-400mm, for example, it can be 360mm, 370mm, 380mm, 390mm or 400mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] The width of the protrusion of the cross-shaped stirring head is 360-400mm, for example, it can be 360mm, 370mm, 380mm, 390mm or 400mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] The height of the raised side of the cross-shaped stirring head is 800-1000mm, for example, it can be 800mm, 850mm, 900mm, 950mm or 1000mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the height of the end of the cross-shaped stirring head near the surface of the molten iron is 200-500mm, for example, it can be 200mm, 250mm, 300mm, 400mm or 500mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the blowing is performed using a blowing device, which includes a spray gun.

[0037] Preferably, the outer diameter of the spray gun is 245-255mm and the inner diameter is 145-155mm.

[0038] The outer diameter of the spray gun is 245-255mm, for example, it can be 245mm, 248mm, 250mm, 252mm or 255mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] The inner diameter of the spray gun is 145-155mm, for example, it can be 145mm, 148mm, 150mm, 152mm or 155mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the depth to which the head of the spray gun is inserted into the molten iron is 1000-1200mm, for example, 1000mm, 1050mm, 1100mm, 1150mm or 1200mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] The depth to which the nozzle of the spray gun penetrates the molten iron needs to be controlled within a reasonable range. If the depth is too large, the desulfurizing agent cannot be drawn into the swirling flow by the agitator, thereby reducing the contact area with the molten iron. If the depth is too small, the desulfurizing agent is prone to agglomerate on the surface of the molten iron, resulting in insufficient mixing with the molten iron.

[0042] Preferably, the distance between the outer wall of the spray gun and the circumcircle of the cross-shaped stirring head is 275-285mm, for example, it can be 275mm, 278mm, 280mm, 282mm or 285mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] The circumcircle of the cross-shaped stirring head refers to the circumcircle formed by connecting the vertices of the cross-shaped stirring head. The distance between the outer wall of the spray gun and the circumcircle of the cross-shaped stirring head is the shortest distance between the two points. This distance has a certain impact on the desulfurization effect. If the distance is too small, the desulfurizing agent will not be easily dispersed in the molten iron; if the distance is too large, the vortex driven by the stirrer will not be able to fully entrain the desulfurizing agent and mix it with the molten iron. Therefore, this invention controls the distance between the outer wall of the spray gun and the circumcircle of the cross-shaped stirring head within a reasonable range.

[0044] Preferably, the distance between the outer wall of the spray gun and the inner wall of the molten iron ladle is 275-285mm, for example, it can be 275mm, 278mm, 280mm, 282mm or 285mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0046] The desulfurizing agent is injected into the molten iron at a pressure of 0.7-1.2 MPa and mechanically mixed for 1-1.5 min at 20-30 r / min. After injection for 1-1.5 min, it is mechanically mixed for 2-5 min at 80-100 r / min. The desulfurized semi-steel is obtained by removing slag.

[0047] The molten iron is placed in a ladle, the outer diameter of which is 3110-3130mm and the inner diameter is 2820-2840mm.

[0048] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head; the length of the protrusion of the cross-shaped stirring head is 360-400mm, the width is 360-400mm, and the side height is 800-1000mm; the height of the end of the cross-shaped stirring head near the surface of the molten iron is 200-500mm.

[0049] The blowing is carried out using a blowing device, which includes a spray gun; the outer diameter of the spray gun is 245-255mm, and the inner diameter is 145-155mm; the head of the spray gun extends into the molten iron to a depth of 1000-1200mm; the distance between the outer wall of the spray gun and the circumcircle of the cross-shaped stirring head is 275-285mm, and the distance between the spray gun and the inner wall of the ladle is 275-285mm.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The desulfurization method for semi-steel provided by this invention combines KR desulfurization with injection desulfurization, and uses reasonable mechanical mixing and injection process parameters, while strictly controlling the relative position of the injection device and the agitator. This allows the desulfurization treatment time to be controlled within 5-7 minutes. Compared with traditional desulfurization methods, the temperature drop of molten iron can be reduced by 10-15℃, and the desulfurization rate is above 89.5%, which can meet the target desulfurization rate of semi-steel. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the cross-sectional structure of the device used for semi-steel desulfurization provided in Example 1;

[0053] Figure 2 This is a top view of the semi-steel desulfurization device provided in Example 1;

[0054] Among them: 1. Cross-shaped stirring head; 2. Spray gun; 3. Ladle of molten iron; 4. Molten iron. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Example 1

[0057] This embodiment provides a method for desulfurization of semi-steel. The cross-sectional structural schematic diagram and top view of the semi-steel desulfurization device are shown below. Figure 1 , Figure 2 As shown, the method includes the following steps:

[0058] Lime and fluorite powder were injected into molten iron 4 under a pressure of 0.8 MPa and mechanically mixed for 1.2 min at 25 r / min. After injection for 1.2 min, mechanical mixing was carried out for 3 min at 90 r / min. After slag removal, desulfurized semi-steel was obtained.

[0059] The molten iron 4 is placed inside the molten iron ladle 3, which has an outer diameter of 3120 mm and an inner diameter of 2830 mm.

[0060] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head 1; the length of the protrusion of the cross-shaped stirring head 1 is 380mm, the width is 380mm, and the side height is 900mm; the height of the end of the cross-shaped stirring head 1 near the surface of the molten iron 4 is 300mm.

[0061] The blowing is carried out using a blowing device, which includes a spray gun 2; the outer diameter of the spray gun 2 is 250mm and the inner diameter is 150mm; the head of the spray gun 2 extends into the molten iron 4 to a depth of 1100mm; the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 is 280mm, and the distance between the spray gun 2 and the inner wall of the ladle 3 is 280mm.

[0062] Example 2

[0063] This embodiment provides a method for desulfurizing semi-steel, the method comprising the following steps:

[0064] Lime and fluorite powder were injected into molten iron 4 at a pressure of 0.9 MPa and mechanically mixed for 1.4 min at 22 r / min. After injection for 1.4 min, mechanical mixing was carried out for 2.5 min at 95 r / min. After slag removal, desulfurized semi-steel was obtained.

[0065] The molten iron 4 is placed inside the molten iron ladle 3, which has an outer diameter of 3115mm and an inner diameter of 2825mm.

[0066] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head 1; the length of the protrusion of the cross-shaped stirring head 1 is 390mm, the width is 390mm, and the side height is 950mm; the height of the end of the cross-shaped stirring head 1 near the surface of the molten iron 4 is 400mm.

[0067] The blowing is carried out using a blowing device, which includes a spray gun 2; the outer diameter of the spray gun 2 is 248mm and the inner diameter is 148mm; the head of the spray gun 2 extends into the molten iron 4 to a depth of 1150mm; the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 is 278mm, and the distance between the spray gun 2 and the inner wall of the ladle 3 is 282mm.

[0068] Example 3

[0069] This embodiment provides a method for desulfurizing semi-steel, the method comprising the following steps:

[0070] Lime and fluorite powder were injected into molten iron 4 at a pressure of 1 MPa and mechanically mixed for 1.1 min at 28 r / min. After injection for 1.1 min, they were mechanically mixed for 4 min at 85 r / min. After slag removal, desulfurized semi-steel was obtained.

[0071] The molten iron 4 is placed inside the molten iron ladle 3, which has an outer diameter of 3125 mm and an inner diameter of 2835 mm.

[0072] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head 1; the length of the protrusion of the cross-shaped stirring head 1 is 370mm, the width is 370mm, and the side height is 850mm; the height of the end of the cross-shaped stirring head 1 near the surface of the molten iron 4 is 250mm.

[0073] The blowing is carried out using a blowing device, which includes a spray gun 2; the outer diameter of the spray gun 2 is 252mm and the inner diameter is 152mm; the head of the spray gun 2 extends into the molten iron 4 to a depth of 1050mm; the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 is 282mm, and the distance between the spray gun 2 and the inner wall of the ladle 3 is 278mm.

[0074] Example 4

[0075] This embodiment provides a method for desulfurizing semi-steel, the method comprising the following steps:

[0076] Lime and fluorite powder were injected into molten iron 4 at a pressure of 1.2 MPa and mechanically mixed for 1.5 min at 20 r / min. After injection for 1.5 min, mechanical mixing was carried out for 2 min at 80 r / min. After slag removal, desulfurized semi-steel was obtained.

[0077] The molten iron 4 is placed inside the molten iron ladle 3, which has an outer diameter of 3110 mm and an inner diameter of 2820 mm.

[0078] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head 1; the length of the protrusion of the cross-shaped stirring head 1 is 360mm, the width is 360mm, and the side height is 800mm; the height of the end of the cross-shaped stirring head 1 near the surface of the molten iron 4 is 500mm.

[0079] The blowing is carried out using a blowing device, which includes a spray gun 2; the outer diameter of the spray gun 2 is 245mm and the inner diameter is 145mm; the head of the spray gun 2 extends into the molten iron 4 to a depth of 1200mm; the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 is 275mm, and the distance between the spray gun 2 and the inner wall of the ladle 3 is 285mm.

[0080] Example 5

[0081] This embodiment provides a method for desulfurizing semi-steel, the method comprising the following steps:

[0082] Lime and fluorite powder were injected into molten iron 4 at a pressure of 0.7 MPa and mechanically mixed for 1 minute at 30 r / min. After injection for 1 minute, they were mechanically mixed for 5 minutes at 100 r / min. After slag removal, desulfurized semi-steel was obtained.

[0083] The molten iron 4 is placed inside the molten iron ladle 3, which has an outer diameter of 3130 mm and an inner diameter of 2840 mm.

[0084] The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head 1; the length of the protrusion of the cross-shaped stirring head 1 is 400mm, the width is 400mm, and the side height is 1000mm; the height of the end of the cross-shaped stirring head 1 near the surface of the molten iron 4 is 200mm.

[0085] The blowing is carried out using a blowing device, which includes a spray gun 2; the outer diameter of the spray gun 2 is 255mm and the inner diameter is 155mm; the head of the spray gun 2 extends into the molten iron 4 to a depth of 1000mm; the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 is 285mm, and the distance between the spray gun 2 and the inner wall of the ladle 3 is 275mm.

[0086] Example 6

[0087] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the blowing pressure to 0.5 MPa, everything else is the same as in Embodiment 1.

[0088] Example 7

[0089] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the injection pressure to 1.5 MPa, everything else is the same as in Embodiment 1.

[0090] Example 8

[0091] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the depth of the nozzle 2 inserted into the molten iron 4 to 800mm, the rest is the same as in Embodiment 1.

[0092] Example 9

[0093] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the depth of the nozzle 2 inserted into the molten iron 4 to 1500mm, the rest is the same as Embodiment 1.

[0094] Example 10

[0095] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the distance between the outer wall of the spray gun 2 and the circumcircle of the cross-shaped stirring head 1 to 270mm, and the distance between the spray gun 2 and the inner wall of the molten iron ladle 3 to 290mm, the rest are the same as in Embodiment 1.

[0096] Example 11

[0097] This embodiment provides a method for desulfurizing semi-steel. The difference from Embodiment 1 is that, except for adjusting the distance between the outer wall of the spray gun 2 and the outer circle of the cross-shaped stirring head 1 to 290mm, and the distance between the spray gun 2 and the inner wall of the molten iron ladle 3 to 270mm, the rest are the same as in Embodiment 1.

[0098] Comparative Example 1

[0099] This comparative example provides a method for desulfurizing semi-steel. The difference from Example 1 is that lime and fluorite powder are injected into molten iron 4 at a pressure of 0.8 MPa and then mechanically mixed at 90 r / min for 1.2 min. After injection for 1.2 min, the second mechanical mixing is continued at 90 r / min for 3 min. After slag removal, desulfurized semi-steel is obtained. The rest is the same as in Example 1.

[0100] Comparative Example 2

[0101] This comparative example provides a method for desulfurizing semi-steel. The difference from Example 1 is that lime and fluorite powder are added to molten iron 4 and mechanically mixed for 4.2 min at 90 r / min, without the blowing step. The rest is the same as Example 1.

[0102] Comparative Example 3

[0103] This comparative example provides a method for desulfurizing semi-steel. The difference from Example 1 is that lime and fluorite powder are injected into molten iron 4 under a pressure of 0.8 MPa, without a mechanical mixing step. All other aspects are the same as in Example 1.

[0104] The desulfurization methods for semi-steel provided in Examples 1-11 and Comparative Examples 1-3 were used for desulfurization treatment, and the results of the iron temperature drop are shown in Table 1; the desulfurization rate of the obtained semi-steel is shown in Table 1.

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Table 1, by comparing Example 1 with Examples 2-5, the semi-steel desulfurization method provided by the present invention, by combining mechanical mixing and blowing processes with reasonable process parameters, can effectively shorten the desulfurization treatment time, reduce the temperature drop of molten iron, and achieve a desulfurization rate of over 89.5%, which can meet the production requirements of semi-steel desulfurization.

[0109] Comparing Examples 1 with Examples 6 and 7, it can be seen that if the blowing pressure is too high, the molten iron surface will experience significant turbulence, resulting in excessive temperature drop; if the blowing pressure is too low, the desulfurizing agent cannot be smoothly injected into the molten iron, and the desulfurizing agent cannot be completely mixed with the molten iron, resulting in a decrease in the desulfurization rate, and low blowing pressure is prone to clogging the spray gun. Comparing Examples 1 with Examples 8 and 9, it can be seen that if the spray gun head extends too far into the molten iron, the desulfurizing agent cannot be drawn into the vortex by the agitator, thereby reducing the contact area with the molten iron and decreasing the desulfurization rate; if the depth is too shallow, the desulfurizing agent is prone to agglomerate on the surface of the molten iron, resulting in insufficient mixing with the molten iron and a decrease in the desulfurization rate. Comparing Examples 1 with Examples 10 and 11, it can be seen that if the distance between the spray gun and the agitator head is too small, the desulfurizing agent is not easily dispersed in the molten iron, resulting in a decrease in the desulfurization rate; if the distance is too large, the vortex driven by the agitator cannot fully draw in the desulfurizing agent and mix it with the molten iron.

[0110] As can be seen from the comparison between Example 1 and Comparative Example 1, the entire process of desulfurization using the second mechanical mixing method results in the desulfurizing agent agglomeration due to the high rotation speed during injection, reducing the contact area with the molten iron and thus lowering the desulfurization rate. As can be seen from the comparison between Example 1 and Comparative Examples 2 and 3, the desulfurization rate decreases when using a single KR mechanical stirring method or injection method for desulfurization, or the temperature drop of the molten iron is higher than that of the semi-steel desulfurization method provided by this invention, resulting in greater physical heat loss and affecting production.

[0111] In summary, the desulfurization method for semi-steel provided by this invention combines KR desulfurization with injection desulfurization, uses reasonable mechanical mixing and injection process parameters, and strictly controls the relative position of the injection device and the agitator. This allows the desulfurization treatment time to be controlled within 5-7 minutes. Compared with traditional desulfurization methods, the temperature drop of molten iron can be reduced by 10-15℃, and the desulfurization rate is above 89.5%, which can meet the target desulfurization rate for semi-steel.

[0112] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for desulfurizing semi-steel, characterized in that, The method includes the following steps: The desulfurizing agent is injected into the molten iron and subjected to a first mechanical mixing. After the injection is completed, a second mechanical mixing is performed. After slag removal, desulfurized semi-steel is obtained. The first mechanical mixing and the second mechanical mixing are carried out independently using a stirrer, which includes a cross-shaped stirring head. The length of the protrusion of the cross-shaped stirring head is 360-400 mm, the width is 360-400 mm, and the side height is 800-1000 mm. The height of the end of the cross-shaped stirring head near the surface of the molten iron is 200-500 mm. The rotational speed of the first mechanical mixing is 20-30 r / min; The rotational speed of the second mechanical mixing is 80-100 r / min; The molten iron is placed in a ladle, the outer diameter of which is 3110-3130mm and the inner diameter is 2820-2840mm. The blowing pressure is 0.7-1.2 MPa; The blowing is performed using a blowing device, which includes a spray gun. The spray gun has an outer diameter of 245-255mm and an inner diameter of 145-155mm. The nozzle head is inserted into the molten iron to a depth of 1000-1200 mm. The distance between the outer wall of the spray gun and the circumcircle of the cross-shaped stirring head is 275-285mm; The distance between the outer wall of the spray gun and the inner wall of the molten iron ladle is 275-285mm.

2. The method according to claim 1, characterized in that, The first mechanical mixing time is 1-1.5 min.

3. The method according to claim 1, characterized in that, The second mechanical mixing time is 2-5 minutes.

4. The method according to claim 1, characterized in that, The blowing time is 1-1.5 minutes.

5. The method according to claim 1, characterized in that, The desulfurizing agent includes any one or a combination of at least two of passivated magnesium, lime, or fluorite powder.

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