Method for reducing smoke amount in early stage of blowing in converter double-slag method smelting process

Abstract

The invention discloses a method for reducing the amount of smoke in the earlier stage of blowing in a converter double-slag smelting process, and belongs to the technical field of converter steelmaking. The converter double-slag method smelting process comprises the steps that waste steel is added into a converter, molten iron is added, lime and a rapid slag forming agent are added immediately, and the melting point of the rapid slag forming agent ranges from 1200 DEG C to 1400 DEG C; and limestone powder and oxygen are mixed and sprayed from an oxygen lance for blowing, iron ore is added in batches after blowing is started, and the size of the added iron ore is 10-50 mm. According to the smelting method, the slagging speed in the early stage of the converter can be increased, rapid rising of the temperature of the molten pool is restrained, and therefore the smoke amount in the early stage of converter smelting can be effectively reduced, and the dephosphorization efficiency can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of converter steelmaking, and more specifically to a method for reducing the amount of smoke in the early stage of blowing in a converter double-slag smelting process. Background Art

[0002] The double slag smelting process has become one of the main methods of converter smelting due to its excellent dephosphorization ability and low smelting cost. In the specific smelting process, the double slag method has two modes: slag retention (hot slag circulation) and no slag retention. In the early stage of smelting of these two methods, due to the slow slag-forming speed of the slag-forming agent, the surface of the molten iron is oxidized, and then smoke is formed. In addition, in the impact pit area formed by the action of the oxygen lance jet and the molten pool, the elements are oxidized in large quantities, causing the temperature in this area to locally exceed 2000°C, or even as high as 3000°C, resulting in a large amount of iron evaporation, further increasing the amount of smoke in the early stage of converter smelting. The increase in the amount of converter smoke will cause high iron loss, thereby increasing the cost of converter smelting. At the same time, when the amount of smoke is too large, it will also cause smoke to overflow and pollute the environment.

[0003] Under the background of the severe economic situation of steel enterprises, how to reduce the iron loss and smoke amount in the smelting process is a technical problem that steel enterprises generally need to solve urgently. After searching, in the process of steel tapping from the converter, such as the application case with the Chinese patent publication number CN108913838A, a method for reducing smoke in the process of semi-steel tapping is disclosed, including the following steps: removing phosphorus or vanadium from molten iron during the converter smelting process to obtain semi-steel; then spraying mist coolant on the semi-steel during the semi-steel tapping process. Another example is the application case with the Chinese patent publication number CN112301181A, which discloses a method for suppressing the generation of smoke from vanadium-extracted semi-steel, including the following steps: sending vanadium-containing molten iron into a vanadium-extracting converter for vanadium extraction, and controlling the terminal temperature of the vanadium-extracted semi-steel to be 1340-1420℃; tapping, using nitrogen to compositely spray slag-making agent and alloy deoxidizer for a first preset time, and then spraying slag-making agent alone for a second preset time, so that the formed pre-melted slag covers the surface of the semi-steel. However, the above two applications are mainly applicable to reducing the amount of smoke and dust in the process of semi-steel tapping.

[0004] During the converter blowing process, for example, the application with Chinese patent publication number CN104498664A discloses a method of spraying water vapor to control the converter molten pool temperature and smoke generation. This application replaces the existing pure oxygen blowing by spraying oxygen and water vapor with a converter oxygen lance to carry out mixed blowing, and controls the water vapor mixing ratio to be 5-15%. By adjusting the mixing ratio of water vapor, the converter molten pool heating rate is controlled, the thermodynamic conditions of dephosphorization in the early stage of blowing are improved, and the dephosphorization rate is increased. Although this application can suppress the evaporation of iron by lowering the temperature of the reaction zone, there are the following problems: (1) The hydrogen in the water vapor dissolves in the molten steel, which will cause the molten steel to increase in hydrogen and deteriorate the performance of the steel; (2) Lowering the temperature of the reaction zone by water vapor will be unfavorable for the dissolution of slag-forming materials such as lime, and the slag will be slow. Summary of the invention

[0005] In view of the problem of large amount of smoke dust in the early stage of blowing in the double-slag smelting process of the converter in the prior art, the present invention provides a method for reducing the amount of smoke dust in the early stage of blowing in the double-slag smelting process of the converter. The smelting method can effectively reduce the amount of smoke dust in the early stage of converter smelting by increasing the slag forming speed in the early stage of the converter and controlling the molten pool temperature, and can improve the dephosphorization efficiency.

[0006] The present invention provides a method for reducing the amount of smoke in the early stage of blowing in a converter double-slag smelting process, comprising:

[0007] Scrap steel and molten iron are added into the converter, followed by lime and a rapid slag-forming agent having a melting point of 1200-1400°C; limestone powder is mixed with oxygen and sprayed from an oxygen gun for blowing, and iron ore is added in batches after the blowing starts, and the size of the added iron ore is 10-50 mm.

[0008] The present invention controls the process parameters of converter smelting, specifically, first, after adding molten iron and scrap steel, the temperature of the molten iron entering the furnace is generally 1250-1500°C, and then lime and fast slag forming agent are added. It should be noted that the timing of adding lime and fast slag forming agent in this application is very important, and they are added to the converter before blowing, that is, they are added to the converter in a cold state; in addition, there are high requirements for the melting point of the fast slag forming agent in this application, and the melting point of the fast slag forming agent is limited to between 1200-1400°C, the melting time of the fast slag forming agent is about 30s, and oxygen blowing starts about 30s after the fast slag forming agent is put into the converter, and the density of the fast slag forming agent is small, and it will float on the surface of the molten iron, so that the fast slag forming agent forms a layer of liquid slag on the surface of the molten iron before the oxygen blowing starts. In addition, the fast slag forming agent can promote the melting of lime, increase the slag forming speed, form a slag with a certain foaming performance and thickness, and further reduce the amount of smoke generated.

[0009] Secondly, limestone powder is mixed with oxygen and sprayed into the oxygen lance for blowing. On the one hand, the limestone powder can be sprayed into the jet impact area in a direction, and the higher temperature in the reaction zone can be used to accelerate the decomposition of the limestone powder to form lime and CO2, as well as promote the melting of the decomposed lime, further speeding up the slag formation rate. The decomposed CO2 can promote stirring and improve the dephosphorization effect. On the other hand, the limestone powder is decomposed in the jet impact area to reduce the temperature of the reaction area.

[0010] Again, after the converter blowing begins, iron ore is added in batches. It should be noted that the size of the iron ore used is very important. The size of the added iron ore is limited to 10 to 50 mm, so that the added iron ore can be stably present in the slag layer to prevent the iron ore from sinking directly below the slag-iron interface due to its large size, so as to reduce the temperature of the slag layer. At the same time, the reduction reaction of the iron ore can be used to further suppress the heating rate of the slag layer. More importantly, the added iron ore can promote slag formation. FeO in the iron ore is a surfactant, which helps the slag to foam and further increase the thickness of the converter slag layer. When the local temperature of the molten iron is too high, the iron vapor formed needs to pass through the slag layer to escape. At this time, the slag layer can cool the iron vapor passing through it well, convert it into liquid or solid state, and then return to the molten iron, thereby filtering and cooling the smoke.

[0011] In summary, the present invention adds lime and rapid slag-forming agent into the converter before blowing, and adds iron ore into the converter in batches immediately after the blowing starts, so as to synergistically optimize the process parameters of the converter double-slag smelting method, so as to promote the melting of the slag layer, increase the thickness of the slag layer, and inhibit the rapid rise of the slag layer temperature, thereby reducing the amount of smoke and improving the dephosphorization effect of the converter.

[0012] Furthermore, the rapid slag-forming agent is a pre-melting type refined slag, which includes the following components in mass percentage: CaO 30-45%, SiO2 10-25%, Al2O3 15-25%, MgO 3-7%, MnO 5%-10%. The rapid slag-forming agent is optimized and pre-melted through the component and mass ratio. The melting point is controlled between 1200 and 1400 ° C. Compared with the slag-forming agent containing iron elements, the rapid slag-forming agent is more stable during the blowing process.

[0013] Furthermore, the amount of the rapid slagging agent added is 10-20 kg / t steel, and / or the amount of the lime added is 3-5 kg / t steel.

[0014] Furthermore, the content of CaO in the lime is ≥85%.

[0015] Furthermore, after the blowing starts, 10-30 kg / t steel of iron ore is added in 2-3 batches, each with an interval of 1-1.5 minutes, and the iron ore is added within 1-3 minutes of the start of blowing. Further preferably, the single addition amount of iron ore does not exceed 60% of the total amount, and is not less than 20%.

[0016] Furthermore, the composition of the slag in the early stage of smelting is controlled to be: CaO / SiO2(R): 1.3-2.0, FeO: 15-25%, MgO: 3-6%, Al2O3: 2-6%, which is conducive to maintaining the appropriate melting point and viscosity required for the slag in the early stage of converter smelting, and contains a certain proportion of surface active substances FeO and Al2O3, which is conducive to the foaming of the slag, increasing the thickness of the slag layer, and thus improving the filtering effect of smoke. Furthermore, the average thickness of the slag layer on the surface of the molten iron in the early stage of smelting is 2-4m, and the slag layer of this thickness can better cool and filter the iron vapor passing through it.

[0017] Furthermore, the injection amount of the limestone powder is 10-20 kg / t steel, and the particle size is less than or equal to 1 mm.

[0018] Furthermore, it also includes: before adding scrap steel into the converter and adding molten iron, slag is left or not left after slag splashing. In the converter double slag smelting process, slag is usually left after slag splashing to improve the dephosphorization capacity. However, due to the high melting point of the slag, it has solidified after slag splashing and adding scrap steel, adhered to the furnace wall and furnace bottom, and does not exist on the surface of molten iron, and cannot play a role in reducing the amount of smoke formation.

[0019] Furthermore, it also includes: performing a slag removal operation when the converter is blown to a slag removal point; and performing decarburization blowing after the slag removal, and tapping the steel after the blowing is completed.

[0020] In summary, the technical solution provided by the present invention can achieve the following beneficial effects compared with the prior art:

[0021] (1) The present invention adds a rapid slag-forming agent and lime in a cold state before blowing, and controls the melting point of the rapid slag-forming agent. The rapid slag-forming agent can quickly form a layer of slag on the surface of molten iron, promote the melting of lime, increase the thickness of the slag layer, and thus reduce the amount of smoke generated.

[0022] (2) The present invention adds iron ore in batches immediately after the start of blowing, and controls the particle size of the iron ore to be 10 mm to 50 mm, so that the added iron ore can be stably present in the slag layer, thereby having the effect of reducing the temperature of the slag layer. At the same time, the reduction reaction of the iron ore can be used to suppress the temperature increase rate of the slag layer. In addition, it is also helpful to increase the thickness of the converter slag layer.

[0023] (3) The present invention further optimizes the slag layer thickness in the early stage of converter smelting, and controls the slag layer thickness to 2-4 m. When the local temperature of the molten iron is too high, the iron vapor formed needs to pass through the slag layer to escape. At this time, the slag layer can well cool the iron vapor passing through it, converting it into liquid or solid state, and then returning to the molten iron, thereby filtering and cooling the smoke. DETAILED DESCRIPTION

[0024] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with embodiments.

[0025] In the present invention, "early stage of converter smelting" refers to "the period from slag splashing to protect the furnace at the beginning of converter smelting to 5 minutes after the start of oxygen blowing in the converter, during which time period the iron ore has entered the converter".

[0026] Example 1

[0027] This embodiment is smelted on a 150t converter, specifically comprising the following steps:

[0028] (a) After slag splashing, slag retention operation is carried out, and the slag retention amount is controlled to 40kg / t steel;

[0029] (b) adding scrap steel and molten iron into a converter, the conditions of the molten iron into the converter are shown in Table 1; then adding 3.4 kg / t of lime and 16 kg / t of rapid slag-forming agent, wherein the content of CaO in the limestone used is 92%, and the mass percentage of the rapid slag-forming agent used is: CaO 40%, SiO2 18%, Al2O3 20%, MgO 5%, MnO 7%, and the rest are unavoidable impurities, and the melting point is 1276°C;

[0030] (c) blowing with an oxygen lance, during which limestone powder mixed with oxygen is sprayed into the lance for blowing, the amount of limestone powder sprayed is 12 kg / t steel, and the particle size is less than or equal to 1 mm; iron ore is added after the start of blowing, the size of the added iron ore is between 20 mm and 40 mm, the average size of the iron ore is 30 mm, and the total amount of iron ore added is 20 kg / t steel, which is added in three times, specifically, 8 kg / t steel is added at the start of blowing, 6 kg / t steel is added after 1.2 min of blowing, and 6 kg / t steel is added after 2.6 min of blowing. The indicators of the slag in the early stage of converter smelting are shown in Table 2;

[0031] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are detailed in Table 2.

[0032] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.8, that is, the CaO / SiO2 ratio is 1.8, the FeO proportion in the slag composition is 17%, the MgO proportion is 4.6%, the Al2O3 proportion is 3.5%, and the slag layer thickness is 3.5m.

[0033] The smoke volume of this embodiment is 8.7 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 62.9%.

[0034] Comparative Example 1

[0035] The conditions of the molten iron in the furnace in this comparative example are shown in Table 1. The difference between this comparative example and Example 1 is that lime and rapid slagging agent are added immediately after the blowing starts, and other operations are basically the same.

[0036] The converter smelting indicators in this comparative example are detailed in Table 2.

[0037] In this comparative example, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.5, that is, the CaO / SiO2 ratio is 1.5, the FeO proportion in the slag composition is 18%, the MgO proportion is 5.2%, the Al2O3 proportion is 3.7%, and the slag layer thickness is 3.2m.

[0038] The smoke amount of this comparative example is 11.4 kg / t steel, which is 2.7 kg / t steel more than that of Example 1; the dephosphorization efficiency in the early stage of converter blowing is 57.9%, and the dephosphorization efficiency of Example 1 is increased by 5.0% relative to this comparative example.

[0039] Comparative Example 2

[0040] The conditions of the molten iron in the furnace in this comparative example are shown in Table 1. The difference between this comparative example and Example 1 is that the iron ore is added after the blowing starts, the size of the added iron ore is 60 mm to 80 mm, and the average size is 70 mm. Other operations are basically the same.

[0041] In this comparative example, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.3, that is, the CaO / SiO2 ratio is 1.3, the proportion of FeO in the slag composition is 25, the proportion of MgO is 3.9%, the proportion of Al2O3 is 4.8%, and the slag layer thickness is 2.5m.

[0042] The smoke amount of this comparative example is 13.7 kg / t steel, which is 5 kg / t steel more than that of Example 1; the dephosphorization efficiency in the early stage of converter blowing is 51.4%, and the dephosphorization efficiency of Example 1 is increased by 11.5% relative to this comparative example.

[0043] Comparative Example 3

[0044] The conditions of the molten iron in the furnace in this comparative example are shown in Table 1. The difference between this comparative example and Example 1 is that the iron ore is added after the blowing starts, the size of the added iron ore is 5-10 mm, and the average size is 8 mm. Other operations are basically the same.

[0045] In this comparative example, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.7, that is, the CaO / SiO2 ratio is 1.7, the FeO proportion in the slag composition is 16%, the MgO proportion is 4.1%, the Al2O3 proportion is 3.9%, and the slag layer thickness is 2.2m.

[0046] The smoke amount of this comparative example is 10.5 kg / t steel, which is 1.8 kg / t steel more than that of Example 1; the dephosphorization efficiency in the early stage of converter blowing is 51.3%, and the dephosphorization efficiency of Example 1 is increased by 11.6% relative to this comparative example.

[0047] Comparative Example 4

[0048] The conditions for charging molten iron in this comparative example are shown in Table 1. The difference between this comparative example and Example 1 is that the timing of adding iron ore is different, specifically, 8 kg / t steel is added when blowing for 2 minutes, 6 kg / t steel is added when blowing for 4 minutes, and 6 kg / t steel is added when blowing for 6 minutes. Other operations are basically the same.

[0049] The converter smelting indicators in this comparative example are detailed in Table 2.

[0050] In this comparative example, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.9, that is, the CaO / SiO2 ratio is 1.9, the proportion of FeO in the slag composition is 22, the proportion of MgO is 5.0%, the proportion of Al2O3 is 3.4%, and the slag layer thickness is 2.7m.

[0051] The smoke amount of this comparative example is 11.4 kg / t steel, which is 2.7 kg / t steel more than that of Example 1; the dephosphorization efficiency in the early stage of converter blowing is 56.1%, and the dephosphorization efficiency of Example 1 is increased by 6.8% relative to this comparative example.

[0052] Comparative Example 5

[0053] The difference between this comparative example and Example 1 is that after the iron addition is completed, only 15 kg / t of lime is added, and no rapid slag-forming agent is added; limestone powder is not sprayed during the blowing process, and iron ore is added after the blowing starts. The total amount of iron ore added is 16 kg / t of steel, which is added in three times, specifically, 6 kg / t of steel is added at the beginning of blowing, 6 kg / t of steel is added after 1.2 minutes of blowing, and 4 kg / t of steel is added after 2.6 minutes of blowing. Other operations are basically the same.

[0054] The converter smelting indicators in this comparative example are detailed in Table 2.

[0055] In this comparative example, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.5, that is, the CaO / SiO2 ratio is 1.5, the FeO proportion in the slag composition is 13%, the MgO proportion is 7.1%, the Al2O3 proportion is 1.1%, and the slag layer thickness is 1.2m.

[0056] The smoke amount of this comparative example is 16.2 kg / t steel, which is 7.5 kg / t steel more than that of Example 1; the dephosphorization efficiency in the early stage of converter blowing is 44.4%, and the dephosphorization efficiency of Example 1 is increased by 18.5% relative to this comparative example.

[0057] Example 2

[0058] This embodiment is carried out on a 150t converter and specifically includes the following steps:

[0059] (a) After slag splashing, slag retention is performed, and the slag retention amount is controlled to 30kg / t steel;

[0060] (b) adding scrap steel and molten iron into a converter, the conditions of the molten iron are shown in Table 1; then adding 5 kg / t of lime and 10 kg / t of rapid slag-forming agent, wherein the content of CaO in the lime used is equal to 85%, and the mass percentage of the rapid slag-forming agent used is: CaO 35%, SiO2 20%, Al2O3 22%, MgO 3%, MnO 10%, and the rest are unavoidable impurities, with a melting point of 1358°C;

[0061] (c) blowing with an oxygen lance, during which limestone powder is mixed with oxygen and sprayed into the lance for blowing, the amount of limestone powder sprayed is 10 kg / t steel, and the particle size is less than or equal to 1 mm; iron ore is added after the start of blowing, the size of the added iron ore is between 40 mm and 50 mm, the average size of the iron ore is 45 mm, and the total amount of iron ore added is 28 kg / t steel, which is added in three times, specifically, 14 kg / t steel is added at the beginning of blowing, 7 kg / t steel is added after blowing for 1 minute, and 7 kg / t steel is added after blowing for 2 minutes. The indicators of the slag in the early stage of converter smelting are shown in Table 2;

[0062] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are detailed in Table 2.

[0063] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.5, that is, the CaO / SiO2 ratio is 1.5, the FeO proportion in the slag composition is 20%, the MgO proportion is 5.1%, the Al2O3 proportion is 4.9%, and the slag layer thickness is 3.9m.

[0064] The smoke volume of this embodiment is 9.4 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 63.2%.

[0065] Example 3

[0066] This embodiment is carried out on a 150t converter and specifically includes the following steps:

[0067] (a) After splashing slag to protect the furnace, pour out the slag and perform slag-free operation;

[0068] (b) adding scrap steel and molten iron into a converter, the conditions for adding steel into the converter and molten iron are shown in Table 1; then adding 3 kg / t of lime and 18 kg / t of rapid slag-forming agent, wherein the content of CaO in the lime used is equal to 88%, and the mass percentage of the rapid slag-forming agent used is: CaO 42%, SiO2 15%, Al2O3 25%, MgO 5%, MnO 6%, and the rest are unavoidable impurities, with a melting point of 1224°C;

[0069] (c) blowing with an oxygen lance. During the blowing process, limestone powder mixed with oxygen is sprayed into the oxygen lance for blowing. The amount of limestone powder sprayed is 20 kg / t steel, and the particle size is less than or equal to 1 mm. After the blowing starts, iron ore is added. The size of the added iron ore is between 10 mm and 20 mm, and the average size of the iron ore is 15 mm. The total amount of iron ore added is 30 kg / t steel, which is added in three times. 15 kg / t steel is added at the beginning of the blowing, 8 kg / t steel is added after 1.4 minutes of blowing, and 7 kg / t steel is added after 2.8 minutes of blowing. The indicators of the slag in the early stage of smelting are detailed in Table 2.

[0070] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are shown in Table 2.

[0071] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 2, that is, the CaO / SiO2 ratio is 2, the FeO proportion in the slag composition is 25%, the MgO proportion is 3.7%, the Al2O3 proportion is 5.1%, and the slag layer thickness is 2.1m.

[0072] The smoke volume of this embodiment is 9.1 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 65.7%.

[0073] Example 4

[0074] This embodiment is carried out on a 150t converter and specifically includes the following steps:

[0075] (a) After splashing slag to protect the furnace, pour out the slag and perform slag-free operation;

[0076] (b) adding scrap steel and molten iron into a converter, the conditions for adding steel into the converter and molten iron are shown in Table 1; then adding 4.2 kg / t of lime and 17 kg / t of rapid slag-forming agent, wherein the content of CaO in the lime used is equal to 88%, and the mass percentage of the rapid slag-forming agent is: CaO 38%, SiO2 20%, Al2O3 17%, MgO 6%, MnO 9%, and the rest are unavoidable impurities, with a melting point of 1376°C;

[0077] (c) blowing with an oxygen lance, during which limestone powder mixed with oxygen is sprayed from the oxygen lance for blowing, the amount of limestone powder sprayed is 17 kg / t steel, and the particle size is less than or equal to 1 mm; iron ore is added after the start of blowing, the size of the added iron ore is between 35 mm and 45 mm, the average size of the iron ore is 40 mm, and the total amount of iron ore added is 10 kg / t steel, which is added in three times, specifically, 5 kg / t steel is added at the beginning of blowing, 3 kg / t steel is added after 1.2 minutes of blowing, and 2 kg / t steel is added after 2.6 minutes of blowing; the indicators of the slag in the early stage of smelting are detailed in Table 2;

[0078] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are shown in Table 2.

[0079] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.3, that is, the CaO / SiO2 ratio is 1.3, the FeO proportion in the slag composition is 15%, the MgO proportion is 4.3%, the Al2O3 proportion is 3.3%, and the slag layer thickness is 2.9m.

[0080] The smoke volume of this embodiment is 8.6 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 61.9%.

[0081] Example 5

[0082] This embodiment is carried out on a 150t converter and specifically includes the following steps:

[0083] (a) After splashing slag to protect the furnace, pour out the slag and perform slag-free operation;

[0084] (b) adding scrap steel and molten iron into a converter, the conditions for adding steel into the converter and molten iron are shown in Table 1; then adding 3 kg / t of lime and 20 kg / t of rapid slag-forming agent, wherein the content of CaO in the lime used is equal to 90%, and the mass percentage of the rapid slag-forming agent is: CaO 45%, SiO2 10%, Al2O3 15%, MgO 7%, MnO 5%, and the rest are unavoidable impurities, with a melting point of 1207°C;

[0085] (c) blowing with an oxygen lance, during which limestone powder mixed with oxygen is sprayed into the lance for blowing, the amount of limestone powder sprayed is 10 kg / t steel, and the particle size is less than or equal to 1 mm; iron ore is added after the start of blowing, the size of the added iron ore is between 10 mm and 30 mm, the average size of the iron ore is 20 mm, and the total amount of iron ore added is 18 kg / t steel, which is added in three times, specifically, 9 kg / t steel is added at the beginning of blowing, 5 kg / t steel is added after 1.2 minutes of blowing, and 4 kg / t steel is added after 2.6 minutes of blowing; the indicators of the slag in the early stage of smelting are detailed in Table 2;

[0086] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are shown in Table 2.

[0087] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.5, that is, the CaO / SiO2 ratio is 1.5, the FeO proportion in the slag composition is 22%, the MgO proportion is 5.2%, the Al2O3 proportion is 3.7%, and the slag layer thickness is 3.1m.

[0088] The smoke volume of this embodiment is 9.3 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 66.0%.

[0089] Example 6

[0090] This embodiment is carried out on a 150t converter and specifically includes the following steps:

[0091] (a) After splashing slag to protect the furnace, pour out the slag and perform slag-free operation;

[0092] (b) adding scrap steel and molten iron into a converter, the conditions for adding steel into the converter and molten iron are shown in Table 1; then adding 4.5 kg / t of lime and 17 kg / t of rapid slag-forming agent, wherein the content of CaO in the lime used is equal to 85%, and the mass percentage of the rapid slag-forming agent is: CaO 30%, SiO2 25%, Al2O3 15%, MgO 7%, MnO 10%, and the rest are unavoidable impurities, with a melting point of 1392°C;

[0093] (c) blowing with an oxygen lance, during which limestone powder mixed with oxygen is sprayed into the lance for blowing, the amount of limestone powder sprayed is 15 kg / t steel, and the particle size is less than or equal to 1 mm; iron ore is added after the start of blowing, the size of the added iron ore is between 30 mm and 50 mm, the average size of the iron ore is 40 mm, and the total amount of iron ore added is 20 kg / t steel, which is added twice, specifically, 10 kg / t steel is added at the beginning of blowing, and 10 kg / t steel is added after 1.5 min of blowing; the indicators of the slag in the early stage of smelting are detailed in Table 2;

[0094] (d) When the converter is blown to the slag discharge point, the slag discharge operation is carried out, followed by decarburization blowing. After the blowing is completed, steel is tapped. The converter smelting indicators are shown in Table 2.

[0095] In this embodiment, the basicity of the slag composition in the early stage of converter smelting is controlled to be 1.6, that is, the CaO / SiO2 ratio is 1.6, the FeO proportion in the slag composition is 18%, the MgO proportion is 3.8%, the Al2O3 proportion is 4.8%, and the slag layer thickness is 3.7m.

[0096] The smoke volume of this embodiment is 8.8 kg / t steel, and the dephosphorization efficiency in the early stage of converter blowing is 65.2%.

[0097] Some indicators of the smelting process of Examples 1-6 and Comparative Examples 1-5 are detailed in Table 1 and Table 2.

[0098] Table 1 Material conditions for converter smelting

[0099]

[0100]

[0101] Table 2 Converter end point smelting index

[0102]

Claims

1. A method for reducing the amount of smoke in the early stage of blowing in a converter double slag smelting process, characterized in that: include: Adding scrap steel and molten iron into the converter, and then adding lime and a rapid slag-forming agent, wherein the melting point of the rapid slag-forming agent is 1200-1400°C; The limestone powder is mixed with oxygen and sprayed from an oxygen lance for blowing. After the blowing starts, iron ore is added in batches, and the size of the added iron ore is 10 to 50 mm.

2. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to claim 1 is characterized in that: The rapid slag-forming agent is a pre-melting refined slag, which includes the following components in percentage by mass: CaO 30-45%, SiO2 10-25%, Al2O3 15-25%, MgO 3-7%, and MnO 5%-10%.

3. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to claim 2, characterized in that: The amount of the rapid slagging agent added is 10-20 kg / t steel, and / or the amount of the lime added is 3-5 kg / t steel.

4. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to claim 3 is characterized in that: The CaO content in the lime is ≥85%.

5. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to any one of claims 1 to 3, characterized in that: After blowing begins, iron ore is added in 2-3 batches, with an interval of 1 to 1.5 minutes between each addition, and a total amount of 10 to 30 kg / t of steel.

6. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to any one of claims 1 to 3, characterized in that: The slag composition in the early stage of smelting is controlled as: CaO / SiO2: 1.3~2.0, FeO: 15~25%, MgO: 3~6%, Al2O3: 2~6%.

7. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to any one of claims 1 to 3, characterized in that: The average thickness of the slag layer on the surface of molten iron in the early stage of smelting is 2 to 4 m.

8. The method for reducing the amount of smoke in the early stage of blowing in a converter double-slag smelting process according to any one of claims 1 to 3, characterized in that: The injection amount of the limestone powder is 10-20 kg / t steel, and the particle size is ≤1 mm.

9. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to any one of claims 1 to 3, characterized in that: Also includes: It is carried out before adding scrap steel and molten iron into the converter, and slag is left or not left after slag splashing to protect the furnace.

10. The method for reducing the amount of smoke in the early stage of blowing in the converter double slag smelting process according to any one of claims 1 to 3, characterized in that: Also includes: When the converter is blown to the slag discharge point, the slag discharge operation is carried out; After slag removal, decarburization and blowing are carried out, and steel is tapped after blowing is completed.

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