A dephosphorizing agent for bottom blowing of a converter and a method for dephosphorizing a converter

Abstract

The application discloses a dephosphorizing agent for converter bottom blowing and a method for dephosphorization of a converter, and belongs to the technical field of converter smelting. The dephosphorizing agent is composed of the following components in mass fraction: lime: 65-80%, silica gel drier: 20-35%, and the mass fraction of SiO2 in the silica gel drier is greater than or equal to 98%, and the silica gel drier has a porous structure. The dephosphorizing agent provided by the application can reduce the plugging frequency of the bottom blowing hole of the converter, reduce the cleaning frequency, improve the production efficiency, and improve the dephosphorization effect.

Description

Technical Field

[0001] This invention belongs to the field of converter smelting technology, specifically relating to a dephosphorizing agent for bottom blowing in a converter and a method for dephosphorizing in a converter. Background Technology

[0002] Bottom-blown powder injection in converters is a widely used technique for efficient converter smelting. This technology injects lime powder into the converter via a bottom-blowing system using carrier gas, providing favorable thermodynamic and kinetic conditions for dephosphorization of molten iron at the bottom of the converter. However, because lime powder often contains a certain amount of moisture, lime particles tend to agglomerate, clogging the bottom-blowing orifices and thus affecting the injection effect.

[0003] Existing technologies often produce passivated lime by adding passivating agents or catalysts during the lime production process. Passivated lime has a low water content, which can reduce the frequency of bottom blowing holes being stuck and blocked during the bottom blowing process of the converter. However, the final moisture content in passivated lime can still reach 0.5% to 1.5%, and it still has a certain water absorption capacity in some humid environments. Before powdering, the moisture content can reach 2.0%. In actual production, the powdering system generally needs to be cleaned after 100 to 200 heats, which seriously affects production efficiency. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a dephosphorizing agent for converter bottom blowing and a method for converter dephosphorization, which at least to some extent alleviates the clogging of bottom blowing holes and reduces the cleaning frequency of converter bottom blowing holes.

[0005] One technical solution of the present invention is to provide a dephosphorizing agent for bottom blowing of a converter, wherein the dephosphorizing agent is composed of the following components by mass fraction: lime: 65-80%, silica gel desiccant: 20-35%, wherein the mass fraction of SiO2 in the silica gel desiccant is ≥98%, and the silica gel desiccant has a porous structure.

[0006] In some embodiments, the lime has a particle size of 0.002-0.02 mm.

[0007] In some embodiments, the particle size of the silica gel desiccant is 0.001-0.1 times the minimum diameter of the bottom blow hole of the converter.

[0008] In some embodiments, the silica gel desiccant has a particle size of 0.05-1 mm.

[0009] Based on the same technical concept as the first aspect, in a second aspect, the present invention also provides a method for dephosphorization in a converter, applicable to the aforementioned dephosphorizing agent for bottom blowing in a converter, the method comprising the following steps:

[0010] Step 1: During the converter smelting process from the start to time t1, lime is blown from the bottom of the converter for dephosphorization; the value of t1 is 1-2 minutes.

[0011] Step 2: During the converter smelting process from time t1 to t2, dephosphorization is carried out by bottom blowing dephosphorizing agent. The bottom blowing flow rate of the dephosphorizing agent is 2.0-4.0 kg / min / t steel; the value of t2 is 7-9 min.

[0012] Step 3: During the converter smelting process from time t2 to the end, oxygen is blown from the bottom of the converter.

[0013] In some embodiments, in step 1, the bottom blowing rate of lime is 1.0-2.0 kg / min / t steel.

[0014] In some embodiments, in step 1, oxygen is used as the carrier gas for bottom blowing of lime, and the oxygen bottom blowing flow rate is 0.3-0.6 Nm³. 3 / min / t steel.

[0015] In some embodiments, in step 2, the dephosphorizing agent uses oxygen as the carrier gas, and the bottom-blowing flow rate of oxygen is 0.5-1.0 Nm³. 3 / min / t steel.

[0016] In some embodiments, in step 3, oxygen is used as the carrier gas for bottom blowing of lime, and the oxygen bottom blowing flow rate is 0.4-0.8 Nm³. 3 / min / t steel.

[0017] In some embodiments, the converter has a capacity of 80-300t.

[0018] The beneficial effects of the present invention include at least the following:

[0019] This invention provides a dephosphorizing agent for bottom blowing in a converter. The dephosphorizing agent is composed of the following components by mass fraction: lime: 65-80%, silica gel desiccant: 20-35%, wherein the mass fraction of SiO2 in the silica gel desiccant is ≥98%, and the silica gel desiccant has a porous structure. Silica gel desiccant generally refers to silica gel, which is a silica gel after dehydration and drying. It has an open porous structure, contains numerous cavities, is sponge-like, has abundant pores and a large specific surface area, and has strong adsorption capacity, enabling it to adsorb moisture. The lime is passivated lime with a moisture content of 0.5-1.5%. When lime and silica gel desiccant are mixed and used as a dephosphorizing agent, the silica gel desiccant can adsorb the moisture in the lime, which can, to a certain extent, prevent lime from sticking together and forming mud lumps inside the bottom blowing holes, reducing the cleaning frequency of the bottom blowing holes and improving production efficiency.

[0020] Furthermore, when silica gel desiccant and lime are blown together into the molten steel in the converter, the following reactions occur: First, phosphorus (P) in the molten steel reacts with FeO to form P2O5, i.e., [P] + FeO → [Fe] + P2O5. Lime reacts with P2O5 to form the slightly less stable 3(CaO)·(P2O5). The SiO2 in the silica gel desiccant reacts with 3(CaO)·(P2O5) to form (CaO)·2(SiO2)·3(CaO)·(P2O5), which is very stable in the molten steel environment. (CaO)·2(SiO2)·3(CaO)·(P2O5) can be directly introduced into the slag along with the molten steel, ensuring dephosphorization efficiency. The dephosphorizing agent provided by this invention can, on the one hand, reduce the frequency of clogging in the converter bottom blowhole, reduce the number of cleaning operations, and improve production efficiency; on the other hand, it can also improve the dephosphorization effect. Attached Figure Description

[0021] Figure 1 A process flow diagram of a converter dephosphorization method according to an embodiment of this application is shown. Detailed Implementation

[0022] To enable those skilled in the art to better understand this application, the technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Even with passivated lime being blown into the bottom of the converter for dephosphorization, the bottom blowing holes are still frequently blocked, affecting production efficiency.

[0024] This invention provides a dephosphorizing agent for converter bottom blowing and a method for converter dephosphorization, which at least to some extent reduces the clogging frequency of bottom blowing holes in the converter bottom blowing device.

[0025] In a first aspect, embodiments of the present invention provide a dephosphorizing agent for bottom blowing of a converter, the dephosphorizing agent being composed of the following components by mass fraction: lime: 65-80%, silica gel desiccant: 20-35%, the silica gel desiccant having a SiO2 mass fraction ≥98%, and the silica gel desiccant having a porous structure.

[0026] Silica gel desiccant generally refers to silica gel, which is a silica gel that has been dehydrated and dried. It is commonly known as silica gel and has an open porous structure containing countless cavities, resembling a sponge. It has a rich porous structure and a large specific surface area, resulting in strong adsorption capacity and the ability to absorb moisture. The lime is passivated lime with a moisture content of 0.5-1.5%. When lime is mixed with silica gel desiccant, it is used as a dephosphorizing agent. The silica gel desiccant can absorb the moisture in the lime, which can, to some extent, prevent the lime from sticking together and forming mud lumps inside the bottom blow holes, reducing the cleaning frequency of the bottom blow holes and improving production efficiency.

[0027] In addition, when silica gel desiccant and lime are blown together into the molten steel in the converter, the following reactions occur: First, P in the molten steel reacts chemically with FeO to form P2O5, i.e., [P] + FeO → [Fe] + P2O5. Lime reacts chemically with P2O5 to form 3(CaO)·(P2O5), which is slightly less stable. SiO2 in the silica gel desiccant reacts chemically with 3(CaO)·(P2O5) to form (CaO)·2(SiO2)·3(CaO)·(P2O5), which is very stable in the molten steel environment. (CaO)·2(SiO2)·3(CaO)·(P2O5) can be directly introduced into the slag along with the molten steel, ensuring dephosphorization efficiency.

[0028] If the mass fraction of lime is too high, the mass fraction of silica gel desiccant will be too low, resulting in limited drying and water absorption capacity. This will increase the risk of bottom blowing holes becoming clogged to some extent and may also reduce dephosphorization efficiency. If the mass fraction of lime is too low, the mass fraction of silica gel desiccant will be too high, resulting in strong drying and water absorption capacity. However, this will reduce the chemical reaction between lime and P2O5 and lower the dephosphorization rate.

[0029] In some embodiments, the lime particle size is 0.002-0.02 mm. The control of the lime particle size is to ensure that it has a relatively large specific surface area, so as to improve the kinetic conditions of its contact with molten steel. If the lime particle size is too large, it will be difficult to blow into the molten steel in the converter to a certain extent, and it will also reduce the specific surface area and reduce the rate of lime dephosphorization; if the lime particle size is too small, it will increase the process cost.

[0030] In some embodiments, the particle size of the silica gel desiccant is 0.05-0.1 times the minimum diameter of the bottom blowing hole of the converter. The size of the silica gel desiccant being smaller than the minimum diameter of the bottom blowing hole of the converter can ensure that the silica gel desiccant can smoothly enter the molten steel in the converter. If the particle size of the silica gel desiccant is too large, the gap between the silica gel desiccant and the bottom blowing hole wall of the converter will be too small, and the silica gel desiccant may increase the risk of blockage of the bottom blowing hole to a certain extent.

[0031] In some embodiments, the silica gel desiccant has a particle size of 0.05-1 mm. Matching the particle size of the silica gel desiccant with that of the lime, the powder flow can generate significant fluctuations during bottom blowing into the molten steel, preventing blockage of the bottom blowing orifice. If the bottom blowing orifice is blocked, the impact force generated by the large-sized silica gel desiccant passing through at high speed can restore its flow and also remove lime powder adhering to the inner wall of the orifice. If the silica gel desiccant particle size is too small, the impact force is weak when lime adheres to the orifice wall, making it difficult to dislodge the lime adhering to the inner wall of the orifice and increasing the difficulty of restoring its flow. If the silica gel desiccant particle size is too large, the silica gel itself increases the risk of blockage of the bottom blowing orifice to some extent.

[0032] Based on the same technical concept as the first aspect, the second aspect of the present invention provides a method for dephosphorization in a converter, applicable to converters with a capacity of 80-300t, using the dephosphorizing agent for bottom blowing in the converter provided in the first aspect. Please refer to... Figure 1 The method includes the following steps:

[0033] Step 1: During the converter smelting process from the start to time t1, lime is blown from the bottom of the converter for dephosphorization; the value of t1 is 1-2 minutes.

[0034] This step is in the early stage of converter smelting, when the Si content in the molten iron is high. After lime enters the molten iron in the converter, SiO2 will first form on the surface of the lime, and then (CaO)·2(SiO2) will be formed. (CaO)·2(SiO2) will then combine with the P element in the molten iron to form a very stable phosphorus-rich phase (CaO)·2(SiO2)·3(CaO)·(P2O5) in the molten steel, which ensures the dephosphorization effect.

[0035] In some embodiments, in step 1, the bottom blowing rate of lime is 1.0-2.0 kg / min / t steel.

[0036] Excessive bottom blowing rate of lime may lead to localized lime excess in molten steel, reducing lime utilization; conversely, insufficient bottom blowing rate may lead to localized lime deficiency in molten steel, reducing dephosphorization efficiency.

[0037] In some embodiments, in step 1, oxygen is used as the carrier gas for bottom blowing of lime, and the oxygen bottom blowing flow rate is 0.3–0.6 Nm³. 3 / min / t steel.

[0038] Oxygen, as a carrier gas, can participate in the decarburization reaction within the converter. Combined with top-blown oxygen, it improves the uniformity of the molten steel's mixing within the converter, thus accelerating the smelting process. However, if the bottom-blown oxygen flow rate is too low, it will affect the amount of lime carried; conversely, if the flow rate is too high, it will not significantly improve the mixing effect.

[0039] Step 2: During the converter smelting process from time t1 to t2, dephosphorization is carried out using bottom-blown dephosphorizing agent. The bottom-blown flow rate of the dephosphorizing agent is 2.0-4.0 kg / min / t steel; the value of t2 is 7-9 min.

[0040] This step is the middle stage of converter smelting. At this time, the silicon content of the molten steel in the converter decreases. First, the phosphorus (P) in the molten steel reacts with FeO to form Fe3P, i.e., [P] + FeO → [Fe] + P2O5. Lime reacts with P2O5 to form the slightly less stable 3(CaO)·(P2O5). The SiO2 in the silica gel desiccant reacts with CaO·3P2O5 to form (CaO)·2(SiO2)·3(CaO)·(P2O5), which is very stable in the molten steel environment. (CaO)·2(SiO2)·3(CaO)·(P2O5) can be directly introduced into the slag along with the molten steel, ensuring dephosphorization efficiency. If only lime is blown from the bottom in this step, the final dephosphorization product will mostly be the slightly less stable 3(CaO)·(P2O5), which is very likely to decompose during the process of floating into the slag phase, forming CaO and P2O5, causing phosphorus re-entry into the molten steel and reducing the dephosphorization effect.

[0041] In some embodiments, in step 2, the dephosphorizing agent uses oxygen as the carrier gas, and the bottom-blowing flow rate of oxygen is 0.5-1.0 Nm³. 3 / min / t steel.

[0042] During the mid-stage of converter smelting, a larger gas volume is used in conjunction with the particle size of the silica gel desiccant in the dephosphorizing agent. This allows for greater fluctuation in the powder flow during bottom blowing of the molten steel, preventing blockage of the bottom blowing holes. If blockage does occur, the impact force generated by the high-speed passage of this large-sized silica gel desiccant can re-open the holes and also remove lime powder adhering to the inner walls of the holes. Insufficient oxygen flow rate increases the risk of blockage to some extent, while excessive oxygen flow rate has limited effect on improving stirring.

[0043] Step 3: During the converter smelting process from time t2 to the end, oxygen is blown from the bottom of the converter.

[0044] This step is in the later stage of converter smelting. At this time, the temperature of the molten steel is high and the dephosphorization task has been completed. In this step, only bottom blowing oxygen is used for decarburization.

[0045] In some embodiments, in step 3, the bottom-blowing oxygen flow rate is 0.4-0.8 Nm³. 3 / min / t steel.

[0046] The following will further illustrate the dephosphorizing agent for bottom blowing of converter and the method for dephosphorizing converter provided by the present invention with reference to specific embodiments.

[0047] Examples 1 to 5

[0048] Examples 1 to 5 provide dephosphorizing agents for bottom blowing in converters and methods for dephosphorizing converters using bottom blowing dephosphorizing agents. The converter dephosphorizing agent is a mixture of passivated lime and silica gel desiccant. The particle size and proportion of passivated lime and silica gel desiccant are shown in Table 1.

[0049] The converter dephosphorization method includes the following steps:

[0050] Step 1: The converter is charged with molten iron and scrap steel for smelting. The mixture of top-blown oxygen and bottom-blown oxygen carries passivating lime. During the process from the start of top and bottom blowing to t1min, the flow rates of top-blown oxygen, bottom-blown oxygen and passivating lime are shown in Table 2.

[0051] Step 2: During the time interval t1 to t2 of top and bottom re-blowing, bottom-blown oxygen carries dephosphorizing agent for dephosphorization. The bottom-blowing flow rate of the dephosphorizing agent is shown in Table 2. Step 3: During the converter smelting process from time t2 to the end, bottom-blown passivating lime powder is used for dephosphorization. The flow rates of bottom-blown oxygen and bottom-blown passivating lime powder in this step are shown in Table 2.

[0052] Comparative Examples 1 to 2

[0053] The dephosphorizing agent for converter bottom blowing provided in Comparative Examples 1 and 2 is passivated lime powder. The bottom blowing powder in each step is passivated lime, and the process control is shown in Tables 2 and 3.

[0054] Table 1

[0055] Table 2

[0056] Table 3

[0057] Table 4

[0058] As shown in Table 4, the dephosphorizing agent for converter bottom blowing provided in Examples 1 to 5 of this invention achieves a dephosphorization rate of 95.12% to 97.63%, demonstrating high dephosphorization efficiency. The lime consumption for removing 0.001% is 18-19 kg / t of steel, indicating low lime consumption. The cleaning frequency of the lime bottom blowing holes is 510-560 heats / cycle, which is also low.

[0059] Using the methods provided in Comparative Examples 1 and 2, the dephosphorization rate was 92.53% to 93.25%, which was lower than that of Examples 1 to 5 of the present invention; the bottom blowing hole cleaning blue was 220-260 furnaces / cycle, which was higher than that of Examples 1 to 5 of the present invention.

[0060] The silica gel desiccant in the converter bottom-blowing dephosphorizing agent provided by this invention has an open, porous structure containing numerous cavities, resembling a sponge. It possesses abundant pores and a large specific surface area, exhibiting strong adsorption capacity. It can adsorb moisture from lime, preventing lime from clumping and adhering to the bottom-blowing holes, thus reducing the cleaning frequency and improving production efficiency. Furthermore, when the silica gel desiccant is bottom-blown into the molten steel of the converter along with lime, it promotes the formation of a highly stable (CaO)·2(SiO2)·3(CaO)·(P2O5) in the molten steel environment. This (CaO)·2(SiO2)·3(CaO)·(P2O5) can directly enter the slag during steel agitation, ensuring dephosphorization efficiency. With improved dephosphorization efficiency, lime consumption is reduced.

[0061] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for dephosphorization in a converter, characterized in that, Includes the following steps: Step 1: During the converter smelting process from the start to time t1, lime is blown from the bottom of the converter for dephosphorization; the value of t1 is 1-2 minutes. Step 2: During the converter smelting process from time t1 to t2, dephosphorization is carried out using a bottom-blown dephosphorizing agent to ensure dephosphorization efficiency. The bottom-blown flow rate of the dephosphorizing agent is 2.0-4.0 kg / min / t steel; the value of t2 is 7-9 min; the dephosphorizing agent is composed of the following components by mass fraction: lime: 65-80%, silica gel desiccant: 20-35%, the mass fraction of SiO2 in the silica gel desiccant is ≥98%, and the silica gel desiccant has a porous structure; Step 3: During the converter smelting process from time t2 to the end, oxygen is blown from the bottom of the converter.

2. The converter dephosphorization method according to claim 1, characterized in that, The lime has a particle size of 0.002-0.02 mm.

3. The converter dephosphorization method according to claim 1, characterized in that, The particle size of the silica gel desiccant is 0.001-0.1 times the minimum diameter of the bottom blowing hole of the converter.

4. The converter dephosphorization method according to claim 3, characterized in that, The silica gel desiccant has a particle size of 0.05-1 mm.

5. The method for dephosphorization in a converter according to any one of claims 1-4, characterized in that, In step 1, the bottom blowing rate of lime is 1.0-2.0 kg / min / t steel.

6. The method for dephosphorization in a converter according to any one of claims 1-4, characterized in that, In step 1, oxygen is used as the carrier gas for bottom blowing of lime, and the oxygen flow rate is 0.3-0.6 Nm³. 3 / min / t steel.

7. The method for dephosphorization of a converter according to any one of claims 1-4, characterized in that, In step 2, the dephosphorizing agent uses oxygen as the carrier gas, and the bottom-blowing flow rate of oxygen is 0.5-1.0 Nm³. 3 / min / t steel.

8. The method for dephosphorization of a converter according to any one of claims 1-4, characterized in that, In step 3, the bottom-blowing oxygen flow rate is 0.4-0.8 Nm³. 3 / min / t steel.

9. The method for dephosphorization in a converter according to any one of claims 1-4, characterized in that, The capacity of the converter is 80-300t.

Images