A low-carbon emission converter smelting method

Abstract

This application discloses a low-carbon emission converter smelting method, solving the technical problem of high carbon emissions in existing technologies. The low-carbon emission converter smelting method of this application includes smelting molten iron and a first type of scrap steel in a dephosphorization furnace, followed by tapping. During the tapping process, a first carbon material is added to obtain a first type of molten steel. The first type of molten steel is then added to a decarburization furnace containing a second type of scrap steel and a second type of carbon material for smelting. During the smelting process, a third type of carbon material is added to the decarburization furnace to complete the converter smelting. The mass of the first type of carbon material added is 10–25 kg / t, the mass of the second type of carbon material added is 5–22 kg / t, and the mass of the third type of carbon material added is 15–30 kg / t. This low-carbon emission converter smelting method can promote carburization, allowing carbon to react with oxygen exothermically to melt the scrap steel, replacing the high-carbon ferrosilicon reheat agent, increasing the scrap steel ratio, and reducing carbon emissions.

Description

Technical Field

[0001] This application belongs to the field of converter smelting technology, specifically relating to a low-carbon emission converter smelting method. Background Technology

[0002] In the traditional long-process steelmaking process of "blast furnace + converter," more than 70% of carbon emissions come from the ironmaking stage. Therefore, increasing the scrap steel ratio and reducing the iron-to-metal ratio in steelmaking are among the main measures to reduce carbon emissions.

[0003] In existing technologies, ferrosilicon is usually added as a heat exchanger in converter smelting to increase the scrap ratio. However, ferrosilicon has a high carbon emission factor, so there is still room for reducing carbon emissions. Summary of the Invention

[0004] To address the technical problem of high carbon emissions in current converter smelting, this application provides a low-carbon converter smelting method.

[0005] In a first aspect of this application, a low-carbon emission converter smelting method is provided, comprising the following steps:

[0006] Molten iron and first scrap steel are placed in a dephosphorization furnace for smelting and then tapped. During the tapping process, first carbon material is added to obtain first molten steel.

[0007] The first molten steel is added to a decarburization furnace containing the second scrap steel and the second carbon material for smelting. During the smelting process, the third carbon material is added to the decarburization furnace to complete the converter smelting.

[0008] The first carbon material is added at a mass of 10-25 kg / t, the second carbon material is added at a mass of 5-22 kg / t, and the third carbon material is added at a mass of 15-30 kg / t.

[0009] In some embodiments, the mass of the second carbon material, the first carbon material, and the third carbon material increases sequentially.

[0010] In some embodiments, the third carbon material is added to the decarburizing furnace when the carbon mass fraction of the molten steel in the decarburizing furnace is less than 0.9% and / or the temperature of the molten steel in the decarburizing furnace is not less than 1550°C.

[0011] In some embodiments, the temperature of the tapped molten steel is 1470°C to 1550°C, and the carbon mass fraction of the tapped molten steel is 0.7% to 1.5%.

[0012] In some embodiments, the temperature of the molten iron is 1300–1500°C, and the carbon mass fraction of the molten iron is 3.5%–5.0%.

[0013] In some embodiments, during the tapping process, 2 to 5 kg / t of heat-insulating agent is added to the surface of the first molten steel to maintain its temperature.

[0014] In some embodiments, during the tapping process, bottom-blown gas is agitated for 1-3 minutes to promote carburization.

[0015] In some embodiments, the second scrap steel and the second carbon material are added to the decarburization furnace in the following manner: first, one-third to one-half of the second scrap steel is added to the decarburization furnace, then the second carbon material is added to the decarburization furnace, and finally the remaining second scrap steel is added to the decarburization furnace.

[0016] In some embodiments, the mass of the first scrap steel added is 170-285 kg / t steel, and the mass of the second scrap steel added is 130-225 kg / t steel.

[0017] In some embodiments, the top-blown oxygen content during the dephosphorization furnace smelting process is 28–35 Nm³. 3 / t, bottom blowing intensity is 0.15~0.25Nm 3 / t / min.

[0018] The low-carbon emission converter smelting method provided in the embodiments of this application includes the following steps: molten iron and first scrap steel are placed in a dephosphorization furnace for smelting and then tapped; during the tapping process, a first carbon material is added to obtain a first molten steel; the first molten steel is added to a decarburization furnace containing a second scrap steel and a second carbon material for smelting; during the smelting process, a third carbon material is added to the decarburization furnace to complete the converter smelting; wherein, the mass of the first carbon material added is 10-25 kg / t, the mass of the second carbon material added is 5-22 kg / t, and the mass of the third carbon material added is 15-30 kg / t.

[0019] The first addition of carbon material occurs during the tapping process after dephosphorization furnace smelting. The favorable kinetics of the tapping process promote carbon dissolution into the molten steel, increasing the carburization rate. The second addition occurs before the first molten steel is added to the decarburization furnace. This allows for thorough mixing, further enhancing the carburization rate. The third addition occurs during the decarburization furnace smelting process. At this stage, the carbon content in the molten steel is low, creating a significant concentration difference between the carbon material and the steel, which is beneficial for increasing the carburization rate. Additionally, the higher temperature of the molten steel after a certain carbon oxidation process further facilitates carbon dissolution, increasing the carburization rate.

[0020] In other words, this application uses three stages of carbon material addition: during steel tapping from the dephosphorizing furnace, before iron addition in the decarburizing furnace, and in the later stages of smelting in the decarburizing furnace. The steel tapping stage and the iron addition stage in the dephosphorizing furnace mainly provide the kinetic conditions for carburizing, while the later stages of smelting in the decarburizing furnace mainly provide the thermodynamic conditions for carburizing, promoting the carburizing rate, allowing carbon to react with oxygen to release heat and melt the scrap steel, increasing the scrap steel ratio, and reducing carbon emissions. Attached Figure Description

[0021] Figure 1 A process flow diagram of a low-carbon emission converter smelting method according to this application is shown. Detailed Implementation

[0022] To enable those skilled in the art to more clearly understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] This application provides a low-carbon emission converter smelting method with high carburization rate, good heat replenishment effect, increased scrap steel ratio, and reduced carbon emissions.

[0024] Please see Figure 1 The low-carbon emission converter smelting method provided in this application includes the following steps:

[0025] Step 1: Molten iron and the first scrap steel are placed in a dephosphorization furnace for smelting and then tapped. During the tapping process, the first carbon material is added to obtain the first molten steel.

[0026] Step 2: The first molten steel is added to a decarburization furnace containing the second scrap steel and the second carbon material for smelting. During the smelting process, the third carbon material is added to the decarburization furnace to complete the converter smelting.

[0027] The converter smelting method described in this application involves first dephosphorizing the molten iron in a dephosphorizing furnace, and then decarburizing it in a decarburizing furnace. In this dual-converter smelting process, the low initial steel temperature is conducive to dephosphorization, while the later stage mainly involves carbon oxidation and temperature rise. For the dual-converter process, carbon is added three times. During oxygen blowing smelting, the carbon can oxidize and release heat to supplement the heat, thereby increasing the scrap steel ratio. Specifically: the first carbon addition occurs during the tapping process after dephosphorizing, taking advantage of the favorable kinetics of the tapping process to promote carbon dissolution into the molten steel and increase the carburization rate; the second carbon addition occurs before the first molten steel is added to the decarburizing furnace, allowing for thorough mixing and further improving the carburization rate. The third carbon material is added during the decarburization furnace smelting process. At this stage, the carbon mass fraction in the molten steel is relatively low, and there is a very large concentration difference between the carbon material and the molten steel, which is conducive to improving the carburization rate. In addition, the temperature of the molten steel is relatively high after a certain carbon oxidation process at this stage. The high temperature is more conducive to the dissolution of carbon material into the molten steel, thereby improving the carburization rate.

[0028] The first, second, and third carbon materials can be the same, such as coke, carburizing agent, biomass carbon, biomass pellets, graphite, etc., with a carbon content of 50% to 99%. In other embodiments, the first, second, and third carbon materials may be different.

[0029] The mass of the second, first, and third carbon materials added increases sequentially. The second carbon material is added in smaller quantities because it is added before the iron is added to the decarburizing furnace. Although the kinetic conditions are good, carbon material has already been added to the molten steel once, and the temperature of the molten steel is relatively low after the iron is added. The third carbon material is added in the largest quantity because the carbon content in the molten steel is low and the temperature is high in the later stages of decarburizing furnace smelting, providing good thermodynamic conditions for carburizing. The first carbon material is added in a moderate quantity because the kinetic conditions are good during the tapping process, and there is also a certain temperature rise.

[0030] In some embodiments, the mass of the first carbon material added during the dephosphorization smelting and steel tapping process in step one is 10-25 kg / t, such as 11 kg / t, 13 kg / t, 15 kg / t, 18 kg / t and 19 kg / t. If the mass of the first carbon material added is too high, carbon saturation may occur, which will reduce the carburization rate to a certain extent; if the mass of the first carbon material added is too low, the carburization amount will be insufficient to a certain extent.

[0031] The reason for not adding carbon materials before dephosphorization smelting is that the carbon content in the molten iron is very high, at 4.0-5.0%, which is saturated and cannot be carburized. Additionally, the temperature of the molten iron is relatively low, at 1300℃-1400℃. Therefore, carbon materials are added during the tapping process. In some embodiments, the tapping temperature of the molten steel is 1470℃-1550℃, and the carbon mass fraction of the tapped molten steel is 0.7%-1.5%. At this temperature, the molten steel is relatively high, which helps to ensure the activation energy of the carburizing reaction. The carbon content is reduced to a certain level, and there is a concentration difference between the carbon materials and the molten steel, providing certain thermodynamic conditions for dissolving carbon.

[0032] In some embodiments, the mass of the first scrap steel added is 170-285 kg / t steel, such as 180 kg / t steel, 190 kg / t steel, 200 kg / t steel and 210 kg / t steel. The heat source of the first scrap steel is mainly molten iron. If the mass of the first scrap steel added is too low, there may be a heat surplus to a certain extent. If the mass of the first scrap steel added is too high, there may be insufficient heat to a certain extent, resulting in a low final temperature of the decarburization furnace.

[0033] Tapping involves transferring molten steel into a ladle. During this process, an insulating agent is added to the surface of the first molten steel, meaning an insulating agent is added to the ladle. Calcium oxide can be used as the insulating agent, as it not only provides insulation but also prevents carbon combustion during transport and pre-melts the lime, reducing lime consumption in the decarburization furnace. In some embodiments, the amount of insulating agent added is 2–5 kg / t of steel, such as 3 kg / t or 4 kg / t. If the amount of insulating agent added is too high, it will cause the semi-molten steel to cool down to some extent, as the insulating agent is a cold material. If the amount of insulating agent added is too low, it will result in insufficient coverage of the semi-molten steel, leaving it exposed to air and causing cooling and oxidation.

[0034] In some embodiments, during the tapping process, bottom-blown gas is used to agitate the molten steel for 1 to 3 minutes to promote carburization. That is, the bottom-blown gas, such as argon, is used to agitate the molten steel to improve the kinetic conditions of the molten steel and promote carburization.

[0035] In some embodiments, the top-blown oxygen content during the dephosphorization furnace smelting process is 28–35 Nm³. 3 / t, for example, 30Nm 3 / t、31Nm 3 / t、32Nm 3 / t、33Nm 3 / t and 34Nm 3 In some embodiments, when the top-blown oxygen content is too low, the tapping temperature may be lower than 1470°C, and the carbon mass fraction of the tapped molten steel may be greater than 1.5%. Low temperature and high carbon content can easily lead to low carburization rate to some extent. When the oxygen blowing content is higher than 35 Nm³, etc., the tapping temperature may be lower than 1470°C, and the carbon mass fraction of the tapped molten steel may be greater than 1.5%.3 At a rate of / t, the temperature of the tapped molten steel may be less than 1550℃, and the carbon mass fraction of the tapped molten steel may be greater than 0.7%. At this point, the converter endpoint is approaching, which may affect the converter endpoint control.

[0036] In some embodiments, during the dephosphorization furnace smelting process, the bottom blowing intensity is 0.15–0.25 Nm. 3 / t / min, for example 0.18Nm 3 / t / min, 0.19Nm 3 / t / min, 0.20Nm 3 / t / min, 0.21Nm 3 / t / min, 0.22Nm 3 / t / min, 0.23Nm 3 / t / min and 0.24Nm 3 / t / min, etc., to ensure the kinetic conditions for scrap steel melting. Bottom blowing intensity is less than 0.15 Nm. 3 At a rate of / t / min, the stirring kinetic energy is reduced to some extent, resulting in slower melting of scrap steel; the bottom blowing intensity is greater than 0.25 Nm. 3 When the stirring kinetic energy is too high at a certain rate (t / min), it can easily lead to splashing.

[0037] In step two, during the iron addition and decarburization smelting, in some embodiments, the mass of the second carbon material added is 5–22 kg / t steel, such as 6 kg / t steel, 7 kg / t steel, 8 kg / t steel, 9 kg / t steel, 10 kg / t steel, 11 kg / t steel, 12 kg / t steel, 13 kg / t steel, and 14 kg / t steel. If the mass of the second carbon material added is too small, it will result in insufficient carburization to some extent, reducing the converter's final temperature. If the mass of the second carbon material added is too large, carbon saturation may occur, which will reduce the carburization rate to some extent.

[0038] In some embodiments, the mass of the second scrap steel added is 130–225 kg / t of steel, such as 132 kg / t, 138 kg / t, 142 kg / t, 145 kg / t, 150 kg / t, 156 kg / t, 159 kg / t, 163 kg / t, 168 kg / t, 175 kg / t, and 178 kg / t. The heat consumed in melting the second scrap steel mainly comes from the residual carbon in the dephosphorized steel, the carburization of the first carbon material, the second carbon material, and the third carbon material. If the mass of the second scrap steel added is too small, the scrap steel ratio will be reduced to some extent. If the mass of the second scrap steel added is too large, the carburization amount needs to be increased, which will prolong the smelting time to some extent.

[0039] In some embodiments, the mass of the third carbon feedstock added is 15–30 kg / t of steel, such as 16 kg / t, 18 kg / t, 19 kg / t, 22 kg / t, 23 kg / t, and 24 kg / t. If the mass of the third carbon feedstock added is too small, it may result in insufficient carburization and a decrease in the converter's final temperature. If the mass of the third carbon feedstock added is too large, the oxygen blowing time may need to be increased to ensure the carbon reaches the final point, thus reducing production efficiency.

[0040] In some embodiments, the third carbon material is added to the decarburizing furnace when the carbon mass fraction of the molten steel in the decarburizing furnace is less than 0.9%, and / or the temperature of the molten steel in the decarburizing furnace is not less than 1550°C. This is because the addition of carburizing materials at low carbon content and / or high temperature in the molten steel is beneficial to improving the carburization rate.

[0041] Because carbon material has a low density and is relatively light, in some embodiments, the second scrap steel and the second carbon material are added to the decarburization furnace in the following manner: first, one-third to one-half of the second scrap steel is added to the decarburization furnace, then the second carbon material is added to the decarburization furnace, and finally the remaining second scrap steel is added to the decarburization furnace. On the one hand, the scrap steel at the bottom can reduce the temperature inside the decarburization furnace, and the scrap steel added last can press the carbon material between the two layers of scrap steel, thereby increasing the carburization rate of the carbon material.

[0042] In some embodiments, the particle size of the first carbon material, the second carbon material, and the third carbon material can all be 3-10 mm.

[0043] The low-carbon emission converter smelting method provided in this application will be further explained below with reference to specific embodiments:

[0044] Examples 1 to 5

[0045] Examples 1 to 5 provide a converter smelting method for IF steel. The smelting furnace includes a dephosphorizing furnace and a decarburizing furnace, the nominal capacities of which are shown in Table 1. The converter smelting method includes the following steps:

[0046] Dephosphorization furnace smelting steps: First scrap steel and molten iron are charged into the dephosphorization furnace. The temperature and carbon mass fraction of the molten iron are shown in Table 2. Then, a slagging agent is added, and top and bottom blowing is performed. After smelting, steel is tapped into the ladle. During tapping, the first carbon material is added; the mass of the first carbon material added is shown in Table 3. Lime is added to the ladle for heat preservation during tapping; the mass of the lime added is shown in Table 3. Simultaneously, argon gas is blown into the bottom for 1-3 minutes with weak stirring.

[0047] Decarburization furnace smelting steps: Half of the second scrap steel is added to the decarburization furnace, followed by the second carbon feedstock. Then, the remaining half of the second scrap steel is added. The molten steel from the ladle in the previous step is then poured into the decarburization furnace. Top and bottom blowing smelting is performed until the carbon mass fraction in the molten steel is as shown in Table 4, and the temperature of the molten steel is as shown in Table 4. Then, the third carbon feedstock is added to the decarburization furnace through the feed hopper. The mass of the third carbon feedstock added is shown in Table 4. Smelting continues until the smelting endpoint is reached.

[0048] Table 1 Nominal capacity of dephosphorization furnace and decarburization furnace

[0049] Serial Number Dephosphorization furnace tonnage / t Decarburization furnace tonnage / t Example 1 120 120 Example 2 210 210 Example 3 300 300 Example 4 300 300 Example 5 300 300

[0050] Table 2 Control parameters for dephosphorization furnace

[0051]

[0052] Table 3 Control parameters for dephosphorization furnace

[0053] Serial Number Smelting endpoint C / % Smelting endpoint T / ℃ Amount of first carbon feed added / t Amount of calcium oxide added / t Example 1 0.7 1550 1.3 0.37 Example 2 1 1520 3.2 0.82 Example 3 1.2 1510 5.9 1.1 Example 4 1.1 1500 6.2 1.2 Example 5 0.9 1517 7.5 1.0

[0054] Table 4 Control parameters of the decarbonization furnace

[0055]

[0056] Comparative Example 1

[0057] Comparative Example 1 is produced by a conventional single converter, and the steel grade is IF steel. The converter first adds 15% scrap steel, which accounts for 85% of the total charge, and then adds molten iron, which accounts for 85% of the total charge. The smelting process is carried out by top and bottom blowing. No heat-replenishing agent ferrosilicon is added during the smelting process. The LCA carbon (Life Cycle Assessment) emission of IF steel is 2.6tCO2 / t material.

[0058] Comparative Example 2

[0059] Comparative Example 2 uses a twin-furnace production process. The dephosphorization furnace adds 10% scrap steel and molten iron to produce semi-steel, while the decarburization furnace adds 20% scrap steel and semi-steel. 17 kg / t of ferrosilicon heat supplement is added to the decarburization furnace. The carbon emission of IF steel LCA is 2.38 tCO2 / t material.

[0060] Table 5

[0061]

[0062] Table 6

[0063]

[0064] In Table 6, the carbon increase in molten steel refers to the increase in the mass fraction of carbon in the molten steel before and after carbon addition. For the first and second carbon materials, the carbon increase was measured by sampling before carbon addition and again 5 minutes after carbon addition. For the third carbon material, the carbon content was measured by sampling before carbon addition and again 1-2 minutes after carbon addition. The carburization rate in Table 6 refers to the ratio of the difference between the mass of added carbon and the mass of carbon entering the molten steel to the total mass of added carbon.

[0065] As can be seen from the data in Table 5, the carburization rate of the converter smelting method provided in this application embodiment is 80.97%-83.25%. The high carburization rate and good heat replenishment effect increase the scrap steel ratio to 31.7%-50.7%, which reduces carbon emissions.

[0066] The converter smelting method provided in this application embodiment involves adding carbon materials during the dephosphorization furnace tapping stage, before the decarburization furnace ferroalloying stage, and in the later stage of decarburization furnace smelting. The dephosphorization furnace tapping stage and the decarburization furnace ferroalloying stage mainly provide the kinetic conditions for carburization, while the later stage of decarburization furnace smelting mainly provides the thermodynamic conditions for carburization, promoting the carburization rate, allowing carbon elements to react with oxygen to release heat and melt scrap steel, increasing the scrap steel ratio, and reducing carbon emissions.

[0067] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0068] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0069] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0070] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0071] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A low carbon emission converter smelting method characterised by, Includes the following steps: Molten iron and first scrap steel are placed in a dephosphorization furnace for smelting and then tapped. During the tapping process, first carbon material is added to obtain first molten steel. The first molten steel is added to a decarburization furnace containing the second scrap steel and the second carbon material for smelting. During the smelting process, the third carbon material is added to the decarburization furnace to complete the converter smelting. When the carbon mass fraction of the molten steel in the decarburizing furnace is less than 0.9%, and / or the temperature of the molten steel in the decarburizing furnace is not less than 1550°C, the third carbon material is added to the decarburizing furnace. The first carbon material is added at a mass of 10-25 kg / t, the second carbon material at a mass of 5-22 kg / t, and the third carbon material at a mass of 15-30 kg / t. The mass of the second carbon material, the first carbon material, and the third carbon material increases sequentially to improve the scrap steel ratio.

2. The low-carbon emission converter smelting method according to claim 1, characterized in that, The temperature of the molten steel being tapped is 1470℃~1550℃, and the carbon mass fraction of the molten steel being tapped is 0.7%~1.5%.

3. The low-carbon emission converter smelting method according to claim 1, characterized in that, The temperature of the molten iron is 1300℃~1500℃, and the carbon mass fraction of the molten iron is 3.5%~5.0%.

4. The low-carbon emission converter smelting method according to claim 1, characterized in that, During the tapping process, 2-5 kg / t of heat-insulating agent is added to the surface of the first molten steel to maintain its temperature.

5. The low carbon emission converter melting process according to claim 4, characterized in that, During the tapping process, bottom-blown gas is used to agitate the steel for 1 to 3 minutes to promote carburization.

6. The low-carbon emission converter smelting method according to claim 1, characterized in that, The second scrap steel and the second carbon material are added to the decarburization furnace in the following manner: first, one-third to one-half of the second scrap steel is added to the decarburization furnace, then the second carbon material is added to the decarburization furnace, and finally the remaining second scrap steel is added to the decarburization furnace.

7. The low carbon emission converter melting process according to claim 6, characterized in that, The first scrap steel is added at a mass of 170~285 kg / t steel, and the second scrap steel is added at a mass of 130~225 kg / t steel.

8. The low carbon emission converter melting process of claim 1, wherein, During the dephosphorization furnace smelting process, the top-blown oxygen content is 28~35 Nm³. 3 / t, bottom blowing intensity is 0.15~0.25Nm 3 / t / min.

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