A method for operating low-carbon and high-silicon hot metal with double-linked silicon reduction and carbon preservation

Abstract

The present invention discloses an operating method for double-linked silicon reduction and carbon preservation of low-carbon and high-silicon molten iron. In view of the characteristics of low-carbon and high-silicon in double-linked molten iron, comprehensive consideration is given to the slag formation route and gun position control. In terms of the slag formation route, an iron slag formation route is adopted. The converter realizes the iron slag formation route by optimizing the coordination of parameters such as oxygen supply intensity and gun position, thereby increasing the (∑FeO) content in the slag and promoting the dissolution of lime as soon as possible. The stirring capacity of the molten pool is improved, and starting from the blowing process parameters, the top blowing oxygen supply intensity, gun position, and bottom blowing intensity are better coordinated in terms of the molten pool stirring effect and desiliconization capacity, thereby obtaining a better desiliconization and carbon preservation smelting effect. In particular, at the end of smelting, the bottom blowing gas supply intensity is increased to ensure that the slag and steel are fully mixed to promote the rapid desiliconization reaction between slag and steel.

Description

Technical Field

[0001] The invention relates to an operating method for double-linked silicon reduction and carbon preservation of low-carbon and high-silicon molten iron. Background Art

[0002] At present, the silicon content of normal high-silicon hot metal is between 1.2%-7.0%, and the carbon content is between 4.5-5.8%. The double-link method is usually used for smelting. After the first smelting, the silicon element is between 0.20-0.50%, and the carbon element is between 2.5-3.0%. The second smelting is carried out by reverse transportation. In the converter metal smelting process, it can be divided into three stages: the initial, middle and final stages of blowing according to the characteristics of molten pool decarburization. The decarburization rate in the first stage increases almost linearly with the blowing time. Although the carbon content in the metal is very high at this time, which is conducive to the oxidation reaction of carbon, due to the low molten pool temperature at the beginning of blowing, the oxidation of silicon manganese and a small amount of iron in the molten iron takes precedence over the oxidation of carbon. Therefore, although the oxidation rate of carbon increases almost linearly with the blowing time, the oxidation rate of carbon is still very small. With the decrease of silicon manganese content and the increase of molten pool temperature, the decarburization reaction intensifies and enters the middle stage of blowing. At this time, the decarburization reaction rate is basically constant. This is because when the molten pool temperature increases, the oxidation rate of carbon increases significantly, and its decarburization rate almost only depends on the oxygen supply intensity. When the carbon content drops to a certain level, the diffusion rate of carbon decreases, becoming the controlling link of the reaction. Especially when the carbon content drops below 0.20%, the oxidation rate of carbon drops sharply. At this time, the oxidation rate of carbon is similar to that in the early stage of blowing, but it depends on the concentration and diffusion rate of carbon and is proportional to the carbon content.

[0003] At present, all steel enterprises are working to reduce the consumption of molten iron according to the price gap between molten iron and scrap steel. There is a process path of adding scrap steel into the molten iron torpedo tank. Under high-temperature molten iron conditions, appropriate scrap steel can be added according to the temperature drop of each ton of scrap steel. Controlling the excessively high temperature of molten iron is more suitable for the temperature control of the converter metal smelting process, while reducing the addition of slag and cooling agent. According to the characteristics of high-silicon molten iron with silicon content between 1.2%-7.0%, carbon content between 4.5-5.8%, and molten iron temperature above 1480℃, it is more suitable to add scrap steel into the torpedo tank to balance the molten iron temperature and excessive silicon content in the torpedo tank. After adding an appropriate amount of scrap steel, the molten iron temperature is controlled between 1320-1350℃, and the silicon content is appropriately reduced, but there is a carbon content in the range of 3.0-3.8%, resulting in a reduction in the carbon content of the molten iron. After the first double desiliconization smelting, the silicon content of the molten iron is between 0.20-0.50%, and the carbon content of the molten iron is between 0.7-1.5%. As a result, the subsequent double second smelting is insufficient in carbon content, insufficient heat in the furnace, and the terminal temperature of the first pouring furnace does not meet the requirements. The temperature is forcibly raised by secondary supplementary blowing, and the terminal carbon content is controlled below 0.03%. The oxygen content of the molten steel in the furnace increases sharply, which has a great impact on the subsequent deoxidation alloying, inclusion control, and furnace maintenance. According to the production needs, starting from the operation method, a low-carbon and high-silicon molten iron double silicon reduction and carbon preservation operation method is invented to meet the current production needs. Summary of the invention

[0004] The object of the present invention is to provide a dual silicon reduction and carbon preservation operation method for low-carbon and high-silicon molten iron, which can make the slag have appropriate basicity, oxidizability and fluidity as soon as possible, so as to quickly remove silicon oxidation in the molten iron to a specified range.

[0005] The technical solution adopted by the present invention is a method for operating low-carbon and high-silicon hot metal with double silicon reduction and carbon preservation, and the specific operating parameters are as follows:

[0006] 1) The initial silicon content of molten iron meets the duplex requirement, and the desiliconization loading is determined according to the converter duplex control model: the total desiliconization loading shall not exceed 125 tons, the maximum tonnage of scrap steel is 40 tons, and when there is still sufficient heat, pellets are used to balance the heat in the furnace;

[0007] 2) Enter the current furnace iron ladle number to confirm the molten iron composition and temperature, and make slag according to the following principles:

[0008] A. The silicon content of molten iron is between 1.5-7.0%, and the carbon content is between 3.0-3.8%. The double desiliconization and carbon retention operation method is selected, the scrap ratio is controlled above 30%, and the pellets are controlled above 35kg / t;

[0009] B. Alkalinity is controlled at 1.2-1.5, MgO is controlled at 7-10%, and lime, magnesite, tailings, and sludge pellets are selected for slag making;

[0010] C. Select oxygen lance oxygen blowing and oxygen-nitrogen automatic in the "oxygen lance operation mode" of the main operation screen of the industrial computer, confirm that all interlocking conditions are intact, and blow oxygen according to the following principles:

[0011] a. The smelting process adopts the "constant pressure variable gun" operation mode: the oxygen gun outlet pressure is 0.83-0.91MPa, and the smelting flow rate is controlled at 22000-28000Nm 3 / h, the liquid level line is based on the thickness gauge 630mm;

[0012] b. During normal smelting, the oxygen lance lowering range is 100-200mm, and the lance raising range is 100-300mm. Hanging and blowing are strictly prohibited;

[0013] c. After the iron is added, the furnace body is shaken to a vertical position, and an assistant closes the fire-blocking door;

[0014] d. Set the ignition gun position to 2200mm, click the blowing point, start the automatic button to smelt the gun, and the oxygen gun will automatically open at 3300mm. Confirm that the flame is normal at the ignition gun position, put slag into the furnace, and then gradually lower the gun to the blowing gun position of 1400-1600mm in 1-2 times: complete this process in 60 seconds; add the temperature regulating agent into the furnace in batches. If the flame in the furnace is abnormal, manually intervene in the smoke hood, and observe the flame to be normal before continuing to lower the gun; if the fire is not ignited after 30 seconds of blowing, the gun must be raised, the furnace must be poured out of the slag, and the condition in the furnace must be observed before blowing;

[0015] e. Adjust the flow rate of the gun to 22000-24000Nm at the beginning of desiliconization 3 / h, the gun position is controlled at 2000mm, after the flame is stable, add 2 / 3 of the total lime and all the magnesite and add a small amount of pelletized slag, and adjust the flow rate to 26000-28000Nm 3 / h, and then add the remaining slag in batches to control the process temperature, and the gun position is gradually lowered to 1400-1800mm;

[0016] f. In the middle stage of desiliconization, the gun position is controlled at 1400-1800mm. By observing the flame at the furnace mouth, the gun position and slag-removing agent are adjusted according to the flame conditions. During the smelting process, the height of the smoke hood is adjusted according to the slag conditions at the furnace mouth;

[0017] g. At the end of desiliconization, the slag begins to dry out, and the "sparks" at the nitrogen seal become dense. At this time, adjust the gun position to 1800-2000mm, and add pellets and tailings to slag or adjust the flow rate to the minimum flow rate. After the slag is dried out, adjust the gun position to 1400-1600mm and restore the flow rate to 26000-28000Nm 3 / h enters the late stage of smelting, and the steel tapping temperature is 1420-1500℃.

[0018] After blowing is completed, the temperature is measured and samples are taken using a molten iron sampler.

[0019]

[0020] By tracking and analyzing the on-site data and adopting the double-link desiliconization and carbon retention operation method, the silicon content of molten iron is controlled between 0.20-0.50%, the carbon content is between 2.8-3.5%, the carbon retention rate reaches 91.96%, and the carbon content of the furnace reaches 92%.

[0021] Improvement effect: The operation method of double silicon reduction and carbon preservation of low-carbon high-silicon hot metal is adopted, which realizes that the silicon content of the hot metal after double desiliconization of low-carbon high-silicon hot metal is stable between 0.20-0.50%, and the carbon content is stable between 2.8%-3.5%. The smelting time of molten steel after stable desiliconization is about 10 minutes, which provides sufficient reaction time for dephosphorization and slag removal in the smelting process, and stabilizes the double smelting operation of low-carbon high-silicon hot metal. The operation method of double silicon reduction and carbon preservation of low-carbon high-silicon hot metal is adopted, and the oxidation rate of carbon element is reduced by optimizing the slag formation route and gun position control. The carbon element retention rate reaches 91.96%, and the carbon element meets the furnace number of 92%, which provides an operating basis for the on-site production of low-carbon high-silicon hot metal. The operation method of double silicon reduction and carbon preservation of low-carbon high-silicon hot metal is adopted to stabilize the operation process of the double process, make the on-site furnace machine production more matched, and further improve production efficiency. This device has great promotion and application value in the steel smelting industry. DETAILED DESCRIPTION

[0022] An operating method for double-linked silicon reduction and carbon preservation of low-carbon and high-silicon molten iron, the specific operating parameters are as follows:

[0023] 1) The initial silicon content of molten iron meets the duplex requirement, and the desiliconization loading is determined according to the converter duplex control model: the total desiliconization loading shall not exceed 125 tons, the maximum tonnage of scrap steel is 40 tons, and when there is still sufficient heat, pellets are used to balance the heat in the furnace;

[0024] 2) Enter the current furnace iron ladle number to confirm the molten iron composition and temperature, and make slag according to the following principles:

[0025] A. The silicon content of molten iron is between 1.5-7.0%, and the carbon content is between 3.0-3.8%. The double desiliconization and carbon retention operation method is selected, the scrap ratio is controlled above 30%, and the pellets are controlled above 35kg / t;

[0026] B. Alkalinity is controlled at 1.2-1.5, MgO is controlled at 7-10%, and lime, magnesite, tailings, and sludge pellets are selected for slag making;

[0027] C. Select oxygen lance oxygen blowing and oxygen-nitrogen automatic in the "oxygen lance operation mode" of the main operation screen of the industrial computer, confirm that all interlocking conditions are intact, and blow oxygen according to the following principles:

[0028] a. The smelting process adopts the "constant pressure variable gun" operation mode: the oxygen gun outlet pressure is 0.83-0.91MPa, and the smelting flow rate is controlled at 22000-28000Nm 3 / h, the liquid level line is based on the thickness gauge 630mm;

[0029] b. During normal smelting, the oxygen lance lowering range is 100-200mm, and the lance raising range is 100-300mm. Hanging and blowing are strictly prohibited;

[0030] c. After the iron is added, the furnace body is shaken to a vertical position, and an assistant closes the fire-blocking door;

[0031] d. Set the ignition gun position to 2200mm, click the blowing point, start the automatic button to smelt the gun, and the oxygen gun will automatically open at 3300mm. Confirm that the flame is normal at the ignition gun position, put slag into the furnace, and then gradually lower the gun to the blowing gun position of 1400-1600mm in 1-2 times: complete this process in 60 seconds; add the temperature regulating agent into the furnace in batches. If the flame in the furnace is abnormal, manually intervene in the smoke hood, and observe the flame to be normal before continuing to lower the gun; if the fire is not ignited after 30 seconds of blowing, the gun must be raised, the furnace must be poured out of the slag, and the condition in the furnace must be observed before blowing;

[0032] e. Adjust the flow rate of the gun to 22000-24000Nm at the beginning of desiliconization 3 / h, the gun position is controlled at 2000mm, after the flame is stable, add 2 / 3 of the total lime and all the magnesite and add a small amount of pelletized slag, and adjust the flow rate to 26000-28000Nm 3 / h, and then add the remaining slag in batches to control the process temperature, and the gun position is gradually lowered to 1400-1800mm;

[0033] f. In the middle stage of desiliconization, the gun position is controlled at 1400-1800mm. By observing the flame at the furnace mouth, the gun position and slag-removing agent are adjusted according to the flame conditions. During the smelting process, the height of the smoke hood is adjusted according to the slag conditions at the furnace mouth;

[0034] g. At the end of desiliconization, the slag begins to dry out, and the "sparks" at the nitrogen seal become dense. At this time, adjust the gun position to 1800-2000mm, and add pellets and tailings to slag or adjust the flow rate to the minimum flow rate. After the slag is dried out, adjust the gun position to 1400-1600mm and restore the flow rate to 26000-28000Nm 3 / h enters the late stage of smelting, and the steel tapping temperature is 1420-1500℃.

Claims

1. A method for operating low-carbon and high-silicon hot metal double-linked silicon reduction and carbon preservation, characterized in that The specific operating parameters are as follows: 1) The initial silicon content of molten iron meets the duplex requirement, and the desiliconization loading is determined according to the converter duplex control model: the total desiliconization loading shall not exceed 125 tons, the maximum tonnage of scrap steel is 40 tons, and when there is still sufficient heat, pellets are used to balance the heat in the furnace; 2) Enter the current furnace iron ladle number to confirm the molten iron composition and temperature, and make slag according to the following principles: A. The silicon content of hot metal is between 1.5-7.0%, and the carbon content is between 3.0-3.8%. The double desiliconization and carbon retention operation method is selected, the scrap ratio is controlled above 30%, and the pellets are controlled above 35kg / t; B. Alkalinity is controlled at 1.2-1.5, MgO is controlled at 7-10%, and lime, magnesite, tailings, and sludge pellets are selected for slag making; C. Select oxygen lance oxygen blowing and oxygen-nitrogen automatic in the "oxygen lance operation mode" of the main operation screen of the industrial computer, confirm that all interlocking conditions are intact, and blow oxygen according to the following principles: a. The smelting process adopts the "constant pressure variable gun" operation mode: the oxygen gun outlet pressure is 0.83-0.91MPa, and the smelting flow rate is controlled at 22000-28000Nm 3 / h, the liquid level line is based on the thickness gauge 630mm; b. During normal smelting, the oxygen lance lowering range is 100-200mm, and the lance raising range is 100-300mm. Hanging and blowing are strictly prohibited; c. After the iron is added, the furnace body is shaken to a vertical position, and an assistant closes the fire-blocking door; d. Set the ignition gun position to 2200mm, click the blowing point, start the automatic button to smelt the gun, and the oxygen gun will automatically open at 3300mm. Confirm that the flame is normal at the ignition gun position, put slag into the furnace, and then gradually lower the gun to the blowing gun position of 1400-1600mm in 1-2 times: complete this process in 60 seconds; add the temperature regulating agent into the furnace in batches. If the flame in the furnace is abnormal, manually intervene in the smoke hood, and observe the flame to be normal before continuing to lower the gun; if the fire is not ignited after 30 seconds of blowing, the gun must be raised, the furnace must be poured out of the slag, and the condition in the furnace must be observed before blowing; e. Adjust the flow rate of the gun to 22000-24000Nm at the beginning of desiliconization 3 / h, the gun position is controlled at 2000mm, after the flame is stable, add 2 / 3 of the total lime and all the magnesite and add a small amount of pelletized slag, and adjust the flow rate to 26000-28000Nm 3 / h, then add the remaining slag in batches to control the process temperature, and gradually lower the gun position to 1400-1800mm; f. In the middle stage of desiliconization, the gun position is controlled at 1400-1800mm. By observing the flame at the furnace mouth, the gun position and slag-removing agent are adjusted according to the flame conditions. During the smelting process, the height of the smoke hood is adjusted according to the slag conditions at the furnace mouth; g. At the end of desiliconization, the slag begins to dry out, and the "sparks" at the nitrogen seal become dense. At this time, adjust the gun position to 1800-2000mm, and add pellets and tailings to slag or adjust the flow rate to the minimum flow rate. After the slag is dried out, adjust the gun position to 1400-1600mm and restore the flow rate to 26000-28000Nm 3 / h enters the late stage of smelting, and the steel tapping temperature is 1420-1500℃.

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