Rapid slagging process for blowing mixture in electric arc furnace by utilizing industrial solid waste

Abstract

The invention relates to the technical field of steelmaking, and particularly discloses a rapid slagging process for an electric arc furnace injection mixture by utilizing industrial solid waste. The invention discloses a rapid slagging process for an electric arc furnace injection mixture by using industrial solid waste. The rapid slagging process comprises the following steps: S1, charging and melting; s2, blowing and slagging are conducted, specifically, the mixture is blown according to the blowing speed of 5-8 kg / min, meanwhile, oxygen is introduced according to the gas inlet speed of 5-10 Nm < 3 > / min, and blowing is stopped till the slag layer thickness of the foamed slag is larger than or equal to 300 mm; the mixture comprises scale and carbon powder in a weight ratio of (2-3.5): 1. According to the technology, the time for forming the foam slag can be shortened by 30%, meanwhile, the metal yield is not lower than 96.3%, the oxygen consumption is reduced by 40% or above on year-on-year basis, industrial waste is effectively utilized, the foam slag forming time is shortened, the oxygen consumption is reduced, and the technology has the industrial value and the environmental protection value.

Description

Technical Field

[0001] This application relates to the technical field of steelmaking, and in particular to a rapid slag-making process for an electric arc furnace injecting mixed materials using industrial solid waste. Background Art

[0002] Electric arc furnace steelmaking is a process that uses the heat energy of an electric arc for steel and iron smelting. It mainly uses scrap steel as raw material, and melts the metal charge and slag through the high temperature of the electric arc generated between the electrodes and the charge, and finally smelts various qualified steels and alloys. The specific process includes the melting period (an electric arc is generated between the electrodes and the charge to melt the scrap steel), the oxidation period (removing impurities such as carbon and phosphorus in the molten steel by means of blowing oxygen, etc.), the reduction period (adjusting the composition of the molten steel, removing impurities such as sulfur, and adjusting the temperature and composition of the molten steel to the tapping requirements), and tapping (pouring the refined molten steel into a ladle for subsequent treatment). In the early stage of electric arc furnace steelmaking, the oxygen-enriched method was adopted, which significantly reduced the power consumption, but this brought about the disadvantages of reduced metal yield and increased slag volume. In addition, due to the large amount of use, the carbon content in the molten steel after the slag is melted is low, the slag is thin, the electric arc heating efficiency is low, and it is difficult to raise the temperature of the molten steel. To eliminate these adverse factors, technicians blow carbon powder into the molten steel in the molten pool during the oxidation period to reduce and recover FeO in the slag, thereby increasing the metal yield.

[0003] Modern electric arc furnace steelmaking technology shortens the smelting time of the electric arc furnace and improves the productivity of the electric arc furnace by adopting a higher secondary voltage for long arc smelting operation, increasing the input of active power, and increasing the melting rate of the charge. However, the strong heat flow of the electric arc radiates to the furnace wall, increasing the heat load of the furnace wall and increasing the melting loss of the refractory material and the heat loss. In order to make as much heat of the electric arc enter the molten steel as possible, the foam slag technology needs to be adopted. Foam slag is a substance formed by gas dispersed in the molten slag. When the conditions such as the temperature, alkalinity, composition, surface tension, and viscosity of the molten slag are appropriate, the molten slag will foam to form foam slag due to the action of gas. The so-called foam slag means that without increasing the slag volume, the furnace slag is in a very thick foam state, that is, there are a large number of tiny bubbles in the molten slag, and the total volume of the bubbles is greater than the volume of the liquid slag. The liquid slag becomes a thin film of the slag in the small bubbles to separate each bubble, and the bubbles are difficult to move freely and stay in the molten slag. This slag-gas system is called foam slag. During the electric arc furnace smelting process, making foam slag can not only effectively reduce the consumption of refractory materials and electrode materials, but also significantly improve the thermal efficiency, thereby reducing the melting time. Moreover, it can also reduce the on-site noise and improve the operation environment of workers. At present, there are various optimized operations for the foam slag process, and the application of industrial solid waste in the slag-making process has also been explored more deeply. Summary of the Invention

[0004] During the electric arc furnace smelting process, first, oxygen is injected into the molten steel, reacting with the carbon in the molten steel to form CO bubbles. At the same time, oxygen also reacts with the iron in the molten steel to form FeO and enter the slag, as shown in reaction equations (1-1) and (1-2). Then, carbon powder is added to the slag, reacting with FeO in the slag to form CO bubbles and promoting the return of the generated Fe to the molten steel, as shown in reaction equation (1-3). In addition, gas is injected into the slag and can also react with the carbon powder in the slag to form CO bubbles. In this process, oxygen and carbon powder can be injected simultaneously to form more CO, thereby promoting the foaming of the slag. The formation process of CO in the electric arc furnace slag is shown in reaction equation 1-4.

[0005] C+(FeO)=CO+Fe (l) 1-3 In order to further optimize the slag-making process and rationally utilize industrial solid waste, the present application provides a rapid slag-making process for an electric arc furnace blowing mixture using industrial solid waste.

[0006] The rapid slag-making process for an electric arc furnace blowing mixture using industrial solid waste provided by the present application includes the following steps: S1. Charging and melting: Scrap steel and hot metal are added in a weight ratio of 8:2, and lime is added to adjust the slag basicity. S2. Blowing slag-making: The mixture is blown at a blowing rate of 5-8 kg / min, and at the same time, oxygen is introduced at an intake rate of 5-10 Nm 3 / min until the thickness of the slag layer of the foamed slag ≥ 300 mm, then stop blowing; the mixture includes scale and carbon powder in a weight ratio of (2-3.5):1.

[0007] By adopting the above technical solution, the formation time of the foamed slag can be significantly shortened, and the time for the slag layer thickness to reach 300 mm is shortened by 30%. Specifically, setting the blowing rate at 5-8 kg / min can ensure that the mixture enters the furnace evenly and stably, avoiding the splashing phenomenon caused by too fast blowing or the problem of extended operation cycle caused by too slow blowing. At the same time, the intake rate is controlled at 5-10 Nm 3Within the range of / min, it not only meets the oxygen supply required for the reaction, but also effectively reduces the oxygen consumption, thereby reducing the production cost. In addition, the iron scale and carbon powder in the mixture are prepared according to a weight ratio of (2 - 3.5):1. While promoting the rapid formation of the foamy slag, it improves the utilization rate of FeO in the slag and reduces its residual amount, thus increasing the metal yield by no less than 96.3%. The reasonable matching among various parameters not only speeds up the slag-making process, but also enhances the stability of the slag layer and extends its maintenance time, greatly improving the smelting efficiency and economic benefits as a whole. Generally speaking, the rapid slag-making process of this application not only effectively utilizes industrial waste, but also shortens the formation time of the foamy slag, reduces the oxygen consumption, and has both industrial value and environmental protection value.

[0008] Preferably, in the step S1, the molten steel temperature is 1530 - 1570 °C, and the slag basicity is 2.2 - 2.5.

[0009] By adopting the above technical solution, this application controls the molten steel temperature and the slag basicity (calculated by the mass ratio of CaO to SiO 2 ), which can significantly improve the stability of the foamy slag formation. Specifically, under these conditions, the chemical reactions in the molten pool are more sufficient, which helps to promote the effective decomposition and absorption of the mixture of iron scale and carbon powder, thereby accelerating the formation speed of the foamy slag and maintaining an appropriate slag layer thickness. In addition, the slag under this condition has good fluidity, which is beneficial to improving the heat and mass transfer efficiency in the metallurgical process, further increasing the metal yield and reducing energy loss.

[0010] Preferably, in the step S2, the content of FeO in the iron scale is not less than 90 wt%, and the water content is not higher than 1 wt%.

[0011] By adopting the above technical solution, it can ensure the stable quality of the iron scale raw material, thereby improving the efficiency and stability of the foamy slag formation. Specifically, limiting the content of FeO in the iron scale to not less than 90 wt% helps to ensure that sufficient oxidants participate in the reaction, promote the efficient progress of the carbon powder reduction process, and thus accelerate the formation of the foamy slag; while limiting the water content to not higher than 1 wt% can avoid the splashing phenomenon caused by excessive water and the adverse impact on the furnace temperature, ensuring the safety and economy of the entire process.

[0012] Preferably, in the step S2, the content of fixed carbon in the carbon powder is not less than 95 wt%.

[0013] By adopting the above technical solution, the fixed carbon content in the carbon powder is not less than 95 wt%, which can improve the CO gas generation efficiency, promote the expansion of the slag layer; reduce the interference of non-effective components during the injection process, and optimize the structural stability of the foamed slag; at the same time, it helps to reduce the temperature drop of the molten steel and maintain the thermal balance state in the furnace, thereby overall improving the reaction activity of the mixture and accelerating the formation process of the foamed slag.

[0014] Preferably, in the step S2, the weight ratio of iron oxide scale to carbon powder is 3:1.

[0015] By adopting the above technical solution, the present application controls the iron oxide scale and carbon powder to be mixed in a weight ratio of 3:1 and then injected. Compared with other ratios, it can reach the target slag layer thickness in a shorter time, thereby effectively shortening the smelting cycle. In addition, this ratio can further reduce the residual amount of FeO in the slag, reduce metal loss, and improve the metal yield. At the same time, the mixture under this ratio helps to optimize the CO generation efficiency, reduce the oxygen consumption while ensuring good chemical reactions, and achieve the purpose of energy conservation and emission reduction.

[0016] Preferably, in the step S2, the injection rate is 6 - 7.5 kg / min.

[0017] By adopting the above technical solution, the present application limits the injection rate to 6 - 7.5 kg / min, which can effectively improve the utilization rate of the mixture, shorten the time for the foamed slag to reach the target thickness, and at the same time reduce the influence of molten steel temperature fluctuations on the smelting process. The injection rate within this parameter range can also better match the oxygen flow rate, promote the reaction between the carbon powder and the iron oxide scale, thereby achieving a higher metal yield and a lower residual amount of FeO in the slag, while ensuring the formation effect of the foamed slag, further optimizing the material consumption and operation stability during the injection process.

[0018] Preferably, in the step S2, the air intake rate is 6 - 8 Nm 3 / min.

[0019] By adopting the above technical solution, the present application limits the air intake rate within the range of 6 - 8 Nm 3 / min, achieving precise control of the oxygen supply amount during the arc furnace injection process, improving the efficiency of foamed slag formation, shortening the formation time while ensuring that the slag layer thickness reaches the target value. Compared with higher or lower air intake rates, the oxygen supply within this range is more sufficient and stable, which can effectively promote the reaction between the iron oxide scale and the carbon powder, increase the CO generation rate and peak concentration, thereby enhancing the foaming effect and its stability of the slag layer. In addition, reasonably regulating the air intake rate helps to reduce the oxygen consumption, further reduce the production cost and improve the economic benefits.

[0020] Preferably, in the step S2, the ejection angle during the injection of the mixture is 30-60°.

[0021] Preferably, in the step S2, the ejection angle during the injection of the mixture is 45°.

[0022] By adopting the above technical solution, the ejection angle of the present application makes the distribution of the iron scale and carbon powder mixture in the molten bath more uniform, increases the proportion of the reaction active area, thereby accelerating the generation rate of CO gas, and enhancing the expansion effect and stability of the foamed slag. The ejection angle during the injection of the mixture being 30-60° can significantly improve the slag-gas mixing efficiency and promote the stable formation of the foamed slag.

[0023] Preferably, in the step S2, the injection pressure is 0.3-0.4 MPa.

[0024] By adopting the above technical solution, the present application limits the injection pressure within the range of 0.3-0.4 MPa, which can effectively control the pressure range during the injection process, avoid the splashing phenomenon caused by too high pressure, ensure the stable ejection of the mixture, significantly improve the safety and controllability of the injection operation, reduce the impact damage to the equipment, further optimize the formation conditions of the foamed slag, and improve the slag-making efficiency and quality.

[0025] In summary, the present application has the following beneficial technical effects: The process of the present application can promote the rapid formation of the foamed slag (shortening the time for forming the foamed slag by 30%), while also improving the utilization rate of FeO in the slag and reducing its residual amount. The metal recovery rate is not less than 96.3%, and the oxygen consumption is reduced by more than 40% year-on-year. It not only effectively utilizes industrial waste, but also shortens the foamed slag formation time and reduces the oxygen consumption, with both industrial value and environmental protection value. Specific Embodiments

[0026] Experimental Principle and Instruments Iron scale powder, an industrial solid waste, with FeO≥90wt% and moisture≤1wt%; The carbon powder is purchased from Fangda Carbon New Materials Technology Co., Ltd., and is FD-TC series high-purity carbon powder with a fixed carbon content≥95wt% and a particle size of 80-200 mesh; Oxygen, with a purity≥99.5%; An electric arc furnace with a capacity of 120 tons, equipped with a dual-channel injection system; On-line monitoring: infrared thermometer, laser slag thickness gauge, and mass spectrometry gas analyzer, among which: The infrared thermometer is a FLIR E98 advanced infrared thermal imager with a maximum temperature measurement range of 1500 °C and an infrared resolution of 640×480; the laser slag thickness gauge is a UK ZSY LEN-10-500 laser ranging sensor with a ranging ability of 0.05 - 500 meters, an accuracy of ±1 mm, a high-frequency measurement of 50 Hz, a temperature tolerance of -10 °C to +50 °C, and an IP65 protection level; The mass spectrometry gas analyzer is a PMA 1000 pulse melting - mass spectrometry gas analyzer of GRINM, covering a content range of 0.4 μg / g to 2%, with a sensitivity of 0.01 μg / g.

[0027] Sampling tools: molten steel rapid sampler, slag sample cooling mold; Auxiliary equipment: drying oven, ball mill, magnetic separator, electronic scale.

[0028] The present application will be further described in detail below in conjunction with examples and comparative examples.

[0029] Example 1 A rapid slag-making process for arc furnace blowing mixture using industrial solid waste, comprising the following steps: S1. Charging and melting: Add 8 tons of scrap steel and 2 tons of hot metal into the arc furnace, and energize to melt until the molten steel temperature reaches 1550 °C. At the same time, add lime to adjust the slag basicity to 2.2 - 2.5; S2. Blowing slag-making: Dry the iron oxide scale at a temperature of 200 °C for 2 h, perform magnetic screening and impurity removal through a magnetic separator and then ball mill it to a particle size not higher than 3 mm, and mix it with carbon powder according to a weight ratio of 3:1. After mixing evenly, the mixture is obtained; Start the mixture blowing, blow at a blowing rate of 7.5 kg / min, and control the blowing angle to 45° and the blowing pressure to 0.35 MPa. At the same time, introduce oxygen at an intake speed of 6 Nm 3 / min until the slag layer thickness of the foamed slag reaches 300 mm, then stop blowing. Take steel water samples to analyze the C and Fe contents, take slag samples to analyze the FeO content, and record the slag layer thickness (mm), molten steel temperature (°C) and CO concentration (vol%) every 60 s during slag-making.

[0030] Example 2 A rapid slag-making process for arc furnace blowing mixture using industrial solid waste, comprising the following steps: S1. Charging and melting: Add 8 tons of scrap steel and 2 tons of hot metal into the arc furnace, and energize to melt until the molten steel temperature reaches 1530 °C. At the same time, add lime to adjust the slag basicity to 2.2 - 2.5; S2. Injection for slag formation: Dry the iron oxide scale at 200 °C for 2 h, perform magnetic screening and impurity removal through a magnetic separator, then ball mill it to a particle size not exceeding 3 mm, and mix it with carbon powder according to a weight ratio of 2:1. After uniformity, obtain the mixture. Start the injection of the mixture, inject it at an injection rate of 5 kg / min, and control the injection angle to 30° and the injection pressure to 0.3 MPa. At the same time, introduce oxygen at an intake speed of 10 Nm 3 / min until the thickness of the slag layer of the foamed slag reaches 300 mm, then stop the injection. Take a steel water sample to analyze the C and Fe contents, take a slag sample to analyze the FeO content, and record the slag layer thickness (mm), molten steel temperature (°C), and CO concentration (vol%) every 60 s during slag formation.

[0031] Example 3 A rapid slag formation process for injecting a mixture in an electric arc furnace using industrial solid waste, comprising the following steps: S1. Charging and melting: Add 8 tons of scrap steel and 2 tons of hot metal into the electric arc furnace, energize and melt until the molten steel temperature reaches 1570 °C, and at the same time add lime to adjust the slag basicity to 2.2 - 2.5; S2. Injection for slag formation: Dry the iron oxide scale at 200 °C for 2 h, perform magnetic screening and impurity removal through a magnetic separator, then ball mill it to a particle size not exceeding 3 mm, and mix it with carbon powder according to a weight ratio of 3.5:1. After uniformity, obtain the mixture. Start the injection of the mixture, inject it at an injection rate of 8 kg / min, and control the injection angle to 60° and the injection pressure to 0.4 MPa. At the same time, introduce oxygen at an intake speed of 5 Nm 3 / min until the thickness of the slag layer of the foamed slag reaches 300 mm, then stop the injection. Take a steel water sample to analyze the C and Fe contents, take a slag sample to analyze the FeO content, and record the slag layer thickness (mm), molten steel temperature (°C), and CO concentration (vol%) every 60 s during slag formation.

[0032] The slag formation process for injecting carbon powder in a comparative example electric arc furnace, comprising the following steps: S1. Charging and melting: Add 8 tons of scrap steel and 2 tons of hot metal into the electric arc furnace, energize and melt until the molten steel temperature reaches 1550 °C, and at the same time add lime to adjust the slag basicity to 2.2 - 2.5; S2. Injection for slag formation: Start the injection of carbon powder, inject it at an injection rate of 7.5 kg / min, and control the injection angle to 45° and the injection pressure to 0.35 MPa. At the same time, introduce oxygen at an intake speed of 6 Nm 3 / min until the thickness of the slag layer of the foamed slag reaches 300 mm, then stop the injection. Take a steel water sample to analyze the C and Fe contents, take a slag sample to analyze the FeO content, and record the slag layer thickness (mm), molten steel temperature (°C), and CO concentration (vol%) every 60 s during slag formation.

[0033] Performance detection 1. Determine the C and Fe contents in the steel water sample using a spectrometer; 2. Determine the FeO content in the slag sample using the XRF method, and calculate the FeO consumption rate % and the metal recovery rate %; 3. Record the time (s) when the slag layer thickness of the foamy slag reaches 300 mm and the maximum stable time (s) that the slag layer can maintain; Calculate the metal recovery rate and oxygen utilization rate according to the following formula and the measured data: FeO consumption rate % = (FeO content in the slag before injection - FeO content in the slag after injection) / FeO content in the slag before injection × 100%; Metal recovery rate % = (amount of molten steel tapped - Fe loss in the slag) / total amount of metal charged into the furnace × 100%; Oxygen utilization rate % = (theoretical CO generation amount / actual CO generation amount) × 100%.

[0034] Table 1 Performance detection table Table 2 Changes in slag layer thickness and CO concentration Data analysis: As can be seen from Tables 1-2, the slag formation time of the mixture injection process of this application is 216 - 340 s, while the slag formation time of the pure carbon powder injection process is 500 s. This application can reduce the slag formation time by as much as 32% - 56.8%. Moreover, the recovery rate of this application process is 96.3 - 97.8%, which is significantly higher than the metal recovery rate of 95.5% of the existing pure carbon powder injection process. And the oxygen consumption of this application process is significantly lower than that of the pure carbon powder injection process, with a maximum reduction of 23% year-on-year. The mass loss of molten steel is also reduced by as much as 30% - 40%. This fully proves that the rapid slag formation process of this application not only effectively utilizes industrial waste, but also shortens the foamy slag formation time, reduces oxygen consumption, and has both industrial value and environmental protection value.

[0035] And it can be seen from Table 1-2 that the slag formation time of Example 1 is significantly shorter than that of Examples 2-3, the metal recovery rate is higher, the oxygen consumption is smaller, the maximum stable time can reach 750 s, the difference in the FeO content in the slag before and after injection is larger, the consumption rate can reach 60%, and the mass loss of the molten steel is also less than that of Examples 2-3. In Example 1, a slag layer with a thickness of 200 mm can be formed at 120 s, which is more than 80 mm thicker than the slag layer thickness of Examples 2-3. At 180 s, a slag layer with a thickness of 290 mm can be formed, which is 70-80 mm thicker than the slag layer thickness of Examples 2-3. And when the thickness growth rate of all groups decreases with the progress of time, the thickness gap between Example 1 and Examples 2-3 remains almost unchanged. This proves that by controlling the mixing ratio of scale and carbon powder at a weight ratio of 3:1, limiting the injection rate to 6-7.5 kg / min, the intake rate to 6-8 Nm 3 / min, and the injection angle when injecting the mixed material to 45°, the reaction between the carbon powder and the scale can be effectively promoted, the expansion effect and stability of the foamed slag can be enhanced, the oxygen consumption can be reduced while ensuring good chemical reactions, the smelting cycle can be shortened, the residual amount of FeO in the slag can be further reduced, the metal loss can be reduced, the metal recovery rate can be increased, and the CO generation efficiency can be optimized.

[0036] The embodiments of this specific implementation manner are all preferred embodiments of this application, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A rapid slag making process for arc furnace spraying mixed material using industrial solid waste, characterized in that: The following steps are involved: S1, charging and melting; S2, slag injection: spray the mixture at a rate of 5-8kg / min, and at the same time at a rate of 5-10Nm 3 Oxygen is introduced at an air intake rate of / min until the thickness of the slag layer of the foamed slag is ≥300mm, and the blowing is stopped; the mixed material includes iron oxide scale and carbon powder in a weight ratio of (2-3.5):

1.

2. The rapid slag making process of arc furnace spraying mixture using industrial solid waste according to claim 1 is characterized in that: In step S1, the temperature of the molten steel is 1530-1570° C., and the basicity of the slag is 2.2-2.

5.

3. The rapid slag making process of arc furnace spraying mixture using industrial solid waste according to claim 1, characterized in that: In the step S2, the content of FeO in the iron oxide scale is not less than 90wt%, and the content of water is not more than 1wt%.

4. The rapid slag making process of arc furnace spraying mixture using industrial solid waste according to claim 1 is characterized in that: In the step S2, the content of fixed carbon in the carbon powder is not less than 95wt%.

5. The rapid slag making process of arc furnace spraying mixture using industrial solid waste according to claim 1, characterized in that: In the step S2, the weight ratio of iron oxide scale to carbon powder is 3:

1.

6. The rapid slag making process of arc furnace spraying mixture using industrial solid waste according to claim 1, characterized in that: In the step S2, the blowing rate is 6-7.5 kg / min.

7. The rapid slag making process of arc furnace spraying mixed material using industrial solid waste according to claim 1, characterized in that: In step S2, the air intake rate is 6-8Nm 3 / min.

8. The rapid slag making process of arc furnace spraying mixed material using industrial solid waste according to claim 1, characterized in that: In the step S2, the spraying angle of the mixed material is 30-60°.

9. The rapid slag making process of arc furnace spraying mixed material using industrial solid waste according to claim 8, characterized in that: In the step S2, the spraying angle of the mixed material is 45°.

10. The rapid slag making process of arc furnace spraying mixed material using industrial solid waste according to claim 1, characterized in that: In the step S2, the blowing pressure is 0.3-0.4 MPa.

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