Bottom electrode combined bottom blowing multimedia system for DC arc furnaces

Abstract

The present invention relates to a steelmaking technology field, and relates to a bottom electrode composite bottom blowing multimedia system and method for DC arc furnace, which includes a bottom blown electrode located at the bottom of the furnace, some of which have a hollow structure, and includes a plurality of bottom electrodes, which are one or more of type I bottom electrode, type II bottom electrode, and type III bottom electrode, a type I bottom electrode for injecting carbon material into the molten bath to carburize the molten bath and promote scrap melting, a type II bottom electrode for injecting slag foaming powder into the molten bath to form molten slag particles in the metal liquid and increase the three-phase reaction boundary area of ​​gas-slag-metal in the dephosphorization reaction process, and a type III bottom electrode for injecting gas into the molten bath to promote the material transition of the molten bath, and further includes a control unit connected to the bottom blown electrode for combining the power supply strength of the bottom blown electrode in the smelting process and adjusting the blowing parameters online. The present invention can reduce the consumption of raw materials and auxiliary materials and improve production efficiency.

Description

[Technical Field]

[0001] The present invention relates to the field of steelmaking technology, in particular to a bottom electrode combined bottom blowing multi-mechanical furnace for a DC arc furnace. Dear System Mu Regarding. [Background technology]

[0002] DC arc furnace steelmaking, one of the main methods of arc furnace steelmaking, uses the bottom of the furnace as the positive electrode of the arc current and strengthens the stirring of the molten bath by the current between the electrodes, which has improved the dynamic conditions of the molten bath to a certain extent. However, due to the influence of the flat hearth structure, the stirring force of the molten bath is weak, the dynamic conditions are poor, the smelting cycle is long, and there are challenges such as difficulty in controlling the phosphorus, nitrogen, and oxygen in the molten steel, which have restricted the development of DC arc furnaces into green and efficient smelting.

[0003] The challenges are mainly manifested in several aspects: 1) The structure of raw materials such as smelting scrap is complex, the nitrogen content is relatively high, and the phosphorus content after melting varies greatly. 2) The carbon content of the molten bath is low, the reaction between carbon and oxygen in the molten bath is insufficient, the flow rate of the molten steel is slow, and the kinetic conditions for dephosphorization and denitrification are poor. 3) In the smelting process, lime is usually added to the molten bath in a lump form, which makes the slag melting and slag formation slow. Although the fluidity of the slag is improved by injecting carbon powder into the furnace wall, the utilization rate of the carbon powder is low, which results in high consumption of raw materials and auxiliary materials, making it difficult to effectively improve the quality of molten steel. 4) Modern electric arc furnace steelmaking generally uses high-power power sources to accelerate scrap melting and shorten the smelting cycle, and the high-temperature arc electrolyzes the N2 in the air, making the molten steel more likely to absorb nitrogen. 5) Strengthening the oxygen supply not only improves smelting efficiency, but also causes problems such as end-point overoxidation, reduced metal yield, and increased alloy consumption after tapping. 6) By using bottom electrode power supply, the local temperature of the furnace bottom is too high, which limits the power supply strength and life of the bottom electrode.

[0004] Therefore, how to improve the kinetic conditions of the smelting reaction in DC arc furnaces, accelerate the reaction rate at the interface between slag and molten steel, and at the same time reduce the consumption of raw materials and auxiliary materials and improve production efficiency are technological bottlenecks that must be resolved in the process of developing DC arc furnace steelmaking into green and efficient production. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of this, an object of the present invention is to provide a furnace bottom electrode for a DC arc furnace in order to improve production efficiency. Extremely Composite Bottom Blowing Multimedia System M The purpose is to provide. [Means for solving the problem]

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] a type I bottom electrode for injecting carbon material into the molten bath to carburize the molten bath and promote scrap melting; a type II bottom electrode for injecting slag foaming powder into the molten bath to form molten slag granules in the metal liquid and increase the gas-slag-metal three-phase reaction boundary area in the dephosphorization reaction process; and a type III bottom electrode for injecting gas into the molten bath to promote material transfer in the molten bath, and further comprising a control unit connected to the bottom electrode for controlling the power supply strength of the bottom electrode and adjusting the injection parameters online during the smelting process.

[0008] Preferably, the type II hearth electrode and the type I hearth electrode are arranged adjacent to each other so as to neutralize the local cold effect caused by the type I hearth electrode, and the type III hearth electrodes are arranged in a dispersed manner so as to promote the flow at the bottom of the molten bath and enhance the heat exchange between the slag and the molten steel.

[0009] Preferably, the carrier gas medium of the type I hearth electrode is air, nitrogen or CO2, and the flow rate is 0 to 1000 Nm 3 / h, the carbon material is carbon powder, coke charcoal, graphite powder or other carbon-enhancing powder, the powder flow rate of one type I hearth bottom electrode is 0~50kg / min, and the powder particle size is ≦1mm.

[0010] Preferably, the carrier gas 2 medium of the type II hearth electrode is O2, O2-N2 mixed gas or O2-CO2 mixed gas, and the carrier gas flow rate is 0-1000 Nm 3 / h, the oxygen volume flow rate ratio is 0~100%, the slag foaming powder is lime powder or limestone powder, the powder flow rate of one II type hearth electrode is 0~50kg / min, and the powder particle size is ≦1mm.

[0011] Preferably, the pure gas bottom blowing medium of the class III hearth electrode is one or more mixed gases selected from N2, Ar, CO2, and O2, and the bottom blowing intensity is 0 to 0.05 Nm 3 / (min·t).

[0012] Preferably, the inner diameter of the hole of the type I hearth electrode and the type II hearth electrode is 4 to 25 mm, and the inner diameter of the hole of the type III hearth electrode is 0.1 to 10 mm.

[0013] Preferably, the bottom blowing connection port of the bottom blowing electrode and the external medium introduction connection port are insulated from each other.

[0014] Preferably, the bottom-blown electrode is entirely attached to the bottom of the arc furnace and is further buried by a furnace bottom ramming material.

[0015] A bottom electrode combined bottom blowing multimedia method for a DC arc furnace, in which some bottom electrodes located at the bottom of the furnace are designed as bottom-blown electrodes with a hollow structure, and one or more media among gas, carbon material, and slag foaming powder that can promote material transfer into the molten bath in the furnace are blown by the bottom-blown electrodes, and the blowing parameters are dynamically controlled in combination with the power supply strength of the bottom-blown electrodes to realize the coordinated operation of the bottom blowing and the bottom electrodes. [Effects of the Invention]

[0016] (1) The bottom electrode combined bottom blowing multimedia system for DC arc furnaces provided by this application utilizes the hollow design of the bottom electrode, and during the smelting process, the solid part of the bottom blowing electrode supplies power to the molten bath, and the hollow part dynamically injects various media into the molten bath, thereby realizing the highly efficient coordinated operation of the bottom blowing and bottom electrode.

[0017] (2) The new DC arc furnace smelting method proposed in this application uses a bottom-blown electrode to blow carbon material and slag foaming powder into the molten bath, which can efficiently increase carbon in the molten bath, promote scrap melting, and efficiently remove impurities, thereby reducing the consumption of raw materials and auxiliary materials and achieving a phosphorus content of ≦0.005% and an end-point N content of ≦50 ppm at the end of smelting.

[0018] (3) The bottom electrode combined bottom blowing multimedia system for DC arc furnaces provided by this application can effectively improve the uniformity of molten steel composition and temperature, reduce energy loss in the smelting process, accelerate the smelting rhythm, shorten the smelting cycle by more than 3 minutes, and reduce the electricity consumption per ton of steel by more than 10 kWh.

[0019] (4) In the present invention, by injecting carbon materials and slag foaming powder into the molten bath in the electric arc furnace steelmaking process, the overoxidation problem at the end of smelting can be effectively controlled, and the metal yield can be improved by 1 to 3%. At the same time, the yield during the tapping alloying process can be improved by 4 to 5% compared to that of an electric arc furnace without bottom blowing function.

[0020] Other advantages, objects and features of the present invention will be set forth in part in the specification which follows, and in part will become apparent to those skilled in the art upon study of the following or may be learned from the practice of the invention. The objectives and other advantages of the present invention may be attained by the following specification. [Brief explanation of the drawings]

[0021] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention is preferably described in detail below in conjunction with the accompanying drawings. [Figure 1] 1 is a schematic diagram of a combined bottom-blowing multimedia bottom-blowing system for a DC arc furnace according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the distribution of a multimedia bottom-blowing electrode in Example 1 of the present invention. [Figure 3] 1 is a schematic diagram of a type I bottom electrode process in Example 1 of the present invention. [Figure 4] 1 is a schematic diagram of a type II bottom electrode process in Example 1 of the present invention. [Figure 5] 1 is a schematic diagram of a type III bottom electrode process in Example 1 of the present invention. [Figure 6] This is a cross-sectional view of the distribution of the multimedia bottom-blown electrode in Example 2 of the present invention. The attached diagram notates a type III bottom electrode bottom-blowing control system 1, a type I bottom electrode bottom-blowing control system 2, a type II bottom electrode bottom-blowing control system 3, a type III bottom electrode system distributor 4, a type I bottom electrode system distributor 5, a type II bottom electrode system distributor 6, an insulating joint 7, a bottom-blown electrode 8, a bottom-blown electrode cold air inlet 9, and a bottom-blown conductive copper bus bar 10. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the implementation of the present invention will be described by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied by other specific examples, and the details of the present specification can be modified or changed in various ways based on different perspectives and applications without departing from the spirit of the present invention. The figures shown in the following examples are merely intended to outline the basic concept of the present invention, and the following examples and features of the examples can be combined with each other without causing any contradiction.

[0023] The drawings are for illustrative purposes only and are schematic rather than concrete drawings, and should not be construed as limiting the present invention. To better explain the embodiments of the present invention, some components in the drawings are omitted, enlarged, or reduced in size, and do not represent the actual product dimensions. Those skilled in the art will understand that some well-known structures and their descriptions may be omitted in the drawings.

[0024] The same or similar symbols in the drawings of the embodiments of the present invention correspond to the same or similar components, and in the description of the present invention, the orientations or positional relationships indicated by terms such as "upper," "lower," "left," "right," "front," and "rear" are based on the orientations or positional relationships shown in the drawings and are intended merely to facilitate and simplify the description of the present invention, and do not indicate or suggest that the devices or elements shown must have a specific orientation, be configured, or operate in a specific orientation. Therefore, the terms indicating the positional relationships shown in the drawings are used for illustrative purposes only and should not be understood as limiting the present invention, and the specific meanings of the above terms will be understood by those skilled in the art depending on the context.

[0025] 1 to 6, a bottom-blown multimedia system for a DC arc furnace includes a plurality of bottom electrodes positioned at the bottom of the furnace, some of which are hollow, needle-shaped electrodes 8 extending into the molten bath within the furnace. The bottom electrodes 8 are one or more of type I, type II, and type III bottom electrodes. The type I bottom electrodes are used to inject carbon material into the molten bath to carburize it and promote scrap melting. The type II bottom electrodes are used to inject slag foaming powder into the molten bath to form molten slag particles in the metal liquid and increase the gas-slag-metal three-phase reaction interface area during the dephosphorization reaction. The type III bottom electrodes are used to inject gas into the molten bath to promote the material transfer of the molten bath. The system also includes a control unit connected to the bottom electrodes 8, which controls the power supply intensity of the bottom electrodes 8 and enables online adjustment of injection parameters during the smelting process.

[0026] To prevent the problems of Type I bottom electrodes, where the cooling rate of molten steel is too fast due to carburization of the molten bath, resulting in clogging at the center of the bottom electrode, and Type II bottom electrodes, where the temperature of molten steel is too high locally due to oxidation of the molten steel, resulting in accelerated hearth burnout, the present invention divides the bottom electrode into several sections, and within each section, the bottom electrode, Type I bottom electrode, Type II bottom electrode, and Type III bottom electrode are intermixed. The bottom electrode supplies energy to the molten bath, and the Type III bottom electrode is distributed to accelerate heat transfer and material transfer between the molten steel, enhance heat exchange between the slag steel, and balance the thermal effects caused by the Type I and Type II bottom electrode sections. The Type II and Type I bottom electrodes are arranged adjacent to each other, which alleviates the cooling effect of the Type I bottom electrode's reaction section on the Type II bottom electrode, allowing the temperature of the molten steel at the hearth to be quickly and uniformly neutralized, achieving the goal of synchronous burnout of each bottom electrode 8. According to the requirements of the smelting process, the proportion of the number of bottom-blown electrodes 8 of each type in each zone can be adjusted, and the distribution rate ranges from 0 to 100%.

[0027] The present invention achieves highly efficient carburization of the molten bath, rapid slag melting and slag formation, impurity removal, and powerful stirring, thereby improving production efficiency and reducing the consumption of raw materials and auxiliary materials.

[0028] Preferably, the carrier gas medium for the I-type hearth electrode is air, nitrogen or CO2, and the flow rate is 0-1000 Nm 3 / h, the carbon material is carbon powder, coke charcoal, graphite powder or other carbon-enhancing powder, the flow rate of one type I hearth electrode powder is 0~50kg / min, and the powder particle size is ≦1mm.

[0029] Preferably, the carrier gas 2 medium of the II type hearth electrode is O2, O2-N2 mixed gas or O2-CO2 mixed gas, and the carrier gas flow rate is 0-1000 Nm 3 / h, the volumetric flow rate of oxygen is 0~100%, the slag foaming powder is lime powder or limestone powder, the flow rate of one type II hearth electrode powder is 0~50kg / min, and the powder particle size is ≦1mm.

[0030] Preferably, the pure gas bottom blowing medium of the type III hearth electrode is one or more mixed gases selected from N2, Ar, CO2, and O2, and the bottom blowing intensity is 0-0.05 Nm 3 / (min·t).

[0031] Preferably, the inner diameter of the hole of the type I hearth electrode and the type II hearth electrode is 4 to 25 mm, and the inner diameter of the hole of the type III hearth electrode is 0.1 to 10 mm.

[0032] Preferably, the inner diameter of the hole of the type I hearth electrode and the type II hearth electrode is 12 mm or 14 mm, and the inner diameter of the hole of the type III hearth electrode is 4 mm or 5 mm.

[0033] Preferably, the bottom blowing connection port of the bottom blowing electrode 8 and the external medium input connection port are insulated to prevent electrical conduction with the bottom blowing electrode during the medium input process, which may cause system failure and further safety accidents.

[0034] Preferably, the bottom-blown electrode 8 is entirely attached to the bottom of the arc furnace and is further buried by a furnace bottom ramming material.

[0035] Preferably, the control unit includes a system distributor connected to the bottom-blown electrode 8 and a control system connected to the system distributor, the system distributor including a type I bottom electrode system distributor 5 and a type II bottom electrode system distributor 6 connected to the type I bottom electrode and the type II bottom electrode, respectively, and the control system including a type I bottom electrode bottom-blown control system 2 and a type II bottom electrode bottom-blown control system 3 connected to the type I bottom electrode system distributor 5 and the type II bottom electrode system distributor 6, respectively.

[0036] The present invention further provides a bottom electrode combined bottom-blowing multimedia method for a DC arc furnace, in which a part of the bottom electrode located at the bottom of the furnace is designed as a bottom-blowing electrode with a hollow structure, and one or more media selected from gas, carbon material, and slag foaming powder, which can promote the material transition of the molten bath in the furnace, are injected into the molten bath in the furnace by the bottom-blowing electrode. The injection parameters are dynamically controlled in combination with the power supply strength of the bottom-blowing electrode, thereby realizing the coordinated operation of the bottom blowing and the bottom electrode.

[0037] In this invention, some of the bottom electrodes are designed as hollow bottom-blown electrodes 8, thereby achieving a combined smelting function of current and bottom-blown multimedia. The solid part of the bottom-blown electrodes 8 supplies power to the molten bath, and the hollow part dynamically injects gas, carrier gas-carbon material, and carrier gas slag foaming powder into the molten bath, which are combined with the bottom electrode to supply power during the smelting process. The multimedia bottom blowing between the bottom-blown electrodes 8 is mutually blended, and the bottom-blown multimedia cools the bottom electrode, achieving highly efficient carburization of the molten bath, rapid slag melting and slag formation, impurity removal, and powerful stirring. At the same time, the composition and temperature of the molten bath are rapidly uniform, shortening the smelting cycle by more than 3 minutes. The metal yield is improved by 1 to 3%, the smelting end point phosphorus is ≦0.005%, the end point N is ≦50 ppm, and the alloy yield during the tapping steel alloying process is improved by 4 to 5% compared to an electric furnace without bottom blowing.

[0038] Example 1 This invention is applied to a 100-ton DC arc furnace. Figure 1 shows a schematic diagram of a bottom-blown multimedia electrode system. The bottom-blown control system 1 for the type III bottom electrode is connected to the type III bottom electrode system distributor 4, which uniformly delivers bottom-blown gas to the hollow bottom-blown electrodes 8, completing the bottom-blown gas delivery process. The bottom-blown control system 2 for the type I bottom electrode and the bottom-blown control system 3 for the type II bottom electrode are connected to the type I bottom electrode system distributor 5 and the type II bottom electrode system distributor 6, respectively. Each distributor is connected to a corresponding bottom-blown electrode 8. Powder is uniformly delivered to each bottom-blown electrode 8 by the distributor, completing the carbon increase and dephosphorization process. An insulating joint 7 is installed on the delivery pipe between the distributor and the bottom-blown electrode 8 to ensure the safety of the injection system. All the bottom electrodes are connected to a bottom electrode conductive copper bus bar 10, and a bottom-blowing electrode cold air intake port 9 is provided on the electrode bottom plate.

[0039] The bottom electrodes are air-cooled, needle-type, bottom-blown electrodes 8. The bottom electrodes are arranged in a circular pattern on the bottom plate. They are 50 mm in diameter and made of stainless steel. As shown in Figure 2, the bottom electrode area is divided into two reaction zones by the solid lines in the figure. Zone 1 consists of three Type I bottom electrodes, two Type II bottom electrodes, and two Type III bottom electrodes. Zone 2 consists of two Type I bottom electrodes, two Type II bottom electrodes, and two Type III bottom electrodes. The adjacent arrangement of the Type II and Type I bottom electrodes neutralizes the local cold effect caused by the Type I bottom electrodes and ensures synchronous erosion of the bottom electrodes. The Type III bottom electrodes are arranged independently, accelerating the flow at the bottom of the molten bath and enhancing the heat exchange between the slag and molten steel. The inner diameter of the Type III bottom electrode hole is 4 mm, and the inner diameters of the Type I and Type II bottom electrode holes are 12 mm.

[0040] Carbon powder and lime powder are used as the carbon material and slag foaming powder, respectively, with a powder particle size of 200 μm. The powder injection rate for one bottom electrode 8 is 0 to 20 kg / min. The carrier gas 1 for the type I hearth electrode is air, and the carrier gas 2 for the type II hearth electrode is O2. The gas flow rate for one bottom electrode 8 is 50 to 500 Nm 3 The bottom-blown stirring gas is Ar, and the gas flow rate of one Class III bottom electrode is 50 to 400 NL / min.

[0041] The process diagrams for one type I bottom electrode, type II bottom electrode and type III bottom electrode are shown in Figure 3, Figure 4 and Figure 5 respectively, and the specific steps are as follows:

[0042] (1) 0-5 min, during the raw material charging stage into the arc furnace, the I-type hearth electrode and the II-type hearth electrode respectively blow air and oxygen into the molten bath, with a flow rate of 50 Nm 3 / h, the Class III bottom electrode blew air into the molten bath at a flow rate of 50 NL / min to prevent clogging of the bottom electrode 8.

[0043] (2) From 6 to 12 minutes, during the carbon increase stage of the molten bath, the I-class hearth electrode injected air-carbon powder into the molten bath, with the powder injection rate of 5 kg / min and the air flow rate of 150 Nm 3 / h. The type II hearth electrode injects oxygen-lime powder into the molten bath at a rate of 2 kg / min and an oxygen flow rate of 100 Nm 3 The type III bottom electrode injects Ar into the molten bath at a flow rate of 100 NL / min.

[0044] (3) 13-20 min: As the scrap melts, the height of the molten bath rises. To promote the melting of the scrap, the I-type hearth electrode blows air-carbon powder into the molten bath. The powder blowing rate is 15 kg / min, and the air flow rate is 200 Nm 3 / h, the carburizing rate of the molten bath was increased. At the same time, the II-type hearth electrode injected oxygen-lime powder into the molten bath, the powder injection rate was 4 kg / min, and the oxygen flow rate was 150 Nm 3The molten steel was dephosphorized at a rate of 100 NL / min. The type III hearth electrode injected Ar into the molten bath at a flow rate of 100 NL / min, accelerating the flow of the molten bath.

[0045] (4) 21-25 min, in the melting stage of the arc furnace, the II type hearth electrode injects oxygen-lime powder into the melting bath, the powder injection rate is 20 kg / min, and the oxygen flow rate is 300 Nm 3 / h, and the molten steel was subjected to rapid deep dephosphorization. The I-class hearth electrode was used to inject air-carbon powder into the molten bath at a powder injection rate of 4 kg / min and an air flow rate of 100 Nm 3 The mass transfer in the molten bath was accelerated by the carbon-oxygen reaction at a flow rate of 200 NL / min. The type III hearth electrode injected Ar into the molten bath.

[0046] (5) From 26 to 31 minutes, the arc furnace melting bath was in the temperature-raising stage, and the I-class hearth electrode injected air-carbon powder into the melting bath, with the powder injection rate of 10 kg / min and the air flow rate of 150 Nm 3 / h. The type II hearth electrode injects oxygen-lime powder into the molten bath, with the powder injection rate of 10 kg / min and the oxygen flow rate of 300 Nm 3 / h, the type III hearth electrode injected O2-CO2 mixed gas into the molten bath, with a CO2 volume ratio of 20% and a flow rate of 300NL / min, which strengthened the reaction of the molten bath.

[0047] (6) 32-35 min, type I hearth bottom electrode, air-carbon powder injection into the molten bath, powder injection rate 8 kg / min, air flow rate 100 Nm 3 / h. The type II hearth electrode injects oxygen-lime powder into the molten bath at a powder injection rate of 5 kg / min and a carrier gas flow rate of 100 Nm 3 / h, the type III hearth electrode injects O2-CO2 into the molten bath, the flow rate is 200NL / min, and the CO2 volume ratio is 30%.

[0048] (7) 36-38 min, the arc furnace was tapped, and the I-type hearth electrode and the II-type hearth electrode were respectively blowing air and O2 into the molten bath, with a flow rate of 50 Nm 3 / h, the type III bottom electrode blew Ar into the molten bath at a flow rate of 50 NL / min to prevent clogging of the bottom electrode 8.

[0049] By using the method of the present invention, the smelting cycle of an electric arc furnace was shortened by 5 minutes, the electricity consumption per ton of steel was reduced by 10 kWh, the phosphorus content in molten steel was controlled to 0.005% or less, the nitrogen content was controlled to 50 ppm or less, the metal yield was improved by 2%, the alloy yield during the tapping alloying process was improved by an average of 3%, the cleanliness of molten steel was significantly improved, and the smelting rhythm was significantly improved.

[0050] Example 2 This invention is applied to a 150-ton continuous-charging DC arc furnace. The bottom electrode is an air-cooled, needle-type, bottom-blown electrode 8. The bottom electrode is arranged in a strip pattern on the bottom plate, has a diameter of 50 mm, and is made of stainless steel. As shown in Figure 6, the bottom electrode area is divided into four reaction zones by the dashed lines in the figure. Each zone contains two Type I bottom electrodes, two Type II bottom electrodes, and one Type III bottom electrode, while the rest are solid bottom electrodes. The adjacent arrangement of the Type II and Type I bottom electrodes neutralizes the local cold effect caused by the Type I bottom electrode and ensures synchronous erosion of the bottom electrode. The Type III bottom electrode is arranged independently to accelerate the flow at the bottom of the molten bath and enhance heat exchange between the claps. The inner diameter of the Type III bottom electrode hole is 5 mm, and the inner diameters of the Type I and Type II bottom electrode holes are 14 mm.

[0051] The carbon material and slag powder are graphite powder and lime powder, respectively, and the particle size of the powder is 100 μm. The powder injection rate of one bottom-blown electrode 8 is 0 to 20 kg / min. Carrier gas 1 is air, carrier gas 2 is oxygen, and the gas flow rate of one bottom-blown electrode 8 is 50 to 500 Nm 3 The bottom-blown stirring gas was Ar, and the gas flow rate of one Class III bottom electrode was 50 to 400 NL / min. The procedure for each stage was as follows:

[0052] (1) 0-8 min, during the raw material charging stage into the arc furnace, the I-class hearth electrode blows air-graphite powder into the molten bath, the powder blowing rate is 10 kg / min, and the air flow rate is 150 Nm 3 / h, and increased carbon in the molten bath. The type II hearth electrode injected oxygen-lime powder into the molten bath at a powder blowing rate of 2 kg / min and an oxygen flow rate of 100 Nm 3 / h, the type III bottom electrode blew Ar into the molten bath at a flow rate of 100 NL / min to prevent clogging of the bottom blown electrode 8.

[0053] (2) From 9 to 22 minutes, as the scrap melts, the height of the molten bath rises. To promote the melting of the scrap, the I-type hearth electrode blows air-graphite powder into the molten bath. The powder blowing rate is 20 kg / min, and the air flow rate is 200 Nm 3 / h, increasing the carburizing rate of the molten bath. At the same time, the II-type hearth electrode injects oxygen-lime powder into the molten bath, with the powder injection rate of 6 kg / min and the oxygen flow rate of 150 Nm 3 The molten steel was dephosphorized at a rate of 150 NL / min. The type III hearth electrode injected Ar into the molten bath at a flow rate of 150 NL / min, accelerating the flow of the molten bath.

[0054] (3) From 23 to 26 minutes, the arc furnace was in the melting stage, and the type II bottom electrode injected oxygen-lime powder into the melting bath. The powder injection rate was 25 kg / min, and the oxygen flow rate was 300 Nm 3 / h, the molten steel was rapidly and deeply dephosphorized. The I-type hearth electrode was blown into the molten bath with air-graphite powder, the powder injection rate was 6 kg / min, and the air flow rate was 120 Nm 3 The mass transfer in the molten bath was accelerated by the carbon-oxygen reaction at a flow rate of 250 NL / min.

[0055] (4) From 27 to 30 minutes, the arc furnace melting bath was in the temperature-raising stage, and the I-class bottom electrode injected air-graphite powder into the melting bath, with the powder injection rate of 10 kg / min and the air flow rate of 150 Nm 3 / h. The type II hearth electrode injects oxygen-lime powder into the molten bath, with the powder injection rate of 10 kg / min and the oxygen flow rate of 300 Nm3 / h. The type III bottom electrode injected O2-CO2 mixed gas into the molten bath, with a CO2 volume ratio of 30% and a flow rate of 400 NL / min, to enhance the reaction of the molten bath.

[0056] (5) 31-33 min, type I hearth bottom electrode, air-carbon powder was injected into the molten bath, powder injection rate was 8 kg / min, air flow rate was 100 Nm 3 / h. The type II hearth electrode injects oxygen-lime powder into the molten bath at a powder injection rate of 5 kg / min and a carrier gas flow rate of 100 Nm 3 / h. The type III hearth electrode injected O2-CO2 into the molten bath at a flow rate of 250 NL / min and a CO2 volume ratio of 30%, to prevent local overoxidation of the molten steel.

[0057] (6) 34-37 min, the arc furnace was tapped, and the I-type hearth electrode and the II-type hearth electrode were respectively blowing air and O2 into the molten bath, with a flow rate of 50 Nm 3 / h, the type III bottom electrode blew Ar into the molten bath at a flow rate of 50 NL / min to prevent clogging of the bottom electrode 8.

[0058] By using the method of the present invention, the smelting cycle of an electric arc furnace was shortened by 7 minutes, the electricity consumption per ton of steel was reduced by 15 kWh, the phosphorus content in molten steel was controlled to less than 0.004%, the nitrogen content was controlled to less than 50 ppm, the metal yield was improved by 1%, the alloy yield during the tapping alloying process was improved by an average of 4%, the cleanliness of the molten steel was significantly improved, and the smelting rhythm was significantly improved.

[0059] This invention is suitable for 10-1000t DC arc furnaces. It utilizes multiple bottom-blown electrodes (8) mounted on the bottom electrode base plate to achieve a combined current and bottom-blown multi-purpose smelting function. The bottom electrodes are connected for power supply during the smelting process, while the bottom-blown electrodes (8) dynamically inject gases (Carrier Gas 1 - carbon material and Carrier Gas 2 - slag foaming powder) into the molten bath. This multi-purpose technology not only alleviates overheating of the molten bath in the bottom electrode area, but also achieves highly efficient carburization of the molten bath, rapid slag melting and slag formation, impurity removal, and powerful stirring. It also rapidly homogenizes the molten bath's composition and temperature, shortening the smelting cycle by more than 3 minutes. Carbon powder yields are improved, metal yields are increased by 1-3%, and alloy yields during the tapping process are improved by 4-5% compared to electric furnaces without bottom-blown smelting. End-point phosphorus is less than 0.005%, and end-point nitrogen is less than 50 ppm.

[0060] Finally, the above examples are intended to illustrate but not limit the technical idea of ​​the present invention, and the present invention has been described in detail with reference to preferred embodiments. However, those skilled in the art will understand that the technical idea of ​​the present invention can be modified or equivalently changed without departing from the spirit and scope of the technical idea of ​​the present invention, and that these modifications and equivalent changes are included in the scope of the claims of the present invention. [Explanation of symbols]

[0061] 1. Type III bottom electrode bottom blowing control system 2. Type I hearth electrode bottom blowing control system 3. Type II bottom electrode bottom blowing control system 4. Type III hearth electrode system distributor 5. Type I hearth bottom electrode system distributor 6. Type II hearth electrode system distributor 7. Insulated joints 8 Bottom blown electrode 9 Bottom-blowing electrode cold air intake 10. Furnace bottom electrode conductive copper bus bar

Claims

1. The bottom electrodes are located at the bottom of the furnace and are a plurality of steel needle-type bottom electrodes, and some of the steel needles among the plurality of steel needle-type bottom electrodes can be hollow as needed. The hollow steel needle-type bottom electrodes are a plurality of bottom electrodes that are one or more of type I, type II, and type III contact needles, and the contact needles can be used to inject lime, etc. as a carbon-increasing powder or a slag foaming powder in a composite manner, and multiple gas media can be used as carrier gases as needed. a type I stylus for injecting carbon material into the molten bath to carburize the bath and promote melting of the scrap; A type II stylus for injecting slag foaming powder into the molten bath to form molten slag particles in the metal liquid and increase the gas-slag-metal three-phase reaction boundary area during the dephosphorization reaction process; a type III stylus for injecting gas into the molten bath to promote material transition in the molten bath; Further comprising a control unit connected to the bottom blown electrode for controlling the power supply intensity of the bottom blown electrode and realizing online adjustment of blowing parameters during the smelting process; The type II stylus and the type I stylus are arranged adjacent to each other so as to neutralize the local cold effect caused by the type I stylus; The type III stylus is distributed so as to promote the flow at the bottom of the molten bath and enhance the heat exchange between the slag and the molten steel. Bottom electrode combined bottom blowing multimedia system for DC arc furnaces.

2. The carrier gas medium of the type I stylus is air, nitrogen or CO ２ and The carbon material is carbon powder, coke charcoal, graphite powder or other carbon-enhancing powder; 2. The bottom electrode combined bottom blowing multimedia system for a DC arc furnace according to claim 1.

3. The carrier gas medium of the type II stylus is O ２ , O ２ -N ２ Mixed gas or O ２ -CO ２ It is a mixed gas, The slag foaming powder is lime powder or limestone powder, 2. The bottom electrode combined bottom blowing multimedia system for a DC arc furnace according to claim 1.

4. The inner diameter of the hole of the type I stylus and the type II stylus is 4 to 25 mm, and the inner diameter of the hole of the type III stylus is 0.1 to 10 mm.

2. The bottom electrode combined bottom blowing multimedia system for a DC arc furnace according to claim 1.

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