Method for improving raw material yield, smelting efficiency and molten steel cleanliness of DRI electric arc furnace

Abstract

The invention provides a method for improving the raw material yield, the smelting efficiency and the molten steel cleanliness of a DRI electric arc furnace, which comprises the following steps of: filling a smelting raw material containing waste steel into the electric arc furnace, starting a power supply, and inputting electric energy into the electric arc furnace through an electrode; an electric arc furnace wall oxygen lance is used for supplying oxygen into the electric arc furnace; after a molten pool is formed in the electric arc furnace, directly reducing iron is continuously added, and oxygen and DRI fine materials are blown into the molten pool through an oxygen lance on the wall of the electric arc furnace; after the direct reduced iron completely enters the molten pool, limestone is added to the surface of the molten pool for slagging; limestone is continuously added into the electric arc furnace for slagging; blowing oxygen and DRI fine materials into the molten pool by using an oxygen lance on the wall of the electric arc furnace; and oxygen and DRI fine materials are continuously blown into the molten pool through the furnace wall oxygen lance of the electric arc furnace. According to the method, the smelting efficiency of the electric arc furnace and the cleanliness of molten steel are synchronously improved while efficient utilization of the DRI fine materials in the smelting process of the electric arc furnace is achieved and the yield of the DRI fine materials is improved.

Description

Technical Field

[0001] The invention relates to a method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in a DRI electric arc furnace, and belongs to the technical field of electric arc furnace steelmaking. Background Art

[0002] At present, the development of electric arc furnace steelmaking is an inevitable choice for the green, low-carbon and high-quality development of the steel industry. Electric arc furnace steelmaking uses scrap steel as the main raw material. However, due to the imperfect system of scrap steel recycling, processing and utilization, scrap steel resources are difficult to meet the needs of electric arc furnace steelmaking. Direct reduced iron (DRI), as a clean and high-quality steelmaking raw material, can replace scrap steel as a raw material for electric arc furnace steelmaking under the current shortage of scrap steel resources.

[0003] However, with the increasing scarcity of high-quality iron ore resources, the phosphorus content in the ore is high. In the hydrogen-based direct reduction process, it is difficult to effectively remove the phosphorus in the ore, resulting in a high phosphorus content in the direct reduced iron entering the electric arc furnace, reaching 0.15%, which seriously affects the quality of the molten steel smelted in the electric arc furnace. High phosphorus content can cause cold brittleness in steel and ultimately affect the performance of steel. On the other hand, during the smelting process of the electric arc furnace, the high temperature of the arc will ionize nitrogen in the air, thereby increasing nitrogen in the molten steel. Due to the low carbon content in the molten steel after the electric arc furnace is smelted, the lack of CO reaction, and the poor denitrification kinetic conditions, the nitrogen content in the molten steel of the electric arc furnace is basically stable at 60ppm and above, which is difficult to meet the requirements of high-quality steel for a nitrogen content of no more than 25ppm. In addition, the CO reaction intensity in the molten pool of the electric arc furnace is low, and the stirring capacity of the molten pool is poor, resulting in low convective heat transfer efficiency between the molten steel and the metal raw materials in the molten pool, poor smelting efficiency, and long smelting time. Therefore, how to efficiently and synergistically improve the smelting efficiency of electric arc furnaces and the cleanliness of molten steel is an important factor in increasing the market share of electric furnace steelmaking.

[0004] During the charging process of the DRI electric arc furnace, due to the insufficient strength of DRI, a part of DRI will be broken into powdery DRI fines during transportation and charging. In the past, the DRI fines were usually added directly to the electric arc furnace or collected and returned to the direct reduced iron manufacturing process, which not only increased the process and cost, but also reduced the yield of DRI. In addition, if this part of the DRI fines is directly added to the electric arc furnace, it will float on the surface of the electric arc furnace slag and will not easily enter the molten steel, resulting in insufficient metal raw material yield in the electric arc furnace. If this part of the DRI fines is collected and returned to the DRI pelletizing process, the operating process will be increased and the manufacturing cost of DRI will be increased. In addition, with the increasingly fierce competition between the electric arc furnace steelmaking process and the blast furnace-converter steelmaking process in terms of smelting efficiency, smelting cost, molten steel cleanliness, market share, etc., and the requirements for nitrogen and phosphorus content of high-quality special steels are gradually increasing, the efficient and coordinated improvement of the DRI electric arc furnace smelting efficiency and molten steel cleanliness is the focus and difficulty of the DRI electric arc furnace smelting process, and it is also a technical problem that urgently needs to be solved. Therefore, how to economically and conveniently utilize the DRI fines produced in the DRI arc furnace charging process and improve the utilization rate of DRI is also a technical problem that must be paid attention to and solved in the DRI arc furnace smelting process.

[0005] The following briefly introduces some prior arts that are relatively relevant to the present invention, so that those skilled in the art can better understand the status of the prior arts and the disadvantages of the prior arts.

[0006] CN118240992A discloses a method for smelting all scrap steel in an electric arc furnace by adding DRI, which solves the problem of deep dephosphorization in high-proportion DRI smelting in an electric arc furnace by optimizing the scrap steel distribution and smelting process in the electric arc furnace, coupling control of power supply, oxygen supply and carbon injection in multiple steps, adding lime and dolomite in multiple batches, and creating a good foam slag state. Although this method can solve the problem of dephosphorization in high-proportion DRI smelting in an electric arc furnace, it fails to simultaneously solve the technical problem of denitrification and nitrogen control of molten steel in an electric arc furnace, and fails to propose a utilization plan for crushed DRI fines.

[0007] CN116837173A discloses a method for controlling nitrogen content in a low-slag smelting process of direct reduced iron in an electric arc furnace, which sprays calcium carbide powder into the molten pool at the end of the melting and oxidation period of the electric arc furnace using a furnace door carbon oxygen gun, and uses the calcium carbide powder to react with oxygen in the molten steel to generate CO bubbles, thereby achieving the purpose of denitrification of the molten steel. In addition, the generated CaO helps to improve the basicity of the slag and increase the dephosphorization capacity of the slag. Although this method can solve the problems of denitrification and dephosphorization of high-proportion DRI steelmaking in the electric arc furnace, since the calcium carbide powder is sprayed into the molten pool through the furnace door carbon oxygen gun of the electric arc furnace, the depth of the sprayed powder entering the molten pool is limited, resulting in the difficulty of the generated CO gas in stirring the bottom of the molten pool, the poor convective heat transfer efficiency between the molten steel and the scrap steel, and the poor smelting efficiency of the electric arc furnace. In addition, this method is also difficult to economically and efficiently utilize the fine materials generated by the DRI crushing during the charging process of the electric arc furnace, thereby reducing the yield of DRI.

[0008] Therefore, providing a new method for improving the raw material recovery rate, smelting efficiency and steel liquid cleanliness of the DRI arc furnace has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0009] In order to solve the above-mentioned shortcomings and deficiencies, the object of the present invention is to provide a method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in a DRI electric arc furnace.

[0010] In order to achieve the above objectives, on the one hand, the present invention provides a method for improving the raw material recovery rate, smelting efficiency and steel liquid cleanliness of a DRI arc furnace, wherein the method comprises:

[0011] S1: Arc starting period and main melting period

[0012] S11: loading smelting raw materials including scrap steel into an electric arc furnace, starting a power supply, and inputting electric energy into the electric arc furnace through electrodes; S12: supplying oxygen into the electric arc furnace using an oxygen lance on the wall of the electric arc furnace; S13: after a molten pool is formed in the electric arc furnace, continuously adding direct reduced iron, and using an oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool; S14: after all the direct reduced iron enters the molten pool, adding limestone to the surface of the molten pool to make slag;

[0013] S2: End of Melting

[0014] S21: continue to add limestone into the electric arc furnace to form slag; S22: use the oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool;

[0015] S3: Oxidation period

[0016] Continue to use the arc furnace wall oxygen lance to spray oxygen and DRI fine material into the molten pool.

[0017] As a specific implementation of the above method of the present invention, in S11, the power supply intensity of the power supply is 0.6-1.2 MVA / t steel.

[0018] In S11 of the above method of the present invention, the smelting raw materials including scrap steel are loaded into an electric arc furnace, the power supply is started, electric energy is input into the electric arc furnace through the electrode, and an arc is generated between the electrode end and the charge to heat and melt the scrap steel.

[0019] In S11 of the above method of the present invention, the smelting raw materials containing scrap steel may be, for example, molten iron and scrap steel.

[0020] As a specific embodiment of the method described above, in S12, the oxygen supply intensity is 0.9-2.5Nm 3 / (min·t steel).

[0021] In S12 of the above method of the present invention, oxygen is supplied into the electric arc furnace by an oxygen lance on the wall of the electric arc furnace so as to cut and melt the scrap steel.

[0022] As a specific embodiment of the method described above, in S13, based on the total weight of the smelting raw materials including scrap steel and the direct reduced iron as 100%, the amount of the direct reduced iron added is 20-50%, and / or the oxygen supply intensity (oxygen injection rate) is 0.7-1.6 Nm 3 / (min·t-steel), and / or the particle size of the DRI fine material is less than 4 mm, the blowing rate is 0.5-1.0 kg / (min·t-steel), and the amount of the DRI fine material is 10-18 kg / t-steel.

[0023] As a specific implementation of the above method of the present invention, in S14, the amount of limestone used is 20-25 kg / t steel.

[0024] As a specific implementation of the above method of the present invention, in S21, the amount of limestone used is 12-18 kg / t steel.

[0025] As a specific embodiment of the method described above, in S22, the oxygen supply intensity (oxygen blowing rate) is 0.9-1.5Nm 3 / (min·t steel).

[0026] As a specific embodiment of the above method of the present invention, in S22, the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.7-1.2 kg / (min·t steel), and the amount of DRI fine material is 3.5-6 kg / t steel.

[0027] As a specific embodiment of the method described above, in S3, the oxygen supply intensity (oxygen blowing rate) is 1.0-2.0 Nm3 / (min·t steel).

[0028] As a specific embodiment of the above method of the present invention, in S3, the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.3-0.8 kg / (min·t steel), and the amount of DRI fine material is 3-7 kg / t steel.

[0029] In the present invention, the "steel" involved in the units of relevant parameters refers to the finished molten steel obtained by smelting.

[0030] The technical solution of the present invention has at least the following beneficial effects:

[0031] The method provided by the present invention uses an electric arc furnace wall oxygen lance to spray DRI fines (preferably DRI fines with a particle size of less than 4 mm) generated during the DRI feeding process into the molten pool during the electric arc furnace smelting process. The carbon in the DRI fines contacts the molten steel and reacts rapidly to generate a large number of CO bubbles. These large numbers of CO bubbles can accelerate the stirring of the molten pool, improve the heat transfer efficiency between the molten steel and the scrap steel, help the scrap steel to melt quickly, and improve the melting rate of the scrap steel and the smelting efficiency of the electric arc furnace; and the generated CO bubbles can carry nitrogen in the molten steel during the floating process, and remove the nitrogen in the molten steel. In addition, the FeO contained in the DRI fines helps to improve the oxidizability of the molten steel, helps the oxidative dephosphorization of the molten steel, and reduces the phosphorus content of the molten steel. In addition, the iron powder in the DRI fines melts in the electric arc furnace molten pool, which can improve the yield of DRI.

[0032] In summary, the method provided by the present invention not only solves the problem of efficient utilization of DRI fine materials in the electric arc furnace smelting process and improves its yield, but also simultaneously improves the smelting efficiency of the electric arc furnace and the cleanliness of the molten steel, which is conducive to the green and efficient development of DRI electric arc furnace steelmaking. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of the structure of the equipment used in the method for improving the raw material recovery rate, smelting efficiency and steel liquid cleanliness of a DRI arc furnace provided in a specific embodiment of the present invention.

[0035] Description of main figures:

[0036] 1. Electric arc furnace; 2. Electrode; 3. Furnace wall oxygen spray gun / furnace wall oxygen lance; 4. Molten steel; 5. Slag; 6. Direct reduced iron; 7. Eccentric bottom tapping (EBT) system; 8. Control system; 9. Gas supply system; 10. Powder spraying system; 11. Oxygen storage tank; 12. Air flow control system; 13. DRI fine powder storage tank; 14. Powder flow controller; 15. Gas and / or powder delivery pipeline. DETAILED DESCRIPTION

[0037] It should be noted that the term "comprises" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] "Scope" disclosed in the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, for a specific parameter, a range of 60-120 and 80-110 is listed, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​listed are 1 and 2, and the maximum range values ​​listed are 3, 4 and 5, then the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0039] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0040] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0041] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0042] In the present invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0043] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments described below are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially. In the embodiment, the smelting yield of DRI = the weight of the finished steel liquid obtained by smelting / (the total weight of molten iron, scrap steel and DRI) × 100%.

[0044] According to a specific embodiment of the present invention, the method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in a DRI electric arc furnace comprises the following steps:

[0045] S1: Arc starting period and main melting period

[0046] S11: loading smelting raw materials including scrap steel into an electric arc furnace, starting a power supply, inputting electric energy into the electric arc furnace through electrodes, generating an electric arc between the electrode ends and the charge to heat and melt the scrap steel, and the power supply intensity of this process is 0.6-1.2 MVA / t steel;

[0047] S12: Use the oxygen lance on the wall of the electric arc furnace to supply oxygen to the electric arc furnace for cutting and melting scrap steel. The oxygen supply intensity is 0.9-2.5Nm 3 / (min·t steel);

[0048] S13: After a molten pool is formed in the electric arc furnace, direct reduced iron is continuously added, and oxygen and DRI fines are sprayed into the molten pool using an oxygen lance on the wall of the electric arc furnace. Based on the total weight of the smelting raw materials including scrap steel and direct reduced iron as 100%, the amount of direct reduced iron added is 20-50%, and the oxygen supply intensity is 0.7-1.6Nm 3 / (min·t steel), the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.5-1.0 kg / (min·t steel), and the amount of the DRI fine material is 10-18 kg / t steel;

[0049] S14: After all the direct reduced iron enters the molten pool, limestone is added to the surface of the molten pool to make slag, wherein the amount of the limestone is 20-25 kg / t steel;

[0050] S2: End of Melting

[0051] S21: continue to add limestone into the electric arc furnace to make slag, the amount of the limestone is 12-18kg / t steel;

[0052] S22: Use the oxygen lance on the wall of the arc furnace to spray oxygen and DRI fine material into the molten pool, and the oxygen supply intensity is 0.9-1.5Nm 3 / (min·t steel), the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.7-1.2 kg / (min·t steel), and the amount of the DRI fine material is 3.5-6 kg / t steel;

[0053] S3: Oxidation period

[0054] Continue to use the arc furnace wall oxygen lance to spray oxygen and DRI fine material into the molten pool, and the oxygen supply intensity is 1.0-2.0Nm 3 / (min·t-steel), the particle size of the DRI fine material is less than 4 mm, the blowing rate is 0.3-0.8 kg / (min·t-steel), and the amount of the DRI fine material is 3-7 kg / t-steel.

[0055] According to a specific embodiment of the present invention, the structural schematic diagram of the equipment used in the method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in the DRI electric arc furnace of the present invention is as follows: Figure 1 As shown, the device includes:

[0056] Electric arc furnace 1, control system 8, gas supply system 9, powder spraying system 10 and gas and / or powder conveying pipeline 15;

[0057] The control system 8 may use a computer to monitor and control various process parameters in the method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in the DRI electric arc furnace;

[0058] The gas supply system 9 includes an oxygen storage tank 11 and an air flow control system 12;

[0059] The powder spraying system 10 includes a DRI fine powder storage tank 13 and a powder flow controller 14;

[0060] The electric arc furnace 1 is provided with at least a plurality of furnace wall oxygen spray guns / furnace wall oxygen lances 3, electrodes 2 and an eccentric bottom tapping (EBT) system 7; during use, the electric arc furnace 1 contains molten steel 4, slag 5 and direct reduced iron 6;

[0061] The oxygen storage tank 11 and the DRI fine powder storage tank 13 are connected to the gas and / or powder delivery pipeline 15 via the airflow control system 12 and the powder flow controller 14 respectively; the gas and / or powder delivery pipeline 15 is connected to a plurality of furnace wall oxygen supply spray guns / furnace wall oxygen guns 3.

[0062] The technical solution of the present invention is described in detail below in conjunction with embodiments and comparative examples.

[0063] Example 1

[0064] This embodiment provides a method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in a DRI electric arc furnace.

[0065] For the 120t Considy electric arc furnace, the transformer capacity is 175MVA, 20wt% direct reduced iron is used for smelting, and 4 furnace wall oxygen lances are configured, with a lance power of 5MW and a flow rate of 3600Nm 3 / h, steel tapping temperature ≥1610℃.

[0066] The method of this embodiment adopts Figure 1 The device shown comprises the following steps:

[0067] Step 1): During the smelting cycle of the electric arc furnace for 0-16 minutes, 40 tons of molten iron and 56 tons of scrap steel are added to the furnace, and the power supply is started with a power supply intensity of 1.0 MVA / t steel; oxygen is supplied to the furnace through an oxygen lance on the wall of the electric arc furnace with an oxygen supply intensity of 2.0 Nm 3 / (min·t steel); When all the scrap steel in the arc furnace enters the molten pool, 24t of DRI is continuously added into the molten pool. At this time, oxygen and DRI fines are sprayed into the molten pool using the furnace wall oxygen lance. The oxygen spray rate is 1.4Nm 3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 1.0kg / (min·t-steel), and the dosage is 16kg / t-steel; when all the direct reduced iron enters the molten pool, limestone is added to the surface of the molten pool to make slag, and the dosage is 20kg / t-steel.

[0068] Step 2): During the 17-22min smelting cycle of the electric arc furnace, continue to add limestone into the molten pool at a dosage of 15kg / t steel; use the oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool at a rate of 1.2Nm 3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 1.0kg / (min·t-steel), and the dosage is 5kg / t-steel.

[0069] Step 3): During the arc furnace smelting cycle of 23-37 minutes, oxygen and DRI fines are sprayed into the molten pool using the arc furnace wall oxygen lance. The oxygen spray rate is 2.0 Nm 3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 0.5kg / (min·t-steel), and the dosage is 6kg / t-steel.

[0070] Step 4): The arc furnace smelting cycle is 38-41 minutes, and steel is tapped from the arc furnace.

[0071] After adopting the method of this embodiment, the arc furnace smelting cycle is 41 minutes, the nitrogen content of the final molten steel is 36 ppm, the phosphorus content is 194 ppm, and the smelting yield of DRI is 92.4%.

[0072] Example 2

[0073] This embodiment provides a method for improving the raw material recovery rate, smelting efficiency and cleanliness of molten steel in a DRI electric arc furnace.

[0074] For the 120t Considy electric arc furnace, the transformer capacity is 175MVA, 30wt% direct reduced iron is used for smelting, and 4 furnace wall oxygen lances are configured, with a lance power of 5MW and a flow rate of 3600Nm 3 / h, steel tapping temperature ≥1610℃.

[0075] The method of this embodiment adopts Figure 1 The device shown comprises the following steps:

[0076] Step 1): During the smelting cycle of the electric arc furnace for 0-18 minutes, add 40 tons of molten iron and 44 tons of scrap steel into the furnace, start the power supply, and the power supply intensity is 0.9 MVA / t steel; use the oxygen lance on the wall of the electric arc furnace to supply oxygen into the furnace, and the oxygen supply intensity is 1.8 Nm 3 / (min·t steel); When all the scrap steel in the arc furnace enters the molten pool, 36t of DRI is continuously added into the molten pool. At this time, oxygen and DRI fines are sprayed into the molten pool using the furnace wall oxygen lance. The oxygen spray rate is 1.6Nm 3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 0.6kg / (min·t-steel), and the dosage is 10.8kg / t-steel; when all the direct reduced iron enters the molten pool, limestone is added to the surface of the molten pool to make slag, and the dosage is 20kg / t-steel.

[0077] Step 2): During the 19-24min smelting cycle of the electric arc furnace, continue to add limestone into the molten pool at a dosage of 17kg / t steel; use the oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool at a rate of 1.0Nm3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 1.1kg / (min·t-steel), and the dosage is 5.5kg / t-steel.

[0078] Step 3): During the arc furnace smelting cycle of 25-40 minutes, oxygen and DRI fines are sprayed into the molten pool using the arc furnace wall oxygen lance. The oxygen spray rate is 1.8 Nm 3 / (min·t-steel), the particle size of DRI fine material is less than 4mm, the blowing rate is 0.4kg / (min·t-steel), and the dosage is 4.8kg / t-steel.

[0079] Step 4): During the arc furnace smelting cycle of 41-44 minutes, steel is tapped from the arc furnace.

[0080] After adopting the method of this embodiment, the arc furnace smelting cycle is 44 minutes, the nitrogen content of the final molten steel is 33ppm, the phosphorus content is 204ppm, and the smelting yield of DRI is 91.7%.

[0081] Comparative Example 1

[0082] This comparative example provides a method for direct reduction of iron in an electric arc furnace.

[0083] For the 120t Considy electric arc furnace, the transformer capacity is 175MVA, 20% direct reduced iron is used for smelting, and 4 furnace wall oxygen lances are configured, with a lance power of 5MW and a flow rate of 3600Nm 3 / h, steel tapping temperature ≥1610℃.

[0084] The method of this comparative example also adopts Figure 1 The device shown comprises the following steps:

[0085] Step 1): During the 0-20min smelting cycle of the electric arc furnace, 40t of molten iron and 44t of scrap steel are added to the furnace, and the power supply is started with a power supply intensity of 0.9MVA / t steel; oxygen is supplied to the furnace through an oxygen lance on the wall of the electric arc furnace with an oxygen supply intensity of 1.8Nm 3 / (min·t steel); when all the scrap steel in the arc furnace enters the molten pool, 36t of DRI is continuously added to the molten pool. At this time, the oxygen supply intensity is adjusted to 1.6Nm 3 / (min·t steel); when all the direct reduced iron enters the molten pool, limestone is added to the surface of the molten pool to make slag, with the amount being 20kg / t steel.

[0086] Step 2): During the smelting period of the electric arc furnace for 21-30 minutes, continue to add limestone into the molten pool at an amount of 17 kg / t steel; use the oxygen lance on the wall of the electric arc furnace to spray oxygen and carbon powder into the molten pool at an oxygen spray rate of 1.0 Nm 3 / (min·t steel), the blowing rate of carbon powder is 0.6kg / (min·t steel).

[0087] Step 3): During the arc furnace smelting cycle of 31-46 minutes, oxygen and carbon powder are sprayed into the molten pool using the arc furnace wall oxygen lance. The oxygen spray rate is 1.8 Nm 3 / (min·t steel), the blowing rate of carbon powder is 0.3kg / (min·t steel).

[0088] Step 4): After the arc furnace smelting cycle is 47-49 minutes, steel is tapped from the arc furnace.

[0089] In this comparative example, the arc furnace smelting cycle was 49 minutes, the nitrogen content of the final molten steel was 41 ppm, the phosphorus content was 212 ppm, and the smelting yield of DRI was 88.7%.

[0090] By comparing the experimental results obtained from Example 1-Example 2 and Comparative Example 1, it can be seen that compared with Comparative Example 1, the electric arc furnace smelting cycle in Example 1-Example 2 of the present invention is shorter, the nitrogen content and phosphorus content of the final molten steel are lower, and the smelting yield of DRI is higher.

[0091] In the method provided by the embodiment of the present invention, during the arc furnace smelting process, the DRI fines (preferably DRI fines with a particle size of less than 4 mm) generated during the DRI feeding process are sprayed into the molten pool by the arc furnace wall oxygen lance. The carbon in the DRI fines reacts rapidly with the molten steel to generate a large number of CO bubbles. These large numbers of CO bubbles can accelerate the stirring of the molten pool, improve the heat transfer efficiency between the molten steel and the scrap steel, help the scrap steel to melt quickly, and improve the melting rate of the scrap steel and the arc furnace smelting efficiency; and the generated CO bubbles can carry the nitrogen in the molten steel during the floating process, and remove the nitrogen in the molten steel. In addition, the FeO contained in the DRI fines helps to improve the oxidizability of the molten steel, helps the oxidative dephosphorization of the molten steel, and reduces the phosphorus content of the molten steel. In addition, the iron powder in the DRI fines melts in the arc furnace molten pool, which can improve the yield of DRI.

[0092] In summary, the method provided in the embodiment of the present invention not only solves the problem of efficient utilization of DRI fine materials in the electric arc furnace smelting process and improves its yield, but also simultaneously improves the smelting efficiency of the electric arc furnace and the cleanliness of the molten steel, which is conducive to the green and efficient development of DRI electric arc furnace steelmaking.

[0093] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A method for improving the raw material recovery rate, smelting efficiency and steel liquid cleanliness of a DRI arc furnace, characterized in that: The method comprises: S1: Arc starting period and main melting period S11: loading smelting raw materials including scrap steel into an electric arc furnace, starting a power supply, and inputting electric energy into the electric arc furnace through electrodes; S12: supplying oxygen into the electric arc furnace using an oxygen lance on the wall of the electric arc furnace; S13: after a molten pool is formed in the electric arc furnace, continuously adding direct reduced iron, and using an oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool; S14: after all the direct reduced iron enters the molten pool, adding limestone to the surface of the molten pool to make slag; S2: End of Melting S21: continue to add limestone into the electric arc furnace to form slag; S22: use the oxygen lance on the wall of the electric arc furnace to spray oxygen and DRI fine material into the molten pool; S3: Oxidation period Continue to use the arc furnace wall oxygen lance to spray oxygen and DRI fine material into the molten pool.

2. The method according to claim 1, characterized in that In S11, the power supply intensity of the power source is 0.6-1.2 MVA / t steel.

3. The method according to claim 1 or 2, characterized in that: In S12, the oxygen supply intensity is 0.9-2.5Nm 3 / (min·t steel).

4. The method according to claim 1 or 2, characterized in that: In S13, based on the total weight of the smelting raw materials including scrap steel and the direct reduced iron as 100%, the amount of the direct reduced iron added is 20-50%, and / or the oxygen supply intensity is 0.7-1.6 Nm 3 / (min·t-steel), and / or the particle size of the DRI fine material is less than 4 mm, the blowing rate is 0.5-1.0 kg / (min·t-steel), and the amount of the DRI fine material is 10-18 kg / t-steel.

5. The method according to claim 1 or 2, characterized in that: In S14, the amount of limestone used is 20-25 kg / t steel.

6. The method according to claim 1, characterized in that In S21, the amount of limestone used is 12-18 kg / t steel.

7. The method according to claim 1, characterized in that In S22, the oxygen supply intensity is 0.9-1.5Nm 3 / (min·t steel).

8. The method according to any one of claims 1, 6-7, characterized in that: In S22, the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.7-1.2 kg / (min·t steel), and the amount of DRI fine material used is 3.5-6 kg / t steel.

9. The method according to claim 1, characterized in that: In S3, the oxygen supply intensity is 1.0-2.0Nm 3 / (min·t steel).

10. The method according to claim 1 or 9, characterized in that: In S3, the particle size of the DRI fine material is less than 4 mm, the injection rate is 0.3-0.8 kg / (min·t steel), and the amount of DRI fine material used is 3-7 kg / t steel.

Images