A method for recovering converter gas in a large scrap steel ratio mode

Abstract

The present invention provides a method for recovering converter gas in a large scrap steel ratio mode, the steps of which are: metal material loading: adding scrap steel and molten iron into the converter in a certain ratio in sequence; converter smelting and gas recovery: after starting converter smelting, a gas-powder mixture is bottom blown by a cross-blowing method, and if the converter recovery conditions are met, converter gas recovery begins until the converter smelting is completed. The beneficial effects of the present invention are that by using multiple processes such as cross-bottom blowing of gas and powdered slag, top blowing of oxygen on the furnace top, and by adding different types of scrap steel in batches and at different locations, the converter smelting in a large scrap steel ratio mode can meet the gas recovery requirements throughout the process, and the converter gas can be fully recovered, with a recovery volume of 200m 3 / t or above, the average CO content can reach more than 48%, creating conditions for improving the level of negative energy steelmaking in converters.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for recovering converter gas in a large scrap steel ratio mode. Background Art

[0002] my country's steel industry is gradually developing in a low-carbon direction, and energy recycling has become a key task. Flue gas is generated during the converter smelting process. After the flue gas passes through the purification and recovery system, coal gas is recovered. In order to avoid high-temperature flue gas explosions, the commonly used coal gas recovery conditions are an oxygen content of 1.5%, and recovery begins when the CO content of the coal gas reaches more than 15%. In the early stages of coal gas recovery, it is mainly the oxidation of silicon and manganese elements in molten iron, the low carbon content in the flue gas, and the incomplete combustion of oxygen, which causes the oxygen content in the flue gas to exceed the standard and cannot be recovered. Under the large scrap steel ratio mode, the proportion of scrap steel used in the converter is getting higher and higher, the heat in the furnace is insufficient, the oxygen content of the flue gas is high due to incomplete combustion, and the CO content does not meet the starting conditions. The starting point of coal gas recovery is further delayed, and the amount of coal gas recovery is low.

[0003] In order to realize the whole process recovery of converter gas, different devices are often used to blow coal and other carbon-containing raw materials. For example, the patent: A converter smelting equipment and method for full recovery of gas (CN114807500A) proposes an operating method of using a coal oxygen gun to blow coal powder in the early stage of smelting. The coal injection method further increases the carbon consumption, which is not in line with the development trend of low-carbon metallurgy.

[0004] Patent: A method for increasing the CO content in converter gas (CN111575431A), which proposes to increase the CO content in gas by adding FeO-containing materials and adjusting the slag making process. This method is suitable for smelting conditions with high heat conditions, but not for smelting modes with a large scrap ratio, and cannot achieve full recovery of converter gas. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a method for recovering converter gas under a large scrap steel ratio mode. When the scrap steel ratio is greater than 35%, through various processes such as bottom blowing gas and powdered slag, the entire converter smelting process can meet the gas recovery requirements, thereby realizing full recovery of the converter gas.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for recovering converter gas in a large scrap steel ratio mode, the steps are:

[0007] Metal material loading: Scrap steel and molten iron are added into the converter in a certain ratio;

[0008] Converter smelting and gas recovery: After starting converter smelting, the gas-powder mixture is bottom blown by cross-blowing. If the converter recovery conditions are met, converter gas recovery begins until the end of converter smelting.

[0009] Furthermore, in the steps of metal material loading, converter smelting and coal gas recovery, the proportion of total molten iron added to the ladle is 60%-65%, and the proportion of total scrap steel is 35%-40%.

[0010] Furthermore, the step of adding the scrap steel and the molten iron into the converter in a certain ratio comprises:

[0011] A first batch of scrap steel is crushed and added into the ladle;

[0012] After the first batch of scrap steel is added, molten iron is poured into the ladle;

[0013] The first batch of scrap steel and molten iron are loaded into the converter to start converter smelting.

[0014] Furthermore, the particle size of the crushed scrap steel is 20-30 mm and the thickness is 3-5 mm; the height of the crushed scrap steel added to the ladle does not exceed 1 / 2 of the height of the ladle;

[0015] After injecting molten iron into the ladle, sampling and analysis are required. If the silicon content in the molten iron is higher than 0.8%, iron mixing is carried out to reduce the silicon content in the molten iron to 0.8% or below; if the silicon content is not higher than 0.8%, the converter smelting and gas recovery steps are entered.

[0016] Furthermore, the converter smelting and gas recovery: after starting the converter smelting, the gas-powder mixture is bottom blown by cross-blowing, and if the converter recovery conditions are met, the converter gas is recovered until the converter smelting is completed. The steps include:

[0017] In the first stage, the converter smelts for 0-60s. The converter blows compressed air and powdered slag at the bottom in turn, and blows oxygen at the top of the converter. When the oxygen content in the flue gas is less than the set value, the converter gas is recovered.

[0018] Furthermore, the pressure of bottom-blowing compressed air is 0.1-0.15Mpa / hole, the flow rate is 50-80Nm³ / min, the top-blowing oxygen flow rate is 10000-12000m³ / h, and the oxygen lance is 2m away from the steel liquid surface;

[0019] The powdered slag material includes lime powder and magnesium powder, with 8-10 kg / t of bottom-blown lime powder and 3-5 kg / t of bottom-blown magnesium powder;

[0020] It is set that when the oxygen content in the flue gas is less than 1.5%, the converter gas recovery starts.

[0021] Furthermore, the converter smelting and gas recovery: after starting the converter smelting, the gas-powder mixture is bottom blown by cross-blowing, and if the converter recovery conditions are met, the converter gas is recovered until the converter smelting is completed, and the steps also include:

[0022] In the second stage, the converter is blown for 61-300s, 15-20% of scrap steel is added from the high-level silo, oxygen and powdered slag are blown crosswise from the bottom of the converter, and oxygen is blown from the top of the converter using an oxygen lance.

[0023] Furthermore, the pressure of bottom blowing oxygen is 0.2Mpa / hole, the flow rate is 100-150Nm³ / min, the top blowing oxygen flow rate is 18000-22000m³ / h, and the oxygen lance is 1.4-1.8m away from the steel liquid surface;

[0024] The powdered slag material includes: lime powder and magnesium powder, with 4-5 kg / t of bottom-blown lime powder and 2-3 kg / t of bottom-blown magnesium powder;

[0025] The thickness of the scrap steel added to the punch is 8 to 10 mm and the diameter is 4 to 6 cm.

[0026] Furthermore, the converter smelting and gas recovery: after starting the converter smelting, the gas-powder mixture is bottom blown by cross-blowing, and if the converter recovery conditions are met, the converter gas is recovered until the converter smelting is completed, and the steps also include:

[0027] In the third stage, the converter is blown for 301-650 seconds, 8-12% of the scrap steel for the punch material is added from the high-level silo, nitrogen and powdered slag are blown crosswise from the bottom of the converter, and oxygen is blown from the top of the converter;

[0028] Preferably, the pressure of bottom blowing nitrogen is 0.4-0.6Mpa / hole, the flow rate is 150-200Nm³ / min, the top blowing oxygen flow rate is 22000-30000m³ / h, and the oxygen lance is 1.4-1.8m away from the steel liquid surface;

[0029] The powdered slag material is lime powder, and the bottom-blown lime powder is 4-5 kg / t;

[0030] The punch material added is 8 to 10 mm thick and 4 to 6 cm in diameter.

[0031] Furthermore, the converter smelting and gas recovery: after starting the converter smelting, the gas-powder mixture is bottom blown by cross-blowing, and if the converter recovery conditions are met, the converter gas is recovered until the converter smelting is completed, and the steps also include:

[0032] In the fourth stage, the blowing lasts for 651 seconds until the end, 0-2% of the scrap steel of the punch material is added from the high-level silo, argon gas and powdered slag are blown from the bottom of the converter in turn, and oxygen is blown from the top of the converter;

[0033] Preferably, the pressure of bottom blowing argon is 0.2-0.3Mpa / hole, the flow rate is 80-120Nm³ / min, the top blowing oxygen flow rate is 28000-32000m³ / h, and the oxygen lance is 1.2-1.4m away from the steel liquid surface;

[0034] The powdered slag material is lime powder, and the bottom-blown lime powder is 4-5 kg / t;

[0035] The punch material is in the shape of a disc, with a thickness of 8 to 10 mm and a diameter of 4 to 6 cm.

[0036] The above technical solution has the following beneficial effects:

[0037] Through cross-bottom blowing of gas and powdered slag, top blowing of oxygen and other processes, different types of scrap steel are added in batches and at different locations, so that the converter smelting process under the large scrap steel ratio mode meets the gas recovery requirements. The converter gas is recovered throughout the process, the recovery amount can be more than 200m³ / t, and the average CO content can reach more than 48%, creating conditions for improving the level of converter negative energy steelmaking. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with embodiments:

[0039] A method for recovering converter gas in a large scrap steel ratio mode, comprising the following steps:

[0040] S1: Metal material charging: Scrap steel and molten iron are sequentially added to the converter according to a certain ratio. In this embodiment, the proportion of total molten iron added to the metal material in the metal material charging and converter smelting and gas recovery steps is 60%-65%, and the proportion of total scrap steel is 35%-40%. Specifically, the following steps are included:

[0041] S11: The first batch of scrap steel is crushed and added into the ladle;

[0042] S12: After the first batch of scrap steel is added, molten iron is poured into the ladle;

[0043] In steps S11 and S12, scrap steel is first added to the bottom of the ladle, and then molten iron is poured into the ladle. In this embodiment, a mechanical gripper is used to crush the scrap steel before iron is released. The crushed scrap steel accounts for 6-10% of the total scrap steel, and the height of the added crushed scrap steel shall not exceed 1 / 2 of the total height of the ladle to prevent the scrap steel from agglomerating and causing the iron to fall when the converter is loaded into the converter for smelting. The first batch of crushed scrap steel added has a particle size of 20-30mm and a thickness of 3-5mm, with a light bulk density, and can achieve rapid melting.

[0044] S13: After injecting molten iron into the ladle, sampling and analysis are carried out. If the silicon content in the molten iron is higher than 0.8%, iron mixing is carried out to reduce the silicon content in the molten iron to 0.8% or below. If the silicon content is not higher than 0.8%, the converter smelting and coal gas recovery steps are entered.

[0045] In step S13 of the present embodiment, the silicon content in the molten iron is detected. Specifically, the silicon content in the molten iron can be detected by using a suitable measuring instrument or tool, such as a spectrometer. Since the existing technology is relatively complete and is not the content protected by the present embodiment, no further limitation is made on this. High-silicon molten iron is prone to cause large-scale splashing, which is not conducive to converter smelting and will also have an adverse effect on coal gas recovery. Therefore, sampling and analysis are required after iron discharge to detect the silicon content. If the silicon content is higher than 0.8%, it can be imagined that molten iron with a silicon content of less than 0.8% should be injected into the molten iron during the iron mixing operation. Specifically, molten iron with a suitable silicon content can be reasonably selected or formulated according to the on-site construction requirements.

[0046] In this iron mixing process, the silicon content is based on 0.8%. For every 0.1% reduction, 1% of steel bar scrap is added, and the amount of scrap added in this process does not exceed 10% of the total scrap. The molten iron is transported to the converter for smelting in packages. When the silicon content in the molten iron ladle is greater than 0.8%, the packages with lower silicon content are used to mix the iron. The amount of scrap added at this stage is determined based on the final silicon content of the molten iron. Compared with the thin and light crushed scrap, the addition of scrap steel during the iron mixing process can effectively avoid the formation of lumps due to its own weight when added.

[0047] S14: Loading the first batch of scrap steel and molten iron into the converter to start converter smelting. In step S14 of this embodiment, no additional scrap steel is added and the smelting process is directly carried out.

[0048] S2: Converter smelting and gas recovery: After starting converter smelting, the gas-powder mixture is blown bottom by cross-blowing. If the converter recovery conditions are met, converter gas recovery begins until the converter smelting is completed. In this process, cross-bottom blowing is adopted, and the bottom blowing sequence is gas-powder-gas-powder-gas-powder. In this embodiment, a 6-hole bottom blowing method is adopted, and the bottom blowing hole diameter is 22 mm. Specifically, the following steps are included:

[0049] S21: In the first stage, during the converter smelting time of 0-60s, the converter sequentially cross-blows compressed air and powdered slag at the bottom, and blows oxygen at the top of the converter. When the oxygen content in the flue gas is less than the set value, the converter gas is recovered.

[0050] Specifically, the pressure of the cross bottom blowing compressed air is 0.1-0.15Mpa / hole, the flow rate is 50-80Nm³ / min, and the top blowing oxygen flow rate is 10000-12000m³ / h. In this embodiment, the bottom blowing powdered slag includes: lime powder and magnesium powder, wherein the bottom blowing lime powder is 8-10kg / t, and the bottom blowing magnesium powder is 3-5 kg / t; in this embodiment, the particle size of the bottom blowing lime powder is ≤30mm, wherein the CaO content is greater than 88%; the particle size of the magnesium powder is ≤30mm, and the MgO content is greater than 75%. When the bottom blowing powdered slag is used, the order of lime powder and magnesium powder is not limited, and the bottom blowing of lime powder first and magnesium powder later or the bottom blowing of magnesium powder first and lime powder later can be all possible. The use of lime powder and magnesium powder, which have small particle size and good metallurgical properties, can reduce the amount of materials used in the large scrap steel ratio mode, reduce the loss of materials to the molten pool temperature, and achieve a rapid increase in the molten pool temperature.

[0051] In this embodiment, the top-blown oxygen adopts an oxygen lance, which can be but not limited to a four-hole Laval lance, and the position of the oxygen lance is controlled to be 2 meters away from the steel liquid surface; the bottom-blown compressed air can realize the direct contact between the oxygen in the compressed air and the steel liquid, and can be used to stir the steel liquid molten pool to cause a deoxidation reaction, generate flue gas containing a certain CO content, and recover it as converter gas after purification. In step S12, bottom-blown pure oxygen is not used, which can control the reaction intensity of the molten pool and reduce the oxygen purification cost to a certain extent. By adopting the top and bottom mixed gas supply mode, the early reaction kinetic conditions are more sufficient, which is convenient for quickly raising the molten pool temperature.

[0052] In step S21, it is set that when the oxygen content in the flue gas is less than 1.5%, the converter gas recovery starts; the top and bottom mixed gas supply mode is adopted, which also ensures that the oxygen content in the flue gas in the early stage quickly meets the requirement of less than 1.5%, thereby meeting the safety conditions of converter recovery. After the flue gas is processed and recovered, the coal gas is obtained, and the converter gas recovery can start. During the recovery process, attention is paid to the trend of the oxygen content in the flue gas, and the oxygen supply and bottom blowing volume are dynamically adjusted. When the oxygen content is high, the oxygen lance position can be appropriately lowered and the oxygen supply of the top blowing oxygen lance can be reduced, and the bottom blowing volume can be increased to promote the increase of CO content in the coal gas and meet the demand for converter gas recovery as soon as possible.

[0053] S22: In the second stage, the converter is blown for 61-300s. As the oxidation of silicon and manganese proceeds, the temperature of the molten pool further increases, and 15-20% of scrap steel is added from the high-level silo. The converter is cross-blown with oxygen and powdered slag at the bottom and oxygen is blown at the top of the converter. The converter gas is continuously recovered in this stage.

[0054] Specifically, the thickness of the scrap steel added in this stage is 8-10mm and the diameter is 4-6cm. The pressure of the bottom-blown oxygen is 0.2Mpa / hole, the flow rate is 100-150Nm³ / min, and the top-blown oxygen flow rate is 18000-22000m³ / h; in this embodiment, the bottom-blown powdered slag includes: lime powder and magnesium powder, wherein the bottom-blown lime powder is 4-5kg / t, wherein the CaO content is greater than 88%; the bottom-blown magnesium powder is 2-3kg / t, and the MgO content is greater than 75%; wherein the order of lime powder and magnesium powder when bottom-blowing powdered slag is not limited, and the bottom-blowing lime powder first and then the bottom-blowing magnesium powder or the bottom-blowing magnesium powder first and then the bottom-blowing lime powder can be used.

[0055] In order to realize the full recovery of converter gas under the large scrap steel ratio mode, the proportion of scrap steel required to be added in this process is relatively high. In order to avoid the molten pool temperature being too low after adding the scrap steel all at once, which is not conducive to smelting, flake-shaped scrap steel is added in batches at this stage, so as to achieve the purpose of recovering converter gas under the large scrap steel ratio. At the same time, by adding flake-shaped scrap steel at this stage, there are fewer impurities and the surface is flat, which can be loaded through hoppers and vibrating feeders, which is convenient and fast without damaging the equipment.

[0056] In this embodiment, the top-blown oxygen adopts an oxygen lance, and the top-blown oxygen gun can be but not limited to a four-hole Laval gun, and the oxygen lance position is controlled to be 1.4-1.8 meters away from the steel liquid surface. During the recovery process, the oxygen supply and bottom blowing gas volume are dynamically adjusted according to the oxygen content and CO content change trend in the flue gas. As the silicon-manganese oxidation proceeds, when the oxygen content is high, the oxygen lance position and the oxygen supply of the top-blown oxygen gun can be appropriately lowered, and the bottom blowing gas volume can be increased to promote the increase of CO content in the flue gas.

[0057] S23: In the third stage, the converter is blown for 301-650s, the oxidation of silicon and manganese is basically completed, and the carbon-oxygen violent reaction period begins. The temperature of the molten pool further increases, and the converter gas recovery enters a peak. At this time, 8-12% of the scrap steel of the punch material is added from the high-level silo, and the converter is cross-blown with bottom nitrogen and powdered slag in turn, and the converter top blows oxygen. The flue gas continues to be recovered at this stage. Specifically, the punch material added in this stage has a thickness of 8-10mm and a diameter of 4-6cm. The pressure of the bottom-blown nitrogen is 0.4-0.6Mpa / hole, the flow rate is 150-200Nm³ / min, and the top-blown oxygen flow rate is 22000-30000m³ / h; in this embodiment, the bottom-blown powdered slag is lime powder, and the bottom-blown lime powder is 4-5kg / t, wherein the CaO content is greater than 88%.

[0058] Similarly, in order to avoid the molten pool temperature being too low after adding scrap steel all at once, which is not conducive to smelting, flake-shaped scrap steel is added in batches at this stage, so as to achieve the purpose of recovering converter gas with a large scrap steel ratio. At the same time, by adding flake-shaped scrap steel at this stage, there are fewer impurities and the surface is flat, which can be loaded through hoppers and vibrating feeders, which is convenient and fast without damaging the equipment.

[0059] In step S23 of this embodiment, oxygen is also blown from the top by an oxygen lance, which can be but is not limited to a four-hole Laval lance, and the position of the oxygen lance is controlled at 1.4-1.8 meters from the steel liquid surface. During the recovery process, dynamic adjustments are made according to the trend of the CO content in the flue gas. When the CO content is low, the position of the oxygen lance can be lowered and the top-blowing oxygen flow rate can be increased. When the CO content is high, the position of the oxygen lance can be increased and the top-blowing oxygen flow rate can be reduced. The CO content is stably controlled at 40%-50%. The carbon-oxygen reaction rate in the molten pool is fed back through the CO content, and the reaction is relatively stable and balanced, making the smelting more stable and the CO quality in the flue gas higher.

[0060] S24: The fourth stage, blowing 651s to the end, at this time the carbon oxygen reaction decays, the converter gas recovery peak gradually decreases, 0-2% of the punch material scrap steel is added from the high-level silo, the converter blows argon and powdered slag in turn, and the converter top blows oxygen, and the flue gas is continued to be recovered in this stage. Specifically, the thickness of the punch material added in this stage is 8-10mm, and the diameter is 4-6cm. The pressure of bottom-blown argon is 0.2-0.3Mpa / hole, the flow rate is 80-120Nm³ / min, the top-blown oxygen lance adopts a four-hole Laval lance, the top-blown oxygen flow rate is 28000-32000m³ / h, and the oxygen lance position is 1.2-1.4m away from the steel liquid surface; in this embodiment, the bottom-blown powdered slag material is lime powder, the bottom-blown lime powder is 4-5kg / t, and the CaO content is greater than 88%; in the recovery process, dynamic adjustment is made according to the changing trend of the CO content in the flue gas. When the CO content is low, the oxygen lance position can be lowered and the top-blowing oxygen flow rate can be increased. When the CO content is high, the oxygen lance position can be increased and the top-blowing oxygen flow rate can be reduced. Example

[0061] This embodiment takes a 100-ton engineering capacity converter as an example, and organizes production according to a total loading volume of 100 tons, wherein the total weight of molten iron loaded is 62 tons, the total weight of scrap steel is 38 tons, and the scrap steel ratio is 38%.

[0062] Before releasing the iron, a mechanical gripper is used to load 6 tons of crushed material to the bottom of the ladle and then the molten iron is poured in.

[0063] After the iron is discharged, sampling and analysis are carried out. The silicon content in the molten iron is 0.60%, the temperature is 1360℃, and 2 tons of steel bar scrap are added into the iron ladle.

[0064] The molten iron containing a certain amount of scrap steel and molten iron is packed into the converter and directly enters the converter smelting stage without adding any scrap steel.

[0065] Start converter smelting, use 6 holes at the bottom to blow the gas-powder mixture in a cross-blowing manner, i.e. gas-powder-gas-powder-gas-powder, and the bottom blowing hole diameter is 22 mm.

[0066] In the first stage, the blowing starts for 0-60s, and the top and bottom mixed gas supply mode is adopted. Compressed air and powdered slag are blown from the bottom of the converter. The bottom blowing pressure is 0.1-0.15Mpa / hole, and the bottom blowing flow rate is 50Nm³ / min. The powdered slag includes lime powder and magnesium powder. The bottom blowing lime powder is 8kg / t, and the magnesium powder is 3kg / t. The top blowing oxygen lance adopts a four-hole Laval lance, and the oxygen flow rate is 10000-12000m³ / h. The oxygen lance position is controlled at 2 meters from the steel liquid surface. According to the trend of oxygen content in the flue gas, the oxygen supply and bottom blowing gas volume are dynamically adjusted. For example, when the oxygen content is high, the oxygen lance position can be appropriately lowered and the oxygen supply of the top blowing oxygen lance can be reduced, and the bottom blowing gas volume can be increased to promote the increase of CO content in the flue gas, so as to meet the demand for recovering converter gas as soon as possible. When the oxygen content in the flue gas is less than 1.5%, the gas recovery begins.

[0067] In the second stage, the blowing time is 61-300s. As the oxidation of silicon and manganese proceeds, the temperature of the molten pool further increases. 18 tons of scrap steel for punch materials are added from the high-level silo. The punch materials are in the shape of discs with a thickness of 8-10mm and a diameter of 4-6cm. The top and bottom mixed gas supply mode is adopted. Oxygen and powdered slag are blown from the bottom of the converter. The bottom blowing pressure is 0.2Mpa / hole and the bottom blowing flow rate is 100-150Nm³ / min. The powdered slag includes lime powder and magnesium powder. Specifically, 4kg / t of lime powder and 2.5kg / t of magnesium powder are blown from the bottom. The top-blown oxygen lance adopts a four-hole Laval lance with an oxygen supply flow rate of 18,000-22,000m³ / h. The oxygen lance position is controlled at 1.4-1.8 meters from the steel liquid surface. According to the changing trends of oxygen content and CO content in the flue gas, the oxygen amount and bottom blowing air volume are dynamically adjusted. As the oxidation of silicon manganese progresses, when the oxygen content is high, the oxygen lance position can be appropriately lowered and the top blowing oxygen supply can be reduced, and the bottom blowing air volume can be increased to promote the increase of CO content in the flue gas.

[0068] In the third stage, the blowing lasts for 301-650s, the oxidation of silicon and manganese is basically completed, and the carbon-oxygen violent reaction period begins. The temperature of the molten pool further increases, and the converter gas recovery enters a peak. 10 tons of scrap steel for the punch material is added from the high-level silo. The punch material is in the form of a disc with a thickness of 8-10mm and a diameter of 4-6cm. The top and bottom mixed gas supply mode is also adopted. Nitrogen and powdered slag are blown from the bottom of the converter. The pressure is 0.4-0.6Mpa / hole and the flow rate is 160Nm³ / min. The powdered slag is lime powder, and the bottom blown lime powder is 4.5kg / t. The top oxygen lance adopts a four-hole Laval lance with an oxygen supply flow of 22000-30000m³ / h. The oxygen lance position is controlled at 1.4-1.8 meters from the steel liquid surface. According to the changing trend of CO content in flue gas, dynamic adjustment is carried out. When the CO content is low, the oxygen lance position can be lowered and the top blowing oxygen supply flow rate can be increased. When the CO content is high, the oxygen lance position can be raised and the top blowing oxygen supply flow rate can be reduced to stably control the CO content at around 45%.

[0069] In the fourth stage, the blowing lasted for 651s until the end, the carbon-oxygen reaction decayed, and the converter gas recovery peak gradually decreased. 2 tons of scrap steel for punch material was added from the high-level silo. The punch material was in the form of discs with a thickness of 8 to 10 mm and a diameter of 4 to 6 cm. The top and bottom mixed gas supply mode was adopted, and argon and powdered slag were blown from the bottom of the converter. The pressure was 0.2-0.3Mpa / hole, and the flow rate was 80 to 120Nm³ / min. The powdered slag was lime powder, and the bottom-blown lime powder was 4.5kg / t. The top-blown oxygen gun adopted a four-hole Laval gun, and the oxygen supply flow rate was 28,000 to 32,000m³ / h. The oxygen gun position was controlled at 1.2 to 1.4 meters from the steel liquid surface. According to the trend of CO content in flue gas, dynamic adjustment was carried out, and the gun position was appropriately lowered to promote continuous CO content. During the recovery process, dynamic adjustments are made according to the changing trend of the CO content in the flue gas. When the CO content is low, the oxygen lance position can be lowered and the top-blowing oxygen supply flow rate can be increased. When the CO content is high, the oxygen lance position can be raised and the top-blowing oxygen supply flow rate can be reduced.

[0070] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for recovering converter gas in a large scrap steel ratio mode, characterized in that: The steps are: Metal material loading: Scrap steel and molten iron are added to the converter in a certain ratio; Converter smelting and gas recovery: After starting converter smelting, the gas-powder mixture is bottom-blown in a cross-blowing manner. If the converter recovery conditions are met, converter gas recovery begins until the converter smelting is completed; In the steps of metal material loading, converter smelting and gas recovery, the proportion of total molten iron added to the ladle is 60%-65%, and the proportion of total scrap steel is 35%-40%; The converter smelting and gas recovery steps include: in the first stage, the converter smelting is 0-60s, the converter sequentially cross-blows compressed air and powdered slag at the bottom, and oxygen is blown at the top of the converter. When the oxygen content in the flue gas is less than the set value, the converter gas is recovered; in the second stage, the converter is blown for 61-300s, 15-20% of the scrap steel for punching material is added from the high-level silo, oxygen and powdered slag are blown at the bottom of the converter sequentially, and oxygen is blown at the top of the converter with an oxygen lance at the top of the converter; in the third stage, the converter is blown for 301-650s, 8-12% of the scrap steel for punching material is added from the high-level silo, nitrogen and powdered slag are blown at the bottom of the converter sequentially, and oxygen is blown at the top of the converter; in the fourth stage, the blow is performed for 651s to the end, 0-2% of the scrap steel for punching material is added from the high-level silo, argon and powdered slag are blown at the bottom of the converter sequentially, and oxygen is blown at the top of the converter.

2. The method for recovering converter gas in a large scrap steel ratio mode according to claim 1, characterized in that: The step of adding scrap steel and molten iron into the converter in a certain ratio comprises: A first batch of scrap steel is crushed and added into the ladle; After the first batch of scrap steel is added, molten iron is poured into the ladle; The first batch of scrap steel and molten iron are loaded into the converter to start converter smelting.

3. The method for recovering converter gas in a large scrap steel ratio mode according to claim 2, characterized in that: The particle size of the crushed scrap steel is 20-30mm and the thickness is 3-5mm; the height of the crushed scrap steel added to the ladle shall not exceed 1 / 2 of the ladle height; After injecting molten iron into the ladle, sampling and analysis are required. If the silicon content in the molten iron is higher than 0.8%, iron mixing is carried out to reduce the silicon content in the molten iron to 0.8% or below; if the silicon content is not higher than 0.8%, the converter smelting and gas recovery steps are entered.

4. The method for recovering converter gas in a large scrap steel ratio mode according to claim 1, characterized in that: In the first stage, the bottom blowing compressed air pressure is 0.1-0.15Mpa / hole, the flow rate is 50-80Nm³ / min, the top blowing oxygen flow rate is 10000-12000m³ / h, and the oxygen lance is 2m away from the steel liquid surface; The powdered slag material includes lime powder and magnesium powder, with 8-10 kg / t of bottom-blown lime powder and 3-5 kg / t of bottom-blown magnesium powder; It is set that when the oxygen content in the flue gas is less than 1.5%, the converter gas recovery starts.

5. The method for recovering converter gas in a large scrap steel ratio mode according to claim 1, characterized in that: In the second stage, the bottom blowing oxygen pressure is 0.2Mpa / hole, the flow rate is 100-150Nm³ / min, the top blowing oxygen flow rate is 18000-22000m³ / h, and the oxygen lance is 1.4-1.8m away from the steel liquid surface; The powdered slag material includes: lime powder and magnesium powder, with 4-5 kg / t of bottom-blown lime powder and 2-3 kg / t of bottom-blown magnesium powder; The thickness of the scrap steel added to the punch is 8 to 10 mm and the diameter is 4 to 6 cm.

6. The method for recovering converter gas in a large scrap steel ratio mode according to claim 1, characterized in that: In the third stage, the bottom blowing nitrogen pressure is 0.4-0.6Mpa / hole, the flow rate is 150-200Nm³ / min, the top blowing oxygen flow rate is 22000-30000m³ / h, and the oxygen lance is 1.4-1.8m away from the steel liquid surface; The powdered slag material is lime powder, and the bottom-blown lime powder is 4-5 kg / t; The punch material added is 8 to 10 mm thick and 4 to 6 cm in diameter.

7. The method for recovering converter gas in a large scrap steel ratio mode according to claim 2, characterized in that: In the fourth stage, the pressure of bottom blowing argon is 0.2-0.3Mpa / hole, the flow rate is 80-120Nm³ / min, the top blowing oxygen flow rate is 28000-32000m³ / h, and the oxygen lance is 1.2-1.4m away from the steel liquid surface; The powdered slag material is lime powder, and the bottom-blown lime powder is 4-5 kg / t; The punch material is in the shape of a disc, with a thickness of 8 to 10 mm and a diameter of 4 to 6 cm.