A method for smelting with a short process of converter gas recycling and a high cold charge ratio

Abstract

The present application provides a method for smelting with a high cold charge ratio by short - process recycling of converter gas, which relates to the metallurgical field. The method includes: separating converter gas generated during converter smelting to obtain carbon dioxide gas and carbon monoxide - containing gas as the preheating and blowing gas sources; after the converter is charged with cold charge, mixing the carbon monoxide - containing gas with top - blown oxygen, and using the oxygen lance in a non - premixed mode to ignite at the remaining hot point in the converter to form a burner mode for preheating the cold charge; lifting the oxygen lance to the water - cooled hood, tilting the converter to a specified position, tapping molten iron and then tilting it back, and then lowering the oxygen lance to a set position and blowing in different modes based on the smelting conditions; using carbon dioxide or steam as the sealing gas for the nitrogen sealing ring throughout the converter smelting process, and tilting the converter to tap steel at a set position. The method provided by the present application realizes the high - value utilization of part of the converter gas through short - process recycling, which has an important impact on increasing the proportion of cold charge charged into the converter and the cleanliness of molten steel.

Description

Technical Field

[0001] This application relates to the metallurgy field, and in particular to a method for smelting with a high cold charge ratio through short - process recycling of converter gas. Background Art

[0002] The proportion of CO2 emissions in industrial emissions is greater than 15%, the CO2 emission intensity is about 2.0 tCO2 / t steel, and the CO2 emissions from the blast furnace process account for more than 50% of crude steel production. Replacing part of the hot metal with low - carbon raw materials such as scrap steel and direct reduced iron can reduce the carbon emissions in crude steel production. However, due to an overly large cold charge ratio, there will be insufficient heat in the converter smelting process, problems such as difficulty in slag melting, and even the inability to complete converter steelmaking.

[0003] Adopting the external cold charge pre - heating technology for converters can effectively increase the proportion of cold charge charged into the converter. However, due to the characteristics of dispersed combustion, effective flue gas collection and treatment cannot be carried out, which is likely to cause environmental pollution and has a low heat efficiency utilization.

[0004] In view of this, this application is specifically proposed. Summary of the Invention

[0005] The purpose of this application is to provide a method for smelting with a high cold charge ratio through short - process recycling of converter gas to solve the above problems.

[0006] To achieve the above purpose, this application adopts the following technical solutions:

[0007] A method for smelting with a high cold charge ratio through short - process recycling of converter gas, including:

[0008] S1. Separating the converter gas generated during the converter smelting process to obtain carbon dioxide gas and carbon monoxide - containing gas as the pre - heating and blowing gas sources;

[0009] S2. After the converter is charged with cold charge, mixing the carbon monoxide - containing gas with top - blown oxygen, and using the oxygen lance in a non - premixed mode to ignite at the remaining hot point in the converter to form a burner mode to pre - heat the cold charge;

[0010] Storing the carbon dioxide flue gas generated by pre - heating the cold charge under the burner mode in a flue gas storage tank;

[0011] S3. After the pre - heating proceeds for a first period of time, lifting the oxygen lance to the cooling hood, rocking the converter to make the cold charge tumble in the converter, and after rocking the converter upright, lowering the oxygen lance to a predetermined height and repeating S2 until the temperature of the cold charge is not lower than 600 °C;

[0012] During the ladle baking process, the temperature of the cold charge is a crucial operating parameter. Ensuring that the cold charge temperature reaches at least 600 °C or above can guarantee the smooth progress of subsequent smelting or processing steps. Below this temperature, it may affect the chemical reactions in the furnace or the product quality.

[0013] S4. Lift the oxygen lance to the water-cooled hood, swing the converter to the designated position, charge the hot metal, then swing it back to the upright position, and then lower the oxygen lance to the set position. Blow the converter in different modes based on the smelting conditions. The top-blown mode includes:

[0014] When the cold charge ratio is less than 20% (for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%) and the hot metal carbon content ≥ 4.0% or the hot metal silicon content ≥ 0.2%, use the SCH-2 mode for smelting, top-blown oxygen and carbon dioxide, or use the SCH-3 mode, top-blown oxygen;

[0015] At this time, there is sufficient heat source, and there is no need to additionally inject CO to supplement heat.

[0016] When the cold charge ratio is 20%-40% (for example, it can be 20%, 25%, 30%, 35% or 40%) and the hot metal carbon content < 4.0% or the hot metal silicon content < 0.2%, use the SCH-1 mode for smelting, top-blown oxygen and carbon monoxide, the heating intensity of the cold charge is 20-150 °C / min·t cold charge (for example, it can be 20 °C / min·t cold charge, 50 °C / min·t cold charge, 100 °C / min·t cold charge or 150 °C / min·t cold charge), and the heating time is 2-8 min (for example, it can be 2 min, 5 min or 8 min);

[0017] At this time, the heat is insufficient, and it is necessary to additionally inject CO to supplement heat. The heating intensity of the cold charge is adjusted within the range of 20-150 °C / min·t cold charge. According to the specific smelting requirements and the temperature distribution in the furnace, the heating rate of the cold charge can be reasonably controlled. This helps to improve the smelting efficiency, save energy and production costs while ensuring the stability of the smelting process.

[0018] The heating time is set between 2-8 minutes to ensure that the cold charge can fully reach the temperature required for smelting, and at the same time avoid problems such as increased energy consumption or unstable smelting process caused by too long heating time. By precisely controlling the heating time, the utilization rate of the cold charge and the smelting effect can be effectively improved.

[0019] When the ratio of cold charge is greater than 40% and the carbon content of molten iron < 4.0% or the silicon content of molten iron < 0.2%, SCH-1 mode is adopted for smelting, with top-blown oxygen and carbon monoxide. The heating intensity of cold charge is 50 - 200 °C / min·t cold charge (for example, it can be 50 °C / min·t cold charge, 100 °C / min·t cold charge, 150 °C / min·t cold charge or 200 °C / min·t cold charge), and the heating time is 3 - 8 min (for example, it can be 3 min, 5 min or 8 min).

[0020] At this time, there is insufficient heat, and additional CO injection is required to supplement heat. When there is more cold charge (greater than 40%), in order to heat the scrap steel to the appropriate smelting temperature more quickly, it is necessary to increase the heating intensity and heating time of cold charge. This helps to improve smelting efficiency and ensure the stability of production capacity and product quality.

[0021] The bottom-blown gas includes one or more of carbon dioxide, nitrogen and argon;

[0022] According to the converter smelting situation, automatically switch the smelting mode and gas injection volume;

[0023] S5. During the whole process of converter smelting, carbon dioxide or steam is used as the sealing gas for the nitrogen sealing ring. Based on the monitoring system of the converter smelting process, when it is determined that the molten steel meets the requirements of the smelting task, lift the oxygen lance and close the gas at the set position, and tilt the converter to pour steel.

[0024] Preferably, the burner mode includes low-intensity heating, medium-intensity heating and high-intensity heating; the heating intensity of cold charge for low-intensity heating is 10 - 50 °C / min·t cold charge (for example, it can be 10 °C / min·t cold charge, 20 °C / min·t cold charge, 30 °C / min·t cold charge, 40 °C / min·t cold charge or 50 °C / min·t cold charge), the heating intensity of cold charge for medium-intensity heating is 51 - 100 °C / min·t cold charge (for example, it can be 51 °C / min·t cold charge, 60 °C / min·t cold charge, 70 °C / min·t cold charge, 80 °C / min·t cold charge, 90 °C / min·t cold charge or 100 °C / min·t cold charge), and the heating intensity of cold charge for high-intensity heating is 101 - 200 °C / min·t cold charge (for example, it can be 101 °C / min·t cold charge, 110 °C / min·t cold charge, 120 °C / min·t cold charge, 130 °C / min·t cold charge, 140 °C / min·t cold charge, 150 °C / min·t cold charge, 160 °C / min·t cold charge, 170 °C / min·t cold charge, 180 °C / min·t cold charge, 190 °C / min·t cold charge or 200 °C / min·t cold charge).

[0025] Preferably, based on heavy scrap steel, the weights of light scrap steel and direct reduced iron are converted according to a coefficient of 0.1 - 0.9 (for example, it can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9).

[0026] The heavy scrap steel and the light scrap steel are single scrap steels, and the direct reduced iron is single direct reduced iron, including hydrogen-based direct reduced iron or coal-based direct reduced iron.

[0027] Preferably, the volume content of carbon dioxide in the flue gas storage tank is 20 - 80% (for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, or 80%).

[0028] Preferably, the carbon monoxide-containing gas is high-concentration carbon monoxide or a carbon monoxide mixture. The volume concentration of the high-concentration carbon monoxide gas is 40 - 99.99% (for example, it can be 40%, 50%, 60%, 70%, 80%, 90%, or 99.99%), and the volume concentration of the carbon monoxide mixture is 30 - 80% (for example, it can be 30%, 40%, 50%, 60%, 70%, or 80%). The gas use pressure is 0.3 - 2.5 MPa (for example, it can be 0.3 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, or 2.5 MPa).

[0029] Preferably, when top-blowing carbon monoxide and oxygen, the volume ratio of high-concentration carbon monoxide is not higher than 60%, or the volume ratio of the carbon monoxide mixture is not higher than 80%.

[0030] The reason for such setting is as follows:

[0031] 1. The use of high-concentration carbon monoxide in the furnace has certain risks. Carbon monoxide is a toxic gas, and at high concentrations, it may lead to safety risks such as explosion or leakage of toxic gas, posing potential hazards to workers and the environment.

[0032] 2. Controlling the volume ratio of carbon monoxide helps to effectively control the redox reaction while top-blowing oxygen. Excessive carbon monoxide content may lead to excessive reduction reactions, affecting the required oxidation effect, and thus affecting the furnace atmosphere and chemical reaction balance during the smelting process.

[0033] 3. Appropriately controlling the usage amount of carbon monoxide can ensure the stability of the smelting process and the expected results of the reaction. Excessive carbon monoxide content may cause fluctuations in the furnace temperature and chemical composition, thereby affecting the quality of the final product and the smelting efficiency.

[0034] Preferably, the volume concentration of the carbon dioxide gas is 60-99.99% (for example, it can be 60%, 70%, 80%, 90% or 99.99%), and the gas use pressure is 0.3-2.5 MPa (for example, it can be 0.3 MPa, 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa or 2.5 MPa).

[0035] Preferably, when top-blown oxygen and carbon dioxide are used, the volume proportion of pure carbon dioxide is not higher than 50%.

[0036] During the smelting process, the top-blown oxygen and carbon dioxide are used to control the gas phase composition and the furnace atmosphere to achieve suitable smelting conditions. An excessively high carbon dioxide content may affect the balance of the redox reaction, thereby affecting the chemical reactions in the molten bath and the quality of the final smelting product.

[0037] In addition, too much carbon dioxide may lead to unnecessary energy losses, increasing the cost and energy consumption of the smelting process.

[0038] Preferably, the proportion of the cold charge is 5%-60% (for example, it can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%), and the end temperature of the preheating is not higher than 1000°C;

[0039] The nominal capacity of the converter is 30-400 t.

[0040] A high proportion of cold charge and an excessively high preheating temperature may lead to a shortened equipment life and increased maintenance costs.

[0041] In addition, too high or too low proportions of cold charge and preheating temperatures may affect the combustion and heat conduction of the furnace gas, thereby affecting the thermal efficiency and production capacity of the smelting.

[0042] Preferably, the separation method includes one or more of chemical absorption method, pressure swing adsorption method, membrane separation method, and cryogenic distillation method.

[0043] Compared with the prior art, the beneficial effects of the present application include:

[0044] The method for smelting with a high cold charge ratio by short-process recycling of converter gas provided by the present application realizes the high-value utilization of part of the converter gas through short-process recycling, which has an important impact on increasing the cold charge charging ratio and the cleanliness of molten steel in converter smelting; based on different smelting conditions, multiple combustion modes are used to dynamically adjust the heating intensity of the cold charge, realizing the improvement of the cold charge charging ratio and the cleanliness of molten steel in the converter, and promoting the development of converter low-carbon smelting technology. Brief Description of the Drawings

[0045] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and should not be regarded as limiting the scope of the present application.

[0046] Figure 1 It is a schematic diagram of a smelting process system for short - process recycling of converter gas with a high cold - charge ratio.

[0047] Reference numerals:

[0048] 1 - Converter, 2 - Oxygen lance, 3 - Gas separation system, 4 - Bottom - blowing element, 5 - Bottom - blowing N2 pipeline, 6 - Bottom - blowing Ar pipeline, 7 - Bottom - blowing CO2 pipeline, 8 - Top - blowing CO2 pipeline, 9 - Converter gas pipeline, 10 - Top - blowing CO pipeline, 11 - Top - blowing O2 pipeline, 12 - Converter gas storage tank, 13 - Flue gas storage tank. Detailed implementation manners

[0049] The following will describe the implementation schemes of the present application in detail in combination with specific embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0050] Embodiment 1

[0051] As Figure 1 shown, this embodiment provides a smelting process for short - process recycling of converter gas with a high cold - charge ratio. Part of the converter gas by - produced during the converter smelting production process is separated through a gas separation device. After separating CO2 and CO in the converter gas, they are used as the gas sources for combined top - and - bottom blowing of the converter, which helps to improve the cold - charge ratio of the converter, reduce dust generation and other beneficial effects, and achieve high - cold - charge - ratio smelting in the converter. Based on the material balance and heat balance of converter smelting, the total amount of heat loss in the case of a high cold - charge ratio is calculated, the total amount of injected fuel and the preheating temperature of cold materials are confirmed, and high - cold - charge - ratio smelting with short - process recycling of converter gas is achieved.

[0052] (1) In this embodiment, the method is applied to 300t converter steelmaking. The nitrogen - sealing ring uses CO2 gas as the sealing gas. The converter gas recovery per ton of steel is 108 Nm 3 , the calorific value of the gas is 7008 kJ / Nm 3 , the CO content is 55.4%, the CO2 content is 35.3%, the outer diameter of the oxygen lance used is 406 mm, and the designed flow rate is 65000 Nm 3 / h, the top-blown gas medium is CO, CO2, O2, the gas pressure is 0.8 - 1.5 MPa, the bottom-blown gas medium is CO2, N2, Ar, and the gas pressure is 0.3 - 0.6 MPa. The gas separation system uses the chemical absorption method, the CO2 separation concentration is 99.6%, and the CO separation concentration is 90%.

[0053] (2) Based on conditions such as the molten iron conditions entering the furnace, the proportion of cold charge charged, and the addition amount of slag-making agent, the secondary smelting system calculates the addition amounts of slag-making agent, coolant, and supplementary heat through static models of material balance and heat balance, considers the heat utilization efficiency, and formulates the converter smelting process regime. The set weight of molten iron is 189 t, the weight of scrap steel is 68 t, the hydrogen-based direct reduced iron is 58 t, and the light-burned dolomite is 9.8 kg / t. According to an alkalinity of 3, the lime addition amount is calculated to be 15 kg / t through formulas 1 - 4. The parameters of molten iron and cold charge are shown in Tables 1 and 2.

[0054] Effective CaO = CaO in lime - R * SiO2 in lime (1)

[0055] The amount of SiO2 already in the slag = the amount brought in by fluorite + the amount brought in by light-burned dolomite + the amount brought in by the furnace lining + the product of Si oxidation

[0056] + the amount of SiO2 in molten iron slag + the amount brought in by the slag splashing layer (2)

[0057] The amount of CaO already in the slag = the amount brought in by light-burned dolomite + the amount brought in by the furnace lining + the amount of CaO in molten iron slag + the amount brought in by the slag splashing layer + the amount brought in by white magnesia balls (3)

[0058] The amount of lime to be added = (R * existing SiO2 - existing CaO) / effective CaO (4)

[0059] Table 1 Parameters of molten iron, scrap steel, hydrogen-based direct reduced iron and molten steel

[0060] Name C / ％ Si / % Mn / % P / ％ S / ％ Temperature / °C Hot metal 3.9 0.19 0.14 0.07 0.018 1372 Scrap steel 0.10 0.05 0.20 0.015 0.010 25 Molten steel 0.05 0.003 0.072 0.012 0.010 1670 Direct reduced iron 2.1 0 0 0.007 0 25

[0061] Table 2 Parameters of lime and light-burned dolomite

[0062] Name CaO / % <![CDATA[SiO2 / %]]> MgO / % CaS / % Loss on ignition / % Lime 91.8 1.2 0 0.18 1.7 Dolomite 49.6 0.9 31.9 0 8.8

[0063] Based on the calculation results of the secondary converter model, the CO and O2 injection flow rates and times are confirmed, and a heat balance calculation is carried out for the converter. At this time, the total heat income is 131956.12 KJ / t of steel, the total heat expenditure is 1663286.57 KJ / t of steel, and the total amount of CO that needs to be supplemented is 10700 Nm 3 , after the previous furnace was smelted conventionally and slag splashing was used for furnace protection, the converter was swung to the set position for adding cold charge, 68 t of scrap steel and 58 t of hydrogen-based direct reduced iron were added into the converter. After the converter was swung back to the upright position, the oxygen lance was lowered to the set position, the O2 valve was opened first, and then the CO valve was opened. The CO flow rate was 20000 Nm3 Increase to 39600 Nm / h 3 / h, the O2 flow rate increases from 10000 Nm 3 / h to 20800 Nm 3 / h, form a burner mode for combustion ignition, preheat the cold charge, and the preheating time is 8 min

[0064] Start the gas separation system to separate CO and CO2 in the converter gas. During the preheating period of the cold charge, start the flue gas storage tank recovery system to store the high-concentration CO2 flue gas during the preheating period, and then start the gas separation system to separate CO2 gas by chemical absorption method

[0065] Lift the oxygen lance to the set position. At the same time, close the CO and O2 valves, rock the converter forward and backward twice to ensure that the cold charge is evenly flipped in the converter, then lower the oxygen lance to the designated position again, and start the combustion preheating mode. The CO flow rate is 39600 Nm 3 / h, the O2 flow rate is 20800 Nm 3 / h, form a burner mode for combustion ignition, preheat the cold charge, and the preheating time is 4 min to ensure that the temperature of the cold charge is not lower than 600 °C

[0066] When the cold charge ratio is 40% and the carbon content in hot metal < 4.0% or the silicon content in hot metal < 0.2%, use the SCH-1 mode for smelting, top-blow oxygen and carbon monoxide

[0067] Lift the oxygen lance to the set position, rock the converter to charge hot metal and then rock it straight, lower the oxygen lance and open the O2 valve, then open the CO valve. Set the first 4 min of smelting, the O2 flow rate is 62000 Nm 3 / h, the CO flow rate is 4480 Nm 3 / h, the bottom-blow CO flow rate is 1100 Nm 3 / h. From the middle and late stage of smelting to 11 min, the O2 flow rate is 63000 Nm 3 / h, the CO flow rate is 2500 Nm 3 / h, the bottom-blow CO2 flow rate is 800 Nm 3 / h. In the late stage of smelting until before tapping, the O2 flow rate is 65000 Nm 3 / h, the CO flow rate is 5000 Nm 3 / h, the bottom-blow CO2+Ar flow rate is 1200 Nm 3 / h

[0068] Use the sublance or other analysis methods. After analyzing that the composition and temperature of the molten steel meet the smelting requirements, rock the furnace to tap. After tapping, splash slag for furnace protection and prepare for the next furnace smelting

[0069] After adopting the process of the present invention, the ratio of cold charge in the converter is increased to 40%, the solid waste of dedusting ash is reduced by 11.5%, the gas recovery is increased by 4.6 Nm 3 / t, and the oxygen content in the molten steel is reduced by 16%.

[0070] Example 2

[0071] (1) In this embodiment, the method is applied to 300t converter steelmaking. The nitrogen sealing ring uses CO2 gas as the sealing gas. The converter gas recovery per ton of steel is 101 Nm 3 , the gas calorific value is 6591 kJ / Nm 3 , the CO content is 52.1%, the CO2 content is 35.3%, the outer diameter of the oxygen lance used is 406 mm, and the designed flow rate is 65000 Nm 3 / h. The top-blown gas medium is CO, CO2, O2, the gas pressure is 0.8 - 1.5 MPa, the bottom-blown gas medium is CO2, N2, Ar, and the gas pressure is 0.3 - 0.6 MPa. The gas separation system adopts the chemical absorption method, the CO2 separation concentration is 99.6%, and the CO separation concentration is 90%.

[0072] (2) Based on conditions such as the hot metal conditions entering the furnace, the cold charge charging ratio, and the amount of slag-making agent added, the secondary smelting system calculates the amount of slag-making agent, coolant added, and supplementary heat through the static models of material balance and heat balance, considers the heat utilization efficiency, and formulates the converter smelting process regime. The hot metal weight is set at 150t, the scrap steel weight is 150t, and the light burned dolomite is 9.8 kg / t. According to an alkalinity of 3, the lime addition amount is calculated to be 4.3 kg / t through formulas 1 - 4. The hot metal and cold charge parameters are shown in Tables 3 and 4.

[0073] Table 3 Hot Metal, Scrap Steel and Molten Steel Parameters

[0074] Name C / ％ Si / % Mn / % P / ％ S / ％ Temperature / °C Hot metal 3.9 0.19 0.17 0.07 0.019 1380 Scrap steel 0.12 0.06 0.20 0.015 0.010 25 Molten steel 0.06 0.003 0.072 0.012 0.010 1670

[0075] Table 4 Lime and Light Burned Dolomite Parameters

[0076] Name CaO / % <![CDATA[SiO2 / %]]> MgO / % CaS / % Loss on ignition / % Lime 92.1 1.1 0 0.18 1.6 Dolomite 49.8 1.7 33.5 0 8.9

[0077] Based on the calculation results of the converter secondary model, the CO and O2 injection flow rates and times are confirmed, and a heat balance calculation is carried out for the converter. At this time, the total heat income is 1007042.04 KJ / t of steel, the total heat expenditure is 1597677.664 KJ / t of steel, and the total amount of CO that needs to be supplemented is 17500 Nm 3 , after the previous furnace was conventionally smelted and slag splashing for furnace protection, the converter was swung to the set position for cold charge addition, 150t of scrap steel was added into the converter. After the converter was swung upright, the oxygen lance was lowered to the set position, and the O2 valve was opened first, then the CO valve was opened. The CO flow rate was increased from 20000 Nm 3 / h to 58600 Nm3 / h, the O2 flow rate is increased from 10000 Nm 3 / h to 30000 Nm 3 / h, ignition for combustion forms a burner mode to preheat the cold charge, and the preheating time is 8 min.

[0078] Start the gas separation system to separate CO and CO2 in the converter gas. During the period of preheating the cold charge, start the flue gas storage tank recovery system to store the high-concentration CO2 flue gas during the preheating period, and then start the gas separation system to separate CO2 gas by chemical absorption method.

[0079] Lift the oxygen lance to the set position. At the same time, close the CO and O2 valves, rock the converter forward and backward twice to ensure that the cold charge is evenly turned over in the converter, then lower the oxygen lance to the designated position again, and start the combustion preheating mode. The CO flow rate is 58600 Nm 3 / h, the O2 flow rate is 30000 Nm 3 / h, ignition for combustion forms a burner mode to preheat the cold charge, and the preheating time is 8 min to make the temperature of the cold charge not lower than 600 °C.

[0080] When the ratio of cold charge is greater than 40% and the carbon content of hot metal < 4.0% or the silicon content of hot metal < 0.2%, SCH-1 mode is adopted for smelting, with top-blown oxygen and carbon monoxide.

[0081] Lift the oxygen lance to the set position. After rocking the converter to charge hot metal and then rocking it back to the upright position, lower the oxygen lance and open the O2 valve, then open the CO valve. Set the first 4 min of smelting, with the O2 flow rate of 61000 Nm 3 [[ID=,23]] / h, the CO flow rate is 6400 Nm 3 / h, the bottom-blown CO2 flow rate is 1100 Nm 3 / h. From the middle and late stages of smelting to 11 min, the O2 flow rate is 63000 Nm 3 / h, the CO flow rate is 5500 Nm 3 / h, the bottom-blown CO2 flow rate is 800 Nm 3 / h. In the late stage of smelting until before tapping, the O2 flow rate is 64000 Nm 3 / h, the CO flow rate is 4900 Nm 3 / h, the bottom-blown CO2 + Ar flow rate is 1200 Nm 3 / h.

[0082] Adopt the sublance or other analysis methods. After analyzing that the composition and temperature of the molten steel meet the smelting requirements, rock the furnace to tap. After tapping, carry out slag splashing for furnace protection and prepare for the smelting of the next furnace.

[0083] After adopting the process of the present invention, the ratio of converter cold charge is increased to 50%, the solid waste of dust removal ash is reduced by 10.5%, and the gas recovery is increased by 4.3 Nm3 / t, the oxygen content of the molten steel decreases by 17%.

[0084] Example 3

[0085] (1) In this example, the method is applied to 120t converter steelmaking. The nitrogen sealing ring uses CO2 gas as the sealing gas. The converter gas recovery per ton of steel is 105 Nm 3 , the calorific value of the gas is 6844 kJ / Nm 3 , the CO content is 54.1%, the CO2 content is 35.3%. The outer diameter of the oxygen lance used is 406 mm, and the designed flow rate is 30000 Nm 3 / h. The top-blown gas medium is CO, CO2, O2, and the gas pressure is 0.8 - 1.5 MPa. The bottom-blown gas medium is CO2, N2, Ar, and the gas pressure is 0.3 - 0.6 MPa. The gas separation system uses the chemical absorption method, the CO2 separation concentration is 99.6%, and the CO separation concentration is 90%.

[0086] (2) Based on conditions such as the hot metal conditions entering the furnace, the proportion of cold charge charged, and the addition amount of slag formers, the secondary smelting system calculates the addition amounts of slag formers and coolants and the supplementary heat through the static models of material balance and heat balance, considers the heat utilization efficiency, and formulates the converter smelting process regime. The weight of the hot metal is set to 114t, the weight of the scrap is 25t, and the light-burned dolomite is 15 kg / t. According to an alkalinity of 3, the lime addition amount is calculated to be 17.6 kg / t through formulas 1 - 4. The hot metal and cold charge parameters are shown in Tables 5 and 6.

[0087] Table 5 Parameters of Hot Metal, Scrap and Molten Steel

[0088] Name C / ％ Si / % Mn / % P / ％ S / ％ Temperature / °C Hot metal 4.25 0.35 0.11 0.067 0.025 1355 Scrap steel 0.09 0.13 0.39 0.022 0.020 25 Molten steel 0.036 0 0.048 0.016 0.008 1670

[0089] Table 6 Parameters of Lime and Light-Burned Dolomite

[0090] Name CaO / % <![CDATA[SiO2 / %]]> MgO / % CaS / % Loss on ignition / % Lime 91.7 1.3 0 0.18 1.8 Dolomite 48.8 0.8 34.1 0 8.7

[0091] Based on the calculation results of the converter secondary model, the CO and O2 injection flow rates and times are confirmed, and a heat balance calculation is performed on the converter. At this time, the total heat income is 1674425 KJ / t of steel, and the total heat expenditure is 1692663.5 KJ / t of steel. Basically, no additional heat needs to be supplemented. After the previous furnace was conventionally smelted and slag splashing for furnace protection, the converter was swung to the set position for cold charge addition. 48t of scrap was added into the converter. After swinging the converter upright, the oxygen lance was lowered to the set position, and the O2 valve was opened first, then the CO valve was opened. The CO flow rate was increased from 8000 Nm 3 / h to 22000 Nm 3 / h, and the O2 flow rate was increased from 4000 Nm 3 / h to 11500 Nm 3At a rate of / h, ignition is carried out to form a burner mode to preheat the cold charge, and the preheating time is 4 min.

[0092] Start the gas separation system to separate CO and CO2 in the converter gas. During the period of preheating the cold charge, start the flue gas storage tank recovery system to store the high-concentration CO2 flue gas during the preheating period, and then start the gas separation system to separate CO2 gas by chemical absorption method.

[0093] Lift the oxygen lance to the set position. At the same time, close the CO and O2 valves, rock the converter forward and backward twice to ensure that the cold charge is evenly turned over in the converter, then lower the oxygen lance to the designated position again, and start the combustion preheating mode. The CO flow rate is 22500 Nm 3 / h, and the O2 flow rate is 11500 Nm 3 / h. Ignition is carried out to form a burner mode to preheat the cold charge, and the preheating time is 2 min to make the temperature of the cold charge not lower than 600 °C.

[0094] When the cold charge ratio is less than 20% and the carbon content in hot metal ≥ 4.0% or the silicon content in hot metal ≥ 0.2%, the SCH-2 mode is adopted for smelting, with top-blown oxygen and carbon dioxide, or the SCH-3 mode is adopted, with top-blown oxygen. In this example, the SCH-2 mode is adopted for smelting, with top-blown oxygen and carbon dioxide.

[0095] Lift the oxygen lance to the set position. After rocking the converter to charge hot metal and then rocking it straight, lower the oxygen lance and open the O2 valve, and then open the CO2 valve. Set the first 4 min of smelting, with an O2 flow rate of 25000 Nm 3 / h, a CO2 flow rate of 1800 Nm 3 / h, and a bottom-blown CO2 flow rate of 440 Nm 3 / h. From the middle and later stages of smelting to 11 min, the O2 flow rate is 26000 Nm 3 / h, the CO2 flow rate is 1000 Nm 3 / h, and the bottom-blown CO2 flow rate is 350 Nm 3 / h. In the later stage of smelting until before tapping, the O2 flow rate is 27000 Nm 3 / h, the CO2 flow rate is 2100 Nm 3 / h, and the bottom-blown CO2 + Ar flow rate is 500 Nm 3 / h.

[0096] Adopt a sublance or other analysis methods. After analyzing that the molten steel composition and temperature meet the smelting requirements, rock the furnace to tap. After tapping, carry out slag splashing for furnace protection and prepare for the next furnace smelting.

[0097] After adopting the process of the present invention, the cold charge ratio of the converter is increased to 40%, the solid waste of dust removal ash is reduced by 12.9%, and the gas recovery is increased by 4.7 Nm 3 / t, the oxygen content of the molten steel decreases by 19%.

[0098] Comparative Example 1

[0099] (1) In this embodiment, the method is applied to steelmaking in a 300t converter. The nitrogen sealing ring uses CO2 gas as the sealing gas. The recovery amount of converter gas per ton of steel is 106 Nm 3 , the calorific value of the gas is 6844 kJ / Nm 3 , the CO content is 54.1%, the CO2 content is 36.3%, the outer diameter of the oxygen lance used is 406 mm, and the designed flow rate is 65000 Nm 3 / h, the top-blown gas medium is CO, CO2, O2, the gas pressure is 0.8 - 1.5 MPa, the bottom-blown gas medium is CO2, N2, Ar, and the gas pressure is 0.3 - 0.6 MPa. The gas separation system adopts the chemical absorption method, the CO2 separation concentration is 99.6%, and the CO separation concentration is 90%.

[0100] (2) Based on conditions such as the conditions of the hot metal charged into the furnace, the proportion of cold charge charged, and the addition amount of slag-making agents, the secondary smelting system calculates the addition amounts of slag-making agents and coolants and the supplementary heat through static models of material balance and heat balance, considers the heat utilization efficiency, and formulates the converter smelting process regime. The weight of the hot metal is 180t, the weight of the scrap is 120t, the addition amount of lime is 26 kg / t, and the addition amount of light-burned dolomite is 9.8 kg / t. The parameters of the hot metal and cold charge are shown in Table 1.

[0101] Table 7 Parameters of Hot Metal, Scrap and Molten Steel

[0102] Name C / ％ Si / % Mn / % P / ％ S / ％ Temperature / °C Hot metal 4.2 0.27 0.17 0.07 0.019 1380 Scrap steel 0.12 0.06 0.20 0.015 0.010 25 Molten steel 0.06 0.001 0.072 0.012 0.010 1670

[0103] Without preheating the cold charge, after heating the scrap, raise the oxygen lance to the set position, rock the converter to pour in the hot metal and then rock it back to the upright position, lower the oxygen lance and open the O2 valve, then open the CO2 valve. Set the first 4 minutes of smelting, the O2 flow rate is 61000 Nm 3 / h, the CO2 flow rate is 4400 Nm 3 / h, the bottom-blown CO2 flow rate is 1100 Nm 3 / h. From the middle and late stages of smelting to 11 minutes, the O2 flow rate is 63000 Nm 3 / h, the CO2 flow rate is 2500 Nm 3 / h, the bottom-blown CO2 flow rate is 800 Nm 3 / h. In the late stage of smelting until before tapping, the O2 flow rate is 6,4000 Nm 3 / h, the CO2 flow rate is 4900 Nm 3 / h, the bottom-blown CO2 + Ar flow rate is 1200 Nm 3 / h.

[0104] During the smelting process, insufficient heat led to the formation of nodules in the converter molten steel, resulting in the failure of the smelting of this furnace of molten steel.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0106] In addition, those skilled in the art can understand that although some of the embodiments herein include certain features included in other embodiments but not other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present application, and should not be regarded as an admission or any form of suggestion that this information constitutes prior art known to those skilled in the art.

Claims

1. A method for smelting with a high cold material ratio by short-circuit recycling of converter gas, characterized in that: include: S1. The converter gas generated during the converter smelting process is separated to obtain carbon dioxide gas and carbon monoxide-containing gas, the carbon dioxide gas as a blowing gas source, the carbon monoxide-containing gas as a preheating and blowing gas source; S2. After the converter is loaded with cold material, the carbon monoxide-containing gas is mixed with top-blown oxygen. The oxygen lance adopts a non-premixing mode and ignites the residual heat in the converter to form a burner mode to preheat the cold material; the proportion of the cold material is 5%-60%, and the end temperature of the preheating is not higher than 1000°C; The carbon dioxide flue gas generated by preheating the cold material under the burner mode condition is stored in a flue gas storage tank; S3. After the preheating is completed for the first time, the oxygen lance is lifted to the cooling hood, the converter is shaken to cause the cold material to tumble in the converter, and after the converter is straightened, the oxygen lance is lowered to a predetermined height and the step S2 is repeated until the cold material temperature is not less than 600°C. S4. The oxygen lance is raised to the water-cooled smoke hood, the converter is shaken to the designated position and molten iron is added and then shaken straight, and then the oxygen lance is lowered to the set position. Different blowing modes are used based on the smelting conditions, wherein the top blowing mode includes: When the cold charge ratio is less than 20% and the carbon content of the molten iron is ≥4.0% or the silicon content of the molten iron is ≥0.2%, the SCH-2 mode is used for smelting with top blowing of oxygen and carbon dioxide, or the SCH-3 mode is used with top blowing of oxygen; When the cold charge ratio is 20%-40%, and the carbon content of molten iron is less than 4.0% or the silicon content of molten iron is less than 0.2%, the SCH-1 mode is used for smelting, with top blowing of oxygen and carbon monoxide, a cold charge heating rate of 20-150℃ / min∙t cold charge, and a heating time of 2-8min; When the cold charge ratio is greater than 40% and the carbon content of molten iron is less than 4.0% or the silicon content of molten iron is less than 0.2%, the SCH-1 mode is used for smelting, with top blowing of oxygen and carbon monoxide, a cold charge heating rate of 50-200℃ / min∙t cold charge, and a heating time of 3-8min; The bottom blowing gas includes one or more of carbon dioxide, nitrogen and argon; Automatically switch smelting mode and gas injection volume according to converter smelting conditions; S5. The nitrogen seal ring of the converter smelting process uses carbon dioxide or water vapor as a sealing gas. Based on the monitoring system of the converter smelting process, the molten steel meets the smelting task requirements, the oxygen lance is promoted, and the gas is closed at the set position, and the converter is shaken to tap steel; The carbon monoxide-containing gas is high-concentration carbon monoxide or a carbon monoxide mixture, the volume concentration of the high-concentration carbon monoxide is 60-99.99%, the volume concentration of the carbon monoxide mixture is 30-50%, and the gas operating pressure is 0.3-2.5 MPa; when top-blowing carbon monoxide and oxygen, the volume proportion of high-concentration carbon monoxide is not higher than 60%, or the volume proportion of the carbon monoxide mixture is not higher than 80%; The volume concentration of the carbon dioxide gas is 60-99.99%, and the gas operating pressure is 0.3-2.5 MPa; when top-blowing oxygen and carbon dioxide, the volume proportion of carbon dioxide is no more than 50%.

2. The method for smelting with high cold material ratio by short-circuit recycling of converter gas according to claim 1, characterized in that: The burner modes include low-intensity heating, medium-intensity heating and high-intensity heating; the cold material heating intensity of the low-intensity heating is 10-50℃ / min∙t cold material, the cold material heating intensity of the medium-intensity heating is 51-100℃ / min∙t cold material, and the cold material heating intensity of the high-intensity heating is 101-200℃ / min∙t cold material.

3. The method for smelting converter gas by short-circuit recycling and high cold material ratio according to claim 1, characterized in that: The cold material is based on heavy scrap steel, and the weight of light scrap steel and direct reduced iron is converted according to a coefficient of 0.1-0.9; The heavy scrap steel and the light and thin scrap steel are single scrap steel, and the direct reduced iron is single direct reduced iron, including hydrogen-based direct reduced iron or coal-based direct reduced iron.

4. The method for smelting with high cold material ratio by short-circuit recycling of converter gas according to claim 1, characterized in that: The volume content of carbon dioxide in the flue gas storage tank is 20-80%.

5. The method for smelting with high cold material ratio by short-circuit recycling of converter gas according to claim 1, characterized in that: The nominal capacity of the converter is 30-400t.

6. The method for smelting with high cold material ratio by short-circuit recycling of converter gas according to any one of claims 1 to 5, characterized in that: The separation method includes one or more of chemical absorption, pressure swing adsorption, membrane separation, and low-temperature distillation.

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