Converter steelmaking collaborative carbon reduction and splashing control method based on lime kiln waste gas recovery

Abstract

The invention provides a converter steelmaking synergetic carbon reduction and splashing control method based on lime kiln waste gas recovery, relates to the technical field of ferrous metallurgy, and aims to solve the problems that in the prior art, industrial waste gas is used for replacing part of oxygen, but the problem of oxygen lance blockage caused by high waste gas dust content is not solved; the desulfurization waste gas of the lime kiln is filtered till the dust content is smaller than 2 mg / Nm < 3 >, then pressurized, mixed with oxygen according to a certain proportion and blown into a converter molten pool, high-slag-remaining operation with the slag remaining amount larger than or equal to 30% is synchronously carried out, the oxidation content in slag is increased, and the slag remaining amount is increased. Therefore, the adverse effect of decarburization rate reduction caused by oxygen concentration reduction is reduced. Compared with an existing waste gas utilization technology, consumption of pure oxygen and steel materials per ton of steel can be reduced, the splashing occurrence rate is effectively reduced, the service life of a furnace lining is prolonged, the purpose of CO2 emission reduction is achieved, and the method has the advantages of being high in process adaptability, remarkable in emission reduction effect, outstanding in economic benefit and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and in particular to a method for coordinated carbon reduction and splashing control in converter steelmaking based on lime kiln waste gas recovery. Background Art

[0002] Traditional converter steelmaking processes typically use supersonic pure oxygen blowing. Producing this oxygen consumes significant electricity, approximately 40-50 kWh per ton of steel. Furthermore, the steelmaking process generates significant carbon dioxide emissions, which runs counter to current trends in energy conservation and emission reduction. Furthermore, the highly oxidizing slag during converter steelmaking can easily cause splashing, which not only results in steel loss but also poses a threat to production safety.

[0003] During the production process, lime kilns produce a large amount of desulfurization waste gas, which contains a high concentration of carbon dioxide. These waste gases are directly discharged into the atmosphere, of which more than 20% of the CO2 is not utilized, which not only causes a waste of resources but also aggravates environmental pollution.

[0004] The existing technology uses industrial waste gas to replace part of the oxygen, but does not solve the problem of oxygen lance blockage caused by high dust content in the waste gas, and does not involve the coordinated optimization of splashing control and slag retention operation, which affects the quality of steelmaking. Therefore, it is particularly important to design a method for coordinated carbon reduction and splashing control in converter steelmaking based on lime kiln waste gas recovery to solve the above technical problems. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that industrial waste gas is used to replace part of the oxygen in the prior art, but the blockage of the oxygen lance caused by the high dust content of the waste gas is not solved, and the problem of coordinated optimization of splashing control and slag retention operation is not involved. Instead, a method for coordinated carbon reduction and splashing control in converter steelmaking based on lime kiln waste gas recovery is proposed.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: A method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery, comprising the following steps: a. Treatment of lime kiln desulfurization waste gas: The lime kiln desulfurization waste gas is sent to the gas storage tank through a pipeline, and a filter is added at the inlet of the gas storage tank to further reduce the dust content in the waste gas to 2 mg / Nm 3Next, the waste gas in the gas storage tank is pressurized to 1.3-1.6MPa. A pipeline is laid in the gas storage tank to send the waste gas to the converter oxygen lance for mixing with oxygen. The pipeline is equipped with a flow control valve and a pressure gauge to control the waste gas flow and pressure entering the furnace. b. Slag retention and mixed blowing: After slag splashing, the amount of newly generated slag is calculated based on the Si and Mn content of the molten iron in the furnace (add slag making material (lime + raw dolomite + limestone / 2) + sinter ore amount / 5 + (molten iron amount + scrap steel amount) * (0.01 + molten iron Si content * 2 + scrap steel Mn content)). After slag dumping, based on the newly generated slag amount and the total slag required for P removal, 30-60% of the slag is retained. If the silicon + manganese content of the molten iron in the furnace is greater than 0.75%, the slag is not retained. In order to prevent the electrostatic precipitator from exploding due to high oxygen content in the flue gas, the proportion of lime kiln desulfurization waste gas is increased to 40-60% when the converter is ignited and blown. After 30-60 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 30-35%.

[0007] Preferably, the steps also include: c. Controlling splashing during the smelting process: The slag after the converter slag retention operation is highly oxidizing and prone to splashing. To prevent splashing during the blowing process, the oxygen supply should be appropriately lowered in the early stages to increase the proportion of desulfurization waste gas mixed into the lime kiln. Material distribution is performed according to a pre-set material calculation model, with batch additions based on the calculated amount. Slag material is then added in a reasonable amount in the early stages to avoid low-temperature splashing.

[0008] Preferably, the working steps also include: d. slag splashing and furnace protection control: after the converter slag retention operation, the relative amount of slag in the furnace is large and the slag is highly foaming. In order to achieve tapping without slag and safe iron addition after slag retention, it is necessary to suppress bubbles and reduce the oxidizing property in the slag before tapping. Therefore, in the later stage of blowing, the proportion of lime kiln desulfurization waste gas is increased to 40-60%, and nitrogen is blown down again for 1-2 minutes. The gun position is controlled at 1000-1500mm. If the slag is thin, raw dolomite is added during the slag splashing process to adjust the slag. The slag splashing time is finally based on the slag being dry; e. coal gas recovery control: according to the existing coal gas recovery conditions CO>7%, O2<1.5%, because CO2 participates in the reaction to increase the amount of CO generated in the coal gas, and also increases the calorific value of the recovered coal gas. Therefore, according to the value displayed by the flue gas analyzer, the coal gas is recovered under the conditions of CO>7% and O2<1.5%.

[0009] Preferably, the filter is made of high-precision filter material, which can effectively intercept dust particles and ensure that the dust content in the exhaust gas is stably reduced to 2mg / Nm 3 the following.

[0010] Preferably, the flow control valve and the pressure gauge can be adjusted automatically to accurately control the flow rate and pressure of the exhaust gas entering the furnace according to the real-time needs of converter steelmaking.

[0011] Preferably, the material calculation model is established based on a large amount of production data and experimental results, and can accurately calculate the type and quantity of required slag according to different molten iron compositions and steelmaking requirements.

[0012] Preferably, the amount of raw dolomite added is adjusted according to the consistency of the slag to achieve the best slag adjustment effect.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are: In the present invention, during use, the lime kiln desulfurization waste gas is filtered to a dust content of less than 2 mg / Nm 3 After pressurization, it is mixed with oxygen in a certain proportion and blown into the converter molten pool. Simultaneously, a high slag retention operation with a slag retention amount of ≥30% is implemented to increase the oxidation content in the slag, so as to reduce the adverse effects of reduced decarburization rate caused by decreased oxygen concentration. The higher CO2 content in the lime kiln desulfurization waste gas can reduce the oxidizing property of the slag during the converter smelting process after being mixed with oxygen and blown, thereby achieving high slag retention operation while avoiding splashing, thereby achieving the purpose of greatly improving coal gas recovery and reducing carbon dioxide emissions. Compared with existing waste gas utilization technologies, the present invention can reduce the consumption of pure oxygen and steel materials per ton of steel, effectively reduce the occurrence rate of splashing, thereby extending the life of the furnace lining, and achieving the purpose of CO2 emission reduction. It has the advantages of strong process adaptability, significant emission reduction effect, and outstanding economic benefits. The implementation of this process is of great significance to energy conservation and carbon reduction in steel mills and reduction of steel material consumption. It solves the problem of using industrial waste gas to replace part of the oxygen in the existing technology, but does not solve the problem of oxygen gun blockage caused by high dust content in the waste gas, and does not involve the problem of coordinated optimization of splashing control and slag retention operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the process of the converter steelmaking coordinated carbon reduction and splashing control method based on lime kiln waste gas recovery of the present invention; DETAILED DESCRIPTION

[0015] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0016] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0017] Example 1 The first case of implementing the method of the present invention in converter steelmaking: Treatment of lime kiln desulfurization waste gas: The lime kiln desulfurization waste gas is sent to the gas storage tank through a pipeline. A high-precision filter is installed at the inlet of the gas storage tank. After filtration, the dust content in the waste gas is reduced to 1.5mg / Nm 3 The exhaust gas in the gas storage tank is pressurized to 1.5MPa by a compressor, and then transported to the converter oxygen lance through a pipeline to mix with oxygen. The flow rate and pressure of the exhaust gas entering the furnace are adjusted by a flow control valve and a pressure gauge to ensure uniform mixing of the exhaust gas and oxygen.

[0018] Slag mixed blowing: After the slag splashing is completed, the composition of the molten iron in the furnace is analyzed. The Si content of the molten iron is 0.3%, the Mn content is 0.2%, and the P content is 0.1%. The amount of molten iron is 90t, the amount of scrap steel is 20t, the additional slag making material (lime + quick white + limestone / 2) is 8t, and the amount of sintered ore is 5t.

[0019] Calculate the newly added slag amount according to the formula: newly added slag amount = 8 + 5 / 5 + (100 + 10) × (0.01 + 0.3 × 2 + 0.2) = 8+1+110×(0.01+0.6+0.2)= 8+1+110×0.81=98.1t. The total slag required for P removal is 150t. After slag dumping, the remaining slag is 51.9t (150-98.1), accounting for 34.6% of the total slag.

[0020] When the converter is ignited and blown, the proportion of lime kiln desulfurization waste gas is increased to 50%. After 40 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 32%.

[0021] Splash control during the smelting process: During the initial oxygen supply phase, the lance height was lowered to 1.8 meters, and the proportion of desulfurization exhaust gas from the lime kiln was increased to 35%. Based on the material calculation model, the initial slag was added in batches: 3 tons of lime and 2 tons of raw dolomite were added in the first batch, and 1 ton of limestone was added in the second batch. No splashing occurred throughout the blowing process.

[0022] Slag splashing and furnace protection control: In the late blowing stage, the proportion of desulfurized waste gas from the lime kiln was increased to 50%. Nitrogen was blown again from the lance for 1.5 minutes, with the lance position controlled at 1200mm. Due to the good fluidity of the slag, 2 tons of raw dolomite were added for slag adjustment. The slag splashing time was 3 minutes, and the slag was finally splashed dry, achieving slag-free tapping and safe iron addition after slag retention.

[0023] After testing, the steel consumption was reduced by 3kg / t and the gas recovery volume was increased by 20m3 in this steelmaking process. 3 / t, carbon dioxide emissions were reduced by 11kg / t.

[0024] Example 2 The second case of implementing the method of the present invention in converter steelmaking: Treatment of lime kiln desulfurization waste gas: The lime kiln desulfurization waste gas is sent to the gas storage tank through a pipeline. A high-precision filter is installed at the inlet of the gas storage tank. After filtration, the dust content in the waste gas is reduced to 1.2mg / Nm 3 The exhaust gas in the gas storage tank is pressurized to 1.6MPa by a compressor, and then transported to the converter oxygen lance through a pipeline to mix with oxygen. The flow rate and pressure of the exhaust gas entering the furnace are adjusted by a flow control valve and a pressure gauge to ensure uniform mixing of the exhaust gas and oxygen.

[0025] Slag mixed blowing: After the slag splashing is completed, the composition of the molten iron in the furnace is analyzed. The Si content of the molten iron is 0.25%, the Mn content is 0.15%, and the P content is 0.09%. The amount of molten iron is 85t, the amount of scrap steel is 15t, the additional slag making material (lime + quick white + limestone / 2) is 7t, and the amount of sintered ore is 4t.

[0026] Calculate the newly added slag volume according to the formula: newly added slag volume = 7+4 / 5+(85+15)×(0.01+0.25×2+0.15) =7+0.8+100×0.66=73.8t. The total slag volume required for P removal is 120t. After slag dumping, the remaining slag volume is 46.2t (120-73.8), accounting for 38.5% of the total slag volume.

[0027] When the converter is ignited and blown, the proportion of lime kiln desulfurization waste gas is increased to 45%. After 40 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 31%.

[0028] Splash control during the smelting process: During the initial oxygen supply phase, the lance position was lowered to 1.9 meters, and the proportion of desulfurization exhaust gas from the lime kiln was increased to 32%. Based on the material calculation model, the initial slag was added in batches: 2.8 tons of lime and 1.8 tons of raw dolomite were added in the first batch, and 0.8 tons of limestone was added in the second batch. No splashing occurred throughout the blowing process.

[0029] Slag splashing and furnace protection control: In the late blowing stage, the proportion of desulfurized waste gas from the lime kiln was increased to 60%. Nitrogen was blown again from the lance for 1.2 minutes, with the lance position controlled at 1400mm. Due to the good fluidity of the slag, 2.2 tons of raw dolomite was added for slag adjustment. The slag splashing time was 2.8 minutes, and the slag was finally splashed dry, achieving slag-free tapping and safe iron addition after slag retention.

[0030] After testing, the steel consumption was reduced by 2.8kg / t and the gas recovery volume was increased by 18m 3 / t, carbon dioxide emissions were reduced by 9.5kg / t.

[0031] Example 3 The third case of implementing the method of the present invention in converter steelmaking: Treatment of lime kiln desulfurization waste gas: The lime kiln desulfurization waste gas is sent to the gas storage tank through a pipeline. A high-precision filter is installed at the inlet of the gas storage tank. After filtration, the dust content in the waste gas is reduced to 1.8mg / Nm 3 The exhaust gas in the gas storage tank is pressurized to 1.4 MPa by a compressor, and then transported to the converter oxygen lance through a pipeline to mix with oxygen. The flow rate and pressure of the exhaust gas entering the furnace are adjusted by a flow control valve and a pressure gauge to ensure uniform mixing of the exhaust gas and oxygen.

[0032] Slag mixed blowing: After the slag splashing is completed, the composition of the molten iron in the furnace is analyzed. The Si content of the molten iron is 0.4%, the Mn content is 0.25%, and the P content is 0.12%. The amount of molten iron is 105t, the amount of scrap steel is 25t, the additional slag making material (lime + quick white + limestone / 2) is 9t, and the amount of sintered ore is 6t.

[0033] Calculate the newly added slag volume according to the formula: newly added slag volume = 9+6 / 5+(105+25)×(0.01+0.4×2+0.25) =9+1.2+130×0.91=128.3t. The total slag volume required for P removal is 150t. After slag dumping, the remaining slag volume is 51.9t (150-98.1), accounting for 34.6% of the total slag volume.

[0034] When the converter is ignited and blown, the proportion of lime kiln desulfurization waste gas is increased to 55%. After 50 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 33%.

[0035] Splash control during the smelting process: During the initial oxygen supply phase, the lance position was lowered to 1.7 meters, and the proportion of desulfurization exhaust gas from the lime kiln was increased to 38%. Based on the material calculation model, the initial slag was added in batches: 3.5 tons of lime and 2.5 tons of raw dolomite were added in the first batch, and 1.2 tons of limestone was added in the second batch. No splashing occurred throughout the blowing process.

[0036] Slag splashing and furnace protection control: In the late blowing stage, the proportion of desulfurized waste gas from the lime kiln was increased to 58%. Nitrogen was blown again from the lance for 1.8 minutes, with the lance position controlled at 1300mm. Due to the good fluidity of the slag, 3 tons of raw dolomite was added for slag adjustment. The slag splashing time was 3.5 minutes, and the slag was finally splashed dry, achieving slag-free tapping and safe iron addition after slag retention.

[0037] After testing, the steel consumption was reduced by 3.2kg / t and the gas recovery volume was increased by 22m3 in this steelmaking process. 3 / t, carbon dioxide emissions were reduced by 11.5kg / t.

[0038] Example 4 The fourth case of implementing the method of the present invention in converter steelmaking: Treatment of lime kiln desulfurization waste gas: The lime kiln desulfurization waste gas is sent to the gas storage tank through a pipeline. A high-precision filter is installed at the inlet of the gas storage tank. After filtration, the dust content in the waste gas is reduced to 1.6mg / Nm 3 The exhaust gas in the gas storage tank is pressurized to 1.3 MPa by a compressor, and then transported to the converter oxygen lance through a pipeline to mix with oxygen. The flow rate and pressure of the exhaust gas entering the furnace are adjusted by a flow control valve and a pressure gauge to ensure uniform mixing of the exhaust gas and oxygen.

[0039] Slag mixed blowing: After the slag splashing is completed, the composition of the molten iron in the furnace is analyzed. The Si content of the molten iron is 0.35%, the Mn content is 0.25%, and the P content is 0.12%. The amount of molten iron is 100t, the amount of scrap steel is 25t, the additional slag making material (lime + quick white + limestone / 2) is 12t, and the amount of sintered ore is 6t.

[0040] Calculate the newly added slag amount according to the formula: newly added slag amount = 12 + 6 / 5 + (100 + 25) × (0.01 + 0.35 × 2 + 0.25) = 12 + 1.2 + 125 × (0.01 + 0.7 + 0.25) = 12 + 1.2 + 125 × 0.96 = 132.2 t. The total slag required for P removal is 190 t. After slag dumping, the remaining slag is 57.8 t (190 - 132.2), accounting for 30.4% of the total slag.

[0041] When the converter is ignited and blown, the proportion of lime kiln desulfurization waste gas is increased to 50%. After 50 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 32%.

[0042] Splash control during the smelting process: During the initial oxygen supply phase, the lance height was lowered to 1.6 meters, and the proportion of desulfurization exhaust gas from the lime kiln was increased to 38%. Based on the material calculation model, the initial slag was added in batches: 4 tons of lime and 3 tons of raw dolomite were added in the first batch, and 1.5 tons of limestone was added in the second batch. No splashing occurred throughout the blowing process.

[0043] Slag splashing and furnace protection control: In the late blowing stage, the proportion of desulfurized waste gas from the lime kiln was increased to 55%. Nitrogen was blown again for 2 minutes at the lance, with the lance position controlled at 1200mm. Due to the good fluidity of the slag, 3.5 tons of raw dolomite was added for slag adjustment. The slag splashing time was 4 minutes, and the slag was finally splashed dry, achieving slag-free tapping and safe iron addition after slag retention.

[0044] After testing, the steel consumption was reduced by 3.3kg / t and the gas recovery volume was increased by 23m 3 / t, carbon dioxide emissions were reduced by 12kg / t.

[0045] Working principle: The present invention filters the lime kiln desulfurization waste gas, pressurizes it and mixes it with oxygen in a certain proportion, blows it into the converter molten pool, and simultaneously implements high slag retention operation to increase the oxidation content in the slag, thereby reducing the adverse effects of reduced decarbonization rate due to decreased oxygen concentration. At the same time, it can reduce the oxidizing property of the slag during the blowing process, avoid splashing while achieving high slag retention operation, greatly improve gas recovery and achieve carbon dioxide emission reduction, ultimately achieving the goals of reducing pure oxygen and steel material consumption per ton of steel, extending the life of the furnace lining, and reducing CO2 emissions. It is of great significance to energy conservation and carbon reduction in steel mills and reducing steel material consumption.

Claims

1. A method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery, comprising: The following steps are included: a. Treatment of lime kiln desulfurization waste gas: send the lime kiln desulfurization waste gas into the gas storage tank through a pipeline, add a filter at the inlet of the gas storage tank to further reduce the dust content in the waste gas to 2mg / Nm 3 Next, the waste gas in the gas storage tank is pressurized to 1.3-1.6MPa. A pipeline is laid in the gas storage tank to send the waste gas to the converter oxygen lance for mixing with oxygen. The pipeline is equipped with a flow control valve and a pressure gauge to control the waste gas flow and pressure entering the furnace. b. Slag retention and mixed blowing: After slag splashing is completed, the amount of newly generated slag is calculated based on the Si and Mn content of the molten iron in the furnace (additional slag making material (lime + raw dolomite + limestone / 2) + sinter ore amount / 5 + (molten iron amount + scrap steel amount) * (0.01 + molten iron Si content * 2 + scrap steel Mn content)). After slag pouring, based on the newly generated slag amount and the total slag required for P removal, 30% to 60% of the slag is reserved. If the silicon + manganese content of the molten iron in the furnace is greater than 0.75%, the operation is carried out without retaining slag. In order to prevent the electrostatic precipitator from exploding due to high oxygen content in the flue gas, the proportion of lime kiln desulfurization waste gas is increased to 40% to 60% when the converter is ignited and blown. After 30 to 60 seconds of blowing, the proportion of lime kiln desulfurization waste gas is gradually reduced to 30% to 35%.

2. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The process also includes: c. Sputtering control during the smelting process: The slag after the converter slag retention operation is highly oxidizing and prone to splashing. To prevent splashing during the blowing process, the oxygen supply should be appropriately lowered in the early stages to increase the proportion of desulfurization waste gas mixed into the lime kiln. Material distribution is carried out according to the provided material calculation model, and the amount is added in batches according to the model's calculated amount. The slag material is added in a reasonable amount in the early stages to avoid low-temperature splashing.

3. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The working steps also include: d. slag splashing and furnace protection control: After the converter slag retention operation, the slag volume in the furnace is relatively large and the slag is highly foaming. In order to achieve slag-free tapping and safe iron addition after slag retention, it is necessary to suppress bubbles and reduce the oxidizing property of the slag before tapping. Therefore, in the late stage of blowing, the proportion of lime kiln desulfurization waste gas is increased to 40% to 60%, and nitrogen is blown again from the gun for 1 to 2 minutes. The gun position is controlled at 1000 to 1500 mm. If the slag is thin, raw dolomite is added during the slag splashing process to adjust the slag. The slag splashing time is finally based on the slag being splashed dry. e. Gas recovery control: According to the existing gas recovery conditions of CO>7% and O2<1.5%, the participation of CO2 in the reaction increases the amount of CO generated in the gas, and also increases the calorific value of the recovered gas. Therefore, according to the values ​​displayed by the flue gas analyzer, the gas is recovered under the conditions of CO>7% and O2<1.5%.

4. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The filter is made of high-precision filter material, which can effectively intercept dust particles and ensure that the dust content in the exhaust gas is stably reduced to 2mg / Nm 3 the following.

5. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The flow control valve and pressure gauge can be adjusted automatically to accurately control the flow rate and pressure of exhaust gas entering the furnace according to the real-time needs of converter steelmaking.

6. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The material calculation model is established based on a large amount of production data and experimental results, and can accurately calculate the type and quantity of required slag according to different molten iron compositions and steelmaking requirements.

7. The method for coordinated carbon reduction and splash control in converter steelmaking based on lime kiln waste gas recovery according to claim 1, characterized in that: The amount of raw dolomite added is adjusted according to the consistency of the slag to achieve the best slag adjustment effect.

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