Safe, rapid and environment-friendly blast furnace shutdown method

Abstract

The invention discloses a safe, rapid and environment-friendly blast furnace blowing-out method which comprises the following steps: 24 hours before blast furnace blowing-out and charge level lowering operation, adjusting fuel to be 20% higher than that of normal production fuel, lowering binary alkalinity of a slag system to be 1.0-1.05 times, and not adding a water gun; after the charge level lowering operation is started, the blast furnace keeps high oxygen enrichment blast smelting, and the oxygen enrichment rate is 15-20%; circulating decarburized coal gas is sprayed into a tuyere, the spraying amount of each ton of iron is 100-150m < 3 > / t, the theoretical combustion temperature of the tuyere is adjusted to be not higher than 2400 DEG C, the water pumping amount of the furnace top is reduced by 30%, and the top temperature is kept not higher than 350 DEG C in the water pumping operation of the furnace top; a pressure regulating valve group is kept in a normally open state during the charge level lowering operation, and the O2 content in the coal gas does not exceed 1%; and the oxygen enrichment rate is kept at 7-10% during the period, decarburized gas tuyere injection is stopped, the top temperature is kept not exceeding 400 DEG C until the tuyere blows through, and the furnace shutdown operation is completed.

Description

Technical Field

[0001] The present invention relates to a safe, rapid and environmentally friendly method for shutting down a blast furnace. Background Art

[0002] Traditional blast furnace shutdowns all adopt the process technology of blowing and smelting to lower the burden surface. During the shutdown period, in order to ensure that the top temperature of the burden surface does not exceed the standard and protect the safety of the top equipment, water spraying operations need to be carried out at the top of the furnace. And controlling a relatively low blowing air volume results in a long shutdown time. During the shutdown period, improper water spraying control is likely to cause internal blast shock in the blast furnace, and in severe cases, it will lead to the accident of furnace shell cracking. Therefore, when the burden surface drops to a certain height, in order to ensure safety, the blast furnace gas will be directly discharged into the atmosphere, causing environmental pollution and waste of resources and energy. Summary of the Invention

[0003] The purpose of the present invention is to provide a safe, rapid and environmentally friendly method for shutting down a blast furnace, which can achieve the safe and environmentally friendly shutdown goals of short shutdown time, less water spraying during shutdown, no internal blast shock in the furnace, and short dispersion time.

[0004] The technical solution adopted by the present invention is as follows: A safe, rapid and environmentally friendly method for shutting down a blast furnace is implemented according to the following steps: 1. Before the operation of lowering the burden surface during the blast furnace shutdown, keep the furnace condition smooth. In the first 24 hours of the burden surface lowering operation, adjust the fuel ratio, which is 20% higher than the normal production fuel ratio, and lower the binary basicity of the slag system by 1.0 - 1.05 times. Do not add new water spray guns, and only ensure that the existing water spray guns have good atomization effects; 2. After the burden surface lowering operation starts, the blast furnace maintains high oxygen enrichment blowing and smelting, with an oxygen enrichment rate of 15 - 20%; 3. Inject recycled decarbonized gas into the tuyere, with an injection volume of 100 - 150 m per ton of iron 3 / tAdjust the theoretical combustion temperature of the tuyere not to exceed 2,400 °C to ensure the smooth and stable operation of the blast furnace. The composition of the decarbonized gas is: CO 70 - 80%, H2 10 - 15%, N2 5 - 7%, CO2 0 - 2%, H2O 2 - 4%; 4. Due to high oxygen enrichment smelting, the tuyere blast volume is reduced by 40% compared with the traditional blast furnace, and the gas generation per ton of iron is reduced by 30%. The heat carried out by the gas is greatly reduced. During the operation of lowering the burden surface, the water injection volume at the top of the furnace is reduced by 30%, and the water injection operation at the top of the furnace keeps the top temperature not exceeding 350 °C; 5. During the operation of lowering the burden surface, the top pressure is kept in the state that the pressure regulating valve group is always open. Through the cooperation of on-line gas analyzer and manual gas sampling detection, the change of gas composition is tracked to ensure that the O2 content in the gas does not exceed 1%; 6. Enable the mechanical sounding rod to track the burden surface position, and calculate the burden surface position in the furnace by tracking the oxygen input. Compare and analyze it with the burden level detected by the sounding rod. Outside the detection range of the sounding rod, calculate the burden surface position with the oxygen input into the furnace. During this period, slag and iron are normally discharged outside the furnace; 7. When the burden surface drops below the bosh, depending on the burden column pressure difference being lower than 10 kPa, directly open the large top gas relief valve, close the network-connected gas cut-off valve and the eyeball valve, stop the gas recovery, and purge and maintain the pressure of the output gas system by introducing nitrogen; 8. Open the taphole to tap the last heat of iron. During this period, keep the oxygen enrichment rate at 7 - 10%, stop the injection of decarbonized gas into the tuyere, and open 2 - 4 water injection guns at the top of the furnace depending on the top temperature to keep the top temperature not exceeding 400 °C until the tuyere is blown through to complete the furnace shutdown operation.

[0005] The method of the present invention: 1. Oxygen enrichment furnace shutdown, with high oxygen content in the blast and fast furnace shutdown speed. 2. During furnace shutdown, decarbonized gas is injected into the tuyere, which can adjust the theoretical combustion temperature of the tuyere and keep the blast furnace running smoothly. At the same time, the recycling of decarbonized gas can also reduce the fuel ratio during furnace shutdown. During the furnace shutdown operation, the temperature of slag and iron is sufficient. 3. Oxygen enrichment furnace shutdown, with low gas generation per ton of iron, easy to control the top temperature, no need to add water injection guns. During the whole furnace shutdown process, the water injection volume is small, and the existing water injection guns can achieve safe and fast furnace shutdown. 4. During furnace shutdown, there is no need to stop blowing and cut off the gas, and no new water injection guns are added. The operation process is simple and the gas relief time is short. The present invention can be popularized and applied in the traditional blast furnace shutdown operation. By adding oxygen enrichment and injecting decarbonized gas in the traditional blast furnace shutdown operation, the goals of fast, safe, environmentally friendly and energy-saving furnace shutdown can be achieved, and it has a wide application prospect. Embodiment

[0006] A safe, fast and environmentally friendly blast furnace shutdown method is implemented according to the following steps: 1. Before the operation of lowering the burden surface during blast furnace shutdown, keep the furnace condition smooth. In the first 24 hours of the operation of lowering the burden surface, adjust the fuel ratio, which is 20% higher than the normal production fuel ratio, and lower the binary basicity of the slag system by 1.0 - 1.05 times. Do not add new water injection guns, and only ensure that the existing water injection guns have good atomization effect; 2. After the operation of lowering the burden surface starts, the blast furnace maintains high oxygen enrichment blast smelting, and the oxygen enrichment rate is 15 - 20%; 3. Inject recycled decarbonized gas into the tuyere, and the injection volume per ton of iron is 100 - 150 m 3 / t Adjust the theoretical combustion temperature of the tuyere not to exceed 2400 °C to ensure the smooth and stable operation of the blast furnace. The decarburized gas composition is: CO 70 - 80%, H2 10 - 15%, N2 5 - 7%, CO2 0 - 2%, H2O 2 - 4%; 4. Due to high oxygen enrichment smelting, the tuyere blast volume is reduced by 40% compared with the traditional blast furnace, and the gas generation per ton of iron is reduced by 30%. The heat carried by the gas is greatly reduced. During the operation of lowering the burden surface, the water injection volume at the furnace top is reduced by 30%, and the water injection operation at the furnace top keeps the top temperature not exceeding 350 °C; 5. During the operation of lowering the burden surface, the top pressure is kept in the state that the pressure regulating valve group is always open. Through the cooperation of on-line gas analyzer and manual gas sampling detection, the change of gas composition is tracked to ensure that the O2 content in the gas does not exceed 1%; 6. Enable the mechanical sounding rod to track the burden surface position, and calculate the burden surface position in the furnace by tracking the oxygen input, and compare and analyze it with the burden level detected by the sounding rod. Outside the detection range of the sounding rod, the burden surface position is calculated by the oxygen input into the furnace. During this period, slag and iron are normally discharged outside the furnace; 7. When the burden surface drops below the belly of the furnace, when the burden pressure difference is lower than 10 kPa, directly open the large top relief valve, close the on-grid gas cut-off valve and the eye valve, stop the gas recovery, and introduce nitrogen into the gas output system for purging and pressure maintenance; 8. Open the taphole and tap the last furnace of iron. During this period, keep the oxygen enrichment rate at 7 - 10%, stop the decarburized gas tuyere injection, and open 2 - 4 water injection guns at the furnace top according to the top temperature, keeping the top temperature not exceeding 400 °C until the tuyere is blown through to complete the furnace shutdown operation.

Claims

1. A safe, fast and environmentally friendly method for shutting down a blast furnace, characterized in that Implement according to the following steps:

1. Keep the furnace condition smooth before the operation of lowering the burden surface of the blast furnace. In the first 24 hours of the operation of lowering the burden surface, adjust the fuel ratio, which is 20% higher than the normal production fuel ratio, and lower the binary basicity of the slag system by 1.0 - 1.05 times. Do not add new water jet guns, just ensure that the existing water jet guns have good atomization effect; 2. After the operation of lowering the burden surface starts, the blast furnace maintains high oxygen enrichment blowing smelting, and the oxygen enrichment rate is 15 - 20%; 3. Inject recycled decarburized gas into the tuyere, with an injection rate of 100 - 150 m 3 / t to adjust the theoretical combustion temperature of the tuyere not exceeding 2400 °C, ensuring the smooth and stable operation of the blast furnace. The composition of the decarburized gas is: CO 70 - 80%, H2 10 - 15%, N2 5 - 7%, CO2 0 - 2%, H2O 2 - 4%; 4. Due to high oxygen enrichment smelting, the blast volume at the tuyere is reduced by 40% compared with traditional blast furnaces, and the gas generation per ton of iron is reduced by 30%. The heat carried out by the gas is greatly reduced. During the operation of lowering the burden surface, the water injection volume at the top of the furnace is reduced by 30%, and the water injection operation at the top of the furnace keeps the top temperature not exceeding 350 °C; 5. During the operation of lowering the burden surface, the top pressure is maintained with the pressure regulating valve group always open. Through the cooperation of on-line gas analyzers and manual gas sampling detection, the change of gas composition is tracked to ensure that the O2 content in the gas does not exceed 1%; 6. Enable a mechanical sounding rod to track the burden surface position, and calculate the burden surface position in the furnace by tracking the oxygen input, and compare and analyze it with the burden level detected by the sounding rod. Outside the detection range of the sounding rod, the burden surface position is calculated by the oxygen input into the furnace. During this period, slag and iron are normally discharged outside the furnace; 7. When the burden surface drops below the bosh, when the pressure difference of the burden column is lower than 10 kPa, directly open the large top gas relief valve, close the network-connected gas cut-off valve and the eyeball valve, stop gas recovery, and purge and maintain pressure in the gas output system by introducing nitrogen; 8. Open the taphole and tap the last furnace of iron. During this period, maintain an oxygen enrichment rate of 7 - 10%, stop injecting decarburized gas into the tuyere, and open 2 - 4 water injection guns at the top of the furnace according to the top temperature, keeping the top temperature not exceeding 400 °C until the tuyere is blown through to complete the furnace shutdown operation.