In the iron and steel industry, the nature and working conditions of flue gas discharged from iron-making blast furnaces, ferrosilicon-smelting electric furnaces and steel-making electric arc furnaces impose strict requirements on dust removal systems and the use of dust removal cloth (filter) bag filter materials.
1. The flue gas discharged from the iron-making blast furnace is dust-laden gas, which is called waste gas. When the blast furnace is in normal operation, the temperature of the flue gas discharged from the blast furnace is (150~250) oC. When the material collapses in the furnace, the instantaneous flue gas temperature can reach 400oC or even 600oC. When the furnace is started and the blast is stopped, the exhaust gas temperature can be reduced to below 100oC, so the filter material of the dust cloth (filter) bag is required to have temperature resistance (250~300oC), anti-paste bag and anti-hydrolysis performance. Blast furnace gas has the characteristics of high pressure, poisonous, flammable, and explosive. It is required that the filter material of dust cloth (filter) bag also has the properties of anti-static, anti-flammable and explosion-proof, and the pulse valve must be injected with inert gas. When the blast furnace is smelting normally, the amount of waste gas per ton is (1400~2000) NM, the pressure is (0.05~0.25) Mpa, the temperature is (150~300) oC, CO accounts for (20~30)%, H Account for (2~5)%, calorific value (3000~3800) KJ/NM. It is rich in physical energy and chemical energy, and has great recovery value. It is required that the filter material of dust removal cloth (filter) bag has dense porosity, surface filtration performance, and excellent filtration performance. The best filtration wind speed is 0.5M/min. The maximum should not be greater than 0.8M/min, and ensure that the emission concentration is less than 5mg/NM. The filter material is required to have comprehensive mechanical strength to improve the service life of the filter material.
2. Ferrosilicon electric arc furnaces mostly use semi-sealed hoods (with movable hanging curtains), and the cold air entering the furnace from outside the hood is mixed with CO emitted during smelting for combustion. Adjusting the movable hanging curtains can adjust the air entering the furnace. and flue gas temperature to enhance combustion. The flue gas temperature should be controlled at ~400oC to prevent sticking bags, and the flue gas temperature should be controlled above 140oC. More than 80% of the dust particle size is less than 1um in the smoke, and the dust is finer and more viscous. The dust is larger than the resistance, and a bag filter must be used. The filter bag has a large charge during operation, and the filtration resistance is large. The filter bag should be anti-static.
3. The steelmaking electric arc furnace is divided into three phases: melting, oxidation and smelting. The oxidation period is to strengthen the decarburization. A large amount of oxygen should be blown into the furnace or ore is added. The amount of flue gas generated in the oxidation period is the largest, and the dust concentration and flue gas temperature are the largest. Therefore, the gas purification system of the steelmaking electric arc furnace is based on the oxidation period. Design. During the oxygen blowing period, the average particle size of the smoke is in the range of 0.01~0.1um, and more than 85% are dust particles below 4um. When the flue gas is exhausted in the furnace, the temperature of the flue gas is high, and cooling measures are required. Generally, the exhaust gas outside the furnace is adopted. The exhaust temperature is generally 100oC during smelting, and 100~200oC when blowing oxygen. The design is based on 150oC. Therefore, the filter material of the dust cloth (filter) bag should have the properties of anti-paste bag, anti-oxidation and anti-hydrolysis.
4. The steelmaking converter is smelted by the liquid pig iron in the air blast furnace. Oxygen blowing converter steelmaking has been adopted in my country. During the oxygen blowing period, the furnace temperature is as high as 1400oC, the CO gas content is as high as 90% (CO gas and air burn immediately), the soot concentration is large, and the particle size is 75% smaller than 1um. The dust removal system should consider CO utilization and flue gas cooling measures.
