After the state proposed PM2.5 control requirements and formulated new pollutant discharge standards, large iron and steel enterprises began to actively study the control standards. The final test showed that in order to truly control the total emission and emission concentration of particulate matter from the source, all processes of the iron and steel industry must vigorously promote PTFE membrane filter material, in order to control the emission concentration below 10mg / m3, Only when the service life of the filter bag is more than 3 years, can PM2.5 be effectively reduced
Sources of dust in iron and steel enterprises
1. Raw material plant 2. Sintering plant 3. Coking plant 4. Lime plant 5. Ironmaking plant 6. Steel making plant 7. Steel rolling plant 8. Public facilities
Characteristics of smoke and dust in iron and steel enterprises
1. A wide range of points, continuous emission
2. Large amount of dust gas emission and high concentration
3. The composition of dust is complex
Development trend of dust removal technology
1. Dry dedusting technology replaces wet dedusting technology
2. Pulse injection soot cleaning method replaces other soot cleaning methods
3. Reduce the concentration of gas emission
Selection of filter media in different processes
There are different working conditions in different processes of iron and steel enterprises, so there are differences in the selection of filter materials.
Coking
The coking flue gas temperature is about 90 ℃, and the instantaneous temperature can reach 130 ℃. The flue gas contains less sulfur and moisture. According to the different parts of the process, the performance requirements of the filter bag are also different. For example, anti-static and flame retardant are required for coke blocking dust removal, anti-static is required for coke table and dry quenching dust removal, and waterproof, anti oil and anti-static are required for coke screening dust removal. After years of use, it has been proved that the performance of PTFE coated polyester needle felt filter bag can meet the requirements of flue gas capture, and the emission concentration of particulate matter is basically controlled at 10mg / m3 ~ 20mg / m3, which can meet the new emission standards and special emission limits.
Sinter
The flue gas of sintering machine head is generally equipped with dry, semi dry and wet desulfurization system after electric dust removal. The bag type dust removal is required after the semi dry desulfurization system. According to the flue gas temperature (about 90 ℃) and composition (a small amount of SO2, NOx and dust) of sintering machine head after desulfurization, the bag type dust removal with PTFE coated polyester needle felt as filter bag can effectively ensure the emission according to the standard. Using PTFE coated polyester needle felt as filter bag, the emission concentration can be kept within 10mg / m3.
Blast furnace ironmaking
According to the characteristics of blast furnace flue gas, all blast furnace flue gas environmental dedusting bags are made of water-proof and oil-proof PTFE coated polyester needle felt, and the emission concentration of particulate matter can be basically controlled within 10mg / m3, which can meet the requirements of the latest national special emission limit of air pollutants; the main components of blast furnace gas are co, CO2, N2, H2 and CH4, of which the combustible component co accounts for about 25%, and is currently used Dry dedusting for its purification, because of its continuous operation of flue gas temperature above 200 ℃, must choose high temperature resistant glass fiber or P84 (polyimide) as filter material, but after practical use, glass fiber filter material is easy to break, short life, can not guarantee the filtration accuracy for a long time, and use PTFE coated P84 (imported from Austria) needle filter material, under normal conditions, the service life can be shortened 3 mg / m3, which can meet the requirement of stable production.
Electric furnace
At present, the three-stage collecting method of four holes, dog house and roof cover is adopted for electric furnace dust removal. The reasonable mixing of high temperature flue gas and normal temperature flue gas can effectively reduce the flue gas temperature at the inlet of the dust collector. However, considering the emergency situation, the flue gas temperature may reach above 200 ℃ instantaneously. Therefore, the selection of PTFE coated metas filter material can not only reduce the operation cost, but also effectively capture the flue gas and efficiently filter, so as to ensure that the emission concentration of particulate matter is controlled below 10mg / m3. Of course, in the field application, due to space constraints, the pipeline between the capture hood and the inlet of the dust collector is short, and the high-temperature flue gas will enter the dust collector in a short time, resulting in a large number of dust bags burning. At this time, the selection of glass fiber filter material can effectively avoid the occurrence of such accidents.
Converter
The secondary flue gas of converter belongs to the normal temperature range. Using PTFE coated polyester needle felt as filter bag, the emission concentration can be maintained at about 10mg / m3, which can meet the latest requirements of particle emission concentration.
AOD
AOD refining process belongs to reduction reaction process. If the flue gas from furnace body and roof cover are separately collected, the filter material selected must be waterproof and alkali resistant due to the high temperature and alkalinity of flue gas from furnace body and leakage of water-cooled flue. PTFE coated metas filter material can be selected, which can be waterproof, alkali resistant and high temperature resistant. For dust removal of roof cover, PTFE coated polyester needle felt is used as filter bag, which can meet the requirements of capture and emission. If the flue gas from the furnace and the roof is mixed and then collected by a dust collector, the flue gas temperature at the inlet of the dust collector can meet the normal temperature requirements due to the mixing effect of the room temperature flue gas from the roof, so the PTFE coated polyester needle felt can be used as the filter bag.
Dust removal in other environments
Generally, in the case of drying and flue gas temperature lower than 100 ℃, PTFE coated polyester needle felt can be used as filter bag for environmental dust collector.
