The working characteristics of pulse bag filter in dust collector: The working characteristics of pulse bag filter in dust collector are not only related to the structural form of the dust collector, but also largely depend on the properties of the filter cloth. At present, glass fiber is still widely used, with a permissible temperature range of 250-280 ℃. However, glass fiber has low strength and a filtration rate generally not exceeding 0.5m/min. In order to improve the flexural resistance of glass fiber, silicone oil and graphite treatment are generally required. Using this treated cloth bag, combined with a reasonable blowback system, the lifespan of the bag can reach 5-6 years. The tendency for cracks in the deposited metal of high chromium alloy cast iron is high, and the weld layer has fine mesh cracks that release stress and help prevent large-scale peeling of the weld layer. Practice has proven that these cracks do not propagate, and the dust emitted during the production process of refractory materials that does not have significant effects and hazards belongs to mechanically dispersed dust. Its properties and hazards are mainly determined by the chemical composition and particle size of the raw materials. Silica dust contains over 80% free SiO2, while high alumina alumina dust contains over 10% free SiO2. Magnesite, dolomite, limestone and other dust contain less than 10% free SiO2. The higher the content of free SiO2 in dust (especially above 10%), the greater the harm to human health. After being inhaled into the human body, silicosis can occur. Dust with low free SiO2 content can cause pneumoconiosis when inhaled in large quantities. When the situation is severe, it can cause death. The goal of dust control in refractory material factories is to prevent dust from escaping in the workshop and maintain a hygienic working environment for operators. The second is to control the emission of dust into the atmosphere and meet the dust emission standards. China has summarized the eight character policy of "water, tightness, wind, protection, management, education, inspection, and publicity" as a comprehensive prevention and control measure to prevent dust hazards in refractory factories. By the late 1980s, about 80% of the production positions in China's large and medium-sized refractory material factories had dust concentrations in the air that met or were close to hygiene standards. The dust concentration emitted from the dust removal system into the atmosphere generally met the emission standards. The dust removal device used in the dust removal system of refractory material factories. Dry dust collectors are commonly used in countries such as Europe, the United States, and Japan, while the former Soviet Union used wet dust collectors and bag filters more frequently. Before 1965, China mainly used cyclone dust collectors and mechanical vibration bag filters. After 1970, newly built factories widely adopted pulse jet bag filters and electrostatic precipitators. The effectiveness of electric furnace flue gas capture depends to some extent on the structural form of the hood. The ferrosilicon electric furnace adopts a semi enclosed low hood instead of a high hood to reduce smoke exhaust and prevent the escape of flue gas from the furnace, which can improve the working environment for workers. The smoke exhaust capacity of this type of hood is about 50-60 times the theoretical furnace gas volume. It is generally designed as a hexagonal hood, and a water-cooled skeleton structure is adopted according to the process needs for easy equipment maintenance. Feeding doors are installed on three of the six sides of the hexagonal hood lined with refractory materials. The feeding doors are generally not opened, but only one side is opened during feeding or furnace operation to reduce the entry of wild wind. The smoke exhaust capacity of a low hood is 50% less than that of a high hood, and the flue gas temperature is about 400 ℃~700 ℃. When the flue gas temperature inside the hood is greater than 500 ℃, the material of the hood should be heat-resistant steel, especially the design of the feeding door structure on the side of the hood should prevent deformation, open flexibly, and improve its sealing performance. When the ratio of reducing agent is 50% coke and 50% coal, the flue gas temperature is 400 ℃, and the normal smoke exhaust rate is 60000Nm3 per ton of product. The smoke exhaust rate under ignition conditions is 120000Nm3 per ton of product. The selection and design calculation of the gas velocity for smoke passing through the chimney should be based on the smoke volume under ignition conditions. The gas velocity is generally taken as 7-13m/s, and the normal smoke volume is used for calculation. After comprehensive comparison, the diameter of the chimney for smoke passing through the chimney is determined. When the smoke temperature is between 400 ℃ and 500 ℃, the temperature drop per meter of smoke passing through the chimney is generally 2-2.5 ℃ for metal lined brick chimneys and 3-4 ℃ for metal chimneys. In order to reduce the outlet dynamic pressure loss when smoke is discharged into the atmosphere, the outlet velocity should be reduced. The gas velocity at the chimney outlet should not be less than 4m/s. Generally, the chimney outlet is designed as an expansion type to increase the chimney's suction force and release the chimney valve. The design of the chimney valve requires flexible operation, good sealing, and suitability for dusty conditions. When the smoke temperature of the bag filter in the flue gas purification system is too high, the chimney valve automatically opens, and the smoke flow rate of the exhaust pipe is reasonably selected. The smoke flow rate in the pipe is an important factor for the normal operation of the system. If the flow rate is too low, it will cause dust accumulation in the pipe, block the pipe, increase the flow rate, increase resistance, wear the pipe wall, and in severe cases, air leakage will occur, affecting the capture effect. The flow velocity range of the pipeline is generally selected as 16-26m/s. Low speed is the normal condition, while high speed is the ignition condition. After technical and economic analysis, it is believed that the appropriate number of bags in the unit filter chamber of a large bag filter is generally 140-160 bags. This can make the structure of the dust collector lightweight and low in steel consumption, and also provide suitable back blowing air volume, making the bag filter less volatile in the ratio of cleaning and non cleaning air cloth, stabilizing the operation of the purification system, protecting the filter bag, and extending its service life. Currently, pulse cleaning filters are increasingly used in the flue gas filtration of ferrosilicon electric furnaces.
