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Long-bag low-pressure pulse bag dust collector controls high-temperature flue gas from silicomanganese ore thermal electric furnaces Author: Wang Zejiang's development of new bag dust removal technology is the common responsibility and obligation of our environmental workers and investors. How to start from the research of production technology and develop cost-effective high-tech treatment technology that can adapt to the flue gas working conditions of various complex pollution sources is a topic before us. The silicon-manganese ferroalloy electric furnace emits a large amount of high-temperature dust-containing flue gas during the smelting and production process. The main components of the flue gas are MnO and SiO2, and the particle size of the flue gas is mostly less than 5um. Therefore, if effective flue gas purification is not adopted, this dusty flue gas containing fine particles will be very harmful to the indoor and outdoor environment and human health. And affect the atmospheric environment around ferroalloys and the physical and mental health of workers. Therefore, controlling the flue gas of silicomanganese ore furnaces is of extremely important significance, both in terms of environmental benefits and social benefits. The smelting of silicon-manganese alloys is divided into closed, semi-closed and open-top submersible electric furnace smelting. The closed submersible furnace does not require material surface operations (furnace pounding, material removal), so the furnace gas volume is not large. To recover the gas, a two-tower and one-weather wet purification process is generally used. The typical example is the 9000KVA silicon-manganese alloy closed submersible electric furnace of Guizhou Zunyi Ferroalloy Factory. The stable operation for many years shows that this technology is a mature process. Due to limitations of smelting conditions, the process of smelting silicon-manganese alloys in semi-closed and open submersible electric furnaces is often used by some production companies. According to the smoke properties and smelting conditions of silicon-manganese alloys smelted in semi-closed and open submersible electric furnaces, combined with the development of dry bag dust removal and purification technology in my country, especially in recent years, the successful application of a large number of new filter materials with high-speed filtration performance that can handle various complex working conditions (such as anti-condensation, high temperature resistance, anti-static, water- and oil-repellent, film-coated filter materials, etc.) provides a more mature technical support for the dry purification process of silicon-manganese electric furnaces. In 2003, during the project implementation of the 8500KVA-6300KVA silicomanganese ore thermal electric furnace dust removal system at Guizhou Yuping Jinpeng Ferroalloy Factory, our company made some developmental attempts to use long bag low-voltage pulse bag dust removal technology for silicomanganese electric furnaces. 1. Physical and chemical properties of silicon manganese dust 1.1 Chemical composition MnO SiO2 Fe2O3 CaO MgO Al2O3 P content 19.94 21.70 4 4.48 3.68 5.10 0.11 1.2 Dust dispersion particle size um >75 50～40 40～30 30～20 20～10 10～5 5～3 <3 % 0 14.2 1.1 1.6 1.9 3 32.9 45.3 1.3 Specific gravity of dust pile: 3g～9g/cm3 1.4 average particle size: 3.24um 1.5 specific surface area: 8.47m2/g 1.6 Moisture content of flue gas: 1.8~2.2% 1.7 Smoke dust concentration: 6g/Nm3 1.8 dew point temperature of flue gas: 70～80℃ 2. Flue gas purification system engineering technology and characteristics 2.1 Process flow Silicon manganese electric furnace flue gas has the characteristics of fine particles, easy dust absorption and high specific resistance, making it difficult to control. Since the flue gas generated by the electric furnace contains manganese, it is easy to produce sparks. In order to prevent sparks from burning the bag and causing the temperature to be too high, the system is equipped with a U-shaped cooler. After the U-shaped cooling and desparking, the flue gas enters the long bag low-pressure sub-chamber air-stop pulse bag dust collector. The purified flue gas is discharged into the atmosphere through the chimney by the induced draft fan. The collected dust falls into the ash hopper through pulse cleaning, is discharged through the spiral ash conveyor and the ash discharge valve, and is packaged and stacked for use. An accident relief valve is also set up, which can be used in conjunction with the pneumatic wild air valve in an emergency. If sparks are encountered or the temperature in the ventilation duct is too high (≥280°C), the relief valve will be opened to avoid filter bag burnout accidents. The pneumatic wild air valve is one each of DN600mm (equipped with 8500KVA) and DN500 (equipped with 6300KVA). The temperature control device is placed in front of the U-shaped cooler. When the flue gas temperature exceeds or 280°C, the wild air valve is opened to ensure the temperature decreases. This ensures the normal operation of the dust removal system. 2.2 Design parameters electric furnace capacity: 8500KVA, one 6300KVA, one electric furnace flue gas volume: (Calculate the flue gas volume based on 10Nm3/KVA plus 30% overload production) 8500KVA flue gas volume = 8500×10Nm3/KVA×1.3=110500 Nm3/h 6300KVA flue gas volume=6300×10Nm3/KVA×1.3=81900 Nm3/h flue gas temperature: 250~280℃ (temperature after cooling) 2.3 Flue gas purification system characteristics 2.3.1 The system has strong adaptability. When abnormal phenomena such as ignition occur during the smelting process, causing the flue temperature to be too high, the safe operation of the system can be ensured through the linkage work of the two valves and the operation of the U-shaped cooler. 2.3.2 A temperature monitoring device is installed on the pipe in front of the wild air valve. 2.3.3 The dust collector adopts the most advanced technology in the country. Its working procedures of pulse cleaning, ash hopper vibration, and air stop in different rooms are all centrally controlled by PLC microcomputer and interlocked with fan start and temperature monitoring. 2.4 Main equipment selection 2.4.1 U-shaped cooler 700m2 (equipped with 8500KVA) 500m2 (equipped with 6300KVA) 2.4.2 G-ZDM medium-sized chamber low-pressure pulse bag dust collector - intensive arrangement 8500KVA: 1953 m2 6300KVA: 1627 m2 total filter area: 3580m2 Its technical parameters are as follows: 2.4.2.1 model: G-ZDM1953 processing power: 111321～128898m3/h filter area: 1953m2 filtered wind speed: 0.95～1.1m/min Number of filter bags: 648 filter bag materials: High temperature resistant glass fiber (temperature resistant 280℃) filter bag specifications: ￠160×6000mm entrance density: 6g/Nm3 2.4.2.2 model: G-ZDM1627 processing power: 92739～107382m3/h filter area: 1627m2 filtered wind speed: 0.95～1.1m/min Number of filter bags: 540 filter bag materials: High temperature resistant glass fiber (temperature resistant 280℃) filter bag specifications: ￠160×6000mm entrance density: 6g/Nm3 2.4.3 Main exhaust fan model: Y4-68 №14D full pressure: 4000Pa flow: 130000m3/h with motor: Y355-4-250/380/IP44 motor power: 280KW motor speed: 1450rpm with electric actuator: DJK5100 model: Y7-51 №13D Full Press: 4500Pa flow: 100000m3/h with motor: Y315-4-200/380/IP44 motor power: 220KW motor speed: 1450rpm with electric actuator: DJK5100 2.4.4 system pipeline (pipe flow rate is calculated as 18/s) 2.4.5 chimney (shared by the system) 2.4.6 two-valve 8500KVA two-valve relief valve: DN1600 (pneumatic) wild air valve: DN500 (pneumatic) (with temperature measuring element) 6300KVA two-valve relief valve: DN1400 (pneumatic) wild air valve: DN450 (pneumatic) (with temperature measuring element) 3. Actual results The construction of this system started in March 2003 and was put into production in June 2003. After monitoring and acceptance by the environmental protection department, it met the standard at one time. References 1999 "Proceedings of the National Bag Dust Removal Committee" 2001 "Proceedings of the National Bag Dust Removal Committee" 2003 "Proceedings of the National Bag Dust Removal Committee" "Ferroalloy Production Technology Manual" (Metallurgical Industry Press) Author's unit: Hubei Qianjiang Guantian Environmental Protection Engineering Co., Ltd.