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Reasons and preventive measures affecting the dust collection efficiency of the dust collector

the production process of cement plant is "two grinding and one burning", and raw materials, semi-finished products and finished products are repeatedly recycled, resulting in a large amount of dust. If the dust is not treated well and the dust collector is not used properly, the pollution in the production area will be more serious. Generally, the cement plant has good application effect and high dust collection efficiency in the initial stage of production and the short time when the dust collector just operates. After using for a period of time, the shell, polar plate and polar line of the electrostatic precipitator will be corroded. With the introduction of hydraulic servo technology and electronic computer technology, the bag filter will paste and drop the bag. The dust collection efficiency will be reduced and the ventilation will be blocked, which will affect the normal operation of the precipitator and the system. This paper analyzes the reasons that affect the efficiency of dust collection and puts forward preventive measures

1. reasons affecting the efficiency of electrostatic precipitator

① the specific resistance of dust is an important factor affecting the efficiency of electrostatic precipitator. When the specific resistance is 103~109f~m, the dust collection effect is the best; When the specific resistance is lower than 1021) m, the dust conducts well. When the charged particles contact the precipitation electrode, they immediately release charges, and obtain the same charge as the precipitation electrode. They are repelled by the precipitation electrode and leave the precipitation electrode, and return to the air flow, forming the secondary flying of dust, reducing the efficiency of dust collection, and even difficult to work. When the specific resistance of dust is above 10911m, the discharge process of dust particles deposited on the precipitation electrode is very slow, so a large voltage gradient is formed between the dust layers, resulting in partial discharge and anti corona phenomenon, which increases the power consumption and reduces the dust collection effect

② thermal insulation of electric dust collection system. In terms of the overall effect, the temperature of the gas entering the electrostatic precipitator is lower, which is conducive to improving the efficiency of dust collection. However, since the dusty gas discharged from mills, kilns, dryers and other equipment contains a certain amount of moisture, the gas temperature is too low, which is easy to form condensation. As the dewed dust adheres to the precipitation electrode and corona electrode, the cathode line is hypertrophy, and the anode plate is covered. When the amount of dust adheres to a certain extent, it will prevent the corona electrode from generating corona, thus reducing the dust collection efficiency. The electrode system and shell of the dust collector will be corroded due to condensation. At present, the thermal insulation layer outside the dust collector of many enterprises has never been replaced since the date of installation, and some places fall off, water and air leakage, resulting in poor thermal insulation effect of the dust collector

③ inlet dust concentration. The electrostatic precipitator corresponds to different treatment areas for different inlet dust concentrations. If the design concentration is exceeded during use, the dust collection efficiency will be affected. When the dust content is too high, most of the gas ion charge is given to the dust particles, and the moving speed of the dust particles in the electric field is far lower than the moving speed of the ions, which reduces the charge activity and the dust collection efficiency

④ air leakage factor of dust collection system. The electrostatic precipitator is usually operated under negative pressure. If there is air leakage, the local wind speed of the precipitator will increase when the external gas enters, so that the dust will be blown into the air flow again, forming a secondary flying. Air leakage can also reduce the temperature of the gas in the dust collector, which may cause condensation, especially in winter with low temperature. Air leakage can accelerate corrosion and wear at the air leakage place, form erosion grooves and acute angles at the air passing place, and also form a small short circuit for the system to process the air volume, making the system air volume insufficient, seriously affecting the dust collection efficiency and system operation. According to the national standard, the air leakage rate of the electrostatic precipitator shall not be greater than 5%, but the actual air leakage rate of the electrostatic precipitator in the cement plant is far greater than this value. For example, the cold smoke chamber does not come to the door, the electric field access door is not tightly closed, and the most important sensing parameters are cutting force, cutting process vibration, cutting process acoustic emission, cutting process electromechanical power, etc. the ash port is half closed and half open, and the zipper machine and screw conveyor do not have a cover plate, etc. are all serious air leakage points

⑤ continuous operation of electrostatic precipitator. The electrostatic precipitator itself is all composed of steel parts. The dew point of dusty gas in the precipitator is generally about 60 ℃. When the electrostatic precipitator is just opened, there is a process of heating and insulation. To reach the temperature of the dust collector body higher than the dew point, the fastest time is about an hour, and the longest time is several hours. In this process, condensation is formed inside the dust collector. There is water vapor, and the voltage cannot rise. The electric dust collector becomes an air duct. Condensation occurs once every time the electric dust collector is started and stopped, which seriously affects the operation of the electric dust collector. It is strictly forbidden to accumulate excessive ash in the ash bucket of the dust collector, and the accumulated ash shall not enter the electric field, so as to avoid squeezing the cathode and anode frame

2. Reasons affecting the dust collection efficiency of bag filter

① selection of filter bag materials of bag filter. Because the environment of each dust collection point, the nature, temperature and technical requirements of dust treatment are different, the corresponding filter bag materials are also different. In order to make the temperature of the filter bag material suitable from lithium ore raw material to basic lithium salt and lithium battery material, with good stripping property, easy ash removal, good permeability, low resistance, high filtration efficiency, high strength, can withstand high-intensity ash removal, and long service life, it is necessary to select materials according to the local conditions and technical requirements

② filtration wind speed is a very important parameter to determine the efficiency of the dust collector, and it is also an important parameter to measure the progressiveness of the bag dust collector. The filtration wind speed is closely related to the dust concentration of the dusty gas, the particle size of the dust and the ash removal method. Generally, when the dust concentration is high, the filtration wind speed should be lower, otherwise it should be higher. The smaller the dust particles are, the smaller the filtering wind speed should be. Excessive filtration wind speed will increase the load of the filter bag and increase the filtration resistance, resulting in short service life and low efficiency of the filter bag

③ air leakage directly affects the dust collection effect. Bag dust collectors generally operate under negative pressure. If air leakage is easy to form a small circuit short circuit, the air volume handled by the dust collection system is not enough, resulting in positive pressure dust. Air leakage also reduces the system temperature, easy to condense and paste bags, increases the dust collection resistance and reduces the dust collection effect

④ heat preservation is also a must for bag dust collection. The purpose of heat preservation is to maintain the temperature of the gas and avoid condensation and sticking the bag

3. preventive measures to improve dust collection efficiency

① strengthen management and raise awareness. The dust collector is not an auxiliary machine of the production system, but a main machine equipment in the production process circulation system. Its operation directly affects the output and quality of the kiln, mill, dryer and other main machines it serves. Ensure the synchronous operation rate and intact rate of the equipment system and the dust collector. The leaders of some units only pay attention to the intact rate of kilns and mills, do not pay attention to the operation of the dust collector, and do not include air leakage, bag shortage and auxiliary machine damage into the management. Sometimes, the dust collector is casually removed and stopped. There is no good analysis and understanding of the fluctuations in output and quality caused by the failure of the dust collector to operate normally

② strengthen the sealing of the dust collection system. The dust collection system mainly includes the dust collector body and other equipment in the dust collection system, such as the rigid impeller feeder, the company has the domestic leading lithium metal smelting and low-temperature vacuum distillation purification technology import and export valves, transmission equipment