1、 Common knowledge of bag filter: 1. Control mode of bag filter. The control of bag filter is mainly based on on-site automatic control, but it has a manual operation mode. In production practice, multi-point control is a method to improve production efficiency. A common misconception in the control circuit of bag filters is that the priority of multi-point control functions is not configured or configured improperly. The solution is: (1) The interface signal led to the control system is generally a source contact or analog signal, and the signal type should meet the user's requirements. (2) Bag filter The main controller of the control cabinet can use a microcontroller or PLC programmable controller, with a time limit of 0.01 seconds. (3) Automatic control should have timing and differential pressure control methods to adapt to different situations. The controller should have the function of easily modifying parameters for optimal operation. (4) In addition to the usual cleaning, unloading, and ash conveying control functions, the control content should also have temperature upper and lower limit alarms and their processing measures for different equipment users, anti condensation and bonding control of ash hoppers, anti coal powder combustion and explosion control measures, etc. (5) The bag filter control cabinet should have two switchable functions: manual and automatic control. Automatic control is divided into two methods: control and local control cabinet control. The control function can be achieved in both the control room and the equipment site, but the on-site control should have the function of "machine side priority". 2. Performance indicators of bag filter (1) Economy: The main factors determining the economy of bag filter are filtration wind speed, cleaning method, type of filter material, and its service life. The performance of a bag filter mainly involves aspects such as filtration wind speed, dust removal efficiency, and filtration resistance. (2) Bag filters have good dust removal effects on both micron and submicron sized dust. The dust concentration of a bag filter is mainly affected by factors such as dust characteristics, filter material characteristics, accumulated dust load on the filter bag, and filtration wind speed. (3) Filtering wind speed: The filtering wind speed of a bag filter is closely related to factors such as the cleaning method, cleaning system, dust characteristics, and inlet dust concentration. The impact of these factors gradually weakens from the beginning to the end. Under the following conditions, a higher filtration wind speed can be selected: using a cleaning method; The cleaning cycle is relatively short; Large and less viscous; Processing ambient temperature flue gas; Using needle punched felt filter material or surface filter material; The dust concentration at the inlet is relatively high. (4) Pressure loss (equipment resistance): The pressure loss of a bag filter mainly includes: the pressure loss of the cleaning filter bag of the dust collector structure; The pressure loss of the dust layer on the filter bag. The pressure loss of a bag filter largely depends on the filtering wind speed. The structure of the dust collector and the pressure loss of the cleaning filter type both increase with the increase of the filtering wind speed. The cleaning method also greatly affects the pressure loss of the dust collector. In addition, the structure and surface silicon condition of the filter material, as well as the filtration time of the dust collector, are important factors that affect pressure loss. The pressure loss of bag filter mainly lies in the filter bag, and the vast majority of it is in the dust layer. The pressure loss of the new filter bag is usually only 50-200Pa, while the pressure loss of the flour dust layer can reach 500-2500Pa. This shows the importance of whether the bag filter operates well or not. 2、 What are the methods of bag filter pipeline? When the conveying medium contains flammable gases or explosive dust, the bag filter system pipeline may explode or catch fire, causing damage to the dust removal equipment. So, what measures should be taken in the pipeline system design? Below, we will introduce them. 1. Fire prevention and explosion relief measures: When designing combustible gas pipelines, the low flow velocity inside the pipeline should be greater than the flame propagation speed during gas combustion to prevent flame propagation; Install flame arresters with several layers of metal mesh or gravel inside the pipeline; Install explosion-proof holes or doors at local locations (dead corners) in the pipeline system; The connection water seal and overflow water seal used in gas pipelines can also play a role in venting explosions. 2. Fire source: Strictly control fire sources that may cause explosions. If a fan is selected and a direct or axial transmission method is used; Adopting electrical components, switches, and motors; Before the materials enter the system, any foreign objects such as iron filings should be removed first. 3. Equipment sealing: When the pipeline and equipment of the bag filter are not sealed properly, combustion and explosion may occur due to air leakage or combustible material leakage. Therefore, the airtightness of the equipment system. 4. Factory ventilation: It is impossible to achieve a sealed pipeline system, so it is necessary to strengthen the ventilation of the factory to prevent the concentration of combustible materials in the workshop from reaching a dangerous level. Moreover, for workshops where a large amount of combustible gas is emitted due to equipment accidents or system malfunctions. An accident exhaust system should be installed for emergency use. 5. Strengthen the detection and control of combustible concentration: In order to prevent the combustible concentration in the pipeline system from reaching explosive concentration, detection instruments should be installed to regularly monitor the system's working status and achieve automatic alarm. When designing the system air volume, in addition to meeting the purification requirements, the concentration of combustibles should also be checked, and the design air volume should be increased to ensure that the concentration of combustibles in the transported gas is below the lower limit of explosive concentration. 3、 The treatment method for old and worn-out filter bags replaced in bag dust collectors is that the filter bags of bag dust collectors are the dust filtration devices of dust removal equipment, so a lot of dust will adhere to them. After replacing the damaged filter bags, some can be cleaned and repaired for secondary use, while those that cannot be reused need to be properly disposed of. If not handled properly, it will cause secondary pollution. There are generally three methods for disposal: 1. On site landfill, which is suitable for some filter material manufacturers, such as cement plants, boiler plants, etc., because the filtered dust is generally ordinary, landfill is not only convenient to dispose of, but also low-cost, which is common among many manufacturers. 2. Burning is a common method used by many manufacturers nowadays, which can greatly reduce the pollution caused by waste filter bags. Although secondary pollution may also occur during the incineration process, incineration can achieve reduction, capacity reduction, and stabilization. After incineration of waste filter bags, synthetic fibers will turn into gases such as CO2 and H2O, while fiberglass filter bags will turn into fibers such as SiO2 after high-temperature incineration, thus achieving chemical conversion. 3. After recycling and cleaning the waste filter bags, they are melted and drawn again in the furnace; Remake fibers and recycle them. However, this method will encounter two problems in practical operation. One is the problem of collection and transportation, because there are a large number of waste filter bags and a lot of dust, and it is necessary to prevent environmental pollution during recycling and transportation. One is the issue of cleaning. The replaced waste filter bags need to be sorted and cleaned due to the different types of dust they filter. When dealing with some dust, attention should also be paid to the treatment of the generated sewage sludge, so cleaning is also quite troublesome, requiring the necessary technology and corresponding supporting facilities to complete.
