1、 The operational performance of a bag filter includes flow rate, pressure loss, dust removal efficiency, air to cloth ratio (filtration wind speed), filter material properties, and the lifespan of auxiliary components. A key indicator of a bag filter is the gas to cloth ratio, which is the total flue gas flow divided by the total filter cloth area. There are many factors that affect the air to cloth ratio, such as smoke temperature, dust holding capacity, filter material, and dust properties. Bag filter As long as one filter bag ruptures or leaks air, it will cause a sharp decrease in the efficiency of the entire dust collector. Therefore, an excellent bag filter design depends on whether it is easy to enter the dust collector for maintenance and replacement of damaged filter bags. Due to the accumulation of charges, the voltage on the settling dust layer can reach several thousand volts. In this situation, it is difficult to clean the dust no matter what method is used. At present, there are fibers that are woven from up to 10% conductive fibers or metal wires, which can minimize the accumulation of static electricity. The efficiency of almost all industrial bag filters is close to or exceeds, but the design of dust cleaning methods varies greatly. The cleaning method is crucial because it not only affects the size and cost of the bag filter, but also relates to its use, maintenance, and online operation. The commonly used industrial bag filter equipment includes vibration, reverse airflow, and pulse blowing bag filters. Vibration or reverse airflow cleaning is an early method used for cleaning dust in bag filters. The filtering chamber isolates the flue gas with a damper for 2-5 minutes during dust cleaning. The anti blowing dust removal has a lighter bending effect on the cloth bag, so the lifespan of the cloth bag is longer. The large dust load (dust holding capacity) per unit area of filter cloth is between 0.1 and 1.0 kg/m2, depending on the properties of the dust and filter material. The air to cloth ratio of a back blowing dust bag filter is generally within the range of 0.5-2m/min. For mechanical vibration bag dust collectors, the residual amount of dust on the bag is related to the number and intensity of vibrations. 2、 The application of bag filters in the boiler industry. Although bag filters are not widely used in boilers in China, with the sustained and steady development of the economy, bag filter products for coal-fired boiler flue gas treatment will inevitably usher in huge development opportunities. Because: 1. Due to the use of automated monitoring and management for the operation, malfunction, and abnormal diagnosis of the dust collector, its operation and management are relatively simple. 2. Through engineering practice, it is feasible to use bag filters for flue gas treatment at the tail of boilers in thermal power plants. The use of bag filters on boilers is quite common, and the service life of filter bags is also very long, generally exceeding 2 years, and some even reaching more than 6 years. 3. Bag filter dust removal, one-time investment saving, small equipment footprint (compared to electrostatic precipitators with four or more electric fields), low operating costs and sewage charges. Especially in recent years, due to the development of manufacturing technology, problems such as corrosion and wear of filter bags have been solved, providing strong support for the application of bag filters. 4. The increasingly strict requirements for environmental protection have prompted the use of bag filters in boilers in China. At present, there are quite a few industrial developments in the world that use bag filters for dust removal in coal-fired boilers. They have solved some of the problems that arise when using bag filters for boilers, and the application of bag filters in boilers has become a mature technology and is being promoted. Therefore, the application of bag filters to purify flue gas in coal-fired boilers is technically mature and economically feasible. I believe that as long as suitable equipment components, operating methods, and designs are adopted for the specific conditions of boiler flue gas, strict requirements are placed on the manufacturing quality of dust collectors, and daily maintenance and management are strengthened, the application of bag filters in boilers can definitely achieve good results. 3、 Pre spraying and shutdown maintenance of bag filter: Before the bag filter is put into operation and restarted after a long shutdown time, a protective layer is pre sprayed on the outer surface of the bag to prevent extremely fine dust from entering the filter cloth and blocking the pores, which is extremely difficult to clean. At the same time, tar substances in the oil fume can also block the filter bag during boiler oil ignition. Shutdown and maintenance of bag filter: If the bag filter is not used for a long time, maintenance measures should be taken to prevent the bag from getting damp, clumping, and corroded. Close all inlet and outlet valves of the dust collector. During the shutdown period, open the inlet and outlet valves at regular intervals, use the chimney for natural ventilation for 4 hours, or turn on the electric heater for heating for 8 hours to remove moisture from the dust collector and keep it dry. 4、 The control mode 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 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. The main controller of the bag filter control cabinet can be a microcontroller or programmable controller, with a time limit of 0.01 seconds. 3. The interface signals leading to the control system are generally source contacts or analog signals, and the signal type should meet the requirements of the user. 4. 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. 5. 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、 Points to note when choosing a bag filter in heating engineering: 1. Pay attention to the temperature resistance, acid resistance, alkali resistance and other requirements of the filter material. Currently, the optional filter materials for bag filters used in boiler matching include Leyden, fiberglass laminating, etc. 2. It is recommended to use pulse back blowing, which can be done with a larger air to cloth ratio to reduce the amount of filter material and shrink the volume of the dust collector. 3. How to discharge and store the fine ash separated by the bag filter also needs to be handled properly, otherwise it will cause secondary pollution. 4. The bypass flue, control device, and ash hopper automatic heating device of the bag filter are all included. Whether water spray or cold air cooling measures are installed before the dust collector needs to be analyzed specifically. 5. According to the pressure of compressed air, bag filters are divided into high-pressure pulse type, medium pressure pulse type, and low-pressure pulse type. There are significant differences in the structure of the dust collector among the three forms, but the dust removal effect is very good, which should be determined according to the specific situation.
