1、 The current situation of bag filter in coal-fired power plants. Domestic coal-fired power plants began to introduce electrostatic precipitators from the late 1970s to the early 1980s and gradually promoted them in the field. As of the end of 1995, the utilization rate of electrostatic precipitators had reached 55.13%, with an annual growth rate of 4% to 5%. But its dust removal efficiency is affected by various factors, such as the power supply and its control system. There is still a significant gap between the various indicators to be controlled, such as flue gas temperature, flue gas flow rate, flue gas composition and ash characteristics, chemical composition, sulfur content, etc., and the increasingly strict environmental requirements. China has a vast territory and complex coal types, and the operating conditions of boilers in various coal-fired power plants also vary greatly. The use of electrostatic precipitators cannot adapt to various working conditions for flue gas dust removal, and cannot meet the standards for smoke and dust emissions. This is why bag filters are used; Provided a new application. In the early 1990s, bag filters were used in several small coal-fired power units in China, but due to objective limitations at the time, they were not persisted. The main reason is that the overall level of bag filters is still relatively backward, and large-scale bag filters with good performance have not yet been developed. There is also a lack of strong, long-lasting filter materials suitable for coal-fired power plants; Domestic pulse valves are also not up to standard and have a short lifespan; The processing and installation of other components are also not very good, coupled with insufficient understanding and experience in using bag filters, resulting in phenomena such as burning bags, sticking bags, leaking bags, jamming, and ineffective dust cleaning. In the past decade, bag filters have developed rapidly, especially with the emergence of large bag filters. With new filter materials and pulse valves, bag filters are not only more effective than electrostatic precipitators in dust removal, but also less affected by dust characteristics and flue gas composition. I believe that in the near future, high-performance large-scale bag filters can be promoted and applied in coal-fired power plants. The output value of bag filters is developing rapidly and the market potential is very large. 2、 The correct shutdown process for a bag filter involves two shutdown steps: one is for shutting down the entire machine, and the other includes shutting down isolated individual rooms. The closure of the filtration chamber is controlled by PLC, and only when a single filtration chamber is offline can it be restored to online operation as soon as possible. When the chamber is offline, the frequency of dust removal by the dust collector will increase. The bag filter is used to achieve the offline operation of the filtration chamber by PLC or manually closing the lift valve and the manual adjustment valve of the air inlet. The inlet and outlet valves of the offline filtration chamber are marked and limited. The entire process of shutting down the bag filter. When the shutdown time of the bag filter exceeds 48 fluctuations, the following operations should be performed: 1. After the bag filter is shut down, the flue gas in the filter chamber of the bag filter contains a lot of water vapor and other condensable gases. 2. Clean the dust bag 3-5 times before cooling the bag filter. 3. Empty the dust from the ash hopper. 4. Close the ash conveying system. 5. Start the induced draft fan and clean the bag filter for about an hour. 6. Turn off the induced draft fan. 7. Before entering the dust bag filter room, use an exhaust fan to ventilate, and after inspection, promptly close all inspection doors. 3、 Inspection of Bag Dust Collector Components 1. Before installing the bag dust collector, the main steel structural components should be inspected, including the names, materials, quantities, specifications, and numbers of parts and components. 2. Before assembling or installing steel structural components, the dimensions and installation positions of each component should be checked according to the drawings. 3. Before installing the dust bag frame, its quality should be checked one by one, and any deformation or detachment should be removed. 4. All bag holes of the flower plate of the bag filter should be inspected one by one and recorded. If any unqualified parts are found, they should be dealt with to make them qualified. 5. During the assembly of steel structural components and before installation, deformed steel structural components should be corrected, and the geometric dimensional deviations and welding quality of columns, beams, various panels (ash hopper wall panels, inlet and outlet smoke box wall panels, roof panels, middle box wall panels, etc.) should be inspected and corrected. 4、 The treatment of flue gas by bag filter: 1. It is difficult to treat dust containing gas containing only tar mist. However, if the oil mist in the gas is not large but the dust content is considerable, it can be directly filtered. For example, in an asphalt concrete plant, the smoke from the stone drying machine can be the main source, and in addition, dust from the conveyor and other exhausts can enter the equipment. At the mixing machine and the discharge of finished materials. The tar mist generated by the heated asphalt concrete also enters the equipment. In this case, the amount of dust accumulated on the filter cloth far exceeds the amount of oil mist, which can prevent the trouble of oil mist adhesion and ensure stable operation. In the manufacturing of electrodes and formed carbon products, tar mist is also generated during the process of mixing powder into the thermal binder. At this point, if dust is mainly generated during crushing and transportation, only a portion of tar mist can be mixed in before use. However, if there is a high amount of tar in the flue gas of the coke tank on the tail tar furnace, an appropriate amount of coke powder should be added before the flue gas enters to adsorb the coke mist, which can achieve satisfactory results. If the gas contains only a small amount of oil mist, it can be treated separately. Adding an appropriate amount of powder as a filter aid on the pipeline can be used. After absorbing tar mist, the added dust should be returned to the manufacturing process as much as possible for utilization. 2. For the treatment of dusty gases with high dust concentration, cyclone dust collectors or gravity dust removal equipment can be installed as pre dust collectors. However, this increases the system's resistance and power consumption. So when dust or finished materials do not need to be classified, bag dust removal equipment is mostly used directly. Not all bag filter equipment can handle gases with high dust concentration. Only bag type dust removal equipment with wide spacing between filter bags and continuous dust cleaning devices installed outside the bag is suitable for handling gases with high dust concentration. When dealing with high dust content, the structure should try to make the dust fall directly into the ash hopper or add some baffles to reduce the amount of dust adhering to the filter bag; To prevent friction damage to the filter cloth, high-speed moving dust should not directly impact the filter cloth. It is also possible to use the middle part of the box as a pre dust collector, and also serve as a dynamic settling chamber for dust and a diversion chamber for inlet gas. The bag filter used for collecting dust in pneumatic conveying devices, although processing air volume is small, requires pressure resistance for dust and the box, so it is mostly cylindrical. Conditional enterprises can replace bag filters with plastic fired plate dust collectors. The entrance of the cylindrical box is designed in a tangential direction to provide separation, and many rotary blowback bag dust collectors adopt this form. Sometimes the ash hopper is made in the form of a cyclone dust collector. The bag filter of the pneumatic conveying system, due to the large amount of powder, needs to be designed with a larger ash hopper volume and discharge port diameter. In addition, the capacity of the dust discharge device should also have sufficient room to avoid the retention of powder in the ash hopper.
