Due to the high dust removal efficiency of the bag filter, and the efficiency of the dust removal is not affected by the change of the coal type, the discharge is generally stable below 20mg/m3. Therefore, the bag filter has been used more and more in the power industry, and with the thermal power plant atmosphere The “Emission Standard for Pollutants” requires that the electrostatic precipitator to be used after the new standard for soot emissions falling below 20-30mg/m3 is issued must be gradually transformed. There are some important differences in the application of bag filter in coal-fired power plants compared with other industries, such as large smoke volume, high operating temperature, strong corrosive flue gas, and high price of filter bags, as they are used in power generation equipment. , that is, applied to the energy industry, which requires that the dust collector must ensure compliance with emissions, safety and reliability, stable operation, and save operating costs, that is, the service life of the dust bag is longer. Further improving the technical performance of the bag filter, especially how to extend the life of the bag, is an important technical issue that needs urgent solution. Therefore, from the point of view of the design and safe operation and maintenance of the bag filter, this paper analyzes the technical measures for prolonging the life of the bag at the design and manufacture of the filter.
【Bag filter main performance analysis】
Because of its advanced filtering and dust collection mechanism, the adaptability of different operating conditions, and the high dust removal efficiency, the bag filter is simple in structure. It is widely used in various industries for ventilation and dust removal. For over half a century of application and innovation, bag filter equipment, dust bags, main parts and control technology have all developed rapidly and made great progress. The design and manufacturing technology of bag filter equipment and the filter material processing technology of needle felts have reached world advanced level by the introduction and innovation. The main indicators for bag filter design are:
1. Export emission concentration: In the equipment manufacturing and installation debugging, the bag filter ensures that the welding seam does not leak gas and the dust bag is in good condition. It can meet the requirements of the national emission standards. The dust emission is generally below 20mg/m3, even It reaches 10mg/m3 or less. Heavy metal mercury and PM2.5 fine dust also have a certain effect.
2. Equipment resistance: Equipment resistance usually refers to the pressure loss between the inlet and outlet of the dust collector. It consists of two parts, namely the mechanical resistance of the equipment and the filtration resistance. The resistance of the mechanical part is related to the air inlet method, the air inlet is evenly distributed, and the diversion structure is relevant. The dust remover adopting the flat-in and flat-out and inlet orifice plate distribution technology has a low mechanical resistance of about 200 PA. The resistance of the filter layer of the dust collector is composed of the resistance of the dust bag, the dust embedded in the deep layer of the dust bag and the initial layer of the dust, and the dust resistance of the surface of the dust bag after cleaning. The dust resistance of the surface area gathered after the filter bag cleaning is periodically changed. The speed at which the resistance rises is related to the concentration of dust and the speed of filtration. With high concentrations and rapid wind speed, the resistance rises quickly.
The resistance value of the equipment is determined by the constant resistance and dust removal control parameters. The index should be determined scientifically. If the equipment resistance is set at 1200pa, the dust resistance on the surface of the dustbag will increase by 600PA-700PA. If it is set to 1000PA, the dustbag will be removed. When the dust resistance on the surface rises by 400-500PA, the dust will begin to clear, which will increase the cleaning frequency of the filter bag, which is unfavorable for the life of the filter bag. In order to prolong the life of the filter bag, it is recommended that the device resistance be set at 1200PA, which is also scientific and economical. of.
3. Dust bag life: There are many factors that affect the life of the bag, which is closely related to the performance of the filter media, the technical level of the equipment, and the operation and maintenance of the equipment. With the improvement of filter material manufacturing technology and technology, the technical properties of filter media such as acid and alkali resistance, high temperature resistance, corrosion resistance, oxidation resistance, wear resistance, and folding resistance have been greatly improved, but the filter material and weaving The choice of process must meet the requirements of the flue gas conditions. The technical factors of the dust collector equipment mainly include: reasonable determination of the filter wind speed; uniformity of the air flow distribution in the filter bag; properness of the dust removal effect and moderate degree of cleaning force. In the operation and management of equipment, it is also very important to operate and maintain strictly according to the operating procedures.
The above three properties are collectively referred to as the three major properties of the bag filter. Among these three major properties, the life of the filter bag directly affects the safe operation and operation and maintenance costs of the equipment.
[Factors affecting the life of the dust removal bag manufactured by the dust removal equipment]
The commonly used filter materials of coal-fired power plant bag filter are expensive, the filtration area is large, the cost of the dust bag is high in the equipment cost, generally about one-third, and the service life is only three to four years, so the power plant and equipment manufacturers All are very concerned about the important performance indicators of filter bag life. The factors that affect the life of the filter bag by the dust removal equipment are:
(1) Filtering wind speed
The filter wind speed is the dominant parameter of the dust collector performance index, and the value of the ratio of the listed flue gas volume to the filter area, but when selecting the size, in addition to considering the performance of the filter material, it also relates to the nature of the gas and dust, the dust collector The overall performance is related. The filtration speed is mainly determined based on experience. There are two principles to follow when choosing the size, one is the running resistance of the equipment and the other is the service life of the filter material. That is to say, the filtration speed is selected to be large. Although the equipment specification is laughing and the price is cheap, the running resistance is large, the filter material life is short, and the operation and maintenance costs are increased; the filter wind speed is small, and the operation and maintenance costs can be reduced. Small, but large equipment specifications, one-time investment, only follow the above principles, a reasonable choice of filtration speed, make the most appropriate cost. The common filtration wind speed of coal-fired power plants is generally 0.85-0.9mg/min.
(2) Cleaning method and cleaning power
At present, the baghouse dust collectors commonly used in power plants are mainly rotary injection pulse and line injection pulse. The rotational purge pulse cleaning gas pressure is 0.085-0.1Mpa, which belongs to low pressure injection and has less damage to the filter bag. And it belongs to probability cleaning, which not only can achieve satisfactory cleaning effect, but also does not damage the dust bag. The pulsed purge gas pressure is 0.2-0.3MPA, which belongs to a pair of medium-injection blowers. The cleaning effect is good. In order to reduce the damage to the dustbag, first, the injection pressure is properly reduced, and the second is an appropriate adjustment of high-definition gray Lower limit resistance (cleaning program start value).
The reasonable setting of equipment pressure can not be ignored. The resistance of bag filter is not as low as possible. Generally, 1200-1500PA is a scientific and economical. Some project bids require equipment manufacturers to guarantee 100PA, or even lower, which inevitably brings two consequences. First, frequent cleaning of the ash reduces the life of the filter bags; Second, high-intensity cleaning, so that the lower limit resistance is very low, that is, the impact of the filter Bag life increases micro-dust emissions. Therefore, it is recommended that the resistance value of the equipment be limited to 1200PA, and the lower limit resistance should not be lower than 800PA.
(3) Uniformity of filter bag load
Under the established flue gas conditions, the filter bag service life is related to the filter wind speed and the cleaning force, and the uniformity of the filter bag load is also an important factor affecting its life. The uniformity of the filter bag load is ensured by the optimal design of the air inlet method, the air flow distribution deflector and the air flow channel. The filter bag is protected from air flow and the uniform load of the filter bags in the bag area is an important condition for improving the life of the filter bag. Therefore, the equipment design of the bag filter of the coal-fired power plant must adopt advanced and reliable technology to ensure the uniformity of the load of the filter bag. Measures.