1. The characteristics of continuous glass fiber filter cloth and its application
The continuous glass fiber filter cloth is made up of round and parallel fiberglass strands, which are woven by the process of retreat and warping. During the retraction process, the fiber bundles are twisted, the warp and weft yarns are very dense, and the airflow passes through the holes where the warp and weft yarns interweave. It is the earliest industrial application of glass fiber filter material.
The CWF-300-FQ filter media is a medium-alkali continuous glass fiber twill structure with a thickness of 0.3-0.35 mm and is post-treated with reactive silicones, polytetrafluoroethylene suspensions and other components. This filter is soft, smooth, easy to clean, can be used continuously at 250°C, and is inexpensive. In Xuzhou Cement Plant Rotary Kiln Kiln Dust Application, the filtration rate is about 0.5m/min, the filtration efficiency is 99.8%, the upper intake negative pressure operation is adopted, and the chamber is bagged and cleaned. Under the above process conditions, this filter bag was operated for a total of 310 days without any damage. The cumulative operating damage rate for 2 years was 28%, of which 50% of the bag life exceeded 3 years.
The most common cement production equipment for small and medium-sized cement plants in China is the machine shaft kiln. The kiln’s exhaust gas temperature fluctuates greatly, and can condense when it is low. It exceeds the capacity of glass fiber at high times. The problem of dust collection has not been very good. In recent years, microcomputer control has been used to solve the problem of excessive temperature fluctuations in the flue gas. The CWF-3OOPSi filter media has played a good role in the dust collection of vertical kiln exhaust gas in dozens of cement plants such as Shijing Cement Plant, Boshan Cement Factory, Zibo Cement Factory, and Tianjin Cement Plant. This filter base material is made of alkali-based glass fiber and is post-treated with PSi formula, which further improves the fold-resistance, wear-resistance and temperature-resistance of the filter cloth.
The cement industry also has a large number of mills. The temperature of the exhaust gas discharged from the dryer is low (near zero temperature), the dust concentration is high, the moisture content is high, and the exhaust gas temperature is close to the zero point temperature. The use of CWF 300-1 FCA filter material, the effect is good, this filter material with a smooth surface of the twill fabric structure, and after the water treatment. The abrasion resistance, folding resistance, and hydrophobicity have been improved a lot. After nearly a decade of application, the filter material has good anti-condensation capability and long service life.
The continuous glass fiber filter cloth is suitable for various bag type dust collectors without frame internal filter back blowing (anti-suction) wind or shrink bag cleaning in the middle of the filter bag, and the filtration speed is generally below 0.5m/min. If the speed is too high, it is easy to blow the filter bag or cause diafiltration. The promotion of dust in the cement industry is relatively high, compared with the same thickness of the bulked yarn filter, the price is cheaper.
2. The characteristics of glass fiber expanded yarn filter and its application
Glass fiber bulk yarn filter is a fabric filter caused by partially bulked yarn. Compared with the continuous fiber filter cloth, the filter performance of the expanded yarn filter cloth is obviously improved. Because of its structural characteristics, the continuous fiber filter cloth can hardly pass through the inside of the twisted yarn, and can only pass through the perforation of the warp and weft yarns. To ensure the breathability of the fabric, the eyelets of the yarn are generally large, even if they are formed. When the powder layer is filtered, the filtration rate cannot be too high, otherwise it will be easily filtered. The bulked yarn filter cloth can increase the surface area of the collected dust due to the bulkiness of the yarn, prolong the time for collecting the dust, and is beneficial to the aggregation of the fine dust into large particles. The structure of the dust filter layer is loose, the void ratio is relatively large, and the bulkiness is increased. The yarn has strong covering ability, which can cover the airflow path at the interweaving position of the weft yarn and the weft yarn so that the filter resistance of the bulked yarn filter cloth is smaller, and the filtering efficiency and the filtering speed are higher. Thicker fabric (such as 0.8mm) of the bulked yarn filter its filtration speed can be increased to about 0.8mm/min. At the same time, it can be applied to an external filter dust collector with a cantilever backflush in the middle. For example, EWTF-800-RH latitude double 0.8mm-thick bulky yarn filter is used in FVB-L vertical kiln microseismic flat bag dust collector. It is used at the end of main shaft kiln. The total filter air volume of this dust collector is 60000m3/ h, the filter area is 2000m2, the maximum filtration rate is 0.58m/min, the gas temperature is generally 50-80°C, and the highest is 200-280°C, and one year filter bag is not damaged. The tested dust removal efficiency is over 99.9%, the dust concentration in the outlet is lower than 50mg/Nm3, and its dust emission concentration is lower than the national standard. Every day, 12 tons of raw clinker can be recovered. According to 300 days/year, the annual recoverable capital is about 600,000 yuan, which produces obvious economic benefits.
3. Glass fiber needle felt filter
The glass fiber needled felt filter material is made of glass fiber chopped strands after being carded into felts and fixed on the glass fiber base cloth by a needle punching method. In order to strengthen the binding fastness between the felt layer and the base cloth, the felt layer and the base cloth are protected. Due to abrasion and corrosion, the powder layer peeling property on the felt surface must be improved by chemical treatment, so as to make a firm and durable glass fiber needle felt filter material. Glass fiber needle felt filter is currently the highest grade and best performance filter material in glass fiber filter. It not only has the high temperature resistance, abrasion resistance, dimensional stability, high elongation, and high strength of fiberglass fabric filter cloth. The merits, but also because the carpet fiber is a single-fiber three-dimensional microporous structure, used for small holes in the filter pore size, high porosity (up to 80%), and its filtration mechanism not only by the filter, but set the filter , Blocking, inertia, especially the role of diffusion, so it is more than the filter fabric filter speed can be increased 1 to 2 times, the filter resistance is small, high dust removal efficiency, is a high-speed and high-efficiency high-temperature filter material. Breakthrough the past, glass fiber filter material can not be used in the high-speed pulse bag filter used in the restricted area, to solve the problem of high temperature flue gas bag filter to the development of miniaturization, theoretically and practically solved the problem of filtering fine particles dust technical problems. Become a gas, especially in the high temperature gas dust filtration and raw material collection of replacement products.
The development of the filter material for glass fiber needle felts in China has played a significant role in promoting the carbon black industry. In the production process of carbon black, the finest products can only be collected by bag filters, and the continuous filtration temperature is about 240°C. The bag filter is not only Environmental protection equipment is more important than production equipment, so it attaches great importance to the filtration performance and service life of the filter media.
ENf-1050 glass fiber needle felt filter material is used in the new carbon black production line of 2500t/a new process in Pingxiang Chemical Plant. The process conditions: filtration speed (m/min); 0.47 to 0.57; flue gas inlet temperature (°C): 200~260; inlet smoke dust (mg/m3): 20; pulse injection time (ms): 10~15; pulse interval time (s): 9~16; pulse injection pressure (kg/cm2) : 3 to 4. The service life of the bag is 21 months under the above conditions.
4. Some lessons learned from the use of filter bags
All kinds of filter materials have certain characteristics, but also have their deficiencies, natural fibers (such as cotton, hemp, silk, wool fibers) and synthetic fibers (such as nylon, polypropylene, polyester, Nomex…) Flexing and abrasion resistance are relatively good, but their temperature resistance is poor. The use of these filters must be strictly controlled the use of temperature, over-temperature use to make the filter bag shrink quickly, or even burn, affect the service life.
The glass fiber filter, whether continuous glass fiber filter cloth, bulky yarn filter cloth, or needled felt filter material, is a cylindrical smooth surface rod material from the microscopic point of view, so its flex resistance And poor wear resistance. Its molecular structure is mainly a tetrahedron composed of silicon-oxygen bonds, with high bond energy, and therefore good temperature resistance. Glass fiber filter must be surface chemical treatment in order to improve its resistance to bending, abrasion and other properties, must be avoided in the course of use, such as glass fiber filter in the packaging, transportation, installation process must prevent the drag on the rough ground , foot or collision with a hard object, friction, contact with the flower board, frame, support ring must be smooth, the welding point must be welded and polished, there must be no off the welding hair, so as not to wear before or during operation Filter bags produce premature breakage of filter bags that should not have occurred.
In addition, during the use of the bag filter, the bag filter caught fire or even exploded. Carbon black industry because the exhaust gas contains a large number of CO, H2, CH4 and other combustible gases, such as operational errors, a lot of oxygen into the bag filter is prone to fire or explosion; when the temperature rises bag filter in the presence of flammable particles will also A fire or explosion occurred. In the process of use, bag filter control and system operation should be considered from the process conditions to ensure safe production.