Selection of filter bag material in thermal power plant
Selection of filter bag material in thermal power plant: coal-fired power plants usually select the PPS needle felt filter bag, which is composed of the PPS+PTFE fiber and the PTFE scrim cloth, instead of the ordinary PPS filter bag, because the mixed PTFE increases the temperature resistance and corrosion resistance of the PPS filter bag, although the price has been improved, longer service life and higher filtration efficiency make composite PPS filter bag a more cost-effective choice.
The filter system of bag filter is made up of dust removal framework and dust removal filter bag. The filter bag is the core component of a bag filter. The quality of dust removal filter bag directly affects the dust removal efficiency of the dust collector, and the service life of the filter bag has a direct impact on the operation cost of the dust collector. Therefore, usually dust filter bags need to choose the right material according to the environment and medium conditions of the dust collector.
The filter materials commonly used in the dust remover of power station are PPS, P84, PTFE and so on. Among them, the PPS dust filter bag is the most commonly used, and the gram weight is 550g/m2, usually using the singeing and heat setting treatment. If the moisture content in the flue gas is more than 10%, or the oxygen content is more than 10% and the temperature is higher than 160, the filter material needs to be impregnated with PTFE to improve the antioxidant and hydrolytic properties of the filter material.
If the operating temperature of the dust collector is above 190 C for a long time, it is more appropriate to use pure PTFE filter material. Because P84 is easy to hydrolize, it is not suitable to be used alone in coal-fired boiler bag filter. PPS is easy to oxidize, and the effect of using it alone can not reach the best. However, the PPS+P84 fiber can be combined into felt, and the content of P84 is usually 10-15%. The compound needling felt can further improve the filtration precision, keep the other performance unchanged, and the corresponding filter bag cost is also a little higher.
Because of the high content of SiO2 and Al2O3 and the coarser dust particles in the power plant fly ash, it is easy to wear out the membrane on the surface of the coated dust filter bag during the process of dust cleaning, and then the membrane falls off, and the membrane filter material is not suitable for the treatment of the dust of the coal-fired boiler.
In the bag type dust collector used in coal-fired power plants, PPS filter material is the first choice because of its high cost performance, but its anti-oxidation performance is poor. It is best to run under 160 C and 9% oxygen content, and its operating life can exceed 30000 hours. At the same time, NO2, SO2 and SO3 should also be controlled, especially the oxidation of NO2 is often ignored. These parameters are related to temperature, which have been verified in laboratory and application, which are important reasons for damaging the strength of filter bag.
At present, coal-fired power plants usually choose the PPS needle felt filter bag, which is composed of the PPS+PTFE fiber and the PTFE base cloth, instead of the ordinary PPS filter bag, because the mixed PTFE increases the temperature resistance and corrosion resistance of the PPS filter bag, although the price has been improved, longer service life and higher filtration efficiency make composite PPS filter bag a more cost-effective choice.