Filter bag dust collector filter cloth material and characteristics
? ? The filter material (filter bag) isbag filterThe core; The filter material should adapt to the conditions of high temperature in the flue gas, high content of SO2, NOx, O2 in the flue gas, and high dust concentration in the flue gas. Therefore, when using filter media in bag filters, the actual situation of the boiler should be considered and filter media should be selected in a targeted manner. There are many types of filter media, which can be divided into natural fibers, inorganic fibers, and synthetic fibers according to their materials. The commonly used filter cloth materials in the power plant boiler industry are:
? ? 1. PPS+P84 and PPS needle punched felt filter bags: generally used as the main filter bags for pulse cleaning bag dust collectors in coal-fired power plant boilers. PPS, also known as polyphenylene sulfide, is an abbreviation for the English name and is suitable for flue gas treatment using low sulfur coal; The process uses high-temperature resistant filter felt for the production and processing of filter materials. The application of PPS needle punched felt depends on its fiber properties. The suitable conditions for dust removal in coal-fired power plant boiler flue gas are: flue gas temperature of 120-160 ℃, SO2 in flue gas less than 800mg/m3, NOx less than 700mg/m3, O2 less than 8%, and coal ash content less than 30%; Before starting the boiler operation, it is necessary to pre coat the ash, spray oil on the furnace, and prevent the boiler from bursting. When the flue gas exceeds the temperature limit, it should not directly enter the bag filter and a bypass flue should be installed; The bag filter is designed with a filtration wind speed of around 1.0m/min and a resistance of 1300-1500Pa. After long-term use, the resistance and temperature resistance of PPS needle felt will deteriorate. PPS+84 fiber is used to make the needle felt, with a P84 fiber content of around 20%.
? 2. PPS and PPS+P84 gradient needle punched felt filter material: The main features of the new structure gradient needle punched felt are:
? 1) Introducing membrane surface filtration technology to traditional needle punched felt, and introducing a surface ultrafine fiber layer to achieve surface filtration effect. Upgrade the ordinary needle punched felt "surface+deep" filtration technology to gradient needle punched surface filtration technology. By using an ultra-fine surface layer to make the surface of the needle punched felt denser, the ability to block fine dust particles is improved, and the surface is easy to clean;
? 2) The surface structure of the needle punched felt adopts a gradient layer structure with increasing fiber fineness layer by layer, and the fluid channels are changed from the traditional needle punched felt with relatively equal width winding channels to relatively narrow front and wide back winding channels. It consists of four layers: surface ultrafine fiber layer, fine fiber layer, base cloth, and coarse fiber layer; After adopting an ultra-fine surface layer, the ability of the filter cloth to block fine dust particles is improved, and the inner layer of the filter material with narrow front and wide back channels is less prone to dust collection, maintaining long-term stable operation of the filter material while slowing down the rate of resistance increase and change;
3) The needle punched felt is treated with polytetrafluoroethylene (PTFE) infiltration to coat the fiber surface with PTFE film. The improved filter material mainly uses technical indicators such as flue gas temperature of 120-180 ℃, SO2 in flue gas less than 1200mg/m3, NOx less than 1000mg/m3, O2 less than 10%, and dust collector resistance of 1100-1300Pa.
? PTFE gradient composite needle punched felt filter material: The bag filter is used in combustion power plant boilers to solve the problems of filter material applicability: high sulfur coal, frequent boiler start-up and shutdown (low temperature of 60-120 ℃, acid condensation corrosion), boiler exhaust temperature in summer of 190-200 ℃, excessive boiler blowing and air preheater leakage causing oxygen content increase, etc. To stabilize the service life of filter material, PTFE fiber needs to be used.