General principle of selection of filter material for dust collector of waste incineration
(1) selection of filter material according to the characteristics of the dust containing dust
Filter material is usually made from natural fiber or synthetic fiber, such as cotton and wool. The raw materials have different physical and chemical properties, and it is impossible to have excellent performance and resistance in temperature, humidity and chemical resistance. Therefore, as the principle of selecting filter material, we must fully grasp the characteristics of dusty gas, including the temperature, humidity, corrosiveness, flammability and explosiveness of the dusty gas, and carefully evaluate the properties of all kinds of fibers and make reasonable selection.
(2) selection of filter material according to the character of dust
The properties of dust include the chemical and physical properties of dust. The selection of material, structure and post treatment of filter material is considered mainly from the physical properties of dust. These traits include the shape and particle size distribution of dust, dust adhesion and cohesion, dust, moisture absorption and deliquescence of grinding dust peck.
(3) select the filter material according to the dust cleaning method of the dust collector
The cleaning method of bag type dust collector is one of the main factors to choose the structure of filter material. The bag filter with different cleaning methods is suitable for the selection of the filter material of different structural varieties because of the different characteristics of the ash cleaning energy and the deformation characteristics of the filter bag.
(4) selection of filter material according to other special requirements
It mainly includes high concentration dust collecting process, high standard emission and occasions with purification requirements, occasions with stable and low resistance operation requirements, oil and mist handling, and special structure dust remover requirements. The principle of selecting the filter material of the garbage incineration flue dust remover from the angle of use
(1) the filtration performance is good and the resistance is low.
(2) uniform texture, stable size, high mechanical strength and long service life.
(3) good chemical stability, acid and alkali resistance, high temperature resistance, antioxidation;
(4) the source of raw materials is wide and the price is cheaper.
It is obvious that it is difficult to meet all of the above conditions, because these conditions are contradictory and restrictive. Therefore, the main factors should be taken into consideration when selecting filter material.
Commonly used garbage incineration filter material for flue gas dust remover
At present, the filter material used in the bag filter of MSW incinerator is mainly composed of PPS filter material, P84 filter material, glass fiber bulked yarn and membrane filter material, glass fiber needle felt, PTFE fiber composite filter material and GORE-TEX and other varieties, and others also have PTFE fiber or PTFE membrane filter material. Among them, PPS filter material and P84 filter material are widely used. Especially in the foreign garbage incinerator bag filter, the use of these two kinds of filter materials is large. Glass fiber bulked yarn coated filter material and glass fiber needle felt are widely used in domestic and Japanese areas.
(1) polyphenylene sulfide (PPS)
Polyphenylene sulfide (PPS) fibers can operate at 190 degrees centigrade and can withstand high temperatures at 232 degrees C (no other chemical composition). PPS fiber filter material is widely used in waste incinerator in addition to its weak oxidation resistance and excellent acid and alkali resistance. However, when the content of oxygen (O2) in the flue gas is over 10% and the operating temperature is over 165, the PPS fiber will also decompose.
(2) glass fiber
Glass fiber can be used to make glass fiber woven fabric, glass fiber bulgous yarn or needle felt. The maximum temperature of the glass fiber filter material is up to 260 C, and the temperature is 290 C at the moment. Under the condition of above 260 C, the glass fiber filter material itself will not be destroyed directly, but the post-processing material used to increase the lubricity of glass fiber (yarn) will be evaporated, which will eventually lead to mechanical wear between glass fibers. Glass fiber filter material is flame retardant, almost no moisture absorption (no hydrolysis), with excellent dimensional stability and reasonable strength properties. The tensile strength of glass fiber fabric is better, but the flexural resistance is relatively weak, so the bending and friction should be avoided in the process of disposal. Glass fiber filter material has relatively good acid resistance, but HF, concentrated sulfuric acid and hot phosphoric acid will have corrosion effect on glass fiber filter. Under high temperature, weak alkali, anhydride and metal oxide will also damage glass fiber filter material. Therefore, the glass fiber filter material can not be used at the dew point temperature.
(3) polyimide (P84)
Polyimide fiber filter is a kind of flame retardant and high temperature stability of fiber filter, at the temperature of 240 DEG C, the mechanical properties of P84 fiber filter does not change, the highest temperature is 260 degrees centigrade. P84 fiber filter material has no melting point temperature, and it is natural golden yellow. The fiber can be used as the base cloth of the filter material and spinning yarn. P84 fiber filter material is not hygroscopic fiber filter material (at 65% relative temperature conditions, water absorption of about 3%). In addition, because the P84 fiber is a profiled (leaf type) section structure with large filtration area and excellent filtration performance, P84 fiber is usually implanted on the surface of filter material (side to face) to improve filtration performance of filter material. Because the P84 fiber filter material has a certain hydrolytic property, it is suggested that the water vapor content in the use condition should be less than 38%. The filter material has a strong adaptability to the concentration of SO2 and has no special requirement for the oxygen content of the flue gas.
(4) polytetrafluoroethylene (PTFE)
Polytetrafluoroethylene synthetic fiber filter material is a unique material. It can withstand any acid acidity when running temperature is 240 degrees, and instantaneous temperature is 260 degrees. Polytetrafluoroethylene fiber filter material has excellent self - moistening, does not absorb moisture, and can withstand ultraviolet radiation. But the wear resistance of PTFE fiber is general, so it is strictly required for the smoothness of the filter bag frame. PTFE fiber can be applied to harsh corrosive conditions and high demand for filter life, and can be mixed with glass fiber to make cost-effective filter material more reasonable.
(5) polytetrafluoroethylene film coated filter material
PTFE film smooth surface and chemical substances, the coating to the ordinary filter material surface, the dust can be entrapped in the membrane surface, the surface of the filter; because of the thin film surface is smooth, with excellent chemical stability, water repellency, aging, the interception can be easily peeled on the surface of dust, so can improve the service life of the filter. Compared with ordinary filter material, it has the following advantages:
1) the pore size of the film is 0.2 ~ 3 mu m, and the filtration efficiency is over 99.99% and almost zero emission. After cleaning the dust, the porosity is not changed, and the efficiency of dust removal is stable.
2) the pressure loss of the membrane filter media is higher than that of the ordinary filter material when it starts to use, but after putting into operation, the pressure loss does not change very much with the increase of the operation time, and the pressure loss of the ordinary filter material will increase with the prolongation of the service time.
3) ordinary filter in use, dust easily into the interior, and piled up, until the pore filter blocked, unable to continue to use. The PTFE membrane filter material can remove the filtered dust easily from the surface of the membrane. The effect of cleaning is good, the cycle is long, and the ash cleaning pressure is low, which can improve the service life of filter material and reduce the running cost of products. The PTFE film filter materials used in waste incinerator are PPS, P84 and glass fiber expanded yarn weaving machine.