Bag filter material
One of the most important factors of the bag filter is whether the bag of the dust filter can be used in the medium to be dusted (within a certain time range) without damage (ie, the service life of the bag). The damage of the filter bag mainly refers to the damage, oxidation contraction, embrittlement, blocking, burning, corrosion, and hydrolysis and differentiation of the filter bag. Therefore, the choice of filter bag has certain requirements, such as temperature resistance, corrosion resistance, low resistance, not sticky ash, good life-to-price ratio, etc. We all know that filter bags are made of filter media. Therefore, the factors that affect filter bag life are the filter bag’s structure, manufacturing process, cleaning methods, and operating conditions. The most important factor is the characteristics and quality of the filter media. .
1, the characteristics of the filter bag mainly has the following indicators (or content)
– Breathability (this characteristic also determines the filter resistance)
–density
– Flex resistance (brittle)
– Breaking strength and elongation at break (horizontal, longitudinal)
-Temperature resistance (this characteristic determines the temperature range of use of the filter)
– Heat shrinkage (horizontal, vertical)
– Hydrolytic stability (in four levels)
– Acid resistance (four levels)
– Oxidation stability (in four levels)
The characteristics of the above filter media are related to the raw material (ie, fibril) components of the filter media, the weaving process, and various post processing methods of the filter media.
2. The raw materials for filter media are mainly divided into three categories:
– Natural fibers: mainly natural cotton and wool fibers.
– Glass fiber: glass fiber.
– Chemical fiber: many types, mainly: polyvinyl chloride (PC). Polypropylene (AC), Polyamide (PI), polyphenylene sulfide (RYTON), polytetrafluoroethylene.
3. The spinning and weaving process of filter material is mainly divided into two categories:
– Woven fabric (plain, twill, satin, etc.)
– Needle felt (basic and needled material can be the same material or different materials)
4, filter post-processing are:
– Surface singeing or calendering
– Heat setting
– Water and oil repellent treatment
– fire prevention
– Coating treatment
– Antistatic treatment
In order to facilitate a better understanding of the properties of the filter media, and to guide the selection of filter media, the following six typical media filters that can be used in power station boilers are introduced.
It can be seen from the table that knitted felts have better air permeability than woven fabrics, and non-circular chemical fiber filter materials have better air permeability. Glass fiber has the best temperature resistance, but its use of fiber is limited due to its brittleness and brittleness, and its weak ability to resist strong acids and bases. ACRYLIC filter materials have low temperature resistance and are very sensitive to temperature. Therefore, the smoke temperature must be strictly controlled during use, and even cooling protection measures must be used.
TEFLON filter fiber is particularly smooth, very helpful in dust removal, in addition to its high mechanical strength, chemical stability, corrosion resistance, is a very good filter, but because the price is expensive, only when necessary consider. Now with TEFLON as the filter material for surface coating treatment, this new type of filter material can achieve very good overall performance and the price is relatively lower. All other kinds of filter media have their own advantages and disadvantages, and they must be used selectively according to their performance. If necessary, they must also take certain protective measures. Now the processing technology of the filter material is further improved and some special treatments are taken to further improve the performance of the filter material.
Glass Fiber Polyethylene NOMEX Aromatic Polyamide RYTON Polyphenylene Sulfide P84 Polyimide TEFLON Polytetrafluoroethylene
Continuous temperature °C280160190240250
Breathable C Braided BA Fiber Cross-section Non-circular BA Fiber Cross-section Non-circular B
Anti-folding rate DBBBBA
Heat Shrinkage ABBBBB
Hydrolytic stability ABCABA
Anti-acid DBCABA
Anti-alkaline CCCACA
Oxidation stability ABBCBA
The price is cheaper, more expensive, more expensive, expensive, and more expensive
Remarks It is only applicable to the flue gas back blowing bag filter. It is very sensitive to temperature and has poor corrosion resistance. When the coal type changes greatly, it must be sensitive to oxidation and strictly control the oxygen content of flue gas. The lack of operating experience is too expensive.
Note: A, B, C, D are four levels in the table, A is the highest and D is the lowest.
The temperature of the flue gas provides a preliminary basis for the selection of filter material for the dust bag. When the temperature exceeds 250°C, only glass fiber materials can be used. When the temperature is lower than 130°C, it is obvious that the use of a polyethylene filter is most suitable. When the temperature is in the range of 130°C to 250°C, it is necessary to comprehensively consider which kind of filter material to choose based on the temperature of the flue gas and the components in the flue gas and the long-term operation conditions.