Whether the dust filter bag can be correctly and reasonably selected determines the service life of the bag filter and the concentration of emissions, so in the face of different industries and different flue gas conditions, how should we select the dust filter bag?
Factors affecting the service life of dust filter bags
The service life of dust filter bag depends on the nature and temperature of the flue gas (continuous working temperature, instantaneous working temperature, dew point temperature, chemical properties, dust concentration, filtration air speed, etc.), dust properties (viscosity, moisture, particle size distribution, flame retardant requirements), dust cleaning factors (pulse dust cleaning <offline, online>, dust cleaning pressure) and system air leakage (oxygen content), etc. In the selection of dust filter bags can be based on the above four points Comprehensive consideration.
Various kinds of needle felt use working conditions
1、P84 needle felt
P84 needle felt is obtained from polyimide fiber by needling, its characteristics are remarkable because of its own fiber fineness. P84 needle felt has the following advantages.
1）Significant temperature resistance: it can be operated for a long time at 260℃, and the short-time operation temperature can reach 280℃
2) Good acid and alkali resistance and oxidation resistance, with some resistance to hydrolysis.
3) Low pressure and high effect; polyimide has irregular fiber cross-section, because P84 needle felt has a large surface area, providing more tiny pores, its surface filtration effect is better than depth filtration so most of the dust only stays on the surface of the needle felt and does not penetrate into the deep layer, thus the backwash pressure is smaller, the filter cake ejection efficiency can be significantly improved, with excellent micro powder collection effect, while the filtration pressure difference is small.
Due to the good temperature resistance of P84 fiber, the anisotropic cross-section of trilobal type (larger specific surface area), the high strength of the fiber, and the oxidation resistance, the instantaneous temperature resistance of the rate material can be improved, the filtration efficiency can be improved, and the load tolerance can be increased. The needle felt is recommended to be used in working conditions with high dust concentration, high temperature and low moisture content.
Technical difficulties: the production process is difficult, including the control of workshop temperature and humidity, production speed parameters and various indicators of the needle felt .
2、PTFE+P84 composite needle felt
PTFE fiber has the following advantages.
1)Superior temperature resistance, with continuous use temperature of 260 degrees and instant 280 degrees.
2) Due to the special molecular structure of PTFE material, it has extremely excellent chemical stability and corrosion resistance, which can improve the chemical erosion of the filter material.
3)Due to the non-stick, water-repellent and non-combustible characteristics of PTFE needle felt , it makes this kind of fiber the most excellent needle felt .
4) This kind of fiber as the base cloth, in the long-term use process basically ensure that the strength does not decay.
The mixture of PTFE and P84 can improve the corrosion resistance and high temperature resistance of the needle felt, and at the same time improve the filtration precision, which can withstand higher dust scouring. The strength of the needle felt decays slowly in the process of use, which can extend the service life of the needle felt . This needle felt is recommended for use in the field of flue gas dedusting where the dust content and oxygen content are high, the temperature is high, and the gas is more corrosive.
Technical Difficulties.
(1) High difficulty in controlling the uniformity of the needle felt because of the large difference in specific gravity of the two fibers.
(2) The high content of PTFE fibers in this solution makes it difficult to hold and poorly card between fibers.
3、PTFE needle felt
PTFE fiber has the following characteristics.
(1) Melting point of 327 ℃, can be used at 260 ℃ high temperature for a long time, the instantaneous use of temperature can exceed 280 ℃. Can not burn, its limit oxygen index reached 95%.
(2) low strength, small elongation at break, the breaking strength of imported brown fiber is only 1.9cn/dtex, and the strength of white imported fiber is basically not more than 4cn/dtex.
(3) low coefficient of friction, so dust is easy to fall off on the surface of the needle felt.
(4) The fiber surface tension is large, and it has good water repellent performance.
(5) The fiber is fine, the filtration efficiency is general, and the gram weight of the needle felt is more than 750g.
(6) Poor textile performance, low holding force, easy to generate static electricity during the fiber textile process.
It is suitable for use in all kinds of furnace cellars, especially electric power coal-fired boilers and waste incinerators. Its disadvantages are tensile and abrasion resistance, poor folding resistance, and high price (equivalent to 10 times of glass fiber needle felt), used a lot in foreign countries, and mostly used in composite needle felt in China.
Ltd. (hereinafter referred to as "Yuanchen Technology") has been specialized in environmental protection industry for 16 years, and dust filter bag is one of our two main products. After the process of needle-punching, burnishing and calendering, emulsion impregnation, high temperature shaping and laminating, we make various kinds of high precision, high temperature, abrasion and corrosion resistant needle felt products required by actual working conditions. It is mainly used in thermal power generation, building materials, iron and steel, waste incineration, chemical industry, glass and other industries, which can comprehensively improve China's air pollution prevention and control ability, realize ultra-clean emission, and meet the national strategic needs in the field of environmental protection.
