Development and Application of Teflon Glass Fiber Sintered High Temperature Filter Media
Abstract: This paper briefly analyzes the technological characteristics of Teflon glass fiber sintered high temperature resistant filter material, introduces its performance, characteristics and engineering application examples, and indicates that Teflon glass fiber sintered high temperature resistant filter material is a high-performance filter material with high temperature resistance, high humidity resistance, and chemical corrosion resistance, and has broad application prospects. Teflon conveyor belt
1 Preface
Polytetrafluoroethylene (Teflon) has many excellent properties:
(1) Excellent high and low temperature performance, wide use temperature range, up to - 190 ℃~260 ℃;
(2) High chemical stability, capable of withstanding all strong acids and bases, including aqua regia, strong oxidants, reducing agents and various organic solvents except molten alkali metals and fluorinated media;
(3) Outstanding non viscosity and lubricity, known solid materials can not adhere to its surface, and it is a solid material with the smallest surface energy;
(4) Excellent atmospheric aging resistance, radiation resistance and low permeability;
(5) Valuable incombustibility, with oxygen limiting index below 90;
(6) It is waterproof.
Although Teflon has quite good heat resistance and chemical resistance, its strength is not very good physically, and its dimensional stability under high temperature conditions is not better than other materials.
Glass fiber is brittle and easy to break, has poor wear resistance, is not resistant to hydrolysis, and has poor corrosion resistance to some chemicals, such as fluoride, which has great limitations in its application as a high-temperature filter material. However, the high strength, heat resistance and dimensional stability of glass fiber cloth are just complementary to Teflon, and the combination of the two materials can form a high-temperature resistant filter material with superior performance and strength. Teflon conveyor belt
Teflon glass fiber sintered high temperature filter material developed based on the respective performance characteristics of Teflon and glass fiber. Its principle is to use imported Teflon polymer raw materials and other chemical additives, and adopt special sintering process flow, so that the glass fiber cloth has higher wear resistance, corrosion resistance and high temperature resistance than glass fiber material, giving the filter material good acid and alkali resistance It has corrosion resistance, high temperature resistance, friction resistance, bending resistance and other properties, and its surface is smooth and hydrophobic. The dust cannot adhere to the surface of the filter material. It is suitable for high temperature, high humidity, high viscosity dust industries or industrial smoke purification with acid, alkali and corrosive chemical gases, as well as other occasions with bad working conditions.
2 Process characteristics of Teflon glass fiber sintered high temperature resistant filter material
2.1 Functions and structural characteristics of the filter material
As glass fiber is brittle and easy to break, its abrasion resistance is poor, and its corrosion resistance to some chemicals, such as fluoride, is also poor, so its application as high-temperature filter material has great limitations; The other kind of Teflon glass fiber composite without sintering process cannot be firmly bonded to the glass fiber due to the low crystallinity of Teflon molecules. The protective layer of Teflon on the glass fiber is easy to fall off, and the filter material made of Teflon has poor performance in high temperature resistance, corrosion resistance, hydrolysis resistance, flexibility, wear resistance, and bending resistance. As a high-temperature filter material, its service life is very short.
2.2 Surface treatment of glass fiber cloth
Generally, there are slurry, grease and other impurities on the glass fiber cloth. If the slurry, self-lubricating agent, sizing agent, grease and other impurities on the glass fiber cloth are not removed, or the impurities are not removed thoroughly and fully, the direct impregnation with Teflon will affect the sintering quality of the filter material, resulting in poor bonding between the glass fiber cloth and Teflon, and poor performance of the filter material. Therefore, the slurry, self lubricant, sizing agent, grease and other impurities on the glass fiber cloth should be completely removed by a cleaning process without physical wear and chemical erosion, so as to make the surface of the glass fiber cloth smooth and clean, which can effectively improve the adhesion and firmness of Teflon and glass fiber. Resistance High temperature conveyor belt
2.3 Characteristics of Teflon glass fiber sintering process
The glass fiber cloth and Teflon after preliminary treatment adopt sintering process. After multiple sintering, the surface of each fiber in the glass fiber filter cloth is coated with a dense Teflon protective layer. In addition, other chemical additives are added into the Teflon solution, which controls the appropriate sintering temperature, speed, pressure and other processes, and improves the crystallinity of Teflon molecules, The adhesive strength and softness of Teflon and glass fiber base cloth are enhanced. Due to the high crystallinity of Teflon molecules and the uniform crystallization of Teflon on the surface of glass fiber, it can effectively improve the firmness and adhesion of the combination of the two. A solid Teflon protective layer is formed on the surface of glass fiber, and Teflon is very firmly bonded to the glass fiber, thus greatly improving the folding resistance, corrosion resistance, wear resistance and strength of filter materials. The bag filter can not only broaden its application range, but also greatly extend its service life.
2.4 Film covering process and function
In order to further improve the working life and filtration performance of the filter material, the expanded Teflon microporous film can be used to melt and composite with the sintered glass fiber cloth through the high-temperature hot pressing process, so that the glass fiber cloth, the Teflon protective layer and the Teflon microporous film layer can be well connected together, forming a high temperature resistance The corrosion resistant Teflon glass fiber sintered membrane covered filter material has further improved its corrosion resistance, folding resistance, wear resistance and service life.
The filter material after film coating has the following properties:
(1) High filtration efficiency: microporous membrane has unique cross microporous characteristics. The porosity of Teflon microporous membrane is more than 90%. It has good filtration performance for ultra-fine dust μ The fine dust of m and above can reach the filtration efficiency of 99.99% and achieve near zero emission;
(2) Low running resistance: because the Teflon film itself has the characteristics of non sticking dust, hydrophobic and stable chemical performance, the working surface of the filter material after film covering is extremely smooth, and the dust stripping performance is very good, especially for the dust with strong moisture absorption and easy to bond and harden;
(3) Corrosion resistance, folding resistance and abrasion resistance are further improved: after the microporous film is compounded with Teflon glass fiber sintered filter material, it has better acid and alkali resistance, high temperature resistance, high humidity resistance and other characteristics;
(4) Long service life, high filtration speed: the resistance of membrane covered filter material is small and stable, and the filtration speed is fast.
3 Performance of Teflon glass fiber sintered high temperature resistant filter material
The main composition of Teflon glass fiber sintered high temperature resistant filter material: glass fiber+Teflon+chemical additives.
4 Characteristics of Teflon glass fiber sintered high temperature resistant filter material
(1) High temperature resistance: the temperature resistance of this kind of filter material is mainly determined by the temperature resistance of glass fiber and Teflon itself. Its long-term use temperature is 260 ℃, short-term and instantaneous temperature can reach 300 ℃, and the heat shrinkage rate is less than 0.5%.
(2) Good acid and alkali resistance: it has very good resistance to acid and alkali and most organic substances, and its resistance to corrosive gases such as acid and alkali, including hydrogen fluoride, is significantly higher than that of ordinary glass fiber filter materials.
(3) Good wear resistance and fatigue resistance, high tensile strength, superior to ordinary glass fiber filter material.
(4) Good hydrophobicity: the surface of the filter material is smooth and hydrophobic. No dust can adhere to the surface of the filter material, and it is easy to clean the dust. It is not afraid of tar and water vapor. Therefore, heat preservation is not required outside the dust remover, and it can be used for filtering flue gas dust containing acid and alkali components and with large humidity fluctuations.
(5) Good thermal stability: the thermal shrinkage rate at 300 ℃ is less than 0.5%, which determines the safety of its use at high temperatures.
(6) High filtering wind speed: its filtering material is a smooth cylinder, with small dust capacity, easy to clean, and has good friction resistance and fatigue resistance. These characteristics determine that it has a high filtering wind speed, and also determines that its competent dust removal methods include reverse air dust removal, rotary reverse air dust removal, mechanical vibration dust removal, pulse dust removal, etc.
(7) The sintered filter material can be compounded with Teflon microporous membrane to form a membrane covered filter material. It has the characteristics of high filtration efficiency, easy ash removal, acid and alkali resistance, and plastid flexibility.
5 Engineering application examples
Teflon glass fiber sintered high temperature resistant filter material has been used for flue gas dust removal in garbage incinerators, cement, chemical industry, smelting, industrial waste incinerators, thermal power plants, product recycling plants, etc. since 2007. Since the successful development of this product, it has been adopted by many domestic users of garbage incinerator dust removal equipment.
Application example: The bag filter of a garbage incinerator is equipped with filter bags made of Teflon glass fiber sintered high temperature resistant filter materials.
Operation effect: The waste incineration treatment technology should be harmless, resourceful and reduced, but the flue gas purification after incineration is difficult. The filter bag is made of Teflon glass fiber sintered high temperature resistant filter material, which greatly improves the dust removal efficiency and the service life of the bag, and the dust removal effect is good. The average dust emission concentration is 29 mg/Nm3, and the smoke blackness (Ringmann blackness) is less than 1, far below the national emission standard. Since the system was started in October 2007, the filter bag has been used well. Therefore, Teflon glass fiber sintered high-temperature filter material is one of the most ideal high-temperature filter materials for dust removal equipment of garbage incinerator.
6 Conclusion
Teflon glass fiber sintered high temperature resistant filter material has good performance of acid and alkali resistance, corrosion resistance, high temperature resistance, friction resistance and bending resistance, and its surface is smooth and hydrophobic. The dust cannot adhere to the surface of the filter material. It is suitable for high temperature, high humidity, high viscosity dust industries or industrial smoke purification with acid and alkali, corrosive chemical gases. With the development of environmental protection in China, Teflon glass fiber sintered high temperature resistant filter media has a wide range of applications in the high temperature flue gas filtration industry, with broad application prospects, mainly for:
(1) Flue gas purification of high temperature and high viscosity dust in garbage incinerator. In particular, the disposal of waste medical supplies (such as disposable syringes, rubber gloves, etc.) and domestic garbage can solve the problems of high-temperature burning bags, high viscosity dust paste bags, chemical gas corrosion cloth bags, etc.
(2) Flue gas purification of blast furnace gas in iron and steel smelters. It can mainly solve the problems of high temperature, high humidity, paste bags below dew point and chemical gas corrosion such as high temperature and sulfur.
(3) Carbon black, flue gas purification of coking furnace. It can mainly solve the problems of difficult dust removal caused by high temperature and high viscosity dust, and early embrittlement of filter material caused by oxidation reaction below dew point after shutdown.
(4) Chemical industry, metallurgy, cement and other industries. It can solve the problems caused by high temperature and high viscosity dust, such as bag pasting of bag filter, high running resistance of equipment, early brittleness and damage of filter material, etc.
(5) Dry desulfurization of flue gas from coal-fired boilers in power plants. Compared with ordinary glass fiber bags, it has the advantages of non sticking bags, easy ash removal, low running resistance of equipment, long service life, etc.
