1 Characteristics of high-temperature exhaust gas dust removal Exhaust gas emitted from various industrial furnaces in the metallurgical, mechanical, chemical, and power industries not only has a high temperature, but also contains a large amount of dust and harmful gases, which is one of the main factors causing environmental pollution. Under high temperature conditions, due to the large change in the viscosity of the exhaust gas, the humidity greatly decreases, and the phenomenon of fine particle agglomeration is greatly reduced, so it is difficult to separate the particles. Bag type dust collectors
cannot withstand the high temperature of exhaust gas, and wet dust removal cannot make comprehensive use of its thermal energy; electrostatic dust removal has problems such as high one-time investment, large floor area and insulation. At present, most of the treatment methods for high-temperature dust-containing exhaust gas in China are through water condensation, reducing the high-temperature exhaust gas to about 200 ° C, and then using a bag filter
to remove dust, which not only increases the investment and operating costs of the condensation equipment, but also causes a large amount of heat energy to be lost. . Therefore, new high-temperature exhaust gas dust removal technology is an important subject that needs to be developed urgently.
2 Types of high-temperature exhaust gas dust removal technology High-temperature exhaust gas dust removal technologies include: cyclone dust removal, wet dust removal, electrostatic dust removal, filter dust removal, and the like.
3 main types of filter dust collector
3. 1 bag filter dust collector
Bag type dust collector is the most commonly used filter type dust collector. Its dust removal efficiency is high, and it also has a high dust removal efficiency for sub-micron dust, which will not cause secondary pollution and facilitate the direct recovery of dry materials. Bag dust collectors have made great contributions to the control of air pollution. At present, they are more and more widely used at home and abroad, accounting for 80% of dust removal equipment. However, in the high-temperature dust removal of coal-fired power plant boilers, bag dust removal technology has not been fully adapted, and needs further improvement and perfection, which is closely related to the improvement of filter material performance and technological progress.
Filter material is the core of the bag filter, and its performance has a great influence on the operation of the bag filter. The characteristics of dust-containing gases, such as dust and gas properties (temperature, humidity, particle size, and dust concentration, etc.) must be considered when selecting the filter material. A good-performance filter should have a large dust holding capacity, low hygroscopicity, high efficiency, low resistance, and long service life. At the same time, it must have the advantages of moisture resistance, wear resistance, corrosion resistance, and high mechanical strength.
3.2 Particle Bed Filter Dust Collector The particle bed dust collector uses solid particles with very stable physical and chemical properties, such as quartz sand, to form a filter layer. The particles play a filtering role through the interstices and zigzag channels to achieve the dust removal of gas. The particle bed dust collector has the advantages of high temperature resistance and good durability, and can realize continuous filtering and dust removal by self-cleaning. The dust removal efficiency is generally more than 90%, and the highest can reach 99%.
3.3 Full filter cake filter dust filter The full filter cake filter dust filter (surface filter) only serves as a framework to support the filter cake, and the system is always maintained within an optimal filter cake thickness range, so that The cake formed by dust efficiently filters dust. It has high temperature resistance (1 000 ℃), is not easy to fog, not easy to block, has good cleaning effect, convenient operation and maintenance, and low price.It can control the mass concentration of flue gas emissions of ultrafine dust (below 5μm) at 5 mg. / m3 or less, especially suitable for handling dust with strong adhesion and hygroscopicity.
3.4 Sintered porous metal filter dust remover Sintered metal dust removal is to use sintered metal porous material to purify dust-containing gas. The sintered porous metal filter can finely remove dust particles below 5 μm. At room temperature, porous metal materials have the advantages of good overall strength (strength is several times that of ceramic materials), no breakage, and stable long-term work. But at high temperature, its strength and corrosion resistance are lower than ceramic materials.
3.5 Porous ceramic filter dust collector Since the 1970s, advanced countries in the world have been continuously researching porous ceramic filters of various materials and structures for high-temperature filtering and dust removal, and have achieved good results. The main physical properties of porous ceramics are porosity, permeability, and bending strength. Studies have shown that compared with other types of dust collectors, porous ceramic filters have high dust removal efficiency, which can reach more than 99%, can remove dust particles more than 5 μm, and have a simple structure.The most important thing is that they can withstand high temperatures and can work at high temperatures. Up to 800 ℃, and has good corrosion resistance in high temperature environments such as oxidation, reduction, so porous ceramic filters can play an important role in high temperature dust removal.