9 factors to be considered in the design of dedusting equipment

（1） The selection of dust dispersion according to the dust dispersion has a great influence on the performance of the dust remover, and even if the dust dispersion occurs in the same equipment, there will be great differences due to different operating conditions Therefore, when choosing the type of dust collector, the first thing is to know the dispersion of dust As indicated in the figure in Section II, when the particle size is more than 10um, centrifugal precipitator shall be selected When the particle size is less than several microns, electrostatic precipitator, filter type precipitator (bag type precipitator) or scrubber (wet type precipitator) shall be selected The specific selection can be based on the particle size distribution and other requirements, refer to the commonly used dust remover type and performance table for preliminary selection Then according to the performance and design requirements of the types and types of dust collectors discussed in the following chapters （2） Considering the dust density has a great influence on the dust removal performance of the precipitator The effect of Zui is obvious in gravity, inertia force and centrifugal force (cyclone) One common point of all dust collectors is that the smaller the stacking density is, the more difficult it is to separate and collect dust particles, and the more serious the secondary flying of dust is Therefore, special measures should be taken in operation and equipment structure According to experience, for dust with the ratio of dust particle density to dust particle accumulation density of more than 10, special attention should be paid to the secondary flying phenomenon of dust For example, the carbon black dust is more than 46, so its secondary flying is very serious, and its dust separation and collection is also very difficult （3） In general, the higher the dust concentration at the inlet, the higher the dust removal efficiency However, in general, this will increase the dust concentration at the outlet, so it can not be generally considered that the dust treatment is good only from the perspective of high dust removal efficiency (2) In the venturi scrubber, jet scrubber and other dust collectors, the initial dust concentration is expected to be below 10g / Nm3, considering the friction loss of the throat section and nozzle blockage (3) In the filter type dust remover, the lower the initial dust concentration is, the better the overall dust removal performance is When the initial dust concentration is high, the continuous ash removal method with small pressure loss change is preferred （4） ESP is generally used in the range of initial dust concentration below 30g/Nm3 （4） It is very complex to consider the adhesion mechanism of dust and wall, but experience has known that it has a great relationship with the specific surface area of dust The specific surface area F of the dust is the surface area of the dust particles per unit volume If D is the diameter of the spherical dust particles, f will be expressed as follows: the smaller the dust particle diameter D is, the larger the specific surface area f is, and the greater the adhesion is In the cyclone, the dust sticks to the wall because of the centrifugal force, so it is dangerous to jam However, it is easy to block the air channel of the bag filter For the ESP, the discharge electrode is easy to be enlarged and the dust collecting electrode is easy to pile up The results show that the adhesiveness of dust plays an important role in forming the primary layer of dust Of course, the adhesion of dust is not only related to its specific surface area, but also to the composition of dust, the nature of gas and the characteristics of dust adhesion （5） Considering the specific resistance of dust, the specific resistance of electrostatic precipitator should be in the range of 10-10i The specific resistance of dust varies greatly with the temperature and humidity of dust gas Generally between 100 and 200, the resistance value Zui is large If humidified in dusty gas, the specific resistance will be reduced Therefore, when selecting ESP, it is necessary to know the specific resistance of dust in advance, and fully consider the selection of dust gas temperature and the adjustment of dust gas property （6） In principle, the dry dedusting equipment must be carried out at a temperature above the dew point of the dust containing gas As shown in the figure, in the dust gas containing sulfur trioxides, even if the sulfur trioxides are small, the dew point will be increased too much In addition: (1) in the wet precipitator, due to the evaporation of water and condensation after discharge to the atmosphere, it should be treated at low temperature as much as possible (2) In the bag filter, the temperature of directly or indirectly treating the dust containing gas should be lower than the heat-resistant temperature of the bag filter The use temperature of glass fiber dedusting bag is generally below 300 ℃ Other filter cloth is under 80-150 degrees (3) In ESP, the operating temperature can reach 400 ℃ The specific resistance of dust shall be considered to select the temperature of dust containing gas （7） Most of the wet dedusters are water If the scale of dust generating equipment is small and harmful gases need to be removed at the same time, or extremely fine carbon black and other dust need to be completely collected, wet dust remover is often used The temperature of the dust containing gas discharged from the wet dust remover is reduced, so in addition to reducing the atmospheric diffusion effect, prolonging the smoke flow, falling smoke, etc., measures need to be taken to deal with the problem of washing sewage （8） For the consideration of the properties of dust containing gas, in order to effectively use the dust remover, the following properties of dust and dust containing gas shall be treated according to the situation (1) When dealing with the exhaust gas containing carbon monoxide, as a measure to prevent explosion, it is necessary to introduce air into the high temperature part of the flue at the furnace outlet to oxidize carbon monoxide into carbon dioxide (2) improve the agglomeration of dust, use indirect cooling such as heat exchangers, direct cooling and humidification of water spray, or use electrostatic coagulation to improve the agglomeration effect of dust (3) Change the specific resistance of dust in the case of high resistance dust, such as in the case of fuel coal, mix with heavy oil and high sulfur coal for combustion, or spray with water, steam, sulfur trioxide and other regulators to reduce the specific resistance of dust On the other hand, when the resistance of the dust generated by burning heavy oil is too low, ammonia can be injected to generate ammonium sulfide with high resistance, and the static resistance of all dust can be adjusted within the range of 10-10 （9） The capacity determines the properties of the dust containing gas, which can vary significantly with the operating conditions or combustion conditions, and has a great impact on the dust removal performance It is very difficult to get the dust in accordance with the design specifications after the actual operation of the precipitator On the other hand, it is not easy to predict whether the environmental conditions of operation and equipment installation place will worsen or improve the equipment performance Therefore, when determining the capacity of the equipment, it is necessary to ensure a certain margin or reserve some space that may increase the equipment -- Wang pengcong