(1) Select according to the dispersion of dust - Wang Pengcong We are a professional Chinese supplier of Preserve Moisture Material; we supply various products of Skin Moisturizing Ingredients; and we can providing product images and basic parameters with each Skin Moisture Lock Ingredients and Activate Skin Water Ingredients. Look forward to your cooperation! Skin Moisturizing Ingredients,Skin Moisture Lock Ingredients,Hyaluronic Acid,Snail Slime,Carbomer Powder Xi'an Quanao Biotech Co., Ltd. , https://www.quanaobiotech.com
Dust dispersion has a great influence on the performance of the precipitator, and the dispersion of dust is the same even if the equipment is dusty, and there are great differences due to different operating conditions. Therefore, when selecting the type of the precipitator, the first thing is to know the dispersion of the dust. As indicated in the second section, the centrifugal dust collector should be selected when the particle size is above 10um. When the particle size is below a few micrometers, the electrostatic precipitator, filter dust collector (bag filter) or Scrubber (wet dust collector). The specific choice, according to the particle size distribution and other requirements, refer to the common dust collector type and performance table for preliminary selection. Then determine the type and type of performance and design requirements of the precipitator discussed in the following chapters.
(ii) Consideration of the severity of dust
The heavy dust has a great influence on the dust removal performance of the dust collector. The effect of this effect is clearly the gravity, inertial force and centrifugal dust collector (cyclone). One common point of all dust collectors is that the smaller the stacking weight, the more difficult it is to separate and trap dust particles, and the more serious the secondary flight of dust, so special measures should be taken in operation and equipment structure.
According to experience, dust with a ratio of dust particle gravity to dust particle weight of 10 or more requires special attention to the secondary flying phenomenon of dust. If the carbon black smoke is more than 46, its secondary flight is very serious, and the separation and collection of dust is also very difficult.
(iii) Consideration of dust concentration
(1) In gravity, inertial force and centrifugal dust collectors, generally speaking, the greater the concentration of dust in the inlet, the higher the dust removal efficiency. However, this generally increases the dust concentration of the outlet, so it is generally not considered that the dust treatment is good only from the high dust removal efficiency.
(2) In the dust collectors such as the Venturi scrubber and the jet washer, it is desirable that the initial dust concentration is 10 g/Nm 3 or less in consideration of the friction loss of the throat section and the nozzle clogging.
(3) In the filter dust collector, the lower the initial dust concentration, the better the overall dust removal performance. In the case of high initial dust concentration, it is desirable to use a continuous cleaning method in which the pressure loss changes little.
(4) Electrostatic precipitators are generally used in the range where the initial dust concentration is 30 g/Nm3 or less.
(iv) Consideration of dust adhesion
The adhesion mechanism of dust and wall is very complicated, but it is known to have 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 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, the larger the specific surface area F, and the greater the adhesion.
In the cyclone, the dust adheres to the wall due to centrifugal force, and there is a risk of clogging. The bag filter is easy to block the pores of the filtered gas. For the electrostatic precipitator, the electrode is enlarged and the dust collecting pole is accumulated. Experiments have shown that the adhesion of dust plays an important role in the formation of dust-forming primary layers of filter-type dust removal.
Of course, the adhesion of dust is not only related to its specific surface area, but also related to the composition of the dust and the nature of the gas and the characteristics of adhesion to the dust.
(5) Consideration of dust specific resistance
The dust specific resistance of the electrostatic precipitator should be within the range of 10 to 10I. The specific resistance of the dust varies greatly depending on the temperature and humidity of the dust-containing gas. Generally between 100 and 200, the resistance value is large. If the gas is humidified, the specific resistance is lowered. Therefore, when selecting an electrostatic precipitator, it is necessary to know the specific resistance of the dust in advance, and fully consider the choice of the temperature of the dust-containing gas and the adjustment of the nature of the dust-containing gas.
(vi) Considerations for the treatment of the temperature of dusty gases
The dry dust removal device must in principle be carried out at a temperature above the dew point at which the dust-containing gas is discharged.
As shown in the figure, in the dust-containing gas containing sulfur trioxide, even if the sulfur trioxide is a trace amount, the dew point is increased too much. In addition:
(1) In wet scrubbers, treatment should be carried out at low temperatures as much as possible due to evaporation of water and condensation after discharge to the atmosphere.
(2) In the bag filter, the temperature of the dust-containing gas treated directly or indirectly should be reduced below the heat-resistant temperature of the dust filter bag. The glass fiber dust bag is generally used at temperatures below 300 degrees. Other filter cloths are below 80 to 150 degrees.
(3) In the electric dust removal, the use temperature can reach 400 degrees. To consider the specific resistance of the dust, choose the temperature to treat the dusty gas.
(vii) Consideration of the use of wet dust removal
Most of the wet scrubbers use water. If the equipment for dusting is small, it is necessary to remove harmful gases at the same time, or when it is necessary to completely collect dust such as extremely fine carbon black, a wet dust collector is often used.
The temperature of the dust-containing gas discharged from the wet dust collector is lowered, so in addition to taking into account that the atmospheric diffusion effect is lowered, the smoke flow is prolonged, the smoke is dropped, and the like, measures for treating the sewage are also required.
(viii) Consideration of the nature of dusty gases
In order to effectively use the dust collector, the following dust and dust-containing gas properties should be treated according to the situation.
(1) Oxidation of carbon monoxide fumes When carbon monoxide-containing flue gas is discharged, as a measure to prevent explosion, air is introduced at a high temperature portion of the furnace outlet flue to oxidize carbon monoxide to carbon dioxide.
(2) Increasing the cohesiveness of the dust The indirect cooling by a heat exchanger or the direct cooling and humidification of the water spray or the coagulation effect of static electricity is used to improve the coagulation effect of the dust.
(3) Changing the specific resistance of dust in the case of high-resistance dust, such as in fuel coal, blending heavy oil with high-sulfur coal for co-firing, or spraying water, steam, sulfur trioxide and other modifiers to reduce the dust ratio resistance. On the other hand, when dust is generated when heavy oil is burned, when the electric resistance is too low, ammonia gas can be injected to form ammonium sulfate having a high electric resistance, and the entire static resistance of the dust is adjusted within a range of 10 to 10.
(9) Capacity decision
The nature of the dust-containing gas can vary significantly depending on operating conditions or combustion conditions, and has a large impact on dust removal performance.
After the dust collector enters the actual operation, it is actually very difficult to obtain dust that meets the design specifications. On the other hand, the environmental conditions of the operation and equipment installation spaces are degraded or improved, and it is not easy to predict. Therefore, when deciding the capacity of the equipment, it is necessary to ensure a certain margin or reserve some space that may increase the equipment.