“The wind speed is a distant indicator in the boiler bag dust removal equipment. If the wind speed is abnormal, the consequences will be very serious. So what causes the wind speed of the boiler bag dust removal equipment to be too high? Today, let’s take a deeper look at the boiler bag dust removal equipment. What is the seriousness of the excessive wind speed?
“
The wind speed is a distant indicator in the boiler bag dust removal equipment. If the wind speed is abnormal, the consequences will be very serious. So what causes the wind speed of the boiler bag dust removal equipment to be too high? Today, let’s take a deeper look at the boiler bag dust removal equipment. What is the seriousness of the excessive wind speed?
Let me introduce to you, the seriousness of the high wind speed of the boiler bag dust removal equipment, what is the related content?
Boiler bag dust removal equipment, the severity of excessive wind speed:
If the filtration wind speed of the dust removal equipment is too large, the general situation is as follows: about a week after the dust removal equipment is put into use, the initial resistance of the filter bag will rise rapidly, the air suction effect of the system will be significantly weakened, the dust removal effect will become worse, and the power consumption of the system will increase. Increasing the cleaning frequency will directly reduce the service life of the filter bag and pulse valve, increase the consumption of compressed air, etc., which will directly constitute a system failure.
Assuming that the filtration wind speed is blindly reduced, it cannot ensure the improvement of dust removal efficiency, nor can it reduce the filtration resistance, and may also cause economic losses; as long as the dust collector body structure design is optimized on the basis of fully understanding the dust properties and system characteristics, the correct economic Only technical analysis can reasonably determine the filtering wind speed.
Even if the theoretical filtration wind speed and other wind speeds are reasonable in the design of the dust removal equipment, assuming that the airflow uniform distribution method is not in place, the actual processing air volume of each bag room will be high or low; even in a bag room, it is assumed that the airflow is uniformly distributed If the method is not in place, the actual filtration wind speed of each cloth bag will be different. Therefore, a gas deflector and an air equalizing plate are required at the air inlet of the dust collector, the opening of the air inlet branch valve needs to be adjusted to balance the air volume of each bag chamber, and an air equalizing plate needs to be set in the ash hopper to distribute a single bag. room air volume.
The dust layer on the surface of the dust bag has a great influence on the working resistance of the dust collector, so the cleaning effect is particularly important. There are many factors that affect the cleaning effect of the low-pressure bag filter, such as injection pressure, cleaning cycle, bag length, and the interval between the dust bag and the bag. Without satisfactory injection pressure and energy, the dust layer on the surface of the dust bag cannot be removed.
But the injection pressure should not be too large, otherwise the service life of the dust bag will be greatly shortened. The injection pressure needs to be controlled in a reasonable design, which needs to be adjusted according to the viscosity of the dust, and the injection pressure should be controlled between 0.2MPa and 0.4MPa. From the point of view of reducing the working resistance of the dust collector, the resistance of the dust filter bag is small when the surface is always in a clean state, which requires repeated blowing and cleaning of the dust filter bag, but this is worth sacrificing the service life of the filter bag. Therefore, in the actual operation process, we need to adjust the cleaning cycle according to the concentration of dust in the flue gas and the viscosity of the dust.
In fact, the problem of the high wind speed of the dust removal equipment is very easy to solve. Don’t think that this is a very troublesome problem and ignore it.
After analysis, the filtration wind speed (also known as the air-to-cloth ratio) of the bag filter is generally closely related to the temperature, dust concentration and particle size of the treated exhaust gas, namely: V=f (T, C, dp).
Among these three parameters, the main particle size is the particle size. In order to clarify the relationship between the filtration wind speed and particle size, we did the following experiments.
From 2003 to 2005, the author designed and manufactured more than 70 baghouse dust collectors, which were used in metallurgy (ferroalloy, steelmaking), cement, coal-fired boilers, machining (electric welding, rust removal), chemical industry (production of calcium carbide) and other industries , After repeated debugging and transformation, the dust removal efficiency of most of the equipment has reached more than 99.9%, the smoke and dust emission concentration is less than 30mg/Nm?, and some are even less than 10mg/Nm?
Here, 19 dust collectors are selected for dust removal of ferroalloy submerged arc furnace flue gas. Due to the fine particle size and high flue gas temperature of ferroalloy submerged arc furnace dust, it is extremely difficult to control, whether mechanical dust collector, wet dust collector, or None of the electrostatic precipitators can meet the standard, only the bag filter is used, and the bag filter can only choose pulse cleaning and reverse air blowing. Before entering the dust collector, all the flue gas of the submerged arc furnace is cooled to reduce the temperature to about 200 ℃, and the dust concentration in the exhaust gas is between 1.2~2.0g/Nm? before entering the dust collector, which basically eliminates the Effects of soot concentration and flue gas concentration on filtration wind speed.
The filtering wind speed of the long-bag low-pressure pulse bag filter is proportional to the logarithm of the particle size of the smoke and dust. At the same time, we found in the laboratory simulation that when the particle size is less than 1um, the filtration wind speed of the pulse dust collector cannot be greater than 0.6m/min, which indicates that the dust with a particle size of less than 1um should be cleaned with a pulse dust collector and backflushing. The filtration wind speed of the dust collector is basically the same (the filtration wind speed of the backflushing dust collector is generally 0.45m/min), but the cost of the backflushing dust collector is much smaller than that of the pulse dust collector with the same filter area, so it is necessary to purify the particle size. When the particles are less than 1um, it is advisable to use a back-flushing dust collector, which can not only remove the dust, but also save investment.
Comprehensive relationship between filtration wind speed and temperature, concentration and particle size
Theoretically, the relationship between the filtration wind speed and temperature should not be close, but the purification of fine dust (particle size)
What is the specific relationship between the filtration wind speed and the temperature of the exhaust gas and the concentration of soot and dust? We can study it experimentally. Table 2 is the working parameter table of the dust collector designed by the author for various industries (only the equipment with a dust removal efficiency above 9919% is selected. or equipment with an outlet discharge concentration of less than 30 mg/Nm²).
The smaller the soot particle size, the smaller the filtration wind speed; from the relationship curves of Figure 2 and Figure 3, it can be seen that the higher the dust concentration in the exhaust gas, the smaller the filtration wind speed; the higher the exhaust gas temperature, the smaller the filtration wind speed. Therefore, it can be approximated that the filtration air velocity is inversely proportional to the exhaust gas temperature and the concentration of soot. Since the three variables of exhaust gas temperature, soot concentration, and soot particle size are independent variables that are not related to each other, the probability density of any independent random variable’s joint occurrence is equal to the product of their respective probability densities, so we can think that the filtration wind speed and the exhaust gas The comprehensive relationship between temperature, soot concentration and particle size is the product of their independent relationships,
The filtration wind speed of the pulse cleaning bag filter is inversely proportional to the temperature of the exhaust gas and the concentration of soot and dust in the exhaust gas, and is proportional to the logarithm of the particle size of the soot and dust.
Although this formula is obtained by curve fitting, when we designed the pulse dust collector after 2005, the selection of the filtering wind speed was calculated by this mode, and the dust removal effect of each dust collector met the requirements (the dust removal efficiency reached 99.9% or vent concentration less than 30g/Nm?).
The selection of filtering wind speed is a key parameter in the design of bag filter, which is directly related to the dust removal efficiency. In this paper, after measuring the relevant parameters of each dust collector in engineering applications, through curve fitting, the mathematical model between the filtering wind speed and the temperature of the exhaust gas, the concentration of soot and dust in the exhaust gas, and the particle size of the soot and dust is obtained. At the same time, it is feasible to use this model to guide the design within a certain range.
If the filtration wind speed is too high, it will affect the dust removal efficiency, increase the difficulty of cleaning, increase the filtration resistance, reduce the service life of the filter bag, and increase the operation and maintenance costs.
In fact, the selection of wind speed is a relatively complicated task. It is far from enough to look at the above advantages and disadvantages in isolation. It is closely related to the nature of dust, the initial concentration of dust-containing gas, the type of filter material, and the method of cleaning. The key to the correct selection of the filtration wind speed is to firstly clarify the properties of dust and dust-containing gas; secondly, it is necessary to correctly understand and understand the relationship between the filtration wind speed and the dust removal efficiency, filtration resistance, and dust removal performance.
Filter wind speed is too high
This situation may be due to the fact that the filtering air speed determined during design is too high, or it may be that the fan’s regulating valve is opened too large during operation, resulting in the treated air volume exceeding the design air volume. At this time, the structural resistance of the dust collector and the filter resistance of the filter bag will significantly exceed the design value.
Resistance reduction measures for “filtered wind speed is too high”
1) If the filter wind speed is designed too high, the number of bag chambers and filter bags should be increased to increase the total filter area, so that the filter wind speed value is controlled within a reasonable range. The selection of filtration wind speed mainly considers factors such as bag filter type, cleaning method, filter material material and dust concentration. amide) filter material, it is recommended that the net filtration air speed should be selected below 1.0m/min. When the filter material is 950g/m2P84 glass fiber composite felt coated filter material, it is recommended that the net filtration air speed should be selected below 0.9m/min.
2) If the opening of the regulating valve is too large, the opening of the regulating valve should be adjusted to a reasonable opening.
The Links: FF150R12KE3G G185BGE-L01 IGBT-PART