There are many types of bag filters. Therefore, the selection calculation is particularly important. If the selection is not appropriate, if the equipment is too large, it will cause unnecessary flow charges. Equipment selection will affect production and it is difficult to meet environmental requirements.

There are many calculation methods for the selection. Generally speaking, the basic process parameters of the flue gas should be known before calculation, such as the flow rate, nature, concentration of the dust-containing gas, and the dispersion, infiltration, and viscosity of the dust. After knowing these parameters, calculate the filter wind speed, filter area, filter material and equipment resistance, and then select the equipment category model.

Handling air volume ÷ Filtration wind speed = filter area , generally bag filter wind speed is about 0.8-1.2 / sec

 (1) Handling air volume

The unit for treating the air volume is generally expressed by m3/min or m3/h , but attention should be paid to the temperature of the place and the flue gas, and the moisture content of the high-temperature gas is large, so the air volume is expressed by the amount of wet air, wherein the water is expressed by the volume fraction. If the flue gas temperature has been determined, the gas is cooled by the dilution method. When calculating the air volume, the amount of diluted air should be considered. When calculating the filtration area required by the bag filter, the filtration speed is the actual filtered wind speed. The air volume design value should increase the insurance factor by 5%-10% based on the normal air volume to ensure that the process adjustment will increase the air volume in the future. The bag filter can continue to be used stably, but it should be noted that the insurance factor should not be too large, otherwise the investment will increase. And operating costs.  

Due to the form of the bag filter and the type and characteristics of the filter material, the filter wind speed is greatly different. Once the process air volume is determined, the filter area can be determined according to the filter wind speed. 

When calculating the processing gas of the bag filter, it is necessary to first determine the amount of gas under working conditions, that is, the gas data actually passing through the bag type dust removal equipment should be determined according to the actual operating experience or test data of the existing factory, if it is necessary The data can be calculated according to the production process (about 20%~40% ). The formula is: Q=Qs- ( 273+Tc ) *101.324/(273*Pa)*(1+K) where Q - the amount of dusty gas passing through the precipitator m3/h ; Qs - produced during production The amount of gas m3/h ; Tc - the temperature of the gas in the precipitator °C; Pa - ambient atmospheric pressure, kPa ; K - the pre-leakage system of the precipitator. It should be noted that if the amount of gas produced during the production process is the amount of gas in the working state, it is necessary to convert to the standard state when performing the selection comparison.  

 (2) Selection of filtered wind speed 

The size of the filtered wind speed depends on the properties of the dust-containing gas, the type of fabric and the nature of the dust. It is generally selected according to the data recommended by the dust collector sample and the user's practical experience. 

The capture wind speed of most anti-air bag dust collectors is between 0.6 and 13 m/s , the filtration wind speed of the pulse bag filter is about 1.2 to 2 m/min , and the filtration speed of the glass fiber bag filter is about 0.5 to 0.8 m/s .   

(3) Determination of the filtration area ( 1 ) Total filtration area  

Total filter area calculation formula: Ad= Q/ v , (m2)   

Where: Ad - filtration area m2 Q - amount of treatment gas m3 / min Vm - filtration wind speed m / min   

In general, the filter dust removal filter area is selected to use the net filter speed. Since the pulse type cleaning time is very short, it can also be calculated by the gross filter wind speed. When the net filtered wind speed is selected, the result of the above calculation is the net filtration area, and the total required filtration area plus the filtration area of the cleaning chamber. When the gross filtration wind speed is selected, the calculation result of the above formula is the total filtration area.

Select the fan according to the air volume

  (1) The average speed of the flue gas before entering the dust collector X The cross-sectional area of the dust collector inlet. It should be noted that the unit should be unified, usually cubic meters per hour.

(2) If it is the renovation engineering department based on the air volume of the induced draft fan, the air volume of the induced draft fan is X95% , that is, the air volume of the dust collector.

 (3) In general bag dust collectors, the air volume is a prerequisite. For example, bag dust collector boiler dust removal, air volume can generally be determined according to the needs of the boiler. The selection of the air volume of the bag filter depends on the experience or the equipment before the bag filter. For example, in the same working condition, it is necessary to estimate the air volume based on experience. If there is a device such as a bag filter, a bag filter device that is larger or smaller than the treatment effect is selected according to the treatment effect. Then the wind speed is selected according to the material filtered by the bag filter. Generally, it is more important, such as casting, steel grinding, etc. The dust has a heavier specific gravity and can be a wind speed of 1.4-1.7 m/min , which is lighter than chemical materials. To choose a lower wind speed, the filter area can be calculated. The air volume and wind pressure of the bag filter are generally matched with the fan behind the bag filter.
   

The calculation of the air volume of the baghouse of the copper melting furnace can be estimated according to the average wind speed in the hood or the hood, or calculated by the heat source radiation, which is more complicated and generally relies on experience to estimate in practice. Take a medium-frequency furnace with a diameter of 800 as an example. If a semi-closed mobile hood is used, the wind speed in the general cover can be 1M to 1.5M , and the air volume of the bag filter can be about 5000 . At the same time, depending on the process, it is necessary to consider the system leakage. The core of the practice of copper furnace dust removal is: the air volume calculation of the bag filter should be accurate, and the temperature treatment of Mars and smoke should be appropriate. There is also a bag filter to prevent sticking problems.

When selecting the dust bag according to the air volume of the bag filter, it is generally impossible to operate the bag filter in excess of the specified air volume. Otherwise, the dust bag is easily blocked, the life is shortened, the pressure loss is greatly increased, and the dust removal efficiency of the bag filter is also reduced; It is also impossible to select the air volume of the bag filter to be too large, otherwise the investment and floor space of the bag filter device will be increased, and the real energy saving and environmental protection will not be achieved. The reasonable choice of the bag filter dust collector is often based on the process conditions and precise calculations. Selected.