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How To Choose The Type Of Bag Filter?Posted: 2018-10-18

How to accurately calculate the filter area of the bag filter? This is the prerequisite for the selection of the bag filter model.

1. Calculation method for the total filtration area of the bag:
Based on the total amount of dust passing through the precipitator and the predetermined filtered wind speed, the total filtration area is calculated as follows.

2. Single dust filter bag area:
During the processing of the dust bag, the filter bag should be fixed on the flower plate or short tube, and some should be hung and fixed on the drop cap. Therefore, both ends of the filter bag need double-layer sewing or even multi-layer sewing: double seam This part of the system has no filtering effect due to the increase of the resistance, and some of the filter bags also have a fixed ring in the middle, and this part has no filtering effect. In the large and medium-sized reverse blower, the filter bag has a length of 10m and a diameter of 0.292m. The nominal filter area is 0.292×10=2.92m. If the area without filtering is 0.75m, the net filter area is 8.25-0.75=7.5. m. It can be seen that the unused filter area of the bag accounts for 5% to 10% of the filter bag area. Therefore, the size of the net filter area should be indicated in the specifications of the large and medium dust collectors. However, in the existing dust collector samples, the filter area mostly refers to the nominal filter area, which should be noted in the design and selection.

3. Number of filter bags:
After determining the total filtration area and the area of a single dust bag, the number of filter bags can be calculated. If the number of filter bags per filter bag chamber is determined, the number of chambers of the entire precipitator can also be calculated therefrom. Although the number of chambers is determined as needed in the design or selection of the precipitator, the number of chambers of the precipitator with more than 8 chambers is often doubled in terms of site layout and maintenance convenience. The dust collectors of less than 6 chambers are defined as a single row.

4. Resistance calculation:
The resistance of the bag filter consists of three parts:

a. The resistance of the structure of the device body refers to the resistance generated by the gas from the inlet of the dust collector to the outlet of the dust collector;

b. The resistance of the filter bag refers to the resistance of the filter material, about 50~150Pa. ;

c. The resistance of the dust layer on the surface of the filter bag is about 7 to 10 times that of the clean filter bag.

The structural resistance of the dust collector body increases with the increase of the filtration wind speed, and the resistance of the bag filters of different sizes and categories are different. Therefore, it is difficult to calculate with a certain expression. When the general filtering wind speed is 0.5~3m/h, the body resistance is generally between 50~500Pa.

There are many types of bag type dust collectors. Therefore, the selection calculation is particularly important. If the selection is not appropriate, if the equipment is too large, it will cause unnecessary waste. If the equipment is selected, it will affect the production and it is difficult to meet the environmental protection requirements.

There are many calculation methods for selecting the type of dust collector. Generally speaking, the basic process parameters of the powder should be known before calculation, such as the flow rate,nature, concentration of the dusty 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 device model.

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