There are many types of bag filter, therefore, the selection calculation is particularly important, improper selection, such as equipment is too large, will cause unnecessary flow fees; equipment selection will affect production, it is difficult to meet the environmental protection requirements.
There are many methods for selection and calculation. Generally speaking, the basic process parameters of the flue gas, such as the flow, nature and concentration of the dust-laden gas, the dispersion of the dust, the infiltration, and the viscosity, should be known before the calculation. After knowing these parameters, select the device category model by calculating the wind speed, filter area, filter media, and device resistance.
1, the calculation of the processing gas volume
When calculating the processing gas of the bag filter, firstly the gas quantity under the operating conditions is required, ie the gas volume actually passing through the bag filter, and the air leakage of the dust collector itself must also be considered. These data should be determined based on the actual operating experience of the existing plant or testing data. If the necessary data is not available, the amount of gas produced by the production process can be increased to increase the amount of air that the gas gathering hood can mix (about 20% to 40%). %) to calculate.
It should be noted that if the amount of gas produced during the production process is the amount of gas in the operating state, the amount of gas in the standard state will need to be converted when the comparison is made.
2, the selection of filter wind speed
The size of the filtration wind speed depends on the nature of the dust-laden gas, the type of fabric, and the nature of the dust. Generally, it is selected according to the recommended data of the dust collector sample and the practical experience of the user. Most of the anti-blow bag filter has a filter speed of 0.6-13/m, the filter bag filter has a wind speed of 1.2-2 m/s, and the glass fiber filter has a filter speed of 0.5-0.8 m. /s.
3, the determination of the filter area
(1) Total filter area The total size and size of the bag filter can be determined after obtaining the total filter area based on the total gas volume passing through the precipitator and the predetermined filtration rate.
(2) Single filter bag area The area of a single circular filter bag
During the processing of the filter bag, the filter bag should be fixed to the flower plate or the short tube, and some should be hung up and fixed on the bag cap. Therefore, the two ends of the filter bag need to be double-sewed or even multi-layered: Double seams This part of the system has no filtering effect due to the increase in resistance. At the same time, some filter bags also need to be fixed in the middle of the filter bag. This part also has no filtering effect.
(3) Number of filter bags After obtaining the total filter area and the area of a single dust bag, the number of filter bags can be calculated. If the number of filter bags in each filter bag room is determined, the number of chambers in the entire filter can also be calculated. Although the number of rooms is determined as needed in the design or selection of the dust remover, the number of rooms for more than six rooms is often set to double in consideration of site layout and maintenance convenience. The chambers of the dust remover for less than 5 chambers were single row.
4, resistance calculation
The resistance of the bag filter is composed of 3 parts: (a) The resistance of the device body structure refers to the resistance of the gas from the population of the dust collector to the outlet of the dust collector; (b) The resistance of the filter bag refers to the filter material when filtering dust. Resistance, about 50 ~ 150Pa; (c) filter bag surface dust layer resistance, dust layer resistance is about 1 to 10 times the clean filter cloth resistance.
In addition, the filter resistance can also be used to find the approximate value of the filter resistance by calculating the dust amount. The resistance of the dust collector body structure increases with the increase of the filter wind speed, and the resistances of bag filters of different sizes and types are all different. Therefore, it is difficult to calculate with a certain expression method. When the general filter wind speed is 0.5 to 3 m/h, the body resistance is generally between 50 and 500 Pa. However, considering the resistance of the body structure, it is necessary to consider a certain amount of reserves at the same time.