When the spun bonded polypropylene filter cartridge works normally, dust-containing gas enters the ash hopper through the air inlet. Due to the expansion of the gas volume, some coarse dust particles fall into the ash hopper due to inertia or natural settlement, etc. Most of the remaining dust particles rise with the air flow into the bag room. After being filtered by the filter bag, the spun bonded polypropylene filter cartridge is used to process the spun bonded polypropylene filter cartridge. The dust particles are retained on the outside of the filter bag, and the purified gas enters the upper box through the filter bag, and then drains into the valve plate hole and the exhaust outlet, so as to achieve the purpose of dust removal. With the continuous progress of filtration, when the resistance reaches the value, the cleaning controller issues the cleaning command to close the valve plate and cut off the filter air flow; Then, the cleaning controller sends a signal to the pulse solenoid valve. As the pulse valve sends the high-pressure reverse airflow used for cleaning into the bag, the filter bag bulges and produces strong shaking, resulting in the dust on the outside of the filter bag to shake off and achieve the purpose of cleaning. Since the equipment is divided into several box areas, the above process is carried out box by box, when one box area is cleaned, the remaining box areas are still working normally, and the continuous normal operation of the equipment is normal. The reason why it can deal with concentrated dust is that the cleaning time required for this strong cleaning is short (0.1 ~ 0.2s).
What should be considered in the design of spun bonded polypropylene filter cartridge?
First, the number of filter bags: After finding 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 in each filter bag chamber is determined, the number of rooms in the entire dust collector can also be calculated from this. Although the number of rooms is determined according to the need in the design or selection of dust collectors, the number of rooms of more than 6 rooms is often set as double rows from the consideration of site layout and maintenance convenience. The chamber of the dust collector with less than 5 chambers shall be defined as a single row.
Second, the calculation of the volume: It should be noted that if the amount of gas generated in the production process is the amount of gas under the working state, it needs to be converted to the amount of gas under the standard state when the selection is compared. When calculating the body of spun bonded polypropylene filter cartridge, the amount of gas under working conditions is required at first, that is, the amount of gas actually passing through the spun bonded polypropylene filter cartridge. And also consider the air leakage of the dust collector itself. These data should be determined according to the actual operating experience or testing data of the existing factory, if the required data is lacking, it can be calculated according to the amount of gas generated in the production process, and then increase the amount of air mixed into the gas collector (about 20% to 40%).
3. Determination of filtration area
(1) Resistance calculation: The resistance of spun bonded polypropylene filter cartridge consists of three parts: (a) The resistance of the equipment body structure refers to the resistance generated by the gas from the dust collector population to the dust collector inlet and outlet; (b) the resistance of the filter bag refers to the resistance of the filter material when filtering dust, about 50 ~ 150Pa; (c) The resistance of the dust layer on the surface of the filter bag, the resistance of the dust layer is about j to 10 times the resistance of the clean filter cloth.
(2) Total filtration area: According to the total gas volume through the dust filter and the predetermined filtration speed, the total filtration area is calculated according to the following formula: After the total filtration area is obtained, the overall size and size of the spun bonded polypropylene filter cartridge can be determined.
(3) the area of a single filter bag: the area of a single round dust bag in the process of filter bag processing, because the filter bag should be fixed on the flower plate or short tube, and some should be hung up and fixed on the bag cap, so the two ends of the filter bag need to be double-layer sewing or even multi-layer sewing: This part of the double-layer sewing has no filtering effect due to increased resistance, and some filter bags also have a fixed ring in the middle, and this part has no filtering effect.
4. Selection of filter wind speed: The size of filter wind speed depends on the characteristics of dusty gas, the type of fabric and the nature of dust, and is generally selected according to the recommended data of dust collector samples and the practical experience of users. The filtration speed of most spun bonded polypropylene filter cartridges is between 0.6 and 13/m. The filter wind speed of the pulsed spun bonded polypropylene filter cartridge is about 1.2 ~ 2m/s. The filtered wind speed of the spun bonded polypropylene filter cartridge is about 0.5 to 0.8m/s.
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