LFGM air case pulse bag filter is an advanced, new and highly efficient dust filter which is introduced from USA Fuller company, compositing the advantage of bag filter which are counter spraying and pulse removing dust in separated chambers. It overcomes the shortcoming of less strength counter spraying, pulse removing dust and filtering at the same time, enlarges the application range of air case pulse bag filter. Due to its special structure, it improves the dust removing efficiecny and delay sthe life of filtering bags. It is a kind of good performance bag filter. There are four series of LFGM air case pulse bag filter which are 33 types of specification. The filteirng area is from 93m2-4361m2, handled air volume is from 69003/h-314000m3/h，It is widely used in building material, cement, metallurgy, mechanical,chemical industry and refractory material, is especially applied in the dust filtering system (removing dust system) in the crushing, drying, coal mill, separating powder, packing, top silo, clinker cooler etc. of cement plant. It is also apllied in filtering dust of coal mill. But explocion prevention measure should be added. The structure of dust filter will be changed correspondingly. It is also appllied in the filtering of high density air, such as coal mill O-Sepa separator, dust density can reach over 1000g/m3(standard). It may not use cyclone dust filter for pre-filtering. In the north chilled place of China, the bag fillter will add attemperater units.
It is a kind of separated chamber in assembling. Remove dust of filtering bag of each room with the help of top silo pulse valve(that is to say offline removing dust). It is different from normal spraying dust filter, Spraying pulse removing dust is to blow and pulse remove dust of the bags row by row in the same filtering room (that is also called online removing dust). Other rows of filtering bag are still being filtered. That is to say, dust removing and filtering are conducted in the same room and at the same time. Dust after the first time removing will scatter the second time. Part of the dust will be collected by the neighbouring filtering bags. It is not beneficial for the filtering of higher density air. LFGM air case pulse bag filter will work on the condition of cutting off the valve in the same chamber. It will not scatter in the second. It is good for filtering high density air, changing filter bags of one room, with no need to stop.
Bag filter have four series which are 32bags per chamber, 64bags per chamber,96 bags per chamber,128 bags per chamber according to the quantity of filtering bags. Each series has many specifications according to the quantity of chamber,there are 33 types in total. The detailed structure refers to the attached selection drawing. It is composed of the following:
(1)Shell：Including clean room (or air purified case and lock case), filtering chamber, separated chamber plate, inspection door and shell structure. The cleaned room is designed lifting valve, flower plate, spraying short pipe:It is arranged filtering and framework.
(2) Dust hopper and dust discharge structure:It is designed screw conveyor, air slide and rigidity impeller feeder(dust discharge valve) according to dust hopper and different series and different inlet dust density.
(3)air inlet and outlet case body：Including air inlet and outlet pipeline and middle separated plate. Single row structure is arranged at one side of the shell. The structure of double platoons(or double rows) is arranged in the middle of the shell. 32 series is smaller and it has no case body. Air inlet and outlet pipelines are respectively connected with dust hopper and clean room.
(4) Pulse removing dust units：Including pulse valve, bubble bag, air cylinder for lifting valve and magnetic valve etc.
(5) Compressed air pipeline and pressure reduced units, oil-water separator, lubricators etc.
(6) Support pole and vertical cadge ladder and handrail.
Dust air goes to the hopper from the air inlet of bag filter (for 32 series,the air will go in from dust hopper) via the inclined separated plate. At the same time, the speed of air flow becomes slow. Affected by inertia, crude grain in the gas will fall into dust hopper. Fine dust grain will enter into filtering room; dust is adhensive to the surface of filtering bag. The purified gas will enter into the top of filtering bag. Each separated clean room will discharge into air outlet opening. Main fan of filtering dust will draw it and discharge into the atmosphere.
As the filtering continues and the dust on the surface of the bags increased, the resistance of the passed air strengthened. When the resistance reaches certain value (eg. 1770Pa), it can be operated manually accordingly, and can also be controlled and stop the lifting valve in the first chamber by fixed time and fixed quantity program controller to cut off the air flow in the filtering room. Then start the pulse vavle and let the compressed air out to the the air cases and remove the dust by blowing the bags, making the bags ballooning. Then the dust on the bags will fall down. The DP in and out of the bags will be the same as that before using. The dust will go into the hopper. Later the program controller will start the lifting valve in fixed time and recover the filtering of the first room. Stop the lifting valve of the second room. Stop the the filtering air flow and start the high pressure compressed air given out from the solenoid valve to remove dust of the bags by pulse blowing. Program controller will start the lifting valve and recover the filtering in the second room. Hereafter, the program controller will remove dust by blowing in the third, fourth… room according to the setted program till that the last chamber finishes removing dust. Close the electronic controller and the fiter recovers to filter and remove dust normally. The program controller will control the the time of wind-stopping and blowing, the interval time among the chambers, the period of dust removal. All the time can be adjusted. Please refer to instruction manual.
Bag filter works normally in the negative pressure, but it may work in the positive pressure. The structure need not to be changed.
Main technical capacity and selection description：
a. Main technical capacity refers to table 3－5.
b. Selection description：
1、Selection of filtering air speed：
Filtering air speed(m/min) is the speed of material going through the filtering bags. Some is called air-to-cloth ratio, which means the passed air volume m/min in unit time and unit area. The selection of filtering air speed must be decided according to the characters, temperature, moisture, dust concentration, dust removing way of the filtering media, powder dust and fume. Filtering air speed can not only decide the size of the filter, but also affect the resistance of filteriing material, the efficiency of dust filtering, the efficiency of ash removal. To ensure the efficiency of ash removal, improve the life of filtering bags and reduce the resistance, filtering speed of this bag filer is normally setted 1.2m/min. The filtering speed is applied according to table 1 for the main dust source in the cement plant.
Net filtering speed means that the filtering air speed m/min of the original air volume going through the other chambers when one chamber is experiencing ash removal and air-stopping.
2、Calculation of filtering area：
According to the following formula：
In the formula：AN—net filtering area of m2，it means the sum of the other filtering area When one of the bag filters is spraying in counter with the air flow. Q—Filtering air volume of dust filter, that is called handled air volume m3/h.
VN—net filtering air speed，m/min
3、Selection of operating temperature and filtering material
The operating temperature is closely relevant to the selection of filtering material. If the filtering material is different, the intlet air temperature will be differerent. Bag filter is usually used terylene needle felt. The allowable continuous using temperature is ≤120℃. When using Nomex, the allowble Max. temperature is 200℃. When using P84 needle felt, the allowable temperature is 260℃. When the temperature is over that of all filteirng materials, some measures to cool down the air before it enter the filter. At the same time, filtering bags should be treated tobe oil resistant, waterproof, sticky resistant and static resistant.
4、Allowable air inlet density
As the special structure of this filter, pulse and spraying dust removing when stopping the air(offline removing dust) is used. Thus the allowable density of the inlet is higher than the traditional pulse spraying dust remving and other normal chamber spraying filters. The air content of 32 series dust filter is allowed 200g/m3(standard), and the other 64、96、128 series dust filters is allowed 1000g/m3(standard). Air density of the outlet of the dust filter is ≤100mg/m3(standard).