Fabric media filtration method is the most widely used & effective technique for the collection of particulate matter from the industrial material handling operations and gas exhaust from various processes.
Bag filters are dry separation air pollution equipment’s for dust particles or for product recovery of useful products from air or any other gas flow of the manufacturing process
Our bag filters can be custom designed depending on the volume flow rate for smallest to the largest size and equipped with electronic monitoring and control devices. Versatility is key: By combining the different design with a wide variety of filter media, we arrive at an ideal solution for your filtration requirements.
Construction & Operation:
Bag Filter is divided in three parts i.e. top part called as Plenum (Clean air chamber), which is heart of the bag filter operation; middle one is called as Housing/casing (Dirty air chamber) and bottom part is called as Hopper. The plenum is separated from the housing by the bag plate/tube sheet where the filter bags and cages (the filtering elements) are supported. The Bag Filter unit is a continuous self- cleaning dust filter, capable of removing dust particles as small as submicron size from gaseous and dust streams.
Bag filter construction is simple and does not have any moving parts, Pulsejet cleaning mechanism with the help of compressed air results into high dust cleaning efficiency.
Dust laden air enter the Bag Filter at housing under suction or pressure. The air travels through the filter bags which retains the dust particles on the surface of the bag and the clean air passes through filter bags to the plenum leading to the outlet of BF due to the suction effect created by centrifugal ID fan.
Dust collected on the outside of the filter bags causes an increase in the pressure differential between the dirty and clean air sides of the bag filter. To control the pressure differential across the bag filter, a sequential timer actuates a series of normally closed pulse valves at preset intervals causing them to open. A momentary rush of high-pressure air (5-7 bar g) flows from the compressed air header to the blow tube and is expelled from the blow tube through venturies at a high velocity (primary air flow). Air from each ventury induces a secondary airflow. The combined effect of the primary and induced secondary air causes an instantaneous pressure rise on the clean side of the filter bags, causing a reverse flow of air through the filter bags, thus dislodging the dust
Above cleaning cycle causes the dust particle to fall down in the collection hopper. Collection hopper store the collected dust temporarily. The dust is discharged from hopper bottom through RAL or Screw conveyor.
Offline Cleaning
For very finer dust particles and material with lower bulk densities or with floating properties, online cleaning pulse jet bag filters are not suitable. For such type of material, offline cleaning principle is used. The Bag filter construction is compartment construction for the offline operation. Depending upon the flow rate it consists of number of chambers i.e. isolated completely with help of dampers at inlet gas line & at outlet gas line.
At time of the cleaning the one specific chamber is isolated i.e. Gas flow cut –off for the particular chamber with help of the damper at outlet gas line. The pulse air purging will take place at that instant in that chamber.
The disconnected row of filter bags is back-flushed by blow tubes located above the filter bags. For this purpose, compressed-air tanks with integrated diaphragm valves and fully enclosed solenoid valves are installed at the inlet of the blow tubes. Solenoid valves are operation in control by the timer.
After all the rows of filter bags are cleaned and a preset time lag. After air is pulsing done in the chamber this chamber again connected to the main gas line by opening the outlet damper, damper which is normally pneumatic operated. After that, next is compartment taken for the air pulsing & so on. Also depending on the requirement each chamber can be isolated for maintenance work by closing damper of inlet & outlet gas line.
Offline cleaning process beneficial for the specific applications like fine particles, low density dust, high dust load process applications etc.
