In today’s world, especially for the under-developed and developing countries, one major problem being faced is of particulate matter level in the air. This is called as PM level in the air and specified as Air Quality Index (AQI). There are many hazardous and detrimental effect to human body respiratory system. Particulate matter directly impacts lungs due to which asthma and other related breathing problem issues can happen. It also affects eyes and the vision. There are many factors which contributes to higher PM level in the atmosphere viz. vehicle pollution, industrial pollution and dust generated due to various day to day human operations. With regards to the industrial pollution, workplace environment has direct impact on employees health as they are directly exposed to various pollution levels inside the factories.
There are various processes and operations in the industry due to which lot of dust gets generated and surrounds in the work environment. The employees get directly exposed to such dust particles and can have various health issues as stated above. Hence, it is important to provide safe and healthy environment to employees by extracting this air borne dust particles.
Dust extraction systems is one of the mainly used method to reduce the work zone emissions and emissions through exhaust stacks and ducts. It is installed on material handling systems or at the vent of production process as a product collection system.
Construction of bag filter
Bag Filter is divided in three parts i.e. top part is 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 i.e. 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 doesn’t have any moving parts. Pulsejet cleaning mechanism with the help of compressed air results into high dust cleaning efficiency.
Refer to the diagram above white plate shown is called as Baffle plate which avoids the direct impact of dusty gases on the bags causing majority of heavy particles to settle down in the hopper. Remaining fine particles travel in upward direction and further filtration is done through filter bags. After filtration clean gases pass through specially designed clean air chamber called as plenum.
Working Principle for DE systems
Dust generating points inside the plants like belt conveyor transfer points, crusher venting, screen venting etc. is connected to the bag filter inlet by duct work.
For Dust Extraction system applications, the no. of points from where the air borne dust is getting generated are provided with suction hoods and manual or motorized dampers in ducting depending upon the application. The dampers are provided for balancing so that optimum suction is obtained at each suction point. These hoods are connected by small duct network to the main duct header which is finally connected to the bag filter.
Dust laden air enters 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 the filter bags to the plenum leading to the outlet of Bag Filter due to the suction effect created by centrifugal ID (induced draft) 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 high velocity (primary air flow). Air from each venturi induces a secondary airflow. The combined effect of the primary and induced secondary air causes an instantaneous pressure to rise on the clean side of the filter bags, causing a reverse flow of air through the filter bags, thus dislodging the dust.
With our experience and expertise, we have solutioned various critical applications. We have the ability to design systems complying to work zone and outlet emissions norms established by pollution control board or client requirement. Emission parameters are achieved by designing the suction hoods, duct network, velocities and pressure at different points based on ACGIH guidelines.
Apart from Bag Filters, electrostatic precipitators or scrubbers can also be used. Our sales and application experts recommend the type of pollution control equipment to be used based on the application requirement.
- Dust free operation
- Minimum utility requirement
- Customized Solution to suit the site layout and process needs
- No constraints for the volume flow rate
- Online and Offline designs
- Work zone emissions as low as 1-2 mg/Nm3 at 1 m distance from the source
There are a wide range of applications and industries where DE systems are installed. To name a few, following is the list of industry:
- and other industries