Level of particulate matters in the air is a matter of concern for both under developed and developing countries. The particulate matters in the air can be measured by Air Quality Index and PM level. The dust particulate matters cause severe harm to the respiratory system of the human body. Asthma, emphysema and other respiratory troubles can occur as the particulate dust matters reside inside the lungs. Not only lungs but also eyes and vision can be affected by these dust particles. Industrial pollution, pollution from vehicles and dusts generated due to everyday activities of humans are responsible for high level of PM. Employees who work in factories under different industrial sectors are directly affected by these dust particles. There are lots of dusts that are generated in these factories and surround the entire environment of the work place. In order to maintain a healthy and safe work environment in the factories it is essential to perform dust extraction. Dust extraction system is widely used to reduce emissions in factories and work places. The emission comes out from exhaust via ducts and stacks. Dust extraction system is installed at the vent of the production process and on the systems used for material handling.
What is the working principle of a dust extraction system?
Belt conveyor transfer points, Screen venting, crush venting etc. are the points inside a factory where from dust is generated. These points are connected to the inlet of bag filter by means of duct work. Suction hoods and motorized or manual dampers in the ducting system are there in all the points that helps in emitting the dust. To make sure that the optimum suction in the process of dust extraction is done in each point, suction dampers are provided. Dampers act like balancers in the process of dust extraction. Small duct network connects these with the main duct header. Finally, the main duct header is connected to the bag filter.
The process of operation of a dust extraction system
The process involved in dust extraction is explained point wise in the following:
- Air containing dust particles enter the bag filter under considerable pressure or suction.
- Dust laden air travels through the filter bags. Dust particles are retained on the bag’s surface.
- Air which is cleaned makes its way through filter bags to the plenum. Outlets of bag filters are created in this process and this happens due to the effect of suction which is created by the centrifugal ID fan.
- Increased differential pressure is created between the clean and dirty air sides of the filter bag. This happens due to collection of dust on the outside part of the filter bags.
- Sequential timer is needed that actuates the normally closed pulse valves at certain intervals which would lead to their opening. Sequential timer is basically needed to control the differential pressure which is generated across the bag filter.
- There occurs a rush of high-pressure air (about 5 to 7 bar g) for the time being and from the compressed air header the air flows to the blow tube. The air is then expelled in high velocity through ventures. This is called primary air flow.
- Induction of secondary air flow occurs due to the passage of air from each venture.
- Pressure on the clean side of the filter bag rises instantly due to combined effect of primary and secondary air flow. This causes the air to flow reversely which dislodges the dust.
It is to be noted that in the process of dust extraction, you can also use electrostatic precipitators or you can go for scrubbers instead of bag filters.
Therefore, to ascertain safety and health of your factory employees install an effective dust extraction system that would improve the wholesome environment of the workplace.