A lot of attention has been directed on development of power generation at cheaper costs, as a process of promoting economic development. In turn, this has led to rapid growth in the manufacturing sectors and extensive utilization of electricity. Power generation using boilers has been an important technology in reducing cost of generation. Coal fired boilers are extensively used due to relatively lower cost and greater heat generation. However, they emit particulate pollutants, which have to be reduced. This is done using the bag filters
Bag Filter Technology
It is one of the most efficient, reliable and cost effective methods of gas stream filtration. It functions through interception and prevention of particle movement. Factors causing separation include diffusion, electrostatic attraction, and gravity. Efficiency of the systems is affected by various factors.
Factors Affecting Efficiency of Bag Filters
Four important factors affect the efficiency of the system. These include the
Importance of Filter Cleaning
Regular filter cleaning is crucial for maintenance of efficiency in the filtration system. Various cleaning systems have been developed for proper cleaning to be achieved.
Filter Cleaning Technologies
The most common technologies in filter cleaning include rapping, Shaking, reverse airflow or backwash and pulsejet cleaning. The pulse jet system is the most recent and most effective whereby a stream of high-pressured air is blown inside the bag. The bag becomes inflated and loosens the dust layer, which falls off to a designated area.
Developing the Cleaning Frequency
The frequency of cleaning is important in the achievement of maximum efficiency. In using the pulse jet cleaning systems, frequency is set by adjustable timer for thorough cleaning to be achieved. It also has lesser moving parts and cleaning done on demand.
Low Ratio versus High Ratio Filters
The arrangement of the filters determines whether it will be a low ratio or high ratio design of filter. Low ratio filters have woven fabrics, inside collection system, off line cleaning, reverse / shaker air cleaning and modular in design. High ratio filters use felted fabric, outside collection, online cleaning, higher filter speeds and pulsejet cleaning system.
Determination of the Filter Media
In choosing the filter media, one must consider the carrier gas temperature, gas composition, flow rate of gas and the size, shape and concentration of dust particles in the gas.
Global utilization of the bag filter technology
Since the bag filter systems utilize mechanical forces for dust collection, sensitivity to coal or ash properties is lower. This has made the systems gain global acceptance in boilers cleaning and reduction of air pollution.
Utilization of the bag filter in power generation stations
The bag filter for boilers is currently the most preferred method of reducing particulate emissions. They have high utilization in power generation in various countries such as Australia, America, Queens land, and India.