Particulate matter (PM) is an air pollutant consisting of a mixture of particles that can be solid, liquid or both, are suspended in the air and represent a complex mixture of organic and inorganic substances. These particles vary in size, composition and origin. Their properties are summarized according to their aerodynamic diameter, called particle size.
There are several Regulations for the emission limits based on the source of pollution. By using suitable unit/units, required emission standards can be achieved. At this point Santes analyze the issue and offers a solution for particulate matter and offers best suited Flue Gas Treatment Unit.
Choice of system depends on the source of particulate matter, existence of other pollutant matters and emission limits applicable to a specific case.
Scrubber systems are a diverse group of air pollution control devices that can be used to remove some particulates.
There are two basic treatment methods:
- Dry Scrubber
- Wet Scrubber
Dry scrubbers are mainly used for particle removal. Santes Manufactures following dry scrubber units for the removal of particulate matter and applies most suitable application to the system based on the characteristics of the flue gas.
The selection of gas cleaning equipment for particulates from the flue-gas is mainly determined by:
- particle load in the gas stream
- the average particle size
- particle size distribution
- flowrate of gas
- flue-gas temperature
- compatibility with other components of the entire FGT system (i.e. overall optimisation)
- required outlet concentrations.
Cyclones are relatively simple devices for removing particulate material from gas streams. Cyclone is the unit operated to remove coarse particulates. Particulate material contained in the combustion gas are removed by centrifugal force and collected in the bottom portion of the unit.
In general, cyclones on their own cannot achieve the emission levels. They can, however, have an important role to play where applied as a prededuster before other flue-gas treatment stages. Energy requirements are generally low as there is no pressure drop across the cyclone. Advantages of cyclones are their wide operational temperature range and robust construction.
Bag Filter is one of the most common techniques to collect particulate matter from the gases. Filters are reliable, efficient and economic method to remove particulates from gas stream. Those filters consist of numerous long vertically hanging bags. Filtration efficiencies are very high across a wide range of particle sizes. Compatibility of the filter medium with the characteristics of the flue-gas and the dust, and the process temperature of the filter are important for effective performance. Santes is selecting the filter element based on the flue gas characteristics such as temperature and acidity.
In continuous operation, there is gradual loss of pressure across the filtering media due to the deposit of particles. When dry sorption systems are used, the formation of a cake on the media helps to provide the acid removal.
Santes manufactures jet pulse bag filter for the removal of particle matters with very high efficiencies. In bag filter unit, the bags are supported on metal wire cages that are suspended from the top of the unit. Particulate-laden gas flows around the outside of the bags, and a dust cake accumulates on the exterior surfaces. When cleaning is needed, a very-short-duration pulse of compressed air is injected at the top inside part of each bag in the row of bags being cleaned. The compressed air pulse generates a pressure wave that moves down each bag and, in the process, dislodges some of the dust cake from the bag.
Wet scrubber systems is another treatment alternative for particulate removal. Although they have a good removal rates for particle matter, they generally preferred when other gaseous pollutant are in concern. There are 4 wet scrubber applications which can remove particle matter from the flue gas stream.
- Venturi Scrubbers
- Spray Towers
- Tray Towers
Santes applies Venturi Scrubber to the flue gas stream as a wet scrubbing method when the particle matter is main concern.
Properties of Venturi Scrubber:
- Main purpose of the venturi scrubber is to decrease the particle concentration in the flue gas.
- It has 3 main sections; namely, Convergent section, Venturi throat, Divergent section
- Gas enters from the top of the unit and moves in the same direction with water
- Main reduction is achieved in the throat section of the unit.
- For efficient removal gas is passing through the stack with very high speed.
- There is a high pressure drop in this unit. The main reason is high speed difference through the venturi.
- Even small particles can be removed by venturi scrubber.
- In addition to the particle reduction, temperature decrease is achieved in the venturi scrubber.
- It has very high removal rates when it is compared with the other treatment methods.