Our Proven Capabilities in Air Pollution Control System:
- Successful installation of Dust Extraction System - 100 m3/hr to 300000 m3/hr gas volume.
- Successful installation of Bag Filter for high temperature application.
- Bag House for flue gas cleaning.
After dust-filled air has been captured by a dry dust collection system, it must be separated, collected, and disposed of. The dust collector separates dust particles from the airstream and discharges cleaned air either into the atmosphere or back into the workplace.Necessity for Dust Collectors
Cleaning dust from the air is necessary to-
- Reduce employee exposure to dust
- Comply with health and air emission standards
- Reduce nuisance and dust exposure to neighbors
- Recover valuable products from the air
Cyclone separators separate dust from gas streams using a combination of forces, such as centrifugal, gravitational, and inertial. These forces move the dust to an area where the forces exerted by the gas stream are minimal. The separated dust is moved by gravity into a hopper, where it is temporarily stored.
Cyclone separators are use for cyclonic action to separate dust particles from the gas stream. In a typical cyclone, the dust gas stream enters at an angle and is spun rapidly. The centrifugal force created by the circular flow throws the dust particles toward the wall of the cyclone. After striking the wall, these particles fall into a hopper located underneath.
Cyclone separators create a dual vortex to separate coarse from fine dust. The main vortex spirals downward and carries most of the coarser dust particles. The inner vortex created near the bottom of the cyclone, spirals upward and carries finer dust particles.
Advantages and Limitations - Cyclone SeparatorAdvantages:
- Have no moving parts
- Can be used as pre cleaners to remove coarser particulates and reduce load on more efficient dust collectors
- Can be designed to remove a specific size range of particles
- Have low collection efficiency for irrespirable particulates
- Suffer decreased efficiency if gas viscosity or gas density increases
- Are susceptible to erosion
- Have drastically reduced efficiency due to reduction in airflow rate
- Cannot process sticky dust
In bag houses, individual bags are supported by a metal cage, which is fastened onto a cell plate at the top of the bag house. Dirty gas enters from the bottom of the bag house and flows from outside to inside the bags. The metal cage prevents collapse of the bag.
Bags are cleaned by a short burst of compressed air injected through a common manifold over a row of bags. The compressed air is accelerated by a venturi nozzle mounted at the top of the bag. Since the duration of the compressed-air burst is short (0.1s), it acts as a rapidly moving air bubble, traveling through the entire length of the bag and causing the bag surfaces to flex.
This flexing of the bags breaks the dust cake, and the dislodged dust falls into a storage hopper below.
Reverse-jet dust collectors can be operated continuously and cleaned without interruption of flow because the burst of compressed air is very small compared with the total volume of dusty air through the collector. Because of this continuous-cleaning feature, reverse-jet dust collectors are usually not compartmentalized.
The short cleaning cycle of reverse-jet collectors reduces recirculation and redeposit of dust. These collectors provide more complete cleaning and reconditioning of bags than shaker or reverse-air cleaning methods. Also, the continuous-cleaning feature allows them to operate at higher air-to-cloth ratios, so the space requirements are lower.
Cartridge/Pleat Type Filter
Cartridge collectors are another commonly used type of dust collector. Unlike bag house collectors in which the filtering media is woven or felt bags, this type of collector employs perforated metal cartridges that contain a pleated, nonwoven filtering media. Due to its pleated design, the total filtering surface area is greater than in a conventional bag of the same diameter, resulting in reduced air to media ratio, pressure drop, and overall collector size.
Cartridge collectors are available in continuous duty designs. In the continuous duty design, the cartridges are cleaned by the conventional pulse-jet cleaning system.Available in a wide variety of media and end fixture configurations:
- Dia. 150 x 1000 mm long
- Dia. 225 x 1000 mm long
- Dia. 150 x 2000 mm long
- Dia. 325 x 500 mm long
- Dia. 225 x 500 mm long
- Dia. 325 x 1000 mm long
Advantages and Disadvantages - Bag Filter/Dust Collector/Dust Extraction SystemAdvantages:
- Have a high collection efficiency of dust
- Can have high air-to-cloth ratio (0.8 to 1.4 m3/min/m2)
- Have increased efficiency and minimal residual dust buildup due to aggressive cleaning action
- Can clean continuously
- Can use strong woven bags
- Have lower bag wear
- Have small size and fewer bags because of high air-to-cloth ratio
- Some designs allow bag changing without entering bag house
- Have low pressure drop for equivalent collection efficiencies
- Require use of dry compressed air
- May not be used readily in high temperatures unless special fabrics are used
- Cannot be used if high moisture content or humidity levels are present in the exhaust gases
Disposal of Collected Dust
After dust-laden exhaust gases are cleaned, the collected dust must be disposed of properly. Ideally, dust can be returned to the product stream and sold; if this is not possible, disposal of dust may become a problem. For example, when dry dust collectors are used, secondary dust problems may arise during unloading and disposal of collected dust; for wet dust collectors, the disposal of wet slurry or sludge can be a problem.
Proper disposal of collected dust can be accomplished in four steps:
- Removing dust from the hopper of the dust collector
- Conveying the dust
- Storing the dust
- Treating the dust for final disposal
Removing Dust from Hopper
Collected dust must be removed continuously (while the dust collector is operating), Rotary air locks or Double dump valves should be used to maintain a positive air seal. If the material in the hopper has a bridging tendency, equipment such as bin vibrators, rappers, or air jets should be used.Conveying the Dust
After the dust has been removed from the collector, it must be transported to a central point for accumulation and ultimate disposal. Conveying of dust can be accomplished by the following methods:
- Use of screw conveyors
- Use of pneumatic conveying
- Use of air slides
- Use of Ash Conditioner/Pug mill to convey slurry
Screw conveyors have been used with a great deal of success. However, trouble areas to be considered are maintenance access, worn-out bearings and casings due to abrasive materials, and air leaks. For wet dust collectors, inclined conveyors can be used to convey the slurry to a settling pond.
Pneumatic conveyors are often selected to convey dry dust because they have few moving parts and can convey either horizontally or vertically. They operated on a high-velocity, low-air-volume principle. Trouble areas include excessive wear and abrasion in the piping and high capital and operating costs.
Air slides are commonly used for nonabrasive, light dust. They work on the principle of air fluidization of dust particles and are useful for heavy horizontal conveying. Trouble areas include ability to maintain a certain downward slope and greater maintenance requirements.
Ash conditioner is used to convey the slurry to a settling pond. However, care must be taken in this method to prevent water-pollution.
Storing the Dust
After the material has been removed and transported from the dust collector, a storage facility must be used to permit disposal in efficient quantities. Elevated storage tanks or silos are normally used to permit loading of dry dust into enclosed trucks underneath.
For wet dust collectors, the accumulation area is a settling pond. A settling pond may require considerable space. Since the storage area can only be decanted and dried out during the dry season, two settling ponds are usually needed. Also, most collected materials have very fine components that may seal the pond and prevent percolation.
Treating the Dust for Final Disposal
In most cases, the disposal of fine dust requires great care to prevent recirculation by the wind. Several final dust disposal methods commonly used are-
- Land filling
- Byproduct utilization
- Backfilling mines and quarries
Gas Cleaning System
Rajdeep has specialized in Gas Cleaning Systems through its experience in the same area. Rajdeep specially Designed Gas Cleaning Systems have helped many organizations not only a hassle free operation but giving a clean environment to the society.
Legal regulations and other social reasons are the necessities for gas cleaning systems for different production processes. Corrosive gases, dust particulate creates adverse effect in environment. Highly polluted air as well as indoor sources greatly contributes to poor indoor air quality. To have clean & healthy environment, it is necessary to clean the exhaust high temperature polluted air. Necessity to have dry gas cleaning plant with gas cooler & bag filter combination. Gas Cleaning Plant consist Isolation damper to take the tapping from exhaust stack, Dilution damper, Settling chamber/spark arrestor to settle the heavy dust & arrest spark, Gas cooler to reduce the gas temperature, Dust Collector/Bag Filter to Collect the Dust & clean air to atmosphere.Features of Gas cleaning System:
- Totally Integrated & control System
- Low Dust Emission (< 50 MG/M3)
- Custom Built design
- Very Effective under Stringent Pollution Control norms.
- Trouble free operation
- Effective design for Gas cooler.
- Low requirement of Power / Compressed air