Fabric filter are manufactured to handle airflows ranging from a few to several thousands of cubic meters per hour. While large units are designed and engineered for each individual application, there are many applications suitable for small pre-engineered, “mass-produced units.”

All fabric filter media are manufactured from yarn—a generic term for continuous strands of fibers, filaments, or other materials which are suitable for knitting, weaving, or otherwise entwining to form a textile fabric. The basic structural unit of yarn is the fiber. Materials that can be used for the construction of the fabrics are: cotton, wool or man-made fibers (e.g., acrylics, polypropylene, polyesters, Teflon, …). Many fabrics are chemically and mechanically treated after manufacture to aid the filtration process. They can be treated with silicon to give them better cake release properties or treated with flame retardants. Obviously, the material chosen for the construction of the fabrics depend by the air flow chemical-physical characteristics. Developments in fabric technology enable baghouses to cope with temperatures in the range of 300 ° C, and to resist corrosive, acidic, and alkaline gases. Dust concentrations handled can range from very light, as is the case in atmospheric air, to very heavy for pneumatic conveying.

Fabric filters can be classified on the basis of:

• types of fabric filters (the most common used are tubular and the envelope shapes)
• methods used for cleaning the media (e.g., shakers, reverse-flow, Hersey-type or blow-ring, and pulse-jet).

Each type has a particular combination of advantages and disadvantages.

The use of fabric filters constitutes one of the more costly methods of dust collection, but this is offset by high efficiency and fabric filtration’s ability to meet most stringent particulate emission codes. Costs for capital equipment vary depending on application and maintenance costs are ap priceable because filter media must be replaced regularly during the life of the collector.

Fabric filters are generally not used where the particulate is combustible or where the product is to be sent back to the process and wetted. For the latter, it is easier to simply use a wet scrubber.

Filters can operate continuously or intermittently.

ADVANTAGES

This system is an optimum compromise between footprint and pollutants removal efficiency. Removal yields are very high; in some cases, a removal efficiency up to 99.9% can be reached.

BOUNDARY CONDITIONS / DESIGN PARAMETERS

Fabric filter performance can be affected by the conditions that the fabric is exposed to and the frequency of cleaning. Minimum operating temperature is especially important where acid gases are expected to be present in the gas stream. Lower temperatures mean acid gases have the potential to condense and corrode the fabric filter casing and other metal parts. Condensation can also cause bag blinding, which blocks air flow through the bag. Fabric filters are also susceptible to damage caused by high temperatures.

APPLICATIONS AND PERFORMANCES
Fabric filters are used in several industrial sectors as: chemical industries, cement plants, wood industries, steel and glass industries, coal treatment and combustion plants, and, sometimes, even in solid wastes treatment plants (e.g., incinerators, compost plants, sewage treatment plants, …).

Fabric filters can provide above 99 percent efficiency for removal of particles larger than 1 µm. Filtering velocities usually vary from 0.5 to 6 m/min. An operating pressure drop of 50 to 250 mm water gauge is standard for most fabric filter in order to save fan horsepower but some collectors can run at substantially higher or lower pressure drops.

ENERGY CONSUMPTION
Energy consumption depends on fan’s power, which are chosen according to the site conditions (e.g., ducts length and diameter). In addition, this system provides use of compressed air that can have a remarkable impact on the cost as well as the cooling/heating system, if necessary. Further energy saving potential can be tapped by the fluid dynamic optimization of the overall system. Further energy saving potential can be tapped by the fluid dynamic optimization of the overall system. The selection of the filter media in combination with a periodic cleaning of the system are crucial issues to reduce energy requirements.

ENVIRONMENTAL FEATURES

Exhaust filters and captured materials have to be disposed of.

RELATED PRODUCTS

• filtering materials
• air compressor
• electro-mechanical equipment.