A filter bag is the core filter component of the bag filter, and the filter bag cost accounts for about 10% -15% of whole baghouse bag filter system. The filter bag material directly determines the performance of the bag filter, such as equipment specification, dust removal efficiency, emission concentration, operating resistance, service life and so on. Therefore, it is very important to choose a filter bag correctly and properly. In this article, we will learn how to choose a right filter bag for your bag filter.
How To Choose Filter Bag
Filter bag selection is usually carried out according to the nature of dusty gas, the property of the dust and the dust cleaning method of the dust collector. The following principles should be followed when choosing:
- 1. reasonable structure and high capture rate;
- 2. good exfoliation, easy to clear dust and not easy to scale;
- 3. suitable air permeability, low resistance and high filtration precision;
- 4. high strength and stable dimension;
- 5. high temperature resistance, chemical corrosion resistance, oxidation resistance, hydrolysis resistance and wide adaptability;
- 6. a wide range of raw material sources, stable and reliable performance;
- 7. low price and long life.
(1) According to Filter Media Properies
Due to the variety of materials and specifications of filter bags in real life. Therefore, when choosing filter bags, we should also choose according to the nature and actual needs of different filter medias.
Polyester filter media are usually used in low temperature situations, and membrane mulching is usually not needed. Only when the discharge requirement < 30 mg/Nm ³, or when the dust is very fine and the humidity is high.
Polytetrafluoroethylene (PTFE), also known as Teflon, is stretched to become a strong multi-porous material with a pore size of 0.1μm ~ 2.0μm, a porosity > 80%, excellent chemical corrosion resistance, cold and heat resistance, long-term use at-200℃ ~ 250℃, good electrical insulation and smooth surface properties.
Polytetrafluoroethylene filter materials are often treated with film mulching or acupuncture to improve dust removal efficiency and prolong filter bag service life.
Nomex filter media can be used for filter bag in the case of higher temperature and thicker dust particles. Nomex has good resistance to high temperature and is more resistant to bending than fiberglass. It can use higher injection pressure and can inject more filter bags with the same pulse valve.
Glass Fiber has good high temperature resistance, tensile resistance, acid-alkali resistance and hydrophobicity, but the glass fiber filter material is not resistant to bending, easy to be damaged in installation and operation, can not be cleaned under high pressure, and has high requirements for filter bag skeleton.
After secondary treatment and film coating, the filtration performance of glass fiber is very excellent, and it has been widely used as filter bag material in Europe and the United States.
The high temperature resistance of P84 filter bag is slightly lower than that of glass fiber, the acid and alkali resistance is good, and the price is more expensive.
Because of its special fiber structure, it is usually unable to cover the membrane, so the filtration efficiency is not as good as that of the coated filter bag.
(2) According To Dusty Gases Properties
The nature of dusty gas has a great influence on the dedusting effect, so we should pay attention to the following points when choosing filter bags:
The temperature of dusty gas is an important factor in the selection of filter bags. Usually, dusty gas < 130℃ is called normal temperature gas, and the dusty gas > 130℃ is called high temperature gas.
Therefore, the filter bags can be divided into 2 types: normal temperature filter bags below 130℃ and high temperature filter bags higher than 130℃. In daily work, a suitable filter bag should be selected according to the flue gas temperature.
The dusty gas is divided into 3 types according to the relative humidity: dry gas (humidity < 30%), general gas (30% < humidity < 80%), and high humidity gas (humidity > 80%).
- (1) When the gas humidity is high, the dust collected on the surface of the filter bag will be wetted and bonded. Filter bags with smooth surface, long fiber and easy dust removal, such as nylon and glass fiber, should be selected.
- (2) High temperature and humidity will affect the filter bags’ temperature resistance. Try to avoid filter bags with poor hydrolytic stability, such as nylon, polyester, imide and so on.
- (3) When the humidity is high, circular filter bags should be used to avoid complex and compact filter bags, such as flat filter bags and diamond filter bags.
- (4) The dusty gas inlet temperature should be higher than the dew point 10-30 ℃.
In all kinds of furnace flue gas and chemical waste gas, it often contains a variety of chemical components, such as acid, alkali, oxidant, organic solvent and so on, and is often affected by temperature, humidity and other factors. Therefore, when choosing the filter bag, we must grasp the main factors and comprehensively consider the chemical composition of the dusty gas.
Finally, when choosing filter bags, we should also consider the dust properties and the dust cleaning method, and comprehensively consider the measurement to ensure that the appropriate filter bag is selected to ensure the dust removal effect.