With the development of bag dust removal technology and the increasing environmental protection requirements, the application range of bag filter is more and more extensive. At present, bag filter can be used to treat high temperature, high humidity, bonding, explosion, abrasive smoke, and even filter air containing ultrafine dust.
- High temperature, high humidity gas
Bag filters are currently capable of handling flue gases below 300 °C. Above this temperature, the flue gas should be pre-cooled. In special cases, the high temperature flue gas of 450~550 °C can be directly treated with metal fiber filter.
The use of bag filter to treat steam boilers, cement kilns, metallurgical furnaces, incinerators and other high temperature furnaces is increasingly common at home and abroad. Although the bag filter is limited by the temperature resistance of its filter material, it can handle high temperature flue gas with temperature up to 1200~1400 °C by proper treatment of the system flue gas.
2. Adhesive dust
The cohesive dust is easy to be kneaded on the surface of the filter bag. The bag filter can treat the cohesive dust by adsorption, that is, the appropriate amount of porous powder is mixed into the system pipe, and the powder is used to adsorb the cohesive dust. Then it is purified by a bag filter.
For example, the refractory plant uses dolomite powder to adsorb and purify bituminous flue gas. The aluminum plant uses alumina to adsorb bitumen and hydrogen oxide. The road company’s asphalt concrete workshop uses limestone powder to adsorb bitumen, and its adsorption efficiency can reach 92~99%.
3. Explosive dust
Explosive dust must explode only when it has the following three conditions: 1. flammable substances are present in the flue gas at appropriate concentrations. 2. there is sufficient oxygen and oxidant. 3. there is a source of ignition.
Therefore, when purifying such gases, measures should be taken to destroy the above three conditions or a certain condition. Simply speaking, it is to control the components, eliminate the fire extinguishing, and eliminate static electricity.
4. Corrosive gas
In the flue gas purification system, there are mainly two kinds of gases, such as gas and dust, which have corrosive effects on the bag filter. Such as coal, heavy oil fuel sulfuric acid gas formed by the presence of sulfur molecules, or water will produce a variety of salt dust. Therefore, the following anti-corrosion measures should be taken when applying the bag filter:
Since the corrosion phenomenon in the flue gas purification occurs when the flue gas temperature appears below the acid dew point, it should be ensured that the system flue gas operates above the dew point temperature.
In the selection of filter materials, the characteristics of corrosive substances should be produced according to the flue gas, and the corresponding filter materials should be used to clean the cleaning system with high corrosion severity, such as pharmaceutical, food, carbon black production, etc. Parts should be made of stainless steel or painted with anti-corrosion coating.
5. Abrasive dust
When processing abrasive dust such as alumina, silica, or sinter, the movement speed of the coarse particles in the soot and the airflow in the bag filter is too high, resulting in strong wear on the filter bag and the casing of the dust collector.