What causes chemical corrosion of dust filter bags

As the heart of the bag filter, the filter bag plays a decisive role in the use effect of the bag filter. In particular, the high temperature filter bag occupies a large proportion of value in the whole dust collector. Protecting the filter bag well can prevent the damage of the filter bag due to various reasons. On the one hand, it can ensure the filtering effect and meet the emission concentration; On the other hand, it can reduce economic losses and ensure the stable operation of the whole equipment.

The most obvious manifestation of chemical corrosion is that the strength of dust bag decreases significantly, which is specifically manifested in acid corrosion, alkali corrosion, oxidation corrosion and hydrolysis corrosion, which lead to the filter bag losing the filtration load it can bear, thus losing the filtration performance. This phenomenon is mainly due to the problems in the selection of filter bags or the use of working conditions beyond the range of fiber, resulting in the loss of filter performance and failure of filter bags.

(1) Acid corrosion

High temperature filter material generally exists acid corrosion, mainly sulfur oxide. Especially in the flue gas dust removal of coal-fired boiler power plant, high sulfur coal is used, and the combination of power bag project, the sulfur oxide content in flue gas is high, can reach 5000mg/Nm3. In high temperature environment, sulfur oxides form sulfite, sulfuric acid, acid corrosion and failure of filter media. If the flue gas contains HF, it can not use glass fiber filter material, which is easy to acid corrosion and cause filter material failure.

Generally, the flue gas operating temperature can be controlled above the acid dew point. If the temperature is lower than the acid dew point, the dust collector system must be closed to avoid corrosion of filter bag. Acid liquid also hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and so on.

(2) alkali corrosion

It often appears in the dust removal of sodium salt and ammonia chemical production process, such as sodium chloride, ammonia water, sodium carbonate and other conditions. For power plants, cement plants, waste incineration plants, steel plants and other fields of flue gas dust removal appeared less.

(3) Oxidative corrosion

Oxidative corrosion refers to the existence of a certain amount of oxidizing substances caused by the damage to the filter material, mainly for the oxidation corrosion of PPS filter material, can cause oxidative damage to PPS filter material nitrogen oxides, oxygen, ozone, concentrated sulfuric acid, etc. Performance as PPS fiber into dark and brittle, the appearance is intact, but the strength drops sharply, only about 200N, close to the end of the filter material service life, lose the filtering effect.