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Why is the filter bag broken?

December 27,2021

Today, let’s talk about the causes of various damage of filter bags?


According to the damage type of filter bag:


Mechanical Damage


It is mainly manifested in the abrasion and falling off of the non-woven layer of the filter material, which is caused by the uneven distribution of air flow and the scouring of dust on the surface of the filter bag under high filtration wind speed; Or the filter bags are not installed in place, resulting in friction between the filter bags and damage; Or the spray pipe is not installed vertically, resulting in holes in the range of 30-40 cm at the mouth and loss of filtration performance.


Specifically, the filter bag mouth is damaged, the filter bag body is damaged, the lower part of the filter bag is damaged, and the bottom of the filter bag is damaged.


  • Filter bag mouth

Most of the damages at the mouth of the filter bag are within 30-40 cm below the mouth of the bag, mostly manifested in the blowing and falling off of the bottom layer of the filter material. Most of them are caused by too high compressed air, deflection of spray pipe, deformation of flower plate and other reasons. Pay attention to the installation quality during installation.


  • Position of filter bag body

The contact part between the filter bag and the skeleton is worn due to pulse injection for a long time, which shows obvious wear marks in the direction of horizontal and vertical ribs. Pay attention to the size matching of the filter bag and the skeleton, the surface finish of the dust removal skeleton, etc.


  • The bottom of the filter bag is damaged

The wear of the bottom of the filter bag is common. The bottom of the bag cage may be too small or the filter bag is too long. The bag cage can only support part of the bag bottom. Excessive action during dust removal and filtration of the filter bag causes wear on the inner side of the filter bag bottom. Or the dust accumulation is too high to form vortex wear filter bag.



Chemical Corrosion Filter Bag


The most obvious manifestation of chemical corrosion is the sharp decrease in the strength of the dust removal cloth bag, which is specifically reflected in acid corrosion, alkali corrosion, oxidation corrosion and hydrolysis corrosion, resulting in the loss of affordable filtration load of the filter bag, resulting in the loss of filtration performance. This phenomenon is mainly due to the problems in the selection of filter bags or the working environment exceeding the bearing range of fibers, resulting in the loss of filter performance and failure of filter bags.


  • Acid corrosion of filter bag

High temperature filter materials generally have acid corrosion, mainly sulfur oxides. Especially in the flue gas dust removal of coal-fired boiler power plant, high sulfur coal is adopted, and the content of sulfur oxide in flue gas is high, which can reach 5000mg / Nm3. In high temperature environment, sulfur oxides form sulfite and sulfuric acid, which cause acid corrosion to the filter material and failure. If the smoke contains HF, glass fiber filter material cannot be used, which is easy to cause acid corrosion and filter material failure.

Generally, the operating temperature of flue gas can be controlled above the acid dew point. If it is lower than the acid dew point, the dust collector system must be closed to avoid corroding the filter bag. Acidic liquids include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, etc.


  • Alkali corrosion of filter bag

It mostly occurs in dust removal of sodium salt and ammonia chemical production processes, such as sodium chloride, ammonia, sodium carbonate and other working conditions. For power plants, cement plants, waste incineration plants, iron and steel plants and other fields, there are few problems in flue gas dust removal.


  • Oxidation corrosion of filter bag

Oxidation corrosion refers to the damage to the filter material caused by the presence of a certain amount of oxidizing substances, mainly the oxidation corrosion of PPS filter material. Nitrogen oxide, oxygen, ozone, concentrated sulfuric acid, etc. can cause oxidation damage to PPS filter material. The PPS fiber becomes dark and brittle, and the appearance is intact, but the strength decreases sharply, only about 200N, which is close to the end of the service life of the filter material and loses the filtering effect.


  • Filter bag hydrolysis

Hydrolysis is defined as a chemical reaction in which water molecules intervene in the polymer of fiber and cause decomposition. Synthetic fibers produced by polycondensation polymers are not resistant to hydrolysis. Including: polyester, polyimide (P84), Nomex, Comex.

High temperature, humidity and chemicals must exist to activate hydrolysis. Polyacrylonitrile homopolymer, PPS fiber and PTFE fiber are not produced from polycondensation polymers and are often selected to replace fibers with hydrolysis problems. Most of the hydrolysis marks are muddy fiber color, the strength of the filter bag is seriously reduced, it can be easily torn by hand, and the sewing thread breaks after hydrolysis without strength.


  • High temperature burning of filter bag

The performance of high temperature burning mainly includes that the filter bag shrinks violently and hardens seriously due to high temperature, and even holes appear on the surface of the filter bag. The main reason is that the temperature in the working conditions of the filter bag exceeds the bearing range of the filter bag, resulting in this phenomenon. Specifically, high-temperature particles, high-temperature flue gas and excessive high-temperature thermal shrinkage of filter bags cause damage to filter materials.

  • Filter bag condensation blockage

The so-called condensation, popularly speaking, refers to the phenomenon that saturated water is precipitated from wet air under a certain pressure and temperature. The temperature point at which water precipitates is called dew point.


The higher the gas pressure in the saturated state, the lower the dew point. The higher the moisture content in the air, the higher the dew point temperature. When the moisture content in the air is certain and the temperature of the humid air is lower than the dew point temperature, moisture will be precipitated in the supersaturated air, that is, condensation will occur; when the air temperature is higher than the dew point, there will be no precipitation of water and no condensation. In addition, if the flue gas contains SO2, the more SO2 content, the higher the dew point of the flue gas

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