What causes corrosion of PTFE Dust filter bags?

Corrosion is one of the most common reasons for bag filter damage. Because the flue gas contains a variety of corrosive substances, the corrosive effect is greater in a high temperature environment, and the PTFE filter bags  will be damaged. The dust filter bag can be said to be the heart of the vacuum cleaner. The choice of the dust filter bag is very important. The dust bag directly affects the dust removal efficiency of the vacuum cleaner. The dust filter bag should pursue an efficient dust removal effect in terms of design and filter materials.

The corrosion of dust filter bag is often caused by three kinds of gases. We have concluded that the following three gases can cause corrosion of the PTFE filter bags.

Strong oxidants.

For example, when the styrene PTFE filter bags works at 160°C, when the oxygen content exceeds the standard (>12%), a large amount of oxygen can attack the S bond in the polystyrene molecule and combine with it. The result of the reaction is that the polystyrene fiber becomes darker and brittle, and its strength is reduced.

We will find that the surface color of the polypropylene fiber bag exposed to the sun will turn brown. If it is not treated for a long time, it is easy to cause the strength of the fiber to decrease, and cause the dust bag to be damaged due to the decrease in strength. The air contains 21% oxygen and 79% nitrogen (volume ratio).

When the temperature is not high, nitrogen is very stable, but high temperature will break the molecular chain of nitrogen and react with oxygen to form NO and NO2. NO2 can be considered too much, but NO2 is a strong oxidant, most of which can oxidize filter fibers . Oxidants include nitrogen oxides, hydrogen sulfide, ammonia, chlorine and the like. Enhancing process and equipment control can reduce oxidation corrosion.

Acid gas.

In the case of using high-temperature filter materials, sulfides are the main ones. When there is a lot of acid gas in the high-temperature flue gas, it is recommended to use a dust-removing filter bag with good acid resistance. Acid gas includes sulfur dioxide, sulfur trioxide, hydrogen sulfide, hydrogen chloride, hydrogen fluoride and so on.

If an ordinary PTFE filter bags is used, the acidic flue gas will corrode the fiber structure in the dust bag, resulting in reduced strength of the PTFE filter bags and eventually damage. The signs of damage are from the outside to the inside. Cooling can reduce the corrosion of the PTFE filter bags by acid gas.

Alkaline gas.

It mainly occurs under ammonia-containing conditions, mainly ammonia. Damage and acid corrosion means that lowering the temperature can reduce the corrosion of the PTFE filter bags by the alkaline gas.