Causes of the paste bags(1)

In actual working conditions, the factors that may cause the paste bag are more complicated. For specific cases, we must start with the analysis of working conditions smoke, dust collector, operation control and other related factors, in order to understand the true inducing factors of the paste bag, so that the problem can be avoided and solved.

Condensation paste bag

Under normal circumstances, the operating temperature requirement of the bag filter must be higher than the acid dew point temperature of more than 25K. It is safer for the bag. This is mainly to avoid the occurrence of condensation. When the operating temperature is lower than the dew point, the liquid will be formed. Water. Liquid water mixed with dust and gathered on the surface of the filter bag will form a paste bag.

Dew point calculation formula:

ts = 186 + 20lgψH2O + 26lgψSO3

ts : the dew point temperature

ψH2O  : the volume fraction of H2O

ψSO3 : the volume fraction of SO3

It can be seen that the higher the moisture content and sulfur trioxide content in the flue gas, the higher the dew point temperature. This means that the continuous operating temperature of the precipitator must be higher. Due to the physical properties and economical operation limitations of the dust removal bag material, the continuous operating temperature of the precipitator must be controlled within a suitable range. If the two are not coordinated, condensation will be inevitable. Therefore, water content, SO3 content and operating temperature are the three main factors determining whether or not condensation occurs.

The picture above shows a photo of the paste bag caused by acid condensation in the filter bag of an industrial waste incineration dust collector. The operating temperature of the dust collector is stable at around 150 °C, but the water and sulfide content in the flue gas varies greatly (water content even exceeds 25%) because the main incineration treatment is waste from chemical companies such as solids, liquids and gases with complex composition, and the dew point temperature fluctuates greatly. Condensation is inevitable and the bag is extremely serious. At the same time, due to the penetration of acidic substances and long-term operation, dust gradually crusts on the surface of the filter bag, resulting in loss of air permeability of the filter bag.

The compressed air temperature is generally much lower than the operating temperature of the precipitator. At the moment of the pulse, the low temperature compressed air reduces the temperature of the upper part of the filter bag and decreases rapidly. When the temperature is lower than the dew point, the outer surface of the filter bag at the part will be knotted. Downstream of the compressed air, the effect on the temperature of the air inside the bag is getting smaller and smaller. Therefore, the paste bag phenomenon within one meter below the general dust bag upper is serious.

Furthermore, the air leakage rate of the precipitator is also a possible cause of condensation. The air leakage rate of the general dust collector is about 1-2%. However, the run-off time will increase and the air leakage rate will increase. If it is in the cold winter, the problem becomes more and more tense. The air leakage rate increases, and the local temperature of the dust collector affects the scale. The risk of the bag in the local position is higher and higher due to condensation.

In addition, although the wall of the precipitator is provided with a thermal insulation layer, since the four walls are the forefront of contact with the outside, the temperature is definitely lower than other parts. In actual situation, we find the degree of the bag of the outer ring dust bag which is usually close to the four walls become earlier than somewhere else.

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