8 factors affecting the service life of filter bags for dust collector
“There is no best filter material, only the most suitable working condition of the filter material”. The so-called working condition, refers to the dust bag work attached to the peripheral environment. Choose what material, what kind of filter material depends on the working conditions, what kind of working conditions to choose the corresponding filter material and match. Only in this way can the service life of the dust bag reach the best state.
In industrial flue gas dust removal, due to the different characteristics of iron and steel, cement, power generation, waste incineration and other industries and the differences of their own working conditions, it is difficult to grasp the working conditions of the manufacturers.
Therefore, in addition to the quality of the filter material itself, in terms of the external environment, there are many factors affecting the service life of filter bags for dust collector, but the main factors are the following eight aspects.
(1) Smoke volume
Since raw coal in most countries and regions has not been selected and classified before use, there are many varieties, mixed coals and different contents, mainly because of their calorific value, sulfur content, volatilization, and other indicators are difficult to distinguish.
High quality coal, such as: raw coal, lean coal, white coal and so on, its calorific value can reach more than 5000 kcal, volatilization is about 17%, carbon powder is small, and the worst kind of coal, such as coal gangue, mud carbon, its calorific value is 800-3000 kcal, its volatilization can reach 50%-70%, carbon powder is large.
It can be seen that different types of coal produce different calorific value, volatilization and toner content. The flue gas produced after coal combustion is called the inlet flue gas through the pipeline into the dust collector. The size of the inlet flue gas affects the service life of the dust filter bag.
In the case of large smoke volume at the entrance, if the filtration area is small and the filtration wind speed is large, the pressure of the dust collector rises, and the pressure of the dust filter bag increases, which aggravates the damage of the filter bag. Because of the quality of coal selection, determine the size of the smoke volume, and the size of the smoke volume directly affects the service life of the filter bag.
(2) Dust content of flue gas
Due to the selection of different types of coal, lead to the flue gas with different amounts of dust, when the dust into the dust collector, due to the different diameter of dust, weight is different, the diameter of dust with gravity to fall down or fall off under the interception of the cloth bag, and the small particle size of dust under the action of wind speed to generate kinetic energy. When the dust is concentrated on the filter bag after being intercepted by the cloth bag, the kinetic energy is converted to zero, which must produce impact force on the dust filter bag:
Under the action of kinetic energy, the dust constantly scour the bag, if the dust content in the flue gas is large, the filter wind speed is large, the filter bag will withstand thousands of times of friction and scouring, and the filter bag surface fiber can not withstand scouring and fall off, damage the filter bag filter efficiency. Therefore, the wear resistance of needled felt should be considered in order to prolong the service life of the filter material.
(3) Dust particles
The dust content in the flue gas of coal burning is usually invisible to the naked eye due to the small particle size. When we observe the dust under the microscope, we will find that they have different shapes, no rules, they look like blades, and they have different diameters. According to particle size, classification can be divided into: coarse dust (more than 40um), fine dust (10um-40um), microscopic dust (10um) below. Because of their different particle size, impact force is different of dust filter bag.
Dust and also contains a large number of acidic and alkaline substances, their diameter are small, when don’t bag interception, the filter under the action of wind, still can’t fall off, residual or entering inside the filter material in the surface of filter material, when combined with water vapor, will usually bag, So that the filter material chemical change to form corrosion. Therefore, in the selection of filter material, the size of dust particle size, can be considered as an indicator.
(4) Types of smoke and dust materials
Due to the different types of coal in soot, the proportion of dust is different. Dust can be divided into organic dust, inorganic dust and mixed dust according to different substances. The flue gas is mainly aimed at the analysis of inorganic dust, mainly including Sio2, CaO, MgO, Mn and other elements. The filter bag is mainly filtered with Sio2 and Fe2o3, whose particle size is very small. Under the action of wind speed, the scouring frequency of the filter bag is high and the damage degree of the filter bag is increased.
According to the previous analysis of coal, Sio2 and Al2O3 contents of different coal types are different. For example, the Sio2 content of raw coal and white coal is about 55%, but the Sio2 content of coal gangue is more than 60%. It is conceivable that their existence directly affects the service life of cloth bags.
(5) Limit index of temperature
Temperature is one of the important indicators of the use of filter material, temperature level directly determines the life of filter material. The temperature that the filter material can withstand can be divided into: Normal temperature (less than 130 degrees), medium temperature filter material (130-200 degrees), high temperature filter material (greater than 200) at present our company production of filter material can withstand the highest temperature in 300 degrees, that is, our company high temperature filter material temperature positioning in (200-300) glass fiber maximum temperature of 300 degrees, but the best use temperature in 260 degrees.
The service life of filter material can be extended only at the optimum service temperature. If the temperature is too high, the filter material with relatively weak flame retardant can easily burn and cause bag burning or even fire, but if the temperature is too low, there will be condensation and corrosion dust collector.
Therefore, the temperature of the filter material is usually increased by 10-20 degrees to the dew point temperature. However, the temperature usually provided by the customer is displayed on the instrument after the sensor test, and cannot reflect the actual temperature of dust. Generally speaking, when recommending filter material to customers, it is advisable to increase the temperature provided by customers by 5-10 degrees to ensure the service life of filter material.
(6) Acid gas
In industrial dust removal, the flue gas produced by coal combustion not only contains dust but also contains acid gas, mainly SO2. Because the flue gas contains water, the production of strong acid, strong alkali is corrosive, strong acid will penetrate into the fiber, and the higher the working temperature, the faster the chemical corrosion. So the content of SO2 is one of the essential factors in the analysis of working conditions.
(7) Oxygen content
It is not surprising that flue gas contains oxygen. But for different filter materials, we must consider: oxygen content, temperature. Filter material in the limit temperature, there is oxygen, oxygen will slowly oxidize the cloth bag, make the bag green, brittle, directly reduce the service life of the filter material itself.
Such as PPS needled felt in 120-180 degrees, and oxygen content, high moisture content under the condition of use, the condition is very good. But when the temperature increases by 10 degrees, its antioxidant capacity rapidly reduces by half, and its acid-base resistance also reduces by half, seriously affecting its life. So when customizing different filter materials, oxygen content can not be ignored. The higher the oxygen content, the higher the moisture content.
(8) Airflow distribution
The distribution of air flow affects the normal use and service life of a dust filter bag. If the distribution of airflow in the design of the dust collector manufacturer is unreasonable, the local airflow is too large, and the dust filter bag will be damaged when it works in this condition for a long time, so the distribution of airflow can not be ignored. The usual solution is to design a diversion plate in the dust collector. The role is to change the direction of the air flow and avoid direct scouring of the dust bag.
In short, the analysis of the working condition is difficult, there are many uncertain factors, and the change of any one factor will affect the service life of the filter bags for dust collector. In the analysis of the working condition, customers need to provide detailed information to figure out the external environment of the product, so as to manufacture and produce high-quality products in line with the specific working environment.