List Of Factors Affecting Filter Function

1. filter material structure and dust layer thickness. The filter material used in bag filter can be fabric or roller felt or needled felt. Different structures of filter media have different effects on dust removal efficiency. The pores in plain cloth exist between meridian, weft and fiber, which account for 30% to 50% of the total porosity.

The dust removal efficiency of bag filter is mainly due to the formation of dust layer on filter material. The filter cloth mainly plays the role of forming dust layer and supporting its skeleton. The general situation is that the pressure loss of bag filter increases rapidly when it is used, but it tends to be stable after 1~2 months.

2. filtration rate. The filtration rate V (or load ratio QF) is an important technical and economic index representing the gas capacity of bag filter. The choice of filtration rate should be considered in terms of economy and requirements for dust removal efficiency.

From the economic point of view, when the filtration rate is high, the volume of filter material needed to deal with the dusty gas with the same flow rate is small, and the volume, area and consumption of the dust collector are also small. Therefore, the investment is small, but the pressure loss, power consumption and filter material damage of the precipitator increase, so the running cost is high. From the perspective of dust removal efficiency, the effect of filtration speed is very significant. The filtering speed of the practical fabric filter cloth is 0.5m/min ~ 2m/min, and the felt filter material is 1m/min ~ 5m/min. From the two aspects of economy and efficiency, this range of filtration speed is the most suitable. When the filtration rate is increased, it will intensify the penetration of dust particles in three ways to filter materials, that is, straight through, extruding and stomatal, thus reducing the efficiency of dust removal.

The above described Dust removal efficiency The characteristics which are significantly decreased with increasing filtration rate cannot be explained by fiber filtration theory. From the point of view of fiber filtration theory, when inertial collision is the main trapping mechanism, the capture efficiency should increase with the increase of filtration rate. Only when diffusion is the main trapping mechanism, will the capture efficiency increase with the decrease of velocity. However, the diffusion effect is not important for particles with a particle size of about 0.2 m or so, and the diameter of particles to be captured is much larger than this.

Three Dust characteristics 。 In the dust characteristics, dust particles are the main factors that affect the efficiency of bag filter. For the dust particles of 0.1 M, the dust removal efficiency can reach 95%. The dust removal efficiency of boiler fly ash is classified. For dust particles larger than 1 m, the dust removal efficiency can be more than 99%. In the dust particles of different sizes, the classification efficiency of dust particles with a particle size of 0.2 m to 0.4 m is the lowest, regardless of whether the filter material or filter material after dust accumulation is basically the same. This is due to the fact that the particle size of this particle size range is caused by the low values of several dust removal efficiencies.

Dust carrying Electrostatic charge It also affects the efficiency of dust removal. The more dust is charged, the higher the efficiency of dust removal. This characteristic has been used to make dust particles charged in the upper reaches of the filter material, thus collecting 1.6 mu m dust particles up to 99.99%.

4. cleaning method. The cleaning method of filter material for bag filter is also an important factor affecting its dust removal efficiency. As mentioned before, the filter efficiency after filtration is the lowest. With the increase of filtration time (i.e. the thickness of dust layer), the efficiency increases rapidly. When the thickness of dust layer increases further, the efficiency is kept at a constant high level.

When dust removal is different, the amount of dust dispersed is different after cleaning, and the amount of dust remaining after ash removal is different. For example, the dust concentration after mechanical vibration cleaning is lower than that after pulse jet cleaning. Direct pulse (compressed air directly to filter bag) and damping pulse (a device in the ash removal system can reduce the pressure in the filter bag when the electromagnetic valve closes). Compared with the pressure rise rate and the maximum reverse pressure, the dust concentration of the former is about several times that of the latter.

5. pressure loss. The pressure loss (equipment resistance) of bag filter not only determines its energy consumption, but also determines the efficiency of dust removal and the time interval of ash removal. The pressure loss of bag filter is related to its structural form, filter material characteristics, filtration speed, dust concentration, ash removal method, gas temperature and gas viscosity.