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Bag filter selection
Feb 27, 2018

Operation temperature of type dust collector

For a bag filter, the use temperature depends on two factors. The first is the maximum temperature of the filter material, and the second is that the temperature of the gas must be above the dew point. The relationship between using temperature and dust removal efficiency is not obvious, which is different from that of electric precipitator. For electrostatic precipitator, the change of temperature will affect the dust removal efficiency, such as specific resistance of dust.

The dust concentration at the entrance of the bag dust collector

For bag cleaners, the following factors will be directly affected by the dust concentration at the inlet:

(1) pressure loss and ash removal period. When the inlet concentration increases, the ash deposition speed on the same filter area increases quickly, and the pressure loss increases, as a result, the number of ash removal times has to be increased.

(2) the wear of filter bag and box. When the dust has strong abrasion ability, the wear amount can be considered to be directly proportional to the dust concentration.

3 is it necessary to collect dust in advance? in front of the entrance of dust precipitator, the first class dust removal equipment is added, also known as the front stage dust removal.

(4) the ash removal capacity of the ash removal unit. The ash removal capacity of the ash removal unit should be based on the dust that can be completely collected, and the dust content is equal to the dust concentration in the inlet multiplied by the treatment air volume.

5 operation mode. Bag dust collector is divided into positive pressure and negative pressure operation mode. In order to reduce fan wear, it is not suitable to adopt positive pressure operation mode with high inlet concentration

3 Dust concentration at outlet

The outlet dust concentration refers to the emission concentration of the dust precipitator, which is expressed in the same way as the dust concentration in the inlet. The size of the dust concentration in the outlet should be determined by the local environmental protection requirements or the requirements of the user. The discharge concentration of the bag dust collector can generally reach below 50 g / Nm3.

 

Treatment air volume of 4 bag dust collector

It refers to the volume of gas that can be purified by a dust removal device in a unit of time. The unit is one of the most important factors in the design of a bag dust collector. When designing or selecting a bag filter according to the air volume, the unit is one of the most important factors in the design of a bag dust collector, either in a cubic meter per hour or in a standard cubic meter per hour. In general, the dust collector cannot be operated in excess of the specified air volume. Otherwise, the filter bag will be easily clogged, the life of the filter bag will be shortened, the pressure loss will be greatly increased, and the dust removal efficiency will also be reduced; however, the air volume shall not be chosen too large, Otherwise, increase equipment investment and occupation area. Reasonable selection of air flow rate is often based on process conditions and experience.

5 pressure loss

In the absence of more appropriate design experience, 75 × 9.8 Pa can be used as typical data at low filtration rate, but a slightly higher value should be taken for a higher filtration rate or dust layer with viscosity or low porosity.

The filtration speed is the air cloth ratio.

It's the ratio of the filtered gas flow rate of M3 / min to the area of the dust-cloth bag in the order of m3 / min. This is the unit of velocity, which represents the average speed of the gas passing through the dust-removing bag, regardless of the fact that many areas are occupied by the fibers that make up the fabric. It is often referred to as "apparent surface velocity".

Filtration rate is a very important factor to determine the performance of bag filter. Too high filtration speed will cause excessive pressure loss, reduce dust removal efficiency, make filter bag clogging and premature damage. Increasing the filtration speed can reduce the filter area required by the bag dust collector, so that the same volume of gas can be treated with smaller dust removal equipment.

There is an optimum filtration rate for a set of design parameters (i.e., the type of dust collector, ash removal mechanism, fabric structure, fabric structure, dust properties, etc.). Generally, fine dust is less fast than coarse dust, Smaller precipitators tend to use higher filtration speeds than large ones. Pulse, reverse jet precipitators can achieve higher filtration speeds than vibratory ones and reverse airflow filters.

For vibratory and reverse flow dust precipitators, the filtration speed can be 0.9m / min for ordinary dust. From the point of view of both investment and maintenance, it is recommended that the maximum filtration speed of feed and grain dust and flour can be 0.98 and 0.75 m / min, respectively.

 








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