How to choose dust filter bags ？
Dust bag (filter bag) is the key component to determine the dust removal efficiency of bag filter, and the cost of replacing the filter bag is the main maintenance cost of bag filter, so the dust bag (filter bag) is particularly important. Dust bag (filter bag) whether the correct and reasonable choice determines the service life of the bag dust collector and the concentration of emissions, so from what aspects to choose the appropriate dust bag (dust filter bags) has become a more important topic, the following Hengke environmental protection technology will answer the key to choose dust bag (filter bag).
First, according to the nature of dust gas selection
(1) Gas temperature. Dust gas temperature is an important factor in the selection of filter material. Usually less than 130 deg C dust gas into normal temperature gas, dust gas more than 130 deg C into high temperature gas, so dust filter can be divided into two categories: lower than 130 deg C room temperature filter and higher than 130 high temperature filters. Therefore, appropriate filter material should be selected according to the temperature of flue gas. Some people put 130~200℃ dust gas called medium temperature gas, but the filter material choose high temperature type.
The temperature resistance of filter material has “continuous long-term use temperature” and “instant short-term temperature two kinds”. Continuous long-term use temperature refers to the filter material can be applied, continuous operation of the long-term temperature, should be selected at this temperature filter material. “Instant short-term temperature two” refers to the maximum temperature of the filter material is not allowed to exceed 10min every day, too long, the filter material will soften and deformation.
(2) Gas humidity. Dust gas can be divided into three states according to relative humidity: dry gas when relative humidity is below 30%, general gas when relative humidity is between 30% and 80%, and high humidity gas when relative humidity is above 80%. For high humidity gas and high temperature state, especially dust gas containing SO3, the gas is cold and will produce condensation phenomenon. This will not only scale and block the surface of the filter bag, but also corrode the structural materials, so special attention should be paid to it.
Two, according to the way of cleaning dust choose dust bag (filter bag)
The cleaning method of bag filter is the first condition for the selection of dust bag (filter bag). It can first decide the dust bag (filter material) is woven, needled felt, compressed felt or dust bag (glass fiber filter bag). As for the dust bag (filter bag) detailed specifications, according to other filtering conditions for further consideration.
(1) Vibration dust cleaning
The characteristic of this method is that the kinetic energy applied to the dust layer is smaller than that of pulse spraying and counter-blowing type, and it is a low energy type, so it is appropriate to use the fabric dust filter bags. The vibration wave transfer of soft fabric is better.
(2) anti-blowing (anti-suction bag) dust cleaning
This dust cleaning method generally uses fabric dust removal bag (filter bag), but can also use light cloth (weight 300 ~ 400g/m2), rich softness, small size change felt. Among them, glass fiber dust removal bag (Dust collector bag) is the most, and used for large bag filter. The lifting and sewing of the dust filter bags have certain requirements. If you do not pay attention to it, it will have a great influence on the service life of the dust filter bags.
(3) Pulse jet dust cleaning
This method has the highest kinetic energy applied to dust layer and is a typical method of external filtration. Dust cleaning force is very strong, dust bag (filter bag) yarn internal residual dust is less, the use of dust bag (filter bag) is generally felt or needled felt. Under the action of pulse spraying, the dust filter bag instantly deforms greatly and produces great stress, so the filter material with strong tensile strength must be used. Dust bag (filter bag) and skeleton often friction, so wear resistant dust filter bags, can also use fabric dust filter bag (filter bag).
(4) Air ring blowing ash
Because this dust cleaning performance is quite good, the dust removal bag (filter bag) is required to have good rigidity, small pores, and good wear resistance, so that when the spray gas ring reciprocating movement, dust removal bag (filter bag) unchanged, not fuzz. So limit the use of felt or needled felt. And the requirement of thick, high density felt. The cloth weight should be 600 ~ 800g/m2.
(5) Pulsating back blowing ash
The kinetic energy exerted by this method on the dust is in the middle of high energy type and low kinetic energy type. This dust cleaning requires that the dust bag (filter material) has softness, and also requires a certain stiffness.
The use of fabric dust filter bags, satin and twill fabric is appropriate, but from the dust removal efficiency, filtration speed, the skeleton of the anti-wear strength and other aspects of consideration, to use needled felt is appropriate, the best choice of 300 ~ 600g/m2 needled felt. Machine – woven fabric is rarely used, and various surface treatments should be made if necessary.
(6) Reverse blowing – vibration dust cleaning
The kinetic energy of dust removal applied to dust layer is low energy. The initial use of fabric dust removal bag (filter bag) in the majority. At present, most of the needled felt, the main reason is to improve the filtration speed, needled felt cloth weight is 280 ~ 350g/m2, thickness is 1.0 ~ 1.3 mm, its permeability is better.
In the sewing and installation of the dust filter bags, we usually pull the dust filter bags tight and prevent the size of the stretch filter, because when the dust filter bag elongation reaches about 2%, the effect of dust removal will deteriorate, so in the dust bag (filter bag) finalize the process, we will consider the technical conditions to prevent the dust filter bags elongation.
