How to treatment special dust by baghouse

1. Gases with high dust concentration

When dealing with gas with high dust concentration, cyclone or gravity dust collector can be installed as pre-precipitator. However, this will increase the resistance of the system and increase the power consumption. Therefore, when dust or finished materials do not need to be graded, most of them directly use baghouse.

Not all baghouse can handle high dust concentration gases. Only the baghouse with wide spacing of filter bags and continuous dust removal device in the form of filter outside bags can be suitable for the treatment of gases with high dust concentration.

When dealing with high dust content, we should try our best to make the dust fall directly into the hopper or some baffles in order to reduce the amount of dust adhering to the filter bag. To prevent the friction damage of filter cloth, the dust moving at high speed should not directly impact the filter cloth. The middle part of the box body can also be used as a pre-precipitator, as well as a power settling chamber of dust and a diversion chamber of inlet gas.

Bag dust collector for pneumatic conveying device collects dust, although the air handling capacity is less, the dust concentration is high, and the box body requires pressure resistance, so the cylinder shape is more. Conditional enterprises can use plastic-fired plate dust collector instead of bag dust collector.

The entrance of cylindrical box body is made into tangential direction, which makes it have separation function. Many rotary back-blown bag dust collectors are in this form. Sometimes the ash hopper part is made into the form of cyclone dust collector. Bag dust collector of pneumatic conveying system, because of the large amount of powder, the volume of ash hopper and the diameter of ash outlet should be designed larger, and the capacity of dust discharge device should be left enough room to avoid the retention of powder in the ash hopper.

2. Dusty Gases Containing Tar Fog

It is difficult to treat the gas containing only tar mist, but it can be filtered directly when the oil mist in the gas is small and the dust content is considerable. For example, in the asphalt concrete plant, the smoke from the stone dryer is the main part, and the dust from the conveyor and other exhaust gas enters the equipment. In addition, the dust from the conveyor and other exhaust gas enters the equipment. At mixer and unloading. The tar mist produced by the heated asphalt concrete also enters the equipment. In this case, the amount of dust accumulated on the filter cloth far exceeds the amount of oil mist, which can prevent the trouble of oil mist bonding and ensure stable operation.

In the manufacture of electrodes and formed carbon products, tar mist is also produced in the process of mixing powder into thermal binder. At this time, if dust is produced mainly in the process of crushing and transportation, it can be used only when a part of tar mist is mixed. However, if there is more tar in the flue gas of the coke tank on the tail tar oven, a suitable amount of coke powder should be added before the flue gas enters in order to adsorb the coke fog, and satisfactory results can be obtained.

If the gas contains only a small amount of oil mist, it can be treated separately. That is to say, adding appropriate amount of powder to the pipeline as filter aid can be used. When the added dust absorbs the tar mist, it should return to the manufacturing process as far as possible and be utilized.

3. Hygroscopic and deliquescent dust

CaO, Na2CO3, NaHCO 3, NaCI and so on are easy to absorb moisture on the surface of filter cloth, or become viscous liquid after deliquescence, resulting in difficulty in ash cleaning, increased pressure loss, and even forced to stop operation. In this case, the general precautions for dealing with hygroscopic and deliquescent dust are listed below.

(1) Firstly, check the operation status of the dust source facilities, then choose whether to start or not, and then start when the dust source facilities start. When dust layers are accumulated on the filter cloth, wet air should not be allowed to pass through. Many dryers and sintering kilns are high temperature and humidity gases. When they stop running, the temperature decreases and the humidity increases, which makes it easy to absorb moisture. Therefore, a small hot air generator should be installed on the dust removal equipment. In this way, when the dust source device stops running, the temperature inside the hot air can be fed into the original state. In the case of local dust collection with low dust concentration, the filter cloth can be pre-coated with other powders, that is, only other powders are supplied to the pipeline. After running for a period of time, the filter cloth is attached with a layer of this kind of dust before collecting the wet dust that needs to be collected.

(2) The filter cloth with non-wool and non-wool surface is adopted. If use felt filter material. Surface treatment should be carried out. The selection principles are:

A. Surface coating, calendering and other post-treatment can also improve wear resistance. For glass fiber filter material, silicone oil, graphite, PTFE resin treatment can improve wear resistance and flexural resistance.

B. Chemical fibers are superior to glass fibers, expanded glass fibers are superior to general glass fibers, and fine, short and curly fibers are superior to coarse, long and smooth fibers.

C. Felts are superior to fabrics. Needle-punching should be used to strengthen the intersection between fibers. Satin fabrics are the best in fabrics. Drawing down on the surface of fabrics is also a measure to improve wear resistance.

(3) Off-line ash removal system should be adopted. The dust on the surface of the filter cloth can be fully removed during the stop working time of the bag filter. 

4. Flammable and Explosive Dust

(1) The control of dust accumulation and the selection of anti-static dust bag are important components of the process system. In the application process, the bag filter often receives dust gas from the pipeline and derives it into a dust layer. When the dust concentration reaches 20-6000g/m3, it is in dangerous state. Therefore, in the design process, the ventilation volume of the dust collector system should be further enhanced, and the dust should be removed in time, so as to ensure the dust concentration below the dangerous range.

At the same time, attention should also be paid to the removal of funnel dust, which will continue to accumulate heat in the loopholes and easily cause spontaneous combustion of dust. In addition, because dust does not exist in a strict state in the process of accumulation, there is circulating air, which creates conditions for the occurrence of dust explosion to a certain extent. Practice has proved that the introduction of double-deck pneumatic ash relief valve can not only reduce the air leakage rate, but also effectively prevent the occurrence of dust spillover.

As for the selection of anti-static and dedusting bags, because many coal dust and chemical dust will increase the probability of explosion accidents when they encounter static electricity, anti-static and dedusting bags can choose two types of products: stripe anti-static and blended anti-static. The former mainly sets copper-permeated complex conductive yarn in needle-punched felt warp yarn, and the latter mainly conducts electricity in material. Fiber-based, specific selection can be combined with the actual production situation to make full use of the anti-static dust bag effect. And ensure that the dust collector has reliable grounding.

(2) Three main measures should be taken to clean up the ignition source.

Firstly, for the ignition sources caused by external fire sources, such as sparks generated by welding or gas cutting, dust removal should be done well in maintenance equipment and explosion-proof awareness of operators should be strengthened.

Secondly, the bag filter may inhale related metal objects such as iron blocks during operation, which may cause sparks due to friction or impact of metal objects. For this reason, the metal can be set in the dust hood, and the metal material can be removed after maintenance, or the pipeline wear can be reduced by controlling the wind speed in the pipeline network.

Thirdly, for the static electricity generated in the operation of bag filter, anti-static measures are also required. The generation of static electricity can be suppressed by reducing the contact potential difference. At the same time, grounding measures of grounding system are also important means to prevent leakage.

(3) The application of explosion-releasing film and the introduction of relevant explosion-proof technology into the installation of explosion-releasing film are important means to achieve the explosion-proof goal of bag dust collector and to improve economic efficiency. Usually, the Stnomograph method can be used to calculate the leakage area (referring to the American NFPA68 standard, the process is clear) to ensure the reasonable leakage area, so as to play the role of explosion-releasing film. In addition, in explosion-proof technology, as mentioned above, explosion accidents can be controlled within a certain range by introducing explosion-proof devices such as emergency shut-off valve. In addition, if the selected dust collector is a large device, it can also introduce the corresponding high-pressure spraying equipment, which can effectively control the occurrence of explosion-proof accidents. Installed in the indoor, the explosion vent pipe is added to the outdoor, and the explosion vent pipe is less than 3 meters.

(4)According to GBT17919, N2, CO2 or other inert gases should be used as dust removal gas source for pulse injection ash bag collector.