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What is a dust filter bag? What does it do? Why are there so many different types of dust bags? How to choose the right dust bag?
What is the function of the dust filter bag?
Why are there so many different types of dust filter bags?
How to choose the right dust filter bag?
The dust collector can well remove wood chips, sawdust and fine sanding dust from the work area, but improperly designed or worn filter bags may better redistribute wood chips throughout the workshop. The woven fabric bags usually provided by machine manufacturers are at best a compromise. The openings between the threads are large enough to pass air efficiently, and dust passes with the same efficiency. A tighter braid will trap smaller dust particles, but it will also generate back pressure and greatly reduce suction. By using the right fabric, after the correct surface treatment and choosing the right air to fabric ratio for the collector, dust particles can be filtered to below 1 micron. For wood chips, we usually recommend single-layer polyester felt. Felt is preferred for filtration due to its high air permeability, fine particle separation and excellent dust agglomeration/release characteristics. Burning felt can make a very thin layer of dust particles accumulate on the surface of the bag. Then, the "dust cake" will actually filter the dust that is subsequently blown into the bag, thereby preventing blind holes in the bag. When the dust cake becomes heavier, the dust cake will fall off the surface of the bag and leave a thin layer to continue this self-cleaning process, thereby maintaining high airflow and allowing the dust collector to fully function.
The size of the dust filter bag is critical to the air handling efficiency of the dust collector. A bag of the correct size can allow dust to enter, slow down and fall, instead of bringing it into the fabric by the force of the air blowing into the dust filter bag. When small dust is blown into a bag that is too small, the high pressure of the air behind it will force the dust to penetrate deeply into the fiber, thereby hindering the free passage of air (blinding). In an appropriately sized bag, the dust-laden air will escape over a large enough surface area and prevent dust particles from penetrating into the fibers. Ideally, the total CFM rating of the bag should be 50-100% greater than the rated air output of the device.
Because so many dust collectors are used in many different industrial processes, the exact requirements for dust bags in each process will inevitably be very different. The performance requirements of cast steel dust bags are very different from those used in food processing plants to collect grain dust. Even in the same industry, different system configurations may require different solutions to meet the dust collection needs of the factory. Power plants may need high efficiency, while chemical plants need to use acid and alkali resistant dust bags, such as those made of Ryton® Felt / PPS. The airflow temperature of cement manufacturers can be very high, so a dust bag is needed to withstand the higher operating temperature, such as a dust bag made of Nomex® or Conex®. Other considerations include price and bag life. Larger companies may be able to purchase dust bags at a higher initial price in order to obtain revenue at the back end through higher efficiency. Smaller garments may require suitcases with a smaller initial capital investment and can sacrifice some suitcases in terms of efficiency.
1. Flue gas temperature: The dust bag is the core component of the bag filter. Whether the selected filter material can adapt to the flue gas temperature is very important. If the normal use temperature of the filter material exceeds the temperature of the flue gas too much, the high cost of the high-temperature filter material leads to an increase in equipment investment. If the normal use temperature of the filter material is lower than the flue gas temperature, it may cause the dust bag to burn and cause huge economic losses. According to the use temperature, filter materials are divided into: normal temperature filter materials below 130°C, medium temperature filter materials at 130~180°C, and high temperature filter materials at 180~280°C.
2. The composition of the flue gas: including the dust content, specific gravity, particle size, viscosity and moisture content of the flue gas. By understanding these factors, you can determine the dust removal method of the dust collector, the post-processing method of the filter material and the filter wind speed. Under normal circumstances, pulse bag filter is used for large dust volume, relatively sticky working conditions, lighter occasions, the filtering wind speed is mostly controlled above 1.2m/min, and a few working conditions are below 1m/min. The post-treatment methods of filter media usually include microporous coating, water and oil repellent, antistatic, easy-to-clean dust treatment, etc.
3. Flue gas processing volume: The processing air volume of the dust collector is usually the air volume under working conditions plus the system air leakage coefficient (10%~15%). Knowing the processing air volume and filtering wind speed of the dust collector, the total filtering area can be obtained by the following formula: S = Q / 60V. Among them, S: total filtration area, Q: system processing air volume, V: filtration wind speed.
Choosing the right dust filter bag is essential to obtain the highest efficiency of the system and the longest filter bag life. If you are looking for a high-quality dust bag at a reasonable price，Jiangsu Aokai Environmental Technology Co., Ltd. will provide you with the best products.
