How to avoid dust collector filter bag leak and keep low emission?

The manufacture of filter bags needs to be leak-proofed as they create pinholes in the stitching and therefore run the risk of increasing the emissions of the baghouse during operation. Preventing leakage ensures that baghouses consistently achieve low emissions. We will discuss how to detect and address leaks in baghouses in a separate article.

1 Filter Bag Leak Prevention Measures

1.1Hot Melt Process

Hot melt can solve the problems of burrs, loose threads, pinholes and other problems that occur in traditional sewing filter bags, especially the pinholes in the body of the bag, the efficiency is about 5 times that of traditional sewing, and it has the advantages of even sewing and strong bonding. However, not all filter bags can be sewn with hot melt process, usually single-layer fibre, thermoplastic fibre filter bags can be sewn with hot melt process. Figure 1.1 shows the schematic diagram of the filter bag after hot melt treatment. After the hot-melt treatment, there are no pinholes in the joints of the filter bag, and there is no risk of penetration of fine dust through the pinholes. Therefore, under the same test conditions, the hot-melt filter bag has the highest filtration efficiency.

Figure 1.1  schematic diagram of the filter bag after hot melt treatment

1.2Coating Process

When hot melt sewing is not possible and thread sewing is used, pinholes are inevitably left in the filter bag. A coating process is often used in the industry to prevent leaks in filter bags. The coating process commences with the selection of an appropriate sealant for complex flue gas conditions. This is achieved through a three-pronged approach: laboratory evaluation, production trials and engineering experience. Once a suitable sealant has been identified, automatic bag coating equipment is employed to apply a layer of sealant to the sewing thread pinholes on the bag. This ensures the stability and uniformity of the coated product surface and optimizes the pinhole sealing. Studies have shown that the filtration efficiency of the coated bags is similar to that of hot melt filter bags.

Figure 1.2 shows a schematic diagram of the pinholes of the bag before and after coating.

Figure 1.2 schematic diagram of the pinholes of the bag before and after coating (upper diagram with adhesive, lower diagram without adhesive)

1.3PTFE tape lamination process for sealing pinholes

An additional method for preventing leakage is the sealing of pinholes through the utilisation of the PTFE tape lamination process. Despite the fact that PTFE tape is a heat-resistant and chemically stable material, there is still a possibility that it may detach from the substrate when it is adhered to it by hot lamination. Once the PTFE tape is fully removed, there is still a possibility of dust permeating the pinholes. As illustrated in Figure 1.3, this is a schematic representation of the pinholes in the body of the filter bag following the sealing process with PTFE tape.

Figure 1.3: Schematic diagram of a filter bag after applying PTFE tape