How to Avoid Dust Bag Leaks and Keep Emissions Low

When manufacturing filter bags, it is important to ensure that they are leak-proof as they create tiny holes in the seams and therefore pose a risk of increasing emissions from the baghouse during operation. Preventing leaks ensures that baghouses consistently deliver low emissions. We will discuss how to detect and fix baghouse leaks in a separate article.

1 Measures to Prevent Filter Bag Leakage

1.1 Hot melt process

Hot melt can solve the problems of burrs, loose threads, pinholes and other problems caused by traditional sewing of filter bags, especially the pinholes in the bag body. The efficiency is about 5 times that of traditional sewing, and it has the advantages of uniform sewing and strong bonding. However, not all filter bags can be sewn by hot melt sewing, generally single-layer thermoplastic fiber filter bags can be sewn by hot melt sewing. Figure 1.1 shows the schematic diagram of the filter bag after hot melt treatment. After hot melt treatment, there are no pinholes left in the joints of the filter bag, and there is no risk of fine dust penetrating 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 a filter bag after hot melt processing

1.2 Coating process

When hot melt stitching is not possible and thread stitching is used, pinholes are inevitably left in the filter bag. The coating process is often used in the industry to prevent leaks in filter bags. The coating process begins with the selection of a suitable sealant for the difficult flue gas exhaust conditions. This is achieved through a three-pronged approach: laboratory evaluation, production testing and engineering experience. Once a suitable sealant is found, automatic bag coating equipment is used to apply a layer of sealant to the sewing thread holes on the bag. This ensures the stability and uniformity of the coated product surface and optimizes the sealing of pinholes. Research has shown that the filtration performance of coated bags is similar to that of hot melt filter bags. Figure 1.2 shows the schematic diagram of the holes in the bag before and after coating.

Figure 1.2 Schematic diagram of the holes in the bag before and after coating (upper diagram with glue, lower diagram without glue)

1.3 Lamination process of PTFE pinhole tape

An additional method to prevent leakage is to seal the pinholes using the PTFE tape lamination process. Although the PTFE tape is a heat-resistant and chemically stable material, there is still a possibility that it may detach from the base when bonded to it by hot lamination. After the PTFE tape is completely removed, there is still a possibility that dust will enter the pinholes. As shown in Figure 1.3, it is a schematic diagram of the pinholes in the filter bag body after the PTFE tape sealing process.

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