Modern medium-efficiency bag filters made of glass fiber usually adopt a carefully designed multi-layer composite structure. Each layer of material plays a unique role, jointly ensuring efficient filtration and long-term use.
(1) Base layer: The core of filtration
The base layer is made of non-woven fabric formed by needle-punching fine-diameter glass fibers. It is the main part of the filtration. The fineness, porosity and thickness of the fibers in this layer have a direct impact on the filtration accuracy and dust holding capacity. The thickness of high-quality glass fiber needle-punched felt is generally controlled at 1.8 – 2.5mm, and the air permeability is between 80 – 120L/m²·s. Fine-diameter glass fibers formed by needle-punching form a three-dimensional network structure, which can effectively intercept most particulate matter. The finer fiber diameter helps to improve the capture efficiency of fine particulate matter, but it will correspondingly increase the initial resistance. Therefore, in practical applications, the fiber diameter and other parameters need to be optimized according to the dust characteristics and system air volume to achieve the best filtration effect.
(2) Reinforcement layer: Enhancing strength and stability
The reinforcement layer usually uses high-strength glass fiber mesh fabric or polyester base fabric, with a weight of 80 – 120g/m². It is usually placed between or on one side of the base layer. The existence of this layer significantly enhances the tensile strength and dimensional stability of the filter material. Relevant test data show that adding the reinforcement layer can increase the breaking strength of the filter material by 50% – 80%. In industrial dust removal systems, pulse cleaning is a common cleaning method, and the filter bags need to withstand the mechanical stress of the pulse airflow. The addition of the reinforcement layer enables the filter bags to better resist such mechanical stress, effectively preventing the bags from cracking, deforming, etc. during cleaning, and prolonging the service life of the filter bags, ensuring the normal operation of the dust removal system.
(3) Surface treatment layer: Improving surface properties
The surface treatment layer applies chemical agents such as PTFE or silicone oil by immersion or spraying to improve the surface properties of the filter material. The common addition amount of the treatment agent is 5% – 15% of the filter material weight. After treatment, the water repellency angle of the filter material can reach above 130°, and the dust shedding rate increases by 30% – 50%. Glass fibers have the disadvantages of high brittleness and poor bending resistance. The surface treatment technology effectively solves these problems. For example, PTFE immersion treatment can make the polytetrafluoroethylene emulsion penetrate the surface of the fibers, forming a micrometer-level coating, which not only significantly improves the flexibility and chemical stability of the filter material, but also raises the usage temperature of the filter material to 280℃, while reducing the surface energy and making the dust accumulation easier to remove; silicone oil treatment can also improve the surface properties of the filter material to some extent, enhancing its anti-fouling ability.
