Filter bags can be woven or non-woven, or a mixture of both types. It is usually made of synthetic fibers to be less susceptible to moisture and more durable. The higher the thickness of the filter fabric, the greater the filtration efficiency. Woven fabrics often use low-pile yarns, large yarn diameters, and high index weaves in a single weave style. The thickness of the fabric is usually about 0.3mm. Weight about 300~500 g/m2.
Non-woven fabric is usually made from wool or raw cotton. People spread the fibers into thin films and put them through a shaping machine to create rough fabrics with a thickness of 3~5mm. Mixed fabrics are woven fabrics, then the surface is treated with glue or fine cotton fibers. This is a popular imported fabric today.
They have a thickness of 1.2~5mm. Filter fabrics are usually sewn into circular filter bags with a diameter of D=125~250 mm or larger and a length of 1.5 to 2 m. Sometimes it can be sewn into a rectangular box with width b=20~60mm; Length l=0.6~2m.
In one device, there can be dozens to hundreds of filter bags. With round and long filter bags, people often sew one end of the bag closed, leaving the other end empty. When working, the empty head is linked to the neck that guides the filter air into the bag on the separating screen of the dust filter chamber. When pre-filtered air enters the bag through the neck, the air flows through the fabric bag to the clean air chamber and escapes.
This move will cause the fabric bag to stretch itself into a circular cylindrical filter surface. With this diagram, the mouth of the bag connected to the sieve surface is often turned downward to remove dust from the bag when cleaning the fabric surface. When allowing air to flow from the outside to the inside of the bag, the bag must have a stretch frame made of metal so that the bag does not collapse when working.
With this diagram, the mouth of the bag connected to the sieve is usually turned upwards. With a rectangular filter bag, there is only one way to let air flow from the outside to the inside of the bag, and inside the bag there must be a fabric bag stretcher frame. The distance between the bags is 30 ~ 100mm. Reconstitution of the filter surface can be done after stopping air passing through the device and cleaning dust from the fabric surface in two ways: – Mechanical shaking thanks to a special mechanism. – Blow back with compressed air or clean air. Because it is characterized by an intermittent working cycle alternating with a recovery cycle, this device always has two or more compartments (or many blocks in the same compartment) so that each compartment (or each block) can be stopped working. block) and shake off the dust.
The air load of a typical filter cloth is 150~200 m/h. The device’s resistance is about 120~150 kg/m2. Dust removal cycle is 2~3 h. Preliminary calculation of the equipment is as follows: Total area of dust filter bag required: F = Q/(150~180)(m2) Area of 1 bag: Round bag: f = p x D x I(m2) Box bag rectangle: f = 2 x (a + b) x l (m2) Number of bags in 1 filter compartment: n = F/f (rounded)/ (bags). With: Q – Exhaust gas flow to be filtered (m3/h) D – Diameter of cylindrical filter bag (m) a; b; l – Width, thickness and length of the box bag (m).