Bag filter

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The principles in the design of bag dust collectors are cost-effectiveness and practicality; they should neither be too large nor too small, with meeting the **specified dust emission standards serving as the basis for the design. When designing a non-standard dust removal system, we need to take comprehensive considerations of the following key factors: 1. Whether the installation site is spacious and unobstructed, whether it is convenient to move in and out the equipment, and whether there are any restrictions regarding length, width, and height. 2. Accurately calculate the actual air handling volume of the system. This is the main factor in determining the size of the dust collector. 3. Select the appropriate filter media based on the temperature, humidity, and stickiness of the flue gas and dust being treated. 4. By referring to the collection experience of similar dusts and relevant materials, the filtration wind speed is selected to ensure that the emission concentration meets the standards, after which it is decided whether to use an online or offline dust cleaning method. 5. Calculate the total filtration area of the filter media used in the dust collector based on the filtered air volume and filtration velocity. 6. The diameter and length of the filter bags are determined based on the filtration area as well as the installation site, with the aim of making the overall height and dimensions of the dust collector as square-shaped as possible. 7. Calculate the number of filter bags and select the cage structure. 8. Design the flower plate for the distributed filter bags. 9. Refer to the model of the dust cleaning pulse valve to design the structural format of the pulse dust cleaning system. 10. Design the enclosure structure, the installation locations of air tanks and injection pipes, the pipeline layout, the air inlet baffles, steps and ladders, safety measures, etc., while giving full consideration to rainproofing measures. 11. Select the fan, ash discharge hopper, and ash discharge device. 12. Select control systems, differential pressure and emission concentration alarm systems, etc., to ensure the safe and stable operation of the dust collector. In the design process of dust removal systems, the most influential factor is the designer’s personal experience. Additionally, there are the promotional experiences and drawings from certain design institutes, as well as the processing capabilities of equipment manufacturers and their past installation experiences and track records. Therefore, when installing a dust collector, it is crucial to find a professional manufacturer of such devices, so as to have dust collection systems that are well-structured, operate stably, and deliver good performance. The framework for dust collectors and dust removal equipment; the equipment used in the production line for manufacturing such frameworks includes wire drawing machines, cutting machines, forming and welding machines, punch presses for manufacturing venturi tubes, lathes, rust removal workshops, curing rooms, galvanizing facilities, and silicone spraying facilities. The daily production capacity can reach over a thousand tons, with a wide variety of skeleton forming molds available. The dust removal framework inside a bag filter functions like our ribs, playing an extremely important role. Its dimensions are perfectly matched to those of the filter bags, so as not to damage them. When the pulse valve releases air under several kilograms of pressure, there is sufficient space between that air and the filter bags for expansion, allowing the system to withstand tens of thousands of cycles of spraying. The manufacturer must carefully determine the size of the holes in the partition plate in order to ensure proper alignment ； On the other hand, if it is lengthened, the dust collector housing must also be extended upward; this requires increased strength of its components, thereby raising the equipment cost ； Before installing the dust removal frame, it is necessary to check whether the quality of the dust collection bags and the frame is satisfactory; the bags should have no loose threads or broken wires, and no ends sticking out, while their dimensions must match those of the frame’s diameter. It is also necessary to check whether the material of the cloth bag matches what was ordered. If there are any discrepancies, please contact the supplier as soon as possible to arrange a replacement. A high-quality dust removal frame should have a smooth surface, without burrs or missed welds. The simplest way to check this is to visually inspect the welded areas, wearing white gauze gloves, to ensure that there are no stray wires. A good dust collection frame should possess sufficient strength, stiffness, verticality, and dimensional accuracy to prevent deformation under pressure, damage during transportation, contact between filter bags once they are installed in the dust collector, as well as difficulties in installing the bags and friction between the bag frames ； During the manufacturing process, all solder joints must be secure; no loose, weak, or missing solder joints are allowed ； The surface is required to be smooth and straight, without burrs, with uniform welding. For surface treatment, powder coating or silicone treatment can be chosen. For applications requiring temperature, humidity control and corrosion resistance, galvanized or stainless steel materials can be chosen. Design and production standards for dust removal filter bags: The manufacture of these filter bags is carried out in strict accordance with the GB/T6719-2009 standard, to ensure a high rate of qualified products upon leaving the factory. Bag types: I. Processing methods: Based on the processing method, they are mainly divided into three types: woven filter media dust collection bags, non-woven filter media dust collection bags, and composite filter media dust collection bags. 1. Woven filter media for dust collectors: Filter media made by weaving warp and weft threads that are arranged perpendicularly to each other according to a certain weaving pattern, denoted by the letter W ； 2. Non-woven filter media dust collection bags: Filter media in sheet form that are created without going through the usual spinning and weaving processes; instead, fibers are formed into a network or yarns are layered together, and then these elements are interlaced, bonded, needle-punched, melt-spun, or spun to create the filter media. Such media are identified using the abbreviation NW along with a code indicating the specific processing method used ； 3. Composite filter media dust collection bags: Dust collection bag filters made using two or more methods or composed of two or more materials, denoted by the letter C. II. Fabric weave: Based on the fabric weave, filter bags are mainly divided into three types: plain-weave filter media, twill-weave filter media, and satin-weave filter media. 1. Plain weave: This is the simplest weaving structure, with each warp thread and each weft thread alternating up and down. However, plain weave has disadvantages such as difficulty in cleaning dust and a tendency to get clogged; as a result, this weaving structure is rarely used as a material for dust removal filters ； 2. Twill weave: It is formed by two warp threads on top and four warp threads below interweaving with the weft threads, with the intersection points of the warp and weft threads moving gradually to the left or right ； Twill weaves are divided into single-faced twill and double-faced twill ； Twill weaving has better flexibility and elasticity than plain weaving; its mechanical strength is slightly lower, and it tends to shift under stress. However, it offers good wear resistance, as well as effective dust removal and cleaning capabilities, making it the most commonly used weave type for woven filter media ； 3. Satin texture: It can be divided into warp-satin and weft-satin depending on whether the warp threads or weft threads are visible on the surface of the fabric ； The characteristics of satin weave are its smoothness, shiny surface, extreme softness, good elasticity, and breathability. Additionally, due to the migratability of the yarns, it is easy to remove dust from it. III. Cross-sectional shape of filter bags: Based on their cross-sectional shape, filter bags are mainly divided into three types: circular, flat, and irregular shapes. 1. Circular: The dust removal filter bag is cylindrical in shape. Its specifications are expressed as diameter × length, i.e., D×L (mm) ； 2. Flat shape: The filter bags of dust collectors are flat in shape, including rectangular and trapezoidal types; their specifications are expressed as perimeter × length, That is, P×L (mm) ； 3. Special-shaped: Filter bags with peculiar shapes; their specifications are indicated by the characteristic parameters of their structure. Filtering method: Based on the filtering method, it is mainly divided into internal filtration and external filtration. 1. Internal filtration dust removal filter bags: As the dust-laden gas passes through the inner surface of the filter bag, the dust is trapped on that inner surface; this type of filtration is known as internal filtration ； 2. External filtration dust collector filter bags: As the dust-laden gas passes through the outer surface of the filter bags, the dust is trapped on the outer surface of these bags; this type of filtration is known as external filtration. V. Normal temperature, medium temperature, high temperature, ultra-high temperature (metal 316L). Normal temperature generally refers to temperatures not exceeding 90 degrees; medium temperature is around 120 degrees; high temperature is around 280 degrees. Ultra-high temperature metal filter bags have a frame and are made of metal 316L, with a temperature resistance range of 300–600 degrees. Features of dust removal filter bags: The fabric and design of these filter bags should aim to achieve efficient filtration, easy removal of dust, and long durability. 1. Capillary fiber oil-absorbing filter bags – consisting of three parts: a pre-filtration layer, a main filtration layer, and a wire mesh cover. It is designed specifically to effectively adsorb oils from liquids. The porosity of the filtering material is as high as 80%, **which increases the product’s service life. The oil absorption capacity is as high as 12 to 20 times the weight of the filter bag itself (the exact value varies depending on the properties of the fluid and grease, as well as the flow rate). 2. Absolute precision: Seamless filter bags – manufactured by thermal melting and spraying of pure polypropylene capillary fibers. The outer layer consists of thickened deep filtration material, which is used to provide layered filtration ； It features a large-diameter inner filter element to further enhance the overall deep filtration effect and improve the capacity to retain impurities. Its service life is on average more than five times that of ordinary polypropylene filter bags. The highest filtration precision is 3um. The collar ring is a plastic ring. 3. Screen filter bags – available materials include nylon monofilament screens, polyester monofilament screens, and polypropylene multi-filament screens. Maximum filtration precision of 20um. Features: absolute filtration precision, high toughness, resistance to damage, no free fibers, and reusability. Structural design of bag dust collectors: Dust collection bags are generally classified into pulse-type dust collection bags, vibration-type dust collection bags, and reverse-blow type dust collection bags, depending on the dust removal method used. Depending on the shape, there are also round bag type, flat bag type, and envelope type. Dust removal bags also come in various options for bag mouth and bag bottom designs. Production standard: The longitudinal seams of the dust removal filter bags must be strong and straight, with no fewer than three seams. The circumferential stitching at the opening of the dust removal bag must be secure and there must be no fewer than two such stitches. The circumferential stitches of the anti-deflation ring for dust collection bags must be secure, with no fewer than two stitches on each side. The circular seam at the bottom of the dust removal bag allows for a single thread, but it must be sewn in more than two loops. The length deviation of the dust collection bag’s lower edge should be within ±10 mm. The stitching density around the perimeter of the bag must be even; the vertical stitching density should not be less than 15 stitches per 250 px, while the horizontal stitching density should be at least 12 stitches per 250 px ； The sewn fabric bags must be free of holes or any defects ； Bag filters with a diameter greater than 200 mm and a length greater than 5000 mm shall undergo a tensile test, and their elongation shall meet the requirements. a) Continuous skipping is not allowed; within a 1m length of suture, there should be no more than 1 stitch, 1 thread, or 1 instance of skipping ； b) No float line ； c) Continuous track deviation is not allowed, and there shall be no more than 1 track deviation within 1 meter. Precautions: 1) New processes and old filter bags should not be used together to prevent damage caused by differences in age from affecting the proper operation of the dust removal equipment. 2) Aging of the fabric bag. It is mainly caused by the following reasons; it is necessary to conduct an investigation into the causes, take corrective measures, and replace the dust collection filters. ①Hardening and shrinking due to abnormally high temperatures ； ②Due to reactions upon contact with vapors of acids, bases, or organic solvents ； ③Reacts with moisture. 3) The filter cloth should not be hung too loosely or too tightly; if it is too loose, dust tends to accumulate, while if it is too tight, it may get damaged. 4) For the replaced cloth bags, first blow them clean with compressed air, then check for any holes. Any bags with holes should be repaired and kept for future replacement. For cloth bags clogged with dust, rinse them with water and let them dry before setting them aside for replacement. 5) Clogging of the dust collection bags. When the bag becomes clogged, the resistance increases, which can be indicated by an increase in the reading of the differential pressure gauge. Bag clogging is the main cause of phenomena such as bag wear, perforation, and detachment. To identify the causes of dust filter bag blockage, check and repair as indicated in the table below. Generally, the following measures are taken: ① Temporarily increase dust cleaning to eliminate blockages in the filter bags ； ②Replace the filter bags in part or in full ； ③Adjust the installation and operating conditions. Formula for calculating the price of dust removal bags: We will show you how to calculate the price of these bags using the most commonly used materials. The formula is: (diameter * 3.14 + 0.03) * length * unit price; this allows one to calculate the cost of a bag. The diameter referred to here is the size of the opening in the ceiling panel you install, while the unit price refers to the cost per square meter (prices vary depending on the material and the manufacturer). Applications for dust collection bags: smoke gas treatment and dust removal systems in iron smelting plants, steel mills, ferroalloy factories, refractory factories, foundries, power plants, etc. Flue gas filtration for waste incinerators, coal-fired boilers, fluidized bed boilers, etc. Asphalt concrete mixing, as well as production sites for building materials, cement and ceramics, lime, gypsum, etc. Filtering of flue gases from aluminum electrolysis, as well as from the smelting of lead, tin, zinc, copper, and other rare metals; recovery of fine particles; separation of liquids from solids. Liquid-solid separation and recovery of fine materials in industries such as chemicals, coke, carbon black, dyes, pharmaceuticals, and plastics. Dust control, purification, and collection in industries such as mining, food processing, flour production, the electronics industry, and wood processing. Pulse bag filter www.czszjxsb.com