Bag dust collectors are a type of dry dust removal device. They are suitable for capturing fine, dry, non-fibrous dust. The filter bags are made of woven fabric or non-woven felt, utilizing the filtering action of the fibrous material to filter dust-laden gas. When the dust-laden gas enters the bag dust collector, particles with large size and high density settle to the bottom due to gravity, falling into the ash hopper. The gas containing finer dust is filtered through the filter material, where the dust is trapped, resulting in purified gas.
After a period of use, due to effects like screening, collision, retention, diffusion, and static electricity, a layer of dust accumulates on the surface of the filter bag, which is known as the initial layer. After this, the initial layer becomes the primary filtration layer of the filter material. Relying on the initial layer's action, filter materials with larger pores can also achieve a high filtration rate. As the dust accumulates on the surface of the filter material, the dust removal rate and resistance of the dust collector increase correspondingly. When the pressure difference between both sides of the filter material is very large, some fine dust particles that have already attached to the filter material will be squeezed through, causing the dust removal rate to decrease. Additionally, an excessively high resistance in the dust collector can significantly reduce the airflow in the dust removal system. Therefore, it is necessary to clean the dust collector promptly once the resistance reaches a certain level. When cleaning, the initial layer must not be damaged to prevent a decrease in the filtration rate.
The high dust removal rate of the bag dust collector is inseparable from its dust removal mechanism. As the dusty gas enters the lower inlet pipe of the collector and flows through the guide plate into the ash hopper, the coarse particle dust falls into the hopper due to the collision with the guide plate and the reduction in gas velocity. The remaining fine particle dust enters the filter bag chamber with the gas. Due to the inertia, diffusion, barrier, hooking, and static electricity of the filter material fibers and fabrics, the dust is trapped inside the filter bags. The purified gas escapes outside the bags and is discharged through the exhaust pipe. The accumulated ash on the filter bags is removed using the reverse air washing method, and the collected dust falls into the ash hopper and is discharged to the conveying system through a double-layer ash discharge valve. The accumulated ash on the filter bags can also be removed by using a jet pulse airflow method to achieve the cleaning purpose, and the collected dust is then removed by the dust discharge system. The excellent dust removal rate of the bag dust collector is also closely related to the filter material. The performance and quality of the filter material directly affect the performance and service life of the bag dust collector. The filter material is the main material used in making filter bags, and its performance and quality drive the progress of bag dust collection technology and influence its application range and service life.
Baghouse dust collectors include fabric filters and granular bed filters. The former typically uses filter bags made of useful fibers or inorganic fiber fabrics as the filtering layer, while the latter often employs a mixture of particles of different sizes, such as quartz sand, river sand, ceramic beads, and slag, etc., to form the filtering layer. As the powder repeatedly adheres to the outer surface of the filter bags, the powder layer thickens continuously, and the resistance value of the baghouse filter increases accordingly. Upon receiving a signal from the pulse valve diaphragm, the pulse valve opens during the submersion of the bags, allowing compressed air from the high-pressure air chamber to flow through. If there is no dust or it is reduced to a certain extent, the mechanical cleaning process will cease.
The low-pressure pulse bag dust collector employs an external filtration method for gas purification. The dusty gas enters the individual filter chambers through a guide tube. Due to the design, the vertical distance from the bottom of the filter bags to the top of the inlet is sufficient and reasonable, allowing for even air distribution throughout the filter chamber through appropriate guidance and natural flow. The particulate dust in the dusty gas is separated and directly falls into the ash hopper by natural sedimentation. The remaining dust, guided by the drainage system, is carried by the air flow into the middle housing filter area and adsorbs on the outer surface of the filter bags. The clean gas after filtration passes through the filter bags and is discharged through the upper housing and exhaust pipe.
The filter bags are cleaned using compressed air through blow-off, with the cleaning mechanism consisting of a gas cylinder, blow-off pipe, and electromagnetic pulse control valve. Each row of filter bags in the filter chamber is equipped with a blow-off pipe at the top, with a blow-off orifice positioned directly below the filter bags. Each blow-off pipe is fitted with a pulse valve connected to the compressed air gas cylinder. During cleaning, the electromagnetic valve opens the pulse valve, allowing compressed air to pass through the blow-off control device (differential pressure or timed, manual control) and activate the electromagnetic pulse blow-off as per the set program. The compressed gas, in a short duration, sequentially passes through each pulse valve and is induced through the nozzles on the blow-off pipe to draw in several times the amount of jet air into the filter bags, creating an air wave. This causes the filter bags to rapidly expand and vibrate from the top to the bottom, effectively cleaning the bags by dislodging dust particles.
Advantages of Baghouse Dust Collectors:
1. The dust removal rate is impressive, with the dust concentration at the outlet of the dust collector staying within tens of mg/m3. It boasts a high separation rate for fine dust with sub-micron particle sizes.
2. Wide range of air volume processing capabilities, from just a few cubic meters per minute for smaller applications to tens of thousands of cubic meters per minute for larger ones, suitable for industrial furnace flue gas dust removal and reduction of atmospheric pollutant emissions.
3. Simple structure, easy maintenance and operation.
4. At the same dust removal efficiency, the cost is lower than that of an electrostatic precipitator.
5. Materials such as glass fiber, polytetrafluoroethylene, and P84, which are heat-resistant, can operate under high temperatures above 200°C.
6. Unaffected by dust characteristics and resistances.
