Baghouse dust collector instruction manual
- Bag dust collector is a dry dust filtering device. It is suitable for capturing fine, dry, non-fibrous dust. The filter bag is made of textile filter cloth or non-woven felt, and uses the filtration effect of the fiber fabric to filter dust-containing gas. When the dust-containing gas enters the bag dust collector, the dust with large particles and heavy specific gravity will be removed due to gravity. The air will settle down and fall into the ash hopper. When the air containing fine dust passes through the filter material, the dust is blocked, thereby purifying the air.
Dust removal mechanism of commonly used bag house dust collectors
Gravity sedimentation dust removal
- When dust-containing gas enters the bag dust collector, dust with large particles and heavy specific gravity settles down under the action of gravity, which has the same function as the settling chamber.
Screening and dust removal
- When the particle diameter of the dust is larger than the gaps between the fibers of the filter material or the gaps between the dust on the filter material, the dust will be blocked when the airflow passes through, which is called sieving. This effect becomes more significant when the accumulation of dust on the filter material increases.
Inertial force dust removal
- When the air flows through the filter material, it can pass around the fibers, while the larger dust particles still move in the original direction under the action of inertial force, and then collide with the filter material and be captured.
Thermal motion dust remova
- The light and small dust movement route is very close to the air flow streamline and can bypass the fiber. However, after being collided with gas molecules undergoing thermal motion, they change their original direction of movement, which increases the chance of contact between dust and fibers, allowing dust to be captured.
Electrostatic dust removal
- If the dust particles suspended in the air flow have a certain charge, they can be separated from the air flow through electrostatic force. Since the electric charge of the dust core is very small in the natural state, in order to obtain better dust removal effect, a special high-voltage electric field must be set up.
Cohesion dust removal
- Condensation is a direct dust removal mechanism. Through the condensation effects such as ultrasonic waves, steam condensation, and humidification, tiny particles can be aggregated and enlarged, and then removed using general dust removal methods.
Dust removal mechanism of bag dust collector
- Dust-containing gas enters the filter bag, and the dust is separated and captured on the inner surface of the filter bag. The purified air passes through the filter bag and is discharged from the exhaust hole. The mesh of the filter material itself is larger, so the dust removal efficiency of the new filter material is not very high. As the particulate matter forms a particle layer on the surface of the filter material and becomes the primary layer, the filtration effect of the filter layer is improved.
- However, as particulate matter accumulates on the surface of the filter bag, the pressure difference on both sides of the filter bag increases, the gaps inside the particulate matter become smaller, and the flow rate of air increases when passing through the holes of the filter material, which will take away the dust particles adhering to the gaps in the filter material, causing Dust removal efficiency decreases.
How to calculate the air volume of dust collector
- Filtration wind speed is another important factor affecting bag dust collector. The filtration wind speed vf refers to the speed of the filter gas passing through the surface of the filter material, the unit is m/min, that is:
Vf=L/60F - In the formula – dust collector air volume, m3/s
F——Filter area, m2 - Choosing a higher filtration wind speed can reduce the filtration area, but it will cause the resistance to rise quickly and make dust cleaning frequent, which will affect the life of the filter bag. The filtration wind speed usually used in current design is 0.60~1.20m/min.
Dust collector filter material selection
- The bag dust collector intercepts dust with a certain particle size in the flue gas based on the inherent physical filtration characteristics of the filter material and the filtration performance of the dust layer attached to the surface of the filter material. It relies on the fiber density of the filter material in the thickness direction to determine the filtration capacity, becoming a deep filtration technology.
- The filter material is the core of the bag dust collector, which is related to whether the dust collector can be used reliably and efficiently for a long time.
- The forms of filter material failure include irrecoverable clogging failure, high temperature failure, corrosive failure, mechanical loss failure, etc. Therefore, the selection of filter materials should mainly consider the following aspects:
- Corrosion of acidic gases in flue gas
- Flue gas temperature
- Oxidation effect of flue gas on filter material
- The role of moisture in flue gas
The influence of flue gas temperature on the selection of dust collector filter materials
- Bag dust collectors are mainly used in flue gas dust removal of compound fertilizer dryers, cement rotary kilns and coal-fired power station boilers. The temperature of such flue gas is often 100°C~300°C. The performance of general chemical fibers will be affected at this temperature, so the filter material of the bag dust collector must be made of high-temperature resistant fiber materials.
The impact of corrosion of acidic gases in flue gas on the selection of filter materials for dust collectors
- When high-sulfur coal is burned or the flue gas is not desulfurized, and the concentration of sulfur oxides and nitrogen oxides in the flue gas is very high, except for FT filter materials, other chemically synthesized fiber filter materials will be corroded and damaged, shortening the life of the filter bag.
The influence of oxidation reaction on the selection of dust collector filter materials
- The influence of oxidation reaction on the selection of dust collector filter materials
Oxygen accounts for 21% in the air. Especially the temperature of the flue gas is relatively high, which will have varying degrees of oxidation on the filter material, so the filter material must have anti-oxidation properties.
The influence of moisture in flue gas on the selection of dust collector filter materials
- When operating under high temperature conditions, when the moisture content of dust in the flue gas exceeds 25%, the dust will easily stick to the bag and block the bag. If the material’s hydrolysis resistance is not high, hydrolysis will also cause damage to the filter material.
Issues that should be paid attention to when using dust collector
- The filter material must be used within the appropriate temperature range. Note that in high-temperature flue gas treatment systems, the flue gas temperature is the lowest temperature of smoke dust. When the operating temperature exceeds the temperature resistance range of the filter material, the cooling methods that can be used include (1) surface heat exchanger (2) mixing in cold air from outside the system.
- When dealing with high-temperature dusty gases, in order to prevent corrosive gas components or water vapor in the gas from condensing, pipes and dust collectors should be insulated. If necessary, local heating of the bag dust collector should be performed, such as at the ash hopper of the dust collector.
- For flue gas with sparks or for dusty flue gas where the flue gas temperature is much higher than the gas temperature, a spark arrester or flue dust preconditioner must be installed.
- For handling dusty gases containing oil mist and sticky particles under operating conditions, a baghouse dust collector must be installed to pre-attach dust. For example, if a coal-fired boiler is equipped with a baghouse dust collector, dust must be pre-attached to the filter bag before the electric furnace.
- When dealing with gases with high dust concentrations, in order to avoid damage to the filter bags caused by frequent cleaning of the bag dust collector, a pre-dust collector should be used for front-stage purification.
- Be careful to prevent dust explosions. Dust explosions can be prevented by adopting explosion-proof structural design, using anti-static filter bags, setting up safety holes, taking necessary detection and fire-fighting measures, equipment grounding measures, and measures to prevent the mixing of sparks.
