Working principle:

The working principle of Long Bag Offline Pulse Dust Collector mainly includes three links: filtration, dust cleaning, and dust treatment, as follows:

Filtration:

Dust-containing gas entry: Dust-containing gas enters the ash hopper from the air intake duct of the dust collector. Under the action of inertia and gravity, large particles of dust fall directly into the bottom of the ash hopper; fine dust enters the middle box and the lower box upward with the air flow.

Gas filtration: The dust-containing gas entering the middle and lower boxes continues to flow upward and encounters the filter bag. The filter bag has a filtering effect, and the dust is intercepted on the outer surface of the filter bag, while the filtered clean gas enters the upper box through the inner side of the filter bag.

Gas discharge: The clean gas in the upper box converges to the clean gas collection pipe, and then passes through the exhaust duct and is discharged into the atmosphere by the exhaust fan.

Clean:

Cleaning trigger condition: As the filtration proceeds, the dust on the outer surface of the filter bag will continue to accumulate, and the filtration resistance will gradually increase. When the resistance reaches the set limit resistance value (generally 1200-1500Pa), the cleaning control device will start the cleaning process.

Offline cleaning operation: The long bag offline pulse dust collector adopts an offline cleaning mechanism with chamber air stop. First, close the clean air outlet duct of one of the filter units to make the filter bag of the unit in a state without airflow.

Pulse spraying: Open the electromagnetic pulse valve and spray compressed air into the filter bag instantly. The compressed air causes the filter bag to deform and vibrate sharply, shaking off the dust attached to the filter bag.

Dust sedimentation: After the spraying is completed, close the electromagnetic pulse valve and let the shaken dust settle under gravity for a period of time and fall into the ash hopper.

Dust treatment: The dust falling into the ash hopper is transported to the ash storage bin by chain conveyors, elevators and other equipment and transported out regularly.

Main factors affecting the cleaning cycle:

1. Dust characteristics

Dust concentration:

High-concentration dust: If the dust concentration in the dust-containing gas is high, dust will accumulate faster on the filter bag, causing the resistance of the dust collector to rise faster, and the cleaning cycle may be shorter. For example, in some mining, metallurgy and other industries, the dust concentration may be as high as thousands of milligrams per cubic meter or even higher. At this time, the cleaning cycle may be from tens of minutes to one or two hours.

Low-concentration dust: For working conditions with low dust concentration, such as some electronics, food processing and other industries, the cleaning cycle will be relatively long, which may be several hours or even longer.

Dust particle size:

Fine dust: When the dust particles are small, it is easy to penetrate into the filter bag, increase the filtration resistance, and the cleaning cycle may be shorter. For example, for fine dust below the micron level, the cleaning cycle may be about one or two hours.

Coarse dust: Coarse dust is relatively easy to settle, and the accumulation speed on the filter bag is slow, so the cleaning cycle may be longer. For example, for coarse dust above the millimeter level, the cleaning cycle may be more than several hours.

Dust viscosity:

High viscosity dust: If the dust has high viscosity, it is easy to adhere to the filter bag and is not easy to fall off, which will cause the filtration resistance to rise rapidly and shorten the cleaning cycle. For example, in some industries such as chemical and coating, when encountering dust with high viscosity, the cleaning cycle may be from tens of minutes to one hour.

Low viscosity dust: Low viscosity dust has less adhesion on the filter bag, so it is relatively easy to clean and the cleaning cycle is longer. For example, for some dry and fluid dust, the cleaning cycle may be more than several hours.

2. Filtration wind speed

High filtration wind speed:

When the dust collector operates at a higher filtration wind speed, the amount of gas passing through the filter bag per unit time increases, the dust accumulation speed on the filter bag is accelerated, and the cleaning cycle will be shortened. Generally speaking, if the filtration wind speed exceeds 1.5 m/min, the cleaning cycle may be about one or two hours.

For example, in some occasions where there are strict restrictions on the volume of the dust collector or the air volume is large, a higher filtration wind speed may be used, and more frequent cleaning is required at this time.

Low filtration wind speed:

A lower filtration wind speed can reduce the accumulation rate of dust on the filter bag, thereby extending the cleaning cycle. If the filtration wind speed is below 1 m/min, the cleaning cycle may be several hours or even longer.

For example, in some working conditions with high dust removal efficiency requirements and complex dust characteristics, a lower filtration wind speed will be selected to ensure good dust removal effect and a longer cleaning cycle.

3. Filter bag material

Differences in air permeability of different materials:

Filter bag materials with good air permeability: Some filter bag materials have good air permeability, such as polyester needle felt, etc. Under the same working conditions, the accumulation rate of dust on the filter bag is relatively slow, and the cleaning cycle may be longer. For example, when using filter bags with good air permeability, the cleaning cycle may be more than several hours.

Filter bag materials with poor air permeability: For materials with poor air permeability, such as some coated filter materials, although the filtration efficiency is high, the resistance rises faster, and the cleaning cycle may be shorter. In this case, the cleaning cycle may be about one or two hours.

Filter bag surface treatment:

Filter bags with special surface treatment, such as antistatic, waterproof and oil-proof treatment, can reduce the adhesion between dust and filter bags, making cleaning easier and thus extending the cleaning cycle. For example, for filter bags that have been treated with antistatic treatment, when dealing with some dust that is prone to static electricity, the cleaning cycle may be longer than that of untreated filter bags.

4. Dust collector operation parameters

Dust collector resistance setting value:

Resistance setting is low: If the resistance setting value of the dust collector is low, cleaning is performed when the resistance reaches the set value, then the cleaning cycle may be shorter. For example, when the resistance is set to about 1000Pa, for some working conditions with complex dust characteristics, the cleaning cycle may be about one or two hours.

Resistance setting is high: When the resistance setting value is high, the filter bag can continue to work for a period of time at a higher resistance, and the cleaning cycle will be extended accordingly. For example, when the resistance is set to more than 1500Pa, the cleaning cycle may be more than several hours.

Pulse spraying parameters:

Spraying pressure and spraying time: Higher spraying pressure and appropriately extended spraying time can more effectively remove dust from the filter bag, making the cleaning effect better, thereby extending the cleaning cycle. For example, the spraying pressure is around 0.4-0.6MPa and the spraying time is between 0.1-0.2 seconds, which can extend the cleaning cycle to a certain extent.

Pulse interval: Reasonable adjustment of the pulse interval time to avoid too frequent or sparse spraying can also affect the cleaning cycle. If the pulse interval is too short, it may cause unnecessary waste of compressed air and may also cause excessive wear on the filter bag; if the pulse interval is too long, too much dust will accumulate on the filter bag, which will increase the difficulty of cleaning and affect the dust removal effect. Generally speaking, the pulse interval can be adjusted between tens of seconds and several minutes according to actual conditions.

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