The use, selection, installation and commissioning of bag dust collectors on the silo roof

The bag dust collectors on the silo roof are mainly installed on the tops of cement silos, powder silos, storage tanks and pneumatic conveying silos. They are used to filter the dust-containing gas discharged from the silo during the feeding process, maintain a reasonable pressure inside the silo, and reduce the spread of dust from the top of the silo.

The equipment is usually used in conjunction with safety valves, material level gauges, conveying pipelines and control systems. It has a compact structure and centralized installation position, and is suitable for storage and transportation systems of cement, fly ash, mineral powder, lime powder and other powdery materials.

1. Working principle of the bag dust collector on the top of the silo

When the powder enters the silo through pneumatic conveying or mechanical conveying, the air in the silo is squeezed and flows to the top of the silo. After the dust-containing gas enters the dust collector on the top of the silo, the dust is trapped on the outer surface by the filter bag. The purified air passes through the filter bag and enters the clean air chamber, and is then discharged from the equipment outlet.

As dust continues to adhere, the dust layer on the surface of the filter bag gradually thickens, and the operating resistance of the equipment increases. When the pressure difference reaches the set value or runs to the set time, the pulse control system starts cleaning.

The compressed air enters the blow pipe through the pulse valve, and then is sprayed into the filter bag through the blow hole, causing the filter bag to rapidly expand and vibrate. The dust attached to the surface of the filter bag falls off and returns to the silo. After the dust cleaning is completed, the equipment continues its filtration work.

2. Main components of the equipment

1. Dust removal box: including filter chamber, clean air chamber, flower board, access door and support structure.

2. Filtration system: composed of filter bags, filter bag frames and flower boards, used to separate gas and dust.

3. Pulse cleaning system: consists of air bag, pulse valve, blow pipe and controller.

4. Connection base: connected to the top of the silo through flanges, clamps or other structures.

5. Exhaust structure: It can exhaust naturally or configure an induced draft fan according to the system resistance and feeding conditions.

6. Control system: used to control pulse cleaning, fan operation and fault alarm.

3. Pre-installation inspection

1. Check whether the equipment, filter bags, pulse valves, controllers and accessories are complete according to the packing list.

2. Check whether the equipment is deformed, cracked, loose or damaged during transportation.

3. Check whether the filter bag is damaged and confirm that the connection between the filter bag and the flower board is sealed reliably.

4. Check whether the flange, clamp, sealing strip and access door are complete.

5. Confirm that the load-bearing capacity of the top of the silo, the size of the installation opening and the location of the interface meet the equipment requirements.

IV. Installation requirements for silo top dust collector

The equipment is usually installed on the top of the silo through the bottom flange or connecting base. During the installation process, appropriate lifting tools should be used and temporary anti-fall measures should be taken to prevent the equipment from tilting or falling.

1. The connection surface between the equipment base and the silo should be flat, and an aging-resistant sealing gasket should be installed.

2. Flange bolts or clamps should be tightened evenly to avoid local stress and dust leakage.

3. Hoisting wire ropes are only used for installation and temporary fixing and cannot replace the formal connection structure.

4. The equipment should be kept vertical after installation to prevent the box from deforming due to stress.

5. The power supply, compressed air pipeline and control circuit should be connected according to the equipment wiring diagram.

6. When installing outdoors, rainproof measures should be taken for the electric control box, pulse valve and gas system.

5. Preparation before starting the equipment

1. Check whether the filter bag, frame and blow pipe are installed in place.

2. Check whether the compressed air pressure is within the equipment requirements.

3. Check whether the pulse valve, controller and electrical circuit are normal.

4. Check whether the access door, flange and connection port are sealed.

5. Check whether the safety valve and material level gauge of the silo are working properly.

6. If an induced draft fan is configured, the fan steering, vibration and protective devices should be checked.

6. Correct operation method

The bag dust collector on the silo roof should generally be started in advance before the start of powder transportation, so that the equipment can first establish normal filtration and exhaust conditions. After stopping feeding, it can continue to run for a period of time to discharge the remaining dust-containing gas in the bin.

1. Start the control system and dust cleaning device.

2. When equipped with an induced draft fan, the fan should be started first and then the powder conveying equipment.

3. Observe whether the pressure difference and exhaust status of the equipment are normal.

4. After the feeding is completed, continue to run for a few minutes, and then stop in sequence.

5. Do not continue feeding when the filter bag is damaged, dust cleaning fails or the equipment is seriously blocked.

7. Basis for selection of bag dust collector on top of silo

When selecting dust collector on top of silo, the exhaust volume generated during the feeding process of the silo should be mainly considered, and the equipment model cannot be determined based only on the diameter or volume of the silo.

1. Silo volume and silo roof installation space.

2. Powder conveying method and maximum feeding speed.

3. The amount of air transported by the pneumatic conveying system.

4. Dust type, particle size, concentration, temperature and humidity.

5. The allowable filtration wind speed and equipment resistance of the filter material.

6. Emission requirements and whether an induced draft fan is required.

8. Determination of filtration area

The filtration area is usually calculated based on the treatment air volume and the design filtration wind speed. The basic calculation method is as follows:

Filter area = actual air volume ÷ design filtration wind speed.

The design filtration wind speed needs to be determined based on dust concentration, particle size, viscosity, humidity and filter material performance. When the dust concentration is high or the dust is difficult to clean, the filtration wind speed should be appropriately reduced and the filtration area should be increased.

The allowable amount of dust accumulated per unit area of ​​a filter bag is not a fixed value and cannot be uniformly selected according to a certain value. It should be determined based on the performance of the filter material, the dust cleaning method and the manufacturer’s design parameters.

9. Is it necessary to configure an induced draft fan?

For silos with low feed speed and small exhaust resistance, the positive pressure in the silo can be used to naturally discharge the gas through the filter bag.

When the silo volume is small, the feeding speed is fast, the filtration resistance is large, or the natural exhaust is insufficient, an induced draft fan can be configured at the outlet of the dust collector for forced exhaust.

The air volume of the induced draft fan should not be too large, otherwise it may cause excessive negative pressure in the warehouse, increase material loss, or dust penetrate the filter material. The fan should be selected based on the actual exhaust volume and system resistance.

10. Requirements for pulse cleaning system

Pulse cleaning is suitable for working conditions where the dust concentration is high or the dust on the surface of the filter bag is difficult to fall off. The compressed air pressure is usually determined based on the equipment structure and the length of the filter bag. The common working range is about 0.4~0.7MPa.

1. The compressed air should be clean and dry to reduce oil and water entering the air bag.

2. The pulse width and injection interval should be adjusted according to the pressure difference of the equipment.

3. Blowing too frequently will increase the consumption of compressed air and affect the life of the filter bag.

4. Insufficient blowing may cause the filter bag resistance to continue to increase.

11. Equipment debugging steps

1. Mechanical inspection: Check fasteners, filter bags, frames, blow pipes and access doors.

2. Electrical debugging: Check the controller, pulse valve and fan wiring.

3. Gas circuit debugging: Check whether the air bag, pressure reducing valve, pulse valve and pipeline are leaking.

4. No-load trial operation: Test the operation of the dust cleaning system and fan without feeding.

5. Linkage debugging: linkage test the dust collector with the powder conveying equipment, material level gauge and safety valve.

6. Load operation: Record the air volume, pressure difference, cleaning cycle and emission status after formal feeding.

12. Setting of cleaning cycle

When it is put into operation for the first time, the time control method can be used to clean the dust and record the pressure difference changes of the equipment. After running for a period of time, adjust the injection interval according to the dust properties, feeding frequency and resistance changes.

When conditions permit, differential pressure control can be used. When the resistance of the equipment reaches the set upper limit, dust cleaning will automatically start. When the resistance drops to the set lower limit, dust cleaning will stop, making the operation more reasonable.

13. Precautions for daily maintenance

1. Regularly check whether the filter bag is blocked, damaged or fallen off.

2. Regularly check whether the pulse valve, air bag and blow pipe are leaking.

3. Check whether the pressure difference of the equipment continues to increase abnormally.

4. Check whether the safety valve and material level gauge are normal.

5. Regularly clean the dust inside the equipment and around the silo top.

6. When replacing the filter bag, check whether the frame is deformed or rusted.

7. Feeding must be stopped, power supply cut off and compressed air released before maintenance.

The processing capacity, filtration efficiency and emission concentration of the silo-top baghouse dust collector are closely related to the processing air volume, dust properties, filter material selection, filtration wind speed and dust cleaning status. Equipment cannot be selected solely based on general efficiency or fixed concentration parameters, but should be designed based on the silo working conditions.