The working principle and explosion-proof measures of wet explosion-proof dust collectors

Wet explosion-proof dust collectors are mainly used to deal with combustible dust, sparks, high-temperature particles and some oil mist generated during polishing machines, grinders, extruders, non-ferrous metal processing and scrap copper processing. The equipment collects dust through water bath, spray or gas-liquid mixing, so that the particles enter the liquid phase, thereby reducing dust suspension and secondary dust.

It should be noted that filter bag filtration, pulse injection and ash hopper cleaning are the working methods of dry bag dust collector. Wet explosion-proof dust collectors usually do not use filter bags and pulse cleaning, but use water, spray liquid, diversion structures and mist removal devices to complete dust collection.

1. Working principle of wet explosion-proof dust collector

After the dust-containing gas enters from the air inlet of the equipment, it first passes through the diversion, deflection or water bath area. Larger particles and high-temperature sparks are initially captured under the action of inertia, gravity and liquid contact.

Subsequently, the air flow comes into full contact with the spray liquid or high-speed atomized droplets. After being wetted, the dust particles collide, intercept and agglomerate with the liquid droplets to form dust-containing droplets with larger mass, and fall into the circulating water tank or sedimentation area.

The dust-removed gas then passes through the baffle or demister to remove the liquid droplets entrained in the air flow, and is finally transported to the exhaust duct by the fan.

2. Main components of the equipment

1. Dust removal box: forming a space for gas-liquid contact and particle separation.

2. Air inlet and diversion structure: Reduce the direct impact of sparks and allow dust-laden airflow to enter the treatment area evenly.

3. Water bath or spray system: Use water or absorbent liquid to moisten and capture dust.

4. Circulating water tank: stores circulating fluid and collects settled dust and sludge.

5. Demist device: Reduce water droplets discharged with the purified gas.

6. Fan and control system: provide processing air volume and monitor the operating status of the equipment.

3. How to reduce dust risks in wet processing

Combustible dust explosions usually require the simultaneous presence of combustible dust, a certain concentration, oxygen, ignition source and restricted space. Wet dust removal can reduce the suspension and accumulation of dust inside the equipment by moistening and transferring the dust into the liquid phase.

1. Water or absorbent liquid can cool and capture some sparks and high-temperature particles.

2. After dust enters the liquid phase, the formation of dust clouds and secondary dust emission can be reduced.

3. Continuous discharge of sewage and cleaning of sludge can reduce long-term accumulation of dust inside the equipment.

4. Reasonable control of the treatment air volume can reduce dust deposition in pipelines and equipment.

4. Explosion-proof safety structure

Wet dust removal can reduce the risk of some dust explosions, but it does not mean that the equipment can completely avoid fires or explosions. For dust with higher hazards, corresponding safety structures should still be configured based on risk assessment.

1. Reliable grounding: Equipment boxes, air ducts, fans and metal parts should be grounded and equipotentially connected.

2. Explosion-proof electrical: Motors, electrical control boxes and sensors should match the requirements of hazardous areas on site.

3. Liquid level monitoring: Prevent the circulating water level from being too low, causing the dust to be unable to fully contact the liquid.

4. Temperature monitoring: Monitor and alarm high-temperature particles, sparks and abnormal temperature rise.

5. Pressure protection: According to the dust hazard and equipment structure, reasonably configure pressure relief or other safety protection measures.

6. Fan interlock: Interlock control can be set up between the circulating water pump, liquid level and fan to avoid water shortage operation.

5. Reasonable design of air inlet and sewage discharge structures

The air inlet of the equipment should prevent dust and sparks from directly impacting key components inside the box. Baffles, fire-stopping structures or pre-separation areas can be set up.

The bottom of the box should be designed with a reasonable slope so that sludge and sediment can concentrate into the sewage outlet and reduce dust accumulation inside the equipment.

For special metal dust such as aluminum powder and magnesium powder, it should also be evaluated whether a chemical reaction or flammable gas may occur after the dust comes into contact with water. Ordinary wet dust removal solutions cannot be directly applied.

6. Common application scenarios

1. Grinding, polishing and abrasive belt processing of metal products.

2. Particles produced by grinders, cutting machines and extrusion equipment.

3. Dust from the processing of scrap copper, scrap aluminum and non-ferrous metals.

4. Processing stations that are also accompanied by sparks, high-temperature particles or some oil mist.

5. It is not suitable for some sticky dust conditions that are filtered by ordinary dry filter bags.

7. Correct start-up and shutdown sequence

Before starting the equipment, check the liquid level of the circulating water tank, spray system, water pump, fan and sewage device. Usually, the circulating water pump should be started first, and the dust removal fan and production equipment should be started after confirming that the water bath or spray system is operating normally.

When shutting down, the dust-producing equipment should be stopped first, and then the dust removal fan should be turned off. The circulating water pump can continue to run for a period of time to flush the inside of the equipment, and then turn off the water pump.

8. Precautions for daily maintenance

1. Check the circulating water level regularly to prevent the equipment from running out of water.

2. Clean the circulating water tank, sedimentation area and sewage pipes regularly.

3. Check whether the nozzle, deflector and mist eliminator are clogged.

4. Check the fans, water pumps and valves for abnormal noise or leakage.

5. Regularly check electrical grounding, liquid level alarm and temperature monitoring devices.

6. Sludge should be cleaned up in time to avoid long-term accumulation, heat or odor.

9. Parameters required for equipment selection

1. Dust name, composition, particle size, concentration and density.

2. Whether the dust is flammable, explosive or reactive with water.

3. Actual processing air volume, number of vacuum points and operating time.

4. Whether there are sparks, high temperature particles, oil mist or corrosive substances.

5. On-site installation space, pipeline direction and power supply conditions.

6. Treatment conditions for wastewater, sludge and circulating fluid.

Wet explosion-proof dust collectors can reduce the risk of suspension, accumulation and secondary dust emission of some combustible dusts, but they cannot guarantee the complete avoidance of dust explosions. The equipment should be specially designed based on dust explosion characteristics, water reactivity, processing air volume and on-site hazardous areas.