Quarries, Rock Dust, Sand and Gravel

AeroPulse, Inc. has sold many units on quarry applications. There is no great mystery in how these units will operate on quarry operations. They would generally be handling nuisance rock dust from bucket elevators, screw conveyors, belt transfer points, and vibrating screens. We will list some typical CFM requirements for pieces of equipment used in the rock industry. We like to operate at a filter rate between 6 or 7 to 1 on nuisance rock dust.

These units need not be insulated and polyester bags are adequate for this application since no temperature is involved.

Listed below are some of the CFM values that would be required for each piece of equipment in a rock quarry:
1. The end of a belt conveyor. “A hood must be put over the end of a belt conveyor at the point where it discharges. It has a tendency to have a fan effect at this point and have this dust be thrown into the air.” Use 500 CFM per foot of belt width. Example: a 36” wide belt would require 1,500 CFM.

2. A dump point on a belt conveyor. This is commonly known as a transfer point where one belt dumps on to the other belt. Use 1,000 CFM for any dump point. (If the 3 foot belt described in Item 1 were dumping onto another 3 foot belt, you would require 1,500 CFM at the discharge of the upper 3 foot belt section and 1,000 CFM at the dump onto the lower belt).

3. A vibrating screen – 50 CFM per square foot of screen deck (top deck only) Example: 4 ft. x 10 ft. vibrating screen vented by 2,000 CFM.

4. Bucket Elevator. Take the cross sectional area of the bucket elevator and multiply by 100 CFM. Example: 2 ft. x 4 ft. bucket elevator requires 800 CFM.

Crushers. Most cone crushers can be vented by approximately 3,000 CFM.

6. Impactors. Most impactors can be vented by 4,000 to 6,000 CFM depending on the size of the impactor. A 4 ft. impactor would be vented by approximately 4,000 CFM.

7. Cage Mill. These mills work like a very efficient fan and can require as much as 10,000 CFM to vent. Please contact the home office and give us the diameter of the cage mill and the rpm if at all possible.

8. Bins. Bins must be totally enclosed and once they are enclosed, they can be vented by approximately 350 cfm or a 4 ft. line.

9. Dryers. Usually the Dryer Manufacturer can give you the amount of cfm required to vent a dryer. Be careful that you do not mix the air from a dryer unequally with the air from a nuisance dust system. The air from a dryer is moist, humid air and could be converted into water on the bags if it is mixed with too much cold air from a nuisance dust system. It is best to use a separate collector on a dryer if at all possible. It frequently is best to insulate collectors on dryers. Also filter rate can vary between 5 to 1 and 6 to 1 depending on the weight of the material being dried and its fineness.

I have listed the main equipment above that you see in a crushing plant, but there are also other types of equipment seen in a quarry plant.