Agglomeration for Processing Systems
Dedusting the fine coal dust is another method of disposal. Fine coal dust does not readily mix with water, so a high-speed pin mixer is used to accomplish the dedusting (Figure 2). No additional chemicals are employed.
This mechanical processing produces a mixture which resembles a rich black soil and will ball when compressed in one's hand, but will fall apart when released. This agglomeration process can be used below one filter or in combination with pneumatic transport so one unit can serve several dust collectors to reduce the airborne dust concentration in the silo or area receiving the coal dust. Agglomeration also offers benefits when the coal is going from car dump to outside stockpile where it is very difficult to prevent dispersion of the coal dust in windy weather. The drawback to agglomeration is the greater complexity. Dust and water must flow consistently into the mixer to provide a consistent product. Since flow from a dust collector is not consistent, a surge hopper with sufficient capacity for the 'end of run purge' must be incorporated into the equipment layout with associated pressure relief venting, fire detection, suppression, and level indication. Also, the agglomeration has to be in a heated building for freeze protection.
The agglomerated dust should not be placed on an empty conveyor belt as it can be very sticky nor in a conventional screw conveyor. Agglomerated coal dust must be placed on top of coal on the belt or directly into a bunker or surge bin.