Page 214 - Wastewater Solids Incineration Systems

180 Wastewater Solids Incineration Systems

conveyance equipment. Both systems typically convey dry ash to storage bins. While
ash is being discharged from the bins to disposal trucks, it is typically wetted with
water to reduce fugitive dust during the loading process. This “wetting” is com-
monly called ash conditioning. The ash is then transported to the ultimate disposal
site or is recycled. Dry conveyance systems are common on MHFs because the
majority of ash is removed in dry form as bottom ash.
Dry conveyance systems are also suitable on fluid bed incinerators that are cou-
pled with baghouses or electrostatic precipitators because the majority of the fly ash
is captured in dry form.

3.2.1 Conveyance
3.2.1.1 Mechanical Conveyance Systems
Mechanical conveying systems frequently transport ash from the discharge point at
the bottom of MHFs to ash storage bins. A vertical chute in the bottom of the inciner-
ator will discharge ash into a clinker breaker. The clinker breaker will break up large
pieces of slag, refractory, or other large items that may be discharged with the bottom
ash. Not all facilities currently in operation use clinker breakers. Some installations
use a simple clinker separator with a sloped bar screen device to catch clinkers and
allow them to roll off into a small hopper adjacent to the ash chute.
Clinker breakers can become jammed with large items. If the clinker breaker
becomes jammed, then an alarm is needed to alert the operator. Clinker breakers
should be equipped with a removable inspection plate. The inspection plate can be
taken off, the object causing the jamb removed, and the clinker breaker restarted. If a
clinker breaker or separator is not installed, then a large object could cause a jam in
downstream conveying equipment, such as screw conveyors or bucket elevators.
Following the clinker handling, the ash typically either discharges directly to a
bucket elevator or to a screw conveyor. If used, a screw conveyor would transport the
ash to a bucket elevator. The bucket elevator will lift the ash vertically to the top of
an ash bin where it discharges to another screw conveyor. This conveyor then trans-
ports the ash to a discharge point at the top-center or directly to the ash bin. The size
of the ash bin and conveying equipment should be sized for maximum loading of the
incinerator. The ash bins commonly have some type of vibratory device mounted to
the side or bottom of the vessel to facilitate discharging to the dump truck below. Bin
vibrators or an activator may be used.
At the bottom of the ash bin is another device that can convey ash from the
storage bin to a truck and simultaneously wet the ash. This device, referred to as a