enclosures,] iron alloy conveyor line, fittings, rotary slide gates,
primary and secondary material separators, tertiary bag filter, [steam
exhauster,] [electric motor driven positive displacement blower (mechanical
exhauster),] [air washer,] silo vent filter, ash silo, rotary ash
conditioner, and equipment that may be necessary for a complete pneumatic
ash handling system. Provide related electrical work required to operate
the ash handling system. Design system so that the ash silo is never
placed under a partial vacuum.
2.11.2
Type
System shall be the intermittent vacuum type, whereby the vacuum is
interrupted permitting periodic discharge of collected materials into the
silo on a programmed time cycle. System shall have sufficient air velocity
to pick up ash that may be deposited in the pipe.
2.11.3
Ash Silo
System shall receive, and on a sequenced basis convey to the ash silo, ash
from the stoker fired boiler [ash storage hoppers,] [ash storage pits,]
[siftings hoppers,] [soot hoppers,] [economizer hoppers,] [baghouse
hoppers,] and other pollution control equipment hoppers. Convey ash from
only one pickup point at a time.
2.11.4
Ash
Discharge ash into the ash storage silo in a dry condition. Arrange silo
equipment for disposal of conditioned ash to trucks. The operation shall
be as nearly dustless as possible.
2.11.5
Maximum Noise Level
The noise level of the operation shall not exceed 85 decibels sound
pressure level 1.50 meters 5 feet from the equipment in any direction.
2.11.6
Dry Ash Storage Hopper
Provide for each boiler to receive and store bottom ash as it is discharged
from the traveling grate. Hopper shall be compatible with the grate ash
discharge enclosure and shall have a net volume to receive and to store
material for an 8 hour period at maximum boiler output. Size hopper for
mean ash level for one meters 3 feet below the stoker floor with ash
density of 640 kg per cubic meter 40 pounds per cubic foot for volumetric
sizing.
2.11.6.1
Construction
Not less than 6 mm 1/4 inch thick, ASTM A 36/A 36M, steel plate, dusttight,
floor supported steel structure with refractory lining. Provide required
steel columns, beams stiffeners and cross bracing. Bolt top section of
hopper to stoker support steel. Base design load of hopper on 1120 kg per
cubic meter 70 pounds per cubic foot. Slope sides at not less than 45
degrees from horizontal to maintain positive feed to outlet.
2.11.6.2
Refractory Materials
As recommended by the manufacturer; minimum total thickness of refractory
and insulating block lining shall not be less than 178 mm 7 inches.
Refractory shall be minimum of 114 mm 4 1/2 inches thick.
SECTION 15501N
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