separation and gravity dump bottom gates to open with interruption of
vacuum and discharge into a silo. Design system so that suction is
positively shut off from receiver during its dumping period, so that no
dust can be sucked out through exhaust while discharge of the receiver is
open or opening. Air from the primary receiver shall enter the external
secondary separator which shall remove approximately 85 percent of the dust
not collected by the primary receiver. Combined efficiency of primary and
external secondary separators shall be not less than 95 percent. Provide
completely contained gate assemblies in a dust-tight enclosure fitted with
access doors large enough to remove the entire gate assembly. Provide
receivers of hard abrasion-resistant cast alloy iron with a Brinell
hardness of not less than 500 constructed as specified below:
2.11.12.1
Primary Receiver-Separator
Not less than [914] [1219] mm [36] [48] inches inside diameter with cast
sections 19 mm 3/4 inch thick and 50 mm 2 inch thick impingement section.
Cylinder, along with discharge hopper shall be of segmental bolted
construction. Construct receiver to ensure dropping of maximum quantity of
solids from transporting air. Provide carbon steel outlet pipe and
discharge gate. Receiver-separator shall have an internal baffle assembly
to prevent reentrainment of ash.
2.11.12.2
Secondary Separator
Not less than [406] [508] [610] mm [16] [20] [24] inches inside diameter of
not less than 8 mm 5/16 inch thick one piece construction with at least 13
mm 1/2 inch thick inlet wear section. Design receiver to minimize
carryover of fly ash into the [air washer] [tertiary bag filter].
Separator shall have an internal baffle assembly to prevent reentrainment
of ash once it has fallen into the collection hopper of the separator.
2.11.12.3
Dusttight Enclosure
Support primary and secondary receivers on not less than 6 mm 1/4 inch
thick, dust tight, carbon steel support boxes with hinged access doors or
removable panels on each side for servicing the receiver swing gates.
Provide support box with airtight roller bearings, hinged, counterweighted
swing gates with removable neoprene seals. Gates may as an option, be air
cylinder operated gates in lieu of the counterweighted gates.
2.11.13
Mechanical Exhausters
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NOTE: When environmental restraints, availability
of steam or water or economics preclude the use of
steam exhausters, use a mechanical (electrical
driven) exhauster with a pulse jet bag filter to
produce the required system air flow.
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Provide two, V-belt drive, positive displacement, blowers with electric
motors and accessories with each capable of producing a vacuum of at least
41 kPa 12 inches of mercury and with air flow necessary for handling ashes
through the system. One blower (exhauster) shall be used as a prime mover
and the other as a standby unit.
SECTION 15501N
Page 99
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