[general-purpose] [dust-tight] [explosion-proof] enclosure.
2.3.1.5
Hoppers
Hoppers shall be constructed of steel plates not less than 6.4 mm 1/4 inch
thick and shall have a capacity of not less than [_____] kg pounds per
feeder. Hoppers shall be provided with cleanout doors in the front of each
feeder. Coal feed to the hoppers shall be fitted with concave type
transitions to ensure the proper distribution of coal and coal fines across
the width of the hoppers. Stoker front plate shall form the front of the
boiler for the full width of the boiler and from the firing floor to some
point above the stoker where it shall connect to the boiler structural
framing. Front shall be cast-iron or steel plate refractory lined with
[auxiliary firing doors and] cleanout doors of refractory lined cast-iron.
Structural framing as required shall support the stoker and its components
from the boiler foundation or boiler room floor. The area under the grates
shall be divided into not less than four air-tight zones for supply of
forced draft having zone control dampers with external indicating operating
and locking devices. All pressure parts for water-cooled grates including
watertubes, headers, and valves furnished by the stoker manufacturer shall
be for boiler pressure specified and shall be constructed in accordance
with ASME BPVC SEC I.
2.3.1.6
Air Systems
Spreader stokers shall be provided with over-fire turbulence and cinder and
dust reinjection systems. Either air or steam can be used as the transport
medium. Air systems shall be provided with operating air by a single, low
volume high-pressure fan driven by a splash-proof electric motor. The
reinjection system ejectors shall be properly designed, located, and sized
for maximum fly ash pickup from all points. Nozzles for each system shall
be equipped with manometer connections and heavy-duty adjustable dampers
fitted with locking devices and position indicators. Nozzles shall provide
maximum combustion efficiency and furnace turbulence. A manometer
connection and a permanent manometer shall be provided immediately
downstream from the main reinjection air supply damper. A portable
manometer shall be provided.
2.3.2
Underfeed Stokers
2.3.2.1
Ram-Type Stokers
Single retort, heavy-duty ram-type stokers shall be equipped with
stationary or moving grates and side dump plates, and shall be provided
with electric motor drive and all necessary auxiliary equipment. Dumping
power cylinders shall be compressed air actuated. Stokers shall be capable
of handling the coal specified. Coal shall be fed from the hopper into the
retort by means of a ram and shall be evenly distributed along the full
length of the retort with auxiliary pusher blocks on a pusher rod located
at the bottom of the retort and actuated by the coal ram. Dampers shall be
provided between ash pits and main air chamber under stoker to permit
control of air distribution to the grate surface. Dampers shall be
arranged for operation from the front plate of the boiler. Air
distribution shall be such that the air pressure is greatest where the fuel
bed is the thickest. Air quantity shall vary in direct proportion with
coal feed rate and shall be controlled automatically.
SECTION 15555A
Page 30
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