less than that specified for the boiler and shall satisfactorily provide
for automatic operation, by means of a combustion control system, within
the range given when burning specified coal and operated in accordance with
manufacturer supplied instructions. Satisfactory operating conditions
shall be obtained throughout the full operating range of the stoker.
Stoker shall be considered as an integral part of the steam generator and
shall be subject to applicable provisions of the boiler design and service
conditions together with requirements of tests, performance guarantees and
other warranties specified for the boiler. Coal analysis shall be as
specified in the Coal Analysis Schedule for the boiler.
2.4.1
Stoker Grate Area and Heat Release Rate
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NOTE: The designer shall refer to the graph of
Stoker Allowable Rating - Percent Of Full Load
Rating Versus Ash Fusion Temperature shown in NAVFAC
DM-3.6, NAVFAC Design Manual, Figure 11 and select
the appropriate combustion rate.
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Provide a grate with area sufficient to give specified steam output when
burning specified coal. Grate shall fit between furnace side wall headers
and between the inside face of the front wall and face of the bridge wall.
Maximum stoker heat release rate shall be not greater than [_____] watt per
square meter Btu per square foot per hour at the specified maximum
continuous rating for the boiler.
2.4.2
Construction
2.4.2.1
Coal Fuel Feed Control
Provide a stoker ram with a constant stroke for feeding fuel to the central
retort and necessary auxiliary rams or pushers to secure an even
distribution of fuel throughout the entire length of the retort and over
the grate surface. Determine rate of coal feed by the length of the rest
period between full strokes. Provide for control by adjustment at a single
point. Design stoker controls for connection to a combustion control
system.
2.4.2.2
Coal Hopper
Provide a [_____] mm inch thick Type 316 stainless steel coal hopper having
a capacity of not less than [_____] kg pounds at the front of each stoker.
2.4.2.3
Stoker Front Enclosure
Provide stoker front with dusttight enclosure of cast iron, or not less
than 10 gage steel plate, of height and width to match boiler front to
eliminate dust from the boiler room and prevent air infiltration to grate.
2.4.2.4
Stoker Grates
Grate surface shall consist of air cooled lateral firebars or grates
inclined downward from the central retort toward side walls of furnace.
Provide for agitation of fuel bed by either an alternating arrangement of
moving and stationary grate bars or an undulating grate bar motion. Moving
grates shall be adjustable to obtain the degree of movement necessary to
suit characteristics of the fuel. Adjustments shall be capable of being
SECTION 15501N
Page 49
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