Page 149 - Boiler plant and distribution system optimization manual
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134 Boiler Plant and Distribution System Optimization Manual
then let it sit idle for long periods; this is wasteful. Advantages/Disadvantages
A longer firing time with lower losses makes more On/Off Controls are simpler, with a lower
sense. Caution may be needed at low firing rates first cost and can be tuned up easily. However,
where the exhaust gas temperature is depressed they waste energy with higher stack temperatures
below the acid dew point which can cause dam- and standby losses. The more complex and more
age to the boiler, breechings and stack. expensive modulating controls can overcome this
problem.
20. REPLACE ON/OFF CONTROLS WITH
21. CONVERT TO AIR OR STEAM
MODULATING CONTROLS.
ATOMIzING BURNERS.
Cost Cost
Moderate Moderate
Potential Savings
Potential Savings
Moderate 2%-8%
Moderate
Description
Description Steam or air atomization allows the firing
Replace on/off type of burner control with of a wide range of fuels and high turndown ap-
controls that can modulate and match load con- proaching 20:1 instead of 4:1, and good efficiency.
ditions, reducing higher stack temperatures and Air and steam atomization produces an aerosol in
standby losses. On/off equipment must be set to which fine droplets are supported by an expand-
match the highest expected demand and when ing cone of air/steam and there is less sensitivity
the demand has been satisfied the equipment to oil viscosity changes. It also allows more flexi-
must shut off. Exhaust temperatures are lowered bility in shaping the flame to conform to furnace
by matching the firing rate to actual demand. conditions.
Also, the losses associated with purging the boil-
er before and after each firing cycle could be elim- Advantages/Disadvantages
inated by having fewer on/off cycles. Table 10.4 The cost of installing and operating a com-
shows typical efficiencies and the enhancements pressed air or steam atomizing system may be
of this type of load matching. a disadvantage. The steam used for atomization
is lost up the stack and its energy must be con-
sidered. Offsetting this is improved performance
turn down ratio and fuel versatility, especially if
fuel quality tends to vary.
22. FUEL OIL VISCOSITY MANAGEMENT
Cost
Low
Savings
Moderate
Description
The design of the atomization system is
Table 10.4—Control system Performance comparison. based on certain fuel oil properties, primarily
