MIL-HDBK-1003/6
Fuel Considerations. Soot blowers shall be provided on boilers
10.4.2
burning solid fuels or heavy oils. They may be required when firing no. 2
fuel oil. Gas-fired boilers do not require soot blowing equipment because gas
is a clean burning fuel. Consult with the boiler and soot blower manufacturer
for specific design requirements.
Spreader Stoker Boilers. The heating surface of a spreader stoker
10.4.3
boiler is generally cleaner than other types of fired boilers. This is due to
scrubbing action of cinders and fines carried along in the flue gas. To avoid
a sand blasting effect on tube wall surface, due to high velocity cinders and
fines, minimize the soot blower's blowing time.
Medium (Compressed Air or Steam). Steam or compressed air can be
10.4.4
used for soot blowing. The designer should determine the most cost effective
medium. Operational costs of the soot blowers depend on utility costs.
Air-Puff Soot Blowers. An air-puff soot blower operational cost
10.4.4.1
will be competitive with steam and it may have a lower first cost. The air-
puff soot blower has a smoother cleaning curve. When evaluating steam and
compressed air soot blowers, take into consideration the air requirements and
the plant air capacity. Include, in the cost evaluation, the cost to increase
the plant compressed air system to meet the additional load of the air-puff
soot blower system.
Air-puff soot blowers dislodge less soot and other matter during
each cycle. Air-puff soot blowers help reduce stack emissions due to
overloading the dust collectors. Small puffs provide more stable boiler
operating conditions and reduce fluctuations in furnace draft experienced with
multiple blowers.
Compressed Air Usage: Air flow through each blower nozzle can be
calculated by an approximate formula (Baumeister, et. al. 1978)
m = 0.53(ACP)//T
(22)
EQUATION:
where:
m
=
discharge in lbs/sec
area of orifice in ft2
A
=
C
=
coefficient of discharge
upstream pressure in lbs/in2 absolute
P
=
T
=
upstream temperature in deg R
Example: A 100,000 lbs/hr steam boiler equipped with compressed air soot
blowers requires the following amount of air:
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