Page 136 - Boiler plant and distribution system optimization manual

Over 100 Ways to Improve Efficiency 121

These heating coils may still be active or may Advantages/Disadvantages
just be sitting there in the air intakes obstructing Soot blowers can do an effective job of keep-
air flows. A check with the boiler manufacturer ing heat exchange surfaces clean and have been
may disclose that these old air preheating sys- used for years. The cost of steam and compressed
tems can be removed saving on steam, mainte- air to run soot-blowers can be very high so close
nance and fan power. control of their use is recommended.

18. SOOT BLOWER OPERATIONS 19. SHUT-DOWN BACKPRESSURE
STEAM TURBINE DURING LOW
Cost STEAM LOAD PERIODS
Routine operational activity
There may be a risk of over pressurizing the
Potential Savings exhaust system of a backpressure turbine being
Moderate used to let steam down to a lower pressure head-
er or system. In the case where this exhaust steam
Description can not be utilized it may well be being dumped
The rule of thumb applies: every 40 degree to atmosphere through a pressure relief valve.
decrease in net stack temperature saves about Occasionally this is evident by a large plume of
one percent in fuel consumption. Soot is an ex- steam venting out through the roof of a plant.
cellent insulator which can retard heat transfer to This is especially evident when standby turbines
a great degree, so soot blowers are used to keep are kept spinning at a low load, the exhaust steam
heat exchange surfaces clean to maintain lower has got to go somewhere.
stack temperatures and higher efficiencies. Also,
there is more of a tendency to form soot with the
heavier residual type fuels. On the other hand, 20. UTILIzE FUEL ADDITIVES TO
soot blowing is an expensive proposition when IMPROVE OPERATING CONDITIONS
you consider the loss of energy involved to just AND ECONOMY
keep the tubes clean. It can cost from 50 to 200
thousand dollars a year for a single boiler, so it is Class I—Improved storage and handling
important to manage soot blowing properly. Both • Sludge and gum inhibitors
too little and too much soot-blowing can waste • Detergents
significant amounts of energy. When low excess • Metal deactivators
air levels are maintained, keeping heat exchange • Corrosion inhibitors
surfaces clean becomes a greater challenge be- • Pour-point depressors
cause the burners are operating closer to their • Anti-static
smoke point. Soot blowers are usually installed • Anti-icing
on water tube boilers, but they are also available • Color stabilizers
for fire tube type units on special order for appli-
cations such as black liquor and other dirty fuel Class II—Improved Combustion
type service. Some plants have even had success- and pollution reduction
ful results with a large ship’s fog horn to remove • Smoke
deposits with low frequency vibrations. They are • Particulates
less expensive to operate than the conventional • Carbon monoxide
units, but their performance has had mixed re- • Hydrocarbons
views. • Nitrogen oxides
• Sulfur oxides