Page 131 - Boiler plant and distribution system optimization manual

116 Boiler Plant and Distribution System Optimization Manual

Advantages/Disadvantages Most boilers do not have a straight line ef-
If you intend to manage a boiler plant and ficiency and operate at different efficiencies de-
control losses, regular tuneups and combustion pending on their firing rate and this must be con-
efficiency checks are necessary. It takes skilled sidered when programming their operation (Fig-
manpower to run these checks and this is an ad- ure 10.10).
ditional expense so judgment should be applied Boilers can have different efficiency levels
to establish the benefit to cost ratio of such a pro- at different load points. At the high end the effi-
gram. ciency may fall off because of high exhaust tem-
peratures. At low loads efficiency may go down
(Very Important: All energy conservation options because of higher excess air needed for proper
should be evaluated from the tuned-up condition to air-fuel mixing. At mid range the efficiency is
eliminate false estimates of the benefits of retrofit op- very good; so what efficiency do you pick to de-
tions.) scribe its efficiency?

4. OPERATE BOILER AT 5. LEAD – LAG BOILER CONFIGURATION
HIGHEST EFFICIENCY LEVELS.
When setting up automatic operations make most
Description efficient units “Lead” elements and less efficient
Having specific efficiency information for units “Lag” elements.
each boiler, they can be matched to loads for most
efficient utilization. Also, by using smaller boil-
ers, which maintain high efficiency during very 6. OPERATE BOILERS AT
light load periods, losses associated with larger LOWER STEAM PRESSURES
boilers can be eliminated. The general answer is
to use the most efficient boiler combinations pos- Lowering Steam Pressure
sible to match system demands. 1. Boiler exhaust temperatures are lower

Figure 10.10—Boiler efficiency often varies with load and other operational influenc-
es. Long term information comparing fuel burned to steam or hot water generated is
needed to understand the true operating efficiency. Quick snap-shot tests are not suit-
able for obtaining the true efficiency.