Page 47 - Boiler plant and distribution system optimization manual

32 Boiler Plant and Distribution System Optimization Manual

Table 3.4—Saturation or boiling temperature S is the potential fuel savings per year.
change with boiler pressure.
W is the fuel use rate in million Btu/Hr
f
E is the ideal efficiency
I
E is the new or existing efficiency
n
C is the cost of fuel per million Btu
f
Hr is operating hours per year

Because boiler efficiency usually chang-
es with load, the potential for fuel savings will
change with the typical load on the boiler based
on the ideal or reference efficiency at the load be-
ing considered. This formula can be used for es-
timating energy saving at the typical load under
study.

Example: a boiler is firing at 100 million Btu/
Hr and its efficiency had dropped from the ideal
of 83% to 78%. The cost of fuel is currently $6.00
per million Btus and it fires at this load for 6,000
hours a year.
This loss of efficiency will cost an estimated
$230,400 in wasted fuel for the year if this loss of
efficiency remains uncorrected.
The actual fuel savings percentage is always
larger than the efficiency increase. Similarly the
fuel loss percentage is always greater than the CARBON DIOxIDE REDUCTION
corresponding efficiency decrease.
The formula for fuel savings or loss resulting The basic data on carbon dioxide emissions
from the change in efficiency is: from different fuels published by the Office of

Global Change of the Environmental Protection
——————————————————————— Agency:
New Efficiency – Old Efficiency
Savings = ————————————————
New Efficiency Lbs per
——————————————————————— Fuel Million Btu
Natural Gas 117
Fuel Oil 173
CALCULATING PERFORMANCE Coal 215
DEFICIENCY COSTS

The cost benefit of maintaining boiler effi- Quick Reference Charts
ciency at a high level is easily calculated with this It is useful to have a quick way to estimate
formula: potential fuel savings based on improvement in
either net stack temperature or excess-air. Figures
W f x E – E x C x Hr 3.2 and 3.3 can be used as a quick reference for
I
f
n
S = —————————————
E n estimating savings potential