Page 198 - Boiler plant and distribution system optimization manual

Boiler Plant Calculations 183

Example 4.
Fuel Type Wood 30% Moisture
[See Table 11-8]
Oxygen 10%
Stack Temperature 680F [360C]
Air Temperature 80F [27C]
Net Temperature 600F [316C]

Efficiency (Ans.: Loss 30% Efficiency 70%)

CALCULATING FUEL SAVINGS e. Wood Moisture
f. Bagasse Moisture
The purpose of this section is to show how to g. Condensate ad Feedwater System Tempera-
compute fuel savings based on change in efficien- ture Changes
cy. h. Changing rpm of Pumps and Blowers

New Efficiency –
As Found Efficiency
Fuel Savings (%) = ——————————— a. Changing excess air by 10% or oxygen by 2%
New Efficiency changes efficiency by 1%.
Example. Excess air has been improved (re-
Example 1. duced) by 15%, what is the estimated effi-
The as-found efficiency of a Natural Gas ciency improvement? ____________
fired boiler is 73%, the boiler is tuned up to a new (Ans. 1.5%)
efficiency of 75%. What is the percent fuel sav-
ings? ____________
(Ans.: 2.67%) b. Each 40F Change in exhaust temperature
changes efficiency by 1%.
Example 2. Example. Burner problems are causing soot
The Maximum Achievable Efficiency for this accumulations and the exhaust temperature
boiler is about 81.7%. What will the % fuel sav- has risen by 120F. How has this changed effi-
ings be when this is achieved? –––––––––– ciency? ____________
(Ans.: 10.6%) (Ans. lower by 3%)

Example 3.
The Maximum Attainable Efficiency for this c. 0.5% or 5,000 ppm carbon monoxide changes
boiler is about 86.2%. What will the % fuel sav- efficiency by 1%.
ings be when this is achieved? ____________ Example. A small boiler is found to have
(Ans.: 15.31%) 1/4% CO (2,500 ppm). What is the energy
loss? ____________
(Ans. 1/2%) (Note- The legal limit in many areas
ESTIMATING LOSSES AND SAVINGS is 400 ppm CO)

a. Excess Air & Oxygen Changes
b. Exhaust Temperature d. A 10% moisture change in coal changes effi-
c. Carbon Monoxide & Combustibles ciency by 1%.
d. Coal Moisture