Page 218 - Boiler plant and distribution system optimization manual

Boiler Plant Calculations 203

ANALYzING COSTS AND BENEFITS OF AN Part II: Economic analysis, Payback Period
ECONOMIzER AND AN OxYGEN
TRIM SYSTEM FC
Payback Period PP = ————
S – C
Part 1: Economic Analysis, Estimating Percent
Savings and Dollar Savings PP = Payback period
PC = First cost
As found conditions: S = Annual fuel savings
Fuel Natural Gas C = Annual maintenance costs
Annual Fuel Bill $100,000
Oxygen O 2 11.0% Option 1. Calculate payback period for the oxy-
Net stack temperature 600F [316C] gen trim system if the maintenance cost is $1,000/
Efficiency 70.3% yr.

Option 1. Install an Oxygen Trim system with an 10,000
PP = —————— = ————YR.
installed cost of $10,000 to reduce excess air to 11,700-1,000
2.0%.
(Ans.: .93 YR.)
New oxygen O level 2%
2
Net stack temperature 600F [316C]
New efficiency 79.6% Option 2. Calculate payback period for an econo-
mizer if the maintenance cost is $1,000/yr.
1. Efficiency Improvement ______%
(Ans.: 9.3%) 30,000
PP = —————— = ————YR.
16,000-1,000
2. Percent Fuel Savings ______%
(Ans.: 11.7%)
(Ans.: 2.0 YR.)

3. Fuel Savings Dollars $______/YR
(Ans.: $11,683/YR)
Part III: Economic Analysis,
Return on Investment
Option 2. Install economizer with an installed
cost of $30,000 to reduce stack temperature to
Return on investment
200F.
S-DC
Oxygen O level 11.0% ROI (%) = ——— x 100
2
Net stack temperature 200F [93C] PC
New efficiency 83.7%
ROI = Return on Investment
4. Efficiency Improvement ______% S = Annual fuel savings $/Yr
(Ans.: 13.4%) DC = Depreciation charge
First cost/Estimated Lifetime
5. Percent Fuel Savings ______% PC = First Cost
(Ans.: 16%)
Option 1. Calculate the ROI for the oxygen trim
6. Fuel Savings Dollars $______/YR system if the estimated lifetime is 15 years:
(Ans.: $16,000/YR)