Page 222 - Boiler plant and distribution system optimization manual

Boiler Plant Calculations 207

5. If the estimate to install a new boiler is $72,000, what is the payback period and
return on investment if the new boilers life is 20 years.

First Cost 72,000
Payback Period = ————— = ————— = 1.5 yr.
Savings $48,250

Savings - Cost/life yrs
Return on Investment = ———————————
First Cost

48,250 – 72,000/20
ROI = ————————— = 62%
72,000

PROGRAMMING BOILER OPERATIONS 1. At 100 psig what is the total heat in the
steam?
The purpose of this example is to show the (Ans.: 1189.6 Btu/lb)
wisdom of conducting efficiency tests of boilers
2. What is the latent heat of 100 psig steam?
then setting up a program for the most econom-
(Ans. 880.7 Btu/lb)
ical operation possible. For this example three
100,000 Pounds Per Hour (PPH), (50 Ton) (100 3. What is the sensible heat in boiler water at
million Btus/hr) units are used. 100 psig?
(Ans.: 308.9 Btu/lb)
1. Review the efficiency profile of Boiler #1.
(Figure 11-1)

2. Review the efficiency profile of Boiler #2.
(Figure 11-2)

3. Review the efficiency profile of Boiler #3.
(Figure 11-3)
4. Review the combined efficiency profile of
boilers #1, #2 and #3. How would you pro-
gram these boilers to insure maximum econ-
omy in the boiler plant? (Figure 11-4)
5. Review the graphic of combined boiler op-
eration between 20 and 300 thousand PPH.
(Figure 11-5)

INTRODUCTION TO THE STEAM TABLES
FOR ACCOUNTING FOR ENERGY

The purpose of the following examples is to
illustrate how to account for energy in steam sys-
tems. (See Tables 11-18 and 11-19.) Figure 11-1