Page 231 - Boiler plant and distribution system optimization manual

216 Boiler Plant and Distribution System Optimization Manual

BOILER BLOWDOWN HEAT RECOVERY Btu/Day x cost/gal
$ saved/day = ————————— =
Btu/gal x E
The purpose of this section is to demonstrate
the potential savings available from managing
(E = Boiler efficiency = 75%)
the boiler water system.

Dollar savings = ..............................................
[Answer: 13.9 Million Btu/Day x
1. Flash Steam Recovery:
$1.00/140,000 x.75 = $132.90/Day]
What percentage of blowdown will flash to
steam at 5 psig from the blowdown of a boiler op-
4. Heat exchanger recovery
erating at 150 psig?
The heat exchanger now reduces the blow-
h – h 2 down water temperature to 90F, how many
1
% Steam Flashed = ——— Btus a day can be recovered from this water?
V 1
Btu/DAY recovered = Blowdown (lb/day) x
h Heat in water leaving boiler. 1- % flashed x h -h =
1
4
2
h Heat in water at flash pressure.
2
V Latent heat of steam at flash pressure. Heat in water at flash pressure (5 psig)...........h =
1
2
_______
[Answer: 195.5 Btu/lb]
STEAM TABLE INFORMATION
Heat in water at heat exchanger outlet (90F)....h
4
Boiler pressure 150 psig h = ____ = _______
1
[Answer: 338.4 Btu/lb] [Answer: 58 Btu/lb]
Flash tank pressure 5 psig h = ____ Btu/day recovered = ....................... = ..............
2
[Answer: 195.5 Btu/lb] [Answer: 9.35 Million

Latent heat of steam at 5 psig V = ____
1
[Answer: 960.5 Btu/lb] Dollar Btu/Day] x $1.00
savings/= —————————— = ————
day 140,000 Btu/GAL x .75
% Steam Flashed= ______ [Answer: 15%]
[Answer: $89.05/Day]
2 How many Btu/day will be recovered from
the flash tank if the daily blowdown is 80,000 5. Total value of blowdown heat recovered:
lb/day.
Flash steam $—————/day
Btu/day = % steam flashed x blowdown lb/ [Answer: $132.90/Day]
day x (Btu/lb @ 5 psi Steam) = (At 5 psig the
energy in the flash steam is 1156 Btu/lb) Heat Exchanger $—————/day
Btu/day= ..................................................... [Answer: $89.05/Day}
[Answer: Btu/Day = .15 x 80,000 x 1156 =
13.9 Million Btu/day] Total $—————/day
[Answer: $221.95/Day]
3. If you are firing a boiler with no. 2 oil with
140,000 Btu/gal which costs $1.00 per gallon, Annual Savings $—————/Yr
how much money can be saved in a day? [Answer: $81,011.75/Yr]