of carbonic acid, which is created when
carbon dioxide is dissolved in the condensate. The major source of CO2 is from the
thermal breakdown of feed water bicarbonate and carbonate within the boiler.
Typical pH levels for condensate need to be
from 8. 2 to 9. 2, or moderately alkaline, for
the condensate to be relatively noncorrosive
to heating system metals. The presence of
acids affects the pH of the condensate. Since
amines are alkaline compounds, they are
used to neutralize carbonic acids and control
the pH.
Adding amines is fine and dandy for
protecting a district heating system’s condensate piping, but what happens when
the steam is used directly for humidification in hospitals, office buildings, university
campuses and district heating systems –
and humans breathe this air or are at least
exposed to these chemicals?
Consequently, only FDA-approved
neutralizing amines are acceptable for
direct steam humidification use. These
include morpholine, cyclohexylamine,
diethylaminoethanol and octadecylamine.
Since most of the above substances are
skin, eye or respiratory irritants, the FDA
and other organizations also have established permissible exposure limits for an
eight-hour day and 40-hour work week
period (table 1).
Stagnant flows or dead-end legs of
piping will accumulate higher concentrations of amines and should be flushed out
periodically to eliminate any exposure
issues if these lines are used for humidification or contact with food. Neutralizing
amines do have a distinct odor of ammonia or a fishy smell at increased concentration levels, so to a certain extent they are
self-alarming, but the American Conference
of Governmental Industrial Hygienists’
concentration threshold to mitigate odors
for cyclohexylamine is 2. 6 ppm.
Now for the results of the quick
IDEA-member survey, which reveals that
most systems contacted use amines,
although some do not:
University of Michigan – Merrill
Willett, plant and environmental
chemistry specialist, and Bill Verge,
associate director – utilities &
plant engineering: Uses four FDA-approved amines and other nonvolatile chemicals (catalyzed sodium
sulfite, sodium hydroxide and an
organic polymer blend). Keeps the
concentration levels well below the
FDA limits and conducts high-grade
monitoring.
University of Wisconsin-Madison –
Dan Dudley, campus utility engineer: Has been using amines successfully for years; steam used directly for
humidification.
University of Minnesota, Twin
Cities – Mike Nagel, energy administrator: Uses FDA-approved amines
for direct humidification; has recently
been promoting indirect steam usage
via steam-to-steam generators to
increase condensate return back to
the boilers.
University of Missouri – Greg
Coffin, superintendent power
plant: Uses steam directly per both
FDA and U.S. Department of
Agriculture regulations (due to meat
processing laboratory) and closely
monitors concentrations.
NRG Energy Center Harrisburg –
Bill Goodwin, senior consultant:
Does not use amines because condensate is not returned back to plant
from each customer.
Citizens Thermal Energy, Indianapolis
– Dave Toombs, general manager:
Does not use amines because condensate is not returned back to plant
from each customer.
Con Ed Steam Operations, New
York City – Vin Badali, business
development manager: Does not use
amines because condensate is not
returned back to plant from each customer.
In closing, any steam system that uses
amines should have a high-grade sampling
and monitoring program; many times an
on-line analyzer is used for this purpose. If
the user does not want to use steam directly,
then using it indirectly with a steam-to-steam generator with a reverse osmosis
water source is an alternate sampling and
monitoring method.
Too bad for me that the University of
Wisconsin-Madison campus steam loop is
not close enough to be extended to our
office. I would love to be able to tap into
the system to help deal with my static
electricity and computer problems. (Our
friends in Orlando probably can’t imagine
such a dilemma.) But after chatting with
our IDEA colleagues, I will at least breathe
easier knowing that the chemicals used
are carefully selected, controlled and monitored. Finally, Bill Goodwin offered some
sage advice – that each district energy
provider should have a planned and prepared
response ready to offer to any customers
with concerns about this issue. As usual,
district energy customers can rest assured
they are in good hands!
Based in Madison, Wis.,
Steve Tredinnick, PE, is
vice president of energy serv-
ices for Syska Hennessy Group,
which has more than 23
locations across the U.S. He
has more than 25 years’
experience related to build-
ing heating, ventilation and air-conditioning
systems. The past 14 years of his work have
been focused on district energy systems.
Tredinnick is a graduate of Pennsylvania State
University with a degree in architectural engi-
neering. He is a member of IDEA and
ASHRAE and is currently immediate past chair
of ASHRAE TC 6. 2 District Energy. Tredinnick
currently serves on IDEA’s board of directors.
He may be reached at stredinnick@syska.com.
Column and previous columns available at
www.districtenergy.org/de_magazine.htm
Also in 1909
The Anglo-Persian Oil Co. was
incorporated following the discovery
of a large oil field in Masjed Soleiman,
Iran. It was the first company to use
Middle East oil reserves.
One barrel of crude oil was 70 cents
($17.11 in 2008 dollars).
Nikola Tesla filed a patent for a
turbine pump that used smooth rotating
disks inside a volute casing. Tesla’s
novel method of fluid propulsion was
based on two basic principles of
physics: adhesion and viscosity.
