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PureLine ClO2 Program Controls
Pathogens and Eliminates Corrosion in a Co-Generation
Cooling System |
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GOAL
To control bacterial growth and bio-fouling
of the surface condenser
while eliminating the destructive corrosion
of critical system components.
SITE
A large co-generation plant in California.
HISTORY
Life expectancy and energy efficiency are
the two most critical factors in protecting
the investment in any co-generation project.
While pathogen control is a must, biologically-influenced
corrosion and
bio-fouled heat exchangers are prevalent problems
that cause irreversible damage to equipment
and reduce heat-exchange efficiency. Producing
cost-effective electricity is the primary
goal of any power plant. Maintaining slime-free
waterside surfaces is crucial to achieving
this goal.
A large California co-generation plant was
using reclaimed municipal sewer water as cooling
tower make-up. The nutrient content and general
organic loading associated with the reclaimed
water, combined with the atmosphere in cooling
tower operations, created a perfect environment
for the
growth of bacteria.
PROBLEM
The rapid growth of bacteria, coupled with
the large volume of make-up water required
by the cooling operations, made the application
of non-oxidizing biocides much too costly.
The plant’s only option was to feed oxidizing
biocides—both chlorine and bromine—into
the system. However, the demand on these products
required very high feed dosages. While sodium
hypochlorite (bleach) fit the plant’s
operating budget, mild steel corrosion rates
were more than 12 mils per year. These rates
not only exceeded the plant’s target
goal of less than 3 mils per year, they were
nearly 3 times the industry standard of less
than 5 mils per year. The use of bromine lowered
the mild steel corrosion rates to between
6 and 8 mils per year. Yet, even these reduced
levels remained above industry standards.
In addition, it was determined that using
bromine was cost prohibitive. The plant also
incurred higher costs for inhibitor chemistries.
Studies indicated that higher inhibitor costs
were directly attributed to chlorine and bromine
attacking the chemical integrity of these
formulations. The dosages of bromine or bleach
required to keep conditions in check were
actually causing aggressive corrosion. This
problem would seriously reduce the projected
30-year life span of the power plant and jeopardize
the projected return on investment.
Since going online, the plant had used every
applicable biocide available. Yet, the traditional
biocides were all considered a failure due
to their high costs, product incompatibilities
or adverse affect on system metallurgy.
SOLUTION
 PureLine
Treatment Systems offered a full-service chlorine
dioxide program using a P-3M Series: Chlorite Based Chlorine Dioxide Generator combined with an innovative, proprietary
control system. After a thorough study of
the co-gen plant’s operations and biological
activity, PureLine worked with the water treatment
service provider to develop a more suitable
biocide program. Since its implementation,
the program has maintained system hygiene
and slime-free waterside surfaces while reducing
mild steel corrosion rates below 3 mils per
year. The projected life expectancy of all
the co-gen facility’s cooling equipment
is now on or above the 30-year target. Additional
program evaluations have proven both biocide
and inhibitor costs have dropped while all
aspects of program efficacy have improved.
Technical studies indicate that these improvements
are directly attributed to three factors:
chlorine dioxide’s effectiveness at low
residuals even in highly contaminated waters;
chlorine dioxide’s compatibility with
inhibitor treatment products; and chlorine
dioxide’s low oxidizing potential which
makes it react less aggressively with the
system metallurgy.
Pure chlorine dioxide was generated using
a traditional three-chemical, wet chemical
generator. PureLine’s full-service chlorine
dioxide program combines professional on-site
service with innovative, site-specific controls
designed to ensure proper operation and treatment
at all times. The client now enjoys hands-off
biocide feed and control of biological activity.
A state-of-the art control system maintains
program efficacy without wasting plant resources
or jeopardizing system metals.
RESULTS
Since implementing the PureLine program, corrosion
has been significantly reduced compared to
the results produced by previous treatment
approaches. The program has provided excellent
corrosion protection while maintaining the
plant’s high standards regarding biological
control. Chlorine dioxide is more cost effective
than the bromine-based program the co-gen
plant formerly used, and it eliminates the
corrosion problems associated with both bleach
and bromine. Additionally, plant personnel
have been freed-up from the risks associated
with chemical handling, as well as time-intensive
daily testing. Now plant personnel spend less
than five minutes per day monitoring and controlling
the plant’s biocide program.
CONCLUSION
PureLine’s innovative full-service program
hasn’t required any capital investment,
and provides the desired efficacy without
compromising the plant’s operational
budget. Meeting and surpassing industry
standard corrosion rates has helped assure
that the co-gen plant will deliver its intended
return—possibly hundreds of thousands
of
dollars—on its capital investment. |
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