Chemical Engineering July 2013 - 21

CLEANING BEYOND
THE COOLING TOWER
W
ith so many processors using reclaimed
water, the challenge becomes
how to treat a reclaimed
water source and turn it into useable
water, notes Kaveh Someah, global director
for the oil and gas industries with
Ovivo USA. " Reclaimed water is often
high in nutrients, which can cause microfouling
that leads to slime on the heat
exchangers. High salt, phosphate and
ammonia levels may coat metals and
create cracking in equipment, so proper
treatments must be found. "
Traditional processes for handling
these issues might include combinations
of biological, physical and chemical
treatments. For example, multimedia
filters might be used to remove total suspended
solids and floating solids. Then,
nutrients might be removed via a clarifier
or other biological treatment, which
may be followed by reverse osmosis to
remove dissolved solids from the stream.
All this would be done prior to running
the water through the cooling system.
" Although these methods combined
with chemistry in the cooling tower may
prevent scale from forming in the cooling
tower, scale will still eventually form. The
chemicals just delay where the scaling occurs, "
says Someah. " As the water leaves
the cooling tower and heads into the process
equipment where the temperature
rises, the salt precipitates out, which can
lead to scaling. However, an online cleaning
system can be installed inside the heat
exchanger and condensers to prevent
and remove scale and fouling. "
To assist, Ovivo offers the Automatic
Tube Cleaning System, which prevents
scale deposits and microfouling 24
hours a day, increasing reliability, performance,
plant output and service life of
the equipment. The system injects elastomer
rubber balls that are slightly larger
than the tube diameter into the water
supply line so that the flow of cooling
water forces them through the condenser
tubes. The balls wipe the tubes clean of
deposits including silt, scale, and biological
fouling. A strainer section in the
cooling water outlet extracts the balls
and a centrifugal pump moves them into
a collector section where they are ready
for the next cycle. Balls can be recirculated
continuously or intermittently to suit
the plant.
❏
www.thyssenkrupp-uhde.de
Often, processors use a blend of
waters, such as reverse osmosis (RO)
reject water, well water, river water
with suspended solids,
blowdown
water from the boiler or cooling-tower
and municipal wastewater. In addition,
many facilities are being forced
to achieve zero liquid discharge, so the
water sources may be highly concenThyssenKrupp
Uhde
trated. This mixed, impaired water
stream can create a host of challenges,
says Thungstrom.
Adding to the water-source-related
issues are tightening discharge issues.
" Processors now have to deal with
meeting regulations that affect effluent
limitations, such as requirements
that demand lower discharge limits on
phosphorus, nitrogen, and BOD/COD
(biochemical oxygen demand and
chemical oxygen demand), " says Nozi
Hamidi, vice president of marketing
with BWA Water Additives (Atlanta,
Ga.; www.wateradditives.com).
The cost of complying with such
limitations, combined with a global
awareness of environmentally reThyssenKrupp
Uhde -
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into solutions that are not only brilliant and innovative, but often
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CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013 21
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Chemical Engineering July 2013

Table of Contents for the Digital Edition of Chemical Engineering July 2013
