Chemical Engineering July 2013 - 22

Newsfront
GE Power & Water
FOOD PROCESSOR USES TECHNOLOGY
TO CONTROL COOLING COSTS
AND WHITE RUST PROBLEM
or one food processor, make-up water hardness was so low, alkalinity so high, and variation
in water chemistry so frequent that white rust - corrosion of galvanized steel - resulted in
capital cost expenditures of $750,000 to replace failed cooling towers.
White rust caused premature failure of galvanized-steel components. A white gelatinous or waxy
deposit often identifies white-rust corrosion. This deposit, a zinc-rich oxide, is porous and generally
non-protective. High alkalinity, high pH and low hardness cause the problem. All of these
conditions existed at this facility and were aggravated by variations in water chemistry that made
control problematic.
The cooling-system make-up water contained 4-6 parts per million (ppm) of calcium hardness,
necessitating high-cycle operation to obtain the minimum 50 ppm calcium hardness recommended
by the Cooling Tower Institute (CTI; Houston; www.cti.org) to prevent white rust. Acid feed was also
required to bring the alkalinity within CTI guidelines.
FIGURE 3. TrueSense Online
for Cooling is an integrated
platform that directly measures
and controls applied chemistries
that are critical for managing
cooling-water efficiency
and preserving key assets in
industrial cooling systems
New evaporative condensers were installed in November 2003, and a very small amount of white
rust became apparent upon inspection months later. Concerned that this condition would result in
further damage to the cooling towers, the plant engineering staff installed Nalco's 3D Trasar system in
January 2004. The technology measures key parameters related to system stress. When upsets occur,
3D Trasar technology takes timely, appropriate, corrective action. It then communicates with system
users, informing them of what happened, as well as the actions taken to compensate.
High-cycle operation required acid feed in order to reduce alkalinity. If the acid-feed system failed,
the tower pH would rise. At higher pH, conditions would be right for white rust formation. Timely attention
to any failure of the acid-feed system was critical to preventing this operational problem. The
automated technology provided alarm notification via cell phone, text message, email, or digital pager,
ensuring the right people knew about any problem immediately and could take corrective action.
Weekly inspections are conducted on the cooling tower and results since installation of the technology
have been excellent. The automation program has been able to better control the system water
chemistry, white rust has been abated and an expected $45,000 per year in cost savings has been
realized. An important key to the success of the program is the alarm notification feature. It contacts
Nalco via cell phone and communicates specific problems so that immediate response can occur.
This has helped keep the program in compliance more than 99% of the time.
No scale or other mild steel corrosion problems have been observed and cost savings have come
from longer expected evaporative condenser life ($25,000 per year), reduced cooling-water sewer
costs ($10,000 per year), reduced treatment chemical costs ($8,000 per year) and labor savings
from reduced testing ($2,500 per year).
❏
Nalco
sponsible use of chemicals, has caused
many processors to pursue controlling
these factors within the plant
rather than passing them on to the
local water treatment facility, which
might be treatment limited or invoke
surcharges for wastewaters with high
levels of certain constituents, says
Hamidi. " This has led to processors
targeting reduction or elimination of
any contributors to the plant effluent
that will tip the limits for phosphorus,
nitrogen and other constituents, " she
says.
" Often,
typical phosphonatebased
cooling water chemistries will
be the largest contributor of phosphorus
and nitrogen, and therefore will
spur substitution to 'P-free and N-free'
cooling-water treatment chemistries. "
Solving combined challenges
Between handling tough-to-treat
water sources and stricter discharge
limits, water treatment experts say a
hybrid water-treatment approach is
needed. New and advanced chemistries
designed to meet the discharge
limits should be combined with technologies
that can help consistently,
accurately and automatically
dose the chemicals and keep
track of making sure nothing is
off balance.
New and advanced chemistries
might include something like BWA
Water
Additives' Belclene 810,
which is a biodegradable " PMA, " or
polymaleic acid, that can be used in
cooling-water treatment programs
where the processor requires Pfree,
N-free or metals-free formulations
and also wants to achieve
very high cycles of concentration
within the cooling tower to save water.
This chemistry is considered " environmentally
acceptable " and is both
a threshold and a crystal growth inhibitor,
which makes it better at scale
inhibition than phosphonates that
are typically just threshold inhibitors,
while meeting P-free and N-free treatment
objectives (Figure 2).
For the processor who has RO membranes
in their operations, BWA has
also developed Flocon 885, a biodegradable,
P-free and N-free antiscal22
CHEMICAL ENGINEERING WWW.CHE.COM JULY 2013
F
FIGURE 4. A technician looks inside a 3D
Trasar Controller, which helps maintain control
over critical cooling assets
ant used to control organic deposits
that can develop on RO membranes.
In addition to chemistries that meet
modern discharge requirements, Thungstrom
says processors also require
more stable and effective chemistries.
GE Power & Water offers GenGard
8000 for control of corrosion and deposits
in open recirculating cooling
systems. GenGard programs can be
applied across the entire pH spectrum
from neutral to alkaline and ensure results
even under stressful conditions.

http://www.cti.org http://WWW.CHE.COM

Chemical Engineering July 2013

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