| Source
Newsletter winter 2001 |
|
 |
15 Seconds
of Fame: Reducing Water and Chemical Use Helps Pillsbury
Keep Its Cool
Pillsbury Bakeries in Chanhassen is converting
its recirculating cooling evaporator/condenser water system
from a system that required chemical treatment of water to
one that uses mechanical water treatment.
The plant ammonia system supplies process
and warehouse refrigeration plus space cooling and chilled
water for production. Minerals in water like calcium and magnesium
build up in the evaporative condenser coils. Minimizing this
buildup ensures proper heat transfer, allowing for efficient
cooling.
"Our ammonia refrigeration operators have
to inspect and work on the condensers. For years, they've
wanted me to find some type of water treatment that didn't
require chemicals," said Dotti Shay, environmental coordinator
at Pillsbury. "They were worried about their exposure to the
chemicals that keep dissolved solids in suspension, and the
algicides and biocides."
Shay's been keeping her eyes open for new
technologies. With assistance from Xcel Energy, Pillsbury
conducted a 92-day test of a mechanical evaporator condenser
system. Xcel helped fund the study because of the potential
to reduce electrical use. Clean towers improve heat transfer
which in turn reduces head pressure on the compressors and
pumps, cutting power use.
During the three-month trial, Pillsbury
saved $37,000. The savings came from reducing incoming water
use and water discharge, and eliminating chemical and water
softening salt use. To compensate for evaporation losses and
to normalize total dissolved solids, water is bled from the
system and replaced. The new mechanical system used under
48,700 gallons of water in one quarter versus 789,000 gallons
used for the chemical system. The system will pay for itself
in less than two years. When the reduced sewer access charges
(SAC) fees are included, payback is less than a year.
In order to feel comfortable with the results
of the trial, Pillsbury hired a consulting firm to verify
the vendor's tests.
Inside the Technology
For cooling towers and condensers, the nonchemical water treatment
technology works by creating an area of very low pressure.
This allows the dissolved carbon dioxide to become a gas that
is then vented. The water chemistry is now changed and prevents
calcium carbonate scaling.
For more information, contact Karl
DeWahl, MnTAP, at 612/624-4645.
|
