BOILER AND COOLING TOWER FEEDWATER AND MAINTENANCE COSTS
and cooling tower scaling is very expensive to control. The easiest
control is no or minimal chemical control. The fewer chemicals you
have to put into your boiler or cooling tower, the longer it will
operate problem free and the the lower your costs will be. Using
a pure water feed with minimal chemical additions, you will:
decrease the frequency of blowdown in your feed and bleed. For
example: If your capacity is 1000 gallons and the feedwater
is at 200 ppm, evaporating 50% and refilling, then blow down
at 1200 ppm, you get about 10 cycles (each cycle adds 100 ppm).
If you put 5 ppm in, you get 478 cycles (each cycle adds 2.5
you purge 1000 gallons, per blowdown, that is a savings of
46,800 gallons over one 1200 PPM cycle!
maintenance and downtime
feedwater costs are associated with the following parameters
and carbon dioxide concentration
systems can be utilized to minimize the need for other types
of treatment and maintenance associated with these parameters.
With the proper pretreatment, water discharge can be reduced
to a small fraction of the present volume that will lower
softening for hardness. Calcium and Magnesium (hardness
ions) are removed by the softening process. Ca and Mg are
exchanged for sodium ions on an ion exchange resin. Hardness
in water causes scale. Scale is usually Calcium and/or Magnesium
carbonate that precipitates out as the ions are concentrated
in the boiler. Chemicals can be added to control scale but
they can be reduced to a very small quantity if a softener
a membrane process or deaerator can be used to remove Oxygen
and CO2 down to very low levels for high pressure boilers.
Only small amounts of chemical oxygen scavengers are required
after oxygen removal.
cause another type of scaling and can be removed with ion
exchange or a membrane process. Membrane systems are preferred
where dissolved ion concentrations are high because of operating
cost considerations. High silicate levels are difficult
and may require co-precipitation with other ions or high
temperature caustic regeneration of ion exchange system.
solids can be removed by ion exchange or Reverse Osmosis
membrane processes. The results are similar with ion exchange
able to remove practically all the ions and RO able to get
very close with lower operating and maintenance costs. With
high TDS concentrating, a combination of the two can be
very cost effective. The advantage of removing dissolved
solids is that you can greatly increase the time between
blowdowns as the makeup water is almost void of solids.
It takes much longer to get to the concentration when the
boiler should be blown.
solids are removed by filtration. Normally, you would want
a backwashing filter followed by a fine cartridge filter
for the best results. The backwashing filter can take high
solids loading before flows are reduced and is self cleaning.
The polishing filter makes sure any residual material does
not get through.
of organics are less of a problem in a properly designed
feedwater system because much less chemistry is required
to maintain the boiler. It is much easier to balance the
system, and in some systems, no oxygen scavenger is required.
the links on the left for more information on the types of
systems available or e-mail us at firstname.lastname@example.org.
a good water analysis is you best friend. We will ask you
for a water analysis. Print out the attached form
if you don't know what you need to measure.
Water Quality Links:
Water Treatment: Lessons Learned (US Army)
Steam System Performance: A Sourcebook for Industry
Handbook: Chapter 2, Water Treatment