APPLICATION SYSTEMS ENGINEERING
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COOLING TOWER/COOLING WATER
Cooling Water is needed in many industrial processes, typically
using Cooling Towers as a means for providing heat transfer from
various process plants heat exchangers.
Two basic approaches are used:
“Once Through” &
“Recirculating”
Once through Cooling Towers use large volumes of surface
water, such as a river, which discharges the heated water back
to the surface water after it has been used to cool the
processes.
Recirculating Cooling Towers conserve water resources &
eliminate some potential harm to aquatic life & the environment.
Used water is typically pumped to the top of the Cooling Tower &
flows down through diverter passages.
Large fans located at the top of the tower exhaust air
with an upward draft through the falling water, adding
additional cooling effect.
Evaporation of some of the water carries away a large
portion of heat. A
collection basin at the base of the Cooling Tower collects water
to be reused in Recirculation Cooling Towers.
As
with Boiler Feedwater, Cooling Towers are plagued
with corrosion of heat exchangers & piping, scaling & algae &
bacteria growth. Water
quality monitoring to control these effects are required.
Cooling Tower water evaporation causes deleterious salt
buildup, which precipitate
after saturation is reached.
Major contributors to scaling are caused by magnesium &
calcium & can be monitored for
their ionic strength,
providing the Operator with blow-down & water refreshing control
parameters. Feedwater
should be monitored for salts (carbonates, sulfates,
chlorine), CO2 & Oxygen.
Corrosion control can be maintained by inhibitors & pH
adjustments or ozone treatments.
Microbial growth can be
controlled by chemical disinfectant additives.
The
primary indicator of water quality is TOC (Total Organic Carbon)
analysis.
Cooling Tower regulations are a subject of EPA regulations, due to the following considerations: A.A. Above 24oC temperatures, fish are stressed & above 28oC lethal effects occur. B. If the system is open to atmosphere, as the cooling water evaporates, air pollutants, including microorganisms are vented to the environment.
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