WSP04054

• File Number: 8410.200.60
• Description: Basin Multi-State Organizations - Missouri River Basin Commission - Reports
• Date: 4/20/1960
• Author: John W. O'Meara
• Title: Saline Water Conversion Program, a eview and a Projection
• Water Supply Pro - Doc Type: Report/Study

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different saline sources, in different locations, for different uses and in
various quantities. The process that is best adapted to supply the require-
ments of an individual farmstead or home may not be a good process for con-
verting millions of gallons per day for a city or an industry. One process
offers economic advantage for the conversion of brackish water, but it is
not competitive with other processes for the conversion of sea water.

,Since the distillation of sea water to fresh has over two centuries
of use and gradual development, it was only natural that improvement of
conventional distillation processes engaged extensive study from the first.

Although there "are several different types of distillation equipment
and cycles, they are all subject to the same limiting bugaboos -- scale
deposition and corrosion. 'Scale forming constituents are precipitated out
of solution as evaporator temperatures rise about 1600 F. The scale clings
to heat transfer surfaces and sharply reduces the heat transfer coefficients.
Continued build-up of the scale can actually impede fluid circulation through
the plant. The hot brine is extremely corrosive, necessitating the use of
expensive alloys.

Consequently, we have been sponsoring a series of research and develop-
ment studies in the fields of heat transfer, scale prevention, and less
expensive corrosion resistant materials of construction.

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vertical tubes in a series of evaporators have been conducted at Wrights-
ville Beach, North Carolina. In this cycle sea water falls through bundles
of 2-inch tubes in a series of evaporators under progressively reduced
pressure.

In the first evaporator, steam around the outside of the tube bundle
causes part of the sea water to boil as it falls through the tubes. At,
the bottom of the evaporator, then, we have a mixture of vapor and hot
brine. The hot brine is pumped to the top of the second evaporator, where
under slightly reduced pressure it again falls through the tube bundle.
The vapor produced in the first effect is also pumped to the second evapor-
ator where it is condensed to fresh water by giving up its latent heat of
vaporization to the sea water falling through the tubes and again causing
part of the water in the tubes to boil. This process can be repeated
through ten or more effects. The number of effects is determined by com-
paring the cost of reducing the pressure in the final effect with the value
of the heat in the remaining vapor.

Distillation equipment now in commercial operation requires the use of
,expensive alloys to withstand the corrosive action of salt. Regular plant
shut-downs causing lost production are required for expensive acid treat-
ment which is necessary to remove the scale from the boiling surfaces. The
effictency of the LTV process depends on scale free operation. Like fighting
fire with fire, the theory was that salt would have an affinity for salt. In
our pilot plant we have added salt crystals to the incoming sea water. Our

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