(GP/GT) for Additional Water Supply in the Lower Rio Grande

A thermodynamic review of the system indicates the number of effects to be between
twelve and sixteen, based upon the water recovery. The implementation of freon (or
CFC-free refrigerant) charged condensers instead of product water charged condensers
will optimize the performance and reduce the actual number of stages required. It
should be noted that there is an approximate 3.0-5.0· F temperature drop across each
stage, based upon the vacuum applied and system insulating capacity. For the
purposes of this review, a 5.0· F temperature drop was considered in the preliminary
design.
With a basic concept of the most applicable type of system to utilize, an evaluation of
the system feed water was performed. Utilizing a modified commercially available
physical-chemistry saturation computer model (Dh-SAT, French Creek Software). the
system was first modeled at the wellhead parameters, at a pressure of 1000 PSI.
Following this evaluation, an evaluation was performed of the brine (reject) stream at
the 75% water recovery level (concentration factor 4.0). at a pressure of 0 PSI.
The results of both were evaluated, with graphical representations attached in
Appendix A. The Dh-SAT program calculates indicators of scale potential for the
following:
barium sulfate Barite
barium carbonate Witherite
calcium carbonate Calcite
calcium sulfate Gypsum
strontium sulfate Celestite
• calcium phosphate Hydroxyapatite and
Tricalcium Phosphate
iron hydroxide Amorphous Iron Hydroxide
iron phosphate Strengite
iron carbonate Siderite
silica Amorphous Silica
calcium fluoride Fluorite
• magnesium hydroxide Brucite
In addition, several scaling indices are calculated, including the following:
• Langelier Index
• Stiff-Davis Index
• Ryznar Index
• Oddo-Tomson Index
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