WSP00451

• File Number: 8273.100
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - BOR
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1969
• Title: Cost Analysis of Six Water Desalting Processes
• Water Supply Pro - Doc Type: Report/Study

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The fixed costs are determined by a number of factors such as the

interest rate, plant life, plant Size, tUbing cost, plant availability,

and tubing heat transfer coefficient, When the preceding factors have

been fixed by study ground rules or by local prevailing conditions, cost

studies can be made for a range of performance ratios to determine the

optimum PR for minimum water costs, On the basis of the ground rules

selected for this study, the optimum PR for various steam costs were de-
termined and the results are shown in Fig. 4, This figure also shows the

generalized effect on optimum performance of other factors that determine

the fixed costs. It is clear that optimization studies are needed for

each plant under consideration to adjust for varying local economic

condi tions,

Figure 5 shows the economic number of stages and the required

evaporator area that result for various steam costs and condenser sur-

face costs. As steam costs are reduced, it is economically advisable to

reduce the number of stages and required condenser surface area at some

expense in thermal efficiency, The reverse is true as-condenser cost

per unit of surface area is reduced, and there is some advantage in in-

creasing the number of stages and the total required condenser surface

area.

The performance ratios shown in Figs, 2 and 4 were used to estimate

water conversion costs, which are shown in Fig, 6. Comparison of the

differential water costs in Fig, 6 with the sum of the differential costs
shown in Figs. 2 and 3 indicates that savings resulting from the optimum

designs based on both condenser surface and steam costs are from I to
3~/kgal greater than when each variable is considered separately.

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