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;".;' r-- ~ '-G' ("'l <-, ~ <:', ", :'~~ :;.1. ~,.-, ".; {', ~~, " .... ': " . .~ ',; ~: " ,l__.__. As the circulating water system's salt concentration is Increased to reduce blowdown, the concentration of other Ions can become a major corrosion ~on- cern. The three of concern for this study include chloride, sulfate and am- monia. Chlorides and ammonia can corrode the normal power plant metal materials of construction while high levels of sulfate will erode normal con- crete used In the tower basin and piping. For purposes of this study, the limit for normal circulating water system materials was considered to be 3,500 to 4,500 mg/I of chlorides, 5 mg/I for ammonia and 10,000 mg/I sulfate. Total dissolved solids Is not a limIting factor In Itself. It Is, however, a good Indicator of the relative concentra- tions of other other Ions In the system which may produce scale or corrosion. Design Criteria For the purposes of this study certain design assumptions were used to es- tImate equipment processing and pond capacities from which capital cost could be estimated. These assumptions referred to IX softenIng, lime/soda soften- Ing, and vapor compression maximum design capacities, surge pond volumes and evaporation pond depth and acreage. The 100% load and high average water source chemistry was used as a basIs for equipment sizing for all configurations selected. Chemical consumption and power usage were based on the 76% load and average chemistry water source. The In-plant flows which vary with load include cooling tower evaporation, coolIng tower blowdown, scrubber system evaporation, scrubber system blowdown and condensate system evaporation. The ash system, regeneration waste and plant drain flows were assumed constant for the two load conditions evaluated sInce under actual power plant operating conditions, they are generally Insen- sitive to load. In process configuratIons where vapor compression evaporators are utIlized, condensate makeup requirements are suppl led by vapor compression evaporator product. Scrubber wastes are discharged to sludge ponds which are separate from the primary evaporation ponds and are not Included In the economics. The surge, pond sizing criteria varies with the position of the surge pond In the plant. Ponds used for plant makeup treatment are sized to contain fIve hours surge capacity at the 100% load condition. Those ponds necessary to support sldestream treatment systems, ,are sized to contain a 12 hour surge at the 100% load condition. Wastewater and recycle surge ponds are assumed to require a four day surge capacity at the 100% load conditIon. AI I the ponds are designed for periodic cleaning, and all pump stations have three 75% capacity pumps for redundancy. The evaporation pond assumptions Include synthetic membrane lining, an average yearly net evaporatIon rate of 2 gpm/acre (3.2 feet/acre) and a pond depth of 15 feet to account for the precIpItation and storage of salts and storm freeboard requirements for the 35 year lIfe of the plant. The net evaporation rate takes Into account the Increased dissolved solIds In the pond. The above design criteria and operating guidelines presented were used to 4-9