Reducing Water Use and Operating Costs Using Softened Makeup Water for Cooling Towers

摘要

Shortages of fresh water and increased costs for makeup water, blowdown disposal and chemical treatment have created a need to increase the cycles of concentration (COC) in cooling tower systems, which decreases fresh water makeup, blowdown to sewer and chemical treatment costs. (Cycles of concentration is defined as the dissolved solids level of a cooling water divided by the dissolved solids level of the makeup water. It is the number of times the water in the cooling system has been concentrated by evaporation.) Unfortunately, increased COC also increases the concentration of hardness ions in the cooling water, making the cycled waters highly scale forming (see Figure 1). Formation of hardness scale in heat exchangers is unwanted, as even a small amount of scale will decrease the efficiency of heat transfer, resulting in increased power consumption for chiller operation and decreased productivity in industrial processes. In severe cases, scale can completely plug heat exchangers and piping.