Reducing water consumption by increasing the cycles of concentration and Considerations of corrosion and scaling in a cooling system

Water consumption of cooling towers can be reduced significantly by minimizing blowdown in coordination with an integrated scaling and corrosion control program. Blowdown is minimized when the concentration cycles increases. In this study, influence of sodium hexametaphosphate (HMP), 2-Mercaptobenzothiazole (MBT) and ZnSO4 inhibitors on the control of corrosion and scaling for carbon steel and,Admiralty brass alloys at two concentration cycles in a power plant cooling system was investigated. The results showed that HMP is hydrolyzed to orthophosphate at higher concentration cycles. Orthophosphate combines with the calcium, magnesium and iron ions, forming the highly insoluble and troublesome orthophosphate scale in the condenser tubes. Decreasing the HMP and pH, and also optimizing the amount of ZnSO4 and MBT effectively reduced scaling and under deposit corrosion. Increasing the cycles of concentration from 6.5 to 9, would save over 1.1 x 10(6) m(3) of water per year while accomplishing the same amount of cooling. (C) 2016 Elsevier Ltd. All rights reserved.