Jamaledin Howeizi - *Research and Technology of National Petrochemical Compnay, Pajouhesh Blvd, Tehran-Karaj High way, PO BOX ۱۴۹۶۵/۱۱۵, Tel:+۹۸-۲۱-۴۴۵۸۰۱۰۰, Fax:+۹۸-۲۱-۴۴۵۸۰۵۰۵

High concentration of existing salt in water inlet to cooling towers causes decrease in concentration cycle, increase of blow down and chemicals additives, but a more important fact is that it leads to increase in scale formation rate, decrease in heat efficiency and life time of heat exchangers. Clarifying unit of Razi Petrochemical Company takes over supplying required water for the complex cooling tower by 2 clarifiers with total production capacity of over 43000 tons per day. In existing research, average hardness of circulating water has been decreased approximately from 900 mgr/l to 300 mgr/l by improving the pre-treatment process of coagulation and flocculation. The outcomes of this research were implemented in clarifying unit of Razi Petrochemical Company and in addition to increase in concentration cycle, decrease in blow down, reduction in consuming chemicals (acid, biocide, anti-scale and anti-corrosion) have mainly caused risk reduction of scale formation and increase in heat transfer efficiency. Annual saving of over Rls.10,000,000,00/- has been estimated regardless of increase in efficiency and life time of heat exchangers.

cooling tower, blow down, heat exchanger, concentration cycle, scale formation