Problems in operating return water cycles and new approaches
to their solution

Summary

The main problems arising in operating water return cycles in process systems with the use of fan-cooling towers are described. These are biological fouling and slime deposits on the heat exchangers, water distributors and cooling tower fillers. The comparative data on the standard requirements to return water and actual data at the industrial enterprises is presented. It is noted that the actual quality of return water does not meet the requirements to the concentration of suspended solids, iron oxides and organic pollutants (permanganate oxidizability, BOD, total microbial count) explaining the difficulties in chemical treatment of return water. A new approach to the calculation of return water pollution with suspended solids in makeup water and air dust for different climatic conditions (flood, winter, drought) at different stripping coefficients is presented. On the basis of the calculations it is concluded that during return water chemical treatment the stripping coefficient shall be preferably maintained less than 2. In order to raise it the removal of suspended solids, iron oxides and organic pollutants from makeup water and part of return water is required. For this purpose by way of example «DYCLAR» technology of dynamic water clarification is presented.

Key words

reagent treatment , biologic fouling , fan-cooling tower , makeup and return water , stripping coefficient , slime deposits , «DYCLAR» technology of water clarification