Abstract: Large quantities of water are required in thermal power plants, of which primarily the circulating cooling water accounts for over 70% of the total water consumption. To explore the operating control technique of the circulating cooling water with high concentration ratio, the make-up water treatment with nanofiltration (NF) processing is studied and tested in a power plant with the processing capacity of 18 m³/h. The test results show that at the recovery of 90%, the desalination rate is about 70%, while the removal rate of divalent ions, such as Ca²⁺, Mg²⁺ and SO₄^2-, is over 80% and the COD of yielding water is not more than 2 mg/L. Then, the NF processed water is used in the static scale inhibition test and the coupon corrosion test. The test results show that the concentration ratio of the circulating water can be maximized by as much as 33.98 times, and at this time, the circulating water system can operate at high concentration ratio with zero cooling tower discharge, which exhibits remarkable water-saving effect and environmental benefits.

Key words: coal-fired power plant, circulating water, make-up water treatment, Nanofiltration, concentration ratio