The Pilot Study On The Reuse Of The Circulating Cooling Discharge Water In The Power Plant By Ultrafiltration

As a part of zero-discharge project, the treatment of discharged water from recirculated cooling water has been investigated. The permeate water of ultrafiltration and reverse osmosis is used as the supply of boiler feed water treating system. The feasibility and the optimum operating conditions of ultrafiltration followed by reverse osmosis are tested through a series of trials.The pilot plant made by HYDRYcapTM60 fouling-resistant hollow fiber membrane of ultrafiltration is designed to be exchangeable in feed direction. The membrane fouling can be reduced with the use of feeding in exchangeable directions and an additional inter-circulation, and the efficiency of ultrafiltration membrane can be increased at the same time. A PLC is used to ensure automatic operation of the pilot plant.At first, the optimum operating pressure is determined by comparing permeate flow declines under different operating pressures. The result shows that the optimum operating pressure is between 0.05MPa ~0.08MPa, and the permeate flow is between 3.5m3/h~4.1m3/h. Then the optimum backwashing dosage is determined by comparing permeate flow declines under four different backwashing dosages under the operating pressure 0.08MPa. The ultrafiltration pilot plant can work stably and the permeate flow decline is almost zero, when the backwashing dosage is 15mg/L(NaClO).During the trials, the turbidity of the permeate is lower than 0.1NTU, and SDI is lower than 2, which reaches the quality standards of feed water for RO. The ultrafiltration pilot plant can partly hold back COD of the water, and the maximum removal of COD is about 60%. The optimum operating condition is that the operating pressure is between 0.05MPa ~0.08MPa, and the period of changing feed directions is 15min, and the back-washing period is 30min.With exchangeable feed direction and additional inter-circulation, the quality of the permeate meets the criteria of feed water for the RO system. The UF & RO treatment is feasible in supplying water for boiler feed water treating system. RO system worked well in a series of trials. The result can be used as a guide for the industrial applications of UF & RO.