Experimental Study On Scale And Corrosion Inhibition Of Circulating Cooling Water Of Guohua Dingzhou Power Plant

The amount of circulating cooling water in thermal power plant take account of 70% of the total water consumption.The amount of make-up water is usually reduced by increasing the concentration ratio of circulating water during operation.For an open cycle cooling system,increase the concentration ratio will accelerate fouling and corrosion.Therefore,the prevention of corrosion and scaling of circulating cooling water at high concentration rate is the focus of the study on circulating cooling water treatment in thermal power plants.In regard to the circulating cooling water quality of Guohua Dingzhou power plant,carried out a series of experiments to simulation circulating cooling system make-up water of Guohua Dingzhou power plant: slow decarburization experiment,static scale inhibition experiment,corrosion coupon experiment and determined the appropriate dosage of lime softener,flocculant ferric chloride,coagulant polyacrylamide,scale and corrosion inhibitor.The results showed that lime 350mg/L,ferric chloride 60mg/L,polyacrylamide(PAM)0.7mg/L is the optimal dosage for circulating cooling water treatment.Under these conditions,the removal rate of total alkalinity was 93.45%,the removal rate of total hardness was 57.48%,the removal rate of calcium hardness was 68.52%,and the removal rate of conductivity and total dissolved solid(TDS)were 34.76% and 34.70% respectively.By evaluating a variety of scale inhibitors for their scale inhibition performance,organic phosphorus scale inhibitor is used to prevent scaling and corrosion of recycled cooling water at high concentration rate.The compound product of 1-Hydroxyethylidene-1,1-diphosphonic acid,maleic anhydride and acrylic acid and amino trimethylene phosphonic acid has the scale inhibiting rate reached 90%.The compound product of sodium molybdate and sodium dodecyl benzene sulfonate has the corrosion inhibiting rate reached 90%.The result of electrochemical test shows that the compound product of corrosion inhibitor is anodic corrosion inhibitor.The result of concentration experiment shows the concentration ratio(by conductivity)can increase to 5.1 or more under the appropriate dosage of scale inhibitor in the water of decarburization treatment.