Determination Method Of Scale And Corrosion Inhibitor In Industrial Circulating Water

With the continuous operation of circulating cooling water,the concentration of minerals with scaling tendencies is increasing.When the concentration of these ions exceeds a certain limit,it will affect the heat transfer efficiency or produce corrosion because of scale deposition in the equipment surface.And adding polymer scale inhibitors is the most common solution.The water treatment agent must reach a certain concentration in order to play the best scale and corrosion inhibition effect.In this paper,the concentration of polymer was analyzed by turbidity method and colloidal titration method.The applicable conditions and disadvantages of the two methods were studied,and the corresponding analytical methods were used for different circulating water systems.The main conclusions of this experiment are as follows:(1)Within certain concentration range,better linear relationships between absorbance,consuming the volume of poly dimethyl diallyl ammonum chloride(PD)and the concentration of polymer inhibitors were observed.(2)The best measurement conditions,influencing factors and elimination of turbidity method:The optimal experimental conditions of PAA:PD concentration of 16 mg/L,pH range of 3.50?5.50 and measurement of the absorbance at 410 nm after placed for 30 min.The relationship between concentration of PAA and absorbance provided an exceptionally linear coefficient of R2=0.9950.Coexisting salt ions and copper corrosion inhibitors had no impact on the determination of PAA in the normal mass concentration range.PO43-and organic phosphine scale inhibitors had a certain influence on the absorbance.The interference can be eliminated by adding 0.75 ml 200 g·L-1 Al2(SO4)3 reagent to solution when the pH was greater than 12.00.The detection limit is 1.04mg·L-1.The optimal experimental conditions of TH-2000:PD concentration of 28.8 mg/L,pH range of 4.50?7.00 and measurement of the absorbance at 425 nm after placing 45 'min.The concentration of TH-2000 vs absorbance give a regression coefficient of R2=0.9990.Similar to the determination of PAA,other substances served no influences on the determination of TH-2000,except for PO43-and organic phosphorus scale inhibitors.This interference can be substantially eliminated by adding Al2(SO4)3 reagent.The detection limit is 0.448 mg·L-1.The optimal experimental conditions of PASP:PD concentration of 35.2 mg/L,pH range of 8.50?10.50 and measurement of the absorbance at 420 nm after placing 25 min.The relationship between concentration of TH-2000 and absorbance provided an exceptionally response correlation of R2=0.9955.Similar to the determination of PAA and TH-2000,other substances had no impact on thedetermination of PASP,except for PO43-and organic phosphorus scale inhibitors.This interference can be substantially eliminated by adding Al2(SO4)3 reagent.The detection limit is 0.738 mg·L-1.(3)The best measurement conditions,influencing factors and elimination of colloidal titration:The optimal experimental conditions of PAA:PD concentration of 40 mg/L,pH range of 8.00?11.00 and titration rate is less than 0.100 mL/s.The concentration of PAA and consumption of PD volume has a linear correlation R2=0.9692.Except for Ca2+?Mg2+,other substances had no impact on the determination of PAA.The interferences can be eliminated by adding desired amount of EDTA-2Na with the least mole ratio of 1:1(EDTA-2Na:Ca2+ or Mg2+).The detection limit was 10 mg/L.The optimal experimental conditions of TH-2000:PD concentration of 40 mg/L,pH range of 9.00?11.00 and titration rate was less than 0.050 mL/s.The relationship between concentration of TH-2000 and consumption of PD volume provided an' exceptionally linear coefficient of R2=0.9869.Similar to the determination of PAA,other substances served no influences on the determination of TH-2000,except for Ca2+?Mg2+.This interference can be substantially eliminated by adding desired amount of EDTA-2Na.The detection limit was 16 mg/L.The optimal experimental conditions of PASP:PD concentration of 40 mg/L,pH range of 8.50?11.00 and titration rate was less than 0.025 mL/s.The concentration of PASP vs consumption of PD volume give a regression coefficient of R2=0.9787.Similar to the determination of PAA and TH-2000,the water treatment agent and coexisting salt ions had no impact on the determination of PASP in the normal mass concentration range,except for Ca2+?Mg2+.This interference can be substantially eliminated by adding desired amount of EDTA-2Na.The detection limit was 10 mg/L.(4)Comparison of two methods found that turbidity method had high precision,low detection limit,while colloidal titration method had the advantages of simplification,low cost,which was suitable for the determination of higher concentrations of scale inhibitors.The establishment of these two methods was conducive to the timely determination of polymer content.Besides,it can promote the improvement of online monitoring system and provide theoretical practical experience for the monitoring of circulating water system.