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CHEMICAL TREATMENT FIGURE 3 product, followed by Chemical C and then Chemical B. With 2 ppm of Zn2+ in brine, Chemical B and C became much more effective than Chemical A. These results suggest that even low concentra- tions of Zn2+ in water should be included in the evaluation tests for selecting the right inhibitor product. For dynamic tubing block tests, bicar- bonate concentration was increased to 1,000 mg/L to shorten the blank scaling time from >60 min to ~30 min. The test duration for scale inhibitor evaluation was chosen at 90 min, which represented three times the blank scaling time. Figure 1 shows the test results of different Zn2+ concentrations in the absence of scale inhibitors, along with two blank runs. It can be seen that 2 and 5 ppm of Zn2+ very little effect on the CaCO3 mation. With 10 ppm of Zn2+ scaling was slightly delayed with scaling time extended to 42 min. The dynamic tubing block tests also demonstrated the impact of Zn2+ Effect of zinc ions on the performance of Chemical B. FIGURE 4 have scale for- , the CaCO3 on scale inhibitor performance, which followed trends similar to those observed in the static bottle tests. The effect of Zn2+ was ZMÆMK\ML Ja KPIVOM[ QV \PM UQVQU]U 1+ value of scale inhibitor and scaling time. An improvement in inhibition perfor- mance led to lower minimum IC and longer scaling time, and vice versa. For Chemical A, its minimum IC was 5 ppm without Zn2+ in the presence of Zn2+ QVO ZML]KML QVPQJQ\QWV MNÅKQMVKa Ja BV2+ The effects of 2 and 5 ppm of Zn2+ and was increased to 6 ppm (Figure 2), indicat- . were similar, although there was a slight differ- ence in scaling times. For Chemical B and C, their minimum IC values were re- duced by Zn2+ prolonged with increasing Zn2+ and the scaling times were concen- trations, suggesting improved effective- ness with Zn2+ . As shown in Figure 3, Chemical B failed quickly at 8 ppm in the absence of Zn2+ Zn2+ , its minimum IC was decreased to 6 NACE International, Vol. 51, No. 11 . With 2 and 5 ppm of XXU :MXMI\ML \M[\ KWVÅZUML \PI\ \PM minimum IC for Chemical B alone was >8 ppm. Additional runs were also per- formed with 0.5 and 1 ppm of Zn2+ . Test results showed a gradual decrease of scal- ing time with reduced Zn2+ tions. While the minimum IC of Chemi- cal B was still 6 ppm with 1 ppm of Zn2+ it increased to 7 ppm when Zn2+ , was re- duced to 0.5 ppm. The performance of Chemical C was less sensitive to Zn2+ compared to Chemicals A and B. Unlike these phosphonate-based products, the minimum IC value of Chemical C was not changed by 2 ppm of Zn2+ (Figure 4). concentra- At 5 ppm of Zn2+ , however, there was a [QOVQÅKIV\ QVKZMI[M QV [KITQVO \QUM IVL the minimum IC was reduced to 5 ppm. These observed changes in inhibition MNÅKQMVKa L]M \W BV2+ Effect of zinc ions on the performance of Chemical C. could be attributed November 2012 MATERIALS PERFORMANCE 63