Stressed Alkaline Cooling Water Deposit Control: High Temperature, Suspended Solids, and Iron Impacts

Paper No.

9422

Libardo A. Perez, Zahid Amjad, and Robert W. Zuhl The Lubrizol Corporation, 29400 Lakeland Blvd., Wickliffe, Ohio 44092 USA

ABSTRACT Water scarcity and environmental issues have necessitated operating cooling systems using poor quality feedwaters or changing process temperature conditions. Safety concerns have driven cooling system users to implement alkaline treatment programs to facilitate acid feed reduction or elimination. Inorganic and/or organic phosphorus components in alkaline cooling water treatment (CWT) programs help prevent corrosion and scale formation. Collectively, water conservation measures and alkaline CWT programs have increased potential metal-phosphate and/or metal-phosphonate scale formation. Understanding deposit control polymers (DCP) perform under stressed conditions is essential for implementing alkaline CWT programs. This paper discusses CWT program metal-phosphate/phosphonate scale formation control efficacy when operating under stressed alkaline conditions (e.g., high temperatures, suspended solids, and iron).

Key words: deposit control polymers, phosphate scale, cooling water, stress conditions, particle dispersion, phosphonate, iron, high temperature.

INTRODUCTION Industrial water systems operated using poorly treated feed water are often plagued by undesirable deposits on equipment surfaces.1 These deposits can be categorized into the following five groups: (a) mineral scales, (b) corrosion products, (c) suspended matter, (d) microbiological mass, and (e) other (e.g., oil grease, formulation component hardness ions salts). These deposits typically accumulate in low- flow circulation areas and may become immobilized during upset conditions resulting in build-up on heat exchanger and equipment surfaces. Among the various strategies adopted to retard or prevent undesired deposits is the use of chemical additives that inhibit nucleation and crystal growth, disperse precipitated salts, and/or particulate matter. Developing cost-effective deposit control solutions is a dynamic challenge.

Effective cooling water treatment (CWT) programs must control scale, corrosion, particulate matter, and microbiological growth. CWT program evolution includes acid/chromate, zinc/chromate, stabilized phosphate, alkaline CWT programs, such as phosphonate/zinc/polymer, and all-organic. Stabilized phosphate formulations typically require acid feed to maintain a neutral pH. Alkaline CWT programs (e.g., all-organic) can minimize or eliminate acid feed. Most formulations contain one or more phosphonate (e.g., 1-hydroxyethylidine 1,1-diphosphonic acid [HEDP], 2-phosphonobutane 1,2,4- tricarboxylic acid [PBTC]) for CaCO3 inhibition and mild steel corrosion control. High performance DCPs are essential components for neutral pH and alkaline CWT programs. DCPs serve dual functions: (1) control calcium phosphate (Ca/P) and calcium phosphonate formation on metal surface and (2) disperse recirculating water suspended solids minimizing potential deposition on system surfaces.

Industrial cooling water system Ca/P scaling has become more prevalent2-4 due to higher phosphate levels caused by increased water reuse, using low quality makeup water (e.g., wastewater treatment plant effluent), and using organo-phosphonates scale and corrosion inhibitors which degrade to orthophosphate. The increased orthophosphate levels, combined with operating conditions, and high hardness levels due to increased cycles of concentration for water conservation cause formation of highly insoluble and thermally non-conductive scale deposits. In our previous studies,5,6 we reported the influence of various factors including recirculating water pH, temperature, heat exchanger metallurgy, and system impurities as contributor to DCP performance variability. These studies indicate that DCP performance is strongly impacted by DCP architecture, i.e., monomer type and the amount, monomer functional group, molecular weight. This paper continues our research efforts to understand how stressed conditions, caused by system water chemistry variability and/or contaminants as well as system operating conditions, impact DCP performance in industrial cooling water treatment programs.

EXPERIMENTAL Solutions were prepared using grade A glassware; double distilled water; and reagent grade calcium chloride dihydrate, sodium bicarbonate, magnesium chloride hexa-hydrate, sodium phosphate dodeca- hydrate, and iron (III) chloride hexahydrate. The reagent grade chemicals and montmorillonite (200 mesh) were obtained from Alfa Aesar. PBTC and TTA (tolyltriazole) were commercial materials obtained from water treatment (WT) industry suppliers. Calcium and magnesium concentrations were determined using standard EDTA colorimetric titrations. Phosphate concentrations were determined by spectrophotometric methods (Hach DR3900).

Table 1 describes the commercial DCPs evaluated in this study and includes both acrylic acid/sulfonic acid (AA/SA) copolymers and AA-based copolymers containing three or more monomers at least one of which is a sulfonate. All DCP stock solutions were prepared in distilled water on an active solids basis as were treatment dosages. Dynamic testing methods were used to assess the performance of these DCPs.

Table 1: Deposit Control Polymers Evaluated Additive Composition MW* CK775 Poly(acrylic acid: [2-acrylamido-2-methylpropane sulfonic acid]**) or AA/SA with <15k 74/26 monomer weight ratio CPD20 Poly(AA/SA) with 80/20 monomer weight ratio 4.5k CPN23 Poly(AA/SA) with 60/40 ratio >10k CK798 Poly(AA : SA : acid: sulfonated styrene) or AA/SA/SS <15k CPD31 Poly(AA : SA : non-ionic) or AA/SA/NI 4.5k CPA54 Poly(AA : meth-methacrylate : 2-propene-1-sulfonic acid, 2-methyl- : benzene 15k sulfonic acid, 4-[(2-methyl-2-propenyl)oxy]-) * MW = Weight average molecular weight. ** AMPS† monomer.

Previously described,5 dynamic simulation test rigs (DSTRs) were used to evaluate DCP efficacy as cooling water system scale and fouling control agents. The DSTR units (Figure 1) were designed to evaluate both scale and corrosion control under heat transfer and dynamic flow conditions simulating typical cooling system conditions. Bulk water and heat transfer surface temperatures, pH, and flow velocity were all controlled. Treated synthetic water was prepared by adding component ions to deionized water. Makeup and blowdown adjustments were made by continuously feeding treated synthetic cooling water containing from the unit’s sump and the sump overflow. Treatment program efficacy was assessed by the deposit mass formed at the heat transfer and other surfaces present in the DSTR unit as well as considering any bulk precipitation (turbidity) and test solution ion concentrations changes.

Figure 1: Dynamic System Testing Rig (DSTR) Schematic Diagram

Table 2 shows the normal or low stress alkaline water chemistry, operating conditions, and the baseline treatment (BLT) used for typical condition DSTR experiments. The BLT used in all tests included orthophosphate to prevent low carbon steel corrosion, tolyltriazole (TTA) to prevent yellow metal corrosion, and PBTC to prevent potential calcium carbonate deposition.

Table 2: DSTR Water Chemistry,* Operating Conditions, and Baseline Treatment Condition: Typical “Low High High Suspended High Iron Parameter Stress” Temperature Solids [Ca] as CaCO3 600 mg/L [Mg] as CaCO3 300 mg/L Alkalinity as CaCO3 250 mg/L Silica as SiO2 50 mg/L pH 8.4 to 8.6 Clay 0 mg/L 0 mg/L 50 mg/L 0 mg/L Iron 0 mg/L 0 mg/L 0 mg/L 5 mg/L Holding-time index 1.75 days Flow velocity 2.75 fps Bulk water temperature 120 °F (48.9 °C) 126 °F (52 °C) 120 °F (48.9 °C) 120 °F (48.9 °C) Skin temperature 140 °F (60 °C) 158 °F (70 °C) 140 °F (60 °C) 140 °F (60 °C) Heat exchanger metallurgy Stainless steel (SS) and admiralty brass (AB) Coupon metallurgy Admiralty brass and low carbon steel (LCS) LSI** @ bulk T / skin T 2.10 / 2.23 2.14 / 2.34 2.10 / 2.23 2.10 / 2.23 HAP-SI** @ bulk T / skin T 52k / 170k 56k / 255k 52k / 170k 52k / 170k Baseline Treatment (BLT) BLT1 BLT2 BLT1 BLT1  Ortho-phosphate as PO4 7.0 mg/L 7.0 mg/L 7.0 mg/L 7.0 mg/L  PBTC 6.0 mg/L 8.0 mg/L 6.0 mg/L 6.0 mg/L  Tolyltriazole (TTA) 2.5 mg/L 2.5 mg/L 2.5 mg/L 2.5 mg/L DCP TBD TBD TBD TBD * Sodium & chloride levels omitted for brevity. ** LSI and HAP-SI calculated using French Creek Software’s WaterCycle† Rx program.

RESULTS AND DISCUSION The DSTR tests were designed to simulate both typical and high stress cooling water conditions; the high stress conditions include higher temperature, suspended solids, and the presence of Fe3+ ions. The testing objectives included (1) evaluating all Table 1 DCPs at one or more dosages under each set of

† Trade name ©2017 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 15835 Park Ten Place, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. 3 DSTR conditions and (2) continuing evaluations until at least two DCPs at the lowest possible dosages provided acceptable results. Initial DCP dosages were based on experience.

A DCP’s primary role in phosphate-based CWT programs includes maintaining PO4 soluble levels needed to facilitate corrosion protection and minimizing deposition. Therefore, a common operating practice is to maintain the recirculating or bulk water delta (Δ) PO4 [the difference between unfiltered (UF) and filtered (F) PO4] below 1 mg/L to prevent phosphate scaling. Other DSTR performance criteria limiting low carbon steel (LCS) and admiralty brass (AB) corrosion rates (CRs) below one (1) mil per year (mpy) and 0.2 mpy, respectively as well as maintaining clean heat transfer surfaces (HTS) for both stainless steel (SS) and AB. A very slight deposit is referred to as an almost clean surface. Photographs taken during the experiments illustrate the HTS deposit observations.

The Table 2 test solutions used during testing were supersaturated with respect to both CaCO3 and Ca/P suggesting that mixed salt scale co-precipitation will occur. PBTC dosages were adjusted as necessary to prevent CaCO3 scale formation. Calcium concentrations were measured during the experiments to monitor potential CaCO3 and/or Ca/P precipitation. However, given the measured calcium concentration (both initial vs. end of experiment) were near the 600 mg/L target (except for the control) and the changes were very small, the data are not reported in the tables herein. Both filtered and unfiltered PO4 measurements were taken during the experiments; initial PO4 values were near the 7.0 mg/L target. For brevity, only the end of experiment Δ PO4 values are reported herein. For experiments where Δ PO4 values >1 mg/L are reported, noticeable scaling / deposition occurred on HTSs and where Δ PO4 values were <1 mg/L (target value), the HTSs were clean.

Typical Alkaline Cooling Water Chemistry and Operating Conditions Results Table 3 shows DSTR results for BLT1 (see Table 2). Acceptable tests results for all performance parameters are in bold font highlighted in light green. With only BTL1 added to the DSTR, heavy deposits formed on both the SS and AB HTSs, high bulk deposition occurred (e.g., 5.8 NTU final turbidity, 4.4 mg/L Δ PO4), and negligible metal surface corrosion was observed.

Table 3: DSTR Results - Typical Alkaline CW Conditions with BLT1 and DCP (e.g., 600 mg/L Ca as CaCO3, pH 8.4 to 8.6, 48.9 ⁰C bulk water, 60 ⁰C skin [LSI @ 2.23 & HAP-SI @ 170k]) Final LCS AB Treatment Final Δ PO4 Turb.* CR** CR** SS HTS Deposit AB HTS Deposit (mg/L) (NTU) (mpy) (mpy) Observations Observations Target performance <1 --- <1 <0.2 Clean Clean 0 mg/L DCP + BLT1 4.4 5.8 0.87 0.12 Heavy Heavy 3 mg/L CK798 + BLT1 1.2 1.1 1.1 0.12 Clean Very Slight 4 mg/L CK798 + BLT1 0.2 0.81 0.81 0.08 Clean Clean 6 mg/L CPD31 + BLT1 0.6 0.98 0.98 0.14 Clean Very Slight 7 mg/L CPD31 + BLT1 0.4 0.98 0.98 0.11 Clean Clean 6 mg/L CPA54 + BLT1 1.2 1.8 1.8 0.09 Slight Slight 9 mg/L CPA54 + BLT1 0.6 0.81 0.87 0.14 Clean Clean 6 mg/L CPN23 + BLT1 0.7 0.65 0.89 0.12 Clean Very slight uniform 7 mg/L CPN23 + BLT1 0.75 0.89 0.78 0.13 Clean Clean 6 mg/L CK775 + BLT1 1.5 1.5 1.5 0.12 Very slight non-uniform Very slight non-uniform 9 mg/L CK775 + BLT1 0.3 0.76 0.79 0.12 Clean Clean 6 mg/L CPD20 + BLT1 2.2 2.5 2.5 0.15 Slight Slight 9 mg/L CPD20 + BLT1 0.4 0.78 0.81 0.13 Clean Very Slight 10 mg/L CPD20 + BLT1 0.2 0.56 0.79 0.09 Clean Clean Notes: * Turb. = Turbidity, ** CR= Corrosion Rate

©2017 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 15835 Park Ten Place, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. 4 Acceptable performance was achieved using only 4 mg/L CK798 in combination with BLT1. Similar results were seen for 7 mg/L CPD31 or CPN23 dosages in combination with BLT1. Higher dosages for the other DCPs were needed to obtain acceptable results. The following DCP performance trend (highest to lowest) was observed:

CK798 > CPD31 ≈ CPN23 > CPA54 ≈ CK775 > CPD20

Figures 2 (a) and b) show end-of-test (EOT) results for the conditions described in Table 3. Figure 2 (a) indicates clean HTSs when BLT1 was used with 4 mg/L CK798 whereas Figure 2 (b) displays clean SS HTSs and very slight deposition on AB HTS when BLT1 was used in combination with 9 mg/L CPD20.

Figure 2: DSTR Low-Stress Conditions using BLT1 and DCP at EOT (a) Clean HTSs using 4 mg/L CK798 (b) Clean SS and very slight AB HTS deposition using 9 mg/L CPD20

Temperature Effect Increasing system temperature affects both scalant supersaturation and DCP performance.4,5 The effect of temperature on DCP efficacy was evaluated by operating the DSTR at higher bulk water (52 ºC) and skin (70 ºC) temperatures than the typical “low stress” conditions (see Table 2). The PBTC dosage was increased to 8 ppm (thereby creating BLT2) to control CaCO3. Table 4 presents DSTR evaluation results for these high temperature conditions (HAP-SI @ 255k and LSI @ 2.34). Acceptable tests results for all performance parameters are highlighted in light green.

Table 4 data indicate that BLT2 plus ≥2 mg/L additional DCP (vs. typical alkaline cooling conditions) was required to provide clean HTSs and acceptable CRs. It is interesting that both CPD31 and CPN23 required 7 mg/L dosages to achieve acceptable results under the typical alkaline conditions whereas 11 and 10 mg/L, respectively dosages were required when operating at higher bulk and skin temperatures. The best performance was provided by 6 mg/L CK798 (vs. 4 mg/L at lower temperatures). The DCP performance ranking (best to worst) is shown below.

CK798 > CPN23 > CPD31 > CPA54 ≈ CK775 > CPD20

Table 4: DSTR Results – High Temperature Alkaline CW Conditions with BLT2 and DCP (e.g., 600 mg/L Ca as CaCO3, pH 8.4 to 8.6, 52 ⁰C bulk water, 70 ⁰C skin [LSI @ 2.34 & HAP-SI @ 255k]) Final Δ Final LCS AB Treatment PO4 Turb.* CR** CR** SS HTS Deposit AB HTS Deposit (mg/L) (NTU) (mpy) (mpy) Observations Observations Target performance <1 --- <1 <0.2 Clean Clean 4 mg/L CK798 + BLT1 1.1 1.22 0.89 0.12 Very Slight Slight 5 mg/L CK798 + BLT1 0.9 1.03 0.79 0.13 Clean Very Slight 6 mg/L CK798 + BLT1 0.3 0.57 0.78 0.09 Clean Clean 8 mg/L CPD31 + BLT1 1.4 1.37 0.98 0.14 Slight Slight 9 mg/L CPD31 + BLT1 1.1 1.05 0.89 0.12 Clean Very Slight 10 mg/L CPD31 + BLT1 0.4 0.85 0.87 0.10 Clean Clean 10 mg/L CPA54 + BLT1 1.0 1.1 0.89 0.13 Very Slight Slight 11 mg/L CPA54 + BLT1 0.4 0.78 0.81 0.11 Clean Clean 8 mg/L CPN23 + BLT1 1.0 1.09 0.87 0.13 Clean Very Slight 9 mg/L CPN23 + BLT1 0.2 0.79 0.78 0.12 Clean Clean 10 mg/L CK775 + BLT1 1.1 1.2 0.81 0.14 Clean Very Slight 11 mg/L CK775 + BLT1 0.4 0.78 0.79 0.12 Clean Clean 11 mg/L CPD20 + BLT1 1.3 1.2 1.1 0.18 Very Slight Very Slight 12 mg/L CPD20 + BLT1 0.6 0.84 0.92 0.14 Clean Clean Notes: * Turb. = Turbidity, ** CR= Corrosion Rate

Figure 3 shows (a) clean HTS surfaces using BLT2 and 6.0 mg/L CK798 and (b) slight HTS deposit using BLT2 and 8.0 mg/L CPD31.

Figure 3: DSTR High Temperature Alkaline CW Conditions using BLT2 plus DCP at EOT HTS (a) Clean Surfaces using 6 mg/L CK798 (b) Slight HTS Deposits using 8 mg/L CPD31

Suspended Solids (Clay) Effect During droughts and heavy rainfall periods, high clay and silt levels are common in makeup cooling waters. High suspended solids levels in makeup cooling waters create additional stress and necessitate higher DCP dosages to maintain acceptable treatment levels. Suspended matters’ (i.e., clay, iron oxide) impact on DCP performance was previously investigated.4,7 These studies showed that adding suspended matter to Ca/P and CaCO3 supersaturated solutions negatively impacts DCP performance. These performance decrease observations may be attributed to DCP adsorption on suspended solids, thus reducing the DCP available for deposit control. By contrast, other laboratory testing indicates that suspended solids (i.e., clay’s presence) had an insignificant impact on silica polymerization inhibitor performance.8

Clay (50 mg/L) was added to the DSTR make-up water to evaluate its impact on DCP performance in alkaline cooling water applications. Table 5 presents these DSTR evaluation results using the DCPs polymers containing three or more monomers. The data include both initial and final turbidity values (the former elevated values reflect clay’s addition). Acceptable tests results for all performance parameters appear in bold font highlighted in light green.

Table 5: DSTR Results – Stressed Alkaline CW Conditions with BLT1, DCP, and 50 mg/L Clay (e.g., 600 mg/L Ca as CaCO3, pH 8.4 to 8.6, 48.9 ⁰C bulk water, 60 ⁰C skin [LSI @ 2.23 & HAP-SI @ 170k]) Final Δ Initial Final LCS AB PO4 Turb.* Turb. CR** CR SS HTS Deposit AB HTS Deposit Treatment (mg/L) (NTU) (NTU) (mpy) (mpy) Observations Observations Target performance <1 ------<1 <0.2 Clean Clean In4 mg/L CK798 + BLT1 0.8 9.8 6.4 0.89 0.13 Very Slight Very Slight 5 mg/L CK798 + BLT1 0.2 10.1 7.9 0.91 0.14 Clean Clean 7 mg/L CPD31 + BLT1 1.1 9.7 4.6 0.87 0.12 Slight Slight 8 mg/L CPD31 + BLT1 0.8 9.8 5.5 0.86 0.13 Clean Very Slight 9 mg/L CPD31 + BLT1 0.6 9.9 7.0 0.90 0.14 Clean Clean 9 mg/L CPA54 + BLT1 1.5 10.2 5.4 0.96 0.13 Slight Slight 10 mg/L CPA54 + BLT1 0.8 9.4 6.3 0.89 0.15 Very Slight Very Slight 11 mg/L CPA54 + BLT1 0.6 9.8 7.1 0.93 0.14 Clean Clean Note: * Turb. = Turbidity, ** CR= Corrosion Rate

Under these clay added stressed conditions, higher DCP dosages were needed to provide acceptable deposit control; i.e., 5 mg/L CK798 (25% higher than w/o clay); 9 mg/L CPD31 (29% higher than w/o clay), 11 mg/L CPA54 (22% higher than w/o clay). Figure 4 shows the high turbidity water maintained using 5 mg/L CK798 and clean HTS surfaces when removed at the EOT.

Figure 4: DSTR Stressed Alkaline Conditions using BLT1 with 50 mg/L Clay & 5 mg/L CK798 EOT HTSs (a) HTSs before Removal from Cooling Water (b) HTSs after Removal from Cooling Water

For the clay added DSTR alkaline cooling water condition evaluations, the DCP performance ranking (highest to lowest) was as follows: CK798 > CPD31 > CPA54

Iron Effect The type and extent of upstream pretreatment process may play a role on the performance of a CWT program containing anionic polymers. Some feedwaters, especially surface waters, may require extensive pretreatment. Waters containing suspended matter are typically treated with coagulating or

©2017 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 15835 Park Ten Place, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. 7 flocculating agents before entering the cooling water system. Commonly used coagulating/flocculating include aluminum and iron based salts and high molecular weight cationic polymers. It is well known that low levels of trivalent metal ions (i.e., Al3+, Fe3+) can markedly antagonize DCP performance.2, 9-11

Iron’s presence in cooling system recirculating waters, originating from either makeup water or corrosion byproducts, can adversely impact CWT program performance and/or increase the DCP demand due to its adsorption on hydrolyzed metal ions. To simulate iron contamination, the DSTRs were run using the typical water chemistry and operating conditions (see Table 2) while continuously adding iron (via makeup water) to maintain 5 mg/L iron in the recirculating water. The DCPs containing three or more monomers were tested.

Table 6 presents results for DSRT evaluation incorporating 5 mg/L iron test data; acceptable results for all performance parameters appear in bold font highlighted in light green. Higher DCP dosages are required to off-set iron’s antagonistic effect and obtain acceptable results; 2 mg/L more for both CK798 (increased from 4 to 6 mg/L) and CPD31 (increased from 7 to 9 mg/L) and 3 mg/L more CPA54 (increased from 9 to 12 mg/L). This marked Fe3+ antagonism is consistent with previously reported trivalent metal ions’ impact on DCP performance.2,9-11

Table 6: DSTR Results – BLT1, DPC, and 5.0 mg/L Iron (e.g., 600 mg/L Ca as CaCO3, pH 8.4 to 8.6, 48.9 ⁰C bulk water, 60 ⁰C skin [LSI @ 2.23 & HAP-SI @ 170k]) Final Δ Final LCS AB Treatment PO4 Turb.* CR** CR** SS HTS Deposit AB HTS Deposit (mg/L) (NTU) (mpy) (mpy) Observations Observations Target performance <1 --- <1 <0.2 Clean Clean 4 mg/L CK798 + BLT1 1.1 1.2 1.10 0.21 Very Slight Slight 5 mg/L CK798 + BLT1 0.8 0.93 0.98 0.13 Clean Very Slight 6 mg/L CK798 + BLT1 0.3 0.89 0.89 0.13 Clean Clean 7 mg/L CPD31 + BLT1 1.5 1.10 1.22 0.20 Slight Slight 8 mg/L CPD31 + BLT1 0.6 0.94 0.97 0.18 Very Slight Very Slight 9 mg/L CPD31 + BLT1 0.2 0.86 0.92 0.15 Clean Clean 9 mg/L CPA54 + BLT1 1.5 1.40 1.51 0.25 Slight Moderate 10 mg/L CPA54 + BLT1 1.1 1.10 1.32 0.22 Very Slight Slight 11 mg/L CPA54+ BLT1 0.6 0.96 0.97 0.18 Clean Very slight 12 mg/L CPA54+ BLT1 0.6 0.92 0.93 0.16 Clean Clean Notes: * Turb. = Turbidity, ** CR= Corrosion Rate

CONCLUSIONS This study used DSTRs to evaluate the impact of water chemistry and operating conditions changes on DCP performance as a component of alkaline cooling water treatment programs. The data reported herein lead to the following observations:  Ca/P inhibition increases with DCP dosage.  Increasing recirculating cooling water bulk and skin temperatures from 120 °F (48.9 °C) to 126 °F (52 °C) and from 140 °F (60 °C) to 158 °F (70 °C), respectively necessitates higher (≥2 mg/L) DCP dosages to achieve clean HTSs and acceptable CRs.  Adding either clay (50 mg/L) or iron [5 mg/L Fe(III)] to the recirculating cooling water markedly antagonizes DCP performance necessitating higher DCP dosages to achieve acceptable deposit control and CRs.  DCP architecture significantly influences performance and the overall DCP performance trend is:

CK798 > CPD31 ≈ CPN23 > CPA54 ≈ CK775 > CPD20

©2017 by NACE International. Requests for permission to publish this manuscript in any form, in part or in whole, must be in writing to NACE International, Publications Division, 15835 Park Ten Place, Houston, Texas 77084. The material presented and the views expressed in this paper are solely those of the author(s) and are not necessarily endorsed by the Association. 8 ACKNOWLEDGEMENTS The authors thank John Zibrida for water scaling indices calculations and The Lubrizol Corporation for permission and support to conduct this investigation and present the results at NACE International’s Annual Convention.

REFERENCES 1. Z. Amjad, K. Demadis, Mineral Scales and Deposits (Amsterdam, Netherlands, Elsevier, 2015). 2. Z. Amjad, J. Pugh, J.F. Zibrida, R.W. Zuhl, “Polymer Performance in Cooling Water: The Influence of Process Variables,” MP 36, 1 (1997): pp. 32-38. 3. Z. Amjad, “Calcium Phosphate in Biological and Industrial Systems,” (Boston, MA, Kluwer Academic Publishers, 1998) Chapter 16, “Development of Calcium Phosphate Inhibiting Polymers for Cooling Water Applications.” 4. Z. Amjad, D. Butala, J. Pugh, “The Influence of Recirculating Impurities on the Performance of Calcium Phosphate Inhibiting Polymers,” CORROSION/99, paper no. 118 (Houston, TX: NACE, 1999). 5. L. Perez, Z. Amjad, R.W. Zuhl, “Stressed Cooling Water Systems Deposit Control Management,” CORROSION/2016, paper no. 7521, (Houston, TX: NACE, 2016). 6. L. Perez, Z. Amjad, R.W. Zuhl, “Stressed Alkaline Cooling Water System Deposit Control,” Paper presented at the 2016 Association of Water Technologies Annual Convention, San Diego, CA (2016). 7. Z. Amjad, J. Penn, “Impact of Iron Oxide on Calcium Carbonate Inhibitors,” MP 53, 12 (2013): pp. 52-56. 8. Z. Amjad, J.F. Zibrida, R.W. Zuhl, “A New Antifoulant for Controlling Silica Fouling in Reverse Osmosis Systems,” paper presented at the International Desalination Association, World Congress on Desalination and Water Reuse, Madrid, Spain (October 1997). 9. E.B. Smyk, J.E. Hoots, K.P. Fivizzani, K.E. Fulks,” The Design and Application of Polymers in Cooling Water Programs,” CORROSION/88, paper no. 14 (Houston, TX: NACE, 1988). 10. Z. Amjad, “Calcium Phosphate Inhibition by Polymeric Inhibitors: The Influence of Aluminum (III), Iron (III), and Iron (II),” Phos. Res. Bull. 9 (1999): pp. 115-124. 11. A. Marshal, B. Greaves, “The Effect of Water Quality on the Performance of Extended Phosphate Technology,” CORROSION/86, paper no. 399 (Houston, TX: NACE, 1986).