ACUMER™ ACUMER™ 5000 - ANIQ

1 ACUMER . WATER TREATMENT POLYMERS. ACUMER 5000. Multipolymer for Silica and Magnesium Silicate Scale Control Cooling water reuse is frequently limited by a ceiling proven by exacting pilot studies and field trials, on the amount of tolerable silica in the recirculation allowing for greater water reuse than ever before. water. Normally, if silica levels exceed about 180 ppm ACUMER 5000 polymer prevents silica-based scale for- SiO2, severe scaling can occur on heat transfer sur- mation by dispersing colloidal silica and by preventing faces. Moreover, the scale that forms is frequently dif- magnesium silicate scale formation at the heat trans- ficult or impossible to remove by conventional fer surfaces. The unique features of ACUMER 5000. means. ACUMER 5000 silica control polymer has polymer in the treatment of silica limited cooling now raised that ceiling to at least 300 ppm SiO 2, water are presented below. Feature Your Benefit Your Customer's Benefit as a Service Company Maximum silica Increased cycles of concentration Increased water reuse.

2 Reduction dispersancy and in silica-limited water. Reduced in chemical use. Maintenance of magnesium silicate blowdown. Maintenance of clean process efficacy. scale inhibition. heat transfer surfaces. Superior dispersant Complete fouling control with a Less risk of fouling due to changing for particulates. single dispersant. Less inventory conditions. required. Effective corrosion No special formulating requirements. Longer plant lifetime. control when used with conventional corrosion inhibitors. Chemically and Usable in single-package formulation. Simplified feed and control. thermally stable. 2005 Rohm and Haas Company PHYSICAL PROPERTIES. The typical physical properties of ACUMER 5000 poly- Colloidal silica, which forms when the solubility level mer are listed in Table 1. of silica is exceeded, is difficult to measure under field conditions, and a total silica mass balance cannot be TABLE 1 achieved with a simple field test.

3 The most effective method of determining total silica is described in TYPICAL PHYSICAL PROPERTIES Standard Methods for the Examination of Water and (these do not constitute specifications) Wastewater , 17th edition (Method 4500-SiC). A sim- pler method that converts other forms of silica to Molecular Weight 5000. molybdate-reactive silica is described in Rohm and Total Solids, % to sm Haas Technical Bulletin FC-267, ACUMER TST , Active Solids, % 42 Total Silica Test for High-Silica Waters . pH to Brookfield Viscosity, cp 700 max. As the colloidal silica passes into the Nernst diffusion layer at the heat transfer surface, it dissolves and Specific Gravity acquires a negative (anionic) charge. Polyvalent Bulk Density, lb/gal (g/cc) 10 ( ). cations, especially magnesium, tend to react with these Lb (Kg) of 100% NaOH to anionic colloidal particles effectively gluing them neutralize 1 lb (kg) of polymer together and ultimately forming a hard, glassy magne- sium silicate scale.

4 FORMATION OF SILICA-BASED SCALE. Figure 1 shows how colloidal silica can dissolve to Silica forms particles with different structures depend- form silicate in the high temperature/high pH envi- ing upon the pH, presence of other ions and process ronment near a corroding cathodic surface where dis- by which the particles are formed. The three main solved oxygen is reduced to hydroxide ions. These forms of silica encountered in cooling water are: freshly formed silicate anions, added to the dissolved Molybdate-reactive silica: frequently referred to as silica already present, can then form magnesium sili- dissolved silica. cate scale (MgSiO3). In addition, colloidal silica Colloidal silica: polymerized silica particles of alone can coprecipitate with magnesium hydroxide to micron or less. form a scale of magnesium silicate having non-stoi- Silicate scale: primarily magnesium silicate, but chiometric ratios of magnesium to silicate.

5 May also be iron or calcium silicate. 2 . FIGURE 1. MAGNESIUM SILICATE SCALE FORMATION. HO OH. O O O iO. Si Si O S Si O O O O. Micron O O. Maximum O. HO SiOSi O Si Si O SiOSi OH. O O O O O O O. i O Si Si OS O O. Si OH. HO O. Bulk Water pH 8-9. Ca OH. Mg Mg Mg Mg Nernst Diffusion Layer Mg Mg pH ~ 10. Mg Mg ~ 5 - 10 C Higher Than Bulk Ca Mg Mg Fe+3. HO HO OH OH. Fe Fe Mg Fe Mg Mg Fe Mg Mg Fe Mg Mg Mg Mg Fe OH HO. Mg Fe Fe HO OH. Composite Particle Fe Mg/Ca/Fe/Silica Mg Mg Mg Ca Mg - OH. Mg Mg Mg Fe Mg HO. Fe+3 OH. Fe Fe+2 Anodic Area HO. Cathodic Area MgSiO3 Scale Fe0 Mild Steel Surface 3 . Mechanism for Controlling Silica MAGNESIUM SILICATE SCALE. PREVENTION WITH ACUMER 5000. The remarkable properties of ACUMER 5000 polymer POLYMER. derive in large part from its three distinctive function- alities. The weak acid (carboxylate) group provides a ACUMER 5000 Polymer Action in means of attaching the polymer to metal ions in solu- Recirculating Water tion and to the surfaces of particles or crystals.

6 This Photomicrographs using cross-polarized lenses can enables the polymer to act as a dispersant to prevent be used to study crystal structures. Figure 3 shows the agglomeration and deposit formation as well as stabiliz- dispersed silica using ACUMER 5000 polymer in the ing contaminants. The strong acid (sulfonate) con- recirculating water versus agglomerated silica parti- tributes to this process by increasing the solubility and cles in Figure 2 without polymer. charge density of the polymer which enhances electro- static repulsion of particles. FIGURE 2. What sets ACUMER 5000 polymer apart, however, is a DRIED FILM OF AGGLOMERATED SILICA. unique third set of functionalities, based on balanced PARTICLES WITHOUT POLYMER AT pH 9. hydrophilicity and lipophilicity (hydrophobicity)1. Where the other functionalities operate primarily through charge-transfer, this so-called HLB functional- ity promotes physical adsorption on the surfaces of contaminant particles especially at higher tempera- tures.

7 By promoting adsorption, this third type of functionality also contributes to the strength of the energy barrier (or the net repulsive force) created by the polymer around the silica particle. ACUMER 5000 polymer adsorbed on the colloid sur- faces provides an energy barrier that prevents precipi- tation and agglomeration. Moreover, even if the silica particles precipitate, they are spaced too far apart for Scale has large well-defined crystals typical of those found magnesium or redissolved silicate anions to bind them on cooler surfaces in cooling towers. together. As a result, the scale formed by these parti- cles will be powdery and, thus, easier to remove. FIGURE 3. For additional information on these mechanisms DRIED FILM OF DISPERSED SILICA. please request the following reprints: PARTICLES WITH ACUMER 5000. POLYMER AT pH 9. Hann, W. M. and Robertson, , Control of Iron and Silica with Polymeric Dispersants , IWC Paper (1990).

8 Hann, W. M., Robertson, and Bardsley, , Recent Experience in Controlling Silica and Magnesium Silicate Deposits with Polymeric Dispersants , IWC Paper (1993). 1 The idea of enhancing adsorption by balancing hydrophilic and lipophilic moieties is borrowed from sur- factant chemists who use the term HLB (hydrophile/. lipophile balance) to describe surfactant solubility and adsorption characteristics. Acumer 5000 polymer does not actually have surfacant-like properties, but it behaves in an Smaller dispersed crystals of colloidal silica. analogous way. 4 . ACUMER 5000 Polymer Action at Heat PERFORMANCE OF ACUMER 5000. Transfer Surface POLYMER. ACUMER 5000 silica control polymer also prevents Accelerated Pilot Cooling Tower Tests formation of magnesium silicate under the condi- A series of 3-day pilot cooling tower (PCT) tests were tions found near a heat transfer surface, as shown in run to compare the dispersing efficiency of Figures 4 and 5.

9 ACUMER 5000 polymer with that of conventional products. The water chemistry and operating para- FIGURE 4. meters of the PCT in these studies are shown in DRIED FILM OF MAGNESIUM SILICATE Tables 2 and 3. SCALE WITHOUT POLYMER PRESENT. AT pH 10. TABLE 2 - MAKEUP WATER CHEMISTRY. Si, as SiO2 50 ppm Ca, as CaCO3 60 ppm Mg, as CaCO3 90 ppm M-Alkalinity, as CaCO3 100 ppm Fe+3, as Fe ppm TABLE 3 - AVERAGE OPERATING CONDITIONS. Crystals are smaller but more numerous than in Figure 2, probably due to the presence of many small magnesium sil- pH icate particles. Cycles of Concentration (start-up). Cycles of Concentration to FIGURE 5. ( after 3 days). DRIED FILM UNDER SAME CONDITIONS. AS IN FIGURE 4, BUT WITH Heat Flux 31,520 W/m2. ACUMER 5000 POLYMER PRESENT Skin Temperature 105-120 F (41-49 C). Bulk Water Temperature 100 F (38 C). The treatment formulation used to evaluate polymer efficacy consisted of 2 ppm tolyltriazole (TTA), 10 ppm active polymer, and a 1/1 blend of 2-phosphonobu- tane-1,2,4-tricarboxylic acid (PBTC) and 1-hydrox- yethylidene-1,1-diphosphonic acid (HEDP) to give 5 ppm total active phosphonate.

10 At start-up, the for- mulation was fed into the system at three times the normal strength to compensate for the high concen- trations of silica, calcium and magnesium. Crystals are very small and sparse due to polymer inhibi- tion of magnesium silicate formation which seeds scale for- mation. 5 . In these accelerated tests, water passed over a series ACUMER 5000 polymer shows only a light dusting of of four heat transfer rods in succession. Scale scale (Figure 6), considerably better than the other formed on all four rods, with each developing more polymers tested (Figures 7 and 8). Within the limits of scale than its immediate predecessor. This progres- experimental error, the scale compositions obtained sive deposition was caused by the water becoming with all tests were approximately the same, >80% mag- hotter as it passed over the rods in succession. As the nesium silicate (Table 5). water temperature rose, the tendency for deposits to form increased.