Robert W. Zuhl

Scale and Deposit Control Polymers for Industrial Water Treatment

The accumulation of unwanted deposits on equipment surfaces is a phenomenon that occurs in virtually all processes in which untreated water is heated. The deposits commonly encountered may be categorized into the following five groups: (a) mineral scales (e.g. CaCO3, CaSO4 ⋅ 2H2O, BaSO4, Ca3(PO4)2, CaF2, SiO2), (b) suspended matter (e.g. mud or silt), (c) corrosion products (i.e., Fe2O3, Fe3O4, ZnO, CuO), (d) microbiological, and (e) metal-inhibitor salts. The deposition of these materials, especially on heat exchanger surfaces in cooling, boiler, geothermal, and distillation systems, can cause a number of operational problems such as plugging of pipes and pumps, inefficient water treatment chemical usage, increased operation costs, lost production due to system downtime, and ultimately heat exchanger failure. Greater water conservation has been a driver for operating industrial water systems at higher cycles of concentrations, thereby increasing the potential for deposit buildup on heat exchanger surfaces. Operating industrial water systems under stressed conditions demands a better understanding of system (feed and recirculating) water chemistry as well as the development of new and innovative agents for controlling scale/deposit, corrosion, and biofouling. Researchers have proposed several chemical addition options for controlling scale formation including the use of acids, chelants, or inhibitors. The most promising scale control method involves contents

Performance of Anionic Polymers as Precipitation Inhibitors for Calcium Phosphonates: The Influence of Cationic Polyelectrolytes

This paper addresses the precipitation of calcium salts of phosphonates (i.e., hydroxyethylidine 1,1 -diphosphonic acid, HEDP; aminotri(methylene phosphonic acid), AMP; 2-phosphono-butane 1,2,4-tricarboxylic acid, PBTC) at pH 8.50 and 50°C. The aim of the study was to investigate the role of cationic polyelectrolytes (i.e., poly(diallyldimethyl ammonium chloride), Poly-E and poly(acrylamide:2-(acrolyloxy)ethyltrimethyl ammonium chloride), Poly-F) on the performance of several anionic calcium phosphonate inhibiting polymers. The anionic polymers studied include: acrylic acid/maleic acid-based homo-, co-, and terpolymers; fulvic acid (FA) and tannic acid (TA). The inhibiting data on several anionic polymers indicate that the performance of polymers depends on the type of the functional groups present in the polymer. It has been found that addition of low concentrations (from 0.25 to 1.0 parts per million) of Poly-E and Poly-F adversely impacts the performance of calcium phosphonate inhibiting polymers. The results also indicate that under similar experimental conditions Poly-F exhibits a stronger antagonistic affect than Poly-E.