(124a) Inhibition of Scale Formation By Surfactants: Fundamentals and Applications

The crystallization of mineral scale plays an important role in many industrial applications such as production of phosphoric acid, desalination, and water treatment. Supersaturation leads to scale formation along the pipe walls and since the thermal conductivity of these scales is very low, thin deposits can create a significant resistance to heat transfer.

Thick deposits reduce the output of the system and require frequent cleaning to maintain efficiency. In phosphoric acid manufacturing, multistage evaporators are frequently used to increase the concentration of dilute phosphoric acid to 52-55 wt. % P₂O₅. The concentrated phosphoric acid solution is supersaturated with respect to calcium sulfate, and other scale forming constituents. Past attempts to develop robust antiscaling additives for the phosphoric industry have not been successful at plant scale.

Solvay has successfully developed and demonstrated an antiscalant technology that substantially reduces the fouling issue in wet-process phosphoric acid production plants. This study focuses on investigating the underlying mechanism of the Phosflow^® additive in inhibiting scale formation. Thus far, the antiscalant additive has been determined to impact induction times and solubility of several scales in various conditions. Work is in progress to investigate the effect of the additive on morphology and adhesion properties of the crystals. Results of these studies would enable a better understanding of the underlying mechanism.