Analyses of foam in Bayer precipitation tanks due to crystal growth modifiers

Foam generation in Bayer precipitation tanks is a major issue that affects the energy efficiency of precipitation in these tanks. However, the factors contributing to foam generation remain poorly understood. This work investigated the relationship between different crystal growth modifiers (CGMs) and foam generation during the precipitation process. Results indicate that in pure sodium aluminate solution, the addition of CGMs directly affects the foam volume. Furthermore, the foam generation potential (FGP) of CGMs varies significantly. CGM-A and CGM-B exhibited minimal FGPs at concentrations up to 300 mg/L in sodium aluminate solution containing aluminum tri-hydroxide (ATH) solids, resulting in practically no foam. In contrast, CGM-C presented stronger FGP at 100 mg/L, generating 8 mL of foam. The FGP of CGMs increased following high-temperature treatment at 260 °C. The FT-IR, GC–MS, and ¹H NMR analyses indicated that the large amounts of unsaturated fatty acids in CGM-C were a major cause of foaming. After high-temperature treatment, numerous alkane molecules were generated in the CGM-C, which served as foam stabilizers. This study provides valuable reference for further improvement of the alumina production capacity.