The inhibition of gypsum and barite nucleation in NaCl brines at temperatures from 25 to 90°C

Abstract

The inhibition of gypsum and barite nucleation in NaCl brines by phosphonates and polycarboxylates was studied at 25, 50, 70 and 90°C in terms of the prolonged induction period. Hexamethylene-diaminetetra (methylene phosphonic) acid (HDTMP) was found to be an effective inhibitor for the scaling of calcium sulfate dihydrate. Hydroxyethylene-1, 1-diphosphonic acid (HEDP) and phosphinopolycarboxylic acid (PPPC) were found to be effective inhibitors for barium sulfate scaling. The inhibition of nucleation through prolongation of the nucleation induction period likely resulted from an increase in the interfacial tension between the crystal and aqueous solution due to the presence of the inhibitors. It was observed that the inhibition of nucleation depends highly on the lattice cation/anion molar ratio and the pH of the solution as well as the degree of supersaturation and temperature for a given inhibitor.