Change of critical supersaturation ratio in CaCO₃ scale formation

The effects of solution temperature, contact time of fouling ions, type and concentration of scale inhibitors on critical supersaturation ratio (CSSR) of CaCO₃ solution were evaluated. The change of surface free energy during crystallizing of CaCO₃ in presence of scale inhibitors was studied according to the light of homogeneous nucleation theory. In the presence of aminotrimethylene phosphonic acid (ATMP), CSSR decreased more with the increase of temperature than that in the presence of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) or polyacrylic acid (PAA). The effect of CaCO₃ nucleation with PBTCA and ATMP on surface free energy was more obvious than that with PAA. Crystalline form of CaCO₃ precipitate transformed from calcite in main into vaterite in main in the presence of scale inhibitors.