Abstract
In this study, a strictly anoxic bottle test setup has been built for FeS scale nucleation and growth kinetic at various temperatures, pH and ionic strength conditions. The FeS was generated by in-situ mixing of ferrous ion (Fe(II)), sulfide ion (S(-II)), dispersant and pH buffer (PIPEs or acetic acid), respectively. The glass vial reactors were then placed into the heating block to reach the designated reaction temperature for 2 hours, and then set at room temperature for another 20 h. The ferrous ion and total sulfide remained in the aqueous phases were filtered and measured to evaluate the control efficiency. Under experimental condition, the iron sulfide scale was effectively controlled by CMC dispersant. The dispersant mechanism was studied combined lab observation and nucleation-diffusion theory. According to our study, iron sulfide particle would go through a very fast nucleation, which is hard to do inhibition control like barite or calcite. While the dispersant like CMC can effectively stop iron sulfide scale formation by crystal growth inhibition. A new numerical theory has been proposed to predict the required amount of CMC to effectively disperse iron sulfide particle and control the size under 1 μm for 22 hours under temperature 23 to 90 °C, pH 4.4 to 6.7 and ionic strength 0.1 to 5M conditions.
