The formation of scale deposits is a serious problem in the operation of oil fields, desalination plants and geothermal wells. Oil field scales are formed mainly from the sparingly soluble sulfates and carbonates of calcium, strontium and barirum. All the available scale prediction models are based on thermodynamics and, hence, can predict only the potential to form scale. To understand and predict actual scale formation, it is necessary to study and incorporate into scale prediction models, the kinetics and mechanism of precipitation from solution over wide ranges of temperature, pressure, ionic strength and supersaturation. The kinetic data available in the literature cover a reasonably wide range of supersaturation, but are in a narrow range of temperature around 298 K. There are hardly any discussions on the effects of ionic strength and pressure on spontaneous precipitation.
In this work, the precipitation of strontium sulfate from supersaturated solutions was studied by monitoring the changes in strontium ion concentration during spontaneous precipitation. This work presents the experimental results on the effects of temperature and ionic strength on the rate constant. Kinetic rate expressions, which may be used in the development of models for predicting scale formation, are developed.