Measuring sparingly-soluble,aqueous salt crystallization kinetics using CSTRs-in-series:methodology development andCaCO3 studies
We present a methodology and results for measuring crystallization kinetics of sparingly-soluble salt mixtures typical of reject/concentrate streams from membrane-based, inland water supply processes. More usable water can be recovered (and lower disposal costs incurred) from these concentrate streams through efficient crystallization. In this work, we present a steady state, continuous stirred tank reactors (CSTRs)-in-series approach to study crystallization kinetics of a model solution mixture that is supersaturated in CaCO3. We have used pH, conductivity and turbidity changes in the system to monitor crystallization. We examined how mixing energy dissipation affects the induction times for crystallization. Notably, discernible crystallization could only be advanced to the 1st CSTR by using a recirculation loop to "fine-tune" the effect of surface area exposure-to-volume ratio, as well as, mixing energy dissipation. A rudimentary, semi-empirical model was used to capture the parametric trends of our experimental results, using the Kolmogorov mixing lengths, surface area-to-volume ratios, flow rates, and nominal diffusion coefficients. This parameterization may be tested further for design scale-up guidance.
Need and Benefit
It is well accepted that a major drawback to widespread adoption of reverse osmosis (RO) desalination for inland areas is the lack of economical and environmentally-satisfying solutions for handling the concentrate streams generated from desalination processes.
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Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Measuring sparingly-soluble,aqueous salt crystallization kinetics using CSTRs-in-series:methodology development andCaCO3 studies (final, PDF, 1.5MB)
By Sankaranarayanan A. Ravichandran, Jordan Krist, Dakota Edwards, Saied Delagah, John Pellegrino
Report completed on September 30, 2020
Measuring Sparingly-Soluble,Aqueous Salt Crystallization Kinetics (final, PDF, 285KB)
By Saied Delagah
R&D Bulletin completed on March 30, 2021