| Scope and method of study. The purpose of this study was to develop a mixed-bed ion-exchange model to handle boron. To achieve this goal, boron solution thermodynamics has been studied; and based on which, rate expressions for boron transfer and polyborate reaction on the resin and inside the resin have been proposed. In addition, the column material balance has been derived in terms of the constituent species concentrations only with modifications for boron. Finally, boron solution chemistry and polyborate reactions were implemented into the model, and the effluent concentrations were determined by solving column material balance equations along with the rate expressions and boron polymerization reactions.; Findings and conclusions. The mixed bed ion exchange column model for boron has been successfully programmed into a computer program and is capable of predicting all inputted ions of the effluent concentration histories, dynamic resin loading, solution concentration, and rate profiles. The model is able to express the variable capacity due to the boron polymerization reaction inside the resin. The column material balance has been satisfied to within 2% for all chemistries studied. The model satisfies the criteria established for validating proper model. Also, the model was tested for a wide range of operating conditions with key variable changes of +/−10% and the results obey acceptable trends. The model maintains electroneutrality at all times. Boron species transfer is adequate, but additional work is required to incorporate molecular constituent mass transfer for a better model. |
