Mathematical Modeling of a pH Swing Precipitation Process and its Optimal Design

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Hauptverfasser: Hiremath, Sandesh Athni, Hegde, Chinmay, Voigt, Andreas
Format: Preprint
Veröffentlicht: 2025
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author Hiremath, Sandesh Athni
Hegde, Chinmay
Voigt, Andreas
author_facet Hiremath, Sandesh Athni
Hegde, Chinmay
Voigt, Andreas
contents In this work we consider the semi-batch process of precipitation of calcium carbonate solids from a solution containing calcium ions by adjusting the pH of the solution. The change in pH is induced either by the addition of alkaline solution such as sodium hydroxide (NaOH) or by the addition of a carbon dioxide gas (CO$_2$) to the given ionic solution. Under this setup we propose a system of degenerate stochastic partial differential equations that is able to explain the dynamical behavior of the key components of precipitation process. In particular, we propose a semi-linear advection equation for the dynamics of particle size distribution (PSD) of the precipitated particles. This is in turn coupled with a system of stochastic differential equations (SDEs) that is able to explain the chemical kinetics between calcium ions (Ca$^{+2}$), calcium carbonate (CaCO$_3$) in aqueous state and pH of the solution. The resulting coupled system is first mathematically studied, in particular conditions for the existence of a mild-solution is established and also the long time behavior of the system is established. Following this we consider the validation of the model for which we consider experimentally obtained lab-scale data. Using this data we propose three methods to fit the model with the data which then also validates the suitability of the proposed model. The three methods include manual intuitive tuning, classical forward backward SDE (FBSDE) method and finally a DNN based method. The FBSDE method is based on the stochastic optimal control formulation for which we provide the necessary and sufficient condition for the existence of an optimal solution. Lastly, we compare the three methods and show that DNN method is the best in terms of lowest error and as the most economical in terms of the compute resources necessary during online use.
format Preprint
id arxiv_https___arxiv_org_abs_2507_08891
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Mathematical Modeling of a pH Swing Precipitation Process and its Optimal Design
Hiremath, Sandesh Athni
Hegde, Chinmay
Voigt, Andreas
Optimization and Control
In this work we consider the semi-batch process of precipitation of calcium carbonate solids from a solution containing calcium ions by adjusting the pH of the solution. The change in pH is induced either by the addition of alkaline solution such as sodium hydroxide (NaOH) or by the addition of a carbon dioxide gas (CO$_2$) to the given ionic solution. Under this setup we propose a system of degenerate stochastic partial differential equations that is able to explain the dynamical behavior of the key components of precipitation process. In particular, we propose a semi-linear advection equation for the dynamics of particle size distribution (PSD) of the precipitated particles. This is in turn coupled with a system of stochastic differential equations (SDEs) that is able to explain the chemical kinetics between calcium ions (Ca$^{+2}$), calcium carbonate (CaCO$_3$) in aqueous state and pH of the solution. The resulting coupled system is first mathematically studied, in particular conditions for the existence of a mild-solution is established and also the long time behavior of the system is established. Following this we consider the validation of the model for which we consider experimentally obtained lab-scale data. Using this data we propose three methods to fit the model with the data which then also validates the suitability of the proposed model. The three methods include manual intuitive tuning, classical forward backward SDE (FBSDE) method and finally a DNN based method. The FBSDE method is based on the stochastic optimal control formulation for which we provide the necessary and sufficient condition for the existence of an optimal solution. Lastly, we compare the three methods and show that DNN method is the best in terms of lowest error and as the most economical in terms of the compute resources necessary during online use.
title Mathematical Modeling of a pH Swing Precipitation Process and its Optimal Design
topic Optimization and Control
url https://arxiv.org/abs/2507.08891