pH control of a fed batch reactor with precipitation

In this paper, the problem of controlling the pH, in a fed batch reactor where precipitation occurs, is considered. Due to the batch nature of the production and the effects of precipitation, the control problem is rather different from the well studied cases of continuous processes, which are usually considered under the assumption of perfect solubility. To fulfill this objective on a presented laboratory reactor used to produce precipitates, a simple control strategy is proposed, which is consistent with the limitations of the apparatus. Interestingly, the reagents under consideration have well known specifications. This point is advantageously taken into account to identify a single-input–single-output model off-line. Then, based on the obtained time-varying equation, pH set point tracking is achieved by imposing linear asymptotically stable dynamics on the amount of strong acid used for neutralization. Finally, simple rules are proposed to deal with precipitation. Representative experimental results obtained on the reactor are presented to prove the relevance of the approach. 2008 Elsevier Ltd. All rights reserved.