Thermal stability criterion integrated in model predictive control for batch reactors

• Published in: Chemical engineering science Vol. 188; pp. 192 - 207
• Main Authors: Kähm, Walter, Vassiliadis, Vassilios S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 12.10.2018
• Subjects: Intensification of batch processes; Model predictive control; Thermal runaway detection; Thermal stability criterion; Model predictive control; Intensification of batch processes; Thermal runaway detection; Thermal stability criterion
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2018.05.032

[Display omitted] •Limitations of current stability criteria for thermal runaway detection identified.•Novel stability criterion for more reliable runaway detection is proposed and tested.•Online integration of stability criterion into MPC scheme.•New robust scheme for optimising control with improved stability performance.•Illustrative case studies with large improvements to stability and productivity. Thermal runaways can have a significant impact on the performance and normal operation of reaction processes, causing safety issues and financial loss, which hinder the intensification of such processes. More specifically, a control system that does not possess proper detection mechanisms of the boundary of stability will by necessity be overly conservative. This leads to poorer performance and the inability to intensify the process, i.e. to reduce process times for example and also to achieve higher yields. For the intensification of batch processes a stability criterion, based on the divergence criterion, is presented. The derivation of the stability criterion and a comparison to the original divergence criterion is shown for several batch reactions. It is shown that the stability criterion classifies the system behaviour more reliably for the case studies considered. This stability criterion is embedded in Model Predictive Control, which is a novel control scheme. This scheme allows the controlled increase of the reaction temperature while keeping the processes in a stable region, hence reducing the risk of thermal runaways. This control system enables batch processes to achieve a target conversion in a reduced completion time of reaction and an intensification of batch processes.