(687g) Safe Parking of Batch Processes

The operation of chemical processes often encounters faults. Owing to the frequency of fault operation and the significant economic, environmental and safety impact, several research efforts have focussed on developing methodologies for handling faults [1,2,3]. Most existing results on fault-tolerant control, however, have focussed on continuous processes, where the objective is to preserve operation around the nominal equilibrium point. More recently, a safe-parking framework [4] has been developed that addresses the problem of faults that preclude the possibility of continued operation at the nominal equilibrium point and prevents the onset of hazardous situations while enabling smooth resumption of nominal operation.

Existing fault handling techniques, and the safe-parking framework of [1], however, are not directly applicable to batch processes due to the fact that the desired process objective, that of producing the required product, is inherently not that of stabilization around an equilibrium point. Motivated by this consideration, this work considers the problem of developing safe-parking framework for batch processes. The key idea is to utilize available control action following a fault to maintain system conditions such that the desired end point can finally be reached upon fault rectification. The ideas are demonstrated through a CSTR example operated in batch mode with 2 inputs and a fed-batch bioreactor system with 1 input.

References

[1] Mhaskar, P., A. Gani, N. H. El-Farra, C. McFall, P. D. Christofides and J. F. Davis, "Integrated Fault Detection and Fault-Tolerant Control of Nonlinear Process Systems,'' AIChE J., 52, 2129-2148, 2006.

[2] P. Mhaskar, ``Robust Model Predictive Control Design for Fault-Tolerant Control of Process Systems,'' Ind. Eng. & Che. Res., 45, 8565-8574, 2006.

[3] Mhaskar, P., C. McFall, A. Gani, P. D. Christofides and J. F. Davis, "Isolation and Handling of Actuator Faults in Nonlinear Systems,'' Automatica, 44, 53-62, 2008.

[4] Mhaskar, P. AND Gandhi, R. (2008). Safe-parking of Nonlinear Process Systems. Computers and Chemical Engineering, 32, in press.