466912 Understanding Rare Safety and Reliability Events Using Transition Path Sampling
A rare-event sampling technique, Transition Path Sampling (TPS), has been developed by the molecular dynamics community. While the time and length scales between molecular dynamics and process dynamics differ greatly, the ratios of the time of the rare events and the waiting time between them are similar. This Monte-Carlo based technique relies on the simulation of perturbed rare-event trajectories – an initial rare-event trajectory is randomly modified such that large numbers of trajectories are generated. Clusters of rare safety-event trajectories can be the basis for alarm and safety-system design, assuring that TPS-generated clusters are preventable. Important modifications to the TPS technique are needed to apply it to process dynamics. The backwards integration, a key attribute of TPS, is not possible for most process simulations – instead a boundary-value optimization technique is used. Furthermore, process models use of the vast amount of process data available for model verification and to estimate the relative likelihood of one trajectory to another. The application of TPS will be demonstrated using a simple jacketed exothermic CSTR, as well as a more complex air separation unit process. This innovative approach allows for a quantitative rationalization of alarm and safety systems to prevent rare, yet serious, safety events.
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