Automatic Start-up of Chemical Processes

During start-up of chemical processes, a wide operating range has to be covered, and a single linearised model is therefore not adequate for control synthesis. We have investigated two approaches that are based on our group s work on hybrid systems: (i) if specifications are coarse enough to be formalised as discrete dynamic models, the problem can be addressed using abstraction-based methods. This has been demonstrated for a two-column distillation system [14]. (ii) If specifications are continuous, we apply a hierarchical scheme, where a discrete high-level controller switches between suitable continuous low-level controllers. In cooperation with the PCP group, this is cur-rently being applied to the start-up of a reactive distillation column.