While current approaches for the safety verification (understood here as the verification that the trajectories of the system remain in a prescribed set in the state space) of hybrid systems yield rigorous proofs for system safety, their applicability is restricted to relatively small systems. In this paper, the safety properties of a logic-controlled industrial processing system with hybrid dynamics are investigated using two optimization-based approaches. In the first approach, the hybrid system is regarded as a black box (i.e. only the input-output behavior is considered), and optimization-based techniques are used to compute worst-case scenarios. The second approach employs a semi-analytical technique by combining rigorous theorem proving that is applied to the dynamic equations of the process with the computation of worst-case scenarios using global non-linear optimization techniques. It is shown that both approaches are able to determine safety-critical evolutions for a rigorous hybrid model of the industrial-scale evaporation system. (C) 2008 Elsevier Ltd. All rights reserved.