(185y) Process Synthesis and Simultaneous Minimization of Inherent Risk

Although process synthesis has received significant attention during last decades, only a few studies on process synthesis with simultaneous consideration of inherent safety have been performed. The safety of processes and their subsystems, however, is among the most important considerations for obtaining operable process plants. The safety can be efficiently enhanced if it is considered at the early stages of the design, as implementation of safety principles and measures during early decision making is both more effective and less costly. The aim of this study is to develop a risk assessment method by which it would be possible to obtain an appropriate trade-off between process economy and inherent risk. A mixed-integer nonlinear programming (MINLP) model has thus been formulated where the inherent risk expressed by monetary cost terms is imbedded in the objective function defined as yearly profit or net present value. The inherent risk is defined as an annual expected cost by multiplication of frequency of failure and estimated money losses due to expected severity of consequences. The developed approach is illustrated by two examples, i) the synthesis of a heat exchanger network and ii) the synthesis of an overall process scheme. The results indicate that the simultaneous approach enables obtaining designs which are significantly safer and yet still economically viable.