A Process Operability Approach for Safety-Critical Chemical and Energy Production

Effective management of exothermic reactions, particularly those involving volatile substances, is crucial in chemical process industries to prevent catastrophic events such as thermal runaways. Thermal runaway occurs when a reaction generates heat that accelerates the reaction further, leading to uncontrollable temperature increases. To mitigate such risks, this study employs a comprehensive risk management approach combining steady-state operability, dynamic operability, and control strategies.

Steady-state operability focused on assessing the achievability of desired operating regions by specifying the range of input variables, known as the Available Input Set (AIS), defined by upper and lower bounds of design and/or operational variables. Input-output mappings generate the Available Output Set (AOS), which represents the outputs that the system can achieve. By the identification of the desired operating boundaries, known as Desired Output Set (DOS), the inverse mapping enables the identification of their respective Desired Input Set (DIS), providing a feasible operating range that ensures desired risk levels. Dynamic operability introduces a time-dependent component, assessing system responses to disturbances. This approach parallels steady-state operability but incorporates variations in heat transfer characteristics over time, allowing for the evaluation of how the feasible ranges of input variables adjust in response to disturbances. The assessment is conducted through both open-loop and closed-loop simulations. In the closed-loop scenario, a Proportional-Integral (PI) controller is employed to manage the system.

This methodology is demonstrated on two safety-critical systems: a Continuous Stirred-Tank Reactor (CSTR), modeled after the T2 Laboratories accident, and an electrolyzer used for hydrogen production from water for clean energy applications. The findings of this study offer a valuable framework for enhancing the safety and efficiency of these critical processes.