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Firefighting strategies at process plants would include simultaneous extinguishment of burning units and cooling of exposed units if firefighting resources are sufficient. This way, the fire can be contained and its propagation to the exposed units can be prevented, which would otherwise cause fire escalation and result in domino effects. However, when the firefighting resources are not sufficient to handle all the critical units—either burning or exposed—at once, firefighters need to decide which burning units to suppress first and which exposed units to cool first to minimize the risks. Making effective decisions in such situations becomes critical knowing that, by spreading the fire to adjacent units, the number of critical units grows exponentially, making the available firefighting resources even more insufficient. In the present study, after modelling fire spread in a tank terminal as a directed graph, closeness centrality—a graph centrality metric—is used to identify the critical units from the viewpoint of their contribution to potential domino effects. Knowing the critical units and considering available firefighting resources for suppression and cooling of these units, mathematical programming is applied for optimal allocation of firefighting resources. A comparison between the results of the present work and previous studies shows the effectiveness of the developed methodology. [ABSTRACT FROM AUTHOR]

To accurately model the consequences of accidental dust explosions, numerical simulations of the flame propagation process are required. A key parameter in these models is the burning velocity (Su), which represents the consumption rate of the reactants by the flame front. Experiments are therefore needed to determine the burning velocity, and the influence of turbulence on this velocity; as well as to validate these models of flame propagation. In this article, aluminum flame propagation inside a vertical duct with obstacles is studied. The aim of the obstacles is first to increase the turbulence just in front of the flame front, in order to quantify its influence on the burning velocity. The second objective of the implementation of the obstacles is to obtain experimental data in a more complex geometry in order to validate the models. During these experiments, the flame propagation is recorded and the unburned flow velocity is measured using the TR-PIV (Time-Resolved Particle Image Velocimetry) technique. This innovative measurement of the unburned flow velocity is important not only for the accurate determination of the burning velocity, but also to validate these numerical simulations. An increase in the propagation velocity and the burning velocity is observed as the flame propagates toward the obstacles. [ABSTRACT FROM AUTHOR]

The increasing global demand for cleaner energy sources implies the use of H2 which poses significant safety issues. One of the major safety issues in H2 management is the storage, based on extreme condition technology (high pressure and/or very low temperatures). Alternatively, instead of H2, ammonia may be used since storage of NH3 is much simpler from a technological point of view. From a safety point, the comparison between the risk of H2 storage and NH3 storage has still to be understood. The energy (H2) sector worldwide is a dynamic and complex system, relying on the mutual interactions between different factors like safety, risk, sustainability, political and social decisions, and economic impact. The understanding and management of global behaviour can be obtained by taking into account all the interactions among these factors. In order to deal with such complex systems, system thinking, and system dynamics approaches could be developed and used. The present work aims to develop an integrated Systems Thinking approach for assessing and managing the safety of storage systems with a particular focus on the comparison between hydrogen and ammonia. The developed models integrate the complex interdependencies considering material properties, environmental conditions, and storage infrastructure. Systems Thinking is used for mapping the intricate network of interdependencies, considering storage vessel design, regulatory frameworks, and emergency response plans. Therefore, by adopting this holistic perspective, potential vulnerabilities and leverage points of the system are identified which lead to improving the overall safety of gas storage systems. Additionally, this research explores the dynamic behaviour of safe storage under different scenarios, including temperature fluctuations, pressure changes, and potential leaks. The development of System Dynamics-based models offers valuable insights for policymakers, industry stakeholders, and researchers alike. The integration of a Systems Thinking approach allows for a better understanding of the complex interactions involved in the safe storage of these technologies for informed decision-making and advancements in gas storage technologies. [ABSTRACT FROM AUTHOR]

The chemical industry often handles, stores, and processes molecules like hydroxylamine (HA) and hydrogen peroxide (HP), which can easily undergo thermal decomposition reactions. Hence, the ideal perspective is to have simple quantitative criteria to use during the equipment design phase, accommodating the possibility of exothermic degradations of substances to enhance process safety and avoid thermal runaways. To this aim, the Frank-Kamenetskii theory of self-heating (FKT) can be involved in determining the critical size of a storage vessel to guarantee the intrinsic safe storage of chemically hazardous materials. Eventually, the proposed design strategy will be implemented to design storage equipment for two commercial aqueous solutions of HA and HP, respectively. In this way, it will be possible to compare the inherent thermal hazard linked to the storage of these mixtures, evaluating the threshold vessel size above which the self-heating phenomenon of the materials becomes no longer controllable. The HA and HP mixtures can be used alone or together in chemical processes as oxidants or precursors for producing hydroxyl radicals. Under comparable conditions free of impurities and organic contamination, the results show that the system made of 50 %w hydrogen peroxide is more stable than hydroxylamine. This is reflected in a larger characteristic size of the storage vessel able to handle appropriately self-heating phenomena potentially leading to runaway. [ABSTRACT FROM AUTHOR]

Flammable liquids typically adopted in chemical and industrial processes can be subjected to intense heat radiation due to nearby hot surfaces or fires. A second cascading event is then likely because the flash point can be easily reached and the surrounding environment can provide sufficient energy for ignition. Nevertheless, the flaming condition is not necessarily reached instantaneously if no direct (e.g., spark) ignition is present. Hence, a time to flaming, i.e., in the absence of an ignition source, is extremely relevant for the active and passive fire protection of flammable liquid, as the minimum time for intervention can be defined before developing a pool fire and for the correct evaluation of domino effects, in analogy with gas fires. In addition, a complete characterization of liquid behaviour under radiant heating is essential to guarantee safe operations, prevention measures, robust databases and optimized design. Therefore, this work reports the results for three liquid solvent representative classes of substances: i) hexane, ii) ethyl acetate, and iii) ethanol. A bench scale facility was adopted for the characterization of mass and energy aspects involving a pool fire of the investigated substances. Among the others, the ignitability and the intensity of the generated pool fires were evaluated experimentally in terms of mass burning rate, heat release rate, and combustion efficiency. Different boundary conditions were tested to identify the optimized set of conditions for a robust evaluation of the safety aspects of liquid. Results showed the most relevant trends in terms of ignitability of liquid species and combustion intensity during the pseudo-steady state regime of a pool fire. In addition, indications on the boundary conditions to be considered for a robust and consistent dataset were provided in this work. [ABSTRACT FROM AUTHOR]