1,721,071 research outputs found
Influence of the shape of mitigation barriers on heavy gas dispersion
Full text linkRegasification plants have become an emerging risk because their numbers are increasing and concern from the general population towards these systems has grown. Consequently, there is increased interest in investigating the effect of mitigation measures to limit the impact of large accidents on the population living close to the plant. Among the various possible mitigation measures, physical barriers present several advantages; however, it is known that the necessary barrier height can became impracticably large to be effective in mitigating the consequences of a large LNG release. Therefore, computational fluid dynamics models were used in this work to analyze the performance of mitigation barriers with different shapes to investigate the possibility of increasing mitigation barrier efficiency by simply changing the main geometrical characteristics of the barrier such as roughness, battlements, or even holes
Definition of a NaTech risk analysis methodology for assessing tornado-related risk for storage tanks
Full text linkNatural catastrophic events, such as storms, earthquakes, flooding, and lightning; impacting industrial activities can trigger accidental scenarios, causing the release of hazardous substances from installations and storage, in events referred to as “Na-Tech” (Natural and Technological). Most of the attention in the literature has been devoted to accidents triggered by floods and earthquakes, while no specific analysis protocols aimed at determining the risk posed by tornadoes and strong gusts of wind on industrial facilities are available. Consequently, the purpose of this paper is to fill a gap in NaTech risk assessment, developing a qualitative methodology for the initial assessment of tornado-related Na-Tech risk for storage tanks, as previous works based on historical analysis have identified storages as the most critical asset, serving as a screening tool to determine which situations require a much more expensive Quantitative Risk Analysis (QRA). In the proposed methodology suitable Key Hazard Indicators (KHIs) were defined, requiring a limited amount of resources and information both on the intensity and frequency of the stormy event and on the plant and the characteristics of the assets in it, organizing them using the Analytical Hierarchy Process as a multi-criteria decision tool. In so doing, a specific Na-Tech risk level can be associated with a given situation (i.e., a process plant located in a given territory). The developed methodology was applied to a case study plant, and then a sensitivity analysis to both the locations and parameters was performed
Influence of large obstacles and mitigation barriers on heavy gas cloud dispersion: an LNG case-study
No full textThe study of the consequences of heavy gases releases is of paramount importance in the safety analysis because of
the large damage areas involved. The Computational Fluid Dynamics (CFD) models, unlike the integral ones that are simpler and
faster, allow for a complete description of complex geometries, such as those involved in industrial plants or urban areas. In this work,
the effect of typical large obstacles present in a real plant has been studied. Moreover, to verify the effectiveness of mitigation barriers
on the dispersion of clouds produced by massive release of heavy gases, several types of walls have been investigated by analyzing the induced changes in the hazardous area
Mechanistic modelling of avascular tumor growth and pharmacokinetics influence—Part I
No full textA mechanistic model for the avascular tumor growth both for in “in vivo” and “in vitro” conditions is presented here. It involves the main
cell physiology, like the growth (by substrate uptake), the mitosis, the apoptosis and the necrosis, all with their corresponding kinetics. The
resulting population balance was solved through the moments’ method. Moreover, the model was combined with the classic equations of
pharmacokinetics to consider also the presence of active drugs affecting either the kinetics of cell necrosis or growth. The model was compared
with literature tumor growth data both for in vivo and in vitro conditions
Definition of a short-cut methodology for assessing the vulnerability of a territory in natural-technological risk estimation
Full text linkNatural disasters may be powerful and prominent mechanisms of direct or indirect release of hazardous material. The main aim of this work was to develop a short-cut methodology for assessing the vulnerability of a territory around an industrial plant in order to evaluate the Natural???Technological (NaTech) risk. In particular the combined use of a global key hazard indicator with the key vulnerability indicator proposed in this work allows the measurement of the NaTech risk arising from the presence of a plant in a territory with given characteristics. The proposed methodology was validated by comparing its results with quantitative risk analysis (QRA) results, involving earthquake-related NaTech events. The agreement of the results obtained with the proposed methodology with those arising from a much more detailed \{QRA\} carried out with the ARIPAR-GIS software in several case study supports the reliability of the proposed approach
Safety of LPG rail transportation: influence of safety barriers
No full textThe risk due to the road and rail transportation of liquefied petroleum gas (LPG) is well
known. Severe scenarios were caused by road or rail accidents involving LPG pressurized tank cars.
Consolidated approaches exist for the analysis, the prevention and the mitigation of risk due to the
transportation of hazardous materials (HazMat) by road or rail. In Europe a specific regulation applies
to the equipment used for the transport of HazMat and specific regulations apply to the qualification of
equipment used for LPG transportation. Nevertheless, on June 29th, 2009, an extremely severe
transportation accident involving LPG took place in the station of Viareggio, in Italy. A train carrying
14 tank cars of LPG derailed and several railcars overturned on the shunts in the Viareggio station. A
tank was punctured, releasing its entire content that ignited causing an extended and severe flash-fire.
The present study focused on the study of the effect of different parameters on the heavy gas cloud
dispersion resulting from the accident, such as meteorological parameters and height of safety walls.
It was found that, to be effective, the mitigation barriers must be carefully designed, with particular
reference to their height with respect to the height of the heavy gas cloud
Influence of active mitigation barriers on LNG dispersion
Full text linkIn recent years, particular interest has been direct to the issues of risk associated with the storage, transport and use of Liquefied Natural Gas (LNG) due to the increasing consideration that it is receiving for energy applications. Consequently, a series of experimental and modeling studies to analyze the behavior of LNG have been carried out to collect an archive of evaporation, dispersion and combustion information, and several mathematical models have been developed to represent LNG dispersion in realistic environments and to design mitigation barriers.
This work uses Computational Fluid Dynamics codes to model the dispersion of a dense gas in the atmosphere after accidental release. In particular, it will study the dispersion of LNG due to accidental breakages of a pipeline and it will analyze how it is possible to mitigate the dispersing cloud through walls and curtains of water vapor and air, also providing a criterion for the design of such curtains
CFD modeling of emulsions inside static mixers
Full text linkEmulsification carried out in continuous devices offers a series of advantages over batch emulsion, such as better control of the droplet size distribution, reduced volume equipment, and lower operative costs. This paper investigates through Computational Fluid Dynamics simulations the emulsification process inside Sulzer Static Mixers. An analysis aimed to identify the most appropriate turbulence model, from a practical point of view, was performed, finding that the realizable Kappa – Epsilon model is more suitable than the well-known Kappa - Omega model. Moreover, an operative correlation linking the Sauter diameter to the main operating parameters, in a wide range of fluid properties and operating conditions, was developed
Heavy gas dispersion in presence of large obstacles: selection of modeling tools
Full text linkA general criterion to foresee whether the presence of an obstacle on the cloud pattern can influence significantly the hazardous distance resulting from the dispersion of a heavy hazardous gas has been proposed. This criterion requires comparing the characteristic dimensions of the obstacles with those of the cloud in open field conditions on a suitable dimensionless space. It can be useful to discriminate between accidental scenarios that can be conservatively simulated using an integral model to that requiring CFD models, to identify which obstacles can be safely neglected when representing the real environment’s geometry in a computational domain without compromising the simulation reliability, and to estimate at a first glance the minimum size of a mitigation barriers able to induce a significant change in the hazardous distance
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