1,720,999 research outputs found
A Numerical Study of Effects of an Industrial Hazardous Release On People Egress
Full text linkThe release and dispersion of toxic materials from industrial equipment may pose severe concerns and have tragic consequences. The assessment of such scenarios relies on broad literature, approaches, and modelling tools that support estimating the impact area. However, hazard assessments do not generally embed the egress modelling and the impact of a toxic release on people evacuating. The present work couples a gas dispersion model with evacuation dynamics to estimate the near-field impact on people approaching a safe place. It is applied to a hypothetical case study concerning a release of dense chlorine, in which the effect of adopting different assumptions is discussed
A review of the basic safety requirements of emerging infrastructures for green transition
Full text linkThe transition to a Climate-Neutral economy requires a reduction of energy-related carbon dioxide emissions and Carbon dioxide capture and geological storage (CCS) is a key technology that will contribute to mitigating climate change. Hazards and risks related to processing, transport, and storage of CO2 are not new aspects, but peculiarities of CO2 safety scenarios can lead to risk underestimation and misperception. Solid-phase occurrence and heavy gas dispersion, multiphase releases, leakages from wells and storage sites, and the integrity of equipment subjected to internal corrosion and cryogenic temperatures, are typical scenarios involved in CCS chains. These are often mentioned in technical standards and regulations and require proper advanced assessment. In this work, the main hazards and risk scenarios in CCS operations with a special focus on atypical instances that are peculiar to the case of CO2 will be reviewed. Open issues concerning the modeling of consequences and specific risk-related topics are discussed
Addressing waste disposal fires in open fields through large eddy simulations
No full textAddressing fires in waste disposal facilities is of topical interest for firefighting and environmental protection. Statistics of fires that involve fuel matrixes made of diversified wastes are escalating and ask for an effective response, both in prevention and mitigation. Crucial to this target is the consideration of underlying phenomena, and modeling of fire dynamics and pollutant emission also via robust numerical simulations. In this work, fires in waste disposal facilities are addressed with Large Eddy Simulation to test the capability to catch the main phenomena of the combustion of wastes made of plastic and the consequent emission of pollutants. This approach is applied to fuel matrixes in form of piles of different sizes, made of polyolefins and polyvinylchloride burned in an open field. The atmospheric dispersion of pollutants, including soot, carbon monoxide, carbon dioxide, and hydrogen chloride are investigated under different environmental conditions. Besides, thermal aspects are addressed to come up with indications of the heat release rate
Study of formation, sublimation and deposition of dry ice from carbon capture and storage pipelines
No full textClimate Change is caused by greenhouse gases such as CO2. Worldwide increases in energy demand coupled with a continued reliance on flues derived from fossil resources have contributed to a significant and severe increase in atmospheric levels of CO2. Scenarios for stabilizing the emissions of CO2 suggest its stabilization through a portfolio of mitigation actions including the deployment of Carbon Capture and Storage projects (CCS). One of the process step consists in the transportation of the CO2 to a storage location and this work focuses on dry ice formation following the accidental release of pressurized CO2 from CCS pipelines. The main aim is to investigate the dynamic and thermal fluid dynamic behaviour of a dry ice particle travelling down to the ground through air after the expansion to atmospheric conditions. This is achieved analyzing the influence of all the variables involved in the phenomenon, that is to say: particle initial diameter, post - expansion velocity and temperature, position and direction of the release point, air temperature, relative humidity and Pasquill atmospheric class of stability. The effect of these parameters on the in - flight life of the particle is discussed assembling an analytical model of equations of motion and of mass and heat transfer in order to establish which one is the most influential. © Copyright 2014, AIDIC Servizi S.r.l
Evaluation of Safety Scenarios for Fires in Waste Disposal Facilities through Numerical Simulations
Full text linkAfter several high-profile fires in waste and recycling facilities, the industry is put under pressure, especially as the materials processed in waste recycling are getting increasingly dangerous. Fire is an ever-present possibility at most waste management sites requiring proper preventive and mitigative strategies because it can cause significant damage to people, property and the environment. Fire risk assessment may benefit from applying the concept of fire safety engineering and numerical tools to approach the phenomena quantitatively. However, the complexity of such fire scenarios requires a detailed analysis that also involves an insight into fundamental processes, including pyrolysis of solid waste matrices and combustion of pyrolizate. These steps are critical for defining safety features of fire scenarios in waste disposal facilities, but the availability of input data may limit the modelling capability of numerical tools. The present work deals with modelling a fire scenario of a bale of plastics starting from literature data in which both pyrolysis and combustion are addressed. Having an accurate reaction model is of paramount importance in modelling solid waste fires. However, full-scale fire tests in open fields will be required to validate and systematize how piles of material burn dependently on boundary conditions
Hazard analysis of carbon sequestration pipelines. The effect of impurities and insulation specs on the release evolution
No full textOn the use of Fire Safety Engineering to Evaluate the Performance of Heat Detectors in High Ceiling Application
Full text linkIn the framework of design and installation of fire detection and fire alarm system in buildings, when high ceilings are involved, it is likely to run into the limits of the more common standards. Several regulations fix a ceiling height limit beyond which heat, smoke, and combustion gas detectors should not be mounted. Among the available technologies, the aspirating smoke detection (ASD) systems have the highest limit (i.e., 40 m according to BS 5839-1:2017). Nevertheless, this technology should not be used when processes that yield smoke, fumes, dust, etc., are present, and an alternative type of fire detector needs to be employed. This is due to the necessity to avoid false alarms, which is critical for successful fire detection and alarm systems. The concomitance of these two situations, i.e., dusty environments and high ceiling height, is not unusual in the industrial sectors. To investigate it, the state-of-the-art solution is adopting the principles of Fire Safety Engineering (FSE). The FSE is based on calculations that consider the conservation of mass and energy and permit to predict several crucial quantities such as the smoke temperature, smoke volume (and layer height), and species concentrations resulting from a fire of a given size (ISO/TS 13447:2013). In this work, a series of Computational Fluid Dynamics (CFD) simulations were conducted to assess the performances of a fire detection system composed of heat detectors installed at heights up to 20 m larger than the standard limit. The characteristics of an actual building adopted for storage of hazardous materials and a real heat detector system were considered. The temperature field resulting from two different types of t2-growth fire, i.e., one ultra-fast and one with slow evolution, were analyzed. The corresponding alarm times were evaluated and compared with ASD characteristics timings, recognized as a benchmark for its high sensitivity
The inclusion of natural hazards in QRA: The seismic event
No full textQRA procedures applied to industrial equipment require special attention when dealing with unconventional hazard scenarios. In this perspective, the role played by severe natural events on the functionality of an industrial system is surely of interest in any exhaustive risk assessment study. The focus on earthquake initiating events is due to their severity and strong destructive potential that can lead to severe damages, domino effects and cross effects on residential and industrial sites. In this work, a probability approach that includes unconventional initiating events in usual Fault Tree and Event Tree analysis procedures is proposed to ensure a reliable earthquake-related event management. Main relevant parameters are evaluated, in addition to the typical expected structural behaviour of the industrial structure. The comparison between the scenario without the seismic event and that aggravated by the earthquake shows that, depending on the both the seism and structural parameters, such an unconventional initiating event worsen the final outcomes. Variations are depending on the site-epicentre distance and the seism magnitude and peculiar effects on the final outcomes are observed both in the FTA and ETA initiating branches. Copyright © 2019, AIDIC Servizi S.r.l
Safety parameters and stability diagram of hydroxylamine hydrochloride and sulphate
Full text linkThe thermal instability of hydroxylamine (HA) poses severe concerns in the process industry, while preventive and mitigative strategies are required to reduce the frequency and magnitude of associated decomposition phenomena. From this perspective, formulating an aqueous solution or using derived salts could be a solution for risk reduction. Nevertheless, the effect of HA-derived salt addition on HA/water solutions has yet to be reported in the literature. For this reason, the scope of the present work is to examine experimentally whether salt addition can reduce the occurrence and severity of HA thermal degradation. Samples containing HA and hydroxylamine sulphate (HAS) or hydroxylamine hydrochloride (HH) were analysed. During the experimental campaign, a calorimeter was used for the assessment of reaction kinetic, thermodynamic, and onset features. The determined parameters were used for safety purposes to understand the related thermal hazards and to provide stability diagrams. The results show, under certain conditions, that the type and amount of HA-derived salt determines an attenuation of the decomposition of HA/water solutions. Moreover, increasing the amount of salt enhances the susceptibility to decomposition of the HA/water solution, while lower salts content could help stabilise the HA mixtures. According to the developed stability diagram, an inherently safe zone for reaction or storage has been established. Eventually, the proposed structured approach can be intended as a strategic procedure to involve the reaction parameters gathered, which is helpful for drawing general guidelines for establishing safer processes and reaction conditions
Investigation of Sublimating Dry-ice due to Accidental Release in the Framework of CCS Risk Analysis
Full text linkDealing with pressurized releases of CO2 from Carbon Capture and Storage systems is of topical interest for the safety assessment of such infrastructures. Evidence shows that a sublimating bank of CO2 can be formed following a loss of containment, which acts as a delayed source of heavy CO2 gas. This source of hazard requires estimation in terms of sublimating mass flow rate, flux, and thermal features. In this work, we illustrate an experimental apparatus to measure the main properties of sublimating CO2 banks for estimating safety parameters. Data concerning mass flow rate, fluxes and temperature were successfully estimated. We measured mass fluxes in the range from 160 to 240 g/(min m2) of CO2, and we observed a relevant temperature variation. From experimental data, we proposed an approach to evaluate a representative driving force that includes the central feature of the CO2 to accumulate in the vicinity of the sublimating bank
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