103,323 research outputs found
Investigation of Sublimating Dry-ice due to Accidental Release in the Framework of CCS Risk Analysis
No full textDealing 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
Safety parameters and stability diagram of hydroxylamine hydrochloride and sulphate
No full textThe 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
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
Evaluation of Safety Scenarios for Fires in Waste Disposal Facilities through Numerical Simulations
No full textAfter 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
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
The prognostic value of serum S100B in patients with cutaneous melanoma: a meta-analysis
No full textS100B protein detected in the serum of patients with cutaneous melanoma has been long reported as a prognostic biomarker. However, no consensus exists on its implementation in the routine clinical setting. This study aimed to comprehensively and quantitatively summarize the evidence on the suitability of serum S100B to predict patients' survival. Twenty-two series enrolling 3393 patients with TNM stage I to IV cutaneous melanoma were reviewed. Standard meta-analysis methods were applied to evaluate the overall relationship between S100B serum levels and patients' survival (meta-risk). Serum S100B positivity was associated with significantly poorer survival (hazard ratio [HR] = 2.23, 95% CI: 1.92-2.58, p < 0.0001). Between-study heterogeneity was significant, which appeared to be related mainly to dissemination bias and the inclusion of patients with stage IV disease. Considering stage I to III melanoma (n = 1594), the meta-risk remained highly significant (HR = 2.28, 95% CI: 1.8-2.89; p < 0.0001) and studies' estimates were homogeneous. Subgroup analysis of series reporting multivariate survival analysis supported S100B as a prognostic factor independent of the TNM staging system. Our findings suggest that serum S100B detection has a clinically valuable independent prognostic value in patients with melanoma, with particular regard to stage I-III disease. Further investigation focusing on this subset of patients is Justified and warranted before S100B can be implemented in the routine clinical management of melanoma. (C) 2008 Wiley-Liss. Inc
Hazard analysis of carbon sequestration pipelines. The effect of impurities and insulation specs on the release evolution
No full textEvaluating the thermal stability of chemicals and systems: A review
No full textIn the realm of chemical processing, particularly at the industrial scale, safety is of utmost importance. A predominant factor causing accidents within the chemical industry is runaway phenomena, primarily initiated by uncontrolled exothermic reactions. This review critically examines the often-overlooked decomposition mechanisms as a significant contributor to thermal energy release, necessitating a comprehensive revision and understanding of both experimental and theoretical strategies for assessing thermal degradation. Key to this discourse is the explication of calorimetry as the principal experimental technique, alongside ab initio quantum chemistry simulations as a robust theoretical framework for quantifying the most relevant properties. However, more than mere cognisance of these methodologies is required for a meticulous thermal stability assessment. The review emphasizes identifying and quantifying fundamental parameters through experimental and theoretical investigations. Only upon acquiring these parameters, including kinetic, thermodynamic, onset, and peak characteristics of the exothermic decomposition reactions, can one effectively mitigate risks and hazards in designing and optimizing chemical processes and apparatus. Furthermore, this review delineates qualitative and quantitative methodologies for hazard assessment, proffering strategies for estimating safe operational conditions and sizing relief devices. The paper culminates in exploring future trajectories in thermal stability assessments, focusing on emerging applications in lithium-ion batteries, electrolyzers, electrified reactors, ionic liquids, artificial intelligence and machine learning approaches. Thus, the paper underlines the evolving landscape of thermal risk management in contemporary and future chemical industries
Enhancing safety in the storage of hazardous molecules: The case of hydroxylamine
No full textHandling large quantities of thermally unstable compounds in storage vessels can result in severe accidents due to runaway reactions. Therefore, developing inherently safe design strategies for storage equipment is crucial for enhancing chemical plant reliability and preventing hazardous scenarios. The Frank-Kamenetskii theory (FKT) of self-heating offers practical tools for designing procedures to address phenomena that could lead to uncontrolled chemical reactions. This study introduces a design procedure based on the FKT for creating intrinsically safe storage vessels. An expanded FKT version incorporating parametric sensitivity analysis has been developed to improve the method's reliability. To understand self-heating phenomena, stability and performance diagrams were created, relating critical design parameters (e.g., the critical value of the Frank-Kamenetskii number) and verification parameters (e.g., maximum reached dimensionless temperature) to the dimensionless activation energy (γ). Additionally, the proposed design strategy includes a procedure for designing relief systems to mitigate the risk of equipment explosions from runaway reactions. The applicability of this procedure was tested using two cases: (I) an aqueous solution containing 50% w/w hydroxylamine (HA) and (II) a 50% w/w HA aqueous solution with 1% w/w hydroxylamine hydrochloride (HA-derived salt). Results indicate that for large γ values, the traditional FKT formulation and the expanded theory yield similar vessel designs. However, for finite γ values (γ≤100), the refined FKT version allows for less conservative storage equipment design. Combining DIERS guidelines with standard procedures for relief systems results in a more versatile and consistent protocol. However, incorporating relief systems is often impractical for large storage vessels due to the excessively large venting areas required for runaway reactions. In such cases, intrinsically safe vessel designs become the only feasible solution to prevent catastrophic incidents
Safe Egress Scenario Detection: From Baseline to Active Events
No full textCrowd management in public walking spaces has been a topical research theme. In fact, in some spaces
such as squares, stations, and commercial areas, there is a strategic need of addressing the uprising
challenges to public safety, ensuring an effective crowd evacuation in emergency scenarios induced
by various hazardous critical events, including malicious actions performed by individuals or groups.
Already existing engineering tools can support the evaluation of the egressing scenario by means of
simulations so that such tools can support emergency operators in finding the best strategy during a
dynamic egress scenario.
However, egress within a space is influenced by many factors, such as the number of bystanders and
their age, or the position of the initiating event. As a result, an infinite number of combinations may
occur, thus is unfeasible to provide a scenario to support emergency operators, which must rely on a
subset of simulations to be called when the egress event starts. Moreover, it is difficult to identify if an
egress event has started since the movement of people is usually recorded via people counter sensors
which are placed at egress exits.
In this paper, a novel approach to safe egress is discussed. Such an approach, starting from pre calculated simulations, defines a baseline of the number of people crossing an exit in a normal scenario.
Such baseline can be compared with the real sensor data to identify anomalies and thus detect egress
start. In this paper, sensor data is replaced with egress simulations for comparison
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