1,720,988 research outputs found
Explosion Scenarios Due to Rapid Phase Transition of Liquefied Natural Gas Released from Offshore Receiving Terminals and Sea Carriers
No full textExplosion Scenarios Due to Rapid Phase Transition of Liquefied Natural Gas Released from Offshore Receiving Terminals and Sea Carrier
Temperature control of Lithium-ion battery packs under high- current abuse conditions
No full textLi-ion batteries are being widely used as power sources in a continuously increasing number of applications (from portable devices to electric vehicles and even more complex systems). Nonetheless these components are still characterized by serious concerns connected with their safety and stability, which often hinder their more widespread use. In particular, their operation is strictly dependent on their temperature which derives from the balance between the heat internally produced during operation and that dissipated towards the external environment. Beyond certain temperatures a thermal runaway can occur with possible dangerous events, such as fires and explosions. In the present paper, 3D simulations have been carried out to investigate the cooling efficiency of an air flow, under different operating conditions, on a cylindrical Li-ion cell located in a whole battery pack. Under the investigated configurations, it was found that, beyond a minimum value of the passing air velocity, it is possible to keep the cell within safe conditions, thus preventing a thermal runaway
Seismic risk in the chemical process industry: A semi-quantitative methodology for critical equipment identification
No full textNatural events, such as earthquakes, floods, etc., can play a significant role in triggering industrial accidents of various intensities (the so-called Na-Tech risk), so that their inclusion in a comprehensive risk assessment is very important. However, a detailed and comprehensive quantitative approach is often unrealistic, because of the extremely large number of calculations to be carried out and of scenarios to be analysed. A preliminary semi-quantitative methodology is here presented for the characterization of the safety level of the different equipment items located in an industrial site, with respect to seismic hazard. Still based on objective evaluations, the presented approach allows to reduce the calculation burden, rank the equipment items in terms of relative seismic risk, and to identify the most critical items which more urgently need further attention. Along with the proposed methodology, an example of its application to a real industrial case is presented
Safety barrier management. Risk‐based approach for the oil and gas sector
Full text linkIn the Oil and Gas sector, risk assessment and management have always been critical due to the possibility of significant accidents associated with the presence of large amounts of flammable hydrocarbons. Methods to provide accurate and reliable risk analysis for an oil platform usually focus on critical equipment and identify causes and consequences of loss of containment. Safety barriers are important elements of such accident scenarios, aiming to reduce the frequency of unwanted events. Estimating the performance of safety barriers is essential for the prevention of major accidents. This work first focuses on the application of risk‐based analysis on the process area equipment of the floating platform Goliat. Such an approach is secondly extended to the most relevant safety systems to prevent fires and explosions and consequent catastrophic domino effects. An additional challenge resides in the fact that safety barriers cannot always be classified as equipment, as they are often composed of operational and organizational elements. Through the application of the ARAMIS Project (Accidental Risk Assessment Methodology for Industries in the Context of the Seveso II Directive) results, the frequency modification methodology based on TEC2O (TEChnical Operational and Organizational factors) and the REWI (Resilience‐based Early Warning Indicators) method, it is possible to quantify the safety barrier performance, to reduce the frequency of unwanted events. While conducting this study, the importance of the management factor in combination with technical and technological aspects of safety barrier performance was analyzed. Starting from the initial project conditions, applying worsening technical factors, and simulating n organizational management for the safety systems, it is possible to quantify the performance of the safety barriers, highlighting the importance of management factors in terms of prevention of major accidents, and to assess the dynamic risk for the overall plant
Protection systems for tanks containing hazardous materials exposed to fire
Full text linkThe catastrophic failure of a tank containing a pressure liquefied gas often gives rise to a physical explosion with serious consequences for the possibly exposed people and structures. In fact, the liquid is at a temperature higher than its boiling temperature at atmospheric pressure, and, once released, it will instantaneously vaporize, with the generation of a shock wave. If the involved chemical is also hazardous (flammable or toxic), additional consequences are also expected (fires or toxic cloud dispersion), so that it is important to prevent the occurrence of this phenomenon as far as possible. Few studies are available in the literature to analyze the dynamics of this scenario, and, given the complexity of setting up experimental facilities, mainly theoretical approaches have been adopted, though some useful experimental results are also reported. The models proposed over the years allow to calculating the trend of the main parameters involved in the accident, but, in most cases, reference to a bare vessel has been made, while less attention has been devoted to assess the influence of protection systems, such as thermal insulation or pressure relief devices. In the present paper, a number of reference scenarios have been simulated involving both unprotected and protected systems, and the results have been analyzed and compared, to identify a proper strategy capable of significantly reducing the probability of failure of the tank
Comparative analysis of calculation methods of pressure drops for two-phase flow through pipelines
No full textDespite the importance of an adequate and correct sizing of emergency relief systems, a high level of uncertainty is still present when two-phase liquid-vapor flow can establish. In such a case, no single correlation is presently generally applicable to calculate the pressure drop through a relief pipeline in a wide range of relief conditions. In the present paper a large number of new experimental data have been produced and compared with two of the most widely known and adopted calculation methods: the Friedel model and the classical Lockhart-Martinelli model. They belong to either of the two main groups of prediction models, the homogeneous and non-homogeneous models. The results provide useful insights in their accuracy and range of applicability, and are expected to be of help in the correct sizing of these fundamental safety systems. © 2015 Taylor & Francis Group
Development of a process for n-butanol recovery from ABE wastewater streams by membrane technology
Full text linkThe aceton-butyl-ethanolic fermentation process (ABE) is a biotechnological process that leads to the production of acetone, n-butanol and ethanol (ABE compounds) from glucose sources and amides by use of certain biomasses. The process was developed initially during the middle of the last century and suffers from decline due to the greater petrochemical production of products and the lowering of the costs of the sector. Nowadays, the ABE process is regaining great interest because the fraction with the highest concentration, i.e. n-butanol, is an excellent constituent for biofuels. The ABE process has been optimized over time to obtain maximum yields of n-butanol, but the problem of separating and concentrating the butanol in the outlet stream of the ABE process persists. To allow an adequate use, often distillation by use of more columns is required. Moreover, the contained biomasses and suspended solids, in high quantity, must be eliminated, leading to overall high treatment costs. This work will report the main idea and some preliminary experimental results for the development and application of a process based on membrane technologies, to separate and concentrate the butanol from ABE process streams to sensibly reduce the difficulty to perform a final distillation. The proposed treatment process is composed by ultrafiltration, pervaporation, nanofiltration and a final mixing/demixing operation. Attention was paid to the productivity, selectivity and longevity of the used membranes. The optimization of these three parameters is essential to achieve a level of reliability and feasibility of the proposed process, in particular the avoidance of membrane fouling
Acoustic analysis of blast waves produced by rapid phase transition of LNG released on water
No full textMassive offshore and onshore storage of fuel have led the international community to raise questions about the hazards on the surrounding installations and people. Among the possible accidental scenarios when cryogenic gas as liquefied natural gas (LNG) is spilled on water at a very fast rate, the phenomenon of rapid phase transition (RPT) may occur: large amounts of energy are released during phase transition which can generate explosions. The related consequences should be added to the possible consequences of fire in terms of flash fire, fireball, pool fire. and vapour cloud explosion for confined and congested geometry Surrounding the release point. In this paper, the analysis of RPT of LNG has been Studied from the point of view of blast wave production, through ab initio acoustic analysis for monopole source. Maximum overpressures, as calculated at the source point and along the blast pathway are compared with results of large scale experiments. Safety distances are given for the sake of comparison with threshold distances reported in the open literature. (C) 2008 Elsevier Ltd. All rights reserved
A simplified model for improving thermal stability of Lithium-ion batteries
Full text linkLithium ion batteries represent a well established technology in a range of applications (laptops, mobile phones, etc.) but they are becoming key factors in many other areas were reliability and safety are of paramount importance (e.g. the space and automobile industries). However, a number of drawbacks still raise concerns about their wider use and hamper a more structured introduction in these additional applications. In particular, the management of heat effects remains a challenge, as an excessive temperature rise can cause reduction of cycle life, battery failures and, above all, may lead to thermal runaway of individual cells or of an entire battery pack, with associated damages to the surrounding people or environment. In the present paper, a simplified model capable of predicting the thermal behaviour of a battery pack refrigerated with a cooling fluid, is presented. It allows to quickly estimating the efficiency of a given cooling system under specific working conditions, and thus identify the range of operation within which a given energy storage system can safely operate
Thermal management of lithium-ion batteries: An experimental investigation
No full textThis paper describes a set of experimental tests carried out to better understand the thermal behavior of Lithium-ion batteries under load and the capability of various cooling fluids in maintaining the working conditions within a safe range for the cells. Despite several theoretical models are available in the literature, very few experimental data are reported. Different types of cells have been analyzed. The generation of hot spots has sometimes been registered, their occurrence being independent of cell geometry and size; instead, the battery's history and age, appeared the main factors in determining the onset of hot spots on the surface of the cell. Two experimental rigs have been set up to test the capability of different cooling fluids in removing the surplus heat generated in a Li-ion battery module, where the cells of interest have been replaced with electrically heated elements with the same thermal characteristics of the cells. It was thus possible to safely investigate “extreme” operating conditions, where the occurrence of a thermal runaway is possible. Among the tested fluids, air was unable to adequately limit the surface temperature increase, while a perfluorinated polyether, allowed to work within the optimal temperature range, even under severe operating conditions
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