1,720,996 research outputs found
Design and Operation of Liquid Hydrogen Storage Tanks
No full textLiquid hydrogen (LH2) is a versatile and efficient energy carrier with numerous applications in space exploration, hydrogen fuel cell vehicles, industrial processes, and the maritime sector. However, its extremely low boiling point and low density present unique challenges in handling, storage, and transportation, particularly in the prevention of loss of containment scenarios. At present, there is still limited knowledge available on the thermodynamics of liquid hydrogen contained in cryogenic storage tanks. This scientific paper delves into an examination of insulation techniques and the operation of liquid hydrogen tanks. Also, self-pressurization is explained and set into context. Furthermore, modelling of specific parameters such as temperature distribution, pressure increase and liquid level play an important role in understanding the thermodynamics inside of LH2 tanks and enable to draw conclusions for the efficient operation when avoiding the loss of hydrogen by releasing boil off gas. The ramifications of this study hold critical importance for industries reliant on hydrogen. The insights gained will facilitate the development of prediction models to enhance operational directives, and the development of effective storage systems
Numerical simulation of LNG tanks exposed to fire
No full textThe increasing use of Liquefied Natural Gas (LNG) as a fuel for ships and vehicles poses relevant safety concerns, extended to the entire LNG supply chain and distribution network. Understanding the phenomena associated with the behavior of LNG tanks exposed to severe heat sources is thus a fundamental issue to identify potential safety-critical scenarios. The experimental data and modeling approaches currently available, mainly referring to small-scale pilot vessels, feature relevant limitations when extended to large-scale applications. In the present study, a two-dimensional non-equilibrium computational fluid dynamics model (2D CFD) of LNG tanks exposed to fire engulfing scenarios was developed. The 2D CFD model was validated against experimental bonfire data and was extended to simulate the behavior of large-scale vessels used in specific industrial applications, as the road transportation of LNG and the fuel supply of ships. A set of Key Performance Indicators (KPIs) was defined to support the safety assessment of LNG tanks, and to identify the potential transition to safety critical regions during fire exposure. The CFD results obtained allowed investigating the influence of operative parameters and geometry on the pressure build-up in the tanks, as well as on the transient evolution of complicating phenomena, such as the thermal stratification. The KPIs defined provide a useful support for the design of safety systems and for decision making in emergency response
Three dimensional CFD simulation of LPG tanks exposed to partially engulfing pool fires
Full text linkThe availability of accurate and robust models for the prediction of the behavior of pressurized tanks under fire exposure is a key requirement to improve the design of fire protection systems. Most of the models present in the literature take into consideration fully engulfing pool fire scenarios only. In the present study, a CFD modelling approach previously validated against full engulfing pool fire tests is used to simulate partial engulfment conditions. The model allowed analyzing local flow field promoting thermal stratification, which in turn drives internal pressurization of the tank. Comparison with fire test results shows good agreement with experimental measurements both in terms of temperature and pressurization curves. The results obtained represent a valuable source of information to support risk management, planning of emergency response and improve fire protection systems design
An innovative three-dimensional approach for the simulation of pressure vessels exposed to fire
No full textThe present study introduces an innovative approach to the detailed simulation of the pressure build-up in equipment containing saturated liquids when exposed to fire. The approach is based on the adoption of a fully three-dimensional (3D) computational fluid dynamics (CFD) model of the inner fluid. Experimental data gathered from literature studies were used to validate the model considering vessels of several scales and geometries exposed to a full engulfing pool fire. The comparison between the results of the 3D CFD model developed and those of two-dimensional (2D) literature models was also carried out. This enabled deriving precise indications on the selection of the most suitable approach based on the type of accidental scenario to reproduce, confirming 2D models as sound and reliable tools to model the fluid behaviour when homogeneous heat exposure conditions are present. On the other side, limitations of 2D approaches in capturing edge effects on i) temperature profiles, ii) recirculation patterns, and iii) energy accumulation in the vessel lading during fire exposure were identified and discussed. The results obtained represent a valuable source of information to support risk management and emergency response planning
LNG Tanks exposed to distant pool fires: A cfd study
Full text linkLiquefied natural gas (LNG) is a viable, environmental-friendly alternative marine fuel. Several LNG-fueled vessels are already operating, and the LNG market is expected to grow further in the next years. A capillary marine LNG infrastructure network is developing to strengthen the fuel supply chain, which includes smallscale LNG storage and bunkering installations. However, safety remains a crucial aspect for the expansion of sustainable and reliable LNG technologies due to flammability hazards of natural gas. Storage tanks are vulnerable units from a safety point of view: External fires might affect LNG tanks leading to their catastrophic failure with a possibility of accident escalation. The present contribution aims at the evaluation of thermal response of storage tanks exposed to high levels of thermal radiation from distant sources, such as a pool fires generated after the ignition of LNG spills. A two-dimension computational fluid dynamic (CFD) approach is applied to predict tank pressurization rate and temperature distribution for a set of case studies. The results obtained give insight about the dynamic response of pressurized cryogenic vessels involved in process accidents, providing a useful contribution to emergency response planning as well as identifying important safety aspects regarding LNG storage and distribution chain
A comparative study on insulation materials in tanks for the storage of cryogenic fluids in fire incidents
No full textLiquefied Hydrogen (LH2) or Liquefied Natural Gas (LNG) establish themselves as important energy carriers in the transport sector. Its storage requires tanks with Thermal Super Insulations (TSI) to keep the transported fluid cold. TSI has proven itself in various applications over a long time, but not in the land transport sector, where accidents involving collisions, fires, and their combination are to be expected. The focus of this study is to investigate the behavior of different types of TSI when exposed to a heat source that represents a fire. Therefore, a High-Temperature Thermal Vacuum Chamber (HTTVC) was used that allows the thermal loading of thermal insulation material in a vacuum and measuring the heat flow through the TSI in parallel. Within this study, 5 samples were tested regarding 3 different types of MLI, rock wool, and perlites. The thermal exposure caused different effects on the samples. In practice, this can be connected to the rapid release of flammable gases as well as a Boiling Liquid Expanding Vapour Explosion (BLEVE). These results are relevant for the evaluation of accident scenarios, the improvement of TSI, and the development of emergency measure
Modelling Fire Response of Cryogenic Liquid Hydrogen Tanks Equipped with Multilayer Insulation (MLI) Systems
No full textIn the context of the growing global interest in hydrogen-based green energy, cryogenic tanks equipped with
multi-layer insulation (MLI) are emerging as a leading solution for storing hydrogen in vehicles. The integrity of
these systems might be threatened during fire exposure. This can trigger the degradation of the MLI materials
and induce rapid pressurization of the tank with a high risk of catastrophic failure. In this work, a novel lumped
model to simulate the thermal response of MLI-equipped cryogenic liquid hydrogen tanks is presented. The
model integrates the accurate database “Coolprop” for hydrogen thermodynamic properties and sub-models for
detailed simulation of MLI degradation, providing a realistic simulation of the experimental data obtained under
normal operating conditions. The application of the model to several case studies considering different numbers
of MLI layers and tank geometries demonstrates that aluminum-based MLI offers scarce protection in case of
exposure to a hydrocarbon poolfire
A Dynamic Assessment of Safety Barriers Effectiveness in Fire Protection of Cryogenic Storage Tanks
No full textLiquid hydrogen (LH2) is believed to play a pivotal role in the energy transition. The main issue of this technology is the boil-off of the cryogenic liquid, particularly in the presence of critical heat sources, such as an external fire. Typically, in addition to the insulation system, safety barriers, such as water deluge systems and water curtains, are introduced as shields to protect the vessel from the fire radiation. Thus, the heat received from the cryogenic equipment depends on the effectiveness of those barriers. The present study aims at providing a dynamic quantification of the time to failure of an LH2 cryogenic tank, based on the performance of the abovementioned safety barriers. The results of this analysis highlight how different parameters affect the effectiveness of the safety systems, suggesting how to implement the most effective configurations. Moreover, the results obtained in terms of heat fluxes are precious input data useful for the definition of the boundary conditions in mathematical models (e.g., analytical and computational fluid dynamic models) used to investigate the behavior of cryogenic tanks engulfed in a fire
From biomass-derived fructose to γ-valerolactone: Process design and techno-economic assessment
No full textThis work proposes a process design and techno-economic assessment for the production of γ-valerolactone from lignocellulosic derived fructose at industrial scale, with the aim of exploring its feasibility, identifying potential obstacles, and suggesting improvements in the context of France. First, the conceptual process design is developed, the process modelled and optimized. Second, different potential scenarios for the energy supply to the process are analyzed by means of a set of economic key performance indicators, aimed at highlighting the best potential profitability scenario for the sustainable exploitation of waste biomass in the context analyzed. The lowest Minimum Selling Price for GVL is obtained at 10 kt/y plant fueled by biomass, i.e. 1.89 €/kg, along with the highest end-of-live revenue, i.e. 113 M€. Finally, a sensitivity and uncertainties analysis, based on Monte Carlo simulations, are carried out on the results in order to test their robustness with respect to key input parameters
Towards risk-informed design and operation of ammonia-powered ships: Critical aspects and prospective solutions
Full text linkAmmonia is a promising fuel for marine propulsion and generation, yet its acute toxicity and associated safety challenges necessitate careful consideration. Current regulations recognize the hazards of ammonia, introducing numerous technical safety measures in response. However, the effectiveness of these measures in ensuring acceptable risk levels for future vessels remains to be fully assessed. This study estimates the risk level onboard ammonia-powered ships, identifying the aspects with the largest and controllable influence on it. Three hypothetical concepts of ammonia fuel supply were developed in this study on an example tanker vessel and analyzed using the quantitative risk assessment (QRA) methodology. The obtained risk profiles were evaluated against the risks by an equivalent liquefied natural gas-fueled system, serving as a benchmark. The results demonstrate that ammonia-fueled ships exhibit individual risk levels for engineering crew with periodic duties in fuel preparation rooms (FPR), or similar compartments, which are 1–1.5 orders of magnitude higher than those observed for a conventional gas-fueled alternative. An analogous increase has been noted for the public potentially present onboard or in proximity. The study underscores the importance of managing human-machine interactions, enhancing the reliability of supply systems, and managing the systems’ complexity to mitigate risks in FPRs. Regarding public safety, the analysis highlights new risk mechanisms introduced by ammonia and examines how storage conditions affect exposure levels. By offering a detailed QRA framework, this research contributes to the development of effective risk management strategies for ammonia-powered ships
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