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Dealing 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

Developing sustainable solutions for power generation and transportation is crucial for reducing greenhouse gases (GHGs). The tendency in fundamental and practical research on this field has been characterized by investigating low or net zero-carbon sources. Among the available options, hydrogen may be employed as a possible energy carrier to reduce the local emissions of harmful gases. However, the intensive use of gaseous hydrogen is still limited by the issues related to its storage and transportation systems. In this framework, injection of compressed hydrogen into the existing natural gas pipelines is seen as a way forward to reduce the quantity of carbon-based fuel and will be studied in this work. Compared to building a dedicated hydrogen infrastructure, this solution permits lower capital costs and ensures system scalability (i.e., the possibility to add hydrogen gradually). However, the possible consequences of a gas pipeline failure can be altered. In this paper, a numerical evaluation is conducted to characterize hydrogen-methane mixture jet fire. The analysis is performed using integral models and computational fluid dynamics (CFD). In the case of the computational fluid dynamic approach, an accurate thermodynamic properties database is employed. The distance from the releasing point at which the maximum temperature is reached (i.e., the length of the jet flame) is used as a monitoring parameter for the comparison. Results are compared with existing literature data and discussed to evaluate the safety impact of adding hydrogen to the natural gas network.

The current trends in environmental impact reduction have promoted natural gas and hydrogen either as shortor long-term solutions. In both cases, liquid transportation in cryogenic form is associated with new concerns in terms of safety aspects. So far, infrastructures based on utilizing the liquefied natural gas (LNG) in port areas have been developed and realized worldwide. However, a uniform guideline and set of monitoring criteria are missing because of the lack of knowledge of the phenomenological aspects. This work deals with the numerical characterization of the visible cloud boundaries in the case of an unintentional release during bunkering operations and its comparison with the standard value for the flammability of cloud, based on the lower flammability limit. To this aim, real-scale computational fluid dynamics (CFD) simulations were performed. Results showed that both flammable and visible clouds were dramatically sensitive to the heat transfer with the substrate in an unconfined environment. Besides, turbulence seems to affect the flammable cloud expansion rather than the visible cloud. Eventually, results indicate that the flammable cloud can be up to 50% larger than the visible for confined and 20% large for unconfined environments, conservatively, on the safe side. These values can be adopted for design and emergency purposes.

QRA 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.

Hydrogen refuelling stations carry the risk of hydrogen leakage from flanges, holes, broken pipes, etc., and the possibility of ignition is high due to the low minimum ignition energy of hydrogen. The length of these hydrogen jet flames may have an impact on damage and should be included in risk assessments. The risk assessment of typical hydrogen refuelling infrastructure is highly dependent on separation distances. These distances are estimated partially by jet flame lengths. The use of reliable physical models, engineering models, and risk analysis tools is hence required for safely operating this infrastructure. Generally, the physical models are adapted from hydrocarbon fuels, and they have to be validated for hydrogen especially in the range of operating pressures of FCEVs and refuelling infrastructures. To fill this gap, large scale hydrogen jet-fires tests were conducted in open space at various hydrogen pressures (up to 450 bar) and orifice diameters (1-5 mm). The jets were visualized by a thermal camera (up to 2000°C) and radiation flux sensors facing the jet at different distances were located. Results showed that the hydrogen flames can cover distances of about tens meters, and cause life-threatening conditions by the flame itself and thermal radiation.

The sustainable development has recently become the cornerstone of the environmental policy worldwide and a leading principle for resource management. The philosophy lies in a continuous demand of innovative choices able to ensure the existing productive systems survival through a new design paradigm shift. In this regard, the technological innovation should be always driven by the sustainability concept: the economic, societal and environmental impact ought to be continuously fostered to the systems' sustainable improvement. This demanding goal can be accomplished with a blended Life Cycle (LCA) and Life Risk (LRA) Assessment to highlight the process potential health and environmental impacts. LRA is the process in which imposed risks by the inherent hazards linked to a process are continuously assessed (quantitatively or qualitatively). LCA instead is the process that analyses and assesses the environmental impact of a material, product or service throughout its entire life cycle. LCA and LRA are typically driven by two different approaches, respectively a deterministic and a stochastic approach. This usually drives an unconnected use of LCA and LRA in the quantification of products and processes potential impact and determines controversial decisions with respect to a balance between environmental impacts and operational risks. The new paradigm suggests a unified blended LCA - LRA approach that is applied at a preliminary stage to an innovative Acid Gas to Syngas (AG2S) process for CO2 emission reduction and on-site reuse, avoiding the costly and hazardous transportation step.

Epoxidated vegetable oils are largely employed as plasticizer instead of harmful phthalates and they represent a sustainable choice to produce lubricants and intermediates. In this work, the epoxidation of soybean oil is carried using hydrogen peroxide (H2O2) 32wt.% and acetic acid instead of the commonly used H2O2 at 60wt.% and formic acid to reduce the risk of detonation and corrosion. The efficacy of an acid catalyst (sulfuric acid) is tested. Particular attention is focussed on a proper mixing program.

Peroxyacids are commonly used in chemical processing, synthesis and bleaching. Recently, they have been demonstrated to be very versatile for the epoxidation of unsaturated oil, aiming at the synthesis of polyepoxide (plasticizer, resins and adhesives). These processes are characterized by high yields and selectivity. However, due to their hazard and instability, the peroxy reactants are often obtained from the corresponding organic acid in situ by combination with hydrogen peroxide, in the presence of a mineral (sulphuric or phosphoric) acid as catalyst. In this paper, the kinetic of decomposition of the peroxyacetic acid in water phase have been studied by using simple thermal screening calorimetry, with or without the catalyst.

Climate 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.

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A "new" antithrombin III abnormality is described in four members of a family. The proposita is a 38 years old female who showed no thrombotic disease and the following laboratory pattern: normal routine clotting tests, normal or near normal AT III activity (chromogenic substrates S-2238 and Chromozym Th) both in plasma and in serum and in the presence or absence of heparin, slightly decreased antifactor Xa activity (chromogenic substrate S-2222), normal progressive antithrombin, normal AT III antigen but abnormal migration in the agarose-heparin bidimensional system. In the latter test, one major abnormal peak, less anodal than the normal counterpart, and a smaller, apparently normal peak, were seen. In agarose without heparin the pattern was similar to normal both in plasma and in serum. Heparin tolerance to heparin in vivo and in vitro was slightly increased but still within normal limits. The two sons and a paternal aunt showed the same pattern. The hereditary pattern seems therefore autosomal dominant. The abnormality described appears different from AT III Budapest. The toponym of antithrombin III Padua is proposed to define this peculiar abnormality.

Hydrogen is becoming an attractive alternative for energy storage and transportation, because of the elevated energy content per unit of mass and possibility to have zero carbon-emission vehicles. For these reasons, hydrogen's share in global market is expected to grow substantially in the coming years. Today, hydrogen-fueled buses and cars are already available, and several refueling stations are operating in different countries around the world. A key role of the deployment of hydrogen fueled-vehicles is the presence of a widespread network of refueling stations, especially close to residential and industrial areas. This fact poses attention to the safety aspects related to hydrogen, with particular interest to its high flammability that can lead to catastrophic consequences for personnel and equipment. As a matter of fact, hydrogen is a comparatively less hazardous fuel compared to conventional fuels such as gasoline and diesel. Hydrogen infrastructures are characterized by operating pressure up to 1000 bar that, in case of an unintended loss of containments, may produce a highly under expanded turbulent jet. If ignited, this hydrogen jet may give rise to very severe scenarios, mainly related to high temperatures and the oriented flows. As recently suggested by Moradi and Groth (Moradi and Groth, 2019), there is a lack of experimental and on-site data for almost all of the storage and delivery technologies relevant to the hydrogen infrastructures. Experimental data is vital to support model validation, especially in the case of the very peculiar combustion process of hydrogen. In this way, a real-scale experimental campaign is proposed to investigate the main characteristic of the hydrogen jet fire resulting from its rapid fired depressurizations. The focus of the experimental campaign is the evaluation of safety distance for person and device (i.e. pressurized tanks) in order to avoid critical conditions and domino effects in refueling station. Different initial conditions, i.e., storage pressures, are exploited, and the resulting jet across specified orifice are investigated. More specifically, temperatures at various locations are measured through an arrangement of thermocouples. Values up to 1200 °C were obtained in the core of the jet. Moreover, it was found that the recorded temperatures, especially those at the outer portion of the jet, are very sensitive to the initial conditions.

Epoxidized vegetable oils are largely employed as plasticizers instead of harmful phthalates, and they can be a sustainable choice to produce lubricants and intermediates. The aim of this work is to study the reaction of soybean oil epoxidation of soybean using safer reactants. The reaction was carried out using hydrogen peroxide 34 wt % and acetic acid instead of the commonly used hydrogen peroxide at 60 wt % and formic acid to reduce the risk of detonation and corrosion. Moreover, the study focuses on the efficacy of the presence of an acid catalyst and sulfuric acid and the effect of its concentration. It was found that it is not possible to carry out the process without acid catalyst with those reactants. In addition, a proper mixing program was set up to improve the selectivity of the reaction. © 2018 American Chemical Society.

The presence of sulfur-based substances in the biogas (sour) produced from the digestion plant imposes several treatments to match the market and regulation requirements. Besides, it lays the production plants open to safety and environmental risks related to the accidental release of toxic species. This work is devoted to the investigation of the consequences of the accidental release of biogas containing hydrogen sulfide up to 10 %vol. To this aim, a schematic 3-D representation of a biogas productive plant was developed and implemented in a Computational Fluid Dynamics (CFD) model. The effects of the initial composition and the wind velocity on the cloud dispersion were evaluated. The calculated stand-off distances for lethality resulted from the numerical simulation were compared with the results of standard integral models commonly adopted in the process industry. Results indicated the dramatic effects of the toxicity of hydrogen sulfide on the downwind safety distance in the case of accidental release of sour biogas, and the negligible effects for the flammability concerns.

The environmental concerns on the use of fossil fuels have incentivized the utilization of cleaner solutions for energy supply. Natural gas in the form of a liquid (LNG) is considered a promising and highly attractive alternative due to the high density and relatively low cost of transportation. In the case of accidental release on water, elevated heat transfer causes rapid evaporation that has the potential to lead to a rapid phase transition (RPT), thus producing significant overpressures. In this work, the effects of composition, release rate, and the fluid dynamic regime of water on the RPT of LNG are analyzed by means of detailed analysis based on computational fluid dynamics and large eddy simulation for the turbulence model. The thermodynamic properties at ultra-low temperature related to the species considered in the mixtures are estimated by using an approach based on quantum mechanics. Results are compared with experimental analysis, quite satisfactorily. A preliminary conclusion shows that calm water, as within port facilities, decreases the likelihood of the RPT or its magnitude to a negligible intensity. On the contrary, the addition of ethane or propane may dramatically affect the explosive phenomenon.

Mitochondria contain their own genome, mitochondrial DNA (mtDNA), essential to support their fundamental intracellular role in ATP production and other key metabolic and homeostatic pathways. Mitochondria are highly dynamic organelles that communicate with all the other cellular compartments, through sites of high physical proximity. Among all, their crosstalk with the endoplasmic reticulum (ER) appears particularly important as its derangement is tightly implicated with several human disorders. Population-specific mtDNA variants clustered in defining the haplogroups have been shown to exacerbate or mitigate these pathological conditions. The exact mechanisms of the mtDNA background-modifying effect are not completely clear and a possible explanation is the outcome of mitochondrial efficiency on retrograde signaling to the nucleus. However, the possibility that different haplogroups shape the proximity and crosstalk between mitochondria and the ER has never been proposed neither investigated. In this study, we pose and discuss this question and provide preliminary data to answer it. Besides, we also address the possibility that single, disease-causing mtDNA point mutations may act also by reshaping organelle communication. Overall, this perspective review provides a theoretical platform for future studies on the interaction between mtDNA variants and organelle contact sites.

Peroxyacids are commonly used in chemical processing, synthesis and bleaching. Recently, they have been demonstrated to be very versatile for the epoxidation of unsaturated oil, aiming at the synthesis of polyepoxides (plasticizer, resins and adhesives). These processes are characterized by high yields and selectivity. However, due to their hazard and instability, the peroxy reactants are often obtained from the corresponding organic acid in situ by combination with Hydrogen Peroxide, in the presence of a mineral (Sulphuric or Phosphoric) acid as catalyst. The aim of this study is to analyse the thermal stability of the catalytic system used for vegetable oil peroxidation with the purpose of operating under safety conditions and then identify the safety parameters necessary to prevent the runaway reaction. This paper presents the study of the decomposition of peroxyacetic acid in aqueous phase by using a Thermal Screening Unit. Also, the effect of the presence of the acid catalysts was analysed. © 2018 Institution of Chemical Engineers

This work is devoted to the prevention of runaway reactions for the esterification of acetic anhydride with methanol in the presence of sulfuric acid. To this aim, a kinetic model has been developed and validated through the comparison with experimental data obtained by means of a batch reaction calorimeter operating in isoperibolic conditions. The model, which shows a good agreement with experimental data, then has been adopted for the prediction of the thermal runaway, which may lead to thermal explosion, through the definition of runaway criteria in a batch reactor and through the definition of stability diagram for the reactive system. © 2018 American Chemical Society.

Hazard studies related to Carbon Sequestration (CCS) and Enhanced Oil Recovery (EOR) lack of appropriate descriptive models of pressurized CO2 releases. The complex inherent phenomena linked to a rapid depressurization in addition to the generalized lack of approachable and targeted experimental data, makes current QRA procedure inadequate. In light of this, the proposed work aims at achieving two correlated targets. Firstly, the results of an experimental campaign performed on CO2 pressurized releases are proposed. Secondly, a source model for multiphase CO2 pressurized releases is illustrated in terms of filling existing gaps. The reported experimental campaign focuses on the estimation of useful parameters to be used in the modeling procedure namely the experimental discharge coefficient and the thermodynamic nature of the expansion transformation. Bulk and discharge orifice pressure and temperature profiles are illustrated, focusing on how a multiphase CO2 release alters main discharge parameters. The proposed modeling approach allows for the collection of details on the expansion degree of reversibility and heat transfer effects are inferred showing that ideal isentropic and isenthalpic paths are never matched. Its application well matches collected data and gives good prediction of the total discharge time. In addition, direct unobservable dynamics inside the closed tank are assessed, notably the instantaneous dense CO2 mass fraction and peculiar evolutions during phase change mechanisms in the liquid-vapor and solid-vapor domains.