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Measuring aerosol size distributions with precision is important to understand the transmission of infectious diseases causing pneumonia-like illnesses, including Legionnaire’s disease and COVID-19. Accurate size measurement can help guide the identification of risk mitigation strategies, a challenging task as the size of pathogen carrying particles can change due to evaporation. Using oil and water-based particles, we compare four measurement instruments that provide aerosol size distributions relying on different measurement principles; phase doppler anemometry, light scattering, electrical mobility and aerodynamic impaction. The size distributions obtained from the different measurement instruments are consistent for oil-based particles but differ significantly for particles experiencing evaporation. Experiments were conducted to quantify the differences in measurement caused by evaporation as well as the measurement losses. The size range covered by the four instruments is from 0.025 to 10 µm. Finally, an approach based on the complete drying of a salt solution is presented to obtain the size distribution at the source of the aerosol generation. Understanding of the infectious dose and the pathogen concentration at the source, the most dangerous size ranges of the aerosols can thus be determined, and actions can be taken to reduce the propagation of these particles.

The exhaust detritiation system (EDS) of the Joint European Torus (JET) active gas handling system removes tritium from exhaust gases and contaminated air prior to discharge to stack. The system was replaced prior to JET’s tritium experimental campaign due to corrosion damage. In this paper, the following topics are presented: system function and description, corrosion and failure of the previous EDS, enhancements for the replacement EDS including testing of acid passivation column, commissioning experience, operating experience and performance. Acids including hydrofluoric were generated in catalytic recombiners following inadvertent halogen ingress. Pitting corrosion was identified with breakthrough failure of condensate pipework. To mitigate a recurrence, a novel acid passivation sub-system was designed. The acid passivation testing demonstrated successful performance of the design and calcium-hydroxide passivation packing tested, with acids below the limit of detectability at the test column outlet. Issues encountered during commissioning are described and key performance metrics such as detritiation factor reported. Finally, operational issues and system performance is presented.

This article describes recent improvements made in the design process of offshore flexible pipes. These improvements consider the more precise complex geometry and architecture of the flexible pipes, while considering their corrosive environment (high pressure, high temperature, acid gases (CO2, H2S), sea water, etc.) and the relevant physics. MOLDITM, the design software that was developed 20 years ago to predict flexible pipes annulus environment, has been constantly upgraded to increase its representativeness: use of chemical potential or fugacity to better describe the mass transport, improvement of the thermodynamic module to better describe the interaction between chemical species and allow to model the purging through gas release valves. Recently, a major advance has been made allowing to cope with flooded annulus flexible pipes. When the annulus is flooded, the tortuosity produced by the presence of steel wires inside the annulus can take a major importance. Therefore, a new model, named 3DIFF, has been developed to describe the 3-dimensional characteristics of the annulus and its impact on fugacity profile across the structure. Depending on permeation properties of each layer, the result is that the presence of water can produce a fugacity gradient within the annulus. This heterogeneity must be considered during the design process to be fully representative of service conditions and allow to select flexible pipes materials with confidence. Experimental devices used to generate permeation database are under constant evolution to study even more complex mechanisms such as the diffusion process in a flooded tortuosity or the compression effects of polymeric material on their permeation properties.

International audience; This paper discusses the effect of porosity and hydrostatic pressure on diffusion kinetics and equilibrium water uptake in a semicrystalline fluoropolymer. Water sorption experiments at atmospheric pressure and under water pressures up to 250 MPa were carried out during 18 months at 40°C on reference and poroussamples. Porosity of samples was induced due to a cavitation process occurring at the highest triaxiality area of waisted and notched specimens during tensile tests.Water uptake was found to be very sensitive to porosity, showing an increase in samples with a high void fraction. On the other hand, water content decreased with increasing pressure suggesting a compaction of the porous space in which water can be stored. Two models describing this water uptake behaviour wereconsidered. The first is a classical model which assumes that sorption occurs only by diffusion following Fick’s law. Fick’s model was found to be in agreement with the experimental results. A “Langmuir-type” sorption model was also proposed to describe water uptake in porous samples, considering a two-phase watertransport mechanism: one portion of the absorbed water diffuses through the polymer matrix and the other portion is stored in voids. This model was implemented in a user subroutine using ABAQUSTM software and simulations were confronted to experimental sorption curves showing satisfactory agreements. The potential of the Langmuir-type sorption model resides on its availability to be coupled to a poro-mechanical model, in order to improve the understanding of coupling between the mechanical behaviour and water sorptionmechanism in a porous polymer.

International audience; The aim of this work was to characterize solute transfer between static and dynamic water during percolation through a solid leach bed reactor. A new experimental procedure was set up to measure the solute exchange rate between macro-and micro-porosity. Tracer tests were performed in closed-circuit recirculation experiments. The water behavior was modeled by a multiphase flow model in a double porosity medium using a previously published methodology. The solute exchange rate between static and dynamic water was described by first-order kinetics. The methodology was applied to wheat straw and solid cow manure beds. The solute exchange rate (hs was 0.054 and 0.324 h−1) for wheat straw and solid cow manure, respectively. The measured data was used to improve the prediction capacity of a CFD tool. The results of this work could be used to develop appropriate leachate recirculation strategies to optimize full-scale dry batch anaerobic digestion processes.

Corrosion is a key issue for operators in the oil and gas industry since production fluids contain some water and both CO2 and H2 S acid gases. In this context, this paper illustrates the development of a reactive barrier polymer against corrosion by H2 S of offshore flexible pipes. The role of this reactive material, called anti-H2 S material, is to avoid H2 S reaching the structural steel layers of the flexible pipe during the whole service life of the structure, usually 20 years, and hence to place the steel layers in a sweet service environment. Placed between the existing pressure sheath and the steel layers, the anti-H2 S material has the ability to neutralize H2 S during its diffusion within the material. The neutralization is ensured by an irreversible chemical reaction on reactive components that are dispersed in the material. The raw material selection is based on both accurate requirements for their use in a flexible pipe and expected performances in a sour service environment over a long period of time. Some laboratory qualifications and experimental techniques are used to qualify the behavior of the material and build the material database. A dedicated multiphysics model is developed based on the coupling of permeation mechanisms and gas-solid reactions. Qualification of both the material and the model is performed thanks to middle-scale and full-scale tests conducted in representative sour service conditions.

International audience; This work aimed at assessing water percolation through a solid cow manure leach bed in dry batch AD processes. A laboratory-scale percolation column and an experimental methodology were set up. Water behaviour was modelled by a double porosity medium approach. An experimental procedure was proposed to determine the main hydrodynamic parameters of the multiphase flow model: the porosity, the permeability and the term for water exchange from macro- to micro-porosity. Micro- and macro-porosity values ranged from 0.42 to 0.70 m3⋅m-3 and 0.18 to 0.50 m3⋅m-3. Intrinsic permeability values for solid cow manure ranged from 5.55⋅10-11 to 4.75⋅10-9 m2. The term for water exchange was computed using a 2nd order model. The CFD tool developed was used to simulate successive percolation and drainage operations. These results will be used to design leachate recirculation strategies and predict biogas production in full-scale dry AD batch processes.

Temperature-phased anaerobic digestion with a 50–70 °C pre-treatment is widely proposed for sludge. Here, such a sludge pre-treatment (65 °C) was studied against the physical, enzymatic and biodegradation processes. The soluble and particulate fractions were analysed in terms of biochemical composition and hydrolytic enzymatic activities. Two kinetics of organic matter solubilisation were observed: a rapid transfer of the weak-linked biopolymers to the water phase, including sugars, proteins or humic acid-like substances, to the water phase, followed by a slow and long-term solubilisation of proteins and humic acid-like substances. In addition, during the heat treatment a significant pool of thermostable hydrolytic enzymes including proteases, lipases and glucosidases remains active. Consequently, a global impact on organic matter was the transfer of the biodegradable chemical oxygen demand (COD) from the particulate to the soluble fraction as evaluated by the biological methane potential test. However, the total biodegradable COD content of the treated sludge remained constant. The heat process improves the bio-accessibility of the biodegradable molecules but doesn't increase the inherent sludge biodegradability, suggesting that the chemistry of the refractory proteins and humic acids seems to be the real limit to sludge digestion.

cited By 43; International audience; Hydrogen induced cracking (HIC) of line pipe steel was investigated through immersion testing and hydrogen permeation measurements. At constant pH and hydrogen sulphide partial pressure (pH2S), the extent of HIC was found to depend on exposure time until a stable level was reached. The time to reach this stable value is affected by pH and pH2S. Results of permeation experiments confirmed that HIC is linked with the increase of hydrogen concentration in the steel. It is also shown that low severity requires longer exposures to reach equilibrium. This must be taken into account for HIC testing in mildly sour environment. © 2009 Elsevier Ltd. All rights reserved.

The selection of materials for application in the oil and gas industry in environments containing hydrogen sulphide (H 2 S) is an important matter for the safety of equipments. In the presence of H 2 S, hydrogen atoms originating from the cathodic corrosion reaction can diffuse into the steel, resulting in cracking mechanisms such as hydrogen-induced cracking (HIC) or sulphide stress cracking (SSC). For the SSC cracking mode, a diagram defining different regions of environmental severity was established in the 1990's. The requirements for SSC testing of steels in a given environment are well defined and accepted by the industry. On the other hand, fit-for-purpose (FFP) testing for HIC remains a subject of debate. The most common practice consists in 96 hours exposure under 1 bar H 2 S. But this test environment is extremely severe, and is often considered to be too conservative for the selection of steels for use in mildly sour environments. However, a universally applicable FFP test method for HIC has not yet been established. In addition to pH and H 2 S partial pressure, test duration is another major parameter for HIC testing. Therefore, this experimental study was launched to investigate the impact of time of exposure on HIC. Experiments consisted of HIC exposure tests based on the NACE TM0284-2003 standard method. Experiments were conducted in different nodes of the pH-pH 2 S diagram respectively between pH 6.5 and 3.5, and between 10 mbar and 1 bar of H 2 S. For each condition, tests with different times of exposure were realised, from only a few hours and up to three months. Characterisation of HIC consisted in ultrasonic testing. Permeation experiments were also performed in selected pH-pH 2 S conditions. Permeation transients were analysed for calculation of diffusion coefficients. Modelling of hydrogen profiles in HIC specimens was then realised, and compared with the results of HIC immersion tests. For each test condition, it was possible to draw the evolution with time of the extent of HIC. Depending on the environment, the minimum duration necessary to initiate HIC was extremely variable, from a few hours in the most severe conditions to several weeks in low severity conditions. The extent of cracking at equilibrium also seemed to vary with pH and H 2 S. A good correlation was found between HIC and permeation results, confirming that HIC is strongly linked with the increase of hydrogen concentration in the steel. These results confirm that low severity conditions require longer exposures to reach equilibrium levels of internal hydrogen. This must be taken into account for FFP HIC testing in mildly sour environment. With that aim, permeation experiments could represent an interesting technique to assess the time to reach a certain level of hydrogen in the material.

International audience; Mechanical friction and impacts is still today a main cause of ignition of explosive atmospheres (ATEX) in the industry and this trend seems to be stable in time. This situation certainly results from a significant gap of knowledge in the underlying mechanisms so that the parameters to play on are not precisely identified. In this programme of European dimensions, the process of degradation of the mechanical energy into heat during friction and impacts have been studied. An extensive experimental programme is presented to this end. The mechanisms of dissipation of the mechanical energy into heat during friction has been studied with rubbing machines in which a slider equipped with temperature sensors rubs against a rotating wheel. For impacts, a new device has been developed using a special "air driven cannon" to propel a projectile accurately up to 50 m/s onto an inclined target. A very significant effort has been reserved to the investigation of the ignition mechanisms, not only for ATEX but also for dust accumulations. Some "simple" modelling is proposed on purpose of practical applications. For frictional situations, a critical rubbing power is calculated without any limitations about any lower boundary concerning the rubbing velocity. For "impacts", the relevant parameter for ignition is not the kinetic energy of the projectile but its velocity and the nature of the materials.

Three-layer polyolefin coatings are being used classically for external pipeline protection in the oil and gas industries over years although cathodic protection is also applied. They are supposed to provide efficient and sustainable corrosion protection to the pipe steel over 20 years service or more, including exposition to humidity and temperature (cycling conditions). However, the permeability of polyolefin topcoat to water is not negligible and thus does not prevent water ingress into sub-layers after a few months service. Then soaked water in the vicinity to the steel pipe conveying hot effluents possibly induces hydrolysis of the epoxy primer layer and interfacial bonds to metal. This could raise questions over the long term corrosion control. Therefore, the inspection of the water ingress and the investigation of the long-term barrier properties of primer and adhesives layers when exposed to water are mandatory. This paper examines the use of Electrochemical Impedance Spectroscopy (EIS) to monitor durability and anticorrosion properties of three-layer coatings while exposed to water at 60 °C (maximum service temperature). The objective was to investigate the water ingress within a bilayer coating with respect to sublayer thickness. EIS was used to characterise the water uptake but also the long term barrier properties of coatings on industrial tubes. In complement, gravimetry measurements were also performed during ageing on FBE primer coated panels cut from industrially coated tubes to determine the water uptake kinetics using classical destructive techniques. Degradation mechanisms of 3LPO and potentiality of EIS technique are discussed in the paper.

Recent case studies reported large scale disbondments of three-layer polyolefin (3-LPE) coatings, which could favour corrosion beneath the coating and lead to possible major damage. Therefore, it is necessary to better investigate the adhesion strength of fusion-bonded epoxy (FBE) primer to steel taking into account the water diffusing through the topcoat within the lifetime of pipeline. A methodology was developed to examine the adhesion of sublayers to steel under wet exposure: peel tests were carried out on pipe rings industrially coated with FBE and adhesive layers only, aged in vapour to simulate the water ingress through the topcoat. This methodology could be included in selection or pre-qualification tests. 1 BACKGROUND Among the two great families of external coatings of pipelines-FBE coatings and 3-LPE-each one has its advantages and disadvantages. In both cases, FBE is applied in direct contact to the freshly grit blasted pipe in order to provide good anchoring to steel.

We determine the complete set of nanofiltration (NF) parameters (rejection rate, electric filtration potential, volume flux density) of single salts using an analytical approach. Our model is based on the hindered extended Nernst−Planck (ENP) and Stokes equations. We solve the transport equations within the scope of the hindered electrotransport (HET) model, which takes into account ion charge and size (rejection is controlled by both electrostatic and steric effects). We also validate these calculations using both an analytical solution to the classic ENP model, which neglects the ion size, and numerical methods via our NF simulation program, Nanoflux. A preliminary application of the model to organic membranes suggests that the HET model provides a coherent description of ion transport in charged nanoporous membranes.