Oxidation of carbon materials

Ce travail s intéresse à l oxydation des charbons actifs utilisés industriellement pour leurs capacités d adsorption des polluants présents dans l air. L objectif est d accéder à une meilleure connaissance des mécanismes physiques et réactionnels impliqués lors de l oxydation de ces matériaux carbonés. Les lits de charbon actif sont actuellement très répandus dans la pratique industrielle. Cependant de nombreux incidents liés à l inflammation spontanée des containers en service ou au repos ont été reportés. Ces inflammations accidentelles résultent de phénomènes mal contrôlés, liés à l introduction d air dans le système ou à l accumulation locale de chaleur produite par des réactions exothermiques. La prévention des accidents d inflammation nécessite une meilleure compréhension des mécanismes initiant l oxydation. Le but de ce travail est de développer des modèles cinétiques capables de prédire la vitesse d oxydation des matériaux en fonction de leurs propriétés et paramètres opératoires. La réactivité du charbon actif est mesurée par des analyses (ATG-DSC) sous atmosphère oxygénée sous différentes conditions de températures. Les résultats d ATG-DSC ont clairement mis en évidence que l oxydation du matériau était initiée à basse température et qu elle pouvait être caractérisée par la mesure du Point d Oxydation Initiale (PIO). Il y a une transition de l'oxydation basse température à l'oxydation haute température qui est accompagnée d une augmentation rapide du flux de chaleur et d une diminution de la masse de l'échantillon. L auto inflammation du matériau est caractérisée par la mesure de paramètres comme les énergies d'activation et SIT (self ignition). Le type d activation du charbon actifs, leur teneur en oxygène et leur propriété poreuse ont une influence sur l oxydation. Des outils statistiques comme la Régression Linéaire Multiple (RLM) permettent de quantifier l influence des propriétés significativesActivated carbons widely used as adsorbents in air treatments are prone to oxidation and self heating due to external heating, exothermic chemical reactions, and adsorption reactions. The aim of this work is to establish a quantitative relationship between the intrinsic properties of activated carbons and their reactivity leading to oxidation and ignition. The correlation is established by analysing a large number of activated carbons samples having diversified origin and characteristics. Carbon samples were characterized for their physical and chemical properties. Their oxidation and ignition reactivity in air were studied using Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). The Point of Initial Oxidation (PIO) representing the beginning of the oxidation reactions and the Spontaneous Ignition Temperature (SIT) where the bed combustion takes place in a self sustaining manner [were experimentally determined. In addition, activation energy (Ea) was calculated from the TG curves indicating the weight loss of the combustion reactions. In a first approach, oxidation and ignition behaviours described by the PIO, SIT, and Ea values versus intrinsic properties of the activated carbon were examined. Global qualitative trends were underlined. In a second step, a more rigorous analysis was realised and quantitative statistical correlations between oxidation and ignition properties and intrinsic characteristics of the porous carbonaceous materials were investigated using multiple linear regression (MLR). Results indicated that the properties of the activated carbons had a significant influence. The surface oxygenated groups and the metal impregnates increased the reactivity of the material whereas the nitrogen content stabilized the reactivity of the samples. The porosity characteristics like the specific surface area, pore volume also contributed to the increase in the reactivity of the materialNANTES-BU Sciences (441092104) / SudocSudocFranceF

Improving sustainability of biomass value chains through process intensification : do we always go towards inherently safer design ?

It is well known that process and economic constraints due to complexity of biomass conversion as well as low cost of fossil fuels context significantly affect the sustainability of biorefining. Ways to tackle such difficulties can be a) operating biorefineries with biomass from waste streams b) producing main or side streams of new molecules or materials with very high added values c) designing biorefinery systems with increased integration of processes, process streams, coproducts and energy and material recycling d) in connection with point c) or not, making extensive use of local or global process intensification. The objective of the present work is to focus and outline the potential conflicts in terms of safety that may arise with the improvement of global sustainability target. Indeed, it is often considered that intensification is necessarily leading to inherently safer production systems. Through a review of literature on the concept of intensification, first promoted by Hendershot and coworkers in the early 80’s and Inherently Safer Design or Engineering (ISD by Keltz in 1978) a key way to consider safety in early stage of process design, the potential impacts on safety of the process is addressed in this work. Illustrations and discussions through examples are provided, outlining the repercussion of intensification (like activating corrosion issues or triggering risks in effluent or emission treatment units)

Application of risk assessment approaches on pilot scale process lines using nanomaterials within the SANOWORK project

Nanomaterials are increasingly used in industrial products and cover a wide range of applications in cosmetics, functional materials, packaging and promising applications like the drug delivery which is still under investigation and development. The nanomaterials may exhibit interesting properties when compared to the same material in the micro scale. On the contrary their hazard potential may also be dramatically changed due to larger surface area and/or modified surface reactivity. Moreover, the nanomaterials due to their small size make the human beings more vulnerable to their exposure and can be transported deeper in the human body than microparticles. The production and handling of engineered nanomaterials in the work place may pose risks of exposure and hazards to workers. This may occur during the reception, storage, production and operations like cleaning of the work places and the equipment and also during the waste disposal. So, in an industrial context, particular attention has to be done on occupational safety issues related to nanomaterials. But, no consensual occupational exposure limits (OELs) are nowadays available for nanomaterials. In this context, a series of control banding approaches specific to nanomaterials were developed in the last decade to manage toxicological risks in workplaces involving nanomaterials. These CB methods for NMs focused on inhalation risks since it can considered to be most critical route of exposure than the ingestion and the dermal route. The present work concerns the project SANOWORK (7th European Framework Program, GA: 280716), whose main objective is to develop and implement design option based remediation strategies that will prevent workers exposure and/or potential hazards. The present contribution aims to present the work realized by INERIS to demonstrate the pertinence of qualitative and semi-quantitative approaches for the assessment of occupational risks. A series of pilot scale process lines were thus investigated by INERIS in the frame to evaluate the available tools in the assessment of occupational risks. The results showed that the application of existing CB tools to the SANOWORK process lines allowed to highlighting their capabilities and limitations for the design of safe industrial process lines involving nanomaterials

Statistical quantification of the influence of material properties on the oxidation and ignition of activated carbons

International audienc

Evaluation des risques liés à la production d'hydrogène par un procédé intensifié de reformage avec technologie integré de capture CO2

La recherche permanente de nouvelles technologies de production hydrogène toujours plus efficaces d'un point de vue énergétique est en passe de conduire à l'émergence industrielle de nouveaux procédés décarbonés avec système de capture de CO2 intégré. Une technologie particulièrement prometteuse par exemple est la technologie RES (qui permet de réaliser au sein même d'un réacteur des réactions de reformage, de gaz à l'eau et de capture du CO2. Comparativement aux technologies classiques, la technologie RES n'utilise que deux réacteurs au lieu de 5 pour un système de reformage à la vapeur avec un système de capture CO2 séparé. L'intensification de la production de H2 est ici rendue possible grâce à l'utilisation de sorbants solides qui permettent non seulement de travailler à basse température mais également d'avoir un taux de production d'hydrogène supérieur à 95%mol en une seule étape contrairement aux procédés conventionnels. Afin d'accompagner le développement industriel de technologies plus efficaces et plus propres, les aspects relatifs à la sécurité doivent être traités le plus tôt possible afin de promouvoir des technologies intrinsèquement plus sûres (ISD) et durables. Dans ce contexte, l'INERIS présentera les résultats propres à l'analyse des risques liés aux technologies RES. Ces résultats seront mis en perspective par rapport aux procédés de reformage conventionnels. L'intégration de ces technologies pour la production d'électricité sera également discutée

Promoting safety in innovative and sustainable biomass value chains

The development of the so-called bio-economy, replacing « black gold » by « green gold » towards industrial ecology as well as the promotion of the circular economy lead to consider wastes and biomass residues of different sources as new and valuable feedstocks. This global context requires a new paradigm in the way we should tackle the issue of material and process safety in advanced biorefineries. This was recently debated in a wokshop organized by DG Research [1] where safety consideration was pointed out as deserving dedicated research in this area. In addition, adequate safety management strategy implemented at early design stage was also perceived as a contributing factor of sustainability and societal acceptance of industry. Based on recently completed or on-going projects like Imidazolium or Evalbioraf (SAS Pivert), HUGS, ALFA-BIRD, ZELCOR, GREENLAND, FLEDGED (EU FP7 & H2020 programmes) or CORABIO (CR Picardy), the presentation will examplify key issues that needs to be considered towards proactive material hazard characterization or process safety in this sector. Final goal of the presentation is ultimately to explain the attendees how to move from conventional risk analysis and simple compliance to existing safety focused regulations towards advanced integration of safety management as a key and measurable sustainability aspect in the context of biorefining. Among material-focused safety issues, the cases of alternative solvents or green solvents like « ionic liquids » (Fig. 1a) [2] or deep eutectic solvents (Fig. 1b) or biofuels will be pointed out to show about ignored or underscored safety issues or on misleading data regarding their fire behaviour at large scale (fuel ethanol). The importance of revisiting self-heating behaviour (see Fig.2) and other safety related issues all along innovative value chains with biobased feedstock [3] will also be outlined with an insight on biobased residues like biomass materials issuing from phytoremediation of polluted soils. The emerging interest on furan derivatives since new biobased routes of productions were shown promising will also been commented in terms of new needs to dig in the relating safety issues. Even more rarely investigated in recent research [4/5], safety aspects mostly addressing the process side (preatreatment, conversion, downprocessing, emission abatement) will be the latter part of the presentation covering key aspects of biorefining as : a) biological conversion processes and « accidental » biological risks, b) upstream and downstream flexibility demand versus safety , c) process intensification and inherently safer design (ISD) potentially antagonistic aspects [6], d) safety issues pertaining to process water, thermal and carbon streams recycling or to process integration, e) hazards pertaining to zero waste and energy self-sufficient targets), f) Corrosive environment problems as compared to classical refineries. This latter issue at frontier of product and process safety will also be debated at light of existing new hazardous property « corrosive to metal » recently introduced in CLP Regulation 1272/2008/EC and findings from the ECORBIO project. Eventually, the interest to link the safety approach and the evaluation of the environmental impacts of biobased processes will be also discussed

Material Properties Influencing the Oxidation and Ignition Reactivity of Activated Carbons: Thermal Analysis, HRTEM Study, and Statistical Modeling

International audienc