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NOx decomposition using Ni- and Fe-loaded biocarbon catalysts
No full textInternational audienceFern and willow (W) impregnated with heavy metals (Ni/Fe) were pyrolyzed (800 °C, N2) to produce heavy metal-loaded biocarbon to catalyze NO decomposition (deNOx). The effects of reaction temperature (200, 350 and 500 °C), biomass type and impregnated metals on deNOx performance were investigated. WFe and WNi achieved the highest deNOx performance at 200 °C (16.5%) and 500 °C (30.6%) respectively. The biocarbon composition and structure were crucial for NO adsorption and metal dispersion, which induced higher CO2 adsorption (TPO), high specific surface area (419.1 m2/g for WNi), and highly dispersed small Ni particles (SEM). The main routes for deNOx evidenced by on-line monitoring were direct decomposition of NO into N2 and O2, and NO reduction to N2, CO and CO2 by biocarbon sites. Dispersed catalytic metals, as well as NO adsorption and reactivity by biocarbon functional groups, reflect the cost-effective and eco-friendly deNOx potential of biocarbon catalysts
A review on biochar briquetting: Common practices and recommendations to enhance mechanical properties and environmental performances: review
No full textInternational audienceBiochar briquettes stand as the current frontrunner for cost-effective and sustainable substitutes for fossil fuels in both energy and industrial sectors. Produced through the thermochemical conversion of biomass to biochar followed by densification, this process yields a renewable briquette that imitate coal in mechanical attributes and combustion efficiency, while maintaining a carbon-neutral profile. Findings indicates that substituting biochar briquettes for coal has the potential to reduce methane (CH4) and carbon dioxide (CO2) emissions by approximately 40%. The densification stage plays a crucial role in converting biochar which has low bulk density (0.2 g cm-3 to 0.4 g cm-3), into a coal-like energy product. Thus, effectively addressing concerns associated with handling, transportation, and storage. To ensure the fabrication of high-quality biochar briquettes, particular attention must be directed towards the choice of binder, compaction technology, and operational conditions. In addition, critical briquette quality parameters such as density, mechanical durability, calorific value, and volatile species are influenced by the binder. The optimal binder loading ranges from 5 - 15% depending on the feedstock and pyrolysis temperature. Biochar briquettes produced under these conditions tend to exhibit durability values ranging from approximately 70% to 90%. While the existing literature offers broad insights into pyrolysis conditions for various biomass types, available densification technologies, and binder options for biochar briquetting, a more comprehensive understanding of how these factors impact the mechanical and environmental performance is lacking. This review aims to bridge this knowledge gap. By enhancing the biochar densification process to improve energy efficiency, increase mechanical strength, and reduce pollutant emissions, there is real potential for accelerating the transition away from traditional fossil fuel like coal in a variety of industrial applications where it is challenging to decarbonize the production systems
Impact of additives on the quality of oxide/oxide tow-pregs obtained by continuous fibre impregnation
No full textInternational audienceThis paper focuses on the formulation of aqueous alumina slurries compatible with manufacturing alumina/alumina ceramic matrix composite (CMC) by a continuous tow impregnation process. Two hygroscopic organic plasticizers, sorbitol and glycerol, along with a gelling powder, boehmite, are evaluated for their impact on both slurry behaviour and the quality of impregnated tows. The interest of using glycerol instead of sorbitol is demonstrated, as glycerol exhibits smaller impact on slurry viscosity and stability, while being more hygroscopic and plasticizing, enabling a reduction in organic content. Combining glycerol with boehmite powder improves the surface and the tack of impregnated tows, although boehmite increases slurry viscosity and shear-thinning behaviour. Furthermore, thermal degradations of sorbitol and glycerol are studied through thermogravimetric analysis, to define an autoclave curing cycle for each plasticizer removing, to achieve optimal compaction of tow-pregs and hence reduce the porosity of the resulting CMCs
Modelling and characterization of novel honeycomb structures with mass gradient produced by additive manufacturing
No full textInternational audienceThe dissemination of additive manufacturing methods has facilitated the design and production of complex structures which have a high strength-to-weight ratio. Cellular materials such as honeycombs have low-weight and high capacity to absorb energy which makes them desirable for the aerospace and automotive industries. The present work covers the study and comparison of metal-based regular honeycombs and functionally graded honeycombs. The latter encompass radial and linear/longitudinal gradients. Three repeating unit cells were studied: regular hexagons, Plateau and lotus. The structures were produced in aluminium using the laser powder bed fusion technique. Selected samples were submitted to a stress-relieving heat treatment. Numerical and experimental methods were used to assess the in-plane compressive properties. Finite element analysis was used to obtain the simulated force–displacement curves of each structure, allowing for the calculation of specific stiffness, absorbed energy and yield strength. The experimental method consisted of the compression of three specimens of three types of regular structures with and without stress-relieving heat treatment. The heat treatment reduced the yield strength and stiffness whilst increasing the ductility of the samples. The mechanical behaviour of the structures was found to depend upon a combined effect of the type of gradient, relative density, and unit cell structure. The results showed that an increase in the relative density would enhance the specific mechanical properties. The lotus configuration displayed the highest specific mechanical properties, as its geometry reduces the stress concentrations. The numerical results showed a reasonable match with the experimental results
How spray drying processing and solution composition can affect the mAbs stability in reconstituted solutions for subcutaneous injections. Part I: Contribution of processing stresses against composition
No full textInternational audienceSpray drying is increasingly being applied to process biopharmaceuticals, particularly monoclonal antibodies (mAbs). However, due to their protein nature, mAbs are susceptible to degradation when subjected to various stresses during a drying process. Despite extensive research in this domain, identifying the appropriate formulation composition and spray drying conditions remains a complex challenge, requiring further studies to enhance the understanding on how process and formulation parameters impact mAb stability in reconstituted solutions. This research aims to explore spray drying as technique for producing pharmaceutical mAbs-based powders intended for reconstitution and subcutaneous injection. In the initial phase of this study, using a model mAb (mAb-A), the influence of dissociated and coupled process stresses on protein stability after solution reconstitution was investigated. The findings revealed a detrimental interplay of mechanical, interfacial, and thermal/dehydration stresses on mAb-A stability, notably characterized by an increase in protein aggregation. Subsequently, in a second phase, the study delved into the impact of spray drying processing conditions, the level of excipients, and protein concentration on mAb-A aggregation in reconstituted solutions. The obtained results highlighted the critical role of formulation composition as a parameter deserving further study, specifically concerning the selection of type and concentration of stabilizers to be added in the liquid mAb-A solution to be dried
Utilizing Computational Methods to Identify Low GWP Working Fluids for ORC Systems
No full textInternational audienceThe Organic Rankine Cycle (ORC) power cycle is a well-established solution for harnessing heat sources to generate energy. Presently, ORC systems predominantly employ hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) as working fluids. However, these substances possess significant greenhouse gas effects and are slated for future bans. To address this, it is imperative to establish rational selection criteria and corresponding techniques for evaluating working fluids suitable for industrial ORC applications. This chapter presents the working fluid selection criteria and screening methods for environmentally friendly working fluids. The chapter is organized as follows: (1) The fundamentals of working fluids section provide a broad introduction to the core principles of working fluids; (2) the working fluid section outlines reasonable selection criteria for identifying potential alternatives; (3) the screening of ORC working fluids section discusses possible working fluid candidates, simulation approach, and thermodynamic models in detail, which is very important to access the thermodynamic performance of ORC cycle; and (4) an example of the simulation of an ORC for working fluid selection section demonstrates the strategy for the selection of a working fluid considering a defined ORC architecture
Biocarbon materials: review
No full textInternational audienceBiocarbons are carbonaceous solids derived from renewable and sustainable feedstocks and their combinations through thermochemical conversion at high temperatures (>350 °C) in the absence of oxygen or in limited oxygen. Expanding their applications from soil and fuel into advanced arenas of polymer composites, energy and environment is the key strategy to substitute for a wide range of conventional fossil-based carbon materials with the added benefits of sustainability and circularity. This Primer discusses biocarbon research, including feedstock selection, characterization, pyrolysis techniques, post-modification strategies, diversified applications and challenges. A critical assessment of carbon sequestration, waste reduction, economic impact, material sustainability and circularity and future perspectives is presented. This Primer mainly focuses on materials (polymer composites), energy (storage and conversion) and environmental remediation (wastewater treatment and CO2 capture). The hurdles that biocarbon-based materials must overcome are effective market propagation, industry-standard adherence and maintenance of a steady flow of feedstocks to guarantee continuous production. Maintenance of reproducibility of biocarbon materials with similar physicochemical and functional properties is another challenging task, which needs more investigation with the support of theoretical modelling and database generation. The Primer also delves into techno-economic analysis, which integrates biomass logistics and their industrial processing, which will enable a new manufacturing platform in biocarbon production for large-scale technological applications
Stable Heuristic Miner 2: Evaluating the Statistical Stability in Event Logs to Discover Business Processes
No full textInternational audienceAbstract Automated process discovery as one of the paradigms of process mining has attracted both industries and academic researchers. These methods offer visibility and comprehension out of complex and unstructured event logs. Over the past decade, the classic heuristic miner and applied heuristic-based process discovery algorithms showed promising results in revealing the hidden process patterns in information systems. One of the challenges related to such algorithms is the arbitrary selection of recorded behaviors in an event log. The offered filtering thresholds are manually adjustable, which could lead to the extraction of a non-optimal process model. This is also visible in commercial process mining solutions. Recently, the first version of the stable heuristic miner algorithm targeted this issue by evaluating the statistical stability of an event log. However, the previous version was limited to evaluating only activities’ behaviors. In this article, we’ll be evaluating the statistical stability of both activities and edges of a graph, which could be discovered from an event log. As a contribution, the stable heuristic miner 2 is introduced. Consequently, the definition of the descriptive reference process model has improved. The novel algorithm is evaluated by using two real-world event logs. These event logs are the familiar Sepsis data set and the urology department patients’ pathways event log, which is recorded by monitoring the interpreted location data of patients on hospital premises and is shared with the scientific community in this article
Proceedings of sixteenth international conference on quality control by artificial vision, 6-8 juin 2023, Albi, France
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Understanding the relationships between heterogeneous microstructures and tensile properties through characterization of plastic strain localization in ti-6al-4v processed by wded.
No full textInternational audienceWire Direct Energy Deposition (WDED) processes enable near-net-shape manufacturing with a high deposition rate and improved size capabilities as compared to powder-based additive manufacturing (AM) processes. They can be classified according to the employed heat source: a beam, either laser for Wire Laser AM (WLAM) or electron for Electron Beam AM (EBAM), or an arc welding for Wire Arc AM (WAAM). Prior studies have enabled us to limit the introduction of defects and contamination issues using WDED technologies. However, the process-inherited heterogeneous microstructures, including strong crystallographic textures, and consequences on anisotropy and variability in mechanical properties are still not fully understood. In particular, Heat Affected Zones (HAZ) are clearly observed in the material and their features are strongly related to the heat source and the scanning strategy. These HAZ are known to produce a highly heterogeneous microstructure at the millimetre scale with a gradient of α-lath thickness and clusters of crystallographic variants. While these areas are prone to a heterogeneous strain distribution, the relation with macroscopic ductility remains unclear for WDED processes. In the present work, deformation heterogeneity was studied in relation to microstructure to clarify the role of the HAZ-induced strain localization on tensile anisotropy. Digital image correlation (DIC) combined with electron back-scattered diffraction (EBSD) was employed for this purpose. In particular, spatial variations in lamella thickness and implications of Burgers Orientation Relationships were considered to understand the heterogeneous development of slip activity