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An innovative approach for project launch decision-making in risk and multi-criteria situations
No full textInternational audienceThe realization of infrastructures and the deployment of processes can follow projectformalism. Generally, a project goes through a design and a realization phase. Betweenthese two phases, there is a crucial milestone: Launching the project, which is not at all an easy decision and constitutes a real problem. The main reasons to this are the numerous numbers of criteria (For Technical, Economic, Social, Environmental dimensions) and risks in the sense of feared event. Criteria and risks are most of the time not considered due to lack of time (for formalization) and the difficulty to handle them. The objective of this paper is to propose a relevant approach to make the decision of launching the project or not. The proposal outlined is innovative in that it can consider indicators based on several appropriate criteria, the associated risks and their ways of management. The fact to consider several criteria and risks, increases the probability of making the right decision. The proposed approach allows managing risks by determining acceptable scenarios, thus maximizing project aptitude to fulfil the objectives
Enhancing Emergency Call Centers' Performance Through a Data-driven Simulation Approach
No full textInternational audienceEmergency Call Centers (ECCs) can be considered as the starting point of the pre-hospital emergency medical system. Although, ECCs exist everywhere, their business processes and their performance levels differ from one place to another, even sometimes in a same country. By definition, users expect a high level of performance, particularly regarding the waiting time and the processing time of the calls. Additionally, ECCs might have difficulties to manage sudden rise of activities following disasters impacting huge number of victims for instance. To support ECCs in their continuous improvement steps, this paper suggests an innovative framework and its associated tools to support both diagnosis of current organizations and enhancement of their performance. Concretely, the proposal is data-driven and simulation oriented. First experiments are shown in order to demonstrate the potential benefits of such an approach. Avenues for further research are also discussed
Life cycle environmental assessment of thermal waste-to-energy technologies and energy–environment–economy model development
No full textInternational audienceStimulated by dwindling reserves of fossil fuels and sustainable energy production, Waste-to-energy (WtE) has started playing an increasingly important role in the recovery of energy from municipal solid waste (MSW). A number of WtE technologies, such as pyrolysis, gasification, and incineration, are being developed. However, selecting a more environmentally sustainable option is still made difficult, and comprehensive comparisons of the existing WtE technologies are fairly rare. In this chapter, the development of different WtE technologies, in particular for pyrolysis and gasification, is introduced. This is followed by a life cycle assessment assessing the environmental sustainability of different WtE technologies. First, seven potential WtE systems involving thermal conversion (pyrolysis, gasification, incineration) and energy utilization (steam cycle, gas turbine/combined cycle, internal combustion engine) are modeled as a theoretical analysis. The results are then compared with four types of commercial plants (incineration, pyrolysis, gasification, gasification-melting) as a case study. The establishment of a life cycle Energy–Environment–Economy model is discussed, as well as a case study comparing landfill (with and without landfill gas recovery) and incineration MSW treatment technologies. Finally, the future prospects for developing WtE technologies are discussed
Three-dimensional point cloud analysis for automatic inspection of complex aeronautical mechanical assemblies
No full textInternational audienceWe present a robust approach for detecting defects on an aircraft electrical wiring interconnection system in order to comply with the safety regulations such as the forbidden interference and allowed bend radius of cables and/or harness in mechanical assemblies. For this purpose, we exploit 3-D point clouds acquired with a 3-D scanner and the 3-D computer-aided design (CAD) model of the assembly being inspected. Our method mainly consists of two processes: an offline automatic selection of informative viewpoints and an online automatic treatment of the acquired 3-D point cloud from said viewpoints. The viewpoint selection is based on the 3-D CAD model of the assembly and the calculation of a scoring function, which evaluates a set of candidate viewpoints. After the offline viewpoint selection is completed, the robotic inspection system is ready for operation. During the online inspection phase, a 3-D point cloud is analyzed for measuring the bend radius of each cable and its minimum distance to the other elements in the assembly. For this, we developed a 3-D segmentation algorithm to find the cables in the point cloud, by modeling a cable as a collection of cylinders. Using the segmented cable, we carried out a quantitative analysis of the interference and bend radius of each cable. The performance of the inspection system is validated on synthetic and real data, the latter being acquired by our precalibrated robotic system. Our dataset is acquired by scanning different zones of an aircraft engine. The experimental results show that our proposed approach is accurate and promising for industrial applications
Effect of steam addition during carbonation, calcination or hydration on re-activation of CaO sorbent for CO2 capture
No full textInternational audienceCalcium looping (CaL), based on cyclic carbonation/calcination using lime-based sorbents, is a promising technology for post-combustion CO2 capture. An important obstacle of this technology is the decay of sorbent over multiple cycles. Steam re-activation is a potential approach to improve the sorbent reactivity, however, the effects of both in-situ high-temperature steam (in carbonator or/and calcinator) and ex-situ low-temperature steam (steam hydration in hydrator) are still a matter of debate. Here, a bubbling fluidised bed reactor was used to investigate three steam addition options: steam addition during carbonation stage, or during calcination stage, or intermediate steam hydration after each CaL cycle. A CaO sorbent was tested under varying steam concentrations up to 40 vol.% for 10 CaL cycles (carbonation: 650 °C, calcination: 900 °C). Compared to the dry condition, steam addition during carbonation and intermediate steam hydration were both found effective for CaO re-activation. For the former, the improved sorbent reactivity was mainly attributed to an increased pore volume enhancing the extent of carbonation in kinetic regime; while for the latter, the formation of cracks accelerated the rate of diffusion. Nevertheless, decreasing the hydration temperature was detrimental to sorbent reactivity due to enhanced sintering upon cooling. In case of steam addition during calcination, the sorbent was affected negatively or positively depending on the concentration of steam. At higher steam concentrations (20, 40 vol.%), the sorbent reactivity was significantly decreased due to sintering associated with larger pores and lower surface areas. Overall, steam addition during carbonation was recommended for sorbent re-activation
How an organogelator can gelate water: gelation transfer from oil to water induced by a nanoemulsion
No full textInternational audienceA hydrogel can be formed by an organogelator in the presence of a nanoemulsion. It is expected that this is due to a gelation transfer from oil to water. The system started with an oil-in-water nanoemulsion prepared according to a phase inversion temperature (PIT) process. Into this nanoemulsion consisting of Kolliphor® RH40 and Brij® L4 as surfactants, and Miglyol® 812 as oil and water, we introduced the organogelator 12-hydroxyoctadecanoic acid (12-HOA) in the oil phase. After cooling at room temperature, a slow reversible gelation of the water phase occurred with persistence of the nanoemulsion. This thermally reversible system was investigated using various techniques (rheology, turbidimetry, optical and electron microscopies, scattering techniques). Successive stages appeared during the cooling process after the nanoemulsion formation, corresponding to the migration and self-assembly of the organogelator from the oil nanodroplets to the water phase. According to our measurements and the known self-assembly of 12-HOA, a mechanism explaining the formation of the gelled nanoemulsion is proposed
Automated and quantitative analysis of plastic strain localization via multi-modal data recombination
No full textInternational audienceA multi-modal data recombination method that enables the automated, quantitative and statistical assessment of strain localization as a function of the microstructure is presented. It consists of merging high resolution digital image correlation (HR-DIC) datasets collected in a scanning electron microscope (SEM), with crystallographic data obtained from electron back-scattered diffraction (EBSD). As the data is typically gathered over large areas (about 1 mm2), this method enables the quantitative assessment of plastic strain localization over hundreds to thousands of grains, yet with a spatial resolution of tens of nanometers. The data is treated in a hierarchical manner so that strain localization phenomena can be studied as a function of phases, texture and grain orientation. The use of discontinuity tolerant DIC codes, such as Heaviside DIC (H-DIC) in the present case, enables identification the active slip system associated with slip band discontinuities. Analyses conducted over thousands of bands in thousands of grains enable the quantitative assessment of fundamental plasticity laws. The capabilities of this method are shown through application to Ti-6Al-4V and Inconel 718 alloys
Rheology evolution of a geopolymer precursor aqueous suspension during aging
No full textInternational audienceGeopolymer based glass‐ceramic matrix composites can be processed at room temperature and a heat treatment below 100°C leads to matrix hardening thanks to the geopolymerization mechanisms. The stabilization of the matrix into glass‐ceramics is achieved via a post‐curing at high temperature. This paves the way of the utilization of cost effective liquid composite molding processes, for which all the necessary equipment is already available for processing temperature ranges related to polymer matrix composites, provided that the rheological behavior of the precursor is suitable to conveniently permeate the fibrous preform. The paper describes the thixotropic rheological behavior of a reference suspension at processing temperature (10‐20°C) and its evolution along ageing at ‐18°C. The changes are interpreted in terms of geopolymerization mechanisms (dissolution and polycondensation) and suspension rheology (predominance of hydrodynamic effects at high shear rate). On this basis, a phenomenological modeling framework, combining two Krieger‐Dougherty equations, is proposed to build a relationship between the effective viscosity of the suspension and the phenomena involved during ageing (dissolution of alumino‐silicate particles) and shearing (microstructure scalar variable)
Valorization of calcium carbonate-based solid wastes for the treatment of hydrogen sulfide in a semi-continuous reactor: Part II - slurry bubble column pilot
No full textInternational audience• H 2 S removal from the gas phase using calcium carbonate based solid wastes. • Validation of a triphasic gas/liquid/ solid process at the pilot scale. • Validation of the process with a real gaseous effluent. Keywords: H 2 S removal Calcium carbonate Solid waste Triphasic process Slurry bubble column pilot This work is devoted to the removal of H 2 S from the gas phase using a suspension of calcium carbonate-based residues, recovered from the production of sodium bicarbonate. A 145 L (1.6 m height and 0.34 m internal diameter) slurry bubble column (SBC) reactor was used. The gaseous effluent was bed from the bottom and get out from the top of the column. The suspension (2-20 wt%) was recirculated from the bottom to the top by a pump. This created a counter-current regime between the gas phase (from the bottom to the top) and the liquid phase (from the top to the bottom) which favor the gas/liquid exchange inside the reactor. The influence of different parameters including solid concentration in the suspension (w s), recirculating rate of the suspension (Q R), inlet gas flow rate (Q G), and volume of the suspension, was investigated. The results obtained with this confirmed those at the lab scale, for both synthetic gaseous effluent (H 2 S diluted in compressed air) and real gaseous effluent emitted by the buffer tank of a wastewater treatment plant. This allows validating the technology before its deployment at the large industrial scale for H 2 S removal from the gas phase
Plastic Fuel Conversion and Characterisation: A Waste Valorization Potential for Ghana
No full textInternational audiencePlastics generally play a very important role in a plethora of industries, fields and our everyday lives. In spite of their cheapness, availability and important contributions to lives, they however, pose a serious threat to the environment due to their mostly non-biodegradable nature. Recycling into useful products can reduce the amount of plastic waste. Thermal degradation (Pyrolysis) of plastics is becoming an increasingly important recycling method for the conversion of plastic materials into valuable chemicals and oil products. In this work, waste Polyethylene terephthalate (PET) water bottles were thermally converted into useful gaseous and liquid products. A simple pyrolysis reactor system has been used for the conversions with the liquid product yield of 65 % at a temperature range of 400°C to 550°C. The chemical analysis of the pyrolytic oil showed the presence of functional groups such as alkanes, alkenes, alcohols, ethers, carboxylic acids, esters, and phenyl ring substitution bands. The main constituents were 1-Tetradecene, 1-Pentadecene, Cetene, Hexadecane, 1-Heptadecene, Heptadecane, Octadecane, Nonadecane, Eicosane, Tetratetracontane, 1-Undecene, 1-Decene). The results are promising and can be maximized by additional techniques such as hydrogenation and hydrodeoxygenation to obtain value-added products