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Analysis of densification mechanisms of dry granulated materials
No full textInternational audienceDry granulation by roll compaction is a continuum manufacturing process to produce granules with improved flowability which can further be easily used in tableting process. However, the granules are non-homogeneous in density and have non-spherical shapes which impact their densification behaviour during die-compaction. The aim of this study was to investigate both the densification mechanism and the failure strength of granules of microcrystalline cellulose (MCC) and mannitol using Cooper-Eaton and Adams models. For both materials, the Cooper-Eaton approach led to the quantification of fractional volume compaction by particle rearrangement and by plastic deformation respectively to explain the difference in densification behaviour of raw material and granules. Moreover, the model showed its ability to capture the effect of granule density and granule sizes and to differentiate the densification mechanisms of MCC as a plastic material and mannitol as a brittle material. The Adams model was used to compute the failure strength of single granule from in-die compression data. The obtained results of the granules were in the range [0.6–1.43 MPa]. However, regarding the effect of granule density, the model showed mixed results indicating that the model is not representative of the studied granules which are not spherical and have a relatively wide range of sizes, nevertheless, the model was derived for near spherical particles with a narrow size distribution
Heat Exchanger Network Design of Palm Oil Mill in Tronoh, Perak for Maximum Energy Recovery
No full textInternational audienceA palm oil mill involves energy-intensive processes. Maximizing thermal efficiency of palm oil mill is crucial forthe plant profitability. Design and analysis of heat exchanger network is important to maximize heat recovery, which aims to lower the overall plant costs. This work implements a pinch analysis technique to maximize heat recovery and thermal efficiency ofa palm oil mill, subject to the existing process constraints. The procedures involve setting the maximum heat recovery targets and cost-effective of the heat exchanger network (HEN). Application of the technique on a palm oil mill processes resulted in reduction of 510 kW heating and cooling load at ∆Tmin of 10oC. The total annual savings in utility consumption is RM 184,735.63 giving the payback period forthe investment of 2.36 years
A new insight on the analysis of residual stresses related distortions in selective laser melting of Ti-6Al-4 V using the improved bridge curvature method
No full textInternational audienceResidual stresses are a major issue in the Selective Laser Melting process, which allows to build near net shape parts by stacking several thousand weld beads. This experimental study aims to investigate the relationships between process parameters and the part distortion. Based on the Bridge Curvature Method (BCM) and 3D topographic measurements of the top surface of the specimens, the effect of the volumetric energy density, the geometry and the scanning strategy are analyzed. The method and the proposed distortion criteria clearly highlight the anisotropy of the residual stress state, which depends on the direction and the speed of the scanning. The main curvature is oriented along scan direction for scanning speed higher than 1000 mm/s. The decrease in volumetric energy increases distortion, below a threshold value. The scan vector length, which can be varied by changing the scanning strategy and the specimen geometry, plays a primordial role on the residual stresses. The distortion amplitude decreases by shortening the scan vectors. Finally, the prospect of an adimensional analytical model taking into account the transient thermal gradient is given
Maritime risks taxonomy: A structured literature review of maritime risks classification
No full textLe congrès a pour titre "Nouvelles avancées et défis pour des industries durables et avisées"International audienceThe purpose of this paper is to investigate the multi-modal Maritime risk classification, which has shown a great global attention in recent years. Disruption and uncertainties in shipping companies are the result of random events which lead to drop performance throughout the maritime transportation supply chain and they severely impact international trade. This study provides an overview of multi-modal supply chain management by reviewing 131 articles in the risk management area. This work also provides a great analysis of transportation risks, their impacts and a risk typology on multi-modal maritime supply chains management. In addition, this paper contributes to the current risk management literature by proposing a novel risk typology that permits to determine which risk carriers and shippers involved in multi-modal containers transportation should address first, thereafter this typology could be used to build a decision support tool in order to detect and mitigate risks in real-time
Strength Loss of Basalt-Based Mineral Fibers after Thermal Desizing
No full textInternational audienceThis study investigates the effects of desizing by heat cleaning on tensile properties of basalt-based mineral fibers. Two heat treatments, which lead to a complete removal of the sizing layer, were considered: one at low temperature (350°C) for a long time (10 h) and one at high temperature (600°C) for a short time (35 min). Desizing greatly affects tensile strength. High temperature and short time treatment conditions lead to the most severe strength degradation (66%). SEM micrographs reveal that failure originates from surface defects. Mechanisms responsible for strength loss were investigated by X-ray diffraction analyses, density measurements and differential thermal analyses. Strength degradation is ascribed to sizing layer removal and to thermally activated structural rearrangement of basalt
A Systematic Model to Model Transformation for Knowledge-Based Planning Generation Problems
No full textInternational audienceThe generation of an optimum planning problem and search for its solution are very complex regarding different business contexts. Generally, the problem is addressed by an optimization formulation and an optimizer is used to find a solution. This is a classical approach for the Operations Research (OR) community. However, business experts often need to express specific requirements and planning goals mathematically on a case by case basis. They also need to compute a planning result within various business constraints. In this paper, we try to support these experts during this preliminary problem design phase using a model driven engineering framework. An OR model could be generated from the knowledge included in a business conceptual model. A model to model transformation is described to support this goal. The Traveling Salesman Problem is used as a simple case study that allows explanation of our model transformation rules. We implemented our approach in the ADOxx meta-modelling Platform
Identification of Isothermal crystallization kinetics of poly(ether-ketone-ketone) based on spherulite growth measurements and enthalpic data
No full textInternational audienceDifferential scanning calorimetry and polarized optical microscopy were used in this study to identify the contributions and interactions of both primary and secondary crystallization processes during the isothermal crystallization of a PEKK 70/30. Primary crystallization, which is related to the growth of spherulites, was monitored by polarized optical microscopy. The data collected allowed identifying the corresponding nucleation density and crystal growth rate that were subsequently used to feed a kinetic model derived from Hillier’s equation and already been reported in literature. The DSC data were then used to determine the contribution of the secondary crystallization mechanism, considering that primary crystallization is related to the instantaneous nucleation and growth of spherulites. From these data, an inverse approach was used to identify the few remaining parameters of the model. The proposed approach has the advantage of providing kinetic parameters representative of the secondary crystallization mechanism that are not dependent on the inverse identification procedure. Doing so, a non-integer Avrami exponent equal to 2.7 is obtained and discussed
Decision-making in the field of Resilience: literature review
No full textInternational audienceIn recent years, the concept of “Decision-making”in the field ofresilience has become particularly important, which explains the frequency of publications in this context.Based on literature published in various journals, this article proposes a classification of 66 articles in the four dimensions of resilience (technical, organizational, economic and social), to help researchers, and decision-makers avoid confusion and optimize their search method
New insights on mercury abatement and modeling in a full-scale municipal solid waste incineration flue gas treatment unit
No full textInternational audienceModeling approaches are generally used to describe mercury transformations in a single step of flue gas treatment processes. However, less attention has been given to the interactions between the different process stages. Accordingly, the mercury removal performance of a full-scale solid waste incineration plant, equipped with a dry flue gas treatment line was investigated using two complementary modeling strategies: a thermochemical equilibrium approach to study the mercury transformation mechanisms and speciation in the flue gas, and a kinetic approach to describe the mercury adsorption process. The modeling observations were then compared to real-operation full-scale data. Considering the typical flue gas composition of waste incineration facilities (high concentrations of HCl compared to Hg), it was found that a process temperature decrease results in better mercury removal efficiencies, associated with a higher oxidation extent of Hg in HgCl2, and the enhancement of the sorbent capacity. Improvements can also be attained by increasing the sorbent injection rate to the process, or the solid/gas separation cycles. An empirical correlation to predict the mercury removal efficiency from the main operating parameters of dry flue gas treatment units was proposed, representing a useful tool for waste incineration facilities. The presented modeling approach proved to be suitable to evaluate the behavior of full-scale gas treatment units, and properly select the most adequate adjustments in operating parameters, in order to respect the increasingly constraining mercury emissions regulations
The environmental cost of recovering energy from municipal solid waste
No full textInternational audienceMunicipal solid waste (MSW) incinerators require effective flue gas treatment (FGT) to meet stringent environmental regulations. However, this in turn generates additional environmental costs through the impacts of materials and energy used in the treatment – these impacts are currently scarcely known. Therefore, this study uses life cycle assessment to estimate the impacts of different FGT systems typically found in modern MSW incinerators. A total of 12 scenarios are modelled to consider different combinations of the following eight technologies: electrostatic precipitators and fabric filters for removal of particulate matter; dry, semi-dry and wet scrubbers for acid gases; selective non-catalytic and catalytic reduction of nitrogen oxides (NOx); and activated carbon for removal of dioxins and heavy metals. The data are sourced from 90 full-scale incinerators operating in France. The results reveal that a dry system using sodium bicarbonate and selective non-catalytic reduction (SNCR) is the best option for seven out of 18 impacts, including climate change (37.1 kg CO2 eq./t MSW). By contrast, a dry system with calcium hydroxide and selective catalytic reduction (SCR) has the highest impacts in six categories, including climate change (102 kg CO2 eq./t MSW). The wet systems have higher impacts than the dry alternatives, with the semi-dry options being in between. Compared to SNCR, the use of SCR decreases the NOx-related impacts (fine particulate matter formation, terrestrial acidification and photochemical ozone formation) but increases other impacts. For example, the SCR systems have 49–284% greater climate change and 43–150% higher depletion of fossil resources than their SNCR counterparts. Overall, all FGT systems reduce significantly fine particulate matter formation (by 81–88%), photochemical ozone formation (76–90%) and terrestrial acidification (83–90%). However, they also cause 14 other impacts which would not be generated if the flue gas was left untreated, thus creating additional environmental costs. These include climate change, resource depletion and human and ecotoxicities. Therefore, these trade-offs should be considered carefully to minimise the unintended environmental consequences of flue gas treatment from incineration of MSW