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De Ville D'Avray M.-A.,École Centrale Paris | Isambert A.,École Centrale Paris | Brochot S.,CASPEO
International Journal of Chemical Reactor Engineering | Year: 2010

In reactive extrusion, the extruder is used as a solvent-free continuous chemical reactor able to process highly viscous materials. The chemical transformation of biopolymers by reactive extrusion appears as a very promising technology. Although punctual applications in this field have already been achieved on a laboratory or pilot scale, the amount of work to carry out is still considerable. A wide range of reactions and raw materials may be explored, and the reactions achieved on a laboratory scale have to be optimized and transposed to an industrial scale. Process modelling and simulation constitute useful tools for process understanding, development, optimization and scale-up. Although reactive extrusion modelling has interested many authors, it still remains a challenge because of the complex geometry and the strong coupling between operating parameters, flow conditions, material rheological behavior and reaction kinetics. A steady-state mathematical model for a biopolymer oxidation process by reactive extrusion is here proposed. The model is based on a hybrid approach combining chemical engineering methods and simplified continuum mechanics laws. The combination of these two approaches enables to simplify the calculations related to chemical reactions while ensuring a predictive character. The flexible structure of the model enabled its implementation within a global process simulator. A method to minimize the amount of experimental data required for model parameter adjustment is also presented. The model was validated by experiments conducted on a semi-pilot corotating twin-screw extruder. Even if it may be refined, the model proposed already constitutes a useful tool for later research work dealing with the development, modelling and simulation of chemical reactions in corotating twin-screw extruders. © 2010 The Berkeley Electronic Press. All rights reserved.

de Ville d'Avray M.A.,École Centrale Paris | Isambert A.,École Centrale Paris | Brochot S.,CASPEO
Computer Aided Chemical Engineering | Year: 2010

Reactive extrusion involves complex interactions between operating parameters, flow conditions, material rheological behavior and reaction kinetics. Although reactive extrusion modelling has interested many authors, it still remains a challenge. We propose here a steady-state reactive extrusion model combining chemical engineering methods and simplified fluid mechanics laws. This steady-state model was derived from the dynamic model proposed by Choulak (2004). A rheo-kinetic model for a biopolymer oxidation process induced by coupled thermo mechanical and chemical effects was developed and integrated into the twin-screw extrusion model. This modelling approach enables to provide a predictive model involving very rapid calculation. The reactive extrusion model was then integrated into a static process simulator. The simulations reproduce available experimental data with a satisfying accuracy. © 2010 Elsevier B.V. All rights reserved.

Maris E.,Institute Of Chambery | Botane P.,CASPEO | Wavrer P.,Bureau de Recherches Géologiques et Minières | Froelich D.,Institute Of Chambery
Minerals Engineering | Year: 2015

Two studies, TRIPLE (For Analyse des gisements DEEE et optimisation des technologies de TRI des PLastiques DEEE (analysis of WEEE and optimization of sorting technologies for WEEE plastics).) and VALEEE (For VALorisation des composants, matières et substances issus du gisement DEEE (Recovery of components, materials and substances from WEEE).), supported by the French State, the Greater Lyon area (Grand-Lyon), the Rhône-Alpes Region and the French eco-organization "Eco-systèmes", and involving laboratories, recycled material users and recycler partners, were conducted concerning the characterization, sorting and recovery of French WEEE (Waste Electrical and Electronic Equipment). To determine the heterogeneity of a 10-ton batch, the WEEE was sorted into families before grinding. Specimens were dismantled and plastic particles were analyzed to estimate their composition. The batch was then crushed and the metals extracted. The residue containing plastics was sampled at the outlet of the plant and analyzed. The detailed characterization of the plastics sample was used to calculate the estimated sampling error and the overall measurement error. The sample size was determined so as to achieve satisfactory accuracy for the most represented polymers likely to be recovered after recycling. A simple characterization methodology for use by recycling plants was proposed in order to determine the plastic composition of this waste. The procedure was validated on a second 10-ton batch of sWEEE collected from another location and treated by a different recycling facility. This article presents the sampling protocol design methodology, then the characterization protocol and its usage limitations. © 2014 Elsevier Ltd.

Botane P.,Caspeo | Brochot S.,Caspeo | D'Hugues P.,Bureau de Recherches Géologiques et Minières | Spolaore P.,Bureau de Recherches Géologiques et Minières
Hydrometallurgy | Year: 2013

This study presents the approach used to develop a model for a continuous bioleaching system in stirred tank reactors. In bioleaching of metallic sulfides, precipitation concurrently occurs with dissolution of sulfides. Therefore, the model incorporates both the leaching and the precipitation kinetics. It is based on a shrinking particle model for the leaching part and a Mixed Suspension Mixed Product Removal (MSMPR) crystallizer model with germination and growing kinetics for the precipitation part. To establish the model, it was necessary to have access to the size distribution of both sulfide and precipitated particles. A procedure for the bioleached residue characterization was developed in the BRGM laboratory to be able to dissociate sulfide and precipitated particles in the solid phase. The current paper presents the analytical procedure, the mathematical model in detail and its application to a continuous pilot plant test. © 2012 Elsevier B.V. All rights reserved.

Brochot S.,CASPEO | Botane P.,CASPEO
26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth - Conference Proceedings | Year: 2012

Sedimentary deposits such as sandstone are formed by the aggregation of cemented sand grains. Phosphates and laterite present similar aggregation of mineral grains. Grains and cement have different mineralogy and chemical characteristics. During size reduction through crushing or coarse grinding, the rocks are crumbled. Mineral grains and cement are then liberated, and the produced size distribution reflects their "natural size distribution". Mathematical modelling of these concomitant effects of crumbling and mineral liberation necessitates a specific material description and the adaptation of the commonly used theories of breakage kinetics and population balance. The coarse particles are mainly agglomerates made of mineral grains and cement particles whereas the fine particles are grains and cement with a natural grain size distribution. The population balance between the different particle size and particle types during size reduction takes into account the breakage rate and the progeny size distribution. The breakage rate can be described by a simple probability function or by a first order kinetics whereas the progeny size distribution is described by a breakage matrix. The model proposed here considers that the agglomerates will produce other agglomerated particles, liberated grains and cement particles; the two latter having their natural size distribution. The liberated grains and cement particles are subject to size reduction and follow the most commonly used theory of breakage. The present paper describes the theoretical approach of the concomitant crumbling and liberation effects. The application to a mathematical model for the cone crusher is presented. The advantage of such approach is then demonstrated through a simulation study for the optimisation of a crushing plant.

Fernandez M.G.,CASPEO | Brochot S.,CASPEO
IMPC 2014 - 27th International Mineral Processing Congress | Year: 2014

HPGR (High-Pressure Grinding Rolls) is widely used today for grinding of various kinds of ores such as iron ore or base and precious metal ores. It can be used as first stage of grinding replacing tertiary crusher and SAG mill, but also as regrinding stage to enhance mineral liberation. In addition to better energy efficiency, the advantage of HPGR is to produce much more internal particle fractures allowing faster leaching as it has been demonstrated for some gold ores. This grinding mode of compression and fracture generation also promotes mineral liberation without overgrinding. Mineral processing modelling and simulation associated to detailed ore characterization constitute a powerful tool for plant design and optimization. The mathematical models of the units of operations (grinding and separation) have to reproduce the mineral deportment for which the mineral liberation plays a central role. The present paper is focused on the HPGR modelling with the objective of plant optimization or advanced design from pilot plant tests. The traditional approach of the population balance linked to the energy dissipation and the residence time distribution is generalized in association with a mineral liberation model. The effect of the specific HPGR breakage matrix and grinding function on the mineral liberation rate is discussed and compared to the tumbling mill. The implementation of this mathematical model into a plant simulation tool is illustrated by the example of the optimization of an iron ore concentrator.

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