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Following previous studies on heterogeneous batch azeotropic distillation, we evaluate the use of heterogeneous entrainers for the separation of binary azeotropic mixtures by extractive distillation. This process is well suited for systems where the entrainer forms a saddle heteregeneous azeotrope with anyone of the original components, such systems being unsuitable for non extractive heterogeneous batch distillation processes. Process feasibility is assessed from the isovolatility curves and the volatility order diagram. It tells us whether the homogeneous original component or the heteroazeotrope is drawn at the column top and establishes the distillation tasks sequence using a batch rectifying column. The theoretical insights are validated via rigourous simulation for the separation of the mixture acetonitrile – water with hexylamin...
Feasibility analysis of the extractive distillation processes mainly considers the general features of the residue curve map. However, the influence of unidistribution and univolatility lines has not been considered to its full extend. In this paper, we demonstrate the essential role of both thermodynamics properties along with the residue curve map for determining the product sequence and the column configuration without any calculation. The analysis is performed through the separation of binary mixtures having a low relative volatility by using heavy and light entrainer. Thermodynamic insight predictions are corroborated by the computing of the map of extractive composition profiles for several operating conditions and using a simplified mass balance. This behaviour is further corroborated by rigorous simulation using ProSim Batch. T...
This article shows how knowledge of the location of univolatility lines and residue curve analysis helps in assessing the feasibility of extractive distillation of minimum-boiling (minT) or maximum-boiling (maxT) azeotropic mixtures or low-relative volatility (low-α) mixtures (A-B) by using a light-boiling entrainer (E), in accordance with the general feasibility criterion of Rodriguez-Donis et al. [Ind. Eng. Chem. Res. 2009, 48 (7), 3544-3559]. Considering all possible locations of the univolatility line αAB, three minT azeotropic mixtures with a light entrainer (1.0-2 class), namely, ethanol-water with methanol, ethanol-toluene with acetone, and methyl ethyl ketone-benzene with acetone; three maxT azeotropic mixtures with a light entrainer (1.0-1a class), namely, water-ethylenediamine with methanol, acetone-chloroform with dichlometh...
En raison de l’impact des phosphates sur la pollution des eaux, un procédé de récupération par précipitation d’un phosphate de calcium a été développé. Le réacteur du procédé est un lit fluidisé, dans lequel le phosphate précipite en continu et s’enrobe sur des grains de sable. Le pilote réalisé permet de traiter des débits de rejet aqueux synthétique ([P]in=50 mg/l) de l’ordre de 0,1 m3/h. La méthodologie découple les phénomènes physico-chimiques présents. La précipitation dans le lit fluidisé est modélisée à l’aide de concepts thermodynamiques tenant
compte des différents phosphates de calcium susceptibles de précipiter en fonction des conditions opératoires (pH, [P], [Ca], T). L’enrobage est modélisé par une réaction cinétique du premier ordre entre les fi nes et les grains de sable, couplée avec un réseau de réacteurs idéaux tradu...
Comparative osmotic compression experiments were performed on colloidal silica dispersions in the presence of various chloride salts at the same 0.01Mconcentration with different counterions and highlighted the influence of ionic specificity on the resistance to water removal.
These results were complemented with frontal ultrafiltration measurements that demonstrate modulation of the permeate flux according to the salt used.
Seasonal differences in the occurrence of aquatic hyphomycete conidia were studied in four streams located along an altitudinal gradient. Samples were taken at monthly intervals for one year using two independent techniques simultaneously: direct sampling of foam, and incubation of leaf litter collected from each stream. The concentration of conidia in foam of the three upland sites exhibited a dramatic increase in Nov.-Dec. The number of species present rose at the same time but a similar, or even higher, increase was also noticed in late spring in all four streams. The following successional pattern of major species emerged: Lunulospora curvula, Heliscus tentaculus (low altitude) and Tricladium chaetocladium (higher altitude) in summer and early autumn, F1agel/ospora curvula, Tetrachaetum elegans and Lemonniera terrestris in autumn, ...
In this study, we propose a new multilevel optimisation process which responds to these requirements. The original optimization problem is decomposed into a system level and several element levels, aiming at the minimization of element weight under inequality constraints. Bounds of these constraints are given by the system level optimisation. In order to speed up the process and avoid local minima–which is met in most multilevel optimisation schemes- we replace the system constraints by a surrogate model. Last, a penalty term added in the "element level" objective allows us to force the equality of some design variables among all elements. The surrogate is incrementally built along system/element level loops from local optimisation results. For this reason, we choose to use Support Vector Regression methodology, which is more suitable ...
Graphene is one of the most interesting candidates for the next generation of transparent conductive electrodes (TCEs) for electrical devices, because of its unique electronic structure. Furthermore, the optical transparency of graphene films surpasses that of conventional TCEs such as indium tin oxide (ITO) [1]. However, graphene anode for Organic Light Emitting Diodes (OLEDs) still presents several problems owing to its low work function and high sheet resistance [1], which may be related to a poor control of graphene quality. Chemical vapor deposition (CVD) on copper from methane seems to be the most efficient approach to form high quality transferable graphene for opto-electronic applications, due to the potential for commercially viable production at large scale. However, CVD processes need to be optimized for obtaining selective ...
Implementation in Europe of large-scale testing to detect bovine spongiform encephalopathy (BSE)-infected cattle and prevent the transmission of this prion disease to humans has recently led to the discovery of novel types of bovine prions. We characterized atypical isolates called BSE L-type by analyzing their molecular and neuropathological properties during transmission to several mouse lines transgenic for the prion protein (PrP). Unexpectedly, such isolates acquired strain features closely similar to those of BSE-type agents when propagated in mice expressing ovine PrP, although they retained phenotypic traits distinct from BSE in other lines, including bovine PrP mice. These findings further underline the relationship between the crossing of species barrier and prion strain diversification, and, although the origin of the epidemi...
The beef sector in North America as in much of Europe has not industrialized as rapidly as other animal production industries (pork, poultry). Alongside this, the market share for beef in household meat consumption has dwindled. Apart from a penalizing price effect, various studies in North America (Wachenhein and Singley, 1999; Goldsmith et al., 2002; Schroeder and Kovanda, 2003) have accounted for this in terms of a lack of vertical coordination in the sector, the absence of a channel captain at the processing stage, and the dearth of product differentiation initiatives directed at customer expectations. The purpose of this contribution is to analyse the case of the French beef sector and to compare and contrast findings with the situation described in the U.S. and Canada.
The processing sector has undergone slow industrialization ...
