Simulation and optimization of steam-cracking processes

Thermal cracking is an industrial process sensitive to both temperature and pressure operating conditions. The use of internally ribbed reactors is a passive method to enhance the chemical selectivity of the process, thanks to a significant increase of heat transfer. However, this method also induces an increase in pressure loss, which is damageable to the chemical yield and must be quantified. Because of the complexity of turbulence and chemical kinetics, and as detailed experimental measurements are difficult to conduct, the real advantage of such geometries in terms of selectivity is however poorly known and difficult to assess. This work aims both at evaluating the real benefits of internally ribbed reactors in terms of chemical yields and at proposing innovative and optimized reactor designs. This is made possible using the Large Eddy Simulation (LES) approach, which allows to study in detail the reactive flow inside several reactor geometries. The AVBP code, which solves the Navier-Stokes compressible equations for turbulent flows, is used in order to simulate thermal cracking thanks to a dedicated numerical methodology. In particular, the effect of pressure loss and heat transfer on chemical conversion is compared for both a smooth and a ribbed reactor in order to conclude about the impact of wall roughness in industrial operating conditions. An optimization methodology, based on series of LES and Gaussian process, is finally developed and an innovative reactor design for thermal cracking applications, which maximizes the chemical yield, is propose

Optical and Electrical Properties of SnO 2

Tin oxide films were deposited on glass substrates by reactive and non reactive r.f. sputtering using different types of targets corresponding to various Sn/F atomic ratio: hot pressed Sn–SnF2 or SnO2–SnF2 mixtures, ceramics obtained by casting either an aqueous SnO2–SnF2 slurry or a suspension of tin oxide in molten tin fluoride. The samples were prepared in oxygen-argon gas mixtures in which the oxygen concentration was varied from 0 mole % up to 30 mole% depending on the target. The optical and electrical properties of the obtained thin films have been studied and compared to those of the films obtained by spray technique

Realization of Solar Cells Based on Silicon/Oxide Junctions

Transparent and conductive films of SrTiO3 , ITO, and Tl2O3 have been deposited by R.F. cathodic sputtering and by anodic oxidation onto Si substrates in order to realize SIS cells. A photoconversion efficiency of 8.8% has been obtained for Si/SiOx/Tl2O3 cells. On the other hand for Si/SiOx/SrTiO3(ITO) the photoconversion efficiency is lower than 1% because of the too large thickness of the SiOx interfacial layer

An evaluation of the complete replacement of both fishmeal and fish oil in diets for juvenile Asian seabass, Lates calcarifer

An experiment was conducted to examine the potential for the complete replacement of fishmeal (FM) and fish oil (FO) in diets for barramundi,Lates calcarifer. A series of diets were formulated to the same digestible protein and energy specifications, but which were designed with FM inclusion levels at 300, 200, 100 or 0g/kg and FO at 100%, 30%, 15% or 0% of the added oil in the diets (4×4 factorial design). Ricebran oil was the alternative oil used in the growth study, while soybean meal and poultry meal were the main alternative protein sources used. For the growth study, fish of an initial weight of 154.4±1.1g were randomly allocated across 48 tanks (three replicates per treatment). After eight weeks, the average weight gain across all treatments was 187.7±2.3g/fish and feed conversion across all treatments averaged 1.04±0.01 feed/gain. A significant effect of FM on both feed intake and weight gain was observed, and this was observed as early as within the first few weeks, but no similar such effect was observed with FO. No effects were observed on protein deposition efficiency, though both lipid and energy deposition efficiencies were affected by FM level. The reduction in FO had a notable effect on the fatty acid composition of the diets and subsequently the fish fatty acid composition. Expression of key LC-PUFA metabolism genes in the liver of the fish was influenced by both FM and FO levels, but was only significant at the extremes of the treatment ranges. The results from this study demonstrate that there is clear potential to replace almost all the FM content of barramundi diets without loss of fish performance, up to and including diets with as little as 100g/kg fishmeal. Replacement of fish oil was more successful with the ability to completely replace all FO demonstrated at all but the lowest inclusion levels of FM. These results clearly demonstrate that the near complete replacement of both FM and FO in barramundi diets is a technical reality

Influence of Thermal Treatment on The Electronic Properties of ITO Thin Films Obtained by RF Cathodic Pulverization. Study of Solar Cells Based on Silicon/(RF Sputtered) ITO Junctions

ITO (Indium Tin Oxide) thin films obtained by R.F cathodic sputtering have been studied. The influence of thermal treatment on the electronic properties of the films has been particularly investigated. Electrical measurements were performed between 95 and 600 K. Free carriers concentration in the film were measured by Hall effect coefficient. Optical indices were determined by computer drawing of charts allowing to simplify Manifacier method

Physical Properties of Sputtered Germanium-Doped Indium Tin Oxide Films (ITO: Ge) Obtained at Low Deposition Temperature

Undoped and Ge-doped ITO films (ITO: Ge) deposited at low temperature (70℃) have been studied. Although both samples have the same carrier concentration, a higher carrier mobility occurs for ITO: Ge. An evaluation of the relative position of the dopant associated energy states has been carried out

Applications of Nanoscale Materials in the Fields of Electrochemistry and Photoelectrochemistry

We have illustrated the important role played by the nanoscale materials in three-up-to-date energy topics

PLR (Plastic Lithium Rechargeable) Batteries Using Nanoscale Materials: A Convenient Electrical Energy Power for the Future?

This communication describes the synthesis of: (i) non toxic and low cost nanocrystalline electrode materials which can be advantageously prepared at low temperature; (ii) highly conductive electrolyte membranes formed by the nano-encapsulation within a poly (acrylonitrile)-based polymer matrix of a solution of LiPF6 in organic solvants. The performances of rechargeable PLR (Plastic Lithium Rechargeable) batteries using the above mentioned components are presented