Étude d'un procédé de pyrolyse rapide du charbon dans un réacteur cyclone

Experimental results on fast pyrolysis of coal in a steady state pilot reactor at a flowrate of 0.1 kg/h are examined in this article. The pyrolysis reactor is a cyclone. Using such a system it was possible to achieve simultaneously the reaction and the separation of semi-cokes from volatiles produced by pyrolysis. A pump enabled gas recycling on the experimental setup and allowed a good hydrodynamic regime in the reactor. Only gases were recycled, liquids and tars being condensed and recovered. Experiments were carried out on a Lorraine coal (Houve well). From 100 grams of coal, 60 grams of semi-coke, 35 grams of liquids, and 5 grams of gas containing 66% hydrogen and 30% methane were obtained. For the interpretation of results, an experimental kinetics study on coal grain pyrolysis is presented for grains in the range of 2.5 to 20 mm and temperatures between 700 C and 1050 C.     

Le cyclone: Un réacteur chimique. Application à la réaction de décarbonatation de NaHCO3

The purpose of the present paper is the experimental and theoretical study of the behaviour of the cyclone working as a chemical reactor. The model reaction is the decarbonation of NaHCO₃. Thanks to the use of scale-up relationships previously determined, it is possible to derive kinetic constants in good agreement with other published values obtained under quite different conditions. The measurements are performed in a wide range of experimental conditions (particle size, residence time of particles, cyclone wall temperatures, solid flow rate). The paper emphasizes two possible fields of utilization for the cyclone: a device for the measurement of kinetic constants, a processing reactor operating with high throughput of solids.     

Adsorptive removal of anionic and non‐ionic surfactants from aqueous phase using Posidonia oceanica (L.) marine biomass

BACKGROUND: In this study, the capability of low‐cost, renewable and abundant marine biomass Posidonia oceanica (L.) for adsorptive removal of anionic and non‐ionic surfactants from aqueous solutions have been carried out in batch mode. Several experimental key parameters were investigated including exposure time, pH, temperature and initial surfactant concentration. RESULTS: It was found that the highest surfactant adsorption capacities reached at 30 °C were determined as 2.77 mg g^?1 for anionic NaDBS and as 1.81 mg g^?1 for non‐ionic TX‐100, both at pH 2. The biosorption process was revealed as a thermo‐dependent phenomenon. Equilibrium data were well described by the Langmuir isotherm model, suggesting therefore a homogeneous sorption surface with active sites of similar affinities. The thermodynamic constants of the adsorption process (i.e. ΔG°, ΔH° and ΔS°) were respectively evaluated as ? 8.28 kJ mol^?1, 48.07 kJ mol^?1 and ? 42.38 J mol^?1 K^?1 for NaDBS and ? 9.67 kJ mol^?1, 95.13 kJ mol^?1 and ? 174.09 J mol^?1 K^?1 for TX‐100. CONCLUSION: Based on this research, valorization of highly available Posidonia oceanica biomass, as biological adsorbent to remove anionic and non‐ionic surfactants, seems to be a promising technique, since the sorption systems studied were found to be favourable, endothermic and spontaneous. Copyright © 2007 Society of Chemical Industry     

Contrôle hydrodynamique de l'evaporation d'un film liquide ruisselant sur une paroi isotherme à symétrie de révolution dans un courant d'air humide

A thin-film evaporation from a surface of a axisymmetrical body in a humid air stream was studied using a finite difference method associated with Thomas' algorithm. The surface of the body is supposed isothermal. The variability of physical properties is taken into account, and a steady-state and laminar regime is supposed. The influence of the main parameters of the system on the evaporation is determined, especially the wall profile. It is shown that, for certain conditions of calculation, it is possible to find a flat ellipsoid of revolution offering a uniformly accessible wall between the pole and the equator.