André Fontana

Self-colour anodizing of titanium

Abstract Relations between the colours and the electrochemical parameters (current density, quantity of electricity and temperature of the electrolyte) during the anodization of titanium sheets were studied in a 1 M H 2 SO 4 solution. Mathematical theories were developed for the kinetics of growth of the anodic film and for the colours of this film. These theories show that the relation between the growth and the colour of the film is complicated. Nevertheless, it was possible to find experimental conditions that led to uniform and well-defined colours.

Behaviour, capture and inertization of some trace elements during combustion of refuse-derived char from municipal solid waste

Abstract An investigation of refuse-derived char (RDC) generated by thermolysis of municipal solid waste (MSW) was undertaken to elucidate the behaviour of some toxic and potentially toxic trace elements (Cr, Cu, Mn, Ni, Pb, Sb, and Zn) plus Fe during combustion of RDC. About 87% of Sb, 66% of Pb, 60% of Cu and significant parts of Fe>Zn>Ni>Mn>Cr from the RDC are volatile at 1200°C, and their behaviour in the temperature interval 500–1200°C is characterized. The use of sorbents (zeolite, kaolinite, montmorillonite, coals enriched in kaolinite and calcite, and lime plus portlandite) for capture, solidification and inertization of the most volatile elements during combustion of RDC is also described. Perspective sorbents and inertants for a retention of the most volatile Pb, Sb and Cu in RDC ash are kaolinite and montmorillonite or coals enriched in these minerals. In addition, when there is an effective RDC washing (dechlorination and desulphurization), the use of sorbents for capture of some metals could be reduced or even avoided. Recommendations are given for RDC utilization and improvisation of the collection, separation procedures and removal efficiency of some heavy-metal, chloride and sulphate compounds from MSW and RDC prior to their use. The results show that a long-term strategy based on detailed understanding of the source, formation, behaviour and fate of the elements and their modes of occurrence in MSW, RDC and combustion waste residues is required in order to validate a perspective waste pyrolytic processes development.

Electrochemical boriding of iron in molten salts

Boride coatings on iron subtrates are obtained by electrodepositions in Na2B4O7 melts at various temperatures (from 900 to 1050°C). The effects on thickness and morphology of the electrolysis parameters (current density and time) are presented. In particular results at high current density(up to 112 A dm−2 are shown. Depending on current density value and duration of the electrolysis the deposits consist of Fe2B or Fe2B layers of teeth form. Thermal post-treatment of two layers deposits decreases the FeB thickness and increases the Fe2B thickness.

Coal hydromethanolysis with coke-oven gas: 2. Influence of the coke-oven gas components on pyrolysis yields

Abstract To improve the economics of the hydropyrolysis of coal by reducing the hydrogen cost, it has been suggested that coke-oven gas be used instead of pure hydrogen. The present paper describes the role of methane and some minor components in the coke-oven gas during pyrolysis and their influence on the oil and gas yields. Pyrolysis was conducted at 765°C under 3 MPa of various gas mixtures simulating coke-oven gas. The results clearly demonstrate the possibility of using coke-oven gas for coal pyrolysis and lead to the conclusion that synergy between metallurgical cokemaking and ‘creaming-off’ coal by hydropyrolysis will be profitable to both processes.

Viscosite de melanges de silicates fondus du systeme CaOSiO2MnO

Viscosities of melts of the ternary system CaOSiO2MnO with 0.5 to 0.35 mole% SiO2 have been measured between the liquidus temperature and 1500°C. Results are given in function of the composition and show the effect of the silica content of the melt and of the substitution of CaO by MnO.

Coal hydromethanolysis with coke-oven gas: 1. Influence of temperature on the pyrolysis yields

Abstract In order to improve the economy of the hydropyrolysis process by reducing the hydrogen cost, pyrolysis of coal has been carried out with a simulated coke-oven gas (55% H2, 30% CH4, 15% N2) as the reactive gas at 3 MPa and between 700 °C and 900 °C. Comparisons have been made with hydropyrolysis, pyrolysis with helium and methanolysis under the same conditions. The results indicate that there are no major obstacles to the use of coke-oven gas as the reactive gas in coal pyrolysis. The experimental conditions have to be improved to optimize the yields of the valuable chemicals.

Conductivites electriques de melanges de silicates fondus du systeme CaOSiO2MnO

Resume Les conductivites electriques specifiques des melanges fondus du systeme CaOSiO 2 MnO ont ete determinees entre la temperature du liquidus et 1550 °C pour des titres en SiO 2 compris entre 0.55 et 0.26. La connaissance du volume molaire moyen des melanges permet le calcul de la conductivite electrique equivalente. Une interpretation structurale des resultats basee sur les theories connues concernant la structure des silicates fondus est proposee.

Upgrading of waste derived solid fuel by steam gasification

Compared to the incineration, thermolysis can be considered as an interesting alternative or complementary way to eliminate the municipal solid waste or other kinds of dispersed waste, especially in rural regions with a low population density. The economic feasibility of the thermolysis depends mainly on the energetic valorization of the solid fuel generated by the process: steam gasification, in selected conditions to avoid toxic metals emissions, is a possible way to valorize this fuel. The results presented here show that steam gasification of waste derived solid fuel produces a synthesis gas with good calorific value. The behaviour of Pb, Cd, Cu and Mn has been studied as a function of the gasification conditions. The main toxic species can be trapped in the ashes in a non-leachable form if kaolinite is added as sorbent during the gasification. The behaviour of the Pb derivative present in the waste derived solid fuel seems to be due to PbCl2 formation during the thermolysis. As an alternative to combustion, energetic valorization of waste derived solid fuel can be considered either by local small scale gasification as well as by co-gasification with coal, rich in kaolinite, in new IGCC processes.

Ultrasonic removal of heavy metals from waste oils

The elimination of lead from used motor oils is performed by ultrasonic lixiviation using nitric acid, the lead being recuperated as lead sulfate during the acid regeneration. Beside the treatment of waste oils by the traditional methods, this new processing way gives alternative routes, not used usually for waste oils, such as introduction through the blowpipes of a blast furnace, addition to the coal in coke oven plants, coprocessing with coal in liquefaction or gasification plants, or even in copyrolysis with coal.

Influence of ultrasound on the kinetic parameters of electrochemical redox reactions.

The aim of this work is to determine the Tafel parameters with and without ultrasound. The total overvoltage has been corrected for diffusion by using rotating disk technique and potentiostatic extrapolation to infinite rotating speed. Three well known redox systems have been selected regardless to their different electrochemical behaviour: the quinone-hydroquinone, the Fe(II)Fe(III) chlorides and Fe(II)-Fe(III) cyanide systems. This work shows that the reversibility is higher with ultrasound only in the case of the quinone-hydroquinone system.