Extended Arc Furnace
A new development in plasma furnace technology in which by relatively simple modifications a more or less conventional arc furnace can be made to produce a long stable plasma flame is described. A very promising application of this technique is in the steel melting as well as in direct reduction of fine iron ore, waste oxides, flotation concentrates, blast furnace dust, fly ash, mill scale, etc.
3-D Flow Modeling of a Three-Phase AC Plasma Torch Working With Air Using a Stationary Source Domain With Gas Radiation
This computational fluid dynamics work is dedicated to the study of heat and mass transfer in a new 100-kW three-phase ac/50 Hz plasma torch operating with air. The transient behavior of the arc is simplified using time-averaged heat and momentum source inputs in a stationary source volume whose form was chosen according to the results from a separate magnetohydrodynamic calculation. A parametric study of source volume and momentum intensity is conducted and shows a little influence on the overall temperature and velocity fields. Radiation from gas and walls is taken into account using the discrete ordinate model. Air radiation data consider both atomic and molecular contributions in the temperature range between 300 and 30 000 K and for the wavelengths from 0.209 μm to the far infrared. The results show a huge impact of radiation on wall temperature and heat losses. Two different methods, Planck and Rosseland, are used for the calculation of mean absorption coefficients. Although Planck's average is recommended in this case, the absolute temperature difference between both averages is below 13%. Finally, this paper allows checking that the temperature of different components of plasma torch remains below the physical limits of the selected materials.
The polymorphism of the oxide Ti3O5
Abstract The oxide Ti3O5 has been prepared by reduction of TiO2(as anatase and as rutile) using Ti metal as reductant and vacuum sintering, or by using CO or H2 as reductant. The oxides produced, and also their oxidation products at 650 °C, were examined by X-ray diffraction. Three forms of Ti3O5 were characterized: 1. (a) a form designated as D-type, produced by the hydrogen reduction of anatase, which yielded rutile only on oxidation; 2. (b) a form designated as D'-type, produced by the hydrogen reduction of rutile, which had an apparently similar X-ray diffraction pattern to that of the D-type, but which yielded a mixture of anatase and rutile on oxidation; 3. (c) a form designated as M-type, produced by the vacuum-sintering of TiO2 with Ti metal, which had a different X-ray diffraction pattern but which also yielded a mixture of anatase and rutile on oxidation. Forms (a) and (b) are similar to the previously-claimed high-temperature form of Magn Eli; form (c) is similar to his low-temperature form; the transition temperature is slightly in excess of 100 °C. The D'-type could be derived from the M-type. The D-type could easily be changed into the M-type by cooling from 1350 °C under vacuum. By annealing experiments, the D-type was shown to be a meta-stable form. Some crystallographic considerations concerning the oxidation behaviour of the various polymorphs of Ti3O5 are proposed, also a possible correlation with the various types of compounds having the pseudobrookite structure.