Thermodynamics of salt roasting of sulphide ores

Thermodynamic analysis of a non-polluting process for the effective treatment of lean multimetallic sulphide ores is presented. The sulphide ore is roasted with sodium chloride in air. Metal sulphides are converted to chlorides that can be separated from the unaffected gangue material. At a temperature of 1100 K the chlorides are present both in gaseous and in condensed states. Volatile chlorides can be easily removed and subsequently condensed. The chlorides present in the condensed state can be leached to separate them from the gangue. The sulphur is trapped as Na2SO4 and thus SO2 emission is minimized. Ellingham diagrams are used to compare data for a large number of elements. The major thermodynamic driving force is provided by the higher stability of Na2SO4 relative to NaCl.

Comparative evaluation of inversion approaches of the radiative transfer model for estimation of crop biophysical parameters

The inversion of canopy reflectance models is widely used for the retrieval of vegetation properties from remote sensing. This study evaluates the retrieval of soybean biophysical variables of leaf area index, leaf chlorophyll content, canopy chlorophyll content, and equivalent leaf water thickness from proximal reflectance data integrated broadbands corresponding to moderate resolution imaging spectroradiometer, thematic mapper, and linear imaging self scanning sensors through inversion of the canopy radiative transfer model, PROSAIL. Three different inversion approaches namely the look-up table, genetic algorithm, and artificial neural network were used and performances were evaluated. Application of the genetic algorithm for crop parameter retrieval is a new attempt among the variety of optimization problems in remote sensing which have been successfully demonstrated in the present study. Its performance was as good as that of the look-up table approach and the artificial neural network was a poor performer. The general order of estimation accuracy for para-meters irrespective of inversion approaches was leaf area index > canopy chlorophyll content > leaf chlorophyll content > equivalent leaf water thickness. Performance of inversion was comparable for broadband reflectances of all three sensors in the optical region with insignificant differences in estimation accuracy among them.