This article describes the development and characterization of a 1kW imaging furnace that allows to investigate materials such as sulfides at ultrahigh temperatures under controlled atmosphere. Peak flux densities up to (15.37±0.66)×106Wm−2 corresponding to a maximum stagnation temperature of 3090K can be reached in the center of the heating zone of 3mm diameter (full width at half height). Individual sample holders can be mounted on a generic sample stage that is aligned in three axes. Together they define an experiment. Experiments can thus be easily interchanged without requiring any realignment. The use of a specific sample holder is reported where the sample rests on a water-cooled tip to avoid contamination by crucible material and where a protective glass dome can be mounted to allow the study of samples releasing condensable or corrosive gases. With the dome in place the peak flux density decreases to a value of (13.59±0.45)×106Wm−2 (Tstag=2980K). The surface temperature of the sample and the average irradiance can be measured simultaneously by the pyrometric method flash assisted multiwavelength pyrometry. The irradiance on the sample and, thus, the temperature reached can be controlled by adjusting the position of the sample. This is effected by a computer controlled fork lift with a resolution of 0.05mm.
Testing the chemical stability of high‐performance ceramics at temperatures above 1800 K is a demanding task. With the aim to provide an experimental set‐up for kinetic studies on gas releasing reactions at temperatures up to 2300 K, a solar reactor has been interfaced to a mass spectrometer. Tracer experiments revealed that the reactor behaves as a continuous ideally stirred tank. This characteristic provides a straightforward path to extract kinetic data for such reactions from gas‐phase analysis. The approach is demonstrated by presenting results of a study on the solar thermal reduction of manganese oxide at 2200 K.
The direct decomposition of copper sulphides under an oxygen free atmosphere in a solar furnace is an intriguing approach for producing copper. The use of concentrated sunlight to affect the decomposition reaction consequently avoids the generation of both toxic sulphur dioxide and carbon dioxide in the extraction process. Analysis of insolation maps shows that many important copper mining districts, e.g. in Chile or Southern Africa, as well as other places close to the growing Asian market, receive sufficient sunlight that recommends its use on an industrial scale. Decomposition experiments on synthetic copper sulphides in an imaging furnace confirmed formation of metallic copper at temperatures between 2000 and 2200 K and provided the parameters for preliminary calculations of the energy demand. They indicate that at suitable places 200 t of copper can be produced per day with a thermal input onto the heliostat field between 40 and 165 MW. Such plant sizes are at the lower limit compared with solar power plants dedicated to the production of solar electricity or of solar fuels. The reduced cost analysis further revealed that the expected production costs for solar copper are up to 30% lower but always comparable with those for conventional production because there is a need neither for SO 2 processing nor for an oxygen plant. The concept of a solar driven extraction can also be applied to other base metal concentrates with similar benefits.
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