Abstract
The use of microwave heating in primary metallurgy is gaining an increasing interest due to the possibility to selectively process ores and to volumetrically heat large amounts of low-thermal conductivity minerals. In this paper the study, development and testing of a new applicator combining the use of microwave and induction heating for rapid reduction of metal containing oxides is described. Numerical simulation was used in order to achieve the proper control over heat generation, considering the use of microwave solid state generators. A prototype, with a capacity up to 5 liters of standard input feed but with the predisposition for continuous processing has been designed, built and tested on reference loads like iron oxide powders and pellets. Results on the microwave heating part of the applicator indicate that it allows to efficiently and rapidly process these kinds of loads, which change from dielectric to conductors as reduction proceeds. The use of variable frequency solid state microwave generators allows to maximize energy efficiency and to controllably change the heating pattern inside the load.
Highlights
Current processes for the extraction of metals from their respective ores are characterized by high energy consumption and the release of environmentally undesirable by-products, including large quantities of fine particulate, SO2, COx and NOx [1]
Ferroalloys are widely used to modify the chemical composition of iron based alloys but in many cases their addition amounts only to a limited percentage of the alloy weight. They possess a high value, especially the low carbon variants, and they could benefit of the use of smaller, electrical-powered units, where reduction is performed by metallothermal reactions or using non-carbon based reductants, possibly under vacuum or controlled atmosphere
Simulation results helped identifying different resonances in the 915 MHz ISM band, confirming that heat generation pattern can be controllably varied by shifting the microwave generator frequency within the band
Summary
Current processes for the extraction of metals from their respective ores are characterized by high energy consumption and the release of environmentally undesirable by-products, including large quantities of fine particulate, SO2 , COx and NOx [1]. Combining efforts of numerical simulation and experimental attempts, based on further understanding of microwave–material interactions, would contribute to successful design of efficient microwave furnaces for commercial and industrial uses in the field of metallurgy and benefit from the exploration of many relevant material processing applications for recognizing the full potential of microwave heating. Ferroalloys are widely used to modify the chemical composition of iron based alloys but in many cases their addition amounts only to a limited percentage of the alloy weight They possess a high value, especially the low carbon variants, and they could benefit of the use of smaller, electrical-powered units, where reduction is performed by metallothermal reactions or using non-carbon based reductants, possibly under vacuum or controlled atmosphere
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