The primary metals industry is one of the most energy intensive in the manu
facturing sector, and is consequently also a major source of climate-alteri
ng gases. The replacement of electrolysis or electrothermal processes with
direct reduction processes using high-temperature solar process heat may we
ll be economical, especially when the costs of CO, emission are included in
the analysis. Ln particular. aluminum production by carbothermal reduction
is a very high-temperature, energy-intensive process. The temperature requ
ired, in the range 2300-2500 K, is too high for practical process heat addi
tion from combustion sources alone. Only electric-are furnaces or highly co
ncentrated solar are capable of supplying process heat at these high temper
atures. The aluminum industry presents unique opportunities for industrial
implementation of solar process heat. Use of high-temperature solar process
heat can drastically reduce the emission of climate-altering gases, reduce
the reliance on electricity, and make possible a direct thermal route from
the ore to metal. Two industrially-researched direct aluminum or aluminum-
silicon alloy producing processes, and one process that forms an intermedia
te AlN compound are proposed for study and demonstration projects for alter
native solar-thermal processes to replace the Hall-Heroult process. (C) 199
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