The Application of Thermal Solar Energy to High Temperature Processes: Case Study of the Synthesis of Alumina from Boehmite

Abstract EN

The aim of this paper is to evaluate the feasibility of obtaining alumina from boehmite using a free, clean, and unlimited power source as the solar energy.

Boehmite was obtained by hydrothermal treatment of a hazardous waste coming from aluminum slag milling.

The waste is considered as a hazardous substance because of it releasing toxic gases (hydrogen, ammonia, methane, and hydrogen sulfide) in the presence of water.

The as-obtained boehmite was transformed into alumina, in air atmosphere, using a solar energy concentrator (Fresnel lens).

The solar installation provides a power density of 260 W·cm−2 which allows reaching temperatures upper than 1000°C at few minutes of exposure.

Tests were performed at different periods of time that ranged between 5 and 90 min.

The percentage of transformation of boehmite into alumina was followed by the water content of samples after solar radiation exposure.

Samples were characterized by X-ray diffraction, infrared spectroscopy, and thermogravimetry.

Metastable aluminas started to appear at 5 min and the crystalline and stable phase corundum at 10 min of solar radiation exposure.