Experimental Carbothermal Reduction of Al2O3 at Low Pressure Using Concentrated Solar Energy

The carbothermal reduction of Al2O3 under primary vacuum using concentrated solar energy is a clean process for the production of energetic aluminum. However, undesirable by-products can be formed if the physico-chemical parameters (pressure, temperature) are not optimized. In the present work, the Sol@rmet reactor has been used to perform this reaction in the following pressure and temperature ranges, respectively, 280 to 880 Pa and in between 1800 and 2200 K. In particular, at total pressures lower than 400 Pa and at temperature around 2050–2150 K, collected powders with Al content higher than 90% have been obtained (maximum achieved Al yield close to 70%). It has also been shown that the use of a binding agent (in the reactants) and/or a change of the partial pressure of CO in the reactor could have a major influence on the formed Al/CO ratio. Finally, kinetic calculations on experiments performed at 380 Pa demonstrate that the phase boundary reaction and the nucleation process dominate the first stage of the carbothermal reduction of Al2O3.