The concept of the centrifugal thermal activation (CTA) of powdered materials on a rotating solid heat carrier is developed. A compact centrifugal flash reactor has been manufactured and tested. The tested set-up provided: the heating of gibbsite powder to the temperature of 400-900 K with the rate more than 10(3) K/s; the duration of the powder thermal treatment less than 1.5 s; the regulation of the treatment duration by changing the speed of the plate rotation and the shape of the rotating heat carrier; the product output up to 40 dm(3)/h; the removal of the extracted steam containing gases and rapid quenching of the thermally activated solid products. The device tested has been used for the thermal activation of commercial aluminium hydroxide AI(OH)(3) (gibbsite). The obtained thermally activated product possesses a high reactivity and can be used for the preparation of various alumina-based compounds. (c) 2004 Elsevier B.V. All rights reserved.