The new, concept of rotating chimney for rotating fluidized beds is experimentally investigated using a step-response technique. The chimney rotates in the same sense as the rotating particle bed, but not necessarily at the same rotational speed. In particular, chimney rotational speeds such that the particles at contact with the chimney obtain a rotational speed higher than the average particle bed rotational speed are possible. The increase of the centrifugal force in the vicinity of the chimney allows to reduce solids losses via the chimney and to build up a higher, solids loading in the fluidization chamber at given fluidization gas flow and solids feeding rates. Alternatively, at given solids loading and fluidization gas flow, rate, the rotating chimney allows to control the particle residence time in the fluidization chamber. The influence of the chimney rotational speed and the fluidization gas flow rate is studied using 1G-Geldart D-type particles. (c) 2008 American Institute of Chemical Engineers.