This paper reports experimental and numerical results obtained in a free-vortex gas-solid separator, in which the classic conical-section of the device is replaced by a larger square chamber, where the vortex is free to evolve. An adjustable vortex-limiting plate is introduced at the cross-section in order to allow the inversion of the coherent structure and guarantee a natural vortex length of the swirling flow according to the inlet velocity in the separator. Both single- phase and multiphase flows were analyzed. hi the latter case, only very low particle concentrations, between 100 and 500 mg/m(3), were considered. Compared to the classic cyclonic separators, the new geometry showed advantages in performance, such as a smaller pressure drop. Moreover, unexpected behavior was observed, since the pressure drop increased by an average of 10% when the particles were injected into the flow at the low concentrations considered. (C) 2020 Elsevier B.V. All rights reserved.