Gas solid fluidized bed (GSFB) is an effective method of dry coal separation. In this study, porous sponge was introduced into a typical gas solid fluidized bed as secondary air distribution layer (PSFB) to stabilize the fluidized bed layer. The difference between PSFB and GSFB in flow pattern transition process was studied. Compared with GSFB, the minimum gas velocity and bed density fluctuation decreased while bed expansion ratio increased in PSFB. Furthermore, the distribution of bubble phase and emulsion phase were more homogeneous in PSFB. Under the operational conditions, the results of coal preparation in a PSFB showed that the ash content of clean coal was 10.25%. The probable error (E) was 0.095 g/cm(3), indicating that PSFB could provide a novel way for a good performance of dry coking coal beneficiation. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.