A separator of solids for separating first and second solids, the diameter and density of the first solids being larger than the diameter and density of the second solids. A first substantially vertical internal baffle (2) forms a passage in the low portion of the separator and forms two compartments (1A, 1B) on the passage of the fluidized solids. The fluidization of each compartment is independently controlled by two fluidization gas inlets (3A, 3B) in order to obtain the desired velocity field for separating the first and second solids in the first compartment (1A) and discharging the second solids through a vent (8), as well as for transferring the first solids into the second compartment (1B). The first baffle (2) is provided on at least one of its substantially vertical faces with fluidization gas ejectors (E2) and the first compartment (1A) is equipped with an internal obstacle arrangement deflecting the path of the solids and at least partially provided with fluidization gas ejectors (E4A) directed towards said first baffle (2).