Abstract: A method of processing granular material by passing a gas in contraflow to a bed of the material descending in an independently rotatable annular chamber of annular width a surmounting an annular eccentrically rotating floor, the outer bed wall being in gas-tight sliding relationship to the floor but the inner wall being spaced above the floor by a distance h, not less than, and not more than 10 percent in excess of, the value satisfying the relationship tan .phi. = h/a where .phi. is the operative angle of repose of the charge material at the bottom of the bed.