Abstract: A first feed comprising particulate material predominantly in the size range 30 mesh to 1/2 in. is fed into an upper portion of an upwardly extending casing, and is a major portion of the particulate material. A second feed, which is a minor portion of the particulate material, comprises at least 50% by weight of fines predominantly in the range 140 mesh to 30 mesh, the remainder being superfines, is also fed into the casing. A gas is fed upwardly along at least a portion of the casing so that the coarse particles, a major portion of the fines and a minor portion of the superfines freely gravitate down the casing in counterflow to the flow of a major portion of the gas and form a packed particulate bed in a container beneath the casing.