Abstract: A circular section column with helical liquid flow is divided by a vertical wall 10 into two gas and vapor tight sectors A and B, each sector housing a series of trays.The trays disposed are designated respectively 1a, 2a and 3a for sector A and 1b, 2b and 3b for sector B.The distance D separating each two successive half trays of a given series is constant.On the other hand, the half-trays of one series are each staggered in the axial direction of the column with respect to the half-trays of the other series by a spacing d which is less than half the distance D.This arrangement allows a greater number of half-trays to be housed in a column of a given height, or the height of a column for a given number of trays to be decreased.

Abstract: The process consists in successively separating increasingly heavy petroleum cuts at the head of a plurality of columns CO1, CO2, CO3 and Cl0 of a first series of columns which feed individually each column of the second series. The column CO7 is a gasoline stabilizing column which feeds an installation for fractionating light petroleum gases. The column CO4 is a gasoline fractionating column. The columns CO5 and CO6 are columns for separating petroleum naphthas from kerosine. The atmospheric residue collected at the bottom of the column Cl0 is processed in the vacuum distillation column Cl2 and the residue from this column is processed in the second vacuum distillation column Cl3 after reheating in a furnace.By carrying out a succession of progressive separations performed in a series of columns of small volume, more efficient utilization of the recovery heat is achieved.