In the paper is presented the design of a separation column for recovery of 1,2-dichloropropane (DCP) from the off-gas released during propylenechlorhydrine (PCH) synthesis. The aim of this separation is to recover DCP with a purity of 99.99 mass%. The simulation of the separation column is performed by means of the professional simulation program HYSYS. The design of the rectification column is based on complete experimental measurements. The calculation is compared with the design of a separation column. which uses for the computation of the equilibrium composition the corresponding database of the simulation program, and with the calculation, in which the complete set of equilibrium data is predicted from the UNIFAC method. By comparison of the results of the rectification column design quite different values of parameters which characterising the rectification column (i.e. reflux ratio, flows and composition of phases on the stages...) were obtained. These could lead to false results in designing the equipment. Within the frame of this work experimental vapour-liquid equilibrium (VLE) data at a pressure of 98.66 kPa and binary solubilities are presented for the system composed of following components: water, propylene oxide (PO), propanal (PA), and DCP. The dependence of activity coefficients on the composition is given by the UNIQUAC equation. The experimental results are compared with those predicted by means of the HYSYS database and with those predicted from the LTNIFAC method.