Two process streams in a propane-propylene fraction separation plant were modernized at Neftekhimiya Co. As a result of replacing the internal contacts in the towers by valve and centrifugal trays, the output of the towers increased, the quality of separation with production of propylene of 95-98% purity improved, the residual content of propylene in the propane fraction decreased to 7-10%, and the pressure drop in the towers decreased.