a process for effectively removing unreacted oil from a surfactant slurry containing the same comprising : continuously feeding steam from one side of a pressure vessel into an anionic surfactant slurry containing unreacted oil in the pressure vessel while maintaining a pressure in the system of at least 5 kg / cm 2 ; and simultaneously discharging the anionic surfactant slurry from the other side of the pressure vessel into a low pressure region to effect vaporization of the unreacted oil from the anionic surfactant slurry .