The invention relates to a process for removing COD (
Chemical Oxygen Demand) in evaporative condensate of POSM (Polyhedral Oriented
Sodium Methyl) waste alkali liquor, belonging to the technical field of
wastewater treatment. A first-effect alkali liquor
circulating pump, a second-effect alkali liquor
circulating pump and a third-effect alkali liquor
circulating pump are respectively arranged at first-section filler
layers of a first-effect flash separation
tower, a second-effect flash separation
tower and a third-effect flash separation
tower; liquid caustic soda is added into a separation reaction section of a flash separation tower, in the separation reaction section, the liquid caustic soda reacts with
phenol in rising steam to generate
sodium phenolate,
sodium phenolate and salt substances, the
boiling point is high, the physical properties are changed, the substances fall back into tower kettle liquid again,
benzene series substances such as methyl
benzyl alcohol and
phenethyl alcohol carried by the
phenol can be separated out due to the fact that an azeotropic
system is damaged, and the content of the
benzene series substances is reduced. The multiple-effect condensate is transferred into the tower kettle liquid, so that the
benzene series in the multiple-effect condensate is greatly reduced compared with a
system without adding the liquid alkali, the concentration of the material in the feeding of the rectifying tower can be reduced, and the content of the benzene series in the tower kettle liquid is reduced after the multiple-effect condensate is separated by the rectifying tower.