VALVE TRAYS IN EXTRACTION COLUMNS

The present invention relates to an extraction method and a countercurrent liquid-liquid extraction column for the extraction of a hydrogen peroxide containing oxidized working solution of an anthraquinone process. The extraction column comprises a plurality of sieve trays, wherein at least one of said sieve trays is a valve sieve tray comprising a downcomer and at least one floating valve comprising a liftable opening member covering a valve hole in the valve sieve tray and can be lifted by the light phase below the sieve tray. A more stable operation of sieve tray extraction columns is possible by using a floating valve so that the flow rate of the oxidized working solution of an AO process and the daily production of hydrogen peroxide can be increased.