Apparatus and process for countercurrent liquid-liquid extraction

Claim 1

IN A PROCESS FOR COUNTERCURRENTLY CONTACTING A LIGHT FLUID WITH A RELATIVELY DENSE LIQUID WHICH IS SUBSTANTIALLY IMMISCIBLE WITH THE LIGHT FLUID IN A VERTICALLY ELONGATED COLUMN HAVING VERTICALLY SPACED PERFORATED PARTITIONS DIVIDING THE COLUMN INTO A PLURALITY OF CONTACTING ZONES, THE METHOD WHICH COMPRISES INTRODUCING SAID DENSE LIQUID INTO THE UPPERMOST CONTACTING ZONE FOR DOWNWARD FLOW THROUGH THE COLUMN, INTRODUCING SAID LIGHT FLUID INTO THE LOWERMOST CONTACTING ZONE FOR UPWARD PASSAGE THROUGH THE COLUMN, MAINTAINING IN EACH OF THE CONTACTING ZONES A LOWER LAYER OF THE DENSE LIQUID AND AN UPPER LAYER OF THE LIGHT FLUID SEPARATED BY AN INTERFACE THEREBETWEEN, PASSING DENSE LIQUID IN SUBDIVIDED FORM FROM THE LOWER LAYER IN EACH OF SAID ZONES EXCEPT THE LOWERMOST THROUGH THE LIGHT FLUID LAYER IN THE NEXT LOWER ZONE AND THEN INTO THE DENSE LIQUID LAYER IN THE LAST-NAMED ZONE, WITHDRAWING LIGHT FLUID AT THE INTERFACE IN EACH ZONE EXCEPT THE UPPERMOST AND PASSING THE SAME UPWARDLY THROUGH AND OUT OF CONTACT WITH THE LIGHT FLUID LAYER IMMEDIATELY ABOVE SAID INTERFACE AND UPWARDLY THROUGH AND OUT OF CONTACT WITH THE DENSE LIQUID LAYER ABOVE THE LAST-NAMED LIGHT FLUID LAYER INTO THE NEXT HIGHER LIGHT FLUID LAYER IN THE COLUMN, REGULATING THE FLOW RATE OF SAID DENSE LIQUID TO MAINTAIN THE INTERFACE IN SAID UPPERMOST ZONE AT A SUBSTANTIALLY CONTACT LEVEL WHEREBY THE INTERFACE IN EACH OF THE LOWER ZONES REMAINS AT A SUBSTANTIALLY CONSTANT PREDETERMINED LEVEL, REMOVING THE CONTACT LIGHT FLUID FROM SAID UPPERMOST ZONE AND FROM THE COLUMN, AND WITHDRAWING THE DENSE LIQUID FROM THE LOWERMOST ZONE AND FROM THE COLUMN.