Method and apparatus for counter current liquid-liquid extraction

A method of liquid-liquid extraction of at least one solute dissolved in a first liquid being a solution of said solute in a solvent therefor, comprising the steps of

• (a) directing a stream of said first liquid through a first elongated channel from an entry end toward a terminal end of said first channel, and maintaining in said first channel a determined pressure above ambient,
• (b) directing a stream of a second liquid of different density, counter-currently to said first liquid stream, through a second elongated channel from an entry end toward a terminal end of said second channel, and maintaining in said second channel a pressure lower than said pressure in said first channel,
• said first and second channels having longitudinal axes, and one of said first and second liquids being the heavier, and the other the lighter one,
• (c) maintaining between said first and second channels, a separating wall zone of liquid-tight elastically resilient material being substantially non-swelling when in contact with water having a temperature of 60.degree. C. or higher, or when in contact with organic extraction solvents, said wall zone having a first and a second contact surface on opposite sides thereof, which surfaces border on said first and second channels, respectively, extending parallel with the axes of said channels;
• said wall zone containing a plurality of crosswise passages therethrough from said first to said second contact surface, said passages being distributed uniformly along said wall zone in axial direction,
• (d) passing a large number of streams of said first liquid, ejected from said first channel through said passages successively into said second channel and intermingling said first liquid streams therein cross-currently with said stream of second liquid flowing countercurrently through said second channel, while at the same time maintaining said exit end of said first channel at least substantially obturated, thereby maintaining in said first channel a determined pressure above the pressure prevailing in said second channel, and maintaining said exit end of said second channel obturated,
• (e) ejecting a large number of fine liquid jets of the resulting liquid mixture iteratively out of said second channel, transversely to the direction of liquid flow through said second channel;
• (f) collecting groups of said liquid jets, from successive ejection zones of said second channel,
• (g) settling the portions of the liquid mixture, obtained from such zones, with phase separation,
• (h) separating the resulting heavier and lighter phases of each liquid portion from each other,
• (i) back-feeding the separated heavier phase of a liquid portion from an intermediate zone of said second channel, into approximately the same zone, but of that channel which contains the stream of the heavier liquid, and
• (j) back-feeding the lighter phase of a liquid portion from an intermediate zone of said second channel, into approximately the same zone of that channel which contains the stream of the lighter liquid;
• (k) recovering from that ejection zone last preceding the terminal end of said second channel one of said phases resulting from the separation of the liquid portion collected from said zone, and back-feeding the other phase into the said first channel, in said last-mentioned ejection zone.