Regeneration of mixed bed demineralizers

Abstract

The invention relates to improved methods for regenerating the exhausted anion and cation exchange resins in a mixed bed demineralizer system. The exhausted bed of resin is directed into a separation vessel which contains a buffer volume of anion and cation resins remaining therein from the previous regeneration cycle. The resin in the separation vessel is classified into an upper anion resin layer, a lower cation resin layer and an intermediate layer of intermingled anion and cation resin. The cation resin is transferred from the bottom of the separation vessel to a cation regeneration vessel through a cation transfer conduit having isolation valves associated with the respective ends thereof. The resin transfer is terminated upon the detection of anion resin in the transfer conduit, at which time the isolation valves are closed so as to isolate the bulk of the intermingled anion and cation resin layer in the cation transfer conduit. The resins remaining in the separation vessel are again classified and the bulk of the anion resin is withdrawn therefrom leaving behind a measurable quantity of anion resin and any remaining cation resin. The resin isolated in the cation transfer conduit is directed back into the separation vessel and combined with the resin therein to form the buffer volume for the next regeneration. Various alternative embodiments are disclosed which incorporate these techniques.