Dual temperature exchange systems

Abstract

Improvements in the dual temperature exchange system wherein the feed supply substance traverses selected portions of one of the two temperature zones, said selected portions being correlated with the availability and/or cost of a supply of the feed substance concerned; e.g. (A) when a large supply of feed substance is available at relatively low cost, advantages are realized by directing at least a part of the feed-to-disposal path through only the region of the impoverishing tower wherein the feed substance has a concentration less than or substantially not greater than the concentration of the feed supply; (B) where a limited supply or a high cost supply of feed substance is involved or a high degree of extraction of the desired material from the feed supply of substance is desired, advantages are realized by employing cyclic circulation not only of the auxiliary fluid but also of the fluid maintained in exchange relation thereto, with correlated provision for enriching the two circulating streams with the desired material from a feed supply substance. Combinations of (A) and (B) are also advantageous. Also disclosed are provisions for improving the heat recovery in such systems, as well as provisions for increasing the output capacity of integrated enrichment systems without physical alteration of the intermediate and/or final enrichment stages thereof.