Intermediate Vapor Expansion Distillation and Nested Enrichment Cascade Distillation

Abstract

Although it is known that incorporating an intermediate reboiler or reflux condenser in a distillation column will improve column efficiency by 15 to 100%, there has been little use of this technique to date." Intermediate vapor compression heat pumping was recently introduced as one practical means of achieving this benefit. Introduced in this paper are two new means having added advantages over compression: intermediate vapor expansion heat pumping, and nested enrichment cascades. In both cases the efficiency advantage is obtained without requiring import of shaft work. With intermediate vapor expansion, the expander is more efficient and less costly than the compressor which achieves comparable improvement in distillation efficiency. With the "nested enrichment" technique, the increased efficiency is obtained without requiring either compressors or expanders.