PNNL

Abstract

The efficiency of air separation is tested using three different small scale cryogenic distillation columns. The performance of a random packed column is compared to the performance of two microchannel distillation columns that use thin wicking structures and gas flow channels to achieve process intensification. The microchannel distillation (MCD) columns tested include a plate-type layered (PTL) column containing altering layers of metal screens, and an additively manufactured porous honeycomb (AMPH) column. For columns with 25.4 cm of active height and run under similar conditions, the packed, PTL, and AMPH columns achieved approximate height equivalent of a theoretical plate (HETP) values of 5.5, 3.7, and 3.2 cm for nitrogen, and 5.9, 4.9, and 3.3 cm for argon respectively. The AMPH column provides the greatest separation efficiency of the three column designs tested. The additively manufactured column is also significantly easier to fabricate than the PTL column. The AMPH column in a distillation system that includes a microchannel recuperator can produce up to 0.4 SLM of 90+% purity oxygen with 12 W of cooling provided by a Stirling cryocooler. These results demonstrate the feasibility of using additive manufacturing to construct MCD devices and pave a way for constructing MCD designs which have heretofore been unavailable due to manufacturing limitations.