Simulation and Optimization of Structured Packing Based on Ultra-High Purity Cryogenic Distillation Experiment

This paper introduces the distillation system utilizing the structured packing named PACK-13C, which is used to remove the krypton from commercially available xenon for PandaX-II dark matter detection experiment in China. Experimental results demonstrate that the purified krypton concentration reached $2\times {10}^{-11}\mathrm{mol}/\mathrm{mol}$ from $3\times {10}^{-9}\mathrm{mol}/\mathrm{mol}$ during the total reflux distillation process. Hence, a computational fluid dynamics (CFD) model incorporating multiphysics coupling is constructed, and the mass transfer coefficient is calculated based on the Delft model to investigate the mass transfer and gas–liquid separation process at the structured packing for extremely low impurity concentration of less than ${10}^{-9}$ mol/mol during the cryogenic distillation. The simulation results agree with the experimental data, with a minimal deviation of merely 0.12%. The structural optimization results demonstrate that the aperture diameter and peak height of the packing significantly influence the mass transfer efficiency. Furthermore, it is found that increasing the wire mesh thickness from 0.3 to 0.5 mm reduces the mass transfer efficiency by 42.5%. The simulation and optimization results highlight the improvement in the efficiency of cryogenic distillation in producing ultra-high purity gas.