Simulation and Optimization of Ultra-High Purity Krypton/Xenon Cryogenic Distillation System Based on HYSYS

To meet the requirements of the low background and high sensitivity of the large-scale dark-matter detector PandaX-4T, nKr/nXe≤1×10 -13 (n is the amount of substance) is required. The ultra-high purity krypton/xenon cryogenic distillation tower was used as an example in this paper. First, the distillation tower and the construction design of the distillation system were briefly introduced. Then, the operation parameters of the distillation tower were simulated and optimized by using HYSYS, and the distributions of the pressure, temperature and Kr concentration in the distillation tower were obtained. After that, the influences of those operational conditions including the feeding point position, the reflux ratio, the feeding flowrate, the heat of the reboiler, the flowrate of the off-gas, and the feeding pressure to the xenon purity of the distillation system were studied, and the optimized operation parameters were proposed. When the column pressure is set at 221 kPa and the reflux radio is set at 145, the krypton content in xenon can be purified from 5×10-7 to 4.1×10-14, which has an important guiding significance for further improvement of the purity of the xenon product of the xenon/krypton cryogenic distillation system.