  An efficient cryogenic distillation system was designed and constructed for
PandaX-4T dark matter detector based on the McCabe-Thiele (M-T) method and the
conservation of mass and energy. This distillation system is designed to reduce
the concentration of krypton in commercial xenon from 5X$10^{-7}$ mol/mol to
$10^{-14}$ mol/mol with 99% xenon collection efficiency at a maximum flow rate
of 10 kg/h. The offline distillation operation has been completed and 5.75 tons
of ultra-high purity xenon was produced, which is used as the detection medium
in PandaX-4T detector. The krypton concentration of the product xenon is
measured with an upper limit of 8.0 ppt. The stability and purification
performance of the cryogenic distillation system are studied by analyzing the
experimental data, which is important for theoretical research and distillation
operation optimization.

Instrumentation and Detectors;High Energy Physics - Experiment