吸附温度低于273 K的Pd/k柱TCAP全回流实验研究

为满足实验室规模的氢同位素分离需求，对少量氚（小于3.7×10¹³ Bq）的高效氢同位素分离方法进行了研究。采用TCAP全回流工艺，将钯/硅藻土（Pd/k）填充色谱柱（长2 m，外径6 mm）吸附H-D混合气体（D丰度为50%）的温度控制在273 K以下，经多次加热 冷却循环后，从分离柱前、后两端加热各提取15%样品气，利用低温色谱法对样品气进行氢同位素丰度分析，对色谱柱的分离性能进行评价。研究结果发现,原料气进入填充柱后（全回流之前）尾端提取气的氘丰度约为98.5%，经5个全回流循环（循环总时间为1.25 h）后，尾端提取气的氘丰度达99.9%。经15个全回流循环后，前端提取气的氘丰度由50%（原料气氘丰度）降至13.6%。通过实验数据对柱中氘分布进行了理论模拟，发现进样速率过快可能是导致前端提取气氘丰度过高的主要原因，柱中氘丰度最低点可能出现在色谱柱的中部。

TCAP Total Reflux of Hydrogen Isotopes in Pd/k Column With Absorption Temperature Below 273 K

For high efficient hydrogen isotope separation in lab-scale application, a palladium/kieselguhr (Pd/k) column （2 m in length） was made. Ethanol was applied as liquid heat transfer medium to cool the Pd/k column below 273 K. TCAP total reflux experiments with different cycles were carried out to test the separation efficiency of the column. Hydrogen isotope mixtures (15% of total column content) were withdrawn both from the bottom and top end after each test. D concentration of the mixtures was tested by cryogenic chromatography. Results show that D concentration in the bottom section rises from 50% to 98.5% at the initial charge before reflux cycling. High purity (99.9%) deuterium is obtained after only five cycles (1.25 h). D concentration in the top section drops from 50% to 13.6% after 15 cycles. Through a simulated D distribution model, fast flow rate through the top section may obviously reduce separation efficiency. The lowest D concentration is found near the middle of the column, and the raffinate with high H concentration will be achieved in the middle position.