低温精馏氢同位素分离技术及其应用

低温精馏是大规模分离氢同位素的有效手段,本文对该工艺涉及的气体纯化、制冷与真空、测量与控制、安全防护等关键技术进行简要介绍。对该工艺在重水生产、重水升级和除氚、聚变堆氘氚燃料循环、武器用氚等领域的国外应用做了回顾。分析了国内对该技术的需求,提出今后开展的研究方向。     

低温精馏氢同位素分离全回流模式研究

为探求全回流模式下低温精馏氢同位素分离过程中有关操作参数的内在联系,研究了再沸器加热功率对脱氘率、床层压降、液氢液位等的影响。当再沸器加热功率从5W增加到12.4W时,脱氘率从88%增加到99.6%,脱氘率与再沸器加热功率基本呈线性关系。随再沸器加热功率的增加,液氢液位下降,床层压降增加,但在该功率范围内未出现液泛现象。随加热功率增加,精馏柱操作压力从100kPa升高到190kPa,冷凝器和冷头为提供更多冷量而温度降低。     

D2/DT低温精馏分离动态模拟

本文建立了氢同位素低温精馏分离的动态模型,利用该模型针对D2/DT体系计算获得了精馏柱上DT浓度的动态变化和空间分布;研究了再沸器滞留量、回流比等参数对系统分离性能的影响.回流比的提高可以显著地提高脱氚率;再沸器中DT浓度不但与滞液量存在显著的依赖关系,而且随时间增长而增长.在理论板数为80时,塔顶与塔底DT浓度相差约3个数量级,分离效果明显.     

低温精馏分离H2/HT/T2理论研究

对有侧线反馈的H2/HT/T2低温精馏分离过程进行理论计算,获得了各组分浓度在再沸器和冷凝器中随时间的动态变化和在精馏柱上的空间分布.研究了操作压力和回流比对系统分离性能的影响.当压力从0.06 MPa升至0.12 MPa时,精馏柱上的温度整体抬升约2 K,同时,压力对脱氚率有显著影响,当压力升至0.12 MPa时,脱氚率降低至81%.回流比对提高脱氚率有显著作用,回流比超过5后,脱氚率超过99%.     

H_2/HD和D_2/DT低温精馏分离影响因素研究

系统研究了低温精馏氢同位素分离中总板数、进料位置、回流比、采出量等对系统分离性能的影响,获得了蒸馏柱上的浓度和温度分布。随着进液位置向底端移动,再沸器和冷凝器中HD(或DT)浓度均减小;随着回流比的增大,再沸器和冷凝器中HD(或DT)浓度均减小;顶端采出量增大,再沸器中HD浓度明显增大;在相同的总板数下,H2/HD,D2/DT两个体系的分离特性明显有差别。     

双组分体系低温蒸馏氢同位素分离理论计算

建立了单根柱的低温蒸馏计算模型,对H2/HD,H2/HT和D2/DT三个双组分体系进行了计算。给出了温度和各组分浓度在柱上的空间分布,结果较好地再现了易挥发组分在柱高端浓集,而难挥发组分在柱底端浓集的分离特征。三个体系以H2/HT最易分离,H2/HD次之,D2/DT最差。对于文中研究的体系,当理论板数为80时,D2/DT不能达到脱氚率99%的分离要求。     

电解精馏级联分离D_2/HD/DT研究

为研究电解精馏级联氢同位素分离过程的规律性,建立了理论模型,以D2/HD/DT为对象计算研究系统分离行为,获得了电解和精馏过程系统的浓集行为。由于分离因子的差异,在电解池中HD趋向贫化,DT趋向富集。第一根柱再沸器中DT随时间呈线性增长,经48h浓缩近68倍。在第二根柱再沸器中,HD降低一个量级,DT降低约两个量级。电解-精馏级联工艺能同时除去D2中微量的HD和DT,可应用于重水升级和除氚。     

H-D体系的低温精馏分离实验研究

在自制低温精馏氢同位素装置上进行了H-D分离的初步实验.结果表明,以D/H比为1.4×10-4的氢气为原料,进料流量5 mol/h,运行120h后,再沸器的D/H比达1.27×10-2;增加原料气氘浓度,其浓集效果明显提高.随着再沸器中氘浓度增加,柱顶氘浓度增加,脱氘率降低.全回流实验下,再沸器加热功率增加,脱氘率增加,但造成柱压力明显增加.为控制精馏过程操作压力,选择适当的再沸器加热功率是必要的.     

低温精馏分离H2/HD

以天然氢为原料的第一次实验,总理论塔板数在20左右,以氘丰度为1.0×10-3的原料气进行的第二次实验,总理论塔板数为24,理论等板高度在15～20 cm.实验表明,在总理论塔板数较小时,冷凝器中氘丰度将随时间增长,再沸器中氘丰度变化实验值与理论值吻合很好,但同时观察到实验过程中液氢液位、温度等运行参数存在扰动.     

联合电解催化交换系统分离氢同位素影响因素研究

利用建立起来的理论模型,深入研究了联合电解催化交换（Combined Electrolysis and Catalytic Exchange,CECE）工艺中各种因素对氢同位素分离性能的影响。电解池分离因子的提高对浓缩倍数和脱氚率均有显著影响,降低电解池滞留量是提高浓缩倍数的有效手段。进料位置在1．5m处系统性能好于3m处;催化剂传质系数在3—4mol·m-3·s-1范围内,浓缩倍数和脱氚率基本呈线性增长。各种因素对HD／H2O和HT／H2O两个体系的影响具有相似的规律性,由于热力学因素的差异,相同条件下,HT／H2O体系分离性能好于HD／H2O。     

低温吸附法分离氦气流中氢同位素的实验研究

采用穿透曲线法研究了液氮温度下活性炭、碳分子筛和碳纳米纤维对氢同位素的吸附等温线和同位素效应。结果表明：活性炭和碳分子筛都是良好的吸附剂，碳纳米纤维对氢同位素的吸附量太低而不具备工程应用的可能性。实验还对吸附剂进行了改性处理，考察了改性吸附剂对氢同位素的吸附性能。     

Tests of the cryogenic target for lithium and hydrogen isotopes extraction from the chamber of T-11M tokamak without its venting

T-11M lithium program is focused on a solution of technological issues of a steady-state tokamak with liquid lithium plasma facing components (PFC). Lithium, collected by the chamber wall of such tokamak is able to capture a considerable amount of tritium, which is unacceptable. In order to restrict the level of lithium deposited on the chamber wall and captured tritium it was suggested early to use a cryogenic target technique. Such target placed in the plasma of glow discharge (GDH, He or Ar) during the tokamak conditioning can play the role of collector of lithium and tritium atoms which were sputtered by GD bombardment of the wall. The collected lithium and tritium can be evacuated mechanically together with target from tokamak chamber through vacuum lock without venting. Cryogenic target, cooled by liquid nitrogen (LN), was installed in the T-11M and tested in different modes of wall conditioning and tokamak operations. The maximum speed of the lithium collection during GDH was 3.5 mg/h, that corresponds “to contamination” of wall by lithium during approximately 200 regular shots of T-11M which are equivalent to two-week regular operations. It was established that considerable part of lithium was collected in ionized state. On this basis it can be suggested the creation in tokamak chamber an equivalent ionic pump for extraction both lithium and tritium from chamber without venting during regular tokamak operation.     

Adsorption capacity of hydrogen isotopes on mordenite

In a fusion reactor system, a monitoring of hydrogen isotopes including tritium is necessary for the safety of system control and operation. A gas chromatography using a cryogenic separation column is one of the methods for hydrogen isotope analysis. Synthesis zeolite such as molecular sieve 5A (CaA) is a candidate material of the separation column, and its property varies by the ratio of silica to alumina, the kinds of cation and so on. If the factor affected the hydrogen adsorption property of the synthesis zeolite is clarified, it may lead to the development of the new zeolite optimized to the separation column. So, in this work, adsorption capacity of hydrogen (H₂) and deuterium (D₂) for mordenite (MOR) and NaY type zeolite (NaY) were investigated at various temperatures, and were compared with CaA. The amount of adsorption per unit weight of MOR was larger than that of CaA, and that of NaY was smaller than that of CaA. The adsorption isotherms were expressed by sum of two Langmuir equations, and the Langmuir coefficients of H₂ and D₂ were proposed. Furthermore, the Langmuir coefficients of HD, HT, DT and T₂ were estimated by the reduced mass. The correlation between the adsorption properties and the physical parameters of the zeolite were not confirmed.     

钛膜中氢同位素的深度分布

为评估氢同位素效应对其在贮氢金属中深度分布的影响,对H/D-Ti、D/T-Ti、D-Ti及T-Ti样品用7.4MeV的4He离子束进行30°方向弹性反冲(ERD)分析.由H/D-Ti样品ERD能谱获得其1.7μm深度的D分布,结合D-Ti样品ERD能谱的～3 μm深度的H、D分布进行了模拟分析.结果表明,H、D含量均随深度增加,其分布曲线基本一致,说明在Ti中H、D的分布互不干涉,样品制备过程中其同位素效应不明显.用同样的方法对DT-Ti样品中的D、T分布进行了模拟分析.结果表明,在1.7 μm深度内D、T的分布基本均匀,但由于D、T的能谱过于靠近,其解谱误差较大.用3.0 MeV的质子对HD-Ti和D-Ti进行的质子背散射(PBS)分析表明,两样品中的D分布趋势一致,证明了Ti中H、D的分布互不干涉,样品制备过程其同位素效应不明显的结论.