【作者】 褚效中；

【导师】 周亚平；

【作者基本信息】 天津大学 ， 化学工程， 2007， 博士

【摘要】 氢同位素在化工、能源、材料、医疗、检测等领域中已得到广泛应用。然而在氢的天然同位素中,重氢含量只有0.015%,如何提取氢气中的氘气至关重要。氘是热核反应的主要原料之一,在以氘氚做燃料的聚变反应堆中,参加反应的氘氚还不到10%,从聚变堆的自持、经济和环境安全考虑,等离子室排出的氘氚需要回收分离并重新进入循环系统。传统的氢同位素分离方法如低温精馏、化学交换、热扩散等具有能耗高以及附属处理设备多的缺点。因此,氢同位素分离受到广泛关注,而且如何寻找一种低成本分离方法对氘氚的工业应用非常关键。通常利用不同组份吸附差异进行分离的成本是较低的,而且吸附法具有方法简便、可靠性高、操作灵活等优点。此外,吸附剂可反复使用,可避免其它分离方法因产生大量氚放射性废物而导致环境污染问题。然而由于氕、氘与氚的性质极其相近,且具有相同的形状和尺寸,在常规吸附剂上平衡吸附量差异也较小,所以如何强化氢同位素之间的平衡吸附差异或动力学吸附差异是吸附分离研究的核心。为此,本课题设计了以低温吸附法来系统研究氢同位素气体在不同吸附剂上的吸附行为,主要内容包括:(1)运用常规气相色谱建立相应的氢同位素气体快速检测方法,为吸附床层内穿透曲线的监测做好准备。(2)测量氢同位素气体在不同分子筛吸附剂上的平衡吸附量与动态吸附速率,并建立相应动力学吸附模型来计算吸附速率常数k。结果表明:氢同位素气体在分子筛孔径约为0.7 nm时吸附容量最大,但是最大动力学吸附差异的吸附剂孔径却在0.5 nm,而且最大平衡吸附量差异出现在介孔吸附剂上。(3)设计氢同位素气体单塔吸附分离的实验装置。测定了不同吸附剂在不同压力、气体流量与吸附床长度条件下的穿透曲线并计算了分离因子,讨论了相同实验条件下氢氘混和气在不同吸附剂上的分离效率以及孔径与比表面积对吸附分离效率的影响。(4)为更好解释和预测氢同位素气体在单塔吸附床层内的动力学吸附过程,构建了一个氢同位素在吸附床层内的动态吸附数学模型,该模型可较好地模拟氢同位素气体在分子筛VP800-5与Y上的吸附行为,并可对不同吸附行为进行预测。更多还原

【Abstract】 Hydrogen isotopes are of great importance due to their wide applications in the fields of chemical industry, energy sources, material, medical cure and detection as a tracer. However, the natural abundance of deuterium is very small, only about 0.015%, so that how to separate deuterium from hydrogen is quite critical. The heavy isotope of hydrogen, deuterium, is an important material in nuclear industry. Moreover, deuterium and tritium combust less than 10% in the nuclear fusion reactor, thus, from the consideration of self-preserve, economy and environmental safety, they must be recovered and separated in order to recycle them after expelling from the plasma. The traditional methods such as cryogenic distillation, chemical exchange and thermal diffusion require incidental facilities and high-energy cost, therefore, the separation of hydrogen isotopes is received great attention, and how to search for a low cost separation method is a key for the industrial application of deuterium and tritium. The separation cost is usually low if the separation is based on the difference of components in adsorption. And the adsorption method has advantages of simplicity, high reliability and flexible operations, furthermore, the adsorbent can be regenerated easily for reuse, which can avoid environmental pollution due to not eject large amount of tritium radwaste. However, the separation between hydrogen isotopes is difficult due to the similarity of isotopes and small difference of their equilibrium amount adsorbed on common adsorbents. Therefore, how to enhance the difference of components in equilibrium and in dynamic adsorption is a focus on studies of adsorption separation. Based on reasons above, we designed cryogenic adsorption method to study behaviors of hydrogen isotopes on different adsorbents systematically, and mainly contents were as follows:(1) A rapid detection method of hydrogen isotopes was established with conventional gas chromatography that was prepared to test breakthrough curves in the adsorption column.(2) Equilibrium amount adsorbed and kinetic adsorption rate on different molecular sieve adsorbents were measured, and a relative kinetic mathematical model was developed to calculate adsorption rate, from which the highest adsorption capacity was observed at approximately 0.7 nm for hydrogen isotopes, but the largest isotope difference in dynamic adsorption was observed at 0.5 nm and the largest isotope difference in equilibrium adsorption was observed at mesoporous size. (3) A one-column experimental apparatus to separate hydrogen isotopes was designed, and we measured breakthrough curves of hydrogen and deuterium on different adsorbents with it and calculated their separation factors for different pressure, gas flow rate and bed length. The separation efficiency of different adsorbents was discussed under the same experimental condition. Moreover, effects of pore size and specific area to hydrogen isotopes separation were also summarized.(4) A kinetic adsorption mathematical model in the adsorption column for hydrogen isotopes was developed in order to explain and forecast adsorption processes well, and results simulated on the molecular sieves VP800-5 and Y were in good agreement with experimental results. Additionally, different adsorption behaviors in the column were forecasted with this model.更多还原