多柱互联低温精馏分离H2/HD过程理论研究

在氢同位素分离中,通常采用多柱级联工艺实现微量氘或氚的浓集。文章提出了三柱级联分离H₂/HD的设计工艺和操作模式,获得了3根精馏柱的分离行为。在合适的操作模式下,三柱级联将HD浓缩了20×10×10倍,表明采用多柱级联可非常有效地浓缩微量组分。进一步研究了压力和回流比等因素对分离性能的影响。压力从0.06MPa增加到0.15MPa,脱氘率从99.79%降到99.44%。回流比从3增长到5,脱氘率从99.67%升到99.81%。     

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.     

电解-精馏级联分离H2／HD过程的理论分析

为研究电解精馏级联氢同位素分离过程的规律性,建立了电解-精馏级联的微分模型,计算了H2／HD系统的分离行为,并获得了电解和精馏过程中系统的浓集行为,即,电解池中HDO摩尔分数从2．88×10^-4增长到8．35×10^-4精馏柱再沸器中HD摩尔分数达到0．033。随时间的延长,脱氘率下降,在精馏柱上HD的摩尔分数整体抬升。进一步研究了回流比对脱氘率的影响,结果显示,回流比为3～7时,平均脱氘率可达0．9828～0．9973。实验结果表明,电解-精馏级联分离氢同位素有明显的浓集效应。     

侧线反馈对H2/HD/D2低温精馏分离的影响

为研究带侧线反馈的低温精馏氢同位素分离规律性,建立了带侧线反馈的低温精馏氢同位素分离计算方法,并以H2/HD/D2体系进行了计算分析.计算结果表明,侧线反馈对分离性能影响显著,再沸器中以D2为主,氘丰度可达到0.90,而无侧线反馈情况下,再沸器中以HD为主,氘丰度不超过0.50;有侧线反馈条件下,系统运行约40 h HD向D2的转化达到峰值,而在无侧线情况下,HD浓缩在40 h已达到饱和;当侧线采出比为1时,脱氘率最高.     

基于LPCE+CD的重水除氚和升级工艺

提出了基于LPCE+CD工艺的重水除氚和升级工艺概念设计,建立了理论模型,在MATLAB平台下编制了计算程序,对整个系统的分离行为进行研究。气液摩尔比为3时,LPCE可以将重水中98.38%的T和98.35%的H转移到气相,气液摩尔比对LPCE过程有显著影响,增大气液摩尔比会显著降低顶端气体中HD和DT浓度。第1根精馏柱再沸器中DT浓缩效应显著,24 h后约为进料含氚重水的30倍。在第2根精馏柱冷凝器中,HD为主要组分,仍然含有10-11水平的DT。低温精馏系统对气体除氚率和除氢率分别为99.30%和97.75%。通过合理的系统设计,可以保持前后两级的一致性,使LPCE+CD成为非常高效的重水除氚和升级工艺。     

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。     

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.     

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。     

低温精馏氢同位素分离影响因素研究

本文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、采出率等操作条件对系统分离性能的影响,获得了精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浓度均减小;随着回流比的增大,再沸器和冷凝器中HD浓度均减小;顶端采出率增大,再沸器中HD浓度明显增大;在相同的总板数下,H2/HD和D2/DT两个体系的分离特性明显有差别.     

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。     

Wavelengths and classifications of emission lines due to 2s22pn−2s2pn + 1 and 2s2pn−2pn + 1 transitions, Z ≤ 28

Tables of wavelengths and classifications of observed emission lines due to 2s²2pⁿ?2s2p^{n + 1} and 2s2pⁿ?2p^{n + 1} transitions are presented. The accuracy of data derived from different experimental methods is discussed. Revised and predicted wavelengths are added. Energy levels are derived from the wavelength data.     

Gd2O3-Nd2O3-ZrO2-CeO2体系的高温固相反应研究

为研究Gd₂O₃-Nd₂O₃-ZrO₂-CeO₂四元氧化物体系的高温固相反应,以Gd₂O₃、Nd₂O₃、ZrO₂、CeO₂混合粉体为原材料,在1 673 K和1 773 K温度下煅烧24、48、72 h,分别制备了系列样品,并对合成样品进行了XRD和SEM分析。结果表明,合成产物为具有缺陷萤石相且伴有少量烧绿石相的Gd_2-xNd_xZr_2-xCe_xO₇（0≤x≤2）晶体化合物。随着煅烧温度的升高和煅烧时间的延长,产物中立方烧绿石相的化合物增多,晶粒尺寸变大,且有少量未知相生成。进而探讨了锆基陶瓷固化多核素的潜在应用,并提出了未来研究的相关热点问题。     

Phasengleichgewichte in den systemen UO2-UO2,67-ThO2 und UO2 + x-NPO2

Solid-state chemical investigations have established that in the compositional range UO₂-UO_2.67-ThO₃ of the U-Th-O ternary system, the following single-phase domains exist: U₃O₈, which does not dissolve any ThO₂ in the solid state; an ordered M₄O₉ phase on the section between U₄O₉ and U₂Th₂O₉, below ≈ 1150 °C; and a phase with fluorite structure which occupies a large part of the system and which at 1250 °C is bounded by the compositions UO₂-UO_2.25 (U_0.43, ThO_0.57)O_0.25-ThO₃. The maximum O/M ratio of the “fluorite” phase is O:(U + Th) = 2.25. The highest oxidation valency of uranium is 5.30; this value falls as more thorium oxide is incorporated in the (U.Th)O_{2 + x} “fluorite” phase.     

Thermophysical properties of NpO2, AmO2 and CmO2

The information on thermal and mechanical properties of the minor actinide dioxides: NpO₂, AmO₂ and CmO₂, is still very scarce, and a large uncertainty exists because of difficulties related to their fabrication and manipulation. Prognosis based on a set of the sound physical models and the similarity principle can be useful in this situation. Using the combination of the macroscopic and microscopic approaches developed earlier for thermodynamic properties of actinide dioxides, and the Klemmens model for their thermal conductivity, a few relationships bounding the main thermophysical properties of the actinide dioxides were deduced. These relationships were applied for the calculation of the isochoric and isobaric heat capacity, the isobaric thermal expansion coefficient, the isothermal bulk elastic modulus and the thermal conductivity of NpO₂, AmO₂ and CmO₂ in a large temperature range. A rather satisfactory agreement with the available experimental data and recommendations was demonstrated.     

Mechanism and Kinetics Analysis of NO/SO2/N2/O2 Dissociation Reactions in Non-Thermal Plasma

The kinetics mechanism of the dissociation reactions in a NO/SO2/N2/O2 system was investigated in consideration of energetic electrons＇ impacts on a non-thermal plasma. A model was derived from the Boltzmann equation and molecule collision theory to predict the dissociation reaction rate coefficients. Upon comparison with available literature, the model was confirmed to be acceptably accurate in general. Several reaction rate coefficients of the NO/SO2/N2/O2 dissociation system were derived according to the Arrhenius formula. The activation energies of each plasma reaction were calculated by quantum chemistry methods. The relation between the dissociation reaction rate coefficient and electron temperature was established to describe the importance of each reaction and to predict relevant processes of gaseous chemical reactions. The sensitivity of the mechanism of NO/SO2/N2/O2 dissociation reaction in a non-thermal plasma was also analysed.     

Electrical properties of annealed, fully metamict REE2FeBe2Si2O10

The electrical properties of annealed, fully metamict gadolinite REEFe²⁺Be₂Si₂O₁₀ are studied as a function of annealing temperature. Changes due to annealing are also probed by ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction. The electrical conductivity measured at f = 100 Hz between 110 and 750 K varies markedly, ranging from 10⁻¹⁰ to 10⁻⁶ S m⁻¹ for untreated samples and 10⁻⁹ to 10⁻³ S m⁻¹ for sample annealed in argon at 1373 K. Average measured activation energies for electrical conduction are 0.47 and 0.63 eV for ranges of 400-450 K and 500-600 K, respectively. The dielectric permittivity shows strong dispersion effects above 235 K. After high temperature annealing, the electrical conductivity shows a marked dispersion below 604 K. The combination of polaron hopping and hydroxyl anion migration is proposed for the electrical conduction mechanism.     

Radiation effects on PbO-Al2O3-B2O3-SiO2 glasses by FTIR spectroscopy

The infrared absorption spectra of PbO-Al₂O₃-B₂O₃-SiO₂ glasses have been measured in the spectral range 600-4000 cm⁻¹ before and after absorbed dose of 50 Gy, 4 kGy and 50 kGy to investigate the structural change due to irradiation. The structural change due to composition has also been discussed. The experimental results clearly indicate that after irradiation, a significant change in structure of lead alumino borosilicate glass network is observed. It was shown that BO₄ groups decreases and BO₃ groups increases with the increase of Al₂O_3.     

Reduction of UO2 by H2

The reactivity of H₂ towards UO₂²⁺ has been studied experimentally using a PEEK coated autoclave where the UO₂²⁺ concentration in aqueous solution containing 2 mM carbonate was measured as a function of time at p_H2∼40 bar. The experiments were performed in the temperature interval 74-100 °C. In addition, the suggested catalytic activity of UO₂ on the reduction of UO₂²⁺ by H₂ was investigated. The results clearly show that H₂ is capable of reducing UO₂²⁺ to UO₂ without the presence of a catalyst. The reaction is of first order with respect to UO₂²⁺. The activation energy for the process is 130 ± 24 kJ mol⁻¹ and the rate constant is k_298K=3.6×10⁻⁹ l mol⁻¹ s⁻¹. The activation enthalpy and entropy for the process was determined to 126 kJ mol⁻¹ and 16.5 J mol⁻¹ K⁻¹, respectively. Traces of oxygen were shown to inhibit the reduction process. Hence, the suggested catalytic activity of freshly precipitated UO₂ on the reduction of UO₂²⁺ by H₂ could not be confirmed.     

Molecular dynamics simulations of C2, C2H, C2H2, C2H3, C2H4, C2H5, and C2H6 bombardment of diamond (1 1 1) surfaces

The sticking and erosion of C₂H_x molecules (where x=0-6), at 300 and 2100 K onto hydrogenated diamond (1 1 1) surfaces was investigated by means of molecular dynamics simulations. We employed both quantum-mechanical and empirical force models. Generally, the sticking probability is observed to somewhat increase when the radical temperature increases and strongly decrease with increasing number of H atoms in the molecule.