天然气提氦技术现状及建议

介绍了天然气提氦资源市场与技术现状,总结了天然气提氦工艺特点,综述公司天然气提氦技术的发展历程,并分析了该技术存在的主要问题,对下一步技术发展提出相关建议。     

The Electron–Phonon Interaction of Low-Dimensional and Multi-Dimensional Materials from He Atom Scattering

Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision.     

Investigation on phase shifting for a 4 K Stirling pulse tube cryocooler with He-3 as working fluid

He-3 is generally recognized for its ability to provide more excellent thermophysical performance than He-4, especially in the 4 K temperature range. However, this was not always the case in our preliminary experiments on a three-stage Stirling-type pulse tube cryocooler (SPTC). Our ongoing studies, as reported in this paper, demonstrate that the different working fluids also affect the performance through their phase shifting capability. This feature has been passed over in large part by researchers considering refrigerant substitution. Unlike previous theoretical analyses that focus primarily on regenerator losses, this report investigates the effects of the working fluid on the phase angle at the cold end in order to quantitatively reveal the relationship between the lowest attainable temperature and the cooling capacity. The analysis agrees well with our experimental results on a three-stage SPTC. While running with the operating parameters optimized for He-3, the lowest temperature of the SPTC decreased from 5.4 K down to 4.03 K. This is the lowest refrigeration temperature ever achieved with a three-stage SPTC.     

4 K节流制冷机预冷温度及压力特性影响研究

空间4 K JT节流制冷是实现深空探测任务的关键技术之一。基于4 K温区开式节流制冷机实验台，理论分析末级预冷温度及高压压力对理论最大制冷量的影响，给出不同工况下最优末级预冷温度及最优高压压力的选择。开展实验测试验证理论计算。分别测试了末级预冷温度为15 K时，五种高压压力（0.829、1.103、1.775、1.837和2.154 MPa）以及高压压力1.773 MPa时三种不同预冷温度（11.5、15.0和18.0 K）下的最大制冷性能，实验结果变化趋势与理论值吻合较好。预冷温度及压力特性影响研究为后续节流系统整体压缩机及预冷机最优状态耦合匹配奠定基础。     

Radiative and conductive heat transfer in a 4-K helium phase separator with minimum heat loss

Improvements in simulation and practice for the heat load of a helium phase separator are discussed. The separator cryostat (volume 100 L, cooling capacity 1.5 W at 4.2 K) re-condenses and stores liquid helium. An additional radiation shield was designed to minimize the radiative heat transfer and to decrease the heat conduction. The experimental results indicate that the heat load of the separator was decreased from 5.56 W to 1.555 W, a gain about 4 W of heat load, which is an improvement by 72%. Liquid helium (50 L) was stored in the separator stably for more than 90 h. Software implementing the finite-element method (FEM) was used to predict the temperature distribution of pipe fittings and the separator heat load with or without the additional radiation shield. The results of these simulations show that the temperatures of the pipe fittings were significantly decreased in the separator with additional radiation shields. For the heat load, the trends of simulation and experimental results were similar. This work provides a simple and effective method to minimize the radiation heat load of a separator. In this paper, we discuss in detail the improvements of the model, the experimental setup and the results of comparisons between experiments and simulations.     

氦离子预注入对钨中氘滞留行为的影响

利用高能离子注入机和直线等离子体模拟装置,本文研究了高能氦离子预注入对氘等离子体辐照后钨中氘滞留行为的影响。采用FIB-SEM、TEM、GD-OES和TDS等分析方法,分析了氦离子预注入对钨中氘滞留行为的影响。结果表明：氦离子预注入在辐照损伤区域形成大量氦泡,钨经过氘等离子体辐照后,表面的氘泡数量明显低于未经过氦离子预注入的样品。GD-OES分析中可以看到在氦捕获位处氘滞留浓度明显升高,同时氦离子预注入增加了氘在钨中的扩散深度,结合TDS分析可知氦离子预注入增加了氘在钨中的滞留总量,这是由于氦离子预注入后,形成的缺陷又为钨中氘的俘获提供大量新的位点,从而导致钨中的氘滞留量明显提高。     

基于Aspen Adsorption的氦气/甲烷吸附分离过程模拟优化

工业氦气主要通过深冷、膜分离和变压吸附（PSA）耦合从天然气提取，其中PSA是获得高纯He的关键。吸附过程模拟可以克服实验局限，有效指导工程设计、优化工艺条件。以体积分数90%的粗He为原料，利用Aspen Adsorption软件建立He/CH₄ 单塔PSA模型，获得穿透曲线。以此为基础，建立双塔分离流程，分析吸附、顺放、逆放、冲洗、升压步骤中吸附塔内气相组成的变化，五步最佳操作时间分别为 60、180、30、60和180 s。在三塔流程中，一个循环周期的最佳吸附时间和均压时间分别为135 s和90 s，产品纯度可达98.42%，回收率达60.45%。在五塔流程中，考虑到各步骤时间的匹配及生产的连续性，需要对一个周期内的循环时间进行优化。循环时间为300~340 s时，产品纯度达到99.07%以上。     

利用氦流法真密度仪研究水泥水化过程

采用氦流法真密度仪测定了水泥水化过程中水泥浆体的绝对体积变化,并根据水泥浆体绝对体积变化曲线将水泥水化过程划分为极速收缩期、收缩暂停期、快速收缩期和收缩趋缓期4个阶段.结果表明:水泥浆体极速收缩期和快速收缩期发生的绝对体积变化最为明显,且变化幅度较大,其与C_3A和C_3S的水化密切相关;水泥浆体收缩暂停期的绝对体积通常呈线性规律缓慢减小,但变化幅度较小,其规律与"欠饱和度理论"相符;水泥浆体收缩趋缓期的绝对体积变化曲线通常会出现"膨胀"假象,不能反映水泥浆体绝对体积变化的实际情况,但与水泥浆体孔结构的发展有关,对水泥水化行为的表征仍具有重要的指导意义;水灰比不仅可以影响水泥水化过程,而且可以对水泥浆体各水化阶段的绝对体积变化产生明显影响.     

Separation of He/N2/CH4 ternary mixtures by a triple-reflux pressure swing adsorption process

Conventional pressure swing adsorption (PSA) processes can only produce one high purity product in a single stage, whereas the state-of-art dual-reflux PSA (DR-PSA) can produce two high purity products simultaneously. However, multicomponent gas separation is often required in the industry, targeting at recovering several valued products at the same time. In this study, we propose a novel adsorption process, namely triple-reflux PSA (TR-PSA), to separate three components simultaneously. A middle product outlet and a middle reflux stream were introduced to the adsorption columns of a conventional DR-PSA process to separate ternary mixtures of nitrogen, methane, and helium. Nonisothermal dynamic models were built to investigate the impacts of operating parameters particularly the location of the middle reflux/product stream and the middle reflux flow rates. Results showed that the TR-PSA process successfully separated ternary mixtures obtaining three enriched products simultaneously in a single stage, yielding a separation performance comparable to that of the double-stage DR-PSA with significantly lower capital and energy cost.