工业规模等温吸附法分离氖氦

我厂氖氦分离,过去一直采用液氢冷凝法及活性炭低温吸附法相结合的生产工艺。液氢冷凝法是使氖氦混合气中的氖气在液氢温度下连续液化排放,所得的氖气质量较好。但由于液氢冷凝分离设备年久失修,氖氦分离效果差,氦气纯度特别低,仅达60%左右,提取率在70%以下。由于氦气纯度差,故增加了后一道工艺——低温吸附的处理量,造成空分塔收集的原料气来不及处理,液氮消耗大,生产一立方米氦气需要大约340升左右液氮。     

BEPC-Ⅱ低温系统的氦气净化技术

氦气净化技术是国家大科学工程北京正负电子对撞机重大改造(BEPC-Ⅱ)中低温系统的关键技术之一.在充分调研国内外大型低温系统氦气净化技术的基础上,结合自身情况,创造性提出氦气储罐内部处理及真空置换方案,一次性充入氦气,将储罐内氦气不纯度控制在40 vpm之内,同时辅之以80 K外置低温吸附器对氦气储罐内以及冷箱和超导设备端的氦气进行净化.高效而又经济的解决了BEPC-Ⅱ低温系统中的氦气纯度问题,成功地进行了制冷机的验收测试和超导设备的调试及运行.     

氖气的液化与氖氦气体的分离

介绍用液氖冷凝法分离纯氖氦混合气的工艺流程与工艺过程,并对原林德公司的工艺进行了改进,加快了氖、氦气的分离速度,提高了氖、氦气的纯度。图2。     

氦气作为增压气体排出贮罐内液氢过程的CFD分析

基于计算流体力学方法,数值模拟了用常温氦气作为增压气体压出贮罐内液氢过程的流动和传热传质特性。构建了基于二维轴对称的VOF多相流以及包含氢气和氦气组分流动的气相多组分数值模型,液氢界面相变传质基于Hertz-Knudsen方程计算。分析了排出过程贮罐内压力、温度、液位及液氢相变率随时间的变化,重点考察气相出现在贮罐出口时间,以及此时气相中氦气含量。发现刚开始增压时,高温氦气和低温氢气传热只发生在氦气进口附近,贮罐内压力增加较慢,液氢界面不存在蒸发现象。随着进入氦气增加,贮罐内气相温度逐渐形成分层,在一定时刻,液面上气体温度开始上升,触发沸腾蒸发,导致压力快速增加。由于贮罐出口液体外流导致的减压效应远小于气相空间的压力增速,贮罐压力急剧增加并超过氦气入口,部分低温气体混合物从入口倒流出贮罐,同时使氦气入口处温度降低。由于贮罐内压力增加,底部液氢出口流量随时间呈线性增加。计算结果揭示了液氢贮罐增压流出过程复杂的流动和传热传质特性,对低温液体的储运有实际工程指导意义。     

电气设备中保护气体监测用SO2F2气体标准物质研制

介绍了钢瓶装氦气中氟化硫酰（SO₂F₂）气体标准物质的研制过程。标准混合气是通过将SO₂F₂和氦气充装到钢瓶中制备而成,研究了气瓶内压力和保存时间对混合气稳定性的影响。对混合气配制的一致性进行了考察,并对引入的不确定度进行了评估,由结果可以看出,每个摩尔分数点混合气的量值一致性均较好。通过对称量法配气与稳定性导致的不确定度的评价,结果显示利用称量法制备的氦气中SO₂F₂气体标准物质在6个月内的稳定性良好,其相对扩展不确定度不大于2%。     

北京航天试验技术研究所低温技术事业部

正北京航天试验技术研究所低温技术事业部是专业从事深冷介质(LH_2、LN_2、LO_2)应用技术研究、开发、试验和各类低温深冷液、气体的生产、贮存、转注、运输、销售与品质检测的航天高科技单位,在氢能综合开发与应用领域处于技术领先地位,是规模化、工业化自行生产和安全应用液氢的单位,拥有北京市氢气、氦气、氮气、氧气、氩气充装、运输资     

氖氦鑑定会义简讯

于1966年12月27日至29日由化工部二局主持邀请了有关科研,使用,生产及领导机关等22个单位共53名代表,在北京氧气厂召开了“用液氢冷冻法”分离氖氦气技术鉴定会议。在会议期间同时讨论和通过了氩氖混合气,灯泡氩气的工厂出厂技术标准。     

氦气钢瓶抽真空处理方法的探讨

在保证钢瓶处理质量的前提下,如何高效率的进行氦气钢瓶抽真空置换处理,对氦气充装企业来说非常重要。通过实验得知,同一排氦气钢瓶的处理时间主要取决于罗茨泵的启动时间,罗茨泵启动后钢瓶内无论是氦气介质还是氮气介质,抽到相同的真空度数值所用时间相差不大。螺杆泵启动后,通入一定量氩气可以大大缩短氦气钢瓶抽真空时间,提高氦气钢瓶的处理效率,同时对钢瓶处理质量不会造成影响。     

氢气置换用量及用时计算

传统的低温加注系统置换,需使用大量稀缺资源氦气,在某新型靶场将采用氢气代替氦气进行置换.现阶段对氢气置换的用量和用时几乎都靠原有经验作估计,利用绝热膨胀和节流孔板两种模型,对氢气置换的消耗量和用时进行计算,为后续置换操作流程设计提供理论依据.     

行波型热声制冷机及混合工质的实验研究

行波型热声制冷机,因采用热声发动机驱动脉冲管制冷机,使消除低温制冷机中的运动部件成为可能.作者建立了行波型热声制冷机实验装置,采用氮气、氦气及其混合气进行了行波型热声发动机与脉冲管制冷机的配合实验,获得73.8℃的最大温降.着重研究了热端气体温度、压力振幅和冷端温降的变化规律.     

氦氢混合制冷工质的爆炸极限试验

在微型低温制冷机中，为了提高制冷机的热力学效率，越来越多地使用氢氦二元混合工质。由于氦气是惰性气体，具有阻燃作用，因此，在使用时容易产生麻痹思想而引发事故。为此对不同配比的氦氢混合气进行爆炸试验，分别得到了它们的爆炸极限。结果表明：氦气对氢气虽然具有一定的阻燃作用，但当样气中氦的摩尔百分含量小于50％时，氦氢混合气的爆炸上、下限随氦的百分含量的增加而有所升高，但其爆炸区间的绝对值几乎与纯氢相近；只有当样气中氦的摩尔百分含量大于50％后，样气的爆炸下限随氢的百分含量的减少迅速递升；直至氦气和氢气摩尔比例大于10时，样气与任何比例的空气混合都不会爆炸，且较氢氮混合气更安全。     

Empirical correlations for the solubility of pressurant gases in cryogenic propellants

We have analyzed data published by others reporting the solubility of helium in liquid hydrogen, oxygen, and methane, and of nitrogen in liquid oxygen, to develop empirical correlations for the mole fraction of these pressurant gases in the liquid phase as a function of temperature and pressure. The data, compiled and provided by NIST, are from a variety of sources and covers a large range of liquid temperatures and pressures. The correlations were developed to yield accurate estimates of the mole fraction of the pressurant gas in the cryogenic liquid at temperature and pressures of interest to the propulsion community, yet the correlations developed are applicable over a much wider range. The mole fraction solubility of helium in all these liquids is less than 0.3% at the temperatures and pressures used in propulsion systems. When nitrogen is used as a pressurant for liquid oxygen, substantial contamination can result, though the diffusion into the liquid is slow.     

混合工质脉管制冷的热力学性能预测

提出了用于预测混合工质脉管制冷热力学性能的改进型Brayton制冷循环,建立了制冷系统制冷量和制冷系数COP的理论表达式。在对多种低温流体的预测计算的基础上,提出了具有应用潜力的混合工质对。计算结果表明,如果用10%氮与90%氦的混合工质对代替纯氦,脉管制冷机在80K温度下的制冷系数和制冷量分别可以提高9.5%和6.7%。此外还讨论了其它可能用于80K温区脉管制冷的混合工质对,如氢-氦、氩-氦、氖-氦混合物等。     

Design and development of a helium injection system to improve external leakage detection during liquid nitrogen immersion tests

The testing of assemblies for use in cryogenic systems commonly includes evaluation at or near operating (therefore cryogenic) temperature. Typical assemblies include valves and pumps for use in liquid oxygen-liquid hydrogen rocket engines. One frequently specified method of cryogenic external leakage testing requires the assembly, pressurized with gaseous helium (GHe), be immersed in a bath of liquid nitrogen (LN₂) and allowed to thermally stabilize. Component interfaces are then visually inspected for leakage (bubbles). Unfortunately the liquid nitrogen will be boiling under normal, bench-top, test conditions. This boiling tends to mask even significant leakage.One little known and perhaps under-utilized property of helium is the seemingly counter-intuitive thermodynamic property that when ambient temperature helium is bubbled through boiling LN₂ at a temperature of −195.8 °C, the temperature of the liquid nitrogen will reduce.This paper reports on the design and testing of a novel proof-of-concept helium injection control system confirming that it is possible to reduce the temperature of an LN₂ bath below boiling point through the controlled injection of ambient temperature gaseous helium and then to efficiently maintain a reduced helium flow rate to maintain a stabilized liquid temperature, enabling clear visual observation of components immersed within the LN₂. Helium saturation testing is performed and injection system sizing is discussed.     

催化分解方法分析高纯氨中微量水分含量

研究高纯氨中微量水分的测试。采用催化分解氨的方法得到氢气和氮气,测试氢氮混合气中的水分,用氦离子放电气相色谱仪检测得到氨中氧含量,换算可以得到高纯氨中的水含量。     

PVT gauging with liquid nitrogen

Experimental results are presented for pressure–volume–temperature (PVT) liquid quantity gauging of a 0.17 m³ liquid nitrogen tank pressured with ambient temperature helium in the normal gravity environment. A previously reported PVT measurement procedure has been improved to include helium solubility in liquid nitrogen. Gauging data was collected at nominal tank fill levels of 80%, 50% and 20% and at nominal tank pressures of 0.3, 1.0, and 1.7 MPa. The test tank was equipped with a liquid pump and spray manifold to circulate and mix the fluid contents and therefore create near-isothermal conditions throughout the tank. Silicon diode sensors were distributed throughout the tank to monitor temperatures. Close-spaced arrays of silicon diode point sensors were utilized to precisely detect the liquid level at the nominal 80%, 50%, and 20% fill levels. The tests simulated the cryogenic tank-side conditions only; helium mass added to the tank was measured by gas flowmeters rather than using pressure and temperature measurements from a dedicated helium supply bottle. Equilibrium data for cryogenic nitrogen and helium mixtures from numerous sources was correlated to predict soluble helium mole fractions. Results show that solubility should be accounted for in the PVT gauging calculations. Mole fractions predicted by Dalton’s Law were found to be in good agreement with the compiled equilibrium data within the temperature–pressure range of interest. Therefore, Dalton’s Law was deemed suitable for calculating ullage composition. Gauging results from the PVT method agreed with the reference liquid level measurements to within 3%.     

一种用于冲击压缩实验的液氦温度低温靶

介绍了研制的一种液氦温度低温靶靶体。该靶体具有独立真空夹层与气冷屏,采用连续流减压降温的液氦制冷方式,在约100 Pa真空环境下,获得了稳定的4.2 K制冷温度。它可以用于氦等气体样品的冲击压缩实验。     

低温氦气体轴承透平膨胀机实验系统设计

设计了一套氦透平膨胀机实验系统,该系统可以用来对工作在液氢—常温区范围内的不同规格的氦透平膨胀机进行性能测试,还可以用于开展以氦为工质的低温环境下透平膨胀机实验研究,以期掌握氦透平膨胀机的关键技术并进一步提高氦透平膨胀机的性能。     

Helium detection in gas mixtures by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy (LIBS) has been evaluated as a tool for monitoring trace levels of helium in gas mixtures consisting mostly of hydrogen. Calibration data for helium in hydrogen was investigated at different helium concentration levels. At high concentrations of helium (>7.25%), the LIBS signal is quenched due to Penning ionization. The hydrogen alpha line (656.28 nm) was observed to broaden as the concentration of helium impurities in the hydrogen gas mixture increased. The helium line at 587.56 nm was selected as the analyte line for helium impurity detection. The effects of laser energy, the delay time between the laser pulse and data acquisition, and the gas pressure on the LIBS signal of helium were investigated to determine the optimum conditions for helium detection. The LIBS signal from the helium line at 587.56 nm shows good linear correlation with helium concentration for He concentrations below 1%. Thus, LIBS can be reliably used to detect the low levels of helium. The limit of detection for helium was found to be 78 ppm.