Helium-neon Mixture Research Articles

Characterization of Silicate Glass/Mullite Composites Based on Coal Fly Ash Cenospheres as Effective Gas Separation Membranes

Membrane technology is a promising method for gas separation. Due to its low energy consumption, environmental safety, and ease of operation, membrane separation has a distinct advantage over the cryogenic distillation conventionally used to capture light inert gases. For efficient gas recovery and purification, membrane materials should be highly selective, highly permeable, thermally stable, and low-cost. Currently, many studies are focused on the development of high-tech materials with specific properties using industrial waste. One of the promising waste products that can be recycled into membrane materials with improved microstructure is cenospheres—hollow aluminosilicate spherical particles that are formed in fly ash from coal combustion during power generation. For this purpose, based on narrow fractions of fly ash cenospheres containing single-ring and network structure globules, silicate glass/mullite composites were prepared, characterized, and tested for helium–neon mixture separation. The results indicate that the fragmented structure of the cenosphere shells with areas enriched in SiO2 without modifier oxides, formed due to the crystallization of defective phases of mullite, quartz, cristobalite, and anorthite, significantly facilitates the gas transport process. The permeability coefficients He and Ne exceed similar values for silicate glasses; the selectivity corresponds to a high level even at a high temperature: αHe/Ne—22 and 174 at 280 °C.

New technology to produce raw neon-helium mixture

Until 2022, Ukraine was a major producer of pure neon gas. The crude neon product is obtained as a byproduct at large cryogenic air separation units (ASUs) that supply oxygen and nitrogen to steelmakers. After the stop of such industries in Ukraine, a global shortage of neon, which is necessary for the production of semiconductor microchips, appeared. The conceptually new technology for obtaining the crude neon product at ASUs, which is not adapted for the selection of a raw neon-helium mixture, is proposed. The enrichment of the neon-helium mixture taken from the ASU condenser-evaporator is carried out by the pressure swing adsorption method. Calculations of the adsorption enrichment processes of the neon-helium mixture were carried out using the wave method. The wave method is based on the physically accurate concept that the nonstationary flow of components occurs as a result of propagation concentration waves in the entire adsorption layer and inside the adsorbent grains. It is shown that the proposed technology makes it possible to obtain a crude neon-helium mixture with a total concentration of neon and helium of more than 90% at an extraction ratio of 40–50%.

Extraction of helium from neon-helium mixture by the adsorption method

Helium is an importantnatural resourceand it hasgreat importance for scientific research. It is currently extracted mainly from natural gas or inlarge air separation units. Heliumandneonareusually separatedfrom an separationcolumntogether. In order to obtain pure neon and helium they are further purified. This article discusses the main methods of extracting helium from the neon-helium mixture.Having compared rectification, freezing, membrane separation and sorption methods, the authors concluded that the adsorption method allows separation at relatively high temperature intervals and is more energy-efficient than the other methods considered. The paper presents existing examples of the application of the adsorption method for the purification of helium from neon, which have been implemented in Chinaand in the CIS. An overview of adsorption separation on new adsorbents, both on metal-organic bases and on single-walled carbon nanotubes, is also presented. In the future, the authors will conduct experiments to fill in the data gaps on adsorption and desorption of neon-heliummixture on different adsorbents.

Improved Technology for Obtaining Enriched Neon-Helium Mixtures

A novel technology for the production of high concentration neon-helium mixtures on different air separation units (including units without fraction separators) is presented. It is proposed to complete the ASU with pressure swing adsorption (PSA) devices for obtaining a neon-helium mixture. The PSA unit enriches the neon-helium mixture due to the energy of compressed gases taken from the ASU condenser-evaporator. The calculations of the PSA technology was performed using the wave approach. The implementation of this approach takes unsteady transient mass transfer processes into account both in the layers of the adsorbent and inside of the grains. It is shown that the proposed technique makes it possible to obtain an enriched neon-helium mixture with a total concentration of neon and helium to 90 and with a recovery ratio of 40–50 %.

Accurate quantum-corrected cubic equations of state for helium, neon, hydrogen, deuterium and their mixtures

Cubic equations of state have thus far yielded poor predictions of the thermodynamic properties of quantum fluids such as hydrogen, helium and deuterium at low temperatures. Furthermore, the shape of the optimal α functions of helium and hydrogen have been shown to not decay monotonically as for other fluids. In this work, we derive temperature-dependent quantum corrections for the covolume parameter of cubic equations of state by mapping them onto the excluded volumes predicted by quantum-corrected Mie potentials. Subsequent regression of the Twu α function recovers a near classical behavior with a monotonic decay for most of the temperature range. The quantum corrections result in a significantly better accuracy, especially for caloric properties. While the average deviation of the isochoric heat capacity of liquid hydrogen at saturation exceeds 80% with the present state-of-the-art, the average deviation is 4% with quantum corrections. Average deviations for the saturation pressure are well below 1% for all four fluids. Using Péneloux volume shifts gives average errors in saturation densities that are below 2% for helium and about 1% for hydrogen, deuterium and neon. Parameters are presented for two cubic equations of state: Peng–Robinson and Soave–Redlich–Kwong. The quantum-corrected cubic equations of state are also able to reproduce the vapor-liquid equilibrium of binary mixtures of quantum fluids, and they are the first cubic equations of state that are able to accurately model the vapor-liquid equilibrium of the helium–neon mixture. Similar to the quantum-corrected Mie potentials that were used to develop the covolume corrections, an interaction parameter for the covolume is needed to represent the helium–hydrogen mixture to a high accuracy. The quantum-corrected cubic equation of state paves the way for technological applications of quantum fluids that require models with both high accuracy and computational speed.

Thermodynamic and economic aspects of the Nelium Turbo-Brayton refrigerator development for the FCC-hh

Within the conceptual design study for the Future Circular Hadron Collider (FCC-hh) it was shown, that a large part of the total cryogenic heat load falls into the temperature range between 40 to 60 K. Thus, additional cryogenic refrigerators for this temperature level are specified for each of the 10 foreseen cryoplants. Such a cryogenic system was developed at the TU Dresden and is based on a Brayton cycle working with a neon-helium mixture as refrigerant and using multistage centrifugal compressors. The duty requirements comprise a 6.2 MW total heat load at 40 to 60 K for beam screens and shielding, additional 2.7 MW at 300 to 40 K for the pre-cooling of the helium cycle and a turndown ratio of up to 3.8. The optimisation of the referenced system was performed in order to obtain a high efficiency of the cryogenic cycle and tolerable costs for system components at the same time. An analysis of the mixture composition influence on the components and on the total gas mass was performed. Restrictions for industrially existing hardware were taken into consideration. Updated cycle parameters are subsequently described.

Innovative neon refrigeration unit operating down to 30 K

A new compact, low-cost, economically competitive and environmentally friendly cryogenic system for cooling a continuous gas flow down to about 30 K is under developing at the ILK Dresden, reported in this paper. The paper shows thermodynamic calculations of cycles on neon and neon-helium mixtures. The assessment of the degree of thermodynamic perfection of the neon cycles in comparison of neon-helium cycles is provided. The use of neon and neon-helium mixture in cryogenic cycles for cryostatting at a temperature level of 27…63 K will increase the thermodynamic efficiency of the cryogenic system and reduce the energy costs of obtaining cold at this temperature level. A technological chain/process, as well as the main economic indicators of the system under development are presented. The availability of such an innovative refrigeration system can be used in a wide range of cryogenic and cooling applications.

Ab initio calculation of rarefied flows of helium-neon mixture: Classical vs quantum scatterings

In order to faithfully simulate rarefied gas flows of light-weight molecules at cryogenic temperatures down to several kelvins, the Boltzmann equation with the differential cross section calculated from the realistic intermolecular potential should be applied. In the present work, the direct simulation Monte Carlo (DSMC) method with ab initio intermolecular potentials is first implemented into the open-source software dsmcFoam+ for the simulation of general rarefied gas flows. Then, Fourier and Couette flows of the helium-neon mixture are studied for the temperature ranging from 10 K to 2000 K, where the differential cross sections calculated from both classical and quantum mechanics have been used. Our simulation results show that the quantum scattering effects on the heat flux and shear stress are non-negligible when the equilibrium temperature is lower than 500 K. Also, for the Fourier flow, the mole fraction distributions calculated from the quantum scattering are significantly different from those of classical scattering.

Study of reverse Brayton cryocooler with Helium-Neon mixture for HTS cable

As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus, helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is appropriate for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for high temperature superconductor (HTS) power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameters for each refrigerant is performed based on a computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the exergy efficiency and equipment considerations. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

РЕЗЕРВЫ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ ПРОИЗВОДСТВА НЕОНОГЕЛИЕВОЙ СМЕСИ В ВРУ НИЗКОГО ДАВЛЕНИЯ

Air processed in large air separation units (ASU) is the only source of such valuable gas as neon. In these plants, neon as well as helium accumulates in the upper portion of the main condenser of a lower column. It is noted that the efficiency of neon extraction from air, especially in older designs of ASU, remains low due to its inevitable losses in the apparatus. In modern ASU АКАр-40/35 и КААр-60 losses are 7...11 %. A relatively high degree of extraction of neon in such ASU is achieved due to the use of steam stripping columns instead of dephlegmators (reflux condensers), as well as the use of automatic control systems. It is shown that the control algorithm of ASU should enable extracting such an amount of a neon helium mixture that would bring about maximum values of neon and helium recovery rates.

Optimization of Design and Operational Parameters of Adsorbers for Purification of Neon-Helium Mixture

The analysis of options for arranging an adsorber composed of several sections is given. The formulas for calculating the geometric parameters of individual adsorber elements were obtained for a specified diameter of the cooling nitrogen bath. The expenditure of refrigerant and energy required to regenerate the sorbent were defined for several constructional variants. The operating costs for a single adsorber cycle were calculated. The optimum regeneration temperature was determined at which the cost of purifying the mixture is minimal.

ПУТИ СНИЖЕНИЯ УДЕЛЬНЫХ ЗАТРАТ НА ОЧИСТКУ НЕОНОГЕЛИЕВОЙ СМЕСИ

The source of obtaining neon is a neon helium mixture extracted in the process of air separation. One of the stages of this technology is the subsequent purification of the concentrate from hydrogen and nitrogen. The results of the feasibility study of the plant for Ne-He mixture purification with the system of adsorption refining are presented in the work. Various operating modes of the purification plant were examined; work of its individual parts was analyzed; unit costs of the refrigerant for the cryogenic provision of the implemented processes were calculated. We found major drawbacks in the work of the plant and determined trends of its improvement, whose implementation will lead to a considerable reduction of the unit costs for Ne-He-mixture purification.

Aspects of surface scanning by direct analysis in real time mass spectrometry employing plasma glow visualization.

Visual monitoring of the Direct Analysis in Real Time (DART) gas impact region during sampling was demonstrated via its metastable plasma glow. It is known that adding neon into helium for DART leads to plasma glow, but this effect has not been used in practice and discussed in the literature so far. A single quadrupole mass spectrometer with a DART SVPA ion source was used for recording of DART mass spectra from different surfaces, using galangin and p-coumaric acid as model analytes. In specific cases, the composition of the mass spectra was clarified using an Orbitrap mass spectrometer. Plasma glow visualization made it possible to track the metastable gas distributions during surface scanning. The influence on the composition of the mass spectra was studied for different carrier gases, i.e. pure helium versus a helium-neon mixture, and for the vacuum pumping rate. The spatial resolution was substantially improved via a DART cap with a narrowed internal diameter, but impaired by a decreased sensitivity. Comparably low signal intensities were obtained for analytes on porous layers due to analyte penetration and metastable gas scattering. Visualization through the plasma glow enables the optimal selection of the coordinates for DART-MS analysis and thus it will support scanning and imaging MS on surfaces, including porous planar chromatographic separation materials.

ДОСЛІДЖЕННЯ ХАРАКТЕРИСТИК ТЕПЛОМАСООБМІННОЇ ПОВЕРХНІ НАСАДКОВИХ КОЛОН, ПЕРСПЕКТИВНИХ ДЛЯ ЗБАГАЧЕННЯ НЕОНОГЕЛІЄВОЇ СУМІШІ

One of the main factors determining nozzle rectifying columns operation is the mass exchange surface. The presented researches focus on the choice of nozzle design unit for neon helium mixture primary enrichment. Created universal experimental setup for studying the processes of rectification allows obtaining the basic characteristics of four nozzles: spiral, spiral-prismatic and two types of mesh saddle (10´10´0,2 mm and 12´12´0,4 mm). From the studied nozzles according to known requirements and taking into consideration a large-scale factor the best mesh saddle nozzle from a wire with a diameter 0,2 mm and the sizes 10×10 mm was chosen. This type of nozzle has low resistance of the irrigated nozzle (48 Pa) that is critical for the studied steam speeds (0,3 … 0,5 m/s).

Calculation of equilibrium adsorption of binary gas mixtures

A method of calculating partial magnitudes in equilibrium low-temperature adsorption of a neon-helium mixture on a base of the carbon adsorbent AG-2 is proposed and good convergence with experiment is obtained. The method of calculation of partial magnitudes may be applicable to adsorption systems in which an adsorbate forms an ideal adsorption solution.

Helium-Neon Gas Mixture Thermosyphon Cooling and Stability for Large Scale HTS Synchronous Motors

Commercial high-temperature superconducting (HTS) wires restrain us to an operation temperature ranging from 20 to 40 K for field-pole magnets applied to rotating machinery. We have proposed to employ a mixture of helium and neon gas in a closed-cycle thermosyphon based on a GM cryo-refrigerator. In this paper, we discuss the temperature stability of the evaporator created by a helium-neon mixture cooling coupled with a closed-cycle thermosyphon, upon an external heat load on a 100-kW-grade HTS synchronous machine. A home-made cooling system, including the condenser, was designed. The evaporator was assembled within the motor in accordance with thermal and mechanical analysis. The cooling of the evaporator with the 100-kW-grade HTS synchronous motor was applied against a variable heat load equivalent with the actual HTS rotor field poles. We report these results and propose its potential application to a large-scale ship propulsion motor.

Technology for Ne–He mixture enrichment in stepped reflux condensers

A series of devices is created for purifying a neon–helium mixture from nitrogen that predominates within it by condensation at 68–78 K. The reflux condensers are distinguished by compactness, that permits location in the immediate vicinity of air separation units, i.e., sources of crude material and liquid nitrogen. A reduction in the concentration of extraneous impurities in the neon–helium mixture makes it possible to reduce transport flow rates and storage delays due to a reduction in the “unproductive” part of the cylinder stock.

The Hartmann–Shprenger effect in the installation of preliminary purification of a neon–helium mixture

A worldwide tendency is noted in an increase in the demand for pure neon and helium. It is shown that contemporary purification devices for a neon–helium mixture have a potential for internal energy that makes it possible to use a gas dynamic method for obtaining low temperatures (the Hartmann–Shprenger effect).

RITM-F facility

For validation of fusion reactors breeding zones feasibility, a facility for functional in-reactor investigations of tritium-breeding models (RITM-F), based on an IVV-2M reactor has been constructed. The test program will be distinguished as functional tests. The RITM-F facility will consist of an experimental channel with a breeding zone model, a tritium extraction system, a cooling system, a monitoring and management system, and a system for processing experimental data. Main characteristics of the RITM-F facility are: models' irradiation environment – helium–neon mixture, pressure – 0.04 MPa; minimum pressure in the channel cavity – 10−2 mmHg; tritium purge-gas – neon + 1% hydrogen, pressure – 0.1–0.2 MPa, flow rate – 0.1–10 cm3/c; interrogation time of parameters' monitoring channels – 2–10 c; temperature of purge-gas channel cooling – 490 K. Thermal and neutron parameters of the main possible positions of the RITM-F channel in the reactor will be presented.

Obtaining Neon from a Neon–Helium Mixture on a Quartz Glass Membrane

Obtaining Neon from a Neon–Helium Mixture on a Quartz Glass Membrane