Gas Feed System Research Articles

Simultaneous probing of bulk liquid phase and catalytic gas-liquid-solid interface under working conditions using attenuated total reflection infrared spectroscopy.

Design and performance of a reactor set-up for attenuated total reflection infrared (ATR-IR) spectroscopy suitable for simultaneous reaction monitoring of bulk liquid and catalytic solid-liquid-gas interfaces under working conditions are presented. As advancement of in situ spectroscopy an operando methodology for gas-liquid-solid reaction monitoring was developed that simultaneously combines catalytic activity and molecular level detection at the catalytically active site of the same sample. Semi-batch reactor conditions are achieved with the analytical set-up by implementing the ATR-IR flow-through cell in a recycle reactor system and integrating a specifically designed gas feeding system coupled with a bubble trap. By the use of only one spectrometer the design of the new ATR-IR reactor cell allows for simultaneous detection of the bulk liquid and the catalytic interface during the working reaction. Holding two internal reflection elements (IRE) the sample compartments of the horizontally movable cell are consecutively flushed with reaction solution and pneumatically actuated, rapid switching of the cell (<1 s) enables to quasi simultaneously follow the heterogeneously catalysed reaction at the catalytic interface on a catalyst-coated IRE and in the bulk liquid on a blank IRE. For a complex heterogeneous reaction, the asymmetric hydrogenation of 2,2,2-trifluoroacetophenone on chirally modified Pt catalyst the elucidation of catalytic activity/enantioselectivity coupled with simultaneous monitoring of the catalytic solid-liquid-gas interface is shown. Both catalytic activity and enantioselectivity are strongly dependent on the experimental conditions. The opportunity to gain improved understanding by coupling measurements of catalytic performance and spectroscopic detection is presented. In addition, the applicability of modulation excitation spectroscopy and phase-sensitive detection are demonstrated.

Non-thermal atmospheric pressure plasma preferentially induces apoptosis in p53-mutated cancer cells by activating ROS stress-response pathways.

Non-thermal atmospheric pressure plasma (NTAPP) is an ionized gas at room temperature and has potential as a new apoptosis-promoting cancer therapy that acts by generating reactive oxygen species (ROS). However, it is imperative to determine its selectivity and standardize the components and composition of NTAPP. Here, we designed an NTAPP-generating apparatus combined with a He gas feeding system and demonstrated its high selectivity toward p53-mutated cancer cells. We first determined the proper conditions for NTAPP exposure to selectively induce apoptosis in cancer cells. The apoptotic effect of NTAPP was greater for p53-mutated cancer cells; artificial p53 expression in p53-negative HT29 cells decreased the pro-apoptotic effect of NTAPP. We also examined extra- and intracellular ROS levels in NTAPP-treated cells to deduce the mechanism of NTAPP action. While NTAPP-mediated increases in extracellular nitric oxide (NO) did not affect cell viability, intracellular ROS increased under NTAPP exposure and induced apoptotic cell death. This effect was dose-dependently reduced following treatment with ROS scavengers. NTAPP induced apoptosis even in doxorubicin-resistant cancer cell lines, demonstrating the feasibility of NTAPP as a potent cancer therapy. Collectively, these results strongly support the potential of NTAPP as a selective anticancer treatment, especially for p53-mutated cancer cells.

A Novel Half-Cell Design and Fabrication for an In-Situ Evaluation of Pem Fuel Cell Electrocatalysts

A novel electrochemical half-cell is designed and fabricated for in-situ evaluating both anode and cathode catalysts that mimic PEM fuel cell operating conditions. Both carbon-supported Pt and Pt0.5Ru0.5 catalysts are used to prepare the catalyst-coated membrane electrodes for this half-cell validation. A gas feeding system is constructed for quantitatively supplying of H2, H2+CO, or O2 gases to the half-cell for measurements. CO-tolerance of the anode catalyst in hydrogen oxidation reaction (HOR) is tested using this cell. The oxygen reduction reaction (ORR) on Pt/C-coated membrane electrode is studied using this half-cell, further confirming the feasibility of this half-cell design and fabrication. It is expected that this half-cell is also useful for catalyst/catalyst layer evaluation for direct liquid fuel cells.

Experimental Investigation of Transient Flow Measurement in the Ram-Accelerator High Pressure Pneumatic System

A high-pressure-pneumatic mass flow control test-bed using inert medium was built in order to study the transient flow characteristic of high pressure gas feed system in ram accelerator. The structure of a new type measurement system of transient flow characteristic experiments applied to the test-bed was introduced as also. Measurement tests that high pressure gas-flow ejecting into a tank with exhaust-back-pressure through a high pressure fueling valve were conducted to ascertain the transient discharge coefficient. The results suggest that: The transient discharge coefficient increases with the inlet pressure difference of high pressure fueling valve according to polynomial law. Correlations between inlet pressure difference and transient discharge coefficient was obtained based on the experimental data. The correlation coefficient between the least square fitting curve of the correlations and experimental results reaches 0.994.The system could be used to study the change regularity of pressure and time in the fueling process of high pressure gas.

Vacuum system of SST-1 Tokamak

Vacuum chambers of Steady State Superconducting (SST-1) Tokamak comprises of the vacuum vessel and the cryostat. The plasma will be confined inside the vacuum vessel while the cryostat houses the superconducting magnet systems (TF and PF coils), LN2 cooled thermal shields and hydraulics for these circuits. The vacuum vessel is an ultra-high (UHV) vacuum chamber while the cryostat is a high-vacuum (HV) chamber. In order to achieve UHV inside the vacuum vessel, it would be baked at 150°C for longer duration. For this purpose, U-shaped baking channels are welded inside the vacuum vessel. The baking will be carried out by flowing hot nitrogen gas through these channels at 250°C at 4.5bar gauge pressure. During plasma operation, the pressure inside the vacuum vessel will be raised between 1.0×10−4mbar and 1.0×10−5mbar using piezoelectric valves and control system. An ultimate pressure of 4.78×10−6mbar is achieved inside the vacuum vessel after 100h of pumping. The limitation is due to the development of few leaks of the order of 10−5mbarl/s at the critical locations of the vacuum vessel during baking which was confirmed with the presence of nitrogen gas and oxygen gas with the ratio of ∼3.81:1 indicating air leak. Similarly an ultimate vacuum of 2.24×10−5mbar is achieved inside the cryostat. Baking of the vacuum vessel up to 110°C with ±10°C deviation was achieved with a net mass flow rate of 0.8kg/s at 1.5bar gauge inlet pressure and supply temperature of 230°C at the heater end. Also during gas feed system installation, the pressure inside the VV was raised from 3.01×10−5mbar to 1.72×10−4mbar by triggering a pulse of lower amplitude of 25 voltage direct current (VDC) for 100s to piezoelectric valve. This paper describes in detail the design and implementation of the various vacuum subsystems including relevant experimental results.

SST-1 Gas feed and Gas Exhaust system

SST-1 tokamak is a long pulse tokamak designed for the plasma operation up to 1000 sec duration. Gas feed system and gas exhaust management will play a very crucial role during plasma discharge. During the different type of operations of tokamak like wall conditioning, diverter operation and neutral beam injection, a large amount of gas will be fed into the vacuum chamber at different locations. Also during plasma operations, the gas will be fed both in continues and pulse mode. Gas feed will be carried out mainly using piezo-electric valves controlled by PXI based data acquisition and control system. Such operations will lead to a huge amount gas exhaust by the main system which requires good exhaust facility to searches, great care should be taken in constructing both. Also initial pumping of cryostat and vacuum vessel of SST-1 will release a large amount of gas. Exhausted gases from SST -1 will be Hydrogen, Nitrogen, Mixture gases or some toxic gases. Dedicated exhaust system controlling the different gases are installed. Special treatment of hazardous/explosive gases is done before releasing to the atmosphere. This paper describes design and implementations of the complete gas feed and exhaust system of SST-1.

Programmable Pulse Generator for Aditya Gas Puffing System

In the Aditya Tokamak, one of primary requirement for plasma generation is to feed the required quantity of the fuel gas prior to plasma shot. Gas feed system mainly consists of piezoelectric gas leak valve and gas reservoir. The Hydrogen gas is prior to 300ms loop voltage for the duration of 4 msec to 7 msec. Gas is puffed during the shot for required plasma parameters and to increase plasma density using the same system. The valve is controlled by either continuous voltage or pulses of different width, amplitude and delay with respect to loop voltage. These voltage pulses are normally applied through standard pulse generator. The standard pulse generator is replaced by micro controller based in housed developed programmable pulse generator system consists of in built power supply, BNC input for external trigger, BNC output and serial interface. This programmable pulse generator is successfully tested and is in operation for gas puffing during ADITYA Tokamak experiments. The paper discusses the design and development aspect of the system.

Active control over carbon deposition by gas feeding for the protection of diagnostic the mirrors in ITER

Deposition of impurities can drastically change optical properties of metallic mirrors used for diagnostics of fusion plasmas. Specifically in ITER, this can become critical for the reactor operation by affecting the quality and reliability of detected signals. A series of experiments was performed in TEXTOR where local gas feeding was used for mitigation of carbon deposition on the mirror surface. A prototype of a diagnostic duct with molybdenum mirrors equipped with a gas feeding system was exposed in scrape-off layer plasma under deposition-dominated conditions. In the case of helium feeding, suppression of deposition was observed, while feeding of deuterium not only demonstrated full suppression of deposition but even favored complete removal of initially pre-deposited a-C:D layers. This paper presents results of experiments along with dedicated modeling of plasma–gas interaction inside the diagnostic duct.

KW-class molten carbonate fuel cell stack

A molten carbonate fuel cell stack consisting of 15 single cells with an electrode area of 250 mm × 400 mm was assembled. The gas feed system works via interior manifolds, and the stack placed in a couple of self-chest, coupled with a heater at the bottom, the top and other fours surrounded, to keep uniformity of temperature. Under ambient pressure and at 650 ℃, fed with hydrogen and air as anode and cathode gases respectively, the OCV of the stack after four thermal circulations reached 16.33V. The output power of the stack attained 1.48 kW at a current density of 150 mA cm -2 after testing at 650 ℃ for 144 h. The performance of the stack while discharging at 10.5 V (average 0.7 V/single cell) maintained at a level of 825 W with little augment of the output power with time in the period of 144 h.

System integration of RF based negative ion experimental facility at IPR

The setting up of RF based negative ion experimental facility shall witness the beginning of experiments on the negative ion source fusion applications in India. A 1 MHz RF generator shall launch 100 kW RF power into a single driver on the plasma source to produce a plasma of density ~5 × 1012 cm-3. The source can deliver a negative ion beam of ~10 A with a current density of ~30 mA/cm2 and accelerated to 35 kV through an electrostatic ion accelerator. The experimental system is similar to a RF based negative ion source, BATMAN, presently operating at IPP. The subsystems for source operation are designed and procured principally from indigenous resources, keeping the IPP configuration as a base line. The operation of negative ion source is supported by many subsystems e.g. vacuum pumping system with gate valves, cooling water system, gas feed system, cesium delivery system, RF generator, high voltage power supplies, data acquisition and control system, and different diagnostics. The first experiments of negative ion source are expected to start at IPR from the middle of 2009.

소형위성의 궤도천이 및 보정을 위한 홀 추력기의 설계

소형 인공위성의 궤도천이 및 보정을 위하여 추력이 약 10 mN이고 비추력이 1500 s인 홀 방식 전기추력기를 설계하였다. 개발된 추력기는 홀 방식의 추력부, 전력공급부 및 연료 공급부로 구성되어 있고, 무게, 소모전력 및 효율은 각각 10 kg, 300 W 및 30%정도이다. 개발된 추력기 시스템에 대한 간략한 소개를 홀 방식의 추력기를 선택하게 된 배경해석과 함께 기술하였다. A small Hall-effect thruster with a thrust range near 10 mN and a specific impulse of about 1500 s has been designed to control or maintain the orbits of small satellites. The thruster system consists of a hall-effect thruster head, a power processing unit and a Xenon (Xe) gas feed system. The total mass, the consumed electric power and the efficiency of the thruster are approximately 10 kg, 300W and 30%, respectively. Analyses results that support the selection of the thruster for small satellites are provided along with a brief description of the thruster system.

Permeability and Selectivity of Sulfur Dioxide and Carbon Dioxide in Supported Ionic Liquid Membranes

Permeabilities and selectivities of gases such as carbon dioxide (CO 2), sulfur dioxide (SO 2), nitrogen (N 2) and methane (CH 4) in six imidazolium-based ionic liquids ([emim][BF 4], [bmim][BF 4], [bmim][PF 6], [hmim][BF 4], [bmim][Tf 2N] and [emim][CF 3SO 3]) supported on polyethersulfone microfiltration membranes are investigated in a single gas feed system using nitrogen as the environment and reference component at temperature from 25 to 45°C and pressure of N 2 from 100 to 400 kPa. It is found that SO 2 has the highest permeability in the tested supported ionic liquid membranes, being an order of magnitude higher than that of CO 2, and about 2 to 3 orders of magnitude larger than those of N 2 and CH 4. The observed selectivity of SO 2 over the two ordinary gas components is also striking. It is shown experimentally that the dissolution and transport of gas components in the supported ionic liquid membranes, as well as the nature of ionic liquids play important roles in the gas permeation. A nonlinear increase of permeation rate with temperature and operation pressure is also observed for all sample gases. By considering the factors that influence the permeabilities and selectivities of CO 2 and SO 2, it is expected to develop an optimal supported ionic liquid membrane technology for the isolation of acidic gases in the near future.

Scale-up analysis and development of gliding arc discharge facility for volatile organic compounds decomposition

The influences of inlet gas flow rate and reactor configuration on volatile organic compounds (VOCs) decomposition efficiency in a traditional gliding arc (T-GA) facility are studied based on laboratory experiments and numerical simulation. The ratio of the nozzle diameter and the shortest distance of two electrodes should be maintained in a suitable value range to guarantee the decomposition efficiency, which indicates simply enlarging the nozzle inner diameter is not a proper way to raise the T-GA treatment capacity in a fixed supply voltage condition. A developed gliding arc gas discharge (D-GA) reactor based on a modified gas feed system is proposed: small flow rate air goes through the bottom nozzle to process the GA evolution, and high flow rate contaminated gas goes frontal through the plasma region and decomposes. The performances of D-GA reactor in the decomposition of VOCs with relative high gas flow rate, including decomposition efficiency and specific energy consumption, are better than T-GA reactor. D-GA reactor also avoids the drawbacks of the increases of power system amount and electric power consumption in multi-electrode GA system.

Diamond volume crystal growth in HF-CVD and monitoring gas phase with laser absorption spectroscopy

In hot-filament CVD we synthesized single diamond crystals up to 100 μm in diameter [1]. In order to enhance growth rate and impede growth defects, it is intended to employ a new gas feeding system. This allows CH4 to be separately applied from H2 to the reactor locally at the substrate position. The effect of this concept on the gas phase was analyzed by Infrared Tuneable Diode Laser Absorption Spectroscopy (IR-TDLAS). The changes in species concentrations of CH4, CH3 and C2H2 with the substrate distance from filaments as well as first growth results are shown.

Status report on the Erlangen AMS facility

The Erlangen AMS facility has been in routine operation since 1995. We present the current status of the facility and recent developments in our laboratory. The main focuses of our research are further improvement and automation of the sample preparation, the development of new sample preparation techniques like the dating of iron artefacts, and the development of an efficient automated gas feeding system for a gas ion source for the measurement of microgram samples for, e.g. environmental or future biomedical applications. The current background level and the long term stability of the facility are presented and discussed.

A Gas Ion Source for Radiocarbon Measurements at 200 kV

The novel tabletop miniaturized radiocarbon dating system (MICADAS) at ETH Zurich features a hybrid Cs sputter negative ion source for the measurement of solid graphite and gaseous CO2 samples. The source produces stable currents of up to 6 μA C− out of gaseous samples with an efficiency of 3–6%. A gas feeding system has been set up that enables constant dosing of CO2 into the Cs sputter ion source and ensures stable measuring conditions. The system is based on a syringe in which CO2 gas is mixed with He and then pressed continuously into the ion source at a constant flow rate. Minimized volumes allow feeding samples of 3–30 μg carbon quantitatively into the ion source. In order to test the performance of the system, several standards and blanks have successfully been measured. The ratios of 14C/12C could be repeated within statistical errors to better than 1.0% and the 13C/12C ratios to better than 0.2%. The blank was &lt;1 pMC.

Kinetics of carbon dioxide absorption and desorption in aqueous alkanolamine solutions using a novel hemispherical contactor—I. Experimental apparatus and mathematical modeling

This two-parts paper summarizes the experimental and theoretical results of a comprehensive and first of its kind study on the kinetics of carbon dioxide (CO 2) absorption and desorption in and from aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), methyl-diethanolamine (MDEA) and 2-amino-2-methyl-1-propanol (AMP) and their mixtures (i.e., MEA + AMP , MEA + MDEA , DEA + AMP and DEA + MDEA ). Part-1 of this paper presents a detailed design of the novel hemispherical apparatus and a rigorous mathematical model applicable to both absorption and desorption conditions with some preliminary results and Part-2 provides detailed results with estimates of kinetic coefficients for CO 2 absorption and desorption for eight different aqueous amine systems. The new hemispherical contactor consists of a 76 mm diameter solid hemisphere housed in a Pyrex glass cylinder with appropriate gas and liquid feed and withdrawal systems. The liquid feed passes through a 4 mm ID tube, which is located in the center of the hemisphere, and discharges at the top. The liquid descends as a well-defined liquid film over the surface of the hemisphere and is collected by a funnel (79 mm ID) at the base of the hemisphere. The interfacial area and hydrodynamics are well defined and the entrance/exit effects as well as surface rippling are minimized. Using this apparatus, the absorption experiments were conducted at near atmospheric pressure with pure CO 2 saturated with water vapor at 293–323 K with initially unloaded solutions and the desorption experiments were performed at 333–383 K for CO 2 loadings between 0.02 and 0.7 moles of CO 2 per mole of amine using humidified nitrogen gas as a stripping medium at total system pressures up to 205 kPa. The new rigorous mathematical model developed to interpret the rate data is based on the principle of diffusional mass transfer accompanied with liquid-phase chemical reactions over a hemispherical liquid film. Also developed in this work is a methodology that uses the rigorous model in conjunction with a non-linear regression technique to estimate kinetic parameters. Preliminary results presented in this part of the paper show that the new experimental apparatus was successful in accurately measuring and the new model and its numerical implementation were successful in accurately predicting both absorption and desorption rates for all aqueous amine systems considered in this study.

An experimental study of gas transport and separation properties of ionic liquids supported on nanofiltration membranes

Permeability of gas molecules H 2, O 2, N 2, and CO in four types of ionic liquids ([C 4-mim][NTf 2], [C 10-mim][NTf 2], [N 8881][NTf 2], [C 8Py][NTf 2]) with a common anion but different cations supported on nanofiltration membranes was studied in single gas feed and under varying gas phase pressure. The separation property in terms of H 2/CO selectivity in the selected ionic liquids was examined in binary gas feed system and also under varying pressure. The adoption of supported ionic liquid membrane (SILM) using nanofiltration (NF) membrane as support is entirely new and its operating stability was investigated aiming to rectify the inherent instability problem associated with normal supported liquid membranes (SLMs) using conventional solvents residing within microporous support structure such as microfiltration membranes. Gas permeation rate through the new SILM exhibited an exponential increase with increasing gas phase pressure in the range from 3.0 to 7.0 bar, and the SILMs based on the NF membrane were remarkably stable even at the high pressure which far exceeded the pressure range for normal SLMs (<0.1 bar). H 2/CO separation factor, up to a maximum value of 4.3, exhibited variation among the ionic liquids, and more interestingly, a nonlinear pattern of decline with increasing gas phase pressure in all four ionic liquids, reversing the trend of exponential increase of permeation rate. Further analysis were carried out in an attempt to relate the gas transport and separation properties to physic-chemical properties of the ionic liquids such as viscosity, polarity, and variation in cation molecular structure. The new SILMs supported on nanofiltration membrane and its good stability at operating pressures relevant to industrial applications opens up new route for exploration of supported liquid membrane technology for gas enrichment, extraction and separation.

Gas Feeding System Supplying the U-400M Cyclotron Ion Source with Hydrogen Isotopes

Automated system feeding into ion source hydrogen isotopes as molecules with preset ratio of the fluxes is described. The control system automatically maintained the working parameters and provided graphic and digital representation of the controlled processes. The radiofrequency (RF) ion source installed at the axial injection line of the cyclotron produced ion beams of HD+, HT+, DT+, D2H+, etc. At a several months DT+ beam acceleration the tritium consumption was less than 108 Bq/hr. The intensity of a 58.2 MeV triton beam (T+ ions) extracted from the cyclotron chamber was about 10 nA.

Gas Feeding System Supplying the U-400M Cyclotron Ion Source with Hydrogen Isotopes

Gas Feeding System Supplying the U-400M Cyclotron Ion Source with Hydrogen Isotopes