Environment-friendly Gas Research Articles

CF3I Gas Mixtures: Breakdown Characteristics and Potential for Electrical Insulation

SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> is a potent greenhouse gas, and there has been research into more environmental friendly alternative gases with the aim of replacing the use of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> gas in high-voltage equipment. So far, the research into alternative gases has shown that CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I gas mixtures have promising dielectric properties comparable to those of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> . This paper provides an overview of research into CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I gas and its mixtures, and gives an insight into its key properties. These include laboratory tests on the gas mixtures and initial applications to electrical power equipment. The insulation capability makes CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I a feasible alternative to SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> as an insulation medium where arc quenching is not required. On the other hand, iodine deposition after electrical discharge means CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> I may not be a suitable arc quenching gas for switchgear applications that require high current interruption unless a solution is found for controlled capture of the iodine.

A novel vortex tube-based N2-expander liquefaction process for enhancing the energy efficiency of natural gas liquefaction

This research work unfolds a simple, safe, and environment-friendly energy efficient novel vortex tube-based natural gas liquefaction process (LNG). A vortex tube was introduced to the popular N 2 -expander liquefaction process to enhance the liquefaction efficiency. The process structure and condition were modified and optimized to take a potential advantage of the vortex tube on the natural gas liquefaction cycle. Two commercial simulators ANSYS® and Aspen HYSYS® were used to investigate the application of vortex tube in the refrigeration cycle of LNG process. The Computational fluid dynamics (CFD) model was used to simulate the vortex tube with nitrogen (N 2 ) as a working fluid. Subsequently, the results of the CFD model were embedded in the Aspen HYSYS® to validate the proposed LNG liquefaction process. The proposed natural gas liquefaction process was optimized using the knowledge-based optimization (KBO) approach. The overall energy consumption was chosen as an objective function for optimization. The performance of the proposed liquefaction process was compared with the conventional N 2 -expander liquefaction process. The vortex tube-based LNG process showed a significant improvement of energy efficiency by 20% in comparison with the conventional N 2 -expander liquefaction process. This high energy efficiency was mainly due to the isentropic expansion of the vortex tube. It turned out that the high energy efficiency of vortex tube-based process is totally dependent on the refrigerant cold fraction, operating conditions as well as refrigerant cycle configurations.

Effect of vacuum oxy-nitrocarburizing on the microstructure of tool steels: an experimental and modeling study

The thermochemical treatments of tool steels improve the performance of the components with respect to surface hardness, wear and tribological performance as well as corrosion resistance. Compared to the conventional gas ferritic nitrocarburizing process, the original vacuum oxy-nitrocarburizing is a time-, cost-effective and environmentally-friendly gas process. Because of the oxidizing nature of the gas atmosphere, there is no need to perform subsequent post-oxidation.In this study, a vacuum oxynitrocarburizing process was carried out onto four tool steels (AISI H10, H11, H21 and D2) at 570 °C, after hardening and single tempering. The structural analysis of the compound and diffusion layers was performed by optical and electron microscopy, X-ray diffraction and glow discharge optical emission spectrometry (GDOES) methods. A largely monophase e- layer is formed with a carbon accumulation at the substrate adjacent area. The overlaying oxides adjacent to the e-carbonitride phase contained Fe 3 O 4 (magnetite) as a main constituent. A thermodynamic modelling approach was also performed to understand and optimize the process. The “Equilib module” of FactSage software which uses Gibbs energy minimization method, was used to estimate the possible products during vacuum oxynitrocarburising process.

Chemical and Electron Interaction Properties of Potential Gaseous Insulation and Arc-quenching Media

The global warming effects of sulphur hexafluoride (SF&lt;sub&gt;6&lt;/sub&gt;) lead researchers to look for new environmentally-friendly gas media in high-voltage electrical apparatus. The present paper discusses basic chemical and electron interaction properties that brings high insulation strength and good arc interruption capability for a gas. The conclusion shows that gaseous compounds composed of elements in the upright area of periodic table of elements generally have stronger electronegative ability and good electrical properties. And double bond or triple bond in gas molecule can effectively improve the dielectric strength. For gas mixtures, good cooperation of gases will generate synergetic effect, which makes its dielectric strength higher than the weighted average value of each gas. Some aspects in searching for new arc interruption media are also discussed.

Environmental Friendly Fluorine Mixture for CVD Cleaning Processes to Replace C2F6, CF4 and NF3

Since the beginning of the 1980’s per fluorinated carbons (PFC’s) such as C2F6 and CF4 have been used as cleaning gases in thin film deposition technology and since the 1990’s NF3 has been used in the same way. PFC’s and NF3 have long atmospheric lifetimes and therefore high global warming potentials. The main applications of these gases are to remove residual films left behind after a chemical vapor deposition process (CVD). The most important materials to remove are dielectric layers like silicon oxides (SiO2), carbon-containing silicon oxides, silicon nitrides (Si3N4) and, to a certain extent, conducting films like doped poly-silicon and silicide layers. According to the World Semiconductor Council the semiconductor industry in 2013 used 7512 t NF3, 1133 t CF4 and 708 t C2F6 on a global basis. Approximately 72% of all semiconductor industry gaseous emissions are caused from these three gases (C2F6, CF4 and NF3). Fraunhofer EMFT and Solvay Special Chem have developed an alternative cleaning process, which can be a replacement for the currently used PFC’s and NF3in semiconductor CVD tools. The target of this work was to find viable alternative gas mixtures for the semiconductor industry, which could be used as a “drop in” to avoid additional high investment costs from equipment modification. Our study has demonstrated that these more environment friendly gas mixtures also provide a more efficient and faster cleaning behavior for most applications. A cleaning efficiency gain of a factor 1.3 up to 17 can be expected, relative to the F2-amount required for cleaning; this gain in efficiency depends on the cleaning gas to be replaced and on the reactor type. A shorter cleaning time can lead directly into a higher equipment throughput and more cost effective usage of thin film tools. To generate data on particle and tool attrition, a first “mini marathon” test run has been performed. The test reactor, a 200mm wafer size CVD tool, was equipped with a mass spectrometer, to verify the end point of the chamber cleaning and to gain an overview of the waste gases going into the abatement system. Figure 1

Environmental friendly and sustainable gas barrier on porous materials: Nanocellulose coatings prepared using spin- and dip-coating

Abstract In this study, environmental friendly and sustainable coatings of nanocellulose (NC) were prepared using spin- and dip-coating methods, on two different porous cellulose substrates. Microscopy studies showed that spin-coating technique was suitable for the substrate with smaller pore size, while the dip-coating was suitable for the substrate with larger pore size. The coating thickness ranged from some hundreds of nanometers for the spin-coated layers, to some micrometers for the dip-coated ones. It was also seen that the contact angle increased with the coating thickness and roughness. NC coating resulted in low oxygen permeability (between 0.12 and 24 mL ∗ μm/(m2 ∗ 24 h ∗ kPa)) at 23% RH, but at 50% RH the oxygen permeability was too high to be measured, except for the dip-coated sample with 23 μm thickness. Also, it was seen that eight month storing reduced the barrier properties of the coatings when compared with fresh materials. These results indicate that NC coatings have a great potential as sustainable alternative coating on paperboard.

The Block Optimizing Selection and Eco-Environmental Problems of China Shale Gas Exploration and Development

China mainland shale gas exploration and development are carrying out gradually. According to shale gas enrichment degree, water resources distribution and the practice of exploration and development, China mainland shale gas resources can be divided into five blocks. On this basis, the author preliminary discussed the distribution of water resources and eco-environmental problems during shale gas exploration and development. Considering the practice of shale gas exploration and development and water resources situation, the author put forward that the Upper Yangtze and Yunnan-Guizhou-Guangxi region would be the most favourable block, and there are problems with China mainland shale gas exploration and development, such as large water consumption, well drilling water leakage and mud loss which would contaminate groundwater. In addition, shale gas well injection (grouting) might cause the occurrence of seismic events. After analyzing the two different kinds of opinions on whether China mainland shale gas exploration and development would cause environmental problems, the author pointed out that, without a doubt, there exist eco-environmental problems during shale gas exploration and development, and further proposed that we should put the environmental protection at first place and take the road of environment-friendly shale gas exploration and development by reference to the exploration and practice of shale gas development both of China and other advanced countries in the world.

THEORETICAL INVESTIGATIONS ON STANDING WAVE THERMOACOUSTIC PRIME MOVER USING DELTAEC

Thermoacoustic is a field of science and technology that studies heat and sound interactions. It deals with the conversion of thermal energy into acoustical energy and vice-versa. Thermoacoustic prime mover is an attractive alternative for a conventional pressure wave generator to drive cryocooler which attains cryogenic temperature below 123K to liquefy gases, to produce ultra-vacuum, etc. Also, it can be used to produce electricity with the help of thermoacoustic electric generator. The cooling effect generated by thermoacoustic refrigerator can be used in areas where there is no supply of electricity. The advantages of thermoacoustic prime mover lie in its less complicated construction, absence of any moving part and use of environmental friendly gases as a working medium. Number of simulations using gases such as He, Ar, N2 and He-Ar mixture were carried out in DeltaEC to investigate the performance of the prime mover in terms of pressure amplitude, onset temperature and resonating frequency. Input parameters like working pressure and heat input was varied to observe the effect on the performance of the prime mover. The results showed that as the working pressure increased, the pressure amplitude and onset temperature also increased. Similar effect was observed in case of heat input. Unlike pressure amplitude and onset temperature, resonating frequency does not depend on working pressure and heat input. It is controlled by the working gas and the geometry of the prime mover. Also the type of the working gas has a profound impact on the performance of the prime mover. Simulations also demonstrated that a mixture of He-Ar can be used to get the optimum output from the prime mover.

제조공기를 이용한 봉전극의 형상 및 갭길이에 따른 절연파괴특성

In this paper the experiments of breakdown characteristics of rod-electrodes by pressure and gap change of imitation-air were described. The results are fundamental data for electric insulation design of distribution power facilities which will be studied and developed in the future. And we could make an environment friendly gas insulation material with mataining dielectric strength by imitation air which generates a lower lever of the global warming effect.

Machining of Tungsten Heavy Alloy under Cryogenic Environment

Abstract The machining of tungsten heavy alloy is very difficult as it has high strength and hardness, which requires special cutting tools and cutting process. Though carbide tools are extensively used in conventional cutting, these lead take high machining time and tool failures which cause to decrease in productivity. To overcome the above, special techniques are being practiced in machining of tungsten alloys, one such technique is machining under cryogenic environment. In this paper, liquid nitrogen is used as coolant in machining of tungsten heavy alloys, because it is cost effective, safe, non flammable and environmental friendly gas, in addition to that it cannot contaminate the work piece and no separate mechanism required for disposal. An experimental investigation has been carried out on machining of tungsten heavy alloys by the solid carbide cutting tools under cryogenic and conventional coolants. The material removal rate, surface integrity and cutting forces were studied for both the coolants. The chip morphology also measured for evaluation of shear stress and shear strain. The cryogenic coolant has enhanced the machinability of tungsten heavy alloys. It is observed that the material removal rate was three times higher in cryogenic cooling method when compared with conventional coolant method and the surface finish of the machined surfaces are extremely good and the magnitude of cutting forces are lesser in cryogenic coolant.

제조공기를 이용한 Rod전극의 절연파괴특성

In this paper the experiments of breakdown characteristics by pressure and gap change of imitation air were described. The results are fundamental data for electric insulation design of distribution power facilities which will be studied and developed in the future. And we could make an environment friendly gas insulation material with mataining dielectric strength by Imitation Air which generates a lower lever of the global warming effect.

Supercritical Carbon Dioxide as Green Product for Effective Environmental Remediation

Abstract The extraction of environmental pollutants from associated matrices is the first and the most important step in an environmental pollution study. Many different methods have been employed in order to concentrate organic components from aqueous solution such as liquid-liquid extraction, adsorption on solid adsorbents and passage through capillary polymeric columns. To date, the vast majority of the work with SFE has centered on the extraction of analytes from solid matrices. That which has been reported for SFE of aqueous matrices has been performed on a large scale such as for waste water treatment. A supercritical fluid is a material which can be either liquid or gas, used in a state above the critical temperature and critical pressure where gases and liquids can coexist. It has the ability to diffuse through solids like a gas, and dissolve materials like a liquid since it is able to penetrate anything by changing density to a great extent in a continuous manner. Sequential supercritical fluid extraction (SSFE) technology is widely used in selective fractionation of crude oil to help provide the effective separation of high molecular polycyclic aromatic hydrocarbons (PAHs) and saturated hydrocarbons from oil based matrices Sites. This paper is designed to present a state of art on supercritical fluid extraction (SFE) technology by treating CO2 as super green environmental friendly gas for separation of PAH and hydrocarbons in environmental remediation. It shows the merits and demerits of two conventional approaches for the extraction of aqueous samples i.e.(1) Liquid matrices that first absorbs it on a solid support and (2) direct SEF of matrix using a special extraction cell. Based on comprehensive study at Libyan Petroleum Institute (LPI) it finds critical optimum parameters for outstanding performance of SEF by using a liquid extraction cell at 2000 to 3000 Psi pressure, 40oC and 15 minutes extraction time. It demonstrates that how sequential supercritical fluid (CO2) extraction (SSFE) when applied to contaminated soils from diverse sources is capable to elucidate the sorption desorption behavior of high molecular aromatic hydrocarbons (PAHs). The method involves five extraction phases that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle. Interesting results from case studies in Libya demonstrate that SEF technology by using CO that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle. Interesting results from case studies in Libya demonstrate that SEF technology by using CO that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle.

Predicting failure within TBC system: Finite element simulation of stress within TBC system as affected by sintering of APS TBC, geometry of substrate and creep of TGO

Demand for economically efficient and environmental friendly gas turbine engines leads to the usage of a thermal barrier coating (TBC) system, which is usually sprayed on the top of a superalloy substrate. The system includes a ceramic TBC, a bond coat (BC) and a thermally grown oxide (TGO) layer. Thermo-mechanical mismatch stresses created within the coating at the end of a thermal cycle lead to spallation of the ceramic coating and a rapid increase in the temperature of the substrate. The thickness of the oxide layer and the amount of aluminium depleted during high temperature operation also affect the lifetime of the TBC. As a first step to the prediction of the failure mechanisms and the lifetimes of TBCs, a preliminary study of how the stress distribution within the TBC system is affected by different factors is required. This paper investigates the effects of the sintering of the ceramic layer, of the geometry of the substrate and of the creep of the TGO, on the stresses built up in the TBC system. Three different TBC system geometries were modelled using plane strain FE models with three different sets of TGO creep properties. An Arrhenius equation was fitted to the temperature dependent modulus of the sintered TBC using results published in the open literature. The equation was later implemented within the FE model. It is concluded that the TBC on the top of flatter regions of substrate produces smaller tensile residual stresses compared to sharp corners of the substrate. It was also found that the initiation and propagation of cracks within a TBC, during steady state operation depends on the choice of the creep parameters of the TGO. At the cooling stage, increase in the modulus of the TBC, due to sintering, has been shown to produce stresses within the TBC near the TGO interface that are as large as twice the value that is predicted using a model without sintering.

Exergetic and environmental assessment of room air conditioners in Turkish market

Abstract This study utilizes two factors, EEF (exergy efficiency factor) or exergetic COP (coefficient of performance) and MTEWI (modified total equivalent warming impact), which was proposed to evaluate exergetic and environmental performance of RAC (room air conditioners) sold in the Turkish market. In the study, vapour compression cooling cycle used whole RAC units is taken as model for the analyses. The results are shown that average EEF value of units using R-22 and R-410A gas are 74.53% and 74.64% respectively. Besides, R-410A gas, which is used in many split systems and marketed as an environmental friendly gas, has an effect that is approximately 23.18% higher than the R-22 gas which is no more in use. The study finally emphasizes the reasons why EEF and MTEWI factors should be given priority in terms of efficiency and environmental effects in the RAC units.

The Insulation Evaluation of N2:O2Mixture Gas

With the improvement of industrial society, high quality electrical energy, simplification of operation and maintenance, and ensuring reliability are being required. Also we request an urgent change from SF? gas to an environment-friendly gas insulation material. In this paper, the experiments of breakdown characteristics by pressure and gap change of N₂/O₂ mixture gas through a GIS (Gas Insulated Switchgear) model were described. This paper reviews basic data of the surface discharge characteristics for Teflon resin in not only pure N2, N₂:O₂ mixture gas as being focused on environmentally-friendly insulating gas, but also SF?. Also, insulation characteristics by breakdown voltage and surface discharge voltage of N₂:O₂ mixture gas in the experimental chamber were studied.

Synthesis of a One‐dimensional Coordination Polymer Based on Copper(II) Nitrate and 1,2‐Bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane

AbstractA one‐dimensional coordination polymer based on copper(II) nitrate and 1,2‐bis(5‐monomethylhydrazinyl‐1H‐tetrazolyl)ethane as ligand was prepared. The thermal and physical stability was determined by differential scanning calorimetry and BAM methods. The polymer was investigated by vibrational spectroscopy and single X‐ray diffraction. Moreover, the ligand itself and the 1,2‐bis(1H‐tetrazolyl)ethane were characterized as energetic material by bomb calorimetric measurements along with calculations using the EXPLO5 software. Both compounds have moderate energetic properties along with a high thermal and physical stability. These findings render these compounds into promising environment friendly gas generating agents.

배전급 전력실비를 위한 제조공기의 절연성 평가

With the improvement of industrial society, the high quality electrical energy, simplification of operation and maintenance, ensuring reliability are being required. We request urgently change a for an environment friendly gas insulation material. In this paper the experiments of breakdown characteristics by pressure and gap change of Imitation-Air in model GIS(Gas Insulated Switchgear) were described. Also assess of breakdown characteristics about Imitation-Air and . It is considered in this paper that the results are fundamental data for electric insulation design of Distribution Power Facilities which will be studied and developed in the future. The pressure to be confronted to gas 1[atm] for Distribution Power Facilities is Imitation-Air 3[atm]. And we could make an environment friendly gas insulation material with maintaining dielectric strength by Imitation-Air which generates a lower level of the global warming effect.

Plasma Etching Technology for Low-k Porous SiOCH Films

An environmental friendly gas, C5F10O, has been proposed for etching low-k SiOCH films using dual frequency (60MHz/2MHz) capacitively coupled plasma. The main ion produced is CF3+, as compared to CF+ produced by the conventional c-C4F8 gas. The advantage of CF3+ over CF+ is the much higher etching rate. With the new etching gas, a high etching rate of about 1000 nm/min with a vertical profile pattern can be achieved. The damage to SiOCH films induced by light, radicals and ions were systematically evaluated. It was found that the most severe damage was caused by ions, followed by VUV. The resist materials can be selectively removed with respect to SiOCH with less damage by employing an O2/Ar surface wave excited plasma. An advanced plasma etching technology with controlled radicals has thus been introduced.

평등전계에서 SF6/CF4혼합가스의 AC절연내력 특성

The excellent dielectric properties of (sulfur hexafluoride) have lead to its wide range of application in the field of high voltage insulation. Because there has been some recent concern regarding the environmental impacts of binary gas mixtures, with as the main component, have been the subject of active research. Scientists have long been interested in the possible use of gaseous fluorocarbons, including (Carton Tetrafluoride), in high voltage applications due to their inert character and high dielectric strength. This paper presents experimental results concerning the AC breakdown characteristics lot various mixtures of in a test chamber and 25.8 kV GIS (Gas Insulation Switchgear) at practical pressures (0.1-04 MPa) and gap lengths (0.5 mm, 1 mm) in a test chamber. In the result, it was observed that an increase in the dielectric strength is attained through the addition of to . It is possible to make an environment friendly gas insulation material while maintaining the dielectric strength by combing and which generates a lower level of the global warming effect.

SF 6 arc plasmas modelling for compact and environmental-friendly gas circuit breakers

In order to calculate the complex arc plasma combined thermal flow dynamics with electromagnetics, we firstly should define the governing equations on these fields and interface them with multidisciplinary simulation techniques, which include thermal flow and electromagnetic fields simultaneously. Through the processes it is very important to make appropriate models on turbulence, radiation, ablation etc. for this type of interruption technique. Also, the study of geometric effects (i.e., nozzle shape) is needed to optimize for the better performance of interruption and compact and environmental-friendly gas circuit breakers.