Mixture Of Methane Research Articles

Liquid Organic Hydrogen Carriers Applied on Methane–Hydrogen-Fueled Internal Combustion Engines: A Preliminary Analysis of Process Heat Balance

One of the main issues that has limited the use of hydrogen as an energy vector for a long time is its low energy density per unit of volume. Alternative chemical storage methods have been developed in recent years to overcome the limitations associated with compressed or liquified hydrogen storage. One of these is the Liquid Organic Hydrogen Carrier (LOHC), which utilizes organic hydrocarbons that can capture hydrogen (through an exothermic hydrogenation reaction) and release hydrogen (through an endothermic dehydrogenation reaction). In this paper, a 0D model of an internal combustion engine fueled with a mixture of hydrogen and methane was used to investigate whether the enthalpy of the exhaust gases can balance the heat rate required to self-sustain the dehydrogenation stage. Two LOHC+ compounds were considered, namely, Perhydro-dibenzyltoluene and Perhydro-N-Ethylcarbazole. Four different hydrogen-to-methane ratios were considered, assuming an engine maximum brake power ranging from 500 to 6000 RPM. An energy balance was performed, balancing the dehydrogenation heat rate and the exhaust gas cooling heat rate, in order to establish the minimum temperatures of the exhaust gases required to self-sustain the LOHC+ dehydrogenation. We demonstrated that the minimum exhaust temperatures required to self-sustain the process in different running regimes and at different hydrogen-to-methane ratios are lower than literature and experimental exhaust temperatures.

Experimental study on the rotating detonation engine based on a gas mixture

A direct connection test of a rotating detonation engine was conducted. The outer and inner diameters of the annular combustors were 206 and 166 mm, respectively. High enthalpy air was used as an oxidizer, and a mixture of hydrogen, carbon monoxide, and methane was used as fuel with a volume fraction of 5/4/1. The mixture was injected through small holes, and air was injected through annular slots. The effects of combustor length, width of annular slots, and the equivalent ratio on formation, development, propagation, and flameout of rotating detonation waves were analyzed, and several modes of rotating detonation were observed. It was found that when the width of the air annular slot was within the range of 3–5 mm, the pressure of the detonation wave was augmented with an increased slot width. As width increased, detonation waves became unstable. In study test conditions, an annular slot width of 6 mm was the critical condition for the formation of stable detonation. When the slot width was 4 mm and combustor length 160 mm, the phenomena of the conversion between single and double waves, double-wave collision, and conversion of the propagation direction occurred at different equivalent ratios. When the equivalent ratio was 1.2/1 and the slot width was within the range of 3–6 mm, the slot width was inversely related to the detonation wave velocity. When the slot width was 4 mm and the equivalent ratio was 1.0/1–1.2/1, the slot width was positively correlated with the detonation wave velocity. When the combustor length was shortened to 80 mm, the propagation mode of the detonation wave was changed to a single wave first and then to a double wave in the same direction, and the velocity reduced from 1130.69 to 1024.16 m/s. The injector used in the test inhibited the propagation of back pressure from the combustor.

EXPERIMENTAL RESEARCH OF MIXING NATURAL GAS IMPINGING JETS AND AIR DURING COMBUSTION AT A VERTICAL REFRACTORY SURFACE

In the work determined the conditions for the start of chemical reactions of natural gas and air mixture at combustion on a refractory surface, when a single submerged turbulent impinging jet is fed from a natural gas collector at the angle α to the vertical refractory surface, at the relative distance L/d0 along the geometric axis of the jet. It is determined that combustion starts under the condition when the excess air coefficient in the mixture reaches about λ = 0.93, at which the laminar flame propagation velocity S°L, m/s, for a premixed mixture of methane and air is maximum. The dependence of the height of the flame Lf, m, on the relative dimensionless step of the location of the nozzles s/d0 in the row was obtained during studying the groups of gas nozzles with the supply of natural gas for combustion through them range diameters 1–3.5 mm (which are used at precent time in the construction of slot bottom burners). It was determined that the flame height of slot bottom burner during its operation on natural gas (tested for the pressure of natural gas in the collector from 2 kPa to 18 kPa, respectively, natural gas outflow velocity, WNG from about 60 m/s to 185 m/s) depends slightly on gas pressure, the relative distance L/d0 that the aerated jet of natural gas travels to the refractory surface in the range of 15 ≤ L/d0 ≤ 30 and the Reynolds number, and strongly depends from on the dimensionless step of the nozzles in the row — s/d0. It has been experimentally proven that by adjusting the dimensionless step of the nozzles (holes) s/d0 in the row of the slot bottom burner, it is possible to adjust the height of the flame and thus obtain the flame of the appropriate height for different heights of fireboxes and boilers powers. Bibl. 29, Fig. 3, Tab. 3.

Study of the effect of some fungi on the yield of biogas

Agricultural and agro-industrial activities generate large quantities of waste which are harmful to the environment. This waste, rich in organic matter, can be recycled and transformed by biotechnological processes which constitute a solution of choice for remedying pollution problems. The aim of this study is the treatment of the organic fraction of waste by anaerobic digestion, which consists of degradation in the absence of oxygen of the organic matter into a mixture of methane (CH4) and carbon dioxide (CO2) called biogas. For this we have chosen the following samples (manure ; manure mixed in bananas, oranges, lemons, potatoes and tomatoes ; manure mixed in breads, zucchinis, carrots, cucumbers and strawberry). We used a biogas plants based on simple tools. Among these samples, the T container (manure) the most productive mixture of biogas and the T (manure) and F2 mixture (manure + breads + zucchinis + carrots + cucumbers + strawberry) degraded faster than the F1 manure + mixture (bananas, oranges, lemons, potatoes and tomatoes). The micromycetes that these samples contain are Penicillium italicum, Penicillium digitatum, Rhizopus sp, Mucor, Aspergillus sp, Cladosporium. Micromycetes give good biogas yield. The genus Aspergillus accelerates the degradation of organic matter. Anaerobic digestion not only prevents pollution, but also produces energy, compost and replenishes nutrients. Anaerobic digestion can turn a waste problem into a source of wealth. This technology is becoming essential in the process of reducing waste and producing biogas, a source of renewable energy.

A Study on Elemental Sulfur Equilibrium Content in Mixtures of Methane, Carbon Dioxide, and Hydrogen Sulfide under Conditions of Natural Gas Pipeline Transmission

The effect of gathering pipeline pressure, temperature, and key components on the solubility of monomeric sulfur in high-sulfur-content natural gas is directly related to the prediction and prevention of sulfur deposition in surface gathering pipelines. Based on our previous study on a prediction model of sulfur solubility in gas with a new formula for the binary interaction coefficient between sulfur and H2S, a new gas–solid thermodynamic phase equilibrium solubility prediction model for monomeric sulfur in high-sulfur-content natural gas was improved based on the gas–solid phase equilibrium principle considering both physical and chemical solution mechanisms. Two new expressions for binary interaction coefficients between sulfur and CO2 and CH4, considering both temperature and solvent density, are proposed in this new solubility prediction model. In this paper, the main factors, such as the gathering pipeline pressure, gathering pipeline temperature, H2S, and CO2, affecting the solubility law of elemental sulfur in high-sulfur-content natural gas are investigated. The results show that the total solubility of elemental sulfur in high-sulfur-bearing natural gas tends to decrease with an increase in the gathering temperature, in which the increase in temperature promotes physical solution, and the physical solution mechanism prevails. Conversely, chemical solution is promoted, and the chemical solution mechanism prevails. With an increase in the gathering pressure, the total solubility of elemental sulfur in high-sulfur-content gas tends to increase, where the physical solubility decreases slightly at first and then increases continuously, with a pressure inflection point of about 2.0 MPa, and the pressure increase has a significant promoting effect on the chemical solubility of elemental sulfur. The increase in the H2S concentration promotes the solution of elemental sulfur in the gas phase in general and significantly promotes the chemical solution of elemental sulfur. The effect on elemental sulfur solubility can be neglected when the molar concentration of CO2 in the gas phase does not exceed 10%.

Assessment of the Safety of Transport of the Natural Gas–Ammonia Mixture

The decarbonisation of many sectors of the economy, including primarily the energy sector, results in the gradual elimination of hydrocarbon fuels, especially coal. During the transition period, it will be possible to use natural gas, the combustion of which is associated with lower carbon dioxide emissions. Further reduction in this emission is possible with the use of mixtures of natural gas with other gases, e.g., ammonia. Ammonia, widely used in many industries, has recently been described as the emission-free fuel of the future. However, both of these gases are hazardous substances. Natural gas is a flammable gas and ammonia is a toxic gas. This paper presents an assessment of the transport safety of natural gas (methane) and its mixture with ammonia. The uncontrolled release of these substances from a damaged gas pipeline may cause a fire or a toxic hazard. This work presents hazard zones arising in the event of such a failure and determines the impact of various mixture compositions on the level of the potential hazard. The level of risk related to the uncontrolled release of a mixture of natural gas and ammonia was analysed. It has been estimated that for pipelines with a diameter of 400 mm and a low-pressure mixture of methane and ammonia in the proportion of 50/50 v/v, the danger zone with the risk of loss of life above 1 × 10−3 is approximately 50 m. In the case of the same pipelines transmitting the mixture of these high-pressure gases, the high-risk zone may extend to approximately 175 m.

Turbulent Flame Propagation in Hydrogen-Air and Methane-Air Mixtures in the Field of Synthetic Turbulence: Direct Numerical Simulation

A technique alternative to the direct numerical simulation of turbulent combustion of gas mixtures is proposed. It is based on the solution of the three-dimensional transport equations for species concentrations and the energy conservation equation in the “synthetic” field of constant-pressure homogeneous, isotropic and statistically stationary (forced) turbulence using the detailed reaction mechanism. The synthetic turbulence with given spatial and temporal correlation functions is generated using the Monte Carlo method, assuming that the components of the vector of fluctuation velocity obey the normal Gaussian distribution. The technique is applied to the problem of turbulent combustion of fuel-lean and stoichiometric mixtures of hydrogen and methane with air at a turbulence intensity up to 10 m/s. The calculated turbulent flame propagation velocities agree satisfactorily with the values measured in the fan-stirred bomb. The predicted volume fractions of active reaction centers H, O, and OH in a turbulent flame are shown to be less than in a laminar flame up to an order of magnitude, which also agrees with the experiment. In general, calculations indicate that the “wrinkled flame” model is applicable to fuel-lean and stoichiometric mixtures of hydrogen and methane with air at turbulence intensities up to 10 m/s

Steam Conversion of Ethane and Methane–Ethane Mixtures in Membrane Reactor with a Foil from Pd–Ru Alloy

The features of steam conversion of ethane and methane-ethane mixtures containing 5, 10 and 15% ethane in a membrane reactor with a 30 μm thick Pd–Ru foil at temperatures of 1800 and 3600 h–1 and steam/feed rations of 3 and 5 have been investigated. Comparative experiments with “non-membrane” reaction have shown that in the membrane reactor the feedstock conversion to form H2 and CO2 increases and ethane hydrocracking decreases. Increasing the rate of H2 recovery through the membrane by permeate evacuation leads to an increase in the yield of H2 and CO2. With a decrease in the steam/feed ratio from 5 to 3, the ethane hydrocracking and the rate of carbon deposits formation increases. Optimal conditions for steam conversion of ethane and methane-ethane mixtures are T = 773 K, feed space velocity of 1800 h–1 and steam/feed ratio of 5. The established regularities are similar to those obtained earlier for other types of raw materials (mixtures of methane with propane, propane, n-butane, a mixture simulating the average composition of associated petroleum gas) in this membrane reactor.

Second stage porous media burner for syngas enrichment

The syngas production from hydrocarbons by porous media combustion (or conventional gasification) processes has been intensively and extensively studied due its calorific value and its applications in the energy sector. However, the syngas produced in a first stage gasifier can still have concentrations of light hydrocarbons (e.g., methane) which can be post-processing for further enrichment of hydrogen and carbon monoxide. The present work numerically investigates the performance of a second stage porous media burner to enrich the syngas content, mainly hydrogen and carbon monoxide. A one-dimensional model based on a two-temperature approximation is implemented, based on the PREMIX code, and supported by CHEMKIN and GRI-MECH 3.0 database and routines. From hybrid porous bed reactor experiments, five types of mixtures in the equivalence ratio range between 0.4 and 2.4 are tested: pure methane as baseline, pure Eucalyptus nitens syngas, pure Pinus radiata syngas, and two mixtures of methane with each of the biomass syngas in equal volume quantities, as transition points. The results obtained show that in the enriched syngas, in comparison to the first content after the first stage reactor, the concentrations of hydrogen and carbon monoxide increase, due to the partial oxidation of methane, however part of the hydrogen is consumed in the process. The intermediate species present in methane processing for pure syngas mixtures have broader reaction zones and in lower concentrations compared to the use of pure methane. For equivalence ratios greater than 1.9, pure syngas mixtures show higher conversion efficiencies compared to the baseline. At the equivalence ratio of 2.4, the pure syngas from Eucalyptus nitens and Pinus radiata has an energy return over energy invested (EROI) of 58.27% and 53.95%, respectively, and a maximum hydrogen and carbon monoxide yields of 31.66% and 48.40%, respectively. In the case of the Pinus radiata, the outlet syngas concentrations of the hydrogen and carbon monoxide on dry basis expose an increment about two times in comparison to the initial concentrations.

EFFECT OF TRIFLUORIODOMETHANE ADDITIVES ON THE IGNITION OF MULTICOMPONENT COMBUSTIBLE MIXTURES BEHIND SHOCKWAVES

The problems of improving the safety of various industrial facilities dealing with combustible mixtures are constantly in the center of increased attention. The introduction of chemically active additives into the gas mixture is considered as one of the most effective ways to prevent ignition and explosion. One of the most promising highly effective and, at the same time, environmentally friendly additives is trifluoroiodomethane CF3I. Recently, the effect of CF3I on the ignition of acetylene and methane has been studied; however, combustible gas mixtures encountered in practice are often far from pure gases in composition and contain impurities that can significantly affect the ignition kinetics. In this work, an experimental study of the effect of CF3I on ignition delays behind shock waves of complex combustible mixtures, including mixtures of hydrogen and carbon monoxide (model mixture “synthesis gas”) as well as mixtures of methane with acetylene additives (model mixture “mine gas”) has been carried out. As a result of the experiments, it is shown that in mixtures simulating synthesis gas, CF3I additives lead to a considerable inhibition of ignition, while in “mine gas,” this effect turned out to be insignificant.

Investigation of the Properties of Anode Electrodes for Lithium–Ion Batteries Manufactured Using Cu, and Si-Coated Carbon Nanowall Materials

The fabrication of high-capacity, binder-free Li–ion battery anodes using a simple and efficient manufacturing process was reported in this research. The anode material for lithium–ion batteries utilized is a combination of two-dimensional (2D) carbon nanowalls (CNWs) and Cu nanoparticles (improved rate performance and capacity retention) or Si (high capacity) nanoparticles. A methane (CH4) and hydrogen (H2) gas mixture was employed to synthesize CNWs on copper foil through microwave plasma-enhanced chemical vapor deposition (PECVD). The Cu or Si nanoparticles were then deposited on the CNW surface using an RF magnetron sputtering equipment with four-inch targets. To analyze the electrochemical performance of the LIBs, CR2032 coin-type cells were fabricated using anode materials based on CNWs and other components. It was confirmed that the Cu−CNW demonstrates improved rate performance, increased specific capacity, and capacity retention compared with traditional anodes. Additionally, CNW combined with Si nanoparticles has enhanced the capacity of LIB and minimized volume changes during LIB operation.

Hydrogen production by the steam reforming of synthetic biogas in atmospheric-pressure microwave (915 MHz) plasma

This paper is a contribution to the development of microwave plasma-based technology aimed at efficient hydrogen (H2) production from a so-called synthetic biogas, considered a mixture of methane (CH4) and carbon dioxide (CO2), which can contain up to 70% CH4. In this work, we tested the performance of a waveguide-supplied metal cylinder-based microwave plasma source (MPS) operating at 915 MHz at atmospheric pressure as a tool for the efficient production of H2 in the steam reforming of the synthetic biogas. The test showed that the steam reforming of the synthetic biogas could be carried out under a wide range of working parameters without soot formation and extinction of the microwave discharge. We found that there is a minimal H2Osteam consumption rate for a given CH4 input volume content, which ensures stable operation of the MPS (no soot). The experiments did not show that increasing the amount of H2Osteam rate above the minimal value for a given CH4 input volume content results in an increase in the H2 production rate, energy yield, CH4 conversion degree, and H2 output concentration. To describe the MPS performance, which also takes into account a factor of the utilization of the CH4 feedstock, we introduced a new parameter, called an energy–CH4 feedstock consumption yield. The best results in terms of the H2 production rate, the energy yield, and the CH4 conversion degree were 239 g[H2]/h 36.8 g[H2]/kWh, and 74.3%, respectively. This shows that the application of the steam reforming, instead of the dry reforming, resulted in a 1.5-fold increase of the H2 production rate and the corresponding energy yield.

Determination of Unstretched Laminar Burning Velocity by Simultaneous Measurements of Flame Radius and Pressure-Time Trace Using Constant Volume Method

ABSTRACT Values of laminar burning velocity obtained by the constant volume method suffer from the inaccuracies introduced by the semi-analytical burned gas mass fraction model and flame stretch. A cylindrical combustion chamber with full optical access was developed in the present study, enabling the photography of the flame until the flame touches the inner wall of the combustion chamber. This enables direct visualization of the flame, thus eliminating the dependency on burned gas mass fraction models. The values of laminar burning velocity obtained by simultaneous measurement of flame radius and pressure-time data using the constant volume method are not stretch-free. This paper also develops a methodology for stretch correction based on the determined laminar burning velocity. Experiments were performed on mixtures of methane and air at initial pressures (0.8–1.05 bar), initial temperatures (293–320 K) and equivalence ratios (0.8–1.2). Stretch-corrected laminar burning velocity for lean, stoichiometric, and rich methane-air flames has been obtained in the present study, and the results obtained are validated against available experimental data and 1-D flame computations. It is expected that the proposed method significantly reduces the inaccuracies in laminar burning velocity obtained by the constant volume method.

Non-dispersive sensing scheme based on mid-infrared LED and differential mode excitation photoacoustic spectroscopy

A robust and simple sensing scheme utilizing a Mid-Infrared Light Emitting Diode (MIR-LED) and based on Differential Mode Excitation Photoacoustic (DME-PA) spectroscopy is presented. A MIR-LED light source in combination with optical correlation is used for simplicity and compactness. The sensing setup takes advantage of the non-linearity in the excitation of various acoustic modes in a cylindrical resonant photoacoustic cell to provide a high selectivity. The sensing device is tested using methane and hydrocarbon mixtures (propane, butane). The obtained limit of detection for methane is 25 ppm m−1. Using the presented DME-PA scheme, the derived gas concentration is hardly affected neither by intensity fluctuations of the light source nor by any microphone or electronics drifts. Furthermore, a considerably improved selectivity is obtained compared to conventional Non-Dispersive Infrared (NDIR) techniques.

Diffusivities in Binary Mixtures of Cyclohexane or Ethyl Butanoate with Dissolved CH4 or R143a Close to Infinite Dilution

This work is part of a series of studies focusing on binary mixtures consisting of a liquid with a dissolved gas close to infinite dilution. A particular focus is on the study of the influence of molecular characteristics on mutual or self-diffusivity. Heterodyne dynamic light scattering (DLS) experiments and equilibrium molecular dynamics (EMD) simulations are applied to determine the Fick diffusion coefficient D11 and the self-diffusion coefficient of the gas solute in the mixture Dself,1. Often, the latter is referred to in the literature as the intradiffusion coefficient, which is equal to D11 in the limit of infinite dilution. Both DLS and EMD simulations are applied in macroscopic thermodynamic equilibrium at or close to saturation conditions. In the present study, mixtures of methane (CH4) or the refrigerant 1,1,1-trifluoroethane (R143a) dissolved in cyclohexane or ethyl butanoate are investigated at temperatures T between 303 and 423 K. The average expanded experimental uncertainty (coverage factor k = 2) of D11 from DLS experiments is 10%, and the average expanded statistical uncertainty (k = 2) of Dself,1 from EMD simulations is 6.4%. Unexpectedly, D11 in mixtures of CH4 dissolved in cyclohexane or ethyl butanoate essentially matches within uncertainties at a given T, and mixtures of cyclohexane with R143a show smaller D11 values in comparison to ethyl butanoate with R143a.

Supersonic Shrouding Methane Mixtures for Supersonic Combustion Coherent Jets

A coherent jet oxygen supply plays a key role in the process of electric arc furnace steelmaking: it provides the necessary oxygen for the smelting of molten steel and promotes the flow of the molten pool. Compared with coherent jets in current use, the supersonic combustion coherent jet shrouded in supersonic methane gas could improve the impact capacity and stirring intensity of the molten pool. In order to reduce the smelting cost, the characteristics of the supersonic combustion coherent jet shrouding the supersonic methane and nitrogen mixtures must be studied. Computational fluid dynamics software is used to simulate the supersonic combustion coherent jet under various methane–nitrogen mixing conditions. The six-component combustion mechanism of methane and the Eddy Dissipation Concept combustion reaction model are selected. In agreement with thermal experiments, the simulation results show that the inclusion of a small amount of nitrogen has little effect on the combustion of supersonic shrouding methane gas. However, as the nitrogen content increases, the combustion region of supersonic shrouding gas becomes shorter in length, resulting in decreases in the lengths of the high-temperature, low-density region, and the high-turbulence-intensity region. These effects weaken the ability of the shrouding gas to envelop the main oxygen jet. The potential core length of the main oxygen jet decreases significantly; this decrease first accelerates and then decelerates. These results demonstrate the feasibility of including a small amount of nitrogen (about 10 wt%) in the supersonic shrouding methane gas without substantial negative impacts on the characteristics of the supersonic combustion coherent jet.

Development and validation of a new reduced diesel/natural gas mechanism under engine-relevant conditions

A simplified mechanism of diesel/natural gas blend was developed for a dual fuel engine built from a previously reported detailed mechanism of a n-dodecane and natural gas. In the model, n-dodecane was selected as the representative substance of diesel and the mixture of methane, ethane and propane was selected as the representative substance of natural gas. The simplified mechanism was obtained by using the direct relation graph, the directed relation graph with error propagation, and the sensitivity analysis simplification method. On this basis, a simplified n-dodecane-natural gas mechanism with 141 species and 739 reactions was established. In addition, the experimental data and detailed mechanism are used to compare with the n-dodecane-natural gas dual fuel simplified mechanism established in this paper, and have been widely verified in 0-D and 1-D combustion systems for the first time, including ignition delay time, laminar flame velocity, premixed flame species, HCCI combustion, which verify the rationality of the new simplified mechanism. Then the mechanism is coupled to CFD software to simulate the spray combustion of constant volume spray under engine like conditions. The results show that the mechanism has high reliability and can be coupled with CFD.

Non-LTE spectroscopy of the tetradecad region of methane recorded in a hypersonic flow

Laboratory spectroscopic data is essential for the modeling of hot exoplanet atmospheres, since molecules such as methane, a major component of hot-Jupiter-type exoplanet atmospheres, have a complex vibrational energy structure that makes computational predictions difficult at high temperatures for ro-vibrational transitions involving highly excited vibrational sates. To better inform line lists used in radiative transfer modeling, the ro-vibrational spectrum of methane has been recorded in the tetradecad region between 1.7 and 1.65 μm (5880–6060 cm−1) through non-local thermodynamic equilibrium (non-LTE) cavity ringdown spectroscopy (CRDS). Non-LTE conditions, characterized by a low rotational temperature (∼39 K) and a high vibrational temperature (up to 1130 K), have been obtained by hypersonic expansion of a pre-heated mixture of argon and methane in a contoured Laval nozzle. The high vibrational temperature increases the intensity of new hot bands, while the very low rotational temperature greatly simplifies their rotational structure, thus facilitating their identification. A close comparison of the recorded CRDS data to the TheoReTS database reveals both inefficient vibrational relaxation between polyads and efficient vibrational relaxation between vibrational states forming a polyad. These effects result in an overpopulation of the lowest vibrational energy level of each polyad, an effect not widely currently incorporated in non-LTE radiative transfer models. A series of new hot band transitions originating from the pentad and octad polyads were assigned and are provided as a line list for use in future databases.

Growth Conditions and Substrate Misorientation Angle Dependences of Silicon Incorporation in Chemical Vapor Deposition Diamond

The results of a study of the incorporation of silicon in diamond depending on the growth conditions of epitaxial layers in a chemical vapor deposition (CVD) reactor in a gas mixture of hydrogen, methane, and silane are presented. A detailed study of the effect of methane and silane flows, substrate temperature, gas mixture pressure, and substrate misorientation angle has been carried out. The influence of the surface misorientation angle on the formation of silicon‐vacancy (SiV) centers in diamond has been studied. It has been found that the carbon content in the gas mixture has a significant effect on the incorporation of silicon into diamond. Studies of the CVD growth of silicon‐doped diamond are carried out simultaneously with studies of the optical spectra of plasma emission in the reactor. The content of silicon in plasma is compared with content of silicon incorporated into diamond during CVD synthesis. The most efficient formation of SiV centers is observed for substrate misorientation angles from 2° to 4°.

RELIABILITY OF WATER CONTENT DATA FOR NATURAL GAS-HYDRATE SYSTEMS USING SEMI-EMPIRICAL CORRELATIONS

Water in natural gas can result in various operational problems, which may lead to equipment failure and plant shutdown. Knowing the amount of water capable of condensing from natural gas is essential. Many methods have been developed for ascertaining the amount of this condensable water (water content) from many gas mixtures. However, when hydrates are present, available methods for estimating the amount of condensable water are scarce and very limited in the open literature. The reliability of the data has always been a cause for concern due to the tendency for the inaccuracy of the results. In this study, two semi-empirical methods for ascertaining the amount of condensable water in natural gas with and without hydrates were used to test the reliability of the water content data of four different published natural gas-hydrate systems, including methane and propane gas mixture, raw/unprocessed, binary (methane + water), and synthetic natural gas. The results showed that only the data set for the methane and propane gas mixture was a reliable gas-hydrate equilibrium system, while the synthetic gas mixture needed further validation. Therefore, the methodology in this study can be used as a quick and simple means for ascertaining the reliability of water content data of natural gas-hydrate systems.