Methane Flow Rate Research Articles

A Comparative Study of a:SiCN:H Thin Films Fabricated with Acetylene and Methane

In this paper we present a comparative study of the properties of amorphous hydrogenated silicon carbonitride (SiCN:H) thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD). The elemental composition, growth rate, density, and refractive index values of the SiCN:H thin films were analyzed as functions of flow rates of pure acetylene (C2H2) and methane (CH4) hydrocarbon precursors. The mechanical properties were studied with nanoindentation measurements to compare hardness and Young’s modulus of the SiCN:H thin films deposited with different carbon sources. Variable angle spectroscopic ellipsometry (VASE), elastic recoil detection (ERD), and Rutherford backscattering spectrometry (RBS) were used to determine thin film properties. Higher carbon content in the thin films was achieved by acetylene compared to methane at the same flow rate due to its lower ionization energy during the deposition. Infrared (IR) absorption spectra of the thin films deposited with acetylene precursor were analyzed to determine the correlation between the hydrocarbon flow rate and the intra-molecular bond intensities in the thin films. We found that the major contribution to the hardness comes from hydrogen (H) in the SiCN matrix which makes the films less dense. Carbon improves the hardness, however, H introduced by the hydrocarbon reduces the mechanical strength.

On design of plasma jet reactor for non-oxidative methane conversion.

Non-oxidative methane coupling in an atmospheric pressure plasma jet reactor with an internal diameter of 3.0 mm has been studied. The jet reactor consisted of a quartz tube surrounded by a copper ring and a stainless-steel tube, which were separated by a variable distance. The stainless-steel tube (inner diameter: 1.0 mm, outer diameter: 1.5 mm) served as high voltage electrode and gas inlet. The jet characteristics with different tip angles of the high voltage electrode were investigated using voltage-current waveforms and gas analysis at a constant methane flow rate of 100 ml min-1. The effect of the length of the ground electrode and the gap between the electrodes on conversion, C2 selectivity and energy efficiency has been studied. The methane conversion was nearly tripled with a sharp angle of the electrode (15°), while the energy consumption was reduced from 150 to 55 kJ molC2H y -1. The carbon deposition was also reduced.

Equivalence ratio independence and dependence ranges of system responses for a nonlinear thermoacoustic oscillation in a Rijke tube

Thermoacoustic instabilities in a combustion system remains a challengeable problem in industry over decades. It usually involves with the nonlinear interaction between unsteady heat release and pressure fluctuations. The nonlinear oscillation excited by this interaction can be intense enough to result in combustion problems even severe damage of the engine. Therefore, it is important to understand the system response to various parameters. In this study, the system nonlinearity to equivalence ratio change was mainly focused on. A Rijke tube system with a premixed methane-air laminar flame was utilised to trigger the self-excited oscillations with varied equivalence ratios (Φ). The time-domain analysis methods including phase difference, Recurrence Plot (RP) and Recurrence quantification analysis (RQA) were applied to obtain the characteristics of system nonlinearities. Both Φ-independence and Φ-dependence ranges of system frequency responses have been discovered. The results of phase difference and recurrence analysis have also validated the finding of both ranges. The corresponding characteristics of system nonlinearity in both ranges have been investigated. The similarity among the systems in the Φ-independence range under the same burner position and methane flowrate can be highlighted from the system frequency response, phase difference and system dynamics. It is found that the phase difference analysis, RP and RQA utilised in this study are capable of investigating the nonlinearities of the self-excited thermoacoustic oscillation.

The Model of Cohesionless Sediment Blowout with an Increase in the Methane Flow Rate

Dissociation of methane hydrates in the Arctic permafrost may lead to explosive gas emission. Methane blowout may be triggered by increasing gas flow rate at a certain depth. The mechanism of rock failure and blowout under the effect of pressurized gas was studied numerically and in laboratory experiments. The problem was formulated for the unsteady flow of compressed gas depending on the flow rate at a given depth, and pore gas pressure variations were calculated as a function of depth and time. The model parameters were chosen with reference to field data. According to the model, the input of gas to friable material at an increasing rate may lead to gas blowout and density loss propagating downward as the gas pressure exceeds the overburden pressure at some depth. The laboratory system was of the type of a Hele-Shaw cell, with small glass balls as friable material confined between two glass panels. The results of physical modeling and calculations show good agreement.

Application of oil in situ combustion for the catalytic methane conversion in the porous medium of the gas reservoir

Catalytic methane conversion (CMC) could be realized in situ in gas reservoirs. Through this process, a new environment-friendly energy carrier - hydrogen-can be generated inside the hydrocarbon field's porous medium. This method can become a new low-carbon, cost-effective method for hydrogen production. For this purpose, the catalyst has to be delivered into the reservoir, and the temperature inside the active zone of the reservoir has to be raised. The effective way to increase the temperature directly inside the reservoir is by injection of air and combustion of saturating liquid hydrocarbons. This research investigates the CMC process at conditions achieved in the reservoir due to oil in situ combustion (ISC). Numerical and physical modeling of in situ hydrogen generation from methane was performed using forward wet ISC of oil to heat the reservoir. The results of the unique experiment on a crushed oil-saturated core-packed model with different inlet flow rates of air, steam, and methane in the combustion tube (CT) are presented in the current study. The experiment consisted of four parts with different regimes and operational parameters: forward ISC of oil, steam methane reforming (SMR) at 450 °C and 8.9 MPa, SMR at 550 °C and 8.9 MPa, SMR at 550 °C and 2.3 MPa. The combination of these processes has led to the generation of hydrogen and methane conversion rates of up to 40% (during the combustion stage). Comparatively, low hydrogen yield was observed within the experiment, possibly due to the secondary reactions. However, irreversible reduction of oil viscosity, density, sulfur, and asphaltenes content was achieved within the experiment. The influence of catalyst and generated hydrogen on oil quality is one of the additional positive effects of in situ hydrogen generation. The numerical simulation of the experiment was performed for further study of the optimal hydrogen generation conditions. The proposed kinetic model consisted of ISC reactions and hydrogen generation reactions. The primary purpose of this experiment was to validate the principle study of the possibility of in situ hydrogen generation and simulate the processes in the core model physically and numerically.

Optimization of sputter-deposited corrosion resistant a-C(:H) films with excellent tribological performance by control of methane flow rate

To meet the lubrication demand in the maritime sector, hydrogenated amorphous carbon (a-C:H) films with low friction coefficient and excellent corrosion resistance were deposited at different methane flow rates by control sputtering technique. Studies have shown that the increment of CH4 flow rate raised the growth rate and compactness of a-C(:H) films while decreased the hardness, the adhesion force was enhanced. The film had the best tribological performance at 5 sccm CH4 gas flow rate, with a friction coefficient of about 0.1 (in air) / 0.04 (in salt solution) and a wear rate of 1.0 × 10−9 mm3/Nm / 6.2 × 10−8 mm3/Nm. With increasing CH4 flow rate, the corrosion resistance of the films improved. And 10 sccm was the optimal for the comprehensive performance of the film.

Effect of radial flows in fuel channels on thermal performance of counterflow tubular solid oxide fuel cells

Increasing the volumetric power density of solid oxide fuel cell (SOFC) stacks could enable their wider adoption in powering vehicles. The radial flows generated by inserts in gas channels of the tubular SOFC could enhance electrochemical reactions in porous electrodes and improve the power density. In this study, numerical simulations are performed to examine the influence of the enhanced exothermic electrochemical reactions on the temperature distributions in a counterflow tubular SOFC with inserts. We show that the radial flow in the fuel channel could improve the SOFC power density by 30% but lead to an increase in the maximum cell temperature gradient from 12 ℃/cm to 23 ℃/cm. The effects of radial flows under different inlet mass flow rates of hydrogen and methane are also examined. Compared with the conventional tubular SOFC, the percentage of power density improvements and the maximum cell temperature gradients of the tubular SOFC with inserts both increase with increasing inlet hydrogen mass flow rates. The maximum cell temperature gradient is increased from 12.8 ℃/cm to 47.5 ℃/cm as the percentage of net power density improvement is increased from 20% to 45%. We also demonstrate that increasing the inlet methane flow rate could adversely affect the SOFC performance, since the strong radial flow can remove the steam in porous anode, which impedes the methane steam reforming reaction and consequently reduces the output power density. The present work helps improve our understanding of heat and mass transfer characteristics of the radial flows in the tubular SOFC and helps build a foundation for SOFC channel designs.

Preparation and Tribological Properties of Graphene-Based Coatings on Tungsten Carbide

The preparation technology of graphene-based coatings on cobalt-based cemented carbides and the friction properties of graphene-based coatings were researched. Based on cooling rate, growth temperature, and methane flow rate, Raman spectroscopy was used to evaluate the influence of chemical vapor deposition (CVD) on graphene-based coatings. The results show that at the growth temperature of 1000 °C, the cooling rate of 15 °C/min and methane flow rate of 10 sccm are more favorable for the growth of pure graphene coating with fewer layers on a cemented carbide surface. As methane flow boosts, the number of graphene layers increases and amorphous carbon is generated. The resulting tribological properties demonstrate that the friction coefficient of graphene-based coatings decreases as the friction load increases. The above results indicate that the graphene-based coating on a cemented carbide surface can be prepared by regulating its composition and defects through technological parameters, and it is viable to use graphene-based coating as anti-wear coating for cutting tools. The results provide a reference for the preparation and properties of cemented carbide surface graphene.

Solar-driven chemical looping reforming of methane over SrFeO3-δ-Ca0.5Mn0.5O nanocomposite foam

Strontium ferrite (SrFeO3-δ) is a very attractive oxygen transfer agent for chemical looping reactions and hydrogen-rich syngas generation. Dispersing SrFeO3 in a medium such as Ca0.5Mn0.5O could enhance the activity and cyclability. In this study, SrFeO3-δ-Ca0.5Mn0.5O (30 wt% SrFeO3-δ) nanocomposite with a reticulated foam structure was explored as the oxygen carrier for chemical looping reforming of methane in a solar tubular reactor. The foam nanocomposite was prepared by a hard-templating method. The performance was investigated at temperatures of 850–1000 °C and methane flowrates of 25–250 STP mL/min, and the oxidative gas was either CO2 or H2O in the oxidation step. In the reduction step of 27 successive redox cycles, the production rate of CO changed marginally and CO yield maintained at about 1.9 mmol/g, even though sintering occurred. The productivity of H2 decreased first and then tended to be stable at 3.8 mmol/g (i.e., twice the CO yield) as the cycling number increased (the average oxygen storage capacity of the material was ∼1.95 mmol/g). Microscopic and X-ray diffraction investigations suggested that the element distribution pattern and crystalline phase of the foam nanocomposite remained almost unchanged after 27 redox cycles, confirming material stability. The maximum solar-to-fuel efficiency for the foam nanocomposite was 5.68%, which was 21.4% higher than that for the powder nanocomposite. To increase syngas productivity and solar-to-fuel efficiency, it is required to conduct the reforming reaction at high temperatures and methane flowrates. However, the energy upgrade factor will decrease as methane flowrate increases.

Modelling of anaerobic digester for the conversion of organic waste into hydrogen & methane

Multistage Anaerobic digestion (AD) nowadays plays a beneficial role compared to single-stage AD to achieve a high rate of waste conversion with higher energy recovery. Hence, obtaining a stable operation with optimal operating conditions is of paramount importance in the modeling study. In the current study, modeling of two stages continuous stirred anaerobic digesters was considered using mass balances over the substrates (organic waste) and biomass in the respective reactor. All the simulation work was performed using MATLAB, from which steady-state concentration values were taken for the calculation of Hydrogen flow rate (QH2) and Methane flow rate (QCH4). The operating volumes of both the reactors were computed by looking at the effect on the production rates (QH2 &QCH4) as a function of dilution rate of first (D1) and second (D2) reactors for constant initial substrate concentration (S0). At last, the effect of Initial substrate concentration on both QH2 &QCH4 was studied by considering different S0 values as 4 g/L, 8 g/L, and 12 g/L. From our modeling result, it was found out that for Maximum Hydrogen production, operating D1 (in day-1) was 0.8, 0.9 & 1 and the Methane production rate was Maximum at operating D2 (inday-1) of 0.25, for S0 values of 4 g/L, 8 g/L, and 12 g/L respectively.

Effect of Staged Methane Flow on Graphene Quality of Low-Pressure Chemical Vapor Deposition

The chemical vapor deposition method and the method using copper are suitable for high-quality large-area graphene synthesis. Here, we present methane flow conditions for obtaining high-quality graphene over a large area. The conditions of gases other than the flow rate of methane were fixed, and the graphene synthesized by adjusting the flow rate of methane and the exposure time of methane was verified through the Raman spectrum. When the methane flow rate was 5 sccm, the growth of graphene was island-shaped and made into a multilayer graphene. When the methane flow rate increases to 8 sccm, the Irish growth of graphene disappears and stably grows into a single layer. However, if the flow rate exceeds 9 sccm, Irish growth disappears. However, in order to minimize the area where graphene in the multilayer is synthesized, the methane exposure time was analyzed in units of 10 minutes from 5 minutes to 25 minutes. When analyzing the I[2d]/I[g] value and I[d]/I[g] value of the Raman spectrum, single-layer graphene of a large area could be observed.

Experimental investigation of the high temperature chlorination of methane in a tubular reactor

High temperature methane chlorination offers an alternative process route to the utilization of methane, since the presence of chlorine lowers the pyrolysis temperature. Chlorine, methane and nitrogen were introduced in a tubular reactor while varying hydrogen to chlorine ratios at temperatures ranging from 600 °C to 1000 °C. The chlorine conversion rates, hydrogen chloride yields, and the chlorine content in the soot were determined. While complete conversion of the limiting reactant was found in most experiments, differing trends were observed for the hydrogen chloride yield. Chlorine was almost always found in the carbon. At the same methane flow rate, a tendency for carbon formation was ascertained to depend on the amount of chlorine supplied, with the most extensive deposits being formed for a hydrogen to chlorine ratio of unity. Furthermore, in the case of high chlorine excess, crystalline products form at the reactor outlet.

Solar energy exploitation and storage in a novel hybrid thermo-electrochemical process with net-zero carbon emissions

The remarkable growth in global energy demand and greenhouse gas emissions necessitates the development of methods for efficient and reliable exploitation of sustainable and carbon-neutral energy sources. Chemical hydrogen storage is one of the efficient methods for converting renewable energy into valuable fuels for energy storage and transportation. This paper designs a novel hybrid process for simultaneous production of liquid methanol, ammonia, and heavy hydrocarbons using the combustion products of hydrocarbons emitted from industrial plants and methane. It mainly consists of several subprocesses including thermo-electrochemical cycle, CO2 capture, ammonia and liquid methanol production, and gas to liquid (GTL). CO2 is captured and utilized for the production of liquid methanol. Photovoltaic panels and parabolic trough collectors provide electrical and part of the thermal required in the process. The structure produces 17.95 kg h−1 methanol, 45.54 kg h−1 heavy hydrocarbons, and 20.44 kg h−1 ammonia. The thermal efficiencies of the methanol production cycle, GTL cycle, and the hybrid structure are 86.64%, 51.06%, and 15.00%, respectively. Exergy analysis indicates that photovoltaic panels have the maximum exergy destruction share (71.09%) followed by reactors (18.72%). Sensitivity analysis results show that the decline in the mass flow rate of methane from 9 to 5 kg h−1 leads to an increase in the integrated structure's total thermal and exergy efficiencies to 18.28% and 28.54%, respectively. Besides, a decrease in the mass flow rate of CO2 from 30 to 10 kg h−1 raises the exergy efficiency of the integrated structure to 21.99%. The methanol production rate and exergy efficiency of the methanol production cycle are reduced to 6.932 kg h−1 and 34.62%.

A Wavelength Modulation Spectroscopy-Based Methane Flux Sensor for Quantification of Venting Sources at Oil and Gas Sites.

An optical sensor employing tunable diode laser absorption spectroscopy with wavelength modulation and 2f harmonic detection was designed, prototyped, and tested for applications in quantifying methane emissions from vent sources in the oil and gas sector. The methane absorption line at 6026.23 cm–1 (1659.41 nm) was used to measure both flow velocity and methane volume fraction, enabling direct measurement of the methane emission rate. Two configurations of the sensor were designed, tested, and compared; the first used a fully fiber-coupled cell with multimode fibers to re-collimate the laser beams, while the second used directly irradiated photodetectors protected by Zener barriers. Importantly, both configurations were designed to enable measurements within regulated Class I / Zone 0 hazardous locations, in which explosive gases are expected during normal operations. Controlled flows with methane volume fractions of 0 to 100% and a velocity range of 0 to 4 m/s were used to characterize sensor performance at a 1 Hz sampling rate. The measurement error in the methane volume fraction was less than 10,000 ppm (1%) across the studied range for both configurations. The short-term velocity measurement error with pure methane was <0.3 m/s with a standard deviation of 0.14 m/s for the fiber-coupled configuration and <0.15 m/s with a standard deviation of 0.07 m/s for the directly irradiated detector configuration. However, modal noise in the multimode fibers of the first configuration contributed to an unstable performance that was highly sensitive to mechanical disturbances. The second configuration showed good potential for an industrial sensor, successfully quantifying methane flow rates up to 11 kg/h within ±2.1 kg/h at 95% confidence over a range of methane fractions from 25–100%, and as low as ±0.85 kg/h in scenarios where the source methane fraction is initially unknown within this range and otherwise invariant.

Effect of methane on magnetron sputtering graphite target deposited films and tribological properties of a‐C:H:Ti/a‐C:H friction pairs

In this study, we prepared a‐C:H films with different nanostructures at different methane flow rates. The effect of the methane flow rate on the tribological properties of 440 steel/a‐C:H friction pairs and a‐C:H:Ti/a‐C:H friction pairs in an atmospheric environment was studied by a reciprocating friction machine. The results show that there is no relationship between the tribological properties of 440 steel/a‐C:H friction pair and methane flow rate. The tribological performance of the a‐C:H:Ti/a‐C:H friction pair was greatly improved. In particular, in the friction pair of a‐C:H:Ti/a‐C:H with a methane flow rate of 20 sccm, superlubricity is shown, and the wear rate is only 4.04 × 10−9 mm3/Nm. After tribological experiments, Raman spectroscopy, XPS, and other characterization methods were used to study the relationship between the nanostructure and tribological properties of a‐C:H:Ti films and a‐C:H prepared with different methane flow rates. This study is great significance to the application of a‐C:H:Ti/a‐C:H friction pair in mechanical parts under atmospheric environment.

Thermodynamic modeling of in-situ rocket propellant fabrication on Mars

SummaryIn-situ resource utilization (ISRU) to refuel rockets on Mars will become critical in the future. The current effort presents a thorough feasibility analysis of a scalable, Matlab-based, integrated ISRU framework from the standpoint of the second law of thermodynamics. The ISRU model is based on existing technology that can utilize Martian resources (regolith and atmosphere) to produce rocket propellants. Model simulations show that the system analysis is theoretically consistent with a positive entropy generation, and the achievable mass flow rates of liquid methane and liquid oxygen can potentially meet the 16-month rocket refueling deadline (on Mars) as desired by the National Aeronautics and Space Administration. However, the model is sensitive to liquid oxygen storage temperatures, and lower temperatures are necessary to minimize compressor work. This proof-of-concept model can open avenues for further experimental evaluation of the system to achieve a higher technology readiness level.

Design of gas collection systems: Issues and challenges.

The design of a gas collection system (GCS) for a landfill involves estimating several critical parameters, such as the radius of influence (ROI), suction pressures, number of wells and their spacing. One of the biggest challenges lies in the estimation of ROI for a particular landfill. In this study, the ROI for a Bagalur landfill is estimated for various possible gas generation rates. ROI for active and passive GCS is estimated with numerical modelling (two-dimensional) for all definitions of ROI at different suction pressures. An inverse correlation was observed between the values of various definitions of ROI at different gas generation rates. Justification for this behaviour is brought out by addressing the conceptual difference between these definitions. The number of wells along with their spacing was then calculated, and the efficiency of the design was assessed with three-dimensional modelling. Passive and active systems had average methane recovery rates of 84% and 88%, respectively, with an atmospheric methane flux ranging from 10-9 to 10-10 kg m-2 s-1. The high recovery rate and low methane flux indicate the effectiveness of the design. The values of the methane flow rate from the extraction well were validated with a theoretical method, suggesting the usability of the model for future investigations.

A novel dynamic method for the storage of calibration gas mixtures based on thermal mass flow controllers

A dynamic method for the storage of calibration gas mixtures is presented using thermal mass flow controllers (MFCs) connected to a dead end volume. The approach relies on barometry to calibrate the unknown constant volume and two MFCs which regulate the flow rate of carbon dioxide and methane respectively. Binary gas mixtures of these components are prepared and stored within the calibrated volume tank up to 9 bar at ambient temperature. Thermodynamic data of pressure, temperature and density of the gas mixtures are retrieved. The expanded uncertainties at 95% confidence level of the molar fraction and the density of the mixture are evaluated. FTIR Spectroscopy is used in situ to analyse the gas mixtures.

The effect of plasma discharge on methane diffusion combustion in air assisted by an atmospheric pressure microwave plasma torch

An atmospheric pressure air microwave plasma torch is employed to assist methane diffusion combustions using a combination of a combustor and burner. Experimentally, the effect of the air microwave plasma on combustion is investigated with respect to the flame morphology and the variation of gas components in the exhaust with the fuel equivalence ratio φ or the methane flow rate by comparing plasma-assisted combustion (PAC) and natural combustion (NC) without plasma application. The combustion degree of CH4 in PACs is found to be much enhanced in rich fuel combustion than in NC in both types of burners, which is measured by Fourier transformation infrared spectrometer (FTIR). In PACs, with the use of an air microwave plasma torch, the radicals originating from excitation, ionization, and dissociation of N2 and O2 and the high gas temperature induced in the plasma discharge play an important role in assisting the combustion.

CO2 Gas Fracturing in High Dip Angled Coal Seams for Improved Gas Drainage Efficiency at Hashatu Coal Mine

Effective gas drainage for the gassy coal seam is a technological measure to prevent excessive gas outing and gas related mine hazards. CO2 gas fracturing (CO2-Frac) is a new technology for coal mine gas control, and its effectiveness has been proven from many coal fields across China. CO2-Frac has been successfully implemented for gas drainage in single gently inclined coal seam, but it has not been experimented in steeply inclined multicoal seam. In this study, a pilot CO2-Frac project was carried out in Hashatu coal mine, a steeply inclined multicoal seam formation. To attain an effective gas drainage, three different types of CO2- Frac boreholes were drilled and experimented for a long-period gas drainage. One borehole type is the penetrating borehole through two seams, and other two types of in-seam boreholes include strike borehole and up-dipping borehole. With continuous field gas drainage and observation results, the gas drainage efficiency was found to be significantly improved in in-seam borehole and penetration borehole with CO2 fracturing, and the maximum methane flow rate increased 2.4 times for a given borehole length and the efficient drainage radius increased 3–4 times. In addition, the drainage effect of original drainage boreholes within the CO2-Frac circle influenced region was also significantly improved due to the borehole interference. The fractures radius of CO2-Frac in the penetrating borehole was larger than the two types of in-seam boreholes in the steeply inclined seam formation. This may be closely related to the developing property of bedding and cleat system in coal seam. This study provides both theoretical and practical evidence for effectiveness CO2-Frac in the area with steeply inclined angle and multicoal seam formations.