Methane In Phase Research Articles

Mathematical model of the liquefied methane phase transition in the cryogenic tank of a vehicle

In order to increase the efficiency of using vehicles (VEH) in mining and quarrying conditions, it is necessary to improve the components of gas equipment (cryogenic tank, gas nozzles, fuel supply cryogenic tubes, etc.) for supplying liquefied natural gas to the engine, as well as storage of liquid methane in a cryogenic tank with a long service life. For this, it is necessary to consider the process of heat and mass transfer of liquefied natural gas in a two-phase liquid-gas medium, taking into account the phase transition in the closed volume of the cryogenic tank under consideration.
 The article presents a model of unsteady heat and mass transfer of a two-phase liquefied methane medium in a developed two-tank cryogenic tank using a Cartesian coordinate system with fractional control volumes in space.
 The experimental data confirm the efficiency of using a cryogenic tank on the VEH platform, in which the run on liquefied methane compared to standard fuels is tripled, the shelf life of liquefied gas in the proposed cryogenic tank is 2-2.5 times longer than in the standard one.

Coexistence of plastic and partially diffusive phases in a helium-methane compound.

Helium and methane are major components of giant icy planets and are abundant in the universe. However, helium is the most inert element in the periodic table and methane is one of the most hydrophobic molecules, thus whether they can react with each other is of fundamental importance. Here, our crystal structure searches and first-principles calculations predict that a He3CH4 compound is stable over a wide range of pressures from 55 to 155 GPa and a HeCH4 compound becomes stable around 105 GPa. As nice examples of pure van der Waals crystals, the insertion of helium atoms changes the original packing of pure methane molecules and also largely hinders the polymerization of methane at higher pressures. After analyzing the diffusive properties during the melting of He3CH4 at high pressure and high temperature, in addition to a plastic methane phase, we have discovered an unusual phase which exhibits coexistence of diffusive helium and plastic methane. In addition, the range of the diffusive behavior within the helium-methane phase diagram is found to be much narrower compared to that of previously predicted helium-water compounds. This may be due to the weaker van der Waals interactions between methane molecules compared to those in helium-water compounds, and that the helium-methane compound melts more easily.

Image-based fracture pipe network modelling for prediction of coal permeability

In coal seam gas (CSG) reservoirs, the underlying fracture networks play a critical role in controlling flow pathways of methane and water phases. Thus, study of flow in fracture networks via different numerical modelling methods is of importance. Compared to direct flow simulation, the Fracture Pipe Network Model (FPNM) is an effective means of modelling fluid flow in a fracture network due to its computational efficiency. However, constructing FPNM for authentic samples is challenging due to the limited fracture data at the core scale. In addition, application of FPNM for coal is challenging due to its complex internal fracture network. With X-ray micro-computed tomography (micro-CT) imaging, internal fracture network of coal samples can be visualised non-destructively, providing deterministic input data for FPNM. However, analysing fractures individually and characterising network connectivity based on micro-CT images are difficult, due to complex interactions, irregular fracture geometry, resolution limitation and image noises. In this paper, we develop a framework for constructing image-based FPNM for real fractured coal cores for fast prediction of permeability. Compared with conventional FPNM, each pipe element of our improved FPNM has the identical properties (orientations, length, aperture and roughness) with its corresponding data from the real sample. By comparing permeability values obtained from FPNMs, micro-CT images and voxelised DFNs, we conclude that FPNM can effectively estimate the permeability of original fracture networks while requiring significantly lower computational cost that make it a suitable framework for expensive multi-phase multiphysics flow simulations.

Coalbed methane diffusion and water blocking effects investigated by mesoscale all-atom molecular dynamic simulations.

In coalbed methane extraction processes, the water blocking effect (WBE) is a formation damage that limits the extraction efficiency. To investigate WBE mechanisms at the molecular level, realistic coal models must be developed to simulate the interplay between methane and liquid phase water in a coal matrix's mesopores and macropores. This study built a massive and highly scalable coal tube model with accurate all-atom force fields. Based on this model, we investigated the adsorption and diffusion of methane and liquid water in the mesopores of coal. We found that methane forms multiple layers of adsorption on the coal surface, and the diffusivity of methane strongly depends on pore sizes and the presence of water. When both methane and liquid water were loaded in the coal tube, the liquid phase formed a nearly impenetrable barrier that prevented methane diffusion. This work provides insights into the mechanism of the WBE and can facilitate further studies on WBE alleviating strategies.

Two-Phase Improves Performance of Anaerobic Membrane Bioreactor Treatment of Food Waste at High Organic Loading Rates.

Anaerobic membrane bioreactors (AnMBRs) are in use at the full-scale for energy recovery from food waste (FW). In this study, the potential for two-phase (acid/gas) AnMBR treatment of FW was investigated as a strategy to increase microbial diversity, thereby improving performance. Two bench-scale AnMBRs were operated in single-phase (SP) and two-phase (TP) mode across incremental increases in organic loading rate (OLR) from 2.5 to 15 g total chemical oxygen demand (COD) L·d-1. The TP acid-phase (TP-AP) enriched total VFAs by 3-fold compared to influent FW and harbored a distinct microbial community enriched in fermenters that thrived in the low pH environment. The TP methane phase (TP-MP) showed increased methane production and resilience relative to SP as OLR increased from 3.5 to 10 g COD L·d-1. SP showed signs of inhibition (i.e., rapid decrease in methane production per OLR) at 10 g COD L·d-1, whereas both systems were inhibited at 15 g COD L·d-1. At 10 g COD L·d-1, where the highest difference in performance was observed (20.3% increase in methane production), activity of syntrophic bacteria in TP-MP was double that of SP. Our results indicate that AnMBRs in TP mode could effectively treat FW at OLRs up to 10 g COD·L day-1 by improving hydrolysis rates, microbial diversity, and syntroph activity, and enriching resistant communities to high OLRs relative to AnMBRs in SP mode.

Hydrocarbons under Pressure: Phase Diagrams and Surprising New Compounds in the C–H System

Understanding the high-pressure behavior of C-H system is of great importance due to its key role in organic, bio-, petroleum and planetary chemistry. We have performed a systematic investigation of the pressure-composition phase diagram of the C-H system at pressures up to 400 GPa using evolutionary structure prediction coupled with ab initio calculations and discovered that only saturated hydrocarbons are thermodynamically stable. Several stable methane-hydrogen co crystals are predicted: 2CH4 * H2, earlier obtained experimentally, is predicted to have I4/m space group and 2-90 GPa stability range at 0 K, and two new thermodynamically stable compounds 2CH4 * 7H2 (P-3m1 space group) and CH4 * 9H2 (Cm space group), as potential energy storage materials. P21/c phase of methane is predicted to be stable at pressures < 8 GPa; bulk graphane (CH) was shown to be thermodynamically stable at 7-18 and 18-50 GPa and 0 K in the P-3m and Cmca phases, respectively; polyethylene is shown to have a narrow field of stability. We report the p-T-x phase diagram of the C-H system and p-T phase diagram of CH4.

Impact of acetic acid in methane production from glycerol/acetic acid co-fermentation

Co-fermentation of glycerol and acetic acid in anaerobic digestion was set up to generate biogas in batch reactors under mesophilic condition, pH 7. The experiments were varied COD ratios of glycerol and acetic acid were varied with the total combined COD of 5,20 0 mg/L. The maximum methane yield was obtained from glycerol/acetic acid ratio of 6:4. The cumulative methane, production rate and lag phase were 240 mL, 14 mL hr−1, and 11 hr. The research indicated acetic acid boosted methane production when it was co-fermented with glycerol.

Investigation of methane/drilling mud phase behavior and its influence to hydrocarbon drilling activity

AbstractKnowledge of methane dissolution behavior in drilling mud is of major importance to early kick detection and well control operation in oil and gas drilling industry. In this work, methane solubility experiments in water‐based and oil‐based muds were conducted over wide ranges of temperature and pressure conditions. The influences of mud compositions and methane phases were investigated accordingly. It is found that methane solubility in water‐based mud is minimal and can be ignored. The data in oil‐based mud were analyzed using different equation of state and mixing rules. Our results show that the combination of our novel binary interaction parameter equations, Peng‐Robinson equation, and van der Waals2 mixing rule provides a very good representation of our data as well as those available in the literature. With the proposed model, the annulus methane solubility profile of a deepwater well in South China Sea was predicted, which provides a better understanding of the annulus flow behavior and further improve the safety of drilling operation.

Thermodynamic properties of CH4, CCl4 and CF4 on the melting line. Theory and computer simulation

Thermodynamic properties of the condensed phases of methane CH4, carbon tetrafluoride CF4 and carbon tetrachloride CCl4 on the melting line and in the high-pressure region were studied using the equations of state developed earlier for methane in the framework of the thermodynamic perturbation theory. We also present the results of Monte Carlo computer simulations of fcc phases of methane, carbon tetrachloride, and of the monoclinic tetrafluoromethane phase using a potential model that takes into account both the central and octupole–octupole interaction. The contribution of the octupole–octupole interaction to the thermodynamic properties of crystals are evaluated. The simulation results are compared with the available experimental data on the sublimation and melting lines, as well as to results of previous calculations based on the equations of state.

Bonding energy and methane amount at the open surface of metamorphic coal

Objective of the studies is to measure and determine regularities of changes in adsorption and methane energy bond with the open surface of mineral carbons within metamorphism series. Donbas mineral carbons have been used as the samples. Volumetric method has been applied in the range of room temperatures and pressures of free methane phase (i.e. 0.015 to 3.5 MPa) to measure methane amount at the open surface of the mineral carbons. Depending upon changes in carbon content, adsorption behaviour is close to parabolic one: adsorption is maximal on the peripheries of metamorphic series, and minimal within its central part. For the first time, methane energy bond with the open surface of mineral carbons has been determined. In the context of the metamorphic series, bonding energy varies from 2 to 10 kJ/mol. Direct linear dependence of adsorption from pressure takes place for coal where carbon content is less than 76 %. It is the result of effect of large area of open surface of low-metamorphized coal. Inversely, nonlinear dependence is observed as for anthracite. The authors connect the fact with filling of all spaces at the open surface when gas phase pressure is 0.1 MPa.

Quantum Impurity Rotator in a Matrix of Quantum Rotors: Electron Paramagnetic Resonance Dynamics of CH3 in Solid CD4 Matrix

The rotational dynamics and the geometry of a light and flexible impurity molecule like methyl, matrix isolated in van der Waals solid, are supposed to be sensitive to the host molecule dynamics and order alterations of the matrix. In addition, the location of the impurity and its interaction with the matrix molecules is of prime importance. Large energy gaps between rotation levels of quantum rotators allow precise investigation of temperature-assisted quantum tunneling effects. The molecular rotation of methyl radicals isolated in the deuterated solid methane isotopomer, CD4, was investigated both by experimental and theoretical electron paramagnetic resonance (EPR) methods. The reduction of the quantum rotation frequency evident from the EPR spectrum of methyl radical at liquid-He temperatures was explained and connected to the irregular ratio of the central doublet to the outer quartet hf transitions. The involvement of temperature in the alteration of methyl symmetry between the C3 and D3 groups and the molecular host-host and guest-host interaction strengths were also examined by constructing temperature profiles of the rotation correlation times in the three phases of solid methane. The present study proves the deep impact that a van der Waals matrix may have on the geometry and the rotation levels of a substitutionally trapped quantum impurity rotor, effects that are yet very little known. This close correlation between dynamics of an impurity particle and the matrix molecules has great potential in developing sensitive physicochemical probes for van der Waals solids.

Fluid–fluid interfaces in metal-organic frameworks

ABSTRACTGrandcanonical Monte Carlo simulations in combination with successive umbrella sampling are used to study interfaces in the metal-organic frameworks (MOFs) IRMOF-1 and IRMOF-8. These interfaces are between coexisting phases of methane (CH) fluids that form on the surface of the framework structures of the latter MOF systems. Approaching the critical point of the corresponding demixing transition, the interfacial free energy as well as the interfacial width show a power-law scaling, as expected for the universality class of the three-dimensional Ising model. Capillary waves are strongly suppressed due to the external potential imposed by the framework structure. In IRMOF-8, density profiles of inhomogeneous systems with fluid–fluid interfaces show pronounced oscillations due to the crystalline framework structure.

Analysis of three-phase equilibrium conditions for methane hydrate by isometric-isothermal molecular dynamics simulations.

To develop prediction methods of three-phase equilibrium (coexistence) conditions of methane hydrate by molecular simulations, we examined the use of NVT (isometric-isothermal) molecular dynamics (MD) simulations. NVT MD simulations of coexisting solid hydrate, liquid water, and vapor methane phases were performed at four different temperatures, namely, 285, 290, 295, and 300 K. NVT simulations do not require complex pressure control schemes in multi-phase systems, and the growth or dissociation of the hydrate phase can lead to significant pressure changes in the approach toward equilibrium conditions. We found that the calculated equilibrium pressures tended to be higher than those reported by previous NPT (isobaric-isothermal) simulation studies using the same water model. The deviations of equilibrium conditions from previous simulation studies are mainly attributable to the employed calculation methods of pressure and Lennard-Jones interactions. We monitored the pressure in the methane phase, far from the interfaces with other phases, and confirmed that it was higher than the total pressure of the system calculated by previous studies. This fact clearly highlights the difficulties associated with the pressure calculation and control for multi-phase systems. The treatment of Lennard-Jones interactions without tail corrections in MD simulations also contributes to the overestimation of equilibrium pressure. Although improvements are still required to obtain accurate equilibrium conditions, NVT MD simulations exhibit potential for the prediction of equilibrium conditions of multi-phase systems.

Variations in Gas and Water Pulses at an Arctic Seep: Fluid Sources and Methane Transport

AbstractMethane fluxes into the oceans are largely dependent on the methane phase as it migrates upward through the sediments. Here we document decoupled methane transport by gaseous and aqueous phases in Storfjordrenna (offshore Svalbard) and propose a three‐stage evolution model for active seepage in the region where gas hydrates are present in the shallow subsurface. In a preactive seepage stage, solute diffusion is the primary transport mechanism for methane in the dissolved phase. Fluids containing dissolved methane have high 87Sr/86Sr ratios due to silicate weathering in the microbial methanogenesis zone. During the active seepage stage, migration of gaseous methane results in near‐seafloor gas hydrate formation and vigorous seafloor gas discharge with a thermogenic fingerprint. In the postactive seepage stage, the high concentration of dissolved lithium points to the contribution of a deeper‐sourced aqueous fluid, which we postulate advects upward following cessation of gas discharge.

Analysis of Biphasic Cracking of Methane for Hydrogen Production Using Solar Energy

Hydrogen can be produced by many processes, by a series of chemical reactions many of which have been known for centuries. However, most of these reactions raise severe environmental and safety problems, while availability of raw materials is a critical problem. One of the partial solutions is solar hydrogen. It appears that cracking of carbon-rich materials is the right solution for this energy. In this context comes this numerical simulation of the methane cracking phenomenon. In the simulation, we have taken in to account the existence of carbon as a homogeneous powder. The mixture is considered to be biphasic formed by a gaseous phase with methane, hydrogen gases and carbon black powder solid phase. This powder is formed by solid particles with same diameter (d=50nm). The cracking phenomenon of the methane into hydrogen and carbon black takes place in a cylindrical cavity of 16 cm in diameter and 40 cm in length under the heat of concentrated solar radiation without any catalyst. A commercial calculation code ANSYS FLUENT is used to simulate the cracking phenomena. Two cases were studied: the first one applying a maximum solar radiation of 16MW/m 2 on the side wall of the reactor and the second one a maximum solar radiation of 5 MW/m 2 . The CH 4 flow rate used at the inlet of the reactor is 0.4 L/min and the low Reynolds K - e turbulence model was applied. A time step of 0.04s has been used.The cracking rate exceeds 90% with a maximum solar radiation of 16MW/m 2 and this rate does not reach 85% with a maximum solar radiation of 5MW/m 2 .The dimensions of the cavity are important and it allows going from the experimental scale to the industrial scale. Working without any catalyst facilitates the separation of the elements after cracking.

Thermophysical properties of aqueous lysine and its inhibition influence on methane and carbon dioxide hydrate phase boundary condition

In this study, the thermophysical properties of lysine amino acid, alongside its methane and carbon dioxide hydrate inhibition effect is reported. The physical properties (density, viscosity, and refractive index) of aqueous lysine solution are measured at 5 wt% and 10 wt% in the temperature range of 298.15–313.15 K at 5 K intervals. The hydrate inhibition potential of lysine is tested in the temperature and pressure range of 1.87–10.45 MPa and 276.45–285.15 K, respectively, at 5 wt% and 10 wt% using the T-cycle method in a sapphire cell hydrate reactor. The density, viscosity and refractive index of the aqueous lysine solution are found to increase with increasing concentration, but decreases with increasing temperature. Furthermore, the presence of lysine significantly inhibited both methane and carbon dioxide hydrate by shifting the methane and carbon dioxide hydrate equilibrium phase boundary condition to higher pressures and/or lower temperatures region. The lysine hydrate inhibition impact is increased with increasing concentration. An average depression temperature of 1.44 K and 1.49 K is observed at 10 wt% for methane and carbon dioxide hydrate, respectively. In addition, the hydrate dissociation enthalpies in the presence and absence of lysine are calculated using the Clausius-Clapeyron equation. The findings are useful as it presents data which can be used to understand the effect of amino acids physical properties on their thermodynamic hydrate inhibition influence.

Refractive indices and density of cryovacuum-deposited thin films of methane in the vicinity of the α-β-transition temperature

Experimental studies of the effect of methane condensation temperature on the value of the refractive index and density of the resulting thin films are reported. The main unit of the installation is a high-vacuum chamber, which routinely operates at 10−8–10−6 Torr. Measurements using a two-beam He–Ne laser interferometer in the vicinity of the methane phase transition temperature T = 20.4 K in the range of 14–32 K were carried out. It has been shown that in the vicinity of T = 20 K the temperature dependence of the refractive index undergoes an abrupt decrease with decreasing temperature. It is assumed that this gap is the result of the phase transition from the orientational disordered phase (α-phase) to the partially ordered phase (β-phase) of solid methane. The calculations of the polarizability of the methane molecules in the solid phase at two values of the deposition temperature T = 16 K and T = 30 K were performed using the Lorentz–Lorenz equation.

Polarizability of Methane Deposits

This paper presents results of an experimental study of the influence of deposition temperature on the refractive indices of methane in the form of cryovacuum deposited thin films. The experiments were performed in the vicinity of temperature of methane phase transition $$T=20.4$$ K. The results allowed to determine the polarizability of methane molecules in the solid phase. The measurements were taken using a two-beam laser interferometer in the temperature range of 14–32 K. Calculations of polarizability were performed using the Lorentz–Lorenz equation by analogy to the calculations of the polarizability of carbon dioxide carried out in Domingo’s article. The polarizability of methane demonstrates the dependence on deposition temperature, and it has small jump at the temperature of a structural phase transformation. It is speculated that the observed abrupt change in the refractive index is due to a difference in the numbers of vibrational and rotational degrees of freedom of the molecules belonging to different structural phases of the methane.

On the effect of laser irradiation and heat treatment on the structure and field-emission properties of carbon nanowalls

The composition and structure of carbon nanowalls formed on silicon substrates from the gas phase of hydrogen and methane activated by a direct-current glow discharge are studied by methods of scanning electron microscopy, X-ray diffractometry, IR spectroscopy, and Raman spectroscopy. It is shown that nanowalls are comprised of a porous material consisting of curved lamellar (flaky) crystallites with a thickness of 3–10 nm. The effect of heat treatment and laser irradiation in air on the structure of the carbon nanowalls is studied, and the current–voltage characteristics of field-emission cathodes on their basis are obtained. The heating temperatures and laser-radiation power densities at which the morphology of the surface of carbon nanowalls changes and the characteristics of field-emission cathodes on their basis are determined.

Direct Measure of the Dense Methane Phase in Gas Shale Organic Porosity by Neutron Scattering

We report the first direct measurements of methane density in shale gas using small-angle neutron scattering. At a constant pressure, the density of methane in the inorganic pores is similar to the gas bulk density of the system conditions. In contrast, the methane density is 2.1 ± 0.2 times greater in the organic mesopores. Classical density functional theory calculations show that this excess density in the organic pores persists to elevated temperatures, typical of shale gas reservoir conditions, providing new insight into the hydrocarbon storage mechanisms within these reservoirs.