Performance of Leach-bed Reactor with Immobilization of Microorganisms in Terms of Methane Production Kinetics
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The 4th IPCC report demonstrated that sea level rise is from 0.18 to 0.59 m and the increase in temperature is from 1.1 to 6.4 degrees. Methane is considered one of the most influential gasses on climate change, and the previous studies demonstrated that about one-fourth of methane emission is given from lakes and wetlands. However, the mechanisms of the occurrence of methane is not clarified enough. Therefore, this study aims to develop the transportation model of methane from a lake by applying 3D numerical model. As a result, it is revealed that methane emission from bottom layer, methane decomposition of an aerobic microbe and methane decomposition of an anaerobic environment are key factors for the emission of methane in a lake.
Methane Emissions
Atmospheric methane
Methane gas
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The influence of length of pressure measurement room and methane release amount in sealing hole on measurement accuracy was analyzed on the basis of methane content in coal body.An expression of original methane pressure,measured methane pressure,length of pressure measurement room and methane release amount in sealing hole was deduced based on ideal gas state equation and Langmiur equation.Methane pressure measured was modified.Calculation showed that length of pressure measurement room was longer,release methane amount was larger in sealing hole and the error between measured methane pressure and original methane pressure was larger.So the length of pressure measurement room should be reduced as much as possible to improve hole-sealing rapid.
Methane gas
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Clathrate hydrate
Methane gas
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In recent years, the use of a natural gas expands to a new energy source. The generation of carbon dioxide from a methane is less than an old fossil fuel. But the storing efficiency of a natural gas is not enough because the methane which is the principal ingredient of the natural gas is a gas in normal temperature and the normal pressure.However, since the methane hydrate contains greater methane than the volume of the methane gas by 100 times, if the methane is made from the methane hydrate the storing efficiency is greatly improved.This paper discusses the behavior of the methane molecules and the water molecules depending on the conditions of the temperature and the density by the computer simulation used Molecular Dynamics method (MD method).
Clathrate hydrate
Methane gas
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Atmospheric methane
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Measurements have been made of the relaxation frequency and vibrational specific heat of mixtures of oxygen and methane, with the methane concentration varying from 0.05% to 1.6%. The temperature in all cases was 23°C and the total pressure of the mixture atmospheric. Results of these measurements show that the relaxation frequency does not vary linearly with methane concentration and that the vibrational specific heat is concentration dependent. Theoretical interpretation of these results indicates that there is a strong coupling of the vibration of oxygen to that of methane and that losses due to radiation from the methane are significant. It is further determined that methane is approximately as effective in exciting vibration in oxygen as in itself and that oxygen is considerably less efficient in exciting vibration in methane. Supplementary measurements were also made on pure methane and methane dilute in gases characterized by their vibrational inertness — N2, Ne, Ar, and Kr. The relaxation time of pure methane was found to be in excellent agreement with values determined by previous investigators. Nitrogen was found to have a measurable effect in shortening the relaxation time of methane; surprisingly, Ne, Ar, and Kr were all found to be more effective than nitrogen.
Vibrational energy relaxation
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The exchange of methane between clathrate phase and gas phase on artificial methane hydrate was studied. Artificial methane hydrate samples were formed in a pressure cell from methane gas with stable carbon isotope composition δ13C of －42.3‰（ methane A）. Methane A remaining in the gas phase was removed from the cell at 77 K and methane gas with stable carbon isotope composition δ13C of －66.9‰（ methane B） was introduced into the cell. The carbon isotope compositions of both clathrate phase and gas phase methane gases were measured after the samples had been maintained at 274.7 K for 7-50 days. The δ13C of the clathrate phase methane was smaller than the initial value of －42.3‰ and that of the gas phase methane was larger than its initial value of －66.9‰. These results suggest that the exchange between the clathrate phase and gas phase methane proceeded in the period of the scale for several weeks.
Clathrate hydrate
Carbon fibers
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Receptor–ligand kinetics
Enzyme Kinetics
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A simple model of the dissociation of methane from a layer of methane-hydrate particles is suggested. The model is based on the assumption that methane-hydrate particles form a flat porous film lying on an adiabatic wall. This film is heated by ambient air convection. It is assumed that when the temperature inside a certain region within the methane-hydrate reaches the critical temperature for the release of methane from the methane-hydrate, all methane is released from the methane-hydrate and the latter turns into ice. The contribution of heat required for the release of methane is considered. The model is based on the analytical solution to the one-dimensional heat transfer equation in the two-layer (methane-hydrate/ice) system. This solution is incorporated into the numerical code and used at each time step of the calculations. Model predictions are compared with experimental data for the heating of a layer of methane-hydrate of porosity 0.3 and thickness 5 mm. It is shown that good agreement between the predictions of the model and experimental data is observed at the initial stage of the process. At longer times, the model predicts faster methane release than observed experimentally unless the effect of self-preservation can be ignored. This deviation between modelling results and experimental data is attributed to the main assumption of the model that all methane is instantaneously released from the methane-hydrate when the methane-hydrate temperature reaches the above-mentioned critical temperature.
Clathrate hydrate
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The methane adsorption of water-preadsorbed carbons of different micropore widths w at 303 K was measured. Although the amount of adsorption of supercritical methane on microporous carbon at 303 K was less than 9.4 mg g-1 at 101 kPa, the presence of the preadsorbed water enhanced noticeably the methane adsorption at 303 K even under subatmospheric pressure. The adsorption increment of methane reached a maximum at 1−2 h after introduction of methane and decreased gradually to a steady value after 20−50 h. The adsorption increment of methane depended on the fractional filling φw of micropores by the preadsorbed water. The maximum increment of 110 mg g-1 for w = 1.1 nm at a methane pressure of 2.6 kPa was obtained at φw = 0.34, corresponding to the estimated adsorption amount at 21 MPa of methane (130 mg g-1). The methane-adsorption increment increased linearly with φw until φw = 0.35, indicating the formation of the stable methane−water clathrate of which the composition of methane to water is 1:2. Thus, the nano-order hydrates of methane should be formed in the micropore. The plausible model of the nanohydrate was proposed on the basis of the experimental results and simulation of methane adsorption.
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