Showing papers on "Methane published in 1979"

Methane formation and methane oxidation by methanogenic bacteria.

Abstract: Methanogenic bacteria were found to form and oxidize methane at the same time. As compared to the quantity of methane formed, the amount of methane simultaneously oxidized varied between 0.3 and 0.001%, depending on the strain used. All the nine tested strains of methane producers (Methanobacterium ruminantium, Methanobacterium strain M.o.H., M. formicicum, M. thermoautotrophicum, M. arbophilicum, Methanobacterium strain AZ, Methanosarcina barkeri, Methanospirillum hungatii, and the "acetate organism") reoxidized methane to carbon dioxide. In addition, they assimilated a small part of the methane supplied into cell material. Methanol and acetate also occurred as oxidation products in M. barkeri cultures. Acetate was also formed by the "acetate organism," a methane bacterium unable to use methanogenic substrates other than acetate. Methane was the precursor of the methyl group of the acetate synthesized in the course of methane oxidation. Methane formation and its oxidation were inhibited equally by 2-bromoethanesulfonic acid. Short-term labeling experiments with M. thermoautotrophicum and M. hungatii clearly suggest that the pathway of methane oxidation is not identical with a simple back reaction of the methane formation process. Images

Anaerobic treatment process stability

Abstract: Controlled anaerobic treatment processes are being considered today as one possible means of recovering energy in the form of methane gas while at the same time reducing the pollu tional load of organic-waste slurries. McC?rty x estimated that the resulting methane produc tion from the anaerobic digestion of municipal sludges and refuse, ariimal wastes, and crop residues in the U. S. would yield an equivalent of about 20% of the current natural gas con sumption. Anaerobic treatment of human wastes and utilization of the resultant methane gas have been practiced since the latter part of the nine teenth century. Various anaerobic process configurations have found widespread usage in the treatment of municipal sludges and more limited application in the treatment of organic industrial wastes including fruitand vegetable processing wastes, packinghouse wastes, and animal manure slurries. Despite its usage since the beginning of the present century, anaerobic treatment is still one of the least understood processes in waste treat ment. Widespread application has been ham pered by a lack of understanding of factors associated with stability of the biological pro cesses involved. The problem has been ac centuated by a perceived lack of reliability in the process. Although recently escalating energy costs have given increased emphasis to anaerobic treatment processes, further develop ment of anaerobic-process technology is de pendent upon a better understanding of process biochemistry and its relationship to process stability than currently exists. The anaerobic fermentation process involves two major groups of bacteria that decompose organic matter in two major phases. In the first stage, numerous species of saprophytic bacteria collectively called "acid formers" hy drolyze and degrade the complex organic mat ter to fatty or volatile acids. The second stage of the process is accomplished by methanogenic bacteria that utilize the volatile acids and pro duce methane gas as one of the byproducts of their metabolism. The two processes occur simultaneously and process stability is depen dent upon maintenance of a delicate biochem ical balance between the fast-growing "acid formers" and the more fastidious "methane formers." Process instability is usually indi cated by a rapid increase in the concentration of volatile acids with a concurrent decrease in methane gas production. Operational factors that have usually been associated with process failure include insuf ficient acclimation of the methane formers to new substrates, overloading, and rapid temper ature fluctuations. Many of the laboratory and pilot-scale studies reporting failure of the an aerobic process have reported very short ac climation periods of one month or less when switching to new substrates. Kotze et al.2 monitored the enzymatic activity of anaerobic digesters receiving different substrates and con cluded that adaptation of a substrate takes more than five weeks. Rapid increases in the rate of organic loading and rapid process temperature changes have also been implicated as contributing to process imbalance. A number of organic and inorganic materials that may be present in the waste play a sig nificant role in process inhibition and toxicity. These include excessive concentrations of vola tile acids, ammonia, alkaline earth-metal salts, heavy metals, and Sulfides. Inhibition by these materials is usually indicated by a decrease in the steady-state rate of methane gas production and volatile-acids concentration, while toxicity is indicated by a total cessation of methan ogenic activity. Pilot-plant studies at the University of Mani toba on anaerobic digestion of swine manure have indicated that extreme process stability could be achieved despite a digester chemical

Methane efflux from lake sediments through water lilies.

Abstract: During winter, when water lilies have no surface leaves, the gases in the rhizome lacunae approach equilibrium with the gases of the sediment water. The resulting increase of internal pressure is manifested by the sustained streams of bubbles (up to 37 percent methane and 6 percent carbon dioxide) that escape when emerging leaves are torn in the spring. Methane continues to enter the roots and rhizome during summer, rapidly moves up the petioles, and passes out through the emergent leaves into the atmosphere.

Hydrogeological Processes and Chemical Reactions at a Landfill.

Abstract: Chemical and isotopic analyses were made of water from wells in and downgradient from a landfill to determine chemical and isotopic effects of generation and migration of leachate on ground water. The distribution and wide concentration range of oxygen and methane permit the delineation of an anaerobic zone, a regional oxygenated zone and an intermediate zone. The ratio of reduced nitrogen to nitrate indicates location of reducing fronts as the leachate migrates. The pH of the native ground water is low (≥5.0) primarily because of the low pH of rainfall and the lack of calcareous or other soluble minerals in the aquifer material. The pH is higher (∼6.6) in the leachate because of generation of carbon dioxide, ammonia, and methane. The native ground water has a low TDS (80 mg/l) while the leachate has an average TDS of 2800 mg/l and is primarily a NaHCO3 type water. Sulfate concentrations are extremely low and H2 S was not detected. We suggest that a major source of cations may be their exchange from the clays by the ammonium generated in the leachate. High concentrations of Fe and Mn are attributed to a source in the refuse but more important to reduction of oxide cements and coatings resulting from degradation of organic matter. The main source of bicarbonate is from organic degradation with minimal CO2 from the soil zone. At one landfill site 52% of the total alkalinity is attributed to organic compounds, mainly organic acid anions. The δ13 C of bicarbonate in the leachate is exceedingly heavy (+18.400 /00 ) which results from fractionation during the formation of methane. The 10 per mil deuterium enrichment of water may be due to decomposition of deuterium-enriched compounds and bacterial processes that preferentially consume the lighter hydrogen isotope.

An Analytical Study of the Shock Tube Ignition of Mixtures of Methane and Ethane

Abstract: An analytical study of the ignition of mixtures of methane and ethane has been carried out, using a numerical model consisting of 25 chemical species and 75 elementary chemical reactions. Computed ignition delay times and effective activation energies are compared with published experimental shock tube results. Initial conditions studied include temperatures from 1300-1900 K. and mixtures ranging from pure methane to pure ethane, with stoichiometric amounts of oxygen, diluted in argon. The analytical model reproduces experimental results for the effective activation energy and ignition delay time for both pure methane and pure ethane. Ignition delay times computed for mixtures of methane and ethane are found to lie between the pure methane and the pure ethane results. Addition of relatively small quantities of ethane to methane rapidly reduces the ignition delay time of the methane-ethane mixtures to values close to those of pure ethane. The chemical kinetic factors involved in the ignition of fu...

Carbon isotope fractionation by Methanobacterium thermoautotrophicum

Abstract: The fractionation of carbon isotopes by Methanobacterium thermoautotrophicum was studied during growth of the bacterium on H2 plus CO2 as sole carbon and energy sources. A 80% H2/20% CO2 gas mixture was continuously bubbled through the culture. At high gassing rates, in the absence of a “closed system effect”, cells and methane were found to be depleted in 13C relative to CO2 in the gas mixture by 2.4% and 3.4%, respectively. At low gassing rates, when more than 90% of the CO2 was converted to methane, the cells were enriched in 13C by 1.3% and methane was depleted in 13C by 0.5%; residual CO2 was enriched in 13C by 3.4%. The magnitude of isotope fractionation suggests that CO2 rather than bicarbonate is the active species of CO2 mainly utilized in both CO2 assimilation and CO2 reduction to methane. The apparent positive 13C-discrimination in cell carbon synthesis, which was observed at low gassing rates, indicates that most of the CO2 assimilated into cell material is not incorporated via reactions involved in CO2 reduction to methane.

Oxidation of methane in the absence of oxygen in lake water samples.

Abstract: Methane was oxidized to carbon dioxide in the absence of oxygen by water samples from Lake Mendota, Madison, Wis. The anaerobic oxidation of methane did not result in the assimilation of carbon from methane into material precipitable by cold 10% trichloracetic acid. Only samples taken at the suface of the sediment of Lake Mendota were capable of catalyzine the anaerobic oxidation of methane. The rate of methane oxidation in the presence of oxygen was highest in samples taken from near the thermocline. Of the radioactive methane oxidized, 30 to 60% was assimilated into material precipitable by cold 10% trichloroacetic acid during aerobic incubation of the samples. These data support the conclusion that two distinct groups of methane-oxidizing organisms occur in stratifield lakes. Enrichments with acetate and methane as the sole sources of carbon and energy and sulfate as the electron acceptor resulted in the growth of bacteria that oxidize methane. Sulfate, acetate, and methane were all required for growth of enrichments. Acetate was not oxidized to carbon dioxide but was assimilated by cells. Methane was not assimilated but was oxidized to carbon dioxide in the absence of air.

Gas fixation solar cell using gas diffusion semiconductor electrode

Abstract: A gas diffusion semiconductor electrode and solar cell and a process for gaseous fixation, such as nitrogen photoreduction, CO 2 photoreduction and fuel gas photo-oxidation. The gas diffusion photosensitive electrode has a central electrolyte-porous matrix with an activated semiconductor material on one side adapted to be in contact with an electrolyte and a hydrophobic gas diffusion region on the opposite side adapted to be in contact with a supply of molecular gas.

Migration of Fluids in Sedimentary Basins

Abstract: The basic mechanisms governing the migration of water and hydrocarbons in sedimentary basins are related ultimately to basinal structural history, rock properties, compaction, and temperature regime, which themselves are interdependent. Compaction of the sedimentary rocks promotes the expulsion of water during the progressive burial of the sediments. The physical-chemical properties of the rocks are responsible for the migration of the expelled water toward the surface and for the distribution in the basin of various parameters such as hydraulic potential, salinity, heat flow, temperature, and cementation. Primary migration is used herein to refer to migration of hydrocarbons soon after their generation; secondary migration refers to their delayed movement. Oil has difficulty migrating in shaly rocks. A possible way of removing oil from a source rock, in addition to the colloidal or true solubilization in water or the flow in a three-dimensional oil-wet kerogen network, is through its solubilization in high-pressure gas generated in the deeper part of the basin and coming up through preferential paths such as faults and fractures. Molecular distillation of the oil occurs because its vapor pressure in the liquid phase is higher than the vapor pressure in the gaseous phase. In the upper part of a lithologic column, retrograde condensation occurs and gas and condensate accumulations start to form below little compacted plastic caprocks. Owing to the high displacement pressures of the gaseous column, gas can pass through the caprock and disperse to the surface while the condensate remains in place. The pore-size distribution of the little compacted shaly caprock is responsible for the chemical and isotopic fractionation of the rising gas; almost pure and isotopically light methane thus is found in the upper layers of a stratigraphic column. High-volatile oil can be easily degraded by circulating water, especially in the presence of sulfate ions, hydrogen sulfide, and bacteria, and transformed progressively to heavy oil. Geochemical tools which can be used by explorationists in prospecting for new oil and gas fields include isotope analysis, hydraulic potential, salinity, temperature, cementation, maturity, and maps of shows.

Gas-liquid equilibrium in binary mixtures of methane with N-decane, benzene, and toluene

Abstract: Compositions of saturated equilibrium liquid and vapor phases are determined in a flow apparatus for mixtures of methane and n-decane at 150, 240, 270, 290, and 310/sup 0/C, for methane and benzene at 150, 190, and 230/sup 0/C, and for methane and toluene at 150, 190, 230, and 270/sup 0/C. Pressures extend to near the criticals of the mixtures starting from 20 atm or from somewhat above the vapor pressure of the solvent whichever is higher. 6 figures, 4 tables.

Catalytic reaction of methane with carbon dioxide

Abstract: High activities and selectivities of Ni on SiO2 catalysts producing CO in the reaction of CH4 with CO2, have been obtained at relatively low temperatures. These aspects are considerably different from the activities or selectivities of other catalysts, and have been explained by assuming that the Ni on SiO2 catalyst markedly suppresses carbon deposition.

Triton: a satellite with an atmosphere.

Abstract: A low-resolution infrared spectrum of Triton in the region 1.4-2.6 microns shows a broad absorption at 2.3 microns which is attributed to gaseous methane. The computed surface partial pressure of CH4, based on a random band model extrapolation of new laboratory spectra, is (1 + or - 0.5) times 10 to the -4th bars, a value consistent with the calculated vapor pressure of methane gas above methane ice at the expected temperature of Triton. There is, however, no compelling evidence for the presence of solid CH4 on the satellite's surface.

Apparatus and method for solar coal gasification

Abstract: Apparatus for using focused solar radiation to gasify coal and other carbonaceous materials. Incident solar radiation is focused from an array of heliostats onto a tower-mounted secondary mirror which redirects the focused solar radiation down through a window onto the surface of a vertically-moving bed of coal, or a fluidized bed of coal, contained within a gasification reactor. The reactor is designed to minimize contact between the window and solids in the reactor. Steam introduced into the gasification reactor reacts with the heated coal to produce gas consisting mainly of carbon monoxide and hydrogen, commonly called "synthesis gas", which can be converted to methane, methanol, gasoline, and other useful products. One of the novel features of the invention is the generation of process steam at the rear surface of the secondary mirror.

Aqueous Solubility of Methane at Elevated Pressures and Temperatures

Abstract: This study reports the solubility of methane in distilled water from 150° to 350°C and from 100 to 28,600 psi (689.5 to 197,197 kPa). Methane solubility greatly increases with increasing temperature above 250°C to maximum values of over 800 standard cu ft (22.66 cu m) of methane per barrel of water at 354°C and 28,600 psi (197,197 kPa). These high methane solubilities suggest that dissolved methane in the pore waters of sediments buried at 20,000 ft (6.10 km) and deeper in the Gulf Coast and other sedimentary basins could be a significant energy resource. These solubilities are also consistent with the concept of primary migration of natural gas and crude oil by molecular solution from the deep sediments of petroleum basins.

Separation of multicomponent gas mixtures

Abstract: Multicomponent gas mixtures containing: (1) hydrogen as primary component, (2) a secondary key component that is more strongly sorbed by the adsorbent than hydrogen, and (3) a minor quantity of one or more dilute components less strongly sorbed than the secondary key component, are subject to selective adsorption in an adiabatic pressure swing cyclic system for the separate recovery of high purity hydrogen and of the secondary component. A given example is the treatment of a shift converter effluent gas from a hydrocarbon reformer plant, wherein hydrogen and carbon dioxide are separately recovered as key components substantially freed of minor dilute components such as methane, carbon monoxide and nitrogen.

Measuring radioactive methane with the liquid scintillation counter.

Abstract: Although a gas proportional counter is the most convenient method of measuring the radioactivity of fixed gases such as methane, it cannot be used when high nonradioactive concentrations of methane are present in the gas phase, due to quenching If only methane and carbon dioxide are present in radioactive form in the gas phase, a liquid scintillation method for measuring these substances can be used The procedure is described in detail, and the solubility of methane in liquid scintillation cocktails is determined

Methane in marine sediments

Abstract: Interstitial methane profiles from six sediment cores taken on the slope and abyssal plain of the Gulf of Mexico can be explained by simple kinetic modeling. Methane is apparently produced at a constant rate and microbially consumed in the sulfate-reducing zone. Rates of production and consumption are estimated from best-fit solutions to a steady-state diagenetic equation. Production and consumption balance to form uniform concentrations of 5 to 10μ11−1 in the first few meters of slope and abyssal sediments. Effects of upward diffusion from large accumulations of methane in sulfate-free zones deeper than about 10 m are not detectable.

Low energy electron scattering from methane

Abstract: Measurements of the exponential attenuation of electron currents in a straight line collision chamber are reported using methane gas as the scattering medium. From the transmission spectra obtained at different methane pressure in the scattering chamber, the total cross sections for the energy range 0–16 eV are derived and compared to previous measurements. A small structure in the region of the Ramsauer–Townsend minimum is observed, confirming earlier interpretations of electron swarm experiments. A possible mechanism of excitation is discussed.