Showing papers on "Methane published in 1976"

Greenhouse effects due to man-made perturbations of trace gases

Abstract: Nitrous oxide, methane, ammonia, and a number of other trace constituents in the earth's atmosphere have infrared absorption bands in the spectral region 7 to 14 µm and contribute to the atmospheric greenhouse effect. The concentrations of these trace gases may undergo substantial changes because of man's activities. Extensive use of chemical fertilizers and combustion of fossil fuels may perturb the nitrogen cycle, leading to increases in atmospheric N_2O, and the same perturbing processes may increase the amounts of atmospheric CH_4 and NH_3. We use a one-dimensional radiative-convective model for the atmospheric thermal structure to compute the change in the surface temperature of the earth for large assumed increases in the trace gas concentrations; doubling the N_2O, CH_4, and NH_3 concentrations is found to cause additive increases in the surface temperature of 0.7°, 0.3°, and 0.1°K, respectively. These systematic effects on the earth's radiation budget would have substantial climatic significance. It is therefore important that the abundances of these trace gases be accurately monitored to determine the actual trends of their concentrations.

Catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen

Abstract: The increasing demand for energy, coupled with the uncertainty and expense of crude oil imports, has renewed interest in the production of fuels and chemicals from hydrogen-deficient materials. These energy sources such as coal, residua, oil shale, and tar sands can be gasified with steam and oxygen to produce a gas containing large quantities of carbon monoxide and hydrogen. Once methane is removed from this CO/H2 mixture it is purified to remove S poisons and then reacted over a catalyst to produce a variety of organic products. The synthesis of hydrocarbon products, with the exception of methane, is commonly referred to as the Fischer-Tropsch synthesis reaction.

Methane production and consumption in anoxic marine sediments

Abstract: The production of methane in anoxic environments can lead to significant accumulations of this gas in appropriate marine sediments. However, the uniformly low methane concentrations in marine, anoxic, sulfate-reducing sea water and sediments represents a balance between production by methanogenic bacteria and consumption by sulfate-reducing bacteria. The primary sink for anaerobically generated methane in marine sediments is sulfate reduction, not aerobic oxidation.

Producing methane from coal in situ

Abstract: A well is drilled from the surface of the earth into an underground coal formation. The coal seam is fractured by fluids injected under pressure. Methane entrained in the cracks and fissures is removed to surface facilities. Coal seam in the vicinity of well bore is partially dewatered. Diameter of well bore in the coal section is enlarged first by underreaming the hole, then by a vertical in situ burn to form a collection chimney. Methane desorbed from the coal is withdrawn to surface facilities.

Interactions of CH4 and Co in the Earth's Atmosphere

Abstract: Global distributions, sources, and sinks of methane and carbon monoxide in upper and lower levels of the earth's atmosphere, and the global budgets of methane and carbon monoxide, are studied, with emphasis on cumulative pollution. Stratospheric contents, vertical profiles of concentrations, simulation of vertical transport through the atmosphere, and latitudinal distributions are examined. Diffuse and localized (urban) concentrations of CO as pollutant are studied, and anthropogenic sources and sinks for CH4 and CO are considered. Perturbation of the CH4-CO-CO2 cycle, crucial to self-cleansing mechanisms of the troposphere, by anthropogenic CO emissions, and the effect of CO long life as global pollutant, are investigated.

The Measurement and Prediction of Hydrate Formation in Liquid Hydrocarbon-Water Systems

Abstract: The University of Alberta obtained equilibrium three-phase water liquid-hydrocarbon liquid-solid hydrate data for the methane--isobutane--water system and for six multicomponent mixtures containing isobutane, at pressures up to 2200 psia and temperatures above 32/sup 0/F. The theory of J.H. van der Waals and J.C. Platteeuw for predicting hydrate forming conditions in gases was modified to make it applicable to gas and liquid mixtures. The method was also applied to the prediction of the four-phase equilibrium locus.

Factors controlling methane oxidation in shield lakes: The role of nitrogen fixation and oxygen concentration1

Abstract: During summer stratification methane-oxidizing bacteria in Lake 227 are confined to a narrow zone within the thcrmoclinc because of their sensitivity to high epilimnctic oxygen concentrations. This oxygen sensitivity is based on the dependence of the oxi- dizers on an oxygen-sensitive nitrogen fixation process. Thus epilimnetic methane oxi- dation is absent during periods of nitrogen limitation, since high epilimnetic oxygen concentrations prevent nitrogen fixation. During periods of overturn and throughout the winter, the methane oxidizers become oxygen insensitive and oxidation occurs rapidly throughout the water column. This oxygen insensitivity likely occurs as a result of high in situ concentrations of dissolved inorganic nitrogen, which replaces nitrogen fixation as a source for fixed nitrogen, Under ice-cover, rapid mcthanc oxidation throughout the water column can be a major cause of total anoxia.

Hydrogen purification by selective adsorption

Abstract: Hydrogen-containing gas mixtures are subjected to selective adsorption in a pressure swing cyclic system to remove carbon dioxide and/or hydrocarbon gases, obtaining high recovery of hydrogen at high purity. The system can also be employed for separation of methane from admixture with CO2.

Method for removing methane from coal

Abstract: A process for removing methane from a subterranean coal deposit. A carbon dioxide-containing fluid is introduced into the coal deposit through an injection well and held therein for a period sufficient to enable a substantial amount of methane to be desorbed from the surfaces of the coal deposit. Following the hold period, the injected carbon dioxide-containing fluid and desorbed methane are recovered through a recovery well or wells spaced from the injection well. The process is repeated until sufficient methane has been removed to enable safe mining of the coal deposit.

Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune, and Titan

Abstract: This paper reports laboratory studies of the visible spectrum of methane at column densities between 0.4 and 5 km-am and confirms the identification of bands at 4410, 4590, 4860, 5090, 5430, 5760, and 5970 A as caused by methane. Detailed equivalent-width measurements at 15 different pressure path lengths are employed to determine curves of growth and band strengths for the bands at 4410, 4860, 5430, and 5760 A. Using the curve-of-growth measurements in the reduction of planetary observations, the methane abundances in the atmospheres of Jupiter and Saturn are found to be between a factor of 3 and 4 larger than previously accepted values based on the analysis of the 3 nu(3) band at 1.1 microns, while the amount on Titan is significantly less than that obtained from an analysis of the same band with the assumption of a pure methane atmosphere. The present results, when combined with the band analysis, suggest a surface pressure on Titan of at least 0.4 atm. Extrapolation of these laboratory data to observations of Uranus and Neptune lead to single-air-mass column densities of 5.8 and 7.6 km-am of methane, respectively.

Factors affecting rate of methane formation from acetic acid by enriched methanogenic cultures.

Abstract: A stable enrichment culture converting acetic acid to methane was successfully obtained from a pear waste digester, using a synthetic substrate solution with acetic acid as the main carbon source. This enrichment culture converted up to 10 mmol of acetic acid per litre per day at 35 °C and did not use hydrogen or formic acid in appreciable amounts as substrate for methane production instead of or in addition to, acetic acid. The rate of conversion of acetic acid to methane was maximum at temperatures of 40–45 °C, at a pH of 6.5 to 7.1, and was adversely affected by exposure to air, reducing agents, and high salt concentrations. The rate of conversion was independent of acetic acid concentration between 0.2 and 100 mM, but dropped markedly at concentrations below 0.2 mM.

Process for gasifying solid carbonaceous fuel

Abstract: A process for continuously gasifying carbonaceous material using fluidizing medium and oxygen-containing gas, under controlled feed rates and certain delivery conditions, and under selective processing conditions to produce a product rich in carbon monoxide and hydrogen is provided If desired, the product can be produced with increased amounts of methane Gasification is conducted under pressure in a fluidized bed to produce a gaseous reaction product, and char solids are coproduced Additional increments of oxygen-containing gas with steam is selectively introduced The product is passed through a dilute-phase, maintained at certain temperatures, at a certain superficial velocity, and for a certain residence time The presence of undesirable heavy hydrocarbon by-products is precluded Char, in removal from the bottom of the bed, is contacted with steam or inert gas to recover sensible heat Cooled product gas is provided having less than about 4 grains of solid per scf at certain conditions Partially spent char is removed from the product for discharge or certain purposes The product is cooled and is conducted in a heat recovery zone to recover heat values at least a part of which are used to produce steam, a portion of which is utilized in the process The cooled product gas is conducted through a high efficiency, high pressure-drop type, a scrubber to remove fine partially spent char particles and provide a gas product containing minimal amounts of solids, a carbon monoxide content of at least about 10 percent (vol), hydrogen, and a desired BTU content The pressure in the gasifier is maintained by means of back-pressure control applied to the gas system at a point downstream of the gasifier

Kinetics of carbon deposition on diamond powder

Abstract: The rate of carbon deposition on 0–1‐μm diamond seed crystals was investigated in the temperature range 1140–1475 °C, methane partial pressures form 10−3 to 44.4 Torr and hydrogen partial pressures from 0 to 16.4 Torr. Two distinct kinetic regimes were found. A relatively rapid initial rate of diamond growth decayed exponentially to a final slow constant rate as graphitic carbon was codeposited and covered the surface. A maximum initial diamond growth rate of 1.06×10−7 g cm−2 min−1, which corresponded to a nominal linear growth rate of only 0.45 μm per day, was observed. Dilution of methane with hydrogen decreased the nucleation rate of graphitic carbon relative to that of diamond resulting in a increase in the diamond yield. The activation energy for diamond deposition from pure methane was 55 kcal mole−1. The dependence of the initial rate data on methane partial pressure could be described by a Langmuir‐type equation. The deposits were identified by chemical etching, chemical analysis, density measurem...

Sorption of oxygen, nitrogen, carbon monoxide, methane, and binary mixtures of these gases in 5A molecular sieve

Abstract: Equilibrium data for the sorption of oxygen, nitrogen, carbon monoxide, and methane in 5A molecular sieve are analyzed in terms of a simple theoretical model isotherm. The model provides an excellent correlation of the single-component isotherms over the entire concentration range, and it is shown that equilibrium data for sorption of binary mixtures of these gases are correctly predicted by the model using the parameters (Henry constants and molecular volumes) derived from analysis of the single-component isotherms. The model predicts that mixtures of two sorbates with equal molecular volumes should show approximately ideal solution behavior in the adsorbed phase. The experimental data of Lederman for the sorption of nitrogen-methane mixtures show the expected behavior over a wide range of pressures.

The thermal decomposition of methane. II. Secondary reactions, autocatalysis and carbon formation; non-Arrhenius behaviour in the reaction of CH3 with ethane

Abstract: In the thermal decomposition of methane at temperatures from 880 to 1103 K, hydrogen and ethane are the only primary products. The rate of formation of ethane falls rapidly towards zero as the reac...

Recovery of hydrogen and nitrogen from ammonia plant purge gas

Abstract: An adiabatic pressure swing adsorption process for separating gas mixtures containing ammonia, argon, methane, nitrogen and hydrogen to recover hydrogen and nitrogen product in which four adsorbent beds are joined so that the adsorbate loaded bed is pressure equalized with two other beds in staged sequence.

Mass-spectrometric measurements of enhanced methanation activity over cobalt and nickel foils. Interim report

Abstract: The kinetics of methane synthesis from H/sub 2//CO mixtures has been studied over Ni, Co, and Fe foils. The gas composition of a flowing reaction cell was analyzed using a differentially pumped, modulated mass-spectrometer. Ni and Co foils that have been previously oxidized, and then reduced in H/sub 2/ at 525-600/sup 0/K show a surprisingly high and specific catalytic activity for methane formation. No unusual activity was observed over iron for any of the surface treatments tried here. Evidence is also presented to support a mechanism for this highly specific reaction involving a labile surface carbon atom intermediate.

Combination solvent-noncondensible gas injection method for recovering petroleum from viscous petroleum-containing formations including tar sand deposits

Abstract: Petroleum may be recovered from viscous petroleum-containing formations including tar sand deposits by injecting into the formation a solvent which is liquid at formation conditions and simultaneously therewith injecting a substance which will remain totally gaseous at the pressure and temperature conditions existing within the reservoir. The presence of noncondensible gas in the formation into which solvent is being injected prevents formation of a impremeable bitumen bank which blocks the further flow of fluids through the formation. The gas should be essentially unreactive with the solvent and formation fluids in order to obtain the desired benefits. Examples of suitable gases for the practice of this invention include methane, ethane, nitrogen, carbon dioxide, and mixtures thereof.

A study of spherical detonation in mixtures of methane and oxygen diluted by nitrogen

Abstract: A study has been made of spherical detonation waves in methane/oxygen/nitrogen mixtures. Using various masses M of solid explosive (Tetryl) as initiator, the detonatability limit in the (x,M) plane at atmospheric pressure has been established for mixtures of composition CH4+202+xN2with 1.4

Dew point study in the vapor--liquid region of the methane--carbon dioxide system

Abstract: Rice University used the elution technique to study the vapor-phase concentration along isotherms in the vapor--liquid region surrounding the vapor--solid region for the methane--carbon dioxide system at -65 to -184/sup 0/F, a temperature range that extends below methane's critical temperature. Pressure conditions ranged from the three-phase solid--liquid--vapor locus to the critical point or the vapor pressure of methane. Measurements were intensified near the critical temperature of methane. The isotherms obtained for the system below methane's critical temperature were consistently linear and differed markedly from the curvatures observed by other investigators.

Kinetics of bituminous coal char gasification with gases containing steam and hydrogen

Abstract: A quantitative mathematical model to describe gasification kinetics of bituminous coal chars in gases containing steam and hydrogen was developed based on experimental information obtained over a wide range of conditions. The model is intended for application to two reaction stages: (1) a high-rate methane formation stage corresponding to a limited period after initial exposure of a coal char containing reasonable volatile matter to a gasifying medium containing hydrogen. During this short-lived period, a coal char exhibits an exceptionally high, though transient, reactivity for methane formation. (2) A low-rate gasification stage corresponding to gasification of a char of relatively low reactivity, which results when reaction in the rapid-rate stage is completed. Correlations defining the model developed are presented, and consistencies between predictions of the model and results obtained from a variety of experimental systems is demonstrated.

Process for manufacturing liquefied methane

Abstract: A process for producing liquefied natural gas from a high pressure hydrocarbon feedstock is shown. In this process, the feedstock is isentropically expanded and distilled at a pressure lower than the critical pressure to form an overhead rich in methane and a bottom fraction. The methane rich overhead is compressed utilizing the energy obtained from the expansion and then the compressed overhead is liquefied in a refrigeration cycle.