Showing papers on "Natural gas published in 2002"

Future directions of membrane gas separation technology

Abstract: During the past 20 years, sales of membrane gas separation equipment have grown to become a $150 million/year business. More than 90% of this business involves the separation of noncondensable gases: nitrogen from air; carbon dioxide from methane; and hydrogen from nitrogen, argon, or methane. However, a much larger potential market for membrane gas separation lies in separating mixtures containing condensable gases such as the C3+ hydrocarbons from methane or hydrogen, propylene from propane, and n-butane from isobutane. These applications require the development of new membranes and processes. In this review, the existing gas separation applications are surveyed, and the expected growth of these and potential new applications of gas separation membranes over the next 20 years are described. The improvements in gas separation technology needed to produce these changes in the membrane industry are also discussed.

Catalysts for combustion of methane and lower alkanes

Abstract: The important greenhouse effect of methane (more than an order of magnitude greater than CO2) makes it essential to eliminate/control the methane emission from natural gas engines/power plants and petroleum industries. Catalytic combustion of methane is favored over homogeneous combustion, because the former greatly facilitates the oxidative destruction of methane. Moreover, use of catalysts for methane combustion in gas-turbines affords lower working temperatures (as compared to gas-fired turbines) and thermodynamically limits NOx (which is an extremely harmful environmental pollutant) emission. A large amount of work has been undertaken to develop catalysts both for controlling methane emission as well as for generating power in high temperature natural gas-turbines. This review will address the different issues related to the variety of catalysts which have been employed for methane/lower alkane combustion. Although all the related important aspects of the combustion catalysts will be addressed, greater emphasis will be placed on recent work in this field.

Energy resource potential of natural gas hydrates

Abstract: The discovery of large gas hydrate accumulations in terrestrial per mafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved be fore gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m3. Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.

Towards a fundamental understanding of natural gas hydrates

Abstract: Gas clathrate hydrates were first identified in 1810 by Sir Humphrey Davy. However, it is believed that other scientists, including Priestley, may have observed their existence before this date. They are solid crystalline inclusion compounds consisting of polyhedral water cavities which enclathrate small gas molecules. Natural gas hydrates are important industrially because the occurrence of these solids in subsea gas pipelines presents high economic loss and ecological risks, as well as potential safety hazards to exploration and transmission personnel. On the other hand, they also have technological importance in separation processes, fuel transportation and storage. They are also a potential fuel resource because natural deposits of predominantly methane hydrate are found in permafrost and continental margins. To progress with understanding and tackling some of the technological challenges relating to natural gas hydrate formation, inhibition and decomposition one needs to develop a fundamental understanding of the molecular mechanisms involved in these processes. This fundamental understanding is also important to the broader field of inclusion chemistry. The present article focuses on the application of a range of physico-chemical techniques and approaches for gaining a fundamental understanding of natural gas hydrate formation, decomposition and inhibition. This article is complementary to other reviews in this field, which have focused more on the applied, engineering and technological aspects of clathrate hydrates.

The geological methane budget at Continental Margins and its influence on climate change

Abstract: Geological methane, generated by microbial decay and the thermogenic breakdown of organic matter, migrates towards the surface (seabed) to be trapped in reservoirs, sequestered by gas hydrates or escape through natural gas seeps or mud volcanoes (via ebullition). The total annual geological contribution to the atmosphere is estimated as 16–40 Terragrammes (Tg) methane; much of this natural flux is ‘fossil’ in origin. Emissions are affected by surface conditions (particularly the extent of ice sheets and permafrost), eustatic sea-level and ocean bottom-water temperatures. However, the different reservoirs and pathways are affected in different ways. Consequently, geological sources provide both positive and negative feedback to global warming and global cooling. Gas hydrates are not the only geological contributors to feedback. It is suggested that, together, these geological sources and reservoirs influence the direction and speed of global climate change, and constrain the extremes of climate.

Coalbed gas systems, resources, and production and a review of contrasting cases from the San Juan and Powder River basins

Abstract: Coalbed gas has been produced commercially from the northern Appalachian basin since the 1930s and from the San Juan basin since the early 1950s. However, the magnitude and economic sig nificance of coalbed gas resources were realized only in the 1970s and early 1980s when the U.S. Bureau of Mines, U.S. Department of Energy, the Gas Research Institute, and oil and gas operators made a concerted effort to demonstrate commercial production of coalbed gas from vertical wells. Exploration and development ex panded in the late 1980s and early 1990s, due partly to an uncon ventional fuels tax credit. By 2000, coalbed gas accounted for 8.8% of the reserves (15.7 tcf [0.44 Tm3]) and 9.2% of the annual pro duction (1.38 tcf [40 Gm3]) of dry gas in the United States. From 1989 through 2000, cumulative United States coalbed gas produc tion was 9.63 tcf (272 Gm3). Today, coalbed gas development has spread to about a dozen basins in the United States, and exploration is progressing worldwide. Coal beds are self-sourcing reservoirs that can contain ther mogenic, migrated thermogenic, biogenic, or mixed gas. Coalbed gas is stored primarily within micropores of the coal matrix in an adsorbed state and secondarily in micropores and fractures as free gas or solution gas in water. The key parameters that control gas resources and producibility are thermal maturity, maceral compo sition, gas content, coal thickness, fracture density, in-situ stress, permeability, burial history, and hydrologic setting. These param eters vary greatly in the producing fields of the United States and the world. In 2000, the San Juan basin accounted for more than 80% of the United States coalbed gas production. This basin contains a gi ant coalbed gas play, the Fruitland fairway, which has produced more than 7 tcf (0.2 Tm3) of gas. The Fruitland coalbed gas system and its key elements contrast with the Fort Union coalbed gas play in the Powder River basin. The Fort Union coalbed play is one of the fastest developing gas plays in the United States. Its production escalated from 14 bcf (0.4 Gm3) in 1997 to 147.3 bcf (4.1 Gm3) in 2000, when it accounted for 10.7% of the United States coalbed gas production. By 2001, annual production was 244.7 bcf (6.9 Gm3). Differences between the Fruitland and Fort Union petroleum systems make them ideal for elucidating the key elements of contrasting coalbed gas petroleum systems.

Introduction to unconventional petroleum systems

Abstract: Ben Law is a consultant and sole proprietor of Pangea Hydrocarbon Exploration LLC. His research interests include basin-centered gas and coalbed methane systems. Prior to his consulting position, he was a member and chief of the U.S. Geological Survey Western Tight Gas Sand Project and regional coordinator of South Asia for the U.S. Geological Survey World Energy Project. He received B.S. and M.S. degrees from San Diego State University, California.John B. Curtis is associate professor and director, Petroleum Exploration and Production Center/Potential Gas Agency at the Colorado School of Mines. He is an associate editor for the AAPG Bulletin and The Mountain Geologist. As director of the Potential Gas Agency, he works with a team of 145 geologists, geophysicists, and petroleum engineers in their biennial assessment of remaining United States natural gas resources. The collection of articles included in this theme issue of the AAPG Bulletin originated in the AAPG …

On the kinetics of hydrocarbons oxidation from natural gas to kerosene and diesel fuel

Abstract: Kinetic reaction mechanisms are necessary for modeling the combustion, oxidation and ignition of commercial fuels consisting of complex mixtures of hydrocarbons. Since they are generally too complex to be considered in the models directly, simple model-fuels are preferred. These model-fuels consist in a simple mixture of hydrocarbons for which kinetic oxidation models are validated. The oxidation of a large variety of hydrocarbons was studied experimentally in a jet-stirred reactor to build the needed kinetic reaction mechanisms. These detailed kinetic reaction mechanisms were assembled to model the oxidation of commercial fuels. The capabilities of these kinetic models to simulate the oxidation of natural gas, kerosene and gas oil are presented together with needs for new kinetic measurements.

Purification of gas with liquid ionic compounds

Abstract: The present invention provides a method for purifying a gas by contacting the gas with a liquid ionic compound. Natural gas may be purified, removing water and carbon dioxide, by contacting the natural gas with a liquid ionic compound.

Compression Ratio Influence on Maximum Load of a Natural Gas Fueled HCCI Engine

Abstract: This paper discusses the compression ratio influence on maximum load of a Natural Gas HCCI engine. A modified Volvo TD100 truck engine is controlled in a closed-loop fashion by enriching the Natural Gas mixture with Hydrogen. The first section of the paper illustrates and discusses the potential of using hydrogen enrichment of natural gas to control combustion timing. Cylinder pressure is used as the feedback and the 50 percent burn angle is the controlled parameter. Full-cycle simulation is compared to some of the experimental data and then used to enhance some of the experimental observations dealing with ignition timing, thermal boundary conditions, emissions and how they affect engine stability and performance. High load issues common to HCCI are discussed in light of the inherent performance and emissions tradeoff and the disappearance of feasible operating space at high engine loads. The problems of tighter limits for combustion timing, unstable operational points and physical constraints at high loads are discussed and illustrated by experimental results. Finally, the influence on operational limits, i.e., emissions peak pressure rise and peak cylinder pressure, from compression ratio at high load are discussed. (Less)

Lng production using dual independent expander refrigeration cycles

Abstract: A process for producing a liquified natural gas stream that includes cooling at least a portion of a pressurized natural gas feed stream by heat exchange contact with first and second expanded refrigerants that are used in independent refrigeration cycles. The first expanded refrigerant is selected from methane, ethane and treated and pressurized natural gas. The second expanded refrigerant is nitrogen.

Powdered Activated Carbons and Activated Carbon Fibers for Methane Storage: A Comparative Study

Abstract: During this study different raw materials, activating agents, and preparation variables were used to compare the behavior of carbon materials with different morphologies in methane storage applications. Two different types of carbon materials have been prepared: (i) chemically activated carbons prepared from an anthracite and a bituminous coal using KOH as activating agent, and (ii) physically activated carbon fibers prepared from petroleum pitch and coal tar pitch-based carbon fibers, by activation with CO2 and steam. Both type of materials have been prepared in order to cover a wide range of surface area. The effects of different properties of the adsorbents (porous texture, packing density, and pore size distribution) in their performance in methane storage applications (methane uptake and delivery) were analyzed. The comparison of both types of materials (powder and carbon fibers) has shown that activated carbon fibers have the advantage of a higher packing density than powdered activated carbons. On...

Apparatus for the liquefaction of natural gas and methods relating to same

Abstract: Apparatuses and methods are provided for producing liquefied gas, such as liquefied natural gas. In one embodiment, a liquefaction plant may be coupled to a source of unpurified natural gas, such as a natural gas pipeline at a pressure letdown station. A portion of the gas is drawn off and split into a process stream and a cooling stream. The cooling stream may sequentially pass through a compressor and an expander. The process stream may also pass through a compressor. The compressed process stream is cooled, such as by the expanded cooling stream. The cooled, compressed process stream is expanded to liquefy the natural gas. A gas-liquid separator separates the vapor from the liquid natural gas. A portion of the liquid gas may be used for additional cooling. Gas produced within the system may be recompressed for reintroduction into a receiving line.

Resource-assessment perspectives for unconventional gas systems

Abstract: Concepts are described for assessing those unconventional gas sys tems that can also be defined as continuous accumulations. Contin uous gas accumulations exist more or less independently of the wa ter column and do not owe their existence directly to the buoyancy of gas in water. They cannot be represented in terms of individual, countable fields or pools delineated by downdip water contacts. For these reasons, traditional resource-assessment methods based on es timating the sizes and numbers of undiscovered discrete fields can not be applied to continuous accumulations. Specialized assessment methods are required. Unconventional gas systems that are also continuous accumu lations include coalbed methane, basin-centered gas, so-called tight gas, fractured shale (and chalk) gas, and gas hydrates. Deep-basin and bacterial gas systems may or may not be continuous accumu lations, depending on their geologic setting. Two basic resource-assessment approaches have been em ployed for continuous accumulations. The first approach is based on estimates of gas in place. A volumetric estimate of total gas in place is commonly coupled with an overall recovery factor to nar row the assessment scope from a treatment of gas volumes residing in sedimentary strata to a prediction of potential additions to re serves. The second approach is based on the production perfor mance of continuous gas reservoirs, as shown empirically by wells and reservoir-simulation models. In these methods, production characteristics (as opposed to gas in place) are the foundation for forecasts of potential additions to reserves.

Exergy analysis of multistage cascade refrigeration cycle used for natural gas liquefaction

Abstract: This paper provides an exergy analysis of the multistage cascade refrigeration cycle used for natural gas liquefaction. The equations of exergy destruction and exergetic efficiency for the main cycle components such as evaporators, condensers, compressors, and expansion valves are developed. The relations for the total exergy destruction in the cycle and the cycle exergetic efficiency are obtained. Also, an expression for the minimum work requirement for the liquefaction of natural gas is developed. It is shown that the minimum work depends only on the properties of the incoming and outgoing natural gas, and it increases with decreasing liquefaction temperature. The minimum work for a typical natural gas inlet and exit state is determined to be 456.8 kJ kg−1 of liquefied natural gas (LNG), which corresponds to a coefficient of performance (COP) of 1.8. Using a typical actual work input value; the exergetic efficiency of the multistage cascade refrigeration cycle is determined to be 38.5% indicating a great potential for improvements. Copyright © 2002 John Wiley & Sons, Ltd.

Greenhouse Gas Emissions from Building and Operating Electric Power Plants in the Upper Colorado River Basin

Abstract: As demand for electricity increases, investments into new generation capacity from renewable and nonrenewable sources should include assessment of global (climate) change consequences not just of the operational phase of the power plants but construction effects as well. In this paper, the global warming effect (GWE) associated with construction and operation of comparable hydroelectric, wind, solar, coal, and natural gas power plants is estimated for four time periods after construction. The assessment includes greenhouse gas emissions from construction, burning of fuels, flooded biomass decay in the reservoir, loss of net ecosystem production, and land use. The results indicate that a wind farm and a hydroelectric plant in an arid zone (such as the Glen Canyon in the Upper Colorado River Basin) appear to have lower GWE than other power plants. For the Glen Canyon hydroelectric plant, the upgrade 20 yr after the beginning of operation increased power capacity by 39% but resulted in a mere 1% of the CO2 e...

Plasma Pyrolysis of Methane to Hydrogen and Carbon Black

Abstract: The plasma-driven gas-phase thermal decomposition of methane yielding hydrogen and solid-phase carbon has been suggested as an environmentally friendly alternative to conventional methods of producing hydrogen from natural gas. The advantage of the process is that hydrogen is obtained directly from methane without producing CO2 as a byproduct. The process was experimentally examined using a modified version of a dc plasma reactor originally developed for the conversion of methane to acetylene. Carbon yields of 30%, a factor of 6 increase, with a corresponding decrease in acetylene yield were obtained by simply increasing the residence or reaction time. A detailed kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons through benzene is described. A model for solid carbon nucleation and growth is included. The model is compared to experimental results and is used to examine process optimization.

Fuel Properties of Hydrogen, Liquefied Petroleum Gas (LPG), and Compressed Natural Gas (CNG) for Transportation

Abstract: Hydrogen has been suggested as a convenient, clean-burning fuel. Hydrogen gas may be stored as a compressed gas or as a liquid. Hydrogen has good properties as a fuel for internal combustion engines in automobiles. Worldwide-liquefied petroleum gas (LPG) production is limited to about 10% of total gasoline and diesel fuel consumption and is used to a great extent for domestic and industrial purposes. Since LPG burns cleaner with less carbon build-up and oil contamination, engine wear is reduced and the life of some components such as rings and bearings is much longer than with gasoline. The high octane of LPG also minimizes wear from engine knock. Natural gas is widely available. CO2 emission of natural gas is lower than both diesel fuel and gasoline, which makes natural gas engines favorable also in terms of the greenhouse effect. Positive contribution of compressed natural gas (CNG) on environmental pollution must also be considered in economical aspects.

Substitution of natural gas for coal: climatic effects of utility sector emissions

Abstract: Substitution of natural gas for coal is one means of reducing carbon dioxide (CO2) emissions. However, natural gas and coal use also results in emissions of other radiatively active substances including methane (CH4), sulfur dioxide (SO2), a sulfate aerosolprecursor, and black carbon (BC) particles. Will switching from coal to gas reduce the net impact of fossil fuel use on global climate? Using the electric utility sector as an example, changes in emissions of CO2, CH4,SO2 and BC resulting from the replacement of coal by natural gas are evaluated, and their modeled net effect on global mean-annual temperature calculated. Coal-to-gas substitution initially produces higher temperatures relative to continued coal use. This warming is due to reduced SO2 emissionsand possible increases in CH4 emissions, and can last from 1 to 30years, depending on the sulfur controls assumed. This is followed by a net decrease in temperature relative to continued coal use, resulting from lower emissions of CO2 and BC. The length of this period and the extent of the warming or cooling expected from coal-to-gas substitution is found to depend on key uncertainties and characteristics of the substitutions, especially those related to: (1) SO2 emissions and consequentsulphate aerosol forcing; and (2) the relative efficiencies of the power plantsinvolved in the switch.

Predicting NOx emissions of a burner operated in flameless oxidation mode

Abstract: This paper deals with the technology of burning natural gas with combustion air preheated to 1300°C. The objective of this work is to assess the potential of several combustion models and NOx postprocessors for their abilities to predict NOx emissions. The steady-state computational results have been compared both with in-furnace measurements and with the measured furnace exit parameters. The following main conclusions have been drawn: (1) with the exception of the small region located within the natural gas jet, the computations resulted in good quality predictions: (2) the NOx has been formed in a thin elongated region (flamelet) located between the natural gas jet and the air jet: (3) the NO has been formed mainly by the thermal path, and the NO-reburning mechanism was of little importance: and (4) there are strong indications that the non-stationary behavior of the weak (fuel) jet must be accounted for if the predictions within the fuel jet were to be perfected.