Showing papers on "Natural gas published in 2007"
TL;DR: The potential reserves of hydrated gas are over 1.5×10 16 m 3 and are distributed all over the earth both on the land and offshore as mentioned in this paper. But, many complex problems have to be studied and new technology for the production of natural gas from gas hydrates has to be developed.
698 citations
TL;DR: This electrohydrogenic process provides a highly efficient route for producing hydrogen gas from renewable and carbon-neutral biomass resources and is shown to be efficient and sustainable from any type of biodegradable organic matter by electroHydrogenesis.
Abstract: Hydrogen gas has tremendous potential as an environmentally acceptable energy carrier for vehicles, but most hydrogen is generated from nonrenewable fossil fuels such as natural gas. Here, we show that efficient and sustainable hydrogen production is possible from any type of biodegradable organic matter by electrohydrogenesis. In this process, protons and electrons released by exoelectrogenic bacteria in specially designed reactors (based on modifying microbial fuel cells) are catalyzed to form hydrogen gas through the addition of a small voltage to the circuit. By improving the materials and reactor architecture, hydrogen gas was produced at yields of 2.01–3.95 mol/mol (50–99% of the theoretical maximum) at applied voltages of 0.2 to 0.8 V using acetic acid, a typical dead-end product of glucose or cellulose fermentation. At an applied voltage of 0.6 V, the overall energy efficiency of the process was 288% based solely on electricity applied, and 82% when the heat of combustion of acetic acid was included in the energy balance, at a gas production rate of 1.1 m3 of H2 per cubic meter of reactor per day. Direct high-yield hydrogen gas production was further demonstrated by using glucose, several volatile acids (acetic, butyric, lactic, propionic, and valeric), and cellulose at maximum stoichiometric yields of 54–91% and overall energy efficiencies of 64–82%. This electrohydrogenic process thus provides a highly efficient route for producing hydrogen gas from renewable and carbon-neutral biomass resources.
594 citations
TL;DR: In this article, the operating envelope, fuel economy, emissions, cycle-to-cycle variations in indicated mean effective pressure and strategies to achieve stable combustion of lean burn natural gas engines are highlighted.
519 citations
TL;DR: In this article, the authors examined nine corn ethanol plant types and found that they can have distinctly different energy and greenhouse gas emission effects on a full fuel-cycle basis, and that greenhouse gas emissions impacts can vary significantly.
Abstract: Since the United States began a programme to develop ethanol as a transportation fuel, its use has increased from 175 million gallons in 1980 to 4.9 billion gallons in 2006. Virtually all of the ethanol used for transportation has been produced from corn. During the period of fuel ethanol growth, corn farming productivity has increased dramatically, and energy use in ethanol plants has been reduced by almost by half. The majority of corn ethanol plants are powered by natural gas. However, as natural gas prices have skyrocketed over the last several years, efforts have been made to further reduce the energy used in ethanol plants or to switch from natural gas to other fuels, such as coal and wood chips. In this paper, we examine nine corn ethanol plant types—categorized according to the type of process fuels employed, use of combined heat and power, and production of wet distiller grains and solubles. We found that these ethanol plant types can have distinctly different energy and greenhouse gas emission effects on a full fuel-cycle basis. In particular, greenhouse gas emission impacts can vary significantly—from a 3% increase if coal is the process fuel to a 52% reduction if wood chips are used. Our results show that, in order to achieve energy and greenhouse gas emission benefits, researchers need to closely examine and differentiate among the types of plants used to produce corn ethanol so that corn ethanol production would move towards a more sustainable path.
487 citations
TL;DR: In this paper, the authors developed models to characterize delivery distances and to estimate costs, emissions and energy use from various parts of the delivery chain (e.g., compression or liquefaction, delivery and refueling stations).
449 citations
TL;DR: In this article, the authors evaluate selected hydrogen production processes based on natural gas steam reforming, coal and biomass gasification and water electrolysis and conclude that these options are expected to play a significant role in the short to medium term.
444 citations
TL;DR: In this paper, the authors compare greenhouse gas (GHG), SOx, and NOx life-cycle emissions of electricity generated with NG/LNG/SNG and coal and show that with the current fleet of power plants, a mix of domestic NG, LNG, and SNG would have lower GHG emissions than coal.
Abstract: The U.S. Department of Energy (DOE) estimates that in the coming decades the United States' natural gas (NG) demand for electricity generation will increase. Estimates also suggest that NG supply will increasingly come from imported liquefied natural gas (LNG). Additional supplies of NG could come domestically from the production of synthetic natural gas (SNG) via coal gasification−methanation. The objective of this study is to compare greenhouse gas (GHG), SOx, and NOx life-cycle emissions of electricity generated with NG/LNG/SNG and coal. This life-cycle comparison of air emissions from different fuels can help us better understand the advantages and disadvantages of using coal versus globally sourced NG for electricity generation. Our estimates suggest that with the current fleet of power plants, a mix of domestic NG, LNG, and SNG would have lower GHG emissions than coal. If advanced technologies with carbon capture and sequestration (CCS) are used, however, coal and a mix of domestic NG, LNG, and SNG ...
329 citations
TL;DR: In this paper, the authors present new experimental data at high pressure TBAB, w = 0.10, TBAB (w = 0, 0.20, and 0.43) + natural gas semi-clathrate phase boundaries.
Abstract: Tetrabutyl ammonium bromide (TBAB) forms a semi-clathrate hydrate, which can incorporate small gas molecules such as methane and nitrogen. It has recently been used for separation of gases. However, there are very limited experimental data on the phase boundaries of the gas hydrate form in the presence of TBAB. In this work, we present new experimental data at high-pressure TBAB, w = 0.10, TBAB (w = 0.10 and 0.43) + hydrogen, TBAB (w = 0.05, 0.10, 0.20, and 0.30) + methane, TBAB (w = 0.10) + nitrogen, TBAB (w = 0.1 and 0.427) + carbon dioxide, and TBAB (w = 0.05, 0.10, and 0.43) + natural gas semi-clathrate hydrate phase boundaries. In another part of this work, the results of visual observations of the methane + TBAB semi-clathrate hydrate morphology and the methane gas bubbles released from methane + TBAB semi-clathrate hydrates on dissociation are presented. Finally, the effect of TBAB mass fraction on hydrate promotion and the stability of the new semi-clathrate hydrate are presented.
291 citations
TL;DR: It is shown that the sample contains structure H hydrate, and thus provides direct evidence for the natural occurrence of this hydrate structure, and the stability field of the complex gas hydrate lies between those of structure II and structure H hydrates, indicating that this form of hydrate is more stable than structure I and may thus be found in a wider pressure–temperature regime than can methane hydrate deposits.
Abstract: Natural gas hydrates — ice-like solids that consist of 'guest' molecules trapped in cages of water molecules — are a potential source of energy and may play a role in climate change and seafloor collapse. Experiments have shown that there are three common gas hydrate structures — sI, sII and sH — but only sI and sII hydrate have been found in the natural environment. Now sH hydrate (in close association with sII hydrate) has been identified in seafloor samples from Barkley canyon, 80 km off Vancouver Island. This complex gas hydrate can trap larger guest molecules than sI or sII, and is more stable than sI hydrate, indicating that gas hydrates could be more widely distributed than previously thought. The discovery of sH hydrate in a sample from Barkley Canyon marks the first time this hydrate has been found in the natural environment. This complex gas hydrate can trap larger guest molecules than sI or sII hydrate, and is stable at higher temperatures and pressures than sI hydrate, indicating that gas hydrates could be more widely distributed than previously thought. Natural gas hydrates are a potential source of energy1 and may play a role in climate change2 and geological hazards3. Most natural gas hydrate appears to be in the form of ‘structure I’, with methane as the trapped guest molecule4, although ‘structure II’ hydrate has also been identified, with guest molecules such as isobutane and propane, as well as lighter hydrocarbons5,6. A third hydrate structure, ‘structure H’, which is capable of trapping larger guest molecules, has been produced in the laboratory7, but it has not been confirmed that it occurs in the natural environment. Here we characterize the structure, gas content and composition, and distribution of guest molecules in a complex natural hydrate sample recovered from Barkley canyon, on the northern Cascadia margin8. We show that the sample contains structure H hydrate, and thus provides direct evidence for the natural occurrence of this hydrate structure. The structure H hydrate is intimately associated with structure II hydrate, and the two structures contain more than 13 different hydrocarbon guest molecules. We also demonstrate that the stability field of the complex gas hydrate lies between those of structure II and structure H hydrates, indicating that this form of hydrate is more stable than structure I and may thus potentially be found in a wider pressure–temperature regime than can methane hydrate deposits.
285 citations
TL;DR: In this article, the application of polymeric membranes to natural gas separation accelerated with the development of asymmetric membranes, which retain their selective characteristics, but after increased permeation rates as compared to their dense counterparts.
Abstract: Various technologies are now available to design engineers to condition raw natural gas to pipeline quality. Conditioning of natural gas involves the removal of acid gases like CO2 and H2S, besides water vapor. Among different separation methods available, membrane technology has emerged to be a viable and valuable option over conventional techniques like amine absorption, in view of its advantages such as economy, process safety and environmentally benign nature. Semi‐permeable membranes were first employed in natural gas processing for more than 20 years. However, the technological breakthrough in the application of polymeric membranes to natural gas separation accelerated with the development of asymmetric membranes, which retain their selective characteristics, but after increased permeation rates as compared to their dense counterparts. Efforts to correlate the basic polymer structure with permeability and selectivity have resulted in the synthesis of novel polymers. Membranes for natural ga...
272 citations
01 Jul 2007
TL;DR: In this article, a wide-range equation of state for the thermodynamic properties of natural gases and other multi-component (and binary) mixtures was developed, called GERG-2004.
Abstract: A wide-range equation of state for the thermodynamic properties of natural gases and other multi-component (and binary) mixtures was developed. The new formulation, adopted by GERG in 2004 and called GERG-2004 equation of state or GERG-2004 for short, is a fundamental equation explicit in the Helmholtz free energy as a function of density, temperature, and composition. The mixture model uses accurate equations of state for the 18 specified natural gas components along with functions that take into account the mixture behaviour. GERG-2004 covers wide ranges of temperature, pressure, and composition and is valid in the gas phase, the liquid phase, the supercritical region, and for vapour-liquid equilibrium states. The equation achieves a high accuracy in the calculation of thermodynamic properties for a broad variety of mixtures. The wide range of validity enables the use of GERG-2004 in both standard and advanced technical applications for natural gases and related mixtures. This includes, e.g. pipeline transport, natural gas storage, improved and integrated processes with liquefied natural gas, the design of separation processes as encountered in natural gas processing, and future applications with natural gas mixtures enriched with hydrogen. (orig.)
TL;DR: In this article, the economic viability of producing baseload wind energy was explored using a cost-optimization model to simulate two competing systems: wind energy supplemented by simple-and combined cycle natural gas turbines (wind+gas) and wind Energy supplemented by compressed air energy storage (Wind+CAES).
TL;DR: In this article, gas conditioning as the processing required in the interface between CO2 capture and transport is studied for nine different natural gas fired power plant concepts and three different CO2 transport processes.
TL;DR: In this paper, the transport and distribution aspects of hydrogen during the transition period towards a possible full-blown hydrogen economy are carefully looked at, and some policy guidelines are offered, both in a regulated and a liberalised energy market.
TL;DR: In this paper, the authors applied the techniques of Magnetic Resonance Imaging (MRI) as a tool to visualize the conversion of CH4 hydrate within Bentheim sandstone matrix into the CO2 hydrate.
24 Jun 2007
TL;DR: In this article, a mathematical model of this problem is formulated as an optimization problem where the objective function is to minimize the integrated gas-electricity system operation cost and the constraints are the power system and natural gas pipeline equations and capacities.
Abstract: This paper integrates the natural gas and electricity networks in terms of power and gas optimal dispatch. It shows the fundamentals of natural gas network modeling including pipelines and compression stations. It also describes the equality constraint that models the energy transformation between gas and electric networks. A mathematical model of this problem is formulated as an optimization problem where the objective function is to minimize the integrated gas-electricity system operation cost and the constraints are the power system and natural gas pipeline equations and capacities. Case studies are presented integrating the IEEE-14 test system and Belgian calorific gas network. The integrated electricity-gas optimal power flow problem is solved using an hybrid approach which combines evolutionary strategy algorithm with Newton's and Interior point method. It hybrid approach fully takes the advantages of both evolutionary strategy optimization and classical methods (such as Newton's and interior point method) which the former is able to jump out of the local optimal point and the latter boats the local exploration ability within the neighborhood of the optimal. It increases the precision and quickens the convergence. The proposed model shows the importance of the integration of the two systems in terms of operation, planning, security and reliability.
TL;DR: In this article, the authors reviewed the cost of methanol production from biomass and CO 2 recovery from the flue gasses of a fossil fuel-fired power station and found that the production cost of CO 2-based methanols was between 500 and 600€/tonne.
TL;DR: In this paper, the authors demonstrate spontaneous ignition from sudden compressed hydrogen releases that is not well documented in the present literature, for which little fundamental explanation, discussion or research foundation exists, and which is apparently not encompassed in recent formulations of safety codes and standards for piping, storage, and use of high pressure compressed gas systems handling hydrogen.
Abstract: This paper demonstrates the "spontaneous ignition" (autoignition/inflammation and sustained diffusive combustion) from sudden compressed hydrogen releases that is not well documented in the present literature, for which little fundamental explanation, discussion or research foundation exists, and which is apparently not encompassed in recent formulations of safety codes and standards for piping, storage, and use of high pressure compressed gas systems handling hydrogen. Accidental or intended, rapid failure of a pressure boundary separating sufficiently compressed hydrogen from air can result in multi-dimensional transient flows involving shock formation, reflection, and interactions such that reactant mixtures are rapidly formed and achieve chemical ignition, inflammation, and transition to turbulent jet diffusive combustion, fed by the continuing discharge of hydrogen. Both experiments and simple transient shock theory along with chemical kinetic ignition calculations are used to support interpretation of observations and qualitatively identify controlling gas properties and geometrical parameters. Although the phenomenon is demonstrated for pressurized hydrogen burst disk failures with different internal flow geometries, similar phenomena apparently do not necessarily occur for sudden boundary failures of storage vessel or transmission piping into open air that have no downstream obstruction. However, subsequent reflection of the resulting transient shock from surrounding surfaces through mixing layers of hydrogen and air may have the potential for producing ignition and continuing combustion. Much more experimental and computational work is required to quantitatively determine the envelope of parameter combinations that mitigate or enhance spontaneous ignition characteristics of compressed hydrogen as a result of sudden release, particularly if hydrogen is to become a major energy carrier interfaced with consumer use. Similar considerations for compressed methane, for mixtures of light hydrocarbons and methane (simulating natural gas), and for larger carbon number hydrocarbons show similar autoignition phenomena may occur with highly compressed methane or natural gas, but are unlikely with higher carbon number cases, unless the compressed source and/or surrounding air is sufficiently pre-heated above ambient temperature. Spontaneous ignition of compressed hydrocarbon gases is also generally less likely, given the much lower turbulent blow-off velocity of hydrocarbons in comparison to that for hydrogen.
TL;DR: In this paper, a review on the use of adsorption and membrane technologies in H2 production is directed toward the chemical and petrochemical industries and it is further estimated that 450 trillion Btu/yr could be saved with a 20%...
Abstract: This review on the use of adsorption and membrane technologies in H2 production is directed toward the chemical and petrochemical industries. The growing requirements for H2 in chemical manufacturing, petroleum refining, and the newly emerging clean energy concepts will place greater demands on sourcing, production capacity and supplies of H2. Currently, about 41 MM tons/yr of H2 is produced worldwide, with 80% of it being produced from natural gas by steam reforming, partial oxidation and autothermal reforming. H2 is used commercially to produce CO, syngas, ammonia, methanol, and higher alcohols, urea and hydrochloric acid. It is also used in Fischer Tropsch reactions, as a reducing agent (metallurgy), and to upgrade petroleum products and oils (hydrogenation). It has been estimated that the reforming of natural gas to produce H2 consumes about 31,800 Btu/lb of H2 produced at 331 psig based on 35.5 MM tons/yr production. It is further estimated that 450 trillion Btu/yr could be saved with a 20% ...
TL;DR: In this article, Lurgi's MegaMethanol technology can bring down the net methanol production cost below US$ 50 per ton wherever low-cost natural gas or coal is available.
Abstract: Publisher Summary There are abundant natural gas reserves providing low-cost feedstock for methanol production and aiming at the better use of natural resources, especially in the case of associated gases being flared. Propylene produced from methanol increases the value of natural gas considerably and offers an exciting potential of growth and a high earning level. A similar reasoning holds true for regions where low-grade coal is found in abundance. The higher investment necessary for coal gasification is compensated by the extremely low feedstock cost afterwards. Lurgi's MegaMethanol® technology can bring down the net methanol production cost below US$ 50 per ton wherever low-cost natural gas or coal is available. This opens up a completely new field for downstream products like DME and propylene. Based on simple fixed-bed reactor systems, conventional processing elements and operating conditions, including commercially manufactured catalysts, provide attractive ways to monetize natural gas and abundant low-grade coal as well. Commercialization of GTP/MTP® has started in earnest and in fullest scale; apart from a smaller project in Iran, two world-scale plants of 471 kt/a propylene capacity are scheduled for erection in China—with the procurement of long lead items already under way.
TL;DR: In this paper, a cell-based methodology for continuous-type (unconventional) resources in the Fort Worth Basin has been used to estimate undiscovered natural gas having potential for additions to reserves in the Mississippian Barnett Shale.
Abstract: Undiscovered natural gas having potential for additions to reserves in the Mississippian Barnett Shale of the Fort Worth Basin, north-central Texas, was assessed using the total petroleum system assessment unit concept and a cell-based methodology for continuous-type (unconventional) resources. The Barnett-Paleozoic total petroleum system is defined in the Bend arch–Fort Worth Basin as encompassing the area in which the organic-rich Barnett is the primary source rock for oil and gas produced from Paleozoic carbonate and clastic reservoirs. Exploration, technology, and drilling in the Barnett Shale play have rapidly evolved in recent years, with about 3500 vertical and 1000 horizontal wells completed in the Barnett through 2005 and more than 85% of the them completed since 1999. Using framework geology and historical production data, assessment of the Barnett Shale was performed by the U.S. Geological Survey using vertical wells at the peak of vertical well completions and before a transition to completions with horizontal wells. The assessment was performed after (1) mapping critical geological and geochemical parameters to define assessment unit areas with future potential, (2) defining distributions of drainage area (cell size) and estimating ultimate recovery per cell, and (3) estimating future success rates. Two assessment units are defined and assessed for the Barnett Shale continuous gas accumulation, resulting in a total mean undiscovered volume having potential for additions to reserves of 26.2 TCFG. The greater Newark East fracture-barrier continuous Barnett Shale gas assessment unit represents a core-producing area where thick, organic-rich, siliceous Barnett Shale is within the thermal window for gas generation (Ro 1.1%) and is overlain and underlain by impermeable limestone barriers (Pennsylvanian Marble Falls Limestone and Ordovician Viola Limestone, respectively) that serve to confine induced fractures during well completion to maximize gas recovery. The extended continuous Barnett Shale gas assessment unit, which had been less explored, defines a geographic area where Barnett Shale is (1) within the thermal window for gas generation, (2) greater than 100 ft (30 m) thick, and (3) where at least one impermeable limestone barrier is absent. Mean undiscovered gas having potential for additions to reserves in the greater Newark East assessment unit is estimated at 14.6 tcf, and in the less tested extended assessment unit, a mean resource is estimated at 11.6 TCFG. A third hypothetical basin-arch Barnett Shale oil assessment unit was defined but not assessed because of a lack of production data.
TL;DR: The sustainable transport energy programme (STEP) is an initiative of the Government of Western Australia, to explore hydrogen fuel cell technology as an alternative to the existing diesel and natural gas public transit infrastructure in Perth This project includes three buses manufactured by DaimlerChrysler with Ballard fuel cell power sources operating in regular service alongside the existing natural gas and diesel bus fleets as discussed by the authors.
TL;DR: In this article, the authors present some of the technological advantages of precious metal monoliths over traditional base metal particulate catalysts for reforming hydrocarbons, such as natural gas, for the generation of distributed hydrogen.
Abstract: Distributed hydrogen for the hydrogen economy will require new catalysts and processes. Existing large‐scale hydrogen plants can not simply be reduced in size to meet the economic, safety, and frequent duty cycle requirements for applications for fuel cells, hydrogen fueling stations, and industrial uses such as hydrogenation reactions, gas turbine cooling, metal processing, etc 1 2. Consequently, there is a need to completely reassess how hydrogen can be made for the emerging hydrogen economy. This article presents some of the technological advantages of precious metal monoliths over traditional base metal particulate catalysts for reforming hydrocarbons, such as natural gas, for the generation of distributed hydrogen.
Patent•
22 Mar 2007
TL;DR: In this paper, a system and method for treating a mixture of hydrocarbon and carbon dioxide gas produced from a hydrocarbon reservoir is described, which includes a gas power turbine adapted to burn the produced gas mixture with oxygen as an oxidizing agent and a capture system to collect the exhaust gas from the power turbine.
Abstract: A system and method is disclosed for treating a mixture of hydrocarbon and carbon dioxide gas produced from a hydrocarbon reservoir. The system includes a gas power turbine adapted to burn the produced gas mixture of hydrocarbon and carbon dioxide gas with oxygen as an oxidizing agent and a capture system to collect the exhaust gas from the power turbine. An inlet compressor receives exhaust gas from the capture system and compresses the exhaust gas for injection of the exhaust gas into a hydrocarbon reservoir and for recycle to the power turbine. The system may further include a membrane system that preferentially removes carbon dioxide and hydrogen sulfide from the produced gas stream before said stream is used as fuel gas in the power turbine. The carbon dioxide and hydrogen sulfide removed by the membrane system is combined with the exhaust gas, and the combined gas is injected into a hydrocarbon reservoir.
TL;DR: In this paper, the authors examined the effects of reservoir heterogeneity on the migration and storage of a 50 million tonne plume over a time scale of 1000 years and showed that heterogeneity had a significant impact on the subsurface behavior of the carbon dioxide.
TL;DR: In this paper, the authors evaluate the importance of Joule-Thomson cooling during CO2 injection into depleted natural gas reservoirs, which is the adiabatic cooling that accompanies the expansion of a real gas.
TL;DR: In this article, a model and simulation of the behavior of a tubular SOFC using GIR and a comparison between utilization in DIR and GIR is presented. But, the authors do not investigate the carbon formation boundary for SOFCs fuelled by methane.
TL;DR: In this article, the authors investigated the adsorption equilibrium and kinetic separation potential of β-zeolite for N2, O2, CO2 and CH4 gases by using concentration pulse chromatography.
TL;DR: In this paper, uncertainties about conventional petroleum resources and substitutes for conventional petroleum, focusing on the impact of these uncertainties on future greenhouse gas (GHG) emissions, were investigated, and the potential effects of a transition to petroleum substitutes on GHG emissions were significant.
Abstract: We investigate uncertainties about conventional petroleum resources and substitutes for conventional petroleum, focusing on the impact of these uncertainties on future greenhouse gas (GHG) emissions. We use examples from the IPCC Special Report on Emissions Scenarios as a baseline for comparison. The studied uncertainties include, (1) uncertainty in emissions factors for petroleum substitutes, (2) uncertainties resulting from poor knowledge of the amount of remaining conventional petroleum, and (3) uncertainties about the amount of production of petroleum substitutes from natural gas and coal feedstocks. We find that the potential effects of a transition to petroleum substitutes on GHG emissions are significant. A transition to low-quality and synthetic petroleum resources such as tar sands or coal-to-liquids synfuels could raise upstream GHG emissions by several gigatonnes of carbon (GtC) per year by mid-century unless mitigation steps are taken.