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00985 Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels
03 Gaseous fuels (economics, business, marketing, policy) lines increases only slightly. Moreover, at 40 bar and 258 K the amount of liquid condensate is slightly less in the case of hydrogen if the same amount of energy is transported.
05•00983 Improved methane storage capacities by sorption on wet active carbons Perrin, A. et al. Carbon, 2004, 42, (7), I249 1256. The possibility of storing large amounts of natural gas within wet active carbons is examined. The sorption isotherms of methane at 2°C and up to 8 MPa are built for four carbonaceous materials. Three of them originate from the same precursor (coconut shell), are physically activated at various burn-offs and are mainly microporous. The fourth material is a highly mesoporous chemically activated pinewood carbon. These adsorbents are wetted with a constant weight ratio water/carbon close to 1. The resulting isotherms all exhibit a marked step occurring near the expected formation pressure of methane hydrates, thus supporting their occurrence within the porous materials. The amount of gas stored at the highest pressures investigated then ranges from 6 to 17 mol/kg of wet adsorbent (i.e., corresponding to 10-36 mol/kg of dry carbon), depending on the material. The results are discussed on the basis of the known pore texture of each adsorbent, and stoichiometries of the formed hydrates are calculated. Considerations about adsorption/desorption kinetics and metastability are also developed.
05•00984 Interaction of hydrogen with carbon coils at low temperature Furuya, Y. et al. Carbon, 2004, 42, (2), 331-335. Hydrogen was adsorbed on carbon coils under 10 MPa hydrogen gas at liquid nitrogen temperature. The equilibrium pressure of hydrogen desorbed from the as-grown carbon coils with an amorphous structure was three to four tim~s greater than those of multi-wall carbon nanotubes (MWNT) and active carbons (AC). The heat treatment of the carbon coils at 850°C contributed to an increase in hydrogen adsorption by 20% compared to the as-grown carbon coils. On the other hand, the adsorption of hydrogen gas on the carbon coils decreased significantly after heat treatment at a temperature higher than 1000°C due to formation of capsule-like carbon composed of 1020 layers on the surface of the carbon coils.
05/00985 Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels Staat, M. International Journal of Pressure Vessels and Piping, 2005, 82, (3), 217-225. Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. F E M suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to F E M limit analyses for all crack dimensions.
05•00986 Studies on improvement of hydrogen storage capacity of AB5 type: MmNi4.6Fe0.4 alloy Singh, A. et al. International Journal of Hydrogen Energy, 2004, 29, (11), 1151-1156. This paper deals with enhancement of hydrogen storage capacity for AB 5 type alloy MmNi4.6Fe0.4 from approximately 1.5 to approximately 2.04 wt%. It has been shown that through suitable processing involving ball milling with specific parameters (200 rpm, 20 rain), the alloy particles besides getting fractured to smaller particles also become strained. The maximum strain, increase in lattice constant and unit cell volume are achieved for ball milling parameters of approximately 200 rpm and 20 rain. It has been suggested that the increase in the unit cell volume results in increase of interstitial hole sizes. This induces higher number of interstitials in unit cell of the material MmN4.6Fe0.4 to be occupied by hydrogen atoms resulting in increase of hydrogen storage capacity from its value of approximately 1.5 wt% obtained in the assynthesized material to approximately 2.04 wt% for ball-milled materials which embody strained particles.
Economics, business, marketing, policy 05100987 Coalbed methane in the Ruhr Basin, Germany: a renewable energy resource? Thielemann, T. et al. Organic Geochemistry, 2004, 35, (l 1-12), 15371549. Around the globe underground hard coal mining leads to a release of methane into the atmosphere. About 7% of the global annual methane emissions originate from coal mining. In the year 2002, 16 countries
f 52 Fuel and Energy Abstracts
May 2005
used coal gas to generate heat and electricity. In many cases, the exact size of coalbed methane reservoirs is not identified. The possibility of a long-term gas production and its profitability at single sites are unknown. To clarify these points, the processes of gas generation as well as the gas-in-place volume have to be determined. Both issues are tackled here for the Ruhr basin. Within this basin, coal gas samples were taken at 13 gas production sites, spread over three samplings within 14 months. There were virtually no changes in the concentrations of gas components at single sites within this period. The isotope composition of methane (61°C-methane: -40.0 to -57.3%o vs. PDB) revealed that the produced methane is a mixture of gases of thermogenic and microbial origin. The microbial contribution of methane seems to be more pronounced at sites of active and especially abandoned coal mining than at unmined places. Ethane and propane are of thermogenic origin, with ethane's isotopic composition tending to heavier values (richer in 13C) with time. This time-dependent phenomenon is interpreted as being caused by desorption. In addition, living methanogenic archaea were detected in mine water samples from depths down to 1200 m.
05100988 Effect of compression ratio, equivalence ratio and engine speed on the performance and emission characteristics of a spark ignition engine using hydrogen as a fuel Sadiq A1-Baghdadi, M. A. R. Renewable Energy, 2004, 29, (15), 22452260. The present energy situation has stimulated active research interest in non-petroleum and non-polluting fuels, particularly for transportation, power generation, and agricultural sectors. Researchers have found that hydrogen presents the best and an unprecedented solution to the energy crises and pollution problems, due to its superior combustion qualities and availability. This paper discusses analytically and provides data on the effect of compression ratio, equivalence ratio and engine speed on the engine performance, emissions and pre-ignition limits of a spark ignition engine operating on hydrogen fuel. These data are important in order to understand the interaction between engine performance and emission parameters, which will help engine designers when designing for hydrogen.
05•00989 Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation Taiima, H. et al. Energy, 2004, 29, (11), 1713-1729. The process energy consumption was estimated for gas separation processes by the formation of clathrate hydrates. The separation process is based on the equilibrium partition of the components between the gaseous phase and the hydrate phase. The separation and capturing processes of greenhouse gases were examined in this study. The target components were hydrofluorocarbon (HFC-134a) from air, sulfur hexafluoride (SF6) from nitrogen, and COz from flue gas. Since these greenhouse gases would form hydrates under much lower pressure and higher temperature conditions than the accompanying components, the effective capturing of the greenhouse gases could be achieved by using hydrate formation. A model separation process for each gaseous mixture was designed from the basis of thermodynamics, and the process energy consumption was estimated. The obtained results were then compared with those for conventional separation processes such as liquefaction separation processes. For the recovery of SF6, the hydrate process is preferable to liquefaction process in terms of energy consumption. On the other hand, the liquefaction process consumes less energy than the hydrate process for the recovery of HFC-134a. The capturing of CO2 by the hydrate process from a flue gas will consume a considerable amount of energy; mainly due to the extremely high pressure conditions required for hydrate formation. The influences of the operation conditions on the heat of hydrate formation were elucidated by sensitivity analysis. The hydrate processes for separating these greenhouse gases were evaluated in terms of reduction of global warming potential (GWP).
05•00990 Improving air quality in large cities by substituting natural gas for coal in China: changing idea and incentive policy implications Mao, X. et al. Energy Policy, 2005, 33, (3), 307-318. Natural gas has long been used in China mainly as chemical raw material. With the increasing emphasis on urban air pollution prevention, the issue of natural gas substitution to coal has been raised in many large Chinese cities. This paper reviews the environmental-economic-technical rationality of dashing-for-gas in urban area, especially for civil use such as cooking and heating in China. Taking Beijing and Chongqing as study cases, a cost-benefit analysis of natural gas substitution is done and the ongoing economic and system barriers to natural gas penetration are analysed. Indications of natural gas penetration incentive policy making are given finally.
05•00983 Improved methane storage capacities by sorption on wet active carbons Perrin, A. et al. Carbon, 2004, 42, (7), I249 1256. The possibility of storing large amounts of natural gas within wet active carbons is examined. The sorption isotherms of methane at 2°C and up to 8 MPa are built for four carbonaceous materials. Three of them originate from the same precursor (coconut shell), are physically activated at various burn-offs and are mainly microporous. The fourth material is a highly mesoporous chemically activated pinewood carbon. These adsorbents are wetted with a constant weight ratio water/carbon close to 1. The resulting isotherms all exhibit a marked step occurring near the expected formation pressure of methane hydrates, thus supporting their occurrence within the porous materials. The amount of gas stored at the highest pressures investigated then ranges from 6 to 17 mol/kg of wet adsorbent (i.e., corresponding to 10-36 mol/kg of dry carbon), depending on the material. The results are discussed on the basis of the known pore texture of each adsorbent, and stoichiometries of the formed hydrates are calculated. Considerations about adsorption/desorption kinetics and metastability are also developed.
05•00984 Interaction of hydrogen with carbon coils at low temperature Furuya, Y. et al. Carbon, 2004, 42, (2), 331-335. Hydrogen was adsorbed on carbon coils under 10 MPa hydrogen gas at liquid nitrogen temperature. The equilibrium pressure of hydrogen desorbed from the as-grown carbon coils with an amorphous structure was three to four tim~s greater than those of multi-wall carbon nanotubes (MWNT) and active carbons (AC). The heat treatment of the carbon coils at 850°C contributed to an increase in hydrogen adsorption by 20% compared to the as-grown carbon coils. On the other hand, the adsorption of hydrogen gas on the carbon coils decreased significantly after heat treatment at a temperature higher than 1000°C due to formation of capsule-like carbon composed of 1020 layers on the surface of the carbon coils.
05/00985 Local and global collapse pressure of longitudinally flawed pipes and cylindrical vessels Staat, M. International Journal of Pressure Vessels and Piping, 2005, 82, (3), 217-225. Limit loads can be calculated with the finite element method (FEM) for any component, defect geometry, and loading. F E M suggests that published long crack limit formulae for axial defects under-estimate the burst pressure for internal surface defects in thick pipes while limit loads are not conservative for deep cracks and for pressure loaded crack-faces. Very deep cracks have a residual strength, which is modelled by a global collapse load. These observations are combined to derive new analytical local and global collapse loads. The global collapse loads are close to F E M limit analyses for all crack dimensions.
05•00986 Studies on improvement of hydrogen storage capacity of AB5 type: MmNi4.6Fe0.4 alloy Singh, A. et al. International Journal of Hydrogen Energy, 2004, 29, (11), 1151-1156. This paper deals with enhancement of hydrogen storage capacity for AB 5 type alloy MmNi4.6Fe0.4 from approximately 1.5 to approximately 2.04 wt%. It has been shown that through suitable processing involving ball milling with specific parameters (200 rpm, 20 rain), the alloy particles besides getting fractured to smaller particles also become strained. The maximum strain, increase in lattice constant and unit cell volume are achieved for ball milling parameters of approximately 200 rpm and 20 rain. It has been suggested that the increase in the unit cell volume results in increase of interstitial hole sizes. This induces higher number of interstitials in unit cell of the material MmN4.6Fe0.4 to be occupied by hydrogen atoms resulting in increase of hydrogen storage capacity from its value of approximately 1.5 wt% obtained in the assynthesized material to approximately 2.04 wt% for ball-milled materials which embody strained particles.
Economics, business, marketing, policy 05100987 Coalbed methane in the Ruhr Basin, Germany: a renewable energy resource? Thielemann, T. et al. Organic Geochemistry, 2004, 35, (l 1-12), 15371549. Around the globe underground hard coal mining leads to a release of methane into the atmosphere. About 7% of the global annual methane emissions originate from coal mining. In the year 2002, 16 countries
f 52 Fuel and Energy Abstracts
May 2005
used coal gas to generate heat and electricity. In many cases, the exact size of coalbed methane reservoirs is not identified. The possibility of a long-term gas production and its profitability at single sites are unknown. To clarify these points, the processes of gas generation as well as the gas-in-place volume have to be determined. Both issues are tackled here for the Ruhr basin. Within this basin, coal gas samples were taken at 13 gas production sites, spread over three samplings within 14 months. There were virtually no changes in the concentrations of gas components at single sites within this period. The isotope composition of methane (61°C-methane: -40.0 to -57.3%o vs. PDB) revealed that the produced methane is a mixture of gases of thermogenic and microbial origin. The microbial contribution of methane seems to be more pronounced at sites of active and especially abandoned coal mining than at unmined places. Ethane and propane are of thermogenic origin, with ethane's isotopic composition tending to heavier values (richer in 13C) with time. This time-dependent phenomenon is interpreted as being caused by desorption. In addition, living methanogenic archaea were detected in mine water samples from depths down to 1200 m.
05100988 Effect of compression ratio, equivalence ratio and engine speed on the performance and emission characteristics of a spark ignition engine using hydrogen as a fuel Sadiq A1-Baghdadi, M. A. R. Renewable Energy, 2004, 29, (15), 22452260. The present energy situation has stimulated active research interest in non-petroleum and non-polluting fuels, particularly for transportation, power generation, and agricultural sectors. Researchers have found that hydrogen presents the best and an unprecedented solution to the energy crises and pollution problems, due to its superior combustion qualities and availability. This paper discusses analytically and provides data on the effect of compression ratio, equivalence ratio and engine speed on the engine performance, emissions and pre-ignition limits of a spark ignition engine operating on hydrogen fuel. These data are important in order to understand the interaction between engine performance and emission parameters, which will help engine designers when designing for hydrogen.
05•00989 Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation Taiima, H. et al. Energy, 2004, 29, (11), 1713-1729. The process energy consumption was estimated for gas separation processes by the formation of clathrate hydrates. The separation process is based on the equilibrium partition of the components between the gaseous phase and the hydrate phase. The separation and capturing processes of greenhouse gases were examined in this study. The target components were hydrofluorocarbon (HFC-134a) from air, sulfur hexafluoride (SF6) from nitrogen, and COz from flue gas. Since these greenhouse gases would form hydrates under much lower pressure and higher temperature conditions than the accompanying components, the effective capturing of the greenhouse gases could be achieved by using hydrate formation. A model separation process for each gaseous mixture was designed from the basis of thermodynamics, and the process energy consumption was estimated. The obtained results were then compared with those for conventional separation processes such as liquefaction separation processes. For the recovery of SF6, the hydrate process is preferable to liquefaction process in terms of energy consumption. On the other hand, the liquefaction process consumes less energy than the hydrate process for the recovery of HFC-134a. The capturing of CO2 by the hydrate process from a flue gas will consume a considerable amount of energy; mainly due to the extremely high pressure conditions required for hydrate formation. The influences of the operation conditions on the heat of hydrate formation were elucidated by sensitivity analysis. The hydrate processes for separating these greenhouse gases were evaluated in terms of reduction of global warming potential (GWP).
05•00990 Improving air quality in large cities by substituting natural gas for coal in China: changing idea and incentive policy implications Mao, X. et al. Energy Policy, 2005, 33, (3), 307-318. Natural gas has long been used in China mainly as chemical raw material. With the increasing emphasis on urban air pollution prevention, the issue of natural gas substitution to coal has been raised in many large Chinese cities. This paper reviews the environmental-economic-technical rationality of dashing-for-gas in urban area, especially for civil use such as cooking and heating in China. Taking Beijing and Chongqing as study cases, a cost-benefit analysis of natural gas substitution is done and the ongoing economic and system barriers to natural gas penetration are analysed. Indications of natural gas penetration incentive policy making are given finally.