The steel with the new microstructure, bimodal submicrometer equiaxed ferrite grains with uniformly dis- tributed nanosized cementite particles, was manufactured by a new approach utilizing simple cold-rolling and sub...The steel with the new microstructure, bimodal submicrometer equiaxed ferrite grains with uniformly dis- tributed nanosized cementite particles, was manufactured by a new approach utilizing simple cold-rolling and subsequent annealing of a dual phase ferrite-martensite starting structure. The mean ferrite grain size and carbide size range of the specimen after 80% cold-rolling and subsequent annealing at 600 ℃ for 20 min were 0.35 μm and 70-140 nm, respec- tively. A combination of bimodal ultrafine ferrite and nanoscale carbides used as a more effective method for achieving an excellent balance in strength-ductility. The strength of the steel with the new microstructure increased to about 880 MPa （nearly 60% higher than that of the as-received state, e.g., 540 MPa）, without significant loss of ductility.展开更多
Methanol has been used to prevent hydrate formation in industrial handling of hydrate forming mixtures containing water for many decades.Ethanol is also used for the same purpose in countries that have easy access to ...Methanol has been used to prevent hydrate formation in industrial handling of hydrate forming mixtures containing water for many decades.Ethanol is also used for the same purpose in countries that have easy access to low price ethanol,like for instance Brasil.Common to these small alcohols is that they also have surfactant properties that will promote hydrate formation,but when added to water in sufficient amounts,the hydrate prevention characteristics will dominate.These alcohols will primarily prevent heterogeneous hydrate formation on the interface between water and a separate hydrate phase.The effect of“alcohol”on both of these routes to hydrate formation are investigated and compared to experimental data.In particular we also investigate the effects of these small alcohols on Gibbs free energy for the hydrate formed on the new,shifted,stability conditions.Gibbs free energy is generally higher than hydrate formed from pure water.Enthalpies of hydrate formation are also higher for hydrate formed from water containing alcohols.These are negative numbers,so in absolute values released formation enthalpy is lower.The presence of these alcohols in water will also prevent homogeneous hydrate formation from dissolved hydrate formers in water.Glycols have more important roles in other routes to hydrate nucleation.Heterogeneous hydrate nucleation towards mineral surfaces is feasible in different ways.Polar hydrate formers like H2S and CO_(2)can adsorb directly on rust,and as discussed here,are able to form hydrate from adsorbed state on rust surface.Non-polar hydrocarbons like,for instance methane might get trapped in structured water and then nucleate to hydrate.Some research on this is published and further research is in progress.Glycols have very strong attraction to rust and corresponding chemical potentials for adsorbed glycols on rust are favourable enough to facilitate phase transition from glycols dissolved in water over to adsorption.Injection of glycol in gas processing plants has been used by industry for many years and in many cases it might even be economically and technically feasible compared to expensive drying units.Exceptions are situations that will lead to water/glycol freezing.But even in multiphase transport of hydrocarbons with various water cuts,mixtures of alcohols might be a technically efficient solution in which the small alcohols may be very efficient as discussed above and glycols may go through adsorption phase transition from water solution over to glycol film on rust and prevent hydrate nucleation towards rust surface.This possible strategy requires more theoretical work as well as experimental investigation.On the basis of thermodynamic analysis and calculations of hydrate formation from different routes,it is argued that real natural and industrial systems are unable to reach thermodynamic equilibrium.It is therefore a need for a consistent thermodynamic platform with a uniform reference system for all phases.We propose and demonstrate a residual thermodynamic model system for all phases.展开更多
The global amount of energy contained in natural gas hydrates is huge,maybe as much as twice all known conventional fossil fuel resources.Unlike the worldwide distribution of conventional fossil fuels,hydrocarbons tra...The global amount of energy contained in natural gas hydrates is huge,maybe as much as twice all known conventional fossil fuel resources.Unlike the worldwide distribution of conventional fossil fuels,hydrocarbons trapped in water as hydrate is also available in countries with limited conventional hydrocarbon resources.The development towards lower global emissions of greenhouse gases requires new strategies for the use of hydrocarbons,whether they are available as conventional resources,or in the form of natural gas hydrates.In this work we outline some possible strategies of utilizing hydrocarbon energy resources in a clean and environmentally friendly way.The use of carbon dioxide for producing hydrates is not new.Results from several experimental studies are available.In this work we shed more light on thermodynamic limitations and the need for additives in order to make the approach technically efficient.Through thermodynamic analysis we show that up to 20 mol per cent N2 is feasible in a CO2/N2 injection gas based on ability to form a new hydrate with free pore water and the released enthalpy needed to dissociate in situ CH4 hydrate.Surfactant is also needed in order to keep the injection gas front free of blocking hydrate films.Small alcohols like methanol and ethanol have surfactant properties.It is demonstrated that even 10 wt%ethanol in liquid pore water still makes it feasible to create a new hydrate from injection gas containing 20 mol per cent N2.Consequences of other components than CH4 in the hydrate are also discussed.And in practical cases with a well-defined source of CO2 it is also important to investigate impact of other components like for instance H2S on the stability of injection gas hydrate,as well as changes in enthalpy of hydrate formation.Another key element of this work is the conversion of produced hydrocarbons over to hydrogen and carbon dioxide using steam cracking.The technology for this is very old and in daily use.展开更多
Mineral surfaces adsorb water to extreme densities and corresponding low chemical potentials.This results in a dual effect in terms of hydrate.Water and slightly polar components adsorb directly on mineral surfaces an...Mineral surfaces adsorb water to extreme densities and corresponding low chemical potentials.This results in a dual effect in terms of hydrate.Water and slightly polar components adsorb directly on mineral surfaces and generate efficient conditions for hydrate nucleation.But due to the extremely low chemical potential of adsorbed water the hydrate nuclei formed towards mineral surfaces have to either detach from the vicinity of mineral surfaces,or be bridged by structured water in a dynamic attachment of hydrate cores some few nm outside mineral surfaces.During transport of gas(CH4,gas mixtures,CO2)the conventional water dew-point analysis will typically result in a substantially higher acceptable water concentration as compared to the concentration for adsorption of water from gas to rust surface.Direct formation of hydrate from water dissolved in gas is thermodynamically feasible,as discussed in open literature.In this work we demonstrate that it is also feasible in terms of mass transport.A new theory for enthalpy of hydrate dissociation has been extended to also direct hydrate formation from water dissolved in gas.The remaining question is whether direct hydrate formation from gas is also feasible in terms of transporting the hydrate formation heat away through a heat insulating medium.We propose further research strategies to enlighten this issue.Addition of glycols to critical points in processing of gas or transport is already in use by companies like for instance EQUINOR.There is,however,a need for more work on how efficient it is and if it can also be used for multiphase transport of hydrocarbons with significant water cut.Some research activities are in progress and briefly outlined here.展开更多
文摘The steel with the new microstructure, bimodal submicrometer equiaxed ferrite grains with uniformly dis- tributed nanosized cementite particles, was manufactured by a new approach utilizing simple cold-rolling and subsequent annealing of a dual phase ferrite-martensite starting structure. The mean ferrite grain size and carbide size range of the specimen after 80% cold-rolling and subsequent annealing at 600 ℃ for 20 min were 0.35 μm and 70-140 nm, respec- tively. A combination of bimodal ultrafine ferrite and nanoscale carbides used as a more effective method for achieving an excellent balance in strength-ductility. The strength of the steel with the new microstructure increased to about 880 MPa （nearly 60% higher than that of the as-received state, e.g., 540 MPa）, without significant loss of ductility.
基金The authors are grateful for financial support through 111 Project(No:D21025)National Key Research and Development Program(No:2019YFC0312300)+1 种基金National Natural Science Foundation Item of China(No:U20B6005-05,51874252 and 5177041544)Open Fund Project of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(No:PLN2021-02 and PLN2021-03).
文摘Methanol has been used to prevent hydrate formation in industrial handling of hydrate forming mixtures containing water for many decades.Ethanol is also used for the same purpose in countries that have easy access to low price ethanol,like for instance Brasil.Common to these small alcohols is that they also have surfactant properties that will promote hydrate formation,but when added to water in sufficient amounts,the hydrate prevention characteristics will dominate.These alcohols will primarily prevent heterogeneous hydrate formation on the interface between water and a separate hydrate phase.The effect of“alcohol”on both of these routes to hydrate formation are investigated and compared to experimental data.In particular we also investigate the effects of these small alcohols on Gibbs free energy for the hydrate formed on the new,shifted,stability conditions.Gibbs free energy is generally higher than hydrate formed from pure water.Enthalpies of hydrate formation are also higher for hydrate formed from water containing alcohols.These are negative numbers,so in absolute values released formation enthalpy is lower.The presence of these alcohols in water will also prevent homogeneous hydrate formation from dissolved hydrate formers in water.Glycols have more important roles in other routes to hydrate nucleation.Heterogeneous hydrate nucleation towards mineral surfaces is feasible in different ways.Polar hydrate formers like H2S and CO_(2)can adsorb directly on rust,and as discussed here,are able to form hydrate from adsorbed state on rust surface.Non-polar hydrocarbons like,for instance methane might get trapped in structured water and then nucleate to hydrate.Some research on this is published and further research is in progress.Glycols have very strong attraction to rust and corresponding chemical potentials for adsorbed glycols on rust are favourable enough to facilitate phase transition from glycols dissolved in water over to adsorption.Injection of glycol in gas processing plants has been used by industry for many years and in many cases it might even be economically and technically feasible compared to expensive drying units.Exceptions are situations that will lead to water/glycol freezing.But even in multiphase transport of hydrocarbons with various water cuts,mixtures of alcohols might be a technically efficient solution in which the small alcohols may be very efficient as discussed above and glycols may go through adsorption phase transition from water solution over to glycol film on rust and prevent hydrate nucleation towards rust surface.This possible strategy requires more theoretical work as well as experimental investigation.On the basis of thermodynamic analysis and calculations of hydrate formation from different routes,it is argued that real natural and industrial systems are unable to reach thermodynamic equilibrium.It is therefore a need for a consistent thermodynamic platform with a uniform reference system for all phases.We propose and demonstrate a residual thermodynamic model system for all phases.
文摘The global amount of energy contained in natural gas hydrates is huge,maybe as much as twice all known conventional fossil fuel resources.Unlike the worldwide distribution of conventional fossil fuels,hydrocarbons trapped in water as hydrate is also available in countries with limited conventional hydrocarbon resources.The development towards lower global emissions of greenhouse gases requires new strategies for the use of hydrocarbons,whether they are available as conventional resources,or in the form of natural gas hydrates.In this work we outline some possible strategies of utilizing hydrocarbon energy resources in a clean and environmentally friendly way.The use of carbon dioxide for producing hydrates is not new.Results from several experimental studies are available.In this work we shed more light on thermodynamic limitations and the need for additives in order to make the approach technically efficient.Through thermodynamic analysis we show that up to 20 mol per cent N2 is feasible in a CO2/N2 injection gas based on ability to form a new hydrate with free pore water and the released enthalpy needed to dissociate in situ CH4 hydrate.Surfactant is also needed in order to keep the injection gas front free of blocking hydrate films.Small alcohols like methanol and ethanol have surfactant properties.It is demonstrated that even 10 wt%ethanol in liquid pore water still makes it feasible to create a new hydrate from injection gas containing 20 mol per cent N2.Consequences of other components than CH4 in the hydrate are also discussed.And in practical cases with a well-defined source of CO2 it is also important to investigate impact of other components like for instance H2S on the stability of injection gas hydrate,as well as changes in enthalpy of hydrate formation.Another key element of this work is the conversion of produced hydrocarbons over to hydrogen and carbon dioxide using steam cracking.The technology for this is very old and in daily use.
基金The authors are grateful for financial support through 111 Project(No:D21025)National Key Research and Development Program(No:2019YFC0312300)+1 种基金National Natural Science Foundation Item of China(No:U20B6005-05,51874252 and 5177041544)Open Fund Project of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(No:PLN2021-02 and PLN2021-03).
文摘Mineral surfaces adsorb water to extreme densities and corresponding low chemical potentials.This results in a dual effect in terms of hydrate.Water and slightly polar components adsorb directly on mineral surfaces and generate efficient conditions for hydrate nucleation.But due to the extremely low chemical potential of adsorbed water the hydrate nuclei formed towards mineral surfaces have to either detach from the vicinity of mineral surfaces,or be bridged by structured water in a dynamic attachment of hydrate cores some few nm outside mineral surfaces.During transport of gas(CH4,gas mixtures,CO2)the conventional water dew-point analysis will typically result in a substantially higher acceptable water concentration as compared to the concentration for adsorption of water from gas to rust surface.Direct formation of hydrate from water dissolved in gas is thermodynamically feasible,as discussed in open literature.In this work we demonstrate that it is also feasible in terms of mass transport.A new theory for enthalpy of hydrate dissociation has been extended to also direct hydrate formation from water dissolved in gas.The remaining question is whether direct hydrate formation from gas is also feasible in terms of transporting the hydrate formation heat away through a heat insulating medium.We propose further research strategies to enlighten this issue.Addition of glycols to critical points in processing of gas or transport is already in use by companies like for instance EQUINOR.There is,however,a need for more work on how efficient it is and if it can also be used for multiphase transport of hydrocarbons with significant water cut.Some research activities are in progress and briefly outlined here.
