Atmospheric escape is an essential process that affects the evolution of the proto-atmosphere.The atmospheric escape of early terrestrial planets was extremely rapid compared with the current scenarios,and the main at...Atmospheric escape is an essential process that affects the evolution of the proto-atmosphere.The atmospheric escape of early terrestrial planets was extremely rapid compared with the current scenarios,and the main atmospheric escape modes were also quite different.During the dissipation of the nebula disk,the primordial atmosphere experienced a brief but violent"boiling"escape,in which most of the primordial atmosphere was lost.After the nebula disk dissipates,hydrodynamic escape and impact erosion are the two most important mass-loss mechanisms for the proto-atmosphere.Hydrodynamic escape is a rapid atmospheric escape process caused by strong solar radiation,while impact erosion refers to the process in which small-large or giant impacts erode the proto-atmosphere.In the early solar system,there were other escape mechanisms,such as non-thermodynamic escape and Jeans escape,but it is generally believed that these mechanisms have relatively little impact.Here we systematically introduce the above-mentioned atmospheric escape mechanisms and then make some suggestions for the existing problems and future research for atmospheric escape models.展开更多
The pressure in liquefied natural gas (LNG) storage tank continues to increase due to the heat transfer from ambient air to low temperature LNG, which raises safety concerns. Accordingly, there is increasing interest ...The pressure in liquefied natural gas (LNG) storage tank continues to increase due to the heat transfer from ambient air to low temperature LNG, which raises safety concerns. Accordingly, there is increasing interest to explore the technical approaches capable of recovering Boil-Off Gas (BOG) and even eliminating the ventilation of LNG storage tank. This research numerically analyzed the greenhouse gas emissions of the re-liquefaction of BOG using the following four approaches: 1) a Claude cycle driven by electrical motor with the electricity produced by burning coal;2) a Claude cycle driven by a gas turbine fuelled by BOG released;3) a Claude cycle driven by a SI engine fuelled by gasoline;4) burning nature gas directly released by BOG. The impact of heat transfer coefficient, LNG tank configuration, size, and percentage of LNG stored in tank on the rate of BOG and energy needed for the re-liquefaction of methane vapor were investigated. The greenhouse gas emissions (GGE) was examined and compared. The data presented in this paper provide guideline for the management of pressure development in LNG storage tank.展开更多
Boil-Off Gas creation and usage has been a source of worry in Liquefied Natural Gas value supply chain. BOG is generated when there is temperature gradient between the environment and LNG temperature within the carrie...Boil-Off Gas creation and usage has been a source of worry in Liquefied Natural Gas value supply chain. BOG is generated when there is temperature gradient between the environment and LNG temperature within the carrier tank, process lines or vessels. In this work, Computer Aided Design for the recovery of BOG from flare in an LNG Plant considered the dynamic nature of the BOG with minimized total energy consumption. A rigorous simulation based optimization model using HYSYS V8.8 was presented. Possible BOG scenarios were formulated in this report and considerations taken from the BOG scenarios to form the basic scope of this work. An Aspen HYSYS Software was used to develop a Process Flow Scheme (PFS) which was simulated using the BOG scenarios formulated. The BOG scenario temperatures considered were -15°C for Warm Ship analogy, -90°C for Cold Ship and -140°C for Normal Design Mode. Assumptions were also made on the feed into the developed PFS before quenching the various BOG temperatures. With HYSYS simulation at assumed constant inlet mass flow rate of 25,000 kg/s for BOG FEED, 6250 kg/s for LNG & LNG1 FEED, quenching at various BOG feed temperature -15°C, -90°C and -140°C, gave a meaningful output. The Mass flow rate recovered from Warm Ship at -15°C for Cold Product was 35,183 Kg/s and for Liquid Product 2317 Kg/s. For Cold ship at -90°C, the Cold Product recovered was 32,174 Kg/s and Liquid Product was 5326 Kg/s. Also, for -140°C, the Cold Product was 28,004 Kg/s and the Liquid Product was 9496 Kg/s. The Energy stream for the Compressor, Cooler and Pump in the Process Flow Stream (PFS) were observed in Table 5. At -15°C, the Compressor energy was 3.22E+07KJ/h, while the Pump energy was 3412KJ/h, and the Cooler gave 1.90E+07KJ/h. The results above showed that excessive BOG from Warm ship can be quenched and recovered for other end users rather than undue flaring of the gases. Extra work needs to be done to ensure minimal energy utilisation, optimal recovery and high efficiency of this developed model.展开更多
液化天然气(LNG)储存运输过程中产生的闪蒸气(boil off gas,BOG)具有一定的安全隐患。本文基于前人关于BOG的研究,查阅大量文献,对BOG的主要组成、产生原因和环境影响进行归纳整理,对以往的传统处理工艺以及新型处理工艺进行总结分析,...液化天然气(LNG)储存运输过程中产生的闪蒸气(boil off gas,BOG)具有一定的安全隐患。本文基于前人关于BOG的研究,查阅大量文献,对BOG的主要组成、产生原因和环境影响进行归纳整理,对以往的传统处理工艺以及新型处理工艺进行总结分析,对减少BOG排放量的相关措施进行评述,并总结目前已经得到应用的新技术,以期为今后更高效地利用BOG提供参考。展开更多
基于Fluent计算软件,对某型天然气焚烧装置(gascombustion unit,GCU)进行数值模拟研究,分别在最高工况和最低工况下,以100%、70%、30%等3种CH4体积分数进行仿真模拟,对燃烧后温度场、速度场和CH4体积分数分布进行数值模拟。模拟结果表明...基于Fluent计算软件,对某型天然气焚烧装置(gascombustion unit,GCU)进行数值模拟研究,分别在最高工况和最低工况下,以100%、70%、30%等3种CH4体积分数进行仿真模拟,对燃烧后温度场、速度场和CH4体积分数分布进行数值模拟。模拟结果表明:在最大工况下,随着蒸发气(boil of gas,BOG)中可燃物组分的降低,排气温度降低,高温区段变短,CH4扩散区域变小,火焰长度变短,宽度无明显变化;在最小工况下,火焰不再聚拢成型,随着BOG中可燃物组分的降低,排气温度降低,高温区域无明显变化。展开更多
基金supported by National Science Foundation(41973063)Strategic Priority Research Program(B)of CAS(XDB18010100,XDB41000000)+1 种基金Pre-research Project of Civil Aerospace Technologies(D020202)Chinese National Space Administration and Chinese NSF Projects(41903019,41530210)。
文摘Atmospheric escape is an essential process that affects the evolution of the proto-atmosphere.The atmospheric escape of early terrestrial planets was extremely rapid compared with the current scenarios,and the main atmospheric escape modes were also quite different.During the dissipation of the nebula disk,the primordial atmosphere experienced a brief but violent"boiling"escape,in which most of the primordial atmosphere was lost.After the nebula disk dissipates,hydrodynamic escape and impact erosion are the two most important mass-loss mechanisms for the proto-atmosphere.Hydrodynamic escape is a rapid atmospheric escape process caused by strong solar radiation,while impact erosion refers to the process in which small-large or giant impacts erode the proto-atmosphere.In the early solar system,there were other escape mechanisms,such as non-thermodynamic escape and Jeans escape,but it is generally believed that these mechanisms have relatively little impact.Here we systematically introduce the above-mentioned atmospheric escape mechanisms and then make some suggestions for the existing problems and future research for atmospheric escape models.
文摘The pressure in liquefied natural gas (LNG) storage tank continues to increase due to the heat transfer from ambient air to low temperature LNG, which raises safety concerns. Accordingly, there is increasing interest to explore the technical approaches capable of recovering Boil-Off Gas (BOG) and even eliminating the ventilation of LNG storage tank. This research numerically analyzed the greenhouse gas emissions of the re-liquefaction of BOG using the following four approaches: 1) a Claude cycle driven by electrical motor with the electricity produced by burning coal;2) a Claude cycle driven by a gas turbine fuelled by BOG released;3) a Claude cycle driven by a SI engine fuelled by gasoline;4) burning nature gas directly released by BOG. The impact of heat transfer coefficient, LNG tank configuration, size, and percentage of LNG stored in tank on the rate of BOG and energy needed for the re-liquefaction of methane vapor were investigated. The greenhouse gas emissions (GGE) was examined and compared. The data presented in this paper provide guideline for the management of pressure development in LNG storage tank.
文摘Boil-Off Gas creation and usage has been a source of worry in Liquefied Natural Gas value supply chain. BOG is generated when there is temperature gradient between the environment and LNG temperature within the carrier tank, process lines or vessels. In this work, Computer Aided Design for the recovery of BOG from flare in an LNG Plant considered the dynamic nature of the BOG with minimized total energy consumption. A rigorous simulation based optimization model using HYSYS V8.8 was presented. Possible BOG scenarios were formulated in this report and considerations taken from the BOG scenarios to form the basic scope of this work. An Aspen HYSYS Software was used to develop a Process Flow Scheme (PFS) which was simulated using the BOG scenarios formulated. The BOG scenario temperatures considered were -15°C for Warm Ship analogy, -90°C for Cold Ship and -140°C for Normal Design Mode. Assumptions were also made on the feed into the developed PFS before quenching the various BOG temperatures. With HYSYS simulation at assumed constant inlet mass flow rate of 25,000 kg/s for BOG FEED, 6250 kg/s for LNG & LNG1 FEED, quenching at various BOG feed temperature -15°C, -90°C and -140°C, gave a meaningful output. The Mass flow rate recovered from Warm Ship at -15°C for Cold Product was 35,183 Kg/s and for Liquid Product 2317 Kg/s. For Cold ship at -90°C, the Cold Product recovered was 32,174 Kg/s and Liquid Product was 5326 Kg/s. Also, for -140°C, the Cold Product was 28,004 Kg/s and the Liquid Product was 9496 Kg/s. The Energy stream for the Compressor, Cooler and Pump in the Process Flow Stream (PFS) were observed in Table 5. At -15°C, the Compressor energy was 3.22E+07KJ/h, while the Pump energy was 3412KJ/h, and the Cooler gave 1.90E+07KJ/h. The results above showed that excessive BOG from Warm ship can be quenched and recovered for other end users rather than undue flaring of the gases. Extra work needs to be done to ensure minimal energy utilisation, optimal recovery and high efficiency of this developed model.
文摘液化天然气(LNG)储存运输过程中产生的闪蒸气(boil off gas,BOG)具有一定的安全隐患。本文基于前人关于BOG的研究,查阅大量文献,对BOG的主要组成、产生原因和环境影响进行归纳整理,对以往的传统处理工艺以及新型处理工艺进行总结分析,对减少BOG排放量的相关措施进行评述,并总结目前已经得到应用的新技术,以期为今后更高效地利用BOG提供参考。
文摘基于Fluent计算软件,对某型天然气焚烧装置(gascombustion unit,GCU)进行数值模拟研究,分别在最高工况和最低工况下,以100%、70%、30%等3种CH4体积分数进行仿真模拟,对燃烧后温度场、速度场和CH4体积分数分布进行数值模拟。模拟结果表明:在最大工况下,随着蒸发气(boil of gas,BOG)中可燃物组分的降低,排气温度降低,高温区段变短,CH4扩散区域变小,火焰长度变短,宽度无明显变化;在最小工况下,火焰不再聚拢成型,随着BOG中可燃物组分的降低,排气温度降低,高温区域无明显变化。
