Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simul...Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies,the investi-gations in which both these problems are considered simultaneously appeared only recently.There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs.At the same time,this information could be useful to understand how to treat the problem of formation of these plugs.In this work,three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture,composition and the features of decomposition process.Powder X-ray diffraction and IR(infrared spectroscopy)analyses showed that the plugs consisted of wax and gas hydrate.Thermovolumetric and DSC(Differential Scanning Calorimetry)experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K.This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure,indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point(273.2 K).It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles,while the hydrate particles were not visible at this magnification,indicating that the hydrate was indeed highly dispersed in the samples.A residual wax was jelly-like after decomposition of hydrate in all the cases.Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil origi-nally used for the experiments.展开更多
Tropospheric ozone is a worldwide phenomenon causing injuries to forest trees. Californian ponderosa and Jeffrey pines are well known for their sensitivity to ozone, while other pine species have varied in their susce...Tropospheric ozone is a worldwide phenomenon causing injuries to forest trees. Californian ponderosa and Jeffrey pines are well known for their sensitivity to ozone, while other pine species have varied in their susceptibility. Sensitive pine species are known for their chlorotic mottle and tip burn symptoms, caused by ozone air pollution. Epistomatal wax plugs and filamentous waxes around stomata are typical for pine needle surfaces. In this study, we investigated epistomatal and epicuticular needle waxes in eight species of field-grown pines in 1985, 1986 and 2006. The epistomatal wax plugs were present in asymptomatic needles without chlorotic mottle (23% of needles). A lack of wax plugs in needles with chlorotic mottle and tip burn symptoms was common (76% of needles). More abundant existence of mottling associated with stomata without wax plugs in two-year-old needles, compared with one-year-old needles (43% and 33%, respectively), indicated chronic injury development over time.展开更多
文摘Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies,the investi-gations in which both these problems are considered simultaneously appeared only recently.There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs.At the same time,this information could be useful to understand how to treat the problem of formation of these plugs.In this work,three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture,composition and the features of decomposition process.Powder X-ray diffraction and IR(infrared spectroscopy)analyses showed that the plugs consisted of wax and gas hydrate.Thermovolumetric and DSC(Differential Scanning Calorimetry)experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K.This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure,indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point(273.2 K).It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles,while the hydrate particles were not visible at this magnification,indicating that the hydrate was indeed highly dispersed in the samples.A residual wax was jelly-like after decomposition of hydrate in all the cases.Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil origi-nally used for the experiments.
文摘Tropospheric ozone is a worldwide phenomenon causing injuries to forest trees. Californian ponderosa and Jeffrey pines are well known for their sensitivity to ozone, while other pine species have varied in their susceptibility. Sensitive pine species are known for their chlorotic mottle and tip burn symptoms, caused by ozone air pollution. Epistomatal wax plugs and filamentous waxes around stomata are typical for pine needle surfaces. In this study, we investigated epistomatal and epicuticular needle waxes in eight species of field-grown pines in 1985, 1986 and 2006. The epistomatal wax plugs were present in asymptomatic needles without chlorotic mottle (23% of needles). A lack of wax plugs in needles with chlorotic mottle and tip burn symptoms was common (76% of needles). More abundant existence of mottling associated with stomata without wax plugs in two-year-old needles, compared with one-year-old needles (43% and 33%, respectively), indicated chronic injury development over time.
