The full alumina dissolution process in aluminum electrolysis cells was investigated using an improved computational fluid dynamics(CFD)model based on the previous researches by consideration of agglomerate formation....The full alumina dissolution process in aluminum electrolysis cells was investigated using an improved computational fluid dynamics(CFD)model based on the previous researches by consideration of agglomerate formation.The results show that the total mass of alumina agglomerate and its maximum size are mainly dependent on the feeding amount and increase with increasing it.Higher superheat can effectively inhibit the agglomerate formation and thus promote the full alumina dissolution behavior.The full alumina dissolution process mainly includes a fast stage and a slow stage,with an average dissolution rate of 17.24 kg/min and 1.53 kg/min,respectively.About 50%(mass percentage)of the total alumina particles,almost all of which are the well-dispersed alumina fine grains,dissolve within the fast dissolution stage of about 10 s.The maximum values of the average dissolution rate and final percentage of the cumulative dissolved alumina mass are obtained with a feeding amount of 1.8 kg for a superheat of 12℃.The formation of the alumina agglomerates and slow dissolution characteristics play a dominant role in the full dissolution of alumina particles.展开更多
Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher pro...Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher proportion of working-age force and a lower dependency ratio tend to have higher savings rates. Because the demographic ＂ center of gravity＂for investment demand falls at a younger point in the age distribution than that of savings supply, countries with a younger age-distribution like those described above generate national savings in excess of domestic investment, resulting in a current account surplus. Numerical simulation supports this hypothesis. But the relative youth or age of a country＇s population reflects temporary demographic trends which change continuously. Therefore, while trade imbalances caused by demographic factors are structural and long-term, they are not permanent, and may be reversed by changes in age structure.展开更多
基金financial supports from the National Natural Science Foundation of China (No. 51704126)the Natural Science Foundation of Jiangsu Province, China (No. BK20170551)Jiangsu Planned Projects for Postdoctoral Research Funds, China (No. 2019K046)。
文摘The full alumina dissolution process in aluminum electrolysis cells was investigated using an improved computational fluid dynamics(CFD)model based on the previous researches by consideration of agglomerate formation.The results show that the total mass of alumina agglomerate and its maximum size are mainly dependent on the feeding amount and increase with increasing it.Higher superheat can effectively inhibit the agglomerate formation and thus promote the full alumina dissolution behavior.The full alumina dissolution process mainly includes a fast stage and a slow stage,with an average dissolution rate of 17.24 kg/min and 1.53 kg/min,respectively.About 50%(mass percentage)of the total alumina particles,almost all of which are the well-dispersed alumina fine grains,dissolve within the fast dissolution stage of about 10 s.The maximum values of the average dissolution rate and final percentage of the cumulative dissolved alumina mass are obtained with a feeding amount of 1.8 kg for a superheat of 12℃.The formation of the alumina agglomerates and slow dissolution characteristics play a dominant role in the full dissolution of alumina particles.
基金This research is supported by： National Social Science Foundation ＂ Study on China＇s imbalanced foreign trade from the perspective of intra-product specialization＂ （10BJY079）.
文摘Demographic transitions occur at different times and speed across different economies, and age structures consequently differ across regions. Using a solvable four-phase model, we show that economies with a higher proportion of working-age force and a lower dependency ratio tend to have higher savings rates. Because the demographic ＂ center of gravity＂for investment demand falls at a younger point in the age distribution than that of savings supply, countries with a younger age-distribution like those described above generate national savings in excess of domestic investment, resulting in a current account surplus. Numerical simulation supports this hypothesis. But the relative youth or age of a country＇s population reflects temporary demographic trends which change continuously. Therefore, while trade imbalances caused by demographic factors are structural and long-term, they are not permanent, and may be reversed by changes in age structure.
