| In the condition of the development of industrialization, the demand of aluminum in various sectors has been high. With exaggeration and development of aluminum electrolysis production scale, China has skills and abilities on independent design and construction of large-scale prebaked anode aluminum reduction cell, and has made considerable progress on flue gas cleaning and automatic control technique. However, series of questions of limited energy and raw materials, even declined advantage of domestic labor year by year, reduction aluminum industry of China is facing great risk and challenge. At the present stage, priority in development strategy of aluminum electrolysis industry in China is shifting to realize the high efficiency and to low consumption. In detail they include design optimization and development of aluminum reduction cell, improment and innovation of process technology, fine control of production management and so on.Only from the standpoint on structural material properties analysis and the relation between production process and materials, and simulation and calculation of physicl field with computer simulation soft ware, the optimal design on aluminum reduction cell is gotten in final by comparing the feasibility and advantages of different design plans. Analysis on quantities of industrial test data is not only research and development premise of cell state diagnosis apparatus, automation programs and systems for operation and control, but also the basis for choosing and creating on mathematical model in physical field calculation. And it is also the basis for validating the accuracy and reliability of simulation and the rationality of cell design. The present researches on electrolytic aluminum in China focus on simulation of muti-physics field and cell state. Because of the limited conditions, including test facilities and the ability to test and so on, there are few professional test groups for large scale industrial test on muti-physics field of aluminum reduction cell. Furthermore, the test data and simpler analysis on date are also used in communicating within the enterprise and are seldom seen outside the enterprise concerned.In this thesis,400kA large-scale prebaked anode aluminum reduction cells which are respectively belonged to Yili aluminum and electric Co. Ltd. affiliated with Nanshan Group in Shandong province and Linfeng aluminum and electric Co. Ltd. affiliated with Yulian Group in Henan province are chosen as the object of study. They are designed by NEUI and the comparison between cells with current flow from bottom vertically and cells with current flow from side vertically horizontally are studyed and analyzed. Besides, ordinary cathode carbon block with same height combination modes, ordinary cathode carbon block by high-low combination mode and complex cathode carbon block with convex plate are also considered. Based on large amount of industrial test data and analysis, including voltage balance, current distribution of anode and cathode, busbar current assignment, energy balance, magnetic induction B and velocity field of liquid aluminum and so on, physical field distribution characteristic of aluminum reduction cell with six different design plans are known fully in practice. A new method on reflecting equidistant voltage drop state of anode rod and liquid aluminum mirror state is presented in this thesis. The main results are as follows:(1) The view is submitted that main whirlpool state in horizontal direction along length direction of the cell can be inferred by the fluctuation curve’s cycle obtained based on equidistant voltage drop state of anode rod and the fluctuation curve’s phase difference with same circle of adjacent rods in the first. Secondly, horizontal current direction based on anode and cathode’s current distribution in A and B side of the cell is only overall average flow direction. Thirdly, the whirlpool state of liquid aluminum in horizontal direction can be confirmed by the test result of flow field, and then the little partial vortex area in vertical direction can be deduced too. A complete mode on industrial test and analysis of muti-physics field is established.(2) By researches and analysis, there are inter-connectedness and reciprocal verifiability in test results of electric, thermal, magnetic and flow field. They are cathode pressure drop, sidewall temperature of aluminum reduction cell, profile ledge shape of cell, precipitation at bottom of cell, horizontal magnetic force and acceleration, cathode current distribution, connection disposition between cathode steel bar and upright post’s busbar, current distribution of current upright post’s busbar, horizontal main whirlpool state of liquid aluminum deduced by equidistant voltage drop curve of anode rod and horizontal velocity of aluminum liquid, the position of test point with maximum or larger horizontal velocity, the position of test point with little partial vortex area in vertical direction, the position of test point with more precipitation.(3) In the research and analyse on equidistant voltage drop curve of anode rod, three especial curving forms are observed. They are the indication of anode effect, bubble or carbon block drift and anode spike respectively. In the test result of flow field, three erosion characteristics of iron rods are also abtained. They are the phenomenon of normal erosioned, turned eroded surface and numerous eroded holes.(4) Operation stability in production and design rationality of aluminum reduction cell with six different design plans is discussed. The improved plans in design are provided appropriately. They are inner material of the cell, bottom structure of the cell, busbars configuration and so on. The main analysis results as follows:firstly, mul-physics field of the cell structure with current flow in side horizontally are more reasonable and there is a major problem on thermal field of the cell designed with current flow in bottom vertically. Secondly, contrasting with ordinary cathode carbon block with same height combination modes, ordinary cathode carbon block by high-low combination modes and complex cathode carbon block with convex plate can change fluid flow in horizontal direction to a certain degree. It will promote fusion between the two adjacent whirlpools and just because of the fusion, the horizontal flow velocity and the fluctuation degree of liquid aluminum is increased. Even more, little partial vortexes also happen. Besides, grooves formed in the surface of complex cathode carbon block, especially channels formed by high-low combination modes of ordinary cathode carbon block easier to make sediment deposit at bottom of the cell. Contrasting with ordinary cathode carbon block with same height combination modes, the other two carbon block mode have not design advantage in these aspects, which are decreasing horizontal current value and magnetic intensity’s absolute value, even improving the site of magnetic intensity maximum.(5) The equation on three-dimensional temperature field is derived by theories of electricity-thermal and heat conductivity. Calculating formulas on reflecting parameters’ relationship are also deduced in research. They are relationship formulas between temperature and current of anode rods, between rod current and liquid aluminum height below the anode rod, between rod temperature and liquid aluminum height below the anode rod respectively. All these proves that there are five variable factors to reflect the state of equidistant voltage drop and liquid aluminum mirror corresponding to different anode rods. They are surface temperature of the rod, temperature and flow velocity of flue-gas around the rods inside the cell covers, the distance from juncture of anode rod and horizontal cell cover to the top of anode rod, the distance from under edge of horizontal anode buabar to upper edge of horizontal cell cover. It is that trod、tflue-gas、vflue-gas、lrod、l1, mentioned in this thesis. The most important, a set of empirical expressions are found by analyzing large amount of industrial test date with fitting techniquea. A new method reflecting the state of equidistant voltage drop and liquid aluminum mirror is presented by fitting curve. The curve is based on online industrial test data of these five factors and derived experience formula in research. Large amount of statistical data show that the correlation coefficients between fitted curve and practical measured curve is larger than 0.90, which shows the general applicability of this new method. |
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