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Alumina vacuum carbothermal reduction experimental study

Author: WangPengCheng
Tutor: DaiYongNian
School: Kunming University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: alumina vacuum carbothermic reduction aluminum mechanism
CLC: TF821
Type: Master's thesis
Year: 2009
Downloads: 53
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Abstract

The aluminum and the aluminium alloy have many virtues, they were widely used in various domains of production and life, and they are the second biggest metals in demand just inferior to the steel, so they have important status in the development of the national economy. Now, the aluminum is produced by the alumina-cryolite fusion electrolysis method, however, this method has many abuses, so, the new technology about the aluminum refines is needed.This paper has observed all kinds of manufacturing methods of the aluminum synthetically, summarized the evolution of the aluminum smelting research; calculated the thermodynamics of the aluminum melting’s alumina carbothermic reduction method at ordinary pressure and in the vacuum respectively; used the graphite as the reducer to analyze the mechanism of the alumina vacuum carbothermic reduction reaction; used the coal as the reducer to analyze the actual application of the alumina vacuum carbothermic reduction.By the thermodynamics analysis, we know that at ordinary pressure, the temperature of the carbon direct reduction alumina is 2000℃-2300℃, however when the vacuum degree is 1Pa, the temperature of the carbon direct reduction alumina is 1300℃-1600℃. Take a view of the thermodynamics, the carbon direct reduction alumina is doable, and use the vacuum equipment will debase the reaction temperature consumedly.The result of the experimentation was inosculated with the thermodynamics analysis., when the vacuum degree is 1Pa and the temperature of the reaction is 1400K-1700K, the reaction of the carbon direct reduction alumina is doable and is able to make a raise of the metal aluminum grain. To analyze the experimentation, we can see that the materiel’s reaction extent was aggrandized when the temperature risen and at 1650℃the system’s pressure increase is the biggest and the materiel’s reaction is the most acutely.By analyzed the experimentation of the alumina vacuum carbothermic reduction between 1450℃-1700℃and use the graphite as the reducer, speculated the reaction mechanism of the alumina vacuum carbothermic reduction, and then elicited the three paths of the metal aluminum’s source:1, the condensing of the aluminum vapour which is created by the alumina and the carbon’s direct reaction; 2, created by the reaction of the alumina and the aluminium carbide; 3, created by the reaction of Al4O4C and the aluminium carbide. The generation of the metal aluminum has two steps:1, created by the alumina and the aluminium carbide reacted at the warming phase; 2, created by the alumina and the aluminium carbide reacted and Al4O4C and the aluminium carbide reacted at the holding phase, of which when the temperature was lower than 1600℃, the reaction between the alumina and the aluminium carbide is the primary reaction in which the aluminum was created, and when the temperature was higher than 1600℃, the reaction between the Al4O4C and the aluminum carbide is the primary reaction in which the aluminum was created. To analyze synthetically, we can see that 1650℃is the excellent temperature of the vacuum carbothermic reduction the alumina to create the aluminum.Use the coal as the reducer to do the alumina vacuum carbothermic reduction experimentation, and proved the feasibility of the alumina vacuum carbothermic reduction’s actual application. The reaction instance is like to the graphite, yet the reaction extent increased, the quality of the metal aluminum grain added, and the material spewing instance reduced. At 1550℃, the impurity Si, Fe in the coal will react with Al and form the alloy.

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