In the production of aluminum, various methods are employed which utilize electric arc furnaces. In one prior art method, a first furnace is charged with carbon in the form of coke along with aluminum oxycarbide slag. The furnace is heated to a temperature of about 2000.degree. C. resulting in the formation of aluminum carbide along with some aluminum and slag. The aluminum carbide is charged into the second furnace either in the molten state or it is first permitted to cool after which it is crushed to a suitable size prior to charging. In the second furnace, the aluminum carbide is reacted with alumina to form aluminum which is recovered and slag which is returned to the first furnace.
Since the temperature required for the reduction of aluminum is relatively high, usually about 2000.degree. C., and since the heat transfer rate between bodies of disparate temperature is directly related to the temperature differences between the two bodies, it is advantageous from an energy conservation standpoint to retain any material being transported from a first reduction stage to a second stage in a high temperature ambient. In smelting processes using separate furnaces, considerable heat is lost, requiring the addition of this lost energy in the second furnace. This is true regardless of whether intermediate products are delivered to the second furnace in a molten or in a solid, crushed state. In addition, exposure of intermediate products to ambient air often results in undesirable chemical reactions.
Prior art smelting processes employing two or three furnaces also have substantial manpower requirements. Because of the additional energy, equipment and manpower required, prior art processes are normally accompanied by unnecessarily high costs. Further, prior art methods result in a degree of physical loss of intermediate or final product due to repeated handling.
A method of producing aluminum in a single vessel which overcomes the aforementioned disadvantages of the prior art would be a significant advance in this technology.
USPTO Backgrounds
USPTO Backgrounds