Opinion ID: 778819
Heading Depth: 3
Heading Rank: 1

Heading: Vanalco's Smelting Operations

Text: 2 During 1992 and 1993, Vanalco was in the business of smelting aluminum. Vanalco operated a smelting facility in Vancouver, Washington, that it purchased in 1987 from ALCOA, which had owned the facility since 1940. 3 Aluminum is made from bauxite, an ore that contains large amounts of aluminum hydroxide. Bauxite is refined to make aluminum oxide, also known as alumina. Aluminum is produced by use of the chemical process electrolysis, which involves the decomposition of a chemical compound into ions by passage of electricity through an electrolytic solution. During the smelting process, large buckets carried by overhead cranes dump alumina into hoppers attached on top of reduction cells (cells). 2 The hoppers feed the alumina down the center of each cell, where it is dissolved in a bath of molten cryolite solution. An anode, which is a cubical carbon block attached to a copper rod, is then introduced into the cell, and an electrical current is passed from the anode, through the alumina/cryolite solution, and into a cathode, which is a carbon block that lines the bottom of each cell. 4 The electrical current separates the alumina into molten aluminum, which accumulates on top of the cathode at the bottom of the cell, and oxygen, which combines with the carbon anode at the top to produce carbon dioxide. This process produces aluminum continuously. At the Vanalco plant, the molten aluminum is removed from the cell every other day and transferred to a casting area called the ingot plant. In the ingot plant, the molten aluminum is poured into molds or combined with other alloys to be cast into pig or log shapes. 5 Vanalco used 636 low current density (LCD) cells and fourteen N-40 cells. The LCD cells were oblong steel shells approximately 22 feet long, 76 inches wide, and 36 inches high. The N-40 cells were the same in all material respects, except that they were shorter in length by about three feet. The shells sat on steel cradles over which anodes hung from a large steel superstructure. 6 Vanalco's 650 cells were divided equally into ten rooms, where the cells were spaced an average of 24 to 28 inches apart. Two rooms of cells were connected together in a cell line consisting of 130 cells, which were connected by busbars that allowed the cells to share the same electrical current. 3 The cells were arranged in such a way that a particular cell could be bypassed when necessary. A cell was bypassed or shunted from the line by disconnecting the riser from the superstructure and redirecting the flow of electricity. On average, eight to 10 cells were taken out of the line for replacement of their linings at any one time; however, without substantial modifications to its electrical system, Vanalco required a minimum of 112 functioning cells in order to operate its system on a sustained basis.