Abstract: In the production of alumina from bauxite by the Bayer process, the present invention provides an improvement for effectively and economically removing organic substances from a circulating alkali aluminate solution by contacting the aluminate solution containing organic substances with molecular oxygen gas or a molecular oxygen-containing gas in the presence of copper ions as a catalyst at an elevated temperature, thereby oxidizing the organic substances, adding a chemical substance to the resulting aluminate solution which reacts with copper ions to deposit a water-insoluble precipitate, and separating the precipitate from the solution, and recycling the precipitate as a copper source to the above-mentioned wet oxidation procedure.

Abstract: A method and apparatus for continuously producing clad metal plate employing a continuous casting apparatus. Sheet metal cladding is fed onto one or both faces of the hot solidified continuously cast strip being withdrawn from the casting means and the assembly is then passed to a hot roll bonding system for cladding. A method of producing clad aluminum or aluminum alloy according to the above process is further disclosed.

Abstract: Continuous casting process for the production of hollow ingot using an improved direct chill casting equipment having a molding system comprising a hollow mold and a movable platform, wherein at least one core and a pipe for introducing outer air are provided, said core being made from a refractory material unwettable with a molten metal and having a convergent taper at the side and an air runner for introducing outer air, which is packed with an air-permeable material, at the bottom, and said pipe for introducing outer air extending upwards from the air runner and passing through the core.

Abstract: In the production of aluminum fluoride, a fluorine compound is absorbed from a gas containing the fluorine compound into a gas absorbing liquor comprising water containing alumina or hydrated alumina, or an aqueous aluminum fluoride solution containing alumina or hydrated alumina, and the absorbed fluorine compound is reacted with alumina or hydrated alumina to precipitate hydrated aluminum fluoride of high quality.