Showing papers by "Kaiser Aluminum published in 1977"

Process for the utilization of waste materials from electrolytic aluminum reduction systems

Abstract: OF THE INVENTION A fully integrated process is provided for the recovery of valuable components from waste materials in electrolytic aluminium reduction systems. The waste materials, such as spent pot linings, channel and trench cleanings, floor sweepings and spent alumina from offgas purifying dry scrubbers, are combined, then pyrohydrolyzed at elevated temperature. Fluoridic values, such as NaF and HF can be recovered from the offgas generated by pyrohydrolysis, while alumina and Na20 values, or if desired, sodium aluminate, is reclaimed from the solid residue of pyrohydrolysis. The fluoridic values from the pyrohydrolysis offgas can be used for the manufacture of both electro-lytes for aluminium reduction cells and also for the production of anhydrous HF. The alumina from the pyro-hydrolysis residue can be reclaimed by a Bayer process-type leach with a caustic solution and the recovered high purity alumina utilized, for example, as reduction cell feed and/or for scrubbing reduction cell offgases. If the solid residue of pyrohydrolysis contains signifi-cant amounts of sodium aluminate, this material can either be directly used for dry scrubbing cell offgases, or if desired, utilized for production of high purity alumina.

Bonding of refractory hard metal

Abstract: The invention is directed to a method of bonding refractory hard metal materials such as TiB 2 wherein aluminum carbide is formed in situ at the interface between the refractory hard metal and a substrate. The bond formation is greatly accelerated by passing an electrical current across the interface.

Observers for linear systems with arbitrary plant disturbances

Abstract: This paper shows how to choose observer parameters so that its estimation error is independent of arbitrary plant disturbances. Contrary to previous research the plant disturbances are not assumed to have any mathematical structure. Also presented are conditions under which an observer can reject plant disturbances and also have its eigenvalues arbitrarily assigned.

Flame retardant cellulosic boards

Abstract: Cellulosic boards, such as hardboards, fiberboards and particle-boards, are flame retarded by incorporation of a synergistically acting alumina trihydrate-ulexite composition in the boards. The alumina trihydrate-ulexite flame-retarding agent provides a board of satisfactory strength properties with a flame spread at least equivalent to that of a commercial Class I-rated hardboard when the loading of the flame-retarding agent in the board is kept at 50% or below of the total weight of the flame-retarded board.

Flame retarding compositions for cellulosic boards

Abstract: Synergistically performing flame retarding compositions are provided for cellulosic boards, such as hardboards, particleboards and fiberboards. The synergistically performing compositions consist of three components, namely, an aluminous material, a naturally occurring borate-containing mineral and a phosphate or sulfate salt. Incorporation of these compositions in the boards allows consistent production of flame-retarded products with a Class I or better fire rating.

Easy open end

Abstract: Improved depressible tab provided with a nose for easy open end closure members and the like, wherein an improved pressure relief means in the form of a unique vent arrangement is incorporated in the nose portion of the depressible tab.

Magnesium aluminate spinel bond for refractory brick

Abstract: A magnesium aluminate spinel-bonded refractory can be formed which does not exhibit undue expansion (due to the reaction of magnesia and alumina to form magnesium aluminate spinel) between the raw, compacted state and the fired, ceramically bonded state when fired to a temperature of 1400° C if a very finely divided alumina with dense particles is used. More specifically, the alumina used has an average particle size of less than 5, preferably less than 2, microns, and a specific surface of less than 30 m 2 /g, preferably about 5 m 2 /g (i.e., the small crystallites or particles are dense and do not have a high surface area, as do finely divided active aluminas).

Pole vibration damper

Abstract: A vibration damper attachable to a pole structure and comprised of a plurality of individual vibration damping discs or weights mounted for controlled and limited movement within a housing together with rods insertable in an improved fashion through openings in the discs and separator washers for vertically stacking the discs along with separator washers within the housing.

Self-grinding valve mechanism

Abstract: Improved self-grinding valve is provided with corrosion-protecting features and an improved floating coupling between the valve stem and valve disc whereby, when the valve disc is brought into contact with its seat, a selected rotation of the valve disc will produce a grinding of the seat, followed by a disengagement of the valve stem from the valve disc. When this disengagement takes place, the full torque load of the stem can be imposed upon the valve disc to obtain the desired seating of the same. The valve stem is advantageously comprised of improved telescoping and theadedly engaged sections that operate to relieve the forces used to hold the valve disc against the seat upon the initial opening of the valve whereby the amount of torque required to ultimately rotate and free the valve disc from its seat is materially reduced and seizing of the valve disc relative to its seat avoided.

Caustic and chlorine production process

Abstract: Alkali metal hydroxide and chlorine are produced in a membrane-equipped electrolysis cell system in a staged manner wherein at least one cell of the system is used to generate a dilute caustic solution and wherein the subsequent cell(s) of the system are used to produce a more concentrated caustic solution by electrolysis of fresh brine and the dilute caustic produced in the first stage which is used in lieu of water in the subsequent stage(s). The stage-wise production of caustic of commercially acceptable concentration results in significant energy savings with corresponding increase in the average life of the membranes employed.

Removal of acidic impurity from chlorofluoromethanes

Abstract: Acidic impurity, such as HCl, is removed from chlorofluoromethanes of the formula CHCln F3-n, where n is 1 or 2, by scrubbing the contaminated fluorocarbon with an aqueous solution made from a mixture of trisodium phosphate and sodium hydroxide. Use of this solution as scrubbing medium allows purification of the contaminated fluorocarbon without appreciable decomposition and also without generation of a significant quantity of environmentally objectionable waste stream of high phosphate content. The presence of NaOH in the scrubbing medium provides in situ regeneration of mono and disodium phosphates to trisodium phosphate.

Pretreatment system for goethitic bauxites

Abstract: A pretreatment system is provided for transforming the goethite constituent [FeO(OH)] of goethitic bauxites to hematite and/or magnetite at high temperatures and pressures. The system employs a number of float-type, liquid displacement pressure pumps, both for charging caustic-containing bauxite slurries of high solids concentration to the system and for discharging the treated slurries. The system operates at temperatures in excess of 250° C and up to temperatures required for the total conversion of the goethite content to hematite or magnetite which, in turn, significantly increases the yield of recoverable alumina. Since the slurry to be pretreated is of high solids concentration, e.g., in excess of 30% by weight and up to about 55-60% by weight, the size of the pressure-resistant equipment is considerably smaller than the size required for conventional pretreatment system operating at much lower solids concentrations and due to the use of the float-type pumps, maintenance, erosion and other mechanical problems associated with the use of customarily employed high pressure pumps and slurry pressure control valves are substantially eliminated.

Production of periclase grain

Abstract: A high purity periclase grain having less than 8 volume % porosity, less than 2% SiO 2 , and a CaO:SiO 2 weight ratio not over 1.0 is produced in a single fire process by mixing from 0.5 to 1.5% finely divided SiO 2 with a magnesium hydroxide containing (on the ignited basis) at least 98% MgO, not over 1.5% CaO, and not over 1.0% SiO 2 , drying the admixture, compacting it at a pressure of at least 10 tons/in 2 (1400 kg/cm 2 ), and firing the compacts at a temperature of at least 1700° C.

Engineering with Aluminum in Petroleum Processing Plants

Abstract: The relevant components of reliability supporting broad application of aluminum alloys in industrial electrical systems are discussed. These include compatibility within the system, corrosion and chemical resistance, corrosion protection, strength, design objectives, selection of alloys, and cost. Corrosion resistance and types of corrosion are treated in detail. The impact of new codes and standards on cable installations in conduit and tray along with applications in hazardous areas is reviewed. A brief primer on the metallurgy of aluminum is presented with the four digit identification system for both wrought and cast aluminum alloys (ANSI H35.1).