Aluminium Pechiney

Rhone-poulenc Chimie

Aluminum Pechiney

Uranium Pechiney

Jean-Michel Lamerant

Pierre-Bernard Personnet

Francois Pallez

Jean Deville

Pierre Maurel

Jean-Claude Bontron

Raymond Roumieu

Bernard Rouit

Odissefs Keramidas

Valerie Martinent-Catalot

A method for the production of aluminum from bauxites containing aluminum monohydate of the diaspore or boehmite type which may contain more than 1.5% by weight of calcium carbonates. The ore is digested by producing feeding a suspension produced from milled bauxite ore and concentrated aluminate liquor to a plant with a series of autoclaves and a series of regulators supplying tubular reheaters across the autoclaves with steam. The suspension first travels across the series of autoclaves, and on exiting, the digestion of the ore is practically complete, and the suspension then travels across the series of regulators. The condensation water from the steam coming from the regulator and feeding the reheater is collected in a purge pot. Within the series of regulators, the suspension is diluted on entering a regulator with the water coming from the condensation of the steam from one or several upstream regulators.

Solubilisation of carbonates by recycling condensates during digestion of monohydrate bauxites under pressure

A method for measuring degree and homogeneity of calcination of alumina utilizing an image analysis device equipped with a sensitive camera in a spectral analysis window corresponding to a wavelength range equal to or in the vicinity of visible light. The method includes the steps of mixing alumina under analysis in a liquid wherein the refractive index is, in the wavelength range, between the refractive index of a lightly calcined alumina and the refractive index of a strongly calcined alumina, preparing a slide for observation of the mixture in the image analysis device, the mixture being illuminated by stable polychromatic radiation compatible with the spectral analysis window, receiving an image by the camera and processing a signal resulting in the definition of an image composed of a given number of pixels with three calorimetric components, and statistically processing the pixels using their calorimetric components and determining the calcination degree and the homogeneity of the calcination.

Method to measure degree and homogeneity of alumina calcination

A process for treating an alumina monohydrate-based bauxite by high temperature caustic digestion includes the steps of introducing alumina trihydrate into the digested slurry at a temperature of less than 200&deg; C., in order to obtain an aluminate liquor at atmospheric pressure having an alumina/caustic weight ratio between 1.20 and 1.30, and diluting the resultant aluminate liquor to result in a caustic concentration between 160 and 175 g Na,O/liter. After settling and filtration, the resulting supersaturated liquor undergoes a further dilution before or during a crystallization step. The alumina trihydrate product is filtered from the spent liquor, which is concentrated and recycled.

Method for processing bauxite rich in alumina monohydrate

The invention concerns a process that uses an ion exchanger resin to recover the sodium contained in industrial alkaline waste and, in particular, in the 'red mud' and sodium effluents coming from the manufacture of aluminum hydrate according to the Bayer process. It includes putting the alkaline resins (1), usually 'red mud' in the form of an aqueous suspension in contact with an RH.sup.+ type cationic resin, preferably, a carboxylic resin to attach the sodium selectively and quantitatively to the resin (5) and then to extract it quantitatively in the form of NaOH (8) by displacement using a lime suspension (6), preferably, lime milk. The resin (9), after attaching the calcium, is then regenerated for reuse at the beginning of the process (2) by elution of the calcium as CaCl.sub.2 (12) with a diluted hydrochloric acid solution (10).

Process for recovering the sodium contained in industrial alkaline waste

The invention concerns a process for the production of alumina for ceramics by calcining alumina trihydrate in the presence of a mineralizer such as a halogenated compound and/or a boron compound, the calcined alumina being constituted by friable agglomerates of elementary particles, or crystallites, of alpha alumina, the average size of which can be fixed as required, with a unimodal narrow distribution of crystallite sizes, characterized in that calcining of the alumina trihydrate is carried out in an industrial kiln in a renewed oxidising atmosphere at a temperature in the range 800.degree. C. to 1300.degree. C. for a period of 0.5 hour to 4 hours in the simultaneous presence of a halogenated compound acting as a mineralizer and a silica based alumina recrystallisation modifier which is uniformly and intimately distributed in the alumina trihydrate charge.

Production of calcined alumina with a crystallite size which can be

A process for eliminating iron from supersaturated sodium aluminate solutions obtained from the alkaline attack according to the Bayer process of the monohydrate bauxite including successively the steps of grinding and eventually of desilicatation in the presence of an aliquot of decomposed liquor, then attack at a temperature higher than 200.degree. C., usually between 240.degree. and 270.degree. C., of the said crushed and eventually desilicatated bauxite by the remaining fraction of the decomposed liquor, to make the alumina hydrate soluble and to form at the end of the attack an insoluble suspension of the residue or red mud in the supersaturated sodium aluminate liquor which, after cooling and dilution, is decanted to separate the mud or insoluble residues from the supersaturated liquor destined to be decomposed in the presence of seeds after filtration, characterized by the fact that at the end of the attack, during the cooling of the suspension achieved by decreasing the pressure in the reactors, one injects in the said suspension at a temperature higher than 140.degree. C. a small quantity of a mixture containing calcium.

Process for removing iron in sodium aluminate liquors obtained from

The invention also relates to a method of recovering the gallium contained in an aqueous solution of strongly alkaline sodium aluminate by chemical exchange between a stationary phase consisting of a microporous adsorbent resin impregnated with 7-(alkyl or alkenyl)-8-hydroxyquinoline and the aqueous phsae of sodium aluminate. According to the invention, the dry resin prior to its impregnation has a specific surface area measured by the BET method which is at least equal to 450 sq.m/g of resin, a pore volume at least equal to 1500 cu.mm/g of resin, a mean pore diameter comprised between 80 and 500 .ANG. with at least 80% of this volume consisting of pores with a diameter comprised between 40 and 5000 .ANG., a rate of expansion of swelling in an aqueous medium which does not exceed 20% and in that it is impregnated with 7-(alkyl or alkenyl)-8-hydroxyquinoline in the proportion of 250 to 350 g/liter of dry resin.

Process for extracting gallium from bayer liquors using an impregnated

A process for the treatment of spent pot linings impregnated with alkali metal cyanide and fluoric products by grinding previously crushed pot linings in the presence of lime, suspending the ground pot linings in an aqueous medium in order to precipitate a flux in the form of CaF.sub.2 accompanied by the release of soda, followed by the heating of the suspension at a temperature T&gt;140.degree. C. in the presence of clay to form, after fixing the free soda, insoluble synthetic silicate compounds of the feldspathoid or zeolite type and finally the separation by filtration of the resulting solid phase from the liquid phase, which liquid phase is recycled to form a new ground pot lining suspension.

Process for the wet treatment of spent pot linings from hall-heroult

A process for extracting and purifying the gallium contained in an industrial solution of sodium aluminate by fixing the gallium on a stationary phase constituted by porous polystyrene adsorbent resin which is impregnated with an extracting agent, optionally in the presence of a surface-active agent. After elution of the gallium in acid medium, the resultant gallium salt is purified and concentrated so as to be reduced directly to the state of high purity metallic gallium, by electrolysis.

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Bouc Bel Air, France

Jean-Michel Lamerant