Abstract: Spherical and rod-shaped proppants and anti-flowback agents made from sillimanite minerals possess high strength and high conductivity. The sillimanite minerals may be selected from the group consisting of kyanite, sillimanite, and andalusite and may be used alone or in combination with other materials, such as bauxite, kaolin, meta-kaolin, pure or technical grade alumina (about 98%-99.9% alumina by weight), alumina-containing slag, zirconia, silica, iron, alkali elements (such as calcium, magnesium, and sodium), and virtually any other mineral containing alumina. The starting material may optionally be milled to achieve better compacity and crush resistance in the final proppant or anti-flowback agent. A fracturing fluid may comprise the rods or spheres alone, or in combination with each other or other proppants or anti-flowback agents of different shapes.

Abstract: A method is provided for manufacturing spherical corundum grains having a bulk density between 1.5 kg/L and 2.5 kg/L, with aluminum oxide being melted in an electric arc furnace with the addition of 0.1 to 1% quartz sand, the melt being poured in a pouring quantity of less than 100 kg/min, and the pouring stream being blown using compressed air at a pressure between 3 to 10 bar.

Abstract: Spherical and rod-shaped proppants and anti-flowback agents made from sillimanite minerals possess high strength and high conductivity. The sillimanite minerals may be selected from the group consisting of kyanite, sillimanite, and andalusite and may be used alone or in combination with other materials, such as bauxite, kaolin, meta-kaolin, pure or technical grade alumina (about 98%-99.9% alumina by weight), alumina-containing slag, zirconia, silica, iron, alkali elements (such as calcium, magnesium, and sodium), and virtually any other mineral containing alumina. The starting material may optionally be milled to achieve better compacity and crush resistance in the final proppant or anti-flowback agent. A fracturing fluid may comprise the rods or spheres alone, or in combination with each other or other proppants or anti-flowback agents of different shapes.

Abstract: A sintered rod-shaped proppant and anti-flowback agent possesses high strength and high conductivity. The sintered rods comprise between about 0.2% by weight and about 4% by weight aluminum titanate. In some embodiments, the sintered rods are made by mixing bauxitic and non-bauxitic sources of alumina that may also contain several so-called impurities (such as TiO2), extruding the mixture, and sintering it. A fracturing fluid may comprise the sintered rods alone or in combination with a proppant, preferably a proppant of a different shape.

Abstract: A sintered rod-shaped proppant and anti-flowback agent possesses high strength and high conductivity. The sintered rods comprise between about 0.2% by weight and about 4% by weight aluminum titanate. In some embodiments, the sintered rods are made by mixing bauxitic and non-bauxitic sources of alumina that may also contain several so-called impurities (such as TiO2), extruding the mixture, and sintering it. The starting material may optionally be milled to achieve better compacity and crush resistance in the final sintered rod. A fracturing fluid may comprise the sintered rods alone or in combination with a proppant, preferably a proppant of a different shape.

Abstract: The invention relates to an abrasive grain containing electro-fused alumina, formed of crystals of hexagonal structure less than 100 &mgr;m in size, preferably less than 30 &mgr;m, and further preferably less than 5 &mgr;m, having a density that is greater than 97%, preferably 98%, of the theoretical density of alumina and a Knoop hardness of more than 2000.

Abstract: The subject of the invention is ceramic fibers for the reinforcement of refractory materials, being constituted by sintered bauxite fibers with a length/diameter greater than 10. Preferably, they have a cylindrical or prismatic shape truncated by two surfaces, for example, substantially planar surfaces perpendicular to the axis of the prism. They enable the mechanical strength and the lifetime of the refractory products to be significantly increased.

Abstract: The invention relates to an abrasive grain based on electromelted alumina consisting of crystals with a hexagonal structure, of size less than 100 &mgr;m, and preferably less than 30 &mgr;m, and more preferably less than 5 &mgr;m, with density higher than 97%, preferably 98%, of the theoretical density of alumina, and a Knoop hardness higher than 2000. The invention also relates to a method for making abrasive grains based on alumina consisting in melting alumina, casting it at a constant flow rate less than 80 kg/mn, and cooling it by dispersing the melted alumina in fine droplets to obtain articles with size less than 1 mm. The dispersion is preferably performed by ultrasound-assisted spraying, at a frequency ranging between 15 and 50 MHz. The inventive grains are used in particular for making grindstones.

Abstract: The invention concerns a method for recuperating thermal energy of hot gases of a submerged-arc furnace designed to make metal alloys by atomization of a powder from solid particles suspended in an aqueous phase. The solid particles are, preferably, derived from the filtering of gases emitted by the electric furnace. The invention also concerns a method for making silica powder with improved properties from fumes of a silicon or ferro-silicon furnace, which consists in preparing a suspension of said fumes in water and atomizing said suspension.

Abstract: Alumina-based abrasive grains having a skin constituted by a mixture of finely dispersed aluminum hydrate and sodium silicate, and a process for the production of such grains consisting of (a) preparing a gel by mixing a solution of sodium silicate and a colloidal solution of aluminum hydrate in acid medium, (b) coating the abrasive grains with the gel in an amount of 0.1 to 5 percent weight, and (c) subjecting the coated grains to a drying treatment at a temperature of between 100 and 500.degree. C. The grains according to the invention are used for the manufacture of cloths and abrasive paper and also grinding wheels.

Abstract: The invention relates to a process for the production of a semipermeable membrane on a porous conductive support. The process involves the stages of finely dispersing in an aqueous or hydroorganic medium, insoluble solid mineral products in the presence of an electrodepositable coating resin, the preparation of an electrophoresis bath by adjusting the composition of the dispersion, deposition by electrophoresis of a layer of resin-coated, solid mineral products on a porous conductive support, possible deposition of several coatings and heat treatment of the porous conductive support and its layer of electrodeposited solid products. This gives filtering membranes suitable for microfiltration, ultrafiltration and reverse osmosis.

Abstract: The present invention relates to a method of manufacturing a medium for microfiltration, for ultrafiltration, or for reverse osmosis, wherein hydrolysis is performed on an alkoxide, an organo-metallic compound, or a metal salt of an organic or an inorganic acid, optionally dissolved in an anhydrous organic solvent, in order to obtain a sol of particles of the oxide or of the hydroxide of the corresponding chemical element, a thickening agent is added to the sol, and the resulting sol is slip cast onto a support layer having pores which are larger than pores desired for the filter medium, the thin layer deposited on the support medium is then dried, and then heat treated to eliminate the thickening agent and to sinter the particles of the deposited thin layer. The thickening agent is added to the sol in conjunction with a strong acid whose anion does not form a complex with ions of the oxide or hydroxide metal, and the slip casting is performed by mere putting into contact without filtering.