Abstract: The sintered ceramic product comprises a granular material bound by a nitrogenous mold. According to the invention, at least one anti-dust agent selected among calcium and boron exists in a surface layer of the product, the mass ratio of all the anti-dust agents in the surface layer being greater than that measured underneath this layer. This product advantageously has a reduced ratio of non-adherent particles to its surface.

Abstract: Compound concrete composition for the manufacture of moulds, comprising: (1) a binder which comprises an alkaline-earth mineral substance, a constituent made up of fine particles of a compound other than an oxide, 90% of which have a particle size of between 1 and 150 .mu.m with a median diameter of between 3 and 20 .mu.m, these fine particles comprising particles of a substance which has a thermal conductivity higher than approximately 30 W/mK, chosen from silicon carbides, silicon carbonitrides, silicon nitrides, boron carbides, titanium carbides and tungsten carbides and a constituent made up of ultrafine particles at least 70% of which have a particle size smaller than 1 .mu.m with a median diameter of between 0.3 and 0.8 .mu.m, (2) water optionally with the addition of a dispersant, and (3) fillers comprising metal granulates and metal fibres, wherein the water/binder ratio is lower than 0.20 and the concrete composition has a thermal conductivity at 200.degree. C.

Abstract: A tuyere opening assembly of a vertical furnace or reactor includes at most four prefabricated elements made of moulded refractory concrete, and a lining therein of ceramized refractory keys of identical shape and size arranged therein for receiving a burner or a tuyere.

Abstract: The invention relates to a refractory composition comprising, by weight:(A) at least 70% of an aggregate based on refractory oxides,(B) from 7 to 25% of a matrix consisting of particles distributed between a fine fraction made up of a proportion of at least 95% of its weight of particles from 1 to 20 .mu.m in size, the median diameter of these particles being between 3 and 8 .mu.m, this fine fraction constituting 1 to 24% of the composition, and an ultrafine fraction consisting of a proportion of at least 70% of its weight of particles smaller than 1 .mu.m in size, the median diameter of these particles being between 0.3 and 0.8 .mu.m, this ultrafine fraction constituting 1 to 24% of the composition, the said matrix comprising(i) at least one oxide chosen from the group consisting of Al.sub.2 O.sub.3 and Cr.sub.2 O.sub.