Abstract: The invention relates to a material which is refractory, porous, resistant to fluorine-containing gases, stable in its volume and heat-insulation, particularly in the form of formed bricks, for a refractory, heat-insulating lining in electrolytic cells, in which metal aluminum is extracted by electrolysis from aluminum oxide dissolved in a fluoride melt; the material has an Al.sub.2 O.sub.3 content of over 50 wt % and a TiO.sub.2 content of 2.5-10 wt % and during the action of fluorine-containing gases at temperatures between 700.degree. and 1000.degree. C. in the area of the material exposed to the fluorine gas, on free surfaces, particularly at the boundary surfaces of intergranular hollow spaces, needle-shaped TiO.sub.2 crystals and/or TiO.sub.2 -containing crystals are formed, growing without regularity into the porous space. The invention furthermore relates to a method for the manufacture as well as the use of the refractory material.

Abstract: The heating flues in an oven are equipped with refractory components to control the feed and mixture of combustion air and gas into each heating flue. In one embodiment, the refractory component forms a plurality of passageways through which air and gas flow into mixture. Initially, the gas is mixed with small amounts of air to obtain substoichiometric combustion in the refractory component. Additional combustion air is supplied to the resulting partially combusted gases and unburned gas to complete the combustion of air and gas in the heating flue. This arrangement serves to optimize the flame control and the heat discharge over the height of the heating flue. In a second embodiment, the refractory component forms a plurality of passageways through which combustion air is supplied to the gas along the passageway outlets which are located at preselected positions along the length of the heating flue.

Abstract: An oven door assembly of a shield-type construction for vented oven doors is achieved by ceramic barrier plates which can be produced in an extrusion process and which are mounted to supports, preferably in the form of cantilever beams fixed with one end to the oven door body and bearing clamps at the other end for clamping the ceramic barrier plates. Each ceramic barrier plate is replaceable and has grooves on the upper and lower side faces to receive the clamps. The clamps are constructed for clamping the ceramic barrier plates by pressure forces acting normal to the upper and lower side faces of the ceramic plates.

Abstract: A supported catalyst suitable for nitrogen oxide reduction has an active catalyst coating containing metal oxides, which has been produced by a sol-gel process, on a solid porous supporting body.

Abstract: Silica brick with a quartz grain structure that can be detected in the matrix and is converted to cristobalite and/or tridymite, where the quartz grain structures are surrounded by a thin layer of tridymite formed from a silica gel and/or silica sol and consisting of fine tridymite crystals matted together.

Abstract: A ceramic catalyst carrier has a honeycombed structure which comprises a plurality of elongated parallel preferably square channels and thin, porous walls. The thickness of the walls is between 0.4 mm and 1.2 mm. The open cross-sectional area of the channels is greater than 80% of the total cross-section of the carrier body. Besides an intended low primary porosity, a secondary porosity is produced by an opening material. The pores of the secondary porosity which enlarge the active surface for the catalyst show a selected pore size distribution curve with negative skewness and a modal value ranging from 4,000 nm to 60,000 nm. The total true porosity amounts preferably between 50 and 70 Vol. % of the ceramic, whereby the ratio between total and secondary porosity is in the range of 1:1 to 6:1. By ceramic fibres the mechanical strength of the thin walls of the soft green clot and of the fired porous structure can be improved.