Abstract: A novel fixed-bed catalyst structure obtained using honeycomb elements, for highly exothermic and endothermic chemical reactions, wherein the required heat exchange, both in the liquid phase and in the gas phase, is forcibly effected in the fixed catalyst bed by means of static mixing elements made of inert ceramic and/or metallic material or completely of catalyst material, between the individual honeycomb elements.

Abstract: A process for the biological purification of effluent which is contaminated with nitrogen in the form of ammonium, nitrite or nitrate ions or in the form of organic compounds, by oxidizing the nitrogen under aerobic conditions and reducing the nitrogen under anaerobic conditions, wherein the sewage to be treated, mixed with activated sludge, is subjected, in an aeration basin, to oxygen-containing gas bubbles introduced from below and is thereby simultaneously enriched with dissolved oxygen, to oxidize carbon compounds and nitrogen compounds, and transported upward, by the buoyancy of the gas bubbles, releases gas at the surface of the liquid and, due to the higher average density of the mixture of lower gas content, in part automatically again flows downward in the aeration basin, to undergo further aeration, while in part it overflows into a denitrification basin which communicates with the aeration basin through an opening at the liquid surface, and an opening at the bottom of the partition, is mixed, in t

Abstract: Fluorine compounds which are contained in the vapors obtained when evaporatively concentrating phosphoric acid are removed by scrubbing with an aqueous solution of fluosilicic acid under reduced pressure at a temperature at which condensation of steam is substantially avoided. The aqueous fluosilicic acid solutions are injected, at a speed of from 15 m/s to 40 m/s, into the upper part of a scrubbing zone, finely dispersed over the entire cross-section of the latter. The vapors are passed through the scrubbing zone at a speed of from 5 to 30 m/s, in co-current with the fluosilicic acid solutions. The residence time of the vapors in the scrubbing zone is from 0.4 to 1.5 s. The fluosilicic acid taken off the scrubbing zone contains from 20 to 28% by weight of H.sub.2 SiF.sub.6.