Abstract: In a method of regenerating a spent pickling solution composed of nitric acid and hydrofluoric acid and containing metal fluorides and metal nitrates, the pickling solution is heated in a reactor to about 300-1,000° C., the metal fluorides and the metal nitrates are pyrohydrolized, and the metal oxides formed as a result are removed as a granulate, and the gas produced in the fluodized bed reactor is dedusted, cooled and fed to an acid recovery unit. The spent pickling solution is initially separated in a separating process into a partial flow with free acid and into a partial flow enriched with metal salts, and the partial flow enriched with free acid is fed to the acid recovery unit and the partial flow enriched with metal salts is fed to the fluidized bed reactor.

Abstract: A process for treating the surface of material composed of high-grade steel, particularly strip-shaped material, wherein the material is treated with a pickling solution in a least one container and is subsequently rinsed. The solution used as the pickling solution contains a hydrochloric acid as the only acid and the material to be treated is subjected in at least one container to a least one spray treatment with the pickling solution containing the hydrochloric acid.

Abstract: A method of producing a cold-rolled strip from a stainless, ferretic or austenitic high-grade steel or a titanium alloy, wherein the strip which has been wound into a coil and has been manufactured by a hot-rolling or casting process is subjected in one pass to the steps of unwinding the coil, mechanically descaling the strip if required, subsequently chemically and/or electrochemically first or black pickling of the strip, then cold-rolling the strip to finished dimensions, degreasing the strip as required, annealing the strip, finish-pickling the strip and, if necessary, passivating, dressing and stretcher-leveling the strip. The pickling step is carried out in a pickling solution which contains hydrochloric acid, sulfuric acid and/or nitric acid.

Abstract: A method operating a pickling installation for pickling rolled strips comprises several consecutively disposed pickling basins filled with a pickling agent containing acid, through which the strip 4 is passed. A pickling agent containing acid is injected through injection nozzles disposed at least on the sides of the basin. A flexible adaptation to the respective pickling task with the aim of a reduced pickling time period is made possible if the nozzle injections on the sides are actuated variably. The pickling installation is provided for this purpose on both sides of the plurality of the basins, with injection nozzles above and below the strip traveling plane and upstream or downstream of base slide pads located in the basin.

Abstract: In a known method for the purification of exhaust air containing impurities which are biologically degradable and difficultly soluble in water, by means of activated sludge washing liquid in an absorption tower, pulverized activated carbon is added to the activated sludge washing liquid. The impurities are initially absorbed by the activated carbon and are subsequently degraded by the microorganisms of the activated sludge. Since the impurities are not transferred directly to the activated carbon, but through the washing liquid, material exchange apparatus having high turbulence are required which have a high energy consumption. By adding a high-boiling, organic solvent, for example, dialkyl phthalate, material exchange apparatus having a low energy consumption can be used, the absorption efficiency is increased and peak loads can be compensated in a buffer-like manner.

Abstract: A liquid-tight lining which is resistant to chemical attack for catch reservoirs, containers or the like of concrete. The lining includes a continuous liquid-tight impervious layer provided above the surface of the concrete. To make possible a simple and safe and repeatable testing of the tightness of the lining, a porous intermediate layer is provided between the concrete and the impervious layer. At least one sensor cable having at least two conductors is placed in the intermediate layer in such a pattern that any location of the intermediate layer is not more than a certain maximum distance away from the cable. The sensor cable is connectible to an electrical monitoring unit.

Abstract: A method and an apparatus for the purification of waste air containing biologically decomposing impurities. The waste water is conducted through an absorption tower in which the impurities are absorbed by washing liquid containing an activated sludge. Subsequently, the impurities are biologically decomposed in an activated sludge basin by the microorganisms of the activated sludge. To ensure that the residual amount of washing liquid to be removed is small and only a small amount of biological excess sludge is produced even if large amounts of impurities must be decomposed, while the activated sludge basin remains relatively small, the waste air is subjected to a preliminary purification in at least two successive stages by means of a highly polluted washing liquid. Subsequently, the waste air is subjected to an after purification by means of an only lightly polluted washing liquid. The two different washing liquids are then conducted in a cascade-like manner through separate activated sludge basins.