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: An arrangement for measuring the thickness of a strip emerging from a rolling mill is provided with a thickness measuring device and at least one linear inductor. The linear inductor exerts a pulling force on the strip which flatens the strip in the vicinity of the measuring device. This permits a measuring beam from the measuring device to pass through the strip in a direction orthogonal to the surface of the strip. In some embodiments, a plurality of linear inductors may be provided on either side of the strip, and on either side of the measuring device. The frequency of operation of the linear inductors may be controlled by a converter, in response to the speed of the emerging strip.

Abstract: A filament-feeding apparatus for a wet freshly dyed yarn has a feed wheel centered on and rotatable about an axis and having a pair of side parts having generally circular peripheries lying in parallel spaced-apart planes perpendicular to this axis, and a plurality of angularly spaced center parts axially bridging the side parts and having outer edges axially aligned with the peripheries. The wheel is open and free of structure in zones radially inward of the peripheries and radially outward of secants extending between the outer edges. A flexible endless belt having a width equal at least to the axial spacing between the peripheries is held by a plurality of pulleys in a circular arc radially against these peripheries so that the belt forms upstream and downstream nips at the ends of the circular arc.