Agitator for nonhomogeneous materials held in a tank. The agitator here in question is particularly intended for use with mixed liquid and solid materials, the solids thereof being of easily damaged nature and wherein the liquid and solid components of the mixture tend to separate. The agitator is thus intended to maintain the materials in a thoroughly mixed condition and to move same lengthwise through a tank to the outlet thereof and yet to do so with minimum physical damage thereto. The agitator of the invention comprises a relatively narrow blade arranged spirally for rotation about an axis positioned in the lower part of a horizontally aligned tank, the blade thereof being either perpendicular or inclinedly positioned with respect to the imaginary cylinder enclosed thereby. If inclined, the outer edge of the blade leads the inner edge as same rotates. The agitator can also be used in vertical alignment if desired and used with or without a central shaft.

The invention relates to a method and a device for producing polyesters such as for example polyethylene terephthalate, polypropylene terephthalate and polybutylene terephthalate from precondensates. According to said method, vapors comprising precondensate components that are distributed therein in the form of an aerosol are guided through a polycondensation reactor in which precondensate components condense on the reactor wall and on a separator in an exit chamber of the reactor. The condensates are guided to the unstirred discharge sump and the upper layers of the discharge sump are continuously recirculated into the stirred reactor area thereby subjecting them to reconversion and additional polycondensation.

For the purpose of introducing or removing gases into liquids or out of liquids, in particular substrates being subject to a biological conversion, rotating plates (3) are immersed into the liquid phase. The plates (3) are rotatably arranged within a tubular receptacle (1) and arranged in at least one axial section such that they alternately include with the axis (2) of rotation extending in parallel relation to the liquid level an angle of more and less than 90.degree.. Shut-off valves (9) for the gas supply conduit and for the gas discharge conduit are connected to the tubular container (1). The plates (3) are provided with a rough surface and are preferably formed of a porous, in particular foamed, material, wire mesh, wire grating or expanded metal sheet. (FIG. 1)

An apparatus and process for the removal and recovery of sulfides from tannery waste water or liquor. The apparatus comprises a closed vessel, the sulfide-bearing liquor is introduced into a first or acidulation zone of the vessel and mixed with acid to decrease the pH, preferably to a value below 4.0, and generate hydrogen sulfide. The acidified liquor is then overflowed into a second or desorption zone of the vessel and slowly agitated and conveyed through the second zone by disc conveyors to release the hydrogen sulfide gas from the liquor. A slight vacuum is drawn on the vessel causing the released hydrogen sulfide gas to be drawn into a third reaction zone of the vessel, where the gas combines with sodium hydroxide solution to form sodium sulfhydrate. The effluent from the second zone can be filtered or dewatered and the filtrate discharged to a disposal site while the proteinaceous solids can be recovered for use as fertilizer. The sodium sulfhydrate produced in the third zone can be used in the unhairing operation of the tanning process.

A device for mixing particulate material and liquid includes a container, an inlet for the introduction of particulate material into the container, a liquid spraying device for spraying liquid over the particulate material in the container, a disc agitator arranged in the container, and an outlet for discharging material mixed with liquid from the container. A fluidization device is provided to fluidize the particulate material in the container during the mixing operation. The inlet is arranged at one lengthwise side wall of the container, so as to extend along that wall. The outlet is arranged in the other lengthwise side wall, so as to extend along the wall.