| 摘要 |
<p>A fraction (3) of the preferably alkaline pickling solution (2) is extracted continuously or intermittently from the pickling bath (1). Solids are separated from this fraction. A permeate low in solids (24; 46) is analyzed. From the results, the desired permeate composition is adjusted. A permeate feed (50) is recycled into the pickling bath to adjust the desired composition of the pickling solution. To separate the solids, filtration (18) is followed by sedimentation (20). The filtration process is dynamic. Preferably micro- or ultra-filtration is used. Permeate is fed to a storage vessel (6). The retentate (26) is sent to the sedimentation vessel (20). It is then circulated to the filter (18) and added to the fraction (3) extracted. The circuit is shut-off when the sedimentation vessel is full. The clear phase (34) arising in the sedimentation vessel is supplied to the storage vessel. A cloudy phase (36) containing high solids content, again arising in the sedimentation vessel, is drawn-off and supplied to a solids separator, preferably a static filter (38). Filtrate (42) is supplied to the storage vessel (6). The filter cake (40) is disposed-of, or sent to other uses. Analysis takes place on-line. Depending on its results, caustic soda and/or additives adjusting the desired permeate composition are supplied to permeate in the storage vessel. Before analysis, first composition solids are separated from the pickling solution. The storage vessel is operated at a lower temperature than the pickling bath. A fraction of the permeate is extracted and fed to a collection vessel (74). Concentration of the permeate/aluminate extracted, is optimized with regard to its subsequent application, by addition of caustic soda and/or additives. This is carried out in a closed system. Before solids separation, a solution from another process stage, e.g. an E0-pickle, a static rinse fluid or first rinse fluid, is added. An independent claim is included for corresponding pickling plant.</p> |
