process and plant for chemical treatment of metallgegenstaenden adjusted in the schlossenem circuit with chemikalienwieder extraction without entgiftungsanlagen

摘要

Metal objects are subjected to chemical surface treatment (I) by spraying or immersion, followed by multi-stage rinsing in which the rinsing water flows in counter-current to the objects. In the novelty, the water from the first rinse is fed to an evaporator, from which the vapour flows via a condenser to the final rinse as pure water, whereas the overflow from the evaporator leads to treatment (I). Chemicals and water corresp. only with the net usage are fed continuously or at intervals to the process. Water from the first rinse may be fed to treatment (I), the latter feeding the evaporator; or the water from the first rinse may be fed to the evaporator and the overflow from the latter fed to a reservoir to which chemicals and water are added and the soln. then fed to treatment (I). The pref. plant consists of a closed circuit including an evaporator and condenser, the evaporator being connected in any of the three ways listed above. Recovery of chemicals and water is obtd., so there use is minimal; no decontamination plant is needed to treat effluents. The process can be used for chromate treatment of Mg objects.