| 摘要 |
PURPOSE:To prevent the generation of environmental contamination by a formed powder, by providing a reducing agent adding process, which concentrates waste water containing an acid mixture containing chromic acid and reduces Cr<6+> in waste water to Cr3+, to the front stage of a spray roasting process. CONSTITUTION:A reducing agent such as ethylene glycol of reducing Cr<6+> in a conc. solution of CR<3+> is added to a concn. tank 19 and a reducing agent such as FeSO4 for reducing Cr<6+> in the precipitated sludge generated on the bottom of the concn. tank 19 to Cr<3+> is further added to said tank 19. A Cr<3+>-containing raw solution is sprayed from the spray nozzle 11 arranged in a spray dryer 10 through a strainer by a feed pump 21. Hot air is blown in the spray dryer 10 from the top part thereof to hold the temp. in the spray dryer 10 to 350-380 deg.C and the conc. solution is heated and roasted by hot air to obtain a powder. |
