| 摘要 |
PURPOSE:To produce iron oxide having a high grade by adding iron or iron compd. to a waste liquid of picking iron or steel, adjusting adequately the pH of the above-mentioned waste liquid and settling or filtering and separating the deposited silica compd. then roasting the waste liquid. CONSTITUTION:The waste liquid 1 of the hydrochloric acid pickling of steel products is conducted through a tank 2 to a pH adjusting tank 3. The iron or iron compd. 4 packed therein is brought into reaction with HCl in the waste liquid 1 to adjust the pH to 2-4. Metallic iron, iron scrap, iron oxide pellets, iron hydroxide, etc., are used as the above-mentioned iron or iron compd. A flocculating agent or aq. ammonia 5 is then added to the waste liquid 1 and is conducted to a settling tank 6. The colloidal silica compd. such as SiO2 deposited therein is settled and separated as sludge 7. The waste liquid 1 is thereafter passed through a filter 8, by which fine SiO2, etc., are removed. The filtrate is supplied to a spray roasting furnace 9 where the filtrate is roasted by hot air 10 of about 800 deg.C and is thermally decomposed, by which the iron oxide 13 of the high grade contg. Si at a low ratio is obtd.
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