1. Neutralizing free acid with lime to produce calcium sulfate
Reducing Fe 3+ to scrap iron as Fe 2+, serum taken in reaction vat, by steam heating to 70 ~ 80 ℃, milk of lime was added slowly with stirring. When approaching the end point, the speed is slower to prevent the local pH from being too large, causing precipitation of Fe 2+ and affecting the quality of calcium sulfate. Neutralization to a pH of 5.4 is the end point (if calcium sulfate is used for white pigment, the pH of the filler can be controlled to be smaller; if used for cement, the pH of the filler can be controlled to be larger), and then stirred until the pH remains unchanged. After standing for 1~2h, it is filtered by a centrifuge, and the filtrate is prepared for the next process. The filter residue is first washed with a small amount of dilute hydrochloric acid to remove hydroxides such as aluminum , vanadium , chromium and titanium , and then washed with water until only a small amount is detected with BaCl 2 . Precipitate. The dried material is dried at 60~70 °C, and then crushed and packaged into calcium sulfate (CaSO 4 · 2H 2 O) finished product. Its reaction formula is as follows:
CaO+H 2 SO 4 ===CaSO 4 +H 2 O
2. Precipitating iron iron oxide red with ammonium sulfide
The filtrate is returned to the original reaction tank, heated to boiling with steam under stirring, and an ammonium sulfide solution is added to form a black precipitate of ferrous sulfide, and heating and stirring are continued for 0.5 h, and the mixture is allowed to stand for 1 hour, and the material can be centrifuged for separation. The filtrate is prepared for the next step. After the filter residue is washed with water and dried, if the ferrous sulfide is produced, it is rapidly dried in a reducing atmosphere at 70 ° C, and then cooled, sealed and packaged to be a finished product; Then, the filter residue can be sent to a reverberatory furnace and calcined at 800 ° C for 1 h, that is, the discharge cooling, pulverization, and packaging are finished products. Its reaction formula is as follows:
FeSO 4 +(NH 4 ) 2 S===FeS↓+(NH 4 ) 2 SO 4
4FeS+7O 2 ===2Fe 2 O 3 +4SO 2 ↑
3. Precipitation of sulfated barium sulfate with barium sulfide
The above-mentioned main ammonium sulfate-containing filtrate is sent to a reaction tank, heated to 70-80 ° C, and a barium sulfide solution is added under stirring to form a barium sulfate precipitate, and stirring is continued for 1 hour, and the plate filter press can be used for pressure filtration. . The filter residue is first washed with dilute hydrochloric acid, then washed with water, and then discharged at 50~70 °C, and then crushed with a universal crusher, and the package is finished with barium sulfate.
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