Claims
- 1. A method of manufacturing wet process phosphoric acid from phosphate rock, comprising the steps of
- i. grinding the phosphate rock in a water slurry sufficiently that the phosphate rock will pass a 30 mesh (Tyler) screen, said slurry containing at least about 20 weight percent water, and said slurry being formed with water containing no more than 2 percent P.sub.2 O.sub.5 ;
- ii. passing the slurry of ground rock to an attack tank and therein contacting and reacting the slurry with diluted sulfuric acid obtained from step (vi) herein to yield a product slurry of crystalline hydrated calcium sulfate in phosphoric acid having a P.sub.2 O.sub.5 value of at least about 25 weight percent, said slurry providing about 15 to 35 weight percent of the water present in said attack tank;
- iii. removing said product slurry from the attack tank;
- iv. subjecting said product slurry to a separation step whereby the crystalline hydrated calcium sulfate is separated from the phosphoric acid;
- v. washing the separated calcium sulfate with water and obtaining spent wash water having a P.sub.2 O.sub.5 value of about 15 to 25 weight percent;
- vi. mixing the spent calcium sulfate wash water with concentrated sulfuric acid having a concentration of at least about 90 percent to obtain diluted sulfuric acid; and
- vii. passing the diluted sulfuric acid to step (ii) above to supply about 60 to 85% of the total amount of water in the attack tank, said concentrated sulfuric acid supplying up to about 5 percent of the water present in said attack tank.
- 2. The method of claim 1 wherein a surface-active agent is added to the slurry of rock in step (i) in an amount sufficient to increase the pumpability of the slurry of ground rock.
- 3. The method of claim 2 wherein the surface-active agent is also effective as a foam inhibitor in the attack tank in step (ii).
- 4. The method of claim 1 wherein sufficient water is present in the attack tank in step (ii) to yeild phosphoric acid having a P.sub.2 O.sub.5 value of about 28 to 32 weight percent.
- 5. The method of claim 4 wherein the phosphate rock slurry of step (i) contains about 22 to 35 weight percent water.
- 6. The method of claim 1 wherein in step (ii) the slurry of ground rock is passed to an attack tank via a constant head line from which the flow rate of the slurry of ground rock into the attack tank is controlled by a control valve.
Parent Case Info
This is a continuation, of application Ser. No. 416,647, filed Nov. 16, 1973 now abandoned.
US Referenced Citations (11)
Foreign Referenced Citations (1)
Number |
Date |
Country |
615,987 |
Jul 1958 |
CA |
Non-Patent Literature Citations (1)
Entry |
Phosphoric Acid Slack, 1969, 187, 183, 200, 201. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
416647 |
Nov 1973 |
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