Process for the preparation of phosphoric acid
AssigneeMizusawa Kagaku Kogyo Kabushiki Kaisha
InventorsYujiro Sugahara, Yoshibumi Noshi, Hiroyuki Naito, Akira Takahashi, Shoji Shoji
Life of this patent
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Abstract
When phosphate rock and sulfuric acid are mixed under such conditions that gypsum dihydrate is stably formed and sulfuric acid is added to the phosphate rock in an amount not exceeding the amount equivalent to a calcium component in the phosphate rock, small masses of the reaction product between the phosphate rock and sulfuric acid can be maintained in the non-disintegrable form throughout extraction of phosphoric acid from said reaction product, and phosphoric acid can be extracted from such reaction product at a high rate in a good yield.
Claims19
In a process for the preparation of phosphoric acid which comprises mixing phosphate rock and sulfuric acid in the presence of water, drying the mixture to obtain a solid reaction product between phosphate rock and sulfuric acid and extracting phosphoric acid from said solid reaction product, the improvement which comprises mixing phosphate rock and sulfuric acid in an amount of 0.7 to 0.97 equivalent to the calcium component in the phosphate rock, in the presence of water at a temperature of 30.degree. to 105.degree.C., under such condition that gypsum dihydrate is stably formed and that the following requirement is satisfied:
- 0.70.gtoreq.C.gtoreq.0.45
- wherein C designates the weight ratio of phosphate rock to the sum of phosphate rock and total water,
- the mixing of phosphate rock and sulfuric acid being carried out for a time sufficient to substantially complete the decomposition of the phosphate rock by sulfuric acid, and drying the mixing reaction product between the phosphate rock and sulfuric acid to solid small masses of the phosphate rock-sulfuric acid reaction product at a temperature not exceeding 200.degree.C. under such drying time and heating conditions that the gypsum dihydrate in said mixing reaction product is converted substantially to anhydrous gypsum or a combination of anhydrous gypsum and gypsum hemihydrate.
In a process for the preparation of phosphoric acid which comprises mixing phosphate rock and sulfuric acid in the presence of water, drying the mixture to obtain a solid reaction product between phosphate rock and sulfuric acid and extracting phosphoric acid from said solid reaction product, the improvement which comprises mixing phosphate rock and sulfuric acid in an amount of 0.7 to 0.97 equivalent to the calcium component in the phosphate rock in the presence of water at a temperature (t.degree.C.) of 30.degree. to 105.degree.C. under such conditions that the P.sub.2 O.sub.5 concentration (P) of phosphoric acid in the phosphate rock slurry is within a range of from 20 to 45 percent, the weight ratio (C) of phosphate rock to the sum of phosphate rock and total water is within a range of from 0.45 to 0.70 and that the following requirement is satisfied:
- t.ltoreq. -0.111 P + 0.00334 P.sup.2 - 0.000593 P.sup.3 + 107.2,
- the mixing of phosphate rock and sulfuric acid being carried out for a time sufficient to substantially complete the decomposition of the phosphate rock by sulfuric acid, and drying said mixing reaction product to small solid masses of the phosphate rock-sulfuric acid reaction product at a temperature not exceeding 200.degree.C. under such drying time and heating conditions that the gypsum dihydrate in said mixing reaction product is converted substantially to anhydrous gypsum or a combination of gypsums anhydrite and hemihydrate.
Dependencies are inferred from the claim text.