EP0087323A1 — A process to manufacture commercially acceptable …

Claim 1

Independent Claim 190 words

A process to manufacture from rock phosphate commercially acceptable phospnoric acid and gypaum comprising reacting coarser samples of rock phosphate with a mixture of phosphoric acid and fluosilicic acid with a minute quantity of sulphuric acid at a temperature from ambient to 100°C. until the phosphate and fluorine contents. in the rock phosphate are substantially dissolved, the resulting slurry being fed into a crystalliser containing slurry from previous batch, the slurry being reacted in the crystalliser with sulphuric acid, the reaction in the crystalliser being continued till gypsum crystal formation is complete, the crystalliser contents being filtered and the residue containing substantially gypsum crystals being washed several times, the filtrate and washings containing a mixtures of phosphoric acid fluosilicic acid, being divided into two unequal portions, the smaller portion containing P 2 O 5 "equivalent" to that contained in the rock phosphate at the beginning of the process, the smaller portion beine concentrated to give phosphoric acid, the fluosilicic acid evolved curing the concentration process being scrubbed and mixed with the larger portion, the last mentioned mixture being recycled to a fresh quantity of rock phosphate to repeat the process.

Claim 2

Dependent Claim 190 words

A process to manufacture from rock phosphate commercially acceptable phospnoric acid and gypaum comprising reacting coarser samples of rock phosphate with a mixture of phosphoric acid and fluosilicic acid with a minute quantity of sulphuric acid at a temperature from ambient to 100°C. until the phosphate and fluorine contents. in the rock phosphate are substantially dissolved, the resulting slurry being fed into a crystalliser containing slurry from previous batch, the slurry being reacted in the crystalliser with sulphuric acid, the reaction in the crystalliser being continued till gypsum crystal formation is complete, the crystalliser contents being filtered and the residue containing substantially gypsum crystals being washed several times, the filtrate and washings containing a mixtures of phosphoric acid fluosilicic acid, being divided into two unequal portions, the smaller portion containing P 2 O 5 "equivalent" to that contained in the rock phosphate at the beginning of the process, the smaller portion beine concentrated to give phosphoric acid, the fluosilicic acid evolved curing the concentration process being scrubbed and mixed with the larger portion, the last mentioned mixture being recycled to a fresh quantity of rock phosphate to repeat the process.

Claim 3

Dependent Claim 68 words

A process to manufacture from rock phosphate commercially acceptable phosphoric acid and gypsum as claimed in Claim 1 wherein the slurry produced by the reaction of rock phosphate with the mixture of phosphoric acid and fluosilicic acid containing a minute quantity of sulphuric acid is filtered to removea insoluble impurities and the filtrate and washings of the resioue are fed into the crystalliser containing slurry from previous batch.

Claim 4

Dependent Claim 141 words

A process to manufacture from rock phosphate commercially acceptable phosphoric acid and gypsum as claimed in claim 2, wherein the filtrate and washings of the residue are divided into two portions, the smaller portion containing P 2 O 5 "equivalent" to that contained in the rock phosphate at the beginning of the process, the smaller portion being concentrated and cooled and filtered, the residue being wet calcium silicofluoride and the filtrate being product phosphoric acid, the cake of wet calcium eilico- fluoride being added to the aforesaid larger portion in a crystalliser containing slurry from previous batch and sulphuric acid being added into the crystalliser, the reaction in the crystalliser being continued till the gypsum crystal formation is complete, the gypsum crystals being filtered and washed, the filtrate being recycled to a fresh quantity of rock phosphate to repeat the process.

Claim 5

Dependent Claim 73 words

. A process for the manufacture of gypsum and phosphoric acid from rock phosphate, which process comprises treating rock phosphate with fluosilicic acid optionally together with phosphoric acid to solubilise the phosphate content thereof, regenerating fluosilicic acid and precipitating gypsum by treating at least part of the product so obtained with sulphuric acid, separating out the gypsum, separating out product phosphoric acid and re-cycling the regenerated fluosilicic acid to treat further rock phosphate.

Claim 6

Dependent Claim 73 words

. A process for the manufacture of gypsum and phosphoric acid from rock phosphate, which process comprises treating rock phosphate with fluosilicic acid optionally together with phosphoric acid to solubilise the phosphate content thereof, regenerating fluosilicic acid and precipitating gypsum by treating at least part of the product so obtained with sulphuric acid, separating out the gypsum, separating out product phosphoric acid and re-cycling the regenerated fluosilicic acid to treat further rock phosphate.

Claim 7

Dependent Claim 25 words

A process as claimed in claim 4, wherein at least part of the solution obtained from the solubilisation step is concentrated iuntil calcium silicofluoride precipitates.

Claim 8

Dependent Claim 49 words

A process as claimed in claim 5, wherein only a portion of the solution obtained from the solubilisation step is concentrated to precipitate calcium silicofluoride, the mother liquor remaining after precipitation constituting the product phosphoric acid and the precipitated calcium silicofluoride being passed to the sulphuric acid treatment step.

Claim 9

Dependent Claim 36 words

A process as claimed in claim 4, wherein substantially the whole of the solution obtained from the dissolution step is treated with sulphuric acid and the gypsum precipitated thereby is separated from the slurry so obtained.

Claim 10

Dependent Claim 30 words

A process as claimed in claim 7, wherein the product phosphoric acid is derived by scrubbing at least a portion of the liquor remaining after the sulphuric acid treatment step.

Claim 11

Dependent Claim 31 words

A process as claimed in any one of claims 4 to 8, wherein the product of the solubilisation step is filtered to remove undissolved impurities prior to the sulphuric acid treatment.

Claim 12

Dependent Claim 18 words

Phosphoric acid and/or gypsum obtained from a process as claimed in any one of claims 1 to 9.

A process to manufacture commercially acceptable phosphoric acid and gypsum from rock phosphate

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