ES270600A3 - PROCEDURE FOR OBTAINING POTASSIUM METAPHOSPHATE - Google Patents

Abstract

<PICT:0832011/III/1> Potassium metaphosphate, (KPO3)n), is prepared by contacting potassium chloride and phosphoric acid at a temperature below the fusion point of the product in the presence of a moving mass of inert particles, whereby the potassium metaphosphate is prepared in granular form. The reactants may be added separately to the inert particles or may be pre-mixed. Reaction temperatures are normally between 350 DEG and 600 DEG C. The inert particles may be constituted by potassium metaphosphate itself or by potassium chloride or sulphate. The phosphoric acid employed may be orthophosphoric, pyro-phosphoric or phosphoric acid having an enhanced P2O5 content due to the addition of phosphorus pentoxide. If it is desired to increase the K2O : P2O5 ratio, sulphuric acid may be added to the phosphoric acid but normally the ratio will be unity. Hydrochloric acid is evolved during the reaction and may be recovered. As shown in the Figure, a slurry of phosphoric acid and potassium sulphate is added through a line 2 to a reactor 1 which contains hot recycled material at a temperature of 500 DEG C. entering through line 3. The material leaves the kiln at 200 DEG C. in a freeflowing condition and is passed to a heated rotary kiln 5 where the temperature is raised again to 500 DEG C. Hydrochloric acid is withdrawn through lines 12 and 13. A portion of the material leaving the kiln is recycled to line 3 but the major portion passes to a cooler 6 from which it is passed to a screen 8 which separates the products, fines and oversize. The desired quantity is recycled through line 11 and recycle heater 4 back to the feed shoot 3. In order to produce a relatively pure hydrochloric acid the phosphoric acid employed may be defluorinated by adding part of the potassium chloride to the acid, thereby precipitating potassium silicofluoride which is removed by filtration, and thereafter reacting the purified acid with further potassium chloride.ALSO:Granular potassium metaphosphate, (KPO3)n is prepared by contacting potassium chloride and phosphoric acid at a temperature below the fusion point of the product in the presence of a moving mass of inert particles, which may be potassium chloride, sulphate or metaphosphate. The reactants may be added separately to the inert particles or may be pre-mixed. Reaction temperature are normally between 350 and 600 DEG C. The phosphoric acid employed may be orthophosphoric, pyro-phosphoric or phosphoric acid having an enhanced P2O5 content due to the addition of phosphorus pentoxide. If it is desired to increase the K2O: P2O5 ratio, sulphuric acid may be added to the phosphoric acid but normally the ratio will be unity.