IL45409A - Potassium phosphate fertiliser - Google Patents

Description

Potassium Phoephate Fertilisers This invention relates to the production of fertilisers and is particularly concerned with the production of potassium dihydrogen phosphate soluble polymerised forms of this These materials are of great value as sources of both potassium phosphorus and can be used as fertilisers directly or together with other Potassium dihydrogen phosphate can be obtained by the reaction of phosphoric acid with chloride according to the The removal of the hydrogen chloride quantitativel from the reaction mass is extremely difficult in unless high temperatures or a large excess of phosphoric acid are In the former the potassium metasphosphate is preferentially formed in the latter the isolation of the salt from the acid is difficult and expensive in According to our invention we provide a process for the production of potassium phosphate or polyphosphate in which potassium chloride and phosphoric acid or a polyphosplioric acid are reacted in a molar of phosphorus to potassium within the range of to air being blown through the reaction mixture to facilitate the removal The preferred ratio of phosphorus to Liquid fertilisers with a very low chloride content may be by dissolving the product in water or alternatively in an ammonia solution or by forming a solution of the reaction product of the hydrolysis product in water and thereafter passing gaseous ammonia through the The process of the invention involves the production of potassium dihydrogen phosphate and polymers of this salt by the reaction of phosphoric acid with potassium chloride according to the C1 Dehydration of the takes place at the elevated temperature to yield pyrophosphate and higher polymeric The temperature of reaction is sufficiently preferably below to avoid the formation of insoluble We have found in accordance with our invention that the removal of from the reaction mass can be easily and effectively carried out with stoichiometric or near stoichiometric quantities of the P to K ratio varying from 1 without the use of very high temperatures or large excesses of by sparging the reaction mass with The process of the invention has the advantage of the preferential formation of water insoluble metaphosphate also the difficult and isolation of the desired potassium dihydrogen phosphate Patent Specification describes and inter the reaction of potassium chloride with an excess of cencentrated phosphoric preferably two molecular valents with three of concentrated phosphoric The disadvantage of using such a large excess of phosphoric acid has been set out Moreover the temperature used in said known reaction is low as higher than that used in the process according to the present In a paper of et at in of a study of the conversion of potassium chloride to potassium phosphate is However the of said paper certainly not realised the advantage of the specific conditions of the process according to the present nder inter the best results obtained by said which are worse than that obtained by the process according to the present invention are obtained with a 2 1 molar ratio of phosphorous to Moreover said authors apparently had in mind a two step process namely one in which the first step is performed at 100 to in order to remove most of the HC1 under vacuum and only the second step is performed at This is certainly a much more complicated procedure than the process according to the present invention The phosphoric acid employed may be the vet proc ss phosphoric acid of commerce with potassium pentoxide content in the range of from to or i may be dehydrated phosphoric acid with a substantially or the superphosphoric acid of or various other grades of phosphoric acid which are commercially The resulting product is polymerised mixture of phosphates with a small amount of free acid present varying from 5 to on the relative quantities of acid and potassium chloride which can be ground up to yield fertiliser of high P 0r and analyses or dissolved in water to yield a liquid fertiliser of high analysis and low chloride The mass is hydolysed by heating with water at A temperatures of substantially the boiling point of water so as to yield the solid potassium phosphate This product can be dried to yield a friable powder or dissolved in water to yield a liquid fertiliser of high analysis containing potassium and phosphate with a very low chloride According to one embodiment of the process according to the the reaction product is recovered as a solid with a chloride content of less than and a free acid content of less than Factors which affect the chloride of the are the reaction temperature an the ratio of phosphoric acid to reaction con hieh the air sparging of the reaction mass as in the following Examples 3 and 2 respect Thus in the following a product having a chloride content of below could be obtained if the ratio of P to K was raised above or if the temperature was raised above or if the residence time The solution of either the reaction or hydrolysis product can be to give a stable solution with analyses for P and K are much higher it been possible to achieve up to now with Wo have found that anaylsis solutions can be with the hydrolysed which is an solutions having even higher analyses can obtained by dissolving polymeric reaction product in The reaction is therefore a useful material for the production of liquid For those purposes in which handlin and transport of the product is necessary or in which a solid product is required the hydrolysed product is advantageously An apparatus which may he used for carrying out the process according to the invention is described with reference to the accompanying drawing in 1 is a of a process according to the invention for making potassium phosphate from muriate of and 2 shows a modi ication of The apparatus shown in 1 comprises a reactor 3 which is fed with phosphoric acid from a stora vessel 1 and muriate of potash from a storage vessel Air is fed in at Hydrochloric acid together with some water vapour is evolved at The product of the reactor may he fed to a hydration apparatus 5 it mixed with water from a conduit The product from the hydratio apparatus to a drying unit 7 thence to storage the product the 3 may he fed to a cooler 9 and thence to a crusher 10 from which is passed to storage 2 shows a modification in which the product a first reactor 3A goes a second 3i where it is again treated with air in at Fertiliser grade potassium chloride of Potash constant rate phosphoric to an air sparged reactor Maintained at The ratio of phosphoric acid to potash in the feeds was such as to give a reactor product containing moles P per mole The reactor was sparged with air at the rate of The product from this reactor was allowed to flow continuously to a reactor where the temperature was and the air sparg rate was again The resulting product was analysed intervals and contained an average free acid expressed as average chloride content of The average analysis total total i 2 K2O The reactor product was divided into one of which was crushed and The other stream was heated with water at 110 for 2 hours to hydrolyse phosphates and the hydrolysed product was dried and The hydrolysed product had an analysis of total total The glass like reactor product and the product were dissolved in water and saturated solutions at 20 The saturated solutions had potassium analyses given product solution roduct solution EXAMPLE 2 Fertiliser grade potassium chloride of Potash reacted at with with wet process phosphoric acid which had been heated to and concentrated to This corresponds to a mole ratio of P to K of to When the evolution of hydrochloric acid had ceased the reaction mass was divided into two parts and each part 1 heated at for 120 One portion was sparged with air through a glass The other portion was The reaction was analysed as Air Sparged Unsparged Residual chloride Total Total EXAMPLE Fertiliser grade potassium chloride of Potash g was reacted at wit stirring with wet process phosphoric acid 356 g which had been concentrated to to a mole ratio of P to K of to When the evolution of hydrochloric acid gas had as indicated by the cessation of the mixture was sparged with air and the temperature maintained at Samples were removed for chloride analysis at The results of these analyses are given Time after cessation of effervescence 120 180 240 Residual chloride CI 6 The product a d the product thereof he to produce products with valuable P for example j ml of a aqueous ammonia solution was mixed with 203 g of reactor The resulting solution containing was formulated as a valuable insufficientOCRQuality

Claims (1)

1. A process for production of potassium phosphate or hate in which potassium chloride arid phosphoric a polyphosphoric acid Amendment at a temperature range of under 65 reacted in a molar ratio of phosphorus to potassium the range of from to air being through the reaction mixture to facilitate the of hydrochloric A in c aim 1 in w the 6f phosphorus to potassium is substantially process as claimed in claim 1 or 2 which the reaction product is recovered as a solid with content of less and a free acid content of less than A process as claimed in claim 1 or 2 in which the reaction product is hydrolysed by heating with water and the hydrolysis product is as a crystalline Λ process as claimed in claim in which the hydrolysis is effected with water at a temperature of to um chloride and phosphoric or a polyphosphoric acid are reacted together in a ratio of phosphorus to potassium within the range of from to air being through the reaction mixture to facilitate the removal of hydrochloric Λ process as claimed in claim 1 in which the ratio of phosphorus to potassium is substantially A process as claimed in claim 1 or 2 in which the reaction product is recovered as a solid with a chloride content of less than a free acid content of less than A process as claimed in claim 1 or 2 in which the product is hydrolysed by heating with wate and the hydrolysis product is recovered as a crystalline A process as claimed in claim in which the hydrolysis is effected with water at a temperature of from 100 to 120 Amendment Potassium phosphate or potassium polyphosphate under 65 when made b a process as in any of the preceding process according to claim in which hydrolysis is effected at substantially 7 A process as claimed in any of claims 1 to 6 in the reaction between the phosphoric or polyphosphoric acid and the potassium chloride is effected in the range of from to A process as claimed in claim 7 in which the reaction is effected in the range of from to A process as claimed in any of claims 1 to 8 in which phosphoric acid with a content in the range of from 30 to is A process as claimed in claim 9 in which phosphoric acid with a content greater than and below is 11 A process according to claim 1 substantially as hereinbefore described with reference to the accompanying drawing any of the specific Potassium phosphate or potassium polyphosphate when made a process as claimed in any of the preceding Amendment product produced by under 65 reaction or product produced by claimed in any of claims 1 to For Applicants Yitzhak 13 The product produced by of the reaction or hydrolysis product produced by a process as claimed in any of claims 1 to For Applicants Yitzhak Hess 13 insufficientOCRQuality