IL23601A - Process for the production of phosphoric acid - Google Patents

Description

PATENTS AND DESIGNS ORDINANCE SPECIFICATION Process for the production of phosphoric aoid CHEMICALS PHOSPHATES an Israel of Haifa Bay HERBERT a citizen of the of Panorama Haifa and an of 3 Aharon Mount Haifa do hereby declare the nature of this invention and what manner the same is to be to be particularly described and ascertained in and by the following Invention relates to the manufacture of phoric acid by the decomposition of rook phosphate with sulfuric In the conventional wet processes for producing phosphoric acid the rock phosphate is subjected to reaction with dilute aoid under conditions tha the product phosphoric acid has a of the order of As the reaction is excessive heat is dissipated by appropriate means in order to maintain the temperatur of the reaction mixture below and the Calcium sulfate produced as a secondary product is in the form of the If the conditions of the reactio are not properly the calcium sulfate Is apt to orm as the which sets on the filter and makes the filtration of the reaction product One of the greatest drawbacks of the wet processes the low content of the product acid as a makes necessary a subsequent concentration large volumes of reaction are involved which sitate correspondingly large reaction a view to producing in one operation a phosphoric acid of higher it has been suggested to decompose the rock phosphate with hot total volumetric acid analysis correspo virtually solid reaction phosphoric acid is extracted with water from the residue of which is in 4 the form of The recovered product acid has a content of about process several drawbacks among which the following should be notedt used as a is the process materials those parts of the apparatus which come into contact with hot oleum be the if the phosphates an appreciable content of these are converted by oleum into sulfonates which reduce the stability of granule of soaked calcium formed as a first reaction cause foaming of the product acid and keep an unduly high proportion of calcium sulfate suspended i the The invention aims at providing a process for the decomposition of rock phosphate with sulfuric acid by whic phoephoric acid having a relatively high content can be produced in one operation and which is substantially free from the drawbacks of the oleum process indicated According to the invention the rock phosphate is heated by itself before being contacted with the sulfuric and the latter is admixed to the hot the temperature to which the phosphate is and the of ration of the sulfuric acid being so chosen that in the resulting reaction highly concentrated sulfuric acid reacts with the phosphate at a temperature of about 100 to the substantially solid and as a rule granular reaction product leached with water for recovering the phosphoric sulfuric acid is used substantially in the stoichiometrically required but an excess of of sulfuric acid is recommendable in order to make the extraction more mm with a rather dilute sulfuric of the order of 60 to by weight for the evaporation of the water contained the acid will lower the temperature of the mixture to the optimal reaction no previous calcination is required and the phosphate is heated only a temperature in the neighbourhood of the desired reaction somewhat above commercial concentrated sulfuric acid of about concentration may be Optimal temperature and concentration of sulfuric acid wil chosen according to the technical and economical conditions given each It is according to the phosphate that has been enriched by calcination whereby its calcium carbonate content is and subsquent separation o the calcium oxide by a process slaking with so little water that the Calcium oxide just converted into dry calcium The slaking operation still leaves the phosphate at a sufficiently high temperature for the purposes of the process according to the In any tho temperature to which the phosphate may be The calcium is entirely in the form of anhydrite which not the subsequent processing of the reaction She reaction mixture is at first plastic but forms stable soli granules after a short granules bo extracted with water without in coun by means of any either or Preferabl those extractors are used which produce no ciable abrasion or disintegration of the For pulsating stationary or or vertical drums or columns internal fixed or moving or extractors be used in the process according to the extracted phosphoric acid still contains a small proportion of sulfate Shis can be removed by the addition of flocculating agents subsequent decantatlon of clarified acid from calcium sulfate sludge settling at Since the phase of this sludge is phosphoric it will as a rule be advisable from a economic point of view to retur the sludge to the to the stage where sulfuric acid is admixed to the water contained in the sludge being evaporated at the moment of alternative way of separating solid calcium sulfate from product acid is by and in this the centrlfugate may be returned to the rock phosphate may be done in any suitable known by means of a rotar kiln In the acoording to the the contained in most Kinds of is almos entirely in the form of silicon fluoride and possibly hydrogen in the decomposition fluorides can be recovered the escaping gases by washing with and if the fluoride solutions may further processed in conventional If the removal of the fluorides is not complete in the reaction hot may be passed through granules forming the reaction gas not only removes virtually all the residua but also the also makes for a better stability of the fines entrained by the gas can be recovered in any suitable known by means of a and be returned to the reaction mixture of hot rock phosphate and sulfuric acid The process according the invention has considerable As compared with known wet processes producing a concentration phosphoric i saves the concentrating operation and greatly the equipment As contrasted to the oleum process it uses cheep ordinar sulfuric acid which is heated before bein contacted with the heated phosphate and less aggressive than the hot The invention Illustrated by the following Examples to which is not 200 kg o phosphate from containing of and of heated to and then admixed kg of sulfuric There ensued liberated and reaction mixture was plastic at in course of than 5 formed solid stable granules of dark granules were extracted counterc with hot wator and the extract leaving the extractor was a phosphoric acid by weigh of o and of free had suspended in it a small amount of dispersed which could be by The extractio residue consisted of nearly of in the form of anhydrite with an admixture of of fluorine and of containing all the originally suspended in the product acid was returned the firs reaction admixed to the hot total loss Of this process was calculated on the amount of calcium sulfate eliminated from the corresponding to about 2 to of the original 2 She phosphate rook was of the same kind as used Example 1 but enriched by calcining and removal of calcium oxide to a Of It was a powder of which passed through a mesh Standard 200 kg of this phosphate were heated to and then mixed wit kg of sulfuric whereby stable granules were These were extracted currently with product acid contained of insufficientOCRQuality

Claims (1)

1. particularly described and ascertained the of our 3aid invention and in what the same to be declare that what we claim A for the production of phosphoric acid of a high content b t e decomposition of phosphate with wherein the phosphate heated by before being contacted with the sulfuric and the latter is admixed to the hot the temperature to which the is and the degree of ration of the eulfuriojacid being so chosen that in resulting reaction highl aoid reacts with phosphate a a temperature of about 100 to and the substantially solid and a rule granular tion product is leaohed with water for recovering the phoriO A process according to Claim wherein the phosphate is heated to a temperature in the neighbourhood of an highly sulfurio acid is ueed as a for A process according to wherein the phosphate is heated a temperature considerabl above i in the of a thermal treatmen calculated to destroy organic matter contained in the crude and of about 50V to tacted at a high temperature aqueous sulfuric aoid for to A process for the production of phosphoric aoid of a high content by the decomposition of phosphate with substantially herein with referenoe to the Phosphoric acid having a of the order of when produced the process according to any of Claims i to Dated this 24th day of 1965 the Applicants insufficientOCRQuality