DE1667425A1 - Process for the production of sodium triphosphate - Google Patents

Description

Patent application "Process for the production of ITodium triphosphate"

Anriolderin: Central Glass Co., Ltd., ITbe-shi, Japan

The priority of the following Italian patent application is claimed: Ur. 13,668 A / 67, filed 13th Harz 1967

The invention "relates to a method of making a very pure U-form sodium triphosphate with good yield, and nwar in either granular or powdery 3? orm, starting out from a heavily contaminated phosphoric acid, the so-called ITaßprozess-Phosphorsa.ure, as it has been caused by treatment of phosphate flour with mineral acid is available.

Since the Haßproseß phosphoric acid usually contains a large amount of contaminating accompanying substances, it was previously necessary to purify the ITauproaeB- ^ jtonphorcic acid in order to produce a very pure ITatriUmtriphosphats when using this starting material -; -. ho. ^r jphorfjäure first pre-clean with an ion exchange resin O'i-er i.iL'c other suitable cleaning agents,

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Then with a "basic compound of Hatriums, whether, for example, sodium carbonate or neutralize Hatriumhydroxyd, wherein the molar ratio swischen ITa ₅ O and P ₂ ⁰ K ^aui 5 ^J 3 is set, then concentrate. obtained neutralized phosphoric su to dehydrating and finally calcining to obtain the desired polyphosphate, namely sodium triphosphate; in this procedure, various cleaning agents were added before, after or also during the neutralization of the prepurified phosphoric acid with the basic compounds of sodium to precipitate the impurities contained therein, whereupon the deposited impurities were separated by filtration.

In this way, a highly purified sodium phosphate solution with a molar ratio of ITa ₉ O to P _D 0c corresponding to about 5: 3 was obtained. These earlier methods of manufacture required the use of expensive ion exchange resins to pre-purify the phosphoric acid, and repeated filtration operations of the phosphoric acid with the addition of expensive cleaning agents were necessary; in spite of all, it was difficult to completely remove the impurities simply by repeating the peeling and filtration steps and for these reasons it was practically impracticable to use

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the earlier methods of producing completely pure products. In addition, one also knows of another process for the production of ITodium triphosphate, in which the following process steps are carried out? Neutralization of the phosphoric acid process with a basic compound of the. • Tatriun, filtration and separation of impurities from the salt formed, separation of pure crystals of primary and secondary sodium phosphate (sodium dihydrogen phosphate and sodium hydrogen phosphate) from the filtered off sodium phosphate solution, mixing of the obtained crystals of substances in such a way that the molar ratio of IJjgO to P ₂ ⁰ S was ^{in the} ratio of 5 i 3 , subsequent heating of the mixture, drying and calcination. The disadvantage of this process is that the crystals of Iiatriumdihydrogenpliospliat (φκ * £ primary sodium phosphate) are very easily soluble and that it is therefore necessary to bring about a further concentration of the neutralized wet process phosphoric acid to cause the separation of crystals of this type. In this concentration process, however, considerable crystal deposits already result and the necessary filtration of the liquid is all the more difficult because the liquid has a high viscosity and a gluey one

Ilasse represents. Filtering off this liquid and the coagulation of the crystals deposited therefrom is true :: u3erot difficult. In addition, the procedural steps uoi .; ErMts_ens, Trocloiens and Calcinieren. ^ The ITodium phosphate

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solution with the colar ratio of the liagO to the P ₃ O ^ corresponding to 5: 3 or of the mixture of the two types of crystals obtained, in which the types of crystals are set to the same molar ratio, for the purpose of producing the desired sodium triphosphate in the following more precisely problems described.

It is known that there are two different crystal modifications of the sodium tj ^ rphosphate giot, ai. referred to as I-shape and U-shape crystals. Crystals of the II-form are mainly used as the starting material for detergents and other industrial chemicals, because they have a solubility superior to that of the other crystal forms. The common way of producing ITodium triphosphate uses a sodium orthophosphate solution with a molar ratio of UaJO to PpOj- which is set to about 5: 3 as the starting material and consists of the following steps: Production of dried sodium orthophosphate by spray drying or other suitable means and then others Heating, elimination of Y / water and condensation of the predried product in a calcining furnace at a temperature in the range between 30O ⁰ G and 4DO ⁰ C. However, this method had the Mach part, that the sodium orthophosphate during its heating and dehydration in a tacky state, transformed with a portion melted thereof, and ^r to the inner Y. andflachen of the furnace

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ansintertej ax further working method was made more difficult and it also happened that the resulting end product unites Content of poorly soluble particles from the sintered material contained. For the production of sodium triphasphate In addition, another method has also been proposed in which the as Starting material used liquid directly into a gas was sprayed at a high temperature. The evaporation of the Liquid according to this procedure, as well as the subsequent elimination of water and condensation, were in a very high temperature completes in a short period of time, which caused the atmosphere to rise to a high temperature was brought. This is economically unfavorable, To make matters worse, there was the problem that various. Heaction conditions, for example the drainage time and the Y / asserdampi 'pressure, had to be coordinated with one another. Finally, it was disadvantageous that the end product usually contains an undesirable proportion of sodium triphosphate crystals. the 1-3? Orn included.

After extensive investigations with the aim of finding a procedure for the production of ITodium triphosphate from ITaUprocess-Phosphorrjü_iire to develop from the aforementioned evils is free, the inventors succeeded in discovering a new and improved method of production from liatrinmtr! phosphate.

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The subject of the invention "ordered accordingly in a Process for the preparation of pure sodium triphospnai; the end crude barrel-shaped phosphoric acid obtained by the following Procedural steps is marked:

a) neutralization of the raw phosphoric acid with ammonia and one or more of the "basic sodium compounds" such as soda ash or caustic soda;

"b) Deposition of crystals from Hatriumanuaoniunihydrogen'-phosphate (UaHJHLHPO ^ .4HpO), the so-called phosphorus salt j

c) Addition of further amounts of the. basic sodium compound (s) to the phosphorus salt until the molar ratio of Ila-O to P ₂ O such as 5 I 3j is reached

d) heating and evaporation of the mixture obtained under. Recovery of the ammonia contained therein;

e) hot-gas treatment of the residual mixture fractionate at a temperature of at least 180 ⁰ C in a J) is ~ pergierkolonne under the ^ ^ 'feildehydratation mixture and

f) calcination of the mixture obtained

s.

The procedure is based on the following equations:

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OfilGiNAL

₅₄ + HH ₃ »HH ₄ H ₂ PO ₄ " ( ¹ )

ItH ₄ H ₂ PO ₄ + HaOH > InI ₄ ITaHPO ₄ MH ₂ O (2)

3HaIHI ₄ HPO ₄ .4-H ₂ O + 2HaOH> 2ITa ₂ IIPO ₄ +

+ HH ₂ O (3)

+ 21Yes ₂ HPO ₄ > Fa ₅ P ₅ O ₁₀ + 2HgO ♦ (4)

For erfi ICTI ... _u o ₀ emäßen methods include the direction indicated by the equation (2) intermediate process step for the preparation of phosphorus salt m. This process step is very advantageous because the phosphorus salt can very easily be obtained in the form of crystals which hardly contain any impurities, and only by neutralizing water-process phosphoric acid with ammonia and one of the basic sodium compounds from the aqueous Solution of the precipitating deposits of the impurities which arise from substances such as Eisany Aluminum ^ ¹ silicon oxide and the like (the impurities do not have to be completely removed)

separated and then with the help of one of the known crystallization processes separates the crystals. After carrying out detailed investigations into the course of the reaction, in which the sodium ortliopliospliate obtained by drying the starting liquid by heating, elimination of water and Condensation is converted into sodium triphosphate, the inventors have found that this reaction takes place in a complicated manner Sequence of steps expires; Various types of intermediate products are formed in the process, in which the ITatriumortliopliocphat only partially deliydraticiert, so that the

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Reaction products during the first half of the Y cleavage reactions Xm is generally converted into a sticky form. The investigations have shown that the second half of the water splitting reactions is decisive for whether products of the IJ? Ori: i or the II-i ^? orm disfigure. It could be seen that the products of the I-form are preferably produced when the heating of the starting liquid is carried out at a high temperature in a short-term process, as has already been briefly mentioned in connection with the description of the spray-drying method is * Although the odorism of the sodium ortliophosphate to the hatriunitr! phosphate leading from the sodium ortliophosphate is complicated, it can be assumed that in one. In the first stage of the dehydration process, the urinary orthophosphate is primarily converted into pyrophosphate and that this pyrophosphate then possibly leads to sodium triphosphate in the further course of the dehydration in its last stage. The dehydration process presumably takes place in the following way:

- First half of the level:

The method according to the invention is based on the utilization of the knowledge lake described above. A distinctive one The feature of the method according to the invention is accordingly that he. which by the addition of basic hetrium compounds to the phosphorus salt already prepared in it with cooling

ORIGINAL BATHROOM

In the molar ratio of the ITa ₂ O aum PgOc corresponding to 5: 3 prepared iratriimorthophosphate solution in a "dispersing column kept at a temperature of 180 ° C. or above

to fo-rt

einrrn-tuit., uobei be? yrοphosphat is formed .. The aehandlungstemperatur -is liüher than that for transferring the ITatritUHorthophosphats in a dry product required iTeaperatur of 11O ⁰ C 'to 140 ° C, so that is higher than the temperature at the same time a γ / purer [drying and the first half of the stage of the Y / water elimination reaction can take place. At this point, the reaction product remains for the entire period of time in which the reaction product tends to become sticky, in a state in which it remains in suspension in contact with the flowing air until it is completely dry . The mixture product, dried in this way, is then brought in an alkaline solution to a temperature in the range from 250 ° C. to 450 ° C. in order to continue the nitrate dehydration reaction and the reaction product in sodium triphosphate of the II type to convict. ■. '. ". ■.

The following description serves to provide a more detailed explanation of the process of the invention.

/iUi.'-'.cJ'St- if the bass pronouns-iiiocphoric acid is neutralized with ammonia, a oll- ¥ ert in the range from 5.2 to 6.0 is reached, 1 ' ¹ Ur den ii'all that one before the .Ifciuralisabion with /lru.toniak the exit fiiüsaiglreit uuruichst. with calcined ■ ^

2 0 9 Ö1 6/1 0 0 9 ^:

Soda or caustic soda neutralized, gets a Zristallicat. -; in extremely fine particles, which causes the iiacliiOlgerLcle. filter large-Schwiex'igkGxten prepares. The Aßuaoniak to be used for the neutralization can be used either in the i'orn of a G-aoeo or in a liquid. However, it is advisable to make the process economical because: "} one uses recovered ammonia for the neutralization, the recovery of which will be described later. It is possible to use an untreated phosphoric acid as the starting material in the processes, such as they do normally obtained by the decomposition of phosphatmelil (phosphate mineral) by means of sulfuric acid. This crude barrel process phosphoric acid has a ΡρΟς concentration of about 30 $ S. The process according to the invention can be made particularly advantageous if the crude phosphoric acid is also used at this point in the process mixed with a mother liquor carried in the ice, which is obtained when the crystalline phosphorus salt is poured off, as will be described in more detail later. This mother liquor contains sodium hydroxide and ammonia. After the phosphoric acid has been mixed with this mother liquor, the neutralization is carried out by addition full of ammonia persists. Uan Namely, by adding a suitable Henge of basic ITatriumverbindung to the iiiosslLorsLLaire before neutralization i / iit Auaoniak precipitation is \ free, in the phosphoric eiithaitHnen Kieselfliiorwassefcsoff- - acid · achieving that separates as fluosilicate atrium. With this trick, a rope is made of phosphoric acid

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-with-the in the recirculated mother liquor existing --- ammonia, neutralized and at the same time the free Hydrofluoric acid, as a precipitate of sodium silicon fluoride. led into firm lorn. As a result, will "in the event of further neutrality of this precipitate" already containing phosphoric acid with ammonia v / more precipitate produced the substances such as disene phosphate, aluminum phosphate and the like and can be easily filtered off.

Thanks to the heat of neutralization, the phosphoric acid comes to the boiling point during the neutralization. It is precisely this state of the phoGi> ionic acid that is necessary for the further implementation of the process according to the invention by Plutsen is avoided, because this would lead to the separation of annonium phosphate. If the neutralization is carried out correctly, only the main mixes of the impurities, namely the compounds of isenium, aluminum, fluorine and silicon, which are present in The solution of ammonium dihydrogen phosphate (ML · H ₂ PO.) obtained in this way still contains a small amount of precipitates; this solution is mixed with the basic sodium compound to be used, especially with Calcined soda or with sodium hydroxide solution, mixed and made to react. One uses from

the latriumverbinduiig such an amount that the molar ratio ■ between ITa ₂ O and ^^ 5 is set approximately to 1: 1. After the reaction is complete, the. Liquid cooled or concentrated to obtain crystals of phosphorus salt. These crystals are then separated and washed. Although the mother liquor from which the phosphorus salt crystals separate out still contains a large amount of impurities, it is possible to obtain phosphorus salt crystals of high purity; the impurities remaining in the mother liquor do not interfere with this. In special cases it can be considered desirable to further purify these crystals by a customary time crystallization technique. However, such a requirement is only in very rare cases. The immediately obtained phosphorus salt crystals contain very small amounts of impurities and there is therefore no need whatsoever to pre-purify the phosphoric acid used as starting material by a special purification step, as was necessary in the earlier processes for the production of the phosphates. In view of the property of the phosphorus salt crystals that they have very high solubility in water at higher temperatures, but dissolve only very little in cold water, it is advantageous to bring about the crystallization by cooling, with a large amount of phosphorus salt can be obtained in a good yield. After the phosphorous salt crystals have been separated off and washed and _{# they} can be dissolved in a small amount of hot water

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and .au! this way a highly concentrated phosphorus salt solution produce. To this solution is added such an amount of "basic I sodium compound that the molar value of the" basic. Iatriunnrerblndung 2/5 mol compared to 1 haul of the phosphorus salt achieved. The mixture is then heated and allowed to evaporate the bulk of the ammonia it contains for distillation {veIj'rächt. The recovered ammonia is in the cycle of • the neutralizing process stage described above the liaßproezßphosphorsäure carried out. The one after the distillation remaining liquid represents a solution of a "mixture which consists of about 1 mole of sodium dihydrogen phosphate (primary sodium phosphate) and about 2 moles of disodium hydrogen phosphate Secondary sodium phosphate) exists and is hardly noticeable Contains amounts of ammonia. This liquid is then sprayed into a dispersing column. The ones in this column maintained temperature is adjusted so that it in the area where the injected liquid is with the heated air is brought into contact, at least to 180 C or above is maintained, with the injected liquid itself having a temperature in the range between. 180 C and 280 C. In view of the fact that the Mixture of sodium orthophosphate in this way the first Passes through half of the process stage of dehydration, i.e., it exceeds the intermediate state of stickiness while the substance is still passing through the hot gas, can then mix the mixture in any of the usual Calcination furnace heated further, dehydrated and condensed

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are in the resulting, water-containing daniprene atmosphere, which forms as a result of the reaction in such ovens, without being in the least sticky. ' In this way, the last half-step of the reaction can be done without Difficulty to be carried out. Although the one in the dispersing column prevailing temperature "can depend on factors such as the type and size of the column used (atomizing column) and also depends on the degree of dispersion achieved, it is in any case necessary to set a temperature in 'Main area of the column to maintain that at least 180 ° C. The term "main area" used here means a place in such a zone in which the dried Product is brought into contact with the jetting gas, a Zone that is not identical to the head section of the column and the areas near the inlet and outlet of the gas.

The following is intended to explain the invention in more detail Description of specific embodiments of the invention. .

Example 1

• Ilan added to 20 kg; of the fed raw phosphoric acid 13.7 l: g of the abundance from the mother liquor, which in the second ' Process step (which will be described later) had been obtained. Subsequently, ammonia is added to the liquid introduced until the pH is adjusted to 5.0. the

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The liquid comes to a boil and the impurities that are separated out are separated off by a centrifugal settling machine. In this way, 29.2 kg of a mother liquor were obtained ... The analytical values (fi) of this mother liquor were found to be as follows:

E ₂ O ₅ SO '3 ITa 2 ° m 30th F. Fe 017 Al. 18.86 4, 21 0, - 713 '7, 0.83 O, 0.063

This was considered still impure mother liquor from the first step at a temperature of 80 ⁰ C Odei about dissolved therein 3.8 kg soda ash and cooled the. then dissolve to 20 ° C. The deposited crystals were separated by a centrifugal separator. The crystals adhering to the screen basket surface of this separator were washed by spraying 2.6 kg of water thereon. As a result, 14> 0 kg of phosphorus salt crystals and 19.8 kg of mother liquor were obtained. The mother liquor also contained the wash liquor that had been used to wash the crystals. The analysis values (#) for the crystals and for the mother liquor were found as follows!

^P 2% ^m 2 ° ⁱⁿ $ SO ₅ . F. Fe Al KriGtalle t 33.80 14.70 8.15 0.053 0.015 0.0014 0.0011

Mother liquor: 4.99 2.23 5 * 13 6.03 1.20 0> 025 0.005

The mother liquor was stepped back in the first process ^ - guided. The separated phosphorus salt crystals were with a small amount of. hot water added and in it

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achieved by further supply of heat on - "is a high-ι concentrated solution obtained This solution was, mixed with 2.20 feg sodium carbonate The resulting solution was then heated \ and distilled for the recovery of the ammonia, the remaining solution was further concentrated to... a Pg ⁰ C concentration of 29 wt .- ^ j the residual liquid was for carrying out the fourth step TERF ahrens it into a sprayed dispersion column. the a! temperature

™ by 5QO ⁰ O heated air was introduced into this dispersion column from a higher point. Meanwhile, the temperatures of the gas quantities, which are located in this higher. Section of the column were, maintained at a temperature of 280 ⁰ C and that quantities of gas were in a deeper part of the column on 21Ö ° Ö. The fed salt solution was dried and at the same time the first part of the dehydration reaction was carried out. It turned out that $ 60 of the t "O" was in this case

m 'converted to iyrophosphate. The remainder consisted of a small amount of orthophosphate and other phosphates. The reaction 'product was then introduced into a small Rotierofen and calcined at a temperature of 35O ⁰ C for 1.5 hours in a suitable water vapor atmosphere. As a result, e-rhielt to 7.7 kg of a product, the $ 97 "Ifatriumtriphospliat the Il-Porm and beyond just -very contained few impurities.

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B e 1 a ρ i e 1 2

• κ Han vermiselite at a speed of 3 m per hour phosphoric acid with the mother liquor, which resulted from the filtration of the phosphorus salt crystals already described,

3 This mother liquor was fed in at a rate of Q> 5 m per hour. The mixing vessel had a Sassungsvermögen of 0.5 m "supplied while the formation of ITi ed he hit of the gravel was sodium fluoride, which converts this resultant mixture containing precipitates in a container having a Fassungavermögen of 3 MR. This container was equipped with a stirrer and it became the recovered ammonia gas, the recovery of which will be described later »together with fresh. Ammonia gas introduced. The introduction took place from the bottom of the container at such a rate that the pH value was maintained at an IT level between 4.0 and 4 * 2. The shower the entstehends ITeutralisatiqnswärme coming to the boil llüssigköi-t.schied more Yerui | Cleaners, such as Tferbindungen of iron, ^ luniiniums, silicon 'and' Pluors from * The resulting liquid was w into another container of about 3 ·] Carrying out the digestive capacity in which the liquid; with its content of excretions kept in motion for about two hours by gentle stirring. Subsequently, the. liquid was fed to a centrifugal sedimentation, in which the heavier precipitates are deposited. In this way one obtained a - filtered liquid

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"was 24? S) at an hourly rate

3
ι of 2, Tm.

The overflowing part of this liquid became continuous

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fed into a container with a capacity of 1.5 m, in the to maintain a container temperature in the range between: 70 ° C and 80 ° 0 a small amount ^ ampf was initiated} here the liquid was stirred vigorously » This container was fed at a speed of 470 kg per hour to neutralize the liquid Sodium carbonate too. This resulted in a solution that was used in

an amount of 2.2 m that contained phosphor sala »piping solution v; urde an installer. fed by the circulatory system on the catch type, ¥ / orin slide solution to a temperature between 48 0 and 50 G Was cooled down with the result that one phosphorus salt crystals at a speed; from Ί580 kg per hour received. Then the obtained phosphorus salt crystals were dissolved in warm water and at the same time. Steam on

3 '

directed. On this catfish one got 5> Q m one hoah concentrated solution of phosphorus salt. solved in this solution sodium carbonate is added at a rate of 257 kg per hour on, the resulting Gemisoh wuide into a 33eatillations column initiated with filling packing. This column had one Diameter of 0> 6 m and a height of 15 m and she was with provided a heating mantle to distill and concentrate the liquid therein. Afterward, the concentrated liquid was atomized into a

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1B67425

Sprayed column, which had a diameter of 5.5 m and a height of 15 m. The injection was carried out from the top / rope of this column * At the same time, 20,000 ares of air heated to 500 ° C. was blown into the upper part of the column. In order to cool the temperature of the treated material at the point of the vent outlet to about 10 G or less, cold air at room temperature was blown in the vicinity of this point. The speed of the blown hot air was regulated so that the temperature in the main room of the. Column to 250 ⁰ C brought in. The resulting mixture of phosphoric acid salts was composed so that about $ 60 was present the existing PPOC content as ealciniertes Mätrinmpyrophosphat while-which consisted rest of HatriumtriphoBphat and at a level of a few percent, from Natriumor-thophosphat. This Gemisoh was m in an on 53Ö ° 0 fueled from the outside rotary kiln having a diameter of 1 and a length of 8 m heated dehydratislert and kondensiertf to obtain 820 kg of a Brodukteö that about 92 i »or more consisted of JTatriumtriphosphat.

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Claims (6)

1. Process for the production of pure Fatriunitr! Phosphate from raw jJaßproaeß-Phosphorsi'Aire, ■ ge Iz e η η aeic Ii η et by the following process steps: a) neutralization of -fiohpliospiiorsäure with ammonia and one or more of the basic I sodium compounds; b) Deposition of crystals from ITatriumammoniumhydrogen -., phosphate (ITaMLHPO ^, 4HpO), the so-called pliosphorsalses j c) Addition of further quantities of the basic ITatrium compound (s) from the pliospliorsala bis. to achieve the molar ratio of Ba ~ 0 to PpO _r like ' 5 i_ 5 j d) heating and evaporation of the cream mixture obtained under Reduced amount of ammonia contained therein; e) Hot gas treatment of the remaining mixture-during. a temperature of at least 100 ° ö in one Dispersing column with fractional dehydration of the mixture and '. ■ '. f) Galcine.tion of the mixture obtained G. ■ - 2. The method according to claim T, characterized in that the crystallization of the phosphorus salt is effected by adding the basic sodium compound to a liquid which is added by adding aanonia 2098 16/1099 BATH ORIGINAL ITass process phosphoric acid and filtering the seh daloei excreted Rainfall has occurred. " 3.: The method according to claim 2, characterized in that g e k e η η, that the mother liquor obtained by filtering off the phosphorus salt is added to the phosphoric acid process, before neutralizing with ammonia * 4. The method according to any one of claims 1 "to 3, characterized geke η η ze ic h η et that one sodium carbonate or llatrium liydroxyd Y ^^^ unx tt as the liasic sodium compound 5. The method according to any one of claims 1 "to 4, characterized ge k e η η ζ e i "c h η e t that the process is carried out continuously and / after filtering the phosphorus salt crystals recovered mother liquor as a solvent for the dilution of the jassproseid-phosphoric acid in the circuit returns. 6. Method according to one of the claims. t "to 5, thereby ge k e η η ζ ei e h η e t that one can recover the Ammonia for. the neutralization of ITaid process phosphoric acid returns in the cycle. Dr.ByrHa 209816/1099