DE1567628C3 - Process for the preparation of citric acid soluble phosphate - Google Patents

Description

3 4

are insoluble in the hot disintegrant or the reaction takes place with swelling of the

poorly soluble, so that they immediately after the reaction apatitic calcium phosphate, whereby the one

lightens the material set out of the reaction without any special cooling. There are other

mixed can be separated in the usual way. extensive, new connections in the decomposition medium

Diluting the reaction mixture with water is 5 insoluble or sparingly soluble and therefore without

not necessary. Cooling separated from the still hot liquor

It is important that the calcium can be used for the digestion. So that the reaction mixture does not

phosphate becomes too stiff in the temperature range between 100 and

180'C of a centrifugation of at least 51 percent by weight is possible after completion of the reaction

Aqueous sodium hydroxide or potassium hydroxide is allowed, the ratio between alkali hydroxide solution

j solution is assumed. When using a rock phosphate and not be too small. The weight less concentrated alkali hydroxide solution runs the ratio of alkali hydroxide solutions to crude phosphate

: implementation too slow; a complete uptake is therefore between 4: 1 and 20: 1. Since the

■ the end of the mineral cannot be reached. With recovered after separation of the product ! increasing alkali hydroxide concentration increases 15 hot alkali hydroxide solutions for new digestions j the speed of implementation is increasing. Above . can be used directly, can easily ! 75% by weight alkali metal hydroxide solutions can use a larger excess of alkali for the reaction j can no longer be used with good success; can be used.

It has been shown that even with comparatively the during the digestion of the rock phosphate

; slight cooling, there is a risk that the 2 ° forming, more or less well crystallized

'The reaction mixture solidifies and so the direct off connections have a hitherto unknown

ι separation of the digested phosphate impossible composition. The weight ratio between

y is. If, however, the reaction mixture is treated with water, CaO and P ₂ O ₅ are not caused by the reaction

i thins, there is a considerable change, there is only alkali oxide or alkali

i conversion into a phosphate hydroxide which is insoluble in citrate solution. The P ₂ O ₅ is after the implementation

j instead. The best results are obtained when treated in a practically open-minded manner. As a loading

■ the rock phosphates with 55 to 70 percent by weight evaluation standard for the mobility of the P ₂ O ₅ in the alkali metal hydroxide solutions, so that these products become the solubility of the

centering range is preferred. P2O5 ^m 2% citric acid solution, in ammonium

The digestion of calcium phosphate minerals with 3 ° citrate solution and in ammoniacal ammonium

I the concentrated alkali hydroxide solution succeeds citrate solution listed.

at temperatures between 100 and 180 ° C., preferred die after separation of the digestion product

wise between 120 and 170'C. A conversion of the remaining, still hot, concentrated aqueous

Calcium phosphate minerals in citrate-soluble compounds usually contain alkali metal hydroxide solutions

Fertilizing is therefore only small amounts of dissolved P ₂ O ₅ in the critical zone 35 above. Usually it is

I designated temperature range from 130 to 140 ^J C. Amount of dissolved P ₂ O ₃ below 1% of the amount used

i easily possible. _{P 2} O ₅ also occurs below 100 ° C. For this reason, the mother liquor

A conversion has already taken place, but the reaction is used again directly for a new digestion

The speed is usually too low to be fast, so that only the one used during the digestion

! to achieve quantitative sales. In the invention 4 ° proportion of alkali metal hydroxide solution is to be added again.

The temperature range according to the I temperature range also remains stronger.

! concentrated alkalis always in a liquid state. Carry out neatly and continuously.

'' Potassium hydroxide solutions generally react better. Of course, the alkali hydroxide solutions can

i as sodium hydroxide solutions. For example, it is also only used in the reaction mixture of compounds

; a crude product / _o be prepared potassium hydroxide solution 45 60 ° with soft in contact with water

i Quantitatively form alkali metal hydroxides at 14O ⁰ C within a few minutes. For example one mixes'

implemented, the digestion with 60% rock phosphates with alkalis and sets the alkali

Caustic soda for the same rock phosphate approximate reaction by adding water.

i 1 hour at I55 ^: C. It is also possible to add aqueous alkali chloride solutions

'■ The reaction is gen generally at normal 5 °, the advertising subjected to chlor-alkali electrolysis

: printing done. Of course, the task of adding rock phosphates in a suitable manner can be

: end also under higher or reduced pressure which then concentrated with the resulting

are made, which is then mainly pre- and hot alkali to implement.

is partaking when of the less focused

Solutions is assumed. Unnecessary entry 55 Example 1 I of carbon dioxide should be avoided as much as possible,

since with alkali carbonate solutions there is practically no conversion of 200 parts of a North African calcium phosphate ■ conversion. Minerals with 37.4% P ₂ O ₅ , 51.0% CaO, 2.4% SiO ₂ The reaction time depends on various factors and 3.8% F were with 2000 parts of an oO weight; fools off. To play especially, as already stated, 6 ° concentrated aqueous potassium hydroxide solution mixed, the concentration of alkali metal hydroxide and and 15 minutes with stirring ι at 135 ⁰ C heated. : the implementation temperature plays a major role. The phosphate swelled during the reaction, so the rate of conversion depends on the degree of fineness that a viscous suspension was formed. Like that of the rock phosphates. since finely divided phosphates usually react very quickly to analyzes of the results obtained by centrifugation. The type and occurrence of 65 crystalline product also showed whether the calcium phosphate mineral used plays a role. Poor P ₂ O ₅ 100% in citric acid solution, 98.6% crystallized minerals are usually attacked faster in Petermann's solution and 98.5% in ammonium than coarse crystalline apatites. citrate solution soluble.

Example 2

200 parts of the rock phosphate mentioned in Example 1 were mixed with 2000 parts of a 100% strength by weight aqueous sodium hydroxide solution and heated to 155 ° C. for 90 minutes with stirring. The reaction took place with lightening and swelling of the phosphate. At the end of the reaction, a fluid suspension was present After centrifugation, a crystalline product was obtained which had the following P ₂ O ₅ solubilities: 100% in citric acid solution, 97% in Petermann solution and 95.6% in ammonium citrate solution.

B e i s ρ i e 1 3

100 parts of a calcium phosphate mineral from Florida with 34.4% P ₂ O ₅ , 49.2% CaO, 4.9% SiO ₂ and 3.9% F were mixed with 800 parts of 60% strength by weight sodium hydroxide solution and stirred for 2 hours Heated to 153 ° C and then centrifuged without cooling. The reaction product was well crystallized and its P ₂ O ₅ content was 99.6% soluble in citric acid solution, 94.5% in Petermann solution and 94.0% in ammonium citrate solution.

B e i s ρ i e 1 4

_{100 parts of a North African rock phosphate with 36.8% P 2} O ₅ , 52.5% CaO, 1.3% SiO ₂ and 4.2% F were stirred into 1000 parts of a 60% strength by weight aqueous potassium hydroxide solution at 110 ° C., and the mixture was then stirred heated and centrifuged within 10 minutes up to 165 ^C C. The reaction product already formed for the most part at about 130''C had a P ₂ O ₅ in solubility of citric acid of 97.5%, in Petermann solution of 95.9% ^un d ' ⁿ ammonium citrate solution of 95.3%.

B e ϊ s ρ i e 1 5

200 parts of a raw phosphate in Example 4 were heated with 1000 parts 70gewichtsprozentiger aqueous potassium hydroxide solution for 10 minutes at about 145 ⁰ C. After the reaction had taken place, it was centrifuged off. The P ₂ O _{5 of} the product was 100% soluble in citric acid solution, 95.6% in Petermann solution and also 95.6% in ammonium citrate solution.

Claims (4)

I 2 rigen sodium carbonate solutions with the formation of patent claims: convert sodium phosphate. Another method is proposed for the production of 1. A process for the production of citric citronensäurelöslichen phosphate fertilizers feinzersäurelöslichem phosphate by digesting 5 kleinerte rock phosphate with an excess of phosphate rock with an excess of aqueous about _100/0 corresponds ° in aqueous sodium hydroxide of about 40 alkali hydroxide solution at elevated temperature, 'to 50 Be ( about 35 to 50 percent by weight) characterized in that one reacts with heating to temperatures of about 180 to the rock phosphate with a 51- to 75 weight-200 C and stirring, then the mass percent alkali metal hydroxide solution under Einhai- io with water to dilute, under faster Using a weight ratio of alkali metal in the temperature zone between 130 and hydroxide solution to rock phosphate of 4: 1 to 140 ° C to temperatures below 100 to 30 ° C. 20: 1 at a temperature between 100 and to cool, convert the phosphate mass from the aqueous 180 ° C and separate the phosphate lye obtained in this way and bring it into a form suitable for use as fertilizer from the mother liquor without significant cooling (German separates patent specification 878 947). A direct rework 2. The method according to claim 1. characterized by the method is not possible, since the pre-drawn, that one 55 to 70 weight percent written measures, namely the use of a Alkali hydroxide solution is used. in particular 40 to 50 percent by weight aqueous 3. The method according to claim Γ and 2. thereby 20 sodium hydroxide solution and heating to temperatures between characterized in that the reaction is carried out at 180 and 200 C while maintaining this soda temperature between 120 and 170 C. caustic concentration. not with ordinary pressure 4. The method according to claim 1 to 3 can thereby be brought into compliance. A sodium hydroxide solution in that the mother liquor is heated after namely can at 180 to 200 ⁰ C at atmospheric pressure, only separation of the citratlöslichen phosphate 25 again, if it uses up 80gewichtsproals Aufschlußmiltel about 75-. is cent. Now the rock phosphate is among these Conditions heated with the sodium hydroxide solution are obtained after working up the reaction mixture through Dilution with water and cooling of this mixture while rapidly passing through the temperature zone between 130 and 140 ° C to temperature The invention relates to a method for manufacturing doors below 100 to 30 ° C, filtering off and washing treatment of citric acid-soluble phosphate with water, a product which is only partially soluble in Digestion of rock phosphate with an excess of citric acid is soluble. But the rock phosphate on aqueous alkali hydroxide solution at elevated temperatures with 40 to 50 percent by weight sodium hydroxide solution temperature. treated, so can only boiling temperatures In agriculture, industry and daily life between 130 and 140 "C. This tempera life will have large amounts of soluble phosphates, doors are in the area of the critical zone, in which, for example, in the form of fertilizers, feed the desired Fertilizers do not represent phosphates, detergents, etc., are required. As outlets 40. Thus, by means of an experiment, solid substances could be used for their industrial production, that by boiling for 2 hours a rock phosphate, which occurs almost exclusively in large deposits, with a 50% by weight Na- Calcium phosphate minerals. These rock phosphates, tron lye in a weight ratio of 1: 3, dilution consisting mainly of fluoroapatite, the mixture with water and cooling of the same must be subjected to a special chemical treatment 45 to about 30 "C, a product of which is obtained So that the phosphorus in one for the p ₂ O ₅ only slightly in C itric acid is soluble. goes over to the purpose of mobile form. The apatitic Both when using a sodium hydroxide solution with pre-structure is completely or largely destroyed, written concentration of about 40 to 50 Ge and depending on the type of reaction partner, vvichtsprozent as well as an aqueous sodium hydroxide solution, products with different characteristics arise. 50 whose boiling point is between 180 and 200 ⁰ C, For the digestion of the rock phosphates several are therefore only products according to this process Processes are known which are in principle obtained in two groups, the citric acid solubility of which does not affect permit. After the first method, this will be peaceful. P ₂ O _{5 of} the rock phosphates by treatment with The process according to the invention for production Mineral acids, for example sulfuric acid, nitric acid, are converted from citric acid-soluble phosphate by acidic acid, phosphoric acid or hydrochloric acid into a soluble circuit of rock phosphate with an excess of form. The second method involves aqueous alkali metal hydroxide solution at increased tempe- rature destruction of the apatite structure by means of an annealing furnace . sinter 60 alkali hydroxide solution while maintaining a Geprozeß or in a entfluorierenden reaction at wight ratio of alkali metal hydroxide solution to temperatures between 1300 and 1700. ^J C (USA.- crude phosphate from 4: 1 to 20: 1 at a temperature Patent 2,995,437). door between 100 and 180 ° C and that Attempts were also made to digest the calcium-containing phosphate from the mother liquor without essential phosphate minerals in the aqueous alkaline medium 65 borrowed cooling separates. perform. Sodium carbonate solutions take effect The crystal lattice of the apatite is in this VerPhosphorite practically not on. Only tricalcium is completely destroyed, and the phosphate is lost to other phosphates gets involved with concentrated water-wide, new compounds. These substances