DE1567590B1 - Process for the purification and concentration of phosphoric acid - Google Patents

Description

1 - 2

The invention relates to the production of purified The threshold values for the phosphoric acid concentration

and possibly more concentrated phosphoric acid tration, below which the solvent is practically

_{from technical H 3} PO ₄ obtained by the wet process from the aqueous acid are not extracted

Phosphoric acid. In the description of the invention. at the same temperature for the different solutions under the designation »technical phosphorus agents 5 different and also differ for

acid «aqueous phosphoric acid, which usually use the same solvent at different temperatures.

Lich through the decomposition of phosphorite with sulfur temperatures. So are the temperatures

acid is produced, an H ₃ P0 ₄ concentration of which a given system solvent -H ₃ PO ₄

not less than 35% and possibly up to about homogeneous or heterogeneous, for the different 90% and the usual impurities io solvents different. All of these values can

contains such a phosphoric acid. can be determined empirically and create a large

It has already been proposed that the technical variability of the conditions under which the ex-phosphoric acid produces a purer phosphoric acid by carrying out a traction process in each special case is that the H ₃ PO _{4 is obtained by extraction with organic solvents, depending on the concentration and extent of solvents} is extracted, whereby 15 of the impurities of the technical phosphoric acid available as starting material for water and impurities as residue and remain. Many very different solvents were given the desired degree of purity and concentration as being suitable for this purpose, although obviously no particular type of solvent was preferred to the extracted phosphoric acid. In a preferred embodiment of the invention. This purification procedure was obtained from sev- 20 to the invention method, the operations are reren not practically applied because: The selectivity of the extraction of the technical phosphoric acid and the solvent is between phosphoric acid and separation tivity of the extract from the remaining technical M water, ie their ability to preferentially Extract H ₃ PO ₃ to niche phosphoric acid at relatively low ™ was too low; the temperature extracted per batch carried out at which a clear, homogeneous amount of H ₃ PO ₄ was too low; extract had to be obtained from the extract, and this extract is heated to the solvent by distillation or re-extraction - a temperature at which an acid phase is removed in water, the former method separating from a solvent phase. These phases require special devices and a large separation can be achieved by adding a small amount of heat, while the phosphoric acid is diluted again by the re-extraction of either water or purified phosphoric acid with water. 30 to the extract while it is being heated, facilitated the subject of the invention is a method to be. The low temperature, which is required according to this recovery of purified and possibly more preferred embodiment during the extra-concentrated phosphoric acid from technical, according to tion, can, for example, phosphoric acid obtained by vacuum wet process by re-evaporation of a corresponding Msngsn for extraction with an organic solvent. 35 Technical-grade phosphoric acid added solvent The process according to the invention is characterized by this. This method is gseignet bssondsrs, characterized in that the phosphoric acid to when the solvent is an ether niedrigsiedsndsr + 8O ⁰ C with such an ester, ketone, glycol ether at about -5. Optionally, the technical phosphoric acid can be extracted in or ether, which has a negative heat exchange with a cooled salt solution temperature gradient with regard to the solubility of phosphorus, namely either before or after the phosphoric acid, the extract phase in the above-mentioned admixture of the solvent. All other suitable temperature range methods separated from the aqueous phase can of course also be used and the separated extract phase can optionally be included. Addition of a small amount of water or more pure water Phosphoric acid to about 2 to 100 ° C, but not its advantage for extraction operations with one run heated above the boiling point of the extractant, can be used. initial H ₃ PO ₄ concentration of the technical Preferred solvents are ethers and esters with phosphoric acid well above the threshold value, a total of 2 to 15 carbon atoms. Ethers of the formula R - O - R ₁ , in which practically no H ₃ PO ₄ extracted, R and R ₁ identical or different aliphatic radicals and so much solvent is used that with Represent 2 to 15 carbon atoms, such as. B. by the single pass the H ₃ PO ₄ -concentrated diethyl, diisopropyl, di-n-butyl, isopropyl-n-butyl, tration of the remaining aqueous phosphoric acid di-n-amyl and diisoamyl ethers. is practically reduced to the threshold value. Because these solvents meet the following conditions: 55 the solvent, the temperature difference between

a) Virtually no H ₃ PO ₄ to extract from an aqueous Phos- the states of clear solution and the phase separation phosphoric acid, its H ₃ PO ₄ concentration in the extract and the initial concentration of the tech below a threshold value of about 35 weight niche phosphoric acid depending on the request be chosen percent lies; can, the inventive method is extreme

b) from an aqueous phosphoric acid with a 60 flexible and adaptable to special needs. Concentration above the above-mentioned threshold. Therefore, the respective Msngsn of purified value _{can extract a substantial amount of H 3} PO ₄ , phosphoric acid and remaining technical phosphorus, the greater, the higher the HgPO ^ -Concentra- phosphoric acid varies depending on the requirements be, tion of the aqueous acid; Pliosphorus produced by a wet process

c) a temperature-dependent ability to acidify. The shelf contains solids that are in suspension solution of phosphoric acid, which are in dated form and settle on storage. Capability at low temperatures is significantly greater. These solids remainn from the cleaning process than it is at high temperature. unaffected, since they return in the aqueous phase

3 4

being held. They ultimately fall in the contaminated area of practically all of the original impurities

impure acid fraction. This property of technical acid. The solvent phase, which is 23.6 kg

the contaminated acid-containing aqueous phase, contained the remaining 7.6 kg of H ₃ PO ₄ , ie

Retaining solids is a very useful feature of 76% of the original H ₃ PO ₄ content of the batch

times the procedure described below: 5 technical phosphoric acid extracted in this way.

a) Various solid compounds, with which the feed acid is saturated The solvent phase was heated to 80 ° C., can be mixed with 1 kg of water during and during the heating. The extraction failed because its solubility product was too high. This resulted in a phase separation. The upper phase is stepped. This is particularly the case with plaster of paris, complexes consisted of the solvent and did not contain any fluophosphates or the like. This precipitation io H ₃ PO ₄ more. The entire H ₃ PO ₄ was not affected in the soil is of the purification process, phase contain the strength aqueous a purified 86% ^E rather it possible to improve the residual phosphoric acid represented containing less than V ₁₀ from the loan acid by the Centrifugal impurities contained iron and aluminum that are originally removed in fuging or settling. the load were present. This cleaned

b) Silicon dioxide as finely ground quartz, active phosphoric acid was neutralized with ammonia Silica, or active clay, known as additives, and resulted in a solution of diammonium phosphate, to improve the color of the after a wet without formation of any precipitate, process produced acid and / or back. .

Maintenance of fluorides can be used, for example, the acid prepared by a wet process before 20 technical phosphoric acid obtained from the wet process carrying out the process according to the invention with an H ₃ PO ₄ content of 70 weight, without an impairment percent and i Propyl ethers were continuously carried out in accordance with the measure ratio carried out according to the invention, 1.7 parts by weight of acid per part by weight; this addition leads to a staining solvent fed to a mixer. The two improved and increased purity of the 25 liquids were mixed at 2 ° C, and the disperser purified acid. sion was kept flowing into a sedimentation vessel,

c) In general, various reagents, which were also kept at 2 ° C, where the dispersion to combine with acid impurity constituents in an upper solvent phase, which split dissolved or are suitable for their precipitation, contained H ₃ PO ₄ , and separated a bottom phase of aqueous, for example, aluminum oxide for fluoride, active carbohydrate phosphoric acid. The phase ratio was a fuel for organic substances or the like, in effective part by weight of soil phase per 1.5 parts of solvent phase used in the present process. The bottom phase, which was 62 percent by weight H ₃ PO ₄ by being added to the feed acid before and the mass of the impurities originally contained in the feed extraction and together with the impure acid, was withdrawn from the acid fraction in the aqueous phase Extractor removed. The upper phase was in to be. Since the contaminated acid fraction is brought to a mixing vessel kept at 30 ° C, where it can be used for solid fertilizers such as a small amount of water, triple superphosphate (1 part water to 13.5 parts solvent phase) . their presence does not result in any adverse effect. The residence time in the mixing vessel was sufficient to allow a large number of reagents to reach 30 ° C, which in order to improve the quality of the liquid. As a result of this increase in temperature, an acid produced by a wet process used an aqueous phase which could be practically all of the H ₃ PO ₄ , together with the water according to the invention and the extract water, can be used from the solution process without any of the medium . The mixed phases were allowed to flow in a sedid, except for the added reagents, 45 mentation vessel, which incurs additional costs at 30 ° C. and in which the phases overlap

d) Calcium hydroxide, dicalcium phosphate, monolayers. The soil phase consisted of purified calcium phosphate and phosphate rock can be added to phosphoric acid with a content of 70 percent by weight of free sulfuric acid, H ₃ PO ₄ . The upper phase resulting from dissolution present in the feed acid; 50 medium, which contains a small amount of acid and water, a calcium sulphate precipitate forms. The contained, existed, was ^{cooled to 2 °} C. and the slurry obtained again is processed directly, for the extraction of additional phosphoric acid mixture, all of the solid calcium salts in the aqueous phase being used. The purified acid was retained for longer. The concentrated from the solvent as 95% H ₃ PO ₄ , without any clean phosphoric acid separated out during the process of evaporation, is therefore practically the result of the evaporation of solids.

table free of sulfuric acid. . .

The following examples illustrate the invention, Example 5

without restricting them to that. 30 parts by weight of technical phosphoric acid

. -I ₁ the wet process, the 80 percent by weight H ₃ PO ₄ ,

Example 1 60 0.9% Fe and 0.5 ° / ° containing Al, were added at 5 ⁰ C.

11.6 kg of technical phosphoric acid from the wet mixed with 70 parts of n-butyl ether, and the process in such a way that the 86.5 percent by weight (about 10 kg) formed dispersion was contained _{in two phases H 3} PO _{4 at 5 ° C} at 3O ⁰ C with 16 kg di- allowed to separate. In this way, only a few n-butyl ether were stirred for 10 minutes, then 30% of the total H ₃ PO ₄ in the technical phos stirring was stopped and the mixture was extracted into two liquid phosphoric acids in the solvent phase. The phases are allowed to settle and the latter separated. remaining technical phosphoric acid contained 76 Ge-The aqueous bottom phase made up 4 kg and contained weight percent H ₃ PO ₄ and was only slightly less than 60 weight percent (about 2.4 kg) H ₃ PO ₄ and purer than the original acid charge.

Claims (3)

5 6 The approximately 54 parts by weight solvent extract example? were mixed with one part by weight of water and The foregoing example was separated using an aqueous phase which repeated virtually all of the same amounts, but containing the acid and the water. This acidic aqueous 5 times the solvent extract under atmospheric phase had an H ₃ PO ₄ concentration of 85 pressure for evaporation and recovery of the weight percent, ie a higher concentration when the solvent was heated. In this way, the feed acid became, and was pure, yielding less than a purified acid having an H ₃ PO ₄ concentration than 0.05% Fe, less than 0.01% Al, and less than about 80%. Contained 0.01% Ca. ok . '"Example8 B e i s ρ i e 1 4 200 ml of one prepared by a wet process 160 g of an acid prepared by a wet process (51% P ₂ O ₅ ) were at 25 ° C with an equal phosphoric acid containing 60.5 percent by weight H ₃ PO ₄ ent- volume of the dibutyl ether of diethylene glycol, were at 20 ° C with 60 g of cyclohexanone are mixed for 10 minutes, with an aqueous phase and 320 g of one stirring for a long time, after which the stirring was stopped. Solvent extract was obtained which contained 140 g of H ₃ PO ₄ (calculated as 100% H ₃ PO ₄ ). The mixture was separated into two phases. This left, which was then separated from each other extract was decanted and heated to 100 ° C, with the. The aqueous phase (lower phase) contained approximately a small amount of water to effect the phase-56% of the introduced phosphoric acid and the large-scale separation was added. In the bottom phase fell ren part of the impurities of the original, 200 g of purified phosphoric acid with a P ₂ O ₅ content acid produced by a wet process. The from 50% on. This acid was converted into a 95% A solvent phase which concentrated the remainder of the original phosphoric acid without containing any phosphoric acid introduced, was heated to 65 ° C. during evaporation; during the heating she became at about 25. . 15 ml of water mixed. A phase center example y occurred on. The upper phase consisted of the 2000 g solution of a wet process middle. The phosphoric technical phosphoric acid contained in the bottom phase (concentration: 70% acid was purified aqueous phosphoric acid with a weight percent H ₃ PO ₄ ) with 3400 g isopropyl concentration of 58% · This purified phosphorus 3 ° ether at 2 ° C for 10 minutes mixed for a long time, whereupon the acid was neutralized with ammonia to give the dispersion for separation into an upper solution solution of diammonium phosphate without the formation of the middle phase containing 35% dissolved H ₃ PO ₄ and any precipitate. soil phase consisting of aqueous phosphoric acid was left standing. 200 g of the solvent extract B e i s ρ i e 1 5 35 tes were with 24 g of ammonia gas in the presence a saturated aqueous solution of diammonium Treated 142 g of a phosphate produced by a wet process. The temperature rose while phosphoric acid, which contained 70 percent by weight H ₃ PO ₄ (underneath neutralization to 6O ⁰ C. The ether vapors were about ICO g H ₃ PO ₄ ), were condensed at 2 ° C with 40 g and collected. The remaining ether was butyl acetate 10 minutes Stirred for a long time, "after which the 40 was decanted. Approximately 102 g of the diammonium stirring was stopped. The mixture separated. Phosphate crystals were filtered off while the courage was allowed to stand into two liquid phases, which were subsequently stored for another test. Bend separated were. The solvent phase containing _.. _{Λ 1η Λ} 38 g H ₃ PO ₄ (calculated on ICO% H ₃ PO ₄ ), the remainder JS e 1 s ρ 1 e. 1 ΐυ | was in the beden phase together with the impurities 45 170 g of phosgene produced by a wet process of the originally supplied technical phosphoric acid (technical) with a concentration of acid. The solvent extract phase was heated to 45 ° C, 70 percent by weight H ₃ PO ₄ and 100 g of isopropyl ether, being mixed with a small amount of water at 2 ° C, whereupon the dispersion was mixed to achieve phase separation into an upper solvent phase , the len. The bottom phase, which contained 5 ° dissolved phosphoric acid from purified aqueous, and an aqueous phosphoric acid with an H ₃ PO ₄ concentration of phosphoric acid bottom phase, which consisted of 65% impurities, was separated and concentrated to 95%, which was originally in contained in the charge without being present during evaporation, was allowed to stand. The upper solids deposit. Phase was ^{heated to 65 0} C, with 59% of the ether . 55 separated from the extract that was decanted Example 6 were. In the event of further evaporation of the extract 50 ml of a prepared by a wet process, 70 g of a purified phosphoric acid (83% phosphoric acid with an H ₃ PO ₄ concentration of H ₃ PO ₄ ) were obtained. % were mixed with ICO ml of ethyl ether for 10 minutes at 25 ° C., 115 g of an extract containing 35% H ₃ PO _{4 being obtained} . At the bottom of the Vessel separated from an aqueous phase, the 27% 1 · method for the recovery of purified and of the original P ₂ O ₅ together with the contaminants, possibly more concentrated phosphorus purifications. The separated solvent acid from technical, according to the wet process extract was obtained by extraction with 65 phosphoric acid obtained to avoid evaporation heated under pressure to 36 ° C, with the separation of an organic solvent, thereby of the extracted P ₂ O _{5 characterized} as purified phosphoric acid that the phosphoric acid took place. at about -5 to + 80 ° C with such an ester, Ketone, glycol ether or ether is extracted, which has a negative temperature gradient with regard to the solubility of phosphoric acid, the extract phase is separated from the aqueous phase in the above-mentioned temperature range and the separated extract phase, optionally with the addition of a small amount of water or pure phosphoric acid, to about 2 to 100 ^° C. , but not heated above the boiling point of the extractant. 2. The method according to claim 1, characterized in that the solvent is di-n-butyl ether, Di-propyl ether, n-butyl ether, cyclohexanone, butyl acetate, Ethyl ether, diethylene glycol dibutyl ether, diisopropyl ether, isopropyl n-butyl ether, din amyl ether and diisoamyl ether is used. 3. The method according to claim 2, characterized in that an ester or as a solvent Ether is used, which contains a total of 2 to 15 carbon atoms. 009547/403