CS231123B1 - Processing method of di-hydrogen ammonium phosphate with quality of fodder - Google Patents

Abstract

The invention discloses manufacturing technology ammonium dihydrogen phosphate NH4HgPO4 low in fluorine and, arsenic refining of fertilizer amophos, T.E. impure mixtures of salts prevailing NH4HgPO4. Amophos boils in water and solution, prooxidize and form arsenate with the addition of oily salts coprecipate with basic phosphate ferric. Eluor in leachate with addition aluminum salts are converted to hexafluoroaluminate, which is a sodium salt or a hydroxide precipitates as cryolite. Clear filtrate is adjusted to a pH of about 4.4, concentrated and concentrated to crystallize the NH4 HgPO3 salt. The mother liquor can be recirculated.

Description

POKORNÁ ZDENKA, PARDUBICE

Process for producing feed grade ammonium dihydrogen phosphate

The invention describes a technology for the production of feed ammonium dihydrogen phosphate NH 4 HgPO 4 with a low fluorine and arsenic content by refining fertilizer amophos, i.e. impure mixtures of salts with a predominant amount of NH4HgPO4. Amophos is boiled in water and reflux solution, oxidized and the arsenate formed is coprecipated with basic ferric phosphate by addition of the iron salt. The eluate in the leachate is converted to hexafluoroaluminate by addition of an aluminum salt, which precipitates as cryolite with sodium salt or hydroxide. The clear filtrate is adjusted to a pH of about 4.4, concentrated and brought to crystallization of the NH4HgPO4 salt. The mother liquor may be recirculated.

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The present invention relates to a process for the production of crystalline ammonium dihydrogen phosphate which, by its quality, satisfies the mineral nutritional needs of animals or microorganisms in fermentation.

For feed phosphates, the fluorine, arsenic and lead contents, the limit values of which are standardized, are of decisive importance; in the CSSR, a maximum concentration of 0.1% fluorine, 7 ppm arsenic and 18 ppm lead is assumed.

Feed phosphates are prepared mainly by neutralization of thermal phosphoric acid, which is always practically free of fluorine and lead, but not arsenic. The high cost of this acid is due to the extra energy consumption of electric furnaces in reducing natural phosphates; another unfavorable price trend to be expected,

Neutralization of the more affordable extraction phosphoric acid with ammonia leads to an impure mixture consisting predominantly of ammonium dihydrogen phosphate. It is used under the technical name arnofos as fertilizers or as components of mixed and combined fertilizers. In international trade, amofos is a tariff advantageous form for the long-distance transport of phosphorus pentoxide as a component of fertilizers. Amofos is unsuitable for feed purposes, or? usually contains approximately 3% fluorine and 100 ppm arsenic,

By refining methods based on recrystallization and cleration of leaches, the fluorine concentration in crystalline ammonium dihydrogen phosphate can be effectively reduced, but not significantly suppressed by arsenic salt contamination, which is probably due to isomorphism of arsenates and phosphates.

The above disadvantages are overcome by the process for producing dihydrogenphospho2

The subject of the invention is the treatment of technical ammonium phosphate of fertilizer quality with water and / or a mother liquor from a previous operation of the same production, in an amount of 100 to 500% by weight. %, based on the weight of the starting raw material, at a temperature of from 60 ° C to the boiling point, the resulting suspension or liquid phase of the suspension is optionally oxidized with an oxidizing agent such as chlorine, alkaline hypochlorite or hydrogen peroxide in an amount of 0.03 to 5% optionally, an iron (III) salt in an amount of from 0.03% iron to 5% by weight of iron relative to the starting material feedstock, preferably an aqueous ferric chloride solution, is added thereto, followed by the addition of a salt aluminum in quantity 15 to 150% by weight of aluminum relative to the mass of fluorine in the feed solution, preferably a solid aluminum sulphate or an aqueous solution, then add a sodium compound, preferably a phosphate- and / or sulphate and / or sodium hydroxide, whereupon the pH of the suspension is adjusted! with an acid or base to a pH value of 4.4-2, the slurry is separated, the filtrate is optionally concentrated and brought to crystallization.

The principle of the invention is that the technical mixture of ammonium phosphates and other salts prepared by the above-mentioned neutralization process of phosphoric acid extraction is leached with hot or boiling water or diluted back solution after crystallization of the previously prepared product. is given by the solubility of the salt mixture in hot water; 100 to 500% by weight of the dissolving liquid, based on the weight of the raw material to be processed · The resulting slurry contains insoluble sludge, mainly phosphates and fluorides or fluorosilicates of caustic earths »The amount of this sludge depends exclusively on the type of amophos being processed. , wash with hot water and refine the resulting solution · Refining processes, as described below, also take place in a slurry containing the primary sludge; however, the reaction of the components in the thick suspension may not be complete. It is also possible to oxidise before filtration.

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The resulting hot liquor, containing dissolved feedstocks and remaining sludge, is oxidized in a conventional manner, preferably with chlorine gas or sodium hypochlorite solution or hydrogen peroxide, so as to convert the iron and arsenic compounds into ferric and arsenic salts. The iron (III) salt, preferably an aqueous solution of 30% by weight, is slowly added to the prooxide solution.

FeClg, used in water supply. The amount of ferric salt required depends on the contamination of the raw material; it is desirable to apply 0.03 to 1% by weight of said solution based on the weight of the amofos charge; an excess of precipitant causes losses of the phosphorus component.

The ferric salt hydrolyzes in the slightly acidic amophosic slurry to form ferric hydroxide, which absorbs arsenic compounds to form hardly definable basic iron arsenates.

Dearsenisation can also be carried out without prior oxidation; the efficiency of this refining then varies greatly depending on the type of raw material.

At a pH ^of 4.4 (all values indicated are mean values pH upon dilution of the liquid phase of the suspension with distilled water or after dissolution of the crystals, so that the measurement solution contained 1 to 2% by weight total salts), which corresponds to the solution of the salt NH ₄ H _{2 4} in water, even in less acidic solutions, the hydrolysis of fluorosilicates to form fluoride or fluorine complexes is virtually complete.

The elimination of fluorine is based on the formation of a slightly soluble salt of trisodium hexafluoroaluminate, known under the mineralogical name cryolite. It proceeds according to the summary reaction

Na ⁺ Al ³ * + 6 F * = Na ₃ Al _g (1)

The required amount of aluminum salt or a solution thereof, preferably aluminum sulphate, used in the water supply as a solution of about 8 wt.% AlgOg or as a solid with about 14 wt.

After the aluminum salt has been introduced into the leach of technical ammonium phosphates, the aluminum phosphate gel is first deposited, which gradually dissolves to form complex ions, in particular hexafluoroaluminate

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- 4 Α1Ρ0 ₄ + 6 F ~ * A1f | ”+ P0 ₄ (1)

Fluoride precipitation proceeds optimally when dosing the aluminum salt according to the stoichiometry of equation (1) with respect to the analytically determined fluorine content of the liquid phase of the amophosic slurry.

For self-precipitation of cryolite according to equation

AlFg + 3 Na + Na 2 AlFg (3) sodium ions are supplied as a suitable sodium salt, preferably hydrogen phosphate or sulfate, or as sodium hydroxide. The sodium ion dosage is determined by the fluorine content of the extract and the stoichiometry of equation (3); is precipitated by a theoretical amount of up to five times the excess sodium compound.

The pH of the suspension is adjusted to 4.4 * 2; failure to comply with this condition would lead to a deterioration in the yield and quality of the salt produced.

The treated suspension is filtered, the filtrate is concentrated in a known manner and, upon cooling, crystalline ammonium dihydrogen phosphate precipitates. The product is usually separated by centrifugation and washed. Shipped moist or dried. The mother liquor and the water after washing the crystal are preferably recirculated and used to further leach the feedstock after water addition.

Depending on the concentration ratios in the solution to be treated, some of the relatively low-soluble ammonium-cryiolite (NH4gAlFg) may be precipitated in addition to cryolite in the course of refining.

The manufacturing process is discontinuous for illustration. The production line can be modified as partially or completely continuous. Dearsenislation and defluorination operations are chemically independent The first or second refining process can be omitted if a fully purified product is not commercially required.

In order to illustrate the invention in more detail, examples are given (where percentages are by weight), but are not intended to be exhaustive or limited thereto.

Examples.

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1) A filtered, otherwise untreated aqueous amophosic liquor was collected at the diammonium hydrogen phosphate manufacturing plant in which 24.5 g F · 1 · 4 and 26 ppm As · were found.

Ke 1 300 ml of this solution was added constant stirring released 210 ml solution of Al ₂ concentration (S0 _{4) 3} = 0.65 mol. Γ Excluded yellowish-white precipitate, z cattle spread quickly letting. After 15 minutes, slowly pour 165 ml of solution with con by centration of NaOH * 5 mol. I ¹ . The resulting white suspension was filtered and washed with cold water. Drying white microcrystalline powder, that was analyzed. Iont Found Na 2 AlF 8 calculated weight% weight% F 56.0 54,30 AI 9.9 12.85 On 17.9 32.85 nh ₄ 12.1 - Total 95.9 100, -

3—

P0 ₄ response was slightly positive ·

2) The sample after 650 ml operational filtered araofosového liquor whose composition is described in Example 1 were boiled with the addition of ml of 30% HgOg then stirring přiléván solution at FEG (S0 _{4) 3} = 1 N · l ^"1 . After sedimentation of the precipitate, a clear solution was analyzed. Found

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Addition of Fe salt solution (ml): 0 5 10 20 60

Determined As (ppm): 26 12 5 6 4

3) At the same time as the filtered extract according to example 1, an unfiltered slurry was taken in the factory after the amofos expansion. 500 ml of this suspension was slightly acidified to pH > 4.6 with phosphoric acid, and cryolite was precipitated by introducing solutions in volume ratios as described in the exemplary embodiment. Ammophos and cryolite sludge separated by co-filtration. The filtrate was evaporated to approximately half volume. After cooling, ammonium dihydrogen phosphate crystallized. The crystals were aspirated, successively just twice dipped with cold water and aspirated again. An approximately 2% solution of crystals in distilled water appeared to be pH = 4.4 and contained

Claims (1)

SUBJECT OF THE INVENTION Process for preparing feed grade ammonium dihydrogen phosphate by purification of a feedstock, characterized in that the feedstock of fertilizer grade ammonium phosphate is treated with water and / or a mother liquor from a previous operation of the same production, in an amount of 100 to 500 wt. ° C to the boiling point, the resulting suspension or liquid phase of the suspension is optionally oxidized with an oxidizing agent such as chlorine, alkaline hypochlorite or hydrogen peroxide in an amount of 0.03 to 5% by weight of the active substance based on the weight of the starting technical feedstock optionally from 0.03% by weight of iron to 5% by weight of iron relative to the feedstock of the feedstock, preferably an aqueous solution of iron (III) chloride, is added thereto, followed by the addition of aluminum salt in an amount of 15 to 150% by weight The sodium compound, preferably phosphate and / or sodium sulphate and / or sodium hydroxide is then added, after which the pH of the suspension is adjusted to pH by acid or base. The slurry is separated, the filtrate is optionally concentrated and crystallized.