DE587589C - Process for the production of low-water ammonium magnesium phosphates - Google Patents

Description

Process for the preparation of low-water ammonium magnesium phosphates Es it is known that phosphoric acid with magnesium salts is obtained from phosphoric acid or phosphate solutions and to precipitate ammonia solutions in excess as ammonium magnesium phosphate, wherein The end product is always the Mg N H 4 P O 4 # 6 H2 O. The salt thus obtained is floury and voluminous. By drying you can remove 5 moles of water from this salt, but this does not happen without loss of ammonia. It remains - the very obtained fine floury form of this salt.

Also a salt became Mg N H4 P 04 # Hz O by boiling like molecules Mg S 04 and (N H4), H P 04 by reaction of the Mgs (P 04) formed as an intermediate, obtain.

In the present process it has now surprisingly been found that when using gaseous ammonia instead of a solution of the same Solutions of phosphoric acid or alkali phosphates and magnesium salts instead of the hexahydrate lower water ammonium magnesium phosphates. can produce which for practical Use, e.g. B. as a fertilizer, due to their physical properties are suitable.

When working with gaseous ammonia, for example, it separates in the cold a salt with 3 mol, in the heat one salt with 1 mol of water. The so obtained In contrast to salt, products are with. 6 moles of water that when using from aqueous ammonia solutions both in the cold and in the heat, coarse crystalline. These salts can be dried easily without loss of ammonia.

The resulting filtrates can be used to recover the ammonia added lime and heated.

There is no need to add lime to decompose the ammonia salts, if magnesium oxide or hydroxide is used instead of the magnesium salts. In in this case the ammonia can only be recovered by heating, or that Driving out the ammonia can be avoided by - the filtrate for a new one Approach can be used.

All processes according to which so far ammonium magnesium phosphate for Technical purposes are related to the manufacture of the analytical Chemistry known salt Mg N H4 P 04 # 6 H, O and not according to the present -Invention to be obtained salts with 3 or 1 mol of water of crystallization. Even the cases in which ammonia was already used in gaseous form, did not lead to any result, because the ammonia gas mixed with large amounts of water vapor was used so that the effect of exposure to an ammonia solution. came right away and therefore only. the known Product obtained with 6 moles of water of crystallization could be. Also recently it has been suggested to mix ammonium magnesium phosphate with either aqueous or gaseous To precipitate ammonia. From this equation, however, it follows that in this too In case the knowledge was missing that if the conditions of the present Invention, the low-water salts are obtained, their preparation and use requires technical progress.

The magnesium ammonium phosphate obtained in the usual precipitation contains 6 mol of crystal water corresponding to .4.4% H20, apart from the adhering Water of the precipitation liquid. However, this high water content influences the content of plant nutrients in these salts, which are very suitable as fertilizers. When trying to determine the percentage of the fertilizer components by driving out the water To increase it, one must either use very low temperatures, which means long Drying times are conditional, or with increasing temperature also with increasing losses of ammonia in the product obtained. This also falls in the usual way produced salt very finely crystalline in a flour-like form, which in itself already is unsuitable for use as a fertilizer. As a result of the large surface Large amounts of mother liquor adhere to this fine form separate salt, a circumstance which makes the already very difficult drying process even more difficult.

In contrast, the salts obtained by the new process contain in itself a lot less water and also fall in a much coarser form which means that the salt obtained is much less adherent mother liquor contains. This makes drying easier and the percentage of nutrients considerably higher increased and the suitability as a fertilizer and compound fertilizer component increased.

Embodiments i. In a solution of 29 kg of conc. Phosphoric acid, . 59 kg of MgCl2 6 H20 and 20 kg of water are passed in gaseous ammonia until saturation. 55 kg of salt are obtained with 370 %, Pz 05, 2% MgO and 9 % N H3, corresponding to 100% MgNH4 PO4-3 H2 O.

.: 2. In. 50 kg W4sset are slurried i2 kg gg0, and with 29 kg conc. H3 P 04 offset. Gaseous ammonia is passed through this mixture until it is saturated. 55 kg of salt are obtained with 37 % (0 P205, 21 % MgO and g 'I, NH, corresponding to 100% MgNH, PO4-3H20.

3.z9 kg conc. H3 P 0, are mixed with 12 kg of MgO to a paste and ammonia is introduced into this paste. This gives 55k dry salt with 3701o P205, 2104 MgO and 911 /, N H "corresponding to 10010 i14gNH, PO4-3H20.

4. 33.5 kg of Mg C12 6H20 are dissolved in 32.5 kg of water and raised to go ° with the addition of 14.7 lcg of conc. H3 P 04 heated. Ammonia gas is passed into this mixture, which is heated to go °. It is filtered off and washed with go ° hot water. 25 kg of salt with 45% P205, 25.5 010 Mg 0 and 10.8 0! 0 \, Ha corresponding to 99 Mg NH, sP0, -iH.0 are obtained.

When using alkali phosphate solutions one naturally obtains the same Products, as can be seen from the following example: 5. 4.z, 2 kg magnesium nitrate [Mg (\ z O3) 2 -6 1-I201 were dissolved in 35 kg of water, this solution was heated to go ° and this added 28.7 kg of dipotassium phosphate. Thereupon was in the still hot solution Ammonia initiated. After filtration, 25.6 kg of Mg N H4 P O4 -H20 and one aqueous solution obtained, which after driving off the ammonia and cooling i8.5 kg of potassium nitrate and 59 kg of a mother liquor containing 24 weight percent potassium nitrate delivered.

Claims (3)

I'ATL: NTANSi'RÜCHL: i. Process for the preparation of ammonium magnesium phosphate by the action of ammonia on solutions of phosphoric acid or alkali phosphates and magnesium salts, characterized in that for the purpose of obtaining the water-poor Ammonium magnesium phosphates Mg N H4 P 04 - 3 H2 O and Mg N H4 P 04 -H20 these salts by gaseous ammonia at normal or elevated temperature in the above Brings solutions to precipitate and the resulting precipitate is separated from the solution. . 2. The method according to claim i, characterized in that instead of the magnesium salts Find magnesium oxide or hydroxide use. 3. The method according to claim i and 2, characterized in that phosphoric acid and magnesium salt or oxide or hydroxide can be used in molecular amounts.