A method of obtaining a solution of ammonium phosphate

 

(57) Abstract:

Usage: as a phosphorus-containing component is completely water-soluble nitrogen-phosphorus-or nitrogen-phosphorus-potassium fertilizers. Essence: the map is treated with water, acidified with nitric acid solution, which is used as the solution containing calcium nitrate and nitric acid mass ratio 20-3:1. The consumption of nitric acid-based solution to support the rate of 0.5-2.5 g of 100% nitric acid and 6.5-10 g of calcium nitrate per 100 g of monoammonium phosphate. Prepare a solution of the tetrahydrate of the calcium nitrate, a by-product of the production of complex fertilizers, with a concentration of 32-38% calcium nitrate, the neutralization is carried out until a pH of 5-6 and separate the desired product from the precipitate of impurities. The technical result consists in a high efficiency purification of the target product from the impurities of iron, aluminum and fluorine, increasing the filterability of the precipitate of impurities is more than 4 times; simplification of the industrial implementation of the method. 3 C.p. f-crystals.

The invention relates to the technology of mineral fertilizers, namely, to obtain from the map solution of ammonium phosphate, which can be used as the phosphorus-containing component is fully vaporware ammonium phosphate by dissolving ammonium sulphate in water, followed by neutralization with ammonia and separating the insoluble precipitate by filtration [ Technology of ammonium nitrate. Ed. by C. M. Olevsky. M.: Chemistry, 1978, S. 164] .

The disadvantage of this method lies in the extremely low filterability of sludge.

Closest to the claimed combination of essential features and the achieved result is a method of obtaining a solution of ammonium phosphate, including the processing of ammophos water followed by acidification with nitric acid, neutralization and separation of the target product from the precipitate of impurities [ed. St. USSR №925921, IPC 05 7/00, publ. 07.05.82].

The disadvantage of this method is low filterability of sludge impurities (0.89 m3/m2h excluding auxiliary operations), which complicates its industrial implementation.

The technical problem solved by the claimed method, is to improve filetreemodel precipitate impurities.

The technical problem is solved in that in the method of obtaining a solution of ammonium phosphate, including the processing of ammophos water followed by acidification with nitric acid solution, neutralization and separation of the target product from the precipitate of impurities, according to the invention as a nitric acid solution using a solution containing calcium nitrate and nitric acid mass ratio 20-3:1. is the calcium in 100 grams of monoammonium phosphate. A solution is prepared from nitrate tetrahydrate calcium, a by-product of the production of complex fertilizers, with a concentration of 32-38% calcium nitrate, and the neutralization is carried out to a pH of 5-6.

Example 1

Experiments are performed with a sample map with the following composition, wt.%: P2O551,6; Sa 0,4; P 0,4; Al 0,4; P 1,8.

100 g of monoammonium phosphate is treated with 150 g of water at a temperature of 60 C for 30 minutes To an aqueous suspension add 25 g of nitric acid solution containing 35% calcium nitrate and 6.4% nitric acid, prepared from crystals tetrahydrate calcium nitrate, a by-product ammonium nitrate.

The mass ratio of calcium nitrate : nitric acid in the nitric acid solution of 5.5:1.

The consumption of nitric acid solution of 1.6 g of 100% nitric acid and 8.75 g of calcium nitrate per 100 g of the map.

The suspension is stirred for 30 min, then neutralized 45 g of an aqueous solution of ammonia with a concentration of 11%. The neutralization is carried out, blending into the reactor with a stirrer at the same time acidified suspension and a solution of ammonia for 20 min, followed by exposure with stirring for 20 minutes the pH of the neutralized suspension of 5.2. In an industrial environment neutral is Renova filtrating) c surface filtration 38 cm2. You get a 275 g of filtrate is the desired product and 45 g of wet sediment contaminants. The duration of the filter 60 C. Specific performance filtering of 4.3 t/m2h the filtrate without regard to subsidiary operations, which is more than 4 times higher than in the prototype.

The composition of the target product, wt.%: P2ABOUT515,3; Sa 0,12; Fe 0,002; Al 0,003; F 0,02; ammonium nitrate 3,5.

The degree of purification of a solution of ammonium phosphate with respect to the original map, Rel.%:

F 96

For Fe 98

By Al 97,5

The density of a solution of 1.14 g/cm3.

The resulting solution of ammonium phosphate of the above composition may be used as the phosphate component in the production of ammonium nitrate with phosphate additive, or upon receipt of a fully water-soluble nitrogen phosphate or nitrogen-phosphate-potash fertilizer.

The wet precipitate impurities contains 64% of the liquid phase, i.e. a solution of ammonium phosphate, and may be disposed of as a phosphate-containing reagent in the production of standard compound fertilizer type nitroammophos or ammonium nitrate. If you cannot recycling the residue washed with water, adding a wash solution to the target product.

- nitric-acid solution prepared by dissolving synthetic chalk in technical nitric acid;

- mass ratio of calcium nitrate and nitric acid in the nitric acid solution change within 20-3:1;

- concentration nitric acid solution of nitrate of calcium is maintained within the range of 32-38 wt.%;

- the consumption of nitric acid solution change in the range of 0.5-2.5 g of 100% nitric acid and 6.5-10 g of calcium nitrate per 100 g of monoammonium phosphate;

- the pH of the slurry after neutralization support within 5-6.

In all experiments provided the required quality of the target product and the high specific capacity of filtration.

From the presented data shows that the inventive method provides high efficiency purification of the target product from the impurities of iron, aluminum and fluorine and allows, in comparison with the prototype, to increase the filterability of the precipitate of impurities is more than 4 times and thereby greatly simplify the implementation of industrial way.

The positive effect of obespecivaet mass ratio 20-3:1. Entered from nitric acid solution of nitric acid dissolves small, most poorly filterable particles precipitate impurities present in the original map, and during the subsequent neutralization in the presence of introduced calcium nitrate formed a well-filterable residue. The claimed interval mass ratio of calcium nitrate and nitric acid is optimal for the given problem. When exceeding the upper limit unduly increasing proportion of phosphates, resulting in precipitate impurities in the form of calcium phosphates, and when exceeding the lower limit increases the flow of fresh nitric acid entering the preparation of nitric acid solution.

The optimum flow rate of nitric acid solution should be maintained at the rate of 0.5-2.5 g of 100% nitric acid and 6.5-10 g of calcium nitrate per 100 g of monoammonium phosphate. At a lower flow rate is reduced filterability of the precipitate impurities, the increase in consumption is impractical for economic reasons.

In industrial conditions, the nitric acid solution if possible cooperation with the production of complex fertilizers on nitrogen-acid technology, it is advisable to cook the tetrahydrate of the calcium nitrate, a by-product, specify the optimal ratio of calcium nitrate : nitric acid provided by the technology selection tetrahydrate calcium nitrate, namely its composition. This solution is the source for processing into synthetic chalk. Part of this solution can be used as a nitric acid solution.

The optimum range of pH by neutralizing at 5-6; at pH less than 5 increases the residual calcium content in the target product that is technologically impractical; at pH greater than 6 is reduced filterability of sludge and there are losses of ammonia for neutralization.

The inventive method, as well as the prototype, provides for the presence of the target product ammonium nitrate. However, this is not a disadvantage of this method, since the ammonium nitrate with ammonium phosphate will be part of the nitrogen-phosphorus-or nitrogen-phosphorus-potassium fertilizers.

1. A method of obtaining a solution of ammonium phosphate, including the processing of ammophos water followed by acidification with nitric acid solution, neutralization and separation of the target product from the precipitate of impurities, characterized in that as a nitric acid solution using a solution containing calcium nitrate and nitric acid mass ratio 20-3:1.

2. The method according to p. 1, characterized in that the flow of nitric acid solution to support from Risa fact, what nitric-acid solution prepared from nitrate tetrahydrate calcium, a by-product of the production of complex fertilizers, with a concentration of 32-38% calcium nitrate.

4. The method according to p. 1 or 2, characterized in that the neutralization is carried out to a pH of 5-6.

 

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FIELD: industrial inorganic synthesis.

SUBSTANCE: invention relates to production of ammonium phosphates, notably ammophos, widely used as mineral fertilizers. Process involves neutralization of phosphoric acid with ammonia at elevated pressure, stirring of resulting mixture in static mixer, and subsequent granulation and drying of product. According to invention, neutralization is carried out in two steps: in the first step, 80-85% H3PO4 of its total amount is added and process is carried out at gauge pressure 3.5-8 atm and, in the second step, the rest of acid is added and pressure is lowered to pressure 1.5-3.0 atm. Stirring is effected simultaneously with ultrasonic treatment of the mixture with pulse power from 100 to 1000 W and, before granulation, pressure is lowered by 0.5-0.8 atm relative to pressure of the second neutralization step. Ultrasonic treatment can likewise be employed in the first neutralization step.

EFFECT: improved process control to form uniform improved-quality product and reduced ammonia emission.

2 cl, 3 ex

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