Ammonium phosphate production process

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

 

The invention relates to the production of ammonium phosphates (such as monoammonium phosphate (map), widely used in agriculture as fertilizers.

A known method of producing ammonium phosphates, including the neutralization of phosphoric acid with gaseous and/or liquid ammonia in a tubular reactor, at a pressure of 3-6 MPa, stirring the mixture in the transport pipeline and feeding the resulting slurry granulation and drying of the product (AS the USSR №1495330, 05, 7/00, 1989).

The disadvantage of this method is that the pulp entering the granulation of the transport pipeline, has a rather heterogeneous composition, which affects the granulation conditions and the quality of the finished product.

The closest to describing the technical essence and the achieved result is another well-known method of producing ammonium phosphates, stated in U.S. patent No. 4133918. CL 01 In 25/28, 1979, including the neutralization of phosphoric acid with ammonia at elevated pressure, the mixture in the static mixer and subsequent granulation and drying of the product. In this way serves to neutralize all the acid and ammonia at a sufficiently high pressure up to 8 MPa. The mixture transport pipe is directed to homogenization in a static mixer and then, if necessary, the product the edge of irout and dried.

The disadvantage of this method is its adaptability to manufacture due to frequent driving equipment at the stage of mixing the pulp (homogenization). In addition, the flow of the reagents in the head process in full due to the high viscosity of the resulting slurry leads to increased energy consumption for its transportation. The process of granulation is difficult to regulate, which affects the uniformity and quality of product.

The task of the developed method was the creation of a technologically advanced, well-regulated process of obtaining a homogeneous product of improved quality while reducing emissions of ammonia.

The problem is solved in the proposed method of producing ammonium phosphates, including the neutralization of phosphoric acid with ammonia at elevated pressure, the mixture in the static mixer and subsequent granulation and drying of the product. In the proposed method neutralization lead in two stages, the first of which serves 80-85% NCRHO4of the total number and the process is conducted at a pressure of 3.5 to 8 MPa, and the second stage serves the remaining amount of acid and reduce the pressure to 1.5 to 3.0 MPa, and mixing are in a static mixer with the processing of pulp ultrasound with a power pulse from 100 to 1000 watts, and before pelleting pressure reduce by 0.5-0.8 MPa comparedwith the pressure of the second stage of neutralization. Perhaps the ultrasonic treatment is additionally performed on the first stage neutralization.

In the proposed method, the first stage of neutralization in the high pressure region serves part of phosphoric acid. This significantly reduces the leakage of ammonia, because the process is in terms of preammonization slurry, the viscosity of which is much smaller. Also lead to a reduced diffusion resistance reaction of neutralization and energy consumption, which must be spent on movement of the pulp. The number given on the 1st stage of phosphoric acid selected from the most appropriate viscosity of the slurry and the required molar relationship, and the high pressure at this stage allows you to more fully absorb the ammonia. The first stage neutralization takes place in the system of gas-liquid. The second stage serves the remaining phosphoric acid and reduce the pressure. On the 11th stage of the process of deoxidation of the pulp, leading to low values of the viscosity of the pulp due to the hysteresis effect of the viscosity of the pulp by neutralizing phosphoric acid pereaminirovanii pulp. This mechanism allows to reduce the high pressure, since the process is in the system liquid-liquid. However, lowering it below 1.5 MPa leads to loss of transportable properties of the pulp, and raising it above a 3.0 MPa leads to increased saving the cost.

This method involves the use of ultrasound primarily at the stage of mixing in a static mixer (homogenization of the pulp). Sonication provides a nearly ideal mixing, completely eliminates the clogging of the mixer. This proskokova concentration of ammonia is approaching equilibrium. The lower limit of the power of the pulse is caused by the process of self-cleaning of the mixer, and the increasing power of the pulse is above the upper limit is impractical because it may be destroyed mixer.

Before pelleting pressure reduce that provides a more uniform distribution of the slurry on the particle reture and, of course, leads to an increase in yield of marketable fraction regulated by a specific size of the granules, as well as to reduce returnest process.

All the process parameters can significantly reduce ammonia losses in the overall process (stage neutralization and at the stage of granulation). The method allows to obtain a stable product as the composition and the chemical composition and the process adaptable and reliable.

The method is illustrated by the following examples.

Example 1

In a tubular reactor serves to 41.6 tonnes of phosphoric acid with a concentration of P2About5- 40% (80% of the total) and mix with 6,120 tons of ammonia at a pressure of 3.5 MPa. the ATEM mixture is sent to the second stage of neutralization, also enter 10.4 tons (20% of the total) phosphoric acid. When applying for the second stage of neutralization reduced pressure to 1.5 MPa. Previously obtained a mixture of products of neutralization in the second stage mix blade static mixer, the blades of which are emitters of ultrasonic vibrations with capacity pulse Nthe acoustic.=100 watts. When this molar ratio NH3:H2RHO4in the products of neutralization in the first stage neutralization supported =1,25, and the second stage =1,17. The obtained homogeneous mixture of products of neutralization and steam (T=125° (C) is reduced to a pressure of 1.0 MPa (pressure drop of 0.5 MPa) to obtain a homogeneous vapor-liquid emulsion (T=120°C), which is then subjected to granulation and drying in the apparatus of the BGS. Recycling of ammonia by our proposed method is 5% (306 kg) from the input to the process, reducing dust recycling 40% (37 g/m3to 22 g/m3). Output - 40 t LFA, grade 12,0-52,0. Output of marketable fractions 2-5 mm - 85%, after BGS.

Example 2

In a tubular reactor serves 42.9 tonnes of phosphoric acid with a concentration of P2O5- 40% (82.5 per cent of the total) and mix with 5,543 tons of ammonia at a pressure of 5.0 MPa. The mixture is then sent to the second stage of neutralization, which also introduced to 9.1 tonnes (17.5% of total) phosphoric acid and sinks. When applying for the second stage it is ralizatsii pressure is reduced to 2.25 MPa. Previously obtained a mixture of products of neutralization in the second stage mix blade static mixer, the blades of which are emitters of ultrasonic vibrations with capacity pulse Nthe acoustic.=500 watts. When this molar ratio NH2:H2RHO4in the products of neutralization in the first stage neutralization supported =1,30, and the second stage =1,08. The obtained homogeneous mixture of products of neutralization and steam (T=125° (C) is reduced to a pressure of 1.55 MPa (reduced pressure 0.7 MPa) to obtain a homogeneous vapor-liquid emulsion (T=120°C), which is then subjected to granulation and drying in the apparatus of the BGS. Recycling of ammonia by our proposed method to 3.0% (161,4 kg), injected into the process, reducing dust recycling 50% (from 37 g/m3to 18.5 g/m3). Output - 40 t LFA, brand 11,1-52,0. Output of marketable fraction fraction 2-5 mm - 90%after BGS.

Example 3

In a tubular reactor serves 44,2 tons of phosphoric acid with a concentration of P2O5- 40% (85.0 per cent of the total) and mix with 5,337 tons of ammonia at a pressure of 8.0 MPa. The resulting mixture of products of neutralization mix blade static mixer, the blades of which are emitters of ultrasonic vibrations with capacity pulse Nthe acoustic.=1000 watts. The obtained homogeneous mixture of products of neutralization and steam (T=130° (C) is reduced to d the effect of 3.0 MPa and is directed to the second stage of neutralization, serving the remaining amount of phosphoric acid - 7.8 tonnes (15% of the total) of phosphoric acid with a concentration of 40% R2About5. The mixture of products of neutralization in the second stage also stirred blade static mixer, the blades of which are emitters of ultrasonic vibrations with capacity pulse Nthe acoustic.=1000 watts. When this molar ratio NH3:H2RHO4in the products of neutralization in the first stage neutralization supported =1,45, and the second stage =1,05. The obtained homogeneous mixture of products of neutralization and steam (T=125° (C) is reduced to a pressure of 2.2 MPa (reduced pressure 0.8 MPa) to obtain a homogeneous vapor-liquid emulsion (T=120°C), which is then subjected to granulation and drying in the apparatus of the BGS. Recycling of ammonia by our proposed method was 2.0% (104,7 kg) from the input to the process, reducing dust recycling 55% (37 g/m3to 18.5 g/m3). Output - 40 t LFA brand 10,8-52,0. Output of marketable fractions 2-5 mm - 93%, after BGS.

1. A method of producing ammonium phosphates, including the neutralization of phosphoric acid with ammonia at elevated pressure, the mixture in the static mixer and subsequent granulation and drying of the product, characterized in that the neutralization lead in two stages, the first of which serves 80-85% NCRHO4of the total number of the quality and the process is conducted at a pressure of 3.5 to 8 MPa, and in the second stage serves the remaining amount of acid and reduce the pressure to 1.5 to 3.0 MPa, and mixing are simultaneously processing the mixture by ultrasound with a power pulse from 100 to 1000 watts and before pelleting pressure reduce by 0.5-0.8 MPa compared to the pressure of the second stage of neutralization.

2. The method according to claims 1 and 2, characterized in that the ultrasonic treatment is additionally carried out and in the first stage neutralization.



 

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FIELD: mineral fertilizers.

SUBSTANCE: method of manufacturing complex granulated mineral fertilizer consists in mixing ammonium nitrate and monoammonium phosphate-containing phosphate additive. The latter is granulated mineral double fertilizer simultaneously containing ammonium nitrate, monoammonium phosphate, and calcium phosphates at total content of digestible phosphorus 13÷21% (calculated as P2O5). Additive is introduced by way of melting it followed by admixing resulting melt to molten ammonium nitrate. Phosphate additive utilizes nitroammophosphate at weight ratio N:P2O5 equal to 23:21 or 26:13 and phosphate additive melt is preliminarily completely or partly separated from infusible solid phase, after which phosphate additive is introduced in amount 2-6% (as P2O5) of the weight of final product. Granulated mineral fertilizer contains ammonium nitrate and monoammonium phosphate with total content of digestible P2O5 within a range of 2÷6%, in which case 0.4÷28.6% of P2O5 is present in the form of dicalcium phosphate.

EFFECT: reduced corrosiveness of process medium, increased nutritive value of fertilizer having physicochemical properties competitive with those of known fertilizers, and simplified manufacturing technology.

5 cl, 1 tbl, 5 ex

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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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