Method of production of diammonium phosphate

FIELD: agriculture; production of mineral fertilizers.

SUBSTANCE: the invention is pertaining to production of ammonium phosphates, in particular, diammonium phosphate widely used in agriculture as mineral fertilizers. The method includes neutralization of phosphoric acid by ammonia at an increased pressure, a stirring action of the produced mixture in a static mixer with its subsequent granulation and drying of the product. Neutralization is conducted in two stages: on the first of which feed 8 - 85 % of ammonia from total amount and the process is conducted under the pressure of 3.5 - 8.0 atm, and on the second stage feed the remained amount of ammonia and reduce pressure to 1.5 - 3.0 atm. At that the stirring action is carried on simultaneously with a treatment of the mixture with ultrasound with a pulse power from 100 up to 1000 W. Before granulation additionally reduce the pressure by 0.5 - 0.8 atm as compared with the pressure of the second stage of neutralization. Ultrasonic treatment additionally conduct and on the first stage of neutralization. The technical result is production of a homogenous product of improved quality, decreased power inputs and losses of ammonia in the general process.

EFFECT: the invention ensures production of a homogenous product of improved quality, decreased power inputs and losses of ammonia in the general process.

2 cl, 3 ex

 

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

A known method of producing ammonium phosphates, including DAP, 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, CL 05 In 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, including DAP (the molar ratio of NH3: H3PO4=1,6-1,8), stated in U.S. patent No. 4313918, CL 01 In 25/28, 1979, including the neutralization of phosphoric acid with ammonia at elevated pressure, the mixture in the static mixer and the 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. Mix on transport trubor the water is directed to homogenization in a static mixer and then if necessary, the product granularit and dried.

The disadvantage of this method is the low efficiency of the process is 8-10 t/h (determined on the basis of the cost of ammonia), increased energy consumption, due to high recycling ammonia, reaching 17% of the total flow rate of 12.5% when receiving pulp with a molar ratio of NH3:H3PO4=1.5 and additional emissions from ammoniator-granulator - 5% by Domenicali charge to the molar relationship=1,8), and the driving node of the statistical mixture of products of neutralization, resulting in the necessity of steaming equipment and disturbance of the smooth operation.

The task of the developed method was the creation of a technologically advanced, well-regulated process, increase its productivity with homogeneous product of improved quality while reducing energy consumption.

The problem is solved in the proposed method of producing DAP, 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% of the ammonia from the total amount and the process is conducted at a pressure of 3.5 to 8 MPa, and the second stage serves the remaining amount of ammonia and snihurivka 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 compared to the pressure of the second stage of neutralization. Perhaps the ultrasonic treatment is additionally performed on the first stage neutralization.

Under the proposed method the flow of ammonia are in two streams, thereby avoiding the leakage of ammonia at the stage of neutralization. In addition, when the separation of fluxes of ammonia decreases the pressure in the supply lines of ammonia as the load increases. So, by way of a prototype back pressure in the supply lines of ammonia by increasing the load increases to 8-10 MPa. Percentage distribution of ammonia caused by the hydraulic process, as well as physico-chemical properties of the resulting pulp. Almost DAF get on stage neutralization unlike the prototype method, where DAF get on the granulation phase. Getting DAP at the stage of granulation is not possible to obtain homogeneous composition, as it is determined by the diffusion processes and the nature of the distribution of the pulp and ammonia. The method involves the reduction of pressure in the second stage of neutralization, which leads to a decrease in the rate of flow of products of neutralization, is a longitudinal mixing (effect of"slip"), is averaged composition, improve the conditions of granulation and, of course, increases the yield of uniform product and increased performance.

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 as it may be the destruction of the 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 is adaptable and reliable.

The method is illustrated by the following examples.

Example 1.

In a tubular reactor serves 47,045 tonnes of phosphoric acid (concentration of P2O5- 44%) and mixed with 8,025 t (85% of the total) ammonia at a pressure of 3.5 MPa. The mixture is then sent to the second stage of neutralization, which also impose 1,417 tons (15% of the total) ammonia. When applying for the second stage of neutralization pressure is reduced to 1.4 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:H3RHO4in the products of neutralization in the first stage neutralization is equal to 1.40, and the second stage is 1.70. 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 to 10.7% (or - 1,012 t) from the input to the process, reducing dust recycling - 40% (37 g/m3to 22 g/m3output - 45 t DAP brand: 15,42-46,0, the finished product fractions 2-5 mm - 85% (after BGS).

Example 2.

In a tubular reactor serves 47,045 tonnes of phosphoric acid (concentration of P2About5- 44%)and mixed with 7,803 ammonia (82,5% of the total) at a pressure of 5.0 MPa. The mixture is then sent to the second stage of neutralization, which also impose 1,656 tons (17.5% of total) ammonia. When applying for the second stage of neutralization 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 NH3:H3RHO4in the products of neutralization in the first stage neutralization supported=1.43 and in the second stage =1,75. 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 in our proposed method, and 9.0% (or 0,784 t) from the input to the process, reducing dust recycling - 50% (from 37 g/m3to 18.5 g/m3output - 45 t DAP brand: 18,1-46, the finished product fractions 2-5 mm - 90% after BGS).

Example 3.

In a tubular reactor serves 47,045 tonnes of phosphoric acid (concentration of P2About5- 44%) and mixed with 7,926 t ammonia (80% of the total) at a pressure of 8.0 MPa. The resulting mixture was then stirred blade static mixer, the blades of which I have are the emitters of ultrasonic vibrations with capacity pulse N the acoustic.=1000 watts. The obtained homogeneous mixture of products of neutralization and steam (T=130° (C) is reduced to a pressure of 3.0 MPa and is directed to the second stage of neutralization, which serves the remaining number - 1,982 tons of ammonia (20% of the total). The resulting mixture was again 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:H3PO4in the products of neutralization in the first stage neutralization supported=1,50, and the second stage=1,85. 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 is 8% (or 0,734 t) from the input to the process, reducing dust recycling - 30% (from 25 g/m3to 17.5 g/m3output - 45 t DAP brand 18,2-46,0, the finished product fractions 2-5 mm - 92% (after BGS).

1. The method of producing DAP, including the neutralization of phosphoric acid with ammonia at elevated pressure, the mixture in the static mixer and the subsequent granulation and drying of the product, characterized in that the neutralization ve is ut in two stages, the first of which serves 80-85% of the ammonia from the total amount and the process is conducted at a pressure of 3.5 to 8.0 MPa, and at a second stage the remaining amount of ammonia 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, the pre-processing stage further reduces the pressure by 0.5-0.8 MPa compared with the pressure in the second stage of neutralization.

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



 

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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.

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