CS264747B1 - A method of producing a liquid multi-component fertilizer - Google Patents

Abstract

The solution relates to a method of producing a liquid multicomponent fertilizer by neutralizing trihydrogenphosphoric acid or solutions containing a phosphorus component with gaseous or liquid ammonia or ammonia water, while the heat released during neutralization is removed by adiabatic evaporation of part of the water from the obtained liquid fertilizer at an absolute pressure of 10 to 70 kPa, thereby maintaining the temperature of the liquid fertilizer at a value of 45 to 90 °C. The solution can be used in the chemical industry.

Description

The invention relates to a method of producing a liquid multicomponent fertilizer.

It is known that during the neutralization of the extractive trihydrogenphosphoric acid with ammonia, the impurities contained in the extractive phosphoric acid precipitate, especially the phosphates of Fe, Al, Mg, Ca in the form of a gel-like precipitate, precipitate. The amount and structure of the sludge thus precipitated depend on the course of the neutralization reaction itself, and the formation of a larger amount of this fraction, characterized by a structure causing its rapid sedimentation, creates significant difficulties in the handling, storage and application of these fertilizers.

Due to the reaction conditions of the neutralization reaction, currently known methods for preparing basic NP solutions can be divided into two main groups.

The first group includes processes in which the precipitated impurities are separated, obtaining a clear NP solution and the separated precipitate is used as a so-called sludge fertilizer, or is incorporated into solid fertilizers. For this purpose, the neutralization process is conducted in such a way as to obtain a precipitate with the highest filtration or sedimentation rate (US 3 264 087, Chemical Engineering Progress, vol. 58, No 9, September 1962, pp. 89-93).

The second group includes processes in which the precipitated impurities are not separated, so that a true NP suspension is obtained. These processes produce a product in which particle sedimentation is slow and the resulting homodisperse particles are so fine that they do not impair the fluidity and handling properties of the product (CS 202 154, 211 279, Agricultural and Food Chemistry, September-October 1961, 343-348).

Furthermore, there are known processes in which various stabilizing additives such as attapulgite, bentonite and kaolin (US 3,179,496, 3,160,495 (, fluorine-containing compounds (CS 200,671, US 3,861,897), or phosphorus-containing compounds in condensed form (US 3,057,711) are added to the finished NP solution.

The above production processes, although they allow the preparation of stable NP fertilizers, have a number of disadvantages:

- relatively complex technological equipment associated with multi-stage neutralization,

- relatively complex neutralization heat removal system, - rapid clogging of heat exchange surfaces with precipitated sludge from the extraction H^PO^,

- the need for equipment to prepare a stabilizing additive,

- when stabilizing bentonite, NP-suspension fertilizer is essentially obtained from solution fertilizer, which, due to its higher viscosity, places increased demands on handling.

It has now been found that the shortcomings of the described methods can be largely eliminated by the method according to the invention. The essence of the invention lies in the fact that the heat released during the neutralization of trihydrogenphosphoric acid or solutions containing a phosphorus component with gaseous or liquid ammonia or ammonia water is removed by adiabatic evaporation of part of the water from the obtained liquid fertilizer at an absolute pressure of 10 to 70 kPa, whereby the temperature of the liquid fertilizer is maintained at a value of 45 to 90 ° C. When processing the extracted trihydrogenphosphoric acid into liquid fertilizers of the solution type, the stabilization of the precipitated sludge-forming impurities occurs as a result of the expansion cooling of the NP solution. This method produces a stable liquid NP fertilizer, which, even though it contains very fine homodisperse, colloidally dispersed particles, retains all the properties of solutions and can be manipulated similarly to clear solution fertilizers.

The production method according to the invention is suitable for implementation in a production plant, one of the possible examples of which is shown in Fig. 1. The plant consists of a trihydrogenphosphoric acid inlet 1, an ammonia inlet 2, a water inlet 3, a product reservoir 4, an expansion vessel 5, a condenser 6, a circulation pump T_ and a vacuum source 2.

The reaction mixture is introduced from the product reservoir 2, as a result of the pressure difference, into the space of the expansion vessel 5, where the pressure is lower than the water vapor pressure, so that its evaporation occurs.

The heat required for the evaporation of water is taken from the heat content of the reaction mixture, whereby the reaction mixture is cooled to a temperature at which the water vapor pressure is equal to the pressure in the expansion vessel j>. The evaporated water is returned to the expansion vessel after condensation in the condenser 6. The required negative pressure is maintained in the cooling system by means of a vacuum source J8. The cooled reaction mixture is drawn from the bottom of the expansion vessel back to the product reservoir ji. Trihydrogenphosphoric acid 1 and ammonia 2 are fed in the required amount into the suction line before entering the expansion vessel 5. Water is fed through stream 2 to the product reservoir 4^. The amount of raw materials fed is regulated according to the pH value and the specific gravity of the product.

The following examples illustrate in more detail, but do not limit the subject matter of the invention.

Example 1

In the device shown in Fig. 1, a liquid fertilizer of the orthophosphate type 8-24-0 was continuously prepared by neutralizing the extracted H ₃ PO ₄ with gaseous ammonia. Trihydrogenphosphoric acid was continuously dosed into the reaction system in an amount of 837 g/min. At the same time, gaseous ammonia was dosed in an amount of 178 g.min and water in an amount of 800 g/min. Using a water-ring pump, the absolute pressure in the cooling system was maintained at 11.2 kPa, thereby achieving a temperature of the circulating NP-solution of 46-53 °C.

The extraction H3PO4 was specified as follows: 52.5 i ^P 2°5 1.1% Mgo 0.534% ^Fe 2°3 0.692% ^a1 2°3

Fertilizers were sampled at hourly intervals. The results are summarized in Table 1, which also shows the properties of NP 8-24-0 prepared under similar conditions using indirect cooling through a tubular heat exchanger.

Table 1

Cooling method expansive ! cooling unpleasant cooling sample no. 1 2 3 4 5 6 7 8 N content (%) 7.2 7.4 7.6 7.5 7.9 7.7 7.2 7.4 content Ι?2θ5 23.7 23.5 23.5 23.6 23.8 23.3 23.6 23.9 pH NP-sol. 6.5 6.6 6.7 6.6 6.8 6.6 6.6 6.5 dynamic viscos. (mPa.s) 14.4 13.2 13.3 14.8 14.6 15.3 14.8 15.1 fluidity (%) 2.9 1.5 2.2 3.7 9.6 9.9 9.2 10.1 temperature of NP solution (°C) 52.6 47.1 46.2 51.1 52.1 49.6 46.4 46.8

Example2

Liquid NP fertilizer of polyphosphate type was prepared in a similar manner as in Example 1 with the difference that the mixed acid (H^PO^ + H^SO^) was dosed in an amount of 1,000 g/min. into the neutralization-dehydration reactor, into which gaseous ammonia was simultaneously dosed in an amount of 255 g/min. The foamed reaction mixture was continuously dissolved in the product tank 4, into which water was dosed in an amount of 465 g/min with constant circulation of the NP solution. The specification of the mixed acid used was as follows: 48.16 % ^P 2°5

5.58% S 1.08% MgO 0.5% ^Fe 2°3 0.57% A1 ₂ O ₃

The absolute pressure in the cooling system was maintained at 21.3 kPa, which achieved a temperature of the NP solution of 58-64 °C. During the experiment, samples were taken at hourly intervals, the specifications of which are given in Table 2. The table also shows the properties of NP solutions prepared under the same conditions, with the difference that a tubular heat exchanger was used to cool the NP product.

Table 2

Method cooling expansively cooling indirect cooling sample no. 1 2 3 4 5 6 7 8 N content (%) 10.7 10.6 10.8 10.9 11.2 10.9 10.9 1.6 content ?2θ5 28.4 28.2 28.6 28.7 28.2 28.8 28.5 27.8 P2°5 conversion 59.6 59.9 59.4 59.3 59.7 60.1 60.1 59.3 pH of NP solution 6.4 6.7 6.7 6.6 6.8 6 L 6.7 6.8 dynamic viscosity (mPa.s) 34.2 32.5 34.2 34.2 35.9 34.2 34.2 32.5 fluidity (%) 2.1 2.2 2.0 1.7 7.4 6.7 8.2 7.6 temperature of NP solution (°C) 59.2 63.8 62.8 58.4 59.2 59.5 62.4 63.3

Example 3

In the apparatus shown in Fig. 1, a liquid fertilizer of the orthophosphate type 8-24-0 was continuously prepared by neutralizing the extracted H2PO4 with gaseous ammonia.

Extracted H2PO4 was continuously fed into the reaction system at a rate of 887 g/min. At the same time, ammonia gas was fed at a rate of 189 g/min. and water at a rate of 856 g/min.

Using a water-ring pump, the absolute pressure in the cooling system was maintained at 60.0 kPa, thereby achieving a temperature of the circulating NP solution of 82-88 θΟ. The H^ΡΟ^ had the specification as in Example 1.

Fertilizer samples were taken at hourly intervals. The results are summarized in Table 3, which also shows the properties of NP 8-24-0 prepared under similar conditions using indirect cooling through a tubular heat exchanger.

Table 3

Cooling method expansion cooling indirect cooling

sample no. 1 2 3 4 5 6 7 8 contents N (§) 7.6 7.4 8.1 7.9 7.4 7.7 7.6 7.5 content P^O^ 23.8 23.6 24.2 23.8 23.9 23.9 23.9 24.1 pH of the ŌP solution 6.6 6.5 6.8 6.7 6.4 6.6 6.6 6.5 dynamic viscosity (mPa.s) 14.6 14.1 14.8 13.9 13.8 13.6 14.4 13.9 fluidity (¾) 3.1 1.9 1.9 2.2 9.8 10.2 10.1 10.3 temperature of NP solution (°C) 84.3 82.1 86.7 87.4 86.1 85.2 84.8 86.4

Claims (1)

SUMMARY OF THE INVENTION A method for producing a liquid multicomponent fertilizer by neutralizing trihydrogenphosphoric acid or solutions containing a phosphorous component with gaseous or liquid ammonia or ammonia water, characterized in that the heat released during neutralization is drained off by vaporizing a portion of the liquid fertilizer water at an absolute pressure of 10 to 70 kPa thereby maintaining the temperature of the liquid fertilizer at 45 to 90 ° C. 1 drawing