CS244349B1 - Condensed ammonium phosphates preparation - Google Patents

Description

(54) Process for preparing condensed ammonium phosphates

2

The invention relates to a process for the preparation of condensed ammonium phosphates formed by the neutralization-dehydration reaction of phosphoric acids with ammonia gas, which takes place continuously on the foamed melt surface resulting from the reaction of urea and sulfuric acid].

The invention can be used in the chemical industry.

The invention relates to a process for the preparation of condensed ammonium phosphates. Tawenna of condensed ammonium phosphates is the basic starting material for the preparation of clear or suspension liquid fertilizers.

It is known that the basis for the preparation of condensed ammonium phosphates is the neutralization of phosphoric acids with ammonia. The literature describes procedures for pressure neutralization of superphosphoric acids (U.S. Pat. Nos. 3,171,733; 3,224,146) and atmospheric neutralization of superphosphoric acids (Rev. Chim. [Bukurest] 16/2 /, 81-83 years [1965!]).

Further, processes for the preparation of condensed ammonium phosphates by direct neutralization of phosphoric acids of commercial concentration are known. These procedures are similar to pressure (NSC Pat. No. 1909 438; Franc. Pat. No. 1493 803) and atmospheric (Franc. Pat. 1436 746) neutralization.

Several types of reactors are used to prepare condensed ammonium phosphates. The most common are jet reactors (U.S. Pat. No. 3,464,808) and T-reactors (Farm. Chemicals 132 (9) (41-47), (U.S. Pat. No. 2,985,513)).

Recently, processes have been developed for the preparation of a melt of condensed ammonium phosphates by means of reactors where the dehydration of the molecular water occurs in the film layer. These can be divided into reactors in which molecular dehydration occurs outside the reaction zone (Cs. AO 205 849) and in the reaction zone (Cs. AO 210 335). The formation of the film layer is accomplished by filling the reactor or grooves upon which the melt flows.

Hydration products of sulfur trioxide or sulfur trioxide itself are introduced into the reaction system to increase the heat released upon neutralization. The increase in neutralization heat has a beneficial effect on the condensation of the ortho-form of the phosphate on the polyform. Urea (Cs. AO 216 856) is also used as the condensing agent, which increases the surface of the reaction mixture upon decomposition.

The disadvantages of the known processes for the preparation of condensed phosphates as well as the use of the reactors mentioned above are, in particular, the high energy consumption of superphosphoric acid processing and the need for construction materials of considerable corrosion resistance.

A further disadvantage is that during the processing of the extractive orthophosphoric acids, the walls of the reactors give rise to heavy metal melts which are present in the extractive phosphoric acids, thereby reducing the luminosity of the reactors and increasing the reactor operating pressure, thereby reducing the reactor operating pressure. it makes it impossible to process extractive phosphoric acids with a higher content of cationic impurities.

The use of urea as a condensing agent is also disadvantageous because of the heat balance of the neutralization-dehydration reaction, since its decomposition is endothermic.

It has now been found that the above drawbacks overcome the process for preparing the condensed ammonium phosphates of the invention. The principle of the invention is that the reaction of phosphoric acid and ammonia gas takes place continuously on the foamed melt surface at a temperature of 180 to 320 ° C, resulting from the reaction of urea and sulfuric acid in the molar ratio of Co (NH2) 2: H2SO4 = 0.7 to

1.3.

The advantage of said method of preparation is mainly the removal of the flow reactor fillings during the processing of the extraction and thermal phosphoric acids of a commercial concentration. This eliminates the possibility of the formation of patches of refractory metal phosphates on the filler, and at the same time it is possible to process the phosphoric acid extracts even with an extreme content of polluting cannon impurities. Sufficient size of the reaction surface of the neutralization-dehydration reaction is achieved by a strong foaming melt, which is the product of the exothermic reaction of sulfuric acid and urea. On the surface of this melt there is a neutralization-dehydration reaction of phosphoric acid and ammonia gas. Another advantage of the process is that the thermal coloration of the sulfuric acid-urea reaction contributes to the overall thermal balance of the neutralization-dehydration reaction.

The following examples illustrate but do not limit the scope of the invention.

EXAMPLE

1.18 kg / min of extraction H3PO4 (54% P2O5) preheated to 60 degrees Celsius were charged to a continuously operating vertical tubular neutralization-dehydration reactor. Simultaneously with the extraction H3PO4, 0.32 kg / min of NH3 gas and 0.35 kg / min of the sulfuric acid-urea reaction product were dosed. The sulfuric acid-urea reaction product, which was prepared in a separate flow reactor by reacting 0.25 kg / min sulfuric acid (98%) preheated to 70 ° C with 0.1 kg / min crystalline urea, was injected at 240 ° C to neutralize. - a dehydration reactor in the form of a thick foamed melt. On the large surface of the thick foamed melt (product of the reaction of sulfuric acid and urea), a neutralization-dehydration reaction of phosphoric acid and ammonia occurred. The melt leaving the reactor had a composition

13.1% N; 49.9% P2O5; 7.5 ° / o S, whereby

32.2% of the phosphorus component is in condensed form. The degree of conversion was 30.86%.

WITH

Example 2

The procedure was as in Example 1. 1.18 kg / min of phosphoric acid (54% P2O5) preheated to 60 ° C was charged into the reactor simultaneously with 0.32 kg / min of ammonia gas and 0.45 kg / min of foamed melt (reaction product of 0.25 kg / min of cybersulfuric acid (98%) preheated to 180 ° C and 0.20 kg / min of molten urea) having a temperature of 310 ° C. The melt leaving the reactor had a composition of 12.4% N, 53.1% P2O5;

7.7% S; wherein 45.3% of the phosphorus component was in condensed form. The degree of conversion was 52.81%.

Claims (2)

SUBJECT Process for the preparation of condensed ammonium phosphates by neutralization-dehydration reaction of extraction and / or thermal phosphoric acids with ammonia gas, characterized in that the neutralization reaction is carried out continuously on the foamed melt surface at 180-320 ° C, resulting from urea sulfuric acid reaction. molar ratio of Co (NH 2) 2: H 2 SO 4 = 0.7 to 1.3.