CS200037B1 - Method of producing liquid fertilisers based on urea and ammonium nitrate - Google Patents

Description

The present invention solves the production of urea and ammonium nitrate liquid fertilizers by the treatment of mother liquors resulting from the production of N, E-dinitrosopentamethylenetetramine, the final product being fertilizers and sodium sulfate.

From the production of Ν, Ν-dinitrosopentamethylenetetramine (DNPT), also defined as 1,5-endomethylene-3,7-dinitroso-1,3,5,7-tetraazacyclooctane, by nitrosating cleavage of hexamethylenetetramine using a combination of sodium nitrite and sulfuric acid, sodium sulfate solution (i.e. mother liquors) containing formaldehyde, some of the preferred sodium nitrite, and ammonium ions. The use of methylene base and sodium nitrite in these wastes for increasing the yield of the nitrosolysis process (Japan. Kokai 76 80,898) by their recirculation after prior ammoniaization, concentration and isolation of most sodium sulfate is described.

From an economic point of view, it is preferable to react hexamethylenetetramine in the form of a concentrated reaction mixture after the ammoniacalization of aqueous formaldehyde (Boujjol, G .: M. Poudres 1952, 34, 7). Similarly, it is preferable to apply sodium nitrite solutions obtained by treating the nitrogen oxides with sodium hydroxide solution. Since the sodium nitrite solutions thus prepared, depending on the reaction conditions, contain a certain amount of sodium nitrate, re-circulation of the treated and thickened ma200 037 i

in this case. Here, there is no choice but to separate the sodium sulphate by crystallization and use sodium nitrate for pr. for the preparation of fertilizers.

The mother liquors from the production of β, β-nitrosopentamethylenetetramine by nitrosation cleavage of hexamethylenetetramine with sulfuric acid and sodium nitrite containing sodium nitrate are sprayed to sodium sulfate and urea-ammonium nitrate complex fertilizer according to the present invention. The undesirable sodium nitrite is removed by the deposition of sulfuric acid with the action of formaldehyde (Z.Anal.Chem.1913.52.21) and ammonium ions (Monatsh.Chem. 1953, 84. 829} Japan. Kokai 74 110,148) at elevated temperature. After the ammoniacalization of the mother liquors thus treated, they are concentrated to a degree such that most of the sodium sulphate crystallizes upon cooling. The liquors after crystallization, representing an aqueous solution of sodium nitrate, ammonium nitrate and sodium sulfate (remaining after crystallization), are then applied as a solvent component of the urea-ammonium nitrate complex fertilizer liquid. The treatment of the mother liquors which have been removed from the nitrosation step by the cleavage of hexamethylenetetramine using sulfuric acid and sodium nitrite containing sodium nitrate has not been described in the literature.

Treatment of the mother liquors from the production of N, N-dinitrosopentamethylenetetramine within the meaning of the present invention will eliminate the toxicity of sodium nitrite and free formaldehyde and isolate the bulk of the dropping sodium sulfate. At the same time, sodium nitrate for plant nutrition is recovered. The secondary effect of the invention is to address the environmental issues associated with the production of N, N-dinitrosopentamethylenetetramine.

Example 1:

Mother liquors from the production of N, β-dinitrosopentamethylenetetramine by nitrosation cleavage of hexamethylenetetramine (taken into reaction in the form of a partially concentrated reaction mixture after the ammoniacalization of an aqueous formaldehyde solution) with sulfuric acid and sodium nitrite containing 33.8% by weight of sodium nitrate were available. calculated on the sodium nitrite content. Hitrozolysis was terminated by neutralizing the entire reaction mixture with 20% sodium hydroxide solution. 1000 ml of these liquors contained:

0.50 g sodium hydroxide 15.11 g sodium nitrite

3.44 g formaldehyde 10.82 g hexamethylenetetramine 32.20 g sodium nitrate 85.97 g sodium sulfate

The chemical oxygen demand was 31 488 mg per 100 ml and the density at 20 ° C was 1.147 -3

g.cm - ² .

The mother liquors of this composition were acidified with 96.2% sulfuric acid to pH 2 to 1 and heated to 94 to 98 ° C for 25 minutes. After cooling to 50-45 ° C, the pH of the reaction mixture was adjusted to 7.5-8 with ammonia gas. By concentrating the resulting solution to 44% of the starting weight of the mother liquors and then cooling the distillation residue to +7 ° C, 51, 8% of all sodium sulfate present in the form of decahydrate containing 1.1% by weight of hexamethylenetetraraine. The filtrate after isolation of the Glauber salt of which. was 37.4% by weight of the mother liquor and had a density of 1.176 g.om -1 at 20 ° C, contained 1.29% by weight of hexamethylenetetramine, 2.65% by weight of sodium nitrate, 4.5% by weight of ammonium nitrate, and 12%, 27% by weight of sodium sulfate.

Example 2:

A solution containing 75% urea was prepared from the treated and concentrated mother liquors of Example 1 and urea at 72-76 ° C. This solution was mixed with a 75% ammonium nitrate solution 80 ° C warm. The resulting liquid fertilizer contained 15.57% ammonium nitrate nitrogen and 18.32% organic nitrogen, thus containing 33.87% total nitrogen. The high temperature was -26.5 ° C. The weight mixing ratio of the solutions was 1: 1.

Example 3:

The urea solution of Example 2 was mixed with 80% ammonium nitrate solution 115 ° C warm. The resulting liquid fertilizer contained 15.85% ammonium nitrate nitrogen and 18.64% organic nitrogen, thus containing 34.49% total nitrogen. The temperature was -22 ° C. The weight mixing ratio of the solutions was 1: 1.

Example 4:

A solution containing 70% urea was prepared from the treated and concentrated mother liquors of Example 1 and urea at 70-74 ° C. This solution was mixed with a 75% ammonium nitrate solution of 115 ° C warm in a 1: 1 weight ratio. The resulting liquid fertilizer contained 14.85% ammonium nitrate nitrogen and 17.4% organic nitrogen, thus containing 32.25% total nitrogen. The high temperature was -22.5 ° C.

Claims (2)

1. A process for the production of liquid urea-ammonium nitrate fertilizers using mother liquors, which is omitted from the production of N, N-dinitrosopentamethylenetetramine by nitrozaone cleavage of hexamethylenetetramine with the aid of technical solutions of sodium nitrite and sulfuric acid, characterized in that The dinitrosopentamethylenetetramine is acidified with nitric acid to a pH of 0 to 2, preferably acidified to a pH of 1 to 2, then heated to 90 to 103 ° C, preferably to 94 to 98, for 10 to 60 minutes, preferably 25 minutes. ° C, and after adjusting the pH with ammonia to a pH of 7 to 9, preferably a pH of 7.5 to 8.0, are concentrated to at least 44% by weight of the mother liquor and cooled to 20 to 0 ° C, preferably at a temperature of 7 ° C, the precipitated sodium sulphate decahydrate is isolated, and urea is then added to the caustic soda lye in an amount such as to form a solution of sodium sulphate. 0 to 80% urea solution, preferably 70 to 75% urea solution, which is then mixed with a 70 to 90% aqueous ammonium nitrate solution, preferably a 75 to 80% aqueous ammonium nitrate solution , in a weight ratio of 1: 1.