RU2805182C1 - Method for producing complex nitrogen fertilizer with prolonged action - Google Patents

Abstract

FIELD: fertilizers.

SUBSTANCE: invention relates to methods for producing complex nitrogen fertilizers comprising microelements, used in various soil and climatic conditions for a variety of agricultural crops. A method has been proposed for producing a complex nitrogen fertilizer with prolonged action, which involves mixing prilled urea with an inorganic salt in the form of sodium tetraborate, or magnesium sulfate, or zinc sulfate, or a mixture thereof, with heating to 40°C, then urea-formaldehyde concentrate “КФК-85” is added to the mixture with the addition of orthophosphoric acid, the reaction mass is continuously stirred and heated to 90±2°C and held under these conditions for 30 minutes, followed by cooling the product to room temperature and grinding, while the mass ratio of the initial components is as follows: prilled urea : inorganic salt : urea-formaldehyde concentrate “КФК-85” : orthophosphoric acid – 100: (3-8) : (3-7) : (1.4-2.2).

EFFECT: improving the method for producing complex nitrogen fertilizer, eliminating residual formaldehyde from its composition with expanding the areas of its use in agriculture, while the developed complex fertilizers more effectively increase productivity, are not washed out of the soil by precipitation and are characterized by a slow release of bound nitrogen both alone and in combination with other products.

1 cl, 1 tbl, 5 ex

Description

The invention relates to methods for producing complex nitrogen fertilizers containing microelements, used in various soil and climatic conditions for a variety of agricultural crops. Unlike traditional agrochemicals, they additionally increase productivity, are not washed out of the soil by precipitation and are characterized by a slow release of fixed nitrogen, both on their own and in combination with other products. This prevents nitrate nitrogen from entering water bodies and significantly slows down the process of water blooming in hot summer weather.

According to published research results [RU No. 2457666, IPC A01G 1/00, A01B 79/02, A23K 1/00, C05C 9/02, 2011], replacing urea with long-acting urea-formaldehyde fertilizer helps increase the collection of Sudan grass feed by 12% , and millet by 6%. A significant increase in yield was also noted for other agricultural crops.

There is a known method for producing a slow-acting complex urea-formaldehyde fertilizer [RU No. 2619301, IPC S05S 9/02, 2017], which involves adding orthophosphoric acid to the wastewater of a woodworking enterprise containing dissolved formaldehyde and urea-formaldehyde resin in order to reduce their pH to a level of 2.0 , subsequent introduction of urea into them to establish a molar ratio of formaldehyde: urea equal to 1.0÷1.5, keeping the treated wastewater for 3.5-4.0 hours, filtering it and drying the resulting sediment, mixing it with ash to achieve potassium oxide content not lower than 10%, wt.

The disadvantages of the method include its low efficiency due to the low content of formaldehyde and urea-formaldehyde resin in industrial wastewater, as well as contamination of the resulting fertilizer with undesirable impurities.

There is a known [SU No. 1047892, IPC C05C 9/02,1983] method of producing granular urea-formaldehyde fertilizer, including mixing urea with formaldehyde and a catalyst, drying, crushing and classification of the finished product with separation of dust, which in an amount of 7÷17% by weight, returned to the original reaction mixture, followed by extrusion in the form of bundles, grinding in a disintegrator and classification of the crushed product on a screen.

The described technology is energy-consuming and involves the use of corrosive sulfuric acid as an acid catalyst, which causes destruction of the technological equipment used. To this should be added the insufficiently high quality of the resulting crushed fertilizer, and, above all, the wide variation in its fractional composition.

The method for producing an agrochemical described in [RU No. 2752942, IPC C05C 9/02, 2021] can be considered the closest in technical essence.

It involves the condensation of urea with a methylol urea composition in an aqueous medium in the presence of phosphoric acid at a temperature of (80±3)°C and pH 2.6÷3.3, neutralization of the resulting suspension to pH (7±0.3) by adding chalk and dolomite dust or aqueous ammonia, followed by filtration of the precipitate and its drying, as well as the return of the aqueous filtrate to prepare the initial solution of urea, and urea-formaldehyde concentrate KFK-85 is used as the methylol urea composition, and the molar ratio of urea: formaldehyde in the resulting product is (2÷1) :1.

The agrochemical synthesized in this way is a long-acting nitrogen fertilizer with a high content of ammonium nitrogen and additionally includes phosphorus, calcium or magnesium as microelements. Its disadvantages include the possible presence in the resulting composition of small amounts of free formaldehyde, which does not exceed 0.1% by weight.

The technical objective of the invention is to improve the method for producing complex nitrogen fertilizer, eliminating residual formaldehyde from its composition, with expanding the areas of its use in agriculture.

This goal is achieved by treating prilled urea granules with inorganic salts and a mixture of a formaldehyde-containing product and orthophosphoric acid, followed by heating the composition at (90±2)°C for 30 minutes, and sodium tetraborate deca-hydrate, magnesium sulfate, and dolomite flour are used as salts , zinc sulfate, the introduction of which into the soil stimulates plant growth and increases their productivity.

As a formaldehyde-containing product, the most suitable is urea-formaldehyde concentrate brand KFK-85 no TU 2223-009-00206492-98 with a molar ratio of formaldehyde: urea equal to 4.8 + 0.2, containing about 85 wt.% a mixture of mono-, di- and trimethylolureas, and formaldehyde and about 15 wt. % water [S.V. Afanasyev, S.V. Makhlai. Urea-formaldehyde concentrate. Technology. Recycling. Monograph ed. Doctor of Technical Sciences Afanasyeva S.V. - Samara. Ed. Samara Scientific Center of the Russian Academy of Sciences. 2012. - 298 p.].

It is important to emphasize that the proposed method involves the use of a simplified technological device to carry out the process, and, as a result, energy costs and time for the synthesis of agrochemicals are reduced.

Thus, the essence of the proposed technical solution is a method for obtaining a complex nitrogen fertilizer of prolonged action by treating prilled urea with inorganic salts and a mixture of a formaldehyde-containing product and orthophosphoric acid, followed by heating the composition at (90±2)°C for 30 minutes, and inorganic salts are used sodium tetraborate decahydrate, magnesium sulfate, zinc sulfate or a mixture thereof, and the formaldehyde-containing product is urea-formaldehyde concentrate KFK-85, with the following mass ratio of components, wt.%: urea: inorganic salt or mixture of salts: urea-formaldehyde concentrate: orthophosphoric acid = 100 :(3÷8):(3÷7):(1.4÷2.2).

Its implementation is carried out as follows.

Example No. 1

200 g of prilled urea according to GOST 2081 2010 and 14.4 g of sodium tetraborate decahydrate were loaded into a laboratory reactor with a capacity of 0.5 l, equipped with a stirrer and heating. The contents were thoroughly mixed, heated to 40°C and 12.0 g of urea-formaldehyde concentrate KFK-85 was added with the addition of 3.8 g of orthophosphoric acid with a concentration of 77.5% by weight. With continuous stirring, the temperature of the reaction mass was raised to (90±2)°C and maintained under these conditions for 30 minutes. The product was discharged from the reactor, cooled to room temperature and ground to the required particle size.

The composition of the resulting fertilizer and its properties are shown in the table.

Example No. 2

Conditions for the synthesis according to example 1.

Instead of sodium tetraborate decahydrate, anhydrous magnesium sulfate was taken in the amount of 15.0 g.

The composition and properties of the resulting complex nitrogen fertilizer are shown in the table.

Example No. 3

Carrying out conditions according to example 1. Instead of sodium tetraborate decahydrate, 8 g of ZnSO ₄ was taken, and the weights of urea-formaldehyde concentrate and orthophosphoric acid were reduced to 10 g and 3.2 g, respectively. The composition and properties of the resulting fertilizer are presented in the table.

Example No. 4

Synthesis conditions according to example 1. Instead of sodium tetraborate decahydrate, a mixture consisting of 8 g of MgSO ₄ and 6 g of ZnSO ₄ was taken. The properties of complex nitrogen fertilizer are shown in the table.

Example No. 5

Synthesis conditions according to example 1. Instead of 14.4 g of sodium tetraborate decahydrate, a mixture of inorganic salts was taken, consisting of 8 g of sodium tetraborate decahydrate, 4 g of magnesium sulfate and 3.4 g of zinc sulfate.

The composition and properties of the synthesized fertilizer according to examples No. 1-5 are presented in the table.

It follows from it that the resulting compositions have a prolongation effect, since the time of their dissolution in water at 25°C is approximately 5-6 times higher than that of urea.

Compared to the prototype, the proposed method for producing complex nitrogen fertilizers has a number of other significant advantages:

- absence of free formaldehyde in the resulting products, since the molar ratio of urea: formaldehyde during their production is over 10;

- the presence in their composition of microelements (B, Mg, Zn. P and S), which increase the productivity of various agricultural crops and expand the scope of urea use;

- absence of insoluble resin-containing sediments when synthesized fertilizers are dissolved in water.

The use of orthophosphoric acid plays a positive role, because in its presence, sodium tetraborate decahydrate is converted into boric acid and sodium phosphate, which are better absorbed by agricultural crops.

And finally, treating prilled urea granules with the addition of urea-formaldehyde concentrate KFK-85 suppresses caking during storage of the resulting complex fertilizers.

Claims (1)

A method for producing complex nitrogen fertilizer with prolonged action, characterized in that it involves mixing prilled urea with an inorganic salt in the form of sodium tetraborate, or magnesium sulfate, or zinc sulfate, or a mixture thereof, heated to 40°C, then urea-formaldehyde concentrate KFK- is added to the mixture. 85 with the addition of orthophosphoric acid, continuously stir the reaction mass with heating to 90±2°C and maintaining under these conditions for 30 minutes, followed by cooling the product to room temperature and grinding, while the mass ratio of the initial components is: prilled urea : inorganic salt: urea-formaldehyde concentrate KFK-85: orthophosphoric acid - 100: (3-8) : (3-7) : (1.4-2.2).