RU2241691C2 - Method of preparing ammonium nitrate granules - Google Patents

Abstract

FIELD: mineral fertilizers.

SUBSTANCE: distinguishing feature of invention consists in that ammonium nitrate is obtained in the form of high-strength granules with calcium nitrate and sulfuric acid additives, wherein calcium nitrate is utilized in the form of dolomite extract containing calcium and magnesium ions (on conversion to CaO) in amounts 0.4-0.7%, whereas sulfuric acid is added in granulation stage in amount required for complete conversion of calcium and magnesium ions into CaSO₄ and MgSO₄.

EFFECT: increased strength of ammonium nitrate granules and thereby facilitated its transportation in bulk and avoided caking on storage.

1 dwg, 1 tbl, 6 ex

Description

The invention relates to a technology for producing ammonium nitrate, which is a nitrogen fertilizer widely used in agriculture.

Ammonium nitrate granules are characterized by reduced strength (0.7-0.9 kg / gran), which leads to its destruction during bulk transport and during application to the soil. At the same time, it contributes to its caking, lumping during open storage. To increase the strength, a solution of dolomite extract with a content of calcium and magnesium ions of 0.3-0.5% in terms of CaO [1. Ammonium Nitrate Technology Ed. prof. Olevsky VM, M., Chemistry, 1978, p. 157-159]. Dolomite extraction is obtained by dissolving dolomite in 56% nitric acid. The strength of such nitrate is low and is 1.1-1.4 kg / gran. This does not ensure the stability of the granules to destruction and, accordingly, to adhesion and caking.

It is known to use sulfuric acid to increase strength and reduce dusting during granulation in towers. The strength of such nitrate is low and amounts to 1-1.2 kg / gran.

The closest in technical essence and the achieved result is a method of obtaining durable granules of ammonium nitrate, including the neutralization of nitric acid with ammonia, the introduction of additives containing calcium nitrate and sulfate additive, evaporation of the solution to obtain melt and its granulation. In this case, the strength of the granules increases from 0.4-0.57 kg / gran to 0.6-0.7 kg / gran [2. Ammonium Nitrate Technology Ed. prof. Olevsky V.M., M., Chemistry, 1978, p.238-239]. The disadvantage of this method is the low strength of the granules, despite its overall increase of 1.3-1.5 times. In this method, the formed calcium sulfate does not provide a structure-forming action and its effect is low.

To increase the strength in the proposed method for producing high-strength ammonium nitrate by neutralizing nitric acid with ammonia and introducing sulfuric acid, evaporating the solution to obtain melt, introducing calcium nitrate into the melt, spraying it in the granulation tower volume, forming granules during free-fall cooling, further cooling in conditions of a fluidized bed with subsequent packaging and storage, the solution of calcium nitrate is introduced in the form of nitric acid dolomite extract after the stage of neutralization with the content ones calcium and magnesium in an amount of 0.4-0.8 wt.% based on CaO, and sulfuric acid is introduced at the granulation step in an amount required for the complete conversion of the Ca and Mg ions to CaSO ₄ and MgSO _4.

Distinctive features of the method is the use of nitric acid dolomite extract containing Ca (NO ₃ ) ₂ and Mg (NO ₃ ) ₂ and its place of input and sulfuric acid.

The presence of magnesium nitrate in the melt and the new procedure for introducing calcium nitrate and sulfuric acid increase the rate of formation of CaSO ₄ by eliminating the stage of formation of (NH ₄ ) ₂ SO ₄ , introducing it into the structure of the crystal of ammonium nitrate, simultaneously with magnesium sulfate and obtaining granules with increased strength 2.5-2.8 kg / gran.

The drawing shows a diagram of a plant for producing ammonium nitrate.

1, 2 - heaters;

3 - reactor for dolomite extraction;

4 - ITN apparatus;

5 - dispenser dolomite hood;

6 - neutralizer;

7 - doupark apparatus;

8 - pressure tank;

9 - capacity of sulfuric acid;

10 - granulation tower;

11 - fluidized bed apparatus;

12 - air heater;

13 - fan;

14 - conveyor of the finished product.

The installation is as follows.

Example No. 1

Nitric acid in the amount of 24 thousand kg, passing the heater (1), enters the ITN apparatus (4), where gaseous ammonia is supplied in the amount of 6.45 thousand kg, after the heater (2). Dolomite extraction is obtained in the reactor (3), where dolomite and 50-56% HNO ₃ are fed, and fed through a dispenser (5) into a solution of ammonium nitrate in an amount that provides the content of calcium and magnesium ions. The resulting solution of ammonium nitrate undergoes neutralization with ammonia in the apparatus (6), evaporation (7) and the resulting melt enters the pressure tank (8), where 95-98% sulfuric acid in the amount of 21 kg is simultaneously supplied. The melt is granulated in the tower (10), cooled in the apparatus (11) and sent to the warehouse by conveyor 14.

The table shows the test results of the proposed method.

Example No. 2

The method is carried out analogously to example 1. The amount of sulfuric acid was 63 kg, the content of calcium and magnesium ions in terms of CaO is 0.5 wt.%.

Example No. 3

The method is carried out analogously to example 1. The amount of sulfuric acid was 141 kg, the content of calcium and magnesium ions in ammonium nitrate in terms of CaO is 0.5 wt.%.

Example No. 4

The method is carried out analogously to example I. The amount of sulfuric acid was 174 kg, the content of Ca and Mg ions in terms of CaO is 0.5 wt.%.

Example No. 5

The method is carried out analogously to example 1. The amount of sulfuric acid was 200 kg, the content of Ca and Mg ions in terms of CaO is 0-5 wt.%.

Example No. 6

The method is carried out analogously to example 1. The amount of sulfuric acid was 280 kg, the content of Ca and Mg ions in terms of CaO is 0.7 wt.%.

Sources of information

1. Ammonium nitrate technology. Edited by prof. V.M. Olevsky, M., Chemistry, 1978, p. 157-159.

2. Polyakov NN, Nevskaya A.N. et al. Auth. testimonial. USSR No. 509567, Bull. fig. N13, 1976.

Claims (1)

A method of obtaining durable granules of ammonium nitrate, including the neutralization of nitric acid with ammonia, the introduction of additives containing calcium nitrate, and sulfate additives, evaporation of the solution to obtain melt and its granulation, characterized in that as an additive containing calcium nitrate, use a dolomite extract containing calcium and magnesium ions in terms of CaO in the amount of 0.4-0.7 wt.%, which is introduced after the stage of neutralization, and as a sulfate additive, sulfuric acid is introduced in the amount of granulation at the granulation stage, necessary for the complete conversion of calcium and magnesium ions to calcium sulfate and magnesium sulfate.