SU1668349A1 - Method for obtaining complex fertilizers - Google Patents

Abstract

The invention relates to a process for the preparation of complex mineral fertilizers in the nitric acid processing of natural phosphates and contributes to reducing the release of nitrogen oxides into the gas phase and increasing the strength of the granules. The method is carried out by the nitric acid-acid decomposition of apatite in the presence of urea, followed by processing the resulting stretch into the final product by ammoniation, evaporation, granulation, and drying. At the same time, before introducing carbamide, at the moment of acid decomposition, ammonium nitrate is introduced in the amount of 0.5-2 kg per 100 kg of apatite. Ammonium nitrate is introduced in the form of a 20-60% solution or salt. Urea is introduced in the amount of 0.3-0.01 kg per 100 kg of apatite 10-20 minutes after the supply of ammonium nitrate. The proposed method makes it possible to reduce the release of nitrogen oxides into the gas phase by a factor of 2 to 3 and to increase the strength of the granules by 10 to 20 kg / m ³ . 3 hp ff, 1 tab.

Description

This invention relates to a process for the preparation of complex mineral fertilizers in the nitric acid processing of natural phosphates.

The aim of the invention is to reduce the release of nitrogen oxides into the gas phase and increase the strength of the granules.

PRI me R 1. 100 kg of apatite concentrate is treated with 146.2 kg of 56% nitric acid containing 1% of N02. and 68.5 kg of 93% sulfuric acid. The resulting mass (314.7 kg) contains 1.46 kg of N02. 0.5 kg of ammonium nitrate in the form of a salt is introduced into the decomposition stage together with nitric acid, and after 10 minutes 0.3 kg of urea are fed. In this case, 7% of nitrogen oxides of the total mass (0.12 kg) are released into the gas phase. The degree of binding of nitrogen oxides is 92%. The resulting extract (315.38 kg) was ammoniated with 10 kg of ammonia, evaporated, mixed with 65 kg of KCI (60% K20), granulated and dried, yielding 325 kg of nitrophosphate. The strength of the granules is 30 kg / m.

Example 2.314.7 kg of the mass obtained in Example 1 was treated with 5 kg of a 20% ammonium nitrate solution (1 kg of salt) and after 15 minutes 0.1 kg of urea was added. In this case, 6% nitrogen oxides of the total mass (0.09 kg) are released into the gas phase. The degree of bonding of nitrogen oxides is 94%. The resulting mass (319.71 kg) is ammoniated with 10 kg of ammonia, evaporated, mixed with 65 kg of KCI, granulated and dried to obtain 325 kg of nitrophosphate. The strength of the granules is 40 kg / m.

P rome FER. 314.7 kg of the mass obtained in example 1 is treated with 3.75 kg of 40% ammonium nitrate solution (1.5 kg of salt) and

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after 20 minutes, 0.05 kg of urea was added. In this case, 5% nitrogen oxides of the total mass (0.07 kg) are released into the gas phase. The degree of bonding of nitrogen oxides is 95%. The resulting extract (318.43 kg) was ammoniated with 10 kg of ammonia, evaporated, mixed with 65 kg of KCI, granulated and dried to obtain 325 kg of nitrophosphate. The strength of the granules leaves Pb kg / m.

PRI m e p4. 314.7 kg of the mass obtained in example 1 was treated with 3.3 kg of a 60% ammonium nitrate solution (1 kg of salt) and after 20 minutes 0.01 kg of urea was added. In this case, 6% nitrogen oxides of the total mass (0.09 kg) are released into the gas phase. The degree of bonding of nitrogen oxides is 94%. The resulting extract (316.72 kg) was ammoniated with 10 kg of ammonia, evaporated, mixed with 65 kg of KCI, granulated and dried to obtain 325 kg of nitrophosphate. The strength of the granules is 33 kg / m.

The table lists examples of the process in the proposed parameter ranges (examples 1-4) and beyond.

Reducing the amount of ammonium nitrate to 0.3 kg per 100 kg of apatite (Example 5) reduces the degree of binding of nitrogen oxides and the quality of fertilizer due to a decrease in its effect on the process of dissociation of nitric acid and granulation.

Increasing the amount of ammonium nitrate to 2.2 kg per 100 kg of apatite (Example 6) impairs the process performance due to its influence on the crystallization process of calcium sulfate, which makes it difficult to granulate the product.

Reducing the amount of carbamide (Example 7) reduces the degree of bonding of nitrogen oxides due to insufficient amounts to decompose nitrogen oxides.

Increasing the amount of urea (Example 8) reduces the performance of the process due to the deterioration of the granulation process.

A decrease in the concentration of ammonium nitrate solution to 15% (Example 9) reduces the degree of binding of nitrogen oxides due to a decrease in the dissociation process of nitrogen

acid.

Increasing the concentration of ammonium nitrate solution (Example 10) makes the technology difficult because of the transport of highly concentrated water.

Reducing the time of entry of urea

(example 11) leads to a decrease in the degree

nitrogen oxide bonding due to lack of

time to stabilize the liquid phase.

Increasing the time of entry of urea

(Example 12) leads to a decrease in the degree of bonding of nitrogen oxides due to a decrease in the effect of urea on the gas evolution process. When carrying out the process according to the proposed method, the release of oxides of nitrogen in the gas phase is reduced by a factor of 2-3 and the strength of the granules increases by 10-20 kg / m3.

Claims (4)

1. The method of obtaining complex fertilizer, including nitric acid decomposition of apatite, introduction of urea into the resulting mass, ammonization of the obtained stretch with ammonia, evaporation, granulation and drying of the finished product, which is characterized by the introduction of t ammonium nitrate in the amount of 0.5-2 kg per 100 kg of apatite. 2. A method according to claim 1, characterized in that the ammonium nitrate is administered in the form of a 20-60% solution. 3. The method according to claim 1, characterized in that the urea is introduced in an amount of 0.30, 01 kg per 100 kg of apatite. 4. A method according to claim 1, characterized in that the carbamide is introduced 10 to 20 minutes after the supply of ammonium nitrate. five