RU2424219C1 - Method of producing compound mineral fertiliser - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: invention relates to production of complex mineral fertiliser containing other nutrients besides nitrogen and phosphorus. The method involves premixing phosphoric acid and ammonia, followed by mixing the obtained ammonium phosphate pulp with sulphuric acid and ammonia, adding a potassium-containing additive, granulating and drying the product. Premixing concentrated phosphoric acid and ammonia is carried out in a reactor-mixer. Subsequent mixture of ammonium phosphate pulp with sulphuric acid and ammonia is carried out in a tubular reactor. The ammonium phosphate pulp and ammonium phosphate are sprayed onto a recycle mixture, potassium chloride and carbamide in an ammoniator-granulator. ^ EFFECT: invention increases efficiency of the process of producing fertiliser, increases content of nutrients in the fertiliser, enables utilisation of heat of neutralisation of sulphuric acid with ammonia to evaporate moisture and pulp, minimises aggressive effect of sulphuric acid on equipment. ^ 1 dwg, 1 ex

Description

The invention relates to the production of complex mineral fertilizers containing, in addition to nitrogen and phosphorus, other useful elements, namely the production of complex mineral fertilizers NPKS (nitrogen, phosphorus, potassium, sulfur) grade 15: 15: 15: 10 with phosphoric and sulfuric acids neutralized by ammonia, and phosphoric acid is produced from raw materials such as Karatau phosphorites.

A known method of producing complex fertilizers / RF Patent No. 2177465, publ. December 27, 2001 /, including the stepwise neutralization of a mixture of phosphoric and sulfuric acids with ammonia, granulation and drying of the product, characterized in that the neutralization is carried out first to a pH of 5.8-6.7 with a vacuum of 10-30 mm water column, and then neutralization of the pulp obtained after the first stage of neutralization to the required pH value. The ratio in the mixture of acids is taken equal to H ₂ SO ₄ : H ₃ PO ₄ = 1: (0,067-3,0) and an additional potassium-containing additive is either introduced into the pulp obtained after the first stage of neutralization, or after de-neutralization in dry form or in the form of an aqueous suspensions. Clay is added to the aqueous suspension of the potassium-containing additive in an amount of 0-2% by weight of the suspension.

According to example 1, when using phosphoric acid at a concentration of 35% P ₂ O ₅ in a mixture with sulfuric acid at a concentration of 75%, potassium sulfate is added in dry form after neutralization. The finished product contains 13.8% nitrogen, 27.6% P ₂ O ₅ , 13.8% K ₂ O, 8.2% sulfur.

According to example 2, when using phosphoric acid at a concentration of 26% P ₂ O ₅ and sulfuric acid at a concentration of 76% and introducing a suspension of potassium chloride into the pulp after the first stage of neutralization and subsequent subsequent neutralization with ammonia, a product is obtained containing: nitrogen 14.4%, P ₂ O ₅ 14.4%, K ₂ O 14.4%, sulfur 11.3%.

The disadvantages of this method, in addition to the complexity of the organization of the process under vacuum, is the following. Neutralization of the mixture of phosphoric and sulfuric acids with ammonia is carried out in the same apparatus - the reactor-mixer, which leads to corrosion of the apparatus as a result of thermochemical exposure and the need to remove from this apparatus a large amount of heat released when neutralizing sulfuric acid with ammonia. The disadvantage of this method is the use of a suspension of potassium chloride due to the increase in subsequent energy consumption for drying products. Potassium sulfate is a fairly expensive reagent.

The prototype of the claimed is a method of obtaining complex mineral fertilizers / Patent of the Russian Federation No. 2116282, publ. 07/27/1998 / by mixing phosphoric and sulfuric acids with ammonia, granulating and drying the product, characterized in that ammonia and phosphoric acid are mixed to a molar ratio of P ₂ O ₅ : N = 1: (2.2-20), followed by the introduction of sulfuric acid and bringing to a ratio of P ₂ O ₅ : N = 1: (5-20) and the process is carried out at 90-150 ° C. A potassium-containing additive is introduced to a molar ratio of P ₂ O ₅ : K ₂ O = 1: (0.5-10). As a potassium-containing additive, potassium chloride, potassium sulfate, and kalimagnesia are introduced either into the suspension or at the granulation stage.

According to an example, extraction phosphoric acid is mixed with ammonia to a ratio of P ₂ O ₅ : N = 1: 3.6; sulfuric acid and ammonia are added to the mixture to a ratio of P ₂ O ₅ : N = 1: 10 and the process is carried out at a temperature of 100 ° C. Potassium sulfate is added to the resulting mixture. The resulting mixture is dried and get a product having the composition: N - 16.0%; P ₂ O ₅ - 16.0%; K ₂ O - 8.0%.

According to another example, phosphoric acid obtained from phosphorite is mixed with ammonia to a molar ratio of P ₂ O ₅ : N = 1: 3.6 and a suspension obtained by preliminary mixing sulfuric acid and ammonia to a ratio of P ₂ O _{5 is} added to the mixture of reagents: N = 1: 10.7; the process is carried out at a temperature of 90 ° C. Kalimagnesia is introduced into the mixture, dried, and a product is obtained which contains 10.6% P ₂ O ₅ ; 10.6% N and 10.6% K ₂ O.

The prototype method is not effective enough for the following reasons. In order to reduce the corrosion ability of a mixture of phosphoric acid, sulfuric acid and ammonia, the process is carried out under conditions of excess water to reduce the reaction temperature, since heating the walls of the mixer to a temperature above 80 ° C leads to thermochemical corrosion of the mixer. The use of dilute phosphoric acid leads, in turn, to significant energy consumption for subsequent drying of the product. Despite the measures taken, the reactor-mixer, where the prototype is pre-mixed with phosphoric acid and ammonia, and subsequent processing of the resulting pulp with sulfuric acid and ammonia or sulfuric acid pre-mixed with ammonia, is subjected to aggressive thermochemical effects of sulfuric acid and, accordingly, corrosion . Potassium sulfate and Kalimagnesia are quite expensive reagents. At the same time, the nutrient content (nitrogen, phosphorus, potassium) in the complex fertilizer obtained by the prototype remains insufficient.

The solved problem and the technical result of the present invention are to increase the efficiency of the method for producing complex fertilizer by diluting in space the processes of neutralizing ammonia with phosphoric and sulfuric acids and increasing the content of nutrients in the product. The dilution of these processes allows, in turn, to efficiently use the heat of neutralization of sulfuric acid with ammonia to evaporate pulp moisture and additionally minimize the aggressive effect on the equipment of sulfuric acid by organizing a special procedure for introducing ammonium phosphate, sulfuric acid and ammonia into the tube reactor. The use of more concentrated phosphoric acid intensifies the process as a whole and, in particular, the process of evaporation of pulp containing less moisture than pulp by the prototype method.

The problem is solved in that the proposed method for producing complex mineral fertilizers, including preliminary mixing of phosphoric acid with ammonia, subsequent mixing of the obtained pulp of ammonium phosphate with sulfuric acid and ammonia, the introduction of potassium-containing additives, granulation and drying of the product, characterized in that the preliminary mixing of concentrated phosphoric acid with ammonia is carried out in a mixing reactor, and subsequent mixing of the pulp of ammonium phosphate with sulfuric acid and ammonia in a tubular eaktore, ammonium phosphate and ammonium sulfate pulp was sprayed onto the mixture retour, potassium chloride and urea in ammonizer granulator. Use phosphoric acid with a P ₂ O ₅ content of 35-40%. The introduction of ammonium phosphate, sulfuric acid and ammonia pulps into the tubular reactor is organized in such a way as to minimize the aggressive effect of sulfuric acid on the walls of the reactor. The product is dried in a tumble dryer.

The reaction of phosphoric acid and ammonia:

3NH ₃ + 2H ₃ PO ₄ → NH ₄ H ₂ PO ₄ + (NH ₄ ) ₂ HPO ₄ + Q ↑

The reaction of sulfuric acid and ammonia:

2NH ₃ + H ₂ SO ₄ → (NH ₄ ) ₂ SO ₄ + Q ↑

Potassium chloride and urea are combined into granules with ammonium sulfate and phosphates, forming a complex fertilizer with a nitrogen content in both ammonium and amide forms:

NH ₄ H ₂ PO ₄ + (NH ₄ ) ₂ HPO ₄ + (NH ₄ ) ₂ SO ₄ + KCℓ + CO (NH ₂ ) ₂

In the proposed method, phosphoric acid is used, concentrated relative to the prototype; it is possible, for example, to use extraction H ₃ PO ₄ obtained from Karatau phosphorite according to the technology of the Applicant, with a content of P ₂ O ₅ = 35-40%; SO ₃ - not more than 4.5%; solids - not more than 2% (in accordance with the Applicant's technological regulations for the production of EPA from Karatau phosphate rock).

The rest of the raw materials - H ₂ SO ₄ , NH ₃ brand "B", urea, KCl - according to GOST.

The installation diagram for implementing the proposed method is shown in the drawing.

Here:

1 - a mixer reactor with a mixer, where preliminary mixing of phosphoric acid with ammonia takes place (the supply of which is shown by arrows; the third arrow is the supply of washing liquid to the reactor mixer);

2 - a tubular reactor, where the subsequent mixing of the pulp of ammonium phosphate (from the mixing reactor 1) with sulfuric acid and ammonia to obtain pulp of ammonium phosphate and ammonium sulfate;

3 - granulator-ammonizer;

4 - a drying drum;

5 - block dosage of potassium chloride and urea in retur.

An original procedure is recommended for introducing into the tubular reactor 2 pulps of ammonium phosphate, sulfuric acid and ammonia, which minimizes the aggressive effect on the walls of reactor 2 of sulfuric acid. The tubular reactor 2 is cylindrical, preferably tapering along the flow of the mixed components, made of metal and lined with a chemical protective material from the inside. In the head of the tubular reactor 2 there are three fittings, with the central fitting, the axis of which is parallel to the axis of the reactor, supplying H ₂ SO ₄ , and the other two fittings installed so that their axes are at an angle to the axis of the reactor and towards each other, serves NH ₃ and the ammonium phosphate pulp from the mixing reactor 1. Thus, the aggressive H ₂ SO ₄ stream in the tubular reactor 2 is isolated from the walls of the reactor 2 by twisting non-aggressive flows of NH ₃ and ammonium phosphate pulp.

An example of a specific implementation of the method

At the first stage, phosphoric acid (produced from Karatau phosphorite according to the Applicant’s technology) with a P ₂ O ₅ content of 36-38% in a volume of 12 m ³ / h is supplied to a reactor-mixer 1 equipped with a stirrer, and washing liquid from the absorption system the amount of 4-5 m ³ / h and liquid NH ₃ 1,0-1,2 t / h, where everything is mixed and where phosphoric acid is partially ammoniated to a molar ratio (mo.a.) of 0.4-0.6. The temperature in the reactor-mixer 1 is from 50 ° C to 60 ° C.

At the second stage, partially ammoniated ammonium phosphate pulp is fed into a tubular reactor 2, where H ₂ SO ₄ , NH _{3 are} mixed and partially ammoniated to m.o. 0.4-0.6 pulps of ammonium phosphate from the reactor-mixer 1. The flow rates of the components supplied to the tubular reactor 2: H ₂ SO ₄ 5.5-6.5 m ³ / h; NH ₃ 4.8-5.2 t / h; partially ammoniated pulp from the reactor-mixer 18-22 m ³ / h Due to the heat of neutralization of sulfuric acid with ammonia in the tubular reactor 2, intensive evaporation of excess moisture at the outlet of the tubular reactor 2 occurs. The temperature of the vapor leaving the tubular reactor 2 is about 140 ° C. In this case, the tubular reactor 2 is not subjected to corrosion due to the above order of introducing into it the mixed components.

At the outlet of the tubular reactor 2, we obtain a pulp of ammonium phosphate and ammonium sulfate, ammoniated to m.o. 1.3-1.4.

Then, from the tubular reactor 2, the pulp is sprayed using a special nozzle onto a mixture of retur, potassium chloride and urea in a granulator-ammonizer 3, where granulation occurs due to the rotation of the latter.

In the granulator-ammonizer 3, under the retur layer with potassium chloride and urea, liquid NH ₃ is supplied in a volume of 0.5-1.0 t / h to bring the degree of ammonization of the granulated charge to mo. 1.4-1.7.

The mixture from granulator-ammonizer 3 with a moisture content of 1.5-2.5% is fed for drying to the drying drum 4, where it is dried to a moisture content of not more than 1.5%.

Before it is fed into the granulator-ammonizer 3, KCl in the amount of 10.5–10.8 t / h and carbamide in the amount of 2.3–2.7 t / h are fed into the granulator-ammonizer 3 by means of dispensers. Supply of KCl in retur - based on adjusting K ₂ O in the finished product to (15 ± 1)%. The supply of urea in retur - based on the calculation of bringing the total nitrogen in the finished product to (15 ± 1)%.

The output is nitrogen-phosphorus-potassium fertilizer brand NPKS 15: 15: 15: 10 with the content of nutrients, respectively,%:

N ( _total ) = 15 ± 1 (including amide nitrogen 2.5-3.0%);

P ₂ O ₅ = 15 ± 1;

K ₂ O = 15 ± 1;

S = 10 ± 1.

The proposed method for producing complex mineral fertilizers is more efficient than the prototype due to the dilution of phosphoric and sulfuric acids by ammonia neutralization processes at different reactors. The dilution of these processes allows, in turn, the use of concentrated phosphoric acid and the production of a correspondingly more concentrated fertilizer, as well as the efficient use of the heat of neutralization of sulfuric acid with ammonia to evaporate pulp moisture. The use of concentrated phosphoric acid intensifies the process as a whole and, in particular, the evaporation of pulp containing less moisture than pulp by the prototype method.

Additional minimization of the aggressive effect on the equipment of sulfuric acid is ensured by the organization of a special procedure for introducing ammonium phosphate, sulfuric acid and ammonia pulp into the tubular reactor.

The use of urea makes the fertilizer more versatile due to the content of nitrogen in it, not only ammonium, but also amide; the use of potassium chloride is more economical than the use of potassium sulfate and / or potassium magnesia.

Claims (3)

1. The method of obtaining complex mineral fertilizers, including pre-mixing phosphoric acid with ammonia, subsequent mixing of the obtained pulp of ammonium phosphate with sulfuric acid and ammonia, the introduction of potassium-containing additives, granulation and drying of the product, characterized in that the preliminary mixing of concentrated phosphoric acid with ammonia is carried out in a reactor mixer, and subsequent mixing of the pulp of ammonium phosphate with sulfuric acid and ammonia in a tubular reactor, the pulp of ammonium phosphate and ammonium sulfate This is sprayed onto a mixture of retur, potassium chloride and urea in an ammonizer granulator. 2. The method according to claim 1, characterized in that they use phosphoric acid with a P ₂ O ₅ content of 35-40%. 3. The method according to claim 1, characterized in that the introduction into the tubular reactor pulp of ammonium phosphate, sulfuric acid and ammonia is organized so as to minimize the aggressive effect on the walls of the reactor of sulfuric acid.