LT5974B - Process for preparing compound fertilizer - Google Patents

Abstract

The present invention provides process for preparing compound fertilizer, the process being less complicated with diminished energy consumption and air pollution. No water or steam is used to moisten starting components thus the step of drying is eliminated. The process claimed is characterized by mixing powdery components, then subjecting the components to granulation which granulation occurs with solidifying mixture of carbamide, sulfuric acid, magnesium and ammonium sulfate. Preparation of solidifying mixture comprises 3 steps: (a) admixing carbamide to concentrated sulfuric acid and adding water; (b) admixing magnesium component to the mixture obtained in (a); (c) admixing the mixture obtained in (b) to ammonium sulfate. The use of process claimed results in fertilizer with high nitrogen level.

Description

Technical field

The invention relates to the mineral fertilizer industry and can be applied to the production of bulk compound fertilizers (NPK) using urea. The present invention also relates to the use of an intending pulp for the production of fertilizers and to the production of fertilizers with a high total nitrogen content.

State of the art

Urea is a concentrated nitrogen fertilizer containing 46 percent. nitrogen, which can be used alone or as a raw material for the production of compound nitrogen, phosphorus, potassium (NPK) fertilizers.

The disadvantage of urea is that it is hydrolyzed at higher temperatures (more than 50-60 ° C) in aqueous solutions, in particular in acids, by decomposition into the initial components ammonia and carbon dioxide. This results in nitrogen losses, environmental pollution and the need for additional treatment equipment to clean up the effluent.

A conventional method of producing granular compound fertilizers is known from the Fertilizer Manual, UNIDO (Vienna, IFDC, Alabama, 1980, p. 353), where conventional bulk fertilizer components such as ammonium phosphate, ammonium nitrate, urea, ammonium sulfate, potassium chloride, superphosphate and others, mixing, wetting with water and / or water vapor, granulating, drying, cooling and fractionating. The disadvantage of this process is that urea interacts with potassium chloride, superphosphate, and gaseous and dust emissions are required which require cleaning. The evaporation of fertilizer moisture to standard requirements requires energy consumption, and does not produce fertilizers with a higher nitrogen concentration.

Known Russian patent RU2217399, priority 2002 Published August 22, 2004 March 10, 2006, which describes a method for producing compound fertilizers, wherein the urea is heat treated with potassium sulphate, granulated and obtained with nitrogen-potassium fertilizers. The process described in this patent simplifies the process, reduces the number of stages and reduces nitrogen losses. The disadvantage of this method is that the fertilizers thus obtained do not contain phosphorus, a very limited range of fertilizers.

The closest prior art is the European patent EP1127035, priority 1998 Published on 29 June 2000. A process for preparing compound fertilizer pellets comprising at least two basic nutrients selected from nitrogen, phosphorus and potassium is described in this application. This patent describes a process for the preparation of compound fertilizer granules by mixing solid raw materials and fine refining, melting a portion of the solid raw materials in a melter, mixing with the rest of the solids, granulating, cooling, sieving and packing. During the process, the dry components are not wetted with water or steam, so the fertilizer is not dried. The drying stage is eliminated and the process is simplified. The disadvantage of this method is that the melting of some of the components (10-40%) is high: high temperature (200-550 ° C) air is supplied to the melter and additional components are heated to 80110 ° C. Also, despite the use of urea, the total nitrogen concentration in compound fertilizers is low, eg fertilizer formula is 18-12-6, 1717-17, there is no fertilizer needed for spring plant fertilization.

Thus, there is a need to produce compound fertilizers that are obtained in a simplified manner, reduce energy costs, reduce air pollution and increase nitrogen concentrations in fertilizers.

The essence of the invention

It is an object of the present invention to provide a method for producing compound fertilizers which, in a simplified manner, i.e. without using the drying step, reduces the air pollution by producing a high nitrogen concentration compound fertilizer.

Patented method for producing bulk compound fertilizer, where dry components are dry blended in a mixer and granulated.

According to the process of the present invention, up to 50% of the curing slurry which supports the granulation process can also be supplied to the mixer. The optimum amount is selected depending on the nature of the starting materials, their physico-chemical properties and the ratio of their components.

In order to simplify the process and reduce energy consumption and air pollution, the granulator is additionally supplied with a solidifying slurry of urea, sulfuric acid, magnesium and ammonium sulfate, wherein the weight ratio of bulk components to the slurry is 1: 0.1-0.6, preferably 1: 0.2-0.5.

The granules are then cooled, sieved, and the fine fraction is returned to a mixer where the weight ratio of the bulk components to the fine fraction is 1.0.5-4.

The pellets are then conditioned and brought to the warehouse. The product is matured in the warehouse for 24-36 hours until the hygroscopic humidity of the fertilizer reaches 1-1.5%.

Curing pulp is obtained in three stages:

(a) urea for up to 5 min. mixed with concentrated sulfuric acid in a weight ratio of 1: 0.05-0.2, preferably in a weight ratio of 1: 0.1-0.2, with sulfuric acid: water 1: 0.5-1.0 45-50 ° C until a density of 1.35-1.39 g / cm ³ and a pH of less than 1.5 are achieved;

(b) mixing the resulting slurry with the magnesium component at a weight ratio of urea: MgO: sulfuric acid of 1: 0.05-0.2: 0.05-0.2, preferably at a weight ratio of 1: 0.090.11: 0, 09-0.11, maintaining a pulp pH of 3.5-5.5 at 75-85 ° C;

(c) mixing the resulting slurry of urea, sulfuric acid and magnesium component with ammonium sulfate at 75-90 ° C at pH 4.5-6.5.

According to an embodiment of the present invention, the magnesium component is a periclase melting product containing more than 75% MgO and a particle size of no more than 2 mm.

The patented method of producing compound fertilizers simplifies the process, reduces energy costs and reduces air pollution by eliminating the need for drying fertilizers.

Brief description of the drawing figures

FIG. 1 is a flow chart for the production of bulk compound fertilizers.

Preferred embodiments

Bulk compound fertilizers are produced as shown in the technological diagram (Fig. 1). The bulk components for fertilizer production are delivered from the hoppers (1) to the scales (2), weighed and fed by mechanical feeders (3,5) and an elevator (4) to the mixer (6) and further to the granulator (11). It also supplies the granulator with a solidifying slurry obtained in Reactor I (7) by mixing urea with dilute sulfuric acid. The resulting slurry of urea and sulfuric acid in reactor II (8) is mixed with the magnesium component and completed in the reactor III (9) by addition of ammonium sulfate. The resulting slurry of urea, sulfuric acid, magnesium and ammonium sulfate is pumped into a granulator (11) by means of a pump (10). Part of the pulp can also be fed to the mixer (6). The granulated compound fertilizer is lifted by means of an elevator (12) into a screen I (13), from which the fine fraction is returned to a mixer (6) and the rest is cooled in a cooler (14), fractionated in a screen II (15). the fraction is crushed in a crusher (16) and fractionated in a screen II (15).

If trace elements or other plant materials are to be added to the fertilizers being manufactured, they are loaded into hoppers (1).

The determination of nitrogen, phosphorus, potassium, magnesium, sulfur and other elements in bulk compound fertilizers, their physico-chemical properties and their merits are determined by standard fertilizer testing methods.

The compound fertilizer was produced in an industrial plant with a capacity of 10 t / h. The following examples illustrate the dry matter and pulp composition used in the production of bulk compound fertilizers.

Example 1. 18-18-18-2MqO-2S Raw material Composition,% Pulpa Volume, kg / t Ammonium sulfate 20.5 N 25.0 Urea 46.0 N 160.0 Magnesite 85.0 MgO 17.0 Vitriol 98.0 26.0 Water 17.0

245.0

Dry raw materials

Ammonium sulfate 20.5 N 8.2 Urea 46.0 N 60.8 Diamophos (DAP) 18.0 N, 46.0 P ₂ O ₅ 387.0 KCI (MOP) 60.0 K ₂ O 297.0 Wax 2.0

755.0

Total: 1000.0 sample. 25-6-6-2MqO-8S

Raw material Composition,% Pulpa Volume, kg / t Ammonium sulfate 20.5 N 40.0 Urea 46.0 N 200.0 Magnesite 85.0 MgO 22.0 Vitriol 98.0 34.0 Water 21.0

317.0

Dry raw materials

Ammonium sulfate 20.5 N 317.4 Urea 46.0 N 133.2 Diamophos (DAP) 18.0 N, 46.0 P ₂ O ₅ 130.4 KCI (MOP) 60.0 K ₂ O 100.0 Wax 2.0

683.0

Total: 1000.0

Example 3. 27-5-6-2.5MqO-6S Raw material Composition,% Pulpa Volume, kg / t Ammonium sulfate 20.5 N 46.7 Urea 46.0 N 300.0 Magnesite 85 MgO 32.7 Vitriol 98 48.2

Water 31.1

458.7

Dry raw materials

Ammonium sulfate 20.5 N 193.0 Urea 46.0 N 137.7 Diamophos (DAP) 18.0 N, 46.0 P ₂ O ₅ 108.6 KCI (MOP) 60.0 K ₂ O 100.0 Wax 2.0

541.3

Total: 1000.0

Example 4. 32-5-5-2.5MgO-2S

Raw material Composition,% Pulpa Quantity, kg Ammonium sulfate 20.5 N 46.7 Urea 46.0 N 300.0 Magnesite 85.0 MgO 32.7 Vitriol 98.0 48.2 Water 31.1

458.7

Dry raw materials

Ammonium sulfate 20.5 N 26.9 Urea 46.0 N 320.4 Diamophos (DAP) 18.0 N, 46.0 P ₂ O ₅ 108.7 KCI (MOP) 60.0 K ₂ O 83.3 Wax 2.0

541.3

Total: 1000.0

The following technological parameters were maintained during production:

pelleting temperature 35-50 ° C, cooled fertilizer temperature 18-40 ° C, compound fertilizer pellet strength 3.2-4.5 MPa.

hygroscopic humidity of the product 3.2-4.0% (only after production),

1.0-1.5% (after 36 h), product fraction (2-5 mm) not less than 98%.

In order to illustrate and describe the present invention, descriptions of preferred embodiments are set forth above. It is not a complete or limiting invention which seeks to determine the exact form or embodiment thereof, the description above should be understood as more than illustration, not limitation. It will be appreciated that many modifications and variations may be apparent to those skilled in the art, embodiments are selected and described to best explain the principles of the present invention and their best practical application for different embodiments with different modifications suitable for a particular application or embodiment. adaptation, as the quantitative adaptations of this application may vary from case to case. The scope of the invention is intended to be defined by the appended definition and its equivalents, in which all of the foregoing terms have the widest meaning unless otherwise indicated. It will be appreciated that the embodiments described by those skilled in the art may make changes which do not depart from the scope of the present invention as defined in the following definition.

Claims (10)

1. A method of producing bulk compound fertilizers by dry mixing the bulk nitrogen, phosphorus, potassium components in a blender, granulating, fractionating, returning the fine fraction to a blender, wherein the urea, sulfur curing agent is supplied to the granulator to simplify the process and reduce energy consumption. acid and magnesium and ammonium sulphate pulp. 2. The method of claim 1, wherein up to 50% of the hardening slurry can also be fed to the mixer. 3. A process according to claims 1 and 2 wherein the weight ratio of the bulk fertilizer components to the curing slurry is 1: 0.1-0.6, preferably 1: 0.2-0.5. 4. A process according to any one of claims 1-3, wherein the weight ratio of the bulk fertilizer components in the mixer to the returned fine fraction is 1: 0.5-4. 5. A process according to any one of claims 1-4, wherein the curing slurry is obtained in three steps: (a) mixing the urea with concentrated sulfuric acid and diluting with water; (b) mixing the resulting slurry of urea and sulfuric acid with the magnesium component; (c) mixing the resulting slurry of the urea, sulfuric acid, and magnesium component with ammonium sulfate. 6. A process according to any one of claims 1 to 5, wherein the urea is mixed with sulfuric acid and water in step (a) for up to 5 minutes at a weight ratio of urea to sulfuric acid of 1: 0.05-0.2, preferably , 1: 0.1-0.2; and sulfuric acid.water 1: 0.5-1.0, and at a temperature of 45-50 ° C until a suspension density of 1.35-1.39 g / cm ^{3 is} reached and a pH of less than 1.5. 7. A process according to any one of claims 1 to 6, wherein the magnesium component is mixed with the urea and sulfuric acid pulp of step (a) in a weight ratio of urea: MgO: sulfuric acid of 1: 0.05 to 0.2: 0. , 05-0.2, preferably in a weight ratio of 1: 0.09-0.11: 0.09-0.11, maintaining a pulp pH of 3.5-5.5 at 75-85 ° C. 8. A process according to claim 7, wherein in step (b) the pulp is mixed with a magnesium component such as a periclase melt product containing at least 75% MgO and a particle size of no greater than 2 mm. 9. A process according to any one of the preceding claims, wherein in step (c) the slurry of the urea, sulfuric acid, magnesium component is mixed with ammonium sulfate at a temperature of 75-90 ° C at a pH of 4.5-6.5. 10. A process according to any one of the preceding claims, characterized in that the produced product is matured for 24-36 hours.