EA020435B1 - Method for producing phosphoric fertilizer - Google Patents

Abstract

The invention relates to manufacture of phosphoric fertilizers widely used in agriculture. A method of producing phosphoric fertilizer comprises mixing phosphoric acid heated to 75-85°C of concentration 48-50% POwith calcium-containing feedstock and a recycle in a mixer, granulation and mixture ripening, drying to residual moisture of 1-3% and product classification, wherein defecate with 4-15% moisture is used as the calcium-containing feedstock, absorption solutions are introduced in the mixer maintaining the ratio of the absorption solution consumption to the defecate within 0.15-0.30, and the mixing is carried out to mass ratio CaO/POin the mixture within (0.45-0.88):1. The method provides to manufacture phosphoric fertilizer of prolonged action, as well as to regulate content of citric-soluble and water-soluble phosphate and their ratio in the product with minimum presence of free acidity (less than 1.0%).

Description

The invention relates to the production of phosphate fertilizers widely used in agriculture.

A known method of producing phosphate fertilizer - dicalcium phosphate, comprising reacting a calcium-containing compound with phosphoric acid at a concentration of 30-40% P ₂ O ₅ at 80-90 ° C, followed by separation of the product by filtration, washing and drying, while taking calcium propionate as a calcium-containing compound molar ratio with phosphoric acid (0.460.81): 1. The method allows to increase the yield of the target product and reduce the duration of the process [Auth. No. 1213010, class C 05B 3/00, C 01B 25/32, 1984].

The disadvantage of this method is the use of calcium propionate as a calcium-containing compound, a deficient type of raw material.

A known method of producing phosphate fertilizer by mixing poor phosphate raw materials with phosphoric or its mixture with sulfuric acid and retur, granulation of the product and subsequent ripening and drying of the product. The phosphorus raw material is pre-moistened to a moisture content of 6-9%, then mixed with acid until a calcium monophosphate: calcium diphosphate ratio of 1-4 is obtained in the pulp, and then retur is added in an amount necessary to achieve a mixture moisture of 7-11%. At the mixing stage, trace elements are introduced into the reaction mass. The method allows to obtain fertilizers of prolonged action with increased strength of the granules and a certain ratio of lemon-soluble and water-soluble phosphates [RF patent No. 2142927, class C 05B 3/00, C05B11 / 00, C05B1 / 02, 1999].

The main disadvantage of this method is the low content of dicalcium phosphate in the product, i.e. the resulting product has a reduced prolonging effect. The disadvantage of this method is the low degree of decomposition of calcium-containing phosphate raw materials, the presence of free phosphoric acid in the finished product (from 1 to 7%). The content of free acidity is significant for a product with a high content of water-soluble phosphates, and upon receipt of a product of prolonged action, i.e. with a high content of lemon-soluble phosphates, the degree of decomposition of raw materials decreases sharply. The addition of sulfuric acid to increase the degree of decomposition of the raw material leads to a decrease in nutrient content due to an increase in the presence of ballast - calcium sulfate in the product. The presence of free acidity impairs the physicochemical properties of the product, the agrochemical effectiveness of the fertilizer.

The closest to the described by the technical nature and the achieved result is a known method for producing phosphate fertilizer - fertilizer precipitate, including mixing phosphoric acid at a concentration of 48-50% P ₂ O ₅ with a calcium-containing reagent and retur in the mixer, granulating and maturing the mixture, drying to achieve residual humidity 1-3% and product classification. As a calcium-containing reagent, limestone or chalk, which is pre-crushed, is used. Before mixing, phosphoric acid is heated to a temperature of 8085 ° C, the mass ratio (m.s.) of CaO: P ₂ O ₅ in the reaction mass is 0.7-0.8. The method allows to obtain phosphorus fertilizer - fertilizer precipitate containing 45.7% P2O5total, 45% P2O5citr.

The disadvantage of this method is the need for preliminary grinding of calcium-containing raw materials, as well as the cost of the product due to the use of limestone and / or chalk. The disadvantage of this method is the presence of free acidity in the product, as well as the inability to control the degree of prolongation of the resulting product due to insufficient chemical activity of calcium-containing raw materials.

We have set the task to create a method for producing sustained-release phosphorus fertilizer with the ability to control the content of lemon-soluble and water-soluble phosphates and their ratio, a product with a minimum content of free acidity (less than 1.0%).

The goal is solved in the proposed method for the production of phosphorus fertilizer, comprising mixing a concentration of 48-50% P2O5 pre-heated to 75-85 ° C with calcium-containing raw materials and retur in a mixer to obtain a mixture, granulating and maturing the mixture, drying to a residual moisture content of 1- 3% and the classification of the product, and the defect with a moisture content of 5-20% is taken as a calcium-containing raw material, and the mixture is mixed until the mass ratio of CaO / P ₂ O ₅ in the mixture is within the range of (0.45-0.88): 1.

Defecate is a by-product of sugar beet production and is formed during the purification of beet juice. The yield of defecate is about 10% of the weight of the processed beets, the stocks of defecate are millions of tons. Defecate contains the following substances, wt.%: Р2О5 - 0.51.7, sugar up to 2, pectin substances 1.0-1.7, nitrogen-free organic substances up to 9.5, nitrogenous organic substances up to 5.9, magnesium 1-2,4, mineral elements (B, 8, Mn, Co, etc.) to 1.2, calcium carbonate CaCO3 55-60, moisture 5-20%. Defecate has a significant neutralizing ability and a fine particle size distribution that does not require additional grinding. Due to the presence of valuable trace elements, such as boron, manganese, cobalt, as well as humic organic substances, phosphorus and nitrogen, defecate is an effective calcium-containing reagent and is superior to conventional calcareous raw materials.

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The essence of the method is as follows. The main components of the phosphate fertilizer obtained by mixing defecate and phosphoric acid are water-soluble monocalcium phosphate (MCF) Ca (H ₂ PO ₄ ) ₂ and lemon-soluble dicalcium phosphate (DCF) CaNRO ₄ . Phosphorus fertilizer containing lemon-soluble DCF has a prolonged effect. The phosphorus fertilizer production technology is aimed at creating conditions for regulating the content of phosphates in lemon and water-soluble forms in the product when reaching the maximum interaction of phosphoric acid and defecate (calcium carbonate CaCO ₃ as part of the defecate) to produce fertilizer with a minimum content of free acidity (less than 1.0 %).

When defecate and phosphoric acid are mixed, the following reactions occur:

CaCO ₃ + 2H ₃ PO ₄ = Ca (H ₂ PO _{4) 2} + CO ₂ + H ₂ O + CaCO H ₃ PO ₄ = CaHPO ₄ + CO ₂ + H ₂ O

Due to the high neutralizing activity of the defecate upon reaching ms. CaO / P ₂ O ₅ in a 0.45: 1 mixture, the neutralization reaction of phosphoric acid proceeds completely to form mainly MKF. With a decrease in defecate consumption below m.s. CaO / P ₂ O ₅ 0.45: 1, the resulting fertilizer cakes due to the presence of free phosphoric acid, and the product also has a low degree of prolongation. With an increase in defecate consumption above m.s. CaO / P ₂ O ₅ 0.88: 1 product granules have low strength. Changing the costs of the starting reagents: defecate and phosphoric acid within m.s. CaO / P ₂ O ₅ , in the reaction mixture (0.45-0.88): 1, the content of MKF, DKF and their ratio in the finished product are regulated. The composition of the lemon-soluble form of phosphates (P ₂ O ₅ lim), extracted with an aqueous solution of citric acid according to GOST 20851.2-75 section 3, also contains a water-soluble form of phosphates (P ₂ O ₅ water). In this regard, the ratio C = (P ₂ About ₅ total - P ₂ About ₅ water) / P ₂ About ₅ total more accurately reflects the degree of prolongation of phosphorus fertilizer.

Maintaining the moisture content of the initial defect in the range of 4-15% provides optimal conditions for mixing the reagents and conducting the process with obtaining a mobile reaction mass and achieving a high degree of decomposition of calcium carbonate. With an increase in the moisture content of the defecate above 15%, transportation and dosage of the defecate is difficult, the process of granulation is disrupted due to the increased moisture content in the reaction mass. With a decrease in humidity below 4%, the reaction mass is not sufficiently mobile, the mixing conditions of the starting reagents worsen, and the degree of decomposition of calcium carbonate decreases.

Maintaining the ratio of the flow rate of the absorption solution and the defecate in the range 0.15-0.30 also provides optimal conditions for mixing the reagents and granulation. With an increase in the flow rate of the absorption solution above the 0.30 ratio, granulation is violated, due to the high humidity of the reaction mass, estrus clogs after the mixer. A decrease in the consumption of the absorption solution below a ratio of 0.15 leads to a decrease in the mobility of the reaction mass, the degree of decomposition of calcium carbonate, and the appearance of free acidity in the finished product.

The method is illustrated by the following examples.

The appropriateness of the selected limits of the process indicators is also presented in table. 2.

Example 1. 500 kg of defecate containing 56% CaCO ₃ and 12% moisture, served in the mixer. 700 kg of phosphoric acid at a concentration of 50% P ₂ O ₅ , 75 kg of absorption solutions, and 500 kg of retur are introduced into the mixer. The ratio of the costs of the absorption solution and the defect is 0.15. The mixing process is carried out to obtain a granular mixture, which is then sent for ripening and drying. Drying is carried out in a drying drum until a residual moisture content of 2% is achieved. The flue gases from the mixing, ripening and drying units are sent to the wet cleaning system. Absorption solutions containing product dust are sent to a mixer. The dried product is subjected to classification, a fraction with a granule size of 1-4 mm is taken as the finished product. A fraction with a granule size of more than 5 mm is crushed and, together with a product fraction with a granule size of less than 1 mm, is returned to the mixing step as a retura. The result is a product of the composition: P ₂ About ₅ total - 40.2%, P ₂ About ₅ assimilation - 40.1%, P ₂ About ₅ lim - 39.2%, P ₂ About ₅ water - 30.8%, moisture 2%, free acidity - 1.0%, m.s. CaO / P ₂ O ₅ - 0.45: 1, ratio C = 0.23. The product has a prolonging effect.

Agrochemical tests of the effectiveness of phosphorus fertilizers were carried out on sugar beets. The composition of phosphorus fertilizer: P ₂ About ₅ total - 33.7%, P ₂ About ₅ assimilation - 33.6%, P ₂ About ₅ lim - 33.5%, P ₂ About ₅ water - 13.5%, moisture 2 %, free acidity is absent, m.s. CaO / P ₂ O ₅ - 0.67: 1, ratio C = 0.60. As a comparative fertilizer sample, granular double superphosphate was used according to GOST 1630680, containing 48.5% P ₂ O ₅ usb, 2.5% free acidity and 3% moisture. The results of agrochemical tests are presented in table. one.

The effect of mineral fertilizers on sugar beet productivity.

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Table 1

Options Dose fertilizers Harvest c / ha Sugar content % Collection Sahara, c / ha Increase the harvest c / ha % The control (without fertilizers) 223 16.1 35.9 Superphosphate double P60 245 16.1 39,4 22 9.9 Phosphoric fertilizer P60 248 16,2 40,2 25 11.2

The results of experiments on the production of phosphate fertilizers based on defecate and phosphoric acid.

Table 2

Indicators Experiences one 2 3 4 5 6 7 8 nine 10 eleven 12 thirteen Loading Defecate consumption, g. fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty EPC consumption, g. 75 70 60 55 fifty 40 37.5 35 thirty fifty fifty fifty fifty Absorption rate solution, g 7.5 7.5 10 fifteen fifteen fifteen fifteen fifteen fifteen 5 twenty fifteen fifteen Reture consumption, g fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty fifty Defect humidity,% 10 10 10 10 10 10 10 10 10 10 10 3 twenty The correlation costs abs.rr / defecate 0.15 0.15 0.20 0.30 0.30 0.30 0.30 0.30 0.30 0.10 0.40 0.30 0.30 Product P2O; Total,% 43.0 40,2 39.6 38.5 37.3 34.6 32,2 30.8 28.3 37,4 37,2 P2O5LNM,% 41.1 39.2 37.5 36.7 36.1 34.2 31.7 29.4 28.1 36.0 36.1 P2O5WATER,% 38.1 30.8 23.3 19.5 13.5 11.1 7.2 4.0 3.0 14.5 14.5 Moisture% 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Freedom, acidity,% 2,8 1, about 0.6 from OTC OTC OTC OTC OTC 2,3 2,5 M.S. CaO / P ₂ O ₅ 0.40 0.45 0.52 0.58 0.66 0.70 0.82 0.88 0.90 Ratio C it 0.23 0.41 0.49 0.64 0.68 0.78 0.87 0.93 Stat. strength, MPa 1,6 1,5 1,5 1,0 0.8 0.6 0.4 Note Product caking is Product scattering is Product caking is The estrus clogs mixer no granulation Product caking is Clogs up estrus mixer. not granulation

The conditions for the process of obtaining phosphorus fertilizer:

the composition of the defect is CaCO ₃ = 57%, the granule size is less than 1 mm, the composition of EPA is 50% P ₂ O ₅ , and the temperature of EPA is 75 ° C.

The duration of mixing the reagents in the mixer is 3 minutes, ripening 30 minutes, drying at a temperature of 105 ° C.

Claims (1)

A method of producing phosphoric fertilizer, comprising mixing a concentration of 48-50% P ₂ O ₅ preheated to 7585 ° C with calcium-containing raw materials and retur in a mixer, granulating and ripening the mixture, drying to a residual moisture content of 1-3% and product classification, different the fact that as a calcium-containing raw material, a defect is taken with a moisture content of 4-15%, absorption solutions are introduced into the mixer, maintaining the ratio of the flow rate of the absorption solution to the defecate in the range 0.15-0.30, and mixing is carried out to the mass ratio Ca O / R ₂ O ₅ in the mixture in the range of (0.45-0.88): 1.