A preparation method of high-nitrogen acidic phosphate fertilizer

Abstract

The invention discloses a method for preparing high-nitrogen acidic phosphate fertilizer, and relates to the technical field of phosphate fertilizer preparation. Slag acid, raffinate acid and wet phosphoric acid are added to a mixed acid tank to form mixed acid A; wet phosphoric acid and sulfuric acid are used to wash the ammonia-containing tail gas generated in the granulation and drying process, and the obtained washing liquid is recycled and introduced into an underground tank to form slurry B; urea granules are added to the underground tank, and stirred and reacted with slurry B to obtain slurry C; slurry C is pumped into the mixed acid tank, and stirred and mixed with mixed acid A to obtain slurry D; slurry D is pumped into a feed tank, and reacted with ammonia in a pre-neutralization tank / tubular reactor to form a neutralized slurry, and spray ammoniation granulation is performed in a rotary drum ammoniation granulator. After granulation, the particles are dried, screened, cooled and wrapped to obtain a high-nitrogen acidic phosphate fertilizer product, which is suitable for northern agriculture, and a large amount of slag acid and raffinate acid are efficiently utilized, and nutrients such as calcium, magnesium and iron that are necessary or beneficial to crops in the slag acid and raffinate acid are retained. The slow-release property of urate can effectively increase crop yields.

Description

Technical Field

[0001] The invention relates to the technical field of phosphate fertilizer preparation, and in particular to a method for preparing high-nitrogen acidic phosphate fertilizer. Background Art

[0002] Granular diammonium phosphate is the most common and main phosphate fertilizer product on the market. However, diammonium phosphate is an alkaline fertilizer (pH is about 7.5-8.0), which is not suitable for the northern regions where the soil is generally neutral and alkaline. It will also cause high ammonia volatilization losses, reduce the utilization of nitrogen nutrients, and increase environmental pollution. Although monoammonium phosphate is an acidic fertilizer, due to its low nitrogen content, when used as a base / bottom fertilizer, a large amount of nitrogen fertilizer (urea) must be applied at the same time, which increases farmers' labor and costs, resulting in low market acceptance. Innovation not only meets market demand (nitrogen (N) content ≥ 12% and available phosphorus (P 2 O 5 ) content ≥ 38%), and meet the agricultural needs of northern my country (acidic fertilizers suitable for calcareous soils) are important directions for the innovation of phosphate fertilizer products in my country. Patent 107892597A discloses a method for preparing thiophosphate urea fertilizer using raw materials such as phosphoric acid, urea, and ammonium sulfate or / and ammonium bisulfate. Although the product is an acidic fertilizer (pH 2.5-4.0) and the nitrogen content (12-18% N) meets the market demand, the maximum effective phosphorus content of the product is 40%P 2 O 5 , which cannot meet the market demand for phosphorus content greater than 40% P 2 O 5 Patent CN104448325A discloses a method for preparing a high-content slow-release nitrogen and phosphorus fertilizer using phosphorus oxyamide and potassium dihydrogen phosphate. The nitrogen and phosphorus content of the product (20-25% N, 60-75% P 2 O 5 ) can meet the market demand, and the product is neutral / alkaline (pH 6.5-9.0), but the production process is complicated and the cost is high, making it difficult to implement industrialization, and it cannot meet the agricultural needs of northern my country. In addition, with the development of new energy, the demand for refined phosphoric acid has increased dramatically, and a large amount of by-product resources such as slag acid and extract acid will be produced during the production of refined phosphoric acid; in addition to containing a high content of phosphorus, extract acid and slag acid also contain nutrients such as calcium, magnesium, sulfur, silicon, and iron that are beneficial to plant growth. How to consume more and more efficiently utilize by-product resources such as slag acid and extract acid is an important problem facing the transformation and upgrading of my country's phosphate fertilizer industry. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a high-nitrogen acidic phosphate fertilizer, so as to solve the problem that the existing monoammonium phosphate is difficult to meet the market demand due to its low nitrogen content, and the existing method for producing diammonium phosphate by extracting nitrogen from ammonia has a high product pH value and is difficult to meet the needs of alkaline soil.

[0004] In order to solve the above technical problems, the present invention adopts the following technical scheme: a method for preparing high-nitrogen acidic phosphate fertilizer, characterized in that it comprises the following steps:

[0005] S1. Add one or two of the residue acid, the raffinate acid and the wet-process phosphoric acid into the mixed acid tank and stir to form a mixed acid A;

[0006] S2. Use wet phosphoric acid and sulfuric acid to wash and absorb the ammonia-containing tail gas generated in the granulation and drying process, and the washing liquid obtained enters the underground tank to form slurry B;

[0007] S3. Add urea granules to the underground tank and stir with slurry B to obtain slurry C;

[0008] S4. Pump slurry C into the mixed acid tank and mix with mixed acid A by stirring to obtain slurry D;

[0009] S5. The slurry D is pumped into the feed tank, and the slurry pump is transported to the pre-neutralization tank / tubular reactor after the flow rate is controlled by the frequency regulator to react with ammonia to form a neutralized slurry, and then sprayed into the return material of the rotary drum ammoniation granulator for spraying ammoniation granulation. The granulated material is dried, screened, cooled and wrapped to obtain a high-nitrogen acidic phosphate fertilizer product;

[0010] The total nitrogen content of high-nitrogen acidic phosphate fertilizer products is 12-18%, of which the amide peptide nitrogen content is 2.5-10.0%; the effective phosphorus content is 39-42%, the water-soluble phosphorus content is 33-36%; and the pH value is 3.0-5.5.

[0011] A further technical solution is that the P in the slag acid 2 O 5 The content of P in the raffinate is 38-42%. 2 O 5 The content of P in the wet-process phosphoric acid is 40-48%. 2 O 5 The content is 42-54%.

[0012] A further technical solution is that in step S1, the amounts of slag acid, raffinate acid and wet-process phosphoric acid are as follows: 0-50 parts of slag acid, 0-30 parts of raffinate acid and 0-90 parts of wet-process phosphoric acid; 2 O 5 The content is 39-47%, the specific gravity is 1.6-1.7 g / l, the stirring time is controlled at 0.1-0.5 h, and the temperature is controlled at 20-85°C.

[0013] A further technical solution is that the concentration of sulfuric acid in step S2 is 3-10%, and the P in slurry B is 2 O 5 The content is 15-45%, the neutralization degree is 0.2-0.3 mol / mol, the specific gravity is 1.35-1.55 g / l, and the temperature is controlled at 20-70°C.

[0014] A further technical solution is that in step S3, the amount of urea granules added is 5-25% of the total mass of the mixed acid A and the slurry B, the stirring time is 0.5-1h, and the temperature is controlled at 20-60°C.

[0015] A further technical solution is that in step S4, the mass of slurry C is 10-70% of mixed acid A, the stirring time is 0.2-0.5h, and the temperature is controlled at 20-70°C.

[0016] A further technical solution is that the pre-neutralization reactor in step S5 can be a pre-neutralization tank or a tubular reactor, and the degree of neutralization in the reaction with liquid / gas ammonia in the pre-neutralization tank / tubular reactor is controlled at 0.8-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 0.95-1.1 mol / mol.

[0017] Reaction mechanism: sulfuric acid and wet phosphoric acid wash the ammonia-containing tail gas, absorb ammonia to form a slurry containing phosphoric acid, sulfuric acid, monoammonium phosphate and ammonium sulfate, and then enter the underground tank; after urea is added to the underground tank, part of the sulfuric acid and phosphoric acid react with it to obtain complex salts such as urea phosphate and urea sulfate, and their pH values ​​are all below 2; because urea reacts first to produce ureate salts, in the subsequent process, it can slow down the precipitation of cations such as iron and magnesium in the residual acid / slag acid in the mixed acid tank, so that its activity is maintained, thereby retaining the activity of iron, magnesium and other essential or beneficial nutrients for crops to the greatest extent. The mixed slurry reacts with liquid / gas ammonia in the pre-neutralization reactor, and then ammoniation and granulation are obtained to obtain high-nitrogen acidic phosphate fertilizer products.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention overcomes the disadvantage that traditional phosphate fertilizers increase the nitrogen content by increasing the amount of ammonia, which leads to an increase in the pH of the fertilizer, thus becoming an alkaline fertilizer (diammonium phosphate), which does not meet the agricultural needs of northern my country. The product and method provided by the present invention can increase the nitrogen content while still keeping the pH of the fertilizer at a relatively low level, and the fertilizer is still acidic, because the neutralization degree of amino acids in the product is controlled at about 1.0, that is, the pH of the product is about 4; at the same time, with the addition of urea in the underground tank, part of the sulfuric acid and phosphoric acid react with urea to generate urea phosphate and urea sulfate, etc., which are all acidic (pH is below 2).

[0020] 2. Urea can retain nutrients better when added in underground tanks than in mixed acid tanks and return material links. The slag acid / raffinate acid in the mixed acid tank contains multiple cations such as magnesium and iron; urea is equivalent to a precipitant for raffinate acid / slag acid, and the impurity removal rate of iron and aluminum in raffinate acid / slag acid reaches more than 98%, and the impurity removal rate of magnesium reaches more than 90%. Adding urea directly to the mixed acid tank is prone to cause the loss of nutrients necessary or beneficial to crops in the by-product acid. Adding urea to the underground tank to react and generate urate first can effectively avoid or slow down the occurrence of the above problems. The presence of ureate in the form of urate can reduce the production of biuret and nitrogen volatilization loss more than the presence of urea, and retain more amide nitrogen to increase the total nitrogen content of the product.

[0021] 3. The present invention can efficiently utilize by-product resources such as slag acid and raffinate acid, and promote the efficient and comprehensive utilization of phosphorus resources. The present invention not only directly utilizes by-product acid raffinate acid / slag acid resources, but also maximizes the retention of trace nutrients such as calcium, magnesium, iron, silicon, etc. in slag acid / raffinate acid that are beneficial to plants, thereby improving the nutrient utilization efficiency in the by-product acid.

[0022] 4. The nitrogen and phosphorus content of the product obtained by the present invention can not only meet the market demand; at the same time, because the product is acidic, the urea phosphate and urea sulfate contained in the product also have other functions such as slow-release characteristics, which can effectively reduce the volatilization loss of ammonia on the alkaline soil in northern my country, improve the ability of crops to resist environmental stress and the yield and quality of crops. In addition, the existing monoammonium phosphate / diammonium phosphate device can be directly used without the need to melt the urea, the device has low technical transformation investment, low cost, convenient operation, and is also green, low-carbon and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1

[0026] 1. Wet-process phosphoric acid (47.3% P 2 O 5 ) and slag acid (38.5% P 2 O 5 ) was added into the mixed acid tank according to (1:2), stirred for 0.5h, and the temperature was controlled at 30℃. 2 O 5 The content is controlled at about 42%, and the specific gravity is controlled at 1.6 g / l to obtain mixed acid A;

[0027] 2. Use wet phosphoric acid and 5% sulfuric acid to wash the ammonia-containing tail gas generated in the granulation and drying steps. The obtained washing liquid is recovered and passed into the underground tank to form slurry B. The neutralization degree of slurry B is controlled at 0.2 mol / mol, the specific gravity is controlled at 1.45 g / l, and the temperature is controlled at 45°C;

[0028] 3. Add granular urea into the underground tank and slurry B to form mixed slurry C. The mass of urea added accounts for 15% of the total mass of the washing liquid and mixed acid. The stirring time is 0.5h and the temperature is controlled at 40-50℃.

[0029] 4. Pump the mixed slurry C into the mixed acid tank and mix it with the mixed acid A to obtain slurry D. The mass of slurry C added is 50% of the mixed acid A. The stirring time is 0.5h and the temperature is controlled at 50-65°C.

[0030] 5. Pump slurry D into the feed tank, and the slurry pump is controlled by the frequency regulator to measure the flow rate and then transported to the pre-neutralization tank / tubular reactor to react with ammonia to form a neutralized slurry, and then enters the ammoniation granulator for spray granulation; after drying, screening, cooling and packaging, high-nitrogen acidic phosphate fertilizer is formed. The degree of neutralization in the tubular reactor or pre-neutralization tank is controlled at 0.8-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 0.95 mol / mol. The analysis results (average value) of the product high-nitrogen acidic phosphate fertilizer are shown in the following table:

[0031] index Total Nitrogen Ammonium Nitrogen Amide nitrogen Available Phosphorus Water soluble phosphorus Water has pH / 14.43 7.58 6.85 39.01 33.26 85.3％ 4.1

[0032] Note: Water-soluble ratio: water-soluble P 2 O 5 With effective P 2 O 5 mass percentage.

[0033] Example 2

[0034] 1. Wet-process phosphoric acid (46.2% P 2 O 5 ) and slag acid (38.5% P 2 O 5 ) was added into the mixed acid tank at a ratio of (1:2) and stirred for 0.5h. The temperature was controlled at 35℃. 2 O 5 The content is controlled at about 41%, and the specific gravity is controlled at 1.65 g / l to obtain mixed acid A;

[0035] 2. Use wet phosphoric acid and 5% sulfuric acid to wash the ammonia-containing tail gas generated in the granulation and drying steps. The obtained washing liquid is recovered and passed into the underground tank to form slurry B. The neutralization degree of slurry B is controlled at 0.25 mol / mol, the specific gravity is controlled at 1.45 g / l, and the temperature is controlled at 50-60°C;

[0036] 3. Add granular urea into the underground tank and slurry B to form mixed slurry C. The added mass of urea accounts for 10% of the total mass of the washing liquid and the mixed acid. The stirring time is 0.5h and the temperature is controlled at 50-60℃;

[0037] 4. Pump the mixed slurry C into the mixed acid tank and mix it with the mixed acid A to obtain slurry D. The added mass of slurry C is 50% of the mixed acid A. The stirring time is 0.5h and the temperature is controlled at 55-65°C.

[0038] 5. Pump slurry D into the feed tank, and the slurry pump is controlled by the frequency regulator to measure the flow rate and then transported to the pre-neutralization tank / tubular reactor to react with ammonia to form a neutralized slurry, and then enters the ammoniation granulator for spray granulation; after drying, screening, cooling and packaging, it forms a high-nitrogen acidic phosphate fertilizer. The degree of neutralization in the tubular reactor or pre-neutralization tank is controlled at 0.8-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 1.0 mol / mol. The analysis results (average value) of the product high-nitrogen acidic phosphate fertilizer are shown in the following table:

[0039] index Total Nitrogen Ammonium Nitrogen Amide nitrogen Available Phosphorus Water soluble phosphorus Water has pH / 13.29 8.64 4.65 41.22 33.74 81.8％ 5.2

[0040] Example 3

[0041] 1. Wet-process phosphoric acid (45.8% P 2 O 5 ) and raffinate (40.8% P 2 O 5 ) are mixed evenly at a ratio of (1:2) to form mixed acid A and enter the mixed acid tank; stir for 0.5h, and control the temperature at 35℃. 2 O 5 The content is controlled at about 42.5%, and the specific gravity is controlled at 1.7 g / l to obtain mixed acid A;

[0042] 2. Use wet phosphoric acid and 5% sulfuric acid to wash the ammonia-containing tail gas generated in the granulation and drying steps. The obtained washing liquid is recovered and passed into the underground tank to form slurry B. The neutralization degree of slurry B is controlled at 0.25 mol / mol, the specific gravity is controlled at 1.5 g / l, and the temperature is controlled at 50-60°C;

[0043] 3. Add granular urea into the underground tank and slurry B to form mixed slurry C. The added mass of urea accounts for 15% of the total mass of the washing liquid and the mixed acid. The stirring time is 0.5h and the temperature is controlled at 30-45℃.

[0044] 4. Pump the mixed slurry C into the mixed acid tank and mix it with the mixed acid A to obtain slurry D. The added mass of slurry C is 50% of the mixed acid A. The stirring time is 0.5h and the temperature is controlled at 45-55°C.

[0045] 5. Pump slurry D into the feed tank, and the slurry pump is controlled by the frequency regulator to measure the flow rate and then transported to the pre-neutralization tank / tubular reactor to react with ammonia to form a neutralized slurry, and then enters the ammoniation granulator for spray granulation; after drying, screening, cooling and packaging, high-nitrogen acidic phosphate fertilizer is formed. The degree of neutralization in the tubular reactor or pre-neutralization tank is controlled at 0.8-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 1.05 mol / mol. The analysis results (average value) of the product high-nitrogen acidic phosphate fertilizer are shown in the following table:

[0046] index Total Nitrogen Ammonium Nitrogen Amide nitrogen Available Phosphorus Water soluble phosphorus Water has pH / 14.58 7.56 7.02 40.10 35.33 88.1％ 3.8

[0047] Example 4

[0048] 1. Wet-process phosphoric acid (48.3% P 2 O 5 ), slag acid (38.5% P 2 O 5 ) and raffinate (40.8% P 2 O 5 ) are mixed evenly in a ratio of (4:3:3) to form mixed acid A and enter the mixed acid tank;

[0049] 2. Use wet phosphoric acid and 5% sulfuric acid to wash the ammonia-containing tail gas generated in the granulation and drying steps. The obtained washing liquid is recovered and passed into the underground tank to form slurry B. The neutralization degree of slurry B is controlled at 0.3 mol / mol, the specific gravity is controlled at 1.40-1.45 g / l, and the temperature is controlled at 55-60°C;

[0050] 3. Add granular urea into the underground tank and slurry B to form mixed slurry C. The added mass of urea accounts for 15% of the total mass of the washing liquid and the mixed acid. The stirring time is 0.5h and the temperature is controlled at 50-55℃.

[0051] 4. Pump the mixed slurry C into the mixed acid tank and mix it with the mixed acid A to obtain slurry D. The added mass of slurry C is 50% of the mixed acid A. The stirring time is 0.5h and the temperature is controlled at 55-60°C.

[0052] 5. Pump slurry D into the feed tank, and the slurry pump is controlled by the frequency regulator to measure the flow and then transported to the pre-neutralization tank / tubular reactor to react with ammonia to form a neutralized slurry, and then enters the ammoniation granulator for spray granulation; after drying, screening, cooling and packaging, it forms a high-nitrogen acidic phosphate fertilizer. The degree of neutralization in the tubular reactor or pre-neutralization tank is controlled at 0.85-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 1.1 mol / mol. The analysis results of the product high-nitrogen acidic phosphate fertilizer are shown in the following table:

[0053] index Total Nitrogen Ammonium Nitrogen Amide nitrogen Available Phosphorus Water soluble phosphorus Water has Effective Magnesium Available Iron Effective aluminum pH / 14.31 7.38 6.93 40.35 36.02 89.3％ 3.37 2.16 2.45 4.2

[0054] Comparative Example 1

[0055] 1. Wet-process phosphoric acid (48.3% P 2 O 5 ), slag acid (38.5% P 2 O 5 ) and raffinate (40.8% P 2 O 5 ) are mixed evenly in a ratio of (4:3:3) to form mixed acid A and enter the mixed acid tank;

[0056] 2. Add granular urea into the mixed acid tank to form mixed slurry B with mixed acid A; the mass of urea added accounts for 15% of the total mass of the washing liquid and the mixed acid, the stirring time is 0.5 to 2 hours, and the temperature is 60 to 80°C;

[0057] 4. Put the washing liquid (35%P 2 O 5 ) is pumped into the mixed acid tank, and mixed with the mixed slurry B in the mixed acid tank by stirring to obtain slurry C, the stirring time is 0.5h, and the temperature is 55-65°C;

[0058] 5. Pump slurry C into the feed tank, and the slurry pump is controlled by the frequency regulator to measure the flow rate and then transported to the pre-neutralization tank / tubular reactor to react with ammonia to form a neutralized slurry, and then enters the ammoniation granulator for spray granulation; after drying, screening, cooling and packaging, it forms a high-nitrogen acidic phosphate fertilizer. The degree of neutralization in the pre-neutralization tank with ammonia is controlled at 0.8-0.9 mol / mol; the degree of neutralization in the ammoniation granulator is controlled at 0.95-1.1 mol / mol. The analysis results of the product high-nitrogen acidic phosphate fertilizer are shown in the following table. It can be seen that compared with adding urea to the washing liquid, the effective nutrient content of magnesium, iron and aluminum in the fertilizer is significantly reduced when urea is added to the mixed acid tank.

[0059] index Total Nitrogen Ammonium Nitrogen Amide nitrogen Available Phosphorus Water soluble phosphorus Water has Effective Magnesium Available Iron Effective aluminum pH / 14.28 12.74 1.54 40.13 35.75 89.1％ 0.83 0.29 0.34 5.7

[0060] Although the present invention is described herein with reference to a number of illustrative embodiments of the present invention, it will be appreciated that those skilled in the art may devise many other modifications and implementations that fall within the scope of the principles disclosed herein. More specifically, within the scope of the present disclosure, drawings, and claims, a variety of variations and modifications may be made to the components or layout of the subject combination arrangement. In addition to variations and modifications made to the components or layout, other uses will also be apparent to those skilled in the art.

Claims

1. A method for preparing a high-nitrogen acidic phosphate fertilizer, characterized in that The steps include: S1. Add one or two of the residue acid and the raffinate acid and wet-process phosphoric acid into a mixed acid tank and stir to form mixed acid A; the P2O5 content of the mixed acid A is 39-47%, the stirring time is 0.1-0.5 h, the specific gravity is 1.6-1.7 g / l, and the temperature is controlled at 20-85°C; S2. The ammonia-containing tail gas generated in the granulation and drying steps is washed and absorbed using wet phosphoric acid and sulfuric acid, and the washing liquid obtained enters the underground tank to form slurry B; the concentration of sulfuric acid used in step S2 is 3-10%, the content of P2O5 in slurry B is 15-45%, the degree of neutralization is 0.2-0.3 mol / mol, the specific gravity is 1.35-1.55 g / l, and the temperature is controlled at 20-70°C; S3. Add urea granules to the underground tank and stir with slurry B to obtain slurry C; in step S3, the amount of urea granules added is 5 to 25% of the total mass of mixed acid A and slurry B, the stirring time is 0.5 to 1 h, and the temperature is controlled at 20 to 60 ° C; S4. Pump slurry C into the mixed acid tank and mix with mixed acid A by stirring to obtain slurry D; S5. The slurry D is pumped into the feed tank, and the slurry pump is transported to the pre-neutralization tank / tubular reactor after the flow rate is controlled by the frequency regulator to react with ammonia to form a neutralized slurry, and then sprayed into the return material of the rotary drum ammoniation granulator for spraying ammoniation granulation. The granulated material is dried, screened, cooled and wrapped to obtain a high-nitrogen acidic phosphate fertilizer product; The total nitrogen content of high-nitrogen acidic phosphate fertilizer products is 12-18%, of which the amide peptide nitrogen content is 2.5-10.0%; the effective phosphorus content is 39-42%, of which the water-soluble phosphorus content is 33-36%; the pH value is 3.0-5.5; In the step S4, the mass of the slurry C is 10-70% of the mixed acid A, the stirring time is 0.2-0.5 h, and the temperature is controlled at 20-70° C.; in the step S5, the degree of neutralization in the reaction with ammonia in the tubular reactor or the pre-neutralization tank is controlled at 0.8-0.9 mol / mol; and the degree of neutralization in the ammoniation granulator is controlled at 0.95-1.1 mol / mol.

2. The method for preparing a high-nitrogen acidic phosphate fertilizer according to claim 1, wherein: The content of P2O5 in the slag acid is 38-42%, the content of P2O5 in the raffinate acid is 40-48%, and the content of P2O5 in the wet-process phosphoric acid is 42-54%.

3. The method for preparing a high-nitrogen acidic phosphate fertilizer according to claim 1, wherein: In the step S1, the amounts of slag acid, raffinate acid and phosphoric acid are as follows by mass: 0-50 parts of slag acid, 0-30 parts of raffinate acid and 0-90 parts of wet-process phosphoric acid.

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