Industrial preparation method of instant monopotassium phosphate

Abstract

The invention relates to the technical field of potassium phosphate preparation, and discloses an industrial preparation method of instant monopotassium phosphate, which comprises the following steps: transforming idle washing powder production equipment into an equipment system for preparing the instant monopotassium phosphate; preparing a potassium hydroxide solution with the concentration of 20-90% in an alkali dissolving tank; the method comprises the following steps: mixing a phosphoric acid solution with a potassium hydroxide solution for reaction to obtain a neutralization solution, and atomizing the neutralization solution into liquid drops through a pressure atomization system at the upper part of a drying tower. By breaking through waste heat recovery and utilization in industrial production, reform of a production process technology and establishment of an LTE (Long Term Evolution) technology, one-step puffing drying of a neutralization solution obtained by reaction of wet-process phosphoric acid and potassium hydroxide in a powder spraying tower is realized, and hollow, loose and porous KDP201 particles are formed.

Description

Technical Field

[0001] The invention relates to the technical field of potassium phosphate preparation, and in particular to an industrial preparation method of instant potassium dihydrogen phosphate. Background Art

[0002] Potassium dihydrogen phosphate (chemical formula: KH2PO4) is a colorless or white shiny orthorhombic crystal (slightly colored for agricultural use) with a relative density of 2.338 g·cm -3 , melting point is 252 ℃, easily soluble in water, easy to absorb moisture and deliquesce, slightly soluble in alcohol, and the aqueous solution is weakly acidic. Potassium dihydrogen phosphate plays a vital role in the phosphate industry and is widely used in many fields. Especially in recent years, with the rapid development of water-soluble fertilizers and the in-depth promotion of the technology of applying potassium dihydrogen phosphate in excess of normal amounts to crops, the demand for potassium dihydrogen phosphate in the fertilizer industry has continued to grow; with the rapid development of the pharmaceutical, food and fish farming industries, the use of potassium dihydrogen phosphate has also increased, and higher standards have been put forward for its quality. In summary, with the continuous development of various industries, the demand for potassium dihydrogen phosphate is increasing, and the requirements for its quality and benefits are also increasing.

[0003] Aerial spraying of pesticides and fertilizers has the remarkable characteristics of high efficiency, precision, convenience and environmental protection. Therefore, the pesticides and fertilizers or additional additives have the requirements of safety, high efficiency, fast solubility, stability and high compatibility. Potassium dihydrogen phosphate is an excellent fertilizer variety promoted by the Ministry of Agriculture and Rural Affairs. It is mainly sold in the form of crystal and ground powder. When used in aerial spraying, both need to be dissolved in advance and configured into a solution of a certain concentration. This process is relatively cumbersome and requires a certain amount of time and skills to ensure the accuracy and uniformity of the configuration. The crystal type dissolves relatively slowly and is prone to incomplete dissolution. Although the ground powder dosage form has increased the dissolution rate to a certain extent compared to the crystal type, it is easily affected by factors such as uneven particle size and insufficient stirring, resulting in failure to disperse quickly and evenly, forming a small ball or agglomerate. In the process of aerial spraying, due to the small amount of water used, if the potassium dihydrogen phosphate is not completely dissolved, it may clog the nozzle, affect the efficiency and effect of aerial spraying, and even damage the machine. During aerial spraying, it is usually necessary to compound pesticides and fertilizers to achieve the effect of applying pesticides and fertilizers simultaneously and improve work efficiency. However, when crystalline and ground powder formulations are compounded with other pesticides, there are compatibility issues or additional processing steps are required to ensure the stability and effectiveness of the compounded solution.

[0004] In summary, the convenience of use, dissolution speed and compatibility of potassium dihydrogen phosphate in crystalline and ground powder form do not meet the requirements of aerial spraying. Therefore, it is particularly important to research and develop a fast-dissolving, convenient, efficient, highly compounded, high-quality and green potassium dihydrogen phosphate production process.

[0005] Phosphoric acid for preparing potassium dihydrogen phosphate is divided into thermal acid and wet acid. The products produced by thermal acid are of high purity and high cost; although the products produced by wet acid are of low cost, there are problems such as complex raw material composition and difficulty in separation and purification. Therefore, most industrial preparation methods of potassium dihydrogen phosphate use thermal phosphoric acid, which leads to high production costs.

[0006] So far, there is no documented record on the transformation of idle laundry detergent equipment to produce expanded instant potassium dihydrogen phosphate (hereinafter referred to as KDP201) by directly using the neutralization solution synthesized from wet-process phosphoric acid and potassium hydroxide and using LTE in a powder spraying tower for one-step expansion and drying. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of the prior art and to propose an industrial preparation method of instant potassium dihydrogen phosphate.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] An industrial preparation method of instant potassium dihydrogen phosphate comprises the following steps:

[0010] Step 1: Transform the idle washing powder production equipment into an equipment system for preparing instant potassium dihydrogen phosphate;

[0011] Step 2: Prepare a potassium hydroxide solution with a concentration of 20% to 90% in an alkali dissolving tank;

[0012] Step 3: Mix 20 to 85 parts of a phosphoric acid solution having a concentration by mass fraction of 20% to 85% with 10 to 55 parts of the potassium hydroxide solution obtained in step 2 to obtain a neutralized solution;

[0013] Step 4: Prepare hot air with a temperature of 150-320°C in the combustion furnace, adjust the total air volume according to the drying load, and then send the hot air into the drying tower;

[0014] Step 5: When the outlet temperature of the drying tower reaches 100°C, the neutralized liquid obtained in step 3 is atomized into droplets with a particle size of about 50 μm through the pressure atomization system at the top of the drying tower. The droplets exchange heat with the hot air sent from the bottom of the drying tower, and start puffing and granulation. The temperature and air volume of the hot air entering the tower are adjusted according to the temperature change in the tower, the dryness and humidity of the powder, and the apparent specific gravity to achieve the best drying effect;

[0015] Step 6: When the top of the drying tower reaches the expansion instant condition (LTE), the powder spraying production begins. During the process, the parameters such as atomization pressure, tower top temperature, tower top negative pressure, tower bottom temperature, etc. are precisely controlled. After powder spraying, the hot air inlet temperature and air volume are adjusted according to the temperature change in the tower, the dryness and humidity of the powder and the apparent specific gravity. The LTE process is used to evaporate the water inside the neutralization liquid rapidly, and the sudden release of pressure causes the volume of the material to expand rapidly, forming hollow, loose, porous and bubble-structured expanded particles; the expanded material produced by powder spraying naturally settles at the bottom of the drying tower, and after one screening, air conveying, and two screenings, it finally enters the finished product warehouse.

[0016] Preferably, in step 3, the phosphoric acid used includes fertilizer grade phosphoric acid, industrial grade phosphoric acid, and food grade phosphoric acid.

[0017] Preferably, in step 3, the neutralization solution temperature is controlled to be 80-100° C., the pH value is controlled to be 4.0-5.0, and the concentration is controlled to be 35%-50%.

[0018] Preferably, in step 4, the method for preparing hot air is: fuel is burned in a combustion furnace and then mixed with cold air; the straight cylinder size of the drying tower is Φ7000 mm×40000 mm.

[0019] Preferably, the fuel comprises phosphorus furnace tail gas, the phosphorus furnace tail gas is yellow phosphorus exhaust gas, and the carbon monoxide content in the phosphorus furnace carbon tail gas is greater than 85%.

[0020] Preferably, in step 5, when the outlet temperature of the drying tower reaches 100°C, the neutralization liquid is pressurized and atomized by a pressure atomization system, and the atomization pressure is controlled at 0.6-1.0 MPa.

[0021] Preferably, in step 6, when the tower top reaches the expansion quick dissolving condition (LTE), the tower top temperature is maintained at 90~200°C and the negative pressure is maintained at -80~-130 Pa.

[0022] Preferably, the finished product obtained in step 6 has a phosphorus pentoxide content (on a dry basis) ≥ 52%, a potassium oxide content (on a dry basis) ≥ 34%, and a potassium dihydrogen phosphate content (on a dry basis) ≥ 99%.

[0023] Preferably, the transformation and transformation method in step 1 is specifically as follows: adding a phosphoric acid storage tank, an alkali dissolving tank, and a batching tank on the basis of an idle washing powder production device; improving the slurry conveying pipeline of the washing powder production device, optimizing the material filtration system and the thermal insulation performance of the tank and pipeline; adding a liquid spraying system to the top of the powder spraying tower in the washing powder production device, adjusting the distribution of the spray gun and the nozzle model, and conveying the solution to the powder spraying tower through a special solution pump for atomization drying and molding; using a combustion furnace to provide hot air, and adjusting the temperature and air volume of the powder spraying tower; providing primary screening, air delivery, and secondary screening equipment to convey the expanded particles to the finished product warehouse.

[0024] Preferably, the powder spraying tower is the drying tower in steps 4 to 6 above.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention realizes the industrialization of instant potassium dihydrogen phosphate (KDP201) by low-cost transformation of idle washing powder devices. By breaking through the waste heat recovery and utilization in industrial production, the reform of production process technology and the creation of LTE technology, the neutralized liquid of the reaction of wet phosphoric acid and potassium hydroxide is expanded and dried in a powder spraying tower in one step to form hollow, loose and porous KDP201 particles.

[0027] 2. The present invention significantly reduces production costs by transforming the washing powder production device to produce KDP201, which is conducive to large-scale production; the phosphorus furnace tail gas is used as fuel to save the use of natural gas or hydrogen, realize industrial tail gas recycling and low-cost equipment transformation, and actively respond to the national call for the renewal and transformation of old chemical plants.

[0028] 3. The present invention ensures that the purity of KDP201 (based on potassium dihydrogen phosphate dry basis) can reach more than 99% by precisely controlling the content of K and P in the neutralization solution, and the product quality is better than the current industrial-grade premium products. The production process does not require the addition of additives, which ensures the main content and appearance quality of the product and achieves strong production continuity.

[0029] 4. Compared with other expansion technologies, LTE technology is more efficient and suitable for modified washing powder devices. It maintains the original quality of the neutralization liquid and avoids quality loss caused by high temperature; the shorter drying time reduces the material residence time and reduces the risk of quality loss; the equipment modification is simple, without the need for complex heating and high-pressure systems, further reducing the cost of equipment modification.

[0030] 5. LTE technology rapidly evaporates the water in the neutralizing liquid, and the sudden release of pressure causes the volume of the material to expand sharply, resulting in changes in the physical structure. Under a microscope, it looks like tiny powder particles with hollow interior, bubbles, porosity, and uneven surface. The porous, bubbled, and hollow structure increases the specific surface area of ​​KDP201, which is 3 times that of the crystal type and 1.5 times that of the ground powder type. This increases the solid-liquid interface area, allowing the solvent to quickly penetrate and fully contact the material, thereby achieving rapid dissolution. The porous and bubble structure, as a catalyst for dissolution, can accommodate water molecules and promote the swelling of particles. As the particles absorb water and expand, the bubbles are compressed, the internal pressure of the particles increases, and the particles are forced to rupture and further accelerate dissolution. The density of KDP201 is about 0.5 times that of the crystal type. The low density results in KDP201 having a superior suspension and self-dispersion ability in water than the crystal type, further increasing the contact surface between the particles and water and accelerating the dissolution rate. When the particles absorb water, the gas in the bubbles compresses and generates pressure, which helps the particles to break and further dissolve; at the same time, the dissolved gas in the liquid will also dissolve into the air in the particles under this pressure, resulting in rapid gas diffusion and liquid absorption inside the particles, and the particles will expand and dissolve instantly. In summary, the unique physical structure of KDP201 enables the rapid dissolution of potassium dihydrogen phosphate.

[0031] 6. In the free sedimentation dilution 300 times dissolution experiment, KDP201 completely dissolved in water during the sinking process (dissolution time 3s), the ground powder dosage form partially dissolved and partially sank to the bottom (dissolution time 13s), while the crystal form completely sank to the bottom and required stirring for about 1min 45s to completely dissolve, thus showing the significant fast-dissolving characteristics of KDP201.

[0032] 7. The one-month stability experiment showed that KDP201 had the best stability and was not easy to agglomerate; the crystal type had the second best stability and slightly agglomerated; the ground powder type had the worst stability and was more severely agglomerated, further proving the excellent stability of KDP201 during storage and use.

[0033] 8. The product prepared by the present invention has the advantages of fast dissolution speed, convenient use, high purity, low apparent specific gravity, good stability, and is conducive to the development of derivative products. It does not need to be stirred and configured in advance, and can be used immediately after being put into use. It can be compounded with high-concentration agents and used immediately after being prepared, which makes up for the shortcomings of existing potassium dihydrogen phosphate products in applications such as aerial spraying and agricultural modernization. It can not only improve the efficiency and utilization rate of fertilizers, but also realize the simultaneous application of fertilizers and drugs, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention provides a process flow chart of an industrial preparation method of instant potassium dihydrogen phosphate. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] Example 1: 5.59 t (69.87 parts) of 20% potassium hydroxide solution was pumped into the batching pot from the alkali dissolving tank, the stirring device was started, and then 2.26 t (28.26 parts) of 85% phosphoric acid solution was accurately pumped in for neutralization, and stirred evenly to prepare a total solid content of 38%, a nitrogen-potassium-phosphorus complex of 0-52-34, and a temperature of 92°C. The reaction principle is as follows:

[0037] H3PO4 + KOH → KH2PO4 + H2O

[0038] The yellow phosphorus exhaust gas with a carbon monoxide content of ≥85% is used as fuel, and the dry clean hot air at about 180°C is prepared by combustion in a hot air furnace, and then introduced into a Φ7000 mm×40000 mm tower from the bottom of the drying tower.

[0039] The pre-configured neutralizing liquid enters the drying tower in six ways through the matching atomization system, ensuring that the angle between each atomizer and the center of the circle is equal, and the angle between adjacent atomizers is 60°. The uniformly atomized droplets undergo countercurrent heat exchange with the dry air constrained by a predetermined ascending path. During the process, the droplets absorb heat and evaporate part of the liquid, forming a surface layer that is semi-permeable to the air flow on the surface. As the temperature of the droplets increases, the steam generated inside moves to the surface of the droplets through the fine pores of the surface layer under the action of capillaries, forming gaps, and when the solvent is completely evaporated, a puffed solid particle material rich in cavities is obtained.

[0040] Most of the dried products are collected at the bottom of the drying tower under the action of gravity. A small amount of fine particles leave the drying tower together with the tail gas, and 99% are separated in the secondary cyclone separator, collected and recycled to the wind lift system through pipelines. The wind lift system transports the products collected from the bottom of the drying tower and the tail gas system to the screening device, removes the part with excessive particles, and enters the finished product silo for packaging as required.

[0041] The vacuum negative pressure in the drying tower is controlled by the tail gas fan and maintained at -80~100 Pa; the tail gas fan capacity is 70000m 3 / h, which is mainly used to discharge the tail gas from the drying tower and separator. The tail gas is purified by the dust removal system before being discharged.

[0042] Example 2: Example 1 was repeated with the following differences: 2.68 t (33.54 parts) of deionized water was pumped into the batching pot, 0.98 t (12.25 parts) of 90% high-quality solid potassium hydroxide was added through the feeding tank, the stirring device was started to fully dissolve, and then 4.33 t (54.19 parts) of 31% phosphoric acid solution was accurately pumped in for neutralization, and stirred evenly to prepare a total solid content of 30%, a neutralized liquid nitrogen potassium phosphorus complex of 0-52-34, and a temperature of 92°C.

[0043] Example 3: Example 1 was repeated with the following differences: Natural gas was used as fuel and burned in a hot blast furnace to prepare dry clean hot air at about 320°C, which was then introduced into a Φ7000 mm×40000 mm tower from near the bottom of the drying tower.

[0044] Example 4: Example 1 was repeated with the following differences: 4.36 t (54.5 parts) of deionized water was pumped into the batching pot, the heating system and stirring device were started, 3.64 t (45.5 parts) of crystalline potassium dihydrogen phosphate were poured in while heating, and the mixture was stirred evenly until dissolved, to prepare 8 t of neutralized solution with a total solid content of 45% and a nitrogen-potassium-phosphorus complex formula of 0-52-34, at a temperature of 92°C.

[0045] Example 5: Example 1 was repeated with the following differences: 6.25 t (78.1 parts) of 36.7% dipotassium hydrogen phosphate solution was pumped into the batching pot from the alkali dissolving tank, the stirring device was started, and 1.75 t (21.9 parts) of 75% phosphoric acid solution was accurately pumped in for neutralization, and stirred evenly to prepare 8 t of neutralized solution with a total solid content of 45% and a nitrogen-potassium-phosphorus complex formula of 0-52-34, and the temperature was maintained at 92°C. The reaction principle is as follows:

[0046] K2HPO4 + H3PO4 → 2KH2PO4

[0047] The product indicators of the expanded instant potassium dihydrogen phosphate prepared in the above examples are shown in Table 1 below:

[0048] Table 1

[0049]

[0050] Comparing the indicators of the expanded instant potassium dihydrogen phosphate product obtained in the above examples with those of commercially available products, it can be seen that the instant potassium dihydrogen phosphate product prepared by the present invention has the following characteristics: K2O ≥ 52%, P2O5 ≥ 34%, purity (in terms of potassium dihydrogen phosphate content) ≥ 99%, pH range 4.3~4.9 (30 g / L solution), complete autolysis in water within 3 minutes, clear liquid, apparent density 0.3~0.5 g / cm³, and overall stable quality, which is superior to commercially available products. The unique physical properties of the product enable it to exhibit excellent instant solubility, excellent drug compatibility, and high stability compared to existing products on the market. It not only solves the limitations of existing KH2PO4 products in applications such as aerial defense and agricultural modernization, but also significantly exceeds the established demand standards.

[0051] The present invention aims to solve the limitations of existing KH2PO4 products in applications such as aerial spraying and agricultural modernization, and to provide an industrial preparation method for transforming idle laundry detergent devices at a low cost and producing KDP201 by using LTE transformation based on wet phosphoric acid. The method has a short process flow and a high product yield. The prepared product has the advantages of fast dissolution speed, high purity, low apparent specific gravity, good stability, and not easy to agglomerate after long storage. It is particularly suitable for aerial spraying operations, which can not only improve the efficiency and utilization rate of fertilizers, but also realize the simultaneous application of fertilizers and pesticides, and the consumption of fertilizer and pesticide solution reaches 1 L / 600 m 2 Although the production cost of potassium dihydrogen phosphate prepared by this method is relatively high, its economic benefits are significantly better than those of traditional potassium dihydrogen phosphate when considering its dosage, fertilizer efficiency, labor costs, utilization of idle equipment, equipment investment, and time consumption.

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An industrial preparation method of instant potassium dihydrogen phosphate, characterized in that: The following steps are involved: Step 1: Transform the idle washing powder production equipment into an equipment system for preparing instant potassium dihydrogen phosphate; Step 2: Prepare a potassium hydroxide solution with a concentration of 20% to 90% in an alkali dissolving tank; Step 3: Mix 20 to 85 parts of a phosphoric acid solution having a concentration by mass fraction of 20% to 85% with 10 to 55 parts of the potassium hydroxide solution obtained in step 2 to obtain a neutralized solution; Step 4: Prepare hot air with a temperature of 150-320°C in the combustion furnace, adjust the total air volume according to the drying load, and then send the hot air into the drying tower; Step 5: When the outlet temperature of the drying tower reaches 100°C, the neutralized liquid obtained in step 3 is atomized into droplets with a particle size of about 50 μm through the pressure atomization system at the top of the drying tower. The droplets exchange heat with the hot air sent from the bottom of the drying tower to start puffing and granulation; Step 6: When the top of the drying tower reaches the expanded quick-dissolving condition (LTE), the powder spraying production begins; the expanded material produced by the powder spraying naturally settles at the bottom of the drying tower, and after the first screening, air conveying, and the second screening, it finally enters the finished product warehouse.

2. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: In step 3, the phosphoric acid used includes fertilizer grade phosphoric acid, industrial grade phosphoric acid, and food grade phosphoric acid.

3. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: In step 3, the neutralization solution temperature is controlled to be 80-100°C, the pH value is controlled to be 4.0-5.0, and the concentration is controlled to be 35%-50%.

4. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: In step 4, the method for preparing hot air is: the fuel is burned in the combustion furnace and then mixed with cold air; the straight cylinder size of the drying tower is Φ7000 mm×40000 mm.

5. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 4, characterized in that: The fuel comprises phosphorus furnace tail gas, the phosphorus furnace tail gas is yellow phosphorus exhaust gas, and the content of carbon monoxide in the phosphorus furnace carbon tail gas is greater than 85%.

6. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: In step 5, when the outlet temperature of the drying tower reaches 100°C, the neutralizing liquid is pressurized and atomized by a pressure atomization system, and the atomization pressure is controlled at 0.6~1.0 MPa.

7. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: In step 6, when the tower top reaches the expansion quick dissolving condition (LTE), the tower top temperature is maintained at 90~200℃, and the negative pressure is maintained at -80~-130Pa.

8. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: The finished product obtained in step 6 has a phosphorus pentoxide content (on a dry basis) ≥ 52%, a potassium oxide content (on a dry basis) ≥ 34%, and a potassium dihydrogen phosphate content (on a dry basis) ≥ 99%.

9. The industrial preparation method of instant potassium dihydrogen phosphate according to claim 1, characterized in that: The transformation method in step 1 is as follows: Add phosphoric acid storage tanks, alkali dissolving tanks and batching tanks to the idle washing powder production equipment; Improve the slurry conveying pipeline of the washing powder production device, optimize the material filtration system and the thermal insulation performance of the tank and pipeline; A liquid spraying system is added to the top of the powder spraying tower in the washing powder production device, the distribution of spray guns and the type of nozzles are adjusted, and the solution is transported to the powder spraying tower through a special solution pump for atomization, drying and molding; Use the combustion furnace to provide hot air and adjust the temperature and air volume of the powder spraying tower; Provide primary screening, air conveying and secondary screening equipment to transport the expanded particles to the finished product warehouse.

10. An industrial preparation method of instant potassium dihydrogen phosphate according to claim 9, characterized in that: The powder spraying tower is the drying tower in the above steps 4 to 6.

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