A production process of fully water-soluble powdered potassium dihydrogen phosphate

Abstract

The invention discloses a production process of a fully water-soluble powdered potassium dihydrogen phosphate, and belongs to the technical field of phosphorus chemical process. The invention uses relatively low-priced industrial monoammonium phosphate as a raw material, first reacts with potassium hydroxide, and subsequently adjusts the pH to 4.2-4.9 after controlling the ammonia content by ammonia evaporation, adds a complexing agent, clarifies the solution, and spray-dries the powdered potassium dihydrogen phosphate obtained within this pH range. The product purity reaches more than 98%, reaches the standard of fertilizer-grade superior products, and the product is fully water-soluble. The invention has a simple process and is easy to operate, and the market price of the powdered potassium dihydrogen phosphate is higher than that of crystalline potassium dihydrogen phosphate, with high profits and good market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphorus chemical process, and specifically relates to a production process of fully water-soluble powdered potassium dihydrogen phosphate. Background Art

[0002] At present, the production processes of potassium dihydrogen phosphate mainly include crystallization process and spray drying process, and the products are in crystal form and powder form respectively. At present, the production processes of potassium dihydrogen phosphate mainly include the following:

[0003] 1. Neutralization method

[0004] This method is to react industrial phosphoric acid (purified or thermal phosphoric acid) with potassium hydroxide to produce industrial potassium dihydrogen phosphate. The process is simple and the product has high purity. It is the main process used by domestic enterprises to produce industrial-grade potassium dihydrogen phosphate, but the cost of the raw material industrial phosphoric acid is high, and the cost of the potassium dihydrogen phosphate product is high.

[0005] 2. Double decomposition method

[0006] Potassium dihydrogen phosphate is produced by double decomposition reaction of potassium chloride and industrial monoammonium phosphate (or agricultural monoammonium phosphate), and a mixed mother liquor of ammonium chloride, potassium chloride, monoammonium phosphate and potassium dihydrogen phosphate is produced as byproduct. The potassium dihydrogen phosphate produced by this process has low purity and needs to be recrystallized to purify the product. The mother liquor can be used as liquid fertilizer or solid fertilizer. This process is relatively complicated and is adopted by a few domestic companies.

[0007] 3. Extraction method

[0008] Phosphoric acid and potassium chloride are used as raw materials, and the extractant is used to react with the dissolving solution in a homogeneous phase, and potassium dihydrogen phosphate is precipitated under the action of salting out and cooling conditions; the extracted organic phase is regenerated by adding ammonia water, and the extractant is recycled. The process mainly includes three steps of dissolving, extracting and stripping. The disadvantage of this process is that the organic solvent is expensive and difficult to industrialize.

[0009] 4. Spray drying

[0010] The solution after the reaction of purified phosphoric acid or thermal phosphoric acid with potassium hydroxide is dried in a spray tower to form powdered potassium dihydrogen phosphate. Compared with crystalline potassium dihydrogen phosphate, this product has the characteristics of flash dissolution, which can solve the problems of slow dissolution and low efficiency of ultra-high concentration preparation at low temperature in the field of foliar spraying by drones. The powdered product of potassium dihydrogen phosphate is a kind of instant fertilizer that has emerged in recent years, and its price is much higher than that of crystalline products. The price of powdered potassium dihydrogen phosphate products of the same quality is higher than that of crystalline potassium dihydrogen phosphate. Domestically, this product is mainly produced by purified phosphoric acid, represented by Wengfu Company. Because the price of raw materials, purified phosphoric acid or thermal phosphoric acid, is high, the cost is high.

[0011] At present, there are various problems in the preparation of potassium dihydrogen phosphate:

[0012] A method for preparing potassium dihydrogen phosphate by atomizing ammonia (CN115072683A) discloses a method for preparing potassium dihydrogen phosphate by high-humidity drying and deammoniation in a countercurrent spray tower after the reaction of monoammonium phosphate and potassium hydroxide. Specific process: using industrial monoammonium phosphate and potassium hydroxide as raw materials to make a solution, the molar ratio of potassium hydroxide to monoammonium phosphate is 0.95-1.1:1, spraying into a countercurrent drying tower, the inlet air temperature of the drying tower is as high as 130-350℃, the outlet temperature is not less than 130℃, the droplet diameter is 30-50um, and the purity of the product after drying is more than 98.5%. The patent only says that the purity of the potassium dihydrogen phosphate product is more than 98.5%, but it does not specify the specific measurement method of purity. The calculation of purity in the industry should be based on phosphorus pentoxide or potassium oxide. It does not introduce any pH of the product, whether the product meets the fertilizer grade potassium dihydrogen phosphate standard or the industrial grade potassium dihydrogen phosphate standard, and lacks data support. And according to the two embodiments in the patent, the molar ratio of potassium hydroxide to monoammonium phosphate is 1.01:1. Due to the excessive potassium hydroxide, the pH of the product after spray drying is at least greater than 5, while the pH of fertilizer-grade potassium dihydrogen phosphate is 4.2-4.9, and the pH of industrial-grade potassium dihydrogen phosphate is 4.3-4.7. The pH of the patented product is unqualified; in addition, the hot air inlet temperature of the spray tower is too high, and the material temperature is greater than 150 degrees. The solid diammonium will melt to form ammonium polyphosphate. The inlet air temperatures of the two embodiments are 200 degrees and 180 degrees respectively. The feed liquid quickly loses water in the countercurrent spray tower and becomes solid. The diammonium phosphate therein polymerizes when it exceeds 150°C, and polyphosphate is generated. In addition, the raw material requires monoammonium phosphate with a purity of up to 98%, which greatly increases the cost. In short, there are many problems with this process and large process defects.

[0013] A method for producing industrial-grade potassium dihydrogen phosphate using agricultural monoammonium phosphate (CN107746045A) discloses a method for producing industrial monoammonium phosphate using agricultural monoammonium phosphate and potassium hydroxide as raw materials through a crystallization method. The specific process is as follows: the agricultural monoammonium phosphate is filtered and further neutralized to pH = 9 to obtain diammonium phosphate, so as to further remove impurities at low cost, and then assisted by other methods to remove impurities, the impurity-removed solution is reacted with potassium hydroxide solution, steam is introduced to evaporate ammonia to pH = 10-11, 85% hot phosphoric acid is added to neutralize to pH = 3.8-4.0, cooled to 25-30°C, crystallized, centrifuged, and dried to obtain the finished product; the mother liquor is recycled, and when the sulfate in the mother liquor accumulates to 0.03-0.04 mol / L, barium salt is added to remove the sulfate. This crystallization process is complicated, and the mother liquor needs to be circulated for a long time to remove sulfate and concentrate to a potassium dihydrogen phosphate content of 40-50%, which increases the complexity of the process. Other impurities in the mother liquor also have a cumulative effect, increasing the instability of production; the pH of the solution after ammonia evaporation is 10-11, and the amount of 85% phosphoric acid added to adjust the pH is too large, which increases the production cost.

[0014] A method for preparing potassium dihydrogen phosphate using monoammonium phosphate clear solution (CN112678789A) discloses the specific steps of: using wet desulfurized phosphoric acid and ammonia to neutralize the filtered solution and react with 48-50% potassium hydroxide solution, then concentrating, filtering and desulfurizing to obtain potassium dihydrogen phosphate solution; concentrating the potassium dihydrogen phosphate solution, cooling, crystallizing, centrifuging, and drying to obtain the finished potassium dihydrogen phosphate product. The process is complicated, the pipeline in the production process is prone to crystallization and clogging, and the mother liquor is difficult to recycle.

[0015] In short, in the existing technology, the production process of potassium dihydrogen phosphate is not mature, and the preparation process of powdered potassium dihydrogen phosphate is even rarer. The production process has various problems such as high cost, complex process, and low product purity. Therefore, developing a low-cost, simple process, and practical application of a fully water-soluble powdered potassium dihydrogen phosphate preparation process is a technical problem that needs to be solved urgently. Summary of the invention

[0016] The invention aims at the problems existing in the prior art and provides a method for producing fully water-soluble powdered potassium dihydrogen phosphate at low cost by using low-cost industrial monoammonium phosphate and potassium hydroxide as raw materials and continuously optimizing process parameters and processes.

[0017] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0018] A production process of fully water-soluble powdered potassium dihydrogen phosphate, characterized in that it comprises the following steps:

[0019] (1) Ingredients: Add industrial monoammonium phosphate and potassium hydroxide into a reaction tank to react and obtain a reaction liquid;

[0020] (2) Ammonia evaporation: placing the feed liquid in a jacketed reactor, adding water, heating and concentrating, so that ammonia gas continuously overflows, and when the nitrogen content of the feed liquid is less than 0.2%, the ammonia evaporation is completed to obtain a slurry; adding water to the slurry to control the specific gravity to 1.30-1.42 g / ml, and maintaining a constant temperature of 90-110° C. so that the slurry is dissolved into a solution again;

[0021] (3) Adjusting pH: adding phosphoric acid to adjust the pH of the solution to 4.2-4.9;

[0022] (4) spray drying: the solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain a finished product;

[0023] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0024] Furthermore, in step (1), at least one of industrial monoammonium phosphate and potassium hydroxide is a solution; when industrial monoammonium phosphate is a solution in step (1), the mass concentration of the solution is 30-70%; when potassium hydroxide is a solution, the mass concentration of the solution is 40-60%; and the amount of potassium hydroxide is controlled to be greater than the amount of industrial monoammonium phosphate.

[0025] Furthermore, step (1) also includes a filtration process, wherein industrial monoammonium phosphate is prepared into a solution, which is first heated at 80-90° C. and then filtered. After filtration, potassium hydroxide solid or solution is added to react to obtain a reaction liquid.

[0026] Furthermore, step (1) also includes a filtration process, wherein the filtration process is to filter the reaction liquid of industrial monoammonium phosphate and potassium hydroxide after keeping it warm at 80-90°C.

[0027] Furthermore, the filtration is carried out by filter pressing, centrifugal filtration or precision filter filtration.

[0028] Furthermore, the specific gravity of the reaction solution obtained in step (1) is 1.25-1.65 g / ml.

[0029] Furthermore, the temperature of evaporation and concentration in step (2) is 90-250°C.

[0030] Furthermore, in step (3), a complexing agent is added for clarification, and the amount of the complexing agent added is 0.3-1.0% of the mass of the solution, and the slurry specific gravity is controlled to be 1.40-1.50 g / ml.

[0031] The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 8, characterized in that the complexing agent in step (3) is one or more of sodium nitrilotriacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriamine pentacarboxylate, tartaric acid, citrate, sodium alginate, sodium gluconate, sodium ethylenediaminetetramethylenephosphate, and diethylenetriaminepenta(methylenephosphonate).

[0032] The industrial monoammonium phosphate solution can be prepared using 72-73% industrial monoammonium phosphate, or industrial monoammonium phosphate produced by recrystallization, or industrial monoammonium phosphate produced by purified acid and thermal phosphoric acid.

[0033] Furthermore, in the spray drying section of step (4), the inlet air temperature of the countercurrent spray tower can be 110-250°C according to the requirements of output and cost; the inlet air temperature of the cocurrent spray tower is greater than or equal to 350°C; the spray drying tower needs to be connected to an ammonia recovery system to recover ammonia.

[0034] The present invention uses a spray tower for drying. Because the nitrogen content in the feed liquid is less than 0.2%, the feed liquid is qualified, and a downstream spray drying tower (hot air temperature entering the tower is greater than or equal to 350°C) or a countercurrent spray drying tower (the temperature of the hot air at the bottom of the countercurrent spray tower is 110-250°C) can be used.

[0035] Beneficial Effects

[0036] The process of producing potassium dihydrogen phosphate by crystallization using monoammonium phosphate and potassium hydroxide is complicated. During the production process, crystals are easy to clog the pipeline, and the mother liquor is difficult to circulate for a long time. This directly causes the problems of difficult operation, instability and high production cost, and the production capacity and profit of the product are limited. At the same time, if potassium dihydrogen phosphate is produced by high-temperature ammonia escape in a countercurrent spray tower, because the escape of ammonia requires time, high temperature and a certain time are required. If the inlet air temperature is higher than 150°C, after the droplets become solid, ammonia mainly exists in the form of diammonium phosphate, and diammonium phosphate will undergo polymerization reaction, and polymerized phosphorus will be generated; if ammonia is allowed to escape as quickly as possible, potassium hydroxide will be excessive, but if potassium hydroxide is excessive, the product pH is greater than 5, and the product is unqualified; if the time in the tower is not enough, the escape of ammonia is insufficient, and the product is also unqualified. Therefore, there are many problems in using a countercurrent spray tower to escape ammonia to produce potassium dihydrogen phosphate.

[0037] The invention uses relatively low-priced industrial monoammonium phosphate as a raw material, first reacts with potassium hydroxide, and then controls the ammonia content by ammonia evaporation and adjusts the pH to 4.2-4.9. The powdered potassium dihydrogen phosphate obtained by spray drying within the pH range has a product purity of more than 98%, reaches the standard of fertilizer-grade superior products, and is fully water-soluble. The invention has a simple process and is easy to operate. The market price of the powdered potassium dihydrogen phosphate is higher than that of crystalline potassium dihydrogen phosphate, with high profits and good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0040] The main chemical reaction equation of the present invention is:

[0041] KOH+NH4H2PO4→KH2PO4+NH3↑+H2O

[0042] In the following examples, industrial monoammonium phosphate with a purity of 73% is used as a raw material to react with potassium hydroxide to prepare potassium dihydrogen phosphate. The analysis results of the raw material industrial monoammonium phosphate are shown in Table 1:

[0043] Table 1: Constant data of raw material industry monoammonium phosphate

[0044] N％ <![CDATA[Water-soluble P2O5]]> Cl％ Water insoluble matter% 12 60.8 0 0.34 (G4 crucible filtration)

[0045] Table 2 Data of trace elements of raw material industrial monoammonium phosphate

[0046]

[0047] Example 1

[0048] A production process of fully water-soluble powdered potassium dihydrogen phosphate comprises the following steps:

[0049] (1) Ingredients: 2 kg of industrial monoammonium phosphate was prepared into a solution with a mass concentration of 50%, and 2.8 kg of potassium hydroxide solution with a mass concentration of 48% were added to a reaction tank at the same time, heated at a constant temperature of 80° C. for 1 hour, and then filtered to remove impurities to obtain a reaction liquid;

[0050] (2) Ammonia evaporation: The reaction liquid is placed in a jacketed reactor, 2 kg of water is added, and the reaction liquid is heated for evaporation and concentration to allow ammonia to continuously overflow. When the nitrogen content of the liquid is 0.05%, the concentrated ammonia evaporation is completed to obtain a slurry. 2 kg of water is added to the slurry, and the temperature is kept at 90-110° C. to dissolve the slurry into a solution again. At this time, the specific gravity of the solution is 1.37 g / ml.

[0051] (3) pH adjustment: add 0.75 kg of 85% industrial grade phosphoric acid to adjust the pH of the solution to 4.9, add 6 g of complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47 g / ml;

[0052] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 3.25 kg of a finished product;

[0053] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0054] Industrial monoammonium phosphate solution is prepared using industrial monoammonium phosphate with a purity of 72-73%.

[0055] The specific gravity of the reaction liquid obtained in step (1) is 1.27-1.30 g / ml.

[0056] In step (1), the filtration is performed by filter press.

[0057] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0058] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0059] The complexing agent in step (3) is sodium citrate.

[0060] The temperature of evaporation concentration in step (2) is 90-120° C., and the concentration time is about 7 hours.

[0061] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the product purity and content were tested, and the results are shown in Table 1-2:

[0062] Table 1 Constant content

[0063] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl％ pH Water insoluble matter% 0.05 51.40 34.60 0.10 0 4.9 0

[0064] Table 2 Trace element content

[0065]

[0066] Example 2

[0067] A production process of fully water-soluble powdered potassium dihydrogen phosphate comprises the following steps:

[0068] (1) Ingredients: 2 kg of industrial monoammonium phosphate was prepared into a solution with a mass concentration of 55%, heated at a constant temperature of 85° C. for 2 hours, and then filtered; 2.6 kg of potassium hydroxide was prepared into a solution with a mass concentration of 48%, and the potassium hydroxide solution and the filtered industrial monoammonium phosphate solution were simultaneously added to a reaction tank to obtain a reaction liquid;

[0069] (2) Ammonia evaporation: The reaction liquid was placed in a jacketed reactor, and 2.5 kg of water was added to heat and evaporate the ammonia gas to concentrate it, so that the ammonia gas continuously overflowed. When the nitrogen content of the liquid was 0.07%, the concentrated ammonia evaporation was completed to obtain a slurry; 2 kg of water was added to the slurry, and the temperature was kept at 90-110° C. to dissolve the slurry into a solution again, and the specific gravity of the solution was 1.36 g / ml;

[0070] (3) Adjusting pH: Add 0.6 kg of 85% industrial grade phosphoric acid to adjust the pH of the solution to 4.7; add 8 g of complexing agent to clarify the solution, and the slurry specific gravity is 1.44-1.46 g / ml.

[0071] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 3.01 kg of a finished product;

[0072] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0073] 72-73% industrial monoammonium phosphate is used to prepare industrial monoammonium phosphate solution.

[0074] The specific gravity of the reaction liquid obtained in step (1) is 1.25-1.27 g / ml.

[0075] In step (1), the filtration is performed using a precision filter.

[0076] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0077] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0078] The temperature of evaporation concentration in step (2) is 120-150°C, and the concentration time is about 8 hours.

[0079] The complexing agent in step (3) is disodium ethylenediaminetetraacetate.

[0080] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the purity and content of the product were tested. The results are shown in Table 3-4:

[0081] Table 3 Constant content

[0082] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> pH Cl％ Water insoluble matter% 0.07 51.60 34.30 0.15 4.7 0 0

[0083] Table 4 Trace element content

[0084]

[0085] Example 3

[0086] A production process of fully water-soluble powdered potassium dihydrogen phosphate comprises the following steps:

[0087] (1) Ingredients: 2 kg of industrial monoammonium phosphate solid was dissolved in water to prepare a solution with a mass concentration of 45%, and 2.4 kg of potassium hydroxide solution with a mass concentration of 48% was added to a reaction tank at the same time, heated at a constant temperature of 90° C. for 3 hours, and then filtered to remove impurities to obtain a reaction liquid;

[0088] (2) Ammonia evaporation: The reaction liquid was placed in a jacketed reactor, 3 kg of water was added, and heated to concentrate so that ammonia gas continuously overflowed. When the nitrogen content of the liquid was 0.08%, the concentrated ammonia evaporation was completed to obtain a slurry; 2 kg of water was added to the slurry, and the temperature was kept at 90-110° C. so that the slurry was dissolved again into a solution, and the specific gravity of the solution was 1.37 g / ml;

[0089] (3) pH adjustment: add 0.39 kg of 85% industrial grade phosphoric acid to adjust the pH of the solution to 4.6, add 10 g of complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47 g / ml;

[0090] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 2.78 kg of a finished product;

[0091] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0092] The specific gravity of the reaction liquid obtained in step (1) is 1.55-1.58 g / ml.

[0093] In step (1), centrifugal filtration is used for filtration.

[0094] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0095] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0096] The temperature of evaporation concentration in step (2) is 150-180° C., and the concentration time is about 5 hours.

[0097] The complexing agent in step (3) is tetrasodium ethylenediaminetetraacetate.

[0098] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the purity and content of the product were tested. The results are shown in Table 5-6:

[0099] Table 5 Constant content

[0100] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> pH Cl％ Water insoluble matter% 0.09 51.90 34.20 0.15 4.4 0 0

[0101] Table 6 Trace element content

[0102]

[0103] Example 4

[0104] A production process of fully water-soluble powdered potassium dihydrogen phosphate comprises the following steps:

[0105] (1) Ingredients: 2 kg of industrial monoammonium phosphate solid was dissolved in water to prepare a solution with a mass concentration of 50%, and 2.2 kg of potassium hydroxide solution with a mass concentration of 48% was added to a reaction tank at the same time, heated at a constant temperature of 80° C. for 1 hour, and then filtered to remove impurities to obtain a reaction liquid;

[0106] (2) Ammonia evaporation: The reaction liquid was placed in a jacketed reactor, 3.3 kg of water was added, and the mixture was heated and concentrated to allow ammonia to continuously overflow. When the nitrogen content of the liquid was 0.11%, the concentrated ammonia evaporation was completed to obtain a slurry. 2 kg of water was added to the slurry, and the temperature was kept constant at 90-110° C. to dissolve the slurry into a solution again. The specific gravity of the solution was 1.38 g / ml.

[0107] (3) Adjusting pH: Add 0.21 kg of industrial-grade phosphoric acid with a concentration of 85% to adjust the pH of the solution to 4.6; add 10 g of a complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47 g / ml.

[0108] (4) spray drying: the solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain a finished product 2.55;

[0109] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0110] The specific gravity of the reaction liquid obtained in step (1) is 1.57-1.62 g / ml.

[0111] In step (1), the filtration is performed using a precision filter.

[0112] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0113] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0114] The temperature of step (2) evaporation concentration is 180-210°C

[0115] The complexing agent in step (3) is sodium alginate.

[0116] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the product purity and content were tested, and the results are shown in Table 7-8:

[0117] Table 7 Constant content

[0118] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl％ pH Water insoluble matter% 0.10 52.00 34.10 0.2 0 4.3 0

[0119] Table 8 Trace element content

[0120]

[0121] Example 5

[0122] A production process of fully water-soluble powdered potassium dihydrogen phosphate comprises the following steps:

[0123] (1) Ingredients: 2 kg of industrial monoammonium phosphate solid was dissolved in water to prepare a solution with a mass concentration of 55%, and 2.1 kg of potassium hydroxide solution with a mass concentration of 48% was added to a reaction tank at the same time, heated at a constant temperature of 80° C. for 1 hour, and then filtered to remove impurities to obtain a reaction liquid;

[0124] (2) Ammonia evaporation: the reaction liquid is placed in a jacketed reactor, 4 kg of water is added, and the reaction liquid is heated and concentrated to allow ammonia to continuously overflow. When the nitrogen content of the liquid is less than 0.18%, the concentrated ammonia evaporation is completed to obtain a slurry. 2 kg of water is added to the slurry, and the temperature is kept at 90-110° C. to dissolve the slurry into a solution again. The specific gravity of the solution is 1.40 g / ml.

[0125] (3) pH adjustment: add 0.11 kg of 85% industrial grade phosphoric acid to adjust the pH of the solution to 4.2, add 10 g of complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47 g / ml;

[0126] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 2.43 kg of a finished product;

[0127] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0128] The specific gravity of the reaction liquid obtained in step (1) is 1.58-1.60 g / ml.

[0129] In step (1), filtration is performed by filter press.

[0130] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0131] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0132] The temperature of evaporation concentration in step (2) is 210-250° C., and the concentration time is about 10 h.

[0133] The complexing agent in step (3) is sodium gluconate.

[0134] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the purity and content of the product were tested. The results are shown in Table 9-10:

[0135] Table 9 Constant content

[0136] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl％ pH Water insoluble matter% 0.19 52.10 34.00 0.15 0 4.5 0

[0137] Table 10 Trace element content

[0138]

[0139] Comparative Example 1

[0140] A production process of powdered potassium dihydrogen phosphate comprises the following steps:

[0141] (1) Ingredients: 2 kg of industrial monoammonium phosphate solid and 2.1 kg of potassium hydroxide solution with a mass concentration of 48% are added to a reaction tank at the same time, heated at a constant temperature of 80° C. for 1 hour, and then filtered to remove impurities to obtain a reaction liquid;

[0142] (2) Ammonia evaporation: the reaction liquid is placed in a jacketed reactor, 4 kg of water is added, and the reaction liquid is heated and concentrated to allow ammonia to continuously overflow. When the nitrogen content of the liquid is less than 0.18%, the concentrated ammonia evaporation is completed to obtain a slurry. 2 kg of water is added to the slurry, and the temperature is kept at 90-110° C. to dissolve the slurry into a solution again. The specific gravity of the solution is 1.40 g / ml.

[0143] (3) pH adjustment: add 85% industrial grade phosphoric acid to adjust the pH of the solution to 4, add 10g of complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47g / ml;

[0144] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 2.43 kg of a finished product;

[0145] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0146] The specific gravity of the reaction liquid obtained in step (1) is 1.58-1.60 g / ml.

[0147] In step (1), filtration is performed by filter press.

[0148] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0149] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0150] The temperature of evaporation concentration in step (2) is 160-180° C., and the concentration time is about 10 hours.

[0151] The complexing agent in step (3) is sodium gluconate.

[0152] This comparative example is the same as Example 5 except that the pH is adjusted to 4 in the pH adjustment section.

[0153] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the product purity and content were tested, and the results are shown in Table 11-12:

[0154] Table 11 Constant content

[0155] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl％ pH Water insoluble matter% 0.18 52.85 33.40 0.15 0 4.1 0.1

[0156] Table 12 Trace element content

[0157]

[0158] Comparative Example 2

[0159] A production process of powdered potassium dihydrogen phosphate comprises the following steps:

[0160] (1) Ingredients: 2 kg of industrial monoammonium phosphate solid and 2.1 kg of potassium hydroxide solution with a mass concentration of 48% are added to a reaction tank at the same time, heated at a constant temperature of 80° C. for 1 hour, and then filtered to remove impurities to obtain a reaction liquid;

[0161] (2) Ammonia evaporation: the reaction liquid is placed in a jacketed reactor, 4 kg of water is added, and the reaction liquid is heated and concentrated to allow ammonia to continuously overflow. When the nitrogen content of the liquid is less than 0.18%, the concentrated ammonia evaporation is completed to obtain a slurry. 2 kg of water is added to the slurry, and the temperature is kept at 90-110° C. to dissolve the slurry into a solution again. The specific gravity of the solution is 1.40 g / ml.

[0162] (3) pH adjustment: add 85% industrial grade phosphoric acid to adjust the pH of the solution to 5, add 10g of complexing agent to clarify the solution, and the slurry specific gravity is 1.45-1.47g / ml;

[0163] (4) Spray drying: The solution after pH adjustment in step (3) is pumped into a countercurrent or cocurrent spray tower for drying to obtain 2.43 kg of a finished product;

[0164] (5) Cooling and packaging: The finished products are cooled and then sent to the packaging section for packaging and storage.

[0165] The specific gravity of the reaction liquid obtained in step (1) is 1.58-1.60 g / ml.

[0166] In step (1), filtration is performed by filter press.

[0167] If ammonia overflows during the filtration process, the ammonia can be connected to the ammonia recovery system.

[0168] During the batching process in step (1), a large amount of ammonia will escape. The ammonia can be connected to an ammonia recovery system and recovered using sulfuric acid or phosphoric acid to generate ammonium sulfate or monoammonium phosphate, which can be circulated or recycled.

[0169] The temperature of evaporation concentration in step (2) is 160-180° C., and the concentration time is about 10 hours.

[0170] The complexing agent in step (3) is sodium gluconate.

[0171] This comparative example is the same as Example 5 except that the pH is adjusted to 5 in the pH adjustment section.

[0172] According to the test methods and standards in standard HG / T2321-2016 "Fertilizer-grade potassium dihydrogen phosphate", the product purity and content were tested, and the results are shown in Table 11-12:

[0173] Table 11 Constant content

[0174] N％ <![CDATA[P2O5%]]> <![CDATA[K2O%]]> <![CDATA[H2O%]]> Cl％ pH Water insoluble matter% 0.15 50.90 34.80 0.22 0 5.3 0.3

[0175] Table 12 Trace element content

[0176]

[0177] Through the above examples and comparative data, we can see that the powdered potassium dihydrogen phosphate obtained by the process of the present invention has good water solubility, high purity and few impurities, and meets the requirements of industry standards. The comparative examples with changed process parameters all show different degrees of decline in their individual parameters. The ammonia evaporation process of the present invention and the subsequent pH adjustment spray drying process are key technical means for achieving the preparation of high-purity fully water-soluble potassium dihydrogen phosphate.

[0178] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A production process for fully water-soluble powdered potassium dihydrogen phosphate, characterized in that: The following steps are involved: (1) Ingredients: Add industrial monoammonium phosphate and potassium hydroxide into a reaction tank to react and obtain a reaction liquid; (2) Ammonia evaporation: Place the feed liquid in a jacketed reactor, add water, heat and concentrate to allow ammonia to overflow continuously. When the nitrogen content of the feed liquid is less than 0.2%, the ammonia evaporation is completed to obtain a slurry. Add water to the slurry to control the specific gravity to 1.30-1.42 g / ml, and maintain a constant temperature of 90-110°C to dissolve the slurry into a solution again. (3) Adjusting pH: Add phosphoric acid to adjust the pH of the solution to 4.2-4.9; (4) Spray drying: the solution after pH adjustment in step (3) is injected into a countercurrent or cocurrent spray tower for drying to obtain a finished product; (5) Cooling and packaging: Cool the finished product and enter the packaging section for packaging and storage; In step (1), at least one of industrial monoammonium phosphate and potassium hydroxide is in the form of a solution; when industrial monoammonium phosphate is in the form of a solution in step (1), the mass concentration of the solution is 30-70%; when potassium hydroxide is in the form of a solution, the mass concentration of the solution is 40-60%; and the amount of potassium hydroxide is controlled to be greater than the amount of industrial monoammonium phosphate.

2. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 1, characterized in that: Step (1) also includes a filtration process, wherein industrial monoammonium phosphate is prepared into a solution, which is first heated to 80-90° C. and then filtered. After filtration, potassium hydroxide solid or solution is added to react to obtain a reaction liquid.

3. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 1, characterized in that: Step (1) also includes a filtration process, wherein the filtration process is to filter the reaction liquid of industrial monoammonium phosphate and potassium hydroxide after keeping it warm at 80-90°C.

4. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 2 or 3, characterized in that: Filtration is carried out by pressure filtration, centrifugal filtration or precision filter filtration.

5. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 1, characterized in that: The specific gravity of the reaction liquid obtained in step (1) is 1.25-1.65 g / ml.

6. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 1, characterized in that: The temperature of evaporation and concentration in step (2) is 90-250°C.

7. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 1, characterized in that: In step (3), a complexing agent is added for clarification, wherein the amount of the complexing agent added is 0.3-1.0% of the mass of the solution, and the slurry specific gravity is controlled to be 1.40-1.50 g / ml.

8. The production process of fully water-soluble powdered potassium dihydrogen phosphate according to claim 7, characterized in that: The complexing agent in step (3) is one or more of sodium nitrilotriacetate, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentacarboxylate, tartaric acid, citrate, sodium alginate, sodium gluconate, sodium ethylenediaminetetramethylenephosphate, and diethylenetriaminepenta(methylenephosphonate).

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