Method for producing NPK fertilizer containing potassium phosphate and ammonium phosphate

Abstract

The present invention relates to a method for producing liquid NPK fertilizer, characterized in that the reactants K2CO3 or KHCO3, NH4HCO3, and H3PO4 are reacted in an aqueous solution to produce potassium and ammonium phosphate salts, particularly K3PO4 and (NH4)3PO4; the reaction is carried out in multiple steps and includes at least one exothermic reaction and at least one endothermic reaction; and the temperature of the reaction is controlled by adjusting the amount and rate of addition of each reactant in the various steps so as to maintain the reaction mixture within a desired temperature range, preferably between 5°C and 50°C, throughout the reaction, without the need for external cooling or heating devices to control the temperature of the reaction. In a more specific embodiment, the method according to the invention is characterized in that at least one exothermic reaction comprises the reaction of K2CO3 with HO to produce KHCO3 and KOH and / or the reaction of KHCO3 with H3PO4 to produce K3PO4, CO2, and HO, and at least one endothermic reaction comprises the reaction of NH4HCO3 with H3PO4 to produce (NH4)3PO4, CO2, and HO.

Description

Technical Field

[0001] Multiple methods for manufacturing NPK fertilizers, i.e., plant fertilizers containing at least the nutrients nitrogen, phosphorus, and potassium, are known in the prior art.

Background Art

[0002] The simplest approach is to manufacture various individual components each containing at least one of the mentioned nutrients and then mix them to produce the desired NPK fertilizer.

[0003] Another approach aims to manufacture all the required individual components simultaneously. For example, Chinese Patent Application CN210595276 U describes a manufacturing system for the co-production of monoammonium phosphate and potassium hydrogen phosphate, in which potassium chloride, ammonium bicarbonate, and phosphoric acid are used as starting materials. Chinese Patent Application CN110423144 discloses a water-soluble NPK fertilizer characterized in that the main component is dipotassium hydrogen phosphate and it is produced by reacting monoammonium phosphate and potassium carbonate in a molar ratio of 2:1.

[0004] In these methods, similar to other conventional methods for manufacturing NPK fertilizers or their individual components, it is necessary to control the temperature of the reaction by cooling (in the case of an exothermic reaction) or heating (in the case of an endothermic reaction) to keep them within an appropriate range. Such measures increase the manufacturing cost and have an adverse impact on the environment due to the accompanying energy consumption.

[0005] [[ID=2)4]]Furthermore, many of the methods known in the prior art are complex in terms of equipment (e.g., the manufacturing system described in the above Patent Application CN210595276 U) and / or involve a relatively long manufacturing time.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] CN210595276 U [Patent Document 2] CN110423144 [Overview of the project] [Problems that the invention aims to solve]

[0007] Against this backdrop, the main objective of the present invention is to provide an improved method for producing NPK fertilizer in which the disadvantages of the prior art are avoided or significantly reduced. [Means for solving the problem]

[0008] According to the present invention, this objective is solved by providing the method according to claim 1. More specific aspects and preferred embodiments of the present invention are the subject of subsequent claims. [Modes for carrying out the invention]

[0009] This invention is based on the remarkable discovery that by linking and precisely controlling appropriate endothermic and exothermic reactions, it is possible to produce an NPK fertilizer that has all the necessary components in a single reaction mixture, without the need to use additional cooling or heating devices to control the reaction temperature.

[0010] The method according to claim 1 for producing a liquid NPK fertilizer containing at least nutrients nitrogen, phosphorus, and potassium, is characterized by reacting reactants K2CO3 or KHCO3, NH4HCO3, and H3PO4 in an aqueous solution to produce potassium phosphate salts and ammonium phosphate salts, in particular K3PO4 and (NH4)3PO4, wherein the reaction is carried out in multiple steps and comprises at least one exothermic reaction and at least one endothermic reaction, and the temperature of the reaction is controlled by adjusting the amount and rate at which each reactant is added in various steps so as to keep the reaction mixture within a desired temperature range throughout the reaction.

[0011] In a more specific embodiment, the method according to the present invention is characterized in that at least one exothermic reaction includes the reaction of K2CO3 with H2O to produce KHCO3 and KOH according to the following reaction formulas (1), (2), and (3), and / or the reaction of KHCO3 with H3PO4 to produce K3PO4, CO2, and H2O, and at least one endothermic reaction includes or constitutes the reaction of NH4HCO3 with H3PO4 to produce (NH4)3PO4, CO2, and H2O according to the following reaction formula (4). (1) 3 K2CO3+ 3 H2O → 3 KHCO3+ 3 KOH (2) 3 KHCO3+ 3 KOH + 2 H3PO4→ 2 K3PO4+ 6 H2O + 3 CO2 (3) 3 KHCO3+ 1 H3PO4→ 1 K3PO4+ 3 H2O + 3 CO2 (4) 3 NH4HCO3+ 1 H3PO4→ 1 (NH4)3PO4+ 3 H2O + 3 CO2

[0012] Those skilled in the art will understand that the main products of these reactions are salts, which are in the form of ions under the reaction conditions in aqueous solution.

[0013] Unless otherwise specified, the scope of this application includes the respective limit values.

[0014] The reaction mixture is typically kept at a temperature range of 5°C to 50°C, preferably 20°C to 50°C, throughout the reaction. If the temperature of the reaction mixture exceeds the upper limit of 50°C, foaming becomes too vigorous and the reaction becomes uncontrollable. Below 20°C, and especially below 5°C, the reaction slows considerably, and the solubility of some reactants, particularly NH4HCO3, decreases significantly.

[0015] In the final step of the method according to the present invention, the pH of the reaction mixture is preferably adjusted to a value in the range of 6.5 to 7.3, preferably 6.5 to 7.1, and particularly preferably 6.5 to 6.9.

[0016] As used herein, the terms "potassium phosphate salts and ammonium phosphate salts" basically include all potassium phosphate salts and ammonium phosphate salts in ionic form that can exist in aqueous solution under the pH conditions and molar ratios of the method according to the present invention. These include, in particular, K3PO4 and K2HPO4, (NH4)3PO4 and (NH4)2HPO4.

[0017] At pH levels above approximately 8.5, generally only K3PO4 and (NH4)3PO4 are present, whereas in the pH range of 6.5 to 7.5, mixtures of K3PO4 and K2HPO4, and mixtures of (NH4)3PO4 and (NH4)2HPO4 are present. After adjusting the pH to a final value of 6.5 to 7.3, the mixing ratios are typically in the range of approximately 45% to 55% K3PO4 versus approximately 55% to 45% K2HPO4, and approximately 45% to 55% (NH4)3PO4 versus approximately 55% to 45% (NH4)2HPO4.

[0018] In a more specific embodiment, the method according to the present invention includes at least the following steps: a) A step of mixing the first portion of K2CO3 or KHCO3 in water while stirring, maintaining the temperature of the reaction mixture at a maximum temperature of 50°C by adjusting the amount and rate of addition, and then mixing the first portion of NH4HCO3, followed by the first portion of H3PO4, maintaining the temperature of the reaction mixture at a temperature of at least 5°C, preferably at least 20°C, by adjusting the amount and rate of addition of NH4HCO3 and H3PO4. b) A step of mixing further amounts of K2CO3 or KHCO3, H3PO4, and NH4HCO3 in this order, and maintaining the temperature of the reaction mixture in the range of 5°C to 50°C, preferably 20°C to 34°C, by adjusting the amount and rate at which each reactant is added. c) Repeat step b) until the total amount of K2CO3 or KHCO3 and NH4HCO3 used is added, d) Optionally, until the total usage amounts of K2CO3 or KHCO3, NH4HCO3, and H3PO4 in steps a) to d) match a predetermined molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4, adding a further amount of H3PO4; e) adding further H3PO4 until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.3; comprising.

[0019] In step a), the concentration of K2CO3 or KHCO3 is typically in the range of 0.05 to 0.2 mol / l - water, preferably in the range of 0.1 to 0.15 mol / l - water, the concentration of NH4HCO3 is in the range of 0.07 to 0.2 mol / l - water, preferably in the range of 0.1 to 0.15 mol / l - water, and the concentration of H3PO4 is in the range of 0.3 to 0.75 mol / l - water, preferably in the range of 0.1 to 0.15 mol / l - water.

[0020] In step a), the initial amount of K2CO3 or KHCO3 is typically 5 to 20% of the total usage amount, preferably 10 to 15% of the total usage amount, the initial amount of NH4HCO3 is 7 to 20% of the total usage amount, preferably 10 to 15% of the total usage amount, and the initial amount of H3PO4 is 30 to 75% of the total usage amount in steps a) to d), preferably 50 to 60% of the total usage amount.

[0021] Furthermore, in step a), the molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4 is usually in the range of 0.05 to 0.2:0.07 to 0.2:0.3 to 0.75, preferably in the range of 0.1 to 0:.15:0.1 to 0.15:0.5 to 0.6.

[0022] Step b) is repeated at least once until step c) is completed, but it is also possible to repeat it more times, for example, 2 to 40 times or 2 to:5 times, typically 12 to 25 times. By using smaller amounts of each reactant and repeating step b more times, more accurate temperature control can be achieved.

[0023] The molar ratio K2CO3:NH4HCO3:H3PO4 resulting from the total amount of K2CO3, NH4HCO3, and H3PO4 used in steps a) to d) may vary in the range of 0.8 to 1.2:0.8 to 1.2:0.8 to 1.2, but an approximately equimolar ratio of reactants in the range of 0.95 to 1.05:0.95 to 1.05:0.95 to 1.05 is preferred, and a ratio of approximately 1:1:1 is particularly preferred.

[0024] In this embodiment of the method according to the present invention, when KHCO3 is used instead of K2CO3, the molar ratio KHCO3:NH4HCO3:H3PO4 resulting from the total amount of KHCO3, NH4HCO3, and H3PO4 used in steps a) to d) may vary in the range of 2.4 to 3.6:2.4 to 3.6:1.6 to 2.4, but a reactant ratio in the range of 2.85 to 3.15:2.85 to 3.15:1.9 to 2.1 is preferred, and a ratio of about 3:3:2 is particularly preferred.

[0025] Adding further amounts of H3PO4 in step d) may be omitted if the total amount of K2CO3 or KHCO3, NH4HCO3, and H3PO4 used in steps a) to c) already matches the predetermined molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4, particularly the molar ratio specified in the preceding paragraph. However, this embodiment of the method according to the present invention preferably also includes step d).

[0026] In the final step of this variant of the method according to the present invention, i.e., typically step e), additional H3PO4 is added (typically about 95% to 100% of the total amount used in steps a) to d) until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.3, preferably in the range of 6.5 to 7.1, and particularly preferably in the range of 6.5 to 6.9).

[0027] Advantageously, all steps of this variation of the method according to the present invention, including the adjustment of the pH of the reaction mixture in the final step, are generally completed within 1 to 2 hours. Typically, the time for step a) is about 10 minutes, the time for steps b) to d) is about 45 to 85 minutes, and the time for step e) is about 5 to 25 minutes.

[0028] In another specific embodiment, the method according to the present invention comprises at least the following steps: a) A step of adding the first portion of K2CO3 or KHCO3, preferably K2CO3, to an aqueous solution of H3PO4 while stirring, and maintaining the temperature of the reaction mixture at a maximum temperature of 50°C by adjusting the amount and rate of addition; and a step of then mixing in the first portion of NH4HCO3, and maintaining the temperature of the reaction mixture at a temperature of at least 5°C, preferably at least 20°C, by adjusting the amount and rate of addition of NH4HCO3. b) A step of mixing K2CO3 or KHCO3, NH4HCO3, and optionally additional amounts of H3PO4 in this order, and maintaining the temperature of the reaction mixture in the range of 5°C to 50°C, preferably in the range of 20°C to 34°C, by adjusting the amount and rate at which each reactant is added. c) Repeat step b) until the total amount of K2CO3 or KHCO3, NH4HCO3, and H3PO4 used in steps a) to c) matches a predetermined molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4. e) Adding more H3PO4 until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.3. Includes.

[0029] In step a), the concentration of H3PO4 is typically in the range of 0.3 to 0.75 mol / l water, preferably in the range of 0.4 to 0.6 mol / l water, the concentration of K2CO3 or KHCO3 is in the range of 0.05 to 0.2 mol / l reaction mixture, preferably in the range of 0.1 to 0.15 mol / l reaction mixture, and the concentration of NH4HCO3 is in the range of 0.07 to 0.2 mol / l reaction mixture, preferably in the range of 0.1 to 0.15 mol / l reaction mixture.

[0030] In step a), the initial amount of K2CO3 or KHCO3 is typically 5-20% of the total amount used, preferably 10-15%, the initial amount of NH4HCO3 is 7-20% of the total amount used, preferably 10-15%, and the initial amount of H3PO4 is 30-100% of the total amount used in steps a) to c), preferably 50-60%.

[0031] Furthermore, in step a), the molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4 is typically in the range of 0.05~0.2:0.07~0.2:0.3~0.75, preferably in the range of 0.1~0.15:0.1~0.15:0.5~0.6.

[0032] Step b) is repeated at least once until step c) is completed, but it can be repeated more times, for example 2 to 40 times or 2 to 5 times, typically 12 to 25 times. By repeating step b) more times using smaller amounts of each reactant, more precise temperature control can be achieved.

[0033] Adding further amounts of H3PO4 in step b) or c) may be omitted if the amount of H3PO4 used in step a) and the total amount of K2CO3 or KHCO3 and NH4HCO3 used in steps b) to c) already match the predetermined molar ratio of K2CO3 or KHCO3:NH4HCO3:H3PO4, particularly the molar ratio specified in a later paragraph. This embodiment is described in Example 2.

[0034] The molar ratio K2CO3:NH4HCO3:H3PO4 resulting from the total amount of K2CO3, NH4HCO3, and H3PO4 used in steps a) to c) may vary in the range of 0.8 to 1.2:0.8 to 1.2:0.8 to 1.2, but an approximately equimolar ratio of reactants in the range of 0.95 to 1.05:0.95 to 1.05:0.95 to 1.05 is preferred, and a ratio of approximately 1:1:1 is particularly preferred.

[0035] In this modified form of the method according to the present invention, when KHCO3 is used instead of K2CO3, the molar ratio KHCO3:NH4HCO3:H3PO4 resulting from the total amount of KHCO3, NH4HCO3, and H3PO4 used in steps a) to c) may vary in the range of 2.4 to 3.6:2.4 to 3.6:1.6 to 2.4, but a ratio of reactants in the range of 2.85 to 3.15:2.85 to 3.15:1.9 to 2.1 is preferred, and a ratio of about 3:3:2 is particularly preferred.

[0036] In the final step d) of this variant of the method according to the present invention, additional H3PO4 is added (typically about 90% to 100% of the total amount used in steps a) to c) until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.3, preferably in the range of 6.5 to 7.1, and particularly preferably in the range of 6.5 to 6.9).

[0037] Advantageously, all steps of this variation of the method according to the present invention, including the adjustment of the pH of the reaction mixture in the final step, are generally completed within 1 to 2 hours. Typically, the time for step a) is about 10 minutes, the time for steps b) to c) is about 45 to 85 minutes, and the time for step d) is about 5 to 25 minutes.

[0038] A further special advantage of the method described in the claims is that, by linking and coordinating the exothermic and endothermic partial reactions according to the present invention, an external cooling or heating device is not required to control the reaction temperature.

[0039] The method according to the present invention is typically carried out in a closed system, and the CO2 produced as a byproduct during the reaction is recovered and optionally provided for further use. In this way, environmental pollution by the method according to the present invention can be prevented.

[0040] The following embodiments are intended to illustrate the methods according to the present invention in more detail, but the present invention is not limited to the specific parameters and method conditions of these embodiments. [Examples]

[0041] In a stirring tank with a volume of 15 liters, potassium carbonate, ammonium bicarbonate, and phosphoric acid were reacted according to the method of the present invention as follows to obtain an NPK fertilizer containing tripotassium phosphate and triammonium phosphate.

[0042] a) In the first step of this method, 9 liters of water (at a temperature of 24.8°C) were filled into the reaction vessel, and then 700 g of K2CO3 was mixed in while stirring. Vigorous foaming occurred, the temperature of the reaction vessel rose to 45.6°C, and the pH reached 12.83. After this exothermic reaction, an endothermic reaction was used to cool the mixture by first mixing in 664 g of NH4HCO3 while stirring. Vigorous foaming occurred again, the temperature of the reaction vessel dropped to 40°C, and the pH dropped to 12.3. Subsequently, 242 g of H3PO4 (78%) was added while stirring. The temperature further dropped to 25.4°C, and the pH reached 9.78.

[0043] b) In the next step of this method, 460 g of K2CO3 was added to the reaction mixture while stirring. Vigorous foaming occurred, the temperature of the reaction vessel rose to 38.0°C, and the pH reached 12.5. Subsequently, 322 g of H3PO4 (78%) was added while stirring. The temperature dropped again to 32.8°C, and the pH reached 9.98. Then, another 409 g of NH4HCO3 was added while stirring again, causing vigorous foaming, the temperature dropped to 26.4°C, and the pH dropped to 9.5.

[0044] c) In this step, 340 g of K2CO3 was added to the reaction mixture while stirring. Vigorous foaming occurred, the temperature of the reaction vessel rose to 30.9°C, and the pH reached 9.8. Subsequently, 436 g of H3PO4 (78%) was added while stirring. The temperature stabilized at 31.8°C, and the pH reached 8.9. Next, 247 g of NH4HCO3 was added again while stirring, causing vigorous foaming, the temperature to drop to 30.2°C, and the pH to 8.8.

[0045] d) After adding 611 g of H3PO4 (78%) while stirring, the temperature stabilized at 30.4°C and the pH reached 8.5.

[0046] e) Next, 436 g of H3PO4 (78%) was added while stirring to substantially neutralize the reaction mixture, convert the bicarbonate to carbonic acid, and remove it from the reaction mixture as CO2. The temperature stabilized at 30.2°C and the pH reached 7.04. The density of the resulting liquid NPK fertilizer mixture was 1.32 g / cm³. 3 That was the case.

[0047] Table 1 below summarizes the essential reaction parameters for steps a) to d) of the embodiment of this model.

[0048] [Table 1] [Examples]

[0049] In a stirring tank with a volume of 4 liters, potassium carbonate, ammonium bicarbonate, and phosphoric acid were reacted according to the method of the present invention as follows to obtain an NPK fertilizer containing tripotassium phosphate and triammonium phosphate.

[0050] a) In the first step of this method, 359 g of H3PO4 (78%) was added to a reaction vessel containing 0.7 L of water (at a temperature of 22.4 °C), and then 62 g of K2CO3 was mixed in while stirring. Vigorous foaming occurred, and the temperature of the reaction vessel rose. After this exothermic reaction, an endothermic reaction was used to cool the mixture by first mixing in 201 g of NH4HCO3 while stirring. Vigorous foaming occurred again, the temperature of the reaction vessel dropped to 23.6 °C, and the pH rose to 4.7.

[0051] b) In the next step of this method, 48 g of K2CO3 was added to the reaction mixture while stirring. Vigorous foaming occurred, the temperature of the reaction vessel rose, and the pH rose further. Subsequently, 83 g of NH4HCO3 was added while stirring again, causing vigorous foaming, and the temperature dropped to 23.6°C and the pH to 8.1.

[0052] c) In this step, 36.5 g of K2CO3 was added to the reaction mixture while stirring. Vigorous foaming occurred, the temperature of the reaction vessel rose, and the pH also increased. Subsequently, 168.7 g of NH4HCO3 was added again while stirring, causing vigorous foaming, and the temperature dropped to 23.6°C and the pH to 8.5.

[0053] d) Addition of phosphoric acid for neutralization: Subsequently, 331 g of H3PO4 (78%) was added with stirring to substantially neutralize the reaction mixture, convert the bicarbonate to carbonic acid, and remove it from the reaction mixture as CO2. The temperature stabilized at 23.7°C and the pH reached 6.7. The density of the resulting liquid NPK fertilizer mixture was 1.32 g / cm³. 3 That was the case.

[0054] Table 2 below summarizes the essential reaction parameters for steps a) to d) of the embodiment of this model.

[0055] [Table 2]

Claims

1. At least the following steps: a) K 2 CO 3 or KHCO 3 The step of mixing in water while stirring the first component of, and maintaining the temperature of the reaction mixture at a maximum temperature of 50 °C by adjusting the amount added and the rate of addition, and then mixing the first component of NH 4 HCO 3 and subsequently mixing the first component of H 3 PO 4 The step of mixing the first component of NH 4 HCO 3 and H 3 PO 4 The step of maintaining the temperature of the reaction mixture at a temperature of at least 5 °C by adjusting the amount added and the rate of addition of b) K 2 CO 3 or KHCO 3 H 3 PO 4 , and NH 4 HCO 3 A step of mixing further amounts of each in this order, and maintaining the temperature of the reaction mixture in the range of 5°C to 50°C, including the endpoint, by adjusting the amount and rate at which each reactant is added. c)K 2 CO 3 or KHCO 3、 and NH 4 HCO 3 The process involves repeating step b) until the total amount is added, d) Optionally, K in steps a) to d) 2 CO 3 or KHCO 3 NH 4 HCO 3 , and H 3 PO 4 The total usage is K 2 CO 3 or KHCO 3 :NH 4 HCO 3 :H 3 PO 4 Until it matches the predetermined molar ratio of H 3 PO 4 The process of adding a further amount of, e) Add more H until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.

3. 3 PO 4 The process of adding A method for producing a liquid NPK fertilizer containing at least the nutrients nitrogen, phosphorus, and potassium.

2. In step a), K 2 CO 3 or KHCO 3 The concentration is in the range of 0.05 to 0.2 mol / l-water. NH 4 HCO 3 The concentration is in the range of 0.07 to 0.2 mol / l-water. H 3 PO 4 The concentration is in the range of 0.3 to 0.75 mol / l-water. The method according to claim 1, characterized in that

3. In step a), K 2 CO 3 or KHCO 3 The initial amount is 5-20% of the total amount used. NH 4 HCO 3 The initial amount is 7-20% of the total amount used. H 3 PO 4 The initial amount is 30-75% of the total amount used in steps a) to d). The method according to claim 1 or 2, characterized in that

4. In step a), K 2 CO 3 or KHCO 3 :NH 4 HCO 3 :H 3 PO 4 The method according to any one of claims 1 to 3, characterized in that the molar ratio of is in the range of 0.05 to 0.2:0.07 to 0.2:0.3 to 0.

75.

5. K in processes a) to d) 2 CO 3 NH 4 HCO 3 , and H 3 PO 4 Total amount used, molar ratio K 2 CO 3 :NH 4 HCO 3 :H 3 PO 4 However, the range is 0.8 to 1.2:0.8 to 1.2:0.8 to 1.2, or, K 2 CO 3 Instead, KHCO 3 When each of these is used, KHCO in steps a) to d) 3 NH 4 HCO 3 , and H 3 PO 4 The molar ratio obtained from the total amount used is KHCO3 3 :NH 4 HCO 3 :H 3 PO 4 The method according to any one of claims 1 to 4, characterized in that the values ​​are in the range of 2.4 to 3.6: 2.4 to 16: 1.6 to 2.

4.

6. In step e), until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.1, H 3 PO 4 The method according to any one of claims 1 to 5, characterized by adding [a specific element].

7. At least the following steps: a) K 2 CO 3 or KHCO 3 The step of adding the first component of to an aqueous solution of while stirring, maintaining the temperature of the reaction mixture at a maximum temperature of 50 °C by adjusting the amount added and the rate of addition, and then 3 PO 4 The step of adding the first component of to an aqueous solution of while stirring, maintaining the temperature of the reaction mixture at a maximum temperature of 50 °C by adjusting the amount added and the rate of addition, and then 4 HCO 3 The step of mixing the first component of, maintaining the temperature of the reaction mixture at a temperature of at least 5 °C by adjusting the amount of added and the rate of addition, and 4 HCO 3 The step of mixing the first component of, maintaining the temperature of the reaction mixture at a temperature of at least 5 °C by adjusting the amount of added and the rate of addition, and It should be noted that there seems to be some incomplete or unclear parts in the original text (such as some missing substances in the chemical formulas), which may affect the full understanding and accuracy of the translation. b) K 2 CO 3 or KHCO 3 NH 4 HCO 3 , and optionally H 3 PO 4 A step of mixing further amounts in this order, wherein the temperature of the reaction mixture is maintained in the range of 5°C to 50°C, including the endpoint, by adjusting the amount and rate at which each reactant is added. c) K in steps a) to c) 2 CO 3 or KHCO 3 NH 4 HCO 3 , and H 3 PO 4 The total usage is K 2 CO 3 or KHCO 3 :NH 4 HCO 3 :H 3 PO 4 The process of repeating step b) until it matches a predetermined molar ratio, d) Add more H until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.

3. 3 PO 4 The process of adding A method for producing a liquid NPK fertilizer containing at least the nutrients nitrogen, phosphorus, and potassium.

8. In step a), H 3 PO 4 The concentration is in the range of 0.3 to 0.75 mol / l-water. K 2 CO 3 or KHCO 3 The concentration is in the range of 0.05 mol to 0.2 mol / l - reaction mixture. NH 4 HCO 3 The concentration is in the range of 0.07 mol to 0.2 mol / l - reaction mixture. The method according to claim 7, characterized in that

9. In step a), K 2 CO 3 or KHCO 3 The initial amount is 5-20% of the total amount used. NH 4 HCO 3 The initial amount is 7-20% of the total amount used. H 3 PO 4 The initial amount is 30-100% of the total amount used in steps a) to c). The method according to claim 7 or 8, characterized by the features described herein.

10. In step a), K 2 CO 3 or KHCO 3 :NH 4 HCO 3 :H 3 PO 4 The method according to any one of claims 7 to 9, characterized in that the molar ratio of is in the range of 0.05 to 0.2:0.07 to 0.2:0.3 to 0.

75.

11. K in steps a) to c) 2 CO 3 NH 4 HCO 3 , and H 3 PO 4 Total amount used, molar ratio K 2 CO 3 :NH 4 HCO 3 :H 3 PO 4 However, the range is 0.8 to 1.2:0.8 to 1.2:0.8 to 1.2, or K 2 CO 3 Instead, KHCO 3 When each of these is used, KHCO in steps a) to c) 3 NH 4 HCO 3 , and H 3 PO 4 The molar ratio obtained from the total amount used is KHCO3 3 :NH 4 HCO 3 :H 3 PO 4 The method according to any one of claims 7 to 10, characterized in that the values ​​are in the range of 2.4 to 3.6:2.4 to 16:1.6 to 2.

4.

12. In step d), until the pH of the reaction mixture reaches a value in the range of 6.5 to 7.1, H 3 PO 4 The method according to any one of claims 7 to 11, characterized by adding [a specific element].

13. The method according to any one of claims 1 to 12, characterized in that all steps of the method, including adjusting the pH of the reaction mixture in the final step, are completed within 1 to 2 hours.

14. The method according to any one of claims 1 to 13, characterized in that no cooling or heating device is used to control the temperature of the reaction.

15. The reaction is carried out in a closed system, and CO is produced during the reaction. 2 The method according to any one of claims 1 to 14, characterized by recovering the following.

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