Production method of potassium humate fertilizer by continuous high-pressure hydrothermal method using potassium feldspar

Abstract

The invention discloses a production method for preparing humic acid potassium fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar, which involves a wet grinding pulping process, a hydrothermal reaction process, a flash filtration and pressure filtering process, a humic acid-modified potassium fertilizer preparation process, and a causticizing and humic acid-modified calcium silicate fertilizer preparation process. The method comprises the following steps: firstly, finely ground potassium feldspar alkaline ore pulp is subjected to a high-pressure tubular hydrothermal reaction and a tower delayed reaction to prepare potassium aluminosilicate and calcium silicate; the alkaline potassium aluminosilicate filter residue obtained by filtration is mixed with humic acid, modified, granulated, and dried to obtain a humic acid-coated long-acting slow-release potassium fertilizer product; the alkaline potassium silicate filtrate is subjected to a causticizing reaction with lime to obtain a KOH solution which is returned to the wet pulping process for recycling; and the alkaline calcium silicate is mixed with humic acid, modified, granulated, and dried to produce a humic acid-coated long-acting slow-release calcium silicate fertilizer product.

Description

1. Technical Field

[0001] The invention provides a production method for preparing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar, and relates to the field of fine chemicals. 2. Background Technology

[0002] Potassium is one of the three essential nutrients for crop growth. It enhances crops' resistance to drought, cold, disease, salt, and lodging, significantly contributing to stable and high yields. Therefore, nearly every crop requires the appropriate application of potassium fertilizer. my country, a vast agricultural country, faces a significant demand for potassium fertilizer. However, due to the extreme scarcity of water-soluble potassium salts used as potash fertilizer, reserves of potassium salts, equivalent to K₂O, are approximately 450 million tons, representing only 2.647% of the world's total. This results in my country, the world's largest consumer of potash fertilizer, having an external dependence of over 50%.

[0003] However, my country possesses extremely abundant water-insoluble potash resources characterized by widespread distribution, high quality, and ease of mining. Potash feldspar is the most representative of these minerals, found in 23 provinces and regions, including Inner Mongolia, Anhui, Heilongjiang, Sichuan, and Xinjiang, with estimated reserves exceeding 20 billion tons. Potash feldspar, with its three-dimensional framework structure formed by Si-Al-O tetrahedra, is chemically stable and virtually resistant to decomposition by acids and bases other than concentrated sulfuric acid and hydrofluoric acid at room temperature and pressure. Therefore, the key to extracting potash salts is to efficiently decompose potash feldspar and convert its water-insoluble potassium into water-soluble potassium compounds.

[0004] More than ten process methods have been developed for producing potassium fertilizer from potassium feldspar at home and abroad, including low-temperature decomposition, hydrothermal decomposition, microbial decomposition, molten salt ion exchange, roasting, blast furnace smelting, high-temperature melting and microwave radiation. However, there are some technical and economic problems, such as single product, excessive energy consumption, serious environmental pollution, overly complicated production process, large amount of tailings residue, excessive alkalinity of potassium fertilizer, and insufficient full resource utilization. So far, large-scale industrial production has not been seen. It is urgent to develop a universal production method and equipment for the large-scale continuous high-pressure hydrothermal production of modified potassium fertilizer from potassium feldspar to solve the problem of full resource utilization of potassium feldspar resources. 3. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of existing potassium feldspar production technology for potassium fertilizer production by continuously high-pressure hydrothermal production of potassium feldspar. The present invention provides a production method for producing humic acid potassium fertilizer by continuous high-pressure hydrothermal production of potassium feldspar. The method comprises the following steps: wet grinding potassium feldspar with a KOH solution to produce an alkaline slurry; subjecting the alkaline slurry to an enhanced hydrothermal reaction in an electromagnetic pipeline reactor and a tower-type delayed reactor; flash separation of the hydrothermal reaction slurry followed by steam heat recovery and slurry dilution, flocculation, and filter pressing; mixing the filter residue with humic acid for modification and granulation to produce a long-acting slow-release potassium fertilizer; causticizing the filtrate with lime to produce a KOH solution, which is then returned to the wet pulping process; and mixing calcium silicate with humic acid for modification and granulation. The method overcomes the shortcomings of the existing potassium feldspar hydrothermal production method for potassium fertilizer production, such as low potassium extraction rate, excessive alkalinity of the potassium fertilizer product, excessive energy consumption, severe environmental pollution, and ineffective utilization of tailings residue, thereby achieving large-scale, clean, and efficient full-resource fertilizer utilization of potassium feldspar resources.

[0006] The technical solution of the present invention:

[0007] The production method of potassium feldspar continuous high-pressure hydrothermal production of potassium humate fertilizer comprises the following steps: (1) wet grinding pulping process: first, KOH solution and crushed potassium feldspar are added to a wet grinder in a weight ratio of 1.5-5:1 and finely ground to produce alkaline ore pulp, the KOH solution concentration is 25wt%-45wt%, and the pulping temperature is less than 80°C; (2) hydrothermal reaction process: the alkaline slurry obtained in the previous step is pressurized by a high-pressure pump and then sent into an electromagnetic pipeline reactor for hydrothermal reaction, wherein the flow rate in the tube is 1-5 m / s, the reaction temperature is 200-350°C, the pressure is the saturated pressure at the reaction temperature, and the reaction time is 1-900 seconds, and then the slurry is sent into a tower delay reactor to extend the reaction time for 30-240 minutes to further strengthen the hydrothermal reaction, and a hydrothermal reaction slurry with a potassium extraction rate of 95%-99.9% is obtained from the bottom of the tower delay reactor; (3) flash evaporation and pressure filtration process: the hydrothermal reaction slurry is passed into a pressure-reducing flash evaporation tower Flash separation, the pressure at the top of the flash tower is normal pressure - 30KPa, the high-temperature steam at the top of the tower is used to preheat the air and then obtain cooling water, the slurry at the bottom of the tower is diluted with cooling water and then filtered to obtain alkaline potassium silicate residue and potassium silicate filtrate; (4) Humic acid modified potash fertilizer preparation process: the alkaline potassium silicate residue is mixed with humic acid in a weight ratio of 1:0.1-0.3 to modify and granulate to produce neutral long-term slow-release potash fertilizer, and the humic acid coating is obtained after heating and drying with hot air. Long-term slow-release potassium fertilizer product; (5) Preparation process of causticizing and humic acid modified calcium silicate fertilizer: alkaline potassium silicate filtrate is causticized with lime in a potassium to calcium molar ratio of 2:1-1.2 to obtain KOH solution which is returned to the wet pulping process for recycling; alkaline calcium silicate and humic acid are mixed and modified in a weight ratio of 1:0.1-0.3 to produce neutral long-term slow-release calcium silicate fertilizer; and humic acid coated long-term slow-release calcium silicate fertilizer is obtained after hot air heating and drying.

[0008] Among them, the electromagnetic heating tubular reactor is a tubular reactor in which, under the action of the electromagnetic heating controller, high-frequency alternating current passes through the coil to generate an alternating magnetic field, and the tubular reactor wall and the internal self-mixing strengthening internal components generate eddy current self-heating, thereby achieving uniform heating, rapid temperature rise and hydrothermal reaction of the high-pressure alkaline slurry; the self-mixing strengthening internal components are regular packing type, X-cross plate type or spiral plate type.

[0009] The tower delayed reactor has a height-to-diameter ratio of 3-30:1, and has filler components, grid self-mixing components or an empty tower inside.

[0010] The flash tower is set to 1-6 stages, and the heat exchanger for flash high-temperature steam cooling is a fire-tube heat exchanger that is easy to clear.

[0011] The humic acid used in the humic acid coated long-acting slow-release potash fertilizer and the humic acid coated long-acting slow-release silicon-calcium fertilizer is a mixture of one or more of biological humic acid, mineral humic acid, molasses waste liquid or monosodium glutamate waste liquid concentrate.

[0012] The potassium aluminosilicate filter residue reacts with biological fulvic acid at a carboxyl to methyl molar ratio of 1-3:1 and a temperature of 15-90°C to generate water-soluble potassium fulvic acid and insoluble aluminum silicate.

[0013] The present invention will be described in detail with reference to embodiments. 4. Description of the Figures

[0014] Attachment Figure 1 Schematic diagram of the present invention.

[0015] Attachment Figure 1 The following is a description of the drawings:

[0016] 1. Crusher 2. Wet Grinding Mill 3. High-Pressure Feed Pump 4. Electromagnetic Heating Tubular Reactor 5. Electromagnetic Heating Controller 6. Tower Delay Reactor 7. Flash Tower 8. Heat Exchanger 9. Flocculation Addition Tank 10. Filter Press 1 11. Mixing and Modifying Granulator 1 12. Dryer 1 13. Causticizing Reactor 14. Filter Press 2 15. Mixing and Modifying Granulator 2 16. Dryer 2A, Flocculant Inlet B, Lime Inlet C, Cold Air Inlet D, Humic Acid-Coated Long-Release Potash Fertilizer E, Humic Acid-Coated Long-Release Silicon-Calcium Fertilizer Outlet

[0017] The process characteristics of the present invention are described in detail below with reference to the accompanying drawings and embodiments. 5. Specific implementation methods

[0018] In the embodiment, a production method for preparing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar comprises the following steps: (1) a wet grinding pulping process: the potassium feldspar crushed by a crusher (1) and a KOH solution are added to a wet grinder (2) in a weight ratio of 1:1.5-5 to prepare an alkaline ore pulp, wherein the concentration of the KOH solution is 25wt%-45wt% and the pulping temperature is less than 80°C; (2) a hydrothermal reaction process: the alkaline pulp obtained in the previous step is pressurized by a high-pressure pump (3) and then sent to an electromagnetic pipeline reactor (4), and the electromagnetic pipeline reactor (4) is heated under the action of an electromagnetic heating controller (5). The wall and internal components generate eddy currents to uniformly heat and perform hydrothermal reaction, wherein the flow rate in the tube is 1-5 m / s, the reaction temperature is 200-350°C, the pressure is the saturated pressure at the reaction temperature, and the reaction time is 1-900 seconds. The reaction is then continued in the tower-type delayed reactor (6) to extend the reaction time by 30-240 minutes to further strengthen the hydrothermal reaction. A hydrothermal reaction slurry containing a potassium extraction rate of 95%-99.9% is obtained from the bottom of the tower-type delayed reactor (6); (3) flash evaporation and filtration step: the hydrothermal reaction slurry is passed into the pressure-reducing flash evaporation tower (7) for flash evaporation separation, and the top pressure of the flash evaporation tower (7) is 100-2000 seconds. The pressure is normal pressure -30KPa, and the high-temperature steam obtained at the top of the tower is passed through the heat exchanger (8) to preheat the air to obtain cooling water. The cooling water is added to the tank (9) after flocculation and then added to the slurry from the bottom of the tower for dilution and flocculation, and then filtered by the filter press 1 (10) to obtain alkaline potassium silicate residue and potassium silicate filtrate; (4) Humic acid modified potash fertilizer preparation process: the alkaline potassium silicate residue and humic acid are mixed and modified in the mixing and modification granulator 1 (11) at a weight ratio of 1:0.1-0.3, and the humic acid coated potassium silicate is dried by hot air in the dryer 1 (12) to produce neutral potassium silicate. Humic acid coated long-term slow-release potassium fertilizer product; (5) causticizing and humic acid modified silicon calcium fertilizer preparation process: alkaline potassium silicate filtrate and lime are subjected to causticizing reaction in a causticizer (13) according to a potassium to calcium molar ratio of 2:1-1.2, and the KOH solution is obtained by a filter press 2 (14) and returned to the wet pulping process for recycling, and alkaline calcium silicate and humic acid are mixed and modified and granulated in a mixing and modification granulator 2 (15) according to a weight ratio of 1:0.1-0.3, and the humic acid coated calcium aluminate is heated and dried with hot air in a dryer 1 (12) to produce a neutral humic acid coated long-term slow-release silicon calcium fertilizer product;

[0019] The electromagnetic heating tubular reactor (4) is configured such that when a high-frequency alternating current is passed through a coil to generate an alternating magnetic field under the action of an electromagnetic heating controller (5), the tubular reactor wall and the self-mixing strengthening internal components therein generate eddy current self-heating, thereby achieving uniform heating, rapid temperature rise, and hydrothermal reaction of the high-pressure alkaline slurry; and the self-mixing strengthening internal components are of a structured packing type, an X-cross plate type, or a spiral plate type.

[0020] The tower-type delayed reactor (6) has a height-to-diameter ratio of 3-30:1, and has a filler component, a grid self-mixing component or an empty tower inside.

[0021] The flash tower (7) is set to 1-6 stages, and the heat exchanger (8) for flash high-temperature steam cooling is a fire-tube heat exchanger that is easy to clear.

[0022] The humic acid used in the humic acid coated long-acting slow-release potash fertilizer and the humic acid coated long-acting slow-release silicon-calcium fertilizer is a mixture of one or more of biological humic acid, mineral humic acid, molasses waste liquid or monosodium glutamate waste liquid concentrate.

[0023] The potassium aluminosilicate filter residue reacts with biological fulvic acid at a carboxyl to potassium molar ratio of 1-3:1 and a temperature of 15-90°C to generate water-soluble potassium fulvic acid and insoluble aluminum silicate.

[0024] The specific reaction conditions and experimental results are as follows:

[0025] (1) A 30 wt% KOH solution and potassium feldspar less than 6 mm and containing 13% potassium are wet-ground into an alkaline ore pulp with a particle size of ≤60 μm at a weight ratio of 3:1 at a temperature of 45°C, and then subjected to a hydrothermal reaction in an electromagnetic pipeline reactor at a flow rate of 2 m / s and a temperature of 280°C for 10 seconds, and then delayed in a tower-type delayed reactor for 50 minutes to obtain a hydrothermal reaction slurry with a potassium extraction rate of 98%; the hydrothermal reaction slurry is flash-stripped in a secondary flash tower, steam heat-exchanged with air and diluted and filtered, and the filtrate is causticized and then filtered, and the obtained potassium aluminosilicate and calcium silicate are respectively mixed by adding 10% biological brown-black humic acid, modified, granulated and dried to obtain a humic acid-coated long-acting slow-release potassium fertilizer product containing 28% potassium and 22% silicon and a humic acid-coated long-acting slow-release silicon-calcium fertilizer product containing 24% silicon. The KOH solution obtained by causticization is circulated and 10% KOH needs to be supplemented.

[0026] (2) 35wt% KOH solution and potassium feldspar less than 6mm and containing 13% potassium are wet-ground into alkaline ore pulp with a particle size of ≤74μm at a weight ratio of 2.5:1 and a temperature of 60°C. The mixture is then hydrothermally reacted in an electromagnetic pipeline reactor at a flow rate of 3 m / s and a temperature of 290°C for 7 seconds, and then delayed reacted in a tower-type delayed reactor for 60 minutes to obtain a hydrothermal reaction slurry with a potassium extraction rate of 99.5%. The hydrothermal reaction slurry is flash-distilled and separated in a secondary flash tower, steam heat-exchanged with air and diluted and filtered, and the filtrate is causticized and then filtered. The obtained potassium aluminosilicate and calcium silicate are respectively mixed by adding 15% of mineral-derived brown-black humic acid, modified, granulated and dried to obtain a humic acid-coated long-acting slow-release potassium fertilizer product containing 27% potassium and 20% silicon and a humic acid-coated long-acting slow-release silicon-calcium fertilizer product containing 24.2% silicon. The causticized KOH solution is circulated and 9% KOH needs to be supplemented.

[0027] (3) 35 wt% KOH solution and potassium feldspar less than 6 mm and containing 13% potassium are wet-ground into alkaline ore slurry with a particle size of ≤74 μm at a temperature of 60°C, and then subjected to hydrothermal reaction in an electromagnetic pipeline reactor at a flow rate of 3 m / s and a temperature of 290°C for 7 seconds, and then delayed reaction in a tower-type delayed reactor for 60 minutes to obtain a hydrothermal reaction slurry with a potassium extraction rate of 99.5%; the hydrothermal reaction slurry is flash-steamed and separated in a secondary flash tower, and steam heat exchanged in an air-cooled reactor. The obtained calcium silicate is filtered through dilution and causticized, and then filtered again. 15% of biological brown-black humic acid is added for mixing, modification, granulation and drying to obtain a humic acid-coated long-acting slow-release calcium silicate fertilizer product containing 24.2% silicon. The KOH solution obtained by causticization is circulated and 9% KOH needs to be supplemented. The obtained potassium aluminosilicate is reacted at a temperature of 65°C according to a carboxyl to methanol molar ratio of 2:1 to generate a potassium fulvic acid solution and a difficult aluminum silicate precipitate. The potassium fulvic acid solution is dried to obtain a potassium fulvic acid product containing 30% potassium.

[0028] The present invention provides a production method for preparing humic acid potassium fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar. The method comprises in-situ KOH wet grinding activation and electromagnetic heating pipeline high-pressure hydrothermal desiliconization, enhanced hydrothermal desiliconization in a tower-type delayed reactor, and flash separation. The separated steam heats air for product drying. The alkaline hydrated desiliconized potassium fertilizer and calcium silicon fertilizer are neutralized, modified, and granulated with humic acid to obtain a universal long-acting slow-control fertilizer. The method improves the potassium extraction rate of potassium fertilizer produced by the original potassium feldspar hydrothermal method from 85% to over 99%, reduces the pH value of the potassium fertilizer product from 13 to 6-8, reduces electromagnetic heating energy consumption by 30%, eliminates dust and wastewater pollution, and realizes large-scale, clean, efficient, and full-resource fertilizer utilization of potassium feldspar resources.

Claims

1. A production method for preparing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar, characterized in that The following steps are involved: (1) Wet grinding and pulping process: first, KOH solution and crushed potassium feldspar are added to a wet grinder in a weight ratio of 1.5-5:1 and finely ground to produce alkaline ore pulp, the KOH solution concentration is 25wt%-45wt%, and the pulping temperature is less than 80°C; (2) Hydrothermal reaction process: the alkaline slurry obtained in the previous step is pressurized by a high-pressure pump and sent to an electromagnetic pipeline reactor for hydrothermal reaction, wherein the flow rate in the tube is 1-5 m / s, the reaction temperature is 200-350°C, the pressure is the saturated pressure at the reaction temperature, and the reaction time is 1-900 seconds, and then enters a tower delay reactor to extend the reaction time for 30-240 minutes to further strengthen the hydrothermal reaction, and a hydrothermal reaction slurry with a potassium extraction rate of 95%-99.9% is obtained from the bottom of the tower delay reactor; (3) Flash evaporation and pressure filtration process: the hydrothermal reaction slurry is passed into a pressure-reducing flash tower for flash separation, and the pressure at the top of the flash tower is atmospheric pressure -30KPa, the top of the tower obtains high-temperature steam to preheat the air and then obtains cooling water, the slurry at the bottom of the tower is diluted with cooling water and then filtered to obtain alkaline potassium silicate residue and potassium silicate filtrate; (4) Humic acid modified potash fertilizer preparation process: the alkaline potassium silicate residue is mixed with humic acid in a weight ratio of 1:0.1-0.3 for modification and granulation to produce a neutral long-term slow-release potash fertilizer, which is then dried by hot air to obtain a humic acid coated long-term slow-release potash fertilizer product; (5) Causticization and humic acid modified silicon calcium fertilizer preparation process: the alkaline potassium silicate filtrate is causticized with lime in a potassium to calcium molar ratio of 2:1-1.2 to obtain a KOH solution which is returned to the wet pulping process for recycling, the alkaline calcium silicate and humic acid are mixed with humic acid in a weight ratio of 1:0.1-0.3 for modification and granulation to produce a neutral long-term slow-release silicon calcium fertilizer, which is then dried by hot air to obtain a humic acid coated long-term slow-release silicon calcium fertilizer product.

2. The method for producing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar according to claim 1, characterized in that In the electromagnetic heating tubular reactor, when high-frequency alternating current passes through the coil to generate an alternating magnetic field under the action of the electromagnetic heating controller, the tubular reactor wall and the internal self-mixing strengthening internal components generate eddy current self-heating, thereby achieving uniform heating, rapid temperature rise and hydrothermal reaction of the high-pressure alkaline slurry; the self-mixing strengthening internal components are structured packing type, X-cross plate type or spiral plate type.

3. The method for producing potassium humate fertilizer by continuous high-pressure hydrothermal production of potassium feldspar according to claim 1, characterized in that The tower delayed reactor has a height-to-diameter ratio of 3-30:1, and has filler components, grid self-mixing components or an empty tower inside.

4. The method for producing potassium humate fertilizer by continuous high-pressure hydrothermal production of potassium feldspar according to claim 1, characterized in that The flash tower is set to 1-6 stages, and the heat exchanger for flash high-temperature steam cooling is a fire-tube heat exchanger that is easy to clear.

5. The method for producing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar according to claim 1, characterized in that The humic acid used in the humic acid coated long-acting slow-release potash fertilizer and the humic acid coated long-acting slow-release silicon-calcium fertilizer is a mixture of one or more of biological humic acid, mineral humic acid, molasses waste liquid or monosodium glutamate waste liquid concentrate.

6. The method for producing potassium humate fertilizer by continuous high-pressure hydrothermal treatment of potassium feldspar according to claim 1, characterized in that The potassium aluminosilicate filter residue reacts with biological fulvic acid at a carboxyl to potassium molar ratio of 1-3:1 and a temperature of 15-90°C to generate water-soluble potassium fulvic acid and insoluble aluminum silicate.

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