A process for producing puffed compound fertilizer by using corn soaking water

Abstract

This invention relates to the field of corn soaking water treatment technology, and particularly to a process for producing expanded compound fertilizer using corn soaking water, comprising the following steps: (1) passing the supernatant of corn soaking water after static sedimentation through an anion exchange resin column; (2) replacing the residual corn soaking water in the anion exchange resin column with compressed air, eluting with potassium sulfate solution, and collecting the first and second eluents respectively; (3) taking the first eluent, adjusting the pH, and then concentrating and hydrolyzing it, the resulting hydrolysate is flash-cooled and filtered, and the collected filtrate is used for later use; (4) taking the filtrate and processing it using a simulated moving bed chromatography separation system to obtain inositol product and phosphate phase; (5) taking the phosphate phase, concentrating and filtering it, adding a decolorizing agent to the collected filtrate, and after decolorization treatment, granulating and drying the decolorized liquid to obtain expanded compound fertilizer. The above process can produce expanded compound fertilizer.

Description

Technical Field

[0001] This invention relates to the field of corn soaking water treatment technology, and in particular to a process for producing expanded compound fertilizer using corn soaking water. Background Technology

[0002] Extruded fertilizers are porous, hollow fertilizers produced through a special processing technique. They feature uniform particle size, good flowability, and are less prone to clumping during storage. They dissolve quickly, making them convenient for transportation and use. In recent years, with the continuous improvement of agricultural technology in my country, drone spraying has become increasingly common. Extruded fertilizers dissolve quickly, offering the advantage of "instant dissolution," making them ideal for drone spraying. Therefore, extruded fertilizers are gaining popularity among growers, and the market prospects are broad.

[0003] Corn soaking water is a byproduct of wet corn starch production, rich in potassium, phosphorus, and protein. Recovering phosphorus from corn soaking water can not only avoid the environmental damage caused by phosphate mining but also alleviate the shortage of phosphate resources in my country, yielding significant economic and social benefits. Currently, there are reports on the production of phosphate fertilizer using corn soaking water, involving either crystallization or liquid fertilizer processes. Crystallization processes require decolorization, crystallization, centrifugation, and drying, resulting in numerous steps, high production costs, and the issue of mother liquor recovery. Liquid fertilizer production processes are relatively simpler but suffer from inconvenient transportation and difficulty in long-term storage. Therefore, it is necessary to develop a process for producing expanded compound fertilizer using corn soaking water to address these issues. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a process for producing expanded compound fertilizer using corn soaking water, in order to address the shortcomings of the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0007] (1) The supernatant of the corn soaking water after standing and settling is adsorbed by an anion exchange resin column, and the effluent is collected for later use.

[0008] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then the anion exchange resin column was eluted with potassium sulfate solution. The first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0009] (3) Take the first desorption solution from step (2), adjust the pH and concentrate it to obtain the concentrated solution, then perform hydrolysis treatment. The hydrolysate is cooled by flash evaporation and filtered. The collected filtrate is used for later use.

[0010] (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain the inositol product and the phosphate phase;

[0011] (5) Take the phosphate phase from step (4), concentrate and filter it, add a decolorizing agent to the collected filtrate, and after decolorization treatment, granulate and dry the decolorized liquid to obtain expanded compound fertilizer.

[0012] As an improved technical solution, in step (1), the resin in the anion exchange resin column is a macroporous weakly basic anion exchange resin, and the supernatant enters the anion exchange resin column at a flow rate of 2-3 BV / h.

[0013] As an improved technical solution, the concentration of potassium sulfate solution in step (2) is 12-18 wt%, and the potassium sulfate solution elutes the anion exchange resin column at a flow rate of 0.5-1.5 BV / h.

[0014] As an improved technical solution, in step (3), the pH of the first desorption solution is adjusted to 5-7, and it is concentrated under vacuum conditions of -0.07 to -0.09 MPa and temperature of 75-95℃ to obtain a concentrated solution with a potassium phytate concentration of 25-35wt%. Then, it is hydrolyzed at 160-180℃ for 8-12 hours. The hydrolysate is flash-evaporated and cooled to 90-100℃, and then filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. The collected filtrate is used for later use.

[0015] As an improved technical solution, in step (4), when using a simulated moving bed chromatography separation system, the simulated moving bed chromatography packing material is a strong acidic cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature of 50-60℃, pressure of 0.1-0.4MPa, valve switching time of 10min, feed flow rate of 5-8L / h, and mobile phase flow rate of 10-20L / h.

[0016] As an improved technical solution, in step (5), the phosphate phase is concentrated under vacuum conditions of -0.05 to -0.09 MPa and temperature of 75-95℃ to obtain a concentrated solution with a solid content of 40-50 wt%, which is then filtered by plate and frame filter with a filter cloth pore size of 400-600 mesh at 90-100℃.

[0017] As an improved technical solution, in step (5), the filtrate collected after filtration is added with 20-40 wt% hydrogen peroxide as the decolorizing agent, the decolorization temperature is 70-80℃, and the decolorization time is 1-2h.

[0018] As an improved technical solution, in step (5), granulation and drying are carried out using a spray fluidized granulation dryer with an inlet air temperature of 160-180℃ and an outlet air temperature of 45-55℃.

[0019] After adopting the above technical solution, the beneficial effects of the present invention are:

[0020] This invention uses the supernatant from corn soaking water after settling as raw material. First, it is adsorbed onto an anion exchange resin column. Compressed air is used to remove residual corn soaking water. Then, potassium sulfate solution is used to elute the resin column, and the eluent is collected in segments. The pH of the eluent with a potassium phytate concentration greater than 5 wt% is adjusted. After concentration, hydrolysis, flash evaporation, and cooling filtration, the collected filtrate is then fed into a simulated moving bed chromatography system for separation. The collected phosphate phase is concentrated and filtered. The collected filtrate is decolorized, and the resulting decolorized solution is granulated and dried to obtain expanded compound fertilizer. In this process, potassium sulfate is used as the desorbent to elute the anion exchange resin column. Compared to potassium chloride or hydrochloric acid as the eluent, this method does not introduce chloride ions and does not corrode subsequent hydrolysis, concentration, or crystallization equipment, significantly reducing equipment investment. Simultaneously, the low solubility of CaSO4 allows for the targeted removal of residual calcium ions from the hydrolysate. Furthermore, hydrogen peroxide is used to oxidize the pigments enriched in the feed solution, reducing the color of the feed solution and improving the product's color. The liquid is then dried using a spray fluidized bed dryer, resulting in spherical hollow porous particles with good flowability and rapid solubility, achieving complete recovery of phosphorus resources and avoiding mother liquor treatment issues. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Example 1

[0023] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0024] (1) 1000L of the supernatant after the corn soaking water has been settled by static sedimentation is passed through an anion exchange resin column (macroporous weak base anion exchange resin, D301--Zhejiang Zhengguang Industrial Co., Ltd.) at a flow rate of 2BV / h, and 1000L of the effluent is collected for later use (for preparing corn steep liquor or extracting substances such as protein and lactic acid).

[0025] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then 100L of anion exchange resin column was eluted with 250L of 12wt% potassium sulfate solution at a flow rate of 0.5BV / h. 200L of the first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and 50L of the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0026] (3) Take 200L of the first desorption solution from step (2), adjust the pH to 5, and concentrate it under vacuum of -0.07MPa and temperature of 75℃ to obtain a concentrated solution with a potassium phytate concentration of 25wt%. Then, hydrolyze it at 160℃ for 8h. The hydrolysate obtained is cooled to 90℃ by flash evaporation and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. Collect 45L of filtrate for later use.

[0027] (4) Take 45L of the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain 100L of inositol product and phosphate phase; the simulated moving bed chromatography packing is a strong acidic cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature 50℃, pressure 0.1MPa, valve switching time 10min, feed flow rate 5L / h, and mobile phase flow rate 10L / h.

[0028] (5) Take 100L of the phosphate phase from step (4) and concentrate it under vacuum of -0.05MPa and temperature of 75℃ to obtain a concentrated liquid with a solid content of 40wt%. The filtration temperature is 90-100℃, and the filter cloth with a pore size of 400-600 mesh is used for plate and frame filtration. Add 0.5% of the filtrate volume of 20wt% hydrogen peroxide to the 25L filtrate. After decolorizing at 70℃ for 1h, granulate the collected decolorized liquid using a spray fluidized granulation dryer with an inlet air temperature of 160℃ and an outlet air temperature of 45℃ to obtain the expanded compound fertilizer.

[0029] Example 2

[0030] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0031] (1) 1000L of the supernatant after the corn soaking water has been collected and allowed to settle is passed through an anion exchange resin column (macroporous weak base anion exchange resin, D301--Zhejiang Zhengguang Industrial Co., Ltd.) at a flow rate of 2.2BV / h, and 1000L of the effluent is collected for later use (for preparing corn steep liquor or extracting substances such as protein and lactic acid).

[0032] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then 100L of anion exchange resin column was eluted with 225L of 13.5wt% potassium sulfate solution at a flow rate of 0.8BV / h. 180L of the first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and 45L of the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0033] (3) Take 180L of the first desorption solution from step (2), adjust the pH to 5.5, and concentrate it under vacuum of -0.08MPa and temperature of 80℃ to obtain a concentrated solution with a potassium phytate concentration of 28wt%. Hydrolyze it at 165℃ for 9h. The hydrolysate is then cooled to 93℃ by flash evaporation and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. Collect 40L of filtrate for later use.

[0034] (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain 100L of inositol product and phosphate phase; the simulated moving bed chromatography packing is a strong acid cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature 52℃, pressure 0.2MPa, valve switching time 10min, feed flow rate 6L / h, and mobile phase flow rate 12L / h;

[0035] (5) Take 100L of the phosphate phase from step (4) and concentrate it under vacuum of -0.06MPa and temperature of 80℃ to obtain a concentrated liquid with a solid content of 43wt%. The filtration temperature is 92℃, and the filter cloth with a pore size of 400-600 mesh is used for plate and frame filtration. Add 0.65% of the filtrate volume of 25wt% hydrogen peroxide to the 24L filtrate. After decolorizing at 72℃ for 1.2h, granulate the collected decolorized liquid using a spray fluidized granulation dryer with an inlet air temperature of 165℃ and an outlet air temperature of 48℃ to obtain the expanded compound fertilizer.

[0036] Example 3

[0037] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0038] (1) 1000L of the supernatant after the corn soaking water has been collected and allowed to settle is passed through an anion exchange resin column (macroporous weak base anion exchange resin, LX-360--Xi'an Lanxiao Technology New Material Co., Ltd.) at a flow rate of 2.5BV / h, and 1000L of the effluent is collected for later use (for preparing corn steep liquor or extracting substances such as protein and lactic acid).

[0039] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then 100L of anion exchange resin column was eluted with 200L of 15wt% potassium sulfate solution at a flow rate of 1BV / h. 160L of the first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and 40L of the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0040] (3) Take 160L of the first desorption solution in step (2), adjust the pH to 6, and concentrate it under vacuum of -0.08MPa and temperature of 85℃ to obtain a concentrated solution with a potassium phytate concentration of 30wt%. Hydrolyze it at 170℃ for 10h. The hydrolysate is then cooled to 95℃ by flash evaporation and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. 38L of filtrate is collected for later use.

[0041] (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain inositol product and 90L of phosphate phase; the simulated moving bed chromatography packing is a strong acid cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature 55℃, pressure 0.3MPa, valve switching time 10min, feed flow rate 6L / h, and mobile phase flow rate 15L / h.

[0042] (5) Take 90L of the phosphate phase from step (4) and concentrate it under vacuum of -0.07MPa and temperature of 85℃ to obtain a concentrate with a solid content of 45wt%. The filtration temperature is 95℃, and the filter cloth with a pore size of 400-600 mesh is used for plate and frame filtration. Add 0.7% of the filtrate volume of 30wt% hydrogen peroxide to the 23.5L filtrate. After decolorizing at 75℃ for 1.5h, granulate the collected decolorized liquid using a spray fluidized granulation dryer with an inlet air temperature of 170℃ and an outlet air temperature of 50℃ to obtain the expanded compound fertilizer.

[0043] Example 4

[0044] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0045] (1) 1000L of the supernatant after the corn soaking water has been collected and allowed to settle is passed through an anion exchange resin column (macroporous weak base anion exchange resin, D315--Shanghai Huazhen Technology Co., Ltd.) at a flow rate of 2.8BV / h, and 1000L of the effluent is collected for later use (for preparing corn steep liquor or extracting substances such as protein and lactic acid).

[0046] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then 100L of anion exchange resin column was eluted with 175L of 17wt% potassium sulfate solution at a flow rate of 1.2BV / h. 140L of the first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and 35L of the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0047] (3) Take 140L of the first desorption solution from step (2), adjust the pH to 6.5, and concentrate it under vacuum of -0.09MPa and temperature of 90℃ to obtain a concentrated solution with a potassium phytate concentration of 32wt%. Hydrolyze it at 175℃ for 11h. The hydrolysate is then cooled to 98℃ by flash evaporation and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. 35L of filtrate is collected for later use.

[0048] (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain inositol product and 80L of phosphate phase; the simulated moving bed chromatography packing is a strong acid cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature 58℃, pressure 0.3MPa, valve switching time 10min, feed flow rate 7L / h, and mobile phase flow rate 18L / h.

[0049] (5) Take 80L of the phosphate phase from step (4) and concentrate it under vacuum of -0.08MPa and temperature of 90℃ to obtain a concentrate with a solid content of 48wt%. The filtration temperature is 98℃. The filter is filtered using a plate and frame filter with a filter cloth pore size of 400-600 mesh. Add 0.8% of the filtrate volume of 35wt% hydrogen peroxide to the 21L filtrate. After decolorizing at 78℃ for 1.8h, granulate the collected decolorized liquid using a spray fluidized granulation dryer with an inlet air temperature of 175℃ and an outlet air temperature of 52℃ to obtain the expanded compound fertilizer.

[0050] Example 5

[0051] A process for producing expanded compound fertilizer using corn soaking water includes the following steps:

[0052] (1) 1000L of the supernatant after the corn soaking water has been collected and allowed to settle is passed through an anion exchange resin column (macroporous weak base anion exchange resin, D315--Shanghai Huazhen Technology Co., Ltd.) at a flow rate of 3BV / h, and 1000L of the effluent is collected for later use (for preparing corn steep liquor or extracting substances such as protein and lactic acid).

[0053] (2) The corn soaking water remaining in the anion exchange resin column in step (1) was replaced with compressed air, and then 100L of anion exchange resin column was eluted with 150L of 18wt% potassium sulfate solution at a flow rate of 1.5BV / h. 120L of the first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and 30L of the second desorption solution with potassium phytate concentration <0.5wt% were collected respectively.

[0054] (3) Take 120L of the first desorption solution in step (2), adjust the pH to 7, and concentrate it under vacuum of -0.09MPa and temperature of 95℃ to obtain a concentrated solution with potassium phytate concentration of 35wt%. Hydrolyze it at 180℃ for 12h. The hydrolysate is then cooled to 100℃ by flash evaporation and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. 32L of filtrate is collected for later use.

[0055] (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain 70L of inositol product and phosphate phase; the simulated moving bed chromatography packing is a strong acid cation exchange resin, and the mobile phase is purified water; the separation conditions are: temperature 60℃, pressure 0.4MPa, valve switching time 10min, feed flow rate 8L / h, and mobile phase flow rate 20L / h.

[0056] (5) Take 70L of the phosphate phase from step (4) and concentrate it under vacuum of -0.09MPa and temperature of 95℃ to obtain a concentrate with a solid content of 50wt%. The filtration temperature is 100℃. The filter is filtered using a plate and frame filter with a filter cloth pore size of 400-600 mesh. Add 1% of the filtrate volume of 40wt% hydrogen peroxide to 20L of the filtrate. After decolorizing at 80℃ for 2h, granulate the collected decolorized liquid using a spray fluidized granulation dryer with an inlet air temperature of 180℃ and an outlet air temperature of 55℃ to obtain the expanded compound fertilizer.

[0057] To better demonstrate that the process method of the present invention can produce extruded compound fertilizer with high yield and good performance indicators, 10 comparative examples are given with reference to Example 3. The product indicators of the extruded compound fertilizers obtained by Examples 1-5 and Comparative Examples 1-10 are detailed in Table 1.

[0058] Comparative Example 1

[0059] Unlike Example 3, in step (1), the supernatant was introduced into the anion exchange resin column at a flow rate of 1 BV / h, and the rest of the operation was the same.

[0060] Comparative Example 2

[0061] Unlike Example 3, the supernatant in step (1) was introduced into the anion exchange resin column at a flow rate of 3 BV / h, and the rest of the operation was the same.

[0062] Comparative Example 3

[0063] Unlike Example 3, the concentration of potassium sulfate solution in step (2) is 10 wt%, while the rest of the operation is the same.

[0064] Comparative Example 4

[0065] Unlike Example 3, the concentration of potassium sulfate solution in step (2) is 20 wt%, while the rest of the operation is the same.

[0066] Comparative Example 5

[0067] Unlike Example 3, in step (2), the potassium sulfate solution was used to elute the anion exchange resin column at a flow rate of 2 BV / h, and the rest of the operation was the same.

[0068] Comparative Example 6

[0069] Unlike Example 3, in step (3), the pH of the second desorption solution is adjusted to 4, and the rest of the operation is the same.

[0070] Comparative Example 7

[0071] Unlike Example 3, in step (3), the pH of the second desorption solution is adjusted to 8, and the rest of the operation is the same.

[0072] Comparative Example 8

[0073] Unlike Example 3, the hydrolysate obtained after hydrolysis in step (3) is flash-cooled to 80°C, while the rest of the operation is the same.

[0074] Comparative Example 9

[0075] Unlike Example 3, in step (5), the concentrated solution of the phosphate phase was filtered at 80°C, and the rest of the operation was the same.

[0076] Comparative Example 10

[0077] Unlike Example 3, in step (5), the concentrated solution of the phosphate phase was filtered at 110°C, and the rest of the operation was the same.

[0078] Comparative Example 11

[0079] Unlike Example 3, in step (5), the filtrate collected after filtration is treated with activated carbon as the decolorizing agent, while the rest of the operation is the same.

[0080] Comparative Example 12

[0081] Unlike Example 3, the temperature during the decolorization process in step (5) is 60°C, while the rest of the operations are the same.

[0082] Comparative Example 13

[0083] Unlike Example 3, the temperature during the decolorization process in step (5) is 90°C, while the rest of the operations are the same.

[0084] Comparative Example 14

[0085] Unlike Example 3, step (5) uses a spray fluidized granulation dryer with an inlet air temperature of 150°C and an outlet air temperature of 35°C. The rest of the operation is the same.

[0086] Comparative Example 15

[0087] Unlike Example 3, step (5) uses a spray fluidized granulation dryer with an inlet air temperature of 190°C and an outlet air temperature of 65°C. The rest of the operation is the same.

[0088] Table 1

[0089]

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for producing expanded compound fertilizer using corn soaking water, characterized in that, Includes the following steps: (1) The supernatant of the corn soaking water after settling is adsorbed by an anion exchange resin column, and the effluent is collected for later use; the supernatant is introduced into the anion exchange resin column at a flow rate of 2-3 BV / h; (2) The corn soaking water remaining in the anion exchange resin column in step (1) is replaced with compressed air, and then the anion exchange resin column is eluted with potassium sulfate solution. The first desorption solution with potassium phytate concentration ≥5wt% and sulfate concentration <2000ppm and the second desorption solution with potassium phytate concentration <0.5wt% are collected respectively. The concentration of the potassium sulfate solution is 12-18wt%, and the potassium sulfate solution is eluted at a flow rate of 0.5-1.5BV / h. (3) Take the first desorption liquid from step (2), adjust the pH and concentrate it to obtain the concentrated liquid, then perform hydrolysis treatment. The hydrolysate is flash-cooled and filtered, and the collected filtrate is used for later use. The pH of the first desorption liquid is adjusted to 5-7, and concentrated under vacuum conditions of -0.07 to -0.09 MPa and temperature of 75-95℃ to obtain a concentrated liquid with a potassium phytate concentration of 25-35wt%. Then, it is hydrolyzed at 160-180℃ for 8-12h. The hydrolysate is flash-cooled to 90-100℃ and filtered through a plate and frame filter with a filter cloth pore size of 300-400 mesh. The collected filtrate is used for later use. (4) Take the filtrate from step (3) and process it using a simulated moving bed chromatography separation system to obtain the inositol product and the phosphate phase; (5) Take the phosphate phase from step (4), concentrate it, filter it at 90-100℃, add a decolorizing agent to the collected filtrate, and after decolorization, granulate and dry the decolorized liquid to obtain expanded compound fertilizer; the added decolorizing agent is 20-40wt% hydrogen peroxide, the decolorization temperature is 70-80℃, and the decolorization time is 1-2h; granulation and drying are carried out using a spray fluidized granulation dryer with an inlet air temperature of 160-180℃ and an outlet air temperature of 45-55℃.

2. The process for producing expanded compound fertilizer using corn soaking water according to claim 1, characterized in that, In step (1), the resin in the anion exchange resin column is a macroporous weakly basic anion exchange resin.

3. The process for producing expanded compound fertilizer using corn soaking water according to claim 1, characterized in that, When using a simulated moving bed chromatography system in step (4), the simulated moving bed chromatography packing material is a strong acidic cation exchange resin, and the mobile phase is purified water. The separation conditions are: temperature 50-60℃, pressure 0.1-0.4MPa, valve switching time 10min, feed flow rate 5-8L / h, and mobile phase flow rate 10-20L / h.

4. The process for producing expanded compound fertilizer using corn soaking water according to claim 1, characterized in that, In step (5), the phosphate phase is concentrated under vacuum conditions of -0.05 to -0.09 MPa and temperature of 75-95℃ to obtain a concentrated solution with a solid content of 40-50 wt%, which is then filtered by plate and frame filter with a filter cloth pore size of 400-600 mesh.

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