A method for treating process water in corn starch production

Abstract

The application discloses a treatment method of process water in corn starch production and belongs to the technical field of corn deep processing. The treatment method comprises the following steps: (1) pretreating corn starch process water to obtain material 1; (2) concentrating the material 1 to obtain clear liquid 2 and material 3; (3) separating part of soluble protein in the material 3 by using a gas floatation method to obtain soluble protein 4 and material 5; (4) heating the material 5 by using a plate heat exchanger, then heat-insulating, so that the protein is denatured, and material 6 is obtained; (5) adding sodium hydroxide into the material 6, adjusting pH, standing, filtering, obtaining liquid 7 and filter residue 8, and the liquid 7 is the treated process water. According to the method, the process water is reasonably treated, the content of nutrient substances in the treated process water is reduced, the treated process water can be used instead of clean water or returned to a process for process water use, water consumption in corn starch production is reduced, water resources are saved, production cost is reduced, and economic benefits are increased.

Description

Technical Field

[0001] This invention relates to a method for treating process water in corn starch production, belonging to the field of corn deep processing technology. Background Technology

[0002] Process water is a type of water used in the deep wet process of corn starch production. To reduce water consumption, this process water is recycled across different processes, and all process water from these processes is collected in the same process water tank. This process water contains approximately 3.05% dry matter, approximately 2.0% nitrogenous substances, and approximately 0.6% reducing sugars, with a high ammonia nitrogen content. Discharging it into a wastewater treatment system would reduce its capacity. Because the process water is recycled and continuously circulated within the processes, it is easily contaminated with microorganisms, leading to fermentation, a decrease in pH, and the production of metabolic byproducts. These factors further affect the quality of the corn starch slurry, increasing the difficulty of subsequent sugar refining, raising syrup production costs, and ultimately impacting product quality.

[0003] Therefore, proper treatment of process water can not only reduce water consumption in corn starch production, but also improve the quality of corn starch slurry, reduce subsequent sugar processing costs, and improve syrup quality. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for treating process water in corn starch production. This method can recover protein, improve the yield of corn gluten powder, and effectively solve the problem of declining quality of corn starch slurry caused by the recycling of process water.

[0005] To address the problems in the existing technology, the technical solution provided by this invention is as follows:

[0006] A method for treating process water in corn starch production includes the following steps:

[0007] (1) Pre-treat the corn starch process water to obtain material 1;

[0008] (2) Concentrate material 1 to obtain clear liquid 2 and material 3;

[0009] (3) The soluble protein in material 3 was separated by air flotation to obtain soluble protein 4 and material 5;

[0010] (4) Heat material 5 with a plate heat exchanger, and then put it into a holding tank to keep it warm, so that the protein denatures and material 6 is obtained;

[0011] (5) Add sodium hydroxide to material 6, adjust pH, let stand, filter, and obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water.

[0012] Furthermore, in step (1), the pretreatment operation is as follows: the corn starch process water is filtered; the pretreatment equipment is a tubular microfiltration membrane or a bag filter. The purpose of pretreatment is to remove large molecular insoluble substances.

[0013] Furthermore, in step (2), the concentration is achieved using a reverse osmosis membrane. The purpose of using a reverse osmosis membrane for concentration is to increase the concentration of dry matter in material 3, which facilitates subsequent processing. At the same time, the resulting clear liquid 2 contains very few impurities and can be used as a substitute for water, as well as as process water in the process, thus reducing the waste of water resources.

[0014] Furthermore, in step (2), the dry matter content of material 3 is 15-30%. When the dry matter content of material 3 is less than 15%, the subsequent processing cost increases; when the dry matter content of material 3 is greater than 30%, it will increase the processing cost of this step and affect the service life of the equipment.

[0015] Furthermore, in step (3), the device used in the air flotation method is an air flotation tank; the soluble protein 4 accounts for 20-50% of the total soluble protein in the material 3. The air flotation method is selected to separate the soluble protein in the material 3, and the easily foaming soluble protein is separated. The obtained soluble protein 4 can be recycled back into the corn starch production process to reduce the waste rate of corn protein.

[0016] Furthermore, in step (4), the temperature of the plate heat exchanger is 80-95℃; the heat preservation time is 1-6h. When heating with a plate heat exchanger, the steam will not come into contact with the material 5, thus not reducing the concentration of the material 5, which is beneficial to the subsequent filtration operation; if heated directly, the steam will enter the material, causing the concentration of the material 5 to decrease.

[0017] Furthermore, in step (5), the pH is 4.8-6.0; the settling time is 1-5 hours; the filtration method is plate and frame filtration, and the filter cloth is 300 mesh. The filter residue is mixed back into the wet protein powder, which can improve the yield of corn protein powder; the treated process water can be used to replace clean water or returned to the process for use as process water. The nutrient content in the treated process water is reduced, which reduces the risk of bacterial fermentation and improves the quality of corn starch slurry.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] (1) The method of the present invention provides reasonable treatment of process water. The nutrient content of the treated process water is reduced, and it can be used to replace clean water or returned to the process for use as process water. This reduces water consumption in corn starch production, saves water resources, reduces production costs, and increases economic benefits.

[0020] (2) The method of the present invention treats process water, recovers corn protein, increases the yield of corn protein powder, reduces the nutrient content in the treated process water, reduces the risk of bacterial fermentation in the process water, improves the quality of process water, and correspondingly improves the quality of corn starch slurry, reduces the cost of subsequent sugar production, and improves the quality of syrup. Detailed Implementation

[0021] Example 1

[0022] A method for treating process water in corn starch production includes the following steps:

[0023] (1) The corn starch process water was filtered using a bag filter to obtain material 1;

[0024] (2) Material 1 is concentrated using a reverse osmosis membrane to obtain clear liquid 2 and material 3. Clear liquid 2 is used as process water or clean water in the process, and the dry matter content of material 3 is 25%.

[0025] (3) Using the air flotation method, a portion of the soluble protein in material 3 is separated in an air flotation tank to obtain soluble protein 4 and material 5;

[0026] (4) Heat material 5 to 85°C using a plate heat exchanger, then put it into a holding tank and keep it at the temperature for 4 hours to denature the protein and obtain material 6.

[0027] (5) Add sodium hydroxide to material 6, adjust the pH to 5.2, let stand for 1 hour, filter with plate and frame filter cloth of 300 mesh, to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. Physicochemical properties of the treated process water: dry matter 0.85%, nitrogenous matter 0.41%, ash 0.09%.

[0028] Example 2

[0029] A method for treating process water in corn starch production includes the following steps:

[0030] (1) The corn starch process water was filtered using a bag filter to obtain material 1;

[0031] (2) Material 1 is concentrated using a reverse osmosis membrane to obtain clear liquid 2 and material 3. Clear liquid 2 is used as process water or clean water in the process, and the dry matter content of material 3 is 28%.

[0032] (3) Using the air flotation method, a portion of the soluble protein in material 3 is separated in an air flotation tank to obtain soluble protein 4 and material 5;

[0033] (4) Heat material 5 to 90°C using a plate heat exchanger, then put it into a holding tank and keep it at the temperature for 3 hours to denature the protein and obtain material 6.

[0034] (5) Add sodium hydroxide to material 6, adjust the pH to 5.6, let stand for 2 hours, filter with a plate and frame filter cloth of 300 mesh, and obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physicochemical properties of the treated process water are: dry matter 0.75%, nitrogenous matter 0.37%, and ash 0.08%.

[0035] Example 3

[0036] A method for treating process water in corn starch production includes the following steps:

[0037] (1) The corn starch process water was filtered using a bag filter to obtain material 1;

[0038] (2) Material 1 is concentrated using a reverse osmosis membrane to obtain clear liquid 2 and material 3. Clear liquid 2 is used as process water or clean water in the process, and the dry matter content of material 3 is 30%.

[0039] (3) Using the air flotation method, a portion of the soluble protein in material 3 is separated in an air flotation tank to obtain soluble protein 4 and material 5;

[0040] (4) Heat material 5 to 95°C using a plate heat exchanger, then put it into a holding tank and keep it at the temperature for 2 hours to denature the protein and obtain material 6.

[0041] (5) Add sodium hydroxide to material 6, adjust the pH to 5.0, let stand for 3 hours, filter with plate and frame filter cloth of 300 mesh, to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. Physicochemical properties of the treated process water: dry matter 0.80%, nitrogenous matter 0.39%, ash 0.09%.

[0042] Example 4

[0043] A method for treating process water in corn starch production includes the following steps:

[0044] (1) The corn starch process water was filtered using a bag filter to obtain material 1;

[0045] (2) Material 1 is concentrated using a reverse osmosis membrane to obtain clear liquid 2 and material 3. Clear liquid 2 is used as process water or clean water in the process, and the dry matter content of material 3 is 20%.

[0046] (3) Using the air flotation method, a portion of the soluble protein in material 3 is separated in an air flotation tank to obtain soluble protein 4 and material 5;

[0047] (4) Heat material 5 to 88°C using a plate heat exchanger, then put it into a holding tank and keep it at the temperature for 5 hours to denature the protein and obtain material 6.

[0048] (5) Add sodium hydroxide to material 6, adjust the pH to 5.8, let stand for 4 hours, filter with a plate and frame filter cloth of 300 mesh, and obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physicochemical properties of the treated process water are: dry matter 0.95%, nitrogenous matter 0.48%, and ash content 0.10%.

[0049] Experimental Example 1

[0050] The content of various substances in the corn starch process water before and after the treatment in Examples 1-4 was tested, and the test results are listed in Table 1.

[0051] Table 1. Content of various substances in corn starch process water before and after treatment

[0052]

[0053] As shown in Table 1, before treatment, the dry matter content of the corn starch process water was higher than 2.98%, the nitrogen content was higher than 1.88%, and the ash content was higher than 0.57%. After treatment, the dry matter content of the corn starch process water was lower than 0.95%, the nitrogen content was lower than 0.48%, and the ash content was lower than 0.10%. It can be seen that after treatment by the method of the present invention, the content of various substances in the corn starch process water is significantly reduced, thereby improving the quality of the process water and solving the problems of excessive nutrients in the process water leading to bacterial contamination and fermentation, and pH reduction.

[0054] Experiment Example 2

[0055] Table 2 lists the water savings and corn gluten meal yield increases in Examples 1-4 after treating corn starch process water using the method of this invention.

[0056] Table 2. Water savings in production and increases in corn gluten meal yield

[0057]

[0058] As shown in Table 2, after treating the corn starch production water using the method of the present invention, the water saving in Example 1 was 20.6%, and the corn gluten powder yield increased by 1.9%; the water saving in Example 2 was 20.0%, and the corn gluten powder yield increased by 2.3%; the water saving in Example 3 was 21.1%, and the corn gluten powder yield increased by 2.0%; and the water saving in Example 4 was 20.9%, and the corn gluten powder yield increased by 2.1%. It is evident that the method of the present invention can save production water, reduce waste of water in corn starch production, lower wastewater treatment costs, conserve water resources, and also recover corn gluten, thereby increasing the yield of corn gluten powder.

Claims

1. A method for treating process water in corn starch production, characterized in that: Includes the following steps: (1) Pre-treat the corn starch process water to obtain material 1; (2) Concentrate material 1 to obtain clear liquid 1 and material 3 with a dry matter content of 15-30%; (3) The soluble protein in material 3 was separated by air flotation to obtain soluble protein 4 and material 5; (4) Heat material 5 to 80-95℃ using a plate heat exchanger, and then keep it in a holding tank for 1-6 hours to denature the protein and obtain material 6. (5) Add sodium hydroxide to material 6, adjust the pH to 4.8-6.0, let stand for 1-5 hours, filter, and obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water.

2. The method for treating process water in corn starch production according to claim 1, characterized in that: In step (1), the pretreatment operation is to filter the corn starch process water.

3. The method for treating process water in corn starch production according to claim 2, characterized in that: The pretreatment equipment is a tubular microfiltration membrane or a bag filter.

4. The method for treating process water in corn starch production according to claim 3, characterized in that: In step (2), the concentration is achieved using a reverse osmosis membrane.

5. The method for treating process water in corn starch production according to claim 4, characterized in that: In step (3), the device used in the air flotation method is an air flotation tank.

6. The method for treating process water in corn starch production according to claim 5, characterized in that: In step (3), the soluble protein 4 accounts for 20-50% of the total soluble protein in material 3.

7. The method for treating process water in corn starch production according to claim 6, characterized in that: In step (5), the filtration method is plate and frame filtration, and the filter cloth is 300 mesh.

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