Treatment method of process water in corn starch production

Abstract

The invention discloses a method for treating 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 a material 1; (2) concentrating the material 1 to obtain a clear liquid 2 and a material 3; (3) separating out part of soluble protein in the material 3 by adopting an air flotation method to obtain soluble protein 4 and a material 5; (4) heating the material 5 by using a plate heat exchanger, and then preserving heat to denature the protein to obtain a material 6; and (5) adding sodium hydroxide into the material 6, adjusting the pH value, standing and filtering to obtain liquid 7 and filter residues 8, and the liquid 7 is the treated process water. According to the method disclosed by the invention, 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 can be used as the process water in the process, water consumption for corn starch production is reduced, water resources are saved, the production cost can be reduced, and economic benefits are increased.

Description

Technical Field

[0001] The invention relates to a method for treating process water in corn starch production, and belongs to the technical field of corn deep processing. Background Art

[0002] Process water is a process water in the deep wet production process of corn starch. In order to reduce water consumption, the process water is recycled in different processes. The process water produced in different processes is collected in the same process water pool. The process water contains about 3.05% dry matter, about 2.0% nitrogen-containing substances, about 0.6% reducing sugar, and high ammonia nitrogen content. If it is discharged into the sewage treatment system, it will reduce the sewage treatment capacity. Since the process water is recycled and has been circulating in the process, it is easy to cause bacterial fermentation, reduce the pH value of the process water, and produce some metabolites, which further affects the product quality of corn starch slurry, thereby increasing the difficulty of subsequent sugar refining, increasing the production cost of syrup, and affecting product quality.

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

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for treating process water in corn starch production, which can recover protein, improve the yield of corn protein powder, and effectively solve the problem of corn starch slurry quality degradation caused by recycling process water.

[0005] In order to solve the problems of the prior art, the technical solution provided by the present invention is: A method for treating process water in corn starch production comprises the following steps: (1) Pretreating corn starch process water to obtain material 1; (2) Concentrating material 1 to obtain clear liquid 2 and material 3; (3) Using air flotation method to separate part of the soluble protein in material 3, so as to obtain soluble protein 4 and material 5; (4) Material 5 is heated by a plate heat exchanger and then placed in a holding tank for heat preservation to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH, let it stand, and filter to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water.

[0006] Furthermore, in step (1), the pretreatment operation is: filtering the corn starch process water; the pretreatment equipment is a tubular microfiltration membrane or a bag filter. The purpose of the pretreatment is to remove macromolecular insoluble substances.

[0007] Furthermore, in step (2), the concentration is performed using a reverse osmosis membrane. The purpose of using a reverse osmosis membrane for concentration is to increase the concentration of dry matter in the material 3, which is convenient for subsequent treatment. At the same time, the obtained clear liquid 2 contains very few impurities and can be used instead of clean water, and can also be used as process water in the process, thereby reducing the waste of water resources.

[0008] Furthermore, in step (2), the dry matter content of material 3 is 15-30%. When the dry matter content of material 3 is lower than 15%, the subsequent processing cost increases; when the dry matter content of material 3 is higher than 30%, the processing cost of this step increases and the service life of the equipment is affected.

[0009] Furthermore, in step (3), the device used for 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 used to separate the soluble protein in the material 3, and the soluble protein that is easy to foam is separated. The obtained soluble protein 4 can be mixed back into the corn starch production process to reduce the waste rate of corn protein.

[0010] Furthermore, in step (4), the temperature of the plate heat exchanger is 80-95°C and the insulation time is 1-6 hours. When heating with a plate heat exchanger, the steam will not contact the material 5, thereby 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.

[0011] Furthermore, in step (5), the pH is 4.8-6.0; the standing time is 1-5 hours; the filtering method is plate and frame filtering, and the filter cloth model is 300 mesh. The filter residue is mixed back into the wet protein powder to increase the yield of corn protein powder; the treated process water can be used instead of clean water or returned to the process for process water use. The nutrient content in the treated process water is reduced, the risk of bacterial fermentation is reduced, and the quality of corn starch slurry is improved.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) The method of the present invention treats process water reasonably. The nutrient content in the treated process water is reduced, and the treated process water can be used instead of clean water or returned to the process for use as process water, thereby reducing water consumption in corn starch production, saving water resources, and reducing production costs and increasing economic benefits.

[0013] (2) The method of the present invention treats process water, recovers corn protein, and improves the yield of corn protein powder. It also reduces the nutrient content in the treated process water, reduces the risk of bacterial contamination and fermentation of the process water, improves the quality of the process water, and correspondingly improves the quality of corn starch slurry, reduces the subsequent sugar processing costs, and improves the quality of the syrup. DETAILED DESCRIPTION

[0014] Example 1 A method for treating process water in corn starch production comprises the following steps: (1) Filter the corn starch process water with a bag filter to obtain material 1; (2) Material 1 is concentrated by 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. The dry matter content of material 3 is 25%; (3) using an air flotation tank to separate part of the soluble protein in material 3 to obtain soluble protein 4 and material 5; (4) Material 5 is heated to 85°C using a plate heat exchanger, and then enters a holding tank and is kept warm for 4 hours to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH to 5.2, let stand for 1 hour, and filter with a plate and frame filter with a filter cloth model of 300 mesh to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physical and chemical indicators of the treated process water are: dry matter 0.85%, nitrogen-containing matter 0.41%, and ash 0.09%.

[0015] Example 2 A method for treating process water in corn starch production comprises the following steps: (1) Filter the corn starch process water with a bag filter to obtain material 1; (2) Material 1 is concentrated by 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. The dry matter content of material 3 is 28%; (3) using an air flotation tank to separate part of the soluble protein in material 3 to obtain soluble protein 4 and material 5; (4) Material 5 is heated to 90°C using a plate heat exchanger, and then enters a holding tank and is kept warm for 3 hours to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH to 5.6, let stand for 2 hours, and filter with a plate and frame filter with a filter cloth model of 300 mesh to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physical and chemical indicators of the treated process water are: dry matter 0.75%, nitrogen-containing matter 0.37%, and ash 0.08%.

[0016] Example 3 A method for treating process water in corn starch production comprises the following steps: (1) Filter the corn starch process water with a bag filter to obtain material 1; (2) Material 1 is concentrated by 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. The dry matter content of material 3 is 30%; (3) using an air flotation tank to separate part of the soluble protein in material 3 to obtain soluble protein 4 and material 5; (4) Material 5 is heated to 95°C using a plate heat exchanger, and then enters a holding tank and is kept warm for 2 hours to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH to 5.0, let stand for 3 hours, and filter with a plate and frame filter with a filter cloth model of 300 mesh to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physical and chemical indicators of the treated process water are: dry matter 0.80%, nitrogen-containing matter 0.39%, and ash 0.09%.

[0017] Example 4 A method for treating process water in corn starch production comprises the following steps: (1) Filter the corn starch process water with a bag filter to obtain material 1; (2) Material 1 is concentrated by 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. The dry matter content of material 3 is 20%; (3) using an air flotation tank to separate part of the soluble protein in material 3 to obtain soluble protein 4 and material 5; (4) Material 5 is heated to 88°C using a plate heat exchanger, and then enters a holding tank and is kept warm for 5 hours to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH to 5.8, let stand for 4 hours, and filter with a plate and frame filter with a filter cloth model of 300 mesh to obtain liquid 7 and filter residue 8. Liquid 7 is the treated process water. The physical and chemical indicators of the treated process water are: dry matter 0.95%, nitrogen-containing matter 0.48%, and ash 0.10%.

[0018] Experimental Example 1 The contents of various substances in the corn starch process water before and after the treatment of Examples 1-4 were tested, and the test results are listed in Table 1.

[0019] Table 1. Content of various substances in corn starch process water before and after treatment As can be seen from Table 1, before treatment, the dry matter content in the corn starch process water is higher than 2.98%, the nitrogen-containing substance content is higher than 1.88%, and the ash content is higher than 0.57%. After treatment, the dry matter content in the corn starch process water is lower than 0.95%, the nitrogen-containing substance content is lower than 0.48%, and the ash content is 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 problem of excessive nutrients in the process water causing bacterial fermentation and reduced pH.

[0020] Experimental Example 2 After the corn starch process water is treated by the method of the present invention, the amount of water saved in the production of Examples 1-4 and the amount of corn protein powder yield increased are listed in Table 2.

[0021] Table 2. Savings in production water and increase in corn gluten meal yield As can be seen from Table 2, after the corn starch process water is treated by the method of the present invention, the production water saving amount of Example 1 is 20.6%, and the corn gluten powder yield is increased by 1.9%; the production water saving amount of Example 2 is 20.0%, and the corn gluten powder yield is increased by 2.3%; the production water saving amount of Example 3 is 21.1%, and the corn gluten powder yield is increased by 2.0%; the production water saving amount of Example 4 is 20.9%, and the corn gluten powder yield is increased by 2.1%. It can be seen that the method of the present invention can save production water, reduce the waste of water for corn starch production, reduce sewage treatment costs, save the use of water resources, and can also recover corn protein and increase the yield of corn gluten powder.

Claims

1. A method for treating process water in corn starch production, characterized in that: The following steps are involved: (1) Pretreating corn starch process water to obtain material 1; (2) Concentrating material 1 to obtain clear liquid 1 and material 3; (3) Using air flotation method to separate part of the soluble protein in material 3, so as to obtain soluble protein 4 and material 5; (4) Material 5 is heated by a plate heat exchanger and then placed in a holding tank for heat preservation to denature the protein, thereby obtaining material 6; (5) Add sodium hydroxide to material 6, adjust the pH, let it stand, and filter to 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: filtering 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 1, characterized in that: In step (2), the concentration uses a reverse osmosis membrane.

5. The method for treating process water in corn starch production according to any one of claims 1 to 4, characterized in that: In step (2), the dry matter content in material 3 is 15-30%.

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

7. The method for treating process water in corn starch production according to claim 1, characterized in that: In step (3), the soluble protein 4 accounts for 20-50% of the total soluble protein in material 3.

8. The method for treating process water in corn starch production according to claim 1, characterized in that: In step (4), the temperature of the plate heat exchanger is 80-95° C. and the insulation time is 1-6 hours.

9. The method for treating process water in corn starch production according to claim 7 or 8, characterized in that: In step (5), the pH is 4.8-6.0 and the standing time is 1-5 hours.

10. The method for treating process water in corn starch production according to claim 9, characterized in that: In step (5), the filtering method is plate and frame filtration, and the filter cloth model is 300 mesh.

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