Clean production method of corn starch in starch sugar industry

Abstract

The invention discloses a clean production method of corn starch in the starch sugar industry, and belongs to the technical field of corn deep processing, energy conservation and emission reduction. The method comprises the following steps: sucking and collecting volatile sulfur dioxide waste gas at exposed parts of materials in a starch workshop by adopting a suction hood, then mixing with clear water to prepare a sulfurous acid solution, introducing the sulfurous acid solution into a corn soaking system by adopting a sulfurous acid solution spraying continuous countercurrent dynamic soaking process, and washing starch milk by using starch sugar evaporation condensate water. According to the clean production method, soluble protein, salt and resin regeneration acid and alkali consumption and wastewater discharge in the starch milk can be reduced, the acid and alkali consumption can be reduced by 30% or above, the product yield can be increased by 5% or above, and the discharge amount of ion exchange water and sewage can be reduced by 35% or above.

Description

Technical Field

[0001] The invention relates to a clean production method of corn starch in the starch sugar industry, and belongs to the technical field of corn deep processing and energy saving and emission reduction. Background Art

[0002] At present, large starch sugar companies at home and abroad basically use corn as raw material, adopt wet process to produce starch, and then further produce various starch sugars. Therefore, the starch sugar industry is a large water consumer. The wastewater discharged from the starch sugar industry is mainly process water and ion exchange wastewater, especially ion exchange wastewater, which can account for more than 80% of the total discharge.

[0003] With the increasing scarcity of water resources and the increasingly stringent national environmental protection requirements, most starch sugar companies adopt a closed-loop process for process water, which only discharges a small amount of process water, and even achieves a completely closed-loop process of process water. The dry matter content in the process water even reaches more than 2.5%. Since the process water contains a large amount of salt, protein, organic acid, etc., using these process waters to grind, wash fiber skins, and germs, especially using process water to prepare sulfite solution to soak corn, will affect the leaching effect, and the recycling of process water directly deteriorates the clean production of starch and reduces the quality of starch milk and various by-products. At the same time, in order to reduce the amount of process water generated, the amount of clean water used is controlled when washing starch. This process reduces the pressure of sewage treatment on the surface, but the salt, organic acid, protein and other components in starch milk remain in the starch in large quantities, greatly increasing the subsequent separation pressure and affecting the separation treatment volume, thereby greatly increasing the discharge of separation wastewater and acid and alkali consumption, not only increasing the pressure of sewage treatment, but also increasing the production cost of starch sugar, while also reducing the quality of by-products. Therefore, there is an urgent need for a clean production method for corn starch in the starch sugar industry. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a clean production method for corn starch in the starch sugar industry, reduce the soluble protein, salt and acid and alkali consumption of resin regeneration in starch milk and wastewater discharge, improve product yield, and reduce the amount of water used for separation and sewage discharge.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is: A clean production method for corn starch in the starch sugar industry, the method comprising: mixing sulfur dioxide waste gas from a recovery workshop with clean water to prepare a sulfite solution, passing the sulfite solution into a corn soaking system using a sulfite solution spraying continuous countercurrent dynamic soaking process, and using evaporation condensed water of starch sugar to wash starch milk.

[0006] Furthermore, the device used for recovering sulfur dioxide waste gas is a suction hood, and the specific operation is: the volatilized sulfur dioxide is sucked and collected by the suction hood at the exposed part of the material in the starch workshop, and then mixed with clean water. The volatilized sulfur dioxide is sucked and collected by the suction hood at the exposed part of the material in the starch workshop and passed into the water for preparing the sulfurous acid solution, which not only improves the working environment of the workers, but also saves the cost of preparing the sulfurous acid solution and reduces air pollution.

[0007] Furthermore, the preparation method of the sulfurous acid solution is: heating clean water, then mixing it with sulfur dioxide waste gas in a spraying manner, and then entering an absorption tower to mix with newly prepared sulfur dioxide to obtain a sulfurous acid solution; the concentration of the sulfurous acid solution is 0.22-0.28%. Clean water is used instead of process water to prepare the sulfurous acid solution, and corn is soaked to maximize the leaching of soluble components in corn kernels from the source.

[0008] Furthermore, the concentration of the sulfite solution is selected according to the raw material conditions. When the raw material is old corn from Shandong and neighboring provinces, the concentration of the sulfite solution is 0.22-0.24%; when the raw material is new corn from Shandong and neighboring provinces or dried corn from Northeast China, the concentration of the sulfite solution is 0.24-0.28%.

[0009] Furthermore, the sulfurous acid solution spraying continuous countercurrent dynamic soaking process is specifically as follows: the newly prepared sulfurous acid solution is sprayed into the first soaking tank with the longest soaking time, and then dynamically countercurrently flows to the soaking tank newly filled with corn; when the soaking time of the corn in the first soaking barrel is reached, the newly prepared sulfurous acid is sprayed into the second soaking tank with the second longest soaking time, and then sprayed to the soaking tank newly filled with corn.

[0010] Furthermore, the corn soaking system consists of 10-14 soaking tanks, with a spray device above the tank, and a sulfurous acid heating device between adjacent tanks, the soaking temperature is controlled to be 48-53°C, and the soaking time is more than 48 hours, among which 7-11 tanks perform normal circulation, 1 tank crushes the soaked corn, 1 tank contains the corn to be crushed after soaking, and 1 tank is used for loading.

[0011] Furthermore, the starch sugar evaporated condensed water is the syrup evaporated condensed water after separation in the starch sugar production process; the evaporated condensed water has a temperature of 35-40°C and a flow rate of 24-26m 3 / h. The condensed water evaporated from the syrup is used for washing to remove the inorganic salts, organic acids and soluble proteins remaining in the starch milk. Compared with clean water, the ash content in the starch milk is greatly reduced, and the ion exchange burden is also greatly reduced, which not only improves the quality and yield of starch sugar products, but also reduces production costs and sewage treatment burden, and realizes the clean production of starch sugar.

[0012] Further, the clean production method of corn starch in the starch sugar industry comprises the following steps: (1) The clean water is heated by a plate heat exchanger, mixed with sulfur dioxide waste gas, and then enters the absorption tower to obtain sulfurous acid solution, which is then flowed into the storage tank; (2) wet-feeding the purified corn with dilute corn syrup, and then soaking the corn in a corn soaking system to obtain soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn to obtain a slurry. The slurry is then transported to the corn feed and concentrated under vacuum to obtain the finished corn slurry. (4) The soaked corn is transported with process water and crushed, the germ is separated and washed, the fiber and skin are separated, washed and dried, and the protein is separated to obtain starch milk; (5) The starch milk is subjected to cyclone washing and washed with condensed water from the syrup evaporated after separation to obtain washed starch milk.

[0013] Furthermore, in step (3), the soaking temperature is 48-52° C. Under this temperature condition, the growth and reproduction of lactic acid bacteria is favorable, and the growth of other harmful bacteria is inhibited. If the temperature is too high, starch gelatinization will occur, and if the temperature is too low, bacteria will easily grow and reproduce, and the purpose of soaking will not be achieved.

[0014] Furthermore, in step (5), the protein content in the washed starch milk is ≤0.35%, and the conductivity is ≤50μs / cm.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The clean production method of the present invention can reduce the salt content in starch milk and the acid and alkali consumption of resin regeneration and wastewater discharge, and the acid and alkali consumption can be reduced by more than 30%, and the product yield can be increased by more than 5%. It also reduces the amount of water used for separation and wastewater discharge, and the water used for separation and wastewater discharge can be reduced by more than 35%.

[0016] (2) The present invention uses clean water instead of process water to produce acid, and truly realizes continuous countercurrent soaking, thereby expanding the osmotic pressure difference between the inside and outside of the corn kernels, so that the non-sugar substances that need to be removed in the starch sugar refining are transferred to the corn syrup component to the greatest extent, and uses the evaporated condensed water from the starch sugar workshop to wash the starch, further removing the residual components such as salt, organic acid, protein, etc. in the starch milk, thereby reducing the pressure of subsequent separation treatment.

[0017] (3) The present invention uses a suction hood to suck and collect the volatilized sulfur dioxide, and preliminarily mixes it with clean water to prepare a sulfite solution, which can not only improve the working environment of workers in the starch workshop, reduce air pollution, save the consumption and cost of the sulfite solution, but also significantly reduce the salt, soluble protein, organic acid and other substances in the process water, thereby improving the quality of corn pulp, fiber skin and germ. DETAILED DESCRIPTION

[0018] Example 1 A clean production method for corn starch in the starch sugar industry comprises the following steps: (1) The clean water is heated to 40°C by a plate heat exchanger, mixed with sulfur dioxide waste gas by spraying, and then enters the absorption tower to obtain sulfurous acid solution. Old corn from Shandong and neighboring provinces is used as raw material. The concentration of sulfurous acid solution is controlled at 0.22-0.24%, and the sulfurous acid solution flows into the storage tank; (2) The purified corn is wet-loaded with dilute corn slurry, and then soaked in a corn soaking system. The corn soaking system consists of 12 soaking tanks and associated pipelines, each tank is loaded with 200 tons of material, 9 of which are in normal circulation, and the other three tanks are used for loading, breaking, and loading. The sulfurous acid solution is continuously and dynamically soaked in countercurrent in a spraying manner. The soaking temperature is 48-52°C, the soaking time is 48-50 hours, and the moisture content of the corn after soaking is 42-45%, thereby obtaining soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn. Each tank requires about 220 ml of sulfurous acid solution. 3 , the slurry is about 80m 3 , and obtain a slurry, which is then transported to the corn feed and then concentrated in vacuum to obtain a finished corn slurry; (4) The soaked corn is transported and crushed with process water, the germ is separated and washed, the fiber skin is separated, washed and dried, and the protein is separated to obtain crude starch milk, finished germ, fiber skin, protein powder and process water respectively; (5) Wash the starch milk with cyclone and use the evaporated condensed water of the syrup after separation. The temperature of the evaporated condensed water is 35-40℃ and the flow rate is 24-26m 3 / h, and the washed starch milk was obtained. The protein content of the starch milk was 0.31%, and the conductivity of the starch milk was 42μs / cm.

[0019] Example 2 A clean production method for corn starch in the starch sugar industry comprises the following steps: (1) The clean water is heated to 40°C by a plate heat exchanger, mixed with sulfur dioxide waste gas by spraying, and then enters the absorption tower to obtain sulfurous acid solution. New corn from Shandong and neighboring provinces is used as raw material. The concentration of sulfurous acid solution is controlled at 0.24-0.28%, and the sulfurous acid solution flows into the storage tank; (2) The purified corn is wet-loaded with dilute corn slurry, and then soaked in a corn soaking system. The corn soaking system consists of 12 soaking tanks and associated pipelines, each tank is loaded with 200 tons of material, 9 of which are in normal circulation, and the other three tanks are used for loading, breaking, and loading. The sulfurous acid solution is continuously and dynamically soaked in countercurrent in a spraying manner. The soaking temperature is 49-53°C, the soaking time is 50-52h, and the moisture content of the corn after soaking is 40-44%, thereby obtaining soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn. Each tank requires about 215m3 of sulfurous acid solution. 3 , the slurry is about 80m 3 , and obtain a slurry, which is then transported to the corn feed and then concentrated in vacuum to obtain a finished corn slurry; (4) The soaked corn is transported and crushed with process water, the germ is separated and washed, the fiber skin is separated, washed and dried, and the protein is separated to obtain crude starch milk, finished germ, fiber skin, protein powder and process water respectively; (5) Wash the starch milk with cyclone and use the evaporated condensed water of the syrup after separation. The temperature of the evaporated condensed water is 35-40℃ and the flow rate is 24-26m 3 / h, and the washed starch milk was obtained. The protein content of the starch milk was 0.33%, and the conductivity of the starch milk was 44μs / cm.

[0020] Example 3 A clean production method for corn starch in the starch sugar industry comprises the following steps: (1) The clean water is heated to 42°C by a plate heat exchanger, mixed with sulfur dioxide waste gas by spraying, and then enters the absorption tower to obtain sulfurous acid solution. Northeast corn is used as the raw material. The concentration of the sulfurous acid solution is controlled to be 0.26-0.28%, and the sulfurous acid solution flows into the storage tank; (2) The purified corn is wet-loaded with dilute corn slurry, and then soaked in a corn soaking system. The corn soaking system consists of 12 soaking tanks and associated pipelines, each tank is loaded with 200 tons of material, 9 of which are in normal circulation, and the other three tanks are used for loading, breaking, and loading. The sulfurous acid solution is continuously and dynamically soaked in countercurrent in a spraying manner. The soaking temperature is 50-52°C, the soaking time is 50-52h, and the moisture content of the corn after soaking is 40-43%, thereby obtaining soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn. Each tank requires about 220 ml of sulfurous acid solution. 3 , the slurry is about 80m 3 , and obtain a slurry, which is then transported to the corn feed and then concentrated in vacuum to obtain a finished corn slurry; (4) The soaked corn is transported and crushed with process water, the germ is separated and washed, the fiber skin is separated, washed and dried, and the protein is separated to obtain crude starch milk, finished germ, fiber skin, protein powder and process water respectively; (5) Wash the starch milk with cyclone and use the evaporated condensed water of the syrup after separation. The temperature of the evaporated condensed water is 35-40℃ and the flow rate is 24-26m 3 / h, and the washed starch milk was obtained. The protein content of the starch milk was 0.34%, and the conductivity of the starch milk was 45μs / cm.

[0021] Comparative Example 1 In the existing process, process water is used to prepare the sulfite solution, and corn is soaked according to the existing intermittent countercurrent soaking process. Since new corn and Northeast corn are less used as raw materials, only old corn from Shandong and neighboring provinces is used. The existing process includes the following steps: (1) The process water is heated to 40°C by a plate heat exchanger, and then it is sprayed into an absorption tower to mix with sulfur dioxide to obtain a sulfurous acid solution. Old corn from Shandong and neighboring provinces is used as the raw material. The concentration of the sulfurous acid solution is controlled to be 0.22-0.24%, and the sulfurous acid solution is flowed into a storage tank; (2) The purified corn is wet-loaded with dilute corn slurry, and then soaked in a corn soaking system. The corn soaking system consists of 12 soaking tanks and associated pipelines, each tank is loaded with 200 tons of material, of which 9 tanks are in normal circulation, and the other three tanks are used for loading, breaking, and loading. Sulfite solution is injected into the soaking tank in an intermittent semi-continuous manner for soaking. The soaking temperature is 48-52°C, the soaking time is 48-50 hours, and the moisture content of the corn after soaking is 42-45%, thereby obtaining soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn. Each tank requires about 220 ml of sulfurous acid solution. 3 , the slurry is about 80m3, and the slurry is obtained. After the slurry is transported to the corn material, it is vacuum concentrated to obtain corn slurry; (4) The soaked corn is transported with process water and crushed, the germ is separated and washed, the fiber and skin are separated, washed and dried, and the protein is separated to obtain crude starch milk; (5) Wash the crude starch milk with clean water in a cyclone at a water temperature of 35-40°C and a flow rate of 24-26 m 3 / h, the washed starch milk was obtained, the protein content of the starch milk was 0.54%, and the conductivity of the starch milk was 580μs / cm. The water used for ion exchange was 6.4 cubic meters / ton of product, the sewage discharge was 8 cubic meters / ton of product, the acid and alkali consumption was 40 kg / ton of product, and the starch sugar product yield was 91%.

[0022] Experimental Example 1 Compared with Comparative Example 1, the reduction in ion exchange water, sewage discharge and acid and alkali consumption and the increase in product yield in Examples 1-3 are calculated and listed in Table 1.

[0023] Table 1. Reduction in water, wastewater discharge, acid and alkali consumption and increase in product yield As can be seen from Table 1, compared with the existing process, the water and sewage discharge of Example 1 is reduced by 37%, the acid and alkali consumption is reduced by 33%, and the product yield is increased by 5.4%. The water and sewage discharge of Example 2 is reduced by 36%, the acid and alkali consumption is reduced by 32%, and the product yield is increased by 5.2%. The water and sewage discharge of Example 3 is reduced by 36%, the acid and alkali consumption is reduced by 31%, and the product yield is increased by 5.1%. It can be seen that the present invention uses clean water instead of process water to prepare sulfurous acid solution for use, which can reduce the subsequent water and sewage discharge of ion exchange, reduce acid and alkali consumption, and improve product yield.

[0024] Experimental Example 2 The protein content and conductivity of the starch milk of Examples 1-3 and Comparative Example 1 are listed in Table 2.

[0025] Table 2. Protein content and conductivity of starch milk As shown in Table 2, the protein content in starch milk of Comparative Example 1 is 0.54%, and the conductivity is 580 μs / cm, the protein content in starch milk of Example 1 is 0.31%, and the conductivity is 42 μs / cm, the protein content in starch milk of Example 2 is 0.33%, and the conductivity is 44 μs / cm, and the protein content in starch milk of Example 3 is 0.34%, and the conductivity is 45 μs / cm. It can be seen that the method of the present invention can reduce the soluble protein content and salt content in starch milk, allow the protein component to be present in corn steep liquor as much as possible, improve the yield of corn steep liquor, and increase economic benefits.

Claims

1. A clean production method for corn starch in the starch sugar industry, characterized in that: The method comprises the following steps: recycling sulfur dioxide waste gas from a workshop and mixing it with clean water to prepare a sulfite solution, passing the sulfite solution into a corn soaking system by using a sulfite solution spraying continuous countercurrent dynamic soaking process, and using evaporation condensed water of starch sugar to wash starch milk.

2. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The device used for recovering sulfur dioxide waste gas is a suction hood, and the specific operation is: the suction hood is used to suck and collect the volatilized sulfur dioxide at the exposed part of the material in the starch workshop, and then mix it with clean water.

3. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The preparation method of the sulfurous acid solution is: heating clean water, then mixing it with sulfur dioxide waste gas in a spraying manner, and then entering an absorption tower to mix with newly prepared sulfur dioxide to obtain a sulfurous acid solution; the concentration of the sulfurous acid solution is 0.22-0.28%.

4. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The concentration of the sulfite solution is selected according to the raw material conditions. When the raw material is old corn from Shandong and neighboring provinces, the concentration of the sulfite solution is 0.22-0.24%; when the raw material is new corn from Shandong and neighboring provinces or dried corn in Northeast China, the concentration of the sulfite solution is 0.24-0.28%.

5. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The sulfurous acid solution spraying continuous countercurrent dynamic soaking process is specifically as follows: newly prepared sulfurous acid solution is sprayed into the first soaking tank with the longest soaking time, drawn out from the bottom and sprayed into the second soaking tank with the second longest soaking time, and then dynamically countercurrently flows into the soaking tank newly filled with corn; when the soaking time of corn in the first soaking tank is reached, it is crushed, and newly prepared sulfurous acid is sprayed into the second soaking tank with the second longest soaking time, and then sprayed into the soaking tank newly filled with corn in sequence.

6. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The corn soaking system consists of 10-14 soaking tanks, with a spray device above the tanks and a sulfurous acid heating device between adjacent tanks. The soaking temperature is controlled to be 48-53°C and the soaking time is more than 48 hours. Among them, 7-11 tanks perform normal circulation, 1 tank crushes the soaked corn, 1 tank contains the corn to be crushed after soaking, and 1 tank is used for loading.

7. The clean production method of corn starch in the starch sugar industry according to claim 1, characterized in that: The starch sugar evaporation condensate is the syrup evaporation condensate after separation in the starch sugar production process; the evaporation condensate has a temperature of 35-40°C and a flow rate of 24-26m 3 / h.

8. A clean production method for corn starch in the starch sugar industry according to claim 1, characterized in that: The following steps are involved: (1) The clean water is heated by a plate heat exchanger, mixed with sulfur dioxide waste gas, and then enters the absorption tower to obtain sulfurous acid solution, which is then flowed into the storage tank; (2) wet-feeding the purified corn with dilute corn syrup, and then soaking the corn in a corn soaking system to obtain soaked corn; (3) The sulfurous acid solution is discharged after passing through the soaking tank filled with corn to obtain a slurry. The slurry is then transported to the corn feed and concentrated under vacuum to obtain the finished corn slurry. (4) The soaked corn is transported and crushed with process water, the germ is separated and washed, the fiber skin is separated, washed and dried, and the protein is separated to obtain crude starch milk, finished germ, fiber skin, protein powder and process water respectively; (5) The starch milk is subjected to cyclone washing and washed with condensed water from the syrup evaporated after separation to obtain washed starch milk.

9. The clean production method of corn starch in the starch sugar industry according to claim 8, characterized in that: In step (2), the moisture content of the corn after soaking is 42-45%.

10. The clean production method of corn starch in the starch sugar industry according to claim 8, characterized in that: In step (5), the protein content in the washed starch milk is ≤0.35%, and the conductivity is ≤50μs / cm.

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