A process and device for recycling waste alkali liquor from agar production

Abstract

The present invention belongs to the technical field of waste alkali liquor recovery, and in particular relates to a process method and device for the recovery and treatment of waste alkali liquor from agar production, including the steps of impurity removal, heating, diffusion dialysis, three-dimensional electrolytic catalytic oxidation, coagulation precipitation and biochemical treatment. The waste alkali liquor after impurities removal is heated; the heated hot waste alkali liquor and clean water are respectively pumped into a cation exchange membrane diffusion dialyzer for diffusion dialysis to obtain alkali recovery liquid and residual liquid; alkali is added to the wastewater after the residual liquid is subjected to three-dimensional electrolytic catalytic oxidation treatment to adjust the pH, and then a coagulant is added to carry out stirring and coagulation reaction, and supernatant is obtained by precipitation; the obtained supernatant is introduced into a subsequent biochemical treatment unit for treatment, and the effluent meets the standards for discharge or reuse. The present invention recovers alkali from agar processing waste alkali liquor through a diffusion dialyzer, with low energy consumption and high recovery efficiency. The recovered alkali liquor can be reused by the enterprise, thereby saving resources, reducing production costs, and bringing visible economic benefits to agar production enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of waste alkali liquor recovery, and in particular relates to a process for recovering and treating waste alkali liquor from agar production. Background Art

[0002] Agar is a highly economically valuable polysaccharide with unique gelling and thickening properties, making it widely used in the food, biology, pharmaceutical, and daily chemical industries. Currently, the agar production industry generally uses an alkali extraction process, which consumes a significant amount of alkali, with 2.5 to 3 tons of sodium hydroxide required for each ton of agar produced. Although the alkali solution can be reused, when the organic matter concentration in the alkali solution reaches a certain level, it becomes too viscous, degrading the agar quality and making it unsuitable for reuse. Typically, 800 to 1,000 tons of waste alkali solution is generated per ton of agar produced. This waste alkali solution is not only rich in 5% to 8% sodium hydroxide, but also contains proteins, carbohydrates, sulfate, calcium, and pigments. Its high alkalinity, high COD (COD concentrations reaching tens of thousands of mg / L), high turbidity, high viscosity, and high color make it difficult to process and, if left untreated, can cause serious environmental pollution.

[0003] Currently, waste lye from agar production is typically treated through a neutralization method involving the addition of acid for pretreatment. The waste is then mixed with other wastewater and processed through a series of physicochemical and biochemical water treatment processes (such as hydrolysis, acidification, and contact oxidation) before being discharged. However, the neutralization method consumes a large amount of acid, resulting in high treatment costs and a waste of resources. Furthermore, due to the high concentration of organic matter and high color, waste lye from agar production is not effectively treated using traditional biochemical treatment methods, making it difficult to meet relevant wastewater discharge standards. The treatment of waste lye from agar production has become a bottleneck restricting the development of agar production enterprises. Therefore, finding suitable technologies to treat waste lye from agar production and reduce treatment costs are of great practical significance.

[0004] In recent years, technologies such as evaporation, nanofiltration membranes, electrodialysis, and diffusion dialysis have attracted attention in the field of waste alkali recovery. The three methods of evaporation, nanofiltration membranes, and electrodialysis have high requirements for processing equipment, complex equipment, large investment, high energy consumption, and serious membrane fouling. Agar production companies produce large amounts of waste alkali liquid with complex components. If evaporation, nanofiltration membranes, electrodialysis and other methods are used to recover the waste alkali liquid, it will incur high economic costs, making it difficult for companies to bear. Compared with evaporation, nanofiltration membranes, and electrodialysis technologies, diffusion dialysis technology is used for waste alkali recovery. It has unique advantages such as low investment, simple operation, almost no electricity consumption (except for pumping liquid), and low operating costs. The recovered alkali can be recycled and is generally considered to be an efficient and energy-saving membrane separation technology. However, the current alkali diffusion dialysis recovery technology and equipment at home and abroad are still immature. Summary of the Invention

[0005] The purpose of the present invention is to provide a process for recycling and treating waste alkali liquor from agar production in order to solve the above-mentioned technical problems, thereby achieving the effects of saving resources, reducing production costs, and bringing visible economic benefits to agar production enterprises.

[0006] In view of this, the present invention provides a process for recycling waste alkali liquor from agar production, comprising the following steps:

[0007] S1, impurity removal: using a screen filtration device to remove impurities from the waste alkali liquid produced by agar production using a screen and a microfiltration membrane in sequence;

[0008] S2, heating: heating the waste alkali liquid after impurity removal;

[0009] S3, diffusion dialysis: pumping the hot waste alkali liquid and clean water after the treatment in step S2 into a cation exchange membrane diffusion dialyzer for diffusion dialysis to obtain an alkali recovery liquid and a residual liquid;

[0010] S4, three-dimensional electrocatalytic oxidation: subjecting the residual liquid obtained in step S3 to three-dimensional electrocatalytic oxidation;

[0011] S5, coagulation and sedimentation: adding alkali to the wastewater treated in step S4 to adjust the pH, then adding a coagulant to carry out stirring and coagulation reaction, and precipitating to obtain a supernatant;

[0012] S6, biochemical treatment: The supernatant obtained in step S5 is introduced into a subsequent biochemical treatment unit for treatment, and the effluent meets the standards for discharge or reuse.

[0013] In this technical solution, a screen and microfiltration are used to pretreat the waste alkali liquor from agar production to remove particulate impurities, prevent the particulate impurities in the waste alkali liquor from clogging the ion exchange membrane, and ensure the smooth operation of the diffusion dialyzer; the waste alkali liquor is heated to form a dispersed system, reduce its viscosity, and prevent the clogging of the ion exchange membrane; the present invention recovers alkali from the waste alkali liquor from agar processing through a diffusion dialyzer, with low energy consumption and high recovery efficiency. The recovered alkali liquor can be reused by the enterprise, thereby saving resources, reducing production costs, and bringing visible economic benefits to the agar production enterprise.

[0014] In view of the high COD and high chroma of waste alkali liquor from agar production, it is proposed to adopt physicochemical treatment processes such as three-dimensional electrolytic catalytic oxidation and polyferric sulfate coagulation and precipitation. On the one hand, it can effectively reduce the organic matter content and chroma in the residual liquid; on the other hand, it can improve the biochemical properties of the residual liquid and reduce the load of subsequent biochemical treatment.

[0015] Furthermore, the pore size of the sieve is 10 μm to 25 μm, and the pore size of the microfiltration membrane is 1.0 to 5.0 μm.

[0016] Furthermore, the waste alkali liquid is heated to a temperature of 60°C to 70°C.

[0017] Furthermore, the waste alkali liquid and clean water flow in a cross-current manner in the diffusion dialyzer, and the flow rate ratio of water to the waste alkali liquid is controlled to be 1.0 to 1.4.

[0018] Furthermore, the three-dimensional electrocatalytic oxidation reaction bed uses a titanium plate as the anode, graphite as the cathode, and the filler is activated carbon loaded with Co-Cu-Mn series composite oxides. An aerator is provided at the bottom of the bed. The initial pH of the wastewater is adjusted to 3.0, and the electrocatalytic oxidation reaction time is 80 minutes.

[0019] Furthermore, in step S5, the pH value is adjusted back to 9, and polyferric sulfate is added as a coagulant in an amount of 25 to 30 mg / L, and the coagulation reaction is stirred for 10 to 15 minutes.

[0020] A device suitable for the above method comprises:

[0021] A waste alkali liquid tank, wherein the waste alkali liquid tank is used to store waste alkali liquid produced by agar;

[0022] A mesh filter device, wherein the mesh filter device is used to remove impurities from the waste alkali liquid;

[0023] A hot waste alkali liquid storage tank is connected to a heater and a temperature controller, and is used to store heated waste alkali liquid;

[0024] A diffusion dialyzer, wherein the diffusion dialyzer is connected to the hot waste alkali liquid storage tank and the clean water storage tank respectively, and the diffusion dialyzer is used for diffusion dialyzing the heated waste alkali liquid;

[0025] A recovery alkali storage tank, wherein the recovery alkali storage tank is used to store the alkali recovery liquid discharged from the diffusion dialyzer;

[0026] The residual liquid storage tank is used to store the residual liquid discharged from the diffusion dialyzer.

[0027] In this technical solution, a screen filter device and a heater are used to pretreat the waste alkali liquor from agar processing, which can remove particulate impurities in the waste alkali liquor, reduce viscosity, and prevent clogging of the diffusion dialysis membrane; a diffusion dialyzer is used to recover alkali from the waste alkali liquor from agar processing, which not only solves the environmental pollution problem of the waste alkali liquor, but also the recovered alkali liquor can be reused by the enterprise, reducing the cost of agar production and bringing visible economic benefits to the agar production enterprise. The system device has a simple process, is easy to operate, has low energy consumption, requires little investment, and has low operating costs.

[0028] Further, the diffusion dialyzer comprises:

[0029] A liquid inlet plate, wherein a waste alkali liquid inlet and a clean water inlet are provided on the liquid inlet plate;

[0030] The membrane assembly comprises alternately arranged partitions and cation exchange membranes, wherein a diffusion chamber and a dialysis chamber are formed between the cation exchange membranes and the partitions on both sides respectively;

[0031] A liquid outlet plate, wherein the liquid outlet plate is provided with an alkali recovery liquid outlet and a residual liquid outlet;

[0032] Wherein, the membrane assembly is arranged between the liquid inlet plate and the liquid outlet plate.

[0033] Furthermore, the partition includes a frame and a mesh body, and liquid distribution holes are respectively provided on the two corners of one set of diagonals of the frame, and liquid holes are provided on the corners of the other set of diagonals. Multiple water distribution channels are provided between the liquid distribution holes and the mesh body, and the liquid distribution holes on the partitions on both sides of the cation exchange membrane are connected in an "X" shape.

[0034] In this technical solution, the waste alkali liquid and clean water can enter the two sides of the cation exchange membrane respectively through the above structure. Driven by the concentration difference, the NaOH in the waste alkali liquid tends to diffuse into the clean water, but the cation exchange membrane itself has a negatively charged active group in the skeleton. According to the common ion exclusion principle of Donnan equilibrium, Na+ will pass through the cation membrane into the dialysis chamber, while the negatively charged ions will be repelled and blocked in the dialysis chamber. According to the principle of electrical neutrality, Na+ has a tendency to attract anions into the diffusion chamber to ensure that the diffusion chamber can achieve electrical neutrality. Compared with other highly charged anions with a larger hydration radius, OH- with low charge, high activity and a smaller hydration radius is more likely to enter the diffusion liquid through the gap of the cation exchange membrane, thereby realizing the separation and recovery of alkali.

[0035] Furthermore, a turbulence enhancer is fixedly provided in the water distribution channel, and the turbulence enhancer is used to enhance the turbulence effect of the waste alkali liquid flowing from the water distribution channel to the mesh body.

[0036] In this technical solution, the setting of the water distribution channel can increase the flow rate of the waste alkali liquid to form turbulence. The turbulence reinforcement can further enhance the turbulence, effectively reduce the flow dead zone area during the diffusion dialysis process, make the diffusion dialysis more uniform, and prevent membrane clogging, thereby improving efficiency.

[0037] Furthermore, the turbulence enhancer includes a square tube that matches the shape of the water distribution channel. The first blocks and the second blocks are alternately arranged along the length direction of the square tube on both side groove walls. The roughness of the first block is higher than that of the second block. The first blocks on the opposite side groove walls of the square tube are orthogonal to each other, and the second blocks are also orthogonal to each other.

[0038] Furthermore, the roughness value of the first block is between 0.05-0.1 mm, and the roughness value of the second block is between 0.01-0.04 mm.

[0039] In this technical solution, the turbulence enhancer can be fixed into the water distribution channel by embedding or welding.

[0040] Furthermore, the waste alkali liquid inlet and the clean water inlet are respectively arranged at the lower part and the upper part of the liquid inlet plate, and the alkali recovery liquid outlet and the residual liquid outlet are respectively arranged at the lower part and the upper part of the liquid outlet plate.

[0041] Furthermore, a residual liquid guiding groove is provided in the liquid outlet plate, the residual liquid guiding groove is arranged from bottom to top, and the upper end of the guiding groove is connected to the residual liquid outlet.

[0042] In this technical solution, the residual liquid guide groove allows the residual liquid to be discharged slowly, allowing the residual liquid to stay longer in the dialysis chamber closest to the liquid outlet plate, further improving the purification rate of the alkali. After the waste alkali liquid enters from the waste alkali liquid inlet, it flows through the first partition plate and then passes through the cation exchange membrane, the second partition plate and the second cation exchange membrane, and then flows through the third partition plate. It flows into the residual liquid guide groove and is discharged from the residual liquid outlet at the upper part of the liquid outlet plate to the residual liquid storage tank. After entering from the clean water inlet, clean water passes through the first partition plate and the cation exchange membrane and then flows through the second partition plate. It then passes through the second cation exchange membrane and the third partition plate and is discharged from the alkali recovery liquid outlet at the lower part of the liquid outlet plate to the recovered alkali storage tank.

[0043] Furthermore, sampling valves are fixedly installed at the bottom water outlet pipes of the recovered alkali storage tank and the residual liquid storage tank.

[0044] Furthermore, a pump and a valve are provided on the pipeline.

[0045] The beneficial effects of the present invention are:

[0046] 1. The present invention recovers alkali from waste alkali liquor from agar processing by a diffusion dialyzer, has low energy consumption and high recovery efficiency, and the recovered alkali liquor can be reused by enterprises, thereby saving resources, reducing production costs, and bringing visible economic benefits to agar production enterprises.

[0047] 2. The present invention recovers alkali from waste alkali liquor from agar processing by using a diffusion dialyzer, has low energy consumption and high recovery efficiency, and the recovered alkali liquor can be reused by enterprises, thereby saving resources, reducing production costs, and bringing visible economic benefits to agar production enterprises.

[0048] 3. The setting of the water distribution channel can increase the flow rate of the waste alkali liquid to form turbulence. The turbulence reinforcement can further enhance the turbulence, effectively reduce the flow dead zone area during the diffusion dialysis process, make the diffusion dialysis more uniform, and prevent membrane clogging, thereby improving efficiency.

[0049] 4. The residual liquid guide groove allows the residual liquid to be discharged slowly, so that the residual liquid can stay longer in the dialysis chamber closest to the liquid outlet plate, further improving the purification rate of alkali. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a process flow chart of the present invention;

[0051] Figure 2 Schematic diagram of a waste alkali solution recovery system device of the present invention;

[0052] Figure 3 is a schematic diagram of a diffusion dialyzer;

[0053] Figure 4 is a schematic diagram of the partition;

[0054] Figure 5 is a schematic diagram of a turbulence enhancer provided in a water distribution channel;

[0055] Figure 6 is a side view of the turbulence enhancer;

[0056] Figure 7 yes Figure 5 Sectional view AA;

[0057] Figure 8 yes Figure 5 Cross-sectional view BB;

[0058] Figure 9 yes Figure 5 A perspective view.

[0059] The marks in the figure are:

[0060] 1. Pipeline; 2. Waste alkali liquid tank; 3. Screen filtration equipment; 4. Hot waste alkali liquid storage tank; 5. Diffusion dialyzer; 6. Recovery alkali storage tank; 7. Residual liquid storage tank; 8. Sampling valve; 9. Pump; 10. Valve; 11. Liquid inlet plate; 12. Membrane assembly; 13. Liquid outlet plate; 14. Waste alkali liquid inlet; 15. Clean water inlet; 16. Partition; 17. Cation exchange membrane; 18. Diffusion chamber; 19. Dialysis chamber; 20. Alkali recovery liquid outlet; 21. Residual liquid outlet; 22. Residual liquid guide groove; 23. Frame; 24. Mesh; 25. Liquid distribution hole; 26. Liquid through hole; 27. Water distribution channel; 28. Turbulence reinforcement; 29. ​​First block; 30. Second block; 31. Clean water storage tank. DETAILED DESCRIPTION

[0061] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of this application.

[0062] In the description of this application, it should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Technologies, methods and equipment known to ordinary technicians in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0063] It should be noted that the terms "first," "second," etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than those illustrated or described herein, and that the objects distinguished by "first," "second," etc. are generally of the same type, and do not limit the number of objects. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0064] It should be noted that, in the description of this application, the directions or positional relationships indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise specified, these directional terms do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of this application; the directional terms "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0065] It should be noted that, in the present application, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the opposite order according to the functions involved. For example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0066] Example 1:

[0067] like Figure 1 As shown, a process for recycling and treating waste alkali liquor from agar production comprises the following steps:

[0068] S1. Impurity removal: impurities are removed from the waste alkali liquid discharged from agar production. The sodium hydroxide content of the waste alkali liquid is 58.2 g / L, the total suspended solids (TSS) content is 393 mg / L, the CODcr is 27163 mg / L, the color is brown-black, and the chroma (dilution multiple) is 560 times. The impurity removal specifically comprises the following steps: using a screen filtration device to sequentially use a screen and a microfiltration membrane to remove impurities from the waste alkali liquid from agar production. A 500-mesh stainless steel sieve (pore size 25 μm), a 1250-mesh stainless steel sieve (pore size 10 μm) and a precision filter (pore size 1.0-5.0 μm) are used to filter and remove particulate impurities in the waste alkali liquid. After impurity removal, the sodium hydroxide content of the waste alkali liquid is 57.2 g / L, the total suspended solids (TSS) content is 13 mg / L, the CODcr is 21350 mg / L, the color is brown, and the chroma (dilution multiple) is 407 times.

[0069] S2, heating: heating the waste alkali liquid after impurity removal to set temperatures (60° C., 65° C., and 70° C.) to obtain hot waste alkali liquid;

[0070] S3, diffusion dialysis: the hot waste alkali liquid and clean water after the treatment in step S2 are pumped into a cation exchange membrane diffusion dialyzer for diffusion dialysis to obtain an alkali recovery liquid and a residual liquid. Specifically, the hot waste alkali liquid and clean water are pumped into the cation exchange membrane diffusion dialyzer by pumps, and a dynamic continuous operation mode is adopted to make the waste alkali liquid and clean water flow in a cross-current manner in the diffusion dialyzer. The temperature of the waste alkali liquid is controlled at 60°C, 65°C and 70°C respectively, and the flow rate of the waste alkali liquid is 0.75L / m 2 h, 1.0L / m 2 h and 1.25L / m 2 h, with the flow rate ratio of water to waste alkali liquor being 1.0, 1.2, and 1.4, a three-factor three-level response surface experiment was conducted. The alkali content of the recovered liquor was measured every half hour. When the alkali content of the recovered liquor detected by three consecutive samplings remained basically unchanged, the diffusion dialysis was considered to have reached a stable state, and sampling was stopped.

[0071] The results of the diffusion-dialysis response surface experiment are shown in Table 1 below.

[0072] Table 1 Diffusion dialysis test results for recycling waste alkali liquor

[0073]

[0074]

[0075] It can be seen from Table 1 that when the waste alkali liquid temperature is 65℃ and the waste alkali liquid flow rate is 0.75L / m 2 h, when the flow rate ratio of water to waste alkali liquor is 1.4, the alkali recovery rate is as high as 84.2%, and the sodium hydroxide content of the alkali recovery liquor is 44.8 g / L. At this time, the main water quality indicators of the alkali recovery liquor are: chemical oxygen demand (CODcr) concentration is 2100 mg / L, total suspended solids (TSS) content is 5 mg / L, and chromaticity is 4 times. The chromaticity of the alkali recovery liquor is small, light yellow, and clear and transparent.

[0076] S4, three-dimensional electrocatalytic oxidation: The residual liquid (high-concentration organic wastewater) produced by the diffusion dialysis process was used as the test wastewater. The total suspended solids (TSS) content was 14 mg / L, the CODcr was 24612 mg / L, the color was brown, and the chroma (dilution factor) was 400 times. The above residual liquid needed to be treated with three-dimensional electrocatalytic oxidation;

[0077] The electrolytic cell of the three-dimensional electrolytic catalytic oxidation experimental device is made of PP plastic, with effective dimensions of L*B*H=12cm*10cm*15cm and an effective volume of 1.8L. It uses a titanium plate as the anode, graphite as the cathode, and the filler is activated carbon loaded with Co-Cu-Mn series composite oxides. An aerator is provided at the bottom of the bed. Power is applied by a high-frequency rectifier (10A 50V), and an electromagnetic air pump is used to aerate the wastewater.

[0078] The orthogonal test selected four factors, namely, particle filler dosage, current density, initial pH value, and electrolysis time. Each factor was set at three levels, with CODcr removal rate as the indicator. The results of the orthogonal test are shown in Table 2.

[0079] Table 2 Results of three-dimensional electrocatalytic oxidation orthogonal test

[0080]

[0081]

[0082] As can be seen from Table 2, the optimal conditions for three-dimensional electrolytic catalytic oxidation treatment of residual liquid are: filler dosage 50g / L, current density 60mA / cm2, initial pH value 3, and electrolysis time 80min. Under these optimal conditions, the three-dimensional electrolytic catalytic oxidation device has a COD removal rate of 87.4% for residual liquid, the effluent CODcr concentration decreases from 24612mg / L to 3101mg / L, the total suspended solids (TSS) content increases from 14mg / L to 387mg / L, and the chromaticity (dilution multiple) decreases from 400 times to 20.

[0083] In S5, the wastewater pH was adjusted using sodium hydroxide solution. An appropriate amount of polyferric sulfate was added. After coagulation and stirring for a specified period, the mixture was allowed to settle for 1 hour. The supernatant was collected and measured for chemical oxygen demand (CODcr), total suspended solids (TSS), and color. An orthogonal experiment was conducted using three factors: polyferric sulfate dosage, solution pH, and coagulation time. Each factor was set at three levels, with TSS and CODcr removal rates as indicators. The results are shown in Table 3.

[0084] Table 3 Coagulation and sedimentation orthogonal test results

[0085]

[0086]

[0087] It can be seen from Table 3 that the optimal conditions for coagulation reaction are: polyferric sulfate dosage is 25g / L, solution pH is 9, and coagulation reaction time is 10min. Under these optimal conditions, the COD removal rate is 62.5%, the effluent CODcr concentration decreases from 3101mg / L to 1163mg / L, the total suspended solids (TSS) content decreases from 387mg / L to 2mg / L, and the chromaticity (dilution multiple) decreases from 20 times to 5.

[0088] S6, biochemical treatment: The supernatant obtained in step S5 is introduced into a subsequent biochemical treatment unit for treatment, and the effluent meets the standards for discharge or reuse.

[0089] The waste alkali liquor from agar production is pretreated by using a screen and microfiltration to remove particulate impurities, prevent the particulate impurities in the waste alkali liquor from clogging the ion exchange membrane, and ensure the smooth operation of the diffusion dialyzer; the waste alkali liquor is heated to form a dispersed system, reduce its viscosity, and prevent the clogging of the ion exchange membrane; the present invention recovers alkali from the waste alkali liquor from agar processing by using a diffusion dialyzer, has low energy consumption and high recovery efficiency, and the recovered alkali liquor can be reused by the enterprise, thereby saving resources, reducing production costs, and bringing visible economic benefits to the agar production enterprise.

[0090] In view of the high COD and high chroma of waste alkali liquor from agar production, it is proposed to adopt physicochemical treatment processes such as three-dimensional electrolytic catalytic oxidation and polyferric sulfate coagulation and precipitation. On the one hand, it can effectively reduce the organic matter content and chroma in the residual night, and on the other hand, improve the feasibility of wastewater and reduce the load of subsequent biochemical treatment.

[0091] Example 2:

[0092] like Figure 2 As shown, a system for recovering waste alkali liquor from agar processing comprises a waste alkali liquid tank 2, a mesh filter 3, a hot waste alkali liquid storage tank 4, a diffusion dialyzer 5, a recovery alkali storage tank 6, and a residual liquid storage tank 7, all connected sequentially via a pipeline 1. The waste alkali liquid tank 2 is used to store waste alkali liquor from agar production; the mesh filter 3 is used to remove impurities from the waste alkali liquid; the hot waste alkali liquid storage tank 4 is connected to a heater and a temperature controller and is used to store heated waste alkali liquid; the diffusion dialyzer 5 is connected to the hot waste alkali liquid storage tank 4 and a clean water storage tank 31, respectively, and is used to perform diffusion dialysis on the heated waste alkali liquid; the recovery alkali storage tank 6 is used to store recovered alkali liquid discharged from the diffusion dialyzer 5; and the residual liquid storage tank 7 is used to store residual waste liquid discharged from the diffusion dialyzer 5. Sampling valves 8 are fixedly installed at the bottom outlet pipes of the recovery alkali storage tank 6 and the residual liquid storage tank 7. A pump 9 and a valve 10 are provided on the pipeline 1.

[0093] The screen filter device 3 and the heater are used to pretreat the waste alkali liquor from agar processing, thereby removing particulate impurities in the waste alkali liquor, reducing viscosity, and preventing clogging of the diffusion dialysis membrane. The diffusion dialyzer 5 is used to recover alkali from the waste alkali liquor from agar processing, which not only solves the problem of environmental pollution caused by the waste alkali liquor, but also allows the recovered alkali liquor to be reused by the enterprise, thereby reducing the cost of agar production and bringing visible economic benefits to the agar production enterprise. The system device has a simple process, is easy to operate, has low energy consumption, requires little investment, and has low operating costs.

[0094] Example 3:

[0095] like Figure 2-3As shown, the diffusion dialyzer 5 includes a liquid inlet plate 11, a membrane assembly 12 and a liquid outlet plate 13. The liquid inlet plate 11 is provided with a waste alkali liquid inlet 14 and a clean water inlet 15; the membrane assembly 12 includes alternately arranged partitions 16 and cation exchange membranes 17, and a diffusion chamber 18 and a dialysis chamber 19 are formed between the cation exchange membrane 17 and the partitions 16 on both sides; the liquid outlet plate 13 is provided with an alkali recovery liquid outlet 20 and a residual liquid outlet 21; the membrane assembly 12 is arranged between the liquid inlet plate 11 and the liquid outlet plate 13. The waste alkali liquid inlet 14 and the clean water inlet 15 are respectively arranged at the lower and upper parts of the liquid inlet plate 11, and the alkali recovery liquid outlet 20 and the residual liquid outlet 21 are respectively arranged at the lower and upper parts of the liquid outlet plate 13. A residual liquid guide groove 22 is opened in the liquid outlet plate 13, and the residual liquid guide groove 22 is arranged from bottom to top, and the upper end of the guide groove is connected to the residual liquid outlet 21.

[0096] The partition 16 includes a frame 23 and a mesh body 24. Liquid distribution holes 25 are respectively provided at the two corners of one set of diagonals of the frame 23, and liquid holes 26 are provided at the corners of the other set of diagonals. Multiple water distribution channels 27 are provided between the liquid distribution holes 25 and the mesh body 24. The liquid distribution holes 25 on the partition 16 on both sides of the cation exchange membrane 17 are connected in an "X" shape.

[0097] The waste alkali liquid and clean water can enter the two sides of the cation exchange membrane 17 respectively through the above structure. Driven by the concentration difference, the NaOH in the waste alkali liquid tends to diffuse into the clean water, but the skeleton of the cation exchange membrane 17 itself carries negatively charged active groups. According to the principle of common ion exclusion of Donnan equilibrium, Na+ will pass through the cation membrane into the dialysis chamber 19, while the negatively charged ions will be repelled and blocked in the dialysis chamber 19. According to the principle of electrical neutrality, Na+ has a tendency to attract anions into the diffusion chamber 18 to ensure that the diffusion chamber 18 can achieve electrical neutrality. Compared with other highly charged anions with a larger hydration radius, OH- with low charge, high activity and a smaller hydration radius is more likely to enter the diffusion liquid through the gap of the cation exchange membrane 17, thereby realizing the separation and recovery of alkali.

[0098] The residual liquid guide groove 22 allows the residual liquid to be discharged slowly, so that the residual liquid can stay in the dialysis chamber 19 closest to the liquid outlet plate 13 for a longer time, further improving the purification rate of the alkali. Figure 2As shown, the thick solid line is the flow path of the waste alkali feed liquid, and the thin dot-dash line is the flow path of the clean water. After entering the waste alkali feed liquid inlet 14, the waste alkali feed liquid flows through the first partition plate 16, passes through the cation exchange membrane 17, the second partition plate 16, and the second cation exchange membrane 17, and then flows through the third partition plate 16. It flows into the residual liquid guide groove 22 and is discharged from the residual liquid outlet 21 at the top of the liquid outlet plate 13 to the residual liquid storage tank 7. After entering the clean water inlet 15, the clean water passes through the first partition plate 16 and the cation exchange membrane 17, flows through the second partition plate 16, and then passes through the second cation exchange membrane 17 and the third partition plate 16. It is discharged from the alkali recovery liquid outlet 20 at the bottom of the liquid outlet plate 13 to the recovered alkali storage tank 6.

[0099] Example 4:

[0100] like Figure 4-9 As shown, a turbulence enhancer 28 is fixedly installed in the water distribution channel 27. The turbulence enhancer 28 is used to enhance the turbulence effect of the waste alkali liquid flowing from the water distribution channel 27 to the mesh body 24. The provision of the water distribution channel 27 can increase the flow velocity of the waste alkali liquid to form turbulence. The turbulence enhancer 28 can further enhance the turbulence, effectively reducing the dead zone area of ​​the flow during the diffusion dialysis process, making the diffusion dialysis more uniform and improving efficiency.

[0101] The turbulence enhancer 28 comprises a square tube shaped to match the shape of the water distribution channel 27. On both sides of the square tube, alternating first blocks 29 and second blocks 30 are arranged along the length of the square tube. The first blocks 29 have a higher roughness than the second blocks 30. The first blocks 29 on the opposite sides of the square tube are orthogonal to each other, and the second blocks 30 are also orthogonal to each other. The roughness of the first blocks 29 is between 0.05 and 0.1 mm, and the roughness of the second blocks 30 is between 0.01 and 0.04 mm. The turbulence enhancer 28 can be fixed to the water distribution channel 27 by inlaying or welding.

[0102] When the inlet flow velocity is the same as 1 mm / s, if the roughness of all sides of the turbulence enhancer is 0.02 mm, the turbulence intensity is 0.57×10 -5 m 2 / s 2 If the roughness of all sides of the turbulence enhancer is 0.09 mm, the turbulence intensity is 0.9×10 -5 m 2 / s 2 If the roughness value of the first block is 0.09 mm and the roughness value of the second block is 0.02, the turbulence intensity value is 1.4×10 -5 m 2 / s 2 .

[0103] The embodiments of the present application are described above in conjunction with the accompanying drawings. Unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A process for recycling waste alkali liquor from agar production, characterized in that: The following steps are involved: S1, impurity removal: using a screen filtration device to remove impurities from the waste alkali liquid produced by agar production using a screen and a microfiltration membrane in sequence; S2, heating: heating the waste alkali liquid after impurity removal; S3, diffusion dialysis: pumping the hot waste alkali liquid and clean water after the treatment in step S2 into a cation exchange membrane diffusion dialyzer for diffusion dialysis to obtain an alkali recovery liquid and a residual liquid; S4, three-dimensional electrocatalytic oxidation: subjecting the residual liquid obtained in step S3 to three-dimensional electrocatalytic oxidation; S5, coagulation and sedimentation: adding alkali to the wastewater treated in step S4 to adjust the pH, then adding a coagulant to carry out stirring and coagulation reaction, and precipitating to obtain a supernatant; S6, biochemical treatment: The supernatant obtained in step S5 is introduced into a subsequent biochemical treatment unit for treatment, and the effluent meets the standards for discharge or reuse; The device used in the process method includes: A waste alkali liquid tank, wherein the waste alkali liquid tank is used to store waste alkali liquid produced by agar; A mesh filter device, wherein the mesh filter device is used to remove impurities from the waste alkali liquid; A hot waste alkali liquid storage tank is connected to a heater and a temperature controller, and is used to store heated waste alkali liquid; A diffusion dialyzer, wherein the diffusion dialyzer is connected to the hot waste alkali liquid storage tank and the clean water storage tank respectively, and the diffusion dialyzer is used for diffusion dialyzing the heated waste alkali liquid; A recovery alkali storage tank, wherein the recovery alkali storage tank is used to store the alkali recovery liquid discharged from the diffusion dialyzer; A residual liquid storage tank, which is used to store the residual liquid discharged from the diffusion dialyzer; The diffusion dialyzer comprises: A liquid inlet plate, wherein a waste alkali liquid inlet and a clean water inlet are provided on the liquid inlet plate; The membrane assembly comprises alternately arranged partitions and cation exchange membranes, wherein a diffusion chamber and a dialysis chamber are formed between the cation exchange membranes and the partitions on both sides respectively; A liquid outlet plate, wherein the liquid outlet plate is provided with an alkali recovery liquid outlet and a residual liquid outlet; Wherein, the membrane assembly is arranged between the liquid inlet plate and the liquid outlet plate; The separator includes a frame and a mesh body. Liquid distribution holes are respectively provided at two corners of one set of diagonal lines of the frame, and liquid through holes are provided at the corners of another set of diagonal lines. Multiple water distribution channels are provided between the liquid distribution holes and the mesh body. The liquid distribution holes on the separators on both sides of the cation exchange membrane are connected in an "X" shape. A turbulence reinforcement member is fixedly provided in the water distribution channel, and the turbulence reinforcement member is used to enhance the turbulence effect of the waste alkali liquid flowing from the water distribution channel to the mesh body; The turbulence enhancer comprises a square tube that matches the shape of the water distribution channel. The groove walls on both sides of the square tube are provided with first blocks and second blocks that are alternately arranged along the length of the square tube. The roughness of the first blocks is higher than that of the second blocks. The first blocks on the groove walls on opposite sides of the square tube are orthogonal to each other, and the second blocks are also orthogonal to each other. The roughness value of the first block is between 0.05-0.1 mm, and the roughness value of the second block is between 0.01-0.04 mm.

2. the processing method of a kind of agar production waste alkali liquor recovery treatment according to claim 1, is characterized in that, The pore size of the sieve is 10 μm to 25 μm, and the pore size of the microfiltration membrane is 1.0 to 5.0 μm.

3. a process for recycling waste alkali liquor from agar production according to claim 2, characterized in that, The waste alkali liquid inlet and the clean water inlet are respectively arranged at the lower part and the upper part of the liquid inlet plate, and the alkali recovery liquid outlet and the residual liquid outlet are respectively arranged at the lower part and the upper part of the liquid outlet plate.

4. the processing method of a kind of agar production waste alkali liquor recovery treatment according to claim 3, is characterized in that, A residual liquid guiding groove is provided in the liquid outlet plate, the residual liquid guiding groove is arranged from bottom to top, and the upper end of the guiding groove is connected to the residual liquid outlet.

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