Resource utilization method and device for evaporation and concentration mother liquor

Abstract

The invention relates to a method for recycling evaporated and concentrated mother liquor, in particular to a process for extracting sodium sulfate from saline water containing organic matter and sodium sulfate / sodium chloride and converting the sodium sulfate into acid and alkali to be reused in a production process, which comprises the following steps: introducing the saline water containing the organic matter and sodium sulfate / sodium chloride into an inorganic membrane device; introducing the permeate of the inorganic membrane device into a freezing crystallization device to obtain sodium sulfate decahydrate; dissolving sodium sulfate decahydrate, and introducing the dissolved sodium sulfate decahydrate into a bipolar membrane device for electrolysis to obtain a sulfuric acid solution and a sodium hydroxide solution; sodium sulfate can be extracted from saline water containing organic matters and sodium sulfate / sodium chloride, and the sodium sulfate is converted into acid and alkali.

Description

Technical Field

[0001] The invention relates to a method for resource utilization of evaporation and concentration mother liquor, belonging to the technical field of resource utilization of high-organic concentrated brine. Background Art

[0002] In the bio-fermentation industry, the fermentation process is the core link in the production of various biological products (such as enzymes, antibiotics, organic acids, amino acids, etc.), and its subsequent processing steps are crucial to the purity and final yield of the product. After the fermentation is completed, the fermentation broth contains the target product and a large amount of nutrients, microbial cells, metabolites and soluble impurities that are not fully utilized. In order to extract and purify the target product, a series of complex downstream processing processes are usually used, among which product concentration and crystallization is an indispensable step.

[0003] The product concentration and crystallization process mainly removes water from the fermentation broth through evaporation, osmotic pressure regulation or membrane separation, so that the target product reaches a supersaturated state and then precipitates crystals. However, this process will produce a large amount of concentrated mother liquor. Although the water content of these mother liquors has been greatly reduced, they are still rich in a variety of complex components, mainly including high-concentration proteins, incompletely separated cell fragments, residual nutrients and a large amount of inorganic salts (such as sodium chloride, sodium sulfate, etc.).

[0004] The presence of these components poses a great challenge to the treatment of concentrated mother liquor. First, high concentrations of protein not only take up a lot of resources, but may also cause problems such as pipe blockage and equipment corrosion, affecting the smooth progress of subsequent treatment. Secondly, the presence of cell debris and other organic impurities increases the difficulty and cost of wastewater treatment because they are difficult to be effectively removed in traditional wastewater treatment processes. Furthermore, large amounts of inorganic salts, especially sodium chloride and sodium sulfate, if discharged directly into the environment, will cause environmental problems such as soil salinization and water pollution, which seriously violates the principle of sustainable development.

[0005] Therefore, how to efficiently, economically and environmentally friendly treat these fermentation concentrated mother liquors has become a technical problem that needs to be solved urgently in the biological fermentation industry. For the treatment of evaporation concentrated mother liquor, natural evaporation in evaporation ponds was generally used in the early days to achieve near-zero emissions. However, the evaporation pond process occupies a large amount of land on the one hand, and the solid salts produced are classified as hazardous waste on the other hand, and the disposal cost is high. In the field of hazardous waste treatment, the concentrated mother liquor after evaporation and concentration is currently mainly returned to the incineration system for incineration, but the incineration system cannot process such concentrated liquids in large quantities, and it brings a lot of load to the downstream disposal system.

[0006] Currently, researchers are actively exploring various methods, such as resource utilization (such as extracting valuable bioactive substances, preparing fertilizers or feed additives), deep processing (such as advanced oxidation, membrane separation technology for further purification) and reuse technology (such as reuse in the fermentation process after proper treatment) in order to maximize resource utilization and minimize waste emissions, and promote the green upgrade and sustainable development of the bio-fermentation industry. Summary of the invention

[0007] In view of the above problems, it is urgent to develop an efficient and low-cost technology to utilize the salt in the evaporation and concentration mother liquor as a resource, so as to solve the problem of hazardous waste disposal and recover inorganic salts with economic value, thereby reducing zero-emission operating costs.

[0008] The present invention provides a method for processing and utilizing evaporation and concentration mother liquor for resource utilization. The method can effectively remove solid impurities and the like in the evaporation and concentration mother liquor, obtain sodium sulfate inorganic salt resources in the mixed salt solution, and also can realize the electrolysis of sodium sulfate inorganic salt into sodium hydroxide and sulfuric acid for use in the front-end process, thereby realizing the resource utilization of sodium sulfate in the evaporation and concentration mother liquor. The method mainly removes solid impurities through inorganic membrane treatment, realizes the preliminary purification of the evaporation and concentration mother liquor, and then enters the freezing crystallization system for crystallization. The sodium sulfate decahydrate obtained by crystallization is dissolved and then electrolyzed by bipolar membrane to produce sodium hydroxide and sulfuric acid, and then is reused in the front-end process, thereby realizing the resource utilization of the evaporation and concentration mother liquor.

[0009] A method for resource utilization of evaporation and concentration mother liquor, comprising the following steps: Step 1, evaporating and concentrating the wastewater in the fermentation process, and then filtering it with a ceramic membrane; Step 2, the permeate of the ceramic membrane is subjected to fractional crystallization to precipitate sodium sulfate; Step 3, after the sodium sulfate is redissolved, it is treated by bipolar membrane electrolysis to obtain sulfuric acid and sodium hydroxide; The wastewater in the fermentation process contains sodium sulfate, sodium chloride and protein.

[0010] The wastewater in the fermentation process is the mother liquor after fermentation crystallization; the water contains NaCl 10-60g / L, Mg 2+ 0.01-0.5 g / L, Ca 2+ 0.01-0.5g / L, COD 1000-20000mg / L, Na2SO4 20-120g / L, protein 20-200mg / L.

[0011] The average pore size of the ceramic membrane is 0.002 μm to 1 μm, or the molecular weight cutoff is 10,000 to 5,000,000 Da.

[0012] The operating pressure range of the ceramic membrane is 0.05-0.5Mpa, and cross-flow filtration is adopted with a flow rate of 1-10m / s.

[0013] During the filtration process of ceramic membranes, filter aids are added to the feed in an amount of 0.5-5%.

[0014] The filter aid is one of diatomaceous earth, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon and acid clay.

[0015] The irreversible contamination during the ceramic membrane filtration process is predicted and calculated by the following formula: R%=α*F 2 -β* F-γ*Ln(H+δ) / (1+ε*P) +ζ; F refers to the backwash frequency, P refers to the filter aid concentration, H refers to the calcium and magnesium ion concentration, and α / β / γ / δ / ε / ζ are parameters.

[0016] The irreversible pollution refers to the percentage decrease compared to the original flux after 30-90 minutes of cross-flow flushing with pure water after the filtration is completed; the irreversible pollution is determined under the following filtration conditions: total calcium and magnesium ion concentration 0.01-0.20g / L, and the calcium-magnesium mass ratio range is 3-8:1, the amount of filter aid added is 0.2-5%, the backwashing frequency is 10-50min, the continuous filtration time is 100-300min, the backwashing pressure is 0.5-1.5Mpa, the backwashing time is 5-20s, the filtration pressure is 0.2-0.4Mpa, and the cross-flow velocity is 2-5m / s.

[0017] The temperature of the fractional crystallization is controlled to be -10°C to 10°C, more preferably 0 to 2°C.

[0018] The operating voltage of the bipolar membrane electrolysis treatment is 1-200V, the current is 1-250A, the feed pressure is 0.02-0.2Mpa, and the membrane material of the bipolar membrane is selected from one or a combination of PVC, PEEK, PES, PET, PVDF, etc.

[0019] A device for resource utilization of evaporation and concentration mother liquor, comprising: A concentration device for concentrating fermentation wastewater; A ceramic membrane connected to the concentrating device and used for filtering the concentrated liquid obtained in the concentrating device; A crystallizer, connected to the permeation side of the ceramic membrane, is used to perform fractional crystallization on the permeate of the ceramic membrane to precipitate sodium sulfate; A solid-liquid separation device, connected to the crystallizer, is used to separate the precipitated sodium sulfate; A dissolving tank, connected to the solid-liquid separation device, for re-dissolving the sodium sulfate; The bipolar membrane is connected to the dissolution tank and is used to perform bipolar membrane electrodialysis on the sodium sulfate obtained by redissolution to obtain sulfuric acid and sodium hydroxide.

[0020] It also includes: an acid tank and an alkali tank, which are respectively connected to the bipolar membrane and are used to receive the obtained sulfuric acid and sodium hydroxide.

[0021] It also includes: a filter aid adding tank, which is connected to the feed side of the ceramic membrane and is used to add the filter aid into the ceramic membrane feed.

[0022] The solid-liquid separation equipment is a centrifuge.

[0023] The concentration side of the ceramic membrane and / or the filtrate side of the solid-liquid separation device are connected to a spray dryer for spray drying the concentrate and the filtrate respectively.

[0024] The ceramic membrane is a single-tube, flat-plate, multi-channel ceramic membrane.

[0025] The average pore size of the ceramic membrane is 0.002 μm to 1 μm, or the molecular weight cutoff is 10,000 to 5,000,000 Da.

[0026] The material of the ceramic membrane is aluminum oxide, zirconium oxide, silicon carbide or titanium oxide.

[0027] The bipolar membrane is a three-compartment bipolar membrane electrodialyzer or a two-compartment bipolar membrane electrodialyzer.

[0028] The diaphragm material in the bipolar membrane is selected from one of PVC, PEEK, PES, PET or PVDF. Beneficial Effects

[0029] The method for resource utilization of evaporation and concentration mother liquor of the present invention can effectively solve the problem of resource utilization of mixed salt concentrated brine with high concentration of organic pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the present invention.

[0031] Figure 2 It is a device diagram of the present invention. Figure 3 is the flux attenuation curve of ceramic membrane Figure 4 is the correlation between the theoretical value and the actual value of the modeling sample Figure 5 Is the correlation between the theoretical value and the actual value of the verification sample

[0032] 1. Concentration device; 2. Ceramic membrane; 3. Crystallizer; 4. Solid-liquid separation equipment; 5. Dissolution tank; 6. Bipolar membrane; 7. Acid tank; 8. Alkali tank; 9. Spray dryer; 10. Filter aid dosing tank. DETAILED DESCRIPTION

[0033] The present invention relates to a method for resource utilization of evaporation and concentration mother liquor, specifically, removing solid impurities through inorganic membrane treatment, achieving preliminary purification of evaporation and concentration mother liquor and then entering into a freezing crystallization system for crystallization, dissolving the sodium sulfate decahydrate obtained by crystallization and then undergoing bipolar membrane electrolysis to produce sodium hydroxide and sulfuric acid, and then recycling them to the front-end process, finally realizing the resource utilization method of evaporation and concentration mother liquor. It can solve the problem of hazardous waste disposal and recover economically valuable inorganic salts, thereby reducing the purpose of zero-emission operation costs.

[0034] Approximations used herein can be used to modify any quantitative expression throughout the specification and claims, and can be allowed to change under the condition that does not cause its related basic function to change. Therefore, the value modified by terms such as "about" is not limited to the specified exact value. In at least some cases, approximations can correspond to the accuracy of the instrument used to measure the value. Unless otherwise indicated in the context or sentence, range limits can be combined and / or interchanged, and this scope is determined as and includes all sub-ranges included herein. Except indicating in the operating examples or elsewhere, the numerals or expressions of the amount, reaction conditions, etc. of all representation components used in the specification and claims should be understood to be modified by the word "about" in all cases.

[0035] The term "removal" in this specification includes not only the complete removal of the target substance but also the partial removal (reduction of the amount of the substance). The term "purification" in this specification includes the removal of any or specific impurities.

[0036] As used herein, the words "comprises," "comprising," "having," or any other variation thereof are intended to encompass non-exclusive inclusions. For example, a process, method, article, or device that includes listed elements need not be limited to those elements, but may include other elements that are not explicitly listed or that are inherent to such process, method, article, or device. It should be understood that when an element is referred to as being "connected" to another element, it may be directly connected to the other element or indirectly connected to the other element with an element interposed therebetween. The percentages described in the present invention are by mass percentages unless otherwise specified.

[0037] Among the evaporation and concentration mother liquors that can be treated, the waste brine produced after the fermentation liquor in the biopharmaceutical fermentation industry is concentrated and crystallized is treated in the following Examples 1 to 4.

[0038] During the fermentation process, microorganisms will use substrates for metabolic activities and produce various metabolites, including water, carbon dioxide, organic acids, alcohols, etc. Among them, some metabolites may exist in the form of salts. For example, lactic acid produced during lactic acid fermentation can combine with sodium ions to form sodium lactate, thereby increasing the salinity of the fermentation broth. In order to ensure the smooth progress of the fermentation process, certain fermentation conditions need to be controlled, such as temperature, pH value, dissolved oxygen content, etc. In some cases, in order to adjust these conditions, a certain amount of salt substances (such as sodium chloride, sodium sulfate, etc.) may be added to the fermentation broth. These substances will remain in the fermentation broth after the fermentation is completed to form waste brine. The raw materials used for fermentation may contain a certain amount of salt, which will gradually dissolve in the fermentation broth during the fermentation process to form waste brine. After the fermentation is completed, the fermentation broth needs to be separated, purified, and other treatments to obtain the final product. In this process, a certain amount of wastewater may be generated, including waste brine generated during the fermentation process. If these wastewaters are directly discharged into the environment, it will not only cause a waste of resources, but also pollute the environment.

[0039] The wastewater obtained after evaporation and concentration mainly contains sodium chloride and sodium sulfate, as well as protein. The main components of the evaporation and concentration mother liquor are NaCl 10-60g / L, Mg 2+ 0.01-0.5 g / L, Ca 2+ 0.01-0.5g / L, COD 1000-20000mg / L, Na2SO4 20-120g / L, protein 20-200mg / L. The above salt concentrations can be determined by ICP method, COD by method, and protein content by Coomassie method.

[0040] The concentrated mother liquor here is first filtered through a ceramic membrane device, which removes most of the proteins, cell fragments and suspended matter in the concentrated mother liquor; the average pore size of the ceramic membrane used here is 0.002μm~1μm, or the retention molecular weight is 10000~5000000Da, the operating pressure range is 0.05-0.5Mpa, and cross-flow filtration is adopted, with a flow rate of 1-10m / s.

[0041] Since the protein content in the evaporation and concentration mother liquor is higher than that in the fermentation broth, and protein is the main cause of irreversible contamination of the ceramic membrane (protein easily forms a gel layer on the surface of the membrane and is difficult to remove by backwashing), in the present invention, filter aids (such as diatomaceous earth, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon, acid clay) are added to the evaporation and concentration mother liquor, and a filter cake layer is formed on the surface of the ceramic membrane by the filter aid, which can effectively avoid the gelation of protein on the surface of the ceramic membrane. The concentration of the filter aid added to the solution can be controlled at 0.5-5%. After the addition of filter aids, during backwashing, the irreversible contamination of the membrane is suppressed. The irreversible contamination model is constructed based on the following assumptions: if the backwashing frequency is too high, the filter cake layer formed on the surface will be unstable, and if the backwashing frequency is too low, gelation will gradually occur; the concentration of calcium and magnesium ions in the feed liquid will also promote the gelation of proteins; if the protein concentration is too high, irreversible contamination will be more likely to occur; when the amount of filter aid added reaches a certain concentration, it can protect the membrane layer and suppress irreversible contamination; on this basis, a prediction method for the irreversible contamination of ceramic membranes in the process of ceramic membrane filtration of concentrated mother liquor containing filter aids is constructed. The following prediction equation is used for R%=α*F 2 -β* F-γ*Ln(H+δ) / (1+ε*P) +ζ. Wherein, F refers to the backwash frequency (min), P refers to the concentration of filter aid (%), H refers to the concentration of calcium and magnesium ions (g / L), and α / β / γ / δ / ε / ζ are parameters. The irreversible contamination in the present invention refers to the percentage decrease in flux compared to the original flux after 30-90 minutes of cross-flow flushing with pure water after the filtration is completed.

[0042] After the ceramic membrane is filtered, the permeate of the ceramic membrane is sent to the freezing crystallization device for treatment to obtain Glauber's salt. The fractional crystallization here can refer to the operating conditions in the prior art. The mixed salt solution containing sodium sulfate and sodium chloride is subjected to fractional crystallization to crystallize sodium sulfate. The process is mainly based on the difference in solubility of the two salts under different conditions and the common ion effect in the solution. The solubility of sodium chloride (NaCl) increases with increasing temperature, but the increase is not large, that is, its solubility is relatively less affected by temperature changes. The solubility of sodium sulfate (Na2SO4) increases with increasing temperature when the temperature is less than 40 degrees Celsius, but when the temperature is greater than 40 degrees Celsius, its solubility decreases with increasing temperature. This characteristic reduces the solubility of sodium sulfate under high temperature conditions, making it easier to precipitate from the solution. In a mixed salt solution, when the ion concentration of one salt increases, it inhibits the dissolution of other salts with the same ions. In a mixed solution of sodium chloride and sodium sulfate, as the concentration of sodium chloride increases, the concentration of chloride ions and sodium ions in the solution increases, which will inhibit the dissolution of sodium sulfate to a certain extent, making it easier to precipitate in the form of crystals. By heating the mixed salt solution, the water in the solution can be evaporated, thereby increasing the concentration of the solution. Since the solubility of sodium sulfate decreases at high temperatures, it is easier for sodium sulfate to reach a supersaturated state and precipitate crystals during the heating process. The solubility of sodium sulfate decreases at high temperatures, while the solubility of sodium chloride does not change much. This solubility difference makes it easier for sodium sulfate to precipitate from the solution than sodium chloride during the heating process. In the actual crystallization process, the crystallization process can be optimized by controlling parameters such as evaporation temperature, evaporation rate, and stirring intensity, so that the crystallization of sodium sulfate is more sufficient and pure. For example, when using an MVR evaporator for evaporation crystallization, the fractional crystallization of sodium sulfate and sodium chloride can be achieved through micro-negative pressure operation and a continuous crystallizer system, further improving the purity and yield of the product. The temperature control of the freezing crystallization device is -10℃~10℃, and more preferably 0~2℃.

[0043] Sodium sulfate decahydrate is dissolved and then enters bipolar membrane electrolysis to obtain sodium hydroxide and sulfuric acid. The preferred operating parameters of the bipolar membrane device electrolysis are: operating voltage of 1-200V, current of 1-250A, and feed pressure of 0.02-0.2MPa. The membrane material is selected from one or a combination of PVC, PEEK, PES, PET, PVDF, etc.

[0044] The concentrated solution obtained during the ceramic membrane filtration process or the mother liquor obtained during the sodium sulfate crystallization process can be spray-dried and treated as solid waste.

[0045] Based on the above process, the device structure provided by the present invention is as follows Figure 2 ,include: A concentrating device 1, used for concentrating the fermentation wastewater; The ceramic membrane 2 is connected to the concentrating device 1 and is used to filter the concentrated liquid obtained in the concentrating device 1; The crystallizer 3 is connected to the permeation side of the ceramic membrane 2 and is used to perform fractional crystallization on the permeate of the ceramic membrane 2 to precipitate sodium sulfate; A solid-liquid separation device 4, connected to the crystallizer 3, is used to separate the precipitated sodium sulfate; A dissolving tank 5, connected to the solid-liquid separation device 4, is used to redissolve the sodium sulfate; The bipolar membrane 6 is connected to the dissolution tank 5 and is used for performing bipolar membrane electrodialysis on the sodium sulfate obtained by redissolution to obtain sulfuric acid and sodium hydroxide.

[0046] It also includes: an acid tank 7 and an alkali tank 8, which are respectively connected to the bipolar membrane 6 and are used to receive the obtained sulfuric acid and sodium hydroxide.

[0047] It also includes: a filter aid adding tank 10, which is connected to the feed side of the ceramic membrane 2 and is used to add filter aids into the ceramic membrane feed.

[0048] The solid-liquid separation equipment 4 is a centrifuge.

[0049] The concentration side of the ceramic membrane 2 and / or the filtrate side of the solid-liquid separation device 4 are connected to a spray dryer 9 for spray drying the concentrate and the filtrate, respectively.

[0050] The ceramic membrane 2 is a single-tube, flat-plate, multi-channel ceramic membrane.

[0051] The average pore size of the ceramic membrane 2 is 0.002 μm to 1 μm, or the molecular weight cutoff is 10,000 to 5,000,000 Da.

[0052] The material of the ceramic membrane 2 is aluminum oxide, zirconium oxide, silicon carbide or titanium oxide.

[0053] The bipolar membrane 6 is a three-compartment bipolar membrane electrodialyzer or a two-compartment bipolar membrane electrodialyzer.

[0054] The diaphragm material in the bipolar membrane 6 is selected from one of PVC, PEEK, PES, PET or PVDF. Example 1

[0055] After the polylactic acid fermentation liquid is extracted, the mother liquor is evaporated and concentrated, containing 40g / L NaCl, 40g / L Mg 2+ 0.01g / L, Ca 2+0.05g / L, COD 10600mg / L, Na2SO496g / L, protein 92mg / L, filtered through a 200nm ceramic membrane device, operating pressure 0.3MPa, cross-flow velocity 3m / s, protein and other solids can be removed to obtain the ceramic membrane permeate. The ceramic membrane permeate is sent to a freezing crystallization device, frozen and temperature controlled at 1°C to obtain sodium sulfate decahydrate crystals. After the sodium sulfate decahydrate is dissolved, it is sent to a bipolar membrane system with an operating voltage of 100V and an operating current density of 600.0A / m 2 , generating H2SO4 and NaOH, with an acid current efficiency of 77.2% and an alkali current efficiency of 81.4%. The mother liquor separated by sodium sulfate crystallization and the ceramic membrane concentrate are sent to spray drying for treatment as solid waste.

[0056] As a comparison, 2 wt% diatomaceous earth filter aid was added to the feed liquid entering the ceramic membrane for filtration. The flux decay curve for the first 20 minutes is as follows: Figure 3 As shown, it can be seen that in the process of filtering the mother liquor to remove the protein, a filter aid can be added to the feed liquid to form a filter cake layer on the surface of the membrane to avoid membrane contamination. Example 2

[0057] After the threonine fermentation liquid is extracted, the mother liquor is evaporated and concentrated to contain 35g / L NaCl, Mg 2+ 0.02g / L, Ca 2+ 0.06g / L, COD 11300mg / L, Na2SO492g / L, protein 87mg / L, filtered through a 100nm silicon carbide membrane device, with an operating pressure of 0.3MPa and a cross-flow velocity of 3m / s, solids such as protein can be removed. The ion content of the silicon carbide membrane permeate obtained is: Mg 2+ Content 0.01mg / L, Ca 2+ Content 0.05mg / L, COD 5800mg / L, sodium sulfate 96g / L, sodium chloride 40g / L. The permeate of the ceramic membrane is sent to the freezing crystallization device, frozen and temperature controlled at 2°C to obtain sodium sulfate decahydrate crystals. After the sodium sulfate decahydrate is dissolved, it is sent to the bipolar membrane system with an operating voltage of 100V and an operating current density of 400.0A / m 2 , generating H2SO4 and NaOH, with an acid current efficiency of 71.2% and an alkali current efficiency of 71.4%. The mother liquor separated by sodium sulfate crystallization and the ceramic membrane concentrated liquid are sent to spray drying for treatment as solid waste. Example 3

[0058] After the glutathione fermentation liquid is extracted, the mother liquor is evaporated and concentrated, containing 45g / L NaCl, Mg 2+ 0.02g / L, Ca 2+0.07g / L, COD 12180mg / L, Na2SO486g / L, protein 63mg / L, filtered through a 50nm ceramic membrane device, operating pressure 0.3MPa, cross-flow velocity 3m / s, protein and other solids can be removed, the ion content of the ceramic membrane permeate obtained is: Mg 2+ Content 0.01mg / L, Ca 2+ Content 0.05mg / L, COD 5500mg / L, sodium sulfate 96g / L, sodium chloride 40g / L. The permeate of the ceramic membrane is sent to the freezing crystallization device, frozen and temperature controlled at 0℃, and sodium sulfate decahydrate crystals are obtained. After the sodium sulfate decahydrate is dissolved, it is sent to the bipolar membrane system with an operating voltage of 100V and an operating current density of 1000.0A / m 2 , generating H2SO4 and NaOH, with an acid current efficiency of 87.2% and an alkali current efficiency of 91.4%. The mother liquor separated by sodium sulfate crystallization and the ceramic membrane concentrate are sent to spray drying for treatment as solid waste. Example 4

[0059] Taking the ceramic membrane clarification of the polylactic acid fermentation wastewater concentrate in Example 1 as an example, the ceramic membrane is periodically backwashed; After the polylactic acid fermentation liquid is extracted, the mother liquor is evaporated and concentrated, containing 40g / L NaCl, 40g / L Mg 2+ and Ca 2+ (The total concentration was artificially prepared into 0.01, 0.02, 0.05g / L, 0.10 g / L, 0.15 g / L, 0.20g / L according to the mutual ratio of 5:1 by weight), COD 10600mg / L, Na2SO4 96g / L, protein 92mg / L, diatomaceous earth filter aid (0.2%, 0.5%, 1%, 2%, 3%, 5%) added to the feed liquid, filtered through a 200nm ceramic membrane device, operating pressure 0.3MPa, cross-flow velocity 3m / s, protein and other solids can be removed, backwash pressure 1.0Mpa, each backwash time 10s, backwash frequency set to 10min, 20min, 30min, 40min and 50min, the ceramic membrane permeate was obtained. After a total running time of 180min, after 50min of pure water cross-flow flushing, the pure water flux was re-measured and the irreversible pollution ratio value was calculated.

[0060] According to the hypothesis, the following prediction equation is used: R%=α*F 2 -β* F-γ*Ln(H+δ) / (1+ε*P) +ζ.

[0061] Among them, F refers to the backwash frequency (min), P refers to the filter aid concentration (%), H refers to the calcium and magnesium ion concentration (g / L), and α / β / γ / δ / ε / ζ are parameters.

[0062] After fitting 10 modeling samples, the prediction equation is: R%=0.06*F 2 -3.53* F-5.94*Ln(H+0.12) / (1+0.12*P) +72.03 The correlation between the theoretical value and the actual value of the modeled sample is as follows Figure 4 As shown, the average error is 10.5%; the correlation between the theoretical value and the actual value of the 5 verification samples is shown in Figure 5 As shown, the average error is 13.5%.

Claims

1. A method for resource utilization of evaporation and concentration mother liquor, characterized in that: The steps include: Step 1, evaporating and concentrating the wastewater in the fermentation process, and then filtering it with a ceramic membrane; Step 2, the permeate of the ceramic membrane is subjected to fractional crystallization to precipitate sodium sulfate; Step 3, after the sodium sulfate is redissolved, it is treated by bipolar membrane electrolysis to obtain sulfuric acid and sodium hydroxide; The wastewater in the fermentation process contains sodium sulfate, sodium chloride and protein.

2. The method for resource utilization of evaporation and concentration mother liquor according to claim 1, characterized in that: The wastewater in the fermentation process is the mother liquor after fermentation crystallization; the water contains NaCl 10-60g / L, Mg 2+ 0.01-0.5 g / L, Ca 2+ 0.01-0.5g / L, COD 1000-20000mg / L, Na2SO4 20-120g / L, protein 20-200mg / L.

3. The method for resource utilization of evaporation and concentration mother liquor according to claim 1, characterized in that: The average pore size of the ceramic membrane is 0.002 μm to 1 μm, or the molecular weight cutoff is 10,000 to 5,000,000 Da; the operating pressure range of the ceramic membrane is 0.05-0.5 Mpa, and cross-flow filtration is adopted, with a flow rate of 1-10 m / s.

4. The method for resource utilization of evaporation and concentration mother liquor according to claim 1, characterized in that: During the filtration process of the ceramic membrane, a filter aid is added to the feed in an amount of 0.5-5%; the filter aid is one of diatomaceous earth, perlite, cellulose, asbestos, graphite powder, sawdust, magnesium oxide, gypsum, activated carbon, and acid clay.

5. The method for resource utilization of evaporation and concentration mother liquor according to claim 1, characterized in that: The irreversible contamination in the ceramic membrane filtration process is predicted and calculated by the following formula: R%=α*F 2 -β* F-γ*Ln(H+δ) / (1+ε*P) +ζ; F refers to the backwash frequency, P refers to the filter aid concentration, H refers to the calcium and magnesium ion concentration, and α / β / γ / δ / ε / ζ are parameters; The irreversible contamination refers to the percentage decrease in flux compared to the original flux after 30-90 minutes of cross-flow flushing with pure water after the filtration is completed.

6. The method for resource utilization of evaporation and concentration mother liquor according to claim 1, characterized in that: The temperature control of fractional crystallization is -10℃~10℃, more preferably 0~2℃; the operating voltage of bipolar membrane electrolysis treatment is 1~200V, the current is 1~250A, the feed pressure is 0.02~0.2Mpa, and the membrane material of the bipolar membrane is selected from one or a combination of PVC, PEEK, PES, PET, PVDF, etc.; the irreversible pollution is determined under the following filtration conditions: the total concentration of calcium and magnesium ions is 0.01-0.20g / L, and the mass ratio of calcium to magnesium is in the range of 3-8:1, the amount of filter aid added is 0.2-5%, the backwash frequency is 10-50min, the continuous filtration time is 100-300min, the backwash pressure is 0.5-1.5Mpa, the backwash time is 5-20s, the filtration pressure is 0.2-0.4Mpa, and the cross-flow velocity is 2-5m / s.

7. An evaporation and concentration mother liquor resource utilization device, characterized in that: include: A concentration device (1) for concentrating fermentation wastewater; A ceramic membrane (2) connected to the concentration device (1) and used for filtering the concentrated liquid obtained in the concentration device (1); A crystallizer (3) connected to the permeate side of the ceramic membrane (2) and used to perform fractional crystallization on the permeate of the ceramic membrane (2) to precipitate sodium sulfate; A solid-liquid separation device (4) connected to the crystallizer (3) for separating the precipitated sodium sulfate; A dissolving tank (5) connected to the solid-liquid separation device (4) for re-dissolving the sodium sulfate; The bipolar membrane (6) is connected to the dissolution tank (5) and is used to perform bipolar membrane electrodialysis on the sodium sulfate obtained by redissolution to obtain sulfuric acid and sodium hydroxide.

8. The evaporation and concentration mother liquor resource utilization device according to claim 7, characterized in that: Also includes: The acid tank (7) and the alkali tank (8) are respectively connected to the bipolar membrane (6) and are used to receive the obtained sulfuric acid and sodium hydroxide.

9. A filter aid adding tank (10), connected to the feed side of the ceramic membrane (2), for adding filter aid to the ceramic membrane feed.

10. The evaporation and concentration mother liquor resource utilization device according to claim 8, characterized in that: The solid-liquid separation device (4) is a centrifuge; The concentration side of the ceramic membrane (2) and / or the filtrate side of the solid-liquid separation device 4 are connected to a spray dryer (9, for spray drying the concentrate and the filtrate respectively; The ceramic membrane (2) is a single-tube, flat-plate, multi-channel ceramic membrane.

11. The evaporation and concentration mother liquor resource utilization device according to claim 8, characterized in that: The ceramic membrane (2) has an average pore size of 0.002 μm to 1 μm, or a molecular weight cutoff of 10,000 to 5,000,000 Da; The material of the ceramic membrane (2) is aluminum oxide, zirconium oxide, silicon carbide or titanium oxide; The bipolar membrane (6) is a three-compartment bipolar membrane electrodialyzer or a two-compartment bipolar membrane electrodialyzer; The diaphragm material in the bipolar membrane (6) is selected from one of PVC, PEEK, PES, PET or PVDF; The device also includes an irreversible pollution calculation module, which is used to predict and calculate the irreversible pollution in the ceramic membrane filtration process by the following formula: R%=α*F 2 -β* F-γ*Ln(H+δ) / (1+ε*P) +ζ; F refers to the backwash frequency, P refers to the filter aid concentration, H refers to the calcium and magnesium ion concentration, and α / β / γ / δ / ε / ζ are parameters; The irreversible contamination refers to the percentage decrease in flux compared to the original flux after 30-90 minutes of cross-flow flushing with pure water after the filtration is completed.

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