Dynamic optimization process for filtration parameters of nanofiltration membrane of glucose mother liquor

Abstract

The invention relates to the technical field of membrane separation, in particular to a glucose mother liquor nanofiltration membrane filtration parameter dynamic optimization process which comprises mother liquor pretreatment, intelligent nanofiltration filtration, clear liquid treatment, residual liquid deep saccharification and finished product preparation. A sulfonated chitosan-graphene modifier is added during pretreatment, a polyamide membrane is adopted for nanofiltration, the temperature, pressure and flow velocity are dynamically adjusted through a PLC-AI system, a TiO-ZnO nano liquid is synchronously added, clear liquid is concentrated, composite saccharifying enzyme is added for reaction, enzyme is added into residual liquid, nano aerogel is saccharified, and a finished product is dried through pulse hot air circulation. According to the process, AI dynamic regulation and control are combined with a nano material, so that the pollution resistance of a nanofiltration membrane is improved, the purity of glucose is improved to 92% or above, the yield is higher than 89%, oligosaccharide residues in saccharified liquid are reduced, drying energy consumption and COD emission are reduced, and high-value utilization of mother liquor is realized.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, in particular to a process for dynamically optimizing filtration parameters of a glucose mother liquor nanofiltration membrane. Background Art

[0002] During the industrial production of crystalline glucose, the mother liquor produced daily contains a large amount of usable glucose. However, due to its low dry matter concentration, easy fermentation, short storage life, and limited transportation, it is often sold at low prices or discharged with wastewater, resulting in waste of starch resources and environmental pressure. Among existing treatment methods, some companies return the mother liquor to the saccharification process for reuse. However, as the number of returns increases, the quality of the crystallized glucose deteriorates and it tends to agglomerate, requiring regular discharge. Another method is to use membrane separation technology to purify the mother liquor, but traditional nanofiltration processes suffer from severe membrane fouling, fixed filtration parameters, and low saccharification efficiency, resulting in insufficient glucose purity to meet the needs of high-end applications.

[0003] Domestic glucose producers generally face a dilemma in mother liquor treatment: increasing the amount reused affects product quality, while reducing it reduces production efficiency. Current mother liquor reuse methods also prevent domestic glucose products from competing with similar foreign products in terms of purity and color, necessitating technological innovation to increase the value of mother liquor utilization. While membrane separation and continuous hydrolysis technologies are currently in use, they lack a dynamic control mechanism, making it difficult to balance filtration efficiency and membrane life, limiting the resource utilization of mother liquor sugars. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a process for dynamically optimizing the filtration parameters of a glucose mother liquor nanofiltration membrane.

[0005] A process for dynamically optimizing nanofiltration membrane filtration parameters of a glucose mother liquor comprises the following steps: S1: Mother liquor pretreatment: Heat the mother liquor to 55°C, add 0.2% sulfonated chitosan-graphene composite modifier, stir for 30 minutes, and adjust the pH to 5.0 with food-grade hydrochloric acid; the mass ratio of chitosan to graphene in the composite modifier is 10:1; S2: Intelligent nanofiltration: Using a polyamide composite nanofiltration membrane, under an operating pressure of 0.5 MPa, the filtration temperature and flow rate are dynamically adjusted according to online infrared spectroscopy data through a PLC-AI linkage system, and 0.05% TiO2-ZnO nanocomposite dispersion is simultaneously added; S3: Supernatant treatment: The supernatant was filtered and concentrated by four-effect concentration, and a thermostable composite saccharifying enzyme was added and reacted at 60°C for 2.5 hours; the composite saccharifying enzyme included α-amylase and saccharifying enzyme; S4: Deep saccharification of the residual liquid: Concentrate the nanofiltration residual liquid, add cellulase, xylanase and nano-SiO2 aerogel, adjust the pH to 5.0, and react at 62°C with nitrogen for 4.5 hours; S5: Preparation of finished product: After the clear liquid is evaporated, crystallized and centrifuged, it is vacuum dried at 85°C and dried using pulse hot air circulation for 3 hours.

[0006] Preferably, the method further comprises the preparation of the sulfonated chitosan-graphene composite modifier in S1: reacting chitosan and sodium 2-hydroxy-3-chloropropanesulfonate at a molar ratio of 1:1.2 in a NaOH solution at 60° C. for 2 hours, and then adding 10% graphene dispersion and ultrasonically blending for 1 hour.

[0007] Preferably, the control logic of the PLC-AI linkage system in S2 is also included: when the membrane flux attenuation rate exceeds 3% / h, the AI ​​algorithm automatically starts pulse backwashing, and at the same time increases the operating pressure by a gradient of 0.02MPa until the flux recovery rate is ≥95%; the backwash pressure of the pulse backwash is 0.8MPa, and the time is 30s.

[0008] Preferably, the preparation method of the TiO2-ZnO nanocomposite dispersion in S2 is: dispersing TiO2 and ZnO in polyethylene glycol 400 at a mass ratio of 1:1, and ultrasonically dispersing at 80°C for 1.5 hours to form a stable dispersion.

[0009] Preferably, the method for improving the thermal stability of the composite saccharifying enzyme in S3 is: replacing the 235th alanine in the active site of the saccharifying enzyme with glycine by site-directed mutagenesis technology, thereby extending the half-life at 60° C. to 8 hours.

[0010] Preferably, the nano-SiO2 aerogel in S4 is added by uniformly loading the aerogel in the residual liquid using fluidized bed spray granulation.

[0011] Preferably, the nanofiltration membrane surface pretreatment process is to form a 100 nm thick amino modified layer on the membrane surface using plasma immersion ion implantation technology; the nitrogen ion energy of the plasma immersion ion implantation technology is 50 keV, and the implantation dose is 1×10 17 ions / cm².

[0012] Preferably, the pulse frequency of the pulse hot air circulation drying in S5 is 1 time / 10 minutes, and the hot air temperature is increased by 10°C each time and restored to 85°C after 5 minutes.

[0013] Preferably, the online monitoring system includes: a near-infrared spectrometer to monitor the glucose content and disaccharide content in real time, and the data is transmitted to the AI ​​controller.

[0014] Preferably, the residual liquid saccharification reaction kettle in S4 adopts the synergistic effect of magnetic stirring and ultrasound, and the power of the ultrasound is 200W and the frequency is 28kHz.

[0015] Compared with the existing technology, the beneficial effects of the present invention are: 1. A PLC-AI linkage system is used to monitor the mother liquor composition in real time, dynamically adjust the filtration temperature, pressure and flow rate, and combine with the addition of nano-composite dispersion to significantly reduce the membrane flux attenuation rate and improve the membrane's anti-pollution ability, so that the glucose purity reaches more than 92% and the yield is increased by more than 10%.

[0016] 2. The sulfonated chitosan-graphene composite modifier introduced into the process works synergistically with the nanoenzyme system, enhancing the pretreatment of the mother liquor while also improving hydrolysis efficiency through the thermostable composite saccharifying enzyme, reducing residual oligosaccharides and achieving a DE value exceeding 95% in the saccharified liquid. Deep saccharification of the residual liquid, combined with the addition of nanoaerogel and ultrasonic assistance, further improves substrate conversion and reduces COD emissions.

[0017] 3. Pulsed hot air drying and segmented temperature control ensure the moisture content of the finished glucose product is below 0.5%, reducing drying energy consumption. This process, which requires no complex equipment modifications and utilizes intelligent control and nanomaterials, achieves high-value utilization of mother liquor sugar, achieving both economic and environmental benefits and serving as a model for clean production in the starch sugar industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a process flow chart for dynamic optimization of filtration parameters of glucose mother liquor nanofiltration membrane proposed by the present invention; Figure 2 is a bar chart comparing the purity and yield of glucose in the examples and comparative examples; Figure 3 is a line comparison chart of the membrane flux attenuation rate of the embodiment and the comparative example; Figure 4 It is a radar comparison chart of the embodiment and the comparative example produced with the same dimension. DETAILED DESCRIPTION

[0019] according to Figures 1 to 4 , the specific implementation of the present invention is as follows: Example 1: Nanofiltration optimization process of glucose mother liquor based on AI dynamic control S1: Mother liquor pretreatment Pump 1000 L of mother sugar liquor with a 50% dry matter content into a jacketed reactor and heat to 55°C with steam. Weigh 2 kg of sulfonated chitosan-graphene composite modifier (chitosan with a molecular weight of 60,000, blended with graphene in a 10:1 mass ratio) and dissolve it in 50 L of deionized water. Add the mixture to the reactor and stir at 200 rpm for 30 minutes. Adjust the pH to 5.0 using 30% food-grade hydrochloric acid. Monitor the temperature with a thermometer to ensure fluctuations of ≤±1°C.

[0020] S2: Intelligent Nanofiltration Filtration was performed using a polyamide composite nanofiltration membrane module with a molecular weight cutoff of 200 Da (membrane area, 50 m²) at an initial operating pressure of 0.5 MPa. An online infrared spectrometer (Antaris II) monitored the feed liquid dry matter content in real time (maintained between 48 and 52%). The PLC-AI linkage system dynamically adjusted the data accordingly: when the dry matter content reached 52%, the filtration temperature was increased from 45°C to 50°C, and the feed flow rate was simultaneously increased from 2.5 m / s to 3 m / s via a frequency converter. During filtration, 5 L of a TiO2-ZnO nanocomposite dispersion (TiO2 to ZnO, 1:1 mass ratio, 30 nm particle size, dispersed in polyethylene glycol 400) was continuously added via a peristaltic pump. The membrane flux was recorded every 30 minutes (initial flux 15 LMH). When the AI ​​system detects that the membrane flux attenuation rate reaches 3.5% / h, it automatically starts pulse backwashing (backwash pressure 0.8MPa, lasting 30s) and increases the operating pressure by 0.02MPa until the flux recovers to above 14LMH.

[0021] S3: Clear liquid treatment The filtered supernatant was then concentrated to a dry matter content of 72% in a four-effect concentrator and pumped into a saccharification reactor. 2.5 kg of a thermostable composite saccharifying enzyme (α-amylase to saccharifying enzyme in a 1:2 mass ratio, modified by site-directed mutagenesis, with a half-life of 8 hours at 60°C) was added. Recirculating water in the jacket was maintained at 60°C for 2.5 hours. After the reaction, a sample was taken and analyzed by high-performance liquid chromatography (HPLC), revealing a glucose purity of 92.3% and residual oligosaccharides of ≤1.2%.

[0022] S4: Deep saccharification of residual liquid The nanofiltration residue was concentrated to a dry matter content of 62% using a triple-effect concentrate and then transferred to a reactor equipped with magnetic stirring. 1 kg of cellulase, 0.5 kg of xylanase, and 0.3 kg of nano-SiO2 aerogel (particle size 1-5 μm, loaded by fluidized bed spray granulation) were added. The pH was adjusted to 5.0 with 10% NaOH. Nitrogen was introduced at a flow rate of 1.5 L / min and the reaction temperature was maintained at 62°C for 4.5 hours. During this time, an ultrasonic-assisted system (power 200 W, frequency 28 kHz) was used, and hourly sampling of the saccharified liquid was performed to determine the DE value, which reached 95.6%.

[0023] S5: Finished product preparation The clear liquid is passed through an evaporation crystallizer (evaporation temperature 80°C) to form a slurry. After separation in a butterfly centrifuge (speed 3000r / min), it is transferred to a vacuum drying oven. A pulsed hot air cycle is used: drying is first performed at 85°C and a vacuum of -0.09MPa for 2 hours. The hot air temperature is then pulsed up by 10°C every 10 minutes (returning to the original temperature after 5 minutes). The total drying time is 3 hours, and the resulting glucose product has a moisture content of ≤0.5%.

[0024] Example 2: Process optimization of high-pollution-resistant nanofiltration membrane S1: Mother liquor pretreatment Pump 1000L of mother sugar liquor with a dry matter content of 50% into a jacketed reactor and heat to 55°C with steam. Weigh 2.5kg of sulfonated chitosan-graphene composite modifier (molecular weight 60,000) and blend it with graphene in a 20:3 mass ratio. Place it in an ultrasonic device and add 50L of deionized water. Ultrasonic blend for 1.5 hours to fully dissolve the modifier. Then add it to the reactor and stir at 200 rpm for 30 minutes. Use 30% food-grade hydrochloric acid to adjust the system pH to 5.2. During this period, monitor the temperature fluctuation in real time using a thermometer to ≤±1°C. S2: Intelligent Nanofiltration A polyamide composite nanofiltration membrane assembly with a molecular weight cutoff of 200Da and a membrane area of ​​50m² was used. The membrane was modified by plasma with a nitrogen ion energy of 50keV and an injection dose of 1×10 17 ions / cm², with an initial operating pressure of 0.6 MPa. An online infrared spectrometer, Antaris II, monitored the feed liquid dry matter content in real time, maintaining it between 48-52%. The PLC-AI linkage system dynamically adjusted the data based on the data: When the dry matter content changed, the filtration temperature was adjusted according to pre-set rules within a dynamic temperature range of 50-55°C, and the feed flow rate was maintained at 3.5 m / s. During the filtration process, a peristaltic pump continuously added 5 L of a TiO2-ZnO nanocomposite dispersion. TiO2 and ZnO were dispersed in polyethylene glycol 400 at a 1:1 mass ratio, with a particle size of 30 nm. The membrane flux was recorded every 30 minutes, with an initial flux of 15 LMH. When the AI ​​system detected a membrane flux decay rate of 2.8% / h, it automatically initiated a pulse backwash at a pressure of 0.8 MPa for 30 seconds, maintaining the operating pressure at 0.55 MPa until the flux returned to a reasonable level. S3: Clear liquid treatment The filtered supernatant was then concentrated to a four-effect concentrator to a dry matter content of 72% before being pumped into the saccharification reactor. 3 kg of thermostable composite saccharifying enzyme (α-amylase:saccharifying enzyme) was added, with a 1:2 mass ratio of α-amylase to saccharifying enzyme, modified by site-directed mutagenesis to have a half-life of 8 hours at 60°C. Recirculating water in the jacket maintained the reaction at 62°C for 2.5 hours. After the reaction, samples were collected and analyzed for relevant parameters using HPLC. S4: Deep saccharification of residual liquid The nanofiltration residue was concentrated to a dry matter content of 62% using a triple-effect concentrate and then transferred to a reactor equipped with magnetic stirring. 1 kg of cellulase, 0.5 kg of xylanase, and 0.4 kg of nano-SiO2 aerogel (1-5 μm in size) were added and loaded via fluidized bed spray granulation. The pH was adjusted to 5.0 with 10% NaOH, and nitrogen was introduced at a flow rate of 1.5 L / min while maintaining the reaction temperature at 62°C for 4.5 hours. During this time, an ultrasonic-assisted system was operated at 200 W and 28 kHz, and the DE value of the saccharified liquid was sampled every hour. S5: Finished product preparation The clear liquid is passed through an evaporation crystallizer at 80°C to form a slurry. This slurry is separated in a butterfly centrifuge at 3000 r / min and then transferred to a vacuum drying oven. A pulsed hot air cycle is used: drying is first performed at 85°C and a vacuum of -0.09 MPa for two hours. The hot air temperature is then pulsed up by 10°C every eight minutes, continued for five minutes, and then restored. The total drying time is three hours, resulting in the final glucose product. Example 3: Nanocomposite enzyme system synergistic saccharification process S1: Mother liquor pretreatment Pump 1000 L of mother sugar liquor with a 50% dry matter content into a jacketed reactor and heat to 55°C with steam. Weigh 2 kg of sulfonated chitosan-graphene composite modifier (molecular weight 60,000 chitosan) and blend it with graphene in a 10:1 mass ratio. Dissolve it in 50 L of deionized water and add it to the reactor. Stir at 200 rpm for 30 minutes. Adjust the pH of the system to 5.0 using 30% food-grade hydrochloric acid. Monitor the temperature with a thermometer to ensure fluctuations of ≤±1°C. S2: Intelligent Nanofiltration Filtration was performed using a polyamide composite nanofiltration membrane module with a molecular weight cutoff of 200 Da and a membrane area of ​​50 m². An Antaris II online infrared spectrometer monitored the feed liquid dry matter content in real time, maintaining it between 48 and 52%. A PLC-AI linkage system dynamically adjusted the filtration temperature based on the data: when the dry matter content changed, the filtration temperature was adjusted according to pre-set rules within a dynamic temperature range of 48-52°C. During the filtration process, a peristaltic pump continuously added 5 L of a TiO2-ZnO nanocomposite dispersion. The TiO2 and ZnO nanocomposite dispersion, with a mass ratio of 2:3 and a particle size of 30 nm, was dispersed in polyethylene glycol 400. Membrane flux was recorded every 30 minutes, with an initial flux of 15 LMH. When the AI ​​system detected a membrane flux decay rate of 3.5% / h, it automatically initiated a pulse backwash at a pressure of 0.8 MPa for 30 seconds, and then increased the operating pressure by 0.02 MPa until the flux returned to above 14 LMH. S3: Clear liquid treatment The filtered supernatant enters a four-effect concentrator, where it is concentrated to a dry matter content of 72% before being pumped into the saccharification reactor. Weigh 2.5 kg of a thermostable composite saccharifying enzyme (α-amylase:saccharifying enzyme) modified by site-directed mutagenesis to have a half-life of 8 hours at 60°C. Add 0.05% of 20 nm nano-SiO2-TiO2 composite particles. Place both in an ultrasonic device and ultrasonically disperse them with an appropriate amount of solvent for 30 minutes before adding them to the saccharification reactor. Recirculating water in the jacket maintains the reaction at 65°C for 2 hours. After the reaction is complete, samples are collected and analyzed for relevant indicators using HPLC. S4: Deep saccharification of residual liquid The nanofiltration residue was concentrated to a dry matter content of 62% using a triple-effect concentrate and then transferred to a reactor equipped with magnetic stirring. 0.75 kg of cellulase, 0.75 kg of xylanase, 0.03% of β-glucosidase, and 0.3 kg of nano-SiO2 aerogel (1-5 μm in size) were added. The mixture was loaded by fluidized bed spray granulation. The pH was adjusted to 5.0 with 10% NaOH, and nitrogen was introduced at a flow rate of 1.5 L / min at 60°C for 5 hours. During this time, an ultrasonic-assisted system was used at 200 W and 28 kHz, and the DE value of the saccharified liquid was sampled every hour. S5: Finished product preparation The clear liquid is passed through an evaporation crystallizer at 80°C to form a slurry. This slurry is then separated in a butterfly centrifuge at 3000 rpm before being transferred to a vacuum drying oven. A pulsed hot air cycle is used: drying is initially performed at 85°C and a vacuum of -0.09 MPa for two hours. The hot air temperature is then pulsed up by 10°C every 10 minutes, continued for five minutes, and then returned to normal. The final glucose product is obtained after a total drying time of three hours.

[0025] Comparative example: traditional nanofiltration process S1: Mother liquor pretreatment 1000 L mother liquor sugar was heated to 50 °C, 0.5% ordinary chitosan was added, stirred for 20 minutes, and the pH was adjusted to 5.5. No graphene was added.

[0026] S2: Nanofiltration Ordinary polyamide nanofiltration membrane (molecular weight cut-off 300Da) was used, with a fixed pressure of 0.4MPa, a temperature of 40°C, a flow rate of 2m / s, and no AI regulation or nanodispersion addition.

[0027] S3-S4: Treatment of clear liquid and residual liquid After the clear liquid was concentrated to 70% dry matter, 0.3% unmodified saccharifying enzyme was added and the reaction was carried out at 55°C for 3 hours. After the residual liquid was concentrated, only cellulase was added and the reaction was carried out at 55°C for 6 hours.

[0028] The performance comparison between the embodiment and the comparative example is shown in the following table: Table 1 .

[0029] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A process for dynamic optimization of nanofiltration membrane filtration parameters of glucose mother liquor, characterized in that: The following steps are involved: S1: Mother liquor pretreatment: Heat the mother liquor to 55°C, add 0.2% sulfonated chitosan-graphene composite modifier, stir for 30 minutes, and adjust the pH to 5.0 with food-grade hydrochloric acid; the mass ratio of chitosan to graphene in the composite modifier is 10:1; S2: Intelligent nanofiltration: Using a polyamide composite nanofiltration membrane, under an operating pressure of 0.5 MPa, the filtration temperature and flow rate are dynamically adjusted according to online infrared spectroscopy data through a PLC-AI linkage system, and 0.05% TiO2-ZnO nanocomposite dispersion is simultaneously added; S3: Supernatant treatment: The supernatant was filtered and concentrated by four-effect concentration, and a thermostable composite saccharifying enzyme was added and reacted at 60°C for 2.5 hours; the composite saccharifying enzyme included α-amylase and saccharifying enzyme; S4: Deep saccharification of the residual liquid: Concentrate the nanofiltration residual liquid, add cellulase, xylanase and nano-SiO2 aerogel, adjust the pH to 5.0, and react at 62°C with nitrogen for 4.5 hours; S5: Preparation of finished product: After the clear liquid is evaporated, crystallized and centrifuged, it is vacuum dried at 85°C and dried using pulse hot air circulation for 3 hours.

2. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, wherein: The method also includes the preparation of the sulfonated chitosan-graphene composite modifier in S1: reacting chitosan and sodium 2-hydroxy-3-chloropropanesulfonate in a molar ratio of 1:1.2 in a NaOH solution at 60° C. for 2 hours, and then adding 10% graphene dispersion and ultrasonically blending for 1 hour.

3. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, wherein: It also includes the control logic of the PLC-AI linkage system in S2: when the membrane flux attenuation rate exceeds 3% / h, the AI ​​algorithm automatically starts pulse backwashing, and at the same time increases the operating pressure by a gradient of 0.02MPa until the flux recovery rate is ≥95%; the backwash pressure of the pulse backwash is 0.8MPa, and the time is 30s.

4. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The preparation method of the TiO2-ZnO nanocomposite dispersion in S2 is as follows: TiO2-ZnO is dispersed in polyethylene glycol 400 at a mass ratio of 1:1, and ultrasonically dispersed at 80°C for 1.5 hours to form a stable dispersion.

5. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The method for improving the thermal stability of the composite saccharifying enzyme in S3 is as follows: replacing the 235th alanine in the active site of the saccharifying enzyme with glycine by site-directed mutagenesis technology, thereby extending the half-life of the composite saccharifying enzyme at 60° C. to 8 hours.

6. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The nano-SiO2 aerogel in S4 is added in a manner of evenly loading the aerogel in the residual liquid by using fluidized bed spray granulation.

7. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The nanofiltration membrane surface pretreatment process is to form a 100 nm thick amino modified layer on the membrane surface by plasma immersion ion implantation technology; the nitrogen ion energy of the plasma immersion ion implantation technology is 50 keV, and the implantation dose is 1×10 17 ions / cm².

8. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The pulse frequency of the pulse hot air circulation drying in S5 is 1 time / 10 minutes, and the hot air temperature is increased by 10° C. each time, and then restored to 85° C. after 5 minutes.

9. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The online monitoring system includes: a near-infrared spectrometer to monitor the glucose content and disaccharide content in real time, and transmit the data to the AI ​​controller.

10. The process for dynamic optimization of nanofiltration parameters of glucose mother liquor according to claim 1, characterized in that: The residual liquid saccharification reaction kettle in S4 adopts the synergistic effect of magnetic stirring and ultrasound, and the power of the ultrasound is 200W and the frequency is 28kHz.

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