Reverse osmosis high concentration process

Abstract

The present application relates to the technical field of water treatment, and in particular to a reverse reverse osmosis high-fold concentration process, comprising the following steps: filtering a lignocellulose hydrolyzate through a filter screen to obtain a filtrate; ultrafiltration of the filtrate through an ultrafiltration device to obtain an ultrafiltrate; reverse osmosis treatment of the ultrafiltrate through a reverse osmosis device to obtain a concentrated solution A, wherein both ends of the reverse osmosis membrane element in the reverse osmosis membrane device are symmetrically provided with water sealing devices; after the operation is completed, the water inlet end of the reverse osmosis device is converted to the water outlet end, and the water outlet end of the reverse osmosis device is converted to the water inlet end, and reverse operation is performed to obtain a concentrated solution B; the concentrated solution A and the concentrated solution B are mixed to obtain a lignocellulose hydrolyzate concentrated solution. Through reverse reverse osmosis treatment and combined with the modification of the reverse osmosis membrane, the technical problem of easy clogging and contamination of the reverse osmosis membrane during the reverse osmosis treatment of the lignocellulose hydrolyzate is solved.

Description

Technical Field

[0001] The present application relates to the technical field of water treatment, and in particular to a reverse osmosis high-multiple concentration process. Background Art

[0002] Producing biofuels from lignocellulosic biomass through biological conversion is an important way to obtain biomass energy, and the most critical step in the conversion process is the hydrolysis of lignocellulosic raw materials. Dilute acid hydrolysis or dilute acid pretreatment followed by enzymatic hydrolysis is currently the most widely used hydrolysis technology, but the lignocellulosic hydrolysate after dilute acid treatment contains a large amount of toxic substances (acetic acid, furans, phenolic toxic substances) produced by high temperature and high pressure degradation, which seriously inhibits the subsequent microbial fermentation process and reduces the yield and yield of the final product (bioethanol). Therefore, these fermentation inhibitors need to be removed before fermentation to ensure efficient utilization of resources. It is planned to use reverse osmosis to treat the lignocellulosic hydrolysate to remove toxic substances, but the lignocellulosic hydrolysate contains a large amount of solid residues and impurities, which will inevitably cause serious membrane pollution and affect the separation and concentration efficiency. Summary of the invention

[0003] The present application provides a reverse osmosis high-concentration process to solve the technical problem of easy clogging and pollution of reverse osmosis membranes in the prior art.

[0004] In a first aspect, the present application provides a reverse osmosis high-concentration process, comprising the following steps:

[0005] S1, filtering the lignocellulose hydrolyzate through a filter screen to obtain a filtrate;

[0006] S2, ultrafiltering the filtrate through an ultrafiltration device to obtain an ultrafiltrate;

[0007] S3, subjecting the ultrafiltrate to reverse osmosis treatment through a reverse osmosis device to obtain a concentrated solution A, wherein both ends of the reverse osmosis membrane element in the reverse osmosis membrane device are symmetrically provided with water sealing devices;

[0008] S4, after the operation is completed, the water inlet end of the reverse osmosis device is converted to the water outlet end, and the water outlet end of the reverse osmosis device is converted to the water inlet end, and reverse operation is performed to obtain a concentrated solution B;

[0009] S5. Mix the concentrated solution A and the concentrated solution B to obtain a lignocellulose hydrolysis concentrated solution.

[0010] Optionally, the reverse osmosis membrane in the reverse osmosis membrane element is a modified polyamide osmosis membrane.

[0011] Optionally, the preparation process of the modified polyamide permeable membrane comprises the following steps:

[0012] E1. Dissolving chitosan in deionized water to prepare a chitosan solution;

[0013] E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8.

[0014] E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution;

[0015] E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 20-40° C. for 7-8 hours to obtain a preliminary modified polyamide permeable membrane;

[0016] E5. Put the preliminary modified polyamide permeable membrane into the chitosan solution for reaction, then take out the polyamide permeable membrane for drying, and wash it repeatedly to obtain the modified polyamide permeable membrane.

[0017] Optionally, the concentration of the chitosan solution is 0.3-0.5% (wt).

[0018] Optionally, the reaction time in step E5 is 40 to 55 seconds.

[0019] Optionally, the chitosan is modified chitosan, and the preparation of the modified chitosan comprises the following steps:

[0020] M1. Add 1 wt% dilute acetic acid to chitosan and stir at 60-70°C for 15-20 min, then add dibutyltin dilaurate and stir for 6-8 min;

[0021] M2. The stirred mixture is heated, and then cyclohexane oxide is slowly added dropwise. After the addition is complete, stirring is continued for 5 to 6 hours to stop the reaction;

[0022] M3. Evaporating the mixed solution obtained after the reaction, then washing it, and finally freeze-drying it to obtain modified chitosan.

[0023] Optionally, the chitosan is heated to 50° C. in step M2.

[0024] Optionally, the mass ratio of the chitosan, the dilute acetic acid solution, the dibutyltin dilaurate and the cyclohexene oxide is 1:100:0.07:6.

[0025] Optionally, the pH of the lignocellulose hydrolysate is 2.5-3.3.

[0026] Optionally, the reverse osmosis treatment temperature is 40°C and the pressure is 22 bar.

[0027] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0028] The embodiment of the present application provides a reverse osmosis high-fold concentration process, which uses a reverse method to concentrate the lignocellulose hydrolyzate after acid hydrolysis, separates the inhibitory substances such as acetic acid, furans, phenols, etc. in the hydrolyzate, and concentrates and recovers the sugars. However, there are a large number of solid residues and impurities in the hydrolyzate, which cause the reverse osmosis membrane to be polluted, so that its concentration and separation effect is greatly reduced. In the reverse process, the pollutants in the reverse osmosis membrane can be flushed out under the action of water, which reduces pollution, prolongs the service life of the reverse osmosis membrane, and improves the separation and concentration effect. The surface of the polyamide permeable membrane is relatively rough and easily polluted. The present invention modifies the polyamide permeable membrane by chitosan to make its surface smooth, further reducing the membrane pollution in the process of treating the lignocellulose hydrolyzate, and the hydrophilicity of the membrane is increased, which greatly improves the membrane flux and improves the separation rate of sugars and inhibitors. However, there is a large amount of acetic acid in the lignocellulose hydrolyzate, and the pH value is low, which makes the reverse osmosis membrane unstable and has a certain adverse effect on the membrane. The present invention modifies chitosan by epoxycyclohexane, and then modifies the reverse osmosis membrane by the modified chitosan, so that it can stably run the reverse osmosis treatment process under acidic conditions, which plays a certain protective role on the reverse osmosis membrane and shows excellent anti-organic and anti-biological pollution performance. The water sealing device is a seal on the reverse osmosis membrane, which realizes the sealing of the liquid. The liquid is pressed into the reverse osmosis membrane under pressure for filtration. The two ends of the reverse osmosis membrane element described in this application are symmetrically provided with water sealing devices to ensure that the reverse osmosis membrane system can run "reversely", that is, the water inlet end can be converted into the water outlet end, and the water outlet end can be converted into the water inlet end, so that the pollutants are washed out by hydraulic action and the function of the reverse osmosis membrane system is restored. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a reverse osmosis system;

[0030] Figure 2 is a front view of the water sealing device;

[0031] Figure 3 Exploded view of reinforcement hoop and reinforcing ring;

[0032] Figure 4 for Figure 3 A magnified view of the fracture and connection of the card block;

[0033] Figure 5 is a side sectional view of a water sealing device;

[0034] Figure 6 for Figure 5The enlarged schematic diagram of the connection between the convex ring strip and the concave ring groove in the middle B;

[0035] Reference numerals:

[0036] 1-reverse osmosis membrane element, 2-housing, 3-water production center tube, 4-first stress resister, 5-first water sealing device, 6-second stress resister, 7-second water sealing device, 8-installation port, 9-reinforcement component, 901-slot, 902-reinforcement hoop, 903-reinforcement ring, 904-fracture, 905-slot, 906-block, 907-concave ring groove, 908-convex ring strip. DETAILED DESCRIPTION

[0037] In one embodiment of the present application, the reverse osmosis high-concentration process comprises the following steps:

[0038] S1, filtering the lignocellulose hydrolyzate through a filter screen to obtain a filtrate;

[0039] S2, ultrafiltering the filtrate through an ultrafiltration device to obtain an ultrafiltrate;

[0040] S3, subjecting the ultrafiltrate to reverse osmosis treatment through a reverse osmosis device to obtain a concentrated solution A, wherein both ends of the reverse osmosis membrane element in the reverse osmosis membrane device are symmetrically provided with water sealing devices;

[0041] S4, after the operation is completed, the water inlet end of the reverse osmosis device is converted to the water outlet end, and the water outlet end of the reverse osmosis device is converted to the water inlet end, and reverse operation is performed to obtain a concentrated solution B;

[0042] S5. Mix the concentrated solution A and the concentrated solution B to obtain a lignocellulose hydrolysis concentrated solution.

[0043] In the present application, water sealing devices are provided at both ends of the reverse osmosis membrane, so that the reverse osmosis equipment can be processed in reverse order. During the reverse processing of the lignocellulose hydrolysate, the pollutants blocking the membrane are flushed out under the action of water, thereby reducing the degree of membrane contamination, allowing the sugars in the hydrolysate to be recovered in large quantities and removing related inhibitors.

[0044] like Figure 1-Figure 6As shown, the water sealing device is arranged on the reverse osmosis membrane element 1, and the shell 2 of the reverse osmosis membrane element 1 is connected to the left and right ends of the water production center pipe 3 through the first stress resister 4 and the second stress resister 6 respectively, and the first water sealing device 5 and the second water sealing device 7 are respectively arranged between the shell 2 and the first stress resister 4 and the second stress resister 6, and the installation form of the first water sealing device 5 and the second water sealing device 7 is symmetrical on the left and right. The water sealing device includes a sealing member and a reinforcement component 9, and the inner side of the sealing member is provided with an installation port 8; the reinforcement component 9 includes a card slot 901 which is concavely opened at the center of the outer side of the sealing member, and a reinforcement hoop 902 and a reinforcement ring 903 which are movably matched and engaged at the inner and outer ends of the card slot 901, and a fracture 904 is also arranged on one side of the reinforcement hoop 902, and a bayonet 905 is opened on one side of the fracture 904, and a block 906 is fixedly installed on the other side of the fracture 904, and the bayonet 905 and the block 906 are matched with each other, and The bayonet 905 and the block 906 are both T-shaped structures, the bayonet 901, the reinforcement hoop 902 and the reinforcement ring 903 are all annular structures, and the reinforcement hoop 902 and the reinforcement ring 903 are made of stainless steel and rubber respectively, and the reinforcement assembly 9 also includes a concave ring groove 907 respectively opened at the upper and lower ends of the bayonet 901, and a convex ring strip 908 is set at the upper and lower ends of the inner side of the reinforcement ring 903, and the convex ring strip 908 matches the concave ring groove 907, and the convex ring strip 908 and the concave ring groove 907 are both annular structures. Before water treatment, it is installed on the reverse osmosis membrane element 1 through the installation port 8, and then the reinforcement hoop 902 is set in the bayonet 901, and the block 906 is engaged in the bayonet 905, and finally the reinforcement ring 903 is set on the outer end of the bayonet 901, so that the convex ring strip 908 is engaged in the concave ring groove 907 at the upper and lower ends of the bayonet 901, and the installation of the water sealing device is completed. The installation of the water sealing device can convert the water inlet end into the water outlet end through the adjustment of the relevant valves of the sub-osmosis treatment system, and perform "reverse" operation, so that the pollutants are flushed out under the action of water, and the function of the reverse osmosis membrane is restored. During the reverse osmosis treatment process, the water molecules and inhibitors such as acetic acid, furans, phenols, etc. in the hydrolyzate pass through the membrane and are discharged from the water production central pipe 3, and the remaining sugar substances are intercepted, so that the sugars in the hydrolyzate are concentrated and discharged from the concentrated water outlet pipe to achieve the purpose of recovery.

[0045] The water inlet of the reverse osmosis membrane element 1 is connected to the water inlet pipe, and the water inlet pipe is provided with a first butterfly valve, a high-pressure pump, a first check valve and a second butterfly valve. The water outlet of the water production center pipe 3 is connected to the clean water outlet pipe, and the concentrated water outlet of the reverse osmosis membrane element 1 is connected to the concentrated water outlet pipe, and the concentrated water outlet pipe is installed with a regulating valve and a second check valve. The end of the water inlet pipe connected to the water inlet is also connected to a first pipe, and the water inlet is communicated with the first pipe. A third butterfly valve is installed at a position of the first pipe between the water inlet pipe and the water inlet, and a fourth butterfly valve is installed at a position of the first pipe extending out of the water inlet. The extended end of the first pipe extends to the concentrated water tank, and a second pipe is connected between the water inlet and the concentrated water outlet, and a fifth butterfly valve is installed on the second pipe. Opening the third butterfly valve and the regulating valve is the "forward sequence" reverse osmosis mode, water enters from the left end of the shell 2, and the produced clean water and concentrated water are discharged from the water production center pipe 3 and the concentrated water outlet pipe at the right end of the reverse osmosis membrane element 1 respectively. Closing the third butterfly valve and the regulating valve, opening the fourth butterfly valve and the fifth butterfly valve is the "reverse sequence" reverse osmosis mode, the water inlet end is opposite, water enters from the right end of the shell 2, concentrated water is discharged from the left end of the shell 2 of the reverse osmosis membrane element 1, and the produced clean water is still discharged from the outlet of the water production center pipe 3.

[0046] As an optional embodiment, the reverse osmosis membrane in the reverse osmosis membrane element is a modified polyamide osmosis membrane, which has a three-layer structure.

[0047] In the present application, the reverse osmosis membrane is modified to improve its membrane flux while further reducing the degree of membrane contamination, improving the recovery rate of sugars (xylose, glucose), and reducing the content of acetic acid in the hydrolyzate.

[0048] As an optional embodiment, the preparation process of the modified polyamide permeable membrane comprises the following steps:

[0049] E1. Dissolving chitosan in deionized water to prepare a chitosan solution;

[0050] E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8.

[0051] E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution;

[0052] E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 20-40° C. for 7-8 hours to obtain a preliminary modified polyamide permeable membrane;

[0053] E5. Put the preliminary modified polyamide permeable membrane into the chitosan solution for reaction, then take out the polyamide permeable membrane for drying, and wash it repeatedly to obtain the modified polyamide permeable membrane.

[0054] In the present application, the polyamide permeable membrane is modified by chitosan to make its surface smooth, further reduce its membrane pollution, extend the life of the reverse osmosis membrane, and improve its hydrophilicity, so that the membrane flux is greatly improved, and the reverse osmosis concentration efficiency is improved.

[0055] As an optional embodiment, the concentration of the chitosan solution is 0.3-0.5% (wt).

[0056] In the present application, the concentration of the chitosan solution is further limited to improve the modification effect and ensure the reverse osmosis concentration treatment effect and anti-pollution property of the modified reverse osmosis membrane.

[0057] As an optional implementation, the reaction time in step E5 is 40 to 55 seconds.

[0058] In the present application, the reaction time is further limited to control the grafting amount of chitosan on the surface of the reverse osmosis membrane, and the purpose is also to ensure the reverse osmosis concentration treatment effect and anti-pollution property of the modified reverse osmosis membrane.

[0059] As an optional embodiment, the chitosan is modified chitosan, and the preparation of the modified chitosan comprises the following steps:

[0060] M1. Add 1 wt% dilute acetic acid to chitosan and stir at 60-70°C for 15-20 min, then add dibutyltin dilaurate and stir for 6-8 min;

[0061] M2. The stirred mixture is heated, and then cyclohexane oxide is slowly added dropwise. After the addition is complete, stirring is continued for 5 to 6 hours to stop the reaction;

[0062] M3. Evaporating the mixed solution obtained after the reaction, then washing it, and finally freeze-drying it to obtain modified chitosan.

[0063] In the present application, chitosan is modified so that the reverse osmosis membrane can operate stably under acidic conditions, thereby ensuring the reverse osmosis concentration treatment effect and protecting the reverse osmosis membrane.

[0064] As an optional embodiment, the chitosan is heated to 50° C. in step M2; the mass ratio of the chitosan, the dilute acetic acid solution, dibutyltin dilaurate and cyclohexene oxide is 1:100:0.07:6

[0065] In the present application, the modification conditions of chitosan are limited to improve the relevant properties of the modified chitosan so that it can give the reverse osmosis membrane relevant optimized properties under acidic conditions.

[0066] As an optional embodiment, the pH of the lignocellulose hydrolysate is 2.5-3.3.

[0067] In the present application, under the condition that the pH of the lignocellulose hydrolysate is 2.5-3.3, a concentration treatment is performed by the reverse osmosis membrane device defined in the present invention, which can achieve a better sugar recovery rate and inhibitor removal rate.

[0068] As an optional embodiment, the reverse osmosis treatment temperature is 40° C. and the pressure is 22 bar.

[0069] In the present application, the reverse osmosis treatment temperature and pressure are limited to ensure the reverse osmosis concentration treatment effect, so that the retention of acetic acid in the hydrolyzate is maintained in an appropriate range, stimulating and promoting the fermentation of the hydrolyzate in the later stage.

[0070] Example 1-1

[0071] The preparation process of the modified polyamide permeable membrane comprises the following steps:

[0072] M1. Add 100 g of 1 wt% dilute acetic acid to 1 g of chitosan and stir at 60 °C and 1600 r / min for 15 min. Then add 6 g of dibutyltin dilaurate and stir for 6 min.

[0073] M2. Heat the stirred mixture to 50°C, then slowly drop 0.07 g of cyclohexene oxide. After the dropwise addition is complete, continue stirring for 5-6 hours to stop the reaction.

[0074] M3, evaporating the mixed solution obtained after the reaction, then washing it with acetone, and finally freeze-drying it to obtain modified chitosan;

[0075] E1, dissolving the modified chitosan in deionized water to prepare a modified chitosan solution with a concentration of 0.3wt%;

[0076] E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8.

[0077] E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution;

[0078] E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 20° C. for 7 hours to obtain a preliminary modified polyamide permeable membrane;

[0079] E5. Put the preliminary modified polyamide permeable membrane into the modified chitosan solution to react for 40 seconds, then take out the polyamide permeable membrane, dry it at 90° C. for 8 minutes, and wash it repeatedly to obtain the modified polyamide permeable membrane.

[0080] Example 1-2

[0081] The preparation process of the modified polyamide permeable membrane comprises the following steps:

[0082] M1. Add 100 g of 1 wt% dilute acetic acid to 1 g of chitosan and stir at 66 °C and 1600 r / min for 17 min. Then add 6 g of dibutyltin dilaurate and stir for 6 min.

[0083] M2. Heat the stirred mixture to 50°C, then slowly drop 0.07 g of cyclohexene oxide. After the dropwise addition is complete, continue stirring for 5.5 h to stop the reaction;

[0084] M3, evaporating the mixed solution obtained after the reaction, then washing it with acetone, and finally freeze-drying it to obtain modified chitosan;

[0085] E1, dissolving the modified chitosan in deionized water to prepare a modified chitosan solution with a concentration of 0.4wt%;

[0086] E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8.

[0087] E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution;

[0088] E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 33° C. for 7 hours to obtain a preliminary modified polyamide permeable membrane;

[0089] E5. Put the preliminary modified polyamide permeable membrane into the modified chitosan solution to react for 50 seconds, then take out the polyamide permeable membrane, dry it at 90° C. for 8 minutes, and wash it repeatedly to obtain the modified polyamide permeable membrane.

[0090] Examples 1-3

[0091] The preparation process of the modified polyamide permeable membrane comprises the following steps:

[0092] M1. Add 100 g of 1 wt% dilute acetic acid to 1 g of chitosan and stir at 70 °C and 1600 r / min for 20 min. Then add 6 g of dibutyltin dilaurate and stir for 8 min.

[0093] M2. Heat the stirred mixture to 50°C, then slowly drop 0.07 g of cyclohexene oxide. After the dropwise addition is complete, continue stirring for 6 hours to stop the reaction;

[0094] M3, evaporating the mixed solution obtained after the reaction, then washing it with acetone, and finally freeze-drying it to obtain modified chitosan;

[0095] E1, dissolving the modified chitosan in deionized water to prepare a modified chitosan solution with a concentration of 0.5wt%;

[0096] E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8.

[0097] E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution;

[0098] E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 40° C. for 8 hours to obtain a preliminary modified polyamide permeable membrane;

[0099] E5. Put the preliminary modified polyamide permeable membrane into the modified chitosan solution to react for 55 seconds, then take out the polyamide permeable membrane, dry it at 90° C. for 8 minutes, and wash it repeatedly to obtain the modified polyamide permeable membrane.

[0100] Example 2-1

[0101] A reverse osmosis high-multiple concentration process comprises the following steps:

[0102] S1, filtering the lignocellulose hydrolyzate through a filter screen to obtain a filtrate; the pH of the lignocellulose hydrolyzate is 2.5;

[0103] S2, ultrafiltering the filtrate through an ultrafiltration device to obtain an ultrafiltrate;

[0104] S3, the ultrafiltrate is subjected to reverse osmosis treatment through the reverse osmosis membrane element 1 in the reverse osmosis equipment, the third butterfly valve and the regulating valve are opened, water is introduced from the left end of the housing 2, and the concentrated water outlet pipe is used to discharge water to obtain concentrated liquid A, and water molecules and inhibitors such as acetic acid, furans, phenols, etc. pass through the membrane and are discharged from the water production center pipe 3; the reverse osmosis treatment temperature is 40° C. and the pressure is 22 bar; the reverse osmosis membrane element 1 adopts the modified polyamide permeable membrane prepared in Example 1-1;

[0105] S4, after the operation is completed, the third butterfly valve and the regulating valve are closed, the fourth butterfly valve and the fifth butterfly valve are opened, water is introduced from the right end of the housing 2, and reverse operation is performed, and water is discharged from the left end of the housing 2 to obtain concentrated liquid B, and water molecules and inhibitors such as acetic acid, furans, and phenols pass through the membrane and are discharged from the water production center pipe 3; the reverse osmosis treatment temperature is 40°C and the pressure is 22 bar;

[0106] S5. Mix the concentrated solution A and the concentrated solution B to obtain a lignocellulose hydrolysis concentrated solution.

[0107] Example 2-2

[0108] Comparing Example 2-2 with Example 2-1, the difference between Example 2-2 and Example 2-1 is that the pH of the lignocellulose hydrolyzate is 3.1; and the reverse osmosis membrane element adopts the modified polyamide osmotic membrane prepared in Example 1-2.

[0109] Example 2-3

[0110] Comparing Example 2-3 with Example 2-1, the difference between Example 2-3 and Example 2-1 is that the pH of the lignocellulose hydrolyzate is 3.3; and the reverse osmosis membrane element adopts the modified polyamide osmotic membrane prepared in Example 1-3.

[0111] Comparative Example 1

[0112] Comparing Comparative Example 1 with Example 2-2, the difference between Comparative Example 1 and Example 2-2 is that the reverse osmosis membrane element adopts an unmodified polyamide permeable membrane.

[0113] Comparative Example 2

[0114] Comparing Comparative Example 2 with Example 2-2, the difference between Comparative Example 2 and Example 2-2 is that the reverse osmosis membrane element adopts an unmodified chitosan-modified polyamide permeation membrane, and the experimental parameters are the same as those of Example 1-2.

[0115] Comparative Example 3

[0116] Comparing Comparative Example 3 with Example 2-2, the difference between Comparative Example 3 and Example 2-2 is that the reverse osmosis membrane element adopts the modified polyamide permeable membrane prepared in the same manner as Example 1-2; and the pH of the lignocellulose hydrolyzate is 2.0.

[0117] Comparative Example 4

[0118] Comparing Comparative Example 4 with Example 2-2, the difference between Comparative Example 4 and Example 2-2 is that the reverse osmosis membrane element adopts the modified polyamide permeable membrane prepared in the same manner as Example 1-2; and the pH of the lignocellulose hydrolyzate is 4.0.

[0119] Comparative Example 5

[0120] Comparing Comparative Example 5 with Example 2-2, the difference between Comparative Example 5 and Example 2-2 is that the reverse osmosis treatment is not performed.

[0121] Related experiments: The lignocellulose hydrolysate after reverse osmosis concentration was tested and compared with the unconcentrated lignocellulose hydrolysate to calculate the recovery rate (%) of related sugars (xylose, glucose) and the decrease rate (%) of related inhibitors (acetic acid, phenols, aldehydes). The experimental results are shown in Table 1. At the same time, the membrane flux (L / m 2 h) was tested. After one year of operation, the reverse osmosis membrane was cleaned with acid and its membrane flux was tested. The test results are shown in Table 2.

[0122] Table 1: Sugar recovery and inhibitor reduction rate of reverse osmosis concentration

[0123] Xylose (%) glucose(%) Acetic acid (%) Phenols (%) Aldehydes (%) Example 2-1 99.64 99.69 76.53 85.54 83.11 Example 2-2 99.59 99.21 77.34 89.71 88.25 Example 2-3 99.81 99.73 75.66 84.06 82.52 Comparative Example 1 91.12 90.02 56.10 42.07 38.93 Comparative Example 2 96.88 94.39 70.41 77.30 68.06 Comparative Example 3 95.21 96.11 76.67 82.15 75.22 Comparative Example 4 89.06 90.64 68.28 80.91 80.08 Comparative Example 5 99.82 99.79 78.12 89.48 89.24

[0124] Table 2: Operational membrane flux

[0125] Example 2-1 Example 2-2 Example 2-3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 1 day 62.57 67.42 66.29 51.81 65.22 66.17 67.15 67.51 3 months 61.28 66.03 63.17 32.37 44.38 55.97 57.19 59.27 6 months 57.82 63.82 60.24 / / 40.29 41.35 33.46 After cleaning 61.29 65.46 63.25 37.62 53.21 63.47 65.84 64.47

[0126] It can be seen from Tables 1 and 2 that one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0127] (1) The reverse osmosis concentration process of the present invention can achieve a higher sugar recovery rate by treating the lignocellulose hydrolysate, reduce the content of inhibitory substances such as acetic acid, phenols and aldehydes in the hydrolysate, and will not have an adverse effect on the later fermentation.

[0128] (2) The reverse osmosis concentration process of the present invention can operate stably for a long time, reduce membrane pollution, and maintain a high membrane flux.

[0129] (3) The reverse osmosis membrane of the present invention can operate stably for a long time and has good regeneration performance and can be put back into use after cleaning.

Claims

1. Reverse osmosis high concentration process, characterized in that: The following steps are involved: S1, filtering the lignocellulose hydrolyzate through a filter screen to obtain a filtrate; S2, ultrafiltering the filtrate through an ultrafiltration device to obtain an ultrafiltrate; S3, performing reverse osmosis treatment on the ultrafiltrate through a reverse osmosis device to obtain a concentrated solution A, wherein both ends of the reverse osmosis membrane element in the reverse osmosis device are symmetrically provided with water sealing devices; S4, after the operation is completed, the water inlet end of the reverse osmosis device is converted to the water outlet end, and the water outlet end of the reverse osmosis device is converted to the water inlet end, and reverse operation is performed to obtain a concentrated solution B; S5, mixing the concentrated solution A and the concentrated solution B to obtain a lignocellulose hydrolysis concentrated solution; The reverse osmosis membrane in the reverse osmosis membrane element is a modified polyamide osmosis membrane; The preparation process of the modified polyamide permeable membrane comprises the following steps: E1. Dissolving chitosan in deionized water to prepare a chitosan solution; E2. Add 0.600 g of trishydroxyaminomethane to 35 ml of 0.1 mol / L hydrochloric acid to prepare a 100 ml buffer solution with a pH of 8. E3, adding 0.06 g of tannic acid to the buffer solution and stirring evenly to obtain a tannic acid modified solution; E4, placing the polyamide permeable membrane into the tannic acid modified solution, and immersing it at 20-40° C. for 7-8 hours to obtain a preliminary modified polyamide permeable membrane; E5, placing the preliminary modified polyamide permeable membrane into the chitosan solution for reaction, then taking out the polyamide permeable membrane for drying, and repeatedly washing to obtain a modified polyamide permeable membrane; The chitosan is modified chitosan, and the preparation of the modified chitosan comprises the following steps: M1. Add 1 wt% dilute acetic acid to chitosan and stir at 60-70°C for 15-20 min, then add dibutyltin dilaurate and stir for 6-8 min; M2. The stirred mixture is heated, and then cyclohexane oxide is slowly added dropwise. After the addition is complete, stirring is continued for 5 to 6 hours to stop the reaction; M3, evaporating the mixed solution obtained after the reaction, then washing it, and finally freeze-drying it to obtain modified chitosan; The pH of the lignocellulose hydrolysate is 2.5-3.

3.

2. The reverse osmosis high concentration process according to claim 1, characterized in that: The concentration of the chitosan solution is 0.3-0.5% (wt).

3. The reverse osmosis high-concentration process according to claim 1, characterized in that: The reaction time in step E5 is 40 to 55 seconds.

4. The reverse osmosis high concentration process according to claim 1, characterized in that: The chitosan is heated to 50° C. in step M2.

5. The reverse osmosis high-concentration process according to claim 1, characterized in that: The mass ratio of the chitosan, the dilute acetic acid solution, the dibutyltin dilaurate and the cyclohexene oxide is 1:100:0.07:

6.

6. The reverse osmosis high-concentration process according to claim 1, characterized in that: The reverse osmosis treatment temperature is 40°C and the pressure is 22 bar.

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