CN113501567B - Multi-stage series reverse osmosis membrane group high-salinity wastewater concentration system and concentration method thereof - Google Patents
Multi-stage series reverse osmosis membrane group high-salinity wastewater concentration system and concentration method thereof Download PDFInfo
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- CN113501567B CN113501567B CN202110823486.9A CN202110823486A CN113501567B CN 113501567 B CN113501567 B CN 113501567B CN 202110823486 A CN202110823486 A CN 202110823486A CN 113501567 B CN113501567 B CN 113501567B
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
- B01D61/026—Reverse osmosis; Hyperfiltration comprising multiple reverse osmosis steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/08—Apparatus therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/10—Accessories; Auxiliary operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/12—Controlling or regulating
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/138—Water desalination using renewable energy
- Y02A20/144—Wave energy
Abstract
The invention belongs to the field of water treatment, and relates to a high-salinity wastewater concentration system with a multistage series reverse osmosis membrane group and a concentration method thereof. The invention recovers a proper amount of water from high-concentration brine in the environment based on a membrane separation process, feeds the high-salinity feed into a reverse osmosis membrane group at high hydraulic pressure, the low-pressure purge flow of the lower brine on the osmotic side is countercurrent to the feed, the hydraulic pressure difference established by the high-pressure feed and the low-pressure purge is larger than the transmembrane osmotic pressure difference, desalinated water is generated by the reverse osmosis membrane group in multiple stages, each stage of the multi-stage series reverse osmosis module is not only used for feeding, but also used for each purge cycle, and the energy consumption of the whole high-concentration brine purification process is reduced by using a plurality of pressure exchangers.
Description
Technical Field
The invention relates to the field of water treatment, in particular to a high-salinity wastewater concentration system with multistage series reverse osmosis membrane groups and a concentration method thereof.
Technical Field
Along with the development of the industry in China, the discharge amount of industrial wastewater is increasing day by day, the major part of the wastewater is high-concentration salt-containing wastewater which has a plurality of hazards to the ecological environment, and the main treatment method in the industry is to utilize high-efficiency salt-tolerant bacteria for treatment or add water for dilution and discharge, so that a large amount of water resources are wasted, and the salt amount discharged into the environment cannot be controlled from the total amount, so that the treatment of the high-concentration salt-containing wastewater becomes a difficult problem which needs to be solved urgently in the domestic environment-friendly industry.
The demand for desalination processes of high salinity brines with total dissolved solids of 50-350g/L is also increasing in the oil, gas, electricity and industry sectors, but current brine dehydration technologies are expensive, energy intensive or limited to low water recovery. The technology of brine dehydration comprises evaporation and non-evaporation methods, the distillation method is the oldest and most common desalination method, the methods comprise multiple methods such as multiple-effect evaporation, multi-stage flash evaporation, compressed air distillation, membrane distillation and the like, in order to solve the problem of high-concentration brine wastewater treatment, a plurality of evaporation concentration crystallization devices are appeared in recent years, but the devices are basically relatively independent operation units, the energy consumption of each unit operation is relatively high, the energy reuse rate is relatively low, and the energy consumption in the evaporation process is far more than the theoretical lowest workload.
Non-evaporative membrane based technologies can reduce the energy intensity of desalination and brine dehydration processes, and reverse osmosis, forward osmosis and pressure assisted forward osmosis provide multiple ways to dehydrate brine on semi-permeable membranes, and in these membrane processes only reverse osmosis directly dehydrates brine, and forward osmosis and pressure assisted forward osmosis require a second process, most commonly a forward osmosis or heat draw solute regeneration step, to produce a pure water permeate.
Processes based on non-evaporating membranes are closer to the thermodynamic minimum for desalination separation of seawater but their effectiveness in treating high salinity brines is limited, reverse osmosis membranes are limited in water recovery for brines with TDS > 50g/L because the water pressure cannot exceed the membrane rupture pressure.
There is therefore a great need for new scalable methods of concentrating brine prior to crystallization or treatment. To this end, we have developed a process for dewatering high-strength brine using multiple series-connected reverse osmosis modules by using water pressure to transport water through a semi-permeable membrane to resist the osmotic pressure differential between the feed and permeate, while also reducing the osmotic pressure differential across the membrane by brine sweeping on the permeate side. This modification enables the delivery of water to recover water from a hydraulically driven membrane process even when the osmotic pressure of the feed exceeds the rupture pressure of the membrane.
Disclosure of Invention
The invention provides a system and a method for dehydrating high-concentration brine by utilizing a multi-stage series reverse osmosis module, aiming at the defect that the water pressure of a reverse osmosis membrane in the prior art cannot exceed the membrane rupture pressure and limit the recovery rate of water for brine with TDS more than 50g/L, wherein the permeate pressure difference across the membrane is reduced by sweeping brine on the permeate side, and the water is recovered from a hydraulic drive membrane process.
In order to achieve the purpose, the invention provides the following technical scheme: a multi-stage series reverse osmosis membrane module high salinity wastewater concentration system that purges brine flow at low salinity on the permeate side in countercurrent with feed to achieve low energy wastewater purification.
Further, the system comprises: the system comprises a 1 st, 2 nd and 3 rd-to-be-.. N-level reverse osmosis module, a high-pressure pump, an external discharge pipe, a pressure exchanger, a 1 st, 2 nd and 3 rd-to-be-N-level feeding pipe, a purging circulation feeding pipe and a product water discharge pipe; the 1 st, 2 nd and 3 rd grade reverse osmosis membrane groups are provided with a high-pressure side and a low-pressure side respectively; the 1 st, 2 nd and 3 rd-grade feed pipes correspond to the 1 st, 2 nd and 3 rd-grade reverse osmosis modules one by one;
the 1 st-stage feed pipe is connected with the high-pressure side of the 1 st-stage reverse osmosis module, the 1 st-stage feed pipe section is provided with a high-pressure pump, the high-pressure side of the 1 st-stage reverse osmosis module discharges concentrated waste liquid through an external discharge pipe, and the low-pressure side of the 1 st-stage reverse osmosis module is connected with the high-pressure side of the 2 nd-stage reverse osmosis membrane module through a 2 nd-stage feed pipe; the high-pressure side of the 2 nd-stage reverse osmosis membrane module is connected with the low-pressure side of the 1 st-stage reverse osmosis module through a purging circulation feeding pipe; a pressure exchanger is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe; the low-pressure side of the 2 nd-stage reverse osmosis module is connected with the high-pressure side of the 3 rd-stage reverse osmosis membrane module through a 3 rd-stage material feeding pipe; the high-pressure side of the 3 rd-level reverse osmosis membrane module is connected with the low-pressure side of the 2 nd-level reverse osmosis module through a sweeping circulating feeding pipe; a pressure exchanger is arranged between the 3 rd-grade feeding pipe and the blowing circulation feeding pipe; 8230, the low-pressure side of the N-1 level reverse osmosis module is connected with the high-pressure side of the N level reverse osmosis membrane module through an Nth progressive material feeding pipe; the high-pressure side of the Nth-stage reverse osmosis membrane module is connected with the low-pressure side of the N-1 th-stage reverse osmosis module through a sweeping circulating feed pipe; a pressure exchanger is arranged between the Nth progressive material pipe and the blowing circulation material pipe; and the low-pressure side of the Nth-stage reverse osmosis membrane group is connected with a product water discharge pipe.
Furthermore, in the system, the reverse osmosis membrane in the reverse osmosis module of the 1 st, 2 nd, 3 rd stage (8230) (\8230); the reverse osmosis module of the N-1 st stage is a flat membrane with countercurrent.
Further, the permeable membrane of the N-stage reverse osmosis module in the system is a conventional reverse osmosis membrane.
Furthermore, the backflow matter which flows back to the low-pressure side of the previous stage reverse osmosis module from the high-pressure side of the next stage reverse osmosis membrane module in the reverse osmosis module in the system through the purging circulation feeding pipe is part of the concentrated flow of the high-pressure side of the next stage reverse osmosis membrane module.
Furthermore, the hydraulic pressure difference established between the high-pressure side feed stream and the low-pressure purging side of each reverse osmosis module in the system is larger than the transmembrane osmotic pressure difference, and the backflow part of the high-pressure side concentrated brine purging can reduce the osmotic pressure difference between two sides of a single osmotic membrane module.
The invention also provides a method for concentrating high-salinity wastewater of a multistage series reverse osmosis membrane module, which comprises the steps that raw liquid to be purified passes through a purifying device formed by connecting the 1 st, 2, 3. The N-stage reverse osmosis modules in series, the raw liquid to be purified passes through a 1 st stage feed pipe of the evolution device, is pressurized by a high-pressure pump and then is connected to the high-pressure side of the 1 st stage reverse osmosis module, concentrated waste liquid is discharged from the high-pressure side of the 1 st stage reverse osmosis module by an external discharge pipe, and penetrating fluid generated at the low-pressure side of the 1 st stage reverse osmosis module flows into the high-pressure side of the 2 nd stage reverse osmosis membrane module by a 2 nd stage feed pipe to be used as feed; the concentrated solution on the high-pressure side of the second-stage reverse osmosis membrane module circulates back to the low-pressure side of the first-stage reverse osmosis module through the purging circulation feeding pipe to be used as supplementary feeding material; a pressure exchanger is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe; penetrating fluid generated at the low-pressure side of the 2 nd-stage reverse osmosis module flows into the high-pressure side of the 3 rd-stage reverse osmosis membrane group through the 3 rd-stage feed pipe to be used as feed; the concentrated solution on the high-pressure side of the 3 rd-stage reverse osmosis membrane module is circulated back to the low-pressure side of the 2 nd-stage reverse osmosis module through a sweeping circulating feed pipe to be used as a supplementary feed; a pressure exchanger is arranged between the 3 rd progressive feed pipe and the blowing circulation feed pipe; 8230the N reverse osmosis modules circulate in the same way; and penetrating fluid generated at the low-pressure side of the Nth-stage reverse osmosis membrane group is product water and is discharged through a product water discharge pipe.
In the method, a flat membrane with countercurrent is adopted as a permeable membrane in a reverse osmosis module of the No. 1, 2, 3, 8230, 8230and the N-1 level; and the permeable membrane of the Nth-stage reverse osmosis module in the purification device is a conventional reverse osmosis membrane.
Further, the pressure applied by a high-pressure pump on the No. 1, 2 and 3 No. N grade feed pipe is 50-70bar.
Further, the water recovery rate of the 1 st, 2 nd, 3 rd grade N reverse osmosis module is 30% -60%.
The scheme of the invention has the beneficial effects that:
the invention recovers a proper amount of water from high concentration brine in the environment based on a membrane separation process, feeds high salinity feed into a reverse osmosis membrane group at high hydraulic pressure, the low pressure purge flow of the lower brine at the permeation side is in counter flow with the feed, the hydraulic pressure difference established by the high pressure feed and the low pressure purge is larger than the osmotic pressure difference across the membrane, and desalinated water is produced by the reverse osmosis membrane group in multiple stages.
The pressure exchanger transfers energy from the high-pressure waste stream to the low-pressure feeding, and then the high-pressure pump pressurizes to the set pressure, so that the energy is saved more directly from zero pressurization, each grade of the multi-grade series reverse osmosis module is used for not only feeding, but also each purging cycle, and the energy consumption of the whole high-concentration salt water purification process is reduced by using the plurality of pressure exchangers.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, the drawings in the description are only one embodiment of the present invention, and it is obvious for those skilled in the art that other drawings may be obtained without creative efforts.
FIG. 1 is a schematic diagram of a multi-stage series reverse osmosis module according to the present invention;
wherein, 1, a reverse osmosis module; 2. a high pressure pump; 3. an outer row of tubes; 4. a pressure exchanger; 5. a feeding pipe; 6. purging a circulating feed pipe; 7. a product water discharge pipe; 8. a high pressure side; 9. the low pressure side.
Detailed Description
In order to make the technical solutions in the embodiments of the present application better understood, the following description clearly and completely describes the technical solutions in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art without making creative efforts based on the embodiments in the present application shall fall within the protection scope of the present application.
The invention provides the following technical scheme: a multi-stage series reverse osmosis membrane module high salinity wastewater concentration system that purges brine flow at low salinity on the permeate side in countercurrent with feed to achieve low energy wastewater purification.
As shown in fig. 1, the system includes: the system comprises a 1 st, 2 nd and 3 rd-to-be-.. An N-stage reverse osmosis module 1, a high-pressure pump 2, an outer discharge pipe 3, a pressure exchanger 4, a 1 st, 2 nd and 3 rd-to-be-An N-stage feeding pipe 5, a purging circulation feeding pipe 6 and a product water discharge pipe 7; the 1 st, 2 nd and 3 rd grade N reverse osmosis membrane groups 1 are provided with a high pressure side 8 and a low pressure side 9; the 1 st, 2 nd and 3 rd-grade feed pipes 5 correspond to the 1 st, 2 nd and 3 rd-grade reverse osmosis modules 1 one by one;
the 1 st-stage feeding pipe is connected with the high-pressure side 8 of the 1 st-stage reverse osmosis module, the 1 st-stage feeding pipe section is provided with a high-pressure pump 2, the high-pressure side 8 of the 1 st-stage reverse osmosis module discharges concentrated waste liquid through an external discharge pipe 3, and the low-pressure side 9 of the 1 st-stage reverse osmosis module is connected with the high-pressure side 8 of the 2 nd-stage reverse osmosis membrane group through the 2 nd-stage feeding pipe; the high-pressure side 8 of the second-stage reverse osmosis membrane module is connected with the low-pressure side 9 of the first-stage reverse osmosis module through a sweeping circulating feed pipe; a pressure exchanger 4 is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe 6; the low-pressure side 9 of the 2 nd-stage reverse osmosis module is connected with the high-pressure side 8 of the 3 rd-stage reverse osmosis membrane module through a 3 rd-stage feeding pipe; the high-pressure side 8 of the 3 rd stage reverse osmosis membrane module is connected with the low-pressure side 9 of the 2 nd stage reverse osmosis module through the purging circulation feeding pipe 6; a pressure exchanger 4 is arranged between the 3 rd stage feeding pipe and the blowing circulation feeding pipe 6; 823080, and the low-pressure side 9 of the N-1 level reverse osmosis module is connected with the high-pressure side 8 of the N level reverse osmosis membrane module through an N level feeding pipe; the high-pressure side 8 of the Nth-stage reverse osmosis membrane module is connected with the low-pressure side 9 of the N-1 th-stage reverse osmosis module through a sweeping circulating feed pipe 6; a pressure exchanger 4 is arranged between the Nth-stage feeding pipe and the blowing circulation feeding pipe 6; the low-pressure side 9 of the Nth-stage reverse osmosis membrane module is connected with a product water discharge pipe 7, and the product water discharged from the product water discharge pipe 7 is low-concentration product water obtained by the treatment of the multistage series reverse osmosis membrane modules.
The reverse osmosis membrane in the 1 st, 2 nd, 3 rd grade 8230, N-1 grade reverse osmosis module in the system is a flat plate membrane with countercurrent, and the reverse osmosis membrane in the N grade reverse osmosis module in the system is a conventional reverse osmosis membrane.
In the system, a backflow matter flowing back to the low-pressure side of the previous reverse osmosis module from the high-pressure side of the next reverse osmosis module through the sweeping circulating feed pipe is part of the high-pressure side concentrated flow of the next reverse osmosis module; the hydraulic pressure difference established by the high-pressure side inflow and low-pressure purging sides of all stages of reverse osmosis modules in the system is larger than the transmembrane osmotic pressure difference, and part of the high-pressure side concentrated saline water in backflow purging can reduce the osmotic pressure difference on two sides of a single osmotic membrane module. The purging concentration of each reverse osmosis membrane group can be adjusted to obtain the same permeation amount as that of the first-stage membrane group by controlling the inlet pressure and the purging flow to be constant, and the purging concentration of the last reverse osmosis membrane group is close to zero, so that the product water permeation can be completed by adopting the conventional reverse osmosis membrane.
Taking a four-stage series reverse osmosis membrane group as an example, the concentration of a first-stage feeding material is 55g/L, a high-pressure pump on a first-stage feeding pipe is pressurized to 65bar, and after the first-stage feeding material is treated by the first-stage reverse osmosis membrane group with the osmotic pressure of 25bar, the concentration of a first-stage sweeping circulation feeding pipe and a concentrated solution discharged by an external discharge pipe is 110 g/L; the concentration of the second-stage feeding is reduced to 40g/L, the high-pressure pump on the second-stage feeding pipe is pressurized to 65bar again, the second-stage blowing circulation feeding pipe is treated by a second reverse osmosis membrane group with the osmotic pressure of 25bar, the reflux concentration of the second-stage blowing circulation feeding pipe is 80g/L, the concentration of the third-stage feeding is reduced to 25g/L, the high-pressure pump on the third-stage feeding pipe is pressurized to 65bar again, the third-stage blowing circulation feeding pipe is treated by a third reverse osmosis membrane group with the osmotic pressure of 25bar, the reflux concentration of the third-stage blowing circulation feeding pipe is 50g/L, the concentration of the fourth-stage feeding is reduced to 10g/L, the high-pressure pump on the fourth-stage feeding pipe is pressurized to 65bar again, the fourth-stage blowing circulation feeding pipe is treated by a fourth-stage reverse osmosis membrane group with the osmotic pressure of 8bar, the reflux concentration of the fourth-stage blowing circulation feeding pipe is 20g/L, the product water with the concentration of 0.1g/L is discharged from the final product water discharge pipe, and the water recovery rate reaches 50%.
The invention also provides a method for concentrating high-salinity wastewater of a multistage series reverse osmosis membrane module, which comprises the steps that raw liquid to be purified passes through a purifying device formed by connecting the 1 st, 2, 3. The N-stage reverse osmosis modules in series, the raw liquid to be purified passes through a 1 st stage feed pipe of the evolution device, is pressurized by a high-pressure pump and then is connected to the high-pressure side of the 1 st stage reverse osmosis module, concentrated waste liquid is discharged from the high-pressure side of the 1 st stage reverse osmosis module by an external discharge pipe, and penetrating fluid generated at the low-pressure side of the 1 st stage reverse osmosis module flows into the high-pressure side of the 2 nd stage reverse osmosis membrane module by a 2 nd stage feed pipe to be used as feed; the concentrated solution on the high-pressure side of the second-stage reverse osmosis membrane module circulates back to the low-pressure side of the first-stage reverse osmosis module through the purging circulation feeding pipe to be used as supplementary feeding material; a pressure exchanger is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe; penetrating fluid generated at the low-pressure side of the 2 nd-stage reverse osmosis module flows into the high-pressure side of the 3 rd-stage reverse osmosis membrane group through the 3 rd-stage feed pipe to be used as feed; the concentrated solution on the high-pressure side of the 3 rd-stage reverse osmosis membrane module is circulated back to the low-pressure side of the 2 nd-stage reverse osmosis module through a sweeping circulating feeding pipe to be used as supplementary feeding material; a pressure exchanger is arranged between the 3 rd progressive feed pipe and the blowing circulation feed pipe; 8230, N reverse osmosis modules circulate in this way; and penetrating fluid generated at the low-pressure side of the Nth-stage reverse osmosis membrane group is product water and is discharged through a product water discharge pipe.
Wherein, in the method, the permeable membrane in the reverse osmosis module of the 1 st, 2 nd, 3 rd grade (8230) \ 8230, N-1 grade (the reverse osmosis module) adopts a flat membrane with counter current; the permeable membrane of the Nth-level reverse osmosis module in the purification device adopts a conventional reverse osmosis membrane; applying pressure of a high-pressure pump on the No. 1, 2 and 3 No. N grading feed pipe to 50-70bar; the water recovery rate of the 1 st, 2 nd and 3 rd grade N reverse osmosis module is 30-60%.
The method is characterized in that the diluted purging concentration is high, the target recovery rate cannot be achieved through reverse osmosis membranes, the diluted purging substance is pressurized and sent to a second-stage reverse osmosis membrane group, the diluted purging substance concentration is lower than the original feeding concentration, the equivalent permeate volume can be achieved through the lower purging substance concentration, the diluted feeding material is re-concentrated by the second-stage reverse osmosis membrane group and flows back to the previous-stage reverse osmosis membrane through the purging flow, the low-pressure side concentration of the previous-stage reverse osmosis membrane group is reduced, the low-pressure percolate of the second-stage reverse osmosis membrane group enters the high-pressure side of the next-stage reverse osmosis membrane group to serve as the feeding material, therefore, each reverse osmosis membrane group can achieve the equivalent permeability, the multiple stages of reverse osmosis membranes are continuously and circularly purged in series, the scanning concentration is continuously reduced until the scanning concentration of the conventional reverse osmosis membrane is low enough, and finally the permeate produced on the low-pressure side of the Nth reverse osmosis membrane group is the product water and is discharged through a product water discharge pipe.
The test shows that:
the purification process of the multistage reverse osmosis membrane group can improve the water recovery rate: the feed pressure was set to 65bar with a recovery of 54% for a sweep with total dissolved solids TDS of 35g/L and zero for a total dissolved solids TDS of 55g/L and 50% for a sweep with total dissolved solids TDS of 75g/L, which sharply decreased to 4% with increasing feed concentration.
For a given feed concentration, the use of a brine reflux purge can improve the recovery of high concentration brine: the highest TDS of total dissolved solids of the fed materials can reach 145g/L, the highest TDS of the recycled high-concentration brine can reach 200g/L, and the recovery rate is more than 30 percent.
As the concentration of the cleaning is gradually increased, the recovery rate of fresh water and the required energy consumption of the reverse osmosis membrane group set number are increased: when the first scan total dissolved solids TDS ranged from 100-225g/L, the recovery of produced water increased from 17% to 42% per square meter, the number of modules increased from 3 to 7 modules, and the energy consumption increased from 5.7kWh to 14kWh.
Increasing membrane area helps to increase fresh water recovery: however, increasing membrane area, while increasing fresh water recovery, also increases membrane pressure drop, salinity permeability, and capital and operating costs. We set the fresh water recovery rate to 35% -40%, and adjust the concentration of the first reverse osmosis module feed to make each variable membrane surfaceThe recovery rate is kept constant, and the membrane area is from 9m 3 Increased to 13m 3 The reduction in total dissolved solids TDS in the first stage was from 185 to 165g/L and 215 to 190g/L, the number of membrane groups was from 5 to 4 and from 7 to 5, and the recovery was 35% and 40%, respectively.
In addition to feed and purge concentrations, feed pressure, recovery, number of modules, energy consumption and module size, the performance of the membranes of reverse osmosis membrane modules also has an impact, and ideal membranes need to have high membrane rupture pressures and low structural parameters.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (9)
1. A multi-stage series reverse osmosis membrane group high-salinity wastewater concentration system is characterized in that low-energy-consumption wastewater purification is realized by sweeping brine flow with low salinity and feeding in a countercurrent manner on a permeation side; the system comprises: the system comprises a 1 st, 2 nd and 3 rd-level reverse osmosis module, a high-pressure pump, an external discharge pipe, a pressure exchanger, a 1 st, 2 nd and 3 rd-level feed pipe, a purging circulation feed pipe and a product water discharge pipe; the 1 st, 2 nd and 3 rd grade reverse osmosis membrane groups are provided with a high-pressure side and a low-pressure side respectively; the 1 st, 2 nd and 3 rd-grade feed pipes correspond to the 1 st, 2 nd and 3 rd-grade reverse osmosis modules one by one; the 1 st-stage feed pipe is connected with the high-pressure side of the 1 st-stage reverse osmosis module, the 1 st-stage feed pipe section is provided with a high-pressure pump, the high-pressure side of the 1 st-stage reverse osmosis module discharges concentrated waste liquid through an external discharge pipe, and the low-pressure side of the 1 st-stage reverse osmosis module is connected with the high-pressure side of the 2 nd-stage reverse osmosis membrane group through the 2 nd-stage feed pipe; the high-pressure side of the second-stage reverse osmosis membrane module is connected with the low-pressure side of the first-stage reverse osmosis module through a sweeping circulating feed pipe; a pressure exchanger is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe; the low-pressure side of the 2 nd-stage reverse osmosis module is connected with the high-pressure side of the 3 rd-stage reverse osmosis membrane module through a 3 rd-stage material feeding pipe; the high-pressure side of the 3 rd-stage reverse osmosis membrane module is connected with the low-pressure side of the 2 nd-stage reverse osmosis module through a purging circulation feeding pipe; a pressure exchanger is arranged between the 3 rd stage feeding pipe and the blowing circulation feeding pipe; the low-pressure side of the N-1 level reverse osmosis module is connected with the high-pressure side of the N level reverse osmosis membrane group through an Nth level feeding pipe; the high-pressure side of the Nth-stage reverse osmosis membrane module is connected with the low-pressure side of the N-1 th-stage reverse osmosis module through a sweeping circulating feed pipe; a pressure exchanger is arranged between the Nth progressive material pipe and the blowing circulation material pipe; the low-pressure side of the Nth-stage reverse osmosis membrane group is connected with a product water discharge pipe.
2. The system for concentrating high-salinity wastewater by multistage series reverse osmosis membrane modules according to claim 1, characterized in that: the reverse osmosis module of the No. 1, 2, 3, 8230A and N-1 level in the system has a flat membrane with countercurrent.
3. The system for concentrating high-salinity wastewater by multistage series reverse osmosis membrane modules according to claim 1, characterized in that: and the permeable membrane of the Nth-level reverse osmosis module in the system is a conventional reverse osmosis membrane.
4. The system of claim 1 for concentrating high salinity wastewater with multiple stages of series reverse osmosis membrane modules, wherein: in the system, a backflow matter flowing back to the low-pressure side of the previous reverse osmosis module through the sweeping circulating feeding pipe at the high-pressure side of the next reverse osmosis module in the reverse osmosis module is part of the concentrated flow at the high-pressure side of the next reverse osmosis module.
5. The system for concentrating high-salinity wastewater by multistage series reverse osmosis membrane modules according to claim 1, characterized in that: in the system, the hydraulic pressure difference established by the high-pressure side inflow stream and the low-pressure purging side of each reverse osmosis module is larger than the transmembrane osmotic pressure difference, and part of the high-pressure side concentrated saline water in backflow purging can reduce the osmotic pressure difference on two sides of a single osmotic membrane module.
6. A method for concentrating high-salinity wastewater with a multi-stage series reverse osmosis membrane group is characterized by comprising the following steps: the method comprises the following steps that raw liquid to be purified passes through a purification device formed by connecting N-stage reverse osmosis modules in series through 1 st, 2 nd and 3. The raw liquid to be purified passes through a 1 st-stage feeding pipe of an evolution device and is pressurized by a high-pressure pump and then is connected to the high-pressure side of the 1 st-stage reverse osmosis module, concentrated liquid generated at the high-pressure side of the 1 st-stage reverse osmosis module is discharged from concentrated waste liquid through an external discharge pipe, and penetrating liquid generated at the low-pressure side of the 1 st-stage reverse osmosis module flows into the high-pressure side of the 2 nd-stage reverse osmosis membrane group through a 2 nd-stage feeding pipe to be used as feeding material; the concentrated solution on the high-pressure side of the second-stage reverse osmosis membrane module circulates back to the low-pressure side of the first-stage reverse osmosis module through the purging circulation feeding pipe to be used as supplementary feeding material; a pressure exchanger is arranged between the 2 nd-stage feeding pipe and the blowing circulation feeding pipe; penetrating fluid generated at the low-pressure side of the 2 nd-stage reverse osmosis module flows into the high-pressure side of the 3 rd-stage reverse osmosis membrane group through the 3 rd-stage feed pipe to be used as feed; the concentrated solution on the high-pressure side of the 3 rd-stage reverse osmosis membrane module is circulated back to the low-pressure side of the 2 nd-stage reverse osmosis module through a sweeping circulating feed pipe to be used as a supplementary feed; a pressure exchanger is arranged between the 3 rd progressive material pipe and the blowing circulation material inlet pipe; 8230the N reverse osmosis modules circulate in the same way; and penetrating fluid generated at the low-pressure side of the Nth-stage reverse osmosis membrane group is product water and is discharged through a product water discharge pipe.
7. The method for concentrating high-salinity wastewater with multiple stages of reverse osmosis membrane modules in series connection according to claim 6, characterized in that: in the method, a flat membrane with counter flow is adopted as a permeable membrane in a reverse osmosis module of the 1 st, 2 nd, 3 nd, 8230A \8230A-1 st level; and the permeable membrane of the Nth-stage reverse osmosis module in the purification device is a conventional reverse osmosis membrane.
8. The method for concentrating high-salinity wastewater with multiple stages of reverse osmosis membrane modules in series connection according to claim 6, characterized in that: the pressure applied by a high-pressure pump on the No. 1, 2 and 3.
9. The method for concentrating high-salinity wastewater with multiple stages of reverse osmosis membrane modules in series connection according to claim 6, characterized in that: the water recovery rate of the 1 st, 2 nd and 3 rd-level reverse osmosis module is 30-60%.
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