Forward osmosis membrane concentration device

Abstract

The application provides a forward osmosis membrane concentration device, which comprises a pretreatment system, a forward osmosis membrane concentration system, a draw solution recovery system and a draw solution cleaning system. The forward osmosis membrane concentration system has a water inlet, a water outlet, a liquid inlet and a liquid outlet. The water inlet is communicated with the pretreatment system, and the liquid inlet is communicated with the liquid outlet end of the draw solution recovery system. The forward osmosis membrane concentration system is used for concentrating coking wastewater and diluting the draw solution. The water outlet is used for discharging the concentrated coking wastewater. The liquid inlet end of the draw solution cleaning system is communicated with the liquid outlet. The draw solution cleaning system is used for filtering the draw solution. The liquid inlet end of the draw solution recovery system is communicated with the liquid outlet of the forward osmosis membrane concentration system and / or the liquid outlet end of the draw solution cleaning system. The draw solution recovery system is used for concentrating the diluted draw solution. The forward osmosis membrane concentration device solves the problems of large amount of concentrated solution and frequent membrane element fouling in the existing membrane concentration technology for treating coking wastewater.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and more particularly to a forward osmosis membrane concentration device. Background Technology

[0002] Coking wastewater mainly refers to the wastewater generated during coal coking, coal gas purification, chemical product recovery, and chemical product refining. Due to the influence of various factors such as the properties of raw coal, product recovery, and production processes, the composition of the wastewater is exceptionally complex. The organic matter in coking wastewater is mainly composed of phenolic compounds, accounting for more than half of the total organic matter. The remaining organic compounds are mainly heterocyclic organic compounds containing sulfur, oxygen, and nitrogen, as well as polycyclic aromatic organic compounds. Traditional processes involve pretreatment and biochemical treatment followed by direct discharge. However, because coking wastewater has poor biodegradability, oils and polycyclic aromatic hydrocarbons are difficult to biodegrade, and the biochemical system cannot degrade all toxic and harmful substances, resulting in environmental impacts from the biochemical effluent. Furthermore, with increasingly stringent environmental policies both domestically and internationally, existing coking wastewater treatment processes suffer from substandard effluent and the inability to recycle water resources.

[0003] Therefore, from the long-term perspective of industry development, advanced treatment of coking wastewater is essential. Membrane separation has advantages such as high treatment efficiency and small footprint, and has been applied to some extent in the advanced treatment of coking wastewater both domestically and internationally in recent years. Traditional membrane treatment mainly involves reverse osmosis, but reverse osmosis suffers from drawbacks such as high requirements for feed water conditions, limited concentration ratio, low recovery rate, large volume of concentrate, high chemical dosage, unstable system operation, and high cost of concentrate treatment. Furthermore, tar-like substances in coking wastewater can foul the reverse osmosis membrane system, leading to system failure. Therefore, finding a more advanced water treatment device to address these challenges and effectively reducing the amount of concentrate from subsequent treatment has become a recognized major challenge and hot topic both domestically and internationally. Summary of the Invention

[0004] The purpose of this invention is to provide a forward osmosis membrane concentration device that solves the problems of large concentrate volume and frequent membrane element fouling in the treatment of coking wastewater by existing membrane concentration technologies. It achieves extreme concentration of coking wastewater, reuses the produced water, and meets the water balance requirements of the coking industry.

[0005] To achieve the above objectives, the present invention provides a forward osmosis membrane concentration device for treating coking wastewater, comprising a pretreatment system, a forward osmosis membrane concentration system, a draw solution recovery system, and a draw solution cleaning system.

[0006] The pretreatment system is used to filter the coking wastewater;

[0007] The forward osmosis membrane concentration system has an inlet, an outlet, a liquid inlet, and a liquid outlet. The inlet is connected to the pretreatment system to receive the filtered coking wastewater. The liquid inlet is connected to the outlet of the draw liquid recovery system to receive the draw liquid. The forward osmosis membrane concentration system is used to concentrate the coking wastewater and dilute the draw liquid. The outlet is used to discharge the concentrated coking wastewater.

[0008] The inlet of the extractant cleaning system is connected to the outlet, and the extractant cleaning system is used to filter the diluted extractant.

[0009] The inlet of the draw solution recovery system is connected to the outlet and / or the outlet of the draw solution cleaning system. The draw solution recovery system is used to concentrate the diluted draw solution and deliver it to the forward osmosis membrane concentration system.

[0010] Optionally, the pretreatment system includes a water supply tank, a booster pump, and a security filter connected in sequence. The coking wastewater stored in the water supply tank is pumped into the security filter by the booster pump, and the outlet of the security filter is connected to the inlet.

[0011] Optionally, the security filter may be arranged in a single stage or multiple stages, and the filtration accuracy of the security filter may be between 5 micrometers and 100 micrometers.

[0012] Optionally, the forward osmosis membrane concentration system is composed of several forward osmosis membrane concentration subsystems connected in series.

[0013] Optionally, the forward osmosis membrane concentration subsystem includes a raw water channel, a draw liquid channel, and a forward osmosis membrane element that separates the raw water channel and the draw liquid channel. The raw water channel, draw liquid channel, and forward osmosis membrane element of two adjacent forward osmosis membrane concentration subsystems are connected accordingly. The coking wastewater enters the raw water channel through the inlet and is discharged from the outlet. The draw liquid enters the draw liquid channel through the inlet and is discharged from the outlet.

[0014] Optionally, a circulating booster pump is provided between the raw water channel of two adjacent forward osmosis membrane concentration subsystems and the draw liquid channel of two adjacent forward osmosis membrane concentration subsystems.

[0015] Optionally, the extractant recovery system includes a first booster pump and an extractant recovery membrane element. The inlet of the first booster pump is connected to the outlet and / or the outlet of the extractant cleaning system. The inlet of the extractant recovery membrane element is connected to the outlet of the first booster pump. The extractant recovery membrane element concentrates the diluted extractant through membrane separation. The extractant recovery membrane element has a clean water outlet and an extractant outlet. The clean water outlet is used to discharge clean water, and the extractant outlet is connected to the inlet.

[0016] Optionally, the extractant cleaning system includes a second booster pump and an extractant cleaning membrane element. The inlet of the second booster pump is connected to the outlet, the inlet of the extractant cleaning membrane element is connected to the outlet of the second booster pump, and the outlet of the extractant cleaning membrane element is connected to the inlet of the extractant recovery system. The extractant cleaning membrane element filters the diluted extractant using a membrane separation method.

[0017] Optionally, control valves are respectively provided between the outlet and the inlet of the extraction liquid cleaning system and the inlet of the extraction liquid recovery system to control the flow direction and flow rate of the diluted extraction liquid.

[0018] Optionally, the extracting liquid is a sodium chloride solution.

[0019] This invention provides a forward osmosis membrane concentration device, which has at least one of the following beneficial effects:

[0020] 1) By treating coking wastewater through a forward osmosis membrane concentration system, the pretreatment steps for deep treatment of coking wastewater are reduced, thereby shortening the process path;

[0021] 2) Forward osmosis has unique anti-fouling properties, and compared with traditional deep treatment processes, the system operates more stably and the membrane cleaning frequency is lower;

[0022] 3) The forward osmosis membrane concentration system has a higher concentration ratio for treating coking wastewater than traditional processes, with less concentrate volume. The concentrate can meet internal consumption needs, and the product water can be reused or discharged externally, resulting in a higher water resource reuse rate. Attached Figure Description

[0023] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:

[0024] Figure 1 This is a schematic diagram of a forward osmosis membrane concentration apparatus provided in an embodiment of the present invention;

[0025] In the attached image:

[0026] 10-Pretreatment system; 11-Feed water tank; 12-Boost pump; 13-Security filter; 20-Forward osmosis membrane concentration system; 21-Inlet; 22-Outlet; 23-Liquid inlet; 24-Liquid outlet; 30-Draw liquid recovery system; 31-First booster pump; 32-Draw liquid recovery membrane element; 40-Draw liquid cleaning system; 41-Second booster pump; 42-Draw liquid cleaning membrane element; 50-Control valve. Detailed Implementation

[0027] To make the objectives, advantages, and features of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clarify the explanation of the embodiments of this invention. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and may sometimes use different scales.

[0028] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature.

[0029] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a forward osmosis membrane concentration device provided in an embodiment of the present invention. This embodiment provides a forward osmosis membrane concentration device for treating coking wastewater, including a pretreatment system 10, a forward osmosis membrane concentration system 20, a draw solution recovery system 30, and a draw solution cleaning system 40.

[0030] The pretreatment system 10 is used to filter the coking wastewater;

[0031] The forward osmosis membrane concentration system 20 has an inlet 21, an outlet 22, a liquid inlet 23, and a liquid outlet 24. The inlet 21 is connected to the pretreatment system 10 to receive the filtered coking wastewater. The liquid inlet 23 is connected to the outlet of the draw liquid recovery system 30 to receive the draw liquid. The forward osmosis membrane concentration system 20 is used to concentrate the coking wastewater and dilute the draw liquid. The outlet 22 is used to discharge the concentrated coking wastewater.

[0032] The inlet of the extractant cleaning system 40 is connected to the outlet 24, and the extractant cleaning system 40 is used to filter the diluted extractant.

[0033] The inlet of the draw solution recovery system 30 is connected to the outlet 24 and / or the outlet of the draw solution cleaning system 40. The draw solution recovery system 30 is used to concentrate the diluted draw solution and deliver it to the forward osmosis membrane concentration system 20.

[0034] The connection between the inlet of the draw liquid recovery system 30 and the outlet 24 and / or the outlet of the draw liquid cleaning system 40 mentioned in this application can be understood as the draw liquid cleaning system 40 being selectively activated. Since the draw liquid inevitably becomes contaminated during recycling, when excessive contaminants are detected in the diluted draw liquid, the draw liquid cleaning system 40 can be activated to filter part or all of the draw liquid, intercepting contaminants and facilitating its reuse. Therefore, the draw liquid discharged from the outlet 24 has the following three destinations:

[0035] Firstly, if the inlet of the draw solution recovery system 30 is only connected to the outlet 24, the diluted draw solution discharged from the forward osmosis membrane concentration system 20 will directly enter the draw solution recovery system 30. In this case, the draw solution cleaning system 40 will not work, indicating that the contaminants in the draw solution do not meet the standards.

[0036] Secondly, the inlet of the extractant recovery system 30 is connected to both the outlet 24 and the outlet of the extractant cleaning system 40. In this case, part of the extractant enters the extractant cleaning system 40 for filtration, and the remaining part of the extractant directly enters the extractant recovery system 30.

[0037] Third, the inlet of the extractant recovery system 30 is only connected to the outlet of the extractant cleaning system 40, indicating that there are many contaminants in the extractant. All extractant discharged from the outlet 24 first enters the extractant cleaning system 40 for filtration, and then enters the extractant recovery system 30.

[0038] In this embodiment, control valves 50 are respectively provided between the liquid outlet and the liquid inlet of the liquid cleaning system and the liquid inlet of the liquid recovery system to control the flow direction and flow rate of the diluted liquid. The above three situations can be achieved by opening the control valves 50 at different positions.

[0039] Specifically, the pretreatment system 10 includes a water supply tank 11, a booster pump 12, and a security filter 13 connected in sequence. The coking wastewater stored in the water supply tank 11 is pumped into the security filter 13 by the booster pump 12, and the outlet of the security filter 13 is connected to the inlet 21.

[0040] Preferably, this application does not limit the specific structure and filtration form of the security filter 13. The security filter 13 is arranged in a single stage or multiple stages, and the filtration accuracy of the security filter 13 is between 5 micrometers and 100 micrometers.

[0041] The forward osmosis membrane concentration system 20 adopts a staged concentration process and is composed of n forward osmosis membrane concentration subsystems connected in series, where n is a positive integer ≥1. The coking wastewater is concentrated by the previous stage forward osmosis membrane concentration subsystem before entering the next stage forward osmosis membrane concentration subsystem.

[0042] In this embodiment, the forward osmosis membrane concentration subsystem includes a raw water channel, a draw liquid channel, and a forward osmosis membrane element that separates the raw water channel and the draw liquid channel. The raw water channel, draw liquid channel, and forward osmosis membrane element of two adjacent forward osmosis membrane concentration subsystems are connected to each other. The coking wastewater enters the raw water channel through the inlet 21 and is discharged from the outlet 22. The draw liquid enters the draw liquid channel through the inlet 23 and is discharged from the outlet 24.

[0043] A circulating booster pump is installed between the raw water channels of two adjacent forward osmosis membrane concentration subsystems and between the draw liquid channels of two adjacent forward osmosis membrane concentration subsystems. The coking wastewater is concentrated in the raw water channel of the preceding forward osmosis membrane concentration subsystem, then pressurized by the circulating booster pump before entering the raw water channel of the next forward osmosis membrane concentration subsystem. After being concentrated at each stage, it is discharged from the outlet 22. The draw liquid is diluted in the draw liquid channel of the preceding forward osmosis membrane concentration subsystem, then pressurized by the circulating booster pump before entering the draw liquid channel of the next forward osmosis membrane concentration subsystem. After being diluted at each stage, it is discharged from the outlet 24.

[0044] In this embodiment, the forward osmosis membrane element is a spiral wound structure, and its material is one or more of the following: cellulose acetate membrane, polyamide composite membrane, polysulfone / polyethersulfone membrane, and polyvinyl alcohol membrane.

[0045] Please continue to refer to Figure 1The draw solution recovery system 30 includes a first booster pump 31 and a draw solution recovery membrane element 32. The inlet end of the first booster pump 31 is connected to the outlet 24 and / or the outlet end of the draw solution cleaning system 40. The inlet end of the draw solution recovery membrane element 32 is connected to the outlet end of the first booster pump 31. The draw solution recovery membrane element 32 concentrates the diluted draw solution through membrane separation. The draw solution recovery membrane element 32 has a clean water outlet end and a draw solution outlet end. The clean water outlet end is used to discharge clean water. The draw solution outlet end is connected to the inlet 23, so that the concentrated draw solution can be reused in the forward osmosis membrane concentration system 20.

[0046] In this embodiment, the recovery of the extract liquid is carried out by membrane separation. Compared with thermal recovery, membrane recovery of extract liquid does not require heating equipment and has no risk of ammonia leakage, making operation and maintenance more convenient.

[0047] In this embodiment, the extractant recovery membrane element 32 has a spiral wound structure and is made of one or more of the following materials: cellulose acetate membrane, polyamide composite membrane, polysulfone / polyethersulfone membrane, and polyvinyl alcohol membrane.

[0048] Please continue to refer to Figure 1 The extractant cleaning system 40 includes a second booster pump 41 and an extractant cleaning membrane element 42. The inlet of the second booster pump 41 is connected to the outlet 24, the inlet of the extractant cleaning membrane element 42 is connected to the outlet of the second booster pump 41, and the outlet of the extractant cleaning membrane element 42 is connected to the inlet of the extractant recovery system 30. The extractant cleaning membrane element 42 filters the diluted extractant through membrane separation.

[0049] In this embodiment, the cleaning method for the draw solution is membrane separation. The draw solution inevitably becomes contaminated during recycling; the draw solution cleaning membrane element 42 filters part or all of the draw solution to intercept contaminants.

[0050] In this embodiment, the absorbent cleaning membrane element 42 has a spiral wound structure and is made of one or more of the following materials: cellulose acetate membrane, polyamide composite membrane, polysulfone / polyethersulfone membrane, and polyvinyl alcohol membrane.

[0051] In this embodiment, the draw solution is a sodium chloride solution. Using sodium chloride solution as the draw solution has the advantages of high osmotic pressure, non-toxicity and no side effects, and ease of preparation and recovery.

[0052] Combination Figure 1 The present application will be further described below through a specific embodiment.

[0053] The coking wastewater from a steel plant, after undergoing oil removal, primary aerobic treatment, primary facultative anaerobic treatment, secondary aerobic treatment, secondary facultative anaerobic treatment, and coagulation sedimentation, has the following water quality indicators: pH 7-8, COD 100-200 mg / L, TDS ≤ 15000 mg / L, suspended solids 20-50 mg / L, calcium 40-150 mg / L, and sulfate 1500-2500 mg / L.

[0054] The coking wastewater is adjusted to a pH of 5-7 in feed tank 11 and then pumped into security filter 13 via booster pump 12. The effluent from security filter 13 is then concentrated stage-by-stage through forward osmosis membrane concentration system 20, with a recovery rate of 85-90%. The water quality indicators of the coking wastewater concentrate are: COD 600-1200 mg / L, TDS 100000-140000 mg / L, suspended solids 50-150 mg / L, calcium 200-500 mg / L, and sulfate 12000-20000 mg / L. The coking wastewater concentrate can be treated and used in on-site slag quenching and other applications, achieving zero discharge of the concentrate.

[0055] In the draw solution channel of the forward osmosis membrane concentration system 20, the concentrated draw solution is a sodium chloride solution of 120,000–150,000 mg / L. This solution is gradually diluted through the forward osmosis membrane concentration system 20. The diluted draw solution is then reconcentrated to 120,000–150,000 mg / L through the draw solution recovery system 30. The concentrated draw solution is then returned to the forward osmosis membrane concentration system 20 for reuse. Clean permeate is obtained in this process. The permeate's water quality indicators are: COD 3–15 mg / L, TDS ≤ 50 mg / L, and no detectable harmful substances such as volatile phenols, cyanides, benzene, or sulfides. This permeate can be directly reused as fresh industrial water in steel or coking processes, significantly reducing the amount of downstream coking wastewater requiring treatment and conserving water resources.

[0056] Because coking wastewater contains organic matter, calcium ions, magnesium ions, fluoride ions, sulfate ions, and other substances that easily foul membranes, the draw solution inevitably becomes contaminated during recycling. Therefore, the diluted draw solution is partially or completely cleaned through the draw solution cleaning system 40 to remove impurities such as organic matter, calcium ions, magnesium ions, fluoride ions, and sulfate ions. The cleaned diluted draw solution then enters the draw solution recovery system 30 for concentration and reuse.

[0057] In summary, this invention provides a forward osmosis membrane concentration device, including a pretreatment system, a forward osmosis membrane concentration system, a draw solution recovery system, and a draw solution cleaning system. Coking wastewater, after being treated by the pretreatment system, enters the forward osmosis membrane concentration system. The coking wastewater is concentrated by the forward osmosis membrane concentration system, and the concentrated coking wastewater is discharged as a concentrate. The draw solution recovery system and the forward osmosis membrane concentration system form a draw solution circulation loop. The draw solution cleaning system is used to clean part or all of the diluted draw solution discharged from the forward osmosis membrane concentration system. The cleaned draw solution is then transported to the draw solution recovery system. The forward osmosis membrane concentration device provided by this invention solves the problems of large concentrate volume and frequent membrane element fouling in existing membrane concentration technologies for treating coking wastewater. It achieves extreme concentration of coking wastewater, reuse of treated water, and meets the water balance requirements of the coking industry. It has advantages such as simple pretreatment, shortened process chain, high concentration ratio, stable operation, and low membrane system cleaning frequency.

[0058] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A forward osmosis membrane concentration device for treating coking wastewater, characterized in that, It includes a pretreatment system, a forward osmosis membrane concentration system, a draw solution recovery system, and a draw solution cleaning system; The pretreatment system is used to filter the coking wastewater; The forward osmosis membrane concentration system has an inlet, an outlet, a liquid inlet, and a liquid outlet. The inlet is connected to the pretreatment system to receive the filtered coking wastewater. The liquid inlet is connected to the outlet of the draw liquid recovery system to receive the draw liquid. The forward osmosis membrane concentration system is used to concentrate the coking wastewater and dilute the draw liquid. The outlet is used to discharge the concentrated coking wastewater. The inlet of the extractant cleaning system is connected to the outlet, and the extractant cleaning system is used to filter the diluted extractant. The inlet of the draw solution recovery system is connected to the outlet and / or the outlet of the draw solution cleaning system. The draw solution recovery system is used to concentrate the diluted draw solution and deliver it to the forward osmosis membrane concentration system.

2. The forward osmosis membrane concentration device of claim 1, wherein, The pretreatment system includes a water supply tank, a booster pump, and a security filter connected in sequence. The coking wastewater stored in the water supply tank is pumped into the security filter by the booster pump, and the outlet of the security filter is connected to the inlet.

3. The forward osmosis membrane concentration device of claim 2, wherein, The security filter is arranged in a single or multi-stage configuration, and its filtration accuracy is between 5 micrometers and 100 micrometers.

4. The forward osmosis membrane concentration device of claim 1, wherein, The forward osmosis membrane concentration system consists of several forward osmosis membrane concentration subsystems connected in series.

5. The forward osmosis membrane concentration device of claim 4, wherein, The forward osmosis membrane concentration subsystem includes a raw water channel, a draw liquid channel, and a forward osmosis membrane element that separates the raw water channel and the draw liquid channel. The raw water channel, draw liquid channel, and forward osmosis membrane element of two adjacent forward osmosis membrane concentration subsystems are connected to each other. The coking wastewater enters the raw water channel through the inlet and is discharged from the outlet. The draw liquid enters the draw liquid channel through the inlet and is discharged from the outlet.

6. The forward osmosis membrane concentration device of claim 5, wherein, A circulating booster pump is installed between the raw water channel of two adjacent forward osmosis membrane concentration subsystems and the draw liquid channel of two adjacent forward osmosis membrane concentration subsystems.

7. The forward osmosis membrane concentration apparatus as described in claim 1, characterized in that, The extractant recovery system includes a first booster pump and an extractant recovery membrane element. The inlet of the first booster pump is connected to the outlet and / or the outlet of the extractant cleaning system. The inlet of the extractant recovery membrane element is connected to the outlet of the first booster pump. The extractant recovery membrane element concentrates the diluted extractant through membrane separation. The extractant recovery membrane element has a clean water outlet and an extractant outlet. The clean water outlet is used to discharge clean water, and the extractant outlet is connected to the inlet.

8. The forward osmosis membrane concentration device of claim 1, wherein, The extractant cleaning system includes a second booster pump and an extractant cleaning membrane element. The inlet of the second booster pump is connected to the outlet, the inlet of the extractant cleaning membrane element is connected to the outlet of the second booster pump, and the outlet of the extractant cleaning membrane element is connected to the inlet of the extractant recovery system. The extractant cleaning membrane element filters the diluted extractant through membrane separation.

9. The forward osmosis membrane concentration device of claim 1, wherein, Control valves are respectively installed between the outlet and the inlet of the extraction liquid cleaning system and the inlet of the extraction liquid recovery system to control the flow direction and flow rate of the diluted extraction liquid.

10. The forward osmosis membrane concentration device of claim 1, wherein, The extracting solution is a sodium chloride solution.

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