A treatment system and method for high-salt and high-pollution wastewater from coal chemical industry

Abstract

The present invention discloses a treatment system and method for high-salt and high-pollutant wastewater from coal chemical industry, including a pretreatment system, a nanofiltration system, a two-stage flat disc DTRO reverse osmosis system and a high-efficiency MVR evaporation system; the pretreatment system is used for softening and filtering high-salt and high-pollutant wastewater from coal chemical industry; the nanofiltration system is used for separating divalent ions from high-salt and high-pollutant wastewater from coal chemical industry; the two-stage flat disc DTRO reverse osmosis system is used for desalting high-salt and high-pollutant wastewater from coal chemical industry; the high-efficiency MVR evaporation system is used for evaporating and crystallizing concentrated water from the two-stage flat disc DTRO reverse osmosis system. The treatment system and method for high-salt and high-pollutant wastewater from coal chemical industry can completely separate and recycle high-salt and high-pollutant wastewater from coal chemical industry to achieve the purpose of zero discharge.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a system and method for treating high-salt and highly polluted wastewater from coal chemical industry. Background Art

[0002] Coal chemical wastewater is a kind of wastewater that is very difficult to treat in industrial wastewater because of its complex composition. It not only contains difficult-to-degrade organic matter, but also has many types and high concentrations of heavy metals and other elements. In recent years, with the development of the membrane industry, there have been many engineering examples for treating wastewater to meet the discharge standards or even reuse it in industrial circulating water systems. However, such a process is often completed by treating the biochemical effluent through reverse osmosis. One problem that cannot be avoided is: the concentrated water of the reverse osmosis process is generally tens to hundreds of tons of water per hour. How to deal with it? This is the most troublesome link for the entire coking industry today. Some companies are simmering slag, and some companies are secretly discharging, but they cannot fundamentally solve the problem. Disposing these waste liquids as liquid hazardous waste to special hazardous waste companies will cost at least several thousand yuan or even tens of thousands per ton of water, and companies cannot afford such high and large expenses. This is also the key point of the solution proposed by the present invention, a practical solution to effectively carry out zero discharge of coal chemical wastewater reverse osmosis concentrated water to solve the historical problems of the coking industry. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to propose a treatment system and method for high-salt and high-polluted wastewater from coal chemical industry. The treatment system and method for high-salt and high-polluted wastewater from coal chemical industry can completely separate the salt and resource the high-salt and high-polluted wastewater from coal chemical industry to achieve the goal of zero emission.

[0004] Based on the above purpose, the present invention provides a treatment system for high-salt and highly polluted coal chemical wastewater, including a pretreatment system, a nanofiltration system, a one-stage flat disc DTRO reverse osmosis system, a two-stage flat disc DTRO reverse osmosis system and a high-efficiency MVR evaporation system; wherein:

[0005] Pretreatment system, used for softening and filtering high-salt and high-pollution wastewater from coal chemical industry to remove hardness and particulate matter from high-salt and high-pollution wastewater from coal chemical industry;

[0006] The nanofiltration system is connected to the pretreatment system and is used to separate divalent ions from high-salt and highly polluted wastewater from coal chemical industry;

[0007] A flat disc DTRO reverse osmosis system is connected to the nanofiltration system to perform preliminary desalination on the permeate water of the nanofiltration system;

[0008] The two-stage flat disc DTRO reverse osmosis system is connected to the one-stage flat disc DTRO reverse osmosis system and is used to further desalinate the concentrated water of the one-stage flat disc DTRO reverse osmosis system;

[0009] The high-efficiency MVR evaporation system is connected to the two-stage flat disc DTRO reverse osmosis system and is used to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals.

[0010] In some embodiments of the present invention, the above-mentioned coal chemical high-salt and high-pollution wastewater treatment system also includes a low-temperature crystallization system, which is connected to the nanofiltration system and is used to low-temperature crystallize the concentrated water of the nanofiltration system to obtain divalent salt crystals.

[0011] In some embodiments of the present invention, the pretreatment system includes a first dosing device, a high-efficiency precipitator, a raw water storage tank, a nanofiltration lift pump and a first security filter; wherein:

[0012] The first dosing device is used to add a hardness reducing agent;

[0013] A high-efficiency precipitator is connected to the first dosing device and is used to mix the hardness reducing agent with the high-salt and high-pollutant wastewater of the coal chemical industry for softening treatment to remove the hardness in the high-salt and high-pollutant wastewater of the coal chemical industry;

[0014] The raw water storage tank is connected to the high-efficiency precipitator and is used to store high-salt and highly polluted wastewater from coal chemical industry;

[0015] The nanofiltration lifting pump is connected to the raw water storage tank and is used to lift the high-salt and highly polluted wastewater from the coal chemical industry in the raw water storage tank to a certain height;

[0016] The first safety filter is connected to the nanofiltration lift pump and is used for filtering and treating the high-salt and high-pollutant wastewater of the coal chemical industry to remove particulate matter in the high-salt and high-pollutant wastewater of the coal chemical industry.

[0017] In some embodiments of the present invention, the one-stage flat disc DTRO reverse osmosis system comprises a reverse osmosis raw water tank, a reverse osmosis raw water pump, a second safety filter and a one-stage flat disc DTRO reverse osmosis device; wherein:

[0018] Reverse osmosis raw water tank, used to store the permeate water of the nanofiltration system;

[0019] A reverse osmosis raw water pump is connected to the reverse osmosis raw water tank and is used to pump the permeated water stored in the reverse osmosis raw water tank into the second security filter;

[0020] The second security filter is connected to the reverse osmosis raw water pump and is used to remove particles in the permeated water;

[0021] A flat disc DTRO reverse osmosis device is connected to the second security filter for preliminary desalination of the permeated water;

[0022] The two-stage flat disc DTRO reverse osmosis system includes a two-stage flat disc DTRO reverse osmosis device, which is used to further desalinate concentrated water from a one-stage flat disc DTRO reverse osmosis device.

[0023] In some embodiments of the present invention, the one-stage flat disc DTRO reverse osmosis device and the two-stage flat disc DTRO reverse osmosis device both include a disc-type membrane assembly, and the disc-type membrane assembly includes a first reverse osmosis membrane, which is composed of a reverse osmosis membrane A and a reverse osmosis membrane B.

[0024] In some embodiments of the present invention, multiple partitions are arranged along the length direction of the membrane column, and a first reverse osmosis membrane is arranged in at least one of the partitions, and a second reverse osmosis membrane or a third reverse osmosis membrane is arranged in the remaining partitions; the second reverse osmosis membrane is composed of two reverse osmosis membranes A, and the third reverse osmosis membrane is composed of two reverse osmosis membranes B.

[0025] In some embodiments of the present invention, the above-mentioned coal chemical high-salt and high-pollution wastewater treatment system further includes a monitoring system and a defluorination system; wherein:

[0026] A monitoring system for real-time monitoring of the water quality and quantity of the inlet water, produced water and concentrated water of the first-stage flat disc DTRO reverse osmosis system, as well as the water quality, water quantity and fluoride ion content of the produced water and concentrated water of the second-stage flat disc DTRO reverse osmosis system;

[0027] The fluoride removal system is connected to the two-stage flat disc DTRO reverse osmosis system and is used to remove fluoride from the concentrated water of the two-stage flat disc DTRO reverse osmosis system.

[0028] Based on the same inventive concept, the present invention also provides a method for treating high-salt and high-pollutant wastewater from coal chemical industry, which is treated by using the above-mentioned treatment system for high-salt and high-pollutant wastewater from coal chemical industry, and comprises the following steps:

[0029] Use pretreatment systems to remove hardness and particulate matter from high-salt and highly polluted wastewater from coal chemical industry;

[0030] Use nanofiltration system to separate divalent ions from high-salinity and highly polluted wastewater from coal chemical industry;

[0031] Use a flat disc DTRO reverse osmosis system to initially desalinate the permeate from the nanofiltration system;

[0032] Use a two-stage flat disc DTRO reverse osmosis system to further desalinate the concentrated water from a single-stage flat disc DTRO reverse osmosis system;

[0033] The high-efficiency MVR evaporation system is used to evaporate and crystallize the concentrated water from the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals.

[0034] In some embodiments of the present invention, after the step of separating divalent ions from high-salt and highly polluted wastewater from coal chemical industry using a nanofiltration system, the step further includes: using a low-temperature crystallization system to evaporate and crystallize concentrated water from the nanofiltration system to obtain divalent salt crystals;

[0035] Before using the high-efficiency MVR evaporation system to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals, the method also includes the step of using a defluorination system to remove fluoride from the concentrated water of the two-stage flat disc DTRO reverse osmosis system.

[0036] In some embodiments of the present invention, after the step of using a high-efficiency MVR evaporation system to evaporate and crystallize concentrated water from a two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals, the method further includes the following steps: the mother liquor evaporated and crystallized using the high-efficiency MVR evaporation system and the mother liquor evaporated and crystallized using the low-temperature crystallization system are collected into a mother liquor tank, and the mother liquor in the mother liquor tank is dried by a dryer;

[0037] The supernatant after evaporation and crystallization using the high-efficiency MVR evaporation system and the supernatant after low-temperature crystallization using the low-temperature crystallization system are returned to the raw water storage tank.

[0038] It can be seen from the above that compared with the prior art, the present invention has the following beneficial effects:

[0039] After the high-salt and highly polluted wastewater from coal chemical industry is separated from divalent ions and monovalent ions by the nanofiltration system in the treatment system of the present invention, a pretreatment system, a low-temperature crystallization system, a flat disc reverse osmosis dual-stage system with excellent pollution resistance (COD up to 35,000 mg / L) and excellent high-pressure resistance (currently up to 160 kg high pressure), a defluorination system and a highly integrated high-efficiency MVR evaporation system are used to achieve the goal of completely separating the salt and resource disposal of traditional reverse osmosis concentrated water (conductivity up to about 20,000) to achieve zero emission. After the system membrane permeated water and the evaporated water are mixed, the water quality requirements of circulating cooling water in the industrial environment can be met and reused, saving a lot of water resources, and providing a solution for the practical zero emission of high-salt and highly polluted wastewater from coal chemical industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of the treatment system of high-salt and highly polluted wastewater from coal chemical industry in the present invention;

[0041] Figure 2 It is a schematic diagram of the structure of the disc-type membrane module in the present invention;

[0042] Figure 3It is a schematic diagram of the working principle of the disc-type membrane module in the present invention;

[0043] Figure 4 It is a schematic diagram of the structure of the guide plate and the disc-type diaphragm in the present invention;

[0044] Figure 5 is a cross-sectional view of the disc-type membrane module in the present invention;

[0045] Figure 6 It is a structural schematic diagram of the integrated energy-saving MVR intelligent evaporation and crystallization system in the present invention. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0047] The treatment system and method for high-salt and high-polluted wastewater from coal chemical industry of the present invention can be used not only to treat high-salt and high-polluted wastewater from coal chemical industry, but also to treat wastewater from metallurgical industry, chemical industry, petroleum industry, textile industry, light industry and food industry, etc.

[0048] In order to illustrate the working process of the treatment system of the present invention and the treatment process of the treatment method of the present invention, coking wastewater will be used as an example for treatment object in the following embodiments. However, in actual application, the treatment object of the treatment system and treatment method of the present invention is not limited to coking wastewater.

[0049] The technical solution provided by the present invention is further described below in conjunction with specific embodiments. The following embodiments are only used to illustrate the present invention and will not limit the protection scope of the present invention.

[0050] The coking wastewater in this embodiment refers to the coking wastewater. After the existing reverse osmosis device 100, the reverse osmosis water is fresh water, which can be directly reused in the cooling water system of the factory as new water. The concentrated water produced by it is difficult to dispose of due to its high salt and high pollution, and needs to be treated by the treatment system of the present invention until zero discharge. The concentrated water produced by the reverse osmosis device 100 needs a more comprehensive analysis of the water quality, including but not limited to the following indicators. The typical pollutant concentrations in the coking wastewater are shown in the following table:

[0051] project unit Pollutant content PH 7.5-7.98 Conductivity μS / cm 12000-23000 COD mg / L 70-100 Cyanide mg / L 2-5 Volatile phenol mg / L 0.012-0.03 Total Phosphorus mg / L 3-8 Petroleum mg / L 0.04-0.06 Fluoride mg / L 70-180 hardness mmol / L 0.1-0.2

[0052] In this embodiment, the existing reverse osmosis device 100 includes a reverse osmosis membrane element, which is a membrane bag spirally wound along a central water production pipe to form a cylindrical shape composed of multiple layers of tight membrane bag layers, that is, a rolled reverse osmosis membrane element. The specific structure is that the rolled reverse osmosis membrane element includes a membrane body, a central tube is provided in the middle of the membrane body, a through hole is provided on the surface of the central tube, a pure water guide net is adhered to the outer wall of the central tube by sealant, a reverse osmosis membrane is attached to the outer wall of the pure water guide net, a water inlet guide net is attached to the outer wall of the reverse osmosis membrane, an outer shell is sheathed on the outside of the water inlet guide net, and an end cap is threadedly connected to the bottom end of the membrane body.

[0053] In the prior art, coking wastewater is first treated by reverse osmosis process, that is, treated by the existing reverse osmosis device 100, but one problem that cannot be avoided is that the concentrated water of the reverse osmosis process is generally tens to hundreds of tons per hour, and how to treat the concentrated water of the reverse osmosis process is an urgent problem to be solved. The treatment system of the present invention can effectively treat the reverse osmosis concentrated water of coal chemical wastewater to achieve the purpose of zero discharge.

[0054] like Figure 1 As shown, this embodiment provides a system for treating high-salt and highly polluted wastewater from coal chemical industry, including a pretreatment system 1, a nanofiltration system 106, a one-stage flat disc DTRO reverse osmosis system 2, a two-stage flat disc DTRO reverse osmosis system 3 and a high-efficiency MVR evaporation system 121; wherein:

[0055] Pretreatment system 1, used for softening and filtering high-salinity and high-pollution wastewater from coal chemical industry to remove hardness and particulate matter from high-salinity and high-pollution wastewater from coal chemical industry;

[0056] Nanofiltration system 106, connected to pretreatment system 1, is used to separate divalent ions from high-salt and highly polluted wastewater from coal chemical industry;

[0057] A flat disc DTRO reverse osmosis system 2 is connected to the nanofiltration system 106 and is used to perform preliminary desalination on the permeate water of the nanofiltration system 106;

[0058] The second-stage flat disc DTRO reverse osmosis system 3 is connected to the first-stage flat disc DTRO reverse osmosis system 2 and is used to further desalinate the concentrated water of the first-stage flat disc DTRO reverse osmosis system 2;

[0059] The high-efficiency MVR evaporation system 121 is connected to the two-stage flat disc DTRO reverse osmosis system 3 and is used to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 to obtain monovalent salt crystals.

[0060] In this embodiment, optionally, the above-mentioned coal chemical high-salt and highly polluted wastewater treatment system also includes a low-temperature crystallization system 4, which is connected to the nanofiltration system 106 and is used for low-temperature crystallization of concentrated water from the nanofiltration system 106 to obtain divalent salt crystals.

[0061] In this embodiment, optionally, the low-temperature crystallization system 4 includes a low-temperature crystallizer 133 and a salt box 134; the temperature of the low-temperature crystallizer 133 is set at -30°C to 0°C, the concentrated water of the nanofiltration system 106 enters the low-temperature crystallizer 133, sodium sulfate is crystallized at low temperature and is collected in the salt box 134, and is dried and packaged for transportation.

[0062] In this embodiment, the nanofiltration system 106 includes a nanofiltration host and a source water pool, a concentrate water pool and a purified water pool connected thereto. A source water pump, a precision filter and a high-pressure pump connected in sequence are provided between the source water pool and the nanofiltration host. The nanofiltration host includes an electrical control mechanism for control connection. Multiple groups of membrane shells of the nanofiltration host are respectively provided with corresponding water outlet flow meters, and independent control valves are respectively provided between the source water pool, the concentrate water pool and the purified water pool. The control valves include independent water inlet valves, concentrate water valves and purified water valves.

[0063] The nanofiltration host is equipped with a nanofiltration membrane. The pore size of the nanofiltration membrane is in the nanometer range. It can intercept substances with a relative molecular mass between 100 and 1000. It is a membrane process between reverse osmosis and ultrafiltration. The nanofiltration membrane is a permeable membrane that can intercept high-valent salts and pass monovalent salts, and selectively intercept ions, especially when separating monovalent salts and divalent salts. It can intercept organic matter with a relative molecular mass of more than 100 and pass small molecular organic matter. Most nanofiltration membranes are derived from reverse osmosis membranes, such as CA, CTA membranes, aromatic polyamide composite membranes, and sulfonated polyethersulfone membranes.

[0064] In this embodiment, the nanofiltration system 106 is used to separate divalent ions from the high-salt and highly polluted wastewater of the coal chemical industry. The divalent ions here refer to sulfate, phosphate, calcium, magnesium, iron, heavy metal ions, etc., that is, the nanofiltration system 106 can separate divalent ions such as sulfate, phosphate, calcium, magnesium, iron, heavy metal ions, etc. from the high-salt and highly polluted wastewater of the coal chemical industry. Monovalent ions pass through the nanofiltration membrane, that is, the permeate water of the nanofiltration system 106 is mainly monovalent salt. The nanofiltration system 106 separates the divalent ions and monovalent ions of the salt in the wastewater, providing the necessary conditions for high-purity salt separation.

[0065] This embodiment uses a one-stage flat disc DTRO reverse osmosis system 2 to perform preliminary desalination on the permeate water of the nanofiltration system 106, and uses a two-stage flat disc DTRO reverse osmosis system 3 to further desalinate the concentrate water of the one-stage flat disc DTRO reverse osmosis system 2. Due to the unique disc structure of the flat disc DTRO, the concentrate flux and passage space are large, which solves the disadvantage of limited pollution tolerance of traditional reverse osmosis, so that the influent has high pollutant concentration and high salt content, and still has excellent desalination performance, and the desalination rate can reach more than 99%.

[0066] Reverse osmosis refers to the opposite phenomenon of the natural osmosis process, that is, the process of allowing the solvent to precipitate through a semipermeable membrane under external pressure. Membrane filtration is a physical separation process that filters particles and molecules of various sizes. As long as the required size and the material of the selected membrane are met, small particles, colloids, micromolecules, and even ions can be separated. Membrane filtration is a purely physical process that will not affect the chemical structure and thermal stability of the membrane material used. DTRO is a form of reverse osmosis that uses pressure to force the water molecules in the leachate to pass through the reverse osmosis membrane, and all pollutants including molecules and ions larger than ammonia nitrogen are retained, thereby achieving the purpose of treating the leachate. Its core technology is the disc-type membrane assembly.

[0067] The disc-type membrane assembly is completely different from the traditional spiral membrane. A set of guide plates and reverse osmosis membranes are tightly assembled into a cylindrical membrane column through a stainless steel tube with threads on both ends. The excellent performance of the disc-type membrane assembly depends on the high-quality reverse osmosis membrane and guide plate. Figure 2 As shown, the disc-type membrane assembly includes: a disc-type diaphragm 5, a guide plate 6, a center tie rod 7, an outer shell 8, connecting bolts 9 and flanges 10 at both ends. The disc-type diaphragm 5 and the guide plate 6 are stacked together, fixed with the center tie rod 7 and the end cover flange 10, and then placed in the pressure-resistant outer shell 8 to form a disc-type membrane assembly.

[0068] like Figure 3 As shown, the disc-type membrane assembly has a special flow channel design form, using an open flow channel. The feed liquid enters the DTRO membrane column through the inlet, and the permeate of the nanofiltration system 106 passes through the gap between the disc-type membrane 5 and the shell 8 and then enters the bottom guide plate 6 through the guide channel. The treated liquid flows through the reverse osmosis membrane quickly at a very short distance, and quickly turns 180° to the next membrane surface. The center of the guide plate 6 is provided with a notch, and then flows into the next disc-type membrane 5, so that the surface of the membrane forms a double "S"-shaped trace from the circumference to the center of the circle, and then from the center of the circle to the circumference. The concentrated liquid (concentrated water) finally flows out from the feed end flange 10. While the permeate of the nanofiltration system 106 flows through the filter membrane, the liquid is continuously discharged through the central collection pipe. The concentrated liquid (concentrated water) and the permeate (product water) are isolated by the O-ring installed on the guide plate 6.

[0069] like Figure 4 and Figure 5 As shown, two concentric ring-shaped reverse osmosis membranes with the same salt removal rate characteristics form a disc-type membrane 5. The commonly used reverse osmosis membrane types are: FILMTEC TM XLE-4040、FILMTEC TM XLE-440、FILMTEC TM XLE-2540、FILMTEC TM HRLE-440、FILMTEC TM LP-4040、FILMTEC TM LP-2540、FILMTEC TM LC HR-4040、FILMTEC TM LC LE 4040, etc. Different types of reverse osmosis membranes have different salt removal rates. In practical applications, it is necessary to select reverse osmosis membranes with different salt removal rates according to the salt content requirements of raw water and produced water. At this time, existing reverse osmosis membranes often cannot meet the requirements. This embodiment uses flat reverse osmosis membranes with different salt removal rate characteristics for compound matching to meet different salt removal rate and water production rate requirements. This is not possible in traditional roll membrane reverse osmosis systems. Only in a single membrane assembly such as a flat disc reverse osmosis system are more than 200 reverse osmosis membranes arranged. Therefore, it is possible to perform compound matching in different proportions according to the salt content requirements of raw water and produced water, thereby achieving any salt removal requirements.

[0070] Specifically, the one-stage flat disc DTRO reverse osmosis device 112 and the two-stage flat disc DTRO reverse osmosis device 116 both include a disc-type membrane assembly, and the disc-type membrane assembly includes a first reverse osmosis membrane, and the first reverse osmosis membrane is composed of a reverse osmosis membrane A and a reverse osmosis membrane B. The reverse osmosis membrane A and the reverse osmosis membrane B are membranes with different desalination rate characteristics. In practical applications, it is necessary to screen the reverse osmosis membrane A and the reverse osmosis membrane B according to the desalination requirements so that the desalination rate of the first reverse osmosis membrane meets the desalination requirements. For example, the reverse osmosis membrane A is a reverse osmosis membrane with a desalination rate of 95%, and the reverse osmosis membrane B is a reverse osmosis membrane with a desalination rate of 98%. In practical applications, only a reverse osmosis membrane with a desalination rate of 96% is needed. If the reverse osmosis membrane A is used, the desalination requirements will not be met. If the reverse osmosis membrane B is used, the desalination requirements can be met, but the energy consumption is increased and the processing cost is increased. The reverse osmosis membrane A and the reverse osmosis membrane B are compounded, which can not only meet the desalination requirements, but also reduce energy consumption, reduce processing costs, and the service life of the membrane is long.

[0071] The same wastewater was treated using reverse osmosis membrane A, reverse osmosis membrane B and composite membrane (composite of reverse osmosis membrane A and reverse osmosis membrane B). The comparative test is as follows:

[0072] project Reverse Osmosis Membrane A Reverse Osmosis Membrane B Composite film Inlet pressure 60 kg 60 kg 60 kg Outlet pressure 52 kg 53 kg 54 kg Water production rate 50％ 51％ 53％ Concentrated water 50％ 49％ 47％

[0073] It can be seen from the table that the composite membrane increases the water output rate by 8%, reduces energy consumption by 10%, makes the sewage flow channel unobstructed, reduces the cleaning frequency, and increases the cleaning frequency from 3 months to 5 months, thereby increasing the membrane life.

[0074] In this embodiment, optionally, multiple partitions are set along the length direction of the membrane column, and a first reverse osmosis membrane is set in at least one of the partitions, and a second reverse osmosis membrane or a third reverse osmosis membrane is set in the remaining partitions; the second reverse osmosis membrane is composed of two reverse osmosis membranes A, and the third reverse osmosis membrane is composed of two reverse osmosis membranes B. For example, a single membrane assembly is provided with 209 reverse osmosis membrane sheets, and the membrane column is divided into two partitions along the length direction of the membrane column, namely, a first partition (100 sheets) and a second partition (109 sheets). At the beginning of the treatment, the salt removal rate requirement is low, so the reverse osmosis membrane A with a low salt removal rate is used in the first partition, and the salt removal rate requirement is high in the subsequent treatment process, so the composite membrane (composite of reverse osmosis membrane A and reverse osmosis membrane B) with a higher salt removal rate is used in the second partition; optionally, the membrane column is divided into three partitions, namely, a first partition (70 sheets), a second partition (70 sheets) and a third partition (69 sheets). At the beginning of the treatment, the salt removal rate requirement is low, so the reverse osmosis membrane A with a low salt removal rate is used in the first partition, and the salt removal rate requirement is high in the intermediate treatment process, so the composite membrane (composite of reverse osmosis membrane A and reverse osmosis membrane B) with a higher salt removal rate is used in the second partition, and the salt removal rate requirement is the highest in the final treatment process, so the reverse osmosis membrane B with the highest salt removal rate is used in the third partition. The above structure can improve the desalination rate, increase the water output rate, reduce energy consumption and increase the membrane life.

[0075] In this embodiment, the pretreatment system 1 includes a first dosing device 101, a high-efficiency precipitator 102, a raw water storage tank 103, a nanofiltration lift pump 104 and a first security filter 105; wherein:

[0076] The first dosing device 101 is used to add a hardness reducing agent; the hardness reducing agent may be lime, sodium carbonate or sodium hydroxide, etc.;

[0077] The high-efficiency precipitator 102 is connected to the first dosing device 101 and is used to mix the hardness reducing agent with the high-salt and high-pollutant wastewater of the coal chemical industry for softening treatment to remove the hardness in the high-salt and high-pollutant wastewater of the coal chemical industry;

[0078] For wastewater with high hardness, it is necessary to use the first dosing device 101 to add a hardness reducing agent and treat it in the stirring and mixing high-efficiency precipitator 102. Through precipitation, the hardness in the water is reduced to an appropriate concentration, which can be ≤1.0mmol / L, so as to facilitate subsequent desalination, concentration, and evaporation treatment;

[0079] The raw water storage tank 103 is connected to the high-efficiency precipitator 102 and is used to store high-salt and highly polluted wastewater from coal chemical industry;

[0080] The nanofiltration lifting pump 104 is connected to the raw water storage tank 103 and is used to lift the coal chemical high-salt and highly polluted wastewater in the raw water storage tank 103 to a certain height;

[0081] The first safety filter 105 is connected to the nanofiltration lift pump 104 and is used for filtering and treating the high-salt and high-pollutant wastewater of the coal chemical industry to remove particulate matter in the high-salt and high-pollutant wastewater of the coal chemical industry.

[0082] The high-salt and highly polluted wastewater from the coal chemical industry with hardness reduced to a suitable concentration enters the raw water storage tank 103 for storage, is lifted by the nanofiltration lift pump 104 and then directly enters the nanofiltration system 106 after passing through the first safety filter 105 .

[0083] In this embodiment, the one-stage flat disc DTRO reverse osmosis system 2 includes a reverse osmosis raw water tank 107, a reverse osmosis raw water pump 108, a second safety filter 109 and a one-stage flat disc DTRO reverse osmosis device 112; wherein:

[0084] A reverse osmosis raw water tank 107 is used to store permeate water from the nanofiltration system 106;

[0085] A reverse osmosis raw water pump 108 is connected to the reverse osmosis raw water tank 107 and is used to pump the permeated water stored in the reverse osmosis raw water tank 107 into the second security filter 109;

[0086] The second security filter 109 is connected to the reverse osmosis raw water pump 108 and is used to remove particles in the permeated water;

[0087] A flat disc DTRO reverse osmosis device 112 is connected to the second security filter 109 and is used for preliminary desalination of the permeated water;

[0088] The two-stage flat disc DTRO reverse osmosis system 3 includes a two-stage flat disc DTRO reverse osmosis device 116 for further desalinating concentrated water from the one-stage flat disc DTRO reverse osmosis device 112 .

[0089] The reverse osmosis raw water pump 108 draws water from the reverse osmosis raw water tank 107, passes through the second safety filter 109 and enters a flat disc DTRO reverse osmosis device 112. After exhausting the system gas, the pre-membrane high-pressure pump is turned on to perform concentration work.

[0090] The conductivity of the produced water of the first-stage flat disc DTRO reverse osmosis device 112 is about 800 or less when the inlet water concentration reaches 60,000 conductivity, and is below 1000 when the raw water concentration is below 100,000, which is completely suitable for recycling into circulating cooling water. The substantial decrease in conductivity means that a large amount of heavy metal ions in the inlet water have been retained. Since the molecular weight of heavy metal ions is much smaller than that of organic pollutants, the substantial decrease in conductivity indicates that the organic pollutants in the inlet water have been basically retained by the reverse osmosis membrane. The produced water of the first-stage flat disc DTRO reverse osmosis device 112 enters the product water tank 127, and is mixed with the produced water of the subsequent second-stage flat disc DTRO reverse osmosis device 116 in the product water tank 127, and is lifted by the first lifting pump 128 and recycled into the circulating cooling water system.

[0091] In actual application, a two-stage flat disc DTRO reverse osmosis device uses a low-pressure 75 kg membrane component in the first stage and a 90 kg membrane component in the second stage due to the high influent concentration. If necessary, 120 kg and 160 kg membrane components can be selected according to the water quality.

[0092] In this embodiment, the above-mentioned coal chemical high-salt and high-pollution wastewater treatment system further includes a monitoring system 11 and a defluorination system 12; wherein:

[0093] The monitoring system 11 is used to monitor the water quality and quantity of the inlet water, produced water and concentrated water of the first-stage flat disc DTRO reverse osmosis system 2 and the water quality, water quantity and fluoride ion content of the produced water and concentrated water of the second-stage flat disc DTRO reverse osmosis system 3 in real time.

[0094] The concentrated water of the first-stage flat disc DTRO reverse osmosis device 112 is used as the inlet water of the second-stage flat disc DTRO reverse osmosis device 116 , so the conductivity of the concentrated water of the first-stage flat disc DTRO reverse osmosis device 112 is also the inlet water conductivity of the second-stage flat disc DTRO reverse osmosis device 116 .

[0095] The monitoring system 11 includes a first conductivity monitor 110, a second conductivity monitor 113, a first flow monitor 111, a second flow monitor 114, a third conductivity monitor 125, a third flow monitor 126, a fourth conductivity monitor 123, a fourth flow monitor 124, a fifth conductivity monitor, a fifth flow monitor and a fluoride ion monitor, wherein the first conductivity monitor 110 and the first flow monitor 111 monitor the water quality and water quantity of the inlet of a flat disc DTRO reverse osmosis device 112 in real time, and the second conductivity monitor 125 monitors the inlet water quality and water quantity of the flat disc DTRO reverse osmosis device 112 in real time. The conductivity monitor 113 and the second flow monitor 114 monitor the quality and quantity of the concentrate from the first-stage flat disc DTRO reverse osmosis device 112 in real time. The booster pump 115 lifts the concentrate from the first-stage flat disc DTRO reverse osmosis device 112 into the second-stage flat disc DTRO reverse osmosis device 116 for deep concentration. The conductivity of the first-stage concentrate is about 40,000-60,000 μS / cm. The produced water from the first-stage flat disc DTRO reverse osmosis device 112 is monitored by the third conductivity monitor 125 and the third flow monitor 126.

[0096] The concentrated water from the first-stage flat disc DTRO reverse osmosis device 112 enters the second-stage flat disc DTRO reverse osmosis device 116 for further deep concentration. The module assembly of the second-stage flat disc DTRO reverse osmosis device 116 adopts a high-pressure membrane assembly. The produced water from the second-stage flat disc DTRO reverse osmosis device 116 is monitored by the fourth conductivity monitor 123 and the fourth flow monitor 124, enters the product water tank 127, and is recycled as circulating cooling water together with the produced water from the first-stage flat disc DTRO reverse osmosis device 112. The concentrated water from the second-stage flat disc DTRO reverse osmosis device 116 is monitored by the fifth conductivity monitor, the fifth flow monitor and the fluoride ion monitor;

[0097] The defluorination system 12 is connected to the two-stage flat disc DTRO reverse osmosis system 3 and is used to remove fluoride from the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3; the defluorination system 13 includes a second dosing device 117 and a defluorination device 118, and then enters the concentrated water tank 119. The second dosing device 117 is used to add a defluorination agent, and the defluorination agent includes calcium salts including CaO, CaCl 2 , Ca(OH) 2 , activated alumina, clinoptilolite, activated magnesium oxide, etc. The defluoridation agent is mixed and precipitated with the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 in the defluoridation device 118 to remove fluoride in the concentrated water.

[0098] The concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 is stored in the concentrated water tank 119, with a conductivity of about 60000-100000μS / cm, and the water volume is basically concentrated by 4-10 times. The second lifting pump 120 is used to lift it to the high-efficiency MVR evaporation system 121, and the evaporated condensed water enters the product water tank 127, and the crystallized monovalent salt crystals enter the salt tank 122. At this point, the divalent main salt sodium sulfate and the monovalent main salt sodium chloride are extracted from the wastewater, with a purity of more than 98%, and can be recycled for industrial production raw materials. In this way, the wastewater is recycled: the salt is extracted for industry, and the water is reused for circulating cooling water.

[0099] In this embodiment, the basic principle of the high-efficiency MVR evaporation system 121 is to generate secondary steam in the evaporator through external raw steam, and then increase the pressure and saturation of the secondary steam through the compression and temperature raising effect of the compressor, and the secondary steam with increased enthalpy is sent to the evaporation system to supplement or completely replace the raw steam. The operating cost is mainly the power consumption of the compressor. The traditional MVR evaporation system occupies a large area and has the problem of heat waste. In this embodiment, some components of the traditional MVR evaporation system are nested and integrated, so that some components are nested in one device. The evaporation and crystallization process is highly integrated and designed, with a small footprint, which is a fraction of the footprint of the traditional MVR evaporation system, and can avoid the waste of useless heat, and is highly intelligent; that is, the high-efficiency MVR evaporation system 121 of this embodiment is an integrated energy-saving MVR intelligent evaporation and crystallization system.

[0100] like Figure 6 As shown, the integrated energy-saving MVR intelligent evaporation and crystallization system includes a preheating heat exchanger 150, a primary evaporator 151, a secondary evaporator 152, a steam compressor 153, a separator 154, and a crystallizer 155 connected in sequence; the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 enters the preheating heat exchanger 150, absorbs the residual heat of the condensed distilled water, enters the primary evaporator 151, and is evaporated into steam by heat exchange with hot steam and enters the secondary evaporator 152 as a heat source, and at the same time, it outputs heat to the secondary evaporation solution together with the compressed steam of the steam compressor 153, generating secondary evaporation. The vaporized steam of the secondary evaporation enters the separator 154, and the separated wastewater flows back to the primary evaporator 151. The steam is sucked out by the steam compressor 153 and compressed to do work, and then the pressure and temperature are increased and transported to the secondary evaporator 152 as a heat source. The non-condensable gas generated by the system is condensed and heat exchanged by the condenser and then discharged from the system. The steam heat source of the secondary evaporator 152 finally enters the condenser and condenses as the heat source of the preheating heat exchanger 150. The concentrated slurry at the bottom of the primary evaporator 151 reaches the designed concentration and is lifted out of the system and enters the crystallizer 155 for crystallization.

[0101] The mother liquor after high-temperature concentrated crystallization of the integrated energy-saving MVR intelligent evaporation crystallization system and the mother liquor after low-temperature crystallization in the low-temperature crystallizer 133 are collected in the mother liquor tank 129, the supernatant returns to the raw water storage tank 103, and the mother liquor slurry is lifted to the dryer 131 by the third lifting pump 130. After being dried by the dryer 131, the impure salts are stored in the impure salt tank 132 and outsourced for hazardous waste disposal.

[0102] At this point, all the wastewater has been recycled, and the salt in it has been separated into crystalline salt, which is disposed of as industrial raw materials or hazardous waste solids by professional institutions, saving a lot of hazardous waste disposal costs and achieving the complete zero emission requirements advocated by the environmental protection department.

[0103] In this embodiment, the two-stage flat disc reverse osmosis DTRO technology is used in conjunction with the integrated energy-saving MVR intelligent evaporation crystallization system to achieve the complete zero emission requirements advocated by the environmental protection department.

[0104] Based on the same inventive concept, the present invention also provides a method for treating high-salt and high-pollutant wastewater from coal chemical industry, which is treated by using the above-mentioned treatment system for high-salt and high-pollutant wastewater from coal chemical industry, and comprises the following steps:

[0105] Use pretreatment system 1 to remove hardness and particulate matter from high-salt and high-pollution wastewater from coal chemical industry;

[0106] Using nanofiltration system 106 to separate divalent ions from high-salinity and highly polluted wastewater from coal chemical industry;

[0107] Using a flat disc DTRO reverse osmosis system 2 to preliminarily desalinate the permeate of the nanofiltration system 106;

[0108] The concentrated water of the first-stage flat plate disc DTRO reverse osmosis system 3 is further desalinated by using the second-stage flat plate disc DTRO reverse osmosis system 3;

[0109] The concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 is evaporated and crystallized using the high-efficiency MVR evaporation system 121 to obtain monovalent salt crystals.

[0110] In some embodiments of the present invention, after the step of separating divalent ions from high-salt and highly polluted wastewater from coal chemical industry using nanofiltration system 106, the following steps are further included: using low-temperature crystallization system 4 to evaporate and crystallize concentrated water from nanofiltration system 106 to obtain divalent salt crystals;

[0111] Before using the high-efficiency MVR evaporation system 121 to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 to obtain monovalent salt crystals, the method also includes the step of using the defluorination system 13 to remove fluoride in the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3.

[0112] In some embodiments of the present invention, after the step of using the high-efficiency MVR evaporation system 121 to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system 3 to obtain monovalent salt crystals, the following steps are further included: the mother liquor evaporated and crystallized by the high-efficiency MVR evaporation system 121 and the mother liquor crystallized by the low-temperature crystallization system 4 are collected into the mother liquor tank 129, and the mother liquor in the mother liquor tank 129 is dried by the dryer 131;

[0113] The supernatant after evaporation and crystallization using the high-efficiency MVR evaporation system 121 and the supernatant after low-temperature crystallization using the low-temperature crystallization system 4 flow back to the raw water storage tank 103.

[0114] By adopting the above-mentioned method for treating high-salt and highly polluted wastewater from coal chemical industry, divalent main salt sodium sulfate and monovalent main salt sodium chloride are extracted from the wastewater with a purity of more than 98%, and the water is recycled as circulating cooling water.

[0115] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A system for treating high-salt and high-pollution wastewater from coal chemical industry, characterized in that: It includes pretreatment system, nanofiltration system, one-stage flat disc DTRO reverse osmosis system, two-stage flat disc DTRO reverse osmosis system and high-efficiency MVR evaporation system; among which: Pretreatment system, used for softening and filtering high-salt and high-pollution wastewater from coal chemical industry to remove hardness and particulate matter from high-salt and high-pollution wastewater from coal chemical industry; Nanofiltration system, connected to the pretreatment system, is used to separate divalent ions from high-salt and highly polluted wastewater from coal chemical industry; A flat disc DTRO reverse osmosis system is connected to the nanofiltration system to perform preliminary desalination on the permeate water of the nanofiltration system; The two-stage flat disc DTRO reverse osmosis system is connected to the one-stage flat disc DTRO reverse osmosis system and is used to further desalinate the concentrated water of the one-stage flat disc DTRO reverse osmosis system; The high-efficiency MVR evaporation system is connected to the two-stage flat disc DTRO reverse osmosis system to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals; The one-stage flat disc DTRO reverse osmosis device and the two-stage flat disc DTRO reverse osmosis device both include a disc-type membrane assembly, the disc-type membrane assembly includes a first reverse osmosis membrane, the first reverse osmosis membrane is composed of a reverse osmosis membrane A and a reverse osmosis membrane B; the reverse osmosis membrane A and the reverse osmosis membrane B are membranes with different salt removal rate characteristics; A plurality of partitions are arranged along the length direction of the membrane column, wherein a first reverse osmosis membrane is arranged in at least one of the partitions, and a second reverse osmosis membrane or a third reverse osmosis membrane is arranged in the remaining partitions; the second reverse osmosis membrane is composed of two reverse osmosis membranes A, and the third reverse osmosis membrane is composed of two reverse osmosis membranes B; It also includes a monitoring system and a defluorination system; among which: A monitoring system for real-time monitoring of the water quality and quantity of the inlet water, produced water and concentrated water of the first-stage flat disc DTRO reverse osmosis system, as well as the water quality, water quantity and fluoride ion content of the produced water and concentrated water of the second-stage flat disc DTRO reverse osmosis system; The fluoride removal system is connected to the two-stage flat disc DTRO reverse osmosis system and is used to remove fluoride from the concentrated water of the two-stage flat disc DTRO reverse osmosis system.

2. The system for treating high-salt and highly polluted wastewater from coal chemical industry according to claim 1 is characterized in that: It also includes a low-temperature crystallization system, which is connected to the nanofiltration system and is used for low-temperature crystallization of concentrated water from the nanofiltration system to obtain divalent salt crystals.

3. The system for treating high-salt and highly polluted wastewater from coal chemical industry according to claim 1 is characterized in that: The pretreatment system includes a first dosing device, a high-efficiency precipitator, a raw water storage tank, a nanofiltration lift pump and a first security filter; wherein: The first dosing device is used to add a hardness reducing agent; A high-efficiency precipitator is connected to the first dosing device and is used to mix the hardness reducing agent with the high-salt and high-pollutant wastewater of the coal chemical industry for softening treatment to remove the hardness in the high-salt and high-pollutant wastewater of the coal chemical industry; The raw water storage tank is connected to the high-efficiency precipitator and is used to store high-salt and highly polluted wastewater from coal chemical industry; The nanofiltration lifting pump is connected to the raw water storage tank and is used to lift the high-salt and highly polluted wastewater from the coal chemical industry in the raw water storage tank to a certain height; The first safety filter is connected to the nanofiltration lift pump and is used for filtering and treating the high-salt and high-pollutant wastewater of the coal chemical industry to remove particulate matter in the high-salt and high-pollutant wastewater of the coal chemical industry.

4. The system for treating high-salt and highly polluted wastewater from coal chemical industry according to claim 1, characterized in that: The one-stage flat disc DTRO reverse osmosis system comprises a reverse osmosis raw water tank, a reverse osmosis raw water pump, a second safety filter and a one-stage flat disc DTRO reverse osmosis device; wherein: Reverse osmosis raw water tank, used to store the permeate water of the nanofiltration system; A reverse osmosis raw water pump is connected to the reverse osmosis raw water tank and is used to pump the permeated water stored in the reverse osmosis raw water tank into the second security filter; The second security filter is connected to the reverse osmosis raw water pump and is used to remove particles in the permeated water; A flat disc DTRO reverse osmosis device is connected to the second security filter for preliminary desalination of the permeated water; The two-stage flat disc DTRO reverse osmosis system includes a two-stage flat disc DTRO reverse osmosis device, which is used to further desalinate concentrated water from a one-stage flat disc DTRO reverse osmosis device.

5. A method for treating high-salt and highly polluted wastewater from coal chemical industry, characterized in that: The method comprises the following steps: Use pretreatment systems to remove hardness and particulate matter from high-salt and highly polluted wastewater from coal chemical industry; Use nanofiltration system to separate divalent ions from high-salinity and highly polluted wastewater from coal chemical industry; Use a flat disc DTRO reverse osmosis system to initially desalinate the permeate from the nanofiltration system; Use a two-stage flat disc DTRO reverse osmosis system to further desalinate the concentrated water from a single-stage flat disc DTRO reverse osmosis system; The high-efficiency MVR evaporation system is used to evaporate and crystallize the concentrated water from the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals.

6. The method for treating high-salt and highly polluted wastewater from coal chemical industry according to claim 5, characterized in that: After the step of separating divalent ions from high-salt and highly polluted wastewater from coal chemical industry using a nanofiltration system, the method further includes: using a low-temperature crystallization system to evaporate and crystallize concentrated water from the nanofiltration system to obtain divalent salt crystals; Before using the high-efficiency MVR evaporation system to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals, the method also includes the step of using a defluorination system to remove fluoride from the concentrated water of the two-stage flat disc DTRO reverse osmosis system.

7. The method for treating high-salt and highly polluted wastewater from coal chemical industry according to claim 6, characterized in that: After the step of using the high-efficiency MVR evaporation system to evaporate and crystallize the concentrated water of the two-stage flat disc DTRO reverse osmosis system to obtain monovalent salt crystals, the step further includes: collecting the mother liquor evaporated and crystallized by the high-efficiency MVR evaporation system and the mother liquor evaporated and crystallized by the low-temperature crystallization system into a mother liquor tank, and drying the mother liquor in the mother liquor tank by a dryer; The supernatant after evaporation and crystallization using the high-efficiency MVR evaporation system and the supernatant after low-temperature crystallization using the low-temperature crystallization system are returned to the raw water storage tank.

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