A high-salinity wastewater end zero-emission treatment method

Abstract

The application discloses a kind of high-salinity wastewater end zero discharge processing methods, comprising: (1) the high-salinity wastewater after pretreatment, into double-compressor MVR evaporation system and is evaporated to concentrate;(2) the high-temperature mother liquor and crystallization salt discharged from double-compressor MVR evaporation system enter heat exchange cooling tank, and cool to room temperature;(3) the supernatant in heat exchange cooling tank is discharged to flocculation reaction tank and carries out flocculation reaction, and the crystallization salt in the lower layer of heat exchange cooling tank is transported to centrifuge and carries out centrifugation, and the liquid after centrifugation enters flocculation reaction tank, and solid is transported outside;(4) the mixture after flocculation reaction enters sedimentation tank and carries out sedimentation, and the supernatant enters double-compressor MVR evaporation system again, and the lower layer material carries out pressure filtration, and the pressure filtrate enters double-compressor MVR evaporation system again.The processing method of the application, process is short, simple and efficient, and the yield of crystallization salt is high, can effectively remove COD and ammonia nitrogen etc. in wastewater, realize end zero discharge, and can also save operating cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-salinity wastewater treatment, and particularly relates to a treatment method for end zero discharge of high-salinity wastewater. BACKGROUND

[0002] In the existing field of landfill leachate and high-salinity wastewater treatment, evaporation and concentration is a very important link. After biochemical treatment, ultrafiltration and reverse osmosis, a large amount of chlorides, nitrates and sulfates are contained in some high-salinity wastewater. Generally, sodium chloride is the most common chloride in high-salinity wastewater, and the solubility of sodium chloride changes little with temperature, and the increase of sodium chloride concentration has little effect on the increase of the boiling point of the solution. However, the solubility of nitrates in water is greatly affected by temperature, and the solubility of nitrates increases with the increase of temperature, and as evaporation and concentration proceed, the concentration of nitrates becomes very high, and the boiling point of the mother liquor also becomes very high.

[0003] At present, in the field of landfill leachate and high-salinity wastewater treatment, the MVR evaporation and concentration equipment only has one compressor, and the temperature of the secondary steam is limitedly increased by the compressor. When the system is just started, the concentration of the concentrated solution is low, and the boiling point is low, and the required temperature for evaporation can still be met, but as evaporation and concentration proceed, after the crystalline salt of sodium chloride and sulfates is separated out, the concentration of nitrates in the mother liquor increases, the boiling point of the mother liquor increases, and the temperature of the secondary steam gradually cannot meet the required temperature for evaporation.

[0004] In the traditional process, the mother liquor after evaporation and concentration is directly introduced into a centrifuge for separation of crystalline salt and mother liquor, but the mother liquor still has a high temperature when it comes out of the evaporation chamber, and nitrates and sulfates are dissolved in a large amount at a high temperature, and the mother liquor coming out of the centrifuge still contains a large amount of nitrates and sulfates.

[0005] In addition, after MVR concentration, the mother liquor contains a very high concentration of COD and ammonia nitrogen. In particular, the COD in the mother liquor cannot be treated by the front-end process, and this part of COD is non-biodegradable, and the treatment effect is poor by using general physicochemical or oxidation process, and the method of incineration not only has high cost, but also produces gaseous pollutants, and cannot achieve zero discharge.

[0006] Therefore, how to provide a treatment method for high-salinity wastewater, which has low cost, good treatment effect, simple process, short process, can effectively remove COD and other substances, and can achieve end zero discharge is a problem to be solved.

[0007] Therefore, the present application is proposed. SUMMARY

[0008] The technical problems to be solved by the present application are to overcome the shortcomings of the prior art and provide a high-salinity wastewater end zero-discharge treatment method.

[0009] To solve the above technical problems, the basic idea of the technical solution of the present application is:

[0010] The first object of the present application is to provide a high-salinity wastewater end zero-discharge treatment method, comprising:

[0011] (1) The pretreated high-salinity wastewater enters a double-compressor MVR evaporation system for evaporation concentration;

[0012] (2) The high-temperature mother liquor and crystallized salt discharged from the double-compressor MVR evaporation system enter a heat exchange cooling tank for cooling;

[0013] (3) The supernatant in the heat exchange cooling tank is discharged to a flocculation reaction tank for flocculation reaction, the crystallized salt in the lower layer of the heat exchange cooling tank is transported to a centrifuge for centrifugation, the liquid after centrifugation enters the flocculation reaction tank, and the solid is transported out;

[0014] (4) The mixture after flocculation reaction enters a sedimentation tank for sedimentation, the supernatant after sedimentation enters the double-compressor MVR evaporation system again, the lower layer material is subjected to pressure filtration, the pressure filtrate enters the double-compressor MVR evaporation system again, and the solid is transported out.

[0015] In a further scheme, in step (1), the double-compressor MVR evaporation system comprises two compressors which can be used in series; when the concentration of nitrate in the mother liquor after evaporation concentration is not greater than 20-40%, a single compressor is used to compress steam; when the concentration of nitrate in the mother liquor after evaporation concentration is greater than 20-40%, the steam enters the two compressors in series for secondary compression and heating;

[0016] Preferably, when the concentration of nitrate in the mother liquor after evaporation concentration is not greater than 30%, a single compressor is used to compress steam; when the concentration of nitrate in the mother liquor after evaporation concentration is greater than 30%, the steam enters the two compressors in series for secondary compression and heating.

[0017] For high-salinity wastewater, the present application uses a double-compressor MVR evaporation system for evaporation concentration, which comprises two compressors which can be used in series. In the initial stage of evaporation, a single compressor is used for evaporation. As the evaporation concentration proceeds, when the concentration of the mother liquor increases and the boiling point rises, the two compressors are used in series to raise the temperature of the secondary steam to a higher temperature, so that the evaporation continues, and the concentration ratio of the mother liquor can be increased and the discharge amount of the mother liquor can be reduced.

[0018] Further, when one compressor works, the mother liquor is concentrated 6-10 times, and the temperature of the mother liquor is 105-112 DEG C; when two compressors work, the temperature of the secondary steam is 130-145 DEG C, and the mother liquor is concentrated 12-20 times.

[0019] As a specific embodiment, one compressor is used for evaporation, and when the evaporation concentration is performed, the mother liquor is concentrated 6-10 times, and the temperature of the mother liquor is 105-110 DEG C; at this time, two compressors are opened and work in series, the temperature of the secondary steam heated by the two compressors is higher, the temperature of the secondary steam is 130-145 DEG C, and the mother liquor is concentrated 12-20 times. The evaporation concentration is continuously performed, the amount of the mother liquor is reduced, the amount of the crystallized salt is increased, and the efficiency of the evaporation system is improved.

[0020] Compared with the existing device, the application adds one compressor, and the floor area is not increased much. The premise of the work of the two compressors is that the mother liquor is concentrated to a certain concentration, and the boiling point of the mother liquor is increased to a certain value; when the boiling point of the mother liquor is lower than the value, only one compressor works, and therefore the operation cost is not greatly increased.

[0021] Further, in step (2), the mother liquor from the double-compressor MVR evaporation concentration system enters the heat exchange cooling tank, so that the temperature of the mother liquor is reduced to room temperature.

[0022] Preferably, the temperature of the mother liquor is reduced to 20-25 DEG C.

[0023] In the double-compressor MVR evaporation system of the application, the mother liquor discharged from the evaporation chamber enters the heat exchange cooling tank first, and after cooling, a large amount of nitrate and sulfate is precipitated from the mother liquor, the salt content in the mother liquor is reduced, at this time, the crystallized salt at the bottom of the heat exchange cooling tank enters the centrifuge, and more crystallized salt is centrifuged, and the yield of the crystallized salt is higher.

[0024] Further, the pretreated high-salt wastewater first flows through the heat exchange cooling tank, and the high-temperature mother liquor in the heat exchange cooling tank is cooled, and at the same time, the high-temperature mother liquor is used for first preheating of the high-salt wastewater.

[0025] The high-salt wastewater after the first preheating is used for heat exchange with the high-temperature condensed water generated by the double-compressor MVR evaporation system, and is second preheated; the high-salt wastewater after the two preheatings enters the evaporator of the double-compressor MVR evaporation system, and is evaporated and concentrated.

[0026] In the application, the high-salinity wastewater is first cooled by a heat exchange cooling tank, and the high-salinity wastewater is used to cool the evaporated concentrated mother liquor, and the high-salinity wastewater is preheated for the first time, and then the high-salinity wastewater is heat-exchanged with the high-temperature condensed water generated by the double-compressor MVR evaporation device to be preheated for the second time, so that the heat generated by the system is used twice, and the waste of heat and water resources is avoided, and the cost is reduced.

[0027] Further, a flocculation reagent is added to the flocculation reaction tank, and the flocculation reagent is stirred uniformly to perform flocculation reaction, and the flocculation reaction time is 10-40 min.

[0028] Preferably, the flocculation reaction tank comprises one or more flocculation reaction tanks to perform one or multiple flocculation reactions.

[0029] Further, the mixture after the flocculation reaction is introduced into a sedimentation tank to perform sedimentation, and the sedimentation time is 30 min-5 h.

[0030] Further, a flocculation reagent is added to the flocculation reaction tank, and the flocculation reagent is a covalent bond type inorganic-organic composite flocculant composed of γ-aminopropyl diethoxymethyl silane and aluminum chloride.

[0031] The amount of the flocculation reagent is 2-10 g / L.

[0032] In the traditional process, the mother liquor is not subjected to flocculation process treatment. If the mother liquor is treated by the traditional flocculation process, the flocculation reagent generally used is PAC and PAM, etc., which can only remove suspended solids and cannot effectively remove COD and ammonia nitrogen.

[0033] After the mother liquor is concentrated by the two-stage compressor MVR system, the concentration multiple is high, and the contents of COD and ammonia nitrogen in the mother liquor are also high, especially the COD, which is the remaining COD after a series of previous treatments, and the biochemical and ordinary oxidation technologies are difficult to remove the COD. If this part of the mother liquor is returned to the MVR system for further concentration, the condensed water generated will contain high COD and ammonia nitrogen, resulting in unqualified water quality of the evaporated water.

[0034] In order to remove the high content of COD and ammonia nitrogen in the mother liquor, the supernatant after cooling is discharged into the flocculation reaction tank for flocculation reaction in the application, the depth flocculation technology is adopted, the flocculant is different from the traditional organic and inorganic flocculants, and is a covalent bond type flocculant combined with inorganic and organic together, has the advantages of organic flocculant and inorganic flocculant, not only has good flocculation effect, but also the sludge produced has faster settling speed. In addition to the flocculation effect, the new reagent also has adsorption effect, can effectively adsorb the difficult-to-treat COD and ammonia nitrogen in water quality, has obvious water quality decolorization effect, and the high concentration of salt in the water body will not affect the treatment effect.

[0035] Further, in the supernatant after precipitation, the COD is 0-50 mg / L, and the ammonia nitrogen is less than or equal to 5 mg / L.

[0036] Preferably, the COD is 0-20 mg / L, and the ammonia nitrogen is less than or equal to 3 mg / L.

[0037] After cooling, depth flocculation and precipitation, most of the liquid is sodium chloride with low boiling point, and the content of nitrate and sulfate is very low, so that the supernatant after precipitation and the filter liquor of the lower layer of material can be returned to the MVR evaporation concentration system, and the evaporation system is not affected.

[0038] Further, in the application, the high-salinity wastewater is landfill leachate.

[0039] After adopting the above technical scheme, the application has the following beneficial effects compared with the prior art.

[0040] 1. In the treatment method of the application, a double-compressor MVR evaporation concentration system is adopted, the temperature of secondary steam is improved, and the discharge amount of mother liquor is reduced.

[0041] When the mother liquor concentration is low at the beginning, one compressor is used to heat the secondary steam, when the mother liquor is concentrated to a certain concentration, the temperature of the mother liquor is increased, another compressor is started, and the two compressors are started at the same time, so that the temperature of the secondary steam is improved to a higher temperature, and the evaporation continues. In this way, the needs of low temperature in the early stage of evaporation concentration and the needs of high temperature in the later stage can be met, the evaporation efficiency is improved, the concentration ratio of the mother liquor is improved, the concentration of the mother liquor is improved, and the amount of the generated mother liquor is reduced. The system has good treatment effect for wastewater with complex salt content.

[0042] The double-compressor MVR evaporation concentration system of the application can switch between single-stage compression and two-stage compression according to the working condition, avoid energy waste, reduce the overall energy consumption, and reduce the comprehensive cost.

[0043] 2、The treatment method of the present application adds a cooling step, reduces the temperature of the mother liquor discharged after evaporation, and reduces the salt content of the mother liquor. The mother liquor discharged from the evaporation chamber of the double-compressor MVR evaporation and concentration system first enters the mother liquor heat exchange cooling tank. After cooling, a large amount of nitrate and sulfate will precipitate from the mother liquor, the salt content of the mother liquor will be reduced, and more crystalline salt which is more affected by temperature will be precipitated. At this time, the crystalline salt at the bottom of the mother liquor heat exchange cooling tank enters the centrifuge, and more crystalline salt will be centrifuged out, thereby improving the yield of crystalline salt.

[0044] 3、The treatment method of the present application uses deep flocculation technology to remove high content of COD and ammonia nitrogen in the mother liquor.

[0045] In the present application, the cooled mother liquor is flocculated using organic-inorganic composite covalent flocculants, which has the effects of flocculation and adsorption, can remove COD and ammonia nitrogen in the mother liquor, has good water quality decolorization effect, and can also remove SS and part of calcium and magnesium ions in the water.

[0046] 4、In the present application, the mother liquor evaporated after cooling, deep flocculation and precipitation removes COD and ammonia nitrogen, and the water quality color also becomes clear and transparent. The remaining salt in the water quality is mainly sodium chloride which is not affected by temperature, and the content of nitrate and sulfate is very low. Therefore, the supernatant after precipitation and the pressure filter liquid of the lower layer material can be returned to the MVR evaporation and concentration system. The reflux of this part of the mother liquor to the double-compressor MVR evaporation and concentration system will not increase the boiling point of the evaporation mother liquor, and will not affect the water quality of the evaporated water due to COD and ammonia nitrogen. Therefore, it will not affect the evaporation system, and greatly shortens the subsequent process flow. The whole process is simple and easy to popularize.

[0047] 5、In the present application, the high-salt wastewater first passes through the heat exchange cooling tank, and the high-salt wastewater is preheated for the first time while cooling the evaporation and concentration mother liquor. Then, the high-salt wastewater is heat exchanged with the high-temperature condensate water generated by the double-compressor MVR evaporation device for the second time. In this way, the generated heat is utilized twice, the temperature of the high-salt wastewater entering the evaporator is increased, the energy consumption is reduced, the waste of heat and water resources is avoided, and the cost is reduced.

[0048] Therefore, in the method of the present application, the generated solids such as crystalline salt and mud cake can be handled by external transportation, and the liquid separated by the centrifuge enters the flocculation reaction tank, and the liquid generated by the sedimentation tank and the filter press can be returned to the double-compressor MVR evaporation and concentration system for further treatment, thereby realizing complete zero discharge at the end.

[0049] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0050] The accompanying drawings, which are part of the present application, serve to provide a further understanding of the present application, and the schematic embodiments of the present application and the descriptions thereof serve to explain the present application but do not constitute an improper limitation on the present application. Obviously, the drawings in the following description are only some embodiments, and other drawings can be obtained from these drawings by those of ordinary skill in the art without any creative effort. In the drawings:

[0051] Figure 1 is a structural schematic diagram of a treatment system for end zero discharge of high-salinity wastewater of the present application;

[0052] Figure 2 is a flow schematic diagram of a treatment method for end zero discharge of high-salinity wastewater of the present application.

[0053] In the drawings: 100, a storage device for high-salinity wastewater, 101, a double-compressor MVR evaporation device, 102, a heat exchange cooling tank, 103, a centrifugal device, 104, a flocculation reaction tank, 105, a sedimentation tank, 106, a pressure filtration device, 107, a flocculant loading device, 108, a stirring device, 109, a wastewater pipeline;

[0054] The double-compressor MVR evaporation device comprises: 1, an evaporator, 2, a first heater, 3, a second heater, 4, a first compressor, 5, a second compressor, 6, a first control device, 7, a second control device, 8, a second control device, 9, a first steam pipeline, 10, a second steam pipeline, 11, a third steam pipeline, 12, a fourth steam pipeline, 13, a feed inlet, 14, a discharge outlet, 15, a circulating pump, 16, a condensate tank, 17, a heat exchanger, and 18, a condensate pipeline.

[0055] It should be noted that these drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to illustrate the present application but not to limit the scope of the present application.

[0057] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0058] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "linking" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected, it can be mechanical connection, or electrical connection, it can be directly connected, or indirectly connected through intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0059] In a first aspect, as shown in the drawings, the present application provides a high-salinity wastewater end zero-emission treatment equipment, comprising: Figure 1

[0060] The double-compressor MVR evaporation device 101 comprises an evaporator 1 and two heaters connected in series, and the evaporator 1 and the two heaters are connected through pipelines to form a liquid circulation and evaporate and concentrate the liquid;

[0061] The heat exchange cooling tank 102 is communicated with the evaporator 1, and the mother liquor after evaporation and concentration is discharged into the heat exchange cooling tank 102;

[0062] The centrifugal device 103 is communicated with the lower part of the heat exchange cooling tank 102;

[0063] The flocculation reaction tank 104 is communicated with the heat exchange cooling tank 102, and the liquid in the heat exchange cooling tank 102 is discharged into the flocculation reaction tank 104;

[0064] The sedimentation tank 105 is communicated with the flocculation reaction tank 104;

[0065] The filter pressing device 106 is communicated with the sedimentation tank 105.

[0066] In the high-salinity wastewater end zero-emission treatment equipment of the present application, the heat exchange cooling tank 102 is included, the mother liquor discharged from the evaporator 1 of the double-compressor MVR evaporation device 101 is first introduced into the heat exchange cooling tank 102, and after the cooling step, a large amount of nitrate and sulfate will be precipitated from the mother liquor, and the salt content in the mother liquor is reduced, at this time, the crystalline salt at the bottom of the heat exchange cooling tank 102 is introduced into the centrifuge, and more crystalline salt can be centrifuged out, and the yield of crystalline salt is higher. The liquid in the heat exchange cooling tank 102 is discharged into the flocculation reaction tank 104 for flocculation, which can effectively remove COD and ammonia nitrogen in the wastewater, and no gas pollutants are produced. The solids produced by the sedimentation tank 105 and the filter pressing device 106 are transported out, and the liquid can be returned to the equipment for reprocessing, so as to realize end zero-emission.

[0067] ​Further, the heat exchange cooling tank 102 comprises a tank body and a jacket arranged outside the tank body, the inlet of the tank body is communicated with the evaporator 1, and the evaporated concentrated mother liquor is discharged into the tank body; the inlet of the jacket is communicated with the high-salinity wastewater storage device 100, and the outlet of the jacket is connected with the wastewater pipeline 109, and the other end of the wastewater pipeline 109 is communicated with the feeding port 13 of the evaporator 1; the high-salinity wastewater first flows through the jacket and the mother liquor in the tank body to exchange heat, and then enters the wastewater pipeline 109 after being preheated for the first time.

[0068] In the application, the outlet of the high-salinity wastewater storage device 100 is connected with the inlet of the jacket of the heat exchange cooling tank 102. Compared with the amount of high-salinity wastewater, the amount of the evaporated concentrated mother liquor in the tank body is small, so that the high-salinity wastewater can well cool the mother liquor through the jacket heat exchange, and the high-salinity wastewater is preheated for the first time, so that the waste of heat can be avoided, the mother liquor does not need to be cooled by additional water resources, the waste of water resources is avoided, and the cost is reduced.

[0069] Further, the double-compressor MVR evaporating device 101 further comprises a condensate tank 16 and a condensate pipeline 18, the inlet of the condensate tank 16 is communicated with the condensate outlets of the two heaters, the outlet of the condensate tank 16 is communicated with the condensate pipeline 18, and the heat exchanger 17 is arranged between the condensate pipeline 18 and the wastewater pipeline 109, and the high-temperature condensate in the condensate pipeline 18 preheats the high-salinity wastewater in the wastewater pipeline 109 for the second time through the heat exchanger 17.

[0070] In the evaporating and concentrating process of the double-compressor MVR evaporating device 101, a large amount of condensate is generated by the heaters and collected in the condensate tank 16, and the temperature of the condensate is very high. In the application, the heat exchanger 17 is arranged, and the heat of the part of the condensate can be used to preheat the high-salinity wastewater in the wastewater pipeline 109 for the second time, so that the heat is reused and the cost is reduced.

[0071] In the application, the heat exchanger 17 can be a plate heat exchanger 17. The high-salinity wastewater in the wastewater pipeline 109 and the high-temperature condensate in the condensate pipeline 18 flow reversely, so that the heat exchange efficiency is improved.

[0072] Further, the double-compressor MVR evaporating device 101 further comprises a first steam pipeline and a second steam pipeline arranged in parallel, one end of the first steam pipeline and the second steam pipeline is communicated with the upper part of the evaporator 1 through a third steam pipeline, and the other end of the first steam pipeline and the second steam pipeline is respectively communicated with the two heaters through a fourth steam pipeline.

[0073] The first compressor is arranged on the fourth steam pipeline, the first control device for controlling the opening and closing of the pipeline is arranged on the first steam pipeline, and the second compressor and the second control device for controlling the opening and closing of the pipeline are arranged on the second steam pipeline.

[0074] For high-salinity wastewater, the application adopts a double-compressor MVR evaporation device 101 for evaporation concentration, including two compressors that can be used in series. In the initial stage of evaporation, one compressor is used for evaporation. As the evaporation concentration proceeds, when the concentration of the mother liquor increases and the boiling point rises, two compressors are used in series to raise the secondary steam to a higher temperature, so that evaporation continues, and the concentration ratio of the mother liquor can be increased, and the discharge amount of the mother liquor can be reduced.

[0075] Compared with existing devices, the application adds one compressor, which does not increase the floor area much. The premise for the two compressors to work simultaneously is that the mother liquor is concentrated to a certain concentration, and the boiling point of the mother liquor is raised to a certain value. When the boiling point of the mother liquor is lower than this value, only one compressor works, so the operating cost is not greatly increased.

[0076] Specifically, the steam coming out of the evaporator 11 can be divided into two paths after passing through the third steam pipeline 11. One path enters the first steam pipeline 9 and then passes through the first compressor 4 on the fourth steam pipeline 12 to enter the heater 2, 3. The other path enters the second steam pipeline and then passes through the second compressor 5 and the first compressor 4 in turn to enter the heater 2, 3. The steam can enter either of the above two paths, and does not proceed simultaneously.

[0077] It should be noted that the "first" and "second" in the application are only examples and do not limit the specific setting position. For example, the second compressor 5 and the second control device 7, 8 for controlling the opening and closing of the pipeline can be arranged on the second steam pipeline 10 or on the first steam pipeline 9. The first control device 6 can be arranged on the first steam pipeline 9 or on the second steam pipeline 10.

[0078] Among them, the first compressor 4 is the main compressor, and the second compressor 5 is the auxiliary compressor. The first compressor 4 and the second compressor 5 can be of the same or different models. The models of the first compressor 4 and the second compressor 5 can be selected according to the material conditions in the system, but the difference between them should not be too large.

[0079] As a specific implementation, the first compressor 4 and the second compressor 5 are both centrifugal compressors.

[0080] The first control device 6 and the second control device 7, 8 are both electric butterfly valves, and the first control device 6 and the second control device 7, 8 cannot be opened or closed at the same time.

[0081] That is, the two paths need to be used alternatively. Specifically, when the first control device 6 is opened and the second control device 7, 8 is closed, only the first compressor 4 is used. When the first control device 6 is closed and the second control device 7, 8 is opened, the first compressor 4 and the second compressor 5 are used simultaneously.

[0082] Two second control devices 7, 8 are arranged on the second steam pipeline 10, and are arranged upstream and downstream of the second compressor 5 respectively.

[0083] In the application, the control devices are arranged upstream and downstream of the second compressor 5, so that when the first compressor 4 is used alone, the two second control devices 7, 8 need to be closed at the same time, thereby avoiding the steam from flowing into the second steam pipeline 10, avoiding the waste of steam, and reducing the overall energy consumption.

[0084] The fourth steam passage is communicated with the upper part of the heater 2, so that the steam compressed by the first compressor 4 or the first compressor 4 and the second compressor 5 enters the upper part of the heater 2, and the liquid in the heater 2 can be heated better, and the efficiency is improved.

[0085] Further, the heater comprises a first heater 2 and a second heater 3, the upper parts of the first heater 2 and the second heater 3 are communicated with the evaporator 1 through pipelines respectively, the lower parts of the first heater 2 and the second heater 3 are communicated with each other through pipelines, and a circulating pump 15 is arranged on the pipeline communicated between the first heater 2 and the second heater 3.

[0086] The double-compressor MVR evaporation device 101 of the application comprises two heaters, the setting height of a single heater can be reduced, the setting difficulty of the equipment is reduced, the production safety is beneficial, and better heating effect can be achieved.

[0087] Through the above arrangement, the steam and the liquid are separated in the first and second heaters 3, the concentrated liquid enters the heater through the pipeline, exchanges heat with the steam compressed once or twice, and is pumped back to the evaporator 1 through the pipeline, so as to circulate and concentrate gradually, and the treatment of the high-salinity wastewater is completed.

[0088] The upper part of the evaporator 1 is provided with a feeding port 13, the feeding port 13 is connected with a wastewater pipeline 109, the bottom of the evaporator 1 is provided with a discharging port 14, and the discharging port 14 is communicated with the inlet of the tank body of the heat exchange cooling tank 102.

[0089] The lower parts of the first heater 2 and the second heater 3 are further provided with a condensate outlet, and the condensate outlet is communicated with a condensate tank 16 through a pipeline.

[0090] The specific operation process of the double-compressor MVR evaporation and concentration system of the application is as follows:

[0091] Condition 1: The system is just running, the concentration of the mother liquor in the system is not very high, the concentration of substances such as nitrate causing the boiling point of the mother liquor to rise is low, and the first compressor is started and runs alone.

[0092] Specifically: open the first control device (electric butterfly valve) 6, close the second control device (electric butterfly valve) 7, 8, the first compressor 4 is operated alone. The secondary steam generated by the evaporator 11 passes through the first steam pipeline where the first control device (electric butterfly valve) 6 is located, enters the first compressor 4, and the heated secondary steam enters the heater 2, 3.

[0093] In the working condition 2, the system has been operated for a period of time, and with the evaporation and concentration, the chlorides and sulfates in the mother liquor are crystallized and discharged from the system. The solubility of the nitrates is relatively large, and the nitrates cannot be crystallized and separated out. The concentration of the nitrates in the mother liquor becomes relatively large, so that the boiling point of the mother liquor is increased. If the secondary steam is only compressed by the first compressor 4, the temperature is only increased to a limited extent, and the temperature cannot meet the requirement of the heat transfer of evaporation. Therefore, the first compressor 4 and the second compressor 5 need to be started to operate simultaneously.

[0094] Specifically: close the first control device (electric butterfly valve) 6, open the second control device (electric butterfly valve) 7, 8, and start the second compressor 5. The secondary steam from the evaporator 11 is first compressed by the second compressor 5, and then compressed by the first compressor 4, so that secondary steam with a higher temperature is generated. The steam enters the heater 2, 3 to heat the mother liquor. In this process, the temperature of the secondary steam is increased, the temperature difference between the secondary steam and the mother liquor is increased, the heat transfer power is increased, the heat transfer efficiency is improved, and the amount of the mother liquor in the system is reduced.

[0095] In the double-compressor MVR evaporation and concentration system of the application, two compressors are used. Generally, one compressor can increase the temperature of the secondary steam by 15-25 DEG C, and after the two compressors are used in series, the temperature of the secondary steam can be increased by 30-45 DEG C. In the MVR evaporation and concentration system, the starting of the two compressors is conditional. When the evaporation system is just started, the concentration of the mother liquor is low, and the boiling point is also low. At this time, one compressor can heat the secondary steam to meet the evaporation requirement. Only when the concentration of the mother liquor is increased to a certain extent, the boiling point of the mother liquor is increased, and one compressor cannot meet the evaporation requirement, the two compressors are started simultaneously and work in series. In this way, the evaporation requirement is met, and the operation cost is also saved.

[0096] In a further scheme, the centrifugal device 103 is connected with the flocculation reaction tank 104 through a pipeline, or connected with the pipeline between the heat exchange cooling tank 102 and the flocculation reaction tank 104. The liquid after centrifugation of the centrifugal device 103 enters the flocculation reaction tank 104 through the pipeline.

[0097] In the application, the solid is crystalline salt after centrifugation of the centrifugal device 103, and is removed. The liquid enters the flocculation reaction tank 104 through the pipeline, and is subjected to flocculation treatment, so that no discharge is generated.

[0098] Further, the flocculation reaction tank 104 comprises one or more; the flocculation reaction tank 104 is provided with a stirring device 108.

[0099] Further, the flocculation agent loading device 107 is further included, the flocculation agent loading device 107 is communicated with the flocculation reaction tank 104 through a pipeline, and the flocculation agent is put into the flocculation reaction tank 104.

[0100] Further, the precipitation tank 105 comprises one or more, or one precipitation tank 105 comprises multiple grids; the bottom of each or each grid of the precipitation tank 105 is conical from top to bottom, and the center is gradually inclined from the periphery.

[0101] Further, the upper part of the precipitation tank 105 is communicated with the high-salinity wastewater storage device 100 through a pipeline, and the upper layer liquid after precipitation returns to the high-salinity wastewater storage device 100; the bottom of the precipitation tank 105 is communicated with the filter pressing device 106 through a pipeline, and the lower layer material enters the filter pressing device 106.

[0102] Further, the filter pressing device 106 is communicated with the high-salinity wastewater storage device 100 through a pipeline, the filter pressing liquid of the filter pressing device 106 returns to the high-salinity wastewater storage device 100, and the solid is transported out.

[0103] The filter pressing device 106 can be a plate-and-frame filter press, the sludge at the bottom of the precipitation tank 105 enters the plate-and-frame filter press, the filter pressing liquid has the same water quality as the supernatant liquid, returns to the high-salinity wastewater storage device 100 again, enters the evaporator 1 of the double-compressor MVR evaporation device 101 to evaporate and concentrate, and the dry sludge after passing through the plate-and-frame filter press is transported out for treatment.

[0104] In the application, the liquid of the precipitation tank 105 and the filter pressing device 106 can return to the high-salinity wastewater storage device 100, pass through the jacket of the heat exchange cooling tank 102, the wastewater pipeline 109, and enter the evaporator 1 again, and be treated again. Therefore, the entire high-salinity wastewater end zero discharge treatment equipment has no wastewater and waste gas discharge at the end of the equipment, and realizes end zero discharge.

[0105] Secondly, as shown in the figure, Figure 2 The application provides a high-salinity wastewater end zero discharge treatment method, which comprises the following steps:

[0106] (1) the pretreated high-salinity wastewater enters a double-compressor MVR evaporation system to evaporate and concentrate,

[0107] (2) the high-temperature mother liquor and the crystalline salt discharged from the double-compressor MVR evaporation system enter a heat exchange cooling tank and are cooled to room temperature;

[0108] (3) The supernatant in the heat exchange cooling tank is discharged into the flocculation reaction tank for flocculation reaction, the crystalline salt in the lower layer of the heat exchange cooling tank is transported to a centrifuge for centrifugation, and the liquid after centrifugation is introduced into the flocculation reaction tank, and the solid is transported out;

[0109] (4) The mixture after flocculation reaction is introduced into a sedimentation tank for sedimentation, the supernatant is introduced into the double-compressor MVR evaporation system again, the lower layer material is subjected to pressure filtration, the pressure filtrate is introduced into the double-compressor MVR evaporation system again, and the solid is transported out.

[0110] In a further scheme, the double-compressor MVR evaporation system comprises two compressors which can be used in series; when the concentration of nitrate in the evaporated and concentrated mother liquor is not greater than 20-40%, a single compressor is used to compress steam; when the concentration of nitrate in the evaporated and concentrated mother liquor is greater than 20-40%, steam is sequentially introduced into the two compressors in series for secondary compression and heating.

[0111] In a further scheme, when the concentration of nitrate in the evaporated and concentrated mother liquor is not greater than 30%, a single compressor is used to compress steam; when the concentration of nitrate in the evaporated and concentrated mother liquor is greater than 30%, steam is sequentially introduced into the two compressors in series for secondary compression and heating.

[0112] For high-salinity wastewater, the double-compressor MVR evaporation system is used for evaporation and concentration, and comprises two compressors which can be used in series. In the initial stage of evaporation, a single compressor is used for evaporation, and as the evaporation and concentration proceed, when the concentration of the mother liquor increases and the boiling point rises, the two compressors are used in series to raise the temperature of the secondary steam to a higher temperature, so that evaporation can continue, and the concentration ratio of the mother liquor can be increased and the discharge amount of the mother liquor can be reduced.

[0113] In the traditional MVR evaporation and concentration device, after the mother liquor is concentrated to a certain concentration, the evaporated and concentrated mother liquor is directly introduced into a centrifuge for separation of the mother liquor and crystalline salt. This process has little effect on the mother liquor mainly containing sodium chloride. However, in landfill leachate, desulfurization wastewater and other high-salinity wastewater, there are not only sodium chloride, but also sulfate and nitrate, especially nitrate, and the temperature has a great effect on the solubility of these salts. Under high-temperature conditions, centrifugation of the mother liquor cannot separate the salts which are greatly affected by the temperature, resulting in a high salt content in the mother liquor. In subsequent treatment, if the mother liquor is returned to the MVR evaporation system, the concentration of nitrate and sulfate in the mother liquor will increase, and the boiling point of the mother liquor will rise, which is extremely unfavorable for the entire MVR evaporation and concentration system; if the mother liquor is subjected to other treatment, such as introduction into a section for removal of COD, the high-concentration salt in the mother liquor will have an adverse effect on the subsequent treatment section, reduce the removal efficiency of COD, and even affect the operation of the section.

[0114] The mother liquor discharged from the evaporation chamber of the double-compressor MVR evaporation system in the application first enters the mother liquor heat exchange cooling tank, after cooling, a large amount of nitrate and sulfate will be precipitated from the mother liquor, the salt content in the mother liquor is reduced, at this time, the crystalline salt at the bottom of the mother liquor heat exchange cooling tank enters the centrifuge, more crystalline salt can be centrifuged out, and the yield of the crystalline salt is higher.

[0115] The temperature of the mother liquor is reduced to room temperature in the heat exchange cooling tank; preferably, the temperature of the mother liquor is reduced to 20-25℃.

[0116] The flocculation reaction time is 10-40 min, and the precipitation time is 30 min-5 h.

[0117] The flocculation reaction agent is added into the flocculation reaction tank, and the flocculation reaction agent is a covalent bond type inorganic organic composite flocculant composed of γ-aminopropyl diethoxymethyl silane and aluminum chloride. Specifically, the flocculation reaction agent of the application adopts the flocculant prepared in Example 1 of the application number 200810115990.8, named “a covalent bond type inorganic organic composite flocculant, preparation process and application” (inventors: Zhao Huazhang, Peng Jianxiong, Sun Juanjuan).

[0118] The amount of the flocculation reaction agent is 2-10 g / L.

[0119] Preferably, the flocculation reaction tank comprises one or more.

[0120] The COD of the supernatant after precipitation is 0-50 mg / L, and the ammonia nitrogen is ≤5 mg / L.

[0121] Preferably, the COD is 0-20 mg / L, and the ammonia nitrogen is ≤3 mg / L.

[0122] After cooling, deep flocculation and precipitation, most of the liquid is sodium chloride with a low boiling point, and the content of nitrate and sulfate is very low, so the supernatant after precipitation and the pressure filtration liquid of the lower layer of material can be returned to the MVR evaporation concentration system, and no influence on the evaporation system is caused.

[0123] Example 1

[0124] A certain landfill leachate treatment site, after the landfill leachate is pretreated, the landfill leachate enters the double-compressor MVR evaporation concentration system of the application, the water inlet amount is 200 m 3 / day. The main indicators of the water inlet are as follows: COD: 10-100 mg / L; TDS: 30-50 g / L; NH3-N: 3-10 mg / L. The structure of the double-compressor MVR evaporation concentration system is shown in Figure 1 .

[0125] High salt wastewater into the evaporator 1, the evaporation system just started running, the mother liquor concentration in the system is low, the boiling point of the mother liquor is low, at this time the electric butterfly valve 7 and 8 are closed, the valve 6 is opened, and the compressor 4 works independently. The temperature of the mother liquor is 100-103℃, and the temperature of the secondary steam is 115-125℃ when one compressor works. With the evaporation and concentration, the concentration of the mother liquor increases gradually, and the concentration of the nitrate in the mother liquor also increases gradually, so that the boiling point of the mother liquor increases. The secondary steam heated by the compressor 4 alone cannot meet the demand of continuous evaporation. After the mother liquor is concentrated 6-10 times, the temperature of the mother liquor is 105-110℃. At this time, the valves 7 and 8 are opened, the valve 6 is closed, and the compressors 4 and 5 are started to work in series. The temperature of the secondary steam heated by the two compressors is higher, and the temperature of the secondary steam is 130-145℃. The mother liquor is continuously concentrated to 12-20 times. The evaporation and concentration continue, the amount of mother liquor is reduced, the amount of crystalline salt is increased, and the efficiency of the evaporation system is improved.

[0126] The mother liquor from the double-compressor MVR evaporation and concentration system enters the mother liquor heat exchange cooling tank, and the temperature of the mother liquor is reduced to room temperature. The nitrate and sulfate in the mother liquor which are greatly affected by temperature can be precipitated. The main indicators of the water quality of the mother liquor after cooling are: COD: 200-2000mg / L; TDS: 200-350g / L; NH3-N: 60-200mg / L.

[0127] The clear liquid in the upper layer of the mother liquor heat exchange cooling tank enters the flocculation reaction tank, and the crystalline salt in the lower layer enters the centrifuge for treatment. The mother liquor from the centrifuge enters the flocculation reaction tank, and the dry crystalline salt treated by the centrifuge enters the subsequent process (external treatment).

[0128] The clear liquid in the upper layer of the mother liquor heat exchange cooling tank and the mother liquor from the centrifuge enter the deep flocculation reaction tank. A certain amount of deep flocculation agent 2-10g / L (the flocculant prepared in Example 1 of 200810115990.8) is delivered from the flocculant loading device, and the agent and the mother liquor perform deep flocculation reaction to remove COD, ammonia nitrogen, SS and part of calcium and magnesium ions in the mother liquor, decolorize the water quality, and make the mother liquor clear and transparent. The mud-water mixture from the deep flocculation reaction tank enters the sedimentation tank, and is allowed to stand to separate the mud and water. The deep flocculation reaction time is 10-40min, and the sedimentation time is 30min-5h. The supernatant in the sedimentation tank enters the evaporation chamber for continuous evaporation, and the sludge at the bottom of the sedimentation tank enters the plate and frame filter press for further separation of mud and water. The filtrate from the plate and frame filter press and the supernatant from the sedimentation tank enter the evaporation and concentration system, and the dry sludge after filtration enters the subsequent process (external treatment). After the deep flocculation treatment of the mother liquor, the main indicators of the water quality of the mixture of the supernatant and the plate and frame filter press filtrate are: COD: 0-20mg / L; TDS: 200-350g / L; NH3-N: 0-3mg / L.

[0129] Example 2

[0130] A certain kitchen wastewater treatment project, kitchen wastewater after pretreatment, into the evaporation concentration system, the water intake is 600m 3 / day.

[0131] Water intake main indicators:

[0132] COD: 100 ~ 250mg / L;

[0133] TDS: 15 ~ 30g / L (potassium nitrate content of 3.5%)

[0134] NH3-N: 4 ~ 15mg / L

[0135] The water quality into the evaporation chamber, the mother liquor temperature is 100 ~ 102℃, a compressor working, the secondary steam temperature is 115 ~ 125℃. The mother liquor is concentrated 8 ~ 10 times, the mother liquor temperature is 107 ~ 112℃. Start two compressors working at the same time, the secondary steam temperature is 130 ~ 145℃, the mother liquor is concentrated to 14 ~ 20 times.

[0136] From the double compressor MVR evaporation concentration system, the mother liquor into the mother liquor heat exchange cooling tank, reduce the temperature of the mother liquor to normal temperature, the mother liquor after cooling the main indicators of water quality are:

[0137] COD: 1400 ~ 5000mg / L;

[0138] TDS: 130 ~ 320g / L;

[0139] NH3-N: 60 ~ 300mg / L.

[0140] The supernatant of the mother liquor heat exchange cooling tank into the flocculation reaction tank, the lower layer of crystalline salt into the centrifuge, the mother liquor from the centrifuge into the flocculation reaction tank, the dry crystalline salt after centrifuge into the subsequent process treatment (external processing).

[0141] The supernatant of the mother liquor heat exchange cooling tank and the mother liquor from the centrifuge into the deep flocculation reaction tank, a certain amount of deep flocculation agent 2 ~ 10g / L (200810115990.8 example 1 prepared flocculant) from the flocculant loading device, the deep flocculation reaction time is 10 ~ 40min, the sedimentation time is 30min ~ 5h. After the mother liquor is treated by deep flocculation, the main indicators of the mixed water quality of the supernatant and the plate and frame filter press filtrate are:

[0142] COD: 0 ~ 20mg / L;

[0143] TDS: 130 ~ 320g / L;

[0144] NH3-N: 0-5 mg / L.

[0145] Comparative Example 1

[0146] Conventional process:

[0147] A landfill leachate treatment plant, after pretreatment of landfill leachate, into the evaporation concentration system, the water inflow is 200 m 3 / day.

[0148] Main indicators of water inflow:

[0149] COD: 10-100 mg / L;

[0150] TDS: 30-50 g / L;

[0151] NH3-N: 3-10 mg / L.

[0152] After the water quality into the evaporation chamber, the mother liquor temperature is 100-103℃, the conventional process only one compressor works, the secondary steam temperature is 115-125℃. The mother liquor is concentrated 6-10 times, the mother liquor temperature is 105-110℃. The mother liquor comes out of the evaporation chamber, without cooling, directly into the centrifuge for mother liquor and crystalline salt separation.

[0153] Main indicators of mother liquor:

[0154] COD: 60-1000 mg / L;

[0155] TDS: 180-350 g / L;

[0156] NH3-N: 18-100 mg / L.

[0157] The mother liquor from the centrifuge does not do flocculation to remove COD and ammonia nitrogen treatment, only other processes can be used, and the treatment cost is higher.

[0158] Other treatment processes commonly used are re-injection and incineration. The re-injection method is to directly re-inject or spray the mother liquor from the centrifuge into the landfill site. In the soil layer and garbage layer of the landfill site, the organic matter in the mother liquor can be degraded by microbial degradation and physical and chemical action, and the stability of the landfill site can be promoted. However, re-injection also has obvious disadvantages. After re-injection, the COD in the subsequent leachate will increase and become more and more difficult to treat; the ammonia nitrogen in the leachate will increase; the conductivity, TDS and salt content in the leachate will increase. The incineration method is to burn the mother liquor from the centrifuge into the incinerator. The incineration method for treating the mother liquor after centrifugation has the advantages of high efficiency and complete treatment of pollutants. However, the incineration method also has obvious disadvantages. The initial investment of the incineration method is relatively large, and the pollutants generated during the incineration process still need to be treated. The treatment of dioxin and mercury pollutants faces certain technical difficulties; if the mother liquor after centrifugation is transported to a waste liquid incineration plant for treatment, the transportation cost is high.

[0159] Compared with double compressors, a single compressor produces less condensate water and more mother liquor.

[0160] In the traditional method, the MVR evaporation concentration system has only one compressor. After the mother liquor comes out of the evaporation chamber, it is directly introduced into the centrifuge for separation of mother liquor and crystalline salt without cooling. The mother liquor contains a high concentration of COD and ammonia nitrogen, which requires other processes to remove COD and ammonia nitrogen. Due to the high salt content in the mother liquor, the process for removing COD and ammonia nitrogen is complex, and the treated mother liquor cannot enter the evaporation system for further evaporation, which brings certain difficulties to the subsequent treatment of the mother liquor.

[0161] Comparative Example 2

[0162] The difference between this comparative example and Example 1 is the lack of a cooling step.

[0163] Specific case: A landfill leachate treatment site, after pretreatment of landfill leachate, the landfill leachate enters the evaporation concentration system, the water inlet quantity is 200m 3 / day.

[0164] Main indicators of water inlet:

[0165] COD: 10-100 mg / L;

[0166] TDS: 30-50 g / L;

[0167] NH3-N: 3-10 mg / L.

[0168] The temperature of the mother liquor is 100-103°C after entering the evaporation chamber, the temperature of the secondary steam is 115-125°C when one compressor is working, and the temperature of the mother liquor is 105-110°C after being concentrated 6-10 times. When two compressors are working, the temperature of the secondary steam is 130-145°C, and the mother liquor is continuously concentrated to 12-20 times. The mother liquor is directly introduced into a centrifuge for separation of salt and mother liquor without cooling, and the mother liquor after centrifugation is introduced into a flocculation reaction tank to react with a flocculating agent, the reaction time is 10-40 min, and the supernatant in the sedimentation tank is introduced into a double-compressor MVR evaporation system after reaction and sedimentation for 30 min-5 h.

[0169] Since the temperature of the mother liquor after centrifugation from the centrifuge is high, part of the crystalline salt is not precipitated from the solution, and the salt content is high, which can reduce the flocculation effect. Compared with the case where the temperature of the mother liquor is first reduced, the high-temperature mother liquor uses 0.5-1 g / L of flocculating agent.

[0170] Since the flocculation reaction time and the sedimentation time are not enough to reduce the temperature of the mother liquor to a lower temperature, the salt content in the supernatant in the flocculation and sedimentation tank is high, especially the nitrate content is high, which is greatly affected by temperature.

[0171] The main indicators of the supernatant water quality are:

[0172] COD: 0-20 mg / L;

[0173] TDS: 240-390 g / L;

[0174] NH3-N: 0-5 mg / L.

[0175] The high nitrate content in the supernatant from the sedimentation tank can also affect the temperature of the mother liquor in the evaporation and concentration system, reduce the evaporation water volume, and reduce the processing capacity of the system.

[0176] Comparative Example 3

[0177] The difference between this comparative example and Example 1 is that there is no flocculation step.

[0178] Specific case:

[0179] A landfill leachate treatment site, after the landfill leachate is pretreated, it is introduced into an evaporation and concentration system, the water inflow is 200 m 3 / day.

[0180] Main indicators of the inflow water:

[0181] COD: 10-100 mg / L;

[0182] TDS: 30-50 g / L;

[0183] NH3-N: 3-10 mg / L.

[0184] After the water quality enters the evaporation chamber, the mother liquor temperature is 100-103°C, the secondary steam temperature is 115-125°C when one compressor is working. After the mother liquor is concentrated by 6-10 times, the mother liquor temperature is 105-110°C. When two compressors are started and work simultaneously, the secondary steam temperature is 130-145°C, and the mother liquor is continuously concentrated to 12-20 times. The main indexes of the water quality after the mother liquor is cooled are:

[0185] COD: 200-2000 mg / L;

[0186] TDS: 200-350 g / L;

[0187] NH3-N: 60-200 mg / L.

[0188] The mother liquor discharged from the centrifuge is not subjected to flocculation, COD and ammonia nitrogen removal treatment, and can only be treated by other processes, and the treatment cost is relatively high.

[0189] The commonly used other treatment processes are recharging and incineration. The recharging method is to directly recharge or spray the mother liquor discharged from the centrifuge in the landfill site. The organic matter in the mother liquor can be degraded through microbial degradation and physical and chemical action in the soil layer and garbage layer of the landfill site, and the stability of the landfill site is promoted. However, the recharging also has obvious disadvantages. After recharging, the COD in the subsequent produced leachate will increase and become more and more difficult to treat; the ammonia nitrogen in the leachate will increase; the conductivity, TDS and salt content in the leachate will increase. The incineration method is to burn the mother liquor discharged from the centrifuge into the incinerator. The incineration method for treating the mother liquor after centrifugation has the advantages of high efficiency and complete treatment of pollutants. However, the incineration method also has obvious disadvantages. The initial investment of the incineration method is relatively large, and the pollutants generated in the incineration process still need to be treated, and the treatment of dioxin and mercury pollutants faces certain technical difficulties; if the mother liquor after centrifugation is transported to a waste liquid incineration plant company for treatment, the transportation cost is relatively high.

[0190] Comparative Example 4

[0191] The combination of commonly used PAM and PAC on the market and the covalent bond type inorganic organic composite flocculant used in the present application are compared in effect.

[0192] Specific case:

[0193] A landfill leachate treatment site, after the landfill leachate is pretreated, enters the evaporation and concentration system, and the water inflow is 200 m 3 / day.

[0194] Main indexes of the water inflow:

[0195] COD: 10-100 mg / L;

[0196] TDS: 30-50 g / L;

[0197] NH3-N: 3-10 mg / L.

[0198] After the water quality enters the evaporation chamber, the mother liquor temperature is 100-103℃, the secondary steam temperature is 115-125℃ when one compressor works, and the mother liquor is concentrated by 6-10 times, the mother liquor temperature is 105-110℃. When two compressors work simultaneously, the secondary steam temperature is 130-145℃, and the mother liquor is continuously concentrated to 12-20 times. After the mother liquor is cooled, the main indexes of the water quality are:

[0199] COD: 200-2000 mg / L;

[0200] TDS: 200-350 g / L;

[0201] NH3-N: 60-200 mg / L.

[0202] (1) After the mother liquor is treated by deep flocculation using the covalent bond type inorganic organic composite flocculant described in the application, the main indexes of the mixed water quality of supernatant and plate and frame filter press filtrate are:

[0203] COD: 0-20 mg / L;

[0204] TDS: 200-350 g / L;

[0205] NH3-N: 0-3 mg / L.

[0206] (2) After the mother liquor is treated by flocculation using the combination of PAC and PAM commonly used on the market, the main indexes of the mixed water quality of supernatant and plate and frame filter press filtrate are:

[0207] COD: 140-1400 mg / L;

[0208] TDS: 200-350 g / L;

[0209] NH3-N: 58-195 mg / L.

[0210] The covalent bond type inorganic organic composite flocculant and the combination flocculant of PAC and PAM described in the application are used, and the effect comparison is shown in Table 1.

[0211] Table 1

[0212] Water quality COD after treatment TDS after treatment treated NH3-N Mother liquor after centrifugation 200-2000 mg / L 200-350 g / L 60-200 mg / L After treatment with the flocculant described in the present invention 0-20 mg / L 200-350 g / L 0-3 mg / L After treatment with PAC and PAM combination 140-1400 mg / L 200-350 g / L 58-195 mg / L

[0213] From the results in the table, it can be seen that the covalent bond type inorganic organic composite flocculant can effectively remove COD and ammonia nitrogen in the mother liquor; the commonly used PAM and PAC on the market have a certain removal rate on COD, but the removal rate is low, generally 20-45%, and the removal of COD is not the same for different water qualities, and has almost no removal effect on ammonia nitrogen.

[0214] In addition, the effect comparison results of the examples and each comparative example are shown in Table 2.

[0215] Table 2

[0216] Amount of crystalline salt precipitated COD after treatment TDS after treatment treatment NH3-N <!-- 13 -->]] Example 1 4500-7500 kg / day 0-20 mg / L 200-350 g / L 0-3 mg / L Comparative Example 1 3000-6000 kg / day 60-1000 mg / L 180-350 g / L 18-100 mg / L Comparative Example 2 3500-6500 kg / day 0-20 mg / L 240-390 g / L 0-5 mg / L Comparative Example 3 3200-6200 kg / day 200-2000 mg / L 200-350 g / L 60-200 mg / L

[0217] Analysis:

[0218] Compared with the traditional method of Comparative Example 1, the process adopted in the examples of the present application produces more crystalline salt and less mother liquor, and the last mother liquor is returned to the evaporation chamber after flocculation treatment, and continues to evaporate and concentrate, which truly realizes zero discharge treatment.

[0219] Compared with Comparative Example 2, in the process adopted in the present application, the mother liquor is cooled and then enters the centrifuge for separation of the mother liquor and the crystalline salt, the salt content in the mother liquor is reduced, which is beneficial to the removal of COD and ammonia nitrogen in the flocculation process, and the amount of flocculant is less, the salt carried by the mother liquor into the evaporation chamber is less, when concentrated to a certain concentration, the amount of condensate produced is higher, the treatment capacity is increased, and the yield of crystalline salt is increased.

[0220] Compared with Comparative Example 3, in the process of the present application, the COD and ammonia nitrogen content in the mother liquor can be reduced to a very low level after the flocculation process, which meets the conditions for entering the evaporation system, and the mother liquor does not need to be treated by other processes, but directly enters the evaporation and concentration system for further treatment, which can realize true zero discharge treatment. In addition, there is rarely a flocculation process in the traditional process for treating mother liquor, and if the mother liquor is treated by using the traditional PAC and PAM flocculants, only suspended solids can be removed, and COD and ammonia nitrogen cannot be effectively removed.

[0221] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application, and any skilled person in the art can make some changes or modifications to the above-mentioned technical content without departing from the technical solution of the present application, and equivalent embodiments with equivalent changes and modifications are equivalent. Any simple modification, equivalent change and modification made to the above examples according to the technical essence of the present application are still within the scope of the present application.

Claims

1. A treatment method of high-salinity wastewater end zero discharge, characterized in that, The method comprises the following steps: (1) the pretreated high-salinity wastewater is fed into a double-compressor MVR evaporation system for evaporation and concentration; The double-compressor MVR evaporation system comprises two compressors which can be used in series; when the concentration of nitrate in the mother liquor for evaporation and concentration is not greater than 20-40%, a single compressor is used to compress steam; when the concentration of nitrate in the mother liquor for evaporation and concentration is greater than 20-40%, the steam is sequentially fed into two compressors in series for secondary compression and heating; (2) the high-temperature mother liquor and crystallized salt discharged from the double-compressor MVR evaporation system are fed into a heat exchange cooling tank for cooling; (3) the supernatant in the heat exchange cooling tank is discharged into a flocculation reaction tank for flocculation reaction, and the crystallized salt in the lower layer of the heat exchange cooling tank is fed into a centrifuge for centrifugation, the liquid after centrifugation is fed into the flocculation reaction tank, and the solid is externally transported; (4) the mixture after flocculation reaction is fed into a sedimentation tank for sedimentation, the supernatant after sedimentation is again fed into the double-compressor MVR evaporation system, the lower layer of the mixture is subjected to pressure filtration, the filtrate is again fed into the double-compressor MVR evaporation system, and the solid is externally transported; In step (1), the pretreated high-salinity wastewater is first fed into the heat exchange cooling tank to cool the high-temperature mother liquor in the heat exchange cooling tank, and the high-temperature mother liquor is used to preheat the high-salinity wastewater for the first time; The high-salinity wastewater after the first preheating is subjected to heat exchange with the high-temperature condensed water generated by the double-compressor MVR evaporation system for the second time, and the high-salinity wastewater after the second preheating is fed into the evaporator of the double-compressor MVR evaporation system for evaporation and concentration.

2. The treatment method according to claim 1, characterized in that, When the concentration of nitrate in the mother liquor for evaporation and concentration is not greater than 30%, a single compressor is used to compress steam; when the concentration of nitrate in the mother liquor for evaporation and concentration is greater than 30%, the steam is sequentially fed into two compressors in series for secondary compression and heating.

3. The treatment method of claim 1, wherein When a single compressor is used, the mother liquor is concentrated by 6-10 times, and the temperature of the mother liquor is 105-112℃; when two compressors are used for secondary compression and heating, the temperature of the secondary steam is 130-145℃, and the mother liquor is further concentrated to 12-20 times.

4. The treatment method according to any one of claims 1 to 3, characterized in that, In step (2), the mother liquor discharged from the double-compressor MVR evaporation and concentration system is fed into the heat exchange cooling tank to reduce the temperature of the mother liquor to room temperature.

5. The treatment method according to claim 4, characterized in that, In step (2), the temperature of the mother liquor is reduced to 20-25℃.

6. The treatment method according to any one of claims 1 to 3, characterized in that, In step (3), a flocculation reaction agent is added to the flocculation reaction tank, stirred uniformly, and subjected to flocculation reaction, and the flocculation reaction time is 10-40 min.

7. The treatment method according to claim 6, characterized in that, The flocculation reaction tank comprises one or more flocculation reaction tanks, and one or more flocculation reactions are performed in sequence.

8. The treatment method of claim 6, wherein The flocculation reaction agent is a covalent bond type inorganic-organic composite flocculant composed of γ-aminopropyl diethoxymethyl silane and aluminum chloride.

9. The processing method according to claim 6, wherein The concentration of the added flocculation reaction agent is 2-10 g / L.

10. The treatment method according to any one of claims 1 to 3, characterized in that, In step (4), the mixture after flocculation reaction is fed into a sedimentation tank for sedimentation, and the sedimentation time is 30 min-5 h.

11. The treatment method according to any one of claims 1 to 3, characterized in that, After sedimentation, the COD in the supernatant is 0-50 mg / L, and the ammonia nitrogen is ≤5 mg / L.

12. The processing method according to claim 11, wherein, The COD is 0-20 mg / L, and the ammonia nitrogen is ≤3 mg / L.

13. The treatment method according to any one of claims 1 to 3, characterized in that, The high-salinity wastewater is landfill leachate.

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