Evaporative crystallization salt separation system and method for high-salinity wastewater

Abstract

The invention discloses an evaporative crystallization salt separation system and method for high-salinity wastewater. The system comprises a first nanofiltration unit, a first concentrated water preheating unit, a first falling film concentration unit, a first primary-effect evaporation unit, a secondary-effect finished salt unit, a last-effect carnallite unit, a carnallite incineration unit, a second nanofiltration unit, a second concentrated water preheating unit and a second falling film concentration unit which are communicated in sequence, a second primary evaporation unit and a second crystallization finished salt unit; the secondary-effect finished salt unit is used for separating out divalent finished salt, the last-effect carnallite unit is used for separating out carnallite, and the crystallized finished salt unit is used for separating out monovalent finished salt. According to the system, through coupling of three processes of nanofiltration pre-concentration, directional crystallization and carnallite incineration regeneration, the bottleneck of a traditional technology is broken through, and carnallite, high-purity sodium sulfate finished product salt and sodium chloride finished product salt are separated out.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment in the petrochemical industry, and particularly relates to a high-salinity wastewater evaporation crystallization and salt separation system and method. BACKGROUND

[0002] The concentrated wastewater produced after pretreatment of current petroleum refining wastewater contains high concentrations of Na + , Cl - , SO4 2- (bivalent ion ratio > 60%), and organic matter with a molecular weight of 200-1000 Da (such as oil and fat, phenols). Conventional multi-effect evaporation or mechanical vapor recompression (MVR) technology cannot effectively separate Na2SO4 and NaCl, resulting in a large amount of impure salt, low purity (only about 90%), low resource value, and high energy consumption for treatment. In addition, the organic matter is prone to adhere to the heat exchange tube wall during the evaporation crystallization process, causing coking and plugging, which requires frequent shutdown for cleaning (period < 30 days), significantly increasing the operation and maintenance cost and affecting the continuous operation efficiency. At the same time, there are problems such as corrosion of equipment caused by unremoved CO2 and O2 in the evaporator, difficulty in direct reuse or discharge of the mother liquor due to high viscosity and the presence of organic impurities, and secondary pollution caused by incomplete incineration of the impure salt. SUMMARY

[0003] In view of the above problems, the present application is proposed in order to provide a high-salinity wastewater evaporation crystallization and salt separation system and method which overcomes the above problems or at least partially solves the above problems.

[0004] As one aspect of the present application, the present application provides a high-salinity wastewater evaporation crystallization and salt separation system, comprising a first nanofiltration unit, a first concentrated water preheating unit, a first falling film concentration unit, a first primary-effect evaporation unit, a secondary-effect product salt unit, a last-effect impure salt unit, an impure salt incineration unit, a second nanofiltration unit, a second concentrated water preheating unit, a second falling film concentration unit, a second primary-effect evaporation unit, and a crystallization product salt unit, which are sequentially connected. The secondary-effect product salt unit is used for precipitating bivalent product salt, the last-effect impure salt unit is used for precipitating impure salt, and the crystallization product salt unit is used for precipitating monovalent product salt.

[0005] Optionally, the first nanofiltration unit comprises a first wastewater mixing tank and a first nanofiltration device in communication; and the second nanofiltration unit comprises a second wastewater mixing tank and a second nanofiltration device in communication.

[0006] The inlet of the first wastewater mixing tank is in communication with the input pipeline of raw water and the outlet of the retentate of the second nanofiltration device, respectively; the permeate outlet of the first nanofiltration device is in communication with the inlet of the second wastewater mixing tank; and the retentate outlet of the first nanofiltration device is in communication with the first concentrated water preheating unit.

[0007] The inlet of the second wastewater mixing tank 0801 is also in communication with the outlet of the salt cake dissolving tank 0702 of the salt cake incineration unit;

[0008] The permeate outlet of the second nanofiltration device 0803 is in communication with the second concentrated water preheating unit.

[0009] Optionally, the first concentrated water preheating unit comprises a first evaporation feed water tank 0201, a first feed water preheater 0203, a first steam preheater 0204 and a degasser 0205 in sequence;

[0010] The retentate outlet of the first nanofiltration device 103 is in communication with the inlet of the first evaporation feed water tank 0201;

[0011] The bottom outlet of the degasser 0205 is in communication with the first falling film concentration unit.

[0012] Optionally, the first primary evaporation unit comprises a first primary crystallizer 0401 and a first primary forced circulation heat exchanger 0403 constituting a first evaporation loop; the secondary product salt unit comprises a secondary crystallizer 0501 and a secondary forced circulation heat exchanger 0503 constituting a second evaporation loop; the final salt cake unit comprises a final crystallizer 0601 and a final forced circulation heat exchanger 0603 constituting a third evaporation loop; the second primary evaporation unit comprises a second primary crystallizer 1101 and a second primary forced circulation heat exchanger 1103 constituting a fourth evaporation loop; the second secondary product salt unit comprises a second secondary crystallizer 1201 and a second secondary forced circulation heat exchanger 1203 constituting a fifth evaporation loop.

[0013] Optionally, the first falling film concentration unit comprises a first falling film evaporator 0301, a first falling film circulating pump 0302 and a first concentrated liquid transfer pump 0303;

[0014] The bottom outlet of the degasser 0205 is in communication with the lower separation chamber inlet of the first falling film evaporator 0301, the separation chamber bottom outlet is in communication with the top liquid tank of the first falling film evaporator 0301 through the first falling film circulating pump 0302, and is in communication with the inlet of the first primary crystallizer 0401 through the first concentrated liquid transfer pump 0303.

[0015] Optionally, the first falling film concentration unit further comprises a first demister 0304, a first steam compressor 0305, a first condensate tank 0306 and a first condensate delivery pump 0307;

[0016] The steam outlet of the separation chamber is communicated with the upper falling film evaporation chamber shell side inlet of the first falling film evaporator 0301 through the first demister 0304 and the first steam compressor 0305;

[0017] The shell side outlet of the falling film evaporation chamber is communicated with the shell side inlet of the first water inlet preheater 0203 through the first condensate tank 0306 and the first condensate delivery pump 0307.

[0018] Optionally, the secondary product salt unit further comprises a first product salt leg 0504, a secondary discharge pump 0505, a secondary hydrocyclone 0506, a secondary crystal slurry tank 0507, a secondary centrifuge 0508, a secondary centrifuge mother liquor tank 0509, a secondary centrifuge mother liquor circulating pump 0510 and a secondary centrifuge mother liquor heater 0511 which are sequentially communicated;

[0019] The inlet of the first product salt leg 0504 is communicated with the bottom outlet of the secondary crystallizer 0501, and the outlet of the secondary centrifuge mother liquor heater 0511 is communicated with the second evaporation loop;

[0020] The secondary product salt unit further comprises a first product salt packer 0513 which is communicated with the secondary centrifuge 0508 and is used for packing the divalent product salt;

[0021] The outlet communicated by the second evaporation loop is further communicated with the inlet of the final crystallizer 0601.

[0022] Optionally, the shell side outlet of the first primary forced circulation heat exchanger 0403 is communicated with the shell side inlet of the secondary centrifuge mother liquor heater 0511.

[0023] Optionally, the secondary centrifuge mother liquor tank 0509 is further communicated with the mixed salt incineration unit through the secondary centrifuge mother liquor circulating pump 0510;

[0024] The bottom outlet of the lower separation chamber of the first falling film evaporator 0301 is communicated with the bottom inlet of the first product salt leg 0504.

[0025] Optionally, the final mixed salt unit is provided to be cut out.

[0026] Optionally, the final mixed salt unit further comprises a mixed salt leg 0604, a final discharge pump 0605, a final hydrocyclone 0606, a final crystal slurry tank 0607, a final centrifuge 0608, a final centrifuge mother liquor tank 0609 and a final centrifuge mother liquor circulating pump 0610 which are sequentially communicated;

[0027] The inlet of the miscellaneous salt leg 0604 is communicated with the bottom outlet of the last effect crystallizer 0601, and the outlet of the last effect centrifugal mother liquor tank 0609 is communicated with the third evaporation loop through a last effect centrifugal mother liquor circulating pump 0610;

[0028] The last effect miscellaneous salt unit further comprises a miscellaneous salt baling machine 0611, which is communicated with the last effect centrifugal machine 0608 and is used for baling miscellaneous salt.

[0029] Optionally, the last effect centrifugal mother liquor tank 0609 is further communicated with the miscellaneous salt incineration unit 7 through the last effect centrifugal mother liquor circulating pump 0610.

[0030] The bottom outlet of the lower separation chamber of the first falling film evaporator 0301 is communicated with the bottom inlet of the miscellaneous salt leg 0604.

[0031] Optionally, the second concentrated water preheating unit comprises a second evaporation water inlet tank 0901, a second water inlet preheater 0903 and a second steam preheater 0904 communicated in sequence.

[0032] The outlet of the second steam preheater 0904 is communicated with a second falling film concentration unit.

[0033] The outlet of the second steam preheater 0904 is communicated with a second falling film concentration unit.

[0034] Optionally, the second falling film concentration unit comprises a second falling film evaporator 1001, a second falling film circulating pump 1002 and a second concentrated liquid transfer pump 1003.

[0035] The bottom outlet of the lower separation chamber of the second falling film evaporator 1001 is communicated with the top liquid groove of the second falling film evaporator 1001 through the second falling film circulating pump 1002, and is communicated with the second primary effect crystallizer 1101 through the second concentrated liquid transfer pump 1003.

[0036] Optionally, the second falling film concentration unit further comprises a second condensate tank 1006 communicated with the shell side outlet of the upper falling film evaporation chamber of the second falling film evaporator 1001, and the outlet of the second condensate tank 1006 is communicated with the shell side inlet of the second water inlet preheater 0903.

[0037] The second falling film concentration unit further comprises a second demister 1004 and a second steam compressor 1005 communicated in sequence with the steam outlet of the lower separation chamber of the second falling film evaporator 1001, and the outlet of the second steam compressor 1005 is communicated with the shell side inlet of the upper falling film evaporation chamber of the second falling film evaporator 1001.

[0038] Optionally, the second secondary effluent product salt unit further comprises a second product salt leg 1204, a second secondary effluent pump 1205, a second secondary effluent hydrocyclone 1206, a second secondary effluent mother liquor tank 1209, a second secondary effluent mother liquor circulating pump 1210 and a second secondary effluent mother liquor heater 1211, which are sequentially connected.

[0039] The inlet of the second product salt leg 1204 is connected with the bottom outlet of the second secondary effluent crystallizer 1201, and the outlet of the second secondary effluent mother liquor heater 1211 is connected with the fifth evaporation loop.

[0040] The second secondary effluent product salt unit further comprises a second product salt packing machine 1212, which is connected with the second secondary effluent centrifuge 1208 and is used for packing monovalent product salt.

[0041] The outlet of the fourth evaporation loop is connected with the inlet of the fifth evaporation loop.

[0042] Optionally, the shell side outlet of the second primary effluent forced circulation heat exchanger 1103 is connected with the shell side inlet of the second secondary effluent mother liquor heater 1211.

[0043] Optionally, the outlet of the second secondary effluent mother liquor tank 1209 is further connected with the mixed salt incineration unit.

[0044] Optionally, the steam outlet of the first primary effluent crystallizer 0401 is connected with the shell side inlet of the secondary effluent forced circulation heat exchanger 0503, and the shell side outlet is connected with the first crystallization condensate tank 0613.

[0045] The steam outlet of the secondary effluent crystallizer 0501, the steam outlet of the last effluent crystallizer 0601 and the shell side outlet of the last effluent forced circulation heat exchanger 0603 are all connected with the inlet of the first crystallization condensate tank 0613.

[0046] The steam outlet of the second primary effluent crystallizer 1101 is connected with the shell side inlet of the second secondary effluent forced circulation heat exchanger 1203, and the shell side outlet is connected with the crystallization condensate tank 1214. The steam outlet of the second secondary effluent crystallizer 1201 is connected with the crystallization condensate tank 1214.

[0047] Optionally, the mixed salt incineration unit comprises a mixed salt incineration unit 0701 and a mixed salt dissolving tank 0702 which are connected.

[0048] The outlet of the first crystallization condensate tank 0613 is connected with the inlet of the mixed salt dissolving tank 0702.

[0049] Optionally, it further comprises a smart control module, configured to monitor data through a self-control instrument, generate a dynamic trend map of the brine concentration, diagnose by comparison with a ternary phase diagram, and intelligently adjust control parameters in real time according to a preset concentration fluctuation threshold and PID parameters.

[0050] As another aspect of the present application, the present application embodiment provides a high-salinity wastewater evaporation crystallization and salt separation method, comprising using any of the above high-salinity wastewater evaporation crystallization and salt separation systems to perform raw water evaporation crystallization and salt separation.

[0051] The above technical solution provided in the present application embodiment has at least the following beneficial effects:

[0052] (1) The high-salinity wastewater evaporation crystallization and salt separation system provided in the present application embodiment breaks through the bottleneck of traditional technology through the triple process coupling of "nanofiltration pre-concentration + multi-effect evaporation directional crystallization + impure salt incineration regeneration", and realizes efficient separation and resource recovery of sodium sulfate and sodium chloride based on the high rejection rate (> 90%) of divalent ions (SO4 2- ) and the low rejection rate (20%~60%) of monovalent ions (Cl - ) by nanofiltration membranes, combined with evaporation crystallization and impure salt incineration technology, avoiding residual mother liquor wastewater; The purity of the product sodium sulfate is ≥99.5% (reaching the I-class standard of GB / T 6009-2014), and the purity of the product sodium chloride is ≥99.2% (reaching the premium standard of GB / T 5462-2015), opening up a new mode of salt separation and resource utilization; At the same time, it also solves the contradiction between energy consumption and purity in the field of high-salinity wastewater treatment, and provides a standardized path for industrial wastewater salt separation and resource utilization.

[0053] (2) The high-salinity wastewater evaporation crystallization and salt separation system provided in the present application embodiment uses the rejection rate difference of divalent ions and monovalent ions by nanofiltration membranes, and realizes the pre-concentration of raw water by two-stage nanofiltration units, selectively rejects different valence ions, reduces the subsequent evaporation scale by 20%~40%, and realizes the salt separation of different inorganic salts.

[0054] (3) The high-salinity wastewater evaporation crystallization and salt separation system provided in the present application embodiment extends the cleaning cycle by 2~3 times by nanofiltration to retain organic matter (molecular weight 200~1000 Da), adding a centrifugal mother liquor heater to stabilize the crystallization temperature, and designing the last-effect impure salt unit to be able to cut out cleaning, thereby ensuring continuous operation of the system.

[0055] (4) The high-salinity wastewater evaporation crystallization and salt separation system provided in the present application embodiment realizes the cascade utilization of energy by using mechanical compression (MVR) to recycle the secondary steam of the falling film concentration unit and using the secondary steam of the previous effect as the heat source of the subsequent effect in the multi-effect evaporation.

[0056] (5) The high-salinity wastewater evaporation crystallization and salt separation system provided in the embodiment of the present application, the centrifugal mother liquor of the last-effect impure salt unit, the second-effect finished salt unit and the crystallized finished salt unit is respectively transported to the impure salt incineration unit, the organic matter is removed through high-temperature incineration (> 800 DEG C), and after dissolution, it is returned to the nanofiltration unit for recycling treatment, so that the mother liquor is zero discharged.

[0057] (6) The high-salinity wastewater evaporation crystallization and salt separation system provided in the embodiment of the present application, the SO4 2- The enriched liquid and Cl - The double-line parallel processing of the enriched liquid reduces the equipment redundancy of the system, and the salt separation is more thorough.

[0058] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and achieved by the structure particularly pointed out in the written description and the appended drawings.

[0059] The technical solutions of the present application will be further described in detail below with the help of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0060] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the embodiments of the present application, and are used to explain the present application, and do not constitute a limitation on the present application. In the drawings:

[0061] Figure 1 The structure schematic diagram of the high-salinity wastewater evaporation crystallization and salt separation system provided in the embodiment of the present application;

[0062] Figure 2 The analysis instrument monitoring schematic diagram in the embodiment of the present application;

[0063] Figure 3 The Na2SO4-NaCl-H2O ternary phase diagram of 50 DEG C and 70 DEG C in the embodiment of the present application.

[0064] Figure 1 The first nanofiltration unit comprises a first wastewater mixing box 0101, a first nanofiltration water inlet conveying pump 0102 and a first nanofiltration device 0103.

[0065] The first concentrated water preheating unit comprises a first evaporation water inlet tank 0201, a first concentrated brine conveying pump 0202, a first water inlet preheater 0203, a first steam preheater 0204 and a degasser 0205.

[0066] The first falling film concentration unit comprises a first falling film evaporator 0301, a first falling film circulating pump 0302, a first concentrated liquid transfer pump 0303, a first defoamer 0304, a first steam compressor 0305, a first condensed water tank 0306, and a first condensed water delivery pump 0307;

[0067] The first primary evaporation unit comprises a first primary crystallizer 0401, a first primary forced circulation pump 0402, a first primary forced circulation heat exchanger 0403, a first primary condensed water tank 0404, and a first primary condensed water delivery pump 0405;

[0068] The secondary product salt unit comprises a secondary crystallizer 0501, a secondary forced circulation pump 0502, a secondary forced circulation heat exchanger 0503, a first product salt leg 0504, a secondary discharge pump 0505, a secondary hydrocyclone 0506, a secondary crystal slurry tank 0507, a secondary centrifuge 0508, a secondary centrifugal mother liquor tank 0509, a secondary centrifugal mother liquor circulating pump 0510, a secondary centrifugal mother liquor heater 0511, a first crystallization balance tank 0512, and a first product salt packer 0513;

[0069] The last-effect miscellaneous salt unit comprises a last-effect crystallizer 0601, a last-effect forced circulation pump 0602, a last-effect forced circulation heat exchanger 0603, a miscellaneous salt leg 0604, a last-effect discharge pump 0605, a last-effect hydrocyclone 0606, a last-effect crystal slurry tank 0607, a last-effect centrifuge 0608, a last-effect centrifugal mother liquor tank 0609, a last-effect centrifugal mother liquor circulating pump 0610, a miscellaneous salt packer 0611, a first crystallization steam condenser 0612, a first crystallization condensed water tank 0613, and a first crystallization condensed water delivery pump 0614;

[0070] The miscellaneous salt incineration unit comprises a miscellaneous salt incineration unit 0701, a miscellaneous salt dissolving tank 0702, and a miscellaneous salt delivery pump 0703;

[0071] The second nanofiltration unit comprises a second wastewater mixing tank 0801, a second nanofiltration feed water delivery pump 0802, and a second nanofiltration device 0803;

[0072] The second concentrated water preheating unit comprises a second evaporation feed water tank 0901, a second concentrated brine delivery pump 0902, a second feed water preheater 0903, and a second steam preheater 0904;

[0073] The second falling film concentration unit comprises a second falling film evaporator 1001, a second falling film circulating pump 1002, a second concentrated liquid transfer pump 1003, a second defoamer 1004, a second steam compressor 1005, a second condensed water tank 1006, and a second condensed water delivery pump 1007;

[0074] The second primary evaporation unit comprises a second primary crystallizer 1101, a second primary forced circulation pump 1102, a second primary forced circulation heat exchanger 1103, a second primary condensate tank 1104 and a second primary condensate delivery pump 1105.

[0075] The second secondary effect product salt unit comprises a second secondary crystallizer 1201, a second secondary forced circulation pump 1202, a second secondary forced circulation heat exchanger 1203, a second product salt leg 1204, a second secondary discharge pump 1205, a second secondary hydrocyclone 1206, a second secondary mother liquor tank 1207, a second secondary centrifuge 1208, a second secondary centrifuge mother liquor tank 1209, a second secondary centrifuge mother liquor circulation pump 1210, a second secondary centrifuge mother liquor heater 1211 and a second product salt packer 1212, a crystallization steam condenser 1213, a crystallization condensate tank 1214 and a crystallization condensate delivery pump 1215. DETAILED DESCRIPTION

[0076] Exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood, and the scope of the present disclosure can be accurately conveyed to those skilled in the art.

[0077] In the description of the present disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", "far", "near", "front", "back", 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 purpose of facilitating the description of the present disclosure 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 disclosure. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0078] In the description of the present disclosure, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances.

[0079] Embodiments

[0080] The embodiment of the present application provides a high-salinity wastewater evaporation crystallization and salt separation system, and the technical route is summarized as one-stage nanofiltration pre-concentration, one-stage MVR+multi-effect evaporation crystallization (secondary-effect salt output), miscellaneous salt incineration, two-stage nanofiltration pre-concentration and two-stage MVR+multi-effect evaporation crystallization (final-effect salt output). The structure of the system is shown in the figure, and the system comprises, in sequence, a first nanofiltration unit, a first concentrated water preheating unit, a first falling film concentration unit, a first primary-effect evaporation unit, a secondary-effect product salt unit, a final-effect miscellaneous salt unit, a miscellaneous salt incineration unit, a second nanofiltration unit, a second concentrated water preheating unit, a second falling film concentration unit, a second primary-effect evaporation unit and a crystallization product salt unit. Figure 1

[0081] The secondary-effect product salt unit is used for precipitating divalent product salt, the final-effect miscellaneous salt unit is used for precipitating miscellaneous salt, and the crystallization product salt unit is used for precipitating monovalent product salt.

[0082] 1. The first nanofiltration unit

[0083] The first nanofiltration unit comprises, in sequence, a first wastewater mixing tank 0101, a first nanofiltration water inlet conveying pump 0102 and a first nanofiltration device 0103.

[0084] The inlet of the first wastewater mixing tank 0101 is in communication with the input pipeline of raw water and the retentate outlet of the second nanofiltration device 0803 respectively; the permeate liquid outlet of the first nanofiltration device 103 is in communication with the inlet of the second wastewater mixing tank 0801, and the retentate liquid outlet of the first nanofiltration device 103 is in communication with the first concentrated water preheating unit.

[0085] The raw water and the wastewater on the retentate side of the second nanofiltration device are conveyed to the first wastewater mixing tank 0101, and are conveyed to the first nanofiltration device 0103 by the first nanofiltration water inlet conveying pump 0102 to be differentially intercepted.

[0086] The ion concentration analyzer 0180 and the flow monitor 0190 are arranged on the water inlet side pipeline of the first nanofiltration device 0103, and the ion concentration analyzer 0181 and the flow monitor 0191 are arranged on the wastewater pipeline on the retentate side of the first nanofiltration device 0103. The flow of the water production side and the retentate side is adjusted by pressure monitoring of the first nanofiltration device 0103, so that the wastewater treatment capacity entering the first and second evaporation crystallization is stabilized.

[0087] 2. The first concentrated water preheating unit

[0088] The first concentrated water preheating unit comprises, in sequence, a first evaporation water inlet tank 0201, a first concentrated brine conveying pump 0202, a first water inlet preheater 0203, a first steam preheater 0204 and a degasser 0205.

[0089] ​The inlet of the first evaporation feed water tank 0201 is communicated with the retentate outlet of the first nanofiltration device 103; the bottom outlet of the degasser 0205 is communicated with the lower separation chamber inlet of the first falling film evaporator 0301 of the first falling film concentration unit.

[0090] According to the properties of the wastewater, a corresponding dosing system, such as NaOH, scale inhibitor, etc., is arranged in the first evaporation feed water tank 0201. The second evaporation feed water tank 0901 is generally not provided with a dosing system. The preheating of the concentrated brine is divided into two stages. The first feed water preheater 0203 preheats the feed water by heat exchange with the secondary steam condensate generated by the first falling film evaporator 0301, thereby recovering the heat of the secondary steam condensate. The heat-exchanged condensate can be sent to a sewage treatment front-end tank. The first steam preheater 0204 uses live steam to further heat the water discharged from the first feed water preheater. The heat-exchanged live steam condensate is drained and then collected in a steam condensate tank for reuse. The heated brine is sent to the degasser 0205.

[0091] The cold and hot medium inlet and outlet main pipelines of the first feed water preheater 0203 are respectively provided with local and online temperature instruments. The temperature regulating valve is arranged at the hot medium inlet of the first steam preheater 0204, and the local and online temperature instruments 0280 are arranged at the cold medium outlet, which are connected to the temperature regulating valve to realize interlocking control.

[0092] The degasser 0205 is used to remove the residual oxygen and carbon dioxide in the feed water. If the carbon dioxide is not fully removed before entering the first falling film evaporator 0301, the carbon dioxide will accumulate on the tube side of the heater in the falling film evaporator, blocking a part of the heat exchange area and reducing the heat exchange efficiency, thereby increasing the system energy consumption. In addition, if there is oxygen in the feed water, it may also cause corrosion to the wet metal material in the falling film evaporator. By removing the carbon dioxide and oxygen in the water through the degasser, the dissolved oxygen is removed to below 20 ppb before entering the first falling film evaporator 0301, thereby preventing corrosion of the equipment.

[0093] The preheated wastewater is sprayed from the top of the degasser 0205. The water flowing down from the top is dispersed. The live steam enters the degasser from the bottom in a countercurrent flow, has a very large contact area with the water, and the non-condensable gases such as CO2 and O2 are desorbed from the water. These non-condensable gases and a small amount of steam are discharged from the top of the degasser. The non-condensable steam is sent to the VOCs collection main pipe, and the condensate is drained to a ditch after being sealed. Under the action of gravity, the degassed wastewater flows to the first falling film evaporator 0301 by gravity.

[0094] The degasser is provided with a dosing system (static mixer) to achieve the best oxygen removal and decarbonization effect. An adjusting valve is arranged on the live steam pipeline of the degasser, and the adjustment thereof needs to meet the production fluctuation adjustment.

[0095] 3. First falling film concentration unit

[0096] The first falling film evaporator 0301, the first falling film circulating pump 0302, the first concentrated liquid transfer pump 0303, the first demister 0304, the first steam compressor 0305, the first condensed water tank 0306, and the first condensed water delivery pump 0307.

[0097] The bottom outlet of the degasser 0205 is communicated with the lower separation chamber inlet of the first falling film evaporator 0301, the separation chamber bottom outlet is communicated with the top liquid tank of the first falling film evaporator 0301 through the first falling film circulating pump 0302, and is communicated with the inlet of the first primary crystallizer 0401 through the first concentrated liquid transfer pump 0303.

[0098] The falling film concentration unit adopts the “mechanical steam compression recirculation vertical falling film evaporator technology”. The degassed concentrated brine flows to the lower separation chamber of the first falling film evaporator 0301 by gravity, mixes with the concentrated liquid, and is delivered to the liquid tank above the falling film tube by the first falling film circulating pump 0302, flows radially through the upper liquid distribution device, and then falls into the lower water distribution tray to uniformly distribute the concentrated water to the top of the heat exchange tube. The two-stage water distribution system can eliminate the radial flow of the recirculated concentrated water, and then uniformly distribute the concentrated water to the top of the heat exchange tube plate through the lower water distribution tray, and a cyclone fitting is arranged on each heat exchange tube.

[0099] The steam outlet of the separation chamber is communicated with the upper falling film evaporation chamber shell side inlet of the first falling film evaporator 0301 through the first demister 0304 and the first steam compressor 0305.

[0100] The secondary steam separated from the lower separation chamber of the first falling film evaporator passes through the first demister 0304, is increased in temperature and pressure by the first steam compressor 0305, and enters the shell side of the first falling film evaporator 0301 as a system heating source. The latent heat of the secondary steam is used to maximize the energy efficiency of the system. The secondary steam condenses in the shell side of the heat exchange tube of the heating chamber and transfers heat to the liquid film in the tube side. The concentrated brine reaches the boiling point or is very close to the boiling point, and the evaporated secondary steam and the concentrated liquid flow downward along the inner side of the heat exchange tube. This two-phase flow is beneficial to maintaining the liquid film on the inner surface of the heat exchange tube, accelerating the flow of the liquid, generating turbulence, and enhancing heat exchange. The descending concentrated liquid and the secondary steam enter the separation chamber, and under the action of gravity, the concentrated liquid falls to the bottom of the separation chamber, and the steam is discharged through the separation exhaust pipe. The concentrated liquid is recirculated by the falling film circulating pump.

[0101] The shell side outlet of the falling film evaporation chamber is communicated with the shell side inlet of the first water inlet preheater 0203 through the first condensed water tank 0306 and the first condensed water delivery pump 0307.

[0102] The secondary steam in the shell side of the first falling film evaporator heating chamber is condensed and enters the first condensate tank 0306, and is sent to the front-end pool of the sewage treatment plant after recovering heat through the water preheater 0203.

[0103] To ensure stable, efficient and automatic operation of the falling film evaporator, local and online instruments are provided, including related instruments such as separation chamber liquid level, pressure, temperature, density, and heat exchange tube shell layer pressure instrument, to ensure accurate and complete interlocking control. A density meter is provided on the outlet pipeline of the falling film circulating pump for online monitoring. An ion concentration analyzer 0380 is provided on the top inlet side of the first falling film evaporator.

[0104] A first demister 0304 is provided on the inlet pipeline of the first steam compressor 0305, which can effectively reduce the small liquid droplets (not greater than 10 microns) entrained by the secondary steam, and the demisting efficiency should be greater than 99.5%. In the mechanical steam recompression process, it is necessary to remove as much liquid droplets formed by the steam as possible to avoid the deposition of inorganic salts on the rotating impeller of the steam compressor, which may cause excessive vibration due to the imbalance of the impeller, and the salts on the impeller and the compressor shell may cause corrosion, resulting in the service life of the steam compressor.

[0105] A sight glass is provided on the inlet side of the first steam compressor 0305. If point-shaped liquid droplets are visible in the sight glass, it indicates that the steam after passing through the first demister 0304 meets the operating requirements of the steam compressor. If liquid film flows down in the sight glass, it indicates that the liquid droplets entrained in the secondary steam are not completely removed, and the secondary steam does not meet the safe operation requirements of the mechanical steam compressor. At any time, if liquid film is observed flowing down in the sight glass, the demister cleaning program needs to be started, and the demister cleaning frequency needs to be adjusted to ensure the safe operation of the mechanical steam compressor.

[0106] 4. First primary evaporation unit

[0107] The first primary evaporation unit includes a first primary crystallizer 0401, a first primary forced circulation pump 0402, a first primary forced circulation heat exchanger 0403, a first primary condensate tank 0404, and a first primary condensate delivery pump 0405.

[0108] The first primary crystallizer 0401, the first primary forced circulation pump 0402, and the first primary forced circulation heat exchanger 0403 constitute a first evaporation loop, and an ion concentration analyzer 0480 is provided.

[0109] Similarly, the sub-efficiency product salt unit, including the sub-efficiency crystallizer 0501, the sub-efficiency forced circulation pump 0502 and the sub-efficiency forced circulation heat exchanger 0503 constituting the second evaporation loop, is provided with an ion concentration analyzer 0580; the final-efficiency impurity salt unit, including the final-efficiency crystallizer 0601, the final-efficiency forced circulation pump 0602 and the final-efficiency forced circulation heat exchanger 0603 constituting the third evaporation loop, is provided with an ion concentration analyzer 0680; the second primary-efficiency evaporation unit, including the second primary-efficiency crystallizer 1101, the second primary-efficiency forced circulation pump 1102 and the second primary-efficiency forced circulation heat exchanger 1103 constituting the fourth evaporation loop, is provided with an ion concentration analyzer 1180; the second sub-efficiency product salt unit, including the second sub-efficiency crystallizer 1201, the second sub-efficiency forced circulation pump 1202 and the second sub-efficiency forced circulation heat exchanger 1203 constituting the fifth evaporation loop, is provided with an ion concentration analyzer 1280.

[0110] The purpose of the first primary-efficiency evaporation unit is to further increase the concentration of the salt solution, so that the concentration of the separated target salt component reaches or approaches the supersaturation state.

[0111] The concentrated solution of the first falling film evaporator 0301 is transported to the first primary-efficiency crystallizer 0401 by the first concentrated solution transfer pump 0303, and the first primary-efficiency forced circulation heat exchanger 0403 provides heat source by live steam, and the concentrated solution flashes in the first primary-efficiency crystallizer 0401 to produce secondary steam, which provides heat source for the sub-efficiency forced circulation heat exchanger 0503.

[0112] The falling film evaporator adopts forced circulation flash evaporation: the first primary-efficiency forced circulation pump 0402 extracts the liquid from the first primary-efficiency crystallizer 0401 and sends it to the first primary-efficiency forced circulation heat exchanger 0403 for heat exchange, and then recycles it back to the first primary-efficiency crystallizer 0401. The primary-efficiency forced circulation heat exchanger, as the heating equipment of the falling film evaporator, adopts a shell-and-tube heat exchanger. In the forced circulation heat exchanger, the liquid is heated and the temperature rises in the heat exchange tube; the liquid in the discharge pipeline has a certain height, which can provide sufficient static pressure to increase the boiling point of the liquid in the heat exchange tube, and the liquid cannot boil and evaporate in the heat exchange tube. The heated liquid enters the falling film evaporator through the pipeline, and when the circulating liquid in the falling film evaporator rises to a certain level, the hydrostatic pressure decreases, the salt water flashes, and the water forms secondary steam, and the concentration of the liquid increases.

[0113] The condensed liquid in the shell side of the first primary-efficiency forced circulation heat exchanger 0403 after heat exchange is transported to the sub-efficiency centrifugal mother liquor heater 0511 through the first primary-efficiency condensed water tank 0404 and the first primary-efficiency condensed water transfer pump 0405, thereby increasing and stabilizing the temperature of the mother liquor flowing back to the first primary-efficiency crystallizer 0401, and effectively improving the stability of the device operation.

[0114] 5、Sub-efficiency product salt unit

[0115] The secondary effluent crystallizer 0501, the secondary effluent forced circulation pump 0502, the secondary effluent forced circulation heat exchanger 0503, the first finished salt leg 0504, the secondary effluent discharge pump 0505, the secondary effluent hydrocyclone 0506, the secondary effluent slurry tank 0507, the secondary effluent centrifuge 0508, the secondary effluent centrifuge mother liquor tank 0509, the secondary effluent centrifuge mother liquor circulation pump 0510, the secondary effluent centrifuge mother liquor heater 0511, the first crystallization balance tank 0512, and the first finished salt packer 0513.

[0116] In the evaporation process, as the temperature rises, the solubility of sodium sulfate in the mixed salt solution decreases, and the solubility of sodium chloride increases. Therefore, high-temperature evaporation and concentration are used to discharge the material, ensuring that the concentration of the secondary effluent sodium chloride is lower than the saturation solubility of the eutectic point, and sodium sulfate product is precipitated.

[0117] The condensed liquid in the secondary steam heat exchange in the shell side of the secondary effluent forced circulation heat exchanger 0503 is sent to the first crystallization balance tank 0512, and through the pressure difference, it is sent to the first crystallization condensate tank 0613.

[0118] The centrifuge has the functions of crystalline salt concentration and dehydration. The centrifugal dehydrator is fully enclosed, which meets the continuous and uninterrupted operation of feeding, separation, discharge of filtrate and crystalline salt, and can also be operated intermittently.

[0119] The density of the feed liquid of the secondary effluent crystallizer 0501 is monitored and controlled. When the concentration multiple reaches a certain value, part of the feed liquid of the secondary effluent crystallizer is transported to the secondary effluent centrifuge 0508 through the secondary effluent slurry tank 0507. The secondary effluent crystallizer 0501 is provided with a stirrer. The filtrate from the secondary effluent centrifuge 0508 is sent to the secondary effluent centrifuge mother liquor tank 0509 and the secondary effluent centrifuge mother liquor circulation pump 0510, and then returned to the secondary effluent crystallizer 0501 after the temperature is stabilized by the secondary effluent centrifuge mother liquor heater 0511. The secondary effluent centrifuge mother liquor tank 0509 is provided with a centrifuge mother liquor stirrer. The finished salt with a moisture content of less than 10% produced by the secondary effluent centrifuge 0508 is packaged by the first finished salt packer 0513 and transported to the finished salt warehouse for storage and sale.

[0120] To effectively extend the cleaning cycle of the secondary effluent finished salt unit, a small amount of centrifuge mother liquor can be discharged to the mixed salt incineration unit.

[0121] 6, the last effluent mixed salt unit

[0122] The last-effect crystallizer 0601, the last-effect forced circulation pump 0602, the last-effect forced circulation heat exchanger 0603, the miscellaneous salt leg 0604, the last-effect discharge pump 0605, the last-effect hydrocyclone 0606, the last-effect crystal slurry tank 0607, the last-effect centrifuge 0608, the last-effect centrifuge mother liquor tank 0609, the last-effect centrifuge mother liquor circulating pump 0610, the miscellaneous salt packing machine 0611, the first crystallization steam condenser 0612, the first crystallization condensate tank 0613, and the first crystallization condensate delivery pump 0614.

[0123] The density of the feed liquid of the last-effect crystallizer 0601 is monitored and controlled. When the concentration multiple reaches the set value, part of the feed liquid of the last-effect crystallizer 0601 is delivered to the last-effect centrifuge 0608 through the last-effect crystal slurry tank 0607 by the last-effect discharge pump 0605, wherein the last-effect crystal slurry tank 0607 is provided with a stirrer. The filtrate from the last-effect centrifuge 0608 returns to the last-effect crystallizer 0601 through the centrifuge last-effect centrifuge mother liquor tank 0609 and the last-effect centrifuge mother liquor circulating pump 0610, wherein the centrifuge last-effect centrifuge mother liquor tank 0609 is provided with a centrifuge mother liquor stirrer. The miscellaneous salt produced by the last-effect centrifuge 0608 is packed by the miscellaneous salt packing machine 0611, and the miscellaneous salt can be sent to a miscellaneous salt incineration unit or temporarily stored.

[0124] The secondary steam in the shell side of the last-effect forced circulation heat exchanger 0603 is heat-exchanged by the first crystallization steam condenser 0612, and the secondary steam condensate goes to the first crystallization condensate tank 0613. Part of the secondary steam condensate is used as the solvent of the miscellaneous salt after incineration in the miscellaneous salt incineration unit, and the remaining secondary steam condensate returns to the front end of the sewage treatment device.

[0125] A water ring vacuum pump provides a negative pressure environment for the secondary-effect crystallizer 0501 and the last-effect crystallizer 0601, and the vacuum degrees are not less than 70 kPa and 90 kPa, respectively.

[0126] To effectively prolong the cleaning cycle of the last-effect miscellaneous salt unit, a small amount of centrifuge mother liquor is discharged to the miscellaneous salt incineration unit.

[0127] 7. Miscellaneous salt incineration unit

[0128] The miscellaneous salt incineration unit 0701, the miscellaneous salt dissolving tank 0702, and the miscellaneous salt delivery pump 0703 are included.

[0129] The secondary-effect and last-effect small amount of centrifuge mother liquor and the last-effect miscellaneous salt are collectively sent to the miscellaneous salt incineration unit in the evaporation crystallization forced circulation section. After the organic matter is incinerated, the last-effect miscellaneous salt is dissolved in the miscellaneous salt dissolving tank again, the concentration of the miscellaneous salt solution is controlled to be close to the saturation concentration, and the miscellaneous salt solution is sent to the second wastewater mixing tank 0801 through the miscellaneous salt delivery pump 0703.

[0130] 8. Second nanofiltration unit

[0131] The second wastewater mixing tank 0801, the second nanofiltration water inlet conveying pump 0802 and the second nanofiltration device 0803 are sequentially connected.

[0132] The inlet of the second wastewater mixing tank 0801 is also connected with the outlet of the salt cake dissolving tank 0702 of the salt cake incineration unit; the permeate liquid outlet of the second nanofiltration device 0803 is connected with the second concentrated water preheating unit.

[0133] The first nanofiltration device permeate side wastewater permeate liquid and the salt cake solution after salt cake incineration are mixed in the second wastewater mixing tank.

[0134] The ion concentration analyzer 0880 and the flow monitor 0890 are arranged on the water inlet side pipeline of the second nanofiltration device 0803; the ion concentration analyzer 0881 and the flow monitor 0891 are arranged on the wastewater pipeline of the permeate side, and the flow of the permeate side and the retention side is adjusted through pressure monitoring of the second nanofiltration device, so as to stabilize the wastewater treatment capacity entering the first and second evaporation crystallization devices.

[0135] 9、Second concentrated water preheating unit

[0136] The second evaporation water inlet tank 0901, the second concentrated brine conveying pump 0902, the second water inlet preheater 0903 and the second steam preheater 0904 are included.

[0137] Compared with the first concentrated water preheating unit, the second evaporation water inlet tank 0901 is not provided with a dosing system. The concentrated brine preheating is also divided into two-stage preheating, the second water inlet preheater 0903 is preheated by heat exchange with the secondary steam condensate generated by the second falling film evaporator 0904, the heat of the secondary steam condensate is recovered, and the heat-exchanged condensate can be sent to a sewage treatment front-end pool; the second steam preheater 0904 uses live steam to continue heating the outlet water of the second water inlet preheater 0903, and the live steam condensate is collected in a steam condensate tank after being drained and reused. Compared with the first concentrated water preheating unit, the second concentrated water preheating unit is not provided with a water inlet degasser. The preheated concentrated brine is directly sent to the lower separation chamber of the second falling film evaporator 1001.

[0138] The cold and hot medium inlet and outlet main pipelines of the second water inlet preheater are respectively provided with local and online temperature instruments, the hot medium inlet of the second steam preheater is provided with a temperature regulating valve, and the cold medium outlet is provided with local and online temperature instruments, which realize interlocking control with the temperature regulating valve.

[0139] 10、Second falling film concentration unit

[0140] The second falling film evaporator 1001, the second falling film circulating pump 1002, the second concentrated liquid transfer pump 1003, the second defoamer 1004, the second steam compressor 1005, the second condensate tank 1006 and the second condensate conveying pump 1007 are included.

[0141] The process route of the second falling film concentration unit is the same as that of the first falling film concentration unit, and the salt separation treatment scale needs to be designed according to the device processing capacity and the ion composition of the raw water.

[0142] 11. Second primary evaporation unit

[0143] It includes a second primary crystallizer 1101, a second primary forced circulation pump 1102, a second primary forced circulation heat exchanger 1103, a second primary condensate tank 1104, and a second primary condensate delivery pump 1105.

[0144] The process route of the second primary evaporation unit is the same as that of the first primary evaporation unit, and the purpose is to further increase the concentration of the salt solution, so that the concentration of the target salt component reaches or approaches the supersaturation state.

[0145] The condensate of the live steam in the shell side of the second primary forced circulation heat exchanger 1103 is sent to the second primary condensate tank 1104 after heat exchange, and is delivered to the second secondary centrifugal mother liquor heater 1211 by the second primary condensate delivery pump 1105, thereby improving and stabilizing the temperature of the mother liquor flowing into the second secondary crystallizer 1201, and effectively improving the stability of the device operation.

[0146] 12. Crystalline finished salt unit

[0147] It includes a second secondary crystallizer 1201, a second secondary forced circulation pump 1202, a second secondary forced circulation heat exchanger 1203, a second finished salt leg 1204, a second secondary discharge pump 1205, a second secondary hydrocyclone 1206, a second secondary crystal slurry tank 1207, a second secondary centrifuge 1208, a second secondary centrifugal mother liquor tank 1209, a second secondary centrifugal mother liquor circulating pump 1210, a second secondary centrifugal mother liquor heater 1211, a second finished salt packer 1212, a crystalline steam condenser 1213, a crystalline condensate tank 1214, and a crystalline condensate delivery pump 1215.

[0148] With the progress of the evaporation process, the concentration of sodium chloride reaches the supersaturation state and gradually precipitates. Due to continuous discharge, sodium sulfate does not accumulate in the saturated salt solution, and sodium sulfate does not precipitate, and sodium chloride continues to precipitate.

[0149] The secondary steam in the shell side of the second secondary forced circulation heat exchanger 1203 is cooled by the crystalline steam condenser, and the secondary steam condensate is sent to the crystalline condensate tank 1214, and is returned to the front end of the sewage treatment device by the crystalline condensate delivery pump 1215.

[0150] The density of the feed liquid of the second secondary crystallizer 1201 is monitored and controlled. When the concentration ratio reaches a certain value, part of the feed liquid of the second secondary crystallizer is transported to the second secondary centrifuge 1208 through the second secondary discharge pump 1205 and the second secondary crystal slurry tank 1207, wherein the second secondary crystal slurry tank 1207 is provided with a stirrer. The filtrate from the second secondary centrifuge 1208 is returned to the second secondary crystallizer 1201 after being stabilized in temperature by the second secondary centrifugal mother liquor tank 1209 and the second secondary centrifugal mother liquor circulating pump 1210, wherein the second secondary centrifugal mother liquor tank 1209 is provided with a centrifugal mother liquor stirrer. The finished salt with a water content of less than 10% produced by the second secondary centrifuge 1208 is packaged by the second finished salt packaging machine 1212 and transported to the finished salt warehouse for storage and sale.

[0151] To effectively prolong the cleaning cycle of the secondary finished salt unit, a small amount of centrifugal mother liquor is discharged to the salt cake incineration device.

[0152] In some embodiments, the above system can also be provided with an intelligent control module. On-line ion concentration analyzers (including Cl - , SO4 2- , etc.) and flow meters are installed on the water inlet side, the retention side and the permeate side of the first and second nanofiltration devices to monitor the ion concentration and flow rate in real time. Based on the real-time ion concentration data (such as the SO4 2- / Cl - ratio), the nanofiltration concentrated water diversion ratio is automatically adjusted to optimize the pre-concentration effect.

[0153] The nanofiltration membrane operating pressure and concentrated water yield are dynamically adjusted by pressure sensors to ensure the pre-concentration efficiency (such as SO4 2- retention rate > 95%, Cl - retention rate 20% ~ 40%).

[0154] The Ca 2+ , Mg 2 + ion concentration of the water inlet of the first falling film evaporator 0301 is monitored in real time on the outlet pipeline of the first steam preheater 0204, and the addition of scale inhibitor is automatically triggered. The dissolved oxygen and CO2residue at the outlet of the degasser are also detected in real time to prevent evaporator corrosion and heat exchange efficiency decline.

[0155] Density meters and temperature detectors are arranged on the outlet of the first falling film circulating pump 0302, the first primary forced circulation pipeline (first evaporation loop), the secondary forced circulation pipeline (second evaporation loop) and the last forced circulation pipeline (third evaporation loop) to monitor the solution concentration and supersaturation state. The operating temperature of the evaporator and the discharge frequency of the crystallizer are dynamically adjusted to ensure that the target salt is in its precipitation concentration range.

[0156] The density meter and flow detection are arranged at the outlet of the mixed salt incineration unit, so that the ion concentration of the second nanofiltration device is stably entered.

[0157] The density meter and temperature detection are arranged on the outlet of the second falling film circulating pump 1002, the second primary forced circulating pipeline (the fourth evaporation loop) and the second secondary forced circulating pipeline (the fifth evaporation loop), so as to monitor the solution concentration and the supersaturation state. The evaporation temperature and the crystallizer discharge frequency are dynamically adjusted to ensure that the target salt content is in the concentration interval of salt precipitation.

[0158] Participate Figure 2 As shown in the analysis instrument monitoring schematic diagram.

[0159] All analysis data are integrated through the automatic control instrument monitoring, a dynamic trend graph of the brine concentration is generated, a real-time diagnosis is performed by comparing the ternary phase diagram, and a concentration fluctuation threshold (for example, ±5%) is preset, so that the alarm or adjustment plan is triggered to avoid the evaporation efficiency and product salt purity from being reduced due to the concentration fluctuation. Figure 3

[0160] The embodiment of the present application sets up the concentrated salt solution ion concentration monitoring intelligent control module based on the Internet of Things, adjusts the operation parameters such as the nanofiltration membrane operation pressure, the concentrated water output rate, the falling film evaporator temperature and the crystallizer operation pressure in real time, integrates all analysis data through the automatic control instrument monitoring, generates a dynamic trend graph of the brine concentration, performs a real-time diagnosis by comparing the ternary phase diagram, and presets a concentration fluctuation threshold (about ±5%) to trigger the alarm or adjustment plan, so as to avoid the evaporation efficiency and product salt purity from being reduced due to the concentration fluctuation.

[0161] The high-salt wastewater evaporation and crystallization desalination system provided by the embodiment of the present application is coupled through the triple innovation of “nanofiltration pre-concentration + multi-effect evaporation directional crystallization + mixed salt incineration regeneration”, the resource treatment cost of the high-salt wastewater is effectively reduced, and the resource utilization rate is improved to more than 99.5%. Specifically, the Na2SO4 / NaCl ratio of the concentrated water side of the first nanofiltration device is 12-16, and the NaCl / Na2SO4 ratio of the water production side of the second nanofiltration device is 10-15. The salt concentration of the first and second falling film evaporators is 15%-25%, the salt concentration of the first and second primary evaporators is 30%-35%, the salt concentration of the first secondary product salt unit is 50%-70%, and the salt concentration of the second crystallization product salt unit is 40%-60%.

[0162] Based on the embodiment, after the raw water is mixed with the second nanofiltration concentrated water, ion sorting is realized through the high-pressure nanofiltration membrane (retention rate: SO4 2- >95%, Cl - 20%-40%) to retain organic matter (molecular weight 200-1000 Da) and reduce the evaporation and crystallization scale of divalent ion inorganic salt by 20%-40%.

[0163] ​In the second nanofiltration unit, the first nanofiltration product water is mixed with the post-incineration impure salt solution, and Cl - The main solution is concentrated, providing a basis for crystallization and purification.

[0164] The first-effect crystallizer (0501) operates at high temperature, and uses the characteristic that the solubility of Na2SO4 decreases with increasing temperature to precipitate high-purity sodium sulfate (up to GB / T 6009-2014 Class I first-grade product).

[0165] The impure salt incineration unit incinerates the first-effect product salt unit centrifugal mother liquor, the first-end-effect impure salt unit centrifugal mother liquor, and the impure salt at high temperature, degrades and removes organic matter in the mother liquor and the impure salt, and realizes deep removal of impurities and salt recycling.

[0166] The second-effect crystallizer (1201) continuously discharges to control the concentration of sodium sulfate, so that Cl - The supersaturated sodium chloride (up to GB / T 5462-2015 industrial wet salt premium) is precipitated, and the mother liquor is discharged to the impure salt incineration device.

[0167] The centrifugal mother liquor of the first-effect product salt unit and the second crystallization product salt unit is returned to the crystallizer and stabilized by the heater (0511 / 1211) before the temperature, reducing the instability of the device operation.

[0168] The falling film evaporator uses secondary steam condensate to preheat the inlet water, recover waste heat, compress the secondary steam for the falling film evaporator shell as a heat source, improve energy efficiency, remove O2 to <20ppb, CO2, prevent equipment corrosion and heat exchange efficiency decline (static mixer dosing is required), and realize efficient use and recovery of energy.

[0169] The falling film evaporation unit adopts "forced circulation + cyclone water distribution" design, and the secondary steam is purified by a demister (>99.5% efficiency) and then compressed for reuse, reducing steam consumption.

[0170] The intelligent control system includes real-time monitoring of the monovalent / divalent ion concentration at the nanofiltration inlet / outlet, the pre-concentration split ratio, the falling film evaporator salt concentration, the crystallizer salt concentration, and the unit equipment temperature and pressure, dynamic matching of the ion concentration ternary phase diagram, real-time diagnosis and adjustment of related control parameters. By real-time monitoring of the monovalent / divalent ion concentration at the nanofiltration inlet / outlet, the pre-concentration split ratio, the falling film evaporator salt concentration, the crystallizer salt concentration, and the unit equipment temperature and pressure, dynamic adjustment is made to ensure that the system operation data is stable in the optimal interval, and fluctuations in product purity are avoided.

[0171] The embodiments of the present application are suitable for oil industry wastewater, and can be extended to salt recovery and collaborative treatment of high-salt wastewater in the production process of new energy material preparation, metallurgical wastewater treatment, coal chemical industry and pesticide, etc. Through the innovative mode of'salt resourceization + mother liquor closed loop treatment', the high-salt wastewater treatment is transformed from the traditional high-energy consumption cost center to the resource recovery value center.

[0172] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. The present disclosure is not limited to the precise structures already described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims. Thus, the present application is also intended to include such modifications and variations as fall within the scope of the claims of the present application and their equivalents.

Claims

1. A high-salinity wastewater evaporative crystallization fractionation system, characterized in that, The first nanofiltration unit, the first concentrated water preheating unit, the first falling film concentration unit, the first primary evaporation unit, the secondary product salt unit, the final miscellaneous salt unit, the miscellaneous salt incineration unit, the second nanofiltration unit, the second concentrated water preheating unit, the second falling film concentration unit, the second primary evaporation unit and the crystallization product salt unit are sequentially connected; The secondary product salt unit is used for precipitating divalent product salt, the final miscellaneous salt unit is used for precipitating miscellaneous salt, and the crystallization product salt unit is used for precipitating monovalent product salt.

2. The system of claim 1, wherein, The first nanofiltration unit comprises a first waste water mixing tank 0101 and a first nanofiltration device 0103 connected in series, and the second nanofiltration unit comprises a second waste water mixing tank 0801 and a second nanofiltration device 0803 connected in series. The inlet of the first waste water mixing tank 0101 is connected with the input pipeline of raw water and the outlet of the retentate of the second nanofiltration device 0803, the permeate outlet of the first nanofiltration device 0103 is connected with the inlet of the second waste water mixing tank 0801, and the retentate outlet of the first nanofiltration device 0103 is connected with the first concentrated water preheating unit. The inlet of the second waste water mixing tank 0801 is also connected with the outlet of the miscellaneous salt dissolving tank 0702 of the miscellaneous salt incineration unit. The permeate outlet of the second nanofiltration device 0803 is connected with the second concentrated water preheating unit.

3. The system of claim 2, wherein, The first concentrated water preheating unit comprises a first evaporation water inlet tank 0201, a first water preheater 0203, a first steam preheater 0204 and a degasser 0205 connected in series. The retentate outlet of the first nanofiltration device 0103 is connected with the inlet of the first evaporation water inlet tank 0201. The bottom outlet of the degasser 0205 is connected with the first falling film concentration unit.

4. The system of claim 3, wherein, The first primary evaporation unit comprises a first primary crystallizer 0401 and a first primary forced circulation heat exchanger 0403 constituting a first evaporation loop, the secondary product salt unit comprises a secondary crystallizer 0501 and a secondary forced circulation heat exchanger 0503 constituting a second evaporation loop, the final miscellaneous salt unit comprises a final crystallizer 0601 and a final forced circulation heat exchanger 0603 constituting a third evaporation loop, the second primary evaporation unit comprises a second primary crystallizer 1101 and a second primary forced circulation heat exchanger 1103 constituting a fourth evaporation loop, and the second secondary product salt unit comprises a second secondary crystallizer 1201 and a second secondary forced circulation heat exchanger 1203 constituting a fifth evaporation loop.

5. The system of claim 4, wherein, The first falling film concentration unit comprises a first falling film evaporator 0301, a first falling film circulating pump 0302 and a first concentrated liquid transfer pump 0303. The bottom outlet of the degasser 0205 is connected with the lower separation chamber inlet of the first falling film evaporator 0301, the separation chamber bottom outlet is connected with the top liquid tank of the first falling film evaporator 0301 through the first falling film circulating pump 0302, and connected with the inlet of the first primary crystallizer 0401 through the first concentrated liquid transfer pump 0303.

6. The system of claim 5, wherein, The first falling film concentration unit further comprises a first demister 0304, a first steam compressor 0305, a first condensate tank 0306 and a first condensate pump 0307; The steam outlet of the separation chamber is communicated with the upper falling film evaporation chamber shell side inlet of the first falling film evaporator 0301 through the first demister 0304 and the first steam compressor 0305; The shell side outlet of the falling film evaporation chamber is communicated with the shell side inlet of the first water preheater 0203 through the first condensate tank 0306 and the first condensate pump 0307.

7. The system of claim 5, wherein, The secondary product salt unit further comprises a first product salt leg 0504, a secondary discharge pump 0505, a secondary hydrocyclone 0506, a secondary mother liquor tank 0507, a secondary centrifuge 0508, a secondary centrifuge mother liquor tank 0509, a secondary centrifuge mother liquor circulating pump 0510 and a secondary centrifuge mother liquor heater 0511 which are sequentially communicated; The inlet of the first product salt leg 0504 is communicated with the bottom outlet of the secondary crystallizer 0501, and the outlet of the secondary centrifuge mother liquor heater 0511 is communicated with the second evaporation loop; The secondary product salt unit further comprises a first product salt packer 0513 which is communicated with the secondary centrifuge 0508 and is used for packing the divalent product salt; The outlet of the second evaporation loop is further communicated with the inlet of the final crystallizer 0601 through a transfer pump 0514.

8. The system of claim 7, wherein, The shell side outlet of the first primary forced circulation heat exchanger 0403 is communicated with the shell side inlet of the secondary centrifuge mother liquor heater 0511.

9. The system of claim 7, wherein, The secondary centrifuge mother liquor tank 0509 is further communicated with the waste salt incineration unit through the secondary centrifuge mother liquor circulating pump 0510; The bottom outlet of the lower separation chamber of the first falling film evaporator 0301 is communicated with the bottom inlet of the first product salt leg 0504.

10. The system of claim 9, wherein, The final waste salt unit is provided in a cutout manner.

11. The system of claim 5, wherein, The final waste salt unit further comprises a waste salt leg 0604, a final discharge pump 0605, a final hydrocyclone 0606, a final mother liquor tank 0607, a final centrifuge 0608, a final centrifuge mother liquor tank 0609 and a final centrifuge mother liquor circulating pump 0610 which are sequentially communicated; The inlet of the waste salt leg 0604 is communicated with the bottom outlet of the final crystallizer 0601, and the outlet of the final centrifuge mother liquor tank 0609 is communicated with the third evaporation loop through the final centrifuge mother liquor circulating pump 0610; The final waste salt unit further comprises a waste salt packer 0611 which is communicated with the final centrifuge 0608 and is used for packing the waste salt.

12. The system of claim 11, wherein, The final centrifuge mother liquor tank 0609 is further communicated with the waste salt incineration unit through the final centrifuge mother liquor circulating pump 0610; The bottom outlet of the lower separation chamber of the first falling film evaporator 0301 is communicated with the bottom inlet of the waste salt leg 0604.

13. The system of claim 4, wherein, The second concentrated water preheating unit comprises a second evaporation water inlet tank 0901, a second water preheater 0903 and a second steam preheater 0904 which are sequentially communicated; The permeate outlet of the second nanofiltration device 0803 is communicated with the inlet of the second evaporation water inlet tank 0901; The shell side outlet of the first falling film evaporator 0301 is communicated with the shell side inlet of the first water preheater 0203. The outlet of the second steam preheater 0904 is communicated with a second falling film concentration unit.

14. The system of claim 13, wherein, The second falling film concentration unit comprises a second falling film evaporator 1001, a second falling film circulating pump 1002 and a second concentrated liquid transfer pump 1003. The bottom outlet of the lower separation chamber of the second falling film evaporator 1001 is communicated with the top liquid tank of the second falling film evaporator 1001 through the second falling film circulating pump 1002, and is communicated with the second primary effect crystallizer 1101 through the second concentrated liquid transfer pump 1003.

15. The system of claim 14, wherein, The second falling film concentration unit further comprises a second condensed water tank 1006 communicated with the shell side outlet of the upper falling film evaporation chamber of the second falling film evaporator 1001, and the outlet of the second condensed water tank 1006 is communicated with the shell side inlet of the second water preheater 0903. The second falling film concentration unit further comprises a second demister 1004 and a second steam compressor 1005 communicated with the steam outlet of the lower separation chamber of the second falling film evaporator 1001 in sequence, and the outlet of the second steam compressor 1005 is communicated with the shell side inlet of the upper falling film evaporation chamber of the second falling film evaporator 1001.

16. The system of claim 14, wherein, The second secondary effect finished salt unit further comprises a second finished salt leg 1204, a second secondary effect discharge pump 1205, a second secondary effect hydrocyclone 1206, a second secondary effect crystal slurry tank 1207, a second secondary effect centrifuge 1208, a second secondary effect centrifugal mother liquor tank 1209, a second secondary effect centrifugal mother liquor circulating pump 1210 and a second secondary effect centrifugal mother liquor heater 1211 communicated in sequence. The inlet of the second finished salt leg 1204 is communicated with the bottom outlet of the second secondary effect crystallizer 1201, and the outlet of the second secondary effect centrifugal mother liquor heater 1211 is communicated with the fifth evaporation loop. The second secondary effect finished salt unit further comprises a second finished salt packer 1212 communicated with the second secondary effect centrifuge 1208 for packing monovalent finished salt. The outlet of the fourth evaporation loop is communicated with the inlet of the fifth evaporation loop.

17. The system of claim 16, wherein, The shell side outlet of the second primary effect forced circulation heat exchanger 1103 is communicated with the shell side inlet of the second secondary effect centrifugal mother liquor heater 1211.

18. The system of claim 16, wherein, The outlet of the second secondary effect centrifugal mother liquor tank 1209 is further communicated with the miscellaneous salt incineration unit.

19. The system of claim 4, wherein, The steam outlet of the first primary effect crystallizer 0401 is communicated with the shell side inlet of the secondary effect forced circulation heat exchanger 0503, and the shell side outlet is communicated with the first crystallization condensed water tank 0613; The steam outlet of the secondary effect crystallizer 0501, the steam outlet of the last effect crystallizer 0601 and the shell side outlet of the last effect forced circulation heat exchanger 0603 are all communicated with the inlet of the first crystallization condensed water tank 0613; The steam outlet of the second primary effect crystallizer 1101 is communicated with the shell side inlet of the second secondary effect forced circulation heat exchanger 1203, and the shell side outlet is communicated with the crystallization condensed water tank 1214, and the steam outlet of the second secondary effect crystallizer 1201 is communicated with the crystallization condensed water tank 1214.

20. The system of claim 19, wherein, The miscellaneous salt incineration unit comprises a miscellaneous salt incineration unit 0701 and a miscellaneous salt dissolving tank 0702 communicated. The outlet of the first crystallization condensate tank 0613 is communicated with the inlet of the salted water dissolving tank 0702.

21. The system of claim 20, wherein, The intelligent control module is further included for monitoring data through the self-control instrument, generating a dynamic trend spectrum of the brine concentration, diagnosing through a ternary phase diagram, and intelligently adjusting control parameters in real time according to preset concentration fluctuation thresholds and PID parameters.

22. A method for evaporation, crystallization, and salt separation of high-salt wastewater, characterized in that, The method comprises evaporating and crystallizing raw water by using the high-salinity wastewater evaporation crystallization and salt separation system according to any one of claims 1-21.

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