Sewage treatment system and method for coupling solar heat collection and MVR evaporative crystallization

Abstract

The invention discloses a sewage treatment system and method coupling solar heat collection and MVR evaporative crystallization, and the sewage treatment system comprises a heat storage system and a heat exchange system, and also comprises a solar heat collection system, an evaporation device, a vapor compressor device and a salt separation system; the solar heat collection system is connected with the heat storage system, the heat storage system is connected with the heat exchange system, and the evaporation device is communicated with the heat exchange system, the steam compressor device and the salt separation system. A flash evaporation device and a falling film evaporator are arranged in the evaporation device; and a centrifugal machine is arranged in the salt separation system. The overall power consumption of the sewage treatment system is reduced, indirect carbon emission in the sewage treatment process is reduced, meanwhile, due to direct utilization of solar heat energy, the conversion link from heat energy to electric energy and then to heat energy is reduced, process loss is reduced, the utilization efficiency of primary energy is improved, and energy conservation and emission reduction are achieved. And more possibilities are provided for more efficiently and cleanly realizing salt-containing sewage treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a wastewater treatment system and method that couples solar thermal collection with MVR evaporation and crystallization. Background Technology

[0002] With the increasing depth of industrialization in modern society, the volume of industrial wastewater awaiting treatment is rising year by year. Direct discharge of industrial wastewater will cause serious pollution to surface water, groundwater, and soil, damaging the ecological environment. Furthermore, the composition of industrial wastewater is complex, containing suspended solids, some dissolved gases, and various mineral salt ions. The presence of mineral components, in particular, makes it difficult for the wastewater to be reused in boilers and to meet discharge standards, significantly increasing the pressure on environmental protection and wastewater treatment. Therefore, developing efficient and low-carbon saline wastewater treatment processes is of great significance for improving wastewater treatment effectiveness and economic benefits.

[0003] For the efficient treatment of high-concentration brine, thermal methods are mainly employed, using evaporation and crystallization to remove inorganic salt ions and recover purified water. Currently, evaporation crystallization technologies mainly include mechanical compression evaporation (MVR), multi-effect evaporation (MED), and vapor compression distillation (MVC). Among these, the MVR process can recover the latent heat of vaporization for use in the evaporation of wastewater and has been gradually applied in the concentration treatment of feed liquids and wastewater in industries such as biochemistry and chemical engineering. MVR is a process for evaporating saline wastewater developed based on MED. It is an advanced energy-saving technology that reduces the energy demand of the evaporation and concentration process by reusing the latent heat of condensation of the secondary steam generated during the evaporation and concentration process. Its principle is that within the evaporator system, under a certain pressure, a steam compressor compresses the non-condensable gas generated during the preheating process in the heat exchanger and the water vapor generated during evaporation, thereby increasing the steam temperature and thermal quality. The heat generated by compressing the secondary steam is also reused multiple times within the evaporator, raising the system temperature by 5-20°C and significantly reducing the evaporator's consumption of fresh steam. This improves thermal efficiency and reduces energy consumption. As a highly efficient energy-saving technology, it has a high rate of heat energy recovery and utilization of secondary steam. In actual production applications, the low-pressure, low-temperature secondary steam evaporated from the production medium is mechanically compressed to increase the steam's pressure, enthalpy, and temperature. The compressed steam then enters the evaporator to exchange heat with the production medium and condense. While generating secondary steam, the production medium is evaporated and concentrated, thus ensuring that the latent heat of steam in the system is fully utilized.

[0004] However, since MVR (Mechanical Vapor Recompression) for saline wastewater treatment primarily consumes electricity, the increasing volume of high-salinity wastewater necessitates large-scale mechanical recompression, leading to significant power load consumption and hindering long-term sustainable development. Furthermore, it is detrimental to improving primary energy efficiency. Solar energy, a renewable energy source with immense potential, is abundant, widely distributed, and clean. By converting solar energy into heat through solar thermal utilization technology, it can directly provide the heat required for the evaporation treatment of saline wastewater. Therefore, there is an urgent need to develop advanced solar thermal collection and MVR evaporation crystallization systems for high-salinity wastewater treatment to further reduce power load consumption and improve primary energy efficiency.

[0005] Publication No. CN108622971B discloses a solar-powered MVR wastewater treatment system, belonging to the field of energy-saving and environmental protection technology. It employs a separation subsystem and a waste heat recovery subsystem to achieve a two-stage preheating / cooling process. Combined with preheating via a solar energy subsystem and steam compression recovery in the concentration and drying subsystems, it maximizes waste heat recovery and effectively reduces costs. The concentration and drying subsystems effectively separate solids, purified water, and waste gas from wastewater, fully leveraging the advantages of heating and distillation methods for wastewater treatment. Based on different saturated steam pressures and temperatures, a stepped utilization method is adopted to reduce external steam consumption and ensure the stable and continuous operation of both MVR systems. It has the advantages of simple structure, ease of implementation, and low investment and operating costs. Its energy-saving and environmental protection effects are extremely significant, and it can be widely applied to the treatment of various types of wastewater and sludge, as well as other fields with similar processes such as food and feed, chemical, and pharmaceutical industries.

[0006] This existing technology utilizes solar energy, but it suffers from problems such as a short concentration process, low wastewater concentration, and low treatment efficiency.

[0007] Publication No. CN216114738U discloses a solar collector for MVR evaporation process, including a forced circulation pump. The inlet of the forced circulation pump is connected to a high-salt water pipeline, the outlet of the forced circulation pump is connected to the solar collector, the solar collector is connected to a heat exchanger pipeline, the heat exchanger is connected to the separator inlet, the separator's circulating material outlet is connected to the forced circulation pump inlet, the separator's outlet is connected to a discharge pump, and the separator's material thickening circulation inlet is connected to the discharge pump outlet pipeline. This utility model applies a flat-plate solar collector to the MVR evaporation crystallization process. Solar radiation passes through a transparent cover plate and is projected onto the heat-absorbing plate, where it is absorbed and converted into heat energy. This heat is then transferred to the heat transfer medium within the heat-absorbing plate, raising its temperature. This heat serves as the useful energy output of the collector, utilizing solar energy to heat the material, achieving energy conservation and emission reduction, and lowering operating costs.

[0008] This existing technology utilizes solar energy, but it suffers from problems such as insufficient heat utilization, short concentration process, low wastewater concentration, and low treatment efficiency.

[0009] Publication (Announcement) No.: CN206915795U, discloses a wastewater treatment device based on an MVR evaporator, including a wastewater tank, a feed pump, a preheater, a water storage tank, a condenser, a controller, a compressor, a steam-water separator, a pressure relief valve, an energy storage tank, an evaporator, a discharge valve, and a centrifuge. The wastewater tank is connected to the feed pump via a pipeline; the preheater is connected to the feed pump via a pipeline; the water storage tank is connected to the condenser via a pipeline; the controller is connected to the feed pump or the compressor via a cable; the compressor is installed on the side of the steam-water separator; the steam-water separator is installed on the top of the evaporator.

[0010] This existing technology utilizes solar energy, but it suffers from problems such as insufficient heat utilization, short concentration process, low wastewater concentration, and low treatment efficiency.

[0011] In summary, the technical solutions, technical problems to be solved, and beneficial effects of the above-disclosed technologies are all different from those of the present invention. Regarding the more technical features, technical problems to be solved, and beneficial effects of the present invention, the above-disclosed technical documents do not provide any technical inspiration. Summary of the Invention

[0012] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a wastewater treatment system and method that couples solar thermal collection with MVR evaporation crystallization. This system enables the evaporation crystallization desalination of high-salt wastewater using solar energy, thereby achieving the recovery of clean water and inorganic salt resources. Simultaneously, it introduces solar energy for heat supply, reducing indirect fossil energy consumption and carbon emissions during the treatment process.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization includes a heat storage system, a heat exchange system, a solar thermal collection system, an evaporation device, a steam compressor device, and a salt separation system. The solar thermal collection system is connected to the heat storage system, the heat storage system is connected to the heat exchange system, and the evaporation device is connected to the heat exchange system, the steam compressor device, and the salt separation system respectively. The evaporation device is equipped with a flash evaporator and a falling film evaporator. The salt separation system is equipped with a centrifuge.

[0015] Furthermore, the solar thermal system includes at least two sets of collector strings, which are connected in parallel.

[0016] Specifically, the collector string includes a collector tube and at least two collector mirrors, the collector tube passes through at least two collector mirrors, and heat-conducting oil is disposed inside the collector tube;

[0017] Specifically, the upper ends of the heat collection tubes of all the collector strings are connected to the first heat transfer pipeline in parallel, and the lower ends are connected to the second heat transfer pipeline in parallel. The first heat transfer pipeline is connected to the heat exchange system.

[0018] Furthermore, the collector string is equipped with a solar tracking system.

[0019] Furthermore, the heat storage system may include a thermally conductive oil tank and a cold thermally conductive oil tank;

[0020] Specifically, the inlet and outlet of the thermally conductive oil tank are respectively connected to the first heat transfer pipeline, and a first flow distribution device and a second flow distribution device are respectively provided at the interface.

[0021] Specifically, the outlet of the cold heat transfer oil tank is connected to the second heat transfer pipeline, and the inlet of the cold heat transfer oil tank is connected to the heat exchange system through the third heat transfer pipeline.

[0022] Specifically, the second heat transfer pipeline is equipped with a flow pump.

[0023] Furthermore, the heat exchange system includes a first heat exchanger, a second heat exchanger, and a third heat exchanger;

[0024] Specifically, the first heat exchanger is equipped with a first sewage pipe and a first clean water pipe;

[0025] Specifically, the second heat exchanger is equipped with a second sewage pipe and a second clean water pipe;

[0026] Specifically, the third heat exchanger is equipped with a third sewage pipe and a heat exchange pipe;

[0027] Specifically, the heat exchange tube is connected to the first heat transfer pipe and the third heat transfer pipe;

[0028] Specifically, the first sewage pipe, the second sewage pipe, and the third sewage pipe are connected in sequence;

[0029] Specifically, the first clean water pipe and the second clean water pipe are connected in sequence.

[0030] Furthermore, the evaporation system includes a flash evaporator, a falling film evaporator, a gas-liquid separator, a transfer pump, and a circulation pump;

[0031] Specifically, the inlet of the flash evaporator is connected to the outlet of the third sewage pipe through the first high-temperature sewage pipe, and the steam outlet of the flash evaporator is connected to the steam compressor device through the first steam delivery pipe.

[0032] Specifically, a third flow distribution device is provided on the first steam conveying pipeline, and the third flow distribution device is connected to the input end of the second clean water pipe through the second steam conveying pipeline;

[0033] Specifically, the concentrated wastewater outlet of the flash evaporator is connected to a transfer pump via a first concentrated wastewater pipeline, and the transfer pump is connected to a circulation pump via a second concentrated wastewater pipeline;

[0034] Specifically, a fourth flow distribution device is installed on the second concentrated wastewater pipeline, and the fourth flow distribution device is connected to the wastewater inlet of the falling film evaporator through the third concentrated wastewater pipeline;

[0035] Specifically, the steam inlet of the falling film evaporator is connected to the steam compressor device through a high-temperature steam pipeline, the condensate outlet of the falling film evaporator is connected to the input end of the first clean water pipe through a first high-temperature condensate pipeline, and the bottom outlet of the falling film evaporator is connected to the inlet of the gas-liquid separation device through a first gas-liquid mixed wastewater pipeline.

[0036] Furthermore, the salt separation system includes a thickener, a centrifuge, and a second circulation pump;

[0037] Specifically, a fifth flow distribution device is provided on the fourth concentrated wastewater pipeline. The fifth flow distribution device is connected to the second circulating pump through the first wastewater mother liquor pipeline. The second circulating pump is connected to the top of the thickener through the second wastewater mother liquor pipeline.

[0038] Specifically, the second sewage mother liquor pipeline is equipped with a sixth flow distribution device, which is connected to the mother liquor outlet of the centrifuge through the third sewage mother liquor pipeline;

[0039] Specifically, the inlet of the centrifuge is connected to the outlet of the thickener through the fifth concentrated wastewater pipeline, the thickener is provided with a mixed salt outlet, and the third concentrated wastewater pipeline is connected to the inlet of the thickener;

[0040] Specifically, a seventh flow distribution device is installed on the first sewage mother liquor pipeline, and the seventh flow distribution device is equipped with a mother liquor output pipe.

[0041] Furthermore, the steam inlet of the steam compressor unit is connected to the first steam pipeline and the second steam pipeline through a mixing device.

[0042] To achieve the above objectives, the present invention adopts the following technical solution:

[0043] A method of using a wastewater treatment system that couples solar thermal collection with MVR evaporation crystallization includes:

[0044] S1. The solar thermal collection system gathers solar rays to generate high-temperature heat energy, and then transmits this high-temperature heat energy to the thermal storage system, or directly uses it as a high-temperature heat source for the heat exchange system.

[0045] S2. The thermal storage system stores excess solar heat and, when needed, supplies this high-temperature heat energy to the heat exchange system.

[0046] S3. The heat exchange system exchanges heat between the incoming sewage and condensate in stages to recover the waste heat of the condensate and output clean water resources.

[0047] S4. The evaporation unit separates saline wastewater by flash evaporation and falling film evaporation, then performs gas-liquid separation, and sends the secondary steam to the steam compressor unit and the concentrated wastewater to the salt separation system.

[0048] S5. The steam compressor unit mechanically compresses the low-pressure, low-temperature secondary steam obtained from evaporation to increase the steam's pressure, enthalpy, and temperature.

[0049] S6. The salt separation system separates the solid crystalline salt from the concentrated wastewater solution, and the crystalline inorganic salt is recycled as a mixed resource.

[0050] Furthermore, when the flow rate of high-temperature heat transfer oil output from the heat collection system exceeds the rated demand of the heat exchange system, the excess heat transfer oil is diverted to the heat tank for temporary storage through the first flow distribution device; when the flow rate of high-temperature heat transfer oil output from the heat collection system is less than the rated demand of the heat exchange system, an appropriate amount of high-temperature heat transfer oil stored in the heat tank is transferred to the heat exchange system through the second flow distribution device to meet the rated heat exchange demand of the heat exchange system.

[0051] The flow rate is matched with the solar radiation intensity so that the solar thermal collector system can obtain a basically stable heat transfer oil temperature under different solar radiation conditions, thus promoting the stable operation of the heat exchange system and the evaporation system.

[0052] Furthermore, a large amount of steam evaporated in the flash evaporator is partially transported to the heat exchange system for wastewater heating, and partially transported to the steam compressor unit for recompression and reuse. The unevaporated concentrated saline wastewater will be pressurized by the transfer pump and transported together with the circulating concentrated wastewater pressurized by the circulation pump to the falling film evaporator for heating and evaporation.

[0053] The heating source for the falling film evaporator is high-temperature steam from the steam compressor. The heating steam from the falling film evaporator condenses into clean water, which enters the heat exchange system. The heated wastewater enters the gas-liquid separator in the form of a gas-liquid mixture for further depressurization evaporation and gas-liquid separation.

[0054] Furthermore, the concentrated wastewater from the evaporation system first enters the thickener, where it settles to enrich the crystallized salt in the solution at the bottom of the thickener, while the upper layer is a clear wastewater without crystallized salt. The high-solids solution at the bottom of the thickener, enriched with crystallized salt, is then transported to a centrifuge for solid-liquid separation.

[0055] The wastewater overflowing from the upper layer of the thickener and the wastewater separated by the centrifuge are collected and then pressurized by the circulating pump. Part of the wastewater is recycled back to the evaporation system to participate in the evaporation process, and part of it is output as concentrated mother liquor. The inorganic salts separated by the centrifuge are output as mixed salts.

[0056] Compared with the prior art, the present invention has the following advantages:

[0057] 1. This invention can utilize the convergence of solar rays to assist in obtaining high temperatures for heating, evaporating, and crystallizing saline wastewater. Furthermore, due to the addition of a solar thermal storage system, the system can maintain continuous operation under various meteorological conditions.

[0058] 2. The proposed scheme reduces the overall power consumption of the wastewater treatment system and reduces indirect carbon emissions during the wastewater treatment process. At the same time, the direct utilization of solar thermal energy reduces the conversion steps from heat energy to electricity and back to heat energy, reducing process losses and improving the utilization efficiency of primary energy. This provides more possibilities for achieving more efficient and cleaner saline wastewater treatment. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the structure of a wastewater treatment system that couples solar thermal collection with MVR evaporation and crystallization according to the present invention;

[0060] In the diagram: A - Parabolic trough solar collector system; B - Thermal storage system; C - Heat exchange system; D - Evaporator; E - Steam compressor unit; F - Salt separation system;

[0061] a-Incoming wastewater; b-Outgoing clean water; c-Concentrated mother liquor; d-Mixed salt;

[0062] 1-Heat collector mirror; 2-Heat collector tube; 3-First flow distribution device; 4-Second flow distribution device; 5-Hot heat transfer oil tank; 6-Cold heat transfer oil tank; 7-Flow pump; 8-First heat exchanger; 9-Second heat exchanger; 10-Third heat exchanger; 11-Flash evaporator; 12-Third flow distribution device; 13-Mixing device; 14-Transfer pump; 15-Falling film evaporator; 16-Gas-liquid separator; 17-First circulating pump; 18-Thickener; 19-Centrifuge; 20-Second circulating pump; 21-Fifth flow distribution device; 22-Sixth flow distribution device; 23-Seventh flow distribution device. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] Example 1:

[0065] To address the issues of high energy consumption and substantial direct or indirect carbon emissions in existing wastewater treatment processes, this disclosure provides a wastewater treatment system that couples solar thermal collection with MVR evaporation crystallization. This system enables the evaporation and crystallization desalination of high-salinity wastewater using solar energy, thereby recovering both clean water and inorganic salt resources. Simultaneously, the introduction of solar energy for heat supply reduces indirect fossil fuel consumption and carbon emissions during the treatment process. A detailed description of the specific solution follows.

[0066] Please see Figure 1 The present invention provides a wastewater treatment system that couples solar thermal collection with MVR evaporation and crystallization, including a solar thermal collection system A, a thermal storage system B, a heat exchange system C, an evaporation device D, a steam compressor device E, and a salt separation system F;

[0067] The solar thermal collector system A is used to collect solar rays to generate high-temperature heat energy and transport the high-temperature heat energy to the thermal storage system B, or directly use it as a high-temperature heat source in the heat exchange system C.

[0068] The heat storage system B is used to store excess solar heat and, when needed, to supplement and transport the high-temperature heat energy to the heat exchange system C.

[0069] The heat exchange system C is used for the step-by-step heat exchange of incoming sewage a and the waste heat recovery of condensate, and outputs clean water resource b.

[0070] The evaporation device D is used for flash evaporation and falling film evaporation of saline wastewater, and delivers the secondary steam to the steam compressor device E, and delivers the concentrated wastewater to the salt separation system F.

[0071] The steam compressor device E is used to mechanically compress the low-pressure, low-temperature secondary steam obtained from evaporation to increase the steam's pressure, enthalpy, and temperature.

[0072] The salt separation system F is used to separate the crystalline salt solid and the concentrated wastewater solution, and the crystalline inorganic salt is recycled as a mixed resource.

[0073] Example 2:

[0074] Based on Example 1, this example describes in detail the composition of each part of the system.

[0075] Specifically, the solar thermal system A includes at least two sets of collector strings connected in parallel to collect solar radiation into high-temperature heat energy, which is then transported to the thermal storage system B or the heat exchange system C via a heat transfer medium.

[0076] The collector string includes a collector tube 2 and at least two collector mirrors 1. The collector tube 2 passes through at least two collector mirrors 1. The collector tube 2 is filled with heat-conducting oil. The collector tube 2 absorbs the high-temperature heat energy gathered by the collector mirrors 1 and the heat is transferred through the heat-conducting oil.

[0077] The upper ends of the collector tubes 2 of all collector strings are connected to the first heat transfer pipeline in parallel, and the lower ends are connected to the second heat transfer pipeline in parallel. The first heat transfer pipeline is connected to the heat exchange system.

[0078] To ensure efficient heat collection by the collector string, a solar tracking system needs to be installed to promote the full utilization of solar radiation.

[0079] Specifically, the thermal storage system B may include a thermally conductive oil tank 5 and a cold thermally conductive oil tank 6. The inlet and outlet of the thermally conductive oil tank 5 are respectively connected to a first heat transfer pipeline, and a first flow distribution device 3 and a second flow distribution device 4 are respectively installed at the interface to control the flow rate of the thermally conductive oil input to the thermally conductive oil tank 5 and the cold thermally conductive oil tank 6. The outlet of the cold thermally conductive oil tank 6 is connected to a second heat transfer pipeline, and the inlet of the cold thermally conductive oil tank 6 is connected to the heat exchange system through a third heat transfer pipeline. The second heat transfer pipeline is equipped with a flow pump 7 to transport the thermally conductive oil to the solar collector system A and to control the flow rate of the transported cold thermally conductive oil.

[0080] The thermal oil tank 5 stores thermal oil from the solar collector system A in quantities exceeding the rated demand. When solar thermal energy is insufficient, it serves as supplementary heat to drive wastewater evaporation. The outer wall of the thermal oil tank 5 is equipped with insulation material to prevent excessive heat loss from the thermal oil.

[0081] The cold thermal oil tank 6 is used to store the thermal oil released from the heat exchange system C. The outer wall of the cold tank 6 is provided with heat insulation material to prevent a large amount of heat loss from the thermal oil and maintain a basically stable thermal oil temperature, thereby reducing the heat demand of the solar thermal collector system A to heat the thermal oil.

[0082] When the flow rate of high-temperature heat transfer oil output from the heat collection system A exceeds the rated demand of the heat exchange system C, the excess heat transfer oil is diverted to the heat tank 5 for temporary storage through the first flow distribution device 3; when the flow rate of high-temperature heat transfer oil output from the heat collection system A is less than the rated demand of the heat exchange system C, an appropriate amount of high-temperature heat transfer oil stored in the heat tank 5 is transferred to the heat exchange system C through the second flow distribution device 4 to meet the rated heat exchange demand of the heat exchange system C.

[0083] When in use, the flow rate is matched with the solar radiation intensity so that the solar thermal collector system A can obtain a basically stable heat transfer oil temperature under different solar radiation conditions, thus promoting the stable operation of the heat exchange system C and the evaporation system.

[0084] Specifically, the heat exchange system C includes a first heat exchanger 8, a second heat exchanger 9, and a third heat exchanger 10. The first heat exchanger 8 is provided with a first sewage pipe and a first clean water pipe. The second heat exchanger 9 is provided with a second sewage pipe and a second clean water pipe. The third heat exchanger 10 is provided with a third sewage pipe and a heat exchange pipe. The heat exchange pipe is connected to the first heat transfer pipeline and the third heat transfer pipeline. The first sewage pipe, the second sewage pipe, and the third sewage pipe are connected in sequence. The first clean water pipe and the second clean water pipe are connected in sequence.

[0085] The cold stream of the first heat exchanger 8 is the incoming sewage a from the first sewage pipe, and the hot stream is the condensate from the first clean water pipe. The heat exchanger is used for preheating the incoming saline sewage a and recovering part of the waste heat from the condensate. The pure condensate b output from the first heat exchanger also has a certain temperature and high purity, and can be used for boiler feedwater and domestic hot water.

[0086] The cold stream of the second heat exchanger 9 is the saline wastewater entering the second sewage pipe, and the hot stream is a portion of the low-pressure saturated steam from the flash tube 11 in the evaporation system D. This portion of steam becomes condensate after heat exchange and is transported to the first heat exchanger 8 for heating the saline wastewater.

[0087] The cold stream of the third heat exchanger 10 is the saline wastewater entering the third sewage pipe, which is then heated and transported to the evaporation system D; the hot stream is the high-temperature heat transfer oil entering the heat exchanger tube, which is then heated and transported to the cold tank for storage.

[0088] In the heat exchange system C, the incoming sewage a is heated step by step through cascade heat exchange, and some of the waste heat from steam and condensate b is recovered. In addition, through the staged heating of heat transfer oil, steam and condensate, the cascade utilization of high-temperature solar energy is realized, reducing irreversible losses in the energy consumption process, which will help improve the utilization efficiency of solar and electrical energy.

[0089] Specifically, the evaporation system D includes a flash evaporator 11, a falling film evaporator 15, a gas-liquid separator 16, a transfer pump 14, and a circulation pump 17. The inlet of the flash evaporator 11 is connected to the outlet of a third sewage pipe via a first high-temperature sewage pipe. The steam outlet of the flash evaporator 11 is connected to a steam compressor device E via a first steam delivery pipe. A third flow distribution device 12 is installed on the first steam delivery pipe. The third flow distribution device 12 is connected to the inlet of a second clean water pipe via a second steam delivery pipe. The concentrated sewage outlet of the flash evaporator 11 is connected to the transfer pump 14 via a first concentrated sewage pipe. The transfer pump 14 is connected to the circulation pump 17 via a second concentrated sewage pipe. A fourth flow distribution device is installed on the second concentrated sewage pipe. The apparatus includes a fourth flow distribution device connected to the wastewater inlet of a falling film evaporator 15 via a third concentrated wastewater pipe; a steam inlet of the falling film evaporator 15 connected to a steam compressor device E via a high-temperature steam pipe; a condensate outlet of the falling film evaporator 15 connected to the input end of a first clean water pipe via a first high-temperature condensate pipe; a bottom outlet of the falling film evaporator 15 connected to the inlet of a gas-liquid separation device 16 via a first gas-liquid mixed wastewater pipe; a gas outlet of the gas-liquid separation device 16 connected to a steam compressor device E via a third steam pipe; a liquid outlet of the gas-liquid separation device 16 connected to a salt separation system F via a third concentrated wastewater pipe; and a bottom outlet of the gas-liquid separation device 16 connected to a circulating pump 17 via a fourth concentrated wastewater pipe.

[0090] The flash evaporator 11 is used to perform depressurized flash evaporation of saline wastewater from the heating system. A large amount of steam evaporated is partially transported to the heating system for wastewater heating and partially transported to the steam compressor for recompression and reuse. The unevaporated concentrated saline wastewater is pressurized by the transfer pump 14 and transported together with the pressurized circulating concentrated wastewater by the circulation pump 17 to the falling film evaporator 15 for heating and evaporation.

[0091] The falling film evaporator 15 is used for heating and evaporating concentrated saline wastewater. Its heating heat source is high-temperature steam from the steam compressor E. The falling film evaporator 15 enhances the heat transfer effect through the film distribution of saline wastewater. The heating steam of the evaporator condenses into clean water and enters the heat exchange system C. The heated wastewater enters the gas-liquid separator 16 in the form of gas-liquid mixture for further depressurization evaporation and gas-liquid separation.

[0092] The gas-liquid separator 16 is used to concentrate saline wastewater and separate it from steam. The obtained secondary steam is sent to the steam compressor E to produce heating steam for the falling film evaporator. In addition, the separated liquid is saline wastewater that is concentrated again. Part of it is sent to the falling film evaporator 15 via the circulation pump 17 to participate in heating and evaporation; the other part is sent to the salt separation system F for crystallization salt separation.

[0093] Specifically, the salt separation system F includes a thickener 18, a centrifuge 19, and a second circulation pump 20. A fifth flow distribution device 21 is installed on the fourth concentrated wastewater pipeline. The fifth flow distribution device 21 is connected to the second circulation pump 20 through a first wastewater mother liquor pipeline. The second circulation pump 20 is connected to the top of the thickener 18 through a second wastewater mother liquor pipeline. A sixth flow distribution device 22 is installed on the second wastewater mother liquor pipeline. The sixth flow distribution device 22 is connected to the mother liquor outlet of the centrifuge 19 through a third wastewater mother liquor pipeline. The inlet of the centrifuge 19 is connected to the outlet of the thickener 18 through the fifth concentrated wastewater pipeline. The thickener 18 is provided with a mixed salt outlet. The third concentrated wastewater pipeline is connected to the inlet of the thickener 18. A seventh flow distribution device 23 is installed on the first wastewater mother liquor pipeline. The seventh flow distribution device 23 is provided with a mother liquor output pipe for outputting concentrated mother liquor c.

[0094] The concentrated wastewater from evaporation system D first enters thickener 18, where sedimentation occurs, resulting in the enrichment of crystalline salts in the solution at the bottom of thickener 18, while the upper layer is a clear wastewater solution free of crystalline salts. The high-solids solution enriched with crystalline salts at the bottom of the thickener is then transported to a centrifuge for solid-liquid separation. This process, due to the increased solids content of the solution from the thickener 18, effectively improves the separation efficiency of the centrifuge.

[0095] The wastewater overflowing from the upper layer of the thickener 18 and the wastewater separated by the centrifuge 19 are collected and then pressurized by the circulation pump 20. Part of the wastewater is recycled back to the evaporation system to participate in the evaporation process, and part of it is output as concentrated mother liquor c. The inorganic salts separated by the centrifuge are output as mixed salt d.

[0096] Specifically, the steam inlet of the steam compressor device E is connected to the first steam pipeline and the second steam pipeline through the mixing device 13.

[0097] It should be noted that all flow distribution devices and mixing devices 13 can adjust the flow between each pair of connected pipes and can also completely connect the connected pipes.

[0098] It should also be noted that the solar tracking system, flash evaporator 11, transfer pump 14, falling film evaporator 15, gas-liquid separation device 16, first circulation pump 17, thickener 18, centrifuge 19, and second circulation pump 20 are all prior art, as those skilled in the art are aware of. The contribution of this invention is to combine them together.

[0099] Example 3:

[0100] This embodiment provides a specific method for using this system:

[0101] S1. When the flow rate of high-temperature heat transfer oil output from the heat collection system A is greater than the rated demand of the heat exchange system C, the excess heat transfer oil is diverted to the heat tank 5 for temporary storage through the first flow distribution device 3; when the flow rate of high-temperature heat transfer oil output from the heat collection system A is less than the rated demand of the heat exchange system C, an appropriate amount of high-temperature heat transfer oil stored in the heat tank 5 is transferred to the heat exchange system C through the second flow distribution device 4 to meet the rated heat exchange demand of the heat exchange system C.

[0102] The flow rate is matched with the solar radiation intensity so that the solar thermal collector system A can obtain a basically stable heat transfer oil temperature under different solar radiation conditions, thus promoting the stable operation of the heat exchange system C and the evaporation system.

[0103] S2. In the heat exchange system C, the incoming sewage a is heated step by step through cascade heat exchange, some of the waste heat from steam and condensate b is recovered, and clean water resources are output.

[0104] S3. A large amount of steam evaporated in the flash evaporator 11 is partially transported to the heat exchange system C for wastewater heating, and partially transported to the steam compressor unit E for recompression and reuse. The unevaporated concentrated saline wastewater will be pressurized by the transfer pump 14 and transported together with the circulating concentrated wastewater pressurized by the circulation pump 17 to the falling film evaporator 15 for heating and evaporation.

[0105] The heating source of the falling film evaporator 15 is high-temperature steam from the steam compressor E. The heating steam of the falling film evaporator 15 is condensed into clean water and enters the heat exchange system C. The heated wastewater enters the gas-liquid separator 16 in the form of gas-liquid mixture for further depressurization evaporation and gas-liquid separation.

[0106] S4. The steam compressor unit mechanically compresses the low-pressure, low-temperature secondary steam obtained from evaporation to increase the steam's pressure, enthalpy, and temperature.

[0107] S5. The concentrated wastewater from the evaporation system D first enters the thickener 18, where it settles to enrich the crystallized salt in the solution at the bottom of the thickener 18, while the upper layer is a clear wastewater without crystallized salt. The high solids solution enriched with crystallized salt at the bottom of the thickener is then transported to a centrifuge for solid-liquid separation.

[0108] The wastewater overflowing from the upper layer of the thickener 18 and the wastewater separated by the centrifuge 19 are collected and then pressurized by the circulation pump 20. Part of the liquid is recycled back to the evaporation system to participate in the evaporation process, and part of it is output as concentrated mother liquor c. The inorganic salts separated by the centrifuge are output as mixed salt d.

[0109] In summary, the wastewater treatment system coupled with solar thermal collection and MVR evaporation crystallization provided by this disclosure can utilize the convergence of solar rays to obtain high temperatures for heating, evaporating, and crystallizing saline wastewater. Furthermore, the addition of a solar thermal storage system allows the system to operate continuously under various weather conditions. This solution reduces the overall power consumption of the wastewater treatment system and decreases indirect carbon emissions during the wastewater treatment process. Simultaneously, the direct utilization of solar thermal energy reduces the conversion steps from heat to electricity and back to heat, minimizing process losses and improving the efficiency of primary energy utilization. This provides more possibilities for more efficient and cleaner saline wastewater treatment.

[0110] All components not discussed in detail in this application, as well as the connection methods of these components, are well-known technologies in this field. They can be directly applied and will not be elaborated further.

[0111] In this invention, the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0112] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0113] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization, comprising a thermal storage system and a heat exchange system, characterized in that, It also includes solar thermal collection systems, evaporation devices, steam compressor devices, and salt separation systems; The solar thermal collector system is connected to the thermal storage system, the thermal storage system is connected to the heat exchange system, and the evaporation device is connected to the heat exchange system, the steam compressor device, and the salt separation system respectively. The evaporation device is equipped with a flash evaporator and a falling film evaporator; the salt separation system is equipped with a centrifuge.

2. The wastewater treatment system coupled with solar thermal collection and MVR evaporation crystallization according to claim 1, characterized in that, The solar thermal system includes at least two sets of collector strings, which are connected in parallel. The collector string includes a collector tube and at least two collector mirrors, the collector tube passes through at least two collector mirrors, and heat-conducting oil is disposed inside the collector tube; The upper ends of the collector tubes of all collector strings are connected to the first heat transfer pipe, and the lower ends are connected to the second heat transfer pipe. The first heat transfer pipe is connected to the heat exchange system.

3. The wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 2, characterized in that, The collector string is equipped with a solar tracking system.

4. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 2, characterized in that, The heat storage system may include a thermally conductive oil tank and a cold thermally conductive oil tank; The inlet and outlet of the thermal oil tank are respectively connected to the first heat transfer pipeline, and a first flow distribution device and a second flow distribution device are respectively installed at the interface. The outlet of the cold heat transfer oil tank is connected to the second heat transfer pipeline, and the inlet of the cold heat transfer oil tank is connected to the heat exchange system through the third heat transfer pipeline. The second heat transfer pipeline is equipped with a flow pump.

5. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 4, characterized in that, The heat exchange system includes a first heat exchanger, a second heat exchanger, and a third heat exchanger; The first heat exchanger is equipped with a first sewage pipe and a first clean water pipe; The second heat exchanger is equipped with a second sewage pipe and a second clean water pipe; The third heat exchanger is equipped with a third sewage pipe and a heat exchange pipe; The heat exchange tubes are connected to the first heat transfer pipe and the third heat transfer pipe. The first sewage pipe, the second sewage pipe, and the third sewage pipe are connected in sequence; The first clean water pipe and the second clean water pipe are connected in sequence.

6. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 5, characterized in that, The evaporation system includes a flash evaporator, a falling film evaporator, a gas-liquid separator, a transfer pump, and a circulation pump; The inlet of the flash evaporator is connected to the outlet of the third sewage pipe through the first high-temperature sewage pipe, and the steam outlet of the flash evaporator is connected to the steam compressor device through the first steam delivery pipe. A third flow distribution device is provided on the first steam delivery pipeline, and the third flow distribution device is connected to the input end of the second clean water pipe through the second steam delivery pipeline; The concentrated wastewater outlet of the flash evaporator is connected to a transfer pump via a first concentrated wastewater pipeline, and the transfer pump is connected to a circulation pump via a second concentrated wastewater pipeline. A fourth flow distribution device is installed on the second concentrated wastewater pipeline, and the fourth flow distribution device is connected to the wastewater inlet of the falling film evaporator through the third concentrated wastewater pipeline; The steam inlet of the falling film evaporator is connected to the steam compressor device through a high-temperature steam pipeline, the condensate outlet of the falling film evaporator is connected to the input end of the first clean water pipe through a first high-temperature condensate pipeline, and the bottom outlet of the falling film evaporator is connected to the inlet of the gas-liquid separation device through a first gas-liquid mixed wastewater pipeline.

7. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 6, characterized in that, The salt separation system includes a thickener, a centrifuge, and a second circulation pump; A fifth flow distribution device is installed on the fourth concentrated wastewater pipeline. The fifth flow distribution device is connected to the second circulation pump through the first wastewater mother liquor pipeline. The second circulation pump is connected to the top of the thickener through the second wastewater mother liquor pipeline. The second sewage mother liquor pipeline is equipped with a sixth flow distribution device, which is connected to the mother liquor outlet of the centrifuge through the third sewage mother liquor pipeline; The centrifuge inlet is connected to the thickener outlet via the fifth concentrated wastewater pipeline. The thickener is equipped with a mixed salt outlet. The third concentrated wastewater pipeline is connected to the thickener inlet. A seventh flow distribution device is installed on the first sewage mother liquor pipeline, and the seventh flow distribution device is equipped with a mother liquor output pipe.

8. A wastewater treatment system coupling solar thermal collection and MVR evaporation crystallization according to claim 7, characterized in that, The steam inlet of the steam compressor unit is connected to the first steam pipeline and the second steam pipeline through a mixing device.

9. A method of using a wastewater treatment system that couples solar thermal collection with MVR evaporation crystallization, characterized in that, include: S1. The solar thermal collection system gathers solar rays to generate high-temperature heat energy, and then transmits this high-temperature heat energy to the thermal storage system, or directly uses it as a high-temperature heat source for the heat exchange system. S2. The thermal storage system stores excess solar heat and, when needed, supplies this high-temperature heat energy to the heat exchange system. S3. The heat exchange system exchanges heat between the incoming sewage and condensate in stages to recover the waste heat of the condensate and output clean water resources. S4. The evaporation unit separates saline wastewater by flash evaporation and falling film evaporation, then performs gas-liquid separation, and sends the secondary steam to the steam compressor unit and the concentrated wastewater to the salt separation system. S5. The steam compressor unit mechanically compresses the low-pressure, low-temperature secondary steam obtained from evaporation to increase the steam's pressure, enthalpy, and temperature. S6. The salt separation system separates the solid crystalline salt from the concentrated wastewater solution, and the crystalline inorganic salt is recycled as a mixed resource.

10. The method of using the wastewater treatment system coupled with solar thermal collection and MVR evaporation crystallization according to claim 9, characterized in that, When the flow rate of high-temperature heat transfer oil output from the heat collection system exceeds the rated demand of the heat exchange system, the excess heat transfer oil is diverted to the heat tank for temporary storage through the first flow distribution device; when the flow rate of high-temperature heat transfer oil output from the heat collection system is less than the rated demand of the heat exchange system, an appropriate amount of high-temperature heat transfer oil stored in the heat tank is transferred to the heat exchange system through the second flow distribution device to meet the rated heat exchange demand of the heat exchange system. The flow rate is matched with the solar radiation intensity so that the solar thermal collector system can obtain a basically stable heat transfer oil temperature under different solar radiation conditions, thus promoting the stable operation of the heat exchange system and the evaporation system.

11. The method of using the wastewater treatment system coupled with solar thermal collection and MVR evaporation crystallization according to claim 9, characterized in that, A large amount of steam evaporated in the flash evaporator is partly transported to the heat exchange system for wastewater heating, and partly transported to the steam compressor unit for recompression and reuse. The unevaporated concentrated saline wastewater will be pressurized by the transfer pump and transported together with the circulating concentrated wastewater pressurized by the circulation pump to the falling film evaporator for heating and evaporation. The heating source for the falling film evaporator is high-temperature steam from the steam compressor. The heating steam from the falling film evaporator condenses into clean water, which enters the heat exchange system. The heated wastewater enters the gas-liquid separator in the form of a gas-liquid mixture for further depressurization evaporation and gas-liquid separation.

12. The method of using the wastewater treatment system coupled with solar thermal collection and MVR evaporation crystallization according to claim 9, characterized in that, The concentrated wastewater from the evaporation system first enters the thickener, where sedimentation occurs, resulting in the enrichment of crystalline salts in the solution at the bottom of the thickener, while the upper layer is a clear wastewater solution free of crystalline salts. The high-solids solution at the bottom of the thickener, enriched with crystalline salts, is then transported to a centrifuge for solid-liquid separation. The wastewater overflowing from the upper layer of the thickener and the wastewater separated by the centrifuge are collected and then pressurized by the circulating pump. Part of the wastewater is recycled back to the evaporation system to participate in the evaporation process, and part of it is output as concentrated mother liquor. The inorganic salts separated by the centrifuge are output as mixed salts.

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