Low-temperature circulation waste heat recycling evaporation zero-emission system

Abstract

The utility model discloses a low-temperature circulation waste heat recycling evaporation zero-emission system. The low-temperature circulation waste heat recycling evaporation zero-emission system comprises a low-temperature circulation evaporation concentration system, a side filtration device, an anti-pollution CDRO system, a denitration hardness reduction system, an impurity removal system, an organic modification system, an ion separation membrane and a flue tail gas evaporation system which are connected in sequence. The strong brine is subjected to forced circulation evaporation and concentration at low temperature and normal pressure, the strong brine is used as circulating water to cool the process equipment, the temperature of the strong brine is increased while the process equipment is cooled, and a large amount of water vapor is gasified while circulating cooling is performed, so that the strong brine is concentrated again; the investment and operation cost of equipment in a high-density sedimentation tank, sand filtration, ultrafiltration, reverse osmosis and other traditional membrane concentration processes is reduced, high-purity gypsum byproducts can be produced, and generation of a large amount of solid waste and hazardous waste is avoided.

Description

Technical Field

[0001] This utility model relates to the field of wastewater treatment technology, and in particular to a low-temperature circulating waste heat recovery and utilization evaporation zero-emission system. Background Technology

[0002] To meet wastewater reuse requirements, chemical plants and coal mines typically employ multi-stage reverse osmosis to concentrate wastewater, reusing the resulting permeate. However, the generated high-salinity wastewater requires further treatment. Currently, the main methods for treating high-salinity wastewater are evaporation pond treatment and zero-discharge treatment. Due to the environmental risks associated with evaporation pond treatment, zero-discharge processes are more commonly used. Zero-discharge processes primarily combine pretreatment, membrane concentration, and evaporation crystallization to reuse all the water in the high-salinity wastewater, while separating the salts as crystalline salts. Traditional zero-discharge wastewater treatment processes are complex, with high construction and investment costs, high operating expenses, and high energy consumption. Furthermore, the treatment process generates large amounts of solid and hazardous waste, imposing a significant economic burden and environmental risks on enterprises. Utility Model Content

[0003] Therefore, it is necessary to provide a low-temperature circulating waste heat recovery and zero-emission evaporation system. This utility model's low-temperature circulating waste heat recovery and zero-emission evaporation system uses forced circulation evaporation to concentrate high-concentration brine at low temperature and normal pressure, and uses the concentrated brine as circulating water to cool the process equipment, saving a significant amount of equipment investment and operating costs compared to traditional membrane concentration processes.

[0004] One embodiment of this application provides a low-temperature circulating waste heat recovery and utilization evaporation zero-emission system.

[0005] A low-temperature circulating waste heat recovery and zero-emission evaporation system includes a low-temperature circulating evaporation concentration system, a side-stream filtration device, an anti-fouling CDRO system, a denitrification and hardening system, a purification system, an organic modification system, an ion separation membrane, and a flue gas evaporation system connected in sequence. The low-temperature circulating evaporation concentration system is used for forced circulation evaporation concentration of concentrated brine wastewater, and the concentrated brine wastewater is used as circulating water to cool process equipment. The side-stream filtration device is used to remove suspended solids and impurities from the water. The anti-fouling CDRO system is used to further concentrate the salt content in the concentrated brine wastewater. The permeate from the anti-fouling CDRO system is reused, and the CDRO concentrate enters the flue gas evaporation system. The denitrification and hardness reduction system removes hardness and sulfate from CDRO concentrate by adjusting the pH value and adding calcium sulfate seed crystals to generate gypsum. The permeate from the denitrification and hardness reduction system enters the impurity removal system, which removes hardness, suspended solids, and macromolecular organic matter from the permeate and modifies the remaining organic matter. The ion separation membrane is used to further separate and concentrate some of the sulfate and organic matter remaining in the permeate from the impurity removal system. The permeate from the ion separation membrane enters the flue gas evaporation system, which evaporates and concentrates the permeate from the ion separation membrane to obtain sodium chloride.

[0006] In some embodiments, the low-temperature circulating waste heat recovery and utilization evaporation zero-emission system further includes a pretreatment system, which includes a high-density sedimentation tank for hardness and silicon removal. The pretreatment system is used to remove hardness, silicon impurities, and suspended solids from concentrated saline wastewater.

[0007] In some embodiments, the side-filter is also connected to the low-temperature circulating evaporation and concentration system to allow a portion of the permeate from the side-filter to be returned to the low-temperature circulating evaporation and concentration system.

[0008] In some embodiments, 80% to 85% of the water produced by the side-filter is recycled to the low-temperature circulating evaporation and concentration system, and 15% to 20% of the water produced by the side-filter enters the anti-fouling CDRO system.

[0009] In some embodiments, the recovery rate of the anti-fouling CDRO system is controlled at 55% to 60%.

[0010] In some embodiments, the denitrification and hardening system adjusts the pH value to 10.5–11.5 by adding lime.

[0011] In some embodiments, the organic modification system includes a modification reaction chamber and a COD interception and removal device. The modification reaction chamber is used to add a special COD modification agent. The special COD modification agent utilizes the principles of adsorption, bridging, and complexation to remove macromolecular organic matter, organic viscous colloids, and suspended impurities in concentrated saline wastewater as precipitates through flocculation and complexation.

[0012] In some embodiments, the ion separation membrane is also connected to the denitrification and hardening system, and the concentrate from the ion separation membrane is returned to the denitrification and hardening system for recycling.

[0013] In some embodiments, the flue gas evaporation system is also connected to the impurity removal system, and a portion of the mother liquor in the flue gas evaporation system is returned to the impurity removal system for recycling.

[0014] In some embodiments, the flue gas evaporation system includes a circulating fluidized bed boiler, a cyclone dust collector, a high-temperature economizer, a low-temperature economizer, an air preheater, an electrostatic precipitator, and a bag filter connected in sequence. After most of the dust is removed by the cyclone dust collector, the flue gas from the circulating fluidized bed boiler enters the high-temperature economizer, the low-temperature economizer, and the air preheater, where the temperature is reduced to below 150°C. After passing through the electrostatic precipitator and the bag filter to remove impurities from the flue gas again, the flue gas is drawn by an induced draft fan for low-temperature vacuum evaporation to produce sodium chloride.

[0015] The aforementioned low-temperature circulating waste heat recovery and zero-emission evaporation system fortifies concentrated brine through forced circulation evaporation at low temperature and normal pressure. This concentrated brine is then used as circulating water to cool the process equipment. Simultaneously, the concentrated brine absorbs heat, increasing its temperature. During the circulating cooling process, a large amount of water vapor is vaporized, further concentrating the brine. This concentration process reduces the investment and operating costs of equipment used in traditional membrane concentration processes such as high-density sedimentation tanks, sand filters, ultrafiltration, and reverse osmosis. It can produce high-purity gypsum as a byproduct and avoids the generation of large amounts of solid and hazardous waste associated with traditional zero-emission concentrated brine processes. Furthermore, this application utilizes flue gas evaporation systems, such as boiler flue gas, to replace the steam and electricity used in traditional evaporation and crystallization processes, enabling the recovery and utilization of boiler waste heat and significantly reducing equipment operating costs. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0018] Figure 1 This is a schematic diagram of a low-temperature circulating waste heat recovery and utilization evaporation zero-emission system according to an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures

[0020] 10. Low-temperature circulating waste heat recovery and utilization evaporation zero-emission system; 100. Low-temperature circulating evaporation concentration system; 200. Side-by-side filter device; 300. Anti-pollution CDRO system; 400. Denitrification and hardening reduction system; 500. Impurity removal system; 600. Organic modification system; 700. Ion separation membrane; 800. Flue gas evaporation system. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0022] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0023] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0025] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0028] This application provides a low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 to solve the problems of traditional wastewater zero-emission treatment processes being complex, having high construction investment costs, high operating costs, high energy consumption, and generating large amounts of solid waste and hazardous waste during the treatment process, resulting in a heavy economic burden and significant environmental risks. The low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 will be described below with reference to the accompanying drawings.

[0029] The low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 provided in this application embodiment is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of the low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 provided in an embodiment of this application. The low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 of this application can be used for wastewater treatment. To more clearly illustrate the structure of the low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10, the following will describe the low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 in conjunction with the accompanying drawings.

[0030] For example, please refer to Figure 1As shown, a low-temperature circulating waste heat recovery and zero-emission evaporation system 10 includes a low-temperature circulating evaporation concentration system 100, a side-stream filter 200, an anti-fouling CDRO system 300, a denitrification and hardening system 400, a purification system 500, an organic modification system 600, an ion separation membrane 700, and a flue gas evaporation system 800 connected in sequence. The low-temperature circulating evaporation concentration system 100 is used for forced circulation evaporation concentration of concentrated brine wastewater, and the concentrated brine wastewater is used as circulating water to cool the process equipment. The side-stream filter 200 is used to remove suspended solids and impurities from the water. The anti-fouling CDRO system 300 is used to further concentrate the salt content in the concentrated brine wastewater. The permeate from the anti-fouling CDRO system 300 is reused, and the CDRO concentrate enters the denitrification and hardening system 400. The denitrification and hardening system 400 removes the CDRO concentrate by adjusting the pH value and adding calcium sulfate seed crystals to generate gypsum. The permeate from the denitrification and hardness reduction system 400, containing hardness and sulfate, enters the impurity removal system 500. The impurity removal system 500 removes hardness, suspended solids, and macromolecular organic matter from the permeate from the denitrification and hardness reduction system 400 and modifies the remaining organic matter. The ion separation membrane 700 is used to further separate and concentrate some of the sulfate and organic matter remaining in the permeate from the impurity removal system 500. The permeate from the ion separation membrane 700 enters the flue gas evaporation system 800. The flue gas evaporation system 800 is used to evaporate and concentrate the permeate from the ion separation membrane 700 to obtain sodium chloride.

[0031] The aforementioned low-temperature circulating waste heat recovery and evaporation zero-emission system 10 forces concentrated brine to evaporate and concentrate it under low temperature and normal pressure. The concentrated brine is also used as circulating water to cool the process equipment. While cooling the process equipment, the concentrated brine absorbs heat and its temperature rises. During the circulating cooling process, a large amount of water vapor is vaporized, which further concentrates the concentrated brine. In the process of concentrating the concentrated brine, the investment and operating costs of equipment in traditional membrane concentration processes such as high-density sedimentation tanks, sand filters, ultrafiltration, and reverse osmosis are reduced. High-purity gypsum by-products can be produced, avoiding the generation of a large amount of solid waste and hazardous waste in traditional concentrated brine zero-emission processes.

[0032] In some embodiments, most of the permeate from the side-filter 200 is recycled back into the low-temperature circulating evaporation and concentration system 100 for forced circulation evaporation and concentration of concentrated brine wastewater, while a small portion of the permeate from the side-filter 200 enters the anti-fouling CDRO system 300. This setup enables highly efficient circulating evaporation and concentration of concentrated brine wastewater, achieving multiple cycles of evaporation and concentration, thus improving the efficiency and effectiveness of evaporation and concentration.

[0033] In this application, the antifouling CDRO system is a membrane separation technology specifically designed for treating wastewater with high pollution levels or containing complex pollutants. CDRO stands for "Concentrated Desalination Reverse Osmosis" or "Circular Disc Reverse Osmosis". Antifouling CDRO systems are particularly suitable for industrial wastewater treatment, such as chemical, pharmaceutical, coking, and landfill leachate treatment industries, where wastewater often contains high concentrations of organic matter, salt, and other difficult-to-treat impurities. Antifouling CDRO systems have shown great potential in wastewater reuse and zero-discharge projects. Antifouling CDRO systems have the following advantages over traditional reverse osmosis (RO) systems: (1) High fouling resistance: The membrane materials and designs used in CDRO systems are better able to resist fouling by organic and inorganic matter, which means they can operate under higher pollution conditions without being as prone to clogging or performance degradation as traditional RO systems. (2) High recovery rate: CDRO systems can achieve a high water recovery rate, typically above 80%, which is higher than that of traditional RO systems, thereby reducing wastewater discharge and concentrate generation. (3) Low energy consumption: CDRO systems save energy compared to traditional RO systems during operation because their design optimizes pressure requirements and fluid dynamics efficiency. (4) Low operating cost: Due to the reduced number of chemical cleanings required and the lower amount of reagents used, the overall operating cost of CDRO systems is lower. (5) Simple maintenance: CDRO systems are relatively simple to operate and easy to maintain, which can reduce labor costs and downtime.

[0034] In some embodiments, 60% to 90% of the water produced by the side-filter 200 is recycled into the low-temperature circulating evaporation and concentration system 100, and 10% to 40% of the water produced by the side-filter 200 is fed into the anti-fouling CDRO system 300.

[0035] Preferably, in some embodiments, 80% to 85% of the water produced by the side-filter 200 is recycled to the low-temperature circulating evaporation and concentration system 100, and 15% to 20% of the water produced by the side-filter 200 enters the anti-fouling CDRO system 300.

[0036] In some embodiments, the low-temperature circulating evaporation and concentration system 100 is used to perform forced circulating evaporation and concentration of concentrated brine wastewater at low temperature and normal pressure, wherein the temperature at low temperature and normal pressure can be -4°C to 4°C, and the conditions are maintained close to standard atmospheric pressure (1 atmosphere, approximately 101.325 kPa).

[0037] In some embodiments, the flue gas evaporation system 800 can be boiler flue gas. This application uses the flue gas evaporation system 800, such as boiler flue gas, to replace traditional evaporation and crystallization energy sources such as steam and electricity, thereby recovering and utilizing boiler waste heat and greatly reducing the operating cost of the equipment in this application.

[0038] In some embodiments, the low-temperature circulating waste heat recovery and zero-emission evaporation system 10 further includes a pretreatment system. The pretreatment system includes a high-density sedimentation tank for hardness and silica removal, used to remove hardness, silica impurities, and suspended solids from concentrated saline wastewater. The pretreatment system is not shown in the accompanying drawings.

[0039] In some of these embodiments, please refer to Figure 1 As shown, the side filter 200 is also connected to the low-temperature circulating evaporation and concentration system 100 to realize the return of part of the product water of the side filter 200 to the low-temperature circulating evaporation and concentration system 100.

[0040] In some embodiments, the recovery rate of the anti-fouling CDRO system 300 is controlled at 55% to 60%.

[0041] In some embodiments, the denitrification and hardening system 400 adjusts the pH value to 10.5–11.5 by adding lime.

[0042] In some embodiments, the organic modification system 600 includes a modification reaction chamber and a COD interception and removal device. A special COD-modifying agent can be added to the modification reaction chamber. Utilizing the principles of adsorption, bridging, and complexation, the COD-modifying agent, through flocculation and complexation, causes macromolecular organic matter, organic colloids, and suspended impurities in concentrated saline wastewater to be intercepted and removed by the COD interception and removal device in the form of precipitates.

[0043] In some embodiments, COD-modifying special agents include: (1) Oxidants: such as hydrogen peroxide, ozone, potassium permanganate, etc. These agents oxidize organic matter into carbon dioxide and water through strong oxidation, thereby reducing COD. (2) Adsorbents: such as activated carbon, zeolite, etc. They can effectively adsorb organic matter in wastewater and reduce COD. (3) Bioenzyme preparations: certain microorganisms produce enzymes that can degrade specific types of organic pollutants. These bioenzyme preparations can accelerate the biodegradation process of organic matter under suitable conditions. (4) COD degrading agents: these are chemical agents specifically designed for COD removal and may contain specific catalysts, oxidants or other active ingredients to promote the decomposition of organic matter. (5) Flocculants and coagulants: such as polyaluminum chloride (PAC), aluminum sulfate, polyacrylamide (PAM), etc. They can help remove suspended solids and colloids in wastewater, indirectly reducing COD. (6) Novel agents: such as certain low molecular weight inorganic compounds. These agents have a high efficiency of destruction and can react rapidly with organic matter in wastewater. They are a new generation of wastewater treatment agents developed in recent years.

[0044] In some of these embodiments, please refer to Figure 1 As shown, the ion separation membrane 700 is also connected to the denitrification and hardening system 400. The concentrate from the ion separation membrane 700 is returned to the denitrification and hardening system 400 for recycling.

[0045] In some of these embodiments, please refer to Figure 1 As shown, the flue gas evaporation system 800 is also connected to the impurity removal system 500. Part of the mother liquor in the flue gas evaporation system 800 is returned to the impurity removal system 500 for recycling.

[0046] In some embodiments, the flue gas evaporation system 800 includes a circulating fluidized bed boiler, a cyclone dust collector, a high-temperature economizer, a low-temperature economizer, an air preheater, an electrostatic precipitator, and a bag filter connected in sequence. After most of the dust is removed by the cyclone dust collector, the flue gas from the circulating fluidized bed boiler enters the high-temperature economizer, the low-temperature economizer, and the air preheater, where the temperature is reduced to below 150°C. It then passes through the electrostatic precipitator and the bag filter again to remove impurities before being drawn by an induced draft fan for low-temperature vacuum evaporation to produce sodium chloride. The circulating fluidized bed boiler, cyclone dust collector, high-temperature economizer, low-temperature economizer, air preheater, electrostatic precipitator, and bag filter are not shown in the accompanying drawings.

[0047] Compared with traditional technologies, the low-temperature circulating waste heat recovery and utilization evaporation zero-emission system 10 of this application has the following beneficial effects:

[0048] (1) This application adopts a denitrification and hardening system, a 500-type impurity removal system, an organic modification system, and an ion separation membrane working together to achieve cyclic impurity removal, denitrification, and removal of organic matter. This greatly reduces the accumulation of impurities in the evaporation and crystallization system and greatly improves the stability of the evaporation and crystallization system and the purity of the sodium chloride product.

[0049] (2) This application can produce high-purity gypsum by-products, avoiding the generation of a large amount of solid waste and hazardous waste in the traditional concentrated brine zero-discharge process.

[0050] (3) This application uses a flue gas evaporation system 800, such as boiler flue gas, to replace the traditional evaporation crystallization of steam, electricity and other energy sources, and recovers and utilizes boiler waste heat, which greatly reduces the operating cost of the equipment in this application.

[0051] (4) This application adopts a zero-emission evaporation technology consisting of low temperature circulation and waste heat recovery, which forces the high-concentration brine to evaporate and concentrate under low temperature and normal pressure, and uses the concentrated brine as circulating water to cool down the process equipment, saving a lot of equipment investment and operating costs compared with the traditional membrane concentration process.

[0052] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0053] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A low temperature cycle waste heat recovery evaporation zero emission system characterized by, The system comprises, in sequence, a low-temperature circulating evaporation concentration system, a bypass filtration device, an anti-pollution CDRO system, a denitration and hardness reduction system, a impurity removal system, an organic modification system, an ion separation membrane, and a flue tail gas evaporation system. The low-temperature circulating evaporation concentration system is used for forced-circulation evaporation concentration of concentrated salt wastewater and cooling of process equipment by the concentrated salt wastewater as circulating water. The bypass filtration device is used for removing suspended impurities in water. The anti-pollution CDRO system is used for further concentration of salt in the concentrated salt wastewater. The water produced by the anti-pollution CDRO system is reused and the CDRO concentrated water enters the denitration and hardness reduction system. The denitration and hardness reduction system generates gypsum by adjusting the pH value and adding calcium sulfate seed to remove hardness and sulfate in the CDRO concentrated water. The water produced by the denitration and hardness reduction system enters the impurity removal system. The impurity removal system removes hardness, suspended impurities, and macromolecular organic matter in the water produced by the denitration and hardness reduction system and modifies the remaining organic matter. The ion separation membrane is used for further separation and concentration of residual part of sulfate and organic matter in the water produced by the impurity removal system. The water produced by the ion separation membrane enters the flue tail gas evaporation system. The flue tail gas evaporation system is used for evaporation concentration of the water produced by the ion separation membrane to obtain sodium chloride.

2. The low temperature cycle waste heat recovery and evaporation zero emission system of claim 1, wherein, The low-temperature circulating waste heat recovery and utilization evaporation zero-emission system further comprises a pretreatment system comprising a high-density sedimentation tank for removing hardness and silicon impurities and suspended solids. The pretreatment system is used for removing hardness, silicon impurities, and suspended solids in the concentrated salt wastewater.

3. The low temperature cycle waste heat recovery and evaporation zero emission system of claim 1, wherein, The bypass filtration device is further connected to the low-temperature circulating evaporation concentration system to realize backflow of part of the water produced by the bypass filtration device into the low-temperature circulating evaporation concentration system.

4. The low temperature cycle waste heat recovery and evaporation zero emission system of claim 3, wherein, 80-85% of the water produced by the bypass filtration device backflows into the low-temperature circulating evaporation concentration system, and 15-20% of the water produced by the bypass filtration device enters the anti-pollution CDRO system.

5. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by, The recovery rate of the anti-pollution CDRO system is controlled to be 55-60%.

6. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by The denitration and hardness reduction system adjusts the pH value to 10.5-11.5 by adding lime.

7. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by The organic modification system comprises a modification reaction tank and a COD interception and removal device. The modification reaction tank is used for adding a COD modification special agent. The COD modification special agent uses adsorption, bridging, and complexation principles to make macromolecular organic matter, organic viscous colloid, and suspended impurities in the concentrated salt wastewater into precipitates which are intercepted and removed by the COD interception and removal device.

8. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by, The ion separation membrane is further connected to the denitration and hardness reduction system. The concentrated water produced by the ion separation membrane backflows into the denitration and hardness reduction system for circulation treatment.

9. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by The flue tail gas evaporation system is further connected to the impurity removal system. Part of the mother liquor in the flue tail gas evaporation system backflows into the impurity removal system for circulation treatment.

10. The low-temperature cycle waste heat recovery and utilization evaporation zero-emission system according to any one of claims 1 to 4, characterized by The flue gas evaporation system comprises a circulating fluidized bed boiler, a cyclone dust collector, a high-temperature economizer, a low-temperature economizer, an air preheater, an electric dust collector and a bag-type dust collector connected in sequence, the flue gas of the circulating fluidized bed boiler enters the high-temperature economizer, the low-temperature economizer and the air preheater after most of the smoke dust is removed by the cyclone dust collector, the temperature is reduced to below 150 DEG C, and then the impurities in the flue gas are removed again by the electric dust collector and the bag-type dust collector, and the flue gas is extracted by an induced draft fan and used for low-temperature vacuum evaporation to prepare sodium chloride.

Images