A multi-stage treatment system for high-salinity wastewater and a high-value utilization method

Abstract

The application discloses a kind of high-salinity wastewater multistage processing system, comprising: water sample detection analysis system: it carries out sampling analysis to high-salinity wastewater at least three batches, obtains wastewater pH, COD, TDS, hardness and the numerical range of each pollutant content;Ozonation system: it is fully contacted with ozone to the high-salinity wastewater after detection analysis, obtains ozonation effluent;Pretreatment system: it is settled, filtration to the ozonation effluent, obtains pretreatment effluent and pretreatment concentrate;Electrolytic hydrogen production system: it is in situ electrolysis to the pretreatment effluent, obtains hydrogen, oxygen and wastewater concentrate;Membrane distillation system: it is membrane distillation treatment to the wastewater concentrate, obtains pure water and membrane distillation concentrate;Evaporation system: it is evaporation treatment to the pretreatment concentrate and membrane distillation concentrate, obtains solid waste.In the application, wastewater utilization rate of whole process of wastewater treatment is greater than 80%, hydrogen purity is greater than 99.9%, and membrane distillation pure water TDS is less than 50mg / L.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a multi-stage treatment system for high-salinity wastewater and a method for its high-value utilization. Background Technology

[0002] Coal-fired power plants generate large amounts of flue gas containing sulfur compounds during operation, requiring desulfurization treatment. Currently, approximately 90% of coal-fired power plants are equipped with wet flue gas desulfurization technology, which produces a large amount of desulfurization wastewater. As a typical example of high-salinity industrial wastewater, desulfurization wastewater has high levels of suspended solids, salt, and hardness, and its heavy metal and COD levels exceed standards. The high corrosiveness of chloride ions makes wastewater treatment difficult, thus making it one of the most challenging end-of-pipe wastewaters to treat from thermal power plants.

[0003] Currently, the main treatment methods for desulfurization wastewater are chemical coagulation and sedimentation (three-stage process) and zero-discharge treatment processes (evaporation and crystallization, etc.). There is currently no research on direct electrolysis of desulfurization wastewater for hydrogen production, due to the complex composition of this wastewater. The mainstream industrial electrolysis hydrogen production technologies (ALK, PEM) have extremely high water quality requirements, using pure water that is almost free of impurities. However, desulfurization wastewater has extremely high suspended solids concentrations and extremely high hardness (10,000-30,000 mg / L, mainly composed of calcium). 2+ and Mg 2+ It usually also contains F exceeding emission standards. - TDS concentrations can reach 10,000-50,000 mg / L (the main component is sodium). + Cl - and SO4 2- It may also contain heavy metals such as Hg, Cr, and Ni, therefore it does not meet the conditions for direct electrolysis to produce hydrogen using ALK or PEM technology.

[0004] In recent years, with the emergence and implementation of a series of environmental protection regulations and policies, improving water use efficiency and achieving water conservation and effective reuse of wastewater have become inevitable choices. High-salt wastewater concentration treatment technologies with application cases are mainly divided into two types: thermal and membrane methods.

[0005] Chinese patent application CN202110218211.2 discloses a thermal and membrane coupled concentration system and method for desulfurization wastewater, belonging to the field of desulfurization wastewater treatment technology. The system includes a wastewater pretreatment system, an induced draft fan, an evaporation tower, a circulating water pump, and a membrane distillation device. It utilizes flue gas after the dust collector as a heat source, directly exchanging heat with the desulfurization wastewater in the evaporation tower, achieving wastewater concentration and volume reduction through evaporation. Simultaneously, a membrane distillation device is added to the desulfurization wastewater circulation loop, utilizing the residual heat after wastewater evaporation to recover high-quality condensate. The membrane distillation cooling medium is low-temperature air, which enters the air preheater after recovering some heat through the membrane distillation system. While this application achieves wastewater concentration and volume reduction through a coupled membrane and thermal system, the above treatment method is complex, requires a large initial investment, and suffers from poor economic efficiency due to the harsh water quality of desulfurization wastewater, high operation and maintenance requirements, and low economic efficiency. Therefore, developing a highly economical high-salinity wastewater treatment technology and process is of great significance. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a multi-stage treatment system for high-salinity wastewater and a method for its high-value utilization.

[0007] The technical solution of the present invention is as follows:

[0008] One objective of this invention is to provide a multi-stage treatment system for high-salinity wastewater, comprising:

[0009] Water sample testing and analysis system: It can take samples of high-salinity wastewater in at least three batches for analysis to obtain the pH, COD, TDS, hardness and the range of various pollutant contents of the wastewater;

[0010] Ozone oxidation system: It fully contacts high-salinity wastewater that has been tested and analyzed with ozone to obtain ozonated effluent;

[0011] Pretreatment system: It settles and filters the ozonation effluent to obtain pretreated effluent and pretreated concentrate. The pretreated effluent enters the next stage of electrolytic hydrogen production system, and the pretreated concentrate enters the evaporation system.

[0012] Electrolytic hydrogen production system: It includes a water collection component and an electrolysis component. The water collection component filters the pretreated effluent to obtain a wastewater concentrate and a dilute electrolyte. The wastewater concentrate enters the next stage membrane distillation system. The electrolysis component performs in-situ electrolysis of the dilute electrolyte to obtain a concentrated electrolyte, hydrogen, and oxygen. The concentrated electrolyte is returned to the water collection component for filtration together with the pretreated effluent.

[0013] Membrane distillation system: It performs membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate, and the membrane distillation concentrate enters the evaporation system;

[0014] Evaporation system: It evaporates the pretreated concentrate and the membrane distillation concentrate to obtain solid waste.

[0015] Furthermore, in the ozonation system, the ozone is generated by an ozone generator.

[0016] Furthermore, in the electrolytic hydrogen production system, the obtained oxygen is returned to the ozone generator in the ozonation system for ozone production.

[0017] Furthermore, the electrolytic hydrogen production system is equipped with a tubular water collection module assembly, which includes a water collection component and an electrolysis component.

[0018] Furthermore, the driving force for the membrane distillation system and the evaporation system is the low-grade waste heat from the power plant.

[0019] Furthermore, the low-grade waste heat from the power plant is either flue gas waste heat or boiler effluent waste heat.

[0020] The second objective of this invention is to provide a method for the high-value utilization of high-salinity wastewater, comprising the following steps:

[0021] Water sample testing and analysis: At least three batches of high-salinity wastewater from the actual production process were sampled and analyzed to obtain the pH, COD, TDS, hardness and the range of various pollutant contents of the wastewater;

[0022] Ozone oxidation treatment: High-salinity wastewater that has been tested and analyzed is fully contacted with ozone to obtain ozonated effluent;

[0023] Wastewater pretreatment: The ozonation effluent is subjected to sedimentation and filtration to obtain pretreated effluent and pretreated concentrate;

[0024] Hydrogen production by electrolysis: The pretreated effluent is filtered and electrolyzed in situ through a tubular water collection assembly to obtain hydrogen, oxygen and wastewater concentrate.

[0025] Membrane distillation treatment: The wastewater concentrate is subjected to membrane distillation treatment to obtain pure water and membrane distillation concentrate;

[0026] Evaporation treatment: The pretreatment concentrate and membrane distillation concentrate are evaporated using the low-grade waste heat of the power plant to remove water and obtain solid waste.

[0027] Furthermore, during the electrolytic hydrogen production process, the pretreated effluent enters the shell side of the tubular water collection module, and the electrolyte flows through the hollow fiber interior of the tubular membrane module. Driven by the water vapor partial pressure difference, water molecules in the pretreated effluent cross the membrane and enter the electrolyte, thus initially concentrating the pretreated effluent and diluting the electrolyte to achieve the purpose of water extraction. The diluted electrolyte is then electrolyzed in the electrolysis module to produce hydrogen gas, and the concentrated electrolyte re-enters the water collection module.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. This invention provides a multi-stage treatment system for high-salinity wastewater, which couples a direct electrolysis hydrogen production system with a membrane distillation pure water production system for treating high-salinity wastewater. The direct electrolysis hydrogen production system uses a high-concentration electrolyte to extract water from the pretreated effluent for electrolysis to generate hydrogen. This system does not require complex purification of the influent. After ozonation, gravity sedimentation, and filtration to remove most of the insoluble solids and reduce the COD value, the high-salinity wastewater can be used in the direct electrolysis hydrogen production system. Since the in-situ electrolysis hydrogen production system and the membrane distillation pure water production system of this invention have low requirements for the quality of the influent water, the wastewater concentrate produced by the in-situ electrolysis hydrogen production system can be directly entered into the membrane distillation system for deep concentration. The resulting pure water has a TDS of less than 50 mg / L and a hardness close to 0, which can reach the level of pure water. In addition, this system can utilize low-grade waste heat from power plants, such as flue gas waste heat and boiler effluent waste heat, as the system's energy consumption.

[0030] 2. The present invention provides a high-value utilization method for high-salt wastewater. After simple pretreatment, the high-salt wastewater enters the direct electrolysis hydrogen production treatment. A portion of the water is electrolyzed to obtain hydrogen and oxygen. The concentrate enters the membrane distillation system for treatment and is concentrated to near saturation. The wastewater utilization rate of the whole process is greater than 80%, the hydrogen purity is greater than 99.9%, and the TDS of the membrane distillation pure water is less than 50 mg / L. Attached Figure Description

[0031] Figure 1 The flowchart illustrates a method for high-value utilization of high-salinity wastewater provided by this invention. Detailed Implementation

[0032] The following describes a preferred embodiment, with reference to the appendix. Figure 1To further illustrate the present invention, the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values; for numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed herein; the materials, reagents, etc. used in the following embodiments are commercially available unless otherwise specified; the experimental methods in the following embodiments are conventional methods unless otherwise specified.

[0033] Example 1

[0034] This embodiment provides a multi-stage treatment system for high-salinity wastewater, including:

[0035] Water sample testing and analysis system: It takes three batches of samples from high-salinity wastewater for analysis, and obtains the pH, COD, TDS, hardness and the range of various pollutant contents of the wastewater.

[0036] Ozone oxidation system: It fully contacts high-salinity wastewater that has been tested and analyzed with ozone to obtain ozonated effluent; the ozone is generated by an ozone generator;

[0037] Pretreatment system: It settles and filters the ozonation effluent to obtain pretreated effluent and pretreated concentrate. The pretreated effluent enters the next stage of electrolytic hydrogen production system, and the pretreated concentrate enters the evaporation system.

[0038] Electrolysis hydrogen production system: It performs in-situ electrolysis on the pretreated effluent to obtain hydrogen, oxygen and wastewater concentrate. The wastewater concentrate enters the next stage membrane distillation system, and the obtained oxygen is returned to the ozone generator in the ozonation system for ozone production.

[0039] In this embodiment, the electrolytic hydrogen production system is equipped with a tubular water collection module assembly, which is used to filter the pretreated effluent.

[0040] Membrane distillation system: It performs membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate, and the membrane distillation concentrate enters the evaporation system;

[0041] Evaporation system: It evaporates the pretreated concentrate and the membrane distillation concentrate to obtain solid waste.

[0042] In this embodiment, the driving force for the membrane distillation system and the evaporation system is the waste heat from the boiler outlet.

[0043] The driving force for the membrane distillation system and evaporation system in this embodiment can also be the waste heat of the flue gas.

[0044] Example 2

[0045] This embodiment provides a method for the high-value utilization of high-salinity wastewater, such as... Figure 1 As shown, it includes the following steps:

[0046] Water sample testing and analysis: Three batches of high-salinity wastewater from the actual production process were sampled and analyzed. The values ​​of pH, COD, TDS, hardness, and the content of various pollutants in the wastewater are shown in the table below:

[0047] Table 1 Summary of Detection and Analysis Results of a Batch of High-Salinity Wastewater

[0048]

[0049]

[0050] Ozone treatment: High-salinity wastewater that has been tested and analyzed is fully contacted with ozone to obtain ozonated concentrate and ozonated effluent;

[0051] Wastewater pretreatment: Flocculant is added to settle the ozonation effluent, and the supernatant is filtered to obtain pretreated effluent and pretreated concentrate;

[0052] Electrolytic hydrogen production: The pretreated effluent enters the shell side of the tubular water collection module, and the electrolyte flows through the hollow fiber of the tubular membrane module. Driven by the water vapor partial pressure difference, water molecules in the pretreated effluent cross the membrane and enter the electrolyte, thus initially concentrating the pretreated effluent and diluting the electrolyte to achieve the purpose of water extraction. The diluted electrolyte is then electrolyzed in the electrolysis module to produce hydrogen. The concentrated electrolyte is then returned to the water collection module to obtain hydrogen, oxygen, and wastewater concentrate.

[0053] In this embodiment, the designed water influent flow rate for direct electrolysis hydrogen production is 1 t / h, the water utilization rate is 10%, the water extraction rate is 100 kg / h, and the hydrogen production is 124 Nm³. 3 / h, oxygen production is 62 Nm³ 3 / h.

[0054] Membrane distillation treatment: The wastewater concentrate is subjected to membrane distillation treatment to obtain pure water and membrane distillation concentrate;

[0055] In this embodiment, the membrane distillation system is designed with an inlet water temperature of 80°C, a cooling water temperature of 30°C, an inlet water heat source provided by waste heat from the flue gas, an inlet water flow rate of 1 t / h, an inlet water TDS of approximately 100 g / L, a high-purity water production rate of 0.8 t / h, a product water TDS of less than 50 mg / L, a concentrate production rate of 0.2 t / d, and a TDS close to saturation.

[0056] Evaporation treatment: The waste heat of flue gas is used to evaporate the ozonation concentrate and the membrane distillation concentrate to remove moisture and obtain solid waste that is easy to handle.

[0057] In this embodiment, the water utilization rate for the entire process is 87%.

[0058] In this embodiment, the waste heat from the boiler outlet can also be used as the driving force for membrane distillation and evaporation treatment.

[0059] In this embodiment, high-salinity wastewater first enters the water sample detection and analysis system. After sampling and analysis by the system, the wastewater is then transported through a pipeline to the ozonation system, where it comes into full contact with ozone to obtain ozonated effluent. The ozonation system is equipped with an ozone generator, which generates the ozone. The ozonated effluent is further transported through a pipeline to a pretreatment system. After sedimentation and filtration, pretreated effluent and pretreated concentrate are obtained. The pretreated effluent is then transported through a pipeline to the direct electrolysis hydrogen production system, and the pretreated concentrate is transported through a pipeline to the evaporation system. The pretreated effluent is then collected in the direct electrolysis hydrogen production system. After the components are assembled, wastewater concentrate and dilute electrolyte are obtained. The wastewater concentrate is transported to the membrane distillation system through pipelines. The dilute electrolyte is electrolyzed in situ by the electrolysis components in the electrolysis hydrogen production system to obtain concentrated electrolyte, hydrogen, and oxygen. The concentrated electrolyte is transported to the water collection components in the direct electrolysis hydrogen production system through pipelines for regeneration. The oxygen is transported to the ozone generator in the ozonation system through pipelines for utilization and to produce ozone mixed gas. The membrane distillation system performs membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate. The membrane distillation concentrate is transported to the evaporation system through pipelines. After the pretreated concentrate and the membrane distillation concentrate are evaporated by the evaporation system, solid waste is obtained, completing the entire process of high-salt wastewater treatment.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A multi-stage treatment system for high-salinity wastewater, characterized in that, include: Water sample testing and analysis system: It can take samples of high-salinity wastewater in at least three batches for analysis to obtain the pH, COD, TDS, hardness and the range of various pollutant contents of the wastewater; Ozone oxidation system: It fully contacts high-salinity wastewater that has been tested and analyzed with ozone to obtain ozonated effluent; Pretreatment system: It settles and filters the ozonation effluent to obtain pretreated effluent and pretreated concentrate. The pretreated effluent enters the next stage of electrolytic hydrogen production system, and the pretreated concentrate enters the evaporation system. Electrolytic hydrogen production system: It includes a water collection component and an electrolysis component. The water collection component filters the pretreated effluent to obtain a wastewater concentrate and a dilute electrolyte. The wastewater concentrate enters the next stage membrane distillation system. The electrolysis component performs in-situ electrolysis of the dilute electrolyte to obtain a concentrated electrolyte, hydrogen, and oxygen. The concentrated electrolyte is returned to the water collection component for filtration together with the pretreated effluent. The electrolytic hydrogen production system is equipped with a tubular water collection membrane component, which includes a water collection component and an electrolysis component. The pretreated effluent enters the shell side of the water collection component, and the electrolyte flows through the hollow fiber of the tubular water collection membrane component. Driven by the water vapor partial pressure difference, water molecules in the pretreated effluent cross the membrane and enter the electrolyte, thus initially concentrating the pretreated effluent and diluting the electrolyte to achieve the purpose of water extraction. The diluted electrolyte is electrolyzed in the electrolysis component to produce hydrogen gas, and the concentrated electrolyte re-enters the water collection component. Membrane distillation system: It performs membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate, and the membrane distillation concentrate enters the evaporation system; Evaporation system: It evaporates the pretreated concentrate and the membrane distillation concentrate to obtain solid waste.

2. The multi-stage treatment system for high-salinity wastewater according to claim 1, characterized in that, In the ozonation system, the ozone is generated by an ozone generator.

3. The multi-stage treatment system for high-salinity wastewater according to claim 2, characterized in that, In the electrolytic hydrogen production system, the obtained oxygen is returned to the ozone generator in the ozonation system for ozone production.

4. The multi-stage treatment system for high-salinity wastewater according to claim 1, characterized in that, The membrane distillation system and the evaporation system are driven by low-grade waste heat from the power plant.

5. A multi-stage treatment system for high-salinity wastewater according to claim 4, characterized in that, The low-grade waste heat from the power plant refers to waste heat from flue gas or waste heat from boiler effluent.

6. A method for high-value utilization of high-salinity wastewater using the system described in claim 1, characterized in that, Includes the following steps: Water sample testing and analysis: At least three batches of high-salinity wastewater from the actual production process were sampled and analyzed to obtain the pH, COD, TDS, hardness and the range of various pollutant contents of the wastewater; Ozone oxidation treatment: High-salinity wastewater that has been tested and analyzed is fully contacted with ozone to obtain ozonated effluent; Wastewater pretreatment: The ozonation effluent is subjected to sedimentation and filtration to obtain pretreated effluent and pretreated concentrate; Hydrogen production by electrolysis: The pretreated effluent is filtered and electrolyzed in situ through a tubular water collection assembly to obtain hydrogen, oxygen and wastewater concentrate. Membrane distillation treatment: The wastewater concentrate is subjected to membrane distillation treatment to obtain pure water and membrane distillation concentrate; Evaporation treatment: The pretreatment concentrate and membrane distillation concentrate are evaporated using the low-grade waste heat of the power plant to remove water and obtain solid waste.

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