High-salinity wastewater multi-stage treatment system and high-value utilization method

Abstract

The invention discloses a multi-stage treatment system for high-salinity wastewater, which comprises a water sample detection and analysis system for performing at least three batches of sampling analysis on the high-salinity wastewater to obtain the pH value, COD, TDS, hardness and the numerical value range of each pollutant content of the wastewater; the ozonization system is used for fully contacting the detected and analyzed high-salinity wastewater with ozone to obtain ozonized effluent; the pretreatment system is used for settling and filtering the ozonized effluent to obtain pretreated effluent and a pretreated concentrated solution; the electrolytic hydrogen production system is used for carrying out in-situ electrolysis on the pretreated effluent to obtain hydrogen, oxygen and a wastewater concentrated solution; the membrane distillation system is used for carrying out membrane distillation treatment on the wastewater concentrated solution to obtain pure water and a membrane distillation concentrated solution; the evaporation system is used for carrying out evaporation treatment on the pretreatment concentrated solution and the membrane distillation concentrated solution to obtain solid waste. In the invention, the wastewater utilization rate in the whole wastewater treatment 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 50mg / L.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a high-salt wastewater multi-stage treatment system and a high-value utilization method. Background Art

[0002] Coal-fired power plant units produce a large amount of sulfide-containing flue gas during operation, which needs to be desulfurized. Currently, about 90% of coal-fired power plants are equipped with wet flue gas desulfurization technology, which produces a large amount of desulfurization wastewater. Desulfurization wastewater is a typical representative of industrial high-salt wastewater. Its suspended solids, salt, hardness and other contents are high, and its heavy metals, COD and other indicators exceed the standards. The strong corrosiveness of a large number of chloride ions makes wastewater treatment more difficult, so it has become one of the more difficult end-of-line wastewaters to treat in thermal power plants.

[0003] At present, the treatment methods for desulfurization wastewater are mainly concentrated on chemical coagulation and sedimentation treatment (three-tank process) and zero-emission treatment process (evaporation crystallization, etc.). There is no research on direct electrolysis of desulfurization wastewater to produce hydrogen. This is due to the complex components contained in desulfurization wastewater. The mainstream industrial electrolysis water hydrogen production technology (ALK, PEM) has extremely high requirements for water quality. The water used is pure water, which contains almost no impurity ions. However, the concentration of suspended matter in desulfurization wastewater is extremely high, and the hardness is extremely high (10000-30000mg / L, and the main component is Ca 2+ and Mg 2+ ), usually also contains F that exceeds emission standards - , TDS concentration can reach 10000-50000mg / L (the main component is Na + , Cl - and SO4 2- ), and may also contain heavy metal elements such as Hg, Cr, and Ni, so it is not possible to directly produce hydrogen through electrolysis using ALK or PEM technology.

[0004] In recent years, with the emergence and implementation of a series of environmental protection laws and policies, improving water use efficiency, achieving water conservation and effective reuse of wastewater has become an inevitable choice. The high-salt wastewater concentration treatment technologies with application cases are mainly divided into thermal and membrane methods.

[0005] The Chinese patent application with application number CN202110218211.2 discloses a system and method for concentrating desulfurized wastewater by coupling thermal and membrane methods, which belongs to the technical field of desulfurized wastewater treatment. The system includes a wastewater pretreatment system, an induced draft fan, an evaporation tower, a circulating water pump and a membrane distillation device; the flue gas after the dust collector is used as a heat source, and heat is directly exchanged with the desulfurized wastewater in the evaporation tower, and the wastewater is evaporated to achieve the concentration and reduction of the wastewater. At the same time, a membrane distillation device is added to the circulation loop of the desulfurized wastewater, and the waste heat after the evaporation of the wastewater is used to realize the recovery of high-quality condensed water. The cooling medium of the membrane distillation is low-temperature air, and the air enters the air preheater after recovering part of the heat through the membrane distillation system; the application realizes the concentration and reduction of wastewater through the membrane method and thermal method coupling system, but the above-mentioned treatment method system is complex, the initial investment scale is large, and due to the poor water quality conditions of the desulfurized wastewater, the operation and maintenance requirements are high, and the economic benefits are poor. Therefore, it is of great significance to develop a high-salt wastewater treatment technology and process route with high economic efficiency. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a high-salinity wastewater multi-stage treatment system and a high-value utilization method.

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

[0008] One of the purposes of the present invention is to provide a high-salinity wastewater multi-stage treatment system, comprising:

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

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

[0011] Pretreatment system: it settles and filters the ozonated effluent to obtain pretreated effluent and pretreated concentrated liquid. The pretreated effluent enters the next-stage electrolytic hydrogen production system, and the pretreated concentrated liquid 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 pre-treated water to obtain wastewater concentrate and dilute electrolyte. The wastewater concentrate enters the next-level membrane distillation system. The electrolysis component performs in-situ electrolysis on the dilute electrolyte to obtain concentrated electrolyte, hydrogen and oxygen. The concentrated electrolyte returns to the water collection component and is filtered together with the pre-treated water.

[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 carries out evaporation treatment on the pre-treated concentrated liquid and the membrane distillation concentrated liquid 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 to prepare ozone.

[0017] Furthermore, in the electrolytic hydrogen production system, a tube bundle type water collection module assembly is provided, and the tube bundle type water collection module assembly includes a water collection assembly and an electrolysis assembly.

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

[0019] Furthermore, the low-grade waste heat of the power plant is flue gas waste heat or boiler outlet water waste heat.

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

[0021] Water sample testing and analysis: Sampling and analyzing at least three batches of high-salt wastewater from the actual production process to obtain the pH, COD, TDS, hardness and the numerical range of various pollutant contents of the wastewater;

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

[0023] Wastewater pretreatment: sedimenting and filtering the ozonated effluent to obtain pretreated effluent and pretreated concentrated liquid;

[0024] Electrolysis for hydrogen production: The pre-treated water is filtered and electrolyzed in situ through a tube bundle water collection assembly to obtain hydrogen, oxygen and wastewater concentrate;

[0025] Membrane distillation treatment: performing membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate;

[0026] Evaporation treatment: Use the low-grade waste heat from the power plant to evaporate the pre-treated concentrate and membrane distillation concentrate to remove moisture and obtain solid waste.

[0027] Furthermore, during the electrolytic hydrogen production process, the pretreated water enters the shell side of the tube bundle water collection component, and the electrolyte flows through the hollow fibers of the tube bundle membrane component. Driven by the water vapor partial pressure difference, the water molecules in the pretreated water cross the membrane and enter the electrolyte. The pretreated water is initially concentrated and the electrolyte is diluted, thereby achieving the purpose of water extraction. The diluted electrolyte is electrolyzed in the electrolysis component to prepare hydrogen, and the concentrated electrolyte enters the water collection component again.

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

[0029] 1. A multi-stage treatment system for high-salt wastewater provided by the present invention couples a direct electrolysis hydrogen production system with a membrane distillation pure water production system to treat high-salt wastewater. The direct electrolysis hydrogen production system uses a high-concentration electrolyte to extract moisture from pretreated effluent for electrolysis to produce hydrogen. The system does not require complex purification of the influent. The high-salt wastewater can enter the direct electrolysis hydrogen production system for use after ozonation, gravity sedimentation, filtration to remove most of the insoluble solids and reduce the COD value. Since the in-situ electrolysis hydrogen production system and membrane distillation pure water production system of the present invention have low requirements on the influent water quality, the wastewater concentrate produced by the in-situ electrolysis hydrogen production system can directly enter the membrane distillation system for deep concentration. The produced 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, the system can utilize low-grade waste heat from power plants, such as flue gas waste heat and boiler effluent waste heat, as system 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 direct electrolysis hydrogen production treatment. A portion of the water is electrolyzed to obtain hydrogen and oxygen, and the concentrated liquid 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 membrane distillation pure water is less than 50 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of a high-value utilization method of high-salt wastewater provided by the present invention. DETAILED DESCRIPTION

[0032] The following is combined with the preferred embodiment and with reference to the attached Figure 1, the present invention is further described. The endpoints and any values ​​of the ranges disclosed in the present invention 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 each range, the endpoint values ​​of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein; the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels; the experimental methods in the following examples, unless otherwise specified, are all conventional methods.

[0033] Example 1

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

[0035] Water sample detection and analysis system: It samples and analyzes three batches of high-salinity wastewater to obtain the pH, COD, TDS, hardness and the numerical range of various pollutant contents of the wastewater;

[0036] Ozonation system: it fully contacts the 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 ozonated effluent to obtain pretreated effluent and pretreated concentrated liquid. The pretreated effluent enters the next-stage electrolytic hydrogen production system, and the pretreated concentrated liquid enters the evaporation system;

[0038] Electrolysis hydrogen production system: it performs in-situ electrolysis on the pre-treated water 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 preparing ozone;

[0039] In this embodiment, the electrolytic hydrogen production system is provided with a tube bundle type water collection module assembly, and the tube bundle type water collection module assembly is used to filter the pre-treated 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 carries out evaporation treatment on the pre-treated concentrated liquid and the membrane distillation concentrated liquid to obtain solid waste.

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

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

[0044] Example 2

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

[0046] Water sample testing and analysis: Three batches of high-salt wastewater from the actual production process were sampled and analyzed, and the pH, COD, TDS, hardness and the numerical ranges of various pollutant contents in the wastewater were shown in the following table:

[0047] Table 1 Summary of the results of a batch of high-salt wastewater testing and analysis

[0048]

[0049]

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

[0051] Wastewater pretreatment: adding a flocculant to settle the ozonated effluent, and filtering the supernatant to obtain pretreated effluent and pretreated concentrated liquid;

[0052] Hydrogen production by electrolysis: the pretreated water enters the shell side of the tube bundle water collection component, and the electrolyte flows through the hollow fiber of the tube bundle membrane component. Driven by the water vapor partial pressure difference, the water molecules in the pretreated water cross the membrane and enter the electrolyte. The pretreated water is initially concentrated, and the electrolyte is diluted, thereby achieving the purpose of water extraction. The diluted electrolyte is electrolyzed in the electrolysis component to prepare hydrogen, and the concentrated electrolyte enters the water collection component again to obtain hydrogen, oxygen and wastewater concentrate;

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

[0054] Membrane distillation treatment: performing membrane distillation treatment on the wastewater concentrate 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 flue gas waste heat, and a designed inlet water flow of 1 t / h, an inlet water TDS of about 100 g / L, a high-purity water production of 0.8 t / h, a produced water TDS of less than 50 mg / L, a concentrated water production of 0.2 t / d, and a TDS close to saturation;

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

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

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

[0059] In this embodiment, the high-salt wastewater first enters the water sample detection and analysis system, and after sampling and analysis by the water sample detection and analysis system, the high-salt wastewater after detection and analysis is transported to the ozonation system through a pipeline, and is fully contacted with the ozone in the ozonation system to obtain ozonated effluent; wherein, an ozone generator is provided in the ozonation system, and the ozone is generated by the ozone generator; the ozonated effluent is further transported to the pretreatment system through a pipeline, and after sedimentation and filtration in the pretreatment system, pretreated effluent and pretreated concentrated liquid are obtained, wherein the pretreated effluent is transported to the direct electrolysis hydrogen production system through a pipeline, and the pretreated concentrated liquid is transported to the evaporation system through a pipeline; the pretreated effluent is collected in the direct electrolysis hydrogen production system After the assembly, wastewater concentrate and dilute electrolyte are obtained, wherein the wastewater concentrate is transported to the membrane distillation system through a pipeline, the dilute electrolyte is electrolyzed in situ by the electrolysis component in the electrolysis hydrogen production system to obtain concentrated electrolyte, hydrogen and oxygen, the concentrated electrolyte is transported to the water collection component in the direct electrolysis hydrogen production system through a pipeline for regeneration, and the oxygen is transported to the ozone generator in the ozonation system through a pipeline for utilization and preparation of ozone mixed gas; the membrane distillation system performs membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate, and the membrane distillation concentrate is transported to the evaporation system through a pipeline; the pretreated concentrate and the membrane distillation concentrate are evaporated by the evaporation system to obtain solid waste, thereby completing the whole process of high-salt wastewater treatment.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A high-salinity wastewater multi-stage treatment system, characterized in that: include: Water sample detection and analysis system: It samples and analyzes at least three batches of high-salinity wastewater to obtain the pH, COD, TDS, hardness and the numerical range of various pollutant contents of the wastewater; Ozonation system: It fully contacts the high-salinity wastewater that has been tested and analyzed with ozone to obtain ozonated effluent; Pretreatment system: it settles and filters the ozonated effluent to obtain pretreated effluent and pretreated concentrated liquid. The pretreated effluent enters the next-stage electrolytic hydrogen production system, and the pretreated concentrated liquid enters the evaporation system; Electrolytic hydrogen production system: It includes a water collection component and an electrolysis component. The water collection component filters the pre-treated water to obtain wastewater concentrate and dilute electrolyte. The wastewater concentrate enters the next-level membrane distillation system. The electrolysis component performs in-situ electrolysis on the dilute electrolyte to obtain concentrated electrolyte, hydrogen and oxygen. The concentrated electrolyte returns to the water collection component and is filtered together with the pre-treated water. 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 carries out evaporation treatment on the pre-treated concentrated liquid and the membrane distillation concentrated liquid to obtain solid waste.

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

3. A high-salinity wastewater multi-stage treatment system 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 to be used for preparing ozone.

4. A high-salinity wastewater multi-stage treatment system according to claim 1, characterized in that: In the electrolytic hydrogen production system, a tube bundle type water collection module assembly is provided, and the tube bundle type water collection module assembly includes a water collection assembly and an electrolysis assembly.

5. A high-salinity wastewater multi-stage treatment system according to claim 1, characterized in that: The driving force of the membrane distillation system and the evaporation system is low-grade waste heat from the power plant.

6. A high-salinity wastewater multi-stage treatment system according to claim 5, characterized in that: The low-grade waste heat of the power plant is flue gas waste heat or boiler outlet water waste heat.

7. A high-value utilization method for high-salinity wastewater, characterized in that: The following steps are involved: Water sample testing and analysis: Sampling and analyzing at least three batches of high-salt wastewater from the actual production process to obtain the pH, COD, TDS, hardness and the numerical range of various pollutant contents of the wastewater; Ozonation treatment: The high-salinity wastewater that has been tested and analyzed is fully contacted with ozone to obtain ozonated effluent; Wastewater pretreatment: sedimenting and filtering the ozonated effluent to obtain pretreated effluent and pretreated concentrated liquid; Electrolysis for hydrogen production: The pre-treated water is filtered and electrolyzed in situ through a tube bundle water collection assembly to obtain hydrogen, oxygen and wastewater concentrate; Membrane distillation treatment: performing membrane distillation treatment on the wastewater concentrate to obtain pure water and membrane distillation concentrate; Evaporation treatment: Use the low-grade waste heat from the power plant to evaporate the pre-treated concentrate and membrane distillation concentrate to remove moisture and obtain solid waste.

8. A high-value utilization method for high-salinity wastewater according to claim 7, characterized in that: During the electrolytic hydrogen production process, the pretreated water enters the shell side of the tube bundle water collection component, and the electrolyte flows through the hollow fibers of the tube bundle membrane component. Driven by the water vapor partial pressure difference, the water molecules in the pretreated water cross the membrane and enter the electrolyte. The pretreated water is initially concentrated and the electrolyte is diluted, thereby achieving the purpose of water extraction. The diluted electrolyte is electrolyzed in the electrolysis component to prepare hydrogen, and the concentrated electrolyte enters the water collection component again.

Images