Thermal power plant water-energy-salt cascade recycling system for multi-membrane integrated coupling flue gas drying

Abstract

The invention discloses a multi-membrane integrated coupling flue gas drying thermal power plant water-energy-salt cascade recycling system, and aims to solve the problems of low resource utilization efficiency, high energy consumption and the like in a thermal power plant wastewater zero discharge technology. Through circulating cooling water cascade recycling, desulfurization wastewater efficient concentration treatment, desulfurization concentrated water flue gas drying treatment and intelligent monitoring and control unit technologies, efficient recycling of water, salt and energy in wastewater is realized. The wastewater is subjected to multi-stage membrane treatment such as ultrafiltration, nanofiltration and reverse osmosis, so that cascade water reuse for different purposes is realized. Calcium and magnesium ions are extracted through chemical precipitation and are used as industrial raw materials, so that the problem of membrane pollution in subsequent processes is effectively relieved. High-salinity wastewater is dried by flue gas waste heat to generate industrial salt, and salt resources are recycled. The system adopts an intelligent monitoring and control system, and through real-time monitoring and automatic adjustment, the operation efficiency of each processing unit is optimized, and the energy consumption is reduced. The method realizes near-zero discharge of wastewater and high-efficiency recycling of resources, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The present application relates to the field of industrial wastewater treatment and resource recycling, and specifically, to a zero-discharge technology for wastewater from a thermal power plant. Background Art

[0002] With the continuous acceleration of industrialization and urbanization, the demand for electricity continues to grow. Coal-fired power generation is currently the main source of electricity in my country, accounting for about 58.4% of the total power generation. In the process of coal-fired power generation, thermal power plants will produce a large amount of high-salt wastewater, the main sources of which include desulfurization, circulating cooling and chemical treatment units. These wastewaters not only contain high concentrations of salt and hardness, but also are accompanied by pollutants such as suspended solids, heavy metal ions, and difficult-to-degrade organic matter. In order to cope with increasingly stringent environmental regulations, many thermal power plants have begun to adopt wastewater zero-discharge treatment technology. However, the current zero-discharge process has not fully utilized the resources and energy in the wastewater, resulting in high overall treatment costs and unsatisfactory operating results.

[0003] Existing wastewater zero-discharge technologies usually use membrane concentration and evaporation crystallization processes. These processes have the following deficiencies: (1) Membrane pollution problems are often encountered during membrane concentration, which is mainly caused by the accumulation of suspended matter, organic matter and inorganic ions (such as calcium, magnesium, sulfate, etc.) in the wastewater. Membrane pollution increases the frequency of maintenance and cleaning, affecting the operating efficiency and long-term stability of the zero-discharge system. (2) The salt produced by the concentrated high-salt wastewater during the evaporation process contains a lot of organic matter and impurities, resulting in these salts can only be treated as industrial waste salt and cannot be recycled. (3) The large amount of flue gas waste heat generated by thermal power plants has not been fully used in the wastewater treatment process, resulting in high energy consumption and low efficiency in the wastewater evaporation and crystallization stage. (4) Existing technologies mainly focus on wastewater reduction treatment, but the refined separation and recycling of salt and calcium and magnesium resources is insufficient, which limits the added value of system products and the potential for resource utilization.

[0004] Therefore, there is an urgent need for a system that can integrate the cascade recycling of water, energy and salt resources. This system must not only meet the requirements of zero wastewater discharge, but also significantly increase the added value of resource recovery, while reducing energy consumption and improving overall economic and environmental benefits. Summary of the invention

[0005] In the first aspect of the present application, the present application proposes a multi-membrane integrated coupled flue gas drying thermal power plant water-energy-salt cascade reuse system, which aims to solve the problems of insufficient resource utilization and high energy consumption in the existing thermal power plant wastewater zero discharge technology, referring to Figure 1Through the cascade reuse of circulating cooling water, efficient concentration treatment of desulfurization wastewater, desulfurization concentrated water flue gas drying treatment and intelligent monitoring and control unit, efficient reuse of water resources, energy and salt resources is achieved, which not only optimizes the energy efficiency of wastewater treatment in thermal power plants, but also reduces operating costs and improves the resource recovery rate of the system.

[0006] The system of this application includes the following core components:

[0007] (1) Circulating cooling water cascade reuse unit

[0008] This unit uses pretreatment and ultrafiltration and nanofiltration multi-stage membrane separation technology to achieve cascade reuse of thermal power plant water quality and improve water resource utilization efficiency. After preliminary pretreatment, wastewater is reused in the circulating cooling water system, and concentrated water enters the desulfurization system to assist the flue gas desulfurization process.

[0009] (2) Desulfurization wastewater high-efficiency concentration treatment unit

[0010] This unit uses nanofiltration and new high-efficiency multi-stage reverse osmosis technology to concentrate and reduce the desulfurization wastewater to produce desulfurization concentrated water to reduce wastewater discharge.

[0011] (3) Desulfurization concentrated water flue gas drying treatment unit

[0012] This unit uses the waste heat from the flue gas of the thermal power plant to dry the desulfurization concentrate, dry and crystallize the salt and calcium and magnesium in the concentrate to generate industrial salt products, thus realizing resource recycling.

[0013] (4) Intelligent monitoring and control unit

[0014] This unit uses big data analysis and artificial intelligence algorithms to monitor the operating status of each processing unit in real time and dynamically adjust various system parameters to ensure efficient and stable operation of the system.

[0015] Compared with the prior art, the system of the present application has the following beneficial effects:

[0016] 1. Save resources and energy. Through multi-membrane separation technology and flue gas waste heat utilization, efficient reuse of water and salt resources and cascade utilization of energy are achieved, significantly reducing the energy consumption of thermal power plants.

[0017] 2. Reduce operating costs. By optimizing the treatment process, the amount of wastewater discharged is reduced, the cost of subsequent treatment and wastewater disposal is reduced, the service life of the equipment is extended, and significant economic benefits are achieved.

[0018] 3. Improve system stability. This application uses an intelligent monitoring and control unit to monitor the operating status of each treatment unit in real time, ensure the efficient operation of the system, and adjust parameters in time to meet different wastewater treatment needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0020] Figure 1 This is a control flow chart of the multi-membrane integrated coupled flue gas drying system of this application;

[0021] Figure 2 This is a schematic diagram of the overall structure of the water-energy-salt cascade reuse system of a thermal power plant with multi-membrane integrated coupled flue gas drying for this application.

[0022] Description of reference numerals:

[0023] 11 is the nanofiltration water reuse, 12 is the ash spraying dust removal, 13 is the chemical treatment water, 14 is the boiler feed water, 21 is the calcium hydroxide and magnesium hydroxide, 22 is the sodium sulfate product, 23 is the sodium chloride product, 31 is the original flue gas, 32 is the high-temperature flue gas, 41 is the central intelligent control system, 42 is the water quality monitoring unit, 43 is the water volume regulation unit, 44 is the salt separation rate monitoring unit, 45 is the membrane pollution monitoring unit, and 46 is the energy monitoring unit. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0025] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0026] The terms "including" and "having" in the specification and claims of the present application and any modifications thereof are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0027] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0028] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0029] In this application, reference is made to Figure 2 The circulating cooling water system is the starting point of the entire process. The system performs preliminary homogenization treatment through the regulating water tank. The role of the regulating water tank is to balance the fluctuation of water quality and remove some large suspended particles to provide a stable water source for subsequent treatment. The circulating cooling water in the regulating water tank first passes through the ultrafiltration unit. The ultrafiltration system can effectively remove suspended solids and large molecular organic matter in the water, significantly reduce the particle pollution load in the water, and ensure the efficient operation of the subsequent membrane separation unit.

[0030] The produced water after ultrafiltration treatment enters the nanofiltration unit. The water produced by the nanofiltration system has good water quality and is reused in the circulating cooling system, which reduces the use of raw water in the power plant. The concentrated water from the nanofiltration unit is rich in calcium and magnesium ions and enters the desulfurization system to assist the flue gas desulfurization process. After preliminary treatment, the flue gas desulfurization wastewater can be used for ash spraying and dust removal, and the remaining concentrated water enters the desulfurization wastewater efficient concentration treatment unit.

[0031] During the efficient concentration treatment of desulfurization wastewater, calcium and magnesium ions in the wastewater are precipitated into 21 calcium hydroxide and magnesium hydroxide through chemical reactions, which can be used for building materials or other industrial purposes. The remaining wastewater enters the multi-media filtration unit, is deeply treated and stored in the water storage tank, and is used as 13 chemical treatment water to meet the water replenishment needs in processes such as dosing.

[0032] At the same time, the concentrated water from the nanofiltration salt separation process is treated by advanced oxidation and freezing crystallization to produce 22 sodium sulfate products. The nanofiltration water enters the new high-efficiency multi-stage reverse osmosis system for further concentration. The reverse osmosis water is reused in the 14 boiler water supply system, which is the part with the highest water quality requirements in the entire system. The concentrated water from the reverse osmosis enters the desulfurization concentrated water flue gas drying treatment unit. This unit uses high-temperature flue gas drying technology to quickly evaporate the desulfurization concentrated water to produce 23 sodium chloride industrial salt and other usable salt products.

[0033] In the whole process, the cascade utilization of flue gas waste heat is the key to improving energy efficiency. Through reasonable temperature control and heat energy distribution, 31 the original flue gas enters the first air heat exchanger to produce 32 high-temperature flue gas (300℃-350℃), which is used to evaporate and crystallize high-salt wastewater and dry it. In this process, the high-temperature flue gas not only effectively completes the evaporation and concentration of wastewater, but also is used to dry the residual solid matter, ensuring the full utilization of flue gas waste heat, thereby significantly improving energy utilization efficiency.

[0034] The 41 central intelligent control system in the system monitors and adjusts the operating data of each unit in real time. The 42 water quality monitoring unit ensures that the water quality meets the requirements of each reuse, the 43 water volume regulation unit controls the amount of water entering the calcium and magnesium ion separation and extraction unit, the 44 salt separation rate monitoring unit controls the nanofiltration operation performance, and the 45 membrane pollution monitoring unit can provide early warning and adjust the cleaning strategy to avoid system shutdown caused by membrane pollution. The 46 energy monitoring unit is used to monitor and dynamically adjust the waste heat utilization efficiency. Through big data analysis and predictive models, the intelligent system can intervene and adjust in advance when there are fluctuations or emergencies in the system operation to ensure the optimal utilization of wastewater, energy, and salt resources.

[0035] This process forms an efficient cascade reuse system of water-energy-salt through the comprehensive application of cascade reuse of circulating cooling water, efficient concentration treatment of desulfurization wastewater, drying treatment of desulfurization concentrated water flue gas and intelligent monitoring and control units, achieving near-zero discharge of wastewater from thermal power plants and efficient recovery of resources.

[0036] The process of the present application is further explained below with a specific embodiment:

[0037] A coal-fired power plant generates a large amount of desulfurization wastewater and circulating cooling concentrated water during daily operation. The power plant uses the multi-membrane integrated coupled flue gas drying water-energy-salt cascade reuse system of the present application to treat the above wastewater. First, the circulating cooling water enters the ultrafiltration device through the regulating water tank to remove more than 99% of suspended solids. The water produced after ultrafiltration is partially reused in the circulating cooling water system of the power plant, and the rest enters the nanofiltration unit for further concentration treatment. The concentrated calcium and magnesium enriched water enters the desulfurization system, and the desulfurization wastewater is chemically precipitated to produce calcium hydroxide and magnesium hydroxide products, which are used as auxiliary materials in the desulfurization link of the power plant. Through this design, more than 90% of the calcium and magnesium ions in the water are reduced, the subsequent high-pressure membrane pollution is effectively slowed down, and the membrane cleaning frequency is reduced by about 30%.

[0038] At the same time, 10% of the desulfurization wastewater that has been initially treated in the triple box is used for dust suppression in the ash field to meet the low water quality requirements of the power plant. The remaining 90% of the water enters the chemical precipitation and multi-media filtration unit. After the water quality after chemical precipitation is further filtered through the multi-media, about 2% is transported to the chemical treatment water system of the power plant.

[0039] The nanofiltration concentrated water is subjected to advanced oxidation to remove organic matter, and industrial-grade sodium sulfate products are produced through freezing and crystallization. The nanofiltration produced water is concentrated by a multi-stage reverse osmosis device, and 100% of the reverse osmosis produced water is used for boiler water replenishment. The high-salt wastewater after reverse osmosis concentration enters the flue gas drying unit. During the drying process, the wastewater is dried and evaporated and crystallized at a high temperature of 300℃-350℃, and finally an industrial-grade sodium chloride product is produced.

[0040] The system is also equipped with an intelligent monitoring and control unit to monitor the operation of each processing unit in real time and dynamically adjust relevant parameters. The energy monitoring system reduces the energy consumption of the entire processing process by more than 20% by optimizing the distribution and utilization of flue gas waste heat, significantly improving the efficiency of resource recycling and ensuring the stable operation and high efficiency of the system.

[0041] The above is only one of the specific embodiments of the present application, which is used to explain the process principle and process of the present application. Any equivalent modification, substitution or deformation made by any technician in this field based on the prior art without departing from the core idea of ​​the present application should be deemed to be included in the protection scope of the present application. These modifications, whether they are adjustments to the system composition, process flow or specific parameters, do not affect the actual effect of the present application and should be included in the patent protection of the present application.

Claims

1. A multi-membrane integrated coupled flue gas drying water-energy-salt cascade recycling system for thermal power plants, characterized in that: Contains the following units: (1) Circulating cooling water cascade reuse unit: It includes pretreatment, ultrafiltration, and nanofiltration devices. It sequentially treats the circulating cooling water of the thermal power plant, reuses the treated clean water in the plant's circulating cooling unit, and the concentrated water enters the desulfurization system to assist the flue gas desulfurization process, thus realizing the cascade reuse of circulating cooling water; (2) Desulfurization wastewater high-efficiency concentration treatment unit: including nanofiltration and multi-stage reverse osmosis treatment devices, which concentrate and reduce the desulfurization wastewater to produce desulfurization concentrated water; (3) Desulfurization concentrated water flue gas drying treatment unit: Use the waste heat of the flue gas from the thermal power plant to dry the desulfurization concentrated water and realize the crystallization of salt and calcium and magnesium in the concentrated water to generate industrial salt products; (4) Intelligent monitoring and control unit: Through big data analysis and artificial intelligence algorithms, the operating status of each processing unit is monitored in real time and dynamically adjusted.

2. The multi-membrane integrated coupled flue gas drying water-energy-salt cascade recycling system for thermal power plants according to claim 1 is characterized in that: The circulating cooling water cascade recycling unit comprises: (1) Regulating tank: used to balance the fluctuation of circulating cooling water quality and quantity and remove some suspended matter; (2) Ultrafiltration unit: removes suspended solids and macromolecular organic matter from wastewater; (3) Nanofiltration unit: Deeply concentrate the wastewater, reuse the produced water in the circulating cooling water system, and the concentrated water enters the desulfurization system.

3. The multi-membrane integrated coupled flue gas drying water-energy-salt cascade recycling system for thermal power plants according to claim 1 is characterized in that: The desulfurization wastewater high-efficiency concentration treatment unit comprises: (1) Chemical precipitation unit: used to convert calcium and magnesium ions in wastewater into precipitates for subsequent treatment; (2) Concentration unit: The wastewater is concentrated and reduced through nanofiltration and multi-stage reverse osmosis treatment devices to produce desulfurized concentrated water.

4. The multi-membrane integrated coupled flue gas drying water-energy-salt cascade recycling system for thermal power plants according to claim 1 is characterized in that: The desulfurization concentrated water flue gas drying treatment unit comprises: (1) Flue gas heat exchanger: Use the waste heat of flue gas from thermal power plants to perform heat exchange treatment on desulfurized concentrated water to achieve evaporation and concentration of desulfurized concentrated water; (2) Cyclone separator: Separates solid particles and gases generated during the drying process to ensure drying efficiency and recover solid products; (3) Waste gas processor: By treating the waste gas generated during the drying process, it ensures that the exhaust gas meets environmental protection standards and further reduces the impact of the system on the environment.

5. The multi-membrane integrated coupled flue gas drying water-energy-salt cascade recycling system for thermal power plants according to claim 1 is characterized in that: The intelligent monitoring and control unit comprises: (1) Water quality and quantity monitoring system: monitor the water quality and flow of each water quality cascade reuse unit; (2) Membrane fouling monitoring system: monitors the fouling status of the membrane unit and dynamically adjusts the cleaning cycle and mode; (3) Energy management system: optimize the utilization of flue gas waste heat and monitor the energy efficiency of the drying unit; (4) Central intelligent control system: controls the operating status of the entire system through big data analysis and predictive models.

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