Water-energy-salt cascade reuse system of power plant by multi-film integrated coupling of flue gas drying

Abstract

The application discloses a power plant water-energy-salt cascade reuse system for flue gas drying integrated coupling, to solve the problems of low resource utilization efficiency and high energy consumption in the zero discharge technology of power plant wastewater. Through the technologies of circulating cooling water cascade reuse, desulfurization wastewater efficient concentration treatment, desulfurization concentrated water flue gas drying treatment and intelligent monitoring and control unit, the efficient reuse of water, salt and energy in the wastewater is realized. The wastewater is treated through multiple membrane processes such as ultrafiltration, nanofiltration and reverse osmosis, so that the cascade water quality reuse for different purposes is realized. The calcium and magnesium ions are extracted through chemical precipitation and used as industrial raw materials, effectively alleviating the membrane pollution problem of subsequent processes. The high-salinity wastewater is dried by flue gas waste heat to produce industrial salt, realizing the recovery of salt resources. The system adopts an intelligent monitoring and control system, realizes real-time monitoring and automatic adjustment, optimizes the operation efficiency of each treatment unit and reduces energy consumption. The application realizes near-zero discharge of wastewater and efficient reuse of resources, and has significant economic and environmental benefits.

Description

Technical Field

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

[0002] With the accelerating pace of industrialization and urbanization, electricity demand continues to grow. Coal-fired power generation is currently my country's main source of electricity, accounting for approximately 58.4% of total power generation. During coal-fired power generation, power plants generate large amounts of high-salinity wastewater, primarily originating from desulfurization, circulating cooling, and chemical treatment units. This wastewater not only contains high concentrations of salt and hardness but also pollutants such as suspended solids, heavy metal ions, and recalcitrant organic matter. To comply with increasingly stringent environmental regulations, many power plants have begun adopting zero-discharge wastewater treatment technologies. However, current zero-discharge processes do not fully utilize the resources and energy within the wastewater, resulting in high overall treatment costs and unsatisfactory operational performance.

[0003] Existing zero-discharge technologies for wastewater typically employ membrane concentration and evaporation crystallization processes. These processes have the following shortcomings: (1) Membrane fouling is a common problem during membrane concentration, mainly caused by the accumulation of suspended solids, organic matter, and inorganic ions (such as calcium, magnesium, and sulfate) in the wastewater. Membrane fouling increases the frequency of maintenance and cleaning, affecting the operating efficiency and long-term stability of the zero-discharge system. (2) The salts produced during the evaporation process of the concentrated high-salt wastewater contain a large amount of organic matter and impurities, which means that these salts can only be treated as industrial waste salts and cannot be utilized as resources. (3) A large amount of waste heat from the flue gas generated by thermal power plants is not fully utilized in the wastewater treatment process, resulting in high energy consumption and low efficiency in the wastewater evaporation crystallization stage. (4) Existing technologies mainly focus on wastewater reduction treatment, but lack the fine-grained recycling and utilization of salts and calcium and magnesium resources, which limits the potential for increasing 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 cascaded recovery and utilization of water, energy, and salt resources. This system must not only meet the requirement 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 this application, a multi-membrane integrated coupled flue gas drying water-energy-salt cascade reuse system for thermal power plants is proposed, aiming to solve the problems of insufficient resource utilization and high energy consumption in existing zero-discharge technologies for wastewater from thermal power plants. (Refer to...) Figure 1By using a cascaded reuse system for circulating cooling water, efficient concentration treatment of desulfurization wastewater, drying treatment of desulfurization concentrate and flue gas, and intelligent monitoring and control units, the system achieves efficient reuse of water, energy, and salt resources. This not only optimizes the energy efficiency of wastewater treatment in thermal power plants but also reduces operating costs and improves the system's resource recovery rate.

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

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

[0008] This unit utilizes pretreatment and multi-stage membrane separation technologies (ultrafiltration and nanofiltration) to achieve cascaded reuse of water from thermal power plants, thereby improving water resource utilization efficiency. After preliminary pretreatment, wastewater is reused in the circulating cooling water system, while concentrated wastewater enters the desulfurization system to assist in the flue gas desulfurization process.

[0009] (2) High-efficiency concentration treatment unit for desulfurization wastewater

[0010] This unit uses nanofiltration and novel high-efficiency multi-stage reverse osmosis technology to concentrate and reduce the volume of desulfurization wastewater, producing desulfurization concentrate to reduce wastewater discharge.

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

[0012] This unit utilizes the waste heat from the flue gas of the thermal power plant to dry the desulfurization concentrate, thereby drying and crystallizing the salts and calcium and magnesium in the concentrate to produce industrial salt products and realize the recycling of resources.

[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 the efficient and stable operation of the system.

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

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

[0017] 2. Reduced operating costs. By optimizing the treatment process, wastewater discharge is reduced, lowering subsequent treatment and wastewater disposal costs, and extending equipment lifespan, resulting in significant economic benefits.

[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, ensuring efficient system operation and enabling timely parameter adjustments to adapt to different wastewater treatment needs. Attached Figure Description

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

[0020] Figure 1 This is the control flow diagram 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 multi-membrane integrated coupled flue gas drying system for the water-energy-salt cascade reuse system in a thermal power plant, as described in this application.

[0022] Explanation of reference numerals in the attached figures:

[0023] 11 is nanofiltration permeate reuse; 12 is ash spraying for dust removal; 13 is chemically treated water; 14 is boiler feedwater; 21 is calcium hydroxide and magnesium hydroxide; 22 is sodium sulfate product; 23 is sodium chloride product; 31 is raw flue gas; 32 is high-temperature flue gas; 41 is central intelligent control system; 42 is water quality monitoring unit; 43 is water quantity regulation unit; 44 is salt separation rate monitoring unit; 45 is membrane fouling monitoring unit; 46 is energy monitoring unit. Detailed Implementation

[0024] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0025] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0026] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0029] In this application, references Figure 2 The circulating cooling water system is the starting point of the entire process. The system performs initial homogenization treatment through a regulating water tank. The regulating water tank's function is to balance water quality fluctuations and remove some large suspended particles, providing a stable water source for subsequent treatment. The circulating cooling water in the regulating water tank first passes through an ultrafiltration unit. The ultrafiltration system effectively removes suspended solids and large organic molecules from the water, significantly reducing the particulate matter load and ensuring the efficient operation of the subsequent membrane separation unit.

[0030] The permeate after ultrafiltration enters the nanofiltration unit. The nanofiltration system produces relatively high-quality permeate (11), which is recycled into the circulating cooling system, reducing the power plant's raw water consumption. The concentrate from the nanofiltration unit, rich in calcium and magnesium ions, enters the desulfurization system to assist in the flue gas desulfurization process. After preliminary treatment, the flue gas desulfurization wastewater (12) can be used for dust removal by spraying ash slag; the remaining concentrate enters the high-efficiency concentration treatment unit for desulfurization wastewater.

[0031] During the high-efficiency concentration treatment of desulfurization wastewater, calcium and magnesium ions in the wastewater are precipitated into calcium hydroxide and magnesium hydroxide through a chemical reaction, which can be used in building materials or other industrial applications. The remaining wastewater enters a multi-media filtration unit for further treatment and is then stored in a storage tank as makeup water for chemical treatment processes such as chemical dosing.

[0032] Meanwhile, the concentrate from the nanofiltration desalination process undergoes advanced oxidation and freeze crystallization to produce sodium sulfate (22). The nanofiltration permeate then enters a new, high-efficiency, multi-stage reverse osmosis system for further concentration. The reverse osmosis permeate is reused in the boiler feedwater system (section 14), which has the highest water quality requirements in the entire system. The reverse osmosis concentrate enters the desulfurization concentrate flue gas drying unit. This unit uses high-temperature flue gas drying technology to rapidly evaporate the desulfurization concentrate, producing usable salt products such as sodium chloride (23).

[0033] Throughout the entire process, the tiered utilization of waste heat from the flue gas is key to improving energy efficiency. Through reasonable temperature control and heat distribution, the raw flue gas (31) enters the first air heat exchanger, generating high-temperature flue gas (300℃-350℃). This high-temperature flue gas is used to evaporate and crystallize high-salt wastewater and perform drying treatment. In this process, the high-temperature flue gas not only effectively completes the evaporation and concentration of wastewater but also dries residual solid matter, ensuring the full utilization of waste heat and thus significantly improving energy efficiency.

[0034] The system comprises: 41. A central intelligent control system that monitors and adjusts the operational data of each unit in real time; 42. A water quality monitoring unit that ensures water quality meets reuse requirements; 43. A water flow regulation unit that controls the amount of water entering the calcium and magnesium ion extraction unit; 44. A salt separation rate monitoring unit that controls nanofiltration performance; 45. A membrane fouling monitoring unit that provides early warnings and adjusts cleaning strategies to prevent system downtime due to membrane fouling; and 46. An energy monitoring unit that monitors and dynamically adjusts waste heat utilization efficiency. Through big data analysis and predictive models, the intelligent system can intervene and adjust in advance in case of fluctuations or emergencies in system operation, ensuring optimal utilization of wastewater, energy, and salt resources.

[0035] This process integrates the cascade reuse of circulating cooling water, efficient concentration treatment of desulfurization wastewater, drying treatment of desulfurization concentrate and flue gas, and intelligent monitoring and control unit, forming a highly efficient cascade reuse system of water-energy-salt, achieving near-zero discharge of wastewater from thermal power plants and efficient resource recovery.

[0036] The process method of this application will be further explained below with reference to a specific embodiment:

[0037] A coal-fired power plant generates a large amount of desulfurization wastewater and circulating cooling concentrate during its daily operation. The power plant employs the multi-membrane integrated coupled flue gas drying water-energy-salt cascade reuse system described in this application to treat this wastewater. First, the circulating cooling water enters an ultrafiltration unit through a regulating tank, removing over 99% of suspended solids. Part of the ultrafiltration permeate is reused in the power plant's circulating cooling water system, while the remainder enters a nanofiltration unit for further concentration. The concentrated calcium-magnesium enriched water then enters the desulfurization system, where the desulfurization wastewater undergoes chemical precipitation to produce calcium hydroxide and magnesium hydroxide products, which are used as auxiliary materials in the power plant's desulfurization process. This design reduces calcium and magnesium ions in the water by over 90%, effectively mitigating subsequent high-pressure membrane fouling and reducing membrane cleaning frequency by approximately 30%.

[0038] Meanwhile, 10% of the desulfurization wastewater initially treated in the triple-tank unit is used for dust suppression spraying at the ash disposal site to meet the power plant's low water quality requirements. The remaining 90% of the water enters the chemical precipitation and multi-media filtration unit. After further multi-media filtration, approximately 2% of the water from the chemically precipitated water is then sent to the power plant's chemical treatment water system.

[0039] Nanofiltration concentrate is subjected to advanced oxidation to remove organic matter, and then freeze-crystallized to produce industrial-grade sodium sulfate. Nanofiltration permeate is concentrated through a multi-stage reverse osmosis unit; 100% of the reverse osmosis permeate is used as boiler feedwater. The high-salinity wastewater remaining after reverse osmosis concentration enters the flue gas drying unit. During the drying process, the wastewater undergoes drying and evaporation crystallization at 300℃-350℃, ultimately producing industrial-grade sodium chloride.

[0040] This system is also equipped with an intelligent monitoring and control unit, which monitors the operation of each processing unit in real time and dynamically adjusts relevant parameters. The energy monitoring system optimizes the distribution and utilization of waste heat from flue gas, reducing energy consumption by more than 20% throughout the entire process, significantly improving resource recovery efficiency, and ensuring stable system operation and high energy efficiency.

[0041] The above description is merely one specific embodiment of this application, used to explain the process principle and flow of this application. Any equivalent modifications, substitutions, or variations made by those skilled in the art based on the prior art without departing from the core idea of ​​this application should be considered as included within the protection scope of this application. These modifications, whether adjustments to system configuration, process flow, or specific parameters, do not affect the actual effect of this application and should be included within the patent protection scope of this application.

Claims

1. A multi-membrane integrated coupled flue gas drying system for the water-energy-salt cascade reuse of thermal power plants, characterized in that, It includes the following units: (1) Circulating cooling water cascade reuse unit: includes a pretreatment unit, an ultrafiltration device, and a nanofiltration device. By sequentially treating the circulating cooling water of the thermal power plant, the treated clean water is reused in the plant's circulating cooling unit, and the concentrated water enters the desulfurization system to assist the flue gas desulfurization process, so as to realize the cascade reuse of circulating cooling water. The pretreatment unit is an equalization tank, used to balance the fluctuations in the quality and quantity of circulating cooling water and remove some suspended solids. The ultrafiltration device is used to remove suspended solids and macromolecular organic matter from the wastewater. The nanofiltration device is used to deeply concentrate the wastewater. Its product water is reused in the circulating cooling water system, and the concentrated water enters the desulfurization system. (2) High-efficiency concentration treatment unit for desulfurization wastewater: includes chemical precipitation unit and concentration unit, used to concentrate and reduce the volume of desulfurization wastewater to produce desulfurization concentrate; The chemical precipitation unit is used to convert calcium and magnesium ions in wastewater into precipitates, and the concentration unit includes a nanofiltration device and a multi-stage reverse osmosis treatment device to concentrate and reduce the volume of wastewater and produce desulfurized concentrate. (3) Desulfurization concentrate flue gas drying treatment unit: The waste heat of flue gas from thermal power plant is used to dry the desulfurization concentrate and crystallize the salt and calcium and magnesium components in the concentrate to generate industrial salt products. The desulfurization concentrate flue gas drying treatment unit includes a flue gas heat exchanger, a cyclone separator, and an exhaust gas processor. The flue gas heat exchanger uses the waste heat of the flue gas from the thermal power plant to perform heat exchange treatment on the desulfurization concentrate to achieve evaporation and concentration of the desulfurization concentrate. The cyclone separator separates the solid particles and gases generated during the drying process to ensure drying efficiency and recover solid products. The exhaust gas processor treats the exhaust gas generated during the drying process to ensure that the emission gas meets environmental protection standards and further reduce the system's impact on the environment. (4) Intelligent monitoring and control unit: Real-time monitoring and dynamic adjustment of the operating status of each processing unit through big data and artificial intelligence algorithms; The intelligent monitoring and control unit includes a water quality monitoring unit, a water quantity regulation unit, a salt separation rate monitoring unit, a membrane fouling monitoring unit, an energy monitoring unit, and a central intelligent control system. The water quality monitoring unit ensures that the water quality meets the various reuse requirements, the water quantity regulation unit controls the amount of water entering the calcium and magnesium ion separation extraction unit, the salt separation rate monitoring unit controls the nanofiltration operating performance, the membrane fouling monitoring unit can provide early warnings and adjust the cleaning strategy to avoid system shutdown caused by membrane fouling, and the energy monitoring unit is used to monitor and dynamically adjust the waste heat utilization efficiency. The central intelligent control system, through big data analysis and predictive models, can intervene and adjust in advance when the system operation fluctuates or is interrupted, ensuring the optimal utilization of wastewater, energy, and salt resources.

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