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CN-121990631-A - Power plant waste heat coupling sea water desalination system and energy efficiency optimization method

CN121990631ACN 121990631 ACN121990631 ACN 121990631ACN-121990631-A

Abstract

The invention discloses a power plant waste heat coupling sea water desalination system and an energy efficiency optimization method, and belongs to the technical field of water treatment. The system comprises a waste heat cascade recovery unit, a hot film cooperative desalination unit, a strong brine treatment unit and an intelligent regulation and control unit, wherein the waste heat cascade recovery unit realizes the graded utilization of waste heat with different temperatures, the hot film cooperative desalination unit adopts a multistage dynamic film group and hot film coupling process, the strong brine treatment unit realizes the zero discharge and the resource recovery of the strong brine, and the intelligent regulation and control unit realizes the full-flow dynamic optimization based on a fuzzy PID algorithm. The optimization method realizes that the utilization rate of the waste heat is more than or equal to 90 percent and the energy consumption of unit water production is less than or equal to 0.6kWh/m <3 > through parameter collection, waste heat distribution optimization, membrane group adaptation optimization, strong brine collaborative optimization and real-time iterative optimization. The invention solves the problems of low utilization rate of waste heat, rough regulation and control and concentrated brine pollution in the prior art, obviously improves the energy efficiency and the operation stability of the system, is suitable for various power plant waste heat coupling seawater desalination scenes, and has important economic and social values.

Inventors

  • WANG ZHIHUA

Assignees

  • 国家能源蓬莱发电有限公司

Dates

Publication Date
20260508
Application Date
20260120

Claims (10)

  1. 1. Waste heat coupling sea water desalination of power plant, its characterized in that: the system comprises a waste heat step recovery unit, a hot film cooperative desalination unit, a strong brine treatment unit and an intelligent regulation and control unit, wherein the units are interconnected and communicated with a control system through pipelines; The waste heat cascade recovery unit comprises a high-temperature waste heat exchanger, a medium-temperature waste heat exchanger and a low-temperature waste heat exchanger which are sequentially connected, and the waste heat cascade recovery unit is respectively and correspondingly connected with different process modules of the hot film collaborative desalination unit and is provided with a waste heat flow and temperature monitoring module; The heat membrane collaborative desalting unit comprises a pretreatment module, a multi-effect distillation module, namely an MED module, a reverse osmosis membrane group module, namely an RO membrane group module and a produced water tempering module, wherein the pretreatment module adopts an ultrafiltration membrane, the pretreated seawater is divided into two paths and respectively enters the multi-effect distillation module and the reverse osmosis membrane group module, the reverse osmosis membrane group module adopts multi-stage membrane modules with different desalination rates, the membrane modules are prepared by interface polymerization reaction regulated and controlled by buffer solution, and the pH value of aqueous phase solutions of the different membrane modules is 6-11.5; the concentrated brine treatment unit comprises a concentrated brine collecting tank, a reduced pressure evaporation module and a salt recovery module, wherein the concentrated brine generated by the RO membrane group enters the reduced pressure evaporation module, the low-temperature waste heat at the tail end of the waste heat recovery unit is utilized for evaporation concentration, the concentrated salt slurry enters the salt recovery module, and the steam generated by evaporation flows back to the pretreatment module; The intelligent regulation and control unit comprises a data acquisition module, an algorithm optimization module and an execution mechanism, wherein the data acquisition module acquires waste heat parameters, seawater parameters, membrane group parameters and water production parameters in real time, the algorithm optimization module builds an energy efficiency optimization model based on a fuzzy PID algorithm, and the execution mechanism responds to an optimization instruction to realize dynamic regulation and control of system parameters.
  2. 2. The power plant waste heat coupling sea water desalination system as set forth in claim 1, wherein the high temperature waste heat exchanger is adapted to 100-120 ℃ waste heat, the medium temperature waste heat exchanger is adapted to 60-100 ℃ waste heat, and the low temperature waste heat exchanger is adapted to 40-60 ℃ waste heat.
  3. 3. The power plant waste heat coupling sea water desalting system according to claim 1, wherein the pretreatment module adopts an ultrafiltration membrane with a molecular weight cutoff of 20000-100000Da, and the ultrafiltration membrane is made of one or a combination of more of polysulfone, polyethersulfone and sulfonated polyethersulfone.
  4. 4. The power plant waste heat coupling sea water desalination system as set forth in claim 1, wherein the pH value of the aqueous phase solution of the first stage membrane assembly is 10-11.5, the pH value of the aqueous phase solution of the second stage membrane assembly is 8-9.5, and the pH value of the aqueous phase solution of the third stage membrane assembly is 6-7.5.
  5. 5. The power plant waste heat coupling sea water desalination system as claimed in claim 1, wherein the evaporation temperature of the decompression evaporation module is controlled to be 45-55 ℃, and the concentration ratio of the strong brine is more than or equal to 10 times.
  6. 6. The power plant waste heat coupling sea water desalination system of claim 1, wherein the data acquisition frequency of the intelligent regulation and control unit is more than or equal to 5Hz, the algorithm optimization module adopts a fuzzy PID algorithm, and the execution mechanism comprises an electromagnetic valve, a variable frequency pump and a membrane group switching device.
  7. 7. The power plant waste heat coupling sea water desalination energy efficiency optimization method based on the system of any one of claims 1-6 is characterized by comprising the following steps: Step 1, initializing and collecting parameters in real time, initializing system operation parameters after an intelligent regulation unit is started, and collecting waste heat temperature, flow, seawater salinity, membrane group transmembrane pressure difference and water production conductivity key parameters in real time by a data collecting module; Step 2, waste heat gradient distribution optimization, wherein an algorithm optimization module dynamically distributes waste heat to the proportion of the MED module to the RO preheating module according to a waste heat temperature grading result, high-temperature waste heat is preferentially supplied to the MED module, medium-temperature waste heat supplements heat requirements of the MED module, and low-temperature waste heat is completely used for RO feeding seawater preheating; Step 3, dynamic adaptation and optimization of the membrane group, namely matching an optimal multi-stage membrane group combination mode from a membrane group configuration rule base according to a seawater salinity detection result, and simultaneously adjusting the operating pressure of the membrane group in real time according to the change of the transmembrane pressure difference; step 4, the concentrated brine treatment is cooperatively optimized, the waste heat supply quantity of the decompression evaporation module is dynamically regulated according to the RO concentrated brine yield and concentration, the evaporation temperature is controlled, the concentrated brine concentration ratio is ensured, and the evaporation steam is recycled to the pretreatment module; And 5, feeding back and performing iterative optimization in real time, continuously monitoring the energy efficiency index of the system by the data acquisition module, and if the energy efficiency index deviates from the optimal threshold value, performing iterative calculation on the optimization parameters by the algorithm optimization module again, and adjusting the running state of the system.
  8. 8. The power plant waste heat coupling sea water desalination energy efficiency optimization method according to claim 7, wherein the waste heat utilization rate in the step2 is more than or equal to 90%.
  9. 9. The method for optimizing the energy efficiency of power plant waste heat coupled seawater desalination according to claim 7, wherein in the step 3, high-salinity seawater adopts a combination mode of leading a high-desalination-rate membrane group and trailing a low-salt-removal-rate membrane group, wherein the salinity of the high-salinity seawater is more than or equal to 35 per mill, and the salinity of the low-salinity seawater adopts a mode of simplifying the number of stages of the membrane group, and the salinity of the low-salinity seawater is less than 35 per mill.
  10. 10. The method for optimizing the energy efficiency of the seawater desalination by coupling waste heat of a power plant as claimed in claim 7, wherein the system energy efficiency index in the step 5 comprises unit water production energy consumption and waste heat utilization rate, and the unit water production energy consumption is less than or equal to 0.6kWh/m < 3 >.

Description

Power plant waste heat coupling sea water desalination system and energy efficiency optimization method Technical Field The invention belongs to the technical field of sea water desalination and comprehensive energy utilization, and particularly relates to a power plant waste heat coupling sea water desalination system and an energy efficiency optimization method, which are suitable for a waste heat recovery and sea water desalination cooperative operation scene of various power plants such as thermal power plants, nuclear power plants and the like. Background The problem of shortage of fresh water resources worldwide is becoming more serious, and sea water desalination has become a key way to solve the water resource crisis in coastal areas. The current mainstream sea water desalination technology comprises Reverse Osmosis (RO), multi-effect distillation (MED) and the like, but all have the problem of high energy consumption, and the energy cost accounts for more than 60% of the water production cost. Meanwhile, a large amount of waste heat is generated in the power generation process of a power plant (especially thermal power and nuclear power), wherein the low-temperature waste heat (40-120 ℃) has extremely high duty ratio, and the waste heat is often directly discharged, so that not only is energy wasted, but also thermal pollution is possibly caused. In order to realize efficient energy utilization, the prior art begins to explore the coupling application of the waste heat of a power plant and the sea water desalination technology. For example, a thermal membrane coupling sea water desalination technology (F-MED-RO) developed by Shanghai electric technology is fused with a membrane technology by a thermal method, so that cascade utilization of heat and sea water is realized, but the technology still has the following core defects: firstly, the waste heat utilization efficiency is low, and the dynamic fluctuation characteristics of the waste heat of the power plant are not accurately matched, so that part of the waste heat cannot be effectively recovered; secondly, the system is coarsely regulated and controlled, runs depending on fixed technological parameters, is difficult to cope with the fluctuation of working conditions such as seawater salinity change, membrane pollution and the like, and has the problems of low desalination rate, high energy consumption and the like; thirdly, the strong brine treatment and the waste heat utilization have poor cooperativity, the direct discharge of the strong brine produced by the membrane method is easy to cause marine ecological pollution, and the independent treatment also needs to consume extra energy. In addition, the dynamic combination of the membrane groups is realized by the existing multistage membrane group seawater desalination system, but the dynamic combination is not fused with the gradient utilization depth of the waste heat of the power plant, and the temperature gradient advantage of the waste heat cannot be fully exerted. Meanwhile, energy efficiency optimization is limited to a single process link, and a cooperative optimization strategy for the whole flow of waste heat recovery, sea water desalination and strong brine treatment is lacked, so that the overall energy efficiency of the system is low. In view of the above, a coupling system and a coupling method capable of realizing accurate recovery of waste heat of a power plant, efficient operation of sea water desalination and full-process energy efficiency optimization are developed, and the coupling system and the coupling method have important significance for promoting low-carbon development of sea water desalination industry and improving comprehensive utilization rate of energy of the power plant, accord with national energy-saving and environment-friendly industry development guidance, and have technical value and social requirements of priority examination. Disclosure of Invention Aiming at the problems of low utilization rate of waste heat of a power plant, rough regulation and control of a sea water desalination system, poor energy efficiency of the whole process and strong brine treatment in the prior art, the invention provides the waste heat coupling sea water desalination system of the power plant and the energy efficiency optimization method, which realize the gradient and accurate utilization of the waste heat, the dynamic adaptation of sea water desalination, the optimal energy efficiency of the whole process and the cooperative treatment of the strong brine, reduce the water production cost and reduce the environmental impact. In order to achieve the above purpose, the present invention provides the following technical solutions: The power plant waste heat coupling sea water desalination system comprises a waste heat cascade recovery unit, a thermal film cooperative desalination unit, a strong brine treatment unit and an intelligent regulation and control unit, wherein the un