Water and electricity cogeneration system for coupling waste heat utilization and seawater desalination of power station and working method thereof
By using low backpressure turbine coupled low-temperature multi-effect seawater desalination device technology in the refining base, using low-grade energy for thermal circulation, the problems of waste and high cost of medium and high-grade energy in the existing technology are solved, and efficient waste heat is achieved Recycling and desalination of seawater.
Patent Information
- Application Number
- CN202411161195.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-22
- Publication Date
- 2025-02-18
AI Technical Summary
When the prior art uses waste heat from the refining base to supply heat to low-temperature multi-effect seawater desalination devices, there are a lot of problems of high-grade energy waste and high costs. Traditional systems require additional design of temperature reduction and pressure reduction devices and vacuum systems, and increase Investment costs.
Low backpressure turbine coupled low-temperature multi-effect seawater desalination device is adopted, and low-grade energy is used to perform thermal circulation through seawater desalination pre-heat exchanger and boiler flue gas heat exchanger to provide thermal energy to low-temperature multi-effect seawater desalination device to reduce high-grade Energy loss and simplify the system structure to avoid designing temperature reduction and pressure reduction devices and vacuum systems.
It realizes efficient recycling and utilization of waste heat resources in the refining and chemical base, significantly reduces the operating cost and comprehensive energy consumption of thermal seawater desalination, and improves the operating stability and economics of the system.
Smart Images
Figure CN119468185A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a water-power cogeneration system for coupling seawater desalination with waste heat utilization of a power station and a working method thereof. Background Art
[0002] With the rapid economic development and growing energy demand in my country, the integrated refining and chemical model has emerged. my country's refining and chemical industry has made remarkable progress, and my country's refining and chemical capacity will continue to be released. At the same time, the development direction of the refining and chemical industry needs to focus on green production and maximizing benefits.
[0003] The heating steam required for the integrated refining and chemical project base mainly comes from the steam direct supply boiler of the power station to which the project belongs or the high-grade steam such as the adjusted extraction steam and back-pressure exhaust steam of the high-parameter steam turbine; in order to meet the needs of various refining and chemical equipment, the power station boiler and steam turbine generator set are usually required to maintain rated operating conditions as much as possible, so that the heating steam pipeline network of the refining and chemical base is stable and the unit operation is economical and reliable; at this time, if there is an imbalance in steam supply and demand due to process changes, equipment maintenance and other reasons, it will cause surplus steam in the heating steam pipeline network. This surplus steam is a medium-high-grade energy that can be recycled.
[0004] At the same time, during the production process of various refining and chemical units, the waste heat boilers in the base can generate steam, and some process units will also generate steam as a byproduct. This type of by-product steam is also a medium-to-high-grade energy that can be recycled.
[0005] The exhaust gas from conventional boilers first passes through an air preheater, and then is discharged from the chimney after dust removal and desulfurization. The exhaust gas at the outlet of the air preheater has a certain amount of thermal energy and is a recyclable low-grade energy source.
[0006] my country's large-scale integrated refining and chemical projects are often built in coastal areas, and some projects are directly built on islands. Because these projects have a very large demand for desalinated water, large-scale low-temperature multi-effect seawater desalination equipment needs to be built simultaneously. There are three main types of seawater desalination for large-scale industrial applications: multi-stage flash evaporation, low-temperature multi-effect and reverse osmosis. Among them, the key to the commonly used low-temperature multi-effect distillation seawater desalination technology is to use a vacuum environment to make the evaporation temperature of seawater below 70°C, thereby distilling and producing fresh water.
[0007] At present, most of the large-scale low-temperature multi-effect distillation and low-temperature multi-effect seawater desalination devices in some large-scale integrated refining and chemical projects built along the coast use superheated steam as the heat transfer medium. The steam provided by the power station is of high quality, high temperature and high pressure. If the power station directly supplies steam to the low-temperature multi-effect seawater desalination device, not only will a large amount of high-quality energy be wasted, but additional equipment such as cooling and pressure reduction devices must be designed to reduce steam parameters to match the needs of the low-temperature multi-effect seawater desalination device, making the cost of thermal seawater desalination remain high.
[0008] If high-temperature water and a flash evaporation device are used to generate saturated steam as the heat transfer medium for a low-temperature multi-effect seawater desalination device, two-phase flow is likely to occur when transporting saturated steam and saturated water, which will erode equipment, pipelines, valves, etc. The relevant equipment, pipelines, valves, etc. need to use erosion-resistant alloy steel materials, which increases investment costs; saturated steam pipelines will produce condensed water, and regular drain devices need to be installed on the steam pipelines. Improper condensed water recovery will cause loss of the working fluid.
[0009] Existing water and power cogeneration systems using multi-effect seawater desalination devices include Figure 1 In this system, the high-grade adjusted extraction steam of the condensing steam turbine 1' needs to be cooled and depressurized by the temperature reduction and pressure reduction device 21 before being used as the steam source of the low-temperature multi-effect seawater desalination device 5, resulting in a large amount of energy loss; the exhaust steam of the condensing steam turbine 1A is discharged to the condenser 20 through the back pressure exhaust pipe 10, and the exhaust steam is directly cooled by seawater into condensed water, resulting in a large amount of cold end loss; the condenser 20 needs to be equipped with a vacuum device 22, which increases the project investment cost.
[0010] Therefore, based on the concept of energy cascade utilization, rationally recycling and utilizing various waste heat resources in the refining base and using low-grade energy to provide heat energy to the low-temperature multi-effect seawater desalination device is a green technical direction to reduce energy consumption and costs. Summary of the invention
[0011] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a water-power cogeneration system and a working method thereof for coupling desalination of seawater with waste heat from power plants with a reasonable structural design, so as to reduce the cost of thermal desalination of seawater and thus reduce the overall energy consumption. At the same time, the system can also produce heating steam and electric energy as a supplement to the plant steam and plant electricity in the base.
[0012] The technical solution adopted by the present invention to solve the above-mentioned problems is: a water-power cogeneration system for coupling the waste heat utilization of power station with seawater desalination, including a main steam pipeline, a low back-pressure steam turbine, a low-temperature multi-effect seawater desalination device and a back-pressure exhaust pipe; the main steam pipeline is connected to the steam inlet of the low back-pressure steam turbine; it is characterized in that it also includes a seawater desalination front heat exchanger, a boiler flue gas heat exchanger, a hot cycle heat medium water pipeline, a cold cycle heat medium water pipeline, a condensate water pipeline, a boiler air preheater outlet flue gas pipeline, a dust collector and a desulfurization device; the exhaust port of the low back-pressure steam turbine is connected to the shell side inlet of the seawater desalination front heat exchanger through the back-pressure exhaust pipe, and the shell of the seawater desalination front heat exchanger is connected to the shell side of the seawater desalination front heat exchanger. The side outlet is connected to the condensate water pipeline; the water side inlet of the heat exchanger before seawater desalination and the boiler flue gas heat exchanger are connected to the cold circulation heat medium water pipeline, and the water side outlet of the heat exchanger before seawater desalination and the boiler flue gas heat exchanger are connected to the hot circulation heat medium water pipeline; the cold circulation heat medium water pipeline is connected to the water outlet of the seawater desalination heat exchanger of the low-temperature multi-effect seawater desalination device, and the hot circulation heat medium water pipeline is connected to the water inlet of the seawater desalination heat exchanger of the low-temperature multi-effect seawater desalination device; the boiler air preheater outlet flue gas pipeline is connected to the shell side inlet of the boiler flue gas heat exchanger, the shell side outlet of the boiler flue gas heat exchanger is connected to the inlet of the dust collector, and the outlet of the dust collector is connected to the inlet of the desulfurization device.
[0013] The low back-pressure steam turbine of the present invention is connected with a generator.
[0014] The seawater desalination preheat exchanger of the present invention is provided with a safety valve.
[0015] The present invention provides a condensate pump on the condensate pipeline.
[0016] The seawater desalination preheat exchanger of the present invention is provided with a hydrophobic cooling section.
[0017] The back pressure exhaust pipe of the present invention is provided with an expansion joint.
[0018] The present invention installs a circulating heat medium water booster pump on the cold circulating heat medium water pipeline.
[0019] The outlet of the dust collector of the present invention is connected to the inlet of the desulfurization device through an induced draft fan.
[0020] A working method of a water-power cogeneration system for coupling waste heat utilization of power stations with seawater desalination, characterized by the following steps: (1) The surplus steam from the heating steam network, or the by-product superheated steam from the waste heat boiler and process unit enters the low back pressure steam turbine to perform work, and the exhaust steam enters the seawater desalination front heat exchanger through the back pressure exhaust pipe; (2) In the heat exchanger before desalination, the heat of the exhaust steam is taken away by the circulating heat medium water from the cold circulating heat medium water pipeline and condensed into saturated water, which enters the deaerator through the condensate water pipeline; the circulating heat medium water absorbs the heat of the exhaust steam and heats up; (3) The flue gas from the boiler air preheater enters the boiler flue gas heat exchanger. The circulating heat medium water from the cold circulating heat medium water pipeline absorbs the heat of the flue gas in the boiler flue gas heat exchanger and then heats up. The cooled flue gas passes through the dust collector and desulfurization device in turn and is discharged to the chimney. (4) The circulating heat medium water that absorbs heat from the seawater desalination front heat exchanger and the boiler flue gas heat exchanger enters the low-temperature multi-effect seawater desalination device through the hot circulating heat medium water pipeline; (5) In the low-temperature multi-effect seawater desalination device, the circulating heat medium water provides the heat required for thermal seawater desalination through the seawater desalination heat exchanger. After the circulating heat medium water is cooled, it re-enters the cold circulating heat medium water pipeline for recycling.
[0021] In steps (2) and (3) of the present invention, the temperature of the circulating heat medium water is increased from 70°C to 95°C.
[0022] Compared with the prior art, the present invention has the following advantages and effects: (1) The low back-pressure steam turbine technology is adopted. The exhaust pressure of the steam turbine is close to 1 standard atmosphere. The back-pressure exhaust steam is low-grade steam with slightly positive pressure and low superheat. The steam turbine generator set can deeply explore the work potential of high-grade new steam for heating and power generation.
[0023] (2) The use of surplus steam from the heating steam network, waste heat boilers and by-product steam from process units as new steam for steam turbines can absorb the by-product steam to achieve the cascade utilization of surplus medium- and high-grade energy. It can also balance the supply and demand of the heating steam network, enhance the flexibility of the network regulation, expand the regulation range of the network, improve the load stability of higher-level boilers and steam turbine generator sets, and ensure the safe operation of process units in refining or other industrial bases.
[0024] (3) The process flow of a low back-pressure steam turbine coupled with a low-temperature multi-effect seawater desalination device is to replace the condenser of a traditional condensing steam turbine with a heat exchanger before seawater desalination. The back-pressure exhaust steam of the steam turbine is used as a heat exchanger to heat the steam. The system does not need to design a cooling and pressure reduction device, and fully utilizes the latent heat of vaporization and part of the sensible heat of low-grade steam. There is no pressure reduction loss or cooling loss, which can maximize the elimination of cold end losses.
[0025] (4) Using heat medium water as the heat transfer medium to provide heat energy to the low-temperature multi-effect seawater desalination device. The water quality is desalted water to avoid scaling of the heat exchange equipment, and the use of a closed cycle can reduce the loss of heat medium water.
[0026] (5) The low-temperature waste heat such as the back-pressure exhaust steam of the low-back-pressure steam turbine and the low-temperature flue gas at the outlet of the boiler air preheater is used to produce heat-cycle heat medium water, so as to realize the cascade utilization of low-grade energy, reduce the loss of high-grade energy, and significantly reduce the operating cost of thermal seawater desalination.
[0027] (6) Heat medium water is unsaturated water, so carbon steel can be used for related equipment and pipeline valves, and the investment cost is lower than that of alloy steel. The heat exchanger before desalination is arranged close to the steam turbine, which can shorten the length of the large-diameter back-pressure exhaust pipe and reduce the investment cost of pipeline steel.
[0028] (7) The back-pressure steam turbine does not need to design a vacuum system, which can save the one-time investment cost of the equipment and pipelines related to the vacuum system; the steam turbine body system is simplified, and the operation and maintenance are relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG1 is a schematic diagram of the structure of the prior art; FIG. 2 is a schematic structural diagram of an embodiment of the present invention. DETAILED DESCRIPTION
[0030] The present invention will be further described in detail below with reference to the accompanying drawings and by way of examples. The following examples are intended to explain the present invention but the present invention is not limited to the following examples.
[0031] The embodiment of the present invention includes a low back pressure steam turbine 1, a generator 2, a seawater desalination front heat exchanger 3, a boiler flue gas heat exchanger 4, a low temperature multi-effect seawater desalination device 5, a condensate pump 6, a circulating heat medium water booster pump 7, a main steam pipeline 8, a back pressure exhaust pipeline 10, a hot cycle heat medium water pipeline 11, a cold cycle heat medium water pipeline 12, a condensate pipeline 13, a boiler air preheater outlet flue gas pipeline 14, a safety valve 15, an expansion joint 16, a dust collector 17, an induced draft fan 18 and a desulfurization device 19.
[0032] The main steam pipe 8 is connected to the steam inlet of the low back-pressure steam turbine 1. The surplus steam of the heating steam network, the by-product steam of the waste heat boiler and the process equipment enters the low back-pressure steam turbine 1 through the main steam pipe 8 as the new steam of the steam turbine. The tail end of the low back-pressure steam turbine 1 is connected to the generator 2, and the new steam flows through the steam turbine to do work and drives the generator to generate electricity.
[0033] The exhaust port of the low back pressure steam turbine 1 is connected to the shell side inlet of the seawater desalination preheat exchanger 3 through the back pressure exhaust pipe 10; the shell side outlet of the seawater desalination preheat exchanger 3 is connected to the condensate pipe 13; a condensate pump 6 is arranged on the condensate pipe 13. The seawater desalination preheat exchanger 3 is provided with a hydrophobic cooling section, which can make the back pressure exhaust steam release the latent heat of vaporization and part of the sensible heat, and then liquefy into condensate with a certain degree of supercooling, so as to avoid the generation of two-phase flow in the condensate pipe 13 from the shell side outlet of the seawater desalination preheat exchanger 3 to the inlet of the condensate pump 6, and protect the inlet of the condensate pump 6 from cavitation. The condensate is pressurized by the condensate pump 6 and supplied to the deaerator for recycling.
[0034] The back-pressure exhaust steam of the low back-pressure steam turbine 1 is a high specific heat capacity steam with a slight positive pressure and low superheat. The diameter of the back-pressure exhaust steam pipeline 10 is relatively large, and the main plant of the waste heat utilization unit and the main plant of the seawater desalination process are usually not close to each other, and there is a certain distance between the main plants. If the back-pressure exhaust steam is directly used as the heat transfer medium of the low-temperature multi-effect seawater desalination device 5, the back-pressure exhaust steam needs to be transported over a long distance, that is, a long large-diameter back-pressure exhaust steam pipeline 10 needs to be arranged, which will increase the steel consumption cost of the pipeline and the construction cost of the pipeline corridor supporting the pipeline; if heat medium water is used as the heat transfer medium, and the heat exchanger 3 before seawater desalination is arranged in the main plant of the seawater desalination process, the above-mentioned cost problem also exists. Therefore, this embodiment uses heat medium water as the heat transfer medium, and the heat exchanger 3 before seawater desalination is arranged in the main plant of the waste heat utilization unit, and is close to the exhaust port of the low back-pressure steam turbine 1, so as to shorten the length of the back-pressure exhaust steam pipeline 10 and reduce the steel consumption. An expansion joint 16 is provided on the back pressure exhaust pipe 10 to absorb the force between the equipments, which can further shorten the length of the pipe.
[0035] The water side pipes of the heat exchanger 3 and the boiler flue gas heat exchanger 4 before seawater desalination are connected in parallel, and the water side inlets of both are connected to the cold circulation heat medium water pipe 12, and the water side outlets are connected to the hot circulation heat medium water pipe 11; the cold circulation heat medium water pipe 12 is connected to the water outlet of the seawater desalination heat exchanger 51 of the low-temperature multi-effect seawater desalination device 5, and the hot circulation heat medium water pipe 11 is connected to the water inlet of the seawater desalination heat exchanger 51 of the low-temperature multi-effect seawater desalination device 5. The water temperatures of the cold and hot circulation heat medium waters are determined according to the process requirements of the low-temperature multi-effect seawater desalination device 5 coupled to the low back pressure steam turbine 1, and the water temperatures of the cold and hot circulation heat medium waters determine the heating steam pressure of the heat exchanger 3 before seawater desalination, that is, the back pressure of the low back pressure steam turbine 1. A circulating heat medium water booster pump 7 is installed on the cold circulating heat medium water pipeline 12. The circulating heat medium water pump 7 overcomes the flow resistance of the pipeline and the heat exchanger in the heat medium water circulation system. The circulating heat medium water only circulates between the seawater desalination front heat exchanger 3, the boiler flue gas heat exchanger 4 and the low-temperature multi-effect seawater desalination device 5. There are mainly pressure losses along the pipeline and local pressure losses at the equipment. Therefore, the head of the circulating heat medium water booster pump 7 does not need to be too high. It can overcome the above pressure loss and leave a margin. The circulating heat medium water booster pump 7 of this embodiment uses a head of 55m. The back pressure of the low back pressure steam turbine 1 of this embodiment is 120kPa (a). The heat exchanger 3 heats the circulating heat medium water to 95°C before desalination. The 95°C circulating heat medium water is sent to the low-temperature multi-effect seawater desalination device 5 via the hot circulating heat medium water pipeline 11. The low-temperature multi-effect seawater desalination device 5 uses the thermal energy of the circulating heat medium water to distill and separate the original seawater into fresh water and concentrated brine. The temperature of the hot circulating heat medium water is cooled from 95°C to 70°C. The 70°C circulating heat medium water is pressurized by the circulating heat medium water booster pump 7 via the cold circulating heat medium water pipeline 12 and then returns to the heat exchanger 3 before desalination to be heated again, thereby forming a cycle.
[0036] A safety valve 15 is provided on the heat exchanger 3 before desalination of seawater to protect the pipeline and equipment from overpressure.
[0037] The flue gas pipe 14 at the boiler air preheater outlet is connected to the shell side inlet of the boiler flue gas heat exchanger 4, and the circulating heat medium water is heated from 70°C to 95°C. The shell side outlet of the boiler flue gas heat exchanger 4 is connected to the inlet of the dust collector 17. The outlet of the dust collector 17 is connected to the inlet of the desulfurization device 19 through the induced draft fan 18, and the flue gas after heat exchange is discharged to the chimney.
[0038] A working method of a water-power cogeneration system for utilizing waste heat from a power station and coupling desalination of seawater, comprising the following steps: (1) The surplus steam from the heating steam network, the waste heat boiler and the by-product superheated steam from the process unit enters the low back pressure steam turbine 1 to perform work, and the exhaust steam enters the seawater desalination front heat exchanger 3 through the back pressure exhaust pipe 10.
[0039] (2) In the heat exchanger 3 before desalination, the heat of the exhaust steam is taken away by the circulating heat medium water from the cold circulating heat medium water pipe 12 and condensed into saturated water. After being pressurized by the condensate water pipe 13 and the condensate water pump 6, it enters the deaerator and can be recycled. The circulating heat medium water absorbs the heat of the exhaust steam and its temperature rises from 70°C to 95°C.
[0040] (3) The flue gas from the boiler air preheater enters the boiler flue gas heat exchanger 4. The circulating heat medium water from the cold circulating heat medium water pipe 12 absorbs the heat of the flue gas in the boiler flue gas heat exchanger 4, and the temperature rises from 70°C to 95°C. The cooled flue gas passes through the dust collector 17 and the desulfurization device 19 in sequence and is then discharged to the chimney. (4) The circulating heat medium water that absorbs heat from the seawater desalination front heat exchanger 3 and the boiler flue gas heat exchanger 4 is combined and then enters the low-temperature multi-effect seawater desalination device 5 through the heat circulating heat medium water pipeline 11.
[0041] (5) In the low-temperature multi-effect seawater desalination device 5, the circulating heat medium water provides the heat required for thermal seawater desalination through the seawater desalination heat exchanger 51, and the temperature drops from 95°C to 70°C, and re-enters the cold circulating heat medium water pipeline 12 for recycling.
[0042] In addition, it should be noted that the shapes and names of the parts and components of the specific embodiments described in this specification may be different, and the above content described in this specification is only an example of the structure of the present invention. All equivalent changes or simple changes made based on the structure, features and principles described in the patent concept of the present invention are included in the protection scope of the patent of the present invention. Technicians in the technical field of the present invention can make various modifications or supplements to the specific embodiments described or replace them in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.
Claims
1. A hydropower cogeneration system for coupling desalination of seawater with waste heat from a power station, comprising a main steam pipeline, a low back-pressure steam turbine, a low-temperature multi-effect seawater desalination device and a back-pressure exhaust steam pipeline; the main steam pipeline is connected to the steam inlet of the low back-pressure steam turbine; and is characterized in that: It also includes a heat exchanger before desalination, a boiler flue gas heat exchanger, a hot cycle heat medium water pipeline, a cold cycle heat medium water pipeline, a condensate water pipeline, a boiler air preheater outlet flue gas pipeline, a dust collector and a desulfurization device; the exhaust port of the low back pressure steam turbine is connected to the shell side inlet of the heat exchanger before desalination through the back pressure exhaust pipe, and the shell side outlet of the heat exchanger before desalination is connected to the condensate water pipeline; the water side inlets of the heat exchanger before desalination and the boiler flue gas heat exchanger are both connected to the cold cycle heat medium water pipeline, and the seawater desalination The water side outlets of the pre-desalination heat exchanger and the boiler flue gas heat exchanger are connected to the hot cycle heat medium water pipeline; the cold cycle heat medium water pipeline is connected to the water outlet of the seawater desalination heat exchanger of the low-temperature multi-effect seawater desalination device, and the hot cycle heat medium water pipeline is connected to the water inlet of the seawater desalination heat exchanger of the low-temperature multi-effect seawater desalination device; the boiler air preheater outlet flue gas pipeline is connected to the shell side inlet of the boiler flue gas heat exchanger, the shell side outlet of the boiler flue gas heat exchanger is connected to the inlet of the dust collector, and the outlet of the dust collector is connected to the inlet of the desulfurization device.
2. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The low back-pressure steam turbine is connected with a generator.
3. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The seawater desalination front heat exchanger is provided with a safety valve.
4. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The condensate water pump is arranged on the condensate water pipeline.
5. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The seawater desalination front heat exchanger is provided with a hydrophobic cooling section.
6. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The back pressure exhaust pipe is provided with an expansion joint.
7. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: A circulating heat medium water booster pump is installed on the cold circulating heat medium water pipeline.
8. The water-power cogeneration system of power station waste heat utilization coupled with seawater desalination according to claim 1 is characterized by: The outlet of the dust collector is connected to the inlet of the desulfurization device through an induced draft fan.
9. A method for operating a water-power cogeneration system for coupling waste heat utilization of power plants with seawater desalination according to any one of claims 1 to 8, characterized in that: The steps are: (1) The surplus steam from the heating steam network, or the by-product superheated steam from the waste heat boiler and process unit enters the low back pressure steam turbine to perform work, and the exhaust steam enters the seawater desalination front heat exchanger through the back pressure exhaust pipe; (2) In the heat exchanger before desalination, the heat of the exhaust steam is taken away by the circulating heat medium water from the cold circulating heat medium water pipeline and condensed into saturated water, which enters the deaerator through the condensate water pipeline; the circulating heat medium water absorbs the heat of the exhaust steam and heats up; (3) The flue gas from the boiler air preheater enters the boiler flue gas heat exchanger. The circulating heat medium water from the cold circulating heat medium water pipeline absorbs the heat of the flue gas in the boiler flue gas heat exchanger and then heats up. The cooled flue gas passes through the dust collector and desulfurization device in turn and is discharged to the chimney. (4) The circulating heat medium water that absorbs heat from the seawater desalination front heat exchanger and the boiler flue gas heat exchanger enters the low-temperature multi-effect seawater desalination device through the hot circulating heat medium water pipeline; (5) In the low-temperature multi-effect seawater desalination device, the circulating heat medium water provides the heat required for thermal seawater desalination through the seawater desalination heat exchanger. After the circulating heat medium water is cooled, it re-enters the cold circulating heat medium water pipeline for recycling.
10. The working method of power plant waste heat utilization coupled with seawater desalination according to claim 9, characterized in that: In steps (2) and (3), the temperature of the circulating heat medium water is increased from 70°C to 95°C.