A waste heat recovery and reuse device and method for flue gas of a boiler of a thermal power plant

Abstract

The application provides a waste heat recovery and recycling device and method for flue gas of a boiler of a thermal power plant, and belongs to the technical field of energy recovery, to solve the problems of low energy conversion efficiency of a traditional coal-fired device, too large waste amount of coal thermal energy of equipment such as a boiler of a thermal power plant, poor energy utilization rate, and high energy procurement cost, a double-layer shell is internally provided with a coil; one side of the double-layer shell is provided with a water storage pool; the double-layer shell is internally provided with a heat exchange plate; one side of the double-layer shell is provided with a generator. In the application, a three-heat nuclear hot water circulation heat absorption equipment combined with heat cascade utilization is used to perform cascade heating on waste gas generated by burning coal, to recycle flue gas waste heat and condensation heat generated by a steam turbine by using a first type of absorption heat pump based on lithium bromide; the device realizes cascade utilization of flue gas waste heat, can greatly improve energy utilization rate, and condensate water after circulation can enter the steam turbine again to realize cyclic utilization, so that the system power generation efficiency is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of energy recovery, and more specifically, relates to a device and method for recovering and reusing waste heat from boiler flue gas in thermal power plants. Background Technology

[0002] Currently, coal-fired power generation remains the primary mode of power generation in my country. The flue gas temperature of coal-fired boilers is generally 120℃~150℃, and the large amount of low-grade waste heat they carry is usually difficult to utilize and ultimately has to be released into the atmosphere. Although the power generation efficiency of thermal power generation has been continuously improving, its basic scale is enormous, so a large amount of heat energy is lost to the atmosphere every year with the flue gas emissions.

[0003] With the continuous iteration and upgrading of energy-saving and environmentally friendly products, research on improving the thermal efficiency of high-emission industries such as boilers is gradually gaining momentum. Boiler efficiency is closely related to its various losses. Boiler losses consist of flue gas losses, mechanical incomplete combustion losses, ash and slag physical losses, chemical incomplete combustion losses, and heat dissipation losses. Among these five losses, flue gas losses have the greatest impact on boiler efficiency, accounting for approximately 5-8%. Therefore, reducing flue gas losses is of great significance for improving boiler efficiency and the overall power generation economy of the plant. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention aims to provide a boiler flue gas waste heat recovery and reuse device that can improve the energy conversion efficiency of traditional thermal power unit boilers and reduce energy costs. This invention can improve the energy conversion efficiency of traditional coal-fired power plants and effectively solve the problem of excessive waste of coal heat energy from boilers and other equipment in thermal power plants, thereby increasing energy utilization and reducing energy procurement costs.

[0005] The purpose and effectiveness of this invention, a waste heat recovery and reuse device for flue gas in thermal power plant boilers, are achieved by the following specific technical means: A waste heat recovery and reuse device for flue gas from a thermal power plant boiler includes: a coil, a water storage tank, a heat exchange plate, a double-layer shell, finned tubes, a generator, a condenser, a heat exchanger, an absorber, an evaporator, a steam turbine, a solution pump, a coal-fired inlet pipe, a flue, and connecting pipes. The double-layer shell contains the coil; a water storage tank is located on one side of the double-layer shell; a heat exchange plate is located inside the double-layer shell; a generator is located on one side of the double-layer shell and is connected to the double-layer shell via the flue; finned tubes are installed in the interlayer of the flue and are located between the double-layer shell and the generator; the generator, condenser, heat exchanger, and absorber form a first-type absorption heat pump structure, and the generator, condenser, heat exchanger, and absorber are connected and coordinated efficiently via connecting pipes.

[0006] Furthermore, the double-layer shell is composed of an inner shell and an outer shell, and a blower is provided in the cavity between the inner and outer shells. A flue gas inlet pipe is provided on one side of the outer wall of the double-layer shell, and a surrounding pipe is provided in the cavity between the inner and outer shells, and the surrounding pipe is connected to the water storage tank.

[0007] Furthermore, the lower part of the inner shell of the double-layer shell is filled with a liquid phase change medium, and the coil is arranged in the upper part of the inner shell. The heat exchange plate is arranged at the bottom of the inner shell of the double-layer shell, and the heat exchange plate corresponds to the liquid phase change medium.

[0008] Furthermore, the condenser is equipped with a condenser tube, one end of which is equipped with a coal heat outlet pipe, and the other end of the condenser tube is connected to the steam turbine through a connecting pipe.

[0009] Furthermore, the heat exchanger is connected between the generator and the solution pump via connecting pipes, and one side of the heat exchanger is connected to two absorbers via connecting pipes.

[0010] Furthermore, the two absorbers are symmetrically distributed on both sides of the evaporator, and one end of each absorber is connected to the condenser tube of the condenser via a connecting pipe, while the other end of each absorber is connected to the solution pump via a connecting pipe.

[0011] Furthermore, the evaporator is connected to the steam turbine via a connecting pipe, and a coal heat inlet pipe is provided on one side of the steam turbine.

[0012] This application also provides a method for waste heat recovery and reuse of flue gas from a thermal power plant boiler, specifically: the driving heat source of the generator is steam or fuel, and the absorber and condenser form a heating circuit to heat the heat medium; the evaporator absorbs heat from a low-grade heat source through the waste heat circuit to generate refrigerant steam; the lithium bromide solution flows out from the solution pump, is heated and purified by the heat exchanger, and then enters the absorber, where it is sprayed onto the surface of the heat transfer tube to absorb the refrigerant steam from the evaporator; after entering the absorber, the heat medium completes the first heating process using the heat absorbed by the lithium bromide solution; in the condenser, the latent heat of condensation of the high-temperature secondary steam from the generator is used to reheat the heat medium from the absorber that has already been heated once, finally becoming a heat medium that reaches the required temperature, and the steam is condensed into condensate and then transported back to the evaporator to continue the cycle of evaporation.

[0013] Furthermore, the tri-core gas water heater utilizes the high heat transfer coefficient of phase change heat transfer to fully utilize the heat of the high-temperature flame for the first heat absorption; simultaneously, by arranging finned tubes in the flue jacket to complete the second heat absorption of the waste heat of the flue gas, it achieves full utilization of the heat generated by gas combustion and improves the heat exchange efficiency of equipment using high-temperature flue gas as a heat source. This heat exchanger uses high-temperature flame or high-temperature flue gas as a heat source and includes at least a double-shell structure; the lower part of the internal space of the inner shell is filled with a liquid phase change medium, and at least one coil is installed in the upper part; the heated fluid flows in the coil; the downstream pipe of the coil passes through the inner shell and forms at least one surrounding pipe in the cavity between the two shells; the bottom heat exchange plate of the inner shell is located above the heat source; the cavity between the two shells forms a flue gas channel, after the heat source heats the bottom heat exchange plate of the inner shell, the flue gas rises from the bottom perimeter of the outer side of the inner shell along the flue gas channel and transfers heat to the heated fluid in the surrounding pipe. Beneficial effects

[0014] 1. This equipment combines a tri-core hot water circulation heat absorption device for cascade heat utilization to heat the waste gas generated by coal combustion in stages, so as to recover the waste heat of flue gas and the condensation heat generated by the steam turbine by using a lithium bromide-based first-class absorption heat pump.

[0015] 2. Simultaneously, a bypass flue is arranged to utilize the waste heat of flue gas to heat feedwater and condensate, which can displace high-temperature extracted steam, increase the work done by the turbine, and improve the unit efficiency. Furthermore, this device realizes the cascade utilization of waste heat from flue gas, which can significantly improve energy utilization. The condensate after circulation can re-enter the turbine for recycling, thereby effectively improving the system's power generation efficiency. Attached Figure Description

[0016] Figure 1 This is a system schematic diagram of the three-thermal-core hot water circulation absorption structure of the present invention.

[0017] Figure 2 This is a system schematic diagram of the first type of absorption heat pump structure of the present invention.

[0018] In the diagram, the correspondence between component names and drawing numbers is as follows: 1. Coil; 2. Water storage tank; 3. Heat exchange plate; 4. Double shell; 401. Blower; 402. Flue gas inlet pipe; 403. Circulating pipe; 5. Finned tube; 6. Generator; 7. Condenser; 701. Condenser tube; 702. Coal-fired heat outlet pipe; 8. Heat exchanger; 9. Absorber; 10. Evaporator; 11. Steam turbine; 12. Solution pump; 13. Coal-fired heat inlet pipe; 14. Flue; 15. Connecting pipe. Detailed Implementation

[0019] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0020] Example: As attached Figure 1 To be continued Figure 2 As shown: This invention provides a waste heat recovery and reuse device for flue gas from a thermal power plant boiler, comprising: a coil 1, a water storage tank 2, a heat exchange plate 3, a double-layer shell 4, finned tubes 5, a generator 6, a condenser 7, a heat exchanger 8, an absorber 9, an evaporator 10, a steam turbine 11, a solution pump 12, a coal-fired inlet pipe 13, a flue 14, and connecting pipes 15. The coil 1 is housed inside the double-layer shell 4; the water storage tank 2 is located on one side of the double-layer shell 4; the heat exchange plate 3 is located inside the double-layer shell 4; and the generator 6 is located on one side of the double-layer shell 4. The generator 6 is connected to the double-layer shell 4 through the flue 14; the flue 14 is sandwiched with a finned tube 5, which is located between the double-layer shell 4 and the generator 6; the generator 6, condenser 7, heat exchanger 8 and absorber 9 form a first-type absorption heat pump structure, and the generator 6, condenser 7, heat exchanger 8 and absorber 9 are connected by connecting pipes 15 to achieve efficient cooperation, realize the reheating of condensate, meet the user's heating and production and domestic water needs, and thus promote the recycling and reuse of resources.

[0021] The double-layer shell 4 is composed of an inner shell and an outer shell, and a blower 401 is provided in the cavity between the inner shell and the outer shell. A flue gas inlet pipe 402 is provided on one side of the outer wall of the double-layer shell 4. A surrounding pipe 403 is provided in the cavity between the inner shell and the outer shell, and the surrounding pipe 403 is connected to the water storage tank 2. The lower part of the inner shell of the double-shell 4 is filled with liquid phase change medium, and the coil 1 is set in the upper part of the inner shell. The heat exchange plate 3 is set at the bottom of the inner shell of the double-shell 4, and the heat exchange plate 3 corresponds to the liquid phase change medium. This device is composed of multi-stage heating devices, which can heat the heat medium water after the steam turbine 11 to a relatively stable state to a certain extent, so as to achieve stable heating, reduce resource waste, and achieve energy conservation and emission reduction.

[0022] The condenser 7 is equipped with a condenser tube 701, and one end of the condenser tube 701 is equipped with a coal heat outlet pipe 702, and the other end of the condenser tube 701 is connected to the steam turbine 11 through a connecting pipe 15. Heat exchanger 8 is connected between generator 6 and solution pump 12 via connecting pipe 15, and one side of heat exchanger 8 is connected to two absorbers 9 via connecting pipe 15. The boiler generates a large amount of waste heat when it is working, and the steam turbine 11 generates a large amount of condensation heat when it is working. In order to avoid these resources being wasted, a first-type absorption heat pump is introduced. The driving heat source of generator 6 is steam or fuel. Absorber 9 and condenser 7 form a heating circuit to heat the heat medium. Evaporator 10 absorbs heat from low-grade heat source through waste heat circuit to generate refrigerant steam. After entering absorber 9, the heat medium completes the first heating process by using the heat absorbed by lithium bromide solution. In condenser 7, the latent heat of condensation of high-temperature secondary steam from generator 6 is used to reheat the heat medium from absorber 9 that has been heated once, and finally it becomes a heat medium that reaches the required temperature. The steam is condensed into condensate and then transported back to evaporator 10 to continue the cycle of evaporation.

[0023] Two absorbers 9 are symmetrically distributed on both sides of the evaporator 10. One end of each absorber 9 is connected to the condenser tube 701 of the condenser 7 via a connecting pipe 15, and the other end of each absorber 9 is connected to the solution pump 12 via a connecting pipe 15. Evaporator 10 is connected to turbine 11 via connecting pipe 15, and a coal-fired heat inlet pipe 13 is provided on one side of turbine 11. This equipment combines a three-core hot water circulation heat absorption device for cascaded heat utilization to heat the waste gas generated by coal combustion in stages; at the same time, a lithium bromide-based first-type absorption heat pump is used to recover the waste heat of flue gas and the condensation heat generated by turbine 11. By utilizing the waste heat of flue gas in stages, the waste heat of flue gas is utilized in a graded manner, and at the same time, some heat energy is fed back to hot water and supplied to turbine 11 to reduce its power consumption. This fully utilizes the heat source of the two important links in the entire power generation system, thereby improving the energy utilization efficiency of coal-fired power generation, improving boiler efficiency, realizing cascaded energy recovery, reducing energy loss rate, and alleviating energy pressure.

[0024] The specific usage and function of this embodiment are as follows: In this invention, the generator 6 of the absorption heat pump unit is driven by steam or fuel. The absorber 9 and condenser 7 form a heating circuit to heat the heat medium. The evaporator 10 absorbs heat from a low-grade heat source through a waste heat circuit to generate refrigerant vapor. The dilute lithium bromide solution is discharged from the solution pump 12, heated and purified by the heat exchanger 8, and then enters the absorber 9. It is sprayed onto the surface of the heat transfer tube and absorbs the refrigerant vapor from the evaporator 10, becoming a dilute lithium bromide solution again. After entering the absorber 9, the heat medium completes the first heating process using the heat absorbed by the lithium bromide solution. In the condenser 7, the latent heat of condensation of the high-temperature secondary steam from the generator 6 is used to reheat the heat medium from the absorber 9, which has already been heated once, until it reaches the required temperature. The steam is then condensed into condensate and transported back to the evaporator 10 for continued evaporation.

[0025] The tri-thermal nuclear gas water heater utilizes the high heat transfer coefficient of phase change heat transfer to fully utilize the heat of the high-temperature flame for the first heat absorption; simultaneously, by arranging finned tubes 5 in the interlayer of the flue 14, it completes the second heat absorption of the waste heat of the flue gas, thus fully utilizing the heat generated by gas combustion and significantly improving the heat exchange efficiency of equipment using high-temperature flue gas as a heat source; the heat exchanger 8 uses high-temperature flame or high-temperature flue gas as a heat source and includes at least a double-layer shell 4; the lower part of the internal space of the inner shell is filled with a liquid phase change medium, and at least one coil 1 is installed in the upper part; the heated fluid flows in the coil 1; the downstream side pipe of the coil 1 extends out After the inner shell, at least one circumferential pipe 403 is formed in the cavity between the two shells 4; the bottom heat exchange plate 3 of the inner shell is located above the heat source; the cavity between the two shells 4 forms a flue gas passage. After the heat source heats the bottom heat exchange plate 3 of the inner shell, the flue gas rises from the bottom periphery of the inner shell along the flue gas passage and transfers heat to the heated fluid in the circumferential pipe 403; the heating equipment using the heat exchanger 8 of this device can significantly improve the heat utilization rate; if used in a gas water heater, it can significantly improve the problems of small heat exchange temperature difference, insufficient heat utilization, and poor outlet water temperature stability of existing gas water heaters.

[0026] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A waste heat recovery and reuse device for flue gas from a thermal power plant boiler, characterized in that: The waste heat recovery and reuse device for boiler flue gas in thermal power plants includes: a coil (1), a water storage tank (2), a heat exchange plate (3), a double-layer shell (4), a finned tube (5), a generator (6), a condenser (7), a heat exchanger (8), an absorber (9), an evaporator (10), a steam turbine (11), a solution pump (12), a coal heat inlet pipe (13), a flue (14), and connecting pipes (15). The double-layer shell (4) is equipped with a coil (1); a water storage tank (2) is provided on one side of the double-layer shell (4); a heat exchange plate (3) is provided inside the double-layer shell (4); a generator (6) is provided on one side of the double-layer shell (4), and the generator (6) is connected to the double-layer shell (4) through the flue (14); the flue (1) 4) A finned tube (5) is provided in the interlayer, and the finned tube (5) is located between the double shell (4) and the generator (6); the generator (6), condenser (7), heat exchanger (8) and absorber (9) form a first type of absorption heat pump structure; the double shell (4) is composed of an inner shell and an outer shell, and a blower (401) is provided in the cavity between the inner shell and the outer shell, a flue gas inlet pipe (402) is provided on one side of the outer wall of the double shell (4), a surrounding pipe (403) is provided in the cavity between the inner shell and the outer shell, and the surrounding pipe (403) is connected to the water storage tank (2); after the downstream pipe of the coil (1) passes through the inner shell, at least one surrounding pipe (403) is formed in the cavity between the double shell (4); The lower part of the inner shell of the double-layer shell (4) is filled with liquid phase change medium, and the coil (1) is set in the upper part of the inner shell. The heat exchange plate (3) is set at the bottom of the inner shell of the double-layer shell (4), and the heat exchange plate (3) corresponds to the liquid phase change medium. The condenser (7) is provided with a condenser tube (701), and one end of the condenser tube (701) is provided with a coal heat outlet pipe (702). The other end of the condenser tube (701) is connected to the steam turbine (11) through a connecting pipe (15). The heat exchanger (8) is connected to the generator (6) and the solution pump through a connecting pipe (15). Between (12), and one side of the heat exchanger (8) is connected to two absorbers (9) respectively through connecting pipe (15); the two absorbers (9) are symmetrically distributed on both sides of the evaporator (10), and one end of the two absorbers (9) is connected to the condenser tube (701) of the condenser (7) through connecting pipe (15), and the other end of the two absorbers (9) is connected to the solution pump (12) through connecting pipe (15); the evaporator (10) is connected to the steam turbine (11) through connecting pipe (15), and a coal heat inlet pipe (13) is provided on one side of the steam turbine (11).

2. A method for recovering and reusing waste heat from boiler flue gas in thermal power plants, characterized in that, Using the waste heat recovery and reuse device for boiler flue gas in thermal power plants as described in claim 1, the driving heat source of the generator (6) is steam or fuel, and the absorber (9) and condenser (7) form a heating circuit to heat the heat medium; the evaporator (10) absorbs heat from the low-grade heat source through the waste heat circuit to generate refrigerant steam; after the lithium bromide solution is discharged from the solution pump (12), it is heated and purified by the heat exchanger (8) and then enters the absorber (9), sprayed on the surface of the heat transfer tube, and absorbs the refrigerant steam from the evaporator (10); after the heat medium enters the absorber (9), it completes the first heating process by using the heat absorbed by the lithium bromide solution; in the condenser (7), the latent heat of condensation of the high-temperature secondary steam from the generator (6) is used to reheat the heat medium that has been heated once from the absorber (9), and finally it becomes a heat medium that reaches the required temperature. The steam is condensed into condensate and then transported back to the evaporator (10) to continue the cycle evaporation.

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