Coal power unit waste heat energy quality recovery method and system based on organic rankine cycle

Abstract

The application discloses a coal power unit waste heat and waste quality recovery method and system based on an organic Rankine cycle, and the method is as follows: waste heat and waste quality are generated during the operation of the coal power unit, the waste quality carries the waste heat, the minimum pressure of the waste quality is selected and calculated after pressure loss, and the pressure is used as the rated pressure during the recovery of the waste heat and the waste quality, the recovered waste heat and waste quality are used for heating organic working medium in the organic Rankine cycle, and the organic working medium expands to do work; the condensed water is heat-exchanged with the waste quality discharged from an evaporator in the organic Rankine cycle in a heat exchanger, the heat discharged from the evaporator is utilized, and the heat-exchanged waste quality is recovered to a condenser, the organic Rankine cycle is combined with the inorganic Rankine cycle, the waste heat contained in the inorganic working medium is absorbed by utilizing the low boiling point characteristic of the organic medium to produce high-quality electric energy, the power supply capacity of the high-quality electric energy of the power plant is improved, the waste heat is used in stages to heat circulating water, the thermal efficiency of the inorganic Rankine cycle is improved, the waste heat utilization maximization is realized, the working medium is recovered, the working medium cost of the power plant is reduced, and the cost reduction and benefit increase of the power plant are promoted.

Description

Technical Field

[0001] This invention belongs to the field of power plant boilers and steam turbine systems, specifically relating to a method and system for recovering waste heat energy from coal-fired power units based on the organic Rankine cycle. Background Technology

[0002] Accelerating the construction of a clean, low-carbon, safe, and efficient energy system, adhering to the energy development strategy of prioritizing energy conservation, strictly controlling energy consumption and carbon dioxide emission intensity, rationally controlling total energy consumption, establishing a comprehensive carbon dioxide emission control system, significantly improving energy utilization efficiency, and strictly controlling fossil energy consumption are the overall goals of the energy industry. Clean and efficient utilization of coal is a crucial part of deepening the energy revolution. Under the goal of reducing carbon emissions, it is further proposed to vigorously promote the "three-pronged" mechanism of energy conservation and carbon reduction transformation of coal-fired power plants, flexibility transformation, and heating transformation. Under the dual control of environmental and carbon emission indicators, further exploring the energy-saving potential of coal-fired power units can, on the one hand, ensure supply, and on the other hand, improve the survivability of thermal power units in the future new power system dominated by new energy sources, alleviating the operational and survival difficulties of coal-fired power units.

[0003] In-depth utilization of low-grade waste heat from power plants, including flue gas waste heat, circulating water heat utilization, direct discharge condensate, and steam, is an effective way to further improve energy efficiency and productivity of coal-fired power units. Currently, flue gas waste heat and circulating water heat are utilized by adding low-temperature economizers and heat pumps, respectively. However, waste heat from deaerator continuous exhaust steam, electrostatic precipitator ash hopper condensate, and soot blowing and warming steam condensate is not fully utilized, resulting in significant waste heat and mass loss. This is a common problem in coal-fired power units. There are still no good solutions for the in-depth recovery and utilization of these medium- and low-temperature waste heats. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering waste heat and energy from coal-fired power plants based on the organic Rankine cycle. This method utilizes a low-boiling-point organic working fluid to absorb waste heat from the power plant, and generates electricity based on the principle of the Rankine cycle using low-boiling-point organic matter as the working fluid, providing high-quality energy and directly bringing benefits to the power plant. Then, the waste heat from the Rankine cycle evaporator is used in a deep cascade manner through a heat exchanger to heat the condensate, improving the cycle thermal efficiency. Finally, the working fluid is recovered to the condenser, fully utilizing and recovering waste heat and energy, reducing the consumption of fossil fuels, saving energy and protecting the environment, and improving efficiency.

[0005] This invention is achieved using the following technical solution: a method for recovering waste heat and energy from coal-fired power units based on an organic Rankine cycle. The coal-fired power unit generates waste heat and waste mass during operation, with the waste mass carrying the waste heat. The lowest pressure in the waste mass is selected and the pressure loss is calculated as the rated pressure for waste heat and waste mass recovery. The recovered waste heat and waste mass are used to heat the organic working fluid in the organic Rankine cycle, and the organic working fluid expands and does work. The condensate and the waste mass discharged from the evaporator in the organic Rankine cycle exchange heat in a heat exchanger. The heat discharged from the evaporator is used to recover the waste mass after heat exchange to the condenser.

[0006] Furthermore, the residual material specifically includes: continuous exhaust steam from the deaerator, condensate drain from the electrostatic precipitator ash hopper, steam condensate drain from the air preheater soot blowing and warming pipes, steam condensate drain from the low-temperature economizer soot blowing and warming pipes, and / or steam condensate drain from the denitrification soot blowing and warming pipes.

[0007] Furthermore, all waste heat and waste mass are collected in the waste heat recovery device. When the waste mass is steam, the steam enters from the bottom of the waste heat recovery device and is cooled down by the waste mass in the recovery device. If the steam content in the waste mass is higher than the set value, the medium in the waste heat recovery device is divided into steam and water for recycling. When the waste mass is water, it is depressurized through a throttle valve and then flows into the waste heat recovery device.

[0008] Furthermore, the method of recycling the flash steam generated during the throttling and depressurization process is determined by the amount of flash steam. If the amount of flash steam is less than the set value, water is recycled from the top of the waste heat recovery device by spraying. If the amount of flash steam is higher than the set value, the medium in the waste heat recovery device is recycled in two parts: steam and water.

[0009] Furthermore, the organic working fluid expands and does work to drive a generator or water pump.

[0010] The present invention also provides a waste heat energy recovery system for coal-fired power units based on an organic Rankine cycle, for implementing the above method, including an inorganic Rankine cycle system, a waste heat recovery system, and an organic Rankine cycle system; wherein the inorganic Rankine cycle system is a thermal power generating unit, and the waste heat recovery system includes a waste heat recovery device and a waste heat heater; the waste heat recovery device is connected to the hot side inlet of the evaporator, and the hot side outlet of the evaporator is connected to the hot side inlet of the waste heat heater.

[0011] Furthermore, the hot-side outlet of the waste heat heater is connected to the inlet of the water treatment device via the hot-side outlet valve of the waste heat heater; the inlet of the waste heat recovery device is equipped with an adjustable valve for each type of waste substance, and the outlet of the waste heat recovery device is equipped with an inlet valve for the waste heat energy booster pump, a waste heat energy booster pump, an outlet valve for the waste heat energy booster pump, and an outlet regulating valve for the waste heat energy booster pump.

[0012] Furthermore, the organic Rankine cycle system includes an evaporator, an expander, a generator, an organic medium condenser, and a working fluid pump. The cold side of the evaporator is connected to the expander in sequence via the evaporator organic medium outlet valve and the expander organic medium inlet valve. The working fluid outlet of the expander is connected to the organic medium condenser via the expander exhaust valve. The organic medium condenser is connected to the working fluid pump via the working fluid pump inlet valve. The working fluid pump is connected to the cold side inlet of the evaporator via the working fluid pump outlet valve and the evaporator organic medium inlet valve.

[0013] Furthermore, temperature transmitters and pressure transmitters are installed at both the inlet and outlet of the waste heat recovery device.

[0014] Furthermore, the inlet of the waste heat recovery device is equipped with a filter screen for each type of waste material.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention combines organic and inorganic Rankine cycles through a waste heat recovery system. It utilizes the low boiling point of the organic medium to absorb waste heat from the inorganic working fluid to produce high-quality electricity, directly increasing the power plant's revenue and improving its ability to supply high-quality electricity. Furthermore, it utilizes waste heat in stages to heat circulating water, improving the thermal efficiency of the inorganic Rankine cycle and maximizing waste heat utilization, thus enhancing the power plant's operational economy. Finally, it recovers the working fluid, reducing water waste and lowering working fluid costs, promoting cost reduction and efficiency improvement. This invention enhances the power plant's competitiveness in terms of both environmental and carbon emission indicators, providing technical support for carbon emission reduction targets. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a waste heat energy recovery method for coal-fired power units based on the organic Rankine cycle according to the present invention.

[0018] Figure 2 This is the Ebsilon calculation result of the ORC system in Example 1;

[0019] Figure 3 This is a further optimized schematic diagram of a waste heat energy recovery method for coal-fired power units based on the organic Rankine cycle according to the present invention.

[0020] Figure 4 This is the Ebsilon calculation result of the ORC system in Example 2;

[0021] In the diagram: 1. Boiler; 2. High-pressure cylinder of steam turbine; 3. Intermediate-pressure cylinder of steam turbine; 4. High-pressure cylinder inlet valve; 5. Intermediate-pressure cylinder inlet valve; 6. Generator; 7. High-pressure cylinder exhaust valve; 8. High-pressure cylinder extraction regulating valve; 9. Intermediate-pressure cylinder extraction regulating valve; 10. Low-pressure cylinder inlet regulating valve; 11. Low-pressure cylinder; 12. Low-pressure cylinder exhaust valve; 13. Micro generator; 14. Condenser; 15. Condenser outlet valve; 16. Condenser inlet valve; 17. High-pressure heater drain valve; 18. Deaerator. 19. Low-pressure heater outlet valve; 20. Low-pressure cylinder extraction steam regulating valve; 21. Low-pressure heater drain valve; 22. High-pressure heater outlet valve; 23. High-pressure heater; 24. Feed water pump outlet valve; 25. Feed water pump; 26. Feed water pump inlet valve; 27. Waste heat heater condensate outlet valve; 28. Low-pressure heater; 29. ​​Condensate pump outlet valve; 30. Condensate pump; 31. Condensate pump inlet valve; 32. Waste heat heater condensate inlet valve; 33. Waste heat pump inlet valve. Valves: 34. Inlet valve for Waste Heat Unit II; 35. Inlet valve for Waste Heat Unit III; 36. Inlet valve for Waste Heat Unit IV; 37. Inlet valve for Waste Heat Unit V; 38. Inlet valve for Waste Heat Unit VI; 39. Waste Heat Recovery Device; 40. Inlet valve for Waste Heat Energy Quantity Booster Pump; 41. Waste Heat Energy Quantity Booster Pump; 42. Outlet valve for Waste Heat Energy Quantity Booster Pump; 43. Outlet regulating valve for Waste Heat Energy Quantity Booster Pump; 44. Hot side inlet valve for Waste Heat Heater; 45. Waste Heat Heater; 46. Hot side outlet valve for Waste Heat Heater; 47. Water treatment unit, 48. Water treatment outlet valve, 49. Evaporator, 50. Evaporator organic medium outlet valve, 51. Expander organic medium steam inlet valve, 52. Evaporator organic medium inlet valve, 53. Expander, 54. Expander exhaust valve, 55. Organic medium condenser, 56. Organic medium condenser circulating water outlet valve, 57. Organic medium condenser circulating water inlet valve, 58. Working fluid pump outlet valve, 59. Working fluid pump, 60. Working fluid pump inlet valve, 61. Working fluid regenerative heater. Detailed Implementation

[0022] The following is in conjunction with the appendix Figure 1 The preferred embodiments of the present invention are described herein. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] This invention provides a method for recovering waste heat and energy quality from coal-fired power units based on an organic Rankine cycle. The system based on this method includes an inorganic Rankine cycle system, a waste heat recovery system, and an organic Rankine cycle system. The inorganic Rankine cycle system is used in conventional coal-fired power units, which directly discharge a significant amount of waste heat and energy quality during daily operation. This waste heat is carried by various sources, such as continuous exhaust steam from deaerators, condensate drains from electrostatic precipitator ash hoppers, steam drains from air preheater soot blowing and warming pipes, steam drains from low-temperature economizer soot blowing and warming pipes, and steam drains from denitrification soot blowing and warming pipes. The waste heat recovery system is used to recover this discharged waste heat and energy quality quality. The lowest pressure among all waste materials is selected, and pressure loss is considered as the rated pressure of the waste heat and energy quality recovery system.

[0024] All waste heat and waste mass are collected in the waste heat recovery unit. If the waste mass is steam, it can be introduced from the bottom of the recovery unit and cooled down by the waste mass in the recovery unit. If the steam content of the waste mass is very high, the medium in the recovery unit can be divided into steam and water for recovery and reuse. If the waste mass is water, it can be depressurized through a throttling valve before flowing into the recovery unit. The flash steam generated during the throttling and depressurization process can determine the recovery and reuse method based on the amount of flash steam. If the flash steam does not exceed the set proportion, the water can be recovered from the top of the recovery unit by spraying. If the amount of flash steam exceeds the set ratio, the medium in the recovery device can be divided into steam and water for recycling. The organic Rankine cycle system utilizes the low boiling point of the organic working fluid to absorb the low-temperature waste heat in the recovery device and evaporate it, thereby driving the expander to generate electricity and directly bringing electricity revenue to the power plant. The heat discharged from the evaporator can be deeply utilized in a cascade manner through the heat exchanger to heat the condensate, further improving the cycle thermal efficiency. Finally, the residual mass is recovered to the condenser. The waste heat and residual mass are utilized and recovered to the maximum extent, reducing the consumption of fossil energy, saving energy and protecting the environment, and improving efficiency.

[0025] This invention can also provide a waste heat and energy recovery system for coal-fired power units based on the organic Rankine cycle, such as... Figure 1As shown, the system supporting the method of the present invention includes a boiler 1, a high-pressure boiler cylinder of a steam turbine 2, an intermediate-pressure cylinder of a steam turbine 3, a high-pressure cylinder inlet valve 4, an intermediate-pressure cylinder inlet valve 5, a generator 6, a high-pressure cylinder exhaust valve 7, a high-pressure cylinder extraction regulating valve 8, an intermediate-pressure cylinder extraction regulating valve 9, a low-pressure cylinder inlet regulating valve 10, a low-pressure cylinder 11, a low-pressure cylinder exhaust valve 12, a micro-generator 13, a condenser 14, a condenser outlet valve 15, a condenser inlet valve 16, and a high-pressure heater drain valve. 17. Water valve; 18. Deaerator; 19. Low-pressure heater outlet valve; 20. Low-pressure cylinder extraction steam regulating valve; 21. Low-pressure heater drain valve; 22. High-pressure heater outlet valve; 23. High-pressure heater; 24. Feedwater pump outlet valve; 25. Feedwater pump inlet valve; 26. Waste heat heater condensate outlet valve; 27. Low-pressure heater; 28. Condensate pump outlet valve; 29. ​​Condensate pump; 30. Condensate pump inlet valve; 31. Waste heat heater condensate inlet valve; 32. 33. Inlet valve for waste heat source 1; 34. Inlet valve for waste heat source 2; 35. Inlet valve for waste heat source 3; 36. Inlet valve for waste heat source 4; 37. Inlet valve for waste heat source 5; 38. Inlet valve for waste heat source 6; 39. Waste heat recovery device; 40. Inlet valve for waste heat energy booster pump; 41. Waste heat energy booster pump; 42. Outlet valve for waste heat energy booster pump; 43. Outlet regulating valve for waste heat energy booster pump; 44. Inlet valve for hot side of waste heat heater; 45. Waste heat heater; 46. Hot side of waste heat heater. 46. ​​Water outlet valve; 47. Water treatment device; 48. Water treatment outlet valve; 49. Evaporator; 50. Evaporator organic medium outlet valve; 51. Expander organic medium steam inlet valve; 52. Evaporator organic medium inlet valve; 53. Expander exhaust valve; 54. Organic medium condenser; 55. Organic medium condenser circulating water outlet valve; 56. Organic medium condenser circulating water inlet valve; 57. Working fluid pump outlet valve; 58. Working fluid pump; 59. Working fluid pump inlet valve; and 60.

[0026] Specifically, the system includes an inorganic Rankine cycle system, a waste heat recovery system, and an organic Rankine cycle system. The inorganic Rankine cycle system is an existing thermal power generating unit. The waste heat recovery system includes a waste heat recovery device 39, a waste heat heater 45, and a water treatment device 47. The waste heat recovery device 39 is connected to the hot side inlet of the evaporator 49, and the hot side outlet of the evaporator 49 is connected to the hot side inlet of the waste heat heater 45. The hot side outlet of the waste heat heater 45 is connected to the inlet of the water treatment device 47 via the hot side outlet valve 46 of the waste heat heater. The outlet of the water treatment device 47 is connected to the condenser 14 of the thermal power generating unit via the water treatment outlet valve 48. The cold side inlet and outlet of the waste heat heater 45 are connected to the condenser 14 and the deaerator 18 of the thermal power generating unit, respectively. The outlet of the condenser 14 is connected to the low-pressure heater 28 and the waste heat heater 45 in sequence via the condensate pump inlet valve 31, the condensate pump 30, and the condensate pump outlet valve 29. The cold side inlet of the waste heat heater 45 is equipped with a condensate inlet valve 32.

[0027] The inlet of the waste heat recovery device 39 is equipped with an adjustable valve for each type of waste substance, and the outlet of the waste heat recovery device 39 is equipped with a waste heat energy booster pump inlet valve 40, a waste heat energy booster pump 41, a waste heat energy booster pump outlet valve 42, and a waste heat energy booster pump outlet regulating valve 43.

[0028] The waste heat recovery device 39 is equipped with inlet valves 33 for waste heat recovery one, 34 for waste heat recovery two, 35 for waste heat recovery three, 36 for waste heat recovery four, 37 for waste heat recovery five, and 38 for waste heat recovery six.

[0029] The organic Rankine cycle system includes an evaporator 49, an expander 53, a micro generator 13, an organic medium condenser 55, and a working fluid pump 59. The cold side of the evaporator 49 is connected to the expander 53 in sequence via the evaporator organic medium outlet valve 50 and the expander organic medium inlet valve 51. The working fluid outlet of the expander 53 is connected to the organic medium condenser 55 via the expander exhaust valve 54. The organic medium condenser 55 is connected to the working fluid pump 59 via the working fluid pump inlet valve 60. The working fluid pump 59 is connected to the cold side inlet of the evaporator 49 via the working fluid pump outlet valve 58 and the evaporator organic medium inlet valve 52.

[0030] In the existing thermal power generating unit, the steam outlet of boiler 1 is connected to the high-pressure cylinder 2 and the intermediate-pressure cylinder 3 of the turbine. The exhaust port of the high-pressure cylinder 2 is connected to the reheat steam inlet of boiler 1 via the high-pressure cylinder exhaust valve 7. The exhaust port of the intermediate-pressure cylinder 3 is connected to the low-pressure cylinder 11. The low-pressure cylinder 11 is connected to the low-pressure heater 28 via the low-pressure cylinder extraction regulating valve 20. The high-pressure cylinder 2, intermediate-pressure cylinder 3, and low-pressure cylinder 11 are connected to generator 6. The exhaust port of low-pressure cylinder 11 is connected to condenser 14. The low-pressure heater 28 is connected to the inlet of condenser 14 via the low-pressure heater drain valve 21. The intermediate-pressure cylinder 3 is connected to deaerator 18 via the intermediate-pressure cylinder extraction regulating valve 9. The high-pressure cylinder 2 is connected to high-pressure heater 23 via the high-pressure cylinder extraction regulating valve 8. The high-pressure heater 23 is connected to deaerator 18 via the high-pressure heater drain valve 17. The outlet of high-pressure heater 23 is connected to the boiler feedwater inlet via the high-pressure heater outlet valve 22. The inlet of the waste heat recovery device 39 is equipped with a filter screen for each type of waste medium, which can effectively prevent impurities from entering the waste heat recovery device 39 and effectively reduce the impurities in its outlet medium.

[0031] In order to monitor the temperature and pressure at the inlet and outlet of the waste heat recovery device 39 in real time, temperature transmitters and pressure transmitters are installed at both the inlet and outlet of the waste heat recovery device 39.

[0032] Implementation Example 1

[0033] A power plant has two 350MW thermal power units, mainly used for power generation. During daily operation, there is a significant amount of direct discharge of waste heat. Various waste heat energy flow parameters are shown in Table 1. This not only wastes waste heat energy and reduces the economic efficiency of the power plant, but also causes visual pollution and has a negative social impact.

[0034] Table 1 Flow parameters of various waste heat energy substances

[0035] Project Content Flow rate t / h Residual heat 52.3 Residual heat 0.6 Residual heat 0.5 Residual heat 0.02 Residual heat five 0.01 Residual heat 0.07

[0036] To completely solve the problem of waste heat and energy emissions from power plants, this invention, a waste heat and energy recovery method based on an organic Rankine cycle for coal-fired power units, was implemented in this power plant. The system based on this method includes an inorganic Rankine cycle system, a waste heat recovery system, and an organic Rankine cycle system. The inorganic Rankine cycle system is a conventional coal-fired power unit, which directly discharges a large amount of waste heat and energy during daily operation, such as: continuous exhaust steam from the deaerator, condensate drain from the electrostatic precipitator ash hopper, condensate drain from the air preheater soot blowing and warming steam, and soot blowing and warming steam from the low-temperature economizer. The system includes a condensate drain, a denitrification and soot blowing steam condensate drain, and a waste heat recovery system to recover the discharged waste heat and waste mass. The lowest pressure among all waste masses, considering pressure loss, is selected as the rated pressure for the waste heat and waste mass recovery system. The rated pressure of this waste heat recovery device is 0.4 MPa. All waste heat and waste mass are collected in the waste heat recovery device. If the waste mass is steam, it can be introduced from the bottom of the recovery device and cooled down by the waste mass within the recovery device. If the steam content in the waste mass is very high, the medium in the recovery device can be divided into steam and heat. Both steam and water are recycled. If the residual substance is water, it can be depressurized through a throttling valve and then fed into the recovery device. The flash steam generated during the throttling and depressurization process determines the recycling method based on the amount of flash steam. If the flash steam does not exceed the set ratio, water can be recovered from the top of the recovery device by spraying. If the flash steam exceeds the set ratio, the medium in the recovery device can be divided into steam and water for recycling. Here, the amount of flash steam is 0.113 t / h, accounting for 0.21% of the total, so there is no need to separately lead out steam and set up a matching pipeline system. The organic Rankine cycle system utilizes the low boiling point of the organic working fluid to absorb the low-temperature waste heat in the recovery device and evaporate it, thereby driving the expander to do work and generate electricity, directly bringing electricity revenue to the power plant. The heat discharged from the evaporator can be deeply utilized in a cascade manner through the heat exchanger to heat the condensate, further improving the cycle thermal efficiency. Finally, the residual substance is recovered to the condenser. The waste heat and residual substance are utilized and recovered to the maximum extent, reducing the consumption of fossil energy, saving energy and protecting the environment, and improving efficiency.

[0037] Figure 2The results are Ebsilon calculations for Example 1. Through the implementation of this invention, on the one hand, it brings considerable economic benefits to the power plant. The organic Rankine cycle system can generate an additional 480kW, bringing the power plant direct electricity sales revenue of 885,000 yuan / year. Under THA conditions, the overall heat consumption of the unit can be reduced by 4kJ / kWh, saving the power plant 194t / year of standard coal and recovering 46,713t / year of demineralized water, resulting in water savings of 4.673 million yuan / year. Specific benefits are shown in Table 2. On the other hand, it also eliminates visual pollution and adverse social impacts. Waste heat and waste mass are deeply utilized and recovered, reducing fossil energy consumption, saving energy and protecting the environment, and improving efficiency.

[0038]

[0039]

[0040] In summary, this invention combines organic and inorganic Rankine cycles through a waste heat recovery system. It utilizes the low boiling point of the organic medium to absorb the waste heat contained in the inorganic working fluid to produce high-quality electricity, directly increasing the power plant's revenue and improving its ability to supply high-quality electricity. Furthermore, it utilizes waste heat in stages to heat circulating water, improving the thermal efficiency of the inorganic Rankine cycle and maximizing waste heat utilization, thus enhancing the power plant's operational economy. Finally, it recovers the working fluid, reducing water waste and lowering the power plant's working fluid costs, promoting cost reduction and efficiency improvement. This invention enhances the power plant's competitiveness in terms of both environmental and carbon emission indicators, providing technical support for carbon emission reduction.

[0041] The following is in conjunction with the appendix Figure 3 The preferred embodiments of the present invention are described herein. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0042] Example 2

[0043] refer to Figure 3 The difference from Example 1 is that a working fluid regeneration heating process is set up, and a working fluid regeneration heater 61 is installed in the system. After the working fluid expands and does work in the expander 53, it enters the working fluid regeneration heater 61 to exchange heat with the condensed working fluid. Then, it enters the organic medium condenser 55 to exchange heat with the circulating cooling water. The condensed working fluid enters the working fluid pump 59 for pressurization. The pressurized condensed working fluid enters the working fluid regeneration heater 61 to absorb the waste heat of the working fluid for preliminary heating. The heated working fluid enters the evaporator 49 to absorb the waste heat of the unit. Other processes are the same as in Example 1, and will not be described again here.

[0044] Figure 4Based on the Ebsilon calculation results of Example 2, after adding the regenerative system, the cycle thermal efficiency of the ORC system increased from 5.82% to 7.75%, and the overall thermal economy of the system was improved.

[0045] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for recovering waste heat energy from coal-fired power units based on the organic Rankine cycle, characterized in that, Coal-fired power units generate waste heat and waste mass during operation. The waste mass carries the waste heat. The lowest pressure in the waste mass is selected and the pressure loss is calculated as the rated pressure for waste heat and waste mass recovery. The recovered waste heat and waste mass are used to heat the organic working fluid in the organic Rankine cycle, where the organic working fluid expands and does work. Condensate exchanges heat with the waste mass discharged from the evaporator in the organic Rankine cycle in a heat exchanger. The heat discharged from the evaporator is used to recover the waste mass after heat exchange to the condenser. The waste mass specifically includes: continuous exhaust steam from the deaerator, condensate from the electrostatic precipitator ash hopper, and air condensate. Steam condensate from the preheater soot blowing and warming pipes, steam condensate from the low-temperature economizer soot blowing and warming pipes, and steam condensate from the denitrification soot blowing and warming pipes; all waste heat and waste mass are collected in the waste heat recovery device. When the waste mass is steam, the steam enters from the bottom of the waste heat recovery device and is cooled down by the waste mass in the recovery device. If the steam content in the waste mass is higher than the set value, the medium in the waste heat recovery device is divided into steam and water for recycling. When the waste mass is water, it is depressurized through a throttle valve and then flows into the waste heat recovery device.

2. The method for waste heat energy recovery from coal-fired power units based on the organic Rankine cycle according to claim 1, characterized in that, The method of recycling the flash steam generated during the throttling and depressurization process is determined by the amount of flash steam. If the amount of flash steam is less than the set value, water is recycled from the top of the waste heat recovery device by spraying. If the amount of flash steam is higher than the set value, the medium in the waste heat recovery device is recycled in two parts: steam and water.

3. The method for recovering waste heat energy from coal-fired power units based on the organic Rankine cycle according to claim 1, characterized in that, When organic working fluid expands and does work, it is used to drive generators or water pumps.

4. A waste heat energy recovery system for coal-fired power units based on the organic Rankine cycle, characterized in that, The method for implementing any one of claims 1-3 includes an inorganic Rankine cycle system, a waste heat recovery system, and an organic Rankine cycle system; wherein the inorganic Rankine cycle system is a thermal power generator set, and the waste heat recovery system includes a waste heat recovery device (39) and a waste heat heater (45); the waste heat recovery device (39) is connected to the hot side inlet of the evaporator (49), and the hot side outlet of the evaporator (49) is connected to the hot side inlet of the waste heat heater (45); the waste heat specifically includes: continuous exhaust steam from the deaerator, condensate drain from the electrostatic precipitator ash hopper, steam condensate drain from the air preheater soot blowing and warming pipes, steam condensate drain from the low-temperature economizer soot blowing and warming pipes, and steam condensate drain from the denitrification soot blowing and warming pipes.

5. The waste heat recovery system for coal-fired power units based on the organic Rankine cycle according to claim 4, characterized in that, The hot side outlet of the waste heat heater (45) is connected to the inlet of the water treatment device (47) via the hot side outlet valve (46) of the waste heat heater; the inlet of the waste heat recovery device (39) is equipped with an adjustable valve for each type of waste substance, and the outlet of the waste heat recovery device (39) is equipped with a waste heat energy booster pump inlet valve (40), a waste heat energy booster pump (41), a waste heat energy booster pump outlet valve (42), and a waste heat energy booster pump outlet regulating valve (43).

6. The waste heat recovery system for coal-fired power units based on the organic Rankine cycle according to claim 4, characterized in that, The organic Rankine cycle system includes an evaporator (49), an expander (53), a generator (13), an organic medium condenser (55), and a working fluid pump (59). The cold side of the evaporator (49) is connected to the expander (53) in sequence via the evaporator organic medium outlet valve (50) and the expander organic medium inlet valve (51). The working fluid outlet of the expander (53) is connected to the organic medium condenser (55) via the expander exhaust valve (54). The organic medium condenser (55) is connected to the working fluid pump (59) via the working fluid pump inlet valve (60). The working fluid pump (59) is connected to the cold side inlet of the evaporator (49) via the working fluid pump outlet valve (58) and the evaporator organic medium inlet valve (52).

7. The waste heat recovery system for coal-fired power units based on the organic Rankine cycle according to claim 4, characterized in that, Temperature transmitters and pressure transmitters are installed at both the inlet and outlet of the waste heat recovery device (39).

8. The waste heat recovery system for coal-fired power units based on the organic Rankine cycle according to claim 4, characterized in that, The inlet of the waste heat recovery device (39) is equipped with a filter screen for each type of waste material.

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