Flexible and efficient coal-fired power generation system coupled with renewable energy sources and operation method of flexible and efficient coal-fired power generation system

Abstract

The invention discloses a flexible and efficient coal-fired power generation system coupled with renewable energy sources and an operation method thereof.The system comprises a traditional coal-fired power generation unit and a two-stage flash evaporation geothermal energy utilization system coupled with the traditional coal-fired power generation unit, and the geothermal energy utilization system adopts a two-stage flash evaporation device to generate steam with different pressures; and a regenerative heater bypass of the coal-fired power generation unit is further arranged, and high-temperature geothermal fluid obtained after flash evaporation is used for heating bypass condensation water and bypass boiler feed water. When the system normally operates, the geothermal energy and the coal-fired power generation unit are combined, the electric power output of the unit is increased while the coal feeding amount of the boiler is not increased, and the consumption of renewable energy sources of a power grid is promoted; when the coal-fired power generation unit is assisted to increase and decrease the load rapidly, the working medium flow of the two-stage flash evaporation geothermal energy utilization system is adjusted, so that the purpose of increasing the load changing rate of the coal-fired power generation unit under the condition that the coal feeding amount of a boiler is not changed is achieved, and the safety of the coal-fired power generation unit in the rapid load changing process is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-energy fusion complementary power generation, and specifically relates to a flexible and efficient coal-fired power generation system coupled with renewable energy and an operation method thereof. Background Art

[0002] my country's energy resource endowment is characterized by "rich in coal, poor in oil, and little gas", but the development and use of a large amount of fossil energy has brought serious environmental pollution problems. The emission of a large amount of greenhouse gases such as carbon dioxide has also caused global warming, frequent disastrous weather, and rising sea levels, which threaten the sustainable development of mankind. To this end, countries around the world have actively taken energy transformation actions to increase the proportion of renewable energy in energy consumption as much as possible, thereby effectively alleviating the world's environmental security problems.

[0003] With the gradual consumption of fossil energy, vigorously developing renewable energy has become an inevitable trend in the development of the energy field. The development and utilization of geothermal energy has the advantages of small footprint and small ecological impact. Compared with intermittent and fluctuating wind energy, solar energy and other energy sources, it is less affected by weather and seasons and has stable energy quality. Vigorously developing the development and utilization of geothermal energy is one of the effective ways to reduce my country's coal consumption and greenhouse gas emissions. However, the temperature of medium and low temperature geothermal energy is relatively low, and directly extracting geothermal energy for power generation has low power generation efficiency and high investment cost. Therefore, the efficient integration of geothermal energy utilization with coal-fired power generation systems can realize the cascade utilization of energy, thereby improving energy utilization efficiency, which is of great significance to my country's promotion of renewable energy consumption and reduction of energy consumption levels of coal-fired units. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a flexible and efficient coal-fired power generation system coupled with renewable energy and its operation method, the system includes a traditional coal-fired generator set and a two-stage flash geothermal energy utilization system coupled thereto, wherein the geothermal energy utilization system firstly adopts a two-stage flash device to generate steam of different pressures, which are respectively injected into the medium-pressure cylinder and the low-pressure cylinder of the steam turbine for power generation, and a heat recovery heater bypass of the coal-fired generator set is also provided, and the high-temperature geothermal fluid after flash evaporation is used to heat the bypass condensate and bypass boiler feed water. When the system is in normal operation, the system increases the power output of the system without increasing the boiler coal feed amount by combining geothermal energy and coal-fired generator sets, thereby promoting the consumption of renewable energy in the power grid; when assisting the coal-fired generator set to quickly increase or decrease the load, the working fluid flow rate of the two-stage flash geothermal energy utilization system is adjusted, so as to achieve the purpose of increasing the load change rate of the coal-fired generator set without changing the boiler coal feed amount. The present invention integrates geothermal energy with coal-fired generator sets through efficient integration, realizes the energy cascade utilization of geothermal energy, and effectively improves the load change rate of the coal-fired generator set.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A flexible and efficient coal-fired power generation system coupled with renewable energy, comprising a coal-fired power generation unit and a double-stage flash geothermal energy utilization system coupled with the coal-fired power generation unit;

[0007] The coal-fired power generation unit comprises a boiler 1, a steam turbine high-pressure cylinder 2, a steam turbine medium-pressure cylinder 3, a steam turbine low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10 and a high-pressure heater 11; the main steam outlet of the boiler 1 is connected to the steam inlet of the steam turbine high-pressure cylinder 2; the extraction steam outlet of the steam turbine high-pressure cylinder 2 is connected to the steam inlet of the high-pressure heater 11, and the steam outlet of the steam turbine high-pressure cylinder 2 is connected to the reheat steam inlet of the boiler 1; the reheat steam outlet of the boiler 1 and the two-stage flash geothermal energy utilization The steam side outlets of the first-stage flash evaporator 14 of the two-stage flash geothermal energy utilization system are combined and connected to the steam inlet of the turbine intermediate pressure cylinder 3; the steam extraction outlet of the turbine intermediate pressure cylinder 3 is connected to the steam inlet of the deaerator 9, and the steam outlet of the turbine intermediate pressure cylinder 3 and the steam side outlet of the second-stage flash evaporator 15 of the two-stage flash geothermal energy utilization system are combined and connected to the steam inlet of the turbine low pressure cylinder 4; the steam extraction outlet of the turbine low pressure cylinder 4 is connected to the steam inlet of the low pressure heater 8, and the steam outlet of the turbine low pressure cylinder 4 is connected to the steam inlet of the condenser 6; the hydraulic The outlet of the working medium of the low-pressure heater 8 is divided into two paths after passing through the condensate pump 7, one path is connected to the water working medium inlet of the low-pressure heater 8, and the other path is connected to the low-temperature side water working medium inlet of the bypass condensate-geothermal fluid heat exchanger 18 of the double-stage flash geothermal energy utilization system through the condensate diversion valve 19; the water working medium outlet of the low-pressure heater 8 and the low-temperature side water working medium outlet of the bypass condensate-geothermal fluid heat exchanger 18 of the double-stage flash geothermal energy utilization system are combined and connected to the water working medium inlet of the deaerator 9; the water working medium outlet of the deaerator 9 is divided into two paths after passing through the feed water pump 10, one path is connected to the high-pressure heater 8, and the other path is connected to the low-temperature side water working medium inlet of the deaerator 9 through the condensate diversion valve 19. The first circuit is connected to the water working medium inlet of the high-pressure heater 11, and the other circuit is connected to the water working medium inlet of the bypass water supply-geothermal fluid heat exchanger 16 of the two-stage flash geothermal energy utilization system through the water supply shunt valve 17; the water working medium outlet of the high-pressure heater 11 and the water working medium outlet of the bypass water supply-geothermal fluid heat exchanger 16 of the two-stage flash geothermal energy utilization system are combined and then connected to the water supply inlet of the boiler 1; the high-pressure cylinder 2 of the steam turbine, the intermediate-pressure cylinder 3 of the steam turbine and the low-pressure cylinder 4 of the steam turbine are connected through a rotating shaft, and jointly drive the generator 5 to output electrical power to the outside;

[0008] The two-stage flash geothermal energy utilization system comprises a geothermal fluid production well 12, a deep well pump 13, a first-stage flash evaporator 14, a second-stage flash evaporator 15, a bypass water supply-geothermal fluid heat exchanger 16, a bypass condensate-geothermal fluid heat exchanger 18 and a geothermal fluid reinjection well 20; the geothermal fluid taken out from the geothermal fluid production well 12 by the deep well pump 13 is connected to the water side inlet of the first-stage flash evaporator 14; the steam side outlet of the first-stage flash evaporator 14 and the reheat steam outlet of the boiler 1 are combined and connected to the steam inlet of the intermediate pressure cylinder 3 of the steam turbine; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the steam side outlet of the first-stage flash evaporator 14 and the reheat steam outlet of the boiler 1 are ... water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected The water side inlet of the evaporator 15 is connected; the steam side outlet of the secondary flash evaporator 15 and the steam outlet of the turbine intermediate pressure cylinder 3 are merged and connected to the steam inlet of the turbine low pressure cylinder 4; the water side outlet of the secondary flash evaporator 15 is connected to the high temperature side water working medium inlet of the bypass feed water-geothermal fluid heat exchanger 16; the high temperature side water working medium outlet of the bypass feed water-geothermal fluid heat exchanger 16 is connected to the high temperature side water working medium inlet of the bypass condensate water-geothermal fluid heat exchanger 18; the high temperature side water working medium outlet of the bypass condensate water-geothermal fluid heat exchanger 18 is sent back to the geothermal fluid reinjection well 20.

[0009] Furthermore, the bypass feedwater-geothermal fluid heat exchanger 16 and the bypass condensate water-geothermal fluid heat exchanger 18 are both partition-type water-water heat exchangers.

[0010] Furthermore, the geothermal energy utilization system includes a two-stage flash evaporation device, a primary flash evaporator 14 and a secondary flash evaporator 15 .

[0011] Furthermore, the bypass feedwater-geothermal fluid heat exchanger 16 and the bypass condensate water-geothermal fluid heat exchanger 18 are respectively arranged in parallel with the high-pressure heater 11 and the low-pressure heater 8 of the coal-fired power generation unit.

[0012] Furthermore, the extracted geothermal fluid first passes through a two-stage flash evaporator to generate steam of different pressures which is injected into a steam turbine for power generation, and then the remaining high-temperature geothermal fluid is used to heat bypass condensate and bypass boiler feed water.

[0013] A method for operating a flexible and efficient coal-fired power generation system coupled with renewable energy is as follows:

[0014] 1) When the coal-fired generator set is in the normal operating load range, the deep well pump 13 can be turned on to extract geothermal fluid. The extracted geothermal fluid first passes through the first-stage flash evaporator 14 and the second-stage flash evaporator 15 to generate steam of different pressures, which are respectively injected into the steam turbine intermediate pressure cylinder 3 and the steam turbine low pressure cylinder 4 for power generation. Then, the remaining high-temperature geothermal fluid is used to heat the bypass boiler feed water and bypass condensate in the bypass feed water-geothermal fluid heat exchanger 16 and the bypass condensate-geothermal fluid heat exchanger 18. The operating goal of this stage is to increase the system's electrical power output without increasing the amount of coal fed to the boiler by combining geothermal energy and coal-fired generator sets, thereby promoting the consumption of renewable energy in the power grid;

[0015] 2) When the coal-fired power generation unit needs to quickly reduce the power load rate, the mass flow rate of the geothermal fluid extracted by the deep well pump 13 is reduced, thereby reducing the steam flow rate generated by the two-stage flash device, and at the same time, the mass flow rate of the bypass boiler feed water and the bypass condensate is reduced accordingly, the steam extraction flow rate of the steam turbine heat recovery system is increased, and the output power of the coal-fired power generation unit is rapidly reduced. The operating goal of this stage is: without reducing the amount of coal fed to the boiler, by adjusting the two-stage flash geothermal energy utilization system to quickly reduce the output power of the coal-fired power generation unit, effectively improve the load change rate of the coal-fired power generation unit;

[0016] 3) When the coal-fired power generation unit needs to quickly increase the power load rate, the deep well pump 13 is increased to extract the geothermal fluid mass flow rate, thereby increasing the steam flow rate generated by the two-stage flash device. At the same time, the mass flow rates of the bypass boiler feed water and the bypass condensate water are increased accordingly, and the steam extraction flow rate of the turbine heat recovery system is reduced. The output power of the coal-fired power generation unit increases rapidly. The operating goal of this stage is to quickly increase the output power of the coal-fired power generation unit by adjusting the two-stage flash geothermal energy utilization system without increasing the boiler coal feed rate, and effectively improve the load change rate of the coal-fired power generation unit.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] (1) The present invention proposes an efficient integration method of a coal-fired power generation unit and a two-stage flash geothermal energy utilization system. First, geothermal fluid is used to adopt a two-stage flash device to generate steam of different pressures, which are respectively injected into the intermediate pressure cylinder and the low pressure cylinder of the steam turbine for power generation. A heat recovery heater bypass of the coal-fired power generation system is also provided, and the high-temperature geothermal fluid after flash is used to heat the bypass condensate and bypass boiler feed water, thereby realizing the cascade utilization of energy and improving the energy utilization efficiency.

[0019] (2) The present invention efficiently integrates geothermal energy utilization with coal-fired power generation units, increasing the system's electrical power output without increasing the amount of coal fed to the boiler. This is of great significance to my country's promotion of renewable energy consumption and reduction of energy consumption levels of coal-fired power generation units.

[0020] (3) The present invention assists the coal-fired power generation unit to quickly increase or decrease the load by adjusting the working fluid flow rate of the two-stage flash geothermal energy utilization system, thereby effectively improving the load change rate of the coal-fired power generation unit without changing the coal feed amount of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the system of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] like Figure 1 As shown, the present invention provides a flexible and efficient coal-fired power generation system coupled with renewable energy, comprising a traditional coal-fired power generation unit and a double-stage flash geothermal energy utilization system coupled thereto;

[0024] The coal-fired power generation unit comprises a boiler 1, a steam turbine high-pressure cylinder 2, a steam turbine medium-pressure cylinder 3, a steam turbine low-pressure cylinder 4, a generator 5, a condenser 6, a condensate pump 7, a low-pressure heater 8, a deaerator 9, a feedwater pump 10 and a high-pressure heater 11; the main steam outlet of the boiler 1 is connected to the steam inlet of the steam turbine high-pressure cylinder 2; the extraction steam outlet of the steam turbine high-pressure cylinder 2 is connected to the steam inlet of the high-pressure heater 11, and the steam outlet of the steam turbine high-pressure cylinder 2 is connected to the reheat steam inlet of the boiler 1; the reheat steam outlet of the boiler 1 and the two-stage flash geothermal energy utilization The steam side outlets of the first-stage flash evaporator 14 of the two-stage flash geothermal energy utilization system are combined and connected to the steam inlet of the turbine intermediate pressure cylinder 3; the steam extraction outlet of the turbine intermediate pressure cylinder 3 is connected to the steam inlet of the deaerator 9, and the steam outlet of the turbine intermediate pressure cylinder 3 and the steam side outlet of the second-stage flash evaporator 15 of the two-stage flash geothermal energy utilization system are combined and connected to the steam inlet of the turbine low pressure cylinder 4; the steam extraction outlet of the turbine low pressure cylinder 4 is connected to the steam inlet of the low pressure heater 8, and the steam outlet of the turbine low pressure cylinder 4 is connected to the steam inlet of the condenser 6; the hydraulic The outlet of the working medium of the low-pressure heater 8 is divided into two paths after passing through the condensate pump 7, one path is connected to the water working medium inlet of the low-pressure heater 8, and the other path is connected to the low-temperature side water working medium inlet of the bypass condensate-geothermal fluid heat exchanger 18 of the double-stage flash geothermal energy utilization system through the condensate diversion valve 19; the water working medium outlet of the low-pressure heater 8 and the low-temperature side water working medium outlet of the bypass condensate-geothermal fluid heat exchanger 18 of the double-stage flash geothermal energy utilization system are combined and connected to the water working medium inlet of the deaerator 9; the water working medium outlet of the deaerator 9 is divided into two paths after passing through the feed water pump 10, one path is connected to the high-pressure heater 8, and the other path is connected to the low-temperature side water working medium inlet of the deaerator 9 through the condensate diversion valve 19. The first circuit is connected to the water working medium inlet of the high-pressure heater 11, and the other circuit is connected to the water working medium inlet of the bypass water supply-geothermal fluid heat exchanger 16 of the two-stage flash geothermal energy utilization system through the water supply shunt valve 17; the water working medium outlet of the high-pressure heater 11 and the water working medium outlet of the bypass water supply-geothermal fluid heat exchanger 16 of the two-stage flash geothermal energy utilization system are combined and then connected to the water supply inlet of the boiler 1; the high-pressure cylinder 2 of the steam turbine, the intermediate-pressure cylinder 3 of the steam turbine and the low-pressure cylinder 4 of the steam turbine are connected through a rotating shaft, and jointly drive the generator 5 to output electrical power to the outside;

[0025] The two-stage flash geothermal energy utilization system comprises a geothermal fluid production well 12, a deep well pump 13, a first-stage flash evaporator 14, a second-stage flash evaporator 15, a bypass water supply-geothermal fluid heat exchanger 16, a bypass condensate-geothermal fluid heat exchanger 18 and a geothermal fluid reinjection well 20; the geothermal fluid taken out from the geothermal fluid production well 12 by the deep well pump 13 is connected to the water side inlet of the first-stage flash evaporator 14; the steam side outlet of the first-stage flash evaporator 14 and the reheat steam outlet of the boiler 1 are combined and connected to the steam inlet of the intermediate pressure cylinder 3 of the steam turbine; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the steam side outlet of the first-stage flash evaporator 14 and the reheat steam outlet of the boiler 1 are ... water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected to the second-stage flash evaporator 20; the water side outlet of the first-stage flash evaporator 14 is connected The water side inlet of the evaporator 15 is connected; the steam side outlet of the secondary flash evaporator 15 and the steam outlet of the turbine intermediate pressure cylinder 3 are merged and connected to the steam inlet of the turbine low pressure cylinder 4; the water side outlet of the secondary flash evaporator 15 is connected to the high temperature side water working medium inlet of the bypass feed water-geothermal fluid heat exchanger 16; the high temperature side water working medium outlet of the bypass feed water-geothermal fluid heat exchanger 16 is connected to the high temperature side water working medium inlet of the bypass condensate water-geothermal fluid heat exchanger 18; the high temperature side water working medium outlet of the bypass condensate water-geothermal fluid heat exchanger 18 is sent back to the geothermal fluid reinjection well 20.

[0026] Furthermore, the bypass feed water-geothermal fluid heat exchanger 16 and the bypass condensate water-geothermal fluid heat exchanger 18 are both wall-type water-water heat exchangers. By heating the bypass condensate water and boiler feed water through geothermal fluid, the steam extraction flow rate of the heat recovery system of the coal-fired generator set can be reduced, thereby increasing the output power of the coal-fired unit.

[0027] Furthermore, the geothermal energy utilization system includes a two-stage flash evaporator, a primary flash evaporator 14 and a secondary flash evaporator 15. The two-stage flash evaporation can effectively utilize the pressure of the geothermal fluid to generate steam of different pressures, which is injected into the steam turbine for power generation.

[0028] Furthermore, the bypass feed water-geothermal fluid heat exchanger 16 and the bypass condensate water-geothermal fluid heat exchanger 18 are respectively arranged in parallel with the high-pressure heater 11 and the low-pressure heater 8 of the coal-fired power generation unit, so as to make full use of the waste heat of the geothermal fluid to heat the bypass condensate water and boiler feed water, thereby improving the load change rate of the coal-fired unit.

[0029] Furthermore, the extracted geothermal fluid first passes through a two-stage flash evaporation device to generate steam of different pressures which is then injected into a steam turbine for power generation. The remaining high-temperature geothermal fluid is then used to heat bypass condensate and bypass boiler feed water, thereby achieving cascade utilization of thermal energy in the geothermal fluid and improving system energy efficiency.

[0030] A method for operating a flexible and efficient coal-fired power generation system coupled with renewable energy is as follows:

[0031] 1) When the coal-fired generator set is in the normal operating load range, the deep well pump 13 can be turned on to extract geothermal fluid. The extracted geothermal fluid first passes through the first-stage flash evaporator 14 and the second-stage flash evaporator 15 to generate steam of different pressures, which are respectively injected into the steam turbine intermediate pressure cylinder 3 and the steam turbine low pressure cylinder 4 for power generation. Then, the remaining high-temperature geothermal fluid is used to heat the bypass boiler feed water and bypass condensate in the bypass feed water-geothermal fluid heat exchanger 16 and the bypass condensate-geothermal fluid heat exchanger 18. The operating goal of this stage is to increase the system's electrical power output without increasing the amount of coal fed to the boiler by combining geothermal energy and coal-fired generator sets, thereby promoting the consumption of renewable energy in the power grid;

[0032] 2) When the coal-fired power generation unit needs to quickly reduce the power load rate, the mass flow rate of the geothermal fluid extracted by the deep well pump 13 is reduced, thereby reducing the steam flow rate generated by the two-stage flash device, and at the same time, the mass flow rate of the bypass boiler feed water and the bypass condensate is reduced accordingly, the steam extraction flow rate of the steam turbine heat recovery system is increased, and the output power of the coal-fired power generation unit is rapidly reduced. The operating goal of this stage is: without reducing the amount of coal fed to the boiler, by adjusting the two-stage flash geothermal energy utilization system to quickly reduce the output power of the coal-fired power generation unit, effectively improve the load change rate of the coal-fired power generation unit;

[0033] 3) When the coal-fired power generation unit needs to quickly increase the power load rate, the deep well pump 13 is increased to extract the geothermal fluid mass flow rate, thereby increasing the steam flow rate generated by the two-stage flash device. At the same time, the mass flow rates of the bypass boiler feed water and the bypass condensate water are increased accordingly, and the steam extraction flow rate of the turbine heat recovery system is reduced. The output power of the coal-fired power generation unit increases rapidly. The operating goal of this stage is to quickly increase the output power of the coal-fired power generation unit by adjusting the two-stage flash geothermal energy utilization system without increasing the boiler coal feed rate, and effectively improve the load change rate of the coal-fired power generation unit.

[0034] In summary, the present invention efficiently integrates geothermal energy utilization with coal-fired power generation units. First, geothermal fluid is used to adopt a two-stage flash evaporation device to generate steam of different pressures, which are respectively injected into the intermediate pressure cylinder and the low pressure cylinder of the steam turbine for power generation. A heat recovery heater bypass of the coal-fired power generation unit is also provided, and the high-temperature geothermal fluid after flash evaporation is used to heat the bypass condensate and the bypass boiler feed water, thereby realizing the cascade utilization of energy and improving the energy utilization efficiency. In addition, the working fluid flow rate of the two-stage flash evaporation geothermal energy utilization system is adjusted to assist the coal-fired power generation unit to quickly increase or decrease the load, thereby effectively improving the load change rate of the coal-fired power generation unit without changing the boiler coal feed amount.

Claims

1. A flexible and efficient coal-fired power generation system coupled with renewable energy, characterized by: It includes a coal-fired power generation unit and a double-stage flash geothermal energy utilization system coupled with the coal-fired power generation unit; The coal-fired power generation unit comprises a boiler (1), a high-pressure cylinder of a steam turbine (2), an intermediate-pressure cylinder of a steam turbine (3), a low-pressure cylinder of a steam turbine (4), a generator (5), a condenser (6), a condensate pump (7), a low-pressure heater (8), a deaerator (9), a feedwater pump (10) and a high-pressure heater (11); the main steam outlet of the boiler (1) is connected to the steam inlet of the high-pressure cylinder of the steam turbine (2); the extraction steam outlet of the high-pressure cylinder of the steam turbine (2) is connected to the steam inlet of the high-pressure heater (11), and the steam outlet of the high-pressure cylinder of the steam turbine (2) is connected to the reheat steam inlet of the boiler (1); the reheat steam of the boiler (1) is connected to the steam inlet of the high-pressure cylinder of the steam turbine (2). The steam outlet of the steam turbine intermediate pressure cylinder (3) is connected to the steam inlet of the steam turbine intermediate pressure cylinder (3) after merging with the steam side outlet of the first flash evaporator (14) of the two-stage flash evaporator geothermal energy utilization system; the steam extraction outlet of the steam turbine intermediate pressure cylinder (3) is connected to the steam inlet of the deaerator (9); the steam outlet of the steam turbine intermediate pressure cylinder (3) and the steam side outlet of the second flash evaporator (15) of the two-stage flash evaporator geothermal energy utilization system are connected to the steam inlet of the steam turbine low pressure cylinder (4) after merging; the steam extraction outlet of the steam turbine low pressure cylinder (4) is connected to the steam inlet of the low pressure heater (8), and the steam outlet of the steam turbine low pressure cylinder (4) is connected to the steam inlet of the condenser (6). The water working medium outlet of the condenser (6) is divided into two paths after passing through the condensate pump (7), one path being connected to the water working medium inlet of the low-pressure heater (8), and the other path being connected to the low-temperature side water working medium inlet of the bypass condensate-geothermal fluid heat exchanger (18) of the double-stage flash geothermal energy utilization system through the condensate diversion valve (19); the water working medium outlet of the low-pressure heater (8) and the low-temperature side water working medium outlet of the bypass condensate-geothermal fluid heat exchanger (18) of the double-stage flash geothermal energy utilization system are combined and connected to the water working medium inlet of the deaerator (9); the water working medium outlet of the deaerator (9) is divided into two paths after passing through the feed water pump (10), One path is connected to the water working medium inlet of the high-pressure heater (11), and the other path is connected to the low-temperature side water working medium inlet of the bypass water supply-geothermal fluid heat exchanger (16) of the two-stage flash geothermal energy utilization system through the water supply shunt valve (17); the water working medium outlet of the high-pressure heater (11) and the low-temperature side water working medium outlet of the bypass water supply-geothermal fluid heat exchanger (16) of the two-stage flash geothermal energy utilization system are combined and then connected to the water supply inlet of the boiler (1); the high-pressure cylinder (2) of the steam turbine, the intermediate-pressure cylinder (3) of the steam turbine and the low-pressure cylinder (4) of the steam turbine are connected via a rotating shaft and jointly drive a generator (5) to output electrical power to the outside; The two-stage flash geothermal energy utilization system comprises a geothermal fluid production well (12), a deep well pump (13), a first-stage flash evaporator (14), a second-stage flash evaporator (15), a bypass water supply-geothermal fluid heat exchanger (16), a bypass condensate water-geothermal fluid heat exchanger (18) and a geothermal fluid reinjection well (20); the geothermal fluid taken out from the geothermal fluid production well (12) by the deep well pump (13) is connected to the water side inlet of the first-stage flash evaporator (14); the steam side outlet of the first-stage flash evaporator (14) and the reheat steam outlet of the boiler (1) are combined and connected to the steam inlet of the intermediate pressure cylinder (3) of the turbine; the water side outlet of the first-stage flash evaporator (14) is connected to the steam inlet of the intermediate pressure cylinder (3) of the steam turbine; The secondary flash evaporator (15) is connected to the water side inlet of the secondary flash evaporator (15); the steam side outlet of the secondary flash evaporator (15) and the steam outlet of the turbine intermediate pressure cylinder (3) are combined and then connected to the steam inlet of the turbine low pressure cylinder (4); the water side outlet of the secondary flash evaporator (15) is connected to the high temperature side water working medium inlet of the bypass feed water-geothermal fluid heat exchanger (16); the high temperature side water working medium outlet of the bypass feed water-geothermal fluid heat exchanger (16) is connected to the high temperature side water working medium inlet of the bypass condensate water-geothermal fluid heat exchanger (18); the high temperature side water working medium outlet of the bypass condensate water-geothermal fluid heat exchanger (18) is sent back to the geothermal fluid reinjection well (20).

2. A flexible and efficient coal-fired power generation system coupled with renewable energy according to claim 1, characterized in that: The bypass feed water-geothermal fluid heat exchanger (16) and the bypass condensate water-geothermal fluid heat exchanger (18) are both partition-type water-water heat exchangers.

3. A flexible and efficient coal-fired power generation system coupled with renewable energy and an operation method thereof according to claim 1, characterized in that: The geothermal energy utilization system comprises a two-stage flash evaporation device, a first-stage flash evaporator (14) and a second-stage flash evaporator (15).

4. A flexible and efficient coal-fired power generation system coupled with renewable energy according to claim 1, characterized in that: The bypass feedwater-geothermal fluid heat exchanger (16) and the bypass condensate water-geothermal fluid heat exchanger (18) are respectively arranged in parallel with the high-pressure heater (11) and the low-pressure heater (8) of the coal-fired power generation unit.

5. A flexible and efficient coal-fired power generation system coupled with renewable energy according to claim 1, characterized in that: The extracted geothermal fluid first passes through a two-stage flash evaporator to generate steam of different pressures, which is then injected into a steam turbine for power generation. The remaining high-temperature geothermal fluid is then used to heat bypass condensate and bypass boiler feed water.

6. The method for operating a flexible and efficient coal-fired power generation system coupled with renewable energy as claimed in any one of claims 1 to 5, characterized in that: 1) When the coal-fired power generation unit is in the normal operating load range, the deep well pump (13) can be turned on to extract geothermal fluid. The extracted geothermal fluid first passes through the first-stage flash evaporator (14) and the second-stage flash evaporator (15) to generate steam of different pressures, which are respectively injected into the steam turbine intermediate pressure cylinder (3) and the steam turbine low pressure cylinder (4) to generate electricity. Then, the remaining high-temperature geothermal fluid is used to heat the bypass boiler feed water and bypass condensate in the bypass feed water-geothermal fluid heat exchanger (16) and the bypass condensate-geothermal fluid heat exchanger (18). The operating goal of this stage is to increase the system's electrical power output by combining geothermal energy and coal-fired power generation units without increasing the amount of coal fed to the boiler, thereby promoting the consumption of renewable energy in the power grid; 2) When the coal-fired power generation unit needs to reduce the power load rate quickly, the mass flow rate of the geothermal fluid extracted by the deep well pump (13) is reduced, thereby reducing the steam flow rate generated by the two-stage flash device, and at the same time, the mass flow rates of the bypass boiler feed water and bypass condensate are correspondingly reduced, the steam extraction flow rate of the turbine heat recovery system is increased, and the output power of the coal-fired power generation unit is rapidly reduced. The operation goal of this stage is to quickly reduce the output power of the coal-fired power generation unit by adjusting the two-stage flash geothermal energy utilization system without reducing the boiler coal feed rate, thereby effectively improving the load change rate of the coal-fired power generation unit; 3) When the coal-fired power generation unit needs to quickly increase the power load rate, the deep well pump (13) is added to extract the geothermal fluid mass flow rate, thereby increasing the steam flow rate generated by the two-stage flash device, and at the same time, the mass flow rates of the bypass boiler feed water and bypass condensate are increased accordingly, the steam extraction flow rate of the turbine heat recovery system is reduced, and the output power of the coal-fired power generation unit increases rapidly. The operating goal of this stage is to quickly increase the output power of the coal-fired power generation unit by adjusting the two-stage flash geothermal energy utilization system without increasing the boiler coal feed rate, thereby effectively improving the load change rate of the coal-fired power generation unit.

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