Supercritical co2 power generation system and method with integrated ejector lignite drying

Abstract

The present disclosure provides a kind of integrated ejector lignite drying supercritical CO2 power generation system and method, by coupling deeply with supercritical CO2 coal-fired power generation system through ejector lignite drying system, utilize high-temperature high-pressure CO2 working substance of high-temperature regenerator outlet to eject low-temperature low-pressure CO2 working substance of low-temperature regenerator outlet, form the medium-temperature medium-pressure working substance matching with the temperature and lignite drying demand, drive rotary drum dryer to carry out pre-drying treatment to high-moisture lignite;At the same time, the water vapor released in drying process is condensed to recover condensate water, and low-moisture lignite after drying is sent into boiler for combustion.The cold source loss is significantly reduced, and the system comprehensive energy efficiency, combustion efficiency and unit power supply efficiency are improved.In addition, the condensate water generated in the process of lignite drying is recovered, which reduces the water consumption of the unit, and energy efficient utilization and resource saving are considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power generation, in particular to a supercritical CO2 power generation system integrated with an ejector lignite drying device and a method thereof. BACKGROUND

[0002] The supercritical CO2 power cycle has the advantages of high efficiency and flexibility, and is expected to replace the steam Rankine cycle and be applied to coal-fired power generation, thereby greatly improving the power generation efficiency and peak shaving performance of coal-fired units, reducing the pollution and CO2 emissions of the units, promoting large-scale consumption of renewable energy, and promoting the low-carbon development of the power industry, which is of great significance to the realization of China's "double carbon" goal.

[0003] However, the current research on supercritical CO2 cycle coal-fired power generation technology does not consider the change of coal types, especially lacking research on lignite power generation systems. China has abundant lignite reserves, with proven reserves of 130 billion tons, accounting for 12% of the country's coal reserves, and the price is low, which is becoming the main fuel for thermal power generation in China. However, due to the high moisture content of lignite, the calorific value is low, and direct combustion of lignite for power generation results in high flue gas moisture, high flue gas temperature, low boiler efficiency, and high equipment cost.

[0004] Therefore, drying the lignite before combustion can effectively solve this problem. SUMMARY

[0005] The first aspect of the present application provides a supercritical CO2 power generation system integrated with an ejector lignite drying device, comprising a supercritical CO2 coal-fired power generation unit and an ejector lignite drying unit.

[0006] The supercritical CO2 coal-fired power generation unit comprises a main compressor (1), a low-temperature regenerator (2), a high-temperature regenerator (3), a boiler (4), a turbine (5), a precooler (6), a first-stage re-compressor (7), and a second-stage re-compressor (8); wherein,

[0007] The outlet of the main compressor (1) is connected to the cold side inlet of the low-temperature regenerator (2), the cold side inlet of the high-temperature regenerator (3), and the inlet of the boiler (4) in sequence.

[0008] The outlet of the boiler (4) is connected to the inlet of the turbine (5), and the outlet of the turbine (5) is connected to the hot side inlet of the high-temperature regenerator (3), the hot side inlet of the low-temperature regenerator (2), and the inlet of the precooler (6) in sequence, and the outlet of the precooler (6) is connected to the inlet of the main compressor (1).

[0009] The inlet of the first-stage re-compressor (7) is communicated with the hot-side outlet of the low-temperature recuperator (2), the outlet of the first-stage re-compressor (7) is connected with the inlet of the second-stage re-compressor (8), and the outlet of the second-stage re-compressor (8) is communicated with the cold-side outlet of the low-temperature recuperator (2);

[0010] The ejector lignite drying unit comprises an ejector (9), a dryer (10) and a condenser (11); wherein,

[0011] The cold-side outlet of the high-temperature recuperator (3) is divided into two paths, the first path is connected with the inlet of the boiler (4), and the second path is connected with the high-pressure inlet of the ejector (9);

[0012] The hot-side outlet of the low-temperature recuperator (2) is connected with the low-pressure inlet of the ejector (9);

[0013] The outlet of the ejector (9) is connected with the hot-side inlet of the dryer (10), and the hot-side outlet of the dryer (10) is communicated with the inlet of the second-stage re-compressor (8);

[0014] The drying coal outlet of the dryer (10) is connected with the fuel inlet of the boiler (4), the exhaust outlet of the dryer (10) is connected with the inlet of the condenser (11), and the condenser (11) is used for recycling the condensed water.

[0015] In combination with the first aspect, the dryer (10) is a rotary drum dryer.

[0016] In combination with the first aspect, a flow distribution valve is arranged in the pipeline between the cold-side outlet of the high-temperature recuperator (3) and the high-pressure inlet of the ejector (9) to adjust the flow of the high-pressure working medium into the ejector (9).

[0017] In combination with the first aspect, the pipeline of the outlet of the first-stage re-compressor (7) and the hot-side outlet of the dryer (10) is combined and connected to the inlet of the second-stage re-compressor (8), and the outlet pressure of the first-stage re-compressor (7) is equal to or within a preset range of the CO2 pressure of the hot-side outlet of the dryer (10).

[0018] In combination with the first aspect, the condensed water outlet of the condenser (11) is used for recycling the condensed water generated in the lignite drying process.

[0019] The second aspect of the present disclosure provides a supercritical CO2 power generation method, comprising the following steps:

[0020] The supercritical CO2 working medium is pressurized by the main compressor (1), sequentially flows through the low-temperature recuperator (2) and the high-temperature recuperator (3) to absorb heat on the cold side, enters the boiler (4) to be heated, and drives the turbine (5) to generate power;

[0021] The working medium at the outlet of the turbine (5) sequentially flows through the hot side of the high-temperature regenerator (3) and the hot side of the low-temperature regenerator (2) to release heat, and is cooled by the pre-cooler (6) and then returned to the main compressor (1);

[0022] Part of the CO2 working medium at the outlet of the low-temperature regenerator (2) is extracted and introduced into part of the CO2 working medium at the outlet of the cold side of the high-temperature regenerator (3) by the high-pressure inlet of the ejector (9) to form mixed CO2 working medium;

[0023] The mixed CO2 working medium enters the dryer (10) to dry the lignite, the dehydrated dried coal is sent into the boiler (4) for combustion, and the wet steam generated by drying is condensed and recovered by the condenser (11);

[0024] The CO2 working medium at the outlet of the dryer (10) is returned to the inlet of the second-stage re-compressor (8) and is pressurized in circulation after being combined with the working medium at the outlet of the first-stage re-compressor (7).

[0025] In combination with the second aspect, the temperature of the mixed working medium of the ejector (9) matches the temperature of the heat source required for drying the lignite, so as to reduce the irreversible loss in the drying process.

[0026] In combination with the second aspect, the condensed water recovered by the condenser (11) is used to supplement the water consumption of the power generation system.

[0027] Beneficial effects: The supercritical CO2 power generation system and method integrating the ejector lignite drying system provided by the present disclosure deeply couple the ejector lignite drying system with the supercritical CO2 coal-fired power generation system, use the high-temperature and high-pressure CO2 working medium at the outlet of the high-temperature regenerator to eject the low-temperature and low-pressure CO2 working medium at the outlet of the low-temperature regenerator, form medium-temperature and medium-pressure working medium matching the drying requirement of the lignite, and drive the rotary drum dryer to perform pre-drying treatment on the high-moisture lignite; at the same time, the water vapor released in the drying process is condensed and recovered to recover condensed water, and the low-moisture lignite after drying is sent into the boiler for combustion. The cold source loss is significantly reduced, and the system comprehensive energy efficiency, combustion efficiency and unit power supply efficiency are improved. In addition, the condensed water generated in the lignite drying process is recovered, the water consumption of the unit is reduced, and energy efficient utilization and resource saving are taken into account. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 FIG. 1 is a structural schematic diagram of a supercritical CO2 power generation system integrating an ejector lignite drying system according to an embodiment of the present disclosure;

[0029] Figure 2 FIG. 2 is a flow schematic diagram of a supercritical CO2 power generation method integrating an ejector lignite drying system according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those disclosed herein.

[0031] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0032] It should be understood that although the terms first, second, third, etc., may be used to describe various information in embodiments of this disclosure, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first information may also be referred to as second information without departing from the scope of embodiments of this disclosure, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0033] like Figure 1 The diagram shown is a structural schematic of a supercritical CO2 power generation system with integrated ejector lignite drying according to an embodiment of the present disclosure, including a supercritical CO2 coal-fired power generation unit and an ejector lignite drying unit.

[0034] The supercritical CO2 coal-fired power generation unit includes: a main compressor (1), a low-temperature regenerator (2), a high-temperature regenerator (3), a boiler (4), a turbine (5), a precooler (6), a first-stage recompressor (7), and a second-stage recompressor (8); wherein,

[0035] The outlet of the main compressor (1) is connected in sequence to the cold side inlet of the low temperature regenerator (2), the cold side inlet of the high temperature regenerator (3), and the inlet of the boiler (4);

[0036] The outlet of the boiler (4) is connected to the inlet of the turbine (5). The outlet of the turbine (5) is connected in sequence to the hot side inlet of the high temperature regenerator (3), the hot side inlet of the low temperature regenerator (2), and the inlet of the precooler (6). The outlet of the precooler (6) is connected to the inlet of the main compressor (1).

[0037] The inlet of the first-stage re-compressor (7) is communicated with the hot-side outlet of the low-temperature recuperator (2), the outlet of the first-stage re-compressor (7) is connected with the inlet of the second-stage re-compressor (8), and the outlet of the second-stage re-compressor (8) is communicated with the cold-side outlet of the low-temperature recuperator (2);

[0038] The ejector lignite drying unit comprises an ejector (9), a dryer (10) and a condenser (11); wherein,

[0039] The cold-side outlet of the high-temperature recuperator (3) is divided into two paths, the first path is connected with the inlet of the boiler (4), and the second path is connected with the high-pressure inlet of the ejector (9);

[0040] The hot-side outlet of the low-temperature recuperator (2) is connected with the low-pressure inlet of the ejector (9);

[0041] The outlet of the ejector (9) is connected with the hot-side inlet of the dryer (10), and the hot-side outlet of the dryer (10) is communicated with the inlet of the second-stage re-compressor (8);

[0042] The drying coal outlet of the dryer (10) is connected with the fuel inlet of the boiler (4), the exhaust outlet of the dryer (10) is connected with the inlet of the condenser (11), and the condenser (11) is used for recovering condensate water.

[0043] Specifically, the supercritical CO2 coal-fired power generation unit is responsible for converting the heat energy generated by lignite combustion into electrical energy, and improving energy utilization efficiency through the closed cycle of CO2. The unit comprises a main compressor (1), a low-temperature recuperator (2), a high-temperature recuperator (3), a boiler (4), a turbine (5), a pre-cooler (6), a first-stage re-compressor (7) and a second-stage re-compressor (8).

[0044] The main compressor (1) is used for pressurizing CO2, so that it enters the cold side of the low-temperature recuperator (2), absorbs the waste heat discharged by the turbine, and increases the temperature. Subsequently, CO2 enters the cold side of the high-temperature recuperator (3), is further heated, and then enters the boiler (4). The high-temperature flue gas in the boiler (4) heats CO2 to a supercritical state, which then enters the turbine (5) to expand and do work, driving the generator to generate electricity.

[0045] The CO2 discharged from the turbine (5) enters the hot side of the high-temperature recuperator (3), the hot side of the low-temperature recuperator (2) and the pre-cooler (6) in turn, and gradually reduces the temperature. Finally, CO2 re-enters the cycle through the main compressor (1), completing the energy conversion process.

[0046] In addition, in order to optimize the system pressure and flow, the first-stage re-compressor (7) and the second-stage re-compressor (8) are respectively used to adjust the flow pressure of CO2 at the hot side of the low-temperature recuperator (2), so that it better adapts to the system requirements and improves the cycle efficiency.

[0047] The ejector lignite drying unit is used for reducing the moisture content of lignite, increasing the fuel heat value, and reducing the humidity of the boiler flue gas, thereby improving the boiler efficiency and reducing the system energy consumption. The unit is composed of an ejector (9), a dryer (10), and a condenser (11).

[0048] In the system, the cold side outlet of the high-temperature regenerator (3) is divided into two paths, one of which directly enters the boiler (4) for heating, and the other enters the high-pressure inlet of the ejector (9). At the same time, the hot side outlet CO2 of the low-temperature regenerator (2) enters the low-pressure inlet of the ejector (9) as low-temperature and low-pressure working medium. In the ejector (9), the two streams of CO2 are fully mixed to form medium-temperature and medium-pressure CO2 with appropriate temperature and pressure, which then enters the dryer (10) to heat and dry the lignite.

[0049] During the drying process, the moisture in the lignite evaporates, and the resulting wet hot gas enters the condenser (11) through the dryer (10) exhaust outlet. The condenser (11) cools the water vapor to condense it into liquid water, realizing the recycling of water resources. At the same time, the dried lignite is transported to the boiler (4) for combustion through the dried coal outlet.

[0050] Beneficial effects: The system uses the high-temperature and high-pressure CO2 to inject the low-temperature and low-pressure CO2 through the ejector (9), not only realizing the reuse of CO2, but also effectively recovering the low-temperature waste heat, reducing the loss of cold source, and improving the overall thermal efficiency. At the same time, the dried lignite can reduce the boiler flue gas temperature, reduce the humidity of the flue gas, improve the combustion efficiency, and reduce the auxiliary power consumption, thereby improving the power generation efficiency. In addition, the condenser (11) recovers the condensed water generated during the lignite drying process, which helps to reduce the water consumption of the unit and optimize resource utilization.

[0051] Further, the dryer (10) is a rotary drum dryer.

[0052] The dryer (10) in the system adopts a rotary drum dryer, which rotates the drum to continuously tumble the lignite during the drying process, thereby enhancing the heat exchange effect. This structure can increase the contact area between the lignite and CO2, make the heat transfer more uniform, and improve the drying efficiency. At the same time, the rotation of the drum can also prevent the lignite from caking or adhering to the inside of the equipment during the drying process, ensuring the stability and continuity of the drying process.

[0053] In the dryer (10), the high-temperature CO2 acts as a drying medium and fully contacts with the lignite to remove the moisture. The dried lignite is transported to the boiler (4) for combustion through the dried coal outlet, while the wet hot gas generated during the drying process enters the condenser (11) for water vapor condensation and recovery through the exhaust port.

[0054] Further, a flow distribution valve is arranged in the pipeline between the cold side outlet of the high-temperature regenerator (3) and the high-pressure inlet of the ejector (9) to adjust the flow of high-pressure working medium into the ejector (9).

[0055] Specifically, to ensure the stable operation of the ejector (9) and adapt to the requirements of different working conditions for the temperature and flow of the drying medium, a flow distribution valve is arranged in the pipeline between the cold side outlet of the high-temperature regenerator (3) and the high-pressure inlet of the ejector (9).

[0056] The function of the flow distribution valve is to adjust the flow of high-pressure working medium into the ejector (9) to ensure that the mixing and ejecting process inside the ejector is in the best working state. When it is necessary to increase the drying temperature or the drying capacity, the opening of the flow distribution valve can be increased to increase the amount of high-temperature and high-pressure CO2 entering the ejector (9); on the contrary, when the demand decreases, the flow of high-pressure working medium is reduced to save energy and optimize the operation of the system.

[0057] Further, the pipeline combined by the outlet of the first-stage re-compressor (7) and the hot side outlet of the dryer (10) is connected to the inlet of the second-stage re-compressor (8), and the outlet pressure of the first-stage re-compressor (7) is equal to or within a preset range of the CO2 pressure of the hot side outlet of the dryer (10).

[0058] Specifically, to optimize the recycling and energy efficiency of CO2, the pipeline combined by the outlet of the first-stage re-compressor (7) and the hot side outlet of the dryer (10) is connected to the inlet of the second-stage re-compressor (8). This design can reduce the loss of CO2, improve the stability of gas circulation, and reduce the pressure drop loss of the system.

[0059] In addition, the outlet pressure of the first-stage re-compressor (7) is equal to or within a preset range (which can be set according to the specific working condition) of the CO2 pressure of the hot side outlet of the dryer (10), which ensures that when the two gas streams are combined, the flow will not be unstable or cause additional energy loss due to excessive pressure difference. This pressure matching design helps to reduce the resistance in gas circulation, improve the working efficiency of the re-compressor, and ensure that the CO2 can be compressed stably after entering the second-stage re-compressor (8), thereby optimizing the energy utilization efficiency of the entire system.

[0060] As shown in Figure 2 FIG. 1 is a flow diagram of an integrated ejector lignite drying supercritical CO2 power generation method according to an embodiment of the present disclosure, which comprises:

[0061] S201: The supercritical CO2 working medium is pressurized by the main compressor (1), and then sequentially flows through the low-temperature regenerator (2) and the cold side of the high-temperature regenerator (3) to absorb heat, and then enters the boiler (4) to be heated to drive the turbine (5) to generate power.

[0062] S202: The working medium at the outlet of the turbine (5) sequentially passes through the hot side of the high-temperature regenerator (3) and the hot side of the low-temperature regenerator (2) to release heat, and is cooled by the pre-cooler (6) before returning to the main compressor (1).

[0063] S203: Part of the CO2 working medium is extracted from the hot side outlet of the low-temperature regenerator (2) and introduced into part of the CO2 working medium at the outlet of the cold side of the high-temperature regenerator (3) by the high-pressure inlet of the ejector (9) to form mixed CO2 working medium.

[0064] S204: The mixed CO2 working medium enters the dryer (10) to dry the lignite, and the dehydrated dry coal is sent to the boiler (4) for combustion, and the wet steam generated by drying is condensed by the condenser (11) for recovery.

[0065] S205: The CO2 working medium at the outlet of the dryer (10) returns to the inlet of the second-stage re-compressor (8) and is combined with the working medium at the outlet of the first-stage re-compressor (7) to increase the pressure and circulate.

[0066] Specifically, the supercritical CO2 working medium is first pressurized by the main compressor (1) to increase its pressure and density. Subsequently, the pressurized CO2 sequentially passes through the cold side of the low-temperature regenerator (2) and the high-temperature regenerator (3) to exchange heat with the high-temperature CO2 circulating back, and then enters the boiler (4) after preheating.

[0067] In the boiler (4), the CO2 working medium absorbs the heat released by combustion and is heated to a supercritical state, driving the turbine (5) to expand and do work, realizing energy conversion and driving the generator to generate electricity. This process utilizes the high density and high thermal efficiency characteristics of supercritical CO2 to improve the energy conversion efficiency of coal-fired power generation.

[0068] After the turbine (5) does work, the discharged CO2 working medium still has a relatively high temperature. To improve the energy utilization rate of the system, this part of CO2 sequentially enters the hot side of the high-temperature regenerator (3) and the low-temperature regenerator (2) to transfer the remaining heat to the low-temperature CO2 before entering the boiler (4), realizing heat recovery.

[0069] Subsequently, the CO2 cooled by heat exchange enters the pre-cooler (6), is further cooled to an appropriate temperature, and returns to the main compressor (1) to complete the closed-loop circulation and prepare for the next round of power generation cycle.

[0070] While the CO2 power generation cycle is running, part of the CO2 working medium is extracted from the hot side outlet of the low-temperature regenerator (2) and introduced into the low-pressure inlet of the ejector (9). At the same time, the high-pressure inlet of the ejector (9) is connected to the cold side outlet of the high-temperature regenerator (3) to provide high-temperature and high-pressure CO2.

[0071] Inside the ejector (9), the two streams of CO2 exchange momentum to form a mixed CO2 working medium, which maintains a certain pressure and has a high temperature, suitable as a drying medium for lignite.

[0072] The generated mixed CO2 working medium enters the dryer (10) to dry the lignite. Due to the good heat transfer capacity and permeability of CO2, it can quickly remove the moisture in the lignite, improving the drying efficiency. The dried lignite has a lower moisture content, improving the combustion performance, and is transported to the boiler (4) through the dried coal outlet for combustion and power generation.

[0073] The wet steam generated during the drying process is discharged from the exhaust outlet of the dryer (10) and enters the condenser (11), where it is cooled and condensed into water. The recovered water can be further treated for industrial production or system water replenishment, reducing water resource waste.

[0074] After the drying process is completed, the CO2 drying medium is discharged from the dryer (10) and enters the second-stage re-compressor (8) for pressurization. At the same time, the CO2 discharged from the first-stage re-compressor (7) is also combined with it and enters the second-stage re-compressor (8) together, ensuring the recovery and efficient recycling of CO2.

[0075] The re-compressed CO2 re-enters the low-temperature regenerator (2) and other heat exchange equipment to continue participating in the power generation and drying cycle, achieving efficient energy utilization and CO2 recycling.

[0076] Further, the temperature of the mixed working medium of the ejector (9) matches the temperature of the heat source required for lignite drying, reducing the irreversible loss of the drying process.

[0077] Specifically, in the system, the temperature of the mixed CO2 working medium output by the ejector (9) matches the temperature of the heat source required for lignite drying, meaning that the temperature of the CO2 working medium needs to fall within the optimal lignite dehydration temperature range (which can be measured in actual working conditions). If the temperature is too high, although it can speed up the evaporation of water, it may cause the lignite surface to dry rapidly and form a crust, making it difficult for internal moisture to diffuse, ultimately affecting the drying effect. If the temperature is too low, the drying rate will decrease and the water will not be fully evaporated, resulting in lignite containing a lot of water when burned, reducing the combustion efficiency. Therefore, ensuring that the temperature of the mixed CO2 matches the drying requirements of lignite can improve the drying efficiency, reduce energy waste, and reduce irreversible loss.

[0078] The above examples are only used to illustrate the technical solutions of the present disclosure, rather than limit the same; although the present disclosure is described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features thereof can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and should be included in the protection scope of the present disclosure.

Claims

1. A supercritical CO2 power generation system for lignite drying with an integrated ejector, characterized in that, Includes a supercritical CO2 coal-fired power generation unit and an ejector lignite drying unit; The supercritical CO2 coal-fired power generation unit includes: a main compressor (1), a low-temperature regenerator (2), a high-temperature regenerator (3), a boiler (4), a turbine (5), a precooler (6), a first-stage recompressor (7), and a second-stage recompressor (8); wherein, The outlet of the main compressor (1) is connected in sequence to the cold side inlet of the low temperature regenerator (2), the cold side inlet of the high temperature regenerator (3), and the inlet of the boiler (4); The outlet of the boiler (4) is connected to the inlet of the turbine (5). The outlet of the turbine (5) is connected in sequence to the hot side inlet of the high temperature regenerator (3), the hot side inlet of the low temperature regenerator (2), and the inlet of the precooler (6). The outlet of the precooler (6) is connected to the inlet of the main compressor (1). The inlet of the first-stage recompressor (7) is connected to the hot-side outlet of the low-temperature regenerator (2), the outlet of the first-stage recompressor (7) is connected to the inlet of the second-stage recompressor (8), and the outlet of the second-stage recompressor (8) is connected to the cold-side outlet of the low-temperature regenerator (2). The ejector lignite drying unit includes: an ejector (9), a dryer (10), and a condenser (11); wherein, The cold side outlet of the high temperature regenerator (3) is divided into two paths. The first path is connected to the inlet of the boiler (4), and the second path is connected to the high pressure inlet of the ejector (9). The hot-side outlet of the low-temperature regenerator (2) is connected to the low-pressure inlet of the ejector (9); The outlet of the ejector (9) is connected to the hot side inlet of the dryer (10), and the hot side outlet of the dryer (10) is connected to the inlet of the second-stage recompressor (8); The dry coal outlet of the dryer (10) is connected to the fuel inlet of the boiler (4), and the exhaust outlet of the dryer (10) is connected to the inlet of the condenser (11), which is used to recover condensate.

2. The power generation system according to claim 1, characterized in that, The dryer (10) is a rotary drum dryer.

3. The power generation system according to claim 1, characterized in that, The pipeline between the cold side outlet of the high-temperature regenerator (3) and the high-pressure inlet of the ejector (9) is equipped with a flow distribution valve to regulate the flow rate of the high-pressure working fluid entering the ejector (9).

4. The power generation system according to claim 1, characterized in that, The outlet of the first stage recompressor (7) and the hot side outlet of the dryer (10) are connected together and then connected to the inlet of the second stage recompressor (8). The outlet pressure of the first stage recompressor (7) is equal to or differs from the CO2 pressure of the hot side outlet of the dryer (10) within a preset range.

5. The power generation system according to claim 1, characterized in that, The condensate outlet of the condenser (11) is used to recover and reuse the condensate generated during the lignite drying process.

6. A method for generating supercritical CO2 based on the system described in any one of claims 1-5, characterized in that, Includes the following steps: After being pressurized by the main compressor (1), the supercritical CO2 working fluid flows through the low-temperature regenerator (2) and the high-temperature regenerator (3) in sequence to absorb heat on the cold side, and then enters the boiler (4) for heating and drives the turbine (5) to generate electricity. The working fluid at the turbine (5) outlet flows sequentially through the hot side of the high-temperature regenerator (3) and the hot side of the low-temperature regenerator (2) to release heat, and returns to the main compressor (1) after being cooled by the precooler (6). A portion of the CO2 working fluid is extracted from the hot side outlet of the low-temperature regenerator (2) and introduced into the cold side outlet of the high-temperature regenerator (3) through the high-pressure inlet of the ejector (9) to form a mixed CO2 working fluid. The mixed CO2 working medium enters the dryer (10) to dry the lignite. The dehydrated coal is sent to the boiler (4) for combustion. The wet steam generated during drying is condensed and recovered by the condenser (11). The CO2 working medium at the outlet of the dryer (10) is returned to the inlet of the second-stage recompressor (8) and combined with the working medium at the outlet of the first-stage recompressor (7) for pressurization and circulation.

7. The method according to claim 6, characterized in that, The temperature of the mixed working fluid in the ejector (9) is matched with the heat source temperature required for drying lignite, so as to reduce irreversible losses in the drying process.

8. The method according to claim 6, characterized in that, The condensate recovered by the condenser (11) is used to supplement the water consumption of the power generation system.

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