Integrated ejector lignite drying supercritical CO2 power generation system and method

Abstract

According to the supercritical CO2 power generation system and method integrating ejector lignite drying, the ejector lignite drying system and the supercritical CO2 coal-fired power generation system are deeply coupled, and a low-temperature and low-pressure CO2 working medium at an outlet of a low-temperature heat regenerator is ejected through a high-temperature and high-pressure CO2 working medium at an outlet of a high-temperature heat regenerator; a medium-temperature medium-pressure working medium with the temperature matched with the lignite drying requirement is formed, and the rotary roller dryer is driven to conduct pre-drying treatment on the high-moisture lignite; and meanwhile, water vapor released in the drying process is condensed to recover condensed water, and the dried low-moisture lignite is fed into a boiler to be combusted. The cold source loss is obviously reduced, the comprehensive energy efficiency, the combustion efficiency and the unit power supply efficiency of the system are improved, in addition, condensed water generated by lignite drying is recycled, the unit water consumption is reduced, and efficient energy utilization and resource saving are both considered.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a supercritical CO2 power generation system and method for integrated ejector lignite drying. Background Art

[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 in the field of coal-fired power generation. It will greatly improve the power generation efficiency and peak-shaving performance of coal-fired units, reduce the unit's pollutant and CO2 emissions, and promote the large-scale consumption of renewable energy, promote the low-carbon development of the power industry, and is of great significance to the realization of my country's "dual carbon" goals.

[0003] However, current research on supercritical CO2 cycle coal-fired power generation technology has rarely considered variations in coal types, particularly lignite-based power generation systems. my country boasts abundant lignite reserves, with proven reserves reaching 130 billion tons, accounting for 12% of the country's total coal reserves. Lignite is also inexpensive and is becoming the primary fuel for thermal power generation in my country. However, due to its high moisture content and low calorific value, direct lignite combustion for power generation results in high moisture content in flue gas, high exhaust temperatures, low boiler efficiency, and high equipment costs.

[0004] Therefore, drying the lignite before burning it to reduce the moisture content of the raw coal can effectively solve this problem. Summary of the Invention

[0005] In a first aspect of the present disclosure, there is provided a supercritical CO2 power generation system integrated with an ejector lignite drying, 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 recompressor (7) and a second-stage recompressor (8); wherein,

[0007] 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);

[0008] 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), and the outlet of the precooler (6) is connected to the inlet of the main compressor (1);

[0009] 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);

[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 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);

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

[0013] 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);

[0014] 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). The condenser (11) is used to recover 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 provided 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 the high-pressure working medium entering the ejector (9).

[0017] In combination with the first aspect, the outlet of the first-stage recompressor (7) and the hot side outlet of the dryer (10) are connected to the inlet of the second-stage recompressor (8) after being merged, and the outlet pressure of the first-stage recompressor (7) is equal to or the difference between the pressure of CO2 at the hot side outlet of the dryer (10) is within a preset range.

[0018] In combination with the first aspect, the condensate outlet of the condenser (11) is used to recycle the condensate generated in the lignite drying process.

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

[0020] After being pressurized by the main compressor (1), the supercritical CO2 working medium 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) to be heated and drive the turbine (5) to generate electricity;

[0021] 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 then returns to the main compressor (1) after being cooled by the precooler (6);

[0022] Extracting part of the CO2 working medium from the hot side outlet of the low-temperature regenerator (2), and introducing part of the CO2 working medium from 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 medium;

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

[0024] The CO2 working medium at the outlet of the dryer (10) returns to the inlet of the second-stage recompressor (8), is combined with the working medium at the outlet of the first-stage recompressor (7), and then is pressurized and circulated.

[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 lignite drying, so as to reduce irreversible losses 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 present disclosure provides a supercritical CO2 power generation system and method for integrated ejector lignite drying. By deeply coupling the ejector lignite drying system with the supercritical CO2 coal-fired power generation system, the high-temperature and high-pressure CO2 working medium at the outlet of the high-temperature regenerator is used to eject the low-temperature and low-pressure CO2 working medium at the outlet of the low-temperature regenerator, forming a medium-temperature and medium-pressure working medium whose temperature matches the lignite drying requirements, and driving the rotary drum dryer to pre-dry the high-moisture lignite. At the same time, the water vapor released during the drying process is condensed and condensed water is recovered, and the dried low-moisture lignite is fed into the boiler for combustion. This significantly reduces the loss of cold source, improves the overall energy efficiency, combustion efficiency and power supply efficiency of the system, and in addition, the recovery of condensed water generated by lignite drying reduces the water consumption of the unit, taking into account both efficient energy utilization and resource conservation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic structural diagram of a supercritical CO2 power generation system for lignite drying with an integrated ejector according to an embodiment of the present disclosure;

[0029] Figure 2 Schematic diagram of a process for supercritical CO2 power generation using an integrated ejector for lignite drying according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Exemplary embodiments are described in detail herein, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numerals in different drawings represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present disclosure.

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

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

[0033] like Figure 1 FIG2 is a schematic structural diagram of a supercritical CO2 power generation system integrated with an ejector lignite drying according to an embodiment of the present disclosure, comprising a supercritical CO2 coal-fired power generation unit and an ejector lignite drying unit;

[0034] 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 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), and the outlet of the precooler (6) is connected to the inlet of the main compressor (1);

[0037] 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);

[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 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);

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

[0041] 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);

[0042] 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). The condenser (11) is used to recover condensed water.

[0043] Specifically, the supercritical CO2 coal-fired power generation unit is responsible for converting the heat energy generated by the combustion of lignite into electrical energy and improving energy utilization efficiency through the closed cycle of CO2. The 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).

[0044] The main compressor (1) is used to pressurize the CO2 and allow it to enter the cold side of the low-temperature regenerator (2), where it absorbs waste heat from the turbine and raises its temperature. The CO2 then enters the cold side of the high-temperature regenerator (3), where it is further heated before entering the boiler (4). The high-temperature flue gas in the boiler (4) heats the CO2, causing it to reach a supercritical state. The CO2 then enters the turbine (5), where it expands and generates work, driving the generator to generate electricity.

[0045] The CO2 discharged from the turbine (5) enters the hot side of the high-temperature regenerator (3), the hot side of the low-temperature regenerator (2), and the precooler (6) in sequence, gradually reducing its temperature. Finally, the 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 recompressor (7) and the second stage recompressor (8) are respectively used to adjust the flow pressure of CO2 on the hot side of the low temperature regenerator (2) so that it can better adapt to the system requirements and improve the cycle efficiency.

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

[0048] In this 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 heat supply, and the other enters the high-pressure inlet of the ejector (9). At the same time, the CO2 at the hot side outlet of the low-temperature regenerator (2) enters the low-pressure inlet of the ejector (9) as a low-temperature, low-pressure working medium. In the ejector (9), the two streams of CO2 are fully mixed to form medium-temperature, medium-pressure CO2 of suitable temperature and pressure, which then enters the dryer (10) to heat and dry the lignite.

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

[0050] Beneficial effects: This system utilizes high-temperature, high-pressure CO2 to eject low-temperature, low-pressure CO2 through the ejector (9), which not only achieves the reuse of CO2 but also effectively recovers low-temperature waste heat, reduces cold source loss, and improves overall thermal efficiency. At the same time, the dried lignite can reduce the boiler exhaust temperature, reduce flue gas humidity, improve combustion efficiency, reduce auxiliary energy consumption, and improve power generation efficiency. In addition, the condenser (11) recovers condensate generated during the lignite drying process, which helps reduce the unit's water consumption and optimize resource utilization.

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

[0052] The dryer (10) in this system adopts a rotary drum dryer, that is, the rotation of the drum causes the lignite to tumble continuously during the drying process to enhance the heat exchange effect. This structure can increase the contact area between the lignite and CO2, making heat transfer more uniform and improving the drying efficiency. At the same time, the rotation of the drum can also prevent the lignite from agglomerating 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), high-temperature CO2 acts as a drying medium, fully contacting the lignite and removing moisture. The dried lignite is then transported to the boiler (4) for combustion through the drying coal outlet. The hot and humid gases generated during the drying process are transported through the exhaust port to the condenser (11) for condensation and recovery of water vapor.

[0054] Furthermore, a flow distribution valve is provided 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 the high-pressure working medium entering the ejector (9).

[0055] Specifically, in order to ensure that the ejector (9) can operate stably and adapt to the requirements of different working conditions for the temperature and flow of the drying medium, a flow distribution valve is provided on 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 rate of the high-pressure working medium entering the ejector (9) to ensure that the mixing and ejection process inside the ejector is in the best working state. When it is necessary to increase the drying temperature or increase 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); conversely, when the demand decreases, the high-pressure working medium flow rate is reduced to save energy and optimize system operation.

[0057] Furthermore, the outlet of the first-stage recompressor (7) and the hot side outlet of the dryer (10) are connected to the inlet of the second-stage recompressor (8) after being combined, and the outlet pressure of the first-stage recompressor (7) is equal to or the difference between the outlet pressure of the CO2 at the hot side outlet of the dryer (10) is within a preset range.

[0058] Specifically, to optimize CO2 recovery and system energy efficiency, the outlet of the first-stage recompressor (7) and the hot-side outlet of the dryer (10) are connected to the inlet of the second-stage recompressor (8) through a combined pipeline. This design can reduce CO2 loss, improve gas cycle stability, and reduce system pressure drop.

[0059] Furthermore, the outlet pressure of the first-stage recompressor (7) is equal to or within a preset range (which can be set according to specific operating conditions) of the CO2 at the hot side outlet of the dryer (10), ensuring that when the two airflows merge, there will be no flow instability or additional energy loss due to a large pressure difference. This pressure matching design helps reduce resistance in the gas cycle, improves the operating efficiency of the recompressor, and ensures that the CO2 can be stably compressed after entering the second-stage recompressor (8), thereby optimizing the energy utilization efficiency of the entire system.

[0060] like Figure 2 FIG. 1 is a flow chart of a supercritical CO2 power generation method for lignite drying with an integrated ejector according to an embodiment of the present disclosure, comprising:

[0061] S201: 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, enters the boiler (4) for heating, and then drives the turbine (5) to generate electricity.

[0062] S202: 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 then returns to the main compressor (1) after being cooled by the precooler (6).

[0063] S203: extracting part of the CO2 working medium from the hot side outlet of the low-temperature regenerator (2), and introducing part of the CO2 working medium from 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 medium.

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

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

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

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

[0068] After the turbine (5) has completed its work, the CO2 discharged still has a relatively high temperature. To improve the energy efficiency of the system, this portion of CO2 enters the hot side of the high-temperature regenerator (3) and the low-temperature regenerator (2) in sequence, transferring the remaining heat to the low-temperature CO2 before entering the boiler (4), thus achieving heat recovery.

[0069] Subsequently, the CO2 cooled by heat exchange enters the precooler (6), is further cooled to a suitable temperature, and then returns to the main compressor (1), completing the closed-loop cycle and preparing for the next round of power generation cycle.

[0070] During the CO2 power generation cycle, in order to achieve efficient drying of the lignite, a portion 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, and is suitable as a drying medium for lignite.

[0072] The generated mixed CO2 working fluid enters the dryer (10) to dry the lignite. Since CO2 has good heat transfer and permeability, it can quickly remove moisture from the lignite, improving drying efficiency. The dried lignite has a lower moisture content, improving combustion performance, and is then 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 processed and used 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 recompressed CO2 re-enters the low-temperature regenerator (2) and other heat exchange equipment to continue participating in the power generation and drying cycles, thereby achieving efficient energy utilization and CO2 circulation.

[0076] Furthermore, the temperature of the mixed working medium in the ejector (9) matches the temperature of the heat source required for drying the lignite, so as to reduce irreversible losses in the drying process.

[0077] Specifically, in this system, the temperature of the mixed CO2 working medium output by the ejector (9) matches the heat source temperature required for lignite drying, which means that the temperature of the CO2 working medium needs to fall exactly within the optimal dehydration temperature range of lignite (measurable in actual working conditions). If the temperature is too high, although it can accelerate the evaporation of water, it may cause the surface of the lignite to dry quickly and form a crust, making it difficult for the internal water to diffuse, ultimately affecting the drying effect. If the temperature is too low, the drying rate is reduced, and the water cannot be fully evaporated, resulting in the lignite still containing a lot of water when burning, reducing the combustion efficiency. Therefore, ensuring that the temperature of the mixed CO2 matches the lignite drying requirements can improve the drying efficiency, reduce energy waste, and reduce irreversible losses.

[0078] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present disclosure, and should all be included in the scope of protection of the present disclosure.

Claims

1. A supercritical CO2 power generation system with integrated ejector lignite drying, characterized in that: Includes supercritical CO2 coal-fired power generation unit and ejector lignite drying unit; 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 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), and 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 comprises 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). The condenser (11) is used to recover condensed water.

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 provided with a flow distribution valve to adjust the flow of the high-pressure working medium 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 to the inlet of the second-stage recompressor (8) after being combined, and the outlet pressure of the first-stage recompressor (7) is equal to or different from the CO2 pressure at 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 recycle the condensate generated during the lignite drying process.

6. A supercritical CO2 power generation method based on the system according to any one of claims 1 to 5, characterized in that: The following steps are involved: After being pressurized by the main compressor (1), the supercritical CO2 working medium 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) to be heated and drive 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 then returns to the main compressor (1) after being cooled by the precooler (6); Extracting part of the CO2 working medium from the hot side outlet of the low-temperature regenerator (2), and introducing part of the CO2 working medium from 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 medium; The mixed CO2 working medium enters the dryer (10) to dry the lignite, and the dehydrated dried coal is sent to the boiler (4) for combustion, and the wet steam generated by the drying is condensed and recovered through the condenser (11); The CO2 working medium at the outlet of the dryer (10) returns to the inlet of the second-stage recompressor (8), is combined with the working medium at the outlet of the first-stage recompressor (7), and then is pressurized and circulated.

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

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

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