A tower type solar energy and lignite coal combined power generation system

Abstract

This invention discloses a tower-type solar and lignite-fired combined power generation system, belonging to the field of power generation technology. It includes a boiler subsystem, a steam turbine and feedwater preheating subsystem, and a flue gas treatment subsystem. The high-temperature flue gas generated in the furnace first flows into the flue gas treatment subsystem for desulfurization and decarbonization, then flows sequentially through a lignite pre-dryer and a feedwater / flue gas heat exchanger before finally being discharged. The lignite is dried by the flue gas in the lignite pre-dryer and then sent to the furnace for combustion. Superheated steam from the boiler subsystem enters the steam turbine to perform work; the exhaust steam is collected and cooled in the condenser, then flows into the feedwater heating assembly for heating, and then is sent back to the boiler subsystem to be heated into superheated steam. The feedwater / flue gas heat exchanger is connected in parallel with the feedwater heating assembly to heat the feedwater. This system has advantages such as saving fuel consumption and improving power generation efficiency, and can solve the integrated problems of coal drying and desulfurization / decarbonization in lignite power plants.

Description

Technical Field

[0001] This invention belongs to the field of power generation technology and relates to a multi-energy integrated power generation system that combines new energy sources and coal, and more particularly to a tower-type solar and lignite coal-fired power generation system that integrates calcium cycle desulfurization and decarbonization, lignite drying and feedwater preheating. Background Technology

[0002] Currently, decarbonization in coal-fired power plants can be divided into pre-combustion decarbonization, post-combustion decarbonization, and oxy-fuel combustion decarbonization. Post-combustion decarbonization is more beneficial for the retrofitting of existing power plants. Ammonia-based absorbents or calcium-based absorbents are commonly used for post-combustion decarbonization. Calcium-based absorbents, due to their widely distributed raw materials in nature, are cheaper and easier to promote. They also serve a desulfurization function. CaO is a common calcium-based absorbent. In the carbonization furnace, CaO reacts with CO2-containing flue gas to generate a large amount of CaCO3. The generated CaCO3 absorbs heat in the calcining furnace to form a mixture of CaO and CO2. The separated CaO re-enters the carbonization furnace for the next carbon cycle, while the separated CO2 is compressed and stored. This process requires a large amount of heat for the decomposition of CaCO3 in the calcining furnace. Currently, additional coal or natural gas is typically burned to provide the necessary heat, which inevitably leads to reduced power plant efficiency and the generation of additional greenhouse gases.

[0003] To balance power plant efficiency with decarbonization, seeking external pathways such as renewable resources to improve energy conversion efficiency is crucial. Solar thermal resources, with their large reserves and wide distribution, are one ideal "external" resource for coal-fired power units. The coupling of solar thermal resources with coal-fired units is feasible. First, existing solar thermal collection technologies can meet the temperature requirements for CaCO3 decomposition. Second, the intermittent and unstable nature of solar irradiance can be overcome by more efficient heat-to-work conversion equipment in coal-fired units. Third, there is significant overlap between coal-rich areas and areas rich in solar energy resources in my country, providing a geographical advantage.

[0004] Existing technologies have proposed recovering waste heat from the tower-type solar-assisted desulfurization and decarbonization process and integrating it into the endothermic process at the system temperature, which is beneficial to improving the system's energy conversion efficiency. However, the above systems do not consider the impact of coal type differences on the technical approach. Currently, my country's proven lignite reserves account for approximately 13% of the country's total coal reserves. Its abundant reserves and low price have gradually made it a major fuel for thermal power generation in my country. However, lignite has a low degree of coal quality, with a moisture content as high as 20%-50%, resulting in a low calorific value. This leads to high investment and low efficiency in lignite power generation systems. Summary of the Invention

[0005] This invention provides a tower-type solar and lignite combined power generation system that integrates calcium cycle desulfurization and decarbonization, lignite drying and feedwater preheating, in order to overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention provides a tower-type solar and lignite combined power generation system, characterized by comprising a boiler subsystem, a steam turbine and feedwater preheating subsystem, and a flue gas treatment subsystem; the boiler subsystem includes a furnace, a lignite pre-dryer, and a feedwater / flue gas heat exchanger; the furnace, flue gas treatment subsystem, lignite pre-dryer, and feedwater / flue gas heat exchanger are sequentially connected, and the lignite pre-dryer is also connected to the furnace; the high-temperature flue gas generated by combustion in the furnace first flows into the flue gas treatment subsystem for desulfurization and decarbonization, and then sequentially flows through the lignite pre-dryer and the feedwater / flue gas heat exchanger. The heat exchanger finally discharges the lignite; after being dried by flue gas in the lignite pre-dryer, the lignite is sent to the furnace for combustion; the turbine and feedwater preheating subsystem includes a turbine, a condenser, and a feedwater heating assembly; the boiler subsystem, turbine, condenser, and feedwater heating assembly are connected in sequence; superheated steam from the boiler subsystem enters the turbine to do work, the exhaust steam is collected and cooled in the condenser, pressurized by the feedwater pump, and then flows into the feedwater heating assembly to be heated, and then sent back to the boiler subsystem to be heated into superheated steam; the feedwater / flue gas heat exchanger is connected in parallel with the feedwater heating assembly to heat the feedwater.

[0007] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: the boiler subsystem further includes a steam drum, a superheater assembly, and an economizer; the furnace is connected to the superheater assembly, which is then connected to the flue gas treatment subsystem, which is connected to the lignite pre-dryer via the economizer; the high-temperature flue gas generated by combustion in the furnace first flows through the superheater assembly for cooling, then enters the flue gas treatment subsystem for desulfurization and decarbonization, and then flows through the economizer for cooling before entering the lignite pre-dryer; the turbine and feedwater preheating subsystem, economizer, steam drum, and superheater assembly are connected in sequence, and the steam drum is also connected to the furnace; the feedwater from the turbine and feedwater preheating subsystem is heated by the economizer and then enters the steam drum; the liquid in the steam drum enters the water-cooled wall for heating and then returns to the steam drum; the gas in the steam drum first enters the superheater assembly for heating, and the generated superheated steam enters the turbine and feedwater preheating subsystem to perform work.

[0008] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the superheating components include a screen-type superheater, a low-temperature reheater, a high-temperature superheater, a high-temperature reheater, and a low-temperature superheater; the furnace is sequentially connected to the screen-type superheater, the low-temperature reheater, the high-temperature superheater, the high-temperature reheater, and the low-temperature superheater, and the low-temperature superheater is then connected to the flue gas treatment subsystem; the high-temperature flue gas generated by combustion in the furnace flows sequentially through the screen-type superheater, the low-temperature reheater, the high-temperature superheater, the high-temperature reheater, and the low-temperature superheater to be cooled before entering... The flue gas treatment subsystem performs desulfurization and decarbonization; the steam drum is sequentially connected to a low-temperature superheater, a screen-type superheater, and a high-temperature superheater, and the high-temperature superheater is then connected to the high-pressure cylinder of the steam turbine; the gas in the steam drum is first heated sequentially by the low-temperature superheater, the screen-type superheater, and the high-temperature superheater, and then enters the high-pressure cylinder of the steam turbine to do work; the high-pressure cylinder, the low-temperature reheater, the high-temperature reheater, and the intermediate-pressure cylinder and the low-pressure cylinder of the steam turbine are sequentially connected; the exhaust steam from the high-pressure cylinder of the steam turbine flows sequentially into the low-temperature reheater and the high-temperature reheater to be heated, and then enters the intermediate-pressure cylinder and the low-pressure cylinder of the steam turbine to do work.

[0009] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the turbine and feedwater preheating subsystem further includes a steam box; the high-temperature superheater is connected to the high-pressure cylinder of the turbine through the steam box; the superheated steam from the high-temperature superheater first enters the steam box, and then enters the high-pressure cylinder of the turbine to do work; the steam box is also connected to the feedwater heating assembly; the superheated steam enters the feedwater heating assembly to heat the feedwater.

[0010] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following feature: wherein, in the turbine and feedwater preheating subsystem, the feedwater heating component heats the feedwater by extracting steam from the turbine.

[0011] Furthermore, the present invention provides a tower-type solar and lignite coal-fired power generation system, which may also have the following features: wherein the feedwater heating assembly includes eight feedwater heaters, the high-pressure cylinder, intermediate-pressure cylinder and low-pressure cylinder of the steam turbine are respectively equipped with eight stages of steam extraction, and the eight stages of steam extraction enter the eight stages of feedwater heaters for heating the feedwater; the sixth to eighth stage feedwater heaters are connected in parallel with the feedwater / flue gas heat exchanger of the boiler subsystem.

[0012] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the flue gas treatment subsystem includes a carbonization furnace, a carbonization furnace gas-solid separator, a purifier, a calcining furnace, a calcining furnace gas-solid separator, a solar collector, and a first air preheater; the boiler subsystem, the carbonization furnace, and the carbonization furnace gas-solid separator are connected in sequence; flue gas from the boiler subsystem enters the carbonization furnace, reacts with CaO to generate CaCO3 and CaSO4, and then enters the carbonization furnace gas-solid separator for gas-solid separation, with the gas flowing back to the boiler subsystem; the calcining furnace is connected to the lignite pre-dryer, and the carbonization furnace gas-solid separator, purifier, and calcining furnace gas-solid separator are connected in sequence. The calcining furnace and the gas-solid separator of the calcining furnace are connected in sequence. The gas-solid separator of the calcining furnace is connected to the carbonization furnace, the solar collector and the first air preheater respectively. The solids separated by the gas-solid separator of the carbonization furnace enter the purifier for purification. The resulting CaCO3 is mixed with the newly added CaCO3 and then enters the calcining furnace. The lignite dried by the lignite pre-dryer enters the calcining furnace and is burned to generate heat. The CaCO3 is heated and decomposed into CaO and CO2. After gas-solid separation by the gas-solid separator of the calcining furnace, the solids enter the carbonization furnace. Some of the gas is heated by the solar collector and then returned to the calcining furnace to provide energy. Some of the gas enters the first air preheater to preheat the air entering the furnace.

[0013] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the flue gas treatment subsystem further includes a dust collector, a first heat exchanger, a second heat exchanger, and a third heat exchanger; the dust collector and the first heat exchanger are sequentially connected between the boiler subsystem and the carbonization furnace, and the first heat exchanger is also connected to the carbonization furnace gas-solid separator; the flue gas from the boiler subsystem first flows through the dust collector for dust removal, then is preheated through the first heat exchanger, and then enters the carbonization furnace; the gas separated by the carbonization furnace gas-solid separator... The flue gas first enters the first heat exchanger to preheat it before flowing back to the boiler subsystem; the third heat exchanger is connected to the purifier, and the second heat exchanger is connected between the purifier and the calcining furnace. The second heat exchanger is also connected to the gas-solid separator of the calcining furnace; the CaO and CaSO4 removed by the purifier enter the third heat exchanger to preheat the newly added CaCO3; the mixed CaCO3 is first preheated in the second heat exchanger before entering the calcining furnace; the gas separated by the gas-solid separator of the calcining furnace first enters the second heat exchanger to preheat the CaCO3 before flowing into the solar collector and the first air preheater.

[0014] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the solar thermal collector includes a solar absorption tower, a heliostat field, and a receiver; the receiver is installed on the top of the solar absorption tower; the heliostat field is arranged around the solar absorption tower, and the heliostat field is composed of several heliostats, each of which is mechanically driven to constantly reflect solar radiation toward the same target point and concentrate it on the receiver at the top of the solar absorption tower; after absorbing and concentrating solar energy, the receiver heats the gas.

[0015] Furthermore, the present invention provides a tower-type solar and lignite combined power generation system, which may also have the following features: wherein the boiler subsystem further includes a second air preheater; the second air preheater is connected to a lignite pre-dryer, and the flue gas from the flue gas treatment subsystem is first cooled in the second air preheater and then flows into the lignite pre-dryer; the first air preheater, the second air preheater and the furnace are connected in sequence; the air preheated by the first air preheater first enters the second air preheater for secondary preheating and then enters the furnace for combustion.

[0016] The beneficial effects of this invention are as follows: This invention provides a tower-type solar and lignite-fired combined power generation system that integrates calcium cycle desulfurization and decarbonization, lignite drying, and feedwater preheating, to solve the integrated problem of coal drying and desulfurization and decarbonization in lignite power plants. Specifically, the solar thermal collector can provide the calcining furnace with high-temperature reaction heat matching the energy level, thereby saving fuel consumption in the desulfurization and decarbonization process; pre-drying the lignite can improve the coal quality and lower heating value, further saving fuel consumption in the desulfurization and decarbonization process; by setting up a feedwater / flue gas heat exchanger in parallel with the feedwater heater, the extraction of steam from the turbine can be saved, thereby improving power generation efficiency; and the integrated optimization of the system enables the cascade utilization of multiple energy sources. Attached Figure Description

[0017] Figure 1 This is an integrated diagram of the tower-type solar and lignite-fired combined power generation system of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0019] like Figure 1 As shown, the present invention provides a tower-type solar and lignite coal-fired power generation system, including a boiler subsystem 1, a steam turbine and feedwater preheating subsystem 2, and a flue gas treatment subsystem 3.

[0020] Boiler subsystem 1 includes a furnace 11, a lignite pre-dryer 12, and a feedwater / flue gas heat exchanger 13. The furnace 11, flue gas treatment subsystem 3, lignite pre-dryer 12, and feedwater / flue gas heat exchanger 13 are connected sequentially. The lignite pre-dryer 12 is also connected to the furnace 11, forming a flue gas path. The high-temperature flue gas generated by combustion in the furnace 11 first flows into the flue gas treatment subsystem 3 for desulfurization and decarbonization, then flows sequentially through the lignite pre-dryer 12 and the feedwater / flue gas heat exchanger 13 before finally being discharged. The lignite is heated and dried by the flue gas in the lignite pre-dryer 12 before being sent to the furnace 11 for combustion.

[0021] The steam turbine and feedwater preheating subsystem 2 includes a steam turbine 21, a condenser 22, and a feedwater heating assembly. The boiler subsystem 1, steam turbine 21, condenser 22, and feedwater heating assembly are connected sequentially to form a steam-feedwater path. Superheated steam from the boiler subsystem 1 enters the steam turbine 21 to perform work. The exhaust steam is collected and cooled in the condenser 22, pressurized by the feedwater pump, and then flows into the feedwater heating assembly for heating before being sent back to the boiler subsystem 1 to be heated into superheated steam.

[0022] The feedwater / flue gas heat exchanger 13 of boiler subsystem 1 is connected in parallel with the feedwater heating component to heat the feedwater.

[0023] In a preferred embodiment, the boiler subsystem 1 further includes a steam drum 14, a superheater assembly, and an economizer 16. In the flue gas path, the furnace 11 is connected to the superheater assembly, which in turn is connected to the flue gas treatment subsystem 3. The flue gas treatment subsystem 3 is connected to the lignite pre-dryer 12 via the economizer 16. The high-temperature flue gas generated by combustion in the furnace 11 first flows through the superheater assembly for cooling, then enters the flue gas treatment subsystem 3 for desulfurization and decarbonization, and then flows through the economizer 16 for further cooling before entering the lignite pre-dryer 12. The turbine and feedwater preheating subsystem 2, the economizer 16, the steam drum 14, and the superheater assembly are connected sequentially. The steam drum 14 is also connected to the furnace 11, forming a feedwater-steam path. Feedwater from the turbine and feedwater preheating subsystem 2 is heated by the economizer 16 and then enters the steam drum 14. The liquid in the steam drum 14 is heated by the water-cooled wall and then returns to the steam drum 14. The gas in the steam drum 14 first enters the superheating components for heating, and the generated superheated steam enters the turbine and feedwater preheating subsystem 2 to do work.

[0024] Specifically, the superheating components include a screen-type superheater 151, a low-temperature reheater 152, a high-temperature superheater 153, a high-temperature reheater 154, and a low-temperature superheater 155. In the flue gas path, the furnace 11 is sequentially connected to the screen-type superheater 151, the low-temperature reheater 152, the high-temperature superheater 153, the high-temperature reheater 154, and the low-temperature superheater 155. The low-temperature superheater 155 is then connected to the flue gas treatment subsystem 3. The high-temperature flue gas generated by combustion in the furnace 11 flows sequentially through the screen-type superheater 151, the low-temperature reheater 152, the high-temperature superheater 153, the high-temperature reheater 154, and the low-temperature superheater 155 to be cooled before entering the flue gas treatment subsystem 3 for desulfurization and decarbonization. In the feedwater-steam path, the steam drum 14 is sequentially connected to the low-temperature superheater 155, the screen-type superheater 151, and the high-temperature superheater 153. The high-temperature superheater 153 is then connected to the high-pressure cylinder 211 of the steam turbine 21. The gas in the steam drum 14 is first heated sequentially by the low-temperature superheater 155, the screen-type superheater 151, and the high-temperature superheater 153 before entering the high-pressure cylinder 211 of the steam turbine 21 to perform work. The high-pressure cylinder 211, the low-temperature reheater 152, the high-temperature reheater 154, and the intermediate-pressure cylinder and low-pressure cylinder 212 of the steam turbine 21 are sequentially connected. The exhaust steam from the high-pressure cylinder 211 of the steam turbine 21 flows sequentially into the low-temperature reheater 152 and the high-temperature reheater 154 to be heated before entering the intermediate-pressure cylinder and low-pressure cylinder 212 of the steam turbine 21 to perform work.

[0025] In a preferred embodiment, the turbine and feedwater preheating subsystem 2 further includes a steam tank 24. The high-temperature superheater 153 is connected to the high-pressure cylinder 211 of the turbine 21 via the steam tank 24. Superheated steam from the high-temperature superheater 153 first enters the steam tank 24, and then enters the high-pressure cylinder 211 of the turbine 21 to perform work. The steam tank 24 is also connected to the feedwater heating assembly. The superheated steam from the high-temperature superheater 153 also enters the feedwater heating assembly to heat the feedwater.

[0026] In the turbine and feedwater preheating subsystem 2, the feedwater heating assembly heats the feedwater through the extraction steam from the turbine 21. The heated and cooled water then flows into the condenser 22 as feedwater. Specifically, the feedwater heating assembly includes eight feedwater heaters 23. The high-pressure cylinder 211, intermediate-pressure cylinder, and low-pressure cylinder 212 of the turbine 21 are each equipped with eight stages of extraction steam, which enters the eight stages of feedwater heaters 23 to heat the feedwater. The sixth to eighth stage feedwater heaters 23 are connected in parallel with the feedwater / flue gas heat exchanger 13 of the boiler subsystem 1. That is, a portion of the feedwater in the condenser 22 is heated by flue gas from the boiler system through the feedwater / flue gas heat exchanger 13, while another portion of the feedwater is preheated in the sixth to eighth stage feedwater heaters 23. The two portions of feedwater are mixed at the inlet of the fifth stage feedwater heater 23.

[0027] The flue gas treatment subsystem 3 includes a carbonization furnace 31, a carbonization furnace gas-solid separator 311, a purifier 32, a calcining furnace 33, a calcining furnace gas-solid separator 331, a solar collector 34, and a first air preheater 35. The boiler subsystem 1, carbonization furnace 31, and carbonization furnace gas-solid separator 311 are connected sequentially to form a flue gas treatment path. CO2-rich flue gas from the boiler subsystem 1 enters the carbonization furnace 31, reacts with CaO to produce CaCO3 and CaSO4, and then enters the carbonization furnace gas-solid separator 311 for gas-solid separation. The gas is then returned to the boiler subsystem 1. The calcining furnace 33 is connected to the lignite pre-dryer 12. The carbonization furnace gas-solid separator 311, purifier 32, calcining furnace 33, and calcining furnace gas-solid separator 331 are connected sequentially. The calcining furnace gas-solid separator 331 is connected to the carbonization furnace 31, the solar collector 34, and the first air preheater 35, respectively, forming a regeneration path. The solids separated by the gas-solid separator 311 of the carbonization furnace enter the purifier 32 for purification. The resulting CaCO3 is mixed with newly added CaCO3 and then enters the calcination furnace 33. The lignite dried by the lignite pre-dryer 12 enters the calcination furnace 33 and is burned to generate heat. CaCO3 is heated and decomposed into CaO and CO2. After gas-solid separation by the gas-solid separator 331 of the calcination furnace, the solids enter the carbonization furnace 31 for CO2 capture. Part of the gas is heated by the solar collector 34 and then returned to the calcination furnace 33 to provide energy. Part of the gas enters the first air preheater 35 to preheat the air entering the furnace 11, and then is compressed and stored.

[0028] In a preferred embodiment, the flue gas treatment subsystem 3 further includes a dust collector 36, a first heat exchanger 37, a second heat exchanger 38, and a third heat exchanger 39. In the flue gas treatment path, the dust collector 36 and the first heat exchanger 37 are sequentially connected between the boiler subsystem 1 and the carbonization furnace 31. The first heat exchanger 37 is also connected to the carbonization furnace gas-solid separator 311. The CO2-rich flue gas from the boiler subsystem 1 first flows through the dust collector 36 for dust removal, then is preheated by the first heat exchanger 37, and then enters the carbonization furnace 31. The gas separated by the carbonization furnace gas-solid separator 311 first enters the first heat exchanger 37 to preheat the CO2-rich flue gas from the boiler subsystem 1 before flowing back to the boiler subsystem 1. In the regeneration path, the third heat exchanger 39 is connected to the purifier 32, and the second heat exchanger 38 is connected between the purifier 32 and the calcining furnace 33. The second heat exchanger 38 is also connected to the calcining furnace gas-solid separator 331. The CaO and CaSO4 removed by the purifier 32 enter the third heat exchanger 39 to preheat the newly added CaCO3. The mixed CaCO3 is first preheated in the second heat exchanger 38 before entering the calcining furnace 33. The gas separated by the gas-solid separator 331 in the calcining furnace first enters the second heat exchanger 38 to preheat the CaCO3 before flowing into the solar collector 34 and the first air preheater 35.

[0029] Specifically, the solar collector 34 includes a solar absorption tower 341, a heliostat field 342, and a receiver 343. The receiver 343 is installed on top of the solar absorption tower 341. The heliostat field 342 is arranged around the solar absorption tower 341 and consists of several heliostats. Each heliostat is mechanically driven to constantly reflect solar radiation toward the same target point and concentrate it at the receiver 343 on top of the solar absorption tower 341. After absorbing and concentrating solar energy, the receiver 343 heats CO2 from the second heat exchanger 38 to approximately 1200°C. The heated CO2 then enters the calcining furnace 33.

[0030] In a preferred embodiment, the boiler subsystem 1 further includes a second air preheater 17. The second air preheater 17 is disposed between the economizer 16 and the lignite pre-dryer 12, i.e., the economizer 16, the second air preheater 17, and the lignite pre-dryer 12 are connected in sequence. The flue gas from the flue gas treatment subsystem 3, after desulfurization and decarbonization, first preheats the feedwater in the economizer 16, then cools it in the second air preheater 17, and then flows into the lignite pre-dryer 12. The first air preheater 35, the second air preheater 17, and the furnace 11 are connected in sequence. The air preheated by the first air preheater 35 first enters the second air preheater 17 for secondary preheating by the flue gas, and then enters the furnace 11 for combustion.

[0031] The working process of the tower solar and lignite combined power generation system provided by this invention is as follows:

[0032] Lignite is burned in furnace 11, generating a large amount of high-temperature flue gas at the furnace 11 outlet. The high-temperature flue gas flows sequentially through screen-type superheater 151, low-temperature reheater 152, high-temperature superheater 153, high-temperature reheater 154 and low-temperature superheater 155. The flue gas at the outlet of low-temperature superheater 155 enters flue gas treatment subsystem 3 for dust removal, desulfurization and decarbonization. After treatment, the flue gas returns to boiler subsystem 1 and continues to flow through economizer 16, air preheater, lignite pre-dryer 12 and flue gas / feed water heater 23, and is finally discharged into the atmosphere through the chimney.

[0033] Meanwhile, the feedwater from the turbine and feedwater preheating subsystem 2 is heated by the economizer 16 and then enters the steam drum 14. The liquid in the steam drum 14 is heated by the water-cooled wall and then returns to the steam drum 14. The gas in the steam drum 14 enters the low-temperature superheater 155, the screen-type superheater 151 and the high-temperature superheater 153 for heating. The generated high-temperature and high-pressure steam enters the high-pressure cylinder 211 of the turbine 21 to do work.

[0034] The low-temperature reheater 152 and high-temperature reheater 154 in boiler subsystem 1 are used to heat the exhaust steam from the high-pressure cylinder 211 of the steam turbine 21. The exhaust steam is heated by the low-temperature reheater 152 and the high-temperature reheater 154 and then enters the intermediate-pressure cylinder and low-pressure cylinder 212 of the steam turbine 21 to do work.

[0035] The lignite pre-dryer 12 in boiler subsystem 1 pre-dries lignite by recovering waste heat from the flue gas. The pre-dried lignite is divided into two parts: one part enters the furnace 11 of boiler subsystem 1 for combustion, and the other part enters the calciner 33 of flue gas treatment subsystem 3 for combustion.

[0036] The second air preheater 17 of boiler subsystem 1 is used to preheat the air preheated by the first air preheater 35 of flue gas treatment subsystem 3. The preheated air enters the furnace 11 and is burned with dried lignite.

[0037] The feedwater / flue gas heat exchanger 13 of boiler subsystem 1 is connected in parallel to the steam turbine 21 and feedwater heaters 23 of No. 6-8 in the regenerative system to preheat part of the condensate.

[0038] In the turbine and feedwater preheating subsystem 2, feedwater from condenser 22 is pressurized by a feedwater pump and preheated by eight feedwater heaters 23 before entering boiler subsystem 1 for heating. Superheated steam from the outlet of high-temperature superheater 153 in boiler subsystem 1 enters the high-pressure cylinder 211 of turbine 21 for expansion and work. Exhaust steam from high-pressure cylinder 211 after work enters the low-temperature reheater 152 and high-temperature reheater 154 of boiler subsystem 1 for reheating. Reheated steam from the outlet of high-temperature reheater 154 of boiler subsystem 1 returns to the intermediate-pressure cylinder of turbine 21 and expands and performs work in both the intermediate-pressure and high-pressure cylinders 211. Finally, the exhaust steam is collected and cooled in condenser 22. To improve cycle efficiency, eight stages of extraction steam are installed in high-pressure cylinder 211, intermediate-pressure cylinder, and low-pressure cylinder 212. The extracted steam enters eight stages of feedwater heaters 23 to heat the feedwater, and after heating, it condenses into water which flows into condenser 22. In addition, the 6th-8th stage feedwater heaters 23 are connected in parallel with the feedwater / flue gas heat exchanger 13 of the boiler subsystem 1. Part of the feedwater from the condenser 22 is heated by the flue gas from the boiler system via the feedwater / flue gas heat exchanger 13, and another part is preheated in the 6th-8th stage feedwater heaters 23. The two parts are mixed at the inlet of the 5th stage feedwater heater 23.

[0039] In boiler subsystem 1, the flue gas discharged from the low-temperature superheater 155 (i.e., CO2-rich flue gas) flows through the dust collector 36 for dust removal, and then is preheated through the first heat exchanger 37. Afterwards, the CO2-rich flue gas reacts with CaO in the carbonization furnace 31 at 650°C to produce CaCO3 and CaSO4. Then, the gas-solid mixture at the outlet of the carbonization furnace 31 is separated into gas and solid by the carbonization furnace gas-solid separator 311. The gas, which is the CO2-lean flue gas, flows through the first heat exchanger 37 to release heat and preheat the CO2-rich flue gas, and then flows back to the economizer 16 of boiler subsystem 1. The solids mainly consist of CaCO3, CaSO4, and unreacted CaO. First, deactivated CaO and CaSO4 are removed in purifier 32. This portion of solids is then preheated by the newly added CaCO3 in the third heat exchanger 39. The remaining purified solids are then mixed with the newly added CaCO3, which has also been preheated in the third heat exchanger 39. The resulting mixture is preheated with pure CO2 in the second heat exchanger 38 before entering the calcining furnace 33. The temperature of the calcining furnace 33 is 1000℃, during which CaCO3 decomposes into CaO and CO2. The gas-solid mixture at the outlet of the calcining furnace 33 is separated into gas and solid by the calcining furnace gas-solid separator 331. The solids enter the carbonization furnace 31 for CO2 capture, forming a new cycle. The gas is pure CO2, which, after being preheated by the second heat exchanger 38, is divided into two parts. One part enters the first air preheater 35 to preheat the air before being compressed and stored. The other part is used as a heat transfer fluid and heated by the solar collector 34 before returning to the calcining furnace 33. The energy required in the calcining furnace 33 is supplied by two parts: one part comes from the combustion of dried lignite under oxygen-enriched conditions, and the other part comes from the heating of CO2 by the solar collector 34. After absorbing and concentrating solar energy, the absorber 343 of the solar collector 34 heats the CO2 from the second heat exchanger 38 to about 1200°C, and the heated CO2 enters the calcining furnace 33.

[0040] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0041] It should be noted that the terms such as "upper", "lower", "left", "right", "front", and "back" used in the invention are only for clarity of description and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0042] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tower-type solar power and lignite combined heat and power generation system, characterized in that: This includes the boiler subsystem, the steam turbine and feedwater preheating subsystem, and the flue gas treatment subsystem; The boiler subsystem includes a furnace, a lignite pre-dryer, and a feedwater / flue gas heat exchanger. The furnace, flue gas treatment subsystem, lignite pre-dryer, and feedwater / flue gas heat exchanger are connected in sequence, with the lignite pre-dryer also connected to the furnace. The high-temperature flue gas generated by combustion in the furnace first flows into the flue gas treatment subsystem for desulfurization and decarbonization, and then flows through the lignite pre-dryer and feedwater / flue gas heat exchanger in sequence before finally being discharged. The lignite is heated and dried by the flue gas in the lignite pre-dryer before being sent to the furnace for combustion. The turbine and feedwater preheating subsystem includes a turbine, a condenser, and feedwater heating components; The boiler subsystem, steam turbine, condenser, and feedwater heating assembly are connected in sequence. Superheated steam from the boiler subsystem enters the steam turbine to do work. The exhaust steam is collected and cooled in the condenser, pressurized by the feedwater pump, and then flows into the feedwater heating assembly to be heated. It is then sent back to the boiler subsystem to be heated into superheated steam. The feedwater / flue gas heat exchanger is connected in parallel with the feedwater heating assembly to heat the feedwater; The boiler subsystem also includes a steam drum, a superheater assembly, and an economizer. The furnace is connected to the superheater assembly, which is then connected to the flue gas treatment subsystem. The flue gas treatment subsystem is connected to the lignite pre-dryer via the economizer. The high-temperature flue gas generated by combustion in the furnace first flows through the superheater assembly to be cooled, then enters the flue gas treatment subsystem for desulfurization and decarbonization, and then flows through the economizer to be cooled before entering the lignite pre-dryer. The steam turbine and feedwater preheating subsystem, economizer, steam drum, and superheater assembly are connected in sequence, and the steam drum is also connected to the furnace. Feedwater from the steam turbine and feedwater preheating subsystem is heated by the economizer and then enters the steam drum. The liquid in the steam drum enters the water-cooled wall for heating and then returns to the steam drum. The gas in the steam drum first enters the superheater assembly for heating, and the generated superheated steam enters the steam turbine and feedwater preheating subsystem to do work. In the turbine and feedwater preheating subsystem, the feedwater heating assembly heats the feedwater through the extraction steam from the turbine. The feedwater heating assembly includes eight feedwater heaters. The high-pressure cylinder, intermediate-pressure cylinder, and low-pressure cylinder of the turbine are each equipped with eight stages of extraction steam, which enters the eight-stage feedwater heaters to heat the feedwater. The sixth to eighth stage feedwater heaters are connected in parallel with the feedwater / flue gas heat exchanger of the boiler subsystem. The flue gas treatment subsystem includes a carbonization furnace, a carbonization furnace gas-solid separator, a purifier, a calcining furnace, a calcining furnace gas-solid separator, a solar collector, and a first air preheater. The boiler subsystem, carbonization furnace, and carbonization furnace gas-solid separator are connected in sequence. Flue gas from the boiler subsystem enters the carbonization furnace, reacts with CaO to produce CaCO3 and CaSO4, and then enters the carbonization furnace gas-solid separator for gas-solid separation. The gas is then returned to the boiler subsystem. The calcining furnace is connected to a lignite pre-dryer. The carbonization furnace gas-solid separator, purifier, calcining furnace, and calcining furnace gas-solid separator are connected in sequence. The separator is connected to the carbonization furnace, the solar collector, and the first air preheater, respectively. The solids separated by the gas-solid separator in the carbonization furnace enter the purifier for purification. The resulting CaCO3 is mixed with newly added CaCO3 and then enters the calcination furnace. The lignite dried by the lignite pre-dryer enters the calcination furnace and is burned to generate heat. The CaCO3 is heated and decomposed into CaO and CO2. After gas-solid separation by the calcination furnace gas-solid separator, the solids enter the carbonization furnace. Some of the gas is heated by the solar collector and then returned to the calcination furnace to provide energy. Some of the gas enters the first air preheater to preheat the air entering the furnace.

2. The tower-type solar and lignite combined heat and power generation system according to claim 1, characterized in that: in, The superheating assembly includes a screen-type superheater, a low-temperature reheater, a high-temperature superheater, a high-temperature reheater, and a low-temperature superheater. The furnace is sequentially connected to a screen-type superheater, a low-temperature reheater, a high-temperature superheater, a high-temperature reheater, and a low-temperature superheater. The low-temperature superheater is then connected to the flue gas treatment subsystem. The high-temperature flue gas generated by combustion in the furnace flows sequentially through the screen-type superheater, the low-temperature reheater, the high-temperature superheater, and the low-temperature superheater to be cooled before entering the flue gas treatment subsystem for desulfurization and decarbonization. The steam drum is connected in sequence to a low-temperature superheater, a screen-type superheater, and a high-temperature superheater. The high-temperature superheater is then connected to the high-pressure cylinder of the steam turbine. The gas in the steam drum is first heated by the low-temperature superheater, the screen-type superheater, and the high-temperature superheater in sequence, and then enters the high-pressure cylinder of the steam turbine to do work. The high-pressure cylinder, low-temperature reheater, high-temperature reheater, intermediate-pressure cylinder, and low-pressure cylinder of the steam turbine are connected in sequence. The exhaust steam from the high-pressure cylinder of the steam turbine flows into the low-temperature reheater and high-temperature reheater in sequence to be heated, and then enters the intermediate-pressure cylinder and low-pressure cylinder of the steam turbine to do work.

3. The tower-type solar and lignite combined power generation system according to claim 2, characterized in that: in, The steam turbine and feedwater preheating subsystem also includes a steam tank; The high-temperature superheater is connected to the high-pressure cylinder of the steam turbine via a steam box; the superheated steam from the high-temperature superheater first enters the steam box, and then enters the high-pressure cylinder of the steam turbine to do work. The steam box is also connected to the feedwater heating assembly; superheated steam enters the feedwater heating assembly to heat the feedwater.

4. The tower-type solar and lignite combined heat and power generation system according to claim 1, characterized in that: in, The flue gas treatment subsystem also includes a dust collector, a first heat exchanger, a second heat exchanger, and a third heat exchanger; The dust collector and the first heat exchanger are connected sequentially between the boiler subsystem and the carbonization furnace. The first heat exchanger is also connected to the carbonization furnace gas-solid separator. The flue gas from the boiler subsystem first flows through the dust collector for dust removal, then is preheated through the first heat exchanger, and then enters the carbonization furnace. The gas separated by the carbonization furnace gas-solid separator first enters the first heat exchanger to preheat the flue gas and then flows back to the boiler subsystem. The third heat exchanger is connected to the purifier, and the second heat exchanger is connected between the purifier and the calcining furnace. The second heat exchanger is also connected to the gas-solid separator of the calcining furnace. The CaO and CaSO4 removed by the purifier enter the third heat exchanger to preheat the newly added CaCO3. The mixed CaCO3 is first preheated in the second heat exchanger and then enters the calcining furnace. The gas separated by the gas-solid separator of the calcining furnace first enters the second heat exchanger to preheat the CaCO3 and then flows into the solar collector and the first air preheater.

5. The tower-type solar and lignite combined heat and power generation system according to claim 1, Its features are: The solar thermal collector includes a solar absorption tower, a heliostat field, and a receiver; The heat absorber is installed at the top of the solar absorption tower; The heliostat field is arranged around the solar absorption tower. The heliostat field consists of several heliostats. Each heliostat is mechanically driven to reflect solar radiation constantly toward the same target point and concentrate it on the absorber at the top of the solar absorption tower. The heat absorber heats the gas after absorbing and concentrating solar energy.

6. The tower-type solar and lignite combined heat and power generation system according to claim 1, Its features are: The boiler subsystem also includes a second air preheater; The second air preheater is connected to the lignite pre-dryer. The flue gas from the flue gas treatment subsystem is first cooled in the second air preheater and then flows into the lignite pre-dryer. The first air preheater, the second air preheater, and the furnace are connected in sequence. The air preheated by the first air preheater first enters the second air preheater for secondary preheating, and then enters the furnace for combustion.

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