Coal power unit flue gas waste heat power generation carbon dioxide capture and comprehensive utilization system

Abstract

The invention discloses a coal power unit flue gas waste heat power generation carbon dioxide capture comprehensive utilization system, which is characterized in that a flue gas waste heat ammonia steam turbine generator set is replaced by a flue gas waste heat low-temperature nitrogen steam turbine generator set or an expansion machine generator set, low-temperature nitrogen after doing work absorbs heat from flue gas, the flue gas is reduced to a lower temperature, and the flue gas waste heat ammonia steam turbine generator set is replaced by the expansion machine generator set. Carbon dioxide trapped after purification treatment is hydrogenated to prepare methanol which returns to the boiler for combustion, and the process is repeated, so that the coal consumption of the boiler can be reduced, and the problems of carbon dioxide absorption and storage are solved; part of power generated by the low-temperature nitrogen steam turbine generator unit or the expansion machine generator unit is used for producing hydrogen / oxygen by electrolyzing water, a low-temperature nitrogen freezing treatment device and other auxiliary machines, and the rest part increases the on-grid power, so that the benefits of the coal power unit are greatly improved. The methanol returns to the boiler for combustion, so that the effects of low-load stable combustion of the boiler and rapid load rising of the boiler can be achieved, and the requirements of deep peak regulation and high load change rate of a new-generation coal power unit are met.

Description

Technical Field

[0001] This invention relates to the field of flue gas recovery and utilization, and in particular to a comprehensive system for capturing and utilizing carbon dioxide in the waste heat power generation of coal-fired power units. Background Technology

[0002] In the operation of coal-fired boilers, flue gas loss is widely recognized as one of the most significant heat losses. This is especially true in my country's thermal power plants, where the flue gas temperature of many boilers generally exceeds design values. For boilers burning anthracite, lean coal, or bituminous coal, the design temperature is typically set at around 120–125℃, while the design value for boilers burning lignite is approximately 150℃. However, in actual operation, the flue gas temperature often exceeds these benchmarks, leading to a significant waste of heat energy. Simultaneously, the flue gas emissions from these boilers are extremely large; for example, the flue gas volume at the outlet of the induced draft fan of a single 600MW unit can reach 300–400 × 10⁻⁶ m³ / h. 4 This increases the heat loss rate to m³ / h, which further amplifies the impact of heat loss.

[0003] Existing technologies mainly reduce flue gas temperature indirectly by optimizing the combustion process, installing waste heat recovery devices, or improving insulation materials. However, due to the complex composition of flue gas, slow equipment response, and low heat exchange efficiency at high flow rates, these methods are difficult to effectively control the temperature to remain stable at or below the design value. This results in continuous high flue gas losses, energy waste, and reduced economic efficiency, and may even fail to meet the national dual-carbon strategy's development requirements for clean and low-carbon coal power. There is an urgent need to develop more efficient technical solutions to address this problem in order to achieve precise reduction of flue gas temperature, energy savings, and improved economic benefits for power plants. Summary of the Invention

[0004] The purpose of this invention is to provide a comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, addressing the aforementioned technical problems and solving the issues of low comprehensive utilization efficiency and energy waste of high-temperature flue gas from coal-fired power plants in the prior art.

[0005] This invention is achieved through the following scheme: A comprehensive utilization system for carbon dioxide capture and generation from waste heat from coal-fired power units includes a flue gas energy recovery unit and a flue gas material recovery unit. The heat exchange end of the flue gas energy recovery unit is embedded in the flue gas pipeline. The oxygen production end of the flue gas material recovery unit is connected to the secondary hot air duct of the coal-fired power unit. The alcohol production end of the flue gas material recovery unit is connected to the boiler burner of the coal-fired power unit.

[0006] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture and utilization of waste heat from coal-fired power unit flue gas, the flue gas energy recovery unit includes a heat exchange unit, an energy conversion unit, a liquid storage unit, and a power unit; the heat exchange unit, energy conversion unit, liquid storage unit, and power unit are sequentially connected by pipelines to form a circulation loop; the heat exchange unit is installed in the pipeline where the high-temperature flue gas is located.

[0007] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture and power generation from waste heat of coal-fired power unit flue gas, the energy conversion section is a nitrogen turbine and a generator, or an expander and a generator; the heat exchange section is a flue gas-nitrogen heat exchanger.

[0008] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, the liquid storage section includes a low-temperature nitrogen refrigeration device and a liquid storage tank; the low-temperature nitrogen refrigeration device is connected to the gas outlet of the energy conversion section and the liquid storage tank respectively.

[0009] Based on the structure of the above-mentioned coal-fired power unit flue gas waste heat power generation carbon dioxide capture and comprehensive utilization system, the power unit includes two parallel lifting pipelines, each of which is equipped with a liquid nitrogen lifting pump; the lifting pipelines are connected in parallel with the entire circulation loop.

[0010] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in waste heat power generation from coal-fired power units, the flue gas material recovery unit includes a flue gas treatment module, a methanol synthesis module, a wastewater treatment module, and an oxygen preparation module. The flue gas treatment module is connected to a flue gas pipeline and is equipped with a purification unit, a carbon dioxide capture unit, and a water separation unit. The purified water outlet of the flue gas treatment module is connected to the oxygen preparation module. The wastewater outlet of the flue gas treatment module is connected to the wastewater treatment module. The carbon dioxide outlet of the flue gas treatment module is connected to the methanol synthesis module. The hydrogen outlet of the oxygen preparation module is connected to the methanol synthesis module.

[0011] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, the methanol synthesis module includes a methanol synthesis unit, a methanol booster unit, a methanol storage tank, a methanol conveying unit, and a methanol outlet pipe. The methanol synthesis unit is connected to the methanol storage tank through the methanol booster unit. The methanol storage tank is connected to the methanol outlet pipe through the methanol conveying unit. The methanol outlet pipe is connected to the superheated burner. The methanol synthesis unit is connected to the carbon dioxide outlet of the flue gas treatment module and the hydrogen outlet of the oxygen preparation module. The methanol booster unit includes two parallel booster pipelines, in which methanol booster pumps are installed. The methanol conveying unit includes two parallel methanol conveying pipelines, in which methanol conveying pumps are installed.

[0012] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, the wastewater treatment module includes a wastewater conveying section and a desulfurization absorption tower; the wastewater outlet of the methanol synthesis unit is connected to the wastewater conveying section, and the wastewater conveying section is connected to the desulfurization absorption tower; the wastewater conveying section includes two parallel wastewater conveying pipelines, and a wastewater pump is installed in the wastewater conveying pipelines.

[0013] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, the oxygen preparation module includes an electrolysis device and an oxygen delivery pipeline; the electrolysis device is provided with two liquid inlets, one of which is connected to the purified water outlet of the flue gas treatment module, and the other is connected to an external water supply pipeline; one end of the oxygen delivery pipeline is connected to the oxygen outlet of the electrolysis device, and the other end extends into the hot secondary air duct; the oxygen delivery pipeline contains two parallel oxygen supply pipelines, and an oxygen booster is installed in the oxygen supply pipelines.

[0014] Based on the structure of the above-mentioned comprehensive utilization system for carbon dioxide capture in the waste heat power generation of coal-fired power units, the heat exchange section is located on the exhaust duct after the induced draft fan and before the desulfurization unit; or the heat exchange section is arranged on the exhaust duct after the air preheater and before the electrostatic precipitator. In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. This solution recovers the energy of high-temperature flue gas generated by coal-fired power units through a flue gas energy recovery unit. The heat exchange medium in the flue gas energy recovery unit exchanges heat with the high-temperature flue gas. After passing through the flue gas energy recovery unit, the temperature of the high-temperature flue gas decreases, forming low-temperature flue gas. Carbon dioxide, clean water, and wastewater in the low-temperature flue gas are recovered in the flue gas material recovery unit, ultimately achieving dual recovery and utilization of the energy and materials of the high-temperature flue gas, greatly improving the recovery efficiency of high-temperature flue gas.

[0015] 2. This scheme uses waste heat from flue gas to heat nitrogen, which is then heated and evaporated in a heat exchanger before entering a steam turbine. The steam turbine drives a generator to produce electricity, part of which is used for hydrogen / oxygen production via water electrolysis, low-temperature nitrogen refrigeration, and other auxiliary equipment. The remainder is used to generate electricity for grid connection, thus making full use of flue gas heat energy and reducing atmospheric heat emissions.

[0016] 3. This plan utilizes nitrogen power generation as an emerging power generation method, offering numerous advantages such as environmental friendliness, high efficiency, and safety, and is gradually gaining attention. Firstly, nitrogen, as an inert gas, is harmless to the environment and does not produce harmful emissions during power generation. Secondly, nitrogen power generation is highly efficient, effectively converting the energy of nitrogen into electrical energy. Finally, because nitrogen is non-flammable and non-explosive, nitrogen power generation also offers significant safety advantages.

[0017] 4. The low-temperature nitrogen gas after doing work absorbs heat from the flue gas, which lowers the temperature of this part of the flue gas. After purification, the captured carbon dioxide is hydrogenated to produce methanol, which is then returned to the boiler for combustion. This cycle repeats, and the return of methanol to the boiler for combustion can achieve stable combustion at low loads and rapid load increases, meeting the requirements of deep peak shaving and high load change rates of the new generation of coal-fired power units.

[0018] 5. A portion of the electricity generated by the low-temperature nitrogen turbine generator set is used for hydrogen production through water electrolysis (water is obtained from liquid flue gas separation, with any shortfall supplemented by the power plant's water treatment system). The oxygen separated from the water electrolysis is pressurized by a booster compressor (if necessary) and then sent to the boiler via hot secondary air to achieve oxygen-enriched combustion. This enhances flame stability, reduces burnout time, makes the combustion process smoother, improves boiler operational reliability, significantly increases boiler combustion thermal efficiency, reduces the excess air coefficient, reduces the amount of flue gas after combustion, ensures complete combustion of unburned solids carried in the flue gas, reduces smoke opacity, and ensures complete combustion of combustible and harmful gases formed during combustion decomposition, reducing the generation of harmful gases. Oxygen-enriched combustion in the boiler is more adaptable to different types of coal, allowing the use of lower-quality raw coal and reducing power generation costs.

[0019] 6. After the flue gas volume at the inlet of the desulfurization absorption tower is reduced, the amount of water evaporated in the absorption tower is reduced, and the water consumption of the desulfurization process is reduced accordingly. In addition, the wastewater from the flue gas purification, CO2 capture, and water separation devices is pumped to the desulfurization absorption tower for reuse, which can achieve the purpose of fully saving water.

[0020] 7. This solution involves hydrogenating the carbon dioxide captured from the flue gas to produce methanol, which is then returned to the boiler for combustion. This not only reduces the coal consumption of the boiler but also solves the problem of carbon dioxide disposal and storage, significantly improving the efficiency of coal-fired power units. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the flue gas energy recovery unit in this invention; Figure 3 This is a schematic diagram showing the positional arrangement of the first type of heat exchanger in this invention; Figure 4 This is a schematic diagram of the location arrangement of the second type of heat exchanger in this invention; Attached reference numerals: 1. Flue gas energy recovery unit; 2. Flue gas material recovery unit; 3. Flue gas pipeline; 4. Hot secondary air duct; 5. Boiler burner; 6. Exhaust fan; 7. Desulfurization unit; 8. Air preheater; 9. Electrostatic precipitator; 11. Heat exchange unit; 12. Energy conversion unit; 13. Liquid storage unit; 14. Power unit; 121. Nitrogen turbine; 122. Generator; 131. Low-temperature nitrogen refrigeration unit; 132. Liquid storage tank; 141. Lifting pipeline; 142. Liquid nitrogen lift pump; 21. Flue gas treatment module; 22. Methanol synthesis module; 23. Wastewater treatment module; 24. Oxygen generator. Modules include: 211 Purification unit; 212 Carbon dioxide capture unit; 213 Water separation unit; 221 Methanol synthesis unit; 222 Methanol pressurization unit; 223 Methanol storage tank; 224 Methanol conveying unit; 225 Methanol outlet pipe; 226 Pressurization pipeline; 227 Methanol booster pump; 228 Methanol conveying pipeline; 229 Methanol conveying pump; 231 Wastewater conveying unit; 232 Desulfurization absorption tower; 233 Wastewater conveying pipeline; 234 Wastewater pump; 241 Electrolysis unit; 242 Oxygen conveying pipeline; 243 Oxygen supply pipeline; 244 Oxygen booster compressor. Detailed Implementation

[0022] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0023] Any feature disclosed in this specification (including any appended claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0024] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a predetermined orientation, or be constructed and operated in a predetermined orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0026] Example 1 like Figures 1-4 As shown, the present invention provides a technical solution: A comprehensive utilization system for carbon dioxide capture and generation of waste heat from flue gas of a coal-fired power unit includes, but is not limited to, a flue gas energy recovery unit 1 and a flue gas material recovery unit 2. The heat exchange end of the flue gas energy recovery unit 1 is embedded in the flue gas pipeline 3. The oxygen production end of the flue gas material recovery unit 2 is connected to the thermal secondary air duct 4 of the coal-fired power unit. The alcohol production end of the flue gas material recovery unit 2 is connected to the boiler burner 5 of the coal-fired power unit.

[0027] Based on the above structure, this scheme recovers the energy of high-temperature flue gas generated by the coal-fired power unit through the flue gas energy recovery unit 1. The heat exchange medium in the flue gas energy recovery unit 1 exchanges heat with the high-temperature flue gas. After passing through the flue gas energy recovery unit 1, the temperature of the high-temperature flue gas decreases to form low-temperature flue gas. The carbon dioxide, clean water and wastewater in the low-temperature flue gas are recovered in the flue gas material recovery unit 2. Finally, the dual recovery and utilization of energy and materials of high-temperature flue gas is realized, which greatly improves the recovery efficiency of high-temperature flue gas.

[0028] As an example, the flue gas energy recovery unit 1 may include a heat exchange unit 11, an energy conversion unit 12, a liquid storage unit 13, and a power unit 14; the heat exchange unit 11, the energy conversion unit 12, the liquid storage unit 13, and the power unit 14 are sequentially connected by pipelines to form a circulation loop; the heat exchange unit 11 is disposed in the pipeline where the high-temperature flue gas is located.

[0029] Based on the above structure, the liquid storage section 13 provides storage space for the heat exchange medium, the power section 14 provides a power source for the heat exchange medium, and the heat exchange section 11 provides the basis for energy exchange of the heat exchange medium. The energy conversion section is used to convert the heat of the heat exchange medium. Finally, the heat exchange medium after energy conversion returns to the liquid storage section 13 for storage, ready for the next cycle pumping. Through cycle heat exchange and energy conversion, the heat exchange section 11 can continuously exchange heat with the high-temperature flue gas in the flue.

[0030] As an example, the energy conversion unit 12 can be a nitrogen turbine 121 and a generator 122, or an expander and a generator 122.

[0031] Based on the above structure, this scheme adopts 122 sets of flue gas waste heat low temperature nitrogen steam turbine generators or 122 sets of expander generators. After the nitrogen does work, the temperature can be as low as -180℃ and below. The low temperature nitrogen after doing work flows back to the liquid storage section 13.

[0032] As an example, the heat exchange section 11 can be a flue gas-nitrogen heat exchanger, through which liquid nitrogen and high-temperature flue gas exchange heat in the flue. The liquid nitrogen is heated and evaporated in the flue gas-nitrogen heat exchanger, and finally the gas and liquid are separated. The gas flows into the energy conversion section 12 to generate electricity.

[0033] As an example, the liquid storage section 13 may include a cryogenic nitrogen refrigeration device 131 and a liquid storage tank 132; the cryogenic nitrogen refrigeration device 131 is connected to the outlet of the energy conversion section 12 and the liquid storage tank, respectively. The cryogenic nitrogen that has completed its work in the energy conversion section enters the cryogenic nitrogen refrigeration device 131 for liquefaction treatment and finally flows into the liquid storage tank 132 for storage.

[0034] As an example, the power unit 14 may include two parallel lifting pipelines 141, each of which is equipped with a liquid nitrogen lifting pump 142; the lifting pipelines 141 are connected in parallel with the entire circulation loop.

[0035] Based on the above structure, by setting up two booster pipelines 141, on the one hand, the efficiency of liquid nitrogen delivery can be increased according to demand, and on the other hand, a backup strategy can be adopted during off-peak hours to avoid damage to the liquid nitrogen booster pump 142 that would lead to a decrease in the overall flue gas energy recovery efficiency.

[0036] As an example, the flue gas material recovery unit 2 includes a flue gas treatment module 21, a methanol synthesis module 22, a wastewater treatment module 23, and an oxygen preparation module 24; the flue gas treatment module 21 is connected to the flue gas pipeline 3, and the flue gas treatment module 21 is equipped with a purification unit 211, a carbon dioxide capture unit 212, and a water separation unit 213; the purified water outlet of the flue gas treatment module 21 is connected to the oxygen preparation module 24; the wastewater outlet of the flue gas treatment module 21 is connected to the wastewater treatment module 23; the carbon dioxide outlet of the flue gas treatment module 21 is connected to the methanol synthesis module 22; and the hydrogen outlet of the oxygen preparation module 24 is connected to the methanol synthesis module 22.

[0037] Based on the above structure, the low-temperature flue gas in this scheme is purified by a purification unit 211, a carbon dioxide capture unit 212, and a water separation unit 213 to obtain carbon dioxide, purified water, and wastewater; the purified water flows into an oxygen preparation module 24, where oxygen and hydrogen are produced by electrolysis; the carbon dioxide flows into a methanol synthesis module 22, where it is hydrogenated to synthesize methanol in a methanol synthesis unit 221; and the wastewater is treated in a wastewater treatment module 23 and then recycled.

[0038] As an example, the methanol synthesis module 22 may include a methanol synthesis unit 221, a methanol pressurization unit 222, a methanol storage tank 223, a methanol delivery unit 224, and a methanol outlet pipe 225; the methanol synthesis unit 221 is connected to the methanol storage tank 223 through the methanol pressurization unit 222; the methanol storage tank 223 is connected to the methanol outlet pipe 225 through the methanol delivery unit 224; the methanol outlet pipe 225 is connected to a superheated burner; the methanol synthesis unit 221 is connected to the carbon dioxide outlet of the flue gas treatment module 21 and the hydrogen outlet of the oxygen preparation module 24. The methanol booster unit 222 may include two parallel booster pipes 226, and a methanol booster pump 227 is installed in the booster pipes 226; The methanol delivery unit 224 may include two parallel methanol delivery pipelines 228, and a methanol delivery pump 229 is installed in the methanol delivery pipelines 228. Based on the above structure, methanol is produced from carbon dioxide and hydrogen in the methanol synthesis unit 221. The methanol is pressurized by the methanol booster unit 222 and sent to the methanol storage tank 223 for storage. The methanol in the methanol storage tank 223 is then transported to the methanol outlet pipe 225 through the methanol conveying unit 224 as needed. Finally, the methanol outlet pipe 225 is directly sent to the boiler burner 5 for combustion, realizing the recovery and utilization of carbon dioxide and hydrogen elements in the flue gas. Both the methanol booster unit 222 and the methanol conveying unit 224 are dual-line conveyors (one for standby and one for use), which can ensure the efficiency of the entire line conveying.

[0039] As an example, the wastewater treatment module 23 can be a wastewater conveying unit 231 and a desulfurization absorption tower 232; the wastewater outlet of the methanol synthesis unit 221 is connected to the wastewater conveying unit 231, and the wastewater conveying unit 231 is connected to the desulfurization absorption tower 232. The wastewater conveying unit 231 may include two parallel wastewater conveying pipelines 233, and a wastewater pump 234 is installed in the wastewater conveying pipelines 233. Based on the above structure, wastewater is pumped by wastewater pump 234 to desulfurization absorption tower 232 for reuse, which can achieve the purpose of fully saving water.

[0040] As an example, the oxygen preparation module 24 may include an electrolysis device 241 and an oxygen delivery pipeline 242; the electrolysis device 241 is provided with two liquid inlets, one of which is connected to the purified water outlet of the flue gas treatment module 21, and the other liquid inlet is connected to an external water supply pipeline; one end of the oxygen delivery pipeline 242 is connected to the oxygen outlet of the electrolysis device 241, and the other end extends into the hot secondary air duct 4.

[0041] Two parallel oxygen delivery pipelines 243 can be included in the oxygen delivery pipeline 242, and an oxygen booster 244 is installed in the oxygen delivery pipeline 243. Based on the above structure, the electrolysis device 241 can recycle the purified water generated in the flue gas treatment module 21 and use it to produce oxygen and hydrogen respectively. The oxygen is transported to the hot secondary air duct 4 for oxygen-enriched combustion, and the hydrogen is used to produce methanol. In the end, both are recycled and reused, which improves the resource utilization rate of flue gas. When the purified water is insufficient, water can be added to the electrolysis device 241 through an external water supply pipeline.

[0042] As an example, the heat exchange section 11 is located on the exhaust flue after the induced draft fan 6 and before the desulfurization device 7; The advantages of this arrangement are: 1) The temperature rise of the flue gas through the induced draft fan 6 is utilized, resulting in significant benefits; 2) The wear of the heat exchange pipes in the flue gas heat exchanger is less, and there is less ash accumulation, greatly reducing operational risks; 3) After the flue gas volume at the inlet of the desulfurization absorption tower 232 is reduced, the amount of water evaporated in the absorption tower is reduced, and the water consumption of the desulfurization process is correspondingly saved, which can achieve the purpose of water conservation.

[0043] The disadvantage of this arrangement is that it cannot take advantage of the reduced power consumption of the electrostatic precipitator 9 and the reduced power of the induced draft fan 6 caused by the reduction in flue gas volume. Another possible arrangement for the heat exchange section 11 is to place it on the exhaust duct after the air preheater 8 and before the electrostatic precipitator 9. This arrangement has two main advantages: 1) The amount of flue gas entering the dust collector is reduced, which reduces the power consumption of the dust collector and thus reduces the plant's power consumption; 2) The amount of flue gas downstream of the dust collector is also reduced accordingly, and the capacity of the flue, induced draft fan 6, etc., can also be reduced accordingly, which can reduce the plant's power consumption; 3) After the amount of flue gas at the inlet of the desulfurization absorption tower 232 is reduced, the amount of water evaporated in the absorption tower is reduced, and the water consumption of the desulfurization process is reduced accordingly, which can achieve the purpose of saving water.

[0044] The disadvantages of this arrangement are: 1) High ash accumulation, wear, and maintenance costs. Since the flue gas does not pass through the electrostatic precipitator 9 for dust collection, the ash content in the flue gas is high, making it prone to ash accumulation when passing through the flue gas heat exchanger, affecting the heat exchange effect. Therefore, effective soot blowing measures need to be implemented in the flue gas heat exchanger to reduce the impact of ash accumulation; 2) The dust removal workload is large when extracting carbon dioxide from the flue gas after heat exchange; 3) The layout of the flue leading from the flue before the dust collector is difficult and requires a large space.

[0045] Example 2 In this scheme, the flue gas energy recovery unit 1 may specifically include a flue gas-liquid nitrogen heat exchanger (hereinafter referred to as the flue gas heat exchanger), a nitrogen turbine 121 or expander, a generator 122, a cryogenic nitrogen refrigeration treatment device 131 and a liquid storage tank 132, and two liquid nitrogen booster pumps. The flue gas-liquid nitrogen heat exchanger is arranged in the flue, where liquid nitrogen is heated, evaporated, and separated into gas and liquid. The nitrogen turbine 121 or expander converts the kinetic and thermal energy of nitrogen into mechanical energy to drive the generator 122 to generate electricity. Part of the generated electricity is used for water electrolysis to produce hydrogen / oxygen, the cryogenic nitrogen refrigeration treatment device 131 and other auxiliary equipment, and the remaining electricity is used to increase the amount of electricity fed into the grid.

[0046] The process flow is as follows: Liquid nitrogen in the liquid nitrogen storage tank 132 is transported to the heat exchanger via the liquid nitrogen booster pump pipeline for heating, evaporation, and gas-liquid separation. The gas is drawn into the steam turbine or expander. After working in the steam turbine or expander, the nitrogen is transported to the low-temperature nitrogen refrigeration treatment device 131 and the liquid storage tank 132 via the exhaust pipe. It is then transported to the flue gas heat exchanger by the liquid nitrogen booster pump, thus forming a closed loop, making full use of the exhaust heat energy and reducing atmospheric heat emissions.

[0047] The flue gas material recovery unit 2 in this scheme includes: 1) a low-temperature flue gas purification, CO2 capture, and water separation device; 2) a methanol synthesis unit 221; 3) two methanol booster pumps; 4) a methanol storage tank 223; 5) a methanol transfer pump 229; 6) an electrolysis water hydrogen / oxygen production unit; 7) two oxygen booster pumps 244; and 8) two wastewater pumps 234.

[0048] The process flow is as follows: Low-temperature flue gas undergoes flue gas purification, CO2 capture, and water separation to extract carbon dioxide and purified water. Wastewater is pumped to desulfurization absorption tower 232 for reuse via wastewater pump 234. Purified water is then processed through a water electrolysis unit to produce hydrogen and oxygen. The oxygen is pressurized by a booster pump (if necessary) and then fed into the boiler through hot secondary air duct 4 to achieve oxygen-enriched combustion. CO2 is hydrogenated to synthesize methanol in methanol synthesis unit 221, which is then pumped to methanol storage tank 223 via methanol booster pump and then returned to the boiler for combustion via methanol transfer pump 229.

[0049] The following effects can be achieved by adopting this solution: 1. This scheme uses waste heat from flue gas to heat nitrogen, which is then heated and evaporated in a heat exchanger before entering a steam turbine. The steam turbine drives the generator 122 to generate electricity, part of which is used for hydrogen / oxygen production via water electrolysis, low-temperature nitrogen refrigeration treatment device 131, and other auxiliary equipment. The remainder is used to generate electricity for grid connection, thus making full use of flue gas heat energy and reducing atmospheric heat emissions.

[0050] 2. Nitrogen power generation, as an emerging power generation method, has many advantages, such as being environmentally friendly, efficient, and safe, and is gradually attracting attention. First, nitrogen, as an inert gas, is harmless to the environment and does not produce harmful emissions during the power generation process. Second, nitrogen power generation is highly efficient, effectively converting the energy of nitrogen into electrical energy. Finally, because nitrogen is non-flammable and non-explosive, nitrogen power generation also has significant advantages in terms of safety.

[0051] 3. The low-temperature nitrogen gas after doing work absorbs heat from the flue gas, which lowers the temperature of this part of the flue gas. After purification, the captured carbon dioxide is hydrogenated to produce methanol, which is then returned to the boiler for combustion. This cycle repeats, and the return of methanol to the boiler for combustion can achieve stable combustion at low loads and rapid load increases, meeting the requirements of deep peak shaving and high load change rates of the new generation of coal-fired power units.

[0052] 4. A portion of the electricity generated by the 122 sets of low-temperature nitrogen turbine generators is used for hydrogen production through water electrolysis (water is obtained from liquid flue gas separation, with any shortfall supplemented by the power plant's water treatment system). The oxygen separated from the water electrolysis is pressurized by a booster compressor (if necessary) and then sent to the boiler via hot secondary air to achieve oxygen-enriched combustion. This enhances flame stability, reduces burnout time, and makes the combustion process smoother, improving boiler operational reliability, significantly increasing boiler combustion thermal efficiency, reducing the excess air coefficient, reducing the amount of flue gas after combustion, ensuring complete combustion of unburned solids carried in the flue gas, reducing smoke opacity, and ensuring complete combustion of combustible and harmful gases formed during combustion decomposition, thus reducing the generation of harmful gases. Oxygen-enriched combustion in the boiler is more adaptable to different types of coal, allowing the use of lower-quality raw coal and reducing power generation costs.

[0053] 5. After the flue gas volume at the inlet of the desulfurization absorption tower 232 is reduced, the amount of water evaporated in the absorption tower is reduced, and the water consumption of the desulfurization process is correspondingly reduced. In addition, the wastewater from the flue gas purification, CO2 capture, and water separation devices is transported to the desulfurization absorption tower 232 for reuse via the wastewater pump 234, which can achieve the purpose of fully saving water.

[0054] 6. This solution involves hydrogenating the carbon dioxide captured from the flue gas to produce methanol, which is then returned to the boiler for combustion. This not only reduces the coal consumption of the boiler but also solves the problems of carbon dioxide disposal and storage, significantly improving the efficiency of coal-fired power units.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coal-fired power plant flue gas waste heat power generation carbon dioxide capture and comprehensive utilization system, characterized in that, The application relates to a flue gas energy and substance recovery device, which comprises a flue gas energy recovery part (1) and a flue gas substance recovery part (2).

2. The system according to claim 1, wherein the system is characterized in that: The flue gas energy recovery part (1) comprises a heat exchange part (11), an energy conversion part (12), a liquid storage part (13) and a power part (14); the heat exchange part (11), the energy conversion part (12), the liquid storage part (13) and the power part (14) form a circulating loop through pipelines in sequence; and the heat exchange part (11) is arranged in a pipeline where high-temperature flue gas is located.

3. The comprehensive utilization system for carbon dioxide capture in waste heat power generation from coal-fired power units according to claim 2, characterized in that: The energy conversion part (12) is a nitrogen turbine (121) and a generator (122), or an expander and a generator (122); and the heat exchange part (11) is a flue gas-nitrogen heat exchanger.

4. The system according to claim 3, wherein the system further comprises a CO2 capture unit. The liquid storage part (13) comprises a low-temperature nitrogen refrigeration treatment device (131) and a liquid storage tank (132); the low-temperature nitrogen refrigeration treatment device (131) is connected with the gas outlet of the energy conversion part (12) and the liquid storage tank respectively.

5. The comprehensive utilization system for carbon dioxide capture in waste heat power generation from coal-fired power units according to claim 4, characterized in that: The power part (14) comprises two parallelly arranged lifting pipelines (141), and a liquid nitrogen lifting pump (142) is arranged on each lifting pipeline (141); and the lifting pipelines (141) are connected with the whole circulating loop in parallel.

6. The system according to claim 5, wherein the system further comprises a CO2 capture unit. The flue gas substance recovery part (2) comprises a flue gas treatment module (21), a methanol synthesis module (22), a waste water treatment module (23) and an oxygen preparation module (24); the flue gas treatment module (21) is connected with a flue gas pipeline (3); the flue gas treatment module (21) is provided with a purification unit (211), a carbon dioxide capturing unit (212) and a water separation unit (213); a purified water outlet of the flue gas treatment module (21) is connected with the oxygen preparation module (24); a waste water outlet of the flue gas treatment module (21) is connected with the waste water treatment module (23); a carbon dioxide outlet of the flue gas treatment module (21) is connected with the methanol synthesis module (22); and a hydrogen outlet of the oxygen preparation module (24) is connected with the methanol synthesis module (22).

7. The system according to claim 6, wherein the system further comprises a CO2 capture unit. The methanol synthesis module (22) comprises a methanol synthesis device (221), a methanol pressure boosting unit (222), a methanol storage tank (223), a methanol conveying unit (224) and a methanol outflow pipe (225); the methanol synthesis device (221) is connected with the methanol storage tank (223) through the methanol pressure boosting unit (222); the methanol storage tank (223) is connected with the methanol outflow pipe (225) through the methanol conveying unit (224); the methanol outflow pipe (225) is connected with the superheated burner; the methanol synthesis device (221) is connected with the carbon dioxide outlet of the flue gas treatment module (21) and the hydrogen gas outlet of the oxygen preparation module (24) respectively; the methanol pressure boosting unit (222) comprises two parallel pressure boosting pipelines (226), and a methanol boosting pump (227) is arranged in the pressure boosting pipeline (226); the methanol conveying unit (224) comprises two parallel methanol conveying pipelines (228), and a methanol conveying pump (229) is arranged in the methanol conveying pipeline (228).

8. The system according to claim 7, wherein the system further comprises a CO2 capture unit. The wastewater treatment module (23) comprises a wastewater conveying unit (231) and a desulfurization absorption tower (232); the wastewater outlet of the methanol synthesis device (221) is connected with the wastewater conveying unit (231), and the wastewater conveying unit (231) is connected with the desulfurization absorption tower (232); the wastewater conveying unit (231) comprises two parallel wastewater conveying pipelines (233), and a wastewater pump (234) is arranged in the wastewater conveying pipeline (233).

9. The system according to claim 8, wherein the system further comprises a CO2 capture unit. The oxygen preparation module (24) comprises an electrolysis device (241) and an oxygen conveying pipeline (242); two liquid inlets are arranged on the electrolysis device (241), one of which is connected with the clean water outlet of the flue gas treatment module (21), and the other is connected with an external water supplement pipeline; one end of the oxygen conveying pipeline (242) is connected with the oxygen gas outlet of the electrolysis device (241), and the other end extends into the hot secondary air duct (4); the oxygen conveying pipeline (242) comprises two parallel oxygen conveying pipelines (243), and an oxygen booster (244) is arranged in the oxygen conveying pipeline (243).

10. The system according to claim 9, wherein the system further comprises a CO2 capture unit. The heat exchange unit (11) is arranged on the flue gas duct after the induced draft fan (6) and before the desulfurization device (7), or the heat exchange unit (11) is arranged on the flue gas duct after the air preheater (8) and before the electric precipitator (9).

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