A system and method for methanol and ammonia assisted boiler low load combustion

Abstract

This invention proposes a system and method for low-load combustion in a methanol and ammonia-assisted boiler. The system includes a coal-fired power unit, a catalytic converter, a flue gas separator, and a storage tank. The flue gas duct of the coal-fired power unit is sequentially connected to the flue gas separator, the catalytic converter, the methanol storage tank, and the liquid ammonia storage tank via pipelines. This invention separates CO2 and N2 from the coal-fired flue gas, utilizes the surplus electricity generated during full-load operation of the coal-fired power unit for electrocatalysis, and simultaneously utilizes solar energy for photocatalysis to synthesize CH3OH and NH3 from the separated CO2 and N2. These are stored in the storage tank and, during low-load operation of the coal-fired power unit, are injected into the main combustion zone and reduction zone through atomizing nozzles and ammonia guns, respectively, for combustion assistance and denitrification. This invention utilizes methanol and ammonia-assisted boiler combustion to ensure stable combustion of the coal-fired power unit under lower loads and reduces NO inside the furnace. x It reduces the content of coal-fired power plants and significantly lowers the operating costs of coal-fired power units.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation technology, and in particular to a system and method for low-load combustion of methanol and ammonia auxiliary boilers. Background Technology

[0002] With the steady progress towards achieving dual-carbon goals, the development of clean energy sources such as wind and solar power has significantly increased, with installed capacity and power generation growing year by year. However, the inherent instability and discontinuity of clean energy power generation make it difficult to maintain grid stability, and large-scale energy storage technology is still under development. Coal-fired power generation needs to adjust peak loads according to grid demand to maintain user electricity needs and ensure grid stability. Therefore, as a supplement to the shortage of clean energy power generation, coal-fired boilers often need to operate at low loads, typically stable at 30%–50% load. However, as clean energy power generation continues to increase, sometimes it is necessary to reduce the boiler load to 30% or below. This results in low furnace temperature, poor flow field uniformity within the furnace, and increased nitrogen oxides (NOx) at the denitrification inlet. x Problems such as high concentration and the possibility of flame extinguishing.

[0003] Currently, the main low-load stable combustion technologies include rich-lean separation technology, changing the secondary air distribution method, laying combustion belts, and using low-load burners. Oil-assisted combustion and gas-assisted combustion are also used. However, the existing technical adjustment methods and low-load burners still have limited ability to improve stable combustion under lower boiler load conditions. Furthermore, some methods involve NO in the furnace. x The NO content will still increase; while using combustion-assisted methods such as oil and gas can make the boiler combustion more stable at low loads, it will also significantly increase operating costs. Therefore, it is necessary to explore how to achieve stable combustion in coal-fired units at lower loads and reduce NO content inside the furnace. x While improving the content, it is still of great significance to significantly reduce the operating cost of coal-fired power units. Summary of the Invention

[0004] The purpose of this invention is to provide a system and method for low-load combustion in a methanol and ammonia-assisted boiler. This system utilizes high concentrations of CO2 and N2 in flue gas to synthesize CH3OH and NH3. During low-load operation, CH3OH is used for pulverized coal flame combustion, and NH3 synergistically removes high concentrations of NO generated at low loads. x This improves the stability of the flame and reduces operating costs.

[0005] The embodiment of one aspect of the present application provides a system for low-load combustion of a boiler assisted by methanol and ammonia, which comprises a coal-fired unit, a catalytic device, a flue gas separation device and a storage tank, wherein the flue of the coal-fired unit is connected to the flue gas separation device, the catalytic device and the storage tank in sequence through pipelines, the storage tank comprises a methanol storage tank and a liquid ammonia storage tank, the methanol storage tank is connected to the burner of the coal-fired unit through a pipeline, the liquid ammonia storage tank is connected to the ammonia lance of the coal-fired unit through a pipeline, and the generator output end of the coal-fired unit is electrically connected to the catalytic device and supplies power to the catalytic device.

[0006] In some embodiments, the catalytic device comprises an electro-catalytic device and a photo-catalytic device, the generator output end of the coal-fired unit is electrically connected to the electro-catalytic device and supplies power to the electro-catalytic device, and the gas outlet of the flue gas separation device is connected to the gas inlet of the electro-catalytic device and the gas inlet of the photo-catalytic device respectively.

[0007] In some embodiments, the flue gas separation device comprises a carbon dioxide separation device and a nitrogen separation device, the electro-catalytic device comprises a first electro-catalytic device and a second electro-catalytic device, the photo-catalytic device comprises a first photo-catalytic device and a second photo-catalytic device, and the flue of the coal-fired unit is connected to the gas inlet of the carbon dioxide separation device through a pipeline.

[0008] The first gas outlet of the carbon dioxide separation device is connected to the gas inlet of the nitrogen separation device, the carbon dioxide gas outlet of the carbon dioxide separation device is connected to the gas inlet of the first electro-catalytic device and the gas inlet of the first photo-catalytic device respectively, and the gas outlet of the first electro-catalytic device and the gas outlet of the first photo-catalytic device are jointly connected to the methanol storage tank.

[0009] The second gas outlet of the nitrogen separation device is connected to a waste gas discharge device, the nitrogen gas outlet of the nitrogen separation device is connected to the gas inlet of the second electro-catalytic device and the gas inlet of the second photo-catalytic device respectively, and the gas outlet of the second electro-catalytic device and the gas outlet of the second photo-catalytic device are jointly connected to the liquid ammonia storage tank.

[0010] In some embodiments, the electro-catalytic device and the photo-catalytic device are both provided with an oxygen outlet, and the oxygen outlet is jointly connected to the burner of the coal-fired unit through a pipeline.

[0011] In some embodiments, the coal-fired unit comprises a boiler, a steam turbine and a generator, the steam outlet of the boiler is connected to the steam turbine and the generator in sequence, and the burner, the ammonia lance and the flue are all arranged on the boiler.

[0012] In some embodiments, a compressor is connected to the gas inlet of the liquid ammonia storage tank, and a gasifier is connected to the pipeline between the gas outlet of the liquid ammonia storage tank and the ammonia lance.

[0013] In some embodiments, the calcium cycle method is used in the carbon dioxide separation device to separate carbon dioxide.

[0014] In some embodiments, the nitrogen separation device uses hollow fiber membrane technology or synthetic molecular sieves to separate nitrogen.

[0015] In some embodiments, the catalyst in the electrocatalytic device is a copper-based catalyst or an iron catalyst, and the catalyst in the photocatalytic device is a titanium dioxide catalyst.

[0016] Another embodiment of this application proposes a method for low-load combustion in a methanol and ammonia assisted boiler, which utilizes the above-mentioned system for low-load combustion in a methanol and ammonia assisted boiler, and includes the following steps:

[0017] The flue gas discharged from the boiler flows into the carbon dioxide separation device. The separated carbon dioxide is fed into the first electrocatalytic device and the first photocatalytic device to generate oxygen and methanol. The oxygen is fed into the boiler burner and the methanol is stored in the methanol storage tank.

[0018] Other gases separated from the carbon dioxide separator are introduced into the nitrogen separator through the first outlet. The separated nitrogen is introduced into the second electrocatalytic device and the second photocatalytic device to generate oxygen and ammonia. The oxygen is introduced into the boiler burner, and the ammonia is compressed into liquid ammonia by the compressor and stored in the liquid ammonia storage tank. Other gases separated from the nitrogen separator are discharged through the exhaust gas emission device.

[0019] When the boiler requires low-load combustion, the methanol storage tank delivers methanol to the boiler burner, and the liquid ammonia output from the liquid ammonia storage tank is vaporized by the vaporizer and then injected into the boiler's reduction zone through the ammonia gun for denitrification.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention separates CO2 and N2 in flue gas to synthesize CH3OH and NH3, effectively capturing and utilizing CO2, strongly promoting carbon neutrality and development. The oxygen produced by electrocatalysis and photocatalysis can be used as an oxidant for normal boiler combustion. Both CH3OH and NH3 are easy to store and transport. After ensuring the needs of the power plant, they can be transported to other energy-consuming locations for application.

[0022] 2. This invention injects the synthesized methanol into the furnace for combustion under low-load combustion conditions in the boiler, which can increase the flame temperature and maintain the stability of the pulverized coal flame. At the same time, it is generated as a byproduct by electrocatalysis and photocatalysis, which reduces the additional cost of purchasing fuel oil and gas required for stable combustion of auxiliary boilers under low load, and greatly reduces operating costs.

[0023] 3. This invention uses synthesized ammonia as a commonly used reducing agent for denitrification. Injecting ammonia into the furnace can remove the additional NO produced under low-load combustion conditions in the boiler. x Reduction, thereby satisfying the requirement for NO in the inlet flue gas of the denitrification equipment.x The concentration limit reduces the operating pressure on denitrification equipment. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0025] in:

[0026] Figure 1 This is a schematic diagram of the system for low-load combustion of methanol and ammonia auxiliary boilers in the embodiments of this application;

[0027] Figure label:

[0028] 1-Boiler; 2-Steam turbine; 3-Generator; 4-First electrocatalytic device; 5-Second electrocatalytic device; 6-First photocatalytic device; 7-Second photocatalytic device; 8-Compressor; 9-Methanol storage tank; 10-Liquid ammonia storage tank; 11-Carbon dioxide separator; 12-Inlet pipe of carbon dioxide separator; 13-Connecting pipe; 14-First control valve; 15-Vaporizer; 16-Nitrogen separator; 17-Outlet pipe of nitrogen separator; 18-Waste gas emission device; 19-Burner; 20-Ammonia gun; 21-Second control valve. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The following describes a system and method for low-load combustion of methanol and ammonia assisted boilers according to embodiments of the present invention, with reference to the accompanying drawings.

[0031] like Figure 1 As shown, one embodiment of this application proposes a system for low-load combustion of methanol and ammonia assisted boilers, including: a coal-fired unit, a catalytic converter, a flue gas separator, and a storage tank. The flue of the coal-fired unit is connected to the flue gas separator, the catalytic converter, and the storage tank in sequence via pipelines. The storage tank includes a methanol storage tank 9 and a liquid ammonia storage tank 10. The methanol storage tank 9 is connected to the burner 19 of the coal-fired unit via a pipeline, and the liquid ammonia storage tank 10 is connected to the ammonia gun 20 of the coal-fired unit via a pipeline. The output terminal of the generator 3 of the coal-fired unit is electrically connected to the catalytic converter and supplies power to the catalytic converter.

[0032] In some specific embodiments, the coal-fired unit includes a boiler 1, a steam turbine 2, and a generator 3. The steam outlet of the boiler 1 is sequentially connected to the steam turbine 2 and the generator 3. The burner 19, ammonia lance 20, and flue are all located on the boiler 1. The steam generated by the boiler 1 is converted into electrical energy by the steam turbine 2, which powers the generator 3 and then the power grid. The surplus electricity generated by the boiler 1 at full load is supplied to the electrocatalytic converter to enable its operation.

[0033] In some specific embodiments, the catalytic device includes an electrocatalytic device and a photocatalytic device. The output terminal of the generator 3 of the coal-fired unit is electrically connected to the electrocatalytic device and supplies power to the electrocatalytic device. The outlet of the flue gas separator is connected to the inlet of the electrocatalytic device and the inlet of the photocatalytic device, respectively.

[0034] In some specific embodiments, the flue gas separation device includes a carbon dioxide separation device 11 and a nitrogen separation device 16, and the electrocatalytic device includes a first electrocatalytic device 4 and a second electrocatalytic device 5. A generator 3 supplies power to these two electrocatalytic devices. The photocatalytic device includes a first photocatalytic device 6 and a second photocatalytic device 7, which directly utilizes solar energy for photocatalysis. During periods of sufficient sunlight, it can continue to operate even when the coal-fired unit is running at low load, continuously generating byproducts such as oxygen, methanol, and ammonia. The flue gas duct of the coal-fired unit is connected to the inlet of the carbon dioxide separation device 11 via a pipeline.

[0035] The first outlet of the carbon dioxide separator 11 is connected to the inlet of the nitrogen separator 16. The carbon dioxide outlet of the carbon dioxide separator 11 is connected to the inlet of the first electrocatalytic device 4 and the inlet of the first photocatalytic device 6, respectively. The outlets of the first electrocatalytic device 4 and the first photocatalytic device 6 are connected to the methanol storage tank 9.

[0036] The second outlet of the nitrogen separation device 16 is connected to the exhaust gas emission device 18. The nitrogen outlet of the nitrogen separation device 16 is connected to the inlet of the second electrocatalytic device 5 and the inlet of the second photocatalytic device 7, respectively. The outlets of the second electrocatalytic device 5 and the second photocatalytic device 7 are connected to the liquid ammonia storage tank 10.

[0037] In some specific embodiments, both the electrocatalytic and photocatalytic devices are equipped with oxygen outlets, which are connected to the burner 19 of the coal-fired power unit via pipelines. The O2 synthesized during the catalytic process can be used as an oxidant in the boiler 1. O2 is directly injected into the furnace through the burner 19 as an oxidant, providing oxidation conditions for pulverized coal and methanol. This method reduces the introduction of N2 from the air, thereby reducing the amount of flue gas emitted by the boiler 1, thus reducing heat loss from the flue gas and saving energy.

[0038] In some specific embodiments, the burner 19 is equipped with a methanol atomizing nozzle, which can atomize the stored CH3OH and spray it into the furnace to assist the boiler 1 in low-load combustion.

[0039] In some specific embodiments, a compressor 8 is connected to the air inlet of the liquid ammonia storage tank 10, and a vaporizer 15 is connected to the pipeline between the air outlet of the liquid ammonia storage tank 10 and the ammonia gun 20. The purpose of the compressor 8 is to compress ammonia gas into liquid ammonia for easy storage. The purpose of the vaporizer 15 is to vaporize the stored liquid ammonia into ammonia gas, which is then introduced into the boiler 1 for use.

[0040] In some specific embodiments, the carbon dioxide separation device 11 employs a calcium cycle method to separate carbon dioxide. CO2 adsorption and release are achieved through the conversion between CaO and CaCO3.

[0041] In some specific embodiments, the nitrogen separation device 16 uses hollow fiber membrane technology or synthetic molecular sieve to separate nitrogen and achieve nitrogen enrichment.

[0042] In some specific embodiments, the catalyst in the electrocatalytic device is a copper-based catalyst or an iron catalyst, and the catalyst in the photocatalytic device is a titanium dioxide catalyst.

[0043] In some specific embodiments, the exhaust gas emission device 18 is a chimney.

[0044] In some specific embodiments, the exhaust gas emission device 18 may also include an exhaust gas purification device, wherein other gases separated in the nitrogen separation device 16 are treated by the exhaust gas purification device and then discharged into the atmosphere through the exhaust gas emission device 18.

[0045] In some specific embodiments, a connecting pipe 13 is connected between the inlet pipe 12 of the carbon dioxide separator and the outlet pipe 17 of the nitrogen separator via a tee. A first control valve 14 is connected to the connecting pipe 13. When the boiler 1 is not producing byproducts or is under maintenance, the second control valve 21 is open and the first control valve 14 is closed, allowing the flue gas to be directly discharged from the exhaust gas emission device 18 through the connecting pipe 13. When the system is operating normally, the first control valve 14 is open and the second control valve 21 is closed.

[0046] In some specific embodiments, the first control valve 14 and the second control valve 21 can both be proportional valves, which can respectively adjust the flow rate of the gas. The ratio of flue gas flowing into the carbon dioxide separator 11 to being discharged directly from the exhaust gas emission device 18 can be controlled by these two control valves.

[0047] Another embodiment of this application proposes a method for low-load combustion in a methanol and ammonia assisted boiler, which utilizes the above-mentioned system for low-load combustion in a methanol and ammonia assisted boiler, and includes the following steps:

[0048] The flue gas generated by the combustion of boiler 1 is discharged from the tail flue of boiler 1. The ratio of flue gas flowing into the gas separation device to being discharged directly from the chimney is controlled by the control valve. The flue gas flows into carbon dioxide separation device 11. The separated carbon dioxide is fed into the first electrocatalytic device 4 and the first photocatalytic device 6 respectively to generate oxygen and methanol. The oxygen is fed into the burner 19 of boiler 1, and the methanol is stored in methanol storage tank 9. Other gases separated from carbon dioxide separation device 11 are fed into nitrogen separation device 16 through the first gas outlet. The separated nitrogen is fed into the second electrocatalytic device 5 and the second photocatalytic device 7 respectively to generate oxygen and ammonia. The oxygen is fed into the burner 19 of boiler 1, and the ammonia is compressed into liquid ammonia by compressor 8 and stored in liquid ammonia storage tank 10. Other gases separated from nitrogen separation device 16 are discharged through exhaust gas emission device 18.

[0049] When boiler 1 requires low-load combustion, methanol storage tank 9 delivers methanol to burner 19 of boiler 1. Methanol is atomized through atomizing nozzles and injected into the furnace before the pulverized coal, increasing the furnace temperature and making the pulverized coal easier to ignite, thus maintaining a stable flame and ensuring stable combustion at low load in boiler 1. Liquid ammonia from liquid ammonia storage tank 10 is vaporized by vaporizer 15 and then injected into the reduction zone of boiler 1's furnace through ammonia gun 20 for denitrification. In the reduction zone of the furnace, the O2 concentration is low, and NO... x High concentrations of NH3 and NO x The reaction produces N2, thus achieving denitrification and reducing the amount of NO produced by boiler 1 under low-load combustion. x This reduces the reduction pressure of denitrification equipment in coal-fired power units and prevents NO from entering the flue gas. x The content exceeds the standard.

[0050] This application separates CO2 and N2 from coal-fired flue gas, utilizes surplus electricity from a coal-fired power unit operating at full load for electrocatalysis, and simultaneously employs solar energy for photocatalysis to synthesize CH3OH and NH3 from the separated CO2 and N2. These are stored in a storage tank and, during low-load operation of the coal-fired power unit, are injected into the main combustion zone and reduction zone via atomizing nozzles and ammonia guns, respectively, for combustion assistance and denitrification. This invention utilizes methanol and ammonia to assist boiler combustion, ensuring stable combustion of the coal-fired power unit under lower loads and reducing NO levels inside the furnace. x It reduces the content of coal-fired power plants and significantly lowers the operating costs of coal-fired power units.

[0051] In some specific embodiments, the electrocatalytic device is powered by the surplus electricity generated by generator 3 when the coal-fired unit is at full load. When the coal-fired unit needs to operate at low load, the electrocatalytic device stops operating, and the product is produced only by the photocatalytic device.

[0052] In some specific embodiments, the system incorporates necessary valves in the pipelines to control the flow rate. For example, the flow rate of flue gas is controlled by controlling the valve before the gas separator, and the concentration ratio of reactants flowing into the catalytic device is controlled by controlling the valve before the photocatalytic device and the electrocatalytic device, thereby controlling the operating status of the catalytic device.

[0053] Methanol, as a high-calorific-value liquid fuel, is highly flammable and can burn rapidly. When injected into the furnace under low-load combustion conditions in a boiler, it can increase the flame temperature and maintain the stability of the pulverized coal flame. At the same time, as a byproduct, it is generated by electrocatalysis and photocatalysis, which reduces the additional cost of purchasing fuel oil and gas required for stable combustion of auxiliary boilers under low load, and greatly reduces operating costs.

[0054] Ammonia is a commonly used reducing agent for denitrification. Injecting it into the furnace can reduce the additional NO produced under low-load combustion conditions in boilers. x Reduction, thereby satisfying the requirement for NO in the inlet flue gas of the denitrification equipment. x The concentration limit reduces the operating pressure on denitrification equipment.

[0055] This application separates CO2 and N2 from flue gas to synthesize CH3OH and NH3, effectively capturing and utilizing CO2, strongly promoting carbon neutrality and development. The oxygen produced by electrocatalysis and photocatalysis can be used as an oxidant for boiler combustion during normal operation. Both CH3OH and NH3 are easy to store and transport, and after ensuring the needs of the power plant, they can be transported to other energy-consuming locations for application.

[0056] The following specific examples will further illustrate this case.

[0057] Example 1

[0058] like Figure 1 As shown, a system for low-load combustion of methanol and ammonia assisted boiler includes: a boiler 1, a steam turbine 2 and a generator 3, a first electrocatalytic device 4, a second electrocatalytic device 5, a first photocatalytic device 6, a second photocatalytic device 7, a carbon dioxide separation device 11, a nitrogen separation device 16, a methanol storage tank 9 and a liquid ammonia storage tank 10.

[0059] The steam outlet of boiler 1 is connected in sequence to steam turbine 2 and generator 3. The steam generated by boiler 1 is converted into electrical energy by steam turbine 2, which powers generator 3 and then the power grid. The surplus electricity generated by boiler 1 at full load is supplied to the electrocatalytic converter to enable its operation.

[0060] The flue of boiler 1 is connected to the inlet pipe 12 of the carbon dioxide separator 11 via a pipeline. The carbon dioxide separator 11 has two outlets: a first outlet and a carbon dioxide outlet. The first outlet of the carbon dioxide separator 11 is connected to the inlet of the nitrogen separator 16 via a pipeline. The carbon dioxide outlet of the carbon dioxide separator 11 is connected to the inlets of the first electrocatalytic converter 4 and the first photocatalytic converter 6 via pipelines. The outlets of the first electrocatalytic converter 4 and the first photocatalytic converter 6 are connected to the methanol storage tank 9 via pipelines. The methanol storage tank 9 is connected to the burner 19 of the coal-fired unit via a pipeline. The burner 19 is equipped with methanol atomizing nozzles, which can atomize the stored methanol and spray it into the furnace to assist the boiler 1 in low-load combustion.

[0061] The carbon dioxide separator 11 separates carbon dioxide from the flue gas and sends it to the first electrocatalytic device 4 and the first photocatalytic device 6 for reaction to produce methanol and oxygen. Other gases in the flue gas besides carbon dioxide are sent to the nitrogen separator 16.

[0062] The nitrogen separator 16 has two outlets: a second outlet and a nitrogen outlet. The second outlet of the nitrogen separator 16 is connected to the chimney via a pipeline. The nitrogen outlet of the nitrogen separator 16 is connected to the inlet of the second electrocatalytic device 5 and the inlet of the second photocatalytic device 7 via pipelines. The outlets of the second electrocatalytic device 5 and the second photocatalytic device 7 are connected to the liquid ammonia storage tank 10 via pipelines. The liquid ammonia storage tank 10 is connected to the ammonia gun 20 of the coal-fired unit via pipelines. A compressor 8 is connected to the inlet of the liquid ammonia storage tank 10, and a vaporizer 15 is connected to the pipeline between the outlet of the liquid ammonia storage tank 10 and the ammonia gun 20. The compressor 8 is used to compress ammonia gas into liquid ammonia for easy storage. The vaporizer 15 is used to vaporize the stored liquid ammonia into ammonia gas before it is introduced into the boiler 1 for use.

[0063] Both the electrocatalytic and photocatalytic devices are equipped with oxygen outlets, which are connected to the burner 19 of the coal-fired power unit via pipelines. The O2 synthesized during the catalytic process can be used as an oxidant in the boiler 1. O2 is directly injected into the furnace through the burner 19 as an oxidant, providing oxidation conditions for pulverized coal and methanol. This method reduces the introduction of N2 from the air, thus reducing the amount of flue gas emitted by the boiler 1, thereby reducing heat loss from the flue gas and saving energy.

[0064] The generator 3 of the coal-fired unit is electrically connected to the electrocatalytic device and supplies power to it. The generator 3 supplies power to the first electrocatalytic device 4 and the second electrocatalytic device 5. The photocatalytic device uses solar energy for direct photocatalysis. During periods of sufficient sunlight, it can continue to operate even when the coal-fired unit is running at low load, continuously generating byproducts such as oxygen, methanol, and ammonia.

[0065] A connecting pipe 13 connects the inlet pipe 12 of the carbon dioxide separator and the outlet pipe 17 of the nitrogen separator via a tee. A first control valve 14 is connected to the connecting pipe 13. When the boiler 1 is not producing byproducts or is under maintenance, the second control valve 21 is open, and the first control valve 14 is open, allowing the flue gas to be directly discharged from the exhaust gas emission device 18 through the connecting pipe 13. When the system is operating normally, both the first control valve 14 and the second control valve 21 can be open, or only the second control valve 21 can be open. Both the first control valve 14 and the second control valve 21 are proportional valves, which can adjust the flow rate of the gas. The ratio of flue gas flowing into the carbon dioxide separator 11 to being directly discharged from the exhaust gas emission device 18 can be controlled through these two control valves.

[0066] In this embodiment, the carbon dioxide separation device 11 uses a calcium cycle method to separate carbon dioxide. CO2 adsorption and release are achieved through the conversion between CaO and CaCO3.

[0067] In this embodiment, the nitrogen separation device 16 uses hollow fiber membrane method or synthetic molecular sieve to separate nitrogen and achieve nitrogen enrichment.

[0068] In this embodiment, the catalyst in the electrocatalytic device is a copper-based catalyst or an iron catalyst, and the catalyst in the photocatalytic device is a titanium dioxide catalyst.

[0069] This embodiment also proposes a method for low-load combustion in a methanol and ammonia assisted boiler, which utilizes the aforementioned system for low-load combustion in a methanol and ammonia assisted boiler and includes the following steps:

[0070] The flue gas generated by the combustion of boiler 1 is discharged from the tail flue of boiler 1. The ratio of flue gas flowing into the gas separation device to being discharged directly from the chimney is controlled by the control valve. The flue gas flows into carbon dioxide separation device 11. The separated carbon dioxide is fed into the first electrocatalytic device 4 and the first photocatalytic device 6 respectively to generate oxygen and methanol. The oxygen is fed into the burner 19 of boiler 1, and the methanol is stored in methanol storage tank 9. Other gases separated from carbon dioxide separation device 11 are fed into nitrogen separation device 16 through the first gas outlet. The separated nitrogen is fed into the second electrocatalytic device 5 and the second photocatalytic device 7 respectively to generate oxygen and ammonia. The oxygen is fed into the burner 19 of boiler 1, and the ammonia is compressed into liquid ammonia by compressor 8 and stored in liquid ammonia storage tank 10. Other gases separated from nitrogen separation device 16 are discharged through exhaust gas emission device 18.

[0071] When boiler 1 requires low-load combustion, methanol storage tank 9 delivers methanol to burner 19 of boiler 1. Methanol is atomized through atomizing nozzles and injected into the furnace before the pulverized coal, increasing the furnace temperature and making the pulverized coal easier to ignite, thus maintaining a stable flame and ensuring stable combustion at low load in boiler 1. Liquid ammonia from liquid ammonia storage tank 10 is vaporized by vaporizer 15 and then injected into the reduction zone of boiler 1's furnace through ammonia gun 20 for denitrification. In the reduction zone of the furnace, the O2 concentration is low, and NO... x High concentrations of NH3 and NO x The reaction produces N2, thus achieving denitrification and reducing the amount of NO produced by boiler 1 under low-load combustion. x This reduces the reduction pressure of denitrification equipment in coal-fired power units and prevents NO from entering the flue gas. x The content exceeds the standard.

[0072] The electrocatalytic device is powered by the surplus electricity generated by generator 3 when the coal-fired unit is at full load. When the coal-fired unit needs to operate at low load, the electrocatalytic device stops operating, and the product is produced only by the photocatalytic device.

[0073] In this system, necessary valves are installed in the pipeline to control the flow rate. For example, the amount of flue gas flowing into the gas separator is controlled by controlling the valve before the gas separator, and the concentration ratio of reactants flowing into the catalytic device is controlled by controlling the valve before the photocatalytic device and the electrocatalytic device, thereby controlling the working status of the catalytic device.

[0074] Methanol, as a high-calorific-value liquid fuel, is highly flammable and can burn rapidly. When injected into the furnace under low-load combustion conditions in a boiler, it can increase the flame temperature and maintain the stability of the pulverized coal flame. At the same time, as a byproduct, it is generated by electrocatalysis and photocatalysis, which reduces the additional cost of purchasing fuel oil and gas required for stable combustion of auxiliary boilers under low load, and greatly reduces operating costs.

[0075] Ammonia is a commonly used reducing agent for denitrification. Injecting it into the furnace can reduce the additional NO produced under low-load combustion conditions in boilers. x Reduction, thereby satisfying the requirement for NO in the inlet flue gas of the denitrification equipment. x The concentration limit reduces the operating pressure on denitrification equipment.

[0076] This application separates CO2 and N2 from flue gas to synthesize CH3OH and NH3, effectively capturing and utilizing CO2, strongly promoting carbon neutrality and development. The oxygen produced by electrocatalysis and photocatalysis can be used as an oxidant for boiler combustion during normal operation. Both CH3OH and NH3 are easy to store and transport, and after ensuring the needs of the power plant, they can be transported to other energy-consuming locations for application.

[0077] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0078] Furthermore, the terms "first" and "second" 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. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0079] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0080] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0081] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0082] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A system for low-load combustion in a methanol and ammonia-assisted boiler, characterized in that, include: The unit comprises a coal-fired power unit, a catalytic converter, a flue gas separator, and a storage tank. The flue of the coal-fired power unit is connected to the flue gas separator, the catalytic converter, and the storage tank in sequence via pipelines. The storage tank includes a methanol storage tank and a liquid ammonia storage tank. The methanol storage tank is connected to the burner of the coal-fired power unit via a pipeline, and the liquid ammonia storage tank is connected to the ammonia gun of the coal-fired power unit via a pipeline. The generator output of the coal-fired power unit is electrically connected to the catalytic converter and supplies power to the catalytic converter. The catalytic device includes an electrocatalytic device and a photocatalytic device. The generator output of the coal-fired power unit is electrically connected to and supplies power to the electrocatalytic device. The outlet of the flue gas separator is connected to the inlet of the electrocatalytic device and the inlet of the photocatalytic device, respectively. The flue gas separation device includes a carbon dioxide separation device and a nitrogen separation device, the electrocatalytic device includes a first electrocatalytic device and a second electrocatalytic device, the photocatalytic device includes a first photocatalytic device and a second photocatalytic device, and the flue of the coal-fired unit is connected to the air inlet of the carbon dioxide separation device through a pipeline. The first outlet of the carbon dioxide separator is connected to the inlet of the nitrogen separator. The carbon dioxide outlet of the carbon dioxide separator is connected to the inlet of the first electrocatalytic device and the inlet of the first photocatalytic device. The outlets of the first electrocatalytic device and the first photocatalytic device are connected to the methanol storage tank. The second outlet of the nitrogen separation device is connected to the exhaust gas emission device. The nitrogen outlet of the nitrogen separation device is connected to the inlet of the second electrocatalytic device and the inlet of the second photocatalytic device. The outlets of the second electrocatalytic device and the second photocatalytic device are connected to the liquid ammonia storage tank.

2. The system for low-load combustion of methanol and ammonia assisted boilers according to claim 1, characterized in that, Both the electrocatalytic device and the photocatalytic device are equipped with oxygen outlets, which are connected to the burner of the coal-fired unit via pipelines.

3. The system for low-load combustion of methanol and ammonia assisted boilers according to any one of claims 1-2, characterized in that, The coal-fired unit includes a boiler, a steam turbine, and a generator. The steam outlet of the boiler is connected to the steam turbine and the generator in sequence. The burner, ammonia lance, and flue are all located on the boiler.

4. The system for low-load combustion of methanol and ammonia assisted boilers according to claim 1, characterized in that, A compressor is connected to the air inlet of the liquid ammonia storage tank, and a vaporizer is connected to the pipeline between the air outlet of the liquid ammonia storage tank and the ammonia gun.

5. The system for low-load combustion of methanol and ammonia assisted boilers according to claim 1, characterized in that, The carbon dioxide separation device uses a calcium cycle method to separate carbon dioxide.

6. The system for low-load combustion of methanol and ammonia assisted boilers according to claim 1, characterized in that, The nitrogen separation device uses hollow fiber membrane technology or synthetic molecular sieves to separate nitrogen.

7. The system for low-load combustion of methanol and ammonia assisted boilers according to claim 1, characterized in that, The catalyst in the electrocatalytic device is a copper-based catalyst or an iron catalyst, while the catalyst in the photocatalytic device is a titanium dioxide catalyst.

8. A method for low-load combustion in a methanol and ammonia assisted boiler, characterized in that, The system for low-load combustion of a methanol and ammonia assisted boiler according to any one of claims 1-7 includes the following steps: The flue gas discharged from the boiler flows into the carbon dioxide separation device. The separated carbon dioxide is fed into the first electrocatalytic device and the first photocatalytic device to generate oxygen and methanol. The oxygen is fed into the boiler burner and the methanol is stored in the methanol storage tank. Other gases separated from the carbon dioxide separator are introduced into the nitrogen separator through the first outlet. The separated nitrogen is introduced into the second electrocatalytic device and the second photocatalytic device to generate oxygen and ammonia. The oxygen is introduced into the boiler burner, and the ammonia is compressed into liquid ammonia by the compressor and stored in the liquid ammonia storage tank. Other gases separated from the nitrogen separator are discharged through the exhaust gas emission device. When the boiler requires low-load combustion, the methanol storage tank delivers methanol to the boiler burner, and the liquid ammonia output from the liquid ammonia storage tank is vaporized by the vaporizer and then injected into the boiler's reduction zone through the ammonia gun for denitrification.

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