CN115127112A - Natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia and operation method - Google Patents

Natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia and operation method Download PDF

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Publication number
CN115127112A
CN115127112A CN202210880050.8A CN202210880050A CN115127112A CN 115127112 A CN115127112 A CN 115127112A CN 202210880050 A CN202210880050 A CN 202210880050A CN 115127112 A CN115127112 A CN 115127112A
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ammonia
gas
outlet
tank
natural gas
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李文锋
邹小刚
申冀康
周飞
车宏伟
李楠
董方奇
何浩
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Xian Xire Boiler Environmental Protection Engineering Co Ltd
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Xian Xire Boiler Environmental Protection Engineering Co Ltd
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Priority to CN202210880050.8A priority Critical patent/CN115127112A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K5/00—Feeding or distributing other fuel to combustion apparatus
    • F23K5/002—Gaseous fuel
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C1/00—Ammonia; Compounds thereof
    • C01C1/02—Preparation, purification or separation of ammonia
    • C01C1/04—Preparation of ammonia by synthesis in the gas phase
    • C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J15/00—Arrangements of devices for treating smoke or fumes
    • F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K5/00—Feeding or distributing other fuel to combustion apparatus
    • F23K5/002—Gaseous fuel
    • F23K5/007—Details
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/005—Regulating fuel supply using electrical or electromechanical means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23K—FEEDING FUEL TO COMBUSTION APPARATUS
    • F23K2900/00—Special features of, or arrangements for fuel supplies
    • F23K2900/05004—Mixing two or more fluid fuels

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Analytical Chemistry (AREA)
  • Inorganic Chemistry (AREA)

Abstract

The invention discloses a natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen and an operation method thereof.A boiler burner is arranged as a natural gas ammonia burner, the natural gas ammonia burner is connected with a gas mixing tank and an air pipeline, and gas and air inlets are provided with flow regulating valves; the first energy saver and the second energy saver are connected in series and are arranged behind a flue at the tail part of the boiler, and the flue gas on-line analyzer is arranged in the flue behind the second energy saver; the outlet of the PSA carbon-nitrogen separation device is respectively connected with a nitrogen buffer tank and a carbon dioxide buffer tank; the inlet of the ammonia synthesis device is respectively connected with the outlets of the nitrogen buffer tank and the hydrogen buffer tank through flow regulating valves, and the outlet is connected with the ammonia buffer tank; the water inlet of the water electrolysis hydrogen production tank is connected with the desalting water tank through a water pump, and the outlet of the water electrolysis hydrogen production tank is respectively connected with the hydrogen buffer tank and the oxygen buffer tank. The invention can realize the combustion of natural gas with ammonia, oxygen enrichment, carbon reduction and low nitrogen, and simultaneously carry out comprehensive recycling on the thermal mass of the flue gas to the maximum extent, water saving and zero carbon emission.

Description

Natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia and operation method
Technical Field
The invention belongs to the technical field of low-carbon low-nitrogen clean power generation of gas fuel, and particularly relates to a natural gas ammonia-doped combustion system for producing ammonia by coupling green hydrogen and an operation method.
Background
Under the background of carbon peak carbon neutralization, a gas-fired boiler mainly burning natural gas also faces great energy-saving and carbon-reduction challenges, and the current mainstream carbon neutralization technical route can adopt zero-carbon fuel part to replace carbon-containing fuel to reduce the whole carbon emission level besides carbon dioxide capture, utilization and storage (CCUS). On the other hand, with the annual and rapid increase of installed capacity of renewable energy and the undeveloped large-scale energy storage, the green electricity abandoning rate is high, and how to effectively utilize the abandoned electricity is also an urgent problem to be solved.
Hydrogen is divided into ash hydrogen, blue hydrogen and green hydrogen, the ash hydrogen produced by global fossil energy currently accounts for more than 95%, but the process of producing green hydrogen by electrolyzing water by utilizing renewable energy is developing vigorously. Compared with hydrogen, ammonia is used as an effective carrier of hydrogen energy, the preparation process is mature, the storage and transportation cost is low, the safety is high, zero-carbon emission can be realized in the whole life cycle, and the fuel is concerned as 'zero-carbon' fuel. The PSA carbon-nitrogen separation device can realize the nitrogen preparation and carbon dioxide capture synchronously by the flue gas pressure swing adsorption process. The existing gas boiler with ammonia-doped combustion is integrated with the existing research situation, and the problems of small ammonia-doped proportion, high emission of nitrogen oxides, insufficient overall heat efficiency and the like exist in the existing gas boiler with ammonia-doped combustion. Therefore, how to realize the maximum carbon reduction and low nitrogen emission of the gas boiler and simultaneously carry out comprehensive recycling of heat and mass has profound significance for developing green recycling economy in petrochemical industry parks, coal industry parks, iron and steel, metallurgy and other industries.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a natural gas ammonia-doped combustion system for coupling green hydrogen to prepare ammonia and an operation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
a natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen comprises a boiler, an energy saver group formed by connecting a plurality of energy savers in series, a PSA carbon-nitrogen separation device, an ammonia synthesis device, a water electrolysis hydrogen production tank, a gas mixing tank and an oxygen buffer tank, wherein the burner of the boiler is a natural gas ammonia burner, the energy saver group is arranged at the tail end of a tail flue of the boiler, a flue gas outlet of the last energy saver in the energy saver group is connected with an inlet of the PSA carbon-nitrogen separation device, a nitrogen outlet of the PSA carbon-nitrogen separation device is connected with a nitrogen inlet of the ammonia synthesis device, a hydrogen outlet of the water electrolysis hydrogen production tank is connected with a hydrogen inlet of the ammonia synthesis device, an oxygen outlet of the water electrolysis tank is connected with an inlet of the oxygen buffer tank, an outlet of the oxygen buffer tank is connected with a combustion-supporting air channel of the natural gas ammonia burner after being connected with an air source, an ammonia outlet of the ammonia synthesis device is connected with an ammonia inlet of the gas mixing tank, a natural gas inlet is also formed in the gas mixing tank, and a mixed gas outlet of the gas mixing tank is connected with a gas channel of the natural gas ammonia burner;
the hydrogen inlet of the ammonia synthesis device, the nitrogen inlet of the ammonia synthesis device, the ammonia inlet of the gas mixing tank, the natural gas inlet of the gas mixing tank, the mixed gas outlet of the gas mixing tank, the outlet of the oxygen buffer tank and the inlet of the combustion-supporting air channel of the natural gas ammonia burner are all provided with flow regulating valves;
the water electrolysis hydrogen production tank is electrically connected with the green.
Preferably, the economizer group comprises a primary economizer and a secondary economizer which are sequentially connected in series, and a flue gas outlet of the secondary economizer is connected with an inlet of the PSA carbon-nitrogen separation device.
Preferably, the natural gas ammonia-doped combustion system for producing ammonia by coupling green hydrogen also comprises a desalting water tank; the temperature of the flue gas can be reduced to be below a water dew point after passing through the secondary economizer, a water outlet is formed in the secondary economizer, the water outlet of the secondary economizer is connected with a demineralized water tank, the demineralized water tank is also connected with a cold end inlet of the secondary economizer, a cold end outlet of the secondary economizer is connected with a cold end inlet of the primary economizer, and a cold end outlet of the primary economizer is connected with a steam-water system inlet of a boiler; and water pumps are arranged on a pipeline for connecting the water outlet of the secondary energy saver with the demineralized water tank, a pipeline for connecting the demineralized water tank with the cold end inlet of the secondary energy saver, a pipeline for connecting the cold end outlet of the secondary energy saver with the cold end inlet of the primary energy saver and a pipeline for connecting the cold end outlet of the primary energy saver with the steam-water system inlet of the boiler, and a flow regulating valve is arranged at a water pump outlet on a pipeline for connecting the demineralized water tank with the cold end inlet of the secondary energy saver.
Preferably, the demineralized water tank is connected with the water electrolysis hydrogen production tank, a water pump is arranged on a pipeline connecting the demineralized water tank and the water electrolysis hydrogen production tank, and a flow regulating valve is arranged at an outlet of the water pump.
Preferably, the natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen further comprises a flue gas online analyzer, and a measuring hole of the flue gas online analyzer is arranged on a pipeline connecting a flue gas outlet of the secondary energy saver and an inlet of the PSA carbon-nitrogen separation device.
Preferably, a nitrogen buffer tank is arranged on a pipeline connecting a nitrogen outlet of the PSA carbon-nitrogen separation device and a nitrogen inlet of the ammonia synthesis device, and a flow regulating valve is arranged at an outlet of the nitrogen buffer tank.
Preferably, an ammonia buffer tank is arranged on a pipeline connecting an ammonia outlet of the ammonia synthesis device and an ammonia inlet of the gas mixing tank, and a flow regulating valve is arranged at an outlet of the ammonia buffer tank.
Preferably, the natural gas ammonia-doped combustion system for producing ammonia by coupling green hydrogen further comprises a flue gas temperature online monitor, and a measuring point of the flue gas temperature online monitor is arranged at a hearth outlet smoke transfer chamber of the boiler.
The operation method of the natural gas ammonia-doped combustion system for producing ammonia by coupling green hydrogen comprises the following steps:
when the boiler is started in a cold state, firstly, the natural gas ammonia burner is controlled to only put in operation natural gas to carry out load increase and hearth temperature increase, after the boiler load reaches more than 20 percent and the hearth temperature rises to more than 650 ℃, the mixing proportion of ammonia gas in the gas mixing tank and the oxygen content in combustion-supporting air begin to be improved, and finally, the stable combustion of the natural gas doped with ammonia and oxygen enrichment is realized; when the boiler is started in a hot state, the natural gas ammonia gas burner is controlled to directly put into operation the mixed gas with the proportion of 10 percent, then the mixing proportion of the ammonia gas and the oxygen content in the combustion-supporting air are gradually improved, and finally the stable combustion of the natural gas with ammonia and rich oxygen is realized;
in the operation stage of the boiler, water vapor enters a power generation device connected to the boiler to generate power, the flue gas is cooled and condensed by an economizer group, a PSA carbon-nitrogen separation device carries out pressure swing adsorption on nitrogen and carbon dioxide in the warm flue gas cooled and condensed by the economizer group, high-purity carbon dioxide generated by the PSA carbon-nitrogen separation device is captured, and the high-purity nitrogen generated by the PSA carbon-nitrogen separation device is sent to an ammonia synthesis device to react; meanwhile, the water electrolysis hydrogen production tank utilizes green electricity to carry out electrolysis, hydrogen generated by electrolysis is sent into the ammonia synthesis device to react, and oxygen generated by electrolysis is converged into the oxygen buffer tank; meanwhile, the ammonia synthesizer synthesizes ammonia gas by using hydrogen and nitrogen, and the synthesized ammonia gas is converged into an ammonia buffer tank;
in the process of changing the load of a boiler or improving the ammonia mixing proportion of fuel gas, the ammonia mixing proportion in a gas mixing tank is adjusted, the oxygen content in combustion-supporting air is adjusted, and the concentration of nitrogen oxides in flue gas can meet the emission requirement cooperatively.
Preferably, the mixing proportion of ammonia gas is 0-80% when the natural gas ammonia gas burner operates, the excess air coefficient is 1.05-1.10, and the oxygen content in the combustion-supporting air is 21Percent is 30 percent; the temperature of the flue gas at the outlet of the boiler hearth is 800-1000 ℃; the concentration of nitrogen oxides in tail flue gas is not higher than 30mg/Nm 3 。
The invention has the following beneficial effects:
the natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen is matched with an energy saver group, a PSA carbon-nitrogen separation device, a water electrolysis hydrogen production tank for preparing green hydrogen and oxygen and an ammonia synthesis device which are formed by connecting a plurality of energy savers in series, realizes the oxygen-enriched combustion of a large proportion of doped ammonia gas on a gas boiler and simultaneously performs heat recovery and utilization, and realizes the integral water saving and zero carbon emission; the invention can dynamically adjust the proportion of the ammonia doped in the natural gas and the oxygen content of the combustion-supporting air by monitoring the temperature of the smoke at the outlet of the boiler hearth and the components of the tail smoke, thereby realizing the stable, efficient and low-nitrogen combustion of the mixed gas in the boiler; the smoke temperature can be reduced to 40-50 ℃ through an economizer group formed by connecting a plurality of economizers in series; carbon dioxide and nitrogen in the flue gas are completely purified and recovered by a PSA carbon-nitrogen separation system, hydrogen and nitrogen are further synthesized into ammonia gas in an ammonia synthesis device and are doped into natural gas by hydrogen and nitrogen electrolysis hydrogen production oxygen production by utilizing green electricity, and oxygen generated by electrolysis is used as a combustion improver and is mixed into air. In conclusion, the invention realizes the combustion of natural gas doped with ammonia, oxygen enrichment, carbon reduction and low nitrogen, simultaneously carries out comprehensive recycling on the thermal mass of the smoke to the maximum extent, saves water and has zero carbon emission, realizes the cascade utilization of energy and the organic circulation of substances, and has profound significance for developing green circular economy in high-carbon industries such as petrochemical industry park, coal chemical industry park, steel, metallurgy and the like.
Furthermore, the boiler can be heated by the desalting water tank and the economizer group, and all condensed water in the flue gas can be recovered.
Drawings
FIG. 1 is a schematic diagram of a natural gas ammonia-blended combustion system coupled with green hydrogen to produce ammonia in accordance with the present invention.
Wherein, 1 is natural gas ammonia gas combustor, 2 is the one-level energy-saving appliance, 3 is the second grade energy-saving appliance, 4 is PSA carbon nitrogen separator, 5 is the ammonia synthesizer, 6 is water electrolysis hydrogen manufacturing groove, 7 is the gas blending tank, 8 is the boiler, 9 is the oxygen buffer tank, 10 is the ammonia buffer tank, 11 is the nitrogen buffer tank, 12 is the hydrogen buffer tank, 13 is the online analyzer of flue gas, 14 is the demineralized water case, 15 is flow control valve, 16 is the water pump, 17 is green electricity, 18 is flue gas temperature on-line monitoring appearance, 19 is power generation facility, 20 is the carbon dioxide buffer tank.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments described in the drawings are merely exemplary in nature and are intended to be illustrative of the invention only and not to be construed as limiting the invention.
In order to improve the combustion stability in a natural gas large-proportion ammonia-doped furnace and realize water-saving zero-carbon emission of the system, the invention provides a natural gas ammonia-doped combustion system for coupling green hydrogen to prepare ammonia, which is a comprehensive system for carrying out large-proportion dynamic ammonia-doped oxygen-enriched combustion and heat recovery by a gas-fired boiler, and referring to figure 1, the natural gas ammonia-doped combustion system for coupling green hydrogen to prepare ammonia comprises a boiler 8, a natural gas ammonia burner 1, a primary energy saver 2, a secondary energy saver 3, a PSA carbon-nitrogen separation device 4, an ammonia synthesis device 5, a water electrolysis hydrogen preparation tank 6, a gas mixing tank 7, an oxygen buffer tank 9, a flue gas temperature online monitor 18 and a flue gas online analyzer 13, wherein the burner of the boiler 8 is arranged as the natural gas ammonia burner 1, the energy saver group is arranged at the tail end of a tail flue of the boiler, the energy saver group comprises the primary energy saver 2 and the secondary energy saver 3 which are sequentially connected in series, the temperature of the flue gas can be reduced to be below a water dew point after passing through the secondary energy saver 3, a flue gas outlet of the secondary energy saver 3 is connected with an inlet of a PSA carbon-nitrogen separation device 4, a nitrogen outlet of the PSA carbon-nitrogen separation device 4 is connected with a nitrogen inlet of an ammonia synthesis device 5, a carbon dioxide outlet of the PSA carbon-nitrogen separation device 4 is connected with a carbon dioxide buffer tank 20, a hydrogen outlet of a water electrolysis hydrogen production tank 6 is connected with a hydrogen inlet of the ammonia synthesis device 5, an oxygen outlet of the water electrolysis hydrogen production tank 6 is connected with an inlet of an oxygen buffer tank 9, an outlet of the oxygen buffer tank 9 is connected with an air source and then is connected with a combustion-supporting air channel of a natural gas ammonia combustor 1, an ammonia outlet of the ammonia synthesis device 5 is connected with an ammonia inlet of a gas mixing tank 7, the gas mixing tank 7 is also provided with a natural gas inlet, and a mixed gas outlet of the gas mixing tank 7 is connected with a fuel gas channel of the natural gas ammonia combustor 1; a water outlet is arranged on the secondary economizer 3, the water outlet of the secondary economizer 3 is connected with a demineralized water tank 14, the demineralized water tank 14 is also connected with a cold end inlet of the secondary economizer 3, a cold end outlet of the secondary economizer 3 is connected with a cold end inlet of the primary economizer 2, and a cold end outlet of the primary economizer 2 is connected with a steam-water system inlet of the boiler 8; a water pump is arranged on a pipeline connecting a water outlet of the secondary energy saver 3 with the demineralized water tank 14, a pipeline connecting the demineralized water tank 14 with a cold end inlet of the secondary energy saver 3, a pipeline connecting a cold end outlet of the secondary energy saver 3 with a cold end inlet of the primary energy saver 2, and a pipeline connecting a cold end outlet of the primary energy saver 2 with a steam-water system inlet of the boiler 8, and a flow regulating valve is arranged at a water pump outlet on a pipeline connecting the demineralized water tank 14 with the cold end inlet of the secondary energy saver 3; the demineralized water tank 14 is connected with the water electrolysis hydrogen production tank 6, a water pump is arranged on a pipeline connecting the demineralized water tank 14 with the water electrolysis hydrogen production tank 6, and a flow regulating valve is arranged at the outlet of the water pump; a measuring hole of the flue gas online analyzer 13 is arranged on a pipeline connecting a flue gas outlet of the secondary energy saver 3 and an inlet of the PSA carbon-nitrogen separation device 4; the measuring point of the flue gas temperature on-line monitor 18 is arranged at a hearth outlet smoke transfer chamber of the boiler 8; a nitrogen buffer tank 11 is arranged on a pipeline connecting a nitrogen outlet of the PSA carbon-nitrogen separation device 4 and a nitrogen inlet of the ammonia synthesis device 5; an ammonia buffer tank 10 is arranged on a pipeline connecting an ammonia outlet of the ammonia synthesizer 5 and an ammonia inlet of the gas mixing tank 7; a hydrogen inlet of the ammonia synthesis device 5, a nitrogen inlet of the ammonia synthesis device 5, an ammonia inlet of the gas mixing tank 7, a natural gas inlet of the gas mixing tank 7, a mixed gas outlet of the gas mixing tank 7, an outlet of the oxygen buffer tank 9 and an inlet of a combustion-supporting air channel of the natural gas ammonia burner 1 are all provided with flow regulating valves 15; the water electrolysis hydrogen production tank 6 is connected with a green battery 17.
When the natural gas ammonia-doped combustion system coupled with green hydrogen ammonia production works, the tail flue gas of a boiler sequentially flows through the primary energy saver 2 and the secondary energy saver 3, after the temperature of the flue gas is reduced to be below a water dew point through step-by-step heat exchange, the flue gas completely enters the PSA carbon nitrogen separation device 4, water in the flue gas is condensed and then is completely recycled from a water outlet of the secondary energy saver 3, and the condensed water is treated and then is collected into the desalted water tank 14. The low-temperature demineralized water from the demineralized water tank 14 sequentially flows through the secondary economizer 3 and the primary economizer 2 through the water pump 16 and the flow regulating valve 15, exchanges heat with the flue gas, enters a steam-water system of the boiler 8, absorbs heat in the heating surface of the boiler 8 to be changed into steam, and enters the power generation device 19 to generate power. The PSA carbon-nitrogen separation device 4 adopts a two-stage pressure swing adsorption method to separate and purify carbon dioxide and nitrogen components in the flue gas, and the carbon dioxide and nitrogen components are respectively converged into the nitrogen buffer tank 11 and the carbon dioxide buffer tank 20 to realize carbon dioxide capture. The natural gas from a natural gas pipe network and the ammonia gas from the ammonia buffer tank 10 respectively enter a gas mixing tank 7, the mixing proportion is regulated by respective flow regulating valves 15, and the mixed fuel gas enters a fuel gas channel of a natural gas ammonia gas burner 1 and then enters a boiler hearth for combustion; oxygen from the oxygen buffer tank 9 is adjusted in flow rate through the flow adjusting valve 15 and mixed with air, and the mixed combustion-supporting air is adjusted in flow rate through the flow adjusting valve 15, enters a combustion-supporting air channel of the natural gas ammonia burner 1 and then enters a boiler hearth to participate in combustion. A measuring point of the online flue gas temperature monitor 18 is arranged at a flue gas transferring chamber at the outlet of the boiler furnace to monitor the flue gas temperature in real time; and a measuring hole of the flue gas on-line analyzer 13 is arranged in a flue behind the secondary energy saver 3 and in front of the PSA carbon-nitrogen separation device 4, so that the concentration of components such as nitrogen oxides, carbon dioxide and the like in the flue gas is monitored in real time.
Specifically, the natural gas ammonia gas burner 1 can realize 0-80% ammonia gas mixing proportion when the excess air coefficient range is 1.05-1.10, the oxygen content range in combustion-supporting air is 21-30%, and the temperature of the flue gas at the outlet of a boiler furnace is 800-1000 ℃, and the concentration of nitrogen oxides in tail flue gas is not higher than 30mg/Nm 3 。
Specifically, when the natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen operates, the natural gas ammonia combustor 1 is controlled to only deliver natural gas to carry out load increase and hearth temperature increase when a natural gas boiler is started in a cold state, other equipment starts to operate synchronously, the ammonia mixing proportion and the oxygen content in combustion-supporting air start to be gradually increased after the boiler load reaches more than 20% and the hearth temperature rises to more than 650 ℃, and finally the natural gas ammonia-doped oxygen-enriched stable combustion is realized; when the natural gas boiler is started in a hot state, the mixed gas with a low proportion (10 percent) can be directly put into operation; in the boiler operation stage, steam enters a power generation device 19 for power generation, the flue gas is cooled and condensed in the second stage, all condensed water is subjected to water treatment and then is gathered in a desalting water tank 14, a PSA carbon-nitrogen separation device 4 performs pressure swing adsorption on nitrogen and carbon dioxide in all low-temperature flue gas, the generated high-purity carbon dioxide is sent into a carbon dioxide buffer tank 20 for carbon dioxide capture, and the generated high-purity nitrogen is sent into a nitrogen buffer tank 11; meanwhile, the water electrolysis hydrogen production tank 6 utilizes green electricity 17 to electrolyze desalted water into hydrogen which is converged into the hydrogen buffer tank 11, and oxygen is converged into the oxygen buffer tank 9; meanwhile, the ammonia synthesizer 5 utilizes hydrogen and nitrogen to catalyze and synthesize ammonia gas under the conditions of high temperature and high pressure and then the ammonia gas is converged into the ammonia buffer tank 10; in the process of changing the load of the boiler or in the process of improving the ammonia mixing proportion of the fuel gas, according to the data such as the concentration and the oxygen amount of the nitrogen oxides in the fuel gas fed back by the online flue gas analyzer 13 in real time, the flow regulating valve 15 is controlled to regulate the ammonia mixing proportion in the gas mixing tank 7, the flow regulating valve 15 is controlled to regulate the oxygen amount in the combustion-supporting air, and the concentration of the nitrogen oxides in the flue gas can meet the ultra-low emission requirement cooperatively. The water electrolysis hydrogen production tank 6 utilizes green electricity 17 to carry out electrolysis hydrogen production, the required demineralized water is provided by a demineralized water tank 14, the amount of electrolyzed water is controlled by a flow regulating valve 15, hydrogen generated by electrolysis enters a hydrogen buffer tank 12, and oxygen generated by electrolysis enters an oxygen buffer tank 9.
Taking a 50T/H SZS50-1.3/310-Q natural gas steam boiler as an example, the water supply temperature is 25 ℃, the designed boiler efficiency is no less than 92 percent, 80 percent of ammonia gas is mixed and burned under the conditions of 1.05 excess air coefficient and 30 percent of oxygen content under the condition of keeping the full load output of the boiler unchanged, and the required ammonia gas flow is approximately 6200Nm 3 The required electrolysis water flow is 9323kg/h (80% of alkaline electrolysis efficiency), and the oxygen flow mixed into the air is about 928Nm 3 And/h, the flow of the co-recoverable condensed water in the flue gas is 9973kg/h, and the water supplement is reduced by 650 kg/h. The operating hours per year are 2500 hours, the green electricity generated by renewable energy sources can be consumed by 0.93 hundred million degrees per year, 930 ten thousand standard prescriptions of oxygen can be supplied externally per year, 1494 ten thousand standard prescriptions of nitrogen can be supplied externally per year, and 7620 tons of carbon dioxide can be collected per year. Can reduce 12743 tons of carbon dioxide emission in the year of not mixing ammonia, and has remarkable social and environmental protection benefits.
According to the invention, the prepared ammonia gas is mixed into the gas boiler through the coupling of the flue gas heat recovery system, the PSA carbon-nitrogen separation system, the water electrolysis hydrogen-oxygen preparation system and the ammonia synthesis system, and the high load adjustability, the hearth and the fuel adaptability are achieved by combining the real-time dynamic feedback of the flue gas temperature online monitor 18 and the flue gas online analyzer 13, so that the zero-carbon operation is realized and the nitrogen oxide emission concentration is controlled not to exceed the standard. In specific implementation, the invention provides a zero-carbon water-saving modification technical route for a gas boiler, improves boiler efficiency while consuming renewable energy sources in a large scale, and reduces operating fuel cost. The natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen realizes the dynamic matching of stable combustion working conditions and low emission of nitrogen oxides in the furnace under different ammonia mixing ratios, and simultaneously carries out comprehensive recycling and utilization of the thermal mass of flue gas to the greatest extent, saves water and has zero carbon emission, thereby realizing the cascade utilization of energy and the organic circulation of substances.
The natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen is matched with a flue gas deep heat recovery system, a PSA carbon-nitrogen separation system, a water electrolysis green hydrogen preparation oxygen preparation system and an ammonia synthesis system, realizes large-proportion ammonia gas doped oxygen-enriched combustion on a gas boiler, and simultaneously performs heat recovery and utilization, thereby realizing integral water saving and zero carbon emission; the ammonia doping proportion of natural gas and the oxygen content of combustion-supporting air are dynamically adjusted by monitoring the temperature of the smoke at the outlet of the hearth and the components of the tail smoke, so that the stable and efficient low-nitrogen combustion of the mixed gas in the furnace is realized; heating boiler feed water by a two-stage economizer, reducing the temperature of the flue gas to 40-50 ℃, and recovering all condensed water in the flue gas; carbon dioxide and nitrogen in the flue gas are completely purified and recovered by a PSA carbon-nitrogen separation system, hydrogen and nitrogen are further synthesized into ammonia gas in an ammonia synthesis subsystem and are doped into natural gas by hydrogen and nitrogen electrolysis hydrogen production oxygen production by utilizing green electricity, and oxygen generated by electrolysis is used as a combustion improver and is mixed into air. In conclusion, the invention realizes the combustion of natural gas doped with ammonia, oxygen enrichment, carbon reduction and low nitrogen, simultaneously carries out comprehensive recycling on the thermal mass of the smoke to the maximum extent, saves water and has zero carbon emission, realizes the cascade utilization of energy and the organic circulation of substances, and has profound significance for developing green circular economy in high-carbon industries such as petrochemical industry park, coal chemical industry park, steel, metallurgy and the like.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. The natural gas ammonia-doped combustion system for preparing ammonia by coupling green hydrogen is characterized by comprising a boiler (8), an energy saver group formed by connecting a plurality of energy savers in series, a PSA carbon-nitrogen separation device (4), an ammonia synthesis device (5), a water electrolysis hydrogen production tank (6), a gas mixing tank (7) and an oxygen buffer tank (9), wherein the burner of the boiler (8) is set as a natural gas ammonia burner (1), the energy saver group is arranged at the tail end of a flue at the tail part of the boiler, a flue gas outlet of the last energy saver in the energy saver group is connected with an inlet of the PSA carbon-nitrogen separation device (4), a nitrogen outlet of the PSA carbon-nitrogen separation device (4) is connected with a nitrogen inlet of the ammonia synthesis device (5), a hydrogen outlet of the water electrolysis hydrogen production tank (6) is connected with a hydrogen inlet of the ammonia synthesis device (5), an oxygen outlet of the water electrolysis hydrogen production tank (6) is connected with an inlet of the oxygen buffer tank (9), an outlet of the oxygen buffer tank (9) is connected with an air source and then is connected with a combustion-supporting air channel of the natural gas ammonia burner (1), an ammonia outlet of the ammonia synthesis device (5) is connected with an ammonia inlet of the gas mixing tank (7), the gas mixing tank (7) is also provided with a natural gas inlet, and a mixed gas outlet of the gas mixing tank (7) is connected with a fuel gas channel of the natural gas ammonia burner (1);
a hydrogen inlet of the ammonia synthesis device (5), a nitrogen inlet of the ammonia synthesis device (5), an ammonia inlet of the gas mixing tank (7), a natural gas inlet of the gas mixing tank (7), a mixed gas outlet of the gas mixing tank (7), an outlet of the oxygen buffer tank (9) and an inlet of a combustion-supporting air channel of the natural gas ammonia burner (1) are respectively provided with a flow regulating valve (15);
the water electrolysis hydrogen production tank (6) is connected with the green battery (17).
2. The natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia according to claim 1, wherein the economizer group comprises a primary economizer (2) and a secondary economizer (3) which are sequentially connected in series, and a flue gas outlet of the secondary economizer (3) is connected with an inlet of a PSA carbon-nitrogen separation device (4).
3. The natural gas ammonia-blended combustion system for coupling green hydrogen to produce ammonia as claimed in claim 2, further comprising a desalting water tank (14);
the temperature of the flue gas can be reduced to be below a water dew point after passing through the secondary economizer (3), a water outlet is formed in the secondary economizer (3), the water outlet of the secondary economizer (3) is connected with a demineralized water tank (14), the demineralized water tank (14) is also connected with a cold end inlet of the secondary economizer (3), a cold end outlet of the secondary economizer (3) is connected with a cold end inlet of the primary economizer (2), and a cold end outlet of the primary economizer (2) is connected with a steam-water system inlet of a boiler (8); the water pump is arranged on a pipeline for connecting a water outlet of the secondary economizer (3) with the demineralized water tank (14), a pipeline for connecting the demineralized water tank (14) with a cold end inlet of the secondary economizer (3), a pipeline for connecting a cold end outlet of the secondary economizer (3) with a cold end inlet of the primary economizer (2) and a pipeline for connecting a cold end outlet of the primary economizer (2) with an inlet of a steam-water system of the boiler (8), and a flow regulating valve is arranged at a water pump outlet on a pipeline for connecting the demineralized water tank (14) with the cold end inlet of the secondary economizer (3).
4. The natural gas ammonia-mixing combustion system for coupling green hydrogen to produce ammonia according to claim 3, wherein the desalting water tank (14) is connected with the water electrolysis hydrogen production tank (6), a water pump is arranged on a pipeline connecting the desalting water tank (14) and the water electrolysis hydrogen production tank (6), and a flow regulating valve is arranged at an outlet of the water pump.
5. The natural gas ammonia-blending combustion system for coupling green hydrogen to prepare ammonia according to claim 2, further comprising a flue gas online analyzer (13), wherein a measuring hole of the flue gas online analyzer (13) is arranged on a pipeline connecting a flue gas outlet of the secondary economizer (3) and an inlet of the PSA carbon-nitrogen separation device (4).
6. The natural gas ammonia-mixing combustion system for coupling green hydrogen to prepare ammonia according to claim 1, wherein a nitrogen buffer tank (11) is arranged on a pipeline connecting a nitrogen outlet of the PSA carbon-nitrogen separation device (4) and a nitrogen inlet of the ammonia synthesis device (5), and a flow regulating valve is arranged at an outlet of the nitrogen buffer tank (11).
7. The natural gas ammonia-blending combustion system for coupling green hydrogen to prepare ammonia according to claim 1, wherein an ammonia buffer tank (10) is arranged on a pipeline connecting an ammonia gas outlet of the ammonia synthesis device (5) and an ammonia gas inlet of the gas mixing tank (7), and a flow regulating valve is arranged at an outlet of the ammonia buffer tank (10).
8. The natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia according to claim 1, characterized by further comprising a flue gas temperature online monitor (18), wherein a measuring point of the flue gas temperature online monitor (18) is arranged at a furnace outlet smoke transfer chamber of the boiler (8).
9. The method for operating the natural gas ammonia-blended combustion system coupled with the green hydrogen ammonia production as claimed in any one of claims 1 to 8, characterized by comprising the following processes:
when the boiler (8) is started in a cold state, the natural gas ammonia burner (1) is controlled to only put in operation natural gas to carry out load increase and hearth temperature increase, after the boiler load reaches more than 20 percent and the hearth temperature rises to more than 650 ℃, the mixing proportion of ammonia gas in the gas mixing tank (7) and the oxygen content in combustion-supporting air begin to be improved, and finally, the stable combustion of the natural gas doped with ammonia and rich oxygen is realized; when a boiler (8) is started in a hot state, a natural gas ammonia burner (1) is controlled to directly put into operation mixed gas with the proportion of 10 percent, then the mixing proportion of ammonia and the oxygen content in combustion-supporting air are gradually improved, and finally, the stable combustion of the natural gas with ammonia and rich oxygen is realized;
in the operation stage of the boiler (8), water vapor enters a power generation device (19) connected with the boiler (8) for power generation, flue gas is cooled and condensed by an economizer bank, a PSA carbon-nitrogen separation device (4) carries out pressure swing adsorption on nitrogen and carbon dioxide in the cooled and condensed flue gas by the economizer bank, high-purity carbon dioxide generated by the PSA carbon-nitrogen separation device (4) is collected, and the high-purity nitrogen generated by the PSA carbon-nitrogen separation device (4) is sent to an ammonia synthesis device (5) for reaction; meanwhile, the water electrolysis hydrogen production tank (6) utilizes green electricity (17) to carry out electrolysis, hydrogen generated by electrolysis is sent into the ammonia synthesis device (5) to react, and oxygen generated by electrolysis is converged into the oxygen buffer tank (9); meanwhile, the ammonia synthesizer (5) synthesizes ammonia gas by utilizing hydrogen and nitrogen, and the synthesized ammonia gas is converged into an ammonia buffer tank (10);
in the process of changing the load of the boiler or improving the ammonia mixing ratio of the fuel gas, the ammonia mixing ratio in the gas mixing tank (7) is adjusted, the oxygen content in the combustion-supporting air is adjusted, and the concentration of the nitrogen oxides in the flue gas meets the emission requirement cooperatively.
10. The operation method of the natural gas ammonia-blending combustion system for coupling green hydrogen to prepare ammonia according to claim 9, wherein the mixing proportion of ammonia gas is 0-80% when the natural gas ammonia gas burner (1) operates, the excess air coefficient is 1.05-1.10, and the oxygen content in combustion air is 21-30%; the temperature of the flue gas at the outlet of the boiler (8) hearth is 800-1000 ℃; the concentration of nitrogen oxides in tail flue gas is not higher than 30mg/Nm 3 。
CN202210880050.8A 2022-07-25 2022-07-25 Natural gas ammonia-doped combustion system for coupling green hydrogen to produce ammonia and operation method Pending CN115127112A (en)

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