System and method for producing ammonia by flexibly adjusting coal power unit

Abstract

The invention belongs to the technical field of thermal power generation, and relates to a system and a method for producing ammonia by flexibly adjusting a coal power unit. The system comprises a boiler body and a fuel cell, the boiler body is connected with the steam turbine; the steam turbine is connected with the generator; the generator is connected with a first electric energy receiving inlet of the load control center; the fuel cell is connected with a second electric energy receiving inlet of the load control center; the first electric energy outlet of the load control center is electrically connected with the power grid; the power grid first load control outlet is electrically connected with the load control center; a second load control outlet of the load control center is electrically connected with the boiler body; and a third load control outlet of the load control center is electrically connected with the fuel cell. The requirement for flexible peak regulation of the unit is met, and a reducing agent is provided for flue gas denitration equipment of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation, and relates to a system and method for producing ammonia by flexible regulation of a coal-fired power unit. Background Art

[0002] In the energy and power sector, traditional coal-fired power has always played a key role in ensuring the stable operation of the power grid. Existing technologies involve traditional coal-fired power units participating in grid peak regulation by reducing their load to adapt to fluctuating power demand during different periods and maintain the supply and demand balance of the power system. Ammonia (NH3) also plays a crucial role in coal-fired power systems. It serves as a reducing agent in coal-fired power unit denitrification equipment. In selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR) denitrification technologies, it selectively reduces nitrogen oxides (NOx) in flue gas to harmless nitrogen (N2) and water (H2O), effectively reducing NOx emissions during coal-fired power generation and minimizing atmospheric pollution.

[0003] However, traditional coal-fired power generation peak-shaving technology presents numerous challenges. First, regarding peak-shaving capacity, traditional coal-fired power units are subject to a minimum steady-fire load limit, typically no less than 30% of rated load. This means that when grid demand decreases further, coal-fired power units cannot continue to reduce their load to meet peak-shaving requirements, limiting their peak-shaving capacity and making it difficult to fully adapt to the grid's increasingly complex peak-shaving demands. Second, from an economic and environmental perspective, when coal-fired power units operate at low load, their coal consumption rate increases significantly. This increase in coal consumption rate not only increases power generation costs but also increases carbon emissions per unit of electricity generated, running counter to the current global trend of energy conservation, emission reduction, and climate change response. Furthermore, regarding ammonia utilization, current water electrolysis technology is expensive, with production costs reaching approximately 4,000 yuan per ton. This significantly limits its large-scale application as a zero-carbon fuel and hydrogen energy carrier. Furthermore, the flexible peak-shaving process of coal-fired power units generates surplus electricity, which is not effectively utilized, resulting in energy waste.

[0004] Therefore, how to solve problems such as insufficient peak-shaving capacity of traditional coal-fired power, high carbon emissions from low-load operation, high cost of ammonia production, and utilization of surplus electricity has become a technical challenge that urgently needs to be overcome in the current energy and power field. Summary of the Invention

[0005] In order to solve the problems in the prior art, the present invention provides a system and method for flexible regulation of ammonia production of coal-fired power units, which not only meets the needs of flexible peak regulation of the units, but also provides a reducing agent for the unit's flue gas denitrification equipment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a flexible regulation ammonia production system for a coal-fired power unit, comprising a boiler body and a fuel cell; the boiler body is connected to a steam turbine; the steam turbine is connected to a generator; the generator is connected to a first power receiving inlet of a load control center; the fuel cell is connected to a second power receiving inlet of a load control center; the first power outlet of the load control center is electrically connected to a power grid; the first load control outlet of the power grid is electrically connected to the load control center; the second load control outlet of the load control center is electrically connected to the boiler body; and the third load control outlet of the load control center is electrically connected to the fuel cell.

[0007] Preferably, the second power outlet of the load control center is electrically connected to an air separation device; and the air separation device is connected to an oxygen storage tank and a nitrogen storage tank respectively.

[0008] Preferably, the second power outlet of the load control center is electrically connected to the electrolyzer; the electrolyzer is connected to a gas separator; and the gas separator is connected to a hydrogen storage tank and an oxygen storage tank, respectively.

[0009] Preferably, the fuel cell and the electrolyzer are electrically connected.

[0010] Preferably, the hydrogen storage tank and the oxygen storage tank are both connected to the fuel cell.

[0011] Preferably, the hydrogen storage tank and the nitrogen storage tank are both connected to an ammonia generator.

[0012] Preferably, the ammonia generator is connected to an ammonia storage tank.

[0013] Preferably, the ammonia generator inlet is connected to the boiler body outlet; the boiler body inlet is connected to the ammonia generator outlet.

[0014] Preferably, the ascending flue of the boiler body is connected to the flue gas denitrification equipment; the ascending flue is connected to the ammonia storage tank.

[0015] In a second aspect, the present invention provides a method for producing ammonia by flexibility regulation of a coal-fired power unit, comprising the following steps: The load control center receives load instructions from the power grid and controls the working load of the boiler body. The boiler body generates steam to the steam turbine to do work, and the steam turbine drives the generator to generate electricity, and the electric energy is transmitted to the load control center; the load control center transmits electric energy to the grid according to the load instructions of the power grid. The vacant power is supplied by the fuel cell controlled by the load control center, and the surplus power is recycled and reused.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention controls the workload of the boiler body and the fuel cell through a load control center. When the boiler load is insufficient, the fuel cell provides energy in a coordinated manner. When the boiler generates surplus electricity, it can be fully utilized. This not only realizes the storage and recycling of electric energy, but also realizes the flexible peak regulation of coal-fired power units, and has the characteristics of flexible regulation, zero carbon and no pollution.

[0017] Furthermore, the present invention utilizes the product of water electrolysis in the flexible peak regulation of coal-fired power units to supply fuel cells as fuel, thereby realizing the secondary conversion and efficient utilization of electric energy.

[0018] Furthermore, the hydrogen and nitrogen produced by the air separation unit are used as raw materials for ammonia production, and the heat source of the boiler itself (high-temperature flue gas / water) is used to power the ammonia production process. The synergistic effect provides a reducing agent for the flue gas denitrification equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a structural schematic diagram of a flexible adjustment ammonia production system for a coal-fired power unit according to the present invention.

[0021] Among them: 1. Boiler body; 2. Steam turbine; 3. Generator; 4. Load control center; 5. Power grid; 6. Fuel cell; 7. Hydrogen storage tank; 8. Oxygen storage tank; 9. Nitrogen storage tank; 10. Gas separator; 11. Air separation unit; 12. Ammonia storage tank; 13. Ammonia generator; 14. Electrolyzer. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0024] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0025] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0027] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0028] The present invention is described in further detail below with reference to the accompanying drawings: The first object of the present invention is to provide a coal-fired power unit flexibility adjustment ammonia production system, such as Figure 1 As shown, it includes a boiler body 1 and a fuel cell 6; the boiler body 1 is connected to the steam turbine 2; the steam turbine 2 is connected to the generator 3; the generator 3 is connected to the first power receiving inlet of the load control center 4; the fuel cell 6 is connected to the second power receiving inlet of the load control center 4; the first power outlet of the load control center 4 is electrically connected to the power grid 5; the first load control outlet of the power grid 5 is electrically connected to the load control center 4; the second load control outlet of the load control center 4 is electrically connected to the boiler body 1; and the third load control outlet of the load control center 4 is electrically connected to the fuel cell 6.

[0029] Boiler 1 burns coal to generate high-temperature, high-pressure steam, which powers steam turbine 2. Its workload is dynamically adjusted by load control center 4. Load control enables rapid response to grid 5 demand and adapts to the volatility of renewable energy sources such as wind and solar power. Steam turbine 2 converts the thermal energy of the high-temperature, high-pressure steam generated by boiler 1 into mechanical energy, driving generator 3. Generator 3 converts the mechanical energy of steam turbine 2 into electrical energy, which is transmitted to load control center 4. Load control center 4 receives load commands from grid 5 and dynamically allocates power flow between boiler 1, fuel cell 6, and grid 5. It adjusts boiler 1 load and fuel cell 6 output in real time based on grid 5 demand to balance supply and demand. Because boiler 1's workload lags behind load commands, rapid load reductions generate surplus power, which can be recycled. Rapid load increases create a power gap, which is supplied by fuel cell 6, enabling flexible peak-shaving requirements for coal-fired power units. Grid 5 issues load commands to load control center 4 and receives power input from it. Through these commands, grid 5 coordinates supply and demand, enhancing grid 5 stability. The fuel cell 6 serves as a backup power source, which can respond to load vacancies, compensate for the regulation delay of the coal-fired power unit, and supplement power supply when the peak regulation capacity of the coal-fired power is insufficient.

[0030] The second power outlet of the load control center 4 is electrically connected to the air separation unit 11; the air separation unit 11 is connected to the oxygen storage tank 8 and the nitrogen storage tank 9, respectively. The surplus power of the load control center 4 provides stable power support for the air separation unit 11, ensuring its efficient operation. The separated oxygen and nitrogen are stored separately, achieving rational energy allocation and utilization, and ensuring the stability and sustainability of the air separation process.

[0031] The second power outlet of the load control center 4 is electrically connected to the electrolyzer 14; the electrolyzer 14 is connected to the gas separator 10; and the gas separator 10 is connected to the hydrogen storage tank 7 and the oxygen storage tank 8, respectively. The excess power of the load control center 4 can also provide stable power support for the electrolyzer 14. The electrolyzer 14 uses this electricity to electrolyze water, continuously producing a hydrogen and oxygen mixed gas. This mixed gas then enters the gas separator 10, where it is separated into high purity using pressure swing adsorption (PSA) or membrane separation technology. The separated hydrogen is stored in the hydrogen storage tank 7, and the oxygen is stored in the oxygen storage tank 8, achieving resource recovery and utilization of oxygen and hydrogen.

[0032] Exemplarily, the fuel cell 6 is electrically connected to the electrolyzer 14. When the boiler body 1 is in a low-load operating state and the load control center 4 has no surplus power, the fuel cell 6 supplies energy, and the generated electricity is directly supplied to the electrolyzer 14 to maintain the electrolytic hydrogen production process.

[0033] The hydrogen storage tank 7 and the oxygen storage tank 8 are both connected to the fuel cell 6. The hydrogen storage tank 7 continuously provides high-purity fuel to the fuel cell 6, while the oxygen storage tank 8 replaces the traditional air oxygen supply method and directly delivers pure oxygen to the fuel cell 6, making the electrochemical reaction more efficient and controllable.

[0034] The hydrogen storage tank 7 and the nitrogen storage tank 9 are both connected to the ammonia generator 13. The inlet of the ammonia generator 13 is connected to the outlet of the boiler body 1; the inlet of the boiler body 1 is connected to the outlet of the ammonia generator 13, and the ammonia generator 13 is connected to the ammonia storage tank 12. The ammonia generator 13 uses high-purity hydrogen and nitrogen to synthesize ammonia under high temperature and high pressure conditions. Its heat source comes from the high-temperature flue gas / water of the boiler body 1. The product is stored in the ammonia storage tank 12, providing a stable ammonia source for the coal-fired power unit equipment. After energy supply, the high-temperature flue gas / water forms low-temperature flue gas / water, which enters the boiler body 1 and is heated again, and circulated to supply energy for the ammonia synthesis reaction. This not only realizes the recycling of the medium, but also can recover the waste heat in the medium after energy supply.

[0035] The flue riser of the boiler body 1 is connected to the flue gas denitrification equipment; this riser is also connected to an ammonia storage tank 12. The ammonia stored in the ammonia storage tank 12 also serves as a reducing agent for the flue gas denitrification equipment. The high-temperature, turbulent flow of the flue riser allows the ammonia to be fully mixed with the boiler flue gas, ensuring sufficient contact and efficient conversion of the SCR / SNCR reaction.

[0036] The present invention combines the electrolysis of water to produce hydrogen with the waste heat utilization technology of flue gas, thereby realizing the effective utilization of resources; by adding ammonia production equipment and fuel cell 6, it not only realizes the demand for flexible peak regulation of the unit, but also provides a reducing agent for the denitrification equipment of the unit, effectively solving the problem of flexible peak regulation. Specifically, the present invention constructs an energy buffer unit through the electrolysis of water device and fuel cell 6, effectively improving the load response rate and deep peak regulation capability of the unit; at the same time, the waste heat of boiler flue gas is used to prepare the ammonia reducing agent required for denitrification, realizing the coordinated optimization of energy cascade utilization and environmental protection and emission reduction. The present invention has the significant advantages of multi-energy coupling and coordinated utilization of resources. It not only solves the contradiction between the peak regulation flexibility of coal-fired power units and the demand for denitrification, but also greatly improves the overall system energy efficiency, and provides an innovative solution for the transformation and upgrading of coal-fired power units in new power systems. It has important engineering application value and social and economic benefits.

[0037] A second object of the present invention is to provide a method for producing ammonia by flexibility regulation of a coal-fired power unit, comprising the following steps: The load control center 4 receives the load instruction from the power grid 5 and controls the working load of the boiler body 1. The boiler body 1 generates steam to the steam turbine 2 to perform work. The steam turbine 2 drives the generator 3 to generate electricity, and the electric energy is transmitted to the load control center 4; the load control center 4 transmits electric energy to the power grid 5 according to the load instruction of the power grid 5. The idle power is supplied by the fuel cell 6 controlled by the load control center 4, and the surplus power is recycled and reused.

[0038] Exemplarily, surplus electricity is supplied to the air separation device 11 and the electrolyzer 14. The air separation device 11 can separate nitrogen and oxygen in the air and store them in the oxygen storage tank 8 and the nitrogen storage tank 9. The electrolyzer 14 produces hydrogen and oxygen by electrolyzing water, which are separated into hydrogen and oxygen by the gas separator 10 and stored in the hydrogen storage tank 7 and the oxygen storage tank 8. When there is no surplus electricity supplied to the electrolyzer 14, the fuel cell 6 can directly supply energy to the electrolyzer 14 to provide sufficient power support for the electrolytic production of hydrogen and oxygen.

[0039] The hydrogen in hydrogen tank 7 and some of the oxygen in oxygen tank 8 serve as fuel for fuel cell 6, where an electrochemical reaction occurs to directly generate electricity. Some of the oxygen in oxygen tank 8 and nitrogen in nitrogen tank 9 are transported to ammonia generator 13, where ammonia is synthesized under high temperature and pressure. The heat source is the high-temperature flue gas / water extracted from boiler 1. The synthesized ammonia is transported to ammonia tank 12 and, when needed, to boiler 1 to provide a reducing agent. After being energized, the high-temperature flue gas / water is converted to low-temperature flue gas / water, which then enters boiler 1 for further heating.

[0040] The present invention achieves rapid response and flexible adjustment of load instructions of the power grid 5 by synergistically integrating the coal-fired power unit with the fuel cell 6 and the ammonia production system. The load control center 4 dynamically allocates the power supply ratio of coal-fired power and fuel cell 6 according to the needs of the power grid 5, which not only ensures the stability of the power grid 5 and meets the needs of flexible peak regulation of the units; it also achieves efficient conversion and storage of energy through ammonia production with surplus electricity, and provides a reducing agent for the denitrification equipment of the coal-fired power unit. The present invention significantly improves the peak regulation depth and operational flexibility of the coal-fired power unit, and at the same time reduces the carbon emission intensity through the multi-energy coupling of electricity, hydrogen and ammonia, providing an innovative path for the low-carbon transformation of traditional thermal power.

[0041] The working principle of the system of the present invention is: When the coal-fired power unit is below the minimum steady-fire load for peak load regulation, since the load instruction of the power grid 5 is less than the minimum load of the unit, the load control center 4 controls the boiler body 1 to generate electricity at the minimum load, and at the same time supplies power to the power grid 5 according to the load instruction of the power grid 5. The surplus power when the minimum load of the boiler body 1 is higher than the load instruction of the power grid 5 is used for hydrogen electrolysis and air separation, and the generated hydrogen, oxygen and nitrogen are stored in the hydrogen storage tank 7, oxygen storage tank 8 and nitrogen storage tank 9 respectively.

[0042] When the coal-fired power unit rapidly reduces its load, the boiler body 1 has a slow load change rate and is unable to adapt to the rapid change of the load instruction. At this time, the load control center 4 controls the boiler body 1 to reduce its load and generate electricity at its maximum change rate, while supplying power to the power grid 5 according to the load instruction of the power grid 5. The surplus power when the actual load of the boiler body 1 is higher than the load instruction of the power grid 5 is used for electrolysis of water to produce hydrogen and air separation, and the generated hydrogen, oxygen and nitrogen are stored in the hydrogen storage tank 7, oxygen storage tank 8 and nitrogen storage tank 9 respectively.

[0043] When the coal-fired power unit increases its load rapidly, the boiler body 1 has difficulty adapting to the rapid change of the load instruction due to its slow load change speed. At this time, the load control center 4 controls the boiler body 1 to increase the load and generate electricity at its maximum change rate, and at the same time supplies power to the power grid 5 according to the load instruction of the power grid 5. The power gap caused by the actual load of the boiler body 1 being lower than the load instruction of the power grid 5 is supplemented by the power generation of the fuel cell 6. The load control center 4 adjusts the power generation load of the fuel cell 6 in real time according to the size of the power gap.

[0044] The present invention flexibly regulates the operation of coal-fired power units under different load conditions through a load control center. Under different load conditions, such as low-load peak shaving, rapid load reduction, and load increase, when the boiler body 1 is underloaded, the fuel cell 6 compensates for the power shortfall. When the boiler body 1 is overloaded, the surplus power is used for hydrogen production through water electrolysis and air separation, recovering hydrogen, oxygen, and nitrogen. This achieves the flexible peak shaving requirements of the unit and the efficient use of electricity. Simultaneously, the heat from the boiler body 1 can be used to produce ammonia, providing a reducing agent for the unit's flue gas denitrification equipment, thus fully utilizing resources.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A flexible adjustment ammonia production system for coal-fired power units, characterized in that: The invention comprises a boiler body (1) and a fuel cell (6); the boiler body (1) is connected to a steam turbine (2); the steam turbine (2) is connected to a generator (3); the generator (3) is connected to a first power receiving inlet of a load control center (4); the fuel cell (6) is connected to a second power receiving inlet of the load control center (4); a first power outlet of the load control center (4) is electrically connected to a power grid (5); a first load control outlet of the power grid (5) is electrically connected to the load control center (4); a second load control outlet of the load control center (4) is electrically connected to the boiler body (1); and a third load control outlet of the load control center (4) is electrically connected to the fuel cell (6).

2. The ammonia production system with flexible regulation of coal-fired power units according to claim 1, characterized in that: The second power outlet of the load control center (4) is electrically connected to the air separation device (11); the air separation device (11) is respectively connected to the oxygen storage tank (8) and the nitrogen storage tank (9).

3. The ammonia production system with flexible adjustment of coal-fired power units according to claim 2, characterized in that: The second power outlet of the load control center (4) is electrically connected to the electrolyzer (14); the electrolyzer (14) is connected to the gas separator (10); and the gas separator (10) is respectively connected to the hydrogen storage tank (7) and the oxygen storage tank (8).

4. A coal-fired power unit flexibility adjustment ammonia production system according to claim 3, characterized in that: The fuel cell (6) and the electrolyzer (14) are electrically connected.

5. The ammonia production system with flexible regulation of coal-fired power units according to claim 3, characterized in that: The hydrogen storage tank (7) and the oxygen storage tank (8) are both connected to the fuel cell (6).

6. The ammonia production system with flexible regulation of coal-fired power units according to claim 3, characterized in that: The hydrogen storage tank (7) and the nitrogen storage tank (9) are both connected to the ammonia generator (13).

7. The ammonia production system with flexible regulation of coal-fired power units according to claim 1, characterized in that: The ammonia generator (13) is connected to the ammonia storage tank (12).

8. The ammonia production system with flexible regulation of coal-fired power units according to claim 7, characterized in that: The inlet of the ammonia generator (13) is connected to the outlet of the boiler body (1); the inlet of the boiler body (1) is connected to the outlet of the ammonia generator (13).

9. The ammonia production system with flexible regulation of coal-fired power units according to claim 7, characterized in that: The ascending flue of the boiler body (1) is connected to the flue gas denitrification equipment; and the ascending flue is connected to the ammonia storage tank (12).

10. A method for producing ammonia by flexible regulation of coal-fired power units, characterized in that: The system according to any one of claims 1 to 9 comprises the following steps: The load control center (4) receives the load instruction from the power grid (5) and controls the working load of the boiler body (1). The boiler body (1) generates steam to the steam turbine (2) to perform work. The steam turbine (2) drives the generator (3) to generate electricity, and the electric energy is transmitted to the load control center (4). The load control center (4) transmits electric energy to the power grid (5) according to the load instruction from the power grid (5). The vacant power is supplied by the fuel cell (6) controlled by the load control center (4), and the surplus power is recycled and utilized.

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