Secondary denitration equipment for flue gas of coal-fired power plant
By designing a secondary flue gas denitrification equipment containing medium and high temperature and ultra-low temperature SCR deburring systems in a coal-fired power plant, the ammonia injection system and high-energy particle grading distribution system are used to solve the problem of ammonia escape at low load by medium and high temperature SCR deburring systems, and lower concentration nitrogen oxide emissions and higher operating reliability are achieved.
Patent Information
- Application Number
- CN202421310091.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-11
- Publication Date
- 2025-06-06
- Estimated Expiration
- 2034-06-11
AI Technical Summary
The medium and high temperature SCR denitrification system cannot operate normally at low loads, resulting in ammonia escape, increasing the resistance of the flue gas system, reducing the economics of power generation, and adversely affecting the unit's operating stability.
A secondary denitrification equipment for flue gas in coal-fired power plants is designed, including medium and high temperature SCR denitrification systems and ultra-low temperature SCR denitrification systems. The ammonia injection system and high-energy particle grading distribution system are further removed in the ultra-low temperature SCR denitrification system to reduce ammonia escape.
It effectively reduces ammonia escape during the working process of the medium and high temperature SCR denitrification system, realizes the emission of nitrogen oxides at lower concentrations of flue gas, improves the operating reliability of tail flue equipment, and reduces maintenance costs.
Smart Images
Figure CN222943255U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of air pollutant treatment, in particular to a secondary denitration device for flue gas in a coal-fired power plant. Background Art
[0002] At present, the reaction temperature range of medium and high temperature SCR denitrification technology is generally in the range of 300-420℃. However, due to the low flue gas temperature during the start-up and shutdown of coal-fired power plant units or at low load, the lower temperature limit required by the technology cannot be reached, resulting in the inability to put the denitrification system into operation. It is necessary to modify this to increase the inlet flue gas temperature of the medium and high temperature SCR denitrification system at low load. When the unit is operating at normal load, the medium and high temperature SCR denitrification device will cause uneven distribution of ammonia nitrogen due to the uneven internal flow field, local ammonia escape, and cause corrosion and blockage of the air preheater after the denitrification system. The resistance of the flue gas system is increased, the power consumption rate of the plant is increased, and the economic efficiency of power generation is reduced. When the blockage is serious, it will have an adverse effect on the stability and reliability of the unit operation. Ammonia escape can also cause corrosion of the pole wires and plates of the electrostatic precipitator, reducing the dust removal efficiency. At the same time, ammonia escape will cause serious scaling in the wet desulfurization tower, make gypsum dehydration difficult, and affect the normal operation of the wet desulfurization system. Therefore, new technologies that can solve the above problems are urgently needed to be developed. Utility Model Content
[0003] The purpose of the utility model is to solve the shortcomings of the prior art and to propose a secondary denitrification equipment for flue gas in a coal-fired power plant, which can greatly reduce ammonia escape during the operation of a medium and high temperature SCR denitrification system, while achieving lower concentration nitrogen oxide emissions in the flue gas, improving the operating reliability of the tail flue equipment and reducing maintenance costs.
[0004] In order to achieve the above purpose, the utility model adopts the following technical solutions:
[0005] A secondary denitration device for flue gas in a coal-fired power plant, comprising a boiler, a medium-high temperature SCR denitration system, an air preheater, an ultra-low temperature SCR denitration system, a desulfurization tower, a chimney, and a fan. The flue gas discharged from the boiler first flows through the medium-high temperature SCR denitration system, then enters the air preheater, and then passes through a dust collector, and then enters the ultra-low temperature SCR denitration system. The flue gas then enters the desulfurization tower for desulfurization, and finally is blown into the chimney by the fan and discharged into the atmosphere.
[0006] The medium and high temperature SCR denitration system performs preliminary denitration on the flue gas and is arranged in the tail flue at the rear end of the boiler;
[0007] The air preheater utilizes the waste heat of the flue gas and cools it down, and is arranged between the medium and high temperature SCR denitrification system and the dust collector;
[0008] The dust collector adopts electrostatic dust removal or bag dust removal and is arranged before the ultra-low temperature SCR denitration system to filter the dust in the flue gas;
[0009] The desulfurization tower is installed at the rear end of the ultra-low temperature SCR denitration system to desulfurize the flue gas;
[0010] The desulfurization tower adopts wet desulfurization using limestone and gypsum, and further removes dust from the flue gas;
[0011] The ultra-low temperature SCR denitration system includes a gas purification system, a particle charging system, a high-energy particle classification distribution system, an instrument control system and an ultra-low temperature SCR catalyst, an SCR denitration reaction tower, an ammonia injection system, an ascending flue, and an exhaust flue;
[0012] The denitration reaction tower is used to install a fixed high-energy particle classification distribution system and an ultra-low temperature SCR catalyst;
[0013] The gas purification system is used to dehumidify the external air, purify impurities, and filter dust;
[0014] Preferably, the particle charging system converts the gas purified by the gas purification system into high-energy particles containing oxygen free radicals and singlet oxygen.
[0015] Preferably, the high-energy particle graded distribution system sprays high-energy particles into the flue gas uniformly and quantitatively while protecting the high-energy particles from energy annihilation.
[0016] Preferably, the high-energy particle classification distribution system is installed at the upper end of the denitration reaction tower to fully mix the high-energy particles with the flue gas before the flue gas passes through the ultra-low temperature SCR catalyst.
[0017] Preferably, the ultra-low temperature SCR catalyst is arranged in a honeycomb or plate type to ensure that the flue gas can fully react with the catalyst.
[0018] Preferably, the ultra-low temperature SCR catalyst is installed at the lower end of the high-energy particle classification distribution system to ensure that it can initially react with the high-energy particles and ammonia that are fully mixed with the flue gas.
[0019] Preferably, the ultra-low temperature SCR catalyst is used to convert NH3 molecules into -NH2 groups, which are used to capture NOx molecules in the flue gas to form NH2-M-NO intermediates.
[0020] Preferably, the ammonia injection system is installed inside the ascending flue, and its function is to control the amount of ammonia injection and to fully mix the ammonia and nitrogen oxides in the flue gas in a certain proportion.
[0021] Preferably, the instrument control system includes a flue gas flow detector and a nitrogen oxide concentration detector.
[0022] Preferably, the instrument control system adjusts the ammonia injection amount of the ammonia injection system and the operating power of the particle charging system in real time according to the flue gas flow rate and the nitrogen oxide concentration.
[0023] The coal-fired flue gas is first passed into the medium-high temperature SCR denitrification system for preliminary denitrification. The outlet is connected to the air preheater to perform heat exchange on the flue gas. The rear end of the air preheater is connected to the dust collector for dust removal. The flue gas after dust removal is passed into the ultra-low temperature SCR denitrification system. The ammonia injection system is installed inside the ascending flue. The instrument control system controls the ammonia injection amount and the particle charging system power according to the detected flue gas flow and nitrogen oxide concentration. The flue gas enters the system through the ascending flue, and the ammonia injection system injects ammonia into the ascending flue to fully mix it with the flue gas. The flue gas flows through the ascending flue to the upper end of the denitrification reaction tower, where a high-energy particle grading distribution system is installed. The high-energy particle grading distribution system sprays high-energy particles containing oxygen free radicals and singlet oxygen generated after dehumidification, impurity purification, dust filtration and particle charging by the gas purification system into the flue gas, mixes with the flue gas, and then passes through a single or multi-layer ultra-low temperature SCR catalyst layer. Inside the catalyst layer, the high-energy particles mixed in the flue gas convert the NH3 molecules adsorbed on the catalyst surface into -NH2 groups, which are used to capture NOx molecules in the flue gas to form NH2-M-NO intermediates, which are thermally decomposed at a relatively low temperature to generate N2 and H2O, completing the denitrification process. The denitrified flue gas is passed into the desulfurization tower to remove sulfur dioxide from the flue gas. The flue gas desulfurized by the desulfurization tower is blown into the chimney by a fan and discharged into the atmosphere.
[0024] The utility model discloses a secondary denitration device for flue gas in a coal-fired power plant, which can greatly reduce ammonia escape during the operation of a medium- and high-temperature SCR denitration system, while achieving lower concentration nitrogen oxide emissions from flue gas, improving the operating reliability of the tail flue equipment and reducing maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 This is a structural schematic diagram of a secondary denitration device for flue gas in a coal-fired power plant proposed by the utility model;
[0026] Figure 2 This is a schematic diagram of an ultra-low temperature SCR denitrification system of a secondary denitrification equipment for flue gas in a coal-fired power plant proposed by the utility model.
[0027] In the figure: 1. Boiler; 2. Medium and high temperature SCR denitrification system; 3. Air preheater; 4. Dust collector; 5. Ultra-low temperature SCR denitrification system; 6. Desulfurization tower; 7. Fan; 8. Chimney; As shown in the figure: 9. Upstream flue; 10. Ammonia injection system; 11. Gas purification system; 12. Instrument control system; 13. High-energy particle classification distribution system; 14. Ultra-low temperature SCR catalyst; 15. Exhaust flue; 16. Denitrification reaction tower; 17. Particle charging system. DETAILED DESCRIPTION
[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.
[0029] Example 1
[0030] This scheme is explained by taking the flue gas of a coal-fired power plant as an example. The specific scheme is as follows:
[0031] The secondary denitration equipment for flue gas in a coal-fired power plant is composed of a boiler 1, a medium-high temperature SCR denitration system 2, an ultra-low temperature SCR denitration system 5, a dust collector 4, a chimney 8, and an air preheater 3.
[0032] The flue gas generated by the boiler 1 flows through the medium and high temperature SCR denitrification system 2, the air preheater 3, the bag filter 4, the ultra-low temperature SCR denitrification system 5, the wet desulfurization tower 6 in sequence, and finally the flue gas is blown into the chimney 8 through the fan 7 and discharged into the atmosphere.
[0033] The desulfurization tower 6 is a limestone-gypsum wet desulfurization tower.
[0034] The ultra-low temperature SCR denitration system 5 is composed of a gas purification system 11, a particle charging system 17, a high-energy particle classification distribution system 13, an instrument control system 12, an ultra-low temperature SCR catalyst 14, a denitration reaction tower 16, an ammonia injection system 10, an ascending flue 9, and an exhaust flue 15.
[0035] The medium-high temperature SCR denitration system 2 is composed of a gas purification system 11 , a particle charging system 17 , an instrument control system 12 , a medium-high temperature SCR catalyst 14 , a denitration reaction tower 16 , an ammonia injection system 10 , an ascending flue 9 , and an exhaust flue 15 .
[0036] The gas purification system 11 is connected to the particle charging system 17, which is composed of the gas purification system 11, the particle charging system 17, the high-energy particle classification distribution system 13, the instrument control system 12, the ultra-low temperature SCR catalyst 14, the denitration reaction tower 16, the ammonia injection system 10, the rising flue 9, and the exhaust flue 15. The two systems are installed near the denitration reaction tower 16 and can be arranged in multiple layers. The high-energy particle classification distribution system 13 is arranged at the upper end of the denitration reaction tower 16, and the ultra-low temperature SCR catalyst 14 is arranged below the high-energy particle classification distribution system 13. The instrument control system 12 includes flue gas flow detection and nitrogen oxide concentration detection.
[0037] During the operation of the system, the flue gas generated by the boiler 1 is passed into the medium-high temperature SCR denitrification system 2 for preliminary denitrification. According to the flue gas flow field conditions upstream of the medium-high temperature SCR denitrification system 2, the denitrification efficiency of the medium-high temperature SCR denitrification system 2 is controlled not to exceed a certain limit, such as 80%, so as to minimize the amount of ammonia sprayed here and prevent ammonia escape. After passing through the medium-high temperature SCR denitrification system 2, the nitrogen oxide concentration in the flue gas is reduced to a lower concentration range, such as below 200 mg. The flue gas after preliminary denitrification is passed into the air preheater 3 for heat exchange to reduce the flue gas temperature to below 150°C, and then passed into the electrostatic precipitator 4. The dust concentration of the flue gas after dust removal is reduced to below 20 mg, and then passed into the ultra-low temperature SCR denitrification system 5. Inside the ultra-low temperature SCR denitration system 5, ammonia is sprayed into the ascending flue 9 through the ammonia spraying system 10 to mix with the flue gas, and the air is purified by the gas purification system 11 and then passed into the particle charging system 17. After the high-energy particles are generated, they are sent to the high-energy particle classification distribution system 13 through the pipeline, and then sprayed into the flue gas. The instrument control system 12 controls the ammonia spraying amount of the ammonia spraying system 10 and the power of the particle charging system 17 according to the flue gas flow rate and the nitrogen oxide concentration. The ammonia and high-energy particles sprayed into the flue gas react with the nitrogen oxides in the flue gas on the catalyst surface with the help of the ultra-low temperature SCR catalyst 14 to generate N2 and H2O, and the nitrogen oxide concentration in the flue gas is reduced to less than 50mg. The flue gas after denitration is discharged through the lower exhaust flue 15 of the denitration reaction tower 16. Then the flue gas is passed into the wet desulfurization tower 6 to remove sulfur dioxide in the flue gas, so that the sulfur dioxide concentration in the flue gas is reduced to less than 35mg, and the dust concentration is reduced to less than 10mg. The treated flue gas is blown into the chimney 8 through the fan 7 and discharged into the atmosphere.
[0038] Based on the above principles, the various structural combinations of this embodiment are as follows:
[0039] like Figure 1-2 As shown, the secondary denitration equipment for flue gas in a coal-fired power plant of this embodiment includes a boiler 1, a medium-high temperature SCR denitration system 2, an air preheater 3, an ultra-low temperature SCR denitration system 5, a desulfurization tower 6, a chimney 8, and a fan 7. The flue gas discharged from the boiler 1 first flows through the medium-high temperature SCR denitration system 2, then passes through the air preheater 3, and then passes through the dust collector 4, and then passes through the ultra-low temperature SCR denitration system 5, and then the flue gas enters the desulfurization tower 6 for desulfurization, and finally blows into the chimney 8 through the fan 7 and is discharged into the atmosphere;
[0040] The medium and high temperature SCR denitration system 2 performs preliminary denitration on the flue gas and is arranged in the tail flue at the rear end of the boiler 1;
[0041] The air preheater 3 utilizes the waste heat of the flue gas and cools it down, and is arranged between the medium and high temperature SCR denitrification system 2 and the dust collector 4;
[0042] The dust collector 4 uses electrostatic dust removal or bag dust removal and is arranged before the ultra-low temperature SCR denitration system 5 to filter the dust in the flue gas;
[0043] The desulfurization tower 6 is installed at the rear end of the ultra-low temperature SCR denitration system 5 to desulfurize the flue gas;
[0044] Desulfurization tower 6 uses wet desulfurization using limestone and gypsum, and further removes dust from the flue gas;
[0045] The ultra-low temperature SCR denitration system 5 includes a gas purification system 11, a particle charging system 17, a high-energy particle classification distribution system 13, an instrument control system 12, an ultra-low temperature SCR catalyst 14, an SCR denitration reaction tower 16, an ammonia injection system 10, an ascending flue 9, and an exhaust flue 15;
[0046] The denitration reaction tower 16 is used to install and fix the high-energy particle classification distribution system 13 and the ultra-low temperature SCR catalyst 14;
[0047] The gas purification system 11 is used to dehumidify the external air, purify impurities, and filter dust;
[0048] In this embodiment, the particle charging system 17 converts the gas purified by the gas purification system 11 into high-energy particles containing oxygen free radicals and singlet oxygen.
[0049] In this embodiment, the high-energy particle classification distribution system 13 sprays high-energy particles into the flue gas uniformly and quantitatively while protecting the high-energy particles from energy annihilation.
[0050] In this embodiment, the high-energy particle classification distribution system 13 is installed at the upper end of the denitration reaction tower 16 to fully mix the high-energy particles with the flue gas before the flue gas passes through the ultra-low temperature SCR catalyst 14 .
[0051] In this embodiment, the ultra-low temperature SCR catalyst 14 is arranged in a honeycomb or plate type to ensure that the flue gas can fully react with the catalyst.
[0052] In this embodiment, the ultra-low temperature SCR catalyst 14 is installed at the lower end of the high-energy particle classification distribution system 13 to ensure that the high-energy particles and ammonia that are fully mixed with the flue gas can react initially.
[0053] In this embodiment, the ultra-low temperature SCR catalyst 14 is used to convert NH3 molecules into -NH2 groups, which are used to capture NOx molecules in the flue gas to form NH2-M-NO intermediates.
[0054] In this embodiment, the ammonia injection system 10 is installed inside the ascending flue 9. Its function is to control the amount of ammonia injection and to fully mix the ammonia and nitrogen oxides in the flue gas in a certain proportion.
[0055] In this embodiment, the instrument control system 12 includes a flue gas flow detector and a nitrogen oxide concentration detector.
[0056] In this embodiment, the instrument control system 12 adjusts the ammonia injection amount of the ammonia injection system 10 and the operating power of the particle charging system 17 in real time according to the flue gas flow rate and the nitrogen oxide concentration.
[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A secondary denitrification equipment for flue gas in a coal-fired power plant, characterized in that: The invention comprises a boiler (1), a medium-high temperature SCR denitration system (2), an air preheater (3), an ultra-low temperature SCR denitration system (5), a desulfurization tower (6), a chimney (8), and a fan (7). The flue gas discharged from the boiler (1) first flows through the medium-high temperature SCR denitration system (2), then enters the air preheater (3), and then passes through a dust collector (4), and then enters the ultra-low temperature SCR denitration system (5). The flue gas then enters the desulfurization tower (6) for desulfurization, and finally is blown into the chimney (8) through the fan (7) and discharged into the atmosphere. The medium-high temperature SCR denitration system (2) performs preliminary denitration on the flue gas and is arranged in the tail flue at the rear end of the boiler (1); The air preheater (3) utilizes waste heat from the flue gas and reduces its temperature, and is arranged between the medium- and high-temperature SCR denitrification system (2) and the dust collector (4); The dust collector (4) uses electrostatic dust removal or bag dust removal and is arranged before the ultra-low temperature SCR denitration system (5) to filter dust in the flue gas; The desulfurization tower (6) is installed at the rear end of the ultra-low temperature SCR denitration system (5) to desulfurize the flue gas; The desulfurization tower (6) uses limestone and gypsum for wet desulfurization and further removes dust from the flue gas; The ultra-low temperature SCR denitration system (5) comprises a gas purification system (11), a particle charging system (17), a high-energy particle classification distribution system (13), an instrument control system (12), an ultra-low temperature SCR catalyst (14), an SCR denitration reaction tower (16), an ammonia injection system (10), an ascending flue (9), and an exhaust flue (15); The denitration reaction tower (16) is used to install and fix the high-energy particle classification distribution system (13) and the ultra-low temperature SCR catalyst (14); The gas purification system (11) is used to dehumidify the external air, purify impurities, and filter dust.
2. The secondary denitration equipment for flue gas from a coal-fired power plant according to claim 1, characterized in that: The high-energy particle classification distribution system (13) is installed at the upper end of the denitration reaction tower (16) to fully mix the high-energy particles with the flue gas before the flue gas passes through the ultra-low temperature SCR catalyst (14).
3. The secondary denitration equipment for flue gas in a coal-fired power plant according to claim 1, characterized in that: The ultra-low temperature SCR catalyst (14) is arranged in a honeycomb or plate type to ensure that the flue gas can fully react with the catalyst.
4. The secondary denitrification equipment for flue gas in a coal-fired power plant according to claim 1, characterized in that: The ultra-low temperature SCR catalyst (14) is installed at the lower end of the high-energy particle classification distribution system (13) to ensure that the high-energy particles and ammonia that are fully mixed with the flue gas can react initially.
5. The secondary denitration equipment for flue gas in a coal-fired power plant according to claim 1, characterized in that: The ammonia injection system (10) is installed inside the ascending flue (9) and its function is to control the amount of ammonia injection and to fully mix the ammonia with the nitrogen oxides in the flue gas in a certain proportion.
6. The secondary denitration equipment for flue gas in a coal-fired power plant according to claim 1, characterized in that: The instrument control system (12) includes a flue gas flow detector and a nitrogen oxide concentration detector.
7. The secondary denitration equipment for flue gas in a coal-fired power plant according to claim 1, characterized in that: The instrument control system (12) adjusts the ammonia injection amount of the ammonia injection system (10) and the operating power of the particle charging system (17) in real time according to the flue gas flow rate and the nitrogen oxide concentration.