Compactly-arranged flue gas system and coal-fired boiler with same

Abstract

The invention discloses a compactly-arranged flue gas system and a coal-fired boiler with the same, and relates to the technical field of coal-fired units of power plants. The tail shaft is provided with an air inlet channel, a middle channel and an exhaust channel which are sequentially communicated, the air inlet channel is provided with an air inlet, the exhaust channel is provided with an air outlet, the middle channel is divided into a furnace front flue and a furnace rear flue through a flue partition wall, and a heat exchange pipe is arranged in the furnace front flue. Flue gas in the gas inlet channel can flow into the furnace front flue and the furnace rear flue respectively and is converged and mixed in the exhaust channel, flue gas heat recycling is achieved through a heat exchange pipe of the furnace front flue, high-temperature flue gas can be reserved in the furnace rear flue, after the flue gas heat and the high-temperature flue gas are mixed, the flue gas temperature at an outlet of the exhaust channel can be accurately increased, and it is ensured that the flue gas temperature at an inlet of the SCR denitration system is in the optimal reaction interval; the problem that the SCR catalyst does not work under low load is solved.

Description

Technical Field

[0001] This invention relates to the field of power plant coal-fired unit technology, specifically to a compactly arranged flue gas system and a coal-fired boiler having the same. Background Technology

[0002] With the vigorous development of new energy power generation technology, coal-fired power units have changed from playing a basic load role to mainly playing an auxiliary role, but they still play a ballast role. As the energy storage equipment of coal-fired power plants, the strength of the deep peak-shaving capacity of coal-fired power plant boilers directly affects the survival of power plants. Environmental indicators are the key indicators that power plants pay close attention to, and NOx emissions are the most important focus of environmental indicators. Under deep peak-shaving and low load conditions, this indicator is still a key issue of concern.

[0003] Large coal-fired power plants commonly use SCR (Selective Catalytic Reduction) denitrification systems to reduce NOx emission concentrations in flue gas. The SCR system utilizes the reduction properties of NH3 on NOx, reducing NOx to environmentally harmless N2 and H2O under the action of a catalyst. The optimal reaction temperature for SCR is 300–400℃, which is equivalent to the flue gas temperature from the economizer outlet to the air preheater inlet. In actual operation, the main problem currently encountered is that at low loads, the flue gas temperature is low, and the SCR catalyst may not work, leading to an increase in NOx concentration in the outlet flue gas. In severe cases, this can cause the power plant to fail to meet environmental protection standards at low loads. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of [the problem]. Furthermore, it provides a compactly arranged flue gas system and a coal-fired boiler having the same.

[0005] The technical solution of the present invention is: a compactly arranged flue gas system, comprising: a tail shaft having an air inlet channel, an intermediate channel and an exhaust channel connected in sequence, wherein the air inlet channel is provided with an air inlet and the exhaust channel is provided with an air outlet;

[0006] The intermediate channel is divided into a front flue and a rear flue by a flue partition wall, and heat exchange tubes are arranged in the front flue.

[0007] The flue gas in the intake channel can flow into the front flue and the rear flue respectively, and then converge and mix in the exhaust channel.

[0008] Furthermore, the furnace front flue has two side by side, with the two furnace front flues located on one side and the furnace rear flue located on the other side.

[0009] Furthermore, the air inlet is located at the top of the tail shaft, and the air outlet is located at the bottom of the tail shaft.

[0010] Furthermore, the flue partition wall is a modular wall structure or a steel plate structure.

[0011] Furthermore, the flue wall of the tail shaft is a membrane wall structure.

[0012] Furthermore, the heat exchange tubes are arranged in a serpentine tube configuration.

[0013] Furthermore, it also includes: a baffle plate disposed in the area where the flue gas duct behind the furnace communicates with the air inlet channel, the baffle plate being used to guide the flue gas into the flue gas duct behind the furnace.

[0014] Furthermore, each of the two furnace front flues and the furnace rear flue outlet is provided with a pull-out first baffle, which adjusts the flue gas volume of each flue.

[0015] Furthermore, a pull-out second baffle is provided at the outlet of one of the furnace front flues, through which the flue gas volume of the two furnace front flues is adjusted.

[0016] A coal-fired boiler includes: a flue gas system with a compact arrangement as described in any of the above embodiments.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The compact flue gas system provided by this invention enables the heat exchange tubes in the flue gas in front of the furnace to recover and utilize the heat of the flue gas, while the flue gas behind the furnace can retain high-temperature flue gas. After the two are mixed, the flue gas temperature at the outlet of the exhaust channel can be precisely increased, ensuring that the inlet flue gas temperature of the SCR denitrification system is in the optimal reaction range, thus solving the problem of SCR catalyst not working under low load.

[0019] 2. The compact flue gas system provided by the present invention integrates the intake channel, intermediate channel and exhaust channel into an integrated connected structure in the tail shaft, and concentrates the flue gas flow path in the same shaft. Compared with the traditional decentralized flue gas bypass system, it greatly reduces the footprint and is suitable for installation scenarios with limited space at the tail of power plants, avoiding the problem that traditional systems cannot be arranged due to insufficient space. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 yes Figure 1 Side view of the flue in front of the furnace.

[0022] In the diagram: 1. Inlet channel; 2. Intermediate channel; 3. Exhaust channel; 4. Inlet; 5. Outlet; 6. Front flue; 7. Rear flue; 8. Heat exchange tube; 9. Guide plate; 10. Flue wall; 11. First baffle; 12. Second baffle; 13. Flue partition wall. Detailed Implementation

[0023] Specific implementation method one: Combining Figure 1 , Figure 2 This embodiment describes a tail shaft, which has an intake channel 1, a middle channel 2, and an exhaust channel 3 connected in sequence. The intake channel 1 is provided with an intake port 4, and the exhaust channel 3 is provided with an exhaust port 5. The middle channel 2 is divided into a front flue 6 and a rear flue 7 by a flue partition wall 13. A heat exchange tube 8 is arranged in the front flue 6. The flue gas in the intake channel 1 can flow into the front flue 6 and the rear flue 7 respectively, and then converge and mix in the exhaust channel 3. The mixed flue gas enters the SCR denitrification system.

[0024] The compact flue gas system of this embodiment allows for the recovery and utilization of flue gas heat through the heat exchange tubes 8 in the flue duct 6 before the furnace, while the flue duct 7 after the furnace can retain high-temperature flue gas. The mixture of the two can precisely increase the flue gas temperature at the outlet of the exhaust channel 3, ensuring that the inlet flue gas temperature of the SCR denitrification system is in the optimal reaction range, thus solving the problem of SCR catalyst not working under low load.

[0025] Specific Implementation Method Two: Combining Figure 1 , Figure 2 This embodiment differs from specific embodiment one in that it has two flue ducts 6 arranged side-by-side, with two flue ducts 6 on one side and one flue duct 7 on the other side, forming a triangular distribution. The symmetrical arrangement of the two flue ducts 6 allows for more uniform flue gas distribution and more stable heat exchange efficiency of the heat exchange tubes 8. The flue duct 7 is arranged independently on one side, reducing airflow interference with the flue ducts 6, ensuring the high-temperature characteristics of the bypass flue gas, and resulting in higher precision in flue gas temperature regulation after mixing. Other components and connections are the same as in specific embodiment one.

[0026] Specific implementation method three: Combining Figure 1 This embodiment differs from Specific Embodiment 1 in that the air inlet 4 is located at the top of the tail shaft, and the air outlet 5 is located at the bottom of the tail shaft. The flue gas flows vertically from top to bottom within the shaft. When the flue gas from the pre-furnace flue 6 and the post-furnace flue 7 converges at the bottom exhaust channel 3, it mixes more thoroughly due to gravity and airflow inertia, avoiding fluctuations in SCR catalyst reaction efficiency caused by uneven local flue gas temperature. Other components and connections are the same as in Specific Embodiment 1.

[0027] Specific implementation method four: Combination Figure 1This embodiment differs from specific embodiment one in that the flue partition wall 13 is a membrane wall structure or a steel plate structure. Membrane walls or steel plate structures offer high strength and good sealing, effectively separating the flue duct 6 before the furnace and the flue duct 7 after the furnace, preventing heat exchange efficiency reduction or flue gas temperature regulation failure caused by flue gas crossflow, while also adapting to the high-temperature, high-pressure working environment at the boiler tail. Other components and connections are the same as in specific embodiment one.

[0028] Specific Implementation Method Five: Combining Figure 1 This embodiment differs from Specific Embodiment 1 in that the flue wall 10 of the tail shaft is a membrane wall structure. The membrane wall structure provides excellent insulation, reducing heat loss from the flue gas in the tail shaft, ensuring the high-temperature characteristics of the bypass flue gas after the furnace, further increasing the temperature of the mixed flue gas. Simultaneously, its good sealing performance effectively prevents high-temperature flue gas from leaking into the environment, avoiding safety hazards and energy waste. Other components and connections are the same as in Specific Embodiment 1.

[0029] Specific Implementation Method Six: Combination Figure 1 This embodiment differs from Specific Embodiment 1 in that the heat exchange tubes 8 are arranged in a serpentine pattern. The meandering path of the serpentine tubes prolongs the contact time between the flue gas and the tube wall, and the dense arrangement of the tubes enhances the heat transfer effect, enabling the working fluid to efficiently absorb heat from the flue gas. Simultaneously, it avoids localized stagnation of flue gas within the flue, ensuring smooth flue gas flow. Other components and connections are the same as in Specific Embodiment 1.

[0030] Specific implementation method seven: Combining Figure 1 This embodiment differs from specific embodiment one in that it also includes a guide plate 9, located in the area connecting the rear flue 7 and the inlet channel 1. The guide plate 9 guides the flue gas into the rear flue 7, ensuring precise entry of the flue gas from the inlet channel 1 into the rear flue 7. This prevents the flue gas from concentrating and flowing towards the front flue 6 due to airflow resistance, ensuring that the rear flue 7 receives sufficient high-temperature flue gas flow and guaranteeing the flue gas temperature regulation effect. Other components and connections are the same as in specific embodiment one.

[0031] Specific implementation method eight: Combination Figure 1 This embodiment differs from specific embodiment one in that it is equipped with a retractable first baffle 11 at the outlet of each of the two pre-furnace flue 6 and the post-furnace flue 7. The first baffle 11 adjusts the flue gas volume of each flue. The first baffle 11 can be connected to a stepper motor, which controls the retraction of the first baffle 11. Adjustment of the first baffle 11 allows for continuous adjustment of the flue gas volume, enabling the system to meet both high-load heat recovery requirements and low-load flue gas temperature enhancement requirements under deep peak shaving conditions, thus broadening the boiler's operating load range. Other components and connections are the same as in specific embodiment one.

[0032] Specific Implementation Method Nine: Combining Figure 1 This embodiment differs from specific embodiment eight in that it includes a retractable second baffle 12 at the outlet of one of the furnace front flues 6. The second baffle 12 adjusts the flue gas volume of both furnace front flues 6. Both the first baffles 11 and the second baffle 12 are independently controlled. Adding a second baffle 12 at the outlet of one of the furnace front flues 6 allows for independent adjustment of the flue gas volume ratio between the two flues, precisely controlling the heat exchange intensity of each furnace front flue 6 according to the working fluid heating requirements, and avoiding uneven heat exchange caused by excessive or insufficient flue gas volume in a single flue. Other components and connections are the same as in specific embodiment eight.

[0033] Specific Implementation Method Ten: Combining Figure 1 This embodiment also provides a coal-fired boiler, including the aforementioned compactly arranged flue gas system. Integrating this system into the boiler allows it to maintain SCR denitrification efficiency even under deep peak-shaving and low-load conditions by increasing flue gas temperature, thus solving the problem of excessive NOx emissions at low loads in traditional coal-fired boilers. Other components and connections are the same as in any of embodiments one through nine.

[0034] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

Claims

1. A compactly arranged flue gas system, characterized in that, include: The tail shaft has an air intake channel (1), a middle channel (2) and an exhaust channel (3) connected in sequence. The air intake channel (1) is provided with an air inlet (4) and the exhaust channel (3) is provided with an air outlet (5). The intermediate channel (2) is divided into a front flue (6) and a rear flue (7) by a flue partition wall (13). A heat exchange tube (8) is arranged in the front flue (6). The flue gas in the intake channel (1) can flow into the furnace front flue (6) and the furnace rear flue (7) respectively, and then converge and mix in the exhaust channel (3).

2. The compactly arranged flue gas system according to claim 1, characterized in that, The furnace front flue (6) has two side by side, with the two furnace front flues (6) located on one side and the furnace rear flue (7) located on the other side.

3. The compactly arranged flue gas system according to claim 1, characterized in that, The air inlet (4) is located at the top of the tail shaft, and the air outlet (5) is located at the bottom of the tail shaft.

4. The compactly arranged flue gas system according to claim 1, characterized in that, The flue partition wall (13) is a modular wall structure or a steel plate structure.

5. A compactly arranged flue gas system according to claim 1, characterized in that, The flue wall (10) of the tail shaft is a membrane wall structure.

6. A compactly arranged flue gas system according to claim 1, characterized in that, The heat exchange tube (8) is arranged in a serpentine tube form.

7. A compactly arranged flue gas system according to claim 1, characterized in that, Also includes: A guide plate (9) is disposed in the area where the flue gas duct (7) and the air inlet channel (1) are connected. The guide plate (9) is used to guide the flue gas into the flue gas duct (7).

8. A compactly arranged flue gas system according to claim 2, characterized in that, Each of the two furnace front flues (6) and the outlet of the furnace rear flue (7) is provided with a pull-out first baffle (11) to adjust the flue gas volume of each flue.

9. A compactly arranged flue gas system according to claim 8, characterized in that, One of the furnace front flues (6) is also provided with a pull-out second baffle (12) at the outlet, through which the flue gas volume of the two furnace front flues (6) is adjusted.

10. A coal-fired boiler, characterized in that, include: The compactly arranged flue gas system according to any one of claims 1-9.

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