Low-temperature flue gas SCR energy-saving denitration system

Abstract

The utility model relates to the technical field of flue gas denitration, in particular to a low-temperature flue gas SCR (Selective Catalytic Reduction) energy-saving denitration system. The low-temperature flue gas SCR energy-saving denitration system comprises a low-temperature flue gas pipeline, a flue gas heat exchanger, an SCR denitration device, a CO catalytic device and a desulfurizing tower, a low-temperature flue gas pipeline is connected with a refrigerant inlet of the flue gas heat exchanger, a refrigerant outlet of the flue gas heat exchanger is connected with a gas inlet of the SCR denitration device through a denitration gas pipe, a gas outlet of the SCR denitration device is connected with a gas inlet of the CO catalytic device, and a gas outlet of the CO catalytic device is connected with a heating medium inlet of the flue gas heat exchanger and a gas inlet of the desulfurization tower through a hot gas pipe and a desulfurization gas pipe respectively. A heating medium outlet of the flue-gas heat exchanger is connected with a desulfurization gas pipe According to the utility model, heat generated by CO catalytic oxidation is recovered for heating low-temperature flue gas, so that the heat energy utilization rate and the CO catalytic oxidation efficiency are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas denitration, in particular to a low-temperature flue gas SCR energy-saving denitration system. Background Art

[0002] The flue gas discharged from thermal power plants contains a large amount of nitrogen oxides (NO x ) and greenhouse gases, which are the main factors leading to global warming, acid rain, haze and ozone layer depletion. Removing these harmful substances will help reduce air pollution, protect the ecological environment and slow down the process of global climate change. Therefore, flue gas needs to pass through a flue gas denitrification device to remove most of the nitrogen oxides before it is discharged into the atmosphere.

[0003] In flue gas denitrification devices, selective catalytic reduction (SCR) technology is currently the most widely used and most effective nitrogen oxide control technology. It has the advantages of large flue gas processing volume, high efficiency, and stable operation. The SCR method is to arrange the catalyst required for the denitrification reaction in the flue area. The flue gas is fully mixed with the reducing agent sprayed into the flue before passing through the catalyst. When the flue gas passes through the catalyst, the nitrogen oxides in the flue gas react with the reducing agent under the action of the catalyst to generate harmless nitrogen and water, thereby removing nitrogen oxides from the flue gas. Generally speaking, the suitable flue gas temperature for traditional commercial vanadium tungsten titanium-based SCR catalysts is about 300℃-400℃. In the denitrification reaction process, the temperature of the flue gas is very important. Too low a flue gas temperature will lead to a decrease in the activity of the catalyst, thereby reducing the denitrification efficiency of the denitrification equipment. The catalyst may not be able to fully exert its catalytic effect at a lower temperature, affecting the reduction effect of nitrogen oxides; in order to control the emission concentration of nitrogen oxides, excessive ammonia may be sprayed. Under low temperature conditions, ammonia and sulfur trioxide may react to form ammonium bisulfate, which is a viscous substance. It will adhere to the denitration catalyst and air preheater and absorb dust, causing the denitration catalyst and air preheater to be blocked, causing the pressure difference between the denitration reactor and the air preheater to slowly increase, thereby reducing the output of the induced draft fan and affecting the output of the entire unit; low temperature conditions may also cause uneven distribution of ammonia flow from the spray gun, resulting in excessive local ammonia concentration and increasing the risk of ammonia escape. Ammonia escape not only increases the cost of denitration, but also poses a threat to the safe operation of the unit.

[0004] When the power plant is in operation, low-temperature flue gas is inevitably generated. The temperature of the low-temperature flue gas does not reach the suitable temperature of the SCR catalyst. If the denitrification effect is to be guaranteed, the low-temperature flue gas needs to be heated to ensure the activity of the SCR catalyst. However, this consumes too much heat energy and is not conducive to energy saving. Utility Model Content

[0005] The technical problem to be solved by the utility model is to propose a low-temperature flue gas SCR energy-saving denitration system, which recovers the heat generated by CO catalytic oxidation to heat the low-temperature flue gas, thereby improving the thermal energy utilization rate and CO catalytic oxidation efficiency.

[0006] The low-temperature flue gas SCR energy-saving denitration system described in the utility model comprises a low-temperature flue gas pipeline, a flue gas heat exchanger, an SCR denitration device, a CO catalytic device and a desulfurization tower;

[0007] The low-temperature flue gas pipeline is connected to the refrigerant inlet of the flue gas heat exchanger, the refrigerant outlet of the flue gas heat exchanger is connected to the air inlet of the SCR denitrification device through the denitrification air pipe, the air outlet of the SCR denitrification device is connected to the air inlet of the CO catalytic device, the air outlet of the CO catalytic device is connected to the heat medium inlet of the flue gas heat exchanger and the air inlet of the desulfurization tower through the hot air pipe and the desulfurization air pipe respectively, and the heat medium outlet of the flue gas heat exchanger is connected to the desulfurization air pipe;

[0008] The CO catalytic device comprises a shell, a catalytic chamber is arranged in the shell, an air inlet pipe and an air outlet pipe are arranged in the catalytic chamber, the catalytic chamber is divided into m catalytic channels by a vertical partition, m is a positive integer, the bottoms or tops of adjacent catalytic channels are connected, the m catalytic channels are connected in series to form a passage, the two ends of the passage are respectively connected to the air inlet pipe and the air outlet pipe, a plurality of catalyst packing layers are arranged in the catalytic channel, the bottom of the catalytic channel is connected to an ash discharge pipe, the ash discharge pipe is connected to a negative pressure device, and an air hammer is arranged on the shell.

[0009] Preferably, an induced draft fan is provided on the low-temperature flue gas duct.

[0010] Preferably, a heater and a temperature sensor are provided on the denitration gas pipe. The temperature sensor monitors the temperature of the flue gas entering the SCR denitration device in real time. When the flue gas temperature is still too low, the heater can heat the flue gas to the required temperature.

[0011] Preferably, an ash discharge valve is provided on the ash discharge pipe.

[0012] Preferably, the negative pressure device is a dust suction fan.

[0013] Preferably, the air hammer is arranged corresponding to the catalyst packing layer.

[0014] Valves can be installed on the pipeline according to control needs, and the flow of materials in the corresponding pipeline can be conveniently controlled and adjusted by opening and closing the valves.

[0015] Compared with the prior art, the beneficial effects of the utility model are:

[0016] 1. The heat generated by catalytic oxidation of CO is used to heat low-temperature flue gas, effectively saving heat energy;

[0017] 2. The gas flux of the hot flue gas after CO removal in the hot gas pipe and the desulfurization gas pipe can be controlled to adjust the gas entering the flue gas heat exchanger, thereby controlling the temperature of the low-temperature flue gas. In addition, a heating device can be set on the denitrification gas pipe to heat the flue gas, so that the flue gas temperature in the denitrification gas pipe is always maintained within the working temperature range of the SCR denitrification device;

[0018] 3. The CO catalytic device divides the catalytic chamber into multiple catalytic channels, which are connected in series, increasing the passage time of the gas in the catalytic channels, allowing the gas to contact the catalyst more fully and improving the CO catalytic efficiency; the CO catalytic device is equipped with an air hammer and an ash discharge pipe. When it is necessary to clean the ash accumulated on the catalyst packing layer, the air hammer causes vibration to make the ash fall to the bottom of the catalytic channel, and the ash can be sucked out through the ash discharge pipe with a negative pressure device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the utility model;

[0020] Figure 2 This is a schematic diagram of the structure of the CO catalytic device of the utility model;

[0021] Figure 3 1. It is a schematic diagram of the structure viewed from above from the catalyst cavity side;

[0022] Figure 4 1. It is a schematic diagram of the structure when viewed from the top of the catalyst chamber;

[0023] In the figure: 1. Low-temperature flue gas duct; 2. Flue gas heat exchanger; 3. SCR denitrification device; 4. CO catalytic device; 5. Desulfurization tower; 6. Denitrification air pipe; 7. Hot air pipe; 8. Desulfurization air pipe; 9. Shell; 10. Catalytic chamber; 11. Inlet pipe; 12. Outlet pipe; 13. Vertical partition; 14. Catalytic channel; 15. Catalyst packing layer; 16. Ash discharge pipe; 17. Negative pressure device; 18. Air hammer; 19. Draft fan; 20. Heater; 21. Temperature sensor; 22. Ash discharge valve. DETAILED DESCRIPTION

[0024] The present invention will be described clearly and completely below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, the low-temperature flue gas SCR energy-saving denitration system described in the utility model includes a low-temperature flue gas pipeline 1, a flue gas heat exchanger 2, an SCR denitration device 3, a CO catalytic device 4 and a desulfurization tower 5;

[0026] The low-temperature flue gas pipeline 1 is connected to the refrigerant inlet of the flue gas heat exchanger 2, the refrigerant outlet of the flue gas heat exchanger 2 is connected to the air inlet of the SCR denitrification device 3 through the denitrification air pipe 6, the air outlet of the SCR denitrification device 3 is connected to the air inlet of the CO catalytic device 4, the air outlet of the CO catalytic device 4 is connected to the heat medium inlet of the flue gas heat exchanger 2 and the air inlet of the desulfurization tower 5 through the hot air pipe 7 and the desulfurization air pipe 8 respectively, and the heat medium outlet of the flue gas heat exchanger 2 is connected to the desulfurization air pipe 8;

[0027] like Figure 2 As shown, the CO catalytic device 4 includes a housing 9, a catalytic chamber 10 is provided in the housing 9, and the catalytic chamber 10 is provided with an air inlet pipe 11 and an air outlet pipe 12. Figure 3 , Figure 4 As shown, the catalytic chamber 10 is divided into 9 catalytic channels 14 by a vertical partition 13. The bottoms or tops of adjacent catalytic channels 14 are connected to each other. The 9 catalytic channels 14 are connected in series to form a passage. The two ends of the passage are respectively connected to the air inlet pipe 11 and the air outlet pipe 12. A plurality of catalyst packing layers 15 are arranged in the catalytic channel 14. The bottom of the catalytic channel 14 is connected to an ash discharge pipe 16. The ash discharge pipe 16 is connected to a negative pressure device 17. An air hammer 18 is arranged on the shell 9.

[0028] The low-temperature flue gas duct 1 is provided with an induced draft fan 19 .

[0029] A heater 20 and a temperature sensor 21 are provided on the denitration gas pipe 6 .

[0030] An ash discharge valve 22 is provided on the ash discharge pipe 16 .

[0031] The negative pressure device 17 is a dust suction fan.

[0032] The air hammer 18 is disposed corresponding to the catalyst packing layer 15 .

[0033] The working process is as follows: the low-temperature flue gas of the thermal power plant enters from the low-temperature flue gas pipeline 1, enters the flue gas heat exchanger 2 through the induced draft fan 19, and exchanges heat with the hot flue gas after CO removal, enters the SCR denitration device 3 through the denitration gas pipe 6, and enters the CO catalytic device 4 after denitration. Under the action of the catalyst, CO undergoes catalytic oxidation and releases heat. The obtained hot flue gas enters the flue gas heat exchanger 2 through the hot gas pipe 7, exchanges heat with the low-temperature flue gas, and then enters the desulfurization gas pipe 8 to go to the desulfurization tower 5 for desulfurization. The heater 20 can be used as an auxiliary heating device to further heat the low-temperature flue gas to ensure that the flue gas temperature entering the SCR denitration device 3 is not too low;

[0034] The flue gas enters the catalytic chamber 10 of the CO catalytic device 4 through the air inlet pipe 11, passes through the catalytic channels 14 connected in series, catalytically oxidizes CO to release heat, and then is discharged through the air outlet pipe 12; when dust accumulates on the catalyst packing layer 15, the air hammer 18 is started to vibrate, so that the accumulated dust falls to the bottom of the catalytic channel 14, and the ash discharge valve 22 can be opened to suck out the accumulated dust through the ash discharge pipe 16 with a dust suction fan.

Claims

1. A low-temperature flue gas SCR energy-saving denitrification system, characterized in that: It comprises a low-temperature flue gas pipeline (1), a flue gas heat exchanger (2), an SCR denitrification device (3), a CO catalytic device (4) and a desulfurization tower (5); The low-temperature flue gas pipeline (1) is connected to the refrigerant inlet of the flue gas heat exchanger (2); the refrigerant outlet of the flue gas heat exchanger (2) is connected to the air inlet of the SCR denitrification device (3) through the denitrification air pipe (6); the air outlet of the SCR denitrification device (3) is connected to the air inlet of the CO catalytic device (4); the air outlet of the CO catalytic device (4) is connected to the heat medium inlet of the flue gas heat exchanger (2) and the air inlet of the desulfurization tower (5) through the hot air pipe (7) and the desulfurization air pipe (8) respectively; the heat medium outlet of the flue gas heat exchanger (2) is connected to the desulfurization air pipe (8); The CO catalytic device (4) comprises a shell (9), wherein a catalytic chamber (10) is provided in the shell (9), wherein the catalytic chamber (10) is provided with an air inlet pipe (11) and an air outlet pipe (12), wherein the catalytic chamber (10) is divided into m catalytic channels (14) by a vertical partition plate (13), wherein m is a positive integer, wherein adjacent catalytic channels (14) are connected at the bottom or the top, wherein the m catalytic channels (14) are connected in series to form a passage, wherein the two ends of the passage are respectively connected to the air inlet pipe (11) and the air outlet pipe (12), wherein a plurality of catalyst packing layers (15) are provided in the catalytic channels (14), wherein the bottom of the catalytic channels (14) is connected to an ash discharge pipe (16), wherein the ash discharge pipe (16) is connected to a negative pressure device (17), and wherein an air hammer (18) is provided on the shell (9).

2. The low-temperature flue gas SCR energy-saving denitration system according to claim 1 is characterized in that: An induced draft fan (19) is provided on the low-temperature flue gas duct (1).

3. The low-temperature flue gas SCR energy-saving denitration system according to claim 1 is characterized in that: A heater (20) and a temperature sensor (21) are provided on the denitration gas pipe (6).

4. The low-temperature flue gas SCR energy-saving denitration system according to claim 1 is characterized in that: An ash discharge valve (22) is provided on the ash discharge pipe (16).

5. The low-temperature flue gas SCR energy-saving denitration system according to claim 1 is characterized in that: The negative pressure device (17) is a dust suction fan.

6. The low-temperature flue gas SCR energy-saving denitration system according to claim 1 is characterized in that: The air hammer (18) is arranged corresponding to the catalyst packing layer (15).

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