Low nitrogen condensation recirculation system and control method thereof

Abstract

The present invention provides a low-nitrogen condensation recirculation system and a control method thereof, wherein the low-nitrogen condensation recirculation system comprises a first heat exchange device, a second heat exchange device, an induced draft fan, a blower, a circulation pump, an air flow pipe and a liquid flow pipe, wherein the first heat exchange device comprises a first tower body, a first spray device and an ejector, a smoke outlet is provided at the top of the first tower body, a smoke inlet is provided at the bottom side wall of the first tower body, the smoke inlet is connected to the smoke exhaust pipe of the boiler through the induced draft fan and the air flow pipe, the first spray device is arranged in the first tower body and is located above the smoke inlet, the ejector is arranged in the first tower body and is located between the first spray device and the smoke inlet; the second heat exchange device comprises a second tower body, a second spray device and a superheater, an air outlet is provided at the top of the second tower body, and the air outlet is connected to the combustion air interface of the burner on the boiler through the air flow pipe. The system can reduce the emission of nitrogen oxides, improve safety and stability, and has the advantages of energy saving and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of low-nitrogen combustion, and in particular to a low-nitrogen condensation recirculation system and a control method thereof. Background Art

[0002] The existing burner flue gas recirculation technology extracts 15-20% of the flue gas after combustion and mixes it into the combustion-supporting fresh air of the burner for combustion, so as to suppress the generation of NOx. This technology reduces the output and efficiency of the boiler (or other furnaces), and the NOx emission is unstable. At the same time, due to the high temperature of the backfired flue gas, safety cannot be guaranteed. Summary of the invention

[0003] In view of the above, the present invention provides a low-nitrogen condensation and recirculation system, which can reduce the emission of nitrogen oxides, improve safety and stability, and has the advantages of energy saving and environmental protection.

[0004] The technical solution involved in the present invention:

[0005] A low-nitrogen condensation recirculation system comprises a first heat exchange device, a second heat exchange device, an induced draft fan, a blower, a circulation pump, an air flow pipe and a liquid flow pipe, wherein the first heat exchange device comprises a first tower body, a first spray device and an ejector, a smoke outlet is provided on the top of the first tower body, a smoke inlet is provided on the bottom side wall of the first tower body, the smoke inlet is connected to the smoke exhaust pipe of the boiler through the induced draft fan and the air flow pipe, the first spray device is arranged in the first tower body and is located above the smoke inlet, and the ejector is arranged in the first tower body and is located between the first spray device and the smoke inlet;

[0006] The second heat exchange device includes a second tower body, a second spray device and a superheater. An air outlet is provided on the top of the second tower body, and the air outlet is connected to the combustion air interface of the burner on the boiler through an air flow pipe. An air inlet is provided on the bottom side wall of the second tower body, and the air inlet is connected to the outside through a blower. The second spray device is arranged in the second tower body and is located above the air inlet. The superheater is arranged in the second tower body and is located between the second spray device and the air outlet.

[0007] A first liquid storage tank is formed at the bottom of the first tower body, and the first liquid storage tank is connected to a liquid flow pipe and a circulation pump. The circulating medium in the first liquid storage tank is respectively injected into the water inlet of the superheater, the water inlet of the second spraying device and the water inlet of the ejector through the liquid flow pipe and the circulation pump;

[0008] A second liquid storage tank is formed at the bottom of the second tower body, and the second liquid storage tank is connected to the water inlet of the first spraying device through a liquid flow pipe and a circulation pump.

[0009] Furthermore, a heat exchanger for exchanging heat with the high-temperature flue gas in the air flow pipe at the input end of the induced draft fan is arranged on the liquid flow pipe connected between the circulation pump and the superheater.

[0010] Furthermore, the airflow pipe connecting the induced draft fan and the smoke exhaust pipe of the boiler is divided into two branches, one branch is connected to the induced draft fan, and the other branch is connected to the airflow pipe at the smoke outlet, and a flue valve is provided for control.

[0011] Furthermore, a support frame is provided in the first tower body between the ejector and the smoke inlet, and a ball ring filler is provided on the support frame.

[0012] Furthermore, a support frame is disposed in the second tower body between the air inlet and the second spray device, and a ball ring filler is arranged on the support frame.

[0013] Furthermore, the first liquid storage tank is provided with a first overflow port, and the second liquid storage tank is provided with a second overflow port.

[0014] Furthermore, a first valve and a first filter are provided on the liquid flow pipe connected between the first liquid storage tank and the circulation pump, and a first check valve is provided on the liquid flow pipe at the output end of the circulation pump.

[0015] Furthermore, a second valve and a second filter are provided on the liquid flow pipe at the input end of the second liquid storage tank, and a second check valve is provided on the liquid flow pipe at the output end of the second liquid storage tank.

[0016] Furthermore, a first electric control valve is provided on the liquid flow pipe between the circulation pump connected to the first liquid storage tank and the ejector, a second electric control valve is provided on the liquid flow pipe between the circulation pump connected to the first liquid storage tank and the second spraying device, and a third electric control valve is provided on the liquid flow pipe between the circulation pump connected to the first liquid storage tank and the superheater.

[0017] A control method for a low-nitrogen condensation recirculation system, wherein the high-temperature flue gas discharged from the boiler is sucked into the first tower body through an induced draft fan, and the low-temperature circulating medium in the second liquid storage tank is sucked to the first spray device through a circulating pump for spraying, and the low-temperature circulating medium contacts and exchanges heat with the high-temperature flue gas, and the low-temperature circulating medium takes away part of the heat and most of the NOx of the high-temperature flue gas. After heat exchange, the high-temperature flue gas is converted into low-temperature flue gas and discharged from the flue gas outlet, and the low-temperature circulating medium is converted into high-temperature circulating medium, and the high-temperature circulating medium descends and is stored in the first liquid storage tank. The high-temperature circulating medium in the first liquid storage tank is pumped into the superheater through the circulating pump, so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body through the superheater; the high-temperature circulating medium in the first liquid storage tank is pumped into the second spray device through the circulating pump for spraying, so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body; The high-temperature circulating medium in the first liquid storage tank is drawn into the ejector through a circulating pump to absorb the flue gas with a low NOx concentration and transport it to the second tower body with the high-temperature circulating medium. The outside air sucked into the second tower body by the blower is mixed with the flue gas with a low NOx concentration and rises, exchanges heat with the high-temperature circulating medium of the second spray device, and exchanges heat with the superheater, so that the mixed gas formed by the outside air and the flue gas with a low NOx concentration rises to a predetermined temperature and flows from the air outlet to the combustion gas input end of the burner; the high-temperature circulating medium of the second spray device becomes a low-temperature circulating medium after heat exchange and descends into the second liquid storage tank, and the low-temperature circulating medium in the second liquid storage tank is sucked into the first spray device by a circulating pump for spraying, thereby circulating back and forth.

[0018] The low nitrogen condensation recirculation system of the present invention can reduce the temperature of the backfired flue gas and the NOx concentration in the backfired flue gas, reduce the concentration of the flue gas in the backfired flue gas, and thus reduce the emission of NOx. The exhaust gas temperature is reduced to below 60°C to fully recover the sensible heat and latent heat in the flue gas, and the recovered heat is used to preheat the burner combustion-supporting fresh air, improve the efficiency of the boiler (or other furnace) system, and ultimately reduce the consumption of fuel gas. The backfired flue gas is fully mixed with the outside air before entering the burner, which can ensure the safe and stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the low nitrogen condensation recirculation system of the present invention. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the protection scope of the present invention.

[0021] See also Figure 1The present invention provides a low-nitrogen condensation recirculation system, which is used in a boiler combustion system and includes a first heat exchange device 1, a second heat exchange device 2, an induced draft fan 3, a blower 4, a heat exchanger 5, a circulation pump 6, an air flow pipe 7 and a liquid flow pipe 8. The first heat exchange device 1 includes a first tower body 11, a first spray device 12 and an ejector 13. A flue gas outlet 111 is provided at the top of the first tower body 11, and the flue gas outlet 111 is connected to the outside through the air flow pipe 7. A flue gas inlet 112 is provided at the bottom side wall of the first tower body 11, and the flue gas inlet 112 is connected to the flue gas exhaust pipe of the boiler through the induced draft fan 3 and the air flow pipe 7, so as to draw the high-temperature flue gas in the boiler into the first tower body 11. The first spray device 12 is arranged in the first tower body 11 and is located above the flue gas inlet 112, so that the circulating medium sprayed by the first spray device 12 can exchange heat with the high-temperature flue gas sucked from the flue gas inlet 112. The circulating medium in this embodiment can be water or other equivalent liquids. The ejector 13 is arranged in the first tower body 11 and is located between the first spray device 12 and the flue gas inlet 112. The second heat exchange device 2 includes a second tower body 21, a second spray device 22 and a superheater 23. An air outlet 211 is provided at the top of the second tower body 21, and the air outlet 211 is connected to the combustion air interface of the burner on the boiler through the air flow pipe 7. An air inlet 212 is provided on the bottom side wall of the second tower body 21, and the air inlet 212 is connected to the outside through the blower 4 to suck the outside air into the second tower body 21. The second spray device 22 is arranged in the second tower body 21 and is located above the air inlet 212, so that the circulating medium sprayed by the second spray device 22 and the outside air sucked from the air inlet 212 can exchange heat. The superheater 23 is arranged in the second tower body 21 and is located between the second spray device 22 and the air outlet 211.

[0022] A first liquid reservoir 110 is formed at the bottom of the first tower body 11 for storing the circulating medium sprayed by the first spray device 12. A liquid adding nozzle 116 is provided on the first tower body 11 to replenish the circulating medium in the first liquid reservoir 110. The first liquid reservoir 110 is connected with a liquid flow pipe 8 and a circulating pump 6. In this embodiment, two circulating pumps 6 are provided, which are mutually reserved. If one of them is broken, the other one can be used, and the system can still be used normally. In order to simplify the system diagram, the circled numbers in the figure represent the terminal numbers of the liquid flow pipe 8, and the terminals with the same numbers in the circle are connected, that is, ① is connected to ①, ② is connected to ②, and ③ is connected to ③. The circulating medium in the first liquid reservoir 110 is respectively injected into the water inlet of the superheater 23, the water inlet of the second spray device 22, and the water inlet of the ejector 13 through the liquid flow pipe 8 and the circulating pump 6. Specifically, the liquid flow pipe 8 at the output end of the circulation pump 6 is divided into three branches, the first branch is connected to the water inlet of the superheater 23, and the first branch is provided with a heat exchanger 5 for exchanging heat with the high-temperature flue gas in the air flow pipe 7 at the input end of the induced draft fan 3, so that the circulating medium in the first branch is heated and then injected into the water inlet of the superheater 23, and the temperature of the flue gas sucked into the induced draft fan 3 is reduced, which not only fully utilizes the thermal energy of the high-temperature flue gas, but also protects the induced draft fan 3. The water outlet of the superheater 23 is connected to the liquid flow pipe 8 at the input end of the circulation pump 6 connected to the first liquid storage tank 110. The second branch is connected to the water inlet of the second spray device 22, so that the circulating medium in the first liquid storage tank 110 is pumped to the second spray device 22 for spraying, thereby heating the air in the second tower body 21. The third branch is connected to the water inlet of the ejector 13 to absorb the flue gas with a low nitrogen concentration in the first tower body 11, and transport the mixture of flue gas and steam water to the second tower body 21 through the air flow pipe 7 for release, and fully mix it into the combustion-supporting air and flow to the burner through the air outlet 211.

[0023] A second liquid storage tank 210 is formed at the bottom of the second tower body 21 to store the circulating medium sprayed by the second spray device 22. The second liquid storage tank 210 is connected to the water inlet of the first spray device 12 through the liquid flow pipe 8 and the circulating pump 6 to pump the circulating medium in the second liquid storage tank 210 to the first spray device 12 for spraying. In this embodiment, two circulating pumps 6 are provided, and the two are standby for each other. If one of them is broken, the other one can be used, and the system can still be used normally.

[0024] As a preferred embodiment, the airflow pipe 7 connecting the induced draft fan 3 and the smoke exhaust pipe of the boiler is divided into two branches, one branch is connected to the induced draft fan 3, and the other branch is connected to the airflow pipe 7 at the smoke outlet 111, and is controlled by a flue valve 71. During normal operation, the flue valve 71 is in a closed state to allow high-temperature smoke to flow into the induced draft fan 3. When maintenance is required, the flue valve 71 is opened, and the high-temperature smoke flows to the outside through the other branch.

[0025] As a preferred embodiment, a support frame 113 is provided between the ejector 13 and the smoke inlet 112 in the first tower body 11, and a ball ring filler 114 is provided on the support frame 113, which serves to increase the contact surface of the gas and liquid so that the gas and liquid can be fully mixed with each other. Similarly, a support frame 113 is provided between the air inlet 212 and the second spray device 22 in the second tower body 21, and a ball ring filler 114 is provided on the support frame 113.

[0026] As a preferred embodiment, the first liquid storage tank 110 is provided with a first overflow port 115, and the first overflow port 115 is connected to a liquid flow pipe 8 to maintain the liquid level in the first liquid storage tank 110 at a certain height. Similarly, the second liquid storage tank 210 is provided with a second overflow port 214, and the second overflow port 214 is connected to a liquid flow pipe 8.

[0027] As a preferred embodiment, the liquid flow pipe 8 connected between the first liquid storage tank 110 and the circulation pump 6 is provided with a first valve 81 and a first filter 82, and the first filter 82 is used to filter impurities in the circulating medium. The first valve 81 and the first filter 82 are connected to the liquid flow pipe 8 at the overflow port 115 through the liquid flow pipe 8, and a second valve 83 is provided on the liquid flow pipe 8 to discharge impurities in the first filter 82. A first check valve 84 is provided on the liquid flow pipe 8 at the output end of the circulation pump 6 to protect the circulation pump 6. Similarly, a second valve 85 and a second filter 86 are provided on the liquid flow pipe 8 at the input end of the second liquid storage tank 210, and a second check valve 87 is provided on the liquid flow pipe 8 at the output end of the second liquid storage tank 210.

[0028] As a preferred embodiment, a first electric control valve 88 for controlling the flow rate of the circulating medium is provided on the liquid flow pipe 8 between the circulating pump 6 and the ejector 13 connected to the first liquid storage tank 110. A second electric control valve 89 for controlling the flow rate of the circulating medium is provided on the liquid flow pipe 8 between the circulating pump 6 and the second spray device 22 connected to the first liquid storage tank 110. A third electric control valve 90 for controlling the flow rate of the circulating medium is provided on the liquid flow pipe 8 between the circulating pump 6 and the superheater 23 connected to the first liquid storage tank 110.

[0029] The working principle of the low-nitrogen condensation recirculation system of the present invention is as follows: the high-temperature flue gas discharged from the boiler is sucked into the first tower body 11 through the induced draft fan 3, and the low-temperature circulating medium in the second liquid storage tank 210 is sucked to the first spray device 12 through the circulating pump 6 for spraying, and the low-temperature circulating medium contacts with the high-temperature flue gas for heat exchange, and the low-temperature circulating medium takes away part of the heat and most of the NOx of the high-temperature flue gas. After heat exchange, the high-temperature flue gas is converted into low-temperature flue gas and discharged from the flue gas outlet 111, and the low-temperature circulating medium is converted into high-temperature circulating medium. The high-temperature circulating medium descends and is stored in the first liquid storage tank 110. The high-temperature circulating medium in the first liquid storage tank 110 is pumped into the superheater 23 through the circulating pump 6, so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body 21 through the superheater 23; the high-temperature circulating medium in the first liquid storage tank 110 is pumped into the second spray device 22 through the circulating pump 6 for spraying, so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body 21; The high-temperature circulating medium in the first liquid storage tank 110 is pumped into the ejector 13 through the circulating pump 6 to absorb the flue gas with a low NOx concentration and transport it to the second tower body 21 with the high-temperature circulating medium. The outside air sucked into the second tower body 21 by the blower 4 is mixed with the flue gas with a low NOx concentration and rises, exchanges heat with the high-temperature circulating medium of the second spray device 22, and exchanges heat with the superheater 23, so that the mixed gas formed by the outside air and the flue gas with a low NOx concentration rises to a predetermined temperature and flows from the air outlet 211 to the combustion gas input end of the burner; the high-temperature circulating medium of the second spray device 22 becomes a low-temperature circulating medium after heat exchange and descends into the second liquid storage tank 210, and the low-temperature circulating medium in the second liquid storage tank 210 is pumped to the first spray device 12 by the circulating pump 6 for spraying, thereby circulating back and forth.

[0030] The low nitrogen condensation recirculation system of the present invention can reduce the temperature of the backfired flue gas and the NOx concentration in the backfired flue gas, reduce the concentration of the flue gas in the backfired flue gas, and thus reduce the emission of NOx. The exhaust gas temperature is reduced to below 60°C to fully recover the sensible heat and latent heat in the flue gas, and the recovered heat is used to preheat the burner combustion-supporting fresh air, improve the efficiency of the boiler (or other furnace) system, and ultimately reduce the consumption of fuel gas. The backfired flue gas is fully mixed with the outside air before entering the burner, which can ensure the safe and stable operation of the system.

[0031] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A low nitrogen condensation recirculation system, characterized in that: The invention comprises a first heat exchange device (1), a second heat exchange device (2), an induced draft fan (3), a blower (4), a circulation pump (6), an air flow pipe (7) and a liquid flow pipe (8); the first heat exchange device (1) comprises a first tower body (11), a first spray device (12) and an ejector (13); a smoke outlet (111) is provided at the top of the first tower body (11); a smoke inlet (112) is provided at the bottom side wall of the first tower body (11); the smoke inlet (112) is connected to the smoke exhaust pipe of the boiler through the induced draft fan (3) and the air flow pipe (7); the first spray device (12) is arranged in the first tower body (11) and is located above the smoke inlet (112); the ejector (13) is arranged in the first tower body (11) and is located between the first spray device (12) and the smoke inlet (112); The second heat exchange device (2) comprises a second tower body (21), a second spray device (22) and a superheater (23); an air outlet (211) is provided at the top of the second tower body (21); the air outlet (211) is communicated with the combustion air interface of the burner on the boiler through an air flow pipe (7); an air inlet (212) is provided at the bottom side wall of the second tower body (21); the air inlet (212) is communicated with the outside through a blower (4); the second spray device (22) is arranged in the second tower body (21) and is located above the air inlet (212); the superheater (23) is arranged in the second tower body (21) and is located between the second spray device (22) and the air outlet (211); A first liquid storage tank (110) is formed at the bottom of the first tower body (11), and the first liquid storage tank (110) is connected to a liquid flow pipe (8) and a circulation pump (6). The circulating medium in the first liquid storage tank (110) is respectively injected into the water inlet of the superheater (23), the water inlet of the second spray device (22), and the water inlet of the ejector (13) through the liquid flow pipe (8) and the circulation pump (6); A second liquid storage tank (210) is formed at the bottom of the second tower body (21), and the second liquid storage tank (210) is connected to the water inlet of the first spraying device (12) through a liquid flow pipe (8) and a circulation pump (6); A heat exchanger (5) for exchanging heat with the high-temperature flue gas in the air flow pipe (7) at the input end of the induced draft fan (3) is provided on the liquid flow pipe (8) connected between the circulation pump (6) and the superheater (23); The airflow pipe (7) connecting the induced draft fan (3) and the smoke exhaust pipe of the boiler is divided into two branches, one branch is connected to the induced draft fan (3), and the other branch is connected to the airflow pipe (7) at the smoke outlet (111), and is provided with a flue valve (71) for control.

2. The low nitrogen condensation recirculation system according to claim 1, characterized in that: A support frame (113) is arranged in the first tower body (11) between the ejector (13) and the smoke inlet (112), and a ball ring packing (114) is arranged on the support frame (113).

3. The low nitrogen condensation recirculation system according to claim 1, characterized in that: A support frame (113) is disposed between the air inlet (212) and the second spray device (22) in the second tower body (21), and a ball ring filler (114) is disposed on the support frame (113).

4. The low nitrogen condensation recirculation system according to claim 1, characterized in that: The first liquid storage tank (110) is provided with a first overflow port (115), and the second liquid storage tank (210) is provided with a second overflow port (214).

5. The low nitrogen condensation recirculation system according to claim 1, characterized in that: A first valve (81) and a first filter (82) are provided on the liquid flow pipe (8) connected between the first liquid storage tank (110) and the circulation pump (6), and a first check valve (84) is provided on the liquid flow pipe (8) at the output end of the circulation pump (6).

6. The low nitrogen condensation recirculation system according to claim 1, characterized in that: A second valve (85) and a second filter (86) are provided on the liquid flow pipe (8) at the input end of the second liquid storage tank (210), and a second check valve (87) is provided on the liquid flow pipe (8) at the output end of the second liquid storage tank (210).

7. The low nitrogen condensation recirculation system according to claim 1, characterized in that: A first electric control valve (88) is provided on the liquid flow pipe (8) between the circulation pump (6) connected to the first liquid storage tank (110) and the ejector (13), a second electric control valve (89) is provided on the liquid flow pipe (8) between the circulation pump (6) connected to the first liquid storage tank (110) and the second spray device (22), and a third electric control valve (90) is provided on the liquid flow pipe (8) between the circulation pump (6) connected to the first liquid storage tank (110) and the superheater (23).

8. A control method for a low nitrogen condensation recirculation system according to any one of claims 1 to 7, characterized in that: The high-temperature flue gas discharged from the boiler is sucked into the first tower body (11) through the induced draft fan (3), and the low-temperature circulating medium in the second liquid storage tank (210) is sucked into the first spray device (12) through the circulation pump (6) for spraying. The low-temperature circulating medium contacts with the high-temperature flue gas for heat exchange, and the low-temperature circulating medium takes away part of the heat and most of the NOx of the high-temperature flue gas. After the heat exchange, the high-temperature flue gas is converted into low-temperature flue gas and discharged from the flue gas outlet (111). The low-temperature circulating medium is converted into high-temperature circulating medium, and the high-temperature circulating medium descends and is stored in the first liquid storage tank (110). The high-temperature circulating medium in the first liquid storage tank (110) is pumped into the superheater (23) through the circulation pump (6), so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body (21) through the superheater (23); the high-temperature circulating medium in the first liquid storage tank (110) is pumped into the second spray device (22) through the circulation pump (6) for spraying, so that the high-temperature circulating medium exchanges heat with the outside air sucked into the second tower body (21); The high-temperature circulating medium in the first liquid storage tank (110) is drawn into the ejector (13) through the circulating pump (6) to absorb the flue gas with a low NOx concentration and transport it to the second tower body (21) along with the high-temperature circulating medium. The outside air drawn into the second tower body (21) by the blower (4) is mixed with the flue gas with a low NOx concentration and rises, exchanges heat with the high-temperature circulating medium of the second spray device (22), and exchanges heat with the superheater (23), so that the mixed gas formed by the outside air and the flue gas with a low NOx concentration rises to a predetermined temperature and flows from the air outlet (211) to the combustion-supporting gas input end of the burner; the high-temperature circulating medium of the second spray device (22) is converted into a low-temperature circulating medium after heat exchange and descends into the second liquid storage tank (210). The low-temperature circulating medium in the second liquid storage tank (210) is drawn into the first spray device (12) through the circulating pump (6) for spraying, thereby performing a reciprocating cycle.

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