High-temperature gas-gas heat exchanger for urea pyrolysis of coal-fired boiler

Abstract

The utility model provides a high-temperature gas-gas heat exchanger for urea pyrolysis of a coal-fired boiler, which comprises an electric heater, a pyrolyzing furnace, a primary fan and an in-furnace heat exchange box arranged in the coal-fired boiler, and the primary fan is connected with a gas inlet end of the in-furnace heat exchange box through a cold dilution air pipe. The air outlet end of the in-furnace heat exchange box is connected with a valve control assembly through a first air conveying pipe, the valve control assembly is communicated with the pyrolyzing furnace through a second air conveying pipe, the electric heater is communicated with one air inlet end of the valve control assembly through a hot dilution air pipe, and the cold dilution air pipe is further provided with two cold air bypasses communicated with the first air conveying pipe. A manual valve I is arranged on one cold air bypass; the two cold air bypasses are arranged on the cold dilution air pipe, so that part of cold dilution air can be conveyed into the first air conveying pipe to cool heated hot air, and damage to related equipment or excessive pyrolytic reaction caused by over-high temperature of the directly heated hot air is avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of urea pyrolysis, in particular to a high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler. Background Art

[0002] The gas-gas heat exchange technology uses the high-temperature hot flue gas generated by a coal-fired boiler to heat the clean cold primary air to the process temperature required by the urea pyrolysis furnace in the SCR denitration ammonia production process (>400 °C), so that the dilution air entering the pyrolysis furnace can meet the requirements of the urea pyrolysis reaction temperature and the ammonia production demand, thereby realizing the function of replacing the electric heater, avoiding the direct consumption of electric energy, and reducing the operating cost.

[0003] After retrieval, the patent with the Chinese patent publication number CN202438306U discloses a device for pyrolyzing urea by using the waste heat of the flue gas of a power plant boiler, including a boiler air preheater and a urea pyrolysis furnace. It also includes a tubular heat exchanger arranged in the boiler flue. The air inlet of the tubular heat exchanger is communicated with the boiler air preheater, and its air outlet is communicated with the urea pyrolysis furnace. The tubular heat exchanger is arranged in the boiler turning chamber of the boiler flue.

[0004] The above patent has the following deficiencies: In this device, the cold air is preheated by the boiler air preheater and then enters the tubular heat exchanger arranged in the boiler flue, and exchanges heat with the boiler flue gas in the tubular heat exchanger to become hot air with a temperature above 600 °C, and then enters the urea pyrolysis furnace to cause the atomized urea solution to undergo a pyrolysis reaction. However, the flue gas temperature generated by the coal-fired boiler is relatively high, and the temperature of the cold air after heating is also relatively high. This device cannot adjust the temperature of the heated hot air, which may cause damage to related equipment and excessive pyrolysis reaction due to too high air temperature.

[0005] Therefore, a high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler is proposed. Content of the Utility Model

[0006] In view of this, the embodiments of the present utility model hope to provide a high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial option.

[0007] The technical solution of the embodiment of the utility model is realized as follows: A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler includes an electric heater, a pyrolysis furnace, a primary air blower, and a furnace internal heat exchange box arranged in the coal-fired boiler. The primary air blower is connected to the air inlet end of the furnace internal heat exchange box through a cold dilution air duct. The air outlet end of the furnace internal heat exchange box is connected with a valve control assembly through an air delivery pipe 1. The valve control assembly is communicated with the pyrolysis furnace through an air delivery pipe 2. The electric heater is communicated with one of the air inlet ends of the valve control assembly through a hot dilution air duct. Two cold air bypasses communicated with the air delivery pipe 1 are also arranged on the cold dilution air duct. A manual valve 1 is arranged on one of the cold air bypasses, and a manual valve 2, an electric valve, and a manual control valve 3 are sequentially arranged on the other cold air bypass along the cold air flow direction.

[0008] In some embodiments, the valve control assembly includes a housing and a slider.

[0009] In some embodiments, the slider is slidably fitted on the inner wall of the housing, and the air delivery pipe 1 and the air delivery pipe 2 are respectively fixedly connected and communicated with both ends of the housing.

[0010] In some embodiments, a through hole adapted to the hot dilution air duct is formed in the inner wall of the slider, and a spring 1 is buckled on the opposite side of the housing and the through hole.

[0011] In some embodiments, the same airbag is connected to the opposite side of the housing and the slider, and a heat exchange pipe is arranged on the inner wall of the air delivery pipe 1.

[0012] In some embodiments, one end of the heat exchange pipe penetrates through the housing and is communicated with the airbag.

[0013] In some embodiments, a chute is formed in the inner wall of the housing, and a ball head limit block is slidably fitted on the inner wall of the chute.

[0014] In some embodiments, a spring 2 is buckled on the opposite side of the ball head limit block and the chute, and two limit grooves for limit cooperation with the ball head limit block are formed in the inner wall of the slider.

[0015] In some embodiments, an electrode ring a is fixed on the lower surface of the top of the housing, and an electrode ring b is fixedly connected to the top of the slider.

[0016] In some embodiments, the electrode ring a and the electrode ring b are connected in series in the power supply circuit of the electric heater.

[0017] Due to the above technical solutions, the embodiment of the utility model has the following advantages:

[0018] 1. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler can send a part of the cold dilution air into the air delivery pipe 1 to cool the heated hot air by arranging two cold air bypasses on the cold dilution air duct, avoiding damage to related equipment caused by too high temperature of the directly heated hot air or excessive pyrolysis reaction.

[0019] 2. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler can compensate the temperature of hot air by setting an electric heater and a heat dilution air duct, avoiding heat loss during the flow of hot air, and the cooperation of spring one, heat exchange tubes and air bags can automatically connect or disconnect the through holes and the heat dilution air duct according to the temperature of hot air, improving the convenience of use of the device.

[0020] 3. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler, by setting electrode rings, automatically controls the opening and closing of the electric heater through the connection and disconnection of the electrode rings, thus simplifying the layout of the controller and the setting of the control logic at the same time.

[0021] The above summary is only for the purpose of the specification and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present utility model will be readily apparent by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is the pipeline diagram of the present utility model;

[0024] Figure 2 It is the pipeline diagram of manual valve one, manual valve two, electric valve and manual valve three of the present utility model;

[0025] Figure 3 It is the connection schematic diagram of the electric heater and the pyrolysis furnace of the present utility model;

[0026] Figure 4 It is the structural schematic diagram of the valve control component of the present utility model;

[0027] Figure 5 It is the sectional view of the internal structure of the housing of the present utility model Figure 1 ;

[0028] Figure 6 It is the sectional view of the internal structure of the housing of the present utility model Figure 2 。

[0029] Reference numerals:

[0030] 1. Coal-fired boiler; 2. In-furnace heat exchange box; 3. Electric heater; 4. Valve control assembly; 5. Pyrolysis furnace; 6. Primary air blower; 7. Manual valve 1; 8. Manual valve 2; 9. Electric valve; 10. Manual control valve 3; 11. Heat dilution air duct; 12. Gas transmission pipe 1; 13. Gas transmission pipe 2; 14. Shell; 15. Slide block; 16. Through hole; 17. Spring 1; 18. Heat exchange pipe; 19. Airbag; 20. Ball head limit block; 21. Slide groove; 22. Spring 2; 23. Limit groove; 24. Electrode ring a; 25. Electrode ring b. Detailed implementation mode

[0031] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary in nature rather than restrictive.

[0032] In the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "above and over", and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "below and under", and "beneath" the second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature has a lower horizontal height than the second feature.

[0033] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0034] Embodiment 1:

[0035] As Figure 1 , 2 shown, a high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler includes an electric heater 3, a pyrolysis furnace 5, a primary air blower 6, and an in-furnace heat exchange box 2 provided in the coal-fired boiler 1.

[0036] The primary air blower 6 is connected to the intake end of the in-furnace heat exchange box 2 through a cold dilution air duct. The outlet end of the in-furnace heat exchange box 2 is connected to a valve control assembly 4 through a gas transmission pipe 12. The valve control assembly 4 is communicated with the pyrolysis furnace 5 through a gas transmission pipe 13. The electric heater 3 is communicated with one of the intake ends of the valve control assembly 4 through a heat dilution air duct 11. The cold dilution air duct is also provided with two cold air bypasses communicated with the gas transmission pipe 12. A manual valve 1 7 is provided on one of the cold air bypasses, and a manual valve 2 8, an electric valve 9, and a manual control valve 3 10 are sequentially provided on the other cold air bypass along the cold air flow direction.

[0037] A stream of clean cold primary air is led out from the primary air fan 6 as cold dilution air and is transported through the cold dilution air duct to the in-furnace heat exchange box 2. The cold dilution air is heated by the hot flue gas in the flue of the coal-fired boiler 1. After heating, it is then transported to the pyrolysis furnace 5 through the first gas transmission pipe 12. During this period, when the air temperature is relatively high, the manual valve II 8, the electric valve 9, and the manual control valve III 10 can be opened, so that a part of the cold dilution air can directly enter the first gas transmission pipe 12 from one of the cold air bypasses to cool down the hot air. The temperature of the hot air can be controlled by adjusting the air intake of the electric valve 9. When the electric valve 9 needs to be repaired, the manual valve II 8 and the manual control valve III 10 are closed and the manual valve I 7 is opened, so that the cold dilution air can enter the first gas transmission pipe 12 through the cold air bypass on the manual valve I 7 for hot air temperature adjustment. After the repair is completed, the manual valve I 7 is kept in a normally closed state and the manual valve II 8, the electric valve 9, and the manual control valve III 10 are opened again.

[0038] By arranging two cold air bypasses on the cold dilution air duct, this device can send a part of the cold dilution air into the first gas transmission pipe 12 to cool down the heated hot air, avoiding damage to related equipment or excessive pyrolysis reaction caused by too high temperature of the hot air after direct heating.

[0039] Embodiment 2:

[0040] A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler. The following improvements are made to this embodiment on the basis of Embodiment 1, as Figures 3 - 6 shown:

[0041] The valve control assembly 4 includes a housing 14 and a slider 15 slidably fitted to the inner wall of the housing 14. The first gas transmission pipe 12 and the second gas transmission pipe 13 are respectively fixedly connected and communicated with both ends of the housing 14.

[0042] A through hole 16 adapted to the hot dilution air duct 11 is provided in the inner wall of the slider 15, and a first spring 17 is buckled on the opposite side of the housing 14 and the through hole 16.

[0043] The same airbag 19 is connected to the opposite side of the housing 14 and the slider 15. A heat exchange tube 18 is provided on the inner wall of the first gas transmission pipe 12. One end of the heat exchange tube 18 penetrates through the housing 14 and is communicated with the airbag 19.

[0044] A chute 21 is provided in the inner wall of the housing 14. A ball head limit block 20 is slidably fitted to the inner wall of the chute 21. A second spring 22 is buckled on the opposite side of the ball head limit block 20 and the chute 21. And two limit grooves 23 for limit cooperation with the ball head limit block 20 are provided in the inner wall of the slider 15.

[0045] When the temperature of the hot air in the first gas transmission pipe 12 is suitable and there is no need to heat it with the heat dilution air, the hot air passes through the heat exchange pipe 18, causing the air in the heat exchange pipe 18 to expand due to heat, and thus the airbag 19 expands. The airbag 19 pushes the slider 15 downward. The ball head limit block 20 is located in the upper limit groove 23. At this time, the heat dilution air pipe 11 and the through hole 16 are misaligned with each other, blocking the heat dilution air. When the temperature of the hot air in the first gas transmission pipe 12 is relatively low, the gas in the heat exchange pipe 18 contracts. The first spring 17 uses its own elasticity to push the slider 15 upward, and the airbag 19 is contracted. The ball head limit block 20 is located in the lower limit groove 23. At this time, the heat dilution air pipe 11, the through hole 16, and the slider 15 are interconnected, so that the heat dilution air in the valve control assembly 4 enters to compensate for the hot air, ensuring that the temperature entering the pyrolysis furnace 5 meets the standard.

[0046] By providing the electric heater 3 and the heat dilution air pipe 11, this device can compensate the temperature of the hot air, avoiding heat loss during the flow of the hot air. Moreover, with the cooperation of the first spring 17, the heat exchange pipe 18, and the airbag 19, the through hole 16 can be automatically connected or disconnected from the heat dilution air pipe 11 according to the temperature of the hot air, improving the convenience of using the device.

[0047] As Figure 6 shown, an electrode ring a 24 is fixed to the lower surface of the top of the housing 14, and an electrode ring b 25 is fixedly connected to the top of the slider 15. The electrode ring a 24 and the electrode ring b 25 are connected in series in the power supply circuit of the electric heater 3.

[0048] When the temperature of the hot air in the first gas transmission pipe 12 does not meet the standard, the slider 15 pushes the airbag 19 to contract upward, causing the electrode ring b 25 to contact the electrode ring a 24. At this time, the circuit of the electric heater 3 is connected, and heat dilution air is conveyed into the housing 14 for compensation. When the temperature of the hot air in the first gas transmission pipe 12 meets the standard, the airbag 19 expands due to heat, causing the slider 15 to move downward, and the electrode ring b 25 is disconnected from the electrode ring a 24, causing the electric heater 3 to power off and no longer convey heat dilution air into the housing 14.

[0049] By providing the electrode ring a 24 and the electrode ring b 25, this device automatically controls the opening and closing of the electric heater 3 by using the connection and disconnection of the electrode ring a 24 and the electrode ring b 25, thus simplifying the layout of the controller and also simplifying the setting of the control logic.

[0050] Working principle: When this device is in use, a stream of clean cold primary air is led out from the primary air blower 6 as cold dilution air, and is transported to the heat exchange box 2 in the furnace through the cold dilution air pipe. The cold dilution air is heated by the hot flue gas in the flue of the coal-fired boiler 1. After heating, the hot air is transported in the direction of the pyrolysis furnace 5 by the first air delivery pipe 12. When the air temperature is relatively high, the manual valve II 8, the electric valve 9 and the manual control valve III 10 can be opened, so that a part of the cold dilution air can directly enter the first air delivery pipe 12 from one of the cold air by-passes to cool down the hot air. The temperature of the hot air can be controlled by adjusting the air intake of the electric valve 9. When the temperature of the hot air in the first air delivery pipe 12 is suitable and there is no need to heat it with the hot dilution air, the hot air passes through the heat exchange pipe 18, causing the air in the heat exchange pipe 18 to expand due to heat, and thus the air bag 19 expands. The air bag 19 pushes the slider 15 downward. The spherical head limit block 20 is located in the upper limit groove 23. At this time, the hot dilution air pipe 11 and the through hole 16 are misaligned with each other, and the downward movement of the slider 15 causes the electrode ring b 25 and the electrode ring a 24 to be disconnected. At this time, the electric heater 3 is powered off and cannot transport the hot dilution air into the housing 14, so that the hot air directly passes through the housing 14 and the second air delivery pipe 13 and reaches the pyrolysis furnace 5 for urea pyrolysis; when the temperature of the hot air in the first air delivery pipe 12 is relatively low, the gas in the heat exchange pipe 18 contracts, and the first spring 17 uses its own elasticity to push the slider 15 upward. The air bag 19 is contracted, and the spherical head limit block 20 is located in the lower limit groove 23. At this time, the hot dilution air pipe 11, the through hole 16 and the slider 15 are in communication with each other, and the upward movement of the slider 15 drives the electrode ring b 25 to be connected with the electrode ring a 24. At this time, the power supply of the electric heater 3 is connected, and the hot dilution air is transported into the housing 14 through the hot dilution air pipe 11 to compensate the temperature of the hot air. Finally, the hot air with qualified temperature enters the pyrolysis furnace 5 through the second air delivery pipe 13 for urea pyrolysis.

[0051] The above is only the specific implementation manner of the present utility model, but the protection scope of the present utility model is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present utility model can easily think of various changes or substitutions thereof, and these should all be covered within the protection scope of the present utility model. Therefore, the protection scope of the present utility model shall be subject to the protection scope of the claims.

Claims

1. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler, comprising an electric heater (3), a pyrolysis furnace (5), a primary air blower (6), and a heat exchange box (2) arranged in the coal-fired boiler (1), characterized in that: The primary air fan (6) is connected to the intake end of the in-furnace heat exchange box (2) through a cold dilution air duct. The outlet end of the in-furnace heat exchange box (2) is connected to a valve control assembly (4) through a first gas transmission pipe (12). The valve control assembly (4) is communicated with the pyrolysis furnace (5) through a second gas transmission pipe (13). The electric heater (3) is communicated with one of the intake ends of the valve control assembly (4) through a heat dilution air duct (11). The cold dilution air duct is also provided with two cold air bypasses communicated with the first gas transmission pipe (12). A first manual valve (7) is arranged on one of the cold air bypasses, and a second manual valve (8), an electric valve (9) and a third manual control valve (10) are sequentially arranged on the other cold air bypass along the cold air flow direction.

2. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 1, characterized in that: The valve control assembly (4) includes a housing (14) and a slider (15).

3. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 2, wherein: The slider (15) is slidably matched with the inner wall of the housing (14). The first gas transmission pipe (12) and the second gas transmission pipe (13) are respectively fixedly connected and communicated with both ends of the housing (14).

4. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 3, characterized in that: A through hole (16) adapted to the heat dilution air duct (11) is formed in the inner wall of the slider (15), and a first spring (17) is buckled on the opposite side of the housing (14) and the through hole (16).

5. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 4, characterized in that: An airbag (19) is connected to the opposite side of the housing (14) and the slider (15). A heat exchange pipe (18) is arranged on the inner wall of the first gas transmission pipe (12).

6. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 5, characterized in that: One end of the heat exchange pipe (18) penetrates through the housing (14) and is communicated with the airbag (19).

7. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 6, wherein: A chute (21) is formed in the inner wall of the housing (14), and a ball head limit block (20) is slidably matched with the inner wall of the chute (21).

8. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 7, characterized in that: A second spring (22) is buckled on the opposite side of the ball head limit block (20) and the chute (21), and two limit grooves (23) for limit cooperation with the ball head limit block (20) are formed in the inner wall of the slider (15).

9. The high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 2, characterized in that: An electrode ring a (24) is fixed to the lower surface of the top of the housing (14), and an electrode ring b (25) is fixedly connected to the top of the slider (15).

10. A high-temperature gas-gas heat exchanger for urea pyrolysis in a coal-fired boiler according to claim 9, characterized in that: The electrode ring a (24) and the electrode ring b (25) are connected in series in the power supply circuit of the electric heater (3).

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