An indirect heat exchange device for gas and air

Abstract

The application discloses an indirect heat exchange device for gas and air, which is applied to the heat exchange field and comprises a control cabinet. An air inlet and an air outlet are formed in the upper end of the control cabinet. A burner connecting port and a flue gas outlet are formed in the front end of the control cabinet. A burner, a blower and an induced draft fan are arranged outside the control cabinet. The output ends of the burner and the blower are respectively connected with air inlet pipe one and air inlet pipe two. The input end of the induced draft fan is connected with an air outlet pipe. The air outlet pipe is communicated with the flue gas outlet. The air inlet pipe one is communicated with the burner connecting port. The air inlet pipe two is communicated with the air inlet. Heat exchange pipe one and heat exchange pipe two are fixedly installed inside the control cabinet. The heat exchange pipe one is communicated with the air inlet. The heat exchange pipe two is communicated with the air outlet. A flue gas pipe one is fixedly installed inside the heat exchange pipe two. A flue gas pipe two is fixedly installed inside the heat exchange pipe one. The heat exchange pipe one and the heat exchange pipe two are communicated. The flue gas pipe one and the flue gas pipe two are communicated. The application has the characteristics of realizing the heat exchange between high-temperature flue gas and air.

Description

Technical Field

[0001] This invention relates to the field of heat exchange technology, specifically to an indirect heat exchange device for gas and air. Background Technology

[0002] The heat exchanger is used to achieve heat exchange between high-temperature flue gas and air, providing hot air for air-using equipment.

[0003] In the current technology, heat exchange devices are mostly equipped with two independent functional chambers, a radiation chamber and a mixing chamber, to complete the dual heat exchange processes of radiation heat exchange and air mixing heat exchange. Heat transfer between flue gas and air is achieved through zoned operation. However, the independent chambers require the installation of supporting pipelines and support structures, which increases the size of the equipment. At the same time, during air mixing heat exchange, high-temperature flue gas and air are directly mixed to complete heat exchange, but the high-temperature flue gas usually carries impurities produced by fuel combustion, causing air pollution and reducing the product qualification rate.

[0004] Therefore, it is necessary to provide an indirect heat exchange device for gas and air to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide an indirect heat exchange device for gas and air to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an indirect heat exchange device for gas and air, comprising a control cabinet and three sets of heat exchange devices, wherein the upper end of the control cabinet is provided with an air inlet, an air outlet and an explosion-proof port, the front end of the control cabinet is provided with a burner connection port and a flue gas outlet, and the side of the control cabinet is provided with an inspection port. The control cabinet is externally equipped with a burner, a blower, and an induced draft fan. The output ends of the burner and the blower are respectively connected to an air inlet pipe one and an air inlet pipe two. The input end of the induced draft fan is connected to an air outlet pipe, which is connected to the flue gas outlet. The air outlet is connected to a process air duct. The output end of the induced draft fan is connected to a smoke exhaust duct. The air inlet pipe one is connected to the burner connection port, and the air inlet pipe two is connected to the air inlet. The control cabinet is internally equipped with heat exchange tube one and heat exchange tube two. Heat exchange tube one is connected to the air inlet, and heat exchange tube two is connected to the air outlet. Flue gas pipe one is fixedly installed inside heat exchange tube two, and flue gas pipe two is fixedly installed inside heat exchange tube one. Flue gas pipe one passes through heat exchange tube two and is connected to the burner connection port. Flue gas pipe two passes through heat exchange tube one and is connected to the flue gas outlet. Heat exchange tube one and heat exchange tube two are connected, and flue gas pipe one and flue gas pipe two are connected.

[0007] According to the above technical solution, a drain pipe is installed inside the control cabinet. One end of the drain pipe passes through the heat exchange tube 1 and is connected to the flue gas pipe 2. A test hole is opened on the control cabinet, which passes through the heat exchange tube 2. A pressure sensor and a temperature sensor 2 are installed outside the control cabinet. The probes of the pressure sensor and the temperature sensor 2 pass through the test hole and enter the interior of the heat exchange tube 2. Temperature sensors 1 are installed on both the process air duct and the flue gas duct.

[0008] According to the above technical solution, the three heat exchange devices are defined from left to right as heat exchange device one, heat exchange device two, and heat exchange device three.

[0009] According to the above technical solution, the outlet pipe of the blower is connected to an air combination valve, the air combination valve includes several output ends, each set of output ends is connected to a pipe one, the output end of the pipe one is connected to an air three-way valve, one set of ports of the air three-way valve is connected to the air inlet pipe two, and the other set of ports of the air three-way valve corresponding to the heat exchange device one is blocked.

[0010] According to the above technical solution, the process air ducts of each heat exchange device are connected to a hot air three-way valve. One port of the hot air three-way valve is connected to pipe two. After the three sets of pipe two converge, they are connected to a hot air valve. The hot air valve is connected to pipe three.

[0011] According to the above technical solution, the other set of ports of the hot air three-way valve corresponding to heat exchange device one and heat exchange device two are connected to a preheating pipe. The preheating pipe of heat exchange device one is connected to the air three-way valve of heat exchange device two. The preheating pipe of heat exchange device two is connected to the air three-way valve of heat exchange device three. The other set of ports of the hot air three-way valve corresponding to heat exchange device three are blocked.

[0012] According to the above technical solution, each group of pipelines is connected in parallel with a bypass pipe, and a bypass valve is connected in series on the bypass pipe. The other end of the bypass pipe is connected to the corresponding process air pipeline.

[0013] According to the above technical solution, each group of exhaust pipes is connected to a recovery three-way valve, and one set of ports of the recovery three-way valve is connected to pipe four. After the pipes four of each group converge, they are connected to an exhaust valve.

[0014] According to the above technical solution, another set of output ends of the recovery three-way valve is connected to pipeline five, and recovery valve one is connected in series on pipeline five. Another set of ports of pipeline five is connected to a recovery pipe.

[0015] According to the above technical solution, a flue gas three-way valve is fixedly connected to the input end of the air inlet pipe one, the burner is connected to the flue gas three-way valve, a set of ports of the flue gas three-way valve is connected to pipe six, pipe six is ​​connected to the recovery pipe, and recovery valve two is connected in series.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention, by setting up heat exchange tube one, heat exchange tube two, flue gas tube one and flue gas tube two, realizes indirect heat exchange between high-temperature flue gas and air without removal, avoiding hot air pollution; by setting up a control cabinet, heat exchange tube one, heat exchange tube two, flue gas tube one and flue gas tube two are integrated and installed, reducing the footprint of the heat exchange device and reducing the production burden. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the pipeline connection of the present invention; Figure 3 This is a schematic diagram of the interior of the control cabinet of the present invention; Figure 4 This is a schematic diagram of the heat exchange tube of the present invention in two halves; Figure 5 This is a schematic diagram of the heat exchange system piping of the present invention; Figure 6 This is the present invention. Figure 5 Schematic diagram of area A; In the diagram: 1. Control cabinet; 2. Air inlet; 3. Air outlet; 4. Explosion-proof port; 5. Burner connection port; 6. Flue gas outlet; 7. Inspection port; 8. Burner; 9. Blower; 10. Exhaust fan; 11. Inlet pipe 1; 12. Inlet pipe 2; 13. Outlet pipe; 14. Process air duct; 15. Exhaust duct; 16. Temperature sensor 1; 17. Heat exchanger tube 1; 18. Heat exchanger tube 2; 19. Flue gas pipe 1; 20. Flue gas pipe 2; 21. Drain pipe; 22. 23. Pressure sensor; 24. Temperature sensor II; 25. Air combination valve; 26. Pipeline I; 27. Air three-way valve; 28. Hot air three-way valve; 29. ​​Pipeline II; 30. Hot air valve; 31. Pipeline III; 32. Preheating pipe; 32. Bypass pipe; 32. Bypass valve; 33. Recovery three-way valve; 34. Pipeline IV; 35. Smoke exhaust valve; 36. Pipeline V; 37. Recovery valve I; 38. Recovery pipe; 39. Flue gas three-way valve; 40. Pipeline VI; 41. Recovery valve II. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figures 1-2 The present invention provides a technical solution: an indirect heat exchange device for gas and air, including a control cabinet 1 and three sets of heat exchange devices. The upper end of the control cabinet 1 is provided with an air inlet 2, an air outlet 3 and an explosion-proof port 4. The front end of the control cabinet 1 is provided with a burner connection port 5 and a flue gas outlet 6. The side of the control cabinet 1 is provided with an inspection port 7.

[0020] The control cabinet 1 is externally equipped with a burner 8, a blower 9, and an induced draft fan 10. The output ends of the burner 8 and the blower 9 are respectively connected to an air inlet pipe 11 and an air inlet pipe 12. The input end of the induced draft fan 10 is connected to an exhaust pipe 13, which is connected to the flue gas outlet 6. The air outlet 3 is connected to a process air duct 14. The output end of the induced draft fan 10 is connected to an exhaust duct 15. The air inlet pipe 11 is connected to the burner connection port 5, and the air inlet pipe 12 is connected to the air inlet 2. The exhaust duct 15 is connected to a flue gas recovery device. The burner 8, the blower 9, the induced draft fan 10, and the flue gas recovery device are existing technologies.

[0021] Temperature sensors 16 are installed on both the process air duct 14 and the smoke exhaust duct 15.

[0022] Please see Figures 3-4 The control cabinet 1 has heat exchange tube 17 and heat exchange tube 28 fixedly installed inside. Heat exchange tube 17 is connected to air inlet 2, and heat exchange tube 28 is connected to air outlet 3. Flue gas pipe 19 is fixedly installed inside heat exchange tube 28, and flue gas pipe 20 is fixedly installed inside heat exchange tube 17. Flue gas pipe 19 passes through heat exchange tube 218 and is connected to burner connection port 5. Flue gas pipe 20 passes through heat exchange tube 17 and is connected to flue gas outlet 6.

[0023] A drain pipe 21 is installed inside the control cabinet 1. One end of the drain pipe 21 passes through the heat exchange tube 17 and is connected to the flue gas tube 20. The other end of the drain pipe 21 passes through the control cabinet 1. The drain pipe 21 is used to guide the water condensed inside the flue gas tube 20 after heat exchange to the recovery equipment (not shown in the figure) outside the control cabinet 1. The recovery equipment is existing technology.

[0024] Heat exchange tube 17 and heat exchange tube 28 are connected, and flue gas tube 19 and flue gas tube 20 are connected.

[0025] A test hole (not shown in the figure) is provided on the control cabinet 1. The test hole passes through the heat exchange tube 2 18. A pressure sensor 22 and a temperature sensor 23 are installed on the outside of the control cabinet 1. The probes of the pressure sensor 22 and the temperature sensor 23 pass through the test hole and enter the interior of the heat exchange tube 2 18.

[0026] Example 1: Natural gas is introduced into burner 8, and the furnace of burner 8 ignites the natural gas. The combustion of natural gas produces high-temperature flue gas. The high-temperature flue gas passes through the inlet pipe 11, the burner connection port 5, and enters the flue gas pipe 19. Since the flue gas pipe 19 and the flue gas pipe 20 are connected, the high-temperature flue gas flows into the flue gas pipe 20 along the flue gas pipe 19 and passes through the flue gas outlet 6 into the exhaust pipe 13. The induced draft fan 10 draws the high-temperature flue gas inside the exhaust pipe 13 into the flue gas duct 15.

[0027] During this process, the heat from the high-temperature flue gas is conducted to heat exchange tube 17 and heat exchange tube 28. When temperature sensor 23 detects that the temperature inside heat exchange tube 28 has reached the target temperature, blower 9 is started. Blower 9 draws air into air inlet pipe 22. The air flows through air inlet 2 into heat exchange tube 17. Since heat exchange tube 17 and heat exchange tube 28 are connected, the air flows along heat exchange tube 17 into heat exchange tube 28, and finally flows into process air duct 14 through air outlet 3. When the air flows inside heat exchange tube 28 and heat exchange tube 17, it absorbs heat and rises in temperature. Process air duct 14 delivers the hot air to the air-using equipment in other stages.

[0028] Temperature sensor 16 detects the temperature of hot air and flue gas in process air duct 14 and exhaust duct 15 respectively. Ideally, the temperature of hot air in process air duct 14 should not be lower than the target temperature, and the temperature of flue gas in exhaust duct 15 should not be higher than the threshold. The threshold is determined by the target temperature and the size of the natural gas combustion flame. When the temperature of hot air in process air duct 14 is lower than the target temperature, the flame of natural gas combustion can be increased by burner 8 to raise the temperature in each heat exchange tube and ensure that the hot air temperature reaches the target temperature.

[0029] Example 2: Since a single heat exchange device is insufficient to meet the hot air requirements of industry, this application also discloses a heat exchange system of an indirect heat exchange device for gas and air, which extends the heat exchange path and realizes the recovery and utilization of waste heat from flue gas.

[0030] The three heat exchange devices are as follows Figure 5 and Figure 6 As shown, the structure of each heat exchange device is the same as that in Embodiment 1. The three heat exchange devices are defined from left to right as Heat Exchange Device 1, Heat Exchange Device 2 and Heat Exchange Device 3.

[0031] The outlet pipe of the blower 9 is connected to an air combination valve 24. The air combination valve 24 includes several output ends. In this embodiment, the air combination valve 24 is provided with three sets of output ends. Each set of output ends is connected to a pipe 25. The output end of the pipe 25 is connected to an air three-way valve 26. One set of ports of the air three-way valve 26 is connected to the air inlet pipe 12. The other set of ports of the air three-way valve 26 corresponding to the heat exchange device is blocked.

[0032] Each heat exchanger's process air duct 14 is connected to a hot air three-way valve 27. One port of the hot air three-way valve 27 is connected to a second pipe 28. The three second pipes 28 converge and are connected to a hot air valve 29. The hot air valve 29 is connected to a third pipe 30. The third pipe 30 is used to deliver hot air to the air-using equipment.

[0033] The other set of ports of the hot air three-way valve 27 corresponding to heat exchange device 1 and heat exchange device 2 are connected to the preheating pipe 31. The preheating pipe 31 of heat exchange device 1 is connected to the air three-way valve 26 of heat exchange device 2, and the preheating pipe 31 of heat exchange device 2 is connected to the air three-way valve 26 of heat exchange device 3.

[0034] The other set of ports of the hot air three-way valve 27 corresponding to heat exchanger three is blocked.

[0035] Each group of pipelines 25 is connected in parallel with a bypass pipe 32, and a bypass valve 321 is connected in series on the bypass pipe 32. The other end of the bypass pipe 32 is connected to the corresponding process air pipeline 14.

[0036] Each set of exhaust pipes 15 is connected to a recovery three-way valve 33. One set of ports of the recovery three-way valve 33 is connected to pipe 4 34. After the pipes 4 34 converge, they are connected to exhaust valves 35. The output end of exhaust valves 35 is connected to the flue gas recovery equipment. The other set of output ends of the recovery three-way valve 33 is connected to pipe 5 36. A recovery valve 1 37 is connected in series on pipe 5 36. The other set of ports of pipe 5 36 is connected to recovery pipe 38.

[0037] A flue gas three-way valve 39 is fixedly connected to the input end of the intake pipe 11. The burner 8 is connected to the flue gas three-way valve 39. A set of ports of the flue gas three-way valve 39 is connected to a pipe 40. The pipe 40 is connected to the recovery pipe 38 and is connected in series with a recovery valve 41.

[0038] Scenario 1: The difference between room temperature and the target temperature of the hot air is significant. A single heat exchanger has a short heat exchange path. If the air needs to be heated to the target temperature quickly, a large amount of natural gas will be required. Therefore, by setting up... Figure 5 The heat exchange device shown extends the heat exchange path and realizes waste heat recovery.

[0039] The hot air path control includes the following steps: control the air combination valve 24 to clear the pipe 25 corresponding to the heat exchange device 1, block the pipe 25 corresponding to the other heat exchange devices, start the blower 9, the blower 9 draws air along the pipe 25, flows through the air three-way valve 26 into the air inlet pipe 12, and finally enters the control cabinet 1.

[0040] The hot air three-way valve 27 corresponding to heat exchange device 1 and heat exchange device 2, and the air three-way valve 26 corresponding to heat exchange device 2 and heat exchange device 3, are used to clear the preheating pipe 31 and block the second pipe 28 of heat exchange device 1.

[0041] The hot air three-way valve 27 of heat exchanger three blocks the corresponding pipeline 28 from the process air pipeline 14.

[0042] The path control of high-temperature flue gas includes the following steps: the flue gas three-way valve 39 of heat exchange device one connects the corresponding burner 8 and the inlet pipe 11, and the flue gas three-way valve 39 and recovery valve 2 41 of heat exchange device two and heat exchange device three connect the corresponding inlet pipe 11 and pipe 6 40.

[0043] The recovery three-way valve 33 and recovery valve 37 corresponding to heat exchange device 1 connect the exhaust pipe 15 corresponding to heat exchange device 1 to pipe 36, while pipe 34 blocks it.

[0044] After completing the path control of hot air and high-temperature flue gas, the burner 8 corresponding to heat exchange device one is started first. Since the flue gas three-way valve 39 of heat exchange device one connects the corresponding burner 8 and the inlet pipe 11, the high-temperature flue gas flows into heat exchange device one along the inlet pipe 11. Since the pipe 36 of heat exchange device one is unblocked, the flue gas with residual heat flows into the recovery pipe 38 along the pipe 36. Since the inlet pipe 11 of heat exchange device two and heat exchange device three is connected to the pipe 40, the residual heat flue gas flows into heat exchange device two and heat exchange device three along the inlet pipe 11 and the pipe 40, preheating the internal pipes of heat exchange device two and heat exchange device three, and realizing the recovery and utilization of heat.

[0045] When the blower 9 is started, since the air combination valve 24 only clears the pipe 25 corresponding to the heat exchange device, air flows into the heat exchange device along the pipe 25 and the air inlet pipe 12 of the heat exchange device.

[0046] The air and high-temperature flue gas exchange heat inside the control cabinet 1 of the heat exchange device, and the heat exchange principle is the same as that in Example 1.

[0047] The hot air generated by heat exchanger 1 flows into process air duct 14. Since the preheating pipe 31 of heat exchanger 1 is unblocked, the hot air flows into the air inlet pipe 12 of heat exchanger 2 along the preheating pipe 31, and further flows into the control cabinet 1 of heat exchanger 2.

[0048] The flue gas three-way valve 39 of heat exchange device two and heat exchange device three connects the corresponding burner 8 and the air inlet pipe 11. The burner 8 of heat exchange device two and heat exchange device three delivers high-temperature flue gas into the corresponding control cabinet 1. Since heat exchange device two and heat exchange device three have been preheated, the natural gas consumption of burner 8 can be effectively saved, and the production cost can be reduced.

[0049] The hot air three-way valve 27 of the heat exchange device 3 connects the corresponding pipeline 28 to the process air pipeline 14. The hot air valve 29 connects the pipeline 28 of the heat exchange device 3 to the pipeline 30 of the heat exchange device 3. The pipeline 30 delivers hot air to the air-using equipment. The hot air generated by the heat exchange device 1 flows through the heat exchange device 2 and the heat exchange device 3 to achieve further heat exchange, extend the heat exchange path of the hot air, and finally make the hot air reach the target temperature. In this process, the waste heat of the flue gas is used to preheat the heat exchange device, which further reduces the consumption of natural gas and saves costs.

[0050] Control all recovery three-way valves 33 to connect each group of exhaust pipes 15 to pipe 4 34, and the heat-exchanged flue gas is discharged to the flue gas recovery equipment through exhaust pipes 15.

[0051] It should be noted that the recovery three-way valve 33 and recovery valve 37 of the heat exchange device 2 can be controlled so that the flue gas with residual heat after heat exchange in the heat exchange device 2 and the residual heat flue gas in the heat exchange device 1 flow together into the heat exchange device 3 for residual heat treatment. The control principle of each group of valves is consistent with the principle in the above scheme.

[0052] Scenario 2: Based on Scenario 1, when any heat exchange device malfunctions or the number of operating equipment needs to be reduced due to production load, but a stable supply of hot air is still required.

[0053] For example, heat exchanger 2 needs to stop working, but hot air output is still required.

[0054] The burner 8 corresponding to the second heat exchange device is shut down, the flue gas three-way valve 39 blocks all pipes, and the air combination valve 24 blocks the air inlet pipe 12 of the second heat exchange device. At this time, the second heat exchange device is in a shutdown state.

[0055] The air three-way valve 26 of the second heat exchanger blocks the second air inlet pipe 12 and opens the bypass valve 321 of the second heat exchanger, so that the bypass pipe 32 is unblocked.

[0056] Based on scenario one, when the waste heat flue gas from heat exchanger one flows through the air three-way valve 26 of heat exchanger two along the preheating pipe 31, the waste heat flue gas flows directly into the process air duct 14 of heat exchanger two along the bypass pipe 32 of heat exchanger two, and further flows along the preheating pipe 31 of heat exchanger two to heat exchanger three, thus realizing the connection of the pipelines of heat exchanger one and heat exchanger three. This allows for the maintenance of heat exchanger two or the reduction of the load of the entire heat exchange system without shutting down the heat exchange system.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0058] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An indirect heat exchange device for gas and air, comprising a control cabinet (1) and three sets of heat exchange devices, characterized in that: The control cabinet (1) has an air inlet (2), an air outlet (3) and an explosion-proof port (4) at its upper end, a burner connection port (5) and a flue gas outlet (6) at its front end, and an inspection port (7) on its side. The control cabinet (1) is equipped with a burner (8), a blower (9) and an induced draft fan (10). The output ends of the burner (8) and the blower (9) are respectively connected to an air inlet pipe (11) and an air inlet pipe (12). The input end of the induced draft fan (10) is connected to an air outlet pipe (13). The air outlet pipe (13) is connected to the flue gas outlet (6). The air outlet (3) is connected to a process air duct (14). The output end of the induced draft fan (10) is connected to a smoke exhaust duct (15). The air inlet pipe (11) is connected to the burner connection port (5). The air inlet pipe (12) is connected to the air inlet (2). The control cabinet (1) is internally fixedly equipped with heat exchange tube one (17) and heat exchange tube two (18). Heat exchange tube one (17) is connected to the air inlet (2), and heat exchange tube two (18) is connected to the air outlet (3). Flue gas tube one (19) is fixedly installed inside heat exchange tube two (18), and flue gas tube two (20) is fixedly installed inside heat exchange tube one (17). Flue gas tube one (19) passes through heat exchange tube two (18) and is connected to the burner connection port (5). Flue gas tube two (20) passes through heat exchange tube one (17) and is connected to the flue gas outlet (6). Heat exchange tube one (17) and heat exchange tube two (18) are connected, and flue gas tube one (19) and flue gas tube two (20) are connected.

2. The indirect heat exchange device for gas and air according to claim 1, characterized in that: The control cabinet (1) is equipped with a drain pipe (21). One end of the drain pipe (21) passes through the heat exchange tube (17) and is connected to the flue gas pipe (20). The control cabinet (1) is provided with a test hole that passes through the heat exchange tube (18). The control cabinet (1) is equipped with a pressure sensor (22) and a temperature sensor (23). The probes of the pressure sensor (22) and the temperature sensor (23) pass through the test hole and enter the interior of the heat exchange tube (18). The process air duct (14) and the flue gas duct (15) are both equipped with a temperature sensor (16).

3. The indirect heat exchange device for gas and air according to claim 2, characterized in that: The three heat exchange devices are defined from left to right as heat exchange device one, heat exchange device two, and heat exchange device three.

4. The indirect heat exchange device for gas and air according to claim 3, characterized in that: The outlet pipe of the blower (9) is connected to an air combination valve (24). The air combination valve (24) includes several output ends. Each set of output ends is connected to a pipe (25). The output end of the pipe (25) is connected to an air three-way valve (26). One set of ports of the air three-way valve (26) is connected to the air inlet pipe (12). The other set of ports of the air three-way valve (26) corresponding to the heat exchange device is blocked.

5. The indirect heat exchange device for gas and air according to claim 4, characterized in that: Each heat exchange device has a process air duct (14) connected to a hot air three-way valve (27). One port of the hot air three-way valve (27) is connected to a second pipe (28). The three sets of second pipes (28) are connected to a hot air valve (29) after they converge. The hot air valve (29) is connected to a third pipe (30).

6. The indirect heat exchange device for gas and air according to claim 5, characterized in that: The other set of ports of the hot air three-way valve (27) corresponding to the heat exchange device one and the heat exchange device two are connected to the preheating pipe (31). The preheating pipe (31) of the heat exchange device one is connected to the air three-way valve (26) of the heat exchange device two. The preheating pipe (31) of the heat exchange device two is connected to the air three-way valve (26) of the heat exchange device three. The other set of ports of the hot air three-way valve (27) corresponding to the heat exchange device three are blocked.

7. The indirect heat exchange device for gas and air according to claim 6, characterized in that: Each of the pipelines (25) is connected in parallel with a bypass pipe (32), and a bypass valve (321) is connected in series on the bypass pipe (32). The other end of the bypass pipe (32) is connected to the corresponding process air pipeline (14).

8. The indirect heat exchange device for gas and air according to claim 7, characterized in that: Each set of exhaust pipes (15) is connected to a recovery three-way valve (33), and one set of ports of the recovery three-way valve (33) is connected to a pipe four (34). After the pipe four (34) of each set merges, they are connected to an exhaust valve (35).

9. The indirect heat exchange device for gas and air according to claim 8, characterized in that: The other output end of the recovery three-way valve (33) is connected to pipeline five (36), and recovery valve one (37) is connected in series on pipeline five (36). The other port of pipeline five (36) is connected to recovery pipe (38).

10. An indirect heat exchange device for gas and air according to claim 9, characterized in that: The inlet pipe 1 (11) is fixedly connected to a flue gas three-way valve (39). The burner (8) is connected to the flue gas three-way valve (39). A set of ports of the flue gas three-way valve (39) is connected to a pipe 6 (40). The pipe 6 (40) is connected to the recovery pipe (38) and is connected in series with a recovery valve 2 (41).

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