System and method for monitoring and treating flue gas at the end of a gas-fired power plant

Abstract

The present application relates to tail flue gas monitoring technical field, especially for gas power plant tail flue gas monitoring, processing system and method, including welding pipe welded on the heating surface pipeline, welding pipe is in the upstream direction of heating surface pipeline, the temperature of upstream direction of heating surface pipeline is lowest, the intermediate position of welding pipe is fixedly connected with the barrel, the barrel includes the inclined part and horizontal part connected head to tail, the fixedly connected fan-shaped part between the side of inclined part close to welding pipe and welding pipe, spiral blade works, can make the flow rate in welding pipe greater than the rest of heating surface pipeline, thereby making welding pipe and the rest of heating surface pipeline produce temperature difference, when adjusting the exhaust gas temperature downward, or the temperature of acid dew point drops, with welding pipe as the representative to detect acid dew point, welding pipe as the vanguard of the rest of heating surface, when the condensate water appears on the surface of welding pipe, timely adjust the exhaust gas temperature, thereby avoiding the condensation of acid water in a large range of heating surface pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of tail flue gas monitoring, and in particular to a system and method for monitoring and treating tail flue gas in a gas-fired power plant. Background Art

[0002] When high-temperature flue gas enters the tail flue gas duct, measures are generally taken to reduce the exhaust temperature in order to reduce exhaust losses. If the exhaust temperature is reduced too much, the acid gas will reach its acid dew point temperature. The acid gas will further combine with water vapor and condense into acidic liquid on the wall of the flue gas duct. The acidic liquid will continuously corrode the heated metal surface.

[0003] Generally, a higher exhaust gas temperature is required to ensure that the low-temperature heating surface is higher than the acid dew point, thereby preventing or slowing down the condensation and corrosion of the acid. However, if the exhaust gas temperature is too high, the exhaust gas heat loss will increase sharply, which is not conducive to energy saving. Only by controlling the temperature difference between the exhaust gas temperature, the low-temperature heating surface and the acid dew point within a reasonable range at the same time can the low-temperature corrosion prevention and control at the tail of the boiler and the maximization of energy utilization be effectively achieved.

[0004] The existing acid dew point measuring device sets a gradually lowering "cold surface" in the furnace through a temperature regulating device until the flue gas condenses into acidic liquid on the insulating patch to achieve the measurement of the acid dew point. It is necessary to set continuously circulating water in the furnace to pass through the detection end to form a "cold surface" to cool the "cold surface". For this purpose, many redundant pipelines are required, making the device difficult to maintain. For example, in the prior art, there is a flue gas acid dew point measuring device disclosed in application number CN113758970A. After the prior art obtains the acid dew point through the temperature of the cold surface, because the causes of condensed acid water include not only temperature but also the roughness of the cold surface, the acid dew point of the "cold surface" in the acid dew point measuring device does not represent the actual temperature of the heated surface where condensed acid water appears, there will be some deviations, resulting in the actual condensation temperature of the heated surface being unclear.

[0005] Therefore, in order to solve the above problems, a system and method for monitoring and treating tail gas of a gas power plant is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a system and method for monitoring and treating tail flue gas in a gas-fired power plant;

[0007] The boiler heating surface is composed of many tube rows, and the heating tubes are installed in parallel. During maintenance, if the wear is too severe, the tubes need to be replaced, and then installed by welding. Compared with the existing technology, the present invention can directly perform acid dew point experiments on the heating surface, and can fully combine the conditions of the heating surface to directly judge whether the temperature of the heating surface is below the acid dew point temperature, thereby reducing the problem that "the acid dew point of the "cold surface" in the acid dew point measurement device cannot represent the actual temperature of condensed acid water on the heating surface, and there will be some deviations, resulting in the actual condensation temperature of the heating surface being unclear."

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The tail flue gas monitoring system of a gas power plant includes a welded pipe welded to a heating surface pipe. The welded pipe is located upstream of the heating surface pipe, where the heat exchange time is short and the temperature is lowest. A cylindrical object is fixedly connected to the middle of the welded pipe. The cylindrical object includes an inclined portion and a horizontal portion connected at both ends.

[0010] A fan-shaped portion is fixedly connected to the welded pipe on one side of the inclined portion close to the welded pipe. A hollow portion on the side of the inclined portion close to the welded pipe forms an outflow channel. A rotating shaft is rotatably connected to the inner side of the inclined portion. A spiral blade is fixedly connected to the side of the rotating shaft close to the welded pipe. The spiral blade is arranged in the outflow channel and does not exceed the outlet end of the outflow channel. An inlet channel is opened on the inner side of the fan-shaped portion. The inlet of the inlet channel is connected to the inner side of the welded pipe. The outlet of the inlet channel is arranged on the input side of the spiral blade. When the spiral blade rotates, a water flow in the same direction as the water flow in the welded pipe is generated at the outlet of the outflow channel, thereby accelerating the water flow velocity in the welded pipe. Compared with the other heated surface pipes, the water flow in the welded pipe has no time to be heated, forming a relatively "cold surface";

[0011] The spiral blades are located in the outflow channel. When the spiral blades are not working, the flow velocity inside the welded pipe is not significantly disturbed. When the spiral blades are working, the flow velocity inside the welded pipe can be greater than that of the other heated surface pipes, thereby creating a temperature difference between the welded pipe and the other heated surface pipes. When the exhaust gas temperature is adjusted downward, or the acid dew point temperature drops, the welded pipe is used as a representative for acid dew point detection. The welded pipe serves as a pioneer for the other heated surfaces. When condensed water appears on the surface of the welded pipe, the exhaust gas temperature is adjusted in time to avoid condensed acid water on a large range of heated surface pipes.

[0012] In the prior art, in order to keep the heated surface above the acid dew point, it is necessary to monitor the wall temperature of the heated surface. However, the present invention does not require the creation of additional cooling water pipes to produce a "cold surface" or temperature monitoring. Because of the existence of roughness and the change in the roughness of the heated surface over time, the present invention directly performs acid dew point detection on the heated surface pipe, which can avoid the problem that the acid dew point of the cold surface in the existing acid dew point measurement device cannot represent the actual temperature at which acid water condenses on the heated surface, resulting in some deviation, resulting in inaccurate inference of the actual condensation temperature of the heated surface and inability to achieve more precise adjustments.

[0013] The inclined portion is used to make the direction of the water flow generated at the outlet of the outflow channel roughly the same as the direction of the water flow in the welded pipe; the inclined portion is also used to achieve a turning direction so that the cylindrical object can extend toward the nearest wall of the flue gas duct;

[0014] The cylinder can be set to be detachable to facilitate maintenance and replacement during inspection. In order to prevent leakage of the welded pipe, valves can be set at both ends of the welded pipe during the inspection process. When leakage occurs, the valves at both ends of the welded pipe can be closed in time.

[0015] The motor is set outside the furnace to reduce the working temperature of the motor and increase its service life;

[0016] An annular insulating ring is fixedly connected to the outside of the welding pipe. The insulating ring can be made of ceramic material. There is a groove on the inside of the insulating ring. Two conductive columns are fixedly connected to the bottom end of one side of the groove. When the exhaust gas temperature drops, acid water condenses first on the welding pipe as the "cold surface". The acid water flows down into the groove. The condensed acidic liquid can conduct the two conductive columns, so that the electrical connection between the two conductive columns can be detected, which is used to remind to increase the exhaust temperature of the flue gas, thereby protecting the other heated surface pipes. After the exhaust temperature rises, the condensed acid water evaporates again.

[0017] As a preferred embodiment of the gas power plant tail flue gas monitoring system of the present invention, the side of the groove facing the flue gas is higher than the side facing away from the flue gas, so that the condensed acid water is collected and concentrated on the side of the groove facing away from the flue gas, thereby improving the sensitivity of detection.

[0018] As a preferred embodiment of the gas power plant tail gas monitoring system of the present invention, the inner side of the inclined portion is fixedly connected to a rotary sealing shaft, and the inner side of the rotary sealing shaft is fixedly connected to the outer side of the rotating shaft.

[0019] As a preferred embodiment of the tail flue gas monitoring system of a gas power plant of the present invention, a collection and control instrument is connected to the inner side of one end of the horizontal portion extending out of the flue gas duct wall, and the collection and control instrument is electrically connected to the conductive column.

[0020] As the gas power plant tail flue gas monitoring system of the application preferably, the included angle between the inclined part and the welded pipe is 10-30°, the included angle between the inclined part and the welded pipe can be reasonably adjusted according to the installation position;

[0021] As the gas power plant tail flue gas monitoring system of the application preferably, the end of the horizontal part is sealed, the end of the horizontal part can effectively avoid the pressure leakage in the welded pipe, is suitable for pressure pipeline, hollow inside, the horizontal part is fixed on the inside of the flue gas pipeline wall, the inside of the one end of the horizontal part extending out of the flue gas pipeline wall is fixedly connected with the motor, the output end of the motor is fixedly connected with the driving shaft, the driving shaft is supported by the support fixedly connected inside the horizontal part, the rotating shaft and the driving shaft are connected through a plurality of universal joints.

[0022] As the gas power plant tail flue gas monitoring system of the application preferably, the inside of the one end of the horizontal part extending out of the flue gas pipeline wall is connected with the thermocouple, the two junctions of the thermocouple are connected with the same height position of the welded pipe and its adjacent heating surface pipeline respectively, for obtaining the temperature difference of the welded pipe and its adjacent heating surface pipeline at the same height position.

[0023] The rotating speed of the motor can be changed, so that the rotating speed of the spiral blade can be changed, thereby changing the temperature difference, the thermocouple is used for measuring the temperature difference, the two ends of the thermocouple are connected with the same height position of the welded pipe and its adjacent heating surface pipeline respectively, the temperature difference between the surface of the welded pipe and the remaining heating surface can be obtained, and reasonable temperature difference can take into account the low temperature corrosion prevention and control and energy utilization of the boiler tail;

[0024] The greater the temperature difference between the adjacent heating surface pipeline and the welded pipe, the lower the temperature of the "cold surface", the earlier the "cold surface" appears condensation acid water, the greater the safety threshold, and the relative thermal efficiency will be reduced, the smaller the temperature difference between the adjacent heating surface pipeline and the welded pipe, the lower the temperature of the "cold surface", the later the "cold surface" appears condensation acid water, the smaller the safety threshold, and the relative thermal efficiency will be increased, so that the temperature difference between the exhaust gas temperature, the low temperature heating surface and the acid dew point is controlled within a reasonable range, which can take into account the low temperature corrosion prevention and control and energy utilization of the boiler tail.

[0025] As the gas power plant tail flue gas monitoring system of the application preferably, the chimney and the induced draft fan are connected, the chimney inlet end is connected with the tail flue, the top end of the chimney is fixedly connected with the exhaust ring, the bottom end inside of the exhaust ring is fixedly connected with the annular groove, the output end of the induced draft fan is communicated with the air inlet pipe, the output end of the air inlet pipe is communicated with the inside of the annular groove, the top end inside of the annular groove is fixedly connected with the elastic ring, the inside of the elastic ring is uniformly provided with the air outlet hole, the inner edge of the exhaust ring is aligned with the inner edge of the chimney, when the induced draft fan works, the high-speed airflow is sprayed out of the air outlet hole on the upper side of the annular groove, so as to increase the flow rate at the chimney outlet, increase the flow rate of the flue, and increase the exhaust gas temperature.

[0026] The existing induced draft fan because the fan blade is arranged in the inner side of the flue gas passage, when the induced draft fan is not working, the blade of the induced draft fan will increase the resistance of the flue gas flow, and the waste heat boiler in the gas power plant can not be provided with an induced draft fan, and the flue gas flow is realized by relying on the back pressure of the gas turbine and the chimney effect, the gas turbine is the main component in the power generation proportion, and the exhaust gas temperature is adjusted by adjusting the power and back pressure of the gas turbine at will, which will seriously affect the power generation efficiency of the gas turbine.

[0027] The induced draft fan in the application can provide the speed of the flue gas flow and improve the exhaust gas speed when the induced draft fan works because the blade is not in the flue.

[0028] The tail flue gas monitoring method of the gas power plant comprises the following steps:

[0029] Step 1: the motor works to rotate the spiral blade, and the outlet of the outflow channel generates water flow consistent with the water flow direction in the welding pipe, so as to accelerate the water flow speed in the welding pipe, compared with the remaining heat receiving surface pipes, the water flow in the welding pipe is not heated in time, and a "cold surface" is formed.

[0030] Step 2: when the exhaust gas temperature decreases, the welding pipe as the "cold surface" first appears acid water condensation, the acid water flows into the groove, so that the electric connection of the two electrically conductive columns is detected, which is used to remind the exhaust gas temperature of the flue gas to be increased, so as to protect the remaining heat receiving surface pipes, and after the exhaust gas temperature rises, the condensed acid water evaporates again.

[0031] The tail flue gas monitoring method of the gas power plant comprises the following steps:

[0032] Step 1: the motor works to rotate the spiral blade, and the outlet of the outflow channel generates water flow consistent with the water flow direction in the welding pipe, so as to accelerate the water flow speed in the welding pipe, compared with the remaining heat receiving surface pipes, the water flow in the welding pipe is not heated in time, and a "cold surface" is formed.

[0033] Step 2: the greater the temperature difference between the adjacent heat receiving surface pipes and the welding pipe, the lower the temperature of the "cold surface", the earlier the "cold surface" appears condensed acid water, the greater the safety threshold, and the relative heat efficiency will be reduced, the smaller the temperature difference between the adjacent heat receiving surface pipes and the welding pipe, the lower the temperature of the "cold surface", the later the "cold surface" appears condensed acid water, the smaller the safety threshold, and the relative heat efficiency will be increased.

[0034] Step 3: according to the method of step 2, the temperature difference between the exhaust gas temperature, the low-temperature heat receiving surface and the acid dew point is controlled within a reasonable range, and the low-temperature corrosion prevention and control and energy utilization of the boiler tail are considered.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. In the tail flue gas monitoring system of the gas power plant, when the spiral blades rotate, a water flow is generated at the outlet of the outflow channel in the same direction as the water flow in the welded pipe, which accelerates the water flow velocity in the welded pipe. Compared with the other heated surface pipes, the water flow in the welded pipe does not have time to be heated, forming a relatively "cold surface"; the spiral blades are in the outflow channel. When the spiral blades are not working, the interference with the flow velocity inside the welded pipe is not obvious. When the spiral blades are working, the flow velocity in the welded pipe can be greater than that in the other heated surface pipes, thereby creating a temperature difference between the welded pipe and the other heated surface pipes. When the exhaust gas temperature is adjusted downward or the acid dew point temperature drops, the welded pipe is used as a representative for acid dew point detection. The welded pipe serves as the pioneer of the other heated surfaces. When condensation water appears on the surface of the welded pipe, the exhaust gas temperature is adjusted in time to avoid condensation of acid water in a large range of heated surface pipes.

[0037] 2. In the prior art, the flue gas monitoring system at the tail end of the gas-fired power plant requires temperature monitoring of the wall temperature of the heated surface in order to keep the heated surface above the acid dew point temperature. The present invention does not require the creation of additional cooling water pipes to produce a "cold surface" or temperature monitoring. Because of the existence of roughness and the change of the roughness of the heated surface over time, the present invention can also avoid the problem that "the acid dew point of the cold surface in the existing acid dew point measurement device cannot represent the actual temperature at which condensed acid water appears on the heated surface, and there will be some deviations, resulting in the inferred actual condensation temperature of the heated surface being unclear, and the adjustment cannot be further accurate."

[0038] 3. In the tail flue gas monitoring system of the gas power plant, an annular insulating ring is fixedly connected to the outside of the welded pipe. The insulating ring can be made of ceramic material. There is a groove on the inside of the insulating ring. Two conductive columns are fixedly connected to the bottom end of one side of the groove. When the exhaust gas temperature drops, acid water condenses first on the welded pipe as the "cold surface". The acid water flows down into the groove. The condensed acidic liquid can conduct the two conductive columns, so that the electrical connection between the two conductive columns is detected, which is used to remind to increase the exhaust temperature of the flue gas, thereby protecting the remaining heated surface pipes. After the exhaust temperature rises, the condensed acid water evaporates again, and the side of the groove facing the flue gas is higher than the side facing away from the flue gas, so that the condensed acid water gathers and concentrates on the side of the groove facing away from the flue gas, thereby improving the sensitivity of the detection.

[0039] 4. In the flue gas monitoring system at the tail end of the gas power plant, thermocouples are used to measure temperature differences. The two ends of the thermocouple are respectively connected to the welded pipe and the adjacent heating surface pipe at the same height, so that the temperature difference between the welded pipe surface and the other heating surfaces can be obtained. Setting a reasonable temperature difference can take into account both the low-temperature corrosion prevention and control and energy utilization at the tail end of the boiler. The greater the temperature difference between the adjacent heating surface pipes and the welded pipe, the lower the temperature of the "cold surface", the earlier the condensed acid water appears on the "cold surface", the larger the safety threshold, and the thermal efficiency will be relatively reduced. The smaller the temperature difference between the adjacent heating surface pipes and the welded pipe, the lower the temperature of the "cold surface", the later the condensed acid water appears on the "cold surface", the smaller the safety threshold, and the thermal efficiency will be relatively increased. The temperature difference between the exhaust gas temperature, the low-temperature heating surface and the acid dew point is controlled within a reasonable range, which can take into account both the low-temperature corrosion prevention and control and energy utilization at the tail end of the boiler.

[0040] 5. In the tail flue gas treatment system of the gas-fired power plant, the existing induced draft fan has its fan blades arranged on the inner side of the flue gas duct. When the induced draft fan is not working, the blades of the induced draft fan will increase the resistance to the flue gas flow. However, the waste heat boiler in the gas-fired power plant can be installed without an induced draft fan, and the flue gas flow can be achieved by relying on the back pressure and chimney effect of the gas turbine. The gas turbine is the main component of power generation. Adjusting the exhaust gas temperature by arbitrarily adjusting the power and back pressure of the gas turbine will seriously affect the power generation efficiency of the gas turbine. The induced draft fan in the present invention has its blades not in the flue. When the induced draft fan is not working, the increase in the flue gas resistance can be ignored. When the induced draft fan is working, it can increase the speed of the flue gas flow and improve the exhaust speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of the overall appearance and structure of the smoke monitoring system of the present invention;

[0042] Figure 2 For the present invention Figure 1 A in the figure shows the enlarged structural diagram;

[0043] Figure 3 This is a schematic diagram of the top view of the insulating ring of the present invention;

[0044] Figure 4 This is a schematic diagram of the overall cross-sectional installation structure of the smoke monitoring system of the present invention;

[0045] Figure 5 For the present invention Figure 4 A schematic diagram of the structure at point B in FIG.

[0046] Figure 6 A further schematic diagram of the appearance and structure of the smoke monitoring system of the present invention;

[0047] Figure 7 This is a schematic diagram of the appearance structure of the chimney top of the present invention;

[0048] Figure 8 This is a schematic diagram of the internal cross-sectional structure of the top exhaust ring of the present invention;

[0049] Figure 9 For the present invention Figure 8 The enlarged structural diagram at C in FIG.

[0050] Figure 10 This is a schematic diagram of the appearance structure of the elastic ring of the present invention.

[0051] In the figure: 1. Heating surface pipe; 2. Welding pipe; 3. Fan-shaped part; 4. Inclined part; 5. Horizontal part; 6. Collection and control instrument; 7. Insulating ring; 71. Groove; 72. Conductive column; 8. Flue gas duct wall; 9. Motor; 10. Support; 11. Universal joint; 12. Rotating shaft; 13. Rotating sealing shaft; 14. Outlet channel; 15. Spiral blade; 16. Inlet channel; 17. Thermocouple; 171. Joint; 18. Chimney; 19. Exhaust ring; 20. Inlet pipe; 21. Induced draft fan; 22. Annular groove; 23. Elastic ring; 24. Air outlet opening; 25. Tail flue; 26. Cylinder; 27. Drive shaft. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0053] Example 1, please refer to Figure 1-5 The present invention provides a technical solution: a flue gas monitoring system for a gas power plant tail, comprising a welded pipe 2 welded to a heating surface pipe 1. The welded pipe 2 is located upstream of the heating surface pipe 1, where the heat exchange time is short and the temperature is lowest upstream of the heating surface pipe 1. A cylindrical object 26 is fixedly connected to the middle of the welded pipe 2. The cylindrical object 26 includes an inclined portion 4 and a horizontal portion 5 connected end to end.

[0054] A fan-shaped portion 3 is fixedly connected between the side of the inclined portion 4 close to the welded pipe 2 and the welded pipe 2. A hollow outlet channel 14 is formed on the side of the inclined portion 4 close to the welded pipe 2. A rotating shaft 12 is rotatably connected to the inner side of the inclined portion 4. A spiral blade 15 is fixedly connected to the side of the rotating shaft 12 close to the welded pipe 2. The spiral blade 15 is arranged in the outlet channel 14 and does not exceed the outlet end of the outlet channel 14. An inlet channel 16 is opened on the inner side of the fan-shaped portion 3. The inlet of the inlet channel 16 is connected to the inner side of the welded pipe 2, and the outlet of the inlet channel 16 is arranged on the input side of the spiral blade 15. When the spiral blade 15 rotates, a water flow in the same direction as the water flow in the welded pipe 2 is generated at the outlet of the outflow channel 14, thereby accelerating the water flow velocity in the welded pipe 2. Compared with the other heated surface pipes, the water flow in the welded pipe 2 has no time to be heated, forming a relatively "cold surface";

[0055] The spiral blades 15 are located in the outflow channel 14. When the spiral blades 15 are not working, the flow velocity inside the welded pipe 2 is not significantly disturbed. When the spiral blades 15 are working, the flow velocity inside the welded pipe 2 is made greater than that of the other heated surface pipes, thereby creating a temperature difference between the welded pipe 2 and the other heated surface pipes. When the exhaust gas temperature is adjusted downward, or the acid dew point temperature drops, the welded pipe 2 is used as a representative for acid dew point detection. The welded pipe 2 serves as a pioneer for the other heated surfaces. When condensed water appears on the surface of the welded pipe 2, the exhaust gas temperature is adjusted in time, thereby avoiding the condensation of acid water in a large range of heated surface pipes.

[0056] In the prior art, in order to keep the heated surface above the acid dew point temperature, it is necessary to monitor the wall temperature of the heated surface. The present invention does not require the creation of additional cooling water pipes to produce a "cold surface" or temperature monitoring. Due to the existence of roughness and the change of the roughness of the heated surface over time, the present invention can also avoid the problem that the acid dew point of the cold surface in the existing acid dew point measurement device cannot represent the actual temperature at which acid water condenses on the heated surface, resulting in some deviation, resulting in the inferred actual condensation temperature of the heated surface being uncertain and making it difficult to achieve more precise adjustments.

[0057] The inclined portion is used to make the direction of the water flow generated at the outlet of the outflow channel 14 substantially the same as the direction of the water flow in the welded pipe 2; the inclined portion is also used to achieve a turning direction so that the cylindrical object 26 can extend toward the nearest flue gas duct wall 8;

[0058] The cylinder 26 can be arranged in a detachable manner to facilitate maintenance and replacement during maintenance. In order to prevent leakage of the welded pipe 2, valves can be provided at both ends of the welded pipe 2 during maintenance. When leakage occurs, the valves at both ends of the welded pipe 2 can be closed in time.

[0059] The motor 9 is arranged outside the furnace to reduce the operating temperature of the motor 9 and increase its service life;

[0060] An annular insulating ring 7 is fixedly connected to the outside of the welding pipe 2. The insulating ring 7 can be made of ceramic material. A groove 71 is provided on the inside of the insulating ring 7. Two conductive posts 72 are fixedly connected to the bottom end of one side of the groove 71. When the exhaust gas temperature drops, acid water condenses first on the welding pipe 2, which serves as the "cold surface". The acid water flows down into the groove 71. The condensed acidic liquid can conduct the two conductive posts 72, so that the electrical connection between the two conductive posts 72 is detected, which is used to remind the user to increase the exhaust gas temperature, thereby protecting the remaining heated surface pipes. After the exhaust gas temperature rises, the condensed acid water evaporates again.

[0061] As a preferred embodiment of the tail flue gas monitoring system of a gas power plant of the present invention, the side of the groove 71 facing the flue gas is higher than the side facing away from the flue gas, so that the condensed acid water is collected and concentrated on the side of the groove 71 facing away from the flue gas, thereby improving the sensitivity of detection.

[0062] As a preferred embodiment of the gas power plant tail flue gas monitoring system of the present invention, a rotary sealing shaft 13 is fixedly connected to the inner side of the inclined portion 4 , and the inner side of the rotary sealing shaft 13 is fixedly connected to the outer side of the rotating shaft 12 .

[0063] As a preferred embodiment of the tail flue gas monitoring system of a gas power plant of the present invention, the inner side of one end of the horizontal portion 5 extending out of the flue gas duct wall 8 is connected to a collection and control instrument 6 , and the collection and control instrument 6 is electrically connected to the conductive column 72 .

[0064] As a preferred embodiment of the gas power plant tail flue gas monitoring system of the present invention, the angle between the inclined portion 4 and the welded pipe 2 is 10-30°, and the angle between the inclined portion 4 and the welded pipe 2 can be reasonably adjusted according to the installation position;

[0065] As a preferred embodiment of the tail flue gas monitoring system of a gas power plant of the present invention, the end of the horizontal part 5 is sealed, and the end sealing of the horizontal part 5 can effectively prevent the pressure in the welded pipe 2 from leaking out. It is suitable for pressure pipelines, and the interior is hollow. The horizontal part 5 is fixed on the inner side of the flue gas pipe wall 8, and the inner side of one end of the horizontal part 5 extending out of the flue gas pipe wall 8 is fixedly connected to a motor 9, and the output end of the motor 9 is fixedly connected to a drive shaft 27. The drive shaft 27 is supported by a support 10 fixedly connected to the inside of the horizontal part 5, and the rotating shaft 12 and the drive shaft 27 are connected in a steering manner through multiple universal joints 11.

[0066] This embodiment also discloses a method for monitoring tail flue gas in a gas-fired power plant, the steps of which are:

[0067] Step 1: The motor 9 is turned on to rotate the spiral blade 15. The outlet of the outflow channel 14 generates a water flow in the same direction as the water flow in the welded pipe 2, which accelerates the flow rate of the water in the welded pipe 2. Compared with the other heated surface pipes, the water in the welded pipe 2 has no time to be heated, forming a "cold surface";

[0068] Step 2: When the exhaust gas temperature drops, acid water condenses first on the welding pipe 2 serving as the "cold surface". The acid water flows down into the groove 71, causing the two conductive posts 72 to be electrically connected and detected, which is used to remind the user to increase the exhaust gas temperature, thereby protecting the remaining heated surface pipes. After the exhaust gas temperature rises, the condensed acid water evaporates again.

[0069] Example 2: This example is a further improvement of Example 1. Figures 1-6 A thermocouple 17 is connected to the inner side of one end of the horizontal portion 5 extending out of the flue gas duct wall 8. The two junction points 171 of the thermocouple 17 are respectively connected to the same height positions of the welded pipe 2 and its adjacent heated surface pipe 1, so as to obtain the temperature difference between the welded pipe 2 and its adjacent heated surface pipe 1 at the same height positions.

[0070] Changing the speed of the motor 9 can change the speed of the spiral blade 15, thereby changing the temperature difference. The thermocouple 17 is used to measure the temperature difference. The two ends of the thermocouple 17 are respectively connected to the same height position of the welded pipe 2 and the adjacent heating surface pipe 1. The temperature difference between the surface of the welded pipe 2 and the other heating surfaces can be obtained. Setting a reasonable temperature difference can take into account both low-temperature corrosion prevention and energy utilization at the tail of the boiler;

[0071] The greater the temperature difference between the adjacent heating surface pipes and the welded pipe 2, the lower the temperature of the "cold surface", the earlier condensed acid water appears on the "cold surface", the larger the safety threshold, and the thermal efficiency will be relatively reduced. The smaller the temperature difference between the adjacent heating surface pipes and the welded pipe 2, the lower the temperature of the "cold surface", the later condensed acid water appears on the "cold surface", the smaller the safety threshold, and the thermal efficiency will be relatively increased, so that the temperature difference between the exhaust gas temperature, the low-temperature heating surface and the acid dew point is controlled within a reasonable range, which can take into account the low-temperature corrosion prevention and control and energy utilization at the tail of the boiler.

[0072] This embodiment also discloses a method for monitoring tail flue gas in a gas-fired power plant, the steps of which are:

[0073] Step 1: The motor 9 is turned on to rotate the spiral blade 15. A water flow in the same direction as the water flow in the welded pipe 2 is generated at the outlet of the outflow channel 14, which accelerates the flow velocity of the water in the welded pipe 2. Compared with the other heated surface pipes, the water in the welded pipe 2 has no time to be heated, forming a "cold surface". The faster the motor 9 rotates, the faster the water flow velocity in the welded pipe 2, and the greater the temperature difference between the adjacent heated surface pipes and the welded pipe 2. The thermocouple 17 is used to obtain the temperature difference between the adjacent heated surface pipes and the welded pipe 2.

[0074] Step 2: The greater the temperature difference between the adjacent heated surface pipes and the welded pipe 2, the lower the temperature of the "cold surface", the earlier acid water condenses on the "cold surface", the larger the safety threshold, and the relatively lower the thermal efficiency. The smaller the temperature difference between the adjacent heated surface pipes and the welded pipe 2, the lower the temperature of the "cold surface", the later acid water condenses on the "cold surface", the smaller the safety threshold, and the relatively higher the thermal efficiency.

[0075] Step 3: According to the method of step 2, the temperature difference between the exhaust gas temperature, the low-temperature heating surface and the acid dew point is controlled within a reasonable range, taking into account the low-temperature corrosion prevention and control and energy utilization at the tail of the boiler.

[0076] Example 3, please refer to Figure 7-10 This embodiment is the disposal mechanism of embodiments 1 and 2, including a chimney 18 and an induced draft fan 21. The inlet end of the chimney 18 is connected to the tail flue. The top of the chimney 18 is fixedly connected to an exhaust ring 19, and the inner side of the bottom end of the exhaust ring 19 is fixedly connected to an annular groove 22. The output end of the induced draft fan 21 is connected to an air inlet pipe 20, and the output end of the air inlet pipe 20 is connected to the inner side of the annular groove 22. The inner side of the top of the annular groove 22 is fixedly connected to an elastic ring 23, and the inside of the elastic ring 23 is evenly provided with air outlet holes 24. The inner edge of the exhaust ring 19 is aligned with the inner edge of the chimney 18. When the induced draft fan 21 is working, the air outlet holes 24 on the upper side of the annular groove 22 eject high-speed airflow, thereby increasing the flow velocity at the outlet of the chimney 18, increasing the flow velocity of the tail flue 25, and increasing the exhaust temperature.

[0077] Because the blades of the existing induced draft fan 21 are set on the inner side of the flue gas channel, when the induced draft fan is not working, the blades of the induced draft fan will increase the resistance to the flue gas flow. However, the waste heat boiler in the gas power plant can be equipped with no induced draft fan, and the flue gas flow is achieved by relying on the back pressure and chimney effect of the gas turbine. The gas turbine is the main component of power generation. Adjusting the exhaust gas temperature by arbitrarily adjusting the power and back pressure of the gas turbine will seriously affect the power generation efficiency of the gas turbine.

[0078] Since the blades of the induced draft fan 21 in the present invention are not in the flue, the increase in flue resistance when the induced draft fan 21 is not working can be ignored; when the induced draft fan 21 is working, it can increase the speed of flue gas flow, improve the exhaust speed, and increase the exhaust temperature.

[0079] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A tail flue gas monitoring system for a gas power plant, comprising a welded pipe (2) welded to a heating surface pipe (1), characterized in that: The welded pipe (2) is located upstream of the heated surface pipe (1), and a cylindrical object (26) is fixedly connected to the middle position of the welded pipe (2). The cylindrical object (26) includes an inclined portion (4) and a horizontal portion (5) connected end to end. A fan-shaped portion (3) is fixedly connected between the side of the inclined portion (4) close to the welded pipe (2) and the welded pipe (2). A hollow outlet channel (14) is formed on the side of the inclined portion (4) close to the welded pipe (2). A rotating shaft (12) is rotatably connected to the inner side of the inclined portion (4). A spiral blade (15) is fixedly connected to the side of the rotating shaft (12) close to the welded pipe (2). The spiral blade (15) is arranged in the outlet channel (14) and does not extend beyond the outlet end of the outlet channel (14). The fan-shaped portion (3) An inlet channel (16) is provided on the inner side of the welded pipe (2), the inlet of the inlet channel (16) is connected to the inner side of the welded pipe (2), and the outlet of the inlet channel (16) is provided on the input side of the spiral blade (15). When the spiral blade (15) rotates, a water flow in the same direction as the water flow in the welded pipe (2) is generated at the outlet of the outflow channel (14), thereby accelerating the flow rate of the water flow in the welded pipe (2). Compared with the other heated surface pipes, the water flow in the welded pipe (2) does not have time to be heated, forming a relatively "cold surface"; An annular insulating ring (7) is fixedly connected to the outer side of the welding pipe (2), and a groove (71) is provided on the inner side of the insulating ring (7). Two conductive posts (72) are fixedly connected to the bottom end of one side of the groove (71). When the exhaust gas temperature drops, acid water condenses first on the welding pipe (2) as the "cold surface". The acid water flows down into the groove (71), so that the electrical connection between the two conductive posts (72) is detected, which is used to remind the user to increase the exhaust gas temperature, thereby protecting the remaining heated surface pipes. The end of the horizontal portion (5) is sealed and the interior is hollow. The horizontal portion (5) is fixed to the inner side of the flue gas duct wall (8). The inner side of one end of the horizontal portion (5) extending out of the flue gas duct wall (8) is fixedly connected to a motor (9). The output end of the motor (9) is fixedly connected to a drive shaft (27). The drive shaft (27) is supported by a support member (10) fixedly connected to the interior of the horizontal portion (5). The rotating shaft (12) and the drive shaft (27) are connected to each other for steering via a plurality of universal joints (11).

2. A gas power plant tail flue gas monitoring system according to claim 1, characterized in that: The side of the groove (71) facing the flue gas is higher than the side facing away from the flue gas, so that the condensed acid water is concentrated on the side of the groove (71) facing away from the flue gas, thereby improving the sensitivity of the detection.

3. A gas power plant tail gas monitoring system according to claim 1, characterized in that: The inner side of the inclined portion (4) is fixedly connected to a rotary sealing shaft (13), and the inner side of the rotary sealing shaft (13) is fixedly connected to the outer side of the rotating shaft (12).

4. The tail gas monitoring system of a gas-fired power plant according to claim 1, characterized in that: The inner side of one end of the horizontal portion (5) extending out of the flue gas duct wall (8) is connected to a collection controller (6), and the collection controller (6) is electrically connected to the conductive column (72).

5. A gas power plant tail gas monitoring system according to any one of claims 1 to 4, characterized in that: The angle between the inclined portion (4) and the welded pipe (2) is 10-30°.

6. A gas power plant tail gas monitoring system according to any one of claims 1 to 4, characterized in that: A thermocouple (17) is connected to the inner side of one end of the horizontal portion (5) extending out of the flue gas duct wall (8). Two junction points (171) of the thermocouple (17) are respectively connected to the welded pipe (2) and the adjacent heated surface pipe (1) at the same height position, so as to directly obtain the temperature difference between the welded pipe (2) and the adjacent heated surface pipe (1) at the same height position.

7. A gas power plant tail flue gas treatment system, used to control the exhaust gas temperature based on the monitoring information obtained by the gas power plant tail flue gas monitoring system according to claim 1 or 6, characterized in that: The invention comprises a chimney (18) and an induced draft fan (21), wherein the inlet end of the chimney (18) is connected to the tail flue, the top end of the chimney (18) is fixedly connected to an exhaust ring (19), the inner side of the bottom end of the exhaust ring (19) is fixedly connected to an annular groove (22), the output end of the induced draft fan (21) is connected to an air inlet pipe (20), the output end of the air inlet pipe (20) is connected to the inner side of the annular groove (22), the inner side of the top end of the annular groove (22) is fixedly connected to an elastic ring (23), the elastic ring (23) is evenly provided with air outlet openings (24), the inner edge of the exhaust ring (19) is aligned with the inner edge of the chimney (18), and when the induced draft fan (21) is working, the air outlet openings (24) on the upper side of the annular groove (22) eject high-speed airflow, thereby increasing the flow velocity at the chimney (18) outlet, increasing the flow velocity of the tail flue (25), and increasing the exhaust temperature.

8. A method for monitoring tail flue gas in a gas-fired power plant, using the gas-fired power plant tail flue gas monitoring system according to claim 1, characterized in that: The steps are: Step 1: The motor (9) is operated to rotate the spiral blade (15), and a water flow in the same direction as the water flow in the welded pipe (2) is generated at the outlet of the outflow channel (14), thereby accelerating the flow rate of the water flow in the welded pipe (2). Compared with the other heated surface pipes, the water flow in the welded pipe (2) does not have time to be heated, forming a "cold surface"; Step 2: When the exhaust gas temperature drops, acid water condenses first on the welded pipe (2) serving as the "cold surface". The acid water flows down into the groove (71), so that the electrical connection between the two conductive columns (72) is detected, which is used to remind the user to increase the exhaust gas temperature, thereby protecting the remaining heated surface pipes. After the exhaust gas temperature rises, the condensed acid water evaporates again.

9. A method for monitoring tail flue gas in a gas-fired power plant, using the gas-fired power plant tail flue gas monitoring system according to claim 6, characterized in that: The steps are: Step 1: The motor (9) is operated to rotate the spiral blade (15), and a water flow in the same direction as the water flow in the welded pipe (2) is generated at the outlet of the outflow channel (14), thereby accelerating the flow velocity of the water flow in the welded pipe (2). Compared with the other heated surface pipes, the water flow in the welded pipe (2) has no time to be heated, forming a "cold surface". The faster the speed of the motor (9) is, the faster the water flow velocity in the welded pipe (2) is, and the greater the temperature difference between the adjacent heated surface pipes and the welded pipe (2). The thermocouple (17) is used to obtain the temperature difference between the adjacent heated surface pipes and the welded pipe (2); Step 2: The greater the temperature difference between the adjacent heated surface pipes and the welded pipe (2), the lower the temperature of the "cold surface", the earlier condensed acid water appears on the "cold surface", the greater the safety threshold, and the thermal efficiency will be relatively reduced; the smaller the temperature difference between the adjacent heated surface pipes and the welded pipe (2), the lower the temperature of the "cold surface", the later condensed acid water appears on the "cold surface", the smaller the safety threshold, and the thermal efficiency will be relatively increased; Step 3: According to the method of step 2, the temperature difference between the exhaust gas temperature, the low-temperature heating surface and the acid dew point is controlled within a reasonable range, taking into account the low-temperature corrosion prevention and control and energy utilization at the tail of the boiler.

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