Warm air system capable of effectively controlling pipe wall temperature of boiler air pre-heater

Abstract

The utility model discloses a warm air system capable of effectively controlling the pipe wall temperature of a boiler air pre-heater, relates to the technical field of boiler air pre-heaters, and solves the problems that the cold end of an existing last-stage air pre-heater has the lowest air temperature, the lowest smoke temperature and the lowest wall temperature of a heated surface, but the pipe wall of the air pre-heater is generally designed to be thinner, so that the cost is low. Therefore, low-temperature corrosion is very easy to generate. Comprising an air pre-heater body, a first heat exchange area on one side and a second heat exchange area on the other side are arranged in the air pre-heater body, a plurality of air supply inlets are formed in the first heat exchange area, air heaters are arranged at the air supply inlets, and first-time heat exchange heating is conducted; a smoke pipeline is arranged in the second heat exchange area and communicated with the smoke channel, an air supply outlet is formed in the side, away from the first heat exchange area, of the second heat exchange area, and supplied air and smoke conduct secondary heat exchange. The inlet air temperature of the last-stage air preheater is controlled through the air heater, it is guaranteed that the pipe wall temperature of the last-stage air preheater is above the acid dew point temperature, and the effect of avoiding low-temperature condensation corrosion is achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of boiler air preheaters, in particular to a warm air system for effectively controlling the temperature of a boiler air preheater tube wall. Background Art

[0002] The installation of air preheater in thermal power boiler system can make full use of flue gas waste heat, reduce exhaust gas temperature and improve boiler efficiency. However, the flue gas desulfurization device of the boiler has certain requirements on flue gas temperature. The air preheater is bound to be in the lowest flue gas temperature area in the boiler, especially the cold end of the final air preheater, where the air temperature is the lowest, the flue gas temperature is also the lowest, and the heating surface wall temperature is the lowest. Due to the need for heat transfer, the wall thickness of the air preheater tube is generally designed to be thin, which makes it very easy to produce low-temperature corrosion.

[0003] Once corrosion occurs, the air leakage rate of the air preheater increases, the forced draft fan operates at overload, and the power consumption of the unit increases; and the boiler combustion oxygen is insufficient, which seriously affects the thermal load of the unit and endangers the safe operation of the unit; how to effectively control the temperature of the tube wall of the final air preheater to avoid condensation of acidic substances in the flue gas on the tube wall of the final air preheater has become a difficult problem that needs to be solved urgently on site. Utility Model Content

[0004] The utility model aims to provide a heating system for effectively controlling the temperature of the tube wall of a boiler air preheater, and controls the inlet air temperature of the final air preheater through the heating system to ensure that the tube wall temperature of the final air preheater is above the acid dew point temperature, thereby avoiding the problem of low-temperature condensation corrosion.

[0005] The above technical objectives of the utility model are achieved through the following technical solutions:

[0006] A warm air system for effectively controlling the temperature of the tube wall of a boiler air preheater comprises an air preheater body, wherein a first heat exchange zone on one side and a second heat exchange zone on the other side are arranged in the air preheater body, the first heat exchange zone is provided with a plurality of air supply inlets, and a heater is arranged at the air supply inlet for performing the first heat exchange and temperature rise; a flue gas pipeline is arranged in the second heat exchange zone and is connected to the flue gas channel, and an air supply outlet is arranged on the side of the second heat exchange zone away from the first heat exchange zone, and the air supply and the flue gas perform a second heat exchange.

[0007] Furthermore, there are two air supply inlets, which are respectively located on both sides of the first heat exchange zone.

[0008] Furthermore, a plurality of wall temperature test pieces are arranged at intervals in the second heat exchange zone along the air supply flow direction.

[0009] Furthermore, the air heater comprises a steam inlet duct.

[0010] Furthermore, the steam inlet pipe is connected to an inlet steam regulating valve to control the inlet steam flow of the heater.

[0011] Furthermore, the steam inlet pipeline is connected to the company's pipeline network to provide auxiliary steam and backup heat source.

[0012] Furthermore, the backup heat source includes steam from the fourth extraction of the steam turbine.

[0013] Furthermore, the steam inlet pipe is connected to a temperature testing piece to detect the inlet steam temperature.

[0014] Furthermore, the steam inlet pipe is also connected to a flow test piece to detect the inlet steam flow.

[0015] In summary, the utility model has the following beneficial effects:

[0016] 1. The utility model can improve the tube wall temperature of the final air preheater by adjusting the air supply temperature, avoid serious low-temperature corrosion of the final air preheater, and extend the service life of the air preheater.

[0017] 2. The utility model can realize automatic adjustment of the tube wall temperature of the final air preheater. By monitoring the tube wall temperature data of the air preheater, the tube wall temperature can be monitored, and the steam flow of the heater can be automatically or manually adjusted based on the temperature, the supply air temperature can be intelligently adjusted, and the inlet air temperature of the final air preheater can be controlled to ensure that the tube wall temperature of the final air preheater is above the acid dew point temperature.

[0018] 3. The utility model improves the stability of the air preheater, greatly reduces the air leakage rate, ensures that the load of the forced draft fan is within a reasonable range, reduces the power consumption of the forced draft fan, and achieves energy saving and consumption reduction in equipment operation.

[0019] 4. The heat source of the utility model uses steam from the internal steam pipe network, and a backup steam source is set from the fourth extraction of the steam turbine, which greatly improves the system reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of a warm air system for effectively controlling the temperature of the boiler air preheater tube wall of the utility model;

[0021] Figure 2 This is a schematic diagram of the top view of the structure of a warm air system for effectively controlling the temperature of the tube wall of a boiler air preheater according to the utility model;

[0022] Figure 3 This is a schematic diagram of the pipe connection of the heater part of a heating system for effectively controlling the tube wall temperature of a boiler air preheater of the utility model;

[0023] Figure 4 The utility model is a schematic diagram of a sensing element in a warm air system for effectively controlling the tube wall temperature of a boiler air preheater.

[0024] In the figure, 1. air preheater body; 11. flue gas pipeline; 2. heater; 21. steam inlet pipe; 22. steam drain outlet pipe; 23. drain system; 3. flue gas channel; 4. wall temperature test piece; 5. inlet steam regulating valve; 6. auxiliary steam from the company's pipeline network; 7. steam from the fourth extraction of steam from the steam turbine; 8. inlet steam test piece. DETAILED DESCRIPTION

[0025] The specific implementation of the utility model is further described below in conjunction with the accompanying drawings, and this embodiment does not constitute a limitation of the utility model. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] A heating system that effectively controls the temperature of the boiler air preheater tube wall, such as Figure 1 and Figure 2 As shown, it includes an air preheater body 1 (final stage air preheater), and the air preheater body 1 is provided with a first heat exchange zone on one side and a second heat exchange zone on the other side. The first heat exchange zone increases the supply air temperature from the natural environment temperature by about 40°C, and the second heat exchange zone transfers heat between the supply air and the hot flue gas to increase the supply air temperature again.

[0027] like Figure 1 As shown, the first heat exchange zone is provided with a plurality of air supply inlets, and a heater 2 is fixed at the air supply inlet to perform the first heat exchange and temperature rise; according to the flue gas temperature requirement at the inlet of the desulfurization device, the lowest flue gas temperature at the outlet of the final air preheater can be calculated, and the lowest air supply temperature when the tube wall temperature is above the acid dew point temperature can be calculated by combining the flue gas heat transfer coefficient and the air supply heat transfer coefficient, thereby calculating the size and layout of the heater 2 equipment;

[0028] In this embodiment, two air supply inlets are provided, which are respectively located on both sides of the first heat exchange zone at one end away from the second heat exchange zone, and both are fixedly located corresponding to the heater 2 at the air supply outlet position.

[0029] like Figure 2 and Figure 3 As shown, the air heater 2 includes a steam inlet pipe 21. In this embodiment, the air heater 2 on one side includes two heat exchange units, each heat exchange unit is connected to a steam inlet pipe 21, and the two steam inlet pipes 21 of each air heater 2 are connected to the same inlet steam regulating valve 5 to control the inlet steam flow of the air heater 2. By adjusting the steam flow, the air supply temperature is controlled, the wall temperature of the final air preheater is improved, the serious low-temperature corrosion of the final air preheater is avoided, and the service life of the air preheater is extended;

[0030] The inlet steam regulating valve 5 may be an electric valve or a manual valve. In some embodiments, the inlet steam regulating valve 5 may be provided with inspection valves at the front and rear, and manual valves may be connected in parallel at both ends.

[0031] like Figure 3 As shown, considering the seasonal ambient temperature difference and the problem of balancing the steam consumption in the company's pipeline network, the heater 2 draws a spare steam heat source pipeline from the fourth extraction, and is connected to the auxiliary steam supply 6 and the spare heat source of the company's pipeline network at the end of the steam regulating valve away from the heater 2; in this embodiment, the spare heat source includes the steam supply 7 of the fourth extraction of the steam turbine, that is, the heat source medium in the heater 2 is connected to a steam pipeline from the steam pipeline network, and then a steam pipeline is connected from the fourth extraction of the steam turbine as a spare heat source;

[0032] When the company's pipeline steam is insufficient, four-extraction steam can be used to maintain the steam heat source of heater 2, or when the ambient temperature is low in winter, four-extraction steam with higher quality can be used as the heat source of heater 2.

[0033] like Figure 3 As shown, the heater 2 is also connected to a steam drain outlet pipe 22, and the other end of the steam drain outlet pipe 22 is connected to a drain system 23. The drain outlet of each heat exchange unit can be connected to a drain tank through a drain outlet pipe, and then one end of the steam drain outlet pipe 22 is connected to the drain tank, and the other end is connected to the drain system 23. The specific structure of the drain system 23 is the existing technology, such as a steam trap, etc., which will not be described in detail here.

[0034] like Figure 1 and Figure 2 As shown, a plurality of vertical flue gas pipes 11 are provided in the second heat exchange zone, through holes are provided on the top plate and the bottom plate at the position of the second heat exchange zone, and corresponding flue gas pipes 11 are fixed between the through holes, so that the flue gas flows up and down along the flue gas pipes 11, and the supply air flows between the pipe fittings along the outer edge of the flue gas pipes 11 for heat exchange; the top plate of the second heat exchange zone is connected to the flue gas channel 3 upward, and the flue gas flows downward from the flue gas channel 3 into each flue gas pipe 11; the second heat exchange zone is provided with an air supply outlet on the side away from the first heat exchange zone, and the supply air entering the second heat exchange zone performs a second heat exchange with the flue gas.

[0035] like Figure 2 and Figure 4 As shown, a plurality of wall temperature test pieces 4 are arranged at intervals along the air supply flow direction in the second heat exchange zone. The wall temperature test pieces 4 are connected to the middle of the pipe wall of the flue gas pipeline 11 and are used for operation analysis and parameter adjustment. The pipe wall temperature is monitored by the wall temperature test pieces 4 to automatically or manually control the opening of the inlet steam regulating valve 5, which can be directly adjusted to a fixed opening according to the value of the lowest temperature;

[0036] In some embodiments, temperature measuring points are embedded at designated points during prefabrication and welding of the final air preheater, armored signal lines are led out and connected to a DCS cabinet, data from the temperature measuring points of the air preheater tube wall are collected and entered into the DCS, and then the output signal is analyzed by an analog automatic adjustment system to adjust the opening of the inlet steam regulating valve 5 of the heater 2; multiple temperature measuring points are arranged by gradient pre-embedding, and the temperature measuring point data are connected to the DCS system. Through air preheater tube wall temperature monitoring, the inlet steam regulating valve 5 of the heater 2 is automatically adjusted to control the inlet steam flow of the heater 2, adjust the air supply preheating temperature, and adjust the tube wall temperature of the final air preheater to ensure that the tube wall temperature of the final air preheater is above the acid dew point temperature, thereby avoiding low-temperature corrosion and extending the service life of the final air preheater.

[0037] like Figure 4 As shown, the steam inlet pipe 21 of the heater 2 is connected to an inlet steam test piece 8. In this embodiment, the inlet steam test piece 8 includes a temperature test piece, a flow test piece and a pressure test piece to detect the inlet steam temperature, flow and pressure. It can also be connected to the DCS, or can be directly used for display for reference by operation or maintenance personnel or the system.

[0038] This embodiment provides a heating system for effectively controlling the tube wall temperature of the boiler air preheater, which can realize tube wall temperature monitoring to adjust the steam flow of the heater 2, and finally control the inlet air temperature of the final air preheater to ensure that the tube wall temperature of the final air preheater is above the acid dew point temperature, thereby avoiding low-temperature condensation corrosion problems;

[0039] The hot steam circulating in the tube of heater 2 exchanges heat with the supply air flowing through the tubes of heater 2, raising the supply air temperature by about 40°C from the natural ambient temperature. The hot air preheated by heater 2 flows through the final air preheater again, and heat is transferred between the tube wall and the hot flue gas in the tube, thereby raising the supply air temperature again and improving the thermal efficiency of the boiler.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions should also be deemed to fall within the protection scope of the technical solution of the present invention.

Claims

1. A warm air system for effectively controlling the temperature of the boiler air preheater tube wall, characterized in that: It includes an air preheater body, which is provided with a first heat exchange zone on one side and a second heat exchange zone on the other side. The first heat exchange zone is provided with a plurality of air supply inlets, and a heater is provided at the air supply inlet to perform the first heat exchange and temperature rise; the second heat exchange zone is provided with a flue gas pipeline and connected to the flue gas channel, and the second heat exchange zone is provided with an air supply outlet on the side away from the first heat exchange zone, and the air supply and flue gas perform a second heat exchange.

2. A heating system for effectively controlling the wall temperature of a boiler air preheater according to claim 1, characterized in that: There are two air supply inlets, which are respectively located on both sides of the first heat exchange zone.

3. A warm air system for effectively controlling the temperature of the boiler air preheater tube wall according to claim 1 or 2, characterized in that: A plurality of wall temperature test pieces are arranged at intervals in the second heat exchange zone along the air supply flow direction.

4. A heating system for effectively controlling the wall temperature of boiler air preheater according to claim 1, characterized in that: The air heater includes a steam inlet duct.

5. A heating system for effectively controlling the wall temperature of boiler air preheater according to claim 4, characterized in that: The steam inlet pipeline is connected to the inlet steam regulating valve to control the inlet steam flow of the heater.

6. A warm air system for effectively controlling the temperature of the boiler air preheater tube wall according to claim 4 or 5, characterized in that: The steam inlet pipeline is connected to the company's pipeline network to provide auxiliary steam and backup heat source.

7. A warm air system for effectively controlling the temperature of the boiler air preheater tube wall according to claim 6, characterized in that: The backup heat source includes steam from the fourth extraction of the steam turbine.

8. A heating system for effectively controlling the wall temperature of boiler air preheater according to claim 4, characterized in that: The steam inlet pipe is connected to a temperature testing piece to detect the inlet steam temperature.

9. A warm air system for effectively controlling the temperature of the boiler air preheater tube wall according to claim 4 or 8, characterized in that: The steam inlet pipe is also connected to a flow test piece to detect the inlet steam flow.

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