System for mixing and heating primary air and secondary air by using large slag waste heat of coal-fired power plant boiler

Abstract

The utility model provides a system for heating primary air and secondary air by mixing large slag waste heat of a coal-fired power plant boiler, which comprises a tubular heat exchanger which is arranged at a dry bottom hopper below a boiler hearth and is arranged along the left-right direction of the bottom of the dry bottom hopper; a cold air inlet and a hot air outlet are formed in the tubular heat exchanger, and the hot air outlet is connected with a primary fan inlet pipeline and a secondary fan inlet pipeline; cold air is heated by heat carried by large slag discharged by a boiler, the cold air is heated into hot air and then is directly mixed with cold air at the inlet of the primary fan and the inlet of the secondary fan, so that the air temperature is improved, and the problem that ammonium bisulfate is condensed in the air pre-heater due to the fact that the air temperature of the air pre-heater is too low is solved. And the resistance of the air pre-heater is increased.

Description

Technical Field

[0001] The utility model belongs to the field of coal burning, and in particular relates to a system for mixing and heating primary and secondary air by utilizing waste heat from large slag of a coal-fired power station boiler. Background Art

[0002] The slag generated by the combustion of pulverized coal in coal-fired power plant boilers falls from the furnace to the slag picker and is taken away after cooling. Before entering the slag picker, its temperature is 600~800℃. After entering the slag picker, it will be cooled to 60~80℃ by air or water and then taken away by the slag picker chain. Therefore, the heat carried by the slag is not used and discharged. This part of heat is included in the physical heat loss of the slag in the process of boiler efficiency calculation. Therefore, making good use of this part of heat can improve the boiler efficiency and improve the economy of the whole plant.

[0003] Due to the tightening of national environmental protection policies, thermal power plants need to denitrify flue gas. In this process, ammonium bisulfate will be produced, and its melting point is 147°C. If the temperature of the flue gas after denitrification treatment entering the air preheater is too low, the ammonium bisulfate will quickly condense in the air preheater, causing the air preheater resistance to rise rapidly, affecting the load and safe operation of the unit. Therefore, sufficient primary and secondary air temperatures must be ensured during the operation of the unit. Summary of the invention

[0004] The utility model aims to provide a system for heating primary and secondary air by utilizing waste heat from large slag of coal-fired power station boilers, thereby solving the defect that the temperature of the air entering the air preheater may be too low.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0006] The utility model provides a system for mixing primary and secondary air with waste heat from large slag of a coal-fired power station boiler, comprising a tubular heat exchanger, which is arranged at a cold ash hopper below the furnace of the boiler and arranged in the left and right directions along the bottom of the cold ash hopper;

[0007] The tubular heat exchanger is provided with a cold air inlet and a hot air outlet, and the hot air outlet is connected to a primary fan inlet duct and a secondary fan inlet duct respectively.

[0008] Preferably, the tubular heat exchanger is provided with a cold air inlet connected to a cold air duct, and a muffler is provided at the inlet of the cold air duct.

[0009] Preferably, the hot air outlet is connected to the primary fan inlet duct and the secondary fan inlet duct through the hot primary air inlet branch pipe and the hot secondary air inlet branch pipe respectively.

[0010] Preferably, a hot primary air damper is provided on the hot primary air inlet branch pipe; and a hot secondary air damper is provided on the hot secondary air inlet branch pipe.

[0011] Preferably, a cold primary air damper and a primary fan temperature measuring point are provided on the primary fan inlet duct; and a cold secondary air damper and a secondary fan temperature measuring point are provided on the secondary fan inlet duct.

[0012] Preferably, the hot primary air damper, hot secondary air damper, cold primary air damper and cold secondary air damper are all connected to the output end of the controller; the primary fan temperature measuring point and the secondary fan temperature measuring point are all connected to the input end of the controller.

[0013] Preferably, the tubular heat exchanger comprises an inlet header, heat exchange tubes and an outlet header, wherein:

[0014] The heat exchange tubes are provided in plurality, and the plurality of heat exchange tubes are evenly distributed on the inlet header and communicated with the inlet header; the free ends of the heat exchange tubes are communicated with the outlet header;

[0015] The inlet header is provided with a cold air duct, and the outlet header is connected with a hot air duct.

[0016] Preferably, the primary fan inlet duct is connected to the primary fan; and the secondary fan inlet duct is connected to the secondary fan.

[0017] Preferably, a primary air muffler is provided at the cold primary air inlet of the primary fan inlet duct; and a secondary air muffler is provided at the cold secondary air inlet of the secondary fan inlet duct.

[0018] Compared with the prior art, the beneficial effects of the utility model are:

[0019] The utility model provides a system for heating primary and secondary air by mixing waste heat from large slag of a coal-fired power station boiler, and heat carried by large slag discharged from the boiler is used to heat cold air. After being heated and converted into hot air, the cold air is directly mixed with cold air at the inlet of a primary fan and a secondary fan to increase the air temperature, thereby solving the defect that ammonium bisulfate condenses in the air preheater due to too low air temperature of the air preheater, causing increased resistance of the air preheater. The system does not require water as a heat exchange medium, reduces the number of heat exchangers, and makes the system simpler. Since the air temperature at the inlet of the primary and secondary fans is improved, the steam extraction of the steam turbine is reduced, so that more steam enters the steam turbine to do work, and the load-carrying capacity of the unit is effectively improved. At the same time, the heat carried by the large slag of the boiler is utilized, and the economy of the whole plant is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the system involved in the utility model;

[0021] Figure 2 It is a schematic diagram of the structure of the tubular heat exchanger involved in the utility model;

[0022] In the figure: 1-furnace; 2-tubular heat exchanger; 3-cold air duct; 4-muffler; 5-hot air duct; 6-hot primary inlet branch pipe; 7-hot secondary air inlet branch pipe; 8-hot primary air damper; 9-hot secondary air damper; 10-primary fan inlet duct; 11-secondary fan inlet duct; 12-primary fan; 13-secondary fan; 14-primary air muffler; 15-secondary air muffler; 16-cold primary air damper; 17-cold secondary air damper; 18-primary fan inlet temperature measuring point; 19-secondary fan inlet temperature measuring point; 22-tubular heat exchanger inlet header; 23-tubular heat exchanger heat exchange tubes; 24-tubular heat exchanger outlet header. DETAILED DESCRIPTION

[0023] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and circuits are omitted to prevent unnecessary details from obstructing the description of the present application.

[0024] Example 1

[0025] like Figure 1 and Figure 2 As shown, the present embodiment provides a system for heating primary and secondary air by mixing waste heat from large slag of a coal-fired power station boiler, comprising a tubular heat exchanger 2, a cold air duct 3, a muffler 4, a hot air duct 5, a hot primary air inlet branch pipe 6, a hot secondary air branch pipe 7, a hot primary air damper 8, a hot secondary air damper 9, a primary fan inlet duct 10, a secondary fan inlet duct 11, a primary fan 12, a secondary fan 13, a primary air muffler 14, a secondary air muffler 15, a cold primary air damper 16, a cold secondary air damper 17, a primary fan inlet temperature measuring point 18 and a secondary fan inlet temperature measuring point 19, wherein:

[0026] A tubular heat exchanger 2 is arranged at the cold ash hopper below the furnace 1. The tubular heat exchanger 2 is arranged in the left and right direction along the bottom of the cold ash hopper. The inlet of the tubular heat exchanger is connected to the cold air duct 3, and a muffler 4 is provided at the inlet of the cold air duct 3.

[0027] The outlet of the tubular heat exchanger is connected to the hot air duct 5, which is divided into a hot primary air inlet branch pipe 6 and a hot secondary air inlet branch pipe 7. A hot primary air damper 8 is arranged on the hot primary air inlet branch pipe 6. The hot primary air inlet branch pipe is connected to the original primary fan inlet pipe 10, and a cold primary air damper 16 and a primary fan temperature measuring point 18 are installed on the original primary fan inlet pipe 10.

[0028] A hot secondary air damper 9 is arranged on the hot secondary air inlet branch pipe, which is connected to the original secondary fan inlet duct 11, and a cold secondary air damper 17 and a secondary fan temperature measuring point 19 are installed on the original secondary fan inlet duct 11.

[0029] The operation mode of this embodiment is as follows:

[0030] After the secondary air fan 13 and the primary air fan 12 are started, before the pulverized coal burner of the boiler is put into operation, the hot primary air damper 8 is kept closed, the cold primary air damper 16 is fully opened, the hot secondary air damper 9 is closed, and the cold secondary air damper 17 is fully opened, so that all the air enters the primary air fan and the secondary air fan through the cold primary air silencer 14 and the cold secondary air silencer 15. When the pulverized coal burner of the boiler is put into operation, the boiler produces large slag, and the hot primary air damper 8 and the hot secondary air damper 9 are slowly opened. The negative pressure generated by the inlet pipes of the primary air fan 12 and the secondary air fan 13 makes the ambient cold air enter the cold air pipe 3 through the silencer 4, and then passes through the tubular heat exchanger 2 to exchange heat with the large slag dropped from the furnace to become hot air, and enters the hot primary air inlet branch pipe 6 and the hot secondary air inlet branch pipe 7 through the pipe 5. After the secondary air enters the primary fan inlet duct 10, it mixes with the cold primary air, which increases the air temperature at the inlet of the primary fan 12. After the hot secondary air enters the secondary fan inlet duct 11, it mixes with the cold secondary air, which increases the air temperature at the inlet of the secondary fan 13. The primary fan inlet temperature 18 monitors the air temperature after the mixing enters the primary fan. When the primary fan inlet temperature needs to be increased, the hot primary air damper 8 is opened and the cold primary air damper 16 is closed. When the primary fan inlet temperature needs to be lowered, the hot primary air damper 8 is closed and the cold primary air damper 16 is opened. When the secondary fan inlet temperature needs to be increased, the hot secondary air damper 9 is opened and the cold secondary air damper 17 is closed. When the secondary fan inlet temperature needs to be lowered, the hot secondary air damper 9 is closed and the cold secondary air damper 17 is opened.

[0031] Example 2

[0032] On the basis of Example 1, this embodiment provides a system for utilizing waste heat from large slag of a coal-fired power station boiler, wherein the tubular heat exchanger 2 includes an inlet header 22, a heat exchange tube 23 and an outlet header 24, wherein:

[0033] A plurality of heat exchange tubes 23 are provided, and the plurality of heat exchange tubes are evenly distributed on the inlet header 22 and communicated with the inlet header 22 ; the free ends of the heat exchange tubes are communicated with the outlet header 24 .

[0034] The inlet header 22 is connected to the cold air duct 3 , and the outlet header 24 is connected to the hot air duct 5 .

[0035] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A system for heating primary and secondary air by using the waste heat from the slag of a coal-fired power station boiler, characterized in that: It includes a tubular heat exchanger, which is arranged at the cold ash hopper below the boiler furnace and arranged along the left and right directions of the bottom of the cold ash hopper; The tubular heat exchanger is provided with a cold air inlet and a hot air outlet, and the hot air outlet is connected to a primary fan inlet duct and a secondary fan inlet duct respectively.

2. According to claim 1, a system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers, characterized in that: The tubular heat exchanger is provided with a cold air inlet connected to a cold air duct, and a muffler is provided at the inlet of the cold air duct.

3. The system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 1 is characterized in that: The hot air outlet is connected to the primary fan inlet duct and the secondary fan inlet duct through the hot primary air inlet branch pipe and the hot secondary air inlet branch pipe respectively.

4. The system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 3 is characterized in that: The hot primary air inlet branch pipe is provided with a hot primary air regulating valve; the hot secondary air inlet branch pipe is provided with a hot secondary air regulating valve.

5. The system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 4 is characterized in that: The primary fan inlet duct is provided with a cold primary air damper and a primary fan temperature measuring point; the secondary fan inlet duct is provided with a cold secondary air damper and a secondary fan temperature measuring point.

6. A system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 5, characterized in that: The hot primary air regulating valve, the hot secondary air regulating valve, the cold primary air regulating valve and the cold secondary air regulating valve are all connected to the output end of the controller; the primary fan temperature measuring point and the secondary fan temperature measuring point are all connected to the input end of the controller.

7. The system for heating primary and secondary air by utilizing waste heat from large slag of coal-fired power station boilers according to claim 1 is characterized in that: The tubular heat exchanger comprises an inlet header, heat exchange tubes and an outlet header, wherein: The heat exchange tubes are provided in plurality, and the plurality of heat exchange tubes are evenly distributed on the inlet header and communicated with the inlet header; the free ends of the heat exchange tubes are communicated with the outlet header; The inlet header is provided with a cold air duct, and the outlet header is connected with a hot air duct.

8. The system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 1 is characterized in that: The primary fan inlet pipe is connected to the primary fan; the secondary fan inlet pipe is connected to the secondary fan.

9. The system for heating primary and secondary air by using waste heat from large slag of coal-fired power station boilers according to claim 1 is characterized in that: A primary air muffler is provided at the cold primary air inlet of the primary fan inlet duct; and a secondary air muffler is provided at the cold secondary air inlet of the secondary fan inlet duct.

Images